Patty's Toxicology Mini Set Volume One and Eight

Industrial Toxicology: Origins and Trends Eula Bingham, Ph.D., John Zapp, Ph.D., (deceased) 1 Introduction Industrial toxicology is a comparatively recent discipline, but its roots are shadowed in the mists of time. The beginnings of toxicology, the knowledge or science of poisons, are prehistoric. Earliest human beings found themselves in environments that were at the same time helpful and hostile to their survival. They found their food among the plants, trees, animals, and fish in their immediate surroundings, their clothing in the skins of animals, and their shelter mainly in caves. Their earliest tools and weapons were of wood and stone. It was in the very early period of prehistory that humans must have become aware of the phenomenon of toxicity. Some fruits, berries, and vegetation could be eaten with safety and to their benefit, whereas others caused illness or even death. The bite of the asp or adder could be fatal, whereas the bite of many other snakes was not. Humans learned from experience to classify things into categories of safe and harmful. Personal survival depended on recognition and avoidance, so far as possible, of the dangerous categories. In a unique difference from other animals, humans learned to construct tools and weapons that facilitated their survival. Stone and wood gave way in time to bronze and then to iron as materials for constructing these tools and weapons. The invention of the bow and arrow was a giant step forward in weaponry, for it gave humans a chance to kill animals or other people from a safe distance. And humans soon used their knowledge of the poisonous materials they found in their natural environment to enhance the lethality of their weapons. One of the earliest examples of the deliberate use of poisons in weaponry was smearing arrowheads and spear points with poisons to improve their lethal effectiveness. In the Old Testament we find at Job 6:4, “The arrows of the Almighty find their mark in me, and their poison soaks into my spirit” (The New English Bible version). The Book of Job is generally dated at about 400 B. C. L. G. Stevenson (1) cites the Presidential Address of F. H. Edgeworth before the Bristol MedicoChirurgical Society in 1916, to the effect that Odysseus is credited in Homer's Odyssey with obtaining a man-killing poison from Anchialos, king of the Taphians, to smear on his bronze-tipped arrows. This particular passage does not occur in modern translations of the Odyssey and, according to Edgeworth, was probably expurgated from the text when Greece came under the domination of Athens, at which time the use of poisons on weapons was considered barbaric and not worthy of such a hero as Odysseus. Because the earliest literature reference to Homer is dated at 660 B. C., well before the Pan-Athenian period, an early origin of the use of poisoned arrows can be assumed. Indeed, the word “toxic” derives from the early Greek use of poisoned arrows. The Greek word for the bow was toxon and for a drug was pharmakon. Therefore, an arrow poison was called toxikon pharmakon, or drug pertaining to the bow. Many Latin words are derived from the Greek, but the Romans took only the first of the two Greek works as their equivalent of “poison,” that is, toxicum. Other Latin words for poison were venenum and virus. In the transition to English, toxicum became “toxin,” and the knowledge or science of toxins becomes “toxicology.” There were practicing toxicologists in Greece and Rome. Stevenson (1) refers to a book by Sir T. C. Albutt (2) according to which the professional toxicologists of Greece and Rome were purveyors of poisons and dealt in three kinds: those that acted quickly, those that caused a lingering illness, and those that had to be given repeatedly to produce a cumulative effect. These poisons were of vegetable or animal origin, except for arsenic. Although the toxicity of lead was described by Hippocrates, and of mercury by Pliny the Elder, these metals were apparently not deliberately employed as poisons before the Renaissance.

There is little doubt that the customers of the early toxicologists were interested in assassination or suicide. Poisons offered a safer means for the assassin of disposing of an enemy than the more visible alternatives that posed the risk of premature discovery and possibly effective retaliation. As a means of suicide, poison often seemed more acceptable than other available means of selfdestruction. Although poisons have continued to be used for both homicide and suicide, their popularity for these purposes has decreased as the popularity of firearms has increased. The use of poisons as adjuncts to other weapons such as the spear or arrow ceased in Western Europe long before the discovery of firearms. It has persisted to this day in primitive civilizations such as those of the African pygmies and certain tribes of South American Indians. The use of poison on a large scale as a primary weapon of war occurred during World War I, when both sides employed poison gases. In the interval between World War I and World War II, the potential of chemical and biological agents as a means of coercion was thoroughly studied by most of the powers, and both sides were prepared to use them, if necessary, in World War II. Although their use in future wars has apparently been renounced, it should not be forgotten that the chemical and biological toxins remain viable means of coercion that could be utilized under appropriate circumstances in future conflicts. It would not be prudent to forget this in thinking about national defense. The early and sinister uses of poisons did result in contributions to toxicology. Furthermore, the knowledge obtained did not require extrapolation to the human species, for humans were the subjects in early experimentation. As mentioned earlier, the professional toxicologists of Greece and Rome had recognized and dealt with poisons that produced acute effects, those that produced lingering effects, and those that produced cumulative effects. We recognize these categories today. The “dose-effects” relationship was also recognized. In Plato's well-known description of the execution of Socrates, Socrates is required to drink a cup of hemlock, an extract of a parsley-like plant that bears a high concentration of the alkaloid coniine. When Socrates asks whether it is permissible to pour out a libation first to any god, the jailer replies, “We only prepare, Socrates, just as much as we deem enough.” The ancients also had some concept of the development of tolerance to poisons. There have come down through the ages the poison damsel stories. In one of these, related by Stevenson (1), a king of India sent a beautiful damsel to Alexander the Great because he guessed rightly that Alexander was about to invade his kingdom. The damsel had been reared among poisonous snakes and had become so saturated with their venom that all of her secretions were deadly. It is said that Aristotle dissuaded Alexander from doing what seemed natural under the circumstances until Aristotle performed a certain test. The test consisted in painting a circle on the floor around the girl with an extract of dittany, believed to be a powerful snake poison. When the circle was completed, the girl is said to have collapsed and died. The poison damsel stories continued to appear from time to time, and even Nathaniel Hawthorne wrote a short story about one entitled “Rappaccini's Daughter.” Kings and other important personages, fearing assassinations, sometimes tried to protect themselves from this hazard by attempting to build up an immunity to specific poisons by taking gradually increasing doses until able to tolerate lethal doses, sometimes—it is said—with results disastrous to the queen. Other kings took the precaution of having slaves taste their food before they ate. When slaves became too scarce or expensive, they substituted dogs as the official tasters and found that it worked about as well. Perhaps we have here the birth of experimental toxicology in which a nonhuman species was deliberately used to predict human toxicity. Little of importance to the science of toxicology developed during the Middle Ages. Such research as was done was largely empirical and involved the search for such things as the Philosopher's Stone, the Universal Solvent, the Elixir of Life, and the Universal Remedy. The search for the Universal Remedy is rumored to have been abandoned in the twelfth century when the alchemists learned how

to make a 60% solution of ethyl alcohol through improved techniques of distillation and found that it had some remarkable restorative properties. Although modern science is generally held to have had its beginnings in the seventeenth century with the work of Galileo, Descartes, and Francis Bacon, there was a precursor in the sixteenth century of some importance to toxicology. This was the physician-alchemist Phillipus Aureolus Theophrastus Bombastus von Hohenheim, known as Paracelsus. Born in 1490, the son of a physician, Paracelsus studied medicine with his father and alchemy at various universities. He was not impressed with the way that either medicine or alchemy was being taught or practiced and decided that more could be learned from the study of nature than from studying books by ancient authorities. Through travel and observation, Paracelsus learned more than his contemporaries about the natural history of diseases, to whose cure he applied his knowledge of both medicine and alchemy. He advocated that the natural substances then used as remedies be purified and concentrated by alchemical methods to enhance their potency and efficacy. He also attempted to find specific therapeutic agents for specific diseases and became highly successful as a practicing physician; in 1526 he was appointed Town Physician to the city of Basel, Switzerland, and a lecturer in the university. Being of an egotistical and quarrelsome disposition, Paracelsus quickly antagonized the medical and academic establishment. In the sixteenth century, syphilis was a more lethal disease than it was to become later, and the medical profession had no interest in it or cures for it. Paracelsus introduced and advocated the use of mercury for treating syphilis, and it worked. The establishment, however, was outraged and denounced Paracelsus for using a poison to treat a disease. Paracelsus loved an argument and responded to this and other accusations with a series of “Defenses,” of which the Third Defense (3) contained this statement with respect to his advocacy of the use of mercury or any other poison for therapeutic purposes: “What is it that is not poison? All things are poison and none without poison. Only the dose determines that a thing is not poison.” Paracelsus lectured and wrote in German, which was also contrary to prevailing academic tradition. When his works were eventually translated into Latin, the last sentence of the above quotation was usually rendered, “Dosis sola facit venenum” or “The dose alone makes a poison.” This principle is the keystone of industrial hygiene and is a basic concept in toxicology. Mercury soon became and remained the therapy of choice for syphilis for the next 300 years until Ehrlich discovered on his 606th trial an arsphenamine, Salvarsan, which was superior. Antimony was widely used as a therapeutic agent from the seventeenth to the nineteenth century, and with the medical profession was sharply divided as to whether it was more poison than remedy or more remedy than poison. The period from the seventeenth to the nineteenth century witnessed little decline in the use of human subjects for the initial evaluation of remedies. In 1604, a book said to have been written by a monk named Basile Valentine, but more probably by an anonymous alchemist, was published under the title The Triumphant Chariot of Antimony. The book states that the author had observed that some pigs fed food containing antimony had become fat. Therefore, he gave antimony to some monks who had lost considerable weight through fasting, to see if it would help them to regain weight faster. Unfortunately, they all died. Up to this time, the accepted name for the element had been stibium (from which we retain the symbol Sb), but it was renamed antimony from the words auti-moine meaning “monk's bane.” The Oxford English Dictionary agrees that this might be the popular etymology of the word. This anecdote can be credited to H. W. Haggard (4).

Industrial Toxicology: Origins and Trends

Eula Bingham, Ph.D., John Zapp, Ph.D., (deceased) 2 Experimental Toxicology Experimental toxicology, as we know, it followed the rise of organic chemistry, which is usually dated at around 1800. The rise was very rapid, and it is estimated that by 1880 some 12,000 compounds had been synthesized, and of these some turned out to be very toxic, in some cases proving fatal to the chemists who prepared them. Two of the war gases employed on a large scale in World War I, that is, phosgene (COCl2) and mustard gas, bis(b-chloroethyl) sulfide, had been prepared in 1812 and 1822, respectively. Early organic chemists were not deliberately looking for poisons, but for dyes, solvents, or pharmaceuticals. For example, toxicity was an unwanted side effect, but if it was there, it had to be recognized. The sheer number of new organic compounds synthesized in the laboratory, along with a growing public disapproval of the practice of letting toxicity be discovered by its effects on people, led to a more extensive use of convenient and available animals such as dogs, cats, or rabbits as surrogates for human beings, much as some of the ancient kings used dogs instead of slaves to test their food before they dined. Loomis (5) credits M. J. B. Orfila (6) with being the father of modern toxicology. A Spaniard by birth, Orfila studied medicine in Paris. According to Loomis: He is said to be the father of modern toxicology because his interests centered on the harmful effects of chemicals as well as therapy of chemical effects, and because he introduced quantitative methodology into the study of the action of chemicals on animals. He was the author of the first book devoted entirely to studies of the harmful effects of chemicals (6). He was the first to point out the valuable use of chemical analyses for proof that existing symptomatology was related to the presence of the chemical in the body. He criticized and demonstrated the inefficiency of many of the antidotes that were recommended for therapy in those days. Many of his concepts regarding the treatment of poisoning by chemicals remain valid today, for he recognized the value of such procedures as artificial respiration, and he understood some of the principles involved in the elimination of the drug or chemical from the body. Like many of his immediate followers, he was concerned primarily with naturally occurring substances for which considerable folklore existed with respect to the harmfulness of such compounds.

A reading of some of the earlier nineteenth century reports indicates a lack of recognition of and concern with either intraspecies or interspecies variation. Sometimes it is not possible to determine from the report which species of animal was tested. Some reports were based on dosage of only one animal, it being assumed that all others would react similarly. In reports of inhalation toxicity, a lethal concentration might be identified without designating the length of the exposure time. The initial recognition of biological variability comes from the study of the action of drugs rather than from the study of the action of chemicals as such. The increased interest in the action of drugs resulted from the availability of so many new organic compounds that could be explored for possible therapeutic activity. In the second half of the nineteenth century, the phenomenon of biological variability was recognized by pharmacologists, as was also the necessity for establishing the margin of safety between a therapeutically effective dose and a toxic dose of a drug. Clinical trials of new drugs with adequate controls began to be accepted as good science. The traditional wisdom and beliefs about therapeutic practice were reexamined by pharmacologists.

Early European efforts are credited by Warren Cook to Gruber (7) who used animals and himself in 1883 to set the boundaries for carbon monoxide poisoning. Lehmann and his colleagues (8) performed toxicity testing on numerous compounds using animals, and these provided the basis for establishing many exposure limits. Korbert (9) provided dose response data on acute exposures for twenty substances that gave information on levels that produced minimal symptoms after several hours, ½ to 1 hour exposures without serious disturbances, and ½ to 1 hour exposures that range from dangerous to rapidly fatal to man and animals. Many of these evaluations are still valid today.

Industrial Toxicology: Origins and Trends Eula Bingham, Ph.D., John Zapp, Ph.D., (deceased) 3 Industrial Toxicology Concerns for the safety of the workplace drove the development of industrial toxicology. The British physician, C.T. Thackrah, noted that, “Most persons who reflect on the subject will be inclined to admit that our employments are to a considerable degree injurious to health ... ” and “Evils are suffered to exist, even when the means of correction are known and easily applied. Thoughtlessness or apathy is the only obstacle to success” (10). In the United States, the first recognition of occupational disease by Benjamin McCready appeared (11) in an essay published by the Medical Society of New York. Illnesses including dermatoses were noted as well as long hours, poor ventilation, and child labor. Certainly, some of the illnesses were from chemical exposures and dust, but it should be noted that ergonomic and human performance concepts are raised in these early writings. Working conditions became a cause for concern among social movements mainly because of child labor. More than a century and a half later we still are concerned about child labor. Recognition of the relationship between chemical agents and disease (industrial toxicology) moved rapidly in Europe during the last decade of the nineteenth century. This activity may have been stimulated in Germany by the passage during Bismarck's rule of the Workingmen's Insurance Law, which set up an insurance fund into which both employers and employees contributed that amounted to about 6% of total wages paid out. For this, the workers obtained free medical care, as well as some compensation during periods of disability. Industrial toxicology in the United States grew out of work in occupational and industrial health by such investigators as Hamilton and Hardy (12), the Drinkers at Harvard (13, 14), Hatch at Pittsburgh (15), and Kehoe (16) and Heyroth (17) at Cincinnati. Government and industry provided financial support for these efforts. There had been no organic chemical industry in the United States before World War I. It was born just after the war, because during the war, the United States felt the lack of useful products such as aniline dyes (used for printing our stamps and currency, among other things) and pharmaceuticals (e.g., aspirin), which had been imported from Germany. Manpower and facilities used during the war for manufacturing munitions became available after 1918, and several companies decided to use them to get into the organic chemical business. Because neither employers nor workers had any previous experience in making and handling organic chemicals, the effects of unanticipated toxicity began to be encountered. That toxicity was not wanted because it was counterproductive and, along with other problems, had to be managed if the industry was to survive. To manage a problem, it must be anticipated, the causes must be identified and analyzed, and practical means of overcoming the problem must be available. As a means to this end, industrial preventive medicine, industrial toxicology, and industrial hygiene became valuable tools. By the mid-1930s, several large chemical companies in the United States had established in-house

laboratories of industrial toxicology, e.g., DuPont, Dow, and Union Carbide. The purpose of these laboratories was to provide management with sufficient information about the toxicity of new chemicals to enable prudent business decisions. Another important source of experimental toxicological data that was used to inform the workplace was from work by Hueper at one time, a pathologist at DuPont and chemists who were interested in chemical carcinogenesis and mechanistic research, e.g., the Millers (18) at Wisconsin and Ray (19) at Cincinnati. Early experimental data captured in Hartwell (20) “Survey of Compounds Which Have Been Tested for Carcinogenic Activity, Federal Security Agency, U.S. Public Health Service” eventually provided the bases for the first early lists of carcinogenic chemicals prepared by the American Standards Association and the American Conference of Governmental and Industrial Hygienists in the 1940s. It should be emphasized that although these beginning efforts in industrial toxicology were occurring in the United States, in Europe experimental toxicology and studies in occupational disease were well underway. For example, early work of the British on coal tars, mineral oils, and other carcinogens (aromatic amines) were widely available (22–25). It is important to recognize that by the 1930s the data from experimental studies in animals, human case reports, and early epidemiological studies reported the causes of many occupationally induced cancers. Table 1.1 (26–36) presents data and references from several of these early studies, and although more investigations have added to the knowledge regarding these carcinogens, these early observations remain valid. Table 1.1. Early Studies in Chemical Carcinogenesis Year 1775 1822 1873 1876 1879 1894 1895 1898 1935 1917 1929

First Reported by

Reported Agent or Process

Pott (26) Soot Paris (27) Arsenic Volkmann (28) Crude wax from coal Bell (29) Shale oil Härting and Hesse (30) Ionizing radiation Unna (31) Ultraviolet radiation Rehn (32) Aromatic amines Mackenzie (33) Creosote Pfeil (34) Chromate production Leymann (35) Crude anthracene (coal tar?) Martland (36) Radium

Site Scrotum Skin Skin Skin Lung Skin Bladder Skin Lung Skin Bone

In the United States, a dramatic change occurred in 1935 with the passage of the Social Security Act. Financial and technical support from the Federal Government were given to the States, mostly to Health Departments, to develop health programs to protect workers. New York and Massachusetts maintained their programs in the Labor Department. This effort was very important in industrial toxicology because all of these programs performed investigations into chemical and physical agents in the workplace and the development of disease. It is important to mention the work of the National Safety Council, which began a series of articles in the 1920s that described the toxicology of certain chemicals in the workplace and provided

recommendations for medical and industrial hygiene monitoring. Recognized leaders in the field wrote these guidelines, usually as a committee document. One example is the classic document on benzol toxicity (37). Although not called “industrial toxicology,” the emergence of industrial medicine and industrial hygiene as significant public health disciplines became embedded in the basic principles of industrial toxicology, that is, connecting chemical exposures with development of disease through measuring exposures, developing dose-response relationships for adverse health effects, and recommending interventions to reduce exposures and disease. From these early beginnings, guidelines to prevent illness (and injuries) were developed as part of recommendations issued by the National Safety Council, American National Standards Institute in the 1920s, and later by the American Conference of Government Industrial Hygiene (TLVs). By 1938, there were enough government-affiliated personnel engaged in the practice of industrial hygiene at the federal, state, and local levels to make possible the formation of the American Conference of Governmental Industrial Hygienists (ACGIH). In 1939, the American Industrial Hygiene Association (AIHA) was founded. These societies sought to bring collective knowledge regarding the toxicology of workplace hazards, mainly chemicals, and the necessary skills to reduce exposures. In the early period, industrial toxicologists were involved in recognizing, evaluating, and controlling hazards of the workplace that cause occupational illness and disability. Eventually, as investigators working in industrial toxicology became more specialized, they formed their own society in the 1960s, the Society of Toxicology, and eventually began to meet separately from the American Industrial Hygiene Association. At the turn of the twentieth century, most industrial toxicological information was gleaned from observations of workers employed in various industries. By the 1930s, experimental industrial toxicology was expanding rapidly with the introduction of studies using animals. Most early studies focused either on cancer or acute toxic responses such as asphyxiation and acute lung injury or neurological symptoms such as dizziness, tremors, convulsions, etc., and death. Probably the development of certain chronic lung diseases resulting from industrial exposures over several years, such as silicosis, coal workers' pneumoconiosis, asbestosis, beryllioses, and the recognition of lead poisoning as a chronic disease, led to the development and use of experimental chronic toxicity studies. Between 1920 and 1970 (i.e., before most environmental and occupational health laws), industrial toxicology was performed mainly by industry in its own laboratories, e.g., DuPont's Haskell Laboratory where one of the authors of this chapter worked, at Dow Chemical Company where V. K. Rowe was a pioneer investigator, and at various university laboratories, such as Harvard, University of Pittsburgh, New York University, University of Cincinnati, and Johns Hopkins University, where the work was supported by industry. The arrangements at these laboratories ranged from contracts to grant relationships and although the interpretation of the results may have involved some controversy, by and large, the experimental results have stood the test of time. A great deal of toxicological data came from industries where physicians, industrial hygienists, or toxicologists reported adverse health responses in certain occupations where a specific chemical was used. It was this collection of industrial toxicological data that was brought together and formed the basis of the first two editions of Patty's. For example, it is common over the years to see the names of industry leaders in health and safety provide “personal communication” as the source of certain toxicological data (e.g., Dr. D. Fassett, Eastman Kodak) in this volume. Often these early references are to industry data or observations and were not published in the peerreviewed literature but remain in files as unpublished reports. Fortunately, some of the reports of early studies are filed in libraries and are public documents (38). 3.1 Acute and Chronic Tests It is interesting to note the role that World War I played in early toxicology. World War I stimulated a great many studies of acute inhalation toxicity for chemical warfare purposes. The number of

compounds examined during World War I as possible chemical warfare agents is estimated to have been between 3,000 and 4,000, and of these, 54 were used in the field at one time or another. During World War I, chemical warfare agents were selected for their irritancy to skin or eyes, rather than for systemic toxicity, and both the techniques developed for their study, as well as the information gained, were useful to postwar industrial toxicology. Although chronic, or cumulative, toxicity had been recognized for centuries, it received much less attention than acute toxicity until more recent times, possibly because acute toxic effects were more likely to be recognized than chronic effects. Chronic toxicity could, however, be investigated by any relevant route of exposure, provided that the dosages used were small enough to permit the chronic damage to appear. The most perplexing question was, “How long should a prolonged exposure be to gain all the necessary information?” Opinions differed, but the majority of toxicologists seemed to feel that 90 days of repeated exposure would be sufficient to elicit all of the important manifestations of chronic toxicity in the rat or mouse, provided that the daily doses were sufficiently high but still consistent with survival. This effort was given impetus by the Food and Drug Administration as it began to require such tests for food additives and pesticides. It should be recalled that until 1970 FDA not EPA prescribed the testing requirements for pesticides. In 1938, as a consequence of the elixir of sulfanilamide tragedy, in which a number of persons died from taking a solution of sulfanilamide in diethylene glycol for therapeutic purposes, the U.S. Food and Drug Administration undertook a comprehensive investigation of the toxicity of the glycols. This investigation culminated in a “lifetime” feeding study with diethylene glycol in rats. In 1945, Nelson et al. (39) reported the results at a meeting of the Federation of American Societies for Experimental Biology. A surprising result of the study was the finding that some of the rats fed a diet containing 4% diethylene glycol had developed bladder stones and that some of those with bladder stones had also developed fibropapillomatous tumors of the bladder. Because neither bladder stones nor tumors had been found in tests of shorter duration, it became obvious that, for some lesions, 90 days was not a sufficient time of exposure. By 1950, the FDA had begun recommending lifetime studies, for which they considered two years in the rat as proper, as part of proof of safety of proposed new intentional and unintentional food additives and pesticides. As a guide to the perplexed, members of the FDA staff prepared an article entitled “Procedures for the Appraisal of the Toxicity of Chemicals in Foods, Drugs, and Cosmetics,” which was published in the September, 1949, issue of Food Drug cosmetic Law Journal (40). It contained a section on how to do long-term chronic toxicity studies and recommended a period of two years for the rat, plus one year for a nonrodent species such as the dog. Although not an official regulation, the article advised every one of the FDA's expectations with respect to data submitted to it as proof of safety of the proposed new food additive or pesticide. A revision of the article appeared in 1955 (41), and a third revision was published in 1959 as a monograph by the Association of Food and Drug Officials of the United States (42). During the same period, the Food Protection committee of the National Academy of Science/National Research Council was publishing and revising “Principles and Procedures for Evaluating the Safety of Food Additives” (43) which were, in general, consistent with the FDA staff's guidelines. One common thread ran through both sets of recommendations. With each revision, the complexity of the tests increased and so did the cost. The FDA's recommended protocol in 1959 (42) for a “lifetime” test with rats called for four groups of a minimum of 25 males and 25 females each. There would be a control group, a low-dose group (a no-effect level, it was hoped), a high-dose group (chosen to be an effect level), and a mid-dose group. All animals would be necropsied for gross pathology. Selected organs would be weighed, and selected organs would be preserved for histopathology. During the course of the experiment, food consumption and weight gains would be measured, blood and urine would be monitored for deviations from normality, and nay-behavioral changes would be noted. A three-generation reproduction study would be carried out at all dose levels. A similar experiment would also be

carried out with four groups of six to eight dogs each for an exposure period of two years to determine whether a nonrodent species responded differently from the rat. Dog reproduction studies were not required. The lifetime of the rat was considered to be two years for the purposes of the test.

Industrial Toxicology: Origins and Trends Eula Bingham, Ph.D., John Zapp, Ph.D., (deceased) 4 Trends 4.1 Toxicological Testing Concerns raised 20 years ago about the costs and validity of toxicological information that may be used for making risk assessments to protect workers and for business decisions on product development are still valid today. When John Zapp wrote the first part of this chapter, it was the late 1970s and the other author, Eula Bingham, Assistant Secretary of Labor for Occupational Safety and Health, was grappling with the need for toxicological data on which to base occupational health and safety standards. It was during this period (1978) that the National Toxicology Program (NTP) began. This effort was intended to expand the carcinogen testing program of the National Cancer Institute that began during the 1960s. Today, the National Toxicology Program (44) provides a significant portion of all new data on industrial chemicals used in the United State and in other countries. At present, 80,000 chemicals are used in the United States and an estimated 2,000 new ones are introduced annually to be used in products such as foods, personal care products, prescription drugs, household cleaners, and lawn care products. The effects of many of these chemicals on human health are unknown, yet people may be exposed to them during their manufacture, distribution, use, and disposal or as pollutants in our air, water, or soil. The National Toxicology Program (NTP) was established by the Department of Health and Human Services (DHHS) in 1978 and charged with coordinating toxicological testing programs within the Public Health Service of the Department; strengthening the science base in toxicology; and providing information about potentially toxic chemicals to health regulatory and research agencies, scientific and medical communities, and the public (See Fig. 1.1). The NTP is an interagency program whose mission is to evaluate agents of public health concern by developing and applying the tools of modern toxicology and molecular biology. In carrying out its mission, the NTP has several goals: • to provide toxicological evaluations of substances of public health concern; • to develop and validate improved (sensitive, specific, rapid) testing methods; • to develop approaches and generate data to strengthen the science base for risk assessment; and • to communicate with all stakeholders, including government, industry, academia, the environmental community, and the public. Nationally, the NTP rodent bioassay is recognized as the standard for identifying carcinogenic agents. However, the NTP has expanded its scope beyond cancer to include examining the impact of chemicals on noncancer toxicities such as those affecting reproduction and development, inhalation, and the immune, respiratory, and nervous systems. Recently a Center for Evaluation of Risks to Human Reproduction and a Center for the Evaluation of Alternative Toxicological Methods were created.

Figure 1.1. National Toxicology Program. The National Toxicology Program (NTP) is headquartered at the NIEHS/NIH, and its director serves as director of the NTP. The Executive Committee composed of the heads of key research and regulatory Federal agencies provides oversight for policy issues. Science oversight and peer review are provided through a mix of Federal, academic, industrial, and public interest science experts. NTP's testing program seeks to use mechanism-based toxicology studies to enhance the traditional approaches. Molecular biology tools are used to characterize interactions of chemicals with critical target genes. Examples of mechanism-based toxicology include identification of receptor-mediated toxicants, molecular screening strategies, use of transgenic animal models, and the development of alternative or complementary in vivo tests to use with rodent bioassays. Inclusion of such strategies can provide insight into the molecular and biological events associated with a chemical's toxic effect and provide mechanistic information that is useful in assessing human risk. Such information can also lead to the development of more specific and sensitive (and often less expensive) tests for use in risk assessment. There is a strong linkage between mechanism-based toxicology and the development of more biologically based risk assessment models. Such models are useful in clarifying dose–response relationships, making species comparisons, and identifying sources of interindividual variability. Genetically altered or “transgenic” mouse models carry activated oncogenes or inactivated tumor suppressor genes involved in neoplastic processes in both humans and rodents. This trait may allow them to respond to carcinogens more quickly than conventional rodent strains. The advantage provided by such an approach compared with standard rodent models is that in addition to chemicals undergoing metabolism, distribution, and relevant pharmacokinetics, the neoplastic effects of agents can be observed in the transgenic models within a time frame in which few if any spontaneous tumors would arise. During the past few years, the NIEHS/NTP has evaluated transgenic strains in toxicological testing strategies. The response for 38 chemicals was compared in two genetically altered mouse strains (p53def: p53+/– heterozygous and Tg.AC: n-Ha-ras transgene) with that of wild-type mice tested in chronic two-year bioassays. Findings from these studies were evaluated by the NTP Board of Scientific Counselors for their suitability in NTP toxicological evaluations. Based upon the NIEHS/NTP review, the transgenic models performed largely according to predictions; they identified all known human carcinogens and most of the multisite/multispecies rodent carcinogens but failed to identify completely rodent carcinogens that produced tumors in selected organs in twoyear studies. The use of these genetically altered mouse models holds promise in carcinogenesis research and testing and clearly is more rapid and less expensive than traditional NTP two-year bioassay studies. The challenge still facing the NTP is to design studies that address remaining questions and concerns and to explore how these models can be used in risk assessment.

The NIEHS Environmental Genome Project is a multicenter effort to identify systematically the alleles of 200 or more environmental disease susceptibility genes in the U.S. population. Information from this human exposure assessment initiative together with the environmental genome project will provide the science base essential for future, meaningful studies of gene/environment interactions in disease etiology. As a part of an interagency human exposure assessment initiative, the NTP and the NCEH/CDC are collaborating on a pilot project to quantify approximately 70 chemicals in either human blood or urine that are considered endocrine disrupters. Biological samples from the National Health and Nutrition Examination Surveys (NHANES) are being tested. These data will be used to estimate human exposure to endocrine disrupting agents within the U.S. population and to identify those of greatest public health concern. This information can be used in prioritizing chemicals for study and in developing biologically based models for estimating human risks. 4.2 Human Genome The revolution in genetics and specifically in mapping the human genome, as well as the development of transgenic animals, will radically change the way we evaluate chemical and physical agents. See chapter 7 by Dan Nebert in this volume. The need to keep toxicologists apprised of the current thinking regarding many new advances in certain toxicological fields has led us to include a special chapter on genetics. Although human variability was recognized as a phenomenon during the last half of the nineteenth century, pharmacogenetics has now become a significant and critical element in understanding dose-response curves in every aspect of toxicology from predicting who can metabolize a chemical to a carcinogen to determining which patient may be at risk of death from a prescribed doses of an anticancer drug. This area will probably bring about the greatest changes in our understanding of worker responses to occupational exposures. 4.3 Global Workplaces The workplaces of concern in early editions of Patty's were mainly those in U.S. factories where chemicals and certain processes occurred. Today, many of those activities and chemicals have moved overseas, and the scene is dynamic and changing as we write. Hopefully, the toxicological information contained in these volumes will be useful in global workplaces. We have welcomed authors from outside the United States, many of whom are outstanding toxicologists in their own countries and are known internationally. It is the hope of the editors that this trend will continue for Patty's in future editions. Without modern telecommunications and E-mail, we would not have the courage to propose such authors. 4.4 Mixtures Mixtures have reemerged as a special concern in toxicology. Mainly during the period (1930–1970) when complex mixtures, particularly those derived from fossil fuels (petroleum fractions, coal tar) were being actively investigated, the issues revolved around finding the critical chemical in the complex mix that was responsible for its toxicology. Chemicals in these mixtures enhanced or inhibited the critical chemical. When chemical exposures occurred either together or in sequence as in chemical carcinogenesis, the concepts of initiation and promotion became part of understanding mixtures. Recognition that contributions from several chemicals affecting the same target organ could be at least additive and perhaps of concern in the workplace led the ACGIH to develop a methodology for simple mixtures. As more information has been produced during the last 10 years regarding the content of hazardous waste sites, once again there are efforts to develop methodologies to account for multiple chemical exposures in attempting to assess risk. One of the most notable is the dioxins and the use of “equivalency factors.” However, the way to determine any potential for interactions among a mixture of chemical exposures remains a problem in toxicology and will continue to require investigation in the future. 4.5 Training and Personnel Current training programs in toxicology place heavy emphasis on genetics. Courses in genetics and molecular biology have largely replaced other fundamental medical disciplines such as biochemistry,

physiology, and pharmacology. Sometimes, aspects of these elements are covered to a small extent in a toxicology course. Courses in risk assessment are usually elective. Most graduate programs in toxicology today provide little background for individuals seeking to work in industrial toxicology. On the other hand, the practical elements that remain as staples in industrial hygiene programs provide much that is useful in industrial toxicology. The deficiency in these programs is the lack of training in the biological sciences, since most industrial hygiene graduates have little or no toxicology unless they take it as an elective. The result is that industry today must be prepared to provide current graduates with on-the-job training equivalent to 2–3 years of a postdoctoral fellowship if they are to work in industrial toxicology. Industrial Toxicology: Origins and Trends Bibliography

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18 J. A. Miller, E. G. Miller, and G. C. Fingen, Cancer Res. 17, 387–398 (1957). 19 F. E. Ray et al., Br. J. Cancer 15, 816–820 (1961). 20 J. L. Hartwell, Survey of Compounds Which Have Been Tested for Carcinogenic Activity, National Institute of Health, National Cancer Institute, Federal Security Agency, U.S. Public Health Service, Washington, DC, 1941. 21 S. A. Henry, N. M. I. Kennaway, and E. L. Kennaway, The incidence of cancer of the bladder and prostrate in certain occupations, J. Hyg. 31, 125–137 (1931). 22 S. A. Henry, The study of fatal cases of cancer of the scrotum from 1911 to 1935 in relation to occupation with special reference to chimney sweeping and cotton mule spinning. Am. J. Cancer 31, 28–57 (1937). 23 G. M. Bonser, Tumours of the skin produced by blast-furnace tar. Lancet 1, 775–776 (1932). 24 G. M. Bonser, Epithelial tumours of the bladder in dogs induced by pure b-naphthylamine. J. Pathol. Bacteriol. 55, 1 (1943). 25 R. A. M. Case et al., Tumours of the urinary bladder in workmen engaged in the manufacture and use of certain dyestuff intermediates in the British chemical industry. I. The role of aniline, benzidine, alpha-naphthylamine and beta-naphthylamine. Br. J. Ind. Med. 11, 75 (1954). 26 P. Pott, Chirurgical Observations Relative to the Cataract, the Polypus of the Nose, the Cancer of the Scrotum, the Different Kinds of Ruptures, and the Mortification of the Toes and Feet, Hower, Clarke, & Pollins, London, 1775. 27 J. A. Paris, Pharmacology, 3rd ed., W. Philipps, London, 1822. 28 R. Volkmann, Beiträge zu kiln. Chirurgie anschliessend an einen Bericht ueber die Täigkeit der chiurgischen Universitäsklink zu Halle, 1873, reprint: Leipzig, 1975. 29 B. Bell, Treatise on the hydrocele or cancer and other diseases of the testis. Edinburgh Med. J. 22 (1876). 30 F. H. Härting and W. Hesse, Vierteljahrsschr. Gerichtl. Med. 30 (1879). 31 P. G. Unna, Die Histopathologie der Haukrankheiten, A. Hirschwald, Berlin, 1894. 32 L. Rehn, Blasengeschwuelste bei Fuchsin-Arbeitern. Arch. Klin. Chir. 50 (1895). 33 S. Mackenzie, Br. J. Dermatol. 10 (1898). 34 E. Pfeil, Lung tumors as occupational disease in chromate plants (in German). Dtsch. Med. Wochenschr. 61, 1197–1200 (1935). 35 Leymann, Zentralbl. Gewerbehyg. Unfallverhuet. 5 (1917). 36 H. S. Martland, Monthly labor review. U. S. Dep. Labor Bull. 28, (1929). 37 National Safety Council, Benzol, Final report of the Committee of the Chemical and Rubber Sections, NSC, Washington, DC, 1926. 38 R. A. Kehoe, Kettering Laboratory Reports, 1920–1970, Heritage History of Medicine Library. 39 A. A. Nelson, O. G. Fitzbugh, and H. O. Calvery, Diethylene glycol. Fed. Proc., Fed. Am. Soc. Exp. Biol. 4, 149 (1945). 40 A. J. Lehman and FDA Staff, Procedures for the appraisal of the toxicity of chemicals in foods, drugs, and cosmetics. Food Drug Cosmet. Law J. (1949). 41 A. J. Lehman and FDA Staff, Procedures for the appraisal of the toxicity of chemicals in foods, drugs, and cosmetics. Food Drug Cosmet. Law J. (1955). 42 FDA Staff, Division of Pharmacology, Appraisal of the Safety of Chemicals in Foods, Drugs, and Cosmetics, Association of Food & Drug Officials of the United States, Baltimore, MD, 1959. 43 National Academy of Sciences/National Research Council, Food Protection Committee/Food & Nutrition Board, Principles and Procedures for Evaluating the Safety of Food Additives, Publ. No. 750, NAS/NRC, Washington, DC, 1959.

44 Environmental Health Prospectives (NIEHS), 106, 10 (1998). Pathways and Measuring Exposure To Toxic Substances Morton Lippmann, Ph.D., CIH 1 Introduction For toxic substances in the environment to exert adverse effects on humans, they must deposit on and/or penetrate through a body surface and reach target sites where they can alter normal functions and/or structures. The critical pathways and target sites can vary greatly from substance to substance and, for a given substance, can vary with its chemical and physical form. A further complication arises from the fact that chemical and/or metabolic transformations can take place between deposition on a body surface and the eventual arrival of a toxic substance or metabolite of that substance at a critical target site. A critical target site is where the toxic effect of first or greatest concern takes place. This chapter reviews and summarizes current knowledge concerning the generic aspects of the environmental pathways and processes leading to (1) deposition of toxicants on body surfaces (skin, respiratory tract, gastrointestinal tract); (2) uptake of toxicants by epithelial cells from environmental media (air, waste, food); (3) translocation and clearance pathways within the body for toxicants that penetrate a surface epithelium; and (4) the influence of chemical and physical form of the toxicant on the metabolism and pathways of the chemical of concern. Where the physical attributes of the toxicant such as the length and biopersistence of airborne fibers are of generic concern, these are also discussed in this chapter. Other aspects of the pathways and the fates of toxicants that are specific to the chemical species that are the subject of the following chapters of this volume are discussed, as appropriate, in those chapters. This chapter also summarizes and discusses techniques for measuring personal and population exposures to environmental toxicants and their temporal and spatial distributions. Quantitative exposure assessment, as a component of risk assessment, involves consideration of (1) the nature and properties of chemicals in environmental media, (2) the presence in environmental media of the specific chemicals that are expected to exert toxic effects, (3) the temporal and spatial distributions of the exposures of interest, and (4) the ways that ambient or workplace exposure measurements or models can be used to draw exposure inferences. In this context, the knowledge of deposition, fate, pathways, and rates of metabolism and transport within the body, to be reviewed later in this chapter, provide appropriate rationales for size-selective aerosol sampling approaches and/or usage of biomarkers of exposure. Finally, this chapter discusses the choices of sampling times, intervals, rates, durations, and schedules most appropriate for exposure measurements and/or modeling that are most relevant to risk assessment strategies that reflect data needs for (1) documenting compliance with exposure standards; (2) performing epidemiological studies of exposure–response relationships; (3) developing improved exposure models; and (4) facilitating secondary uses of exposure data for epidemiological research, studies of the efficacy of exposure controls, and analyses of trends.

Pathways and Measuring Exposure To Toxic Substances Morton Lippmann, Ph.D., CIH 2 Nature of Toxic Substances 2.1 Physical Properties of Toxic Air Contaminants Chemicals can be dispersed in air at normal ambient temperatures and pressures in gaseous, liquid, and solid forms. The latter two represent suspensions of particles in air and were given the generic term “aerosols” by Gibbs (1) by analogy with the term “hydrosol,” used to describe dispersed systems in water. Although hydrosols generally have uniformly sized particles, aerosols do not.

Gases and vapors, which are present as discrete molecules, form true solutions in air. Particles composed of moderate- to high-vapor-pressure materials evaporate rapidly because those small enough to remain suspended in air for more than a few minutes (i.e., those smaller than about 10 mm) have large surface to volume ratios. Some materials with relatively low vapor pressures can have appreciable fractions in both vapor and aerosol forms simultaneously. Once dispersed in air, contaminant gases and vapors generally form mixtures so dilute that their physical properties, such as density, viscosity, and enthalpy, are indistinguishable from those of clean air. Such mixtures follow ideal gas law relationships. There is no practical difference between a gas and a vapor except that the latter is generally the gaseous phase of a substance that can exist as a solid or liquid at room temperature. While dispersed in the air, all molecules of a given compound are essentially equivalent in their size and capture probabilities by ambient surfaces, respiratory tract surfaces, and contaminant collectors or samplers. Aerosols are dispersions of solid or liquid particles in air and have the very significant additional variable of particle size. Size affects particle motion and, hence, the probabilities of physical phenomena such as coagulation, dispersion, sedimentation, impaction onto surfaces, interfacial phenomena, and light-scattering. It is not possible to characterize a given particle by a single size parameter. For example, a particle's aerodynamic properties depend on density and shape, as well as linear dimensions, and the effective size for light scattering depends on refractive index and shape. In some special cases, all of the particles are essentially the same size. Such aerosols are considered monodisperse. Examples are natural pollens and some laboratory-generated aerosols. More typically, aerosols are composed of particles of many different sizes and hence are called heterodisperse or polydisperse. Different aerosols have different degrees of size dispersion. Therefore, it is necessary to specify at least two parameters in characterizing aerosol size: a measure of central tendency, such as a mean or median, and a measure of dispersion, such as an arithmetic or geometric standard deviation. Particles generated by a single source or process generally have diameters that follow a log-normal distribution, i.e., the logarithms of their individual diameters have a Gaussian distribution. In this case, the measure of dispersion is the geometric standard deviation, which is the ratio of the 84.16th percentile size to the 50th percentile size. When more than one source of particles is significant, the resulting mixed aerosol will usually not follow a single log-normal distribution, and it may be necessary to describe it by the sum of several distributions. 2.1.1 Particle and Aerosol Properties Many properties of particles, other than their linear size, can greatly influence their airborne behavior and their effects on the environment and health. These include Surface: For spherical particles, the surface varies as the square of the diameter. However, for an aerosol of given mass concentration, the total aerosol surface increases with decreasing particle size. For nonspherical or aggregate particles, the particles may have internal cracks or pores, and the ratio of surface to volume can be much greater than for spheres. Volume: Particle volume varies as the cube of diameter; therefore, the few largest particles in an aerosol dominate its volume (or mass) concentration. Shape: A particle's shape affects its aerodynamic drag, as well as its surface area, and therefore its motion and deposition probabilities. Density: A particle's velocity in response to gravitational or inertial forces increases as the square root of its density. Aerodynamic diameter: The diameter of a unit-density sphere that has the same terminal settling velocity as the particle under consideration is equal to its aerodynamic diameter. Terminal settling velocity is the equilibrium velocity of a particle that is falling under the influence of gravity and

fluid resistance. Aerodynamic diameter is determined by the actual particle size, the particle density, and an aerodynamic shape factor. 2.1.2 Types of Aerosols Aerosols are generally classified in terms of their processes of formation. Although the following classification is neither precise nor comprehensive, it is commonly used and accepted in the industrial hygiene and air pollution fields. Dust: An aerosol formed by mechanical subdivision of bulk material into airborne fines that have the same chemical composition. Dust particles are generally solid and irregular in shape and have diameters greater than 1 mm. Fume: An aerosol of solid particles formed by condensation of vapors formed at elevated temperatures by combustion or sublimation. The primary particles are generally very small (less than 0.1 mm) and have spherical or characteristic crystalline shapes. They may be chemically identical to the parent material, or they may be composed of an oxidation product such as a metal oxide. Because they may be formed in high concentrations, they often coagulate rapidly and form aggregate clusters of low overall density. Smoke: An aerosol formed by condensation of combustion products, generally of organic materials. The particles are generally liquid droplets whose diameters are less than 0.5 mm. Mist: A droplet aerosol formed by mechanical shearing of a bulk liquid, for example, by atomization, nebulization, bubbling, or spraying. The droplet size can cover a very large range, usually from about 2 to greater than 50 mm. Fog: An aqueous aerosol formed by condensation of water vapor on atmospheric nuclei at high relative humidities. The droplet sizes are generally larger than 1 mm. Smog: A popular term for a pollution aerosol derived from a combination of smoke and fog. The term is commonly used now for any atmospheric pollution mixture. Haze: A submicrometer-sized aerosol of hydroscopic particles that take up water vapor at relatively low relative humidities. Aitken or condensation nuclei (CN): Very small atmospheric particles (mostly smaller than 0.05 mm) formed by combustion processes and by chemical conversion from gaseous precursors. Accumulation mode: A term given to the particles in the ambient atmosphere ranging in diameter from 0.1 to about 1.0 mm. These particles generally are spherical, have liquid surfaces, and form by coagulation and condensation of smaller particles that derive from gaseous precursors. Too large for rapid coagulation and too small for effective sedimentation, they accumulate in the ambient air. Coarse particle mode: Ambient air particles larger than about 2.5 mm in aerodynamic diameter and generally formed by mechanical processes and surface dust resuspension. 2.1.3 Physical Properties of Toxic Liquid and Solid Components For liquids and solids deposited on human skin or taken into the gastrointestinal (GI) tract by ingestion, penetration to and through the surface epithelium depends upon their physical form, their solubility in the fluids on the surface, and the structure and nature of the epithelial barrier. Dissolved chemicals can penetrate by diffusion, whereas chemicals present as particles or droplets must find access via pores or defects in the barrier associated with injury caused by trauma or corrosive chemicals or by dissolution in solvents that alter the barrier function.

Pathways and Measuring Exposure To Toxic Substances Morton Lippmann, Ph.D., CIH 3 Human Exposure Pathways and Dosimetry

People can be exposed to chemicals in the environment in numerous ways. The chemicals can be inhaled, ingested, or taken up by and through the skin. Effects of concern can take place at the initial epithelial barrier, i.e., the respiratory tract, the gastrointestinal (GI) tract, or the skin, or can occur in other organ systems after penetration and translocation by diffusion or transport by blood, lymph, etc. As illustrated in Fig. 2.1, exposure and dose factors are intermediate steps in a larger continuum ranging from the release of chemicals into an environmental medium to an ultimate health effect in an exposed individual. There are, of course, uncertainties of varying magnitude at each stage. The diagram could also be applied to populations as well as to individuals. In that case, each stage of the figure would include additional variance for the interindividual variability within a population associated with age, sex, ethnicity, size, activity patterns, dietary influences, use of tobacco, drugs, alcohol, etc.

Figure 2.1. Framework for personal exposure assessment and exposure-response (modified from Ref. 1a). Exposure is a key and complex step in this continuum. The concept of total human exposure developed in recent years is essential to the appreciation of the nature and extent of environmental health hazards associated with ubiquitous chemicals at low levels. It provides a framework for considering and evaluating the contribution to the total insult from dermal uptake, ingestion of food and drinking water, and inhaled doses from potentially important microenvironments such as workplace, home, transportation, recreational sites, etc. More thorough discussions of this key concept have been prepared by Sexton and Ryan (2), Lioy (3), and the National Research Council (4). Guidelines for Exposure Assessment have been formalized by the U.S. Environmental Protection Agency (5). Figure 2.2 outlines possible approaches for estimating contaminant exposures of populations, as well as individuals, in a conceptual sense, and Fig. 2.3 indicates terminologies used by EPA to describe exposures and their distributions within a population.

Figure 2.2. Possible approaches for analyzing contaminant exposures.

Figure 2.3. EPA guidance on terminology for exposures in the general population. Toxic chemicals in the environment that reach sensitive tissues in the human body can cause discomfort, loss of function, and changes in structure leading to disease. This section addresses the pathways and transport rates of chemicals from environmental media to critical tissue sites, as well as retention times at those sites. It is designed to provide a conceptual framework as well as brief discussions of (1) the mechanisms for—and some quantitative data on—uptake from the environment; (2) translocation within the body, retention at target sites, and the influence of the physicochemical properties of the chemicals on these factors; (3) the patterns and pathways for exposure of humans to chemicals in environmental media; and (4) the influence of age, sex, size, habits, health status, etc. 3.1 Terminology An agreed on terminology is critically important when discussing the relationships among toxic chemicals in the environment, exposures to individuals and populations, and human health. Key terms used in this chapter are defined as follows:

Exposure: Contact with external environmental media containing the chemical of interest. For fluid media in contact with the skin or respiratory tract, both concentration and contact time are critical. For ingested material, concentration and amount consumed are important. Microenvironments: Well-defined locations that can be treated as homogeneous (or well characterized) in the concentrations of a chemical or other stressor. Deposition: Capture of the chemical at a body surface site on the skin, the respiratory tract, or the GI tract. Clearance: Translocation from a deposition site to a storage site or depot within the body or elimination from the body. Retention: Presence of residual material at a deposition site or along a clearance pathway. Dose: The amount of chemical deposited on (applied dose) or translocated to a site on or within the body where toxic effects can take place (delivered dose). Target tissue: A site within the body where toxic effects lead to damage or disease. Depending on the toxic effects of concern, a target tissue can extend from whole organs to specific cells and to subcellular constituents within cells. Exposure surrogates or indices: Indirect measures of exposure, such as: (1) concentrations in environmental media at times or places other than those directly encountered; (2) concentrations of the chemical of interest, a metabolite of the chemical, or an enzyme induced by the chemical in circulating or excreted body fluids, generally referred to as a biomarker of exposure; and (3) elevations in body burden measured by external probes.

Pathways and Measuring Exposure To Toxic Substances Morton Lippmann, Ph.D., CIH 4 Pathways 4.1 Respiratory Tract The respiratory system extends from the breathing zone just outside of the nose and mouth through the conductive airways in the head and thorax to the alveoli, where respiratory gas exchange takes place between alveoli and the capillary blood flowing around them. The prime function of the respiratory system is to deliver oxygen (O2) to the gas-exchange region of the lung, where it can diffuse to and through the walls of the alveoli to oxygenate the blood passing through the alveolar capillaries, as needed over a wide range of work or activity levels. In addition, the system must also: (1) remove an equal volume of carbon dioxide (CO2) that enters the lungs from the alveolar capillaries; (2) maintain body temperature and water vapor saturation within the lung airways (to maintain the viability and functional capacities of the surface fluids and cells); (3) maintain sterility (to prevent infections and their adverse consequences); and (4) eliminate excess surface fluids and debris, such as inhaled particles and senescent phagocytic and epithelial cells. It must accomplish all of these demanding tasks continuously during a lifetime and do so with highly efficient performance and energy utilization. The system can be abused and overwhelmed by severe insults, such as high concentrations of cigarette smoke and industrial dust, or by low concentrations of specific pathogens that attack or destroy its defense mechanisms or cause them to malfunction. Its ability to overcome and/or compensate for such insults as competently as it usually does is a testament to its elegant combination of structure and function. 4.2 Mass Transfer The complex structure and numerous functions of the human respiratory tract have been summarized concisely by a Task Group of the International Commission on Radiological Protection (6), as shown in Fig. 2.4. The conductive airways, also known as the respiratory dead space, occupy about 0.2 liter

(L). They condition the inhaled air and distribute it by convective (bulk) flow to approximately 65,000 respiratory acini that lead off the terminal bronchioles. As tidal volumes increase, convective flow dominates gas exchange deeper into the respiratory bronchioles. In any case, within the respiratory acinus, the distance from the convective tidal front to alveolar surfaces is short enough so that efficient CO2–O2 exchange takes place by molecular diffusion. By contrast, submicrometer sized airborne particles whose diffusion coefficients are smaller by orders of magnitude than those for gases, remain suspended in the tidal air and can be exhaled without deposition.

Figure 2.4. Structure and function of the human respiratory tract. A significant fraction of the inhaled particles do deposit within the respiratory tract. The mechanisms that account for particle deposition in the lung airways during the inspiratory phase of a tidal breath are summarized in Fig. 2.5. Particles larger than about 2 mm in aerodynamic diameter (the diameter of a unit density sphere that has the same terminal settling (Stokes) velocity) can have significant momentum and deposit by impaction at the relatively high velocities present in the larger conductive airways. Particles larger than about 1 mm can deposit by sedimentation in the smaller conductive airways and gas-exchange airways where flow velocities are very low. Particles smaller than 0.1 mm are in Brownian motion, and their random walk while in small airways causes them to diffuse to and deposit on small airway walls at a rate that increases with decreasing size. Finally, particles whose diameters are between 0.1 and 1 mm, which have a very low probability of depositing during a

single tidal breath, can be retained within the approximately 15% of the inspired tidal air that is exchanged with residual lung air during each tidal cycle. This volumetric exchange occurs because of the variable time constants for airflow in the different segments of the lungs. Because of the much longer residence times of residual air in the lungs, the low intrinsic particle displacements of 0.1 to 1 mm particles within such trapped volumes of inhaled tidal air become sufficient to cause their deposition by sedimentation and/or diffusion over the course of successive breaths.

Figure 2.5. Mechanism for particle deposition in lung airways. The essentially particle-free residual lung air that accounts for about 15% of the expiratory tidal flow acts like a clean-air sheath around the axial core of distally moving tidal air, so that particle deposition in the respiratory acinus is concentrated on interior surfaces such as airway bifurcations, whereas interbranch airway walls have relatively little particle deposition. The number of particles deposited and their distribution along the respiratory tract surfaces, along with the toxic properties of the material deposited, are the critical determinants of pathogenic potential. The deposited particles can damage the epithelial and/or the mobile phagocytic cells at or near the deposition site or can stimulate the secretion of fluids and cell-derived mediators that have secondary effects on the system. Soluble materials deposited as, on, or within particles can diffuse into and through surface fluids and cells and be rapidly transported throughout the body by the bloodstream. The aqueous solubility of bulk materials is a poor guide to particle solubility in the respiratory tract. Generally solubility is greatly enhanced by the very large surface to volume ratio of particles small enough to enter the lungs. Furthermore, the ionic and lipid contents of surface fluids within the airways are complex and highly variable and can lead to enhanced solubility or to rapid precipitation of aqueous solutes. In addition the clearance pathways and residence times for particles on airway surfaces are very different in the different functional parts of the respiratory tract. The ICRP (6) Task Group's clearance model identifies the principal clearance pathways within the respiratory tract that are important in determining the retention of various radioactive materials and thus the radiation doses received by respiratory tissues and/or other organs after translocation. The ICRP deposition model is used to estimate the amount of inhaled material that enters each clearance pathway. These discrete pathways are represented by the compartment model shown in Fig. 2.6. They correspond to the anatomic compartments illustrated in Figure 2.4 and are summarized in Table 2.1, along with those of other groups that provide guidance on the dosimetry of inhaled particles.

Figure 2.6. Compartment model.

Table 2.1. Respiratory Tract Regions as Defined in Particle Deposition Models

Anatomic Structures Included

ACGIH Region

Nose, nasopharynx

Head airways (HAR)

Mouth, oropharynx, laryngopharynx Trachea, bronchi, and conductive bronchioles (to terminal bronchioles) Respiratory bronchioles, alveolar ducts, alveolar sacs, alveoli

ISO and CEN

1966 ICRP

1994 ICRP

Regions

Task Group Region

Task Group Region

Extrathoracic (E) Nasopharynx (NP)

Anterior nasal passages (ET1) All other extrathoracic (ET2)

Tracheobronchial Tracheobronchial Tracheobronchial Trachea and (TBR) (B) (TB) large bronchi (BB) Bronchioles (bb) Gas exchange Alveolar (A) Pulmonary (P) Alveolar(GER) interstitial (Al)

4.3 Extrathoracic Airways As shown in Figure 2.4, the extrathoracic airways were partitioned by ICRP (6) into two distinct clearance and dosimetric regions: the anterior nasal passages (ET1) and all other extrathoracic

airways (ET2), i.e., the posterior nasal passages, the naso- and oropharynx, and the larynx. Particles deposited on the surface of the skin that lines the anterior nasal passages (ET1) are assumed to be subject only to removal by extrinsic means (nose blowing, wiping, etc.). The bulk of material deposited in the naso-oropharynx or larynx (ET2) is subject to fast clearance in the layer of fluid that covers these airways. The 1994 ICRP model recognizes that diffusional deposition of ultrafine particles in the extrathoracic airways can be substantial, whereas earlier ICRP models did not (7–9). 4.4 Thoracic Airways Radioactive material deposited in the thorax is generally divided between the tracheobronchial (TB) region, where deposited particles are subject to relatively fast mucociliary clearance (duration in hours to 1 or 2 days), and the alveolar-interstitial (AI) region, where macrophage-mediated particle clearance is much slower (duration up to several weeks), and dissolution rates for insoluble particles not cleared by macrophages can have half-times measured in months or years. For purposes of dosimetry, the ICRP (6) divided the deposition of inhaled material in the TB region between the trachea and bronchi (BB) and in the more distal, small conductive airways, known as bronchioles (bb). However, the subsequent efficiency with which mucociliary transport in either type of airway can clear deposited particles is controversial. To be certain that doses to bronchial and bronchiolar epithelia would not be underestimated, the ICRP Task Group assumed that as much as half the number of particles deposited in these airways is subject to relatively “slow” mucociliary clearance that lasts up to about 1 week. The likelihood that an insoluble particle is cleared relatively slowly by the mucociliary system depends on its size. 4.5 Gas-Exchange Airways and Alveoli The ICRP (6) model also assumed that material deposited in the AI region is subdivided among three compartments (AI1, AI2, and AI3) each of which is cleared more slowly than TB deposition, and the subregions clear at different characteristic rates. 4.6 Regional Deposition Estimates Figure 2.7 depicts the predictions of the ICRP (6) Task Group Model in terms of the fractional deposition in each region as a function of the size of the inhaled particles. It reflects the minimal lung deposition between 0.1 and 1 mm, where deposition is determined largely by the exchange in the deep lung between tidal and residual lung air. Deposition increases below 0.1 mm as diffusion becomes more efficient with decreasing particle size. Deposition increases with increasing particle size above 1 mm as sedimentation and impaction become increasingly effective.

Figure 2.7. Fractional deposition in each region of the respiratory tract for a reference light worker (normal nose breather) in the 1994 ICRP model. Although aerodynamic diameter is an excellent index of particle behavior for relatively compact

particles that differ greatly in shape and density, it is inadequate for fibers that deposit by interception, as well as by inertia, gravitational displacement, or diffusion. The aerodynamic diameter of mineral or vitreous fibers whose aspect ratio (length/width) is greater than 10 is about three times their physical diameter. Fibers whose diameters are less than 3 mm can penetrate into bronchioles whose diameters are less than 500 mm. For thin fibers longer than 10 or 20 mm, interception, whereby an end of the fiber touches a surface and is collected, accounts for a significant enhancement of deposition (10). Less complex models for size-selective regional particle deposition have been adopted by occupational health and community air pollution professionals and agencies, and these have been used to develop inhalation exposure limits within specific particle size ranges. Distinctions are made between: (1) those particles that are not aspirated into the nose or mouth and therefore represent no inhalation hazard; (2) the inhalable (aka inspirable) particulate mass (IPM), i.e., those that are inhaled and are hazardous when deposited anywhere within the respiratory tract; (3) the thoracic particulate mass (TPM), i.e., those that penetrate the larynx and are hazardous when deposited anywhere within the thorax; and (4) the respirable particulate mass (RPM), i.e., those particles that penetrate through the terminal bronchioles and are hazardous when deposited within the gasexchange region of the lungs. These criteria are described in more detail later in this chapter in the sections devoted to exposure assessment. 4.7 Translocation and Retention Particles that do not dissolve at deposition sites can be translocated to remote retention sites by passive and active clearance processes. Passive transport depends on movement on or in surface fluids that line the airways. There is a continual proximal flow of surfactant to and onto the mucociliary escalator, which begins at the terminal bronchioles, where it mixes with secretions from Clara and goblet cells. Within midsized and larger airways are additional secretions from goblet cells and mucus glands that produce a thicker mucous layer that has a serous subphase and an overlying more viscous gel layer. The gel layer that lies above the tips of the synchronously beating cilia is found in discrete plaques in smaller airways and becomes more of a continuous layer in the larger airways. The mucus that reaches the larynx and the particles carried by it are swallowed and enter the GI tract. The total transit time for particles cleared during the relatively rapid mucociliary clearance phase varies from ~2 to 24 hours in healthy humans (11). Macrophage-mediated particle clearance via the bronchial tree takes place during a period of several weeks. Compact particles that deposit in alveolar zone airways are ingested by alveolar macrophages within about 6 hours, but the movement of the particle-laden macrophages depends on the several weeks that it takes for the normal turnover of the resident macrophage population. At the end of several weeks, the particles not cleared to the bronchial tree via macrophages have been incorporated into epithelial and interstitial cells, from which they are slowly cleared by dissolution and/or as particles via lymphatic drainage pathways, passing through pleural and eventually hilar and tracheal lymph nodes. Clearance times for these later phases depend strongly on the chemical nature of the particles and their sizes, and half-times range from about 30 to 1,000 days or more. All of the characteristic clearance times cited refer to inert, nontoxic particles in healthy lungs. Toxicants can drastically alter clearance times. Inhaled materials that affect mucociliary clearance rates include cigarette smoke (12, 13), sulfuric acid (14, 15), ozone (16, 17), sulfur dioxide (17a), and formaldehyde (18). Macrophage-mediated alveolar clearance is affected by sulfur dioxide (19), nitrogen dioxide and sulfuric acid (20), ozone (16, 20), silica dust (21), and long mineral and vitreous fibers (22, 23). Cigarette smoke affects the later phases of alveolar zone clearance in a dosedependent manner (24). Clearance pathways and rates that affect the distribution of retained particles and their dosimetry can be altered by these toxicants. Long mineral and manufactured vitreous fibers cannot be fully ingested by macrophages or epithelial cells and can clear only by dissolution. Most glass and slag wool fibers dissolve relatively rapidly within the lung and/or break up into shorter length segments. Chrysotile asbestos is more

biopersistent than most vitreous fibers and can subdivide longitudinally, creating a larger number of long fibers. The amphibole asbestos varieties (e.g., amosite, crocidolite, and tremolite) dissolve much more slowly than chrysotile. The close association between the biopersistence of inhaled long fibers and their carcinogenicity and fibrogenicity has been described by Eastes and Hadly (25), and additional data on the influence of fiber length on the biopersistence of vitreous fibers following inhalation was described by Bernstein et al. (26). 4.8 Ingestion Exposures and Gastrointestinal (GI) Tract Exposures Chemical contaminants in drinking water or food reach human tissues via the GI tract. Ingestion may also contribute to the uptake of chemicals that were initially inhaled, because material deposited on or dissolved in the bronchial mucous blanket is eventually swallowed. The GI tract may be considered a tube running through the body, whose contents are actually external to the body. Unless the ingested material affects the tract itself, any systemic response depends on absorption through the mucosal cells that line the lumen. Although absorption may occur anywhere along the length of the GI tract, the main region for effective translocation is the small intestine. The enormous absorptive capacity of this organ results from the presence in the intestinal mucosa of projections, termed villi, each of which contains a network of capillaries; the villi have a large effective total surface area for absorption. Although passive diffusion is the main absorptive process, active transport systems also allow essential lipid-insoluble nutrients and inorganic ions to cross the intestinal epithelium and are responsible for the uptake of some contaminants. For example, lead may be absorbed via the system that normally transports calcium ions (27). Small quantities of particulate material and certain large macromolecules such as intact proteins may be absorbed directly by the intestinal epithelium. Materials absorbed from the GI tract enter either the lymphatic system or the portal blood circulation; the latter carries material to the liver, from which it may be actively excreted into the bile or diffuse into the bile from the blood. The bile is subsequently secreted into the intestines. Thus, a cycle of translocation of a chemical from the intestine to the liver to bile and back to the intestines, known as the enterohepatic circulation, may be established. Enterohepatic circulation usually involves contaminants that undergo metabolic degradation in the liver. For example, DDT undergoes enterohepatic circulation; a product of its metabolism in the liver is excreted into the bile, at least in experimental animals (28). Various factors modify absorption from the GI tract and enhance or depress its barrier function. A decrease in gastrointestinal mobility generally favors increased absorption. Specific stomach contents and secretions may react with the contaminant and possibly change it to a form with different physicochemical properties (e.g., solubility), or they may absorb it, alter the available chemical, and change the translocation rates. The size of ingested particulates also affects absorption. Because the rate of dissolution is inversely proportional to particle size, large particles are absorbed to a lesser degree, especially if they are fairly insoluble in the first place. Certain chemicals, e.g., chelating agents such as EDTA, also cause a nonspecific increase in the absorption of many materials. As a defense, spastic contractions in the stomach and intestine may eliminate noxious agents via vomiting or by accelerating the transit of feces through the GI tract. 4.9 Skin Exposure and Dermal Absorption The skin is generally an effective barrier against the entry of environmental chemicals. To be absorbed via this route (percutaneous absorption), an agent must traverse a number of cellular layers before gaining access to the general circulation (Fig. 2.8) (29). The skin consists of two structural regions, the epidermis and the dermis, which rest on connective tissue. The epidermis consists of a number of layers of cells and varies in thickness depending on the region of the body; the outermost layer is composed of keratinized cells. The dermis contains blood vessels, hair follicles, sebaceous and sweat glands, and nerve endings. The epidermis represents the primary barrier to percutaneous absorption, the dermis is freely permeable to many materials. Passage through the epidermis occurs

by passive diffusion.

Figure 2.8. Idealized section of skin. The horny layer is also known as the stratum corneum. From Birmingham (29). The main factors that affect percutaneous absorption are the degree of lipid solubility of the chemicals, the site on the body, the local blood flow, and the skin temperature. Some environmental chemicals that are readily absorbed through the skin are phenol, carbon tetrachloride, tetraethyl lead, and organophosphate pesticides. Certain chemicals, e.g., dimethyl sulfoxide (DMSO) and formic acid, alter the integrity of skin and facilitate penetration of other materials by increasing the permeability of the stratum corneum. Moderate changes in permeability may also result following topical applications of acetone, methyl alcohol, and ethyl alcohol. In addition, cutaneous injury may enhance percutaneous absorption. Interspecies differences in percutaneous absorption are responsible for the selective toxicity of many insecticides. For example, DDT is about equally hazardous to insects and mammals if ingested but is much less hazardous to mammals when applied to the skin. This results from its poor absorption through mammalian skin compared to its ready passage through the insect exoskeleton. Although the main route of percutaneous absorption is through the epidermal cells, some chemicals may follow an appendageal route, i.e., entering through hair follicles, sweat glands, or sebaceous glands. Cuts and abrasions of the skin can provide additional pathways for penetration. 4.10 Absorption Through Membranes and Systemic Circulation Depending upon its specific nature, a chemical contaminant may exert its toxic action at various sites in the body. At a portal of entry—the respiratory tract, GI tract, or skin—the chemical may have a topical effect. However, for actions at sites other than the portal, the agent must be absorbed through one or more body membranes and enter the general circulation, from which it may become available to affect internal tissues (including the blood itself). Therefore, the ultimate distribution of any chemical contaminant in the body is highly dependent on its ability to traverse biological membranes. There are two main types of processes by which this occurs: passive transport and active transport. Passive transport is absorption according to purely physical processes, such as osmosis; the cell has

no active role in transfer across the membrane. Because biological membranes contain lipids, they are highly permeable to lipid-soluble, nonpolar, or nonionized agents and less so to lipid-insoluble, polar, or ionized materials. Many chemicals may exist in both lipid-soluble and lipid-insoluble forms; the former is the prime determinant of the passive permeability properties of the specific agent. Active transport involves specialized mechanisms, and cells actively participate in transfer across membranes. These mechanisms include carrier systems within the membrane and active processes of cellular ingestion, phagocytosis and pinocytosis. Phagocytosis is the ingestion of solid particles, whereas pinocytosis refers to the ingestion of fluid containing no visible solid material. Lipidinsoluble materials are often taken up by active-transport processes. Although some of these mechanisms are highly specific, if the chemical structure of a contaminant is similar to that of an endogeneous substrate, the former may also be transported. In addition to its lipid-solubility, the distribution of a chemical contaminant also depends on its affinity for specific tissues or tissue components. Internal distribution may vary with time after exposure. For example, immediately following absorption into the blood, inorganic lead localizes in the liver, the kidney, and in red blood cells. Two hours later, about 50% is in the liver. A month later, approximately 90% of the remaining lead is localized in bone (30). Once in the general circulation, a contaminant may be translocated throughout the body. In this process it may (1) become bound to macromolecules, (2) undergo metabolic transformation (biotransformation), (3) be deposited for storage in depots that may or may not be the sites of its toxic action, or (4) be excreted. Toxic effects may occur at any of several sites. The biological action of a contaminant may be terminated by storage, metabolic transformation, or excretion; the latter is the most permanent form of removal. 4.11 Accumulation in Target Tissues and Dosimetric Models Some chemicals concentrate in specific tissues because of physicochemial properties such as selective solubility or selective absorption on or combined with macromolecules such as proteins. Storage of a chemical often occurs when the rate of exposure is greater than the rate of metabolism and/or excretion. Storage or binding sites may not be the sites of toxic action. For example, carbon monoxide produces its effects by binding with hemoglobin in red blood cells; on the other hand, inorganic lead is stored primarily in bone but exerts its toxic effects mainly on the soft tissues of the body. If the storage site is not the site of toxic action, selective sequestration may be a protective mechanism because only the freely circulating form of the contaminant produces harmful effects. Until the storage sites are saturated, a buildup of free chemical may be prevented. On the other hand, selective storage limits the amount of contaminant that is excreted. Because bound or stored toxicants are in equilibrium with their free form, as the contaminant is excreted or metabolized, it is released from the storage site. Contaminants that are stored (e.g., DDT in lipids and lead in bone) may remain in the body for years without effect. However, upon weight loss and mobilization of body reserves, the stored chemicals can enter the circulation and produce toxic effects. For example, pregnant women who had prior excessive exposure to lead can increase their own blood lead levels and also create high and possibly damaging levels of lead exposures to their fetus. Accumulating chemicals may also produce illnesses that develop slowly, as occurs in chronic cadmium poisoning. A number of descriptive and mathematical models have been developed to permit estimation of toxic effects from knowledge of exposure and one or more of the following factors: translocation, metabolism, and effects at the site of toxic action. More complex models that require data on translocation and metabolism have been developed for inhaled and ingested radionuclides by the International Commission on Radiological Protection (6– 9).

Pathways and Measuring Exposure To Toxic Substances Morton Lippmann, Ph.D., CIH 5 Measuring and Modeling Human Exposures Direct measurement data on personal exposures to environmental toxicants would be ideal for risk assessments for individuals, and personal exposure data on large numbers of representative individuals would be ideal for performing population-based risk assessments. However, considerations of technical feasibility, willingness and ability to participate in extensive measurement studies among individuals of interest, and cost almost invariably preclude this option. Instead, more indirect measures of exposure and/or exposure models are relied on that combine a limited number of direct measurements with general background knowledge, historic measurement data believed to be relevant to the particular situation, and some reasonable assumptions based on first principles and/or expert judgements. When monitoring exposures, it is highly desirable to have benchmarks (exposure limits) as references. There are well-established occupational exposure limits for hundreds of air contaminants, including legal limits such as the Permissible Exposure Limits (PELs) established by the U.S. Occupational Safety and Health Administration (OSHA), as well as a larger number of Threshold Limit Values (TLVs) recommended by the American Conference of Governmental Industrial Hygienists (ACGIH) as professional practice guidelines. For ingested chemicals, there are acceptable daily intake values (ADIs), such as those adopted by the Food and Drug Administration (FDA) and the U.S. Department of Agriculture. Until now, comparable exposure limits have not been available for dermal exposure. However, Bos et al. (31) recently proposed a procedure for deriving such limits, and Brouwer et al. (32) performed a feasibility study following the Bos et al. proposal. Table 2.2 from Bos et al. (31) summarizes the nature and applications of such dermal exposure limits. Table 2.2. Some Characteristics of Available Exposure Limitsa Route of Entry

Respiratory Gastrointestinal Tract Tract Name

Skin

Maximum Acceptable daily Skin accepted intake (ADI) denotation concentration (MAC) Threshold limit value (TLV) Qualitative Quantitative Quantitative Qualitative or quantitative

Miscellaneous or Combined Biological limit value; (BEI, BAT-Werte, biological monitoring guidance value) Quantitative

Target Working population population

General population

Dimensions mg/m3

mk/kg/food

parts per mg/kg body million (ppm) weight

fibres n/m3 Monitoring Environmental Food residues or methods monitoring contaminants in (EM) combination with food intake data

Personal air sampling (PAS)

a

No specific worker monitoring method

Working population

Working population or general population Not (a) mg/L blood, applicable; mg/L urine, however mg/m3 exhaled air likely to be (b) assessed as mg cholinesterase inhibition, zinc protoporphyrin, DNA adducts, mutations, etc. (mg/cm2) For example, Biological environmental media: blood, surface wipe- urine, exhaled off; patches, air, feces, hair gloves, coveralls; tracer methods; skin washings; or skin stripping

From Bos et al. (31).

In routine monitoring of occupational exposures, it is quite common to collect shift-long (~ 8 hour) integrated breathing zone samples using passive diffusion samplers (for gases and vapors) or batterypowered personal samplers that draw a continuous low flow rate stream of air from the breathing zone through a filter or cartridge located in the breathing zone that captures essentially all of the air contaminants of interest for subsequent laboratory analyses. Such sampling is typically performed on only a single worker or at most on a small fraction of the workforce on the basis that the exposures of the sentinel worker(s) represent the exposures of other, unmonitored workers in the same works environment. In this case, the modeling of the other worker's exposures is relatively simple. Shift-long sampling can provide essential information for cumulative toxicants, but that information may be inadequate when peak exposure levels are important (as for upper respiratory irritants or asphyxiants). Continuous readout monitors would be ideal for evaluating such exposures, but may be impractical because of their size and/or cost. Spot or grab samples can be informative for evaluating of such exposures but require prior knowledge of the timing and locations of peak exposures. In such situations, peak exposures can be estimated using fixed-site continuous monitors in the general vicinity and supplementary information or experience-based models that relate breathing zone levels to general air levels in the room. Time-activity pattern data on each worker can be combined with measured or estimated concentrations at each work site or with specific work activities to construct a time-weighted average exposure (TWAE) for that worker to supplement estimates of peak exposures. The characteristics of equipment used for air sampling in industry are described in detail in Air Sampling Instruments (33). In constructing exposure estimates or models for community air or indoor air exposures for the general population, this time-weighted averaging approach is generally known as

microenvironmental exposure assessment. For community air pollutants of outdoor origin, data are often available on the concentrations measured at central monitoring sites, and population exposures to these pollutants are based on models incorporating time-activity patterns (indoors and outdoors), as well as factors representing the infiltration and persistence of the pollutants indoors. Such models should recognize the substantial variability of time-activity patterns among and between subsegments of the population (children, working adults, elderly and/or disabled adults, etc.). 5.1 Biomonitoring An alternate approach to measuring exposures directly is the use of biomarkers of exposures, determined from analyses of samples of blood, urine, feces, hair, nails, or exhaled air. The levels of the contaminant, its metabolites, changes in induced enzyme or protein levels, or characteristic alterations in DNA may be indicative of recent peak or past cumulative exposures. Exposure biomarkers may be complementary to and, in some cases, preferable to direct measures of environmental exposures. In any case, they are more biologically informative than indirect measures based on models and knowledge of sources or qualitative measures of exposure such as questionnaires about work and/or residential histories. There are diverse types of biomarkers that range from simple to complex in measurement requirements, and they are diverse in their relationships to either remote or recent exposures. There is also a range of biological relevance among exposure biomarkers: some provide indices that are directly biologically relevant, e.g., the level of carbon monoxide in end-tidal air samples and the risk of myocardial ischemia, whereas others, although broadly related, may not cover the temporally appropriate exposure window, e.g., nicotine levels in biological fluids and lung cancer risk from smoke exposure. For the near term, extensive development of new molecular level biomarkers relevant to malignant and nonmalignant diseases can be anticipated. However, most of these new exposure biomarkers remain to be validated, and few will be ready for translation to the population in the short term. Anticipated applications include epidemiological studies of responses to low-level exposures to environmental agents. Biomarkers will also be used to validate other exposure assessment methods and to provide more proximate estimates of dose. Exposure biomarkers may be applied to groups that have unique exposure or susceptibility patterns, to monitor the population in general, and to document the consequences of exposure assessment strategies designed to reduce population exposures. Exposure biomarkers validated against the end point of disease risk and used in conjunction with other measurements and metrics of exposure should prove particularly effective in risk assessment. However, biomarkers of exposure may pose new and unanticipated ethical dilemmas. Information gained from biomolecular markers of exposure may provide an early warning of high risk or preclinical disease; capability for early warning will require a high level of, and an accepted socialregulatory framework for follow-up actions. They may also cause false alarms and needless stress for individuals warned about the presence of uncertain signals. In summary, exposure represents contact between a concentration of an agent in air, water, food, or other material and the person or population of interest. The agent is the source of an internal dose to a critical organ or tissue. The magnitude of the dose depends on a number of factors: (1) the volumes inhaled or ingested; (2) the fractions of the inhaled or ingested material transferred across epithelial membranes of the skin, the respiratory tract, and the GI tract; (3) the fractions transported via circulating fluids to target tissues; and (4) the fractional uptake by the target tissues. Each of these factors can have considerable intersubject variability. Sources of variability include activity level, age, sex, and health status, as well as such inherent variabilities as race and size. With chronic or repetitive exposures, other factors affect the dose of interest. When the retention at, or effects on, the target tissues are cumulative and clearance or recovery is slow, the dose of interest can be represented by cumulative uptake. However, when the agent is rapidly eliminated or when its effects are rapidly and completely reversible on removal from exposure, the rate of delivery may be the dose parameter of primary interest.

5.2 Determining Concentrations of Toxic Chemicals in Human Microenvironments The technology for sampling air, water, and food is relatively well developed, as are the technologies for sample separation from copollutants, media, and interferences and for quantitative analyses of the components of interest. However, knowing when, where, how long, and at which rate and frequency to sample to collect data relevant to the exposures of interest is difficult and requires knowledge of the temporal and spatial variability of exposure concentrations. Unfortunately, we seldom have enough information of these kinds to guide our sample collections. Many of these factors that affect occupational exposures are discussed in detail in the chapters of Patty's Industrial Hygiene, 5th ed. (33) The following represents a very brief summary of some general considerations. 5.3 Water and Foods Concentrations of environmental chemicals in food and drinking water are extremely variable, and there are further variations in the amounts consumed because of the extreme variability in dietary preferences and food sources. The number of foods for which up-to-date concentration data for specific chemicals are available is extremely limited. Relevant human dietary exposure data are sometimes available in terms of market basket survey analyses. In this approach, food for a mixed diet is purchased, cleaned, processed, and prepared as for consumption, and one set of specific chemical analyses is done for the composite mixture. The concentrations of chemicals in potable piped water supplies depend greatly on the source of the water, its treatment history, and its pathway from the treatment facility to the tap. Surface waters from protected watersheds generally have low concentrations of dissolved minerals and environmental chemicals. Well waters usually have low concentrations of bacteria and environmental chemicals but often have high mineral concentrations. Poor waste disposal practices may contribute to groundwater contamination, especially in areas of high population density and/or industrial sources of wastes. Treated surface waters from lakes and rivers in densely populated and/or industrialized areas usually contain a wide variety of dissolved organics and trace metals, whose concentrations vary greatly with the season (because of variable surface runoff), with proximity to pollutant sources, with upstream usage, and with treatment efficacy. The uptake of environmental chemicals in bathing waters across intact skin is usually minimal compared to uptake via inhalation or ingestion. It depends on both the concentration in the fluid surrounding the skin surface and the polarity of the chemical; more polar chemicals have less ability to penetrate intact skin. Uptake via skin can be significant for occupational exposures to concentrated liquids or solids. 5.4 Air Although chemical uptake through ingestion and the skin surface is generally intermittent, inhalation provides a continuous means of exposure. The important variables that affect the uptake of inhaled chemicals are the depth and frequency of inhalation and the concentration and physicochemical properties of the chemicals in the air. Exposure to airborne chemicals varies widely among inhalation microenvironments, whose categories include workplace, residence, outdoor ambient air, transportation, recreation, and public spaces. There are also wide variations in exposure within each category, depending on the number and strength of the sources of the airborne chemicals, the volume and mixing characteristics of the air within the defined microenvironment, the rate of air exchange with the outdoor air, and the rate of loss to surfaces within the microenvironment. For community air pollutants that have national ambient air quality standards, particulate matter (PM), sulfur dioxide (SO2), carbon monoxide (CO), nitrogen dioxide (NO2), ozone (O3), and lead (Pb), there is an extensive network of fixed-site monitors, generally on rooftops. Although the use of these monitors generates large volumes of data, the concentrations at these sites may differ substantially from the concentrations that people breathe, especially for tailpipe pollutants such as CO. Data for other toxic pollutants in the outdoor ambient air are not generally collected routinely. 5.5 Workplace

Exposures to airborne chemicals at work are extremely variable in composition and concentration and depend on the materials being handled, the process design and operation, the kinds and degree of engineering controls applied to minimize release to the air, the work practices followed, and the personal protection provided. 5.6 Residential Airborne chemicals in residential microenvironments are attributable to air infiltrating from out of doors and to the release from indoor sources. The latter include unvented cooking stoves and space heaters, cigarettes, consumer products, and volatile emissions from wallboard, textiles, carpets, etc. Indoor sources can release enough nitrogen dioxide (NO2), fine particle mass (FPM), and formaldehyde (HCHO) that indoor concentrations for these chemicals can be much higher than those in ambient outdoor air. Furthermore, their contributions to the total human exposure are usually even greater because people usually spend much more time at home than outdoors. 5.7 Conventions for Size-Selective Inhalation Hazard Sampling for Particles In recent years, quantitative definitions of Inhalable particulate matter (IPM), Thoracic particulate matter (TPM), and Respirable particulate matter (RPM) have been internationally harmonized. The size-selective inlet specifications for air samplers that meet the criteria of ACGIH (34), ISO (35), and CEN (36) are enumerated in Table 2.3 and illustrated in Figure 2.9. They differ from the deposition fractions of ICRP (6), especially for larger particles, because they take the conservative position that protection should be provided for those engaged in oral inhalation and thereby bypass the more efficient filtration efficiency of the nasal passages.

Figure 2.9. Effect of size-selective inlet characteristic on the aerosol mass collected by a downstream filter. IPM = inhalable particulate matter; TSP = total suspended particulate; TPM = thoracic particulate matter; (aka PM10); RPM = respirable particulate matter; and PM2.5 = fine particulate matter in ambient air.

Table 2.3. Inhalable, Thoracic and Respirable Dust Criteria of ACGIH, ISO and CEN, and Criteria of U.S. EPA

Inhalable

Thoracic

PM10

Respirable

Particle Inhalable Particle Thoracic Particle Respirable Particle Th Aerodynamic Particulate Aerodynamic Particulate Aerodynamic Particulate Aerodynamic Par Mass Mass Diameter Mass Diameter (TPM) Diameter (RPM) Diameter Ma (TP (mm) (IPM) (%) (mm) (%) (mm) (%) (mm) 0 1 2 5 10 20 30 40 50 100

100 97 94 87 77 65 58 54.5 52.5 50

0 2 4 6 8 10 12 14 16 18 20 25

100 94 89 80.5 67 50 35 23 15 9.5 6 2

0 1 2 3 4 5 6 7 8 10

100 97 91 74 50 30 17 9 5

0 2 4 6 8 10 12 14 16

1

The U.S. Environmental Protection Agency (36a) set a standard for ambient air particle concentration known as PM10, i.e., for particulate matter less than 10 mm in aerodynamic diameter. It replaced a poorly defined size-selective criterion known as total suspended particulate matter (TSP), whose actual inlet cut varied with wind speed and direction. PM10 has a sampler inlet criterion that is similar (functionally equivalent) to TPM but, as shown in Table 2.3, has somewhat different numerical specifications. In 1997, following its most recent thorough review of the literature on the health effects of ambient PM, the EPA concluded that most of the health effects attributable to PM in ambient air were more closely associated with the fine particles in the fine particle accumulation mode (extending from about 0.1 to 2.5 mm) than with the coarse mode particles within PM10 and promulgated new National Ambient Air Quality Standard (NAAQS) based on fine particles, defined as particles whose aerodynamic diameters (dae) are less than 2.5 mm (PM2.5), to supplement the PM10 NAAQS that was retained (37). The selection of dae = 2.5 mm as the criterion for defining the upper bound of fine particles in a regulatory sense was, inevitably, an arbitrary selection made from a range of possible options. It was arrived at using the following rationales: • Fine particles produce adverse health effects more because of their chemical composition than their size (see Table 2.4) and need to be regulated using an index that is responsive to control measures applied to direct and indirect sources of such particles. Table 2.4. Comparisons of Ambient Fine and Coarse Mode Particlesa Fine Mode

Coarse Mode

Formed Gases from Formed by Chemical reaction; nucleation; condensation; coagulation; evaporation of fog and cloud droplets in which gases have dissolved and reacted Composed Sulfate, SO 2–; nitrate, NO –; 4 3 of + ammonium, NH4 ; hydrogen

Large solids/droplets Mechanical disruption (e.g., crushing, grinding, abrasion of surfaces); evaporation of sprays; suspension of dusts

Resuspended dusts (e.g., soil dust, street dust); coal and oil fly ash; metal oxides of crustal + elements (Si, Al, Ti, Fe); ion, H ; elemental carbon; organic compounds (e.g., PAHs, CaCO3, NaCl, sea salt; pollen, PNAs); metals (e.g., Pb, Cd, V, mold spores; plant/animal Ni, Cu, Zn, Mn, Fe); particlefragments; tire wear debris bound water Solubility Largely soluble, hygroscopic, Largely insoluble and non and deliquescent hygroscopic. Sources Combustion of coal, oil, Resuspension of industrial dust gasoline, diesel, wood; and soil tracked onto roads; atmospheric transformation suspension from disturbed soil products of NOx, SO2, and (e.g., farming, mining, unpaved organic compounds including roads); biological sources; biogenic species (e.g., terpenes); construction and demolition; coal and oil combustion; ocean high temperature processes, spray smelters, steel mills, etc. Lifetimes Days to weeks Minutes to hours Travel 100s to 1000s of kilometers 10% per year) in recent years, and production was estimated at 180,000 tons in 1988 (148). Wollastonite was first mined for the production of mineral wool. The most important use at present is in ceramics which accounts for more than half of the consumption. Ceramic materials may include up to 70% wollastonite. It is also used as an extender in paints and coatings and as a filler in plastics. Some of the recent increase in use is attributable to its increasing importance as a replacement for asbestos. It is combined with binders, fillers, and organic fibers to make heat containment panels, ceiling and floor tiles, brake linings, and high-temperature appliances. 4.4 Toxicity Occupational exposures to wollastonite involve a significant exposure to fibers (67). Fiber concentrations ranging from 1 to 45 fibers/cm3 have been measured in air at a Finnish quarrying operation and concentrations between 8 and 37 fibers/cm3 were measured in the flotation and bagging plant. Fiber concentrations in the air in a mill in the United States ranged from 0.8 to 48 fibers/cm3. Very little relevant information is available about the potential health effects of wollastonite. Intrapleural administration of wollastonite to rats resulted in a significant increase in pleural sarcomas when the implanted material contained fibers > 4 mm long and < 0.5 mm in diameter (67). Mild changes characteristic of pneumoconiosis and pleural thickening have been seen in some workers exposed to wollastonite at facilities in Finland and the United States (144). In one small cohort mortality study of workers at a Finnish quarry, there was no indication of increased cancer mortality. In view of the increase in the use of wollastonite as an asbestos replacement, much more research is needed regarding its potential health effects.

Silica and Silica Compounds Richard Lemen, Ph.D., Eula Bingham, Ph.D. 5.0 Attapulgite 5.0.1 CAS Number: [12174-11-7] 5.0.2 Synonyms: Palygorskite 5.0.3 Trade Names: Attaclay; Attacote; Attagel; Attasorb; Diluex; Min-U-Gel FG; Permagel; Pharmasorb-colloidal; 2000/P-RVM; RVM-FG; X-250; Zeogel 5.0.4 Molecular Weight: NA 5.0.5 Molecular Formula: (Mg, Al)2 Si4 O10 (OH) · 4H2O 5.1 Chemical and Physical Properties 5.1.1 General The structure of attapulgite is similar to that of minerals of the amphibole group and differs only in minor respects from that of sepiolite. It occurs as elongated, lath-shaped crystals in

bundles that comprise thin sheets composed of minute interlaced fibers. Hardness: Soft Density: 2.2 Color: White, gray; translucent; dull 5.2 Production and Use This material is closely related to sepiolite and is categorized as a hormitic clay. Attapulgite has a structure similar to minerals of the amphibole group. This structure results in long, thin crystals that are similar to chrysolite asbestos fibrils (144). Attapulgite occurs in large deposits in the southeastern United States. The term “fuller's earth” has been used to describe commercially mined absorbent clays in the United States, and most of this material is attapulgite. Worldwide attapulgite production in 1983 was estimated at about 1.1 million tons, of which 84% came from the United States (144). The primary use of attapulgite is as an animal waste absorbent (cat litter). Other important uses of attapulgite in the United States are as a component of drilling muds, as oil and grease absorbents, and in fertilizer and pesticide formulations. 5.3 Exposure Assessment 5.3.3 Workplace Methods No ACGIH TLV standards or guidelines have been developed for attapulgite (149). 5.4 Toxicity The results of long-term surveillance of workers at two sites in the United States where attapulgite was mined and milled indicated that there was an increased prevalence of pneumoconiosis and that the incidence increased with age and with duration of exposure (144). A decrease in pulmonary function was associated with total cumulative exposure to respiratory dust in the workers at one of these facilities. The evidence relevant to the possible carcinogenic effects of attapulgite was reviewed by the IARC working group (144). Studies in which attapulgite was administered to rats by either intraperitoneal or intrapleural administration indicated that attapulgite containing significant number of fibers > 5 mm long produced mesotheliomas and sarcomas. A single epidemiological study of miners and millers exposed to high concentrations of attapulgite dust for long durations indicated that there was increased mortality from lung cancer, but no information on smoking behavior was determined. The working group concluded that there was limited evidence that attapulgite was carcinogenic in experimental animals but that the human evidence was inadequate to support a conclusion. 5.5 Standards, Regulations, or Guidelines of Exposure No exposure standards or guidelines have been developed for attapulgite by OSHA, NIOSH, or ACGIH (150–152).

Silica and Silica Compounds Richard Lemen, Ph.D., Eula Bingham, Ph.D. 6.0 Sepiolite 6.0.1 CAS Number: [18307-23-8], [15501-74-3] 6.0.2 Synonyms: Meerschaum 6.0.3 Trade Names: NA 6.0.4 Molecular Weight:

NA 6.0.5 Molecular Formula: Mg2Si3O8·2H2O 6.1 Chemical and Physical Properties 6.1.1 General Sepiolite is similar to attapulgite but has an additional SiO4 tetrahedron at regular intervals on the chain, so that the united cell is about 50% larger than that of attapulgite (21); usually clay-like, nodular and fibrous; also compact massive (meerschaum) or leathery (mountain skin) (153, 154). Hardness: 2–2.5 on Mohs' scale Density: ~2 Color: White with tints of grey-green or red; also light yellow 6.2 Production and Use A particularly pure form of sepiolite mined in Europe and the Middle East is known as “meerschaum” and has been used historically for carving pipes and cigarette holders. Sepiolite production in 1983 was less than half of the estimated 1.1 million of attapulgite in the world. A primary use of sepiolite was as an animal waste absorbent (cat litter). 6.3 Exposure Assessment 6.3.1 Workplace Methods No ACGIH TLV standards have been developed for sepiolite (155). 6.4 Toxicity Little information is available regarding the potential effects of sepiolite. A limited study of workers and residents in a village in Turkey who were exposed to sepiolite during mining and trimming indicated that exposed individuals did have clinical and radiological evidence of pulmonary fibrosis but no cases of mesothelioma or other pleural diseases were observed. The IARC working group concluded that the animal evidence was inadequate and that there was no human evidence available to evaluate the potential carcinogenicity of sepiolite (144). 6.5 Standards, Regulations, or Guidelines of Exposure No exposure standards or guidelines have been developed for sepiolite by OSHA, NIOSH, or ACGIH (150–152).

Silica and Silica Compounds Richard Lemen, Ph.D., Eula Bingham, Ph.D. 7.0 Kaolin 7.0.1 CAS Number: [1332-58-7] 7.0.2 Synonyms: Kaolinite; china clay; bolus alba; porcelain clay; aluminum silicate hydroxide; Kaopectate; aluminum silicate (hydrated); aluminum silicate dihydrate 7.1 Chemical and Physical Properties Kaolin is a hydrous aluminosilicate mineral that is found in large natural deposits of kaolinite in Georgia, South Carolina, and Texas (156). A typical kaolin contains 38.5% by weight aluminum oxide, 45.5% silicon dioxide, 13.9% water, and 1.5% titanium dioxide, with small amounts of calcium, magnesium, and iron oxides. A single crystal consists of a layer of silicon dioxide that is covalently bonded to a layer of aluminum oxide. When the clay is processed by centrifugal classification, it can be separated into fractions consisting of stacks of the hexagonal plates (< 2 mm in diameter and particles greater than 2 mm in diameter consisting of stacks of the hexagonal plates). Kaolin, as mined, contains other minerals including quartz, muscovite, and altered feldspars (157). The purification process removes much of the crystalline silica, so that commercial products

typically contain less than 3% crystalline silica and the respirable dust contains less than 1%. On the other hand, if kaolin is calcined, some of it may be converted to cristobalite. Color: white to yellowish or grayish powder (149) 7.2 Production and Use Domestic production of kaolin was estimated at 8.6 million tons in 1988 (158). More than 80% was produced in Georgia. A major use of kaolin is as a filter and a pigment in the manufacture of coated paper. Kaolin is also used as an extender and pigment in paints, in ceramics, rubber, thermosetting resins, and adhesives. 7.3 Exposure Assessment 7.3.3 Workplace Methods The recommended methods for determining workplace exposures to kaolin are NIOSH Method #0500 for total dust and #0600 for respirable dust (31). 7.4 Toxicity The health effects of exposure to kaolin dust by inhalation have not been adequately studied. Historically, reports of respiratory diseases among workers exposed to kaolin were attributed to possible contamination of the kaolin by crystalline silica. Before 1991, the ACGIH TLV for kaolin was that for a nuisance dust, namely, 10 mg/m3 TWA. However, in 1991, ACGIH reviewed the available information and issued a notice of intended change (157). The ACGIH cited a number of case reports and epidemiological studies of workers who were exposed to kaolin during mining and processing in Georgia. For the most part, Georgia kaolinite contains little or no crystalline silica. In workers who were exposed to kaolin dust during the milling and bagging of kaolin, there was an increased prevalence of pneumoconiosis. The prevalence of pneumoconiosis was correlated with both the intensity and duration of exposure. Pneumoconiosis incidence was not increased in open pit miners, who were exposed to significantly lower dust concentrations than workers involved in milling, bagging, and loading. As with many epidemiological studies of the effects of respiratory particulate matter, quantitative data on past exposure for these workers were of poor quality, but exposure levels in the past were unquestionably very high. There are no reports to suggest that workers exposed to kaolin free silica have a history of malignant respiratory diseases. The carcinogenic potential of kaolin has not been systematically studied in either experimental animals or exposed workers, however. Based on the available evidence that kaolin induces pneumoconiosis. 7.5 Standards, Regulations, or Guidelines NIOSH has a recommended exposure limit of 10 mg/m3 (total); 5 mg/m3 (resp); OSHA has a standard of 15 mg/m3 (total); 5 mg/m3 (resp) (149). The ACGIH TLV standard is 2 mg/m3 for matter containing no asbestos and 30 Tremolitic 221 years talc; 6 to 5,000 mppcf in mines; 20 to 215 mppcf in milling

Rubber worker

37 years Norwegian or 1 Canadian varieties of talc 28 1 years

Fatal pneumoconiosis Respiratory disorder

Millers

Talc pneumonoconiosis

32

Findings

Date

Of 33 patients exposed to high concentrations of dust, 22 had pneumoconiosis of varying severity. Persons with low exposures showed no signs of pneumoconiosis. Fibrosis was found 1943 in 32 people. All of them had been exposed for at least 10 yrs. The highest incidence, 40.6 %, occurred with those who had been exposed 15 to 19 yrs. Of the eight workers who had worked >30 yrs, six had fibrosis. At autopsy, both lungs were found to be moderately pneumoconiotic. X-ray revealed two, dense, homogeneous, opaque masses with round irregular contours in the upper portion of the pulmonary field. Talc plaques observed in all but one case. Six of 11 electrocardiographic configurations were abnormal. Four persons died who ranged in age from 48 to 84.

Miners

Mortality studies

10 mo to 27 years

Soapstone workers Pneumoconiosis

16 to 60 mo.

Rubber workers

Talcosis

19 years average

Lead casters

Talc pneumoconiosis

15 to 39 years

Miners

Miners

>20 years

Pneumoconiosis

>12 years

8

Causes of death: five died of cor pulmonale or TB; one of congestive cardiac failure; one of nephritis with cardiac complications; and one unknown. 8 Extent of disease varied with the time of exposure. Clinical signs included cough, mucopurulent sputum with talc bodies, dypsnea on exertion, and weakness. 12,000 During TB screening, 16 cases of symmetrical, modular foci of the lungs w/o swelling of the hilar glands, nine cases of definite talcosis (19 yrs exposure) and seven cases of slight talcosis (12 yrs exposure)were found. 7 One death from cor pulmonale and talc pneuomoconiosis after 15 yrs. exposure. Chest Xrays of all patients showed the presence of scattered opacities thoughout the lungs which coalesced to form larger masses with indefinite margins and uneven density. 60 All had pneumoconisis; those with greater exposure had more severe disease. 260 First radiographic

Grinders

Pneumoconiosis

10 to 20 years

25

Rubber workers

Pneumoconiosis

Unknown

72

Pneumoconiosis

24 years average

6

Miners/millers

Pulmonary function 23 years Talc admixed 20 average with tremolite, anthopyllite, and free silica: >50 mppcf

Pulmonary function >10 years 62.3 mppcf

Electrical fitter

43

Pulmonary talcosis 15 years Pharmacy talc 1

signs of pneumoconiosis appeared in 89% after 12 yrs; after 22 yrs. it was 100%. Incidence of pneumoconiosis was 52% after 10 to 20 yrs. Exhibited linear pneumoconiosis in 11% of workers. The most frequent pathological change was diffuse fibrosis containing macrophages with absorbed dust particles. Also found were diffuse or localized emphysema and granulomatous formation made up of focal areas of epitheliod and foreign body giant cells. 1964 Changes in pulmonary function indicate a restrictive or obstructive breathing disorder. No consistent correlation exists between degree of functional lung impairment and clinical symptoms or X-ray findings. Predominant symptoms were dyspnea, cough, basilar crepitations, and clubbing. Poor correlation between impairment and clinical and X-ray results. Thoracic radiography revealed large nodular trabecular

Miners or millers

Mortality

>15 years Talc mixed 91 with serpentine and tremolite

Rubber workers

Talcosis

20 to 40 years

5

25 > MAC for years talc

50

Milling

16.2 years

Mortality

Rubber workers

Respiratory function

>15 years

Commercial 39 talc with tremolite and anthophyllite

260

80

images with fairly abundant rounded spots in both lungs. Nine lung carcinomas, one fibrosarcoma of the pleura, two stomach cancers, one case each of colon, rectal, and pancreatic cancer; 25 cardiac arrests and 28 deaths from pneumoconiosis. Granular pneumoconiosis resulting from longterm or intense exposures. Sixteen cases of talc pneumoconiosis diagnosed. One worker showed a chest X-ray consistent with pneumoconiosis. Talc containing tremolite and anthophyllite may be less fibrogenic than chrysotile or amosite at the same exposure levels. The overall proportional mortality due to carcinoma of the lung and pleura was four times that of the general population. The carcinogenic effect was significant in workers exposed 15 to 24 yrs. Workers exposed below 20 mppcf showed a greater prevalence of productive cough and positive criteria for COPD than control workers.

Workers with < 10 yrs. exposure showed decreased FEV1. TWA exposures below 25 mg/m3 are recommended. Rubber workers Stomach cancer 17,000 There was an association between exposure to talc materials and 100 cases of stomach cancer. Miners/millers Morbidity study NY State talc 121 With 15 yrs. increased prevalence of pleural calcification. Radiographic findings occur primarily after 15 yrs. Talc miners Mortality patterns 1,260 Death was due primarily to pneumoconiosis and tuberculosis. Talc millers Mortality patterns 22 years 11 mppcf 218 Radiographic evidence of pneumoconiosis after 22 years of exposure but little cancer. Mining/milling Mortality/morbidity 13 years N.Y. State talc 398 Significant increase 1979 in mortality due to bronchogenic cancer, nonmalignant respiratory disease, and respiratory tuberculosis. Four of 10 bronchogenic cancer deaths occurred in individuals with less than 1 yr. of exposure. Grinding(milling) Interstitial lung U.S., 6 Large amounts of disease Australian, talc and talc bodies and French were found in the talc BAL fluid of all of

Mining

Morbidity/mortality > 1 year Talc with (cancer) (1944– < 1% quartz 1972)

94

Milling

Morbidity/mortality > 2 years Talc with (cancer) (1935– 15 years

Before 1976: 1 86 mg/m3; after 1976: 3.5 mg/m3. Smoked 21 cigarettes/day for 21 yrs.

Talc factory

Respiratory health

1.87 mg/m3 to 139 15 mg/m3

Latex glove mfg.

Respiratory function

7.7 mg/m3 total dust; 1.9 mg/m3 resp. dust

17

the workers 21 yrs. after last exposure. The authors suggest that examination of BAL fluid can provide information about talc exposure. 27 deaths, with 15 cases of cancer; cancers were of the stomach, prostate, and lung. 90 deaths, with 31 cases of cancer; cancers of the bladder and kidney were elevated. Pulmonary function testing revealed a restrictive ventilatory defect and impaired diffusing capacity. Open lung biopsy revealed bronchiolitis. Increased exposure decreased FVC and FEV1 FVC and FEV1 were lower in latex workers than controls.

As can be noted from Table 13.1, a number of studies looked at the rate of cancer among talc workers. There have been several individual case reports of cancer, including a lung adenocarcinoma following talc pleurodesis (79) and a pleural mesothelioma following occupational exposure to talc (80–82). Talc mining is attributed to causing four cases of mesothelioma reported to the tumor registry of the Cancer Control Bureau, New York Department of Health. These mines contain high levels of fibrous tremolite (83). 1.4.2.3.7 Other Health Effects In 1995, a workshop on consumer uses of talc was organized and held under the joint sponsorship of the U.S. Food and Drug Administration (FDA), the Cosmetic, Toiletries and Fragrances Association (CFTA), and the International Society of Regulatory Toxicology and Pharmacology (ISRTP). One of the issues discussed was the association of perineal talc exposure with ovarian cancer. The attendees agreed that, although some weak association between talc exposure and ovarian tumors has been reported, so far there was insufficient evidence for concern. Although it is theoretically possible that talc could reach the ovaries, the actual access to or the presence of talc in ovarian tissue has not yet been documented (84).

Standards, Regulations, or Guidelines of Exposure A number of countries have standards, regulations, and guidelines for regulating exposure to talc in the workplace. The exposure limits vary depending upon whether the talc contains asbestos or silica or if it is total dust or respirable dust only. Total dust exposures for talc are 10 mg/m3 in Switzerland and the United Kingdom, 5 mg/m3 in Finland, 2.5 mg/m3 in Australia, and 2 mg/m3 in Belgium and Germany. Respirable dust exposures for talc are 2 mg/m3 in Bulgaria, Columbia, Jordan, Korea, New Zealand, Singapore, and Vietnam; and 1 mg/m3 in the United Kingdom (85). In the United States, the OSHA PEL for talc not containing asbestos and containing less than 1% quartz is 20 mppcf. For talc containing no asbestos but 1% or more of quartz, the OSHA PEL is calculated from the formula for silica. For talc containing asbestos, the asbestos limit is used (86). The ACGIH has a TLV of 2 mg/m3 for talc dust containing no asbestos and a TLV of 0.1 f/cc for talc containing asbestos (87). Talc Bibliography

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Rock Wool and Refractory Ceramic Fibers Carol Rice, Ph.D., CIH 1 Introduction Man-made vitreous fibers (MMVF) is a generic descriptor for a group of fibrous materials made from melting inorganic substances such as sand, clay, glass, or slag. Synthetic vitreous fibers (SVF) or man-made synthetic vitreous fibers (MSVF) may also be used to describe these groups of materials. These terms have generally replaced earlier use of man-made mineral fibers (MMMF). MMVF are further classified by the raw material used in production; major categories include glass fibers (glass wool or continuous filament), mineral wool (rock or slag), and refractory ceramic fibers. The latter two types are covered in this chapter; glass fibers are described in Chapter. Within each category, a variety of commercial products have been produced and may be identified by manufacturer and product name and number. Each has a slightly different formulation and characteristics; therefore it is important where possible to identify the particular product number. Dimension, durability, and dose delivered to the target organ are critical factors in the toxicity of MMVF. Fibers are generally distinguished from other particles by having a length to width ratio (aspect ratio) of at least 3:1. A maximum or minimum for one or more of the dimensions may also be specified. For example, a fiber meeting WHO (1) criterion has an aspect ratio of at least 3:1 and a diameter of 3 mm or less. MMVF counted in airborne exposure assessments in the United States are generally described as having an aspect ratio of at least 5:1, a diameter of 3 mm or less, and at least 5 mm long (2). Long fibers are thought to be more biologically active than shorter fibers (3). MMVF are characterized by length (L) and diameter (D). The arithmetic mean or median of the observed distribution of lengths and diameters may be given as the count mean or median diameter (CMD) or length (CML). If the observed values are transformed by taking the natural logarithm of the measured parameters, the geometric mean (GM) of each dimension may be given with a geometric standard deviation (GSD). The size determinations may be made by either scanning (SEM) or transmission (TEM) electron microscopy. TEM has the lower limits of detection by which investigators can characterize fibers with diameters in the nanometer range. Dose by some routes of administration may be further described by the mass of material, for example, in implantation or single bolus injection studies. For inhalation studies, GM and GSD length and diameter are usually listed for the exposure aerosol, and often the number of fibers within specific size ranges are listed; for example, the number of WHO fibers or the number longer than 20 microns may be tabulated.

Following inhalation, fibers may be deposited on surfaces within the respiratory tract or exhaled. For the fibers that are deposited, the site of deposition (dose) depends upon the characteristics of the fiber and results from one of five mechanisms: impaction, interception, sedimentation, electrostatic precipitation, or diffusion. The majority of the deposition of MMVF is probably governed by the first three mechanisms. Impaction and interception occur when the fiber is removed from the airstream by physically contacting the surface of the airway or a bifurcation. Sedimentation occurs in the lower airways, where the velocity of the fiber becomes low enough for it to settle on the airway surface. Electrostatic precipitation results when the fiber carries a charge opposite to that of the airway surface; for mineral wool fibers, no reports have been found on surface charge measurements. Deposition due to diffusion requires that the air molecules collide with the fiber, resulting in movement toward the surface. This mechanism could contribute to deposition of very thin fibers, e.g., those with diameters substantially less than one-half micron, but few of them are expected in the work environment (4). The clearance mechanism of the deposited fibers depends upon the characteristics of the fiber and the site of deposition. Fibers deposited in the tracheobronchial region are cleared with the mucous by the cilia and swallowed. This process is completed in a matter of days, during which little change in fiber dimensions would be anticipated. Fibers deposited lower in the respiratory tract are cleared more slowly. Here the fibers are cleared by translocation to another area of the lung or dissolve; translocation may be facilitated by partial dissolution of the fiber or breakage into particles of shorter length. When fibers recovered from the lung or other tissue are characterized by dimensions, comparison with the parent material provides information on deposition and distribution. Solubility has been investigated as an indicator of durability. Guldberg et al. (5) noted that testing at pH 7.2 to 7.8 represents the neutral conditions of the lung; testing at an acidic pH of 4.5 to 5 represents the environment created by contact with the phagolysosomes. End points include 95% loss of leachable elements, 75% total mass loss, and mass lost in a specified number of days. Both pH values should be considered when evaluating biopersistence (6). The formulation of the test fluid for solubility studies also influences results (5, 7); however, for a given fluid, the rank order of dissolution rates is unchanged (5). The interpretation of short-term bioassay results is still under study (8). Bernstein et al. (8a) suggested that the results of dissolution at neutral pH are correlated with in vivo biopersistence. Others report that the dissolution rates of MMVF that have high aluminum content are much greater in acidic environments (9). Evidence from animal studies shows that the macrophages may interact with long fibers and that multiple macrophages attach to a single fiber which can lead to dissolution (10–13). Two reviews of animal studies should be consulted by the reader interested in contrasting the observations of effects among two or more MMVF (14, 15). The contribution of various types of studies to the overall assessment of the toxicity of MMVF was the focus of a 1994 workshop (16), and a 1995 review by De Vuyst et al. (17).

Rock Wool and Refractory Ceramic Fibers Carol Rice, Ph.D., CIH 1.0 Mineral Wool 1.0.1 CAS Number: none 1.0.2 Synonyms: rock wool, slag wool

1.0.3 Trade Names The major U.S. suppliers and product types include American Rockwool, Inc. Rock/slag wool building insulation Rock/slag wool fire-accoustical thermal spray systems Rock/slag loose wool industrial and OEM fibers and insulation Celotex Corporation Slag wool ceiling tile Fibrex, Inc. Rock wool board, pipe and blanket insulation Slag blowing wool building insulation Rock wool roof insulation Rock wool marine insulation Isolatek International Slag wool insulation (bulk) Slag wool fire protection (sprayed) Slag wool building insulation (sprayed) MFS, Inc. Slag wool insulation (bulk) Slag wool fire protection (sprayed) Slag wool insulating cement (troweled, sprayed) OCHT Rock wool pipe, board, and blanket insulation Rock Wool Manufacturing Co. Slag wool building insulation Slag wool pipe and board insulation Slag wool commercial insulation Roxul, Inc. Rock wool building insulation Rock wool pipe, board, and blanket insulation Rock wool roof insulation Sloss Industries Corporation Slag wool insulation (bulk) Slag wool ceiling tile Slag blowing wool insulation Thermafiber LLC Slag wool board and blanket insulation

Slag wool building insulation Slag wool ceiling tile USG Interiors, Inc. Slag wool ceiling tile Brand names are not given because a single supplier may have 200 products, each with a unique trade name. (Source: North American Insulation Manufacturers Association, Washington, DC, 1999).

Rock Wool and Refractory Ceramic Fibers Carol Rice, Ph.D., CIH 2.0 Refractory Ceramic Fibers (RCF) 2.0.1 CAS Number: [142844-00-6] 2.0.2 Synonyms: NA 2.0.3 Trade Names United States trade names: Anchor Loc Cerafiber Cerawool Cerafelt Durablanket Duraboard Duraset Fiberfrax Kaowool Kaoset K-Lite Pre Flex Pre Mix Pyro-blanket Pyro-fold Thermotect Ultrafelt Uni-Bloc Z-Bloc (Source: Refractory Ceramic Fiber Coalition, Washington, DC, 1999) 2.0.4 Molecular Weight The molecular weight varies depending upon the raw materials used in the formulation.

Rock Wool and Refractory Ceramic Fibers Bibliography

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follow-up. J. Occup. Med. 32, 594–604 (1990). 57 O. Wong, D. Foliart, and L. S. Trent, A case-control study of lung cancer in a cohort of workers potentially exposed to slag wool fibers. Br. J. Ind. Med. 48, 818–824 (1991). 58 R. Saracci et al., Mortality and incidence of cancer of workers in the man made vitreous fibres producing industry: an international investigation at 13 European plants. Br. J. Ind. Med. 41, 425–436 (1984). 59 L. Simonato et al., The man-made mineral fiber European historical cohort study: Extension of the follow-up. Scand. J. Work Environ. Health 12(Suppl. 1), 34–47 (1986). 60 L. Simonato et al., The International Agency for Research on Cancer historical cohort study of MMMF production workers in seven European countries: extension of the follow-up. Ann. Occup. Hyg. 31, 603–623 (1987). 61 J. Cherrie and J. Dodgson, Past exposures to airborne fibers and other potential risk factors in the European man-made mineral fiber production industry. Scand. J. Work Environ. Health 12 (Suppl. 1), 26–33 (1986). 62 P. Boffetta et al., Cancer mortality among man-made vitreous fiber production workers. Epidemiology 8, 259–268 (1997). 63 Z. Skuric and D. Stahuljak-Beritic, Occupational exposure and ventilatory function changes in rock wool workers. In T. Guiter, ed., Biological Effects of Man-Made Mineral Fibers (Proc. WHO/IARC Conf.). Vol. 1, World Health Organization, Copenhagen, 1984, pp. 436– 437. 64 H. Weill et al., Respiratory health in workers exposed to man-made vitreous fibers. Am. Rev. Respir. Dis. 128, 104–112 (1983). 65 H. Weill et al., Respiratory health of workers exposed to MMMF. In T. Guiter, ed., Biological Effects of Man-Made Mineral Fibers (Proc. WHO/IARC Conf.), Vol. 1, World Health Organization, Copenhagen, 1984, pp. 387–425. 66 N. Esmen et al., Summary of measurements of employee exposure to airborne dust and fiber in sixteen facilities producing man-made mineral fibers. Am. Ind. Hyg. Assoc. J. 40, 108– 117 (1979). 67 T. Schneider et al., Dust in buildings with man-made mineral fiber ceiling boards. Scand. J. Work Environ. Health 16, 434–439 (1990). 68 S. A. M. T. Jaffrey et al., Levels of airborne man-made mineral fibres in UK dwellings II. Fibre levels during and after some disturbance of loft insulation. Atmos. Environ. 24A, 143– 146 (1990). 69 W. C. Miller, Refractory fibers. In M. Grayson and D. Eckroth, eds., Kirk Othmer Encyclopedia of Chemical Technology, 3rd ed., Vol. 20, John Wiley, New York, 1982, pp. 65–77. 70 G. S. Hall et al., A comparison of exposures to refractory ceramic fibers over multiple work shifts. Ann. Occup. Hyg. 41, 555–560 (1997). 71 G. Strubel and L. Faul, Pollutant load caused by ceramic fibres and new results about their behaviour of recrystallization. Ann. Occup. Hyg. 38(Suppl. 1), 713–722 (1994). 72 T. J. Lentz, The potential significance of airborne fiber size parameters to the development of pleural plaques in workers who manufacture refractory ceramic fibers. Ph.D Dissertation, University of Cincinnati, Cincinnati, OH, 1997. 73 G. A. Hart et al., Cytotoxicity of refractory ceramic fibers to chinese hamster ovary cells in culture. Toxicol. In Vitro 6, 317–326 (1992). 74 G. D. Leikauf et al., Refractory ceramic fibers activate alveolar macrophage eicosanoid and cytokine release. J. Appl. Physiol. 87, 164–171 (1995). 75 R. W. Mast et al., Studies on the chronic toxicity (inhalation) of four types of refractory ceramic fiber in male Fischer 344 rats. Inhalation Toxicol. 7, 425–467 (1995). 76 R. W. Mast et al., Multiple-dose chronic inhalation toxicity study of size-separated kaolin

refractory ceramic fiber in male Fischer 344 rats. Inhalation. Toxicol. 7, 469–502 (1995). 77 E. E. McConnell et al., Chronic inhalation of a kaolin-based refractory ceramic fiber in Syrian golden hamsters. Inhalation Toxicol. 7, 503–532 (1995). 78 T. R. Gelzleichter et al., Pulmonary and pleural responses in Fischer 344 Rats following short-term inhalation of a synthetic vitreous fiber. 1. Quantitation of lung and pleural fiber burdens. Fundam. Appl. Toxicol. 30, 31–38 (1996). 79 J. M. Beekmans, The deposition of asbestos particles in the human respiratory tract. Intl. J. Environ. Stud. 1, 31–34 (1970). 80 R. L. Harris, Jr., and D. A. Fraser, A model for deposition of fibers in the human respiratory system. Am. Ind. Hyg. Assoc. J. 38, 73–89 (1976). 81 B. Asgharian and C. P. Yu, Deposition of inhaled fibrous particles in the human lung. J. Aerosol. Med. 1, 37–50 (1988). 82 R. G. Sussman, B. S. Cohen, and M. Lippmann, Asbestos fiber distribution in a human tracheobronchial cast II. Empirical model. Inhalation Toxicol. 3, 161–179 (1991). 83 C. P. Yu et al., Clearance of refractory ceramic fibers (RCF) from the rat lung: Development of a model. Environ. Res. 65, 243–253 (1994). 84 C. P. Yu et al., A clearance model of refractory ceramic fibers (RCF) in the rat lung including fiber dissolution and breakage. J. Aerosol. Sci. 27, 151–159 (1996). 85 H. Yamato et al., Retention and clearance of inhaled ceramic fibres in rat lungs and development of a dissolution model. Occup. Environ. Med. 51, 275–280 (1994). 86 J. C. Wagner, G. Berry, and V. Timbrell, Mesotheliomata in rats after inoculation with asbestos and other materials. Br. J. Cancer 28, 173–185 (1973). 87 J. M. G. Davis et al., The pathogenic effects of fibrous ceramic aluminum silicate glass administered to rats by inhalation or peritoneal injection. In T. Guiter, ed., Biological Effects of Man-Made Mineral Fibers (Proc. WHO/IARC Con.), Vol. 2, World Health Organization, Copenhagen, 1984, pp. 303–322. 88 J. Indulski, J. Stetkiewicz, and E. Wiecek, Refractory ceramic fibres health effects, experimental data and hygienic standards. Eur. J. Oncol. 3, 385–389 (1998). 89 T. R. Gelzleichter et al., Pulmonary and pleural responses in Fischer 344 Rats following short-term inhalation of a synthetic vitreous fiber. 11. Pathological responses. Fundam. Appl. Toxicol. 30, 39–46 (1996). 90 G. W. Wright, Respiratory morbidity of MMMF production workers—a review of previous studies. In T. Guiter, ed., Biological Effects of Man-Made Mineral Fibers (Proc. WHO/IARC Conf.), Vol. 1, World Health Organization, Copenhagen, 1984, pp. 381–386. 91 A. A. Fisher, Contact Dermatitis, 2nd ed., Lea & Febiger, Philadelphia, 1973. 92 W. N. Trethowan et al., Study of the respiratory health of employees in seven European plants that manufacture ceramic fibres. Occup. Environ. Med. 52, 97–104 (1995). 93 C. E. Rossiter et al., Refractory ceramic fibre production workers. Analysis of radiograph readings. Ann. Occup. Hyg. 38(Suppl. 1), 731–738 (1994). 94 G. K. Lemasters et al., Radiographic changes among workers manufacturing refractory ceramic fibre and products. Ann. Occup. Hyg. 38(Suppl. 1), 745–751 (1994). 95 J. E. Lockey et al., Refractory ceramic fiber exposure and pleural plaques. Am. J. Respir. Crit. Care Med. 154, 1405–1410 (1996). 96 G. K. Lemasters et al., An industry-wide pulmonary study of men and women manufacturing refractory ceramic fibers. Am. J. Epidemiol. 148, 910–919 (1998). 97 J. E. Lockey et al., Longitudinal estimates of pulmonary function in refractory ceramic fiber manufacturing workers. Am. J. Respir. Crit. Care Med. 157, 1226–1233 (1998). 98 C. H. Rice et al., Estimation of historical and current employee exposure to refractory ceramic fibers during manufacturing and related operations. Appl. Occup. Environ. Hyg. 12,

54–61 (1997).

Fiberglass R. A. Lemen, Ph.D. 1.0 Fiberglass 1.0.1 CAS Number: (none) 1.0.2 Synonyms: Glass wool; Fiberglas®; Fiberglass insulation; boron silicate glass fibre; Saint Gobain; JM 100; JM 102; JM 104; JM 110; TEL 1.1 Chemical and Physical Properties 1.1.1 General Physical properties are listed in Table 15.1. Table 15.1. Physical Properties of Fiberglassa Glass Type I II III IV V VI a

Form Textiles Mats Textiles Wood (coarse) Packs (coarse) Wool, fine Ultrafine Textile

Fiber Diameter Range (mm)

Specific Gravity (g/cm3)

Refractive Index

6–9.5 10–15 6–9.5 7.5–15

2.596 2.540

1.548 1.541

2.605

1.549

115–250

2.465

1.512

0.75–5 0.25–0.75 6–9.5

2.568

1.537

4.3

—

NIOSH (4) and taken from IARC (5).

Relative density of fiberglass is 2.5–2.6 (water = 1). It is not soluble in water. Components are listed below.

Continuous Glass Filamenta Glass Woolab (Mohr and Rowe, Ref. 1) % by Component % by Weight Weight

SiO2

52–56

63

CaO Al2O3

16–25 12–16

7 (+Fe2O3)6

B2O3

8–13

6

MgO Na2O

0–6 0–3

3 14

K2O

0–3

1

TiO2

0–0.4

—

Fe2O3

0.05–0.4

—

F2

—

0.7

a

Ref. 2. Glass wool is an amorphous silicate manufactured from glass and may contain a binder and an oil for dust suppression (3).

b

1.1.2 Odor and Warning Properties Fiberglass can irritate the eyes, skin and the respiratory tract (3). It can also cause an itch called fiberglass itch (6). 1.2 Production and Use Fiberglass is produced as a glass wool or glass filament by drawing, centrifuging, or blowing molten glass into fibers of certain predetermined widths and lengths or by continuously drawing or extruding glass filaments from molten glass (5). Glass fiber production is in the 100s of million kg per year and continues to grow (5. 1.3 Exposure Assessment 1.3.1 Air: NA 1.3.2 Background Levels Fiber concentrations in the atmosphere have been generally low and range from undetectable to 0.00004 to 0.009 fiber/cm3 (5). 1.3.3 Workplace Methods Fiberglass can be sampled by using a filter (0.45 to 1.2 mm cellulose ester membrane, 25-mm; conductive cowl on cassette) and measured by the light microscope, phase contrast technique. This allows a manual count of all fibers. If used for detecting one fiber type it will not be successful because other fibers with similar diameters and lengths will interfere. The working range is between 0.04 to 0.5 fibers/cc for a 1000-L air sample. The limit of detection depends on sample volume and the quantity of interfering dust, but in the absence of such interferences, the quantitative concentration goes down to 7 days >3 days >7 days >7 days

— 9h — 8h

— 50% plasma In petri dish 5% serum on glass

a

D10 = amount of time required to reduce viral infectivity by 1 log or 90%.

b

RT = room temperature (20–27°C).

35 34 35 36

Martin, as well as other authors (38, 39), reported inactivation of HIV-1 suspensions at 56°C within 10–20 min (D10 value = 2 min). Resnick et al. (34), however, found that heating at 56°C for 5 h was necessary, calculating a D10 value of 20 min. The reason for discrepancies in these studies is undetermined. A 1988 survey of laboratories evaluating HIV-1 tests for CDC (40) reported that 3.9% of the laboratories heat-inactivated serum specimens at 56°C as a safety measure before testing. However, the heating process can cause false-positive results for enzyme immuno assay (EIA) and Western Blot tests (41, 42), changes in laboratory enzyme levels, and turbidity problems with plasma (43). The CDC recommended that heat inactivation of serum does not preclude the use of standard precautions and should not be used as a routine means of protection of laboratory workers (40). The heating process has better applicability in the preparation of safe therapeutic blood products. Piszkiewicz (44) found that pasteurization of antithrombin III concentrate at 60°C for 7 min reduced HIV-1 to below detectable levels. Others have found alternative methods of inactivation of blood products, including exposure to tri- (n-butyl) phosphate and sodium cholate for 20 min at room temperature (45). A promising method that destroys HIV-1 but does not effect changes in hematological parameters is the “photodynamic method,” a hematoporphyrin photosensitizer (46). 1.3 Epidemiology Since the recognition and reporting of AIDS in 1981, more than 650,000 persons with AIDS have been reported to public health departments in the United States (9). In the United States, AIDS was the leading cause of death among those aged 25–44 years in 1993 (47), but dropped to the fifth leading cause in 1997 (48). Worldwide, at the end of 1997, approximately 30.6 million people were living with HIV infection, 20.8 million of them in sub-Saharan Africa (49). Epidemiological information gathered since the early 1980s indicate that the modes of transmission of HIV-1 have remained the same. HIV-1 is transmitted through sexual contact, percutaneous or mucous membrane exposure to blood, birth, or breastfeeding from an infected mother, or transfusion of HIV-contaminated blood. However, trends of HIV infection for certain populations reflect the evolution of the epidemic. For example, in the United States, AIDS cases attributed to homosexual or bisexual behavior decreased from 65% of cases in 1984 to 48% in 1998. Heterosexual contact cases increased from 1.2% in 1984 to 10% in 1998 (50, 51). The findings demonstrate a disproportionate increase in U.S. women and racial[sol ]ethnic minorities. Women accounted for only 7% of AIDS cases in 1984 (50), 10% in 1987 (52), and increased to 16% in 1998 (51). The overall rate of AIDS per 100,000 population in 1998 was 34; however, the rate for African-Americans was 125 (51). Dr. Helene Gayle (53) noted that AfricanAmericans make up 13% of the U.S. population, but accounted for 48% of all AIDS cases in 1998, and that higher annual infection rates are seen with young homosexual men, intravenous drug users, women, and minorities. The annual incidence of AIDS cases associated with blood transfusions and therapeutics for hemophilia stabilized with about five cases per year after the serological screening of blood donations and heat-treatment of clotting factors was initiated in 1985. Currently (at the time of writing), it is estimated that the risk of any unit of blood being contaminated with HIV after the

screening process is 1:200,000–1:2,000,000 (54). The American Red Cross began testing donated blood units via nucleic acid testing (NAT) in June 1999 for early detection of viruses, such as HIV and hepatitis C virus (HCV) (55). Because NAT detects viral DNA or RNA, rather than the donor [apos ]s antibodies, it can detect HIV virus within 6–10 days after exposures and HCV within about 41 days after exposure. This reduces the risk of transmission of undetected HIV or HCV via blood transfusions. In 1998, 8% of all AIDS cases were assigned to a “no identified risk” (NIR) category, representing a large caseload of those recently diagnosed (51). For many of these cases, follow-up investigation is incomplete or the patient has died before an investigation could be performed. Historically, on investigation, 83% of the NIRs are classified into an identified risk category.

Bloodborne Pathogens In the Workplace Debra L. Hunt, Jerry J. Tulis, MD 2 Occupational HIV-1 Transmission 2.1 AIDS in Healthcare Workers National surveillance data about AIDS in healthcare workers demonstrate that there is no high risk for working in the healthcare or laboratory setting. As of 1998, approximately 20,769 (5.1%) of reported AIDS cases whose work history was known had related a history of working in a healthcare or laboratory setting since 1978 (4). This percentage is comparable to the proportion of the U.S. population working in the healthcare area (56). The occupations of those healthcare workers with AIDS are as follows: 22% nurses, 21% health aides, 13% technicians, 8% physicians, 5% therapists, 2% dental workers, and 2% paramedics (4). Overall, 75% of the cases of AIDS in healthcare workers have died. 2.2 Prevalence Studies More indirect evidence that the risk of transmission of HIV-1 in the healthcare setting is small is found in HIV prevalence studies conducted on cohorts of healthcare workers around the country, many of whom work in areas of high community seroprevalence. These studies have examined 7595 U.S. and European healthcare workers with reported HIV exposures and found nine seropositives (0.12%) in workers with no identified community risk (57–69). The prevalence of infection in healthcare workers does not appear to be any higher than that of the comparable population at large. The lack of association of HIV transmission in the healthcare setting has also been demonstrated in a recent serosurvey of hospital-based surgeons in 21 hospitals in moderate to high AIDS incidence areas across the United States conducted by the CDC Serosurvey Study Group (70). This study also found a low prevalence of 0.14% (one seropositive in 740 surgeons with no community risk identified). This same finding is demonstrated in prevalence studies from Kinshasa, Zaire (71, 72), where community prevalence of HIV is high (6–8%), infection control practices are limited, and needles and syringes are usually washed by hand, sterilized, then reused. No higher rates of seropositivity were found in the hospital staff, nor were there any significant differences among the medical, administrative, and manual workers (6.5, 6.4, and 6%, respectively). These findings reaffirm the apparent low risk for occupational transmission of HIV. 2.3 Documented Case Studies Occupational HIV infection following a specific exposure is the best indicator of the mode of HIV transmission in the healthcare setting. Although the risk of occupational HIV transmission appears to be low, case reports of healthcare workers infected with the virus through occupational exposure have been reported. Between 1981 and 1998, 54 healthcare workers in the United States have been documented as having seroconverted to HIV following occupational exposures. Twenty-five have developed AIDS. Individuals who seroconverted include 22 nurses, 19 laboratory workers (16 of whom were clinical laboratory workers), 6 physicians, 2 surgical technicians, 1 dialysis technician, 1 respiratory therapist, 1 health aide, 1 embalmer[sol ]morgue technician, and 1 housekeeper[sol ]

maintenance worker (4). The modes of transmission in these cases appear to be: 46 percutaneous (puncture[sol ]cut injury) exposures, 5 mucocutaneous (mucous membrane and[sol ]or skin) exposures to blood, 2 had both percutaneous and mucocutaneous exposure, and 1 unknown. Fortynine exposures were to HIV-infected blood, 3 to concentrated virus in a laboratory, 1 to visibly bloody fluid, and 1 to an unspecified fluid. Additionally, 133 other cases of HIV infection or AIDS have been reported among healthcare workers who were found to have no other social risk factors for HIV infection, but who experienced nondocumented occupational exposures to blood, body fluids, or laboratory levels of HIV. These include 33 nurses, 18 clinical laboratory workers, 17 physicians, 15 health aides, 12 paramedics, 10 housekeepers[sol ]maintenance workers, 9 technicians, 7 dental workers, 3 dialysis technicians, 2 surgical technicians, 2 embalmers[sol ]morgue technicians, 2 respiratory therapists, and 2 others (9). Worldwide, including the United States, 94 documented and 170 possible occupational HIV infections have occurred among healthcare workers as of September 1997 (73). The United States accounted for 62.9% and Europe for 28.4% of documented and possible cases. Of the European countries, France had the highest number with 14.3% of cases. According to case descriptions, the majority of documented infections occurred among nurses or clinical laboratory workers (70.2%) after contact with infected blood (89.4%) from patients with AIDS (76.5%) by percutaneous exposure (88.3%) during a procedure involving placement of a device in an artery or vein (68%).

Bloodborne Pathogens In the Workplace Debra L. Hunt, Jerry J. Tulis, MD 3 Occupational Risk Assessment Prevalence and epidemiological studies indicate that occupational HIV infection seldom occurs. Documented HIV seroconversion due to exposures demonstrate that an occupational risk of HIV transmission exists. Factors that may contribute to the magnitude of that risk include the type and extent of injury, the body fluid involved, the “dose” of inoculum, environmental factors, and recipient susceptibility. The interactions and additive effect of these factors on the individual laboratory worker are complex and unknown. However, some data are available that can help further define risks associated with several procedures or circumstances. The type, extent, and frequency of occupational HIV-1 exposure are summarized in Table 20.2. Table 20.2. Summary of Published Prospective Studies of the Risk for Occupational HIV-1 Transmission in the Clinical Setting

Exposure Type Percutaneous Mucous membrane Cutaneous Routine patient care activities (no exposures) a

N N N Studiesa Exposures Infected 23 13 1 3

6202 1364 5568 929

20 1 0 0

Infection Rate (%) 0.32 0.07 0 0

Refer to text for references (N = number of).

3.1 Route and Extent of Exposure 3.1.1 Parenteral Of the 54 occupationally acquired HIV infections reported, 46 (85%) have been

associated with parenteral exposure (needlesticks, cut with contaminated objects, or nonintact skin exposure to blood) (4). In 1995, a case control study described risk factors associated with occupational HIV infection after percutaneous exposures in cases reported from national surveillance systems in the United States, France, Italy, and the United Kingdom (74). The findings indicate an increased risk for occupational infections following a percutaneous exposure if it involved a larger quantity of blood, such as a device visibly contaminated with the patient's blood, or a procedure that involved a large-gauge, hollow-bore needle, particularly if used for vascular access. Other factors associated with increased risk include a source patient in the terminal stage of illness and lack of zidovudine prophylaxis of the healthcare worker (discussed in more detail later). The best direct measure of risk of HIV transmission from a single exposure is accomplished through prospective cohort studies that document an HIV exposure event with follow-up serological monitoring of the exposed healthcare worker. In 23 prospective studies that have reported 6202 percutaneous exposures in healthcare workers, 20 instances of seroconversion have been documented, for an overall risk of transmission per percutaneous injury from an HIV-infected patient of 0.32% (66, 75–88). The risk of 0.3% is the average of all the types of percutaneous exposures to blood from patients in various stages of HIV infection. Certain factors, discussed below, contribute to a subset of exposures for which the risk is higher than 0.3%. There have been two cases of HIV transmission from bites reported (89, 90). Both indicated that blood was involved. In one case (90), the biter died of AIDS 13 days after the bite. 3.1.2 Mucous Membrane Four mucous membrane exposures resulting in HIV infection have been reported in healthcare workers (91, 92, 92a), although in both instances, nonintact skin contact with blood could not be ruled out as a route of exposure. One of them was a laboratory worker whose face was splattered with blood when a vacutainer top flew off the tube while she collected blood from a patient. She also reported having acne (91). Thirteen prospective studies have included mucous membrane exposures in their risk evaluations and have reported only one seroconversion from 1364 exposures (66, 75–77, 79–82, 84–87). Therefore, the risk of transmission of HIV via mucous membrane is extremely low (0.07%), much lower than that of a percutaneous injury: 1 TCID50 by intravenous injection were persistently infected for up to 18 months. Chimpanzees inoculated with low doses (0.1 TCID50) did not become infected, suggesting that immune systems can contain small inocula of virus. A large inoculum of HIV-infected blood such as a unit of transfused blood carries a higher likelihood of virus transmission. Donegan et al. (105) examined recipients of infected blood units with no other risk factors for HIV infection and found 89.5% were seropositive. Ho et al. (22) estimates that 250 mL of HIV-contaminated blood contains 104–106 TCID50 of HIV. In contrast, a much lower risk is associated with occupational exposures (0.3%) in which the amount of blood involved is unknown, but calculated by Ho to contain 0.06–7 TCID50 of HIV. A risk factor for occupational HIV infection identified by a CDC case control study (74) was injury with a large-gauge, hollow-bore needle, which may be directly associated with the amount of blood exposure. This is consistent with laboratory studies that have indicated that less blood is transferred by suture needles (solid bore) than by phlebotomy needles (hollow-bore) of similar diameter (106, 107). The concentration of virus in blood or body fluid is dependent on the stage of the patient's illness and the antiviral treatment of the patient (21, 22). In the CDC case control study of occupationally acquired HIV infections transmitted by percutaneous injury, a factor associated with increased risk of infection was exposure to a source patient in the terminal stage of illness (74), and may have a direct association with the amount or dose of virus present at the time of exposure. Saag et al. (21) evaluated the plasma viremia levels in patients infected with HIV and found that (1) none of the asymptomatic adults, (2) 12% of adults with AIDS-related complex, and (3) 93% of AIDS patients had cell-free infectious virus in their plasma. Titers of the virus ranged from 10 to 108 TCID/mL of plasma, with a mean of 102.8 TCID/mL in patients with AIDS. Patients with acute HIV infection had viral titers of 10–103 TCID/mL. Saag et al. (21) also found that therapy with zidovudine (AZT) led to a significant decline in titer. Ho et al. (22) found a 25-fold lower titer mean in AIDS patients treated with AZT versus untreated AIDS patients. Reverse transcriptase inhibitors, such as AZT, and protease inhibitors protect uninfected cells from becoming infected and, therefore, reduce the viral burden in patients' blood (108). Research or production laboratory workers, by the nature of the work performed, are placed at greater risk because of the high viral concentrations in culture (>108 TCID/mL). Published recommended barrier protection and precautions developed by NIH and CDC reduce worker exposure to high risk operations (6, 109, 110). 3.2.2 Specimen Age The length of time the blood has been removed from the source prior to exposure may also influence the number of infectious viruses present in the inoculum. Although most occupational infections have occurrred after exposure to “fresh” blood, HIV has demonstrated stability in the environment in both liquid and dry states (34), and may survive for hours to days at room temperature. 3.2.3 Other Other factors contributing to the overall risk of HIV transmission may include the virulence of the viral strain (111), post exposure first aid or prophylactic practices, or inflammation around the exposure site (numbers of CD4[plus ] cells available) (77). Other healthcare-worker-

related factors contributing to risk are skin integrity and immunological status (66). Pinto et al. (112) demonstrated that parenteral exposure to HIV can induce cell-mediated immune response in the absence of seroconversion. It is possible that this immune response is protective against a low HIV infection, and may contribute to the low infectivity rates of healthcare workers.

Bloodborne Pathogens In the Workplace Debra L. Hunt, Jerry J. Tulis, MD 4 Hepatitis Viruses At the time of writing, at least six viruses are known to cause hepatitis: hepatitis A, B, C, D, E, and G. Epidemiologically, the viruses can be divided into two groups according to mode of transmission. The hepatitis A and E viruses are transmitted primarily by the fecal–oral route. The hepatitis B, C, D, and G viruses are transmitted by direct contact with blood or body fluids. Hepatitis B and C viruses are frequently responsible for occupational infections. 4.1 Hepatitis B Virus (HBV) Hepatitis B virus is transmitted parenterally, sexually, and perinatally, and is the major cause, worldwide, of acute and chronic hepatitis, cirrhosis, and hepatocellular carcinoma. High risk groups in industrialized countries include intravenous drug users, homosexual men, and those with multiple sexual partners (113). Others at substantial risk of infection include hemodialysis patients, institutionalized patients, and healthcare workers with occupational exposure to blood (114). Healthcare personnel have been known to be at greater risk for HBV infection than the general population (115, 116). The incidence of clinical cases of hepatitis B in healthcare workers before the availability of the hepatitis B vaccine (i.e., before 1982) was reported to be between 50 and 120 per 100,000 (117, 118), much higher than that of the general population of 200 are all radioactive. Ultimately, radioactive decay reduces the ratio of neutrons to protons, but in chain decay there may be a temporary increase in the ratio due to electron emission. Alpha decay involves the emission of helium nuclei, each consisting of two protons and two neutrons. This reduces Z by 2 and A by 4. Beta decay is equivalent to converting a neutron to a proton, and it results in an increase in Z. The resulting nuclide may be stable or in a excited state which is relieved by the emission of a gamma ray. The energy of alpha radiation emitted by a given radionuclide is constant; usually, the shorter the half-life, the more energetic. However, beta rays are not monoenergetic but exhibit a spectrum of energies which is characteristic of the radionuclide. More unusual forms of decay involve (1) positron emission (positive electrons) which is the equivalent of converting a proton to a neutron, (2) electron capture with the apparent engulfment of a K orbital electron by the nucleus to convert a proton to a neutron and with the emission of a K electron X ray, (3) Auger electron emission which is the equivalent of electron capture where the fluorescent X ray itself is captured by an orbital electron which is then ejected from the M shell of the decayed atom. Both electron capture and Auger emission reduce the value of Z by one. Radionuclides undergo decay by a number of alternative pathways so that mixed forms of decay are frequent. The relative frequency and energies of gamma radiation constitute a signature that can be used to identify radionuclides by gamma spectroscopy. Radionuclides have the property of decaying on a probabilistic basis. Each radioactive atom has a 50% chance of decaying in a fixed period of time, called a “half-life.” In each successive half-life, the number of undecayed radioactive atoms is reduced by a factor of 2. Half-lives range from fractions of a second to billions of years. Most of the stable lead in the world came from the decay of

the uranium and thorium series. The parent isotopes, uranium-238 and thorium-232, have half-lives in the billions of years (9). Radioactive decay series involve two or more sequential decays before a stable isotope is reached. Starting with a pure sample of the parent isotope, the buildup and decay of the successive daughter isotopes can have complex patterns that are a function of their respective half-lives. These patterns are readily calculable by using partial differential (Bateman) equations. When a decay series reaches equilibrium, the decay rate (e.g., disintegrations/second) is equal for each member of the series; the number of radioactive atoms of each member is proportional to its half-life. The mean life of an isotope is 1.44 times its half-life. The mean life is useful for calculating the total number of atoms of an isotope at time zero; the number of atoms of an isotope is the disintegration rate (disintegrations/minute) multiplied by the mean life (in minutes). The dose rate from radionuclides deposited in the body decreases as the radioactive atoms decay and because the radionuclide is excreted. If the excretion is exponential, there is an “effective half-life” of the radionuclide in the body which is the product of the radiological and biological half-lives divided by their sum. For example, if the radiological and biological half-lives are each 2 hours, the effective half-life in hours 2 × 2/2 + 2 = 1. The original metric for radioactive decay rate was the curie (Ci) which is the number of disintegrations per second in a gram of radium-226. One Ci = 3.7 × 1010 d/s. One mCi = 3.7 × 107 d/s. One mCi = 3.7 × 104 d/s or 2.2 × 106 dpm. A more recent unit for radioactivity is the becquerel (Bq) which is 1 disintegration per second. Isotopes of a given element differ chemically only in atomic mass which affects the diffusion rate. The fissionable isotope, uranium-235, was isolated from its parent uranium-238 by gaseous diffusion despite the small mass differential; this was the essential step in the development of atomic energy. Biologically, the mass differences are significant only with the lightest elements. Significant diffusion differences exist between stable hydrogen and heavy hydrogen (deuterium) and tritium (hydrogen-3). Otherwise the behavior of radionuclides is essentially identical to the normal stable isotopes found in living organisms. This is the reason that they can be used as biological tracers. 2.5 Measurement of Radiation Many commercial instruments are used for measuring ionizing radiation, but the basic principles behind their operation are relatively few. Ionization devices depend on the ionization of air or other gases by radiation. One of the oldest instruments is the gold leaf electroscope, in which a strip of gold foil is hung over an insulated arm, forming two adjacent but connected leaves. The application of an electrostatic charge to the foil causes the leaves to fly apart where they remain until ionization of the air discharges them and causes them to fall toward each other. The extent to which they do so in a given time is a measure of the radiation dose. The loss of a static charge is the basis for the commonly used pocket dosimeters. Ionization chambers measure current flow from ionized gas in a voltage field applied to parallel conducting plates. A cascade of ions in a high-voltage field between a cylinder wall and a central electrode is the basis for the Geiger counter which records individual ionization as clicks or as current flow. Depending on the thickness of the walls of an ionization chamber, they can be adapted to measuring gamma rays, beta rays of different energies, or alpha particles. Photographic film responds to ionizing radiation much as it does to visible light. A piece of uranium ore unwittingly placed on a wrapped sheet of unexposed film led to the discovery of radioactive isotopes by Becquerel. Film packs are commonly used as personal dosimeters. Single crystals of sodium or cesium iodide are commonly used scintillation detectors. When struck by penetrating radiation, they emit a flash of light whose intensity is proportional to the energy of the radiation. Photomultiplier tube(s) placed against the scintillation detectors convert the flash of light into an electrical impulse whose size is proportional to the intensity of the flash. Scintillation

detectors count both the number and energy of the detected radiation, providing an energy spectrum that can be useful in identifying the radiation source, generally of gamma-emitting isotopes. These devices are used extensively for imaging in nuclear medicine by using multiple, small, columnated scintillation detectors for gamma radiation and for coincidence counting of positrons that annihilate to form 0.511 MeV gamma rays that are released back-to-back, 180° apart. Liquid scintillation counters are widely used to measure radionuclides whose radiations are too weak to penetrate the light seal around solid scintillation detectors. The radiation-emitting samples are suspended or dissolved in the fluorescent liquid. As with solid detectors, the intensity of the light signal can be used to count isotopes with different energies, such as tritium-3 and carbon-14, simultaneously. Thermoluminescent detectors, such as lithium fluoride pellets, store radiation energy during exposure; heating releases the stored energy in the form of light. The intensity of the light is a function of the amount of absorbed energy. Because of their small size, thermoluminescent dosimeters can be very useful in determining the dose distribution in tissue-equivalent phantoms that simulate the radiation of body parts.

Ionizing Radiation Roy E. Albert, MD 3 Radiation Damage at the Molecular Level The biological effects of radiation result principally from damage to DNA. Other molecules in the cell are also damaged but they are either present in large numbers or can easily be replaced. DNA may be damaged directly by deposition of ionizing energy within the molecule itself or indirectly by the diffusion of radiation-induced free radical ionization products of water into the DNA molecule. 3.1 Radiation Chemistry The radiative chemistry of water is extremely complicated (10). However, the most important sequence of reactions between water and radiation is the production of an ionized (charged) water radical, H2O+, which reacts with a normal water molecule to yield a free OH* (hydroxyl) radical. The hydroxyl radical accounts for most of the indirect radiative damage and has a lifetime of only about 10–5 seconds. Its short lifetime limits the diffusion distance to a cylinder of about twice the diameter of the DNA molecule. Hence, free water radicals have to be produced in the immediate vicinity of DNA molecules to do damage. About two-thirds of the radiation damage is indirect, caused by water radicals. Molecular radiation damage can be reversed by several mechanisms. Recombination of radicals and ions can occur before they diffuse apart, within the first 10–11 seconds. This is the coming together of the ion and radical pairs to produce the original molecule. A molecule such as DNA can be restituted by reaction of the free radical on DNA with a sulfhydryl molecule, yielding a sulfide radical and normal DNA.

The free radical on DNA is thereby transferred to the sulfhydryl moiety restoring the DNA to a normal state. Enzymatic repair, as discussed later, can also reconstitute DNA to its normal state. The OH* radical can react by extraction of hydrogen atoms as in

The OH* radical can undergo addition reactions as in

with the formation of a carbonium ion. Oxygen can play an important role in the fixation of radiation damage as in

This peroxidation radical is relatively stable and, more importantly, prevents chemical restitution. The presence of oxygen has a dramatic effect in increasing the biological damage from ionizing radiation, as discussed later. 3.2 DNA Damage Radiation of DNA can damage purine and pyrimidine bases, as well as the sugar backbone (11). The most important mode of radiative damage is to the sugar backbone and results in either single- or double-strand breaks. The single-strand breaks are repaired rapidly within a period of minutes and so efficiently that the DNA is restored to normal with a high degree of freedom from errors in the sequence of base pairs. Single-strand breaks undergo excision repair in which the gap is trimmed back and then reconstituted by polymerase enzymes using the intact strand as a template. Damaged bases per se are removed by glycoylase enzymes, and then the strand is reconstructed by an excision repair process. Double-strand breaks are much more serious because rejoining the broken ends can result in abnormalities of chromosomal structure. Double-strand breaks can be formed when two singlestrand breaks occur simultaneously from an ionization track or if the two single-strand breaks are formed sequentially within ten bases of each other in a period less than that required for repair. Double-strand breaks take hours to be rejoined. With low-LET radiation, single-strand breaks occur about one hundred times more frequently than double-strand breaks. Double-strand breaks are much more common with high-LET radiation. The principal form of nonlethal genetic damage caused by radiation is the loss (deletion) of chromosomal segments. Less important is single base pair damage that results in point mutations, that is, altered base sequences. One double-strand break on an unreplicated chromosome results in a broken arm that can rejoin (with some loss of DNA) or remain fragmented either in the form of a rod or, when the ends fuse, as a ring (12). Both the damaged chromosome and the fragment can replicate to form two short-arm chromosomes and acentric fragments. The acentric fragments remain in the parent cell, and the short-armed chromosome segregates into the parent and daughter cells. Two double-strand breaks on one arm of a prereplicated chromosome can lead to the displacement and loss of the segment between the breaks and also results in a short-armed chromosome and a fragment. Acentric fragments, those that have no centromeres, can become encapsulated in a membrane. Such structures are called microsomes and are useful quantitative markers for the action of genotoxic agents, including chemicals and radiation. The microsomes eventually disappear. When multiple double-strand breaks occur on different chromosomes in close proximity, rejoining can lead to a wide variety of chromosomal abnormalities. Lethal abnormalities include dicentric and ring lesions. Abnormalities that are not necessarily lethal include deletions and translocations. A double-strand break on each arm of two nearby unreplicated chromosomes can result in a translocation in which the chromosomal fragments switch places. Alternatively, the amputated arm of each unreplicated chromosome can anneal to form a single chromosome with two centromeres. The dicentric chromosome can replicate and become observable in metaphase preparations during

mitosis. If cells are irradiated after the chromosomes have replicated (during the G2 period) but before being separated during mitosis, a lethal lesion can be formed that is called an anaphase bridge. This is caused by a simultaneous break in the arms of the paired (replicated) chromosomes and subsequent annealing of the stumps. The parent and daughter cells cannot separate during anaphase because of the chromosomal bridge, and they die. These chromosomal abnormalities are important because they are a mechanism of cell killing and genotoxicity. They can be quantitated in metaphase spreads giving informative dose–response relationships. The shape of the dose–response curve for dicentrics and rings is linear-quadratic. At low doses, the curve is linear because some of the two double-strand breaks are produced simultaneously by a single ionization track. The quadratic higher dose portion of the curve is due to production of each of the two double-strand breaks by separate ionization tracks. Here the probability that two chromosomes are hit by separate tracks within a short time in about the same location is a function of the square of the dose. These relationships make it possible to reconstruct the radiation dose received by an individual by quantitating chromosomal abnormalities in circulating lymphocytes; some lymphocytes have a long residence time in the blood and can be stimulated to undergo cell replication.

Ionizing Radiation Roy E. Albert, MD 4 Radiation Effects at the Cellular Level Cell death is reproductive in nature. This means that cells die when they try to divide. This phenomenon was shown in the classic studies of Spear with X irradiation of fibroblast cultures (13). The number of mitotic cells falls promptly after radiation. The magnitude and duration of the decrease in mitosis increases with dose. The presence of necrotic cells first makes its appearance at about the time when there is recovery from mitotic depression. It follows that the first appearance of radiation damage is a function of the proliferative rate of tissues. For example, white blood cells have a rapid turnover of precursors in the bone marrow and a short life in the peripheral circulation. There is a prompt decrease in white blood cell counts shortly after radiation in contrast to red blood cells whose precursors have a slower reproductive rate in the marrow, and the red cells have a relatively long life in circulation. 4.1 Cell Survival Curves A great deal of quantitative information about reproductive cell killing, cellular repair, and dose– response relationships has been obtained by using the colony formation method developed by Puck (14). This approach involves dispersing cultured cells into single-cell suspensions. Aliquots are loaded into petrie dishes where they settle and attach. The petrie dishes may have a “feeder” layer of lethally irradiated cells that cannot multiply but are metabolically active and facilitate the growth of the single-cell aliquots. After attaching, the reproductively competent cells grow to form colonies several millimeters in diameter in a few weeks. Irradiation of the petrie dishes at the single-cell stage reduces the number of reproductively viable cells monotonically with increasing dose. Colony counts at two weeks give the fraction of cells, corrected for the plating efficiency of controls, that are rendered sterile. Those cells that are “reproductively dead” actually survive and multiply a few times but cannot form colonies. A plot of the log of the fraction of the plated cells, normalized to unity on the basis of the plating efficiency of the controls plotted against the dose on an arithmetic scale, gives a survival curve. The survival curve for high-LET radiation is exponential, a straight line on a semilog plot. The slope is a function of the sensitivity of the types of cells that are exposed to a given type of radiation. The slope is expressed as the D0 dose, a reduction of survival to 37% which is equivalent to an average of one “hit” per cell. Typical D0 values are on the order of 1–2 Gy.

The survival curves for low-LET radiation have a flat shoulder in the low-dose region, where relatively little cell killing occurs (15). At higher doses, the curves tend to become exponential, a straight line on a semilog plot. The shoulder reflects repair of the radiative damage. This can be shown by irradiating cells twice with an increasing amount of time between the two exposures. With increasing intervals and replating the cells soon after the second exposure, the shoulder reappears, growing from a small size to the magnitude encountered with single radiative exposures. The repair is complete in a few hours and likely represents the repair of single-strand breaks. After sufficient time for repair, the surviving cells behave as if they had not been previously irradiated. They show the same shoulder and the same survival slope as cells that are irradiated for the first time. This kind of radiative damage, called “sublethal” refers to damage that will be repaired unless additional radiation is administered before the repair period is over. The lack of a shoulder with high-LET radiation indicates that there is no repair, and the interval between split radiative exposures has no effect on the kinetics of survival. There is another kind of damage that is called “potentially lethal.” It is a form of damage that is inevitably lethal unless circumstances interfere with the progress of the cell cycle, as with confluent growth in tissue culture where cell-to-cell contact inhibits proliferation. Under these circumstances, the irradiated cells have a chance to recover somewhat from the potentially lethal damage, probably by repairing double-strand breaks. The repair of potentially lethal damage is considerably slower that of sublethal damage. Back-extrapolation (from high dose to low dose) of the exponential slope to a survival of unity gives a quasi-threshold measure of the width of the shoulder. This varies according to cell type by a factor of 2–3. Some survival curves with a “true” exponential high-dose region can be construed to reflect a multihit process; back-extrapolation of the linear slope to zero dose gives an intercept that can be interpreted as a “hit” number, the number of hits required to render the cell reproductively sterile. The magnitude of the hit number is also an indication of the size of the shoulder. Some survival curves show a gradually increasing slope without a convincing linear exponential portion. These curves are better interpreted as linear-quadratic in nature. There is a low-dose linear portion and a quadratic portion in the higher dose range. The equation for the linear quadratic dose response, where R is reproductive cell death, D is dose, and A and B are constants, is

This is the same equation used to describe the dose response for the induction of chromosomal damage discussed earlier, and the same interpretation holds that the cell killing has a single-hit component and a two-hit component. The linear and quadratic components of the cell killing are equal when the dose D is equal to the ratio of the constants A and B:

or

There is compelling evidence that cell death is a function of chromosomal damage, for example, in terms of a linear relationship between the number of chromosomal aberations (dicentrics and rings) per cell and the log of the cell survival. Other evidence includes cell lethality by tritiated thymidine which is incorporated in DNA and which irradiates only DNA, the increased sensitivity to cell killing by halogenated pyrimidines that are incorporated into DNA, etc.

Tissues of a given type tend to show a relatively narrow range of sensitivities. However, tumors that arise in a given tissue tend to show a broader range of radiosensitivities, some higher and others lower than normal but with considerable overlap. This is an impediment to effective radiative treatment. The kinetics of cell killing with the Puck technique have proved to be comparable to the kinetics observed in vivo. Estimates of cell survival in cancer radiotherapy have some utility. Because singlecell preparations from freshly excised tissue do not do well in the Puck technique, surrogates based on cell numbers in agar suspensions and total DNA content of tumors have been used as measures of reproductive survival. Radiotherapy involves repeated exposures at intervals that allow for repair in normal tissues. Survival curves for repeated irradiation are exponential without a shoulder because the cell killing from each radiative fraction combines with subsequent fractions multiplicatively. For example, four successive fractions, each reducing survival by a factor of 0.6 will combine to reduce survival to 0.6 × 0.6 × 0.6 × 0.6 = 0.13. This type of multiplicative interaction yields an exponential survival curve. Survival curves provide the basis for useful radiotherapeutic calculations. For example with a tumor of 109 cells, a 90% chance of cure would involve reducing the population by a factor of 10–10. This target would be achieved with an estimated dose of 69 Gy. This estimate is based on a survival curve without a shoulder, a D0 of 3 Gy and daily dose fractions of 2 Gy. A tenfold reduction in survival would be equal to 2.3 × D0. Therefore a dose required to reduce survival by ten orders of magnitude (D10) would be D10 = 2.3 × 3 = 6.9 Gy × 10 = 69 Gy. 4.2 Modifiers of Radiation Damage Survival curves provide a useful means of quantifying the effects of modifiers of radiation damage. For example, the oxygen effect increases the slope of the survival curve by a factor of about 2–4 from the hypoxic to the aerated state (16). The character of the survival curve stays the same, but the effect of oxygen is to decrease the dose by a constant factor for the same level of effect. This applies to both the high-dose quadratic and the low-dose linear portion of the survival curve, although the factor, called the “oxygen enhancement ratio” (OER), is 3.5 for the former and 2.5 for the latter. By contrast, the (OER) is smaller for the higher LET radiations. For example, for alpha radiation, it is 1.0 (no effect), and the OER is 1.6 for 15 MeV neutrons. Equal total doses given at low dose rates for low-LET radiation have a smaller effect than higher dose rates because the lower dose rates permit repair. This is not true for high-LET radiation. However, if the dose protraction becomes large, the mitotic cycle has an effect because different parts of the mitotic cycle have different radiosensitivities. The mitotic cycle has a quiescent phase, called G1, which, depending on the proliferative rate, can last for a matter of hours to weeks. Then cells given appropriate stimulation enter the phase of DNA replication, called the S period, which lasts on the order of ten hours. A short period, called G2, follows that lasts a few hours, in which the chromosomes condense. Finally the mitotic phase, called M, takes place which also lasts a few hours; here, the chromosomes line up at an equatorial plate and are pulled by spindle fibers to opposite sides of the cell which then divides in the middle to form two cells. Then the divided cells are either in the G1 phase, and the cycle repeats itself, or are in a G0 phase which is out of the cell cycle. The influence of the cell cycle on radiation sensitivity can be easily studied in tissue culture because cells in mitosis round up and are easily detached from the surface of the culture dish by gently agitating the medium. Then the harvest of synchronized mitotic cells can be studied by the Puck technique of colony formation after radiation. The pattern varies with cell type, but the constant feature is that the sensitivity is highest in the G2 and M phases and lowest at the end of the S period.

In some cell types sensitivity is increased at the begining of the G1 period as well (17). Radiative sensitivity, according to cell cycle, plays a role in the effects of dose rate on cell survival. The effect of dose rate on cell survival is complicated but predictable on the basis of what is known about the dynamics of DNA repair and the effects of the cell cycle on radiative sensitivity. When low-LET radiation is given in a short period at relatively high dose rates, the typical survival curve is obtained with its shoulder and high-dose exponential fall-off. As the dose rate is decreased, the first effect is an increase in the size of the shoulder and a more shallow exponential drop, that is, the D0 increases. This is due to the fact that DNA repair proceeds during the radiative exposure and nullifies some of its damaging effects. At this level of dose rate, cells are substantially arrested at the junction between G1 and S and between S and G2. The rate of mitosis is much depressed. The reason for the arrest at these checkpoints is the action of the p53 gene. DNA damage activates the p53 gene which then expresses more of its protein. The p53 protein interacts with proteins of related genes to activate the checkpoints that arrest the flow of cells through the mitotic cycle. The effect of this arrest is to give more time for DNA repair, which, if inadequate, triggers cell death by apoptosis. With a further lowering of dose rate, the checkpoint block is only partial, and cells move through the cycle into G2 and M, where they are more radiation sensitive. This reverses the trend toward shallower survival curves, and the slope of the survival curve increases toward those of the higher dose rates. As the dose rate further decreases, the flow of cells into mitoses is further increased toward normal, and cell proliferation counterbalances the losses due to reproductive death. This further decreases the slope of the survival curve, and it may be flat or have a positive slope indicating that the number of cells increases during radiation.

Ionizing Radiation Roy E. Albert, MD 5 Cell Survival in Tissues A number of assays have been developed to determine the survival of clonogenic cells in tissues. These cells include the skin, the villi of the small intestine, the testes, the tubules of the kidney, and cells of the bone marrow and thyroid. The skin assay depends on the formation of regenerating nodules on the skin surface arising from cells that have migrated upward from the underlying hair follicles that have survived the radiative exposure (18). The intestine assay examines the proportion of the villi that are regenerating after irradiation (19). The bone marrow assay looks at colony formation in the spleen after irradiated cells have been injected into the bloodstream and have been deposited there (20). The testes assay determines the proportion of tubules that contain spermatogenic epithelium (21). These assays are done with graded doses of single, multiple, or split exposures. The results of these studies resemble those with cell cultures in terms of a wide range of widths of the shoulders and fairly uniform high-dose slopes. Assays have been done on functional end points in contrast to cell survival. Typical of such studies are the effects of X rays on skin reactions in the mouse (erythema, desquamation, and ulceration) with single and fractionated exposures. It is evident that fractionation permits a great deal of radiative repair in the skin. As shown later, this holds true for skin carcinogenesis as well.

Ionizing Radiation Roy E. Albert, MD

6 Radiation Sensitivity According to Cell Type As early as 1906, Bergonie and Tribondeau (22) noted that different kinds of mammalian tissues have very different radiation sensitivities. The most sensitive were those that have a high mitotic rate, undergo many cell divisions, and are primitive in character, that is, are undifferentiated. Rubin and Casarett's categorization of types of cells according to decreasing levels of radiosensitivity is still used (23). Category I includes the most radiosensitive: these are cells like the basal cells of the epidermis that undergo regular cell division and show no differentiation between divisions. Category II cells are like myelocytes in the bone marrow that also divide regularly but do undergo some differentiation between divisions. Category III cells are relatively resistant like the hepatocytes in the liver that normally divide very infrequently but can be triggered into rapid mitosis. In the case of the liver, this occurs with toxic liver damage or partial hepatectomy. Category IV has the most resistant cells, including muscle cells and the neurons of the central nervous system. These cells are highly differentiated, and it is questionable that they divide at all once the organism reaches maturity. Cell death is reproductive in nature. It follows that the first appearance of radiation damage is a function of the proliferative rate of tissues. For example, white blood cells have a rapid turnover of precursors in the bone marrow and a short life in the peripheral circulation. There is a prompt decrease in white blood cell count shortly after radiation, in contrast to red blood cells whose precursors have a slower reproductive rate in the marrow, and the red cells have a relatively long life in the circulation (24).

Ionizing Radiation Roy E. Albert, MD 7 Chemicals that Modulate Radiation Effects Some chemicals increase and others decrease radiation effects. One class of chemicals that increases radiosensitivity is the halogenated pyrimidines, including 5-bromodeoxyuridine (BUdR) and 5iododeoxyuridine (IUdR) (25). The halogen is recognized as a methyl group, and these chemicals are treated metabolically as if they were thymidine and are incorporated into DNA. The DNA bonds are weaker with the halogen moieties, and radiation-induced strand breakage occurs more readily. The degree of incorporation is a function of the rate of cell proliferation. Therapeutic effectiveness for cancer depends on the relative rates of turnover of cancer cells compared to normal surrounding tissues. In cultured cells, the dose required to reduce survival to a given level of reproductive death is about one-half in halogenated pyrimidine treated cells compared to untreated cells. The use of these agents has received some clinical attention. There are chemicals that increase the radiation sensitivity of hypoxic cells but not those that are well oxygenated (26). Their potential use in cancer radiotherapy depends on the presence of hypoxic cells in tumors because such cells are relatively radioresistant. These chemicals belong to the class of nitroimidazoles such as etanidazole. They mimic the action of oxygen and fix radiative damage by preventing chemical restitution of the damaged molecules. They have an enhancement ratio of about 2. Their use is limited by neurotoxicity. They also sensitize cells to cancer chemotherapeutic drugs, particularly alkylating agents. Chemicals that decrease radiation effects are called radioprotectors. The sulfhydryl compounds are an important class of radioprotectors, including the natural amino acid cysteine and its metabolite cysteamine (27). The factor for dose reduction (the ratio of doses for equal effect) is about 2 for these compounds. They work by scavenging free radicals and promote chemical repair by restitution. Because of the short life of free radicals, the radio protector must be present at the time of irradiation. Their behavior with respect to LET is analogous to the oxygen effect, strong for the low-

LET radiations and minimal for the high-LET radiations. Like the oxygen effect, the maximum dose reduction factor would be 3. The nausea and vomiting produced by cysteine and cysteamine are reduced by covering the SH moiety with a phosphate. Such a compound is activated intracellularly by metabolic removal of the phosphate. The best of the synthetic compounds is WR2721 which is S(2-(3-amino propylamino)) ethylphosphothioic acid (28). Its effectiveness depends on penetration of cells. Its failure to protect the central nervous system is due to the blood–brain barrier. Radioprotective agents do not have important uses. For practical reasons they are of no help in radiation accidents, where the administration is necessarily delayed. Their use for anticipated exposure is limited by hypotensive toxicity. Use in cancer radiotherapy is problematic because benefit requires protection of normal tissues but not the tumor which cannot be readily determined except after the fact.

Ionizing Radiation Roy E. Albert, MD 8 Let and RBE As indicated earlier, gamma and X rays are sparsely ionizing; there is substantial separation of the ionization in tissue. Particulate radiation such as alphas, protons, and neutrons are densely ionizing because they produce dense columns of ionization (29). LET refers to the energy deposition per micron of path length. Typical values are 0.3 keV/mm for 1 MeV gamma rays, 2 keV/mm for 250 keV X rays and 100–2,000 keV/mm for heavy charged particles. The relative biological effect (RBE) is the ratio of doses for equal biological effect for a given type of radiation relative to the benchmark radiation of 250 keg X rays. RBE increases with LET to a peak of 100 keV/mm and decreases at higher LETs (30). The reason for this pattern is that at 100 keg/mm the average separation between ionizations is about 2 nm which is similar to the diameter of the DNA helix, thus maximizing the efficiency of a double-strand break. LETs less than 100 keg are more likely to produce single-strand breaks that are more readily repaired than double-strand breaks. LETs higher than 100 keg represent overkill for double-strand breaks and are less efficient and more wasteful of radiation dose. The RBE for high-LET radiation compared to low-LET radiation increases at lower doses because of the shoulder in the dose–response curve for low-LET radiation, whereas the high-LET radiation is linear. Hence, RBEs are not dose invariant. RBEs differ according to tissue type and tend to be higher where DNA repair is rapid for sublethal damage so that the shoulder on the dose–response curve is broad. The oxygen enhancement ratio (OER) is about 3 for low-LET radiation. It decreases when the LET reaches 30 keV/mm and reaches unity at 160 keV/mm (31).

Ionizing Radiation Roy E. Albert, MD 9 Whole Body Radiation Syndrome The duration of survival and the nature of the effects of brief whole body exposure to penetrating ionizing radiation is related to dose. Most of our information on the whole body radiation syndrome in humans has been the result of accidental nuclear criticality incidents and the study of atom bomb survivors (32). At the highest doses in the domain of ten thousand rads (100 gray), the reaction is immediate. One example is that of an individual who worked in a uranium-235 recovery plant. Uranium 235 is the fissionable isotope of the uranium-238 decay chain. Late Friday afternoon, he inadvertently poured a

container held under his left arm, filled with a solution of 235U-enriched uranium, into a barrel already containing a similar solution. He apparently lost track of how much fissionable material the barrel contained. The amount he added exceeded criticality. There was a blue flash as the liquid exploded, and he was drenched with the radioactive fluid. He immediately became disoriented. His coworkers did a partial decontamination. He was taken by ambulance to a series of hospitals which refused admission. An admitting hospital was finally located, and he was installed in an evacuated emergency ward, placed on a rubber sheet and further decontaminated by sponging with wet towels. During the night, his blood pressure dropped sufficiently to warrant continuous intravenous vasopressor medication. The next morning, his left arm and the left side of his face abruptly became severely edematous. In spite of the vasopressor medication, he went into irreversible shock and died that afternoon about 22 hours after exposure. This pattern is known as the central nervous system/cardiovascular syndrome. The disabling effect of high doses of radiation on the function of the nervous system was the basis for considering the wartime use of atomic weapons to disable pilots. The gastrointestinal syndrome predominates at doses of about 1000 rads (10 gray). It is expressed as a cholera-like syndrome that results from denuding the lining of the small intestine. Nausea and vomiting are immediate and intense. Diarrhea begins in a day or two. If not treated, the outcome is fatal in about 9 days. The reason for the GI syndrome is the radiosensitivity of the stem cells of the crypts of the intestinal villi. These villi are numerous finger-like projections of the intestinal mucosa that enormously increase the absorptive capacity of the small intestine. As the stem cells reproduce, the daughter cells move up the villi, undergo differentiation, and eventually slough off the tips of the villi. The proliferating stem cells at the base of the villi are more radiosensitive than the postmitotic cells on the villi. The effect of the radiation is to cut off the supply of new cells on the villi. After a number of days, the surface of the intestine is denuded. Transmucosal water transport is deranged, and fluids pour into the lumen of the intestine causing diarrhea which can be bloody. Supportive therapy with fluid replacement and antibiotics to restrain bacterial growth in the gut can be helpful but the damage at doses of 1000 rads or greater is too severe to permit survival. Death can supervene before the lethal consequences of hemopoietic damage take effect. The radiation dose required to kill half the population of humans (LD50) is about 400 rads if no medical treatment is used. With treatment by antibiotics and the use of sterilized environments, the LD50 is about 800 rads. The cause of death is the hemopoietic syndrome or bone marrow death. The mechanism is similar to the GI syndrome. The stem cells in the bone marrow are more radiosensitive than their differentiated offspring, and they stop replicating. There is a drop in the concentration of circulating blood cells which is a function of the life spans of the various types of blood cells. The drop in red blood cells is slow because of the 120-day life span of mature erythrocytes. Adult lymphocytes are unusual in being directly destroyed by radiation, and their disappearance from the blood is precipitous. Leukocytes and platelets fall in a matter of 2–3 weeks. When the concentration of leukocytes and platelets falls to critical levels, the irradiated individual develops infection particularly in the mouth and oropharynx and bleeding of the skin (petechia) and from the kidney into the urine. Transfusion of bone marrow cells has been used to treat the hemopoietic syndrome by replacing stem cells of the marrow. There is a relatively narrow window for success. Doses at or greater than 1000 rads are lethal because of the GI syndrome, and doses up to double the LD50, 800 rads, are recoverable with medical treatment. So the dose range where bone marrow transfusion is life-saving is between 800–1000 rads. The dosimetry of radiative accidents is generally uncertain, so the need for bone marrow transfusion is mostly with high-dose radiotherapy of disseminated cancer such as leukemia. The required bone marrow dose is on the order of 2 × 109 cells. Ancillary damage with the whole body radiation syndrome on the order of the LD50 is hair loss because of the relatively high sensitivity of cells in hair follicles. This sensitivity was the basis for

the Adamson–Keinbock method of depilation of the scalp by X radiation for treating scalp ringworm (Tinea capitis). Previous to this, the hair was pulled out manually to decontaminate the scalp of the fungus. Hair grew back in a few months.

Ionizing Radiation Roy E. Albert, MD 10 Heritable Effects As indicated earlier, ionizing radiation can produce genetic damage by chromosomal breakage or single base pair changes (point mutations). Classic studies by Muller in the 1920s on Drosophila demonstrated the linearity of the dose–response for mutations (33). There was no effect of dose rate or fractionation. Effects on the male gametes depend on the stage of sperm development, and mature sperm (spermatogonia) are the least sensitive, and dividing meiotic cells are eight times more sensitive. Oocytes are relatively insensitive. Concern about the applicability of these data to humans led to massive studies of millions of mice by the Russells at Oak Ridge (34). Using a number of specific traits such as various hair colors, they confirmed the linearity of the dose–response but found that, unlike Drosophila, there is a pronounced dose–rate effect that amounts to a reduction factor of 3 in dose for a given level of mutagenic effect. The female is so much less sensitive than the male that for practical purposes almost the entire burden of radiation-induced mutations falls on the male. It was found that a delay of a few months in conception after radiation in the mouse markedly reduced the number of mutations. Humans are advised to delay conception for 6 months after heavy radiation. This reduction is presumed to be due to a repair mechanism. Based on the mouse data, the estimated doubling dose in humans, the dose required to double the background incidence of mutations, is about 100 rads (1 gray) (35). Using a variety of indicators, the doubling dose in A-bomb survivors was in the same domain, about 156 rads although the data were not statistically significant (36). The ICRP uses an estimate of 0.6 × 10–4 per rem for radiationinduced hereditary disorders in a working population. The effect of radiation on the induction of congenital malformations is far more important than on heritable effects.

Ionizing Radiation Roy E. Albert, MD 11 In Utero Effects Radiation damage at the preimplantation stage leads to fetal death. In the period of organogenesis, radiation causes structural malformations. In the stage after organogenesis, called the period of fetal development, radiation causes growth retardation manifested by low birth weight which may or may not be reversible during childhood. The stages of preimplantation, organogenesis, and the fetal period corresponds to 0–9 days, 10 days to 6 weeks, and 6 weeks to term, respectively, in humans. All in utero effects are due to cell killing, abnormal differentiation, and impairment of cell migration in the brain (37). Irradiation during organogenesis in mice results in major malformations such as anencephaly, evisceration, and spinal bifida, as well as minor terata such as extra ribs. Humans are apparently not as susceptible as mice to the induction of malformations although some have been reported anecdotally from clinical experience. In the study of Japanese survivors of the A-bomb, growth

retardation, microcephaly, and mental retardation have been encountered (38). The occurrence of mental retardation peaked at 8–15 weeks (fetal age) of irradiation. There was a fairly linear dose– response relationship that reached 60% at doses in the range of 135 rads (39). Before and after this period of fetal development, radiation produced little mental retardation. Radiation before 8 weeks can lead to microcephaly without mental retardation. The dose response for mental retardation suggests a threshold at 25 rem. Minimal doses with effects on the embryo and fetus include oocyte death in primates (LD50 = 5 rads), CNS damage in mice at 10 rads, brain damage in rats at 6 rads, small head circumference in humans at 6 rads (38). The NCRP recommends that the maximum permissible dose during the entire gestation period in women should not exceed 0.5 rem and the monthly exposure should not exceed 0.05 rem (40). The data on mental retardation suggest that a reduction in IQ would be undetectable at 10 rads. Exposure of the conceptus/fetus during the period 10 days to 26 weeks, which is the period of sensitivity to malformations, reduction in head circumference, and mental retardation, to radiation above 10 rads should raise concern about the advisability of therapeutic abortion.

Ionizing Radiation Roy E. Albert, MD 12 Carcinogenesis Radiation is probably the most thoroughly studied of all known carcinogens in both animals and humans. The impetus for this effort stemmed from the frequent appearance of cancer in X ray pioneers at the beginning of this century, soon followed by the demonstration that radiation can induce cancer in animals. These findings made it clear that radiation is dangerous and that there is a need to protect the large numbers of individuals involved in the extensive use of radiation in medicine and in the atomic energy industry that was developed during and after World War II. Some generalizations can be made about radiation in relation to other carcinogens. Radiation can induce cancer in virtually every organ of mammalian species but not necessarily in the same species. It can induce cancer de novo in tissues that do not normally develop cancer, and can accelerate the spontaneous occurrence of cancer. The kinds of cancers that are induced by radiation do not differ from those that occur spontaneously or are induced by other carcinogens. This makes it difficult to detect small carcinogenic effects of radiation. Radiation behaves like other carcinogens. Higher doses elicit tumors faster than low doses. As with other carcinogens, there is a substantial delay from the onset of exposure to the induction of cancer by radiation. As with other carcinogens and with spontaneous cancer, the latency is a function of the life span of the species in which cancer is induced; the shorter the life span, the shorter the latency. Latency in humans is a matter of years and can range from a few years up to about 40 years, depending on the target organ and the level of exposure. For example, leukemia induction in Japanese atom bomb survivors began to appear in a few years, whereas excesses of solid tumors in this group did not begin to appear until several decades after exposure. Most cancers take on the order of 15 years to develop after the onset of exposure. Most cancers induced by radiation or chemicals, once started, continue to appear unabated over the lifetime. Leukemia induction by radiation is an exception because it peaked at 5 years. Among chemical carcinogens, bis-chloromethyl ether was also unusual in having a wave of tumor induction in humans. The cause of either the continuous or limited response pattern is not known. All of the types of radiation can produce cancer if they penetrate to the target cells of the target organ. Generally, high-LET radiations have a linear dose–response pattern, whereas low-LET radiations generally have a linear quadratic shape. This makes the RBE of high-LET radiation

greater in the low-dose range. Radiation can induce cancer by external exposure or internal exposure from implanted isotopic sources or from inhaled or ingested radioactive isotopes. The mechanism of action of radiation is similar to that of chemical carcinogens in their ability to damage DNA with the activation of oncogenes or the deactivation of tumor suppressor genes. The former involves a “single hit” process. Activation of an oncogene on one allele is tumorigenically sufficient. By contrast, it is necessary to deactivate both alleles of tumor suppressor genes to induce cancer most effectively. Radiation interacts with other environmental carcinogens. For example the interaction between irradiation of the lung by radon and cigarette smoking is multiplicative and therefore far larger than the effects of either agent separately. The induction of cancer by radiation is similar to other biological effects in terms of the importance of repair processes. Generally, there is a comparable reduction in the effectiveness of cell killing and tumorigenesis by low-LET radiation with split-dose or low-dose rate exposures. No such effects occur with high-LET radiation. There are exceptions to this generalization such as the more efficient induction of lymphoma by split X ray doses in mice (41) and increased cell killing and tumorigenesis with neutron radiation. Radiation is unusual among carcinogens in that a single dose can induce cancer, whereas with chemical carcinogens, repeated doses are required to induce tumors. Tissue damage is a common accompaniment to the induction of malignancy. Although these generalizations are valid, they do not give the flavor of the complexity of tumor induction in individual tissues, different species, and by different kinds of radiation. We illustrate the point by considering skin cancer induced by radiation in the rat, compared with the mouse and humans. 12.1 Skin Tumorigenesis With single beta-ray exposures of the back of the rat, radiation induces a wide variety of tumor types, most of which resemble the differentiation patterns of various parts of the hair follicle: the sebaceous glands, the external sheath, the hair germ, and the squamous keratinization pattern (squamous carcinomas) of the upper part of the hair follicle or the surface epidermis (42). There are also tumors whose cells are undifferentiated that arise from the hair follicles and from the surface epithelium. All of these tumor types are seen in humans, but with radiation of the scalp most of the tumors are of the basal cell variety; squamous carcinomas arise from irradiation of relatively nonhaired parts like the hands. Squamous tumors are the only type induced in the mouse skin with radiation (43). Skin tumors in the mouse therefore have a more limited range of differentiation than in either the rat or human. The dose–response pattern in the rat does not fit any simple formulation, linear quadratic or dose square. The dose–response has a sigmoid shape with a sharp peak and a rapid fall with further increases in dose. The fall is associated loss of viable skin due to increasingly severe and extensive ulceration with progressively narrower scars. The tumor types also change with increasing dose. Hair follicle tumors are not formed in the ulcerating dose range, only squamous carcinomas. The growth rate of the tumors increases with dose even among the squamous carcinomas. In the high-dose range, the rats generally carry one or two large squamous carcinomas on their backs. In the lowest tumorigenic dose range, all of the tumors are sebaceous cysts that look like clusters of mature sebaceous glands. The clumps of overreplicated sebaceous glands are nodular. These quasi-tumors give way at higher doses to the less differentiated hair follicle and squamous tumors. Hence, this rat skin model is not consistent with the stochastic concept of carcinogenesis, namely, that malignancy is independent of dose, that is, only the incidence is a function of dose. Similarly, in the harderian gland tumor model, the lesions are more benign at low dosage, although of the same histological type (44). The relationship of dose to malignancy is insufficiently studied in the field of both radiation and chemical carcinogenesis. Its importance relates to the cancer risks of low levels of

exposure to carcinogens. The hair follicle tumors in the rat can be seen histologically to arise from atrophic hair follicles at a ratio of about one tumor per 2000 atrophic follicles. The follicles are completely eliminated at higher doses where the tumor type is limited to squamous lesions. This suggests that the differentiation pattern of tumors reflects that of the surviving cells. The shapes of the dose–response for tumors and hair follicle damage are very similar. The both have the typical sigmoid shape of toxic responses. The mouse is different from the rat. With increasing dose, the hair follicles survive intact up to the point where they are obliterated completely. There is no intermediate form of partially killed (atrophic) follicles. This is apparently the reason that the mouse does not develop hair follicle tumors. The tumor induction in the mouse appears at dose levels that eliminate hair follicles. Chemical carcinogens show a different response pattern in the rat, as illustrated by a study with the polycyclic aromatic carcinogen, anthramine. No hair follicle killing was observed, but there was a profuse yield of hair follicle tumors and squamous tumors. Thus, the association of hair follicle atrophy would seem to rest on the similarity of the dose response for cell killing and malignant cell transformation, not the role of tissue damage in the cause or enhancement (promotion) of tumor induction (R.E. Albert, personal communication). The skin is markedly sensitive to the depth of penetration of radiation (45). This was first noted with proton irradiation of rat skin where doses up to 10,000 rads to the skin surface produced no tumors. The penetration of the proton radiation was only about 200 microns. Subsequent studies showed that with electron radiation, tumor formation increased for equal surface doses when the penetration of the radiation was increased by increasing the energy of the electrons. Subsequent studies showed that the effects of penetration depth could be reconciled by relating the tumor responses to the dose at a depth of 330 microns in the skin. This is the location of the hair follicle bulge region that contains the stem cells for the hair follicles. Thus, the tumor response is related only to the dose to the stem cells. This finding has subsequently been confirmed by studies of chemical carcinogenesis. It is now commonly assumed that the target cells for tumor induction in every tissue are its stem cells. Split doses with low-LET radiation showed dramatic reductions in tumor formation indicating the importance of repair processes. Increasing the intervals between the two doses from 1 to 24 hours demonstrated that the repair has a half-life of about 2 hours (46). This is consistent with the time required to repair double-strand breaks in DNA, suggesting that the dominant process in skin tumorigenesis is chromosomal damage. Skin exposed to high-LET radiation such as acceleratorproduced argon nuclei showed no repair with split doses. Apparently, the amount of damage to DNA by high-LET radiation is too great to repair. The characteristics of tumors are so closely linked with those of the parent tissues that cancer is frequently considered a collection of individual diseases that have some features in common. Although this is an exaggerated idea, it conveys the point that extrapolation of carcinogen-induced responses of one tissue to another should be done with circumspection. 12.2 Epidemiological Studies Many epidemiological studies have been done to characterize the nature and magnitude of the carcinogenic effects of radiation in humans (47). These populations include Japanese atom bomb survivors and patients treated by X radiation for ankylosing spondylitis, acute mastitis of the breast, tinea capitis infection, and thymic enlargement in infants. Follow-up studies have been done on children whose mothers were given X-ray pelvimetry when they were in utero, as well as women who had repeated fluoroscopic examinations for tuberculosis in relation to their breast cancer experience. Studies have been done on uranium miners and miners of other ores that are contaminated with uranium to determine the effect of radon exposure on lung cancer induction. Women who were occupationally exposed to radium were studied for bone cancer, and a number of studies have been done on radiation workers in the atomic energy industry to determine their cancer experience at low levels of exposure.

Only a relatively few studies characterize dose–response relationships in radiation-induced cancer in humans. The rest are useful for giving estimates of risk at one specific dose level. Two approaches have been used to characterize cancer incidence or death rates in epidemiological studies. One method is to subtract background cancer from the observed response and to regard the excess as the radiation effect. This is known as the “absolute risk” model. The underlying idea is that the radiation effect is independent of whatever it is that causes background cancer. The alternative method is the “relative risk” model which regards radiation as interacting with whatever it is that causes background cancer. This approach is similar to the doubling dose concept mentioned above in the context of the mutagenic response to radiation. Experience with a wide variety of radiation cancer responses tends to support the use of the relative risk model, although not exclusively. The kinds of tumor studies that provide dose–response relationships include leukemia, breast cancer, lung cancer from radon and bone cancer from radium. Leukemia induction has been studied mainly in two populations: atomic bomb survivors in Japan and patients with ankylosing spondylitis, a form of rheumatoid arthritis of the spine, which is treated with X radiation. A wave pattern of leukemia was found in both studies. Leukemia in the Japanese peaked at 10 years after exposure and declined thereafter without returning to normal. The same was true for the spondylitics, except that leukemia began earlier at about 2 years postexposure. Japanese up to 20 years of age at the time of irradiation showed an earlier peak than those over 20 years of age at irradiation with a more rapid decline, so that the overall risk was about the same. The dose– response in the Japanese for leukemia is consistent with a linear nonthreshold pattern with the lowest dose at 40 rem and a peak induction at 300–400 rem. Above this dose range, the incidence declines with increasing dose presumably due to the killing of potentially leukemogenic cells. The relative excess risk was 4.2–5.2. No excess cases of chronic lymphocytic leukemia were observed. The effect was limited mainly to acute and chronic myelogenous leukemia. The leukemia risks in the spondylitics were considerably lower than in the Japanese presumably due to the partial bone marrow exposure, because the radiation was centered over the spine, the radiation was more protracted, and the population was older. The effect of radiation in inducing breast cancer in women has been studied in Japanese atom bomb survivors, tuberculosis cases that were repeatedly fluoroscoped, and cases of X-irradiated postpartum mastitis. These studies have all shown low-dose linearity of cancer induction. There was no effect of fractionation on the cancer response. The cancer risk was highest in women who were less than 20 at the time of radiation; those over 40 showed no increase in the incidence of cancer. The latency of breast cancer was about 10 years with a peak incidence at 15–20 years after exposure and a peak in mortality about 5 years later. There was no effect of dose on latency. Whether this was due to the relatively short period of exposure is not clear. Short periods of exposure in animals do not show much of a dose effect on latency, compared to chronic lifetime exposure. Lung cancer has been studied mainly in Japanese atom bomb survivors and uranium miners, as well as in ankylosing spondylitics. There are dose–response data only for the uranium and other underground miners exposed to radon. Here again the dose–response is consistent with a linear nonthreshold character (48). It is apparent that most of the data on dose–response relationships is linear, suggesting that there is no level of exposure that does not have an associated cancer risk. However, in all of these cases the lowest doses are substantial, for example, 40 rem in the Japanese leukemia data. Hence for radiation protection purposes, it is assumed that the radiative dose response is linear nonthreshold. A considerable body of information has been accumulated on cancer risks in the absence of dose– response data. There is considerable variation in the radiosensitivity among the various organs, on the order of a factor of 7 at the extremes (47).

Ionizing Radiation Roy E. Albert, MD 13 Cataracts of the Optic Lens One of the important nonstochastic late effects of ionizing radiation is damage to the lens of the eye (49). The lens is an onion-structured epithelial tissue located inside a fibrous capsule that is situated immediately behind the pupil. The epithelial cells constitute the outer anterior layer. They divide near the equator of the lens. The replicated cells are displaced inward where they flatten and become transparent fibers. There is no mechanism for removing damaged cells. When the proliferating cells are damaged by radiation, they migrate as opaque granules to the posterior surface of the lens. If the amount of damage is mild as with scattered radiation to the eyeball from tinea capitis radiation, where the dose was about 50 rads, the only observed effect was scattered posterior granules. These had no effect on eyesight. Furthermore, the damage was not progressive (50, 51). The threshold for sight-impairing cataracts is on the order of 250 rads. Doses of this magnitude and greater produce more extensive opacities on the posterior face of the lens which can become progressive to the point of obscuring eyesight. The experience with radiation-induced cataracts has been largely with the untoward effects of radiation therapy. Workers around accelerators in the early days were particularly at risk for cataracts because of the high RBE of neutrons (52). The dose response in mice for neutron radiation is linear, unlike that from low-LET radiation. The RBE at high doses is on the order of 10. At low doses, the RBE is in the range of 50. In humans, the time for developing cataracts depends on the dose and can range from months to decades. The latency is on the order of 8 years for doses between 250 and 650 rads. The reason for the long delay and the progressive nature of some cataracts is not clear. Presumably, it has to do with the delays associated with reproductive cell death, where consecutive normal cell replications can occur before cell death supervenes; the slowly accumulating cellular debris is undoubtedly a factor. 13.1 Other Late Nonstochastic Tissue Effects Late irreversible and progressive damage to tissues results from clonal depletion of tissue cells with particular reference to blood vessels (53). This process leads to fibrosis and circulatory insufficiency. Depletion of cells can occur in terms of functional subunits, such as, kidney nephrons. Damage to the vasculature can occur at the level of both the larger vessels and the microcirculation. An example of the former is the case of accidental radiation of the lower extremities from cyclotron-produced X rays. This resulted in progressive sclerosis of the major arteries in the lower extremities requiring amputation about 6 months after exposure. Other examples of late damage include fibrosis and stenosis of the esophagus, fibrous atrophy of the stomach and intestinal mucosa, atrophy of the epidermis of the skin and permanent loss of hair follicles, fibrosis of the lung, and necrosis of the brain. Fractionation and dose protraction generally reduce the effectiveness of low-LET radiation in inducting late tissue damage.

Ionizing Radiation Roy E. Albert, MD 14 Health Effects of Radionuclides The health significance of radionuclides lies in their ability to enter the body where their biological

behavior is determined by their chemical properties and their radioactive properties allow them to irradiate tissues in which they localize. Thus alpha- and low energy beta-emitting isotopes, which are essentially innocuous outside the body, can produce radiation damage when taken into the body. The two principle routes of exposure to nuclides are inhalation and ingestion. If the inhaled particles are soluble, they are absorbed promptly from the lung and distributed in the body according to their chemical properties. If insoluble, the particles deposited on the bronchial mucosa are swept out of the lung by ciliary action and swallowed. The particles that are deposited in the air spaces of the lung (alveoli) can remain there for long periods of time if they are sufficiently insoluble, such as thorium dioxide which has a half-life of years. Such particles can be slowly relocated to the pulmonary lymph nodes. Particles that are ingested or swallowed after inhalation can be absorbed from the gut and distributed in the body. Some chemicals such as the actinides, thorium and plutonium, are not absorbed regardless of their solubility. Of the hundreds of radionuclides only relatively few constitute a source of health concern. 14.1 Nuclear Fission Products The enormous number of nuclear fragments resulting from the fission of nuclear materials in bombs and fuels in nuclear reactors constitutes a potentially dangerous radioactive source of external and internal exposure. Large-scale release of fission products such as happened at Chernobyl (54) can make large geographic areas uninhabitable for years and is one of the deadliest consequences of nuclear war or reactor accidents. The decay of fission isotopes follows a log-log pattern with a rapid initial disappearance of short-lived isotopes and slower disappearance of the residual long-lived isotopes. Yet the quantities of isotopes are so large in nuclear fuels that liquid storage in tanks requires refrigeration to prevent their boiling and exploding. The core of the earth is molten because of heat from the decay of uranium and thorium. Fallout from atomic weapons testing in this country resulted in the dissemination of two important isotopic health hazards: iodine-131 and strontium-90; these are cancer hazards for the thyroid gland and bone, respectively. 14.2 Radium-226 Radium-226 is one of the elements in the decay chain of the naturally occurring uranium-238 decay chain. Radium-226 has a half-life of 1600 years and decays to the gas Radon-222, and then to a series of bismuth, polonium, and lead isotopes to stable lead (55). Young women painted aircraft instrument dials with luminous paint that contained mainly radium-226 mixed with a phosphor so that the dials would glow in the dark. To paint thin lines, the women tipped the brushes with their tongues and thereby ingested substantial amounts of radium (55). Metabolically, radium behaves like calcium, and the major site of deposition was in the calcified parts of the bone. Radiation, primarily from the alpha rays, heavily damaged the bone and caused cancer in skeletal and nasal sinuses of the most heavily exposed individuals. Follow-up studies were done on many of the women involving evaluation of the skeletal burdens by measuring radon in exhaled air and direct measurement of the skeletel radium-226 in whole body counters. These coumters are steel chambers on the order of 6 inches thick that reduced the ambient background to very low levels and permit measuring the gamma rays from radium-226 with large sodium iodide scintillation detectors. By following the urinary excretion of radium and successive whole body counts, the effective disappearance of radium from the body was determined to be a log-log function, and back-extrapolation gave the initial body burdens. The exposure standard for radium-226 was set at 0.1 mCi because no evidence of bone cancer was seen at this level of exposure. The dose–response curve for bone cancer looks like a threshold response (56). When it became evident that strontium-90 from atomic weapons tests was widely disseminated in the environment and from there into milk via grazing cattle, great efforts were made to formulate standards of exposure in relation to radium-226. This was done by comparing skeletal cancer induction by radium-226 with strontium-90 in dogs. It was felt that the dosimetry of these bone-seeking isotopes was too complex to rely on comparisons of the isotopes in terms of absorbed dose. The distribution of the radionuclides was spotty in the bone and partially buried in the calcium matrix, and there was uncertainty about which cells were the targets for cancer induction. Hence the comparison was based on skeletal burdens in relation to tumor induction.

Another isotope of radium, radium-224 (thorium X), a 3.6-day half-life, alpha emitter has been used to treat children with tuberculosis and ankylosing spondylitis. Bone tumors (osteosarcomas) were induced with appearance times of 3–22 years after the initial injection (57). 14.3 Plutonium-239 and Plutonium-238 Plutonium-239 and Plutonium-238 are alpha-emitting man-made elements (48). Plutonium-239 has a half-life of 24,400 years and is the principle fissionable material in atomic weapons. Plutonium 238 has a half-life of 86 years, is intensely radioactive, and is used mainly as a heat source to power thermoelectric devices such as cardiac pacemakers and batteries for use in space vehicles. Plutonium localizes principally in the liver and skeleton. Like other actinides (thorium), plutonium is taken up on the trabecular and periosteal bone surfaces not in the calcium matrix like radium and strontium. In the bone, plutonium is in relatively close proximity to cancer-inducing target cells and is a formidable bone carcinogen. Both the GI tract and the skin are impermeable even to the soluble forms of plutonium, except for penetrating wounds of the skin, and the main route of exposure is by inhalation. The residence time of insoluble forms of plutonium in the lung is a matter of years, a half-life of 1500 days. With high levels of exposure in dogs, there is induction of pneumonitis, followed by pulmonary fibrosis and lung cancer. With inhalation exposure to soluble plutonium, there is rapid redistribution to the liver and skeleton and induction of cancer in both organs. Although five thousand to ten thousand people have been exposed to plutonium in the atomic energy industry, the levels have not been sufficient to cause perceptible injury to date. 14.4 Iodine-131 Iodine-131 is a beta-gamma emitting fission-product isotope with a half-life of 8 days that attracted a great deal of attention because of its wide dissemination via milk from atomic weapons testing (58). Even with atmospheric tests of atomic weapons as far away as the USSR, iodine-131 was easily measured in the thyroid glands of children living on the east coast of the United States. Like strontium-90, iodine-131 posed a cancer threat to children. Iodine is a component of the thyroid hormone and is concentrated in the thyroid. Thyroid uptake of radioiodine, as measured by external gamma-ray counting, is used as a diagnostic test of thyroid function. Its localization in the thyroid gland is also the basis for treating hyperthyroidism by destroying thyroid tissue to reduce the production of thyroid hormone. Thyroid tumors can be induced by ionizing radiation, especially in children. This was shown in children whose thyroid glands were exposed in association with irradiation of the thymus gland as infants (59). External exposures of the thyroid gland at doses as low as 5–10 rads in children who were treated by X radiation for ringworm of the scalp showed in the induction of thyroid adenomas and carcinomas (60). However, equivalent average doses of radiation from iodine-131 have not produced tumors of the thyroid gland. This apparent discrepancy may be due to inaccurate dosimetry because some of the beta radiation is lost to the gland when deposited in its outer portions, and much of the radioiodine is in the inert colloid storage areas in the gland where some of the radiation is absorbed. However, there is no question that radioactive iodine can produce cancer of the thyroid gland as evidenced by the study of populations exposed to radioactive fallout in the Marshall Islands and in the USSR from the Chernobyl release. 14.5 Radon-222 Radon-222 and its decay products are the most important radiation hazard to the lungs (61). It was the cause of a mysterious illness known since the Middle Ages as “mountain sickness” among miners in the central European silver mines of Jochimsthal and Schneeberg. The disease was identified as lung cancer only in the 1920s. Since then lung cancer has occurred among domestic uranium miners, Chinese tin miners, and other types of miners of different countries where significant amounts of radon occur. Radon-222 has a half life of 3.82 days and is the immediate gaseous decay product of radium-226. In turn, it decays through eight daughters of bismuth, polonium, and lead to reach the stable isotope, lead-206. The series has an effective half-life of about 30 minutes down to the sixth daughter, Lead210, which has a half-life of 22 years and effectively stops radiation in the lung. The series is a

composite of alpha and beta emitters but the alpha radiation accounts for most of the dose. Radon itself, distributes throughout the body and localizes in fat; its dose in the lung is unimportant compared to the radiation dose to the mucosa of the lung from the daughters. Radon decay products are solids and when formed in the air, attach to a considerable extent to smaller airborne particles. The deposition pattern in the lung follows that of the particles to which the daughters are attached except for those that are unattached ions. The ions have a high velocity in air and plate out in the upper part of the respiratory tract, whereas those that are attached to small particles tend to deposit deeper in the lung in the lower part of the tracheobronchial tree and in the alveoli. Once deposited on the bronchial mucosa, the radon daughters are entrained in the mucus layer that coats the mucosa which is propelled by the beating of the mucosal cilia toward the top of the trachea from whence they are swallowed. The daughters are presumably mixed in with the mucus as it is being transported. The alpha particles are the most important component of the radiation, but their penetration is limited to about 70 microns which barely reaches the basal cells of the mucosa; these cells seem to be the target cells for cancer induction, but this is not known for sure. Inhalation of the analog of radon-222 daughters, namely, the gamma-emitting daughters of thoron-220 which have an effective half-life of 10 hours, did not show any clearance from the lung at all (62). It was not possible with the scintillation counting equipment available at the time to determine whether there was any redistribution in the bronchial tree. It is evident that the dosimetry of radon daughters is complex and uncertain. Of environmental importance is the fact that some homes are situated on radium-rich soils which emit substantial amounts of radon gas into the homes. Using a linear dose–response model based on the radon cancer data in mines and extrapolating the risk to homes, it can be estimated that at the average indoor radon levels of about 15 Bq/m3 (0.1–0.2 WLM), about 5–10% of the total lung cancer incidence can be attributed to radon. In homes on radium-rich soils, where the radon concentration can be 20 times higher, close to 50% of the total lung cancer incidence can be attributed to radon (63). The presumed factor of the greater susceptibility of children to the carcinogenic effects of radiation lends concern to these estimates. However, the dosimetry of radon in mines is crude, and there is evidence for a strong interaction with cigarette smoking in the miners which is applicable to children only in terms of passive exposure to cigarette smoke in the households of smokers.

Ionizing Radiation Roy E. Albert, MD 15 Background Radiation Background radiation occurs from sources external to and within the body. External sources include cosmic radiation and gamma radiation from uranium and thorium decay chains in soil, rocks, and building material. Radiation from within the body arises from naturally occurring radionuclides, mainly potassium-40. Naturally occurring radioactive isotopes that originate outside the body and enter the body include the gas, radon, and its decay products that arise from radium-226 deposits in soil that are inhaled and carbon-14 which is produced by the interaction of cosmic radiation in the atmosphere. Another source of background radiation stems from the diagnostic and therapeutic uses of radiation. The effective dose from background sources is the dose in rads (or grays) multiplied by the radiative weighting factor, which is 20 for alpha particles emitted by radon daughters and multiplied by the tissue weighting factor which is 0.12 for the lungs. The annual effective dose to the U.S. population is about 646 millirems of which more than half comes from radon (55%); a total of 82% comes from natural sources: cosmic (8%), terrestrial (8%), and internal (11%). Man-made sources (18%) include

medical X rays (11%), nuclear medicine (4%), and consumer products (3%). Less than 1% comes from other sources, including occupational exposure (0.3%) (64). The intensity of cosmic radiation is a function of altitude. Radiation in Denver is about twice that of regions at sea level. There are regions of high radiative background on the Colorado Plateau because of the high content of uranium and thorium in the soil and rocks. A number of places around the world have high backgrounds for similar reasons. For example, in Kerala, India, the background is triple that in the United States at 1.3 rem/year. There has been a lack of perceptible increases in cancer or severe heritable defects in such areas, lending credence to the position that restricting excess radiation exposures to levels that are double the background level will ensure that no “detectable” harm will be suffered.

Ionizing Radiation Roy E. Albert, MD 16 Radiation Protection Historically, occupational standards were developed separately for radon-222, radium-226, and for whole body exposure. 16.1.1 Radon-222 Setting a standard for radon-222 to prevent lung cancer is complicated by the fact that radon-222 rarely exists in equilibrium with its daughters. The difficulty was circumvented by using, as a unit of radon activity, the Working Level (WL), defined as any combination of radon daughters in one liter of air that releases 1.3 × 105 MeV of alpha energy. This is equivalent to 100 pCi per liter of radon222 in equilibrium with its daughters. A pCi is 10–12 Ci. A Ci is 3.7 × 1010 disintegrations per second (d/s). Therefore 100 pCi is 3.7 d/s for each of the isotopes in the decay chain. Most of the dose to the tracheobronchial mucosa comes from the alpha-emitting isotopes, polonium-218 (Ra A) and polonium-214 (Ra C'). When the disintegration rate equivalent to one WL continues for a working month, which is 170 hours, the cumulative exposure is called a Working Level Month (WLM). So far as the tracheobronchial mucosa is concerned, a WLM is a total dose from about 1.5 × 107 disintegrations of Ra A and Ra C'. This number of disintegrations can occur during any period of time, for example, a year. The dose to the bronchial epithelium is 0.2 mrem/year per pCi/L using a radiation weighting factor of 20. The occupational standard for radon-222 is 4 WLM per year. This is equivalent to a bronchial dose of 80 rem/year (65). Radon in homes in the United States averages from 0.5–1.6 pCi/L and 2.7 pCi/L in Scandinavia. The U.S.EPA has set an “action level at 4 pCi/L suggesting that remedial action should be taken at levels higher than this. This affects 1 in 12 homes in the United States, a total of about 6 million. The action levels in Europe are 2 to 5 times higher. The EPA action level of 4 pCi/L is 100 times lower than the occupational standard. This action level translates into an effective dose of 0.8 rem/year and a cancer risk of 4 × 10–4/year. Despite the complexity and uncertainty of the lung dosimetry, these crude dose estimates for the occupational standard are far higher than those permitted for external exposure. The bronchial dose associated with the EPA action level for background radon exposure is far higher than the background exposure from other sources. 16.1.2 Radium-226 A standard for radium-226 was based on studies of radium dial workers. The standard is a maximum body burden of 0.1 mCi. This value was picked because at that body burden, no cases of bone cancer were observed. Subsequently, the standards for other bone-seeking isotopes were derived mainly from dog studies that compared the potency of radium-226 with strontium-90 and plutonium-239. The dosimetry of radioisotopes in bone is so complex that the standards were based on skeletal burdens rather than on dose estimates. 16.1.3 External Radiation Standards

External radiation standards were originally focused on preventing acute responses, first skin erythema in the 1920s. Later, with higher energy X-ray machines, the concern shifted to deeper tissues, particularly the bone marrow, as manifested by depressed white blood counts. Subsequently there was a shift to preventing more sensitive responses, namely, cancer and mutations. Today, standards are based largely on preventing cancer. All of these changes were accompanied by progressively lower standards. As indicated earlier, the absorbed dose is absorbed energy per gram of tissue (100 ergs/gram). The absorbed dose is expressed in rads or Grays (Gy = 100 rads). The radiation weighting factor (Wr) is based on the RBE combined with judgment factors about the relative effectiveness of different kinds of radiation at low doses. The radiation weighting factor converts the absorbed dose to equivalent dose measured in rems or sieverts (Sv = 100 rems). The radiation weighting factor for gamma rays and electrons = 1; protons = 5; alpha particles, fission fragments and heavy nuclei = 20; neutrons = 5–20, depending on energy (66). The concept of effective dose is used for stochastic effects (cancer and hereditary effects) with uniform whole-body radiation. It is a measure of the total harm that can be ascribed to the sum of the deleterious effects on individual organs. Therefore, effective dose is the sum of the equivalent dose multiplied by the tissue weighting factor (WT) for each organ. WT = 0.20 for the gonads; 0.12, for the colon, lung and stomach; 0.05 for the bladder, breast, liver, esophagus, and thyroid; 0.01 for the skin and bone surfaces; and 0.05 for the remainder (66). The concepts of committed equivalent dose and committed effective dose are applied to internally deposited radionuclides where the total dose is obtained by integrating over a period of 50 years. The concept of collective equivalent dose and collective effective dose is used to express the radiative dose to an exposed population. It is the average individual dose multiplied by the number of people exposed. When combined with the cancer risk per unit dose, for example, the collective dose gives the number of people who will get cancer. The collective equivalent dose is expressed in person-rads or person-Gy and the collective effective dose is expressed as person-rem or personsievert. The basic NCRP occupational whole body radiation standard is 1 rem/year (0.01 Sv/year). Occupational radiation exposure is not permitted under the age of 18, except for training purposes when the limit is that for the general population described later. The maximum occupational exposure in any one year, as an effective dose, is 5 rem (0.05 Sv). Extra exposure is allowed for limited areas of the skin (50 rem/year) and 15 rem/year for the lens of the eye. Emergency occupational limits up to 50 rem/year are allowed but with subsequent restrictions on exposure. Occupational exposure of the fetus after pregnancy is declared should be no more than 50 millirem/month (0.0005 Sv/month). The limit for general population exposure is 0.1 rem/year (0.001 Sv) or 0.5 rem/year if such exposure is very infrequent. Individuals under the age of 18, if in occupational training, are allowed the general population exposure limit. A uniform whole-body exposure to a population is estimated to produce a total detriment of 5.6 × 10–4/rem. This is made up of the sum of 4 × 10–4/rem for fatal cancer and equal contributions from nonfatal cancer and hereditary effects of 0.8 × 10–4/rem each. The comparable figures for the general population are somewhat higher because of the higher sensitivity of the young, namely, 7.3 × 10–4/rem, which is made up of 5 × 10–4/rem for fatal cancer, 1 × 10–4/rem for nonfatal cancer, and 1.3 × 10–4/rem for hereditary effects (66). A negligible individual dose is one millirem (0.01 mSv). This is the dose below which further

expenditure to improve radiative protection are unwarranted. It carries a risk of between 10–6 and 10–7 of carcinogenesis or heritable effects. For occupational radionuclide exposures, the Annual Limit On Intake (ALI) (67) is the maximum intake in a year whose committed equivalent dose would not exceed the occupational limit. All of the radiative standards are coupled with the ALARA principle: as low as reasonably achievable, given economic and social factors. This makes the standards upper limits of exposure. The concept is that all exposure is potentially harmful. No unnecessary exposure should be allowed. Facilities should be designed to keep exposure to a minimum and not as much as the standard. No exposure should be permitted unless risks, benefits, and alternatives are considered. Ionizing Radiation Bibliography

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Research Council, Washington, DC, 1988, pp. 24–158. 62 R. E. Albert and L. C. Arnett. Clearance of radioactive dust from human lung. AMA Arch. Environ. Health 12, 234–242 (1955). 63 W. Jacobi, Carcinogenic effects of radiation on the human respiratory tract. In A. C. Upton et al., eds., Radiation Carcinogenesis, Elsevier, New York, 1986, pp. 261–278. 64 National Council on Radiation Protection (NCRP), Ionizing Radiation Exposure of the Population of the United States, NCRP Rep. No. 93, NCRP, Washington, DC, 1987. 65 National Council on Radiation Protection (NCRP), Evaluation of Occupational and Environmental Exposures to Radon and Radon Daughters in the United States, NCRP Rep. No. 78, NCRP, Washington, DC, 1984. 66 International Commission on Radiological Protection, Recommendations, Rep. No. 60, Pergamon, New York, 1991. 67 International Commission on Radiation Protection, Limits for Intake of Radionuclides by Workers, ICRP Publ. No. 30, Pergamon, New York, 1979.

Metallocenes Gary P. Bond, Ph.D., DABT 1 Introduction to Metallocenes Metallocenes are organometallic complexes with a central metal atom attached to aromatic ligands. Group II iron, which has a 2+ valence, was in one of the earliest metallocenes, but group IV metals such as titanium are currently more common. For group IV metallocenes, halides (e.g., chlorine), pseudohalides (e.g., carboxylates), or other similar molecules can also be attached to the metal. There is some debate among metallocene scientists whether one or two aromatic ligands are required for the complex to be a metallocene, but it is currently generally accepted that two aromatic ligands attached to the metal are a basic definitional criterion for metallocenes (1). Metallocenes have been used as chemical intermediates, antiknock additives to gasoline, lubricants, and for other uses, but the main current application is as catalysts in the plastics industry. Metallocenes are also currently being actively investigated as a cancer treatment agent. Catalysts, substances that initiate or speed up desirable chemical reactions, have made possible the development of several modern plastic polymers. Metallocene catalysts are improved over the initial plastics polymerization catalysts of the 1950s of Karl Ziegler and Giulio Natta (Ziegler–Natta catalysts), which catalyzed polymerization of ethylene and propylene into polyethylene and polypropylene. Metallocenes provide better control of polymerization, making it possible to create plastics with physical properties designed for particular uses. For example, precise control over polymer growth allows making plastics that are durable for gearwheels or can withstand high temperatures for piping. The billions of pounds of plastics produced and sold every year can be light, waterproof, resistant to corrosion, and used in such items as water pipes, trash bags, hair combs, fibers for clothing and road construction, and packaging for food and medicines, just to name a few uses. Metallocene catalysts, first synthesized in 1953 by John Birmingham, contain a metal. Unlike the Ziegler–Natta catalysts, metallocenes contain just a single atom of metal. The basic metallocene structure is

The metal is frequently titanium or zirconium but can be hafnium, tin, germanium, or another group IV metal. Group II metals, chromium, cobalt, and iron, can also be the metal in the metallocene. Group IV metals are linked to two rings of carbon atoms (e.g., cyclopentadienyl or a wide variety and complexity of other cyclic molecules), which can be linked to one or more other groups. These other groups are often other carbon atoms with attached hydrogens (2). The other carbon-based groups attached to the cyclic molecules can also vary in complexity from methyl groups to longer chain carbon groups, some with unsaturated double bonds. For a more complete and thorough description of the chemistry of the metallocene catalysts refer to such technical references as the Kirk–Othmer Encyclopedia of Chemical Technology (3). Because of the widespread production of plastics via metallocene catalysts, metallocenes have become worthy of consideration for potential effects on the worker and the workplace. The antitumor effects of metallocenes underscore the importance of this consideration for protecting workers from workplace chemicals that interact with nuclear material and the cellular duplication process. Two important examples of metallocene catalysts discussed in this chapter are ferrocene and titanocene. Ferrocene, an atypical group II metallocene that has iron (Fe) as the central metal with two cyclopentadiene cyclic groups has no halide groups and is considered first because it was one of the early metallocenes. Ferrocene is the first metallocene to have the “sandwich” structure created by two cyclopentadiene rings attached to the metal. Titanocene, with group IV titanium as the metal, has two cyclopentadiene rings and two chlorine molecules attached to the metal. Little toxicological data are available at present for most metallocenes and limits the number of metallocenes covered in this chapter. If metallocenes are developed into anticancer agents for humans, the amount of available toxicological data will certainly increase. The initial chemical listed, dicyclopentadiene, although not a metallocene, is presented as a baseline for its health effects, and the intention is to compare it to dicyclopentadiene iron and the other metallocenes presented.

Metallocenes Gary P. Bond, Ph.D., DABT 2 Metallocenes as Cytostatic Anticancer Drugs Numerous studies have compared the cancer potency and toxicity of several metallocenes (4–14). The anticancer potential of metallocenes has been investigated in cell culture and in intact animals. Metallocene dichlorides were the first organometallic complexes that exhibited both antitumor and antiviral activities. Although early studies considered that they act similarly to the cell cycle arresting agent cisplatinum, later studies suggested that the metallocene dihalides have additional cytostatic mechanisms. Metallocene dihalides form DNA adducts, and they also disrupt DNA, RNA, and protein synthesis. Because of these additional cytostatic effects on cancerous cells at doses that are relatively nontoxic and clearly less toxic than cisplatinum, metallocene dihalides are being considered for development as human cancer treatment drugs for such human cancers as ovarian cancer. Different structural variants of metallocene dihalides have been tested. In vitro testing of group IV metals showed that vanadium is ~ 10- to 100-fold more potent than titanium and molybdenum which were ~ 10- to 100-fold more potent than zirconium and hafnium. Similar potency relationships were observed in vivo. Titanium-based metallocene exhibits increased potency compared to the vanadium metallocene.

Metallocenes Gary P. Bond, Ph.D., DABT 1.0 Dicyclopentadiene 1.0.1 CAS Number: [77-73-6] 1.0.2 Synonyms: 1,3-Cyclopentadiene dimer; 3A,4,7A-tetrahydro-4,7-methanoindene; biscyclopentadiene 1.0.3 Trade Names: NA 1.0.4 Molecular Weight: 132.22 1.0.5 Molecular Formula: C10H12 1.0.6 Molecular Structure:

1.1 Chemical and Physical Properties (15, 16) 1.1.1 General Dicyclopentadiene is a colorless crystalline solid. Boiling point 172°C Melting point 33.6°C Solubility (at 20° insoluble in water; soluble in 95% ethanol, carbon tetrachloride, acetic acid, and C) petroleum ether Flash point 32°C (90°F) Stability stable Density 0.93 g/mL at 35°C Specific gravity 0.979 at 20/20°C Vapor pressure 10 mm Hg at 47.6°C Vapor density 4.55 g/mL Viscosity 0.736 centipoise at 21°C Octanol/water partition coefficient log Kow = 2.89 (estimated) 1.1.2 Odor and Warning Properties Dicyclopentadiene has a disagreeable, camphor-like odor that is not distinguishable from the odor of other hydrocarbons with closely related structures, such as terpenes. Human sensory response studies indicate that dicyclopentadiene can be detected in the range of 0.003–0.2 ppm but does not become noticeably irritating below 10 ppm. It must be inhibited and maintained under an inert atmosphere to prevent polymerization. 1.2 Production and Use Dicyclopentadiene is produced by recovery from hydrocarbon streams from high temperature cracked petroleum fractions. It is also a by-product of the coke oven industry. Cyclopentadiene polymerizes to dicyclopentadiene on standing. It is used as a chemical intermediate for insecticides, certain (e.g., EPDM) elastomers, metallocenes, paints and varnishes, and flame retardants for plastics (15, 16). 1.3 Exposure Assessment 1.3.1 Air Although no air-specific method of exposure assessment was reported, analysis of products

and residues of dicyclopentadiene can be done by gas–liquid chromatography with a flame ionization detector (16). 1.3.2 Background Levels Dicyclopentadiene has been reported in effluent samples as a result of pesticide production. 1.3.3 Workplace Methods None reported. 1.3.4 Community Methods None reported. 1.3.5 Biomonitoring/Biomarkers None reported. 1.4 Toxic Effects 1.4.1 Experimental Studies 1.4.1.1 Acute Toxicity (15–18) Dicyclopentadiene causes mild to severe eye, skin, and respiratory tract irritation, and severe response of the eyes and skin result from 24hour exposure. The acute toxicity varies with the route of exposure. The LD50/LC50 in mice has been reported as 200 mg/kg (i.p.), 190 mg/kg (oral), and 145 ppm/4 hours (inhalation). The LD50 and LC50 in rats has been reported as 200 mg/kg (i.p.), 353 mg/kg (oral), and 500 ppm/4 hours (inhalation). The LD50 and LC50 in rabbits have been reported as 5080 mg/kg (dermal) and 771 ppm/4 hours (inhalation). The inhalation LC50 in guinea pigs is 770 ppm/4 hours and the oral LD50 in cattle is 1200 mg/kg. Pathological findings following acute lethal exposures were typical for large doses of irritant hydrocarbons, namely, general congestion, hyperemia, and focal hemorrhage in affected organ tissues such as the lung, kidney, and bladder. 1.4.1.2 Chronic and Subchronic Toxicity Rats were exposed to dicyclopentadiene by inhalation for 7 hours per day, 5 days per week for 10 days at levels of 72, 146, and 332 ppm (17, 18). Death, observed only in the highest dose group, included all six males and females by day 4 of dosing and was characterized by convulsions, hemorrhage in the lungs, blood in the intestines, and blood in the thymus (females only). In similarly exposed mice at 47, 72, and 146 ppm, all mice exhibited convulsive deaths on the first day of exposure. Death at 72 ppm occurred in five of six mice of each sex during the 10 days of exposure and was not associated with the convulsions or gross lesions observed in rats. No deaths occurred at 47 ppm and no other effects of treatment were observed. Male beagles (1 per group) were also exposed similarly to levels of 20, 40, and 72 ppm. Signs of toxicity included inactivity at 72 ppm, diarrhea and excessive salivation on day 2 with hind quarter spasticity on day 9 at 47 ppm, and diarrhea at 20 ppm. No treatment-related gross lesions were reported. Groups of 12 male and female rats were exposed to dicyclopentadiene by inhalation at levels of 19.7, 35.2, and 73.8 ppm, 7 hours per day, 5 days per week for 89 days (17, 18). Some convulsions were observed only in the highest dose group. Mean body weight gains were significantly reduced for the highest dose group through only the first four days of exposure. Organ weights exhibited no clear treatment-related effects. Kidney effects, which included tubular degeneration, were observed in males and females of the two high-dose groups, and males exhibited increased frequency and severity. Three dogs per group of male beagles were exposed using the same dosing schedule of 8.9, 23.5, and 32.4 ppm. Clinical chemistry was the only biological parameter affected by treatment with dicyclopentadiene, and this occurred only at the highest dose. The microscopic pathology of 28 organs and electrocardiograms were normal. The results of other chronic and subchronic toxicity tests were reported in the literature but could not be confirmed by obtaining the original literature. Refer to various databases in Ref. 16 for additional information. 1.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms (16) In general, although some dicyclopentadiene can be exhaled unchanged, most of that absorbed is hydroxylated in the liver,

undergoes glucuronide conjugation, and is excreted in the urine. When dicyclopentadiene was given by mouth to lactating cows, only trace amounts were secreted in the milk, and the majority was contained in the urine and feces. 1.4.1.4 Reproductive and Developmental (19) The National Toxicology Program (NTP) reported the completion of teratology studies in rats and rabbits at doses of 50, 200, 300, 400, and 500 mg/kg. Dicyclopentadiene was administered by oral gavage. The results of these studies were not available. 1.4.1.5 Carcinogenesis None reported. 1.4.1.6 Genetic and Related Cellular Effects Studies The NTP (19) and the EPA GENETOX (16, 20) programs reported that dicyclopentadiene was negative in the Salmonella typhimurium histidine reversion assay. 1.4.1.7 Other: Neurological, Pulmonary, Skin Sensitization None reported. 1.4.2 Human Experience Human sensory responses to dicyclopentadiene were studied in three human volunteers (18). The odor threshold was reported as low as 0.003 ppm. In two of the subjects exposed to 1 and 5.5 ppm for 30 minutes, one subject experienced mild eye and throat irritation after 7 minutes at 1 ppm, and the other subject reported olfactory fatigue after 24 minutes. Eye irritation was reported after 10 minutes, but no olfactory fatigue was reported by either test subject at 5.5 ppm. The researcher interpreted these results to indicate that dicyclopentadiene does not lose its warning properties under conditions of longer exposures. During the conduct of these studies, which also included animal studies as reported in section 1.4, workers accidentally exposed to dicyclopentadiene reported headaches during only the first 2 months of the 5-month study period. No other information was found regarding human effects of exposure to dicyclopentadiene (17, 18). 1.5 Standards, Regulations, or Guidelines of Exposure The ACGIH TLV for dicyclopentadiene is 5 ppm as an 8-hour TWA. The NIOSH REL is 5 ppm as a 10-hour TWA. The OSHA PEL is 5 ppm as an 8-hour TWA. The ACGIH TLV has been adopted and/or is the same value as standards in numerous other countries such as those in Europe, Australia, Colombia, Jordan, Korea, and New Zealand (15–17). 1.6 Studies on Environmental Impact None reported.

Metallocenes Gary P. Bond, Ph.D., DABT 2.0 Ferrocene 2.0.1 CAS Number: [102-54-5] 2.0.2 Synonyms: dicyclopentadienyl iron; biscyclopentadienyliron; iron bis (cyclopentadiene) 2.0.3 Trade Names: Catane, Ferrosten 2.0.4 Molecular Weight: 186.05 2.0.5 Molecular Formula: (C5H5)2Fe 2.0.6 Molecular Structure:

2.1 Chemical and Physical Properties 2.1.1 General Ferrocene is an orange crystalline solid (16). Boiling 249°C point Melting 173–174°C point Solubility 19 g/100 g benzene, 10 g/100 g catalytically cracked gasoline, 6 g/100 g jet fuel (JP4), 5 g/100 g diesel fuel, insoluble in water, slightly soluble in petroleum ether Flash point unknown Stability stable Sublimes >100°C Specific unknown gravity Vapor 0.03 mm Hg at 40°C pressure Iron content 29.4–30.6% 2.1.2 Odor and Warning Properties Ferrocene has a camphor-like odor and reacts violently with ammonium perchlorate. It is classified as a flammable solid. 2.2 Production and Use Ferrocene is produced from the reaction of cyclopentadiene with reduced iron in the presence of metal oxides. It is used as a catalyst for vulcanization acceleration and polymerization, as a chemical intermediate for polymeric compounds such as high temperature polymers, as an antiknock additive for gasoline, as a coating for missiles and satellites, and as a high-temperature lubricant (16). 2.3 Exposure Assessment 2.3.1 Air NIOSH Methods 173 (21) and 351 (20, p. v7 351-1) are available air sampling methods for iron, and the analytical laboratory methods use atomic absorption and atomic emission spectroscopy, respectively (16). 2.3.2 Background Levels None reported. 2.3.3 Workplace Methods See 2.3.1. 2.3.4 Community Methods See 2.3.1. 2.3.5 Biomonitoring/Biomarkers No information is available for ferrocene. The use of biomonitoring/biomarkers for iron should be considered in instances of suspected ferrocene overexposure. Refer to the section on iron in this publication. 2.4 Toxic Effects The toxicological properties of ferrocene have not been extensively investigated. Toxic effects have usually been associated with the iron in the ferrocene, but some data indicate that cyclopentadienyl may be a causative agent in liver cirrhosis (see 2.4.1.2). 2.4.1 Experimental Studies 2.4.1.1 Acute Toxicity Ferrocene may cause eye, skin, and respiratory tract irritation. The LD50 in mice has been reported as 335 mg/kg (i.p.), 178 mg/kg (i.v.), 600 mg/kg (oral), and 832 mg/kg (oral). In the rat, the LD50 is 500 mg/kg (i.p.) and 1320 mg/kg (oral) (16, 22). 2.4.1.2 Chronic and Subchronic Toxicity Male and female rats and mice were exposed to vapors of

ferrocene for 6 hours/day for 2 weeks at target concentration levels of 2.5, 5, 10, 20, and 40 mg/m3 (actual levels of 2.33, 5.29, 9.89, 20.02, and 36.47 mg/m3) (23). No mortality, clinical signs of toxicity, or gross histological effects were observed. Decreased body weight gains in treated versus control animals were observed for the male rats and mice exposed to 40 mg/m3 ferrocene and the female mice exposed to 10, 20, and 40 mg/m3. Relative liver weights decreased in male rats (40 mg/m3). Dose-related decreases were observed in relative liver and spleen weights (male and female mice) and relative spleen weights (female mice). The thymus weights were increased in a dose-related manner in male mice. Nasal turbinates, lungs, liver, and spleen were observed microscopically. The only effect observed was inflammation of the nasal turbinates in both species with a dose-dependent severity. Observed toxic effects from ferrocene inhalation were attributed to iron. Male and female dogs received ferrocene in gelatin capsules at doses of 30, 100, and 300 mg/kg/day for 6 months and at 1000 mg/kg for 3 months (24). No deaths or urinalysis differences, except for an amber color of urine, were associated with ferrocene exposure. A dose-related accumulation of iron with hemosiderosis was observed (liver, spleen, bone marrow, adrenals, lungs, gastrointestinal tract, lymph nodes, testes). Blood effects (decreased hemoglobin, packed cell volume, and erythrocyte count) occurred within 4 weeks at 300 mg/kg. Liver cirrhosis, considered to be related to the cyclopentadiene, was observed in the 300- and 1000-mg/kg group. Dose-related testicular hypoplasia was observed. Treatment of other dogs with ferrous sulfate determined that only liver cirrhosis was specifically ferrocene-related because the other effects were related to iron overload. No other effects were observed during 12–26 months after treatment ended. Male and female rats and mice were exposed to vapors of ferrocene for 6 hours/day, 5 days/week for 13 weeks at target concentration levels of 3, 10, and 30 mg/m3 (actual levels of 3.06, 10.06, and 29.89 mg/m3) (25). No mortality, clinical signs of toxicity, or gross histological effects were observed. Decreased body weight gains versus control animals were observed in the male rats at 3 and 30 mg/m3 of ferrocene and in female mice at 3 and 10 mg/m3. Increases in the lung burden of iron were dose- and time-related. Decreased thymus and testes weights in male rats and liver weights in female rats (3 and 30 mg/m3) and decreased liver (all doses), heart, and spleen (30 mg/m3) in female mice were observed. Increased relative liver weights (30 mg/m3 male rats, 10- and 30-mg/m3 female rats, and 30-mg/m3 male mice) and kidney weights (30-mg/m3 male rats) were observed. Decreased relative liver weights were observed in female mice (3 mg/m3). No ferrocene-related changes were observed in respiratory function, lung biochemistry, bronchoalveolar lavage cytology, total lung collagen, clinical chemistry, and hematology. Exposure-related histopathological lesions, primarily iron accumulation, were observed in the nose, larynx, trachea, lung, and liver of both species and in the kidneys of mice. Nasal lesions were dose-related in severity and included necrotizing inflammation, metaplasia, and regeneration. Observed toxic effects from ferrocene inhalation were attributed to iron ions released from the ferrocene. 2.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms The metabolism of ferrocene was studied in rats following a 17-minute inhalation exposure (26). Ferrocene deposition was significant in the nasopharynx and lungs. The half-life for clearance of radiolabeled iron was 200 days for the bronchopulmonary region and 70 days for the nasopharyngeal region. Within 24 hours after exposure, 75% of the radiolabeled hydrogen was cleared from the respiratory tract. For the retained radiolabeled iron, 90% was in the bronchopulmonary and nasopharyngeal regions of the lungs, 10% was in the liver, and 1% was in the spleen. 2.4.1.4 Reproductive and Developmental Dose-related testicular hypoplasia was observed in dogs that received ferrocene in gelatin capsules at doses of 30, 100, and 300 mg/kg/day for 6 months and at 1000 mg/kg for 3 months (24). Treatment of other dogs with ferrous sulfate determined that this effect was related to iron overload because administered ferrous sulfate caused similar effects.

2.4.1.5 Carcinogenesis Ferrocene was administered by intramuscular injection at a dose of 5175 mg/kg/2 years. By the criterion established by the Registry of Toxic Effects of Chemical Substances (RTECS), ferrocene was an equivocal tumorigenic agent and tumors were most evident at the site of multiple injections (16, 27). 2.4.1.6 Genetic and Related Cellular Effects Studies Ferrocene was tested for the potential to cause genetic mutations by point and frameshift mutations in bacteria (Salmonella typhimurium), by sister chromatid exchange in Chinese hamster ovary cells, and by heritable effects (sex chromosome loss/nondysjunction and heritable translocation test) in Drosophila melanogaster (28–30). Results indicate that ferrocene is not mutagenic. 2.4.2 Human Experience None reported. 2.5 Standards, Regulations, or Guidelines of Exposure (16) The ACGIH TLV for ferrocene is 10 mg/m3 as an 8-hour TWA. The NIOSH REL is 10 mg/m3 as a 10-hour TWA for total dust and 5 mg/m3 for the respirable fraction. The OSHA PEL is 15 mg/m3 as an 8-hour TWA for total dust and 5 mg/m3 for the respirable fraction. The ACGIH TLV has been adopted and/or is the same value as standards in numerous other countries. The U.S. EPA, Canada, and Mexico have drinking water standards for iron of 0.3 mg/L. 2.6 Studies on Environmental Impact None reported.

Metallocenes Gary P. Bond, Ph.D., DABT 3.0 Titanocene Dichloride 3.0.1 CAS Number: [1271-19-8] 3.0.2 Synonyms: dicyclopentadiene titanium; dichlorotitanocene; bis (cyclopentadienyl) titanium dichloride 3.0.3 Trade Names: NA 3.0.4 Molecular Weight: 248.99 3.0.5 Molecular Formula: (C5H5)2TiCl2 3.0.6 Molecular Structure:

3.1 Chemical and Physical Properties (16) 3.1.1 General Titanocene dichloride is a reddish-orange crystalline solid. Melting point 289°C Solubility moderately soluble in toluene, chloroform, alcohol, and other hydroxylic solvents; sparingly soluble in water, petroleum ether, benzene, ether, carbon disulfide, and carbon tetrachloride Stability stable (tetravalent titanium compounds are the most stable of the variable

Density/specific gravity

valence compounds of titanium) 1.6

3.1.2 Odor and Warning Properties (16) Titanocene dichloride is irritating to the skin and mucous membranes. 3.2 Production and Use Titanocene dichloride is produced by the reaction of titanium tetrachloride with cyclopentadienyl sodium. It is used as a research chemical, as a catalyst in Ziegler–Natta polymerization reactions, and as an implant material in orthopedics, oral surgery, and neurosurgery. Titanocene dichloride is being investigated as a chemotherapeutic agent (16). 3.3 Exposure Assessment 3.3.1 Air Atmospheric concentrations of titanium have been reported at an average urban concentration of 0.04 mg/m3 with a maximum concentration of 1.10 mg/m3 (16, 31). 3.3.1 Background Levels Titanium, an apparently nonessential metal for humans or animals, has been detected in North American rivers at levels of 2–107 mg/L with mean concentrations in U.S. drinking water of 2.1 mg/L. Titanium has been detected in food and seafood (levels unreported) (31). 3.3.2 Workplace Methods NIOSH Methods 7300 (32), 600 (33), and 500 (34) are available air sampling methods for titanium, and the analytical laboratory methods use atomic emission spectroscopy, gravimetric (respirable dust fraction), and gravimetric (airborne particulate matter) procedures, respectively (16). 3.3.3 Community Methods NIOSH method 3111 is available for determining titanium in water and wastewater by using direct aspiration atomic absorption spectrometry (35). 3.3.4 Biomonitoring/Biomarkers (16) 3.3.4.1 Blood None reported. 3.3.5.2 Urine NIOSH method 8310 is available for detecting titanium in urine by using atomic emission spectroscopy (36). 3.3.5.3 Other The estimated body burden of titanium is ~15 mg, most of which is in the lungs as a result of inhalation exposure (31). 3.4 Toxic Effects (16) The toxicological properties of titanium dichloride have not been extensively investigated. Toxic effects have usually been associated with the titanium. 3.4.1 Experimental Studies 3.4.1.1 Acute Toxicity Titanocene dichloride may cause skin and mucous membrane irritation. The LD50 in mice has been reported as 60 mg/kg (i.p.), and 180 mg/kg (i.v.). In the rat, the LD50 is 25 mg/kg (i.p.) (16, 22). 3.4.1.2 Chronic and Subchronic Toxicity In studies conducted as part of the National Toxicology Program (NTP), titanocene dichloride was administered by gavage in corn oil to male and female rats for 14 days, 13 weeks, or 2 years (37). In the 14-day study, titanocene dichloride was administered at doses of 0, 65, 125, 250, 500, or 1,000 mg/kg (37). All high-dose rats and four of the five males and two of the five female rats given 500 mg/kg died during the studies. A dose-related decrease in body weight gain was seen in rats at all but the 65-mg/kg dose. Treatment-related lesions included hepatocellular necrosis, tubule necrosis in the kidney, erosions and ulcers of the glandular stomach, and hyperplasia of the

forestomach epithelium. In the 13-week study, titanocene dichloride was administered at doses of 0, 8, 16, 31, 62, or 125 mg/kg (37). One female rat in the highest dose group died due to the titanocene dichloride during the fourth week of the studies. Body weight gain was reduced compared to controls in rats given 62 or 125 mg/kg. Histopathological lesions related to treatment with titanocene dichloride were observed in the stomachs of high-dose males and all groups of females. Hyperplasia and metaplasia of the glandular stomach and hyperplasia and hyperkeratosis of the forestomach were observed. In the 2-year study, titanocene dichloride was administered at doses of 0, 25, and 50 mg/kg (37). These doses were selected based on the stomach and body weight effects observed in the 3-week study. The principal toxic effects of administering titanocene dichloride for 2 years occurred in the stomach. Lesions observed at 15 months were similar to, but less severe than, those observed at 2 years. The lesions included focal erosions of the glandular mucosa, inflammatory responses, hyperplastic and metaplastic responses, and fibrotic changes. Effects were observed in both groups administered titanocene dichloride, but not in control animals. Macrophages with blue-gray pigment accumulated in many organs of dosed rats including the gastrointestinal tract, liver, lung, and lymph nodes. The pigment was believed to contain titanium. Inflammation of the nasal mucosa and lung was also attributed to administration of titanocene dichloride, resulting from reflux and/or regurgitation and aspiration of gavage solution due to the severe stomach lesions. 3.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms 3.4.1.3.1 Absorption Titanium compounds are generally considered to be poorly absorbed upon ingestion and inhalation (38). However, detectable amounts of titanium can be found in the blood, brain, and parenchymatous organs of individuals in the general population; the highest concentrations are found in the hilar lymph nodes and the lung. Titanium is excreted with urine (16). 3.4.1.3.2 Distribution The subcellular distribution of titanium in the liver of mice was determined at 24 and 48 hours after administering titanocene dichloride (39). At 24 hours, titanium was accumulated mainly in the cytoplasm of endothelial and Kupffer cells lining the hepatic sinusoids. Titanium was also detected in the nucleoli and the euchromatin of liver cells. It was packaged as granules together with phosphorus and oxygen. At 48 hours, titanium was still present in cytoplasmic inclusions within endothelial and Kupffer cells, but there were only a few deposits in hepatocytic nucleoli. Titanium was found in hepatocyte cytoplasm, incorporated into cytoplasmic inclusion bodies which were considered most likely to be lysosomes. Location of these inclusions near bile canaliculi with occasional extrusion of the content into the lumen of bile capillaries suggests biliary elimination of titanium. Titanium concentrations were not elevated in mouse embryos after injection (i.p.) of pregnant mice on day 10, 12, or 14 of gestation compared to untreated controls (40). On day 16 of gestation, after the period of organogenesis, small amounts of titanium were detectable in the fetal compartment in excess of that of controls. These results are consistent with the result of a teratology study in which there was an absence of histological lesions in developing embryonal organs and a lack of multiple teratogenic effects in newborns after application of therapeutic doses of titanocene dichloride to pregnant mice during embryonal organogenesis (see section 3.4.1.4). The teratogenic effect is considered to result from indirect effects on the maternal animal such as altered hormonal status (40– 42). 3.4.1.3.3 Excretion (16) Titanium is excreted with urine, and gastrointestinal excretion via the bile is possible (38, 39). 3.4.1.4 Reproductive and Developmental The teratogenic and embryotoxic effects of titanocene dichloride were investigated after intraperitoneal injections of single therapeutic doses of titanocene dichloride (30 or 60 mg/kg) to pregnant mice on days 8, 10, 12, 14, or 16 of gestation (43). The

fetuses were removed on day 18 by caesarean section and examined for external, internal, and skeletal malformations, as well as for toxic effects of treatment. Cleft palate was observed in numerous fetuses (10% of the fetuses at 30 mg/kg; 40–50% of the fetuses at 60 mg/kg) after titanocene dichloride administration on days 10 and 12. Skeletal malformations were observed in some fetuses. No other malformations were observed. Toxic effects of treatment included a decreased number of live fetuses per litter, dose-dependent reduction of mean fetal body weight, and delayed skeletal ossification. The lack of a broad range of effects observed with other cytostatic chemicals was consistent with effects on maternal hormonal status, namely, increased cortisol release (42). 3.4.1.5 Carcinogenesis Based on the results of 2-year gavage studies, the National Toxicology Program determined that there was equivocal evidence of carcinogenic activity of titanocene dichloride in male and female rats based on a marginal increase in the incidence of forestomach squamous cell effects. Refer to study results in section 3.4.1.2 for more details (37). 3.4.1.6 Genetic and Related Cellular Effects Studies (16) Titanocene dichloride was evaluated for mutagenic potential as part of the EPA GENETOX and National Toxicology Programs. Positive and negative mutagenic effects were observed, consistent with the equivocal carcinogenic data and characterization by the National Toxicology Program. The results were as follows: positive in Salmonella typhimurium strain TA100 in the absence of exogenous metabolic activation/S9 microsomal enzymes and negative in TA100 with S9 (44); negative in all other Salmonella typhimurium strains with or without S9 (44); inconclusive in bacteria Escherichia coli polA point mutation assay without S9 microsomal enzymes (45); negative in yeast Saccharomyces cerevisiae host-mediated assay (45); positive and dose-responsive in mouse cell transformation (45); negative for sister chromatid exchanges or chromosomal aberrations in Chinese hamster ovary cells, with or without S9 (45); positive in unscheduled DNA synthesis assay using human fibroblasts (in vitro) (45); positive in SHE-clonal assay and in the transformation of rat embryo cells (45); positive in neoplastic transformation of a cloned mouse cell line, hamster embryo cells, and virally-infected rat embryo cells (20); 3.4.1.7 Other: Neurological, Pulmonary, Skin Sensitization None reported. 3.4.2 Human Experience The spermicidal activity of several metallocene complexes on human sperm was investigated (46). Of the metallocene complexes investigated, neither titanocene dichloride nor any other metallocenes except vanadium-based metallocenes caused immobilization of sperm. 3.5 Standards, Regulations, or Guidelines of Exposure None reported. 3.6 Studies on Environmental Impact None reported.

Metallocenes Gary P. Bond, Ph.D., DABT 4.0 Vanadocene Dichloride 4.0.1 CAS Number: [12083-48-6]

4.0.2 Synonyms: cyclopentadienylvanadiumdichloride, bis; bis (cyclopentadienyl) vanadium dichloride 4.0.3 Trade Names: NA 4.0.4 Molecular Weight: 252.04 4.0.5 Molecular Formula: (C5H5)2VCl2 4.0.6 Molecular Structure:

4.1 Chemical and Physical Properties 4.1.1 General Vanadocene dichloride is a pale green crystalline solid (15, 16). Boiling not available point Melting >250°C point Solubility (at 10–50 mg/mL in DMSO; 50% directly absorbed from the nasal cavity (50). 3.4.1.3.2 Distribution Strontium is either deposited in bone or distributes into an exchangeable pool composed of plasma, cellular fluids, soft tissues, and bone surfaces. Orally administred Sr(NO3)2 accumulated in rat skeletons proportional to the administered dose, averaging 2.7% (1). 90SrCl2 administered via inhalation (aerosol) was rapidly translocated from the lung to the skeleton, behaving similarly to intravenously administered soluble Sr on reaching the bloodstream (51). Following intravenous administration of 89SrCl2 at two different doses (0.74 kBq/g body weight or 74 kBq/g), approximately 1.30 and 1.50%, respectively, of the administered dose was retained in the femurs 7 days after administration (52). Skeletal Sr can be mobilized during late pregnancy and lactation, migrating to the fetal skeleton and to the infant via breast milk (53). An active transplacental transfer of strontium has been demonstrated, with discrimination between strontium and calcium early in pregnancy and equal transplacental transport of the two ions later in pregnancy (54).

3.4.1.3.3 Excretion Excretion of unabsorbed Sr is predominantly via the feces, with smaller amounts in urine and sweat (1). 3.4.1.4 Reproductive and Developmental In a multigenerational miniature swine study, dams were fed 90Sr at various levels, and then the offspring were exposed via lactation and feed. It was observed that levels of 90Sr high enough to affect fetal or neonatal mortality would not permit the survival of the dam through gestation (51). Injection of pregnant mice with 90Sr was associated with a decrease in the number of fetal oocytes (20 mCi on gestational day 11 or 16) and skeletal malformations (5–10 mCi) (14). 3.4.1.5 Carcinogenesis The carcinogenicity of stable (nonradioactive) strontium chromate was attributed solely to intracellular soluble chromium (1). 90Sr has been examined in long-term studies in four species, involving beagles, mice, monkeys, and pigs. A summary of the findings of these studies can be found in Ref. 51. Following intravenous injection of 90Sr at doses ranging from 0.027 to 362 × 104 Bq/kg, the most prominent 90Sr-induced endpoint was bone sarcoma. Neoplasms involving the soft tissues near bone in the oronasopharynx and paranasal sinuses and bone marrow dysplasia were also significantly elevated over controls. Feeding studies in beagles extending from the in utero period to age 540 days resulted in the development of the same array of tumors, and, in addition, myeloproliferative disorders. Inhalation exposure to 90SrCl2 was associated with multiple carcinogenic and non-neoplastic lesions in dogs, with an excess of bone tumors reported as the major finding. Interestingly, inhalation exposure of dogs to insoluble forms of 90Sr was associated with lung tumors, but not bone tumors (51). In an additional study in which beagle dogs were injected with low levels of 90Sr (21.1 kBq/kg, or 5 times the maximum permissible (retained) body burden), 90Sr was not associated with a decrease in survival time (55). It has been estimated that 90Sr is approximately two orders of magnitude less toxic than radium (56). Two monkey studies were also summarized by the Council on Radiation Protection and Measurements (51). One of these studies involved administration of single intravenous injections of 90Sr (0.10–6.21 MBq) to rhesus monkeys. These monkeys had no symptoms or disease attributable to 90Sr 20 years after exposure. In another study, administration of 1.85 or 3.7 MBq of 90Sr as a single oral dose resulted in bone sarcomas (51). 3.4.1.6 Genetic and Related Cellular Effects Studies Oral administration of strontium chloride to mice resulted in dose-dependent chromosomal aberrations in bone marrow metaphase preparations (57). An increased mutation frequency was noted in the bone marrow, but not liver or spleen, in the lacZ transgenic mouse (Muta mouse) following intravenous administration of 74 MBq/kg of 89Sr (58). 3.4.2 Human Experience 3.4.2.1 General Information In general, the nonradioactive salts of strontium are of little toxicological concern, particularly on oral administration, because of the low GI bioavailability of the strontium ion. However, strontium is highly dangerous in its radioactive forms. On absorption, strontium concentrates primarily in bones. 3.4.2.2 Clinical Cases 3.4.2.2.1 Acute Toxicity In patients administered 89SrCl2 for relief of bone pain associated with metastatic bone cancer, the major side effects noted are bone marrow supression and thrombocytopenia (5). 3.4.2.2.2 Chronic and Subchronic Toxicity: NA 3.4.2.2.3 Pharmacokinetics, Metabolism, and Mechanisms: NA

3.4.2.2.4 Reproductive and Developmental Leikin and Paloucek (5) list 89SrCl2 as a pregnancy risk factor D, meaning that there is positive evidence of fetal risk, but the benefits from use in pregnant women may be acceptable despite the risk. There are equivocal data, summarized in Shepard (14), regarding the relationship between fetal 90Sr body burden and incidence of birth defects in humans. 3.4.2.3 Epidemiology Studies 3.4.2.3.1 Acute Toxicity: NA 3.4.2.3.2 Chronic and Subchronic Toxicity: NA 3.4.2.3.3 Pharmacokinetics, Metabolism and Mechanisms: NA 3.4.2.3.4 Reproductive and Developmental: NA 3.4.2.3.5 Carcinogenesis The U.S. EPA has categorized stable strontium as a cancer group D, which indicates that there is inadequate or no human or animal evidence of carcinogenicity (59). Strontium chromate is a suspected human carcinogen, an effect attributable to the chromate component. 3.5 Standards, Regulations, or Guidelines of Exposure Strontium is listed by the U.S. EPA as a candidate for establishment of a maximum contaminant level, but none presently exists. The reference dose (RfD) for strontium has been estimated at 0.6 mg/kg per day; this corresponds to a daily level of exposure that is likely to be without appreciable risk of deleterious effects over a lifetime. The TLV TWA for strontium chromate is 0.0005 mg/m3 as chromate, because strontium chromate is regarded as a class A2, or suspected human, carcinogen.

Magnesium, Calcium, Strontium, Barium, and Radium Mary Beth Genter, Ph.D., DABT 4.0 Barium 4.0.1 CAS Number: [7440-39-3] 4.0.2 Synonyms: NA 4.0.3 Trade Names: UN 1399, UN 1400, UN 1854 4.0.4 Molecular Weight: 137.33 4.0.5 Molecular Formula: Ba 4.1 Chemical and Physical Properties 4.1.1 General Melting point: 725°C; boiling point: 1640°C; specific gravity: 3.51 at 20°C. Barium exists as multiple isotopes: 138 (71.66%); 137 (11.32%); 136 (7.81%); 135 (6.59%); 134 (2.42%); 132 (0.097%); 130 (0.101%) (4). Barium participates in chemical reactions typical of alkaline-earth metals, that is, it reacts violently with acids, water, and carbon tetrachloride. Pure barium metal exists as yellowish-white, slightly lustrous lumps that are somewhat malleable and very easily oxidized (must be kept under petroleum or other oxygen-free liquid to exclude air). Typical of other alkaline-earth metals, barium decomposes in water, evolving hydrogen gas. There are approximately 40 different barium salts. Of these barium salts, approximately half are freely soluble in water, whereas others are practically insoluble (notably barium sulfate and carbonate). Solutions of soluble barium salts give a white precipitate with sulfuric acid or soluble sulfates, and they color nonluminous flame green. Water or acid soluble barium salts should be regarded as poisonous.

4.1.2 Odor and Warning Properties Most barium salts are odorless or have an odor and characteristic of the associated anion. 4.2 Production and Use Barium carbonate occurs in nature as the mineral witherite; barium sulfate occurs in nature as the mineral barite; also as barytes, heavy spar. Barium is used as a carrier for radium. Alloys of barium with Al or Mg are used as getters in electronic tubes. Barium carbonate is used as rodenticide (4, 60) and in paints, enamels, and marble substitutes (4). Barium sulfate (multiple trade names, including Bakontal, Esophotrast, Micropaque, Raybar) is used as an X-ray-contrast material (4) and as a weighting substance for golf balls (61). Barium nitrate is used in the manufacture of pyrotechnics and green signal lights. Barium sulfide is used as a depilatory and in luminous paints. 4.3 Exposure Assessment 4.3.1 Air Barium can be released into the air during mining and in various industrial processes. 4.3.2 Background Levels Barium's abundance in earth's crust is approximately 0.05%. The background concentration of Ba in groundwater is approximately 0.1 mg/L, although significant regional excursions from this value have been documented (62). Seawater reportedly contains approximately 13 mg/L (5). Various measurements have revealed soil concentrations to range from 15 to 3000 ppm, and the average atmospheric concentration in North America is reported to be 0.12 mg/m3 (5). Brazil nuts are exceptionally high in barium, with a concentration of 3000–4000 ppm (5). Depending on the geographic site, daily barium intake is estimated to be 300– 1700 mg/person (63, 64). 4.3.3 Workplace Methods Barium-containing fluxes used in welding can result in significant airborne barium fumes and elevated urinary barium concentrations in exposed workers (65). 4.3.4 Community Methods In addition to workplace exposures, consumer products can be a source of barium exposure. For example, about half of a sample of crayons was demonstrated to contain barium capable of migrating, thus representing a potential source of exposure for children (66). It has also been predicted that some lipsticks can represent a significant source of barium exposure (64). 4.3.5 Biomonitoring/Biomarkers No biomarkers of exposure to barium have been recognized, although methods to measure barium in various physical media have been described (67). 4.3.5.1 Blood Inductively coupled plasma–atomic absorption spectrometry (ICP-AES) has been used for measurement of barium compounds (as Ba) in biological materials, including blood. The detetion limit for Ba in blood by this method is reported to be 0.6 mg/L of blood (68). Neutron activation analysis has also been used for determining levels of Ba in human blood, with detection limits of 7 mg Ba/L of red blood cells and 66 mg Ba/L of plasma (7). 4.3.5.2 Urine Barium concentrations in urine of workers exposed to barium welding fumes reportedly increased, but the method used was not described (65). Subsequently, methods for detecting barium in urine have been published (6, 68, 69). The detection limit for Ba in urine measured by ICP-AES is reported to be 0.26 mg/L of urine (68). A proposed reference value for Ba in urine for biological monitoring purposes is 1.98 g/kg and the inhalation LD50 of barium zirconate was calculated to be 0.42 g/kg (71). A soluble form of barium, barium chloride, was considerably more acutely toxic in rats, with the LD50 calculated to be 220 mg/kg (as Ba) in weanling rats, and 132 mg/kg (as Ba) for adult rats (72). Elevated blood pressure, bronchoconstriction, ECG abnormalities, and myocardial hyperexcitability were demonstrated in guinea pigs administered barium-containing fume extract. These effects could be modified by nifedipine and propranolol (73). Similarly, intravenous administration of barium chloride to rabbits resulted in severe ventricular dysrhythmias, which were relieved by treatment with doxepin or verapamil (74). 4.4.1.2 Chronic and Subchronic Toxicity Barite dust inhaled by guinea pigs was reportedly associated with nodular pulmonary granulation, characteristic of human baritosis (1). A more recent study revealed no pulmonary granulomas following inhalation exposure to barium zirconate, although thickening of alveolar walls, as well as the medial layer of arteriole walls, was noted, with the general picture of a chronic interstitial pneumonitis (71). The results of at least three subchronic barium chloride drinking-water studies have been published. In the first of these, groups of young adult Charles River rats of both sexes were exposed at concentrations of barium chloride of 250 mg/L (ppm) for 4, 8, or 13 weeks. No significant toxic effects were noted. A tissue distribution study revealed that barium concentration in several tissues increased with dose, but not duration of exposure, and that the highest concentrations were found in bone (72). A subsequent subchronic study in which Fischer 344/N rats and B6C3F1 mice were administered barium chloride in the drinking water at levels up to 4000 ppm revealed renal toxicity as the major toxicological finding (75). Barium-treated male and female rats exhibited higher serum phosphorous than did controls, but other electrolytes and hematological values were within normal ranges. In both species, the animals in the 4000-ppm treatment group exhibited alterations in motor activity, grip strength, and thermal sensitivity. Central nervous system effects were also reported after subchronic–chronic subcutaneous injection of barium chloride (43). A third barium chloride drinking water study was designed to evaluate the potential in vivo cardiovascular effects of long–term barium exposure. Long–term administration of barium chloride (100 ppm) resulted in hypertension, hypersensitivity to barbiturate anesthesia, disturbances in myocardial energy metabolism, and depressed cardiac excitability, preferentially in the arterioventricular nodal region of the heart (76). 4.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms The barium ion is a chemical antagonist to potassium, and it appears that symptoms of barium poisoning are attributable to Ba2+-induced hypokalemia (77). a-Adrenergic responsiveness was found to be enhanced in barium-treated Purkinje fibers (78). Barium mimics calcium in its effects, but their kinetics in subcellular stores may be different (79). Barium also inhibits Ca2+-activated K+ channels, which prolongs excitation and can cause potentially lethal neuroexcitatory and spasmogenic effects (30). 4.4.1.3.1 Absorption Barium, in food sources, is absorbed from the GI tract into the bloodstream at approximately 6% of the administered dose (5). Approximately 75% of inhaled barium is absorbed (5). In beagle dogs, respiratory tract absorption of inhaled particles (1.2–2.1 mm median aerodynamic diameter) contributed significantly to the absorption of BaCl2. Approximately 75% of the body burden was absorbed into the circulatory system within hours of inhalation exposure; 55% was attributed to absorption deposited in the pulmonary regions of the lung and 2% to GI absorption (50). 4.4.1.3.2 Distribution Studies in rats showed that barium is cleared from the serum by deposition in bone and teeth (5, 80). Barium is also deposited in muscles, and is stored in lung, with little retention in liver, kidneys, spleen, brain, heart, or hair (81).

4.4.1.3.3 Excretion A study of the metabolism of 140Ba in rats showed the urinary and fecal excretions to be 7 and 20%, respectively (1). The half life in the human body is estimated to be 3.6 days (5). 4.4.1.4 Reproductive and Developmental A subchronic study in which Fischer 344/N rats and B6C3F1 mice were administered barium chloride in the drinking water at levels of 4000 ppm revealed no anatomical effects in either species, but the offspring of the high dose rats exhibited a marginal reduction in pup weight. No effects were seen on reproductive indices (75). An earlier study in which BaCl2 (20 mg) was injected into chick yolk sacs revealed curled toes in 50% of the surviving chicks (Ridgeway and Karnofsky, cited in Ref. 14). 4.4.1.5 Carcinogenesis A National Toxicology Program (NTP) 2-year study with male and female rats and mice, in which barium chloride hydrate was administered in drinking water, reported no evidence of carcinogenicity in either species (82). Bronchogenic carcinomas reportedly developed in rats injected intratracheally with [35S]BaSO4 (80). 4.4.1.6 Genetic and Related Cellular Effects Studies Barium nitrate was not positive in the Ames assay (S. typhimurium strains TA1535, TA1537, TA1538, TA97a, TA98, TA100, TA102c) with or without metabolic activation, with plate incorporation assay and preincubation assay methods. It was also negative in the mitotic crossing-over test, in the mitotic genic conversion test, and in the retromutation test in Saccharomyces cerevisiae D7 strain with or without metabolic activation (83). Genotoxicity studies with barium chloride hydrate were positive in the mouse lymphoma assay but negative in Salmonella assays and assays for increased frequencies of chromosomal aberrations and sister–chromatid exchanges in cultured Chinese hamster ovary cells (82). 4.4.2 Human Experience 4.4.2.1 General Information: NA 4.4.2.2 Clinical Cases Epidemic poisonings from soluble barium salts are rare. The most common poisoning occurs after ingestion of barium carbonate, which is used as a rodenticide (60). Onset of symptoms occurs within minutes to hours of ingestion and includes perioral paresthesias, vomiting, and severe diarrhea. Hypertension and cardiac dysrhythmias may follow. Profound hypokalemia and weakness progressing to flaccid paralysis are additional characteristics of barium poisoning. In one instance, a family was poisoned following accidental ingestion of barium carbonate, and one of these individuals also developed respiratory failure and rhabdomyolysis (60). Following intentional ingestion of approximately 13 g of BaCl2, a patient was hospitalized with intractable diarrhea, abdominal pain, weakness, and hiccups (84). The patient developed paralysis and profound hypokalemia, despite aggressive potassium replacement therapy. The patient also developed renal failure, possibly because he was administered intravenous magnesium sulfate. Oral magnesium sulfate is the treatment of choice to precipitate insoluble barium sulfate, thus preventing systemic absorption of barium; intravenous administration may have contributed to this patient's renal failure as a result of precipitation of barium sulfate in the bloodstream and/or kidneys (84). 4.4.2.2.1 Acute Toxicity The lethal dose of barium by ingestion is reported to be between 1 and 15 g (85), or 56 mCi/kg (5). The initial symptoms of toxicity are irritation of the gastrointestinal tract with nausea, vomiting, and diarrhea. Premature ventricular contraction and systemic hypertension often follow. The poisoned victim may progress to hiccups, convulsions, and flaccid paralysis. The paralysis often progresses centrally, and death occurs as a result of respiratory or cardiac arrest (84). Barium hydroxide and barium oxide are strongly alkaline in solution, causing severe burns of the eye and irritation of the skin (61). 4.4.2.2.2 Chronic and Subchronic Toxicity A benign pneumoconiosis, baritosis, was first described in humans in the 1930s (1). The condition occurs in individuals exposed to finely-ground BaSO4 as

well as barite miners (1, 86). Because of the high radiopacity of barium, the chest radiologic picture shows discrete, dense images; however, no symptoms, abnormal physical signs, interference with lung function, or increased susceptibility to thoracic disease is believed to occur. The radiographic abnormalities disappear slowly with cessation of exposure (86). Bronchial irritation has been associated with BaCO3, and BaO dust is considered a potential agent for dermal and nasal irritation (1). 4.4.2.2.3 Pharmacokinetics, Metabolism, and Mechanisms The toxicity of barium is related to its direct stimulation of smooth, striated, and cardiac muscles and to severe depression of serum potassium levels. The reduced serum potassium levels are the result of increased intracellular potassium, rather than increased urinary excretion. 4.4.2.2.4 Reproductive and Developmental: NA 4.4.2.2.5 Carcinogenesis: NA 4.4.2.2.6 Genetic and Related Cellular Effects Studies: NA 4.4.2.2.7 Other: Neurological, Pulmonary, Skin Sensitization, etc There is some debate as to the appropriateness of the use of insoluble BaSO4 as a contrast material in patients with obstructive bowel disease. The controversy centers on the fact that, whereas BaSO4 is an excellent contrast material, it causes serious peritonitis when in contact with the peritoneal cavity; such contact could potentially occur if the patient requires surgery or if there is a rupture of the bowel (87). 4.4.2.3 Epidemiology Studies 4.4.2.3.1 Acute Toxicity: NA 4.4.2.3.2 Chronic and Subchronic Toxicity There are a number of epidemiological studies which together are inconclusive concerning the health impacts of barium in drinking water. An epidemiological study released in 1979 (88) associated an elevated risk of cardiovascular mortality with barium concentrations in drinking water > 1 ppm. The area in question was a region of northern Illinois where the barium concentration in drinking water was in the range of 7–10 ppm. However, another study in the same area did not reveal an associated elevation in blood pressure in individuals consuming high barium drinking water (62). A systematic follow-up study to these reports was conducted in eleven healthy men who were monitored for cardiovascular risk factors following 4 weeks of drinking water with 0 ppm of barium, followed by 4 weeks of drinking water with 5 ppm of barium, followed by 4 weeks of drinking water with 10 ppm of barium. Diet and water volume consumption were strictly monitored. It was determined that there were no changes in blood pressure, plasma cholesterol, lipoprotein, or apolipoprotein levels, serum potassium or glucose levels, or urine catecholamine levels. There were no arrhythmias related to barium exposure. Therefore, it was concluded that barium exposure at 5 or 10 ppm in the drinking water did not appear to affect any of the known modifiable cardiovascular risk factors (89). 4.5 Standards, Regulation, or Guidelines of Exposure The U.S. Environmental Protection Agency (U.S. EPA) has established a maximum contaminant level (MCL) of 2 ppm of barium in the drinking water. The MCL represents the maximum level of a contaminant in water that is delivered to any user of a public water-supply system. U.S. EPA also requires that discharges or environmental spills of 10 lb or more of barium cyanide be reported. The Occupational Safety and Health Administration (OSHA), the National Institute for Occupational Safety and Health (NIOSH), and the American Conference of Governmental Hygienists (ACGIH) have set occupational exposure limits of 0.5 mg/m3 (threshold limit value [TLV]) for an 8-h workday, 40 h/week for soluble barium compounds. The OSHA limit for barium sulfate dust in air is 10 mg/m3 (total particulate; 5 mg/m3 for respirable particles). NIOSH currently recommends that a level of 50 mg/m3 be considered immediately dangerous to life and health. Australia and the United Kingdom have established exposure values of 0.5 mg/m3 as Ba. Germany has additional exposure

values for the inhalable fraction of the aerosol: TWA short-term, 0.5 mg/m3 1 mg/m3; 30 min, 4 times per shift.

Magnesium, Calcium, Strontium, Barium, and Radium Mary Beth Genter, Ph.D., DABT 5.0 Radium 5.0.1 CAS Number: [7440-14-4] 5.0.2 Synonyms: 228Ra (mesothorium); 223Ra (actinium X); 224Ra (thorium X) 5.0.3 Trade Names: NA 5.0.4 Molecular Weight: 226.03 5.0.5 Molecular Formula: Ra 5.1 Chemical and Physical Properties 5.1.1 General Pure metallic radium is brilliant white when freshly prepared, but blackens on exposure to air, likely because of formation of the nitride. Radium and its salts exhibit luminescence; like other alkaline-earth metals, radium decomposes on exposure to water and is more volatile than barium. Radium imparts a carmine red color to a flame. There are four naturally occurring isotopes of radium: 226Ra, 228Ra, 223Ra, and 224Ra. All isotopes of radium are radioactive, emitting a, b, and g rays. 226Ra (half-life 1600 years) emits a radiation with an energy of 4.87 MeV. The endpoint of 226Ra radioactive decay, emitting radioactive radon gas (222Rn), is the formation of lead. 224Ra has a much shorter half-life (3.62 days) and also decays via a particles (5.8 MeV). 222Ra has a half-life of 11.4 days and similarly emits an a particle in its decay (5.98 MeV), whereas 228Ra (half-life 5.7 years) decays by release of a b particle. Radium is over a million times more radioactive than the same mass of uranium (90). Melting point: 700°C, boiling point: 1737°C, d: 5.5. 5.2 Production and Use Radium is extremely scarce but may be found in uranium ores such as pitchblende at approximately 1 g/ton. The commonly occurring salts are the chloride, bromide, carbonate, and sulfate. Radium may be made on a very small scale by the electrolysis of molten radium chloride (90). Radium was discovered in the early twentieth century, and found medicinal uses and, because of its luminescence, use in the painting of watch and clock dials, as well as military instruments. Radium therapy (226,228Ra) was accepted by the American Medical Association (AMA) for treatment of rheumatism and as a general tonic, as well as for the treatment of mental disorders. 224Ra was used in Europe for over 40 years in the treatment of tuberculosis and ankylosing spondylitis. The isotopes 223Ra, 224Ra, 226Ra, and 228Ra have all been used as radiation sources for treating neoplasms in humans (5). 5.3 Exposure Assessment 5.3.1 Air The combustion of coal is probably the most important mechanism of release of radium into the atmosphere. The mean concentration of 226Ra in coal is on the order of 1 pCi/g. Radium combustion products may condense onto coal fly ash. The concentration of 226Ra in fly ash ranges from 1 to 10 pCi/g; the 228Ra content has been reported to vary from 1.8 to 3 pCi/g (91). It has been estimated that 2.2 Ci of total radium is released in this manner annually in the United States. Global release of 226Ra is estimated at 150 Ci per year. 226Ra concentrations in glacial ice samples have increased 100 fold since the 1920s, likely as a result of the increased combustion of fossil fuels (92).

5.3.2 Background Levels The concentration of radium in surface water is generally quite low. Shallow wells reportedly have lower 226Ra concentrations than do deeper wells, and the total content in municipal water supplies is generally lower than that in untreated well water. A summary of several sampling studies reveals that 226Ra generally occurs at concentrations ranging from 0.1 to 0.5 pCi/L in surface water, and the mean concentration in drinking water is 0.91 pCi/L. 228Ra activity in several midwestern states in the United States ranged from 0.3 to 32 pCi/L, with typical concentrations < 1 pCi/L. The main source of radium contamination in water is believed to be from uranium mine tailings. Radium in water exists as the divalent cation and can interact significantly with sediments and dissolved solids in water. The mean concentration of 226Ra in soil in 33 states was 1.1 pCi/g, similar to levels reported for various types of rocks (91). Analysis of garden plots in Port Hope, Ontario, Canada revealed radiumcontaminated plots with up to 830 pCi/g soil, compared to 1.2–2.6 pCi/g in plots uncontaminated by adjacent uranium mines (93). It has been estimated that the mean concentration of radium in the diet is approximately 0.73 pCi/kg of food (94). 5.3.3 Workplace Methods: NA 5.3.4 Community Methods: NA 5.3.5 Biomonitoring/Biomarkers Exposure to radium can be determined by the use of a whole body counter to measure the g radiation emitted by radium (95, 96). 5.3.5.1 Blood Radium can be measured in urine, feces, and other biological media by use of g-ray spectroscopy (91). 5.3.5.2 Urine Radium can be measured in urine, feces, and other biological media by use of g-ray spectroscopy (91). 5.3.5.3 Other The body burden of radium can be established by quantitation of radon in exhaled breath (94). 5.4 Toxic Effects 5.4.1 Experimental Studies 5.4.1.1 Acute Toxicity: NA 5.4.1.2 Chronic and Subchronic Toxicity For a variety of reasons, rodent studies examining the effects of a-particle emitters have been difficult to extrapolate to humans. Therefore, because of its long lifespan and the similarity of its biological properties to those of humans with regard to target organs, the beagle dog has been used as the model for study by several groups. Studies in beagle dogs indicate that a particles emitted by 226Ra are bone-seeking and associated with bone tumors, whether administered as a single or repeated doses (97). Primary bone tumors (n = 155) were reported in 131 of 246 beagles injected with 226Ra (5 primary bone sarcomas in 4 of 158 unexposed controls). The predominance of these (94%) were osteosarcomas (98). Mice injected with 224Ra (69– 550 Bq/g body weight) developed myeloid leukemia and osteosarcoma, with a dose–response correlation observed for both tumor types (99). In terms of extrapolating to human carcinogenic response to radium, these studies were interesting because a number of the mice in this study developed leukemia in the absence of osteosarcoma, and historically leukemia has not been a cancer linked to radium exposure (97, 100, 101). C57Bl/Do (black and albino) mice receiving approximately 10 mCi/kg of 226Ra similarly developed bone sarcomas (102). In a beagle dog study designed to evaluate the appropriateness of permissible body burdens for humans, 228Ra, administered at 16.6 times the human maximum permissible body burden (MPB), caused a shortened lifespan, whereas 226Ra at 10 times the MPB was associated with neither a significant number of excess bone tumors or shortened lifespan (55).

5.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms 5.4.1.3.1 Absorption In rats, oral administration results in 1–7% retention 400–500 days after administration; in contrast, 77% retention was observed 140–300 days after intradermal administration (91). In a study in which human volunteers ingested small amounts of 224Ra, 20% of the ingested dose reached the bloodstream (95). Following oral administration of radium, 80% appeared in the feces 10 days following expousre, with 20% retained and distributed systemically. The fecal:urine excretion ratio was also high (30:1) following IV administration (91). Accidental human inhalation exposure was associated with sequestration of radium in the bones, suggesting absorption from the lung and distribution via the bloodstream (91). 5.4.1.3.2 Distribution Following ingestion, radium is similar to calcium in its metabolism and is incorporated on bone surfaces into the mineralized portion of bone. The long half-life of 226Ra allows for distribution throughout the mineral skeleton over life. 5.4.1.3.3 Excretion The loss of radium from the body by excretion was determined to follow a relatively simple power function: R = 0.54t–0.52, where R = total body retention and t = time in days (103). As more data became available, it became apparent that the Norris equation is relatively accurate except at very long times after exposure e.g., (106). In practical terms, one year after exposure, approximately 2% of a dose of radium is retained in the body, but after 30 years, 0.5% still remains (104). 5.4.1.4 Reproductive and Developmental An old study (14) revealed that intravenous or subcutaneous administration of 5 mCi of radium to rats late in pregnancy caused fetal death associated with hemorrhage in the head and dorsal areas. 5.4.1.5 Carcinogenesis Although the National Toxicology Program has not classified radium with regard to its carcinogenicity, multiple laboratory studies document the ability of radium isotopes to cause cancer in animals. 5.4.2 Human Experience 5.4.2.1 General Information The maximum permissible (retained) body burden for bone of 226Ra for humans has been tentatively set at 1 mCi (3.7 kBq) for a 70-kg man, or 0.529 kBq/kg (55). This body burden is expected to be without radiation-induced injury. 5.4.2.2 Clinical Cases 5.4.2.2.1 Acute toxicity: NA 5.4.2.2.2 Chronic and Subchronic Toxicity Two types of cancer—sarcomas of the bone and carcinomas of the paranasal sinuses and mastoid air cells (called “head cancers”)—have been shown to be associated with radium exposure (105, 106). It is significant to note that, although all isotopes of radium are bone-seeking, and despite laboratory animal studies in which rodents exposed to radium developed both leukemia and bone sarcomas, human leukemia is not recognized as a longterm sequela of radium exposure. Raabe et al. (107) modeled bone sarcoma risk in the human, dog, and mouse and determined that there is a threshold dose and dose rate, representing a dose low enough so that bone cancer will not appear within a human lifespan; this dose is 0.04 Gy/day, or a total dose of 0.8 Gy to the skeleton. A population of 900 German patients, both juveniles and adults, who had been treated with 224Ra had 54 patients who developed bone sarcomas. The average skeletal dose in this population was 4.2 Gy. In a second cohort followed by Wick et al. (91), two ankylosing spondylitis patients (mean skeletal dose = 0.65 Gy) have developed osteogenic sarcoma, with no cases in the control group. 5.4.2.2.3 Pharmacokinetics, Metabolism, and Mechanisms The a-particles emitted by radium, once deposited on bone surfaces, can penetrate approximately 70 mm. The long half-life of 226Ra allows distribution throughout the mineral skeleton over a lifetime. The target cells for osteogenic sarcoma reside in marrow on endosteal surfaces approximately 10 mm from the bone surface (104). With its

shorter half-life, 224Ra delivers its a dose while the radium is still on bone surfaces (104). 5.4.2.2.4 Reproductive and Developmental Although many of the humans occupationally exposed to radium were women, there is little published about reproductive or developmental consequences of radium exposure. It has been reported that the adult heights of humans injected as children with 224Ra for treatment of tuberculosis were markedly lower than the heights of nontreated persons (91). 5.4.2.2.5 Carcinogenesis The U.S. EPA has classified radium as a class A carcinogen, meaning that there are sufficient data to support a link between exposure to radium and the development of human cancer. The a-particle radiation associated with radium is recognized as the causative agent for sarcomas of the bone and carcinomas of the paranasal sinuses in humans (106). A study attempting to ascertain the dose–incidence relationship for induction of these tumors examined 1474 women employed in the U.S. radium dial painting industry before 1930. This population exhibited 61 known cases of bone sarcoma and 21 cases of carcinoma of the paranasal sinuses or the mastoid air cells (106). Of these individuals, the radium body burden was known for 759, among whom there were 38 cases of bone sarcoma and 17 head carcinomas. 5.4.2.2.6 Genetic and Related Cellular Effects Studies In an analysis of a number of human protooncogenes in persons with internal systemic exposure to radium, alterations in the c-mos protooncogene were found in many, but not all, tissues from 6 of 7 subjects (105). The changes were EcoRI restriction fragment length alterations, and these were noted in normal (i.e., neoplasm-free) tissues from these individuals. 5.4.2.2.7 Other: Neurological, Pulmonary, Skin Sensitization, etc Leikin and Paloucek (5) report that adverse reactions associated with the use of radium in the treatment of neoplasms include leukopenia, cirrhosis, and cataracts. 5.4.2.3 Epidemiology Studies 5.4.2.3.1 Acute Toxicity: NA 5.4.2.3.2 Chronic and Subchronic Toxicity Evans (95) summarized quantitative studies of more than 450 humans who carried skeletal deposits of 226Ra and 228Ra for up to 50 years. For residual skeletal burdens >0.5 mCi, the occurrence of osteoporosis, dense-bone necrosis, trabecular coarsening, and spontaneous bone fractures increased with increasing skeletal burden. 5.4.2.3.3 Pharmacokinetics, metabolism, and mechanisms: NA 5.4.2.3.4 Reproductive and Developmental: NA 5.4.2.3.5 Carcinogenesis Evans (95) summarized >450 cases of humans with skeletal burdens of and/or 228Ra. For residual skeletal burdens ranging from 0.5 to 60 mCi of 226Ra, the fractional incidence of osteogenic sarcoma and carcinoma of the paranasal sinuses or mastoids was about 40% and appeared to be independent of residual body burden. However, in individuals with tumors, the latency period was determined to be related to the residual body burden. It has been noted that breast cancer, liver cancer, and chronic myeloid leukemia have also been associated with radium exposure (5). 5.5 Standards, Regulation, or Guidelines of Exposure No oral reference dose or inhalation reference concentration for radium has been established. The USEPA has established a maximum contaminant level of 5 pCi/L for combined 226Ra and 228Ra in drinking water and has classified radium as a class A carcinogen; this represents an agent for which sufficient evidence exists to support a causal relationship between exposure and cancer. 226Ra

Magnesium, Calcium, Strontium, Barium, and Radium

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‘normal’ tissues from humans exposed to radium. Cancer Res. 49, 2668–2673 (1989). 106 R. E. Rowland, A. F. Stehney and H. F. Lucas, Dose-response relationships for female radium workers. Radiat. Res. 76, 368–383 (1978). 107 O. G. Raab, S. A. Book, and N. J. Parks, Bone cancer from radium: Canine dose response explains data for mice and humans, Science 208, 61–64 (1980). Zinc and Cadmium Marek Jakubowski, Ph.D. 1 Zinc and Zinc Compounds 1.0 Zinc 1.0.1 CAS Number: [7440-66-6] 1.0.2 Synonyms: Zinc dust, zinc powder 1.0.3 Trade Names: Asarcor; L15; Blue Powder; CI 77945; CI pigment Metal 6; Emanay Zinc Dust; Granular Zinc; JASAD; Merrilite; PASCO (97). 1.0.4 Molecular Weight: 97.45 1.0.5 Molecular Formula: Zn 1.1 Chemical and Physical Properties 1.1.1 General Zinc is a relatively soft, bluish-white shiny metal. It exhibits a strong tendency to react with both the inorganic compounds (e.g., oxides, sulfates, and phosphates) and the organic ones. The physical and chemical properties of zinc are displayed in Table 29.1. Table 29.1. Physical and Chemical Properties of Zinc and Zinc Compounds

CAS Compound # Zinc

[744066-6]

Zinc oxide [131413-2] Zinc [764685-7] chloride Zinc sulfate [773302-0] Zinc [55734-6] acetate Zinc [55705-1] stearate Zinc [7783ammonium 24-6] sulfate

Molecular Formula

Boiling Melting Solubility Refractive P Point Point (° Specific in Water Index (20° MW (°C) C) Gravity (at 68°F) C)

Zn

65.38

ZnO

81.38

ZnCl2 ZnSO4 Zn(C2H3O2)2 Zn(C18H35O2)2 (NH4)2SO4 ZnSO4 6H2O

908

419.5

7.14 at Insoluble 25°C

—

No 100 5.607 at data (decomp.) 20°C 136.29 732 290 2.907 at 25°C

0.0016 g/L at 29°C 4320 g/L at 25°C

—

161.44

1667 g/L at 25°C 300 g/L at 20°C Insoluble

—

No 600 3.54 at data (decomp.) 25°C 183.47 — 200 1.84 (decomp.) 632.23 — 130 — 401.66

—

Decomp.

1.931 70 g/L at 0°C

1 H 4

—

— — 1.489, 1.493, 1.495

N

Zinc and Cadmium Marek Jakubowski, Ph.D. 2 Cadmium and Cadmium compounds 1.0 Cadmium 1.0.1 CAS Number: [7440-43-9] 1.0.2 Synonyms: Cadmium dust fume, cadmium powder, colloidal cadmium 1.0.3 Trade Names: NA 1.0.4 Molecular Weight: 112.40 1.0.5 Molecular Formula: Cd 1.1 Chemical and Physical Properties 1.1.1 General Cadmium (oxidation state 2, density 8.6, melting point 320.9°C, boiling point 765°C), is a silver-white metal that belongs to the group IIb in the periodic table. Its natural isotopes are 106 (1.22%), 108 (0.88%), 110 (12.37%), 111 (12.75%), 112 (24.07%), 113 (12.26%), 112 (24.07%), 1139 (12.26%), 114 (28.86%), and 116 (7.59%). Cadmium is insoluble in water and soluble in acids. It has a relatively high vapor pressure. In ambient air cadmium vapor is oxidized rapidly to produce cadmium oxide. In the presence of reactive gases or vapors, such as carbon dioxide, water vapor, sulfur dioxide, sulfur trioxide, or hydrogen chloride, cadmium vapor reacts to produce, respectively, cadmium carbonate, hydroxide, sulfite, sulfate, or chloride. These compounds may be formed in stacks and emitted to the environment. The physical and chemical properties of major cadmium salts are summarized in Table 29.4. Table 29.4. Physical and Chemical Properties of Cadmium and Cadmium Compounds Vapor Boiling Melting Solubility Refractive Pressure Molecular Point (° Point (° Specific in Water Index (20° (mm Compound CAS # Formula MW C) C) Gravity (at 68°F) C) Hg) Cadmium Cadmium chloride Cadmium oxide Cadmium sulfide

[7440- Cd 43-9] [10108- CdCl2 64-2] [1306- CdO 19-0] [1306- CdS 23-6]

Zinc and Cadmium

112.41 765

320.9

183.32 960

568

8.642 Insoluble

4.047 at 1400 g/L 25°C at 20°C 128.41 Sublimes No data 8.15 Insoluble at 1559 144.47 No data 1750 at 4.82 0.0013 g/L 100°C at 18°C

— — — 2.506 2.529

1 at 394° C 10 at 656°C 1 at 1000°C No data

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Mercury Ernest Foulkes, Ph.D. Introduction Mercury is a heavy metal widely distributed in nature, both as the metallic element (Hg0) and as inorganic or organic compounds of its oxidation products, the mercurous (Hg+) and mercuric (Hg2+) ions. These mercury species are readily interchangeable in the environment and in the body, and evidence suggests that their toxicity in many cases reflects the actions of the mercuric ions formed by oxidation of mercury or by breakage of the mercury–carbon bond. To that extent, different toxicities of individual compounds can largely be attributed to differences in their toxicokinetic properties such as rates of absorption, distribution, degradation, or oxidation to Hg2+, and finally excretion. Monosubstituted organic compounds of mercuric mercury may also react directly with biological molecules before degradation to Hg2+. Although all biological tissues contain traces of mercury, no essential biological function has been identified for the metal. To the contrary, because the end product of the metabolism of mercury and mercurials is usually the mercuric ion, which has high affinity for proteins and other biological molecules, many of the organic and inorganic compounds of the metal strongly inhibit biological reactions in very low concentrations. The high chemical reactivity of Hg2+ also helps explain the relatively nonspecific nature of mercury toxicity in the target organs. For instance, mercuric mercury accumulates primarily in the kidney, but in that organ it inhibits a large number of different enzymatic and other functions. Natural sources of mercury include primarily deposits of the metal itself or of insoluble mercuric sulfide (HgS, cinnabar). Most of the world's production of mercury comes from mines in Algeria, China, Spain, and Kyrgyzstan. The background concentration of mercury in the environment reflects outgassing from the earth's crust and the result of volcanic activity. Large amounts of mercury are also contributed to the environment by human activities. The use of Hg by humans has been traced back thousands of years, and the high morbidity observed in mercury miners was well recognized in Roman days. Among major anthropogenic contributions to mercury pollution are the combustion of fossil fuels, the application of inorganic fertilizers and sewage sludge to agricultural lands, the amalgam process of extraction and purification of noble metals, losses incurred during the extensive use of mercury and its compounds in industry, and leaks from waste disposal. Natural and anthropogenic releases of mercury into the atmosphere in the 1980s were roughly equivalent and reached values of more than 6000 tons per year (quoted in Ref. 1). Human exposure to mercury and mercurials also was, and in part still is, associated with their direct application for cosmetic and therapeutic purposes. Even in the twentieth century, such uses have included topical treatment with mercury-containing skin whiteners, antiseptics, and infants' teething powder. Organic mercurials have also been prescribed routinely as diuretics for treating salt and water retention. These human applications have mostly been abandoned, but the presence of the element in dental amalgams remains a significant and continuing source of human exposure.

The interchangeability of various mercury species in the environment and in the body and the overlap between the toxic effects of individual mercurials and between the biomarkers available for monitoring exposure to these mercurials make it impractical to consider the different mercurials under entirely separate headings. This chapter, therefore, discusses the occupational toxicology of mercury and selected mercury compounds under three main overlapping headings: A. Elemental Mercury, B. Inorganic Mercury Compounds (primarily the chloride salts of mercuric and mercurous mercury, although other inorganic mercury salts are also cited), and C. Organic Mercury Compounds (mostly methylmercuric chloride and phenylmercuric acetate). A very extensive literature has accumulated on all of these topics. However, no attempt will be made here to provide an exhaustive survey; a detailed listing, for instance, of all occupational uses and reported health effects of each chemical species of mercury in every animal species tested and in humans, under all exposure conditions would have to cover thousands of references and is hardly necessary to emphasize the major problems potentially associated with human occupational and general exposure to mercury and its compounds. Additional details on mercury and mercurials may be obtained from a number of informative recent publications, including the EPA document on mercury (2), a toxicological profile placed into the Federal Register by the Agency for Toxic Substances and Disease Registry (ATSDR) (3), the NIOSH Manual of Analytical Methods (4), and the authoritative review of Clarkson (5). The volume edited by Chang on the Toxicology of Heavy Metals (6) provides an extensive discussion of the toxic properties of mercury. Environmental health criteria for inorganic mercury were discussed by WHO (7). An earlier volume on the history of mercury contains much fascinating information on this important element (8).

Mercury Ernest Foulkes, Ph.D. A. Elemental Mercury Although elemental mercury is readily oxidized to mercuric ions, the industrial applications and the toxicity of the two mercury species differ greatly. This is related to their physicochemical properties and their different distributions in the body. It is therefore appropriate to discuss the two species under separate headings. 1.0 Mercury 1.0.1 CAS Number: [7439-97-6] 1.0.2 Synonym: Quicksilver 1.0.3 Trade Names: NA 1.0.4 Molecular Weight: 200.61 1.0.5 Molecular Formula: Hg0 1.1 Chemical and Physical Properties 1.1.1 General Metallic mercury at room temperature is a silvery and volatile heavy liquid (specific gravity 13.546) with a vapor pressure of 0.0012 mmHg at 20°C. The metal is slowly oxidized to mercuric oxide (HgO) near its boiling point (356.9°C) in the presence of oxygen. This reaction is reversed at higher temperatures. Similarly, the element may be reversibly oxidized to mercuric mercury in the environment and in the body. The metal reacts with halogens and sulfur and dissolves in nitric acid or concentrated sulfuric acid; it is little affected by hydrochloric acid (1). Mercury vapor is very slightly soluble in water (56 mg/L at 25°C). Among physical and chemical properties which make the metal important for many technical

purposes are (1) the high vapor pressure of Hg0, which permits purification of the metal by distillation. Vaporization also provides a convenient tool for spectroscopic analysis of mercury (see section 1.3). The volatility of mercury makes inhalation exposure an important potential risk. (2) The high surface tension of Hg0 reduces wetting of glass and other surfaces. This property, together with its uniform thermal expansion, makes the metal ideal for use in thermometry. (3) The high electrical conductance of Hg0 is important in thermostats, electrical switches, electrodes, etc. (4) The high specific gravity of Hg0 is important in manometers, barometers, and other control devices. (5) Hg0 forms amalgams with gold and other metals that are used extensively in extracting and purifying of noble metals and in dental fillings. 1.1.2 Odor and Warning Properties The metal is odorless, but its presence can readily be detected by UV spectroscopy or cold-vapor atomic fluorescence measurements, as proposed by the EPA (9). These techniques have also proven useful for analyzing biological and other samples for trace amounts of inorganic mercury compounds following their reduction to the element by reagents such as stannous chloride (see section 2.1.2). Listing of other techniques for estimating total mercury content may be found in Ref. 1. 1.2 Production and Use Mercury is mined primarily in underground mines as the metal or as the red sulfide cinnabar (HgS). Like HgO, the sulfide decomposes at higher temperatures. Heating of the ore and condensation of the mercury vapor constitute a convenient procedure for reducing, extracting, and purifying mercury from its ore. Total world production fell from 8698 metric tons in 1975 to 1760 in 1994, reflecting in part increasingly prohibitive environmental, health, and safety regulations. In the United States, mercury is produced primarily from secondary sources; this involves recycling a variety of industrial waste products. Total consumption of the element in the United States in 1995 amounted to 463 metric tons (3). More than 150,000 workers are believed to have been potentially exposed to mercury and its compounds in the United States in 1990 (10); the majority of these exposures involved mercury vapor. Some of the many uses of the metal have been described in section 1.1.1. Others include, for instance, mercury vapor lamps, and as a heavy liquid in fluid bearings and clutches. A major application is as a cathode in chloralkali plants that produce NaOH and chlorine by electrolyzing NaCl. The significance of the exposure from this process can be illustrated by the work of Langworth et al. (11) who found fourfold increases in blood Hg levels and 13-fold increases in normalized urinary levels in workers engaged in this process. The toxicity of mercury and the cost of its safe disposal have led to the search for alternative, Hg-free processes. Thus, total U.S. consumption of mercury fell from 1503 tons in 1988 to 621 in 1992. By way of illustration, about 50% of chloralkali plants used Hg-free processes in 1994 (2). Although as much as 16% of mercury consumed by industry has been recovered and recycled (3), the remaining major portion represents a very significant addition to the environment. 1.3 Exposure Assessment Exposure to elemental mercury, as well as to most of its compounds, can best be monitored by the total levels of mercury in blood and urine. A difficulty in relying on the level of blood mercury for quantitatively evaluating an earlier exposure to mercury vapor is posed by the peak in the blood concentration that occurs 2–4 days after exposure; blood analyses after longer periods are therefore generally less informative. Another problem in evaluating mercury exposure especially from blood mercury levels arises from the likelihood of mercury release from tissues. Peaks of mercury concentration in urine after exposure appear and decline more slowly than in blood. Total mercury concentrations in urine following exposure to mercury vapor are of interest especially because of the oxidation of Hg0 to Hg2+; the latter accumulates primarily in the kidney, from which it may directly enter the urine (see section 2.4). The significance of exhaled Hg0 following acute exposure may be confounded by the output from dental amalgam and by the possibility of the reduction of Hg2+ in the body.

Hair analysis has also proven useful, and reasonably good correlations have been observed between hair and blood mercury contents. Segmental analysis of scalp hair, growing at a rate of around 3 mm/week, can provide some indication of the history of exposure over relatively long periods. Hair analysis is particularly useful in providing evidence of exposure to methylmercury because this compound is incorporated into hair as such (see section 4). The estimation of mercury and its compounds is discussed in greater detail in section 2.3. In environmental or biological samples, as emphasized before, the interchangeability of the various chemical species of Hg makes total mercury levels more significant than those of elemental Hg. Mercury vapor can pose health problems in occupational settings and also following, for instance, accidental breakage of such instruments as thermometers and barometers in the home or the use of mercury and mercurials for cosmetic, therapeutic, and other purposes. A major contribution of mercury from such sources at present results from the application of Hg amalgams in dental fillings. Urinary levels of mercury, ultimately derived from dental amalgams, have attained or even exceeded occupational health limits. To quote just one of many papers, urine collected from individuals carrying more than 36 dental amalgam restorations contained on the average 30 nmol Hg/L, compared to 6 nmol/L in the urine of control subjects without amalgams (12). According to WHO reports (7), occupational exposure to 50 mg Hg vapor/m3 air increases the rate of urinary Hg excretion to more than 30 nmol/mmol creatinine. The potential internal Hg exposure due to dental amalgams may also be judged by the report that mean levels of Hg0 in the breath of subjects who carry amalgam restorations was 8.2 ng/L (or mg/m3), more than 100 times higher than in the breath of subjects without amalgam fillings (3). Individuals who have many amalgam restorations may absorb 10–12 mg of mercury per day (12). Exposure of dental health professionals also results from present practice, and one report describes an increased frequency of reproductive failures in female dentists and dental assistants (13). Overall, however, no clear-cut health effects of amalgam exposure have been described (14), and its toxicological significance remains under discussion. 1.3.1 Biomonitoring/Biomarkers Blood and urine levels of Hg are commonly assayed and provide at least a qualitative measure for evaluating exposure to mercury. This topic has already been considered earlier in section 1.2 Exposure Assessment. Because elemental mercury is fairly rapidly oxidized to Hg2+ in body fluids, exposure to Hg0 is generally evaluated by blood and urine analysis for elemental plus inorganic mercury. This commonly involves reducing the inorganic mercury to the element and using UV spectroscopy for Hg vapor. Analysis specifically for Hg0 in the presence of Hg2+ omits the reduction step. Further details will be given under the heading of mercuric chloride (section 2.3). 1.4 Toxic Effects Because the element is relatively inert, it exerts little direct toxic action. On the other hand, it is readily oxidized to mercuric ions. One biological mechanism for this oxidation involves the enzyme catalase in presence of hydrogen peroxide; the reverse reaction, the reduction of Hg2+ to Hg0, has also been observed in animals. In any case, all evidence points to Hg2+ as the ultimate toxicant during exposure to mercury vapor, salts of mercurous mercury, and in part also to organic mercurials. Many aspects of the toxicity of elemental mercury will therefore be included in section 2.4 under the heading of Toxic Effects of Hg2+. The fact that Hg0 to some extent like methylmercury (see section C on Organic Mercury Compounds), but in contrast to Hg2+, acts primarily on the central nervous system can be explained by its lipid solubility and consequent ability to cross cell membranes such as those in the blood–brain barrier. After moving across this barrier, elemental mercury is likely to be extensively oxidized to Hg2+ and consequently to become trapped in the central nervous system. 1.4.1 Experimental Studies Liquid (metallic) mercury is very poorly absorbed from the gastrointestinal tract. Release of mercury vapor in the intestine may be retarded by a coating of insoluble HgS formed in the intestine. This may help explain the survival of patients treated in

former centuries for constipation by ingestion of the metal. Inhalation is the most important route of exposure to Hg0: as much as 80% of inhaled vapor is retained in the lungs (15). As pointed out by Clarkson (5), this high value represents essentially complete absorption across the alveolar membranes. Dermal absorption of elemental mercury has also been described but, though not insignificant, is much smaller. Thus, for every mg of Hg/liter of air, the vapor is taken up by the skin at an average rate of 0.24 mg/cm2·min. The calculated amount of mercury thus retained amounted only to about 2% of simultaneous pulmonary absorption. Moreover, only half of the Hg0 taken up in the skin could be recovered as systemic mercury (16); the remaining portion presumably is retained and accumulates in dermal cells and is subsequently lost upon their desquamation. Mercury vapor is rapidly distributed throughout the body, readily penetrates cellular barriers such as the placenta and the blood–brain barrier, and appears in milk and other secreted body fluids. Once it has crossed the placenta and the blood–brain barrier, elemental mercury is oxidized and becomes largely trapped as Hg2+ in the central nervous system. Inhalation of the vapor by rats and mice, leads to mercury accumulation primarily in the gray area of the central nervous system. The highest levels are in certain neurons of the cerebellum, the spinal cord, the medulla, the pons, and the midbrain (17). Such inhalation is, therefore, associated primarily with neurotoxic effects. Similar lesions are produced by methylmercury, also reflecting the trapping of mercury in the brain (see section 4). Toxic effects of Hg0 on the developing central nervous system have been described in rat fetuses and pups. Limited evidence only has been found for carcinogenic actions of elemental mercury (see the genotoxicity of Hg2+ in section 2.4), and it is not classified as carcinogenic by the USEPA. Sarcomas have been reported in rats following intraperitoneal injection (18). In general, many of the cytotoxic actions of the metal resemble those of its oxidation product, the mercuric ion (see section 2.4). Differences in their overall toxicity are mostly related to their usual portals of entry and to their different distributions in the body. Thus, the first pass of Hg0 through the lungs during inhalation exposes these organs to much higher concentrations of mercury than the kidneys; the inverse is true for Hg2+ following ingestion. Similarly, the ready passage of mercury vapor across the blood–brain barrier, in contrast to the essential impermeability of that barrier to Hg2+, helps to explain the primarily neurotoxic effects of the vapor. 1.4.2 Human Experience Hursh et al. (15) studied the clearance of radioactive mercury vapor inhaled by human subjects. Seven percent of inhaled mercury in their study was exhaled again, with a halftime of 18 h. The half-life of total mercury in the kidney region was as long as 64 days, consonant with oxidation to Hg2+ and preferential renal uptake. Acute inhalation of mercury vapor at a concentration in excess of 1 mg/m3 may cause damage to the lungs; renal malfunction has also been observed. The major functional lesions, however, are found in the central nervous system. They are manifested by behavioral and other deficits. Erethism, a peculiar form of emotional instability, has long been recognized as a symptom of mercury intoxication. Other symptoms include tremor, weight loss, gingivitis, headache, and drowsiness. Acute exposure can also cause pneumonitis and contact dermatitis. Overt toxicity may be expected in populations exposed to time-averaged air concentrations of Hg0 that exceed 0.1 mg/m3. There are conflicting reports in the literature on reproductive effects of human exposure to metallic mercury. The potential problems encountered by workers exposed to dental amalgam have already been discussed in section 1.3 Exposure Assessment. Reproductive toxicity in males was studied by Cordier et al. (19) whose results indicate that paternal exposure prior to conception might increase the subsequent risk of spontaneous abortion. Elemental mercury does not react with chelators (see section 2.4). Their successful therapeutic use following exposure to Hg0 therefore indicates, as already mentioned, that the element is oxidized to Hg2+ in the body. Indeed, about 80% of Hg0 taken in by humans is subsequently excreted as

mercuric mercury. 1.5 Standards, Regulations or Guidelines of Exposure OSHA, NIOSH, and the American Conference of Government Industrial Hygienists (ACGIH) have selected a permissible exposure level (PEL) (time-weighted average) of 50 mg Hg0/m3 of air. The USEPA Integrated Risk Information System (see Ref. 52) quotes a reference concentration in air of 0.3 mg/m3; no NOAEL was determined for chronic inhalation exposure, but a LOAEL, adjusted for occupational inhalation and workweek was calculated as 9 mg/m3 (2). 1.6 Studies on Environmental Impact Because of the ready interchangeability of elemental, inorganic, and organic mercury, the problem of general environmental impact of mercury will be considered here under a common heading for the element and its compounds. Additional information is provided in section 4.6 for methylmercury, a frequent and potentially very toxic contaminant of the human food chain. This compound is formed by bacterial methylation of inorganic mercury, a further reason for minimizing levels of total mercury in the environment. Mercury is added to the environment from two main sources: “natural” mercury, and mercury arising from human activities (anthropogenic mercury). Natural sources include degassing of mercury from the earth's crust and from volcanic eruptions. The presence of mercury in fish (mostly in the form of methylmercury, see section 4.6) such as sword fish, which is at the top of the marine food chain and is harvested far from likely industrial sources of mercury, has thus been attributed ultimately to mercury from volcanic activity. The anthropogenic origin of mercury is associated with mining, coal combustion and incinerators, agricultural and industrial applications, surface waste disposal and other activities; these anthropogenic sources contribute a major fraction of the Hg added to the atmosphere each year (20). Atmospheric Hg0 becomes oxidized to Hg2+, and as such may be deposited on land or water. Deposited Hg, in turn, tends to be reduced to the volatile metal. Because of this volatility, elemental mercury is continuously cycled through various environmental compartments and becomes widely distributed throughout the environment. However, it is only in proximity to specific point sources that environmental damage is likely to become significant. The total mercury content of unpolluted waters usually falls below 1 ng/L. The average daily intake of total mercury from air by the general population in the United States has been estimated at 0.04 mg/day; a similar value was found for drinking water (0.05 mg/day). The total intake in nonfish food was calculated as 3.6 mg/day; normal fish consumption raised this value to 6.6 mg/day. Note that intake of Hg0 from dental amalgams can rise as high as 21 mg/day. Section 1.2 already referred to the considerable scope for minimizing the anthropogenic input of mercury into the environment, especially by substituting Hg-free processes for those that depend on mercury. It was noted, for instance, that washing of coal reduces its mercury content by an average of 21% (2). Further reductions are probably achievable with the development of new procedures. Of course, washing of coal only transfers the metal to waste slurries and thereby does not automatically reduce the concentration in the environment. The magnitude of the human contribution to environmental pollution is reflected in the two to fivefold increase in atmospheric Hg since the beginning of the Industrial Revolution. The persistent problem of such contributions is dramatically emphasized by the report that during a period of 33 years, about 213 metric tons of mercury and mercuric nitrate were spilled into creeks at the Oak Ridge National Laboratory (3). Mercury remaining at that site is present now primarily as insoluble HgS; bacterial oxidation to the more soluble sulfate, however, will continue to make the metal slowly available for reactions in the biosphere.

Mercury Ernest Foulkes, Ph.D. B. Inorganic Mercury Compounds Occupational exposure to inorganic mercury compounds occurs during mining for the major mercury ore, cinnabar (mercuric sulfide, HgS), and as a result of their extensive industrial applications. Among these compounds, for instance, is mercuric oxide (HgO), once a common constituent of many types of batteries, including Zn–carbon cells, Zn–silver oxide cells, and others. Mercuric sulfate has also been used in paints and is a catalyst in the chemical industry (see section 4.2). Mercuric nitrate was formerly applied in the felting process for beaver furs in the hat industry (thence the suggested origin of the term “a mad hatter,” believed to have been originally applied to an affected victim of occupational exposure in the hatting industry). Mercuric fulminate is a common constituent of percussion caps of firearm ammunitions. Mercuric acetate and bromide are common laboratory reagents. Several mercuric mercury salts have, in the past, also been extensively used as antibacterial compounds. Among important mercurous salts are mercurous chloride (calomel), employed as the standard calomel electrode, and mercurous sulfate, also found in batteries. Mercurous acetate, iodide, phosphate, and tannate salts have all been used at one time to treat syphilitic lesions. Mercurous chromate has served as green colorant for chinaware. The various salts of mercurous (Hg+) and mercuric (Hg2+) ions are all more or less toxic; the toxic entity is usually the mercury ion. The actual toxicity of the compounds also depends, of course, on their water solubility and thence their availability for absorption. The actions of mercurous ions in the body have been attributed to their oxidation to the mercuric form; this, in turn, readily reacts with biological molecules. Mercurous mercury (Hg–Hg)++ in aqueous solution decomposes into mercuric and elemental mercury according to the equation

Mercuric ions in solution readily form a variety of coordination complexes. For instance, in the presence of high chloride concentrations such as in physiological saline, Hg2+ exists mostly as polychloride anions like HgCl3–; such anions are involved in the intestinal absorption of mercuric mercury (21). Iodide complexes such as K2HgI4 are freely available. Complexes are also produced with ammonia or amino groups, as in Hg(NH3)2Cl2. Mercuric ions also form relatively stable covalent mercury–carbon bonds to produce the organic mercurials; these are used for many purposes and will be discussed further under heading C. Organic Compounds of Mercury. Some organic mercury compounds are relatively nontoxic, whereas others, especially the short-chain alkyl derivatives, are potent neurotoxins. Although mercury vapor is absorbed primarily through the lungs, uptake of inorganic mercury compounds mostly follows ingestion. Table 30.1, based on Ref. 22, summarizes the daily retention of mercury and mercurials by adults in the general environment. Table 30.1. Daily Retention of Mercury and Mercurials by Adults in the General Environmenta Source Air Food: fish

Hg vapor Inorganic mercury Methylmercury 0.024 0

0.001 0.042

0.0064 2.3

Non-fish Water Dental amalgams Total

0 0 >3.0 >3.0

0.250 0.003 0 0.3

0 0 0 2.3

a

Values represent individual retention (in mg/day) of different species of mercury taken in from air, food, and water, or from dental amalgam. Calculations are based on 80% fractional retention of inhaled Hg vapor and 7% and 96% fractional intestinal absorption of ingested inorganic and methylmercury, respectively.

Several points in this table deserve special emphasis. Note in particular that dental amalgam represents the major source of total mercury uptake and retention, significantly higher than that from background levels in food, water, and air. Mercury as mercuric chloride and similar salts is not well absorbed; the same is even truer of essentially insoluble mercurous salts. In contrast, methylmercury, derived mostly from fish in the diet, is strongly retained in the body (see section 4.4.1). It represents the major source of body mercury in populations that consume larger than average amounts of fish in their diet. These observations were made in studies of several isolated populations, and their toxicological significance is further reviewed in section 4.4. In an unpolluted environment, the FDA Total Diet Study (23) on populations not primarily dependent on fish consumption reported for the period 1982–1984 an average daily Hg intake in the general environment of approximately 50 ng/kg body weight; this applied to all age groups except young children. To this daily dose must be added any mercury taken in as a result of cosmetic and therapeutic uses of mercury and its compounds. The percutaneous toxicity of inorganic heavy metal compounds, including those of mercury, is generally relatively low (24). The two representative inorganic salts selected for more detailed discussion are mercuric and mercurous chloride.

Mercury Ernest Foulkes, Ph.D. C. Organic Compounds of Mercury As mentioned in the introduction to section B, the mercuric ion readily forms covalent bonds with carbon; some organic mercurials contain Hg–N bonds, as in mercuric succinimide. A large number of carbon–mercury compounds have been synthesized, and some are extensively used in agriculture and industry, for instance, for seed dressing and as antifungal compounds in paints and other materials. Some organic mercurials have also been employed for therapeutic purposes, although especially systemic administration is rare now. Mercurials such as mercurochrome (dibromohydroxymercurifluorescein) and merthiolate (ethylmercurithiosalycilate) have been applied as topical antiseptics. Among widely used systemic mercurial drugs were the diuretic isopropyl alcohol derivatives whose general structure is R · CH2 · CH(OY) · CH2 · HgX, where X stands for chloride, thioacetate, or other residues, and Y is commonly a methyl group. The Hg · X bond is ionic, leaving one mercury valence free to react with tissue components. The same important property is found in the monoaryl or monoalkyl derivatives of mercuric mercury. Thus, parachloromercuribenzoate is a common sulfhydryl reagent, extensively used in biochemical laboratories, and monomethylmercury forms biologically active complexes with L-cysteine or glutathione (see section 4.1).

Although monosubstituted organic mercurials may react directly in this manner with, and thereby inhibit the function of, critical sulfhydryl groups, much of their toxic potential is associated with the likelihood of degradation to free mercuric ions. The highly neurotoxic dimethylmercury, which is very lipid-soluble and rapidly absorbed through the skin and taken up across the blood–brain barrier into the brain, is presumably demethylated at least to the monomethyl compound before exerting any effects. Risks of exposure to dimethylmercury are exacerbated by the ability of the compound to pass through latex gloves; this apparently permitted the fatal poisoning of a laboratory worker, as reported recently in the news media. The mercurial diuretics and many of the other organic mercurials are relatively nontoxic and possess little occupational relevance; they will therefore not be discussed in detail here. However, exceptions to the generally low toxicity of many organic mercurials are the extremely toxic short-chain alkylmercurials. Of primary interest from the environmental and toxicological points of view are monomethylmercury salts, as further discussed in section 4.0. The dimethyl compound is a volatile and extremely potent neurotoxin; it is very easily absorbed through the skin or by inhalation, but poses little threat outside the laboratory. As already mentioned in section 1.4, the high neurotoxicity of methylmercury compounds, in contrast to the primarily nephrotoxic action of inorganic mercury, can be explained by their respective abilities rapidly to cross the blood–brain barrier. The alkylmercurial selected here for more detailed discussion is the chloride salt of monomethylmercury (see section 4). Other salts, like the nitrate, are biologically indistinguishable from the chloride. Ethyl mercury, another short-chain monosubstituted alkylmercury compound, has also been used as a biocide and exhibits toxic effects similar to those of the methyl derivative. A large number of aryl and alkoxyalkyl mercury compounds are known. The aryl compounds especially are used in occupational settings. A well-known example is the application of phenylmercury as a biocide in paints and agricultural products. Parachloromercuribenzoate (PCMB) is an aryl compound frequently employed in biochemical laboratories as a sulfhydryl reagent. The arylmercurial selected here for more detailed consideration is the acetate salt of phenylmercury (see section 5). The nature of the alkyl or aryl residue in organic mercury compounds largely determines their ability to reach especially intracellular target sites in selected organs and the stability of the mercury–carbon bond. Generally, long-chain alkyl mercurials are more readily dealkylated than short-chain compounds. 4.0 Methylmercuric Chloride 4.0.1 CAS Number: [115-09-3] 4.0.2 Synonyms: Chloromethylmercury; MMC; methylmercury chloride; monomethyl mercury chloride; caspan; methylmercury (II) chloride 4.0.3 Trade Name: Caspan 4.0.4 Molecular Weight: 251.10 4.0.5 Molecular Formula: CH3 · HgCl 4.0.6 Molecular Structure:

4.1 Chemical and Physical Properties 4.1.1 General Monomethylmercuric mercury is a univalent cation. Despite its ionic nature, however, it is significantly more lipid-soluble than inorganic mercury compounds. The chloride salt is a white crystalline solid at room temperature and has a melting point of 170°C. Its specific gravity is 4.06,

and its vapor pressure at 25°C is 0.0085 mmHg. At higher temperatures, it volatilizes with a disagreeable odor. It is slightly soluble in water ( 25% by weight Soluble with hydrocarbon solvents 7.2 Production and Use

Major uses as polymerization catalyst; intermediates in silicones, certain polymers and organic acid synthesis. 7.3 Exposure Assessment NIOSH methods 7300 (10) and 7013 (9) can be used to analyze air. 7.4 Toxic Effects Essentially no toxicity data have been reported, although the known corrosive properties of the family of compounds is well established. It has been reported that contact with solutions of < 20% concentration (172) may be without hazard. Corrosive action can be expected on eye contact (173). Atmospheric exposures to fumes of Al2O3 will result following pyrophoric and/or explosive reactions as a consequence of oxidation of the aluminum of this compound. Although numerous investigators have suggested that metal-fume fever might result from the aluminum oxide fume so formed, no primary source can be found for that assertion. 7.5 Standards, Regulations, or Guidelines of Exposure A TLV has been set by the ACGIH for the alkyl aluminum compounds as a class, recognizing the paucity of experimental and/or human exposure data. Although they recognize that their major thermal decomposition product of these metalloalkyls would be Al2O3, they also note that many species in this class are halogenated. (see introductory paragraph preceding Section 7.0). Consequently, it could be assumed that pyrolysis would also be accompanied by the formation of halogen acid gases. Given the (possible) presence of such acid gases, ACGIH recommended a blanket guideline lower than that set for aluminum welding fume, specifically 2 mg/m3 for those alkyl aluminum compounds not otherwise classified (NOC). 8.0 Triisobutylaluminum 8.0.1 CAS Number: [100-99-2] 8.0.2 Synonyms: Aluminum triisobutyl; aluminum, tris (2-methylpropyl)-; Tibal; aluminum triisobutamide; triisobutylalane 8.0.3 Trade Names: NA 8.0.4 Molecular Weight: 198.33 8.0.5 Molecular Formula: C12H27Al 8.0.6 Molecular Structure:

8.1 Chemical and Physical Properties 8.1.1 General Clear, colorless liquid Melting point 6°C Boiling point 86°C (at 10 mm Hg) Vapor pressure 1 mm Hg (at 47°C) Pyophoric or explosive in water Explosive reactions with alcohols, benzene

8.1.2 Odor or Warning Properties White fumes with musty odor. 8.2 Production and Use Major use is as a polymerization catalyst in synthesis of polybutadiene, polyisoprene, primary alcohols, and olefins; also as an intermediate in synthesis of phosphate insecticides, and as a reductant. 8.3 Exposure Assessment NIOSH methods 7300 (10) and 7013 (9) can be used to analyze air. 8.4 Toxic Effects See Section 7.4. 8.5 Standards, Regulations, or Guidelines of Exposure The ACGIH guideline TLV is 2.0 mg/m3. (For discussion of rationale, see Section 7.5.) Aluminum Bibliography

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Staffordshire potteries. Br. J. Ind. Med. 20, 255–263 (1963). 169 National Research Council (NRC), Drinking Water and Health, Vol. 4, National Academy Press, Washington, DC, 1981, p 1641. 170 R. Ondreicka, Gunter, and J. Kortus, Chronic toxicity of aluminium in rats and its effects on phosphorus metabolism. Br. J. Ind. Med. 23, 305–312 (1966). 171 A. Spurgeon, D. Gompertz, and J. M. Harrington, Modifiers of non-specific symptoms in occupational and environmental syndromes. Occup. Environ. Med. 53(6), 361–366 (1996). 172 A. Rowland et al., Water contamination in north cornwall: A retrospective cohort study into the acute and short-terms effects of the aluminium sulfate incident in July 1989. J. R. Soc. Health 110(5), 166–172 (1990). 173 T. M. McMillan et al., Camelford water poisoning accident: Serial neuropsychological assessments and further observations on bone aluminium. Hum. Exp. Toxicol. 12, 37–42 (1993). 174 T. M. McMillan, G. Dunn, and S. J. Colwil, Psychological testing on schoolchildren before and after pollution of drinking water in North Cornwall. J. Child Psychol. Psychiatry Allied Discip. 34, 1449–1459 (1993). 175 P. J. Owens and D. P. Miles, A review of hospital discharge rates in a population around Camelford in North Cornwall up to the fifth anniversary of an episode of aluminium sulfate absorption. J. Public Health Med. 17, 200–204 (1995). 176 R. J. Huggett et al., The marine biocide tributyltin: Assessing and managing the environmental risks. Environ. Sci. Technol. 26, 232–237 (1992). 177 P. E. Newton et al., Inhalation toxicity of phosphine in the rat: Acute, subchronic and developmental. Inhalation Toxicol. 5, 223–239 (1993). 178 H. E. Stokinger, The metals:Aluminum. In G. Clayton and F. Clayton, eds., Patty's Industrial Hygiene and Toxicology, 3rd ed., Vol. 2A, Wiley, New York, 1981, pp. 1493– 2060. 179 R. Bonari and E. Martini, Toxicity of the fumes of the metallorganic compounds (aluminum alkyls). Med. Lav. 58, 290–296 (1967). Gallium, Indium, and Thallium Guillermo Repetto, MD, Ana del Peso A. Gallium and Gallium Compounds 1.0 Gallium 1.0.1 CAS Number: [7440-55-3] 1.0.2 Synonyms: Gallium, gallium metal 1.0.3 Trade Names: UN2803 1.0.4 Molecular Weight: 69.72 1.0.5 Molecular Formula: Ga 1.1 Chemical and Physical Properties 1.1.1 General The chemical element gallium (Ga), of atomic number 31, is a bluish metal of group IIIA in the periodic table. Gallium is a relatively rare metal that is becoming increasingly important in the manufacture of semiconductor electronic devices. Gallium was isolated for the first time from zinc sulfide ore in 1875 by the French chemist Lecoq de Boisbaudran, who named it after Gallia, the Latin name for France. Later the same year Dmitry Mendeleyev showed that gallium was the missing group IIIA element predicted in his theory of chemical periodicity, below aluminum and above indium.

Gallium is present in the earth's crust in a concentration of 5–15 ppm. It often occurs in small amounts in the sulfide ores of its neighbors in the periodic table, zinc and germanium; because of its chemical similarity to aluminum, it is a minor component of all aluminum ores. It is not present in significant concentrations in the ocean. The richest source, which is located primarily in southwestern Africa, is the mineral germanite, a sulfide. Germanite may contain 0.5–0.7% of gallium, but gallium is widely distributed in small amounts in zinc blends, aluminum clays, feldspars, and coal, and in the ores of iron, manganese, and chromium. Bauxite, the clay-like ore from which aluminum is obtained, contains 0.0002–0.008% gallium, whereas some tin ores contain 0.01–0.05% of gallium. Gallium is a lustrous, silvery liquid or bluish metal or a gray solid. It is the only metal, except for mercury, caesium, and rubidium, that can be liquid near room temperatures; this makes possible its use in high-temperature thermometers. It has one of the longest liquid ranges of any metal and has a low vapour pressure even at high temperatures. Ultrapure gallium has a beautiful, silvery appearance, and the solid metal exhibits a conchoidal fracture similar to that of glass (1). Molten gallium expands by as much as 3.2% on solidifying; therefore, it should not be stored in glass or metal containers, as they may break while the metal solidifies. Bismuth is the only other metal having this property. High purity gallium is attacked only slowly by mineral acids. Gallium arsenide is capable of converting electricity directly into coherent light, as it is a key component of LEDs (light-emitting diodes).

Gallium, Indium, and Thallium Guillermo Repetto, MD, Ana del Peso B. Indium and Indium Compounds 8.0 Indium 8.0.1 CAS Number: [7440-74-6] 8.0.2 Synonyms: Indium metal 8.0.3 Trade Names: NA 8.0.4 Molecular Weight: 114.82 8.0.5 Molecular Formula: In 8.1 Chemical and Physical Properties 8.1.1 General Indium is a rare, lustrous silver-white metal with atomic number 49 and In as its atomic symbol. It is widely distributed in the earth's crust in minute quantities (0.1 ppm) and is also found in the hydrosphere. Indium belongs to group IIIA in the periodic table. It was found and spectroscopically identified as a minor component in zinc ores and isolated in 1863 by Ferdinand Reich and Theodore Richter. Indium is so named for the indigo blue color that its salts lend to flames. Indium resembles tin in its physical and chemical properties and to some extent in its toxicological properties. It is extremely soft and malleable, with a Brinell test hardness of less than 1 and a Mohs scale hardness of 1.2. In the electromotive series it appears between iron and tin, and does not decompose in water at boiling temperature. It is stable in air, but when heated, it burns with a nonluminous, blue-red flame yielding indium oxide. The surface of indium remains bright up to its melting point; above this, it forms an oxide film. Indium has a density of 7.3 g/mL (at 20°C), a melting point of 156.61°C, a boiling point of 2000°C, and a specific heat of 0.0568 cal g–1 °C–1. Indium is insoluble in hot or cold water, soluble in acids,

and very slightly soluble in sodium hydroxide (163). There are two natural isotopes: 115 (95.77%) and 113 (4.23%). Indium-115 is a b-emitter, with a half-life of 6 × 1014 years. The artificial radioactive isotopes are 107–112, 114, and 116–124 (1–5). Indium forms mono-, di-, and trivalent compounds, of which the last is the most common. The trichloride is deliquescent; the sulfate is hygroscopic. Intermetallic semiconductors are formed from group III and group V elements. Most used are InSb, InAs, and InP. All require very high element purity (0.1 ppm). InSb is employed in infrared detectors and magnetoresistors. It wets glass, as does gallium. It is useful for making low melting alloys. An alloy of 24% indium and 76% gallium is liquid at room temperature. 8.1.2 Odor and Warning Properties Indium is flammable in the form of dust, yielding indium oxide when exposed to heat or flame. Mixtures of indium with sulfur ignite when heated. Indium reacts explosively with dinitrogen tetraoxide plus acetonitrile. Indium exhibits a violent reaction with mercury(II) bromide at 350°C. Indium is unaffected by water, is attacked by mineral acids and is very resistant to alkalies (7).

Gallium, Indium, and Thallium Guillermo Repetto, MD, Ana del Peso C. Thallium and Thallium Compounds 14.0 Thallium 14.0.1 CAS Number: [7440-28-0] 14.0.2 Synonyms: Thallium, rod; thallium metal, ramor 14.0.3 Trade Names: NA 14.0.4 Molecular Weight: 204.383 14.0.5 Molecular Formula: Th 14.1 Chemical and Physical Properties 14.1.1 General Thallium is a soft, gray-white metal. It is a member of group IIIA in the periodic table. The name derives from the Greek root thallos, meaning green or young twig. Thallium metal was isolated in 1861 by William Crookes and, independently, by the French chemist Claude-Auguste Lamy. Thallium's innate toxicity was recognized shortly after its discovery, when Crookes suffered from its effects. Thallium does not occur in nature in the elemental state but is present as a trace compound in many minerals, mainly associated with potassium and rubidium. Although thallium is widely distributed in the earth in an estimated abundance of 0.3 ppm, its wide distribution belies its availability, for it occurs chiefly as a minor constituent in iron, copper, sulfide and selenide ores, crooksite (TlCuAg)2Se, orabite (TlAs2SbS5), and lorandite (TlAsS3), mainly in Texas and Brazil. One exception is the occurrence of lorandite in gold ore in Nevada, which contains an average of 60% thallium. The deposits of thallium minerals are so small as to have no commercial significance at present. Thallium metal is somewhat softer and more malleable than lead and, when freshly melted, resembles tin in whiteness. Thallium, however, oxidizes rapidly, turning gray, then brownish black from an oxide coating. For this reason thallium rods are often paraffin-coated. The metallurgical properties of thallium are unknown because of limited use of the metal. The most interesting properties include boiling point 1457°C, melting point 303.5°C, commencement of volatilization at 174°C, density 11.85, vapor pressure 1 mm Hg at 825°C and 20 mm Hg at 1040°C, specific heat at 20°C 0.13 J/g, first ionization energy 590 kJ/mol, fusion heat 21.1 J/g, atomic volume 5.15 × 10+30 W/(C.m), thermal conductance 0.39 W/(cm K), covalent radius 0.148 nm, electronegativity 1.8

according to Pauling's scale, linear coefficient of expansion 28 × 10–6, electrical resistivity 18 mW/cm, tensile strength 9.0 MPa, bond strength 50% in ethyl alcohol, chloroform, ethyl ether, ethyl acetate, toluene, glycerol, and olive oil (2). 1.1.1 General: NA 1.1.2 Odor and Warning Properties Phenol has a distinct, aromatic, somewhat sickening sweet and acrid odor discernable at 0.5–5 ppm. It has a sharp and burning taste.

Phenol and Phenolics Ralph Gingell, Ph.D., DABT, John O'Donoghue, Ph.D., DABT, Robert J. Staab, Ph.D., DABT, Ira W. Daly, Ph.D., DABT, Bruce K. Bernard, Ph.D., Anish Ranpuria, MS, E. John Wilkinson, Daniel Woltering, Ph.D., Phillip A. Johns, Ph.D., Stephen B. Montgomery, Ph.D., Larry E. Hammond, Ph.D., Marguerita L. Leng, Ph.D. Acknowledgment The authors thank Brendan Dunn of Allied Signal for his thorough review of the section on phenol.

Phenol and Phenolics Ralph Gingell, Ph.D., DABT, John O'Donoghue, Ph.D., DABT, Robert J. Staab, Ph.D., DABT, Ira W. Daly, Ph.D., DABT, Bruce K. Bernard, Ph.D., Anish Ranpuria, MS, E. John Wilkinson, Daniel Woltering, Ph.D., Phillip A. Johns, Ph.D., Stephen B. Montgomery, Ph.D.,

Larry E. Hammond, Ph.D., Marguerita L. Leng, Ph.D. 2.0 Pyrocatechol 2.0.1 CAS Number: [120-89-9] 2.0.2 Synonyms: Catechol; 1,2-benzenediol; o-dihydroxybenzene; pyrocatechin; 1,2-dihydroxybenzene; obenzenediol; benzcatechin; Catechol–pyrocatechol; 1,2-dihydroxybenzene (Catechol) 2.0.3 Trade Names: Catechol 2.0.4 Molecular Weight: 110.11 2.0.5 Molecular Formula: C6H6O2 2.0.6 Molecular Structure:

2.1 Chemical and Physical Properties 2.1.1 General Physical state Colorless to white crystalline solid that discolors in air and light; sublimes readily; volatile in steam Specific 1.344 (4°C) gravity Melting point 105°C Boiling point 245.5°C (decomposes at 240 to 245°C) Vapor density 3.79 (air = 1) Solubility Soluble in water, alcohol, ether Flash point 137°C (closed cup) 2.1.2 Odor and Warning Properties There is a faint, characteristic odor. 2.2 Production and Use Pyrocatechol may be obtained by the fusion of o-phenolsulfonic acid with alkali, by heating chorophenol with a solution of sodium hydroxide at 200°C in an autoclave, or by cleavage of the methyl ether group of guaiacol (obtained from beechwood tar) with hydroidic acid (107). Pyrocatechol is used for various purposes, but particularly as an antioxidant in the rubber, chemical, photographic, dye, fat, and oil industries. It is also employed in cosmetics as couplers in oxidative hair dyes (108, 109), but is no longer used as an antiseptic. 2.3 Exposure Assessment 2.3.1 Air: NA 2.3.2 Background Levels: NA 2.3.3 Workplace Methods: NA 2.3.4 Community Methods: NA 2.3.5 Biomonitoring/Biomarkers 2.3.5.1 Blood

2.3.5.2 Urine The methods of Baernstein or Tompsett can be used to determine pyrocatechol in urine and in other biologic materials (13). In another study, 24 h urine samples examined after 7–9 h of exposure to air polluted with pyrocatechol and phenol gave pyrocatechol levels of 24.2 mg, but control values of 19.2 mg, which were considered background (110). The 24-h urinary levels of pyrocatechol were 4.4 mg in nonsmokers, and 6.8 mg in smokers, indicating that diet is a major factor in determining pyrocatehcol intake (111). 2.4 Toxic Effects 2.4.1 Experimental Studies 2.4.1.1 Acute Toxicity Pyrocatechol is moderately toxic in acute studies. Phenol-like signs of illness are induced in experimental animals given toxic or lethal doses. Unlike phenol, large doses of pyrocatechol can cause a predominant depression of the central nervous system (CNS) and a prolonged rise of blood pressure (13). Pyrocatechol is more toxic than phenol except by inhalation (111). The oral LD50 in rats is 0.3 g/kg. The dermal LD50 in rabbits is 0.8 g/kg. It is an irritant to eyes and skin, but less irritating to the skin than phenol. After 8h of inhalation at concentrations of 2 or 2.8 g/m3 rats showed signs of intoxication (irritation and tremors) for ~24 h after exposure. At 1.5 g/m3 no signs were observed (111). Flickinger (17) reported hyperemia of the stomach and intestines after lethal oral doses in rats, and loss of toes and tips of tails of rats after exposure to high concentrations (2 or 2.8 g/m3) in a chamber. Dietering reported degenerative changes in the kidney tubules (13). 2.4.1.2 Chronic and Subchronic Toxicity The repeated absorption of sublethal doses by animals may also induce methemoglobinemia, leukopenia, and anemia. 2.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Pyrocatechol is readily absorbed from the GI tract and through the intact skin of mice, and probably through the lungs (13). Part of the catechol is oxidized with polyphenol oxidase to benzoquinone. Another fraction conjugates in the body with glucuronic, sulfuric, and other acids and is excreted in the urine, with a little “free” pyrocatechol. The conjugates hydrolyze easily in the urine with the liberation of the “free” catechol, which is oxidized by air with the formation of dark-colored substances that impart to the urine a “smokey” appearance (13). Rabbits administered pyrocatechol orally excreted in the urine 18% as sulfate, 70% as monoglucuronide, and 2% as free pyrocatechol (112). When mice were exposed to cigarette smoke containing radiolabeled pyrocatechol, pyrocatechol was distributed readily into the blood and tissues; 90% of the radioactivity was excreted in the urine within 24 hrs (113). 2.4.1.4 Reproductive and Developmental Pyrocatechol was reported to be a moderately active maternal toxicant, and an active developmental toxicant in a preliminary screening assay (114). Sprague–Dawley rats were administered pyrocatechol at oral doses of 333, 667, or 1000 m g/kg on day 11 of gestation, and allowed to deliver normally. Both mid and high doses caused maternal lethality and weight gains. Litter size and weights were reduced at the maternally toxic doses. Malformations involving limbs, tail and urogenital systems were reported at all doses (114). 2.4.1.5 Carcinogenesis Pyrocatechol has been extensively studied for its role in carcinogenesis of the rat glandular stomach; it was concluded that pyrocatechol was carcinogenic (109). When rats and mice were administered 0.8% pyrocatechol in their feed for life, there was an increase in glandular stomach adenocarcinoma in both male and female rats. Pyrocatechol also caused hyperplasia of the glandular stomach in both rats and mice, a mechanism that could cause promotion of carcinogeninitiated cells (115); no effects on the esophagus or urinary bladder were reported. There were no cutaneous neoplasms when pyrocatechol was applied in dermal studies. Pyrocatechol may be classified as a cocarcinogen because it enhanced the number and/or incidence of lesions in the stomach induced by several carcinogenic nitrosamines, and cutaneous neoplasms when administered dermally together with several carcinogens (109).

2.4.1.6 Genetic and Related Cellular Effects Studies Pyrocatechol has been tested in a variety of bacterial and mammalian tests systems, and both positive and negative results were obtained (summarized in Ref. 109). For example, pyrocatechol was negative in the Ames assay, but induced SCEs (sister chromatid exchanges) in CHO (Chinese hamster ovary) V79 cells (116). In in vivo mouse micronucleus assays, in which the conjugation enzymes responsible for detoxication were present, both positive (117, 118) and negative results (119) were reported. 2.4.1.7 Other: Neurological, Pulmonary, Skin Sensitization Undiluted pyrocatechol was severely irritating to rabbit eyes, with permanent changes including corneal opacity (17). Pyrocatechol was a skin sensitizer in guinea pigs (120). In in vitro studies, pyrocatechol has been shown to affect several immunologic and other properties of murine bone marrow cells, both alone and when combined with hydroquinone (summarized in Ref. 108). 2.4.2 Human Experience 2.4.2.1 General Information: NA 2.4.2.2 Clinical Cases 2.4.2.2.1 Acute Toxicity Inhalation results in a burning sensation in the throat and lungs and, subsequently, a pronounced increase in the rate of breathing (13). 2.4.2.2.2 Chronic and Subchronic Toxicity Cases of industrial or accidental poisoning have been rare. 2.4.2.2.3 Pharmacokinics, Metabolism, and Mechanisms The calculated biological half-life of pyrocatechol in humans was 3–7h (110). 2.4.2.2.4 Reproductive and Developmental: NA 2.4.2.2.5 Carcinogenesis: NA 2.4.2.2.6 Genetic and Related Cellular Effects Studies: NA 2.4.2.2.7 Other: Neurological, Pulmonary, Skin Sensitization, etc Contact with the skin has been known to cause an eczematous dermatitis. Absorption through the skin, in a few instances, has resulted in symptoms of illness resembling closely those induced by phenol, except for certain central effects (convulsions) that were more marked (13). Apparently pyrocatechol acts by mechanisms similar to those reported for phenol. The rise of blood pressure appears to be due to peripheral vasoconstriction. Death apparently is initiated by respiratory failure (13). A woman developed acute contact dermatitis after using a permanent cream for eyelashes and eyebrows; when she was patch-tested, pyrocatechol evoked strong positive reactions (121). Another woman became allergic to pyrocatechol from her occupational exposure as a radiographer (122). 2.4.2.3 Epidemiology Studies 2.4.2.3.1 Acute Toxicity: NA 2.4.2.3.2 Chronic and Subchronic Toxicity: NA 2.4.2.3.3 Pharmacokinetics, Metabolism, and Mechanisms: NA 2.4.2.3.4 Reproductive and Developmental: NA 2.4.2.3.5 Carcinogenesis Between 35 and 45% of American women dye their hair, often at monthly intervals, over a period of years. A number of epidemiological studies have investigated the association between cancer and occupation as a hairdresser or barber, or personal use of hair dyes. IARC (123) concluded that there is inadequate evidence that personal use of hair colorants entails exposures that are carcinogenic. However, IARC concluded that “occupation as a hairdresser or barber entails exposures that are probably carcinogenic.”

2.5 Standards, Regulations, or Guidelines of Exposure The ACGIH TLV-TWA for pyrocatechol is 5 ppm (23 m g/m3) (124). The NIOSH REL is also 5 ppm (20 m g/m3) (105). The “S” skin notation in the listing refers to the “potential significant contribution to the overall exposure by the cutaneous route, including mucous membrane and the eyes, either by contact with vapors or, of probable greater significance, by direct skin contact with the substance (124)”. 2.6 Studies on Environmental Impact The EC50 for Pimephales promelas (fathead minnow) was 9.00 mg/L for 96 h; the effect determined was loss of equilibrium. Similarly, the LC50 was reported to be 9.22 mg/L for 96 h (125).

Phenol and Phenolics Ralph Gingell, Ph.D., DABT, John O'Donoghue, Ph.D., DABT, Robert J. Staab, Ph.D., DABT, Ira W. Daly, Ph.D., DABT, Bruce K. Bernard, Ph.D., Anish Ranpuria, MS, E. John Wilkinson, Daniel Woltering, Ph.D., Phillip A. Johns, Ph.D., Stephen B. Montgomery, Ph.D., Larry E. Hammond, Ph.D., Marguerita L. Leng, Ph.D. 3.0 Resorcinol 3.0.1 CAS Number: [108-46-3] 3.0.2 Synonyms: 1,3-Benzenediol; m-dihydroxybenzene, resorcin, 1,3-dihydroxybenzene, 3-hydroxyphenol, CI 76505; m-hydroquinone 3.0.3 Trade Names: Eskamel 3.0.4 Molecular Weight: 110.11 3.0.5 Molecular Formula: C6H6O2 3.0.6 Molecular Structure:

3.1 Chemical and Physical Properties White, needle-shaped crystals or rhombic tablets and pyramids, which turn pink on exposure to light and air. It is an acid with pKa values of 9.51 and 11.32 in water at 30°C. Specific gravity 1.2717 Melting point 109–111°C Boiling point 280°C Vapor density 3.79 (air = 1) Percent in “saturated” air 2.64% by volume (25.1°C) Density of “saturated” air 1.0739 (air = 1) Solubility Soluble in water, alcohol, glycerol, ether (1)

Flash point

127°C (closed cup) 127°C (closed cup)

3.1.1 General 3.1.2 Odor and Warning Properties Resorcinol has a faint, characteristic odor and a sweetish, followed by a bitter, taste. 3.2 Production and Use Resorcinol is usually prepared by fusing sodium m-benzenedisulfonate with sodium hydroxide. The major use is in the production of resorcinol–formaldehyde adhesives used in tires, automobile belts and hoses, bonding wood products, and neoprene rubbers. It is also used in tanning, in photography, and in the manufacture of explosives, dyes, cosmetics, organic chemicals, antiseptics, resins, and adhesives (13). A minor use is as a bacteriocide in pharmaceuticals for the treatment of acne, psoriasis, eczema, seborrheic dermatitis etc. Resorcinol is used to remove warts, corns, and calluses. Resorcinol is most effective when delivered as an aerosol spray germicide (126). 3.3 Exposure Assessment NIOSH (127) estimated that 100,000 workers are potentially exposed to resorcinol. 3.3.1 Air: NA 3.3.2 Background Levels: NA 3.3.3 Workplace Methods Air samples can be collected with impingers containing distilled water. If Millipore™ filters are used, about 50% may pass through the filter (17). Analysis can be performed with ultraviolet spectroscopy at 273.5 nm using a 10-cm cell. 3.3.4 Community Methods: NA 3.3.5 Biomonitoring/Biomarkers 3.3.5.1 Blood Detection of free resorcinol in plasma and urine requires the use of HPLC and a simple ethanol extraction. This method is useful to concentrations as low as 0.5%, at which it gives recoveries of greater than 90% with good reproducibility (13). 3.4 Toxic Effects 3.4.1 Experimental Studies 3.4.1.1 Acute Toxicity The primary signs of intoxication resemble those induced by phenol, and include initial stimulation of the CNS, followed by depression, renal glomerular and tubular degeneration, central hepatic necrosis, myocardial depression, pruitis and reddening of the skin. Resorcinol has been reported to be less toxic than phenol or pyrocatechol by oral and dermal routes. The oral LD50 in rats is 0.98 g/kg, and the dermal LD50 in rabbits is 3.36 g/kg (17). It is irritating to the eyes and skin; eye irritation included corneal ulcerations that were not reversible. At high dermal doses, it causes irritation and necrosis in a dose-related response (17). Inhalation of aqueous aerosols by rats for 1h at 7.8 g/m3 (1733 ppm) or 8 h at 2.8 g/m3 (625 ppm) caused no deaths or gross lesions. 3.4.1.2 Chronic and Subchronic Toxicity Groups of 10 male and female F344 (Fischer 344) rats were given 0, 32, 65, 130, 260, or 520 m g/kg resorcinol by gavage 5 days/week for 13 weeks (126). Most animals at the top dose died. Daily doses of 65 m g/kg produced increased liver weights, but no other toxic effects were reported. When B6C3F1 mice were similarly treated, most mice at the high dose died, but only reduced adrenal weight was noted at other dose levels (126). In subacute inhalation studies rats, rabbits, and guinea pigs were exposed to 34 m g/m3 (8 ppm) 6 h daily for 2 weeks without any gross toxic effects (17). 3.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Resorcinol was readily absorbed from the GI tract after oral administration to rats, rapidly metabolized and excreted in the urine (128). After an

oral dose of 122–225 m g/kg, >90% of the dose was excreted in the urine and 2% in the feces; 50% of the administered dose underwent enterohepatic circulation. The monoglucuronide conjugate accounted for 70% of the urinary metabolites, together with the monosulfate, diglucronide, and mixed sulfate/glucuronide. There was no evidence of bioaccumulation. Essentially identical results occurred after five pretreatment doses, indicating that conjugation was not saturated at these doses (128). Similar results were obtained after subcutaneous (SC) administration of 50 or 100 m g/kg of resorcinol to rats (129). Resorcinol was distributed to all tissues but did not accumulate. After 1 h, 62% of the radiolabel appeared in the urine, and 98% within 24 h. Elimination was biphasic with half-lives of 20 min and 8–10hrs. Essentially the same results were obtained after a 30-day pretreatment of 100 m g/kg resorcinol (129). 3.4.1.4 Reproductive and Developmental Resorcinol is not a primary developmental toxicant. When pregnant rabbits were administered resorcinol orally at 40, 80, or 250 m g/kg per day on days 6–18 of gestation, there was no increase in embryonic or fetal deaths, or in congenital malformations (130). Oral administration to pregnant rats on days 6–15 of gestation at 125, 250, or 500 m g/kg per day caused maternal toxicity (reduced body weight) at the top dose, but there was no evidence of developmental toxicity. In a subsequent study rats were dosed with 80 m g/kg per day throughout gestation, producing overt maternal toxicity and some evidence of embryotoxicity; 40 m g/kg per day was a NOEL (130). In another study, daily doses of 125, 250 or 500 m g/kg were administered orally to Sprague–Dawley rats during days 6–15 of gestation (131). There was a slight reduction in maternal body weight gain at the top dose, but no effect on the number of litters, nor on the number of fetal anomalies or malformations. 3.4.1.5 Carcinogenesis Resorcinol was administered in water by gavage 5 days per week for 104 weeks to F344 rats and B6C3F1 mice at maximally tolerated doses; there was no evidence of carcinogenicity in any sex or species (126). Resorcinol at concentrations of 5, 10, or 50% in acetone was applied twice weekly to the ears of rabbits for 180 weeks; there were no local tumors or evidence of systemic toxicity (132). Orally administered resorcinol did not induce proliferative lesions in hamster forestomach or bladder (133), and was not a promoter of carcinogenesis by other chemicals in these organs in rats (134). However, intraperitoneal (IP) injections of resorcinol did increase the incidence of esophageal tumors induced by a carcinogenic nitrosamine (135). 3.4.1.6 Genetic and Related Cellular Effects Studies Despite positive genotoxic findings in some in vitro genotoxicity assays, no positive findings have been reported in any in vivo studies in which the conjugation pathways are active (see see Table 53.2) (136–146). Table 53.2. Genotoxicity of Resorcinol Test System

Results

Ref.

In vitro Assays Salmonella typhimurium bacterial mutagenicity Negative 14–19, 47, 60, 136– 139 Drosophila melanogaster sex-linked recessive Negative 75 lethal Mouse lymphoma mammalian mutagenicity Positive 140 Chinese hamster ovary chromosomal Positive 141

aberrations Human lymphocytes chromosomal aberrations In vivo Assays Mouse bone marrow micronucleus Inhibition of rat DNA synthesis in rat testicular cells Rat bone marrow micronucleus Rat bone marrow sister chromatid exchange

Positive 142 Negative 75, 143 Negative 144 Negative 145 Negative 146

3.4.2 Human Experience 3.4.2.1 General Information Few reports of the toxicity of resorcinol have been published. Oral ingestion in humans may cause methemoglobinemia, cyanosis, and convulsions, whereas dermal exposure has been reported to cause dermatitis, hyperemia, and pruritis (13). Industrial inhalation exposures are rather rare, but could occur in any industry if the compound is heated beyond 300°F. 3.4.2.2 Clinical Cases 3.4.2.2.1 Acute Toxicity Pathology reported for humans includes anemia, marked siderosis of the spleen and marked tubular injury in the kidney, fatty changes of the liver, degenerative changes in the kidney, fatty changes of the heart muscle, moderate enlargement and pigmentation of the spleen, and edema and emphysema of the lungs (13). The cutaneous application of solutions or salves containing 3–5% resorcinol may result in local hyperemia, itching, dermatitis, edema, corrosion, and the loss of the superficial layers of the skin. The allergic/sensitization reactions also include eczematous reactions, erythema, edema, and the formation of vesicles. Burning sensations may also be noted (13). These changes, if they are severe, may be associated with some or all of the following effects: enlargement of regional lymph glands, restlessness, methemoglobinemia, cyanosis, convulsions, tachycardia, dyspnea, and death (13). Ingestion of resorcinol induces similar signs and symptoms. Thus a child, after accidentally swallowing 4 g, complained of dizziness and somnolence. The ingestion of 8 g, in another case, induced an almost immediate hypothermia, fall in blood pressure, and decrease in the rate of respiration, with tremors, icterus, and hemoglobinuria. Recovery was noted 2 h after the poisoning (13). Other cases are on record in which similar doses apparently had no ill effects (13). 3.4.2.2.2 Chronic and Subchronic Toxicity: NA 3.4.2.2.3 Pharmacokinetics, Metabolism, and Mechanisms Resorcinol is believed to be readily absorbed from the GI tract and, in a suitable solvent, is readily absorbed through the human skin. The compound is excreted in the urine, as are other phenols, in a free state and conjugated with glucuronic, sulfuric, or other acids (13). 3.4.2.3 Epidemiology Studies 3.4.2.3.1 Acute Toxicity In a study of 268 workers in a motorcycle tire manufacturing plant, the presence of dermatitis was directly correlated with exposure to the processes involving resorcinol use (147). 3.4.2.3.2 Chronic and Subchronic Toxicity Resorcinol in certain resins was reported to cause respiratory problems in the rubber industry (13). An epidemiologic study of rubber workers exposed to a hexamethylenetetramine–resorcinol rubber system revealed no specific symptoms caused by resorcinol. The concentrations of resorcinol in air were less than 0.3 m g/m3 (148). In another study there were no reports of irritation or discomfort by workers when concentrations were 10 ppm or less for periods of 30 min (17).

3.4.2.3.3 Pharmacokinetics, Metabolism, and Mechanisms: NA 3.4.2.3.4 Reproduction and Developmental: NA 3.4.2.3.5 Carcinogenesis: NA 3.4.2.3.6 Genetic and Related Cellular Effects Studies: NA 3.4.2.3.7 Other: Neurological, Pulmonary, Skin Sensitization, etc Resorcinol has been reported to cause sensitization and cross-sensitization with other phenolic materials and to cause goiter (13). 3.5 Standards, Regulations, or Guidelines of Exposure The TLV TWA is 10 ppm (45 m g/m3). The STEL (short-term exposure limit) is 20 ppm (90 m g/m3) (149). There is no proposed biological exposure index (BEI). NIOSH REL TWA 10 ppm (45 m g/m3) STEL/CEIL(c) 20 ppm (90 m g/m3).

Phenol and Phenolics Ralph Gingell, Ph.D., DABT, John O'Donoghue, Ph.D., DABT, Robert J. Staab, Ph.D., DABT, Ira W. Daly, Ph.D., DABT, Bruce K. Bernard, Ph.D., Anish Ranpuria, MS, E. John Wilkinson, Daniel Woltering, Ph.D., Phillip A. Johns, Ph.D., Stephen B. Montgomery, Ph.D., Larry E. Hammond, Ph.D., Marguerita L. Leng, Ph.D. 4.0 Hydroquinone 4.0.1 CAS Number: [123-31-9] 4.0.2 Synonyms: 1,4-Benzenediol, benzohydroquinone, 1,4-dihydroxy benzene, hydroquinol, a-hydroquinone, phydroxyphenol, b-quinol, p-benzenediol, benzoquinol, p-dihydroxybenzene, hydroquinole, phydroquinone, quinol 4.0.3 Trade Names: The only trade name identified for hydroquinone was Tecquinol. This trade name is no longer used. 4.0.4 Molecular Weight: 110.11 4.0.5 Molecular Formula: C6H6O2 4.0.6 Molecular Structure:

Phenol and Phenolics

Ralph Gingell, Ph.D., DABT, John O'Donoghue, Ph.D., DABT, Robert J. Staab, Ph.D., DABT, Ira W. Daly, Ph.D., DABT, Bruce K. Bernard, Ph.D., Anish Ranpuria, MS, E. John Wilkinson, Daniel Woltering, Ph.D., Phillip A. Johns, Ph.D., Stephen B. Montgomery, Ph.D., Larry E. Hammond, Ph.D., Marguerita L. Leng, Ph.D. 5.0 Quinone 5.0.1 CAS Number: [106-51-4] 5.0.2 Synonyms: Benzoquinone, p-benzoquinone, 1,4-benzoquinone, 2,5-cyclohexadiene-1,4-dione, 1,4dioxybenzene, 1,4-dione, quinone, cyclohexadienedione, 1,4-cyclohexadienedione, cyclohexadiene1,4-dione 5.0.3 Trade Names: Chinone, Steara PBQ 5.0.4 Molecular Weight: 108.10 5.0.5 Molecular Formula: C6H4O2 5.0.6 Molecular Structure:

5.1 Chemical and Physical Properties Physical state Large, yellow, monoclinic prisms Specific gravity 1.318 (20°C) Melting point 115.7°C Boiling point 293°C Vapor pressure Considerable; sublimes readily on gentle heating Flash point 38°C Solubility Soluble in alcohol and ether. Solubility in water 2.5% at 38°C, 1.4% at 25°C, 1% at 12°C 5.1.1 General Quinone can decompose violently at elevated temperatures and has combustible vapors. 5.1.2 Odor and Warning Properties Quinone has an acrid odor similar to that of chlorine. The vapors are irritating enough to cause sneezing. 5.2 Production and Use Quinone was produced as early as 1838 by oxidation of quinic acid with manganese dioxide (302). Quinone can be prepared by oxidation starting with aniline or by the oxidation of hydroquinone with bromic acid. More recently quinone has been made biosynthetically from D-glucose (302). The compound has been used in applications in the dye, textile, tanning, and cosmetic industries primarily because of its ability to transform certain nitrogen-containing compounds into a variety of colored substances. In the past, large amounts of quinone were produced as an intermediary for hydroquinone production. Newer production methods eliminate the need for quinone.

5.3 Exposure Assessment Methods of controlling exposure during manufacture are largely a matter of reducing release by using containment systems and adequate ventilation. Severe local damage to the skin and mucous membranes may occur following contact with solid quinone, solutions of quinone, or quinone vapors condensing on exposed parts of the body (particularly moist surfaces) (303). Thus, skin contact is to be avoided and contaminated clothing should be removed immediately. Personal protection (full-face mask, air-supplied respirator) may be necessary in operations where other controls are not feasible (303). Quinone may be present in areas in which hydroquinone is used, as hydroquinone can be oxidized to quinone under moist or alkaline conditions. 5.3.1 Air Airborne quinone levels in a hydroquinone manufacturing operation have been reported to have declined from a high of 0.27 ppm to 1995 levels, which were 20 nm adducts/g protein (309). Quinone precursors from dietary and endogenous sources are proposed to explain high background levels. Quinone is a metabolite of benzene, phenol, hydroquinone, and acetaminophen; therefore, hemoglobin and albumin adducts do not represent biomarkers specific to quinone. Because of the high level of background adducts in blood, hemoglobin and albumin adducts are not likely to be useful biomarkers for occupational exposure to quinone. Quinone and hydroquinone are closely related metabolically as quinone can be readily converted enzymatically and nonenzymatically to hydroquinone. Because of this close relationship, background levels of hydroquinone metabolites detected in the blood and urine of individuals without occupational exposure to either quinone or hydroquinone would include background levels of quinone (154). 5.4 Toxic Effects 5.4.1 Experimental Studies 5.4.1.1 Acute Toxicity Single dose oral LD50 values of 130 and 165 mg/kg have been reported for rats (4, 13, 14). Unlike hydroquinone, quinone does not produce tremors or convulsions, and death may be delayed for days after dosing (310, 311). Respiratory impairment was the primary effect observed as acute effects following quinone exposure (304). Parenteral exposure results in an LD50 value (IV LD50 – 25 mg/kg) that is significantly less than the oral LD50 (310, 311). No dermal toxicity studies were found in the literature. Woodard reported that quinone vapor was very irritating, causing coughing and sneezing (311). Solid quinone or relatively concentrated solutions are very irritating to the rabbit eye (312). Ocular sensory irritation is seen at a concentration of 0.0001% and acute conjunctivitis at 0.001%. A solution of 0.002% produced cloudiness of the cornea in 24 h and neovascularization in 4 days. The airborne concentration of

quinone that decreases the respiratory rate of mice by 50% (RD50) is reported to be 22.5 m g/m3 (313). 5.4.1.2 Chronic and Subchronic Toxicity Rats given 25 mg/kg quinone twice a week by SC injection for 2.5–5 months had anemia, methemoglobinemia, decreased serum albumin, and decreased serum cholinesterase (314). Rats exposed to 2.7–3.6 m g/m3 quinone 4 h/day for 4 months lost weight, showed easy tiredness, transient anemia, and thrombopenia (314). Two of eight rats exposed to 0.27–0.36 m g/m3 quinone, 4 h/day for 4 months showed thrombopenia (314). Mice given 2 mg/kg quinone IP, 6 days/week for 6 weeks manifested decreased red blood cells and lymphocytes, and increased polymorphonuclear leukocytes in their peripheral blood (184). Decreased bone marrow cellularity, decreased relative thymus weight, and increased relative spleen and lymph node weights were also observed in the quinone-dosed mice when compared to a control group. The usefulness of these data is diminished by incomplete reporting of results. Parenteral administration of quinone is a confounding factor in interpreting these data as the hemogram can be expected to be altered in response to tissue inflammation and destruction caused by exposure to a highly irritating material. 5.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms There are no data available on the pharmacokinetics and metabolism of quinone using expected routes for occupational or environmental exposures. Much of the available mechanistic information has been collected using in vitro systems that attempt to model quinone interactions relevant to benzene toxicity. Quinone vapor can be expected to be readily absorbed through the lungs, and quinone solutions should be readily absorbed from the GI tract. Absorption of solid quinone is likely to be slow because of its low water-solubility unless ingestion with an organic solvent occurs. Absorption of quinone through the skin can be expected; however, binding of quinone to epidermal proteins may reduce absorption when dilute solutions are encountered. Concentrated solutions of quinone may damage the barrier properties of the skin enhancing absorption. Quinone can be expected to undergo transformations, including (1) enzymatic or nonenzymatic reduction and conjugation with glucuronide or sulfate resulting in detoxication and metabolites that are readily excreted in the urine; (2) covalent binding to proteins such as hemoglobin and albumin; (3) binding to glutathione, which may lead to detoxication or activation depending on the electrochemical state of the metabolite, and (4) one-electron reduction by reductases or diaphorases, which may produce a semiquinone and reactive oxygen species via redox cycling. Mean half-lives of 0.68 and 3.5 h have been reported following incubation of 50 mM quinone with fresh F344 rat or human blood at 37°C (309, 315). Hemoglobin and albumin have second-order rate constants of 18 and 76L mol–1 h–1 for human samples and 180 and 74L mol–1 h–1 for rat samples (309, 315). Covalent binding of quinone to critical proteins is an expected mode of action in vivo. However, because of its reactive nature, it may not be possible to achieve a toxicologically significant internalized dose at systemic target sites when exposures occur via occupationally or environmentally relevant routes of exposure. 5.4.1.4 Reproductive and Developmental Studies Studies on reproductive and developmental effects for quinone have not been reported. However, these endpoints have been studied for hydroquinone, which is a precursor to quinone (228–230). On the basis of analogy with hydroquinone, quinone would not be expected to be a reproductive or developmental toxicant by common routes of occupational and environmental exposure. In an in vitro system, quinone was lethal to rat embryos at

100 mM and reportedly dysmorphogenic at 10 mM but not 50 mM (220). 5.4.1.5 Carcinogenesis Quinone has been tested for carcinogenicity in mice by skin application or inhalation and in rats by subcutaneous injection. None of these studies were considered sufficient to evaluate carcinogenicity (316, 317). A cancer bioassay of tribolium infested flour has been conducted but lack of quantification of quinone and methodological issues make the data difficult to interpret (305). Quinone has produced negative results in studies designed to examine its ability to promote carcinogenicity. In a liver bioassay, quinone did not increase the formation of GGT-positive foci in the liver (241). Quinone did not promote induction of stomach or skin tumors in mice dosed with 7,12-dimethylbenzanthracene (318, 319). 5.4.1.6 Genetic and Related Cellular Effects Studies Genotoxicity assays with quinone have recently been reviewed by IARC (317). The results of several Ames/Salmonella assays were as a group inconclusive; however, mutations in Neurospora were increased. DNA strand breaks, mutations at the hgprt locus, and micronuclei were induced in mammalian cells in vitro. Weakly positive micronuclei responses were observed in mice dosed by gavage. A dominant lethal assay in mice given quinone IP was negative at a dose level of 6.25 mg/kg. These test results indicate that quinone is weakly positive for genotoxicity in vivo. 5.4.1.7 Other: Neurological, Pulmonary, Skin Sensitization Quinone produced an extreme skin sensitization response in the guinea pig maximization test (Magnusson–Kligman test) and positive response in the mouse local lymph node assay (261). Rajka and Blohm (256) found that quinone sensitized 19 of 20 guinea pigs given 10 daily injections of 0.001% quinone. Studies on cross sensitization with p-phenylenediamine are inconclusive (320, 321). Numerous cytotoxicity tests have been conducted with quinone (314). Most of these studies have examined bone marrow cells in attempts to elucidate the mode of action of benzene, as quinone is one of the metabolites of benzene. These studies do not provide information that is readily applicable to common routes of quinone exposure. 5.4.2 Human Experience 5.4.2.1 General Information Skin contact with quinone can be expected to temporarily stain the skin a brownish color. 5.4.2.2 Clinical Cases 5.4.2.2.1 Acute Toxicity Reports of acute toxicity following exposure to quinone have not been published. 5.4.2.2.2 Chronic and Subchronic Toxicity Sterner et al. (270), Anderson (272), Anderson and Oglesby (275), and Oglesby et al. (271) reported that in a manufacturing process that produced hydroquinone by reduction of quinone, discoloration of the eyes and in some cases more serious ocular damages were seen among production workers. The changes occurred over a period of years, and no serious ocular cases were observed with less than 5 years of exposure. Initially, there was brown staining of the conjunctiva. This pigment deposition in the conjunctiva did not impair vision; however, its presence was evidence of exposure, and its increase or decrease was used as an indication of the severity of exposure to hydroquinone dust and quinone vapor. With continued eye exposure to high concentrations of hydroquinone and quinone, pigment deposition extended into the cornea, and structural alterations of the cornea occurred that impaired vision. One of the first complaints of individuals with corneal involvement was difficulty driving at night as light beams from oncoming automobiles were scattered and reflected by the corneal alterations. The reports by Sterner et al. (270), Anderson (272), and Oglesby et al. (271) led to the establishment

of an ACGIH TLV of 0.1 ppm quinone vapor. No evidence of systemic toxicity was seen in a group of hydroquinone production workers who were exposed to quinone vapor and hydroquinone dust (154, 280). 5.4.2.2.3 Pharmacokinetics, Metabolism, and Mechanisms Pharmacokinetics and metabolism studies with quinone have not been published. 5.4.2.2.4 Reproductive and Developmental Studies Case studies of reproductive or developmental toxicity following quinone exposure have not been reported. 5.4.2.2.5 Carcinogenesis Case studies of carcinogenicity following exposure to quinone have not been reported. 5.4.2.2.6 Genetic and Related Cellular Effects Studies Case studies of adverse genotoxic effects following exposure to quinone have not been reported. 5.4.2.2.7 Other: Neurological, Pulmonary, Skin Sensitization, etc Case studies of neurologic, pulmonary, sensitization or other adverse health effects following quinone exposure have not been reported. 5.4.2.3 Epidemiology Studies A cohort study of hydroquinone production workers who were also exposed to quinone reported significantly lower mortality due to a number of disease endpoints including cancer when compared to a general population control (279). Pifer et al. (280) reported that a cohort of 879 men and women involved in manufacturing hydroquinone using a process that included production of quinone had significantly lower death rates for malignant and nonmalignant diseases when compared to general population and employed referent groups. 5.5 Standards, Regulations, or Guidelines of Exposure The ACGIH TLV, OSHA PEL, NIOSH REL, and German MAK values for quinone are 0.1 ppm as an 8 h TWA. The NIOSH IDLH value was 100 mg/m3. 5.6 Studies on Environmental Impact In the past, large amounts of quinone were produced in the United States as an intermediary for hydroquinone production. Newer production methods eliminate the need for quinone. Therefore, releases of quinone from U.S. manufacturing sites to the environment have been decreasing steadily for several years according to Toxic Release Inventory (TRI) reports. TRI reports for the year 1997 included no releases of quinone to air, water, or land (322). In countries such as China, and India, where the aniline oxidation method continues to be used to produce hydroquinone, releases of quinone to the environment may occur. Environmental surveys of industrial sites in the United States have failed to detect quinone in surface waters (301, 307, 308). Because of its low water solubility and vapor pressure, quinone is likely to partition into the atmosphere, if released. As a result of photolysis and chemical lability, quinone is expected to be short-lived in the environment following release (306). Since chemical structures such as quinone are readily metabolized by microorganisms, biodegradation is expected to be rapid. Polymeric forms of quinone are known as humic acids, which are common constituents of soil.

Phenol and Phenolics Ralph Gingell, Ph.D., DABT, John O'Donoghue, Ph.D., DABT, Robert J. Staab, Ph.D., DABT, Ira W. Daly, Ph.D., DABT, Bruce K. Bernard, Ph.D., Anish Ranpuria, MS, E. John

Wilkinson, Daniel Woltering, Ph.D., Phillip A. Johns, Ph.D., Stephen B. Montgomery, Ph.D., Larry E. Hammond, Ph.D., Marguerita L. Leng, Ph.D. 6.0 Pyrogallol 6.0.1 CAS Number: [87-66-1] 6.0.2 Synonyms: Pyrogallic acid; pyro; 1,2,3-trihydroxybenzene; 1,2,3-benzenetriol; fouramine base ap; Benzenetriol 6.0.3 Trade Names: CI 76515; CI Oxidation Base 32; Fouramine Brown AP; Fourrine 85; Fourrine PG; Piral 6.0.4 Molecular Weight: 126.11 6.0.5 Molecular Formula: C6H6O3 6.0.6 Molecular Structure:

6.1 Chemical and Physical Properties Physical state White, or nearly white needle or leaf-shaped crystals or crystalline powder Specific gravity 1.453 (4°C) Melting point 131–134°C Boiling point 309°C (decomposes at 293°C) Solubility Soluble in water (1–2), alcohol (1–1.5), and ether (1–2) at 25°C 6.1.2 Odor and Warning Properties Pyrogallol is practically odorless. 6.2 Production and Use Pyrogallol is prepared by heating dried gallic acid at about 200°C with the loss of carbon dioxide (13) or by the chlorination of cyclohexanol to tetrachlorocyclohexanone, followed by hydrolysis (323). Pyrogallol's commercial use is based primarily on the fact that it is easily oxidized in alkaline solutions (even by atmospheric oxygen), so that such solutions become potent reducing agents. It is used specifically as a developer in photography and for maintaining anaerobic conditions for bacterial growth. It is additionally used in dyeing operations, the oxidized products being dark blue, process engraving, and as a topical antibacterial agent (13). 6.3 Exposure Assessment 6.3.1 Air: NA 6.3.2 Background Levels: NA 6.3.3 Workplace Methods: NA 6.3.4 Community Methods: NA 6.3.5 Biomonitoring/Biomarkers 6.3.5.1 Blood: NA 6.3.5.2 Urine The content of pyrogallol in the urine can be determined by various methods (324). 6.4 Toxic Effects

6.4.1 Experimental Studies 6.4.1.1 Acute Toxicity The oral LD50 for technical synthetic pyrogallol (92%, as a 500 mg/kg aqueous solution) in Sprague–Dawley rats was 1270 (males) and 800 (females) mg/kg (summarized in Ref. 323). Clinical observations included cyanosis, reduced activity, reduced muscle tone, body tremors, ataxia, lacrimation, salivation, piloerection, coolness to touch, hunched posture, pale extremities, and general soiling. General observations on gross necropsy included cyanosis, dark and/or enlarged spleen, dark kidneys, brown or pale liver and lungs, distension of the stomach and bladder, and fluid in the intestines. Because of its marked reducing action, pyrogallol has a tremendous affinity for the oxygen of the blood. There was extensive destruction and fragmentation of the erythrocytes. Death is initiated by respiratory failure. The urine of poisoned animals may contain casts, glucose, hemoglobin, methemoglobin, urobilin, and other compounds that cause discoloration (323). The dermal LD50 in rats administered pyrogallol in aqueous solution for 24 h under occlusion exceeded 2100 mg/kg (323). Clinical observations in females included cyanosis and pale extremities; the treated skin and surrounding fur of all animals was stained brown. 6.4.1.2 Chronic and Subchronic Toxicity Repeated absorption of toxic but sublethal concentrations into the tissues of animals has been found to cause severe anemia, icterus, nephritis, and uremia. The approximate lethal dosages of pyrogallol in aqueous solution for various animals species, under varying conditions of administration, was reported to be (324) rabbit, 1.1 g/kg (orally); rabbit or guinea pig, 10 g/kg (SC); dog or cat, 0.35 g/kg (SC); and dog, 0.09 g/kg (IV). Pathological changes in animals caused by pyrogallol include edema and hyperemia of the lungs, and moderate fatty degeneration, round cell infiltration, and necrosis of the liver. The kidneys may show hyperemia, necrosis of the epithelium, granular pigmentation, and glomerular nephritis (13). Changes of the bone marrow and myeloid changes in the spleen were noted after chronic administration of this compound (13). 6.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Pyrogallol is readily absorbed from the GI tract and from parenteral sites of injection. Little is absorbed through the intact skin. The bulk of absorbed pyrogallol is readily conjugated with glucuronic, sulfuric, or other acids and excreted within 24 h via the kidneys (13). When rats were administered 100 mg/kg pyrogallol, both pyrogallol and 2-O-methylpyrogallol were recovered in the urine as hydrolyzable conjugates; there was no unconjugated pyrogallol. Traces of resorcinol were detected in the feces suggesting that pyrogallol could be reduced (325). 6.4.1.4 Reproductive and Developmental A multigeneration rat reproduction study was conducted with a hair dye containing 0.4% pyrogallol applied to the skin twice per week during mating, gestation, and lactation through weaning (323). There were no treatment-related effects on reproduction, and only mild skin reactions at the application site noted intermittently. Pyrogallol in propylene glycol was administered to pregnant Sprague–Dawley rats during days 6–15 of gestation at doses of 100, 200, or 300 mg/kg. There were no maternal mortalities, but at the top dose there was a decrease in maternal body weight gain, smaller fetuses, and an increase in the number of fetal resorptions. The numbers of fetal implants and abnormalities were not affected (326). 6.4.1.5 Carcinogenesis Pyrogallol was not carcinogenic in mouse and rabbit chronic dermal studies. Mice were treated twice weekly with pyrogallol in acetone (50%) on the shaved flank for life. There was no increase in dermal or systemic tumors (327). A similar study in rabbits also revealed no skin tumors, although positive controls showed an increase in tumors in both mice and rabbits (132). Pyrogallol was considered to be cocarcinogenic when administered dermally three times a week together with the skin carcinogen benzo[a]pyrene for 440 days; pyrogallol administered alone caused

no increase in skin tumors (231). 6.4.1.6 Genetic and Related Cellular Effects Studies Pyrogallol was mutagenic in nearly all systems (323). Most of the assays were performed in vitro, but pyrogallol was also positive in in vivo assays. There was an increase in sex-linked recessive lethal mutations in Drosophila melanogaster, in mouse micronuclei (75), and in chromatid breaks in bone marrow cells of mice injected intraperitoneally with pyrogallol (323). 6.4.1.7 Other: Neurological, Pulmonary, Skin Sensitization Powdered pyrogallol was an ocular irritant, but not when tested at a concentration of 1% in propylene glycol (323). Powdered pyrogallol was slightly irritating when tested under dermal occlusion for 24 h in rabbits, and a 50% aqueous solution was slightly irritating in guinea pigs (323). Pyrogallol was reported to be a skin sensitizer when tested in guinea pigs by one unconventional procedure, but was negative in a second study using intradermal and dermal induction, and topical challenge applications (323). 6.4.2 Human Experience 6.4.2.1 General Information: NA 6.4.2.2 Clinical Cases 6.4.2.2.1 Acute Toxicity Cases of human poisoning have not been frequent. Cases reported in the older literature include one man who ingested an aqueous solution containing 8g of pyrogallol and who recovered after suffering an acute intoxication; another, who ingested 15 g of this compound, died despite prompt vomiting (13). Signs of acute intoxication include vomiting, hypothermia, fine tremors, muscular incoordination, diarrhea, loss of reflexes, coma, and asphyxia (13). When applied to the human skin in the form of a salve, it can cause local discoloration, irritation, eczema, and even death. Repeated contact with the skin has been reported to cause sensitization (13). The symptoms observed in acute intoxications in humans resemble closely the signs of illness displayed by experimental animals. 6.4.2.2.2 Chronic and subchronic Toxicity: NA 6.4.2.2.3 Pharmacokinetics, Metabolism, and Mechanisms Pyrogallol detected in human urine presumably results from intestinal bacterial decarboxylation of gallic acid, an ingredient in tea (324). 6.4.2.2.4 Reproductive and Developmental: NA 6.4.2.2.5 Carcinognesis: NA 6.4.2.2.6 Genetic and Related Cellular Effects Studies: NA 6.4.2.2.7 Other: Neurological, Pulmonary, Skin Sensitization, etc Positive skin sensitization reactions to pyrogallol were reported in 25 patch-tested patients with leg ulcers (328). In contrast, there were no positive responses when 8230 patients with allergic contact dermatitis were patch tested with pyrogallol (1% in petrolatum) (329).

Phenol and Phenolics Ralph Gingell, Ph.D., DABT, John O'Donoghue, Ph.D., DABT, Robert J. Staab, Ph.D., DABT, Ira W. Daly, Ph.D., DABT, Bruce K. Bernard, Ph.D., Anish Ranpuria, MS, E. John Wilkinson, Daniel Woltering, Ph.D., Phillip A. Johns, Ph.D., Stephen B. Montgomery, Ph.D., Larry E. Hammond, Ph.D., Marguerita L. Leng, Ph.D. 7.0 o-Cresol 7.0.1 CAS Number:

[95-48-7] 7.0.2 Synonyms: 2-Methylphenol; phenol, 2-methyl; 2-cresol; o-cresylic acid; 1-hydroxy-2-methylbenzene; 2hydroxytoluene; o-hydroxytoluene; o-methylphenol; o-methylphenylol; o-oxytoluene; o-toluol 7.0.3 Trade Names: NA 7.0.4 Molecular Weight: 108.14 7.0.5 Molecular Formula: C7H8O 7.0.6 Molecular Structure:

7.1 Chemical and Physical Properties Physical state

colorless, yellowish, or pinkish crystals, darkens with age and exposure to light and air (330, 331). o-Cresol can also appear as a liquid Odor Phenolic odor, with an odor threshold of 5 ppm; sometimes referred to as an empyreumatic odor Specific gravity 1.030–1.038 (o-), (m-), (p-) Melting point 11–35°C (mixture)/31°C (o-)/12°C (m-)/35°C (p-) (330, 332) Boiling point 191–203°C (mixture)/191°C (o-)/202°C (m-)/202°C (p-) (330) Vapor density 3.72 (air = 1) (332) Vapor pressure (25°C) 0.29torr (o-)/0.14torr (m-)/ 0.11torr (p-) at 25°C Refractive index 1.537 Density of 1.00089 [air = 1] saturated air Flash point 82°C (mixture)/81°C (o-)/86°C/m- p-) (all closed cup) (332) Other characteristics are as follows: Flammability. o-Cresol is combustible and presents a marked fire hazard. Fires can be extinguished with water, carbon dioxide, appropriate foam, or dry chemicals. Mixtures of air and 1.47% o-cresol are explosive (332). Solubility. o-Cresol is soluble in organic solvents, vegetable oils, alcohol, ether, glycerin, chloroform, and dilute alkali; also in 40 parts water (330, 333). 7.1.1 General: NA 7.1.2 Odor and Warning Properties o-Cresol has a distinct phenolic odor discernible at 5 ppm. Taste has not been noted in the available literature. 7.2 Production and Use The cresols (cresylic acids) are methyl phenols and generally appear as a mixture of isomers (330). o-Cresol is a 2-methyl derivative of phenol (335) and is prepared from o-toluic acid or obtained from coal tar or petroleum (333, 336). Crude cresol is obtained by distilling “gray phenic acid” at a temperature of ~180–201°C. o-Cresol may be separated from the crude or purified mixture by

repeated fractional distillation in vacuo. It can also be prepared synthetically by diazotization of the specific toluidine, or by fusion of the corresponding toluenesulfonic acid with sodium hydroxide. o-Cresol is used as a disinfectant and solvent (330). Lysol™ disinfectant is a 50% v/v mixed-cresol isomer in a soap emsulion formed on mixing with water. Besides disinfection products at solutions of 1–5% (333), the cresols are used as degreasing compounds, paintbrush cleaners, and additives in lubricating oils (334). Cresols were previously widely used for disinfection of poultry houses, but this use was discontinued because of their toxicity; they cause respiratory problems and abdominal edema in young chicks (337). o-Cresol has been used in synthetic resins, explosives, petroleum, photographic, paint, and agricultural industries. 7.3 Exposure Assessment With rare exceptions, human exposure in industry has been limited to accidental contact of o-cresol with the skin or inhalation of vapors (335). 7.3.1 Air: NA 7.3.2 Background Levels: NA 7.3.3 Workplace Methods Air sampling and analytical methods for personal monitoring are essentially the same manner as for phenol. Cresol is absorbed in dilute alkali and determined colorimetrically with diazotized p-nitroaniline reagent (339), absorbed in spectrograde alcohol with direct determination by ultraviolet spectrophotometry (340), or absorbed on silica and determined by gas–liquid chromatography (341). One sampling procedure consists of drawing a known volume of air through a silica gel tube consisting of two 20/40-mesh silica-gel sections, 150 and 75 mg, separated by a 2-mm portion of urethane foam. Acetone desorbed samples can be analyzed using gas chromatography with a flame ionization detector. The column is packed with 10% free fatty-acid polymer in 80/100 mesh, acid-washed DMCS Chromosorb W. The useful range of this method is 5– 60 mg/m3 (341). 7.3.4 Community Methods: NA 7.3.5 Biomonitorng/Biomarkers A sensitive method for the detection of cresol and metabolites in serum has been reported (342). 7.4 Toxic Effects 7.4.1 Experimental Studies 7.4.1.1 Acute Toxicity Dermal. The dermal LD50 of o-cresol was 890 mg/kg in rabbits (18). Toxic symptoms are similar after oral and dermal routes. Inhalation. No verifiable LC50 values have been reported, but rats survived a 1-h, exposure to 1220 mg/m3 (340) and mice apparently survived a 2-h exposure [179 mg/m3] to o-cresol (340). Irritation and Sensitization. o-Cresol, undiluted and in solution, can cause severe local irritation and corrosion following dermal and ocular exposure. Irritant effects include severe skin lesions, edema, erythema, and necrosis. In a study using rabbits that were dosed with 524 mg o-cresol for 24 h under occlusion, severe skin effects were produced (340). Eye irritation can be severe and include corneal opacity. 7.4.1.2 Chronic and Subchronic Toxicity o-Cresol was tested for subchronic toxicity in animal studies of 28 and 90days' duration by dietary administration. Ingestion by Diet In a 28-day study, F344/N rats and B6C3F1 mice of both sexes (5/sex/group) were given o-cresol at concentrations of 300–30,000 ppm in the diet. All rats survived until study termination; some mice died at the 10,000- and 30,000-ppm dietary levels. Increased liver weights and kidney weights were noted in both species at doses as low as 3000 ppm. No microscopic

changes were associated with the organ weight changes. Bone marrow hyperplasia and atrophy of the uterus, ovary, and mammary gland were seen in the 10,000- and 30,000-ppm dietary groups (343). In a 90-day study, F344/N rats (20/sex/dose) and B6C3F1 mice (10/sex/dose) of both sexes received dietary administration of 30,000 ppm o-cresol (rats) and 20,000 ppm o-cresol (mice). No deaths in either species were related to administration of o-cresol. Hematology, clinical chemistry, and urinalysis were unremarkable; however, bile acid accumulation in the high dose rats was observed. Mild bone marrow hypocellularity in rats and forestomach hyperplasia in mice was revealed in animals with the higher doses (343). 7.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Cresol is absorbed through the skin, open wounds, and mucous membranes of the gastroenteric and respiratory tracts. The rate of absorption through the skin depends on the size of the area exposed rather than the concentration of the material applied (340). The metabolism and the rate of absorption, detoxification, and excretion of the cresols are much like those for phenol; they are oxidized and excreted as glucuronide and sulfate conjugates. 7.4.1.3.1 Absorption: NA 7.4.1.3.2 Distribution: NA 7.4.1.3.3 Excretion The major route of excretion of the cresols is in the urine. The o- and m- cresols are ring-hydroxylated to a small extent, whereas the p-cresol gives rise to the formation of some phydroxybenzoic acid. 2,5-Dihydroxytoluene has been isolated from the urine of rabbits fed o- and mcresols, and p-hydroxybenzoic acid and p-cresylglucuronide from those administered p-cresol (340). 7.4.1.4 Reproductive and Developmental Although no reproductive or developmental toxicity studies were conducted on o-cresol, two subchronic assays did investigate the effect on the reproductive organs. In a 28-day subchronic study of o-cresol at doses of 30,000 ppm in the diet to both sexes of rats and mice, reproductive tissue evaluations showed no indication of adverse effects in the male reproductive system. The estrus cycle was, however, lengthened in rats and mice receiving 10,000 or 20,000 ppm o-cresol (343). In a 90-day study of o-cresol administered in the diet to rats and mice of both sexes, the reproductive organs were evaluated. Atrophy of the female reproductive organs was noted occasionally at 10,000 ppm, but more consistently at 30,000 ppm (343). 7.4.1.5 Carcinogenesis o-Cresol has been investigated for tumor promotion following induction by polycyclic aromatic hydrocarbons, but does not appear to be a tumorigen. Skin Application Female Sutter mice (27–29/group) were dosed with a single application of dimethylbenzanthracene followed one week later by 25 mL of a 20% solution of o-cresol in benzene twice weekly for 12 weeks. Benzene-treated controls did not experience mortality, although many of the cresol mice died. o-Cresol produced 10/17 tumors (papillomas) on surviving mice (234). In another promotion study, mice were painted with a 20% solution of o-cresol for 11 weeks following initiation with dimethylbenzanthracene. No carcinomas were produced (344). 7.4.1.6 Genetic and Related Cellular Effects Studies In an unscheduled DNA synthesis assay, ocresol was shown to be negative using rat hepatocytes (345). A cell transformation assay using BALB/3T3 cells showed o-cresol to be negative (346). Salmonella assays of various strains, both with and without liver homogenate, showed no mutagenic activity (59, 60, 347). In a mouse lymphoma forward mutation assay with liver homogenate, o-cresol was not mutagenic (345). Sister chromatid exchange (SCE) assays produced no evidence of mutagenicity in CHO (Chinese hamster ovary) cells (346). o-Cresol induced sister chromatid exchange in human lung fibroblasts (345, 348).

7.4.2 Human Experience 7.4.2.1 General Information Cresols can cause local and systemic toxicity in humans after exposure by oral or dermal exposure. 7.4.2.2 Clinical Cases Approximately 20 mL of a 90% solution of mixed cresol solution caused chemical burns, cyanosis, unconsciousness, and death within 4h when accidentally poured on an infant's head. Hepatic necrosis; cerebral edema; acute tubular necrosis of the kidneys; and hemorrhagic effusions from the peritoneum, pleura, and pericardium were observed postmortem. Blood cresol concentration was 120 mg/mL (349). 7.4.2.2.1 Acute Toxicity Oral lethality data from Lysol™ (which contains 50% mixed cresols) has been estimated to be between 60 and 120 mL (352). Ingestion is associated with corrosivity to body tissues and toxicity to the vascular system, liver, kidneys, and pancreas (344). 7.4.2.2.2 Chronic and Subchronic Toxicity Chronic cresol poisoning has been infrequently reported. About 10 subjects were exposed to o-cresol at 1.4 ppm and complained of respiratory tract irritation (350). Documentation was not confirmed. Seven workers who were exposed to mixed cresols vapor for 1.5–3 years experienced headaches, nausea, and vomiting. Some of those exposed also had elevated blood pressure, signs of impaired kidney function, blood calcium imbalance, and marked tremors (350). 7.4.2.2.3 Pharmacokinetics, Metabolism, and Mechanisms Cresols are normally present in human urine. 7.5 Standards, Regulations, or Guidelines of Exposure The American Conference of Governmental Industrial Hygienists (ACGIH) TLV TWA for cresol is 5 ppm (22 mg/m3) with a “skin” notation (351). The OSHA permissible exposure limit (PEL) is also 5 ppm (22 mg/m3) with a skin notation (351). The “skin” notation in the listing refers to “the potential significant contribution to the overall exposure by the dermal route, including mucous membranes and the eyes, either by contact with vapors or, of probable greater significance, by direct skin contact with the substance. The NIOSH REL TWA is 2.3 ppm (10 mg/m3); the IDLH is 250 ppm. Treatment of Cresol Ingestion Treatment should be supportive and symptomatic. There are no known antidotes (335). Skin Decontamination Treatments after Accidental Exposure of Phenol Skin contact should be treated by washing with copious amounts of water, then bathing in glycerol, propylene glycol, or polyethylene glycol. Patients may require ventilatory support (335).

Phenol and Phenolics Ralph Gingell, Ph.D., DABT, John O'Donoghue, Ph.D., DABT, Robert J. Staab, Ph.D., DABT, Ira W. Daly, Ph.D., DABT, Bruce K. Bernard, Ph.D., Anish Ranpuria, MS, E. John Wilkinson, Daniel Woltering, Ph.D., Phillip A. Johns, Ph.D., Stephen B. Montgomery, Ph.D., Larry E. Hammond, Ph.D., Marguerita L. Leng, Ph.D. 8.0 m-Cresol 8.0.1 CAS Number: [108-39-4] 8.0.2 Synonyms: 3-Methylphenol; phenol, 3-methyl; 3-cresol; m-cresylic acid; 1-hydroxy-2-methylbenzene; 3-

hydroxytoluene; m-hydroxytoluene; m-methylphenol; m-methylphenylol; m-oxytoluene; m-toluol; m-cresylic; 3-methyl-1-hydroxybenzene; 1-hydroxy-3-methylbenzene; m-kresol; hydroxy-3methylbenzene 8.0.3 Trade Names: NA 8.0.4 Molecular Weight: 108.14 8.0.5 Molecular Formula: C7H8O 8.0.6 Molecular Structure:

8.1 Chemical and Physical Properties Physical state Colorless, yellowish, or pinkish liquid, darkens with age and exposure to light and air (330, 331) Odor Phenolic odor, with an odor threshold of 5 ppm; sometimes refered to as an empyreumatic odor Specific 1.030–1.038 (mixture) gravity Melting point 11–35°C (mixture)/31°C (o-)/12°C (m-) Boiling point 191–203°C (mixture)/191°C (o-)/202°C (m-) Vapor density 1.034 air = 1 Flash point 82°C (mixture)/81°C (o-)/86°C (m-, p-) (all closed cup) Other properties are as follows: Flammability. m-Cresol is combustible and presents a marked fire hazard. m-Cresol fires can be extinguished with water, carbon dioxide, appropriate foam, or dry chemicals. Mixtures of air and 1.47% m-cresol are explosive (332). Solubility. m-Cresol is soluble in organic solvents, vegetable oils alcohol, ether, glycerin, chloroform, and dilute alkali; also in 40 parts water (330, 331). 8.1.1 General: NA 8.1.2 Odor and Warning Properties m-Cresol has a distinct phenolic odor discernable at 5 ppm. 8.2 Production and Use The cresols (cresylic acids) are methyl phenols and generally appear as a mixture of isomers (334). m-Cresol is prepared from m-toluic acid or obtained from coal tar or petroleum (331, 335, 336). Crude cresol is obtained by distilling “gray phenic acid” at a temperature of ~180–201°C. The mcresol may be separated from the crude or purified mixture by repeated fractional distillation in vacuo. It can also be prepared synthetically by diazotization of the specific toluidine, or by fusion of the corresponding toluenesulfonic acid with sodium hydroxide. m-Cresol is used as a disinfectant and solvent (330). Lysol™ disinfectant is a 50% v/v mixed-cresol isomer in a soap emulsion formed on mixing with water. The isomer m-cresol is an oily liquid with

low volatility. Besides disinfection at solutions of 1–5% (331), the cresols are used in degreasing compounds, paintbrush cleaners, and additives in lubricating oils (334). Cresols were once widely used for disinfection of poultry houses but this use has been discontinued because they cause respiratory problems and abdominal edema in young chicks (337). m-Creosl has been used in synthetic resins, explosives, petroleum, photographic, paint, and agricultural industries. 8.3 Exposure Assessment With rare exceptions, human exposure in industry has been limited to accidental contact of m-cresol with the skin or inhalation of vapors (335). 8.3.1 Air: NA 8.3.2 Background Levels: NA 8.3.3 Workplace Methods Air sampling and analytical methods for personal monitoring are essentially the same as for phenol. Cresol is absorbed in dilute alkali and determined colorimetrically with diazotized p-nitroaniline reagent (339), absorbed in spectrograde alcohol with direct determination by ultraviolet spectrophotometry, or absorbed on silica and determined by gas–liquid chromatography (340). One sampling procedure consists of drawing a known volume of air through a silica-gel tube consisting of two 20/40-mesh silica gel sections, 150 and 75 mg, separated by a 2mm portion of urethane foam. Acetone-desorbed samples can be analyzed using gas chromatography with a flame ionization detector. The column is packed with 10% free fatty-acid polymer in 80/100mesh, acid-washed DMCS Chromosorb W. The useful range of this method is 5–60 mg/m3 (341). 8.3.4 Community Methods 8.3.5 Biomonitoring A sensitive method for the detection of cresol and metabolites in serum has been reported (342). 8.4 Toxic Effects 8.4.1 Experimental Studies 8.4.1.1 Acute Toxicity Ingestion. Orally administered m-cresol is moderately to acutely toxic in animals. After oral administration to rats, the LD50 value was determined to be 2.02 g/kg body weight (340). It is considered to have about the same general degree of toxicity as phenol, but to be slightly less corrosive than phenol with slower absorption, which accounts for slightly milder systemic effects. m-Cresol is somewhat less toxic and less irritating than phenol (340). Corrosion to the GI tract and mouth is expected following cresol exposure with similar effects as phenol. Following oral administration, kidney tubule damage, nodular pneumonia, and congestion of the liver with pallor and necrosis of the hepatic cells is seen. Acute exposure can cause muscular weakness, GI disturbances, severe depression, collapse, and death. Dermal. The dermal LD50 in rabbits of m-cresol was 2050 mg/kg (340). Toxic symptoms are similar after oral and dermal routes. Inhalation. No verifiable LC50 values have been reported, but rats survived 1 h exposure to 710 mg/m3 (340). Irritation and Sensitization. m-Cresol, undiluted and in solution, can cause severe local irritation and corrosion following dermal and ocular exposure. Irritant effects include severe skin lesions, edema, erythema, and necrosis. In a study using rabbits that were dosed with 517 mg m-cresol for 24 h under occlusion, severe skin effects were produced (340). Eye irritation can be severe and include corneal opacity. 8.4.1.2 Chronic and Subchronic Toxicity m-Cresol was tested for subchronic toxicity in animal studies of 28 and 90 days duration by dietary administration.

Ingestion by Diet In a 28-day study, F344/N rats and B6C3F1 mice of both sexes (5/sex/group) were given m-cresol at concentrations of from 300–30,000 ppm in the diet. All rats survived until study termination; some mice died at the 10,000 and 30,000 ppm dietary levels. Increased liver weights and kidney weights were noted in both species at doses as low as 3000 ppm. No microscopic changes were associated with the weight changes. Bone marrow hyperplasia and atrophy of the uterus, ovary, and mammary gland were seen occasionally in both the 10,000- and 30,000-ppm groups (343). 8.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Cresol is absorbed through the skin and open wounds and mucous membranes of the gastroenteric and respiratory tracts. The absorption rate through the skin depends on the size of the area exposed rather than the concentration of the material applied (340). The metabolism and the rate of absorption, detoxification, and excretion of the cresol are much like those for phenol; they are oxidized and excreted as glucuronide and sulfate conjugates. 8.4.1.3.1 Absorption: NA 8.4.1.3.2 Distribution: NA 8.4.1.3.3 Excretion The major route of excretion of the cresols is in the urine. Both o- and m-cresols are ring-hydroxylated to a small extent, whereas p-cresol gives rise to the formation of some phydroxybenzioc acid. 2,5-Dihydroxytoluene has been isolated from the urine of rabbits fed o- and mcresols, and p-hydroxybenzoic acid and p-cresylglucuronide from those administered p-cresol (340). 8.4.1.4 Reproductive and Developmental: NA 8.4.1.5 Carcinogenesis m-Cresol has induced a few papillomas but no carcinomas in tumor studies. Skin Application Female Sutter mice (27–29/group) were dosed with a single application of dimethylbenzanthracene followed one week later by 25 mL of a 20% solution of m-cresol in benzene twice weekly for 12 weeks. Benzene-treated controls did not experience mortality, although many of the cresol-treated mice died. m-Cresol produced 7/17 tumors (papillomas) in surviving mice (234). In another promotion study, mice were painted with a 20% solution of m-cresol for 11 weeks following initiation with dimethylbenzanthracene; no carcinomas were produced (344). 8.4.1.6 Genetic and Related Cellular Effects studies Salmonella assays of various strains, both with and without liver homogenate, showed no mutagenic activity (57, 60, 345–348). Sister chromatid exchange assays produced no evidence of mutagenicity in CHO cells (346). 8.4.2 Human Experience 8.4.2.1 General Information Cresols can cause local and systemic toxicity in humans after exposure by oral or dermal routes. 8.4.2.2 Clinical Cases Approximately 20 mL of a 90% solution of mixed-cresol solution caused chemical burns, cyanosis, unconsciousness, and death within 4h when accidentally poured on an infant's head. Hepatic necrosis; cerebral edema; acute tubular necrosis of the kidneys; and hemorrhagic effusions from the peritoneum, pleura, and pericardium were observed postmortem. Blood cresol concentration was 120 mg/mL (349). 8.4.2.2.1 Acute Toxicity Oral lethality data from Lysol™, which is 50% mixed cresols, has been estimated to be between 60 and 120 mL (352). Ingestion is associated with corrosivity to body tissue and toxicity to the vascular system, liver, kidneys, and pancreas (344). 8.4.2.2.2 Chronic and Subchronic Toxicity Chronic cresol poisoning has been infrequently reported.

Seven workers who were exposed to mixed-cresol vapor for 1.5–3 years experienced headaches, nausea, and vomiting. Some of those exposed also had elevated blood pressure, signs of impaired kidney function, blood calcium imbalance, and marked tremors (344). 8.4.2.2.3 Pharmacokinetics, Metabolism, and Mechanisms Cresols are normally present in human urine. 8.4.2.2.4 Reproductive and Developmental: NA 8.4.2.2.5 Carcinogenesis: NA 8.4.2.2.6 Genetic and Related Cellular Effects Studies: NA 8.4.2.2.7 Other: Neurological, Pulmonary, Skin Sensitization, etc All isomers of cresol cause renal toxicity, hepatic toxicity, and CNS and cardiovascular disturbances (335). 8.5 Standards, Regulations, or Guidelines of Exposure The ACGIH TLV TWA for cresol is 5 ppm (22 mg/m3) with a “skin” notation (351). The OSHA PEL is also 5 ppm with a “skin” notation (350). The “skin” notation in the listing refers to “the potential significant contribution to the overall exposure by the dermal route, including mucous membranes and the eyes, either by contact with vapors or, of probable greater significance, by direct skin contact with the substance.” The NIOSH REL TWA is 2.3 ppm (10 mg/m3); the IDLH value is 250 ppm. Treatment of Cresol Ingestion Treatment should be supportive and symptomatic. There are no known antidotes (335). Skin Decontamination Treatments after Accidental Exposure of Phenol Skin contact should be treated by washing with copious amounts of water, then bathing in glycerol, propylene glycol, or polyethylene glycol. Patients may require ventilatory support (335).

Phenol and Phenolics Ralph Gingell, Ph.D., DABT, John O'Donoghue, Ph.D., DABT, Robert J. Staab, Ph.D., DABT, Ira W. Daly, Ph.D., DABT, Bruce K. Bernard, Ph.D., Anish Ranpuria, MS, E. John Wilkinson, Daniel Woltering, Ph.D., Phillip A. Johns, Ph.D., Stephen B. Montgomery, Ph.D., Larry E. Hammond, Ph.D., Marguerita L. Leng, Ph.D. 9.0 p-Cresol 9.0.1 CAS Number: [106-44-5] 9.0.2 Synonyms: 4-Methylphenol; phenol, 4-methyl; 4-cresol; p-cresylic acid; 1-hydroxy-4-methylbenzene; 4hydroxytoluene; p-hydroxytoluene; p-methylphenol; p-methylphenylol p-oxytoluene; p-toluol; 1methyl-4-hydroxybenzene; p-methylhydroxybenzene; p-tolyl alcohol 9.0.3 Trade Names: NA 9.0.4 Molecular Weight: 108.14 9.0.5 Molecular Formula: C7H8O 9.0.6 Molecular Structure:

9.1 Chemical and Physical Properties Physical state Colorless, yellowish, or pinkish liquid, darkens with age and exposure to light and air (330, 331); p-cresol can also appear as a liquid Odor Phenolic odor, with an odor threshold of 5 ppm; sometimes refereed to as an empyreumatic odor Specific 1.034 gravity Melting point 32–34°C Boiling point 202°C (330) Vapor density 3.7 (air = 1) (332) Vapor 0.11 torr (25°C) pressure Refractive 1.537 index Flash point 86°C (closed cup) Other characteristics are as follows: Flammability. p-Cresol is combustible and presents a marked fire hazard. Fires can be extinguished with water, carbon dioxide, appropriate foam, or dry chemicals. Mixtures of air and 1.47% p-cresol are explosive (332). Solubility. p-Cresol is soluble in organic solvents, vegetable oils, alcohol, ether, glycerin, chloroform, and dilute alkali; also in 40 parts water (330, 333). 9.1.1 General: NA 9.1.2 Odor and Warning Properties p-Cresol has a distinct phenolic odor discernable at 5 ppm. Taste has not been noted in the available literature. 9.2 Production and Use The cresols (cresylic acids) are methyl phenols and generally appear as a mixture of isomers (334). p-Cresol is a 4-methyl deriviative of phenol (335) and is prepared from m-toluic acid or obtained from coal tar or petroleum (333, 336). Crude cresol is obtained by distilling “gray phenic acid” at a temperature of ~180–201°C. p-Cresol may be separated from the crude or purified mixture by repeated fractional distillation in vacuo. It can also be prepared synthetically by diazotization of the specific toluene, or by fusion of the corresponding toluenesulfonic acid with sodium hydroxide. p-Cresol is used as a disinfectant and solvent (330). Lysol™ disinfectant is a 50% v/v mixed-cresol isomer in a soap emulsion formed on mixing with water. Besides disinfection products at solutions of 1–5% (333), the cresols are used as degreasing compounds, paintbrush cleaners, and additives in lubricating oil (334). Cresols were previously widely used for disinfection of poultry houses, but this use was discontinued because they cause respiratory problems and abdominal edema in young chicks (337). p-Cresol has been used in synthetic resins, explosives, petroleum, paint, photographic and agricultural industries. p-Cresol is used safety in foods as a synthetic flavoring substance and adjuvant (338). 9.3 Exposure Assessment

With rare exceptions, human exposure in industry has been limited to accidental contact of p-cresol with the skin or to inhalation of vapors (335). 9.3.1 Air: NA 9.3.2 Background Levels: NA 9.3.3 Workplace Methods Air sampling and analytical methods for personal monitoring are essentially the same manner as for phenol. Cresol is absorbed in dilute alkali and determined colorimetrically with diazotized p-nitroaniline reagent (339), absorbed in spectrograde alcohol with direct determination by ultraviolet spectrophotometry, or absorbed on silica and deteremined by gas– liquid chromatography (340). One sampling procedure consists of drawing a known volume of air through a silica-gel tube consiting of two 20/40-mesh silica-gel sections, 150 and 75 mg, separated by a 2-mm portion of urethane foam. Acetone desorbed samples can be analyzed using a gas chromatography with a flame ionization detector. The column is packed with 10% free fatty-acid polymer in 80/100-mesh, acid washed DMCS Chromosorb W. The useful range of this method is 5 to 60 mg/m3 (341). 9.3.4 Community Methods: NA 9.3.5 Biomonitoring/Biomarkers A sensitive method for the detection of cresol and metabolites in serum has been reported (342). 9.4 Toxic Effects 9.4.1 Experimental Studies 9.4.1.1 Acute Toxicity Ingestion. Orally administered p-cresol is moderately acutely toxic in animals. After oral administration to rats, the LD50 value was 1.8 g/kg body weight (340). This is considered to have about the same degree of toxicity as phenol but to be slightly more corrosive than phenol with slower absorption, which accounts for slightly milder systemic effects (340). Corrosion of the GI tract and mouth is expected following oral cresol exposure similar to phenol. Following oral administration, kidney tubule damage, nodular pneumonia, and congestion of the liver with pallor and necrosis of the hepatic cells is seen. Acute exposure can cause muscular weakness, GI disturbances, severe depression, collapse, and death. Dermal. The dermal LD50 in rats was 750 mg/kg (340). Toxic symptoms are similar after oral and dermal routes. Inhalation. No verifiable LC50 values have been reported, but rats survived 1 h exposure to 710 mg/m3 (340). Irritation and Sensitization. p-Cresol, undiluted and in solution, can cause severe local irritation and corrosion following dermal and ocular exposure. Irritant effects include severe skin lesions, edema, erythema, and necrosis. Eye irritation can include severe irritation with corneal opacity. 9.4.1.2 Chronic and Subchronic Toxicity p-Cresol has been tested for subchronic toxicity in animal studies of 28 days' duration by dietary administration. Ingestion by Diet In a 28-day study, F344/N rats and B6C3F1 mice of both sexes (5/sex/group) were given p-cresol at concentrations of 300–30,000 ppm in the diet. All rats survived until study termination; some mice died at the 10,000 and 30,000 ppm dietary levels. Increased liver weights and kidney weights were noted in both species at doses as low as 3000 ppm, but no microscopic changes were associated with the organ weight changes. Bone marrow hyperplasia, and atrophy of the uterus, ovary, and mammary gland were seen in the 10,000- and 30,000-ppm dietary groups (343).

9.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms 9.4.1.3.1 Absorption Cresol is absorbed through the skin, open wounds, and mucous membranes of the GI and respiratory tracts. The rate of absorption through the skin depends on the size of the area exposed rather than the concentration of the material applied (340). The metabolism and the rate of absorption, detoxification, and excretion of the cresols are much like those of phenol; they are oxidized and excreted as glucuronide and sulfate conjugates. 9.4.1.3.2 Distribution: NA 9.4.1.3.3 Excretion The major route of excretion of the cresols is in the urine. Both o- and m-cresols are ring-hydroxylated to a small extent, whereas p-cresol gives rise to the formation of some phydroxybenzoic acid. 2,5-Dihydroxytoluene has been isolated from the urine of rabbits fed o- and mcresols, and p-hydroxybenzoic acid and p-cresylglucuronide from those administered p-cresol (340). 9.4.1.4 Reproductive and Developmental Toxicity: NA 9.4.1.5 Carcinogenesis o-Cresol has been induced a few papilloma but no carcinomas in tumor studies. Skin Application Female Sutter mice (27–29/group) were dosed with a single application of dimethylbenzanthracene followed one week later by 25 mL of a 20% solution of p-cresol in benzene twice weekly for 12 weeks. Benzene treated controls did not experience mortality, although many of the cresol mice did die. p-Cresol produced 7/20 tumors (papillomas) on surviving mice (234). In another promotion study, mice were painted with a 20% solution of p-cresol for 11 weeks following initiation with dimethylbenzanthracene. Four of fourteen mice treated with p-cresol produced papillomas; no carcinomas were produced (344). 9.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms: NA 9.4.1.4 Reproductive and Developmental: NA 9.4.1.5 Carcinogenesis: NA 9.4.1.6 Genetic and Related Cellular Effects Studies In Vitro Effects In an unscheduled DNA synthesis assay, p-cresol was shown to be negative using rat hepatocytes (345). A cell transformation assay using BALB/3T3 cells showed o-cresol to be negative (346). Salmonella assays of various strains, both with and without liver homogenate, showed no mutagenic activity (59, 60, 347). In a mouse lymphoma forward mutation assay with liver homogenates, o-cresol was not mutagenic (345). Sister chromatid exchange assays produced no evidence of mutagenicity in CHO cells (346). oCresol induced SCEs in human lung fibroblasts (345, 348). 9.4.1.7 Other: Neurological, Pulmonary, Sensitization Depigmentation occurred when CBA/J mice were treated topically with a laundry ink containing p-cresol (353). 9.4.2 Human Experience 9.4.2.1 General Information Cresols can cause local and systemic toxicity in humans after exposure by oral or dermal routes. 9.4.2.2 Clinical Cases Approximately 20 mL of a 90% solution of mixed-cresol solution caused chemical burns, cyanosis, unconsciousness, and death within 4h when accidentally poured on an infant's head. Heptaic necrosis; cerebral edema; acute tubular necrosis of the kidneys; and hemorrhagic effusions from the peritoneum, pleura, and pericardium were observed postmortem. Blood cresol concentration was 120 micrograms/ml (349).

9.4.2.2.1 Acute Toxicity Oral lethality data from Lysol™ (which contains 50% mixed cresols) has been estimated to be between 60 and 120 mL (352). Ingestion is associated with corrosivity to body tissue and toxicity to the vascular system, liver, kdineys, and pancreas [Proctor 88]. 9.4.2.2.2 Chronic and Subchronic Toxicity Chronic cresol poisoning has been reported infrequently. About 10 subjects were exposed to o-cresol at 1.4 ppm and complained of respiratory tract irritation (350). Documentation was not confirmed. Seven workers who were exposed to mixed-cresol vapor for 1.5–3 years experienced headaches, nausea, and vomiting. Some of those exposed also had elevated blood pressure, signs of impaired kidney function, blood calcium imbalance, and marked tremors (344). 9.4.2.2.3 Pharmacokineics, Metabolis, and Mechanisms Cresols are normally present in human urine. The normal human excretes 16–39 mg p-cresol/day (340). 9.4.2.2.4 Reproductive and Developmental: NA 9.4.2.2.5 Carcinogenesis: NA 9.4.2.2.6 Genetic and Related Cellular Effects Studies: NA 9.4.2.2.7 Other: Neurological, Pulmonary, Skin Sensitization, etc All isomers of cresol cause renal toxicity, hepatic toxicity, and CNS and cardiovascular disturbances (335). 9.5 Standards, Regulations, or Guidelines of Exposure The ACGIH TLV TWA for cresol is 5 ppm (22 mg/m3) with a “skin” notation (351). The OSHA PEL is also 5 ppm with a “skin” notation (351). The “skin” notation in the listing refers to “the potential significant contribution to the overall exposure by the dermal route, including mucous membranes and the eyes, either by contact with vapors or, of probable greater significance, by direct skin contact with the substance.” The NIOSH REL TWA is 2.3 ppm (10 mg/m3); the IDLH value is 250ppm. Treatment of Cresol Ingestion Treatment should be supportive and symptomatic. There are no known antidotes (335). Skin Decontamination Treatments after Accidental Exposure of Phenol Skin contact should be treated by washing with copious amounts of water, then bathing in glycerol, propylene glycol, or polyethylene glycol. Patients may require ventilatory support (335).

Phenol and Phenolics Ralph Gingell, Ph.D., DABT, John O'Donoghue, Ph.D., DABT, Robert J. Staab, Ph.D., DABT, Ira W. Daly, Ph.D., DABT, Bruce K. Bernard, Ph.D., Anish Ranpuria, MS, E. John Wilkinson, Daniel Woltering, Ph.D., Phillip A. Johns, Ph.D., Stephen B. Montgomery, Ph.D., Larry E. Hammond, Ph.D., Marguerita L. Leng, Ph.D. 10.0 Creosote 10.0a Coal-Tar Creosote 10.0.1a CAS Number: [8001-58-9] 10.0.2a Synonyms: Creosote oil; creosotes; coal-tar oil; naphthalene oil; heavy oil; cresylic creosote; AWPA #1; brick oil; creosote p1; creosotum; liquid pitch oil; Preserv-o-sote; tar oil; wash oil; dead oil; Smoplastic-F; Osmoplastic-D; original carbolineum

10.0.3a Trade Names: NA 10.0.4a Molecular Weight: varies with purity 10.0.5a Molecular Formula: NA 10.0.6a Molecular Structure: NA 10.0b Wood Creosote 10.0.1b CAS Number: [8021-39-4] 10.0.2b Synonyms: Beechwood creosote; creasote; Fagus sylvatica creosote 10.0.3b Trade Names: NA 10.0.4b Molecular Weight: Varies with purity 10.0.5b Molecular Formula: NA 10.0.6b Molecular Structure: NA 10.1 Chemical and Physical Properties Coal-tar creosote is a translucent black or brown, oily liquid. It is heavier than water. Wood creosote is a colorless or yellowish oily liquid.

Wood Creosote Coal-Tar Creosote Specific gravity 1.09 1.1 Melting point –4°C Not available Boiling point 428°C at 0mmHg 203–220°C (decomposes) Vapor pressure 39mmHg (51°C) 42mmHg (22°C) Flash point Closed cup 74°C 73.9°C Open cup — 85°C

10.1.1 General: NA 10.1.2 Odor and Warning Properties Coal-tar creosote has a characteristic aromatic smoky odor. Wood creosote has a characteristic smoky odor and a caustic burning taste. 10.2 Production and Use Wood creosote is obtained from wood tars, from beech and the resin from leaves of the creosote bush, and by distillation and is composed mainly of phenols, xylenols, guaiacol, and creosol. Coaltar creosote is produced by high temperature carbonization and distillation of bituminous coal. Coaltar creosote contains liquid and solid aromatic hydrocarbons, tar acids, and tar base (354). At least 75% of the coal-tar creosote mixture is polyaromatic hydrocarbons (355). Purification of the crude preparation is accomplished by distillation and extraction from suitable oils.

Coal-tar creosote has been used as a wood preservative pesticide in the United States since the late 1890s. This accounts for over 97% of coal tar creosote production (356). Coal-tar creosote prevents animal and plant growth on concrete marine pilings and is a component of roofing pitch. (355). Other uses include animal and bird repellent, insecticide, animal dip, fungicide, and pharmaceutical applications (357). Beechwood creosote has, in the past, been used for medicinal purposes. It is rarely used in the United States for medical purposes today (355). 10.3 Exposure Assesment Workers most likely to be exposed are carpenters, railroad workers, farmers, tar distillers, glass- and steel-furnace attendants, and engineers. Injuries to the skin or eyes have occurred mainly among male workers engaged in dipping and handling mine timbers and woods for floors and other purposes. Recent studies indicate that dermal exposure to creosote contribute more significantly to total body burden than respiratory exposure (358). There is limited risk of exposure to wood creosote due to its limited commercial use. 10.3.1 Air According to the Toxic Release Inventory (TRI), coal-tar creosote manufacturing and processing facilities listed for 1993, the major portion of creosote released to the environment is released to the air. An estimated total of 1,152,129lb of coal-tar creosote, amounting to 99.2% of the total environmental release, was discharged to the air from manufacturing and processing facilities in the Unites States in 1993. No major sources of wood creosote releases to the environment have been reported (355). 10.3.2 Background Levels No information was found on atmospheric ambient concentrations of wood or coal-tar creosote components. Results from 2 years of groundwater monitoring at a wood treatment facility in Conroe, Texas, where coal-tar creosote had been used for about 20 years showed that monitoring wells were contaminated with naphthalene, methylnaphthalene, dibenzofuran, and fluorene (359). 10.3.3 Workplace Methods GC/MS has been employed to determine creosote levels in workplace air from impregnated wood. Detection levels of 10–50 × 10–6g creosote/m3 sample, and recoveries of 82–102% were acheived (360). 10.3.4 Community Methods: NA 10.3.5 Biomonitoring/Biomarkers No biomarkers uniquely specific to wood creosote or coal-tar creosote have been identified (355). The levels of creosote in biological mateials can be estimated by measuring the polycyclic aromatic hydrocarbon (PAH) content in biological samples. Available methods include GC/FID, GC/MS, and HPLC. GC/MS and HPLC have been employed to detect creosote derived polyclyclic aromatic hydrocarbon complexes in human tissues, including adipose tissue, blood, and urine (361, 362). 10.3.5.1 Blood NA 10.3.5.2 Urine NA 10.3.5.3 Other NA 10.4 Toxic Effects 10.4.1 Experimental Studies 10.4.1.1 Acute Toxicity Ingestion The acute toxicity of wood creosote in both rats and mice was evaluated following single-gavage administration of a 10% aqueous solution (363). The oral LD50 of wood creosote was 885 mg/kg (males) and 870 mg/kg (females) in rats and 525 mg/kg (male) and 433 mg/kg (female) in mice. Most animals died within 24 h. The oral LD50 for coal tar creosote is reported to be 725 mg/kg in rats and 433 mg/kg in mice (355). A study by Pfitzer (364) reported a rat LD50 of 1700 mg/kg. The acute lethal dose of coal tar creosote in sheep and calves is 4 g/kg (365).

Dermal The dermal LD50 of coal-tar creosote is >7950 mg/kg following 24-h application to intact and abraided skin (364). Inhalation Pfitzer (364) exposed rats by inhalation to near-saturated vapors generated from coal-tar creosote for one day. The animals exhibited dyspnea, slight nasal irritation, and eye irritation. The dose level was not determined. 10.4.1.2 Chronic and Subchronic Toxicity Ingestion No treatment related deaths were observed when rats were administered wood creosote in the feed at dose levels up to 1224 mg/kg/day in males or 768 mg/kg per day in females for 3 months (363). Male and female Wistar rats fed diets containing up to 313 or 394 mg/kg wood creosote per day for 96 weeks exhibited deaths in all groups. Treatment related deaths were observed in the males at the high dose only and were attributed to chronic progressive nephropathy (366). 10.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Generally, the PAH components of coaltar creosote are metabolized by oxidative enzymes in the liver and lungs to generate active metabolites that can bind to macromolecules. The principal products include phenols, dihydrodiols, quinones, anhydrides, and conjugates of these products (355). 10.4.1.3.1 Absorption No studies specific to the absorption of wood creosote or coal tar creosote were found. 10.4.1.3.3 Distribution No studies specific to the distribution of wood creosote or coal tar creosote were found. 10.4.1.3.3 Excretion Creosote appears to be excreted in the urine mainly in conjugation with sulfuric, hexuronic, and other acids (367, 368). Oxidation also occurs with the formation of compounds that impart a “smoky” appearance to the urine. Traces are excreted by way of the lungs. 10.4.1.4 Reproductive and Developmental The only available study in animals reported dermal contact with coal-tar-creosote-treated wood by pregnant sows (369). Four sows were confined in wooden crates for 2–10 days before delivery. The crates were coated with three applications of 98.5% coal-tar creosote. Of 41 pigs delivered, 21 were dead at birth; 11 pigs died by day 3 postfarrowing. No toxic effects were evident in the sows. These findings were considered suggestive of developmental toxicity. 10.4.1.5 Carcinogenesis The carcinogenicity of creosote oils has been studied quite thoroughly using mice (370, 371). Studies indicate that coal-tar cresosote and several of its fractions can be carcinogenic when applied to the skin of mice and rabbits. Dermally applied coal-tar creosote can also act as a tumor-initiating agent when applied prior to croton-oil treatment (355). 10.4.1.6 Genetic and Related Cellular Effects Studies The genotoxic potential of coal-tar creosote has been investigated using in vitro assays of the material and of urine from exposed animals. The available genotoxicity data indicate that creosote is an indirect mutagen and induces gene mutation in bacteria and mouse lymphoma cells (355). Bos et al. (372) identified fluoranthene as one of the major volatile components of creosote responsible for the genotoxicity observed in Salmonella typhimurium strains. 10.4.1.7 Other: Neurological, Pulmonary, Skin Sensitization Neurological Effects. Rats and mice treated via gavage administration of a single high dose of beechwood creosote (300 mg/kg rats) exhibited muscle twitching followed by convulsions within 1–2 min. This was followed by asphyxiation, coma, and death (363). Pulmonary Effects. Beechwood creosote failed to produce an adverse effect on lung weights when

fed to rats (1224 mg/kg per day males; 1570 mg/kg per day females) in the feed for 3 months (363). Thickening of tracheal mucous membrane was observed in mice who ingested feed (474 mg/kg males, 532 mg/kg females) containing beechwood creosote for 52 weeks. This was attributed by the author to inhalation of volatile components rather than to oral toxicity (363). Immunological and Lymphoreticular Effects. Daily exposures to beechwood creosote at 805 or 1224 mg/kg in the diet for 3 months resulted in increased relative spleen weight of male rats. Similar effects were not seen in mice (363). 10.4.2 Human Experience 10.4.2.1 General Information: NA 10.4.2.2 Clinical Cases 10.4.2.2.1 Acute Toxicity Ingestion Fatalities have occurred 14–36 h after the ingestion of about 7g of coal-tar creosote by adults or 1–2 g by children (373). The symptoms of systemic illness included salivation, vomiting, respiratory difficulties, thready pulse, vertigo, headache, and loss of pupillary reflexes, hypothermia, cyanosis, and mild convulsions. The repeated absorption of therapeutic doses from the GI tract may induce signs of chronic intoxication, characterized by disturbances of vision and digestion (increased peristalsis and excretion of bloody feces). In isolated cases of “self-medication,” hypertension, and general cardiovascular collapse have been described (374). Acute toxic hepatitis has been attributed to the ingestion of chaparral, an herbal supplement derived from the leaves of the creosote bush (375). Icterus and jaundice were observed in a 42-year-old male who consumed 500 mg of chaparral a day for 6 weeks. Elevated bilirubin, g-glutamyltranspeptidase, AST, and LDH were observed. Recovery occurred in approximately 3 weeks. Dermal Creosote burns were observed in construction workers who handled creosote-treated wood (376). The majority of these cases were mild and were characterized by erythema of the face. Coaltar creosote is capable of inducing phototoxicity of the skin (355). 10.4.2.2.2 Chronic and Subchronic Toxicity: NA 10.4.2.2.5 Pharmacokinetics, Metabolism, and Mechanisms: NA 10.4.2.2.4 Reproductive and Developmental No studies on reproductive or developmental effects of wood creosote or coal-tar creosote were identified. A site-surveillance program was conducted by the Texas Department of Health in 1990 at a housing development that was built on an abandoned creosote wood treatment plant. No reproductive or developmental findings were evident (355). 10.4.2.2.5 Carcinogenesis Cookson (377) described a 66-year-old coal-tar creosote factory worker who developed a squamous-cell carcinoma of the right hand after 33 years of heavy exposure. Autopsy revealed metastases to the lungs, liver, kidneys, heart, and lymph nodes. A similar case was reported in which a worker developed squamous-cell papillomas of the hands, nose, and thighs after several years of employment in the creosote impregnation of logs (378). Lenson (379) reported on a 64-year-old creosote shipyard worker who developed several primary carcinomas of the face. 10.4.2.2.6 Genetic and Related Cellular Effects Studies: NA 10.4.2.2.7 Other: Neurological, Pulmonary, Skin Sensitization, etc Contact of creosote with the skin or condensation of vapors of creosote on the skin or mucous membranes may induce an intense burning and itching with local erythema, grayish yellow to bronze pigmentation (376), papular and vesicular eruptions, gangrene, and cancer (380–382). Heinz bodies were noted in the blood of a patient 1 year after his exposure to creosote (379). Jonas (376) made similar observations following percutaneous absorption. On contact with the eyes, creosote caused protracted keratoconjunctivitis. This involves loss of corneal epithelium, clouding of the cornea, miosis, irritability, and photophobia. Subsequently, both blurring of vision and superficial keratitis can occur (334).

10.4.2.3 Epidemiology Studies Most of the available information on the effects of coal-tar creosote in humans comes from cases of acute poisoning following accidental or intentional exposure to coaltar creosote and from occupational exposures in the wood preserving and construction industries. These studies are limited by lack of exposure concentrations and duration and by exposure to other potentially toxic substances. The few available studies are limited by small sample size, short followup periods, and brief exposure periods. These studies suggest that coal-tar creosote is a dermal irritant and a carcinogen following dermal exposure. Additional well-controlled epidemiological studies are needed (355). 10.4.2.3.1 Acute Toxicity: NA 10.4.2.3.2 Chronic and Subchronic Toxicity: NA 10.4.2.3.3 Pharmacokinetics, Metabolism, and Mechanisms: NA 10.4.2.3.4 Reproductive and Developmental A site-surveillance program was conducted by the Texas Department of Health in 1990 at a housing development that was built on an abandoned creosote wood treatment plant. No reproductive or developmental findings were evident (355). 10.4.2.3.5 Carcinogenesis Case reports and occupational surveys associate occupational creosote exposure with the development of skin cancer (355). These reports outline a similar disease etiology for different groups of workers exposed to creosote that include the development of dermatoses that progressed to carcinoma, usually squamous-cell carcinoma. Cancer of the scrotum in chimney sweeps has been associated with prolonged exposure to coal-tar creosote. The latency period for the development of dermatoses was usually 20–25 years (377, 383, 384). More recent studies suggest that prolonged exposure to coal-tar creosote and other coal-tar products may cause cancer of the skin and other organs (385–387). 10.4.2.3.6 Genetic and Related Cellular Effects Studies: NA 10.4.2.3.7 Other: Neurological, Pulmonary, Skin Sensitization, etc Leonforte (388) reported several cases of acute allergic dermatitis subsequent to contact with a creosote bush and confirmed by a patch test. 10.5 Standards, Regulations, or Guidelines of Exposure The USEPA has classified coal-tar creosote as a class B1 carcinogen (Probable human carcinogen) (389). IARC classifies creosote as a human carcinogen (class 2A) (390). Creosotes are listed by the California Environmenal Protection Agency under Proposition 65 as chemicals known to cause cancer (391). The Occupational Safety and Health Administration (OSHA) has set an exposure limit of 0.2 mg/m3 of coal-tar pitch volatiles in the workplace during an 8 h workday, 40 h workweek. The American Conference of Governmental Industrial Hygienists (ACGIH) recommends the same level for coal tar pitch volatiles. The National Institute for Occupational Safety and Health (NIOSH) recommends a maximum level of 0.1 mg/m3 of coal-tar pitch volatiles for a 10 h workday, 40 h workweek (392). 10.6 Studies on Environmental Impact Coal-tar creosote materials encountered in old production facilities or waste-disposal sites within the top several feet of soil have become weathered, as virtually all of the phenolic and heterocyclic fractions have volatilized, oxidized, or biodegraded (355, 393). The lighter fractions of PAH will have degraded, and the remaining material shows limited ability to migrate. Johnston et al. (394) concluded that aqueous partitioning and volatilization are probably the main processes that control modification of coal-tar at gasworks sites. Spills of newly produced creosote may pose a more serious toxicity concern.

Phenol and Phenolics Ralph Gingell, Ph.D., DABT, John O'Donoghue, Ph.D., DABT, Robert J. Staab, Ph.D., DABT, Ira W. Daly, Ph.D., DABT, Bruce K. Bernard, Ph.D., Anish Ranpuria, MS, E. John Wilkinson, Daniel Woltering, Ph.D., Phillip A. Johns, Ph.D., Stephen B. Montgomery, Ph.D., Larry E. Hammond, Ph.D., Marguerita L. Leng, Ph.D. 11.0 Pentachlorophenol and Sodium Pentachlorophenate 11.0a Pentachlorophenol 11.0.1a CAS Number: [87-86-5] 11.0.2a Synonyms: Pentachlorophenate; 2,3,4,5,6-pentachlorophenol; pentachlorofenolo; pentachlorphenol; penta; Dowicide 7; Dowicide EC-7; penchlorol; Santophen 20; Chlorophen; Pentacon; Penwar; Sinituho; PCP; pentachlorofenol; pentachlorophenol, dp-2; Dow pentachlorophenol dp-2 antimicrobial; chemtol; cryptogil oil; Dowicide 7; durotox; EP 30; fungifen; grundier arbezol; lauxtol; lauxtol a; liroprem; term-i-trol; Thompson's wood fix; penta-kil; peratox; permacide; permagard; permasan; permatox dp-2; permatox penta; permite; priltox; santobrite; Pol-NU; Oz-88; Osmoplastic; Forepen; Dura-Treet (395) 11.0.3a Trade Names: Block Penta, Forpen-50, GlazD Penta, K-Ban, Osmose, Penta Concentrate, Penta OL, Pentacon, Pentacon-5, Pentacon-7, Pentacon-10, Pentacon-40, Pentasol, Penta-WR, Penwar, Penwar 1-5, PolNu, Pol-Nu-Pak, Treet II, Vulcan Premium Four # Penta (PCP2) Concentrate, Woodtreat (396–398) 11.0.4a Molecular Weight: 266.35 (395) 11.0.5a Molecular Formula: C6HCl5O 11.0.6a Molecular Structure:

Phenol and Phenolics Ralph Gingell, Ph.D., DABT, John O'Donoghue, Ph.D., DABT, Robert J. Staab, Ph.D., DABT, Ira W. Daly, Ph.D., DABT, Bruce K. Bernard, Ph.D., Anish Ranpuria, MS, E. John Wilkinson, Daniel Woltering, Ph.D., Phillip A. Johns, Ph.D., Stephen B. Montgomery, Ph.D., Larry E. Hammond, Ph.D., Marguerita L. Leng, Ph.D.

Table 53.6. Physicochemical Properties of Various Chlorophenols

Name

Odor Specific Vapor Vapor CAS Threshold Gravity MP Density Pressure D Number Appearance ( mg/mL) (g/mL) (°C) BP (°C) (mmHg) (mmHg) (g

2,3,4,5[4901Tetrachlorophenol 51-3] 2,3,4,6[58-90Tetrachlorophenol 2] 2,3,5,6[935-95Tetrachlorophenol 5] 2,3,4[15950Trichlorophenol 66-0] 2,3,5[933-78Trichlorophenol 8] 2,3,6[933-75Trichlorophenol 5] 2,4,5[95-95Trichlorophenol 4] 2,4,6[88-06Trichlorophenol 2] 3,4,5[609-19Trichlorophenol 8] 2,3[576-24Dichlorophenol 9] 2,4[120-83Dichlorophenol 2] 2,5[583-78Dichlorophenol 8] 2,6[87-65Dichlorophenol 0] 3,4[95-77Dichlorophenol 2] 3,5Dichlorophenol 2-Chlorophenol 3-Chlorophenol 4-Chlorophenol

Beige solid N/A

1.6

116

Sublimes N/A

N/A

N/

Beige solid N/A

1.839

70

150

N/A

1–60

N/

Beige solid N/A

1.6

164

N/A

N/A

N/

Light peach solid White chalky solid Purple crystals Off-whitesolid Orange-andwhite-solid Off-white solid Brown crystals White solid

N/A

N/A

Sublimes N/A

N/A

N/

N/A

N/A

248–249 N/A

N/A

N/

300

N/A

114– 116 77– 79 57– 59 56

253

N/A

N/A

N/

N/A

68

253

>1

1–5

1.5

N/A

69.5 244.5

N/A

1–5

N/

N/A

N/A

101

271–277 N/A

N/A

N/

30

N/A

59

206

N/A

N/A

N/

45

210

5.62

1

N/

N/A

57

211

N/A

N/A

N/

N/A

67

219

1–10

N/A

N/

N/A

67

N/A

N/A

N/

N/A

68

233

N/A

N/A

N/

175.6

N/A

1–22

1.2

214

N/A

1–5

1.2

4.4

0.1

1.6

210

White 30 crystals Purple 3–200 crystals Brown and 100 yellow crystals [591-35- Pink crystals N/A 5] [95-57- Yellow 20 8] liquid [108-43- White 1–5 0] crystals [106-48- White N/A 9] crystals

43.2– 220 43.7

M.P = Melting Point; B.P. = Boiling Point; V.D. = Vapor Density; V.P. = Vapor pressure; Sub. = Sublimes.

Table 53.7. Solubilites of Various Chloro-phenols

Name

DMSO Ethanol Ethyl Acetone Water ( mg/mL) CH3OH ( mg/mL) ether ( mg/mL) Benzene CCl4 ( mg/ml)

2-Chlorophenol 3-Chlorophenol 4-Chlorophenol 3,5Dichlorophenol 3,4Dichlorophenol 2,3Dichlorophenol 2,6Dichlorophenol 2,5Dichlorophenol 2,4Dichlorophenol 3,4,5Trichlorophenol 2,4,6Trichlorophenol 2,4,5Trichlorophenol 2,3,6Trichlorophenol 2,3,5,6Tetrachlorophenol 2,3,5Trichlorophenol 2,3,4,6Tetrachlorophenol 2,3,4,5Tetrachlorophenol 2,3,4Trichlorophenol

100 100 100 100

N/A N/A N/A N/A

100 100 100 100

N/A N/A N/A N/A

100 100 100 100

N/A N/A N/A N/A

N/A N/A N/A N/A

10–50 10–50 10–50 5 g/kg in rabbits. Repeated applications did not cause delayed hypersensitivity in guinea pigs (658, 659). The sodium salt (SOPP) is slightly more toxic, with LD50 values of 800–900 mg/kg bw in male and female mice, and 850–1700 mg/kgbw in male and female rats. It can cause severe skin burns and severe eye irritation with corneal injury due to its high alkalinity; a 1% solution of SOPP has a pH of 11.2–11.6 (658, 659). 16.4.1.2 Chronic and Subchronic Toxicity OPP and its sodium salt (SOPP) have been studied extensively in Japan, Germany, and the United States as required for pesticide registration and reregistration. Only subchronic and chronic studies with OPP are reviewed here; humans are not exposed to SOPP in the diet, such as on washed fruit, because it readily hydrolyses to OPP during the fungicidal treatment. The many feeding studies conducted with SOPP at high levels in the diet of rats are considered to be of little relevance for the assessment of potential toxicity in humans

exposed to low levels of OPP (658, 659). 16.4.1.2.1 Subchronic Toxicity Two similar short-term studies were conducted in Japan in which groups of 10–12 rats of each sex were fed OPP at dietary levels of 0.125 or 0.156, 0.313, 0.625, 1.25, and 2.5% for 12 or 13 weeks. The dietary NOEL was 0.625% in each study, reported to be equivalent to a dose level of ~780 mg/kgbw per day in one study (661) and to ~420 mg/kgbw per day in the other (662). Body weights and body weight gains were severely depressed in males and females fed 2.5% OPP in the diet. Only 73% of males survived compared to 92% of females at this high dietary level equivalent to a dose level of ~2500 mg/kgbw per day, and all rats in lower dose groups lived to the end of these short-term studies. Absolute and relative weights of many organs were depressed in male rats fed 2.5% OPP, and proliferative lesions of the urinary bladder and slight nephrotoxic lesions were noted (662). In a U.S. study, 30 male rats were fed a diet containing 2% OPP (~1250 mg/kgbw daily) and were sacrificed at intervals for 90 days. Food consumption was greatly reduced with consequent weight loss during the first week, which improved but remained somewhat depressed throughout the study. Seven of the rats died of apparent malnutrition. Observations included small amounts of blood in the urine, significantly decreased urine specific gravity at 65 and 90 days, increased sizes of liver and kidneys, and discolored focal areas of the kidneys at the end of the study. On microscopic examination slightly swollen liver cells were seen, as well as signs of kidney pathology that were not considered severe enough to seriously impair renal function and did not increase in severity on days 30–90 of treatment. No treatment-related urinary bladder lesions were seen in this study (663). 16.4.1.2.2 Chronic Toxicity Groups of 50 mice of each sex were fed diets to provide dose levels of 0, 250, 500, and 1000 mg/kgbw daily for 2 years. Satellite groups of 10 mice/sex/dose level were sacrificed at 1 year for evaluation of general chronic toxicity. In-life observations, mortality, hematology, clinical chemistry, and urinalyses were not affected. Significantly decreased body weights and body weight gains were noted in all groups except low dose males. The primary target organ was the liver, based on increased absolute and/or relative weights at all dose levels, and on gross and histopathology. Microscopic changes in the liver suggested adaptation to OPP metabolism, associated with a statistically significant increased incidence of liver cell adenomas in middle and high dose males. No oncogenic effects were observed in low dose males or in females at any dose level. The minor effects observed in the low dose groups suggest that a long-term NOEL would likely be 100 mg/kgbw OPP daily in mice (664). To confirm the adverse findings in male rats in short-term studies, several longer-term studies were conducted with OPP in Japan using small groups of male rats. In a 91-week study at dietary levels of 0.63, 1.25 and 2.5% OPP, survival rates and mean body weights were significantly lower in middose and high-dose groups. Bladder tumors were seen in 23/24 males in the mid-dose group, but in only 4/23 of high dose group. Moderate to severe nephrotic lesions were found in 3/24 of the group fed 1.25% OPP and in all 23 of the male rats fed 2.5% OPP for 91 weeks (662). In another study, no tumors were induced when male rats were fed 2% OPP for 36 or 64 weeks, or 1.25% for 96 weeks followed by 8 weeks on untreated diet. In the latter 104-week study, only papillary or nodular hyperplasia of the bladder was seen in 3/27 male rats fed 1.25% OPP (665). In a recent study conducted according to U.S. pesticide guidelines, groups of 70–75 rats of each sex per dose level were fed OPP at constant nominal dietary concentrations of 0, 0.08, 0.4, and 0.8% (males) or 1.0% (females). These levels were equivalent to average daily dose levels of 39/49, 200/248, and 402/647 mg/kgbw in male and female rats, respectively. Satellite groups of 20 rats/sex/dose level were sacrificed at 1 year to evaluate interim toxicity; remaining rats were sacrificed at 2 years to evaluate long-term toxicity and carcinogenicity. Food consumption remained unchanged, but mean body weights were decreased in mid-dose and high dose males and females. Increased mortality was noted in highdose males fed 0.8% but not in females fed 1.0% OPP. Clinical observations included abnormal urine color and various staining, and an increased incidence of blood in the urine of high dose males. Postmortem findings included wet/stained ventrum, urinary bladder

masses, and pitted zones and abnormal texture in the kidney. No effect on organ weights was noted. Histopathological findings in mid-dose and high dose males were characterized as structural alterations in the kidney and urinary bladder, including evidence of urothelial hyperplasia and/or neoplasia (papilloma and transitional-cell carcinoma). Neoplastic changes were not observed in highdose females at a dose level ~60% higher than in males. The NOEL for systemic chronic toxicity was 0.08% OPP in the diet, equivalent to daily dose levels of 39 and 49 mg/kgbw in male and female rats, respectively (666). 16.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Extensive studies have been conducted in the United States and Japan on the metabolism of OPP in mice, rats, cats, and dogs given relatively high single or multiple oral doses. The results are compared in a recent publication, which also reports a metabolism study in human male volunteers exposed to a low dermal dose of radiolabeled OPP (667). 16.4.1.3.1 Absorption When single oral doses of 500 mg/kg of 14C-OPP or 14C-SOPP were given to male rats, both compounds were absorbed rapidly as demonstrated by recovery of ~90–95% of the radioactivity in urine and 5–6% in feces, chiefly in the first 24 h. The disposition of the radioactivity was not greatly affected by preconditioning the rats by feeding equimolar amounts of unlabeled OPP (1.3%) or SOPP · 4H2O (2.0%) in the diet for 2 weeks before administration of the labeled compounds. SOPP appeared to be eliminated somewhat more rapidly than OPP (663). 16.4.1.3.2 Distribution OPP is distributed rapidly via enterohepatic circulation and does not bioaccumulate in tissues after either oral or dermal exposure in experimental animals (658, 659). 16.4.1.3.3 Excretion Absorbed OPP is excreted rapidly in urine primarily as the sulfate and glucuronide conjugates. Administration of high doses results in saturation of the sulfation pathway and some conversion of OPP to 2,5-dihydroxybiphenyl (phenylhydroquinone), which is also excreted as sulfate and glucuronide conjugates (663, 667). 16.4.1.4 Reproductive and Developmental In a reproduction study, groups of 30 rats of each sex were fed OPP at dietary concentrations to provide dose levels of 0, 20, 100 or 500 mg/kgbw daily over two generations. Animals in the high dose groups exhibited parental toxicity consisting of reduction in male and female body weights, urine staining in males, bladder calculi in males, and histological changes in the kidneys, bladder, and ureter of males. No reproductive effects were observed at any dose level. The parental and neonatal NOEL was 100 mg/kgbw per day, and the NOEL for reproductive effects was 500 mg/kgbw per day (659, 668). A teratogenicity study was conducted in which groups of 25–27 female rats were bred and given daily doses of 100, 300, or 700 mg OPP/kgbw by gavage on days 6–15 of gestation. No evidence of maternal or fetal toxicity was produced by administration of the two lower dose levels. The high dose did not cause embryotoxic or teratogenic effects, but was slightly toxic to the dams as evidenced by decreased body weight gain and food consumption during the treatment period (659, 669). Another teratogenicity study was conducted in groups of 16–24 artificially inseminated female New Zealand white rabbits by oral gavage of OPP in corn oil at targeted daily dose levels of 0, 25, 100, or 250 mg/kgbw on days 7–19 of gestation. The high dose caused increased mortality (13%), gross pathological alterations of the GI tract, and histopathological alterations of the kidneys. The NOEL for maternal toxicity was 100 mg/kgbw per day and the embryonal/fetal NOEL was 250 mg/kgbw per day, the highest dose level tested in rabbits (659, 670). 16.4.1.5 Carcinogenesis IARC classified SOPP as a B2 carcinogen in 1983, based on reports from Japan that high dietary levels of this sodium salt caused bladder tumors in male rats (671, 672). Both sodium saccharin and sodium cyclamate also cause bladder tumors at high doses in male rats, but

classification of these food additives as B2 carcinogens was recently rescinded by IARC at a meeting in 1998. OPP was not classified by IARC because little published data were available when this form was evaluated in 1983 (671, 672). Since then, several conventional long-term studies have been conducted with OPP in both sexes of mice and rats. Groups of 50 mice/sex were fed dietary levels of OPP to provide dose levels of 0, 250, 500, or 1000 mg/kgbw daily for 2 years. The liver was identified as the target organ, with microscopic changes suggestive of adaptation to OPP metabolism. No oncogenic effects were observed in females at any dose level or in low dose males, but a statistically significant increased incidence of liver cell adenomas was seen in male mice given 500 or 1000 mg/kgbw daily for 2 years. These dose levels also caused significantly decreased body weights and body weight gains, indicating that the MTD had been exceeded (664). OPP was also administered to groups of 50 rats/sex/dose level at nominal dietary concentrations of 0, 800, 4000, and 8000 ppm in males and at 0, 800, 4000, and 10,000 ppm in females for 2 years. The equivalent dose levels in both male and female rats were reported to be 39/49, 200/248, and 402/647 mg/kg bw per day. No neoplastic changes were observed in females, including the high-dose group given 60% more than the high-dose males. Histopathological findings in mid-dose and high-dose males were characterized as structural alterations in the kidney and urinary bladder, including urothelial hyperplasia and/or neoplasia (papilloma and transitional cell carcinoma). A statistically significant increase in incidence of these neoplasms was seen only in male rats given 402 mg OPP/kgbw daily for 2 years (666). The U.S. National Toxicology Program conducted a skin-painting study with OPP in groups of 50 mice per sex. The OPP was applied as an acetone solution on 3 days per week for 2 years, both alone and as a promoter with 7, 12-dimethylbenz(a)anthracene (DMBA). No skin neoplasms were observed in either sex treated with OPP alone, and there were no tumor enhancing or inhibiting effects when OPP and DMBA were given in combination (673). 16.4.1.6 Genetic and Related Cellular Effects Studies OPP, SOPP, and the oxidative metabolites phenylhyroquinone (PHQ) and phenylbenzoquinone (PBQ) have been tested for genotoxic properties in a variety of test systems. Most in vitro and in vivo assays were negative, but the metabolites had a tendency to bind with DNA. OPP is probably not genotoxic, but SOPP and PBQ are possibly genotoxic at high doses (658, 659). 16.4.1.7 Other: Neurological, Pulmonary, Skin Sensitization No evidence of delayed contact hypersensitivity was found in standard Buehler tests with OPP and SOPP in guinea pigs (658, 659). In an early study in humans, the potential for skin sensitization was tested in 200 unselected subjects, 100 males and 100 females, by placing patches impregnated with OPP or SOPP in direct contact with the skin on the back, covering with an impervious film and taping into place. The first application was kept in constant contact with the skin for 5 days before removal, and any reaction was recorded. A second application was made in the same way 3 weeks later and kept in direct contact for 48 h before removal. Each subject was examined immediately and again 3 days and 8 days later. OPP did not cause primary irritation when tested as a 5% solution in sesame oil, and did not cause sensitization. Applications of aqueous solutions of SOPP caused no irritation at 0.1% and very slight simple irritation at 0.5%, but were significantly irritating at 1 and 5%. However, no skin sensitization was produced by SOPP at these concentrations (674). 16.4.2 Human Experience 16.4.2.1 General Information Products containing OPP or SOPP have been used extensively as antimicrobials and sanitizers, and for fungicidal treatment of fruits and vegetables since the 1940s without adverse effects. 16.4.2.2 Clinical Cases 16.4.2.2.1 Acute Toxicity: NA 16.4.2.2.2 Chronic and Subchronic Toxicity: NA

16.4.2.2.3 Pharmacokinetics, Metabolism, and Mechanisms OPP was rapidly eliminated following dermal exposure to a single dose of ~0.4 mg on the forearm of six human male volunteers. The radiolabeled test substance was applied to a 4 × 6-cm area of shaved volar surface as a 100-mL aliquot of a 0.4% w/v solution in isopropyl alcohol. A protective dome was placed over the treatment site and was left in place for 8h. The treated sites were then wiped with cotton swabs dipped in isopropanol, rinsed with alcohol, and stripped with tape at ~1, 23, and 46 h after removal of the protective dome to determine the amount of residual activity associated with surface layer of skin. The radioactivity in blood, urine, and feces was measured at intervals for 5 days. Under the conditions of this study, ~43% of the applied OPP was absorbed through the skin, and 99% of the absorbed dose was recovered in the urine collected within the first 48 h after exposure. The urinary metabolites consisted of 69% OPP sulfate, 4% OPP glucuronide, 15% as conjugated phenylhydroquinone (PHQ), and 13% as the sulfate of 2,4'-dihyroxybiphenyl. Little or no free OPP, and no free PHQ or PBQ metabolites were found in urine following this dermal exposure to a representative low level in humans (667). Using data from this dermal exposure study, a pharmacokinetic model was developed to simulate the potential for bioaccumulation of OPP from repeated dermal exposures. A worst-case occupational scenario was selected, with continuous occluded dermal exposure to 6 mg OPP/kg body weight for 8 h per day on 5 consecutive days per week. The calculated half-lives for absorption and excretion were 10 and 0.8h, respectively, indicating that OPP is unlikely to bioaccumulate in exposed workers (675). 16.5 Standards, Regulations, or Guidelines of Exposure National and international tolerances or maximum residue limits (MRLs) were established in many countries during the past 45 years for residues remaining on the surface of fresh fruits and vegetables treated post-harvest with either OPP or SOPP to retard spoilage during storage and transportation to market. These MRLs have ranged from 3 ppm in/on cherries and nectarines to 25 ppm in/on apples and pears (676), but many have been rescined in the absence of new data reflecting current good agricultural practice. At their joint meeting in Rome in September 1999, the United Nations food and Agriculture Organisation (FAO) and the World Health Organization (WHO) recommended withdrawl of remaining MRLs except for 10 ppm in/on citrus fruits, and added 0.05 ppm for orange juice and 60 ppm for dried citrus pulp. FAO/WHO also increased the Acceptable Daily Intake (ADI) to 0.4 mg/kg bw for humans and agreed that an acute RfD was not necessary (659). 16.6 Studies on Environmental Impact Metabolism on OPP in soil and and by aquatic microorganisms is fairly rapid and is complete under conditions resembling those of activated sludge systems, under both aerobic and anaerobic conditions. Complete degradation OPP of was obtained within 2 days under simulated biological wastewater treatment conditions for loadings at 30 and 100 mg/L. However, the antimicrobial properties of OPP slowed its degradation at levels higher than 100 mg/L in wastewater. Studies with 14C-OPP showed that it is readily degraded to CO at the low concentrations likely to occur in the 2 natural environment, such as in river water, and that the rate of degradation is enhanced in activated sludge, especially after acclimation (678).

Phenol and Phenolics Ralph Gingell, Ph.D., DABT, John O'Donoghue, Ph.D., DABT, Robert J. Staab, Ph.D., DABT, Ira W. Daly, Ph.D., DABT, Bruce K. Bernard, Ph.D., Anish Ranpuria, MS, E. John Wilkinson, Daniel Woltering, Ph.D., Phillip A. Johns, Ph.D., Stephen B. Montgomery, Ph.D., Larry E. Hammond, Ph.D., Marguerita L. Leng, Ph.D. 17.0 Di-tert-Butylmethylphenol 17.0.1 CAS Number: [29759-28-2]

17.0.2 Synonyms: DBMP, 4-methyl-2,6-di-tert-butylphenol, 2,6-di-tert-butyl-p-cresol, di-tert-butylhydroxytoluene 17.0.3 Trade Names: Deenax, Paranox, DBPC Antioxidant, Ionil 17.0.4 Molecular Weight: 17.0.5 Molecular Formula: 17.0.6 Molecular Structure: 17.1 Chemical and Physical Properties 17.1.1 General Physical state Slightly yellow, crystalline solid Melting Point 70°C Boiling point 265°C 17.2 Production and Use Di-tert-butylmethylphenol (DBMP) is an antioxidant that prevents the deterioration of fats, oils, waxes, resins, and plastic films. It is incorporated into many edible vegetable or animal fats and oils, into baked and fried foods, and into waxes or plastic films used for coating food wrappers or containers. It acts as an anti-skidding agent when added to paints and inks, and its antioxidant qualities allow it to be used in cosmetics and pharmaceuticals (11). 17.3 Exposure Assessment: NA 17.4 Toxic Effects 17.4.1 Experimental Studies 17.4.1.1 Acute Toxicity When absorbed in toxic concentrations into the tissues of unanesthetized animals, DBMP induced signs of intoxication resembling those seen after absorption of a toxic dose of a parasympathetic drug (salivation, a mild degree of miosis, unsteadiness, restlessness, hyperexcitability, diarrhea, and tremors) (13). When given intravenously to a dog under pentobarbital anesthesia, DBMP (25 mg/kg) induced a prompt reduction of blood pressure. Atropine sulfate partially antagonized this depressor effect. Large doses of DBMP produced a gross disturbance of sodium, potassium, and water balance in the rabbit (13). It was concluded that the increase in sodium and aldosterone excretion was due to pyelonephritis, and that death was due to potassium depletion. 17.4.1.2 Chronic and Subchronic Toxicity From the results of chronic toxicity studies using dogs and rats (13), it was concluded that DBMP is a relatively innocuous compound for occupational handling. 17.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Metabolism studies in rats, dogs, and humans showed some differences in excretion patterns (13). In the rat there was slower excretion than in humans, and evidence of enterohepatic circulation was not apparent in humans. In humans more metabolites are excreted in the urine and overall excretion is more rapid than in rats (13). 17.4.1.4 Reproductive and Developmental: NA 17.4.1.5 Carcinogenesis The oral feeding of DBMP increased the detoxification and inhibited cancer induction by known carcinogens (2).

Phenol and Phenolics Ralph Gingell, Ph.D., DABT, John O'Donoghue, Ph.D., DABT, Robert J. Staab, Ph.D., DABT, Ira W. Daly, Ph.D., DABT, Bruce K. Bernard, Ph.D., Anish Ranpuria, MS, E. John Wilkinson, Daniel Woltering, Ph.D., Phillip A. Johns, Ph.D., Stephen B. Montgomery, Ph.D., Larry E. Hammond, Ph.D., Marguerita L. Leng, Ph.D.

18.0 Dodecylthiophenol 18.0.1 CAS Number: [36612-94-9] 18.0.2 Synonyms: NA 18.0.3 Trade Names: NA 18.0.4 Molecular Weight: NA 18.0.5 Molecular Formula: NA 18.0.6 Molecular Structure: NA 18.1 Chemical and Physical Properties: NA 18.2 Production and Use: NA 18.3 Exposure Assessment: NA 18.4 Toxic Effects 18.4.1 Experimental Studies 18.4.1.1 Acute Toxicity The acute toxicity of this material is of a low order. An intramuscular dose of 20 g/kg is not fatal in the rat; lethal oral doses range from 20 to 30 g/kg. When applied to the skin of the rat, rabbit, and guinea pig, the material induces loss of hair in 6–12 days. When applied to the human skin, the material may induce local eczema but apparently does not cause loss of hair (13).

Phenol and Phenolics Bibliography

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641 J. L. Mattsson, K. A. Johnson, and R. R. Albee, Lack of neuropathologic consequences of repeated dermal exposure to 2,4-dichlorophenoxyacetic acid in rats. Fundam. Appl. Toxicol. 6, 175–181 (1986). 642 U.S. Environmental Protection Agency (USEPA), Assessment of Potential 2,4-D Carcinogenicity, An SAB Report, Rep. No. EPA-SAB-EHC-94-005, Science Advisory Board/Science Advisory Panel, 1994. 643 International Agency for Research on Cancer (IARC), Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans, Suppl. 7, IARC, Lyon, France, 1987, pp. 150– 160. 644 M. M. Anders et al., Expert Panel on Carcinogenicity of 2,4-D, Canadian Centre for Toxicology, Guelph, Ontario, 1987. 645 Harvard School of Public Health, The Weight of the Evidence on the Human Carcinogenicity of 2,4-D, Report on Workshop, Program on Risk Analysis and Environmental Health, Boston, MA, 1990. 646 M. A. Ibrahim et al., Weight of the evidence on the human carcinogenicity of 2,4-D. Environ. Health Perspect. 96, 213–222 (1991). 647 E. Delzell and S. Grufferman, Mortality among white and nonwhite farmers in North Carolina, 1976–1978. Am. J. Epidemiol. 121(3), 391–402 (1985). 648 V. K. Sharma and S. Kaur, Contact sensitization by pesticides in farmers. Contact Dermatitis 23(1), 77–80 (1990). 649 A. Fausitini et al., Immunological changes among farmers exposed to phenoxy herbicides. Preliminary observations. Occup. Environ. Med. 53, 583–585 (1996). 650 R. D. Wilson, J. Geronimo, and J. A. Armbruster, 2,4-D dissipation in field soils after applications of 2,4-D dimethylamine salt and 2,4-D 2-ethylhexyl ester. Environ. Toxicol. Chem. 6(6), 1239–1246 (1997). 651 World Health Organization (WHO), Pesticide Residues in Food—1997, Evaluations 1997, Part. II, WHO/PCS/98.6, WHO, Geneva, 1997, pp. 254–346. 652 Food and Agriculture Organization (FAO), Pesticide residues in food—1997, Report sponsored jointly by FAO and WHO. Report 1996. FAO Plant Prod. Prot. Pap. 145, 81–86 (1997). 653 Reference Handbook of Chemistry and Physics, 60th ed., CRC Press, Boca Raton, FL, 1979, p. C-432. 654 D. L. Geiger, D. J. Call, and L. T. Brooke, eds., Acute Toxicities of Organic Chemicals to Fathead Minnows (Pimephales Promelas), Vol. IV, University of Wisconsin-Superior, Superior, 1988. 655 Unpublished information provided by Great Lakes Chemical Corporation, West Lafayette, IN. 656 A. Lyubimov, V. Babin, and A. Kartashov, Developmental neurotoxicity and immunotoxicity of 2,4,6-tribromophenol in Wistar rats. Neurotoxicology, 19(2), 303–312 (1998). 657 E. Zeiger et al., Salmonella mutagenicity tests: Results from testing of 255 chemicals. Environ. Mutagen. 9(9), 1–109 (1987). 658 M. L. Leng, Review on Toxicology of OPP and SOPP, submitted to the World Health Organization, Geneva (1998). 659 FAO/WHO, Pesticide Residues in Food – 1999, Report of Joint Meeting held 20–29 September 1999 in Rome. FAO Plant Production and Protection Paper 153, Rome, Part 4.24: 2-phenylphenol, pp. 169–179, and Annex I, 1999, p. 226. 660 H.-P. Harke and H. Klein, Resorption of 2-phenylphenol from disinfectants used for hand washing. Zentralbl. Bakteriolo., Mikrobiolo. Hyg., Ser. B 174(3), 274–278 (1981). 661 S. Iguchi et al., Subchronic toxicity of o-phenylphenol (OPP) by food administration to rats.

Annu. Rep. Tokyo Metrop. Rese. Lab. Public Health 35, 407–415 (1984). 662 K. Hiraga and T. Fujii, Induction of tumors of the urinary bladder in F344 rats by dietary administration of o-phenylphenol. Food Chem. Toxicol. 22(11), 303–310 (1984). 663 R. H. Reitz et al., Molecular mechanisms involved in the toxicity of orthophenylphenol and its sodium salt. Chem.-Biol. Interact. 43, 99–119 (1983). 664 J. F. Quast, R. J. McGuirk, and R. J. Kociba, Results of a two-year dietary toxicity/oncogenicity study of ortho-phenylphenol in B6C3F1 mice. Toxicologist 36(1, Pt. 2) (Abstr. 1734) (1997). 665 S. Fukushima et al., Cocarcinogenic effects of NaHCO3 on o-phenylphenol-induced rat bladder carcinogenesis. Carcinogenesis (London) 10, 1635–1640 (1989). 666 B. S. Wahle et al., Technical grade ortho-phenylphenol: A combined chronic toxicity oncogenicity testing study in the rat. Toxicologist 36(1, Pt. 2) (Abstr. 1733) (1997). 667 M. J. Bartels et al., Comparative metabolism of ortho-phenylphenol in mouse, rat and human. Xenobiotica 28(6), 579–594 (1998). 668 D. A. Eigenberg et al., Evaluation of the reproductive toxicity of ortho-phenylphenol (OPP) in a two-generation rat reproductive toxicity study. Toxicologist 36(1, Pt. 2) (Abstr. 1808). 669 J. A. John et al., Teratological evaluation of orthophenylphenol in rats. Fundam. Appl. Toxicol. 1, 282–285 (1981). 670 C. L. Zablotny, W. J. Breslin, and R. J. Kociba, Developmental toxicity of orthophenylphenol (OPP) in New Zealand white rabbits. Toxicologist 12, 103 (Abstr. 327) (1992). 671 International Agency for Research on Cancer (IARC), Ortho-phenylphenol and its sodium salt. IARC Monogr. Eval. Carcinoge. Risk Chem. Hum., Misc. Pestic. 30, 329–344 (1983). 672 International Agency for Research on Cancer (IARC), Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans, Suppl. 7, IARC, Lyon, France, 1987, pp. 37– 40, 46, 53, 70–71. 673 National Toxicology Program (NTP), Toxicology and Carcinogenesis Studies of orthophenylphenol Alone and with 7, 12-Dimethylbenz(a)anthracene in Swiss CD-1 Mice (Dermal Studies), Tech. Rep. No. 301, NTP, Washington, DC, 1986. 674 H. C. Hodge et al., Toxicological studies of orthophenylphenol (DOWICIDE 1). J. Pharmacol. Exp. Ther. 104(2), 202–210 (1952). 675 C. Timchalk et al., The pharmacokinetics and metabolism of 14C/13C-labeled orthophenylphenol formulation following dermal application to human volunteers. Hum. Exp. Toxicol. 17, 411–417 (1998). 676 U.S. Code of Federal Regulations, Title 40, Part 180.129 o-phenylphenol and its sodium salt; tolerances for residues (1998). 677 Joint FAO/WHO Food Standards Programme, Codex Maximum Limits for Pesticide Residues, ortho-Phenylphenol and Its Sodium Salt, 2nd ed., Vol. XIII, 056-iv, Codex Alimentarius Commission (CAC), 1986. 678 S. J. Gonsior et al., Biodegradation of o-phenylphenol in river water and activated sludge. J. Agric. Food Chem. 32, 593–596 (1984).

Aliphatic Nitro, Nitrate, And Nitrite Compounds Candace Lippoli Doepker, Ph.D. A. Aliphatic Nitro Compounds

Nitroalkanes, or nitroparaffins, are derivatives of alkanes with the general formula CnH2n+1, in which one or more hydrogen atoms are replaced by the electronegative nitro group (–NO2). Nitroalkanes are classed as primary, RCH2NO2, secondary, R2CHNO2, and tertiary, R3CNO2, using the same convention as for alcohols. Some examples of commercial nitroalkanes, are nitromethane, nitroethane, 1-nitropropane, and tetranitromethane (1). The nitroalkanes are produced in large commercial quantities by direct vapor-phase nitration of propane with nitric acid or nitrogen peroxide. The reaction product is a mixture of nitromethane, nitroethane, and 1- and 2-nitropropane. The individual compounds are obtained by fractional distillation. The chemical and physical properties of a number of nitroalkanes are described in Table 54.1 and in the individual summaries following. Nitroparaffins are colorless, oily liquids with relatively high vapor pressures. Their solubility in water decreases with increasing hydrocarbon chain length and number of nitro groups. As expected, their boiling and flash points are higher than their corresponding hydrocarbons. Table 54.1. Properties of the Mononitroalkanes and Tetranitromethane Conver unit

Name Nitromethane

Mol. B.p. wt. (°C)

Solubility in H2O Vapor at 20°C pressure Vapor (Closed/open) (% by (mmHg) density flash point (° 1 mg/L 1 Specific (ppm) (m gravity vol.) (°C) (Air = 1) F)

61.04 101.2 1.139 9.5 27.8 (20/20°C) (20) Tetranitromethane 196.04 125.7 1.6629 Insoluble 8.4(20) (25°C) Nitroethane 75.07 114.8 1.052 4.5 15.6 (20/20°C) (20) 1-Nitropropane 89.09 131.6 1.003 1.4 7.5 (20) (20/20°C) 2-Nitropropane 89.09 120.3 0.992 1.7 12.9 (20/20°C) (20) 1-Nitrobutane 103.12 153 0.9728 0.5 5(25) (15.6/15.6° C) 2-Nitrobutane 103.12 139 0.9728 0.9 8(25) (15.6/15.6° C)

2.11

95/110

400.7

0.8

—

124.7

2.58

82/106

325.7

3.06

96/120

274.7

3.06

—/102

274.7

3.6

—

237.1

3.6

—

237.1

The uses of nitroalkanes depend on their strong solvent power for a wide variety of substances including many coating materials, waxes, gums, resins, dyes, and numerous organic chemicals. Most organic compounds, including aromatic hydrocarbons, alcohols, esters, ketones, ethers, and

carboxylic acids, are miscible with nitroalkanes. Thus, they are used in products such as inks, paints, varnishes, and adhesives. Another important use is in the production of derivatives such as nitroalcohols, alkanolamines, and polynitro compounds. In some cases, they provide better methods of manufacturing well-known chemicals such as chloropicrin and hydroxylamine. They are also used as special fuel additives, rocket propellants, and explosives. Nitroalkane vapor pressures are sufficient to produce high vapor levels in the workplace unless controlled. Thus, the chief industrial hazard is respiratory irritation when these compounds are inhaled. The odors of nitroalkanes are easily detectable, and concentrations below 200 ppm are disagreeable to most observers (2). However, the odor and sensory symptoms are not considered dependable warning properties. The fire and explosion hazards of nitroalkanes are considered low for they have relatively high flash points. Despite these high flash points, shock explosion can result under certain conditions of temperature, chemical reaction, and confinement. Nitroalkanes are acidic substances. Polynitro compounds are even stronger acids than the corresponding mononitroalkanes. They are rapidly neutralized with strong bases and readily titrated. Tautomerism, a general property of primary and secondary mononitroalkanes, gives rise to a more acidic “aci” form, or nitronic acid. In organic solvents, primary and secondary mononitroalkanes exist as neutral nitroalkanes. However, in aqueous solutions, they exist in a state of equilibrium between the protonated neutral nitroalkane, the nonprotonated nitronic acid and its anion, or nitronate. Tautomerism is important for understanding the biological effects of nitroalkanes and also forms the basis of a number of important chemical reactions through the formation of nitroalkane salts. Mercury fulminate, Hg(ON C)2, is one of the better-known compounds that is derived from the mercury salt of nitromethane [(CH2 NO2)2Hg]. Except for chloropicrin, the production of chloronitroparaffins, uses tautomerism. The important intermediate methazonic acid, which is a starting product for a number of

well-known compounds (e.g., nitroacetic acid and glycine) also uses tautomerism. Additionally, many nitro derivatives are a source of guanidine [H2NC( NH)NH2] by reaction with ammonia. A number of other useful products such as primary amines, nitrohydroxy compounds, aromatic amines, and b-dioximes, which in turn can yield isoxazoles by hydrolysis, are also among the armamentarium of the nitroalkane reaction possibilities. Early methods (1940–1959) of determining nitroalkanes used colorimetric procedures (see chemical summaries below for more details). Since 1970 these have been replaced by instrumental methods. References to the colorimetric procedures are included here because these procedures were used for monitoring animal exposures, which provide the toxicity data in Table 54.2. Instrumental methods of mass spectroscopy and gas chromatography are now used routinely, and infrared has been used in animal exposure studies (3). Table 54.2. Results of Inhalation Experiments (13)a Nitromethane

Nitroethane No.

No.

No. guinea No. guinea rabbits pigs Concn Ti rabbits pigs Concn Time Concn Time (hr) Concn × time killed killed (%) (hr) Concn × time killed killed (%) (h (%) 1.0 3.0 5.0

3.0 1.0 0.5 0.25 0.10 2.25 3.0 0.5

1.0 3.0

6 2 1

1 3 6 12 30 1 0.5 3

6 6 5

2 2 2

2 2 2

3 3 3 3 3 2.25 1.5 1.5

0 0 1 2 0 0 0 0

2 2 1 1 2 1 1 1

1 1 0.25 0.75

0 0

0 0

0.05

140

7.0

0

0c

0.1

48

4.8

1c

1c

a b c

2.5 3.0 3.0 1.0

2 1.25 1 3

5 3.75 3 3

2 2 1 2

0 2 1 1

3.0 0.5 0.1 0.5 1.0 0.25 0.1 0.05

0.5 3 12 2 1 3 6 30

1.5 1.5 1.2 1 1 0.75 0.6 1.5

1 2 1 1 1 0 0 0

0 0 0 0 0 0 0 b

0.05

140 7.0

0

0c

1.0

3

0.5

3

1.0

1

Two rabbits and two guinea pigs in each experiment. No animals exposed. One monkey exposed.

The primary mononitroalkanes on which toxicity data were determined, were analyzed colorimetrically by measuring the color developed from an HCl-acidified alkaline solution containing FeCl3 (4). Analytical data on the secondary nitroalkanes were determined by measuring ultraviolet radiation at a wavelength of 2775 Å through an alcoholic solution in a Beckman spectrophotometer (5). A more sensitive spectrophotometric determination of primary nitroalkanes uses the coupling reaction with p-diazobenzenesulfonic acid (3). Simple, secondary nitroalkanes do not interfere as do some complex secondary nitro alcohols. Mass spectrography, gas chromatography, and infrared spectroscopy are the current methods of choice for determining nitroalkanes in air (6). Mass spectra have been determined for eight C1 to C4 mononitroalkanes (6, p. 418). The different conditions recommended for analyzing nitroalkane mixtures including chloronitroparaffins by gas chromatography, along with their chromatograms, are given in Ref. 6 on pp. 425–429 and 430–433, and for nitroalcohols, on pp. 441–443. Because nitroparaffins can cause respiratory irritation, inhalation toxicity data have always been of interest. The inhalation toxicity data on the nitroalkanes gathered in the late 1930s and summarized

below lacked some of the refinements of late work with these compounds. Exposure “chambers” consisting of steel drums of 233-liter capacity lacked the space to expose what is now considered an adequately sized complement of animal species (7). The exposure concentrations at levels of 5000 to 50,000 ppm must be considered “nominal” because of measurement by interferometer, the chamber airflow characteristics, and fan circulation of air. Incomplete information on polynitroalkanes indicates that an increased number of nitro groups results in increased irritant properties. Thus, the chlorinated nitroparaffins are more irritating than the unchlorinated compounds (8). This reaches a severe degree with trichloronitromethane (chloropicrin). Unsaturation of the hydrocarbon chain in the nitroolefins also increases the irritant effects (9, 10). The primary nitroalkanes fail to show significant pharmacological effects on blood pressure or respiration (11). Oral doses result in symptoms similar to those produced by inhalation except for the additional evidence of gastrointestinal tract irritation. They are less potent methemoglobin formers than aromatic nitro compounds. In general, applications of nitroalkanes to the skin give no evidence of sufficient absorption to result in systemic injury. After application of the nitroalkanes in five daily treatments to the clipped abdominal skin of rabbits, no systemic effects or evidence of weight loss was reported (2). Nitroalkanes are readily absorbed through the lungs and through the gastrointestinal tract (12). Animals that die following brief inhalation of the nitroalkanes show general visceral and cerebral congestion. After exposure at high concentrations, there is pulmonary irritation and edema, but the latter is inadequate to be the sole cause of death. Oxidative denitrification of nitroalkanes occurs by two mechanisms. The microsomal cytochrome P450 monooxygenase system of rat and mouse liver metabolizes nitroparaffins in vitro (13, 14). Specific activities are greatest for 2-nitropropane, followed by 1-nitropropane, nitromethane, and tetranitromethane. One study found up to 25% of residual denitrifying activity with mouse liver microsomes under anaerobic conditions (15), suggesting that an oxygen-independent mechanism may exist. Dayal et al. found that 2-nitro-2-methylpropane was not denitrified by the monooxygenase system (16). This indicates that a hydrogen atom is required in the position alpha to the nitro group for oxidative cleavage of the neutral tautomeric form. They also showed that the nitronate anion of 2-nitropropane was denitrified 5 to 10 times faster than the neutral form. Because the tautomeric equilibrium of primary nitroalkanes, such as 1-nitropropane, lies far to the neutral side of physiological pH, the authors suggest that this may explain the slower reaction rate with these compounds relative to 2-nitropropane. A second mechanism of oxidative denitrification has been demonstrated for various flavoenzyme oxidases (17–20). The relative reactivity rates of the nitroalkanes are similar to those of the microsomal systems, except that tetranitromethane was inert (18). The interesting aspect of this pathway is that a superoxide radical is produced either as an intermediate (18) or as an initiator/propagator of the reaction (20). Superoxide radical and other active oxygen species produced from it (oxygen free radicals, hydrogen peroxide, hydroxyl radical) have been associated with toxicity and mutagenicity. Official Occupational Safety and Health Administration (OSHA) standards and ACGIH threshold limit values (TLVs) have been adopted for the seven nitroalkanes listed in Table 54.3. No TLVs have been established for any nitroolefin or nitroalcohol. For the basis of TLVs, see Documentation of TLVs published by the ACGIH. Table 54.3. Occupational Exposure Limits for Nitroalkanes

TLVa

OSHA Standard

Compound

ppm

mg/m3

ppm mg/m3

Nitromethane Nitroethane 1-Nitropropane

100 100 25

250 310 90

20 100

2-Nitropropane

25

90

Tetranitromethane 1 Chloropicrin 0.1 1-Chloro-1-nitropropane 20 a b c

8 0.7 100

25b

50 307 91

10c 36, A2 1 8 0.1 0.67 2 10

From 1999 list. Not classified as human carcinogen. Confirmed animal carcinogen with unknown relevance to humans.

Table 54.4. Acute Toxicity of Nitromethane (13, 27) Route Oral

Animal Dog

Dose

Mortality

0.125 g/kg 0/2 0.25–1.5 g/kg 12/12 Rabbit 0.75–1.0 g/kg Lethal dose Mouse 1.2 g/kg 1/5 1.5 g/kg 6/10 Subcutaneous Dog 0.5–1.0 ml/kg Minimum lethal dose Intravenous Rabbit 0.8 g/kg 2/6 1.0 g/kg 2/6 1.25–2.0 g/kg 9/9 Inhalation Rabbit 30,000 ppm 7,500 Oral 11,300 Oral 280 Oral 1050 Oral 430 Oral 370 Oral 200 Oral

Organ Liver, lung Liver, kidney Liver, nasal Liver Liver, esoph. Liver, esoph. Liver, nasal Liver Liver, esoph. Liver, bladder Liver, bladder Liver, esoph. Nasal, trachea Lung, nasal Liver, nasal Nasal Liver, esoph. Nasal, trachea Esoph, nasal Pancreas, liver Esoph, nasal

pyrrolidine diphenylamine sarcosine proline dibenzylamine nornicotine methylurea

Rat Rat Rat Rat Rat Rat Rat

Oral Oral Oral Oral Oral s.c. Oral

Hamster s.c. ethylurea Rat Oral methylnitro-guanidine Rat Oral a

900 3,000 5,000 5,000 900 1,000 180 70 300 100

Oral Oral Oral Oral Oral Oral Oral i.v. Oral Oral Oral

Liver Bladder Esophagus Inactive Inactive Esoph, nasal Brain, stomach, uterus, breast Spleen, stomach Breast, stom. etc Gland. stomach

mg/kg body weight as a single dose by gavage or injection.

Although it is understandable that some nitrosamines might be toxic but not carcinogenic (e.g., nitrosiminodiacetonitrile, methylnitroso-tert-butylamine, methylnitrosomethoxyamine, nitrosodiallylamine in rats) because their toxicity is through some unconventional mechanism, it is more difficult to understand why some reasonably potent carcinogens (e.g., nitrososarcosine, nitrosodiethanolamine, ethylnitrosoethanolamine) are not toxic (or not measurably so). The cyclic nitrosamines pose a particular dilemma because little is known about their activation, the products of their metabolism, or the reasons for the differences in their carcinogenicity. The simplest cyclic compound, nitrosoazetidine, is almost not toxic; toxicity increases up to nitrosopiperidine and nitrosohexamethyleneimine and declines as the ring grows larger. All are toxic to rat liver, although not all induce liver tumors in rats (5, 6). There are differences between species in response to the toxicity of a given N-nitroso compound, as there are to carcinogenicity; mice are often less responsive than rats, as mice are to carcinogenesis by many N-nitroso compounds. However, most N-nitroso compounds are both toxic and carcinogenic (6). As already mentioned, there is no parallel between toxicity and carcinogenicity among different species or within structurally related groups of N-nitroso compounds.

N-Nitroso Compounds William Lijinsky B. Mutagenesis and Cell Transformation One N-nitroso compound, N-methyl-N-nitroso-N'-nitroguanidine (MNNG), was one of the first known chemical mutagens (36) and since then a large number of N-nitroso compounds have been examined for mutagenic and cell-transforming properties, apparently propelled by the wish to develop quick ways of identifying carcinogens instead of the lengthy and expensive chronic toxicity test in animals (rodents). In looking for parallels between carcinogenic and mutagenic activities, there are striking differences, even among groups of N-nitroso compounds of similar structure. It is almost always necessary to test a nitrosamine for mutagenicity by incorporating a metabolic activation system, usually the S-9 fraction of liver homogenate, called the “microsomal fraction,” which was introduced by Ames into his microbial (Salmonella) mutagenic assay (37). It is assumed that this mimics the activation of nitrosamines in vivo. Most alkylnitrosamides are directly acting mutagens (i.e., they do not need metabolic activation), although not proportional in activity to their carcinogenic activity. On the other hand, almost all nitrosamines require metabolic activation to uncover their mutagenic activity. A large proportion of the nitrosamines that have been tested for carcinogenic activity have also undergone mutagenic

testing, exhaustive in the case of some compounds, (e.g., NDMA, NDEA). NDMA with rat liver microsomal activation is not measurably mutagenic to Salmonella strain TA1535 in the simple “plate test,” although it is powerfully carcinogenic to rat liver. Both NDMA and NDEA are more readily activated to bacterial mutagens by hamster liver microsomes than by rat liver microsomes, although by no means are these two nitrosamines more potent carcinogens in hamsters than in rats (38). The greater activity of hamster liver microsomes in this regard is true for a large proportion of nitrosamines tested, although most are more potent carcinogens in rats than in hamsters (6, 39), and includes the large series of methylnitrosoalkylamines, which, it is assumed, act (as mutagens and carcinogens) by metabolic formation of the same methylating intermediate. These comparisons throw into doubt the current concept of the close relationship—perhaps identity—of the mechanisms of carcinogenesis and mutagenesis. These discrepancies also apply to the large number of cyclic nitrosamines that have been studied, in which the superiority of hamster liver microsomes over rat liver microsomes in activating them to mutagens is even greater to the extent that several compounds are activated to mutagens only by hamster liver enzymes, not by rat liver enzymes. This is also true of many acyclic nitrosamines, and especially so of those nitrosamines that have oxygen functions (hydroxyl- or carbonyl-) in their side chains. A number of carcinogenic nitrosamines are not activated by either rat or hamster liver microsomes to mutagens (39); these include such liver carcinogens as nitrosodiethanolamine, methylnitrosoethylamine, nitroso-3-hydroxypyrrolidine, and methylnitrosoethanolamine, as well as methylnitrosoaniline, methylnitroso-3-carboxypropylamine, and nitrosodiphenylamine, which induce tumors in other organs, but not in the liver (40). Most of the noncarcinogenic nitrosamines (which include most nitrosamino acids) are not mutagenic, but some that are mutagenic are not carcinogens (nitrosoguvacoline, nitrosophenmetrazine, nitrosodi-n-octylamine). The usefulness of the mutagenic assays in predicting the probable carcinogenicity of N-nitroso compounds is obvious, although there is no quantitative parallel, but the many unexpected exceptions (e.g., MNEA) indicate that mutagenesis is not a guide to understanding the carcinogenic mechanisms of these compounds. This conclusion is fortified by the mutagenic studies of alkylnitrosamides, which show a huge disparity between carcinogenic potency and mutagenic effectiveness. For example, a series of methylnitrosocarbamate esters (most of which are N-nitroso derivatives of pesticides, e.g., nitrosocarbaryl) vary 10- to 200-fold in mutagenicity (41, 42), but have very similar carcinogenic potencies (43); the ratio of their mutagenicities is similarly large versus methylnitrosourea, which is a much more potent carcinogen. Yet, all of these compounds, it is believed, act as mutagens or carcinogens by directly forming the same alkylating intermediate, the methyldiazonium ion. Part of the discrepancies might be explained by differences in uptake by the bacteria, as shown in Hemophilus influenzae (44). Among the many alkylnitrosoureas tested as bacterial mutagens, which, it is believed, act by forming the corresponding alkyldiazonium ion, there is not a large difference among most of them in mutagenic potency, although this tends to increase with increasing molecular weight (45). Some unusual structures such as hydroxyethylnitrosourea, isopropanolnitrosourea, and 2-phenylethylnitrosourea are especially potent, whereas benzylnitrosourea and n-tridecylnitrosourea are almost inactive, but overall there is no parallel between mutagenicity and carcinogenicity among these directly acting N-nitroso compounds. The same is true of the limited number of alkylnitrosoguanidines tested, of which MNNG is almost the standard mutagen but is not a particularly potent carcinogen; the nitroso derivative of a widely used drug, nitrosocimetidine, is quite mutagenic but is not a carcinogen (46). N-nitroso compounds act as mutagens or transforming agents in mammalian cells in culture or in bacteriophage induction. It is claimed that their activity depends largely on the formation, directly or following enzymic activation, of an alkyldiazonium ion that alkylates DNA. All have the same or similar drawbacks and discrepancies which have been discussed earlier in connection with bacterial mutagenic assays. The cell transformation assays (47) seem to have some characteristics that do not depend on alkylation of DNA because compounds such as nitrosodiphenylamine, which do not form

an alkylating product, produce positive results in these assays. However, the results do not uniformly parallel the carcinogenic activity of these compounds, indicating again that the mechanisms of the various biological activities differ (47).

N-Nitroso Compounds William Lijinsky C. Metabolism and Activation Although there are differences and discrepancies among the mutagenicity, carcinogenicity, and other biological activities of the directly acting alkylnitrosamides, it is credible that one of the underlying actions is the direct formation of a reactive intermediate, such as an alkyldiazonium ion, common to many of them (e.g., the methylating compounds). On the other hand, in the case of the nitrosamines, it is not readily apparent that formation of a simple alkylating intermediate (such as an alkyldiazonium ion) is the underlying process. Rather, there is evidence that extensive and varied metabolism is frequently required to bring about carcinogenesis, or even mutagenesis. As shown by the lower activity as mutagens or carcinogens of nitrosamines labeled with deuterium in the positions alpha to the nitroso group, alpha-oxidation is a rate-limiting step in the biological activation of most nitrosamines (48–50). This finding is fortified by the observation that substituting methyl or other alkyl groups in the alpha positions of nitrosamines, cyclic or acyclic, reduces or abolishes carcinogenic or mutagenic activity. In the case of acyclic nitrosamines, alpha-oxidation forms an unstable alpha-hydroxy derivative (51), which is reactive and decomposes to release an alkyldiazonium ion, that can alkylate macromolecules (and presumably the alpha-hydroxy derivative can also). In the case of cyclic nitrosamines, such as nitrosomorpholine or nitrosopiperidine, the fate of the alpha-hydroxy derivative is much less clear, particularly the identity of the products related to carcinogenesis or mutagenesis, and those that are simply products of detoxication. There have been many studies of the metabolism and activation of nitrosamines, including those of the series of methylnitroso-n-alkylamines, that show striking differences in the target organ for carcinogenesis as the chain becomes longer. In fact, it is through beta-oxidative chain shortening (Knoop) that the longer chain compounds produce a metabolite (methylnitroso-2-oxopropylamine) that induces bladder tumors in rats (39), whereas the short-chain compounds induce tumors of the liver or esophagus. Oxidation of nitrosamines in animals can be extensive, as shown by the formation and excretion of derivatives of nitroso dialkylamines such as nitrosodi-n-propylamine and nitrosodi-n-butylamine hydroxylated at most positions of the alkyl chain (52) and in the studies of metabolites of methylnitroso-n-amylamine by Mirvish (53). The complex interrelationships between 2,6-dimethylnitrosomorpholine (DMNM—which unlike nitrosomorpholine induces no liver tumors in rats, although it does in hamsters, together with pancreas tumors), nitrosobis-2-oxopropylamine (NBOPA), nitrosobis-2-hydroxypropylamine (nitrosodi-isopropanolamine—NBHPA) and nitrosohydroxypropyl-oxopropylamine (NHPOPA) pose another unsolved problem in explaining their carcinogenic properties (54, 55). The conventional wisdom is that N-nitroso compounds exert their carcinogenic (and probably toxic) effects by forming of an alkylating intermediate (alkyldiazonium compound) that alkylates DNA, causes mutations (and leads to cancer), but this is an oversimplified and unsatisfactory explanation of the experimental data. For example, the compounds in the preceding paragraph all methylate DNA of the liver and other organs in vivo in rats and hamsters to similar extents (somewhat lower with DMNM). They all induce liver tumors in hamsters (but to different extents) but in rats DMNM and NBHPA induce only tumors of the esophagus, NBOPA induces liver tumors, and NHPOPA induces both (39, 56). These results indicate that alkylation of DNA by these nitrosamines might

play a role in inducing of tumors (in the liver, for example), that alone is insufficient and other factors and properties of the nitrosamine are equally or more important, but these are largely unknown. And so it is with a large number of N-nitroso compounds that methylate DNA, for example, in rat liver. Only some of them give rise to liver tumors, but often to tumors in other organs in which they produce less methylation of DNA. Examples are methylnitrosourea, MNNG, NDMA in high doses (at which kidney tumors are induced) (57), although at low doses liver tumors are induced, and not kidney tumors (58); the same is true of azoxymethane (isomeric with NDMA), which induces tumors in the colon, as well as the liver (59). Most N-nitroso compounds are both carcinogenic and mutagenic, but about 10% of those tested (more than 300) are not carcinogenic. Few of the noncarcinogens are mutagens, but several carcinogens are not mutagenic. Particularly interesting are those nitrosamines that are rat liver carcinogens, yet are not activated to mutagens by rat liver enzymes (e.g., nitrosodiethanolamine, nitrosodi-isopropanolamine, and methylnitrosoethylamine), although several of them are activated by hamster liver enzymes. In the context of this volume, this fact is important only because there is increasing reliance on “short-term” assays for predicting the carcinogenicity of newly discovered substances, and it would be easy to overlook a nonmutagenic nitrosamine as unlikely to be a carcinogen, forestalling a chronic toxicity test. Whether a nonmutagen (e.g., NDELA) alkylates DNA to a very small extent, usually remains to be determined (60). Another important consideration is that there are considerable differences in susceptibility to toxicity and carcinogenicity among species, even those as closely related as rats, mice, and hamsters. In general, rats are more susceptible than either hamsters or mice (in that order). In the case of NDELA, massive doses are needed to induce liver tumors in mice, whereas modest doses are adequate in rats; NDELA did not induce liver tumors in hamsters, but did induce tumors of the nasal cavity (61, 62). This suggests that it might be unwise to consider that rats represent the species most sensitive to Nnitroso compounds and that humans are no more sensitive. In fact there is evidence from the great effectiveness of tobacco-specific nitrosamines in cigarette smokers and in smokeless tobacco users (in whom exposure is small, but the cancer incidence high) compared with the comparable responsiveness of rats or hamsters to much higher doses, that humans might be considerably more susceptible to the carcinogenic effects of N-nitroso compounds than the routinely used test animals.

N-Nitroso Compounds William Lijinsky D. Chronic Effects—Carcinogenicity From the extensive literature on the biological testing and evaluation of N-nitroso compounds, numerous results frustrate the proposal of a single mechanism by which these compounds induce tumors because of the complexity of the tumor responses in different species to a particular N-nitroso compound. For example, consider the series of methylnitroso-n-alkylamines from C2 (methylnitrosoethylamine, MNEA) to C12 (methylnitroso-n-dodecylamine) all of which are metabolized to form a methylating agent that methylates DNA in rat liver (63) (although not necessarily to the same extent) and all of which are carcinogenic (64). In contrast, methylnitrosotert-butylamine, which cannot be metabolized to form a methylating agent, is not carcinogenic; on the other hand, methylnitrosoaniline, which also cannot be metabolized to form a methylating agent is carcinogenic to rats and forms esophageal tumors. However, there the simplicity ends because the lowest members of the homologous series, NDMA and MNEA, induce tumors of the liver and lung in rats (as well as tumors of the esophagus in the case of MNEA). The C3, C4 and C5 compounds give rise only to tumors of the esophagus in rats, whereas the C6, C7 and C8 compounds induce tumors of the esophagus, liver, and lung in rats, the proportions depend on whether the nitrosamine

is administered in drinking water or by gavage. Methylnitroso-n-octylamine (C8) also causes bladder tumors in many rats. The larger C9 to C12 molecules are almost insoluble in water and had to be administered by gavage in oil, and compounds with an odd number of carbons in the chain induced liver and lung tumors in rats. Those with an even number of carbons in the chain induced tumors of the bladder and lung, but seldom liver tumors, although these nitrosamines are extensively metabolized in the rat liver. The metabolism (beta-oxidation) of those compounds with evennumbered carbon chains terminates at methylnitroso-3-carboxypropylamine, which is beta-oxidized and decarboxylates to form methylnitroso-2-oxopropylamine, which induces bladder tumors in rats when injected into the bladder (65). Beta-oxidation of nitrosamines that have odd-numbered carbon chains produces a different end product. In contrast with their varied carcinogenic properties in rats, the response to this series of methylnitroso-n-alkylamines is quite uniform in hamsters and consists of liver and lung tumors and occasionally tumors of the nasal cavity and bladder tumors with the even-numbered carbon chain compounds larger than C6; there were no esophageal tumors in hamsters (no N-nitroso compound induces esophageal tumors in hamsters, although a large proportion of nitrosamines given to rats has induced tumors of the esophagus). This leads to another perplexing finding, that no alkylnitrosamide—although they are directly acting alkylating agents—induces tumors of the esophagus or nasal cavity in rats, even when given in drinking water; many nitrosamines induce tumors of the esophagus in rats, whether given in drinking water or by gavage, even when administered by intraurethral injection or by subcutaneous injection. Such findings led to the conclusion that N-nitroso compounds usually act systemically, rather than locally. However, several alkylnitrosamides produce skin tumors when painted frequently on the skin of mice (66), as well as systemically in rats by oral administration (6). No nitrosamine has produced skin tumors by local action, although when painted on the skin, they can be absorbed and in some cases induce tumors of internal organs. Alkylnitrosoureas in rats induce tumors of the nervous system, of the glandular stomach (similar to human stomach), and of the mammary gland and mesotheliomas (in males), which have not been induced by any nitrosamine; in hamsters, alkylnitrosoureas have induced hemangiosarcomas of the spleen almost exclusively (together with tumors of the forestomach, probably induced locally); in splenectomized hamsters, few tumors were induced by 2-hydroxyethylnitrosourea, mainly some forestomach tumors (67). Alkylnitrosoureas did not induce tumors of the nervous system, glandular stomach, mammary gland or mesotheliomas in hamsters, although they are directly acting alkylating agents. There has been no adequate explanation of these profound differences, which do not depend primarily on the presence of particular activating enzymes in certain tissues or organs, and the results make it difficult to accept the conventional simple alkylation of DNA as the mechanism of such organ and species-specific carcinogenesis by N-nitroso compounds. The difference in response of different species to N-nitroso compounds has been discussed using rats and hamsters as examples. Mice tend to follow rats in the pattern of tumors induced by particular Nnitroso compounds, although rats seem to be more sensitive than mice or hamsters (perhaps by a factor of 10). The limited evidence that can be used to compare humans with rats suggests that humans might be considerably more sensitive (68). Perhaps the most important property of carcinogens in relation to human health is the ability to induce tumors transplacentally because a fetus is more susceptible (i.e., responsive to smaller doses) to the action of many carcinogens than adults (as is true also of infants and young children). In the case of N-nitroso compounds, there has been considerable interest in this aspect, particularly by Ivankovic who induced tumors of the nervous system in rats transplacentally by treating their mothers with alkylnitrosoureas during the last third of pregnancy (21). The same result was achieved using N-methylnitroso ethyl carbamate (methylnitrosourethane) (69). This use of an alkylnitrosamide is one of the few models for human childhood brain cancer. No nitrosamine administered to pregnant animals has induced brain cancer in offspring, although several nitrosamines have induced other types of tumor transplacentally, albeit not with as great efficacy as alkylnitrosoureas. Usually, one or two mice or rats per litter with tumors has resulted, even after a substantial dose to the mother.

Because humans are exposed to rather small quantities of N-nitroso compounds, the importance of transplacental exposure to other than alkylnitrosamides might be small. The large difference in the incidence of many common cancers between the industrialized world and the “less-developed” world (70) is a conundrum, compounded by the studies of vast populations of migrants, who within one or two generations often develop the pattern of cancer of their new country, instead of that of their ancestors. This suggests that environmental exposure to carcinogens is a large factor in many common cancers, compared with a smaller genetic factor. (The difference in the incidence of some cancers, such as breast cancer, in black Americans compared with West African women can be as much as tenfold or more higher in the United States.) A subject of great interest is the extent to which tumor models in animals can be used as surrogates for human cancers. In some cases, N-nitroso compounds represent the best or only models. For example, derivatives of N-nitroso-2-oxopropylamine given to hamsters give rise to tumors of the pancreatic ducts, a common and nasty human cancer, prevalent in idustrialized countries (Western Europe and North America). A number of nitrosamines that have this structure (or convertible metabolically into it) have induced pancreatic tumors more or less effectively; the most effective is nitrosobis-(2-oxopropyl)-amine; strangely, 2-oxopropylnitrosoureas, although quite carcinogenic, do not have this property (71). Many nitrosamines have induced tumors of the esophagus in rats (although not in hamsters) and provide a model for the human tumor, which is common in certain areas of the world and is often associated with smoking tobacco and drinking alcoholic beverages. The linking of alkylnitrosoureas (and probably alkylnitrosocarbamate esters) with transplacentally induced brain and nervous system tumors in rats provides another rare model of common human cancers. The same alkylnitrosoureas in rats give rise to tumors of the colon and other parts of the lower gastrointestinal tract, another rare model of common human tumors, whereas in hamsters they induce mainly hemangioendothelial sarcomas of the spleen (but not of other organs) and few other tumors. This and other species differences in response to N-nitroso compounds is one of the intriguing aspects of carcinogenic studies and has a probable bearing on understanding the induction and development of cancer in general. Perhaps less important in relevance to human cancer is the large number of nitrosamines that induce tumors of the nasal cavity in rats, mice and hamsters and that do not have to be inhaled to do so (these tumors appear when the nitrosamines are given by gavage or even when injected into the bladder), in contrast with formaldehyde, acetaldehyde, and numerous halogenated hydrocarbons. The marked difference in response of different species to many N-nitroso compounds make it impossible to predict which organs or tissues in humans would be responsive to those same compounds. But it is unwise to assume that any N-nitroso compound that is carcinogenic in rodents would be inactive in humans. Indeed, it is not improbable that humans are more susceptible to carcinogenic N-nitroso compounds than rats, which are more susceptible than hamsters or mice. The great effectiveness of cigarette smoke in producing lung cancer (and other cancers) in human smokers is surprising because cigarette smoke has a low content of carcinogens, of which nitrosamines are the most important. The dose of nitrosamines to a heavy cigarette smoker is approximately 0.06 mg/kg body weight/day (72), compared with the minimal effective dose of the most potent carcinogenic nitrosamines in rats (NDMA and NDEA) of 20–40 mg/kg body weight/day (58). Like most carcinogens, with increasing doses, N-nitroso compounds show an increase in the proportion of animals with tumors or a decrease in the time before tumors appear, or both (4, 73). Dose–response studies, mainly in rats, with a number of nitrosamines (including nitrosodiethylamine, nitrosomorpholine, nitrosopiperidine, nitrosopyrrolidine, nitrosodiethanolamine, nitroso-1,2,3,6-tetrahydropyridine, dinitrosohomopiperazine, and nitrosoheptamethyleneimine) have shown the same effect, often down to very low doses of a few micrograms per day. At this level there was virtually no life-shortening effect because tumors arose toward the end of the life span. These compounds induced a variety of tumors including those of liver, esophagus, and lung at the higher dose rates.

N-Nitroso Compounds William Lijinsky E. Risk Assessment Because NDMA is the N-nitroso compound that has the most widespread human exposure (but possibly not the largest), risk assessment has focused on this compound and the possibility that exposure to it increases the risk of cancer. Although it is highly toxic, the possibility nowadays that exposure to it could be in such high concentrations as to lead to immediate toxic effects is essentially nil (other than deliberate poisoning) (74). In few cases, governmental regulatory agencies have calculated the long-term cancer risks of exposure, based on the results of tests in animals. The U. S. Environmental Protection Agency has declared that a concentration of 7 parts per trillion (1012) of NDMA in drinking water or water for recreation represents a cancer risk of 1 in 106, and the State of California claims that exposure to 0.004 mg of NDMA per day presents a cancer risk of 10–6. In the case of nitrosodiethanolamine (NDELA), the EPA has determined that the cancer risk of occupational exposure to 10–5 mg per kg per day is 10-6, and in Europe a similar risk is posed by exposure to 0.0002 mg of NDELA per kg per day in cosmetics. These numbers are quite approximate.

N-Nitroso Compounds William Lijinsky F. Specific Chemicals N-Nitroso Compounds Bibliography

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Aliphatic and Alicyclic Amines Finis L. Cavender, Ph.D., DABT, CIH 1 General Considerations Aliphatic and alicyclic amines are nonaromatic amines that have a straight chain, a branched chain, or a cyclic alkyl moiety attached to the nitrogen atom. Aliphatic amines are highly alkaline and tend to be fat soluble. As such, they have the potential to produce severe irritation to skin, eyes, and mucous membranes. Corrosive burns as well as marked

allergic sensitization may also occur (1). Volatile amines, which are characterized by boiling points lower than 100°C, are highly irritating and include methylamine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, n-propylamine, isopropylamine, diisopropylamine, allylamine, n-butylamine, isobutylamine, sec-butylamine, tert-butylamine, and dimethylbutylamine. Workplace practice must consider these properties in developing strategies to protect workers. Toxicity information in humans continues to be limited. Although great strides in understanding the process of carcinogenicity have been made in recent years, controversies regarding potential aliphatic amine carcinogenicity are far from being resolved. Of considerable interest is the possibility of nitrosamine formation, which is both compound specific and pH dependent. 1.1 Chemical and Physical Properties Aliphatic amines are highly alkaline derivatives of ammonia where one, two, or three of the hydrogen atoms are replaced by alkyl or alkanol radicals of six carbons or fewer. In addition, primary and secondary amines can also act as very weak acids (Ka approximately 10–33) (2). Many of the lower aliphatic amines have low flash points and are flammable liquids or gases. Branching of the alkyl chain tends to enhance volatility, whereas hydroxy substitution as in the alkanolamines decreases volatility (2a–2c). Methylamine solutions are good solvents for many inorganic and organic compounds. Most aliphatic amines have a distinctly unpleasant odor. The fishy or fishlike odor of methylamines increases from mono- to trimethylamine, and in high concentrations they all have the odor of ammonia (2). Olfactory fatigue occurs readily. No symptoms of irritation are produced from chronic exposures to less than 10 ppm (1). Deodorization of ammonia and amines can be achieved with the use of dihydroxyacetone, which is reportedly nontoxic to humans and domestic animals and reacts rapidly with ammonia or amines (1b). Amoore and Furrester reported that about 7% of humans are unable to smell (Anosmic) trimethylamine (1c). Odor threshold measurements on 16 aliphatic amines were made with panels of specific anosmics and normal observers. The anosmia was most pronounced with low-molecularweight tertiary amines, but was also observed to a lesser degree with primary and secondary amines. This specific anosmia apparently corresponds with the absence of a new olfactory primary sensation, the fishlike odor. The aliphatic amines are conveniently classified as primary, secondary, and tertiary amines according to the number of substitutions on the nitrogen atom. If only one hydrogen is replaced with an alkyl group, the amine is a primary amine, even though the alkyl substituent may have a secondary or tertiary structure (1).

Aliphatic and Alicyclic Amines Finis L. Cavender, Ph.D., DABT, CIH 2 Methylamine 2.0.1 CAS Number: [74-89-5] 2.0.2 Synonyms: Monomethylamine, anhydrous monomethylamine, aminomethane, methanamine, and MMA 2.0.3 Trade Names: NA 2.0.4 Molecular Weight: 31.06 2.0.5 Molecular Formula: CH5N

2.0.6 Molecular Structure:

2.1 Chemical and Physical Properties 2.1.1 General Methylamine is a colorless, flammable gas at room temperature and atmospheric pressure. It is readily liquefied and is shipped as a liquefied gas under its own vapor pressure. 2.1.2 Odor and Warning Properties It has a characteristic fishlike odor in lower concentrations, readily detectable at 10 ppm, becomes strong at 20–100 ppm, and becomes intolerably ammoniacal at 100–500 ppm (8b). The odor threshold reportedly ranges from 0.0009 to 4.68 ppm, and becomes irritating at 24 mg/m3 (62, 63). 2.2 Production and Use Methylamine can be manufactured by reacting ammonia and methyl alcohol in the presence of silica–alumina catylst at elevated temperature and pressure; by reductive amination of formaldehyde; or by heating methyl alcohol, ammonium chloride, and zinc chloride to about 300°C. It is used in tanning, fuel additives, photographic developers, and rocket propellants (64), in the manufacture of dyestuffs, in the treatment of cellulose acetate rayon, and in organic synthesis. 2.3 Exposure Assessment 2.3.1 Air NIOSH (65). 2.3.2 Background Levels Bouyoucos and Melcher (66). 2.3.3 Workplace Methods Fuselli et al. (67). OSHA method #40 is recommended for determining workplace exposure (OSHA Analytical Methods, 1990, 1993). 2.3.4 Community Methods Leenheer et al. (68). 2.4 Toxic Effects 2.4.1 Experimental Studies 2.4.1.1 Acute Toxicity Methylamine has been reported to cause liver toxicity in laboratory animals (69). A drop of 5 percent solution in water applied to animal eyes was reported to cause hemorrhages in the conjunctiva, superficial corneal opacities, and edema (70, 71, p. 680). 2.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms When administered to humans, dogs, or rabbits as the hydrochloride, methylamine is rapidly absorbed and only traces of the unchanged compound was observed to be excreted in the urine by early investigators (Salkowski, 1877; Schiffer, 1880) (15). Salkowski claimed that very small amounts of methylurea were excreted by rabbits, but this was not observed in the case of dogs by Schmiedeberg (1878) (15). In 1893, Pohl claimed that small amounts of formate were excreted by dogs receiving methylamine hydrochloride (15), and urea formation was demonstrated in a perfused dog liver experiment by Loffler in 1918 (15). Kapellar-Adler and Krael (1931) were the first to postulate that the amino group was probably split off as ammonia (26). In 1937 Richter put the two concepts together and proposed that the reaction may be split into two stages in which the amine is first dehydrogenated to the corresponding intermediate imine, which reacts spontaneously with water forming an aldehyde and ammonia. Richter believed that most amines were oxidized by amine oxidase, according to the following reaction in the case of primary amines (26):

Methylamine and trimethylamine are also reportedly metabolized to a small extent to dimethylamine in the body (8), and Alles and Heegaard (1943) demonstrated that methylamine could be oxidized, although with difficulty, in vitro by MAO (9, 10). 2.4.1.4 Reproductive and Developmental Treatment of CD-1 mice by daily intraperitoneal injection of 0.25, 1, 2.5, or 5 mmol/kg from day 1 to day 17 of gestation demonstrated no adverse reproductive effects. In the same experiment, dimethylamine was also without effect; trimethylamine decreased fetal weight without affecting maternal body weight gain. None of the amines caused a significant increase in external or internal organ or skeletal abnormalities (8). 2.4.2 Human Experience Brief exposures to 20–100 ppm produce transient eye, nose, and throat irritation; no symptoms of iritation are produced from longer exposures at less than 10 ppm; olfactory fatigue occurs readily (8b). In one plant a case of allergic or chemical bronchitis occurred in a worker exposed to 2–60 ppm, although masks or respirators were reportedly worn during “greatest exposures” (64). 2.5 Standards, Regulations, or Guidelines of Exposure An ACGIH threshold limit value (TLV)-time-weighted average (TWA) value of 5 ppm (6.4 mg/m3) and a short-term exposure limit (STEL) of 15 ppm (19 mg/m3) have been adopted (72). The OSHA PEL and NIOSH REL is 10 ppm. 2.6 Studies on Environmental Impact Aliphatic amines including methylamine were determined in oil-shale retort water (68).

Aliphatic and Alicyclic Amines Finis L. Cavender, Ph.D., DABT, CIH 3 Dimethylamine 3.0.1 CAS Number: [124-40-3] 3.0.2 Synonyms: DMA, N-methylmethanamine 3.0.3 Trade Names: NA 3.0.4 Molecular Weight: 45.08 3.0.5 Molecular Formula: C2H7N 3.0.6 Molecular Structure:

3.1 Chemical and Physical Properties 3.1.1 General The molecular formula for dimethylamine is (CH3)2NH. DMA is a flammable, alkaline, colorless gas at room temperature and atmospheric pressure (73, 74). It is readily liquefied and is shipped in steel cylinders as a liquefied gas under its own vapor pressure (75). 3.1.2 Odor and Warning Properties DMA has a characteristic rotten fishlike odor in lower concentrations (62, 63). The odor threshold ranges from 0.00076 to 1.6 ppm, and becomes irritating

at 175 mg/m3 (62, 63). In higher concentrations (100–500 ppm) the fishlike odor is no longer detectable and the odor is more like that of ammonia. 3.2 Production and Use Dimethylamine is manufactured by reaction of ammonia and methanol over dehydrating catalysts at 300–500°C or by catalytic hydrogenation of nitrosodimethylamine (51). DMA has been used as an accelerator in vulcanizing rubber, in the manufacture of detergent soaps, and for attracting boll weevils for extermination (73, 74). It has been used as a depilating agent in tanning, as an acid gas absorbent, in dyes, as a flotation agent, as a gasoline stabilizer, in pharmaceuticals, in soaps and cleaning compounds, in the treatment of cellulose acetate rayon, in organic syntheses, and as an agricultural fungicide (75). 3.3 Exposure Assessment 3.3.1 Air NIOSH (65). 3.3.2 Background Levels NIOSH (76). 3.3.3 Workplace Method NIOSH Method 201D (65). 3.3.4 Community Methods Cross et al. (77). 3.4 Toxic Effects 3.4.1 Experimental Studies Dimethylamine is irritating and corrosive to both the eyes and skin of test animals (78). Several DMA inhalation studies have been reported. Exposure of rats, mice, guinea pigs, and rabbits to 97 or 185 ppm of DMA 7 h/d, 5 d/wk for 18–20 wk revealed corneal injury in eyes of guinea pigs and rabbits as well as central lobular fatty degeneration and necrosis of the liver in all species (79). However, histopathological examination of rats, guinea pigs, rabbits, monkeys and dogs exposed to 9 mg/m3 of DMA continuously for 90 d produced only mild inflammatory changes in the lungs of all species; dilated bronchi in rabbits and monkeys were noted (80). Steinhagen et al. reported an acute 6-h whole-body exposure of male F344 rats to DMA concentrations ranging from 600 to 6000 ppm for 6 h, which produced a spectrum of pathological changes in the nasal passages, including severe congestion, ulcerative rhinitis, and necrosis of the nasal turbinates (81). Lesions outside the respiratory tract were evident in livers of rats exposed to 2500–6000 ppm, and corneal edema was observed in the eyes of rats at 1000 ppm; corneal ulceration, keratitis, edema, and loss of Descement's membrane was present at 2500–6000 ppm; in addition, many rats exposed to 4000 or 6000 ppm had necrosis of the iris and severe degeneration of the lens, suggestive of acute cataract formation. From a 10-min head-only exposure of male F344 rats to DMA concentrations ranging from 49 to 1576 ppm, a concentration–response curve indicated that a 10-min exposure of 600 ppm would be expected to result in a 51% decrease in respiratory rate; the corresponding calculated response dose, RD50, was 573 ppm. In an experiment to determine whether pathological changes occurred in the respiratory tract of mice after inhalation exposure to various sensory irritants at their respective RD50 concentrations, 16–24 male Swiss–Webster mice were exposed to 510 ppm DMA, 6 h/d for 5 d; lesions induced in the respiratory epithelium ranged from epithelial hypertrophy or hyperplasia to erosion, ulceration, inflammation, and squamous metaplasia (82). In a 1-year inhalation study, male and female F344 rats and B6C3F1 mice were exposed to 0, 10, 50, or 175 ppm DMA for 6 h/d, 5 d/wk for 12 months. The mean body weight gain of rats and mice exposed to 175 ppm was depressed to 90% of control after 3 weeks of exposure. The only other treatment-related effects were the dose-related lesions confined to the nasal passages, which were very similar in rats and mice; however, after 12 months of exposure, rats had more extensive olfactory lesions (83).

DMA was not shown to have reproductive effects in mice by intraperitoneal injection (8). 3.4.1.5 Carcinogenesis In a 2-year inhalation study in male F344 rats exposed to 175 ppm, no evidence of carcinogenicity was observed, and in addition, despite severe tissue destruction in the anterior nose following a single 6-h exposure, the nasal lesions exhibited very little evidence of progression, even at 2 years of exposure; it was concluded that this indicated possible regional susceptibility to DMA toxicity or a degree of adaptation by the rat to continued DMA exposure. A detailed evaluation of mucociliary apparatus function and response to alterations of nasal structure was presented by the authors (84). 3.4.2 Human Experience DMA is considered to be a severe lung and skin irritant in humans (85). Occupational exposure to vapors of DMA at concentrations too low to cause discomfort or disability during several hours of exposure have been associated with misty vision and halos that appeared several hours after the exposure occurred. Therefore, DMA does not have good warning properties. Edema of the corneal epithelium, the effect principally responsible for disturbance of vision, usually clears without treatment within 24 h. However, after exceptionally intense exposures, the edema and blurring have taken several days to clear and have been accompanied by photophobia and discomfort from roughness of the corneal surface (86). 3.5 Standards, Regulations, or Guidelines of Exposure An ACGIH TLV-TWA value of 5 ppm (9.2 mg/m3) and a STEL of 15 ppm (27.6 mg/m3) have been adopted (72). The NIOSH REL and OSHA PEL is 10 ppm.

Aliphatic and Alicyclic Amines Finis L. Cavender, Ph.D., DABT, CIH 4 Trimethylamine 4.0.1 CAS Number: [75-50-3] 4.0.2 Synonyms: TMA, N,N-dimethylmethanamine, and N,N-dimethylmethamine 4.0.3 Trade Names: NA 4.0.4 Molecular Weight: 59.11 4.0.5 Molecular Formula: C3H9N 4.0.6 Molecular Structure:

4.1 Chemical and Physical Properties 4.1.1 General It is readily soluble in water and is also soluble in ether, benzene, toluene, xylene, ethylbenzene, and chloroform. TMA is a flammable, alkaline, colorless gas at ambient temperature and atmospheric pressure. Trimethylamine is shipped as a liquefied compressed gas in cylinders, tank cars, and cargo tank trucks. 4.1.2 Odor and Warning Properties The odor threshold reportedly ranges from 0.00011 to 0.87 ppm and the odor is a characteristic pungent, fishlike one in low concentrations, but in higher

concentrations (100–500 ppm) the fishy odoer is no longer detectable, and the odor is more like that of ammonia (63, 75). 4.2 Production and Use Trimethylamine is manufactured by heating methanol and ammonia over a catalyst at high temperatures; or by heating paraformaldehyde and ammonium chloride; or by the action of formaldehyde and formic acid on ammonia (51). TMA is used primarily in the manufacture of quaternary ammonium compounds, in the manufacture of disinfectants, as a corrosion inhibitor, in the preparation of choline chloride, in various organic syntheses (75), and as a warning agent for natural gas (64). 4.3 Exposure Assessment 4.3.1 Air None available. 4.3.2 Background Levels Bouyoucos and Melcher (66). 4.3.3 Workplace Methods None available. 4.3.4 Community Methods Hoshika (77). 4.4 Toxic Effects 4.4.1 Experimental Studies A 1% solution applied to animal eyes resulted in severe irritation, 5% causes hemorrhagic conjunctivitis, and 16.5% causes a severe reaction with conjunctival hemorrhages, corneal edema, and opacities, followed by some clearing but much vascularization (71, p. 1060). In contrast to MMA and DMA, TMA has been demonstrated to cause embryo toxicity in mice (decreased fetal weight of CD-1 pups) (8). 4.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms TMA can be detected in mammalian urine and may arise from choline. When administered to humans, dogs, or rabbits (Linzel, 1934; HoppeSeyler, 1934), it is partly degraded to ammonia and subsequently to urea, and oxidized to trimethylamine oxide (15); according to Muller (1940) about 50% of the dose of trimethylamine hydrochloride (administered orally to dogs) was eliminated unchanged together with traces of dimethylamine, suggesting that trimethylamine was N-dealkylated (26). In 1941, Green reported that tertiary amines are also oxidized by amine oxidase to the corresponding formaldehyde and secondary amine and proposed the following reaction (26):

It was also proposed that the secondary amine can then form a primary amine and this eventually would yield ammonia. In vivo, therefore, the nitrogen of a tertiary amine could be expected to appear in part as urea. The second reaction involved the oxidation of the amine to the amine oxide as follows (15):

N-dealkylation can be expected to occur with most amines, with an available a-carbon hydrogen. The reaction is essentially the same as oxidative deamination, that is, cleavage of the carbon– nitrogen bond with transfer of two electrons with the formation of a carbonyl compound and a dealkylated amine. It is therefore unlikely that tertiary aliphatic amines will be easily N-dealkylated to secondary amines. However, it may depend on the size of the alkyl groups. For example, trimethylamine has been reported to be N-dealkylated to dimethylamine, and studies have also shown that a t-butyl group can be removed through initial hydroxylation of one of the t-methyl groups, resulting in C-dealkylation to the corresponding carbinol or alcohol product (87).

In cases, therefore, where tertiary amines have a small, easily removed group (methyl, ethyl, isopropyl), then oxidative N-dealkylation can probably proceed with preferential removal of the smaller substituents, dissociating into a secondary amine and aldehyde via microsomal P450 (88, 89). Trimethylamine oxide occurs in large amounts in the tissues of fish, and its transformation into trimethylamine by bacteria containing trimethylamine oxide reductase is largely responsible for the spoiling of fish (15). 4.4.2 Human Experience In humans, N-oxidation to trimethylamine oxide is apparently the major route of metabolism; although N-demethylation to dimethylamine can also occur, it is a virtually negligible minor route (8, 90). 4.5 Standards, Regulations, or Guidelines of Exposure The ACGIH TLV-TWA value of 5 ppm (12 mg/m3) and a STEL of 15 ppm (36 mg/m3) have been adopted (72). The NIOSH REL is 10 ppm. 4.6 Studies on Environmental Impact In conjugated form, TMA is widely distributed in animal tissue and especially in fish (73, 74). It is also found in nature as a degradation product of nitrogenous plant and animal residues and is responsible for the odor of rotting cartilaginous marine fish (64).

Aliphatic and Alicyclic Amines Finis L. Cavender, Ph.D., DABT, CIH 5 Ethylamine 5.0.1 CAS Number: [75-04-7] 5.0.2 Synonyms: MEA, monoethylamine, aminoethane, ethanamine, and EA 5.0.3 Trade Names: NA 5.0.4 Molecular Weight: 45.08 5.0.5 Molecular Formula: C2H7N 5.0.6 Molecular Structure:

5.1 Chemical and Physical Properties 5.1.1 General It is a flammable, colorless gas. 5.1.2 Odor and Warning Properties The odor threshold reportedly ranges from 0.027 to 3.5 ppm, having a sharp fishy, ammoniacal odor, which becomes irritating at 180 mg/m3 (62, 63). It is miscible with water, alcohol, and ether (71, p 76; 73, 74). 5.2 Production and Use Ethylamine is manufactured by the hydrogenation of nitroethane; the reaction of ethyl chloride and alcohol ammonia under heat and pressure; or by the hydrogenation of aziridines in the presence of catalysts (51). It is used in resin chemistry, as a stabilizer for rubber latex, as an intermediate for dyestuffs, and in pharmaceuticals, and in oil refining and organic syntheses (73, 74).

5.3 Exposure Assessment 5.3.1 Air: NA 5.3.2 Background Levels: NA 5.3.3 Workplace Methods Analytical method S144 is recommended for determining workplace exposures to ethylamine (103). 5.3.4 Community Methods Hoshika (77). 5.4 Toxic Effects 5.4.1 Experimental Studies Ethylamine is a primary skin irritant (85), as well as an eye and mucous membrane irritant (77a), and when tested on rabbit eyes, was severely damaging (86). A 70% solution applied to the skin of guinea pigs resulted in prompt skin burns leading to necrosis; when it was held in contact with guinea pig skin for 2 h, there was severe skin irritation with extensive necrosis and deep scarring (8b). In a comparative inhalation study, Brieger and Hodes exposed rabbits repeatedly to measured concentrations of ethylamine, diethylamine, and triethylamine (91, 92). The three amines produced lung, liver and kidney damage at 100 ppm. The triethylamine produced definite degenerative changes in the heart at 100 ppm, whereas this was an inconstant finding with ethylamine and diethylamine; 50 ppm of these amines was sufficient to produce lung irritation and corneal injury (delayed until 2 weeks with ethylamine). Ethylamine has been reported to cause adrenal cortical gland necrosis, which, according to Ribelin (93), can also be expected following exposure to short three- or four-carbon chain alkyl compounds bearing terminal electronegative groups. Of the three adrenal gland areas, medulla, zona glomerulosa, and zona fasciculata/reticularis, the last is most sensitive to toxic injury, which is the case with ethylamine. Sensitivity of endocrine glands to toxic insult occurs in the following decreasing order: adrenal, testis, thyroid, ovary, pancreas, pituitary, and parathyroid (93). 5.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Monoethylamine (MEA) is less readily metabolized than methylamine, and although a large proportion may be destroyed, its nitrogen being converted into urea (Schmiedeberg, 1878; Loffler, 1918), nearly one-third of the dose may be excreted unchanged by humans when administered as the hydrochloride. Schmiedeberg suggested that dogs might excrete traces of ethylurea after ethylamine (15). 5.4.2 Human Experience Ethylamine vapor has also reportedly produced vision disturbances and decreased olfaction sensitivity in humans (94); therefore, the warning properties associated with odor should not be relied upon. 5.5 Standards, Regulations, or Guidelines of Exposure The ACGIH TLV-TWA value of 5 ppm (9 mg/m3) has been adopted as well as a STEL of 15 ppm (72, 78). Both the NIOSH REL and OSHA PEL are 10 ppm.

Aliphatic and Alicyclic Amines Finis L. Cavender, Ph.D., DABT, CIH 6 Diethylamine 6.0.1 CAS Number: [109-89-7] 6.0.2 Synonyms: DEA, N,N-diethylamine, diethamine, and N-ethylethanamine

6.0.3 Trade Names: NA 6.0.4 Molecular Weight: 73.14 6.0.5 Molecular Formula: C4H11N 6.0.6 Molecular Structure:

6.1 Chemical and Physical Properties 6.1.1 General The molecular formula for diethyalmine is (C2H5)2NH. It is a colorless, flammable, strongly alkaline liquid, miscible with water and alcohol (73, 74). 6.1.2 Odor and Warning Properties The odor threshold ranges from 0.02 to 14 ppm, having a fishlike odor that becomes ammoniacal and irritating at 150 mg/m3 (62, 63). 6.2 Production and Use Diethylamine is manufactured by heating ethyl chloride and alcoholic ammonia under pressure or by hydrogenation of aziridines in the presence of catalysts (51). DEA is used as a solvent, as a rubber accelerator, in the organic synthesis of resins, dyes, pesticides, and pharmaceuticals, in electroplating, and as a polymerization inhibitor (73, 74). Other applications include uses as a corrosion inhibitor. It was reported noneffective as a skin depigmentator (95). 6.3 Exposure Assessment 6.3.1 Air: NA 6.3.2 Background Levels: NA 6.3.3 Workplace Methods NIOSH method 2010 is recommended for determining workplace exposures to diethylamine (65). 6.3.4 Community Methods Hoshika (77). 6.4 Toxic Effects 6.4.1 Experimental Studies DEA is an eye and mucous membrane irritant and primary skin irritant (85). Smyth et al. reported an acute 4-h LC50 value of 4000 ppm, the oral LD50 for rats was reported as 540 mg/kg, and the dermal LD50 in rabbits was reported to be 580 mg/kg; a 10% dilution caused severe eye burns (96). Drotman and Lawhorn reported histological evidence of liver damage and elevations of serum enzymes following intraperitoneal administration to rats (97). In addition to these acute studies, Brieger and Hodes exposed rabbits at 50 and 100 ppm DEA vapor for 7 h/d, 5 d/wk for 6 wk and all animals survived (91). Lungs exposed to 100 ppm exhibited cellular infiltration and bronchopneumonia, livers showed marked parenchymatous degeneration, and kidneys showed nephritis. Similar changes to a lesser degree were observed in animals exposed to 50 ppm. There was slight cardiac muscle degeneration at 50 ppm. Lynch et al., in a followup study to investigate heart muscle degeneration reported by Brieger and Hodes were unable to find any evidence of cardiac muscle degeneration or any changes in electrocardiograms in F344 rats of both sexes exposed to DEA vapor concentrations of 25 or 250 ppm for 6.5 h/d, 5 d/wk for 30, 60, or 120 exposure days (91, 92). Rats exposed at 25 ppm showed no effect in any measured parameter. In contrast to DMA observations previously discussed the incidence of histopathological effects (bronchiolar lymphoid hyperplasia) was noted in both controls and the 25-ppm dosage groups; however, the incidence was not dose-related and did not increase with increasing DEA exposure (81). The authors therefore concluded that the lesions of the

respiratory epithelium (consisting of squamous metaplasia, suppurative rhinitis, and lymphoid hyperplasia) were not considerd to be of toxicologic significance but were considered a result of irritation. No evidence of cardiac muscle degeneration or of changes in electrocardiograms were seen for up to 24 weeks. It was noted that these negative findings may reflect a species difference in susceptibility to DEA cardiotoxicity previously reported by Brieger (91). In a followup parallel inhalation study with DEA and triethylamine, no respiratory lesions were observed with triethylamine in F344 rats exposed to 25 or 250 ppm (98). 6.4.2 Human Experience Adverse ocular effects have been reported following human exposure (94). 6.4.2.2.3 Pharmacokinetis, Metabolism, and Mechanisms Diethylamine (DEA) is mainly excreted unchanged by humans when it is administered as the hydrochloride (15). 6.5 Standards, Regulations, or Guidelines of Exposure The ACGIH TLV-TWA value of 5 ppm (15 mg/m3) and a STEL of .5 ppm (37.5 mg/m3) have been adopted (72). The NIOSH REL is 10 ppm and the OSHA PEL is 25 ppm.

Aliphatic and Alicyclic Amines Finis L. Cavender, Ph.D., DABT, CIH 7 Triethylamine 7.0.1 CAS Number: [121-44-8] 7.0.2 Synonyms: N,N-diethylethanamine and TEA 7.0.3 Trade Names: NA 7.0.4 Molecular Weight: 101.19 7.0.5 Molecular Formula: (C2H5)3N 7.0.6 Molecular Structure: Liquid,

7.1 Chemical and Physical Properties 7.1.1 General It is a colorless, flammable, volatile liquid. It is slightly soluble in water and miscible with alcohol and ether (73, 74). 7.1.2 Odor and Warning Properties The odor threshold reportedly ranges from 0.10 to 29 ppm, having a fishlike, pungent odor, which becomes ammoniacal and irritating at 200 mg/m3 (62, 63). 7.2 Production and Use Triethylamine is manufactured by heating ethyl chloride and alcoholic ammonia under pressure or by hydrogenation of aziridines in the presence of catalysts (51). TEA is used as a solvent and in the synthesis of quaternary ammonia wetting agents (73, 74); it is also reportedly used in penetrating and waterproofing agents, as a corrosion inhibitor, and in the synthesis of other organic compounds (73, 74). 7.3 Exposure Assessment 7.3.1 Air: NA

7.3.2 Background Levels: NA 7.3.3 Workplace Methods NIOSH method S152 is recommended for determining workplace exposure to triethylamine (103). 7.3.4 Community Methods Hoshika (77). 7.4 Toxic Effects 7.4.1 Experimental Studies TEA is a skin and eye irritant (85). The acute oral LD50 in rats has been reported to be 0.46 g/kg; the rabbit dermal LD50, 0.57 mL/kg; and the acute 4 h LC50, apparently 500 ppm (64). Chronic exposure of rabbits to TEA vapors at concentrations as low as 50 ppm causes multiple erosions of the cornea and conjuctiva, as well as injuries of the lungs in the course of 6 weeks (91). Male and female F344 rats exposed to vapor concentrations of 0, 25, or 250 ppm up to 28 weeks showed no physiological or pathological evidence of cardioxicity; no treatment-related effects were observed (99). However, as in the case with diethylamine, this may be species dependent. 7.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Biotransformation metabolites eliminated in human urine following inhalation at 10, 20, 35, and 50 mg/m3 for 4 or 8 h included unchanged TEA and triethylamine N-oxide (100). Pharmacokinetics in four male volunteers have been studied. The doses of TEA and TEAO were 25 and 15 mg orally and 15 mg/h × 1 h intravenously, respectively. TEA was efficiently absorbed from the gastrointestinal (GI) tract (90–97%), no significant first-pass metabolism. The apparent volumes of distribution during the elimination phase were 192 L for TEA and 103 L for TEAO. TEA was metabolized into triethylamine N-oxide (TEAO) by addition of oxygen to the nucleophilic nitrogen. TEAO was also absorbed from the GI tract. Both TEA and diethylamine (DEA) appeared in the urine after ingestion of TEAO, but not after an intravenous route of administration. This indicates that TEAO is reduced into TEA or dealkylated into DEA only within the GI tract. The TEA and TEAO had plasma half-lives of about 3 and 4 h, respectively. Exhalation of TEA was minimal; more than 90% of the dose was recovered in the urine as TEA and TEAO. The authors recommend that the sum of TEA and TEAO be used for biologic monitoring (101). Previously reported symptoms of visual disturbances in humans (foggy vision, blue haze) (102) were not observed following systemic administration (101). 7.4.2 Human Experience It has also been reported that TEA inhalation in humans has resulted in EEG changes (94). 7.5 Standards, Regulations, or Guidelines of Exposure The ACGIH TLV-TWA value of 1 ppm (4.1 mg/m3) and a STEL of 3 ppm (12.5 mg/m3) have been adopted (72). The OSHA PEL is 25 ppm. NIOSH questions whether the OSHA PEL is adequate to protect workers.

Aliphatic and Alicyclic Amines Finis L. Cavender, Ph.D., DABT, CIH 8 Isopropylamine 8.0.1 CAS Number: [75-31-0] 8.0.2 Synonyms: MIPA, 2-aminopropane, 2-propanamine, monisopropylamine, 2-propylamine, and sec-propylamine

8.0.3 Trade Names: NA 8.0.4 Molecular Weight: 59.08 8.0.5 Molecular Formula: (CH3)2CHNH2 8.0.6 Molecular Structure:

8.1 Chemical and Physical Properties 8.1.1 General It is a colorless, flammable liquid. Isopropylamine is miscible with water, alcohol, and ether (73, 74). 8.1.2 Odor and Warning Properties The odor threshold reportedly ranges from 0.21 to 0.70 ppm; the pungent, ammoniacal odor becomes irritating at 24 mg/m3 (63). 8.2 Production and Use Isopropylamine is manufactured by reacting isopropanol and ammonia in the presence of dehydrating catalysts; by reacting isopropyl chloride and ammonia under pressure; or by the action of acetone and ammonia (51). It is used as a solvent, as a depilating agent (64), in the chemical synthesis of dyes and pharmaceuticals, and in other organic syntheses (64a). 8.3 Exposure Assessment 8.3.1 Air NIOSH Method S147 (103). 8.3.2 Background Levels Kuwata et al. (104). 8.3.3 Workplace Methods NIOSH Method S147 is recommended (103). 8.3.4 Community Methods Koga et al. (105). 8.4 Toxic Effects 8.4.1 Experimental Studies Isopropylamine in either liquid or vapor form is irritating to the skin and may cause burns; repeated lesser exposures may result in dermatitis (1, 85). The acute oral LD50 in rats is reportedly 820 mg/kg (96, in Ref. 73, 74). Dudek (106) reported a no observable effect level (NOEL) in Sprague–Dawley rats to be 0.1 mg/L in air following a 30-d inhalation study. 8.4.2 Human Experience Humans exposed briefly to isopropylamine at 10–20 ppm experienced irritation of the nose and throat. Workers complained of transient visual disturbances (halos around lights) after exposure to the vapor for 8 h, probably owing to mild corneal edema, which usually cleared within 3–4 h. The liquid can cause severe eye burns and permanent visual impairment (107) 8.5 Standards, Regulations, or Guidelines of Exposure The ACGIH TLV-TWA value of 5 ppm (12 mg/m3) and a STEL of 10 ppm (24 mg/m3) have been adopted (72). The OSHA PEL is 5 ppm. NIOSH questions whether 5 ppm is adequate.

Aliphatic and Alicyclic Amines Finis L. Cavender, Ph.D., DABT, CIH

9 n-Propylamine 9.0.1 CAS Number: [107-10-8] 9.0.2 Synonyms: 1-aminopropane, MNPA, 1-propanamine, propylamine, monopropylamine, propyl amines, propan-1amine, and mono-n-propylamine 9.0.3 Trade Names: NA 9.0.4 Molecular Weight: 59.11 9.0.5 Molecular Formula: C3H9N 9.0.6 Molecular Structure:

9.1 Chemical and Physical Properties 9.1.1 General It is a colorless, flammable, alkaline liquid, and is miscible with water, alcohol, and ether (73, 74). 9.1.2 Odor and Warning Properties MNPA has a strong ammoniacal odor (73, 74). 9.2 Production and Use n-Propylamine is manufactured by reacting propanol and ammonia in the presence of dehydrating catalysts; by reacting n-propyl chloride and ammonia under pressure; or by the action of acetone and ammonia (51). It is used as a solvent and in organic syntheses. 9.3 Exposure Assessment 9.3.1 Air NIOSH Method S147 (103). 9.3.2 Background Levels Kuwata et al. (104). 9.3.3 Workplace Methods None is recommended. 9.3.4 Community Methods Koga et al. (105). 9.4 Toxic Effects 9.4.1 Experimental Studies During lethal exposure in rats, n-propylamine caused clouding of the cornea at 800 ppm (108). Application to rabbit eyes caused severe injury after 24 h (109). The acute oral LD50 in rats is reportedly 0.57 g/kg (109, in Refs. 73, 74). It is a possible skin sensitizer (73, 74). 9.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms n-Propylamine appears to be more readily metabolized than ethylamine in humans, and in dogs Bernhard (1938) found none of the administered amine to be excreted unchanged (15). 9.5 Standards, Regulations, or Guidelines of Exposure Standards have not been adopted.

Aliphatic and Alicyclic Amines Finis L. Cavender, Ph.D., DABT, CIH 10 n-Dipropylamine

10.0.1 CAS Number: [142-84-7] 10.0.2 Synonyms: di-n-propylamine, DNPA, N-propyl-1-propanamine, and N,N-dipropylamine 10.0.3 Trade Names: NA 10.0.4 Molecular Weight: 101.19 10.0.5 Molecular Formula: C6H15N 10.0.6 Molecular Structure:

10.1 Chemical and Physical Properties 10.1.1 General It is a colorless, flammable liquid. n-Dipropylamine is freely soluble in water and alcohol (73, 74). 10.1.2 Odor and Warning Properties The odor threshold reportedly ranges from 0.08 to 227 mg/m3; the odor is ammoniacal (62). 10.2 Production and Use Di-n-propylamine is manufactured by reacting propanol and ammonia in the presence of dehydrating catalysts; n-propyl chloride and ammonia under pressure; or by the action of acetone and ammonia (51). Specific uses were not identified in the literature (51). 10.3 Exposure Assessment 10.3.1 Air None is recommended. 10.3.2 Background Levels None is recommended. 10.3.3 Workplace Methods None is recommended. 10.3.4 Community Methods Hoshika (77). 10.4 Toxic Effects 10.4.1 Experimental Studies Dipropylamine is a severe eye irritant (86), and the acute oral LD50 in rats is reportedly 0.93 g/kg (109, in Refs. 73, 74); it may also be a possible skin sensitizer (73, 74). 10.5 Standards, Regulations, or Guidelines of Exposure Standards have not been adopted.

Aliphatic and Alicyclic Amines Finis L. Cavender, Ph.D., DABT, CIH 11 Diisopropylamine 11.0.1 CAS Number: [108-18-9] 11.0.2 Synonyms: N,N-diisopropylamine and DIPA 11.0.3 Trade Names: NA 11.0.4 Molecular Weight:

101.19 11.0.5 Molecular Formula: (CH3)2CHNHCH(CH3)2 11.0.6 Molecular Structure:

11.1 Chemical and Physical Properties 11.1.1 General It is a flammable, strongly alkaline liquid. Diisopropylamine is soluble in water and alcohol (73, 74). 11.1.2 Odor and Warning Properties The odor threshold ranges from 0.017 to 4.2 ppm; the fishlike odor becomes irritating at 100 mg/m3 (62, 63, 86). 11.2 Production and Use Diisopropylamine is manufactured by reacting isopropanol and ammonia in the presence of dehydrating catalysts; by reacting isopropyl chloride an ammonia under pressure; or by the action of acetone and ammonia (51). It is used as a solvent and in the chemical synthesis of dyes, pharmaceuticals, and other organic syntheses (64a, 73, 74). 11.3 Exposure Assessment 11.3.1 Air NIOSH (65). 11.3.2 Background Levels Kuwata et al. (104). 11.3.3 Workplace Methods NIOSH Methods S141 (103). 11.3.4 Community Methods Koga et al. (105). 11.4 Toxic Effects 11.4.1 Experimental Studies The acute oral rat LD50 is reportedly 0.77 g/kg (110); the compound is irritating to the eyes, skin, and mucous membranes (73, 74, 85). Experimental exposures of rabbits, guinea pigs, rats, and cats have established that the vapor is injurious to the corneal epithelium; this presumably is the cause of the visual disturbances observed in humans. Exposure of experimental animals to vapor concentrations from 260 to 2200 ppm for several hours causes clouding of the cornea from epithelial injury and stromal swelling. The highest concentrations were lethal in many instances, owing to severe pulmonary damage, but the corneas of surviving animals ultimately returned to normal (111). Exposure of several species of animals to 2207 ppm for 3 h was fatal; effects were lacrimation, corneal clouding, and severe irritation of the respiratory tract. At autopsy, findings were pulmonary edema and hemorrhage (111a). 11.4.2 Human Experience Temporary impairment of vision has occurred in humans after exposure to vapor concentrations possibly as low as 25–50 ppm during distillation of diisopropylamine (111, 112). Diisopropylamine is considered to be a severe pulmonary irritant in animals and humans (85). Workers exposed to concentrations between 25 and 50 ppm complained of disturbances of vision described as “haziness,” or “halos” around lights (85). Therefore, the warning properties of diisopropylamine are not protective. There have also been reports of nausea and headache (85a, 85b). Prolonged skin contact is likely to cause dermatitis (85c).

11.5 Standards, Regulations, or Guidelines of Exposure The ACGIH TLV-TWA value of 5 ppm (21 mg/m3) has been adopted (72). The NIOSH REL and OSHA PEL are the same.

Aliphatic and Alicyclic Amines Finis L. Cavender, Ph.D., DABT, CIH 12 Tripropylamine 12.0.1 CAS Number: [102-69-2] 12.0.2 Synonyms: TNPA 12.0.3 Trade Names: NA 12.0.4 Molecular Weight: 143.27 12.0.5 Molecular Formula: C9H21N 12.0.6 Molecular Structure:

12.1 Chemical and Physical Properties 12.1.1 General It is a flammable liquid (73, 74). 12.2 Production and Use Tripropylamine is manufactured by reacting propanol and ammonia in the presence of dehydrating catalysts; by reacting n-propyl chloride and ammonia under pressure; or by the action of acetone and ammonia. No specific uses were located in the literature. 12.3 Exposure Assessment 12.3.1 Air None available. 12.3.2 Background Levels None available. 12.3.3 Workplace Methods NIOSH Method S147 (103). 12.3.4 Community Methods Koga et al. (105). 12.4 Toxic Effects No toxicology information was located. 12.5 Standards, Regulations, or Guidelines of Exposure Standards have not been adopted (72).

Aliphatic and Alicyclic Amines Finis L. Cavender, Ph.D., DABT, CIH

13 n-Butylamine 13.0.1 CAS Number: [109-73-9] 13.0.2 Synonyms: MNBA, 1-butanamine, 1-aminobutane, aminobutane, butyl amine, 1-butanamine, norralamine, mono-n-butylamine, tutane, and monobutylamine 13.0.3 Trade Names: NA 13.0.4 Molecular Weight: 73.14 13.0.5 Molecular Formula: C4H11N 13.0.6 Molecular Structure:

13.1 Chemical and Physical Properties 13.1.1 General n-Butylamine is a flammable volatile liquid. It is miscible with water, alcohol, and ether (73, 74). 13.1.2 Odor and Warning Properties The odor threshold ranges from 0.24 to 13.9 ppm; the sour, fishlike, ammoniacal odor becomes irritating at 30 mg/m3 (62, 63). 13.2 Production and Use n-Butylamine is manufactured by the reaction of ammonia and n-butanol at elevated temperature and pressure in the presence of silica–alumina, by reductive amination of n-butyraldehyde; or by reduction of butyraldoxime. It is used as a solvent and as an intermediate for pharmaceuticals, dyestuffs, rubber chemicals, emulsifying agents, insecticides, and synthetic tanning agents (73, 74). It is also present in fertilizer manufacture, rendering plants, fish processing plants, and sewage plants (51) and has been reported to be effective (0.1M) in inhibiting the corrosion of iron in concentrated perchloric acid (6). 13.3 Exposure Assessment 13.3.1 Air: NA 13.3.2 Background Levels Kuwata et al. (104). 13.3.3 Workplace Methods NIOSH method 2012 is recommended for determining workplace exposure. 13.3.4 Community Methods Petronio and Russo (113). 13.4 Toxic Effects 13.4.1 Experimental Studies n-Butylamine vapor is only mildly irritating to the eyes, but the liquid tested on animals' eyes is as severely injurious as ammonium hydroxide; the injurious effect seems to be attributable to the alkalinity of butylamine because, as with other amines, its damaging effects on the cornea is prevented if it is neutralized with acid before testing (114–116). Other references indicate that n-butylamine is a potent skin, eye, and mucous membrane irritant, and direct skin contact causes severe primary irritation and blistering (73, 74). The acute oral LD50 for Sprague– Dawley rats (male + female) has been reevaluated and reported as 371 mg/kg (117). n-Butylamine at measured concentrations of 3000–5000 ppm produces an immediate irritant response, labored breathing, and pulmonary edema, with death of all rats in minutes to hours. Ten and 50% vol/vol aqueous solutions and the undiluted base produce severe skin and eye burns in animals. The immediate skin and eye reactions are not appreciably altered by prolonged washing or

attempts at neutralization when these are commenced within 15 sec after application (8b). 13.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms n-Butylamine is as readily metabolized in humans as methylamine, and Pugh (1937) demonstrated in guinea pig liver slices that one of its metabolites is acetoacetic acid (15). 13.4.2 Human Experience Direct skin contact with the liquid causes severe primary irritation and deep second-degree burns (blistering) in humans. The odor of butylamine is slight at less than 1 ppm, noticeable at 2 ppm, moderately strong at 2–5 ppm, strong at 5–10 ppm, and strong and irritating at concentrations exceeding 10 ppm. Workers with daily exposures of from 5 to 10 ppm complain of nose, throat, and eye irritation, and headaches. Concentrations of 10–25 ppm are unpleasant to intolerable for more than a few minutes. Daily exposures to less than 5 ppm (most often between 1 and 2 ppm) produce no complaints or symptoms. 13.5 Standards, Regulations, or Guidelines of Exposure NIOSH, OSHA, and the ACGIH have all adopted a ceiling value of 5 ppm (72).

Aliphatic and Alicyclic Amines Finis L. Cavender, Ph.D., DABT, CIH 14 2-Butylamine 14.0.1 CAS Number: [13952-84-6] 14.0.2 Synonyms: 2-aminobutane, sec-butylamine, 2-butanamine, 1-methylpropylamine, and Butafume. Butafume is available as (R) B.P. 63°C, (+/–) B.P. 63°C, and (S) B.P. 62.5°C; the corresponding CASRNs are [13250-12-9], [33966-50-6], and [513-49-5] (73, 74) 14.0.3 Trade Name: NA 14.0.4 Molecular Weight: 73.14 14.0.5 Molecular Formula: CH3CH2CH(NH3)CH3 14.0.6 Molecular Structure:

14.1 Chemical and Physical Properties 14.1.1 General It is a flammable liquid. 14.2 Production and Use 2-Butylamine is manufactured by the condensation of methyl ethyl ketone with ammonia–hydrogen in the presence of Ni catalyst (51). It has been used as a fungistat (73, 74). 14.3 Exposure Assessment 14.3.1 Air None available, however, NIOSH methods may be applicable. 14.3.2 Background Levels Kuwata et al. (104). 14.3.3 Workplace Methods NIOSH method 2012 may be used. 14.3.4 Community Methods Hoshika (77).

14.4 Toxic Effects 14.4.1 Experimental Studies The acute oral LD50 for Sprague–Dawley rats (males + females) has been reported to be 152 mg/kg (117). An earlier acute study reported an LD50 value of 380 mg/kg (female, Harlan Wistar rats) (118). 2-Butylamine is irritating to the skin and mucous membranes (73, 74). Seven male rats exposed to saturated vapor (280 mg/L) for 5 h exhibited intense eye and nose irritation, respiratory difficulty, and convulsions; all died. Cornea lesions were opaque and white, and all other organs appeared normal. All amines examined showed irritant and central nervous system stimulant effects; these increased with the degree of substitution, but the higher members had too low a volatility to present a significant vapor hazard. Other amino compounds studied included di-sec-butylamine, tributylamine, nonylamine, dinonylamine, trinonylamine, hexamethylenediamine, diethylenetriamine, 2aminobutan-1-ol, and 1-diethylaminoentan-2-one (119). 14.5 Standards, Regulations, or Guidelines of Exposure Standards have not been adopted.

Aliphatic and Alicyclic Amines Finis L. Cavender, Ph.D., DABT, CIH 15 Isobutylamine 15.0.1 CAS Number: [78-81-9] 15.0.2 Synonyms: IBA, 1-amino-2-methylpropane, 2-methylpropylamine (73, 74), monoisobutylamine, valamine, 2methyl-1-propanamine, and 2-methylpropanamine 15.0.3 Trade Names: NA 15.0.4 Molecular Weight: 73.14 15.0.5 Molecular Formula: C4H11N 15.0.6 Molecular Structure:

15.1 Chemical and Physical Properties 15.1.1 General It is a flammable liquid, miscible with water, alcohol, and ether (73, 74). 15.2 Production and Use Isobutylamine is manufactured from isobutanol and ammonia or by the thermal decomposition of valine to isoleucine (51). 15.3 Exposure Assessment 15.3.1 Air Nishikawa and Kuwata (120). 15.3.2 Background Levels Kuwata et al. (104). 15.3.3 Workplace Methods: NA 15.3.4 Community Methods Hoshika (77).

15.4 Toxic Effects 15.4.1 Experimental Studies The acute oral LD50 for Sprague–Dawley rats (males + females) has been reported to be 228 mg/kg (117). 15.4.2 Human Experience Skin contact can result in erythema and blistering; inhalation causes headache and dryness of the nose and throat (73, 74). 15.5 Standards, Regulations, or Guidelines of Exposure Standards have not been adopted.

Aliphatic and Alicyclic Amines Finis L. Cavender, Ph.D., DABT, CIH 16 Diisobutylamine 16.0.1 CAS Number: [110-96-3] 16.0.2 Synonyms: 1-butamine, N-butyl, di-N-butylamine, DIBA, 2-methyl-N-(2-methylpropyl)-1-propanamine, and bis (2-methylpropyl) amine 16.0.3 Trade Names: NA 16.0.4 Molecular Weight: 129.24 16.0.5 Molecular Formula: C8H19N 16.0.6 Molecular Structure:

16.1 Chemical and Physical Properties 16.1.1 General It is a colorless, flammable liquid, very slightly soluble in water and soluble in alcohol or ether (73, 74). 16.1.2 Odor and Warning Properties 16.2 Production and Use Diisobutylamine is manufactured from isobutanol and ammonia (51). Specific uses were not located in the literature (51). 16.3 Exposure Assessment 16.3.1 Air: NA 16.3.2 Background Levels Kuwata et al. (104). 16.3.3 Workplace Methods: NA 16.3.4 Community Methods Hoshika (121). 16.4 Toxic Effects Specific toxicity data were not located in the literature. 16.5 Standards, Regulations, or Guidelines of Exposure Standards have not been adopted.

Aliphatic and Alicyclic Amines Finis L. Cavender, Ph.D., DABT, CIH 17 Di-n-butylamine 17.0.1 CAS Number: [111-92-2] 17.0.2 Synonyms: Dibutylamine, n-dibutylamine, DNBA, N-butyl-1-butanamine, di-n-butylamine, and N,Ndibutylamine 17.0.3 Trade Names: NA 17.0.4 Molecular Weight: 129.24 17.0.5 Molecular Formula: C8H19N 17.0.6 Molecular Structure:

17.1 Chemical and Physical Properties 17.1.1 General The molecular formula for di-n-butylamine is (C4H9)2NH. It is colorless liquid, soluble in water, alcohol, and ether (73, 74). 17.1.2 Odor and Warning Properties The odor threshold reportedly ranges from 0.42 to 2.5 mg/m3; the fishlike odor becomes ammoniacal at higher concentrations (62). 17.2 Production and Use Dibutylamine is manufactured by the reaction of ammonia and n-butanol at elevated temperature and pressure in the presence of silica–alumina; from butyl bromide and ammonia; or by reaction of butyl chloride and ammonia (51). Dibutylamine is used as a solvent and in organic syntheses. 17.3 Exposure Assessment 17.3.1 Air: NA 17.3.2 Background Levels Kuwata et al. (104). 17.3.3 Workplace Methods: NA 17.3.4 Community Methods Hoshika (121). 17.4 Toxic Effects Animal studies have demonstrated that dibutylamine is severely irritating to the eyes (86). An acute oral rat LD50 value of 550 mg/kg has been reported (110) 17.5 Standards, Regulations, or Guidelines of Exposure Standards have not been adopted.

Aliphatic and Alicyclic Amines Finis L. Cavender, Ph.D., DABT, CIH

18 Tri-n-butylamine 18.0.1 CAS Number: [102-82-9] 18.0.2 Synonyms: Tributylamine, TNBA, N,N-dibutyl-1-butanamine; and n-tributylamine 18.0.3 Trade Names: NA 18.0.4 Molecular Weight: 185.34 18.0.5 Molecular Formula: C12H27N 18.0.6 Molecular Structure:

18.1 Chemical and Physical Properties 18.1.1 General It is a hygroscopic liquid, sparingly soluble in water and very soluble in alcohol and ether (73, 74). 18.2 Production and Use Tributylamine is manufactured by the reaction of ammonia and n-butanol at elevated temperature and pressure in the presence of silica–alumina; from butyl bromide and ammonia; or by reaction of butyl chloride and ammonia. It is used as a solvent, an inhibitor in hydraulic fluids, a dental cement, and in isoprene polymerization (51). 18.3 Exposure Assessment 18.3.1 Air: NA 18.3.2 Background Levels Kuwata et al. (104). 18.3.3 Workplace Methods: NA 18.3.4 Community Methods Hoshika (77). 18.4 Toxic Effects Exposure of four male and four female rats to 120 ppm for 19 6-h exposures caused nose irritation, restlessness, incoordination, and tremors; organs appeared normal at autopsy (119). An LD50 (rat oral) of 540 mg/kg has been reported (122). Tributylamine has reportedly caused central nervous system (CNS) stimulation and skin irritation and sensitization (73, 74). 18.5 Standards, Regulations or Guidelines of Exposure Standards have not been adopted.

Aliphatic and Alicyclic Amines Finis L. Cavender, Ph.D., DABT, CIH 19 tert-Butylamine 19.0.1 CAS Number: [75-64-9] 19.0.2 Synonyms: Trimethylcarbinylamine, t-butylamine, 2-aminoisobutane, 1,1-dimethylethylamine, and

trimethylaminoethane 19.0.3 Trade Names: NA 19.0.4 Molecular Weight: 73.14 19.0.5 Molecular Formula: (CH3)3CNH2 19.0.6 Molecular Structure:

19.1 Chemical and Physical Properties 19.1.1 General It is a colorless, flammable liquid, miscible with alcohol (73, 74). 19.2 Production and Use tert-Butylamine is manufactured by reacting isobutylamine with sulfuric acid followed by cyanide to tert-butylformamide. Hydrolysis yields t-butylamine. It is used as a solvent and in organic syntheses. 19.3 Exposure Assessment 19.3.1 Air Nishikawa and Kuwata (120). 19.3.2 Background Levels Kuwata et al. (104). 19.3.3 Workplace Methods Crommen (123). 19.3.4 Community Methods Hoshika (77). 19.4 Toxic Effects The acute oral LD50 for Sprague–Dawley rats (males + females) has been reported to be 80 mg/kg (117). Liver toxicity NOEL was reported to be 0.20 mg/L for female Sprague–Dawley rats (122). 19.5 Standards, Regulations, or Guidelines of Exposure Standards have not been adopted.

Aliphatic and Alicyclic Amines Finis L. Cavender, Ph.D., DABT, CIH 20 Triisobutylamine 20.0.1 CAS Number: [1116-40-1] 20.0.2 Synonyms: TIBA (73, 74), 2-methyl-N,N-bis (2-methylpropyl)-1-propanamine, and tris(2-methylpropyl)amine 20.0.3 Trade Names: NA 20.0.4 Molecular Weight: 185.36 20.0.5 Molecular Formula: C12H27N 20.0.6 Molecular Structure:

20.1 Chemical and Physical Properties 20.1.1 General 20.2 Production and Use Triisobutylamine is manufactured from isobutanol and ammonia under heat and pressure (51). 20.3 Exposure Assessment 20.3.1 Air: NA 20.3.2 Background Levels Kuwata et al. (104). 20.3.3 Workplace Methods: NA 20.3.4 Community Methods Hoshika (77). 20.4 Toxic Effects No toxicology information was located in the literature (51). 20.5 Standards, Regulations, or Guidelines of Exposure Standards have not been adopted.

Aromatic Nitro and Amino Compounds Elizabeth K. Weisburger, Ph.D., Vera W. Hudson, MS General Logically, aromatic nitro and amino compounds should be discussed together because their toxic responses are often similar due to a common metabolic intermediate. Synthetically, amines are generally derived from nitro compounds, but in some cases nitro compounds can be prepared through amines when other methods fail to afford specific compounds. There are good and bad attributes to these types of compounds. Some act as sensitizers and contingent on physical properties, may be absorbed through the skin or mucous membranes. They may also cause methemoglobinemia, depending on such factors as the structure and the particular organism. Some members of this class are known as animal and human carcinogens; for humans the urinary bladder is the most prominent target organ. Nevertheless, these compounds and their derivatives have enlivened our world through their use as dyestuff intermediates or as photographic chemicals, they alleviate pain as components of widely used analgesics, and they cushion or insulate us through their use in flexible and rigid foams. Other important uses include production of pesticides, including herbicides and fungicides, as ingredients in adhesives, paints and coatings, antioxidants, explosives, optical brighteners, rubber ingredients, and as intermediates in many other products.

Aromatic Nitro and Amino Compounds Elizabeth K. Weisburger, Ph.D., Vera W. Hudson, MS Aromatic Nitro Compounds Aromatic nitro compounds are generally made by nitrating an aromatic hydrocarbon such as benzene

or toluene. Production has moved to continuous processes; in some facilities, jet impingement reactors allow more rapid production and lower formation of unwanted by-products; in vapor phase reactors, nitric acid and benzene flow through a solid catalyst in a continuous phase. These processes are beneficial in reducing waste. Production figures vary from year to year, depending on economic conditions, but in 1994 U.S. production of nitrobenzene was of the order of 740,000 tons (1). The nitro aromatics are starting materials for further syntheses. Most are reduced to the corresponding amines that provide convenient substituents or “handles” for many other syntheses. The toxic properties of aromatic nitro compounds were discussed in the previous edition of this series (2). These attributes of the compounds are well-known and various regulatory agencies worldwide have set exposure limits for them.

Aromatic Nitro and Amino Compounds Elizabeth K. Weisburger, Ph.D., Vera W. Hudson, MS Aromatic Amino Compounds Reduction of aromatic nitro compounds afford the amines that are starting materials for further syntheses. The amines share many of the toxic properties of the nitro compounds, as discussed previously (2), including skin sensitization, anemia, methemoglobinemia, irritation, hematuria, and for certain ones, bladder carcinogenesis. This aspect of aromatic amines has led to banning the manufacture of some and strict exposure limits on others. Nonetheless, research on some aromatic amines, especially 2-acetylaminofluorene (2-AAF), has led to a better understanding of the steps involved in carcinogenesis (3). 1.1 Chemical and Physical Properties This topic was discussed fairly extensively in the previous edition, and no significant new information was found. 1.4 Toxic Effects 1.4.1 Experimental Studies One of the initial toxic responses to aromatic amines or nitro compounds is the formation of methemoglobin within the red blood cells and subsequent deleterious effects. There are decided species differences in response to methemoglobin formers (2). The complete tertiary structures of hemoglobin and its subunits have been mapped and described. Normal adult hemoglobin is an oligomeric protein (MW about 67,000) that has four separate globin peptide chains: two alpha chains and two beta chains (4). Each of these peptide chains has a noncovalently bound porphyrinic heme group that is enclosed in a hydrophobic pocket by the globin chain. If oxidation of the ferrous iron to ferric occurs in the center of the protoporphyrin IX ring, the resulting greenish-brown to black pigment cannot combine reversibly with oxygen, leading to symptoms of oxygen deficiency such as cyanosis and a consequent bluish tinge to the skin. There are three types of substances that produce methemoglobin (5): 1. Those active either in vitro or in vivo include sodium nitrite, aminophenols, phenyl- and other hydroxylamines, and amyl nitrite. Phenylhydroxylamine can act cyclically; after reducing oxyhemoglobin, it generates nitrosobenzene that is reduced again to phenylhydroxylamine by the red cell enzymes, thus generating more methemoglobin. 2. Those active only in vivo, indicating the need for some process before the primary compound interacts with hemoglobin; this group encompasses aromatic nitro and amino compounds. An example is that the N-hydroxy metabolite of p-aminopropiophenone (PAP) is recognized as the moiety actually responsible for the methemoglobin-inducing action of PAP. 3. A third group includes compounds that are more active in lysates or in solutions of hemoglobin than in intact cells; specific examples are potassium ferricyanide, molecular oxygen, and methylene blue.

Although methemoglobinemia from exogenous substances can induce a dramatic change in skin color and can be serious condition, a relatively benign hereditary type can also occur due to a genetic deficiency in cytochrome b5 (6). Treatment of methemoglobinemia involves cessation of exposure to the toxin and limited intravenous administration of methylene blue due to possible hemolysis if more than two doses are given. Methemoglobin reductase enzyme or cytochrome b5 is the electron carrier between NADH and methemoglobin, facilitated by formation of a complex between the two molecules. The cytochrome binds to four lysine moieties in the heme pocket in both chains, and a hydrogen bond between one of the lysines of the cytochrome is a bridge between two heme propionic acid side chains of both heme proteins and affords a micropath for electron transport. In this chapter, occupational exposure to aromatic amines and nitro compounds is the primary concern. However, medicinal agents that contain aromatic amino or acetylamino groupings may also cause methemoglobinemia, especially from continued exposure (7–9). Thus, methemoglobinemia, besides being an occupational concern, can be an environmental one, if one considers the total environment. 1.4.2 Human Experience Research on aromatic amines has usually emphasized the adducts of the active metabolic intermediates with deoxyribonucleic acid (DNA) as indicators of possible genetic damage. It has been recognized that the metabolites also form hemoglobin adducts that are present in much larger amounts than DNA adducts. These adducts are not repaired as are DNA adducts, and they have a finite half-life (10–12). Using gas chromatography/mass spectrometry, hemoglobinaromatic amine adducts can be measured fairly readily. These types of studies have demonstrated that aromatic amines, including aniline derivatives and the carcinogens 4-aminobiphenyl, 2naphthylamine, and 2-aminofluorene, are present in tobacco smoke and form hemoglobin adducts (12, 13). Although there appeared to be a baseline level, adduct levels were increased 3- to 10-fold in the blood of smokers (9, 11) and were found in fetuses exposed to tobacco smoke in utero (12). Persons who acetylated aromatic amines more slowly had higher levels of the adducts than those who were rapid acetylators (10), implying that the free amine was necessary to initiate hemoglobin binding. This was supported by an extensive study of more than 20 nitroarenes and the corresponding amines that aimed at developing structure-activity relationships for hemoglobin binding in rats. The amine bound to a greater extent than the nitroarene. The highly substituted nitroarenes 2,4-dimethyl-, 3,4-dimethyl-, 2,6-dimethyl- and 2,4,6-trimethylnitrobenzene and 2,3,4,5,6-pentachloronitrobenzene did not bind to hemoglobin. All of the corresponding amines, except for pentachloroaniline, bound to hemoglobin. The implications were that due to structural interference, nitro reductase enzymes were prevented from acting on these nitroarenes, and thus hemoglobin binding was blocked (14). 1.4.3 Pharmacokinetics, Metabolism, and Mechanisms During metabolism, aromatic nitro and amino compounds may go by either of two pathways, detoxication or activation to toxic intermediates. Hydroxylation on the aromatic ring to yield a phenol is the first phase of detoxication. Further oxidative reactions may lead to demethylation of dimethylanilines or formation of quinoid derivatives of aminophenols. Conjugation of the phenol thus formed with glucuronic and/or sulfuric acid affords more soluble compounds that are readily excreted. Acetylation of an aromatic amine or formation of N-glucuronides are also detoxication pathways. Removal of a nitro group from some dinitroarenes and conjugation with glutathione ending as a mercapturic acid occurred (2, 15–17). Activation to a toxic intermediate often leads to a common substance from nitro- or aminoarenes. Amines/amides undergo oxidation of the nitrogen to form N-hydroxylamines or amides; nitro compounds are reduced through nitroso and hydroxylamine stages. The hydroxylamines are largely responsible for the methemoglobinemia from these materials. Overall, many metabolites may be formed from one compound, depending on the structure and the animal species. Carcinogenic aromatic amines follow the same metabolic paths as other amines, namely ring hydroxylation, conjugation, and excretion. Hydroxylation of the nitrogen, followed by formation of a

reactive sulfate or acetate ester that yields a reactive electrophilic arylnitrenium ion (Ar-N+-H) is involved. The nitrenium ion can arylate DNA, which is considered a crucial event in carcinogenesis (17), at least for genotoxic carcinogens. Further discussion follows in Section 1.4.5. Although the P450 system is a major factor in oxidative detoxication and activation of nitro- and aminoarenes (15, 18–20), flavine-dependent enzymes and peroxidases such as prostaglandin H synthase also oxidize amines, including benzidine and 2-aminofluorene (21). The P450 system was so named for the wavelength of the carbon monoxide derivative of the reduced form of the hemoprotein, namely, 450 nm (20). Originally though to be only one protein, further research aided by better separation methods has indicated there may be several hundred, if not more, isoforms of this enzyme, depending on the species. Thus P450 consists of a superfamily of hemoproteins that are important in metabolizing both xenobiotics and endogenous substances. Nomenclature of the P450 enzymes was originally based on the method used to induce them; this changed to a system based on the protein and now based on the chromosomal location (19, 20). Accordingly, P450IIA1 is being replaced by CYP2A1; corresponding changes for other isoforms hold. There are seven steps involved in the oxidation of a chemical by a P450 isoform: (1) binding of the substrate to the ferric form of the enzyme, (2) reduction to the ferrous form by NADPH-cytochrome P450 reductase, (3) binding of molecular oxygen, (4) introduction of a second electron from P450 reductase and/or cytochrome b5, (5) dioxygen cleavage that releases water and forms the active oxidizing species, (6) substrate oxygenation, and (7) product release (18). The P450 enzymes can be induced by numerous substances, including phenobarbital, ethanol, aromatic hydrocarbons such as 3-methylcholanthrene, dioxin, and the pesticides DDT and chlordane. Likewise, they can be inhibited by certain benzoflavones, thiocarbamates, disulfiram, and some heterocyclic nitrogen compounds. Selective induction and inhibition of the P450 isoforms has been demonstrated in laboratory experiments. Experimentally, the carcinogenicity of aromatic amines could be decreased or inhibited by simultaneous administration of certain enzyme inducers. Similarly, deleterious effects in humans have sometimes occurred from drug/drug or drug/environmental substance interactions due to induction/inhibition of P450 enzymes. Environmental substances include those from occupations, hobbies, food, alcohol, and tobacco smoke. P450 isozymes important in metabolizing nitro- and aminoarenes include CYP1A2 for phenacetin, 4-aminobiphenyl, 2-naphthylamine, and 2-AAF; CYP2A6 for 6-aminochrysene and 4,4'-methylene bis(2-chloroaniline) MOCA®; CYP2B for the same two compounds; CYP2E1 for aniline, acetaminophen, and p-nitrophenol. CYP3A is involved in oxidative metabolism of MOCA®, 6amino- and 6-nitrochrysene, and 1-nitropyrene, among others (20). The expression of the P450 enzymes is also mediated by the genetic background that leads to differences in the rate of oxidation. One study showed that most Australians were rapid metabolizers, but some were in the slow and intermediate categories. Chinese and Japanese were mostly intermediate, whereas residents of Arkansas and Georgia in the southern United States were largely intermediate, although persons in the slow and rapid classes were also in this population (22). The relationships among aromatic amine acetylation, genetic background, and susceptibility to the carcinogenic effect of amines were recognized some decades ago. Interest in this area has been fairly intensive and led to many publications on N-acetyl-transferases. The acetyl transferase enzyme has at least two forms: NATI that is monomorphic and acetylates aromatic amines; NAT2 that is polymorphic and N-acetylates aromatic amines but also O-acetylates hydroxylamines. These enzymes have molecular weights of approximately 29 and 31 kDa (23, 24). Slow human acetylators

are associated with increased risk of bladder cancer, and rapid acetylators are associated with higher rates of colorectal cancer. The implication is that localized metabolic activation of arylamine type carcinogens is facilitated by NAT2 in colon tissue. Apart from occupational exposure to aromatic amines, other sources of exposure to such compounds are from smoking tobacco or eating large amounts of meat. Various heterocyclic amines are formed by the ordinary methods for cooking meat (grilling, frying) which are animal carcinogens and act like aromatic amines in their metabolic pathways. Only NAT2 acetylated these compounds (25). Besides leading to partial identification of the acetyl transferase enzymes, molecular techniques, led to construction of transgenic animals which delineated the characteristics of the isozymes to a greater extent (26, 27). Experiments with such animals supported the human epidemiological results; animals that were rapid acetylators showed a higher response to colon carcinogens (28, 29). 1.4.4 Carcinogenesis The United States, as do many other developed countries, has an aging population and increased age leads to a higher risk of cancer. It is estimated that 565,000 people will die of cancer in 1998. During many decades of life, the cells in individual organs undergo trillions or more of cell divisions, and opportunities for error occur in each one of those divisions. Biologically, cell proliferation or division is considered a risk factor for cancer. In addition, many factors in the environment may be responsible for human cancer. A monumental epidemiological study concluded that 2-4% of cancers in the United States were ascribable to occupation, 8–28% to the use of tobacco, 40–57% to diet, 8% to exposure to sunlight, and unknown or undefined factors were responsible for 16–20% (30). Less well defined influences include genetic background, viruses, certain medicinal agents, radiation, alcohol use, certain types of behavior, socioeconomic status, and even methods for cooking or preserving foods (31, 32). Although the estimate of the percentage of cancers ascribed to occupation is relatively low, it still is necessary to follow the guidelines promulgated by various regulatory and advisory agencies to minimize the risk of developing cancer. For nitro- and aminoarenes, avoidance of direct contact is important because they are fairly readily absorbed through the skin at levels sufficient to cause toxicity. Thus, the numerous “skin” notations in the advisory listings of the American Conference of Governmental and Industrial Hygienists (ACGIH) are necessary. The carcinogenicity of aromatic amines for the human bladder was noted about 30 years after widespread use of these compounds occurred in dyestuff factories. After another 40 years, animal studies supported this premise (2, 3). Even with improved workplace conditions and much lower exposures than the original dyestuff workers had, more current surveys still indicate an increased risk of bladder cancer (33). Aromatic amines generally did not induce tumors at the point of application, but at distant sites, including liver, intestine, and bladder. The actual organs affected varied with the species and strain; 2-naphthylamine targets the bladder in humans, monkeys, dogs, and hamsters but has little effect in rabbits. 2-AAF affected the liver and mammary gland in most strains of rats and mice, but X/Gf mice and guinea pigs were resistant. Metabolic and mechanistic studies provided clues for the differences in some cases (i.e., guinea pigs do not N-hydroxylate 2AAF) but not in others (34). The carcinogenicity of any particular molecular structure can often be altered dramatically by adding substituents (35). A premise that adding a methyl group ortho to the amino moiety in 2naphthylamine would reduce carcinogenicity was shown erroneous when 3-methyl-2-naphthylamine turned out to be more active than the parent amine (36). On the other hand, adding polar moieties has nullified carcinogenic action. Sulfonic acid derivatives of 2-naphthylamine (37) and 4,4'diaminostilbene were inactive (38). However, even if an aromatic amine is not carcinogenic, other possible toxic effects such as methemoglobinemia should be kept in mind. Carcinogens are divided into groupings, depending on their mode of action. Because of their structures, direct acting ones react as such with cellular macromolecules, especially DNA. Usually such compounds are not stable and are not a hazard to the general population. In contrast, nitro- and

aminoarenes, are indirect acting because they require metabolic activation before they interact with cellular targets. Metabolic activation is influenced by many factors: species, strain, sex, age, diet, enzyme inducers/inhibitors, and immune status, plus others. Once activated, the intermediates react with the cell's genetic material and thus are considered genotoxic carcinogens. Some carcinogens such as chloroform, trichloroacetic acid, and unleaded gasoline caused animal tumors but did not attach to cellular DNA. These compounds are called nongenotoxic or epigenetic carcinogens (39). Mechanisms for the action of epigenetic carcinogens are varied and usually show little or no relevance to human risk. Classification of carcinogens has been addressed before (2), but changes have occurred to some extent in how governmental and other groups have developed systems for classifying the degree of risk associated with chemical carcinogens. In 1969, the International Agency for Research on Cancer (IARC) initiated a program to evaluate the risk in humans according to the following system: Group 1—The agent (mixture) is carcinogenic to humans; Group 2A—The agent is probably carcinogenic to humans; Group 2B—The agent is possibly carcinogenic to humans; Group 3—The agent is not classifiable as to its carcinogenicity to humans; Group 4—The agent is probably not carcinogenic to humans (40). The National Toxicology Program (NTP) of the U.S. Department of Health and Human Services has only two categories in its various reports on carcinogens: (1) substances or groups of substances, occupational exposures associated with a technological process, and medical treatments that are known to be carcinogenic; and (2) substances or groups of substances and medical treatments that may reasonably be anticipated to be carcinogens. Known carcinogens are defined as those for which the evidence from human studies indicates that there is a causal relationship between exposure to the substance and human cancer. Reasonably anticipated to be carcinogens encompasses those for which there is limited evidence of carcinogenicity in humans or sufficient evidence from tests in experimental animals (41). The U.S. Environmental Protection Agency (EPA) formerly had an A to E system as follows: A— known human carcinogen; B—probably carcinogenic to humans; C—possibly carcinogenic to humans; D—not adequately tested; E—tested and negative. The EPA is moving toward a narrative system that takes into account differences between humans and experimental animals in metabolism and mechanism of action. The system is as follows: Known/likely—the available tumor effects and other key data are adequate to convincingly demonstrate carcinogenic potential for humans. Cannot be determined—available tumor effects or other essential data are suggestive or conflicting or limited in quality and thus are not adequate to demonstrate a carcinogenic potential convincingly in humans. Not likely—Experimental evidence is satisfactory to decide that there is no basis for concern as to human hazard. The EPA system is not final, and new EPA classifications for industrial/environmental chemicals have not been published. The U.S. Occupational Safety and Health Administration (OSHA) included the following aromatic amines or derivatives in its 1974 standards to minimize or control exposure: 2-AAF, 4aminobiphenyl, benzidine, 3,3'-dichlorobenzidine, 4-dimethylaminoazobenzene, 1-naphthylamine, 2naphthylamine, and 4-nitrobiphenyl (2). The ACGIH, which is active in setting exposure limits for workplace chemicals, adopted the following system approximately 10 years ago: 1. Confirmed human carcinogen. The agent is carcinogenic to humans based on the weight of the evidence from epidemiologic studies.

2. Suspected human carcinogen. The agent is carcinogenic in experimental animals at dose levels, by route(s) of administration, at site(s) of histologic type(s), or by mechanism(s) that are considered relevant to worker exposure. Available epidemiological studies are conflicting or insufficient to confirm an increased risk of cancer in exposed humans. 3. Animal carcinogen. The agent is carcinogenic in experimental animals at a relatively high dose, by route(s) of administration, at site(s), of histological type(s) or by mechanisms(s) that are not considered relevant to worker exposure. Available epidemiological studies do not confirm an increased risk of cancer in exposed humans. Available evidence suggests that the agent is not likely to cause cancer in humans except under uncommon or unlikely routes or levels of exposure. 4. Not classifiable as a human carcinogen. There are inadequate data on which to classify the agent in terms of carcinogenicity in humans and/or animals. Substances for which animal tests are negative without further evidence of relevant mechanisms fall into this category. 5. Not suspected as a human carcinogen. The agent is not suspected to be a human carcinogen on the basis of properly conducted epidemiological studies in humans. These studies have sufficiently long follow-up, reliable exposure histories, sufficiently high dose, and adequate statistical power to conclude that exposure to the agent does not convey a significant risk of cancer to humans. Evidence that suggests a lack of carcinogenicity in animals will be considered if it is supported by other relevant data (42). Increased emphasis on cooperation between countries and the formation of the European Union make it expedient to be informed of the systems employed by the Union and the German MAK (Maximum allowable concentration) Commission (43). The European Union proposes the following: 1. Substances known to be carcinogenic to humans 2. Substances that should be regarded as if they are carcinogenic to humans 3. Substances that cause concern for humans owing to possible carcinogenic effects 1. Substances that are well investigated 2. Substances that are insufficiently investigated The German MAK system is as follows: 1. Substances that cause cancer in humans. 2. Substances that are considered carcinogenic to humans. 3. Substances that cause concern that they could be carcinogenic to humans but which cannot be assessed conclusively because of lack of data. 4. Substances with carcinogenic potential for which genotoxicity plays no or at most a minor role. No significant contribution to human cancer risk is expected, provided that the MAK value is observed. 5. Substances with carcinogenic and genotoxic potential, the potency of which is considered to be so low, provided that the MAK value is observed, that no significant contribution to human cancer risk is to be expected. In the MAK system, more emphasis is placed on the genotoxicity of substances, as detected by mutagenicity or other short-term tests, than on animal tests for carcinogenicity. For reasons of cost and time, determining the mutagenic potential of a substance in specific strains of bacteria has become a surrogate for long-term studies. The most widely used of these tests involves measuring the ability of a substance to induce mutations and thus bacterial colony growth in strains of Salmonella typhimurium. Of the S. typhimurium strains, TA1538, which has a frameshift mutation, is more likely to respond to aromatic amines. New strains are developed frequently, but baseline data for many compounds have been obtained for strains TA100, TA98, TA1535, TA1537, and TA1538.

Addition of a liver fraction (S9) to the test culture allows measuring the effect of metabolic activation on mutagenicity (44). However, the correlation between mutagenicity in bacteria and carcinogenicity in animals is not absolute and holds in approximately 60% of cases. It was found that using additional types of shortterm tests involving animal cells or systems did not appreciably increase the accuracy of the test. Accordingly, the Salmonella system represents the easiest and least expensive of the short-term systems and has an accuracy comparable to other more expensive and more complicated tests. On the downside, the Salmonella system is not totally accurate in detecting carcinogens, and the opposite can occur. Sodium azide was an active mutagen, but it was inactive in animal tests for carcinogenicity. Conversely, benzene and hexamethylphosphoramide are not mutagens in the usual test systems, but they are carcinogens in humans and animals, respectively. The fairly potent animal carcinogens o-anisidine and p-cresidine were not genotoxic in three animal-based short-term tests, namely, unscheduled DNA synthesis, DNA single-strand breaks, and effects in micronuclei. The tests were performed with four strains of rats and two strains of mice (45). Thus, total reliance on short-term tests can be misleading. Many potentially useful compounds have been discarded along the path to development because of positive mutagenicity tests. But the results from short-term tests, if used judiously, can afford clues as to which compounds are more likely to be active in long-term animal studies. Such efforts are costly and require several years and involvement from people trained in many disciplines to complete a study well (46). In the United States, the NTP is the one agency that is primarily responsible for testing compounds in chronic studies. 1.4.5 Genetic and Related Cellular Effects Studies The advances in knowledge about the association between specific enzymes and the possible increased risk of developing cancer from occupational exposure have led to a new social concern. Employers may wish to use genetic screening to differentiate workers at greater risk from those less likely to be affected, but there are many uncertainties in the screening tests that make total reliance on them problematic (47–49). Furthermore, because of the genetic polymorphisms that involve enzymes which metabolize xenobiotics such as aromatic amines, matters of individual variation and individual rights must be considered. As mentioned previously, there are slow, intermediate, and rapid metabolizers of xenobiotics due to levels of expression of CYP1A2 in most populations. Likewise, although persons of certain backgrounds are more likely to acetylate aromatic amines rapidly, this is not absolute. Based on the identification of up to 9 different alleles for the slow acetylator phenotype, 45 different slow acetylator genotypes, 9 heterozygous rapid genotypes, and 1 homozygous wild-type rapid genotype, all combined with the slow, intermediate and rapid CYP1A2 types, it becomes evident that many combinations are possible. Thus an observed “polymorphism” may reflect a great number of genotypes. Instead of a well-defined genetic polymorphism, there can be much biochemical individuality in a population (22, 50). Any test to differentiate individuals into the different categories must be accurate, but false negatives and false positives complicate the picture. In addition, enzyme induction by dietary or other exposures, including alcohol, tobacco, and medications is a further complication. Available genetic screening tests are not sufficiently validated for routine use. For the individual, matters of decisional autonomy, confidentiality of medical information, beneficence, nonmaleficence, and equity are issues of concern. Possible discrimination, protection of equal employment opportunity, and potential stigmatization must also be considered. These concerns have been raised worldwide (51–55). Experts in this area concluded that in view of the uncertainties, removing the chemical carcinogen from the workplace by substituting a noncarcinogenic compound or achieving a zero level of exposure is more effective in preventing occupational cancer than genetic screening (50). These issues will probably remain a matter of discussion for years to come. 1.4.6 Reproductive and Developmental The previous edition of this chapter pointed out the toxicity of nitrobenzene for the male reproductive system when given at doses up to 30 times the limit set for

occupational exposure (2). The related substance, 1,3-dinitrobenzene, also produces testicular toxicity, affecting the Sertoli cells of the testis. Further studies have implicated the metabolite 3nitrosonitrobenzene as the prime candidate for the toxic effect because the other metabolites 3nitrophenylhydroxylamine and 3-nitroaniline were not active (56). Similarly, other nitroarenes such as 2,4- and 2,6-dinitrotoluene were toxic to the testis, indicating that workplace exposures to such compounds should be kept to a minimum. Additional investigation revealed that nitrobenzene at 300 mg/kg and 1,3-dinitrobenzene at 30 mg/kg suppressed the formation of proteins usually secreted during spermatogenesis. With labeled methionine incorporation as a marker, nitrobenzene decreased formation of proteins usually secreted during stages VI-VIII and IX-XII, but had no effect in the earlier stages II–IV. Results were comparable for 1,3-dinitrobenzene except that incorporating methionine at stages II-V was increased. Six marker proteins for which secretion was reduced greatly after the nitobenzenes were studied; two of these proteins corresponded to two androgen-regulated proteins thought to be products of the Sertoli cell (57). A survey of aromatic nitro and amino compounds tested for reproductive/teratogenic effects indicated that in general, relatively high doses of most aromatic amines to the maternal organism were required to produce a result. In some cases, doses of 5 g/kg or more were needed (2, 58). Thus, by observing hygienic guidelines, the risk of reproductive toxicity would be relatively small. However, aromatic amines may lead to “oxidative stress,” methemoglobinemia, anemia, and other types of toxicity. They may also target the hypothalamus and pituitary (59). Collectively, these actions are likely to influence fertility or successful completion of a pregnancy. 1.5 Studies on Environmental Impact Although nitroarenes and amines are toxic to many species, biodegradation of such compounds is facilitated by the nitro reductase and oxidative enzymes present in sewage bacteria (60). Most of the aromatic amines are oxidatively degraded by bacteria in wastewater unless adsorbed to soil, where they are more resistant to action. However, in the presence of denitrifying and methanogenic microbial activity, aniline was released from the soil and degraded readily (61). Additional substituents in the molecule often led to slower breakdown (62). Acclimating activated sludge with both aniline and toluenediamine, which has been considered a resistant-type compound, led to a reasonable rate of biodegradation of the toluenediamine (63). Biodegradation of multiring aromatic amines was highly dependent on microbial activity, as shown by increases in decomposition at higher temperatures (30°C). Consistent relationships between breakdown of the amines and soil properties were not noted (64). 2,4,6-Trinitrotoluene (TNT) and associated compounds that occur in wastewaters are both toxic and phototoxic to many organisms usually found in streams; one metabolite 2-amino-4,6-dinitrotoluene was more phototoxic than TNT and 4-amino-2,6-dinitrotoluene. The toxicities of TNT and the two derivatives to stream organisms were decreased by glutathione conjugation (65). Although 4-chloroaniline delayed somewhat the various lifestages of small fish (66), 3,4dichloroaniline, a degradation product of the herbicide propanil, is of special concern. It affects various benthic invertebrates, leading to complete extinction of some and reduction in the number of surviving individuals in others (67, 68). A mixture of 3,4-dichloroaniline and lindane had an additive effect and influenced growth somewhat in early life stages of small fish (69). If the fish were exposed for the whole life span, they stopped reproducing (70). There was no single clear-cut mechanism to explain the toxicity of 4-nitro- and 2,4-dinitroaniline to various environmental eukaryotes and prokaryotes (71). Currently, there are many efforts to develop special strains of bacteria to degrade industrial wastes. Similarly, production of bacterial strains with enhanced P450 protein expression has been suggested as a useful tool to biodegrade industrial and other contaminants (72). Such methods of cleaning industrial sites and waste dumps are less disruptive than other methods currently used or proposed.

Although most of the nitroarenes mentioned in this chapter generally are industrial materials, some have been detected in ambient airborn particulates, including those from diesel engine exhausts (Table 57.1). Nitrogen oxides react with polycyclic aromatic hydrocarbons (PAHs) in the heated engine exhaust to form nitroarenes at nano- to picogram/m3 levels; at least 25 have been detected in such exhausts (73–76). Almost 100 PAHs have been found in engine exhausts (75), and the number of nitroarenes formed is correspondingly large because each PAH is amenable to nitration at several positions. However, only about 25 have been positively identified (74, 75). Nitroarenes generally are mutagens in Salmonella (77–79). Tests for carcinogenicity have shown varying potencies. 1Nitronaphthalene was inactive in a feeding study with rats and mice (80), but most of the other environmental nitroarenes have shown surprising potency (81–84). Many organ systems were affected, including lung, colon, and breast. There have been any number of investigations on the metabolism and DNA binding of nitroarenes and only a few are cited here (85, 86). In general, these compounds are hydroxylated to phenols that are excreted as sulfate and glucuronide conjugates. Reduction to the amine with N-hydroxylation and DNA binding also occurs (87). The metabolic pattern and degree of DNA binding did not always correlate with the carcinogenic potency of a particular nitroarene (86). Table 57.1. Physical Properties of Some Nitroarene Air Pollutantsa

Compound

CAS Number

3,7Dinitrofluoranthene 3,9Dinitrofluoranthene 2,7-Dinitrofluorene

[10573571-5] [22506-532] [5405-538] 2,7-Dinitrofluorenone [31551-458] 1,3-Dinitropyrene [75321-209] 1,6-Dinitropyrene [42397-648] 1,8-Dinitropyrene [42397-659] 9-Nitroanthracene [602-60-8] 7-Nitrobenzo[a] [20268-513] anthracene 1-Nitrobenzo[a] [70021-997] pyrene 3-Nitrobenzo[a] [70021-986] pyrene 6-Nitrobenzo[a] [63041-907] pyrene 6-Nitrochrysene [7496-028] 3-Nitrofluoranthene [892-21-7] 2-Nitrofluorene

[607-57-8]

Molecular Weight

Melting Point (°C) Physical Form

292.3

203–204

Yellow needles

292.3

275–276

256.2

334

270.2

292–295

292.3

297–298

292.3

310

292.3

300

223.2 273.3

145–146 160–163

297.3

250–250.5

Yellow-orange crystals Light yellow solid Deep yellow solid Orange crystals Yellow crystals Fluffy yellow crystals Yellow needles Yellow crystals Orange solid

297.3

211–212

Orange solid

297.3

255–256

Orange solid

273.3

209

247.3

156–160

211.2

156

Orange-yellow needles Yellow crystals Light yellow

4-Nitronaphthalene 2-Nitronaphthalene 3-Nitroperylene 1-Nitropyrene 2-Nitropyrene 4-Nitropyrene

[86-57-7] [581-89-5] [20589-633] [5522-430] [789-07-1]

173.2 173.2 297.3

61.5 79 210–212

247.3

155

247.3

197–199

[57835-924]

247.3

190–192

needles Yellow needles Yellow needles Brick-red crystals Yellow needles or prisms Yellow crystals Orange needles

a

Data bases: AIDSLINE, DART, EINECS, GENE-TOX, CANCERLIT, CCRIS, EMIC, EMICBACK, IARC, MEDLINE, MESH, RTECS, TSCAINV, TOXLINE, SUPERLIST.

The relevance to human cancer has been addressed both theoretically (88) and practically (89). Assays of excised lung tumors from nonsmoking Japanese demonstrated the presence of 1nitropyrene, 1,3-dinitropyrene, and 1-nitro-3-hydroxypyrene in the tissues (89). In similar specimens from rural Chinese who had been exposed to open cooking fires, some 1-nitropyrene was detected, but the levels of PAHs were many times higher than in the Japanese specimens. Nitroarenes could thus be a possible factor in lung and other types of cancers. Reduction in both PAHs and nitrogen oxides in engine exhausts is needed to decrease this possible cancer risk.

Aromatic Nitro and Amino Compounds Elizabeth K. Weisburger, Ph.D., Vera W. Hudson, MS Specific Compounds In this section, compounds with one aromatic ring will be discussed first, then those with two rings, et cetera. Any new developments regarding toxicity or mechanisms of action are emphasized. Because this is an age of computerized databases or inventories, for each compound, the bases/inventories which list that specific compound will be mentioned. The codes for these lists or inventories are given in Table 57.2. Table 57.2. Database/List Acronyms for Chemicals Acronym ATSDR CA65 CAA1 CAA2 CANCERLIT

Name Agency for Toxic Substances and Disease Registry California List of Chemicals Known to Cause Cancer or Reproductive Effects Hazardous Air Pollutants Ozone Depletion Chemicals List Cancer Literature Bibliographic File

Producer ATSDR, Atlanta, GA CA EPA US EPA, Washington, DC US EPA, Washington, DC National Cancer Institute (NCI)

CATLINE CCRIS CGB CGN ChemID DART DEA DIRLINE DOT DSL EINECS ELIN EMIC & EMICBACK ETICBACK FIFR GENE-TOX GRAS HSDB IARC IL INER IRIS MA

Catalog on Line

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Aromatic Nitro and Amino Compounds Elizabeth K. Weisburger, Ph.D., Vera W. Hudson, MS Single-Ring-Compounds 1.0 Nitrobenzene 1.0.1 CAS Number: [98-95-3] 1.0.2 Synonyms: Nitrobenzol, and an old name of uncertain origin is oil of mirbane. 1.0.3 Trade Names: NA 1.0.4 Molecular Weight: 123.11 1.0.5 Molecular Formula: C6H5NO2 1.0.6 Molecular Structure:

Databases or inventories where listed: CAA1, CA 65, CANCERLIT, CCRIS, CGN, DART, DOT, DSL, EINECS, HSDB, IARC, MA, MI, MPOL, NJ, PA, PEL, REL, RQ, RTECS, S302, TLV, TSCAINV 1.1 Chemical and Physical Properties (2) Physical state Colorless to pale yellow liquid Density 1.2037 (20/4°C) Melting point 5.7°C Boiling point 210.9°C Vapor density 4.1 Refractive index 1.55291 Solubility Slightly soluble in water: very soluble in ethanol, ether; soluble in benzene, oils Flash point 88°C (closed cup) Odor Bitter almond 1.2 Production and Use Nitrobenzene is generally made by a continuous reaction process involving nitric acid and benzene in vapor-phase or jet-impingement reactors (1). Nitrobenzene is an intermediate in the preparation of aniline, in making cellulose esters and acetate, in shoe and metal polishes, in soap perfumes, paint solvents, leather dressings, and in refining lubricating oils to the extent of close to 2 billion pounds/year. 1.3 Exposure Assessment Analytical methods: NMAM 4th ed. method # 5053. 1.4 Toxic Effects The previous edition of this chapter mentioned the toxic effects of nitrobenzene which include skin and eye irritation, cyanosis, methemoglobinemia, hemolytic anemia, spleen and liver damage, jaundice, neural toxicity with renal and testicular damage also present. Although nitrobenzene depressed the immune response of female B6C3F1 mice, their resistance to microbial/viral infection

was not markedly altered (90). Noteworthy new information on nitrobenzene is that it also is carcinogenic in mice and rats (91). The study included male and female B6C3F1 mice, male and female F344 rats, and male CD rats. The mice were exposed by inhalation to 0,5, 25, or 50 ppm for 6 h/day, 5 days/week for 2 years, and rats were exposed to 0,1,5, or 25 ppm under the same time span as the mice. Survival of test animals was not significantly affected by nitrobenzene exposure, and body weights did not exceed a 10% deviation from controls. The exposure affected hematic parameters in both mice and rats, and there were significant differences in the incidences of nonneoplastic and neoplastic lesions. The incidence of alveolar/bronchiolar adenomas increased to a significant degree in 25- and 50-ppm exposed male mice, and the number of mice that had either adenomas or carcinomas was higher in all exposed groups. Alveolar/bronchiolar hyperplasia was increased in the 25- and 50-ppm males. Follicular cell adenomas of the thyroid were significantly higher in the 50-ppm males, and hyperplasia occurred in the 25- and 50-ppm males. In the female mice, mammary gland adenocarcinomas were increased at the 50-ppm level, plus a positive trend for hepatocellular adenoma related to nitrobenzene concentration. Hepatocytomegaly, multinucleated hepatocytes, inflammatory lesions of the nose, epididymal hypospermia, and other nonneoplastic effects were noted in the mice. In male F344 rats, nitrobenzene at 25 ppm led to increases in hepatocellular adenoma or carcinoma, renal tubular adenomas, or either renal adenoma or carcinoma with a positive trend for follicular cell adenoma or adenocarcinoma of the thyroid. Female F344 rats had a significant increase in endometrial stromal polyps of the uterus at 25 ppm. In both male and female rats, nitrobenzene exposures led to a striking decrease in mononuclear cell leukemia. Male F344 rats showed increases in extramedullary hematopoiesis (1 and 5 ppm) and pigmented macrophages (25 ppm). Increased focal inflammation of the olfactory region with pigment deposition was noted in both sexes. The male CD rats responded to nitrobenzene with significant increases in hepatocellular adenomas and spongiosis hepatis in the 25-ppm group. Centrilobular hepatocytomegaly and Kupffer cell pigmentation, atrophy of the testes, and nasal pigment deposition also occurred. The locations where tumors were induced differed based on species, sex, and for rats, on strain also. Some of the differences could possibly be related to differences in the metabolism of nitrobenzene, but the actual mechanism for the carcinogenicity of nitrobenzene has not been delineated. Because carcinogenic effects were noted at 25 ppm, industrial hygienists should monitor carefully so that workplace exposure does not exceed the permissible limit. 1.5 Standards, Regulations, or Guidelines of Exposure The current ACGIH TLV-TWA is 1 ppm with a skin and A3 notation; Australia 1 ppm, skin; Germany (BAT value), 100 mg/l; Sweden, 1 ppm; United Kingdom, 1 ppm; OSHA PEL and NIOSH REL is 1 ppm.

Aromatic Nitro and Amino Compounds Elizabeth K. Weisburger, Ph.D., Vera W. Hudson, MS A. Monochloronitrobenzenes 2.0 1-Chloro-2-nitrobenzene 2.0.1 CAS Number: [88-73-3]

2.0.2 Synonyms: o-Chloronitrobenzene, 2-chloro-1-nitrobenzene, 2-chloronitrobenzene, 2nitrochlorobenzene, 1-nitro-2-chlorobenzene, o-CNB, 2-CNB 2.0.3 Trade Names: NA 2.0.4 Molecular Weight: 157.56 2.0.5 Molecular Formula: C6H4NO2Cl 2.0.6 Molecular Structure:

Databases or inventories where listed: CGB, CGN, DOT, IARC, MA, NTPT, PA, WHMI, CANCERLIT, CCRIS, DART, EINECS, EMIC, EMICBACK, ETICBACK, HSDB, MEDLINE, MESH, RTECS, TOXLINE, TSCAINV, SUPERLIST. 2.1 Chemical and Physical Properties (2) Physical state Yellow crystals Melting point 34–35°C Boiling point 245–246°C Solubility Soluble in ethanol, benzene, ether, acetone 2.2 Production and Uses 1-Chloro-2-nitrobenzene is an important intermediate in preparing dyes and lumber preservatives and in making photographic chemicals, corrosion inhibitors, and agricultural chemicals (92). 2.4 Toxic Effects A 13-week inhalation study in male and female F344/N rats and male and female B6C3F1 mice at levels of 0, 1.1, 2.3, 4.5, 9, and 18 ppm for 6 h/day 5 days a week, demonstrated that hepatocellular necrosis and inflammation occurred in mice along with lesions of the spleen and hemosiderin deposition. In rats, these exposures led to hyperplasia of the epithelium lining the nasal cavity. Methemoglobinemia was noted in the rats (93). In the male mice and rats, there were decreases in sperm motility or spermatid count (92). A continuous breeding study in Swiss mice given 40, 80, or, 160 mg/kg by gavage showed no reproductive toxicity, but methemoglobinemia was observed in the parental animals (94). 1-Chloro-2-nitrobenzene was absorbed through the skin of male F344 rats to the extent of 33–40% in 72 h (92). Metabolism studies with 14C-labeled compound showed rapid excretion in the urine with up to 23 metabolites. Only about 5% remained in the animals by 72 h, mostly in the liver. Older rats absorbed and metabolized and then excreted the labeled compound at approximately the same rate as young rats. Hepatocytes from male F344 rats converted the nitro compound to 2-chloroaniline to a major extent, but 2-chloroaniline N-glucuronide, and S-(2-nitrophenyl)glutathione were also formed to an appreciable extent (92). Oral administration to male and female CD-1 mice at 3000 or 6000 ppm for 8 months followed by 1500 or 3000 ppm for 10 months led to increases in hepatocellular carcinomas in both males and females. In male CD rats, 1000 or 2000 ppm for 6 months, followed by 500 or 1000 ppm for 12

months, led to increased numbers of rats with multiple tumors (92). 2.5 Standards, Regulations, or Guidelines of Exposure Standards not assigned. 3.0 1-Chloro-3-nitrobenzene 3.0.1 CAS Number: [121-73-3] 3.0.2 Synonyms: 1-Chloro-3-nitrobenzene, m-chloronitrobenzene, 3-chloro-1-nitrobenzene, 3nitrochlorobenzene; 1-nitrochlorobenzene, MNCB, 3-CNB, m-CNB, nitrochlorobenzene 3.0.3 Trade Names: NA 3.0.4 Molecular Weight: 157.56 3.0.5 Molecular Formula: C6H4NO2Cl 3.0.6 Molecular Structure:

Databases or inventories where listed: DOT, IARC, MA, PA, WHMI, CANCERLIT, CCRIS, DART, EINECS, EMIC, EMICBACK, HSDB, MEDLINE, MESH, RTECS, TOXLINE, TSCAINV, SUPERLIST 3.1 Chemical and Physical Properties (2) Physical state Melting point Boiling point Solubility

Yellow prisms from ethanol 46°C

235–236°C Soluble in hot ethanol, chloroform, ether, carbon disulfide, benzene; insoluble in water Flash point 103°C 3.2 Production and Use 1-Chloro-3-nitrobenzene is an intermediate in the production of dyes and fungicides (92). 3.4 Toxic Effects In hepatocytes isolated from male rats, 1-chloro-3-nitrobenzene was converted mainly to 3chloroaniline with much lower amounts of 3-chloroaniline N-glucuronide. No glutathione conjugate was found (92). 3.5 Standards, Regulations, or Guidelines of Exposure None assigned. 4.0 1-Chloro-4-nitrobenzene 4.0.1 CAS Number: [100-00-5] 4.0.2 Synonyms: PNCB; nitrochlorobenzene; 1,4-chloronitrobenzene; 4-nitrochlorobenzene; 4chloro-1-nitrobenzene; para-nitrochlorobenzene 4.0.3 Trade Names: NA 4.0.4 Molecular Weight: 157.56

4.0.5 Molecular Formula: C6H4NO2Cl 4.0.6 Molecular Structure:

Databases and inventories where listed: DOT, IARC, IL, MA, MTL, NTPT, PA, PEL, PELS, REL, TLV, WHMI, CANCERLIT, CCRIS, DART, DSL, EINECS, EMIC, EMICBACK, HSDB, MEDL, MESH, RTECS, TOXLINE, TSCAINV, SUPERLIST. 4.1 Chemical and Physical Properties (2) Physical state Yellow crystals Specific gravity 1.52 Melting point 82–84°C Boiling point 242°C Vapor pressure 0.009 torr at 25°C Flash point 127°C (closed cup) Solubility Sparingly soluble in water; soluble in ether, carbon disulfide, ethanol, acetone 4.2 Production and Use 1-Chloro-4-nitrobenzene is employed in producing dyes, drugs, herbicides, antioxidants, and as an intermediate in synthesizing various compounds (92). 4.4 Toxic Effects A 13-week inhalation study in male and female F344/N rats and B6C3F1 mice at levels of 0, 1.5, 3, 6, 12, and 24 ppm, 6 h/day for 5 days/week led to increases in liver and spleen weights in rats, along with changes in kidney tubules and hematopoiesis. Methemoglobinemia was more severe than with the 2-isomer. Mice also showed changes in liver and spleen, and in females hyperplasia of the forestomach epithelium was noted (93). In male rats, spermatid counts were lower, but females were not affected. Mice showed no significant change (92). In a continuous breeding study with Swiss mice, exposure to 62.5, 125, or 250 mg/kg by gavage reduced the birth weight and viability of the pups (95). A dermal absorption study with F344 rats demonstrated that 51–62% of labeled 1-chloro-4nitrobenzene was absorbed within 72 h, and 43–45% was excreted in the urine. As with the 2isomer, the metabolism of the 4-isomer was not greatly influenced by age (92). In longshoremen accidentally exposed to 1-chloro-4-nitrobenzene, the same urinary metabolites were identified as in rats, namely, N-acetyl-S-(4-nitrophenyl)-L-cysteine, 4-chloroaniline, 4chloroacetanilide, 4-chloro-oxanilic acid, 2-amino-5-chlorophenol, 4-chloro-2-hydroxyacetanilide, 2,4-dichloroaniline and 2-chloro-5-nitrophenol (96). In a longer term study of 1-chloro-4-nitrobenzene, CD male and female mice fed 3000 or 6000 ppm in the diet for 18 months showed increases in hepatocellular carcinomas and vascular tumors in the males and vascular tumors in the females. Male CD rats given levels from 250 to 4000 ppm showed no increase in tumors (92). 4.5 Standards, Regulations, or Guidelines of Exposure The current ACGIH TLV-TWA is 0.1 ppm (0.64 mg/m3) with a skin notation; Australia, 0.1 ppm (skin); United Kingdom, 1 ppm (skin)

Aromatic Nitro and Amino Compounds Elizabeth K. Weisburger, Ph.D., Vera W. Hudson, MS B. Chlorodinitrobenzenes 5.0 2-Chloro-1,3-dinitrobenzene 5.0.1 CAS Number: [606-21-3] 5.0.2 Synonyms: 1-Chloro-2,6-dinitrobenzene 5.0.3 Trade Names: NA 5.0.4 Molecular Weight: 202.55 5.0.5 Molecular Formula: C6H3N2O4Cl 5.0.6 Molecular Structure:

Databases or inventories where listed: EINECS, EMICBACK, GENETOX, HSDB, RTECS, TOXLINE, TSCAINV 5.1 Chemical and Physical Properties (2) Physical state Yellow crystals Melting point 86–87°C Boiling point 315°C Solubility Soluble in ethanol, ether, toluene 5.2 Production and Use No specific uses were found, but the commercial mixture of chlorodinitrobenzenes is used to synthesize other compounds (2). 5.4 Toxic Effects No toxicological information was found. 5.5 Standards, Regulations, or Guidelines of Exposure None assigned. 6.0 2-Chloro-1,4-dinitrobenzene 6.0.1 CAS Number: [619-16-9] 6.0.2 Synonyms: 1-Chloro-2,5-dinitrobenzene 6.0.3 Trade Names: NA 6.0.4 Molecular Weight: 202.55 6.0.5 Molecular Formula: C6H3N2O4Cl 6.0.6 Molecular Structure: NA

Databases or inventories where listed: TOXLINE. 6.1 Chemical and Physical Properties (2) Physical state Light yellow crystals Melting point 64°C Solubility Soluble in ethanol, ether; insoluble in water 6.2 Production and Use Uses are the same as other isomers such as 4-chloro-1,2-dinitrobenzene (2). 6.4 Toxic Effects No specific information found. 6.5 Standards, Regulations, or Guidelines of Exposure None assigned. 7.0 3-Chloro-1,2-dinitrobenzene 7.0.1 CAS Number: [602-02-8] 7.0.2 Synonyms: 1-Chloro-2,3-dinitrobenzene 7.0.3 Trade Names: NA 7.0.4 Molecular Weight: 202.55 7.0.5 Molecular Formula: C6H3N2O4Cl 7.0.6 Molecular Structure:

Databases or inventories where listed: None listed. 7.1 Chemical and Physical Properties (2) Physical state Crystals Melting point 78°C Boiling point 315°C Refractive index 1.6867 (16.5°C) Solubility Soluble in ethanol, ether; insoluble in water 7.2 Production and Use Uses are same as other isomers. 7.4 Toxic Effects No specific information located. 7.5 Standards, Regulations, or Guidelines of Exposure None assigned. 8.0 4-Chloro-1,2-dinitrobenzene 8.0.1 CAS Number: [610-40-2] 8.0.2 Synonyms: 1,2-Dinitro–4-chloro benzene; 3,4-dinitrochlorobenzene; 1-chloro-3,4dinitrobenzene 8.0.3 Trade Names: NA

8.0.4 Molecular Weight: 202.55 8.0.5 Molecular Formula: C6H3N2O4Cl 8.0.6 Molecular Structure:

Databases or inventories where listed: EINECS, ETICBACK, TOXLINE, TSCAINV 8.1 Chemical and Physical Properties (2) Physical state Monoclinic prisms, needles Melting point a, 36°C; b, 37°C; g 40–41°C Boiling point 16°C; 4 mmHg Solubility Soluble in ether, benzene, carbon disulfide, hot ethanol; insoluble in water 8.2 Production and Use No specific uses found. 8.4 Toxic Effects This compound is a sensitizer (2). 8.5 Standards, Regulations, or Guidelines of Exposure None assigned. 9.0 1-Chloro-2,4-dinitrobenzene 9.0.1 CAS Number: [97-00-7] 9.0.2 Synonyms: 2,4-Dinitro-1-chlorobenzene, 2,4-dinitrochlorobenzene, 1,3-dinitro-4chlorobenzene, dinitrochlorobenzene, chlorodinitrobenzene, DNCB, 4-chloro-1,3-dinitrobenzene 9.0.3 Trade Names: NA 9.0.4 Molecular Weight: 202.55 9.0.5 Molecular Formula: C6H3N2O4Cl 9.0.6 Molecular Structure:

Databases or inventories where listed: AIDSDRUGS, AIDSLINE, AIDSTRIALS, CANCERLIT, CCRIS, DART, DSL, EINECS, EMIC, EMICBACK, ETICBACK, HSDB, MA, MEDLINE, MESH, PA, RTECS, TOXLINE, TSCAINV, SUPERLIST. 9.1 Chemicals and Physical Properties (2) Physical State Yellow crystals Melting point a, 53°C; b, 43°C Boiling point 315°C (762 mmHg)

Solubility Soluble in ether, benzene, hot ethanol; insoluble in water 9.2 Production and Use DNCB is used in the manufacture of dyes and explosives, as a reagent, and as an algicide (2). 9.4 Toxic Effects This compound is a potent sensitizer (2), and it has been used as such in many experiments. Examples include dose-response studies (97, 98), the effect of vehicle on absorption (99), and the effect of rat strain on sensitivity to DNCB (100). This compound depletes liver glutathione levels (2), and more recent data show that it irreversibly inhibits another enzyme involved with sulfur. Human thioredoxin, a dimeric enzyme that catalyzes reduction of the disulfide in oxidized thioredoxin, was inhibited and the effect persisted after removal of DNCB (101). 9.5 Standards, Regulations, or Guidelines of Exposure None assigned. 10.0 5-Chloro-1,3-dinitrobenzene 10.0.1 CAS Number: [618-86-0] 10.0.2 Synonyms: 1-Chloro-3,5-dinitrobenzene 10.0.3 Trade Names: NA 10.0.4 Molecular Weight: 202.55 10.0.5 Molecular Formula: C6H3N2O4Cl 10.0.6 Molecular Structure: NA Databases or inventories where listed: None found. 10.1 Chemical and Physical Properties (2) Physical state Colorless needles Melting point 59°C Solubility Soluble in ethanol, ether; insoluble in water 10.2 Production and Use No specific uses were noted, but it reportedly could be used for the same purposes as 4-chloro-1,2dinitrobenzene (2). 10.4 Toxic Effects No new information was located. 10.5 Standards, Regulations, or Guidelines of Exposure No standards assigned. 11.0 Pentachloronitrobenzene 11.0.1 CAS Number: [82-68-8] 11.0.2 Synonyms: Avical; Eorthcicle; Fortox; Kobu; Marison Forte; Pkhnb; Terrafun; Tri PCNB; PCNB; Quintozine; quintobenzene; Terrachlor; Terraclor; Avicol; Botrilex; Earthcide; Kobutol; Pentagen; Tilcarex; SA Terraclor 2E; SA Terraclor; nitropentachlorobenzene; brassicol; quintocene; batrilex; fartox; fomac 2; fungiclor; gc 3944-3-4; KP 2; olpisan; quintozen; saniclor 30; tritisan 11.0.3 Trade Names: NA 11.0.4 Molecular Weight: 295.34 11.0.5 Molecular Formula: C6Cl5NO2 11.0.6 Molecular Structure:

Databases or inventories where listed: CAA1, FIFR, IARC, MA, MI, NJ, NTPT, PA, RQ, TLV, TRI, CANCERLIT, CCRIS, DART, EINECS, EMIC, EMICBACK, ETICBACK, GENETOX, HSDB, IRIS, MEDLINE, MESH, RTECS, TOXLINE, TRIFACTS, TSCAINV, SUPERLIST. 11.1 Chemical and Physical Properties (2) Physical state Colorless solid Specific gravity 1.718 at 25°C Melting point 142–145°C technical grade Boiling point 328°C at 760 mmHg Solubility Soluble in benzene, carbon disulfide, chloroform 11.2 Production and Uses PCNB has been used as a fungicide for seeds, soil, and turf (2). 11.4 Toxic Effects The previous edition provided a thorough account of the toxicity and metabolism of PCNB (2). It was not carcinogenic and did not act as a reproductive toxicant or a teratogen. It does lead to methemoglobinemia in cats. However, in a rat study, PCNB did not form an adduct with hemoglobin (14). probably due to steric hindrance from the chlorine substituents. 11.5 Standards, Regulations, or Guidelines of Exposure The ACGIH TLV-TWA is 0.5 mg/m3 with A4 notation.

Aromatic Nitro and Amino Compounds Elizabeth K. Weisburger, Ph.D., Vera W. Hudson, MS C. Dinitrobenzenes 12.0 1,2-Dinitrobenzene 12.0.1 CAS Number: [528-29-0] 12.0.2 Synonyms: o-Dinitrobenzene; 1,2-dinitrobenzol 12.0.3 Trade Names: NA 12.0.4 Molecular Weight: 168.11 12.0.5 Molecular Formula: C6H4N2O4 12.0.6 Molecular Structure:

Databases or inventories where listed: CA65, DOT, MA, MTL, NJ, PA, PEL, RQ, TLV, TRI, WHMI, CANCERLIT, CCRIS, EINECS, EMIC, EMICBACK, HSDB, IRIS, MEDLINE, MESH,

RTECS, TOXLINE, SUPERLIST. 12.1 Chemical and Physical Properties (2) Physical state White to yellow, monoclinic plates Density 1.565 (17/4°C) Melting point 117–118.5°C Boiling point 319°C (773 mm Hg) Vapor density 5.79 (air = 1) Flash point 302°F (closed cup) Solubility Soluble in ethanol, chloroform, benzene, methanol; slightly soluble in water 12.2 Production and Use Dinitrobenzene is usually made as a mixture of three isomers that are used in producing dyestuffs, explosives, and other intermediates. 12.3 Exposure Assessment NMAM IInd ed., vol 4, 1978 #S214. 12.4 Toxic Effects 1,2-DNB is the least toxic of the three isomers, but it is absorbed through the skin and can cause methemoglobinemia. It did not lead to testicular damage in rats at doses where 1,3-DNB had such an effect. 12.5 Standards, Regulations, or Guidelines of Exposure The ACGIH TLV-TWA, NIOSH REL and OSHA PEL is 0.15 ppm (1 mg/m3) with a skin notation. 13.0 1,3-Dinitrobenzene 13.0.1 CAS Number: [99-65-0] 13.0.2 Synonyms: Dinitrobenzol; m-dinitrobenzene; 2,4-dinitrobenzene; binitrobenzene; 1,3dinitrobenzol 13.0.3 Trade Names: NA 13.0.4 Molecular Weight: 168.11 13.0.5 Molecular Formula: C6H4N2O4 13.0.6 Molecular Structure:

Databases or inventories where listed: CA65, DOT, MA, MTL, NJ, PA, PEL, REL, RQ, S110, TLV, TRI, WHMI, CANCERLIT, CCRIS, DART, DSL, EINECS, EMIC, EMICBACK, GENETOX, HSDB, IRIS, MEDLINE, MESH, RTECS, TOXLINE TSCAINV, SUPERLIST. 13.1 Chemical and Physical Properties (2) Physical Colorless to yellow rhombic needles or plates state Density 1.571 (0/4°C) Melting 89–90°C point Boiling point 302.8°C (770 mmHg)

Flash point Solubility

302°F (closed cup) Soluble in ethanol, ether, benzene, toluene, chloroform, ethyl acetate; slightly soluble in water 13.2 Production and Uses 1,3-DNB is used in producing nitroaniline, 1,3-phenylenediamine, dye intermediates, and some explosives. 13.3 Exposure Assessment NMAM IInd ed., vol. 4, 1978 method #S214. 13.4 Toxic Effects The toxicity and metabolic reactions of 1,3-DNB were discussed in the previous edition (2). A major concern is testicular toxicity (56, 57) and reproductive effects. Additional studies showed that the toxicity of 1,3-DNB was greater in older rats, probably due to their slower rate of excretion (102). Route of administration, whether oral vs. i.p. had little effect on the degree of testicular damage in rats, although more was excreted in the feces after an oral dose (103). Examination of the metabolic capacity of different tissues from rats revealed that besides intestinal mucosa (104), rat brain also metabolized 1,3-DNB, presumably to toxic intermediates (105). The net result was that 1,3-DNB caused brain stem lesions in rats (106), which may explain the neurotoxicity noted in some previous studies (2). 13.5 Standards, Regulations, or Guidelines of Exposure The ACGIH TLV-TWA, NIOSH REL and OSHA PEL is 0.15 ppm (1 mg/m3), with a skin notation. 14.0 1,4-Dinitrobenzene 14.0.1 CAS Number: [100-25-4] 14.0.2 Synonyms: p-Dinitrobenzene 14.0.3 Trade Names: NA 14.0.4 Molecular Weight: 168.11 14.0.5 Molecular Formula: C6H4N2O4 14.0.6 Molecular Structure:

Databases or inventories where listed: CA65, DOT, MA, MTL, NJ, PA, PEL, RQ, TLV, TRI, WHMI, CCRIS, DSL, EINECS, EMIC, EMICBACK, HSDB, MEDLINE, MESH, RTECS, TOXLINE, TSCAINV, SUPERLIST. 14.1 Chemical and Physical Properties (2) Physical state Colorless to yellow monoclinic needles Density 1.625 (20/4°C) Melting point 173–174°C Boiling point 298–299°C (777 mmHg) sublimes Solubility Soluble in chloroform, benzene, ethanol; somewhat soluble in water 14.2 Production and Use Uses are identical with those of 1,2-dinitrobenzene (2). 14.3 Exposure Assessment NMAM IInd ed., vol. 4, 1978 method #S214. 14.4 Toxic Effects Although 1,4-DNB did not cause testicular toxicity in rats, it led to cyanosis, splenic enlargement,

and methemoglobinemia from prolonged exposure (2). 14.5 Standards, Regulations, or Guidelines of Exposure The ACGIH TLV-TWA, NIOSH REL and OSHA PEL is 0.15 ppm (1 mg/m3) with a skin notation. 15.0 Trinitrobenzene 15.0.1 CAS Number: [99-35-4] 15.0.2 Synonyms: Benzite; 1,3,5-trinitrobenzene; sym-trinitrobenzene; trinitrobenzene, TNB 15.0.3 Trade Names: NA 15.0.4 Molecular Weight: 213.11 15.0.5 Molecular Formula: C6H3N3O6 15.0.6 Molecular Structure:

Databases or inventories where listed: DOT, MA, NJ, PA, RQ, S110, CANCERLIT, CCRIS, DART, EINECS, EMIC, EMICBACK, HSDB, IRIS, MEDLINE, MESH, RTECS, TOXLINE, TSCAINV, SUPERLIST. 15.1 Chemical and Physical Properties (2) Physical state Orthorhombic bipyramidal plates Melting point 121–122.5°C Boiling point 315°C Solubility Soluble in acetone, benzene 15.2 Production and Use Trinitrobenzene occurs as a by-product of trinitrotoluene (TNT) production and as a contaminant in water systems where it is formed by photolysis of TNT. It is not biodegraded readily and thus occurs in water, in TNT production waste disposal sites, and in soils at many military installations (107). It is not manufactured except for research purposes. 15.4 Toxic Effects Since the previous edition, there has been appreciable interest in the toxicity of TNB. TNB was given to male and female rats at 0, 50, 200, 400, 800, or 1200 mg/kg diet for 14 days. Levels of 400 mg/kg and higher led to reduced food intake and lower body weights. Testicular weights were lower in males, and an increase in spleen weights was noted in both sexes. Susceptible organs were kidney (hyaline droplets), spleen (extramedullary hematopoiesis), brain (hemorrhage, malacia, and gliosis), and testes (seminiferous tubular degeneration). Red blood cell counts and hematocrit decreased while Heinz bodies and methemoglobin increased (107). Additional studies were done on the organ systems thus affected. TNB-treated male F344 rats had a dose-related accumulation of hyaline droplets with alpha-2-m-globulin in the proximal tubules of the kidney, but this did not occur in female F344 or male NBR rats (108). There was a steep dose-response curve for the effect on the brain (109). In a similar manner, the testicular effects were explored; 71 mg/kg for 10 days led to cessation of spermatogenesis, and half that dose for 10 days led to testicular lesions. The effects were partially reversible after a recovery period of 10 to 30 days (110, 111). However, although a reproductive toxicity screen with Sprague–Dawley rats given 30, 150, or 300 TNB mg/kg of diet for 14 days showed spleen depletion and degeneration of seminiferous tubules in males and methemoglobinemia and splenic hemosiderosis at higher doses in both sexes, no adverse effects were noted in mating or fertility indices, length of gestation, sex ratio, gestation index, or mean

number of pups per litter (112). Absorption studies with human, rat, and hairless guinea pig skin showed that absorption through rat skin was very similar with either acetone or aqueous solutions of TNB. In human skin, absorption from water was much greater than from acetone, whereas the reverse held for guinea pig skin. The fluid in the receptor cell from human or rat skin contained 3,5-dinitroaniline and 1,3,5triacetylaminobenzene. Guinea pig skin also metabolized TNB to 1-nitro-3,5-diacetamidobenzene and 3,5-diaminonitrobenzene to a minor extent (113). Thus, TNB was absorbed and metabolized to a similar extent by human and rodent skin. Liver microsomes from male F344 rats produced 3,5diaminobenzene as a major metabolite of TNB (114). 15.5 Standards, Regulations, or Guidelines of Exposure None assigned.

Aromatic Nitro and Amino Compounds Elizabeth K. Weisburger, Ph.D., Vera W. Hudson, MS D. Nitrophenols 16.0 2-Nitrophenol 16.0.1 CAS Number: [88-75-5] 16.0.2 Synonyms: 2-Hydroxynitrobenzene; ONP 16.0.3 Trade Names: NA 16.0.4 Molecular Weight: 139.11 16.0.5 Molecular Formula: C6H5NO3 16.0.6 Molecular Structure:

Databases and inventories where listed: CCRIS, EINECS, RTECS, TSCAINV, HSDB, CGB, MA, WHMI, NJ, TRI, RG, CGN, UN 1663, DOT, PA, EMIC, EMICBACK, GENETOX, MEDLINE, TOXLINE, SUPERLIST. 16.1 Chemical and Physical Properties (2) Physical state Light yellow crystals Density 1.657 (20°C) Melting point 44–46°C Boiling point 214–216°C Solubility Soluble in ethanol, ether, acetone, benzene, alkali; somewhat soluble in water 16.2 Production and Use 2-Nitrophenol is an intermediate in dyestuff production and a chemical indicator. 16.4 Toxic Effects No new information was found. o-Nitrophenol causes central and peripheral vagus stimulation, central nervous system (CNS) depression, methemoglobinemia, and dyspnea in animal experiments.

The oral LD50 in mice is 1.297 g/kg; in rats, 2.828 g/kg (2). o-Nitrophenol was negative in the Ames mutagenicity test (115), and it was metabolically reduced less readily to the corresponding amino derivative than the meta or para isomers (116). 16.5 Standards, Regulations, or Guidelines of Exposure None assigned. 17.0 3-Nitrophenol 17.0.1 CAS Number: [554-84-7] 17.0.2 Synonyms: 3-Hydroxy-nitrobenzene; 3-hydroxy-1-nitrobenzene 17.0.3 Trade Names: NA 17.0.4 Molecular Weight: 139.11 17.0.5 Molecular Formula: C6H5NO3 17.0.6 Molecular Structure:

Databases and inventories where listed: CCRIS, DART, EINECS, EMIC, EMICBACK, GENETOX, HSDB, MEDLINE, MESH, RTECS, TOXLINE, TSCAINV, SUPERLIST. 17.1 Chemical and Physical Properties (2) Physical state Colorless to yellowish crystals Density 1.485 (20°C) Melting point 97°C Boiling point 194°C (70 mmHg) Solubility Soluble in ether, benzene, alkali, ethanol, acetone; appreciably soluble in water 17.2 Production and Use 3-Nitrophenol is also used in synthesizing some dyestuffs and drugs and as an indicator, (117). 17.4 Toxic Effects No new information found. In contrast to the ortho isomer, m-nitrophenol is more readily biotransformed to its corresponding amino derivative; however, it is reportedly nonmutagenic in the Ames bacterial mutagenicity test (2, 116). 17.5 Standards, Regulations, or Guidelines of Exposure None assigned. 18.0 4-Nitrophenol 18.0.1 CAS Number: [100-02-7] 18.0.2 Synonyms: 4-Hydroxynitrobenzene; Niphen; PNP; mononitrophenol 18.0.3 Trade Names: NA 18.0.4 Molecular Weight: 139.11 18.0.5 Molecular Formula: C6H5NO3

18.0.6 Molecular Structure:

Databases and inventories where listed: CANCERLIT, CCRIS, DART, DSL, EINECS, EMIC, EMICBACK, ETICBACK, GENETOX, HSDB, IRIS, MEDLINE, MESH, RTECS, TOXLINE, TRIFACTS, TSCAINV, SUPERLIST. 18.1 Chemical and Physical Properties (2) Physical state Colorless to yellowish monoclinic prisms Density 1.479 (20°C) Melting point 113–116°C Boiling point 279°C (sublimable) Solubility Soluble in ethanol, ether, benzene, acetone, alkali; somewhat soluble in water 18.2 Production and Use 4-Nitrophenol is used in dyestuff and pesticide synthesis, as a fungicide, bactericide, and wood preservative, as a chemical indicator, and as a substrate for experiments on cytochrome P450 2E1 (118). 18.4 Toxic Effects p-Nitrophenol undergoes glutathione and glucuronide conjugation (119, 120). Isolation of a rat liver glucuronosyltransferase isozyme has also been reported; this enzyme is responsible for the glucuronide formation (121). In addition, p-nitrophenol can readily undergo reduction to its amino derivative. However, in vivo nitro reduction conditions require bacterial enzymes in the natural anaerobic environment of the gut (possibly in localized cellular ischemic conditions); in vitro, mammalian enzymes are required under artificial anaerobic conditions (116). p-Nitrophenol is nonmutagenic in the Ames assay (2). The oral LD50 in mice is 467 mg/kg, and in rats, 616 mg/kg. Since the last edition, there have been additional studies with 4-nitrophenol. Differences in sulfate conjugation by different species and organs were noted, using guinea pig, rat, and rabbit liver and platelets from rats, guinea pigs, rabbits, and dogs. Biphasic effects were observed in platelets and liver from rats and guinea pigs, similar to the result in humans (122). Abnormal physiological states such as bile duct ligation of rats increased 4-nitrophenol glucuronide formation at high doses; at low doses, ligation decreased conjugation (123). Hyperglycemia led to increased sulfate conjugation (124), but formation of a sulfate was practically nil in isolated rat intestinal loops (125). Cytochrome P450 2E1-mediated 4-nitrophenol hydroxylation was inhibited by benzene, toluene, and 2bromophenol (126), whereas ethanol treatment of rats increased hydroxylation (127). When applied to porcine skin flaps, 4-nitrophenol did not evaporate significantly; there was greater penetration with acetone than with ethanol solutions (128). Data from a single chemical did not predict of absorption of binary mixtures of 4-nitrophenol and phenol (129). 4-Nitrophenol was tested by the NTP in a dermal study with mice; the results were negative for carcinogenicity (130). 18.5 Standards, Regulations, or Guidelines of Exposure None assigned.

Aromatic Nitro and Amino Compounds Elizabeth K. Weisburger, Ph.D., Vera W. Hudson, MS

E. Dinitrophenols 19.0 2,3-Dinitrophenol 19.0.1 CAS Number: [66-56-8] 19.0.2 Synonyms: NA 19.0.3 Trade Names: NA 19.0.4 Molecular Weight: 184.11 19.0.5 Molecular Formula: C6H4N2O5 19.0.6 Molecular Structure:

Databases or inventories where mentioned: CANCERLIT, CCRIS, EINECS, MESH, RTECS, TOXLINE. 19.1 Chemical and Physical Properties (2) Physical state Yellow monoclinic prisms, flammable Melting point 144–145°C Solubility Soluble in ether, benzene, ethanol; slightly soluble in water 19.2 Production and Use Specific uses were not located. 19.4 Toxic Effects No new information was found. Dermal exposure to 2,3-dinitrophenol causes yellow staining of skin and it may also cause dermatitis or allergic sensitivity. Systematically, it disrupts oxidative phosphorylation causing increased metabolism, oxygen consumption, and heat production. Chronic exposure may result in kidney and liver damage and cataract formation (2, 131). 19.5 Standards, Regulations, or Guidelines of Exposure None assigned. 20.0 2,4-Dinitrophenol 20.0.1 CAS Number: [51-28-5] 20.0.2 Synonyms: alpha-Dinitrophenol; aldifen; Fenoxyl Carbon N; 1-hydroxy-2,4-dinitrobenzene; 2,4-DNP; solfo black b; solfo black bb; tertrosulfur black pb; dinofan; maroxol-50; solfo black 2b supra; solfo black g; solfo black sb; tertrosulfur pbr; nitro kleenup; fenoxyl; dinitrophenols 20.0.3 Trade Names: NA 20.0.4 Molecular Weight: 184.11 20.0.5 Molecular Formula: C6H4N2O5 20.0.6 Molecular Structure:

Databases or inventories where mentioned: CAA, FIFR, MA, NJ, PA, RQ, S110, TRI, WHMI, AIDSLINE, CANCERLIT, CCRIS, DART, DSL, EINECS, EMICBACK, ETICBACK, GENETOX, HSDB, IRIS, MEDLINE, MESH, RTECS, TOXLINE, TRIFACTS, TRI, TSCAINV, SUPERLIST. 20.1 Chemical and Physical Properties (2) Physical state Pale yellow rhombic crystals or needles, flammable Melting point 115–116°C Solubility Soluble in ethanol, ether, chloroform, benzene; somewhat soluble in water 20.2 Production and Use Dinitrophenol is a dyestuff intermediate and is used as an insecticide, fungicide, bactericide, and wood preservative. 20.4 Toxic Effects The action of 2,4-dinitrophenol in increasing metabolic rate was presented in the previous edition (2). Further work indicated that it could damage the myofilaments of the rat heart (132) and that various metabolic systems were activated in response (133, 134). High levels of environmental contamination could lead to adverse consequences in some wildlife. 20.5 Standards, Regulations, or Guidelines of Exposure None assigned. 21.0 2,5-Dinitrophenol 21.0.1 CAS Number: [329-71-5] 21.0.2 Synonyms: gamma-Dinitrophenol 21.0.3 Trade Names: NA 21.0.4 Molecular Weight: 184.11 21.0.5 Molecular Formula: C6H4N2O5 21.0.6 Molecular Structure:

Databases or inventories where mentioned: MA, NJ, PA, RQ, CCRIS, EINECS, EMICBACK, HSDB, MESH, RTECS, TOXLINE, SUPERLIST. 21.1 Chemical and Physical Properties (2) Physical state yellow needles, flammable Melting point 108°C Solubility Soluble in ether, benzene, hot water and ethanol 21.2 Production and Use Specific applications not located. 21.4 Toxic Effects No specific studies located. Toxicity is assumed to be identical to that of 2,3-dinitrophenol (2, 131).

21.5 Standards, Regulations, or Guidelines of Exposure None assigned. 22.0 2,6-Dinitrophenol 22.0.1 CAS Number: [573-56-8] 22.0.2 Synonyms: beta-Dinitrophenol 22.0.3 Trade Names: NA 22.0.4 Molecular Weight: 184.11 22.0.5 Molecular Formula: C6H4N2O5 22.0.6 Molecular Structure:

Databases or inventories where mentioned: MA, NJ, PA, RQ, CCRIS, EINECS, HSDB, MESH, RTECS, TOXLINE, SUPERLIST. 22.1 Chemical and Physical Properties (2) Physical state Pale yellow rhombic crystals, flammable Melting point 63–64°C Solubility Soluble in benzene, acetone, hot water, ethanol, ether 22.2 Production and Use No specific applications found. 22.4 Toxic Effects No specific studies were located. Toxicity is assumed to be identical to that of 2,3-dinitrophenol (2, 131). 22.5 Standards, Regulations, or Guidelines of Exposure None assigned. 23.0 3,4-Dinitrophenol 23.0.1 CAS Number: [577-71-9] 23.0.2 Synonyms: NA 23.0.3 Trade Names: NA 23.0.4 Molecular Weight: 184.11 23.0.5 Molecular Formula: C6H4N2O5 23.0.6 Molecular Structure:

Databases or inventories where mentioned: CCRIS, EINECS, RTECS, TOXLINE. 23.1 Chemical and Physical Properties (2) Physical state Colorless needles, flammable Melting point 134°C Solubility Very soluble in ethanol, ether 23.2 Production and Use Specific applications not located. 23.4 Toxic Effects No new information located. No specific studies were located. Toxicity is assumed to be identical to that of 2,3-dinitrophenol (2, 131). 23.5 Standards, Regulations, or Guidelines of Exposure None assigned. 24.0 3,5-Dinitrophenol 24.0.1 CAS Number: [586-11-8] 24.0.2 Synonyms: NA 24.0.3 Trade Names: NA 24.0.4 Molecular Weight: 184.11 24.0.5 Molecular Formula: C6H4N2O5 24.0.6 Molecular Structure:

Databases or inventories where mentioned: RTECS, TOXLINE. 24.1 Chemical and Physical Properties (2) Physical state Colorless monoclinic prisms, flammable Melting point 134°C Solubility Soluble in ethanol, ether, chloroform, benzene 24.2 Production and Use No specific uses located. 24.4 Toxic Effects No new information located. No specific studies were located. Toxicity is assumed to be identical to that of 2,3-dinitrophenol (2, 131). 24.5 Standards, Regulations, or Guidelines of Exposure None assigned. 25.0 Picric Acid 25.0.1 CAS Number: [88-89-1] 25.0.2 Synonyms: Picronitric acid; Melinite; pertite; carbazotic acid; 2,4,6-trinitrophenol; trinitrophenol; lyddite; shimose; phenol trinitrate; 2-hydroxy-1,3,5-trinitrobenzene; C. I. 10305; TNP

25.0.3 Trade Names: NA 25.0.4 Molecular Weight: 229.11 25.0.5 Molecular Formula: C6H3N3O7 25.0.6 Molecular Structure:

Databases or inventories where mentioned: DOT, IL, INER, MA, NJ, PA, PEL, REL, TLV, TRI, WHMI, AIDSLINE, CANCERLIT, CCRIS, DART, DSL, EINECS, MEDLINE, MESH, RTECS, TOXLINE, TRIFACTS, TSCAINV, SUPERLIST. 25.1 Chemical and Physical Properties (2) Physical state White to yellowish needles, flammable Melting point 122–123°C Boiling point >300°C (sublimes, explodes) Solubility Soluble in ethanol, ether, benzene, acetone; slightly soluble in water Cautionary note: Picric acid is very explosive when dry; for safety it is usually mixed with 10–20% water; it explodes when heated rapidly or subjected to percussion. 25.2 Production and Use Picric acid is used in making explosives; as a burster in projectiles; in rocket fuels, fireworks, colored glass, batteries, and disinfectants; in the pharmaceutical and leather industries; as a fast dye for wool and silk; in metal etching and photographic chemicals; and as a laboratory reagent. 25.3 Exposure Assessment NMAM IInd edition, vol 4, 1978 method #S228. 25.4 Toxic Effects Picric acid causes sensitization dermatitis (135). Allergic hepatitis has been induced in guinea pigs by picric acid (136). Dust or fumes cause eye irritation, that can be aggravated by sensitization (137). It dyes animal fibers yellow (including skin) upon contact (2, 131). Systemic absorption can cause weakness, myalgia, anuria, polyuria, headache, fever, hyperthermia, vertigo, nausea, vomiting, diarrhea, and coma. High doses may cause destruction of erythrocytes, hemorrhagic nephritis and hepatitis, yellow coloration of the skin (“pseudojaundice”), including conjunctiva and aqueous humor, and yellow vision (138, 139). The strange visual effects where objects appear yellow may be related to the fact that systemic toxicity results in coloring all tissues yellow, including the conjunctiva and aqueous humor, so that yellow vision appearing under these circumstances is explained by optical effects (137). It is reportedly nonmutagenic in the Ames assay (115). Picric acid is metabolized largely to picramic acid. A more definitive study of the metabolism of picric acid has appeared (140). In male F344 rats, the oral LD50 was 290 mg/kg; in females 200 mg/kg. After a single oral dose of 14-C labeled compound, 56–60% appeared in the urine of the rats by 24 h, and 6–10% in feces. Gut contents accounted for

23% of the dose, and 3–6% remained in blood, muscle, and gut tissue. Up to 60% of the picric acid was excreted unchanged in the urine, and N-acetylisopicramic acid accounted for 15% of urinary activity, picramic acid 18.5%, and N-acetylpicramic acid for almost 5%, respectively. Thus, metabolic reactions consisted of reduction of the nitro to amino groups and conjugation with acetate. 25.5 Standards, Regulations, or Guidelines of Exposure ACGIH TLV-TWA, 0.1 mg/m3; OSHA PEL and NIOSH REL, 0.1 mg/m3 (skin); Australia, 0.1 mg/m3 (skin); Germany, 0.1 mg/m3 (skin); United Kingdom, 0.1 mg/m3.

Aromatic Nitro and Amino Compounds Elizabeth K. Weisburger, Ph.D., Vera W. Hudson, MS F. Dinitrocresols 26.0 4,6-Dinitro-o-cresol 26.0.1 CAS Number: [534-52-1] 26.0.2 Synonyms: DNOC; DNC; 3,5-dinitro-2-hydroxytoluene; Nitrador; 2-methyl-4,6dinitrophenol; dinitrocresol; antinonnin; Detal; Dinitrol; Elgetol; K III; K IV; Ditrosol; Prokarbol; Effusan; Lipan; Selinon; Dekrysil; 2,4-dinitro-o-cresol; 2,4-dinitro-6-methylphenol; antinonin; dinitrosol; Elgetox; 3,5-dinitro-6-hydroxy-toluene; 4,6-DNOC; Elgetol 30; methyl-4,6-dinitrophenol; Sinox; dinitro-o-cresol 26.0.3 Trade Names: NA 26.0.4 Molecular Weight: 198.13 26.0.5 Molecular Formula: C7H6N2O5 26.0.6 Molecular Structure:

Databases or inventories where listed: CAA1, DOT, FIFR, IL, MA, MI, MPOL, PA, PEL, REL, RQ, S110, S302, TLV, TRI, WHMI, CANCERLIT, CCRIS, DART, DSL, EINECS, EMIC, EMICBACK, ETICBACK, GENETOX, HSDB, MEDLINE, MESH, RTECS, TOXLINE, TRIFACTS, TSCAINV, SUPERLIST. 26.1 Chemical and Physical Properties (2) Physical state Yellow prisms Melting point 86.5°C Solubility Soluble in ether, acetone; slightly soluble in water 26.2 Production and Use This compound and its isomers are used as herbicides, fungicides, and wood preservatives. Release into aquatic environments can be harmful to various organisms. 26.3 Exposure Assessment NMAM, IInd edition, vol 5, 1979 Method #S166. 26.4 Toxic Effects

No new information was located. 26.5 Standards, Regulations, or Guidelines of Exposure The ACGIH TLV-TWA, NIOSH REL and OSHA PEL is 0.2 mg/m3 with a skin notation. A similar value holds for Australia, Germany, and the United Kingdom. 27.0 2,6-Dinitro-p-cresol 27.0.1 CAS Number: [609-93-8] 27.0.2 Synonyms: 2,6-DNPC; 4-methyl-2,6-dinitrophenol; 2,6-dinitro-p-cresol, moist solid containing up to 10% water 27.0.3 Trade Names: NA 27.0.4 Molecular Weight: 198.13 27.0.5 Molecular Formula: C7H6N2O5 27.0.6 Molecular Structure:

Databases or inventories where listed: DSL, EINECS, EMICBACK, HSDB, RTECS, TOXLINE, TSCAINV. 27.1 Chemical and Physical Properties (2) Physical state Long yellow prisms Melting point 85°C Solubility Soluble in benzene, ethanol, ether; insoluble in water 27.2 Production and Use Uses are the same as those of the isomer 4,6-dinitro-o-cresol. 27.4 Toxic Effects No new information was located. The toxicity of 2,6-dinitro-p-cresol is reportedly identical to that of the ortho isomer (131). Peripheral neuropathy (dying back) has been reported following exposure (2) but was not definitive. 27.5 Standards, Regulations, or Guidelines of Exposure None assigned. 28.0 2-Nitroanisole 28.0.1 CAS Number: [91-23-6] 28.0.2 Synonyms: 2-Methoxynitrobenzene, o-nitrophenyl methyl ether, 1-methoxy-2-nitrobenzene 28.0.3 Trade Names: NA 28.0.4 Molecular Weight: 153.14 28.0.5 Molecular Formula: C7H7NO3 28.0.6 Molecular Structure:

Databases and inventories where listed: CA65, IARC, NTPA, NTPT, WHMI, CANCERLIT, CCRIS, EINECS, EMIC, EMICBACK, GENETOX, HSDB, MEDLINE, MESH, RTECS, TOXLINE, TSCAINV, SUPERLIST. 28.1 Chemical and Physical Properties (92) Physical state Colorless to yellowish liquid Boiling point 277°C Melting point 10.5°C Density 1.254 (20°C/4°C) Solubility Soluble in ethanol, ether; moderately soluble in water 28.2 Production and Use 2-Nitroanisole is used as an intermediate in dyestuff and pharmaceutical production. 28.4 Toxic Effects The oral LD50 is 740 mg/kg body weight in rats and 1300 mg/kg in mice. In 14-day studies in F344 rats (583–9330 ppm) and B6C3F1 mice (250–4000 ppm), the male rats showed methemoglobinemia at levels of 1166 ppm or more. Body weights were lower and absolute liver weights higher in both male and female rats. Aside from lower body weights, mice had no treatment-related effects. In 13week studies at 200, 600, 2000, 6000, or 18,000 mg/kg diet, various manifestations of toxicity were noted, and rats were more susceptible (92). Administration in the diet at levels of 0, 666, 2000, or 6000 mg/kg to male and female B6C3F1 mice for 103 weeks led to significant increases in hepatocellular adenomas and carcinomas in both sexes, in addition to hepatic hemorrhages, Kupffer cell pigmentation, focal necrosis, and cytological alteration. Levels of 0, 222, 666, or 2000 mg/kg to F344 rats for 103 weeks caused increases in mononuclear cell leukemia in both sexes. When F344 rats were fed a 6000 or 18,000 mg/kg diet for 27 weeks and kept on a control diet for 77 weeks more, the incidences of carcinomas of the urinary bladder, adenomatous polyps of the large intestine, and transitional cell tumors of the kidney increased in both sexes (92). Metabolism studies in rats with labeled 2-nitroanisole showed about 7% excreted in the feces and 70% in the urine after 7 days. Urinary metabolites identified were 2-nitrophenyl sulfate (63%), 2nitrophenyl glucuronide (11%), 2-nitrophenol (1.5%), and o-anisidine (0.6%) (92). 28.5 Standards, Regulations, or Guidelines of Exposure None assigned.

Aromatic Nitro and Amino Compounds Elizabeth K. Weisburger, Ph.D., Vera W. Hudson, MS G. Nitrotoluenes 29.0 2-Nitrotoluene 29.0.1 CAS Number: [88-72-2] 29.0.2 Synonyms: Methylnitrobenzene; 2-methyl-1-nitrobenzene; 1-methyl-2-nitrobenzene; 2methylnitrobenzene; ONT; 2-nitrotoluol; o-nitrophenylmethane; alpha-methylnitrobenzene, onitrotoluene, 2NT

29.0.3 Trade Names: NA 29.0.4 Molecular Weight: 137.14 29.0.5 Molecular Formula: C7H7NO2 29.0.6 Molecular Structure:

Databases and inventories where listed: CGN, DOT, IARC, MA, MPOL, MTL, NTPT, PA, PEL, REL, RQ, TLV, WHMI, CANCERLIT, CCRIS, DART, DSL, EINECS, EMIC, EMICBACK, HSDB, MEDLINE, MESH, RTECS, TOXLINE, TSCAINV, SUPERLIST. 29.1 Chemical and Physical Properties (2) Physical state Yellow liquid Density 1.163 (20/4°C) Melting point –9.5°C Boiling point 221.7°C Vapor pressure 1.6 mmHg (60°C) Refractive index 1.54739 (20.4°C) Solubility Soluble in ethanol, ether, benzene, chloroform; slightly soluble in water 29.2 Production and Use 2-Nitrotoluene is used to produce dyestuff intermediates and in manufacturing agricultural and rubber chemicals. 29.3 Exposure Assessment NMAM IV ed., Method #2005. 29.4 Toxic Effects The single oral LD50 in male Sprague–Dawley rats is 891 mg/kg, in male Wistar rats 2100 mg/kg, in female Wistars 2100 mg/kg, and in male CF1 mice 2463 mg/kg. In a 13-week subchronic study, male and female F344 rats and male and female B6C3F1 mice were given diets containing 0, 625, 1250, 2500, 5000 or 10,000 mg/kg (ppm) of 2-NT. Several male rats at the two highest dose levels had mesotheliomas of the tunica vaginalis on the epididymis, an unusual finding (141). Hyaline droplet nephrotoxicity also increased in the male rats; in this respect, 2-NT was the most toxic of the three isomers. In the mice there was degeneration and metaplasia of the olfactory epithelium but no hepatic toxicity. In a 14-day study, 2-NT was given to F344 rats at levels from 625 to 20,000 mg/kg in the diet. Livers of 4/5 male rats at 10,000 ppm showed minimal oval-cell hyperplasia (92). Male and female B6C3F1 mice in the 14-day study received 2-NT at doses of 388 to 10,000 mg/kg; this led to an increase in relative liver weights of the males on the highest dose. Rats given labeled 2-NT excreted 86% in the urine and nine metabolites were identified. A low percentage was 2aminobenzoic acid; all other metabolites were nitrobenzyl derivatives conjugated with glutathione, cysteine, sulfate, and glucuronic acid (92). The NTP has done a chronic study of 2-NT in rats and mice, but the report is not yet available. 29.5 Standards, Regulations, or Guidelines of Exposure The ACGIH TLV-TWA and NIOSH REL is 2 ppm (11 mg/m3) with a skin notation. The OSHA PEL is 5 ppm. 30.0 3-Nitrotoluene 30.0.1 CAS Number: [99-08-1]

30.0.2 Synonyms: m-Nitrotoluol, 1-methyl-3-nitrobenzene; 3-methylnitrobenzene, mnitrophenylmethane, 3-NT 30.0.3 Trade Names: NA 30.0.4 Molecular Weight: 137.14 30.0.5 Molecular Formula: C7H7NO2 30.0.6 Molecular Structure:

Databases and inventories where listed. DOT, IARC, MA, MPOL, MTL, NTPT, PA, PEL, REL, RQ, TLV, WHMI, CANCERLIT, CCRIS, DART, DSL, EINECS, EMIC, EMICBACK, HSDB, MEDLINE, MESH, RTECS, TOXLINE, TSCAINV, SUPERLIST. 30.1 Chemical and Physical Properties (2) Physical state Pale yellow liquid Density 1.157 (20/4°C) Melting point 15.5°C Boiling point 232.6°C Vapor pressure 1.0 mmHg (60°C) Refractive index 1.5475 (20°C) Solubility Soluble in ethanol, ether, benzene; slightly soluble in water 30.2 Production and Use 3-NT is also used in producing dyestuffs, rubber and agricultural chemicals, explosives, and as a chemical intermediate. 30.3 Exposure Assessment NMAM IV ed., 1994 Method #2005. 30.4 Toxic Effects The single dose oral LD50 in male Sprague–Dawley rats was 1072 mg/kg, in male Wistars 2200 mg/kg, in female Wistars 2000 mg/kg, and in male CF-1 mice 330 mg/kg (92). 3-NT was given in the diet to male and female F344 rats (625–20,000 mg/kg in the diet) and B6C3F1 mice (388–10,000 mg/kg in the diet) for 14 days. At the 2500-mg level, weight gains of male rats were less than that of controls, and the relative liver weights of mice were increased at 2500 and 5000 ppm 3-NT. In a 13-week study, hyaline droplet nephropathy was noted in male rats. In mice on 3-NT for 13 weeks, no hepatic toxicity was noted, even though liver weight increased. 3-NT decreased testicular function in male rats at the higher dose levels and increased the length of the estrus cycle in females, but there was no adverse effect on reproduction. The exposed mice showed no change in reproductive system evaluations, compared with controls (92, 141). 3-NT at 200– 600 mg/kg to female B6C3F1 mice decreased the IgM response and response to Listeria monocytogenes but response to other bacteria was not affected (142). After a dose of labeled 3-NT, male rats excreted 68% in the urine. Eight metabolites were separated; 3-aminobenzoic acid and its acetyl derivative were among them; the other metabolites were nitrobenzyl conjugates (92).

30.5 Standards, Regulations, or Guidelines of Exposure The ACGIH TLV-TWA and NIOSH REL is 2 ppm with a skin notation (11 mg/m3). The OSHA PEL is 5 ppm. 31.0 4-Nitrotoluene 31.0.1 CAS Number: [99-99-0] 31.0.2 Synonyms: 4-Methylnitrobenzene; 1-methyl-4-nitrobenzene; 4-nitrotoluol; PNT; pnitrophenylmethane, 4-NT 31.0.3 Trade Names: NA 31.0.4 Molecular Weight: 137.14 31.0.5 Molecular Formula: C7H7NO2 31.0.6 Molecular Structure:

Databases and inventories where listed: CGN, DOT, IARC, MA, MPOL, MTL, NTPT, PA, PEL, REL, RQ, TLV, WHMI, CANCERLIT, CCRIS, DART, DSL, EINECS, EMIC, EMICBACK, HSDB, MEDLINE, MESH, RTECS, TOXLINE, SUPERLIST. 31.1 Chemical and Physical Properties (2) Physical state Yellowish rhombic needles Density 1.280 (20°C) Melting point 54.5°C Boiling point 238.3°C Vapor density 4.72 (air = 1) Vapor pressure 1.3 mmHg (65°C) Refractive index 1.5346 (62.5°C) Solubility Soluble in ethanol, benzene, acetone, chloroform, ether; slightly soluble in water 31.2 Production and Use 4-NT is used as a dyestuff intermediate in producing rubber and agricultural chemicals and explosives, and as a chemical intermediate. 31.3 Exposure Assessment NMAM IV ed., 1994 Method #2005. 31.4 Toxic Effects The single-dose oral LD50 in male Sprague–Dawley rats was 2144 mg/kg, in male Wistar rats 4700 mg/kg, in female Wistars 3200 mg/kg, and in male CF-1 mice 1231 mg/kg (92). In 14-day studies, male and female F344 rats had doses of 625–20,000 mg/kg in the diet, and B6C3F1 mice had doses of 388–10,000 mg/kg. In male rats, doses over 5000 mg led to decreased body weight gain, but females were less susceptible. Although no treatment-related gross lesions were noted after 4-NT, in male rats liver weights were increased in a dose-related fashion. No hepatic toxicity was seen in mice (92).

A 13-week feeding study in F344 rats (625–10,000 ppm) and B6C3F1 mice led to hyaline droplet nephropathy in male rats and mild enlargement of proximal tubule epithelium in both male and female rats, testicular degeneration in male rats at 10,000 ppm, no discernible estrus cycle in female rats at 10,000 ppm, increased liver weights in mice but no hepatic toxicity or effect on reproductive parameters (92, 141). Administration of 200–600 mg/kg daily for 14 days led to suppression of the IgM response and resistance to Listeria monocytogenes but not to other bacteria (143). After a single dose of 14C-labeled 4-NT to male rats, about 77% was excreted in the urine within 72 h and eight metabolites were separated; 4-nitrobenzoic acid and 4-acetamidobenzoic acid were the chief metabolites (92). 31.5 Standards, Regulations, or Guidelines of Exposure The ACGIH TLV-TWA NIOSH REL is 2 ppm (11 mg/m3) with a skin notation. The OSHA PEL is 5 ppm. 32.0 Dinitrotoluene Technical Grade 32.0.1 CAS Number: [25321-14-6] 32.0.2 Synonyms: DNT; dinitrotoluene (mixed isomers); methyl dinitrobenzene (mixed isomers); dinitrotoluene mixture; dinitrotoluene, all isomers; dinitritoluene (mixed isomers); methyldinitrobenzene; dinitrotoluene (2,4 and 2,6 mix); dinitrophenylmethane; TDNT; toluene, ar,ar-dinitro 32.0.3 Trade Names: NA 32.0.4 Molecular Weight: 182.14 32.0.5 Molecular Formula: C7H6N2O4 Commercial or technical grade dinitrotoluene is a mixture of about 76% of the 2,4- isomer, 19% of the 2,6- compound and 5% is made up of 2,3-, 2,5-, 3,4- and 3,5-dinitrotoluenes (2). The mixture is absorbed through the skin and can cause toxic effects. 32.3 Exposure Assessment OSHA method #44 uses filter with linax GC tube and GC with thermal energy analyzer detection. 32.5 Standards, Regulations, or Guidelines of Exposure OSHA PEL and NIOSH REL is 1.5 mg/m3. 33.0 2,4-Dinitrotoluene 33.0.1 CAS Number: [121-14-2] 33.0.2 Synonyms: DNT; 2,4-DNT; dinitrotoluol; 1-methyl-2,4-dinitrobenzene; 2,4-dinitrotoluol 33.0.3 Trade Names: NA 33.0.4 Molecular Weight: 182.14 33.0.5 Molecular Formula: C7H6N2O4 33.0.6 Molecular Structure:

Databases and inventories where listed: CAA1, CA65, IARC, MA, MTL, NJ, NTPT, PA, RQ, S110, TRI, WHMI, CANCERLIT, CCRIS, DART, DSL, EINECS, EMIC, EMICBACK, ETICBACK, GENETOX, HSDB, IRIS, MEDLINE, MESH, RTECS, TOXLINE, TRIFACTS, TSCAINV, SUPERLIST. 33.1 Chemical and Physical Properties (2) Physical state Yellow or orange crystals Boiling point 300°C Melting point 71°C Density 1.3208 Solubility Soluble in ethanol, ether, acetone, benzene 33.2 Production and Use 2,4-Dinitrotoluene is used largely, along with the 2,6-isomer, to make toluene diisocyanate. The DNT mixture is hydrogenated to yield the diamine which is reacted with phosgene to form the diisocyanate which is reacted with polyols to make polyurethane foams (2). DNT is also employed to some extent in manufacturing explosives. 33.4 Toxic Effects The toxicity of 2,4-DNT was discussed thoroughly in the previous edition (2) and by IARC (92). Although there are conflicting reports on carcinogenicity, depending on the animal model, 2,4-DNT is not a hepatocarcinogen. It can affect testicular function, but the toxicity is half that of the 2,6isomer. The various isomers of DNT are considerably less toxic to the mouse, with the possible exception of 2,3-dinitrotoluene, indicating widely differing capacities for metabolism. The oral LD50s for 2,4dinitrotoluene are 268 (rat) versus 1625 (mouse) (144). 2,4-DNT is reportedly a nonsensitizer (145). 2,4-DNT is rapidly absorbed via skin exposure, and repeated dermal applications to rabbits have produced cyanosis, lipemic plasma, depressed hemoglobin and red blood cells, liver hyperplasia and focal necrosis, bone marrow damage, congested spleen, distended bladder, and brain edema; testicular atrophy and aspermatogenesis were reported in beagles. Adverse neuromuscular effects, tremors, and brain lesions in dogs following oral administration have also been reported (145). 2,4-Dinitrotoluene is also rapidly absorbed after oral administration. Little reduction of dinitrotoluene occurs in isolated perfused liver preparation, in isolated hepatocytes, or in microsomal preparations incubated under air (146). The first step in metabolism in male or female Fischer 344 rats is oxidation at the methyl group to yield dinitrobenzyl alcohols, followed by conjugation with glucuronic acid, preparing the alcohol for bile excretion, which occurs to a much greater degree in male than in female rats (146). Intestinal microflora hydrolyze the glucuronides and reduce one of the nitro groups (to an amino group via nitroso intermediates) (147); the reduced metabolites, aminonitrobenzyl alcohols, are then reabsorbed, whereby, it is postulated, the 2,6 isomer is activated (146). All six dinitrotoluene isomers were metabolized to aminonitrotoluenes by an Escherichia coli isolated from human intestinal contents (148), as well as by the intestinal microflora of rats and mice (147). The human urinary metabolites of 2,4-dinitrotoluene in volunteers exposed to dinitrotoluene are 2,4-dinitrobenzoic acid, 2-amino-4-nitrobenzoic acid, 2,4-dinitrobenzyl glucuronide, and 2-(Nacetyl)amino-4-nitrobenzoic acid. The first three of these are found in rat urine; the last differs in the position of reduction and acetylation. The most abundant metabolites of dinitrotoluenes in human urine were the dinitrobenzoic acids; in rats the most abundant metabolites were dinitrobenzyl glucuronides. The appearance of a reduced metabolite of 2,4-dinitrotoluene indicates either that human hepatic enzymes are capable of nitro group reduction of dinitrotoluene or that 2,4dinitrotoluene (or one of its metabolites) gains access to the intestinal microflora (146). The biliary excretion/nitro reduction pathway for bioactivation of 2,6-DNT may occur to a lesser extent in humans than in rats, making an important difference in risk assessment (149).

In a dominant lethal mutation study of 2,4-DNT (60, 180, or 240 mg/kg/day for 5 days, Sprague– Dawley male rats by gavage), lethal mutations were not detected, and no changes were observed in the number of preimplantation losses or implantation sites; however, reproductive performance was adversely affected at the 240 mg dose level (150). Reproductive toxicity evaluation of 2,4-dinitrotoluene in adult male rats fed 0.1 or 0.2% DNT for 3 weeks demonstrated a marked change in Sertoli cell morphology following 0.2% DNT exposure. Circulating levels of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) were increased in 0.2% DNT-treated animals. Raised serum levels of FSH reportedly are frequently, if not always, associated with Sertoli cell malfunction. Reduced weights of the epididymides and decreased epididymal sperm reserves were also observed. The authors concluded that DNT can induce testicular injury, directly or indirectly disturb pituitary function, and exert a toxic effect at the late stages of spermatogenesis. A direct effect on the hypothalamic-hypophyseal axis was not precluded, according to the authors, because testosterone concentrations remained within the normal range, whereas LH levels were elevated (151). Exposure to 2,4-DNT reportedly decreased human sperm count and increased spontaneous abortions in the workers’ wives (technical-grade dinitrotoluene is assumed) (145); however, in a follow-up epidemiological study, no effect on sperm levels was found in workers (152). The initial carcinogenicity study in 1978 was conducted by NCI and involved a dietary feeding study of 2,4-DNT continuously for 18 months to male and female F344 rats and B6C3F1 mice at 0.008 or 0.02% (and 0.008 or 0.04%, respectively), followed by a 6-month observation period. Because the incidence of hepatic neoplasms in treated animals and control animals was not significantly different, the NCI bioassay was considered negative for hepatocarcinogenesis in both rats and mice. In this study, 2,4-DNT was the primary component (95% 2,4-DNT, < 5% 2,6-DNT) (153). However, there was an increased incidence of fibroma of the skin and subcutaneous tissue in the high- and low-dose male rats and an increased incidence of mammary gland fibroadenoma in high-dose female rats (153, 154). A second study evaluated 2,4-DNT (containing approximately 2% 2,6-DNT) in Sprague–Dawley (CD) rats and mice (CD-1) for 2 years (155). The high doses were toxic to both mice and rats, and the life span of mice was shortened by 50%. About half of the high-dose and approximately 25% of the control male rats died by the end of the 20th month. 2,4-DNT was hepatocarcinogenic, resulting in a 21% incidence of hepatocellular carcinomas in male rats of the high-dose (34 mg/kg/day) group dying or killed after 1 year of age. By comparison, high-dose female rats had a 53% incidence of hepatocellular carcinomas (155). The reason for the higher incidence of hepatocellular carcinoma in female rats compared with male rats, the inverse of that observed in a third study, is not clear; differences in strain of rat, the isomeric composition of the DNT, or other unspecified variances in protocols may be the basis for the differences in sex response between these two studies (154). The results of further study demonstrated that 2,6-DNT is a complete hepatocarcinogen; in contrast, 2,4-DNT was not hepatocarcinogenic when fed at twice the high dose of 2,6-DNT during the same time period. The authors concluded that 2,4-DNT may act as a promoter but cannot initiate carcinogenesis. The hepatocarcinogenicity of technical-grade DNT is mainly due to 2,6-DNT (154, 155). In an analytically controlled comparative bioassay 2,4-dinitrotoluene was not carcinogenic in male F344 rats (155); the lack of hepatocarcinogenicity of 2,4-DNT was consistent with the conclusion that 2,4-DNT is not a hepatocarcinogen. The difference between these studies could simply be due to strain differences, the greater amount of 2,6-DNT contaminating the 2,4-DNT used, the slightly higher dose of 2,4-DNT used (34 versus 27 mg), or the extended duration of feeding (2 years versus 1 year) (155). The positive response by 2,4-dinitrotoluene in the Ames assay is unclear (115).

IARC, NIOSH, OSHA, and ACGIH have not classified this isomer as a potential carcinogenic risk. 33.5 Standards, Regulations or Guidelines of Exposure The ACGIH TLV-TWA is 0.2 mg/m3 with a skin notation and an A3 rating. The actual listing is for the technical grade mixture, but it applies to the components. 34.0 2,6-Dinitrotoluene 34.0.1 CAS Number: [606-20-2] 34.0.2 Synonyms: 2-Methyl-1,3-dinitrobenzene; 2,6-DNT; 1,3-dinitro 2-methylbenzene 34.0.3 Trade Name: NA 34.0.4 Molecular Weight: 182.14 34.0.5 Molecular Formula: C7H6N2O4 34.0.6 Molecular Structure:

Databases or inventories where listed: CA65, IARC, MA, NJ, PA, RQ, S110, TRI, CANCERLIT, CCRIS, DART, DSL, EINECS, EMIC, EMICBACK, ETICBACK, GENETOX, HSDB, MEDLINE, MESH, RTECS, TOXLINE, TSCAINV, SUPERLIST. 34.1 Chemical and Physical Properties (2) Physical state Yellow rhombic crystals Melting point 64–66°C Density 1.2833 Solubility Soluble in ethanol 34.2 Production and Use 2,6-Dinitrotoluene is used primarily, along with the other isomers, in producing toluene diisocyanate; production of the diisocyanate ranges from 100 million to almost a billion pounds each year. 34.4 Toxic Effects The toxicity and metabolic interactions of 2,6-dinitrotoluene have been reviewed in the previous edition (2) and by IARC (92). In F344 rats, the 2,6-isomer gave four distinct DNA adducts versus three for the 2,4-isomer, and with a much higher level of binding than 2,4-DNT (92, 156). In male B6C3F1 mice, only two such adducts were detected (157). A metabolite, 2-amino-6-nitrotoluene, gave the same adducts as 2,6-DNT, but at 30-fold lower levels (158). Intestinal microflora were important in activating 2,6-DNT to mutagenic metabolites (159), and the genotoxicity was increased by pretreating the rats with the enzyme inducers Aroclor 1254 or creosote (160, 161). 35.0 3,5-Dinitrotoluene 35.0.1 CAS Number: [618-85-9] 35.0.2 Synonyms: 1-Methyl-3,5-dinitrobenzene 35.0.3 Trade Name: NA 35.0.4 Molecular Weight: 182.14 35.0.5 Molecular Formula: C7H6N2O4

35.0.6 Molecular Structure:

Databases or inventories where listed: IARC, CANCERLIT, DART, EINECS, EMIC, EMICBACK, ETICBACK, GENETOX, HSDB, MEDLINE, MESH, RTECS, TOXLINE, SUPERLIST. 35.1 Chemical and Physical Properties (92) Physical state Yellow rhombic needles Boiling point Sublimes Melting point 93°C Density 1.2772 (11/4°C) Solubility Soluble in benzene, chloroform, ether, ethanol 35.2 Production and Use 3,5-Dinitrotoluene occurs in technical grade dinitrotoluene and has no specific uses by itself. 35.4 Toxic Effects No specific studies of the toxicity of this isomer were located, although it may contribute to the effects of technical grade dinitrotoluene. The 3,5-isomer was mutagenic in the Salmonella test without metabolic activation and in some strains with the rat liver S9 fraction. It was not active in causing mutation in Chinese hamster ovary cells, and it did not induce unscheduled DNA synthesis in rat liver cells in culture (92). For the remaining dinitrotoluenes, the only data found related to the databases in which they were listed. 36.0 2,3-Dinitrotoluene 36.0.1 CAS Number: [602-01-7] 36.0.2 Synonyms: 1-Methyl-2,3-dinitrobenzene 36.0.3 Trade Names: NA 36.0.4 Molecular Weight: 182.14 36.0.5 Molecular Formula: C7H6N2O4 36.0.6 Molecular Structure:

Databases and inventories where listed: CCRIS, EINECS, EMIC, EMICBACK, ETICBACK, GENETOX, HSDB, MESH, RTECS, TOXLINE, TSCAINV. 37.0 2,5-Dinitrotoluene 37.0.1 CAS Number: [619-15-8]

37.0.2 Synonyms: 2-Methyl-1,4-dinitrobenzene 37.0.3 Trade Names: NA 37.0.4 Molecular Weight: 182.14 37.0.5 Molecular Formula: C7H6N2O4 37.0.6 Molecular Structure:

Databases and inventories where listed: CCRIS, EINECS, EMIC, EMICBACK, ETICBACK, GENETOX, HSDB, RTECS, TOXLINE, TSCAINV. 38.0 3,4-Dinitrotoluene 38.0.1 CAS Number: [610-39-9] 38.0.2 Synonyms: 4-Methyl-1,2-dinitrobenzene; 1,2-dinitro–4-methylbenzene 38.0.3 Trade Names: NA 38.0.4 Molecular Weight: 182.14 38.0.5 Molecular Formula: C7H6N2O4 38.0.6 Molecular Structure:

Databases and inventories where listed: MA, PA, RQ, CANCERLIT, CCRIS, EINECS, EMIC, EMICBACK, ETICBACK, GENETOX, HSDB, MESH, RTECS, TOXLINE, TSGAINV, SUPERLIST. 39.0 2,4,6-Trinitrotoluene 39.0.1 CAS Number: [118-96-7] 39.0.2 Synonyms: TNT; trinitrotoluol; sym-trinitrotoluene; trinitrotoluene; 2-methyl-1,3,5trinitrobenzene; entsufon; 1-methyl-2,4,6-trinitrobenzene; methyltrinitrobenzene; tolite; trilit; strinitrotoluene; s-trinitrotoluol; trotyl; sym-trinitrotoluol; alpha-trinitrotoluol 39.0.3 Trade Names: NA 39.0.4 Molecular Weight: 227.13 39.0.5 Molecular Formula: C7H5N3O6 39.0.6 Molecular Structure:

Databases and inventories where listed: DOT, IARC, IL, MA, NJ, PA, PEL, REL, S110, TLV, WHMI, CANCERLIT, CCRIS, DART, DSL, EINECS, EMIC, EMICBACK, GENETOX, HSDB, IRIS, MEDLINE, MESH, RTECS, TOXLINE, TSCAINV, SUPERLIST. 39.1 Chemical and Physical Properties (2) Physical state Specific gravity Melting point Boiling point Vapor pressure Solubility

Colorless to pale yellow crystals or monoclinic prisms 1.654 (20°C) 82°C 240°C (explodes) 0.046 mmHg (82°C)

Soluble in ether, benzene, chloroform, carbon tetrachloride, toluene, acetone; slightly soluble in water 39.2 Production and Use TNT has been used in explosives for almost 100 years. It must be exploded by a denonator, but it can be poured into shells when molten. 39.3 Exposure Assessment OSHA Analytical method # 44 using linax GC tube and analysis by GC with thermal energy analyzer detection with explosives package. 39.4 Toxic Effects The toxic effects of TNT in exposed workers are well known and include hepatitis, irritation of eyes, nose, throat and skin, methemoglobinemia, and cararacts, in addition to other symptoms (2). Workers exposed to TNT in a packing site, where levels of TNT exceeded 1 mg/m3 had skin levels after each shift that were threefold those of unexposed workers. This correlated with total blood levels of TNT and the metabolites 4-amino-2,6-dinitrotoluene and 2-amino-4,6-dinitrotoluene (162). Furthermore, the levels of Cu, Zn, Na, Mg, and Se in the semen of these workers were significantly decreased, and sperm viability was less. Sperm malformations increased (162). A county in Germany contaminated with TNT residues from explosives manufacture had a higher risk for leukemia than neighboring counties (92). Thus, biodegradation of TNT residues from military or manufacturing sites is a matter of interest. One study found that reduction to nitroamines (2-amino-4,6dinitrotoluene, 4-amino-2,6-dinitrotoluene 2,4-diamino-6-nitrotoluene), reduction to 2,4,6triaminotoluene, and formation of azoxy compounds (2,2', 6,6'-tetranitro-4,4'azoxytoluene and 4,4', 6,6'-tetranitro-2,2'-azoxytoluene) occurred. In addition, p-cresol and methylphloroglucinol were identified, indicating removal of the nitrogens (163). Labeled TNT residues in compost from TNTcontaminated soil were not excreted readily in rats and accumulated in the kidneys, indicating that a unique TNT derivative had formed (164). A 6-month oral toxicity study in beagle dogs at levels of 0.5, 2, 8, or 32 mg/kg/day led to anemia, methemoglobinemia, splenomegaly, and effects on the liver, similar to those in exposed workers. Only the highest dose was lethal, despite the toxicity (165). Reportedly a 24-month chronic study in mice and rats led to tumors in female rats but not in mice or male rats (164). The toxicity, mutagenicity, and metabolism of TNT have been covered in a review by IARC (92). 39.5 Standards, Regulations, or Guidelines of Exposure The ACGIH TLV is 0.1 mg/m3 with a skin notation. The OSHA PEL is 1.5 mg/m3 with a skin notation and the NIOSH REL is 0.5 mg/m3 with a skin notation. 40.0 Tetryl

40.0.1 CAS Number: [479-45-8] 40.0.2 Synonyms: 2,4,6-Trinitrophenylmethylnitramine; N-methyl-N,2,4,6-tetranitroaniline; nitramine; tetralite; trinitrophenylmethylnitramine; 2,4,6-tetryl 40.0.3 Trade Names: NA 40.0.4 Molecular Weight: 287.15 40.0.5 Molecular Formula: C7H5N5O8 40.0.6 Molecular Structure:

Databases and inventories where listed: DOT, IL, MA, NJ, PA, PEL, REL, TLV, WHMI, CANCERLIT, CCRIS, EINECS, EMIC, EMICBACK, HSDB, MEDLINE, MESH, RTECS, TOXLINE, TSCAINV, SUPERLIST. 40.1 Chemical and Physical Properties (2) Physical state Yellow monoclinic crystals Density 1.57 at 19°C Melting point 130°C Boiling point 187°C, explodes Solubility Soluble in ethanol, ether; insoluble in water 40.2 Production and Use Tetryl is used in various types of explosive devices. 40.3 Exposure Assessment NMAM IInd ed., vol 3, 1977 Method #S225. 40.4 Toxic Effects Tetryl is a sensitizer and causes dermatitis (2). Practically no information on toxicity studies was located, but tetryl reportedly is under study by the U.S. EPA and military groups (115). Plant oxidoreductase enzymes under anaerobic conditions could remove the N-nitro group as nitrite, yielding N-methyl-trinitroaniline (166). 40.5 Standards, Regulations, or Guidelines of Exposure The OSHA-PEL, NIOSH REL and ACGIH TLV-TWA are 1.5 mg/m3 with a note that it causes dermatitis.

Aromatic Nitro and Amino Compounds Elizabeth K. Weisburger, Ph.D., Vera W. Hudson, MS H. Aniline and Derivatives 41.0 Aniline 41.0.1 CAS Number: [62-53-3]

41.0.2 Synonyms: Benzamine; aniline oil; phenylamine; aminobenzene; aniline oil; phenylamine; aminophen; kyanol; benzidam; blue oil; C.I. 76000; C.I. oxidation base 1; cyanol; krystallin; anyvim; arylamine 41.0.3 Trade Names: NA 41.0.4 Molecular Weight: 93.13 41.0.5 Molecular Formula: C6H7N 41.0.6 Molecular Structure:

Databases and inventories where listed: CAA1, CA65, CGB, DOT, IARC, IL, MA, MI, MTL, NJ, PA, PELS, REL, RQ, S302, TLV, TRI, WHMI, AIDSLINE, CANCERLIT, CCRIS, DART, DSL, EINECS, EMIC, EMICBACK, ETICBACK, GENETOX, HSDB, IRIS, MEDLINE, MESH, RTECS, TOXLINE, TRIFACTS, TSCAINV, SUPERLIST. 41.1 Chemical and Physical Properties (2) Physical state Oily liquid Density 1.002 (20/4°C) Melting point –6.3°C Boiling point 184.4–186°C Vapor density 3.22 (air = 1) Vapor pressure 15 mm Hg (77°C) Refractive 1.5863 (20°C) index Solubility Soluble in ethanol, ether, benzene, chloroform, carbon tetrachloride, acetone; somewhat soluble in water 41.2 Production and Use In 1992, more than 900 million pounds were produced, mostly by hydrogenation of nitrobenzene (167). Aniline is used in manufacture of dyestuffs, various intermediates, in rubber accelerators and in antioxidants, pharmaceuticals, photographic chemicals, plastics, isocyanates, hydroquinones, herbicides, fungicides, ion-exchange resins, whitening agents, and as an intermediate for various other chemicals. 41.3 Exposure Assessment NMAM IVth ed., 1994 Method #2002. 41.4 Toxic Effects The toxic effects of aniline have been discussed (2); in humans, they include headaches, methemoglobinemia, tremors, narcosis and coma. Although historically bladder cancers in dyestuff workers were called aniline cancers, recent epidemiological studies indicate that o-toluidine, a probable contaminant, was more likely the cause of the bladder tumors (168). Although high doses of aniline hydrochloride led to no excess tumors in B6C3F1 mice, levels of 3000 or 6000 ppm in the diet led to hemangiosarcomas or fibrosarcomas of the spleen in rats. Several publications have addressed the mechanism of this effect of aniline. Study of the hematopoietic toxicity of aniline in rats showed that blood methemoglobinemia peaked at 37% in 0.5 h and increased lipid peroxidation occurred in the spleen (169). Tests for up to 90 days with 600 ppm aniline hydrochloride showed that the spleens of test rats had striking histopathological changes and damage to erythrocyte iron was

increased (170). It was surmised that reaction of aniline or a metabolite with erythrocytes led to their accumulation, as well as iron deposition in the spleen (171); thus oxidative stress was responsible for the splenotoxicity of aniline (172). Exposure of rats to an atmosphere of 15,000 ppm aniline for 10 minutes, a situation simulating an industrial accident, also caused an increase in lipid peroxidation in the mitochondrial portions of the cerebellum, brain stem, and brain cortex (173). Treatment of rats with 10% ethanol in the drinking water for 12 or 36 weeks stimulated the level of P450 and the degree of aniline hydroxylation (127). Human hemoglobin, as well as P450, cause aniline to be metabolized to the 2- and 4-aminophenols (174), but in vitro, exclusive 4-hydroxylation of aniline occurred in the presence of singlet oxygen (175). Aniline is readily absorbed through the skin. Thus the various occupational and industrial hygiene “skin” notations are necessary. 41.5 Standards, Regulations, or Guidelines of Exposure The ACGIH TLV-TWA is 2 ppm (7.6 mg/m3) with A3 and skin notations. The OSHA PEL is 5 ppm. NIOSH considers it a carcinogen. 42.0 N-Methylaniline 42.0.1 CAS Number: [100-61-8] 42.0.2 Synonyms: MA, N-methylbenzeneamine, monomethylaniline, N-methyl-phenylamine, Nmonomethylaniline, methyl aniline, methylphenylamine, anilinomethane, (methylamino) benzene, N-methylaminobenzene, N-phenylmethylamine 42.0.3 Trade Names: 42.0.4 Molecular Weight: 107.15 42.0.5 Molecular Formula: C7H9N 42.0.6 Molecular Structure:

Databases and inventories where listed: DOT, IL, MA, PA, PEL, REL, TLV, WHMI, CANCERLIT, CCRIS, DART, DSL, EINECS, EMICBACK, ETICBACK, HSDB, MEDLINE, MESH, RTECS, TOXLINE, TSCAINV, SUPERLIST. 42.1 Chemical and Physical Properties (2) Physical state Colorless to slightly yellow liquid; turns brown on exposure to air Specific gravity 0.989 at 20°C Melting point –57°C Boiling point 194.6–196°C Flash point 79.4°C (closed cup) Solubility Soluble in ethanol, ether; slightly soluble in water 42.2 Production and Use N-Methylaniline is used as a solvent and an intermediate. 42.3 Exposure Assessment NMAM IVth ed., 1994, Method #3511. 42.4 Toxic Effects No new information was located. 42.5 Standards, Regulations, or Guidelines of Exposure The ACGIH TLV-TWA and NIOSH REL is 0.5 ppm with a skin notation. OSHA PEL is 2 ppm. 43.0 N,N-Dimethylaniline

43.0.1 CAS Number: [121-69-7] 43.0.2 Synonyms: Dimethylaniline, Versneller NL 63/10, N,N-dimethylbenzenamine; (dimethylamino)benzene, dimethylphenylamine, N,N-dimethylphenylamine, dimethylphenylamine, DMA 43.0.3 Trade Names: NA 43.0.4 Molecular Weight: 121.18 43.0.5 Molecular Formula: C8H11N 43.0.6 Molecular Structure:

Databases and inventories where listed: CAA1, DOT, IARC, IL, MA, MTL, NJ, NTPT, PA, PEL, REL, TLV, TRI, WHMI, CANCERLIT, CCRIS, DART, DSL, EINECS, EMIC, EMICBACK, ETICBACK, HSDB, IRIS, MEDLINE, MESH, RTECS, TOXLINE, TRIFACTS, TRI, TSCAINV, SUPERLIST. 43.1 Chemical and Physical Properties (2) Physical state Yellow liquid Density 0.9557 (20/4°C) Melting point 2.45°C Boiling point 192.5°C Vapor density 4.17 (air = 1) Refractive index 1.55819 (20°C) Solubility Soluble in ethanol, ether; slightly soluble in water Flash point 145°F (closed cup) 170°C (open cup) 43.2 Production and Use N,N-Dimethylaniline is used in production of dyestuffs, as a solvent, a reagent in methylation reactions, and a hardener in fiberglass reinforced resins. 43.3 Exposure Assessment NMAM IVth ed., 1994 Method #2002. 43.4 Toxic Effects The previous edition reported that N,N-dimethylaniline can undergo both N-oxidation and Ndemethylation (2). Further studies showed that P4502B1 from rats converts this compound to the Noxide or dealkylates it in the ratio of 6 parts N-oxide to 1020 parts of dealkylated product, probably by one-electron oxidation (176, 177). In another metabolic system (rabbit liver microsomes), superoxide and P4502B4 were considered the active entities (178); this was reviewed by IARC (179). 43.5 Standards, Regulations, or Guidelines of Exposure The ACGIH TLV-TWA NIOSH REL is 5 ppm with a STEL of 10 ppm and skin and A4 notations. OSHA PEL is also 5 ppm with skin notation. 44.0 N-Ethylaniline 44.0.1 CAS Number: [103-69-5]

44.0.2 Synonyms: Ethylphenylamine; N-ethyl aniline; anilinoethane; N-ethylaminobenzene 44.0.3 Trade Names: NA 44.0.4 Molecular Weight: 121.18 44.0.5 Molecular Formula: C8H11N 44.0.6 Molecular Structure:

Databases and inventories where listed: DOT, MA, PA, WHMI, CCRIS, EINECS, EMICBACK, HSDB, MESH, RTECS, TOXLINE, TSCAINV, SUPERLIST. 44.1 Chemical and Physical Properties (2) Physical state Colorless liquid, darkens in air Boiling point 204.5°C Melting point –63.5°C Solubility Soluble in acetone, benzene; miscible with ethanol, ether; insoluble in water 44.2 Production and Use N-Ethylaniline is used an an explosive stabilizer and in dyestuff manufacture. 44.4 Toxic Effect No specific new information located. 44.5 Standards, Regulations, or Guidelines of Exposure None assigned. 45.0 N,N-Diethylaniline 45.0.1 CAS Number: [91-66-7] 45.0.2 Synonyms: Diethyl aniline, N,N-diethylbenzenamine, N,N-diethylaminobenzene, diethylphenylamine, 45.0.3 Trade Name: NA 45.0.4 Molecular Weight: 149.24 45.0.5 Molecular Formula: C10H15N 45.0.6 Molecular Structure:

Databases and inventories where listed: CAA1, DOT, MA, PA, WHMI, CCRIS, DSL, EINECS, EMIC, EMICBACK, HSDB, RTECS, TOXLINE, TSCAINV, SUPERLIST. 45.1 Chemical and Physical Properties (2)

Physical state Colorless or yellow or brown oil (flammable) Density 0.93507 (20/4°C) Melting point –38.8°C Boiling point 215.5-216°C Refractive index 1.54105 (22°C) Solubility Soluble in ethanol, ether; fairly soluble in water 45.2 Production and Use Diethylaniline is used as an intermediate in synthesizing of dyestuffs and pharmaceuticals. 45.4 Toxic Effects During oxidative metabolism, as with N,N-dimethylaniline, a much greater proportion of the diethylaniline was dealkylated, rather than forming an N-oxide (176). 45.5 Standards, Regulations, or Guidelines of Exposure None assigned.

Aromatic Nitro and Amino Compounds Elizabeth K. Weisburger, Ph.D., Vera W. Hudson, MS I. Chlorinated Anilines 46.0 2-Chloroaniline 46.0.1 CAS Number: [95-51-2] 46.0.2 Synonyms: 2-Chlorobenzenamine; 1-amino-2-chlorobenzene; fast yellow gc base; OCA 46.0.3 Trade Name: NA 46.0.4 Molecular Weight: 127.57 46.0.5 Molecular Formula: C6H6ClN 46.0.6 Molecular Structure:

Databases and inventories where listed: CCRIS, DSL, EINECS, EMIC, EMICBACK, GENETOX, HSDB, MEDLINE, MESH, RTECS, TOXLINE, TSCAINV. 46.1 Chemical and Physical Properties (2) Physical state Colorless liquid Density 1.2125 (20/4°C) Melting point a, –14°C; b, –1.9°C Boiling point 208.8°C Refractive index 1.5895 (20°C) Solubility Soluble in acetone, ether; miscible with ethanol; insoluble in water 46.2 Production and Use It is reportedly used as an intermediate in dyestuffs (2).

46.4 Toxic Effects The NTP has done short-term toxicity studies of 2-chloroaniline in rats and mice, but the reports were in peer review. 2-Chloroaniline was the most potent of the isomeric chloroanilines in F344 rats with regard to nephrotoxic and hepatoxic effects (2). In contrast, when the chloroanilines were acetylated, the toxicity was greatly decreased and 2-chloroacetanilide was the least toxic of the isomers (180). Possible metabolites were tested for nephrotoxicity, but they were less potent than the parent chloroaniline (181). 46.5 Standards, Regulations, or Guidelines of Exposure None assigned. 47.0 3-Chloroaniline 47.0.1 CAS Number: [108-42-9] 47.0.2 Synonyms: 3-Chlorobenzenamine, MCA, m-aminochlorobenzene, 1-amino-3-chlorobenzene, 3-chlorophenylamine, fast orange gc base, orange gc base 47.0.3 Trade Names: NA 47.0.4 Molecular Weight: 127.57 47.0.5 Molecular Formula: C6H6ClN 47.0.6 Molecular Structure:

Databases and inventories where listed: WHMI, CCRIS, DART, DSL, EINECS, EMICBACK, GENETOX, HSDB, MESH, RTECS, TOXLINE, TSCAINV, SUPERLIST. 47.1 Chemical and Physical Properties (2) Physical state Colorless liquid Melting point –10.3°C Boiling point 229.8–230.5°C Refractive index 1.59424 (20°C) Solubility Soluble in acetone, benzene, ether; miscible with ethanol; insoluble in water 47.2 Production and Use Uses are reportedly the same as those of the other isomers. 47.4 Toxic Effects Although 3-chloroaniline is readily absorbed through the skin and thus can cause the toxicity associated with aromatic amines, in F344 rats, it had the lowest nephrotoxicity of the isomeric chloroanilines. However, the situation was reversed for the acetyl derivatives, and 3chloroacetanilide was the most toxic (180). The various 3-haloanilines (iodo, bromo, chloro, and fluoro) had different orders of nephrotoxic potential in vivo and in vitro for unknown reasons. They were not potent nephro- or hepatotoxicants at sublethal doses (182). Tests of possible phenolic metabolites of 3-chloroaniline did not show hepatotoxicity, but 4-amino-2-chlorophenol retained nephrotoxic activity at the highest dose level tested (183). 47.5 Standards, Regulations, or Guidelines of Exposure None assigned. 48.0 4-Chloroaniline 48.0.1 CAS Number: [106-47-8]

48.0.2 Synonyms: p-Chlorophenylamine; 4-chlorobenzenamine, 4-chloro-1-aminobenzene, 1-amino4-chlorobenzene, p-aminochlorobenzene 48.0.3 Trade Names: NA 48.0.4 Molecular Weight: 127.57 48.0.5 Molecular Formula: C6H6ClN 48.0.6 Molecular Structure:

Databases and inventories where listed: CA65, IARC, MA, NJ, NTPT, PA, RQ, TRI, WHMI, CANCERLIT, CCRIS, DART, DSL, EINECS, EMIC, EMICBACK, ETICBACK, GENETOX, HSDB, IRIS, MEDLINE, MESH, RTECS, TOXLINE, TSCAINV, SUPERLIST. 48.1 Chemical and Physical Properties (2) Physical state Colorless solid, rhombic crystals Density 1.427 (19/4°C) Melting point 72.5°C Boiling point 231-232°C Solubility Soluble in ether; miscible with ethanol; insoluble in water 48.2 Production and Use 4-Chloroaniline is used as a dye intermediate. 48.4 Toxic Effects The metabolism, excretion pattern, and carcinogenicity of 4-chloroaniline were discussed (2, 179). A patient who was acutely poisoned by 4-chloroaniline excreted conjugates of the parent compound and 2-amino-5-chlorophenol in the urine, indicating that ortho-hydroxylation had occurred, similar to results in other species (179). 4-Chloroaniline was somewhat less toxic to the liver and kidney of F344 rats than 2-chloroaniline, but upon acetylation, it had higher nephrotoxic potential (180). A study of possible phenolic metabolites showed that they had lower renal toxicity than the parent chloroanilines but still retained some toxicity (181, 184). P450 enzymes cause removal of the chlorine to yield 4-aminophenol (185, 186). Contrary to the situation with many halogen-substituted compounds, a fluoro substituent in the 4-position was removed more easily than other halogens (185). 48.5 Standards, Regulations, or Guidelines of Exposure None assigned. 49.0 2,3-Dichloroaniline 49.0.1 CAS Number: [608-27-5] 49.0.2 Synonyms: 2,3 Dichlorobenzenamine 49.0.3 Trade Names: NA 49.0.4 Molecular Weight: 162.02 49.0.5 Molecular Formula: C6H5NCl2 49.0.6 Molecular Structure:

Data bases and inventories where listed: EINECS, HSDB, RTECS, TOXLINE, TSCAINV. 49.1 Chemical and Physical Properties (2) Boiling point 252°C Melting point 24°C Solubility Soluble in acetone, ethanol, ether 49.2 Production and Use No specific uses were located. 49.4 Toxic Effects 2,3-Dichloroaniline was the least nephrotoxic of the dichloroaniline isomers (187). 49.5 Standards, Regulations, or Guidelines of Exposure None assigned. 50.0 2,4-Dichloroaniline 50.0.1 CAS Number: [554-00-7] 50.0.2 Synonyms: 2,4 -Dichlorobenzenamine, 2,4-dichloroaniline, pract. 50.0.3 Trade Names: NA 50.0.4 Molecular Weight: 162.02 50.0.5 Molecular Formula: C6H5NCl2 50.0.6 Molecular Structure:

Data bases and inventories where listed: CCRIS, DSL, EINECS, EMIC, EMICBACK, ETICBACK, GENETOX, HSDB, MESH, RTECS, TOXLINE, TSCAINV. 50.1 Chemical and Physical Properties (2) Boiling point 245°C Melting point 63–64°C Solubility Soluble in ethanol, ether 50.2 Production and Use Specific uses not located. 50.4 Toxic Effects 2,4-Dichloroaniline was one of the isomers considered to have low nephrotoxicity, compared with the 3,5-isomer (187). The relative order of toxicity was the same in vitro as in vivo (188). 50.5 Standards, Regulations, or Guidelines of Exposure None assigned. 51.0 2,5-Dichloroaniline 51.0.1 CAS Number: [95-82-9]

51.0.2 Synonyms: 2,5-Dichlorobenzenamine, amarthol fast scarlet gg base; azoene fast scarlet 2g base; C.I. 37010; C.I. azoic diazo component 3; fast scarlet 2g; scarlet base gg; 1-amino-2, 5dichlorobenzene; 2-amino-1, 4-dichlorobenzene; 2,5-dichlorobenzamine 51.0.3 Trade Names: NA 51.0.4 Molecular Weight: 162.02 51.0.5 Molecular Formula: C6H5NCl2 51.0.6 Molecular Structure:

Databases and inventories where listed: CCRIS, EINECS, EMIC, EMICBACK, HSDB, RTECS, TOXLINE, TSCAINV. 51.1 Chemical and Physical Properties (2) Boiling point 251°C Melting point 50°C Solubility Soluble in ethanol, ether, benzene 51.2 Production and Use No specific uses were located. 51.4 Toxic Effects The nephrotoxicity of 2,5-dichloroaniline in F344 rats was somewhat lower than that of the 3,5isomer but greater than that of the other isomers (187). A possible metabolite, 2-amino-4chlorophenol, had low nephrotoxic potential (183). 51.5 Standards, Regulations, or Guidelines of Exposure None assigned. 52.0 2,6-Dichloroaniline 52.0.1 CAS Number: [608-31-1] 52.0.2 Synonyms: 2,6-Dichlorobenzenamine 52.0.3 Trade Name: NA 52.0.4 Molecular Weight: 162.02 52.0.5 Molecular Formula: C6H5NCl2 52.0.6 Molecular Structure:

Databases and inventories where listed: EINECS, TOXLINE, TSCAINV. 52.1 Chemical and Physical Properties (2)

Melting point 39°C Solubility Soluble in ether 52.2 Production and Uses No specific uses located. 52.4 Toxic Effects 2,6-Dichloroaniline had moderately low nephrotoxic effects in F344 rats, compared with the 3,5isomer (187). 52.5 Standards, Regulations, or Guidelines of Exposure None assigned. 53.0 3,4-Dichloroaniline 53.0.1 CAS Number: [95-76-1] 53.0.2 Synonyms: 1-Amino-3, 4-dichlorobenzene, 3,4-dichlorobenzenamine; 3,4-DCA; 4,5dichloroaniline 53.0.3 Trade Names: NA 53.0.4 Molecular Weight: 162.02 53.0.5 Molecular Formula: C6H5NCl2 53.0.6 Molecular Structure:

Databases and inventories where listed: MA, MTL, PA, WHMI, CANCERLIT, CCRIS, DART, DSL, EINECS, EMIC, EMICBACK, GENETOX, HSDB, MEDLINE, MESH, RTECS, TOXLINE, TSCAINV, SUPERLIST. 53.1 Chemical and Physical Properties (2) Melting point 71–72°C Boiling point 272°C Solubility Soluble in ethanol, benzene; almost insoluble in water 53.2 Production and Use It has some use in herbicide production. 53.4 Toxic Effects 3,4-Dichloroaniline causes methemoglobinemia in mice and chloracne in humans (2). However, its nephrotoxic effect was relatively low, compared with that of the 3,5-isomer (187). A possible metabolite had some renal toxicity at a high dose (183). 53.5 Standards, Regulations, or Guidelines of Exposure None assigned. 54.0 3,5-Dichloroaniline 54.0.1 CAS Number: [626-43-7] 54.0.2 Synonyms: 3,5-Dichlorobenzenamine; m-dichloroaniline; BF 352-31 54.0.3 Trade Names: NA 54.0.4 Molecular Weight: 162.02

54.0.5 Molecular Formula: C6H5NCl2 54.0.6 Molecular Structure:

Databases and inventories where listed: CCRIS, DART, EINECS, EMICBACK, HSDB, MEDLINE, MESH, TOXLINE, TSCAINV. 54.1 Chemical and Physical Properties (2) Boiling point 260°C Melting point 51–53°C Solubility Soluble in ethanol, benzene, ether 54.2 Production and Use No specific uses were located apart from its use in research. 54.4 Toxic Effects Of all of the dichloroanilines, the 3,5-isomer had the highest nephrotoxic action in F344 rats (187). Further studies examined this effect more throughly. When administered intraperitoneally in dimethyl sulfoxide solution, the rats died within 24 hrs; if given as a solution in saline or sesame oil, no renal toxicity was noted (189). Treatment of rats with various enzyme inducers and inhibitors and then 3,5-dichloroaniline did not cause much change in the renal or hepatic effects of the 3,5-isomer. These results indicated that the parent compound was directly toxic (190). A putative metabolite, 4amino-2, 6-dichlorophenol, retained the nephrotoxic action of the parent (191). However, another possible metabolite, 3,5-dichlorophenylhydroxylamine, was the most potent inducer of hemoglobin oxidation, the parent 3,5-dichloroaniline was the least active, and 4-amino-2, 6-dichlorophenol was intermediate in activity (192). 54.5 Standards, Regulations, or Guidelines of Exposure None assigned.

Aromatic Nitro and Amino Compounds Elizabeth K. Weisburger, Ph.D., Vera W. Hudson, MS J. Nitroanilines 55.0 2-Nitroaniline 55.0.1 CAS Number: [88-74-4] 55.0.2 Synonyms: 1-Amino-2-nitrobenzene; 2-nitrobenzenamine; azoene fast orange gr base; azoene fast orange gr salt; azofix orange gr salt; azogene fast orange gr; azoic diazo component 6; brentamine fast orange gr base; brentamine fast orange gr salt; C.I. azoic diazo component 6; devol orange b; diazo fast orange gr; fast orange base gr; fast orange base jr; fast orange gr base; fast orange gr salt; fast orange o base; fast orange o salt; fast orange salt jr; hiltonil fast orange gr base; hiltosal fast orange gr salt; hindasol orange gr salt; natasol fast orange gr salt; o-nitraniline; C.I. 37025; orange base ciba ii; orange base irga ii; orange grs salt; orange salt ciba ii; orange salt irga ii 55.0.3 Trade Names: NA

55.0.4 Molecular Weight: 138.13 55.0.5 Molecular Formula: C6H6N2O2 55.0.6 Molecular Structure:

Databases and inventories where listed: DOT, WHMI, CCRIS, DSL, EINECS, EMIC, EMICBACK, HSDB, RTECS, TOXLINE, TSCAINV, SUPERLIST. 55.1 Chemical and Physical Properties (2) Physical state Golden yellow to orange rhombic needles Density 1.442 (20/4°C) Melting point 69–71.5°C Boiling point 284.1°C Solubility Soluble in ethanol, ether, acetone, benzene; somewhat soluble in water 55.2 Production and Use 2-Nitroaniline is an intermediate for dyestuffs. 55.4 Toxic Effects Although 2-nitroaniline was not mutagenic in four strains of Salmonella (TA97, TA98, TA100, TA102), with or without metabolic activation, it was clastogenic in vitro and induced chromosomal aberrations in Chinese hamster ovary cells (193). 55.5 Standards, Regulations, or Guidelines of Exposure None assigned. 56.0 3-Nitroaniline 56.0.1 CAS Number: [99-09-2] 56.0.2 Synonyms: 1-Amino-3-nitrobenzene; 3-nitrobenzenamine; m-nitrophenylamine; mnitroaminobenzene; amarthol fast orange r base; m-aminonitrobenzene; azobase mna; C.I. 37030; C.I. azoic diazo component 7; daito orange base r; devol orange r; diazo fast orange r; fast orange base r; fast orange m base; fast orange mm base; fast orange r base; hiltonil fast orange r base; naphtoelan orange r base; nitranilin; m-nitraniline; orange base irga 1 56.0.3 Trade Names: NA 56.0.4 Molecular Weight: 138.13 56.0.5 Molecular Formula: C6H6N2O2 56.0.6 Molecular Structure:

Databases and inventories where listed: DOT, MTL, WHMI, CCRIS, DSL, EINECS, EMIC, EMICBACK, GENETOX, HSDB, RTECS, TOXLINE, TSCAINV, SUPERLIST. 56.1 Chemical and Physical Properties (2)

Physical state Yellow rhombic needles Density 1.430 (20/4°C) Melting point 114°C Boiling point 305–307°C Solubility Soluble in ethanol, ether; slightly soluble in water 56.2 Production and Use It is used as an intermediate in the production of dyestuffs. 56.4 Toxic Effects As reported in the previous edition, 3-nitroaniline causes methemoglobinemia and associated effects; the vapor is toxic, and it is absorbed through the skin (2). A 28-day repeated dose toxicity study in F344 rats has been undertaken (194). Male and female F344 rats received oral doses of 15, 50, or 170 mg/kg/day; lower body weight gain, but no deaths, occurred. Testicular atrophy, reduction in spermatogenesis, hemolytic anemia, and increases in liver, spleen and kidney weight occurred, but ovarian function was not affected. After a 14-day recovery period, the conditions eased or disappeared. The NOEL was less than 15 mg/kg/day. 56.5 Standards, Regulations, or Guidelines of Exposure None assigned. 57.0 4-Nitroaniline 57.0.1 CAS Number: [100-01-6] 57.0.2 Synonyms: p-Aminonitrobenzene; 4-nitrobenzenamine; PNA; C.I. 37035; 1-amino-4nitrobenzene; p-nitrophenylamine; azofix red gg salt; azoic diazo component 37; C.I. developer 17; developer P; devol red gg; diazo fast red gg; fast red base 2j; fast red base gg; fast red 2g base; fast red 2g salt; shinnippon fast red gg base; fast red salt 2j; fast red salt gg; nitrazol cf extra; red 2g base; fast red gg base; fast red mp base; fast red p base; fast red p salt; naphtoelan red gg base; azoamine red 2H; C.I. azoic diazo component 37 57.0.3 Trade Names: NA 57.0.4 Molecular Weight: 138.13 57.0.5 Molecular Formula: C6H6N2O2 57.0.6 Molecular Structure:

Databases and inventories where listed: DOT, IL, MA, MTL, NJ, NTPT, PA, PEL, REL, RQ, TLV, TRI, WHMI, CANCERLIT, CCRIS, DART, DSL, EINECS, EMIC, EMICBACK, MESH, MEDLINE, RTECS, TOXLINE, TSCAINV, SUPERLIST. 57.1 Chemical and Physical Properties (2) Physical state Pale yellow crystals Specific gravity 1.442 Melting point 146–149°C Boiling point 331.7°C Vapor pressure m- > o-isomer. In genotoxicity assays, pchloroaniline has been shown to yield positive results in virtually all assays, whereas only mixed results have been obtained on the o, and m-isomers (154). m-Nitro, o-chloro-, m-chloro, and 2,4dichloroanilines are also irritants to the skin and mucous membrane. Several dichloro-anilines have been demonstrated to be skin sensitizers. Except for p-nitroaniline, there is no evidence that these compounds are reproductive or developmental toxicants. They are inactive in most mutagenicity tests in Salmonella typhimurium (except in strain TA98 with a co-mutagen), but have been shown to induce gene mutations and chromosomal aberrations in other genotoxicity assay systems. Although there is limited or equivocal evidence of carcinogenicity in rodent studies, they are considered suspect human carcinogens. 2.0 Aniline 2.0.1 CAS Number: [62-53-3] 2.0.2–2.0.3 Synonyms and Trade Names: Benzamine, aniline oil, phenylamine, aminobenzene, phenylamine, aminophen, kyanol, benzidam; blue oil, C.I. 76000, C.I. oxidation base 1, cyanol, krystallin, anyvim, and arylamine 2.0.4 Molecular Weight: 93.128 2.0.5 Molecular Formula: C6H7N 2.0.6 Molecular Structure:

Aromatic Amino and Nitro–Amino Compounds and their Halogenated Derivatives Yin-Tak Woo, Ph.D., DABT, David Y. Lai, Ph.D., DABT B. Toluidines Toluidines are aromatic amines with an amino group and a methyl group attached to benzene. There are three toluidine isomers: o-, m-, and p-toluidines, designated with respect to the positions of the amino group and the methyl group. They are used primarily as intermediates in the manufacture of azodyes for the textile industry. Major clinical signs of toxicity observed in humans exposed to toluidines and their chloro and nitro derivatives are methemoglobinemia and hematuria. Toluidines are suspected human carcinogens, with o-toluidine being the strongest suspect. An excess of bladder tumors has often been found in workers exposed to varying combinations of dyestuffs containing toluidines. In experimental studies, significant increases of multiple-site tumor incidence have been observed in rats and/or mice on chronic administration of various toluidines in the diet. 22.0 o-Toluidine 22.0.1 CAS Number: [95-53-4] 22.0.2–22.0.3 Synonyms and Trade Names: C.I. 37077, o-methylaniline, 2-methyl-1-aminobenzene, 2-methylaniline, 2-methylbenzenamine, 2-aminotoluene, 1-amino-2-methylbenzene, 2-amino-1methylbenzene, 1-methyl-2-aminobenzene, o-tolylamine, and methyl-2-aminobenzene 22.0.4 Molecular Weight: 107.15 22.0.5 Molecular Formula: C7H9N 22.0.6 Molecular Structure:

22.1 Chemical and Physical Properties o-Toluidine is a light yellow to reddish brown liquid. It has a density of 0.9984 (20/4°C), a melting point of –14.7°C, a boiling point of 200.2°C, a refractive index of 1.57276 (20°C), and a flash point of 86°C (closed cup). It is slightly soluble in water and soluble in alcohol and ether (155, 156). 22.2 Production and Use Commercial production was first reported in the United States in 1922 for o-toluidine and in 1956 for o-toluidine hydrochloride. In 1983, U.S. production of o-toluidine was between 11 and 21 million pounds; 34 companies were identified as suppliers. In 1990, two suppliers of o-toluidine and ten suppliers of o-toluidine hydrochloride were identified; no production volumes are available (60). oToluidine and its hydrochloride salt are used primarily as an intermediate in the manufacture of dyes, including azo pigment dyes, triarylmethane dyes, sulfur dyes, and indigo compounds. These dyes are used primarily for printing textiles, in color photography, and as biologic stains. o-Toludine is also used as an intermediate for rubber vulcanizing chemicals, pharmaceuticals, and pesticides. The greatest potential for exposure to o-toluidine and its hydrochloride salt are dyemakers and pigment makers through inhalation and dermal contact in the workplace. The National Occupational Hazard Survey estimated that from 1972 to 1974, 13,053 workers were potentially exposed to otoluidine. The National Occupational Exposure Survey conducted from 1981 to 1983 indicated that 5,440 workers were exposed to o-toluidine. A total of 54,000 pounds of o-toluidine were reported to be released to the environment by 17 industrial facilities in the United States in 1990 (60). oToluidine is also present in cigarette smoke and is a metabolite of the local anesthetic prilocaine

(177). 22.3 Exposure Assessment 22.3.3 Workplace Methods The recommended method for determining workplace exposures to otoluidine is NIOSH Analytical Method 2002 (111a). 22.3.5 Biomonitoring/Biomarkers An increased level of methemoglobin measured in blood of workers is a nonspecific indicator of exposure to methemoglobin-inducing chemicals, including otoluidine. Investigations regarding other possible biomonitoring methods have recently demonstrated that o-toluidine binds to both albumin and hemoglobin and that a linear dose relationship exists for hemoglobin (178). Additionally, the biologic half-lives for the protein adducts are several times that reported for elimination of o-toluidine or its metabolites via the urine, thus providing evidence that these proteins may be valuable biomarkers of exposure to o-toluidine in the occupational setting (178). The formation of hemoglobin adduct has recently been developed as a biomonitoring method to assess worker exposure to o-toluidine in a chemical plant with known bladder cancer excess (93). 22.4 Toxic Effects The oral LD50 in rats is reported to be 900–940 mg/kg; that of the hydrochloride salt, diluted in water, in rats is 2950 mg/kg (179). Oral, dermal, or respiratory tract absorption of o-toluidine can result in methemoglobinemia, reticulocytosis, hematuria, skin and eye irritation, and irritation of the epithelium of kidneys and bladder (163, 179). o-Toluidine was reported to yield positive results in a variety of mutagenicity and related assays, which included Ames Salmonella, in vitro chromosome aberration, in vitro sister chromatid exchange (SCE), mouse lymphoma cell mutation, in vitro cell transformation, and in vitro unscheduled DNA synthesis tests (100, 116). It also caused somatic mutation in Drosophila but was negative in in vivo mouse micronucleus test (116). An IARC working group (111) reported that there were not adequate data to evaluate the carcinogenicity of o-toluidine hydrochloride in humans. Although an excess of bladder tumors has often been found in workers exposed to varying combinations of dyestuffs, no population of workers exposed to o-toluidine alone has been described, and either the data were insufficient, or insufficient followup time has prevented a clear association being made with the exposure. An excess number of bladder cancers has recently been reported in workers exposed to o-toluidine and aniline; the authors concluded that it is more likely that o-toluidine is responsible for the observed excess number of cases of bladder cancer, although aniline may have played a role (93, 180). There is sufficient evidence for the carcinogenicity of o-toluidine (as the hydrochloride salt) in experimental animals. When administered in the diet, o-toluidine induced various types of tumors in multiple sites, including hepatocellular carcinomas or adenomas in female mice and hemangiosarcomas at multiple sites in male mice of one strain, hemangiosarcomas and hemangiomas of the abdominal viscera in both sexes of another strain, increased incidences of sarcomas of multiple organs in rats of both sexes and mesotheliomas in male rats, and carcinomas of the urinary bladder in female rats (111). 22.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Forty-eight hours after the subcutaneous injection of a single dose of 400 mg/kg body weight o-[methy- 14C]-toluidine hydrochloride to male Fischer 344 rats, 83.9% of the 14C appeared in the urine, 3.3% in the feces, and 1.4% was exhaled as 14CO . Various hydroxy- and N-acetyl derivatives were identified as urinary metabolites (111). 2 22.5 Standards, Regulations, or Guidelines of Exposure The ACGIH TLV-TWA adopted by ACGIH is 2 ppm with skin notation; the compound is considered a confirmed animal carcinogen with unknown relevance to humans (A3 classification) by the ACGIH (160). The OSHA exposure limit is 5 ppm. NIOSH considers this compound to be an occupational carcinogen (110) and recommends appropriate worker protection. The NIOSH immediately dangerous to life or health concentration (IDLH) is 50 ppm (110).

23.0 m-Toluidine 23.0.1 CAS Number: [108-44-1] 23.0.2 Synonyms: m-Tolylamine; 3-methylbenzenamine, 3-aminophenylmethane, 3-methylaniline, m-toluamine, and m-aminotoluene 23.0.3 Trade Names: NA 23.0.4 Molecular Weight: 107.15 23.0.5 Molecular Formula: C7H9N 23.0.6 Molecular Structure:

23.1 Chemical and Physical Properties m-Toluidine is a liquid. It has a melting point of –30°C, a boiling point of 203.3°C, and a vapor pressure of 1 torr at 41°C. It is slightly soluble in water, soluble in alcohol, ether, acetone, and benzene (155, 156). 23.2 Production and Use The major uses of m-toluidine and its hydrochloride are as intermediates in the manufacture of dyes and other chemicals. Production has been limited because its nonplanar configuration, due to steric hindrance, limits its use in direct dyes. It is used in only 12 dyes; none is of major importance (181). Exposure to m-toluidine is primarily occupationally via inhalation and dermal contact. m-Toluidine may be released in wastewater during its production and use in the manufacture of dyes and other chemicals. 23.3 Exposure Assessment 23.3.5 Biomonitoring/Biomarkers An increased level of methemoglobin measured in blood of workers is a nonspecific indicator of exposure to methemoglobin-inducing chemicals including mtoluidine. 23.4 Toxic Effects Clinical signs of intoxication in humans include methemoglobinemia and hematuria; it is absorbed orally, dermally, and via the respiratory tract. There are no epidemiologic studies on workers who have been exposed only to m-toluidine. The oral LD50 of m-toluidine (rats) is reported to be 974 mg/kg (179). In an 18-mo carcinogenicity diet evaluation in male CD rats (8,000 ppm for 3 mo, then 4,000 ppm for an additional 15 mo; or 16,000 ppm for 3 mo, then 8,000 for an additional 15 mo), and male and female CD-1 mice (16,000 ppm for 5 mo, then 4,000 ppm in males and 8,000 ppm in females for an additional 13 mo; or 32,000 ppm in both sexes for 5 mo and then 8,000 ppm in males and 16,000 ppm in females for additional 13 mo), there was no evidence of a significant increase of incidence of any kind of tumor in the rats, and only a significant increase in liver tumors in male mice (182). 23.5 Standards, Regulations, or Guidelines of Exposure The ACGIH TLV-TWA is 2 ppm, with a skin notation (160). 24.0 p-Toluidine 24.0.1 CAS Number: [106-49-0] 24.0.2–24.0.3 Synonyms and Trade Names: 4-Aminotoluene, 4-methylaniline, naphthol as-kgll, and

4-methylbenzenamine 24.0.4 Molecular Weight: 107.15 24.0.5 Molecular Formula: C7H9N 24.0.6 Molecular Structure:

24.1 Chemical and Physical Properties p-Toluidine occurs in the form of plates or leaflets. It has a melting point of 43°C, a boiling point of 201.5°C, a refractive index of 1.5532 (59.1°C), a flash point of 86°C (closed cup), and a vapor pressure of 1 torr at 42°C. It is slightly soluble in water and soluble in alcohol, ether, acetone, methanol, or carbon disulfide. It has an aromatic, winelike odor and a burning taste (155, 156). 24.2 Production and Use p-Toluidine and its hydrochloride are used primarily in the synthesis of dyes and in the preparation of ion exchange resins. No information on production volumes is available. Exposure to p-toluidine is primarily occupationally via inhalation and dermal contact. p-Toluidine may be released in wastewater during its production and use in the manufacture of dyes and other chemicals. It is also released during the thermal degradation of polyurethane products. 24.3 Exposure Assessment 24.3.3 Biomonitoring/Biomarkers An increased level of methemoglobin measured in blood of workers is a nonspecific indicator of exposure to p-toluidine, which is a potent methemoglobin inducer. 24.4 Toxic Effects Clinical signs of toxicity in humans include anoxic methemoglobinemia and hematuria. It is absorbed orally, dermal, and via the respiratory tract. There are no epidemiologic studies reported on workers who have been exposed only to p-toluidine. The oral LD50 of p-toluidine is 656 mg/kg in rats and 794 mg/kg in mice; its hydrochloride salt in water was 1285 mg/kg in rats; the LD50 (rabbit dermal) is 890 mg/kg (179). In an 18-mo p-toluidine hydrochloride diet carcinogenicity study, male CD rats (1000 and 2000 ppm for 18 mo) did not develop statistically significant increases of tumors; however, CD-1 male and female mice (1000 ppm for 6 mo and then 500 ppm for an additional 12 mo; or 2000 ppm for 6 mo and then 1000 ppm for an additional 12 mo) showed significant increases in liver carcinomas, in males in both dose levels and in females in the high-dose level (182). 24.5 Standards, Regulations, or Guidelines of Exposure The ACGIH TLV-TWA is 2 ppm (approximately 9 mg/m3) with skin notation; it is classified as a confirmed animal carcinogen with unknown relevance to humans (A3 classification) by the ACGIH (160). 25.0 4-Chloro-o-toluidine 25.0.1 CAS Number: [95-69-2] 25.0.2–25.0.3 Synonyms and Trade Names: para-Chloro-ortho-toluidine, 4-chloro-2-methylaniline, 4-chloro-2-methylbenzenamine, 2-amino-5-chlorotoluene, azoene fast red tr base, brentamine fast red tr base, 5-chloro-2-aminotolueue, 4-chloro-6-methylaniline, daiz red base tr, deval red k, deval red tr, deazo fast red tra, fast red base tr, fast red 5ci base, fast red tr 11, fast red tro base, kako red tr base, kambamine red tr, 2-methyl-4-chloroaniline, mitsui red tr base, red base nir, red tr base, sonya fast red tr base, and tula base fast red tr

25.0.4 Molecular Weight: 141.60 25.0.5 Molecular Formula: C7H8ClN 25.0.6 Molecular Structure:

25.1 Chemical and Physical Properties 4-Chloro-o-toluidine occurs in the form of leaflets. It has a melting point of 27°C and a boiling point of 241°C. It is soluble in alcohol (155, 156). 25.2 Production and Use Commercial production of 4-chloro-o-toluidine was first reported in the United States in 1939. However, production has been stopped since 1979, and all importation was discontinued in 1986. The U.S. International Trade Commission (USITC) reported that 89,753 pounds of 4-chloro-otoluidine and its hydrochloride salt were imported in 1980, 83,098 pounds in 1981, 31,747 pounds in 1982, and 44,147 pounds in 1983 (112). It is used as an azo coupler in the synthesis of azo dyes used in the textile industry and for the manufacture of the insecticide chlordimeform (3, 112). The greatest potential for exposure to 4-chloro-o-toluidine and its hydrochloride salt are dyemakers, pigment makers, and manufacturers of chloridimeform through inhalation and dermal contact in the workplace. The National Occupational Hazard survey, conducted by NIOSH from 1972 to 1974, estimated that 1379 workers were potentially exposed to 4-chloro-o-toluidine. The National Occupational Exposure survey (1981–1983) indicated that 1357 workers, including 675 women, were potentially exposed to 4-chloro-o-toluidine and 4-chloro-o-toluidine hydrochloride. As a decomposition product of chlordimeform, 4-chloro-o-toluidine has been identified in field samples of plant materials treated with chlordimeform, a potential source of human exposure to 4-chloro-otoluidine by the ingestion route (112). 25.3 Exposure Assessment 25.3.3 Biomonitoring/Biomarkers An increased level of methemoglobin measured in blood of workers is a nonspecific indicator of exposure to methemoglobin-inducing chemicals, including 4chloro-o-toluidine. Hemoglobin adduct formation has been demonstrated in rats exposed to 4-chloroo-toluidine and may be used as a dosimeter for human exposure to the chemical (73). 25.4 Toxic Effects The intraperitoneal LD50 of 4-chloro-o-toluidine hydrochloride was 560–700 mg/kg in rats and 680– 720 mg/kg in mice. Hematuria and hemorrhagic cystitis have been reported in workers exposed to 4chloro-o-toluidine (112). 4-Chloro-o-toluidine has been demonstrated to be genotoxic in a variety of prokaryotic and mammalian in vitro and in vivo test systems (112). According to the IARC working group, limited human evidence and sufficient animal data are available to classify this agent a Group 2A compound and therefore probably carcinogenic to humans (112, 116). Between 1982 and 1990, 7 cases of urinary bladder cancer were detected in a group of 49 workers producing the insecticide chlordimeform from 4-chloro-o-toluidine on an irregular basis for an average of 18 years. The incidence of bladder tumors in these workers was significantly higher than that of the cancer registers. In other studies, increased incidences of cancer were also observed in workers exposed to 4-chloro-o-toluidine and several other compounds that are known or suspected carcinogens. In experimental studies, a significant increase in hemangiosarcomas or hemangiomas was observed in both sexes of two strain of mice on chronic administration of 4-chloro-o-toluidine hydrochloride

in the diet (112, 116). 25.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Following oral administration of [14Cmethyl]-4-chloro-o-toluidine to male and female rats, 71% of the administered radioactivity was eliminated in the urine and 24.5% in the faeces within 72 h. 4-Chloro-o-toluidine binding to DNA was demonstrated in vitro with calf thymus DNA and in vivo when it was administrated by intraperitoneal injection to rats (112). 25.5 Standards, Regulations, or Guidelines of Exposure OSHA regulates 4-chloro-o-toluidine and 4-chloro-o-toluidine hydrochloride under Hazard Communication Standard. 4-Chloro-o-toluidine hydrochloride is regulated as a hazardous constituent of waste under the Resource Conservation and Recovery Act (RCRA) and is subject to reporting/recordkeeping requirements under RCRA and Section 313 of the Emergency Planning and Community Right-to-Know Act of EPA. The Toxic Substances Control Act (TSCA) of the EPA also subjects 4-chloro-o-toluidine and its hydrochloride salt to reporting requirements applicable to any significant new use (60). 26.0 5-Chloro-o-toluidine 26.0.1 CAS Number: [95-79-4] 26.0.2–26.0.3 Synonyms and Trade Names: 5-Chloro-2-methylaniline, 5-chloro-2methylbenzenamine, 2-amino-4-chlorotoluene, 1-amino-3-chloro-6-methylbenzene, 4-chloro-2aminotoluene, 3-chloro-6-methylaniline, acco fast red kb base, ansibase red kb, azoic diazo component 32, azoene fast red kb base, fast red kb amine, fast red kb base, fast red kb salt, fast red kb salt supra, fast red kbs salt, genazo red kb soln, hiltonil fast red kb base, lake red bk base, metrogen red former kb soln, naphthosol fast red kb base, pharmazoid red kb, red kb base, spectrolene red kb, stable red kb base, C.I. Azoic Diazo Component No. 32, C.I. 37090, 2-methyl-5chloroaniline, and 5-chloro-2-methyl-benzamine 26.0.4 Molecular Weight: 141.60 26.0.5 Molecular Formula: C7H8ClN 26.0.6 Molecular Structure:

26.1 Chemical and Physical Properties 5-Chloro-o-toluidine has a melting point of 22°C and a boiling point of 237°C (155, 156). 26.2 Production and Use Specific production volumes for 5-chloro-o-toluidine are not available. In 1977, the compound and its hydrochloride salt were produced or sold in excess of 1,000 pounds by one U.S. company. In 1974, U.S. imports of 5-chloro-o-toluidine amounted to 42,163 pounds. 5-Chloro-o-toluidine is used as an azo coupler in the synthesis of azo dyes used in the textile industry (3). The greatest potential for exposure to 5-chloro-o-toluidine is for workers in the chemical and dye manufacturing and textile industries. 26.3 Exposure Assessment 26.3.3 Biomonitoring/Biomarkers Hemoglobin adduct formation has been demonstrated in rats exposed to 5-chloro-o-toluidine and may be useful dosimeter for human exposure (73). 26.4 Toxic Effects No specific acute toxicity data for 5-chloro-o-toluidine are available. The compound may induce a similar spectrum of toxicity as other toluidines. The chloro derivatives of toluidines are generally

more potent than toluidines in producing methemoglobinemia and hematuria. A bioassay for the possible carcinogenicity of 5-chloro-o-toluidine was conducted using Fischer 344 rats and B6C3F1 mice. Groups of 50 male and 50 female rats and mice were given 5-chloro-otoluidine in the diet at 2500 or 5000 ppm for rats and 2000 or 4000 ppm for mice. The compound was administered for 78 wk to both rats and mice, followed by an observation period of up to 26 wk for rats and 13 wk for mice. Under the conditions of this bioassay, 5-chloro-o-toluidine was carcinogenic to the mice, inducing hemangiosarcomas and hepatocellular carcinomas in both males and females. There was no conclusive evidence of the carcinogenicity of the compound in the rats (183). 26.5 Standards, Regulations or Guidelines of Exposure No information is available. 27.0 6-Chloro-o-toluidine 27.0.1 CAS Number: [87-63-8] 27.0.2–27.0.3 Synonyms and Trade Names: 6-Chloro-2-methylaniline, 2-chloro-6-methylaniline, 2chloro-6-methylbenzenamine, 2-amino-3-chlorotoluene, and 6-chloro-2-toluidine 27.0.4 Molecular Weight: 141.60 27.0.5 Molecular Formula: C7H8ClN 27.0.6 Molecular Structure:

6-Chloro-o-toluidine has a melting point of 2°C, a boiling point of 215°C, and a flash point of 98°C. It is soluble in water and has a specific gravity of 1.152. 28.0 5-Nitro-o-toluidine 28.0.1 CAS Number: [99-55-8] 28.0.2–28.0.3 Synonyms and Trade Names: 2-methyl-5-nitrobenzenamine; 2-methyl-5-nitroaniline; 2-amino-4-nitrotoluene; 1-amino-2-methyl-5-nitrobenzene; 4-nitro-2-aminotoluene; amarthol fast scarlet g base; amarthol fast scarlet g; salt; azoene fast scarlet gc base; azoene fast scarlet gc salt; azofix scarlet g salt; azogene fast scarlet g; C.I. 371.05; C.I. azoic diazo component 12; dainichi fast scarlet g base; daito scarlet base g; devol scarlet b; devol scarlet g salt; diabase scarlet g; diazo fast scarlet g; fast red sg base; fast scarlet base g; fast scarlet base j; fast scarlet g; fast scarlet g base; fast scarlet gc base; fast scarlet j salt; fast scarlet mN4t base; fast scarlet t base; hiltonil fast scarlet g base; hiltonil fast scarlet gc base; hiltonil fast scarlet g salt; kayaku scarlet g base; lake scarlet g base; lithosol orange r base; mitsui scarlet g base; naphthanil scarlet g base; naphtoelan fast scarlet g base; naphtoelan fast scarlet g salt; PNOT; scarlet base ciba ii; scarlet base irga ii; scarlet base nsp; scarlet g base; sugai fast scarlet g base; symulon scarlet g base; Fast Red G Base; C.I. Azoic Diazo Component No. 12. 28.0.4 Molecular Weight: 152.15 28.0.5 Molecular Formula: C7H8N2O2 28.0.6 Molecular Structrure:

28.1 Chemical and Physical Properties 5-Nitro-o-toluidine occurs in the form of yellow monclinic prisms. It has a melting point of 107.5°C. It is soluble in acetone, benzene, chloroform, diethyl ether, and ethanol (155, 156). 28.2 Production and Use Production of 5-nitro-o-toluidine in the United States was reported to 180 ton in 1972 and 57 ton in 1975 (112). It has been used as a precursor in the synthesis of a wide varieties of azo dyes. It is also used as a coupling component in the synthesis of organic textile dyes such as Naphthol Red M. The nitro moiety serves as a chromophore (in common with other groups such as nitroso, carbonyl, thiocarbonyl, azo, azoxy, azomethine, and ethenyl, in which the double bonds contribute to the absorption of visible light); the amino group serves as an auxochrome (in common with other groups such as alkylamino, dialkylamine, methoxy, or hydroxy), which functions by intensifying or modifying the color (184). The greatest potential for exposure to 5-nitro-o-toluidine is for workers at dye manufacturing facilities. 28.3 Exposure Assessment 28.3.3 Biomonitoring/Biomarkers An increased level of methemoglobin measured in blood of workers is a nonspecific indi cator of exposure to methemoglobin-inducing chemicals, including 5nitro-o-toluidine. 28.4 Toxic Effects Methemoglobinemia was induced in guinea pigs and cats after IP injection of the compound (112). It is also the major toxic effect observed in workers following excessive exposure. In addition, upon dermal contact the compound may irritate the skin and cause dermatitis. 5-Nitro-o-toluidine has been demonstrated to be genotoxic in a variety of prokaryotic and mammalian in vitro and in vivo test systems (112). There are no data available for evaluating carcinogenic risk to humans. When 5-nitroo-toluidine was administered as a dietary feeding study to F344 rats (50 or 100 ppm) and B6C3F1 mice (1200 or 2300 ppm) of both sexes, hepatocellular carcinomas were produced in mice but not in rats (185). 28.5 Standards, Regulations, or Guidelines of Exposure No information is available.

Aromatic Amino and Nitro–Amino Compounds and their Halogenated Derivatives Yin-Tak Woo, Ph.D., DABT, David Y. Lai, Ph.D., DABT C. Aminophenols and Nitroaminophenols Aminophenols and nitroaminophenols are widely used for manufacture of dyes and pharmaceuticals. They are also directly used, along with many other chemicals, as ingredients of hair dyes/colorants and related products and therefore may lead to occupational and consumer exposure. The International Agency for Research on Cancer (37) has extensively reviewed various epidemiological and case-control studies showing excess risk for cancer of the urinary bladder in male hairdressers and barbers and possible excess risk for cancer of the lung and other target sites and concluded that there is evidence, albeit somewhat limited, that occupation as a hairdresser or barber entails exposures that are probably carcinogenic (Group 2A). In contrast to professional exposure, there is inadequate evidence to evaluate the carcinogenic risk of personal use of hair dyes/colorants.

In general, the introduction of the hydrophilic hydroxy group to aromatic amines is expected to decrease its absorption and increase its excretion and therefore may appear to be detoxifying in nature. However, if the hydroxy group is ortho or para to the amino group, highly reactive and toxic quinoneimine intermediates may be generated after oxidation. The introduction of an additional nitro group to aminophenol may yield an additional amino group via reduction or may confer acute toxicity by acting as an uncoupler of oxidative phosphorylation. 29.0 o-Aminophenol 29.0.1 CAS Number: [95-55-6] 29.0.2–29.0.3 Synonyms and Trade Names: 2-Aminophenol, 2-amino-1-hydroxybenzene, basf ursol 3ga, benzofur gg, C.I. 76520, C.I. oxidation base 17, fouramine op, o-hydroxyaniline, nako yellow 3ga, paradone olive green b, pelagol 3ga, pelagol grey gg, zoba 3ga, and 2-aminobenzenol 29.0.4 Molecular Weight: 109.13 29.0.5 Molecular Formula: C6H7NO 29.0.6 Molecular Structure:

29.1 Chemical and Physical Properties o-Aminophenol occurs as colorless, odorless rhombic needles or plates that readily become grayish or yellowish brown upon exposure to air and light. It has a molecular weight of 109.13, a density of 1.33 g/cm3 and a melting point of 175°C and is sublimable. It is soluble in water (2 g/100 mL cold water), alcohol (5 g/100 mL), freely soluble in ether, and slightly soluble in benzene (155, 186). 29.2 Production and Use There is a scarcity of production data on aminophenols because they are often reported as aniline derivatives (186). o-Aminophenol is used as an azo and sulfur dye intermediate and for dyeing fur and hair; it is widely used in the cosmetics, dye, and drug industries. Occupational exposure may occur to hairdressers, barbers, and dye workers. Occasional exposure may also occur through personal use of hair dyes/colorants. 29.3 Exposure Assessment Biomonitoring data are not available. 29.4 Toxic Effects o-Aminophenol is not readily absorbed through intact skin but may prove to be a sensitizing agent with resultant contact dermatitis. When inhaled in excessive amounts, it may cause methemoglobinemia as well as bronchial asthma. Intraperitoneal administration (100–200 mg/kg) to Syrian golden hamsters on day 8 of gestation produced a significant teratogenic response similar to that of p-aminophenol (see section 31), including neural tube defects (exencephaly, encephalocele, and spina bifida), eye defects, and skeletal defects (129). However, no teratogenicity study by the oral route of administration was found. The compound was reported to be mutagenic in the Ames test (100). 29.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Aminophenols are generally metabolized by N-acetylation with the relative rate following the order p- > m- > o- (187). The phenolic group may also be conjugated (e.g., glucuronide) to facilitate excretion. Reactive electrophilic quinoneimine derivatives may be formed by oxidation of o or p isomer but not the m isomer. The oxidation product of o-aminophenol has been shown to bind to protein; however, there was no evidence of binding to nucleic acids (188).

29.5 Standards, Regulations, or Guidelines of Exposure There is no information on setting of hygienic standards of permissible exposure 30.0 m-Aminophenol 30.0.1 CAS Number: [591-27-5] 30.0.2–30.0.3 Synonyms and Trade Names: 3-Aminophenol, 3-amino-1-hydroxybenzene, 3hydroxyaniline, m-hydroxyaminobenzene, basf ursol bg, C.I. 76545, C.I. oxidation base 7, fouramine eg, fourrine 65, fourrine eg, furro eg, futramine eg, nako teg, pelagal eg, renal eg, tetral eg, ursol eg, zoba eg, and m-hydroxyphenylamine 30.0.4 Molecular Weight: 109.13 30.0.5 Molecular Formula: C6H7NO 30.0.6 Molecular Structure:

30.1 Chemical and Physical Properties m-Aminophenol occurs as colorless, odorless prisms at room temperature and is relatively more stable than its o or p isomer. It has a melting point of 125°C; it is soluble in cold water (2.5 g/100 mL) and very soluble in alcohol, petroleum ether, and hot water (155, 156, 186). 30.2 Production and Use m-Aminophenol is used chiefly in the synthesis of dyes and occasionally as a hair dye [red-brown color obtained with p-phenylenediamine or light orange with p-aminophenol (189)] and in the manufacture of p-aminosalicylic acid. Occupational exposure may occur to hairdressers, barbers, and dye workers. Occasional exposure may also occur through personal use of hair dyes/colorants. 30.3 Exposure Assessment Biomonitoring data are not available. 30.4 Toxic Effects Intraperitoneal administration (100–200 mg/kg) of m-aminophenol to Syrian golden hamsters on day 8 of gestation produced inconsistent results. A teratogenic response was demonstrated at the mid dose of 150 mg/kg, but not at the high dose of 200 mg/kg (129). In a followup teratology study in which Sprague–Dawley rats were fed a diet of 0.1, 0.25, and 1.0% m-aminophenol for 90 d prior to mating, maternal toxicity was demonstrated at the highest dose level, and a significant reduction in body weight was noted in the 0.25% group, but there was no evidence of teratogenic or embryo-fetal toxicity at any dose level tested. Accumulation of iron-positive pigment within the liver, kidneys, and spleen was observed in dams fed a 1% diet, together with significant reduction in red blood cell count and hemoglobin level, as well as an increase in mean corpuscular volume, indicating a hemolytic effect; histomorphologic appearance of the thyroid indicated hyperactive activity (at 0.25 and 1.0% diet) (190). In contrast to o- and p-aminophenol and their glucuronides, neither maminophenol nor its conjugate with glucuronic acid has been shown to form methemoblobin in vitro (191). The compound was reported to be mutagenic in the Ames test (100). 30.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Aminophenols are generally metabolized by N-acetylation, with the relative rate following the order p- > m- > o- (187). The phenolic group may also be conjugated (e.g., glucuronide) to facilitate excretion. Unlike its o- or p-isomer, maminophenol does not undergo oxidation to quinone imine derivative. 30.5 Standards, Regulations, or Guidelines of Exposure Hygienic standards of permissible exposure levels have not been assigned.

31.0 p-Aminophenol 31.0.1 CAS Number: [123-30-8] 31.0.2–31.0.3 Synonyms and Trade Names: 4-Aminophenol, p-hydroxyaniline, 4-amino-1hydroxybenzene, Azol, Certinal, Citol, Paranol, Rodinal, Unal, Ursol P, paramidophenol, Kodelon, Energol, Freedol, Indianol, Kathol, basf ursol p base, benzofur p, C.I. oxidation base 6a, fouramine p, fourrine 84, PAP, pelagol grey p base, tertral p base, ursol p base, zoba brown p base C.I. 76550, durafur brown rb, fourrine p base, furro p base, nako brown r, pelagol p base, renal ac, 4hydroxyaniline, and 4-aminobenzenol 31.0.4 Molecular Weight: 109.13 31.0.5 Molecular Formula: C6H7NO 31.0.6 Molecular Structure:

31.1 Chemical and Physical Properties p-Aminophenol occurs as orthorhombic plates that deteriorate upon exposure to air and light. It has a melting point of 189°C and a boiling point of 284°C, and is sublimable. It is soluble in water (0.39% at 15°C, 0.65% at 24°C, 1.5% at 50°C, 8.5% at 90°C), very soluble in methyl ethyl ketone and absolute ethanol, but practically insoluble in benzene and chloroform (155, 156, 186). 31.2 Production and Use p-Aminophenol is used in the manufacture of sulfur and azo dyes and in dyeing furs. The hydrochloride salt is used as a photographic developer in conjunction with sodium or potassium carbonates. p-Aminophenol was tried as an analgesic because of the belief that acetanilid was ultimately oxidized to p-aminophenol; however, it was found to be more toxic than its predecessor, acetanilid (192). Phenacetin, the ethyl ether of N-acetyl-p-aminophenol, also known as acetophenetidin, has been widely prescribed as an analgesic. Occupational exposure may occur to hairdressers, barbers, and dye workers. Occasional exposure may also occur through personal use of hair dyes/colorants as well as through the use of OTC drugs that yield p-aminophenol as a metabolite. 31.3 Exposure Assessment Biomonitoring data are not available. 31.4 Toxic Effects 31.4.1 Experimental Studies p-Aminophenol is a cytotoxic chemical; one mechanism associated with its cytotoxicity has been attributed to its activity as a tissue respiratory (oxidative phosphorylation) inhibitor (193). Intraperitoneal administration (100–200 mg/kg) of the compound on day 8 of gestation to Syrian golden hamsters produced a significant teratogenic response including encephalocele and limb, tail, and eye defects; rare malformations observed included ectopic heart, cleft palate, occult cranioschisis, and abnormal genitalia. It was proposed that the mechanism may be related to the formation of a reactive quinone/quinoneimine. In contrast to IP administration, the compound was not teratogenic by the oral route at the same dosages (129). p-Aminophenol was nonteratogenic in Sprague–Dawley rats fed a diet containing 0.07, 0.2, or 0.7% for up to 6 mo. After 13 wk, 25 females/group were mated to untreated males in a teratology study; after 20 wk, 20 males/group were mated to untreated virgin females in a dominant lethal mutagenicity study. Dose-related nephrosis was seen in both sexes after 13 and 27 wk and in the high-dose males that were removed from the test diet for a 7-wk recovery period. The authors noted

an increase in developmental variations associated with maternal toxicity at the mid- and high-dose levels. The dominant lethal study was equivocal (194). p-Aminophenol has also been demonstrated to be nephrotoxic to rats. Administration of 25– 100 mg/kg to male F344 rats resulted in a dose-related proximal nephropathy. The observed increased excretion of enzymes, glucose, and urine total protein, resulting in glycosuria and amino aciduria, indicated functional defects in the proximal tubule and reduced solute reabsorption efficiency (196). The necrosis is apparently restricted to the straight segment of the proximal tubule of the Fischer 344 rat; Sprague–Dawley rats, on the other hand, are more resistant to the nephrotoxicity of acetaminophen and its nephrotoxic metabolite p-aminophenol. The authors postulated that the strain differences in p-aminophenol-induced nephrotoxicity may be related to differences in the intrarenal activation of p-aminophenol (197). Mutagenicity studies of p-aminophenol yielded mixed results: negative in Ames (100), positive in L5178 mouse lymphoma assay, and negative in CHO/HGPRT assay (51). Although a number of derivatives (e.g., phenacetin) of p-aminophenol have been reported to be carcinogenic (116, 198), there appears to be no evidence to indicate that p-aminophenol is carcinogenic. 31.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Aminophenols are generally metabolized by N-acetylation with the relative rate following the order p- > m- > o- (187). The phenolic group may also be conjugated (e.g., glucuronide) to facilitate excretion. Reactive electrophilic quinone imine derivatives may be formed by oxidation of the o or p isomer but not the m isomer. 31.4.2 Human Experience p-Aminophenol is considered a minor nephrotoxic metabolite of acetaminophen in humans. Long-term use of acetaminophen can result in an increased lipofuscin deposition in kidneys. In vitro studies have demonstrated that p-aminophenol can undergo oxidative polymerization to form melanin, a component of soluble lipofuscin. Hemolysis accompanies this process in whole blood. Long-term excessive use of phenacetin or acetaminophen has been associated with chronic renal disease, hemolytic anemia, and increased solid lipofuscin deposition in tissues (195). 31.5 Standards, Regulations, or Guidelines of Exposure Hygienic standards of permissible exposures have not been assigned. 32.0 2-Amino-5-nitrophenol 32.0.1 CAS Number: [121-88-0] 32.0.2–32.0.3 Synonyms and Trade Names: 2-Hydroxy-4-nitroaniline, 5-nitro-2-aminophenol, C.I. 76535, rodol yba, and ursol yellow brown a 32.0.4 Molecular Weight: 154.13 32.0.5 Molecular Formula: C6H6N2O3 32.0.6 Molecular Structure:

32.1 Chemical and Physical Properties 2-Amino-5-nitrophenol is an orange crystalline solid at room temperature. It has a melting point of 200°C; it is insoluble in water but soluble in alcohol, benzene, and most common organic solvents (155, 199). 32.2 Production and Use

2-Amino-5-nitrophenol is not produced in commercial quantities in the United States. The import volume between 1973 and 1979 was in the order of 13,400 kg per year. It is used as a colorant in semipermanent hair dyes and in the manufacture of azo dye (e.g., C.I. Solvent Red 8) for synthetic resins, lacquers, and wood stains (199). In view of its widespread use in hair dyes, occupational (hairdressers and barbers) exposure is expected. A National Occupational Hazard Survey conducted by NIOSH in 1981–1983 estimated that a total of 14,512 U.S. workers, including 11,827 women, were potentially exposed to 2-amino-4nitrophenol in 1339 beauty salons (105). Occasional consumer exposure may also occur through the personal use of hair dye products. 32.3 Exposure Assessment Biomonitoring studies are not available. 32.4 Toxic Effects The LD50 of 2-amino-5-nitrophenol in rats was reported to be greater than 4 g/kg by oral and 800 mg/kg by intraperitoneal administration (200). Mutagenicity and related genotoxicity studies indicated that the compound is positive in the Ames test with metabolic activation, positive in mouse lymphoma L5178Y assay without metabolic activation, positive in chromosomal aberrations and sister chromatid exchanges assays in CHO cells with and without metabolic activation (199), but negative in dominant lethal mutation in rats (200). The potential carcinogenicity of 2-amino-5-nitrophenol was tested by NTP (199) by oral administration (gavage) in corn oil to F344/N rats (100 and 200 mg/kg) and B6C3F1 mice (400 and 800 mg/kg) for 2 years. There was some evidence of carcinogenic activity in low-dose male rats, as indicated by increased incidence of acinar cell adenomas of the pancreas. No evidence of carcinogenic activity was found among female rats and the low-dose groups of male and female mice. The poor survival rates in the high-dose male rats and high-dose male and female mice reduced the sensitivity for detecting potential carcinogenic response. 32.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms There is no information on the disposition or metabolism of 2-amino-5-nitrophenol. However, the disposition of the closely related 2-amino-4nitrophenol has been studied. Up to 1.67% of 2-amino-4-nitrophenol has been shown to be absorbed after dermal application to rats. Absorbed material was excreted in the urine within 24 h. Absorption has also been demonstrated after oral administration. Virtually all absorbed material was excreted in 5 d. 32.5 Standards, Regulations, or Guidelines of Exposure Hygienic standards of permissible exposure have not been assigned. The use of 2-amino-5nitrophenol in cosmetic products is prohibited in the European Economic Communities (36). 33.0 4-Amino-2-nitrophenol 33.0.1 CAS Number: [119-34-6] 33.0.2–33.0.3 Synonyms and Trade Names: p-Aminonitrophenol, C.I. 76555, fourrine 57, fourrine brown pr, fourrine brown propyl, 4-hydroxy-3-nitroaniline, o-nitro-p-aminophenol, oxidation base 25, 3-nitro-4-hydroxyaniline, and C.I. oxidation base 25 33.0.4 Molecular Weight: 154.13 33.0.5 Molecular Formula: C6H6N2O3 33.0.6 Molecular Structure:

33.1 Chemical and Physical Properties 4-Amino-2-nitrophenol has a melting point of 131°C (155). 33.2 Production and Use 4-Amino-2-nitrophenol has been used in dyeing human hair and animal fur. The typical concentration in the “semi-permanent” hair dyes was estimated to be in the order of 0.1--1.0% (36). In view of its use in hair dyes, occupational (hairdressers and barbers) exposure is expected. Occasional consumer exposure may also occur through the personal use of hair dye products. 33.3 Exposure Assessment Biomonitoring studies are not available. 33.4 Toxic Effects The LD50 of 4-amino-2-nitrophenol in rats was reported to be 3.3 g/kg by oral and 302 mg/kg by intraperitoneal administration (200). The compound was reported to be mutagenic in the Ames test and the mouse lymphoma L5178Y assay (100). The potential carcinogenicity of 4-amino-2nitrophenol was tested by NCI (201) by dietary administration (1250 or 2500 ppm) to F344/N rats and B6C3F1 mice for 2 years. Under the conditions of the bioassay, the compound was carcinogenic in male rats inducing transitional-cell carcinomas of the urinary bladder (controls 0/15, low dose 0/46, high dose 11/39). The same tumor was also observed in three dosed female rats and may have been associated with the administration of the chemical. No evidence of carcinogenic activity was found in the mice. 33.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms There is no information on the disposition or metabolism of 4-amino-2-nitrophenol. However, the disposition of its isomer 2-amino-4nitrophenol has been studied. Up to 1.67% of 2-amino-4-nitrophenol has been shown to be absorbed after dermal application to rats. Absorbed material was excreted in the urine within 24 h. Absorption has also been demonstrated after oral administration. Virtually all absorbed material was excreted in 5 d. 33.5 Standards, Regulations, or Guidelines of Exposure Hygienic standards of permissible exposure have not been assigned.

Aromatic Amino and Nitro–Amino Compounds and their Halogenated Derivatives Yin-Tak Woo, Ph.D., DABT, David Y. Lai, Ph.D., DABT D. Phenylenediamines and Derivatives Phenylenediamines (PDAs) are aromatic amines with two amino groups attached to benzene. There are three possible isomers: ortho-, meta-, and para-phenylenediamine (o-, m-, and p-PDA). Their primary uses are in the synthesis of polymers (primarily polyurethanes) and dyestuffs, and as components of hair dye formulations. Several of their nitro and chloro derivatives are also widely used in the hair dye industry. Phenylenediamines are methemoglobin-forming agents and skin sensitizers. Among the three isomers, m-PDA is the most potent methemoglobin-forming agent and p-PDA is more toxic and a stronger skin sensitizer than o- and m-PDA. 2-Nitro-p-PDA was reported to cause developmental toxicity in mice. All three isomers of PDA and a number of their nitro and chloro derivatives have

been shown to induce gene mutagen in bacteria and/or cultured mammalian cells. Many of them also induced chromosomal aberrations, sister chromatid exchange, and cell transformation in cultured mammalian cells. The m and p isomers of PDA did not show any carcinogenic effects in limited carcinogenicity studies in rodents. However, there is sufficient evidence of carcinogenicity in longterm animal studies for o-PDA, 2-nitro-p-PDA, 4-chloro-o-PDA, 4-chloro-m-PDA, and 2,6-dichlorop-PDA. Addition of chlorine atom(s) in the phenyl ring appeared to increase the carcinogenicity of phenylenediamines.

Aromatic Amino and Nitro–Amino Compounds and their Halogenated Derivatives Yin-Tak Woo, Ph.D., DABT, David Y. Lai, Ph.D., DABT E. Toluenediamines There are six possible isomers of toluenediamines (TDA), or diaminotoluenes. They are usually synthesized commercially by dinitration of toluene, yielding a mixture of approximately 76% 2,4TDA, 19% 2,6-TDA, 2.5% 3,4-TDA, 1.5% 2,3-TDA, 0.7% 2,5-TDA, and traces of 3,5-TDA (85). Among these isomers, 2,4-TDA and 2,6-TDA (both also known as m-TDA) are the most widely used diamines principally as chemical intermediates for the manufacture of toluene diisocyante (TDI), the predominant diisocyanate in the flexible foam and elastomer industries. In addition, TDA isomers are also used in hair dyes and a variety of other uses. Four isomers (2,4-, 2,5-, 2,6-, and 3,4-) of TDA have been shown to be mutagenic in the Ames assay. In addition, both 2,4-TDA and 2,6-TDA yielded positive results in in vitro chromosome aberration and sister chromatid exchange assays (100). In contrast to genotoxicity assays, differential results have been observed in carcinogenicity studies. Whereas several studies indicated 2,4-TDA to be clearly carcinogenic in rats and mice, bioassays of 2,5-TDA and 2,6-TDA gave negative results. Mechanistic studies (83) showed that although both 2,4-TDA and 2,6-TDA are capable of binding to DNA, 2,4-TDA is about 6500 times more effective than 2,6-TDA. In addition, 2,4-TDA has been shown to induce hepatocellular proliferation (227) and exhibit tumorigenesis-promoting activity inducing liver foci from diethylnitrosamine-initiated hepatocytes (83), whereas 2,6-TDA lacks such activities indicating that genotoxicity alone is insufficient to induce complete carcinogenesis. NIOSH Analytical Method 5516 is recommended for determining workplace exposure for all toluenediamine isomers (111a). 44.0 2,3-Toluenediamine 44.0.1 CAS Number: [2687-25-4] 44.0.2 Synonyms: 3-Methyl-1,2-benzenediamine, toluene-2,3-diamine, and 2,3-diaminotoluene, and o-TDA 44.0.3 Trade Names: NA 44.0.4 Molecular Weight: 122.17 44.0.5 Molecular Formula: C7H10N2 44.0.6 Molecular Structure:

47.1 General 2,3-Toluenediamine has a boiling point of 255°C and a melting point of 63 to 64°C; it is soluble in water, alcohol, and ether. The most significant commercial use of o-TDA is in the manufacture of tolyltriazoles, which are used as corrosion inhibitors, photographic chemicals, and catalysts. It is also used as a chemical intermediate in the synthesis of polyols and antioxidants (85). No toxicology information was located in the literature. No hygienic standards of permissible exposure have been assigned. In the absence of data, NIOSH considers all TDA isomers as possible occupational carcinogens. 45.0 2,4-Toluenediamine 45.0.1 CAS Number: [95-80-7] 45.0.2–45.0.3 Synonyms and Trade Names: Toluene-2,4-diamine, toluenediamine, 2,4diaminotoluene, 4-methyl-1,3-benzenediamine, 3-amino-p-toluidine, 5-amino-o-toluidine, tolylene2,4-diamine, 1,3-diamino-4-methylbenzene, 2,4-diamino-1-methylbenzene, 2,4-diamino-1-toluene, 2,4-diaminotoluol, 4-methyl-m-phenylenediamine, C.I. 76035, C.I. oxidation base, C.I. oxidation base 20; C.I. oxidation base 35; C.I. oxidation base 200, developer 14, developer b, developer db, developer dbj, developer mc, developer mt, developer mt-cf, developer mtd, developer, azogen developer h, benzofur mt, eucanine gb, fouramine, fouramine j, fourrine 94, fourrine m, MTD, nako tmt, pelagol j, pelagol grey j, pontamine developer tn, renal md, Tertral g, zoba gke, zogen developer h, 4-methylphenylene-1,3-diamine, and 2,4-TDA 45.0.4 Molecular Weight: 122.17 45.0.5 Molecular Formula: C7H10N2 45.0.6 Molecular Structure:

45.1 Chemical and Physical Properties 2,4-Toluenediamine has a boiling point of 292°C and melting point of 99°C; it is soluble in water, alcohol, and ether. It is a colorless to brown, needle-shaped crystal or powder that tends to darken on storage (85, 155). 45.2 Production and Use 2,4-Toluenediamine is a widely used industrial chemical intermediate. It is produced in very large volumes with worldwide production estimated to be 6.9 × 105 metric tons in 1991 (85). The major use for 2,4-TDA is in the manufacture of toluene diisocyanate (TDI), the predominant isocyanate in the flexible polyurethane foams and elastomers industry. It is also used as an intermediate for the synthesis of dyes and pigments and was used in hair dye formulations until 1971 (36). Human exposure to 2,4-TDA may occur indirectly via exposure to 2,4-toluene diisocyanate, which is known to hydrolyze to 2,4-TDA rapidly upon contact with water. Workers in some plastics and elastomers industries may be exposed to atmospheres containing TDI (228). Direct exposure to 2,4TDA per se could also occur to hairdressers and barbers through the use of hair dye formulations. 45.3 Exposure Assessment Biomonitoring methods to measure hemoglobin adducts of 2,4-TDA as a dosimeter of exposure have been developed (95, 102). Immunoassays to measure DNA adducts with 2,4-TDA have also been developed (21). 45.4 Toxic Effects Clinical effects in humans include methemoglobinemia, especially when red blood cell-reducing

mechanisms are impaired, such as in G6PD deficiency, which occurs in humans in the absence of glutathione reductase, glutathione, or glutathione peroxidase. It is an eye irritant that may cause corneal damage, and delayed skin irritation reportedly occurs, which can result in blistering (1). 45.4.1 Experimental Studies Reproductive toxicity in the rat has been demonstrated. Reduced fertility, arrested spermatogenesis, and diminished circulating testosterone levels have resulted in rats fed 0.03% 2,4-TDA; electron microscopy revealed degenerative changes in Sertoli cells and a decrease in epididymal sperm reserves; after 3 wk of 0.06% TDA feeding, sperm counts were further reduced and accompanied by a dramatic increase in testes weights, intense fluid accumulation, and ultrastructural changes in Sertoli cells (130). In previous studies testicular atrophy, hormonal effects, and aspermatogenesis were also observed in Sprague–Dawley rats given a 0.1% diet for 9 wk (131, 132). 2,4-TDA is mutagenic in the Ames assay with metabolic activation in the presence of S-9; it gave weakly positive results in the micronucleus test at near toxic doses (231, 232). In vitro chromosome aberration and sister chromatid exchange assays were reported to be positive (100). Its in vivo genotoxic activity has recently been demonstrated using the Big Blue transgenic mouse mutation assay (81). When 2,4-TDA was administered in the diet to male and female F344 rats (79 or 170 ppm) or B6C3F1 mice (100 or 200 ppm), hepatocellular carcinomas were produced in female mice, hepatocellular carcinomas in male rats, and mammary adenomas or carcinomas in female rats, but no carcinomas in the male mice (233). Also male Wistar rats have reportedly been shown to develop hepatocarcinomas following treatment with 2,4-TDA (234). A skin painting study in Swiss–Webster mice was reportedly noncarcinogenic (235). However, it has also been observed that mice appear to be less sensitive than rats; this difference may be based upon differences in metabolism (236). 45.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Metabolism studies (16, 21, 232, 236) indicated that 2,4-TDA is metabolically activated by N-hydroxylation followed by N-acetylation to yield the N-acetoxy derivative as the ultimate DNA reactive and mutagenic intermediate. Based on analysis of the DNA adducts, the 4-amino group appears to be the preferential (80%) site of metabolic activation (21). At an equimolar dose of 250 mg/kg, 2,4-TDA was shown to be 6500 times more active in binding to DNA in rats liver than its 2,6-isomer (83). In addition, 2,4-TDA has been shown to induce hepatocellular proliferation (227) and exhibit tumorigenesis-promoting activity inducing liver foci from diethylnitrosamine-initiated hepatocytes (83). In contrast, the mutagenic but noncarcinogenic 2,6-TDA lacks such tumorigenesis-promoting activities indicating that genotoxicity alone is insufficient to induce complete carcinogenesis. 45.4.2 Human Experience However, epidemiological studies of workers exposed to commercial mixtures of dinitrotoluene and/or toluenediamine at three chemical plants indicated that the fertility of men had not been reduced significantly and reported no observable effects on the fertility of workers (229, 230). However, other reports have suggested that human exposure may disrupt spermatogenesis and cause an excess of miscarriages (131, 132). Biliary tract cancer has been reported in industrial workers (237); however, it could not be determined whether 2,4-TDA played a significant role. An IARC working group concluded that, despite the lack of human data, there are sufficient animal data to classify 2,4-TDA a Group 2B compound, an agent possibly carcinogenic to humans (116). 45.5 Standards, Regulations, or Guidelines of Exposure NIOSH recommends that 2,4-TDA be treated as a possible occupational carcinogen. 46.0 2,5-Toluenediamine 46.0.1 CAS Number: [95-70-5] 46.0.2–46.0.3 Synonyms and Trade Names: 2,5-Diaminotoluene, toluene-2,5-diamine, 2-methyl-1,4-

benzenediamine and 2,5-TDA 46.0.4 Molecular Weight: 122.17 46.0.5 Molecular Formula: C7H10N2 46.0.6 Molecular Structure:

46.1 Chemical and Physical Properties 2,5-Toluenediamine has a boiling point of 273 to 274°C and a melting point of 64°C; it is soluble in water, alcohol, and ether (85, 155). 46.2 Production and Use 2,5-Toluenediamine is used primarily in hair dye formulations as one of the major oxidation dye precursors (36). It is also used in the synthesis of saframine, a family of dyes used as biological stain and may be present in indelible ink, antifreeze, and nail polish (238). As may be expected from its use in hair dye formulations, hairdressers and barbers may be exposed to 2,5-TDA (36). Workers in the dye manufacturing industry may also be exposed. 46.3 Exposure Assessment No biomonitoring data or studies are available. 46.4 Toxic Effects 2,5-Toluenediamine is toxic following oral, inhalation, and dermal exposure causing hepatotoxicity and hemolytic anemia. The compound is considered highly irritating to skin and eye (239). Myotoxicity (to both cardiac and skeletal muscle) has also been observed in rats exposed to 2,5TDA; a number of more highly ring-methylated analogs (2,3,5,6-tetramethyl-, 2,5-dimethyl- and 2,6dimetyl-p-phenylenediamine) are even more myotoxic (240). Ames test showed positive mutagenicity with metabolic activation (100). The possible carcinogenicity of 2,5-TDA (as sulfate salt, CAS # [6369-59-1]) was tested by the National Cancer Institute in a dietary feeding study (238). Groups of 50 male and female F344 rats (600 or 2000 ppm) and B6C3F1 mice (600 or 1000 ppm) were given diets containing 2,5-TDA for 78 wk and then observed for an additional period of 28–31 wk for rats and 16–19 wk for mice. The only statistically significant increased incidence was in lung tumors in high-dose female mice, but the evidence was not convincing enough to be attributed to 2,5-TDA. Overall, the compound was considered noncarcinogenic (238). 46.5 Standards, Regulations, or Guidelines of Exposure No hygienic standards of permissible exposure have been assigned. 47.0 2,6-Toluenediamine 47.0.1 CAS Number: [823-40-5] 47.0.2–47.0.3 Synonyms and Trade Names: Toluene-2,6-diamine, 2-methyl-1,3-benzenediamine, 2,6-diaminotoluene, 1,3-diamino-2-methylbenzene, 2,methyl-m-phenylenediamine, 2,6-diamino-1methylbenzene, 2-methyl-1,3-phenylenediamine, 2,6-toluylenediamine, and 2,6-toluenediamine and 2,6-TDA 47.0.4 Molecular Weight: 122.17 47.0.5 Molecular Formula: C7H10N2

47.0.6 Molecular Structure:

47.1 Chemical and Physical Properties 2,6-Toluenediamine has a melting point of 106°C; it is soluble in water and alcohol. The dihydrochloride of 2,6-TDA is usually more stable than the free amine (85, 155). 47.2 Production and Use 2,6-Toluenediamine is usually produced as a byproduct with 2,4-TDA in mixtures containing 20% 2,6- and 80% 2,4-isomer. It is used primarily in the manufacture of toluene diisocyanate (TDI), the predominant isocyanate in the flexible polyurethane foams and elastomers industry (228). Human exposure to 2,6-TDA may occur indirectly via exposure to toluene diisocyanate mixture containing 2,6-toluenediisocyanate, which is known to hydrolyze to 2,6-TDA rapidly upon contact with water. Workers in some plastics and elastomers industries may be exposed to atmosphere containing TDI (228). 47.3 Exposure Assessment Biomonitoring methods to measure hemoglobin adducts of 2,6-TDA as a dosimeter of exposure have been developed (102). 47.4 Toxic Effects 2,6-Toluenediamine is positive in the Ames test, in vitro chromosome aberration, and sister chromatid exchange assays (100). Long-term bioassay of 2,6-TDA (as dihydrochloride salt, CAS [15481-70-6]) in an NCI feeding study using male and female F344 rats (250 or 500 ppm) and B6C3F1 mice (50 or 100 ppm) showed no evidence of carcinogenicity (241), although the doses used in the mosue study did not reach the maximum tolerated dose. 47.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Metabolism and mechanistic studies (83, 229, 242) showed that 2,6-TDA is metabolically activated to a mutagenic and reactive intermediate capable of binding to DNA. However, unlike its hepatocarcinogenic 2,4-isomer, 2,6-TDA lacks tumorigenesis promoting activities as indicated by its failure to induce hepatocellular proliferation (227) and promote development of liver foci from diethylnitrosamine-initiated hepatocytes (83). Thus the genotoxicity of 2,6-TDA alone is insufficient to confer complete carcinogenic activity. 47.5 Standards, Regulation, or Guidelines of Exposure No hygienic standards of permissible exposure have been assigned. 48.0 3,4-Toluenediamine 48.0.1 CAS Number: [496-72-0] 48.0.2 Synonyms: 3,4-Diaminotoluene, 4-methyl-1,2-benzenediamine, diaminotoluene, toluene-3,4diamine, and 4-methyl-o-phenylenediamine 48.0.3 Trade Names: NA 48.0.4 Molecular Weight: 122.17 48.0.5 Molecular Formula: C7H10N2 48.0.6 Molecular Structure:

3,4-Toluenediamine has a melting point of 88°C and a boiling point of 265°C (sublimes); it is soluble in water. The most significant commercial use of o-TDA is in the manufacture of tolyltriazoles, which are used as corrosion inhibitors, photographic chemicals, and catalysts. It is also used as chemical intermediate in the synthesis of polyols and antioxidants (85). The compound was reported to be mutagenic in the Ames test in one study (100), but negative in another (243). No hygienic standards of permissible exposure have been assigned. In the absence of data, NIOSH considers all TDA isomers as possible occupational carcinogens. 49.0 3,5-Toluenediamine 49.0.1 CAS Number: [108-71-4] 49.0.2 Synonyms: 5-Methyl-1,3-benzenediamine and 3,5-diaminotoluene 49.0.3 Trade Names: NA 49.0.4 Molecular Weight: 122.17 49.0.5 Molecular Formula: C7H10N2 49.0.6 Molecular Structure:

There is no information available on this isomer in the open literature.

Aromatic Amino and Nitro–Amino Compounds and their Halogenated Derivatives Yin-Tak Woo, Ph.D., DABT, David Y. Lai, Ph.D., DABT F. Chlorinated Nitrobenzene Compounds Chlorinated nitrobenzene compounds are important chemical intermediates for the synthesis of dyes, rubber, agricultural and pharmaceutical chemicals, as well as for some explosives. The chemical reactivity and toxicity of chlorinated nitrobenzene compounds depend on the number of chloro and nitro groups on the ring and their relative position. The ring nitro group(s) may contribute to toxicity either by reduction to aromatic amines or by activating the chloro group to become a leaving group, thereby yielding a direct-acting arylating agent. To yield an arylating agent, the electronwithdrawing nitro group(s) must be situated ortho or para to the chloro group. The strongest arylating agents are 1-fluoro-2,4-dinitrobenzene and 1-chloro-2,4-dinitrobenzene. There is good evidence that the mutagenicity of halogenated nitrobenzene compounds may be correlated to their arylating activity. A comparative mutagencity study (244), using Ames assay, of 21 chloro/fluoronitrobenzene and 9 chloro-/fluorobenzene compounds indicated that mutagenicity (base-pair substitution only) was exhibited by all compounds having a chloro or fluoro group at the ortho or para position in the nitrobenzene nucleus. Chlorinated nitrobenzene compounds are also notorious as inducers of methemoglobinemia; this activity is less dependent on the relative positions of chloro

and nitro groups. All three isomers (o-, m-, p-) of chloronitrobenzene have been shown to be potent inducers of methemoglobinemia. 50.0 o-Chloronitrobenzene 50.0.1 CAS Number: [88-73-3] 50.0.2–50.0.3 Synonyms and Trade Names: 1-Chloro-2-nitrobenzene, 2-chloro-1-nitrobenzene, Oncb, 2-nitrochlorobenzene, 2-CNB, and o-CNB 50.0.4 Molecular Weight: 157.56 50.0.5 Molecular Formula: C6H4ClNO2 50.0.6 Molecular Structure:

50.1 Chemical and Physical Properties o-Chloronitrobenzene usually occurs as oily yellow crystals at room temperature. It has a melting point of 34°C and a boiling point of 246°C; it is soluble in alcohol, benzene, ether, and acetone but insoluble in water. At room temperature, its vapor pressure is sufficiently high to lead to significant volatilization (62). As an aromatic nitro compound, it is easily reducible to corresponding aromatic amino compounds (26). The chlorine atom can be easily replaced by OH, OCH3 OC6H5, etc., by nucleophilic attack. 50.2 Production and Use The annual production of o-CNB in the United States in 1993 was 19,000 metric tons (2) and on the order of 50,000–70,000 metric tons in Germany (26). It is used as a chemical intermediate for the synthesis of o-aminophenol, which is used as a photographic developer. It is also used in the preparation of dyes, corrosion inhibitors, and agricultural chemicals. Human exposure may occur to dyestuff workers but the extent is uncertain because of its use as a chemical intermediate. o-Chloronitrobenzene has been detected in the surface water of the Rhine River in a concentration range of 0.1–0.5 mg/L (26). Concentration levels of up to 1 mg/kg were reportedly found in fish in Europe (26). 50.3 Exposure Assessment No biomonitoring studies are available. 50.4 Toxic Effects o-Chloronitrobenzene has been reported to cause a variety of toxic effects, which include skin, eye, and respiratory tract irritation, pulmonary edema, methemoglobinemia, neurotoxicity, dermatitis, skin sensitization, and hepatic, pancreatic, and renal disorders (163, 245). Toxicity studies by NTP (62) showed that o-CNB is mutagenic in the Ames test, positive in the sister chromatid exchange assay, and capable of inducing chromosomal aberrations in Chinese hamster ovary cells but negative in sex-linked recessive lethal mutation assays in Drosophila melanogaster. Inhalation exposure of rats and mice to o-CNB resulted in methemoglobin formation and oxidative damage to red blood cells, leading to a regenerative anemia and a spectrum of tissue damage secondary to erythrocyte injury. Hyperplasia of the respiratory epithelium was also observed in rats exposed to o-CNB. The increase in methemoglobin occurred in rats exposed to as low as 1.1 ppm o-CNB. The NOAEL was 6 ppm for mice in a 13-wk inhalation study. Reproductive toxicity study indicated evidence of decreased spermatogenesis in rats exposed to o-CNB. A planned carcinogenicity study by NTP was cancelled. 50.4.1.3 Pharmacokinetics, Metabolism, amd Mechansims o-Chloronitrobenzene can be readily

absorbed by oral, dermal, and inhalation routes (62). It has been reported to be metabolized to ochloroaniline, indicating nitroreduction, and conjugated with GSH to S-(2-nitrophenyl)glutathione, indicating the arylating activity (1). 50.5 Standards, Regulations, or Guidelines of Exposure No hygienic standards of permissible exposure have been assigned. In Germany, this compound has been considered a substance suspected of having carcinogenic potential (246). 51.0 m-Chloronitrobenzene 51.0.1 CAS Number: [121-73-3] 51.0.2–51.0.3 Synonyms and Trade Names: 3-Nitrochlorobenzene, 1-chloro-3-nitrobenzene; MNCB, nitrochlorobenzene, and m-CNB 51.0.4 Molecular Weight: 157.56 51.0.5 Molecular Formula: C6H4ClNO2 51.0.6 Molecular Structure:

51.1 Chemical and Physical Properties m-Chloronitrobenzene has a melting point of 43°C and a boiling point of 236°C. It is soluble in hot alcohol, chloroform, ether, carbon disulfide, and benzene, but relatively insoluble in water (2). Unlike the o- and p-isomers, the chlorine atom in m-CNB is not activated for nucleophilic substitution. 51.2 Production and Use m-Chloronitrobenzene is of lesser economic importance than its ortho and para isomers, with no U.S. production reported (2). The annual production in Germany was reported to be in the order of 1000–3000 metric tons. It has limited use in the manufacturing of dyes and agricultural chemicals. There is no information on potential exposure. Chloronitrobenzene has been detected in the surface water of the Rhine River with concentrations between 20 and 500 ng/L and in fish at levels of up to 1 mg/kg (26). 51.4 Toxic Effects The main toxicological concern for m-CNB is the induction of methemoglobinemia, which could be observed in rats given dermal administration of 800–2000 mg/kg of the compound. Cats are substantially more susceptible to the methemoglobin-forming activity of m-CNB. A single IP dose of 5–10 mg m-CNB/kg body weight was sufficient to generate methemoglobinemia with the greatest effect observed 10 h after the administration (26). In contrast its o and p isomers, m-CNB has been basically shown to be nonmutagenic in the Ames test, sister chromatid exchange, and chromosome aberration assays (26, 100, 247). 51.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Absorption studies indicated that m-CNB may be absorbed via oral, dermal, and inhalation routes. Metabolism studies in rabbit showed mchloroaniline and its phenolic derivatives as the major metabolites. There is no evidence of GSH conjugation indicating the lack of arylating activity. There is evidence that the mode of action of methemoglobinemia is most likely caused by the formation of hydroxylamine derivative during metabolism (26). 51.5 Standards, Regulations, or Guidelines of Exposure No hygienic standards of permissible exposure have been assigned. 52.0 p-Chloronitrobenzene

52.0.1 CAS Number: [100-00-5] 52.0.2–52.0.3 Synonyms and Trade Names: 4-Chloronitrobenzene, PNCB, nitrochlorobenzene, 1chloro-4-nitrobenzene, 1,4-chloronitrobenzene, 4-nitrochlorobenzene, 4-chloro-1-nitrobenzene, pnitrochlorobenzene, 1-chloro-4-nitrobenzene, and p-CNB 52.0.4 Molecular Weight: 157.56 52.0.5 Molecular Formula: C6H4ClNO2 52.0.6 Molecular Structure:

52.1 Chemical and Physical Properties p-Chloronitrobenzene occurs as yellow crystals at room temperature. It has a melting point of 83.6°C and a boiling point of 242°C; it is soluble in alcohol, benzene, ether, and acetone, but insoluble in water. At room temperature, its vapor pressure (0.009 torr at 25°C) is sufficiently high to lead to significant volatilization (62). As an aromatic nitro compound, it is easily reducible to the corresponding aromatic amino compound (26). The chlorine atom can be easily replaced by OH, OCH3, OC6H5, etc. by nucleophilic attack. 52.2 Production and Use The annual production of p-CNB in the United States in 1993 was 35,000 metric tons (2) and on the order of 50,000–70,000 metric tons in Germany (26). It is used as an intermediate in the manufacture of dyes, rubber, and agricultural chemicals. Human exposure may occur to dyestuff workers but the extent is uncertain because of its use as a chemical intermediate. p-Chloronitrobenzene has been detected in the surface water of the Rhine River at a concentration range of 0.1–6.38 mg/L (26). 52.3 Exposure Assessment 52.3.3 Workplace Methods NIOSH Analytical Method 2005 is recommended for determining workplace exposures to p-CNB (111a) The measurement of blood methemoglobin level has been used as a nonspecific indicator of biological exposure to p-CNB. 52.4 Toxic Effects The most significant toxicity is methemoglobinemia, which may occur after oral, dermal, or inhalation exposure. Symptoms of methemoglobinemia, which include headache, dizziness, vomiting, weakness, cyanosis, and anemia, have been observed in workers exposed to p-CNB via skin contact or inhalation. Skin penetration is rapid, and p-CNB is more potent than aniline in terms of potential to produce cyanosis and anemia (26). Animal studies also indicated the methemoglobinemia-inducing capability of p-CNB (26). A recent NTP subchronic inhalation toxicity study showed evidence of methemoglobinemia in F344/N rats exposed to as low as 1.5 ppm p-CNB. No NOAEL could be achieved for rats in this study while a NOAEL of 6 ppm was established for B6C3F1 mice (62). Mutagenicity studies by NTP (62) showed that p-CNB is mutagenic in the Ames test, positive in the sister chromatid exchange assay, and capable of inducing chromosomal aberrations in Chinese hamster ovary cells but negative in sex-linked recessive lethal mutation assay in Drosophila melanogaster. A teratogenicity study of p-CNB was conducted in groups of Sprague–Dawley rats administered 5, 15, or 45 mg/kg/d by gavage on days 6 to 19 of gestation and in New Zealand rabbits dosed with 5, 15, or 40 mg/kg/d on gestation days 7 to 19 by gavage (168). In the rat study, there was evidence of

embryotoxicity (increased resorptions) and teratogenicity (increased incidences of skeletal anomalies) only at the high-dose group, which is slightly maternally toxic. In the rabbit study, the high dose was highly toxic to the dams, whereas the mid- and low-doses caused small increases in the incidences of skeletal malformations that were not statistically significant (168). p-CNB was reported to be noncarcinogenic in Sprague–Dawley rats and equivocal in HaM/ICR mice given maximally tolerated dietary doses (rats: initially 4000 ppm, reduced to 500 ppm after 3 mo and then raised to 1000 ppm after 2 mo; mice: 6000 ppm) and half of those doses for 18 mo followed by 6 mo (rats) or 3 mo (mice) observation (182). In another long-term bioassay in which rats were given p-CNB orally at 0.1, 0.7, or 5.0 mg/kg/d, the only predominant adverse effect was apparently significant methemoglobinemia observed at mid- and high-dose levels (1). In view of the uncertainties, NTP originally planned a carcinogenicity bioassay but subsequently decided to discontinue after the subchronic toxicity studies. 52.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Absorption studies indicated that p-CNB can be readily absorbed by all routes of exposure (62). In vitro studies have demonstrated that pCNB can be reduced to p-chloroacetanilide as well as p-chloroaniline, and that cytosolic GSH transferase is involved in the conjugation with GSH to form S-(4-nitrophenyl)glutathione. Urinary metabolites of male Sprague–Dawley rats following a single IP dose of 100 mg/kg of p-CNB diluted in olive oil included trace amounts of unchanged p-CNB, p-chloroaniline, 2,4-dichloroaniline, pnitrothiophenol, 2-chloro-5-nitrophenol, 2-amino-5-chlorophenol, 4-chloro-2-hydroxyacetanilide, and a small amount of p-chloroacetanilide (248). 52.5 Standards, Regulations, or Guidelines of Exposure The ACGIH TLV–TWA is 0.64 mg/m3 (0.1 ppm) with skin notation. The ACGIH also considers pCNB a confirmed animal carcinogen with unknown relevance to humans (160). NIOSH considers pCNB as a potential occupational carcinogen. The current OSHA PEL is 1 mg/m3 with skin notation. The NIOSH immediately dangerous to life or health concentration (IDLH) is 100 mg/m3 (110). In Germany, p-CNB is considered a suspect carcinogen (246) and subject to a variety of legal regulations and orders with a maximum workplace concentration of 1 mg/m3 assigned (26). 53.0 1-Chloro-2,4-dinitrobenzene 53.0.1 CAS Number: [97-00-7] 53.0.2–53.0.3 Synonyms and Trade Names: 2,4-Dinitro-1-chlorobenzene, 2,4-dinitrochlorobenzene, 1,3-dinitro-4-chlorobenzene, dinitrochlorobenzene, chlorodinitrobenzene, DNCB, and 4-chloro-1,3dinitrobenzene 53.0.4 Molecular Weight: 202.55 53.0.5 Molecular Formula: C6H3ClN2O4 53.0.6 Molecular Structure:

53.1 Chemical and Physical Properties 1-Chloro-2,4-dinitrobenzene occurs as yellow crystals at room temperature. It has a melting point of 53–54°C (for a form) or 43°C (for b form) and a boiling point of 315°C; it is insoluble in water but readily soluble in ether, benzene, or hot alcohol. With two electron-withdrawing nitro groups situated at ortho and para positions, the chlorine is activated to become a good leaving group, thus

making the compound a good arylating agent (155, 156). 53.2 Production and Use 1-Chloro-2,4-dinitrobenzene is the best-known chlorodinitrobenzene isomer. It has been used in the manufacture of dyes, as a reagent for the detection of pyridine compounds, as an algicide in coolant water of air conditioning systems, and as a positive control in sensitization experiments. Incidents of occupational exposure have been reported. The highly potent sensitizing activity of DNCB has limited its uses to closed systems. 53.4 Toxic Effects Although not known to be a potent systemic toxicant with rat oral LD50 reported to be 1.07 g/kg (155), this chemical is a notoriously potent sensitizer. Dermal exposure can result in contact urticaria and yellow discoloration of the skin, as well as violent dermatitis (211). Adams et al. (249) reported a case in which DNCB had been used as an algicide in the coolant water of air conditioning systems. Four repairmen working on these systems suffered severe contact dermatitis that was very difficult to treat. The conclusion was that because DNCB is extremely allergenic and should be used only in closed systems that afford no human contact (167). In fact, DNCB has been used since 1927 for experimental induction of contact sensitivity and in allergenic cross-sensitization screening programs (137). A detailed review of the use of DNCB in experimental sensitization studies, including dose– response relationships and species differences, has been published (25). 1-Chloro-2,4-dinitrobenzene has been shown to be mutagenic in the Ames test without metabolic activation (244, 250). The presence of glutathione may reduce the direct-acting mutagenicity of DNCB by forming glutathione conjugate; however, the glutathione conjugate may be further activated by nitroreduction (250). A preliminary carcinogenicity study of DNCB in Charles River rats and Ham/ICR mice by dietary administration for 12–13 months was reported to be negative (182); however, in view of its being a direct-acting arylating agent, testing by dermal and inhalation routes may be more appropriate. 53.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Metabolism studies have demonstrated that DNCB depletes hepatic GSH levels by the biotransformation displacement of chlorine to yield 1-SG-2,4-dinitrobenzene (251). A reactive intermediate may be involved, for further studies have also demonstrated that DNCB was less mutagenic in a GSH-deficient derivative of Salmonella typhimurium TA100 (TA100/GSH-) than in TA100 itself, suggesting that the mutagenicity depends on GSH. Further investigations indicated that halogenated aromatics may react with bacterial DNA and produce premutagenic alterations according to two mechanisms: direct attack on the DNA through nucleophilic substitution (SN2) of the halogen atoms, or activation through GSH conjugation and subsequent nitroreduction of the conjugate or its metabolic products to more reactive intermediates (250). 53.5 Standards, Regulations, or Guidelines of Exposure 1-Chloro-2,4-dinitroenzene is on OSHA's List of Highly Hazardous Chemicals. The highly potent sensitizing activity of DNCB has limited its uses to closed systems. 54.0 1-Chloro-2,5-dinitrobenzene 54.0.1 CAS Number: [619-16-9] 54.0.2 Synonyms: 2-Chloro-1,4-dinitrobenzene 54.0.3 Trade Names: NA 54.0.4 Molecular Weight: 202.55 54.0.5 Molecular Formula: ClC6H3(NO2)2 54.0.6 Molecular Structure:

1-chloro-2,5-dinitrobenzene occurs as light yellow crystals at room temperature, has a melting point of 64°C, and is soluble in alcohol, and ether (155). There is no specific information on its production. Its uses are reported to be identical with those of 1-chloro-2,4-dinitrobenzene, and its toxicity is assumed to be also similar. Information on exposure and regulations is not available. 55.0 1-Chloro-2,6-Dinitrobenzene 55.0.1 CAS Number: [606-21-3] 55.0.2 Synonyms: 2-Chloro-1,3-dinitrobenzene 55.0.3 Trade Names: NA 55.0.4 Molecular Weight: 202.55 55.0.5 Molecular Formula: C6H3ClN2O4 55.0.6 Molecular Structure:

1-Chloro-2,6-dinitrobenzene occurs as yellow crystals at room temperature; it has a melting point of 86–87°C and a boiling point of 315°C and is soluble in alcohol, ether, and toluene. With both nitro groups ortho to the chlorine, this compound is expected to be a good arylating agent. There is no specific information on its production and uses, although chlorodinitrobenzene isomers and mixtures have been used in the manufacture of dyestuffs, other dye intermediates, and certain explosives (167). Information on exposure, toxicology, and regulation is not available. 56.0 1-Chloro-2,3-dinitrobenzene 56.0.1 CAS Number: [602-02-8] 56.0.2 Synonyms: 3-Chloro-1,2-dinitrobenzene 56.0.3 Trade Names: NA 56.0.4 Molecular Weight: 202.55 56.0.5 Molecular Formula: ClC6H3(NO2)2 56.0.6 Molecular Structure:

1-chloro-2,3-dinitrobenzene has a melting point of 78°C and a boiling point of 315°C, is insoluble in water, and is soluble in alcohol and ether. There is no specific information on its production and uses, although chlorodinitrobenzene isomers and mixtures have been used in the manufacture of dyestuffs, other dye intemediates, and cartain explosives (167). Information on exposure, toxicology, and regulation is no available. 57.0 1-Chloro-3,4-dinitrobenzene 57.0.1 CAS Number: [610-40-2] 57.0.2–57.0.3 Synonyms and Trade Names: 1,2-Dinitro-4-chlorobenzene and 3,4dinitrochlorobenzene 57.0.4 Molecular Weight: 202.55 57.0.5 Molecular Formula: C6H3ClN2O4 57.0.6 Molecular Structure:

1-chloro-3,4-dinitrobenzene occurs as monoclinic prisms and needles at room temperature, has melting points of 36°C (a form), 37°C (b form), 40–41°C (g form), a boiling point of 16° at 4 mm Hg; it is insoluble in water, but soluble in ether, benzene, carbon disulfide, and hot alcohol. There is no specific information on its production and uses, although chlorodinitrobenzene isomers and mixtures have been used in the manufacture of dyestuffs, other dye intermediates, and certain explosives (167). The compound was reported to be a skin sensitizer, causing contact dermatitis ranging from a few itching, vesicular papules to a generalized exfoliative dermatisis (167). Information on exposure and regulation is not available. 58.0 1-Chloro-3,5-dinitrobenzene 58.0.1 CAS Number: [618-86-0] 58.0.2 Synonyms: 1-Chloro-3,5-dinitrobenzene 58.0.3 Trade Names: NA 58.0.4 Molecular Weight: 202.55 58.0.5 Molecular Formula: ClC6H3(NO2)2 58.0.6 Molecular Structure:

1-chloro-3,5-dinitrobenzene occurs at colorless needles at room temperature; it has a melting point of 59°C, is insoluble is water, but is soluble in alcohol and ether. There is no specific information on its production and uses, although chlorodinitrobenzene isomers and mixtures have been used in

manufacture of dyestuffs, other dye intermediates, and certain explosives (167). Information on exposure, toxicology, and regulation is not available. 59.0 Pentachloronitrobenzene 59.0.1 CAS Number: [82-68-8] 59.0.2–59.0.3 Synonyms and Trade Names: Avical, Eorthcicle, Fortox, Kobu, Marison Forte, Pkhnb, Terrafun, Tri PCNB, PCNB, Quintozine, quintobenzene, Terrachlor, Terraclor, Avicol, Botrilex, Earthcide, Kobutol, Pentagen, Tilcarex, SA Terraclor 2E, SA Terraclor, nitropentachlorobenzene, brassicol, quintocene, batrilex, fartox, formac 2, fungiclor, gc 3944-3-4, KP 2, olpisan, quintozen, saniclor 30, and tritisan 59.0.4 Molecular Weight: 295.34 59.0.5 Molecular Formula: C6Cl5NO2 59.0.6 Molecular Structure:

59.1 Chemical and Physical Properties Pentachloronitrobenzene is a colorless solid at room temperature. It has a melting point of 144°C (technical grade) and a boiling point of 328°C; it is slightly soluble in water (0.044 mg/L at 20°C; 2 mg/L at 25°C) and freely soluble in carbon disulfide, benzene, and chloroform. Technical-grade PCNB often contains impurities, which include hexachlorobenzene, pentachlorobenzene, and tetrachlorbenzene (155, 156, 252). 59.2 Production and Use Approximately 2 million pounds of PCNB are used annually in the United States for agricultural purposes. It has been used as a soil or seed fungicide for the control of Botrytis disease, club root of crucifers, scab of potato, and Rhizoctonia damping-off disease of seedlings (253). It is also used as a turf fungicide to prevent root rotting. As may be expected from its agricultural uses, occupational exposure may occur during its production and direct application as a soil fungicide. The general population may also be exposed through occasional consumer use or through ingestion of foods or drinking water containing PCNB residues. 59.3 Exposure Assessment Biomonitoring data are not available. 59.4 Toxic Effects Exposure to PCNB can induce contact sensitization (211). Methemoglobinemia has been demonstrated in cats, which have an unusually high sensitivity due to the low rate of methemoglobin reductase activity, following a single high oral dose of 1.6 g/kg (254). The reported oral LD50 for male rats (in corn oil) is 1.74 g/kg, and the LD50 (dermal) for rabbits was found to be >4 g/kg (255). The reported LC50 values are 1.4 g/m3 for rats and 2.0 g/m3 for mice (179). Subchronic toxicity studies of PCNB by NTP (256) in rodents exposed to diets containing 33, 100, 333, 1000, or 2000 ppm of the compound indicated hyaline droplet nephropathy in male rats exposed to the two highest doses, minimal thyroid follicular cell hypertrophy in rats, and centrolobular hepatocellular hypertrophy in both rats and mice. The no-observed effect levels (NOELs) for histologic lesions were 33 ppm for male rats, 333 ppm for female rats, 100 ppm for female mice; no

NOEL could be determined for male mice in this study. No adverse effects were reported in a three-generation reproductive study in which CD rats were administered a diet of PCNB at concentrations of 0, 5, 50, or 500 ppm (255). A followup teratogenic study in Charles River strain albino rats, administered PCNB at dosages of 100–1563 ppm in corn oil, did not demonstrate any treatment-related developmental effects (257). Nonteratogenicity was also confirmed in Wistar rats following oral administration (258). In a comparative study using contaminated PCNB (11% hexachlorobenzene) and purified PCNB (7500 (170) >5000 ALD (170)

— Dog (mg/kg) >5000 (170) Skin ALD Rabbit (mg/kg) >5000 (171) >5000 (172) >5000 (173) >2000 (174) Skin irritation Rabbit None (175) None (172) None (173) Slight (174, 176) Guinea pig Mild (177) Mild to moderate (171) None (173) Sensitization Guinea pig None (178, 179) None (178, 180) Mild (173) Eye irritation Rabbit Mild (181) Mild (171) Mild (182) Inhalation LC50 (4 h) >4.8 (183) >5.2 (184) >4.4 (185) Rat (mg/L) a

>5.2 (186)

Numbers in parentheses are references.

Table 60.5. Genetic Toxicity Tests on Substituted Uracilsab Assay/End Point Salmonella typhimurium

Esherichia coli Saccharomyces cerevisiae Drosophila melanogaster

Mouse lymphoma assay

Bromacil –(214–218) +(219, 220) –(218, 222, 224, 225) –(217, 225–227) +(205, 217, 218, 224, 225) –(220, 238) +(217, 218, 224,

Lenacil

Terbacil

–(221) –(215, 216, 222, 223) –(216, 222)

–(206, 229)

225) –(224, 225, 230) –(225, 230)

Chinese hamster ovary Unscheduled DNA/human fibroblasts in vivo mouse micronucleus –(224, 225, 232) in vivo mouse dominant lethal –(217, 225, 233– 235) a b

–(229, 231)

+ = positive result; – = negative result. Reference numbers in parentheses.

Table 60.6. Acute Toxicity of Quaternary Herbicides in Various Speciesa (240, 241)

Oral LD50 (mg/kg)

PQ Rat Mouse Rabbit Guinea pig Monkey

a

100– 200 —

DQ

130– 400 125– 170 — 101– 190 22–80 100– 123 50 100– 300

Inhalation LC50

Dermal LD50 (mg/kg)

DFQ

PQ

(mg/m3)

DQ DFQ PQ

DQ

DFQ

270

80–350 650

—

1–10 35–83 —

31– 44 470

62

430

—

—

—

—

>400 3540 —

—

—

—

236– 500 319

400

—

4

38

—

—

—

—

—

—

—

—

PQ = paraquat; DQ = diquat; DFQ = difenzoquat; — = No data.

Alkylpyridines and Miscellaneous Organic Nitrogen Compounds Henry J. Trochimowicz, Sc.D., Gerald L. Kennedy, Jr., Ph.D., CIH, Neil D. Krivanek, Ph.D. B s-Triazine Herbicides Alkylpyridines and Miscellaneous Organic Nitrogen Compounds Bibliography

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Compound

Hydrogen cyanide Sodium cyanide Potassium cyanide Calcium cyanide Cyanamide Calcium Cyanamide Cyanogen Cyanogen chloride Cyanogen bromide

CAS Number

[74-908] [143-339] [151-508] [592-018] [420-042] [156-627] [460-195] [506-774] [506-683]

Dimethyl cyanamide

Acrylonitrile Methyl acrylonitrile Acetonitrile Propionitrile n-Butyronitrile Isobutyronitrile 3-Hydroxypropionitrile

[107-131] [126-987]

Molecular Formula

Cyanides HCN Colorless 27.03 liquid NaCN White 49.01 crystals KCN White 65.12 crystals Ca(CN)2 White 92.11 powder CH2N2 Elongated 42.04 tablets CaCN2 White 80.11 crystals Colorless 52.04 C2N2 gas ClCN Colorless 61.47 liquid or gas BrCN Colorless 105.9 crystals (CH3)2CN2 Colorless 70.1 liquid Nitriles CH2 CHCN Colorless 53.06 liquid CH2 C(CH3) Colorless 67.09 liquid CN

[75-05CH3CN 8] [107-12CH3CH2CN 0] [109-74- CH3CH3CH2CN 0] [78-82(CH3)2CHCN 0] [109-78- HOCH2CH2CN 4]

Lactonitrile

[78-977]

C3H5NO

2-Methyllactonitrile

[75-865] [107-16-

C4H7NO

Glycolonitrile

Meltin Physical Molecular Boiling Point ( Formula Weight Point (°C) C)

25.7

–13.2

—

563

—

634

—

—

—

—

—

1300

–27.17

–27.9

13.8

–6

61.6

52

—

–41

77.5–77.9

–83.55

90.3

–35.8

Colorless liquid Colorless liquid Colorless liquid Colorless liquid Colorless or straw liquid Colorless or straw liquid Liquid

41.05

81.6

–43

55.08

97.1

–98

69.11

116

–112.6

69.11

107

–75

71.08

221

–46

71.08

103

–40

85.11

95

–20

Colorless

57.05

183

4]

oily liquid Succinonitrile [110-61- CNCH2CH2CN Colorless 2] waxy solid Adiponitrile [111-69- CN(CH2)4CN Colorless 3] liquid Glycolonitrile [107-16HOCH2CN Clear 4] pale yellow liquid Colorless 3[1738(CH3) liquid Dimethylaminopropionitrile 25-6] 2NCH2CH2CN 3[7249(CH3) Liquid Isopropylaminopropionitrile 87-8] 2CH2NHCH2CN 3-Methoxypropionitrile 3-Isopropoxypropionitrile 3-Chloropropionitrile 3-Aminopropionitrile 3,3'-Iminodipropionitrile Malononitrile Cyanoacetic acid 2-Cyanoacetamide Chloroacetonitrile Methyl cyanoacetate Ethyl cyanoacetate Methyl cyanoformate Ethyl cyanoformate Methyl isocyanate Cyanuric chloride Bromophenylacetonitrile

[110-678] [110-474] [542-767] [151-188] [111-944] [109-773] [372-098] [107-915] [107-142] [105-340] [105-566] [1764015-2] [623-494] [624-839] [108-770] [579879-8]

HOCH2CN

CH3OCH2CH2CN Colorless liquid (CH3)2CH2OCH2 Liquid ClCH2CH2CN

Colorless liquid NH2CH2CH2CN Liquid solid HN(CH2CH2CN)2 Colorless liquid CH2(CN2)2 White powder CNCH2COOH White cystals CNCH2CONH2 White powder Colorless C2H2ClN liquid CH3OOCCH2CN Liquid

80.09

265–267

57–57.

108.1

295

1–3

57.05

183

= 365 days), there was increased mortality in 1000 ppm exposed male mice. There was no effect on survival of male or female rats. See Section 1.4.1.5 for the carcinogenicity aspects of this study. Although old reports suggest no effect after 6 months of 6-h daily exposure to 300 ppm (21), newer studies suggest that 50 ppm is the NOEL in rats and mice after 2 years of repeated exposure (22). The seminiferous tubules of the testes of rats were severely affected by exposure to 1000 ppm after 6 months or more. Exposure to 250 or 50 ppm caused no adverse effect in either male or female rats except for a questionable decrease in growth of female rats at 250 ppm. B6C3F1 mice were in general much more severely affected than rats, but 50 ppm was considered to be without effect after 2 years of exposure. At 1000 ppm, severe neurofunctional impairment (tremors and paralysis) with supporting histopathological injury was observed, as were splenic atrophy and hepatocellular necrosis and degeneration in the livers of male mice. Renal tubuloepithelial hyperplasia and karyomegaly were seen in mice after 12 months of exposure to 1000 ppm as well as kidney tumors in male mice only. 1.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms The 1998 ATSDR Toxicological Profile (10), in the section on metabolism, indicates that methyl chloride is rapidly absorbed from the lungs and rapidly reaches equilibrium with levels in blood and expired air approximately proportional to the exposure concentrations. At high concentrations, kinetic processes such as metabolism or excretion may become saturated, limiting the rate of uptake. Animal studies show that methyl chloride is absorbed from the lungs and extensively distributed througout the body. Methyl chloride is metabolized by conjugation with glutathione to yield S-methylglutatione, S-methylcysteine, and other sulfur-containing compounds that are excreted in the urine or further metabolized to methanethiol. Cytochrome P450–dependent metabolism of methanethiol may yield formaldehyde and formic acid, whose carbon atoms are then available to the one-carbon pool for incorporation into macromolecules or for formation of CO2. Alternatively, formaldehyde may be directly produced from chloromethane via a P450 oxidative dechlorination. The conjugation of chloromethane with glutathione is primarily enzyme-catalyzed. In contrast to all other animal species investigated (rats, mice, bovine, pigs, sheep, and rhesus monkeys), human erythrocytes contain a glutathione transferase isoenzyme that catalyzes the conjugation of glutathione with methyl chloride. There are two distinct human subpopulations based on the amount or forms of this transferase. Considerable variation in toxic response related to sex, species, and strain in animal studies may be due to qualitative and quantitative differences in metabolism. Differences in individual metabolism are also apparent in controlled human exposure studies, with two distinct subpopulations identified in several studies. Methyl chloride does not appear to methylate directly, and incorporation into macromoleculars such as RNA, DNA, protein, and lipid is due to rapid conversion to formate and metabolism as part of the one carbon pool. The metabolism scheme presented in the previous edition is still appropriate (23) and is shown in Figure 62.1.

Figure 62.1. Proposed metabolism of methyl chloride in the rat (From Ref. 23). Conjugation with glutathione is the major pathway. In discussing this diagram the authors state “The metabolic scheme depicted ... accounts for the present as well as previous findings on the metabolism of methyl chloride.” The reaction of CH3Cl with glutathione was previously demonstrated both in vitro (24) and in vivo (25). The reaction appears to be primarily enzymecatalyzed, probably by glutathione-transferase, as has been demonstrated for methyl iodide (26). The product of this reaction, methylglutathione, may be metabolized by transpeptidases to Smethylcysteine, which has been detected in the urine of rats (27) and humans (28) exposed to methyl chloride. However, no relationship between urinary S-methylcystine excretion and 6 h of exposure to 50 or 10 ppm of methyl chloride was found in human studies (13); nor was S-methylcystine a sensitive indication of exposure in beagle dogs, although the metabolite did occur in rats (27). Peters et al. (29) have shown that erythrocyte cytoplasm from rats, mice, bovines, swine, sheep, and rhesus monkeys did not convert methyl chloride. However, 60% of human blood samples showed conversion to S-methylglutathione whereas 40% did not. An enzyme, glutathione-S-transferase, present in some blood samples and not in others, accounted for the differences. This is consistent with the observation by Landry et al. (27) that human blood samples being analyzed for methyl chloride per se had to be quickly heated to 100°C for 1 min to stop enzymatic reactions whereas rat blood samples were stable for several hours. Because the major metabolic pathway involves conjugation with reduced glutathione, possibly leading to production of potent vasoconstrictors (leukotrienes), it has been postulated that the toxic action on sperm, the subsequent “dominant lethal affect,” as well as effects in the liver, kidneys, and brain, are the result of these inflammatory responses (30). In a study comparing biochemical effects in rat and mice livers and kidneys, it was concluded that renal tumors observed in male mice at 1000 ppm are probably not evoked by intermediates or in situ–produced formaldehyde (31). 1.4.1.4 Reproductive and Developmental Reproduction studies in animals have been conducted and the specific action of methyl chloride on the epididymis clearly influenced the results. Exposures that did not cause inflammation of the epididymis did not affect reproduction in rats. NIOSH (32) reviewed studies on the reproductive and/or developmental effects from exposure to

methyl chloride. Pregnant mice were exposed via inhalation at concentrations of 0, 100, 250, 500, 750, or 1500 ppm methyl chloride on days 6–18 of gestation. Exposure at 1500 ppm was terminated due to excessive maternal morbidity. Exposure at 500 or 750 ppm caused a statistically significant increase in the numbers of cardiac malformations. Exposure at concentrations of 250 or 100 ppm was considered to be nonteratogenic. Offspring of rats exposed similarly to methyl chloride showed no terata. Daily exposure of male F344 rats at 1500 ppm for 10 weeks by Hamm et al. (33) caused severe testicular degeneration; no males sired litters during a subsequent 2-week breeding period. The highest no-observed-adverse-effect level (NOAEL) concentration was 150 ppm; however, the authors stated that the actual no-effect concentration was more likely 475 ppm. In a study by Wolkowski-Tyl et al. (34), the authors concluded that in B6C3F1 mice, an inhalation exposure to 1492 ppm chloromethane resulted in severe maternal toxicity; exposure to 102 and 479 ppm chloromethane resulted in severe maternal toxicity. No deaths were observed in female rats. In a reproductive and developmental effects study of methyl chloride inhalation Wolkowski-Tyl et al. (35) concluded that an inhalation exposure to methyl chloride during Gd 6-17 resulted in maternal toxicity at 750 ppm, but not 500 ppm. Exposure to pregnant mice to 250 ppm chloromethane produced neither maternal nor fetal toxicity nor teratogenicity. Although teratological studies in rats have been negative and at most questionable in mice, methyl chloride has been shown in longer studies to have a severe effect on epididymis and sperm, with significantly altered reproductive capability. Furthermore, fetal toxicity, possibly secondary to maternal toxicity, has been shown to be severe at neurotoxic concentrations. 1.4.1.5 Carcinogenesis Classifications are IARC Group 3, Not classifiable as to its carcinogenicity to humans. MAK Group 3, Possible human carcinogen. NIOSH Carcinogen, with no further categorization. TLV A4, Not classifiable as a human carcinogen. The National Institute for Occupational Safety and Health (NIOSH) (36) reviewed the final report from an inhalation carcinogenesis bioassay by Pavkov (37) in which B6C3F1 mice and F344 rats of both sexes were exposed at methyl chloride concentrations of 0, 50, 225, or 1000 ppm for 6 h/day, 5 days/week for 2 years. This study showed renal degenerative changes (cortical tubular epithelial hypertrophy and hyperplasia with or without karyomegaly) and hepatocellular degeneration. A statistically significant increase in both malignant and nonmalignant renal tumors occurred in only the male mice exposed at 1000 ppm, including renal cortical adenomas and adenocarcinomas, papillary cystadenomas and cystadenocarcinomas, and tubular cystadenomas. Additionally, chronic inhalation of 1000 ppm methyl chloride induced functional limb muscle impairment and degeneration and atrophy of the internal granular layer of the cerebellum in male and female mice. Male and female mice exposed at 1000 ppm also exhibited atrophy of the spleen. Male and female rats exposed to methyl chloride failed to exhibit a significant increase in neoplastic lesions or to develop the other gross and histopathologic lesions observed in mice. Male rats developed bilateral atrophy of the testicular seminiferous tubules; no such change occurred in the male mice, indicating that male mice were more sensitive to the toxic effects of inhaled methyl chloride than female mice and that both sexes of mice were more sensitive than were male or female F344 rats. In a 2-year oncogenicity study by CIIT (20), a high incidence of renal tumors was found in male mice exposed to 1000 ppm methyl chloride, no evidence of carcinogenicity was found in male or female rats exposed to concentration of 1000 ppm in this study. In 1986 IARC concluded that there was inadequate evidence for the carcinogenicity of methyl

chloride in animals; however, NIOSH (36) has classified methyl chloride as a potential occupational carcinogen. 1.4.1.6 Genetic and Related Cellular Effects Studies When studied in rats, there has been no evidence of alkylation of DNA, even in a study designed to maximize analytic sensitivity (38). However, in certain in vitro and in vivo studies, methyl chloride appears to be a weak, direct-acting mutagen for bacteria, Drosophila, and mammalian cells. Although positive in a dominant lethal study in rats, the effect appears to be secondary to injury of a specific area of the epididymis. Dominant lethal mutations were indicated by increased preimplantation loss in male F344 rats exposed 6 h/day at 3000 ppm administered for 5 consecutive days throughout the 8 weeks following exposure (i.e., after treatment of spermatogonia, spermatocytes, spermatids, and spermatozoa), and a slight increase in postimplantation loss was found only during the first week after exposure (i.e., after treatment of spermatozoa) (39). Subsequently the authors indicated that the postimplantation loss was a secondary effect due to methyl chloride-induced inflammation of the epididymis (40). 1.4.1.7 Other: Neurological, Pulmonary, Skin Sensitization Exposure to animals results in neurological effects. Rats, mice, rabbits, guinea pigs, dogs, cats, and monkeys exposed to chloromethane until death all displayed signs of severe neurotoxicity (41, 42). A limited number of animal (not human) studies report ocular effects but the results are mixed. 1.4.2 Human Experience Since the mid-1960s or so, methyl chloride was used as a refrigerant, and many human deaths resulted from exposure to methyl chloride vapors from leaks in home refrigerators and industrial cooling and refrigeration systems (43). The principal route of absorption is by inhalation, but methyl chloride can be absorbed through the skin. Symptoms may include headache, elevated blood concentrations of carboxyhemoglobin, nausea, and irritation of the skin and eyes. Central nervous system depression, pulmonary edema, hemolysis, chronic intoxication, and paresthesia may also occur. Other symptoms include narcosis, temporary neurobehavioral effects, increase in serum bilirubin, increased urinary formic acid concentrations, and increased risk of spontaneous abortion. In addition, intravascular hemolysis, unconsciousness, lack of response to painful stimuli, rapid followed by slowed respiration, erythema, blistering, toxic encephalopathy, painful joints, swelling of the extremities, mental impairment, diabetes, skin rash, aspiration pneumonia, gross hematuria, reduction of blood pH, gastrointestinal injury, and narrowing of the intestinal lumen may also occur. Symptoms may include upper respiratory tract irritation, giddiness, stupor, irritability, numbness, tingling in the limbs, and hallucinations. A dry, scaly, and fissured dermatitis, skin burns, coma and death may also result. Other symptoms may include dizziness, sense of fullness in the head, sense of heat, dullness, lethargy, and drunkenness. In addition, mental confusion, lightheadedness, vomiting, weakness, somnolence, lassitude, anorexia, depression, fatigue, vertigo, liver damage, nose and throat irritation, anesthetic effects, smarting and reddening of the skin, blood dyscrasias, acceleration of the pulse, and congestion in the head may result. Staggering may also occur. Symptoms of exposure may include neurasthenic disorders, digestive disturbances and acoustical and optical delusions. Arrhythmias produced by catecholamines may also result. Additional symptoms include edema, faintness, loss of apetite, and apathy. Hyporeflexia, gross hemoglobinuria, epiglottal edema, metabolic acidosis, GI hemorrhage, ulceration of the duodenojejunal junction, and diverticula may also occur. Other symptoms may include kidney damage, lung damage, corneal injury, abdominal pain, and an increase in salivary gland tumors. Cyanosis may also occur. Exposure may also cause altered sleep time, convulsions, euphoria and a change in cardiac rate. 1.4.2.1 General Information Generally, case reports do not describe respiratory effects in human exposures. No effects on pulmonary function were observed in volunteers who were exposed to 150 ppm (44).

Cardiovascular effects (electrocardiogram abnormalities, tachycadia, increased pulse rate, and decreased blood pressure) have been described in case reports of humans exposed occupationally or accidentally to refrigerator leaks (45). In an extensive study with human subjects, Stewart et al. (46) gave males single or repeated exposures to 0, 20, 100, or 150 ppm and females to 0 or 100 ppm. Exposures were generally held at a constant level, but in one case were allowed to range from 50 to 150 ppm, averaging 100 ppm. Exposures were for 1, 3, or 7 h/day, 5 days/week. Using a wide battery of behavioral, neurological, electromyographic, and clinical chemical tests, no significant decrements were found. No increase in methyl alcohol was found in the urine, and methyl chloride in expired air dropped so rapidly as to be of little or no value in quantifying exposure. There was a remarkable difference in individual responses, with some subjects consistently showing several times the blood and expired air concentrations found in others. This bimodal distribution has also been reported by Putz et al. (47). Kegel et al. (48) and McNally (49) reported clinical cases of acute poisoning from leaking refrigerators. Hansen et al. (50) observed the effects of excessive exposure after a spill. Fifteen workers manifested signs of dizziness, blurred vision, incoordination, and GI complaints. Recovery was complete in 10–30 days. Although rarely in the United States, some methyl chloride may still be used as a refrigerant in other countries. A 1976 report describes poisoning of four members of a family due to a leaking refrigerator (45). Klimkova-Dentschova (51) observed the neurological pictures in 100 workers. The report stated: “Involvement of the internal organs (kidney, optic disturbances) was absent even where nervous and mental changes indicated a severe form of poisoning.” Levels of exposure were not indicated. Numerous other studies described the effect of acute exposure, but reports of chronic low level exposure are less common. One report described the nonspecific nature of six cases and reports many of the symptoms discussed earlier (52). Recovery seemed to occur in all subjects, but often several months were required. Another report of eight cases is given by MacDonald, who described similar effects, ascribing them to exposure below 100 ppm in one subject, and to have resulted in permanent injury in another. However, there is uncertainty in the exposure estimates. Exposure to methyl chloride in excess of 200 ppm resulted in serious disturbances in CNS function in a husband and wife who stored foamed plastic panels in their new house (53). The house was of tight, energy-efficient construction (0.06 air changes/h), and the foam sheets were being stored prior to installation. After several days, complete exhaustion, labyrinthitis, and unsteadiness of gait were observed. Recovery appeared to have been complete. It was concluded that the foam panels had not offgassed adequately before being placed in the house. An epidemiological study by Holmes (54) is discussed in Section 1.4.2.3.5. 1.4.2.2 Clinical Cases Numerous case reports of humans exposed to methyl chloride vapors as a result of industrial leaks describe neurological effects (43). In general, symptoms develop within a few hours after exposure and include fatigue, drowsiness, staggering, headache, blurred and double vision, mental confusion, tremor, vertigo, muscular cramping and rigidity, sleep disturbances, and ataxia. The symptoms may persist for several months, and depression and personality changes may develop. In some cases, complete recovery occurs, but in severe poisoning, convulsion, coma, and death are possible. Microscopic examination of the brain of an individual who died following an exposure showed accumulation of lipoid-filled histiocytes in the leptomeninges of the hemispheres, hyperemia of the cerebral cortex, and lipoid droplets in the adventitia cells of the capillaries throughout the brain (55). Exposure to animals also results in neurological effects. Rats, mice, rabbits, guinea pigs, dogs, cats, and monkeys exposed to chloromethane until death all displayed signs of severe neurotoxicity (41, 42).

Exposure to high concentrations of methyl chloride can result in moderate to severe neurological effects. Refrigerator repairmen developed neurological symptoms after exposure from leaks at concentrations as high as 600,000 ppm, but there were no deaths (56). Numerous case reports of humans exposed to methyl chloride describe symptoms of nausea and vomiting, but these symptoms may be associated with the concomittant CNS toxicity (43). Generally animal studied do not support gastrointestinal damage. Case reports of humans exposed to methyl chloride describe indicators of renal toxicity, such as albuminuria, increased serum creatinine and blood urea nitrogen, proteinuria, and anuria (45). Animal studies generally support kidney injury. 1.4.2.3 Epidemiology Studies A retrospective epidemiologic study of workers exposed in a butyl rubber manufacturing plant found no statistical evidence that the rate of death due to diseases of circulatory system was increased when compared to U.S. mortality rates (54) discussed in the next section. 1.4.2.3.5 Carcinogenesis A retrospective epidemiology study of male workers exposed to chloromethane in a butyl rubber manufacturing plant produced no statistical evidence of cancer deaths (54). Rafnsson and Gudmundsson (57) reported excess mortality from cancer in a long-term follow-up after an acute high level exposure of crew members to a leaking refrigerator. The authors reported an excess mortality from all causes associated with chloromethane exposure, including an elevated mortality from all cancers and lung cancer, but conclusions from the study are limited because of possibly faulty assumptions with regard to matching the control group. The USEPA has not assigned a carcinogenicity classification. Health advisories published by the EPA Office of Water assign chloromethane to cancer group C, which indicates that the substance is a possible human carcinogen. IARC has classified chloromethane as group 3 (not classifiable). The NTP has not classified the chemical with regard to carcinogenicity. NIOSH recommends that methyl chloride be treated as a potential occupational carcinogen. 1.4.2.3.6 Genetic and Related Cellular Effects Studies Uniquely, human erythrocytes contain a glutathione transferase isoenzyme that catalyzes the conjugation of glutathione with methyl chloride. There are two distinct human subpopulations based on the amount or forms of this transferase. They are known as “fast metabolizers” and “slow metabolizers” or conjugators and nonconjugators. There is considerable variation among ethnic groups and this aspect has significant effect on toxicity. 1.5 Standards, Regulations, or Guidelines of Exposure ACGIH TLV TWA is 50 ppm (103 mg/m3) and the ACGIH TLV STEL is 100 ppm (207 mg/m3). NIOSH considers methyl chloride a carcinogen and recommends that exposures be limited to the lowest feasible concentration; NIOSH IDLH is 2000 ppm. The OSHA PEL is 100 ppm, the ceiling is 200 ppm and 300 ppm is 5-min the maximum peak in any 3 hours. In the provisions of the Clean Air Act Amendments (CAAAs) of 1990, methyl chloride is among 189 compounds designated as hazardous air pollutants. Regulations in other countries include Australia—50 ppm, STEL 100 ppm (1990); (Former Federal Republic of) Germany—50 ppm, short-term level 100 ppm, 30 min, 4 times per shift, group 3, Possible human carcinogen, pregnancy group B, a risk of damage to the developing embryo or fetus must be considered to be probable and cannot be excluded when pregnant women are exposed under conditions where MAK and BAT values are observed (1998); Sweden—50 ppm, 15-min short-term

value 100 ppm (1990); United Kingdom—50 ppm, 10-min STEL 100 ppm (1991); U.S. NIOSH— lowest feasible concentration, carcinogen, IDLH 2000 ppm. 1.6 Studies on Environmental Impact: NA

Saturated Methyl Halogenated Aliphatic Hydrocarbons Jon B. Reid, Ph.D., DABT 2.0 Methyl Bromide 2.0.1 CAS Number: [74-83-9] 2.0.2 Synonyms: Monobromomethane; bromomethane 2.0.3 Trade Names: Dowfume MC-2; Dowfume MC-33; Edco; Embafume; Halon 1001, Iscobrome; MB, MBX, MEBR; Metafume; Methogas; Pestmaster; Profume; Rotox; Terr-O-Gas 100; Zytox 2.0.4 Molecular Weight: 94.95 2.0.5 Molecular Formula: CH3Br 2.0.6 Molecular Structure:

2.1 Chemical and Physical Properties 2.1.1 General Physical state Specific gravity Melting point Boiling point Solubility

Colorless gas 1.732 (0/0°C)

–93.66°C 3.56°C 0.09 g/100 mL water at 20°C; soluble in ethyl ether, ethanol, benzene, carbon tetrachloride Flammability Practically nonflammable; flame propagation is in the narrow range of 13.5–14.5% by volume in air; ignition temperature is 537°C

1 mg/L = 257 ppm and 1 ppm = 3.89 mg/m3 at 25°C, 760 torr 2.1.2 Odor and Warning Properties Methyl bromide has practically no odor or irritating effect and therefore no warning, even at physiologically hazardous concentrations. At high concentrations it has a chloroform odor. Some mixtures of methyl bromide used for fumigation contain chloropicrin as another active ingredient or as a warning agent. The chloropicrin may give warning of significant concentrations of methyl bromide from leaking containers; however, experience has shown that chloropicrin vapor may disappear before methyl bromide vapor and therefore the warning properties are lost. Charcoal-gas mask canisters also preferentially remove chloropicrin. With prolonged use,

methyl bromide may penetrate the charcoal in harmful concentrations with no odor of chloropicrin. 2.2 Production and Use Methyl bromide is used in ionization chambers, refrigerants, fire extinguishing agents, organic synthesis as an methylating agent, preparation of quarternary ammonium compounds, organotin derivatives, and antipyrine. It is also used as a soil and space fumigant; in the disinfestation of potatoes, tomatoes, and other crops; as an acaricidal fumigant; as an industrial solvent for extraction of plant oils; as a fungicide, herbicide, nematocide, rodenticide, and insecticide; and in degreasing wool, nuts, seeds, and flowers. Other uses include food sterilization for pest control in fruits, vegetables, and dairy products. Much environmentally occurring methyl bromide is the result of biologic activity, particularly by seaweed (58). Automobile exhaust from leaded gasoline was formerly a significant source. The largest single industrial use for methyl bromide is as a fumigant used to treat soil, a wide range of grains, and other commodities, mills, warehouses, and houses. The principal problems have been associated with the fumigating personnel and control of other people who may enter the area being fumigated. Some methyl bromide is used as a chemical intermediate. In the United States use as a refrigerant is no longer significant. It once was used as a fire-extinguishing agent, particularly in automatic equipment for the control of engine fires on aircraft, but because of the toxicity of this material, its use as a fire extinguisher must be limited to specialized applications. A number of reports of injury from use as a fire extinguisher can be found in the European literature. 2.3 Exposure Assessment Because methyl bromide is a gas at ordinary temperatures and has essentially no warning properties, dangerous concentrations may rapidly accumulate in a work area without warning to the operator. Owing to the high volatility, one can readily attain high concentrations in a work atmosphere. Such high concentrations can be attained without recognition. These factors and the fact that methyl bromide is quite toxic create a potentially high hazard. It must be used only by individuals who are well acquainted with proper methods of handling and fully cognizant of the consequences of exposure to excessive amounts. In industrial operations regularly using methyl bromide, it is advisable to have some kind of warning or monitoring system for continuous analysis of the air. In fumigation operations, suitable analytic equipment is required and personnel must have proper protective equipment for the operation. Charcoal used in respiratory protective devices has limited capacity to remove methyl bromide. A survey by NIOSH estimated that between 1981 and 1983, about 105,000 workers were exposed to methyl bromide. The primary route of potential occupational exposure is inhalation, although some intoxications have also been reported after dermal exposure. 2.3.3 Workplace Methods NIOSH Method 2520 is recommended for determining workplace exposures to methyl bromide (11). 2.3.5 Biomonitoring/Biomarkers Blood bromide levels in humans are elevated by exposure to methyl bromide and may be useful in establishing whether exposure to methyl bromide has occurred, but bromide ion determination is not totally satisfactory for quantifying exposure. Numerous other sources of bromide, such as food, water, and medications, may interfere, particularly at the low blood levels that result from repeated exposure to concentrations considered acceptable for occupational exposure. “Normal” bromide ion concentration is below 1 mg/100 mL of blood serum, in the absence of the above dietary sources. A concentration of 5 mg/100 mL may be considered evidence that exposure to methyl bromide has occurred; 15 mg/100 mL of blood is consistent with toxic symptoms. Because bromide from ingested drugs may reach 150 mg/100 mL% or more, it is obvious that the source of the bromide must be considered in interpreting the analytic results 2.4 Toxic Effects Methyl bromide is toxic by inhalation, by ingestion, or through skin absorption. It is readily absorbed through the skin. It is irritating to the eyes, skin, mucous membranes, upper respiratory tract, and lungs. It is narcotic at high concentrations. It may cause lacrimation from irritation of the eyes. When

heated to decomposition it may emit toxic fumes of carbon dioxide. It may also emit toxic fumes of hydrogen bromide. Methyl bromide is one of the most toxic of the common organic halides and is reported to be 8 times more toxic on inhalation than ethyl bromide. Moreover, because of its greater volatility, it is a much more frequent cause of poisoning. Fatal poisoning has always resulted from exposure to relatively high concentrations of methyl bromide vapors (8600–60,000 ppm). Nonfatal poisoning has resulted from exposure to concentrations as low as 100–500 ppm. Inhalation is by far the most significant route of exposure, although serious skin burns may occur from confined contact, especially under clothing or in shoes and gloves. Absorption through the skin has been reported, but very high vapor concentrations were involved, and some inhalation may have occurred as leakage around the respirators. Unless the concentration is high enough to cause rapid narcosis and death from respiratory failure, the most striking response to exposure at high concentrations will be lung irritation with congestion and edema. These symptoms are observed in both animals and humans and often develop into a typical confluent bronchial pneumonia. At lower levels of exposure, this lung condition may account for delayed deaths. If it leads to secondary infection, the delay may be a matter of days. At threshold concentrations, this lung condition is not observed. The response is almost entirely referable to the nervous system and usually shows up only after prolonged and repeated exposures. Excitation and even convulsions have been observed in animals; but if they survive repeated exposures, the later signs are paralysis of the extremities. Paralysis of the extremities is most typical of threshold toxic response from repeated exposures over a long period of time. Animals that have been seriously paralyzed have recovered, although the recovery is somewhat slow. Human experience indicates that there is a high probability of complete recovery although the time necessary may be quite long, even months. Several reviews are available (59–61). 2.4.1 Experimental Studies 2.4.1.1 Acute Toxicity Because methyl bromide is a gas at 4°C, oral toxicity is of minor concern. Nevertheless oral doses of 60–65 mg/kg were reported to be the minimal amount lethal to rabbits (62); a dose of 100 mg/kg, to be lethal to rats 5–7 h after exposure (63); and 214 mg/kg, to be an oral LD50 (64). Toxic response appears to differ significantly between test animal strains and species (65). The 8 h survival dose for rats was reported to be approximately 1 mg/L (260 ppm). Rats survive 5200 ppm for 6 min and 2600 ppm for 24 min. The 6-h survival dose for rabbits is approximately 2 mg/L (520 ppm). The authors studied rats, rabbits, guinea pigs, and monkeys. They described the response of most animals as typically one of lung irritation. If the exposure was severe enough, this resulted in lung edema and usually a typical confluent bronchial pneumonia. An 8 h LC50 of 302 ppm (267–340 ppm) was determined for male rats. (Sprague–Dawley/Charles River Japan) (66). Deaths were accompanied by lung hemorrhages and convulsions. Mice were exposed for 1 h to concentrations of 0.87–5.93 mg/L (220–1500 ppm). An LC50 of 1200 ppm was determined for the 1 h exposures. At 1.72 mg/L no toxic response was noted. Exposure for 1 h to 2.2–2.7 mg/L was reported to cause decreased lung and liver weight. Above 3.5 mg/L kidney lesions were observed. Mortality occurred above 3.82 mg/L (980 ppm) accompanied by weight loss and other clinical signs. At still higher concentrations, liver lesions, decreased motor coordination, tremors, seizures, paralysis, and other effects also occurred. Gluthathione depletion and an increase in blood bromide were observed and related to exposure concentration (67). Rats were exposed 6 h/day for 5 days to 0, 90, 175, 250, or 325 ppm in order to study histopathology (68). Exposure to 325 ppm required premature sacrifices after 4 days, but the other groups were anesthesized and perfused 1–2 h after their fifth exposure. Clinical signs confined to the 250- and

325-ppm groups were diarrhea, hemoglobinuria, gait disturbances, and convulsions. At all concentrations except 90 ppm there were degenerative changes in the adrenals, cerebellar granular cells, and nasal olfactory epithelium. Hepatocellular degeneration was confined to the 250- and 325ppm groups. The kidneys and epididymides were not affected, but cerebral cortical degeneration and minor testicular changes were seen in the 325-ppm group. Male rats were exposed 4 h/day to four different concentrations of methyl bromide gas, 150 ppm for 5 days/week, 11 weeks (55 times), and to 200, 300, or 400 ppm for 6 weeks (30 times) (69). Body weight, hematology, organ weight, residual bromide concentrations, and histopathology of several organs were studied. In addition, a 4 h acute LC50 was determined to be 780 ppm with 95% confidence limits of 760–810 ppm. As in other studies, a remarkably steep dose response was observed with 0 and 100% lethal concentrations of 650 and 900 ppm. Neurological signs were manifest at 300 and 400 ppm with necrosis of the brain at 400 ppm. Necrosis of the heart was apparent at all concentrations with little response in other organs. Certain blood enzyme levels generally considered to be associated with pathological changes in the heart were not changed at either 150 or 200 ppm, but at 300 and 400 ppm aspartic transaminase, lactic dehydrogenase, LAP (not defined by the authors), and hydroxybutyrate dehydrogenase were elevated. 2.4.1.2 Chronic and Subchronic Toxicity Oral Exposure According to IRIS (online), the USEPA determined critical effect for oral exposure as epithelial hyperplasia of the forestomach with an NOAEL of 1.4 mg/kg/day [LOAEL: 7.1 mg/kg/day] and a RfD of 1.4 × 10–3. The previous oral RfD [4.0 × 10–4 mg/kg/day] was based on the inhalation studies by Irish et al. (65). According to the EPA (IRIS), inhalation studies are inappropriate for oral risk assessment extrapolation for bromomethane because portal-of-entry effects are observed for both the inhalation route (lung pathology) and oral route (stomach hyperplasia). In addition, neurological effects reported after inhalation exposures have not been reported after oral exposures. The current EPA reference dose (RfD) for oral exposure is based on the Danse et al. (64) study, on carcinogenic effects in the rat forestomach for the oral route of exposure. Treatment of groups of 10 male and 10 female Wistar rats by gavage 5 days/week for 13 weeks with bromomethane at 0, 0.4, 2, 10, or 50 mg/kg resulted in severe hyperplasia of the stratified squamous epithelium in the forestomach at a dose of 50 mg/kg/day and slight epithelial hyperplasia in the forestomach at a dose of 10 mg/kg/day. At the 50-mg/kg/day dose level, decreased food consumption, body weight gain, and anemia were observed in the male rats. Slight pulmonary atelectasis was observed, at the two higher dose levels, in both male and female rats; however, the investigators stated that the possible inhalation of bromomethane-containing oil during the gastric intubation procedure might have been responsible for this effect. No neurotoxic effects were observed at any dose level tested. Renal histopathology was not evaluated. Adverse effects were not observed at 0.4 or 2 mg/kg. This 90-day gastric intubation study was conducted in groups of Wistar rats (10 of each sex) given 0, 0.4, 2, 10, or 50 mg/kg methyl bromide in peanut oil. Findings included squamous cell papillomas (2 males) and carcinomas (7 males and 6 females) of the forestomach at the 50-mg/kg dose level. In a similar study by Boorman et al. (70) 6-week-old male Wistar rats were gavaged 5 times/week at 50 mg/kg, either for 13 weeks with a 12-week recovery period or continuously for a period of 25 weeks. At week 13, inflammation, acanthosis, fibrosis, and a high incidence of pseudoepitheliomatous hyperplasia of the forestomach were observed. At week 25, rats previously treated with methyl bromide still exhibited more severely perplastic lesions than vehicle controls. One of 15 rats showed malignancy, which was considered an early carcinoma. However, there was a clear regression of the overall incidence of proliferative lesions at the end of the recovery period. Mitsumori et al. conducted a 2-year oral chronic toxicity/carcinogenicity study (71) in F344 rats fed a diet containing 80–500 ppm total bromide following fumigation with methyl bromide. Of 60 male and 60 female rats per dosage group, 10 were sacrificed at 52 and 104 weeks, respectively, in order to perform urine analysis, hematology, blood chemistry, and pathology. Rats killed in moribund

condition or found dead and all survivors sacrificed at the end of the 2-year dosing period were examined for pathologic lesions. No marked toxic effects were observed at any of the dose levels administered except for a slight decrease in body weight gain in males fed the 500-ppm methyl bromide-containing diet at week 60 onward. The conclusion was that residues of 500 ppm total bromide in the diet fumigated with methyl bromide are not carcinogenic in F344 rats of either sex. The NOEL in males was given as 200 ppm [6.77 mg total bromide/kg/day]. None was determinable from the data in females because they showed slightly higher incidence of focal fatty change of the adrenal cortex than controls. However, control values in this study were lower than historical controls with regard to this very common lesion in aging female F344 rats. Inhalation Exposure For inhalation, the EPA (IRIS) considers the critical effect for chronic inhalation to be degenerative and proliferative lesions of the olfactory epithelium of the nasal cavity with a LOAEL of 11.7 mg/m3 (3 ppm), adjusted to 2.08 mg/m3, giving a RfC of 5.0 × 10–3 based on a 29-month rat inhalation study by Ruezel in 1987 and 1991 (72, 73) where a series of inhalation toxicity studies of bromomethane were conducted under the sponsorship of the National Institute of Public Health and Environmental Hygiene of the Netherlands. In a chronic inhalation study, 50 male and 60 female Wistar rats were exposed to 0, 3, 30, or 90 ppm (0, 11.7, 117, or 350 mg/m3, respectively) 98.8% pure bromomethane 6 h/day, 5 days/week (duration-adjusted concentrations are 0, 2.08, 20.9, or 62.5 mg/m3, respectively) for up to 29 months. Three satellite groups of 10 animals/sex/exposure level were sacrificed at 14, 53, and 105 weeks of exposure. Animals were observed daily, and body weight was recorded weekly for the first 12 weeks and monthly thereafter. Hematology, clinical chemistry, and urinalyses were conducted at 12–14 weeks and 52–53 weeks in the satellite groups. Eleven organs were weighed at necropsy, and approximately 36 tissues, including the lungs with trachea and larynx; 6 cross sections of the nose; heart; brain; and adrenal glands were examined histopathologically. The test atmosphere was measured by gas chromatography every 30 min during exposure. Males and females exposed to 90 ppm exhibited decreased body weight gains; no treatment-related changes in hematological, biochemical, or urine parameters were observed. A significant concentration-related decrease in relative kidney weights was reported in the 30- and 90-ppm males. A decrease in mean absolute brain weight was reported to occur in the 90-ppm females at weeks 53 and 105, but there was no change in relative brain weight or in brain histology. Microscopic evaluation revealed that the nose, the heart, and the esophagus and forestomach were the principle targets of bromomethane toxicity in this study. Very slight to moderate hyperplastic changes in the basal cells accompanied by degeneration in the olfactory epithelium in the dorsomedial part of the nasal cavity were observed in all exposed groups of both sexes at 29 months of exposure. At the lowest concentration, the lesion is described as very slight. These changes were concentration-related in both incidence and severity and were statistically significant at 29 months. Incidence of basal cell hyperplasia in control, 3-, 30-, and 90-ppm groups were 4/46, 13/48, 23/49, and 31/48 in males and 9/58, 19/58, 25/59, and 42/59 in females, respectively. Slight increases in incidence of basal cell hyperplasia in the 30- and 90-ppm groups (n = 7–10) at 53 and 105 weeks were not statistically significant. Lesions in the heart were statistically significant in the males (cartilaginous metaplasia and thrombus), and the females (myocardial degeneration and thrombus) exposed to 90 ppm. The authors attributed part of the increased mortality in the high concentration animals to the cardiac lesions. A statistically significant increase in hyperkeratosis of the esophagus was observed in the 90-ppm males after 29 months of exposure. Slight increases in forestomach lesions were not statistically significant. No effects were observed in the tracheobronchial or pulmonary regions of the respiratory tract. No other exposurerelated effects were noted. Based on these results, a LOAEL of 3 ppm for nasal effects was established. Male Sprague–Dawley rats were exposed by inhalation for 24 h at 120 ppm or continuously for 3 weeks at 10 ppm methyl bromide, which resulted in a dose-dependent decrease in the concentration of norepinephrine in the hypothalamus, cortex, and hippocampus (74). Typical high dose effects of methyl bromide inhalation in rats (200, 300, or 400 ppm for 6 weeks; 150 ppm for 11 weeks) are liver necrosis with sinusoidal infiltration, degeneration of the kidney tubular epithelium, necrosis of

the excretory pancreas epithelium, focal necrosis of the heart muscle, and necrosis of the brain cortex (69). Additional high dose effects reported were diarrhea, hemoglobinuria, and degeneration of the zona fasciculata of the adrenals and of the olfactory epithelium (68). The latter appeared reversible 10 weeks after cessation of exposure (75). These effects were corroborated by other studies and also in other species (76, 77). Expected similarities between the toxicity profile of methyl bromide and methyl chloride were also noted. Inhalation by rabbits at 27 ppm methyl bromide for 8 months for a total exposure duration of 900 h resulted in no observable neurotoxic or other adverse signs. At 65 ppm, severe neuromuscular losses were seen. These subsided 6–8 weeks after exposures were terminated (78, 79). Rats exposed at 55 ppm via inhalation of methyl bromide for 36 weeks with a total affective duration of 1080 h showed no signs of a neurologic deficit (79). In a chronic mouse study, virtually the same lesions were reported as observed in subchronic studies at somewhat lower doses than expected (77). This mouse (77) and rat (73) inhalation bioassay has been performed. These studies show clear mutagenicity but not carcinogenicity under the conditions of the bioasssays. The NTP 2-year inhalation study (77) was carried out with 70 male and female B6C3F1 mice exposed 6 h/day, 5 days/week at 0, 10, 33, or 100 ppm of methyl bromide. After 20 weeks, exposure of the high dose group (100 ppm) was discontinued because of excess mortality (31% in males, 8% in females). Similar lesions were observed as reported in Section 2.4.1.2 of this TLV documentation, without the occurrence of excess neoplastic lesions. A NOEL was not presented in the NTP (77) study, but there were no effects at 33 ppm. Male and female Wistar rats were exposed by inhalation 6 h/day, 5 days/week for 29 months at 0, 3, 30, or 90 ppm methyl bromide (73). Interim sacrifices were conducted after 3, 12, and 24 months. Excess mortality was first observed at 114 weeks in the high dose group. Dose-dependent increases in the incidences of degenerative and hyperplastic changes of the nasal olfactory epithelium were observed. The lesions were characterized as very slight, slight, or moderate. A statistically significant difference was found between controls and the low dose group (3 ppm) at the end of the exposure period (29 months) in terms of total lesions. At the highest dose level, effects (thrombi, myocardial degeneration, hyperkeratosis of the esophagus and forestomach) were observed. 2.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Methyl bromide is converted to bromide ion, in vivo. At all concentrations that could be tolerated by animals, inhaled methyl bromide was rapidly eliminated (65). Circulating bromide concentrations in untreated rabbits were approximately 10 ppm and those in rabbits with methyl bromide–induced paralysis were approximately 110 ppm (65). The blood bromide level tends to correlate with the severity of the clinical signs (80). Although methyl bromide is metabolized to methanol, the quantities of methanol produced are insufficient to account for methyl bromide's toxicity (65, 80). The toxicity of methyl bromide is with the intact molecule. The bromide ion has been shown to be much slower in leaving the body following exposure to methyl bromide. A half-life of 5 days has been reported for rats (66). The investigators also concluded that neither bromide ion nor methanol was involved in the toxicity but rather the parent compound or an incorporation of the methyl group into some other substance was involved. Bonnefoi et al. (81) have shown that glutathione depletion occurs and may be related to subsequent toxic effects. Methyl bromide showed a significant non-enzymatic conjugation in human erythrocyte cytoplasm. In the majority of the subjects there was also enzymatic conjugation but a minority lack this enzymatic activity. Methyl bromide had a higher affinity for the conjugating enzyme(s) (possibly erythrocyte glutathione transferases) than methyl chloride or methyl iodide (82).

2.4.1.4 Reproductive and Developmental Adult male F344 rats were exposed to 0 or 200 ppm 6 h/day for 5 days and examined after 1, 3, 5, 6, 8, 10, 17, 24, 38, 52, and 73 days. The only effects were a transient decrease in plasma testosterone and testicular nonprotein sulfhydryl. In contrast to the very specific effects of methyl chloride there were no lasting effects on sperm quality or spermatogenesis. However, Eustis et al. (76) reported testicular degeneration in male rats exposed to 160 ppm 6 h/day, 5 days/week for 3–6 weeks, and Kato et al. (69) reported testicular atrophy after 6 weeks of repeated 4 h/day, 5 days/week exposures to 400 ppm but not 300 ppm. In an abstract reporting preliminary results in the F0 generation of a two-generation reproduction study in CD rats (83), there were no reproductive effects reported after repeated 6 h/day, 5 day/week exposures to 0, 3, 30, or 90 ppm. There are little data to indicate anything but extremely low, if any, potency for methyl bromide for teratogenic/reproductive toxicity. Although methyl bromide, acutely and subchronically, causes varying degrees of testicular alterations and transiently reduced plasma testosterone concentrations, inhalation exposure of male Fischer 344 rats for 6 h/day at 200 ppm methyl bromide for 5 days had “no lasting effect on sperm quality or spermatogenesis” in this rat strain (75). In a study by Sikov et al. (84), neither maternal or fetotoxic nor teratogenic effects were observed in Wistar rats exposed by inhalation to methyl bromide 5 days/week at 20 and 70 ppm for 3 weeks prior to mating and during gestation. 2.4.1.5 Carcinogenesis The USEPA consideres the animal data for carcinogenesis as “Inadequate” (IRIS) (5). Bromomethane was administered by gavage to groups of 10 male and female Wistar rats (64). Animals were administered doses of 0, 0.4, 2, 10, or 50 mg/kg/day bromomethane in arachis oil 5 days/week for 13 weeks, at which time the experiment was terminated. There was an apparent dose-related increase in diffuse hyperplasia of the forestomach. The authors reported a forestomach papilloma incidence of 2/10 in the high dose males and forestomach carcinoma incidences of 7/10 and 6/10 in the high dose males and females, respectively. These results were subsequently questioned (85, 86). A panel of NTP scientists reevaluated the histological slides and concluded that the lesions were hyperplasia and inflammation rather than neoplasia. Rosenblum et al. (87) reported a 1-year study in which beagle dogs (4 per treatment group, 6 per control) were provided diets fumigated to residue levels of 0, 35, 75, or 150 ppm bromomethane. No tumors were observed at any dose level; however, there was no indication that the dogs were examined for tumors. In addition, 1-year observation is considered to be inadequate by the EPA for tumor induction in dogs. Bromomethane is structurally related to bromoethane which, when tested in mice and rats of both sexes, has shown clear evidence of carcinogenicity in some cases and equivocal in others. NTP (88) conducted an inhalation bioassay on bromoethane, and the results were recently released in a draft report. Groups of F344/N rats (50/sex) and B6C3F1 mice (50/sex) were exposed to 0, 100, 200, or 400 ppm bromoethane 6 hours/day for 5 days/week. A statistically significant increase in uterine adenomas, adenocarcinomas, or squamous cell carcinomas was observed in female mice exposed to 200 and 400 ppm, indicating clear evidence of carcinogenic activity. Equivocal evidence of carcinogenic activity was reported for male and female rats and male mice. Although alveolar and bronchiolar adenomas or carcinomas and pheochromocytomas were observed in male rats, the incidences were not dose-related and were within the historical ranges for NTP studies. Granular cell tumors of the brain were also observed in male rats and, although not statistically significant, the incidence was higher than historical incidence in either the study lab or NTP studies. The incidence of alveolar/bronchiolar neoplasms in exposed male mice was marginally greater than control or historical incidence. An increased incidence of gliomas in exposed female rats was significant by the trend test; however, the incidence was not significantly greater when compared with the controls in the study and the controls used in NTP studies.

In a rather short oral gavage study, squamous-cell carcinomas were reported to be produced in 13/20 rats dosed 5 days/week with 50 mg/kg body weight (64). Marked diffuse hyperplasia of the epithelium of the forestomach was reported at this level after only 90 days, with less effect at 10 and 2 mg/kg and none at 0.4 mg/kg. However, in rats similarly exposed in a second study (70) with an extended recovery period, it was found that nearly all lesions regressed, suggesting they were not malignant. Furthermore, the 29-month inhalation study in Wistar rats discussed subsequently failed to support the finding of carcinogenicity in the rat forestomach. In the 29-month study male and female rats were exposed to 0, 3, 30, or 90 ppm of methyl bromide gas 6 h/day, 5 days/week (47). Ten rats per sex were killed at 13, 52, and 104 weeks for interim information. Mortality was increased at week 114 but only in the 90-ppm group, which also had lowered body weights. Increased incidences of degenerative and hyperplastic changes in the nasal olfactory epithelium were observed in a dose-related manner in all groups. The lesions did not appear to progress with time. Exposure to 90 ppm was associated with an increased incidence of thrombi and myocardial degeneration in the heart and hyperkeratosis in the esophagus and forestomach. There was no indication of a relationship between exposure and tumor incidence. In the a 2-year oral chronic toxicity/carcinogenicity study, Mitsumori et al. (71) concluded that residues of 500 ppm total bromide in the diet fumigated with methyl bromide are not carcinogenic in F344 rats of either sex. More information on this study was given in Section 2.4.1.2. 2.4.1.6 Genetic and Related Cellular Effects Studies Bromomethane has been shown to produce mutations in Salmonella strains sensitive to alkylating agents and to Escherichia coli both with and without the addition of a metabolic activation system (89–92). Bromomethane was also mutagenic in a modification of the standard Salmonella assay employing vapor-phase exposure (93–96). Bromomethane was observed to be mutagenic for Drosophila and for mouse lymphoma cells (89, 91). Methyl bromide is genotoxic in in vivo and in vitro tests. Positive results were obtained in the Salmonella (90, 91), and Drosophila (97), gene mutation assays, the sister chromatid exchange (SCE) test with human lymphocytes (97), the test for SCE induction in female mice, and the micronuclei test (98) (the latter two on peripheral erythrocytes). 2.4.1.7 Other: Neurological, Pulmonary, Skin Sensitization In a subsequent study performed by this group (78) that was designed to assess the neurotoxic effects of bromomethane in rabbits with longer-term exposures at low concentrations, male New Zealand white rabbits were exposed to 0 (n = 2) or 26.6 ppm (103 mg/m3, n = 6) 99% pure bromomethane 7.5 h/day, 4 days/week for 8 months (78). Exposure concentrations were monitored every 12 min by an infrared analyzer. Neurobehavioral tests examined the latency rates of the sciatic and ulnar nerves and the amplitude of the eyeblink reflex of the orbicularis oculi muscle. No other parameters, including respiratory effects, were monitored. No exposure-related neurological effects were observed. As part of this study, the animals exposed to 252 mg/m3 bromomethane for 4 weeks (79) were allowed to recover for 6–8 weeks and the neurological tests were repeated. The animals demonstrated partial, but not complete, recovery within the 6-week period. Therefore rabbits, which are sensitive to the neurotoxic effects of high level exposures to bromomethane, can tolerate long-term low level exposure to bromomethane, and appear to be able to recover from severe neurological effects after cessation of exposure. 2.4.2 Human Experience According to IRIS, the most common signs of acute intoxication with bromomethane in humans are neurotoxic in nature and include headache, dizziness, fainting, apathy, weakness, tiredness, giddiness, delirium, stupor, psychosis, loss of memory, mental confusion, speech impairment, visual effects, limb numbness, tremors, muscle twitching, paralysis, ataxia, seizures, convulsions, and unconsciousness. Several studies have been conducted on the longer-term effects of occupational exposure to bromomethane. None of these studies can serve as the basis for the derivation of an RfC for bromomethane because of concurrent exposures to other chemicals,

inadequate quantification of exposure levels and/or durations, and other deficits in study design. Possible symptoms include anorexia, nausea, vomiting, corrosion to the skin, severe skin burns, enlarged liver, kidney damage with development of albuminuria, and in fatal cases, cloudy swelling and tubular degeneration. Central nervous system effects include blurred vision, mental confusion, numbness, and tremors. Death following acute poisoning is usually caused by its irritant effect on the lungs. In chronic poisoning, death is due to injury to the central nervous system. Direct skin contact may cause prickling, itching, cold sensation, erythemia, vesication, damage to peripheral nerve tissue, and delayed dermatitis. It may also cause double vision, dizziness, headache, convulsions, muscular tremors, fatal pulmonary edema, and neurological and GI disturbances. It may cause skin irritation. Other symptoms may include mental excitement, acute mania, bronchitis, pneumonia, and severe eye damage. It may cause abdominal pain and death from respiratory or circulatory collapse. It may also cause unconsciousness leading to a prompt “anesthetic” death, malaise, ataxia, myoclonus, exaggerated (or absent) deep reflexes, positive Romberg's sign, paroxysmal abnormalities of the EEG, great agitation, change of personality, coma, and mild euphoria. Exposure to this compound may also cause muscle weakness, loss of coordination and gait, hyperthermia, hepato- and nephrotoxicity, behavioral changes, paralysis of extremities, delirium, epileptiform attacks, and skin lesions. It may cause respiratory tract irritation, organic brain syndrome, psychological depression, seizures, prominent cerebellar and parkinsonian signs, renal failure due to tubula necrosis, jaundice, elevations of liver enzyme activity in serum and abnormal liver function, lassitude, slurring of speech, staggering gait, diplopia, epileptiform convulsions, perhaps with a Jacksonian-type of progression, rapid respirations, cyanosis, pallor and collapse, areflexia, impaired superficial sensation, absent or hypoactive distal-tendon reflexes, and bronchopneumonia after severe pulmonary lesions. It may also cause severe mucous membrane burns. Other symptoms may include DNA mutations and large chromosome alterations and congestion with coughing, chest pain, shortness of breath, confusion, shaking and unconsciousness, severe pulmonary irritation and neurotoxicity, narcosis at high concentrations, vertigo, tremor of the hands, dyspnea, hallucinations, anxiety, inability to concentrate, conjunctivitis and dry, scaling, and itching dermatitis. It may also cause lacrimation from irritation of the eyes, transient dimming of vision and blindness for 12 h, nystagmus on lateral gaze, delirium, apathy, and aphasia, edema of the papilla, and punctiform hemorrhages may be found, as well as optic atrophy. In addition, it causes sleepiness, digestive problems, loss of stability, lack of motor coordination, sensorial problems, and impaired hearing. Somnolence, permanent brain damage, lethargy, and sensory disturbances can occur. It may cause anuria, hyperactivity, blood pressure fall, papilledema, fainting attacks, and bronchospasm. It may also cause retinal and submucous hemorrhages, stomach congestion, and congestion of the brain with multiple hemorrhages associated with degenerative changes, such as necrosis. 2.4.2.1 General Information Reports of a toxic absorption of methyl bromide gas through the skin have been published, but very high exposure concentrations (8000–10000 ppm) were involved and it is possible some leakage around or through respiratory protective devices occurred (99). Obviously skin contact with the liquid and vapor must be minimized in addition to prevention of vapor exposure. There are difficulties in handling methyl bromide in the drug industry. Repeated splashes on the skin resulted in severe skin lesions. Severe cases showed “vesicles or blebs.” In a less rigorous exposure, severe itching dermatitis was observed. One report by Longley and Jones (100) describes serious systemic effects following gross skin contact with liquid methyl bromide, but inhalation may have been significant despite the absence of lung damage. Methyl bromide may cause difficulty when it is held in contact with skin by clothes. This is a special problem with gloves and shoes. In the case of shoes, it is suspected that a fairly high concentration of vapor near the floor may actually be absorbed into the leather and cause skin irritation. Spills onto or into a shoe may cause a severe burn if allowed to remain in contact with the skin. When methyl bromide is handled, care should be taken to avoid splashes onto the clothing or shoes. When there is a fairly high vapor concentration, as in an accidental spill, care should be taken to prevent seepage into the shoes or on protective clothing, and exposure to the vapor should be minimized.

Liquid methyl bromide can cause severe corneal burns but the vapors do not appear to be painful. Furthermore, a full-face respirator should always be used if vapor concentrations are significant; hence the eyes will be protected from exposure. Numerous reports attest to the high toxicity of methyl bromide to humans. Many reports indicate failure to use reasonable recommended handling precautions. The symptoms observed in humans from acute exposure have been reported by a number of authors whose reports have been reviewed by von Oettingen (59, pp. 15–30). The early symptoms may be a feeling of illness, headache, nausea, and vomiting. Tremors and even convulsions may be observed, much as they are in animals, as well as lung edema and an associated cyanosis. If the patient survived an acute exposure for the first 2 or 3 days, the probability of complete recovery was very high. Observations of 10 cases acutely and chronically exposed have been summarized by Hine (101) and electroencephalographic studies on seven cases by Mellerio et al. (102). 2.4.2.2 Clinical Cases Cases of severe methyl bromide poisoning in humans, some of them fatal, were frequently reported. For example, von Oettinger (59) recorded 47 fatal and 174 nonfatal cases of methyl bromide intoxication between 1899 and 1952. Acute poisoning was characterized by lung irritation. The toxicity was manifested as paralysis of extremities, delirium, convulsions, and even typical epileptiform attacks. Some of these symptoms were persistent, and recovery occurred in a matter of months, sometimes incompletely with permanent disability. In all cases, the conditions of exposure are inadequately described, neither the methyl bromide concentration nor the exposure duration are exactly known. However, by retrospective estimate, the methyl bromide concentration could have been as high as 60,000 ppm (103) in some instances. Severe poisoning with some fatalities resulted from soil disinfection by injection of methyl bromide into greenhouse soil (104). These workers measured methyl bromide levels following application rates ranging from 30–3000 ppm. They found peak values of 200 ppm persisting for a few seconds on initial injection with airborne levels above the soil declining to 4 ppm 5 days posttreatment. Tilling the soil can produce exposures at 15 ppm as long as 9 days after soil treatment (105). Tourangeau and Plamondon (106) reported that tests made in date-processing and date-packing houses, where a number of employees had been stricken, showed concentrations ranging up to 100 ppm in the general workroom air, up to 500 ppm near the walls of ineffectively sealed chambers, and over 1000 ppm at the breathing zone of workers entering the chamber to remove the fumigated fruit. Tourangeau and Plamondon (36, 106) found concentrations up to 390 ppm in a plant where one fatal and one nonfatal case of intoxication occurred. Hine (101) reported concentrations of about 100 ppm in plants where two of his clinical cases were found. Johnstone (107) reported mass poisoning (34 cases) in the date-packing industry. The industrial hygiene survey conducted by the California Department of Health, Division of Industrial Hygiene, indicates that the packers were exposed to less than 50 ppm; however, during the purging of a fumigation chamber, the methyl bromide concentrations in the packing room reached 100 to 500 ppm. Watrous (108) described nausea, vomiting, headache, skin lesions, and symptoms of mild systemic poisoning in workers (90 people) exposed for 2 weeks at concentrations generally below 35 ppm. Liquid methyl bromide may penetrate through all articles of clothing and may cause superficial burns with much vesication when in contact with skin. Three authors (99, 100, 109) demonstrated the possibility of absorption by the skin of toxic quantities of methyl bromide. Longley and Jones (100) reported severe skin irritation in workers fumigating a medieval castle. Six people were occupationally exposed to ~ 35 g/m3 (9000 ppm) methyl bromide during a 40-minute fumigation process in spite of adequate airway protection. After a few hours, all fumigators developed sharply demarcated erythema with multiple vesicles and large bullae. Particularly affected were the axillae, groin, and abdomen. Histopathological examination of early skin lesions revealed necrosis of keratinocytes, severe edema of the upper dermis, subepidermal blistering, diffuse infiltration of

neutrophils, and to a lesser extent, eosinophils. Two of the patients developed an urticarial rash about one week post exposure. These late lesions showed the combined features of spongiotic dermatitis and urticaria. No immunopathology was observed. The skin returned to normal in all workers after 4 weeks except for some residual hyperpigmentation. Average plasma bromide levels immediately following exposure (9 mg/L) and 12 h postexposure (6.8 mg/L) strongly suggest dermal absorption of methyl bromide. 2.4.2.2.5 Carcinogenesis Assessment of EPA Classification D (Not classifiable as to human carcinogenicity on the basis of inadequate human and animal data) was based on a single mortality study from which direct exposure associations could not be deduced and studies in several animal species with too few animals, too brief exposure, or observation time for adequate power. A prospective mortality study was reported for a population of 3579 white male chemical workers. The men, employed between 1935 and 1976, were potentially exposed to 1,2-dibromo-3-chloropropane, 2,3-dibromopropyl phosphate, polybrominated biphenyls, DDT, and several brominated organic and inorganic compounds (110). Overall mortality for the cohort, as well as for several subgroups, was less than expected. Of the 665 men exposed to methyl bromides (the only common exposure to organic bromides), two died from testicular cancer, as compared with 0.11 expected. This finding may be noteworthy as testicular cancer is usually associated with a low mortality rate. Therefore, there could be more cancer cases than there appear to be based on mortality. The authors noted that it was difficult to draw definitive conclusions as to causality because of the lack of exposure information and the likelihood that exposure was to many brominated compounds. 2.5 Standards, Regulations, or Guidelines of Exposure OSHA PEL

In 1989, OSHA established a PEL TWA of 5 ppm, with a skin notation, for methyl bromide. This limit was promulgated to protect workers from the significant risk of incapacitating neurotoxic disease and other systemic effects. As a consequence of the 1992 decision by the U.S. Court of Appeals for the Eleventh Circuit the PELs promulgated under the 1989 rulemaking where vacated; however, it currently has a ceiling limit of 20 ppm, with a skin notation. NIOSH The NIOSH REL for methyl bromide is an exposure to the lowest feasible limit. REL/IDLH NIOSH based the REL on its position that methyl bromide be considered a potential occupational carcinogen. NIOSH did not concur with the 1989 PEL and recommended that methyl bromide be addressed in a full section 6(b) rulemaking. NIOSH established an IDLH value of 250 ppm (NIOSH Carcinogen) for this substance. ACGIH Rationale Methyl bromide remains as a substance suspected of carcinogenic potential. In for TLVs that addition, its capacity for dermal absorption, marked neurotoxicity and Differ from the significant nasal and dermal irritation warrant a greater degree of caution and a PEL or REL reduction in the previously recommended TLV for occupational exposure. The ACGIH TLV for methyl bromide is 1 ppm. Carcinogenic classification: IARC Group 3, Not classifiable as to its carcinogenicity in humans MAK Group IIIB, Justifiably suspected of having carcinogenic potential NIOSH Carcinogen, with no further categorization. TLV A4, Not classifiable as a human carcinogen. Other nations: Australia—5 ppm, skin (1990); (Former Federal Republic of) Germany—no MAK value, skin, group IIIB, Justifiably suspected of having carcinogenic potential (1996); Sweden— 15 ppm, short-term value 10 ppm, 15 min, skin (1990); United Kingdom—5 ppm, 15-min STEL 15 ppm, skin (1997). 2.6 Studies on Environmental Impact:

NA

Saturated Methyl Halogenated Aliphatic Hydrocarbons Jon B. Reid, Ph.D., DABT 3.0 Methyl Iodide 3.0.1 CAS Number: [74-88-4] 3.0.2 Synonyms: Iodomethane; monoiodomethane; methyl iodide; Halon 10001; methyl iodine; methyl iodide (iodomethane). 3.0.3 Trade Names: Halon 10001 3.0.4 Molecular Weight: 141.95 3.0.5 Molecular Formula: CH3I 3.0.6 Molecular Structure:

3.1 Chemical and Physical Properties 3.1.1 General Methyl iodide is a colorless liquid that turns yellow, red, or brown when exposed to light and moisture. Specific gravity 2.279 (20/4°C) Melting point –66.5°C Boiling point 42.50°C Vapor pressure 400 torr (25°C) Refractive index 1.5293 (21.0°C) Percent in “saturated” air 53 (25°C) Solubility 1 vol/125 vol water at 15°C; soluble in ethanol, ethyl ether Flammability Methyl iodide is nonflammable by standard tests in air UEL, LEL Not available (UEL, LEL = upper, lower exposure limits) 3.1.2 Odor and Warning Properties Methyl iodide has a sweet ethereal odor with poor warning properties. 3.2 Production and Use Methyl iodide has had very limited use as a chemical intermediate (methylations), and in microscopy because of its high refractive index, as imbedding materials for examening diatomes, and in tests for pyridine. It has been proposed as a fire extinguisher and insecticidal fumigant. It is a product of natural biologic processes. 3.3 Exposure Assessment 3.3.1 Air: NA

3.3.2 Background Levels: NA 3.3.3 Workplace Methods NIOSH Method 1014 is recommended for determining workplace exposures to methyl iodide (11). 3.4 Toxic Effects Little new information (from previous editions) was found. Methyl iodide has not been used extensively; therefore, toxicological investigations and experience have been limited. It is primarily a CNS depressant, but there are also indications of lung irritation and kidney involvement from acute exposures. Because radioactive iodine can be released as methyl iodide, the nuclear industry has investigated its absorption, distribution, and to some extent toxicity when inhaled, ingested, and injected. 3.4.1 Experimental Studies 3.4.1.1 Acute Toxicity Few new data have been published since the last edition. Buckell (111) determined the LD50 for rats dosed either subcutaneously or orally to be 150– 200 mg/kg of body weight. This author also reported that it would produce a “vestibular burn” if closely held to the human skin. It was indicated that clothing contaminated with methyl iodide should be removed immediately. Johnson (112) reported that the acute oral LD50 for mice was 76 mg/kg, but that repeated doses of 30–50 mg/kg were without effect. Single oral doses of 70 mg/kg were lethal to rabbits, but several oral doses of 50 mg/kg were necessary before they caused death. Penetration of methyl iodide through the skin (species not indicated) was reported by Shugaev and Mazkova (113), who considered absorption to be of more concern than local irritative effects. Von Oettingen (33, pp. 30–32), reported a 15-min exposure at 3800 ppm that was fatal to rats. Buckell (111) reported a LC50 for mice at 900 ppm (57-min exposure). A 4 h LC50 of 232 ppm was reported by Deichman and Gerarde (114). Bachem (115) studied the response of mice to methyl iodide. His work is summarized in Table 62.1. Chambers et al. (116) reported the lethal concentration for rats for a 15-min exposure to be 22 mg/L in air (3790 ppm). The rats died within a period of 11 days. They showed lung irritation and pulmonary edema. Buckell (111) reported the LC50 for mice to be 5 mg/L in air from a 57-min exposure. Table 62.1. Acute Effects of Methyl Iodide Concentration

mg/L 454.4 105.1 42.6 21.3– 31.6 0.43– 4.26 0.31

ppm

Response

78,700 Rapid narcosis; death after 10-min exposure 18,100 Death after 30-min exposure 7340 After 15–50 min, side position, no complete narcosis, death 1 h after beginning of exposure 3670– Death after 2–2.5 h of exposure 5370 73–730 Death of all animals within 24 h 54

Death of all animals within 24 h; no marked toxic

symptoms

3.4.1.2 Chronic and Subchronic Toxicity Blank et al. (117) exposed rats by inhalation for 14 weeks at 30 and 60 ppm. Findings were ocular irritation and depressed body weights but no clinical or microscopic pathologic changes. Mortality occurred in 4 weeks at an exposure of 143 ppm. The studies by Druckery et al. (118) and Poirier et al. (119) are discussed in Section 3.4.1.5. 3.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms The metabolism of methyl iodide is not yet certain, but there appears to be rapid release of iodide ion and methylation of glutathione in rats dosed orally. The process is enzymatically catalyzed (112). Subcutaneous injection produced similar results (120). In the available abstract (121), more recent investigators indicate that the addition of reduced, but not oxidized, glutathione inhibited methyl iodide toxicity to rat brain neocortical cultures in vitro. Alveolar absorption of inhaled 132I-methyl iodide by humans resulted in retention of 53–93% depending on the concentration inhaled and the rate of respiration (122). 3.4.1.4 Reproductive and Developmental No data on teratogenesis were found. 3.4.1.5 Carcinogenesis Carcinogenicity classification: IARC Group 3, Not classifiable as to its carcinogenicity to humans. MAK Group 2, probably human carcinogen. NIOSH Carcinogen, with no further classification NTP has not conducted genetic toxicology or long-term toxicology and carcinogenesis effects studies on methyl iodide. Druckrey et al. (118) reported local sarcomas following weekly subcutaneous injection in BD-strain rats. Strain A mice (a susceptible strain) that were injected with methyl iodide were reported to have a slight but significant increase in the number of lung tumors per mouse. 3.4.1.6 Genetic and Related Cellular Effects Studies Mutagenic tests on Salmonella have been reported by McCann et al. (123) to be weakly positive, but details of the study are lacking. Newer data confirm reported positive results in mutagenic tests in Salmonella, mouse lymphoma, Chinese hamster ovary, and mouse lymphoma. Binding of methyl iodide in male and female rat organs has been reported (124). According to the abstract, Male and female F344 rats were exposed to 14C-labelled methyl iodide orally or by inhalation in a closed exposure system. DNA adducts were detected in the liver, lung, stomach, and forestomach of the exposed animals. [14C]3-Methyladenine, [14C]7-methylguanine and [14C]O6-methylguanine could be identified by a combination of three different methods of hydrolysing DNA and subsequent HPLC or GC/MS analysis. The highest values of methylated guanines were determined in the stomach and forestomach of the animals following both oral and inhalative exposure. These results demonstrate a systemic genotoxic effect of methyl iodide.

Binding appeared to be due to alkylation rather than metabolic incorporation into DNA. Methyl iodide was mutagenic for Salmonella typhimurium bacterial strains TA1535 and TA100 and also a direct acting mouse lymphoma L5178Y/%K±cells (36). 3.4.2 Human Experience 3.4.2.1 General Information Garland and Camps (125) reported two cases of exposure of humans to the vapors of methyl iodide from industrial operations. The first case was quoted from Jaquet as reported in 1901. This case showed symptoms of vertigo, diplopia, and ataxia, there was evidence of urinary iodine, and the individual developed delirium and serious mental disturbances. The second case was one observed by Garland and Camps. The patient was found to be drowsy and unable to walk, with slurred, incoherent speech. He had iodine in the urine. Death occurred 7–8 days after exposure. Serious CNS involvement was also reported in a chemical worker by Baselga-Monte et al. (122), but the route of exposure was not given. Depression and psychological disturbance persisted for several weeks; complete recovery required 122 days. A report by Appel et al. (126) of a 41-year-old chemist exposed to the vapor of methyl iodide presents similar symptoms. These authors summarize much of the available literature. Skin irritation has been reported even while wearing protective gloves (127). 3.5 Standards, Regulations, or Guidelines of Exposure The ACGIH TLV TWA is 2 ppm (12 mg/m3). The OSHA PEL is 5 ppm and the NIOSH REL is 2 ppm. Other countries (8): Australia—2 ppm, category 3, Suspected human carcinogen, skin, (1990); (Former Federal Republic of) Germany—no MAK, 2, Probably human carcinogen (1998); Sweden—1 ppm, 15-min short-term value 5 ppm, skin, carcinogenic (1991); United Kingdom— 5 ppm, 10-min STEL 10 ppm, skin (1991). 3.6 Studies on Environmental Impact: NA

Saturated Methyl Halogenated Aliphatic Hydrocarbons Jon B. Reid, Ph.D., DABT 4.0 Methylene Chloride 4.0.1 CAS Number: [75-09-2] 4.0.2 Synonyms: Dichloromethane; methylene dichloride; methane dichloride; methylene bichloride 4.0.3 Trade Names: Aeothene MM, DCM, Narkotil, Solaesthin, Solmethine, NCI-C50102, R30, UN 1953; Refrigerant 30; Freon 30; DCM; Plastisolve 4.0.4 Molecular Weight: 84.93 4.0.5 Molecular Formula: CH2Cl2 4.0.6 Molecular Structure:

4.1 Chemical and Physical Properties Methylene chloride is a clear, colorless, nonflammable, volatile liquid with a penetrating ether-like odor. It is slightly soluble in water, alcohols, phenols, aldehydes, ketones, and organic liquids. Methylene chloride is miscible with chlorinated solvents, diethyl ether, and ethanol. It will form an explosive mixture in an atmosphere with a high oxygen content, or in the presence of liquid oxygen, nitrite, potassium, or sodium. When heated to decomposition, it emits highly toxic fumes of phosgene. 4.1.1 General Physical state Colorless liquid Specific gravity 1.3266 at 20°C Melting point –95.1°C Boiling point 40°C Vapor pressure 440 torr (25°C) Refractive index 1.4237 (20°C) Percent in “saturated” air 55 (25°C) Solubility 2 g/100 mL water at 25°C; soluble in ethanol, ethyl ether, acetone Flammability No flash point or fire point by standard tests in air 15.5–66 vol% Autoignition temperature 624°C UEL, LEL 19%, 12% 1 mg/L = 288 ppm and 1 ppm = 3.48 mg/m3 at 25°C, 760 torr 4.1.2 Odor and Warning Properties Methylene chloride has a “not unpleasant,” sweetish odor at concentrations above 300 ppm, but at about 1000 ppm the odor becomes unpleasant for most people. At 2300 ppm the odor is strong, intensely irritating; there may be dizziness after 5 min exposure. It has a chloroformlike odor. 4.2 Production and Use Methylene chloide is used principally as a solvent in paint removers. It is also used as an aerosol propellant, processing solvent in the manufacture of steroids, antibiotics, vitamins, and tablet coatings; as a degreasing agent; in electronics manufacturing; and as a urethane foam blowing agent. Methylene chloride is also used in metal cleaning, as a solvent in the production of polycarbonate resins and triacetate fibers, in film processing, in ink formulations, and as an extraction solvent for spice oleoresins, caffeine, and hops. Methylene chloride was once registered for use in the United States as an insecticide for commodity fumigation of strawberries, citrus fruits, and a variety of grains. Methylene chloride has been used as a blowing agent for foams and as a solvent for many applications, including coating photographic films, pharmaceuticals, aerosol formulations, and to a large extent in paint stripping formulations. It is used as a solvent in a number of extraction processes, where its high volatility is desirable. It has high solvent power for cellulose esters, fats, oils, resins, and rubber, and is more water soluble than most other chlorinated solvents. Formulations for paint stripping may contain other solvents as well as methylene chloride and are frequently found outside the workplace. These formulations often contain other ingredients that retard evaporation and in the process increase the likelihood of skin irritation. 4.3 Exposure Assessment The exposure characteristics of methylene chloride are discussed in the 1993 ATSDR Toxicological Profile (128). The primary routes of potential human exposure to methylene chloride are inhalation and ingestion. Dermal absorption has been observed, although it occurs more slowly than absorption after ingestion or inhalation. The principal route of exposure for the general population to methylene chloride is inhalation of ambient air. Inhalation exposure may also occur through the use of consumer products containing methylene chloride. USEPA has estimated that over one million workers are currently exposed to methylene chloride. The National Occupational Hazard Survey,

conducted by NIOSH from 1972 to 1974, estimated that 2.5 million workers were potentially exposed to methylene chloride vapors. On the basis of health hazard evaluations of various U.S. companies conducted in 1973 and 1974 by NIOSH, the concentrations of methylene chloride to which workers might be exposed in the following occupations were determined: servicing diesel engines, 11 ppm; spray-painting booths, 1–74 ppm; chemical plant, 0–5520 ppm with an 8-h TWA of 875 ppm; ski manufacture, 0–36 ppm; cleaning foam heads, 3–29 ppm; cleaning nozzles in plastics manufacture, 5–37 ppm; plastic tank construction, several ppm. A 1973 study of occupational exposure to hairspray propellants determined that methylene chloride exposure of beauticians exceeded a daily mean concentration of 1–2 ppm. The use of methylene chloride in hairsprays has been banned by the FDA. An estimated 500 million lb methylene chloride was produced in the United States in 1988. From the data obtained in the EPA Consumer Use and Shelf Survey, the CPSC calculated average individual 45-year risks. They ranged from zero for some of the automotive products to highs of 409 per million for adhesive removers and 95 per million for paint strippers, when the risk was based on malignant tumors in mice in the NTP bioassay; the risks were 924 per million for adhesive removers and 214 per million for paint strippers when the risks were based on malignant plus benign tumors in mice in the NTP bioassay. The Toxic Chemical Release Inventory (EPA) listed 1475 industrial facilities that produced, processed, or otherwise used chloromethane in 1988. In compliance with the Community-Right-to-Know Program, the facilities reported releases of methylene chloride to the environment that were estimated to total 127 million lb. Methylene chloride occurs in surface water, groundwater, finished drinking water, commercially bottled artesian well water, and surface water sites in heavily industrialized river basins. Methylene chloride was the sixth most frequently detected organic contaminant in groundwater from hazardous disposal sites investigated in 1987; it had a frequency detection of 19%. 4.3.2 Background Levels See above (Section 4.3). 4.3.3 Workplace Methods NIOSH Method 1005 is recommended for determining workplace exposures to methylene chloride (11). 4.3.4 Community Methods: NA 4.3.5 Biomonitoring/Biomarkers DiVincenzo et al. (1927) and Stewart et al. (129) discussed biologic monitoring for methylene chloride in expired air. The latter report includes graphs of expired air concentrations following exposures to known concentrations of methylene chloride. Within certain limits these may be useful in determining the exposures of workers. Carboxyhemoglobin levels in blood may also be of some value but interpretations are complicated by other sources of carbon monoxide and because carboxyhemoglobin is not elevated in a linear dose-dependent manner (130). 4.3.5.1 Blood See above (Section 4.3.5). 4.4 Toxic Effects Methylene chloride is a poison by intravenous route and is moderately toxic by ingestion, subcutaneous, and intraperitoneal routes and mildly toxic by inhalation. It is an experimental carcinogen and tumorigen and an experimental teratogen, and it has experimental reproductive effects. It is severe eye and skin irritant. Methylene chloride is the least acutely toxic of the four chlorinated methanes. The toxic effect is predominantly narcosis. Methylene chloride and some other dihalomethanes are metabolized to carbon monoxide. The principal problem from use is the “drunkenness” that may cause inept operation, which may result in injury to the employee or other workers in the area. The symptoms of excessive exposure may be dizziness, nausea, tingling or numbness of the extremities, sense of fullness in the head, sense of heat, stupor, or dullness, lethargy, and drunkenness. Exposure to very high concentrations may lead to rapid unconsciousness and death. Prompt removal from exposure prior to death usually results in complete recovery. Epidemiological data indicate no increase in cancer in workers exposed to methylene chloride.

Positive results have been found in experimental mice (Section 4.4.1.5). Numerous reviews are available (128, 131, 132), and detailed studies of pharmacokinetics and risk assessments have been published (133–135). Industrial experience with methylene chloride has resulted in few reports of serious adverse effects. Although dermatitis has been reported due to its common usage in paint remover formulations, only a few anesthetic deaths have occurred, all at very excessive concentrations. Reports of systemic injury are rare, and many are of questionable authenticity. Methylene chloride is known to be metabolized to carbon monoxide, but carboxyhemoglobin levels alone are not a good measure of the toxic effect of methylene chloride. Other sources of carbon monoxide such as automotive exhaust and smoking must be considered in evaluating occupational exposure to methylene chloride. 4.4.1 Experimental Studies 4.4.1.1 Acute Toxicity Methylene chloride has a low to moderate acute oral toxicity in laboratory animals. The acute oral LD50 of methylene chloride in rats is about 2000 mg/kg. Slight narcosis occurs at 4000–6100 ppm in several species of animals (136). The lethal concentration for an exposure of 7 h is about 15,000 ppm (33, pp. 35–41; 136, 137). Instillation of liquid methylene chloride directly into eyes of rabbits produced inflammation of the conjunctiva and eyelid, which persisted for 2 weeks; keratitis and irritis; and a 59% increase in corneal thickness at 6 h, which returned to normal by 9 days (138). Methylene chloride is mildly irritating to the skin of rabbits on repeated contact if allowed to evaporate. Svirbely et al. (137) reported that the LC50 for mice was approximately 50 mg/L or 15,000 ppm for an 8-h exposure. Survival of all animals was observed at approximately 11,000 ppm. Lehmann and Schmidt-Kehl (139) reported levels of narcosis in cats; 32 mg/L or 9000 ppm caused “displacement of equilibrium” in 20 min but no narcosis. At 37.5 mg/L or 10,000 ppm, light narcosis occurred in 220 min and deep narcosis at 293 min. They reported that cats and rabbits tolerated 6–7 mg/L for 8–9 h/day for 4 weeks with no significant observable changes. Subsequent studies have confirmed these early data. Plaa and Larson (140) and Gehring (141) investigated the renal and hepatotoxicity of methylene chloride and concluded that the compound had a very low toxicity toward these organs. 4.4.1.2 Chronic and Subchronic Toxicity Heppel and associates (142) reported no pathology or growth depression in dogs, puppies, rats, guinea pigs, or rabbits exposed to 5000 ppm 7 h/day, 5 days/week for 6 months. They did not detect CNS depression by ordinary observation but did not conduct specific tests. At 10,000 ppm they observed light to moderate narcosis. Several animals died, apparently from pulmonary congestion. Heppel and Neal (143) reported experiments with young male rats in an activity cage. At a concentration of 5000 ppm the animals showed definite reduction in activity. Lifetime exposure of rats and hamsters to 3500, 1500, or 500 ppm 6 h/day for 2 years resulted in “non-life-shortening treatment-related changes, similar to those seen in aging animals, in the livers of male and female rats at all exposure levels.” The details of this study are discussed in Section 4.4.1.5 (144). Hamsters were less affected than rats, with survival of female hamsters much higher than in the control group. Haun et al. (145) summarized the data from exposure studies in which animals were exposed repeatedly and also described the results of continuous (24 h daily) exposure of rats, mice, monkeys, and dogs for 100 days to either 25 or 100 ppm of methylene chloride vapors. Except for increased carboxyhemoglobin levels, dogs and monkeys were unaffected by this continuous exposure. Mice exposed to 25 ppm were likewise without effect, but the livers of the mice exposed to 100 ppm and rats exposed to both concentrations showed positive fat stains. Cytoplasmic vacuolization was noted in rats, as well as degenerative and regenerative changes in the kidneys. Carboxyhemoglobin was more elevated in the monkeys than in the dogs, which showed no elevation at 25 ppm and about 1.5% elevation at 100 ppm. Levels in monkeys were increased by ~ 1% at 25 ppm and 3–4% at

100 ppm. In a second continuous exposure study, gerbils appeared to be unusually susceptible to methylene chloride (146). Continuous exposure to 700 ppm resulted in premature termination of the study after 7 weeks and 350 ppm at 10 weeks. Gerbils exposed continuously to 210 ppm were exposed for the intended 3 months. Survivors from the 350- and 210-ppm groups were kept on recovery for 4 months. One female exposed to 210 ppm died, but no control gerbils died. The gerbils exposed to 210 ppm were reported to gain weight normally. Carboxyhemoglobin in the 210-ppm group was 11.5%, versus 10.3% in the 350-ppm group after 3 weeks, which is consistent with other findings of 10 weeks. An extensive study of neurotoxicologic effects in rats following exposure to 50 ppm (below metabolic saturation), 200 ppm (just below metabolic saturation), and at 2000 ppm (well above metabolic saturation) failed to show deleterious effects (147). Carbon monoxide was similarly studied at 135 ppm in air. Exposure to both substances were 6 h/day, 5 days/week for 13 weeks. Carboxyhemoglobin levels of 10% were attained with the CO as they were with 200 ppm methylene chloride. Postexposure functional tests included an observational battery, hind-limb grip strength, and a battery of evoked potentials (flash, auditory brainstem, somatosensory, caudal nerve). After functional tests were completed, rats from all groups were perfused with fixative and a comprehensive set of nervous tissues from the high exposure group and from controls were examined by light microscopy. The investigators concluded that subchronic exposures as high as 2000 ppm methylene chloride or 135 ppm CO had no deleterious effects on any of the measures of this study. Methylene chloride is mildly irritating to the skin of rabbits on repeated contact if allowed to evaporate. Additional studies are discussed in Section 4.4.1.5. 4.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms The metabolism of methylene chloride to carbon monoxide and the subsequent production of carboxyhemoglobin (COHb) has been studied in animals and man. In the rat, metabolism appears to be saturable with disproportionately less COHb formed and more unchanged methylene chloride expired as exposure increased (148). Production of carbon monoxide and carboxyhemoglobin has been shown to occur in animals (149) as well as humans. Von Oettingen et al. (18) studied the absorption and excretion of methylene chloride. They reported that it was rapidly absorbed and largely excreted by the lungs. Although this appears to be partly true, a significant amount is metabolized to carbon dioxide and carbon monoxide. Figure 62.2 taken from Andersen et al. (133), indicates that CO2 is produced by either a route involving glutathione S-transferase or a route using cytochrome P450 mixed-function oxidase (MFO). Carbon monoxide, however, is produced only in the MFO route. According to Reitz et al. (134), the MFO system plays a protective role, has a higher affinity for methylene chloride, and metabolizes most of the methylene chloride at low concentrations. They conclude that after saturation of the MFO pathway at about 300–500 ppm, the glutathione pathway increases disproportionately.

Figure 62.2. Proposed metabolic pathways for methylene chloride metabolism. From Ref. 133. Different routes of exposure, dosage level/rates of metabolism, respiratory rates, and other factors have been used to develop a physiologically based pharmacokinetic model useful in explaining differences in response in the carcinogenic studies described previously (133). Perhaps the most important result is the calculation that target tissue doses in humans are 140–170-fold lower (by inhalation) or 50–210-fold lower (by drinking water) than would be expected from the customary linear extrapolation and body surface area adjustment used in older risk assessments. However, in 1988 USEPA felt that a nine-fold reduction was more appropriate, despite a report (150) cited in Section 4.4.2 that after a 30-year latency human cancers were not elevated and were well below that predicted by animal studies. In vitro data (134) provide support for the Andersen et al. Model. 4.4.1.3.1 Adsorption See above (Section 4.4.1.3). 4.4.1.3.2 Distribution See above (Section 4.4.1.3). 4.4.1.3.3 Excretion See above (Section 4.4.1.3). 4.4.1.4 Reproductive and Developmental Schwetz et al. (151) found no teratogenic effects in rats or mice exposed to 1225 ppm vapor, 7 h/day on days 6–15 of gestation. The young of exposed (4500 ppm) pregnant rats were reported by Bornschein et al. (152) to show retarded behavioral habitation to novel environments. The authors did not attempt to determine whether the effect was due to methylene chloride, carboxyhemoglobin, or the combination of the two. They were also hesitant to extrapolate to possible effects at concentrations of 200–500 ppm. Rats fed up to 4% methylene chloride in their diet showed no teratological effect (153). Neonatal weight was reduced during an 8-week observation period following exposure to 4% in the diet but not after 0.4%. Wistar rats fed about 2.8 mg/kg of body weight/day in their drinking water (125 ppm) for 91 days were mated or sacrificed at the end of the exposure period; no adverse effects were noted on estrus or reproduction (154). Nitschke et al. (130) exposed rats and reported the following. Reproductive parameters in Fischer

344 rats were evaluated following inhalation of methylene chloride (MeCl2) for two successive generations. Thirty male and female rats were exposed to 0, 100, 500, or 1500 ppm MeCl2 for 6 h/day, 5 days/week for 14 weeks and then mated to produce F1 litters. After weaning, 30 randomly selected F1 pups/sex/group were exposed to MeCl2 for 17 weeks and subsequently mated to produce F2 litters. Reproductive parameters examined included fertility, litter size and neonatal growth, and survival. All adults and selected weanlings were examined for grossly visible lesions. Tissues from selected weanlings were examined histopathologically. No adverse effects on reproductive parameters, neonatal survival, or neonatal growth were noted in animals exposed to methylene chloride in either F0 or F1 generation. Similarly, there were no treatment-related gross pathologic observations in F0 or F1 adults or F1 or F2 weanlings. Histopathologic examination of tissues from F1 or F2 weanlings did not reveal any lesions attributed to methylene chloride. Thus, exposure of rats to concentrations as high as 1500 ppm methylene chloride, which has been shown in a 2-year study to produce treatment-related effects, did not effect any reproductive parameters. 4.4.1.5 Carcinogenesis IARC classifies methylene chloride in group 2B, Probably carcinogenic in humans; MAK, group B, Suspected of having carcinogenic potential; NIOSH, Carcinogen, with no further classification; ACGIH TLV, A3, Confirmed. Animal carcinogen with unknown relevance to humans. Animal evidence is considered by EPA to be “sufficient” for carcinogenesis. Methylene chloride administered in the drinking water induced a significant increase in combined hepatocellular carcinoma and neoplastic nodules in female F344 rats and a nonsignificant increase in combined hepatocellular carcinoma and neoplastic nodules in male B6C3F1 mice (155, 156). Two inhalation studies with methylene chloride have shown an increased incidence of benign mammary tumors in both sexes of Sprague–Dawley (144) and F344 (157) rats. Male Sprague–Dawley rats had increased salivary gland sarcoma (144) and female F344 rats had increased leukemia incidence (157). Both sexes of B6C3F1 mice developed liver and lung tumors after methylene chloride treatment (157). In a 2-year study by the National Coffee Association (155, 156), groups of 85 F344 rats/sex/dose received 5, 50, 125, or 250 (mg/kg)/day of methylene chloride in the drinking water. Control groups consisted of 135 rats/sex. In female rats the incidence of combined hepatocellular carcinoma and neoplastic nodules was statistically significantly increased in the 50- and 250-mg/kg dose groups when compared with matched controls (0/134, 1/85, 4/83, 1/85, and 6/85 in the five dose groups 0, 5, 50, 125, and 250 (mg/kg)/day, respectively). The incidence of hepatocellular carcinoma alone was not significantly increased (0/134, 0/85, 2/83, 0/85, 2/85). The combined incidence of hepatocellular carinoma and neoplastic nodules in controls and the four dose groups (472 rats: 4 with carcinoma and 8 with neoplastic nodules) was similar to that for historical controls (419 rats; 5 with carcinoma, 19 with neoplastic nodules). Male rats showed no increase in liver tumors. Also, in this study, B6C3F1 mice received 0, 60, 125, 185, or 250 mg/kg/day of methylene chloride in drinking water. Treatment groups consisted of 50 female mice and 200, 100, 100, and 125 male mice (low to high dose). One hundred females and 125 males served as controls. Male mice had an increased incidence of combined neoplastic nodules and hepatocellular carcinoma (24/125, 51/200, 30/100, 31/99, 35/125). The increase was not dose-related, but the pairwise comparisons for the two middose groups were reported to be statistically significant (132). The hepatocellular carcinoma incidence alone for male mice (which was about 55–65% of the total) was not significantly elevated. Female mice did not have increased liver tumor incidence. The EPA (158) regarded this study as suggestive but not conclusive evidence for carcinogenicity of methylene chloride. Inhalation exposure of 107–109 Syrian hamsters/sex/dose to 0, 500, 1500, or 3500 ppm of methylene chloride for 6 h/day, 5 days/week for 2 years did not induce neoplasia (144). Sprague–Dawley rats (129/sex/dose) were exposed under the same conditions. Female rats administered the highest dose

experienced significantly reduced survival from 18–24 months. Female rats showed a dose-related increase in the average number of benign mammary tumors per rat (1.7, 2.3, 2.6, 3.0), although the numbers of rats with tumors were not significantly increased. A similar response was observed in male rats, but to a lesser degree. In the male rats there was a statistically significant positive trend in the incidence of sarcomas of the salivary gland (1/93, 0/94, 5/91, 11/88); the incidence was significantly elevated at the high dose. There is a question as to whether these doses reached the MTD, particularly in the hamsters and the male rats. Groups of 50 each male and female F344/N rats and B6C3F1 mice were exposed to methylene chloride by inhalation, 6 h/day, 5 days/week for 2 years (157). Exposure concentrations were 0, 1000, 2000, or 4000 ppm for rats and 0, 2000, or 4000 ppm for mice. Survival of male rats was low; however, this apparently was not treatment-related. Survival was decreased in a treatment-related fashion for male and female mice and female rats. Mammary adenomas and fibroadenomas were significantly increased in male and female rats after survival adjustment, as were mononuclear cell leukemias in female rats. Among treated mice of both sexes there were significantly increased incidences of hepatocellular adenomas and carcinomas, and of alveolarbronchiolar adenomas and carcinomas, by life-table tests. Adenomas and carcinomas were significantly increased alone as well as in combination. In addition, there were significant dose-related increases in the number of lung tumors per animal multiplicity in both sexes of mice. 4.4.1.6 Genetic and Related Cellular Effects Studies Methylene chloride was mutagenic for Salmonella typhimurium with or without the addition of hepatic enzymes (159) and produced mitotic recombination in yeast (160). Results in cultured mammalian cells have generally been negative, but methylene chloride has been shown to transform rat embryo cells and to enhance viral transformation of Syrian hamster embryo cells (161, 162). Although chlorinated solvents have often been suspected of acting through a nongenotoxic mechanism of cell proliferation, Lefevre and Ashby (163) found methylene chloride to be unable to induce hepatocellular division in mice. Jongen et al. (164) have used methylene chloride in an Ames test with Salmonella typhimurium TA98 and TA100. Increased reversions occurred in both strains of bacteria. The activity was only slightly increased by the addition of rat liver homogenate. 4.4.2 Human Experience Symptoms of exposure to this compound may include headache, elevated blood concentrations of carboxyhemoglobin, nausea, and irritation of the skin and eyes. Central nervous system depression, pulmonary edema, hemolysis, chronic intoxication, and paresthesia may also occur. Other symptoms include narcosis, temporary neurobehavioral effects, increase in serum bilirubin, increased urinary formic acid concentrations, and increased risk of spontaneous abortion. In addition, intravascular hemolysis, unconsciousness, lack of response to painful stimuli, rapid followed by slowed respiration, erythema, blistering, toxic encephalopathy, painful joints, swelling of the extremities, mental impairment, diabetes, skin rash, aspiration pneumonia, gross hematuria, reduction of blood pH, GI injury, and narrowing of the intestinal lumen may also occur. Other symptoms may include upper respiratory tract irritation, giddiness, stupor, irritability, numbness, tingling in the limbs, and hallucinations. A dry, scaly and fissured dermatitis, skin burns, coma, and death may also result. Other symptoms may include dizziness, sense of fullness in the head, sense of heat, dullness, lethargy, and drunkenness. In addition, mental confusion, lightheadedness, vomiting, weakness, somnolence, lassitude, anorexia, depression, fatigue, vertigo, liver damage, nose and throat irritation, anesthetic effects, smarting and reddening of the skin, blood dyscrasias, acceleration of the pulse, and congestion in the head may result. Staggering may also occur. Other symptoms of exposure to this compound may include neurasthenic disorders, digestive disturbances, and acoustical and optical delusions. Arrhythmias produced by catecholamines may also result. Additional symptoms include edema, faintness, loss of appetite, and apathy. Hyporeflexia, gross hemoglobinuria, epiglottal edema, metabolic acidosis, gastrointestinal hemorrhage, ulceration of the duodenojejunal junction, and diverticula may also occur. Other symptoms may include kidney damage, lung damage, corneal injury, abdominal pain, and an increase in salivary gland tumors. Cyanosis may also occur. Exposure may also cause altered sleep time, convulsions, euphoria, and a

change in cardiac rate. 4.4.2.1 General Information Experience in use of methylene chloride has generally been favorable, confirming the low toxicity observed in animals. Most commonly, recovery of exposed workers, even from anesthetic concentrations, has been rapid and without sequelae other than carboxyhemoglobin, which appears to persist slightly longer than that resulting from carbon monoxide itself. Between 1961 and 1980, 33 excessive exposures to methylene chloride were reported to the British Health and Safety Executive (166). Thirteen subjects were unconscious, 9 had headaches, 11 were dizzy, and 13 had GI symptoms, but liver injury was reported only in one subject who also had xylene exposure. One death was reported. Several laboratory and epidemiologic studies in humans have been reported. An extensive laboratory study of healthy adult test subjects exposed repeatedly 7 h/day to 250 ppm showed no untoward subjective health responses (129). McKenna et al. (148) exposed six healthy male volunteers “to 100 and 350 ppm methylene chloride (CH2Cl2) during each of two 6-h exposure periods. Measurement of blood CH2Cl2 and carboxyhemoglobin (COHb) levels and CH2Cl2 and carbon monoxide (CO) in expired air were performed during exposure and for the first 24 h thereafter. Dose-dependent metabolism of CH2Cl2 was evident from both CH2Cl2 blood levels and the concentration of CH2Cl2 in the expired air when the data from the 100 and 350 ppm exposure experiments were compared. Blood COHb levels and exhaled CO were less than expected following exposure to 350 ppm CH2Cl2, indicative of dose-dependent or saturable metabolism of CH2Cl2 to CO. The rate of total CH2Cl2 metabolism for each subject was calculated from the inspired–expired air concentration and minute ventilation rate obtained at apparent steady-state. The relationship of the rate of CH2Cl2 metabolism during exposure to the CH2Cl2 exposure concentration followed apparent Michaelis– Menten kinetics.” These authors derived a pharmacokinetic model to allow prediction of the extent of methylene chloride metabolism and production of carboxyhemoglobin following exposure to methylene chloride in laboratory animals and humans. An assessment of the carcinogenic risk to humans has been published in which it is concluded the risk to humans is very low particularly at levels of exposure producing no other adverse effect (135). 4.4.2.2 Clinical Cases See Section 4.4.2.1. 4.4.2.2.1 Acute Toxicity Severe skin burns were observed in a worker found unconscious after about 30 min in a vessel with a high concentration of methylene chloride (165). He was in severe shock and almost pulseless after being taken to the hospital while on oxygen. He was continued on oxygen and 1 h after being rescued still had 12% carboxyhemoglobin despite being on oxygen. When he was discharged 8 days later, the blood protein was reported to be normal, as were liver and renal function tests. The problem in humans may be accentuated if the chemical is confined to the skin by shoes or tight clothing. The situation may be more severe with paint-remover formulations that form a skin or film to prevent evaporation. Limited absorption through skin occurs, but probably is not of toxicologic significance in industrial situations (167). 4.4.2.2.5 Carcinogenesis An IARC Working Group reported that the data available on methylene chloride were inadequate for an evaluation of its carcinogenicity in humans. The data from a study of 751 occupationally exposed workers also were considered inadequate to assess the carcinogenicity of methylene chloride in humans by later IARC Working Groups.

An epidemiological mortality analysis of a male population exposed to methylene chloride has been reported (168). This study, a follow-up of previously published reports, confirms earlier findings of no increase in cancer. In a series of five papers the health status and mortality experience of a group of several hundred exposed workers has been described (169). Industrial hygiene measurements indicated exposure of 140 to 475-ppm 8-h time-weighted averages. Cause of death, included ischemic heart disease and cancer, was unaffected. Except for the expected effects of carbon monoxide there were no health affects related to exposure. 4.5 Standards, Regulations, or Guidelines of Exposure The ACGIH TLV is 50 ppm with an A3 designation. NIOSH considers methylene chloride a carcinogen and recommends the lowest feasible exposure level and an IDLH of 2300 ppm. The OSHA PEL is 25 ppm and a STEL of 125 ppm. USEPA has published water-quality criteria under CWA and established a reportable quantity (RQ) of 1000 lb for methylene chloride under CERCLA. This chemical is exempted from a tolerance for residues, and is regulated as a toxic inert ingredient of pesticides under FD&CA. Methylene chloride is a listed hazardous substance under RCRA. USEPA has included methylene chloride on a list of priority hazardous substances under SARA. Further regulatory testing is proceeding under TSCA. FDA regulates methylene chloride as a limited food additive. Specified residues are permitted in spice oleoresins, hops extract, and decaffeinated coffee. 4.6 Studies of Environmental Impact None found.

Saturated Methyl Halogenated Aliphatic Hydrocarbons Jon B. Reid, Ph.D., DABT 5.0 Methylene Chlorobromide 5.0.1 CAS Number: [74-97-5] 5.0.2 Synonyms: Bromochloromethane; bromochloromethane (DOT); chlorobromomethane; chlorobromomethane (ACGIH, OSHA); halon 1011; CB; CBM; monochloromonobromomethane; mil-b-4394-b 5.0.3 Trade Names: Halon 1011; Methane, bromochloro-; MIL-B-4394-B; Mono-chloromono-bromo-methane; UN1887 (DOT) Bromochloromethane; Chlorobromomethane Monochloromonobromomethane; Monochloromono-bromo-methane methane; Bromochloro-CB; CBM; Halon; 1011; MIL-B-4394-B, UN 1887; CH2BrCl, CB, BCM 5.0.4 Molecular Weight: 129.39 5.0.5 Molecular Formula: CH2ClBr 5.0.6 Molecular Structure:

5.1 Chemical and Physical Properties

Physical state Specific gravity Freezing point Boiling point Vapor pressure Refractive index Percent in “saturated” air Solubility Flammability

Colorless liquid 1.93 at 20°C –86.5°C 67°C 117 torr at 20°C 1.4850 (26°C) 21 (25°C) Insoluble in water; soluble in organic solvents No flash or fire points by standard tests in air; it is an effective fire extinguisher

1 mg/L = 189 ppm and 1 ppm = 5.3 mg/m3 at 25°C, 760 torr 5.1.1 General: NA 5.1.2 Odor and Warning Properties Methylene chlorobromide has a distinctive odor at 400 ppm, and hence has warning properties below any acutely hazardous concentration. Although the odor is distinctive at the acceptable concentration and so gives some warning, it is not disagreeable enough to drive anyone from the area. Employees may tolerate a level well above the acceptable level for chronic exposure. 5.2 Production and Use This compound is used in fire extinguishers and in organic synthesis. 5.3 Exposure Assessment 5.3.1 Air: NA 5.3.2 Background Levels: NA 5.3.3 Workplace Methods NIOSH Analytical Method: 1003 is recommended (11). 5.4 Toxic Effects Methylene chlorobromide is one of the least acutely toxic halomethanes. It falls roughly in a class with methylene chloride in acute and short-term toxicity. The primary response to this material is CNS depression. There appears to be very little organic injury following either acute or repeated chronic exposure except possibly lung irritation from acute exposure at high levels. The compound is metabolized to carbon monoxide and produces carboxyhemoglobin as well as inorganic bromide. Few new data were found since the last revised edition. Reviews are available (170, 171). Methylene chlorobromide is mildly toxic by ingestion and inhalation. This material has a narcotic action of moderate intensity, although of prolonged duration. This compound is corrosive. It is harmful if swallowed, inhaled, or absorbed through the skin. It is extremely destructive to tissue of the mucous membranes, upper respiratory tract, eyes, and skin. It may cause eye, throat, and skin irritation. When heated to decomposition, it emits toxic fumes of carbon monoxide, carbon dioxide, hydrogen chloride gas, and hydrogen bromide gas. 5.4.1 Experimental Studies 5.4.1.1 Acute Toxicity Highman et al. (172) reported that administration of methylene chlorobromide by stomach tube to mice caused no changes at doses of 500 mg/kg. Single doses of 3000 and 4500 mg/kg were followed by fatty degeneration of the liver and kidneys. These same authors observed no liver or kidney injury in animals exposed to the vapors. They commented that the difference in liver injury could be due to a different pathway of absorption from the GI tract than from the lungs. Svirbely et al. (137) reported the LC50 by inhalation for mice exposed for 7 h to be 12.03 mg/L of air

(2273 ppm). Comstock et al. (173) reported that concentrations as low as 3000 ppm produced light narcosis in rats. Transient pulmonary edema was observed at concentrations below 27,000 ppm. At higher concentrations, interstitial pneumonitis resulted in delayed deaths. Delayed deaths were also observed after exposure to 20,000 ppm. Deaths during exposure occurred only from exposures above 27,000 ppm. Matson and Dufour (174) reported limited acute studies on guinea pigs. The principal toxicological observation from the exposure was lung injury. Van Stee et al. (175) exposed dogs to 0.3–1.0% in oxygen to determine the effect on the cardiovascular system. Disturbances in myocardial energy metabolism occurred, including cardiac arrhythmias, but the studies were conducted on anesthetized animals and the industrial significance cannot be ascertained. 5.4.1.2 Chronic and Subchronic Toxicity Repeated exposures by inhalation were reported by Svirbely et al. (137). They exposed animals 7 h/day, 5 days/week for a period of 14 weeks to a concentration of 1000 ppm. Rats, rabbits, and dogs survived these exposures and showed no evidence of toxic response. Growth was normal, and there were no histopathological changes. Torkelson et al. (176) indicate that female rats and dogs survived without significant effect, 370 ppm in air, 7 h/day, 5 days/week for 6 months, but that some liver pathology was observed at 500 ppm. Male rats, male and female guinea pigs, and rabbits showed no effect except for elevated blood bromide at 500 ppm. However, at 1000 ppm several effects were noted, including histopathological changes in the livers and testes in addition to increased blood bromide. In a similar study, rats and dogs were exposed to methylene chlorobromide vapors 6 h/day for a total of 124 exposures in a 6-month period (177). The exposure levels of 500 and 1000 ppm produced no adverse effect except for an apparent failure of rats to gain as much weight as their controls. The authors suggested that the lower weight might have been related to sedation owing to the elevated levels of bromide ion in the blood. In about 20 days serum bromide levels in both rats and dogs reached an equilibrium of about 150 mg/100 mL in dogs and 140 mg/100 mL in rats exposed to 1000 ppm. Exposures to 500 ppm resulted in equilibrium concentrations of 125 and 100 mg/100 mL in the two species. 5.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Svirbely et al. (137) determined inorganic bromide in blood serum and urine in dogs exposed to 1000 ppm of methylene chlorobromide in air. These animals were exposed 7 h/day, 5 days/week. During the third week, the blood serum inorganic bromide had increased from a normal of 5–10 mg/100 mL to >200 mg. By the 13th and 14th weeks, the concentration was greater than 300 mg of inorganic bromide per 100 mL of blood. The same authors determined the blood concentration of volatile bromide expressed as milligrams of methylene chlorobromide per 100 mL of blood. Taken immediately at the end of the exposure, concentrations between 5 and 9 mg of methylene chlorobromide per 100 mL were observed. At periods of 17–65 h after the end of the last exposure, no volatile bromide was observed in one dog and concentrations of 1000 mg/kg. It is only slightly irritating to the eye and skin of rabbits and does not appear to be absorbed significantly even when applied repeatedly (The Dow Chemical Co., Midland, MI, unpublished data). Although it has been shown by increased blood bromide and increased carboxyhemoglobin that some absorption of the liquid and vapor does occur through rat skin, the investigator concluded that only 5% of the inhaled dose would penetrate the skin during vapor exposure (187). It is sufficiently volatile that inhalation of the vapors can cause anesthesia and

even death. A concentration of 17–20 mg/L (2400–2800 ppm) caused “disorders in the central nervous system” (188). The duration of the exposure and other details were not stated in the available abstract. When an essentially saturated atmosphere was inhaled by rats, anesthesia occurred in 3 min, with 50% mortality in 18 min (The Dow Chemical Co., Midland, MI, unpublished data). 6.4.1.2 Chronic and Subchronic Toxicity In a very limited study methylene bromide was administered orally to a small group of rabbits at the rate of 300 mg/kg/day (60 doses in 92 days) with no alteration in weight gain, general appearance, or histopathology of the liver. Similar treatment with 400 mg/kg produced marked anesthesia (The Dow Chemical Co., Midland, MI, unpublished data). In limited studies in which 10 rats and one rabbit of each sex were exposed to a nominal concentration of 1000 ppm (900–1000 ppm recovered analytically), there was no overt evidence of adverse effect in the rabbits, but liver and kidney degeneration was observed at autopsy following 54 exposures in 73 days (The Dow Chemical Co., Midland, MI, unpublished data). Blood bromide was elevated. Rats were much more affected. Incoordination and staggering were apparent during exposure. Failure to gain weight, possible increased mortality, and histopathological changes in the lungs, liver, and kidneys were observed in rats receiving 30–40 7 h exposures. In a second equally limited study by this same group, 79 exposures in 114 days to 200 ppm resulted in much less effect, but evidence of stress was still present. The weights of the livers of male rats were elevated when compared to the controls, and histological changes were found in the livers and kidneys of rats and rabbits. When inhaled 4 h/day for 2 months, 0.25 mg/L (35 ppm) methylene bromide was reported to cause “disorder in the protein-prothrombin and glycogenesis functions of the liver and the filtration capacity of the kidneys.” It was considered less toxic than bromoform (189). The same investigator reported that 2.5 mg/L of the vapor for 10 days (duration of exposure not stated) when inhaled by rabbits produced the same effects with dystrophic changes in these organs. A “threshold” concentration of 0.23 mg/L (32 ppm) was claimed for chronic exposures. When doses of 100– 200 mg/kg were injected subcutaneously for 10 days in guinea pigs, pronounced liver and kidney effects were reported. Dykan's report is not consistent with a more extensive study on rats and dogs discussed below. In another study, 115 male rats, 15 female rats, 4 male and 4 female rabbits, and 3 male beagle dogs were exposed to 0, 25, 75, or 150 ppm methylene bromide vapor 6 h/day, 5 days/week for 13 weeks (190). Male rats received 62 exposures, female rats 63 exposures, and dogs 70 exposures. On the day after their last exposure, 15 male and 15 female rats and the dogs were necropsied. The balance of the male rats were kept for 2 years in a very limited oncological study. Female rats showed a slight increase in liver weight at 75–150 ppm, but other parameters were normal, including mortality, clinical observations, body weight, hematology, clinical chemistry, and gross pathology and histopathology. There was definite evidence of metabolism of methylene bromide; free bromide ion, total bromine, and blood carboxyhemoglobin were increased in a dose-related manner. In the male rats kept for a limited oncological study there were no treatment-related effects grossly or microscopically after 1 year or at the termination of the study except for a possible decrease in body weight beginning on day 121 of the study. Only gross pathological examination of the 2-year animals was conducted and no oncological changes related to exposure were observed at any of the three exposure levels. 6.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Methylene bromide was determined in the plasma of dogs following repeated 6-h exposures to 25, 75, or 150 ppm for 90 days. The plasma clearance was at least biphasic with an ill-defined alpha phase and a terminal phase (t1/2 of

103 ± 14 min) at all three concentrations. Blood bromide was elevated markedly in rabbits exposed to ~ 1000 ppm of the vapors, 7 h/day for a month. After 54 exposures in 73 days the blood levels had reached 280–315 mg Br/100 mL of blood. After 79 exposures in 114 days to a vapor concentration of about 200 ppm, blood bromide levels of 85–100 mg Br/100 mL were found in rabbits (190). Methylene bromide, like many of the dihalomethanes, is metabolized to produce carbon monoxide (149, 178, 191, 192). Intraperitoneal injection of 520 mg/kg of methylene bromide in corn oil elevated carboxyhemoglobin in rats to 14% 5 h after injection. Repeated daily injection did not result in any significant difference in carboxyhemoglobin concentrations from single injection. In vitro studies (178, 193) show that microsomal enzymes in the presence of NADPH and molecular oxygen convert methylene bromide to carbon monoxide and inorganic bromide. There was not significant contribution of glutathione to the overall metabolism of methylene bromide (194). Cytochrome P450 is involved in its metabolism. 6.4.1.4 Reproductive and Developmental No teratological or reproductive data were found, and only the unusual oncological study reported above is available. Methylene bromide has been shown to be mutagenic in certain test systems with bacteria. Methylene bromide has been tested in three strains of Salmonella typhimurium activated with liver homogenate and in Saccharomyces cerevisiae D3. It was at most weakly mutagenic in Saccharomyces and negative in Salmonella (The Dow Chemical Co., Midland, MI, unpublished data). In a study attempting to relate chemical reactivity, glutathione transferase activity, and mutagenicity for a series of dihalomethanes, there was no strong correlation (180). Mixed results were obtained, and methylene bromide was not strongly mutagenic in E. coli and S. typhimurium systems. Incubation with rat liver microsomes inhanced mutagenic activity (195). 6.5 Standards, Regulations, or Guidelines of Exposure: NA 6.6 Studies on Environmental Impact: NA

Saturated Methyl Halogenated Aliphatic Hydrocarbons Jon B. Reid, Ph.D., DABT 7.0 Chloroform 7.0.1 CAS Number: [67-66-3] 7.0.2 Synonyms: Trichloromethane, Methenyl chloride, methane trichloride, methyl trichloride, formyl trichloride Methane Trichloride Methane, Trichloro- Methenyl Chloride Methenyl Trichloride Methyl Trichloride, Trichloroform, trichloroform; R 20, r 20 (refrigerant), Refrigerant R20 7.0.3 Trade Names: Freon 20, R20, R 20 refrigerant, NCI-CO2686, R-20 TCM, UN 1888 7.0.4 Molecular Weight: 119.38 7.0.5 Molecular Formula: CHCl3 7.0.6 Molecular Structure:

7.1 Chemical and Physical Properties Physical state Colorless liquid Specific gravity 1.49845 (15/4°C) TLV 1.484 at 20°C Melting point –63.2°C Boiling point –61.3°C Vapor pressure 200 torr (25°C) 159 torr at 20°C TLV Solubility 1.0 g/100 mL water at 15°C; soluble in ethanol, ethyl ether, acetone, CS2 Flammability UEL, LEL

Not flammable by standard tests in air Not available

1 mg/L = 206 ppm and 1 ppm = 4.89 mg/m3 at 25°C, 760 torr 7.1.1 General Chloroform is a colorless, volatile nonflammable liquid with a pleasant, nonirritating odor and slightly sweet taste. It is slightly soluble in water and is miscible with oils, ethanol, ether, and other organic solvents. It is unstable when exposed to air, light, and/or heat, which cause it to break down to phosgene, hydrochloric acid, and chlorine. It is usually stabilized by the addition of 0.6–1% ethanol. When heated to decomposition, chloroform emits toxic fumes of hydrochloric acid and other chlorinated compounds. 7.1.2 Odor and Warning Properties Chloroform has a sweetish odor. Lehmann and Flury (136) indicated that the lowest concentration that could be detected was 200–300 ppm. This might be considered as some warning from exposure to acutely hazardous amounts, but it is by no means low enough to be considered a warning from chronic exposure. 7.2 Production and Use Chloroform is used primarily in the production of chlorodifluoromethane (hydrochlorofluorocarbon 22 or HCFC-22) used as a refrigerant for home air conditioners or large supermarket freezers and in the production of fluoropolymers. It has also been used as a solvent, a heat-transfer medium in fire extinguishers, and an intermediate in the preparation of dyes and pesticides. Its use as an anesthetic has been discontinued. Chloroform is still used as a local anesthetic and solvent in certain dental endodontic surgery procedures. Significant commercial production in the United States began in 1992. Since the 1980s, production increased by 20–25% because of a higher demand for HCFC-22. Estimated annual production capacity from the major facilities was 460 million lb. In 1994 it was 565 million lb. Chloroform has been identified as a hazardous waste by USEPA, and disposal is regulated under RCRA. Ultimate disposal can be accomplished by controlled incineration. Complete combustion must be ensured to prevent phosgene formation and an acid scrubber should be used to remove the haloacids produced. Miscellaneous uses of chloroform include use as a solvent in the extraction and purification of some antibiotics, alkaloids, vitamins, and flavors; as a solvent for lacquers, floor polishes, artificial silk manufacture, resins, fats, greases, gums, waxes, adhesives, oils, and rubber; as an industrial solvent in photography and dry cleaning; as a heat-transfer medium in fire extinguishers; and as an intermediate in the preparation of dyes and pesticides. At least one grain fumigant mixture had contained chloroform with carbon disulfide. Chloroform formulated with other ingredients is used to control screw worm in animals. Its use as an anesthetic has been largely discontinued. 7.3 Exposure Assessment

An ATSDR Toxicological Profile (Update) for 1998 summarizes relevant material (196). Chloroform is both a synthetic and naturally occurring compound, although anthropogenic sources are responsible for most of the chloroform in the environment. Chloroform is released into the environment as a result of its manufacture and use; its formation in the chlorination of drinking water, municipal and industrial wastewater, and swimming-pool and spa water; and from other water treatment processes involving chlorination. Most of the chloroform released into the environment will eventually enter the atmosphere. In the atmosphere chloroform may be transported long distances before ultimately being degraded by indirect photochemical reactions with such free radicals as hydroxyl. The compound has been detected in ambient air in locations that are remote from anthropogenic sources. Chemical hydrolysis is not a significant removal process. Under aerobic conditions, some bacteria can dehalogenate carbon tetrachloride to release chloroform. While microbial biodegradation of chloroform can take place, such reactions are generally possible only at low concentration levels. Microbial biodegradation may also be inhibited because of high levels of other aromatics, chlorinated hydrocarbons, or heavy metals. Because of its low soil adsorption and slight water solubility, chloroform will readily leach from soil to groundwater. In groundwater, chloroform is expected to persist for a long time. The general population is probably exposed to chloroform through drinking water and beverages, eating food, inhaling contaminated air, and through dermal contact with water. The occupations that may involve significant exposure include chemical plants or chlorination process in drinking-water plants, paper-and-pulp plants, and hazardous- and municipal-waste incinerators. A maximum of 3.8 × 10–3 ppm was found in the air in an activated sludge waste-water treatment plant (197). The National Occupational Hazard Survey, conducted by NIOSH from 1972 to 1974, estimated that 215,000 workers were potentially exposed to chloroform in the workplace. A National Occupational Exposure Survey (NOES) conducted by NIOSH from 1981 to 1983 estimated that 95,778 workers in the United States are potentially exposed to chloroform (198). The NTP database (4) indicates the following. The primary routes of potential human exposure to chloroform are ingestion, inhalation, and dermal contact. Potential human exposure may occur by breathing air contaminated with chloroform, eating food or drinking water that contains chloroform, or absorption of chloroform through the skin. Chloroform has been detected in the atmosphere at concentrations ranging from 0.02 to 13 g/m3 and in indoor air at 0.07–3.6 g/m3. Foods such as dairy products, oils/fats, vegetables, bread, and beverages may contain small amounts of chloroform. Drinking-water supplies may contain chloroform as a by-product of chlorination for disinfection purposes. Occupational exposure may occur during the manufacture of chloroform or during one of its uses. Chloroform is used in a number of industries, including building and paperboard industries, iron and steel manufacturing, internal-combustion engine industries, pesticide manufacturing, breweries, dry cleaning, and food processing industries. The Toxic Chemical Release Inventory (USEPA) listed 167 industrial facilities that produced, processed, or otherwise used chloroform in 1988. In compliance with the Community Right-to-Know Program, the facilities reported releases of chloroform to the environment which were estimated to total 23.9 million lb. 7.3.1 Air See above (Section 7.3). 7.3.2 Background Levels Information from 1982 to 1985 reported background level of air over the northern Atlantic Ocean as 2–5 × 10–5 ppm (199); in 1976–1979, 4-4 × 10–5 ppm. Typical median indoor air concentrations range from 2 × 10–4 to 4 × 10–3 ppm (200). The air around swimming pools may contain chloroform in the range of 10–2 ppm (201). Finished drinking water collected in 1988 from 35 sites across the United States contained median concentrations of chloroform ranging from 9.6 to 15 mg/L (202). Chloroform in sediment samples taken in 1980 from 3 passes of a lake in

Louisiana had concentrations ranging from 1.7 to 18 mg/kg (203). Chloroform has been detected in various foods (196). A maximum of 13.8 × 10–3 ppm was found in the air in an activated-sludge wastewater treatment plant (197). Since chloroform is highly volatile and shows little tendency to bioconcentrate or bioaccumulate in higher lifeforms, it is not ordinarily included in the types of persistent pollutants that are the focus of state fish consumption advisory programs. 7.3.3 Workplace Methods NIOSH Method 1003 is recommended for determining workplace exposures to chloroform (11). Numerous analytical methods for determining chloroform are presented in the ATSDR Toxicological Profile for 1998 (10). It is essential to take precautions during sampling, storage, and analysis to avoid loss of chloroform. Methods commonly used in air are based on either adsorption onto a sorbent column followed by thermal or solvent desorption with subsequent analysis using GC or directly from a parcel of air (cryogenic). The disadvantages of the sorption tubes are that sorption and desorption efficiencies may not be 100%, and that the background impurities in the sorbent tubes may limit the detection limit for samples at low concentrations. In addition, storage may limit the detection at low concentrations. 7.3.4 Community Methods: NA 7.3.5 Biomonitoring/Biomarkers Analytical sample procedures for biological matrices are given in the ATSDR profile for 1998 (10). Methods exist for analyzing chloroform in biological matrices, including breath, blood, urine and tissues. None of these methods have been standardized by an organization or federal agency, although a blood method by Ashley et al. (204) was developed at the Center for Disease Control and Prevention. Sample preparation methods are based on headspace analysis, purge-and-trap, or solvent extraction. Sample preparation for breath samples typically utilizes an absorbent followed by thermal desorption or direct analysis of an aliquot of breath. These methods all use gas chromatography with various detection methods as analytical techniques. No metabolite has been identified in the blood or urine that can be considered as a useful guide for evaluating occupational exposure to chloroform at concentrations considered acceptable for occupational exposure. 7.4 Toxic Effects Chloroform is a human poison by ingestion and inhalation, an experimental poison by ingestion and intravenous routes. It is moderately toxic experimentally by intraperitoneal and subcutaneous routes. It is a suspected human carcinogen, an experimental carcinogen, neoplastigen, tumorigen, and teratogen. Much of our toxicological information has been developed because of the interest in chloroform as an anesthetic. The literature is replete with papers on anesthetic potency or liver and kidney injury as measured by changes in some enzyme level or other parameter. Most of these have limited value to the industrial toxicologist or hygienist. The most outstanding effect from acute exposure is CNS depression. High concentrations of chloroform result in narcosis, anesthesia, and death. Responses associated with exposure to concentrations below anesthetic or preanesthetic level are typically inebriation and excitation, passing into narcosis. Vomiting and GI upsets may be observed. Exposure to high concentrations may result in cardiac sensitization to adrenalin and similar compounds, as well as liver and kidney injury. In cases of more chronic or repeated exposure to chloroform, liver injury is most typical in humans. This is not unlike the effect of carbon tetrachloride. Although injury to the kidney is not as common as that to the liver, it may be observed from either acute or chronic exposure. The sperm of mice were reported to be affected in one study, but injury has not been observed in many other studies. Teratogenic effects have not been consistently found but retarded fetal development has occurred in some studies.

Chloroform has at most weak mutagenic potency and the positive results found in some carcinogenic studies appear to be the result of a nongenetic response to organ injury. There appears to be considerable difference in toxic potency between sexes, strains, and species, probably due to differences in the rate of metabolism and other pharmacokinetic parameters. ATSDR has prepared a Toxicological Profile for Chloroform (10), which provides references to much of the pertinent literature. Extensive effort has been spent developing physiologically based pharmacokinetic models which are described in great detail in the ATSDR update. Chloroform is considered to be highly fetotoxic, but not teratogenic (205). 7.4.1 Experimental Studies 7.4.1.1 Acute Toxicity When chloroform was administered to rats and mice, the oral LD50s have been reported to range within 444–2000 mg/kg for rats and 118– 1400 mg/kg for mice (196). Liver and kidney lesions are found at lower dosages. Deaths at high dosages are probably anesthetic, but organ damages related to metabolism caused delayed death at lower dosages. It has been postulated with some supporting evidence that injury to the organs is due to metabolism in each organ and that species, sex, and strain differences are related to the individual organ's ability to metabolize chloroform to phosgene. Because of marked differences in response in mice dosed orally with chloroform in water or in corn oil in lifetime carcinogenic studies, Bull et al. (206) conducted a 90-day study using water and corn oil as diluents. Male and female mice were fed 0, 60, 130, or 270 mg/kg/day chloroform either in 2% Emulphor in water or in corn oil. Much greater toxicity was observed in mice fed the corn oil solutions. Decreased body weight, increased liver weight, liver pathology, and blood enzyme changes were all significantly less in water-treated mice than oil-treated. Slight evidence of toxic stress was evident even at the lowest dosage level, 60 mg/kg/day in corn oil. In a similar but shorter study a no-effect level of 50 mg/kg/day was reported for CD1 mice treated for 14 consecutive days with chloroform in an aqueous solution in Emulphor (207). Thompson et al. fed pregnant rats 20 mg/kg/day (10 doses) without effect on the dams; 50 mg/kg appeared to cause fatty changes (208). These data are discussed in more detail in the section on teratology. Oettel (209) indicated that chloroform was more irritating to the skin and eyes than many other chlorinated solvents. Oettel's conclusions have been confirmed by Torkelson et al. (210). One or two 24 h applications on the skin of rabbits resulted in hyperemia and moderate necrosis. Healing of abraded skin appeared to be delayed by application of a cotton pad soaked in chloroform. Absorption through the intact skin of rabbits occurs as indicated by weight loss and degenerative changes in the kidney tubules, but doses as high as 3980 mg/kg were survived. When the liquid was instilled in the eyes of rabbits, some corneal injury was evident in addition to conjunctivitis. The authors concluded that chloroform was more irritating to rabbit skin and eyes than many common organic solvents tested by the same technique in their laboratory. 7.4.1.2 Chronic and Subchronic Toxicity Major target organs for chloroform are the liver, kidney, and CNS for both humans an animals. Chloroform-induced hepatotoxicity in various animal species has been reported in several studies. Despite its long usage, few reports of histological examination following repeated exposure of laboratory animals are available. Repeated 7 h exposures 5 days/week for 6 months to either 85, 50, or 25 ppm of the vapor of chloroform resulted in adverse effects in all or some of the species studied, rats, rabbits, guinea pigs, or dogs. The effects of 25 ppm were slight and reversible. Rats exposed 4, 2, or 1 h/day were not adversely affected. Cloudy swelling of the kidneys and centrilobular granular degeneration and necrosis of the liver were the principal adverse effects (210). The paper by Heywood et al. (211) describes beagle dogs that were administered chloroform in a

toothpaste base [0.5 mL of toothpaste base/kg/day] in gelatin capsules. A control group composed of 16 males and 16 females received the vehicle, and additional control groups of eight animals/sex were administered an alternative toothpaste or were left untreated. Experimental groups of eight male and eight female dogs received 15 or 30 mg chloroform/kg/day for 6 days/week. Treatment was continued for 7.5 years. Fatty cysts, considered to be treatment-related, were observed in livers of some dogs in both treatment groups. Nodules of altered hepatocytes were considered treatmentrelated but not dose-dependent. A dose-related increase in SGPT levels was noted and a less marked increase in SGOT was noted in the high dose animals. The LOAEL was determined to be 12.9 mg/kg/day, and an RfD was set at 0.01 mg/kg/day. 7.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms The metabolism of chloroform is well understood. Approximately 50% of an oral dose of 0.5 g was metabolized to carbon dioxide in humans (212). Metabolism was dose-dependent, decreasing with higher exposure. Approximatly 38% of the dose was converted in the liver, and < 17% was exhaled unchanged from the lungs before reaching the systemic circulation. Metabolism studies indicated that chloroform was, in part, exhaled from the lungs or was converted by oxidative dehydrochlorination of its carbon–hydrogen bond to form phosgene (213). This reaction was mediated by cytochrome P450 and was observed in the liver and kidneys (214). Covalent binding of chloroform to lipids can occur under anaeroic and aerobic conditions, binding to protein occurs only under aerobic conditions (215). Chloroform can induce lipid peroxidation and inactivation of cytochrome P450 in rat liver microsomes under anaerobic conditions (216). Evidence that chloroform is metabolized at its carbon–hydrogen bond is provided by experiments using the deuterated derivative (217). 7.4.1.4 Reproductive and Developmental Several studies indicate that inhalation exposure to chloroform may cause reproductive effects in animals (205). Studies by Bader and Hofmann (218) indicated that exposure to as little as 30 ppm chloroform resulted in increased fetal resorptions. A significant increase in the percentage of abnormal sperm was observed in mice exposed to 400 ppm for 5 days (219). Chloroform-induced fetotoxicity and teratogenicity were observed in experimental animals (220). The effect of inhaled chloroform on embryonal and fetal development was evaluated in CF1 mice. Pregnant mice were exposed to 0 or 100 ppm of chloroform for 7 h/day on days 6–15, 1–7, or 8–15 of gestation. Exposure to chloroform on days 6–15 or 1–7 produced a significant decrease in the incidence of pregnancy but did not cause significant teratogenicity. In comparison a significant increase in the incidence of cleft palate was observed among the offspring of mice inhaling chloroform on days 8–15 of gestation, but no effect on the incidence of pregnancy was discerned. A significant increase in SGPT activity was observed in mice exposed to chloroform on days 6–15 of gestation; among the mice exposed to chloroform, nonpregnant bred mice had a significantly higher SGPT activity than did pregnant bred mice. Different results were reported by Dilley et al. (221), who exposed pregnant rats to 20.1 mg/L of chloroform vapor (duration of daily exposure not stated) and produced fetal mortality and decreased fetal weight but no teratological effects. Thompson et al. (208) also failed to produce teratogenic effects in Sprague–Dawley rats by intubation of 0, 30, 50, or 126 mg/kg/day or in Dutch, Belted rabbits given daily doses of 0, 20, 35, or 50 mg/kg. These authors state: “The occurrence of anorexia and weight gain suppression in dams of both species, as well as subclinical nephrosis in the rat and hepatotoxicity in the rabbit, indicated that maximum tolerated doses of chloroform were used. Fetotoxicity in the form of reduced birth weights was observed at the highest dose level in both species. There was no evidence of teratogenicity in either species at any dose tested.” It appears that chloroform has more fetotoxic effect when inhaled than when given by gavage. Thompson et al. (208) speculate that doses given by gavage may result in different blood levels of chloroform, which account for the apparent discrepancy with the effects seen on inhalation. Given the pronounced effect of corn oil on carcinogenic response, it is quite possible that route of exposure might greatly influence reproductive response.

Burkhalter and Balster (222) found no difference in reproductive parameters in control and male and female mice repeatedly gavaged with vehicle (Emulphor-saline) or chloroform. The daily dosage of 31.1 mg/kg was given to both males and females for 21 days prior to mating and throughout mating, and to the dams through gestation and lactation. Pups were dosed beginning on days 7–21. Ruddick et al. (223) treated pregnant rats and rabbits with 200 or 400 mg/kg/day. Fetal weight of only the 400-mg/kg/day rat pups was reduced. Other parameters were unaffected. 7.4.1.5 Carcinogenesis The USEPA classifies chloroform as B2, Probable human carcinogen based on increased incidence of several tumor types in rats and three strains of mice. Chloroform has been tested for carcinogenicity in eight strains of mice, two strains of rats and in beagle dogs. USEPA derived a q1* of 8 × 10–2 [mg/kg/day]–1 for inhalation exposure to chloroform based on mouse liver tumor data from a chronic gavage study (1976 IRIS). In a gavage bioassay Osborne– Mendel rats and B6C3F1 mice were treated with chloroform in corn oil 5 times/week for 78 weeks. On a daily basis, 50 male rats received 90 or 125 mg/kg; females initially were treated with 125 or 250 mg/kg for 22 weeks and 90 or 180 mg/kg thereafter. Male mice received 100 or 200/mg/kg, raised to 150 or 300 mg/kg at 18 weeks; females were dosed with 200 or 400 mg/kg, raised to 250 or 500 mg/kg. A significant increase in kidney epithelial tumors was observed in male rats and highly significant increases in hepatocellular carcinomas in mice of both sexes. Liver nodular hyperplasia was observed in low dose male mice not developing hepatocellular carcinoma. Hepatomas have also developed in female strain A mice and NLC mice gavaged with chloroform (224, 225). In 1985 Jorgenson et al. (226) administered chloroform (pesticide quality and distilled) in drinking water to male Osborne–Mendel rats and female B6C3F1 mice at concentrations of 200, 400, 900, and 1800 mg/L for 104 weeks. These concentrations were reported by the author to correspond to daily dosages of 19, 38, 81, and 160 mg/kg for rats and 34, 65, 130, and 263 mg/kg for mice. A significant increase in renal tumors in rats was observed in the highest dose group. The increase was dose-related. The liver tumor incidence in female mice was not significantly increased. This study was specifically designed to measure the effects of low doses of chloroform. 7.4.1.6 Genetic and Related Cellular Effects Studies Very mixed results have resulted from mutagenic studies (227). Chloroform is, at most, a weak mutagen and not likely to be of concern at concentrations considered acceptable for industrial exposure. This conclusion is supported by the low level of binding of chloroform to DNA. The majority of tests for genotoxicity of chloroform have been negative. These negative findings include covalent binding to DNA, mutation in Salmonella, a Drosophila sex-linked recessive, tests for DNA damage in a micronucleus test, and transformation of BHK cells. By contrast, one study demonstrated binding of radiolabeled chloroform to calf thymus DNA following metabolism by rat liver microsomes (228). Chloroform caused mitotic recombination in Saccharomyces (160) and sister chromatid exchange (SCE) in cultured human lymphocytes and in mouse bone marrow cells exposed in vivo (229). The carcinogenicity of chloroform may be a function of its metabolism to phosgene, which is known to crosslink DNA. A host-mediated assay using mice indicated that chloroform was metabolized in vivo to a form mutagenic to Salmonella strain TA1537. Likewise, urine extracts from chloroformtreated mice were mutagenic (230). Chloroform administered to mice in drinking water promoted growth and metastasis of Ehrlich ascites cells injected intraperitoneally (IP) (231). Inhalation of 400 ppm chloroform for 5 days increased the percentage of abnormal sperm in mice (219). 7.4.2 Human Experience 7.4.2.1 General Information The NTP DataBase indicates the following: Symptoms of exposure to this compound include nausea, vomiting, eye and skin irritation, unconsciousness, and death. Other symptoms include drowsiness, giddiness, headache, anesthesia, and conjunctivitis. Central nervous system depression may occur. Respiratory failure may also

occur. Exposure may cause lassitude, digestive disturbances, dizziness, and mental dullness. It may also cause coma and an enlarged liver. Other symptoms include hepatotoxicity, nephrotoxicity, reduced cardiac output, cardiac arrhythmias, and abdominal pain. It may also cause cardiac sensitization, GI upset, sensation of fainting, salivation, intracranial pressure, and fatigue. Severe anoxia has been reported. Exposure may lead to chest pain, serious disorientation, hepatomegaly, and, in high concentrations, blepharospasm. It may also lead to ventricular tachycardia, bradycardia, necrosis and hepatomas of the liver, cardiovascular depression, and ventricular fibrillation. Irritation of the upper respiratory tract, nervous system disturbances, and renal or cardiac damage may also occur. Nervous aberrations and profound toxemia may follow exposure. Inhalation may cause hallucinations, distorted perceptions, unspecified gastrointestinal effects, dilation of the pupils, reduced reaction to light, reduced intraocular pressure, feelings of warmth of the face and body, irritation of the mucous membranes, excitation, motor disturbances or loss of reflexes, and loss of sensation. Prolonged inhalation may cause paralysis followed by cardiac respiratory failure. Other symptoms of exposure via inhalation include irritation of the nose and throat, drunkenness, and narcosis. Inhalation of large doses may result in hypotension, respiratory depression, and myocardial depression. Inhalation or ingestion of this compound may cause cardiac irregularities, cardiac arrest, convulsions, reduced blood pressure, and uncontrollable hyperthermia (rare). Ingestion may cause burning of the throat and mouth. Skin contact may result in smarting and reddening. Prolonged skin contact may result in burns. Prolonged or repeated skin contact may cause dermatitis through defatting of the skin. Eye contact may cause immediate burning pain, tearing, reddening of the conjunctiva, and injury of the corneal epithelium. Chronic exposure may result in jaundice, cirrhosis and damage of the liver, and kidney damage. Alcoholics seem to be affected sooner and more severely. In humans, chloroform affects the central nervous system, liver, and kidneys. Breathing about 900 ppm in air for a short time causes fatigue, dizziness, and headache. Consuming elevated levels in food can damage liver and kidneys. Large amounts can cause sores on the skin. Considering the long history of chloroform, there is surprisingly little clinical literature on chronic exposure. There have been almost no quantitative toxicological studies of the response from chronic exposure of humans to chloroform. An attempt to study “causes of death of anesthesiologists from the chloroform era” was limited to too few cases to draw conclusions and certainly did not quantitate exposure (232). Challen et al. (233) studied an industrial operation where chloroform was being used. Groups exposed to concentrations varying between 77 and 237 ppm exhibited definite symptoms. Apparently, there were also some high peak concentrations for very short periods of time. Symptoms were GI distress and depression. Another group with shorter service was exposed to concentrations of 21–71 ppm. They also showed symptoms of comparable nature. Tests of both groups were made to determine possible liver injury, but none were found. It should be remembered, however, that liver function tests are often insensitive to anything except severe liver injury. It is quite possible, as indicated by these authors, that there may have been mild liver injury in these cases. The recommendation of these authors that atmospheric exposure should be kept well below 50 ppm is entirely in order. Humans are exposed to small amounts of chloroform in drinking water and in beverages made using water that contains chloroform. The amount of chloroform expected to be in air ranges of 0.02– 0.05 ppb of air and 2–44 ppb in treated drinking water. The average amount of chloroform that a human may be exposed on a typical day from breathing ranges from 2–5 mg in rural areas to 200 mg in cities to 2200 mg in areas near major sources (10). 7.4.2.2 Clinical Cases See above (Section 7.4.2). 7.4.2.2.1 Acute Toxicity The human lethal dose is 10 mL; the IDLH value is 1000 ppm. Humans and animals can withstand very high concentrations of chloroform for a short period of

time. Table 62.2, adapted from Lehmann and Flury, gives indications of the response to be expected in humans (136). The response to acute exposures has been indicated in the summary as CNS depression, liver and kidney injury, and possible cardiac sensitization. At the levels of exposure currently considered acceptable for industrial workers, anesthesia and cardiac sensitization are not of practical concern. Table 62.2. Physiological Response to Various Concentrations of Chloroform in Humans Concentration

mg/L

ppm

Response

70–80 14,336–16,384 Narcotic limiting concentration 20 4096 Vomiting, sensation of fainting 7.2 1475 Dizziness and salivation after a few minutes 5 1024 Dizziness, intracranial pressure, and nausea after 7 min 5 1024 Definite after effects; fatigue and headache still felt later 1.9 389 Endured for 30 min without complaint 1–1.5 205–307 Lowest amount that can be detected by smell

It has been reported that exposures to 40,000 ppm may be lethal unless brief and that surgical anesthesia required 10,000–20,000 ppm. These concentrations and those listed in the table must be used cautiously because the data are old and in many cases involved other drugs during surgery. 7.4.2.2.2 Chronic and Subchronic Toxicity Several studies show kidney toxicity in humans after inhalation exposure. The liver is a primary target of chloroform toxicity in humans. 7.4.2.2.3 Pharmacokinetics, Metabolism, and Mechanisms Chloroform enters the body by skin contact or breathing contaminated air and quickly enters the blood from lungs or intestines. Chloroform usually collects in body fat, but its volatility ensures that it will eventually be removed once the exposure has been removed. Some of the chloroform leaves unchanged and some is broken down. 7.4.2.2.4 Reproductive and Developmental Whether chloroform has caused harmful reproductive effects or birth defects has not been determined. 7.4.2.2.5 Carcinogenesis The USEPA considers the information Inadequate with regard to human carcinogenesis. There are no epidemiological studies of chloroform itself. Chloroform and other trihalomethanes are formed from the interaction of chlorine with organic material found in water. Several ecological and case-control studies of populations consuming chlorinated drinking water in which chloroform was the major chlorinated organic show small significant increases in the risk of rectal, bladder, or colon cancer on an intermittent basis. Many other suspected carcinogens were also present in these water supplies. There is a possible link between drinking chlorinated water and colon and urinary bladder cancer. However, it is not determined if liver and kidney cancer would develop after long-term exposure in drinking water. The Department of Health and Human Services (DHHS) has determined that

chloroform may reasonably to anticipated to be a carcinogen. IARC has determined that chloroform is possibly carcinogenic to humans (class 2B). The USEPA has determined that chloroform is a probably human carcinogen. An IARC Working Group considered the evidence for the carcinogenicity of chloroform in humans to be inadequate. Several epidemiological and ecological studies indicate that there is an association between cancer of the large intestine, rectum, and/or urinary bladder and the constituents of chlorinated water. Although data may suggest a possible increased risk of cancer from exposure to chloroform in chlorinated drinking water, the data are insufficient to evaluate the carcinogenic potential of chloroform. 7.4.2.2.6 Genetic and Related Cellular Effects Studies See Section 7.4.2.2.5. 7.4.2.2.7 Other: Neurological, Pulmonary, Skin Sensitization, etc The CNS is a major target for chloroform toxicity in humans and in animals. Once widely used as an anesthetic for humans, levels of 3000–30,000 ppm were reached. A concentration of approx. 40,000 ppm over several minutes can cause death. Dizziness and vertigo were observed in humans after exposure to 920 ppm chloroform for 3 min; headache and slight intoxication occurred at higher concentrations. 7.4.2.3 Epidemiology Studies Most of the data regarding inhalation exposure in humans were obtained from clinical reports describing health effects under anesthesia. 7.4.2.3.1 Acute Toxicity See above (Section 7.4.2.3). 7.4.2.3.2 Chronic and Subchronic Toxicity Chloroform-induced hepatotoxicity is one of the major toxic effects observed in both humans and animals after inhalation exposure. Workers exposed to 14–400 ppm chloroform for 1–6 months developed toxic hepatitis and other effects, including jaundice, nausea, and vomiting without fever. In contrast, toxic hepatitis was observed in workers exposed to 2-205 ppm. 7.4.2.3.4 Reproductive and Developmental No studies show reproductive effects or developmental effects in humans after inhalation exposure. 7.4.2.3.5 Carcinogenesis No studies were located regarding cancer in humans or animals after inhalation exposure. Epidemiological studies suggest an association between cancer in humans and the consumption of chlorinated drinking water, but the results are not conclusive at this time. Many confounding effects in these studies are still unaccounted for. The studies dif-fered regarding the type of cancer associated with consumption of chlorinated water. Confounding factors include the presence of other trihalomethanes, haloacetic acids, halo-acetonitriles, halogenated aldehydes, ketones and furanones, and chlorine. Overall, the human data are insufficient to support a conclusion regarding carcinogenicity in humans. 7.4.2.3.6 Genetic and Related Cellular Effects Studies No studies indicated genotoxic effects in humans after inhalation studies. 7.4.2.3.7 Other: Neurological, Pulmonary, Skin Sensitization, etc Epidemiological studies indicate that chloroform can cause cardiac effects in patients under anesthesia. 7.5 Standards, Regulations, or Guidelines of Exposure NIOSH recognizes chloroform as a carcinogen, and recommends a STEL of 2 ppm; ACGIH, TLV TWA is 10 ppm, with an A3 designation. OSHA has a ceiling limit of 50 ppm. WHO has a drinking water guideline of 30 mg/L.

IARC classifies chloroform as a group 2B (possibly carcinogenic to humans, and EPA as a B2, probable human carcinogen The NTP database gives the following information. EPA regulates chloroform under the Clean Water Act (CWA), Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), Food, Drug, and Cosmetic Act (FD&CA), Resource Conservation and Recovery Act (RCRA), Safe Drinking Water Act (SDWA), and Superfund Amendments and Reauthorization Act (SARA). Chloroform is a toxic pollutant of air and water. EPA has established water-quality criteria for chloroform, effluent guidelines, rules for regulating hazardous spills, general threshold amounts, and requirements for handling and disposal of chloroform wastes. A reportable quantity (RQ) of 10 lb has been established for chloroform under CERCLA and CWA. Chloroform is exempted under FD&CA from tolerances for pesticide chemicals. Chloroform is recognized as an inert ingredient of toxicological concern under FD&CA. A rebuttable presumption against registration of chloroform-containing pesticides has been issued under FIFRA. Chloroform is regulated as a hazardous constituent of waste under RCRA. USEPA requires removal of chloroform from drinking water and establishes a maximum contaminant level (MCL) of 100 mg/L under SDWA. Under EPCRA, EPA identifies chloroform as an extremely hazardous substance and established a threshold planning quantity (TPQ) of 10,000 lb for chloroform. FDA regulates chloroform as an indirect food additive for adhesive components in food packaging materials and as a component of materials that come into contact with food. The use of chloroform in food, drugs (for both humans and animals), and cosmetics for use in cough preparations, liniments, cosmetics, and toothache drops is banned under the Federal Food, Drug, and Cosmetic Act 7.6 Studies on Environmental Impact: NA

Saturated Methyl Halogenated Aliphatic Hydrocarbons Jon B. Reid, Ph.D., DABT 8.0 Bromoform 8.0.1 CAS Number: [75-25-2] 8.0.2 Synonyms: Methenyl tribromide, tribromomethane; methyl tribromide 8.0.3 Trade Names: NCI-C55130, RCRA Waste Number U225, UN 2515 8.0.4 Molecular Weight: 252.73 8.0.5 Molecular Formula: CHBr3 8.0.6 Molecular Structure:

8.1 Chemical and Physical Properties 8.1.1 General Bromoform is a colorless, nonflammable, heavy liquid, similar to chloroform in odor

and taste. Physical state Colorless liquid Specific gravity 2.890 (20/4°C) Melting point 9°C Boiling point 149.5°C Vapor pressure 5 torr at 20°C Refractive index 1.5980 (19°C) Percent in “saturated” air 0.7 (25°C) Solubility 0.3 g/100 mL water at 30°C; soluble in ethanol, ethyl ether, benzene Flammability Not flammable by standard tests in air 1 mg/L = 97 ppm and 1 ppm = 10.34 mg/m3 at 25°C, 760 torr 8.1.2 Odor and Warning Properties Bromoform has a sweetish, chloroformlike odor but odor should not be considered as a warning property. 8.2 Production and Use Bromoform has quite limited use as a chemical intermediate. It was formerly used as an antiseptic and sedative. It is formed during the chlorination of certain water supplies and sewage. It is also used to make high density liquids for geologic analysis and in the shipbuilding and aircraft industries. 8.3 Exposure Assessment Bromoform may be absorbed through the lungs, from the GI tract, and, to a certain extent, through the skin. The brain contains higher concentrations of bromoform than blood and liver following inhalation (234). After oral administration, bromoform is rapidly absorbed. Gastrointestinal absorption following oral exposure has been estimated to be 60–90% complete following a single gavage dose; this percentage of the administered dose was recovered in the expired air, in urine, or in the tissues (235). Tribromomethane has been identified as a drinking-water contaminant resulting from water chlorination. 8.3.3 Workplace Methods NIOSH Analytical Method 1003 is recommended for determining workplace exposures to bromoform (11). 8.3.4 Community Methods: NA 8.3.5 Biomonitoring/Biomarkers Blood bromide might be useful in monitoring exposure to bromoform, but at this time data are inadequate to quantitate exposure. 8.4 Toxic Effects This compound is a lacrimator. It can damage the liver to a serious degree and cause death. It is an irritant of the skin, eyes and respiratory tract and has narcotic effects. When heated to decomposition it emits toxic fumes of bromine. It may be absorbed through the skin. Bromoform causes anesthesia and sedation in animals that may take days for recovery following treatment. The health effects of exposure to tribromomethane have been reviewed (236). In the early 1900s, tribromomethane was administered as a sedative to children suffering from whooping cough, and several deaths resulted from accidental overdoses (59, pp. 65–67). The most obvious clinical sign in these fatal cases was profound CNS depression that was manifested as unconsciousness, stupor, and loss of reflexes. Death was usually the result of respiratory failure. These case reports are of limited value because doses were not quantified; however, the doses were likely in the range of 20–40 drops (150–300 mg/kg) daily. Very limited industrial experience is reported for bromoform. Data from studies in animals indicate pronounced CNS effects, moderate acute and chronic liver and kidney toxicity, and a probably carcinogenic response in rats but not mice. An ATSDR review is available (237).

8.4.1 Experimental Studies The principal cause of death in laboratory animals following acute oral exposure to tribromomethane is CNS depression (238). Moody and Smuckler (239) exposed Sprague–Dawley rats (n = 3) to single-gavage doses of 1000 mg/kg tribromomethane and observed significant reductions in the liver microsomal cytochrome P450 content and aminolevulinic acid– dehydratase activity and increases in porphyrin and glutathione content. These effects suggest disturbances in hepatic heme metabolism, because porphyrins are major intermediates in heme synthesis. Chu et al. (240) reported that female rats were more sensitive than male rats to lethal doses of tribromomethane based on LD50 values of 1388 and 1147 for males and females, respectively. 8.4.1.1 Acute Toxicity Dogs were exposed to an atmosphere of bromoform at 7000 ppm. The dogs were deeply anesthetized after 8 min and died after a 1 h exposure (241). An inhalation LCLo of 4500 mg/m3 for the rat from a 4 h exposure to bromoform has been reported (242). Results of subcutaneous administration have been reported. An LD50 of 1820 mg/kg for the mouse was reported by Kutob and Plaa. (243). Narcosis and hepatotoxic effects were observed. Undiluted bromoform was moderately irritating to rabbit eyes, but healing was complete in 1–2 days. Repeated skin contact caused moderate irritation to rabbit skin (244). 8.4.1.2 Chronic and Subchronic Toxicity The results of 2-year gavage study are discussed in the section on carcinogenicity (245). Low-level inhalation exposure of humans to tribromomethane results in irritation, lacrimation, and reddening of the face, suggesting the potential for portal-of-entry effects. The information available on inhalation exposure in laboratory animals comes primarily from older studies that employed high concentrations for short durations. In these studies, the CNS, liver, and kidney are major target organs following acute inhalation exposures. Exposure to tribromomethane vapors may also cause irritation to the respiratory tract and lacrimation (59, pp. 65–67). In another study, 10 F344/N rats/sex were gavaged with 0, 12, 25, 50, 100, or 200 mg/kg bromoform and 10 B6C3F1 mice/sex were gavaged with 0, 25, 50, 100, 200, or 400 mg/kg bromoform 5 days/week for 13 weeks. Complete histology was conducted on high dose and vehicle control groups of both species. Liver histology was conducted on all rats and on male mice receiving doses of > 100 mg/kg. Females of both species did not show any chemically-related effects. A decrease in body weight of both sexes of mice was reported, but was not dose-related. The male mice showed fatty metamorphosis of the liver at doses of 200 and 400 mg/kg. The only effect reported for male rats was a dose-related increase in clear cell foci of the liver. A Fisher Exact Test showed that the incidence of the clear cell foci at doses of 50 mg/kg (the LOAEL) or above was statistically elevated relative to the vehicle control (p = .035); therefore, 25 mg/kg is the NOEL for F344/N rats (246). The health effects data for bromoform (tribromomethane) were reviewed by the USEPA RfD/RfC Work Group (5) and determined to be inadequate for the derivation of an inhalation RfC. The verification status for this chemical is currently “Not verifiable.” The only studies of subchronic-duration inhalation exposure are reported in abstracts that do not provide sufficient detail for critical evaluation. Tribromomethane had a narcotic effect on rabbits administered single inhalation exposures of 1064–1741 ppm tribromomethane (188). Rats administered 240 ppm tribromomethane vapor for 10 days developed CNS effects and dystrophic and vascular alterations of the liver and kidney (188). Vapor concentrations of 24 ppm for 2 months also induced hepatic disorders, characterized by decreased blood clotting and impaired glycogenesis, and altered renal filtration capacity (189). A concentration of 4.8 ppm tribromomethane in rats did not elicit any adverse effects in rats after 2 months of exposure (188). These reports provide no details regarding exposure generation or characterization, specific effect measures, or results and are

inadequate for derivation of an RfC. Studies of 14–90 days' duration in rats and mice exposed by gavage have reported liver, kidney, and thyroid effects, as well as transient lethargy at high concentrations (207, 246). In the NTP (246) study, the incidences of hepatocyte vacuolization in male rats were 3/10, 6/10, 5/10, 8/10, 8/10, and 10/10 for the control, 12, 25, 50, 100, and 200 mg/kg groups, respectively. In mice, 5/10 male mice that received 200 mg/kg and 8/10 male mice that received 400 mg/kg tribromomethane developed cytoplasmic vacuolization. This dose-related, minimal-to-moderate change involved only a few cells or was diffuse. Behavioral effects (decreased response rate in an operant-conditioning test) were also reported in mice treated by gavage with 100 or 400 mg/kg daily for 60 days (247). A 2-year chronic gavage bioassay was conducted in F344/N rats and B6C3F1 mice (50/sex/group), in which doses of 0, 100, or 200 mg/kg (rats and female mice) or 0, 50, or 100 mg/kg (male mice) dibromomethane were administered 5 days/week for 103 weeks (246). In the high dose rats (both sexes), mean body weights were significantly (10–28%) lower than controls throughout the second year of the study. Survival of the male rats administered 200 mg/kg was significantly reduced (p < .001) after week 91. Dose-related lethargy was observed in male and female rats. Nonneoplastic changes, including fatty change and scattered minimal necrosis (males) and mixed-cell foci (females), occurred in the liver of treated rats. The incidence of focal or diffuse fatty change in both sexes was increased (males—23/50, 49/50, and 50/50; females—19/50, 39/50, and 46/50). The lowest daily dose tested in this bioassay (100 mg/kg) induced effects on the liver, salivary gland, prostate gland, lungs, and forestomach, and thus is considered a LOAEL for rats. High dose female mice developed an increased incidence of follicular cell hyperplasia of the thyroid gland (5/49, 4/49, and 19/47). Female mice in both groups exhibited increased incidences of minimal-to-mild fatty change of the liver consisting of scattered hepatocyte foci with vacuolated cytoplasm (1/49, 9/50, and 24/50). Thus, 100 mg/kg also is considered a LOAEL for liver changes in female mice. The database for tribromomethane is inadequate for the derivation of an RfC. No chronic or subchronic inhalation studies on tribromomethane, and no reproductive or developmental studies that employed an inhalation exposure regimen were found. The toxicokinetic data for the inhalation route are insufficient for route-to-route extrapolation from oral data, and the potential for portal-of-entry respiratory tract toxicity has not been adequately characterized. 8.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms The metabolism of tribromomethane is similar to the metabolism of other trihalomethanes (248, 249). Protein synthesis and lipid peroxidation were evaluated in rat liver slices in the presence of oxidants and protein synthesis inhibitors (2, 3). The ability of carbon tetrabromide (and several other halogenated compounds) to inhibit protein synthesis was correlated with its ability to induce lipid peroxidation and was also correlated with their toxicity as indicated by the LD50. 8.4.1.4 Reproductive and Developmental Developmental effects were monitored following gavage administration of 50, 100, or 200 mg/kg/day tribromomethane to pregnant Sprague–Dawley rats (15/group) from days 6–15 of gestation (223). Slight increases in several skeletal anomalies were observed in treated animals and, to a lesser extent, in controls. No other significant maternal toxicity, fetotoxicity, or teratogenicity was observed. In a reproductive study, effects of tribromomethane were assessed in Swiss CD1 mice (n = 17– 20/group) exposed by gavage to 0, 50, 100, or 200 mg/kg/day (250). Postnatal survival was significantly decreased in the 200-mg/kg/day group. No other reproductive effects were seen in the F1 or F2 generations. The reproductive toxicology has recently been reviewed in Environmental Health Perspectives (251).

8.4.1.5 Carcinogenesis The USEPA classification is B2, Probable human carcinogen on the basis of inadequate human data and sufficient evidence of carcinogenicity in animals, (viz., an increased incidence of tumors after oral administration of bromoform in rats and IP administration in mice). Bromoform is genotoxic in several assay systems. Also, bromoform is structurally related to other trihalomethanes (e.g., chloroform, bromodichloromethane, dibromochloromethane) that have been verified as either probable or possible carcinogens. The USEPA considers the animal information “sufficient.” Bromoform has been tested for carcinogenicity in two species, rat and mouse (245), by oral or intraperitoneal administration (252). In a gavage study (245), F344/N rats (50/sex/group) and B6C3F1 mice (50/sex/group) were administered bromoform in corn oil by gavage 5 days/week for 2 years at 0, 100, or 200 mg/kg (rats and female mice) or 0, 50, or 100 mg/kg (male mice). Decreased body weight and survival in rats and female mice suggest that the MTD was reached. In male rats, mean body weight was decreased in the high and low dose groups by 12–28% and 5–14%, respectively. Survival was significantly lower in the high-dose males after week 91. In female rats, body weight was decreased in the high dose group by 10–25%. In male mice, body weight and survival were comparable to controls. In female mice, however, body weight was decreased in the high and low dose groups by 5–16% and 6–11%, respectively; survival was significantly lower in both dose groups after week 77. Neoplastic lesions (adenomatous polyps or adenocarcinomas) were observed in the large intestine (colon or rectum) of male rats (0/50, 0/50, 3/50) and female rats (0/50, 1/50, 8/50). Adenocarcinomas alone were not significantly increased compared with controls. The reduced survival of male rats in the high dose group may account for the lower incidence of lesions in this group. No treatment-related tumors were observed in mice at either dose level. Under the conditions of this study, the NTP judged that there was clear evidence of carcinogenicity for female rats, some evidence of carcinogenicity for male rats, and no evidence of carcinogenicity for male and female mice. Theiss et al. (252) administered bromoform by IP injection to male A/St mice (20/group). Doses of 100, 48, and 4 mg/kg were given 3 times/week for a total of 24, 23, or 18 injections, respectively. Mice in the control group received 24 IP injections of the vehicle, tricaprylin. Animals were sacrificed 24 weeks after the first injection and the lungs were examined for surface adenomas. Some surface nodules were examined histologically to confirm the morphological appearance of adenomas. The number of lung tumors/mouse for the control, low, mid, and high dose groups were 0.27, 0.53, 1.13, and 0.67, respectively. Only the ratio of the middose group was statistically significantly elevated over that of controls. In a feeding study with microencapsulated bromoform, Kurokawa (253) observed no evidence of carcinogenicity in male or female Wistar rats exposed for 24 months at concentrations of 400, 1600, or 6500 ppm. 8.4.1.6 Genetic and Related Cellular Effects Studies Bromoform is not strongly mutagenic but positive results have been observed. Pereira et al. (254, 255) determined that bromoform did not induce GGTase-positive foci in the rat liver at 1 mM (253 mg/kg) or 0.8 mM (202 mg/kg) following a 2/3 hepatectomy and promotion with phenobarbital. However, Pereira found that bromoform is a potent inducer of ornithine decarboxylase, which is an indication of tumor promotion activity in the skin and liver. Bromoform has been shown to produce mutations in Salmonella typhimurium strains TA97, TA98, TA100, and TA1535 with and without rat hepatic homogenates (245). Bromoform also produces mutations at the TK locus in mouse cells (245); SCE induction in Chinese hamster ovary cells, human lymphocytes (in vitro) and mouse bone marrow cells (in vivo) (245); chromosomal aberrations in Chinese hamster ovary (CHO) cells (256); cell cycle delay in human lymphocytes (229); and an increased incidence of micronuclei in bone marrow erythrocytes from mice given

bromoform IP (245). 8.4.1.7 Other: Neurological, Pulmonary, Skin Sensitization The undiluted liquid was moderately irritating to rabbit eyes, but healing appeared complete in 1–2 days. It was only moderately irritating to rabbit skin even on repeated contact. Single doses of 2000 mg/kg under a cuff on the intact skin of rabbits were survived by two rabbits treated with undiluted bromoform. Lethargy and slight weight loss were noted from these 24 h applications. 8.4.2 Human Experience Exposure to bromoform vapor is reported to have caused irritation of the respiratory tract, pharynx, and larynx, as well as lacrimation and salivation. Accidental ingestion of the liquid has produced CNS depression with coma and loss of reflexes; smaller doses have led to listlessness, headache, and vertigo (59, pp. 65–67). 8.4.2.1 General Information Symptoms of exposure to this compound may include irritation of the eyes, skin, and respiratory tract. Ingestion may cause respiratory difficulties, tremors, and unconsciousness. Dizziness, disorientation, slurred speech, and death may also result from ingestion. Inhalation may be fatal as a result of spasm, inflammation, and edema of the larynx and bronchi; chemical pneumonitis; and pulmonary edema. Other symptoms may include liver and kidney damage and CNS depression. Inhalation may cause irritation of the respiratory tract, pharynx, and larynx, producing lacrimation and salivation. It can also cause skin and eye irritation. Repeated or prolonged contact may cause dermatitis. Much of the experience in poisoning cases in humans has been from the oral administration of the material. This was summarized by von Oettingen in 1955 (59, pp. 65–67) and ATSDR in 1990 (237). Anesthesia including respiratory failure has been reported. It has been speculated that an oral dose of 250–500 mg/kg may be lethal to a child, with death be due to CNS depression. 8.4.2.2.5 Carcinogenesis The USEPA considers the information with regard to human carcinogenicity as “inadequate.” Cantor et al. (257) suggest a positive correlation between levels of trihalomethane in drinking water and the incidence of several human cancers. Additional geographic studies of bromoform indicate that there may be an association between the levels of trihalomethanes in drinking water and the incidence of bladder, colon, rectal, or pancreatic cancer in humans. However, the information from these studies is considered incomplete and preliminary because their designs do not permit consideration of several possible variables that may be involved (e.g., personal habits, information on residential histories, and previous exposures) (245). 8.5 Standards, Regulations, or Guidelines of Exposure Bromoform exposure limits (TWAs) are as follows: NIOSH/OSHA 0.5 ppm; NIOSH IDLH 850 ppm. The ACGIH recommendation (8) is as follows. Because of its irritant qualities and reported skin absorption, in addition to its potential to cause liver damage and by analogy to related bromine compounds, a TLV TWA of 0.5 ppm, with a skin notation, is recommended for bromoform. At this time, no STEL is recommended until additional toxicological data and industrial hygiene experience become available to provide a better base for quantifying on a toxicological basis what the STEL should be. The reader is encouraged to review the section on excursion limits in the “Introduction to the Chemical Substances” of the current TLV/BEI booklet for guidance and control of excursions above the TLV TWA, even when the 8-h TWA is within the recommended limits. In light of the recent reports on the genotoxicity and carcinogenicity of bromoform, this substance is under review by the TLV Committee. 8.6 Studies on Environmental Impact: NA

Saturated Methyl Halogenated Aliphatic Hydrocarbons Jon B. Reid, Ph.D., DABT 9.0 Iodoform 9.0.1 CAS Number: [75-47-8] 9.0.2 Synonyms: Triiodomethane jodoform (Czech); methane, triiodo-; NCI-C04568; triiodomethane; trijodmethane (Czech) 9.0.3 Trade Names: NA 9.0.4 Molecular Weight: 393.78 9.0.5 Molecular Formula: CHI3 9.0.6 Molecular Structure:

9.1 Chemical and Physical Properties Iodoform is a yellow or greenish-yellow powder or crystalline solid that is volatile with steam and contains 96.69% iodine. It has a very characteristic pungent odor. An odor threshold of 0.005 ppm has been reported. 9.1.1 General Physical state Yellow solid Specific gravity 4.008 (20.4°C) Melting point 119°C Flammability Not flammable by standard tests in air Boiling point 210°C, sublimates, explodes Refractive index 1.800 (20°C) Solubility 0.01 g/100 mL water at 25°C UEL, LEL Not available 1 mg/L = 62.1 ppm and 1 ppm = 16.1 mg/m3 at 25°C, 760 torr 9.2 Production and Use Iodoform has limited use as a chemical intermediate and for medicinal purposes as disinfectant and antiseptic. It may still be used in veterinary medicine. 9.3 Exposure Assessment 9.3.1 Air: NA 9.3.2 Background Levels: NA 9.3.3 Workplace Methods: NA 9.3.4 Community Methods: NA 9.3.5 Biomonitoring/Biomarkers Increased iodine and carboxyhemoglobin levels may occur in the blood but data are inadequate to evaluate their usefulness in monitoring occupational exposure. 9.4 Toxic Effects

Little additional information was found. This material is irritating to the skin, eyes, and mucous membranes. It may be absorbed through the skin. When heated to decomposition this compound emits toxic fumes of carbon dioxide, carbon monoxide, and hydrogen iodide. Decomposition becomes violent at 204°C (400°F). Most of the problems associated with iodoform have been related to its topical application as an antiseptic material and to oral administration. Absorption of significant amounts of this material may result in CNS depression and injury to the heart, liver, and kidneys. Serious injury to the eyes has been reported following early use of iodoform as a topical and intravitreal antiseptic. 9.4.1 Experimental Studies 9.4.1.1 Acute Toxicity According to the available information, iodoform has oral LD50s of 355, 810, and 487 mg/kg for rats, mice, and guinea pigs, respectively (258). Drowsiness and low activity were first observed without loss of motor activity, but bloody nasal exudate, breathing disturbances, tonic–clonic convulsions, and paralysis of the extremities preceded death. Daily oral administration of 35.5 mg/kg (carrier not described) caused liver and kidney injury. The report also described changes in the brain and thyroid. This report does not appear to be consistent with the NCI report discussed in the section on carcinogenesis. Administration of iodoform to rats has produced an acute hepatic necrosis, not unlike that observed following exposure to carbon tetrachloride (259). No reports on testing of iodoform in the eyes of animals were found. Old medical literature describes serious injury to the eyes following treatment of humans with iodoform as an antiseptic. According to Grant (260), iodoform formerly was employed as a topical and intravitreal antiseptic. Systemic intoxication and visual disturbances resulted from absorption of excessive amounts applied to wounds or abscesses, or from ingestion of large quantities, but not from application to the eye. Numerous cases of visual disturbance were reported early in the twentieth century. Most characteristically vision was impaired by retrobulbar neuritis with accompanying central scotoma. In rare instances transitory complete blindness occurred. In some cases the bulbar portion of the optic nerve was involved, with neuroretinitis and occasional retinal hemorrhages. As a rule, recovery was slow, requiring many months. In most cases vision was completely or partially recovered, but residual pallor of the temporal part of the optic nervehead was common. Exceptionally the whole nervehead became atrophic and white and little vision was recovered. A percutaneous LD50 of 1184 mg/kg was determined in rabbits for a 70% ointment of iodoform (258). Some veterinary reports indicate toxicity from use on the skin of dogs and cats, but it is not clear whether the material was absorbed dermally or ingested. Rats were exposed once or 7 times to iodoform vapors (261). A 7 h LC50 of 183 ppm was determined for the single exposure of rats. Seven 7 h exposures were given to 0, 1, or 14 ppm (verified analytically). There were no changes in rats' appearance, food or water intake, urine and feces output, or SMR (standardized mortality rate) 12/60 blood value for any group. The only histological manifestation was mineralized deposits in medullary renal tubules of some rats exposed to 14 ppm. Kutob and Plaa (243) administered iodoform subcutaneously to mice in an investigation of hepatotoxicity of a series of halogenated methanes. The LD50 by this route was 1.6 mmol/kg (630 mg/kg) compared to 27.5 mmol/kg for chloroform and 7.2 mmol/kg for bromoform. The doses causing changes in a phenobarbital sleeping time study were 0.59, 1.7, and 2.3 mmol/kg for iodoform, chloroform, and bromoform, respectively. Histological damage to the liver was noted at 1.28 mmol/kg (504 mg/kg) but not at 0.32 mmol/kg.

9.4.1.2 Chronic and Subchronic Toxicity No adequate study to determine the chronic toxicity of iodoform exists. Although survival and body weight were affected in the NCI bioassay reported in Section 9.4.1.1 (262), the doses fed were so high as to be improbable as vapor concentrations. They would indicate a low order of systemic toxicity. 9.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms The limited data that are available indicate iodoform exposure results in increased carboxyhemoglobin levels in rats. A rat liver microsomal fraction requiring both NADPH and molecular oxygen produced the carbon monoxide (248, 263). A mixed-function oxidase has been reported to be involved. 9.4.1.5 Carcinogenesis Iodoform has been included in the NCI daily bioassay program (262). According to their summary: the high and low time-weighted average daily dosages of iodoform were, respectively, 142 and 71 mg/kg for male rats, 55 and 27 mg/kg for female rats, and 93 and 47 mg/kg for male and female mice. A significant positive association between dosage and mortality was observed in male rats but not in female rats or in mice of either sex. Adequate numbers of animals in all groups survived sufficiently long to be at risk from late-developing tumors. No statistical significance could be attributed to the incidences of any neoplasms in rats or mice of either sex when compared to their respective controls. Under the conditions of this bioassay, no convincing evidence was provided for the carcinogenicity of iodoform in Osborne–Mendel rats or B6C3F1 mice. 9.4.1.6 Genetic and Related Cellular Effects Studies Limited data indicate some mutagenic potency, but the data appear inadequate to draw a conclusion toward industrial significance. 9.4.2 Human Experience The 1980s–1990s literature deals mainly with the veterinary uses of the compound. Used as an antiseptic, iodoform produces acute depression of the central nervous system, systemic toxicity, vomiting, coma, and kidney, liver, and heart damage (264). Only one instance of delirium and hallucination has been reported (265). 9.4.2.1 General Information Symptoms of exposure to this compound may include dermatitis, vomiting, varying degrees of cerebral depression or excitation (including delirium, hallucinations, coma, and death), very rapid pulse, possible slight fever, CNS depression, collapse, frequent liquid stools, abdominal pain, thirst, metallic taste, shock, anuria, stupor, esophageal stricture, diarrhea, vesiculation and oozing of skin, intense itching, burning pain, tenderness, nausea, uremia, respiratory distress, and circulatory collapse. Exposure may also result in injury to the heart, liver, and kidneys. No reports in the literature were found for industrial use of iodoform. 9.4.2.2 Clinical Cases There are several reports of iodoform toxicity caused by medical uses. Authors warn that iodoform toxicity is not as rare as thought and has been underdiagnosed. A case of iodoform toxicity caused by use of 5% iodoformed bandages in occlusive surgical dressings caused signs and symptoms of iodoform toxicity syndrome (266). In another paper (267), where three cases of iodoform toxicity were described following dressings with 10% iodoform gauze on extended wounds, the author indicated that 5, 10, and 16 days after beginning of dressings, the patients became confused, hallucinated, and one of them was subsequently comatose. Within a few days (3– 8) after the iodoform dressings were discontinued, the signs of iodoform toxicity disappeared. The author suggests that the toxicity of iodoform is probably unrecognized if the rarity of the observations published and the amount of iodoform gauzes annually sold are compared. 9.5 Standards, Regulations, or Guidelines of Exposure The ACGIH TLV TWA is 0.6 ppm (10 mg/m3). The NIOSH REL is also 0.6 ppm. HSE OES (United Kingdom) 0.6 TWA ppm 9.8

TWA mg/m3 STEL/CEIL© ppm

1

STEL/CEIL© mg/m3

16

The ACGIH (8) reports are as follows. Toxicologic data on inhaled iodoform are very limited. Depression of the CNS and damage to the kidneys, liver, and heart following topical application of high, local concentrations to damaged skin have occurred in humans. Accordingly, a TLV TWA of 0.6 ppm is recommended for iodoform. This value is slightly greater than that for bromoform, but on a molar basis, it is considerably higher. Both limits should be used with caution, as there are only scant data and little pertinent use experience with inhaled iodoform. The iodoform TLV approximates that of methyl iodide on an iodine basis. At this time, no STEL is recommended until additional toxicological data and industrial hygiene experience become available to provide a better base for quantifying on a toxicological basis what the STEL should be. International occupational exposure values: Australia TWA 0.6 ppm (10 mg/m3) January 1993. Belgium

TWA 0.6 ppm (10 mg/m3) January 1993.

Denmark

TWA 0.2 ppm (3 mg/m3) January 1993.

Finland

TWA 0.2 ppm (3 mg/m3); STEL 0.6 ppm (10 mg/m3); Skin January 1993.

France

TWA 0.6 ppm (10 mg/m3) January 1993.

Ireland

TWA 0.6 ppm (10 mg/m3); STEL 1 ppm (20 mg/m3) January 1997.

The Netherlands TWA 0.2 ppm (3 mg/m3) October 1997. TWA 0.6 ppm (10 mg/m3) January 1993. 9.6 Studies on Environmental Impact: NA Switzerland

Saturated Methyl Halogenated Aliphatic Hydrocarbons Jon B. Reid, Ph.D., DABT 10.0 Carbon Tetrachloride 10.0.1 CAS Number: [56-23-5] 10.0.2 Synonyms: Tetrachloromethane; methane tetrachloride; perchloromethane; tetrachlorocarbon; tetrachloromethane; carbon tet; R10, r 10 (refrigerant), Refrigerant R 10; necatorina; benzinoform, carbon chloride; carbona; flukoids; necatorine; tetrafinol; tetraform; tetrasol; univerm; vermoestricid 10.0.3 Trade Names: Benzinoform, Carbona, ENT 4,705, ENT 27164, Fasciolin, Flukoids, Necatorina, Necatorine, R 10, Tetrachlorormetaan, Tetrafinol, Tetraform, Tetrasol, Un 1846, univerm, vermoestricid, R10 (Refrigerant) 10.0.4 Molecular Weight: 153.84 10.0.5 Molecular Formula: CCl4

10.0.6 Molecular Structure:

10.1 Chemical and Physical Properties Carbon tetrachloride is a colorless, highly volatile liquid with a strong ethereal odor similar to chloroform. It mixes sparingly with water. When heated to decomposition, it emits highly toxic fumes of phosgene. 10.1.1 General Physical state Colorless liquid Specific gravity 1.589 at 25°C Freezing point –23°C Boiling point 76.5°C Vapor pressure 115.2 torr at 25°C Refractive index 1.46305 (15°C) Percent in “saturated” air 15 (25°C) Solubility 0.08 g/100 g water at 20°C; miscible with alcohol, ethyl ether, benzene Flammability Not flammable by standard tests in air; will not support combustion UEL, LEL Not available 1 mg/L = 159 ppm and 1 ppm = 6.29 mg/m3 at 25°C, 760 torr 10.1.2 Odor and Warning Properties Carbon tetrachloride has a sweetish odor. It is not considered particularly disagreeable by most people, although some people may be nauseated by small amounts. The odor is one to which the average individual becomes readily adapted. The odor would certainly not be considered a satisfactory warning of excessive exposure. According to one reference, the threshold of detection of the odor of carbon tetrachloride is approximately 79 ppm and the odor is strong at 176 ppm (268). Another reference states that 100% of a small panel of test subjects recognized 21 ppm of carbon tetrachloride produced from carbon disulfide and 100 ppm of carbon tetrachloride produced by chlorination of methane (269). 10.2 Production and Use Our understanding of the industrial hygiene measures necessary to handle carbon tetrachloride has changed little since Irish prepared his chapter in Patty's Toxicology for the second revised edition of Volume 2. Awareness of its hepato- and renal toxicity and the availability of less hazardous solvents have resulted in virtually no use as a solvent; most of current production is consumed in the production of fluorocarbons. Use of carbon tetrachloride in fire extinguishers has essentially disappeared, as has use in fumigant mixtures. Carbon tetrachloride is used primarily as a chemical intermediate in the production of the refrigerants Freon 11 and 12. Freon 11 and 12 are also used as solvents, in plastic and resin production, and as foam blowing agents, and previously as aerosol propellants. Carbon tetrachloride also is used as a general solvent in industrial degreasing operations. Its use as a grain fumigant was banned by USEPA in 1985. Chemical and Engineering News reported that 271 million lb of carbon tetrachloride was produced domestically in 1990. U.S. imports of carbon tetrachloride have tended to increase, and exports have tended to decrease. Carbon tetrachloride imports exceeded 111 million lb in 1987. Imports increased to over 57 million lb in 1985 from 7 million lb in 1983. Exports decreased from 86 million lb in 1980 to 36 million lb in 1985.

10.3 Exposure Assessment The primary routes of potential human exposure to carbon tetrachloride are inhalation, ingestion, and dermal contact. The greatest risk of occupational exposure to carbon tetrachloride occurred most likely during fumigation processes before this use was banned in 1985. NIOSH estimated that workers exposed to carbon tetrachloride are primarily those at blast furnaces and steel mills, in the air transportation industry, and in motor vehicle and telephone and telegraph equipment manufacturing. About 4500 workers are possibly exposed during production processes, and 52,000 during industrial use of the chemical. OSHA estimated that 3.4 million workers may possibly be exposed to carbon tetrachloride directly or indirectly. Exposure to carbon tetrachloride used to occur in dry-cleaning establishments, where ambient-air concentrations have been determined to average between 20 and 70 ppm. Average exposures of 206 and 338 ppm with excursions of 1252 and 7100 ppm have been reported during dry-cleaning machine operations. Occupational exposure is also possible during its use in the manufacture of Freon 11 and 12. Exposure during fluorocarbon production is most likely to be experienced by tank farm and process operators, who may be exposed to emissions arising from storage tank vents or resulting from transfer of the chemical or process equipment leaks or spills. The National Occupational Hazard Survey, conducted by NIOSH from 1972 to 1974, estimated that 160,000 workers were exposed to carbon tetrachloride in the workplace, including 25,000 workers exposed during grain fumigation. The National Occupational Exposure Survey (1981–1983) estimated that 77,315 workers, including 12,605 women, potentially were exposed to carbon tetrachloride. ACGIH has noted the potential contribution to overall exposure by the cutaneous route, including mucous membranes and eyes, either by airborne, or more particularly, by direct contact with the substance. The Toxic Chemical Release Inventory (EPA) (4) listed 95 industrial facilities that produced, processed, or otherwise used carbon tetrachloride in 1988. In compliance with the Community Right-to-Know Program, the facilities reported releases of carbon tetrachloride to the environment which were estimated to total 3.9 million lb. These releases indicate that a large proportion of the general population is possibly exposed to the chemical. EPA estimated that 8 million people living within 12.5 m of manufacturing sites are possibly exposed to average levels of 0.5 g/m3, with peaks of 1580 g/m3. Carbon tetrachloride is readily volatile at ambient temperature and is a stable chemical that is degraded very slowly, so there has been a gradual accumulation of carbon tetrachloride in the environment (270). It is broken down, by chemical reactions in air, but this occurs so slowly that elimination of 50% of the carbon tetrachloride takes between 30 and 100 years. Carbon tetrachloride is formed in the troposphere by solar-induced photochemical reactions of chlorinated alkenes. Concentrations of 0.1 ppb in air are common worldwide with somewhat higher values (0.2–0.6 ppb) in cities (270). Of 113 public water systems surveyed, 10% had mean concentrations of carbon tetrachloride ranging from 2.4 to 6.4 g/L. Investigators also found the chemical in 45% of surfacewater supplies and in 25% of groundwater samples, at concentrations of 0.001–0.40 mg/L. Estimates indicate that 19 million people may potentially be exposed to carbon tetrachloride through ambient air, 20 million possibly through contaminated drinking water, and 2 million possibly through contaminated soil or landfills. Assuming inhalation of 20 m3/day by a 70-kg adult and 40% absorption of carbon tetrachloride across the lung, typical levels of carbon tetrachloride in ambient air (~ 1 g/m3) yield daily exposure levels of ~ 0.1 g/kg per day (270). Somewhat higher exposures could occur near point sources of carbon tetrachloride. For water, consumption of 2 L/day by a 70-kg adult at a typical carbon tetrachloride concentration of 0.5 g/L yields a typical intake by this route of ~ 0.01 g/kg per day. Carbon tetrachloride may possibly have been ingested as a contaminant of foods that were treated with the chemical prior to its banning as a grain fumigant in 1985. When carbon tetrachloride was used as a fumigant on stored grain, residue concentrations of the chemical ranged from 3.0 to 72 mg/kg. Carbon tetrachloride may possibly be ingested in water contaminated with the chemical (reported concentrations range 0.2–18 ppm). Also, the chemical possibly may be ingested as a contaminant of drinking water treated with chlorine. Investigators have found carbon

tetrachloride in human tissues in concentrations of 1–13 ppm. 10.3.1 Air See above (Section 10.3). 10.3.2 Background Levels See above (Section 10.3). 10.3.3 Workplace Methods NIOSH Method 1003, for halogenated hydrocarbons, is recommended for determining workplace exposures to carbon tetrachloride (11). 10.3.4 Community Methods: NA 10.3.5 Biomonitoring/Biomarkers Unchanged carbon tetrachloride can be measured in the expired air following exposures. Stewart et al. (271) have shown the relationship of exposure concentration and time to exhaled concentration, and it would appear that at the low levels of exposure considered safe for chronic exposure, breath samples are of very limited value. Expired air may be of value in definitive diagnosis of acute exposure and possibly in semiquantitation of the magnitude of exposure. At present, metabolites in blood or urine appear to be of limited value in monitoring exposure at levels recognized as acceptable for industrial exposure because exposure to 5 ppm vapor permits daily intake of only 4.5 mg/kg (272). 10.4 Toxic Effects Carbon tetrachloride is a human poison by ingestion and possibly other routes and a poison by subcutaneous and intravenous routes. It is mildly toxic by inhalation; an experimental carcinogen, neoplastigen, tumorigen, teratogen and suspected human carcinogen; and an eye and skin irritant. Individual susceptibility varies widely. It has a narcotic action resembling that of chloroform, although not as strong. The aftereffects following recovery from narcosis are more serious than those of delayed chloroform poisoning, usually taking the form of damage to the kidneys, liver, and lungs. When recovery takes place, there may be no permanent disability. Marked variation in individual susceptibility to this compound exists; some persons appear to be unaffected by exposures that seriously poison their fellow workers. Concentrations on the order of 1000–1500 ppm are sufficient to cause symptoms if exposure continues for several hours. Repeated daily exposure to such concentrations may result in poisoning. Exposure to high concentrations of carbon tetrachloride results in depression of the central nervous system and possibly cardiac sensitization. If the concentration is not high enough to lead to rapid loss of consciousness, other indications of CNS effects such as dizziness, vertigo, headache, depression, mental confusion, and incoordination are observed. Many individuals also show GI responses such as nausea, vomiting, abdominal pain, and diarrhea. This may be a conditioned reflex or a direct CNS effect. Functional and destructive injury of the liver and kidney may occur from a single acute exposure, but it is much more likely to occur from repeated exposures. In a case of long-term chronic exposure to low concentrations, kidney and liver injury dominate the picture. The milder the exposure, the greater the tendency for the injury to be predominantly in the liver. At threshold concentrations, the injury of the liver appears mostly as malfunction and/or enlargement. Many enlarged livers are observed in animals at the threshold of response and enlargement appears reversible. The detection of an enlarged liver in humans should be considered important, although enlargement may occur from a great many other causes. It has been recognized that the concurrent or past intake of significant amounts of alcohol with exposure to carbon tetrachloride may greatly increase the probability of injury. Other chemicals such as isopropyl alcohol, acetone, chlorinated insecticides, phenobarbital, and many other mixed-function oxidase inducers may also be involved. Diabetes and certain nutritional deficiencies have been implicated in enhanced toxic effects from carbon tetrachloride (273). Because metabolism of carbon tetrachloride is required for most of its toxic effects, there are many examples of species and strain differences in toxicity. Carcinogenic effects ascribed to carbon tetrachloride appear likely to be due to organ injury.

An ATSDR profile (270) exists for carbon tetrachloride, and numerous other reviews are available. Excellent reviews of metabolism, mode of toxic action, and detailed discussion of biochemical effects are presented in two standard reference books (272, 274). Much of our understanding of metabolism by the liver and toxic effects on that organ by other chemicals has come from the numerous studies on carbon tetrachloride. 10.4.1 Experimental Studies 10.4.1.1 Acute Toxicity This compound is toxic by ingestion, inhalation, or skin absorption. It is an irritant of the skin, eyes, mucous membranes, and respiratory tract. It is readily absorbed through the skin. It may cause lacrimation. It is narcotic. When heated to decomposition it emits irritating fumes and toxic fumes of chlorine, carbon monoxide, carbon dioxide, hydrogen chloride, and phosgene. It may also emit other hydrocarbon products (273). The former availability of carbon tetrachloride in odd containers around the home and shop made ingestion a serious problem. The LD50 for rats is reported by McCollister et al. as 2920 mg/kg (275). The Registry of Toxic Effects of Chemical Substances (1983/84 Supplement) lists LD50s of 2800 mg/kg for the rat, 12,800 mg/kg for the mouse, 6380 mg/kg for the rabbit; and 3680 mg/kg for the hamster (276). Numerous values for other routes of exposure are also cited. Liver injury occurs in animals at levels well below those causing death. The therapeutic dose previously used in humans for treatment of ascariasis ranged from 32 mg/kg for infants to 90–100 mg/kg for adults. Consumption of alcohol caused serious complications in some cases. Because carbon tetrachloride is a good lipid solvent, it removes the fats from the skin and, in so doing, causes a dry disagreeable feeling and may facilitate secondary infection. Contact with the eyes may cause a transient disagreeable irritation but does not lead to serious injury. 10.4.1.2 Chronic and Subchronic Toxicity The IRIS database indicates the study by Bruckner et al. (277) as the basis for subchronic toxicity of the compound. Male Sprague–Dawley rats were given 1, 10, or 33 mg carbon tetrachloride/kg per day by corn oil gavage, 5 days/week for 12 weeks. Liver lesions, as evidenced by mild centrilobular vacuolization and statistically significant increases in serum sorbitol dehydrogenase activity, were observed at the 10- and 33-mg/kg/day doses in a dosesrelated manner. Therefore, the LOAEL was established at 10 mg/kg/day [converted to 7.1 mg/kg/day] and the NOAEL was 1 mg/kg/day) [converted to 0.71 mg/kg/day]. Adams et al. (278) reported the response of laboratory animals to a single exposure to various concentrations of carbon tetrachloride. The maximum time-concentrations in air survived by rats were as follows: 12000 ppm for 15 min, 7300 ppm for 1.5 h, 4600 ppm for 5 h, and 3000 ppm for 8 h. The maximum time-concentrations in air having no adverse effects in male rats were as follows: 3000 ppm for 6 min, 800 ppm for 30 min, and 50 ppm for 7 h. Similar data were reported for rabbits by Lehmann. The data from these two sources indicated that rabbits and guinea pigs show a somewhat greater tolerance for carbon tetrachloride than rats do. In any case, the acute data given for the different animals are in the same range. The responses observed in animals and humans are reasonably comparable. There seems to be a higher probability of significant kidney response in humans than is observed in animals. Qualitatively, such injury is observed in both animals and humans. Histopathological and biochemical studies of acutely injured animals show marked hepatic injury, as has been demonstrated by increased plasma prothrombin clotting time, an increase of serum phosphatase, an increase in liver weight, an increase of total lipid content of the liver, and central fatty degeneration of the liver. Renal injury was not apparent in the acute exposure of rats in the studies of Adams (278). Quite significant kidney injury has been reported, however, from what were thought to be single exposures in humans. Although responses referable to the nervous system or GI tract may still be observed in chronic exposure, they are much less important factors. These effects may not be noticed at all following a

long period of chronic exposure to low concentrations; the organic and functional injury of the internal organs becomes predominant, particularly of the liver and the kidney. It is noticeable in the literature that carbon tetrachloride has become a classic agent for producing liver injury for laboratory investigations. One comprehensive toxicologic investigation in animals is that of Adams et al. (278). These investigators studied rats, guinea pigs, rabbits, and monkeys, which were given repeated 7 h daily exposures 5 days/week. At a concentration of 400 ppm (2.52 mg/L), rats and guinea pigs suffered severe intoxication. Less than half of them lived for 127 exposures during a period of 173 days. There was an increase in liver weight up to twice that of the controls and a moderate increase in kidney weight. Histological examination of the tissues showed central fatty degeneration with cirrhosis of the liver and slight parenchymatous degeneration of the tubular epithelium of the kidneys. Animals examined after 2 weeks of exposure demonstrated advanced liver and kidney changes by that time. At a concentration of 200 ppm (1.26 mg/L), rats and guinea pigs still showed a definite response and high mortality. Biochemical and histological studies were comparable but less severe than in the 400-ppm exposure. At a concentration of 100 ppm (0.63 mg/L), rats, rabbits, guinea pigs, and monkeys tolerated 146–163 exposures without evidence of adverse effect on gross appearance, behavior, growth, and other parameters. They all showed histopathological changes. The changes were equivocal in the monkey. A continuous exposure at 61 mg/m3 (10 ppm) resulted in the deaths of three guinea pigs, as well as growth depression and liver damage in the survivors of all species. A second continuous exposure at 6.1 mg/m3 (1 ppm) did not cause deaths or visible toxic signs in any species. All species except the rat exhibited slight growth depression but no hematological or histopathological evidence of toxicity, at 6.1 mg/m3. Alumot et al. (279) fed rats diets containing carbon tetrachloride for 2 years. On the basis of growth, fertility, reproduction, biochemical tests, and apparently limited histological examination, primarily of the liver, the authors concluded that they had fed a no-effect level of 200 ppm. On the basis of food consumption, this was calculated to be 10–18 mg CCl4/kg body weight per day. They also reported fatty livers occurred in rats after 5–6 weeks on a diet containing 275 ppm CCL4, ~ 40 mg/kg/day, and decreased weight gain in male rats fed 520 ppm. Total lipid and triglycerides were significantly higher at 275 and 520 ppm but not 150 ppm after 5–6 weeks. 10.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Early studies to measure absorption and excretion of carbon tetrachloride were handicapped by analytic difficulties. Studies were made only at very high concentrations. McCollister et al. (280) were among the first who studied the absorption, distribution, and elimination of carbon tetrachloride by using radioactive carbon. This allowed them to study these factors at concentrations that were physiologically significant from a chronic exposure point of view. They exposed monkeys to concentrations of 46 ppm (0.290 mg/L) of carbon tetrachloride that was 14C labeled. Approximately 30% was absorbed. The equivalent of at least 51% of the radioactivity due to carbon tetrachloride absorbed during an inhalation period was estimated to have been eliminated in the expired air within 75 days. The remainder was excreted largely in the urine and feces. Approximately 4.4% was eliminated as carbon dioxide. Some 94.3% of the radioactivity in the urine was a nonvolatile, unidentified intermediate. Small amounts occurred as urea and carbonate. Numerous subsequent references to the metabolism of carbon tetrachloride have been published. The review by ATSDR (270) summarized in a diagram the metabolism of carbon tetrachloride as adapted from Shah et al. (281). Metabolism is primarily in the liver but many other organs have also been shown to metabolize it. The identified products underlined in Figure 62.3 support a NADP H-dependent cytochrome P450 isoenzyme reductive dehalogenation, formation of a trichloromethyl free radical, binding to microsomal lipids and proteins, and a number of other reactions to form products such as carbon dioxide, carbon monoxide, hexachloroethane, chloroform, and phosgene. Metabolism is thought to be dose-dependent and saturable, and to involve destruction

of the cytochrome P450 during the metabolism process.

Figure 62.3. Pathways of CCl4 metabolism. Products identified as carbon tetrachloride metabolites are underlined. [Adapted from Ref. 281.] Dose–response ratio, time course, and pharmacokinetics following single oral gavage doses of 14Clabeled CCl4 to rats were studied extensively (282). Carbon dioxide was identified as a major metabolite, with 20–30 times less bound to liver macromolecules. An intermediate amount was excreted in the liver and feces. Metabolism changed extensively as doses were increased. Chloroform, for example, was the least abundant metabolite at low doses, but the second most abundant at high doses. Metabolism by the pathways leading to CO2 and CHCl3 were more associated with concurrent liver injury as measured by increased transaminase activity than it was to pathways leading to metabolites bound to liver or excreted in urine. Metabolism of CCl4 clearly impaired the pathway to CO2 after 2 h of exposure. A significant first-pass effect through the liver is apparent after gavage; unfortunately, few data on metabolism after inhalation are available. The fatty changes that are characteristic of carbon tetrachloride toxic effect on the liver are due to accumulation of triglycerides, but the mechanism is not yet clear (283). The mechanism is not the same as that producing liver necrosis, another characteristic effect of carbon tetrachloride. Metabolism of carbon tetrachloride is certainly required and lipid peroxidation may play a key role. 10.4.1.3.1 Adsorption Absorption through the skin of monkeys from the vapor phase was studied by McCollister et al. (280). By using radioactive carbon tetrachloride, they were able to detect small amounts in the blood after exposure of the skin to vapor concentrations of 485 and 1150 ppm. Although traces were absorbed through the skin under these conditions, their conclusions were that “absorption through the intact skin would appear to be of no practical significance in considering the hazard to the health of industrial workers exposed to concentrations of at least as high as 1150 ppm in the air.” Stewart and Dodd (167) considered absorption of the liquid through the skin to present a potential problem based on a limited study on human subjects. In view of the high potential hepatotoxicity of carbon tetrachloride, contact of the skin with the liquid should be prevented, particularly if it could lead to repeated exposure. 10.4.1.3.2 Distribution See Section 10.4.1.3.1.

10.4.1.3.3 Excretion See Section 10.4.1.3.1. 10.4.1.4 Reproductive and Developmental Schwetz et al. (283) exposed pregnant rats 7 h/day to either 330 or 1000 ppm carbon tetrachloride vapors from days 6–15 of pregnancy. These exposures had no effect on fetal resorptions but At both concentrations fetal body weight and crown-rump length were significantly less than that of controls. No anomalies were seen upon gross examination of the fetuses. A significant incidence of subcutaneous edema was observed at 300 ppm but not at 1000 ppm. The incidence of sternal abnormalities was significantly increased in the fetuses of rats exposed to 1000 ppm CCl4. Considerable hepatotoxicity was observed in the dams at both concentrations. The authors concluded that carbon tetrachloride is not teratogenic, but is embryo toxic at these concentrations, and that these are not related to hepatotoxicity in the mothers. Smyth et al. (284) observed three generations of rats exposed to 50–400 ppm vapor. In these studies no evidence of reduced fertility or embryonic or fetal abnormalities were observed. Alumot et al. (279) fed rats diets fumigated with carbon tetrachloride for 2 years. Storage of diets was in hematically sealed containers and diets were assayed at 80 ± 5 and 200 ± 20 ppm CCl4. The females were rebred at 2-month intervals for a total of seven matings. From this somewhat unusual experimental design, they concluded that exposure of both male and female rats to diets containing 80–200 ppm had no effect on male fertility, female fertility, or reproductive parameters. On the basis of food consumption during the 2-year period, this amounted to 10–18 mg/kg/day. After 6 months of repeated 7-h exposure to 200 ppm vapor, the testicular germinal epithelium of rats was adversely affected, perhaps as a secondary effect (278). 10.4.1.5 Carcinogenesis The USEPA (5) classifies carbon tetrachloride as B2 (Animal carcinogenicity data is sufficient); probable human carcinogen on the basis of carcinogenicity in rats, mice, and hamsters. Carbon tetrachloride has produced hepatocellular carcinomas in rats, mice, and hamsters, the species evaluated to date. Hepatocellular carcinomas developed in Osborne–Mendel, Japanese, and Wistar rats, but not Sprague–Dawley or black rats, following subcutaneous (SC) injection of carbon tetrachloride. Hyperplastic nodules were noted in Buffalo rats treated SC (285–287). Sensitivity varied among strains, and trends in incidence appeared inversely related to severity of cirrhosis. Fifty Osborne– Mendel rats/sex were administered carbon tetrachloride by corn oil gavage at 47 and 94 mg/kg/injection for males and 80 and 159 mg/kg for females 5 times/week for 78 weeks. At 110 weeks, only 7/50 high-dose males and 14/50 high-dose females survived; 14/50 low-dose males and 20/50 low-dose females survived. The incidence of hepatocellular carcinomas was increased in animals exposed to carbon tetrachloride as compared with pooled colony controls. The apparent decrease in the incidence of hepatocellular carcinomas in high dose female rats compared with the low dose females (1/14 vs. 4/20, respectively) was attributed by the authors to increased lethality before tumors could be expressed (288–290). In this same study, using the same dosing schedule, male and female B6C3F1 mice received 1250 or 2500 mg/kg carbon tetrachloride. The incidences of hepatocellular carcinomas in males were 5/77, 49/49, and 47/48 in the control, low and high dose groups, respectively, and 1/80, 40/40, and 43/45 in the control, low, and high dose groups, respectively. Carbon tetrachloride administered by gavage has also been shown to produce neoplastic changes in livers of five additional strains of mice (C3H, A, Y, C, and L). In the last study, 56 male and 19 female L mice, which have a low incidence of spontaneous hepatomas, were treated with 0.1 mL of

40% carbon tetrachloride 2 or 3 times/week over 4 months, for a total of 46 treatments. Animals were killed 3–3.5 months after the last treatment. The combined hepatoma incidence of treated male mice was 47% (7/15 vs. 2/71 in the untreated male controls); treated females showed an incidence of 38% (3/8 vs. 0/81 in the untreated female controls). As part of a large study of liver carcinogens, Della Porta et al. (290a) treated Syrian golden hamsters (10/sex/dose) with carbon tetrachloride by gavage, weekly for 30 weeks. For the first 7 weeks, 0.25 mL of 0.05% carbon tetrachloride in corn oil was administered; this dose was halved for the remainder of the exposure period. All animals were observed for an additional 25 weeks. All of the 10 hamsters that were killed or died between weeks 43 and 55 had liver cell carcinomas, compared with none in controls. IARC (294, 295) states that there is sufficient evidence for the carcinogenicity of carbon tetrachloride in experimental animals. When administered by gavage, carbon tetrachloride increased the incidences of hepatomas and hepatocellular carcinomas in mice of both sexes. By the same route of administration, the compound increased the incidence of neoplastic nodules of the liver in rats of both sexes. When administered by subcutaneous injection, carbon tetrachloride induced hepatocellular carcinomas in male rats and mammary adenocarcinomas and fibroadenomas in female rats. When administered by inhalation, carbon tetrachloride induced liver carcinomas in rats. When administered intrarectally, the compound induced nodular hyperplasia of the liver in male mice. 10.4.1.6 Genetic and Related Cellular Effects Studies Carbon tetrachloride was not mutagenic to either S. typhimurium or E. coli. At low concentrations, carbon tetrachloride did not produce chromatid or chromosomal aberrations in an epithelial cell line derived from rat liver (291). In vivo unscheduled DNA synthesis assays have likewise been negative in male Fischer 344 rats (292). Carbon tetrachloride produced mitotic recombination and gene conversion in Saccharomyces cerevisiae, but only at concentrations that reduced viability to 10% (160). Carbon tetrachloride may be metabolized to reactive intermediates capable of binding to cellular nucleophilic macromolecules. Negative responses in bacterial mutagenicity assays may have been due to inadequate metabolic activation in the test systems. 10.4.2 Human Experience 10.4.2.1 General Information Symptoms of exposure to this compound may include headache, mental confusion, CNS depression, fatigue, anorexia, nausea, vomiting, coma, abdominal cramps, dizziness, unconsciousness, weakness, amnesia, paresthesia, tremors, jaundice, and liver and kidney damage. It may also cause depression, loss of appetite, bronchitis, internal irritation, stupor, and damage to the heart and nervous system. Skin contact may remove the natural lipid cover of the skin and it may also lead to a dry, scaly, fissured dermatitis. Other symptoms include GI disturbances, abdominal pain, diarrhea, enlarged and tender liver, toxic hepatitis, diminished urinary volume, red and white blood cells in the urine, and albuminuria. It may also cause narcosis, lung damage, acute nephrosis of the kidney, polyneuritis, narrowing of visual fields and other neurological changes, cirrhosis of the liver, lacrimation, burning of the eyes, malaise, dark urine, renal casts, uremia, epigastric distress, visual disturbances (such as blind spots, spots before the eyes, visual “haze” and restriction of the visual fields), and death. Exposure to this compound depresses and injures almost all cells of the body, including the CNS, liver, kidney, and blood vessels. Depression of the heart muscle may result in ventricular arrhythmias. Damage to the kidneys may result in marked edema and fatty degeneration of the tubules. Other symptoms include slowed respiration, slowed or irregular pulse, fall of blood pressure, sudden weight gain, azotemia, anemia, blurred vision, and loss of peripheral color vision. It may also cause drowsiness, giddiness, oliguria, cellular necrosis of the liver, acute nephritis, and aplastic anemia. Eye and skin irritation, dyspnea, hematemesis, hematuria, proteinuria, weight loss, cyanosis, and miosis have also been reported. Ingestion of this compound with alcohol will intensify the effects of the chemical. Other symptoms include hepatomegaly, optic atrophy, optic neuritis, and pulmonary edema. It may also cause a permanent reduction in vision, deafness, and retrobulbar neuritis. Mucous membrane irritation and anesthesia have also been reported. Hepatic nodular hyperplasia may also occur. Other symptoms include sleepiness, increased peristalsis, erythema, gastroenteritis, and death from

ventricular fibrillation. It may cause disorientation. Alveolitis has occurred. It may cause irritation of the nose and throat, a sense of fullness in the head, convulsions, hepatic steatosis, hypertension, acidosis, and sudden death from depression of vital medullary centers. Other symptoms include flatulence, fatty liver, elevated SGOT, and elevated serum bilirubin. It may also cause incoordination, vertigo, and increased nitrogen retention. Other symptoms are pupillary constriction, unspecified respiratory system and GI system effects, somnolence, severe GI upset, and liver enlargement (273). Numerous reports of injury and death following acute and repeated exposure of humans to carbon tetrachloride can be found. Few, if any, epidemiological, studies have been completed on an occupationally exposed population, nor have there been laboratory studies of long duration. Stewart and Dodd (167) and Stewart et al. (271) have conducted experimental human exposure studies with volunteer subjects. These reports indicate that absorption of the liquid through the skin may be significant, particularly in chronic exposure. They have also determined the concentration of carbon tetrachloride in expired air following exposure to the vapor. 10.4.2.2.5 Carcinogenesis An IARC Working Group (294, 295) reported that there were no adequate data to evaluate the carcinogenicity of carbon tetrachloride in humans. Three case reports described liver tumors associated with cirrhosis in humans exposed to carbon tetrachloride. A mortality study of laundry and dry cleaning workers exposed to a variety of solvents suggested an excess of respiratory cancers, liver tumors, and leukemia. The EPA considers the human data re: carcinogenesis as “inadequate.” There have been three case reports of liver tumors developing after carbon tetrachloride exposure. Several studies of workers (293) who may have used carbon tetrachloride have suggested that these workers may have an excess risk of cancer. The International Agency for Research on Cancer (IARC) reviewed the available carcinogenicity data in 1972 (294) and again in 1979 (295). Carbon tetrachloride is grouped with 18 chemicals considered “probably carcinogenic for humans” and, according to IARC, is to be regarded “as if it presented a carcinogenic risk to humans.” The EPA reached a similar conclusion in 1988 (296). In a study by the NCI bioassay program, hepatocellular carcinomas developed in mice that received gavaged daily doses of 2500 or 1250 mg/kg for 78 weeks (297). These massive doses also resulted in adrenal tumors. The amount of noncancerous pathology in the liver was not discussed, but may have been significant. Rats were fed doses of 100 (male) or 150 (female) mg/kg, 5 days/week for 78 weeks and then kept for 32 additional weeks. Half of these doses were fed to second groups of rats. According to Weisburger (297), in rats “carbon tetrachloride caused neoplastic nodules and a few carcinomas of the liver. However, the incidence was lower than anticipated.” Considering the low mutagenic activity and the failure to alkylate DNA, a relationship of liver injury to causation of liver tumors seems plausible. There appear to be no data on tumors resulting from inhalation of carbon tetrachloride. 10.5 Standards, Regulations, or Guidelines of Exposure Exposure limits: NIOSH carcinogen, lowest feasible concentration, with a STEL of 2 ppm and an IDLH of 200 ppm. OSHA PEL is 10 ppm, ceiling is 25 ppm and 5-min peak in any 4 hrs is 200 ppm. The ACGIH TLV TWA is 5 ppm and the STEL/C is 10 ppm with an A2 notation. CPSC banned the use of carbon tetrachloride under the authority of the Federal Hazardous Substances Act (FHSA), as well as mixtures containing the chemical, except for unavoidable manufacturing residues of carbon tetrachloride in other chemicals that do not, during use, result in an air concentration greater than 10 ppm. EPA regulates carbon tetrachloride under the Clean Air Act (CAA), Clean Water Act (CWA), Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA), Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA), Food, Drug,

and Cosmetic Act (FD&CA), Resource Conservation and Recovery Act (RCRA), Safe Drinking Water Act (SDWA), and Superfund Amendments and Reauthorization Act (SARA). Carbon tetrachloride is designated as a hazardous air pollutant under CAA, hazardous waste under RCRA, and a hazardous substance under CWA. Under CAA, EPA has set emission standards for carbon tetrachloride for point-source categories and any stationary source for which the standards apply. Effluent discharge guidelines have been set under CWA. Carbon tetrachloride is subject to reporting rules under CWA, CERCLA, RCRA, and SARA. Under CERCLA, EPA has lowered the reportable quantity (RQ) of 5000 lb established under CWA to 10 lb (SARA final RQ). EPA has banned the use of carbon tetrachloride as a grain fumigant under FIFRA. Under FD&CA, EPA published data collection and labeling requirements for pesticides containing carbon tetrachloride as an inert ingredient. Carbon tetrachloride is regulated as a hazardous constituent of waste under RCRA (hazardous-waste number, U211; regulatory level, 0.5 mg/L). Under SDWA, EPA set a maximum contaminant level goal (MCLG; 0 mg/L) and a maximum contaminant level (MCL; 0.005 mg/L) for carbon tetrachloride. The World Health Organization (WHO) recommends that no detectable residues (limit: 0.01 ppm) of carbon tetrachloride be allowed on food or feed, but permits 50 mg/kg on cooked cereals. FDA regulates, under FD&CA, the amount of carbon tetrachloride in bottled water and indirect food additives. 10.6 Studies on Environmental Impact: NA

Saturated Methyl Halogenated Aliphatic Hydrocarbons Jon B. Reid, Ph.D., DABT 11.0 Carbon Tetrabromide 11.0.1 CAS Number: [558-13-4] 11.0.2 Synonyms: Tetrabromomethane 11.0.3 Trade Names: Bromid uhlicity (Czech); Carbon bromide 11.0.4 Molecular Weight: 331.63 11.0.5 Molecular Formula: CBr4 11.0.6 Molecular Structure:

11.1 Chemical and Physical Properties 11.1.1 General Physical state Colorless solid when pure; often yellow to brown Specific gravity 3.42 (20°C) Melting point (a) 48.4°C; (b) 90.1°C (slight decomposition on melting) Boiling point 189.5°C (slight decomposition) Refractive index 1.59998 (99.5°C) Solubility 0.24 g/100 mL water at 30°C; soluble in ethanol, ethyl ether, chloroform

Flammability

Not flammable by standard tests in air

1 mg/L = 74 ppm and 1 ppm = 13.58 mg/m3 at 25°C, 760 torr 11.1.2 Odor and Warning Properties Carbon tetrabromide has significant lacrimatory effect on the eye at low concentrations. This may be reasonably good warning of acute exposure, but may not be adequate to prevent excessive repeated exposure. 11.2 Production and Use Carbon tetrabromide is used to a limited extent as a chemical intermediate. It has been isolated from red algae, Asparagopsis toxiformis, found in the ocean near Hawaii. 11.3 Exposure Assessment: NA 11.4 Toxic Effects Carbon tetrabromide is a highly toxic material, based on the limited amount of toxicologic data available. Little new information is available since the previous edition. 11.4.1 Experimental Studies 11.4.1.1 Acute Toxicity Acute exposure to high concentrations causes upper respiratory irritation and injury to the lungs, liver, and kidneys. The response to chronic exposure at very low concentrations is primarily liver injury. The material is a lacrimator, even at low levels. The LD50 by oral administration was found to be 1800 mg/kg body weight in the rat. In the eyes of rabbits, the undiluted material caused severe irritation and permanent corneal damage. When the material was promptly washed from the eyes, pain and irritation were noted but the corneal damage was temporary. Skin contact causes relatively slight irritation in rabbits. If the material is confined tightly to the skin, it may cause hyperemia and a moderate edema. From observations made when the material was repeatedly bandaged onto the skin, there was no indication of toxic absorption, but no attempt was made to quantify the dosage. The hepatotoxic and nephrotoxic effects of carbon tetrabromide were studied in male Sprague– Dawley rats following a single IP administration in a dose range of 25–125 mL/kg. Carbon tetrabromide did not cause hepatotoxic effects when given alone or in combination wth prior exposure to chlorodecone. It caused renal dysfunction, but these effects were abolished by dietary chlordecone pretreatment. In vitro incubation of renal cortical slices obtained from treated animals revealed a significant depression of organic anion transport. 11.4.1.2 Chronic and Subchronic Toxicity Exposure of rats to carbon tetrabromide “fumes” (0.01– 1 mg/L) (0.07–74 ppm), 4 h/day for 4 months was reported to cause irritation of the eyes and respiratory tract. In another (unpublished) study, repeated exposures of rats 7 h/day, 5 days/week for 6 months to the vapors of carbon tetrabromide were studied. When the concentration in air was determined by combustion of air samples and determination of halogen, the concentration without effect was found to be 0.1 ppm by volume. When the concentration in air was determined by a polarographic method, the concentration was 0.3–0.5 ppm by volume. Higher concentrations than this caused poor growth and fatty and degenerative changes in the liver. 11.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms The small amount of data that is available suggests that either hydrolysis or metabolism produces some bromide ion. Carbon tetrabromide would not be expected to produce physiologically significant quantities of bromide ion in the blood at levels of exposure considered acceptable by inhalation. Carbon tetrabromide is metabolized in vitro to produce carbon monoxide, but the in vivo significance has not been established.

Like classic lipid peroxidation chemicals such as carbon tetrachloride, carbon tetrabromide show similar activity. Protein synthesis and lipid peroxidation were evaluated in rat liver slices in the presence of oxidants and protein synthesis inhibitors (2, 3). The ability of carbon tetrabromide (and several other halogenated compounds) to inhibit protein synthesis was correlated with its ability to induce lipid peroxidation and was also correlated with their toxicity as indicated by the LD50. The authors suggest that oxidant-induced lipid peroxidation and protein synthesis damage occurs concurrently, and that protein synthesis inhibition may be involved in cell injury or death mediated by free radicals. Carbon tetrabromide (as well as some other brominated and chlorinated methanes) undergoes oxidate metabolism to electrophilic halogens by liver microsomes. 11.5 Standards, Regulations, or Guidelines of Exposure The ACGIH TLV TWA is 0.1 ppm and the STEL/C is 0.3 ppm. The NIOSH REL is 0.1 ppm with an STEL of 0.3 ppm. OSHA currently does not have a PEL. International occupational exposure values: Australia TWA 0.1 ppm (1.4 mg/m3); STEL 0.3 ppm (4 mg/m3) January 1993. Belgium

TWA 0.1 ppm (1.4 mg/m3); STEL 0.3 ppm (4.1 mg/m3) January 1993.

Denmark

TWA 0.1 ppm (1.4 mg/m3) January 1993.

Finland

TWA 0.1 ppm (1.4 mg/m3); STEL 0.4 ppm; “skin” notation January 1993.

France

TWA 0.1 ppm (1.4 mg/m3) January 1993.

Ireland

TWA 0.1 ppm (1.4 mg/m3); STEL 0.3 ppm (4 mg/m3) January 1997.

The Netherlands TWA 0.1 ppm (1.4 mg/m3) October 1997. Switzerland TWA 0.1 ppm (1.4 mg/m3) January 1993. United Kingdom TWA 0.1 ppm (1.4 mg/m3) STEL/C: 0.3 ppm. 11.6 Studies on Environmental Impact: NA Saturated Methyl Halogenated Aliphatic Hydrocarbons Bibliography

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NCI, Bethesda, MD, 1976. 289 National Cancer Institute (NCI), Carcinogenesis Bioassay of Trichloroethylene, Carcinog. Tech. Rep. Ser. No. 2, NCI-CG-TR-2, NCI, Bethesda, MD, 1976. 290 National Cancer Institute (NCI), Bioassay of 1,1,1-Trichlorethane for Possible Carcinogenicity, Carcinog. Tech. Rep. Ser. No. 3, NCI-CG-TR-3, North-Holland Biomedical Press, New York, pp. 249–258, 1977. 290a G. Della Parta, B. Terrocini, and P. Shubic, Induction with carbon tetrachloride of liver cell carcinomas in hamsters. J. Natl. Cancer Inst. 26, 855–863 (1961). 291 B. J. Dean and G. Hodson-Walker, Mutat. Res. 64, 329–337 (1979). 292 J. C. Mirsalis, C. K. Tyson, and B. E. Butterworth, Environ. Mutagen. 4, 553–562 (1982). 293 A. Blair, P. Decoufle, and D. Grauman, Am. J. Public Health 69(5), 508–511 (1979). 294 International Agency for Research on Cancer (IARC), Monographs on the Evaluation of the Carcinogenic Risks to Humans, Vol. 1, IARC, Lyon, France, 1972, p. 53. 295 International Agency for Research on Cancer (IARC), Evaluation of the Carcinogenic Risks of Chemicals to Humans, Vol. 20, IARC, Lyon, France, 1979, p. 371. 296 U.S. Environmental Protection Agency (USEPA), Integrated Risk Information System Computer Printout for Carbon Tetrachloride, USEPA, Washington, DC, 1988. 297 E. K. Weisburger, Environ. Health Perspect. 21, 7 (1977).

Saturated Halogenated Aliphatic Hydrocarbons Two To Four Carbons Jon B. Reid, Ph.D., DABT Ethyl Chloride 1.0.1 CAS Number: [75-00-3] 1.0.2 Synonyms: Chloroethane, hydrochloric ether, monochloroethane, and muriatic ether 1.0.3 Trade Names: Aethylos chloridium, Anodynon, Chelen, Chlorene, Chloretilo, Chloroethyl, Chloryl, Chloryl anesthetic, Dublofix, Ether chloratus, Hydrochloric ether, Kelene, Monochloroethane, Moriatic ether, Narcotile, and NCI-C06224 1.0.4 Molecular Weight: 64.52 1.0.5 Molecular Formula: CH3CH2Cl 1.0.6 Molecular Structure:

1.1 Chemical and Physical Properties Ethyl chloride is a colorless gas with an ethereal, somewhat pungent odor and burning taste. It is highly flammable, even at ordinary temperature and pressure, and a severe fire and explosion risk. Under increased pressure and lower temperatures, it is a very volatile liquid.

Physical Specific gravity Melting Point Boiling Point Vapor pressure Solubility

Colorless gas 0.8917 (25/25°C)0.897 at 20°C –138.7 12.3 1200 torr (25°C) 1000 torr at 20°C 0.57g/100 mL water at 20°C, 48 g/100 mL ethanol at 21°C 0.6% in H2O

Flammability limits 3.8–15.4% by volume in air Autoignition temperature 519°C Flash point –50°C (closed cup); –43°C (open cup) 1.1.1 General The principal problem in industrial use of ethyl chloride is that typical of an anesthetic material where “drunkenness” and incoordination may lead to inept operation and therefore the possibility of an injury. Cardiac arrhythmia are possible, but high concentrations are required (6). The older data were summarized by von Oettingen (7), and an ATSDR profile (update) has been published by the U.S. Public Health Service in December, 1998 (8). 1.1.2 Odor and Warning Properties Ethyl chloride has an ethereal, somewhat pungent odor recognizable at concentrations of 100–600 ppm (9). High concentrations are necessary for potentially serious physiological effects, which may be considered a possible warning property for acute effects. According to AD Little (9), in humans, 50% of the subjects detected the odor of ethyl chloride at 140 ppm and 100% detected 680 ppm. An odor threshold of 4.2 ppm has been reported by Amoore (10). 1.2 Production and Use Ethyl chloride is used in the manufacture of tetraethyl lead, ethylcellulose, dyes, drugs, and perfumes. It is also used as an alkylating and analytical agent, in organic syntheses, and as a solvent for fats, oils, waxes, phosphorus, acetylene, and many resins. It is also used as a propellant, an anesthetic, in refrigeration, and in the formulation of insecticides. Ethyl chloride has been used as a chemical intermediate, as a topical anesthetic, and to a limited degree as a refrigerant. The most serious problems have been with its use as an anesthetic. The major problems encountered in industry has been fire and explosion. 1.3 Exposure Assessment According to the ATSDR toxicity profile (8), humans can be exposed to chloroethane from environmental, occupational, and consumer sources. In the 1970s and 1980s, chloroethane was found in outdoor air at levels of 41–140 ppt, but current levels are expected to be lower because of decreased production. Extremely low levels of chloroethane are present in drinking water, which may form during chlorination. There are no data on chloroethane in food. Exposure can result from contact with consumer products such as paints and refrigerants via skin. Occupational exposure may result from inhalation or skin contact. According to a NIOSH survey between 1981 and 1983, an estimated 49,212 workers in the United States were exposed to chloroethane in the workplace at that time. 1.3.1 Air See the preceding. 1.3.2 Background Levels See the preceding. 1.3.3 Workplace Methods NIOSH Method 2519 is recommended for determining workplace exposures to ethyl chloride. 1.3.4 Community Methods Environmental methods are given in the ATSDR profile (8). These address: ambient air, air from a contaminated site, air from a landfill, raw/treated water, finished drinking/ raw source water, water, wastewater, groundwater, soil and sediment, solid and liquid

waste. 1.3.5 Biomonitoring/Biomarkers Biological monitoring of expired air would appear to be of little value owing to the physical properties of ethyl chloride, which suggest rapid excretion. The ATSDR profile (8) gives a table of methods for biological samples, including exhaled air, human milk, blood and urine, urine and adipose tissue, and also for fish and marine biota. The purge and trap method is used for both environmental and biological samples. 1.3.5.1 Blood The ATSDR profile (8) offers a method for blood and urine: The sample is mixed with water and antifoaming agent, purged at 50°C, trapped in Tenax, and thermal desorption, followed by Cryofocus—using high-resolution gas chromatography, flame ionization chromatography, and mass spectrometry. The detection limit is 3 mg/L of blood and 3 mg/L of urine with >80% recovery. 1.3.5.2 Urine See the preceding. 1.4 Toxic Effects According to Sax (1) ethyl chloride has moderate toxicity via oral and inhalation routes. It is an irritant of skin, eyes, and mucous membranes. The liquid is harmful to the eyes and can cause smoke irritation. In the case of guinea pigs, symptoms attending exposure are similar to those caused by methyl chloride, except that the signs of lung irritation are not as pronounced. It gives some warning of its presence because it is irritating, but it is possible to tolerate an exposure until one becomes unconscious. It is the least toxic of all the chlorinated hydrocarbons, but at high concentrations ethyl chloride can cause narcosis, anesthesia, and even death on single exposure. It can cause narcosis, although the effects are usually transient. Animal experiments show some evidence of kidney irritation and accumulation of fat due to this material in the kidneys, cardiac mucles, and liver. It is also readily absorbed through the skin. It is a highly dangerous fire hazard and forms phosgene on combustion. When heated to decomposition, ethyl chloride may emit toxic fumes of HCl and may also release fumes of CO. 1.4.1 Experimental Studies 1.4.1.1 Acute Toxicity A single reference reports allergic eczematous eruption in two subjects after ethyl chloride was sprayed on the skin in an allergy-testing procedure (11). The wide use of ethyl chloride as a local anesthetic suggests that these must have been rare subjects. Rats were anesthetized for 2 h with ethyl chloride (12). Complete disappearance of glycogen in the liver, a decrease in acid phosphatase levels, and increases in alkaline phosphatase and succinic dehydrogenase levels were reported. A 2 h LC50 of 152 mg/L (57,600 ppm) has been reported (13). Deaths were anesthetic in nature but hyperemia, edema, and hemorrhages were reported in the internal organs, brain, and lungs. Repeated 2 h exposures for 60 d to 14 mg/L (5300 ppm) were alleged to cause a decrease in the phagocytic activity of the leukocytes, lowered hippuric acid formation in the liver, and histological or pathological changes in the liver, brain, and lungs. However, Troshina's results are not consistent with newer data. In the limited study on rats and dogs, exposures to 0, 1600, 4000, or 10,000 ppm were given 6 h/d, 5 d/wk for 2 wk (14) there were no adverse effects on any of the extensive number of toxicological parameters studied except for a slight increase in liver to body weight ratios in rats exposed to 4000 and 10,000 ppm. Nonprotein sulfhydryl was decreased in rats and mice. In a 11 d study in which mice were exposed 23 h/d to 0, 250, 1250, or 5000 ppm the only effect was a slight liver weight increase and hepatocellular vacuolization at 5000 ppm (17). In a teratological study at 0, 500, 1500, or 5000 ppm reported in a subsequent section, no toxicologic effects were noted in pregnant mice after 10 consecutive 6 h daily exposures to 500, 1500, or 5000 ppm (18). As part of a lifetime carcinogenic study also reported in a subsequent section, rats and mice were exposed 1, 10, or 65 times (19). Then 6 h exposures 5 d/wk for 14 d to 19,000 ppm also produced no

evidence of toxicity in male and female rats. Ethyl chloride has been demonstrated to be a cardiac sensitizer (31) in dogs at or near concentrations producing anesthesia, 30,000–45,000 ppm (32). In this condition, cardiac tissue is hypersensitized to the effects of stimulatory endogenous catecholamines, which can result in arrhythmias and cardiac arrest. 1.4.1.2 Chronic and Subchronic Toxicity In a 13 wk study, rats were exposed 6 h/d, 5 d/w (65 exposures) to 0, 2500, 5000, 10,000 or 19,000 ppm. The only effect was a slight liver weight increase at 19,000 ppm as well as slightly lowered body weights in both sexes. Based on the effects seen with similar compounds, and limited data on dogs, sensitization of the heart to adrenaline could be a hazard at very high (anesthetic) concentrations (20, 21). It is not possible to determine whether deaths that occurred during the short period of time it was used as a general anesthetic were due to anesthesia and/or cardiac toxicity or to some other conditions related to surgery. In an NTP study (19), groups of F344 rats and B6C3F1 mice (50/group/sex) were exposed to either 0 (air) or 15,000 ppm of 99.5% ethyl chloride (39.6 g/m3) 5 d/wk, 6 h/d for 102 wk (rats) or 100 wk (mice). The duration-adjusted concentration becomes 7.1 g/m3. The exposure level was set at this limit because of safety considerations for explosions. A single level of exposure was chosen as no exposure-related changes were seen in the 90-d study at a slightly higher concentration (19,000 ppm). Survival of female mice after week 82 was significantly lower than controls, apparently due to an increase in deaths from carcinomas of the uterus; there were no other statistically significant differences in survival between control and treated animals of either species. Mean body weights were decreased in both male and female rats. In females, the maximum difference in body wieghts between exposed and control animals was 13% and occurred at 59 wk of exposure when 49 of 50 test animals were still alive. Although some fluctuations towards normalcy were observed from this time forward, terminal body weights of 23 surviving treated animals were still 10% less than their corresponding controls. In male rats, mean body weights were also decreased when compared with controls, although the decrease achieved a miximum differential of only 8%. The mean body weights of mice were not affected by exposure. Based on the mild decrease in mean body weight gain, 15,000 ppm is judged as a free-standing NOAEL. The NOAEL (HEC) = 7.1 g/m3. Groups of F344 rats and B6C3F1 mice (10/group) were exposed to either 0 (air), 2500 ppm (6.6 g/m3), 5000 ppm (13.2 g/m3), 10,000 ppm (26.4 g/m3), or 19,000 ppm (50.1 g/m3) of 99.5% ethyl chloride 5 d/wk, 6 h/d for 13 wk (19). The duration-adjusted concentrations are 0, 1.2, 2.4, 4.7, or 9.0 g/m3, respectively. Monitoring for toxicological effects was by daily observation, body weights, and a complete necropsy and histologic examination including tissues of the entire respiratory tract and brian. No exposure-related clinical signs or gross or histopathological effects were observed in either species. Relative liver weights were slightly increased in the male rats (14%) and female mice (18%) exposed to 19,000 ppm. Slight decreases in mean body weights were noted in the rats (8% in the males, 4% in the females) exposed to 19,000 ppm; no dose-related tendency could be discerned from the data. As no toxicity was apparent, 19,000 ppm is considered as a free-standing NOAEL in this study. The NOAEL(HEC)= 9.0 g/m.3 The results obtained in the two studies of Troshina (13, 22) are not consistent with those of NTP (19) or Landy et al. (14, 17). Deficiencies preclude consideration of these studies as a reliable source of information about the toxic effects of this chemical. 1.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Conjugation with glutathione has been shown to occur at a much higher rate in mice than rats (25). These data suggest that this conjugation,

which is species specific and dose dependent, may be extremely important in understanding the development of toxicity and tumors in female mice. A nongenetic (hormonal) mechanism of uterine tumors induction has been suggested. 1.4.1.4 Reproductive and Developmental In a developmental study conducted in groups of 30 CF-1 mice, Scortichini et al. (18) exposed animals to mean time-weighted averages of 0 (air), 491 ± 37 ppm (1.3 g/m3), 1504 ± 84 ppm (4000 mg/m3), and 4946 ± 159 ppm (13,000 mg/m3) 99.9% ethyl chloride for 6 h/d on days 6 through 15 of gestation. The animals were sacrificed on the eighteenth day of gestation. (These values are not duration adjusted.) This study shows that exposure to ethyl chloride results in fetotoxicity. The exposure concentration of 1504 ppm is the NOAEL of this study NOAEL(HEC) = 4000 mg/m3 based on foramina of the skull bones. The highest concentration used in this study, 4946 ppm, is a LOAEL, (HEC) = 13,000 mg/m3. According to Hanley et al. (23), the reproductive organs were not affected following subchronic inhalation exposures to ethyl chloride. Exposures to mice at concentrations of 500, 1500, or 5000 ppm during organogenesis produced no teratogenic effects. The presence of a few small unossified areas in the skull bones at 5000 ppm suggest very slight fetotoxicity. Experiments conducted by Breslin et al. (24) suggest that exposure to ethyl chloride may disrupt the estrus cycle of mice. Two groups (10/group) of female B6C3F1 mice were acclimated in exposure chambers over a 2 wk period or until the estrus cycles of most mice was a 4–6 d interval (as judged by a vaginal lavage technique). Males were included in each chamber to synchronize and promote regular estrus cyclicity. Following acclimatization one group was exposed to 15,000 ppm (39.6 g/m3 ethyl chloride 6 h/d for a minimum of 14 consecutive days (through 3 estrus cycles). No effects on behavior, gross, or histopathology were observed in the group undergoing exposure, although the mean body weights in the exposed group were significantly increased rather than decreased. The mean length of the estrus cycle in exposed mice was 5.6 d, significantly longer in duration than the pre-exposure duration for the same group (5.0 d) and for the corresponding controls (4.5 d). The protraction of the period could not be attributed to an increase in any particular phase of the estrus cycle and is therefore suggestive of a general stress response. A direct exposure-related effect of ethyl chloride on neuroendocrine function cannot be excluded. As this effect is regarded as a systemic effect, the exposure is duration adjusted to establish a free-standing LOAEL of 6.6 g/m3. The LOAEL(HEC) = 6.6 g/m3. 1.4.1.5 Carcinogenesis The EPA (IRIS) has not made a carcinogenicity assessment at this time. Increased cancer of the uterus of female mice has been produced by exposure to 15,000 ppm, but lower concentrations have not been studied. Rats and mice were exposed to 0 or 15,000 ppm of ethyl chloride in an NTP 2-year study with mixed results (19). Results in male rats were considered equivocal based on a combined total of five skin tumors versus none in the control male rats. Likewise female rats results were considered equivocal because three astrocytomas were found versus none in the female control rats. The male mouse group had such poor survival that it was deemed an inadequate study although combined alveolar/bronchiolar adenomas and carcinomas were reported (10/48 versus 5/50 in the control male rats). Female mice exposed to 15,000 ppm had clear evidence of an effect, for 43/50 mice had endometrial uterine carcinomas versus 0/49 in the female control mice. In addition, there was a suggestion of an increase in combined hepatocellular adenomas and carcinomas in the female mice (8/48 exposed versus 3/49 control). 1.4.1.6 Genetic and Related Cellular Effects Studies According to the NTP report of carcinogenic studies, ethyl chloride was found to be mutagenic in Salmonella both with and without S-9 activation. The report considers the effect to be consistent with alkylating activity in base substitution strains TA100 and TA1535. Studies of chromosomal aberration in the bone marrow of mice exposed for 2 years were negative (19), as were all transformation studies in mouse BALB/c-

3T3 cells (26). 1.4.2 Human Experience Exposure to ethyl chloride can cause irritation of the eyes. It can also be iritating to the nose, throat, and respiratory tract. At concentrations of approximately 2% (molar), it can cause an anesthetic or narcotic effect. This can result in headache and nausea and also dizziness. At higher concentrations, exposure can cause unconsciousness. It may also produce central nervous system depression. This depression is usually brief and reversible. Due to its rapid rate of evaporation, it can cause tissue freezing or frostbite on dermal contact. Other symptoms include drowsiness, noisy talkativeness, and sensitizing effects on the myocardium. It may also cause irregular heart beat. It may cause liver and kidney damage, incoordination, and abdominal cramps. It may cause slight symptoms of inebriation. Exposure may also cause lung irritation, damage to internal organs, excitement, and paralysis of respiration. It may cause lung damage. Ethyl chloride may irritate the kidneys and cause fat accumulation in the kidneys, cardiac muscles, and liver. It is absorbed readily through the lungs, and rapidly given off through the lungs. Other symptoms reported include cardiac arrhythmias at high concentrations; rare allergic eczematous eruptions when sprayed on skin; and hyperemia, edema, and hemorrhages in the internal organs, brain, and lungs. It may also cause weak analgesia. It may cause stupor. The most serious problem from severe acute exposure, other than the anesthetic effect, is the possibility of the potentiation of adrenalin, and the resultant cardiac problems (27, p. 247). Exposure to this compound may cause death due to respiratory or cardiac arrest. Deaths are anesthetic in nature. Although used as a surgical anesthetic, ethyl chloride has a narrow margin of safety for this purpose as anesthesia occurs at 20–30 mg % and respiratory failure at 40 mg % (28). Ethyl chloride is explosive at 4% (40,000 ppm, 106 g/m3) in air, overlapping the concentrations required to produce anesthesia (3–4.5%) Neurological symptoms have been observed in human case studies in instances of ethyl chloride abuse. Hes et al. (29) noted cerebellar-related symptoms including ataxia, tremors, dysarthria (speech difficulties), slowed reflexes, nystagmus (involuntary movement of the eyeball), and hallucinations in a 28-year old female who sniffed 200–300 mL of ethyl chloride off her coat sleeve daily for 4 mo. Examination revealed that her liver was enlarged (3 cm) and slightly tender and was accompanied by a mild and transient disturbance (not clinically described) of liver function. All symptoms were resolved by the end of 4 wks. Similar neurological symptoms were noted in a 52-year-old male who had a 30-year history of intermittent ethyl chloride (as well as alcohol and barbiturate) abuse (30). Questioning upon hospitalization revealed that he had been inhaling at least 100 mL of ethyl chloride daily for the previous 4 mo. No liver effects were reported, and the patient fully recovered from the neurological symptoms by 6 wk after admission. Ethyl chloride has been used experimentally and clinically as a topical and inhalation anesthetic in human subjects; reviews are available (6, 7). In a study by Davidson (33) ethyl chloride was administered to humans. Intoxication started at 1.3%, memory loss at 1.9%, incoordination at 2.5%, and at 3.36%, incoordination was followed by cyanosis, nausea, and vomiting. 1.4.2.1 General Information The acute toxicity for animals was reported by Sayers et al. (15) (see Table 63.1) and the narcotic concentrations for humans were reported by Lehann and Flury (16) (see Table 63.2). More recent data have not changed their conclusion significantly. Table 63.1. Response of Guinea Pigs to Ethyl Chloride Vapor in Air (15) Concentration (%)

Exposure time (min)

23–24

5–10

Response Unconscious, some deaths

15.3

40

9.1

30

5 4

40 122 270

2

540 270 540

1

810

Some deaths in 30 min; some survived 40 min Survived; histopathological changes in lungs, liver, etc. Survived; lungs congested Survived; returned to normal Survived; histopathological changes in lungs, liver, and kidneys Some deaths Survived; returned to normal Survived; histopathological changes in liver and kidneys Survived; returned to normal

Table 63.2. Narcotic Ethyl Chloride Concentrations in Humans Concentrations in Humans Concentration

mg/L ppm

Response

105.6 40,000 After 2 inhalations, stupor, irritation of eyes, and stomach cramps 88.7 33,000 After 30 sec, quickly increased toxic effect 66.0 25,000 Lack of coordination 52.8 20,000 After 4 inhalations, dizziness and slight abdominal cramps 50.4 19,000 Weak analgesia after 12 min 34.3 13,000 Slight symptoms of poisoning

1.4.2.2.4 Reproductive and Developmental Early and late pregnancy toxemias have been observed in women occupationally exposed to ethyl chloride and other chemicals such as ethyl bromide and butanol (34). Women who were exposed occupationally to unknown concentrations of ethyl chloride along with ethylenediamine, ammonia, polyethylene polyamines, vinyl chloride, and hot summer temperatures had genital disorders that included inflammatory diseases of the cervix and uterus and vaginitis (35). 1.4.2.2.5 Carcinogenesis The EPA (IRIS) has not made a carcinogenicity assessment at this time (36). 1.5 Standards, Regulations, or Guidelines of Exposure The ACGIH TLV TWA is 100 ppm with an A3 designation (confirmed animal carcinogen with

unknown relevance to humans). The NIOSH considers that ethyl chloride be treated in the workplace with caution because if its structural similarity to chloroethanes shown to be carcinogenic in animals. The OSHA PEL is 1000 ppm. Other Nations: Australia: 1000 ppm (1993); Federal Republic of Germany: no MAK, Group B carcinogen, justifiably suspected of having carcinogenic potential (1995); Sweden: 500 ppm, short-term value 700 ppm, 15 min (1993); United Kingdom: 1000 ppm, 15 min STEL 1250 ppm (1995). 1.6 Studies of Environmental Impact None found.

Saturated Halogenated Aliphatic Hydrocarbons Two To Four Carbons Jon B. Reid, Ph.D., DABT 1,1-Dichloroethane 2.0.1 CAS Number: [75-34-3] 2.0.2 Synonyms: Ethylidene chloride, ethylidene dichloride 2.0.3 Trade Names: Chlorinated hydrochloric Ether, HSDB 64 2.0.4 Molecular Weight: 98.97 2.0.5 Molecular Formula: CH3CHCl2 2.0.6 Molecular Structure:

2.1 Chemical and Physical Properties Dichloroethane-1,1 is a colorless, oily liquid with a chloroformlike odor. Physical state Colorless liquid Specific gravity 1.175 (20°C) Melting point –96.98°C Boiling point 57.3°C Vapor pressure 234 torr (25°C) Refractive index 1.41655 (20°C) Percent in “saturated;”air 30.8(25°C) Solubility 0.5 g/100 MI water at 20°C; soluble in (5500 mg/L) ethanol, ethyl ether Flash point 14°C (open cup); –8.33°C (closed cup) Flammability limits 5.6–11.4% by volume in air Ignition temperature 493°C

2.1.1 General 2.1.2 Odor and Warning Properties 1,1-Dichloroethane has been stated to have a “chloroformlike” odor, but the level at which this odor is detectable has not been determined. 2.2 Producton and Use 1,1-Dichloroethane is flammable and has limited use as a solvent. Its major use is as a chemical intermediate. Formerly used as an anesthetic, it is of no importance in this field today. It appears to be an environmental breakdown product of some commonly used chlorinated solvents. An ATSDR toxicology profile is available (3). 2.3 Exposure Assessment Exposure routes are inhalation, ingestion, skin, and/or eye contat. The substance can be absorbed into the body by inhalation and by ingestion. A harmful concentration in the air can be reached rather quickly on evaporation of this substance at 20°C. The vapor is heavier than air and may travel along the ground; distant ignition possible. 2.3.3 Workplace Methods NIOSH Method 1003 for halogenated hydrocarbons is recommended for determining workplace exposures to 1,1-dichloroethane. 2.3.5 Biomonitoring/Biomarkers Although biologic monitoring for expired 1,1-dichloroethane in air might be useful for determining recent exposure, inadequate data are available to quantify exposure. Urinary metabolites (dichloroacetic acid and monochloroacetic acid) would be expected only in low concentrations if present at all. 2.4 Toxic Effects 1,1-Dichloroethane may be harmful by inhalation, ingestion, or skin absorption. Vapor or mist is irritating to the eyes, mucous membranes, skin, and upper respiratory tract. When heated to decomposition, it emits toxic fumes of carbon monoxide, carbon dioxide, hydrogen chloride gas, and phosgene. It is narcotic in high concentrations. It may also have anesthetic effects at high concentrations. It is a lacrimator. Much less has been published on the toxicity of 1,1-dichloroethane than on its more toxic isomer 1,2-dichloroethane (ethylene dichloride). 1,1-Dichloroethane is rather low in toxicity. It is capable of causing anesthesia, but has a relatively low capacity to cause liver or kidney injury even on repeated exposure. Massive doses by gavage in oil were questionably carcinogenic in rats and mice, but when fed in drinking water, no increase in liver cancer occurred in a limited study in male mice. 2.4.1 Experimental Studies 2.4.1.1 Acute Toxicity Although the 1985 NIOSH Registry of Toxic Effects of Chemical Substances (42) lists an oral. LD50 of 725 mg/kg for rats based on a 1967 article, this must be an error, because repeated daily doses higher than this were given by gavage for 78 wk (43). No original reference is given for a report of an oral LD50 of 14.1 g/kg for rats. In a study by Muralidhara et al. (44), adult male Sprague–Dawley rats were given single doses of 0, 0.5, 1.0, 2.0, 4.0, and 8.0 g/kg in corn oil. There was significant mortality only at 8 g/kg and no evidence of treatment-related effects on serum or urinary enzyme levels, organ weights, or tissue morphology. Rats received repeated oral doses of 0, 0.5, 1.0, 2.0, or 4.0 g/kg 5 d/wk for 12 wk. There was marked CNS depression and high mortality only in the 4-g/kg group but little evidence of toxicity other than transient CNS depression at lower levels. Inhalation Acute: In 1956, Smyth (45) found that rats survived an 8 h exposure to 4000 ppm but were killed by 16,000 ppm. Deaths were probably due to anesthesia. Schwetz et al. (46) showed that pregnant and nonpregnant rats survived 10 repeated 7 h exposures to 6000 ppm with no effect except for a slight liver weight increases in nonpregnant rats. Intraperitoneal: Plaa and Larson (47) found little liver and kidney toxicity following intraperitoneal

injection. Doses of 1000 mg/kg produced no renal necrosis in mice but some evidence of tubular swelling was reported. Urinary protein was increased after injection of 2000 mg/kg and urinary glucose increased after 4000 mg/kg. Klinkead and Leahy (48) report on a 4 h male, rat, inhalation exposure which gave a LC50 of ca. 13,000 ppm. In the same paper the authors reported no toxic effects in rabbits dermally exposed to an upper limit of 2 mL/kg body weight for 24 h for 14 d. Mueller (49) observed anesthetic effects in mice that inhaled 8,000–10,000 ppm for 2 h with a minimum lethal dose of 17,300 ppm. 2.4.1.2 Chronic and Subchronic Toxicity In two studies by Muralindhara and Ramanthan (44), rats were given a single oral bolus of 0, 500, 1000, 2000, or 4000 mg 1,1-dichloroethane/kg body weight for 5 or 10 consecutive days. Glutathione showed a dose-dependent increase in the kidney after 5 and 10 d of exposure, but liver GSH and other indices were not different from controls. Reported in the same paper was a subchronic study where rats were given single oral doses of 0, 500, 1000, 2000, or 4000 mg/kg body weight 5 d/wk for up to 12 wk. CNS depression, marked and high mortality occurred in the 4000 mg/kg group, but little signs of toxicity were seen at lower dosage levels. Hofmann et al. (50) reported that rats guinea pigs, rabbits, and cats tolerated 6 h daily exposures to 500 ppm 5 d/wk for 13 wk with no adverse effects. Rats, guinea pigs, and rabbits also tolerated an additional 13 wk at 1000 ppm, but cats showed histological evidence of kidney injury and increased blood urea. In a study by Schwetz et al. (46) pregnant female rats were exposed on days 6 to 15 of gestation to 3800 or 6000 ppm 1,1-dichloroethane vapors. Exposures were for 7h/d. Essentially no effect occurred in either the dams or fetuses except for slight but statistically significant decreases in food consumption and weight gain by the dams and delayed ossification in the fetuses. No teratological effects were related to exposures. Liver weights of a group of nonpregnant rats were increased by similar exposure, but no histological changes were apparent grossly or microscopically. 2.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms In a study by McCall et al. (51) the authors proposed that 1,1-dichloroethane is metabolized by hepatic microsomal cytochrome P-450 in vitro, and this metabolism is important in the toxicity of the compound. Mitoma et al. (52) studied the metabolism of 1,1-dichloroethane after chronic oral dosing of adult mice and rats at maximum tolerated doses. The results are presented in Table 63.3. The maximum tolerated dose was 700 mg/kg for rats and 1800 mg/kg for mice. Animals were treated 5 d/wk for 4 wk with unlabeled 1,1-dichloroethane prior to a single gavage dose of labeled material in corn oil. The animals were placed in metabolism cages for 2 d following treatment. Rats excreted 86% as unchanged 1,1-dichloroethane and mice 70%. Total metabolism (primarily CO2) was 7.5 and 29%, respectively, and the metabolic products were similar in the two species. Although the investigators report radioactivity as “bound” the “binding” may have been due to incorporation as metabolites rather than due to alkylation. Table 63.3. Metabolic Disposition of Chlorinated Hydrocarbons in Rats and Mice Percentage of the Administered Dose Average (S.D.)

Metabolized a+b+c Dose Expired CO2 Excrete Carcass Species (mmol/kg) Air (a) (b) (c) Recovery Expired Air 1,1-Dichloroethane Rat 7.07 Mouse

18.19

1,2-Dichloroethane Rat 1.01 Mouse

1.51

86.13 5.12 0.92 (8.53) (0.43) (0.35) 70.42 25.23 1.64 (5.50) (5.37) (0.29)

1.41 (0.19) 2.43 (1.04)

93.46 (8.45) 99.74 (2.81)

7.45

11.48 8.20 69.51 (7.19) (3.93) (5.11) 7.65 18.21 81.88 (7.27) (3.22) (6.92)

7.05 (1.48) 2.37 (0.23)

96.26 (14.07) 110.12 (1.85)

84.76

1.20 (0.28) 0.72 (0.03)

89.26 (3.95) 99.04 (3.15)

4.12

5.08 (1.45) 3.09 (0.90)

72.10 3.85 (11.94) (0.54) 75.92 2.29 (1.97) (0.29)

90.53 (8.77) 88.11 (2.48)

81.03

1.80 (1.18) 3.89 (0.86)

21.64 (2.47) 66.65 (4.06)

6.67 (0.92) 11.08 (1.78)

87.54 (5.16) 99.81 (7.20)

30.11

1.98 (0.25) 10.14 (2.95)

46.01 (0.85) 30.29 (0.21)

30.75 (2.10) 27.44 (0.74)

85.77 (1.59) 77.57 (3.41)

78.74

1.47 (0.84) 2.08 (0.60)

60.09 (5.27) 77.21 (3.51)

3.20 (0.80) 5.04 (0.58)

98.90 (2.66) 90.22 (5.28)

64.76

1.94 2.39 (0.69) (0.12) 2.45 14.35 (0.48) (1.85)

0.77 (0.17) 5.40 (1.24)

84.30 (9.17) 79.65 (9.13)

5.1

2.37 6.33 (0.76) (2.39)

20.02 (3.70)

93.28 (6.23)

1,1,1-Trichloroethane Rat 22.48 83.13 (3.25) Mouse 29.98 92.94 (2.89) 1,1,2-Trichloroethane Rat 0.52 9.49 (2.64) Mouse 2.24 6.81 (2.10) Trichloroethylene Rat 9.89 57.41 (2.97) Mouse 15.22 18.18 (3.59) 1,1,2,2-Tetrachloroethane Rat 0.59 7.03 (1.01) Mouse 1.19 9.69 (1.13) 1,1,1,2-Tetrachloroethane Rat 1.19 34.14 (6.91) Mouse 2.38 5.89 (0.08) Tetrachloroethylene Rat 6.03 79.19 (8.99) Mouse 5.42 57.46 (9.79) Hexachloroethane Rat 2.11 64.55 (6.67)

0.87 2.05 (0.14) (0.46) 2.01 3.36 (0.07) (0.35)

29.3

102.46

6.09

81.3

81.62

67.87

84.33

22.2

28.72

Mouse

4.22

71.51 1.84 16.21 (5.09) (0.94) (3.76)

5.90 (1.60)

95.47 (9.59)

23.95

Thompson et al. (53) reported in vitro studies that confirmed that little 1,1- dichloroethane is metabolized. Cytochrome P450 appears to play a major role in metabolism and the addition of substances that increase P450 increase metabolism of 1,1-di-chloroethane. Addition of glutathione had a protective effect. 2.4.1.4 Reproductive and Developmental See the study by Schwetz et al. (46) reported in the subchronic/chronic section. 2.4.1.5 Carcinogenesis The EPA (IRIS) (2) classifies 1,1-dichloroethane as C; possible human carcinogen based on no human data and limited evidence of carcinogenicity in two animal species (rats and mice) as shown by an increased incidence of mammary gland adenocarcinomas and hemangiosarcomas in female rats and an increased incidence of hepatocellular carcinomas and benign uterine polyps in mice. The EPA offers no estimate of carcinogenic risk from inhalation or oral exposure. The EPA states (IRIS) that because of similarities in structure and target organs, the carcinogenic evidence for 1,2-dichloroethane is considered to be supportive of the classification of 1,1-dichloroethane in group C, a possible human carcinogen. The EPA considers the animal carcinogenicity “limited.” The NCI bioassay (43), provides limited evidence for the carcinogenicity of 1,1-dichloroethane in Osborne–Mendel rats and B6C3F1 mice. This is based on significant dose-related increases in the incidence of hemangiosarcomas at various sites and mammary carcinomas in female rats and statistically significant increases in the incidence of liver carcinomas in male mice and benign uterine polyps in female mice. The study is limited by high mortality in many groups. The low survival rates precluded the appearance of possible latedeveloping tumors and decreased the statistical power of this bioassay. Technical-grade 1,1dichloroethane in corn oil was administered by gavage 5 d/wk for 78 wk to groups of 50 Osborne– Mendel rats/sex/dose. All surviving animals were necropsied following a 33 wk observation period. Due to toxicity, dosing was not continuous (3 wk on, then 1 wk off), making the TWAs for 5 d/wk 382 and 764 mg/kg/d for low- and high-dose males and 475 and 950 mg/kg/d for low- and high-dose females, respectively. Both a vehicle and an untreated (not intubated) control group (20 rats/sex/group) were included in the study. A high incidence of pneumonia (approximately 80%) in all 4 groups of each sex was considered to be the cause for the low survival at termination of the study. Survival at 111 wk was 30, 5, 4, and 8% in the untreated control, the vehicle control, the lowdose, and the high-dose male rat groups, respectively. Survival at termination for the female rat groups was 40, 20, 16, and 18% for the untreated control, vehicle control, low- and high-dose groups, respectively. In female rats there was a statistically significant positive dose-related trend in incidence of hemangiosarcomas (0/19 for matched vehicle controls, 0/50 for the low-dose group, and 4/50 for the high-dose group). The incidence of mammary gland adenocarcinomas (1/20 for the untreated group, 0/19 for the vehicle control group, 1/50 for low-dose, and 5/50 for high-dose groups) showed a statistically significant dose-related positive trend in those female rats surviving at least 52 wk; tumor incidence was 0/16, 1/28, and 5/31 for vehicle control, low- and high-dose groups, respectively. (Tumor incidence at termination for the untreated control females surviving at least 52 wk was not reported.) This bioassay was conducted before the life table tests were implemented; so results adjusted for mortality are not available. No mammary gland adenomas or hemangiosarcomas were observed in the dosed-male rats. In the same NCI (43) study, groups of 50 B6C3F1 mice/sex/group were administered technical-grade 1,1-dichloroethane in corn oil by gavage 5 d/wk for 70 wk. As in the rat study, the dosage pattern was 3 wk on and 1 wk off; the surviving animals were necropsied 13 wk after the termination of dosing. The TWAs for 5 d/wk for the low- and high-dose groups were 1442 and 2885 mg/kg/d for

male and 1665 and 3331 mg/kg/d for female mice. Control groups, indentical to those in the rat study and consisting of 20 mice/sex/group, were also used. Survival at termination was 80, 80, 80, and 50% for the untreated control group, the vehicle control group, the low- and high-dose females, respectively. In male mice survival was 35, 55, 62, and 32% in the untreated control group, the vehicle control group, the low- and high-dose groups, respectively. An increased incidence of hepatocellular carcinoma in male mice was not statistically significant by either pairwise or trend test (2/17 in the untreated control group, 1/19 in the vehicle control group, 8/49 in the low-dose, and 8/47 in the high-dose groups). The incidence of hepatocellular carcinoma in male mice surviving at least 52 wk was 1/19, 6/72, 8/48, and 8/32 in the matched vehicle control group, a pooled vehicle control group consisting of mice from this and identical controls from other concurrent experiments, and the low- and high-dose groups, respectively; this positive trend was statistically significant. In female mice, liver carcinomas were reported in only the vehicle control (1/19) and the low-dose groups (1/47), no liver tumors were seen in the untreated controls or in the high-dose group. A statistically significant increase in benign uterine endometrial stromal polyps (4/46) was observed in high-dose females; these were not observed in any other group. A preliminary report of the NCI (43) study was published by Weisburger (54). To determine if 1,1-dichloroethane in drinking water could act as a tumor promoter or a complete carcinogen, Klaunig et al. (55) exposed groups of 35 male B6C3Fl mice to 1,1-dichloroethane in drinking water at 0, 835, or 2500 mg/L for up to 52 wk following a 4-wk treatment with either drinking water containing 10 mg/L diethyl nitrosamine (DENA-initiated groups) or with deionized water (noninitiated groups). The investigators estimated that the approximate weekly dose of 1,1dichloroethane was 3.8 mg/g/wk (corresponding to 543 mg/kg/d) for the groups exposed to 2500 mg/L. Upon sacrifice at the end of either 24 wk (10 mice/group) or 52 wk (25 mice/group) of promotion, all tissues were examined for gross pathologic lesions and histologic sections of the liver, kidneys, and lungs were examined. Neither the initiated nor the noninitiated 1,1-dichloroethanetreated groups showed a significant increase in the incidence of liver or lung tumors compared with initiated or noninitiated controls, respectively. The authors concluded that 1,1-dichloroethane was not carcinogenic to mice and did not act as a tumor promotor following initiation with DENA. These conclusions may not be entirely justified, since the duration of the study may have been inadequate for the development of tumors in noninitiated 1,1-dichloroethane-treated animals. In addition, the incidence of liver tumors in DENA-initiated controls was 70% at 24 wk and 100% at 52 wk, and the number of tumors/mouse in DENA-initiated controls at these times was 3.00 and 29.30, respectively. Hence, an increase in tumors or decrease in latency in 1,1-dichloroethane-treated DENA-initiated animals would have to be marked in order to be detectable. Carcinogenicity Classifications: EPA Group C, Possible Human Carcinogen ACGIH TLV A4, Not classifiable as a Human carcinogen 2.4.1.6 Genetic and Related Cellular Effects Studies As reported in the ATSDR Toxicological profile (56) 1,1-dichloroethane has been shown to be weakly mutagenic in some but not all test systems primarily with metabolic activation and without glutathione, which appears to play a detoxification role. Addition of glutathione reduces the extent of metabolic covalent binding to macromolecules, raising the question of the suitability of bacterial test systems that are low in glutathione in evaluating mammalian toxicity. 2.4.2 Human Experience Symptoms of exposure to this compound may include liver and kidney damage, skin and eye irritation, dermatitis, and skin burns. It may cause unconsciousness, central nervous system depression, and drowsiness. It may also cause nausea, vomiting, faintness, irritation of the respiratory tract, salivation, sneezing, coughing, dizziness, lacrimation, reddening of the

conjunctiva, cyanosis, circulatory failure, and slight smarting of the eyes and respiratory system. It is narcotic in high concentrations. No reports of human experiments or experience were found. A published report by Hamilton and Hardy (57) indicated that 1,1-dichloroethane is irritating to the eyes and respiratory tract, produces salivation, sneezing, and coughing, is associated with dizziness, nausea, and vomiting. Hepatic and renal injury were present in severe and fatal cases. 2.5 Standards, Regulations, or Guidelines of Exposure The ACGIH TLV for 1,1-dichloroethane is 100 ppm with an A4 designation, not classifiable as a human carcinogen. The NIOSH REL is 100 ppm with an IDLH of 3000 ppm. The OSHA PEL is also 100 ppm. Other Occupational Exposure Values: Australia: 200 ppm, STEL 250 ppm, substance under review (1993); Federal Republic of Germany: 100 ppm, short-term level 200 ppm, 30 min, 4 times per shift, pregnancy group D, insufficient evidence for a final evaluation (1997); United Kingdom: 200 ppm, 15-min STEL 400 ppm (1995). 2.6 Studies of Environmental Impact None found.

Saturated Halogenated Aliphatic Hydrocarbons Two To Four Carbons Jon B. Reid, Ph.D., DABT Ethylene Dichloride 3.0.1 CAS Number: [107-06-2] 3.0.2 Synonyms: 1,2-Dichloroethane, sym-dichloroethane, 1,2-bichloroethane, 1,2-ethylene dichloride, alpha, betadichloroethane, glycoldichloride 3.0.3 Trade Names: Borer sol, Brocide, Destruxol Borer-sol, Dichloremulsion, Dutch oil, Di-chlor-mulsion, Dutch liquid, Freon 150, Dichlor-ulsion, Dichloremulsion 3.0.4 Molecular Weight: 98.960 3.0.5 Molecular Formula: C2H4Cl2 or ClCH2CH2Cl 3.0.6 Molecular Structure:

3.1 Chemical and Physical Properties Ethylene dichloride is a colorless liquid with an odor typical of chlorinated hydrocarbons. An odor threshold of 88 ppm has been reported (10). Chemical and physical properties include (58): Physical state Colorless liquid Specific gravity 1.2569 at 20°C (20/4°C) Melting point –35.5°C Boiling point 83.5°C

Vapor pressure 87 torr (25°C) Refractive index 1.44432 (20°C) Percent in “saturated”air 11.5 (25°C) Solubility 0.9 g/100 ML water at 20°C; soluble in ethanol, ethyl ether Flash point 18.3°C (open cup); 13°C (Closed cup) Explosive limits 6.2–15.9% by volume in air Ignition temperature 415°C 3.1.1 General An ATSDR Toxicological Profile for this material is available. 3.1.2 Odor and Warning Properties Ethylene dichloride has a sweetish, not particularly disagreeable odor. The odor is barely detectable at 50 ppm in air and is definite but not unpleasant at 100 ppm. Although it is pronounced at 200 ppm, it still would not be considered unpleasant. Even though the odor may be definite enough to act as a warning of acutely hazardous concentrations, it is probably not sufficiently striking to be considered a significant warning of hazardous chronic exposure. This is particularly true because one can adapt to the odor at low concentrations. 3.2 Production and Use In the United States almost all the current production of ethylene dichloride is used as the starting material for preparation of vinyl chloride monomer. Other applications are much smaller. It was formerly used in antiknock fluids for gasoline, in fumigant mixtures, and as a solvent. Because of its toxicity and flammability, usage as a solvent has decreased considerably as less hazardous replacements have become available. 3.3.3 Workplace Methods NIOSH Method 1003, for halogenated hydrocarbons, is recommended for determining workplace exposures to 1,2-dichloroethane (10a). 3.3.5 Biomonitoring/Biomarkers No references were found that would indicate biologic monitoring to be satisfactory for industrial hygiene control at acceptable levels of exposure. 3.4 Toxic Effects 1,2-Dichloroethane is toxic by ingestion, inhalation, and skin contact. It can be absorbed through the skin. It is an irritant of the skin, eyes, and respiratory tract. The vapor is heavier than air and may travel a considerable distance to a source of ignition and flash back. When heated to decomposition, it emits toxic fumes of carbon monoxide, carbon dioxide, hydrogen chloride gas, and phosgene. The toxicity of ethylene dichloride has been extensively investigated both in animals and humans. It has been reviewed by several authors (7, 59–62). At very high concentrations, ethylene dichloride is irritating to the eyes, nose, and throat. Other symptoms are largely related to CNS depression or gastrointestinal upset, that is, mental confusion, dizziness, nausea, and vomiting. Cardiac sensitization appears to be less important. At subacute levels, similar symptoms of CNS depression and gastrointestinal upset are observed. Definite liver, kidney, and adrenal injury may occur at these levels. From chronic exposure to lower concentrations, some indications of CNS depression are still observed. Nausea and vomiting are quite common in humans. The sympton of nausea and vomiting for ethylene dichloride is quite striking and similar to that often observed from carbon tetrachloride. The pathological picture from repeated exposure is injury of the liver, kidneys, and adrenals. This general pattern has been consistent in animal investigative work and in experience from human exposure. Ethylene dichloride does not appear to be teratogenic or to have significant reproductive effects, but current animal data suggest it may have mutagenic, and possibly carcinogenic, potential. There is also a question of its immunologic suppression that remains unanswered. Human studies have not supported the carcinogenic or immunologic effects seen in animal studies, but as is often the case in epidemiology, the study populations have been small.

3.4.1 Experimental Studies 3.4.1.1 Acute Toxicity Animal studies show liver and kidney injury. Smyth et al. (63) calculated an oral LD50 in rats of 770 mg/kg. Opacity of the cornea was reported in dogs and foxes following administration of ethylene dichloride (7, p.144). 3.4.1.2 Chronic and Subchronic Toxicity The results of lifetime oral studies are discussed in the carcinogenesis section. 3.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms The metabolism of ethylene dichloride has been recently reviewed (62). Figure 63.1 has a proposed metabolic map taken from Loew et al. (64). It is readily absorbed via the lungs and gastrointestinal tract and to a lesser degree through the skin. Although steady-state blood concentrations in the rat were achieved in 2–3 h at 150 ppm, the equilibrium concentration in blood at 6 h was exponentially related to the inhaled concentration. Blood levels of 1.4, 8.3, and 31.3 mg/mL were found after exposure to 50, 150, and 250 ppm in air for 6 h. About 70% of the inhaled ethylene dichloride was absorbed in a 6 h exposure to 150 ppm, and clearance from the blood was rapid. Elimination following oral doses was also rapid, resulting in both cases in nonlinear kinetics. Approximately 85% of radioactivity was excreted in the urine as thiodiacetic acid and thiodiacetic sulfoxide with some exhalation of unchanged [14C]1,2dichloroethane. The parent compound, as well as 2-chloroethanol, monochloroacetic acid, and 2chloroacetadehyde, has been found in the organs of cadavers following acute poisoning (65). Two paths of metabolism involve microsomal cytochrome P450 or cytosolic glutathione transferase. The cytosolic pathway was considered responsible for the mutagenicity and covalent DNA binding (66), but other investigators found no evidence of covalent binding from the cytosol route (67). A physiologically based pharmacokinetic model has been developed that described glutathione depletion and resynthesis in rats and mice (68).

Figure 63.1. Proposed metabolism of 1,2-dichloreothane (from Ref. 64). 3.4.1.4 Reproductive and Developmental In the available abstract, Vozovaya (69) states he produced

decreased fertility and other adverse effects in pregnant female rats and the progeny of the first generation, but not of the second, by giving them repeated 4 h/d exposures to 57 mg/m3 (14 ppm). However, an attempt to confirm this report failed to do so, even though the rats were exposed to 100 ppm 7 h/d for several months (70). Furthermore, pregnant Sprague–Dawley rats and New Zealand white rabbits were exposed to 0, 100, or 300 ppm of ethylene dichloride on days 6 through 15 (rats) and 6 through 18 (rabbits) of gestation. Severe maternal toxicity was observed among rats exposed to 300 ppm of ethylene dichloride; two-thirds of the dams died during the exposure period. No signs of toxicity were observed among rats at the 100-ppm dose level. Maternal toxicity was noted in rabbits as evidenced by maternal deaths at both dose levels. No adverse effects on embryonal or fetal development were observed among litters from the exposed rats at 100 ppm or among those from exposed rabbits. Owing to the severe maternal toxicity observed, no conclusions could be drawn concerning the teratogenic potential of inhaled ethylene dichloride in the rat at 300 ppm; ethylene dichloride was not embryotoxic or teratogenic in rats inhaling either 100 ppm or in rabbits inhaling 100 or 300 ppm of the compound during gestation (70). Pregnant CD mice were fed water containing a mixture of potential water contaminants including ethylene dichloride with no effects on the usually teratological parameters (71). The reproduction and developmental effects of ethylene dichloride were studied in a multigeneration study (72). Male and female ICR Swiss mice received 0, 5.14, 15.4, or 49.7 mg/kg/d. There appeared to be no dose-dependent effects on fertility, gestation, viability, or lactation indices. Pup survival and weight gain were not adversely affected. Gross necropsy of male and female F0 generation mice treated with 1,2-DCE or 1,1,1-TCE failed to reveal compound or dose-related effects. 3.4.1.5 Carcinogenesis The EPA classifies ethylene dichloride as B2; probable human carcinogen on the basis of the induction of several tumor types in rats and mice treated by gavage and lung papillomas in mice after topical application. There are no human carcinogenicity data. An NCI study in 1978 (73) is the basis for the conclusion. The International Agency for Research on Cancer (74, p. 62) classified ethylene dichloride in group 2B, possibly carcinogenic to humans, based on sufficient evidence for carcinogenicity in animals and no adequate data for humans. In the NCI (75) study, 1,2-dichloroethane in corn oil was administered by gavage to groups of 50 each male and female Osborne–Mendel rats and B6C3F1 mice. Treatment was for 78 wk followed by an additional observation period of 12–13 weeks for mice or 32 wk for low-dose rats. TWA dosages were 47 and 95 mg/kg/d for rats, 97 and 195 mg/kg/d for male mice, and 149 and 299 mg/kg/d for female mice. All high-dose male rats died after 23 wk of observation; the last highdose female died after 15 wk. Male rats had significantly increased incidence of forestomach squamous-cell carcinomas and circulatory system hemangiosarcomas. Female rats and mice were observed to have significant increases in mammary adenocarcinoma incidence. Mice of both sexes developed alveolar/bronchiolar adenomas, females developed endometrial stromal polyps and sarcomas, and males developed hepatocellular carcinomas. In the studies by Spencer et al. (76) and Maltoni et al. (77) inhalation exposure of Wistar, Sprague– Dawley rats, and Swiss mice did not result in increased tumor incidence. An elevation that was not statistically significant in lung adenomas was seen in A/st mice treated IP with 1,2-dichloroethane in tricaprylin (78). ICR/Ha Swiss mice treated topically had a significant increase in benign lung papillomas, but not skin carcinomas (79). Carcinogenicity Classification:

EPA IARC MAK NIOSH NTP ACGIH TLV

Group B2, Probable human carcinogen; sufficient evidence from animal studies; inadequate evidence or no data from epdemiologic studies. Group 2B, Possibly carcinogenic in humans. Group 2, Probable human carcinogen. Carcinogen, with no further categorization. Reasonably anticipated to be a human carcinogen (RAHC). A4, Not Classifiable as a Human Carcinogen.

3.4.1.6 Genetic and Related Cellular Effects Studies 1,2-Dichloroethane was mutagenic for Salmonella in assays wherein excessive evaporation was prevented; exogenous metabolism by mammalian systems enhanced the response (80–82). Both somatic cell mutations and sex-linked recessives were induced in Drosophila (83–86). Metabolites of 1,2-chloroethane have been shown to form adducts with DNA after in vitro or in vivo exposures. 3.4.2 Human Experience Symptoms of exposure to this compound may include irritation of the skin, eyes, and respiratory tract, corneal clouding, and dermatitis. It may cause conjunctivitis, corneal ulceration, headache, mental confusion, depression, fatigue, albuminuria, central nervous system depression, convulsions, diarrhea, hepatomegaly, hypoglycemia, jaundice, narcosis, and pulmonary edema. It may also cause flaccid paralysis without anesthesia, somnolence, cough, nausea, vomiting, hypermotility, ulceration, fatty liver degeneration, change in cardiac rate, cyanosis, coma, edema of the lungs, and toxic effects on the kidneys. It may cause feelings of drunkeness or drowsiness, unconsciousness, and death from respiratory and cardiac failure, defatting of the skin, swelling of the skin, and chemical pneumonia. Other symptoms may include mental confusion, abdominal pains, and liver and kidney damage. It can also cause watery stool, weak and rapid pulse, and internal bleeding. It may cause corneal opacity. Other symptoms may include edema of the brain, vascular congestion in the lungs, heart, and spleen, weight loss, and oliguria. It may also cause dizziness, narcosis, intestinal hemorrhages, weakness, trembling, and severe shock. Chronic exposure may result in loss of appetite, epigastric distress, tremors, nystagmus, leukocytosis, and low blood sugar levels. 3.4.2.2 Clinical Cases There have been clinical cases of acute exposure to ethylene dichloride reported in the literature that confirm the picture observed in the animals. Menschick (87) reported four acute cases showing a “hepato-renal syndrome.” The author also lists 27 cases of poisoning by inhalation collected from the literature. Ethylene dichloride does present a problem from oral ingestion. There are a significant number of the poisoning cases reported in the literature by this route. The response is CNS depression, gastrointestinal upset, and injury to the liver, kidneys, and the lungs, and delayed deaths. The Criteria Document (88) cited papers that indicate fatalities from inhalation in concentrations insufficient to cause anesthesia. Two epidemiologic studies, one positive and one negative, have been reported, but the results are not conclusive owing to mixed exposures or small sample size (89, 90). 3.4.2.3 Epidemiology Studies Two epidemiologic studies, one positive and one negative, have been reported, but the results are not conclusive owing to mixed exposures or small sample size (89, 90). 3.5 Standards, Regulations, or Guidelines of Exposure The ACGIH TLV is 10 ppm with an A4 notation, not classifiable as a human carcinogen. The

NIOSH REL is 1 ppm and the STEL is 2 ppm. NIOSH considers this chemical a carcinogen. The OSHA PEL is 50 ppm while the ceiling is 100 ppm and the 5 min peak in any 3 hours is 200 ppm. Other Occupational Exposure Values: Australia: 10 ppm (substance under review) (1990); Federal Republic of Germany: no MAK, Group 2, probably human carcinogen (1998); Sweden: 1 ppm, 15min short-term value 5 ppm, skin, carcinogenic (1989); United Kingdom: 10 ppm, 10-min STEL 15 ppm, carcinogenic substance, R45-may cause cancer (1991). 3.6 Studies on Environmental Impact None found.

Saturated Halogenated Aliphatic Hydrocarbons Two To Four Carbons Jon B. Reid, Ph.D., DABT Methyl Chloroform 4.0.1 CAS Number: [71-55-6] 4.0.2 Synonyms: 1,1,1-Trichloroethane, methyltrichloromethane, alpha-trichloroethane, chloroethene, chlorothene, 1,1,1-TCE 4.0.3 Trade Names: Aerothene TT, Chloroetene, Chloroethene NU, Chlorothane NU, Chlorothene (inhibited), Chlorothene NU, Chlorothene VG, Chlorten, Inhibisol, NCI-C04626, RCRA Waste Number U226, Solvent 111, Strobane, Alpha-T, Tri-ethane, UN 2831, Trichloroethane, 1,11-Trichloroetano, Triethane 4.0.4 Molecular Weight: 133.42 4.0.5 Molecular Formula: C2H3Cl3 4.0.6 Molecular Structure:

4.1 Chemical and Physical Properties Methyl chloroform is a colorless, nonflammable liquid with an chloroformlike odor and an odor threshold of 120 ppm. It burns only in excess oxygen or in air if a strong source of ignition is present. Because of its reactivity with magnesium, aluminum, and their alloys, inhibitors (usually 1,4-dioxane, 1,3-dioxolane, isobutyl alcohol, or nitroethane) are often added to increase the stability of the solvent. Physical state Colorless liquid Specific gravity 1.3376 at 20°C Boiling point 74.1°C Melting point (°C) –32.5 Vapor pressure 127 torr (25°C) Refractive index 1.43765 (21°C) Percent in “saturated” air 16.7 (25°C) Solubility 0.09 g/100 mL water at 20°C; soluble in ethanol and ethyl ether

Flammability

(see following note)

Note: The flammable characteristics of methyl chloroform are similar to those of trichloroethylene. It has no flash point or fire point by ASTM procedures for Tag closed-up and Cleveland open-cup tests. Limits of flammability of vapors of inhibited 1,1,-trichloroethane have been found to be 10– 15.5% in air with hot wire ignition. A considerable amount of energy is required for ignition. It will not sustain combustion (91). 4.1.1 General An ATSDR Toxicological profile exists for 1,1,1-trichloroethane (3). 4.1.2 Odor and Warning Properties Although methyl chloroform has a typical sweetish odor, it is not striking enough to be considered a good warning. The odor may be noticeable at concentrations near 100 ppm, well below those known to cause physiological response. However, the odor at 500 ppm and even 1000 ppm is not so unpleasant as to discourage exposure. The odor has been described as strong and unpleasant at 1500–2000 ppm. Stewart et al. (92) reported that female test subjects exposed to 350 ppm objected to the odor; however, this has not been an industrial problem. 4.2 Production and Use According to the NTP database, methyl chloroform is used in cold-type metal cleaning, in plastic cleaning, in vapor degreasing, as a chemical intermediate for vinylidene chloride, in aerosols (as a vapor pressure depressant, solvent, and carrier), in adhesives (as a resin solvent), and as a lubricant carrier to inject graphite, grease, and other lubricants. It is used alone and in cutting oil formulations as a coolant and lubricant for drilling and tapping alloy and stainless steels. It is also used to develop printed circuit boards, in motion picture film cleaning, in stain repellants for upholstery fabrics, in wig cleaning, in textile processing and finishing, and as a solvent in drain cleaners, shoe polishes, spot cleaners, insecticide formulations, and printing inks. It is also used as a solvent for cleaning precision instruments. Methyl chloroform is used almost exclusively as a solvent with a few percent used as an intermediate. As a solvent for adhesives, 69% of the U.S. production is consumed in metal degreasing. Another 23% is used in the manufacture of vinylidene chloride (93). Because of the environmental issue of depletion of stratospheric ozone, future use can be expected to decline. Most commercial methyl chloroform, which is sold under several trade names, contains inhibitors to prevent reaction of the solvent with aluminum and alloys. This reaction produces hydrogen chloride and in confined vessels may produce high pressures. 4.3 Exposure Assessment 4.3.3 Workplace Methods NIOSH Method 1003, for halogenated hydrocarbons, is recommended for determining workplace exposures to methyl chloroform. 4.3.5 Biomonitoring/Biomarkers Stewart et al. (92) have produced a series of graphs making it possible to quantify exposure based on expired air samples. Analysis of urine for metabolites probably has limited value. Monster (94) has also published extensive studies on biologic monitoring of 1,1,1-trichloroethane. Although it has been suggested that urinary trichloroacetic acid and trichloroethanol may be of value in quantifying exposure to methyl chloroform, and the ACGIH in 1992–1993 recommended biological exposure indices, such indices are of most value in discerning average exposure levels and not peak exposures. Thus it is possible that “acceptable false negative” urinary levels of these substances may be found following exposure considered excessive from the standpoint of anesthetic effects. The same caveat must be considered in considering expired air samples collected at the end of the workday or workweek. 4.4 Toxic Effects Extensive testing and human experience indicate 1,1,1-trichloroethane is probably the least toxic of the chlorinated solvents, but its high volatility and careless use and abuse have resulted in deaths from gross exposure usually in confined spaces or due to deliberate inhalation.

Methyl chloroform is harmful by inhalation, ingestion, and skin absorption. It can be absorbed through the lungs, gastrointestinal tract, and skin. It is an irritant of the skin, eyes, mucous membranes, and upper respiratory tract. It may be narcotic in high concentrations. It may also cause slight lacrimation. When heated to decomposition, it emits irritating gases and toxic fumes of carbon monoxide, carbon dioxide, hydrogen chloride gas, chlorine, and phosgene. The principal and first response from acute or chronic exposure to excessive amounts of methyl chloroform is depression of the central nervous system. Possibly as a result of very little metabolism of the compound, it has little capacity to produce organ injury from either single or repeated exposures but at high levels can sensitize the heart to epinephrine, possibly leading in some cases to death. Overall the available human and animal data indicate that the compound is not teratogenic, mutagenic, or carcinogenic, although the 1,1,1-trichloroethane isomer is considerably less toxic than the 1,1,2-trichloroethane isomer. Owing to an error in the literature, several authors have indicated the reverse, as documented by Torkelson et al. (95). Concentrations in excess of 14,000–15,000 ppm are fatal to animals. Human fatalities due to anesthesia (and/or cardiac arrhythmia) have occurred in confined spaces when exposures to high concentrations have not been promptly terminated. In cases where the victim has been alive when removed from the high concentration, recovery has generally been rapid and complete. Abuse (sniffing) has also resulted in deaths. Several reviews have been published (5, 62, 96–100). 4.4.1 Experimental Studies 4.4.1.1 Acute Toxicity Torkelson et al. (95) reports that the oral toxicity is low with an LD50 in rats, mice, rabbits, and guinea pigs ranging from 5.7 to 12.3 g/kg. The LD50 for rabbits (skin absorption) is 16 g/kg. Wolverton et al. (101) report that the inhalation toxicity is also low with an EC50 for motor control loss (mice) for 30 min at 5173 ppm. No significant toxic responses were reported for rats, 500 ppm, 6 h/d, 4 d (102), mice to 1300 ppm, 1 h, rats to 3000 ppm for 0.5–4 h (103) baboons, 1400 ppm 4 h (104). Inhalation: As an anesthetic, methyl chloroform can cause dealth in excess of 14,000–15,000 ppm (105). Adams et al. (106) reported on the response of animals to acute inhalation exposure. Maximum time concentrations in air survived by rats were as follows: 6 min at 30,000 ppm, 1.5 h at 15,000 ppm, and 7 h at 8000 ppm. Maximum time concentrations in air with no detectable injury in rats were as follows: 18 min at 18,000 ppm and 5 h at 8000 ppm. It should be noted that the maximum level with no detectable injury is very close to the maximum level survived. This information has been confirmed by Torkelson et al. (95) using inhibited solvent. Bruckner et al. (107) performed an acute and subacute study in rats. Several parameters were studied in addition to lethality. Single oral doses up to 4 g/kg in corn oil did not cause death or treatmentrelated effects on serum enzymes organ weights, or histological findings in the livers and kidneys of Sprague–Dawley rats 24 h after gavage. Rats treated with nine doses in 11 d were scheduled for sacrifice on the twelfth day. Doses of 0, 0.5, 5.0, or 10.0 g/kg were administered. Doses of 5 and 10 g/kg/d caused hyperexcitability and protracted narcosis as well as some fatalities, but there was little evidence of toxicity in the survivors or in the 0.5 g/kg/d group. In a 12 wk oral study doses of 0, 0.5, 2,5, or 5.0 g/kg were given 5 d/wk. Reduced body weight and CNS effects were seen only in the 2.5- and 5.0-g/kg groups and 35% of the rats in these groups died, but only the 5.0-g/kg group showed serum enzyme changes. The 0.5-g/kg (500 mg/kg) group developed no alterations in toxicity during the 12 wk study.

Torkelson et al. (95) reported on eyes, skin, and skin absorption: The material caused only minor, transient irritation in the eyes of rabbits, and no reports of human injury have been reported following eye contact. The skin shows only slight reddening and scaliness from contact. The reaction is somewhat increased on repreated exposures. Confinement of the liquid on the skin results in considerable pain and irritation. Applied under a cuff for 24 h, 3.9 g/kg was survived by all rabbits; 15.8 g/kg failed to kill all the rabbits treated with the undiluted liquid. Others have reported similar low hepato- and renal toxicity in rats and other species (47, 108–110). Gehring (111) determined that at 13,500 ppm the LT50 (lethal time, 50%) was 595 min but that liver function as measured by serum glutamic-oxalic-transaminase (SGOT) was virtually unaffected unless exposures approached those causing anesthetic death. Klaassen and Plaa reported an intraperitoneal LD50 of 3.9 g/kg in rats (110) and an LD50 of 120 mmol/kg (16 g/kg) in mice (108). 4.4.1.2 Chronic and Subchronic Toxicity The EPA (2) reports that the oral RfD for 1,1,1trichloroethane had been withdrawn on 08/01/1991 pending further review by the RfD/RfC Work Group and that no reference concentration is available. Please see the section on carcinogenicity for additional information. Adams et al. (106) exposed animals 7 h/d, 5 d/wk for 1–3 mo. At 10,000 ppm rats showed staggering gait and weakness in 10 min. By 3 h, they showed loss of color, irregular respiration, and semiconsciousness. Survivors had completely recovered by the following morning. For those that succumbed, death seemed to be due to either cardiac or respiratory failure. At 5000 ppm, there was definite but mild narcotic effect within 1 h. There was reduced activity. Rats survived for 31 exposures over 41 d without apparent injury. Rabbits showed slight retardation of growth at 5000 ppm. At 3000 ppm, rabbits and monkeys showed no response over a 2-mo period. Guinea pigs showed a barely significant retardation of growth at 650 ppm. Torkelson et al. (95) reported results of exposures of female guinea pigs and male rats for 3 mo, exposed for 0.05–3 h/d at 1000–10,000 ppm. Some pathologic changes in the livers and lungs of guinea pigs exposed for 3 or 1.2 h/d at 1000 ppm and for 0.2 or 0.5 h/d at 2000 ppm. The anesthetic effect was paramount. No significant toxic changes were reported for exposures to the vapor at 500 ppm for 7 h/d, 7 days/week, for 6 m in rats, guinea pigs, rabbits, or monkeys. Prendergrast et al. (112) performed continuous (24 h/d) exposure for 14 wk and showed that it produced little injury to rats, mice, dogs, and monkeys at 1000 ppm and essentially no effect at 250 ppm except minor, apparently reversible cytoplasmic alterations in the livers of mice. After exposure to 1000 ppm dogs and monkeys were considered unaffected by the exposure, but the rats and mice exhibited significant increases in liver weight and liver triglycerides and fatty and necrotic changes visible microscopically in the livers. Quast et al. (113) repeatedly exposed groups of 96 rats of each sex to 875 or 1750 ppm, 1,1,1trichloroethane vapor 6 h/d, 5 d/w for 1 yr with no adverse effects (see section on carcinogenicity). Several other subchronic studies indicated minor and reversible effects (114–116). The section on carcinogenicity also describes a 2-yr inhalation exposure study of rats and mice with effects only at 1500 ppm in rats, but not at 500 or 150 ppm. There was no effect on mice at any concentration. 4.4.1.3 Pharamacokinetics, Metabolism, and Mechanisms Absorption from the skin of humans and rodents after topical application (#51, 52, 53, 54) (117–120) has been shown.

Both in vivo and in vitro systems metabolize methyl chloroform by microsomal P-450 to trichloroethanol (121, 122). This metabolite is conjugated with glucuronic acid and the trichloroethanol-glucuronide appears in the urine (96). The trichloroethanol can also be oxidized to trichloroacetic acid. It can account for considerable metabolites in rodent and human urine (115, 123–126). Pulmonary absorption by humans is from 30 to 60% depending on the duration and concentration of the exposure (123, 127). Gehring et al. (62) indicated that the low systemic toxicity of methyl chloroform is related to the small amount of metabolism that occurs in animals and humans. Because of its low toxicity, it has been used as a model compound in absorption–excretion studies (95, 128). In one of the first metabolic studies on this compound, Hake et al. (129) reported 97.6% of radioactive methyl chloroform injected intraperitoneally was excreted unchanged by the lungs, and only 0.85% of the radioactivity was found in the urine. This and subsequent studies on humans and animals indicate that only small amounts of trichloroacetic acid and trichloroethanol may be found in the urine after injection or inhalation (115, 126, 130–132), but that most of the dose is expired unchanged no matter what the route of administration. As reported by Schumann et al. (126), rats and mice eliminated 96% of their body burden within 24 h following 6 h inhalation exposure to 150 or 1500 ppm [14C]1,1,1,-trichloroethane. Exhalation of the parent compound was very high, 87–97% of the body burden in mice and 94–98% in rats at 150 and 1500 ppm, respectively. The remaining 14C activity (2–13%) was recovered either as CO2 in expired air or as nonvolatile radioactivity in urine, feces, carcass, or cage wash. Although quantities were small, mice metabolized two to three time more than rats on a body weight basis. Fat contained the highest concentrations of 14C activity. Prior long-term repeated exposure to nonradioactive 1,1,1-trichloroethane did not increase the rate of metabolism of a radioactive dose. Reitz et al. (133) have developed pharmacokinetic models for interspecies, high-dose/low-dose, and dose route extrapolations, as models for regulatory risk analysis (134). According to VanDyke and Wineman (135) the small amount of metabolism that takes place appears to occur in a saturable process. Enzymatic dechlorination by rat liver microsomes in vitro is very low and apparently not enhanced by enzyme inducers. VanDyke (136) reports that the reaction is catalyzed by cytochrome P450 in the presence of oxygen. Kawai et al. (137) reported that only 2% of absorbed 1,1,1-trichloroethane was excreted in the urine of the 48 male printing workers they studied. Occupational Exposures: Imbriani et al. (138) examined occupationally exposed persons and found intact methyl chloroform in the urine from 33 to 314 mg/L. Nolan et al. (124) exposed six humans at 35 or 350 ppm for 6 h and calculated the urinary elimination of trichloroethanol and trichloroacetic acid at 27 and 76 h, respectively. 4.4.1.4 Reproductive and Developmental Schwetz et al. (139) reported that pregnant female rats and mice were exposed 7 h/d on days 6 to 15 of gestation and the mothers and fetuses examined for effects. The inhaled vapor concentration was 875 ppm of an inhibited formulation containing 5.5% inhibitors. No effects related to exposure were observed on either the mothers or fetuses. The NTP (NTP 1987 (140, 141)) found no signs of developmental toxicity at doses where maternal intoxication was present when given to male and female CD rats prior to mating and throughout pregnancy in drinking water at 30 ppm. Bogen and Hall (134) used these data to determine a “virtually safe dose” of 14–28 mg/d based on the delivered dose to the rat embryo.

York et al. (142) repeatedly exposed female Long–Evans rats to 2100–2200 ppm of methyl chloroform vapors 2 wk before breeding and until day 20 of gestation without effect on teratogenicity or subsequent neurobehavioral studies of the offspring allowed to be delivered normally. Riddle et al. (72) modified a multigeneration reproduction study to include screening for dominant lethal and teratogenic effects. Mice were fed water containing methyl chloroform so that daily dosage levels were 0, 99.4, 264, or 852 mg/kg. According to the authors, “There appeared to be no dose-dependent effects on fertility, gestation, viability, or lactation indices. Pup survival and weight gain were not adversely affected. Gross necropsy of male and female F/0 generation mice treated with 1,2-DCE or 1,1,1-TCE failed to reveal compound or dose-related effects.” George et al. (143) reported that when methyl chloroform was fed in drinking water to CD rats at 0, 3, 10, or 30 ppm using 0.05% Tween 80 as an emulsifying agent for 14 d prior to and 13 d after cohabitation, “there was no indication of an increase in the incidence of cardiac or other malformations.” These data as well as all other studies appear to refute adequately an allegation of teratological effect reported by Dapson et al. (144). 4.4.1.5 Carcinogenesis The EPA (IRIS) reports that there are no human carcinogenic data and classifies this material as D, not classifiable as to human carcinogenicity and that the animal carcinogenicity data are “Inadequate.” In 1987, IARC reviewed the existing information and concluded that there was inadequate evidence for carcinogenicity in animals (74, p. 73). Three animal studies are relevant an NCI bioassay (gavage) and two inhalation studies by Quast et al., (145, 146), none of which gave clear evidence of carcinogenic activity. The NCI (147) treated Osborne–Mendel rats (50/sex/dose) with 750 or 1500 mg/kg technical-grade 1,1,1-trichloroethane 5 times/wk for 78 wk by gavage. The rats were observed for an additional 32 wk. Twenty rats of each sex served as untreated controls. Low survival of both male and female treated rats (3%) may have precluded detection of a significant number of tumors late in life. Although a variety of neoplasms was observed in both treated and matched control rats, they were common to aged rats and were not dose related. Similar results were obtained when the NCI (147) treated B6C3F1 hybrid mice with the time-weighted average doses of 2807 or 5615 mg/kg 1,1,1trichloroethane by gavage 5 d/wk for 78 wk. The mice were observed for an additional 12 wk. The control and treated groups had 20 and 50 animals of each sex, respectively. Only 25–45% of those treated survived until the time of terminal sacrifice. A variety of neoplasms was observed in treated groups, but the incidence not statistically different from matched controls. Quast et al. (145) exposed 96 Sprague–Dawley rats of both sexes to 875 or 1750 ppm 1,1,1trichloroethane vapor for 6 h/d, 5 d/wk for 12 m, followed by an additional 19 mo observation period. The only significant sign of toxicity was an increased incidence of focal hepatocellular alterations in female rats at the highest dosage. It was not evident that a maximum tolerated dose (MTD) was used, nor was a range-finding study conducted. No significant dose-related neoplasms were reported, but these dose levels were below those used in the NCI study. In another study, Quast et al. (146) used an inhibited formulation of 1,1,1-trichloroethane. Fischer 344 rats and B6C3F1 mice of both sexes were exposed to 0, 150, 500, or 1500 ppm 6 h/d, 5 d/wk for 2 yr. The authors indicate that there were no indications of an oncogenic effect in rats or mice following 2 yrs of exposure to the 1,1,1-trichloroethane formulation and a no-observed-adverseeffect-level (NOAEL) of 500 ppm for adverse effect of any kind. The ATSDR reviewed this information (56) and determined that the study adequately demonstrated negative evidence of carcinogenicity in animals by lifetime inhalation up to 1500 ppm. It should be noted that an isomer of methyl chloroform, namely, 1,1,2-trichloroethane, is

carcinogenic in mice, inducing liver cancer and pheochromocytomas in both sexes. Dichloroethanes, tetrachloroethanes, and hexachloroethanes also produced liver cancer in mice and other types of neoplasms in rats and further that 1,4-dioxane, a known animal carcinogen that causes liver and nasal tumors in more than one strain of rats and hepatocellular carcinomas in mice, is a contaminant of technical-grade 1,1,1-trichlorethane. 4.4.1.6 Genetic and Related Cellular Effects Studies According to the EPA (IRIS), mutagenicity testing of 1,1,1-trichloroethane has produced positive results in S. typhimurium strain TA100 (148) as well as some negative results (149). Methyl chloroform was mutagenic for S. typhimurium strain TA1535, both with exogenous metabolic activation (150) and without activation (80). 1,1,1-Tricholoroethane did not result in gene conversion or mitotic recombination in Saccharomyces cerevisiae (150), nor was it positive in a host-mediated forward mutation assay using Schizosaccharomyces pombe in mice. The chemical also failed to produce chromosomal aberrations in the bone marrow of cats (151), but responded positively in a cell transformation test with rat embryo cells (152). The extensive summary (98) of genotoxic studies on methyl chloroform concludes that the potential for genetic damage is very small at acceptable exposure conditions. 4.4.2 Human Experience Symptoms of exposure to this compound may include irritation of the eyes, dizziness, incoordination, unconsciousness, and death. Irritation of the mucous membranes and respiratory tract may occur. Fainting may also occur. Other symptoms may include decreased reaction time, impaired manual dexterity, ataxia, lightheadedness, positive Romberg test, diarrhea, respiratory arrest, and nausea. It causes a proarrhythmic activity that sensitizes the heart to epinephrine, resulting in cardiac arrhythmias. This sometimes will cause cardiac arrest, particularly when massive amounts are inhaled. Inhalation can cause euphoria. High concentrations may cause narcosis. Exposure can cause headache, drowsiness, burning sensation on the eyes and skin, irritation of the throat, cardiac sensitization, aspiration of vomitus during anesthesia, blood pressure depression, chemical pneumonitis, and pulomary edema with hemorrhage. It can also cause anesthesia, cardiac fibrillations, slight reddening of the skin, central nervous system impairment, helplessness, loss in equilibrium, and mild eye and nasal discomfort. Other symptoms are hallucinations, distorted perceptions, motor activity changes, irritability, aggression, hypermotility, and other gastrointestinal changes. Impaired judgement has been reported. Increased reaction time has also been reported. Repeated skin contact may result in a dry, scaly, and fissured dermatitis due to its defatting properties. Prolonged skin contact may result in considerable pain and irritation. Other symptoms may include difficult breathing, asphyxiation, slight lacrimation, and slight smarting of the eyes and respiratory system. It may cause impaired psychophysiological functions. It may also cause irregular heart beat, lassitude, and coma. High concentrations cause central nervous system depression. Hemorrhage in the brain may also result from exposure to high concentrations. Eye contact may lead to superficial and transient injury to the eyes. It may also lead to mild conjunctivities. Chronic exposure may result in liver and kidney damage. Exposure to and/or consumption of alcohol may increase its toxic effects. Findings in laboratory animals is consistent with humans (105). Numerous deaths due to CNS depression or cardiac arrhythmias have been reported from poorly ventilated areas (153–162). Several authors (163, 164) have evaluated methyl chloroform as a surgical anesthetic, but for several reasons, including lack of potency and effects on cardiac function, it was abandoned from serious consideration. If the subject has been alive when removed from exposure, recovery has generally been rapid and complete. Table 63.4 on the probable effects of exposure to humans to the vapor of methyl chloroform has been published for establishing emergency exposure limits.

Table 63.4. Probable Result of Single Exposure to the Vapors of 1,1,1Trichloroethane (210) Exposure time (min)

5

15

30

60

Concentration in Air (ppm)

20,000 10,000 5,000 2,000 10,000 2,000 1,000 10,000 5,000 2,000 1,000 20,000 10,000 5,000 2,000 1,000 500 100

Expected Effect in Humansa Complete incoordination and helplessness (R) Pronounced loss of coordination (R) Definite incoordination (R, M) Disturbance of equilibrium. Odor is unpleasant but tolerable (H) Pronounced loss of coordination (R) Loss of equilibrium (H) Possible beginning loss of equilibrium (H) Pronounced loss of coordination (R) Incoordination (R, M) Loss of equilibrium (H) Mild eye and nasal discomfort; possible slight loss of equilibrium (H) Surgical anesthesia, possible death (R) Pronounced loss of coordination (R) Obvious loss of coordination (R, M) Loss of coordination (H) Very slight loss of equilibrium (H) No detectable effect, but odor is obvious (R, H) Apparent odor threshold (H)

Laboratory Studies: Numerous laboratory studies in humans have permitted confirmation of many of the toxicologic data derived in animals. Stewart et al. (92), in a series of papers have evaluated the use of expired air for monitoring employee exposure and have produced a series of graphs based on expired air concentration following known exposures to various concentrations for different periods of time. These studies have also investigated metabolism and urinary excretion and evaluated clinical chemical parameters. Most important, however, are their studies to evaluate equilibrium, coordination, alertness, and other signs of anesthetic action. Based on these studies it has been concluded that, except for possible objections to odor, no untoward responses are observed even after repeated prolonged exposures of human subjects to 350 ppm. A few subjects may respond as concentrations approach 500 ppm, and if allowed to inhale 800–1000 ppm, some subjects show minor CNS impairment. Other investigators (165) have found similar results, but Gamberale and Hultengren (166) reported effects at lower vapor concentrations. Gamberale and Hultengren, however, used a mask to administer the vapors, and this may have influenced their test results. Monster (94) has published extensive studies on biologic monitoring of 1,1,1-trichloroethane,

trichloroethylene, and perchloroethylene. Liquid methyl chloroform has been shown by Stewart and Dodd (167) as well as Fukabori et al. (168) to be absorbed through the intact skin, but Riihimaki and Pfaffli (169) have shown that the vapors are not absorbed in toxicologically significant amounts. Industrial Experience: Although chronic effects have been shown to be of little consequence in industrial exposure (170), failure to recognize the high vapor pressure of methyl chloroform and to prevent inhalation of high concentrations, has resulted in reports of death. The number of deaths per year (2–3 worldwide) appears to be decreasing relative to consumption, as proper precautions are being taken to avoid exposure. Nonoccupational cases of deliberate sniffing have been reported, but generally a consistent pattern of use of the solvent in a confined space without regard for ventilation is the cause of industrial death. Stewart (171) discussed the consequencs of overexposure and the treatment of overexposed subjects. A single report (172) alleging chronic cardiac toxicity following repeated exposure to 1,1,1trichloroethane is inconsistent with all other reports of rapid recovery as well as epidemiologic evidence (170). Furthermore, there are obvious discrepancies in claiming urinary excretion of 1,1,1and 1,1,2-trichloroethane long after exposure, suggesting the report is in error. A rather extensive study of an industrial population exposed to methyl chloroform for up to 6 yr confirms the data derived from animals (170). No effect of exposure was found in a matched-pair study of 151 subjects and 151 controls despite particular emphasis placed on hepato- and cardiotoxic effects. Mattsson et al. (173) conducted an elaborate investigation in which male and female Fischer 344 rats were exposed to 1,1,1-trichloroethane vapors for 6 h/d, 5 d/wk, for 13 wk. Exposure levels were 200, 630, and 2000 ppm. Rats were clinically examined regularly and were given a functional observational battery monthly (FOB, including forelimb and hindlimb grip performance testing). After 13 wk of exposure, the functional integrity of the nervous system was evaluated by FOB and by visual, auditory, somatosensory, and causal nerve evoked potentials. After functional testing, a subgroup of rats had histopathologic examination of brain, spinal cord, peripheral nerves, and limb muscles. No treatment-related findings were discovered in any parameter except for a slightly smaller forelimb grip performance in the 2000-ppm exposure group. A subgroup of rats was examined for grip performance 6 wk postexposure; forelimb grip performance was still smaller in 2000-ppm rats. Forelimb nerves and muscles from these rats then were examined histopathologically, and no treatment-related lesions found. No reason was discovered for this difference in forelimb grip performance. It normally decreases (habituates) over time as a function of experimental conditions, and it is speculated that the daily acute-sedative effect of 2000 ppm 1,1,1trichloroethane has an interaction with the habituation process. Other than a possible indictor of acute sedation, there was no recognized toxicologic significance to this difference in forelimb grip performance. Furthermore, histopathological examination of rats exposed to 2000 ppm for 13 wk found no effects related to exposure in any organ, including the nervous system. 4.4.2.2.5 Carcinogenesis The EPA (IRIS) classifies methyl chloroform as – D; not classifiable as to human carcinogenicity on the basis that there are no reported human data, and animal studies (one lifetime gavage, one intermediate-term inhalation) have not demonstrated carcinogenicity. Technical-grade 1,1,1-trichloroethane has been shown to be weakly mutagenic, although the contaminant, 1,4-dioxane, a known animal carcinogen, may be responsible for this response. Carcinogenicity Classification: EPA Group D, Not Classifiable as to Human Carcinogenicity IARC Group 3, not classifiable as to its carcinogenicity to humans ACGIH TLV A4, Not Classifiable as a Human Carcinogen

4.5 Standards, Regulations, or Guidelines of Exposure The ACGIH TLV, NIOSH REL ceiling and the OSHA PEL are all 350 ppm. The ACGIH STEL/C is 450 ppm. ACGIH has an A4 designation for this chemical. Other Occupational Exposure Values: Australia: 125 ppm (1990); Federal Republic of Germany: 200 ppm, short-term level 1000 ppm, 30 min, twice per shift, pregnancy group C, no reason to fear a risk of damage to the developing embryo or fetus when MAK and BAT values are observed (1998); Sweden: 50 ppm, 15-min short-term value 90 ppm (1990); United Kingdom: 350 ppm, 10-min STEL 450 ppm (1991). 4.6 Studies on Environmental Impact None found.

Saturated Halogenated Aliphatic Hydrocarbons Two To Four Carbons Jon B. Reid, Ph.D., DABT 1,1,2-Trichloroethane 5.0.1 CAS Number: [79-00-5] 5.0.2 Synonyms: Vinyl trichloride, beta-trichloroethane, 1,2,2-trichloroethane, and ethane trichloride (not recommended because of confusion with 1,1,1-trichloroethane) 5.0.3 Trade Names: NCI-C04579, RCRA Waste Number U227, RCRA Waste Number U359, beta-T 5.0.4 Molecular Weight: 133.40 5.0.5 Formula: C2H3Cl3, ClH2C–CHCl2 5.0.6 Molecular Structure:

5.1 Chemical and Physical Properties Physical state Molecular weight Specific gravity Melting point Boiling point Vapor pressure Refractive index Percent in “saturated”air Solubility Flammability

Colorless liquid 133.41 1.4397 at 20°C (20/4°C) 36.5°C 113.8°C 25 torr (25°C) 19 torr (20°C) 1.4711 (20°C) 3.3 (25°C) 0.44 g/100 g water at 20°C; soluble in ethanol and ethyl ether; 4.50 g/L at 20°C Not flammable by standard tests in air

5.1.1 General 5.1.2 Odor and Warning Properties Although 1,1,2-trichloroethane is reported to have an odor similar to chloroform, no quantitative data were found concerning odor or warning properties. In view of its high systemic toxicity, odor cannot be used to protect against excessive acute or chronic exposure. 5.2 Production and Use The use of 1,1,2-trichloroethane is quite restrictive. It is used to a slight extent as a specialty solvent but mostly as a chemical intermediate; a solvent for fats, waxes, natural resins, alkaloids, and various other organic materials; intermediate in production of vinylidene chloride and teflon tubing; component of adhesives. The availability of other less toxic solvents discourages its use. Upwards of 95% of this compound manufactured in the United States is consumed in producing vinylidene chloride. Domestic production is about 410 million pounds. It must not be confused with its much less toxic isomer, 1,1,1-trichloroethane. 5.3 Exposure Assessment 1,1,2-Trichloroethane has been detected in ambient urban air at concentrations up to 0.223 m/m3 (174). It is degraded in the troposphere by reaction with hydroxyl radicals (t1/2 = 24 d) (1) to hydrochloric acid, phosgene, formyl chloride, and chloroacetyl chloride. 5.3.3 Workplace Methods NIOSH Method 1003, for halogenated hydrocarbons is recommended for determining workplace exposures to 1,1,2-trichloroethane. 5.3.5 Biomonitoring/Biomarkers 1,1,2-Trichloroethane is absorbed from the lungs and no doubt also is excreted in the breath. Although no data are available, it seems probable that the low concentrations that could be present in expired air after exposure to levels considered safe for occupational exposure will not be useful for monitoring workers exposure. Qualitative analysis might verify that exposure to 1,1,2-trichloroethane has occurred. Ikeda and Ohtsuji (130) have shown a positive Fujiwara reaction in the urine of rats and mice treated with 1,1,2-trichloroethane, but the value of this determination in humans does not appear to have been investigated. At the low levels of exposure considered acceptable, it may have limited value. 5.4 Toxic Effects 1,1,2-Trichloroethane is toxic by ingestion or inhalation. It is an irritant of the skin, eyes, mucous membranes, and upper respiratory tract. It may be absorbed through the skin, and in high concentrations, it is narcotic. It is a positive animal carcinogen. When heated to decomposition it emits toxic fumes of carbon monoxide, carbon dioxide, hydrogen chloride gas, and phosgene gas. The principal physiological responses to 1,1,2-trichloroethane are depression of the central nervous system and liver injury. With regard to the CNS effects, it is considerably more potent than chloroform by inhalation (7, pp. 155–156; 175). At narcotic concentrations, ocular and upper respiratory tract irritation is present. Similarity in chemical names has resulted in some confusion in older literature that misquoted work by Lazarew (175) and stated that the 1,1,2 compound was less toxic than 1,1,2-trichloroethane. Torkelson et al. (95) have explained the source of the error, which could be serious because 1,1,2trichloroethane is much more hepatotoxic when given to animals by single or repeated doses. Even current literature occasionally confuses the two substances or fails to distinguish between them. No new published reports of human injury were found. 5.4.1 Experimental Studies 5.4.1.1 Acute Toxicity Concentrations of 13,600 ppm for 2 h exposures produce deep narcosis, respiratory arrest, and death (7, 175). Carpenter et al. (176) indicated that exposure of 2000 ppm for 4 h was lethal to rats. Torkelson and Rowe (105) reported hepatic and

renal necrosis for rats inhaling 250 ppm for 4 h. Smyth et al. (63) and Di Vincenzo and Krasavage (177) reported rat oral LD50 values for male and female mice at 378 and 491 mg/kg body weight, respectively. Klaassen and Plaa (109) reported a dog interperitoneal LD50 of 648 mg/kg. Wahlberg (178) published that repeated applications of 0.5 mL or more to guinea pig skin caused death in all 20 animals in 3 d. Wright and Shaffer (179) reported that the oral lethal dose for dogs was 0.5 mL/kg. Irish (180) indicated an LD50 for rats of 0.1–0.2 g/kg. Liver and kidney pathology were seen at considerably lower doses. Gehring (111) included 1,1,2-trichloroethane in a series of chlorinated solvents evaluated for hepatotoxicity and considered it less hepatotoxic in the rat than carbon tetrachloride or chloroform, but markedly more toxic than 1,1,1-trichloroethane. Klaassen and Plaa (110) and Plaa et al. (181) have confirmed this in mice as well as rats. Watrous and Plaa (182) have indicated that kidney injury also occurs following oral and subcutaneous treatment of mice. Inhalation: Pozzani et al. (183) reported that a single 7 h exposure to 500 ppm of the vapor was lethal to about half of the rats so exposed. Carpenter reported the acute lethal concentration for about half of the exposed rats to be 2000 ppm for a 4-h exposure followed by a 14-d observation period (176). 5.4.1.2 Chronic and Subchronic Toxicity The critical effect for oral administration, as determined by the EPA (IRIS), is clinical serum chemistry with a NOAEL of 20 mg/L (drinking water 39 mg/kg/d), giving an oral reference dose (RfD) of 4E-3. This was determined from a mouse subchronic drinking water study with a LOAEL of 200 mg/L (drinking water). References for this study are White et al. (184) and Sanders et al. (185). The studies by White et al. (184) and Sanders et al. (185) were selected by the EPA as the basis for the derivation of the oral RfD because they are considered adequate studies in which mice of both sexes were exposed to 1,1,2-trichloroethane in drinking water for 90 d. Concentrations provided were 0, 20, 200, or 2000 mg/L, which resulted in intakes of 0, 4.4, 46, and 305 mg/kg/d for males and 0, 3.9, 44, and 384 mg/kg/d for females. Clinical chemistry indications of adverse effects on the liver occurred in both sexes at 2000 mg/L. Effects on the erythrocytes occurred only in females, and depressed humoral immune status occurred in both sexes at 200 and 2000 mg/L. The concentration of 20 mg/L, corresponding to 3.9 mg/kg/d for female rats is the NOAEL at which significant adverse effects were not observed and is chosen as the basis for the derivation of an oral RfD. The previous oral RfD (2E-1 mg/kg/d) was based on the NCI (186) study in rats. This study's major weakness was its lack of reporting of noncancer effects. Also, doses far below the NCI (186) NOAEL (65.7 mg/kg/d) have been shown to alter levels of clinical serum chemistries, which are indicative of systemic tissue damage. At present the EPA (IRIS) does not provide a reference concentration (RfC) for inhalation exposure. 5.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Yllner (187) injected 14C-labeled, 1,1,2trichloroethane intraperitoneally in mice. The site of labeling on the molecule was not stated. When collected over a 3-d period, 73–87% of the activity was recovered in the urine. Less than 2% was in the feces; this may have been the result of contamination by urine. Expired air contained 16–22% of the radioactivity (60% [14C]CO2 and 40% unchanged 1,1,2-trichloroethane). 1–3% of the labeled compound remained in the animal. Metabolism by microsomal cytochrome P450 appeared to proceed through chloroacetic acid (188), indicating oxidative dechlorination or dechlorination followed by oxidation of 1,1,2-trichloroethane at the carbon containing two chlorine atoms. According to VanDyke (136, 189). This is followed by further oxidation of the chloroacetaldehyde

to the corresponding acid. Cytochrome P450 is probably involved in the dechlorination. MacDonald et al. (190) speculated that glutathione is involved in the metabolism of 1,1,2-trichloroethane. 5.4.1.3.1 Absorption Absorption of the liquid through the skin has shown to occur in guinea pigs (174). Jakobson and other workers also investigated the kinetics of absorption through the guinea pigs' skin as well as the nature of injury to the skin with prolonged contact (174, 191). Wahlberg (178) reported that repeated applications of 0.5 mL or more to the skin killed all the guinea pigs in 3 d, but 0.25 mL killed only 5 of 20 animals treated for a longer period of time. Although absorption does not appear to be a serious problem from acute exposure, prolonged or repeated exposure of the skin may result in manifestations of chronic toxicity. 5.4.1.4 Reproductive and Developmental According to Seidenberg et al. (192) pregnant ICR/SIM mice were intubated on days 8 to 12 of gestation with evaluation of the usual parameter of developmental toxicity. The dose (not stated) was selected to produce minimal toxicity based on weight reduction, mortality, or other signs of toxicity. The test results were reported to be negative. No other details were given. 5.4.1.5 Carcinogenesis According to the NCI (185), 1,1,2-trichloroethane has been included in the NCI bioassay program, in which it was fed by gavage to rats and mice. As in many of these studies with hepatotoxic compounds, hepatocellular carcinomas occurred in mice but not rats fed for 78 wk. Rats were kept an additional 35 wk and mice 13 wk following treatment. Pheochromocytomas were also observed in mice. The doses fed were 92 and 46 mg/kg/d for rats and 390 and 195 mg/kg/d for mice. Mortality was accelerated in female mice but not in the rats or male mice. The NCI report does not indicate the degree of noncarcinogenic histopathology produced by these doses. In a bioassay conducted by NCI (185), technical-grade (92.7%-pure) 1,1,2-trichloroethane was administered by gavage in corn oil to Osborne–Mendel rats and B6C3F1 mice: (50/species/sex/dose) for each of two doses and 20 animals/species/sex for each of two control groups. Administration was 5 times/wk for 78 wk, during which time doses for rats were increased from 70 and 30 mg/kg/d to 100 and 50 mg/kg/d and doses for mice were increased from 300 and 150 mg/kg/d to 400 and 200 mg/kg/d. By two statistical tests, treatment of mice was found to be associated with increased incidence of hepatocellular carcinomas. A dose-related increase in pheochromocytomas was also confirmed in female mice. Tumors found in treated but not control rats included adrenal cortical carcinomas; transitional-cell carcinomas of kidney; renal tubular adenomas; and hemangiosarcomas of spleen, pancreas, abdomen, and subcutaneous tissue. There was, however, no statistically significant increase in tumor incidence in rats as a function of treatment. 5.4.1.6 Genetic and Related Cellular Effects Studies There are numerous references to mutagenic studies on 1,1,2-trichloroethane. It would appear at most to be weakly positive in some systems but negative in others. Mirsalis et al. (193) show that it did not induce unscheduled DNA synthesis but was positive in an S-phase synthesis. 1,1,2-Trichloroethane was found to be nonmutagenic for Salmonella typhimurium (194). In rats and mice acutely exposed to 1,1,2-trichloroethane by inhalation and intraperitoneal injection, trichloroacetic acid, trichloroethanol, chloroacetic acid, and thiodiacetic acid were among the urinary metabolites identified (130, 187). 5.4.2 Human Experience Symptoms of exposure to this compound may include irritation of the skin, eyes, nose, mucous membranes, and upper respiratory tract; eye damage; skin cracking and crythema; central nervous system depression; liver and kidney damage; narcosis; drowsiness; incoordination; unconsciousness; and death. Other symptoms may include headache, tremor, dizziness, peripheral paresthesia, hyposthesia, or anesthesia. The only human studies found relate to permeability in the skin and distribution in the body after inhalation of a radioactive charge. Morgan et al. (195, 196) calculated a blood–air partition coefficient of 44. They also found that 3% of the inhaled chlorine was recovered in exhaled air,

indicating a relatively slow elimination. The USEPA (197) determined a permeability coefficient for intact human skin at 8.4 × 10–3 cm/h. Using these data, Tsuruta (198) calculated the dermal uptake of 13.9 mg if both hands were exposed for 1 min. Wahlenberg (199) determined that a 1.5-mL application to the forearms of adult males for 5 min caused localized hyperemia, transient blanching pain, and burning sensation. 5.4.2.1 General Information 5.4.2.2.5 Carcinogenesis The EPA classifies this compound as - C; possible human carcinogen on the basis of: hepatocellular carcinomas and pheochromocytomas in one strain of mice. Carcinogenicity was not shown in rats. 1,1,2-Trichloroethane is structurally related to 1,2-dichloroethane, a probable human carcinogen. There are no human carcinogenicity data. 5.5 Standards, Regulations, or Guidelines of Exposure The ACGIH TLV is 10 ppm with an A4 notation. NIOSH considers 1,1,2-trichloroethane as a carcinogen and recommends lowest feasible exposure and an exposure limit of 10 ppm. The OSHA PEL is also 10 ppm with a skin notation. 5.6 Studies on Environmental Impact None found.

Saturated Halogenated Aliphatic Hydrocarbons Two To Four Carbons Jon B. Reid, Ph.D., DABT 1,1,2,2-Tetrachloroethane 6.0.1 CAS Number: [79-34-5] 6.0.2 Synonyms: Acetylene tetrachloride, 1,1-dichloro-2,2-dichloroethane, sym-tetrachloroethane, 1,1,2,2-TCA 6.0.3 Trade Names: Bonoform, Cellon, Westron, Acetosol 6.0.4 Molecular Weight: 167.86 6.0.5 Molecular Formula: CHCl2CHCl2 6.0.6 Molecular Structure:

6.1 Chemical and Physical Properties Physical state Molecular weight Specific gravity Melting point Boiling point

Colorless liquid 167.86 1.586 (25°C) –44°C 146.3°C

Vapor pressure 6 torr (25°C) Refractive index 1.4918 (25°C) Percent in “saturated”air 0.79 (25°C) Solubility 0.32 g/100 mL water at 25°C; soluble in ethanol and ethyl ether Flammability Not flammable by standard tests in air 1 mg/L 145.8 ppm and 1 ppm 6.86 mg/m3 at 25°C, 760 torr. This compound has the highest solvent power of the chlorinated hydrocarbons. 6.1.1 General An ATSDR toxicological Profile for 1,1,2,2-trichloroethane is available (3). 6.1.2 Odor and Warning Properties 1,1,2,2-Tetrachloroethane has a mild, sweetish odor similar to several other chlorinated hydrocarbons. Lehmann and Schmidt-Kehl (200) reported 3 ppm to have a noticeable odor and 13 ppm to be tolerated for 10 min. Concentrations of 186 ppm inhaled for 30 min, or 335 ppm inhaled for 10 min, have a disagreeable and marked odor, causing upper respiratory irritation and CNS effects. Because the odor is not particularly striking, and because the acceptable level is 1 ppm, odor does not appear to be of value as a warning property. Amoore and Hautala (10) reported 1.5 ppm was detectable by humans. 6.2 Production and Use 1,1,2,2-Tetrachloroethane was formerly used as a solvent for cleaning and extraction processes and is still used to some extent as a chemical intermediate. Present usage is quite limited because less toxic solvents are available. 6.3 Exposure Assessment 6.3.3 Workplace Methods NIOSH Method 1019 is recommended for determining workplace exposures to 1,1,2,2-tetrachloroethane. 6.3.5 Biomonitoring/Biomarkers The apparent high toxicity of 1,1,2,2-tetrachloroethane would suggest that neither breath nor urine analysis would be adequately sensitive for monitoring exposures at the low level considered acceptable for occupational exposures. 6.4 Toxic Effects According to Sax and Lewis (201), 1,1,2,2-tetrachloroethane is a poison by inhalation, ingestion, and intraperitoneal routes and is moderately toxic by several other routes. It is considered to be the most toxic of the common chlorinated hydrocarbons. It is considered to be a very severe industrial hazard, and its use has been restricted or even forbidden in certain countries. Its narcotic action is stronger than that of chloroform, but because of its low volatility, narcosis is less severe and much less common in industrial poisoning than in the case of other chlorinated hydrocarbons. It is a lacrimator and irritant of the skin, eyes, nose, throat, mucous membranes, and respiratory tract. When heated to decomposition, it emits toxic fumes of carbon monoxide, carbon dioxide, hydrogen chloride gas, and phosgene. The most significant injury from subacute or chronic exposures has been reported to be in the liver. The first indication may be a greatly enlarged and palpable liver, which may progress to fatty degeneration, jaundice, and cirrhosis. Injury to the kidneys may also be observed. This compound also causes CNS depression, dizziness, and incoordination, as do many chlorinated hydrocarbons. In very severe acute exposures, unconsciousness and death from respiratory failure may be seen. Central nervous system depression is not a striking part of the response to usual industrial exposure because of low volatility and because other injurious effects predominate at lower levels. Respiratory irritation may be observed and may lead to pulmonary damage. A significant irritation in the gastrointestinal tract is also observed and may result in nausea, vomiting, and gastric pain.

Literature reviews are available (7, 202, 203), but there is a remarkable lack of quantitative data in animals to support the apparent high toxicity in humans. It is possible, however, that inhaled concentrations have been underestimated, that dermal contact has been more significant than realized, or that the purity of industrial 1,1,2,2-tetrachloroethane available at that time was less than later production. Limited data on the 1,1,1,2 isomer (204) indicate that this isomer may be less toxic than the symmetrical isomer. 6.4.1 Experimental Studies 6.4.1.1 Acute Toxicity Barsoum and Saad (205) reported that an oral dose of 0.7 g/kg body weight in dogs is a toxic dose, but Wright and Schaffer (179) reported that a lethal dose for dogs was 0.3 mL/kg (0.5 g/kg) given orally. Smyth et al. (63) reported an oral LD50 of 200 mg/kg in rats, but did not specify which isomer they used, although a prior publication refers to the 1,1,2,2-tetrachloroethane isomer (45). Gohlke et al. (206) reported deaths of rats treated with 250 mg/kg. Schwander (207) indicated that 1,1,2,2-tetrachloroethane may be absorbed through the intact skin. However, it does not have a high acute toxicity by this route; Smyth (45) reported an acute dermal LD50 of 4 g/kg in rabbits. Based on experience, repeated exposure may be of considerable concern. It has a solvent effect on the skin, but no data on eye irritation by the liquid were found. Although there are a number of animal experiments with this material, a clean-cut quantitative study of animal response from acute exposure has not been reported. Smyth et al. (63) quoted unpublished work by their laboratory indicating that rats were found to survive a 4 h exposure at 500 ppm but would not survive 4 h at 1000 ppm. They also reported three of six rats exposed to 1000 ppm for 4 h died. In a report that does not appear to be consistent with oral studies, daily doses of 100–800 mg/kg (17– 130 mg/kg/d) were injected intraperitoneally for 7 d in male rats with no toxic symptoms. Liver enzymes and possible hematologic changes were reported (208). 1,1,2,2-TCA is moderately irritating to the skin, and vapors appear nonirritating to the eye of the dog (209). Liver damage involving cytochrome P450 and possibly mediated through free radicals interfering with in vivo lipid peroxidation has been reported in mice following single 300 or 600 mg/kg doses (210). The acute inhalation toxicity of 1,1,2,2-TCA has been thoroughly studied and is relatively low. A 4 h LC50 of 1000 ppm for rats has been reported (176); a second investigation found lethality beginning at 1000 ppm (211). The corresponding number for the mouse is 655 ppm, with all mice dying at 786 ppm (212). Narcosis is seen in mice inhaling 625 ppm (49) and in cats at 1000 ppm (175) for 1 h. Guinea pigs show eye irritation when exposed at 576 ppm, narcosis at 5050 ppm, and death at 6310 ppm (213). Reflex reactivity in mice is reduced within 30 min when inhaling 1091 ppm 1,1,2,2-TCA (175). At the lower end of the dose–response curve, a decrease in spontaneous motor activity was seen in rats inhaling 200 ppm for a single 6 h period (214), and no effects were reported following a 30-min exposure at 576 ppm (213). 6.4.1.2 Chronic and Subchronic Toxicity The EPA (IRIS) has not determined a reference dose or reference concentration for this material (2). Lehmann and Flury (16) reported data from limited vapor experiments on cats and rabbits, which were exposed to a concentration of 100 to 160 ppm for 8–9 h daily for 4 wk. No typical organ

changes were found. These observations are rather surprising when, as is discussed later, industrial experience indicates that injury to humans has occurred at much lower concentrations. Navrotskii et al. (215) exposed rabbits to tetrachloroethane (presumably the 1,1,2,2 isomer) vapor for 7–11 m. The 3–4-h daily exposures were to 100 mg/m3 (14.6 ppm). According to the available abstract, only slight effects on the liver were observed. Schmidt et al. (216) also reported only slight effects in rats exposed to 15 mg/m3 (2 ppm) for 265 d and considered their results somewhat inconclusive. Some toxicologic parameters deviated during the exposure but were not different from the controls at the end. Mortality was not affected, but histological examination appears to have been inadequate to evaluate chronic effects. Truffert et al. (217) reported exposing rats 6 h/d, 5 d/wk for 15 wk to 260 ppm with no effect on the respiratory or renal toxicity, but increased deposits were found in the liver. 6.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Studies have shown that 1,1,2,2trichloroethane is readily absorbed via the lungs or gastrointestinal tract. Some authors have indicated absorption by the skin. It is apparently readily excreted by the lungs. Yllner (218) injected 14C-labeled 1,1,2,2-tetrachloroethane intraperitoneally in female albino mice at doses of 0.21 to 0.32 g/kg and studied the elimination for 3 days. About half the dose, 45 to 61 percent, was exhaled as carbon dioxide with 28 percent excreted in the urine. About 16 percent remained in the animal and only 4 percent was expired unchanged. Several products were found in the urine with half the urinary activity unaccounted for. Both enzymatic and nonezymatic activity was postulated. Enzymatic hydrolytic fission of chlorine-carbon bonds results in dichloroacetic acid and glycolic acid. Nonenzymatic dehydrochlorination results in trichloroethylene and subsequently trichloroethanol and trichloroacetic acid. When fed to rats and mice, more than 90 percent of the dose was metabolized (219). Although there was incorporation in mouse DNA, it was not by adduct formation. These authors concluded that their data supported a cytotoxic rather than a genetic mechanism of carcinogenesis observed in mice. Ikeda and Ohtsuji (130) also found trichloro products in the urine of mice and rats exposed for 8 h to 100 ppm of 1,1,2,2-tetrachloroethane vapor. 6.4.1.4 Reproductive and Developmental A very limited reproduction study by Rosenkrantz (220) indicated no gross reproductive or teratological effect in rats exposed daily for 9 mo prior to mating. A second report by Schmidt (221) describes fetotoxic (lethal) effects in two strains of mice given intraperitoneal injections of tetrachloroethane, presumably the 1,1,2,2-isomer. The doses administered, 300, 400, or 700 mg/kg/d were given singly or on several days of pregnancy. According to the author's summary, the compound was fetotoxic and faintly teratogenic. The reproductive organs have not been target organs in the limited studies in animals. 6.4.1.5 Carcinogenesis The EPA (IRIS) has classified this material as –C, possible human carcinogen on the basis of increased incidence of hepatocellar carcinomas in mice (222). The National Cancer Institute (222) has included 1,1,2,2-tetrachloroethane in their bioassay series using rats and mice. Their summary states that the time-weighted average doses (by gavage) were 108 and 62 mg/kg/d for male rats, 76 and 43 mg/kg/d for female rats, and 282 and 142 mg/kg/d for all mice. There was a highly significant positive dose-related trend in the incidence of hepatocellular carcinoma in mice of both sexes. No statistically significant incidence of neoplastic lesions was observed in male or female rats. However, 2 hepatocellular carcinomas and 1 neoplastic nodule, which are rare tumors in the male Osborne–Mendel rat, were observed in the high-dose males. Under the conditions of this bioassay, orally administered 1,1,2,2-tetrachloroethane was a liver carcinogen

in B6C3Fl mice of both sexes. The results did not provide conclusive evidence for the carcinogenicity of 1,1,2,2-tetrachloroethane in Osborne–Mendel rats. 6.4.1.6 Genetic and Related Cellular Effects Studies Mixed results have been obtained in mutagenic studies with most results negative (203). Schumann et al. (219) found little binding to DNA of rats and mice due to adduct formation, indicating a low potential for direct mutagenic activity. 6.4.2 Human Experience Symptoms of exposure to this compound may include irritation of the skin, eyes, nose, throat, mucous membranes, and respiratory tract. Lacrimation may occur. Corrosion may also occur. Other symptoms of exposure include drowsiness, headache, jaundice, abdominal pain or distress, tremor, fatigue, constipation, insomnia, irritability, anorexia, loss of appetite, pulmonary edema, nephritis, albumin and casts in the urine, and kidney damage. Giddiness and unconsciousness have occurred. Central nervous system effects include general anesthesia, somnolence, hallucinations, and distorted perceptions. Other effects include narcosis, acute yellow atrophy of the liver, liver cirrhosis, fatty degeneration of the kidneys and heart, brain changes, changes in the peripheral nerves, hemolysis, salivation, restlessness, dizziness, nausea, vomiting, coma, and death. Monocytosis, dermatitis, liver tenderness and damage, delirium, and convulsions may occur. Oliguria, cyanosis, central nervous system depression, uremia, peripheral paresthesia, and hypesthesia may also occur. Exposure may cause prickling sensation and numbness of limbs, loss of kneejerk, sweating, paralysis of the interossei muscles of the hands and feet, disappearance of ocular and pharyngeal reflexes, peripheral neuritis, liver dysfunction, general malaise, an unpleasant taste in the mouth, mental confusion, stupor, hematemesis, purpuric rashes, and blood changes, including an increase in mononuclear leukocytes, progressive anemia, and slight thrombocytosis. Gastrointestinal disturbances may occur. It may also cause liver necrosis, nervousness, incoordination, respiratory failure, and enlargement and fatty degeneration of the liver. Heart damage has been reported. Neurological disturbances have also been reported. It can cause hepatitis, gastric pain, vertigo, and leukopenia. It can also cause a deep dusky coloration of the skin, weight loss, pain over the liver, dark urine, and bilirubinuria. Pulmonary damage, gastrointestinal irritation, barely perceptible pulse, and shallow and rapid respiration may result. Other symptoms that may occur are polyneuritis (inflammation of the nerves), conjunctivitis, extreme exhaustion, hematuria, mental instability, cardiac irregularity, and epigastalgia. Skin contact may result in dryness, scaling, and inflammation. Severe lesions may occur. Eye contact may result in burning and serious eye damage. Inhalation may cause a burning sensation, wheezing, coughing, laryngitis, and shortness of breath. Ingestion may cause diarrhea and severe mucosal injury. The review by von Oettingen (7) summarizes much of the old data on human experience and based on numerous cases describes the rather severe effects discussed earlier in this section. Sherman (223) reported on eight humans who were given 3 mL of tetrachloroethane by mistake. It was given with 30 g of magnesium sulfate and water. Within 1.5–2.5 h, all were comatose. Reflexes were absent and the pulse barely perceptible. Respiration was shallow and rapid. The patients all recovered and showed no after-effects. Gurney (224) reported a number of cases of chronic exposure to 1,1,2,2-tetrachloroethane. He studied 277 individuals of whom 75 had symptoms and 55 had enlarged livers. There were nearly as many with enlarged livers among those who did not show symptoms as there were among those who did. Coyer (225) reported on six cases, one of which was fatal. It is evident from clinical reports of exposure to 1,1,2,2-tetrachloroethane that the principal effect involves the liver. Symptoms referrable to gastrointestinal injury may also be observed. A study of mortality of army personnel who treated clothing with impregnite for protection against mustard gas in World War II has been reported (226). Tetrachloroethane was used as a solvent for the impregnite (N,N-dichlorohexachlorodiphenylurea). The exposed group was compared with a control group that used a water-based system and with unexposed personnel from the same unit.

Overall deaths during the 31 yr follow-up period were less than expected, possibly related to the screening process used in selection of military personnel. The investigators, however, considered that some other cancers may have shown an increase. The adverse health effects of 1,1,2,2-TCA first became apparent at the beginning of World War I with reports of numerous poisonings of workers in the aircraft industries of several European countries (227, 228), Many deaths were reported, and most cases presented a clinical picture characterized by gastrointestinal, hepatic, and nervous system effects. Although none of a large number of clinical cases contains quantitative exposure data, they consistently indicate primary involvement of the liver (229–232). In domestic airplane factories, complaints of headaches, drowsiness, and nausea, without more serious signs, were attributed to a limited production and short exposure time (lesser exposures) (233). From suicide cases that present similar clinical findings, estimates of a human fatal oral dose ranging from 285 (234) to 6000 mg/kg (235) have been made. The lowest adverse effect level has been estimated to be 100 mg/kg. Seventy-five workers employed at a plant producing and using 1,1,2,2-TCA were studied for their cardiovascular status. Exposure concentrations ranged from 0.37 to 3.20 ppm, with occasional peaks to 40 ppm. The authors concluded that chronic low-level exposure caused no greater occurrence of cardiovascular lesions than that in the general population (236). In humans, 97% of an inhaled single-breath dose of 1,1,2,2-TCA is absorbed with very little (3.3%) exhaled as unchanged chemical; urinary excretion was 0.015%/min (195). The metabolism and kinetics in humans have not been as well developed as for chlorinated solvents such as trichloro- and tetrachloroethylene (for which biologic exposure indices exist). Of 380 workers examined in the workplace where 1,1,2,2-TCA was the solvent for cellulose acetate, 192 were in direct contact, and some of the remaining 188 workers were occasionally exposed to its vapors. The signs of poisoning in the workers were most frequently of the nervous system. These symptoms were characterized by tremor and increased with the amount of solvent in the air. Jaundice was not detected in any of the workers (237). Early work of Lehman suggests that, in humans, a concentration of 3 ppm 1,1,2,2-TCA may be detected by odor, 13 ppm may be tolerated without effect for 10 min, and inhalation of 145 ppm for 30 min or 334 ppm for 10 min will cause irritation of the mucous membranes, pressure in the head, vertigo, and fatigue (200). 6.4.2.3.5 Carcinogenesis Carcinogenic Classification: EPA Group 3, possible human carcinogen. IARC Group 3, not classifiable as to its carcinogenicity in humans MAK Group B, justifiably suspected of having carcinogenic potential NIOSH Carcinogen, with no further categorization TLV A3, animal carcinogen 6.5 Standards, Regulations, or Guidelines of Exposure The ACGIH TLV is 1 ppm with an A3 and skin notation. NIOSH considers 1,1,2,2-TCA a carcinogen and recommends the lowest feasible exposure and an REL of 1 ppm. The OSHA PEL is 5 ppm with a skin notation. Other Nations: Australia: 1 ppm, skin (1993); Federal Republic of Germany: 1 ppm, skin, Group B, justifiably suspected of having carcinogenic potential (1997). 6.6 Studies on Environmental Impact None found.

Saturated Halogenated Aliphatic Hydrocarbons Two To Four Carbons Jon B. Reid, Ph.D., DABT Pentachloroethane 7.0.1 CAS Number: [76-01-7] 7.0.2 Synonyms: Ethane pentachloride 7.0.3 Trade Names: Pentalin 7.0.4 Molecular Weight: 202.29 7.0.5 Molecular Formula: CHCl2CCl3 7.0.6 Molecular Structure:

7.1 Chemical and Physical Properties Physical state Colorless liquid Specific gravity 1.6712 (25/4°C) Melting point –29°C Boiling point 162°C Vapor pressure 3.4 torr (25°C) Refractive index 1.50250 (24°C) Percent in “saturated air” 0.45 (25°C) Solubility 0.05 g/100 mL at 20°C; soluble in ethanol, ethyl ether Flammability Not flammable by standard tests in air 7.1.1 General No new information was found since last edition. 7.1.2 Odor and Warning Properties Pentachloroethane has a sweetish odor, not unlike chloroform. The threshold at which the odor is detected has not been determined, and therefore its value as a warning is not known. 7.2 Production and Use Pentachloroethane has been used as a solvent and chemical intermediate but has had little commercial utilization. Pentachloroethane is used as a solvent for oil and grease in metal cleaning; in the separation of cola from impurities by density difference; as a chemical intermediate, in the manufacture of tetrachloroethylene and dichloroacetic acid; as a solvent for cellulose acetate, certain cellulose ethers, resins, and gums; as a drying agent for timber by immersion at temperatures greater than 100°C; in dry cleaning and soil sterilizing. 7.3 Exposure Assessment No information found.

7.3.3 Workplace Methods NIOSH Method 2517 is recommended for determining workplace exposures to pentachloroethane. 7.4 Toxic Effects Sax and Lewis (242) report that pentachloroethane is a poison by inhalation and intravenous routes and is an experimental carcinogen, and moderately toxic by ingestion and subcutaneous routes. It is irritating to the eyes, lungs, corneas, upper respiratory tract, the skin, and mucous membranes. It is very toxic by inhalation, or skin absorption. It has a strong narcotic effect. When heated to decomposition, this compound emits highly toxic fumes of CO, CO2, and HCl. Toxicologic data on pentachloroethane are quite limited. Pentachloroethane has a narcotic effect that has been indicated to be even greater than that of chloroform. Exposure to this material may also result in injury to the liver, lungs, and kidneys, but rats and mice have tolerated rather high doses without injury. It has caused liver tumors in mice but not in rats. 7.4.1 Experimental Studies 7.4.1.1 Acute Toxicity Barsoum and Saad (205) reported the lethal oral dose to be 1.75 g/kg of body weight. Lehmann and Flury (16) indicated that cats inhaled 1 mg/L of air (120 ppm) 8–9 h daily for 23 d without overt symptoms of poisoning. However, they showed significant pathological changes in the liver, lungs, and kidneys. Dogs exposed to the vapor for 3 wk showed fatty degeneration of the liver and injury to the kidneys and lungs. 7.4.1.2 Chronic and Subchronic Toxicity Navrotskii et al. (215) exposed rabbits to 100 or 10 mg pentachloroethane vapor per cubic meter of air 3–4 h daily for 7–11 m. Only limited data are discussed in the available abstract. Antibody titers were reported to be elevated after 1–1.5 m exposure to 100 mg/m3 (12 ppm). The abstract also states that toxic effects occurred at 10 mg/m3 but the nature of the toxic effects is not specified. Pentachloroethane containing 4.2% hexachloroethane was studied by Mennear et al. (243). The material was administered by gavage to rats and mice of both sexes. Prechronic studies of 2 and 13 wk failed to reveal specific target organ toxicity at 10, 50, 100, 500, or 1000 mg/kg. However, all rats fed 1000 mg/kg/d died within 4 d, although the same dose was lethal to only one female mouse. The 500-mg/kg/d dose was lethal to 3/5 rats of each sex between the fourth and tenth day. Decreased motor activity and lethargy were observed but little body weight loss. There were no gross or histological changes. When fed 5 d/wk for 13 wk at doses of 5, 10, 50, 125, or 250 mg/kg/d to rats or 5, 10, 50, 100, or 500 mg/kg/d to mice, weight loss was the only parameter affected by treatment. All rats survived, and only those fed 250 mg failed to gain weight at the rate of the controls. Only one mouse treated with 500 mg/d died, but weight gain of this group was 29% less than controls. Gross and histopathology were considered normal after 13 wk. 7.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Yllner (244) injected 14Cpentachloroethane subcutaneously in mice at doses of 1.1–1.8 g/kg and determined the excretion over a 3 d period. About 1/3 of the dose (12–51%) was expired unchanged; 16–32% was excreted as 2,2,2-trichloroethanol, and 9–18% as trichloroacetic acid in the urine. The expired air also contained trichloroethylene (3–9% of the dose), indicating both dechlorination and dehydrochlorination. Town and Leibman (245) reported that a cytochrome P450–dependent monooxygenase system was involved in the dechlorination of pentachloroethane to trichloroethylene and 1,1,2,2tetrachloroethane. Bronzetti et al. (246) considered P448 to be more important. In a report available only as an abstract, weak covalent binding was reported following intraperitoneal injection (247). Labeled pentachloroethane was reported to be bioactivated by cell-free microsomal and cytosolic enzymes from mouse and rats organs.

The role of a-2m-globulin and protein droplet formation in the male rat kidneys has been studied because it is possibly involved in the production of kidney pathology and cancer in male rats (248). 7.4.1.4 Reproductive and Developmental No information on teratology or reporoduction were found. The reproductive organs were not affected in any of the studies reported previously. 7.4.1.5 Carcinogenesis When fed 5 d/wk to male rats for 104 wk at doses of 75 and 150 mg/kg/d, mortality was excessive and body weight gain was below controls starting at 76 wk. Weight gain was decreased in female rats at both levels starting at 42 wk, but mortality in both sexes was increased only at 150 mg/kg/d. No increase in tumors was found, but there was a dose-related increase in the incidence of chronic renal inflammation of male rats and mineralization of renal papillae. Survival of mice similarly treated with 250–500 mg/kg/d was significantly shortened, and hepatocellular carcinomas were increased. The only other tumor showing an increase was in female mice, where there was a dose-related increase in hepatocellular adenoma. The cause of death did not appear to be either the renal lesions in male rats or the liver tumors in mice, and no other target organs were found to explain the deaths. 7.4.1.6 Genetic and Related Cellular Effects Studies Mutagenic data are limited and equivocal in yeast (246) and negative in S. typhimurium (249). 7.4.2 Human Experience Symptoms of exposure to this compound may include irritation of the eyes, lungs, and upper respiratory tract. It may cause irritation of the skin and mucous membranes. It may also cause drowsiness, giddiness, jaundice, headache, and, in high concentrations, unconsciousness. It may also affect the central nervous system and the blood. Overexposure to this compound may damage the liver and kidneys. 7.5 Standards, Regulations, or Guidelines of Exposure No standards have been proposed for pentachloroethane. It is probably not possible to set a reliable standard because of the limited toxicologic information and experience reported on this material. It is obvious that a concentration safe for repeated exposure would be well below the 121 ppm that was shown to cause pathological change. The unconfirmed report of Navrotskii suggests that exposures be kept much lower. NIOSH recommends that this substance be handled with caution in the workplace. 7.6 Studies on Environmental Impact None found.

Saturated Halogenated Aliphatic Hydrocarbons Two To Four Carbons Jon B. Reid, Ph.D., DABT Hexachloroethane 8.0.1 CAS Number: [67-72-1] 8.0.2 Synonyms: Carbon hexachloride, ethane hexachloride, hexachloroethylene, 1,1,1,2,2,2-hexachloroethane, HCE, ethylene hexachloride, and perchloroethane 8.0.3 Trade Names: A Vlothane, Distokal, Distopan, Distopin, Egitol, Falkitol, Fasciolin, Mottenhexe, Phenohep 8.0.4 Molecular Weight: 236.74

8.0.5 Molecular Formula: C2Cl6, Cl3CCCl3 8.0.6 Molecular Structure:

8.1 Chemical and Physical Properties Physical state Solid rhombic crystals Specific gravity 2.091 (20°C) Melting point Sublimes at 186.8°C Boiling point 189°C Solubility 0.005 g/100 mL water at 22°C; soluble in ethanol, ethyle ether Flammability Not flammable by standard tests in air 8.1.1 General An ATSDR Toxicological profile for hexachlorethane is available (250). It is found as colorless crystal. 8.1.2 Odor and Warning Properties Hexachloroethane is reported to have a camphorous odor. 8.2 Production and Use Hexachloroethane has been used as a chemical intermediate, in pyrotechnics, as an insecticide, and as a parasiticide in animals. It is an undesired by-product of certain chlorination processes and is of environmental concern in soil and water. 8.3 Exposure Assessment HCE has been employed in veterinary practice as an anthelmintic for livestock, but it is doubtful that it is still used for this purpose. While some may be used as an insecticide and in chemical manufacture, large amounts are used by the United States Army in pyrotechnics and smoke devices (251). It is a by-product of certain chlorination processes, sometimes appearing in waste tars. HCE is produced in France, Spain, and the United Kingdom; it is not manufactured in the United States (252). HCE imported for 1985 was reported to be 1,124,000 kg (253). 8.3.3 Workplace Methods NIOSH Method 1003, for halogenated hydrocarbons is recommended for determining workplace exposures to hexachloroethane (10a). 8.3.5 Biomonitoring/Biomarkers Biologic monitoring of exposed workers may determine if exposure has occurred, but at this time available data appear inadequate to quantify exposure. 8.4 Toxic Effects According to Sax (254), hexachloroethane has high toxicity via intravenous and moderate via oral, intraperitoneal, and dermal routes. It is irritating to the skin, eyes, mucous membranes, and upper respiratory tract. When heated to decomposition, it emits toxic fumes of CO,CO2, HCl gas, and phosgene. It is absorbed through the skin. It is a positive animal carcinogen. Much of the experience with this material has come about because of its use as a parasiticide in animals, although more recent articles indicate renewed interest in this chemical because of environmental concerns, and its use in pyrotechnics. Von Oettingen (7) reviewed the literature available in 1955 and Oak Ridge National Laboratory in 1988 (255). It is possible that some of the effects ascribed to hexachloroethane in the older literature may have been due to impurities in the samples tested. It has been shown to produce liver cancer in mice and kidney cancer in male rats.

The kidneys appear to be the target organ, and males are more affected that female laboratory animals. 8.4.1 Experimental Studies 8.4.1.1 Acute Toxicity Hexachloroethane has a low acute oral toxicity. Thorpe (256) reported the LD50 for rats to be 5.9 g/kg, a value consistent with Reynolds and Yee (257), who reported rats survived 6.16 g/kg for up to 24 h, and Barsoum and Saad (205), who reported dogs survived 6 g/kg. A dose of 6 g/kg over a 2-d period was lethal to cats (258). Similar figures are given in Table 63.5 taken from Weeks et al. (251). Table 63.5. Lethal Dosages for Animals Following Single Administration of Hexachloroethane Animal Rabbit, male Rat, male Rat, female

Treatmenta

Diluent

Dosage (mg/kg)

Oral ALD Methylcellulose Intraperitoneal ALD Corn oil Corn oil Oral LD50

>1,000 2,900 4,460

Oral LD50

Methylcellulose Corn oil

7,080 5,160

Guinea pig, male Oral LD50

Methylcellulose Corn oil

7,690 4,970

Rabbit, male

Water paste

Rat, male

Dermal LD50

32,000

The toxicity in larger species such as dogs and cattle is consistent with the laboratory animals. Twelve daily oral doses of 1000 mg/kg to rabbits cause significant reduction in body weight and increased relative liver and kidney weights. Gross and histology injury occurred in the liver and kidneys. Daily doses of 320 mg/kg caused liver injury, but 100 mg/kg caused no significant effect (251). When fed to rats to determine the maximum tolerated dose in the NTP studies discussed subsequently, the following results were reported (259). In the 16-d studies (dose range, 187– 3000 mg/kg), all rats that received 1500 or 3000 mg/kg and 1/5 males and 2/5 females that received 750 mg/kg died before the end of the studies. Final mean body weights of rats that received 750 mg/kg were 25% lower than that of vehicle controls for males and 37% lower for females. Compound-related clinical signs seen at 750 mg/kg or more included dyspnea, ataxia, prostration, and excessive lacrimation. Other compound-related effects included hyaline droplet formation in the tubular epithelial cells in all dosed males and tubular cell regeneration and granular casts in the tubules at the corticomedullary junction in the kidney in males receiving 187 and 375 mg/kg. Weeks et al. (251) reported reversible injury when crystalline hexachloroethane was applied to the cornea of rabbit eyes for a prolonged period. It produced little or no skin irritation and did not appear to be significantly absorbed percutaneously. The dermal LD50 was greater than 32 g/kg by this route. The compound did not sensitize the skin of guinea pigs. Rats exposed to 2.5 mg/L (260 ppm) of the vapors for 8 h showed no adverse effects, but 57 mg/L caused severe injury, including death. The higher concentration was supersaturated and contained particles of hexachloroethane (251). Barsoum and Saad (205) indicated that an intravenous dose of 325 mg/kg in dogs resulted in death.

A corresponding dose for pentachloroethane was found to be 100 mg, and for chloroform, 90 mg. This would indicate that hexachloroethane is intrinsically less toxic than the other materials, or is absorbed much more slowly. Weeks et al. found the approximate lethal dose (ALD) when injected intraperitoneally in male rats to be 2900 mg/kg, and Baganz et al. (260) determined an LD50 for white mice of 4500 mg/kg by this route. Weeks et al. (251) published the oral lethal dose (approximate) for rabbits as greater than 1000 mg/kg, the oral LD50 for rats at 4460 mg/kg (corn oil) Applied to the shaved skin of rabbits, the dermal LD50 was 32,000 mg/kg, and it did not sensitize guinea pigs. Rats exposed for 8 h at a calculated 59,000 ppm vapor showed severe toxic signs and death, but no toxic effects were observed for 8 h at 260 ppm. 8.4.1.2 Chronic and Subchronic Toxicity The EPA (IRIS) considers the critical effect for oral exposure is “atrophy and degeneration of the renal tubules, with a NOAEL of 1 mg/kg/d and a LOAEL of 15 mg/kg/d and a reference dose (RfD) of 1E-3. This is based on a rat subchronic dietary study by Gorzinski et al. (261), as summarized here: Groups of 10 male and 10 female Fischer 344 rats were treated with diets containing hexachloroethane for 16 wk. Dosages were 0, 1, 15, or 62 mg/kg/d, as determined by the investigators. The rats were evaluated for overt signs of toxicity, body weight gain, food consumption; urinalysis, hematological and clinical chemistry parameters; organ weights; and gross pathology. Comprehensive histologic examination was performed on the control and 62 mg/kg/d groups, while histologic examination of the 1- and 15-mg/kg/d groups was limited to the liver and kidney. At 15 and 62 mg/kg/d, male rats had dose-related increased incidences of renal lesions, including renal atrophy, degeneration, hypertrophy, and dilation. At 62 mg/kg/d, males had increased absolute and relative kidney weights and peritubular fibrosis; females had slight renal tubular atrophy and increased liver weights. No other effects were observed. Thus 15 mg/kg/d is the LOAEL and 1 mg/kg/d is the NOAEL. In a draft report for a subchronic gavage study (262) rats were treated by gavage with 0, 47, 94, 188, 375, or 750 mg/kg/d, 5 d/wk for 13 wk. Body weight gain was reduced at 750 mg/kg/d, behavioral signs of toxicity were seen at 94 mg/kg/d, and increased relative liver and kidney weights occurred at 375 mg/kg/d. Dose-related increased incidences of renal tubular regeneration occurred at 47 mg/kg/d. In a 6 wk inhalation study, rats, dogs, and guinea pigs were exposed to hexachloroethane 6 h/d, 5 d/wk for 6 wk at 0, 145, 465, or 2520 mg/m3 (251). Neurobehavioral effects occurred in rats and dogs, and reduced body weights, increased relative liver weights, and deaths occurred in guinea pigs at 2520 mg/m3. No effects were observed at 465 mg/m3. Based on this inhalation NOAEL in rats, an RfD of 0.03 mg/kg/d could be calculated using an uncertainty factor of 1000. However, a later 16 wk oral study by Gorzinski et al. (261) is a better basis for the RfD. When fed for 3 wk at dosages much higher than used by Gorzinski, NTP (259) reported the following results: In the 13 wk studies (dose range, 47–750 mg/kg), 5/10 male rats and 2/10 female rats that received 750 mg/kg died before the end of the studies. The final mean body weight of male rats that received 750 mg/kg was 19% lower than that of vehicle controls. Compound-related clinical signs for both sexes included hyperactivity at doses of 94 mg/kg or higher and convulsions at doses of 375 or 750 mg/kg. The relative weights of liver, heart, and kidney were increased for exposed males and females. Kidney lesions were seen in all dosed male groups, and the severity increased with dose. Papillary necrosis and tubular cell necrosis and degeneration in the kidney and hemorrhagic necrosis in the urinary bladder were observed in the five male rats that received 750 mg/kg and died before the end of the studies; at all lower doses, hyaline droplets, tubular regeneration, and granular casts were present in the kidney. No chemical-related kidney lesions were

observed in females. Foci of hepatocellular necrosis were observed in several male and female rats at doses of 188 mg/kg or higher. Rats, dogs, guinea pigs, and quail were exposed 6 h/d, 5 d/wk for 6 wk to hexachloroethane vapor (van Haaften (263)). Extensive studies were conducted to determine possible injury including behavioral, reproductive, clinical chemical, hematologic, and histological examinations. Animals exposed to 260 ppm were seriously affected, including death (except for quail). Quail showed no adverse effect at any dosage. There was no evidence of injury of any type in any species at 15 ppm. Exposure to 48 ppm caused minimal injury. The most significant effects appeared to be irritation of the eyes and respiratory tract. Apparently liver and kidney injury were not significant at these levels of exposure. 8.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Jondorf et al. (264) reported that an oral dose of 0.5 g/kg of body weight in a rabbit was slowly metabolized. Approximately 5% appeared in the urine in a period of 3 d and from 14 to 24% in the expired air. These authors used chromatographic and isotopic dilution techniques to determine the nature of the metabolities in the urine. These were reported as percent of the dose given: trichloroethanol, 1.3; dichloroethanol, 0.4; trichloroacetic acid, 1.3; dichloroacetic acid, 0.8; monochloroacetic acid, 0.7; and oxalic acid, 0.1. Fowler reported different results for sheep and Leghorn cockerels (265, 266), but the differences in the methods used make it impossible to compare the data from these species with those from rats. Interestingly, hexachloroethane is reported to be a metabolite of carbon tetrachloride but not chloroform. For details see the section on metabolism of chloroform. Gorzinski et al. (261) analyzed liver, kidneys, blood, and adipose tissue from rats fed hexachloroethane in a 110 d dietary feeding study described in a preceding section. After 57 d the authors reported that the “concentration of HCE in the kidneys of male rats was significantly higher at all dose levels when compared to females (mg HCE/g of kidney with increasing dose males: 1.4, 24.3, 95.1; females: 0.4, 0.7, 2.0); this is consistent with the more pronounced renal toxicity noted for male rats. However, the results of the tissue analysis indicated that HCE was cleared in an apparent first-order manner with a half-life estimated to be 2–3 days.” The metabolism (reductive dechlorination) of hexachloroethane in rats and mice is mediated by microsomal cytochrome P450 with oxidation of NADPH. Dechlorination with loss of two chlorines in a two-step process produces the major metabolite tetrachloroethylene. Much less pentachloroethane and trichloroethylene are produced. Further metabolism results in some of the same substances as tetrachloroethylene itself. Hexachloroethane, being fat soluble, enters those tissues that are lipoid in nature, but has been shown to be present at higher concentrations in male rat kidneys than in females. This is consistent with greater toxicity in males (261). Gorzinski (261) fed doses of 0, 1, 15, or 62 mg/kg/d in the diet for 16 wk (see preceding section on oral toxicity for details). Clearance, due to metabolism and elimination, was first order at 62 mg/kg/d, indicating nonsaturation. The half-time was approximately 2.5 d for fat, liver, kidney, and blood. They concluded that elimination from the rat was more rapid than that reported for other species. Table 63.6 taken from Gorzinski (261), shows the organ concentration after 16 wk on the respective diets. Table 63.6. Concentration of Hexachloroethane in the Tissues of Rats Fed Hexachloroethane in the Diet for 16 Weeks

mg HCE/g Tissuea Dose Sex (mg/kg/d) M

F

1 15 62 1

Blood

0.079 ± 0.057 0.596 ± 0.653 0.742 ± 0.111 0.067 ± 0.039 (3) 15 0.162 ± 0.049 (3) 62 0.613 ± 0.231

Liver 0.291 ± 0.213 1.736 ± 1.100 0.713 ± 0.343 0.26 ± 0.035 (2) 0.47 ± 0.204 0.631 ± 0.262

Kidney

Fat

1.356 ± 0.29 3.15 ± 0.37 24.33 ± 5.73 37.90 ± 6.10 95.12 ± 11.56 176.1 ± 14.50 0.369 ± 0.51 2.59 ± 0.72 0.688 ± 0.17 45.27 ± 11.33 2.01 ± 0.66

162.1 ± 7.10

Mitoma et al. (52) fed a series of chlorinated ethanes and ethenes to rats and mice to determine the amount of metabolism. Rats were given the NCI maximum tolerated dose (MTD) in corn oil for 5 d/wk for 4 wk followed by a corresponding radio-labeled dose. In rats 93% was recovered and in mice 95.5%. Their data for hexachloroethane are given in Table 63.3. They concluded the biochemical parameters they measured including protein binding provided no clue to differentiate the carcinogens from the noncarcinogenic compounds. Lattanzie et al. (267), however, concluded that hexachloroethane “bound” to DNA and other macromolecules of the rat and mouse. They reported it less reactive than tetrachloroethane and similar to 1,2-dichloroethane. 8.4.1.4 Reproductive and Developmental Weeks et al. (251) carried out teratological studies in pregnant rats fed by gavage or exposed by inhalation. Oral doses of 50, 100, or 500 mg/kg were fed on days 6 through 16 of gestation. Separate groups were also exposed 6 h/d to 15, 48, or 260 ppm of the vapors. Although body weight gain of the dams in the 500-mg/kg oral and 260-ppm inhalation groups was lower than the controls, there appeared to be no teratological effects on the fetuses. There were adverse effects on gestation indexes and on the number of fetuses alive at the highest oral dose. The fetal reabsorption rate was increased in this group. 8.4.1.5 Carcinogenesis The EPA (IRIS) (2) classifies hexachoroethane as C, possible human carcinogen on the basis of observation of carcinomas in one mouse strain after oral exposure. There are no human carcinogenicity data. The EPA considers the animal carcinogenicity data as “limited.” Technical-grade hexachloroethane (98% pure) was administered by gavage to Osborne–Mendel rats and B6C3F1 mice (50 each male and female) (268). Rats were treated with either 250 or 500 mg hexachloroethane/kg/d, 5 d/wk for 23 wk. After this time animals were rested 1 wk and gavaged for 4 succeeding weeks up to week 78; an observation period of 33–34 wk followed. Final TWA treatment doses were 212 and 432 mg/kg/d. There was no evidence of hexachloroethane-induced neoplastic growth in rats. Mice were administered 500 or 1000 mg/kg/d, 5 d/wk, continuously. At week 9 the doses were increased to 600 and 1200 mg/kg/d, and this dosage was maintained until week 78. Mice were observed for 12–13 wk after cessation of treatment. The TWA doses were 590 and 1179 mg/kg/d. Mice of both sexes showed a significant increase in the incidence of hepatocellular carcinoma. When hexachloroethane was restudied in F344/N rats at doses of 0, 10, or 20 mg/kg/d 5 d/wk to

male rats and 0, 80, or 160 mg/kg doses to female rats, body weight was only slightly depressed toward the end of the 2 yr gavage period (259). Surrival was not affected in any group. The following nonneoplastic and neoplastic effects were reported in the 2 yr studies: Incidences of kidney mineralization (vehicle control, 2/50; low dose, 15/50; high dose, 32/50) and hyperplasia of the pelvic transitional epithelium (0/50; 7/50; 7/50) were increased in dosed male rats. Renal tubule hyperplasia was observed at an increased incidence in high-dose male rats (2/50; 4/50; 11/50). These lesions have been described as characteristic of the hyaline droplet nephropathy that is associated with an accumulation of liver-generated a-globulin in the cytoplasm of tubular epithelial cells. The severity of nephropathy was increased in high-dose male rats (moderate vs. mild), and the incidences and severity of nephropathy were increased in dosed females (22/50; 42/50; 45/50). The incidences of adenomas (1/50; 2/50; 4/50), carcinomas (0./50; 0/50; 3/50), and adenomas or carcinomas (combined) (1/50; 2/50; 7/50) of the renal tubule were also increased in the high-dose male group. One of the carcinomas in the high-dose group metastasized to the lung. No compound-related neoplasms were observed in females. The incidence of pheochromocytomas of the adrenal gland in low-dose male rats was significantly greater than that in vehicle controls (15/50; 28/45; 21/49), and the incidences for both dosed groups were greater than the mean historical control incidence (28– 11%). The relationship of hyalin droplet formation to kidney tumors in the rat has been the subject of several investigations, because the phenomenon appears to be more important in male rats than in female rats or humans. This is particularly important because the mutagenic potency of hexachloroethane appears to be low. 8.4.1.6 Genetic and Related Cellular Effects Studies Hexachloroethane was tested against one yeast strain, Saccharomyces cervisiae, and five strains of Salmonella typhimurium with and without rat liver activation with no evidence of mutagenic effects (263). Hexachloroethane was not mutagenic in S. typhimurium strains TA98, TA100, TA1535, or TA1537 when tested with and without exogenous metabolic activation. In Chinese hamster ovary cells, hexachloroethane did no induce chromosomal aberrations with or without metabolic activation but did produce sister chromatid exchanges in the presence of exogenous metabolic activation (259). 8.4.2 Human Experience Symptoms of exposure to this compound include skin, eye, mucous membrane, and upper respiratory tract irritation. Chronic effects include liver damage and nervous system disturbances. High concentrations can cause narcosis. A report of inhalation exposures to humans describes the effects of a military smoke bomb in a fraternity house (269). However, it is probably not appropriate to ascribe the effects specifically to hexachloroethane because a variety of chemicals would be present in the smoke. Exposure of workmen to the fumes of hot hexachloroethane has been reported to cause blepharospasm, photophobia lacrimation, and reddening of the conjunctiva but no corneal injury and no permanent damage (270, 271). However, the available citation does not give details of the exposure conditions or duration. 8.4.2.2.5 Carcinogenesis There is no human carcinogenicity data. EPA (IRIS) (2) classifies hexachloroethane as C, possible human carccinogen on the basis of observation of carcinomas in one mouse strain after oral exposure. (See animal section on carcinogenesis.) Carcinogenic Classification: IARC Group 3, agent is not classifiable as to its carcinogenicity in humans NIOSH Carcinogoen without further classification NTP Reasonably anticipated to be a human carcinogen (RAHC) ACGIH TLV A3, Confirmed Animal Carcinogen with Unknown Relevance to Humans 8.5 Standards, Regulations, or Guidelines of Exposure The ACGIH TLV for hexachloroethane is 1 ppm with a notation indicating possible skin absorption.

The NIOSH considers hexachloroethane a potential carcinogen and recommends the lowest possible exposure, and an REL of 1 ppm. The OSHA PEL is also 1 ppm. Other countries: Australia: 10 ppm, proposed change 1 ppm (1990); The former Federal Republic of Germany: 1 ppm (1998); United Kingdom: vapor 5 ppm (50 mg/m3), total inhalable dust 10 mg/m3, respirable dust 5 mg/m3 (1987). 8.6 Studies on Environmental Impact None found.

Saturated Halogenated Aliphatic Hydrocarbons Two To Four Carbons Jon B. Reid, Ph.D., DABT 1-Propyl Chloride 9.0.1 CAS Number: [540-54-5] 9.0.2 Synonyms: n-Chloropropane 9.0.3 Trade Names: NA 9.0.4 Molecular Weight: 78.541 9.0.5 Molecular Formula: CH3CH2CH2Cl, C3H7Cl 9.0.6 Molecular Structure:

9.1 Chemical and Physical Properties Physical state Colorless liquid Specific gravity 0.8910 (20/4°C) Melting point –122.8°C Boiling point 46.4°C Vapor pressure 350 torr (25°C) Refractive index 1.38838 (20°C) Percent in “saturated”air 44.5 Solubility 027 g/100 mL water at 20°C; soluble in ethanol, ethyl ether Flammability Flash point 3.2 g/kg ether (Na salt) (202) Eugenol Rat: Mouse: 2680 mg/kg 630 mg/kg (203) (209)b Rat: 1930 mg/kg (204) Mouse: 3000 mg/kg (203) Guinea pig: 2130 mg/kg (203) Isoeugenol Rat: Mouse: 1.56 g/kg 600 mg/kg (205) (209)b Guinea pig: Mouse: 1.41 g/kg 365 mg/kg (205) (205) Mouse: 540 mg/kg (205) Methyl Rat: Mouse: eugenol 1179 mg/kg >640 mg/kg (206) (209)b Mouse:

(99) Rabbit: 170 mg/kg 2.5 g (199) (211) Guinea pig: 0.9 g/kg (199) Rat: 0.9 g/kg (199)

—

—

2 g/human produces chills, temperture drop, collapse, death due to respiratory failure (199) Rabbit: 4.6 g/kg (211) —

—

—

—

—

—

—

—

—

—

—

—

—

—

Mouse: 112 mg/kg (207)

Rabbit: >2025 mg/kg (206)

Methyl isoeugenol

—

Butylated Rat: 4– hydroxyanisole 5 g/kg in corn oil (201, 207, 208) Rat: 2.5 g/kg in propylene glycol (201, 207, 208) Vanillin (212) Rabbit: 3.0 g/kga Rat: 1.58 g/kg Rat: 2.0 g/kg

540 mg/kg (210) Mouse: 640 mg/kg (209)b Mouse: 570 mg/kg (210) —

Rat: 1.16 g/kg

—

Mouse: 181 mg/kg (207)

—

—

—

—

Rat: 1.8 g/kgc Dog: 1.32 g/kg Rat: 1.5 g/kg slow infusion

—

Mouse: 475 mg/kg Mouse: 0.78 g/kg Rat: 2.8 g/kg Guinea pig: Guinea pig: 1.19 g/kg 1.40 g/kg Mouse: Rat: Dog: — Ethyl vanillin Rat: >2000 mg/kg 750 mg/kg 1800 mg/kg 760 mg/kg (213) Rabbit: Guinea pig: 3000 mg/kg 1140 mg/kg Phenyl ether Rat: — — — — d (174) 4.0 g/kg Rat: 2.0 g/kge Rat: 3.99 g/kg Guinea pig: 4.0 g/kgd Guinea pig: 1.0 g/kge Eye Irritation Skin Irritation Sensitization Fish LC50 Phenetole Guaiacol

—

Rabbit: slight — (174) Rabbit: Rabbit: several — exposures Severe, necrosis produced severe (174) Rabbit: irritation, 10% in burning, loss of

—

—

—

—

propylene sensation, glycol—mild dermatitis with (174) vesication (150) Hydroquinone Rabbit: Guinea pig: monomethyl moderate 40% solution in ether corneal olive oil and damage acetone—slight (174) or moderate Hydroquinone — Guinea pig: dimethyl ether 40% solution in olive oil and acetone—slight or moderate Rabbit: slight Methyl Rabbit: eugenol slight (206) (206)

Guinea pig: negative (202)

Guinea pig: — negative (202)

—

—

Rainbow trout: 6 ppm, 96 h (206) Bluegill sunfish: 8.1 ppm, 96 h (206)

a

Minimum lethal dose. Dosed simultaneously with hexobarbital or zoxazolamine. c Lethal dose. d Total mortality. e Total survival. b

Ethers Myron A. Mehlman, Ph.D. G. Hydroquinone Ethers Repeated exposure to these chemicals may result in depigmentation of skin. Excessive skin contact may cause dermatitis. Trapping the dust of hydroquinone ethers with filter devices and their vapors with organic solvents and subsequent analysis by chromatography, spectroscopy, or other method suitable for the detection of the aromatic ring should be adequate for an accurate atmospheric analysis. Physical and chemical properties are presented in Table 72.1. Table 72.16. Toxic Effects of Butylated Monochlorodiphenyl Oxide Mixtures and Related Compounds in Experimental Studies Compound

Species

Butylated Rat monochlorodiphenyl Rat oxide mixture

Test

Results

Acute Exposure Oral LD50 >10 g/kg Inhalation at 25° No observable

Reference

305

C, 50°C Eye irritation

effect Rabbit No observable effect Rabbit Skin irritation No observable effect Rabbit Ear No observable acneigenicity effect Guinea Skin No observable pig sensitization effect Fathead 96-h static LC50 15.4 mg/L minnow Flow-through 1.81 mg/L threshold Daphnia 48-h static LC50 0.24 mg/L magna Rat Pharmacokinetic Radio-labeled profile, gavage compound is 90% absorbed from the gut. The elimination is biphasic and 75% excreted in feces within 3 days. Monobutylated component halflife is 65 hr. Dibutylated component halflife is 71 h. Monkey Pharmacokinetic Radiolabeled profile, gavage compound was 90% recovered. Major route of excretion was urine. Animal was constipated. Monochlorodiphenyl Fathead 96 h static LC50 1.75 mg/L oxide minnow Flow-through 0.090 mg/L threshold Daphnia 48 h static LC50 0.39 mg/L magna Subacute Exposure Butylated Rabbit Skin irritation Very slight effect monochlorodiphenyl Rat Diet feeding At levels of 5 to oxide mixture 90 mg/(kg)(day) for 90 or 156 days, no treatment effect noted for demeanor, hematology, urinalysis, clinical

306

306

307

307 307

Rat

Teratology

Rabbit

Teratology

chemistry, porphyrin excretion, or ophthalmology. Body weight reduction noted. Reversible liver and kidney changes noted at 45 and 90 mg/ (kg)(day). Test material stored in fat. At levels of 5001000 mg/(kg) (day), no teratogenic response was noted. At levels of 1 to 10 mg/(kg)(day), no teratogenic response was noted.

308

308

Table 72.17. Chlorinated Phenyl Ethers Survey of Single-Dose Oral Feeding Studies on Guinea Pigs After 4 Days

Material 1X 2X 3X 4X 5X 6X

After 30 days

Lethal Dose (g/kg)

Survival Dose (g/kg)

Lethal Dose (g/kg)

Survival Dose (g/kg)

0.7 1.3 2.2 3.0 3.4 3.6

0.2 0.4 0.4 0.4 1.8 0.4

0.60 1.00 1.20 0.05 0.10 0.05

0.1 0.05 0.2 0.0005 0.005 0.005

Table 72.18. Chlorinated Phenyl Ethers Results of Repeated Oral Feeding

of Rabbits

Material 1X 2X 3X

4X 5X Pentachlorophenyl ether (highly purified) 6X

Dose, g/kg

No. of Doses

No. of Days

0.1 0.1 0.1 0.05 0.01 0.05 0.005 0.05 0.1

19 19 5 20 20 4 20 8 20

29 29 12 29 29 10 29 21 29

0.01 0.001 0.005 0.001 0.0001

20 20 8 20 20

29 29 10 28 28

Effect None Mild liver injury Death Slight liver injury No effect Death Severe liver injury Death Moderate liver injury; no growth Slight liver injury No effect Death Severe liver injury No effect

Ethers Myron A. Mehlman, Ph.D. H. Cyclic Ethers General Information 38.0 Cellulose Ethers General Physical and Chemical Properties The cellulose ethers—methylcellulose, hydroxypropyl methylcellulose, carboxymethylcellulose sodium salt, ethylcellulose, and hydroxyethylcellulose—are all formed by reacting alkali-cellulose of predetermined average molecular weight with various materials to form the respective ether. Each anhydroglucose unit of the cellulose polymer has three free hydroxyl groups that can be etherified. The degree to which this is effected and the nature of the substituent group influence markedly the physical properties, particularly solubility, of the product. The molecular weight of the alkali-cellulose markedly affects the viscosity of the final product. All the ethers are odorless, tasteless, and very stable chemically (304). Exposure Assessment All the cellulose ethers may be trapped from the air by filtration through a membrane filter. The water-soluble ethers can also be trapped in cold water. Ethylcellulose can be trapped in organic solvents.

The determination of methylcellulose and ethylcellulose can be accomplished in various media for methoxyl and ethoxyl groups. ASTM methods D1347-56 for methylcellulose and D914-50 for ethylcellulose should be consulted. The colorimetric methods of Samsel and DeLap (313) and of Kanzaki and Berger (314) for methylcellulose and of Samsel and Aldrich (315) for ethylcellulose also are very useful. The method of Morgan (316) is generally the basis for determining the hydroxyalkyl ethers of cellulose. It is based on the hydrolysis of the ether with hydriodic acid, which yields the alkyl iodide and the corresponding olefin. Measurement of the olefin formed can be accomplished by absorbing in Wijs solution with subsequent determination of the iodine number (174). Hydroxypropyl methylcellulose may be determined by employing the method of Samsel and McHard (317) to determine the methoxyl content, and the method of Lemieux and Purves (318) as modified (319) for determining hydroxypropyl content. Carboxymethylcellulose can be determined by the anthrone colorimetric method described by Black (320). It can also be estimated by hydrolyzing and determining the resulting glycolic acid by the method of Calkins (321). ASTM method D1439-58T may also be adaptable. Toxic Effects The cellulose ethers are all very low in toxicity when administered by normal routes. They are not irritating to the skin or other delicate membranes of the body. When swallowed, they are not absorbed to any appreciable degree and appear unchanged in the feces. No inhalation studies have been conducted, but exposure of humans to the dust in manufacturing operations over many years has not led to any known adverse effects. Parenteral administration of the water-soluble ethers has led to serious adverse effects in animals and it would seem unwise to administer them by such routes to human subjects (304).

Ethers Myron A. Mehlman, Ph.D. I. Crown Ethers 44.0a 6-Crown-2-Ether 44.0b 12-Crown-4-Ether 44.0c 15-Crown-5-Ether 44.0d 18-Crown-6-Ether 44.0e Dicyclohexyl-18-Crown Ether 44.1 Chemical and Physical Properties 44.2 Production and Use Very little information exists in the literature on the physical and chemical properties of the crown ethers. The name “crown” was first used in 1967 (322) and derives from the stereochemical structure, which for 15-crown-5 may be drawn as follows:

Available chemical and physical properties are presented in Table 72.19. During distillation 18crown-6-ethers may convert to p-dioxane and present an explosion hazard due to clogging of traps (323–325).

Table 72.19. Chemical and Physical Properties of the Crown Ethers CAS Number

Compound

Molecular Formula

6-Crown-2-Ether 12-Crown-24-Ether

[294-93-9]

C8H16O4

15-Crown-25-Ether

[33100-27- C10H20O5 5]

18-Crown-26-Ether

[17455-13- C12H24O6 9]

Dicyclohexyl-18Crown-6

[16069-36- C20H36O6 6]

These compounds may be liquid or solid at room temperature. No satisfactory procedure has been developed for analyzing these materials in the atmosphere (326). 44.4 Toxic Effects 44.4.1 Experimental Studies 44.4.1.1 Acute Toxicity The oral LD50 for the following crown ethers has been determined to be as follows:

Ether

Mice (327) Oral LD50, g/kg

6-Crown- 6.0 2 12-Crown- 3.15 4 15-Crown- 1.02 5 18-Crown- 0.705 6

Time to Death 1 day

1.39

Oral administration of 18-crown-6 to healthy dogs produced transitory signs of tremulous movement and paralysis of the hind limbs 2–12 h after administration (329). Leong (330) reported that a single

oral dose of 12-crown-4 at a level of approximately 100 mg/kg in rats produced central nervous system (CNS) effects and testicular atrophy. The dosages of higher aliphatic crowns, which were capable of producing CNS effects, were 1–10 times higher. This author also reported that skin absorption of 12-crown-4 in rabbits could produce CNS effects, but larger macrocyclic crowns only produced slight skin redness. Pedersen (322) reported the approximate lethal dose of 300 mg/kg for dicyclohexyl-18-crown-6 by ingestion in rats. Death occurred within 11 min. No deaths occurred at 200 mg/kg. Skin absorption in experimental animals was fatal at a dose level of 130 mg/kg for dicyclohexyl-18-crown-6. This material was irritating to the skin and eyes. It was reported that permanent eye damage may result if the eye is not washed with water after exposure. 44.4.1.2 Chronic Toxicity Leong et al. (326) exposed rats to 0.5 and 1.0 ppm of 12-crown-4 vapors 7 h/day, 5 days/week, for 3 weeks. Both levels produced marked testicular atrophy that was associated with degeneration of the germinal epithelium. This effect persisted up to 4 months postexposure. Atrophy of the prostate and seminal vesicles was also noted. Exposure to 1 ppm of 12crown-4 vapors produced prominent degradation of conditioned behavioral performances, depression of food and water intake, retardation of growth, and body tremors. These effects were reversible. 44.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms It is believed that the crown ethers complex with electrolytes, thus changing the permeability of Na+ and K+ across cell membranes (326, 331–334). Investigations thus far indicate the nerve conduction changes are fully reversible. 44.4.1.7 Neurological Gad et al. exposed three species to 18-crown-6 with a repeated dose regimen that involved ever-increasing dose levels in each animal over the exposure time period (328). Rabbits were exposed intravenously 5 days/week at dose levels increasing from 6 mg/kg to 12.5 mg/kg for 3 weeks. Rats were dosed intraperitoneally to ever-increasing dose levels of 20 mg/kg through 80 mg/kg for more than 1 month. Mice were intraperitoneally dosed from 20 mg/kg to 160 mg/kg. Signs of nervous system effects included tremors, hyperactivity, loss of limb strength, muscle twitching, and decreased awareness of light stimuli. Exposure levels were increased in each species because of accommodation to each dose level in a few hours to 3 days. No clinical or histopathological changes were observed. These authors claim to have observed increasing behavior changes, which are completely reversible, with increasing molecular size of crown ethers. 44.5 Standards, Regulations, or Guidelines of Exposure No hygienic standards for occupational exposure have been established for the crown ethers.

Ethers Bibliography

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National Institute of Environmental Health Sciences, Department of Health and Human Services, 2000.

Aldehydes and Acetals Maria T. Morandi, Ph.D., CIH, Silvia Maberti, MS A. Saturated Aliphatic Aldehydes

Aldehydes and Acetals Maria T. Morandi, Ph.D., CIH, Silvia Maberti, MS B. Unsaturated Aliphatic Aldehydes Alpha and beta unsaturated carbonyl compounds (enals) are ubiquitous in the human environment. They are used in the manufacture of chemicals for the production of plastics, pharmaceutical drugs, and cosmetics, and in the rubber industry. They are also formed endogenously, for example, during lipid peroxidation or after oxidative stress. These compounds are highly reactive and are suspected genotoxic mutagens or carcinogens (204, 205). Unsaturated carbonyl compounds are mutagenic toward S. typhimurium in the absence of an activating system (206–208) but not in some strains (209, 210). Table 73.3 shows the effect of unsaturation on the inhalation toxicity of aldehydes. Table 73.3. Effect of Unsaturation on the Inhalation Toxicity of Aldehydes

Compound

Formula

Acetaldehyde

CH3CHO

Ketene

CH2

CHO

LC50 (ppm) in Rats

Time of exposure (min)

20,000

30

130

30

Proionaldehyde CH3CH2CHO Acrolein CH2 CHCHO

26,000

30

130

30

Isobutyraldehyde (CH3)2CHCHO

> 8,000

4h

CH2 C(CH3) CHO n-Butyraldehyde CH3(CH2)2CHO

250

4h

Methacrolein

Crotonaldehyde CH3CH

60,000

CHCHO 1,400

30 30

Table 73.4. Physical and Chemical Properties of Unsaturated Aliphatic Aldehydes

Compound Acrolein Citronellal Crotonaldehyde 2-Ethyl-3propylacrolein

CAS Number Molecular Formula [107-028] [106-230] [417030-3] [2626668-2]

Sol. in Boiling Melting Water Vap Mol. Point Point (° Specific at 68° press Wt. (°C) C) Gravity F (mmh

CH2

CHCHO

56.06

CH3

CHCHO

CH3CH

CHCHO

0.84

4

210

152.23 229.0

0.8898

2

5

70.10 104.0

0.87

19

–49.8 –151.0

Gas

> 76

68.4

0.84

5

136.5

0.8581

1

60.0

0.9152

5

146.5

0.8491

C4H9CH C(CH3) 126.22 CHO Ketene [463-51- CH2 CO 42.02 4] Methacrylaldehyde [78-85- CH2 C(CH3)CHO 70.09 3] Methyl-b[623-36- C6H10O 98.14 9] ethylacrolein Mucochline [87-56- CHOCCl CClCOOH 168.97 9] Propionaldehyde [624-67- CH C CHO 54.05 9] trans-2-Hexenal [6728- C3H7CH CHCHO 98.14 26-3]

52.6

–87.7

125.0

Table 73.5. Toxic Effects of Unsaturated Aliphatic Aldehydes

Chemical Name Ketene

Species

Exposure Route Approximate Dose

Treatment Regimen

Mouse

Inh

23 ppm/30 m

LCLo

Monkey

Inh

200 ppm/10 m

LCLo

Cat

Inh

750 ppm/10 m

LCLo

Ob Conv effect thresh Ptosi pulm Acute edem struct of sal

Acrolein

Rabbit

Inh

53 ppm/2 H

LCLo

Guinea pig

Inh

Man

Inh

153 ppm/10 m

LCLo

Rat

Inh

LC50

Rat

I.p.

18 mg/m3/4 h 4 mg/kg

Rat

Inh

Rat

Inh

Acute edem

LCLo

LD50

Mouse

Oral

13900 mg/kg

Mouse

I.p.

9008 mg/kg

Pre-treatment with RD50 15 ppm HCHO, 6 h/d, 9 d; challenge on the 10th day 6 h/d, 1–3 d Redu glutat transf glutat after expos activi ghuta perox In vitro Inhib reduc LD50 Somn loss o weigh LD50

Mouse

S.c.

30 mg/kg

LD50

Cat

Inh

Rabbit

Inh

Hamster

Inh

LCLo 1570 mg/m3/2 h 4900 ppb/6 h/13 W- TCLo I 4 ppm/7 h/52 W-I TCLo

Human Rabbit Rabbit

Eye Skin Eye

Rat liver

0.25, 0.67, 1.40 ppm

14 mmol/L

500 ppb/12 m 5 mg open 1 mg 10 mM

Human: alveolar macrophages

10 mM

S. typhimurium

50 mg/plate (+S9)

Acute toxicity Acute toxicity Acute toxicity In vitro

Mutation in

Gene fatty degen Chan weigh Chan lung, weigh Sever Sever Inhib tyros phosp Inhib macr cytok and a

E. coli Fibroblasta D. melanogaster

286 nmol/L Oral

5, 10, 20 mmol/L

microorganisms DNA adduct DNA adduct SMART

Nonp induc spots D.melanogaster Parenteral 0.5, 1, 2.5, 5, Sex-linked recessive No ef 10 mmol/L lethal D. melanogasterI.p. 0.5, 1, 2.5, Sex linded recesaive Incre parenteral frequ 5 mmol/L lethal decre 5 mM morta D. melanogaster Sex linked recessive Cell d repair mec. Human 30 mmol/L DNA damage In vitro 1.0, 3.0, 4.5 mM Human pulmonary Monothelial cells Dose alrety endothelial were incubated in an incre cells acrolein-containing dehyd releas solution decre glutat sulfhy no ef oxidi Human fibroblast 100 mmol/L DNA adduct 5 mmol/L Sister chromatid exchange Human:fibroblast 200 nmol/L Gene mutation in mammalian cells Hamster:lung 500 nmol/L Gene mutation in mammalian cells Calf thymus DNA 58 gm/L/3 h DNA adduct E. coli In vitro 150 mM pUC13 plasmid One c labeling/incobation 270 k in media Mammal:lymphocyte 80 mmol/L DNA inhibition Chinese hamster Sister ovary excha S. typhimurium TA100 No ef S. typhimurium TA 100 Stron effect S. typhimurium Ames test, 0.9 mmol Incubation in Muta TA104 serum/food S. typhimurium Ames 0, 3.13, 6.25, 12.5, Plate incorporation Dose Test 25, 50, 100, 200 method with reapo metabolic effect asctivation capab

Methacryladehyde Rat

Skin/eye irritant Oral 140 mg/kg

Rat

Inh

125 ppm/4 h

LCLo

Rabbit

Skin

430 mL/kg

LD50

500 mmol/L(+s9) 500 mmol/L(–S9)

S. typhimurium S. typhimurium 2-Ethyl-3propylacrlein

Crotonaldehyde

LD50

Rat

Inh

8400 ppm/45 m

Ames test, TA104 mutation in microorganisms LCLo

Rat

I.p.

800 mg/kg

LD50

Mouse

Oral

> 3200 mg/kg

LD50

Mouse

I.p.

400 mg/kg

LD50

Dog

Inh

> 1000 ppm/4 h

LCLo

Rabbit

Skin

2520 mL/kg

LD50

Rabbit Guinea pig

Eye Skin

5 mL/24 h > 10 mL/kg

LD50

Rat

Inh

E. coli

In vitro

Human lymphoblast cells

8.5 mM 10, 100, 500 mM

Human lymphocyte Incubation 5–250 mM cells/Namalva cells

Skin/eye irritant

Muta

Ataxi gener orven dyspn Alter musc somn weak Musc ataxia Chan or fun saliva nause Somm convu effect thresh Mode

Pretreatment with RD50 15 ppm HCHO, 6 h/d, 9 d; challenge on the 10th day pUC13 plasmid One c labeling/incubation plasm in media Shuttle vector Dose treated and then incre transgened frequ Incubated in Signi medium, stimulation relate of lymphocytes with SCE phytohemagglutinine micro struct chrom aberr clasto

Methyl-bethylacrolein

trans-2-Hexenal

Rat

Oral

4290 mg/kg

LD50

Rat

Inh

2000 ppm/4 h

LC50

Rabbit

Skin

4500 mL/kg

LD50

Rat

Skin/eye irritant Oral 780 mg/kg

LD50

Rat

I.p.

180 mg/kg

LD50

Mouse

I.p.

100 mg/kg

LD50

Rabbit

Skin

600 mg/kg

LD50

Rabbit Human buccal cells

Skin Oral

500 mg/24 h 10 ppm

Human lymphocyte cells/Namalva cells

Oral

S. typhimurium

Lacri regio arteri dilati struct of sal Lacri regio arteri dilati struct of sal Lacri regio arteri dilati struct of sal

Acute toxicity Mode 4 Mouth rinses/d 3 Incre day; analysis of micro buacal smear muta 5–250 mM Incubated in Signi medium, stimulation relate of lymphocytes with SCE phytohemagglutinine micro aneup induc aneug 2 mM, serum, lipid Ames test, TA104 Muta peroxidation, food

Aldehydes and Acetals Maria T. Morandi, Ph.D., CIH, Silvia Maberti, MS

C. Halogenated and Other Substituted Aldehydes Halogenation tends to increase the local irritating action and general toxicity of the aldehyde. 31.0 Chloroacetaldehyde 31.0.1 CAS Number: [107-20-0] 31.0.2 Synonyms: 2-Chloro-1-ethanal; 2-chloroacetaldehyde; monochloroacetaldehyde; 2chloroethanal; chloroethanal; alpha-chloroacetaldehyde; chloroacetaldehyde, 45% aqueous solution (CAA) 31.0.3 Trade Names: NA 31.0.4 Molecular Weight: 78.50 31.0.5 Molecular Formula: C2H3ClO 31.0.6 Molecular Structure:

31.1 Chemical and Physical Properties See Table 73.6. Table 73.6. Physical and Chemical Properties of Halogenated Aldehydes

Compound Chloral hydrate Chloroacetaldehyde

Sol. in Boiling Melting Water Vapor LelCAS Molecular Mol. Point Point (° Specific (at Pressure Uel Number Formula Wt. (°C) C) Gravity 68°F) (mmHg) (%) [302-17- CCl3CH=O 165.40 98.0 0] H2O

[107-200] Fluoroacetaldehyde [154446-3] Trichloroacetaldehyde [75-876] Trifluoroacetaldehyde [421-534]

ClCH2CHO 78.50

62.0

85.5

–16.3

CCl3CH=O 147.39 97.8

–57.5

1.9081

4 100

FCH3CH=O 62.05

C2–H3– F3O2

1.512

4

35

116.05

31.2 Production and Use Chloroacetaldehyde is used in the manufacture of 2-aminothiazole and other compounds. It is also used to facilitate bark removal from tree trunks and as a fungicide. 31.3 Exposure Assessment 31.3.2 Background Levels Chloroacetaldehyde has been identified as a chlorination by-product in drinking water supplies and is also a metabolite of vinyl chloride (287).

31.3.3 Workplace Methods NIOSH Method 2015 is recomended for determining workplace exposures to chloroacetaldehyde (141). 31.4 Toxic Effects 31.4.1 Experimental Studies 31.4.1.1 Acute Toxicity The LD50, for chloroacetaldehyde in four species via three routes of entry were rat: 23.0 mg/kg oral and 2.0 mg/kg intraperitoneal; mouse: 21.0 mg/kg oral and 2.0 mg/kg intraperitoneal; rabbit: 1.39 mg/kg intraperitoneal and 67.0 mg/kg skin; and guinea pig: 0.636 mg/kg intraperitoneal (288). Chloroacetaldehyde is acutely toxic to mice via inhalation (289). 31.4.1.2 Chronic and Subchronic Toxicity At doses less than the acute LD50, rats that succumbed after 30 days of injections of chloroacetaldehyde exhibited hematological disturbances, but the most obvious effects were bronchitits and pneumonitis (289). 31.4.1.6 Genetic and Related Cellular Effects Studies Chloroacetaldehyde was mutagenic in the S. typhimurium reversion test, the forward mutation system of the Aspergillus nidulans and the forward and backward mutation system of Streptomyces coelicor (288). Chlroacetaldehyde is a potent toxicant and has DNA reactivity (287). It is an effective inhibitor of DNA synthesis, forms interstrand linkage with DNA in vitro, modifies DNA conformation (292), and reacts with nucleotide bases (292a). For additional information on the toxic effects of chloroacetaldehyde, see Table 73.7. Table 73.7. Toxic Effects of Halogenated Aldehydes

Chemical Name Chloroacetaldehyde

Species

Exposure Route

Approximate Dose

Treatment Regimen

Observ Effect

Rat

Oral

89 mg/kg

LD50

Rat

Inh

650 mg/m3/1 h

LC50

Rat

Parenteral

58 mg/kg/12 W-I

TDLo

Rat

I.p.

113 mg/kg/30 D-I

TDLo

Rat Mouse

I.v. Oral

Rabbit

Skin

5 gm/kg DNA inhibition 17 mg/kg/day/104 w TDLo Increase in weight, hepatocellu necrosis, an liver tumor 267 mg/kg LD50

Rabbit

I.p.

5522 ug/kg

LD50

BP elevatio not characteriz autonomic section; respiratory obstruction Lung fibro changes in erythrocyte count, deat Changes in brain and kidney wei

Guinea pig

Inh

S. typhimurium E. coli

400 pm/30 M

LCLo

400 umol/L (+S9)

E. coli B. subtilis B. subtilis S. cerevisiae A. nidulans S. coelicolor S. pombe Salmon; sperm Human; lymphocyte Rat liver cells Salmon:testis In vitro Rat liver cells

Mutation in microorganisms 1 mmol/L (–S9) Mutation in microoganisms 10 mg/plate DNA repair 5 mmol/L (–S9) Mutation in microorganisms 100 mmol/L DNA repair 3100 mmol/L (+S9) Mutation in microorganisms 40 ml/plate (–S9) Mutation in microorganisms 25 ml/plate (–S9) Mutation in microorganisms 6250 mmol/L (+S9), Mutation in 20 mmol/L (–S9) microorganisms 20 mmol/L DNA damage 100 umol/L

DNA damage

47 mmol/L 3 gm 47 mM

DNA adduct Incubation at 37°C for 30 min LC50

Trichloroacetaldehyde Rat

Inh

440 mg/m3/4 h

Rat

Inh

80 mg/m3/4 h/2 W-I TCLo

Dog

Inh

5900 mg/m3/4 h

S. typhimurium S. cerevisiae

Hallucinati distorted perceptions dyspnea

1 mg/plate (+S9), 10 mg/plage (–S9) 1 gm/L (+S9)

LC50

Duplicated percentage IF-DNA Ptosis; somnolenc dyspnea Acute pulmonary edema; cha in adrenal weight, we loss or decreased weight gain Lacrimatio convulsion effect on se threshold, a Mutation in microorgan Mutation in microorgan

S. coloericolor Chloral hydrate

40 mg/plate

Mutation in microorgan

Mouse

Hepatotoxic Oral 15.7 mg/kg day LOAEL Oral 3 g/t (3 W pre-3 W TDLo post) Oral 10 mg/kg TDLo

Mouse

Oral

Mouse

Intratesticular 300 mg/kg

Mouse

Oral

Mouse lymphoma cells

Suspension

Mouse Mouse

0 to 1600 mg/ml

In vitro incubation without metabolic activation

Man/woman Oral

1000/960 mg/kg

TDLo

Child

Oral

219 mg/kg

TDLo

Effects in newborn Hepatic adenoma Hepatocell necrosis, hyperplasia Decreased spermatoge Hepatic DN damage Induced cytotoxicit very weak mutagenic response, weakly clastogenic Pulse rate increased without fal BP Arrythmias

Child

I.v.

39 mg/kg

TDLo

Somnolenc

166 mg/kg day

In vitro Humanlymphocyte

211–1000 mg/L

S. typhimurium S. coloericolor In vitro Rat liver cells

1 mg/plate (+/S9)

Trifluoroacetaldehyde Mouse Mouse

TDLo

Aneuploidy sister-chrom exchanges

Oral/I.p.

mutation in microorganisms 10 mg/plate mutation in microorgaaisms 25, 100, or 250 mM Incubation at No detecta 37°C for effect 30 min 600 mg/kg LD50

I.v.

660 mg/kg

LD50

Change in motor activ

31.5 Standards, Regulations, or Guidelines of Exposure The ACGIH ceiling/STEL for chloroacetaldehyde is 1 ppm. The OSHA PEL and the NIOSH REL are also 1 ppm. 32.0 Trichloroacetaldehyde 32.0.1 CAS Number: [75-87-6]

32.0.2 Synonyms: Chloral; grasex; 2,2,2-trichloroacetaldehyde; trichloroethanal; chloral, anhydrous, inhibited 32.0.3 Trade Names: NA 32.0.4 Molecular Weight: 147.39 32.0.5 Molecular Formula: C2HCl3O 32.0.6 Molecular Structure:

32.1 Chemical and Physical Properties See Table 73.6. 32.4 Toxic Effects For information on the toxic effects of trichloroacetaldehyde, see Table 73.7. 33.0 Chloral Hydrate 33.0.1 CAS Number: [302-17-0] 33.0.2 Synonyms: Trichloroacetaldehyde monohydrate; 1,1,1-trichloro-2,2-ethanediol; nycton; rectules; somnos; nortec; kessodrate; hydral; trichloroacetaldehyde hydrate; bi 3411; sk-chloral hydrate; trawotox; Escre; 2,2,2-trichloro-1,1-ethanediol 33.0.3 Trade Names: Noctec; Aquachloral; Chloraldurat; Dormal; 1,1-Ethanediol, 2,2,2-trichloro(9CI); Felsules; Hydral; Lorinal; Nycoton; Phaldrone; Somni SED; Somnos; Sontec 33.0.4 Molecular Weight: 165.40 33.0.5 Molecular Formula: C2H3Cl3O2 33.0.6 Molecular Structure:

33.1 Chemical and Physical Properties See Table 73.6. 33.2 Production and Use Chloral hydrate is made by adding water to trichloroacetaldehyde. The major use of chloral hydrate is in medicinals. Chloral hydrate is used before some surgeries or procedures to help relieve anxiety and to induce sleep. It is widely used to sedate children undergoing dental and medical procedures and imaging studies (294). Chloral hydrate is available as a suppository, syrup, or capsule. 33.4 Toxic Effects 33.4.1.2 Chronic and Subchronic Toxicity Sanders et al. (295) dissolved chloral in water to form chloral hydrate. Groups of 140 male and 140 female CD-1 mice were maintained on the aqueous solution at concentrations of 0.07 or 0.7 mg/mL as chloral, for 90 days starting at 4 weeks of age; 260 mice/sex received deionized water and served as controls. Low and high TWA dosages based on

measured water intake were reportedly 15.7 and 159.8 mg/kg/day for the males and 18.2 and 173.4 mg/kg/day for females, respectively. Growth, hematology, and serum chemistry parameters, liver enzyme activities and microsomal parameters, organ (liver, lungs, spleen, thymus, kidneys, testes and brain) weights, and gross pathology were evaluated. Significant effects included doserelated increased final body weights in males, increased final body weights in high-dose females, dose-related increased relative liver weights in males, increased serum LDH and SGOT in high-dose males, and increased microsomal cytochrome b5 content and aminopyrine N-demethylase and aniline hydroxylase activities in high- and low- dose males. Therefore, the liver appears to be a target organ for chloral toxicity, and the dose of 15.7 mg/kg/day in males is the LOAEL. Because this was the lowest dose tested, this study does not define a NOAEL or NOEL. Dividing the LOAEL of 15.7 mg/kg/day by an uncertainty factor of 10,000 yields an RfD of 0.002 mg/kg/day, or 0.1 mg/day for a 70-kg person. In female mice, the immune system, particularly the ability to produce IgM antibody to a Tdependent antigen, is the most sensitive indicator (296). In male mice, the liver is the most sensitive organ. Both effects occurred at the lowest concentration tested, 0.07 mg/mL or 15.7 mg/kg (295). The adverse effects on the immune system observed at the 15.7-mg dosage level support the LOAEL used to derive the RfD. Offspring from mice that were exposed throughout pregnancy to 204 mg/kg/day but not 21.3 mg/kg/day chloral in the drinking water had a behavioral impairment (impaired learning retention of a passive avoidance task) (293). Gross malformations or effects on maternal reproductive parameters were not noted. 33.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Some concern regarding the potential carcinogenicity of chloral hydrate is based on the assumption that it is a reactive metabolite of trichloroethylene and is responsible for the carcinogenicity of this compound (295). Nevertheless, it has been proven that the carcinogenicity of trichloroethylene is due to a reactive epoxide metabolite, rather than chloral hydrate (297). 33.4.1.4 Reproductive and Developmental Intratesticular injection of 300 mg/kg chloral hydrate produced decreased spermatogenesis in mice (298). 33.4.1.5 Carcinogenesis Chloral hydrate has not been adequately tested for teratogenicity, reproductive effects, or chronic toxicity. Similarly, no histological evaluations have been conducted. 33.4.1.6 Genetic and Related Cellular Effects Studies Administration of 40 ml/plate of chloral hydrate to S. coloericolor induces mutagenic activity and death in the cell. No effect is noted with a dose of 10 mg/plate of A. nidulans (288). 33.4.2 Human Experience Chloral hydrate acts on the central nervous system to induce sleep. At normal doses, this sleep induction does not affect breathing, blood pressure, or reflexes. When used in combination with analgesics, it can be used to manage pain. 33.4.2.2.1 Acute Toxicity Acute overdoses may cause cardiorespiratory depression (298). On rare occasions excessive or repetitive doses have been associated with cardiac arrythmias (299). Side effects in adults include drowsiness, low body temperature, slurred speech, weakness, difficulty breathing, shortness of breath, nausea, vomiting, confusion, convulsions, and hallucination. 33.4.2.2.3 Pharmacokinetics, Metabolism, and Mechanisms Chloral hydrate is metabolized to trichloroethanol and trichloroacetic acid, both of which are pharmacologically active and may contribute to the acute toxicity of chloral hydrate. The half-life of trichloroethanol ranges from 9 to 40 hours, depending on the age of the subject (300). The younger the patient, the longer the half-life. This induces the accumulation of active metabolites during repetitive doses (300). In fact, toxicity

characterized by respiratory depression and hypotonia associated with a trichloroethanol plasma concentration seven times that associated with sedation in adults was reported in an infant who received multiple doses of chloral hydrate while on mechanical ventilation (294). There is evidence that chloral hydrate and/or trichloroethanol may increase the risk of both direct and indirect hyperbilirubinemia in newborns (301). 34.0 Fluoroacetaldehyde 34.0.1 CAS Number: [1544-46-3] 34.0.2 Synonyms: NA 34.0.3 Trade Names: NA 34.0.4 Molecular Weight: 62.05 34.0.5 Molecular Formula: C2H4FO 34.1 Chemical and Physical Properties See Table 73.6. 35.0 Trifluoroacetaldehyde Monohydrate 35.0.1 CAS Number: [421-53-4] 35.0.2 Synonyms: Trifluoroacetaldehyde monohydrate; trifluoroacetaldehyde hydrate; trifluoroacetaldehyde monohydrate, tech. 35.0.3 Trade Names: NA 35.0.4 Molecular Weight: 116.05 35.0.5 Molecular Formula: C2H3F3O2 35.0.6 Molecular Structure:

35.1 Chemical and Physical Properties See Table 73.6. 35.2 Production and Use Trifluoroacetaldehyde monohydrate is used as an agricultural chemical, a drug and therapeutic agent, a fungicide, bactericide, and wood preservative. 35.5 Standards, Regulations or Guidelines Russia has a STEL of 5 mg/m3 for trifluoroacetaldehyde monohydrate.

Aldehydes and Acetals Maria T. Morandi, Ph.D., CIH, Silvia Maberti, MS D. Aliphatic Dialdehydes A number of dialdehydes have become available commercially and although not all of their properties are completely known, some toxicological data have become available. These materials

have many of the same properties as the monoaldehydes but because of their bifunctionality, may provide different types of useful cross-linking reactions. They tend to polymerize readily and are sometimes available only in an aqueous solution in the presence of polymerization inhibitors. Table 73.8. Physical and Chemical Properties of Aliphatic Dialdehydes

CAS Number

Compound

Glutaraldehyde [111-308] Glutaraldehyde [742089-5] disodium bisulfite 3not Methylglutar- known aldehyde Glyoxal [107-222] Hexa-2,4[142-836] dienal Succinaldehyde [638-379] Succinaldehyde [545096-4] disodium bisulfite Adipaldehyde not known

Molecular Formula O

CH(CH2)3CH

O 100.12 188.0

C5H12O8S2

C4

CHCH

O

58.04 O

CH(CH2)CH H8

5

1.3826

4

17

O)2

CH3(C2H2)2CH O

1.1

264.47

CH3CH(CH2CH O

Sol. in Boiling Melting Water Vapo Mol. Point Point (° Specific (at pressu Wt. (°C) C) Gravity 68°F) (mmH

O8

O

50.4

15.0

96.13 174.0

0.898

86.10 169.0

1.064

1

S2 2Na 294.22

C6H10O2

114.14

Table 73.9. Toxic Effects of Aliphatic Dialdehydes Chemical Name Hexa2,4dienal

Species

Exposure Route

Approximate Dose

Treatment Regimen

Observed Effect

Rat

Oral

300 mg/kg

LD50

Rat

Inh

2000 ppm/4 h

LCLo

Rabbit

Skin

270 mL/kg

LD50

Guinea pig

Skin

2500 mg/kg

LCLo

1 mM, lipid peroxidation

Ames test, TA 104 Mutagenic

480 mg/m3/4 h

LD50

S. typhimurium Glutaralde- Rat

Inh

hyde Rat

I.v.

9800 mg/kg

LD50

Rabbit

Skin

560 mL/kg

LD50

Duck

Oral

820 mg/kg

LD50

Rat

Oral

Rat

Oral

Rat

Inh

Rat

Inh

Rat

Oral

Mouse

Oral

Mouse

Inh

Somnolence, food intake 12376 mg/kg/2Y-C TDLo Changes in urine composition and kidney weight, weig loss or decreased weight gain 11410 mg/kg/7D-I TDLo Weight loss decreased weight gain 5 ppm/6 h/2 W-I TCLo Effects on olfactory system, changes in lung, death 1000 ppb/6 h/13 W- TCLo Weight loss I decreased weight gain 0, 25, 50, Once a day by Dose-related 100 mg/Kg intraperitoneal response of intubation on days maternal 6–15 of pregnancy lethality, no effect below 50 mg/kg, decrease of liver weight and skeleton malfonnation no teratogeni effects 50 gm/kg (6–15 D TDLo Specific preg) development abnormalitie (central nervous syste craniofacial, musculoskel system) 1000 ppb/6 h/13 W- TCLo Effects on I olfactory system, changes in lung, weight loss or decreased

weight gain, death Mouse:lymphocyte

8 mg/L

Hamster:ovary

160 mg/L

Hamster:ovary

110 mg/L

E. coli

In vitro

8 mM

Human

Skin

6 mg/3DI

Human:lymphocyte Rabbit Skin Rabbit Eye

10 mmol/L 13 mg open 1 mg

S. typhimurium

500 nmol/L (+S9)

S. typhimurium

500 nmol/L (+S9)

S. typhimurium

Ames Test

0–1000 mg/plate

E. Coli

Ames Test

0–1000 mg/plate

B. subtilis

Ames Test

1 mg/L

S. typhimurium S. typhimurium S. typhimurium

Preincubation mg/l?? ± S9 Vaporization mg/l?? ± S9 > 0.5 mM

Gene mutation in mammalian cells Cytogenetic analysis Sister chromatid exchange pUC13 plasmid One cross-lin labeling/Incubation per 270 kbp in media DNA Acute toxicity Severe irritation DNA damage Acute toxicity Mild irritatio Acute toxicity Severe irritation Mutation in microorganisms Mutation in microorganisms Plate incorporation Dose-related method without response metabolic mutagenic activation effect, crosslinking capability Plate incorporation Dose-related method without response metabolic mutagenic activation effect, crosslinking capability Incubation with RD50 = 2.4. and without Dose-related metabolic mutagenic stimulation effect on bot strains Mutagenicity Mutagenic Mutagenicity Mutagenic Ames test, TA104 Mutagenic

Aldehydes and Acetals Maria T. Morandi, Ph.D., CIH, Silvia Maberti, MS E. Aromatic and Heterocyclic Aldehydes The chemical and physical properties of a number of the aromatic and heterocyclic aldehydes are summarized in Table 73.10. The toxic effects are summarized in Table 73.11. Additional information about these compounds is provided with the specific chemical. Table 73.10. Physical and Chemical Properties of Aromatic and Heterocyclic Ald

Compound

CAS Number

Molecular Formula

Mol. Wt.

Cinnamaldehyde

[104-55- C6H5 CH CH- 132.16 2] -CH O Furfural [98-01- C5H14O2 96.09 1] m-Nitrobenzaldehyde [99-61- C7H5NO3 151.12 6] p-(Dimethylamino) [100-10- C9H11NO 149.19 7] benzaldehyde p-(n-Propoxy) [5736- C10H12O2 164.20 85-6] benzaldehyde p163.18 [122-85- C9H9NO2 Acetamidobenzaldehyde 0] p-Aminobenzaldehyde [17625- C7H7NO 121.15 83-1] p[123-08- HOC6H4CHO 122.12 Hydroxybenzaldehyde 0] Piperonal [120-57- C8 H6 O3 150.14 0] p-Nitrobenzaldehyde [555-16- C7H5NO3 151.12 8] p-Tolualdehyde 120.15 [104-87- C8H8O 0] Salicyladehyde [90-02- C7H6O2 122.12 8] Benzaldehyde [100-52- C7H6O 106.12 7]

Boiling Melting Point Point (° Specific Sol. in Wa (°C) C) Gravity 68°F 251

–7.5

slight

161.7

–36.5

1.1594 3

164.0

58.5

1.2792 2

176.0

74.5

1.0254 2

154

117.0

1.1294 2

37.0

2

107.0

1.496 2

204.5

1.0194 2

197.0

–7.0

1.1674 2

179

–26

1.045 < 0.01 g/10 19.5°C

Table 73.11. Toxic Effects of Aromatic and Heterocyclic Aldehyde

Chemical Name

Species

Exposure Route

Approximate Dose

Treatment Regimen

p-Nitrobenzaldehyde

Rat

Oral

4700 mg/kg

LD50

Rat

Skin

16 mg/kg

LD50

S. typhimurium B. subtilis

p-Tolualdehyde

Furfural

100 mg/plate (S9+) 500 mg/disv

Rat

Skin/Eye Irritant Oral

Rat

Inh

Rat

So no So no Mu DN

So

1600 mg/kg

LD50 LC

I.p.

> 2200 mg/m3 800 mg/kg

LD50

So

Mouse

Oral

3200 mg/kg

LD50

So

Mouse

I.p.

400 mg/kg

LD50

So

Rabbit Rabbit S. typhimurium

Skin Eye

Rat

Inh

Rat

I.p.

500 mg Acute toxicity M 100 mg Acute toxicity M 1 mM in expired air Ames tast, TA No 104 175 ppm/6 h LC50 W de 20 mg/kg LD50

Rat

S.c.

148 mg/kg

LD50

Mouse

Oral

400 mg/kg

LD50

Dog

Oral

950 mg/kg

LD50

Guinea pig

Oral

541 mg/kg

LD50

Rat

Inh

Rabbit Mouse

Skin Oral

500 mg/m3/4 h/4W- TCLo I 500 mg/24 h Acute toxicity M 90125 mg/kg/2Y-C TDLo Tu (ca RT 5000 ppm Specific locus

D. melanogaster— oral D. melanogaster— oral D. melanogaster— parenteral

5000 ppm

100 ppm

Sex chromosome loss and nondisjunction Sex chromosome loss and

Co on Tu an Co on ata vo He he zo Ch tub

Benzaldehyde

Salicylaldehyde

Human:Hela cell Human:lymphocyte

3 mmol/L 70 mmol/L

Mouse:lymphocyte

200 mg/L

Hamster:lung

1 gm/L

Hamster:ovary

11,700 mg/L

S. typhimurium

1 mM in food, plasma, urine

nondisjunction DNA inhibition Sister chromatid exchange Gene mutation in mammalian cells Cytogenetic analysis Sister chromatid exchange Ames test, TA No 104

Rat

Skin/Eye Irritant Oral

52 gm/kg/13W-I

TDLo

Rat

Inh

500 ppm/6h/14d

TCLo

Rat

S.c

5 mg/kg

LD50

Mouse

Oral

28 mg/kg

LD50

Re

Mouse

I.p.

9 mg/kg

LD50

So

Rabbit Skin Human lymphocyte

500 mg/24 h 1 mmol/L

M

Mouse lymphocytes Mouse lymphocytes Hamster ovary cells

400 mg/L

Acute toxicity Sister chromatid exchange Specific locus

400 mg/L

Fa de in Hy red act na

Mouse

Oral

S. typhimurium S. typhimurium Rat

Preincubation mg/1??+/-S9 Vaporization mg/1??+/-S9 Oral 520 mg/kg

Gene mutation in cells Sister chromatid exchange TDLo To tum Mutagenicity No Mutagenicity No LD50

Rat

Subc

900 mg/kg

LD50

Mouse

Oral

504 mg/kg

LD50

Rabbit

Skin

3 mg/kg

LD50

50 mg/L 154 g/kg/2Y-C

Guinea pig

Skin

20 ml/kg

LD50

Rat

S.c.

400 mg/kg (11D preg)

TDLo

p-Aminobenzaldehyde

Mouse

I.p.

912 mg/kg

LD50

m-Nitrobenzaldehyde

Mouse

I.p.

> 500 mg/kg

LD50

Mouse

I.v.

180 mg/kg

LD50

B. subtilis Rat

Oral

600 mg/plate(+S9), 300 mg/plate(–S9) 5 mg/disc 400 mg/kg

Mouse

Oral

1380 mg/kg

Mutation in microorganisms DNA repair LD50 So co on res LD50

Oral

> 3200 mg/kg

LD50

Rat

I.p.

800 mg/kg

LD50

Mouse

Oral

1600 mg/kg

LD50

Rat

Oral

2700 mg/kg

LD50

Rat

Skin

> 5 mg/kg

LD50

Rat

I.p.

1500 mg/kg

LDLo

Mouse

I.p.

480 mg/kg

LD50

Rat

Oral

2.2 g/kg

LD50

Guinea pig

Oral

1.6 g/kg

LD50

Mouse

I.p.

0.2 g/kg

LD50

Mouse

I.p.

2.3 g/kg

LD50

Rabbit

Skin

0.59 mL/kg

LD50

S. typhimurium

2,4Dihydroxybenzaldehyde

2,5Rat Dimethoxybenzaldehyde

Piperonal

Cinnamaldehyde

S. typhimurium

Po mo cra de ab M car

Mu reg art dil Dy So ex we So ex So we Re De an ap wi Co 4d

I mM in expired air Ames test, TA No 104

A number of these aldehydes occur naturally as components of essential oils or plant products. They are widely used in perfumes and as flavoring agents. There has been a limited number of studies of their toxicity, but a considerable amount of work devoted to studying their metabolic fate was summarized initially by Williams in 1959 (313). Recent information is provided when available for a specific chemical. The metabolism of these aromatic aldehydes follows the pattern established for aromatic acids. In general, the aldehyde grouping in compounds such as benzaldehyde is converted to the acid, probably by liver aldehyde dehydrogenases. This may occur at a relatively slow rate, but it is usually complete. If the aromatic ring contains phenolic groups, as in the case of p-hydroxybenzaldehyde, the compound may be excreted partially as the glucuronide and partially as the free acid or as the conjugated acid. Reduction of the aromatic aldehyde group to an alcohol has not been observed. Benzaldehyde itself is not excreted in any such appreciable amounts as an ester glucuronide, but some substituted aldehydes such as 3,4-dimethoxybenzaldehyde are oxidized to the corresponding acid and excreted as ester glucuronides. Nitrobenzaldehydes are oxidized to nitrobenzoic acids which are either excreted as such or in conjugation with hippuric acid or as acetamidobenzoic acids. p-Dimethylaminobenzaldehyde may undergo partial demethylation. The literature references to the aromatic aldehydes did not give many details of the type of toxic reactions found in the past (314). Dr. Fassett did mention, however, the following observations noted in the course of screening tests: p-Acetamidobenzaldehyde: the only symptoms noted were moderate weakness in rats that received up to 3200 mg/kg orally. pweakness, ataxia, unconsciousness, and tremors were noted in mice Dimethylaminobenzaldehyde: that received up to 1600 mg/kg orally or up to 400 mg/kg intraperitoneally. Repeated intraperitoneal injection in mice at levels of 100 to 200 mg/kg caused weakness and ataxia, but there was no significant reduction of hemoglobin during such treatment. No difference was found between the pure and technical grade samples. p-Nitrobenzaldehyde: in doses of 50 or 400 mg/kg orally in the rat, the symptoms were prostration and cyanosis. 2,4-Dihydroxybenzaldehyde: rats that received 50 to 3200 mg/kg orally showed weakness, tremors, and violent convulsions. 2-Hydroxyl-5the symptoms in mice (either orally or intraperitoneally) were chlorobenzaldehyde: weakness, ataxia, gasping respirations, and unconsciousness. Skin irritation was more marked with this compound than with the corresponding 5-bromo compound. 2-Hydroxy-5oral or intraperitoneal admnistration in mice or rats caused bromobenzaldehyde: weakness, ataxia, and unconsciousness.

Aldehydes and Acetals Maria T. Morandi, Ph.D., CIH, Silvia Maberti, MS F. Acetals Since 1963, when D. W. Fassett provided information about the physical properties and toxicity of acetals, the published literature about their toxicity changed very little. Much of the information

provided in the 2nd edition of Patty's Industrial Hygiene and Toxicology is reprinted here for the use and convenience of the reader (314). Any additional information, such as the CAS number, the molecular structure, synonyms and trade names, etc., is provided as currently available in the information from the previous edition. Acetals or ketals are produced by reactions of aldehydes with alcohols. Their industrial use is increasing, and they may be used as solvents, chemical intermediates, plasticizers, or they may be used to generate aldehydes in the presence of acid. These materials have some of the properties of ethers and are stable under neutral or slightly alkaline conditions but hydrolyze readily in the presence of acids to generate aldehydes (see Table 73.12). This latter reaction makes them capable of hardening natural adhesives, such as glue or casein (333). Table 73.12. Physical and Chemical Properties of Acetals

Compound Acetal Chloroacetal

CAS Molecular Number Formula [105-57- CH3CH 7] (OC2H5)2 [621-62- CH2ClCH 5] (OC2H5)2

Sol. in Boiling Melting Water Vapor LelMol. Point point (° Specific (at Pressure Uel Wt. (°C) C) Gravity 68°F) (mmHg) (%) 118.18 102.2 –100.0 1.3834 152.60 157.0

3

1.026

[871-22- CH3CH 174.28 203.3 –69.1 0.8319 7] (OC4H9)2 Dichloroethylformal [111-91- C5H10Cl2O2 1] Dimethylacetal [534-15- CH3CH 90.12 64.5 –113.2 0.8501 6] (OCH3)2

20

Dibutylacetal

Ethylal Ketoacetal Methylal

[462-95- CH2 104.20 89.0 3] (OC2H5)2 [5436- C8H18N2O2 132.16 21-5] [109-87- CH2(OCH3) 76.10 42.0 5]

–67.0

0.824

3 2

60

–104.8 0.8593

2

The hazards of using acetals in industry are not known with certainty, but a number of them have received a certain amount of experimental study, some of which is summarized in Table 73.13. The physiological properties of the simple unsubstituted acetals are characterized by an etherlike anesthetic action and by a relatively low degree of primary irritation compared to the parent aldehyde. A number of them have been studied for their anesthetic properties, although at present they are not used for this purpose. Bacq and Dallemagne (334–335) and Knoefel (336–338) have investigated methylal, acetal, and a number of other similar materials. The toxicity of methylal has

recently been investigated by Weaver et al. (339). These authors reviewed some of the older literature and pointed out that a number of attempts have been made to use methylal as an anesthetic and that Bacq and Dallemagne (334–335) had investigated this intensively in both dogs and humans. Apparently, anesthesia could be produced in humans, but the onset was slower than with ether and the effect more transitory. Table 73.13. Toxic Effects of Acetals Chemical Name

Exposure Species Route

Methylal

Rat

Inh

15,000 ppm

LC50

482

Rat

I.p.

5 gm/kg

LDLo

483

Rabit Skin Mouse Inh Ethylal

Rabbit Oral

> 16 mL/kg mg/m3/7

35,100 I 2604 mg/kg

LD h/22D- TCLo

Iritis Ataxia

484 485

LD50

486

20 g/kg

LD50

487

3000 ppm/4 h

LC50

Anesthetic

488

Rabbit Skin

500 mg/24 h

Mild

489

Rabbit Oral

3545 mg/kg

Acute toxicity LD50

Rat

900 mg/kg

LD50

Dimethylacetal Rabbit Dermal Rat Acetal

Approximate Dose

Treatment Observed Regimen Effect Reference

Inh

I.p.

486 490

The experiments of Weaver et al. (339) were concerned principally with the effects on guinea pigs and mice of inhaling various concentrations. At extremely high levels, 153,000 ppm, anesthesia occurred in 20 minutes, and death occurred in about 2 hours. At these levels, definite evidence of irritation was noted in the guinea pig, including squinting, lacrimation, sneezing, and nasal discharge. Other pronounced signs of eye and respiratory-tract irritation were also noted at lower levels, and the LC50 in mice for a 7-hour exposure was about 18,000 ppm. Most of the deaths occurred during exposure. Experiments were also carried out with repeated inhalations in the case of mice. A group of fifty mice received fifteen 7-hour exposures at concentrations of approximately 11,000 ppm. Only minor irritation was noted at this level, although lack of coordination appeared after about 3 or 4 hours of exposure. Recovery was usually complete in 1 hour after removal from the chamber. Six deaths occurred in the fifty animals during the 22-day exposure period. Repetition of these experiments at 14,000 ppm showed more evidence of irritation a greater degree of anesthesia. About 30% of the group of mice succumbed during a 17-day exposure. Attempts were made to determine the metabolism of methylal in these animals by testing for formaldehyde and formic acid in vitreous humor and urine. No evidences of these metabolic products were found. However, in view of the rather marked irritation that occurred during inhalation and the necrosis following subcutaneous injections in guinea pigs, it seems possible that hydrolysis to formaldehyde takes place. This is readily metabolized so that it would be difficult to

detect under these conditions. Histopathological studies were made on the guinea pigs and mice exposed by inhalation. Guinea pigs exposed to very high levels and sacrificed 16 to 74 hours after the beginning of exposure showed moderate to severe fatty degeneration of the liver and kidney and extensive bronchopneumonia. Other guinea pigs sacrificed 23 hours after three successive 7-hour exposures showed similar changes in the lungs, liver, and kidneys. However, guinea pigs exposed to five daily 7-hour inhalations at levels of about 45,000 ppm showed no significant changes. Mice that had about 15 seven-hour exposures at levels up to 14,000 ppm showed occasional evidence of pulmonary edema and slight fatty changes in the kidney. No changes were found in the optic nerves or retinas of mice that could be attributed to methylal. Occasionally some corneal blebs were seen, but these could not be attributed with certainty to the methylal exposure. These authors conclude that the threshold for producing toxic effects in guinea pigs and mice is of the order of 11,000 ppm. They extrapolate from this to the conclusion that 1000 ppm might be safe for an 8-hour working day. The present threshold limit is 1000 ppm (27). No studies of workers exposed to such concentrations over long periods of time have been reported, and the validity of this level is uncertain now. Safe handling precautions should include the use of adequate ventilation to be certain that the average concentrations are well below 1000 ppm and avoidance of excessive or prolonged skin contact. Methylal should be handled with due regard for its flammable properties. Ethylal produced only minor symptoms of weakness in the rat; even at high dose levels, no typical anesthesia was noted (37). It is of interest that the halogenated compound, dichloroethyl formal, possesses a high degree of toxicity in the rat orally or in the guinea pig by skin contact. It was also highly potent by inhalation in the rat, giving 100% fatalities at levels as low as 120 ppm. It was only a slight skin or eye irritant in the rabbit (340). It is obvious that this halogenated material should be handled with considerable care. Dimethylacetal in animal experiments is somewhat similar to methylal. The pathological effects have not been reported, however (21, 341). Acetal also has anesthetic properties (342). Knoefel (336) believes that it is probably rapidly hydrolyzed in the stomach. Hydrolysis would give rise to either a hemiacetal or to acetaldehyde and ethyl alcohol. The introduction of a halogen, as in chloroacetal, also greatly increased toxic properties upon oral administration in rats. (Note the similarity to the toxicity increase in the case of dichloroethylformal.) This suggests that the hydrolysis of this compound gives rise to chloracetaldehyde and ethanol (37). The influence of unsaturation on an acetal is indicated by the high degree of intraperitoneal toxicity in the mouse for crotonaldehyde acetal (340). Ketoacetal is interesting in that the presence of the keto group in the beta position to the acetal grouping did not enhance the toxicity (37). Not enough compounds have been studied to predict the effect of unsaturation on aldehyde groups adjacent to acetal groups, but from the fragmentary data available, the same principles would apply as mentioned for aldehydes. In the view of the lack of specific information, it is well to regard substituted acetals as capable of hydrolysis to the component alcohols and aldehydes and to take precautions to avoid excessive skin contact or inhalation. Aldehydes and Acetals

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Acetone David A. Morgott, Ph.D., DABT, CIH

1.0 Acetone 1.0.1 CAS Number: [67-64-1] 1.0.2 Synonyms: 2-Propanone; b-ketopropane; dimethyl ketone; dimethyl formaldehyde; methyl ketone; propanone; pyroacetic acid; pyroacetic ether; allylic alcohol; dimethylketal; ketone propane; and acetone oil 1.0.3 Trade Names: NA 1.0.4 Molecular Weight: 58.08 1.0.5 Molecular Formula: (CH3)2CO 1.0.6 Molecular Structure:

1.1 Chemical and Physical Properties The commercial grade of acetone is generally 99.5% pure and contains less than 0.4% water and 0.1% organic matter (1). Other important chemical and physical properties of the material are listed in Table 74.1 (2–8). Table 74.1. Important Chemical and Physical Properties of Acetone Property

Value

Empirical formula

C3H6O

Freezing point Boiling point Density

–94.7°C 56.2°C at 760 mmHg 0.790 g/cm3 at 20°C

Reference

2 2 1

0.784 g/cm3 at 25°C Vapor pressure

Partition coefficient

Henry's law constant Water solubility Vapor density Flash point

0.780 g/cm3 at 30°C 70 mmHg at 0°C 185 mmHg at 20°C 410 mmHg at 40°C –0.24 (log Koctanol/water)

3

4

–0.50 (log Koil/water)

5

–2.82 (log Kair/water)

6

–2.34 (log Kair/saline)

5

–2.44 (log Kair/blood)

7

2.05 atm Infinite 2.0 (air = 1.0) Cleveland open cup: –9°C Tag closed cup: –17°C Autoignition temperature 465°C

6 1 8 1 8

Flammability

Lower limit: 2.5% (v/v) at 25°C Upper limit: 13.0% (v/v) at 25°C Hazard identification code Health: 1 (slight) Flammability: 3 (high) Reactivity: 0 (stable)

8 8

Acetone Bibliography

Cited Publications 1 J. A. Riddick, W. B. Bunger, and T. K. Sakano, eds., Physical properties and methods of purification. In Organic Solvents, 4th ed., Vol. II, Wiley, New York, 1986, pp. 336–337. 2 S. Sifniades, Acetone. In W. Gerhartz et al., eds., Ullmann's Encyclopedia of Industrial Chemistry, 5th ed., Vol. A1, VCH, Deerfield Beach, FL, 1985, pp. 79–96. 3 W. L. Howard, Acetone. In J. I. Kroschwitz and M. Howe-Grant, eds., Kirk-Othmer Encyclopedia of Chemical Technology, 4th ed., Vol. 1, Wiley, New York, 1991, p. 76. 4 G. G. Cash and R. G. Clements, Comparison of structure-activity relationships derived from two methods for estimating octanol-water partition coefficients. QSAR Environ. Res. 5, 113–124 (1996). 5 P. Poulin and K. Krishnan, Molecular structure-based prediction of the partition coefficients of organic chemicals for physiological pharmacokinetic models. Toxicol. Methods 6, 117– 137 (1996). 6 H.-J. Benkelberg, S. Hamm, and P. Warneck, Henry's law coefficient for aqueous solutions of acetone, acetaldehyde and acetonitrile, and equilibrium constants for the addition compounds of acetone and acetaldehyde with bisulfite. J. Atmos. Chem. 20, 17–34 (1995). 7 E. Wigaeus, S. Holm, and I. Astrand, Exposure to acetone. Uptake and elimination in man. Scand. J. Work Environ. Health 7, 84–94 (1981). 8 National Fire Protection Association (NFPA), Fire hazard properties of flammable liquids, gases, and volatile solids. In Fire Protection Guide on Hazardous Materials, 12th ed., NFPA, Quincy, MA, 1997, pp. 325–310. 9 D. A. Boiston, Acetone oxidation. Br. Chem. Eng. 13, 85–88 (1968). 10 American Industrial Hygiene Association (AIHA), Odor Thresholds for Chemicals with Established Occupational Health Standards, AIHA, Fairfax, VA, 1997, pp. 42–43. 11 F. Patte, M. Etcheto, and P. Laffort, Selected and standardized values of supra-threshold odor intensities for 110 substances. Chem. Senses Flavour 1, 283–305 (1975). 12 M. Devos et al., in Standardized Human Olfactory Thresholds, Oxford University Press, Oxford, UK, 1990, p. 145. 13 J. H. E. Arts et al., An Analysis of Human Response to the Irritancy of Acetone Vapours, TNO Rep. V98.357s, Nutrition and Food Research Institute, 1998. 14 C. J. Wysocki et al., Odor and irritation thresholds for acetone in acetone-exposed factory workers and control (occupationally-nonexposed) subjects. Am. Ind. Hyg. Assoc. J. 58,

704–712 (1997). 15 P. Dalton et al., Perceived odor, irritation and health symptoms following short-term exposure to acetone. Am. J. Ind. Med. 31, 558–569 (1996). 16 P. G. C. Odeigah, Smell acuity for acetone and its relationship to taste ability to phenylthiocarbamide in a Nigerian population. East Afr. Med. J. 71, 462–466 (1994). 17 K. M. Hau and D. W. Connell, Quantitative structure-activity relationships (QSARs) for odor thresholds of volatile organic compounds (VOCs). Indoor Air 8, 23–33 (1998). 18 R. W. Moncrief, Olfactory adaptation and odor intensity. Am. J. Psychol. 70, 1–20 (1957). 19 W. S. Cain, Odor intensity: Differences in the exponent of the psychophysical function. Percept. Psychophys. 6, 349–354 (1969). 20 B. Berglund et al., Individual psychophysical functions for 28 odorants. Percept. Psychophys. 9, 379–384 (1971). 21 M. Chastrette, T. Thomas-Danguin, and E. Rallet, Modeling the human olfactory stimulusresponse function. Chem. Senses 23, 181–196 (1998). 22 S. N. Bizzari, CEH Marketing Research Report Acetone, Chemical Economics Handbook, SRI International, Menlo Park, CA, 1996. 23 O. Wieland, Ketogenesis and its regulation. Adv. Metab. Disord. 3, 1–47 (1968). 24 J. M. Daisey et al., Volatile organic compounds in twelve california office buildings: Classes, concentrations and sources. Atmos. Environ. 28, 3557–3562 (1994). 25 C. W. Lewis and R. B. Zweidinger, Apportionment of residential indoor aerosol VOC and aldehyde species to indoor and outdoor sources, and their source strengths. Atmos. Environ. 26A, 2179–2184 (1992). 26 A. Jonsson, K. A. Persson, and V. Grigoriadis, Measurements of some low molecularweight oxygenated, aromatic, and chlorinated hydrocarbons in ambient air and in vehicle emissions. Environ. Int. 11, 383–392 (1985). 27 D. L. Heavner, W. T. Morgan, and M. W. Ogden, Determination of volatile organic compounds and respirable suspended particulate matter in New Jersey and Pennsylvania homes and workplaces. Environ. Int. 22, 159–183 (1996). 28 M. Dechow, H. Sohn, and J. Steinhanses, Concentrations of selected contaminants in cabin air of airbus aircrafts. Chemosphere 35, 21–31 (1997). 29 O. B. Crofford et al., Acetone in breath and blood. Trans. Am. Clin. Climatol. Assoc. 88, 128–139 (1977). 30 F. H. Jarke, A. Dravnieks, and S. M. Gordon, Organic contaminants in indoor air and their relation to outdoor contaminants. ASHRAE Trans. 87, 153–166 (1981). 31 H. B. Singh et al., Acetone in the atmosphere: Distribution, sources, and sinks. J. Geophys. Res. 99, 1805–1819 (1994). 32 National Library of Medicine (NLM), Toxicology Data Network—TOXNET, NLM, Washington, DC, 1999. Toxic Releases (TRI) Search: http://toxnet.nlm.nih.gov/servlets/simple-search? 33 D. A. Morgott, Acetone. In G. D. Clayton and F. E. Clayton, eds., Patty's Industrial Hygiene and Toxicology, 4th ed., Vol. II, Pt. A, Wiley, New York, 1993, pp. 149–281. 34 R. B. Zweidinger et al., Detailed hydrocarbon and aldehyde mobile source emissions from roadway studies. Environ. Sci. Technol. 22, 956–962 (1988). 35 R. B. Chatfield, E. P. Gardner, and J. G. Calvert, Sources and sinks of acetone in the troposphere: Behavior of reactive hydrocarbons and a stable product. J. Geophys. Res. 92, 4208–4216 (1987). 36 H. B. Singh et al., High concentrations and photochemical fate of oxygenated hydrocarbons in the global troposphere. Nature (London) 378, 50–54 (1995). 37 L. E. Booher and B. Janke, Air emissions from petroleum hydrocarbon fires during

controlled burning. Am. Ind. Hyg. Assoc. J. 58, 359–365 (1997). 38 F. Grimaldi et al., Study of air pollution by carbonyl compounds in automobile exhaust. Pollut. Atmos. 149 68–76 (1996). 39 Y. Hoshika, Y. Nihei, and G. Muto, Pattern display for characterization of trace amounts of odorants discharged from nine odour sources. Analyst (London) 106, 1187–1202 (1981). 40 M. A. K. Khalil and R. A. Rasmussen, Forest hydrocarbon emissions: Relationships between fluxes and ambient concentrations. J. Air Waste Manage. Assoc. 42, 810–813 (1992). 41 J. Brosseau and M. Heitz, Trace gas compound emissions from municipal landfill sanitary sites. Atmos. Environ. 28, 285–293 (1994). 42 D. E. Euler, S. J. Davé, and H. Guo, Effect of cigarette smoking on pentane excretion in alveolar breath. Clin. Chem. (Winston-Salem, N.C.) 42, 303–308 (1996). 43 V. A. Isidorov, I. G. Zenkevich, and B. V. Ioffe, Volatile organic compounds in the atmosphere of forests. Atmos. Environ. 19, 1–8 (1985). 44 B. L. Oser and R. A. Ford, Recent progress in the consideration of flavoring ingredients under the food additives amendment 6. GRAS substances. Food Technol. 27, 64–67 (1973). 45 L. Andersson and K. Lundström, Milk and blood ketone bodies, blood isopropanol and plasma glucose in dairy cows; methodological studies and diurnal variations. Zentralbl. Veterinaer. Med. A. 31, 340–349 (1984). 46 H. A. George et al., Acetone, isopropanol, and butanol production by Clostridium Beijerinckii (Syn. Clostridium Butylicium) and Clostridium Aurantibutyricum. Appl. Environ. Microbiol. 45, 1160–1163 (1983). 47 A.-L. Sunesson et al., Volatile metabolites produced by two fungal species cultivated on building materials. Ann. Occup. Hyg. 40, 397–410 (1966). 48 R. P. Collins and K. Kalnins, Carbonyl compounds produced by cryptomonas ovata Var. Palustris. J. Protozool. 13, 435–437 (1966). 49 M. S. Smith, A. J. Francis, and J. M. Duxbury, Collection and analysis of organic gases from natural ecosystems: Application to poultry manure. Environ. Sci. Technol. 11, 51–55 (1977). 50 J. E. Yocom, G. M. Hein, and H. W. Nelson, A study of the effluents from backyard incinerators. J. Air Pollut. Control Assoc. 6, 84–89 (1956). 51 A. M. Hartstein and D. R. Forshey, Coal Mine Combustion Products. Neoprenes, Polyvinyl Chloride Compositions, Urethane Foam, and Wood, Rep. No. 7977, U.S. Department of the Interior, Washington, DC, 1974. 52 F. Lipari, J. M. Dasch, and W. F. Scruggs, Aldehyde emissions from woodburning fireplaces. Environ. Sci. Technol. 18, 326–330 (1984). 53 D. Grosjean and B. Wright, Carbonyls in urban fog, ice fog, cloudwater and rainwater. Atmos. Environ. 17, 2093–2096 (1983). 54 L. H. Keith et al., Identification of organic compounds in drinking water from thirteen U. S. cities. In Identification and Analysis of Organic Pollutants in Water, 1979, pp. 329–373. 55 K. Mopper and W. L. Stahovec, Sources and sinks of low molecular weight organic carbonyl compounds in seawater. Mar. Chem. 19, 305–321 (1986). 56 R. E. Rathbun et al., Fate of acetone in water. Chemosphere 11, 1097–1114 (1982). 57 H. Meyrahn et al., Quantum yields for the photodissociation of acetone in air and an estimate for the life time of acetone in the lower troposphere. J. Atmos. Chem. 4, 277–291 (1986). 58 F. B. Dewalle and E. S. K. Chian, Detection of trace organic's in well water near a solid waste landfill. J. Am. Water Works Assoc. 73, 206–211 (1981). 59 J. F. Corwin, Volatile oxygen-containing organic compounds in sea water: Determination.

Bull. Mar. Sci. 19, 504–509 (1969). 60 G. V. Sabel and T. P. Clark, Volatile organic compounds as indicators of municipal solid waste leachate contamination. Waste Manage. Res. 2, 119–130 (1984). 61 G. A. Jungclaus, V. Lopez-Avila, and R. A. Hites, Organic compounds in an industrial wastewater: A case study of their environmental impact. Environ. Sci. Technol. 12, 88–96 (1978). 62 D. E. Line et al., Water quality of first flush runoff from 20 industrial sites. Water Environ. Res. 69, 305–310 (1997). 63 V. P. Aneja, Organic compounds in cloud water and their deposition at a remote continental site. J. Air Waste Manage. Assoc. 43, 1239–1244 (1993). 64 P. H. Howard et al., Acetone. In Handbook of Environmental Fate and Exposure Data for Organic Chemicals, 1990, pp. 9–18. 65 K. W. Brown and K. C. Donnelly, An estimation of the risk associated with the organic constituents of hazardous and municipal waste landfill leachates. Hazard. Waste Hazard. Mater. 5, 1–30 (1988). 66 T. M. Holsen et al., Contamination of potable water by permeation of plastic pipe. J. Am Water Works Assoc. 83, 53–56 (1991). 67 L. W. Whitehead et al., Solvent vapor exposures in booth spray painting and spray glueing, and associated operations. Am. Ind. Hyg. Assoc. 45, 767–772 (1984). 68 C. Winder and P. J. Turner, Solvent exposure and related work practices amongst apprentice spray painters in automotive body repair workshops. Ann. Occup. Hyg. 36, 385– 394 (1993). 69 B. Young et al., Vapors from colloidon and acetone in an EEG laboratory. J. Clin. Neurophysiol. 10, 108–110 (1993). 70 M. Nasterlack, G. Triebig, and O. Stelzer, Hepatotoxic effects of solvent exposure around permissible limits and alcohol consumption in printers over a 4-year period. Int. Arch. Occup. Environ. Health 66, 161–165 (1994). 71 I. Ahonen and R. W. Schimberg, 2,5-Hexanedione excretion after occupational exposure to n-Hexane. Br. J. Ind. Med. 45, 133–136 (1988). 72 N. A. Nelson et al., Historical characterization of exposure to mixed solvents for an epidemiologic study of automotive assembly plant workers. Appl. Occup. Environ. Hyg. 8, 693–702 (1993). 73 M. F. Hallock et al., Assessment of task and peak exposures to solvents in the microelectronics fabrication industry. Appl. Occup. Environ. Hyg. 8, 945–954 (1993). 74 E. Mitran et al., Neurotoxicity associated with occupational exposure to acetone, methyl ethyl ketone, and cyclohexanone. Environ. Res. 73, 181–188 (1997). 75 M. Schultz, J. Cisek, and R. Wabeke, Simulated exposure of hospital emergency personnel to solvent vapors and respirable dust during decontamination of chemically exposed patients. Ann. Emerg. Med. 26, 324–329 (1995). 76 E. De Rosa et al., The importance of sampling time and co-exposure to acetone in the biological monitoring of styrene-exposed workers. Appl. Occup. Environ. Hyg. 11, 471–475 (1996). 77 G. Franco et al., Serum bile acid concentrations as a liver function test in workers occupationally exposed to organic solvents. Int. Arch. Occup. Environ. Health 58, 157–164 (1986). 78 A. A. Jensen et al., Occupational exposures to styrene in Denmark 1955–88. Am. J. Ind. Med. 17, 593–606 (1990). 79 T. Satoh et al., Relationship between acetone exposure concentration and health effects in acetate fiber plant workers. Int. Arch. Occup. Environ. Health 68, 147–153 (1996). 79a NIOSH. Manual of Analytical Methods, 4th ed., U.S. Govt Printing Office, Supt. of Docs,

Washington, DC, 1994. 80 T. M. Sack et al., A survey of household products for volatile organic compounds. Atmos. Environ. 26A, 1063–1070 (1992). 81 A. Brega et al., High-performance liquid chromatographic determination of acetone in blood and urine in the clinical diagnostic laboratory. J. Chromatogr. 553, 249–254 (1991). 82 M. D. Trotter, M. J. Sulway, and E. Trotter, The rapid determination of acetone in breath and plasma. Clin. Chim. Acta 35, 137–143 (1971). 83 M. Kimura et al., Head-space gas-chromatographic determination of 3-hydroxybutyrate in plasma after enzymic reactions, and the relationship among the three ketone bodies. Clin. Chem. (Winstan Salem N.C.) 31, 596–598 (1985). 84 S. Levey et al., Studies of metabolic products in expired air. II. Acetone. J. Lab. Clin. Med. 63, 574–584 (1964). 85 V. C. Gavino et al., Determination of the concentration and specific activity of acetone in biological fluids. Anal. Biochem. 152, 256–261 (1986). 86 S. Felby and E. Nielsen, Congener production in blood samples during preparation and storage. Blutalkohol 32, 50–58 (1995). 87 F. Brugnone et al., Blood and urine concentrations of chemical pollutants in the general population. Med. Lav. 85, 370–389 (1994). 88 T. J. Buckley et al., Environmental and biomarker measurements in nine homes in the Lower Rio Grande Valley: Multimedia results for pesticides, metals, PAHs, and VOCs. Environ. Int. 23, 705–732 (1997). 89 D. L. Ashley et al., Blood concentrations of volatile organic compounds in a nonoccupationally exposed US population and in groups with suspected exposure. Clin. Chem. (Winston Salem, N.C.) 40, 1401–1404 (1994). 90 A. W. Jones et al., Concentrations of acetone in venous blood samples from drunk drivers, type-I diabetic outpatients, and healthy blood donors. J. Appl. Toxicol. 17, 182–185 (1993). 91 G. Wang et al., Blood acetone concentration in “normal people” and in exposed workers 16 h after the end of the workshift. Int. Arch. Occup. Environ. Health 65, 285–289 (1994). 92 G. Pezzagno et al., Urinary concentration, environmental concentration, and respiratory uptake of some solvents: Effect of the work load. Am. Ind. Hyg. Assoc. J 49, 546–552 (1988). 93 A. W. Jones, Breath acetone concentrations in fasting male volunteers: Further studies and effect of alcohol administration. J. Anal. Toxicol. 12, 75–79 (1988). 94 B. O. Jansson and B. T. Larsson, Analysis of organic compounds in human breath by gas chromatography-mass spectrometry. J. Lab. Clin. Med. 74, 961–966 (1969). 95 C. N. Tassopoulos, D. Barnett, and T. R. Fraser, Breath-acetone and blood-sugar measurements in diabetes. Lancet 2, 1282–1286 (1969). 96 G. Rooth and S. Östenson, Acetone in alveolar air, and the control of diabetes. Lancet 2, 1102–1105 (1966). 97 R. D. Stewart and E. A. Boettner, Expired-air acetone in diabetes mellitus. N. Engl. J. Med. 270, 1035–1038 (1964). 98 J. E. Smialek and B. Levine, Diabetes and decomposition. A case of diabetic ketoacidosis with advanced postmortem change. Am. J. Forensic Med. Pathol. 19, 98–101 (1998). 99 B. J. Dowty, J. L. Laseter, and J. Storer, The transplacental migration and accumulation in blood of volatile organic compounds. Pediatr./Res. 10, 696–701 (1976). 100 M. J. Sulway et al., Acetone in uncontrolled diabetes. Postgrad. Med. J. 47, 383–387 (1971). 101 A. Zlatkis et al., Profile of volatile metabolites in urine by gas chromatography mass chromatography. Anal. Chem. 45, 763–767 (1973).

102 E. D. Pellizzari et al., Purgeable organic compounds in mother's milk. Bull. Environ. Contam. Toxicol. 28, 322–328 (1982). 103 H. Göschke and T. Lauffenburger, Aceton in der Atemluft und Ketone im Venenblut bei Vollständigem Fasten Normal und Übergewichtiger Personen. Res. Exp. Med. 165, 233–244 (1975). 104 K. E. Wildenhoff, Diurnal variations in the concentrations of blood acetoacetate, 3hydroxybutyrate and glucose in normal persons. Acta Med. Scand. 191, 303–306 (1972). 105 E. M. P. Widmark, The kinetics of the ketonic decomposition of acetoacetic acid. Acta Med. Scand. 53, 393–421 (1920). 106 C. Grampella et al., Health surveillance in workers exposed to acetone. Proc. 7th Int. Symp. Occup. Health Prod. of Arti. Org. Fibres, 1987, pp. 137–141. 107 D. Dyne, J. Cocker, and H. K. Wilson, A novel device for capturing breath samples for solvent analysis. Sci. Total Environ. 199, 83–89 (1997). 108 S. K. Kundu and A. M. Judilla, Novel solid-phase assay of ketone bodies in urine. Clin. Chem. (Winston-Salem, N.C.) 37, 1565–1569 (1991). 109 J. Schuberth, A full evaporation headspace technique with capillary GC and ITD: A means for quantitating volatile organic compounds in biological samples. J. Chromatogr. Sci. 34, 314–319 (1996). 110 S. C. Connor et al., Antidiabetic efficacy of BRL 49653, a potent orally active insulin sensitizing agent, assessed in the C57BL/KsJ db/db diabetic mouse by non-invasive 1H NMR Studies of Urine. J. Pharm. Pharmacol. 49, 336–344 (1997). 111 O. E. Owen et al., Acetone metabolism during diabetic ketoacidosis. Diabetes 31, 242–248 (1982). 112 H. Crato, G. Walther, and A. Hermann, Das Vorkommen Von Aceton in Zur AlkoholBestimmung Eingesandten Blutproben. Beitr. Gerichtl. Med. 36, 275–279 (1978). 113 M. Kupari et al., Breath acetone in congestive heart failure. Am. J. Cardiol. 76, 1076–1078 (1995). 114 F. Brugnone et al., Isopropanol exposure: Environmental and biological monitoring in a printing works. Br. J. Ind. Med. 40, 160–168 (1983). 115 G. Pezzagno et al., Urinary elimination of acetone in experimental and occupational exposure. Scand. J. Work Environ. Health, 12, 603–608 (1986). 116 T. Kawai et al., Urinary excretion of unmetabolized acetone as an indicator of occupational exposure to acetone. Int. Arch. Occup. Environ. Health 62, 165–169 (1990). 117 T. Kawai et al., Curvilinear relationship between acetone in breathing zone air and acetone in urine among workers exposed to acetone vapor. Toxicol. Lett. 62, 85–91 (1992). 118 A. Fujino et al., Biological monitoring of workers exposed to acetone in acetate fibre plants. Br. J. Ind. Med. 49, 654–657 (1992). 119 T. Satoh et al., Acetone excretion into urine of workers exposed to acetone in acetate fiber plants. Int. Arch. Occup. Environ. Health 67, 131–134 (1995). 120 R. R. Vangala et al., Biomonitoring of human experimental exposures to acetone and ethyl acetate. In N. V. C. Swamy and M. Singh, eds., Physiological Fluid Dynamics III, Nora Publishing House, New Delhi, India, 1992, pp. 354–359. 121 R. D. Stewart et al., Acetone: Development of a biologic standard for the industrial worker by breath analysis. U.S. C.F.S.T.I., PB Rep. PB82-172917 (1975). 122 F. Brugnone et al., Solvent exposure in a shoe upper factory. I. n-hexane and acetone concentration in alveolar and environmental air and in blood. Int. Arch. Occup. Environ. Health 42, 51–62 (1978). 123 F. Brugnone et al., Biomonitoring of industrial solvent exposures in workers' alveolar air. Int. Arch. Occup. Environ. Health 47, 245–261 (1980).

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Ketones of Four Or Five Carbons David A. Morgott, Ph.D., DABT, CIH, Douglas C. Topping, Ph.D., DABT, John L. O'Donoghue, VMD, Ph.D., DABT Introduction A ketone is an organic compound containing a carbonyl group (C and can be represented by the general formula

O) attached to two carbon atoms

Several billion pounds of ketones are produced annually for industrial use in the United States. Those with the highest production volumes include acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, 4-hydroxy-4-methyl-2-pentanone, isophorone, mesityl oxide, and acetophenone. Common methods used to manufacture ketones include aliphatic hydrocarbon oxidation, alcohol dehydration with subsequent oxidation, dehydrogenation of phenol, alkyl aromatic hydrocarbon oxidation, and condensation reactions. Ketones are used because of their ease of production, low manufacturing cost, excellent solvent properties, and desirable physical properties such as low viscosity, moderate vapor pressure, low to moderate boiling points, high evaporation rates, and a wide range of miscibility with other liquids. The low-molecular-weight aliphatic ketones are miscible with water and organic solvents, whereas the high-molecular-weight aliphatic and aromatic ketones are generally immiscible with water. Most ketones are chemically stable. The exceptions are mesityl oxide, which can form peroxides, and methyl isopropenyl ketone, which polymerizes. Most ketones are generally of low flammability. Ketones are commonly used in industry as solvents, extractants, chemical intermediates, and to a lesser extent, flavor and fragrance ingredients. Ketones have also been reported in the ambient air, in wastewater treatment plants (1), and in oil field brine discharges (2).

Ketones of Four Or Five Carbons David A. Morgott, Ph.D., DABT, CIH, Douglas C. Topping, Ph.D., DABT, John L. O'Donoghue, VMD, Ph.D., DABT Occupational Exposures In an occupational setting, the primary routes of exposure to ketones are inhalation and skin contact. Ingestion is rare. Since most ketones have a significant vapor pressure at room temperature, exposure by inhalation in the workplace is likely to occur. The principal hazard associated with exposure to ketone vapors is irritation of the eyes, nose, and throat. Many ketones have excellent warning properties and can be easily detected by their odor. Accidental overexposure should be relatively rare provided warning properties are not ignored and olfactory fatigue does not occur. The classic symptoms produced by an overexposure to ketones include, progressively, irritation of the eyes, nose, and throat, headache, nausea, vertigo, uncoordination, central nervous system depression, narcosis, and cardiorespiratory failure. Recovery is usually rapid and without residual toxic effects. In the case of accidental spills, personnel should wear protective clothing including respiratory protection. Contaminated clothing should be removed promptly, and the exposed areas of the body should be thoroughly flushed with water. Many ketones are absorbed through the skin; therefore,

caution should be exercised to avoid repeated or prolonged skin contact. The vapors produced by accidental spills may present a fire or explosion hazard.

Ketones of Four Or Five Carbons David A. Morgott, Ph.D., DABT, CIH, Douglas C. Topping, Ph.D., DABT, John L. O'Donoghue, VMD, Ph.D., DABT Toxic Effects Although the relative toxicity of most ketones is low and the effects of acute exposures are well recognized, the effects of chronic exposure have received less study. In some cases, metabolic studies have helped to elucidate the toxic effects of several ketones. Generally, when ketones are absorbed into the bloodstream, they may be eliminated unchanged in the expired air, or metabolized by a variety of metabolic pathways to secondary alcohols, hydroxyketones, diketones, and carbon dioxide. Recent studies indicate that carbonyl reduction, a and –l oxidation, decarboxylation, and transamination play important roles in the metabolism of aliphatic ketones. Aromatic ketones and ketones such as cyclohexanone and isophorone may undergo oxidative metabolism by dehydrogenation, ring hydroxylation, or substituent group oxidation. In addition, aromatic and aliphatic ketones may be conjugated with glucuronic acid, sulfuric acid, or glutathione prior to excretion in the urine. Glucuronic and sulfuric acid conjugation usually occur after a ketone is reduced to a secondary alcohol or oxidized to a carboxylic acid. Of the various conjugation mechanisms that occur, glucuronic acid conjugation appears to be the predominant pathway. Ketone exposure may alter the toxicity of other chemicals, including other ketones that are metabolized by cytochrome P450 enzymes. Under certain circumstances non-neurotoxic ketones may potentiate the neurotoxicity of other ketones or organophosphates or the hepatotoxicity and renal toxicity of haloalkanes. Data on these interactions are referred to in sections on specific ketyones in Chapters 74, 75, and 76. Table 75.1. Physical–Chemical Properties

M Refractive Vapor Vapour Va

Boiling Melting

Compound

Molecular Mol. Formula Wt.

Co Point Point (° Specific Index (20° Pressure Density (p (°C) C) Gravityab C) (mmHg) (Air = 1) 20

Acetone

C3H6O

58.08

56.2

–95.4

0.791

1.3588

180

2.0

23

Methyl ethyl C4H8O ketone 3-Butyn-2-one C4H4O

72.11

79.6

–86.6

1.3788

77.5 (20)

2.4

102

68.08

85.0

—

0.807 (20/4) 0.879

1.4024

40.0

Methyl n-propyl C5H10O ketone Methyl

86.17

102.2

–76.9

1.3895

16.0

3.0

21

86.14

93.0

–92.0

0.809 (20/4) 0.803

1.3879

isopropyl C5H10O ketone 3-Pentyn-2-one C5H6O Methyl C5H8O isopropenyl ketone 2,4-Pentanedione C5H8O2

(20/0)

52

82.10

133.0

–28.7

0.910

1.141

84.12

97.7

–53.7

0.855

1.4220

42.0

100.12 138.3

–23.2

0.976

1.4494

7.0

d

S = readily soluble, Sl = slightly soluble, I = insoluble. At 25°C, 760 mmHg. a Specific gravity is at 20/20°C unless otherwise noted. b Vapor pressure is at 25°C unless otherwise noted. c Closed cup unless otherwise noted, [O.C.] open cup. Figures in parentheses are °C. e

Table 75.2. Comparison of the MEK Concentrations Found in Different Environmental Samples Airborne Concentration

Sample Type Composting effluent Poultry manure dryers Inside home Indoor air Summer indoor air Summer outdoor air Outside ambient air Urban air City air Inside office area Ventilation return air Inside machine shop Outside furniture factory Outside paint incinerator Automobile exhaust Oil fire Chemical waste site Factory exhaust gas Outside laboratory oven Municipal land fill gas

(mg/m3)

(ppb)

7800 8–260 0–19 4.1–14.3 1.4–6.9 0.8–2.7 0–3 1.9–8.5 0.2–58 2.4 5.7–40.9 1.2 0.7–1.2 0.9 90 10–170 1.5–33.0 20–680 1800 3092–5200

Reference 27 28 29 30 31 31 29 32 33 33 34 33 33 33 35 36 37 38 39 40

54 3.5

4,

Table 75.3. Toxicologic Properties of Ketones

Compound Acetone Methyl ethyl ketone 3-Butyn-2-one Methyl n-propyl ketone Methyl isopropyl ketone 3-Pentyn-2-one Methyl isopropenyl ketone 2,4-Pentanedione

Approximate Oral Rat LD50 (mL/kg)

Lowest Reported Lethal Air Conc. Rat (ppm/h)

8–11 3–7

16,000/4 2,000/4

Sl Sl

M Sl

0.01 3.7

10/4 30,000/1

SV Sl

SV M

4–7

5,700/4

Sl

Sl

0.1 0.2

Sat'd./0.1 125/4

SV M

SV M

1

1,000/4

Sl

M

Skin Ocular a Irritation Injurya

a

Sl, slight; M, moderate; SV, severe; skin irritation and ocular injury ratings are for direct application of liquids.

Table 75.4. Hygienic Standards for Ketones

a

d

ACGIH TLV OSHA PEL

NIOSH RELe DFG MAKf

Compound Methyl ethyl ketone 3-Butyn-2-one Methyl n-propyl ketone Methyl isopropyl ketone 3-Pentyn-2-one Methyl isopropenyl ketone 2,4-Pentanedione

TWAb STELc TWA STEL TWA STEL

TWA

200 — 200

300 — 250

200 — 200

— — —

200 — 150

300 — —

200 — 200

200

—

—

—

200

—

—

— —

— —

— —

— —

— —

— —

— —

—

—

—

—

—

—

—

a

American Conference of Governmental Industrial Hygienists threshold limit values. Occupational Safety and Health Administration permissible exposure limits. e U.S. National Institute for Occupational Safety and Health recommended exposure limit. f Deutsche Forschungsgemeinschaft (Federal Republic of Germany) maximum concentration values in the workplace. b Time-wighted average (ppm). c Short-term exposure limit (ppm). d

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Ketones of Six To Thirteen Carbons Douglas C. Topping, Ph.D., DABT, David A. Morgott, Ph.D., DABT, CIH, John L. O'Donoghue, VMD, Ph.D., DABT Introduction Ketones of carbon number 6–13 are important commercial and industrial materials. Their primary use is as solvents that find use in numerous products and industrial applications. Due to their volatility, environmental regulations have been directed at restricting emissions, particularly to the atmosphere. A number of the ketones discussed in this chapter can undergo photochemical transformations that contribute to their abiotic degradation but may also contribute to the formation of smog. Regulations limiting or prohibiting release of materials that may contribute to smog formation are leading to reductions in the use of some of these materials.

Ketones of Six To Thirteen Carbons Douglas C. Topping, Ph.D., DABT, David A. Morgott, Ph.D., DABT, CIH, John L. O'Donoghue, VMD, Ph.D., DABT Occupational Exposures As for the short-chain ketones discussed in Chapter 75, the ketones covered in this chapter are mainly of concern due to inhalation and dermal exposure routes. Acute exposure to high vapor concentrations of these materials may result in narcosis; however, such exposures are rare except in cases of accidents. Low levels of exposure to many of these ketones can be expected in the environment and through endogenous exposure because ketones are common substrates for many of the enzymes associated with intermediary metabolism in organisms from bacteria to man.

Ketones of Six To Thirteen Carbons Douglas C. Topping, Ph.D., DABT, David A. Morgott, Ph.D., DABT, CIH, John L.

O'Donoghue, VMD, Ph.D., DABT Toxic Effects Acute exposures to ketone vapors may result in irritation to the eyes and throat. Repeated dermal exposures may result in defatting of the skin, resulting in dryness, cracking, peeling, and inflammation of the epidermis. The more serious effect of exposure to some of the ketones covered in this chapter is peripheral neuropathy, which has been reported to occur in occupational environments. Other effects including hematologic effects and altered activity levels of various enzyme systems have been reported in experimental animal systems but not in human clinical cases.

Ketones of Six To Thirteen Carbons Douglas C. Topping, Ph.D., DABT, David A. Morgott, Ph.D., DABT, CIH, John L. O'Donoghue, VMD, Ph.D., DABT Structure–Activity Relationships Alkanes, primary and secondary alcohols, carboxylic acids, glycols, diketones, epoxides, hydroxy acids, and ketones are metabolically related in many biologic systems. Thus a knowledge of the structure–activity relationships of these various compounds adds to our understanding of their individual and/or combined toxicities. Much of our present knowledge about the structure–activity relationships of ketones has been developed in response to an occupationally related outbreak of neurotoxicity. Since this incident, the emphasis on ketone toxicity has been directed primarily toward neurotoxicity. It must be realized, however, that these same ketones produce effects other than neurotoxicity. Table 76.1 lists ketones and related compounds that have been examined for neurotoxicity (1–18). Those indicated as positive are substances that showed a specific anatomic and morphologic types of nerve degeneration characterized by large multifocal axonal swellings, often referred to as “giant axonal” neuropathy. These swellings are filled with masses of disorganized neurofilaments and other organelles. Myelin damage also occurs but is generally considered to be a secondary effect. Clinical symptomatology in man includes bilaterally symmetrical paresthesia, best described as a “pins and needles” feeling, and muscle weakness, primarily in the legs and arms. Table 76.1. Neurotoxicity of Ketones and Related Substances Chemical

Structure

Neurotoxicitya Ref.

Six-Carbon Structures n-Hexane

CH3(CH2)4CH3

+

1

Practical-grade hexanes 1-Hexanol

Mixed hexanes

+

1

HOCH2(CH2)4CH3

–

1, 2

2-Hexanol

CH3CHOH(CH2)3CH3

+

1, 2

6-Amino-1hexanol

HOCH2(CH2)5NH2

–

3

Methyl n-butyl ketone Methyl isobutyl ketone 2,5-Hexanediol 1,6-Hexanediol

CH3CO(CH2)3CH3

+

CH3COCH2CH(CH3)2

–

CH3CHOH(CH2)2CHOHCH3

+

1, 3– 7 3, 6, 7 1, 8

HOCH2(CH2)4CH2OH

–

8

5-Hydroxy-2CH3CO(CH2)2CHOHCH3 hexanone 2,3-Hexanedione CH3COCO(CH2)2CH3

+

1

–

2,4-Hexanedione CH3COCH2COCH2CH3

–

2,5-Hexanedione CH3CO(CH2)2COCH3

+

3, 8, 9 3, 8, 9 1, 3, 8–10

Seven-Carbon Structures n-Heptane

CH3(CH2)5CH3

–

3

–

11

Methyl n-amyl CH3CO(CH2)4CH3 ketone Methyl isoamyl CH3CO(CH2)2CH(CH3)2 ketone Ethyl n-butyl CH3CH2CO(CH2)3CH3 b ketone Di-n-propyl CH3(CH2)2CO(CH2)2CH3 ketone 2,5-Heptanedione CH3CO(CH2)2COCH2CH3

–

3

+

3

–

3

+

3, 9

2,6-Heptanedione CH3CO(CH2)3COCH3

–

3, 9

3,5-Heptanedione CH3CH2COCH2COCH2CH3

–

8

3-Methyl-2,5hexanedione

+

12

3,6-Octanedione CH3CH2CO(CH2)2COCH2CH3 5-Methyl-3CH3CH2COCH2CHCH3CH2CH3 heptanone 3-Acetyl-2,5CH3COC(CH3CO)CH2COCH3 hexanedione 3,4-DimethylCH3COCHCH3CHCH3COCH3 2,5-hexanedione 3,3-DimethylCH3COC(CH3)2CH2COCH3 2,5-hexanedione Nine-Carbon Structures

+

3, 9

+

13

–

14

+ –

14– 17 15

5-Nonanone

CH3(CH2)3CO(CH2)3CH3

+

3

5-Methyl-2-

CH3CO(CH2)2CHCH3(CH2)2CH3

c

3

CH3COCHCH3CH2COCH3 Eight-Carbon Structures

octanone Diisobutyl ketone (CH3)2CHCH2COCH2CH(CH3)2

–

3

3,4-Diethyl-2,5- CH3COCH(CH3CH2)CH(CH3CH2)hexanedione COCH Eleven-Carbon Structures

–

16

Diisoamyl ketone (CH3)2CH(CH2)2CO(CH2)2CH(CH3)2

–

3

–

18

Ten-Carbon Structure

Twelve-Carbon Structure 3,4-Diisopropyl- CH3COCH(CH3CH3CH2)CH2,5-hexanedione (CH CH CH )COCH 3 3 2 3 a

– Indicates that the material was tested experimentally and found not to be neurotoxic; + indicates the material may produce giant axonal neuropathy. b Ethyl n-butyl ketone is metabolized to 2,5-heptanedione, which is neurotoxic. c Commercial samples of 5-methyl-2-octanone may contain 5-nonanone, which is neurotoxic. 5-Methyl-2-octanone enhances 5-nonanone neurotoxicity.

The metabolic interrelationships of some of these neurotoxins are shown in Figure 76.1. Initially, studies of n-hexane and methyl n-butyl ketone neurotoxicity revealed that the g-diketone 2,5hexanedione was a neurotoxin. Subsequently, a series of diketones were examined for their ability to produce “giant axonal” neuropathy in rats. Table 76.2 lists these compounds and further emphasizes the necessity of the g-diketone spacing for the production of neuropathy. These findings have led to the theory that neurotoxicity is related to a common metabolic pathway leading to the formation of a g-diketone, which is the toxic metabolite that produces the neuropathy. Except for 2,5-heptanedione and 3,6-octanedione, all metabolic interconversions are oxidation of the

-1 carbon(s), first to an

alcohol or diol, then to a g-diketone. In the case of n-heptane, where -1 oxidation may occur, the ketone formed would be a d-diketone such as 2,6-heptanedione, which is not neurotoxic. When the carbon is oxidized in preference to the hexanol, no g-diketone is formed.

-1 carbon, as when n-hexane is converted to 1-

Figure 76.1. Relationships of alkanes, alcohols, and ketones that produce “giant axonal” neuropathy. Hydrogen atoms are included only when present as hydroxyl ions. * Further oxidative and decarboxylative pathways lead to the formation of methyl n-butyl ketone and 2,5-hexanedione (see Fig. 76.2). **The 5-methyl-3-heptanone metabolic scheme is an hypothesized pathway that is consistent with the observed neurotoxicity of this material.

Table 76.2. Structure–Activity Relationships of Diketones Ketone Structure

Spacing

Ketone Giant Neuropathy Axonal

2,4-Pentanedione CH3COCH2COCH3 2,3-Hexanedione CH3COCO(CH2)2CH3

b a

–a –

2,4-Hexanedione CH3COCH2COCH2CH3 2,5-Hexanedione CH3CO(CH2)2COCH3

b

–

g

+

3-Methyl-2,5hexanedione 3,4-Dimethyl2,5-hexanedione 3,3-Dimethyl2,5-hexanedione 2,3Heptanedione 2,5Heptanedione 2,6Heptanedione 3,6-Octanedione

CH3COCHCH3CH2COCH3

g

+

CH3COCHCH3CHCH3COCH3

g

+

CH3COC(CH3)2CH2COCH3

g

–

CH3CH2COCH2COCH2CH3

b

–

CH3CO(CH2)2COCH2CH3

g

+

CH3CO(CH2)3COCH3

d

–

CH3CH2CO(CH2)2COCH2CH3

g

+

3-Acetyl-2,5CH3COC(CH3CO)CH2COCH3 hexanedione 3,4-Diethyl-2,5- CH3COCH(CH3CH2)CHhexanedione (CH3CH2)COCH3

g

–

g

–

3,4-diisopropyl- CH3COCH(CH3CH3CH2)CH2,5-hexanedione (CH CH CH )COCH 3 3 2 3

g

–

a

2,4-Pentanedione produces central nervous system damage, which is clinically, anatomically, and morphologically distinguishable from “giant” axonal neuropathy.

These data also suggest that, as chain length increases, the neurotoxicity of the diketone decreases, possibly owing to steric hindrance. However, chain length may not be as important for some materials such as 5-nonanone. The neurotoxicity of 5-nonanone appears to involve two metabolic pathways, one to 2,5-nonanedione, a mechanism similar to that of the other compounds shown in Figure 76.1, and the other to methyl n-butyl ketone via a series of oxidative and decarboxylative pathways (Fig. 76.2).

Figure 76.2. Metabolism of 5-Nonanone. *Designates actual metabolites found in blood or urine. A third modifying factor affecting the neurotoxic potential of these substances is the number and size of substituent groups located between the g-spaced carbonyls. Single methyl groups on the carbons located between the carbonyl groups increase the potential neurotoxicity of the g-diketone (i.e., 3methyl-2,5-hexanedione or 3,4-dimethyl-2,5-hexanedione, Table 76.1). Two methyl groups positioned on one of the methyl groups between the carbonyls (i.e., 3,3-dimethyl-2,5-hexanedione) eliminate neurotoxicity. Metabolism to a substituted g-diketone may play a role in the neurotoxicity of 5-methyl-3-heptanone (Fig. 76.1).

Ketones of Six To Thirteen Carbons Douglas C. Topping, Ph.D., DABT, David A. Morgott, Ph.D., DABT, CIH, John L. O'Donoghue, VMD, Ph.D., DABT Summary A summary of the acute toxicologic properties of the ketones is presented in Table 76.3. During the past 30 years, a significant amount of data has been accumulated on the biologic and toxicologic effects of ketones in experimental animals and man. With the exception of certain studies that have shown that ketones with a particular structure produce a toxic polyneuropathy, these findings support the existing concepts of the relatively innocuous biologic effects of most ketones. The most widely and extensively used ketones appear to be the least toxic. Table 76.3. Toxicologic Properties of Ketones

Compound Methyl n-butyl ketone Methyl isobutyl ketone Mesityl oxide 4-Hydroxy-4methyl-2pentanone Methyl n-amyl ketone Methyl isoamyl ketone Ethyl n-butyl ketone Di-n-propyl ketone Diisopropyl ketone 2-Octanone 3-Octanone 5-Methyl-3heptanone 5-Nonanone Diisobutyl ketone Trimethyl nonanone 2,5-Hexanedione Cyclohexanone

ApproximateOral Rat LD50 (mL/kg)

Lowest Reported Lethal Air Conc. Rat (ppm/h)

3

8000/4

Sl

Sl

5–6

4000/4

Sl

Sl

1 4

500/8 >Sat'd./8

Sl Sl

M M

2

4000/4

M

Sl

4

3813/6

Sl

Sl

3

4000/4

M

Sl

4

2670/6

Sl

Sl

4

>2765/6

Sl

Sl

3 >5 4

>1673/6 — 3484/4

M M Sl

Sl — M

>2 6 9

— Sat'd./8 >Sat'd./4

— Sl Sl

— Sl Sl

3 2

>Sat'd./1 2000/4

Sl M

M M

Ocular Skin a Irritation Injurya

Methyl cyclohexanones Acetophenone Propiophenone Isophorone Benzophenone

2

2800/4

M

M

3 >4 2–>3 2–3

>Sat'd./8 >Sat'd./8 1840/4 —

M Sl Sl Sl

SV Sl SV Sl

a

Sl, slight; M, moderate; SV, severe. Skin irritation and ocular injury ratings are for direct application of liquids.

Table 76.4. Physical–Chemical Pr

Compound Methyl n-butyl ketone Methyl isobutyl ketone Mesityl oxide

Vapor Pressure Boiling Melting Refractive CAS Molecular Mol. Point Point (° Specific Index (20° (mmHg) b Number Formula Wt. (°C) C) Gravitya C)

[591-786] [108-101] [141-797] 4-Hydroxy-4-methyl- [123-422] 2-pentanone 2,5-Hexanedione [110-134] Cyclohexanone [108-941] Methyl n-amyl ketone [110-430] Methyl isoamyl [110-123] ketone Ethyl n-butyl ketone [106-354] Di-n-propyl ketone [123-193] Diisopropyl ketone [565-800] 2[583-60Methylcyclohexanone 8] 3[591-24-

C6H12O

100.16 127.5

–59.6

0.821

1.4007

3.8

C6H12O

100.16 115.8

–84.7

0.802

1.3959

18.8

C6H10O

98.14 129.6

–53

0.857

1.4440

9.5

C6H12O2 116.16 168.0

–43

0.941

1.4242

1.2

C6H10O2 114.14 194.0

–5.5

0.973

1.4230

1.6

C6H10O

98.14 155.7

–32.1

1.4507

4.8

C7H14O

114.19 151.1

–35

0.948 (20/4) 0.817

1.4073

2.1

C7H14O

114.19 144.0

–73.9

0.813

1.4062

4.5 (20)

C7H14O

114.19 147.4

–39.0

0.818

1.3994

5.6

C7H14O

114.19 143.7

–32.6

1.4069

5.5 (20)

C7H14O

114.19 124.0

–69

C7H12O

112.17

165

–13.9

0.817 (20/4) 0.803 (20/4) 0.925

C7H12O

112.17

169

–73.5

0.914

10 (37) 1.4440 (25) 1.4449

Methylcyclohexanone 2] 4[589-92Methylcyclohexanone 4] Acetophenone [98-862] 2-Octanone [111-137] 3-Octanone [106-683] 5-Methyl-3[541-855] heptanone Propiophenone [93-550] Isophorone [78-591] 5-Nonanone [502-567] Diisobutyl ketone [108-838] Trimethyl nonanone [123-182] Benzophenone

C7H12O

112.17

170

C8H8O

120.13 202.0

19.6

C8H16O

128.21 172.9

–16.0

C8H16O

128.21 167.0

C8H16O

128.21 160.5

–56.7

C9H10O

134.19 218.0

C9H14O

(20/4) 0.914 (20/4) 1.0281 (20/4) 0.819 (20/4) 0.822

–40.6

1.4451

10 (54)

1.5363

0.37 (25)

1.4151

1.2

1.4150

2.0

1.4160

2.0

18.6

0.820 (0/4) 1.010

1.5269

1.5 (25)

138.21 215.2

–8.0

0.923

1.478

0.26 (20)

C9H18O

142.24 188.4

–50

0.822

1.4195

C9H18O

142.24 168.1

–46.0

0.807

1.4210

0.817

1.4273

1.1108 (18/4)

1.5975 (45.2)

C12H24O 184.32 207– 228

[119-61- C13H10O 182.22 305.4 9]

48.5

1.7

1 (108)

a

Specific gravity is at 20/20°C unless otherwise noted. Vapor pressure is at 25°C unless otherwise noted. c Closed cup unless otherwise noted, [OC] open cup. Figures in parentheses are °C. d S, readily soluble; Sl, slightly soluble; I, insoluble. e At 25°C, 760 mm Hg. b

Table 76.5. Hygienic Standards for Ketones

ACGIH TLV

Compound Methyl n-butyl ketone Methyl isobutyl ketone Mesityl oxide 4-Hydroxy-4-

a

OSHA PELd

NIOSH RELe

DFG CAS b c No. TWA STEL TWA STEL TWA STEL MAKfTWA [591- 5(S)g 78-6] [108- 50 10-1] [147- 15 79-7] [123- 50

10

100

—

1

—

5

75

100

—

50

75

20

25

25

—

10

—

25

—

50

—

50

—

50

methyl-2pentanone 2,5Hexanedione Cyclohexanone

42-2]

[110- — 13-4] [108- 25(S)g 94-1] A4j Methyl n-amyl [110- 50 43-0] ketone Methyl isoamyl [110- 50 12-3] ketone Ethyl n-butyl [106- 50 35-4] ketone Di-n-propyl [123- 50 19-3] ketone Diisopropyl [565- — 80-0] ketone Methyl [583- 50(S)g cyclohexanone 60-8]

—

—

—

—

—

—

—

50

—

25(S)

—

—

—

100

—

100

—

—

—

100

—

50

—

—

75

50

—

50

—

—

—

—

—

50

—

—

—

—

—

—

—

—

75

—

50(S)

75

50

—

—

—

—

Acetophenone [9886-2] 2-Octanone [11113-7] 3-Octanone [10668-3] 5-Methyl-3[54185-5] heptanone Propiophenone [9355-0] Isophorone [7859-1]

10

—

100 (S)g —

—

—

—

—

—

—

—

—

—

—

—

—

—

—

25

—

25

—

25

—

—

—

—

—

—

—

—

—

—

25

—

4

—

2

5-Nonanone

—

5(CL)h A3i —

—

—

—

—

—

25

—

50

—

25

—

50

—

—

—

—

—

—

—

—

—

—

—

—

—

—

[50256-7] Diisobutyl [10883-8] ketone Trimethyl [12318-2] nonanone Benzophenone [11961-9]

a

g

American Conference of Governmental Industrial Hygienists Threshold Limit Values. Occupational Safety and Health Administration Permissible Exposure Limits. e U.S. National Institute for Occupational Safety and Health Recommended Exposure Limit. f Deutsche Forschungsgemeinschaft (Federal Republic of Germany) maximum concentration values in the workplace. b Time-weighted average (ppm). c Short-term exposure limit (ppm). g Indicates a skin notation applicable to TLV. j A4 Not classifiable as a human carcinogen. d

h i

Indicates ceiling limit applies. A3 Confirmed animal carcinogen with unknown relevance to humans.

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Monohydric Alcohols—C1 to C6 C. Bevan, Ph.D., DABT Chemical and Physical Properties The physical and chemical properties for the C1 to C6 monohydric alcohols are listed in Table 77.1. At ambient temperature, the vapor pressure decreases with increasing carbon number as shown in Table 77.1. The water solubility also decreases with an increasing carbon number. The National Fire Protection Association (NFPA) has prepared a rating system to assess the physical and chemical hazards of chemicals with respect to flammability, health, and reactivity (1, 2). The C1 to C6 monohydric alcohols are flammable, but not reactive.

Table 77.1. Chemical and Physical Properties of C1 to C

Compound Methanol Ethanol 1-Propanol Isopropanol 1-Butanol Isobutanol 2-Butanol tert-Butyl alcohol 1-Pentanol 2-Pentanol 3-Pentanol

CAS # [6756-1] [6417-5] [7123-8] [6763-0] [7136-3] [7883-1] [7892-2] [7565-0] [7141-0] [603229-7] [58402-1] [13732-6] [12351-3] [7585-4] [59875-4] [7584-3]

2-Methyl-1butanol 3-Methyl-1butanol tert-Amyl alcohol 3-Methyl-2butanol 2,2Dimethyl-1propanol 1-Hexanol [11127-3] 2-Hexanol [62693-7] 2-Methyl-1- [105-

Mol. formula

Mol. wt.

Boiling Melting point point (° C) (°C) –97.8

Sp. gr.

Refractive index (20° C)

Vapor Maxim pressure vapo (mmHg) concn (°C (°C)

CH4O

32.0

65

0.792

1.3285

160 (30)

21.05

C2H6O

46.1

79 –114.1 0.789

1.3614

50 (25)

6.58 (

C3H8O

60.1

97 –126.2 0.804

1.3850

21 (25)

2.7 (2

C3H8O

60.1

83

–88.5

0.785

1.3777

44 (25)

5.8 (2

C4H10O

74.1

118

–90.0

0.810

1.3991

6.5 (25)

0.86 (

C4H10O

74.1

108 –108.0 0.803

1.3959

12.2 (25)

1.61 (

C4H10O

74.1

100 –111.7 0.807

1.3972

23.9 (30)

31.4 (

C4H10O

74.1

82

25.6

0.787

1.3841

42.0 (25)

5.53 (

C5H12O

88.2

138

–79.0

0.815

1.4100

10 (44.9)

0.77 (

C5H12O

88.2

119

—

0.809

1.4053

—

—

C5H12O

88.2

116

–75.0

0.822

1.4098

2 (20)

—

C5H12O

88.2

128 5 g/kg Tetradecanol (CAS #11272-1) Eicosanol >64 mL/kg >20 mL/kg (mixed isomers) (CAS #62996-9) 3,5,53.45 g/kg 2.8 mL/kg Trimethyl cyclohexanol (CAS #11602-9) 3-Butyn-2-ol 34 mg/kg 32–36 (CAS mg/kg #2028-69-9)

Methyl 1.9 g/kg butynol (CAS #1159-5)

>5 g/kg

Methyl 0.8 g/kg pentynol (CAS #7775-8) Ethyl 2.1 g/kg octynol (CAS # [5877-42-9]) 3,7>5 g/kg Dimethyl-1octonol (CAS #10621-8)

>1 g/kg

a

No deaths, Slight Moderate 4 hr satd. vapor — Moderate —

—

105

—

274

—

Slight

—

275

Slight

—

43

Moderate Very severe

—

102

—

216

Severe (10% in H2O not irritating) Severe

Possibly

216

Possibly

216

No

No deaths, Slight 8 hr satd. vapor —

1 hr LC50; — std. vapor 6 min exposure, 100% lethal 1 hr LC50; None >20 mg/La 1 hr LC50; Slight

Very severe

>20 mg/Lb 0.2–1.0 g/kg —

—

—

Possibly

34

2.4 g/kg

Yes. unspec.

—

—

106

—

A single 4-hr exposure of rats to 3000 ppm methyl butynol caused death, but a 7-hr exposure to 2000 ppm did not. Both exposures caused liver and kidney injury. A single 7-hr exposure to 1000 ppm did not cause grossly apparent injury. Rats that received 81 7-hr exposures to 76 ppm for 115 day exhibited no adverse effects. b A single 4-hr or 7-hr exposure of rats to 4600 ppm methyl pentynol caused anesthesia, considerable injury to the lungs, liver, and kidney, and death. A 2-hr exposure did not cause death but did cause kidney injury and weight loss. A few deaths occurred after 4- and 7-hr exposures to 2000 ppm, whereas all survived a 7-hr exposure to 1000 ppm, although kidney

injury was noted. Groups of rats tolerated 67 7-hr exposures to 100 ppm for 98 days without adverse effects.

Monohydric Alcohols—C7 to C18, Aromatic, and Other Alcohols Bibliography

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Esters of Mono- and Alkenyl Carboxylic Acids and Mono- and Polyalcohols Michael S. Bisesi, Ph.D., CIH A. Introduction Overview This volume contains three chapters reviewing 12 classes of the organic compounds called esters. Chapter 79, this chapter, reviews (1) esters of monocarboxylic acids and mono- and polyalcohols and (2) esters of alkenyl carboxylic acids and monoalcohols; Chapter 80 reviews (3) esters of aromatic monocarboxylic acids and monoalcohols, (4) esters of monocarboxylic acids and di-, tri-, and polyalcohol; (5) dicarboxylic acid esters; (6) alkenyl dicarboxylic esters; (7) esters of aromatic diacids; (8) tricarboxylic acid esters; and, Chapter 81 covers (9) esters of carbonic and orthocarbonic acid; (10) esters of organic phosphorous compounds; (11) esters of monocarboxylic halogenated acids, alkanols, or haloalcohols; and (12) organic silicon esters. The sequence of the compounds has been organized according to the chemical structure of the major functional metabolites. This involves the ester hydrolyzates, primarily the acid and secondarily the alcohol. The reason for this sequence was the general observation that the degree of toxic effect, in addition to that of the original material, more often was the result of the toxicity of the acid rather than the response of the alcohol. Esters are important from an industrial hygiene perspective since exposure can occur during the process of manufacturing esters, the process of manufacturing materials containing or composed of esters, handling and use of products containing or composed of esters, and treatment of wastes containing esters. In turn, exposure to esters is important from a toxicological perspective because of the correlated observations of adverse physiological responses exhibited by laboratory animals and humans. Overviews of the physical, chemical and toxicologic (i.e., physiologic responses) properties of many subclasses of esters and/or of specific compounds are provided. In addition, summaries of relative manufacturing and use information are also included for many compounds. General Properties of Some Esters Chemically, esters are organic compounds commonly formed via the combination of an acid, typically an organic ( COOH) mono- or polyacid, plus a hydroxyl ( OH) group of a mono-or polyalcohol or phenol; water (H OH) is generated as a by-product of the reaction. For example, the reaction (esterfication) of acetic acid (CH3COOH) with methyl alcohol (CH3OH) to form methyl acetate proceeds [CH3(C O)OCH3] as follows:

The forward reaction (right; k1) is known as esterification; the reverse (left; k2) as hydrolysis. The occurrence of esterification or hydrolysis reactions depends on the differential reaction rates k1 versus k2 and the physical properties of the respective final products. The ratio of the concentrations of products [C] of k1 divided by k2 will give a reaction constant Ks indicative of the stability of the final product:

The esters are widely used in industry and commerce. They can be prepared by the reactions of acids with alcohols, by reacting metal salts of acids with alkyl halides, acid halides with alcohols, or acid anhydrides with alcohols by the interchange of radicals between esters. Most esters exist in liquid form at ambient temperatures, but some possess lower boiling points than their original starting

materials. They are relatively water-insoluble, except for the lower molecular weight members. Their flash points are in the flammable range. The monocarboxylic acid esters have high volatility and pleasant odors, whereas the di- and polyacid esters are relatively nonvolatile and exhibit essentially no odor. The monocarboxylic esters occur frequently in natural products, as, for example, in fruits, to which they lend their pleasant odor and taste. Because of the different properties of esters from the original acids and alcohols, esterification can be used for their isolation or to chemically protect specific carboxy or hydroxy functions. General Toxicity of Some Esters Absorbed esters and/or metabolites derived from biotransformed esters can initiate toxic effects in some mammalian systems, including humans, and cause adverse physiological responses. Indeed, the underlying causes of physiological responses are due to initial interactions biochemically within a system. Within these chapters, a summary of reviewed literature will reveal that, in general, toxic effects associated with exposure to various esters include primary irritation to ocular, upper and lower respiratory, and dermal systems; depression of the central nervous system (CNS) (e.g., anesthesia, narcosis); dermal hypersensitization; impact to the gastrointestinal (GI), hepatic, and renal systems; abnormal cardiac rhythm; and carcinogenesis. Indeed, these and some additional effects, are based predominantly on rodent studies. A review of the literature reported here, however, indicates that the most commonly reported effects in animals and humans are irritation and, to some extent, CNS depression. Data are reported in this chapter for several classes of esters, including formates (1), acetates (2), acrylates and methacrylates (3), propionates (4), and lactates (5). Ocular, dermal, respiratory, and even GI irritation is reportedly associated with both the parent ester compounds and the corresponding acid metabolites produced via hydrolytic cleavage reactions (1). Some compounds, such as the aliphatic esters used as lacquer solvents, may cause CNS depression when inhaled in sufficiently high concentrations (6). As expected from Overton theories substantiated by Munch (7) in experiments using rabbits and tadpoles, the more highly watersoluble, lower molecular weight derivatives, such as the methyl and ethyl formates and acetates, are less potent than butyl and amyl acetates. Thus, when Munch used tadpoles to evaluate the potency of aliphatic alcohols and their alkyl esters, he observed a direct relationship between CNS depression and increase in homologous series (7). He concluded that the intact ester was the primary causative agent. Their anesthetic potency is weaker than that of lower chlorinated hydrocarbons and usually less than that of ethyl ether, but greater than that of ethanol, acetone or pentane. When inhaled, aliphatic esters readily pass through the alveoli, owing to their relatively high solubility in plasma fluid. Those materials with higher water solubility have higher blood–air distribution coefficients and thus presumably reach saturation more slowly. This group of esters appears to be readily hydrolyzed and the resulting alcohols and acids rapidly metabolized. Most of the aliphatic esters possess some degree of irritation on exposed surfaces. The formates are especially irritating to the eyes and respiratory tract. Ethyl acetates may be irritating at concentrations of 400–800 ppm, whereas ethanol is devoid of effects up to 1000 ppm. The irritant range of butyl acetate, however, coincides with that of its corresponding alcohol. The irritant effect of the higher homolog is a function of the esterified rather than the hydrolyzed material. The local skin effects resemble those of other solvents; namely, defatting and cracking may occur. Practically all the common aliphatic and aromatic esters, except for some phosphates used as plasticizers, are inert. At the most, minor degrees of irritation may follow inhalation of heated vapors or prolonged skin exposure. Some of the literature also suggests that reported skin sensitization appears more likely in the presence of impurities or side products. Many of the materials are so inert that any LD50 value is impractical to determine. Specific pathology is usually absent, even when the materials is fed in massive quantities to the point of nutritional deprivation. Oily or watery excretion products, sometimes observed at high feeding levels, indicate lack of absorption. The apparent nontoxicity may also be a sign of rapid hydrolysis, metabolism, and excretion. The resins are

completely inert, unabsorbed in the gastrointestinal tract, and nonirritant at the surface of the skin and pulmonary system. Industrial Hygiene Evaluation One part of industrial hygiene evaluation of esters involves collecting and analyzing air samples to determine their airborne concentrations. To date, published industrial hygiene air sampling and analytical methods are available for relatively few esters compared to the number of ester compounds. In addition, although methods for biological monitoring of laboratory animals and exposed humans can be conducted to determine levels of absorbed esters and metabolites that originate from biotransformed esters, there are few established limits for comparing biological monitoring data. Contemporary air sampling methods most commonly involve the use of solid absorbents, such as charcoal, carbosieve, and XAD (8, 9). Following desorption of the solid adsorbents using a specified solvent, samples are typically analyzed using gas chromatography with flame ionization detection (GC-FID). The concentration of a given sample is determined by dividing the mass of the ester detected and measured using GC-FID by the volume of air sampled. Concentrations of air samples may be subsequently used to calculate time-weighted averages (TWAs) for comparison to applicable occupational exposure limits (OELs). Presently, there also are relatively few OELs compared to the number of ester compounds. There are threshold limit values (TLVs) and permissible exposure limits (PELs) established by the American Conference of Governmental Industrial Hygienists (ACGIH) and the Occupational Safety and Health Administration (OSHA), respectively, for some of the ester compounds discussed in this chapter (9– 11). In addition, other applicable agencies, such as the National Institute for Occupational Safety and Health (NIOSH), provide published recommendations concerning limits for occupational exposure to some esters (9). Industrial hygiene sampling and analytical methods for some ester compounds are presented in Table 79.1 along with their respective OELs. Since sampling and analytical methods and occupational exposure limits are subject to periodic revision; however, the reader is encouraged to refer to current publications of ACGIH, OSHA, and NIOSH. Table 79.1. Summary of Occupational Exposure Limits (OELs) and Monitoring Methods for Some Esters (8–11) Compound

OSHA (ppm)

ACGIH (ppm)

NIOSH (ppm)

OEL Monitoring Notations

PEL STEL C TLV STEL C REL STEL C Methyl formate

100

—

— 100

Ethyl formate 100

—

— 100

Methyl acetate

200

—

— 200

Ethyl acetate

400

—

— 400

150 — 100 150 — — — 100

—

—

250 — 200 250 —

—

— — 400

—

—

—

—

—

Carbosieve B tube GCFID Charcoal tube GCFID Charcoal tube GCFID Charcoal

n-Propyl acetate

200

—

— 200

250 —

Isopropyl acetate

250

—

— 250

310 —

n-Butyl acetate

150

—

— 150

200 —

sec-Butyl acetate

200

—

— 200

——

tert-Butyl acetate

200

—

— 200

——

Isobutyl acetate

150

—

— 150

——

n-Amyl acetate

100

—

— 50a 100a —

sec-amyl acetate

125

—

— 125

——

Isoamyl acetate

100

—

— 100a

——

sec-Hexyl acetate

50

—

—

50

——

Vinyl acetate

—

—

—

10

15 —

Methyl acrylate

10

—

—

2

——

Ethyl acrylate

25

—

—

5

15 —

n-Butyl acrylate

—

—

—

2

——

Methyl methacrylate

100

—

— 100

——

Butyl lactate

—

—

—

——

5

tube GCFID 200 250 — — Charcoal tube GCFID — — — — Charcoal tube GCFID 150 200 — — Charcoal tube GCFID 200 — — — Charcoal tube GCFID 200 — — — Charcoal tube GCFID 150 — — — Charcoal tube GCFID 100 — — — Charcoal tube GCFID 125 — — — Charcoal tube GCFID 100 — — — Charcoal tube GCFID 50 — — — Charcoal tube GCFID — — 4 NIOSH Carbosieve carcinogen B tube GCACGIH FID A3 10 — — Skin Charcoal ACGIH tube GCA4 FID — — — Skin Charcoal ACGIH tube GCA4 FID 10 — — Sensitizer Charcoal ACGIH tube GCA4 FID 100 — — ACGIH XAD-2 A4 tube GCFID 5 — — — —

a

Notice of intended change, changed as of 2000.

Esters of Mono- and Alkenyl Carboxylic Acids and Mono- and Polyalcohols Michael S. Bisesi, Ph.D., CIH B. Esters of Monocarboxylic Acids and Mono- and Polyalcohols Grouped into this category are the naturally occurring fatty acid esters of C1–C24 acids and C1–C30 alcohols.

Esters of Mono- and Alkenyl Carboxylic Acids and Mono- and Polyalcohols Michael S. Bisesi, Ph.D., CIH Formates The esters called formates are alkyl or aryl derivatives of formic acid HCOOH. These esters have various uses ranging from flavoring agents to industrial solvents. As is the case for most esters of toxicological significance, ocular, respiratory, and dermal irritation, and, at higher concentrations, CNS depression, are the major effects associated with exposure. The inhalation hazard decreases with increased molecular weight due to an observed progressive decrease in vapor pressure. There also is an observed decrease in water solubility with increasing molecular weight. von Oettingen reports that the decreased water solubility is associated with increased resistance to acid hydrolysis of the higher homologues. Accordingly, the lowest homologe, methyl formate, may pose a higher hazard potential because of its high vapor pressure and water solubility, but the higher homologs exhibit higher potency as central nervous system depressants (1). A summary of physical and chemical properties is found in Table 79.2 (12) and summaries of toxicologic data are shown in Tables 79.3 (13–16) and 79.4 (17). Table 79.2. Summary of Physical and Chemical Properties of Some Form Compound

CAS Molecular Molecular Boiling Melting Specific Solubilitya Refractive Vap Number Formula Weight Point Ponint Gravity in Water Index (at Dens (°C) (°C) (at 25° (at 68°F) 20°C) (Air = C)

Methyl formate Ethyl formate n-Propyl formate Isopropyl formate n-Butyl

[107-313] [109-944] [110-747] [625-558] [592-84-

C2H4O2

60.05

31.5

–100

0.987

v

1.3433

2.0

C3H6O2

74.08

54.3

–80

0.923

s

1.3598

2.5

C4H8O2

88.12

81.3

–92.9

0.91

d

1.3779

3.0

C4H8O2

88.12

68.2

—

0.873

d

1.3678

3.0

102.13

106.8

–91.9

0.911

d

1.3912

3.5

formate Isobutyl formate n-Amyl formate Isoamyl formate Vinyl formate Cyclohexyl formate Benzyl formate a b

7]

C5H10O2

[542-552] [638-493] [110-452] [692-455] [435154-6] [104-574]

C5H10O2

102.13

98.4

–95.8

0.89

d

1.3857

—

C6H12O2

116.16

132.1

–73.5

0.893

d

1.3922

4.0

C6H12O2

116.15

124.2

–93.5

0.89

d

1.3976

4.0

C3H4O2

72.08

—

—

—

—

—

2.4

C7H12O2

128.17

162.5

—

—

i

1.4430

4.4

C8H8O2

136.16

203b

—

1.081

i

1.5154

4.7

Solubility in water: v = very soluble; s = soluble; d = slightly soluble; i = insoluble. At 747 mm Hg.

Table 79.3. Summary of Inhalation Toxicity Data for Some Formates Compound Species Exposure Approximate Treatment Observed Ref. Mode Dose or Regimen Effect Concentration Methylformate

Ethyl formate

Human Inhalation 1,500 ppm

1 min

13

30 min

No symptoms Lethal

Guinea pig Guinea pig Guinea pig Guinea pig Human

Inhalation 50,000 ppm Inhalation 25,000 ppm

60 min

Lethal

13

Inhalation 10,000 ppm

3–4 h

Lethal

13

Inhalation 3,500 ppm

8h

No deaths

13

Inhalation 330 ppm

5 min

13

Inhalation Inhalation Inhalation Inhalation

5 min 4h 4h 20 min

Eye and nose irritation No deaths 5/6 deaths No deaths Eye irritation, dyspnea Eye irritation, dyspnea Eye

Rat Rat Rat Mouse

Satd. vap. 8,000 ppm 4,000 ppm 10,000 ppm

Mouse Inhalation 5,000 ppm

20 min

Cat

80 min

Inhalation 10,000 ppm

13

14 1 15 16 16 16

n-Butylformate

Cat

Inhalation 5,000 ppm

20 min

Dog

Inhalation 10,000 ppm

4h

Human Inhalation 10,000 ppm

20 mL No absorption LD50 Propyl formate n-Butyl formate Isoamyl formate

17 7 14 4 7 4 14

Oral LD50 Rat

3.980

4–18 h

4

Oral LD50 Mouse

3.4

Few min–6 h

4

Oral LD50 Rabbit

2.656

—

7

Oral LD50 Rat

9.84

Depression immediately following administration 4 h–4 days

4

Rabbit

3.0

7

Vinyl formate

Oral LD50 Rat

2.820

—

14

Dermal LD50

3.170

—

14

0.124

—

4

Rabbit

Allyl formate Oral LD50 Rat

Esters of Mono- and Alkenyl Carboxylic Acids and Mono- and Polyalcohols Michael S. Bisesi, Ph.D., CIH Acetates The saturated aliphatic acetates, especially the ethyl and butyl acetates, serve as important solvents in the lacquer industry. The aromatic and cyclic acetates are used as flavoring agents for food and scenting of perfumes, soap, and similar articles. Physiological effects of some are relatively low, since some acetates are, resemble, or convert into natural body metabolites. In both humans and experimental animals, however, administration of excessive quantities produce effects that consist of eye, throat, and nose irritation, followed by gradual onset of narcosis and slow recovery after termination of the exposure (2, 6)). Orally administered high concentrations of acetates to rabbits appeared to cause loss of coordination in decreasing order: ethyl = isopropyl > butyl > methyl = isoamyl acetate (30). This may be due to the rapid hydrolysis into acetic acid and the corresponding alcohols, causing a simultaneous decrease of the blood PCO2 and PO2 (30). There is a tendency to acidosis, especially with high concentrations of methyl acetate (30). No anesthetic symptoms developed in men exposed to 400–600 ppm of ethyl or butyl acetate for 2– 3 hrs. Eye irritation has been reported with 200–300 ppm exposure concentrations, but not the characteristic temporary corneal edema, which is caused by the corresponding alcohol (31). An eye injury healed promptly with the C4 but more slowly with the C3 acetate (32). No skin sensitization or dryness has been reported to date. The alkyl acetates possess increased narcotic potential (7), and the C3 and C8 members may have neurotoxic tendencies (33). The cyclic and aromatic acetates produce narcosis and death more readily than do the aliphatic esters. This may be due to the resulting hydrolytic products, which, however, are normally rapidly hydroxylated and excreted (2). For example, phenylacetyglutamine has been found to be excreted daily in 250–500-mg quantities in human urine (34). A study indicated that thresholds for nasal pungency, odor, and eye irritation decreased logarithmically with the length of carbon chains for acetates, as observed for homologous series of alcohols, and also as seen with narcotic and other toxic responses (35). Data from another study that rated ocular irritation based on corneal thickness suggest that the rating potential for irritation is alcohols >acetates or ketones >aromatics (36). Physical and chemical properties are summarized in Table 79.5, and toxicologic data are summarized in Tables 79.6 (37–43) and 79.7 (44, 45).

Table 79.5. Summary of Physical and Chemical Properties of Some Ace Compound

CAS Molecular Molecular Boiling Melting Specific Solubilitya Refractive Vap Number Formula Weight Point Point (° Gravity in Water Index at dens (°C) C) at (25° at (68 ° F) (20°C) (Air = C)

Methyl acetate Ethyl acetate n-Propyl acetate Isopropyl acetate n-Butyl acetate Isobutyl acetate tert-Butyl acetate n-Amyl acetate Isoamyl acetate 2-Amyl acetate n-Hexyl acetate n-Ocyl acetate Vinyl acetate

[79-209] [141-786] [109-604] [108-214] [123-864] [110-190] [540-885] [628-637] [624-419] [626-380] [142-927] [112-141] [108-054]

a

C3H6O2

74.08

56.9

–98

0.9342

v

1.3593

2.5

C4H8O2

88.10

77

–83.6

0.902

s

1.3723

3.0

C5H10O2

102.13

101.6

–95

0.887

d

1.3842

3.5

C5H10O2

102.13

89

–73.4

0.870

s

1.3773

3.5

C6H12O2

116.16

126

–77

0.882

d

1.3941

4.0

C6H12O2

116.16

116

–99

0.871

d

1.3902

4.0

C6H12O2

116.16

96

—

—

i

1.3853

4.0

C7H14O2

130.18

148.8

–70

0.879

d

1.4023

4.5

C7H14O2

130.19

142

–78.5

0.870

d

1.4003

4.4

C7H14O2

130

134

–78.5

0.861

i

1.3960

4.5

C8H16O2

144.22

338

—

—

i

1.4092

—

C10H20O2

172.27

205

–38.5

—

i

1.4190

—

C4H6O2

86.09

72.3

–93.2

0.9317

i

1.3959

3.0

S = Solubility in water; v = very soluble; s = soluble; d = slightly soluble; i = insoluble.

Table 79.6. Summary of Inhalation Toxicity Data for Some Acetates Compound Species Approximate Dose or Concentration Methyl acetate

Human 330 ppm

Treatment Regimen

Short

Observed Effects Ref.

Fruity odor

22

Human 4,950 ppm

Short

Human 9,900 ppm

Short

Mouse 55,440 ppm

10–20 min

Mouse 41,580 ppm

23–35 min

Mouse 26,400 ppm

31–42 min

Mouse 11,220 ppm

4–5 h

Mouse 7,900 ppm

6h

Mouse 5,000 ppm Cat 53,790 ppm

20 min 14–18 min

Cat

34,980 ppm

29–30 min

Cat

18,480 ppm

4–4.5 h

Cat

9,900 ppm

10 h

Ocular and 22 respiratory irritation Ocular and respiratory irritation Immediate 37 irritation, dyspnea, narcosis, lethal from pulmonary edema Irritation, dyspnea, 37 convulsion, 1/2 deaths, 3 min postexposure Moderate eye 37 irritation, narcosis, 1/2 deaths, 3 h postexposure Eye irritation, 37 fatigue, dyspnea, narcosis, lethal 10 h postexposure due to pneumonia 1/2 narcosis, 37 irritation, dyspnea, recovery, 1/2 no effects No effect 37 Irritation, 37 salivation, dyspnea, 1/2 convulsions, narcosis, lethal 1– 9 min, later with diffuse pulmonary edema Irritation, 37 salivation, dyspnea, 1/2 convulsions, narcosis, histology: lateral emphysema or edema Eye irritation, 37 dyspnea, 1/2 vomiting and convulsions, narcosis, slow recovery Eye irritation, 37 salivation,

Ethyl acetate

Cat

5,000 ppm

20 min

Cat

6,600 ppm

6 h / day

Cat 19,000 ppm Human 278 ppm

6h Short

Human 400 ppm

Short

Human 4,170 ppm Mouse 20,000 ppm Mouse 12,225 ppm Mouse 10,000 ppm

Mouse 5,000 ppm Mouse 2,000 ppm Guinea 2,000 ppm pig Cat 8,000 ppm

Vinyl acetate n-Propyl acetate

Irritation of nose and throat Short Ocular and respiratory irritation 45 min Toleration of side position 3h 10/20 died 45 min 1/2 lethal, corneal turbidity; 1/4 lethal, immediately. 1/4 in 24 h 3–4 h Corneal turbidity 17 h Irritation to eyes and nose, dyspnea 65 exposures No notable effects 20 min

Cat

9,000 ppm

450 min

Cat

43,000 ppm

14–16 min

Cat

20,000 ppm

45 min

Cat

12,000 ppm

5h

Rat

4,000 ppm

4

Human 240 ppm

Short

Human 4,595

Short

Cat

0.5 h

24,000 ppm

somnolence, recovery Eye irritation, salivation Weight loss, weakness, slow recovery Narcosis Fruity odor

Ocular and respiratory irritation Irritation and moderate dyspnea Deep narcosis, death Deep narcosis, recovery Lowest narcotic concentration Lowest lethal dose Ocular, nose, pharyngeal irritation Ocular and respiratory irritation Within 5–16 min assumes side

37 37 22 37 38 37 2 39 2

2 2 6 2 2 2 2 22 40 22 22 2

Isopropyl acetate

n-Butyl acetate

Isobutyl acetate Isomyl acetate

Human 200 ppm

—

position; 13– 18 min narcosis; 1/4 death 4 days postexposure Staggering within 30–45 min; deep narcosis 4.5–5.5 h; 1/4 death after 5.5 h Moderate irritation, salivation Eye irritation

Rat

Concentrated vapor Rat 32,000 ppm Human 3,300 ppm

>30 min

Lethal

14

4h Brief

2 42

Human 200–300 ppm

Brief

Mouse Guinea pig Guinea pig Guinea pig Cat

7,400 ppm 14,000 ppm

3h 4h

7,000 ppm

13 h

3,300 ppm

13 h

17,500 ppm

30 min

Cat Cat

12,000 ppm 4,200 ppm

30 min 6 h/6 days

Cat

900 ppm

Lethal 5/6 animals Marked irritation to eyes and nose Mild irritation to eyes and nose Narcosis, recovery Eye irritation, narcosis, lethal Eye irriation, deep narcosis, recovery Eye irritation, no other symptoms Narcosis, lethal to some Narcosis, recovery Weakness, loss of weight, minor blood changes Weakness

Rat

21,000 ppm

65 experiments,6 h/day 150 min Narcosis, lethal, 6/6 6h No symptoms 30 min Irritation of nose and throat, headache, weakness 1h Nasal irritation, drowsiness 24 h Light narcosis, delayed death due to pneumonia 20 min Irritation to eyes and nose

Cat

7,400 ppm

5.5 h

Cat

5,300 ppm

6 h/day

Rat 3,000 ppm Human 950 ppm

Dog

5,000 ppm

Cat

7,200 ppm

Cat

4,000 ppm

2

2 41

2 2 42 42 42 2 2 2 6 22 22 2

2 2 2

n-Amyl acetate

sec-Amyl acetate

Human 200 ppm

30 min

Cat

2,182 ppm

215 min

Cat

10,600 ppm

115 min

Human 1,000 ppm

1h

Guinea 10,000 ppm pig

5h

Guinea 5,000 ppm pig

13 h

Guinea 2,000 ppm pig

13 h

n-Hexyl Rat 4,000 ppm acetate Cyclohexyl Human 516 ppm acetate Rabbit 700 ppm

4h Brief 4.8 h

Rabbit 1,700 ppm Cat 1,700 ppm

4.8 h 10 h

Cat

860 ppm

9h

Cat Cat Dog

1,600 ppm 637 ppm 637 ppm

8 h/5 days 8 h/30 days 8 h/30 days

Lowest irrirated dose Salivation, no other effects Marked salivation, lacrimation, irregular respiration, loss of reflexes after 85 min Serious toxic effects Eye and nose irritation, narcosis, lethal Eye and nose irritation, narcosis recovered Eye and nose irritation, no narcosis, recovered Lowest lethal dose

38

Irritation to eyes and throat Irritation to nose and eyes, recovery Lethal Deep narcosis and death Irritation plus light narcosis

2

No symptoms No symptoms

2 2

2 2 2 2 2

43 43 43 2 2 2 2

Table 79.7. Summary of Oral, Dermal, Subcutaneous, and Intraperitoneal Toxicity Data for Some Acetates Compound Route of Entry Methyl

Oral

Parameter Determined

Species Tested

Dose or Concentration

Ref.

LD50

Rabbit

3.7 g/kg

7

LDLO

Guinea pig 3.0 g/kg

44

SC

LDLO

Cat

3.0 g/kg

Oral

TLm96 LDLO

Aquatic Rat

1000–100 ppm 11 g/kg

LD50

Rabbit

4.94 g/kg

LD50

Guinea pig 3.0 g/kg

44

LD50

Cat

3.0 g/kg

44

Oral

TLm96 LD50

Aquatic Rabbit

1000–100 ppm 6.64 g/kg

17 7

SC

LD50

Guinea pig 3.0 g/kg

44

LDLO

Cat

3.0 g/kg

44

Oral

TLm96 LD50

Aquatic Rabbit

1000–100 ppm 6.95 g/kg

17 7

Aquatic Rat

>1000 ppm 6.73 g/kg

17

Cyclohexyl Oral

TLm96 LD50

Dermal

LD50

Rabbit

10.1 g/kg

Oral

LD50

Rat

1.63 g/kg

Ethyl

SC

n-Propyl

Isopropyl

Phenyl

7 17 14 7

45

Table 79.8. Summary of Physical and Chemical Properties of Some Fatty Compound

CAS Molecular Molecular Boiling Melting Specific Solubilitya Refractive Number Formula Weight Point Point (° Gravity in Water Index at (°C) C) at (25° at (68°F) (20°C) C)

Methyl [554-12- C4H8O2 1] propionate Ethyl propionate [105-37- C5H10O2 3] Ethyl 3[763-69ethoxypropionate 9] Methyl butyrate [623-42- C5H10O2 7] Methyl [547-63- C5H10O2 7] isobutyrate Ethyl butyrate [105-54- C6H12O2 4] Ethyl isovalerate [108-64- C7H14O2 5]

88.10

79.85

–87.5

0.910

d

1.3775

102.13

210

–99.4

0.891

d

1.3839

146.19

170.1

–75

0.95

—

—

102.13

102.3

–95

0.8721

d

1.3878

102.13

92.3

–84.7

0.8930

d

1.3840

116.16

252

–135.4

0.879

d

1.4000

130.19

271

–146.2

0.868

—

1.3962

Ethyl caproate

[123-660] Ethyl enanthate [106-309] Ethyl caprylate [106-321] Ethyl [123-295] pelargonate Ethyl caprate [110-383] Ethyl crotonate [623-701] Vinyl crotonate [1486106-4] a

C8H16O2

144.22

168

–67

0.873

i

1.4073

C9H18O2

158.24

372

–86.8

0.868

d

1.4100

C10H20O2

172.27

208.5

–47

—

i

1.4178

C11H22O2

186.30

119

–36.7

0.865

i

1.4220

C12H24O2

200.33

245

–20

0.862

i

1.4256

C6H10O2

114.14

143

+45

0.92

i

1.4243

C6H8O2

112.13

134

—

0.94

—

—

Solubility in water: v = very soluble; s = soluble; d = slightly soluble; i = insoluble.

Table 79.9. Summary of Toxicity Data for Some Propionates, Butyrates, and Higher Esters Compound

Species

Route of Parameter Entry

Result (g/kg)

Time to Ref. Death

2.02

7

Methyl

Rabbit

Oral

Propionate LD50

Ethyl

Rabbit

Oral

LD50

5.71

7

n-Propyl

Rabbit

Oral

LD50

3.94

7

Isobutyl

Rabbit

Oral

LD50

5.6

7

Isoamyl

Rabbit

Oral

LD50

6.9

7

Ethylethoxy

Rat

Oral

LD50

5.0

97

Dermal

LD50

>10.0

97

3.38

7 4

Methyl

Rabbit

Oral

Butyrate LD50

Ethyl

Rat

Oral

LD50

13.0

Rabbit

Oral

LD50

5.23

4–18 h

7

n-Propyl

Rat

Oral

LD50

15.0

1–3 days

4

Amyl

Rat

Oral

LD50

12.2

4

Oral

LD50

11.95

Allyl

Guinea pig Rat

Few min– 2h 2 h–6 days

Oral

LD50

.25

4 years–5 days

4

4

Linalyl iso-

Rat

Oral

LDLO

>36.3

Mouse

Oral

LDLO

15.1

4 h–4 days

4

Benzyl

Rat

Oral

LDLO

2.33

4 h–4 days

4

Pentyl pentanoate

Rat

Oral

LD50

>35.4

Guinea pig Rat

Oral

LD50

>17.3

2–6 days

4

Oral

LD50

0.50

4–18 h

4

Oral

LD50

0.44

4 h–3 days

4

Oral

LD50

25.9

4 h–4 days

4

Oral

LD50

>43.0

4

Oral

LD50

>24.2

4

Oral

LD50

>32

4

IP

LD50

>32

4

Allyl heptanoate

Guinea pig Ethyl caprylate Rat Ethyl nonanoate

Rat

Guinea pig Butyl stearate Rat Rat

4

4

Esters of Mono- and Alkenyl Carboxylic Acids and Mono- and Polyalcohols Michael S. Bisesi, Ph.D., CIH C. Esters of Alkenylcarboxylic Acids and Monoalcohols

Esters of Mono- and Alkenyl Carboxylic Acids and Mono- and Polyalcohols Michael S. Bisesi, Ph.D., CIH Acrylates, Methacrylates, and Crotonates Acrylates are esters of propenoic acids and mono- or polyalcohols. Chemically, the acrylic monomers are substituted 2-propene carboxylic acid esters of the type CH2: CHCOOR. They polymerize readily, with heat or even on standing;the latter reaction is catalyzed by light or oxygen, unless an inhibitor has been added. Uncontrolled polymerization is exothermic and may proceed with explosive force. Methacrylic esters are 2-methyl derivatives of acrylic esters. Chemically, they are of the general structure CH2: C(CH3)COOR. The higher molecular weight derivatives polymerize to gels or highly viscous liquids. Crotonates are 3-methyl isomers of methacrylates or

butanoic acid esters and bear the general structure CH3CH: CHCOOR. Lower molecular weight acrylic monomers are liquids having relatively higher vapor pressures. The characteristic odors of the monomers can be unpleasant. See Table 79.10 for a summary of physical and chemical properties. Table 79.10. Summary of Physical and Chemical Properties of Some Acrylates, Metha Compound

CAS Molecular Molecular Boiling Melting Specific Solubilitya Refractive Va Number Formula Weight Point Point (° Gravity in Water Index at den (°C) C) at (25° at (68° F) (20°C) (Air C)

Methyl [96-333] acrylate Ethyl [140-885] acrylate n-Butyl [141-322] Acrylate 2-Ethylbutyl [395310-4] acrylate 2-Ethyl hexyl [103-117] acrylate Methyl [80-62methacrylate 6] Ethyl [97-63methacrylate 2] n-Butyl [97-88methacrylate 1] Isobutyl [97-86methacrylate 9] 2[688-84Ethylisohexyl 6] methacrylate Methyl [623-438] crotonate a

C4H6O2

86.09

80.5 –75

0.95

d

1.4040

2

C5H8O2

100.11

99.4 –71.2

0.92

d

1.4068

3

C7H12O2

128.17

146.8 –64

0.8986

i

1.4185

4

C9H16O2

156.22

–70

0.896

—

—

5

C11H20O2

184.28

213.5 –90

0.887

i

—

6

C5H8O2

100.13

101

–48

0.945

d

1.4142

3

C6H10O2

114.14

117

–75

0.911

d

1.4147

3

C8H14O2

142.20

160

–75

0.89

i

1.4240

4

C8H14O2

142.20

155

—

0.886

—

—

—

C12H22O2

198.30

113

—

—

—

—

6

C5H8O2

100.12

121

–42

0.946

i

1.4242

3

82

Solubility in water: v = very soluble; s = soluble; d = slightly soluble; i = insoluble.

Some acrylates occur naturally in several organisms as intermediates in lipid biosynthesis and degradation. The alkyl monomers exist primarily in liquid form, whereas the formed polymers range from clear, glass-like, brittle masses to highly flexible films, solids, or emulsions. They are widely used in commerce and industry as vinyl, acrylic, or higher molecular weight alkene resins. The acrylic monomers are highly important base components in the manufacture of thermoplastics, acrylic resins, and emulsion polymers. They are also used as solvents, plasticizers, latex coatings, adhesives, fibers, floor finishes, and lubricant additives and serve in medical and dental technology as surgical cement for medical devices and prostheses. The methacrylates sometimes serve as bases for acrylic resins with multifunctional effects. These materials find use in surgical organ repair, in compositing contact lenses, for adhesive dental pretreatment, and for a variety of other applications.

The acrylates can be manufactured by a number of procedures. These include dehydration of the corresponding hydroxyalkanoic acid, saponification of the alkene nitrile, catalytic hydration of acetylene and carbon monoxide, or the reaction of acetone with hydrocyanic acid. The methacrylates can be synthesized by catalytic oxidation of isobutylene and subsequent esterification with the appropriate alcohol, or by reacting acetone with hydrocyanic acid and subsequent esterification in sulfuric acid with the appropriate alcohol. The low molecular weight monomers are lacrimators and irritants to the eyes, skin, and mucous membranes (3). The main potential for human exposure is by the dermal and respiratory routes;however, the irritating properties of these chemicals may serve as a deterrent to repeated exposures. Nonetheless, chronic inhalation of acrylic acid esters can lead to tissue changes or lesions due to local irritant or inflammatory reactions from acrylic acid or its esters that hydrolyze to form the acid. The acute toxicity of acrylates decreases with increasing molecular weight. For example, results from animal studies indicated that the acute lethal toxicity of methyl acrylate was twice that of ethyl acrylate based on inhalation exposure. Another study, based on 24-h LC50 concentrations using rats, indicated that the order of acute toxicity was methyl acrylate > ethyl acrylate > n-butyl acrylate > butyl methacrylate > methyl methacrylate. In the same study, rat inhalation exposures to 110 ppm 4 h/day, 5 days/week for 32 days did not cause significant changes in body weight, tissue weight, blood chemistry, gross metabolic performance, or small-intestine motor activities when compared to a control group (134). Structure-toxicity relationships of acrylates, including methacrylates, were analyzed in mice and found to be dependent on the log of the partition coefficient and log of rate order constant (135). In general, the toxicity is theorized to mechanistically involve alkylation of cellular nucelophies via Michael is addition (136). The introduction of unsaturation into a fatty acid, as, for example, comparing the methyl or ethyl esters of propionic acid with the equivalent propenoic or acrylic acid derivatives, shows a tenfold increase in acute toxicity. Comparing acute toxicity of straight with branched-chain acrylates, ethyl acrylate by the oral route may be only half as toxic as methyl acrylate, but 8 times as toxic as methyl methacrylate, and 13 times as toxic as ethyl methacrylate (137). Acute inhalation of higher concentrations may cause narcosis, salivation, and pronounced nasal, occular, and pulmonary irritation or edema. Prolonged skin or eye contact may result in severe tissue damage. The pathology from single exposure is not particularly characteristic, contrary to repeated exposure effects, which include pulmonary congestion or hemorrhage and cloudy swelling and organ weight changes of the liver and kidney, reported following subchronic exposures to excessive concentrations. Acrylic acid and a series of methacrylates were shown to produce hemangiomas and increase resorptions following intraperitoneal injection of pregnant rats (138). Some compounds, such as the methyl-, ethyl-, n-propyl-, or butyl methacrylates, can produce inhibition of barium chloride–induced contraction of the isolated guinea pig ileum (139). Animal studies using rats revealed that some acrylates and methacrylates are embryotoxic. The doses of monomers used in the animal studies, however, were much higher than concentrations likely encountered by workers (3). Allergic reactions have been reported for some acrylates. Although methyl, ethyl, and butyl methacrylates are potent skin sensitizers, experimental simulation proved rather difficult, owing to the rapid evaporation of the materials tested (140). Despite this, causes of human sensitization may occur. Methyl acrylate, methyl methacrylate, ethyl methacrylate, and butyl methacrylate caused allergic contact dermatitis due to working with artificial nail-bonding chemicals (141). Indeed, a study reviewing 10 y of patch testing data showed that 48 of 275 patients exhibited dermal allergic reactions to at least one acrylate. The most common acrylates that caused allergic reactions were 2hydroxyenthyl acrylate (12.1%), 2-hydroxypropyl acrylate (12%), and 2-hydroxyethyl methacrylate (11.4%). No allergic response were recorded for 2-ethylhexyl acrylate (141). Acrylates and methacrylates are detoxified predominantly via conjugation with glutathione via the Michaelis addition reaction or glutathoine-S-transferase. They are also likely to be hydrolyzed via

carboxylesterases (142). The lower molecular weight esters are rapidly metabolized and eliminated, therefore, will not likely cause cumulative toxicity (3). The literature revealed much more data regarding methylacrylates than the crotonates. Although the irritant and lacrimatory effects of the crotonates are known, no low level exposure effects in humans have been reported so far. Physiologically, they are somewhat less reactive than the acrylates. They appear to be rapidly metabolized and excreted, possibly because crotonyl and methacrylyl groups are also formed during the normal metabolism of butyryl and isobutyryl derivatives (111). General toxicological data for acrylates, methacrylates, and crotonates are summarized in Tables 79.11 (143, 144) and 79.12 (145–150). Table 79.11. Summary of Inhalation, Oral, Dermal, Subcutaneous, and Intraperitoneal Tox Acrylates Acrylate

Oral LD50

Species

Methyl

Ethyl

IP Dermal LD50 LD50 Rabbit Mouse (g/kg) (g/kg)

g/kg

Rat

0.300

Rabbitb

0.280

Rat

1.02

Rabbit

1.0

Inhalation

Concen. Time (ppm) (h) 1.3

1.95

0.256 1000 (143) 95

Isobutyl

3.4 (105)

Rat (105) 9.05

2.0

Rat (75)

7.07 4.49 (75)

2-Ethylbutyl Rat 6.5 Rat (105) 5.6 2-Ethylhexyl Rat Rat

5.66 6.4–

8.5 (105)

Rat

TCLO

Rabbit

1.325 (143)

Rat

LC80

Rat

1204

7

LCLO

Rabbit

1204

7

LCLO

10.0ab (105)

Ethyl

Inhalation

1.8 Rat (147)

2.0 Mouse (39) Mouse (39) Rabbit (145) Guinea pig (145) 25.0e Rat (147) 1.22 Guinea pig

0.150 Short

T L

15

L

47.7c

L

61.8c 3

L

17.5 4.5

L

19.0c 5

L

72.1c 4.5

L

Rabbit 3.63 (145) Rabbit >10ad (105)

n-Butyl

Rat >20 (145) Rabbit >6.3 (145)

Isobutyl

Rat (105)

>6.4

(39) Rat (147) 0.37 Dog (39) Mouse 1.25 Dog (146) (39) Mouse 1.37 Mouse (148) (39) Rat (147) 2.3 f

Mouse (146)

41.2 3

L

72.1 1.5

L

41.2 0.5/day×15 L 41.2 1.5/day × 15 L

1.49 Guinea pig (39)

39.3 3.0/day × 15 L 65.5c 3.0/day × 3 L 41.2 0.5/day × 15 L

Rat (147) 1.4 Dog (39)

46.8 0.5/day × 15 L Mouse (145) Methyl

Rat (105) Mouse (105) Guinea pig (105) Ethyl Rat (149) Guinea pig (105) 2Rat Ethylhexyl (105) Guinea pig (105) Vinyl Rat (105) Guinea pig (105)

>3.2 2.6–3.2 10– 20a,d 3.0 >10a,d >3.2 >20a 6.5 >10a

a

Dermal LD50.

b

mL/kg. Liver degeneration and focal necrosis. TDLO.

c e

1.19

46.8 1.5/day × 8 L

Crotonate Rat (105) Rabbit 3300 (105) Rat (150)

15 3

L

8

L

6.0

Rat (105) Rat (149)

19,000

6

L

Saturated vapor

8

L

Rat (105) Rat (105)

2500

6

L

Saturated vapor

6

L

Rat (105) Rat (105)

4000

4

L

2000

4

L

Rat (105)

Saturated vapor

1

L

f

Teratogenic TDLO.

d

mL/kg.

Table 79.13. Summary of Physical and Chemical Properties of Some Lactates and Compound

CAS Molecular Molecular Boiling Melting Specific Solubilitya Refractive Vap Number Formula Weight Point(° Point (° Gravity in Water Index (at dens 20°C) (Air = C) C) (at 25° at (at C) 68° F)

Methyl [547-648] lactate Ethyl [97-643] lactate Isopropyl [617-516] lactate n-Butyl [138-227] lactate Amyl [638206-5] lactate Methyl pyruvate Ethyl [617-356] pyruvate Allyl [591-877] acetate Geranyl [105-873] acetate Linalyl [115-957] acetate Cyclohexyl [622-457] acetate Phenyl [122-792] acetate Methyl [105-45acetoacetate 3] Ethyl [141-97acetoacetate 9] a

104.1

35

1.092

s

1.414

118.13

153

1.033

s

1.413

132.2

157

0.991

s

1.410

146.19

188

0.984

s

1.422

160.2

207

0.964

s

1.424

C4H6O3

102.09

d

1.4046

C5H8O3

116.12

134– 137 144

d

1.4052

C5H8O2

100.13

103.5

d

1.4049

C12H20O2

196.28

242

C12H20O2

196.29

220

i

1.4544

C8H14O2

142.20

173

i

1.4401

4.9

C8H8O2

136.16

195.7

1.073

d

1.5033

4.7

C5H8O3

116.12

171.7

–80

1.077

v

1.4184

4.0

C6H10O2

130.14

–45.4

180.8

1.03

v

1.4194

4.4

C5H10O3

C7H14O3

0.928

Solubility in water: v = very soluble; s = soluble; d = slightly soluble; i = insoluble.

Table 79.14. Summary of Acute Oral and Inhalation Toxicity of Some Lactates (202)

3.4

Compound Parameter Species Methyl

Oral LD50 Rat Inhalation LC50/4 h

Ethyl

Oral LD50 Rat Inhalation LC50/4 h

Propyl

Oral LD50 Rat

Isoprophyl Oral LD50 Rat Butyl

Oral LD50 Rat Inhalation LC50/4 h

Isobutyl

Inhalation LC50/4 h

Rat

Dose

Observed Effects

>2000 mg/kg Pilorection 24 h; absence of gross necroscopy changes 3 >5030 mg/m During exposure decreased breathing rates and wet nares; postexposure wet fur; gross necropsy showed 7/10 with grayish lungs and two lungs with irregular surfaces >2000 mg/kg Pilorection up to 24 h; absence of gross necropsy changes >5400 mg/m3 During exposure decreased breathing rates, pilorection, lachrymation, and wet nares; gross necropsy showed pale lungs with spots >2000 mg/kg Sluggishness 4 h; absence of gross necropsy changes >2000 mg/kg Pilorection 24 h; absence of gross necropsy changes >2000 mg/kg Pilorection 24 h and diarrhea; absence of gross necropsy changes >5140 mg/m3 During exposure decreased breathing rates and wet head and fur. absence of necropsy changes >6160 mg/m3 During exposure decreased breathing rates, pilorection, and hunched appearance; postexposure apnea; absence of gross necropsy changes

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to ethyl acrylate and methyl methacrylate. Scand. J. Work Environ Health 17, 7–19 (1991). 170 C. B. Frederick and I. M. Chang-Mateu, Contact site carcinogenicity: Estimation of an upper limit for risk of dermal dosing site tumors based on oral dosing site carcinogenicity. In T. R. Gerrity and C. J. Henry, eds. Principles of Route-to-Route Extrapolation for Risk Assessment, Elsevier, New York, 1990, pp. 237–270. 171 C. B. Frederick et al., Toxicol. Appl. Pharmacol. 114, 246–260 (1992). 172 D. Parker and J. C. Turk, Contact sensitivity to acrylate compounds in guinea pigs. Contact Dermatitis 9, 55–60 (1983). 173 B. B. Levine, Studies on the mechanism of the formation of the penicillin antigen. I. Delayed allergic cross reactions among pencillin G and its degradation products. J. Exp. Med. 112, 1131–1157 (1960). 174 G. Engelhardt and H. J. Klimisch, n-Butyl acrylate: Cytogenetic investigations in the bone marrow of Chinese hamsters and rats after 4-day inhalation. Fundam. Appl. Toxicol. 3(6), 640–641 (1983). 175 A. Sapota, The dynamics of distribution and excretion of butyl-(2,3-14C)-acrylate in male Wistar albino rats. Pol. J. Occup. Med. 4(1), 55–66 (1991). 176 J. Merhle and H. J. Klimisch, n-Butyl acrylate: Prenatal inhalation toxicity in the rat. Fundam. Appl. Toxicol. 3, 443–447 (1983). 177 F. Motoc et al., Arch. Mal. Prof. Med. Trav. Secur. Soc. 32(10–11), 653 (1971). 178 H. G. Boehling, U. Borchard, and H. Drouin, Arch. Toxicol. 38, 307 (1977). 179 A. A. Fisher, Contact Dermatitis, 2nd ed., Lea & Febiger, Philadelphia, PA, 1973, p. 358. 180 B. Scolnick and J. Collins, J. Occup. Med. 28(3), 196–198 (1986). 181 M. J. Kessler, J. L. Kupper, and R. J. Brown, Accidental methyl methacrylate toxicity in a rhesus monkey (Macaca mulatta). Lab. Ani. Sci. 27(3), 388–390 (1977). 182 L. G. Lomax, N. D. Krivanek, and S. R. Frame, Chronic inhalation toxicity and oncogenicity of methyl methacrylate in rats and hamsters. Food Chem. Toxicol. 35(3–4), 393–407 (1997). 183 Z. Bereznowski, In vivo assessment of methyl methacrylate metabolism and toxicity. Int. J. Biochem. Cell Biol. 27(12), 1311–1316 (1995). 184 Z. Bereznowski, Methacrylate uptake by isolated hepatocytes and perfused rat liver. Int. J. Biochem. Cell Biol. 29(4), 675–679 (1997). 185 H. M. Solomon et al., Methyl methacrylate: Inhalation developmental toxicity study in rats. Teratology 48(2), 115–125 (1993). 186 F. E. Reno, 18-Month Vapor Inhalation Safety Evaluation Study in Hamsters, unpublished, Proj. No. 417–354. Hazelton Laboratories America, Inc., 1979. 187 National Toxicology Program (NTP), Toxicology and Carcinogenesis Studies of Methyl Methacrylate (Cas No 80-62-6) In F344/N Rats and B6C3F1 Mice (Inhalation Studies), Tech. Rep. Ser. 314, NTP, Washington, DC, 1987. 188 H. Schweikl, G. Schmalz, and K. Rackebrandt, The mutagenic activity of unpolymerized resin monomers in Salmonella typhimurium and V79 cells. Muta. Rese. 415(1–2), 119–130 (1998). 189 M. M. Moore et al., Genotoxicity of acrylic acid, methyl acrylate, ethyl acrylate, methyl methacrylate, and ethyl methacrylate in L5178Y mouse lymphoma cells. Environ. Mol. Mutagen. 11(1), 49–63 (1988). 190 L. Kanerva et al., A single accidental exposure may result in a chemical burn, primary sensitization and allergic contact dermatitis. Contact Dermatitis 31(4), 229–235 (1994). 191 L. Kanerva et al., Occupational allergic contact dermatitis caused by photobonded sculptured nails and a review of (meth) acrylates in nail cosmetics. Am. J. Contact Dermatitis 7(2), 109–115 (1996).

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Esters of Carbonic and Orthocarbonic Acid, Organic Phosphorous, Monocarboxylic Halogenated Acids, Haloalcohols, and Organic Silicon Michael S. Bisesi, Ph.D., CIH I. Introduction

Esters of Carbonic and Orthocarbonic Acid, Organic Phosphorous, Monocarboxylic Halogenated Acids, Haloalcohols, and Organic Silicon Michael S. Bisesi, Ph.D., CIH A. Overview This chapter covers (1) esters of carbonic and orthocarbonic acid, (2) esters of organic phosphorous compounds, (3) esters of monocarboxylic halogenated acids, alkanols, or haloalcohols, and (4) organic silicon esters. Other classes of esters are summarized in Chapters 79 and 80. Refer to the Introduction in Chapter 79 for a more detailed overview of general properties of esters. Unfortunately, as shown in the two prior chapters, mainly fragmented toxicological evaluations are available for esters. Most of these esters are characterized by low toxicity. Indeed, as expressed in Chapter 79, lethal dose (e.g., LD50) values are frequently difficult or impractical to measure. Localized dermal irritation is one common effect characteristic of exposures to most organic solvents. Few esters are readily absorbed, but there are exceptions, such as tri-o-cresyl phosphate (TOCP). Several of the halogenated derivatives, such as ethylchloro- and ethylbromo-, are potent lacrimators. Ethyl fluoroacetate and fluoroacetic acid exhibit about the same mode of action, which may indicate that the acetate is rapidly hydrolyzed and metabolized in the mammalian system. The unsaturated carbonates are also associated with high lacrimatory activity. TOCP is an example of an ester that can cause neuropathy in a variety of animal species. The initial weakness and paralysis are normally reversible in early stages, but repeated or massive assaults result in demyelination of the nerve fibers. The mechanism of action is not yet certain, but it appears to involve phosphorylation of proteins. Only selected phosphates exhibit neuropathic effects, including diisopropyl fluorophosphorate and N,N'-diisopropyl phosphorodiamidic fluoride.

Esters of Carbonic and Orthocarbonic Acid, Organic Phosphorous, Monocarboxylic Halogenated Acids, Haloalcohols, and Organic Silicon Michael S. Bisesi, Ph.D., CIH B. Industrial Hygiene Evalution As was expressed in Chapter 79, industrial hygiene evaluation of esters involves collecting and analyzing air samples to determine their airborne concentrations. Published industrial hygiene air sampling and analytical methods, however, are unavailable for most esters. In relation, there are few occupational exposure and biological limits. A list of ester compounds covered in this chapter that have industrial hygiene sampling and analytical methods are presented here in Table 81.1 along with their respective occupational exposure limits, established by the American Conference of Governmental Industrial Hygienists (ACGIH), the Occupational Safety and Health Administration (OSHA), and the National Institute for Occupational Safety and Health (NIOSH) (1–4). As stated in

Chapter 79, since sampling and analytical methods and occupational exposure limits are subject to periodic revision, the reader is encouraged to refer to current publications of ACGIH, OSHA, and NIOSH. Table 81.1. Summary of Occupational Exposure Limits (OELs) and Monitoring Methods for Some Esters (1–4) OSHA

Compound

PEL 3 mg/m3

Triphenyl phosphate

STEL —

ACGIH

TLV 3 mg/m3

Methyl — — 1 ppm silicate Ethyl silicate 100 ppm 700 ppm 10 ppm

STEL Notations

ACGIH A4 3 mg/m3

1000

—

—

1 ppm

—

—

—

10 ppm

0.1 mg/m3 —

0.1 mg/m3 —

Trimethyl phosphite

—

2 ppm

a b

REL

NIOSH Monitorin IDLH Method

—

Tri-o-cresyl phosphate

—

NIOSH

—

700 ppm XAD-2; CS2; GCFID NIOSH #5264b Skin; CNS 0.1 mg/m3 40 mg/m3 Filter; cholinergic; diethyl ACGIH ether; GCA4; BEI FPD NIOSH #5037a 2 ppm — —

NIOSH MAM, 4th ed., 1994. NIOSH MAM, 2nd ed., vol. 3, 1977.

Esters of Carbonic and Orthocarbonic Acid, Organic Phosphorous, Monocarboxylic Halogenated Acids, Haloalcohols, and Organic Silicon Michael S. Bisesi, Ph.D., CIH II Esters of Carbonic and Orthocarbonic Acid

Filter; diethyl ether; GCFPD NIOSH #5038a —

Esters of Carbonic and Orthocarbonic Acid, Organic Phosphorous, Monocarboxylic Halogenated Acids, Haloalcohols, and Organic Silicon Michael S. Bisesi, Ph.D., CIH A. Overview The hypothetical hydration of carbon dioxide produces two compounds, carbonic acid, C(O)(OH)2, and orthocarbonic acid, C(OH)4. These acids have never been isolated, although they may be formed and exist in aqueous solution. However, numerous esterified derivatives have been prepared chemically. Only very few of them have been toxicologically investigated in great detail. The majority of toxicological data reported is limited range-finding studies. Organic carbonates are chemically RO(CO)OR, the ortho esters, RC(OR')3, whereby R may equal R' or consist of alkyl, alkenyl, cyclane, or aromatic moieties. These di- and triortho esters have similar physical properties; however, the latter resemble acetals more than carboxylates. The general toxicological impacts are also expected to be similar but nonsignificant, owing to the esters' low stability in acid solutions and their resemblance to normal mammalian metabolites. A summary of physical and chemical properties is found in Table 81.2 (5), and a summary of toxicological data is shown in Table 81.3 (6, 7). Table 81.2. Chemical and Physical Properties of Representative Esters of Carbonic and Ortho (5)

Compound

Boiling Point (° Melting Refractive Vapor a CAS Molecular C) Point (° Solubility Index (20° density No. Formula MW (mmHg) C) Density in Water C) (Air=1)

Dimethyl [616- C3H6O3 38-6] carbonate Diethyl [105- C5H10O3 58-8] carbonate Ethylene [96- C3H4O3 49-1] carbonate Propylene [108- C4H6O3 32-7] carbonate Triethyl [122- C7H16O3 orthoformate 51-0] Triethyl [78- C8H18O3 39-7] orthoacetate Triethyl [115- C7H20O3 orthopropionate 80-0]

90.08

89.7

3 1.0694

i/s/s

1.3687

118.13

127

–43 0.9752

i/s/s

1.3845

4.1

243 (740) 102.09 241.7

36.4 1.3218

d/v/v

1.4158

3.04

–55 1.2057

v/v/v

1.4189

148.20

146

–76 0.8909

d/s/s

1.3922

162.23

142

0.8847

i/v/v

1.3980

0.886

-/v/v

1.4000

88.06

176.26 155~160

a

Solubility in water: v = very soluble; s = soluble; d = slightly soluble; i = insoluble db: decomposes when dissolved; –68c and 84c: Freezing point (°C).

Table 81.3. Summary of Inhalation, Oral, Dermal, Subcutaneous, and Intraperitoneal Toxicity Data for Some Esters of Carbonic and

5.11

Orthocarbonic Acids

Compound Dimethyl carbonate

Mode or Route Chemical of Dose or Formula Entry Parameter Species Concentration Ref. C3H6O3 Oral

Inhale

LD100/2h

Mouse; rat Mouse; rat Guinea pig Rat

LD50

Rat

IP

LD50 LD50

Dermal LD50

Ethylene carbonate

C3H4O3

Oral

Propylene carbonate Triethyl orthoformate

C4H6O3

Dermal LD50 Oral LD50

Triethyl orthoacetate

C8H18O3 Oral

C7H16O3 Oral

LD50

0.8–1.6 g/kg

6

10 mL/kg

6

8000 ppm

6

10.4 g/kg

7

Rabbit 0.20 mL/kg

7

Rabbit 20 mL/kg

6

Rat

6

3.2–6.4 g/kg

LD50 LD50

Rat

12.8–25.6 g/kg 6

Guinea pig Rat; rabbit Rat; rabbit Rabbit

>10 mL/kg

6

6.4–12.8 g/kg

6

6.4–12.8 g/kg

6

>10 mL/kg

6

Dermal LD50 Triethyl C9H20O3 Oral orthopropionate IP

6

Guinea >10 mL/kg pig Rat 6.4–12.8 g/kg

Dermal LD50

IP

6.4–12.8 g/kg

LD50 LD50

Dermal LD50

6 6

Esters of Carbonic and Orthocarbonic Acid, Organic Phosphorous, Monocarboxylic Halogenated Acids, Haloalcohols, and Organic Silicon Michael S. Bisesi, Ph.D., CIH B. Carbonates 1.0a Dimethyl Carbonate 1.0.1a CAS Number: [616-38-6]

1.0.2a Synonyms: Carbonic acid dimethyl ester 1.0.3a Trade Names: NA 1.0.4a Molecular Weight: 90.08 1.0.5a Molecular Formula: C3H6O3 1.0.6a Molecular Structure:

1.0b Diethyl Carbonate 1.0.1b CAS Number: [105-58-8] 1.0.2b Synonyms: Carbonic acid diethyl ester 1.0.3b Trade Names: NA 1.0.4b Molecular Weight: 118.13 1.0.5b Molecular Formula: C5H10O3 1.0.6b Molecular Structure:

1.1 Chemical and Physical Properties 1.1.1 General Dimethyl carbonate is miscible with most acids and alkalis, soluble in most organic solvents, but insoluble in water. Diethyl carbonate is miscible with aromatic hydrocarbons, most organic solvents, and castor oil, but not with water. 1.1.2 Odor and Warning Properties Dimethyl carbonate has a pleasant odor. Diethyl carbonate has a weak odor resembling that of ethyl oxybutyrate. 1.2 Production and Use The compound diethyl carbonate is manufactured via a reaction of phosgene and ethanol to produce ethyl chlorocarbonate, followed by reaction with anhydrous ethanol. It is used as a solvent for nitrocellulose, in the manufacture of radio tubes, and for fixing elements to cathodes. 1.3 Exposure Assessment 1.3.3 Workplace Methods: NA 1.4 Toxic Effects 1.4.1 Experimental Studies 1.4.1.1 Acute Toxicity The undiluted dimethyl carbonate liquid has an oral LD50 in the rat and the mouse between 6.4 and 12.8 g/kg and an intraperitoneal LD50 in the range of 800 to 1600 mg/kg (6). Symptoms were weakness, ataxia with gasping, and unconsciousness. A dermal LD50 in the guinea pig was found to be greater than 10 mL/kg. Some weight loss was noted, and minimal skin absorption was suspected. However, the degree of irritation was relatively slight (6). Exposure by inhalation appeared relatively hazardous, since 8000 ppm

caused rapid onset of gasping, loss of coordination, frothing from the mouth and nose, and pulmonary edema with death of all rats in a period of 2 h. Diethyl carbonate is estimated to be moderately toxic via ingestion, dermal, and ocular contact. Intraperitoneally injected diethyl carbonate showed a slight neoplastic effect on the skin at the injection site in the mouse at about 11.4 mg, but not when administered orally at 12.5 mg (8). 1.4.1.2 Chronic and Subchronic Toxicity: NA 1.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Metabolically, the dimethyl and diethyl carbonates may possess alkylating properties similar to those of dimethyl and ethyl sulfate. 1.4.1.4 Reproductive and Developmental A teratogenic effect in 7.6–16.6% of 8-d pregnant hamsters was observed at a diethyl carbonate doses of 0.5–1.0 g/kg when injected intraperitoneally (9). 1.4.1.5 Carcinogenesis A study using male and female mice treated with 0, 50, 250, or 1000 ppm (0– 140 mg/kg/d) diethyl carbonate in drinking water indicated no carcinogenic effects (10).

Esters of Carbonic and Orthocarbonic Acid, Organic Phosphorous, Monocarboxylic Halogenated Acids, Haloalcohols, and Organic Silicon Michael S. Bisesi, Ph.D., CIH C. Cyclic Carbonates 2.0a Ethylene Carbonate 2.0.1a CAS Number: [96-49-1] 2.0.2a Synonyms: Ethylene carbonate, ethylene glycol carbonate, and 1,3-dioxolan- 2-one 2.0.3a Trade Names: NA 2.0.4a Molecular Weight: 88.06 2.0.5a Molecular Formula: C3H4O3 2.0.6a Molecular Structure:

2.0b Propylene Carbonate 2.0.1b CAS Number: [108-32-7] 2.0.2b Synonyms: Propylene carbonate and 4-methyl-1,3-dioxolan-2-one 2.0.3b Trade Names: NA 2.0.4b Molecular Weight: 102.09 2.0.5b Molecular Formula: C4H6O3

2.0.6b Molecular Structure:

2.2 Production and Use Used as intermediates in plastic industry. 2.3 Exposure Assessment 2.3.3 Workplace Methods: NA 2.4 Toxic Effects 2.4.1 Experimental Studies 2.4.1.1 Acute Toxicity A range-finding study using ethylene carbonate by Smyth et al. (7) has recorded an oral LD50 value of 10.4 g/kg in the rat and a dermal LD50 of .20 mL/kg for the rabbit. Inhalation of the concentrated vapor for 8 h caused no deaths in rats. It proved to be a very low irritant to the skin, but moderately irritating to the eye of the rabbit. From a range-finding study using propylene carbonate, an oral LD50 in the rabbit above 20 mL/kg was determined. Inhalation of the concentrated vapor for 8 h was not lethal to rats. The undiluted material was a slight irritant to the skin and a moderate irritant to the rabbit eye. 2.4.1.2 Chronic and Subchronic Toxicity: NA 2.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms The mechanistic toxicity of ethylene carbonate was determined to be similar to the toxicity of ethylene glycol (11). Ethylene carbonate is enzymatically metabolized to ethylene glycol, and an enzyme has recently been isolated (12). 2.4.2 Human Experience 2.4.2.2.3 Pharmacokinetics, Metabolism, and Mechanisms A dermal absorption study using living skin from human donors indicated that propylene carbonate had permeability constants of 0.7 > 0.4 g/m2/h and 0.6 > 0.3 cm3/m2/h (13).

Esters of Carbonic and Orthocarbonic Acid, Organic Phosphorous, Monocarboxylic Halogenated Acids, Haloalcohols, and Organic Silicon Michael S. Bisesi, Ph.D., CIH D. Ortho Acid Esters 3.1 Chemical and Physical Properties 3.1.1 General Triethyl orthoformate is a stable liquid, even in sunlight. Triethyl orthoacetate is liquid at ambient temperature. Triethyl orthopropionate is a highly soluble liquid. 3.3 Exposure Assessment 3.3.3 Workplace Methods: NA 3.4 Toxic Effects 3.4.1 Experimental Studies 3.4.1.1 Acute Toxicity Oral LD50 values in the rat between 3.2 and 6.4 mg/kg of triethyl orthoformate have been recorded (6). Symptoms of toxicity included dyspnea

and weakness. Conversely, a dermal LD50 in the guinea pig was found to be above 10 mL/kg, indicating that the material was practically not absorbed. No skin irritation was noted. The oral LD50 for triethyl orthoacetate has been documented (6) between 6.4 and 12.8 g/kg for the rat, the intraperitoneal LD50 even higher, as 12.8 to 25.6 g/kg. It is not absorbed through guinea pig skin, and a dermal LD50 was found to be above 10 mL/kg. A very low dermal irritation was observed. Similar to triethyl orthoacetate, the LD50 for triethyl orthopropionate ranges in the rat and rabbit are 6.4 to 12.8 g/kg by oral and intraperitoneal administration, and >10 mL/kg in the rabbit when tested dermally (6).

Esters of Carbonic and Orthocarbonic Acid, Organic Phosphorous, Monocarboxylic Halogenated Acids, Haloalcohols, and Organic Silicon Michael S. Bisesi, Ph.D., CIH III Esters of Organic Phosphorus Compounds

Esters of Carbonic and Orthocarbonic Acid, Organic Phosphorous, Monocarboxylic Halogenated Acids, Haloalcohols, and Organic Silicon Michael S. Bisesi, Ph.D., CIH A. Overview This class of esters includes phosphines, phosphinates, phosphonates, phosphites, and phosphates. The basic compound of the series is phosphine, PH3, which then is successively alkylated, oxygenated, and esterified. The progressive series then contains phosphines, R2PH or R3P, phosphine oxide, R2P(O)H or R3P(O), phosphinic acid esters, phosphinates, R2P(O)OR, phosphites, (RO)3P7, phosphonic acid esters, RP(O)(OR')2, and phosphites (RO)3P(O), where R and R' can comprise alkyl or aryl groups for any of these compounds. Some physical and chemical properties and characteristics are listed in Table 81.4 and toxicological information in Tables 81.5 (14–45) and 81.6. Table 81.4. Chemical and Physical Poperties of Selected Organic Phosphorous

Compound Tributyl phosphine

CAS No.

Molecular Formula

[998-403]

C12H27P

Boiling Point (° Melting Refractive V C) Point (° Solubilitya Index (20° d MW (mmHg) C) Density in Water C) ( 202.32 240~242

0.812

Triisooctyl phosphine Triphenyl phosphine Octyl O-butyl phosphinate Phenyl O-ethyl phosphinate Butyl phenyl O-allyl phosphinate O-Dimethyl phosphonate Methane Odimethyl phosphonate O-Ethyl propyl phosphonate Diisopropyl phosphonate Octyl Odibutyl phosphonate Dibutyl phenyl phosphonate Phenyl propyl 2-propynyl phosphonate Vinyl, bis(2chloroethyl) phosphonate Methyl ethyl chlorophenyl phosphonate Diisopropyl fluoro phosphonate Ethyl Omethyl O-pnitrophenyl phosphonate Ethyl O-ethyl O-pnitrophenyl phosphonate Methyl OisopropylO-pnitrophenyl phosphonate Ethyl O-

[1013888-2] [603-350]

C24H51P

370.64

C18H15P

262.29 377

80

1.132

i

1.6358

s

1.4128

C12H27O2P 234.32 [251109-3]

C8H11O2P

170.15

C13H19O2P 238.29 [868-859]

[2192196-0] [180920-7] [592967-9]

C2H7O3P

110.05 170.5

1.1029

C3H9O3P

124.08

1.1507

C5H13O3P

152.13 181

C6H15O3P

166.16 72~75 (10) C16H35O3P 306.42 C14H23O3P 222.31

[1870522-1]

C12H15O3P 238.22 C6H11Cl2O3P 233.03

[033232- C9H12ClO3P 234.62 85-8] [3323285-8]

C6H14FO3P 214.20

[2553601-3]

C9H12NO5P

[546-71- C10H14NO5P 259.22 4] [15536- C10H14NO5P 259.22 03-5] C11H16NO5P 273.25

245.19

0.997

1.4099

isopropyl O-pnitrophenyl phosphonate Isopropyl Oethyl O-pnitrophenyl phosphonate Isopropyl O[7284isopropyl O-p- 60-8] nitrophenyl phosphonate Pentyl O-ethyl [3015O-p75-6] nitrophenyl phosphonate Heptyl O-ethyl O-pnitrophenyl phosphonate Octyl O-ethyl O-pnitrophenyl phosphonate Ethyl O-phenyl O-pnitrophenyl phosphonate Phenylpropyl O-ethyl O-pnitrophenyl phosphonate Phenylbutyl Oethyl O-pnitrophenyl phosphonate Phenylvinyl Oethyl O-pnitrophenyl phosphonate O-ethyl propylphenyl O-pnitrophenyl phosphonate Ethyl butylphenyl Op-nitrophenyl Phosphonate [762-04Diethyl 9] phosphite Cyclic

C11H16NO5P 273.25

C12H18NO5P 287.28

C13H20NO5P 301.31

C15H24NO5P 329.37

C16H26NO5P 343.40

C14H14NO5P 335.32

C17H20NO5P 349.32

C18H22NO5P 363.35

C16H16NO5P 333.30

C17H20NO5P 349.32

C18H22NO5P 363.35

C4H11O3P C2H4O3P

138.10 50~51 (2) 107.72

1.0720

d

1.4101

ethylene phosphite Dibutyl [1809C8H19O3P 194.21 118~119 0.995 19-4] phosphite (11) 1.046 Trimethyl [121-45- C3H9O3P 124.08 111–112 –78 9] phosphite 0.97 Triethyl [122-52- C6H15O3P 166.16 156 1] phosphite 0.9417 Tripropyl [923-99- C9H21O3P 208.24 206–207 9] phosphite Triisopropyl [116-17- C12H21O3P 208.24 63~64 0.844 6] phosphite (11) Tributyl [102-85- C12H27O3P 250.32 118~125 –80 0.9259 2] phosphite (7) Triisosooctyl [25103- C24H51O3P 418.64 12-1] phosphite Br > Cl > F. According to Dixon (108), the lacrimatory mechanism may involve specific reactions of the halogen with certain enzyme-sulfhydryl groups. The ester groups appear to enhance this activity. The reaction appears to occur rapidly, is reversible at low and irreversible at very high concentrations in some tissues (109, 110). Some physical and chemical properties and characteristics are listed in Table 81.7 and toxicological information in Tables 81.8, 81.9, 81.10 (111–117) (118, 119). Table 81.7. Chemical and Physical Properties of Representative Esters of Monocarboxylic Ha Haloalcohols (5) Boiling Point (° Melting Refractive V a C) Point (° Solubility Index (20° D ( MW (mm Hg) C) Density in Water C)

CAS No.

Molecular Formula

Methyl chloroformate

[79-221]

C2H3ClO2

–61

1.223

db

1.3868

Ethyl chloroformate Propyl chloroformate Isopropyl chloroformate Allyl chloroformate Benzyl chloroformate Trichloromethyl chloroformate Chloroethyl chloroformate Methyl chloroacetate Ethyl chloroacetate

[54141-3] [109- C4H7ClO2 61-5] [108- C4H7ClO2 23-6] [2937- C4H5ClO2 50-0] [501- C8H7ClO2 53-1] [503C2Cl4O2 38-8] [627- C3H4Cl2O2 11-2] [96-34- C3H5ClO2 4] C4H7ClO2

–81

1.135

db

1.3947

1.0901

db

1.4035

122.55 104.6– 104.9 120.54 110

1.08

i

1.4013

1.14

i

170.60 103 (20)

1.20

db

1.5160

1.64

i

1.4566

1.3847

i

1.4465

–33

1.238

db

1.4218

–27

1.145

i

1.4125

Compound

94.50 70.4– 70.9 (752) C3H5ClO2 108.52 93 122.55 105

197.83 128 142.97 155.7– 156.0 108.52 131 122.55 144 (740)

–57

Butyl [590- C6H11ClO2 150.60 183 02-3] chloroacetate 2,4,5C8H4Cl4O2 273.93 Trichlorophenyl chloroacetate 2[5459- C7H9ClO4 192.60 Chloroallylidene 90-5] 3,3-diacetate chloroacetate Methyl [17639- C4H7ClO2 122.55 chloropropionate 93-9] Ethyl [535- C5H9ClO2 136.58 146–149 chloropropionate 13-7] 2-Chloro-3-(4C10H10Cl2O2 233.09 chlorophenyl) propionic acid methyl ester 2-Chloroethyl [2206- C5H7ClO2 134.56 51–53 89-5] acrylate Methyl C2H3FO2 78.04 40 fluoroformate Ethyl C3H5FO2 92.07 53–54 fluoroformate Methyl [453C3H5FO2 92.07 18-9] fluoroacetate Ethyl [459C4H7FO2 106.10 119.2 72-3] fluoroacetate (753) Propyl C5H9FO2 120.12 fluoroacetate Isopropyl C5H9FO2 120.12 fluoroacetate Allyl C5H7FO2 118.12 fluoroacetate 2-Chloroethyl C4H6ClFO2 140.54 fluoroacetate 2-Fluoroethyl C4H7FO2 106.10 acetate [105- C4H7BrO2 167.00 159 Ethyl 36-2] bromoacetate Ethyl 2-bromo- [535- C5H9BrO2 181.03 156~160 11-5] propionate Ethyl 2-bromo- [533- C6H11BrO2 195.06 177.5 68-6] butyrate (765) Ethyl [623C4H7IO2 214.00 178–180 48-3] iodoacetate a b c

1.0704

i

1.072

i

1.4297

i 1.06 –80

0.917

s

1.3597

1.5059

i

1.4489

1.394

i

1.4490

1.321

i

1.4475

1.098

–38c

1.808

Solubility in water: v = very soluble; s = soluble; d = slightly soluble; i = insoluble. Decomposes when dissolved. Freezing point (°C).

1.5079

Esters of Carbonic and Orthocarbonic Acid, Organic Phosphorous, Monocarboxylic Halogenated Acids, Haloalcohols, and Organic Silicon Michael S. Bisesi, Ph.D., CIH B. Chloroesters

Esters of Carbonic and Orthocarbonic Acid, Organic Phosphorous, Monocarboxylic Halogenated Acids, Haloalcohols, and Organic Silicon Michael S. Bisesi, Ph.D., CIH V. Organic Silicon Esters

Esters of Carbonic and Orthocarbonic Acid, Organic Phosphorous, Monocarboxylic Halogenated Acids, Haloalcohols, and Organic Silicon Michael S. Bisesi, Ph.D., CIH A. Overview The alkyl silicon esters can be classified into several categories, namely, the silanes, which are alkylsubstituted silicon tetrahydrides (R4S) and the next more highly oxygenated derivatives only, silanols (R3SiOR' R2Si(OR')3). Some silanols can be polymerized to form silicones of the type [RxSiO(4–x/2)]n. The most highly oxygenated compound is silicic acid and its esters, the silicates, which are chemically Si(OR)4. Some of these compounds are important industrial raw materials used to produce a variety of widely used end products, such as the silicones that serve as lubricating fluids, oil baths, resins, and plastic copolymers. The toxicological effects vary from inert to caustic, depending on the oxidation potential and the molecular size. Some chemical and physical properties and characteristics are listed in Table 81.11 and toxicological information in Table 81.12 (127–130). Table 81.11. Chemical and Physical Properties of Representative Esters of Organic

Compound

CAS No.

Molecular Formula

Boiling Point (° Melting Refractive a C) Point (° Solubility Index (20° MW (mmHg) C) Density in Water C)

Tetrachloro silane [10026Cl4Si 169.90 57.6 –70 1.483 04-7] Methyltrichloro [75-79- CH3Cl3Si 149.48 66 1.27 –77c 6] silane Dimethyldichloro [75-78- C2H6Cl2Si 129.06 70.0 –16 1.07 5] silane Ethyltrichloro [115C2H5Cl3Si 163.51 168 –105.6 1.2381 21-9] silane Diethyldichloro [1719- C4H10Cl2Si 157.12 128–130 –96.5 1.0504 52-5] silane Dimethyldiethoxy [78-62- C6H16O2Si 148.28 114 0.865 6] silane Methyltriethoxy [2031- C7H18O3Si 178.30 141–143 0.8925 67-6] silane 0.8594 Ethyltriethoxy [78-07- C8H20O3Si 192.33 158.9 9] silane Amyltriethoxy [2761- C11H26O3Si 234.41 198 0.889 24-2] silane Vinyltriethoxy [78-08- C8H18O3Si 190.31 160–161 0.903 0] silane Tri(2C6H13Cl3O3Si 267.61 chloroethoxy) silane Methyl silicate [681C4H12O4Si 152.22 121–122 –2°c 1.0232 84-5] Ethyl silicate [78-10- C8H20O4Si 208.30 168 –85 0.933 4] Hexamethyl [107C6H18OSi2 162.38 101 –59 0.764 46-0] disiloxane Dodecamethyl [141- C12H36O4Si5 384.84 229 –84c 0.8755 63-9] pentasiloxane (710) a b c

db db db d

1.4257

db

1.3835 i

1.3955

i, db i

1.3818

i

1.3925

Solubility in water: v = very soluble; s = soluble; d = slightly soluble; i = insoluble. Decomposes when dissolved. Freezing point (°C).

Table 81.12. Summary of Oral, Inhalation, and Contact Toxicity Data for Some Org Oral LC50

Species g/kg Species Compound Silane Methyltrichloro Rat 0.8 Dimethyldichloro Rat 0.8

LD50

g/kg

LD50

Inhalation (Rat)

Mortality Con Exposure or Species g/kg (ppm) (h) Effects Rat Rat

~0.06 ~0.06

Ethyltrichloro Diethyldichloro Trimethylethoxy Methyltrimethoxy

Rat Rat Rat Rat

0.8 2.0 9.33 12.5 Rabbit 10

Trimethylethoxy Rat

12.5 Rabbit 10

Dimethyldiethoxy Rat

Rat Rat

2.5

~1.0 ~0.6

2000 8

0/5 LC00

4000 8

4/5 LC80

500

Sl. inc. heart wt. 0/5 LC00

10 × 7

4000 8 2000 7 Methyltriethoxy

Rat

5.0

0/5 LC00

4000 8

4/5 LC80

125 250

5–30 × 7 Sl. effects 4–10 Wt. loss, renal and lung damage 500 3–5 × 5 d Decr. wt., renal effects, lung irrit. 1000 3 × 7 Decr. wt., other signs

Tetraethoxy

Amyltrimethoxy Amyltriethoxy

Rat Rat

4.92 Rabbit 10.0 19.6 Rabbit 7.13

Vinyltrimethoxy Vinyltriethoxy Tri(2chloroethoxy) Silicate Tetramethoxy

Rat Rat Rat

11.3 Rabbit 3.54 22.5 Rabbit 10.0 0.19 Rabbit 0.089 mL/kg

4000 4

1/6

Rat

0.7a 0.2– 0.4b

1000 8

4/5

Tetraethoxy

2-Ethylbutyl Silicones Siloxane Hexamethyldi-

Rat

Rat

19.7 Rabbit >10

Guinea >50e

Rat

0.9– 2000 4 3.5 4000 4 23– 88c 500d Several

3/5 5/5 None

2000d 1

None

None

pig Dodecamethylpenta- Guinea 40f pig a

Minimal lethal dose with renal damage. No-effect level. c Guinea pig and rat. d Guinea pig. e No symptoms. f 10–30 mL/kg have laxative effect 8 h post administration. b

Esters of Carbonic and Orthocarbonic Acid, Organic Phosphorous, Monocarboxylic Halogenated Acids, Haloalcohols, and Organic Silicon Michael S. Bisesi, Ph.D., CIH B. Silanes For comparative purposes, some physical properties and range-finding toxicological data are presented in Tables 81.11 and 81.12. Toxicological data show high oral and intraperitoneal toxicities for the methyl and ethyl chlorosilanes. Tetrachlorosilane, SiCl4, an irritant gas, has been used as a warfare agent and to prepare smoke screens (128). The chlorinated derivatives appear to be most toxic of this series, as shown with tri(2-chloroethoxy)silane, HSI(OCH2CH2Cl)3.

Esters of Carbonic and Orthocarbonic Acid, Organic Phosphorous, Monocarboxylic Halogenated Acids, Haloalcohols, and Organic Silicon Michael S. Bisesi, Ph.D., CIH C. Silanol Esters The silanol esters are commonly called silanes, but should more correctly be called silanates. They represent the basic raw materials for the commercial production of silicones. Range-finding toxicological data are shown in Table 81.12. Trimethylethoxysilane (ethoxytrimethylsilane), (CH3) 3SiOC2H5, is a liquid at ambient temperatures. Intraperitoneal injections of 1000 mg/kg tetramethoxysilane (TMOS), tetraethoxysilane (TEOS), tetrapropoxysilane (TPOS), and tetrabutoxysilane (TBOS) caused renal toxicologic effects in mice. TMOS and TEOS caused acute tubular necrosis; TEOS, TPOS, and TBOS caused elevated creatinine and blood urea nitrogen; and TMOS exposed mice died exhibiting cytolysis suggestive of spleen damage (131). Mice exposed via inhalation to 100 ppm TEOS 6 h/d, 5 d/wk, for 2–4 wk developed tubulo-interstitial nephritis (132). The mice exposed to 50 ppm TEOS for the same period did not develop nephritis; however, histopathological changes developed in their nasal mucosa. Dimethyldiethoxysilane (diethoxydimethylsilane), (CH3)2Si(OC2H5)2, is a liquid at ambient temperatures. A mixture of dimethyldiethoxysilane and glycerol has successfully been applied in the rabbit as a model for the

prevention of arterial wall and metabolic disorders (133). Amyltriethoxysilane (amyltriethoxysilanate), C5H11Si(OC2H5)3, is of relatively low toxicity.The vinyl triethoxy derivative appears in the same toxicity range.

Esters of Carbonic and Orthocarbonic Acid, Organic Phosphorous, Monocarboxylic Halogenated Acids, Haloalcohols, and Organic Silicon Michael S. Bisesi, Ph.D., CIH D. Silicates 16.0a Methyl Silicate 16.0.1a CAS Number: [681-84-5] 16.0.2a Synonyms: Tetramethyl orthosilicate, silicic acid tetramethyl ester; methyl orthosilicate, Tetramethoxysilane, tetramethyl silicate, and TMOS 16.0.3a Trade Names: Dynasil M 16.0.4a Molecular Weight: 155.22 16.0.5a Molecular Formula: C4H12O4Si 16.0.6a Molecular Structure:

16.0b Ethyl Silicate 16.0.1b CAS Number: [78-10-4] 16.0.2b Synonyms: Silicic acid tetraethyl ester 16.0.3b Trade Names: NA 16.0.4b Molecular Weight: 208.30 16.0.5b Molecular Formula: C8H20O4Si 16.0.6b Molecular Structure:

16.3 Exposure Assessment 16.3.3 Workplace Methods NIOSH Method S264 is recommended for determining workplace exposures to ethyl silicate.

Alkyl silicates, tetraalkyloxysilanes, are organic derivatives of hydrocarbons esterified with silicic acid of the type Si(OR)4. The methyl and ethyl silicates have industrial uses in protective coatings and as preservatives or waterproofing agents for stone and concrete. Range-finding toxicological data are shown in Table 81.12. Methyl silicate (tetramethyl orthosilicate; silicic acid tetramethyl ester), Si(OCH3)4, is a liquid under ambient conditions. Methyl silicate has been used in the ceramic industry for closing pores, including those in concrete and cement, for coating metal surfaces and as a bonding agent in paints and lacquers. It is of moderate toxicity, and under certain humid conditions effects progressive necrosis of the cornea. Ethyl silicate (silicic acid tetraethyl ester), Si(OC2H5)2, is a high-boiling liquid. Ethyl silicate is used as a preservative for stone, brick, concrete, and plaster. It is used in water, weather- and acidproofing processes, heat- and chemical-resistant paints, and protective coatings. Orally, the ethyl silicate is moderately toxic, but may be narcotic in high concentrations. Injected into the skin of the rabbit, it produced transient erythema, edema, and slight necrosis at the injection site (128). In the rabbit eye, it produced transient irritation (128). Inhalation of 400 ppm by rats for 7 h/d for 30 d caused mortalities and lung, liver, and kidney pathological effects. Under similar conditions, 88 ppm caused no effects. Inhalation exposure of the guinea pig to ethyl silicate revealed that humid air was related to more severe effects than dry air (130). 6.5 Standards, Regulations, or Guidelines of Exposure Both the ACGIH TLV and the NIOSH REL are 1 ppm for methyl silicate. The ACGIH TLV and the NIOSH REL for ethyl silicate is 10 ppm while the OSHA PEL is 100 ppm for ethyl silicate.

Esters of Carbonic and Orthocarbonic Acid, Organic Phosphorous, Monocarboxylic Halogenated Acids, Haloalcohols, and Organic Silicon Michael S. Bisesi, Ph.D., CIH E. Silicones (Siloxanes) 17.0a Hexamethyl Disiloxane (HMS) 17.0.1a CAS Number: [107-46-0] 17.0.5a Molecular Formula: C6H18OSi2 17.0.6a Molecular Structure:

17.0b Dodecamethylpentasiloxane 17.0.1b CAS Number: [141-63-9] 17.0.5b Molecular Formula: C12H36O4Si5 17.0.6b Molecular Structure:

The silicones, organopolysiloxanes, may be divided into the commercial materials, the fluids, and the resins, structurally R2[R2SiOn–1]n for the linear compounds. The final products are water repellent, insoluble in most solvents, and resistant toward oxidation and chemical attack (128). Silicones are used medically and for cosmetic prosthetic devices. In chronic feeding experiments, rats on HMS showed widespread systemic irritation. Rabbits injected intradermally with HMS showed irritation with edema and necrosis at the injection site (128). Siloxanes injected into the rabbit eye resulted in transient irritation with complete clearing after 48 h (128). When inhaled at 4400 ppm for 19–26 d, HMS caused slight depression in the rat and the guinea pig, with a very slight increase in rat liver and kidney weights (128). Silicone resins had no influence on health when fed for 94 d to rats, and did not result in irritation to the rabbit skin or eye or when injected into rats intraperitoneally (128). It has been postulated and reported in the literature, however, that implanted silicone prostheses may cause granulomas, lymphadenopathy, cancer, and various autoimmune diseases in humans (134–136). Other reports indicate, however, that a definite correlation has not yet been confirmed by scientific data (137, 138). Esters of Carbonic and Orthocarbonic Acid, Organic Phosphorous, Monocarboxylic Halogenated Acids, Haloalcohols, and Organic Silicon Bibliography

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132 K. Omae et al., Sangyo Eiseigaku Zasshi 37(1), 1–4 (1995). 133 J. B. Fourtillan and J. P. Dupin, Chim. Ther. 8(2), 207 (1973). 134 W. Kaiser and J. Zazgornik, Urologe, Ausgabe A 30(2), 302–305 (1991). 135 H. P. Frey, G. Emperie, and K. Exner, Handchir. Mikrochir. Plast. Chir. 24(4), 171–178 (1992). 136 T. Randall, J. Am. Med. Assoc. 268(1), 12–13 (1992). 137 H. Berkel, D. C. Birdsell, and H. Jenkins, N. Engl. J. Med. 326(25), 1649–1653 (1992). 138 F. Samdal et al., Tidssk. Nor. Laegeforen. 112(15), 1971–1973 (1992). Epoxy Compounds—Olefin Oxides, Aliphatic Glycidyl Ethers and Aromatic Monoglycidyl Ethers John M. Waechter, Jr., Ph.D., DABT, Lynn H. Pottenger, Ph.D., Gauke E. Veenstra, Ph.D. Introduction An epoxy compound is defined as any compound containing one or more oxirane rings. An oxirane ring (epoxide) consists of an oxygen atom linked to two adjacent (vicinal) carbon atoms as follows for the example compound, ethylene oxide:

The term alpha-epoxide is sometimes used for this structure to distinguish it from rings containing more carbon atoms. The alpha does not indicate where in a carbon chain the oxirane ring occurs. The oxirane ring is highly strained and is thus the most reactive ring of the oxacyclic carbon compounds. The strain is sufficient to force the four carbon atoms nearest the oxygen atom in 1,2epoxycyclohexane into a common plane, whereas in cyclohexane the carbon atoms are in a zigzag arrangement or boat structure (1). As a result of this strain, epoxy compounds are attacked by almost all nucleophilic substances to open the ring and form addition compounds. For example,

Among agents reacting with epoxy compounds are halogen acids, thiosulfate, carboxylic acids, hydrogen cyanide, water, amines, aldehydes, and alcohols. A major portion of this chapter presents information on the two olefin oxides, ethylene oxide and propylene oxide, which are produced in high volume and are largely used as intermediates in the production of the glycol ethers. In addition, these compounds are used in the production of several other important products (e.g., polyethylene glycols, ethanolamines, and hydroxypropylcellulose) and have minor uses as fumigants for furs and spices and as medical sterilants. The other olefin oxides discussed are used as chemical intermediates (e.g., vinylcyclohexene mono- and dioxide), as gasoline additives, acid scavengers, and stabilizing agents in chlorinated solvents (butylene oxide) or in limited quantities as reactive diluents for epoxy resins. The discussion of the toxicology of certain olefinic oxides may be pertinent to their respective olefin precursors. However, it must be pointed out that the olefinic precursors of these different oxides demonstrate widely varying degrees of toxicity in mammalian models, mostly attributable to pharmacokinetic/metabolism differences in metabolic conversion of olefins to their respective oxide metabolites. For example, chronic bioassay results range from repeated negatives (ethylene, propylene) to clear positives (butadiene). A major use of the glycidyl ethers discussed in this chapter are as reactive diluents in epoxy resin mixtures. However, some of these materials are also used as intermediates in chemical synthesis as well as in other industrial applications.

The concept that epoxides, through their binding to nucleophilic biopolymers such as DNA, RNA, and protein, can produce toxic effects is well established. However, the magnitude and nature of physiological disruption depend on the reactivity of the particular epoxide (2–4), its molecular weight, and its solubility (5), all of which may control its access to critical molecular targets. In addition, the number of epoxide groups present, the dose and dose rate, the route of administration, and the affinity for the enzymes that can detoxify or activate the compound may affect the degree and nature of the physiologic response. A key enzyme for epoxide detoxification is microsomal epoxide hydrolase (EH), which is widely distributed throughout the body, but it is organ, species, and even strain variant (6). It should be noted that mouse tissues have a much lower level of EH activity than human tissue; in fact, at least two strains of mice, C57BL/6N and DBA/2N, have no EH activity in their skins (7). Hence, the relevance of risk assessment based on the toxicity findings from studies of epoxides in mice is moot. Epoxy compounds may also be metabolized by the cytoplasmic enzyme glutathione-S-transferase (GST), which conjugates epoxides with its co-substrate, glutathione (GSH), leading to formation of 2-alkylmercapturic acids. This enzyme, because it is in the aqueous phase, may play a minor role in the detoxification of larger more lipophilic epoxides but is active against low-molecular-weight epoxides (8, 9). GST also exhibits organ, species, and strain differences in expression and activity as well as genetic polymorphisms. Acute toxic effects most commonly observed in animals have been dermatitis (either primary irritation or secondary to induction of sensitization), eye irritation, pulmonary irritation, and gastric irritation, which are found in these tissues after direct contact with the epoxy compound. Skin irritation is usually manifested by more or less sharply localized lesions that develop rapidly on contact, more frequently on the arms and hands. Signs and symptoms usually include redness, swelling, and intense itching. In severe cases, secondary infections may occur. Workers show marked differences in sensitivity. Most of the glycidyl ethers in this chapter have shown evidence of delayed contact skin sensitization, in either animals or humans. The animal and human data available on skin sensitization of epoxy compounds do not assist in determining the structural requirements necessary to produce sensitization, but do provide some practical guidance for industrial hygiene purposes. Specifically, of the alkyl glycidyl ethers, only the C8–C10 alkyl glycidyl ether appears to be a human sensitizer. Despite equivocal results in tests for delayed contact sensitization in guinea pigs, n-butyl glycidyl ether and cresyl glycidyl ether do produce dermal sensitization in some humans. Skin sensitization reactions can be elicited from much less agent than is required for an irritative response. Because this condition is difficult to treat, sensitized individuals may require transfer to other working areas. Animals exposed to vapors of gaseous or volatile epoxy compounds, primarily ethylene oxide and propylene oxide, have shown pulmonary irritation. Sequelae of this effect may include pulmonary edema, cardiovascular collapse, and pneumonia. However, this route of exposure is unlikely for some of the other epoxy compounds owing to their lower volatility. For those epoxy compounds for which repeat exposures have been conducted, respiratory epithelium or nasal mucosa (when inhalation was the route of exposure) and stomach (when given by gavage) appear to be the major target organs. In some cases liver and kidney have been target organs. These effects on the liver and kidney have been relatively nonspecific or adaptive, as indicated by an increased organ weight without accompanying histopathology. Exceptions include ethylene oxide, which caused renal tubular degeneration and necrosis in mice; vinylcyclohexene dioxide, which produced kidney tubule cell necrosis; n-butyl glycidyl ether, which produced liver necrosis; and phenyl glycidyl ether, which produced atrophic liver and kidney effects in rats. Ovarian toxicity and depression of hematopoesis have also been observed in laboratory animals for butadiene dioxide and vinylcyclohexene dioxide. Respiratory epithelium and nasal mucosa effects have been responses typical of irritation, such as flattening or destruction of epithelial cells. Although all of the compounds described in this chapter were mutagenic to bacteria (excluding

epoxidized glycerides) as well as positive in other in vitro genotoxicity assays, not all have produced genotoxicity in in vivo studies. Ethylene oxide was positive in the mouse micronucleus assay and mouse dominant lethal assay. In contrast, propylene oxide, although positive in all the in vitro assays in which it was tested, was negative in all of the in vivo mammalian assays where propylene oxide was administered via the relevant inhalation route. These negative mammalian studies include a mouse micronucleus assay (although positive by IP injection of high doses), mouse sperm cell analysis, and a rat dominant lethal assay. In addition, propylene oxide failed to cause chromosomal changes (SCE and chromosomal aberrations) in monkey lymphocytes following chronic exposures to 300 ppm. Other compounds showing positive or equivocal effects in vitro but negative effects in vivo are styrene oxide, and many of the glycidyloxy compounds used in epoxy resin formulations. There has been no evidence of teratogenicity for glycidyl ethers or olefin oxides, except ethylene oxide (EO), when tested by oral or inhalation exposure in conventional developmental toxicity studies. Fetal toxicity has been observed at maternally toxic doses for ethylene oxide, propylene oxide by inhalation in rats, and 1,2-epoxybutane by inhalation in rabbits. No evidence for fetal toxicity, in some instances even at maternally toxic doses, has been observed for phenyl glycidyl ether by inhalation in rats, 1,2-epoxybutane by inhalation in rats, or propylene oxide or styrene oxide by inhalation in rabbits. Additionally, repeated intravenous infusion of ethylene oxide was teratogenic in mice. Inhalation of extremely high levels of EO (600–1200 ppm compared to the ACGIH-recommended 8-h TWA–TLV of 1 ppm) in mice at the time of fertilization or early zygote development has led to fetal deaths or malformations in some survivors. However, no teratological effects have been demonstrated by inhalation exposures up to 150 ppm in rats or rabbits. A number of these epoxide compounds have been found to be carcinogenic in rodents, although there has been no clear epidemiologic evidence for cancer in the workplace. In rats and/or mice, many epoxy compounds produce a carcinogenic response in the tissues of first contact. These compounds include ethylene oxide, butylene oxide, propylene oxide, styrene oxide allyl glycidyl ether, phenyl glycidyl ether, and neopentyl glycol diglycidyl ether. A few of them, such as ethylene oxide, butadiene dioxide, and vinylcyclohexene dioxide, have produced tumors at sites other than the “portal of entry.”

Epoxy Compounds—Olefin Oxides, Aliphatic Glycidyl Ethers and Aromatic Monoglycidyl Ethers John M. Waechter, Jr., Ph.D., DABT, Lynn H. Pottenger, Ph.D., Gauke E. Veenstra, Ph.D. B. Glycidyl Ethers Epoxy Compounds—Olefin Oxides, Aliphatic Glycidyl Ethers and Aromatic Monoglycidyl Ethers Bibliography

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Epoxy Compounds—Aromatic Diglycidyl Ethers, Polyglycidyl Ethers, Glycidyl Esters, and Miscellaneous Epoxy Compounds John M. Waechter, Jr., Ph.D., DABT, Gauke E. Veenstra, Ph.D. Introduction The principal focus of this chapter is on the epoxy compounds frequently encountered in industrial use as uncured epoxy resins. These resins are marketed in a variety of physical forms from lowviscosity liquids to tack-free solids and require admixture with curing agents to form hard and nonreactive cross-linked polymers. They are in demand because of their toughness, high adhesive properties (polarity), low shrinkage in molds, and chemical inertness. It is the uncured resins that are of main interest to toxicologists, for a well-cured resin should have few or no unreacted epoxide groups remaining in it. The toxicology of the curing agents is not treated in this chapter. They are most frequently bi- or trifunctional amines, di- or tricarboxylic acids

and their anhydrides, polyols, and compounds containing mixed functional groups, such as aminols and amino acids, as well as other resins containing such groups (1). Some of the other epoxide compounds described in this chapter are used as reactive diluents in epoxy resin mixtures; others are of commercial importance for their multiple uses in the synthesis of other compounds (specifically, epichlorohydrin). As reactive diluents, monomeric epoxides are added to epoxy resins to reduce viscosity and modify the handling characteristics of the uncured materials. The epoxide functionalities of these diluents react with the resin curing agents in the same manner as the resin to become part of the finished polymer. Epoxy resins have found application as protective coatings, adhesives for most substrates (metals included), caulking compounds, flooring and special road paving, potting and encapsulation resins, low-pressure molding mixtures, and binding agents for fiber glass products. Uncured, they are used as plasticizers and stabilizers for vinyl resins. Epoxy resin coating formulations can generally be limited to one of three forms: solution coatings, high-solids formulations, and epoxy powder coatings. Solid epoxies are used in coating applications, as solid solutions or heat-converted coating. Solution coatings are often room-temperature applications, and typically there is little potential for vapor exposure. The potential clearly exists for skin contact during application of coatings of this type. Heat-converted coatings are usually applied and cured by mechanical means and exposure to vapors or contact with skin is minimal. Solid resins are used for other applications such as electrical molding powders and decorative or industrial powder coatings. For applications of this kind, exposure to vapors and dust can occur and is greatest during formulating and grinding. Considering that epoxides can react with nucleophiles, particularly basic nitrogens, one might expect the epoxides to react with cellular biomolecules such as glutathione, proteins, and nucleic acids, and indeed this has been demonstrated for some of these epoxide compounds. The nature and magnitude of these interactions with these biomolecules is most likely related to the toxicity and observed for any given molecule in this class of compounds. However, the potential for any epoxide to react with cellular nucleophilic biomolecules is dependent on several factors, including the reactivity of the particular epoxide, the dose and dose rate, as well as the molecular weight, and solubility, these latter two influencing access to molecular targets within the cell. In addition, the efficiency of metabolism via epoxide hydrolase or other metabolic routes of detoxication may significantly influence the toxicologic potential and potency of these materials. Epoxide hydrolase activity is widely distributed throughout the body, but it is organ, species, and even strain variant (2). The liver, testes, lung, and kidney have considerable epoxide hydrolase activity; the activities in the skin and gut, however, are considerably lower. In this regard it should be noted that mouse tissues have a much lower level of EH activity than does human tissue; in fact, at least two strains of mice, C57BL/6N and DBA/2N, have no EH activity in their skins (3). Therefore, it may be questioned if toxicity or treatment-related effects observed in dermal mouse studies are relevant for hazard evaluation. Epoxy compounds may also be metabolized by the cytoplasmic enzyme glutathione-S-transferase, which converts epoxides to 2-alkylmercapturic acids. This enzyme because it is in the aqueous phase, may play a minor role in the detoxification of large lipophilic epoxides, but is active against low-molecular-weight epoxides (4, 5). Due to differences in physio-chemical properties and the effectiveness and nature of the detoxification of these materials through metabolism, the toxicity of these compounds ranges from the highly active, electrophilic, low-molecular-weight mono- and diepoxides to the nontoxic and inert cured materials, which possess only a few epoxy groups per molecule. In general, the acute toxicity of epoxy resin compounds as observed in laboratory animals can be considered low; oral and dermal LD50 values generally range from about 2000 to greater than 10,000 mg/kg in rodents; there are not marked differences in acute toxicity among the structurally

diverse categories of epoxy resin compounds. The acute toxicity of low-molecular-weight epoxides such as epichlorohydrin and glycidol is significantly greater (oral LD50 values range from 90 to about 500 mg/kg). Lung irritation following inhalation or gastrointestinal irritation following gavage has also been observed in animals. It is generally difficult to achieve acutely toxic levels of epoxy compounds by dermal exposure. Usually the irritating properties of epoxy liquids or vapors limit significant exposure to produce systemic toxicity. Effects most commonly observed in animals have been dermatitis (either primary irritation or secondary to induction of sensitization), eye irritation, pulmonary irritation, and gastric irritation, which are typically found in the tissues that are the first to come into contact with the epoxy compound. In general, it appears that epoxy compounds of higher molecular weight (e.g., epoxy novolac resins and diglycidyl ether of bisphenol A) produce less dermal irritation than those of lower molecular weight. In some instances, liquid epoxy compounds splashed directly into the eye may cause pain and, in severe cases, corneal damage. Skin irritation is usually manifested by more or less sharply localized lesions that develop rapidly on contact, more frequently on the arms and hands. Signs and symptoms usually include redness, swelling, and intense itching. In severe cases, secondary infections may occur. Workers show marked differences in sensitivity. Devices made from epoxy resins have produced severe dermatitis when not properly cured and when in prolonged contact with the skin (6). Skin irritation also has been reported from exposure to epoxy vapors (7). Most of the epoxy compounds have the ability to produce delayed contact skin sensitization, although there are notable exceptions, such as the advanced bisphenol A/epichlorohydrin resins. The higher molecular weight of these resins may be responsible for the absence of dermal sensitization (8, 9). Skin sensitization reactions can be elicited from much less agent than is required for a primary irritation response. Because this condition is difficult to treat, sensitized individuals may require transfer to other working areas. Particular attention should be paid to vapors and fine airborne dusts. Animals exposed to vapors of epichlorohydrin have shown pulmonary irritation. Sequelae of this effect may include pulmonary edema, cardiovascular collapse, and pneumonia. However, this route of exposure is unlikely for many of these epoxy compounds owing to their low volatility. For the glycidyloxy compounds for which LC50s have been determined, it appears that none of these compounds can be considered highly acutely toxic by the inhalation route. For those epoxy compounds for which repeat dosing studies have been conducted, generally the liver, kidneys, respiratory epithelium or nasal mucosa (when inhalation was the route of exposure), and stomach (when given by gavage) appear to be the major target organs. Respiratory epithelium and nasal mucosa effects have been responses typical of irritation, such as flattening or destruction of epithelial cells. Disruption of hematopoesis, primarily leukopenia, has also been demonstrated in laboratory animals with a polyglycidyl ether of substituted glycerin and resorcinol diglycidyl ether, but similar changes have not been observed in workers as a result of occupational exposures. The testes have been found to a target organ for glycidol and epichlorohydrin. Glycidol was also embryotoxic in laboratory animals when administered by a route not relevant to occupational exposure (intra-amniotic injection). However, no developmental toxicity has been observed for any other compounds in this chapter where there are data available. In addition, a two-generation reproduction study in rats on the diglycidyl ether of bisphenol A also indicated that this material did not produce adverse effects on either male or female reproduction. There is evidence in rats from a National Toxicology Program study that glycidol produces neurotoxicity (10), and this finding suggests that glycidyl esters, if metabolized to glycidol, could have this effect. However, glycidyl ethers have shown no evidence of neurotoxic effects in numerous acute or repeated dosing subchronic studies in rodents. A recently completed neurotoxicity study of diglycidyl ether of bisphenol found no evidence of neurotoxic effects in rats dosed dermally.

Generally, in vitro genetic toxicity testing of the epoxide compounds has resulted in positive (genotoxic) responses; the majority of the studies of genotoxic potential have been carried out using bacteria. These results are not surprising because many of these compounds have been tested in strains TA1535 and TA100 of S. typhimurium or in other gene mutation assays that are specifically sensitive to base-pair substitution, Metabolic activation was not required for most of the epoxides, which showed mutagenic in these tests. Many other in vitro assays examining both gene mutation and chromosomal effects have been employed to test the epoxy compounds, including assays in E. coli, yeast, Chinese hamster ovary cells (CHO/HPGRT), mouse lymphoma cells, and cultured human lymphocytes; the results have usually been mixed or positive. Fewer epoxy compounds have been tested using in vivo assays for genotoxic effects, although some have been extensively studied. Glycidol was positive in the Drosophila sex-linked recessive lethal assay and mouse micronucleus assay and produced chromosomal aberrations in the bone marrow of mice dosed orally or intraperitoneally. Glycidaldehyde was positive in the Drosophila sex-linked recessive lethal assay. In contrast, epichlorohydrin, also a low-molecular-weight epoxy compound, was negative in both the mouse micronucleus test following intraperitoneal administration and the mouse dominant lethal assay following oral or intraperitoneal administration, although it was positive in many of the in vitro assays. Another compound showing positive or equivocal effects in vitro but negative effects in vivo is the diglycidyl ether of bisphenol A. Of the compounds in this chapter, four (resorcinol diglycidyl ether, epichlorohydrin, glycidaldehyde, and glycidol) were the subject of studies in which there was clear evidence of tumorigenic effects in rodents. Larger-molecular-weight glycidyloxy compounds such as castor oil glycidyl ether, the diglycidyl ether of bisphenol A, and advanced bisphenol A/epichlorohydrin epoxy resins have been negative in dermal bioassays. Epidemiology studies have not provided any evidence for an association between workplace exposure and cancer to any of the materials in this chapter.

Epoxy Compounds—Aromatic Diglycidyl Ethers, Polyglycidyl Ethers, Glycidyl Esters, and Miscellaneous Epoxy Compounds John M. Waechter, Jr., Ph.D., DABT, Gauke E. Veenstra, Ph.D. Aromatic Diglycidyl Ethers

Epoxy Compounds—Aromatic Diglycidyl Ethers, Polyglycidyl Ethers, Glycidyl Esters, and Miscellaneous Epoxy Compounds John M. Waechter, Jr., Ph.D., DABT, Gauke E. Veenstra, Ph.D. Polyglycidyl Ethers Table 83.1. Effects on the Hematopoietic System of Exposure to the Polyglycidyl Ether of Substituted Glycerin (161)

Route

Species

Dose (g/kg)

No. of Doses

Responsea

Respiratory

Rat

Intramuscular Rat

Saturated 50 (8 h vapors each) 0.10 6 0.20 6

Intramuscular Dog

0.2

Intravenous

0.2

Dog

Intravenous Rabbit 0.1 Percutaneous Rat 1.0 2.0 4.0

a

No effect noted

No effect Depression of WBC count and bone marrow nucleated cell count 2 Marked depression of WBC (1/week) count; neutropenia; leukocytosis; ulceration and abscess of injection site. 1 Progressive decline in WBC count Death from overwhelming infection 2 Decrease in total WBC 20 No effect 20 No effect 20 Depression of bone marrow nucleated cell count (only)

WBC, white blood cells.

Epoxy Compounds—Aromatic Diglycidyl Ethers, Polyglycidyl Ethers, Glycidyl Esters, and Miscellaneous Epoxy Compounds John M. Waechter, Jr., Ph.D., DABT, Gauke E. Veenstra, Ph.D. Glycidyl Esters

Epoxy Compounds—Aromatic Diglycidyl Ethers, Polyglycidyl Ethers, Glycidyl Esters, and Miscellaneous Epoxy Compounds John M. Waechter, Jr., Ph.D., DABT, Gauke E. Veenstra, Ph.D. Miscellaneous Epoxy Compounds Table 83.2. Summary of Acute Toxicity Data on Epichlorohydrin Route Oral

Species Rats

Dose 0.09 g/kg

Parameter of Toxicity LD50

a

Oral

Guinea pigs

0.178 g/kg

LD50

Oral

Mice

0.238 g/kg

LD50

Intravenous Rats

0.154 g/kg

LD50

Intravenous Mice

0.178 g/kg

LD50

Percutaneous Rabbits

0.88 ml/kg

LD50

Percutaneous Rats (3 applications) 0.5 mL/kg

LD50

Inhalation

Mice

2370 ppm

0/30a

Inhalation

Mice

8300 ppm

Inhalation

Rats

250 ppm (8 h)

20/20a LC50

Inhalation

Rats

500 ppm (4 h)

LC50

Inhalation

Guinea pigs

561 ppm (4 h)

LC50

Inhalation

Rabbits

445 ppm (4 h)

LC50

Inhalation

Rats (males)

3617 ppm (1 h)

LC50

Inhalation

Rats (females)

2165 ppm (1 h)

LC50

Number of deaths over the number of animals exposed.

Epoxy Compounds—Aromatic Diglycidyl Ethers, Polyglycidyl Ethers, Glycidyl Esters, and Miscellaneous Epoxy Compounds Bibliography

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Organic Peroxides Jon B. Reid, Ph.D., DABT Introduction A review of the literature for these compounds has resulted in very little new information. Consequently, the content of this chapter is drawn heavily from the previous authors, including the tables. The only compounds where there has been publishing activity are: dibenzoyl peroxide,

methyl ethyl ketone peroxide, t-butyl hydroperoxide, isopropylbenzene hydroperoxide, and peroxyacetic acid. A recent review compared the skin tumor promoting activity of different organic peroxides in SENCAR mice (especially t-butyl peroxide, dicumyl peroxide, and also dibenzoyl peroxide) (1). Much of this literature is, however, irrelevant to health. The introduction presented in the previous edition is entirely correct and relevant. Peroxides are highly reactive molecules due to the presence of an oxygen–oxygen linkage. Under activating conditions, the oxygen–oxygen bond may be cleaved to form highly reactive free radicals. These highly reactive radicals can be used to initiate polymerization or curing. Consequently, organic peroxides are used as initiators for free-radical polymerization, curing agents for thermoset resins, and cross-linking agents for elastomers and polyethylene. In some cases they can be used as antiseptic agents. These materials must be handled and stored with caution. If free radicals are formed during storage in concentrated form, an accelerated decomposition could result, leading to the release of considerable heat and energy. It has been determined that decompositions of commercially available peroxides are generally low-order deflagrations rather than detonations (2). There have been several investigations into the types of physical hazards represented by organic peroxides (2–5). These compounds may possess the combination of thermal instability, sensitivity to shock, and/or friction, as well as flammability. Organic peroxides tend to be unstable, with the instability increasing with greater concentrations. Because of their instability, many peroxides are stored/handled in inert vehicles (6). It has been shown by Tamura (3) that the ignition sensitivity and the violence of deflagration for each organic peroxide may have a tendency to increase with increasing active oxygen content among the same type of organic peroxide, with a few exceptions. The ignition sensitivity and the violence of deflagration for each type of organic peroxide may decrease in the following order, given the same active oxygen content: diacyl peroxides > peroxyesters > dialkyl peroxides > hydroperoxides (3). Basically only acute health testing has been performed on organic peroxides. Exposures should be well controlled, primarily owing to the decomposition or deflagration hazard of the organic peroxide. The health data presented in Tables 84.1–84.9 were collected and furnished by the Organic Peroxide Producers Safety Division of the Society of the Plastics Industry to the previous authors of this chapter and are presented again in this edition. This represents an effort by industry to evaluate their products and provide that information to the public. Most of the information in the table has been previously published (7) in an industry bulletin. The analytic method should also be specific for each organic peroxide. NIOSH has fully validated a high-performance liquid chromatography/ultraviolet light method for benzoyl peroxide (8). Very few of the other organic peroxides have fully validated analytic methods. One of the first conventional methods to determine concentrations of organic peroxides was the titration of iodine from sodium iodide. However, it was not specific for organic peroxides. The polarographic method came into use with the visible-recording polarograph because hydroperoxides could be distinguished from other peroxides. This method could identify the functional groups and also quantify mixtures. Di-t-butyl peroxide is an exception because it is not reduced polarographically (9). Many analytical methods that have not been subjected to review by consensus standard organizations or regulatory agencies are in use. Some examples include gas chromatography (dialkyl peroxides such as di-t-butyl peroxide), high-pressure liquid chromatography (peroxyketals), and iodometric titration (peroxyesters, diacyl peroxides, hydroperoxides, and peroxydicarbonates). Some degree of selectivity in iodometric titrations may be obtained by variation of the reducing agent employed and the reaction conditions.

Organic Peroxides Jon B. Reid, Ph.D., DABT A. Peroxydicarbonates Table 84.1. Toxic Properties of Peroxydicarbonates (7)*

Peroxydicarbonate

CAS No.

Diisopropyl [105-64-6] peroxydicarbonate 100% 30% in toluene

LC50, Oral Dermal Primary Salmonella LD50 LD50 Skin Eye ppm typhimuriu (mg/kg) (mg/kg) Irritationa Irritationa (mg/L)b Assay

2140 3720

45% in Soltrol 8500 130 45% in 6500 cyclohexane-benzene Di-n-propyl [16066-38-9] peroxydicarbonate 100% 3400

2025 1.7c 4.0c

>6800

Mod. irritant Ext. irritating V. severe irritant V. severe irritant

Ext. irritating Mod. irritating Irritant

Ext. irritating Ext. irritating

Ext. irritating Ext. irritating

Irritant

85% in 4600 methylcyclohexane Di-sec-butyl [19910-65-7] peroxydicarbonate 100% 7600

3500

75% in odorless mineral spirits

Not toxic at 2000d 1200

Irritant

Not toxic at 2000d

Irritant

>4640

75% in Soltrol 9300 130 Di-(2-ethylhexyl) [16111-62-9] peroxydicarbonate 97% min

75% in Soltrol 130 40% in Soltrol

1020 20,800

Irritant gas

>22.7 (>0.19) 1 h >1433 (>12) 1 h

172 ppm— no adverse effects (1 h)

130 40% in dimethyl 3690 phthalate Di-(4-t[15520-11-3] >5000 butylcyclohexyl) peroxydicarbonate Di-n-butyl [16215-49-9] peroxydicarbonate 50% in aromatic10c free mineral spirits Di-(3-methylbutyl) [4113-14-8] peroxydicarbonate 20% in white spirits

Diacetyl peroxydicarbonate 75% wet Di-(2phenoxyethyl) peroxydicarbonate Di-(2-chloroethyl) peroxydicarbonate Di-(3-chloropropyl) peroxydicarbonate Di-(4-chlorobutyl) peroxidicarbonate Di-(2-butoxyethyl) peroxidicarbonate * a b

[26322-14-5] 5000

Not an irritant

1.7 ppm— no toxic signs; slight nose irritation Not an irritant

[6410-72-6] 4000400 [34037-78-0] 1500 [14245-74-0] 5200 [6410-72-6] 4000

*All studies used rats. V = Very; ext = extremly; mod = moderately. All LC50 tests lasted 4 h unless noted otherwise.

c

LD50 reported in ml/kg.

d

According to the Federal Hazardous Substances Act.

B. Diacyl Peroxides

Negative

V. servere Slight irritant irritant

[41935-39-1] >20,000 >20,000

Organic Peroxides Jon B. Reid, Ph.D., DABT

Not an irritant

Not an irritant

Negative

Mild irritant

Negative

Table 84.2. Toxic Properties of Diacyl Peroxides (7)*

Diacyl peroxide

Oral Dermal Primarry LD50 LD50 Skin Eye CAS No. (mg/kg) (mg/kg) Irritation Irritation

Dibenzoyl proxide [94-36-0] 78% wet

Not toxic at 5000b

Di-(2,4[133-14-2] dichlorobenzoyl) peroxide 50% in silicone >12.918 >8000 fluid Di-p[94-17-7] 500(IP) chlorobenzoyl peroxide Di-(2[3034-79-5] methylbenzoyl) peroxide 78% wet >5000 Didecanoyl [762-12-9] >5000 peroxide Dilauroyl peroxide [105-74-8] >5000b

Diacetyl peroxide [110-22-5] Diproprionyl [3248-28-0] peroxide22.7% in white spirits

Di-n-octanoyl peroxide

[762-16-3]

Not an irritant

LC50 (mg/L)a

Not >24.3 irritanting (5 min wash) Strongly irritating, but not corrosive (24 h wash)

Salmonella typhimurium Assay (Unle Specified) Negative

Negativec

Not an irritant Negativec

Severe irritant Mod. irritating Not an irritant

Irritant Negative (unwashed) Slight Negative irritation Not an Toxic at NegativeNegat irritant 200 RTECSmoderatef Severe Saturated— Negative 1.5 h—all animals died; 100 ppm— nose and eye irritation, respiratory difficulty, 1 death Severe Slight Negative irritation irritation

50% in Shellsol >5000 T Di-(3,5,5[3851-87-4] trimethylhexanoyl) peroxide 75% in 12.7e isododecane

* a

Very Irritant sereve irritation

Negative

All studies used rats. All LC50 tests lasted 4 h unless noted otherwise.

b

According to the Federal Hazardous Substances Act. Tumor cell growth assay. f Registry of Toxic Effects of Chemical Substances Classified it as moderate irritant. d Mouse lymphoma forward mutation assay, with/without metabolic activation. e LD reported in mL/kg. 50 c

Table 84.3. Toxic Properties of Peroxyesters (7)*

Peroxyester

CAS No.

Primary Oral LD50 Dermal Skin (mg/kg) LD50 Irritation

Eye Irritation

LD50 (mg/L)

a

Salm Assay

t-Butyl peroxyacetate [107-71-1] 2562

75% in OMSc 70% in benzene (mice) 50% in Shellsol T t-Butyl peroxypivalate

Irritant

6.1

450 (8 hr) [927-07-1] 4169–4640 2500

Mod to severe

Not an irritant 7.79

4270

Not an Not an irritant >9.5 irritant Not an Slight >.26 irritant or irritation sensitizer

[29240-17-3]

75% in OMSc t-Butyl peroxybenzoate

Slight irritant

1900

75% in OMSc t-Amyl perioxypivalate

4757

[614-45-9]

Mice t-Butyl peroxy-2[3006-82-4] ethylhexonate t-Amyl peroxy-2[686-31-7] ethylhexonoate t-Butyl peroxy-3,5,5- [13122-18-4] trimethylhexanoate

>2000

3639–4838 3817

914–2500 >10,000 16,818 Not an Not an irritant 42.2 irritant >5000 >2000 Slightly Not an irritant irritating d Mod. to Not an irritant >0.8 17.4 severe

Slightl positiv

Negati

t-Butyl peroxyneodecanoate 50% Shellosol T

[26748-41-4] >12,918

t-Butyl peroxy-2[34443-12-4] >5,000 ethylhexylcarbonate t-Butyl peroxycronate [23474-91-1] 4100 t-Amyl peroxybenzoste Cumyl peroxyneodecanoate 90%

>8000

Mod. to Not an irritant 50.0 severe >2000 Mildly Not an irritant irritating Moderate irritant

[4511-39-1]

Negati

[26748-47-0] 5126

>7940

Not an irritant

20.2

12,918 (2ethylhexonoylperoxy) hexane Di-t-butyl [16580-06-6] diperoxyazelate >5000 75% in OMSc 1,1,3,3[59382-51-3] Tetramethylbutyl peroxyphenoxyacetate 30% in Shellosol T >12.0d c (OMS ) t[2372-21-6] 5.0d Butylperoxyisopropyl carbonate t-Butyl [1931-62-0] 16(Ip) monoperoxymaleate Di-t-butyl [15042-77-0] 128 (Ip) diproxyphylate Cumyl [130097-36-8] ~5000 peroxyneoheptanoate [104852-44-0]

>8000 Not an irritant

>2000

*

Severe irritant

Not an irritant

Severe irritant

Not an irritant >24 ppm

>10,000 Not an irritant

75% in OMSc

All studies used rats unless otherwise specified.

>20.4 slight dyspnea, eye squint and wt. loss Not an irritant >800

Mildly irritating

Conjunctivitis

a

All LC50 test lasted 4 h unless noted otherwise.

b

±CHO indicates a positive or negative finding in Chinese hamster ovary cells. The following +/– indicating with/without metabolic activation. ±ML indicates a positive or negative finding in the mouse lymphoma forward mutation assay. c Odorless mineral spirits. d LD reported in mL/kg. 50

Organic Peroxides Jon B. Reid, Ph.D., DABT C ketone peroxides Table 84.4. Toxic Properties of Ketone Peroxides (7)*

Ketone Peroxide Methyl ethyl ketone peroxide OPPSD composite

CAS No. [1338-23-4]

Acetyl acetone peroxide

Positive >500 200 irritant Irritant 4000

Negativ

Irritant 200 ppm Corrosive 17

Very severe irritant Not an irritant

Sereve irritant

Very severe irritant

Severe irritant

Very severe irritant

Very severe irritant Severe irritant

Severe irritant

33 1.5

Negativ

Not a hazard at 13.1 mg/L for 1 h 0.54 Negativ

1,1[2699-11-9] Dihydroperoxycyclohexane 21% in DMPb Cyclohexanone peroxide

1.08d [12262-58-7]

Slightly positive

Di-(1-hydroxycyclohexyl) [2699-12-9] peroxide 100% (mice) 900 850 60% in DBPc (mice) 1-Hydroperoxy-1hydroxydiclohexyl peroxide 100% (mice)

[78-18-2] 880 740

c

60% in DBP (mice) * a b

Irritating Irritating

Irritating Irritating

All studies used rats unless otherwise specified. All LC50 tests lasted 4 h unless noted otherwise.

d

DMP dimethyl phthalate. LD50 reported in ml/kg.

c

DBP dibutyl phthalate.

Organic Peroxides Jon B. Reid, Ph.D., DABT D. Dialkyl Peroxides Table 84.5. Toxic Properties of Dialkyl Peroxides (7)*

Dialkyl Peroxide

CAS. No

Di-t-butyl peroxide [110-05-4]

Oral Dermal Primary LD50 LD50 Skin Eye (mg/kg) (mg/kg) Irritation Irritation >25,000

Mice

>20.0b >10,000

Mice

>50.0b >32,000 4100

2,5-Dimethyl-2,5di-(t-butylperoxy) hexane 2,5-Dimethyl-2,5di-(t-butylperoxy) hexyne-3 In dodecane 90%

[78-63-7]

Not an irritant

Not an irritant

LC50a >4103 ppm

[1068-27-5] >7680

Moderate irritatant Not an irritant

Nontoxicc

Sa typ

Ne

Dicumyl peroxide 96% min

[80-43-3] 4100

Dust from 40% on Filter 20% in corn oil 50% in corn oil

Ne

Mild irritation, no sensitizer 2.24 mg/L no effect (6 h)

~4000 Mild (unwahed) conjuctivities

a,a'-Bis(t[25155-25-3] butylperoxy) [2781-00-2] diisopropylbenzenes 96% min >23,100

Slight Minimal irritation, irritation not a sensitizer

>6000 ppm— Ne vapor >180 mg/m3—dust >180 mg/m3—dust

Mice t-Butyl cumyl peroxide 92% 4-(t-Butylperoxy)4-methyl-2pentanone * a

>4500 [3457-61-2] 5.18b [26394-04-7] 3949

Severe irritant >20,000

Not an >140 ppm irritant (1.2 mg/L) Slight >2.3 mg/L (1 h) irritation (unwashed)

Ne

All studies used rats unless rats unless otherwise specified. All LC50 tests lasted 4 hr unless noted otherwise.

b

LD50 reported in ml/kg.

c

According to the Fedral Hazardous Substances Act.

Organic Peroxides Jon B. Reid, Ph.D., DABT E. Peroxyketals Table 84.6. Toxic Properties of Peroxyketals (7)*

Peroxyketal

LC50 Oral Dermal Primary Salmonella LD50 LD50 (mg/L) typhimurium Skin Eye a CAS No. (mg/kg) (mg/kg) Irritation Irritation Assay

1,1-Di-(t[6731-36-8] butylperoxy)-3,3,5Trimethylcyclohexane >12,918 >8000

75% in DBPb

Not an irritant

~800

Not an irrtation

>207.2

1,1-Di(t-butylperoxy) [3006-86-8] cyclohexane 16,653

Not an irritant

50% in DBPb

23.2c

50% in mineral oil

>30.0c

Mod. Slight >2.42 irritating irritation Slight irritation

65% in DBPb 2,2-Di(t-butylperoxy) [2167-23-9] butane

n-Butyl 4,4-di-(t[995-33-5] butylperoxy)valerate 40% in chalk >5000 2,2-Di-(cumylperoxy) [4202-02-2] propane 50% in odorless 11.5c mineral spirits * a b c

Not an irritant

Slight irrtation

Severe irritant

Not an irritant

Negative

Negative

All studies used rats. All LC50 tests lasted 4 h unless noted otherwise. Dibutyl phthalate. LD50 reporterd in mL/kg.

Organic Peroxides Jon B. Reid, Ph.D., DABT F. Hydroperoxides Table 84.7. Toxic Properties of Hydroperoxides (7)*

Hydroperoxide t-Butyl

CAS No. [75-91-2]

Oral Dermal Primary Salmone LC50, ppm LD50 LD50 typhimur Skin Eye (mg/kg) (mg/kg) Irritation Irritation (mg/L)a Assay

Hydroperoxide 70%

560

80% 20% di-tbutyl peroxide a-Cumyl [80-15-9] hydroperoxide 80–83% in corn oil

406

Extreme irritant >10,000 Irritating

0.5b

800–1600 >200

73% 382 1-Phenylethyl [3071-32-7] hydroperoxide 30% in 800 1700 ethylbenzene 1,1,3,3[5809-08-5] 0.92b Tetramethylbutyl hydroperoxide 1,2,3,4-Tetrahydro- [771-29-9] 250 1-naphthyl (unk.route hydroperoxide in mice) 1-Vinyl-3[3736-26-3] 1440 cyclohexen-1-yl hydroperoxide Diisopropylbenzene [26762-93-6] hydroperoxide 53% 6200

p-Menthyl Hydroperoxide 55%

* a b

Severe irritation corrosive (DOT) Irritating

Severe irritant Very severe irritant

Extreme 502 (1.85) irritant Irritant 500

Irritant

700 (4.3) (6 h)

Irritating 220

Severe irritant Very severe irritant

Severe Severe irritation irritant (immidiate) corrosive (DOT)

Positive ( text)

Inconclus

20–33 mg/L >480 (2.85) Negative

4.5 mg/L (6 h)

[26762-92-5] 3700

Severe Severe 9.2 mg/L irritation irritation (6 h) (immediate) corrosive (DOT)

Positive

All studies used rats. All LC50 tests lasted 4 h unless noted otherwise. LD50 reported in mL/kg.

Table 84.8. Toxic Properties of Peroxyacids (7)*

Salmonella

Peroxyacids

Oral LD50 CAS No. (mg/kg)

Peroxyacetic acid [79-21-0] 100% 1540 40% in acetic 1230 acid p[943-39-5] Nitroperoxybenzoic acid *

Dermal LD50

Primary Skin Eye Irritation Irritation

1410 mg/kg 0.71 mL/kg Severe irritant

typhimurium Assay (Unless Specified)

LC50 (ppm)

Negative Severe irritant

>50010010,000 No toxic Inflammation 0.68 (9 mg/L) signs ~2.5 >10,000 No toxic Slight signs irritation 0.006–0.009 mg/L

All studies used rats. All LC50 tests lasted 4 h unless noted otherwise.

Organic Peroxides Jon B. Reid, Ph.D., DABT G. Sulfonyl Peroxides 75.0 Acetyl Cyclohexanesulfonyl Peroxide 75.0.1 CAS Number: [3179-56-4]

>22.3

75.0.2 Synonyms: NA 75.0.3 Trade Names: NA 75.0.4 Molecular Weight: 222.2 75.0.5 Molecular Formula: C8H14O5S 75.0.6 Molecular Structure:

75.1 Chemical and Physical Properties 75.1.1 General No information was located for this compound. 75.2 Production and Use No information was located for this compound. 75.3 Exposure Assessment 75.3.1 Air No air collection method or analytic method was located for this compound. 75.4 Toxic Effects The only toxicity data found for acetyl cyclohexanesulfonyl peroxide were as follows (7): It had an oral LD50 of >4640 mg/kg, a dermal LD50 of >2000 mg/kg, and was classified as an eye irritant. At a concentration of 29% in dimethyl phthalate, its oral LD50 was 1710 mg/kg. An acute inhalation study was performed exposing 40 rats to 25, 50, 100, and 200 mg/L of this chemical. At the lowest concentration, 25 mg/L, bloody nasal discharge and congested lungs were noted. One death was noted. The LC50 was judged to be 58.3 mg/L with 95% confidence limits of 46–74 mg/L (159).

Organic Peroxides Jon B. Reid, Ph.D., DABT H. Silyl Peroxides

Organic Peroxides Bibliography

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Property CAS Number

Ethylene Glycol [107-21-1]

Diethylene Glycol [111-46-6]

Triethylene Glycol [112-27-6]

Propylene Glycol [57-55-6]

Molecular formula

C2H6O2

C4H10O3

C6H14O4

C3H8O2

Molecular weight Specific gravity (25/4°C) Boiling point, °C (760 mmHg) Freezing point, °C Vapor pressure, mmHg (25°C) Refractive index (25° C) Flash point, °F (o.c.) Percent in saturated air (25°C)

62.07 1.11

106.12 1.12

197.4

245

150.1 76.1 1.125 (20/20° 1.033 C) 287.4 187.9

–13.4 –8.0 0.06 (20°C) 3800 mg/kg (rat) and >7940 mg/kg (rabbit), respectively (Monsanto, Younger Laboratories, 1975). An oral LD50 was also determined in rabbits and was in the range 7500 to 8750 mg/kg (Monsanto, Scientific Associates, 1974). It was practically nonirritating in rabbit eye and skin irritation studies (Monsanto, Younger Laboratories, 1975). In a delayed contact sensitization assay in guinea pigs (modified Buehler), challenges from 0.5% and 2% petrolatum formulations elicited positive responses (118). A strong positive response was also reported in a Magnusson–Kligman guinea pig sensitization assay (119).

Dietary administration for 4 weeks to rats at levels of up to 2500 ppm reduced body weight increments in males at levels above 1500 ppm and in females at 2000 ppm and above. Increased liver weights were observed in all treated groups. 2-Mercaptobenzothiazole was administered by gavage (diluted in corn oil) to rats and mice of both sexes for 13 weeks at dosages up to 3000 mg/kg in rats and 1500 mg/kg in mice. Mortality was noted in rats at 3000 mg/kg and in mice at dosages of 750 mg/kg and above. Reduced body weight gains were noted in rats and mice at 750 mg/kg and above. Necrosis of the renal distal convoluted tubular epithelium was seen in rats at 3000 mg/kg (Monsanto, Monsanto Environmental Health Laboratory, 1988). 2.4.1.4 Reproductive and Developmental In a rat teratology study 2-mercaptobenzothiazole was administered to pregnant rats on days 6 to 15 of gestation at dosages of 300, 1200, and 1800 mg/kg. Signs of maternal toxicity were seen at 1200 mg/kg and above. There were some equivocal intergroup differences in postimplantation loss, but these are unlikely to be of toxicological significance. 2-Mercaptobenzothiazole was also administered to pregnant rabbits on days 6 to 18 of gestation at dosages of 50, 150, and 300 mg/kg. Signs of maternal toxicity were seen at 300 mg/kg. There were no indications of fetal or developmental toxicity at any dosage (Monsanto, Springborn Laboratories, 1991). In a two-generation reproduction study in rats, parental animals received diets that contained 2500, 8750, or 15,000 ppm from the premating period through gestation and weaning. Body weights of F1 pups were reduced at 8750 ppm and higher; similar effects were noted in all groups from day 14 of lactation in all treatment groups in the F2 generation. Reproductive indexes were unaffected by treatment at any level. Renal changes (pigmentation of proximal convoluted tubules and kidney weight increases) were seen at 8750 ppm and above in both the F0 and F1 animals. Hepatocyte hypertrophy in both sexes was seen at 8750 ppm and above in the F1 generation, which was accompanied by hepatomegaly at 8750 ppm and higher in males and at 15,000 ppm in females (Monsanto, Springborn Laboratories, 1981). 2.4.1.5 Carcinogenesis Some evidence of carcinogenicity was reported in male (increased incidences of preputial and adrenal tumors) and female F344 rats (increased pituitary and adrenal tumors). No increased tumor incidences were seen in either male or female B6C3F1 mice (Monsanto, 1993). 2.4.1.6 Genetic and Related Cellular Effects Studies 2-Mercaptobenzothiazole was not mutagenic in Ames S. typhimurium, S. cerevisiae, L5178Y mouse lymphoma, CHO/HPRT, mouse micronucleus, or dominant lethal assays (Monsanto, Bionetics, 1976; Monsanto, Pharmakon Research International, 1986; Monsanto, Litton Bionetics, 1986; Monsanto, Springborn Laboratories, 1991). 2.4.1.7 Other: Neurological, Pulmonary, Skin Sensitization In an acute neurotoxicity evaluation in rats at dosages of 500, 1250, and 2750 mg/kg, responses to treatment were confined to nonspecific effects such as decreased motor activity, salivation, and decreased vocalization. Motor activity testing and a functional observation battery indicated that the responses were likely to be related to nonspecific effects (Monsanto, Bio-Research Laboratories, 1991). 2.4.2 Human Experience There was no evidence of primary skin irritation or delayed-contact skin sensitization following a repeated insult patch test in 50 human volunteers (Monsanto, Product Investigations, 1976). Skin sensitization reactions have been reported in humans repeatedly exposed to rubber articles containing 2-mercaptobenzothiazole (120). Positive reactions to 2mercaptobenzothiazole or 2-mercaptobenzothiazole mixtures containing other sulfur rubber accelerators have also been reported (121, 122). Individuals that responded to 2mercaptobenzothiazole often responded to other rubber additives, although similar cross-reactions were not seen by other investigators (123, 124). 3.0 N-Isopropyl-2-benzothiazolesulfenamide 3.0.1 CAS Number: [10220-34-5] 3.0.2 Synonyms: N-(1-methylethyl)-2-benzothiazolesulfenamide; N-isopropylbenzothiazol-2sulfenamide 3.2 Production and Use

N-Isopropyl-2-benzothiazolesulfenamide is a solid material used as an accelerator in rubber vulcanization. 3.4 Toxic Effects 3.4.1 Experimental Studies 3.4.1.1 Acute Toxicity The acute oral and dermal toxicity is low; LD50 values are >7940 mg/kg (rat) and >7940 mg/kg (rabbit), respectively. Exposure of a group of six rats for 1 h to a nominal concentration of 200 mg/L did not cause any mortality (Monsanto, Younger Laboratories, 1975). Slight eye irritation but no skin irritation were noted in rabbit irritation studies (Monsanto, Younger Laboratories, 1975). Oral administration for 3 months to rats of both sexes at 0, 10, 50, 125, or 500 mg/kg/day reduced body weight gains in males at 500 mg/kg and increased liver weights in females at the same level. There was no other evidence of systemic toxicity, and microscopic examination of the livers from female animals did not provide any corroborative evidence for an adverse effect on the liver of females at the high dosage (Monsanto, Monsanto Environmental Health Laboratory, 1988). 3.4.1.6 Genetic and Related Cellular Effects Studies No evidence of genotoxicity was found in an Ames S. typhimurium assay with and without metabolic activation, an in vitro cytogenetics assay in Chinese hamster ovary cells with or without metabolic activation, or in an in vitro unscheduled hepatocyte DNA synthesis (UDS) assay (Monsanto, Stanford, Research Institute, 1986). 3.4.2 Human Experience Patch testing of a panel of 54 human volunteers using a 1% preparation demonstrated the material was not a primary skin irritant but one individual demonstrated a positive response for delayed contact sensitization. The material is considered to possess weak sensitization potential at this concentration (Monsanto, Product Investigations, 1986). 4.0 N,N-Diisopropyl-2-benzothiazolesulfenamide 4.0.1 CAS Number: [95-29-4] 4.0.2 Synonyms: N,N-Bis(1-methylethyl)-2-benzothiazolesulfenamide 4.1 Chemical and Physical Properties It is completely hydrolyzed to mercaptobenzothiazole and isopropylamine during an 8-day period at pH 8.0; hydrolysis occurs more readily at lower pH values (Monsanto, ABC Laboratories, 1984). 4.2 Production and Use It is a solid material used as an accelerator in rubber vulcanization. 4.4 Toxic Effects 4.4.1 Experimental Studies 4.4.1.1 Acute Toxicity The acute oral and dermal toxicity is low; LD50 values are 5700 mg/kg (rat) and >2000 mg/kg (rabbit), respectively. An oral LD50 value in mice was 3892 mg/kg (Monsanto, Bio/dynamics Inc., 1982). Slight eye (mild, transient irritation of the conjunctiva) and slight skin (slight erythema and edema) irritation were observed in rabbit irritation studies (Monsanto, Bio/dynamics Inc., 1982). Oral administration to rats of both sexes for 3 months at 0, 250, 500, or 100 mg/kg/day reduced body weight increments in males at 500 mg/kg and higher. Increased absolute and relative liver weights in both sexes at all dosages were related to hepatocellular hypertrophy. There was an accumulation of hyaline droplets in the renal tubular epithelium in males at all dosages. This finding was not present in females, but a brown pigment was present in the same cells in females at dosages of 500 mg/kg and above (Monsanto, Monsanto Environmental Health Laboratory, 1987). 4.4.1.6 Genetic and Related Cellular Effects Studies No evidence of mutagenicity was found in an Ames S. typhimurium assay or in S. cerevisiae (Monsanto, Bionetics, 1976). It was also negative in an in vitro unscheduled heptocyte DNA synthesis assay. An in vitro chromosomal aberration assay in Chinese hamster ovary cells was positive without metabolic activity but not when a source of

metabolic activation was included (Monsanto, SRI International, 1986). This positive result is not considered indicative of a clastogenic hazard when compared to a negative in vivo rat bone marrow cytogenetics assay following oral administration of 2850 mg/kg and bone marrow cell harvests at 6, 18, and 30 h after administration (Monsanto, Pharmakon Research International, 1987). 4.4.2 Human Experience Patch testing of a panel of 54 human volunteers using a 1% preparation in petrolatum indicated that the material was neither a primary skin irritant nor a delayed contact sensitizer (Monsanto, Product Investigations, 1986). Patch testing of humans previously demonstrated as sensitized to 2-mercaptobenzothiazole gave positive results, although the likely presence of impurities and inadequate documentation of sample quality and source render the validity of this result questionable (123). 5.0 N-tert-Butyl-2-benzothiazolesulfenamide 5.0.1 CAS Number: [95-31-8] 5.0.2 Synonyms: N-(1,1'-dimethylethyl)-2-benzothiazolesulfenamide 5.1 Chemical and Physical Properties It is completely hydrolyzed to 2-mercaptobenzothiazole and tert-butylamine within a 25-h period at pH 7.0; the hydrolysis rate is slower at pH 9.0 (Monsanto, ABC Laboratories, 1984). 5.2 Production and Use It is a solid material used as an accelerator in rubber vulcanization. 5.4 Toxic Effects 5.4.1 Experimental Studies 5.4.1.1 Acute Toxicity The acute oral and dermal toxicities are low; LD50 values are >6310 mg/kg (rat) and >7940 mg/kg (rabbit), respectively. Slight eye irritation and minimal skin irritation were defined in rabbit irritation studies (Monsanto, Younger Laboratories, 1973). A 25% solution in ethanol did not induce any delayed-contact sensitization reactions in a guinea pig sensitization (Buehler) assay (Monsanto, Pharmakon Research International, 1982). Oral administration for 3 months to rats of both sexes at 0, 100, 300, or 1000 mg/kg/day reduced body weight increments in males at dosages of 300 mg/kg and higher. Liver and kidney weights were also increased in females at 1000 mg/kg, but there was no microscopic evidence of morphological change in these organs and the findings were not considered of toxicological significance (Monsanto, Monsanto Environmental Health Laboratory, 1982). A dust inhalation study of rats (6 h/day, 5 days/week) for 4 weeks at 0, 2.4, 29, and 84mg/m3 elicited morphological effects on the liver and lymph nodes at 84mg/m3 that were detected during microscopic examination (Monsanto, International Research and Development Corporation, 1978). Repeated daily dermal applications of 0, 125, 500, or 2000 mg/kg/day caused slight dermal irritation but no evidence of systemic toxicity (Monsanto, International Research and Development Corporation, 1979). 5.4.1.4 Reproductive and Developmental No maternal toxicity, fetal toxicity, or developmental toxicity were seen in rats following oral administration of 0, 50, 150, or 500 mg/kg/day to pregnant female rats on days 6 to 15 of gestation (Monsanto, International Research and Development Corporation, 1978). 5.4.1.6 Genetic and Related Cellular Effects Studies No evidence of mutagenicity was found in Ames S. typhimurium, E. coli, S. cerevisiae, or Chinese hamster ovary HPRT assays (125; Monsanto, Bionetics, 1978). Positive results were obtained in mouse lymphoma assays of L5178Y cells with metabolic activation (Monsanto, Bionetics, 1978). Cell transformation was noted at the highest concentration tested in BALB/3T3 cells, but significant cytotoxicity may confound the relevance of this finding (Monsanto, Monsanto Environmental Health Laboratory, 1993). 5.4.2 Human Experience Patch testing of a panel of 54 human volunteers using a 60% preparation in petrolatum indicated the material was not a primary skin irritant, but a strong delayed contact sensitization response occurred (Monsanto, Product Investigations, 1982). Patch testing of humans previously demonstrated to be sensitized to 2-mercaptobenzothiazole gave positive results, although

the likely presence of impurities and inadequate documentation of sample quality and source render the validity of this result questionable (123). 6.0 N-Cyclohexyl-2-benzothiazolesulfenamide 6.0.1 CAS Number: [95-33-0] 6.1 Chemical and Physical Properties It is a pale, buff-colored powder or granule completely hydrolyzed within 25 h at pH 7.0 (Monsanto, ABC Laboratories, 1984). 6.2 Production and Use N-Cyclohexyl-2-benzothiazolesulfenamide is used as an accelerator in rubber vulcanization. 6.4 Toxic Effects 6.4.1.1 Acute Toxicity The acute oral and dermal toxicities are low; LD50 values are 5300 mg/kg (rabbit) and >7940 mg/kg (rat), respectively (Monsanto, Younger Laboratories, 1973). It is slightly irritating to the rabbit eye (Monsanto, Younger Laboratories, 1973) and practically nonirritating to rabbit skin (Monsanto, Pharmakon Research International, 1982). In a guinea pig delayed-contact skin sensitization assay (Buehler) using a 25% preparation in ethanol, no evidence of sensitization was found after challenge with the 25% solution. No evidence of comedogenicity was detected in rabbits when solutions in chloroform up to 10% were applied to the inner surface of the ears for 4 weeks (Monsanto, Pharmakon Research International, 1982). Dermal application of up to 2000 mg/kg/day to intact and abraded skin of rabbits for 21 days did not elicit any evidence of toxicity (Monsanto, International Research and Development Corporation, 1979). Inhalation exposure of rats for 4 weeks (5 days/week) to dust concentrations of 4.3, 14.4, and 48.0 mg/m3 caused microscopic lesions of the conjunctivas, lymph nodes, and spleen at 48 mg/m3. Elevated aspartate aminotransferase activities at 14.4 mg/m3 and above were not associated with any morphological abnormalities (Monsanto, International Research and Development Corporation, 1978). Administration to rats of diets that contained levels approximating 100, 250, 500, 1000, or 3000 mg/kg for 4 weeks reduced food intake and body weight gain at 500 mg/kg and higher; there was no other evidence of systemic toxicity (Monsanto, International Research and Development Corporation, 1979). Administration to rats by gavage for 5 weeks (5 days/week) of dosages up to 1.25 mg/kg/day reduced body weight gain and increased thyroid weights relative to body weight. There was no evidence of pathological change, so the thyroid weight finding may reflect reduced body weight gain (Monsanto, 1993). superscript Excretion After a single oral dosage of 250 mg/kg of 14C-labeled material 65 and 24% of the dose was excreted with in 3 days in the urine and feces, respectively. Biliary excretion over this period accounted for approximately 5% of the dose. There was no evidence of selective accumulation or concentration in any organs. The urinary metabolites were identified as cyclohexylamine and 2-mercaptobenzothiazole (129). 6.4.1.4 Reproductive and Developmental Oral administration to pregnant rats of dosages of up to 500 mg/kg on days 6 to 15 of gestation caused maternal toxicity at 500 mg/kg and concomitant reduction in fetal body weight; there were no teratological responses at this dosage. No maternal or fetal effects were noted at 300 mg/kg (Monsanto, International Research and Development Corporation, 1978). In a separate study, oral administration, of dosages of 50, 150 and 450 mg/kg to pregnant rats during organogenesis, produced maternal toxicity at the highest dosage and dosedependent fetal toxicity (fetuses/litter and hydrocephalus) (126). These investigators found that the dosage of 450 mg/kg produced embryotoxicity, shown by increases in late resorptions and post implantation losses, decreased fetal body weight and length, and subcutaneous hemorrhage (127). In another study, dietary administration at dietary levels approximating dosages of 0.7, 7.1, 69.6, and 288.8 mg/kg to pregnant female rats on days 0 to 20 of gestation caused reduced maternal food intake and body weight gains at 288.8 mg/kg and a concomitant reduction of fetal body weight. Maternal body weight gain was also reduced at 69.6 mg/kg, although there were no effects on fetal body weight. No effects on pre- or postimplantation loss, litter size, or the incidence of

malformations or visceral or skeletal variations were reported (128). 6.4.1.6 Genetic and Related Cellular Effects Studies No evidence of mutagenicity either with or without metabolic activation was found in the Ames S. typhimurium, E. coli, or Chinese hamster ovary HPRT assays (Monsanto, Bionetics, 1976; Monsanto, 1993), the S. cerevisiae assay (Monsanto, Bionetics, 1976), or the L5178 mouse lymphoma assay (Monsanto, Bionetics, 1978). 6.4.2 Human Experience Occupational exposure reportedly causes irritation of the eyes, skin and upper respiratory tract. Patch testing of a panel of 51 human volunteers using a 70% preparation in petrolatum did not cause primary or cumulative irritation, but sensitization responses occurred in 5 of the 51 subjects (Monsanto, Product Investigations, 1982). The literature contains many reports of skin sensitization, but in most cases the patients were also sensitized to other components of the “mercapto mix” used for skin testing. Industrial experience indicates that this material is a weak sensitizer. 7.0 N,N-Dicyclohexylbenzothiazolesulfenamide 7.0.1 CAS Number: [4979-32-2] 7.0.2 Synonyms: N,N-dicyclohexyl-1-benzothiazolesulfenamide. 7.2 Production and Use It is an off-white solid, a powder or pellet, that is used as an accelerator in rubber vulcanizing. 7.4 Toxic Effects 7.4.1 Experimental Studies 7.4.1.1 Acute Toxicity The material has low acute oral and dermal toxicities; LD50 values are >5000 mg/kg (rat) and >2000 mg/kg (rabbit), respectively. It was practically nonirritating in rabbit skin and eye assays (130); (Monsanto, Bio/Dynamics Inc., 1984). Using the Magnusson–Kligman maximization assay for delayed-contact cutaneous sensitization, it was concluded that it is not a skin sensitizer (Monsanto, International Research and Developmental Corporation, 1984). 7.4.1.2 Chronic and Subchronic Toxicity Administration to rats in the diet for 4 weeks at 2000 to 10,000 ppm caused a dose-related decrease in food consumption and body weight increments at all dietary concentrations. There was no evidence of any systemic toxicity based on evaluations of the cellular and chemical constituents of blood, organ weight analysis, or macroscopic pathology examinations (130); (Monsanto, Bio/Dynamics Inc., 1987). Administration to rats in the diet for 13 weeks at 2500 or 5000 ppm decreased food intake and reduced body weight increments at both dietary concentrations. There was no evidence of any systemic toxicity or microscopic pathology changes at either dietary concentration. The no-effect level on subchronic administration in the diet was 500 mg/kg diet (130; Monsanto, Monsanto Environmental Health Laboratory, 1988). 7.4.1.5 Carcinogenesis An increased incidence of sarcomas occurred at the site of subcutaneous administration of 20 g/kg body weight, administered as 1 g/kg body weight at irregular intervals during 413 days (130). However, there was no evidence for mutagenic or clastogenic effects in the Ames S. typhimurium assay, the Chinese hamster ovary HPRT assay, and an in vitro hepatocyte DNA repair (UDS) assay, or in an in vivo rat bone marrow chromosomal aberration assay after oral administration of a single 1000-mg/kg dose (130); (Monsanto, Pharmakon International, 1984; Monsanto, Hazelton Laboratories, 1984; Monsanto, 1993; Monsanto, SRI International, 1984). General Internet site references with chemical and safety information: http://ecdin.etomep.net Environmental Chemicals Data Infor-mation Network http://ecphin.etomep.net European Community Pharmaceutical Information Network http://www.jrc.org.isis Institute for Systems Information and Safety http://www.msdsonline.com MSDS Information http://www.safety.utoledo.edu/safety/msds.htm MSDS links

http://www.chem.uky.edu/resources/msds.html One of the better MSDS and chem-istry information sites http://www.aitl.uc.edu Academic Information Technology and Libraries at the University of Cincinnati http://www.vmi.edu/~chem/ind-home.html Chemical Industries Homepages http://www.chemweb.com Chemistry information site

Organic Sulfur Compounds Bibliography

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included here for only 30 organophosphate pesticides. Information on other pesticides registered or undergoing reregistration in the United States can be readily obtained from the previously mentioned website. 1.1 Production and Use Organophosphates are the most widely used insecticides today; more than 40 are currently registered for use in the United States (3). They were the number one cause of symptomatic illnesses reported in 1996, according to the American Association of Poison Control Centers (3). The earliest organophosphates (e.g., schradan) were initially developed as war gases, and they have also been used as therapeutic agents, gasoline additives, hydraulic fluids, cotton defoliants, fire retardants, plastic components, growth regulators, and industrial intermediates (363). Their use as insecticides far exceed these uses.

Organophosphorus Compounds Jan E. Storm, Ph.D 2.0 Azinphos-Methyl 2.0.1 CAS Number: [86-50-0] 2.0.2 Synonyms: Phosphorodithioic acid O,O-dimethyl-S-((4-oxo-1,2,3,-benzotirazin-3 (4H)-yl)methyl)ester; metiltriazotion guthion; Guthion, Gusation; S-(3,4-dihydro-4-oxobenzo[d][1,2,3]triazin-3-ylmethyl) O,O-dimethyl phosphorodithioate; Azinphos-Me; Gusathion; Methyl guthion; Guthion(R); Phosphorodithioic acid O,O-dimethyl S-[4-oxo-1,2,3-benzotriazin-3(4H)-yl)methyl] ester; phosphorodithioic acid O,O-dimethyl ester, S-ester with 3-mercaptomethyl-1,2,3-benzotriazin-4 (3H)-one; Bayer 17147; Cotnion-methyl; Gusathion M; Azimil; Bay; R 1582; Gusthion M; Gution; O,O-dimethyl S-(4-oxobenzotriazino-3-methyl) phosphorodithioate; S-(3,4-dihydro-4-oxo-1,2,3benzotriazin-3-ylmethyl) O,O-dimethyl phosphorodithioate; azinophos-methyl; bay 9027; bay 17147; bayer 9027; 3-(mercaptomethyl)-1,2,3-benzotriazin-4(3H)-one O,O-dimethyl phosphorodithioate; carfene; cotneon; crysthion 21; crysthyon; DBD; O,O-dimethyl S(benzaziminomethyl) dithiophosphaate; O,O-dimethyl S-(1,2,3-benzotriazinyl-4-keto)methyl phosphorodithioate; O,O-dimethyl S-(3,4-dihydro-4-keto-1,2,3-benzotriazinyl-3-methyl) dithiophosphate; dimethyl dithiophosphoric acid N-methylbenzazimidyl ester; O,O-dimethyl S-(4oxo-3H-1,2,3-benzotriazine-3-methyl) phosphorodithioate; O,O-dimethyl S-(4-oxo-1,2,3benzotriazino (3)-methyl) thiothionophosphatae; O,O-dimethyl S-4-oxo-1,2,3-benzotriazin-3(4H)ylmethyl phosphorodithioate; gothnion; gusathion-20; gusathion 25; gusathion k; gusathion methyl; 3-(mercaptomethyl)-1,2,3-benzotriazin-4(3H)-one O,O-dimethyl phosphorodithioate S-ester; methylazinphos; N-methylbenzazimide, dimethyl dithiophosphoric acid ester; metiltriazotion; Beetle Buster; Ketokil No. 52; Crysthyon 2L; Dimethoxy ester of (4-oxo-1,2,3-benzotriazin-3(4H)-yl) methyl ester of dithiophosphoric acid; dimethyl S-((4-oxo-1,2,3-benzotriazin-3(4H)-yl)methyl) phosphorodithioate; dimethyl S-(3-(mercaptomethyl)-1,2,3-benzotriazin-4(3H)-one) phosphorodithioate; Methyl gusathion; Guthion (Azinphos-Methyl) 2.0.3 Trade Names: Guthion®, Gusathion®, methyl Guthion, Azimil, Bay 9027, Bay 17147, Carfene 2.0.4 Molecular Weight: 317.34 2.0.5 Molecular Formula: C10H12N3O3PS2 2.0.6 Molecular Structure:

2.1 Chemical and Physical Properties Pure azinphos-methyl is a white crystalline solid; the technical material is a brown, waxy solid. Specific 1.44 at 20°C gravity Melting point pure 73–74°C; technical 65–68°C; unstable at temperatures higher than 200°C Solubility soluble in methanol, ethanol, propylene glycol, xylene, and other organic solvents: slightly soluble in water (33 mg/L) Vapor 75% inhibition) RBC cholinesterase inhibition (64). Cholinergic signs occurred only in dogs given 300 ppm. When rats were given diets that contained 5, 15, and 45 ppm azinphos-methyl (equivalent to 0, 0.25, 075, and 2.33 mg/kg/day (males); 0.31, 0.96 and 3.11 mg/kg/day (females)) for up to 24 months, no cholinergic signs occurred, nor was clinical chemistry affected (242). There was, however, a marked inhibition of RBC, plasma and brain cholinesterase at 45 ppm, inhibition of RBC cholinesterase in males at 15 ppm, and, inhibition of RBC and plasma cholinesterase in females at 15 ppm. At 5 ppm, RBC cholinesterase decreased by 12% in male rats. When rats were fed a diet that had 50 ppm azinphos-methyl for 47 weeks followed by 100 ppm for 49 weeks, consistently depressed brain, plasma, and RBC cholinesterase activity occurred. When they were given a diet of 20 ppm for 97 weeks, depression of plasma and RBC cholinesterase activity occurred that decreased as the study progressed; exposure to diets of 2.5 or 5 ppm had no effect (64). Convulsions were seen in a “small number of female rats” (sic) (5/40) after increasing their dietary exposure from 50 to 100 ppm. When azinphos-methyl was fed to mice at 0, 5, 20, or 40 ppm (about 0.79, 3.49, 11.33 (males); 0.98, 4.12, 14.30 (females)) for two years, no compound-related toxicity or evidence of cancer occurred

(242). However, up to 80% inhibition of plasma, RBC, and brain cholinesterase activity occurred in mice given 20 and 40 ppm. At 5 ppm, RBC cholinesterase was still slightly inhibited. In a chronic bioassay, rats were fed diets that contained 78 or 156 ppm (males) or 62.5 or 125 pm (females) azinphos-methyl for 80 weeks, then observed for 34-35 weeks, and mice were fed diets that contained 31.3 or 62.5 ppm (males) or 62.5 or 125 ppm (females) for 80 weeks, then observed for 12–13 weeks (65). Body weight gain decreased in male rats and mice given either diet and in female rats or mice given the high dose diet. Signs of organophosphate intoxication (hyperactivity, tremors, dyspnea) occurred “in a few animals of both species” (sic) fed the higher dose diets. During the second year, cholinergic toxicity occurred at both dietary levels. An equivocal increase in the incidence of tumors of the pancreatic islets and follicular cells of the thyroid suggested, but did not provide sufficient evidence of, carcinogenicity in male rats. There was no increased incidence of tumors of any kind among mice. 2.4.1.6 Genetic and Related Cellular Effects Studies Azinphos-methyl with and without metabolic activation showed no evidence of mutagenicity in Salmonella typhirium (242). Azinphos-methyl was also negative in the reverse mutation induction assay with Sacharomyces cerevisiae and in the primary rat hepatocyte unscheduled DNA synthesis assay (242). In an in vitro cytogenetics assay using human lymphocytes, azinphos-methyl was clastogenic only with a metabolic activating system (242). However, a clastogenic effect was not observed in femoral marrow prepared from mice treated intraperitoneally with 5 mg/kg azinphos-methyl (242). 2.3.5 Biomonitoring/Biomarkers Among rats exposed dermally to 100, 200 or 400 mg azinphosmethyl on the shaved dorsal skin in the scapular region, there was a good correlation between dose and amount of dimethylthiophosphate in urine (69). Studies of agricultural field workers exposed to azinphos-methyl have shown that they excrete dimethyl phosphate (DMP), dimethyl thiophosphate (DMTP), and dimethyl dithiophosphate (DMDTP) in urine (59, 60, 69–71). However, urinary metabolite excretion is not always well correlated with serum or RBC cholinesterase inhibition (60, 71). 2.4.2 Human Experience 2.4.2.2.1 Acute Toxicity A pilot who had spilled azinphos-methyl concentrate on his hands experienced visual disturbances, headache, tightness in the chest, abdominal cramps, nausea, vomiting, weakness and some excessive salivation (72). 2.4.2.2.2 Chronic and Subchronic Toxicity Work in orchards treated with azinphos methyl is associated with blood cholinesterase activity reductions of up to 70% (30% of pre exposure baseline) and that intake is primarily due to dermal exposures (70). It was estimated that workers who sprayed apple orchards (with solutions of 0.5 to 6 lb of 25% wettable powder per 100 gallons of water) were exposed to 0.05 to 2.55 mg/m3 (average 0.64 mg/m3) azinphos-methyl for periods of 15 to 45 minutes; workers responsible for filling tanks were exposed to 0.26 to 6.20 mg/m3 (average 2.76 mg/m3) azinphos-methyl for brief periods; and formulators were exposed to 1.07 to 9.64 mg/m3, presumably for 8 hours/day. In all cases, dermal exposures exceeded inhalation exposure when quantified on a milligram per day basis. Serum cholinesterase activities were slightly depressed (78–91% of preexposure levels) after exposure, but no other effects were noted (73). Orchardists who sprayed azinphos-methyl (wettable powder) were potentially exposed to an average concentration of 0.05 mg/m3 (range 0.02–0.11 mg/m3) based on air concentrations “measured near the spraymen during spraying operations,” although inhalation exposures were probably significantly less than this because workers reportedly wore respirators. Dermal exposures were estimated at from 9 to 43 mg/kg. No evidence of serum or RBC cholinesterase inhibition was observed (57a). However, in another study of orchard workers, where exposures were primarily dermal (ranging up to 8,315 mg/hand wipe sample in thinners; up to 14,498 mg/sample on shirts of harvesters), median RBC cholinesterase activity declined by about 19% during a 6-week spraying season, and median

plasma activity fell by about 12% (60). Workers engaged for 5 days in thinning a peach orchard after it was treated with azinphos-methyl, showed very slightly inhibited RBC cholinesterase activity (mean decrease of about 6% compared to baseline) and essentially no change in plasma cholinesterase activity. No symptoms associated with cholinesterase inhibition occurred. Daily urinary excretion of dimethyl phosphate (DMP) and dimethyl phosphorothionate (DMPT) increased in exposed workers, and daily mean DMP and DMTP excretion was highly correlated with the mean percentage decline in RBC cholinesterase activity from baseline (74). No changes in plasma or RBC cholinesterase activities occurred in human volunteers given oral doses 4, 4.5 or 6 mg/day (0.06, 0.06 or 0.09 mg/kg/day) (75); 7, 8 or 9 mg/day (0.10, 0.11 or 0.13 mg/kg/day) (76); or, 10, 12, 14 or 16 mg/day (0.14, 0.17, 0.20 or 0.23 mg/kg/day) for 30 days (77). 2.5 Standards, Regulations, or Guidelines of Exposure All azinphos-methyl liquids with a concentration greater than 13.5% are classified as restricted use pesticides by the U.S. EPA because of their high toxicity. The ACGIH TLV for azinphos-methyl is 0.2 mg/m3 and is associated with a skin notation (154). OSHA has established a PEL-TWA of 0.2 mg/m3 with a skin notation, NIOSH has established a REL-TWA of 0.2 mg/m3 with a skin notation, and most other countries have also established Occupational Exposure Limits of 0.2 mg/m3 (e.g., Australia, Austria, Belgium, Denmark, Federal Republic of Germany, Netherlands, Philippines, Switzerland, Thailand, United Kingdom). Finland has established an OEL of 0.02 mg/m3.

Organophosphorus Compounds Jan E. Storm, Ph.D 3.0 Chlorpyrifos 3.0.1 CAS Number: [2921-88-2] 3.0.2 Synonyms: (O,O-diethyl O-(3,5,6-trichloro-2-pyridinyl) phosphorothioate, Dursban; Lorsban; Dursban(R); chlorpyrifos-ethyl; Dowco 179; Pyrinex; phosphorothioic acid O,O-diethyl O-(3,5,6-trichloro-2pyridinyl) ester; Brodan; Chloropyrifos; O,O-diethyl O-(3,5,6-trichloro-2-pyridyl) phosphorothioic acid; O,O-diethyl O-3,5,6-trichloro-2-pyridyl phosphorothioate; O,O-diethyl O-(3,5,6-trichloro-2pyridinyl) phosphorothioic acid; 3,5,6-trichloro-2-pyridinol O-ester with O,O-diethyl phosphorothioate; chlorpyriphos-ethyl; detmol u.a.; dursban f; oms-0971; stipend; dursban 4E; chloropyriphos; killmaster; dursban 10cr; suscon; lorsban 50sl; coroban; terial 401; terial; danusban; durmet; O,O-diethyl O-(3,5,6-trichloro-2-pyridinyl) phosphorothioate; Dursban/Lorsban; Lorsban 4E-SG; Chlorpyrifos 4E-AG-SG; diethyl O-(3,5,6-trichloro-2-pyridyl) phosphorothioatae; diethyl O(3,5,6-trichloro-2-pyridinyl) phosphorothioate; Dursban HF; Eradex; Pyrindol. 3,5,6-trichloro-, Oester with O,O-diethyl phosphorothioate; Super I.Q.A.P.T.; Trichlorpyriphos 3.0.3 Trade Names: Dursban®; Dowco 179®; ENT-27,311; Eradex®; Lorsban®; Pyrinex ® 3.0.4 Molecular Weight: 350.57 3.0.5 Molecular Formula: C9H11Cl3NO3PS 3.0.6 Molecular Structure:

3.1 Chemical and Physical properties Pure chlorpyrifos is a white crystalline powder; technical chlopyrifos is an amber to white crystalline powder. Specific gravity 1.398 g/cm3 at 43.5°C Melting point 42.5–43°C Boiling point decomposes at approximately 200°C Vapor pressure 1.87 × 10–5 mmHg at 20°C Solubility soluble in most organic solvents; 0.00013 g/100 mL in water 3.1.2 Odor and Warning Properties Mild mercaptan odor due to diethyl disulfide in technical product. 3.2 Production and Use Chlorpyrifos is a broad spectrum pesticide and acaracide that acts as a contact poison. Originally used to control mosquito larvae, it is no longer registered for this use. It has a wide range of applications on crops, lawns, ornamental plants, domestic animals, and a variety of building structures. Chlorpyrifos is available as 25% wettable powders, 1–10% granules, and emulsifiable concentrates of 2 and 4 lb/gal. 3.3 Exposure Assessment Most exposures to chlorpyrifos are anticipated to be via inhalation of aerosols during its application; dermal absorption in humans is not significant (56, 199). Chlorpyrifos metabolism yields a unique urinary metabolite, 3,5,6-trichloro 2 pyridinol (TCP), which has been correlated to chorpyrifos exposure if analyzed within 48 hours of exposure (200, 201). 3.4 Toxic Effects 3.4.1.1 Acute Toxicity Chlorpyrifos is an organophosphate compound that has moderate toxicity and oral LD50s of 80–250 mg/kg (64a, 202). Inhalation LD50s of 78 and 94 mg/kg were calculated for female mice and rats, respectively, based on lethality observed after 60- to 180-minute exposures to aerosol concentrations of 5900 mg/m3–7900 mg/m3 (203). In female and male rats, 20 and 80% mortality occurred following 4-hour exposure to 5300 mg/m3 chlorpyrifos, respectively, whereas no mortality occurred after exposure to 2500 mg/m3 (56). A dermal LD50 of 202 mg/kg was reported in rats (64a). There is evidence that young animals are more sensitive than older animals; and that females are more sensitive than males to the lethal effects of chlorpyrifos (64a, 203a, 204). Signs typically associated with organophosphate poisoning do not necessarily precede death caused by chlorpyrifos (203). “Apparent” (sic) tremors occasionally occurred in neonatal rats treated with a maximum tolerated dose (MTD) (45 mg/kg), but typical signs of a “cholinergic crisis” were not noted. Adult mice treated with a MTD (279 mg/kg) showed only slight to moderate signs of toxicity (e.g., diarrhea, fasciculations, lacrimation, slight tremors) (204). Cholinergic toxicity associated with sublethal exposure to chlorpyrifos was reflected only as mild diarrhea and hypoactivity evident only for the first two days following single s.c. injection of 279 mg/kg and not evident at all following repeated s.c. injections of 40 mg/kg (1×, 4 days, 16 days) (205, 206). Brain cholinesterase activity, however, was markedly depressed for at least 6 weeks following a single subcutaneous dose of 279 mg/kg and for at least 4 days following repeated subcutaneous doses of 40 mg/kg.

Prolonged cholinesterase inhibition occurred in rats given single subcutaneous injections of 0, 60, 125, or 250 mg/kg and examined up to 53 days later (207). Cholinergic toxicity was evident as a fine tremor in rats given 250 mg/kg but not 60 mg/kg (tremors in the 125 mg/kg group were not reported). Tremor intensity reached a peak in 9 days and returned to normal by 14 days after dosing. No overt signs of cholinergic toxicity occurred in rats treated with 0, 30, 60, or 125 mg/kg subcutaneously at any time from 1 to 35 days after dosing, although RBC cholinesterase activity was significantly inhibited in all groups (44). However, deficits in conditioned behavior occurred 2–16 days after dosing rats with 60, 125, or 250 mg/kg (207), and single oral doses of 12.5, 25, 37.5, or 50 mg/kg chlorpyrifos (or repeated doses of 12.5 mg/kg/day 5 days/week for eight weeks) caused significant deficits in response acquistition and performance measurements in a conditioned behavior task (208). In rats given single oral doses of 20, 50, or 100 mg/kg chlorpyrifos by gavage, cholinergic signs peaked at 3½ hours in the 100-mg/kg group, were still present at 24 hours, and had disappeared by 72 hours after dosing (324). Only hypoactivity occurred in the 20-mg/kg group. When rats were given single oral doses of 10, 30, 60, or 100 mg/kg chlorpyrifos, no cholinergic effects occurred at 10 mg/kg, rats exhibited cholinergic signs at 30 mg/kg, tremors were also evident at 60 mg/kg, and cholinergic symptoms were present and severe at 100 mg/kg (43). The time of peak effect was always 3½ hours after dosing, and by 24 hours all symptoms had disappeared in the 30 mg/kg, but ataxia and hypoactivity were still evident in the 60- and 100-mg/kg group. Brain, plasma, and RBC cholinesterase inhibition were significantly and dose-dependently depressed at all dose including the 10 mg/kg group at both 3½ and 24 h. Thus, behavioral and biochemical effects of chlorpyrifos exposure were poorly correlated; and, behavioral signs showed recovery at 24 h whereas cholinesterase activity did not (43). When rats were given 10, 50, or 100 mg/kg chlorpyrifos orally and observed 1, 8, and 15 hours later, cholinergic effects occurred only on day 1 in 100-mg/kg treated female rats (209). One female rat treated with 50 mg/kg had tremors, two exhibited incoordination, and one showed pronounced lacrimation. One male rat given 100 mg/kg exhibited only minimal tremor, and one male exhibited incoordination and lacrimation. Rats treated with 50 or 100 mg/kg were significantly hypoactive only on day 1. Thus, cholinergic effects were widespread at 100 mg/kg, minor at 50 mg/kg, moderated over a few days, and were more severe in females than males. Responses of adult rats given single oral doses of 80 mg/kg were compared with those of 17-day-old rats treated with single doses of 15 mg/kg; these doses were equally effective in inhibiting cholinesterase (203a). Compared to adults, young rats showed similar behavioral changes and cholinesterase inhibition although at a fivefold lower dose. The onset of maximal effects was somewhat delayed, cholinesterase activity recovered more quickly, more extensive muscarcinic receptor down-regulation occurred, and no gender-related difference in sensitivity was noted. Chlorpyrifos caused neurotoxicity, indicated by leg weakness. Onset was 3-18 days after dosing and lasted from 10–20 days when given subcutaneously to atropinized chickens at a dose of 200 mg/kg but not 100 mg/kg (64a). 3.4.1.2 Chronic and Subchronic Toxicity No treatment-related signs of toxicity, changes in body weight; or, in plasma, RBC, or brain cholinesterase activities occurred among rats exposed for 6 h/day, 5 days/week, 13 weeks, nose-only, to 72, 143, or 287 mg/m3 chlorpyrifos (210). Nor was there any adverse effect at any exposure level based on urinalysis, clinical chemistry, hematology, gross pathological or histopathological evaluation. When rats were exposed to 0.1, 1, 5, 15 mg/kg/day chlorpyrifos via the diet for 13 weeks, mild clinical effects (perineal soiling) were noted in females given 5 and 15 mg/kg/day (209). Plasma cholinesterase was significantly inhibited in males and females given 1 mg/kg or more, RBC cholinesterase was significantly inhibited in females given 1 mg/kg or more, and, brain

cholinesterase was inhibited in both males and females given 5 or 15 mg/kg. Motor activity of males and females given 15 mg/kg mildly decreased only at week 4 of exposure, and no treatment related differences were apparent subsequently, consistent with the occurrence of tolerance upon repeated exposure to chlorpyrifos. Oral treatment of hens with 1, 5, or 10 mg/kg/day chlorpyrifos for 13 weeks did not induce neurotoxicity (1237). 3.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms There are no studies available that describe the pharmacokinetics of chlorpyrifos following inhalation exposure. However, absorption via inhalation was demonstrated indirectly in mice and rats who experienced lethality when exposed to 5900–7900 mg/m3 aerosolized chlorpyrifos for 27–180 minutes (203). Indirect evidence of inhalation absorption in humans was provided in a study showing urinary excretion of diethyl phosphate chlorpyrifos metabolities by pesticide workers involved in treating structures with a spray emulsion of chlorpyrifos and vaponite (212). Chlorpyrifos is well absorbed orally. Nearly 90% of orally administered chlorpyrifos was eliminated by rats in urine by 48–66 hours after dosing (201, 200a). The remaining 10% was eliminated in the feces. Chlorpyrifos was distributed especially to tissues involved in metabolism and excretion (liver and kidney), to tissues with considerable blood circulation (e.g., muscle, heart, lungs, spleen, testes, and bone), and to tissues high in lipids (e.g., fat and skin). It was eliminated nearly exclusively in urine (primarily as 3,5,6-trichloro-2-pyridinol phosphate). Elimination half-lives for liver, kidney, muscle, and fat were 10, 12, 16, and 62 hours, respectively, indicating considerable storage in fat. About 72% of an oral dose of chlorpyrifos was absorbed (following a 1–2 hour delay), metabolized, and nearly completely eliminated (primarily as 3,5,6-trichloro-2-pyridinol (TCP)) in urine by male volunteers within 120 hours (199). Following either exposure route, chlorpyrifos was widely distributed and was eliminated from blood with a half-life of about 27 hours. In three individuals who ingested a concentrated solution of chlorpyrifos, its elimination was biphasic (276). An average elimination half-life for chlorpyrifos of 6 ± 2 hours in the initial elimination phase and of 80 ± 25 hours in a slower elimination phase was calculated. Skin absorption of chlorpyrifos by humans is limited (56). In humans, less than 3% of a dermal dose of 5 mg/kg was absorbed (following a 22 hour delay) and was eliminated in urine within 180 hours (199). Considerable dermal absorption of chlorpyrifos has been reported in animals, although irritation and/or blistering from some high doses may have compromised the skin barrier. For example, 80–96% of a 22-mg/kg dermal dose was absorbed by goats by 12–16 hours after dosing and was distributed primarily to blood, liver, and fat, and lesser amounts were distributed to heart, gastrointestinal tract, and skeletal tissue (56, 57). About 60% of a dermal dose of chlorpyrifos (3– 15 mM/5.6 cm2) applied to rats was absorbed by 72 hours after dosing; young rats absorbed up to 90% of the applied dose. Eight hours after dermal treatment of mice with 1 mg/kg chlorpyrifos, about 74% of the dose was found primarily in urine and feces, carcass, blood, intestine, liver, and kidney, and an elimination half-life of 21 hours was estimated (213). Chlorpyrifos is metabolized to chlorpyrifos oxon via cytochrome p450-dependent desulfuration (16, 215, 216). The oxon is rapidly hydrolyzed to 3,5,6-trichloro-2-pyridinol (TCP) via microsomal esterase (including paraoxonase and chlorpyrifos oxonase) (49, 217, 218) or via a nonenzymatic process (14, 215, 216). Alternatively, chlorpyrifos is dearylated to form diethyl thiophosphoric acid and TCP in a reaction also catalyzed by microsomal enzymes. TCP is a relatively unique metabolite of chlorpyrifos and it (or one of its conjugates) is almost exclusively (90%) excreted in the urine (200a, 201). Chlorpyrifos oxon binds to and irreversibly inhibits acetylcholinesterase. However, the relative affinity of chlorpyrifos oxon for plasma and hepatic esterase exceeds that for acetylcholinesterase

(13, 14, 219). Moreover, chlorpyrifos oxon causes relatively greater and longer lasting inhibition of hepatic esterase in vivo compared to brain acetyklcholinesterase (13, 14, 219). Noncatalytic binding of chlorpyrifos oxon to hepatic and plasma esterase represents a significant detoxication mechanism because it prevents much hepatically generated chlorpyrifos oxon from entering the general circulation and target tissues (56). High rates of hepatic dearylation and esterase binding may represent protective factors but it should also be recognized that chlorpyrifos can be activated in extrahepatic tissues such as brain (219). Comparative differences in the rates of hepatic esterase binding and rates of dearylation have been implicated as contributors to the greater sensitivity of female rats to chlorpyrifos toxicity compared to male rats, to the greater sensitivity of some tissues (e.g., brain) to chlorpyrifos compared to other tissues (17), to the greater sensitivity of young animals to chlorpyrifos toxicity compared to adults (18), and to the greater toxicity of parathion compared to chlorpyrifos (13, 15, 19, 221). Although human chlorpyrifos oxonase has not been shown to exhibit clear genetic polymorphism as has been shown for paraoxonase (218, 222), a 13-fold variation in chlorpyrifos oxonase activity has been found in human serum (223–225). 3.4.1.4 Reproductive and Developmental No effects on reproduction, fertility indexes, or neonatal development were noted in two generations of rats fed diets that contained 0.1,1.0, and 5 mg/kg/day chlorpyriphos (211). Parental toxicity at the highest dose was accompained by a decrease in pup body weight and increased pup mortality in the F1 litters. Chlorpyrifos was not fetotoxic to rats given 0, 0.1, 3.0, or 15 mg/kg/day chlorpyriphos by gavage on days 6 through 15 of gestation (211). When pregnant mice were given 0,1,10, or 25 mg/kg/day chlorpyriphos by gavage on gestation days 6 through 15, minor fetotoxic responses and skeletal variations were noted at 25 mg/kg/day, a dose that also caused severe maternal toxicity (589). Teratogenicity (exencephaly) was observed in one pup at 1 mg/kg/day, but was not noted at 10 or 25 mg/kg/day. 3.4.1.5 Carcinogenesis Neither rats maintained for 2 years nor dogs maintained for 1 or 2 years on diets that contained 0.01, 0.03, 0.1, 1, or 3 mg/kg chlorpyrifos showed signs of cholinergic toxicity or carcinogenicity at 12, 18, or 24 months (202). However, RBC cholinesterase activity was intermittently depressed among female rats given 0.1 mg/kg (at 30 and 365 days only) and was consistently depressed among male and female rats given 1 mg/kg and 3 mg/kg (202). Brain cholinesterase activity in rats was intermittently depressed in both sexes given 1 mg/kg (at 180 days and 547 days in females; at 365 and 730 days in males), and was consistently depressed in both sexes given 3 mg/kg. RBC and brain cholinesterase returned to normal levels within 7–8 weeks in a subset of exposed rats after they were switched to control diets. RBC cholinesterase activity was significantly depressed in dogs given 1 or 3 mg/kg diets from day 30 through 730. Brain cholinesterase activity in dogs exposed for 1 or 2 years was slightly depressed in the 3-mg/kg group (81–92% of control levels). No evidence of cholinergic toxicity occurred in rhesus monkeys given 0.08, 0.40, or 2.0 mg/kg/day chlorpyrifos orally for six months, although plasma cholinesterase activity was reduced in all dose groups and RBC cholinesterase activity was reduced in the 0.40- and 2.0-mg/kg/day groups (220). 3.4.1.6 Genetic and Related Cellular Effects Studies Chlorpyrifos is genotoxic based on a recent review (56). Chlorpyrifos induced micronuclei in erythroblasts and caused cytogenetic effects in human lymphoid cells in a dose-related fashion (56). Chlorpyrifos produced significant increases in sister chromatid exchanges and caused X chromosome loss in Drosophila melanogaster and chromosomal aberrations and sister chromatid exchanges in spleen cells. Spindle poisoning and induction of micronuclei and polyploidy have been reported following chlorpyrifos exposure. Sexlinked recessive lethals have also been produced in Drosophila melanogaster by chlorpyrifos exposure, indicating that chlorpyrifos is genotoxic to both somatic and germ cells.

3.3.5 Biomonitoring/Biomarkers TCP is a unique urinary metabolite of chlorpyrifos. Variation in urinary TCP was investigated in termite control workers frequently involved in spraying chemicals in closed environments (226). Variation in the urinary TCP level corresponded to the termite control season and the length of the working period. 3.4.2 Human Experience 3.4.2.2 Clinical Cases Unconsciousness, cyanosis, wheezing, and uncontrolled urination and diarrhea occurred within 18 hours after an individual ingested an estimated dose of 300 mg/kg chlorpyrifos (227). In another suicide attempt, a 27-year-old male experienced extreme agitation, diaphoresis and excessive oral secretions, muscle weakness and fasciculations 14 hours after ingestion of an unknown amount of chlorpyrifos (228). RBC cholinesterase activity was within normal limits. He was administered atropine, pralidoxime, and ventilatory support, and symptoms resolved after 72 hours without permanent sequelae. In another case of chlorpyrifos poisoning, a woman presented with stupor, increased muscle tone, absence of superficial reflexes, and striking choreoathetotic movements of all limbs (229). Serum and RBC cholinesterase activities were markedly depressed (about 20 and 2% of normal, respectively). Atropine relieved the symptoms, and the patient was completely well one month later. A 5-year-old girl who ingested an unknown amount of Rid-A-Bug® which contains chlorpyrifos and a 3-year-old boy who experienced frothing at the mouth, coma, pinpoint pupils, nasal secretions, fasciculations of the eyelids, and twitching of the extremities after ingesting an unknown amount of Dursban®, survived through treatment with atropine and pralidoxime (230, 231). In the boy, a distal polyneuropathy developed 18 days later, but all symptoms were fully resolved by day 52. An intermediate syndrome that required endotracheal intubation and intermittent positive pressure ventilation followed by vocal cord paralysis was reported in an individual who had recovered from a cholinergic crisis due to acute chlorpyrifos ingestion (232). Immediate and delayed toxicity was reported in eight individuals exposed to Dursban® presumably via inhalation and dermal contact as a result of its use as a commercial fumigant (233). Immediate symptoms included nausea, vomiting, and lightheadness in a worker after chlorpyrifos was inadvertently introduced into the workplace ventilating system, and headaches, nausea, and painful muscle cramps in a family of four after their house was sprayed with chlorpyrifos by an exterminator. About 4 weeks after initial exposure, the affected worker developed paresthesia in his feet, urinary frequency and pain in the suprapubic, groin, and thigh regions, and the affected family developed numbness and paresthesias especially in the legs which was accompanied by reported memory impairment. Nerve conduction studies were consistent with distal axonopathy. Delayed sensory neuropathies were also described in two women whose houses had been treated with chlorpyrifos 3–4 weeks earlier and in an exterminator who was exposed repeatedly to chlorpyrifos during a 6-month period (233). All symptoms resolved by 2 weeks–3 months after exposure stopped. No estimates of exposure or cholinesterase activity levels were provided. A spectrum of common birth defects that involved central nervous system malformations, ventricular, eye, and palate defects, hydrocephaly, microcephaly; mental retardation; blindness; hypotonia; widely-spread nipples; and deformities of the teeth, external ears and external genitalia was described in four infants (two of whom were siblings) and attributed to maternal exposure to chlorpyrifos during the first trimester of pregnancy either in the home or at work (234, 235). However, no confirmation of exposure either through chlorpyrifos measurements or cholinesterase activities was provided nor was any estimate of dose attempted. Reports of an additional nine cases of birth defects that had the same or similar spectrum of effects associated with in utero chlorpyrifos exposure were provided to the EPA and reviewed by the Centers for Disease Control (CDC) (236). The EPA concluded that the cases did not support a finding of teratogenicity (236). 3.4.2.2.2 Chronic and Subchronic Toxicity The prevalence of selected illnesses and symptoms in 175 employees involved in producing chlorpyrifos for more than one day between 1 January 1977 and 31 July 1985 and in 335 individually matched controls were compared (237). Subjects were subdivided into three exposure groups (high, moderate, and low) on the basis of job title and air monitoring data.

Estimated TWA concentrations of chlorpyrifos were not provided by exposure group, but for all employees reporting ranged from 0.01 to 0.37 mg/m3. Company medical records were examined for evidence of gastrointestinal tract and nervous symptoms. No significant differences in illness or prevalence of symptoms were observed between the exposed and unexposed groups or among the three exposure subgroups. The observation period was extended to 31 December 1994, and the study group size was increased to 496 potentially exposed employees and 911 controls in a follow-up study (238). High, moderate, low, and negligible exposures were defined as 0.2 mg/m3 chlorpyrifos or high potential for dermal exposure, 0.03 mg/m3 or moderate potential for dermal exposure, 0.03 mg/m3 or low potential for dermal exposure, and 0.01 mg/m3 or negligible dermal exposure, respectively. Employees were categorized into moderate, low or negligible exposure levels on the basis of plasma cholinesterase activities. Prevalence odds ratios for various nervous, respiratory, and digestive system symptoms were calculated by exposure as well as plasma cholinesterase inhibition, and no exposure-related effects were observed. An increase in the frequency of blurred vision, flushing of skin, and decreased urination were reported by pet control employees who used chlorpyrifos within the previous three months (239). However, no estimates of chlorpyrifos exposure were obtained, and exposure was not confirmed with biomarkers of exposure. Volunteers were treated with 0.014, 0.03 or 0.10 mg/kg/day chlorpyrifos by capsule for a total of 20 days at the low and mid-dose and for 9 days at the high dose (95). Treatment of the high-dose group was discontinued after 9 days due to a runny nose and blurred vision in one individual. Mean plasma cholinesterase in this group was inhibited by about 65%. No effect on RBC cholinesterase activity was apparent at any dose. No signs of toxicity were reported among human volunteers given daily oral doses of 0.014, 0.030, or 0.100 mg/kg chlorpyrifos for up to four weeks (210). Plasma cholinesterase inhibition was reported in the 0.100-mg/kg group, but RBC cholinesterase was reportedly unaffected at all exposure levels. No signs of toxicity or depression in RBC acetylcholinesterase activity occurred among human volunteers given 0.5 mg/kg orally or 0.5 or 5 mg/kg dermally. Plasma cholinesterase activity was reduced to 15% of predose levels after the 0.5 mg/kg oral dose, but RBC cholinesterase activity was unchanged after this dose or the 5 mg/kg dermal dose (199). 3.5 Standards, Regulations, or Guidelines of Exposure The EPA established a 24-hour reentry interval for crop areas treated with emulsifiable concentrate or wettable powder formulations of chlorpyrifos unless workers wear protective clothing. Chlorpyrifos is undergoing reregistration by the EPA (242). The ACGIH TLV and the NIOSH REL-TWA for chlorpyrifos is 0.2 mg/m3 with a skin notation (154). There is no OSHA TWA-PEL for chlorpyrifos. Most other countries have also established Occupational Exposure Limits of 0.2 mg/m3 with skin notation for chlorpyrifos (e.g. Australia, Belgium, Denmark, Finland, France, Netherlands, Switzerland, and United Kingdom). NIOSH has also established a 0.6 mg/m3 STEL for chlorpyrifos.

Organophosphorus Compounds Jan E. Storm, Ph.D 4.0 Coumaphos 4.0.1 CAS Number: [56-72-4] 4.0.2 Synonyms:

O,O-diethyl O-(3-chloro-4-methyl-2-oxo-2H-1-benzopyran-7-yl) phosphorothioate; 3-chloro-7diethoxyphosphinothioyloxy-4-methylcoumarin; Diolice; Meldane; Muscatox; Resistox; Asuntol; Bay 21/199; Bazmix; Umbethion; phosphorothioic Acid O-(3-chloro-4-methyl-2-oxo-2H-1benzopyran-7-yl) O,O-diethyl ester; Asantol; Baymix; Resitox; O,O-diethyl O-(3-chloro-4-methyl-2oxo-2H-1-benzopyran-7-yl)phosphorothioate; 3-chloro-7-hydroxy-4-methylcoumarin O-ester with O,O-diethyl phosphorothioate; 3-chloro-4-methylumbelliferone, O-ester with O,O-diethyl phosphorothioate; O,O-diethyl O-(3-chloro-4-methyl-7-coumarinyl) phosphorothioate; O,O-diethyl O-(3-chloro-4-methylumbelliferone); 3-chloro-7-hydroxy-4-methyl-coumarin O,O-diethyl phosphorothioate; 3-chloro-4-methyl-7-coumarinyl diethyl phosphorothioate; 3-chloro-4-methyl-7hydroxycoumarin diethyl thiophosphoric acid ester; O,O-diethyl O-(3-chloro-4-methyl-2-oxo-2Hbenzopyran-7-yl)phosphorothioate; asunthol; coumafos; agridip; O-(3-chloro-4-methyl-2-oxo-2H-1benzopyran-7-yl) O,O-diethyl phosphorothioate; Coumarin, 3-chloro-7-hydroxy-4-methyl-, O-ester with O,O-diethylpyrophosphorothioate; diethyl O-(3-chloro-4-methyl-2-oxo-2H-1-benzopyran-7-yl) phosphorothioate; Umbelliferone, 3-chloro-4-methyl-, O,O-diethyl phosphorothioate 4.0.3 Trade Name: Agridip; Asuntol®; Bay 21; Baymix®; Co-Ral®; ENT-17957; Meldane®; Muscatox®; Negashunt; Resitox®; Suntol, Umbethion 4.0.4 Molecular Weight: 362.8 4.0.5 Molecular Formula: C14H16ClO5PS 4.0.6 Molecular Structure:

4.1 Chemical and Physical Properties Technical coumaphos is a colorless or white and tan powder. Coumaphos is stable under normal use conditions but hydrolyzes slowly under alkaline conditions Specific 1.47 at 20°C gravity Melting 91–92°C point Boiling 20°C at 1 × 10–7 mmHg point Vapor 1 × 10–7 mmHg at 20°C pressure Solubility soluble in acetone and diethyl phthalate; much less soluble in denatured alcohol and xylene; only slightly soluble in octanol, hexane and mineral spirits; insoluble in water 4.1.2 Odor and Warning Properties Slight sulfur odor. 4.2 Production and Use Coumaphos is an organophosphate insecticide used to control anthropoid pests on beef cattle, dairy cows, goats, horses, sheep, and swine. Formulations include wettable powders, emulsifiable liquids, flowable concentrate, ready-to-use liquids, and dusts. Coumaphos is applied by aerosol can, dust bags, hand-held dusters, dip vats, high- and low-pressure hand-held sprayers, back rubber oilers, mechanical dusters, shaker can, and squeeze applicators (241). The EPA issued a Registration Standard for coumaphos in 1989 and a Reregistration Standard in 1996 (45). Currently 26

coumaphos products are registered (243). 4.4 Toxic Effects 4.4.1.1 Acute Toxicity Coumaphos is highly toxic and has an oral LD50 of 16–41 mg/kg in rats (64a). However, the EPA noted that the oral LD50 in male rats was >240 mg/kg and oral LD50 in female rats was 17 mg/kg (241). The dermal LD50 for coumaphos was previously reported as 860 mg/kg in rats (Gaines 1969) although EPA noted that the dermal LD50 was >2400 mg/kg in male and female rats (241). One-hour LC50s of 1081 mg/m3 and 341 mg/m3 and 341 mg/m3 were reported for male and female rats (241). When male rats were given single oral doses of 250 mg/kg and female rats were given single oral doses of 17.5 mg/kg, cholinergic signs occurred and lasted for 12–13 days (242). RBC cholinesterase activity was depressed at 2 mg/kg in both sexes. When sheep were given 2 or 4 mg/kg/day coumaphos orally for 6 days, 4 mg/kg/day caused RBC cholinesterase inhibition and signs of cholinergic toxicity (sic); 2 mg/kg/day inhibited RBC cholinesterase but caused no apparent overt cholinergic toxicity (240). Treatment with coumaphos did not significantly alter the anticholinesterase effects of the second treatment 6 weeks later, suggesting no cumulative effect. Simultaneous treatment with coumaphos (4 mg/kg/day) and an intravenous dose of trichlorfon (insufficient to cause significant inhibition of RBC cholinesterase alone) resulted in an additive effect on RBC cholinesterase inhibition (240). When rats were treated dermally for 2 or 5 days with 0, 2.5, 5, 10, 20, or 50 mg/kg/day coumaphos, no cholinergic toxicity was noted (241). Brain, plasma, and RBC cholinesterase activity, however, were depressed at 50 mg/kg after 2 days, and RBC and brain cholinesterase activity were depressed at 20 mg/kg/day after 5 days (241). Coumaphos is a mild eye irritant, but is not irritating to the skin and is not a skin sensitizer; nor does it produce delayed neurotoxicity in hens (241). 4.4.1.2 Chronic and Subchronic Toxicity No signs of cholinergic toxicity were observed at any dose in rats fed diets that contained 0, 2, 5, or 10 ppm coumaphos for 13 weeks (about 0, 0.2, 0.5, or 1.0 mg/kg/day) (241). However, plasma cholinesterase was inhibited at 10 ppm (1 mg/kg/day), and RBC cholinesterase was inhibited at all dose levels. Brain cholinesterase was not inhibited at any time at any dietary level. When rats were dermally treated with 2, 4, 20, or 100 mg/kg/day coumaphos for 21 days, cholinergic toxicity (muscle fasciculation, tremors) occurred at 20 or 100 mg/kg/day (241). RBC cholinesterase was inhibited at all doses, and brain cholinesterase was inhibited at 20 and 100 mg/kg. In another 21day dermal study, when female rats were given 0, 0.1, 0.5, 1.1, or 2.1 mg/kg/day coumaphos, no signs of cholinergic toxicity were observed at any dose, although RBC cholinesterase was significantly inhibited at 1.1 and 2.1 mg/kg/day (242). 4.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Coumaphos is well absorbed orally. The plasma half-life for coumaphos following oral exposure ranges from 2–3 hours at 1.0 mg/kg and 3–5 hours at 15.0 mg/kg (241). Urinary excretion is rapid; and 63–87% of an administered dose was excreted within 24 hours, and 76–96% of an administered dose was excreted within 168 hours. Tissue residues were highest in fat, kidney, liver, and muscle. Seven days after rats were given single oral doses of about 1 mg/kg coumaphos, about 55% had been excreted in urine and about 24% has been excreted in feces (246). The remaining dose was distributed primarily to the liver, abdominal fat, skin, and kidney. The fate of dermally applied coumaphos was examined in lactating goats given about 14 mg/kg coumaphos (243). During the 7 days after treatment, an average of –25°C Boiling point 134°C at 2 mmHg Vapor pressure 3.4 × 10–4 mmHg at 20°C (mixture) Solubility

slightly soluble in water; soluble in most organic solvents

5.1.2 Odor and Warning Properties Pronounced mercaptan-like odor. 5.2 Production and Use Demeton is a systemic insecticide effective against sap-feeding insects and mites. Before 1989 when it was discontinued by the manufacturer, it was available as emulsifiable concentrates of varying active ingredient content (1). Because demeton is no longer an active ingredient in any registered pesticide product, its registration has been canceled by the U.S. EPA (45). 5.4 Toxic Effects 5.4.1.1 Acute Toxicity Demeton is a highly toxic organophosphate compound that has oral LD50s of

2–6 mg/kg (64a, 248, 249). The oral LD50 for the P–S isomer (demeton-O) in rats was 7.5 mg/kg and for the P–O (demeton-S) isomer was 1.5 mg/kg (250). The sulfoxide and sulfone metabolites of demeton are as lethal as demeton itself; they have oral LD50s in rats of 1.9 to 2.3 mg/kg (251). The dermal LD50s are 8.2–14 mg/kg in rats, nearly equivalent to its acute oral toxicity (64a). However, formulation impacts the dermal toxicity of demeton. An equal volume of emulsifier changed the LD50 from less than 24 to 620 mg/kg, whereas dilution of the mixture to the strength used for spraying greatly increased the toxicity, so that a lethal dose was about 5 mg/kg (478). A single 2-hour exposure to 18 mg/m3 demeton was fatal within 50–90 minutes to all of a group of six rats (250). Rats exposed to 3 mg/m3 demeton for 2 hours/day experienced “no signs of illness during the first exposure” (sic), tremors during the second exposure, lacrimation and more severe tremors during the third exposure, and mortality in 10 of 17 rats during the fourth exposure. Rats exposed to 3 mg/m3 demeton for only 1 hour/day experienced no signs of intoxication after two days; mild tremors after 4 days; marked tremors, lacrimation, and 5% mortality (1/20) after 6 days; and 37% mortality (7/19) after 12 days. One and four-hour LC50 values of 175 and 47 mg/m3 were obtained for rats (123). Demeton was not associated with signs of organophosphate-induced delayed neuropathy when administered subcutaneously to atropinized chickens at doses that ranged from 5–80 mg/kg and were then observed for 30 days (190). 5.4.1.2 Chronic and Subchronic Toxicity When rabbits were given greens sprayed with demeton so that intake was 2.3, 1.5, 0.5, 0.1, or 0.07 mg/kg/day for 40, 30, 100, 98, and 94 days, respectively, no effects occurred in the 0.07- or 0.1-mg/kg/day groups, one of six rabbits fed 0.5 mg/kg/day died after 64 days, four of six rabbits fed 1.5 mg/kg died, and three of six rabbits fed 2.3 mg/kg/day died (250). Rats fed diets that contained 50 ppm demeton containing 48% of the more potent P O isomer (equivalent to 2.6 mg/kg) for 11–16 weeks exhibited cholinergic toxicity (fasciculations, weakness, tremors, lacrimation, and salivation) at 11 weeks, but by 16 weeks they were exhibiting no signs of cholinergic toxicity despite severe brain cholinesterase inhibition (253). No cholinergic signs were observed in rats given diets that contained 1, 3, or 20 ppm demeton for 11–16 weeks. When rats were given 0.4, 0.66, 0.9, and 1.89 mg/kg/day demeton by gavage for 65 days during a 90-day period, signs of cholinergic toxicity (hyperexcitability, tremors) occurred in rats given the two highest doses after 21 days (250). There was one death in the group fed 1.89 mg/kg. In dogs given diets that contained 1, 2, or 5 ppm demeton (0.025, 0.047, or 0.149 mg/kg/day) for 24 weeks, plasma cholinesterase activity was maximally inhibited after about 12 weeks in dogs given the 5-ppm diet and after 16 weeks in dogs given the 2-ppm diet (193). RBC cholinesterase activity was unaffected by the 1- or 2-ppm diets and was slightly inhibited by the 5-ppm diet. When demeton and parathion were in the same diet at levels necessary for cholinesterase inhibition, the effects were additive (193). In an unpublished study submitted to EPA, overt cholinergic toxicity reportedly occurred in rats fed a diet that delivered 0.9 mg/kg/day demeton but not 0.7 mg/kg/day (95). In another unpublished study, cholinsterase inhibition (sic) reportedly occurred in female rats fed diets that contained 3 ppm demeton for 77–112 days but not in rats fed 1 ppm). Cholinergic effects evidently occurred at 20 ppm but not at 10 ppm (95). 5.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms The principal metabolic pathway for both the O- and S-isomers is oxidation of the 2-ethylthioether to sulfoxide and sulfone. In the case of demeton-O, a secondary pathway involves oxidation of P S to P O and subsequent oxidation to sulfoxide and sulfone (257). These oxidation products are more potent inhibitors of

acethylcholinesterase than the parent compound. Studies in mice are consistent with the notion that oxidation of the mercapto sulfur of the ethylmercaptoethyl portion of demeton and the P–O isomer to the corresponding sulfoxide and finally to the sulfone is an important metabolic pathway for demeton (258). 5.4.1.4 Reproductive and Developmental Administration of 7 or 10 mg/kg demeton to mice as a single intraperitoneal dose or as three consecutive doses of 5 mg/kg each between days 7 and 12 of gestation was embryo toxic, as evidenced by decreased fetal weight and slightly higher mortality of the young (254). Fetuses that had intestinal hernias were found at 16 but not at 18 days. The high dose (10 mg/kg) administered on days 8, 9, or 10 of gestation had no effect on litter size at birth or on the survival rate of the young. Ducklings hatched from eggs innoculated with demeton at the rate of 0.01 mg/egg on day 13 of incubation had partial to complete loss of voluntary control of one or both hind legs. Some were excitable and ataxic. The difficulties gradually disappeared about 1 week after hatching, but the growth of treated ducklings remained retarded. Histological examination of the skeletal muscles revealed areas of degenerative change and other areas of marked regenerative activity (255, 256). 5.4.1.5 Carcinogenesis No published studies of the chronic toxicity or oncogenicity of demeton were identified. In an unpublished study submitted to the EPA, dogs were fed diets that contained demeton (all levels not specified) for 24 weeks (95). RBC cholinesterase was inhibited at a dietary concentration of 5 ppm (about 0.125 mg/kg/day), and plasma cholinesterase was inhibited at a dietary concentration of 2 ppm (about 0.05 mg/kg/day). A dietary level of 1 ppm (0.025 mg/kg/day) was without effect on either on either plasma or RBC cholinesterase. In another unpublished study submitted to EPA, cholinesterase (sic) was reportedly inhibited at 0.5 mg/kg/day but not at 0.15 mg/kg/day in rabbits that were given demeton orally for 106 days (95). 5.4.1.6 Genetic and Related Cellular Effects Studies Demeton was reportedly both positive and negative in in vitro tests of bacterial mutagenicity and negative in a sex-linked lethal mutation assay using D. melanogaster (545). 5.4.2 Human Experience 5.4.2.2 Clinical Cases Demeton has been associated with numerous deaths after high accidental and intentional exposures and from occupational exposures (1). Estimates of exposure are not available. A man who spilled 60 mL of concentrated liquid demeton on his thigh, then rinsed his thigh with water but continued wearing the pants, suddenly experienced nausea, vomiting and, weakness after about 9 hours, was treated with atropine, and recovered uneventfully (1). Twelve of fourteen agricultural workers exposed to about 1 mg/m3 demeton reportedly had lowered cholinesterase levels (sic) but displayed no clinical evidence of poisoning (sic) (259). In another study, air concentrations of up to 6 mg/m3 were reportedly without clinical effect, although they were associated with reduced serum cholinesterase activity (259). Eighteen different doses of demeton were evaluated in men who were given oral doses of demeton that began at 0.75 mg per day for 30 days (260). Doses of 4.5 to 6.375 mg/day (equivalent to about 0.06 to 0.09 mg/kg/day assuming a 70-kg body weight) produced average inhibition of plasma cholinesterase that was indistinguishable from normal variation. Doses of 6.75 mg/day (0.10 mg/kg/day) produced an average temporary inhibition of plasma cholinesterase, and a dose of 7.124 mg/day (0.10 mg/kg/day) produced an average of 40% inhibition by day 25. This dose was also associated with an average 16% inhibition of RBC cholinesterase inhibition. However, one of five test subjects had a marked decrease in plasma and RBC cholinesterase activities of 59% and 29%, respectively, after 24 days when given 4.125 mg/day (equivalent to 0.06 mg/kg/day). No clinical signs were observed or reported at any exposure level.

Three volunteers were exposed for two consecutive days to 9–27 mg/m3 Metasystox (30% demetonS-methyl, 70% demeton-O-methyl) while spraying with a hand-held nebulizer. Exposure lasted for 3 and 6 hours on the first and second days, respectively. Plasma and RBC cholinesterase activities measured up to 14 days after exposure did not show significant decreases (262). 5.5 Standards, Regulations, or Guidelines of Exposures Demeton is not registered for use by the U.S. EPA. The ACGIH TLV for demeton is 0.11 mg/m3 with a skin notation (154). The OSHA PEL-TWA is also 0.1 mg/m3 with a skin notation. NIOSH established an IDLH of 10 mg/m3 and REL-TWA of 0.1 mg/m3 with a skin notation. Many other countries have also established Occupational Exposure Limits (OELs) of 0.1 mg/m3 for demeton with a skin notation (Australia, Austria, Belgium, Denmark, Finland, France, Germany, India, The Netherlands, The Philippines, Switzerland, Thailand, and Turkey).

Organophosphorus Compounds Jan E. Storm, Ph.D 6.0 Demeton-S-methyl 6.0.1 CAS Number: [919-86-8] 6.0.2 Synonyms: Ethanethiol, 2-(ethylthio)-S-ester with O,O-dimethyl phosphorothioate; BAY 18436; Bayer 25/154; phosphorothioic acid S-[2-(ethylthio)ethyl] O,O-dimethyl ester; Metasystox (I); metasytox thiol; S(2-(ethylthio)ethyl) O,O-dimethyl phosphorothioate; Methyl-S-Demeton 6.0.3 Trade Names: Demetox®; DEP 836 349; Duratox®; Isometasystox®; Isomethylsystox®; Metaisoseptox®; Metaisosytox; Metasystox (I)® 6.0.4 Molecular Weight: 230.3 6.0.5 Molecular Formula: C6H15O3PS2 6.0.6 Molecular Structure:

6.1 Chemical and Physical Properties Demeton-S-methyl is an oily, colorless to pale yellow liquid. It is hydrolyzed by alkali and oxidized to the sulfoxide (oxydemeton-methyl) and sulfone (demeton-S-methylsulfone). Specific 1.21 at 20°C gravity Boiling 74°C at 0.15 mmHg; 92°C at 0.2 mmHg; 102°C at 0.40 mmHg; 118°C at 1 mmHg point Vapor 1.6 × 10–4 mmHg at 10°C; 4.8 × 10–4 at 10°C; 1.45 × 10–3 at 30°C; 3.8 × 10–3 mm pressure Hg at 40°C Solubility soluble in water (3.3 g/L); readily soluble in most organic solvents (e.g., dichloromethane, 2-propanol, toluene); limited solubility in petroleum solvents

6.1.2 Odor and Warning Properties Unpleasant odor. 6.2 Production and Use Demeton-S-methyl was first marketed in 1957. It replaced technical grade methyl demeton which had been introduced in 1954 and was a 70:30 mixture of O,O-dimethyl-O-ethylthioethyl phosphorothioate (demeton-O-methyl or O-isomer) and O,O-dimethyl-S-ethylthioethyl phosphorothioate (Demeton-S-methyl or S-isomer). Demeton-S-methyl is a systemic and contact insecticide and acaricide used to control aphids, red spider mites, whiteflies, leafhoppers, and sawflies on garden crops, fruit, and hops (155). It is applied as an emulsifiable concentrate formulation, mainly as a spray, and usually at a concentration of 0.025% active ingredient. 6.4 Toxic Effects 6.4.1.1 Acute Toxicity Demeton-S-methyl is an organophosphate that has high oral toxicity with oral LD50s of 33–130 mg/kg (262). The toxicity of demeton-S-methyl is markedly increased when it is allowed to age and forms sulphonium derivatives (263) Intravenous and oral LD50s for the sulfoxide and sulfone derivatives of demeton-S-methyl were 22–47 mg/kg and 32–65 mg/kg, respectively (261). Intraperitoneal LD50s of 7.5 and 10 mg/kg were also reported for demeton-S-methyl, suggesting that oral absorption may be slightly limited and/or that bypassing first-pass hepatic metabolism enhances toxicity (262). Dermal LD50s from 45 to 200 mg/kg, depending on formulation and duration of exposure, were reported for rats, indicating that dermal exposures are about as potent as oral exposures on a milligram per kilogram basis (262). Dermal application of 10 mg/kg to the backs of cats caused mild signs (sic); application of 20 or 100 mg/kg caused death (no other details provided) (IPSC 1997). Four hour LC50s for rats were 210–500 mg/m3 (545). Demeton-S-methyl applied to the shaved skin of rabbits for four hours caused mild erythema and edema that disappeared after three days (262). No signs of eye irritation occurred in rabbits whose eyes were treated with a 0.5% aqueous solution of demeton-S-methyl, but an undiluted formulation caused severe lacrimation and miosis. Mild corneal opacity and discrete redness and edema of conjunctivae were observed that disappeared within about 7 days (262). Demeton-S-methyl had skin sensitizing potential when assessed using the guinea pig mazimization test but did not have skin sensitizing potential when assessed using the Buehler epidermal patch test on guinea pigs (262). 6.4.1.2 Chronic and Subchronic Toxicity When groups of six rats were fed diets that contained 50, 100, or 200 ppm (aged) demeton-S-methyl (5, 10, and 20 mg/kg/day, respectively) for six months, cholinergic signs (slight tremors, fasciculations) occurred at 200 ppm during the first 5 weeks (263). Decreased body weight gain in the 10- and 20-mg/kg/day rats and decreased brain and RBC cholinesterase activities occurred at 5 ppm and higher. 6.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Demeton-S-methyl is completely absorbed and very rapidly eliminated following either oral or intravenous administration. Blood concentration decreased, and the half-life was about 2 hours during the first 6 hours and then about 6 hours for the next 48 hours following oral administration of demeton-S-methyl to rats. The half-life thereafter was even longer. The half-life of urinary elimination was 2–3 hours during the first 24 hours and 1.5 days thereafter. Elimination through feces and exhaled air was minimal and accounted for 0.5–2% and about 0.2% of the dose, respectively. Except for RBCs which tended to bind the demeton-S-methyl, it was distributed uniformly in various body tissues and organs. At 2, 24, and 48 hours after dosing, about 60%, 1%, and 0.5% of the administered dose, respectively, remained in the body. By 10 days, demeton-S-methyl was almost undetectable in most organs except in the RBCs (262). The main metabolic route of demeton-S-methyl is oxidation of the side chain leading to the formation of the corresponding sulfoxide, oxydemeton methyl, and to lesser extent, after further oxidation, the sulfone (262). O-demethylation also occurs. Neither glucuronide nor sulfate conjugates have been identified (262).

6.4.1.4 Reproductive and Developmental Pup viability, lactation index, and body weight gain were reduced in F1 offspring when rats were fed a diet that contained 25 ppm demeton-S-methyl for two generations (202). Offspring of rats fed 1 or 5 ppm were unaffected. No compound-related malformation was found in animals of any of the treatment groups. No alterations of physical appearance or behavior occurred in dams or fetuses from dams given 0, 0.3, 1, or 3 mg/kg demeton-S-methyl by gavage on days 6 to 15 of gestation (262). The numbers of live fetuses and resorptions, fetal weight, number of fetuses with malformations, and number of implants were comparable in all groups. No treatment-related visceral or skeletal abnormalities were observed (262). No abortions or increases in the numbers of implantations per day, preimplantation losses, postimplantation losses, resorptions, living and dead fetuses, or sex ratios occurred in rabbits given 3, 6, and 12 mg/kg/day demeton-S-methyl by gavage on gestation days 6 to 18. Diarrhea, decreased food consumption, and decreased fetal body weight occurred in the 12 mg/kg/day treated animals. There was no treatment-related increase in gross, skeletal, or visceral malformations (262). 6.4.1.5 Carcinogenesis When dogs were fed diets containing 1, 10, or 100 ppm (day 1–36) followed by 50 ppm (day 37-termination) demeton-S-methyl (equivalent to 0.036, 0.36, and 4.6 followed by 1.5 mg/kg/day), diarrhea and vomiting occurred at all levels (262). Multifocal slight/moderate atrophy and/or hypertrophy of proximal renal tubules also occurred in the high dose group. Plasma and RBC cholinesterase activity was reduced at 10 and 100 ppm, and, brain cholinesterase activity was reduced at 10 ppm. There was no evidence of carcinogenicity in mice given diets with 1, 15, or 75 ppm demeton-Smethyl (0.24, 3.47, or 17.81 mg/kg/day (males); 0.29, 4.18, or 20.0 mg/kg/day (females)) for two years (271). Cholinergic signs were not observed at any level nor did mortality differ among groups. Plasma, RBC, and brain cholinesterase activity decreased in mice at 15 and 75 ppm. There was no evidence of carcinogenicity in rats given 1, 7, or 50 ppm demeton-S-methyl in their feed (0.05, 0.31, or 2.59 mg/kg/day (males); 0.06, 0.41, or 3.09 mg/kg/day (females)) for 24 months (262). Hair loss and diarrhea occurred more frequently at 50 ppm. Body weight was reduced in males at 7 ppm and in both males and females at 50 ppm. Plasma, RBC, and brain cholinesterase activites decreased in groups given the 7- or 50-ppm diet. Increased incidence of retinal atrophy and keratitis was observed in mice given the 50-ppm diet. 6.4.1.6 Genetic and Related Cellular Effects Studies Available information is insufficient to permit an adequate assessment of the genotoxic potential of demeton-S-methyl (262). Demeton-S-methyl did not induce DNA damage in the Pol test in E. coli with or without metabolic activation, but it did increase mutation rates in the Ames test and in the mouse lymphoma forward mutation assay with or without metabolic activation. In in vivo tests, no sister chromatid exchanges (SCEs) were found in the bone marrow of Chinese hamsters treated with high doses of demeton-S-methyl, and, bone marrow micronucleus and dominant lethal tests in mice treated with demeton-S-methyl gave negative results. However, chromosomal aberrations were found in the bone marrow of Syrian hamsters treated with a commercial formulation of demeton-S-methyl (262). 6.3.5 Biomonitoring/Biomarkers Urinary levels of the metabolite dimethyl phosphorothiolated potassium salt (DMPThK) and plasma and whole blood cholinesterase activities were monitored in agricultural workers exposed to demeton-S-methyl for 3 consecutive days (262). Exposed subjects were identified as either mixers, sprayers, or others not directly involved in handling the pesticide. Levels of DMPThK in urine from mixers had a medium (sic) value of 83 mg/liter and a range of 0– 822 mg/liter (neither corrected for creatinine nor for urine volume); urine from sprayers had a mean value of 30 mg/liter (limit of detection) and a range of 0–208 mg/liter, and urine from other subjects not directly exposed had a mean value of 30 mg/liter and a range of 0–100 mg/liter. Whole blood cholinesterase activity was not affected by exposure, and plasma cholinesterase activity was slightly reduced compared to preexposure levels in mixers. No correlation was found between DMPThK levels and plasma cholinesterase activity (269).

6.4.2 Human Experience 6.4.2.2 Clinical Cases Six hundred seventy-three occupational cases of organophosphate poisoning, including three deaths, reportedly occurred in Egypt about 1 week after demeton-S-methyl began to be used for spraying cotton (265). Two children evidently accidentally exposed to demeton-S-methyl via inhalation while waiting for their father (a sprayman) to finish work, became unconscious for a few minutes. When aroused, they vomited and complained of abdominal colic. Another girl who evidently ate beans contaminated during spraying also vomited and suffered abdominal colic. One woman attempted suicide by ingesting “1 or 2 mouthfuls” of Metasystox I (25% demeton-Smethyl). On admission to hospital she was comatose, sweating, salivating and had pinpoint pupils. Plasma and RBC cholinesterase activites were less than 10% of normal. She was successfully treated and released after 30 days at which time plasma cholinesterase values had returned to normal, but RBC cholinesterase activity was still below normal (262). In another suicide attempt, a 41-year-old pregnant woman was admitted to a hospital about 3.5 hrs after ingesting an estimated 12 g of methyl demeton. Upon admission, blood (sic) cholinesterase was 10% of normal. About 12 hours after admission, she became comatose and was treated with atropine, odoxime, haemoperfusion, and artificial ventilation. She recovered and was discharged 24 days later (262). A man who had been an agricultural applicator for five years worked with demeton-S-methyl, mainly as a flagman in aerial spraying but also in preparing the spray and in cleaning containers after spraying. For about a month and half, he was potentially exposed for periods that varied from 20 minutes to 6¾ hours. Symptoms (headaches, nausea, dizziness) gradually increased in severity during the week and subsided during the weekend. Later, he developed anorexia and loss of ability to concentrate. At the end of 6 weeks, his symptoms became worse while he was driving a tractor applying disulfoton. After 2 hours, he became dissatisfied with his control of the machine and sought medical aid. Clinical findings were normal, but cholinesterase activity was low (266). The author concluded that the man had suffered from gradually worsening organophosphate poisoning primarily due to absorption of demeton-S-methyl through the skin (despite the use of required protective clothing) that began about 2–3 weeks after initial exposure. Organophosphate poisoning following demeton-S-methyl exposure was described in six men engaged in packaging bulk loads of demeton-S-methyl concentrate (500 g/L) into one liter containers (267). The first poisoned worker experienced cholinergic symptoms (nausea, dizziness, weakness, difficult breathing, and diarrhea) after working 1 day filling containers; the second experienced symptoms (giddiness, nausea, weakness, sweating, and cramps) after 72 hours. The filling procedure was modified to decrease worker exposure by requiring more protective clothing and performing operations in a fume “cupboard,” but a third worker experienced symptoms (nausea, abdominal cramps, and weakness) after working 2 days using the revised procedure. Plasma and RBC cholinesterase activities measured 15–30 days after exposure were below the lower limit of the normal range and did not completely recover to the normal range until 60 days after exposure. Chemical analysis of vapor in the fume hood and of residue on gloves and other clothing indicated that exposure had occurred primarily via dermal absorption that resulted from contamination of external and internal surfaces of gloves. Six workers engaged in hop cultivation using Metasystox I (reported to contain demeton-O-methyl instead of demeton-S-methyl as the commercial name implies) were monitored. They sprayed up to 2400 liters of a 0.1% solution (in water) of the insecticide in 1 day. No significant inhibition of blood acetylcholinesterase was observed at the end of exposure or 1 or 2 days later. One subject, who was exposed twice, showed a 29% decrease in blood (sic) acetylcholinesterase after the second exposure. No cholinergic toxicity was observed in these workers (262). In a group of men who sprayed cotton fields with demeton-S-methyl, signs and symptoms of cholinergic toxicity (gastrointestinal disturbances, dizziness, persistent general weakness and fatigue, respiratory manifestations, headache, sweating, salivation or lacrimation, tremors of outstretched

hands, intention tremors, ataxia, exaggerated superficial and deep reflexes, hiccough, and muscular fasciculations) occurred after 1–18 days of exposure, and the mean latency period was 3 days (265). Serum cholinesterase activity estimates were performed within 24 hours after the onset of symptoms in some patients and after the cessation of symptoms in some others. In most cases, they were repeated two to three times at various intervals up to 40 days from the onset of symptoms. In general, serum cholinesterase activity underwent a marked initial fall followed by a rise above normal levels after about 30–40 days (265). 6.5 Standards, Regulations, or Guidelines of Exposure Demeton-S-methyl is not registered by the EPA for use. It is anticipated that most other national registrations for demeton-S-methyl were probably transferred soon after 1998 to oxydemeton-methyl (262). No Occupational Exposure Limits were identified for demeton-S-methyl. In the 2000 ACGIH TLVs, in the notice of intended changes, ACGIH proposes a TLV of 0.05 mg/m3, for demeton-Smethyl.

Organophosphorus Compounds Jan E. Storm, Ph.D 7.0 Diazinon 7.0.1 CAS Number: [333-41-5] 7.0.2 Synonyms: O,O-diethyl O-2-diethyl O-2-isopropyl-4-methyl-6-pyrimidinyl thiophosphate; phosphorothioic acid, O,O-diethyl-O-(2-isopropyl-6-methyl-4-pyrimidinyl)ester; Dimpylate; O,O-diethyl O-(2-isopropyl6-methyl-4-pyrimidinyl), phosphorothioate; O,O-diethyl O-(6-methyl-2-(1-methylethyl)-4pyrimidinyl) phosophorothioatae; phosphorothioic acid O,O-diethyl O-[6-methyl-2-(1-methylethyl)4-pyrimidinyl] ester; thiophosphoric acid 2-isopropyl-4-methyl-6-pyrimidyl diethyl ester; O,Odiethyl O-2-isopropyl-4-methyl-6-pyrimidyl thiophosphate; Knox Out; dianon; gardentox; kayazinon; g-24480; diethyl 2-isopropyl-6-methyl-4-pyrimidinyl phosphorothionate; O,O-diethyl O(6-methyl-2-(1-methylethyl)-4-pyrimidinyl) phosphorothioate; Dipofene; Diazitol; AG-500; Antigal; Dacutox; Dassitox; Dazzel; Diagran; Diaterr-fos; Diazajet; Diazide; Diazol; diethyl 2-isopropyl-4methyl-6-pyrimidinyl phosphorothionate; diethyl 2-isopropyl-4-methyl-6-pyrimidyl thionophosphate; diethyl O-(2-isopropyl-6-methyl-4-pyrimidinyl) phosphorothioate; Dimpylatum; Drawizon; Dyzol; Exodin; Fezudin; Flytrol; Galesan; isopropylmethylpyrimidyl diethyl thiophosphate; Kayazol; Knox out 2FM; Neocidol; Nipsan; Nucidol; Sarolex; Dizinon; O,O-diethyl O-(2-isopropyl-4-methyl-6-pyrimidinyl) thiophosphoric acid 7.0.3 Trade Names: Spectracide®, Basudin®, Diazitol®, Dipofene®, Neocidol®, Nucidol® 7.0.4 Molecular Weight: 304.36 7.0.5 Molecular Formula: C12H21N2O3PS 7.0.6 Molecular Structure:

7.1 Chemical and Physical Properties Diazinon is a colorless liquid. Specific gravity Boling point Melting point Vapor pressure Solubility

1.116–1.118 at 20°C 83–84°C at 0.002 torr >120°C (dec) 1.4 × 10–4 mmHg at 20°C slightly soluble in water (0.004 g/100 mL); freely soluble in petroleum solvents; miscible with alcohol, ether, benzene, and similar hydrocarbons

7.1.2 Odor and Warning Properties Faint ester-like odor. 7.2 Production and Use Diazinon is a nonsystemic insecticide used on a wide variety of agricultural crops such as rice, fruit trees, corn, tobacco, and potatoes and to control fleas and ticks. Various types of formulations are available, including dusts, emulsifiable concentrates, impregnated material, granules, microencapsulated forms, pressurized sprays, soluble concentrates, and wettable powders (55). 7.4 Toxic Effects 7.4.1.1 Acute Toxicity Diazinon is a moderately toxic organophosphate compound that has oral LD50s of 250–466 mg/kg (64a). Oral LD50s for an impure formulation were 76–108 mg/kg (Gaines, 1960). The dose–lethality curve is steep as illustrated by the observation that acute LD01s are only 30–36% smaller than LD50s (64a) and that an acute oral dose of 528 mg/kg was lethal to rats whereas a dose of 264 mg/kg was not (55). Dermal LD50s were 455–900 mg/kg (64a, 268). The dermal LD50 for male rats of a sample allowed to completely crystallize in air for several weeks was 34 mg/kg, demonstrating that acute dermal toxicity increases significantly with an impure diazinon formulation (268). Onset of symptoms and death following acute exposures to diazinon occurs between 1 and 6 hours from oral exposures (81, 271) but may be delayed following dermal exposure by about 10 hours (272). A 4-hour LC50 of 3500 mg/m3 was reported for rats; a 4-h LC50 of 1600 mg/m3 was reported for mice, and a 4-hour LC50 of 55,500 mg/m3 was reported for guinea pigs (545). No deaths occurred among rats exposed to 2330 mg/m3 diazinon for 4 hours in inhalation chambers and observed for 14 days, although decreased activity and increased salivation were noted (55). No signs of organophosphate toxicity occurred in rats exposed to 0.05, 0.46, 1.57, or 11.6 mg/m3 for 6 h/day, 5 days/week for three weeks (55). Serum cholinesterase activity decreased in females exposed to 0.46 mg/m3 and higher and in males exposed to 1.57 mg/m3 and higher; RBC acetylcholinesterase activity decreased in females exposed to 11.6 mg/m3, and brain acetylcholinesterase activity decreased in females exposed to 1.57 and 11.6 mg/m3. Among male rats that were given single doses of 100, 200, or 400 mg/kg diazinon by gavage, cholinergic signs (lacrimation, salivation, miosis, hypoactivity, ataxia, increased landing foot splay, decreased tail-pinch response, tremors, chewing (smacking), and hypothermia) peaked at 4 hours in the 400-mg/kg group and were still present at 24 hours, but had disappeared by 72 hours after dosing (55). Cholinergic toxicity also occurred in the 200-mg/kg group, and only hypoactivity and decreased defecation occurred in the 100-mg/kg group. Among rats given single oral doses of 2, 132, 264, or 528 mg/kg diazinon, cholinergic signs (autonomic (smacking), neuromuscular (ataxia, abnormal gait)) occurred at 132 mg/kg and higher (55). Serum cholinesterase and RBC

acetylcholinesterase activity was reduced at all levels (55). Diazinon was not neurotoxic in atropinized hens given 11.3 mg/kg twice orally, 21 days apart (55). 7.4.1.2 Chronic and Subchronic Toxicity No cholinergic toxicity occurred in rats fed diets that contained up to 1000 ppm technical diazinon for four weeks (82), in rats or mice fed diets that contained up to 1600 ppm for 13 weeks (87), in rats given diets that contained up to 25 ppm diazinon for up to 92 days (79, 80) or in rats fed diets, that contained up to 125 ppm diazinon for 15–16 weeks (81). Subchronic exposures in the 3- to 100-ppm range were associated with inhibition of RBC acetylcholinesterase activity, and exposures to 1000 ppm were associated with brain acetylcholinesterase inhibition (79–82). Six week exposures of rats to up to 180 mg/kg/day via their diet caused no cholinergic toxicity, although RBC acetylcholinesterase activity was inhibited at doses of 8 or 9 mg/kg/day (83). Thirteen-week exposures of rats to 168 or 212 mg/kg/day resulted in cholinergic signs (soft stools and hypersensitivity to touch and sound), although RBC acetylcholinesterase activity was inhibited at doses as low as 15 mg/kg/day (83). No cholinergic toxicity occurred in dogs given diazinon via their diet (0.25, 0.75, or 75 ppm) for 12 weeks, although RBC acetylcholinesterase activity was inhibited for 6 weeks after termination of dosing to dogs given the 75-ppm diet (84). When dogs were given diets that contained 0.1, 0.5, 150, and 300 ppm diazinon for 13 weeks, cholinergic signs (emesis and diarrhea) occurred but were not dose-related (90). Significant reductions in RBC and brain acetylcholinesterase levels occurred in rats fed the 150-ppm diet. 7.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Absorption of diazinon following oral exposures is rapid and complete. Nearly 100% of orally administered diazinon was recovered in urine (70–80%) and feces (16–24%) within 168 hours in rats (98). Diazinon was not detected later than 2 days after a final repeated dose of diazinon, demonstrating that it does not accumulate in tissues (98). The biological half-life of diazinon was 12 hours. In dogs, absorption was at least 85% after a single oral dose (99). About 68% of an oral dose of diazinon was detected in urine 60 minutes after dosing in mice. In all cases, diazinon is widely distributed to tissues, especially adipose tissue, muscle, brain, and liver (101). Similar results were observed in dogs, guinea pigs, goats, sheep, and cows (55). The pharmacokinetics of diazinon following inhalation exposure has not been studied. However, pharmacokinetic studies following intravenous administration of diazinon to dogs indicated rapid absorption and an elimination half-life of 6 hours (99). Recovery in urine was 58% of the administered dose after 24 hours and was primarily diethyl phosphoric and phosphorothioic acid. In rats given diazinon intravenously, plasma diazinon levels declined rapidly during the distribution phase and more slowly during the elimination phase and were characterized by an elimination halflife of about 6 hours (102). In another study that examined the toxicokinetics of diazinon in rats following oral and intravenous exposure, the elimination half-lives were 1.8 and 4.7 hours, respectively, suggesting that hepatic metabolism enhances elimination (102). In four rhesus monkeys dosed intravenously with 32 mg diazinon, about 56% was excreted in urine, and 23% was eliminated in feces after 7 days, accounting for about 70% of the total dose. Most of the dose was excreted in urine on day 1 (103). Total dermal absorption of diazinon was estimated at about 3–4% of the dose applied to the forearm or abdomen (2 mg/cm3) of humans during 7 days regardless of whether the vehicle was acetone or lanolin (103). Absorption measured in human skin placed in an in vitro diffusion cell was about 14%. The metabolism of diazinon is complex. The primary pathways are desulfuration by cytochrome P450 enzymes to the metabolite diazoxon which then either binds to acetylcholinesterase and other esterases or is further metabolized to diethyl phosphoric acid and oxidative products such as 2-

isopropyl-4-methyl-6-hydropyrimidine (104, 105). Alternatively, diazinon is dearylated and hydrolyzed by cytochrome P450 enzymes to diethyl phosphorothioic and phosphoric acid and other oxidation products (e.g. 2-isopropyl-4-methyl-6-hydropyrimidine) which are excreted mostly in urine, although minor amounts of these metabolites and some unchanged diazinon have been detected in feces (98, 100, 104). 7.4.1.4 Reproductive and Developmental Diazinon did not cause adverse effects on fertility in rats fed 0.05 mg/kg/day diazinon in the diet for 60 days before weaning for four generations (89). No gross or histological treatment-related damage to reproductive tissues occurred in rats given up to 168 mg/kg/day (males) or 212 mg/kg/day (females) diazinon for 13 weeks (83), in rats given up to 10 mg/kg/day (males) or 12 mg/kg/day (females) for 98 weeks (86), or in dogs given up to 11 mg/kg/day for 13 weeks (90). In another study, testicular atrophy and arrested spermatogenesis were observed in one dog given 10 mg/kg/day and in all dogs given 20 mg/kg/day for 8 months via corn oil capsule (85). No teratogenic or fetotoxic effects occurred in rabbits given 7–100 mg/kg/day diazinon by gavage during gestation (91, 92). Cholinergic signs occurred in dams given 30 mg/kg or more. In hamsters, no embryo- or teratogenicity occurred at doses up to 0.25 mg/kg/day during gestation, although cholinergic toxicity occurred in parents (diarrhea, salivation, and incoordination). In another study, however, diazinon caused an increased incidence of stillbirths in dogs given 1.2 or 5 mg/kg/day by gavage (85). In rats, doses greater than or equal to 70.6 mg/kg/day during gestation increased fetal resorptions when given on days 8 to 12 or 12 to 15; no effects occurred at doses less than 70.6 mg/kg/day (93). In another study, no differences were observed in litter size, fetal body weight, fetal brain weight, number of resorptions, or corpora lutea among rats given diazinon via peanut oil gavage at 0, 40, 50, 60, or 75 mg/kg/day on gestation days 7 through 19 (94). Pregnant mice given 0, 0.18, or 9 mg/kg/day diazinon throughout gestation (18 days) gave birth to viable offspring, although pups exposed to 9 mg/kg grew more slowly than controls (590). Mature offspring of both treated groups displayed impaired endurance and coordination on rod cling and inclined place tests of neuromuscular function. Morphological abnormalities in brain occurred among offspring of dams exposed to 9.0 mg/kg/day. 7.4.1.5 Carcinogenesis No signs of cholinergic toxicity occurred in rats given diets containing 10 to 1000 ppm diazinon for 72 weeks or in dogs given up to 4.6 mg/kg/day diazinon via capsule 6 days/week for up to 46 weeks (82). Doses of 4.3 to 4.6 mg/kg/day, however, caused significant RBC cholinesterase inhibition in dogs after two week (82). Cholinergic signs (soft stools) occurred in dogs given 9.3 mg/kg by 30 days and excitability and tremors occurred in one dog given 25 mg/kg/day for 6 days. In dogs given 2.5, 5.0, 10.0, or 20.0 mg/kg/day diazinon by gavage for 8 months, cholinergic signs were observed in one dog given 10 mg/kg/day and emesis, fasciculation and mortality occurred in dogs given 20.0 mg/kg/day (85). No cholinergic toxicity occurred in pigs given 1.25 mg/kg/day for eight months; but cholinergic signs were observed pigs given 2.5–10 mg/kg/day (85). No signs of cholinergic toxicity occurred in rats given diazinon via their diet at doses of 0.004, 0.06, 5, or 10 mg/kg/day (males) and 0.005, 0.07, 6, or 12 mg/kg/day (females) for 52 or 98 weeks (86). After 1 year, RBC acetylcholinesterase activity decreased in males given 5 and 10 mg/kg/day and in females given 6 or 12 mg/kg/day; brain acetylcholinesterase activity was unchanged in males but decreased in females given 6 or 12 mg/kg/day. During a 4-week recovery period, RBC acetylcholinesterase activity returned to normal in males, whereas that of females dosed at 12 mg/kg/day remained decreased; brain acetylcholinesterase activity returned to normal in females. Results were similar at 98 weeks. Diazinon was not carcinogenic in rats or mice when they were given diets containing 400 or 800 ppm diazinon (rats) or 100 or 200 ppm diazinon (mice) for 2 years (87). However, clinical signs of hyperactivity were noted in low- (males) and high-dose (males and females) rats and in all dosed mice (sic). Bloating, vaginal bleeding, and vaginal discharge were also noted in the dosed female

rats. No cholinergic, hematological, clinical chemistry, or histopathological signs occurred at any dose in monkeys given oral doses of 0, 0.05, 0.5, or 5 mg/kg diazinon 6 days/week for two years via gavage, although serum and RBC cholinesterase activities were inhibited in monkeys given 0.5 or 5 mg/kg/day (88). 7.4.1.6 Genetic and Related Cellular Effects Studies The genotoxicity of diazinon is equivocal. In vitro test results showed that diazinon was positive for gene mutations in the S. typhimurium test assay with metabolic activation and in the mouse lymphoma cell forward mutation assay without metabolic activation (55, 96). Diazinon was also positive for chromosomal aberrations in Chinese hamster cells with metabolic activation (55). But in other tests, diazinon was negative for gene mutations in the S. typhimurium test assay (97) and in the rec assay utilizing strains of Bacillus subtilis (55) both of which were conducted without metabolic activation. Tests for sister chromatid exchange in Chinese hamster V79 cells with and without metabolic activation (55) and for chromosomal aberrations in human peripheral blood lymphocytes (55) were also negative. 7.4.2 Human Experience 7.4.2.2 Clinical Cases Ingestion of diazinon causes typical organophosphate poisoning that varies in intensity with dose (107–109). Lethality followed adult ingestion of an estimated 293 mg/kg diazinon (110) and child ingestion of 20 mg/kg (111), although the latter estimate may have been complicated by the possible simultaneous ingestion of parathion and/or chlordane. A summary of 76 fatal cases of diazinon poisoning indicated a high incidence of miosis, froth from nose and mouth, acute pulmonary edema and congestion, acute ulcers, blood stained gastric contents, CNS hemorrhage, and evidence that death was due to asphyxiation (109). No estimates of exposure levels were provided. Cholinergic symptoms (nausea, epigastric pain, headache, miosis and unreactive pupils, tachycardia) occurred in a woman who ingested an estimated 1.5 mg/kg diazinon (112). Severe toxicity (bradycardia, tachycardia, clonus, stupor, profuse diaphoresis, sialorrhea, miosis, hyperreflexia, weakness, dysdiadokinesis, abdominal pain, nausea, coma, twitching, restlessness, and bronchospasm) was reported in five individuals who intentionally ingested estimated doses of 240 to 986 mg/kg diazinon and recovered (113). Signs of organophosphate poisoning (profuse sweating, nausea, vomiting, and abdominal cramps) were reported in children who had eaten oatmeal contaminated with about 2.5–244 ppm diazinon (114). An earlier report indicated that oatmeal contaminated by home spraying with a 25% concentrate of diazinon caused organophosphate poisoning (nausea, vomiting, abdominal cramps, diaphoresis, muscular weakness, rolling eye movements, ataxia, and muscle cramps) in eight children from two different families (115). A man died from cardiac arrest, despite atropine therapy, following inhalation exposure to a commercial insecticide formulation containing diazinon and malathion, but no estimate of exposure was provided (115a). Inhalation exposures to a diazinon spray used to kill cockroaches in an adjoining apartment were implicated in the organophosphate poisoning of twin infants (116). Depressed serum cholinesterase activities were only sometimes accompanied by signs of cholinergic toxicity in individuals occupationally exposed to diazinon primarily via inhalation (117). However, cholinergic symptoms (headache, blurred vision, dizziness, fatigue, nausea, and vomiting) began within 15 minutes in mushroom workers exposed to diazinon when it was sprayed around the only entrance to a room in which they were working. Reduced serum and RBC cholinesterase activities also occurred within 48 hours, and serum cholinesterase activities remained depressed for 15 days (118). Based on comparison with stabilized cholinesterase measurements taken in affected individuals 15 days after exposure, the authors estimated that plasma cholinesterase activities had been inhibited by about 30–34% and RBC acetylcholinesterase activities had been inhibited by about 27–34%. In another report that involved multiple routes of exposure, several family members experienced

diazinon poisoning (headache, vomiting, fatigue, and chest heaviness) associated with slightly depressed serum cholinesterase activities for several months after their home had been treated with diazinon (118a). Surface concentrations in the home ranged from 126 to 1051 mg/m2, air concentrations were between 5 and 27 mg/m3, and some clothing showed contamination (0.5 to 07 mg/g). Dermal exposure to diazinon caused cholinergic signs (cyanosis, forthing at the mouth, drowsiness, nausea, vomiting, abdominal colic, diarrhea, tachpnea, miosis, and sinus tachycardia) in two female gardeners (119), but estimates of exposure were not available. Exposure to diazinon via multiple routes was estimated at an average of 0.02 mg/kg/day in 99 workers exposed to diazinon granules 8 h/day for 39 days during an insecticide application program. Slight neurological functional deficits (postshift symbol-digit speed and pattern memory accuracy) were reported among the workers, but these effects were not statistically significant (120). 7.5 Standards, Regulations, or Guidelines of Exposure Diazinon is under reregistration by the EPA (78). The ACGIH TLV for diazinon is 0.1 mg/m3 with a skin notation (154). The OSHA PEL-TWA and NIOSH REL-TWA are 0.1 mgm3 with a skin notation. Most other countries have also established an Occupational Exposure Limit of 0.1 mg/m3 for diazinon (Australia, Belgium, Denmark, Finland, France, Germany, India, The Netherlands, and the United Kingdom).

Organophosphorus Compounds Jan E. Storm, Ph.D 8.0 Dichlorvos 8.0.1 CAS Number: [62-73-7] 8.0.2 Synonyms: O,O-dimethyl-O-2,2-dichlorvinyl dimethyl phosphate; 2,2-dichlorovinyl dimethylphosphate; DDVP; dichlorophos; Equigand; No-Pest Strip; 2,2-dichlorovinyl-O,O-dimethyl phosphate; phosphoric acid 2,2-dichloroethenyl dimethyl ester; phosphoric acid 2,2-dichlorovinyl dimethyl ester; SD 1750; Astrobot; Atgard; Canogard; Dedevap; Dichlorman; Divipan; Equigard; Equigel; Estrosol; Herkol; Nogos; Nuvan; 2,2-dichloroethenyl dimethyl phosphate; 2,2-dichlorovinyl dimethyl phosphoric acid ester; 2,2-dichloroethenyl phosphoric acid dimethyl ester; dimethyl 2,2-dichloroethenyl phosphate; dimethyl 2,2-dichlorovinyl phosphate; O,O-dimethyl dichlorovinyl phosphate; O,O-dimethyl O-2,2dichlorovinyl phosphate; 2,2-dichlorovinyl alcohol dimethyl phosphate; apavap; atgard c; atgard v; bay-19149; benfos; bibesol; brevinyl; brevinyl e50; chlorvinphos; deriban; derribante; devikol; duokill;duravos; estrosesel; fecama; fly-die; fly fighter; herkal; krecalvin; MAFU; mafu strip; marvex; mopari; nerkol; nogos 50; nogos g; no-pest; NUVA; nuvan 100ec; OKO; OMS 14; phosvit; szklarniak; TASK; Tenac; task tabs; tetravos; UDVF; unifos; unifos 50 ec; vaponite; vapora ii; verdican; verdipor; vinylofos; vinylophos; bayer 19149; O,O-dimethyl 2,2-dichlorovinyl phosphate; fekama; insectigas d; nefrafos; nogos 50 ec; novotox; nuvan 7; panaplate; winylophos; 2,2dichloroethenol dimethyl phosphate; Cekusan; Cypona; Delevap; Derriban; Dichloroethenyl dimethyl phosphate; Equiguard; Prentox; Verdisol; DichlorvosI [Dimethyl Dichlorovinyl Phosphate] 8.0.3 Trade Names: Vapona® 8.0.4 Molecular Weight: 220.98 8.0.5 Molecular Formula:

C4H7Cl2O4P 8.0.6 Molecular Structure:

8.1 Chemical and Physical Properties Dichlorvos is a colorless to amber, oily liquid. It hydrolyzes at a rate of 3% per day in saturated aqueous solution at room temperature; at high pH or in boiling water, it completely hydrolyzes in 1 hour. Dichlorvos decomposes to toxic gases and vapors (such as hydrogen chloride gas, phosphoric acid mist, and carbon monoxide) Specific 1.415 g/ml at 25°C gravity Boiling point 140°C at 20 mmHg; 221°C at 760 mmHg Melting point –60°C Vapor 0.012 torr at 20°C pressure Solubility slightly soluble in water (1 g/100 mL at 20°C); miscible with aromatic and chlorinated hydrocarbon solvents and alcohols 8.1.2 Odor and Warning Properties Mild chemical odor. 8.2 Production and Use Dichlorvos is used against a wide variety of insects in greenhouses, outdoor fruit and vegetable crops, and is also used in aquaculture to rid fish of various skin parasites. In addition, it is used to control severe internal and external parasite infestations in animals and humans (57). It is a available as soluble concentrates and aerosols and is also formulated with other pesticides. 8.4 Toxic Effects 8.4.1.1 Acute Toxicity Dichlorvos is an organophospahte that has high oral toxicity, oral LD50s of 56–98 mg/kg in rats, and oral LD50s 133–139 mg/kg in mice (57). Dose–lethality curves are steep; oral LD01s are about one-half or less the LD50 value (62, 64a), and death occurs quickly within minutes. Cholinergic signs occurred within 7–15 minutes in dogs given a single oral dose of 11 or 22 mg/kg dichlorvos (62a). Three of 12 dogs given 22 mg/kg died within 10–155 minutes of treatment. Similar effects occurred when dogs were given 2–11 mg/kg dichlorvos intravenously, but death occurred slightly more rapidly, by 7 minutes in one case. When rats were given single oral doses of 0.5, 35, or 70 mg/kg dichlorvos by gavage, the 35- and 70-mg/kg groups exhibited cholinergic signs within 15 minutes after dosing (120a). Several animals in the 70-mg/kg group died. No signs of toxicity were apparent in any rats given 0.5 mg/kg or in any of the 35- or 70-mg/kg treated rats that survived 7 days after dosing (120a). Severe cholinergic signs occurred in dogs given 15–30 mg/kg/day for 12–24 days via corn oil capsule, and less severe cholinergic signs occurred in dogs given 1–10 mg/kg/day for 16–24 days (95). Doses of 0.1 mg/kg/day for up to 24 days had no effect. Dermal LD50s are 75–107 mg/kg in rats (64a). Cholinergic signs and death occurred in monkeys after a single 100 mg/kg dermal dose, after eight 50-mg/kg/day doses during 10 days, and after ten 75-mg/kg doses during 12 days, suggesting that dermal exposures may be cumulative (121). Inhalation exposures are more potent on the basis of body weight than oral exposures (122). Four and one-hour LC50s for dichlorvos in rats are 455 and 340 mg/m3 (123). A saturated atmosphere of

dichlorvos (230–341 mg/m3) caused deaths among rats after 7 to 62 hours (121). Rabbits are more sensitive than rats or mice to dichlorvos vapor. Deaths occurred in 9 of 16 rabbits exposed to 6.25 mg/m3 and in 6 of 20 rabbits exposed to 4 mg/m3 for 23 h/day for 28 days during gestation (37), whereas no deaths occurred in mice or rats exposed to the same concentrations. Even exposures up to 56 mg/m3 for 14 days did not cause deaths in rats (124). No deaths occurred in mice exposed to 30–55 mg/m3 for 16 hours (125) or in pregnant mice or rabbits exposed to 4 mg/m3 for 7 h/day (126). No adverse effects occurred in rhesus monkeys exposed to 0.48, 2.3, 2.6, or 12.9 mg/m3 for 2 h/day for 4 days, although RBC cholinesterase was inhibited in monkeys exposed to 12.9 mg/m3 (127). Delayed neuropathy occurred in chickens after 35 days treatment with 6.1 mg/kg/day dichlorvos; 3.1- and 4.4-mg/kg/day doses were ineffective (128). Two doses of 16.5 mg/kg dichlorvos 21 days apart to hens did not cause acute delayed neurotoxicity, although signs of cholinesterase inhibition were apparent shortly after dosing (120a). In a guinea pig mazimization test, induction with dichlorvos by intradermal injection and topical application and subsequent challenge with topical dichlorvos solutions showed sensitization (129). 8.4.1.2 Chronic and Subchronic Toxicity A 90-day LD50 > 70 mg/kg was determined in rats fed dichlorvos in their diet for 90 days (196). Because this value was more than the single dose LD50 of 56 mg/kg, it was concluded that dichlorvos does not have a cumulative effect. When rats were given feed that delivered 0–360 mg/kg/day for 6 weeks, all rats that consumed 180 mg/kg or more died whereas none that consumed 90 mg/kg/day or less died (130). When mice were given feed that delivered 0–1080 mg/kg/day for six weeks, four of five females given 720 mg/kg/day died; all mice given 1080 mg/kg/day died (130). Cholinergic signs occurred in dogs given 0.625 or 1.25 mg/kg/day dichlorvos by capsule for 70–90 days (65). RBC and brain cholinesterase activities were inhibited in dogs given 0.625 mg/kg/day. Ninety-day studies of dichlorvos in rats have shown that dietary levels up to 1000 ppm (about 70 mg/kg/day) do not result in overt cholinergic toxicity, although exposures to levels of 200 ppm or greater inhibit RBC cholinesterase (56, 57). Oral gavage studies show lower effect levels. Daily administration of 7.5 mg/kg/day or more to rats via gavage for 13 weeks is associated with cholinergic toxicity (131) as well as significant RBC and brain acetylcholinesterase inhibition. Daily administration of 160 mg/kg/day by gavage for 13 weeks caused death in mice (131) as well as significant RBC and brain acetylcholinesterase inhibition. Gavage doses up to 40 mg/kg/day had no effect. 8.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms At least 85% of an oral dose of dichlorvos is absorbed (145). Dichlorvos is well absorbed following inhalation exposure based on the occurrence of toxic symptoms associated with inhalation exposures and the detection of specific dichlorvos metabolites (dichloroethanol and dimethyl phosphate) in urine of individuals exposed to dichlorvos (137, 138). Excretion is very rapid based on the observation that dichlorvos could not be detected in the blood of two male volunteers immediately after exposure to dichlorvos vapor (145). An elimination half-life of 13.5 minutes was estimated based on dichlorvos concentration in rat kidney after 2 or 4 hours exposure to 5 mg/m3 (145). In mice and rats given single oral doses of dichlorvos, 59–65% was eliminated in urine, 3–7% was eliminated in feces, 14–18% was eliminated as CO2 by 4 days after dosing, and the vast majority was eliminated by 24 hours (138). Retained dichlorvos following either oral or inhalation exposures is high because it is incorporated into intermediary metabolism (139). Dichlorvos binds to acetylcholinesterase forming dimethoxy-phosphorylated acetycholinesterase and dichloroacetaldehyde (140). Alternatively, it is metabolized (primarily in the liver but also in the

blood, adrenal, kidney, lung, and spleen) via two pathways (141). The major pathway is catalyzed by A-esterases and produces dimethyl phosphate and dichloroacetaldehyde (140). Dichloroacetaldehyde is converted to dichloroethanol which is then excreted as the glucuronide. Alternatively, dichloroacetaldehyde is dehalogenated and the carbon atoms are incorporated into normal tissue constituents via intermediary metabolism (137, 138, 141). The second minor pathway is catalyzed by glutahione-S-transferase and produced desmethyl dichlorvos and S-methyl glutathione. Subsequent degradation of desmethyl dichlorvos to dichloroacetaldehyde and monomethyl phosphate is catalyzed by A-esterases. S-methyl glutathione is broken down to methylmercapturic acid and excreted in urine. CO2 is also the major metabolite following inhalation exposures. The major urinary metabolite following either oral or inhalation exposures is dichloroethanol glucuronide. Dichlorvos is rapidly metabolized in human blood by A-esterases (142, 143). Unlike paraoxonse which exhibits polymorphism in the human population (144), dichlorvos A-esterase appears to be normally distributed. Half-lives for degradation of dichlorvos in whole blood after inhalation were 8.1 minutes for men and 11.2 minutes for women (145). 8.4.1.4 Reproductive and Developmental Several studies indicated that dichlorvos is not a reproductive or developmental toxin. No impairment of male fertility occurred in mice exposed to 30 or 55 mg/m3dichlorvos for 16 hours or to 2.1 or 5.8 mg/m3 for 23 hours daily for 4 weeks (37). However, estrus was delayed 10 days in female rats that were continuously exposed from birth to 2.4 mg/m3 dichlorvos vapors from a Shell “No-pest Strip” (132). Number, viability, and growth rate were normal in offspring of swine fed up to 37 months on diets containing 200–500 ppm dichlorvos (133). No maternal or reproductive toxicity occurred in rats given dichlorvos for three generations at a dietary level of 0.1–500 ppm (about 0.005–25 mg/kg/day) (95). No adverse effect on fetuses occurred when pregnant rats were given injections of 15 mg/kg dichlorvos on gestation day 11 (379), 0.1–21 mg/kg/day dichlorvos on gestation days 6 through 15 (95), or were exposed to 0.25–6.25 mg/m3 dichlorvos vapor for 23 h/day on gestation day 1 through 20 (37). No adverse effect on fetuses occurred when pregnant mice were given the maximal tolerated dose of dichlorvos (60 mg/kg) on gestation days 6 through 15 or were exposed to 4 mg/m3 dichlorvos vapor for 7 h/day (126). No adverse effect occurred on fetuses when pregnant rabbits were administered doses of 0.1 to 7.0 mg/kg/day dichlorvos by gavage on gestation days 7 through 19 (120a) or when rabbits were exposed for 23 h/day to 0.25 to 6.25 mg/m3 dichlorvos vapor on gestation days 1 through 28 (37). 8.4.1.5 Carcinogenesis Dichlorvos was not carcinogenic when rats were exposed to 0.05, 0.48, or 4.70 mg/m3 dichlorvos for 23 h/day, 7 days/week for up to two years (136). Nor were any cholinergic signs observed in any group. The EPA's Carcinogenicity Peer Review Committee (CPRC) considered this study sufficient evidence that dichlorvos does not cause cancer via inhalation (68). Carcinogenicity was not observed in rats given diets of 0, 150, or 326 ppm dichlorvos (equivalent to doses of about 8–14 and 16–29 mg/kg/day) for 80 weeks and then observed for an additional 30 weeks (130). The results of this study, however, were questioned because of an extraordinarily high mortality rate in control rats. Therefore, the chronic toxicity and carcinogenicity of dichlorvos was reevaluated in rats dosed with dichlorvos by gavage at levels of 0, 4, or 8 mg/kg/day dichlorvos for 5 days/week for 103 weeks (131). Cholinergic signs of toxicity occurred and RBC acetylcholinesterase activity decreased in both groups. Significant increase in mammary gland neoplasms in females and a significant trend (not dose related) for mononuclear cell leukemia was observed in males. Peer review panels characterized these results as “some evidence” of carcinogenic activity in males and equivocal evidence” in females (131). EPA's CPRC concluded that increased incidence of leukemia in rats may not be biologically significant (68, 120a).

Carcinogenicity was not observed in mice given diets that delivered 57 or 114 mg/kg/day dichlorvos for 80 weeks (130). However, a positive trend for squamous cell papilloma and carcinomas of the forestomach was observed in mice given 10–40 mg/kg/day dichlorvos by gavage for 5 days/week for 102 weeks (131). Significantly decreased RBC acetylcholinesterase activity was also observed at all levels. Peer review panels characterized these results as “some evidence” of carcinogenicity in male mice and “clear evidence” in female mice (131). However, the relevance of forestomach tumors to humans is questionable. Carcinogenicity was not reported in male or female mice given 58 or 95 mg/kg/day or 56 or 102 mg/kg/day, respectively, in their drinking water for 2 years (95). However, there was a dose-related decrease in absolute and relative weight of the gonads of males, and testicular atrophy increased in males given the high dose (95 mg/kg/day). The absolute and/or relative weight of the pancreas also decreased in treated females. When dogs were given dichlorvos by capsule for 52 weeks at doses of 0, 0.1, 1.0, or 3.0 mg/kg/day, one male in the 3.0 mg/kg/day group exhibited cholinergic toxicity only at week 33 (57). RBC cholinesterase was inhibited at doses of 0.1 mg/kg/day and higher, and brain cholinesterase was inhibited in the 1.0-mg/kg/day (males only) and 3.0-mg/kg/day groups. 8.4.1.6 Genetic and Related Cellular Effect Studies Dichlorvos is not genotoxic when tested in in vivo system but is generally genotoxic or mutagenic in in vitro test when metabolizing enzymes are not present (57). Dichlorvos increased the frequency of chromosomal damage and micronucleus formation in Chinese hamster ovary cells; induced sister chromatid exchange, chromosomal aberrations, and transformation in cultured rat tracheal epithelial cells; induced DNA single-strand breaks in isolated rat hepatocytes; and caused increases in cell transformation of hamster embryo cells (134). Dichlorvos was negative in the sex-linked lethal mutation test in Drosophila. However, increased mutations and chromosomal abnormalities occurred in flies given dichlorvos-contaminated food. Dominant lethal mutations did not occur in mice given an intraperitoneal dose or oral doses of 5 or 10 mg/kg dichlorvos or in mice exposed to dichlorvos via inhalation (30 or 55 mg/m3). No chromosome damage occurred in mice given drinking water containing 2 mg/L dichlorvos for 7 weeks, no aberration in chromosomal structure or number occurred in bone marrow cells of mice given intraperitoneal injections of dichlorvos for 2 days, and no chromosomal abnormalities occurred in mice exposed to 64–82 mg/m3 dichlorvos for 16 h or to 5 mg/m3 for 21 days (134). There is a report that intraperitoneal injection of mice with lethal (LD50, ½ LD50) amounts of dichlorvos causes chromosomal aberrations in bone marrow (146). However, the usefulness of this study in predicting in vivo genotoxicity has been challenged because of the toxic dose administered (134). In other in vivo studies, an increase in the percentage of hair follicles that contained nuclear aberrations occurred in mice 24 hours after a single dermal dose of dichlorvos (134a) and an increase in the incidence of micronuclei occurred in cultured skin cells from mice given a single dermal dose of dichlorvos (135). It has been suggested that dichlorvos is not genotoxic in vivo, despite its methylating ability, because the phosphorus atom of the molecule is a stronger electrophile than the methyl carbons. Hence, in vivo, dichlorvos is much more likely to react with A-type esterases, serum cholinesterase, or acetylcholinesterase than with DNA (57, 134). 8.3.5 Biomonitoring/Biomarkers The major metabolites of dichlorvos, dimethyl phosphate, and the glucuronide conjugate of dichloroethanol, are rapidly excreted in urine and could conceivably be used to monitor acute dichlorvos exposure. However, because other organophosphates, naled and trichlorphon, are metabolized to dichlorvos, exposure to them would have to be ruled out before a definitive exposure of dichlorvos could be made. 8.4.2 Human Experience 8.4.2.2 Clinical Cases Death has followed accidental or intentional ingestion of liquid dichlorvos or cake-like baits containing both malathion and dichlorvos (504).

Two workers in Costa Rica died after splashing a concentration formulation of dichlorvos on their bare arms and failing to wash it off (504). Persistent contact dermatitis has also been reported following skin contact with dichlorvos (148). RBC acetylcholinesterase activity marginally decreased in one of two dichlorvos applicators exposed to an estimated level of 0.02 mg/m3 for about 25.5 minutes and 0.028 mg/kg/hr dermally (149). RBC acetylcholinesterase activity was reduced in some residents exposed to an estimated level of 0.2 mg/m3 dichlorvos for about 15.8 hours, and some residents complained of headache (149). Average air concentrations of 0.13 mg/m3 resulting from the use of resin strips in residences had no effect on RBC acetylcholinesterase activity (149a). Airbone levels of dichlorvos that caused slight to moderate RBC cholinesterase depression were 0.7 mg/m3 averaged over 1 year in factory workers who produced dichlorvos vaporizers (149b). No significant change in RBC acetylcholinesterase activity occurred in babies exposed to an estimated 0.05 to 0.16 mg/m3 dichlorvos for 18 h/day for 5 days (150). Exposure of men to 0.1 to 0.3 mg/m3 dichlorvos in 39 half-hour periods during 14 days had no effect on RBC, plasma cholinesterase, or physiological function (151). When the intensity of exposure was kept the same but the frequency of exposure increased to 96 half-hour exposures during 21 days, plasma cholinesterase activity slightly decreased, and when exposure concentration was increased to 0.4 to 0.5 mg/m3, plasma cholinesterase activity significantly decreased. RBC cholinesterase activity was unaffected under any exposure conditions. No cholinergic signs or RBC acetylcholinesterase inhibition occurred in men exposed to average dichlorvos concentrations of 0.49 or 2.1 mg/m3 for 1 or 2 hours on 4 consecutive days in a simulated aircraft cabin (127). No cholinergic signs or RBC acetylcholinesterase inhibition occurred in men given 1- to 2.5-mg doses of dichlorvos via two corn oil capsules daily for up to 28 days (152) or in men given 0.9 mg dichlorvos three times a day for 21 days (152a). No adverse clinical signs or RBC acetylcholinesterase inhibition occurred in men given two oral doses of 35 mg dichlorvos (0.5 mg/kg/day), 12 or 15 daily doses of 21 mg dichlorvos (0.3 mg/kg/day), or 21 daily doses of 7 mg/kg dichlorvos (0.1 mg/kg/day) (120a). When the same individuals were given 70 mg dichlorvos for 14 days, however, RBC acetylcholinesterase was significantly inhibited. Cholinergic toxicity did not occur in volunteers given single oral doses of dichlorvos in slow release polyvinyl resin pellets ranging from 0.1 to 32 mg/kg, despite the fact that RBC acetylcholinesterase was dosedependently inhibited because it was maximal at 24 mg/kg (153). Repeated daily administration of 8 to 38 mg/kg for 7 days caused cholinergic toxicity and dramatically decreased RBC acetylcholinesterase activity, so the experiment was terminated in most subjects in less than 7 days. Six of 59 males and 9 of 48 females in an occupational study of flower growers showed positive reactions on patch testing of dichlorvos for an overall rate of 14%. Twelve of 18 subjects who had positive skin patch test reactions to triforine (1,4-bis (2,2,2-trichlor-1-formamidoethyl)piperazine) also showed positive reactions to dichlorvos (129). 8.5 Standards, Regulations or Guidelines of Exposure Dichlorvos is undergoing reregistration by the EPA (9a). The ACGIH TLV for dichlorvos is 0.9 mg/m3 with a skin notation (154). The OSHA PEL-TWA and NIOSH REL-TWA are 1 mg/m3 with a skin notation. Most other countries have established OELs of 0.1 ppm as well (Republic of Egypt, Australia, Austria, Belgium, Denmark, Finland (1 mg/m3) (Jan. 93), France, Germany 0.11 ppm (1 mg/m3), Hungary STEL 0.2 mg/m3 (Jan. 93), India, The Netherlands, The Philippines 1 mg/m3 (Jan. 93), Poland 1 mg/m3 (Jan. 93), Russia 0.2 mg/m3 (Jan. 93), Switzerland, Thailand, United Kingdom 0.1 ppm (0.92 mg/m3).

Organophosphorus Compounds Jan E. Storm, Ph.D 9.0 Dicrotophos 9.0.1 CAS Number: [141-66-2] 9.0.2 Synonyms: O,O-dimethyl-O-(3-dimethylamino-1-methyl-3-oxo-1-propenyl) phosphate; 3dimethoxyphosphinyloxy-N,N-dimethylisocrotonamide; Bidirl; C709; Diapadrin; SD3562; phosphoric acid (E)-3-(dimethylamino)-1-methyl-3-oxo-1-propenyl dimethyl ester; dimethyl 1methyl-3-(N,N-dimethylamino)-3-oxo-1-propenyl phosphate, (E)-; Penetrex; Chiles' Go-Better; Mauget Inject-A-Cide B; phosphoric acid, 3-(dimethylamino)-1-methyl-3-oxo-1-propenyl dimethyl ester, (E)-; phosphoric acid, dimethyl ester, ester with 3-hydroxy-N,N-dimethylcrotonamide, (E);Carbomicron; crotonamide, 3-hydroxy-N,N-dimethyl-, cis-, dimethyl phosphate; dimethyl cis-2dimethylcarbamoyl-1-methylvinyl phosphate; dimethyl O-(N,N-dimethylcarbamoyl-1-methylvinyl) phosphate; dimethyl phosphate ester with 3-hydroxy-N,N-dimethyl-cis-crotonamide; dimethylcarbamoyl-1-methylvinyl dimethylphosphate; hydroxy-N,N-dimethyl-cis-crotonamide dimethyl phosphate; Karbicron; Oleobidrin 9.0.3 Trade Name: Bidrin®; Carbicron®; Ektafos® 9.0.4 Molecular Weight: 237.21 9.0.5 Molecular Formula: C8H16NO5P 9.0.6 Molecular Structure:

9.1 Chemical and Physical Properties Pure dicrotophos is an amber liquid; the commercial grade which consists of 85% E-isomer is brown in color. Dicrotophos is stable when stored in glass or polyethylene containers up to 40°C but decomposes after 31 days at 75°C or after 7 days at 90°C. Dicrotophos emits toxic fumes of phosphorus and nitrogen oxides when heated to decomposition. Specific 1.216 at 15°C; 8.6 × 10–5 mmHg at 20°C gravity Boiling point 440°C at 760 mmHg Vapor 1 × 10–4 mmHg at 20°C pressure Solubility slightly soluble in xylene, kerosene, and diesel fuel; miscible with water, acetone, alcohol, 2-propanol, and other organic solvents 9.1.2 Odor and Warning Properties A mild ester odor. 9.2 Production and Use Dicrotophos was introduced in 1956 as a systemic and contact organophosphorus insecticide effective against sucking, boring, and chewing pests and is recommended for use on coffee, cotton, rice, pecans, and other crops. It is also used to control ticks and lice on cattle (155). Dicrotophos is available as 24% and 85% concentrates, as 40% and 50% emulsifiable concentrates, water-soluble concentrates, and ultra low volume formulations (155).

9.4 Toxic Effects 9.4.1.1 Acute Toxicity Dicrotophos is an organophosphate that has high oral toxicity and oral LD50s of 16–21 mg/kg (64a). The dermal LD50 of dicrotophos is 42–43 mg/kg in rats (64a) and 225 mg/kg in rabbits (155). A 4-hour LC50 of 90 mg/m3 and a 1-hour LC50 of 610–910 mg/m3 was reported for rats (545). 9.4.1.2 Chronic and Subchronic Toxicity Cholinergic toxicity did not occur in rats fed diets that contained 0, 15, or 150 ppm dicrotophos for 4 weeks, although whole blood and plasma cholinesterase activites were markedly inhibited at both dose levels (156). 9.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms The oral, intraperitoneal, and intravenous LD50s for dicrotophos are equivalent (ranging from 9–17 mg/kg), indicating that it is essentially completely absorbed orally. Experimental studies show it is well absorbed via other routes of exposure as well. After 6 hours, 65% of a subcutaneously injected dose (10 mg/kg) was excreted, and after 24 hours, 83% was excreted in the urine alone (159). Similar results were obtained in other studies of rats and other species (160). Dicrotophos is metabolized in part to monocrotophos, and the concentration of monocrotophos in tissues may be higher than that of the parent compound a few hours after administration, as reflected by analysis of rat urine and goat milk (1). Residues of both compounds are dissipated almost entirely within 24 hours, as indicated by a rapid decrease in unhydrolyzed metabolites in urine or milk. Hydrolysis of the vinyl phosphate bond of dicrotophos and/or its oxidative metabolites (monocrotophos) to produce dimethyl phosphate is the predominant metabolic reaction (159). The proportion of dimethyl phosphate in the urine of rats increases rapidly after dosing and reaches 50% of all metabolites present in less than 4 hours and more than 80% in 20 hours. During this interval, there is a correspondingly rapid decrease in the excretion of the parent compound and its oxidation products. Desmethyl dicrotophos and inorganic phosphate are also found in minor concentrations in the urine of treated rats (159). Dimethyl phosphate has been confirmed in the urine of an individual who accidentally ingested dicrotophos (161). 9.4.1.4 Reproductive and Developmental When rats were fed diets that contained 2, 5, 15, or 50 ppm dicrotophos (0.1, 0.25, 0.75, and 2.5 mg/kg/day) for two generations, decreased pup survival was observed at 5 ppm (95). Other effects (weakness, emaciation, and CNS effects) were seen at 50 ppm. No effects occurred at 2 ppm. No morphological anomalies occurred in offspring of pregnant mice given intraperitoneal injections of 1, 2, 4, or 7.5 mg/kg dicrotophos on gestation day 11, 13, or days 10–12 (157). In other mice, a dose of 5 mg/kg/day on gestation days 8 though 16 did not change the developmental patterns of brain acetylcholinesterase or choline acetyltransferase in offspring through day 42, even though this dose on day 11 reduced embryonic or fetal acetylcholinesterase to 1.8% of control levels (157). The fetal brain enzyme level returned to normal by day 19 following dosing of the mother on days 8 through 16 of gestation. 9.4.1.5 Carcinogenesis When rats were fed dicrotophos in their diets at concentrations of 0, 1, 10, or 100 ppm for two years, there were no detectable effects at the 1-ppm concentration (95). Plasma cholinesterase was inhibited at 1 ppm (95). At 10 and 100 ppm, decreased body weights and reduced cholinesterase (RBC, plasma, brain not specified) activities occurred. Dogs given dicrotophos in their diets at 0, 0.16, 1.6, or 16 ppm for two years showed some instances of slightly excessive salivation (95). At 16 ppm, both plasma and RBC cholinesterase activity was decreased.

9.4.1.6 Genetic and Related Cellular Effects Studies Dicrotophos is considered mutagenic on the basis of its similarity in structure to monocrotophos and the observation that it induced increases in sister chromatid exchanges in cultures of Chinese hamster ovary cells (158). 9.4.2 Human Experience An individual who inhaled a spray that contained dicrotophos and was being used to control mosquitoes in the home developed organophosphate poisoning (162). Upon hospital admission, he had abdominal cramps, nausea, vomiting, and diarrhea; the next day he exhibited increased sweating, salivation, dyspnea, coarse tremor of both legs, and generalized weakness. Plasma and RBC cholinesterase activities were nonexistent. The patient responded to atropine and pralidoxime. However, on the sixth day, respiratory paralysis occurred (typical of “intermediate syndrome”), and he required an artificial respirator for 5 days. He was discharged on day 22. In another case, a 52-year-old man accidentally drank a solution that contained dicrotophos in turpentine (163). He was brought to the hospital where he was treated effectively with atropine and pralidoxime chloride, but he required assisted respiration for more than a week. 9.5 Standards, Regulations, or Guidelines of Exposure Dicrotophos is undergoing reregistration by the EPA (9a). Dicrotophosis is a Restricted Use Pesticide (RUP) which can be purchased and used only by certified applicators. Some specific state restrictions may apply. The ACGIH TLV for dicrotophos (intended change in the 2000 TLVS is 0.05 mg/m3) and monocrotophos is 0.25 mg/m3 with a skin notation (154). The NIOSH TWA-REL is also 0.25 mg/m3 with a skin notation.

Organophosphorus Compounds Jan E. Storm, Ph.D 10.0 Dioxathion 10.0.1 CAS Number: [78-34-2] 10.0.2 Synonyms: 2,3-p-Dioxanedithion S,S-bis-(O,O-diethyl phosphorodithioate); Hercules AC528; Ruphos; Navadel; Delnatex; Delnav; 1,4-dioxan-2,3-diyl-bis(O,O-diethyl phosphorothiolothionate); Delanov; Delnav (R); Phosphorodithioic acid S,S'-1,4-dioxane-2,3-diyl O,O,O',O'-tetraethyl ester; phosphorodithioic acid S,S'-p-dioxane-2,3-diyl O,O,O',O'-tetraethyl ester; AC 528; dioxation; 1,4-dioxan-2,3-diyl O,O,O',O'-tetraethyl di(phosphoromithioate); 2,3-p-dioxane S,S-bis(O,O-diethylphosphorodithioate); p-dioxane-2,3-dithiol, S,S-diester with O,O-diethyl phoshorodithioate; p-dioxane-2,3-diyl ethyl phosphorodithioate; dioxothion; hercules 528; kavadel; deltic; 2,3-p-dioxanedithiol S,S-bis(O,Odiethyl phosphorodithioate); S,S'-1,4-dioxane-2,3-diyl O,O,O',O'-tetraethyl phosphorodithioate; Cooper Del-Tox Delnav; Dextrone X; 1,4-dioxane-2,3-dithiol, S,S-diester with O,O-diethyl phosphorodithioate; 1,4-dioxane-2,3-diyl O,O,O',O'-tetraethyl phosphorodithioate; 1,4dioxanedithiol S,S-bis(O,O-diethyl phosphorodithioate) 10.0.3 Trade Names: Delnav®; Hercules AC528®; Navadel® 10.0.4 Molecular Weight: 456.54 10.0.5 Molecular Formula: C12H26O6P2S4 10.0.6 Molecular Structure:

10.1 Chemical and Physical Properties Dioxathion is a nonvolatile, chemically stable, dark amber liquid. Specific 1.257 at 26°C gravity Melting point –20°C Boiling point 60–68°C Solubility insoluble in water; soluble in aromatic hydrocarbons, alcohols, ethers, esters and ketones 10.2 Production and Use Dioxathion is the common name for an organophosphate product that contains 70% cis and trans (1:2 ratio) isomers of 2,3-p-dioxanedithiol S,S-bis-(O,O-diethyl phosphorodithioate) as the principal ingredient (164). It was formely used in the United States on citrus, grapes, walnuts, and stone fruits. It was also used to control ticks, lice, and horn flies on cattle, goats, hogs, horses, and sheep when sprayed or dipped. Until 1989, when its manufacture and use in the United States was discontinued, dioxathion was available as a 25% wettable powder and a 48% emulsifiable concentrate (1, 155). 10.4 Toxic Effects 10.4.1.1 Acute Toxicity Dioxathion is an organophosphate compound that has moderately high oral toxicity and oral LD50s of 23–64 (64a, 164). An intraperitoneal LD50 of 30 mg/kg was obtained for rats suggesting (by comparison with the oral LD50 of 23 mg/kg) that dioxathion is well absorbed orally. The oral LD50 for dogs is 10–40 mg/kg. The dermal LD50 for dioxathion is 63–235 mg/kg in rats and 85 mg/kg in rabbits (64, 545). One-hour LC50 values of 1398 and 340 mg/m3 were reported for rats and mice (164). The acute symptoms of dioxathion are typical of other organophosphates, but the rate of onset is “somewhat slower” (164). When dogs were given 0.25, 0.80, 2.5, or 8.0 mg/kg/day dioxathion by capsule for 5 days/week for two weeks, those given 8.0 mg/kg/day developed signs of cholinergic toxicity (diarrhea, hypersalivation, termors, ataxia, and depression) (sic). Doses of 0.8 mg/kg/day and higher significantly inhibited plasma cholinesterase, and doses of 2.5 and 8.0 mg/kg/day significantly inhibited RBC cholinesterase (164). Dioxathion showed additive or less than additive toxicity when administered in equitoxic ratios with 15 other anticholinesterase insecticides. However, when dioxathion was administered 4 hours before malathion, potentiation as great as 5.4-fold was observed (164). When rats were given single intraperitoneal injections of 4, 8, or 16 mg/kg, liver and plasma carboxylesterase activities were 19–55%, RBC cholinesterase activity was 76%, and, brain cholinesterase activity was 96% of control in rats given 4 mg/kg/day dioxathion (165). Thus dioxathion more effectively inhibits carboxylesterases than acetylcholinesterase. A similar tendency of dioxathion to inhibit carboxylesterases to a greater extent than acetylcholinesterase was observed when enzymatic activity was examined in rats fed diets that contained 4, 10, 20 or 40 ppm dioxathion for 7 days (165). Brain acetylcholinesterase was unaffected at any level, and RBC cholinesterase was significantly inhibited at 20 and 40 ppm; however, liver carboxylesterases were significantly inhibited at all levels. Further, rats given diets that contained 4 or 10 ppm dioxathion were more susceptible than untreated rats to inhibition of brain cholinesterase by a single 100- or 200-mg/kg dose of malathion (165).

When 75 mg/kg dioxathion was given subcutaneously to rats, they displayed muscular fibrillation at 2 hours and convulsions at 4 to 8 hours (166). Symptoms of organophosphate poisoning continued several days before recovery. Oral administration of dioxathion to rats at 5 mg/kg/day for up to 21 days resulted in plasma, RBC, and brain cholinesterase inhibition within 1 day (166). Dioxathion produced mild, transient conjunctivitis but no transient or permanent corneal damage when 0.1 mL was instilled into the eyes of rabbits (164). Dioxathion did not produce neurotoxicity in surviving hens that received single oral doses of 10– 1000 mg/kg or subcutaneous doses of 25–200 mg/kg, even though the higher rates killed some of the birds (164). However, a slightly larger subcutaneous dose, 320 mg/kg, in hens protected by atropine produced a temporary neurotoxic effect that lasted 3–31 days (164). 10.4.1.2 Chronic and Subchronic Toxicity When rats were fed diets that contained 100 or 500 ppm dioxathion for 1–13 weeks, a dietary level of 500 ppm caused marked food refusal and loss of body weight within the first week (164). Female rats given 100 ppm (about 7.5 mg/kg/day) showed hyperexcitability and slight tremor, but males remained well. Both sexes showed marked inhibition of brain, plasma, and RBC cholinesterase activity. In another study, rats were fed diets that contained 1, 3 or 10 ppm dioxathion for 13 weeks. A dietary level of 10 ppm (0.78 mg/kg/day) produced no inhibition of brain cholinesterase but significantly reduced plasma and RBC cholinesterase activity. Dietary levels of 3 and 1 ppm (0.22 and 0.077 mg/kg/day) did not alter brain, plasma, or RBC cholinesterase activity (164). No adverse effects occurred in dogs given 0.013, 0.025, or 0.075 mg/kg/day dioxathion for 5 days/week for 90 days via capsule (164). 10.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Dioxathion is well absorbed orally or dermally. Rats treated orally with dioxathion for 10 consecutive days excreted dioxathion primarily in the urine (about 50% of daily administered dose) and to a lesser extent in the feces (about 20% of daily administered dose) (166). Rats given 25 mg/kg of different components of the technical product excreted about 36–45% in the urine and about 6 to 25% in the feces, depending on the component administered, by 48 hours. Hydrolytic products identified in the urine included diethyl phosphoric, phosphorothioic, and phosphorodithioic acids. When rats were given 25 mg/kg dioxathion and sacrificed after 48 hours, fat had “appreciable” (sic) amounts of the dose. When rats were given 5 or 10 mg/kg dioxathion for several days, the maximum level in fat (0.6 ppm) was reached within 3 days and held constant through 21 days. The metabolism of dioxathion was examined in rats treated orally and in rat liver microsomes (168). Both the trans, and cis, isomers were rapidly and extensively metabolized by rat liver microsomes in the presence of NADPH (indicating the involvement of microsomal oxidases) and by rats in vivo to the corresponding oxons and dioxon. The compound also underwent oxidative O-deethylation and hydroxylation of the ring resulting in ring cleavage and the loss of both phosphorus moieties. The more toxic cis isomer was metabolized more rapidly to form oxon and dioxon and also to form CO2 from the ethoxy group (168). Of the dose administered, 80–87% was excreted by 96 hours in urine and most of this occurred in the first 24 hours. Unmetabolized dioxathion appeared in feces. 10.4.1.4 Reproductive and Developmental In a three-generation study, rats were fed diets containing 0, 3, or 10 ppm dioxathion (167). There were no measurable abnormalities among either parental animals or their progeny. 10.4.1.5 Carcinogenesis No evidence of carcinogenicity was observed in rats or mice given diets that contained dioxathion for 78 weeks and then observed for an additional 33 or 12–13 weeks, respectively (585). Time-weighted average dietary concentrations were 180 and 90 ppm for male rats, 90 and 45 ppm for female rats, 567 and 284 ppm for male mice, and 935 and 467 ppm for

female mice. 10.4.1.6 Genetic and Related Cellular Effects Studies Dioxathion was positive in the Salmonella assay and in cultured Chinese hamster ovary (CHO) cells for the induction of sister-chromatid exchanges but was negative in the mouse lymphoma assay and in cultured CHO cells for the induction of chromosomal aberrations (65). 10.4.2 Human Experience 10.4.2.2 Clinical Cases A 5-year-old boy, who ingested about threequarters of a teaspoon of a 21% dioxathion formulation intended to be diluted for use as a flea dip (about 57 mg/kg) when it was mistaken for cough medicine, vomited and exhibited profuse diarrhea (169, 170). Within 2 hours, the child was mentally dull and unable to stand; he had shallow rapid respirations, muscle fasciculations, tearing, and miosis. After 12 hours of appropriate treatment, he recovered. Volunteers were given 0.075 mg/kg/day dioxathion in divided doses three times/day, 7 days/week via capsule for 4 weeks. After 4 weeks, two of the subjects continued on this dose; other subjects received 0.150 mg/kg/day, and, the other six continued to receive 0.075 mg/kg/day dioxathion, but also received 0.150 mg/kg malathion. A dose of 0.075 mg/kg/day produced no effect on plasma or RBC cholinesterase activity. There was a slight inhibition of plasma cholinesterase activity in subjects that received 0.015 mg/kg/day. There was no effect on RBC cholinesterase activity and no clinical effect. Plasma cholinesterase measurements showed slight but statistically uncertain decreases when dioxathion was administered daily for 60 days at a rate of 0.075 mg/kg/day and malathion was given at a rate of 0.15 mg/kg/day simultaneously for the last 30 of these days (164). 10.5 Standards, Regulations, or Guidelines of Exposure All registrations and tolerances for dioxathion have been revoked by the EPA (78). The ACGIH TLV for dioxathion is 0.2 mg/m3 (154). NIOSH has recommended a REL-TWA of 0.2 mg/m3 with a skin notation. Most other countries have occupational Exposure Limits of 0.2 mg/m3 with a skin notation for dioxathion (Australia, Belgium, Denmark, France, The Netherlands, Switzerland, United Kingdom).

Organophosphorus Compounds Jan E. Storm, Ph.D 11.0 Disulfoton 11.0.1 CAS Number: [298-04-4] 11.0.2 Synonyms: O,O-Diethyl-S-ethylmercaptoethyl dithiophosphate; phosphorodithioc acid O,O-diethyl-S-(ethylthio) ethyl) ester; Thiodementon; Solvirex; Thiodemeton; Disyton(R); phosphorodithioic acid O,O-diethyl S-[2-(ethylthio)ethyl] ester; O,O-diethyl-S-ethylmercaptoethyl dithiophosphate; dithiodemeton; BAY 19639; Dithiosystox; Di-Syston; Frumin AL; Frumin G; Frumen AL; disulfoton+; O,O-diethyl S-(2(ethylthio)ethyl) phosphorodithioate; thiometon-ethyl; Root-X; Dot-Son Brand Stand-Aid; Rigo Insyst-D; Terraclor Super-X; Diethyl S-(2-(ethylthio)ethyl) phosphorodithioate; diethyl S-(2ethylmercaptoethyl) dithiophosphate; Dimaz; Disipton; Disystox; Ekatin TD; ethylthiometon; Glebofos 11.0.3 Trade Names: Di-Syston®; Dithiosystox® 11.0.4 Molecular Weight: 274.38 11.0.5 Molecular Formula: C8H19O2PS3

11.0.6 Molecular Structure:

11.1 Chemical and Physical Properties Pure disulfoton is a colorless oil that has low volatility and water solubility. The technical product is yellow. Specific gravity 1.144 at 20°C Boiling point 108°C at 0.01 mmHg Vapor pressure 0.00018 torr at 20°C Solubility insoluble in most organic solvents; slightly soluble in water (25 mg/L) 11.2 Production and Use Disulfoton is an organophosphate insecticide effective against aphids, leafhoppers, thrips, spider mites, and coffee leaf miners. It is used on cotton, tobacco, sugar beets, corn, peanuts, wheat, ornamentals, potatoes, and cereal grains. Disulfoton is used to treat seeds and is applied to soils or plants as an emulsifiable concentrate and in granular or pelletized forms. 11.4 Toxic Effects 11.4.1.1 Acute Toxicity Disulfoton is a highly toxic organophosphate that has oral LD50s of 2.3– 12.7 mg/kg for rats, mice, and guinea pigs (54, 64a). Dermal LD50s are 3.6–20 mg/kg for rats, demonstrating a relatively high dermal toxicity (64a). Two of two rabbits died after dermal application of 10 mg/kg/day disulfoton that lasted 6 hours, whereas no rabbit similarly treated with 0.4 or 2.0 mg/kg/day for five days died. Treatment of rabbits five days/week for three weeks with 0.4, 0.8, 1.0, 1.6, 3.0, or 6.5 mg/kg resulted in marked cholinergic toxicity following 6.5 mg/kg, cholinergic signs and significant RBC and brain cholinesterase inhibition following 3.0 mg/kg, slight but significant RBC cholinesterase inhibition following 1.0 or 1.6 mg/kg, and, no cholinesterase inhibition following 0.4 or 0.8 mg/kg (171). One-hour LC50s values for disulfoton aerosol for rats are 290 mg/m3 and 63 mg/m3 for males and females, respectively; four-hour LC50 values are 60 mg/m3 and 15 mg/m3 for males and females, respectively (178). Repeated inhalation exposures are more lethal than single exposures. When female rats were exposed to disulfoton 4 h/day for 5 days, the LC50 was between 1.8 and 9.8 mg/m3 (sic) (178). Symptoms caused by acutely toxic levels of disulfoton are similar to those caused by other organophosphates and develop beginning about 30 minutes after exposure, depending on dose. Time of death depends on dose; it generally occurs within 48 hours at lethal doses but is sometimes delayed by several days for doses near the LD50 (172). When rats were given single gavage doses of 1.5 and 5.2 mg/kg (males) and 0.76 and 1.5 mg/kg (females) disulfoton, cholinergic toxicity developed within 0–3 days and resolved by day 4 after treatment (178). RBC cholinesterase was inhibited in mid- and high-dose females and in high-dose males. Tolerance to the cholinergic toxicity of disulfoton occurs upon repeated, subtoxic exposures. Male rats given 2.0 or 2.5 mg/kg/day disulfoton for 1–14 days exhibited cholinergic signs whose severity diminished with repeated dosing (173, 174). When rats were given 3.5 mg/kg/day for 3–4 days, clinical cholinergic signs were more severe than those exhibited by rats pretreated with 2.5 mg/kg/day for 6 days and then given 3.5 mg/kg/day for 6 more days (173, 174). Thus, rats pretreated with 2.5 mg/kg/day became tolerant to even higher doses of disulfoton. After 3 days on a diet that provided 1 mg/kg/day disulfoton, rats developed severe cholinergic signs that diminished

markedly during a 62-day period despite the fact that brain and diaphragm cholinesterase activity was depressed at day 6 and remained depressed throughout the study (173). Inhalation exposure of rats to 0.02 mg/m3 disulfoton for 6 h/day, 5 days/week for three weeks did not cause any signs of cholinergic toxicity (171). Exposure to 0.1 to 0.5 mg/m3 resulted in behavioral changes linked to inflammatory changes in the respiratory system, and exposure to 3.1 or 3.7 mg/m3 caused cholinergic symptoms (muscle tremors, convulsions, increased salivation, dyspnea). Five of ten females exposed to 3.7 mg/m3 died after three to twelve exposures, and three of twenty females exposed to 3.1 mg/m3 died after eight to fifteen exposures. No deaths occurred in males at any exposure level. RBC cholinesterase was significantly inhibited at 0.1 mg/m3 or more, and brain cholinesterase was significantly inhibited at 0.5 mg/m3 in females and 3.7 mg/m3 in males. In another 21-day study, rats exposed to 0.006, 0.07, or 0.7 mg/m3 disulfoton showed no compoundrelated mortality or clinical signs of toxicity in any group. However, RBC cholinesterase was significantly inhibited at 0.7 mg/m3. Brain cholinesterase activity was unaffected. Neuronal degeneration was evident in some hens administered disulfoton (30 mg/kg) twice 22 days apart (95) 11.4.1.2 Chronic and Subchronic Toxicity The mortality rate was 20% in rats given daily intraperitoneal injections of 1.0 mg/kg/day disulfoton and 100% in rats given 1.2 or 1.5 mg/kg/day for 60 days (172). After the first two doses of 1.0 mg/kg, rats displayed cholinergic signs immediately after each dose for up to 7 or 10 days. Then the rats began to recover in spite of daily treatment. Intraperitoneal doses of 0.25, 0.5, and 1.0 mg/kg produced rapid dose-related inhibition of brain and serum cholinesterase that persisted throughout the entire study period, even though cholinergic signs disappeared (175). Disulfoton caused no cholinergic clinical signs, or adverse effects on mortality, ophthalmology, feed consumption, or body weight gain in rats exposed to 0.018, 0.16, or 1.4 mg/m3 for 6 h/day, 5 days/week for 13 weeks (178). However, RBC, brain and plasma cholinesterase activities were significantly inhibited in rats exposed to 1.4 mg/m3. No adverse effects occurred in rats fed diets that contained 1, 2, 4, 5, 6, 10, or 16 ppm disulfoton (0.1, 0.2, 0.5, or 1.0 mg/kg/day) for 13 or 16 weeks, other than decreased body weight gain at 16 ppm and urine stains in females at 4 ppm (63, 171). However, RBC, brain, plasma, and tissue (submaxillary gland) cholinesterase activity was significantly inhibited in females given 2 ppm or more and in males given 5 ppm or more. In mice fed diets that provided 0.63–0.71 mg/kg/day disulfoton, cholinesterase was inhibited in all tissues, although the tissues were not specified (176). No-effect levels were 0.13–0.14 mg/kg/day. Dogs fed diets that contained 1, 2, or 10 ppm disulfoton for 12 weeks exhibited no signs of toxicity, although plasma and RBC cholinesterase activity were significantly inhibited in dogs given 2 or 10 ppm (171). 11.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Disulfoton is rapidly absorbed after oral exposure. An average of 80–84%, 6–8%, and 9% of a single oral dose of disulfoton was eliminated by rats in urine, feces, and expired air, respectively, in the 10 days following exposure that accounted for 96–100% of the administered dose (171). The rate of excretion was significantly lower in females—males eliminated one-half the dose in 4–6 hours, whereas females required 30–32 hours. Another experiment showed that 72 hours after an oral dose of disulfoton to rats, about 97% was eliminated in urine, 2% was eliminated in feces, and less than 1% remained in the body (171). Similar results were obtained at 12 hours in rats given 15 consecutive doses of disulfoton. There was no accumulation of disulfoton in the body. Tissue and blood levels of disulfoton peaked at 6 hours

and were highest in liver followed by kidney, plasma, fat, whole blood, skin, muscle, and brain. However, on a percentage of dose basis, female livers contained a much greater amount of disulfoton than males (34% vs. 10% at 6 hours; 3% vs. 9% at 12 hours), possibly indicating slower metabolism and accounting for longer elimination in females. Dermal absorption of 0.85, 8.5, or 85 mg/cm2 of a disulfoton formulation ranged from 39–44% of an applied dose applied to the skin (15 cm2) of rats (178). There was no concentration-dependent effect; the majority of absorption occurred within the first hour, and, the majority of the absorbed dose (66– 91%) excreted was found in the urine. Disulfoton is rapidly metabolized via oxidation to sulfoxides and sulfones, oxidation to oxygen analogs, and/or hydrolysis to produce a corresponding phosphorothionate or phosphate (54). Metabolism is accompanied by inhibition of microsomal enzymes (183). In humans exposed to disulfoton, sulfones (disulfoton sulfone and demeton S-sulfone) were detected in blood (104), and diethyl phosphate (DEP), diethyl thiophosphate (DETP), diethyl dithiophosphate (DEDPT), and diethyl phosphorothiolate were detected in urine (184). Similar metabolic products were detected in the urine of rats and mice administered disulfoton intraperitoneally or orally and in liver homogenates of treated rats (54). The oxidation reactions are toxification reactions that create metabolic products that bind to cholinesterase. In an oral study of rats, the metabolites, disulfoton sulfoxide, disulfoton sulfone, demeton-S-sulfoxide, and demeton S-sulfone caused mortality and signs of toxicity at lower doses than disulfoton itself (171a). The hydrolytic reactions create more polar products that are eliminated in the urine and therefore are detoxification reactions. 11.4.1.4 Reproductive and Developmental Two-generation reproductive studies indicates that diets that contained 3 or 9 ppm disulfoton have adverse reproductive effects; diets that contained 0.5– 2 ppm do not (242). Adverse outcomes among rats fed 9-ppm diets include decreased body weight gain during pregnancy and lactation; decreased number of implantations; decreased litter size, weights and viability; and decreased brain cholinesterase activity in F1a pups. Adverse outcomes among rats fed 3 ppm disulfoton include decreased litter size, weights, and viability in the F2 generation. Cholinergic signs were evident in rats fed 9 ppm; decreased brain cholinesterase activity occurred in rats fed a 0.5-ppm diet or more. Reproductive effects were also reported in a study in which male and female rats were given 0.5 mg/kg/day disulfoton for 60 days before and/or during mating. Two-fifths of the treated females failed to become pregnant (182). There was no indication of a teratogenic effect in any rats given 0, 0.1, 0.3, or 1.0 mg/kg/day disulfoton via gavage on gestation days 6–15 (171). Significant depressions of RBC cholinesterase activity occurred in dams given 0.3 and 1.0 mg/kg/day. A significant increase in the incidence of incomplete ossification of the sternebrae was observed in fetuses at 1.0 mg/kg/day which was considered an effect of growth retardation due to maternal toxicity. There was no evidence of teratogenicity or embryo toxicity in rabbits given 0, 0.3, 1.0, or 3.0 mg/kg/day disulfoton (95). The highest dose was lowered to 2.0 and later to 1.5 in some but not all of the high-dose animals due to severe toxic responses and mortality. 11.4.1.5 Carcinogenesis There was no evidence of carcinogenicity or any other adverse effect among rats fed diets that contained 1 or 2 ppm disulfoton for 104 weeks or 0.5 ppm for 80 weeks followed by 5 ppm for 24 weeks (242). Females fed 5 ppm, however, exhibited significantly inhibited plasma and brain cholinesterase. Rats fed diets that contained 10, 25, or 50 ppm disulfoton for 178 days had significantly inhibited brain cholinesterase activities but exhibited no signs of cholinergic toxicity (177). There was no evidence of carcinogenicity in rats given feed that contained 0, 1, 4, or 16 ppm disulfoton, (0.05, 0.2, and 0.1 mg/kg/day) (178). Females given the 16-ppm diet had a 40% mortality rate during the last week of the study compared with a 12% mortality in controls, and both sexes

given the 16-ppm diet exhibited cholinergic signs and increased relative brain weight. There was an increased incidence of optic nerve degeneration in males given the 4-ppm diet and in females given the 4- or 16-ppm diet. Increased incidences of mucosal hyperplasia and chronic inflammation of the forestomach occurred in females given 16 ppm. Cystic degeneration of the Harderian gland occurred in male rats given 16 ppm and in female rats given 4 ppm. Corneal neovascularization was significantly increased in rats given 16 ppm. RBC and brain cholinesterase activity was inhibited in rats given 1 ppm. There was no evidence of cancer in mice fed diets that contained 0, 1, 4, or 16 ppm disulfoton for 99 weeks (171). Nor was there any adverse effect on behavior, feed consumption, hematology, or organ weights. Significant depression of RBC, plasma, and brain cholinesterase activity occurred in mice fed diets that contained 16 ppm (equivalent to 2–2.5 mg/kg/day). Dogs did not exhibit cholinergic signs, opthalmoscopic changes, hematological or clinical chemical changes, or any evidence of carcinogenicity when given diets that contained 0.5 or 1.0 ppm disulfoton for two years (equivalent to 0.03 or 0.14 mg/kg/day) (242). Nor was RBC cholinesterase activity inhibited. RBC cholinesterase activity was inhibited in dogs after five months exposure to 0.5 mg/kg/day given by capsule and when they were fed diets that contained disulfoton at a dose of 0.06 mg/kg/day for 40 weeks (242). Moderate inhibition of RBC cholinesterase occurred in dogs given diets that contained 5.0 ppm for 69 weeks (equivalent to about 0.7 mg/kg/day). Brain cholinesterase was not inhibited in dogs given a 0.5- or 1.0-ppm diet for two years but was markedly inhibited in dogs given diets that contained 2.0 ppm or more. Ocular effects (myopia and astigmatism) associated with degenerative changes in the ciliary muscle cells occurred after 12 months in dogs given 0.63 mg/kg/day disulfoton for two years (128, 179). The myopia became progressively worse until dosing ceased. Necrosis and atrophy of the optic nerve and retina was observed in dogs given disulfoton (0.5–1.5 mg/kg/day) for 2 years (180). However, no ophthalmological effects occurred in dogs given diets that contained 0.5, 4, or 12 ppm disulfoton (0.015, 0.1, or 0.3 mg/kg/day) for 1 year (181). Dogs given the 4-ppm diets “demonstrated intermediate toxicity” (sic), and those given the 12-ppm diet “demonstrated systemic toxicity near the Maximum Tolerated Dose” (sic). RBC cholinesterase was significantly inhibited in females given 4 and 12 ppm, corneal cholinesterase was significantly depressed at 4 and 12 ppm in both sexes, retinal cholinesterase was significantly inhibited at 4 ppm in females in 12 ppm in males, and ciliary body cholinesterase was significantly inhibited at 12 ppm in both sexes. 11.4.1.6 Genetic and Related Cellular Effects Studies The genotoxicity of disulfoton in in vitro assays has been reviewed and was mainly negative (54). Positive results for reverse mutation occurred in single assays with LT-2 or TA1535 stains of S. typhimurium without activation but not in several other assays with or without activation (54). Similarly, both positive and negative results for reverse mutation have been reported in E. coli and S. cerevisiae (54). Disulfoton was negative of gene conversion, mitotic crossing over and recombinants, and for DNA damage in S. cerevisiae with or without activation but was positive in an assay for chiasmatic frequency (genetic recombinants), mitotic index, chromosomal aberrations, and pollen fertility in barley (54). Disulfoton was positive or weakly positive for sister chromatid exchange in Chinese hamster ovary cells in some studies, but negative in others; negative for HGPRT mutations in Chinese hamster ovary cells with or without activation; positive for forward mutations in mouse lymphoma cells for unscheduled DNA synthesis in human lung fibroblasts, and for growth inhibition and increased protein synthesis in human HeLa cells; and negative for chromosomal aberrations in human hematopoietic cell lines and for alterations of DNA or RBA synthesis in human HeLa cells (54). 11.3.5 Biomonitoring/Biomarkers The presence of disulfoton and/or its metabolites in urine is a reliable biomarker for disulfoton exposure. At 2–10 days post exposure, 30–84% of an oral dose can be accoun-ted for in the urine of animals. Although precise relationships between disulfoton exposure and urinary DEP have not been established, DEP is considered a relatively sensitive

biomarker for exposure to disulfoton and other diethyl organophosphate esters (54). 11.4.2 Human Experience 11.4.2.2 Clinical Cases A 30-year-old man was found dead after consuming an unknown amount of disulfoton, as evidenced by the presence of disulfoton in urine and blood (186). A 75-year-old woman who ingested an unknown quantity of disulfoton as DiSyston (5%, granular) experienced severe organophosphate poisoning from 3.5 hours to 11 days, characterized first by vomiting and diarrhea, followed by nausea, fasciculations, and then confusion, miosis, and cardiac arrhythmias. She recovered after 28 days (186a). A farmer who had worn disulfoton-contaminated gloves for several days developed signs of disulfoton toxicity (weakness, fatigue, and cyanosis) and had to be hospitalized (187). The inhalation exposure potential of wet and dry mix procedures used to prepare disulfoton fertilizer mixtures were compared by measuring disulfoton on special filter pads used in place of the usual outer absorbent filter pads that cover the filter cartridges of respirators worn by workers (31). Dermal exposure was measured by attaching layered gauze absorbent pads to various parts of the body or clothing and allowing workers to be exposed for a timed period of work. Air exposures during dry mix operations averaged 0.633 mg/m3 1–5 meters from the work station and, during wet mix operations, averaged 0.06 mg/m3 1–5 meters from the work station. Dermal exposures averaged 2.0 mg/h and 0.09 mg/h during dry and wet mix operations, respectively. RBC cholinesterase values for dry mix workers were reportedly depressed by about 23% after 9 weeks of work, but it was not clear whether these measurements were from workers wearing respirator or not—which would have decreased the anticholinesterase effect. 11.5 Standards, Regulations, or Guidelines of Exposure Disulfoton is undergoing reregistration by the EPA (178). The ACGIH TLV for disulfoton is 0.1 mg/m3 with a skin notation (154). NIOSH has recommended a REL-TWA of 0.1 mg/m3 with a skin notation. Most other countries also have Occupational Exposure Limits of 0.1 mg/m3 (Australia, Belgium, Denmark, France, The Netherlands, Switzerland, and the United Kingdom).

Organophosphorus Compounds Jan E. Storm, Ph.D 12.0 EPN 12.0.1 CAS Number: [2104-64-5] 12.0.2 Synonyms: O-ethyl O-p-nitrophenyl phenylphosphonothioate; PIN; EPN; phenylphosphonothoic acid, O-ethyl O-o-nitrophenyl ester; O-ethyl O-p-nitrophenylbenzenethionophosphonate; O-ethyl O-p-nitrophenyl benzenephosphonothioate; phenylphosphonothioic acid O-ethyl O-(4-nitropheny) ester; ethyl pnitrophenyl benzenethiophosphonate; O-ethyl O-(4-nitrophenyl) phenylphosphonothioate; ethoxy((4-nitrophenoxy) (phenyl) phosphine) sulfide; ethyl (p-nitrophenyl) phenylphosphonothioate; ethyl (p-nitrophenyl) benzenethionophosphonate; ethyl O-(4-nitrophenyl) benzenethionophosphonate; ethyl O-(p-nitrophenyl) benzenethionphosphonate; Ethyl O-(p-nitrophenyl) phenylphosphonothioate; ethyl p-nitrophenyl thiobenzene phosphonate; ethyl phenyl (p-nitrophenyl) thiophosphonate; ethyl phenylphosphonothioic acid O-(4-nitrophenyl) ester; phenol, p-nitro-, O-ester with O-ethyl phenyl phosphonothioate; Santox; O-ethyl O-p-nitrophenyl phenylthiophosphonate; ethyl p-nitrophenyl Benzenethiophosphate 12.0.3 Trade Names: Santox 12.0.4 Molecular Weight: 323.31 12.0.5 Molecular Formula:

C14H14NO4PS 12.0.6 Molecular Structure:

12.1 Chemical and Physical Properties EPN is a noncombustible, light yellow solid or brown crystalline substance. Contact of EPN with strong oxidizers may cause fires and explosions. Toxic gases and vapors (e.g., oxides of sulfur and nitrogen, phosphoric acid mist, and carbon monoxide) may be released when EPN decomposes. Specific gravity 1.268 at 25°C Melting point 36°C Boiling point 215 at 5 mmHg Vapor pressure 0.0003 torr at 100°C Solubility soluble in acetone, alcohols, ether, toluene; slightly soluble in water 12.2 Production and Use EPN was introduced in 1949 for use as a nonsystemic insecticide and acaricide. It was used primarily on cotton to control the boll weevil and lepidopterous pests and was available as a 45% emulsifiable concentrate, as granules, and in combination with other insecticides (188). EPN is no longer registered for use in the United States (45). 12.4 Toxic Effects 12.4.1.1 Acute Toxicity EPN is an organophosphate compound that has high oral toxicity and oral LD50s of 14.5–91 mg/kg for rats (64a). Oral doses of 2–75 and 2–50 mg/kg technical EPN were fatal to female and male dogs, respectively (277). Oral and intraperitoneal LD50s for the mouse were 12.2 and 8.4 mg/kg, respectively, and an oral LD50 for the dog was 20 mg/kg (545). EPN was about five times more potent in young rats compared to adult rats; the intraperitoneal LD50 in 23-day-old rats was 8 mg/kg, whereas it was 33 mg/kg in adults (189). Dermal LD50s were 25–230 mg/kg in rats (64a). A dermal LD50 for the rabbit was 30 mg/kg (529), and the lethal range for dermal exposure to EPN for rabbits was 30–150 mg/kg (277). The only acute inhalation toxicity value available for EPN is a 1-hour LC50 of 160 mg/m3 that was reported for rats (545). The magnitude of brain, plasma, and RBC cholinesterase activity inhibition and its rate of recovery in rats was determined following a sublethal dose of 25 mg/kg EPN (38). Maximum brain cholinesterase inhibition occurred 4–24 hours after exposure and recovered to normal by 2 weeks, maximum plasma cholinesterase inhibition occurred at 4 hours and recovered by 72 hours, and maximum RBC inhibition occurred at 24 hours and recovered by 4 weeks (the same rate at which new rat RBCs are formed) (38). Adult, atropinized hens treated subcutaneously with doses of EPN equivalent to the hen subcutaneous LD50 (60 mg/kg) developed leg weakness immediately after dosing that persisted for more than 48 hours and occurred in addition to cholinergic symptoms (140). Only 3 of 21 animals that exhibited leg weakness survived. In another study, EPN produced neurotoxicity when administered subcutaneously to atropinized hens at doses of 40 mg/kg or more, but not at doses of

20 mg/kg. Although this effect was prompt in onset and lasted as little as 6 days in some hens, it persisted for more than 330 days in others (64a). High, lethal, single oral exposures (65–100 mg/kg) also caused delayed neuropathy in atropinized hens (191). Delayed neurotoxic ataxia was also observed in mice following oral dosing. A sublethal oral dose (20 mg/kg) produced an irreversible neurotoxic ataxia in mice after 29 days (192). EPN potentiates malathion toxicity and is itself potentiated by malathion. Oral LD50s for EPN and malathion given by gavage to rats were 65 and 1400 mg/kg, respectively. When given together at approximately equitoxic doses (about a 25:1 malathion: EPN ratio), a tenfold potentiation was observed. The LD50 for malathion was 167 mg/kg and for EPN was about 6.6 mg/kg (193, 194). Similarly, when single doses of EPN were administered to dogs, 200 mg/kg was fatal, and 50– 100 mg/kg caused moderate to severe symptoms; however, when EPN was administered simultaneously with as little as 100 mg/kg malathion (1125 to 2400 mg/m3, and, 4-hour LC50s range from 454–2400 mg/m3 (123, 321). When 4-hour exposures were repeated for 5 days, the LC50 was reduced to approximately 212 mg/m3 for males and to between 55 and 212 mg/m3 for females (321). Acute exposures of 209 mg/m3 resulted in deaths in 2/20 female rats and ataxia and tremors in both sexes (322, 323). Lethal doses of fenthion, when given in fractions on successive days, are lower than they are when given as a single dose, indicating cumulative toxicity. There was 75% mortality in female rats given 50 mg/kg via gavage for 5 days (about one tenth the LD50) and 100% mortality in female rats given 100 mg/kg for 5 days (about one sixth the LD50) (318). The dermal LD50 for a dose applied on 5 consecutive days was 73 mg/kg/day, whereas the single-dose dermal LD50 was 500 mg/kg. Daily intraperitoneal doses of 10 mg/kg for 60 days caused no mortality, but doses of 20 mg/kg caused 80% mortality by 30 days, doses of 40 or 50 mg/kg caused 100% mortality by 10 days, and, a dose of 100 mg/kg caused 100% mortality by 5 days (315). When rats were given single oral doses of 0, 20, 75, or 150 mg/kg fenthion, cholinergic signs occurred in all groups that peaked at 1.5 hours and persisted for at least 24 hours (324). When rats were given single oral dose of 0, 1, 50, or 125 mg/kg (males) and 0, 1, 75, and 225 mg/kg (females) fenthion, clinical signs of acute cholinergic toxicity occurred in mid- and high-dose rats of both sexes (325). RBC and brain cholinesterase activities were inhibited in the mid- and high-dose males and in the low-, mid- and high-dose females. A no-effect level for RBC cholinesterase of 0.7 mg/kg was derived from these data. Dogs given a single oral dose of 220 mg/kg fenthion exhibited cholinergic signs, that disappeared by 5 days after dosing (326). RBC cholinesterase was inhibited 20 minutes after exposure, increased to pre-exposure levels by 3–12 hours after exposure, but then decreased again below control levels from 24 hours to 30 days after dosing. One of the relatively unique toxic effects associated with fenthion is acute ocular toxicity (327). Four days after single intramuscular doses of 0.005, 0.05, 0.5, or 5.0 mg/kg fenthion, electroretinograms (ERG) in rats were supernormal (sic) 4 days after a dose of 25 mg/kg, the ERG was normal; and 4 days after a 100-mg/kg dose, the ERG was subnormal (327–329). Retinal acetylcholinesterase was unaffected 4 days after 0.005- or 0.05-mg/kg doses but decreased after doses of 0.5–100 mg/kg (327–329). Further study indicated that supernormal ERG changes associated with 5 mg/kg peaked at 10 days and returned to normal by two months, supernormal ERG changes associated with 25 mg/kg peaked at four days then became subnormal and recovered by two months, and ERGs associated with 50 mg/kg remained subnormal for at least 66 days (327). Single acute intraperitoneal doses of 100 mg/kg fenthion were associated with retinotoxicity and characterized by inhibition of retinal cholinesterase and temporary down-regulation of muscarinic receptors in the retina (330). Fenthion is not considered as an eye or dermal irritant and does not cause dermal sensitization (317a). 16.4.1.2 Chronic and Subchronic Toxicity Rats fed a daily diet that contained 300 ppm fenthion for approximately 30 days showed symptoms of organophosphate intoxication (331). When rats were given diets that contained 5, 10, 20, or 250 ppm fenthion (equivalent to daily doses of about 3, 5–6, 11–12, and 100–138 mg/kg/day) for 4 weeks, symptoms of cholinergic poisoning were mild and transient and occurred only in the 250-ppm group (318). Brain cholinesterase activities in rats from all groups were significantly inhibited. Among rats fed 0.25, 0.5, 2.5, or 5.0 mg/kg/day fenthion for 12 weeks, cholinergic signs occurred in those fed 2.5 or 5 mg/kg (331a). RBC cholinesterase activity was significantly inhibited in rats fed 0.5 mg/kg or more, and tissue cholinesterase (heart, liver) was significantly inhibited in female rats fed 0.25 mg/kg/day or more and male rats fed 0.50 mg/kg/day

or more. when rats were fed diets that contained 0, 2, 25, or 125 ppm fenthion for 13 weeks (equivalent to 0, 0.13–0.17, 1.6–2.2, and 8.5–12.6 mg/kg/day, clinical cholinergic signs and a doserelated decrease in RBC and brain cholinesterase activities occurred in rats given the 25- or 125-ppm diet (317a). There were no treatment-related opthalmologic findings. When mice were fed diets that contained 0, 50, and 100 ppm fenthion for approximately (sic) 5 weeks, no cholinergic signs were observed in any group, but marked RBC and brain cholinesterase inhibition occurred in mice at all treatment levels (333). When rats were exposed to 0, 1, 3, or 16 mg/m3 fenthion aerosol for 6 h/day, 5 days/week for 3 weeks, females in the two higher group exhibited behavioral disturbances (sic) (334). Male rats tolerated these exposures without clinical symptoms. RBC and brain cholinesterase activity were inhibited in both sexes at 3 mg/m3. When rabbits were dermally treated with 5, 50, or 100 mg/kg fenthion for 6 h/day, 5 days/week for 3 weeks, no cholinergic effects occurred (317a). Inhibition of RBC cholinesterase in males and inhibition of brain cholinesterase in females occurred only at the highest dose. Dermal treatment of rabbits with 150 mg/kg according to the same paradigm caused cholinergic signs and significant RBC and brain cholinesterase inhibition (317a). When shaved (one-half abraded) rabbits were dermally treated with 5 or 25 mg/kg fenthion applied as a dilute solution in Cremophor for 21 days, RBC and brain acetylcholinesterase were inhibited at 5 mg/kg/day (317a). 16.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Fenthion is quickly absorbed in the digestive tract, and lung, and skin and is hydrolyzed either unchanged or after enzymatic oxidation. Elimination occurs via urine and feces within 3 days. In lactating cows, fenthion was readily distributed to and eliminated in milk (350). Peak concentrations of fenthion in milk occurred 18 or 8 hours after dermal or intramuscular exposure, respectively, and by 14–20 days after treatment accounted for 1.1% and 2.2% of the dermal or intramuscular dose, respectively. Fenthion was rapidly degraded and eliminated primarily in the urine. Following topical administration of fenthion of lactating cows, 45–55% was excreted in urine, 2–2.5% was eliminated in feces, and 1.5–2% was eliminated in milk during a period of 4 weeks (350). EPA estimated that dermal absorption would be about 20% of an applied dose (317a) based on a comparison between cholinesterase inhibition no-effect levels in rabbits treated dermally or orally which were 1 mg/kg/day and 5 mg/kg/day, respectively. The delayed and prolonged effect from a single dose of fenthion suggests that a large portion of a dose is stored and then slowly released to be metabolized (318). Fenthion (and/or fenthion metabolites) is lipid-soluble, and there is evidence that it readily accumulates in the body. In a postmortem analysis following ingestion of fenthion, greater concentrations of fenthion were detected in human organs and fat than in blood (351). It has been proposed that the sulfoxide and sulfone of the thioether of fenthion are produced before P S to P O oxidation takes place (352, 353). Both of these compounds given orally to rats are more toxic than fenthion itself, and their effects occur more rapidly than after fenthion. However, neither compound actively inhibits acetylcholinesterase, so presumably these compounds are oxygenated to forms that readily inhibit acetylcholinesterase (318). 16.4.1.4 Reproductive and Developmental Decreased epididymal weight, decreased fertility, increased maternal weight gain during premating, decreased weight gain during gestation, decreased pup weight gain during lactation, and inhibition of brain acetylcholinesterase occurred in rats given a diet containing 100 ppm fenthion (about 5 mg/kg/day) for two generations (317a). Cytoplasmic vacuolation of the epithelial ductal cells of the epididymis and inhibition of RBC acetylcholinesterase occurred in parents and offspring fed 14 ppm (about 0.7 mg/kg/day). Diets that contained 1 or 2 ppm fenthion had no adverse reproductive effect. When mice were given water that

contained 60 ppm fenthion (delivering doses of between 9.5–10.5 mg/kg) for five generations, there was no consistent effect on mating success, although treated mice exhibited longer periods to produce first litters in the first three generations and pup survival and growth decreased in the second, third, and fourth generations (254). A slightly higher rate of resorptions occurred among rats given 18 mg/kg/day fenthion by gavage on gestation days 6–16 (317a). Adverse developmental effects did not occur in rats given 1 or 4.2 mg/kg/day. Cholinergic signs and decreases in body weight gain also occurred in the 18mg/kg/day dosed pregnant rats. RBC and brain acetylcholinesterase were inhibited at 1 mg/kg/day and higher. Fetal brain acetylcholinesterase was also inhibited in the high-dose group at day 20. In rabbits given 0, 1, 2.75, or 7.5 mg/kg/day fenthion by gavage on gestation days 6 through 18, a slight increase in resorptions occurred in the 2.75- and 7.5-mg/kg/group, and increases in unossified metacarpals occurred in the 7.5-mg/kg/day group. Dams exhibited “soft stools” at 2.75 mg/kg/day, a weight gain decrease at 7.5 mg/kg/day, and inhibition of brain and RBC acetylcholinesterase at both 2.75 and 7.5 mg/kg/day (317a). 16.4.1.5 Carcinogenesis There was no cholinergic toxicity, lens opacification, clinical chemistry effects, or hematotoxicity among rhesus monkeys that received a daily oral dose of 0.02, 0.07, or 0.2 mg/kg via corn oil gavage for 2 years (317a). However, RBC acetylcholinesterase had a threshold for inhibition at 0.07 mg/kg/day (frequent inhibition at this level up to 39% for the first 3 months of the study). More consistent inhibition was noted at 0.20 mg/kg/day. When dogs were fed diets containing 0, 2, 5, or 50 ppm fenthion (equivalent to about 0.06, 0.3, and 1.2 mg/kg/day) for 1 year, no signs of cholinergic toxicity occurred at any dose, although the 50-ppm dose caused marked inhibition of RBC and brain cholinesterase (335). No carcinogenicity or other toxicity occurred among dogs given diets containing 0, 3, or 10 ppm fenthion for 104 weeks or among dogs given diets that contained 30 ppm from week 1 to week 64, 60 ppm from week 65 to week 67, and 60 ppm from week 68 to week 104 (317a). However, RBC cholinesterase was inhibited at 10 ppm and higher in males and at 30 ppm and higher in females; brain cholinesterase was inhibited at 30 and 60 ppm. No cholinergic signs, tumors, or other toxicity occurred in dogs given diets that contained 0, 2, 10, or 50 ppm fenthion for 1 year (336). RBC cholinesterase activity was inhibited at 10 or 50 ppm, and brain cholinesterase was inhibited at 50 ppm. When rats were fed diets that contained 0, 2, 3, 5, 25, or 100 ppm for 1 year, the 100-ppm diet caused decreases in body weight gain, increased mortality and inhibition of RBC, brain and submaxillary gland cholinesterase; the 25-ppm diet increased mortality in female rats and inhibition of RBC, brain, and submaxillary gland cholinesterase; the 5-ppm diet inhibited RBC cholinesterase; and the 3-ppm diet had no effect (335). No gross or microscopic lesions were observed in any group hemosiderosis in the spleen of rats fed 100 ppm. No carcinogenicity, cholinergic toxicity, hematoxicity, or alterations in clinical chemistry occurred in rats given diets that contained 3, 15, or 75 ppm fenthion (about 0.2, 1.0, or 5.0 mg/kg/day) for 24 months (586). However, the 75-ppm diet decreased body weight gain in males and slightly increased mortality in both sexes, and the 15-and 75-ppm diets significantly inhibited RBC cholinesterase in both sexes. There was no evidence of carcinogenicity in rats fed diets that contained 5, 20, or 100 ppm fenthion (about 0, 0.02–0.03, 0.8– 1.3, and 5.2–7.3 mg/kg/day) for 2 years (336). However, clinical cholinergic signs, retinal degeneration, and posterior subcapsular cataract formation were observed in the 100-ppm groups; and electroretinograms were flat or suppressed in females given the 20- or 100-ppm diet. Significant RBC and brain acetylcholinesterase inhibition occurred at 5 ppm. Subnormal ERGs occurred by 3 months and disappeared completely by 1 year among rats injected subcutaneously with 50 mg/kg fenthion once every 4 days for 1 year. Significant histopathology was evident in the retina that included disappearance of the retinal pigmentary epithelial layer, the outer nodes, inner nodes and outer granular layer, and photoreceptor cells (327, 328, 329, 337). ERGs were also extinguished and retinal degeneration was extensive in rats treated subcutaneously with 50 mg/kg twice a week for 1 year (327).

There was no evidence of carcinogenicity in rats or in female mice given fenthion in the diet at 10 or 20 ppm for 103 weeks and then observed for 0–2 additional weeks (338). Doses were 0.49 and 0.98 mg/kg/day for rats and 1.3 and 2.6 mg/kg/day for mice. Some cholinergic signs were noted at both doses in rats and mice. No evidence of carcinogenicity, cholinergic toxicity, hematotoxicity, or other toxicity was seen in mice given diets that contained 0, 0.09, 0.9, 4.6, or 25 ppm fenthion (equivalent to 0, 0.03, 0.4–0.5, 1.95–2.25, and 9.42–10.23 mg/kg/day) for 102 weeks (317a). RBC and brain cholinesterase inhibition was significant at a dietary level of 25 ppm. 16.4.1.6 Genetic and Related Cellular Effects Studies In vitro tests of fenthion (339–342) and in vivo tests in mice (343, 344) showed no mutagenic effect of fenthion. Fenthion was negative in the dominant lethal mutation assay in male mice (345, 346) and negative or weakly clastogenic at acutely toxic doses in the mouse micronucleus test (347). Among rats treated with two oral doses of 54 mg/kg fenthion (one-fourth LD50) 21 hours apart, there was a fivefold increase in hepatic and brain lipid peroxidation and a 3.5-fold increase in hepatic single-strand DNA breaks (348). Increased numbers of single chromatid gaps and breaks were detected in human lymphocytes incubated in variable concentrations of 98% technical grade fenthion (349). 16.4.1.7 Other: Neurological, Pulmonary, Skin Sensitization Fenthion caused neurotoxicity that lasted from 3 to 10 days when given subcutaneously at a dose of 25 mg/kg to atropinized chickens (64). The lowest lethal dose was 40 mg/kg, indicating that neurotoxicity occurred at a sublethal dose. Atropinized hens treated with 40 mg/kg (orally) or 200 mg/kg (dermally) two times 21 days apart and observed for a total of 42 days showed no behavioral or histopathological signs of delayed type neuropathy (317a). Additionally, no evidence of pathological changes in the structure of brain or peripheral nerve indicative of delayed type neuropathy were observed in hens treated orally by gavage with 0, 084, 1.7, or 3.2 mg/kg/day for 90 days (317a). 16.4.2 Human Experience 16.4.2.2 Clinical Cases A 26-month-old male experienced abdominal pain and vomiting for 8–18 hours after dermal (and possibly oral) exposure of a flea killer that contained fenthion. About 42 hours after exposure, he experienced respiratory arrest accompanied by miosis, hyperactive bowel sounds, pulmonary edema, and diminished muscle tone and reflexes. Therapy with atropine, 2-PAM, and ventilation saved his life, and he recovered about 32 days after exposure (1). A 71-year-old farmer who was estimated to have ingested about 83 mg/kg fenthion suffered nausea, was hospitalized unconscious after 13 hours, and died 4 days later. A 40-year old individual who drank as estimated 25 mg/kg fenthion was unconscious for about 4 days but survived (1). In another attempted suicide, a 44-year-old man was thought to have ingested 310 mg/kg fenthion. He showed only a few mild signs of poisoning when hospitalized 3 hours after ingestion. However, he experienced two relapses in spite of adequate drug therapy and required tracheotomy during recovery (1). Fenthion blood levels and plasma cholinesterase activity were followed in a 41-year-old male who ingested an unknown amount of fenthion and died after 7 days (354). Blood fenthion concentration was 0.27 mg/L on admission (20 hours after ingestion) but rapidly increased to 0.78 mg/L coincident with worsening cholinergic symptoms. Even after 5 days, fenthion blood concentration still varied within the 0.2–0.3 mg/L level. In another case of fenthion poisoning, a 43-year-old man ingested about 30 mL of Lebaycid, corresponding to about 18 g fenthion (355). Signs of cholinergic toxicity were seen 31 hours after ingestion at which time RBC acetylcholinesterase were totally inhibited. The relatively long half-life of fenthion was illustrated in another case report of a woman who experienced severe poisoning after ingesting fenthion in a suicide attempt. A fat biopsy obtained 22 days after ingestion, after recovery from an acute cholinergic phase of poisoning but before experiencing a delayed intermediate type syndrome, indicated fat residues of about 0.15 ppm fenthion. By day 31 when all symptoms had been resolved, fat residues had decreased to zero. Neurological symptoms that ranged from occasional tingling and numbness of the hands and feet to

multiple shooting pain, back pain, numbness, and generalized muscle weakness were reported by five employees in a veterinary hospital who routinely used topical applications of a 20% fenthion solution on dogs and took no precautions to avoid dermal contract (356, 357). When the use of fenthion was discontinued, the symptoms stopped. The characteristics of an intermediate syndrome (respiratory insufficiency, weakness of muscles, innervated by cranial nerves and weakness of proximal limb muscles) were described in four cases of fenthion poisoning (two of the people died) that occurred 2–6 days following resolution of an acute cholinergic crises and which lasted 5–18 days (358). Unusual transient dystonic movements also occurred in two of these cases. Symptoms that comprised an “intermediate syndrome” (i.e., weakness of external ocular, facial, neck, proximal limb, and respiratory muscles) and extrapyramidal signs (dystonia, rest tremor, cog-wheel rigidity, and choreoathetosis), occurred from 4 to 40 days after acute poisoning with fenthion, and resolved after 1 to 4 weeks in survivors were described in six cases of people who ingested 15–60 mL of fenthion (359). Several publications report an association between an increased incidence of adverse visual effects (myopia and a visual disease syndrome termed “Saku” disease) and agricultural use of organophosphates, including fenthion, in Japan. The recently reviewed studies vary in quality and usefulness, but nevertheless suggest that the association is probable (327). However, only one study is available that suggests a specific link between fenthion exposure and ocular toxicity. In this study, neurological function, visual acuity, refraction, color vision, and the condition of the fundus oculi were assessed in 79 individuals who worked 5–6 h/day spraying an aqueous suspension of fenthion and were compared to equivalent observations of 100 control subjects (327). Macular changes (hypopigmentation, irregularity of background pigmentation, and dull foveal relex) were evident in 15 (19%) workers and in 3 (3%) control subjects. Other visual symptoms reported in workers who had macular change included visual impairment, reduced visual acuity, abnormal color vision, and constriction of visual fields. Pathological myopia (associated with “Saku”) disease was not observed. Symptoms reported among thirty-one workers who sprayed aqueous suspensions of fenthion (100 mg in 100 L water) by a hand-operated sprayer for 5–6 hours/day, 6 days/week included headache (56%) giddiness (44%), eye irritation (20%), anorexia and paresthesia (11%), but no signs specific for cholinergic toxicity (360). On neurological examination, two subjects had loss of ankle reflex, and one had coarse tremors. Additionally, subtle subclinical effects on psychometric tests and event related potentials were observed. However, no estimate of exposure was provided. Fenthion administered to human volunteers at dose levels of 0.02 or 0.07 mg/kg daily for up to 4 weeks produced no physical signs or symptoms; no alterations in clinical chemistry, hematology or urinalysis; and no inhibition of RBC cholinesterase activity (361). 16.5 Standards, Regulations, or Guidelines of Exposure Fenthion has been reregistered for use by the EPA. The ACGIH TLV for fenthion is 0.2 mg/m3 with a skin notation (154). There is no OSHA PEL-TWA or NIOSH REL-TWA for fenthion. Other countries have Occupational Exposure Limits of 0.2 mg/m3 for fenthion (Australia, Belgium, Germany, and Japan); others have OELs of 0.1 mg/m3 (Denmark, The Netherlands, and Switzerland).

Organophosphorus Compounds Jan E. Storm, Ph.D 17.0 Fonofos 17.0.1 CAS Number:

[944-22-9] 17.0.2 Synonyms: (O-ethyl-S-phenyl ethylphosphonodithioate; O-ethyl S-phenyl ethyldithiophosphonate; Ethyl Sphenylethylphosphonothiolthionate; Diphonate; Fonophos; O-ethyl Sphenylethylphosphonothiolothionate; ethylphosphonodithioic acid O-ethyl S-phenyl ester; Dyfonate II; N-2790; O-ethyl S-phenylethylphosphonodithioate; Stauffer N-2790; ethyl s-phenyl ethylphosphonodithioate; Dyphonate 17.0.3 Trade Names: Dyfonate®; Difonate; Dyphonate 17.0.4 Molecular Weight: 246.32 17.0.5 Molecular Formula: C10H15OPS2 17.0.6 Molecular Structure:

17.1 Chemical and Physical Properties Fonofos is a light yellow liquid. Specific 1.154 at 20°C gravity Boiling point 130°C at 0.1 mmHg Flash point >94°C, closed cup Vapor 0.00021 torr at 25°C pressure Solubility very slightly soluble in water (13 mg/L at 20°C); miscible with organic solvents such as kerosene, xylene, and isobutyl ketone 17.1.2 Odor and Warning Properties Pungent, mercaptan-like odor. 17.2 Production and Use Fonofos was introduced in 1967 for use as a soil insecticide to control corn borers, rootworms, cutworms, symphylans (garden centipedes), wireworms, and other soil and foliar pests. It is formulated as an emulsifiable concentrate and as granules. Registration of fonofos in the U.S. has been voluntarily cancelled. 17.4 Toxic Effects 17.4.1.1 Acute Toxicity Fonofos has high oral toxicity, and oral LD50s are 3–18.5 mg/kg for rats (64a). Cholinergic signs and death occur rapidly after lethal exposure (364). The oral LD50 for a racemic mixture of fonofos was 14 mg/kg, which was less than the oral LD50 of 32 mg/kg for the (S) p isomer but greater than the oral LD50 of 9.5 mg/kg for the (R)p isomer (362). The acute i.p. LD50 for the fonofos racemic mixture was 4.8 mg/kg, suggesting an overall detoxification role of first-pass hepatic metabolism. The dermal LD50 for rats is 147 mg/kg and for guinea pigs is 278 mg/kg (363). Application of 0.5 ml undiluted fonofos to the skin of rabbits caused on dermal irritation, but all animals died within 24 hours (154). The 4-hour LC50 of fonofos for rats is 900 mg/m3, and the 1hour LC50 is 460 mg/m3 (363).

Technical fonofos (0.1 mL) instilled into the eye of albino rabbits caused death during the first 24 hours after administration of the chemical, but local eye irritation was negligible (363). 17.4.1.2 Chronic and Subchronic Toxicity Dietary feeding of fonofos of groups of dogs for 14 weeks indicated a no-observed effect level of 8 ppm (approximately 0.2 mg/kg) (120a). 17.4.1.3 Pharmacokinetic, Metabolism, and Mechanisms Fonofos is well absorbed orally. After a single oral dose of fonofos, 98% was excreted in the urine (91%) and feces (7.4%) of rats within 96 hours. Prior exposure to fonofos did not change in excretion pattern. Tissue residues were very small and had virtually disappeared by day 16 (365). Similar results were obtained in white mice given the enantiomer of fonofos orally (365a). Fifty percent of the most toxic isomer and 95% of the less toxic isomer where eliminated within 96 hours. Fonofos is first oxidized by microsomal enzymes to the oxon and also, by a different reaction, to Oethyl-ethylphosphonothioic acid (ETP) and thiophenol. The oxon, in turn, is hydrolyzed to O-ethylethylphosphoric acid (EOP) and thiophenol (366, 367). The oxon is not found in vivo due to its rapid hydrolysis (368). The other metabolites were much less toxic than the parent compound. 17.4.1.4 Reproductive and Developmental No adverse effects were noted on overall reproductive performance at either level among the parental animals or on the numbers, well-being, or integrity of the offspring among rats fed 10 or 31.6 ppm fonofos for three generations (95). EPA noted a fetotoxic no-observed-effect level of 1.58 mg/kg/day in rats and a fetotoxic noobserved-effect level and lowest observed effect level of 2 and 6 mg/kg/day, respectively, in mice (95, 364). 17.4.1.5 Carcinogenesis There was no evidence of carcinogenicity when fonofos was given in the diet to rats for 105 weeks (95). This study produced a no-observed-effect level of 10 ppm (0.5 mg/kg/day) for brain acetylcholinesterase inhibition and a lowest observed effect level of 1.58 mg/kg/day based on RBC cholinesterase inhibition (95). There was no evidence of carcinogenicity in dogs that were fed 0, 0.2, 1.5, and 12 mg/kg/day fonofos via their diet for 2 years (95). No compound-related effects were observed at 0.2 mg/kg/day; moderate (sic) inhibition of RBC cholinesterase, increased liver weight, tremors, lacrimation, and salivation occurred at 1.5 mg/kg/day; and, these symptoms plus microscopic lesions of the small intestines and liver occurred at 12 mg/kg/day. 17.4.2 Human Experience Four members of a family were poisoned by pancakes mistakenly made with fonofos instead of flour; one family member died (368a). Soon after eating the pancakes, one family member developed nausea, vomiting, salivation, and sweating and was taken to a hospital where she suffered cardiorespiratory arrest. She was resuscitated and transferred to a medical center where she was artificially ventilated, exhibited muscle fasciculations, low blood pressure, pinpoint pupils, and profuse salivary and bronchial secretions. Treatment continued and she was eventually released 2 months later. Gallo and Lawryk (1) noted that, although not reported in the original paper, three other members of the family were poisoned by the pancakes, and one of them died. A fifth family member who may have mixed the batter, but did not eat pancakes, remained well. 17.5 Standards, Regulations, or Guidelines of Exposure The registration of fonofos has been voluntarily cancelled in the United States and tolerances are being revoked. The ACGIH TLV for fonofos is 0.1 mg/m3 with a skin notation (154). The NIOSH REL-TWA for fonophos is 0.1 mg/m3 with a skin notation. Most other countries also have Occupational Exposure Limits of 0.1 mg/m3 for fonophos (Australia, Belgium, France, and Switzerland).

Organophosphorus Compounds Jan E. Storm, Ph.D 18.0 Malathion 18.0.1 CAS Number: [121-75-5] 18.0.2 Synonyms: (O,O-Dimethyl dithiophosphate of diethyl mercaptosuccinate; O,O-dimethyl-S-(1,2dicarbethoxyethyl)-phosphorodithioate; diethyl [(dimethoxyphosphinothioyl)thio]butanedioate; Maldison; O,O-dimethyl phosphorodithioate ester of diethyl mercaptosuccinate; [(Dimethoxyphosphinothioyl)thio]butanedioic acid diethyl ester; mercaptosuccinic acid diethyl ester S-ester with O,O-dimethyl phosphorothioate; insecticide no. 4049; phosphothion; Cythion; dicarboethoxyethyl O,O-dimethyl phosphorodithioate; O,O-dimethyl S-(1,2-dicarbethoxyethyl) dithiophosphate; O,O-dimethyl S-(1,2-dicarbethoxyethyl)phosphorodithioate; diethyl mercaptosuccinate, O,O-dimethyl phosphorodithioate; 1,2-di(ethoxycarbonyl)ethyl O,O-dimethyl phosphorodithioate; chemathion; emmatos; karbofos, kop-thion; malagran; malamar; MLT; sadofos; S-(1,2-bis(carbethoxy)ethyl) O,O-dimethyl dithiophosphate; S-1,2-bis(ethoxycarbonyl)ethyl O,Odimethyl dithiophosphate; calmathion; carbetox; carbethoxy malathion; carbetovur; celthion; cinexan; compound 4049; detmol ma; S-(1,2-di(ethoxycarbonyl)ethyl) dimethylphosphorothiolothionate; diethyl (dimethoxyphosphinothioylthio)succinate; diethyl mercaptosuccinate, O,O-dimethyl dithiophosphate, S-ester; diethyl mercaptosuccinate, O,O-dimethyl thiophosphate; diethyl mercaptosuccinate S-ester with O,O-dimethylphosphorodithioate; diethyl mercapatosuccinic acid O,O-dimethyl phosphorodithioate; O,O-dimethyl-S(1,2-bis(ethoxycarbonyl) ethyl)dithiophosphate; O,O-dimethyl-S(1,2-dicarbethoxyethyl) thiothionophosphate; O,O-dimethyl S-1,2-di(ethoxycarbonyl)ethyl phosphorodithioate; O,O-dimethyldithiophosphate diethyl mercaptosuccinate; phosphorodithioic acid, O,O-dimethyl ester, S-ester with diethyl mercaptosuccinate; Malaspray; dicarbethoxyethyl-O,O-dimethyldithiophosphate; diethyl mercaptosuccinic acid, S-ester of O,O-dimethyl phosphorodithioate; dimethyl dithiophosphate of diethyl mercaptosuccinate; dimethyl phosphorodithioate of diethyl mercaptosuccinate; Ethiolacar; Etiol; Cleensheen; Lice Rid 18.0.3 Trade Names: Carbophos; Extermathion; Forthion; Fosfothion; Fyfanon; Malacide;Malatox; Maldison; Mercaptothion 18.0.4 Molecular Weight: 330.36 18.0.5 Molecular Formula: C10H19O6PS2 18.0.6 Molecular Structure:

18.1 Chemical and Physical Properties Malathion is a noncombustible, yellow to deep brown liquid. Malathion is rapidly hydrolyzed at pH>7 or >5 and is stable in aqueous buffered pH 5.6 solutions. It can corrode iron, steel, tinplate,

lead, and copper. It is a solid below 37°C. Specific 1.23 at 25°C gravity Melting 2.85–3.7°C point Density 1.23 at 25°C Boiling 156-157°C at 0.7 torr Point Solubility slightly soluble in water (145 ppm); completely soluble in alcohols, esters, ketones, ethers, aromatic solvents, and hexane, limited solubility in petroleum oils 18.1.2 Odor and Warning Properties A mild skunk-like odor. 18.2 Production and Use Malathion is a broad-spectrum insecticide and one of the earliest organophosphate insecticides developed. It is used to control sucking and chewing insects on fruits, vegetables, and ornamental plants. It is also used to control mosquitos, flies, household insects, animal parasites, and head and body lice. 18.4 Toxic Effects 18.4.1.1 Acute Toxicity Malathion is an organophosphate compound that has low acute toxicity and rat oral LD50s are generally in the 1,000–12,500 mg/kg range, depending on the formulation and gender tested (64, 268). An intraperitioneal LD50 of 750 mg/kg was reported, showing that route of exposure markedly impacts toxicity (369). This was also illustrated in a study where oral and intraperitioneal LD50s in mice were 1025 and 420 mg/kg, respectively (370). Following lethal oral doses, maximal symptoms are often delayed for several hours, but death generally occurred within 2 days after poisoning (369). Technical grade malathion is more toxic than the pure product. Oral LD50s for rats of 65% technical grade malathion, 90% technical grade malathion and 99% undiluted malathion were 369, 1156, and 5843 mg/kg, respectively (370). Commercial preparations of malathion vary in their toxicity due to the presence of impurities which bind to and inhibit acetylcholinesterase and also the carboxylesterase that detoxifies malathion (371–373). A precise dermal LD50 for malathion has not been identified. The dermal LD50s for rats for a 57% emulsifiable concentrate was greater than 4444 mg/kg (64a, 268). In rabbits, single dermal doses of up to 4 ml/kg 90% technical malathion or the 25% wettable powder caused no overt signs of toxicity, except for temporary irritation at the site of application (370). However, mortality occurred after four daily applications of 0.5 or 1 mL/kg/day and after two daily applications of 2 mL/kg. In each case, symptomology was characteristic of acute organophosphate poisoning (370). An acute inhalation LC50 for malathion is not available, although a 4-hour LC50 of >5200 mg/m3 has been reported (155). However, an intravenous LD50 of 50 mg/kg was reported in rats (373a) which is at least 20 times smaller than reported oral LD50s. In dogs, an intravenous dose of 100 mg/kg resulted in immediate and profuse salivation and tremors (370). In a 5-hour exposure of mice of 7 mg/L 95% technical grade malathion (7000 mg/m3), there were no signs of cholinergic toxicity and no deaths (203). Overt toxicity has rarely been identified following single, sublethal exposures to malathion, although they cause RBC and brain cholinesterase inhibition. RBC cholinesterase activity maximally decreased in rats 45 minutes after an intraperitoneal dose of 300 mg/kg (370). Repeated daily intraperitioneal doses of 300 mg/kg produced a cumulative inhibitory action on cholinesterase activity of brain, submaxillary gland, and serum in rats so that after 5 days, activities were about 30, 50, and 25% of control, respectively (369). Rats could not tolerate longer periods of treatment.

Repeated administration of 200 mg/kg also progressively decreased cholinesterase activity of the brain and submaxillary gland. An important characteristic of malathion acute toxicity is its potentiation by other organophosphates. When malathion and EPN were administered to rats separately, LD50s were 1400 and 65 mg/kg, respectively. However, when malathion and EPN were administered simultaneously at a ratio of about 25:1, oral LD50s were reduced to 167 and 7 mg/kg, respectively (184). The onset of symptoms for individual compounds was slow, and death usually occurred several hours after administration. However, when given together at or near the LD50, symptoms developed much more rapidly, and death usually occurred within 1 hour. In dogs, oral doses of 2000 or 4000 mg/kg malathion alone were not fatal; however, when EPN was given simultaneously (2 or 5 mg/kg) with malathion, doses of 50, 100, and 200 mg/kg were lethal (184). Potentiation of malathion toxicity is due to the inhibition of carboxyesterase by EPN (and other organophosphates), an enzyme important in detoxifying of malathion (as well as the more toxic metabolic product malathion, malaoxon) (165, 374). Evidence that malathion causes a paralytic type of neurotoxicity was observed in hens given 100 mg/kg or more malathion subcutaneously and observed for up to 30 days (190). Neurotoxicity, reflected by the occurrence of leg weakness that lasted for 4–14 days, occurred in atropinized chickens given single, subcutaneous doses of 100 mg/kg malathion (64a). Atropinized rats were given 600, 1000, or 2000 mg/kg malathion (88% pure) via oral gavage and were observed for signs of delayed neuropathy at 14–21 days; only the 2000-mg/kg dosed rats showed signs of gait alterations indicative of delayed neuropathy (375). 18.4.1.2 Chronic and Subchronic Toxicity Mortality was 20, 60 and 100%, respectively, among rats given 100, 200 or 300 mg/kg/day malathion intraperitoneally for 60 days (369). Rats fed lentil diets that contained 0.95 or 6.51 ppm malathion (equivalent to about 0.06 and 0.44 mg/kg/day) exhibited no signs of cholinergic toxicity (376). However, both exposure levels were associated with increased blood urea nitrogen and increased white blood cells, and the 0.44-mg/kg/day group had decreased serum cholinesterase activity. Brain and RBC cholinesterase activity were unaffected. Similarly, mice fed soybean seeds contaminated with 7 ppm malathion of 75 days exhibited no signs of cholinergic toxicity and no effect on RBC cholinesterase activity (376). There is evidence that malathion is a sensitzer. In a field study, 3% of workers involved in spraying malathion for mosquito control and 5% of poultry ranchers who had used malathion for at least one season showed positive reactions when malathion (95%) was applied under adhesive tape to the skin of the upper arm and allowed to remain in place for 2 days (406). In another study of ten subjects who had reported skin reactions to malathion bait, none had a reaction to patch testing of malathion. Only one exhibited a positive reaction to the bait and another had irritant reactions to both bait and malathion (407). 18.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Approximately 90% of ingested malathion is relatively slowly absorbed and excreted in urine (1, 106, 389). Six hours after an oral dose of malathion, 75% remained in the stomach, 8% was in the small intestine, and 7% was in saliva. Thus a very small amount had been absorbed. Similar results were obtained in rats fed a lentil diet contaminated with malathion (376). After 48 hours, about 35% of the dose was excreted in urine; 45% in feces, 1.5% in exhaled air, and tissues contained about 9%. In rats given malathion orally, it is distributed to blood, adipose tissue, muscle, liver, and brain and then eliminated from these tissues at half-lives of 1.4, 2.4, 3.7, 19.4, and 17.6 days, respectively (101, 388). Absorption of malathion via inhalation is expected to be high and elimination via urine extremely rapid and nearly complete based on pharmacokinetic studies following intravenous dosing. Among male volunteers, approximately 90% of an intravenous dose of malathion was excreted in urine within 5 days and the an elimination half-life was 3 hours (66). Thirty minutes following intravenous

administration of malathion to rats most had been distributed to tissues; liver, small intestine, lung, urinary tract, and kidney accumulated extremely high levels (389). Distribution pattern at 1 and 2 hours were similar. In mice, 25% of a 1-mg/kg dermal dose of malathion was absorbed within 60 minutes, and 67% of the dose was absorbed by 8 hours (213). Distribution of malathion was equal in liver and blood; slightly greater in urine, feces, and expired air; and greatest in the rest of the carcass at 60 minutes. By 8 hours, 30% of the dose had been excreted, 30% remained in the carcass, and about 2.5% was distributed to lungs, kidney, bladder, stomach, intestine, liver, and blood. Whole body autoradiography of rats treated dermally with a single dose of malathion indicated that after 8 hours most of the dose was equally distributed between the application site (28%), remaining skin (29%), and the small intestine and urinary bladder (23%) (389). Among human volunteers, about 8% of an applied malathion dermal dose of 4 mg/cm2 was absorbed by 120 hours after application to the ventral forearm (66). In vitro absorption by human skin was about 9% from an aqueous ethanol solution and about 0.6 to 4% from cotton sheets to which malathion had been added (389a). Malathion is either oxidized in the liver to malaoxon by microsomal cytochrome P450 enzymes or to monoacids by a microsomal carboxyesterase. Malaoxon is the toxic metabolite of malathion that binds and inhibits acetylcholinesterase and leads to the typical cholinergic sequelae associated with organophosphate poisoning. The other products of malathion and malaoxon metabolism are detoxification products. Malaoxon is also subject to hydrolysis and carboxyesterase (105, 390, 391). There is evidence that the linkage at P–S is enzymatically broken by another cytosolic esterase as well (A-esterase) and forms O,O-dimethyl phosphorothioate (390). There is some evidence the monoacids can then be S-methylated, and that the C–S bond of either malaoxon or malathion can be further hydrolyzed (392, 393). The rate of malathion desulfuration is not as critical as the rate of hydrolysis by carboxyesterase or hydrolysis of the C–S bond, both of which are detoxication reactions, in determining the toxicity of malathion (393). Female rats that are more sensitive to malathion toxicity have relatively lower levels of liver carboxylesterase activity (394). Further, pretreatment of mice with the microsomal inducer phenobarbital failed to decrease the mouse intraperitoneal LD50 (i.e., failed to increase the toxicity) of malathion, whereas it did decrease the i.p. LD50 of dimethoate which is not subjected to detoxification reactions as extensive as those for malathion (391). Additionally, oral LD50s for rats and three strains of mice were significantly correlated with their carboxyesterase titer in liver and plasma (371). Carboxyesterase activity (also termed hydrolase B) occurs in mouse, rat, and human liver microsomal preparations and it has been shown, is markedly inhibited by a common impurity of malathion, isomalathion (372). This inhibition is associated with the potentiation of malathion toxicity (395a). Finally, it is believed that malathion and/or malaoxon inactivate carboxyesterase, so that additional dose of malathion are less effectively detoxified. This contributes to the phenomenon whereby pretreatment with malathion increases the toxicity of subsequent doses (374). No polymorphism of carboxylesterase was detected in 12 human livers, but the range of individual activity toward malathion was about 10-fold (395). In humans, carboxyesterase is expressed only, in the liver, whereas in rodents, carboxyesterase is expressed in the serum and liver. This could provide a basis for a greater sensitivity of humans to malathion compared to rodents, although that has not been adequately explored. 18.4.1.4 Reproductive and Developmental Viability and growth decreased in fetuses of rats fed diets that contained about 4000 ppm technical grade (95%) malathion (240 mg/kg) for 5 months (377). Pregnant rats on protein-deficient or protein-adequate diets given 500 mg/kg/day malathion orally on gestation days 6, 10, and 14 showed decreased maternal weight gain, a decreased number of implantations and live fetuses, and decreased brain acetylcholinesterase activity (392a). Protein

deficiency enhanced an effect of malathion on fetal crown to rump and tail length, fetal body weight, and retardation of skeletal ossification. No detectable increases in the number of resorptions, fetal size, and external or visceral anomalies occurred in rabbits given malathion (70%) at 100 mg/kg by gavage on gestation days 7 through 12 (378). Pregnant rats given 600 or 900 mg/kg malathion via intraperitioneal injection on gestation day 11 showed signs of maternal toxicity but did not produce malformed or low birth weight pups (379). Malathion caused a dose-dependent inhibition in brain acetylcholinesterase activity in dams and pups among rats given 138, 276, and 827 mg/kg/day malathion via intraperitoneal injection on gestation days 6 through 13 (380). 18.4.1.5 Carcinogenesis No cholinergic toxicity or inhibition of whole blood cholinesterase activity occurred in rats fed diets that contained 100 or 200 ppm (2.5 or 6.25 mg/kg/day) for 8 weeks (194). However, when the diet contained 25 ppm (0.625 mg/kg/day) EPN, as well as 500 ppm malathion, whole blood cholinesterase was significantly inhibited. No cholinergic signs occurred in dogs fed diets that contained 25, 100, or 250 ppm malathion for 12 weeks, but RBC cholinesterase was significantly inhibited in dogs fed 250 ppm (194). In rats fed 100, 1000, or 10,000 ppm 65% technical malathion, 90% technical malathion, or 99%+ malathion in the diet (equivalent to about 6, 60, or 600 mg/kg/day) for 2 years, cholinergic toxicity was not described, but among rats given the more toxic 65% and 90% technical products, RBC and brain cholinesterase activities were inhibited in the 1000- and 10,000-ppm groups and were unaffected in the 100-ppm group (370). There was no evidence of carcinogenicity in rats given diets that contained 4700 or 8150 ppm (about 270 mg/kg and 466 mg/kg) for 80 weeks and observed for an additional 33 weeks, in rats given diets that contained 2000 or 4000 ppm malathion (about 115 mg/kg/day and 230 mg/kg/day) for 103 weeks, or in rats given diets that contained 500 or 1000 ppm malaoxon for 103 week (482). There was no evidence of carcinogenicity in mice given diets that contained 8,000 or 16,000 malathion (about 800 and 1600 mg/kg/day) for 80 weeks and observed for an additional 14 or 15 weeks (482). During the second year, clinical signs including alopecia, rough and discolored coats, poor food consumption, hyperexcitability, and abdominal distension occurred with increasing frequency in dosed animals. A few animals appeared hyporeactive, and some had hunched appearances. During weeks 71 to 79, five high-dose females exhibited generalized body tremors. 18.4.1.6 Genetic and Related Cellular Effect Studies Mammalian in vivo and in vitro studies of technical or commercial grade malathion and its metabolite malaoxon show a pattern of induced chromosomal damage, as measured by increased chromosomal aberrations, sister chromatid exchanges, and micronuclei (381, 382), as well as increased mutations (383, 384). Purified (>99%) malathion gave weak or negative results in cytogenetic assays. Technical malathion was generally negative in mammalian gene mutation assay, but malaoxon was positive. Studies of human lymphocytes indicated that in vitro incubation with malathion increased the frequency of DNA mutations (383, 384). Malathion were positive in a modified SOS microplate assay in which the induction of b-galactosidase in E-coli PQ37 was used as a qualitative measure of genotoxic activity (385). Dermal exposure caused cytogenetic damage in test animals at doses near those that produce positive results by intraperitioneal injection (381). Workers involved in a Mediterranean fruit fly aerial spraying eradication program in California in the early 1990's exhibited no increase in micronuclei formation or mutation frequency assessed by the glycophorin A (GPA) assay (386, 387). However, a significant increase in micronuclei occurred in whole blood cultures and in human lymphocytes at dose levels that also caused cytotoxicity and strong inhibition of proliferation (386, 387). 18.4.2 Human Experience 18.4.2.2 Clinical Cases There have been many reports of organophosphate poisoning from the intentional or accidental ingestion of malathion (1). There are a few reports of poisoning from dermal exposure of children that occurred when their hair was washed with a 50% solution of malathion to eliminate lice. Poisoning following inhalation exposures have

been reported but were probably confounded by simultaneous ingestion (1). Cholinergic symptoms appear rapidly from minutes to 3 hours following ingestion, but may be delayed by 12–14 hours after dermal exposure. Estimates of lethal doses of malathion obtained from case study reports range from 68 to 3855 mg/kg (1). Actual estimates of ingestion obtained from reports of poisonings where the quantity was approximately known indicated that a life-threatening dose is 500–1000 mg/kg (371). Doses associated with serious but sublethal toxicity have ranged from approximately 500 mg/kg for dogs (larger doses caused emesis), 640 mg/kg

for rabbits, and 3140 mg/kg for male guinea pigs (41, 64a). In rats given single oral doses of 250, 500, or 1000 mg/kg ronnel by gavage, RBC acetylcholinesterase was unaffected 24 hours after dosing (41). A specific dermal LD50 could not be determined but was larger than 5000 mg/kg for rats (64a). The rabbit dermal LD50 was 1600 to 2000 mg/kg (445a). When ronnel was dermally applied to rabbits under an impervious cuff for 24 hours, one of twelve died at a dose of 1000 mg/kg, six of twelve died at a dose of 2000 mg/kg, and eight of eight died at a dose of 4000 mg/kg (41). No cholinergic effects occurred in rats given 25, 50, 100, or 200 mg/kg ronnel via intraperitoneal injection, although brain and RBC cholinesterase were inhibited at the 200-mg/kg dose (165). Plasma carboxyesterases were markedly inhibited even at the 25-mg/kg dose. Similar effects occurred in cows given 100 mg/kg via gelatin capsule (521). When rats were given diets that contained 5, 10, or 30 ppm ronnel for 30 days or, 10, 30, 100, 300, or 500 ppm ronnel for 7 days, adverse cholinergic effects were not reported, and only the rats fed 300- or 500-ppm diets (equivalent to about 0.5, 1.0, 3.0, 10.0, 30.0, or 50.0 mg/kg/day) for 7 days exhibited significantly inhibited brain and RBC cholinesterase (165). Other esterases, however, were significantly inhibited in all rats except those fed 5-ppm diets. Overall, plasma and liver carboxyesterases were about ten times more sensitive to ronnel inhibition than brain or RBC cholinesterase. Moreover, 30-ppm diets had no effect on brain or RBC cholinesterase activity regardless of whether exposures were for 7 or 30 days, suggesting that ronnel lacks a cumulative effect. However, though the 30-ppm diet for 7 days did not inhibit brain cholinesterase, it increased the degree of cholinesterase inhibition produced by a challenge dose of malathion. The percentage inhibition of brain cholinesterase produced by 200 mg/kg malathion was three times as great as expected on the basis of additive effects in ronnel-fed rats. A small (unspecified) amount of ronnel powder placed in the eye of a rabbit caused slight discomfort and a transient conjunctival irritation that disappeared in 48 hours (41). “A very slight hyperemia of the skin” was produced in rabbits whose skin was treated ten times during 14 days with ronnel under a gauze bandage (519). 25.4.1.2 Chronic and Subchronic Toxicity Albino rats that received 328 and 164 mg/kg ronnel developed cholinergic signs of poisoning within 2 weeks. Some of the rats died. No signs were observed in rats that received 16.4 and 8.2 mg/kg (522). Among steers given diets that contained 0, 44, 88, or 176 ppm ronnel (equivalent to about 0, 1, 2, or 5 mg/kg/day), growth was promoted and thyroid function was altered (increased plasma T4) only in the 176-ppm group—no other effects were reported (523). Repeated dermal exposure to ronnel apparently cured generalized demodicosis in eighteen of twenty dogs treated for 5–20 weeks, although it also caused lethal organophosphate poisoning in one of twenty (524). 25.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms In rats given three acute oral doses of about 18.6 or 186.5 mg/kg/day ronnel 24 hours apart, approximately 14 and 8% of the dose was eliminated in urine as the alkyl metabolites dimethyl phosphoric acid and dimethyl phosphorothioic acid, and 41 and 47% of the dose was eliminated as 2,4,5-trichlorophenol within 48 hours of the last dose. On the third day of dosing, ronnel was distributed to body fat (370 ppm) but by the eighth day the concentration dropped significantly (0.40 ppm) (280). Maximum concentrations in fat occur after 12 hours, and residues at 7 days are equivalent and persist longest in subcutaneous and mesenteric fat, followed by spleen, kidney, and liver. 25.4.1.4 Reproductive and Developmental Ronnel treatment did not alter the number of total

implants, live fetuses, dead fetuses, resorptions, or fetal weight in pregnant rats given 0, 400, 600, or 800 mg/kg ronnel via gavage on gestation days 6 through 15 (525). However, increases in the incidence of extra ribs were observed in fetuses from dams given 600 or 800 mg/kg. When pregnant rabbits were given oral doses of 0, 12.5, 25, and 50 mg/kg ronnel on gestation days 6 through 18, an increase in malformed fetuses occurred in the 12.5- and 50.0-mg/kg group, an increase in fetuses that had malformations in the cardiovascular system occurred in the 50-mg/kg treated group, and fetuses that had cerebellar hypoplasia increased in the 25.5- and 50.0-mg/kg group (526). 25.4.1.5 Carcinogenesis A single female dog given 25 mg/kg ronnel for 11 months reportedly experienced no adverse effects, although RBC and brain cholinesterase activity were below normal (41). Dogs given 0.3, 1, 3, or 10 mg/kg ronnel via their diet for 1 year exhibited no adverse effects, although RBC cholinesterase activity was inhibited in dogs given 10 mg/kg. No evidence of carcinogenicity, cholinergic toxicity, or adverse effects were seen in dogs given diets that contained 15, 45, or 150 ppm ronnel (equivalent to daily doses of 1, 3, or 10 mg/kg/day) for 2 years (587). Neither brain nor RBC cholinesterase activities were inhibited. There was no evidence of carcinogenicity in rats fed diets that delivered doses of 0.5, 1.5, 5, 15, or 50 mg/kg/day ronnel for 2 years (41). Among rats given 50 mg/kg/day, there was some evidence of slight granular degeneration or cloudy swelling of the parenchymal cells of the liver and cloudy swelling and vacuolation of renal tubular epithelium of the kidney. RBC and brain acetylcholinesterase were inhibited at 15 or 50 mg/kg/day. 25.4.2 Human Experience There was no indication of sensitization among thirty men and twenty women given three patch applications of ronnel per week for 3 weeks and then challenged 2 weeks after the last application (41). Five of twenty-one patients treated orally for creeping eruptions (larva migrans) with ronnel at 10 mg/kg/day for 5 or 10 days, reported nausea, weakness, blurred vision, and/or serpiginous ulcers (527). After ronnel was discontinued, the side effects spontaneously disappeared. Nausea, headaches, and irritations of the throat and facial skin were occasionally reported by veterinarians who treated group infestations in cattle with pour-on applications of ronnel or other organic phosphorus pesticides (famphur, coumaphos, fenthion, trichlofon) in poorly ventilated areas. Neither plasma nor RBC cholinesterase activities were reduced in these cases, although correlations between specific exposures and cholinesterase measurements appeared imprecise. In support of this, alkyl phosphate metabolites were only occasionally found in the urine at the same times at which blood was drawn for cholinesterase determinations (528). 25.5 Standards, Regulations, or Guidelines of Exposure Ronnel is no longer registered by the EPA for use (EPA, 1998). The ACGIH TLV for ronnel is 10 mg/m3 (154). The OSHA PEL-TWA is 15 mg/m3. The NIOSH REL-TWA is 10 mg/m3. Most other countries have Occupational Exposure Limits for ronnel of 10 mg/m3 (Australia, Belgium, Denmark: 5 mg/m3 (Jan 93), Russia: STEL 0.3 mg/m3 (Jan 93), France, The Netherlands, The Philippines, Switzerland, and the United Kingdom).

Organophosphorus Compounds Jan E. Storm, Ph.D 26.0 Sulfotepp

26.0.1 CAS Number: [3689-24-5] 26.0.2 Synonyms: Tetraethyl dithionopyrophosphate; tetraethyl dithiopyrophosphate; tetraethyl dithiopyrophosphate; tetraethyl pyrophosphorodithionate; thiodiphosphoric acid tetraethyl ester; Bladafum; Dithione; thiopyrophosphoric acid, tetraethyl ester; ASP-47; bay-g-393; bayer-e 393; bis-O,Odiethylphosphorothionic anhydride; bladafun; dithiodiphosphoric acid, tetraethyl ester; dithiofos; dithiophos; di(thiophosphoric) acid, tetraethyl ester; dithiotep; E393; ethyl thiopyrophosphate; lethalaire g-57; pirofos; plant dithio aerosol; plantfume 103 smoke generator; pyrophosphorodithioic acid, tetraethyl ester; pyrophosphorodithioic acid, O,O,O,O-tetraethyl ester; sulfatep; Tedtp; O,O,O,O-tetraethyl dithiopyrophosphate; tetraethyl thiodiphosphate; Dithio Insecticidal Smoke; dithiopyrophosphoric acid, tetraethyl ester; thiopyrophosphoric acid ([HO)2P(S)]2O), tetraethyl ester 26.0.3 Trade Names: Dithion®; Dithiophos®; Sulfotepp®; TEDP; Thiotepp® 26.0.4 Molecular Weight: 322.30 26.0.5 Molecular Formula: C8H20P2S2O5 26.0.6 Molecular Structure:

26.1 Chemical and Physical Properties Sulfotepp is a pale yellow, noncombustible liquid. Specific gravity 1.196 at 25°C Boiling point 136–139°C Vapor pressure 0.00017 torr at 20°C Solubility slightly soluble in water (25 mg/L); soluble in alcohol and most organic solvents 26.1.2 Odor and Warning Properties Possesses a garlic odor. 26.2 Production and Use Sulfotepp is registered for use in greenhouses only as a fumigant formulation to control aphids, spider mites, whiteflies, and thrips (529a). It is formulated as impregnated material in smoke generators (canisters) containing 14 to 15% active ingredient. Smoke generators are placed in greenhouses and then ignited using inserted sparklers to generate a thick white smoke for fumigation. 26.4 Toxic Effects 26.4.1.1 Acute Toxicity Sulfotepp is extremely toxic following oral, dermal or inhalation exposures. Oral LD50s are 5–13.8 mg/kg for rats (529, 530). Oral LD50 values are 21.5–29.4 mg/kg for mice; 25 mg/kg for rabbits, 3 mg/kg for cats, and 5 mg/kg for dogs (530). In rats, maximum acetylcholinesterase inhibition occurred 24 hours after an oral dose, was greater in RBCs than in plasma, and returned to normal after 7 days (530). Intraperitoneal LD50s are about one-half oral LD50s for mice and rats, suggesting delayed oral absorption and/or an overall detoxifying role for the liver. Rat dermal LD50s of 65 and 262 mg/kg have been reported (530). A rabbit dermal LD50 of

20 mg/kg has also been reported. One-hour and 4-hour LC50s for rats were 160–330 mg/m3 and 38– 59 mg/m3, respectively. One-hour and 4-hour LC50s for mice were 155 mg/m3 and 40 mg/m3, respectively. Typical symptoms of organophosphate poisoning were observed, and animals died in 24 hours (530). Following any route of exposure, symptoms occur within 1 hour and death occurs within 24 hours; surviving animals completely recover in 1–4 days. Sulfotepp applied to the skin of rabbits at 0.4 gm for a period of 24 hours produced no noticeable effects on the skin (530). When sulfotepp was instilled into a rabbit eyes, the conjunctiva reacted slightly but returned to normal within 24 hours (530). Nonatropinized and atropinized hens that received single oral doses of sulfotepp that ranged from 10 to 50 mg/kg body weight exhibited no signs of ataxia or paralysis of extremities during a 4-week observation period (530). 26.4.1.2 Chronic and Subchronic Toxicity When rats were exposed to 0, 0.89, 1.94, and 2.83 mg/m3 sulfotepp aerosols for 6 hours/day, 5 days/week for 12 weeks, no changes in appearance, behavior, or body weight gain occurred at any dose. RBC acetylcholinesterase was not inhibited at any dose; however, plasma cholinesterase activity was inhibited in rats exposed to 2.83 mg/m3. Absolute and relative lung weights of females exposed to 2.83 mg/m3 were significantly higher than those of controls due to edema. No effects were observed at sulfotepp concentrations less than 2.83 mg/m3 (530). When rats were fed diets that contained sulfotepp at concentrations of 0, 5, 10, 20, and 50 ppm for 3 months, plasma cholinesterase activity was significantly reduced in female rats at 20 and 50 ppm and in male rats at 50 ppm. RBC acetylcholinesterase activity was significantly reduced in both sexes at 20 and 50 ppm (530). The highest dietary concentration tested for 12 weeks that was reportedly without symptoms in rats was 60 ppm; 180 ppm produced both illness and histological change (529). When dogs were given diets that contained 0, 0.5, 3, 15, or 75 ppm sulfotepp (equivalent to about 0, 0.014, 0.11–0.12, 0.55–0.57, or 2.75–3.07 mg/kg/day) for 13 weeks, food consumption and body weight gain decreased at 75 ppm (529a). Plasma cholinesterase activity was inhibited at 3 ppm or higher, whereas RBC cholinesterase was inhibited at 15 ppm sulfotepp or higher. Occasional diarrhea and vomiting occurred in dogs at 15 ppm and were common in dogs at 75 ppm. RBC and plasma cholinesterase activity was inhibited at 75 ppm, and plasma cholinesterase was inhibited at 3 ppm and more. Brain cholinesterase was unaffected at any dose. 26.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms There are no available data on the absorption, distribution, elimination, or metabolism of sulfotepp. However, based on what is known about other organophosphates, it is likely to be well absorbed via all routes of exposures, rapidly oxidatively desulfurated to oxon derivatives, and/or hydrolyzed to dimethyl thiophosphoric acid or diethyl phosphoric acids. 26.4.1.4 Reproductive and Developmental No embryo toxic or teratogenic effects occurred in rats given 0.1, 0.3, or 1.0 mg/kg/day sulfotepp by gavage on gestation days 9 to 15 (593). No embryo toxic or teratogenic effects occurred in rabbits given 0.1, 1.0, or 3.0 mg/kg/day on gestation days 6 to 18 (533). 26.4.1.5 Carcinogenesis No signs of carcinogenicity or other adverse effects occurred at any dose level in mice or rats given diets that contained 0, 2, 10, or 50 ppm (equivalent to 0, 0.29, 1.43, or 7.14 mg/kg/day (mice); 0.13, 0.67 or 3.33 mg/kg/day (rats)) sulfotepp for 2 years (531). There were no signs of toxicity other than inhibition of plasma and RBC cholinesterase at 50 ppm.

26.4.1.6 Genetic and Related Cellular Effects Studies Sulfotepp was mutagenic in S. typhimurium strain TA1535 with metabolic activation (78). However, sulfotepp was not mutagenic to S. typhimurium strains TA100, TA98, TA1537, and TA1535 with or without metabolic activation (534, 535). A micronucleus test in rats was negative (536). A dominant lethal assay, in which sulfotepp was administered orally to mice, was also negative (537). 26.4.2 Human Experience Two men suffered from acute poisoning when spraying a mixture of sulfotepp and tetraethylpyrophosphate which had decomposed from diazinon. Symptoms were similar to those observed from organophosphorus insecticide poisonings (nausea, vomiting, burning eyes and blurred vision, difficulty breathing, headache, muscle twitching in arms and legs, and weakness). Blood cholinesterase activity showed a marked reduction but recovered 20 days after the poisoning incident in one individual and 28 days in the other individual (538). In a review of available epidemiological information on sulfotepp EPA described an instance where a greenhouse worker experienced symptoms of organophosphate poisoning (headache, nausea, diarrhea, vomiting, cough, dizziness, sweating, fatigue, abdominal pain, anxiety, muscle aches, chest tightness, drowsiness, restlessness, shortness of breath, and excessive salivation) when applying the compound. Skin lesions have been reported during the spraying of sulfotepp. 26.5 Standards, Regulations, or Guidelines of Exposure Sulfotepp is undergoing reregistration by the EPA. The ACGIH TLV for sulfotepp is 0.2 mg/m3 with a skin notation. The OSHA PEL-TWA for sulfotepp is 0.2 mg/m3 with a skin notation; the NIOSH REL-TWA for sulfotepp is 0.2 mg/m3 with a skin notation.

Organophosphorus Compounds Jan E. Storm, Ph.D 27.0 Sulprofos 27.0.1 CAS Numbers: [35400-43-2] 27.0.2 Synonyms: O-Ethyl O-(4-(methylthio)phenyl)-S-propyl phosphorodithioate; BAY NTN 9306; Phosphorodithioic acid O-ethyl O-[4-(methylthio)phenyl] S-propyl ester; merdafos; O-ethyl O-(4-(methylthio)phenyl) S-propyl phosphorodithioate; O-ethyl O-[4-(methylthio)phenyl]phosphorodithioic acid S-propyl ester; Bolstar 6; O-ethyl O-(4-methylthiophenyl) S-propyl dithiophosphate; Heliothion; ethyl O-(4(methylthio)phenyl) S-propyl phosphorodithioate; Morpafos 27.0.3 Trade Names: Bolstar®; Helothion® 27.0.4 Molecular Weight: 322.43 27.0.5 Molecular Formula: C12H19O2PS3 27.0.6 Molecular Structure:

27.1 Chemical and Physical Properties Sulprofos is a tan colored liquid that hydrolyzes in basic conditions and is stable in acid or neutral conditions. Specific gravity 1.20 at 20°C Melting point 3840 mg/m3 were reported for rats; a 4-hour LC50 of >490 mg/m3 was reported for mice and hamsters (539). Five 4-hour exposures of rats to 37, 94, or 259 mg/m3 sulprofos caused cholinergic signs and inhibition of RBC and plasma cholinesterase activities. In rats given single doses of 0, 29, 71, or 206 mg/kg sulprofos, cholinergic signs occurred in females at all dose levels and in males at the two higher doses (539). RBC cholinesterase activity was inhibited at all doses. No lesions were seen at necropsy or during histopathological examination of skeletal muscles, peripheral nerves, and tissues from the central nervous system. Following single oral exposures, the no-observed-effect-levels for plasma and brain cholinesterase inhibition were 7.5 and 30 mg/kg, respectively, in male rats (a no-observed-effect level for RBC cholinesterase inhibition was not identified). The lowest observed effect levels for plasma, RBC, and brain cholinesterase inhibition were 15, 30, and 90 mg/kg, respectively. In female rats, no-observed-effect levels for plasma, RBC, and brain cholinesterase inhibition were 4.5, 8.5, and 17 mg/kg, respectively. The lowest observed effect levels for plasma, RBC, and brain cholinesterase inhibition were 8.5, 17, and 50 mg/kg, respectively (539). In female dogs, no-observed-effect levels for plasma and RBC inhibition were 1 and 10 mg/kg, respectively. A lowest observed effect level for plasma inhibition was 5 mg/kg, but a lowest observed effect level for RBC cholinesterase inhibition was not identified. Inhibition was most severe within the first 24 hours after the acute oral dose, and brain cholinesterase was less affected than plasma and RBC cholinesterase (539). A combination of sulprofos and malathion caused a fivefold potentiation of acute oral toxicity in rats, based on oral LD50s (539). Similarly, a simultaneous dosing of sulprofos and azinphos-ethyl yielded a threefold potentiation of toxicity (539). In rats exposed to 6, 14, or 74 mg/m3 sulprofos aerosol for 6 hours/day, 5 days/week for 3 weeks, cholinergic signs (“general health impairment”, trembling) occurred only at 74 mg/m3 (539).

Exposures of 6 or 14 mg/m3 reportedly had no detrimental effects on behavior, physical appearance and growth rate, hematology, clinical chemistry, urinalysis, macroscopic pathology, or histopathology. Plasma, RBC, and brain cholinesterase activities were inhibited in males exposed to 74 mg/m3 and in females exposed to 14 or 74 mg/m3. When rats were given 0.1, 1.0, and 10 mg/kg/day sulprofos by gavage for four weeks, the only parameters affected were dose- and time-dependent depressions of plasma, RBC, and brain cholinesterase enzymes (539). Plasma cholinesterase activity was inhibited in the 1.0-mg/kg/day group, and RBC and brain cholinesterase activity were inhibited in the 10-mg/kg/day group. No other treatment-related changes were seen in weight gain, blood chemistry urinalysis, gross pathology, or histopathology. Sulprofos was not an eye or dermal irritant when tested in rabbits and did not cause dermal sensitization in guinea pigs (539). Hens given antidote doses of pyridine-2-aldoxime methiodide and atropine sulfate followed by two doses of 65 mg/kg sulprofos (the LD50 for the hen) 3 weeks apart exhibited no ataxia or paralysis, nor any changes in the histopathological examinations of brain, spinal cord, or sciatic nerves. There was no evidence of delayed neurotoxicity (539). 27.4.1.2 Chronic and Subchronic Toxicity When groups of twenty male and female Sprague–Dawley rats were fed diets that contained 10, 30, 100, or 300 ppm (0.54–0.65, 3.0–3.5, and 15– 17 mg/kg/day) for 90 days, reduced body weight gain occurred in females given the 300-ppm diet (539). Plasma cholinesterase activity was depressed at 30 ppm and above in both sexes. RBC cholinesterase activity was depressed at 100 ppm in males and 30 ppm in females. Brain cholinesterase activity was depressed in both sexes at 100 ppm and higher. No other effects were noted in blood parameters, urine parameters, or pathology examinations. In rats fed diets that contained 0, 9, 47, or 226 ppm sulprofos (equivalent to 0, 0.54–0.65, 3.0–3.5, or 15–17 mg/kg/day) for 90 days, cholinergic signs occurred only in rats given the 226-ppm diet (539). Brain cholinesterase activity was inhibited at 226 ppm, RBC cholinesterase was inhibited at 47 and 226 ppm, and plasma cholinesterase was inhibited at 9 ppm (females only). No treatment-related effects were seen during gross pathology or histopathological examination of skeletal muscle, peripheral nerves, eyes, and tissues from the central nervous system. In dogs given diets that contained 0, 10, 20, or 200 ppm (equivalent to 0, 0.26–0.32, 0.52–0.64, 5.2– 6.4 mg/kg/day) for 90 days, diarrhea and regurgitation occurred at 200 ppm (539). Reduced body weights, and decreased plasma, RBC, and the brain cholinesterase activity also occurred at 200 ppm, as well as thickening of the small intestinal wall; decreased liver, kidney, brain and lung weights (males only); increased brain and liver weights, relative to body weight; increased relative lung weights (females only); and increased relative heart weights (males only). Plasma and RBC cholinesterase were also inhibited at 20 ppm. No treatment-related effects were seen in ophthalmic examinations. No changes occurred in blood or urine parameters, behavior, clinical signs, food consumption, body weights, organ weights, mortality, or in necropsied tissues in mice given diets that contained 0, 2.5, 5, 100, 200, or 400 ppm (equivalent to 0, 0.38–43, 0.76–0.86, 15.2–17.2, 30.4–34.4, or 60.8– 68.8 mg/kg/day) for 10 months (539). At 5 ppm and higher, plasma and RBC cholinesterase were inhibited and, at 200 ppm and higher. 27.4.1.3 Pharmacokinetics, Metabolism, and Mechanisms Sulprofos is rapidly and nearly completely absorbed following oral exposures. In rats, more than 98% of an oral dose of sulprofos was eliminated within 48–72 hours after dosing (539). Rats that received one 11-mg/kg dose or ten 10mg/kg doses of sulprofos during 15 days also excreted >96% of the dose (or last dose) within 24

hours. The primary route of excretion was through the urine, and less than 11% was excreted in the feces. Conjugated and nonconjugated phenol accounted for 11% of the administered dose, conjugated phenol sulfide accounted for 33–36% of the administered dose, and conjugated phenol sulfone accounted for 41–45% of the administered dose (539). Tissues and organs retained 2% of the dose; the highest residues were in the fat, ovaries, skin, and liver. Less than 1% of the dose was expired as CO2 or volatile organic compounds from any exposure. A previous study had demonstrated that female Sprague–Dawley rats dosed at 10 mg/kg excreted >92% within 24 hours (540). Pigs rapidly excreted an oral dose of sulprofos. More than 95% of the dose was excreted in urine by 24 hours. The major urinary excretion metabolites were the conjugated phenol, free and conjugated phenol sulfoxide, and free and conjugated phenol sulfone. Maximum blood levels occurred 4 hours posttreatment, at which time tissue levels were 10 times the maximum dimension of the source. For lasers or other collimated sources, this law can be used only at very large distances from the source. The region in which the inverse square relationship applies is called the “far” field. It does not hold in the “near” field region at distances close to the source.

Infrared, Visible and Ultraviolet Radiation Maurice Bitran, Ph.D., William Murray, MS 7 The Biological effects of optical radiation The wavelengths in the optical radiation range have limited penetration into the human body. Therefore, the main organs affected by optical radiation are the skin and the eyes, although systemic effects have also been identified. Evolving in an environment where the sun is the main source of optical radiation, humans have developed adaptive characteristics, such as skin pigmentation, a hairy scalp, receded eyes, and aversion responses to bright lights and to excessive heat. These characteristics, however, provide only partial protection against optical radiation. Optical radiation can act on biological tissue through thermal and photochemical processes. The extent of damage depends on the intensity of the radiation, the wavelength, the exposure time, and the optical and physiological characteristics of the tissue exposed. The variability in biological effectiveness of different wavelengths (three orders of magnitude within the ultraviolet range) is particularly striking. This has led to the definition of “biologically effective” quantities, which are obtained by using a biological spectral effectiveness function. Both the eye and the skin are at risk of acute and chronic injury from optical radiation. The ocular media transmit visible and near-infrared radiation to the retina, but most ultraviolet and far-infrared radiation are absorbed in the cornea and the lens. The response of the skin depends strongly on its albedo and pigmentation. 7.0 Optical Radiation Optical radiation extends between X-rays and microwave radiation in the electromagnetic spectrum and includes ultraviolet radiation (UVR), visible radiation or light, and infrared radiation (IR). These regions are further subdivided and receive various names. 7.1 Synonyms

Ultraviolet radiation, ultraviolet light (incorrect) Visible radiation, light Infrared radiation, radiant heat 7.2 Physical Properties 7.2.1 General Several schemes are used to divide the optical wavelengths into spectral bands, but that of greatest importance to the photobiologist and health professionals is that adopted by the Committee on Photobiology of the International Commission on Illumination (Commission International de l'Eclairage, CIE) (3, 4). Although sharp demarcation points have been given to the regions, there is no physical basis for these transition points. Rather they serve only as a convenient framework for discussing the biological effects and exposure hazards. In the CIE classification, ultraviolet radiation extends between 100 and 400 nm and is subdivided into 3 bands: UV-A, UV-B, and UV-C: Infrared, Visible and Ultraviolet Radiation Bibliography

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Lasers

David H. Sliney, Ph.D. 1.1 Properties of Lasers Laser light is produced from transitions between atomic or molecular energy levels. Generation of light requires two energy levels, E1 and E2, separated by the photon energy Ep of the light that is to be produced. (1) where h is Planck's constant, c is the velocity of light, and E1 and E2 are, respectively, the lower and higher energy levels. The relevant energy levels may be those of atoms or molecules in a gas, as in the case of the helium–neon laser, or of ions embedded in a solid host material, as in a ruby laser, or they may be energy levels that belong to a crystalline lattice as a whole, as in the aluminum gallium arsenide AlGaAs, semiconductor laser. The light emitted by a laser has a number of unusual properties that distinguish it from light emitted by conventional light sources. Unusual properties include a high degree of collimation, a narrow spectral linewidth, good coherence, and the ability to focus to an extremely small spot. Because of these properties, there are many possible applications for which lasers are better suited than conventional light sources. For example, alignment applications utilize the collimation of laser light. Spectroscopic and photochemical applications depend on the narrow spectral linewidth of tunable laser sources. Interferometric and holographic applications require a high degree of coherence. 1.1.1 Collimation One of the most important characteristics of laser radiation is its highly directional collimated beam. Although the beam divergence angle is very small, it is not zero. 1.1.2 Spectral Linewidth Laser light is highly monochromatic; that is, it has a very narrow spectral linewidth. This linewidth is not zero, but is typically much less than that of conventional light sources. The discussion of linewidth is complicated by the presence of the resonant longitudinal cavity modes. The spacing between the longitudinal modes is given by c/2D, where c is the velocity of light and D is the length of the laser. Several longitudinal modes may be present simultaneously in the laser output. 1.1.3 Coherence Coherence implies a regular, orderly progression of the vibrations of the electromagnetic radiation. Coherence can be understood only by reference to a considerable body of mathematical development, a detailed discussion of which can be found in the literature (9). Conventional light sources do not share the property of coherence; rather these sources have a certain amount of randomness or irregularity in the oscillations of the light waves. Radio waves exhibit coherence, or orderliness, and because of coherence properties information can be impressed on radio waves for communications applications. The advent of lasers made available coherent light sources of reasonably high intensity in the visible portion of the spectrum. Coherence is important in any application in which the laser beam is to be split into parts, such as interferometry and holography. Such applications rely on the high coherence of the laser beam. The time period Dt in which the light wave undergoes random changes is called the coherence time. It is related to the linewidth Dn of the laser by the equation (2) 1.1.4 Focusing Laser Light One of the most important properties of laser radiation is the ability to collect all the radiation using a simple lens and to focus it to a spot. It is not possible to focus the laser beam down to a mathematical point; there is always a minimum spot size, set by the physical phenomenon of diffraction. A convenient equation is

(3) where Dm is the smallest focal diameter that can be obtained, F is the focal length of the lens, and q is the beam divergence angle of the laser beam. 1.1.5 Spatial Profiles The cross sections of laser beams have certain well-defined spatial profiles called transverse modes. The word mode in this sense should not be confused with the same word as used to discuss the spectral linewidth of lasers. Transverse modes represent configurations of the electromagnetic field determined by the boundary conditions in the laser cavity. 1.1.6 Temporal Characteristics Laser operation may be characterized as either pulsed or continuous. There are a number of distinctive types of pulsed laser operation having widely different pulse durations. The earliest solid-state lasers, such as ruby lasers, were simply pulsed by discharging a capacitor through a flashlamp, without any attempt to control the duration of the laser output. Such lasers typically had durations around 1 ms. The pulses were called normal or free-running laser pulses.

Lasers David H. Sliney, Ph.D. 1.2 Production The widespread interest in lasers is based on practical applications. Lasers are used to perform many useful functions in science, engineering, industry, and education. Additionally, many other applications are under development. An application such as welding depends on the collimation and focusing ability of the beam, which leads to high power density. A conventional light source, even one having higher total radiant power than a welding laser, cannot be focused well and thus is not useful for welding. Most applications for which lasers are used were originally demonstrated using conventional light sources. In many cases, the application was only marginally successful using conventional sources and required the development of laser light sources to be practical. 1.2.1 Material Processing Laser radiation can be used for a variety of material processing functions such as welding, cutting, shaping, marking, and drilling (10–12). Even a fairly modest pulsed laser can be focused to produce a power density greater than 109 W/cm2; lasers can melt and vaporize materials. Spot welding using pulsed lasers was demonstrated in the 1960s (13). Seam welding is possible by overlapping pulses, or using continuous lasers. However, the penetration depth for such welding is limited. The energy is deposited at the surface of the workpiece. For complete penetration of the weld through the workpiece, thermal conduction has to carry heat energy through the entire thickness of the specimen. In practice, this factor limited maximum weld depths to perhaps 0.1 cm, depending on the thermal conductivity of the sample. The advent of multikilowatt carbon dioxide lasers in the early 1970s eased the 0.1-cm restriction (14, 15). The beam can drill a hole into the workpiece, then, as the beam is translated, the hole moves through the material. Molten material flows into the region behind the moving hole and resolidifies. Thus a continuous seam is produced. Because the energy is deposited at the bottom of the hole, limitations because of slowness of thermal conduction do not apply. Welds having much greater depth can be produced by this technique, called deep-penetration laser welding. Welds as deep as 5 cm have been produced in stainless steel (16). Laser welding has become widely used in practical industrial processing (17–19).

High-power laser beams can vaporize material, leading to applications such as hole drilling and cutting. Higher power densities are used for these applications than for hardening and welding. Hole drilling in ceramic materials has become common. There is a need for small (less than 0.5-mm) holes in the alumina substrates used in many electronic applications. Holes drilled before the ceramic is fired tend to change dimension during firing. After firing, the material is very hard, brittle, and difficult to drill by conventional techniques. Laser drilling offers an improved technique for producing holes in the fired ceramic, and has become an important application for lasers in the electronics industry. High-power lasers have impressive capabilities for cutting both metallic and nonmetallic materials. The cutting rates can be increased by the presence of gases. Typically oxygen is used but other gases have sometimes been employed. A jet of oxygen or air is blown on the workpiece at the position where the beam strikes it. The exothermic chemical reaction with the oxygen can greatly increase the cutting rate for reactive materials. Laser cutting is widely used in many practical applications, such as cutting titanium in the aerospace industry, cutting steel plates in the automotive industry, and cutting fabric in the garment industry. Another important application involving material processing is trimming of resistors. Thick-film resistors used in many electronic circuits must be trimmed to the final desired value. This can be done by fabricating the resistor using a low value of resistance and then cutting part way through it with a laser. The resistance can be monitored as cutting proceeds. Trimming is terminated when the desired value is reached. Repetitively Q-switched Nd:YAG lasers are commonly used for resistor trimming. Laser trimming has become a standard procedure in the electronics industry.

Lasers David H. Sliney, Ph.D. 1.3 Use 1.3.1 Measurement Applications Lasers have been used for measurement of many physical parameters. These include length and distance, velocity of fluid flow and of solid surfaces, dimensions of manufactured goods, and the quality of surfaces, including flaw detection and determination of surface finish. Lasers are used in measurement of lengths in a variety of ways (20, 21). A very short pulse of highpower laser light may be directed toward a target the distance of which is desired. A photodetector viewing the target collects a signal resulting from light reflected by the target. The time t between the outgoing pulse and the detection of the reflected signal, that is, the time for the light to make a round trip from the laser to the target and back, is measured. Because the velocity of light is known, the range R to the target is (4) where n is the index of refraction of the air through which the pulse travels. Because the index of refraction depends on air temperature, pressure, altitude, and other factors, this method is subject to some uncertainties. It has been used for accurate measurement of the distance from the earth to the moon. Table 103.2 lists methods using lasers for measuring distances. Table 103.2. Distance Measurement Using Lasers Method

Laser type

Range Typical application

Round-trip time-of-flight

Q-switched solid many state km He–Ne, AlGaAs km

Phase comparison of amplitude-modulated beam Interferometry Frequencyfew stabilized He–Ne meters Laser Doppler displacement He–Ne to 120 m

Military ranging, satellite ranging Surveying Machine-tool control Machine-tool control

1.3.2 Holography Holography, a photographic process that yields three-dimensional images, was invented in the prelaser era in 1948 (22). Light sources available at that time were not adequate for making good holograms and holography became practical only after the invention of the laser (23). The properties of coherence and monochromaticity offered by lasers are important for holography. 1.3.3 Medical Applications Lasers have been used for a variety of medical applications. Perhaps the repair of tears and holes in the retina may be the best-known example. Laser photocoagulation also has been widely used to treat diabetic retinopathy, one of the leading causes of blindness in the United States. Laser removal of tattoos and of colored birthmarks has been widely studied. A high-power pulsed laser at a wavelength absorbed by the pigment is used to vaporize the pigment and to bleach the colored area. Ruby, Nd:YAG, and dye lasers are favored for this purpose. High-power carbon dioxide lasers have been used for surgery. Absorption by tissue is very high at the 10-mm wavelength of the carbon dioxide laser. Laser surgery provides a possibility for simultaneous cutting and cauterization. Use of carbon dioxide lasers for bloodless surgery has been widely studied, especially for blood-rich organs such as the liver. Laser surgery has also been widely used for ear, nose, and throat procedures. Laser angioplasty, a procedure in which laser energy is delivered through an optical fiber inserted into a blood vessel to a location of a blockage in the vessel and used to burn through the blockage, was studied extensively during the 1980s. Early enthusiasm for the procedure as a treatment for coronary disease seems to have waned because blockages can recur at the same locations. The development of so-called photodynamic therapy uses lasers for treatment of cancer. The patient is injected with a substance called hematoporphyrin derivative, which is preferentially localized in cancerous tissues. The patient is later irradiated with laser light, often with a dye laser at a wavelength around 630 nm. The light energy catalytically photooxidizes the hematoporphyrin derivative, releasing materials that kill the nearby cancerous tissue. Normal tissue that did not retain the chemical is not harmed. Photodynamic therapy offers promise as a new form of cancer treatment. 1.3.4 Communications The advent of the laser improved prospects for optical communications enormously. The coherence of the laser meant that techniques developed in the radio portion of the electromagnetic spectrum could be extended to the optical portion of the spectrum. Because lasers operate at frequencies near 1015 Hz, they offer a potentially wide bandwidth, equal to about 107 television channels of width (ca. 108 Hz). It has not proved possible to take advantage of this full bandwidth because devices such as modulators capable of operating at 1015 Hz are not available.

Laser communication systems based on free-space propagation through the atmosphere suffer drawbacks because of factors like atmospheric turbulence and attenuation by rain, snow, haze, or fog. Nevertheless, free-space laser communication systems were developed for many applications (24–26). They employ separate components, such as lasers, modulators, collimators and detectors. Some of the most promising applications are for space communications, because the problems of turbulence and opacity in the atmosphere are absent. The most important application of fiber-optic laser-based communication is in long-distance telecommunications (27, 28). Fiber-optic systems offer very high capacity, low cost-per-channel, light weight, small size, and immunity to crosstalk and electrical interference. Laser-based fiber-optic telecommunications has had a revolutionary impact on long-distance telephone communication and is now expanding into many new applications areas. 1.3.5 Consumer Products Laser-based products have emerged from the laboratories and become familiar products used by many millions of people in everyday circumstances. Examples include the supermarket scanner, the laser printer, and the compact disk. 1.3.6 Spectroscopic Applications Laser technology has led to a revolution in spectroscopic techniques. Absorption spectroscopy can be carried out at much higher resolution than is available from conventional spectrometers. 1.3.7 Laser Photochemistry Photochemical applications of lasers generally employ tunable lasers that can be tuned to a specific absorption resonance of an atom or molecule. Examples include the tunable dye laser in the ultraviolet, visible, and near-infrared portions of the spectrum; the titanium-doped sapphire, Ti:sapphire, laser in the visible and near infrared; optical parametric oscillators in the visible and infrared; and line-tunable carbon dioxide lasers, which can be tuned with a wavelength-selective element to any of a large number of closely spaced lines in the infrared near 10 mm. Other uses include purification of materials, deposition of thin films, isotope separation, and laserassisted thermonuclear fusion.

Lasers David H. Sliney, Ph.D. 1.4 Toxic Effects Laser radiation can pose significant risks to vision when the eye is located within the beam (intrabeam viewing), and occupational Exposure Limits (ELs) have been developed for these conditions (1–10). Lasers pose a more significant optical radiation hazard than conventional light sources because lasers have a far greater brightness (radiance) and because a typical laser has a collimated beam, which can present a hazard to the eye at a significant distance. The potential hazards vary with wavelength, and this is particularly true for the eye, which is the more vulnerable organ because of its special optical properties. The eye is particularly vulnerable to injury in the retinal hazard region from 400 nm at the short-wavelength end of the visible spectrum to 1400 nm in the near-infrared part of the spectrum (29, 30). Within this spectral band, a collimated beam can be focused to a 15–20-mm-diameter retinal spot (i.e., much smaller than the diameter of a human hair). The gain in beam irradiance from cornea to retina is approximately 100,000 times in the visible spectrum. Hence, a corneal beam irradiance of 1 W/cm2 becomes 100 kW/cm2 at the retina. Vision loss can vary from temporary after-images to a permanent blind spot (scotoma) or even total loss of vision in an eye (29). Figure 103.1. illustrates that because of the great brightness of a laser, its radiant energy can be greatly concentrated when focused (e.g., upon the retina) as compared to the rays from conventional light sources, which are much less bright. This very high radiance can be

expressed as MW and TW cm–2 sr–1, and this radiance is responsible for the laser's great value in material processing and laser surgery. When compared to a xenon arc or the sun, even a small He– Ne alignment laser or diode laser pointer is typically ten times brighter.

Figure 103.1. The great brightness (radiance) of a laser permits its beam to be greatly concentrated when focused as compared to the rays from conventional light sources, which are much less bright. Although the laser focal image on the retina may cover only 20–30 cone cells, the retinal injury is always larger because of heat flow and acoustic transients (29). Even a small disturbance of the retina can be significant. This is particularly important in the region of central vision referred to by eye specialists as the macula lutea (Latin for “yellow spot”), or simply the “macula.” The central region of the macula, the fovea centralis, is responsible for detailed “20/20” vision. Damage to this extremely small (about 150-mm-diameter) central region can result in severe vision loss even though 99% of the retina remains unscathed. The surrounding (peripheral) retina is useful for movement detection and other tasks but possesses little acuity. The eye moves across a line of print to read, because an individual's detailed vision covers only a very small angular subtense centered in the fovea. Outside the 400–1400-nm retinal hazard region the cornea—and even the lens—can be damaged by laser beam exposure (29, 30). Diffuse reflections of laser beams are normally safe to view, since the energy is dissipated upon reflection into all directions and the resulting image on the retina is normally that of an extended source. However, under special conditions, it is a realistic possibility to produce a hazardous diffuse reflection. This can result from a diffuse reflection of a Q-switched (1–100-ns) laser in the retinal hazard region (29). This retinal injury hazard from diffuse reflections was one of the criteria for placing some pulsed lasers in the high-risk category known as Class 4 (29, 30). The adverse effects associated with viewing lasers or other bright light sources such as the sun, arc lamps, and welding arcs have been studied for decades (31–35). Injury thresholds for acute injury in experimental animals for corneal, lenticular and retinal effects have been corroborated for the human eye from accident data. 1.4.1 Injury Mechanisms For most exposure durations (t>1 s), laser-induced injury is dominated by either photochemically or thermally initiated events taking place during or immediately following the absorption of radiant energy. At nanosecond (1 ns = 10–9 s) or shorter durations, nonlinear mechanisms may play a role (29, 31, 36). Following the initial insult, biological repair responses may play a significant role in determining the final consequences of the event (38, 39). While inflammatory, repair responses are

intended to reduce the sequellae, in some instances, this response could result in events such as scarring, which could have an adverse impact upon biological function (40). Within the first several weeks, the inflammatory reaction itself (e.g., edema) may interfere with function (40, 41). Laser damage thresholds vary with wavelength, duration, and spot size. However, photochemical and thermal effects vary differently depending on the wavelength, the exposure duration, and the size of the irradiated area. Indeed, experimental biological studies in humans and animals make use of these different relationships to distinguish between which of several competing mechanisms is playing a dominant role in observed injury (39). Photochemical injury is highly wavelength dependent, while thermal injury depends upon exposure duration. Each of these factors will be examined in the following. 1.4.1.1 Exposure Duration The Bunsen–Roscoe Law of photochemistry describes the reciprocity of exposure rate and duration of exposure. This law applies to any photochemical event. The product of the irradiance or dose rate (in watts per square centimeter) and the exposure duration (in seconds) equals the exposure dose (in joules per square centimeter at the site of absorption) to produce a threshold injury. Radiometrically this is expressed as: The irradiance E in W/cm2 multiplied by the exposure duration t is the radiant exposure H in J/cm2. (5) Repair mechanisms and other biochemical changes over long periods (hours) and photon saturation for extremely short (submicrosecond) periods will lead to reciprocity failure. This reciprocity helps to distinguish photochemical injury mechanisms from thermal injury (burns). Because of heat conduction, thermal injury generally requires a very intense exposure within seconds to cause photocoagulation; otherwise, surrounding tissue conducts the heat away from the absorption site (e.g., a retinal image). Thermal injury is a rate process dependent upon the volumic absorption of energy across the spectrum. The thermochemical reactions that produce coagulation of proteins and cell death require critical temperatures for detectable biological injury. The critical temperature for an injury gradually decreases with the lengthening of exposure duration. This approximate decrease in temperature varies over many orders of magnitude in time and deceases approximately as the exposure duration t raised to the – 0.25 power [i.e., f(t–0.25)]. 1.4.1.2 Wavelength Action Spectrum As with any photochemical reaction, the action spectrum should be known (42). The action spectrum describes the relative effectiveness of different wavelengths in causing a photobiological effect. For most photobiological effects (whether beneficial or adverse), the full width at half-maximum of the action spectrum is less than 100 nm, and a long-wavelength “cutoff” exists where photon energy is insufficient to produce the effect. This is not at all characteristic of thermal effects, where the effect occurs over a wide range of wavelengths where optical penetration and tissue absorption occur. For example, significant radiant energy can penetrate the ocular media and be absorbed in the retina in the spectral region between 400 and nearly 1400 nm, and the absorbed energy can produce retinal thermal injury (29, 30). Although the action spectra for acute photochemical effects upon the skin, cornea, lens, and retina have been published (43), the action spectra of some other effects appear to be quite imprecise or even unknown (35, 41, 43, 44). 1.4.1.3 Eye Movements Several physiological factors must be considered for CW exposures (generally thought of as greater than 0.25 s), where the person's visual task will limit the exposure duration and the retinal area illuminated. Physiological factors, such as pupillary activity, eye movements, breathing, heartbeat, blood flow, other bodily movements, and visual task behavior become important. In addition, at short visible wavelengths, another injury mechanism

(photochemical) plays an important role. All these factors were considered in setting the ELs for exposure durations greater than 10 s. Eye-movement studies of Ness et al. (53) showed that the retinal image can remain remarkably still for a few seconds, but that within 30 s, the central retina (the fovea) must move to other points in space for cognition. Two viewing conditions were studied: with a stabilized head (as could occur with ophthalmic instrument applications of lasers), and without head restraint (normal conditions) while volunteers attempted to fixate on a small “point” light source. Results are evaluated in a variety of ways. The fixation history of the small retinal image diameter dr (< 30 mm) can be plotted as a function of time to determine the integration of retinal exposure dose. The accumulated radiant exposure in the retinal image area directly predicts the extent and position of photochemical retinal injury, since retinal radiant exposure determines the risk of photoretinitis for a given wavelength. While these data permitted the determination of the photoretinitis (“blue-light hazard”) EL value, the determination of the thermal hazard ELs was more complex, since thermal retinal injury thresholds decrease for increasing retinal spot size. The determination of the potential for retinal thermal injury for long fixation times requires an examination of three factors: 1. The time-averaged retinal irradiance 2. The thermal effects that result from the way eye movements transform a fixed retinal image into the equivalent of a repetitive-pulse exposure 3. The manner in which image size affects the retinal thermal injury threshold due to radial heat flow during and after the exposure The time-averaged retinal irradiance must not exceed the CW irradiance permitted for a fixed image. The thermal repetitive-pulse exposure obeys what is referred to as the N–0.25 additivity rule, where the net effect is modified as the number of pulses N raised to the –0.25 power (N–0.25). Correction factors for eye movements are only important for viewing durations exceeding 10 s. Only the thermal mechanism is important at durations less than 1 s for small images. Although the physiological eye movements known as saccades do spread the absorbed energy in minimal retinal images (of the order of 25 mm or less) within the 0.1 to 10 s time regime, the limits recommended in these guidelines provide an added safety factor for this viewing condition. At 0.25 s with unrestrained head viewing, the mean retinal spot illuminated is spread out to approximately 50 mm. By 10 s, the illuminated retinal zone becomes approximately 75 mm, and the added safety factor for the minimal image condition becomes 1.7 over a stabilized eye, with the spot-size dependence taken into account. By 100 s, it is rare to achieve an illuminated zone (measured at 50% points) as small as 135 mm, and this means that there is, in effect, an additional safety factor of 2.3 or more above the minimal image condition. The data from eye-movement studies and retinal thermal injury studies were combined to derive a break-point in viewing time T2 at which eye movements compensated for the increased theoretical risk of thermal injury for increased retinal exposure durations if the eye were immobilized. The impact of eye movements is dramatic for minimal retinal spot sizes and permits a leveling of the thermal EL for a > 1.5 mrad to a constant irradiance of 1 mW/cm2 in the visible spectrum (400– 700 nm) for t > 10 s. However, as would be expected, there is only a small impact for a source size of 100 mrad, and the plateau of no further risk of retinal injury due to eye movements does not occur until 100 s. For photochemical injury, eye movements had already been incorporated into the visible laser limits for exposure durations between 10 and 100 s. Beyond 100 s, it is probably unreasonable to assume that fixation could realistically take place, and it was concluded that the limits for all but very large sources (greater than 100 mrad) should end there. 1.4.2 Acute Effects upon Vision

Accidental exposure of the eye to intense laser radiation can result in a range of visual effects. Three general effects upon vision are of particular importance. These three effects are: scotoma, visual disturbances, and acute injury to the cornea. Within the retinal hazard region, a scotoma, or blind spot can appear in the injured person's visual field. The scotoma will appear instantaneously if the injury from thermocoagulation and acoustic disruption of the retina is caused by a pulsed laser beam (approximately 420–1300 nm) focused on the retina. The result of this injury can be permanent functional loss depending upon the severity of the initial injury and whether scarring takes place in the retina which can produce a larger lesion than if biological repair is optimal. At levels below the MPE, temporary visual disturbances may occur. There are two sources of such a transient vision disturbance: (1) Veiling glare and (2) afterimages, or “flashblindness.” Veiling glare from a CW laser is comparable to viewing oncoming automobile headlights while driving. While this glare can make it difficult to see (disability glare) or can be very uncomfortable (discomfort glare), it exists only as long as the laser illuminates the eyes. An afterimage (flashblindness) is most pronounced for low ambient illuminations. The duration of the afterimage is greatest for low ambient illumination (i.e., at night) and for the brightest sources. Although these transient effects are difficult to quantify, they may result in a transient, partial scotoma. The third category of visual effect results from acute injury to the cornea or lens. The effect may be immediate from thermal coagulation or thermal ablation, or it may be delayed for 9–24 h following UV photochemical injury. These injuries can cause the entire visual field to become cloudy due to light scatter. 1.4.3 Types of Injury The human eye is actually quite well adapted to protect itself against the potential hazards from ambient environmental optical radiation (ultraviolet, visible, and infrared radiant energy) from sunlight unless ground reflections are unusually high, as when snow is on the ground, and reflected UV radiation can produce “snow blindness.” Another exception to the general rule occurs during a solar eclipse, when some individuals stare directly at the solar disc for more than a couple of minutes without eye protection and incur an “eclipse burn” of the retina (photoretinitis) (29, 34). Lasers may injure the eye when the normal defense mechanisms of squinting, blinking, and aversion to bright light are overcome, as can occur when viewing pulsed lasers or when the eye is exposed to an invisible infrared or ultraviolet beam. There are at least six separate types of injuries to the eye from lasers and other intense optical sources (listed with the approximate spectral region noted in parentheses):3 1. Ultraviolet photochemical injury to the cornea (photokeratitis)—also known as “welder's flash” or “snow blindness (180–400 nm) (41, 44) and erythema (“sunburn”) of the skin (29, 43). 2. Ultraviolet photochemical injury to the crystalline lens (cataract) of the eye (295–325 nm, and perhaps to 400 nm) (29, 30, 44). 3. Blue-light photochemical injury to the retina of the eye (principally 400–550 nm; unless aphakic, 310–550 nm) (34, 35). 4. Thermal injury (photocoagulation) to the retina of the eye (400 to nearly 1400 nm), and thermoacoustic injury at very short laser exposure durations. 5. Near-infrared thermal hazards to the lens (approximately 800–3000 nm) (45, 46). 6. Thermal injury (burns) of the cornea of the eye (approximately 1400 nm to 1 mm) or to the skin (approx 320 nm to 1 mm) (29, 30). The range of the aforementioned potential hazards to the eye and skin are illustrated in Figure 103.2, which shows how specific effects are generally dominant in certain CIE photobiological spectral bands, UV-A, -B and -C and infrared A, B, and C (47). Although these photobiological bands are useful shorthand notations, they do not define fine lines between no effect and an effect in accordance with changing wavelengths.

Figure 103.2. The potential hazards to the eye and skin as a function of wavelength. Certain effects are generally dominant in each CIE photobiological spectral band.

Figure 103.3. A typical probit presentation of experimental laser retinal threshold injury data where the ED50 has a probit value of 5.0. Strictly speaking, the probit value of 5.0 occurs at a 50% probability value. 1.4.3.1 Photokeratitis The relative position of the laser source and the degree of lid closure can greatly affect the proper calculation of this ultraviolet exposure dose low-level; scattered UV from excimer lasers has produced photokeratitis in workers. For assessing risk of photochemical injury, the laser wavelength is of great importance. Wavelengths between 260 and 280 nm are at the peak of the action spectrum and are the most dangerous (44). 1.4.3.2 Cataract Ultraviolet cataracts can be produced from exposure to UVR of wavelengths between 295 and 325 nm (and perhaps to 400 nm). Action spectra can only be obtained from animal studies, which have shown that cortical and anterior subcapsular cataract can be produced by intense exposure delivered over a period of days. Human cortical cataract has been linked to chronic, lifelong UV-B radiation exposure. Although the animal studies and some epidemiological studies suggest that it is primarily UV-B radiation in sunlight (44), and not UV-A, that is most injurious to the lens, biochemical studies suggest that UV-A radiation may also contribute to accelerated aging of

the lens. Since there is an earlier age of onset of cataract in equatorial zones, UVR exposure has frequently been one of the most appealing of a number of theories to explain this latitudinal dependence (35, 48). Laser exposure from the xenon–chloride laser at 308 nm is of particular concern, since this wavelength is in the narrow action spectrum for acute cataract. The ACGIH TLV and ICNIRP laser and noncoherent UVR guidelines are also intended to protect against cataracts (31, 36, 49, 50). Since the only direct pathway of UVR to the inferior germinative area of the lens is from the extreme temporal direction, it has been speculated that side exposure is particularly hazardous. In the case of the lens, the germinative layer where lens fiber cell nuclei are located is of great importance. The DNA in these cells is normally well shielded by the parasol effect of the irises. However, Coroneo et al. have shown that the focusing of very a peripheral 308-nm beam by the temporal edge of the cornea can enter the pupil and focus in the equatorial region (48, 51). The Coroneo effect argues for assuring well-fitting side shields on UV laser eye protectors. 1.4.3.3 Photoretinitis The principal retinal hazard resulting from lengthy staring at bright CW light sources is photoretinitis. The best example is solar retinitis with an accompanying scotoma (“blind spot”), which results from staring at the sun. Solar retinitis was once referred to as “eclipse blindness” and associated “retinal burn.” At one time, solar retinitis was thought to be a thermal injury, but it has been since shown conclusively to result from a photochemical injury related to exposure of the retina to shorter wavelengths in the visible spectrum, that is, violet and blue light (52). For this reason, it has frequently been referred to as the “blue-light” hazard. The action spectrum for photoretinitis peaks at about 445 nm in the normal phakic eye (34, 52). Laser exposure limits were revised to better characterize and quantify the risk from these blue laser wavelengths in 1999. As a consequence of the Bunsen–Roscoe Law of photochemistry, blue-light retinal injury (photoretinitis) can result from viewing either an extremely bright blue laser reflection for a short time, or a less bright source for longer periods. The approximate retinal threshold for a helium– cadmium laser at 441.6 nm is approximately 22 J/cm2; hence a retinal irradiance of 2.2 W/cm2 delivered in 10 s, or 0.022 W/cm2 delivered in 1000 s, will result in the same threshold retinal lesion (34). Eye movements will reduce the hazard, and this is particularly important for sources subtending an angle less than 11 mrad. Saccadic motion even during fixation is of the order of 11 mrad. In 1999 laser exposure limits were adjusted to provide for dual limits (photochemical or thermal) for retinal exposure and for the effect durations greater than 1–10 s (53). 1.4.3.4 Infrared Cataract Infrared cataract in industrial workers appears only after a lifetime of exposure to radiances of the order of 80–150 mW/cm2 (29, 45). Although thermal cataracts were observed in glassblowers, steel workers, and others in metal industries at the turn of the century, they are rarely seen today (45). These irradiances are almost never exceeded in modern industry, where workers will be limited in exposure duration to brief periods above 10 mW/cm2 or they will be wearing eye protectors. Good compliance in wearing eye protection occurs at higher irradiances if only because the worker desires comfort of the face. This is not a realistic exposure condition from infrared laser radiation. Laser heat treating of metal surfaces can produce reasonably high reflected irradiances, but levels of concern would be felt and considered quite uncomfortable. Thus a lengthy exposure of today's worker to such levels is unrealistic. 1.4.4 Experimental Studies ELs for laser radiation are based largely upon experimental ocular injury studies. Most threshold data have been obtained from animal studies (primates and rabbits), although some limited human data exist for confirmation of the animal model. W. T. Ham, Jr., and others studied (54) the effect of cumulative long-term exposure to pulsed laser on retinal injury in rhesus monkeys and cynomolgus monkeys. The main optical source was a continuous-wave argon/krypton laser (ArKrL) with emission lines at 647, 514.5, and 488 nm. The

pulses were produced at pulse repetition frequencies (PRFs) of 100, 200, 400, and 1600 Hz by chopping with a rotating disk. A helium/neon laser (HeNeL) was used to compare the ocular effects of 632.8-nm light width with the 647-nm line emitted by the ArKrL. The appearance of a visible minimal lesion in the paramacular area of the retina at 48 h postexposure was the biological threshold. The mean exposure damage level was determined by interpolation. A comparison of thresholds between wavelengths 632.8 and 647-nm for 500-mm-diameter retinal images at exposure times of 1, 16, 100, 1000, 3000, and 10,000 s showed that up to exposure times of 1000 s there was no significant difference between the thresholds for retinal damage from the krypton 647-nm and from the HeNeL 632.8-nm exposures. Beyond the 1000-s exposures the 632.8-nm wavelenght had a significantly lower threshold than the 647-nm line. The threshold for minimal retinal injury was always lower for the blue than for the red pluse trains. For 1000-s exposures at PRF of 1600 Hz the threshold was lower than for continuous-wave red light. The authors concluded that no ocular hazards exist in conventional application of nominal 1 mW HeNeL, such as those used in supermarket scanners. W. T. Ham, Jr., and others also (55) exposed seven rhesus monkeys (14 eyes) to 1064-nm radiation in single pulses of 25 to 35 ps from a mode-locked Nd:YAG laser. Threshold injury resulted from single pluse with a mean energy of 13 mJ. Electron microscopy of the retina revealed that damage was highly localized in the photoreceptor and pigmented epithelial cells at the outer retina. Membrane disruption, distorted outer segments, and abnormal melanin granules resembling fetal premelanosomes were observed. D. N. Farrer and others (56) conducted studies to evaluate retinal threshold burns and subthreshold exposures of the mammalian macula in terms of visual acuity. Rhesus monkeys (Macaca mulatta) were trained by a reward system to respond to the automated presentation of Landolt rings. After appropriate training, these animals were exposed to threshold and subthreshold levels of retinal energy density ranging from 3.2 to 10.7 J/cm2, exposure time approximately 135 ms, spectral quality approximately that of color, a temperature of 6000 K with wavelength above 900 nm removed, and image sizes on the retina of about 1 nm in diameter, covering a major portion of the monkey macular area. Results, in terms of visual acuity decrement (monocular), indicated that energy densities on the retina below 5 J/cm2 were not statistically significant, whereas energy densities greater than 5 J/cm2 produced losses in visual acuity (monocular) that were significant. These results indicate that, at levels of energy density on the retina 80–50% below the threshold burn level, no loss in visual acuity can be detected in the rhesus monkey by the Landolt-ring testing system adopted for this investigation. The ELs must be based upon an understanding of the mechanisms of laser/tissue interaction as well. A major point of discussion in the EL derivation process relates to the level of uncertainty of the threshold of injury. An indication of the level of uncertainty relates to the slope of the transformed dose-response curve, or the “probit plot” of the data. The most important point on the probit plot is the exposure which represents a 50% probability of injury: the ED50. It is this value that is frequently referred to as the “threshold,” even though some experimental damage points exist below this “threshold.” An analysis of any number of example data sets reveals that the slope in most experiments could not be explained by biological variation alone. This type of critical analysis is essential in deriving ELs. For example, if the slope is not very steep, as with some retinal injury studies, the probit curve may suggest that at one-tenth the ED50 energy value, there might be a 0.1% risk of injury—a risk generally not acceptable in the laser safety community. Yet, from fundamental biophysical principles, this result could be shown clearly to be flawed. If the ED50 energy corresponds to a retinal temperature elevation of 150, an energy of 10% of the ED50 must correspond to 1.50 (10% of the ED50

temperature elevation), which could not produce photocoagulation. This aptly illustrates that any derivation of human exposure limits for laser-induced injury requires one to estimate the true biological variation and separate this from the added experimental errors which reduces the probit slope. Analysis of reported experimental data indicates that the thermal and thermoacoustic damage mechanisms apparently have an intrinsic slope of approximately 1.15 to 1.2. However, experimental threshold data from retinal studies give slopes that are often much greater (e.g., 1.5–1.7), which is really not surprising. The enormous difficulty of seeing a minimally visible lesion and focussing the laser beam to produce the nearly diffraction-limited image leads to this greater spread of data and shallower slopes. A probit curve applied to the derivation of exposure limits should have a slope of 1.2 or less with the ED50 point shifted to a lower value. The steepness of the probit curve is therefore not only related to the type of damage mechanism and variation among individual animals, but also indicates problems in conducting the experiment. Traditionally, all of these factors are assessed collectively in order to derive an appropriate “safety factor” for deriving the EL from the ED50. The safety factor is not a true ratio between a true “threshold of injury” and the EL, but represents a committee judgement of uncertainties. Greater safety factors have been applied when uncertainties are greatest, and considerations of extrapolation from animal to human are also part of the process. In an ideal experiment where the experimental errors introduced by the beam propagation through the ocular media were not present, the true spread of retinal threshold data would be much smaller than that obtained by current experimental methods aimed at determining the minimum visible lesion (MVL). The type of damage mechanism will affect the absolute spread of threshold data. Based upon the current understanding of the retinal injury mechanisms by short-pulsed lasers, thermal photocoagulation dominates for pulse durations of 10 ns to many milliseconds. Injury thresholds appear to vary little from 10 ns to about 18–50 ms. At longer durations, the thresholds increase because heat flow occurs during the exposure. At subnanosecond exposure durations, other nonlinear damage mechanisms come into play, such as self-focusing and laser-induced breakdown. The thermal and thermomechanical mechanisms have sharply defined thresholds in experiments where tissue is directly exposed without confounding factors, as in CO2 laser-induced corneal injury. More stochastic effects appear in the subnanosecond regime (37, 40). In the determination of thresholds of laser-induced injury, direct observation by ophthalmic instrument is most frequently used. For retinal studies, the ophthalmoscope or slit-lamp microscope is used by the experimentalist to observe the retinal location where the laser exposure takes place. In some cases the visibility of the laser-induced lesion can be improved by a technique known as fluorescein angiography, and some workers have even used light and electron microscopy to examine the exposed tissue. These measures claim to have greater sensitivity, but are more costly and less practical. Although fluorescein angiography is frequently used, the detailed histological studies with microscopic examination of thin slices of exposed tissue have only been carried out for specified laser wavelengths and exposure durations to quantify the reduction in the ophthalmoscopically determined ED50 by the more elaborate techniques. The quantitative value of ED50 and the spread of data points can change by varying the experimental techniques. One of the most critical elements of the experimental protocol is the delay between laser exposure and time of examination, because biological changes undergo a time course following injury. Typical delays for examination range from 5 min to 48 h, with 1 and 24 h being the most frequently used. Depending upon damage mechanism (i.e., thermal, thermomechanical, photochemical, etc.), the optimum period to determine the ED50 changes as the time course varies for the biological response and amplification of the initial biophysical tissue insult. Another factor that affects the ED50 value is the choice of experimental animal. One of the most

frequently used animals in ophthalmic research is the rabbit; it is used most often for corneal injury studies and in many early retinal studies. However, the optical quality of the rabbit eye is poor, leading to distorted retinal images and inaccurate threshold determinations (1–2). There have been studies employing ophthalmic contact lenses and careful optical alignment of the anesthetized rabbit to eliminate most corneal aberrations in the eye. These conditions produce nearly diffraction-limited retinal images and low threshold values; however, the required extrapolation to the human eye with its reduced optical performance leads to some level of uncertainty. Hence the currently most favored animal model has become the rhesus monkey for retinal studies by most investigators, and this has greatly increased the cost of the experiment, leading to fewer threshold determinations. Still another factor, the retinal pigmentation, will determine the fraction of incident energy absorbed at each wavelength and thereby affect the resulting ED50. Pigmentation in the retinal pigment epithelium (RPE) and choroid varies with the individual subject, the species, and the retinal location. Although the color of the rabbit retina appears to more closely resemble the human retina, it has been argued that the pigment density in the rhesus monkey is more similar to that of humans. In any case, these variables are accounted for in the derivation of MPEs and are considered in this report. Another factor of concern is the refractive state of the experimental subject. As this refractive state determines whether the minimal retinal image size of a collimated laser beam is achieved, this is critical. A one-diopter error in the refractive state can result in an increase in the achieved retinal blur circle from approximately 25 mm to about 120 mm—a change in image area of 22 times. Investigators therefore normally attempt to correct the animal's state of refraction in the visible, but even this does not take into account the chromatic aberrations—also of the order of one diopter across the visible spectrum. Investigators are able to correct the refraction to within 0.25 D, which leads to an uncertainty in actually achieved minimal retinal image diameter of approximately 20– 50 mm. Furthermore, during an investigative session, the animal's refractive state will vary slightly from exposure to exposure, the degree depending upon the level of anesthesia. Eye movements during the experimental exposure will also affect the outcome. These eye movements will only be of concern for exposures lasting more than 10 ms. In the derivation of ELs, the impact of anesthetized animal exposures on the retinal injury threshold is measured (50, 53). This showed that laser energy was concentrated in a much smaller retinal area for exposures of several seconds, with the effect of eye movements considered in the derivation. The actual site of retinal exposure will influence the ED50. This occurs for two reasons. The optical quality of the eye for off-axis beams is somewhat less than for axial exposures to the fovea. Furthermore, the pigmentation and thickness of the neural retina vary from the center of the fovea, through the macula to the para-macular regions. As a general rule, the ED50 values will be less in the fovea than parafoveal or paramacular. This variation is of the order of twofold. The state of the ocular media (cornea, aqueous, lens, and vitreous) influences the distribution of radiant energy at the retina. Intraocular scatter diffuses the beam, and depending upon the nature and size of the scattering centers in the ocular media, small-angle forward scatter and diffuse scatter will vary. The age of the eye, the care taken by the experimentalist to preserve corneal clarity by frequent irrigation of the cornea (or use of contact lens), and the potential for subtle lenticular opacities (early stages of cataractogenesis) all play a role in producing scatter. The ability of the experimental investigator observing the retina to detect a just-perceptible minimum visible lesion (MVL) also influences the ED50 value. As investigators have more experience, the reported ED50 traditionally decreases. The visual contrast of the threshold injury is usually low, making the task of correct lesion detection difficult. Furthermore, the chance of scoring the presence of a very small lesion when an injury is actually not present (i.e., false positive) will increase if the retina appears mottled or otherwise exhibits abnormalities that could be mistaken for a laser-induced

lesion. It may also be difficult to discern the edges of some very large lesions, making positive identification difficult. Nevertheless, our review of the published threshold studies that provide doseresponse slopes show a general trend for a steeper slope for larger images, suggesting the greater difficulty of executing the small-lesion experiments. The optical quality of the incident laser beam influences the minimal retinal image size. In earlier studies, multimode lasers were frequently used, leading to a larger retinal image area and increased values of the ED50. Today, most lasers used in these experiments have been carefully aligned to achieve a single transverse mode. The presence of apertures in the beam path can also alter the quality of the retinal image. It is evident that aside from false positive identification of a lesion, all the other aforementioned sources of error will tend to increase the ED50 values and the spread of the data from which they are derived.

Lasers David H. Sliney, Ph.D. 1.5 Standards, Regulations, or Guidelines of Exposure A number of national and international groups have recommended occupational or public exposure limits (ELs) for laser radiation for wavelengths extending from 180 nm in the ultraviolet (UV) region, to 1000 mm (1 mm) in the far infrared (IR). These ELs apply for pulse durations from 100 fs (10–13 s) to 30 ks (8 h). In the United States, both the American Conference of Governmental Industrial Hygienists (ACGIH) and the American National Standards Institute (ANSI) have produced comprehensive sets of exposure limits (31, 49, 57). These ELs are virtually identical, although ELs are termed threshold limit values (TLVs) by ACGIH and maximum permissible exposure limits (MPEs) in the ANSI Standard Z-136.1. On the international scene, the International Commission on Non-Ionizing Radiation Protection (ICNIRP) publishes Guidelines on Limits of Exposure to Laser Radiation (36, 50). ICNIRP guidelines are developed through collaboration with the World Health Organization (WHO) by jointly publishing criteria documents that provide a scientific database for the exposure limits (30). The International Electrotechnical Commission (IEC) uses the ICNIRP guidelines (10). The ICNIRP ELs are essentially identical to the ACGIH, and ANSI limits (31, 32, 36, 40, 49, 50, 57). The ELs based in large part on ocular injury data from animal studies and from data from human retinal injuries resulting from viewing lasers, the sun, and welding arcs. All the guidelines have an underlying assumption that outdoor environmental exposures to visible radiant energy is normally not hazardous to the eye except in very unusual environments such as snow fields and deserts (29, 30). The ACGIH ELs and ICNIRP ELs are generally applied to derive accessible emission limits (AELs) used in product safety standards of the International Electrotechnical Commission, the American National Standards Institute, and other technical standards groups. The U.S. Food and Drug Administration also uses these AELs in the Federal Laser Performance Standard (21 CFR 1040). These product safety standards must have carefully defined measurement conditions to simulate “worst-case” ocular exposure conditions (Tables 103.3–103.6). Table 103.3. Intrabeam Laser Ocular Threshold Limit Values

Wave length l

Expos. t (s)

Threshold Limit Value EL (J/cm2 or

(nm)

Duration t

W/cm2)

Restrictions

Ultraviolet 180–302

1 ns–30 ks

3 mJ/cm5

303

1 ns–30 ks

4 mJ/cm5

304

1 ns–30 ks

6 mJ/cm5

305

1 ns–30 ks

10 mJ/cm5

306

1 ns–30 ks

16 mJ/cm5

307

1 ns–30 ks

25 mJ/cm5

308

1 ns–30 ks

40 mJ/cm5

309

1 ns–30 ks

63 mJ/cm5

310

1 ns–30 ks

0.1 J/cm5

311

1 ns–30 ks

0.16 J/cm5

312

1 ns–30 ks

0.25 J/cm5

313

1 ns–30 ks

0.40 J/cm5

314

1 ns–30 ks

0.63 J/cm5

315–400

1 ns–10 s

0.56t3/4 J/cm5

315–400

10 s–30 ks

1.0 J/cm5 Visible and IR-A

400–700

1 ns–18 ms

0.5 mJ/cm5

400–700

18 ms–10 s

1.8t3/4 mJ/cm5

400–550

10 s–10 ks

10 mJ/cm5

550–700

10–T1 s

1.8t3/4 mJ/cm5

550–700

T1 s–10 ks

10 CB mJ/cm5

400–700

10–30 ks

CB mW/cm5

700–1050

1 ns–18 ms

0.5 CAmJ/cm5

700–1050

18 ms–1 ks

1.8 CAt3/4 mJ/cm5

1051–1400

1 ns–50 ms

5 CC mJ/cm5

1051–1400

50 ms–1 ks

9.0 CCt3/4 mJ/cm5

700–1400

1–30 ks

320 CACC m/cm5

All ELs for l less than 315 nm must be 0.56t3/4 J/cm5

7 mm limiting aperture

Far Infrared 1400–1500 nm 1 ns–1.0 ms

0.1 J/cm5

1400–1500 nm 1.0 ms–10 s

0.56t1/4 J/cm5

1500–1800 nm 1 ns–10 s

1.0 J/cm5

1801–2600 nm 1 ns–1.0 ms

0.1 J/cm5

1801–2600 nm 1.0 ms–10 s

0.56t1/4 J/cm5

2601 nm–1 mm 1–100 ns

10 mJ/cm5

3.5 mm limit. aperture

2601 nm–1 mm 100 ns–10 s

0.56t1/4 J/cm5

1400 nm–1 mm 1.0 s–30 ks

100 mW/cm5

NOTES: Time: All values of t in s; 1 ks = 1000 s, and 30 ks = 8 h. spectral correction factors: CA = 1 for l = 400–700 nm; CA = 10[0.02(l–700)] if l = 700–1050 nm CB = 1 for l = 550 nm; CB = 10[0.015(l–550)] for l = 550–700 nm CC = 1 for l = 1150; Cc = 10[0.0181(l–1150)] for 1150 < l < 1200 CC = 8 for 1200

l < 1400

10[0.02(l–550)]

for l = 550–700 nm TI = 10 × Extended-source TLVs: For extended-source laser radiation (e.g., diffuse reflection) viewing at wavelengths between 400 and 1400 nm, the intrabeam viewing TLVs can be increased by the following correction factor CE provided that the angular subtense of the source (measured at the viewer's eye) is greater than lmin, where lmin is: lmin = 1.5 mrad for t < 0.7 s lmin = 2 t3/4 mrad for 0.7 lmin = 11 mrad for t

t < 10 s

10 s.

CE = l/lmin for lmin < l < 100 mrad CE = l2/(lminlmax) for l CE =

10l2/l

min

for l

100 mrad 100 mrad for l expressed in rad

The angle of 100 mrad may also be referred to as lmax, at which point the extended source limits can be expressed as a constant radiance using the last equation written in terms of lmax. LTLV = (8.5 × 103)(TLVpt source) J/(cm2 sr) for t < 0.7 s LTLV = (6.4 × 103 t–3/4)(TLVpt source) J/(cm2 sr) for 0.7 103)TLV

LTLV = (1.2 × aor W/(cm2@sr)

pt source)

J/(cm2

sr)a

for t

t < 10 s

10 s

for point-source limits expressed in W/cm2 Terminology: The term exposure limit (EL) is used by IRPA. The same values are termed MPEs (maximum permissible exposure limits) by ANSI and TLVs (threshold limit values) by ACGIH. Essentially all groups have the same limit values.

Table 103.4. Laser Threshold Limit Values for Skin Exposure Wave length l (nm)

Expos. t (s) Duration t

Threshold Limit Value EL (J/cm2 or W/cm2)

Restrictions

Ultraviolet 200–400

1 ns–30 ks

400 nm–1 mm

1–100 ns

20 CA mJ/cm5

400 nm–1 mm

100 ns–10 s

1.1 CAt1/4 J/cm5

400 nm–1 mm

10 s–30 ks

0.2 CA W/cm5

Same as eye ELa Visible and IR-A

Far Infrared 1400 nm–1 mm 1 ns–30 ks for Same as eye EL 2601 nm–1 mm Note: See Notes, Table 103.3.

3.5 mm limit. aperture

a

Or W/(cm2@sr) for point-source limits expressed in W/cm2.

Table 103.5. Limiting Apertures Applicable to Laser TLVs (mm) Spectral Region

Duration Eye (mm) Skin (mm)

180–400 nm 1 ns–0.25 s 1 180–400 nm 0.25 s–30 ks 3.5 400–1400 nm 1 ns–0.25 s 7 400–1400 nm 0.25 s–30 ks 7 1400 nm–0.1 mm 1 ns–0.25 s 1 1400 nm–0.1 mm 0.25 s–30 ks 3.5 0.1–1.0 mm 1 ns–30 ks 11

3.5 3.5 3.5 3.5 3.5 3.5 11

Table 103.6. Selected Occupational Threshold Limit Values (TLVs) for Some Common Lasers Type of Laser

Wavelength Threshold Limit Value

Argon–fluoride

193 nm

3.0 mJ/cm2 over 8 h

Xenon–chloride

308 nm

40 mJ/cm2 over 8 h

Argon ion

488,514.5 nm 3.2 mW/cm2 for 0.1 s 2.5 mW/cm2 for 0.25 s

Helium–neon

632.8 nm

1.8 mW/cm2 for 1.0 s 1.0 mW/cm2 for 10 s

Krypton ion Helium–neon

568,647 nm 632.8 nm 17 mW/cm2 for 8 h Neodymium–YAG 1064 nm 5.0 mJ/cm2 for 1 ns to 100 ms 5 mW/cm2 for 10 s Erbium glass

1540 nm

1.0 J/cm2 for 1 ns–10 s

Erbium:YAG

2940 nm

10 mJ/cm2 for 1–100 ns

Hydrogen fluoride 2.7–3.1 mm 10 mJ/cm2 for 1–100 ns Carbon dioxide 10.6 mm 100 mW/cm2 for 10 s to 8 h, limited area 10 mW/cm2 for >10 s Source: ACGIH TLVs. Note: To convert TLVs in mW/cm2, multiply by exposure time t in s; e.g., the He-Ne or argon TLV at 0.1 s is 0.32 mJ/cm2.

1.5.1 Examples Several representative exposure limits are shown in Table 103.4 for the most commonly available lasers. One should also remember that the way most of the laser safety standards are organized, one

makes use of a laser's hazard classification (initially based upon ELs) to perform a hazard evaluation, rather than to perform measurements of beam exposure for comparison with ELs. The ELs are actually used only in special instances where human exposure is intended and the laser beam irradiance or radiant exposure may actually be measured or calculated to determine if the EL will be exceeded. 1.5.2 Discussion 1.5.2.1 Exceeding the Exposure Limits In deriving the ELs for all optical radiations, the ACGIH and ICNIRP generally applied a factor of 10 to reduce the 50% probability of retinal injury by a factor of 10. This is not a true “safety factor” because there is a statistical distribution of damage and this factor was based upon several considerations. These included the difficulties in performing accurate measurements of source radiance or corneal irradiance; measurement of the source angular subtense; as well as histological studies showing retinal changes at the microscopic level at levels of approximately 2 below the ED50 value.3 In actual practice, this means that an exposure at 2–3 times the EL would not be expected to actually cause a physical retinal injury. At five times the EL, one would expect to find some injuries in a population of exposed subjects. As with other TLVs, the laser ELs are guidelines for controlling human exposure and should not be considered as fine lines between safe and hazardous exposure. With benefit versus risk considerations, it should therefore be considered appropriate to have some relaxed guidelines; however, to date, no standards group has seen the need to do this. This may apply to the development of safety standards for ophthalmic medical instruments. 1.5.2.2 Application of Limits in Laser Safety Standards Laser safety standards exist in the United States and worldwide. All the standards group manufactured laser products into four general hazard classes and provide safe measures for each hazard class (1 through 4) (36, 44). U.S. Federal regulations (21 CFR 1040) require all commercial laser products to have a label indicating the hazard class. The safety measures recommended in workplace safety standards are quite obvious (e.g., beam blocks, shields, baffles, eye protectors), once one understands and recognizes the hazards. The ocular hazards are generally of primary concern. Figure 103.4 illustrates the relative retinal hazard from intrabeam viewing of a laser in comparison with the hazard of viewing conventional light sources.

Figure 103.4. Relative retinal irradiances for staring directly at various light sources. Two retinal exposure risks are depicted: retinal thermal injury, which is image-size dependent, and photochemical injury, which depends on the degree of blue light in the source's spectrum. The horizontal scale indicates typical image sizes. Most intense sources are so small that eye movements and heat flow will spread the incident energy over a larger retinal area. The range of photoretinitis (the “blue-light hazard”) is shown to be extending from the normal outdoor light levels and above. The xenon arc lamp is clearly the most dangerous of nonlaser hazards. The primary workplace safety standard in the United States is the American National Standard, ANSI Z136.1-2000, The Safe Use of Lasers. It is a national consensus standard for laser safety in the user environment. It has evolved through several editions since 1973. Although the ELs are termed maximum permissible exposure (MPE) limits by ANSI, they are all the same values. MPEs are provided for all wavelengths from 180 nm to 1 mm, and for exposure durations of 100 fs to 30 ks (8h workday) the MPEs appear at the end of the safety standard. Since almost all control measures are based upon the laser's hazard class (1 through 4), the MPEs are seldom actually used. The MPEs did form the basis for deriving the hazard classifications. For example, the accessible emission limits (AELs) for class 1 are derived to prevent human access to levels above the MPE under reasonably foreseeable worst-case laser operating conditions. The Class 1 AELS are derived by multiplying the MPE for the longest foreseeable exposure duration by the area of the limiting aperture specified for that MPE. For example, the limiting aperture for visible lasers is 7 mm based upon a dark-adapted pupil. The resulting AEL has units of energy or power. Nevertheless, health and safety specialists want the simplest expression of the limits, but some more mathematically inclined scientists and engineers on standards committees argue for sophisticated formulas to express the limits (which belie the real level of biological uncertainty) and the health and safety specialists at the same time demand greater simplification. These exposure limits (and the

identical ELs of ACGIH) formed the basis for the U.S. Federal Product Performance Standard (21 CFR 1040). The latter standard regulates only laser manufacturers. On the international scene, IEC standard 825-1 (1993) grew out of an amalgam of the ANSI standard for user control measures, the WHO-endorsed exposure limits of ICNIRP, ACGIH, and ANSI, and the CDRH product classification regulation. The International Commission on Nonionizing Radiation Protection (ICNIRP) has a special relationship with the World Health Organization in developing criteria documents on laser radiation and recommending exposure limits for laser radiation (ICNIRP, 1996). These standards are all basically in agreement. 1.5.2.3 Acute Exposure In realistic workplace settings, accidental and therefore exposures to a hazardous laser beam represent a low probability, but exposures can have severe consequences. This is illustrated by a typical accident in which a young investigator in a physical chemistry laboratory is aligning a short-pulse (10-ns) laser beam to direct it into a gas cell to study photodissociation parameters for a particular molecule. Leaning over a beam director, he glances down over an upward, secondary beam and approximately 80 mJ enters his left eye. The impact produces a microscopic hole in his retina, a small hemorrhage is produced over his central vision, and he sees only red in his left eye. Within an hour he is rushed to an eye clinic where an opthalmologist tells him he has only 20/400 vision (41). In a university laboratory, a physics graduate student attempts to realign the internal optics in a Q-switched Nd:YAG laser system—a procedure normally performed by a service representative that the student had witnessed several times before. A “weak” secondary beam reflected from a beam splitter enters the student's eye, producing a similar hemorrhagic retinal lesion with a severe loss of visual acuity (Fig. 103.5). Similar accidents occur each year, and frequently do not receive publicity because of litigation or for administrative reasons. Scientists and engineers working with open-beam lasers really need to realize that almost all such lasers pose a very severe hazard to the eye if eye protection is not worn or other safety measures are not observed.

Figure 103.5. A “weak” secondary beam reflected from a beam splitter can enter the unprotected eye, as during laser alignment. An beam energy of only 0.1 mJ can produce a hemorrhagic retinal lesion with a severe loss of visual acuity. In virtually all accidents, eye protectors were available but not worn. The probability that a small beam will intersect a 3–5-mm pupil of a person's eye is small to begin with, so injuries do not always happen when eye protectors are not worn.

Lasers David H. Sliney, Ph.D. 1.6 Guidelines The one area of TLV guidelines being considered for possible revision relates to further refinements of correction factors in the IR-B, that is, in CD. Recently ELs for visible and near-infrared laser radiation in the subnanosecond pulse regime have been developed and have been published (37). Exposure limits for lengthy viewing have also just been modified. These changes would still not affect most applications. As in the past, the understanding of the basic interaction mechanisms is critical to setting limits. Lasers Bibliography

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Occupational Ergonomics: Principles and Applications Amit Bhattacharya, Ph.D., Nancy Talbott, MS, PT, Laurel Kincl, MS 1 Introduction This chapter provides the basic principles that underlie the field of ergonomics and their application to some of the current issues of importance in the workplace. Sections 2 to 4 deal with the physiology of muscles; biomechanics; cellular responses to tissue, nerve, and joint injuries as they relate to cumulative trauma disorders; and common types of overuse syndromes. The remaining sections deal with applications of the principles to workplace ergonomic issues and proposed ergonomic regulations.

Occupational Ergonomics: Principles and Applications Amit Bhattacharya, Ph.D., Nancy Talbott, MS, PT, Laurel Kincl, MS 2 Principles of Ergonomics The word “ergonomics” is made up of two Greek words, “ergo” meaning work and “nomas” meaning laws. The field of ergonomics is highly interdisciplinary. It applies principles from engineering, physiology, medicine, and psychology to the understanding of the interaction of humans with their workplace. The interaction of humans with their workplace may consist of identifying the relationship between job physical risk factors and physiological responses. For example, a specific ergonomic problem of paramount importance in the occupational health and safety is the issue of work-related musculoskeletal disorders (WMD). Some of these issues are discussed further in this chapter. The specific areas of application relevant for the field of ergonomics are defined and briefly explained in the following. 2.1 Physiology of Muscle Contraction and Movements 2.1.1 Structure of Muscles and Contraction Characteristics The generation of forces and movements in living cells such as muscles requires special protein molecules and contractile proteins. These

types of proteins are available in great abundance in the muscle cell. These proteins can convert chemical energy such as adenosine triphosphate (ATP) into mechanical energy (1). There are three major types of muscles in the human body: skeletal, smooth, and cardiac. Skeletal and cardiac muscles are striated muscles. Skeletal muscles such as muscles of the arms, legs, and back perform most of the voluntary actions, and smooth muscles such as muscles in the internal organs perform involuntary actions. The cardiac muscles also act autonomically (2). The major focus of this section is the skeletal muscle. The skeletal muscle, the largest of the tissues in the human body, constitutes about 45% of the total body weight. The skeletal muscle is made up primarily of 75% water and the remaining 25% is protein, inorganic salts and high energy phosphates, urea, lactic acid, enzymes, minerals, etc (3). There are about 600 muscles in the human body. Each muscle is made up of many thousands of muscle fibers. Small muscles have only a few hundred fibers whereas larger muscles may contain several hundred thousand fibers. Each end of the whole muscle is attached to a bone by bundles of collagen fibers called tendons that can transmit forces from the muscles to the bones. Tendons have great strength, but unlike the muscle fibers, they cannot contract. Each muscle fiber is composed of thousands of myofibrils, the contractile element of the skeletal muscle. These myofibrils are about 1 micron (=1/1000 mm) in diameter. Each of these myofibrils has millions of filaments made up of two proteins, actin and myosin. Actin is known as the thin filament and myosin is called the thick filament. During electrical stimulation via nerve, attractive forces between the actin and myosin filaments cause muscle to contract. Table 104.1 gives a list of the major sequence of events between nerve action potential and contraction and relaxation of muscle fiber (2). Table 104.1. Sequence of Events for Muscle Contraction 1 An action potential is generated in a motor axon. 2 Release of acetylcholine from the axon terminal at the neuromuscular junction known as muscle end plate. 3 A motor end plate potential is produced at the muscle end plate. 4 The motor end plate potential depolarizes the muscle membrane (to about– 15 mV) causing it to generate a muscle action potential that travels along the surface of the muscle membrane. Acetylcholine-esterase (enzyme) immediately destroys acetylcholine so that the depolarized membrane returns to its resting potential of about–90 mV. 5 Depolarization of transverse tubules by the muscle action potential causes release of calcium ions from the sarcoplasmic reticulum around the myofibrils. 6 Calcium ions cause the actin-myosin filaments to slide, thereby producing contraction of the muscle fiber. 7 As the concentration of calcium ions falls, the actin-myosin sliding action reduces and the muscle relaxes.

2.1.2 Motor Neurons and Motor Units A neuron consists of the soma (main body), the dendrites, and the axon. The axon carries signals away from the neuron cell body, and dendrites bring signals from other neurons. However, one exception is the sensory nerve fiber, which is a single dendrite that transmits sensory signals from a peripheral receptor. Each neuron has many dendrites but only one axon. In the center of axon is a gel-like substance called axoplasm. Some nerve fibers have an additional layer surrounding their membranes called a myelin sheath. The myelin sheath is broken at

the nodes of Ranvier. The myelin sheath has insulating properties and is instrumental in propagating an electric signal along the axon by allowing it to jump from one node of Ranvier to the next. This process of impulse “jumping” decreases the amount of energy required for signal transmission. A motor unit consists of a single motor neuron and all the muscle fibers controlled by it. Generally, large muscle fibers that perform strong body motions have more motor units than those for the smaller muscles. When excited, these motor units respond to activate all of the muscle fibers connected to them (4). 2.1.3 Energy Transform and Use The human body gets its energy from foodstuff (carbohydrates, fats, and proteins) it consumes. However, the foodstuffs have to be converted to a certain chemical form before the cells in the human body can use it as a supply of energy. This chemical compound is called adenosine triphosphate (ATP). This compound contains high-energy phosphate bonds. Each mole of ATP releases 8000 calories of energy each time a phosphate radical is broken away from ATP at the high-energy bond. This released energy is used as an immediate supply of energy for a variety of functions such as transport of glucose through the membrane, synthesis of chemical compounds inside the cell, muscle contraction, and neuronal activity. Once this ATP is used it becomes like a discharged battery known as adenosine diphosphate (ADP) which needs to be recharged with foodstuff via much slower chemical reactions with oxygen (5). The formation of ATP within the cell uses carbohydrates, fats, and proteins. The absorption of carbohydrates forms glucose that is then used as an energy source by the cells. Two processes release energy from glucose; (1) glycolysis which does not require oxygen and (2) oxidation. The oxidative process releases much more energy than that released by glycolysis. For each molecule of glucose metabolized, the oxidative process produces thirty-four molecules of ATP whereas glycolysis produces only two molecules. The overall efficiency of energy transfer from glucose to ATP is about 39%; the remaining energy is lost as heat (of 686,000 calories of available energy in a mole of glucose, only 266,000 calories are stored in ATP). The 20% of total energy used by the cells is from the oxidation of glucose, and the remainder comes from fats and proteins (3). In addition to ATP as an immediate source of energy, the cells have another source of energy, known as phosphocreatine, that contains high-energy phosphate bonds. Cells contain phosphocreatine in amounts much larger than that of ATP. The ATP and phosphocreatine help in each other's resynthesis to build up their presence in the cells. These reactions to resynthesize ATP and phosphocreatine are much more rapid than the oxidative process. Therefore, ATP and phosphocreatine serve as the rapid and immediate sources of energy in tasks such as the 100-yard dash and weight lifting. 2.1.4 Metabolism During Physical Exertion The source of energy varies depending upon the intensity and duration of physical exertion. For intense physical exertions that last less than one minute, the body relies primarily on the existing energy supplies of ATP and phosphocreatine in the muscles. The anaerobic glycolytic processes are used to provide energy for tasks of intense levels that last about 1–2 minutes. Once the physical exertion continues for several minutes, the primary source of energy becomes dependent on the aerobic process. In general, daily energy expenditure varies from 2700 to 3000 kcal for men and 2000 to 2100 kcal for women. Several factors such as age, level of physical activity, health status, and genetics can modify the daily expenditure. During physical exercise, skeletal muscle blood flow, mean arterial pressure, systolic arterial pressure, cardiac output, and heart rate may increase as much as 175%, 15%, 50%, 120% and 100%, respectively (2). 2.2 Skeletal System The skeletal framework in the human body is needed to support its structure, muscles, nerves, organs, and blood vessels. This framework consists of “living girders,” bones that can sustain the stresses and strains produced by the body's weight and the daily tasks of living. The performance of any task requires movement of body segments relative to each other. The skeletal joints that connect two adjacent bones allow articulating motion. Therefore, joints provide mobility to the

musculoskeletal system. There are three types of joints in the human skeletal system: (1) synarthrodial joints that do not allow any relative motion (skull bones), (2) amphiarthrodial joints that allow slight motion (vertebrae), and (3) diathrodial joints (knee, elbow, hip and shoulder) that allow much more relative motion than the other two. In general, joints that have a higher degree of mobility or relative motion suffer from reduced stability that makes them more prone to injuries. 2.3 Biomechanics Biomechanics is the science of applying the laws of mechanics to understand the biology of work. The field of biomechanics relies on applying static and dynamic equilibrium conditions for calculating the forces experienced at the articulating bone surfaces (joints) during human body movements. When these forces appear repeatedly, they may cause trauma to the joint surfaces that gives rise to the development of musculoskeletal disorders. 2.3.1 Basic Concepts and Relevant Terminology (6) 2.3.1.1 Terms • Center of mass: A point in an object about which the mass is equally distributed. Gravity acts upon it as though all mass was concentrated at that point. • Moment of inertia (kg · m2 or N · msec2): The resistance to change in angular velocity depends upon the mass of the body and its distribution about the center of rotation. This resistance to change in angular velocity is called the moment of inertia (I).

In angular motion, the moment of force (M) is proportional to the angular acceleration (a). • Radius of gyration (r): In angular motion, the mass is not considered concentrated at the center of mass (or center of gravity). Therefore, the radius of gyration is defined as the radial distance from the axis of rotation at which the mass of the body could be concentrated without altering the moment of inertia of the body about that axis. • Ground reaction force (Newton): Forces imposed upon the body due to direct contact with the ground. • Center of pressure: The point at which the resultant force is applied. • Impulse (N · sec): The area under the force–time curve (or the integral of the force–time curve). • Linear momentum (kg · m/sec): Mass × linear velocity. • Angular momentum (kg · m2/sec): Moment of inertia × angular velocity. • Kinematics: The science of motion. • Kinetics: The science of forces (and vectors) and torques associated with the motion of the body. 2.3.1.2 Types of Motion The types of motion in joints include the following: • Rotatory or angular: Few joints have pure rotational movement. The superior radioulnar joint moves in a spin-like movement, and the hip also makes an almost pure arc during flexion and extension. • Translatory or linear (gliding): Compression, distraction, and gliding are most common. The lever arm moves towards the articulating surface, away from the surface, or in an anterior/posterior or medial/lateral direction. • Curvilinear: This is the most common type of motion; the majority of joints move by a combination of rotation and compression. As rotation occurs, the lever arm also glides in one or more directions. 2.3.1.3 Laws Relevant to Biomechanics • Law of inertia: Newton's first law of motion states that a body remains at rest or in uniform motion until acted upon by an unbalanced or outside set of forces. If the body is in equilibrium, then the

sum of all forces (FXYZ) is zero. For a body to be in static equilibrium, the following condition must be met:

• Law of acceleration: Newton's second law of motion states that the acceleration of a body is proportional to the unbalanced force acting upon it and inversely proportional to the mass of the body. For a body to be in dynamic equilibrium, the following condition must be met:

• Law of reaction: Newton's third law states that for every action there is an equal and opposite reaction. Forces come in pairs, and gravity exerts a force on all objects. Two objects in contact exert a force on each other. 2.3.1.4 Friction Friction is the resistance offered to the relative motion of two bodies in contact. As one body slides over another, the force that opposes the motion is called the force of friction. The magnitude depends on the kind of materials in contact with each other and how tightly the two surfaces are pressed together. Friction is a potential force that occurs only if movement is attempted. • Static friction: The force that opposes a body at rest from being put into motion

where F(N) = the perpendicular force holding the two bodies in contact(s) = the coefficient of static friction of the material • Kinetic friction: The force that opposes a body in motion from continuing that motion. Kinetic friction is always less than static friction.

(k) = the coefficient of kinetic friction of the material 2.3.1.5 Torque Torque or moment is the ability of any force to cause rotation of a lever arm. The use of pulleys changes the direction of muscle force. Its use can also improve the ability of the muscle to generate torque by increasing the line of action of the muscle away from the axis of the joint. In the human anatomy, the patella serves as a pulley to transfer muscle force from the quadriceps to the ligament connecting to the tibia. The patella also increases the lever arm of the tibio-femoral muscle ligament providing an increased torque to flex and extend the knee joint. 2.3.1.6 Joint Reaction Forces Joint reaction forces are the forces applied by one segment on its

adjacent segment during joint compression. Joint reaction forces come in pairs. Forces between two joint surfaces in contact with each other can be resolved into components, contact or normal force and shear force. The contact or normal force is the component of the force that lies perpendicular to the contacting surfaces, and the shear force is the component of force that lies parallel to the contacting surfaces. Force applied perpendicular to a bony lever and parallel to the contacting joint surfaces will create a torque around the joint axis and a shear between the joint surfaces. A force applied parallel to a bony lever but not intersecting the joint axis will create compression or distraction and a small amount of rotation. 2.3.1.7 Stress and Strain • Stress: Stress for a body that can be either stretched or compressed is the ratio of the applied force acting on the body to the cross-sectional area of the body. • Strain: The ratio of the change in length to the original length of a body that can be either stretched or compressed, is called the strain. The change in length (the strain) is directly proportional to the magnitude of the applied force, inversely proportional to the cross-sectional area of the body, and directly proportional to the original length:

Y Young's modulus of elasticity (material dependent) F magnitude of the applied force A cross-sectional area Lo original length L change in length • Limits: The elastic limit is the point where the stress on a body becomes so great that the atoms of the body are pulled permanently away from their equilibrium position in the lattice structure. When stress exceeds the elastic limit, the material will not return to its original size or shape when the stress is removed. • Shear: The elastic ability of a body to deform by changing shape when a stress is applied. 2.3.2 Application of Mechanical Lever System to Human Body Mechanical lever system laws are applicable to the human body. The bone, muscle, and joint are analogous to the mechanical lever system components, fulcrum, load, and effort. 2.3.2.1 Application of Lever Systems in Biomechanics • Muscle moment or lever arm: The perpendicular distance from the action line of the muscle or tendon to the axis of rotation of the joint (fulcrum). • Load moment or lever arm: The perpendicular distance between the center of gravity of the external load and the axis of rotation of the joint (fulcrum). Load, force, lever arm, and fulcrum relationships:

The three types of joints include the • Hinge joint, such as the elbow • Ball and socket joint, such as the hip • Plate joint, such as the atlas joint in the neck The mechanical laws of levers apply to each of these bone–muscle–joint systems. Each joint involves two bones that are in contact. A knowledge of the location, function, and limitations of anatomical levers involved in specific occupational movements is essential for ergonomic analysis and evaluation of operator-task systems. The three bone–joint–muscle lever systems include the: • First class lever: Fulcrum between load and force. Best suited for precision work. • Second class lever: Load between fulcrum and force. Best suited for ballistic motion. • Third class lever: Force between load and fulcrum. Best suite for heavy work. Figure 104.1 gives examples of bone–joint–muscle lever systems from human anatomy.

Figure 104.1. Three classes of lever systems. Examples from human anatomy (taken from Ref. 6). Each class of levers is specifically suited to perform certain types of movements and postural adjustments efficiently without undue strain and risk of accidents. There is a potential of failure in a operator-task system if the 1. Degree of movement required exceeds that of the lever system employed.

2. Lever system performs at a mechanical disadvantage. 3. Muscles used are too small. 4. Blood supply to the muscles is impaired. 5. Sensory feedback is defective. Example: Biomechanical Analysis of Holding an Object in Hand [see Figure 104.2]

Figure 104.2. Biomechanical analysis of holding a weight in the hand. Calculate the muscle force and the reaction force at the elbow joint (humerus against ulna).

Given:

Find:

Solution:

Resultant reaction forces at the elbow joint:

Conclusion: It takes muscle force levels more than seven times the weight being held by the worker because the human lever system works at a mechanical disadvantage. For this reason, even holding small weights for a prolonged period or repetitively can cause muscle sprain and strain in a worker. 2.3.2.2 Biomechanical Loading of the Wrist Previous studies have shown that cumulative trauma disorders such as tenosynovitis, bursitis, and carpal tunnel syndrome are associated with repeated deviations (or extensions) and excessive use of force by the hand. Biomechanical studies (7, 8) have shown that tasks that require excessive and repeated use of force in nonneutral (deviation and flexion) wrist/hand postures produce stress concentrations on the tendons and tendon sheaths. The buildup of excessive strain might weaken the tendon and/or create inflammatory reactions. The following example illustrates the use of biomechanical models of wrist to estimate tendon force while holding a tool. Example: Biomechanical Loading of the Wrist.Figure 104.3 shows the forces that act on the hand of a person who operates a screwdriver. Calculate the tendon force FT and the reaction (or radial supporting) force FR. For the purpose of this example, the grip force P acting at the finger may be assumed to be 1.5 newton. Assume a small hand in operation on a small grip size. Also assume that the subtended angle (wrist deviation or contact angle =

) is 40°.

Figure 104.3. Internal forces acting on the wrist during flexion (taken from Ref. 6). Solution: Using the equation for small object grasp (with a small hand) developed by Armstrong (9),

Using the simple pulley model of the wrist developed by Armstrong (10), the equation for FR is

2.3.3 Anthropometry Anthropometry is the science of measuring human body dimensions. Because people come in different sizes and shapes, it is critical to quantitate the characteristics of their body dimensions so that this information can be used to design workplaces. The major goal of anthropometry is to match the dimensions of workers' workstations with the appropriate body dimensions so that body postures used are neutral and exert minimal strain on the musculoskeletal systems. For example, people who have fifth percentile reach or short will be forced to extend their forearms excessively to reach for objects in workstations which are designed for a ninetieth percentile population or a population that has a longer reach. Therefore, it is critical to base workstation design on an anthropometric database that represents the user population well. The principles and practices of anthropometrics accommodate the diversity of human body size in designing equipment and workplace environments. In general, the anthropometric goal is to design a workplace so that 90% of the working population is accommodated. The anthropometric parameters to be measured depend on the application. For example, workstation designs generally require measuring linear dimensions of body segments such as height, length, depth, and breadth. However, clothing design requires measures of body segment circumferences and contours. In biomechanical modeling, anthropometric measures of interest are the location of body joint centers of rotation, body segment centers of mass, interjoint link lengths, and radii of gyration. A detailed discussion of these issues can be found in the literature (11, 12). 2.3.4 Work Physiology The job or work demand should be matched or be comparable to the individual's work capacity, otherwise the potential for injury increases. The field of work physiology gives us tools to quantify the physiological work demand of a task. The individual work capacity or capability depends on a variety of factors such as genetics, training/adaptation, gender, age, body size, environmental (temperature, altitude, and air pollution), and attitude/motivation. The science of work physiology is essential for performing ergonomic evaluation of a task at the workplace. All physical work requires the use of muscles. Therefore, the foundation of work physiology is based on the principles of classical exercise physiology (1, 5). The ergonomic evaluation of work uses appropriate physiological measures that can directly or indirectly assess the workers' cardiopulmonary performance. It is a common practice in the classical exercise physiology literature, to measure whole body oxygen consumption as a direct indicator of physiological work done, but this measure may not be practical to obtain at a workplace. Therefore, ergonomists have used heart rate as a practical (yet scientifically acceptable) surrogate of whole body oxygen consumption during task performance at workplace. For example, it is a common practice to calculate “work pulse” to indicate the physiological workload of a task performed by a worker. “Work pulse” is defined as the average heart rate during task performance minus the workers' resting heart rate. The use of resting heart rate in the calculation of work pulse incorporates the fitness level effect (a fitter person generally has a lower resting heart rate) of the worker. Based on research studies where both oxygen consumption and heart rate were measured, ergonomic criteria for “acceptable” work pulses for men and women are 35 beats per min and 30 beats per minutes, respectively (13). Based on research studies by work physiologists in academia and NIOSH, physiological workload guidelines have been developed for task performance for various time periods without causing whole body fatigue (14, 15). NIOSH determined that any manual task, performed for an 8-hour period at a workload of more than 33% of the worker's maximum oxygen consumption capacity will produce unacceptable fatigue (13, 15). For occasional lifting tasks that last 1 hour or less, metabolic energy costs should not exceed 9 kcal/min for physically fit males and 6.6 kcal/min for physically fit females. Primary tasks variable that affect metabolic demand during a lifting task are the load lifted, the vertical location at the beginning of the lift, the vertical distance, and the frequency of the lift. Based on these metabolic cost criteria, one can then determine the need for appropriate rest periods during task performance.

2.3.5 Psychophysics The field of ergonomics relates workplace factors to human response, so it is reasonable to apply established principles of psychology to capture the subjective perception of the workers who perform a task. One such principle is Fechner's law (16), that relates physical stimulus intensity (I) to strength of sensation (S) logarithmically:

where k is a constant. Stevens (17) further modified this as a power law in 1960 to accommodate a wider range of physical stimuli:

where k is a constant of a particular unit of measurement and the exponent n depends on the type of physical intensity being tested. The values of n for muscular force, handgrip force, and light brightness are 1.6, 1.7, and 0.33, respectively. Psychophysical methods are ideally suited for simultaneously assessing workers' subjective perceptions of exposure to a physical stimulus. For example, during a lifting task, the body is exposed to a physiological demand and a biomechanical stress in the low back area. The human brain does not evaluate this lifting task demand separately as physiological and biomechanical; rather it assesses the total demand simultaneously. The CNS performs the simultaneous evaluation, but modern day technology lacks methods for a directly and objectively measuring this simultaneous evaluation. Therefore, in the lifting task example, we have to rely on workers' perceptions of their CNS's assessment of the total (physiological and biomechanical) workload of the lifting task. The ergonomic literature provides examples of psychophysical scales developed to capture whole body cardiopulmonary exertion (BORG's scale) (18), localized muscle fatigue, body part discomfort, perceived sense of slipperiness (19), and perceived sense of fall (20). These scales have been tested and validated by objective measures. Because these measures use only a paper and pencil questionnaire (usually one-page long) type of scale, they are ideally suited for epidemiological studies that generally use large cohorts.

Occupational Ergonomics: Principles and Applications Amit Bhattacharya, Ph.D., Nancy Talbott, MS, PT, Laurel Kincl, MS 3 Physiological Effects Injuries of any source are attributable to trauma. Whether the trauma is chemical, mechanical, thermal or due to some other agent, otherwise normal tissue must respond to a load that is either too large (macrotrauma) or repeated too often for recovery to occur (microtrauma). Macrotrauma usually involves insults that are sudden and direct and produce immediate symptoms. Microtrauma, the focus of the problem in most overuse syndromes, is the result of repeated loads in a physiological range. It is unlikely that one incident of exposure to the smaller loads involved in microtrauma will result in dysfunction. Instead, it is the longstanding and recurrent nature of the trauma that is responsible for tissue changes. It is also important to recognize that the extent of the repetitive microtrauma is likely to continue to affect the tissue that undergoes the load and also will result in abnormal effects on structures at secondary sites that are attempting to compensate for the impaired function. This propagation of the original insult can lead to microtrauma at the secondary site and further compensation at a more distal or proximal segment. An example of such a chain of events occurs with shoulder bursitis. Inflammation of the bursa due to repetitive stress from painting leads to pain and limited movement in the glenohumeral joint. The scapulothoracic joint substitutes for the

limited movement and increases the tension in the upward rotators of the scapula (upper and lower trapezius). Due to overuse during the substitution, the lower trapezius, fatigues and cannot maintain the depression of the scapula. The scapula elevates as it upwardly rotates and results in abnormal force, pain, and dysfunction of the trapezius. Cervical spine disorders may result. As shown in Table 104.2, the sources of trauma are varied. The table summarizes some of the more common types of insults that can result in injury. The effects of these injuries can include decreased vascular supply, disruption of cells via direct force, damage by microorganism, or immunological responses that cause further harm to a wide range of tissues. If the initial insult is repeated, as in the case of overuse syndromes, further tissue reactions can perpetuate inflammation and result in changes in tissue size, cell size, cell function, and cell number. Most areas of the body consist of connective tissue along neurovascular bundles and muscle, and therefore a complex series of reactions occurs during the injury and repair process. Further complicating this scenario is the recognition that the effect of an insult on a group of cells is not always uniform. Cell injury is usually mild at the periphery of the application of a force. The damage to the cell can be reversible if it is limited in magnitude and short-lived. In such cases, the nucleus is preserved and continues to function. Cytoplasmic changes, however, occur. The injury produces an environment of decreased oxygen and energy and, under these conditions, the sodium pump cannot maintain the appropriate levels of ions. As Na+ and Cl– enter the cell, water follows and swelling occurs in the cytoplasm and in the mitochondria. Anaerobic glycolysis becomes the major source of energy production that results in higher levels of lactic acid. The lactic acid decreases pH slowing metabolism in the energydeprived state. Protein synthesis decreases, and organelles may be damaged if lysosomal enzymes leak. Because the nucleus and the cell membrane are still intact, energy will slowly be restored. In time, the cell will return to the normal state. Changes, though, have occurred during the period of recovery, and cell function is altered. It follows that the ability of the cell to resist another insult is decreased and it is more susceptible to a lethal injury during this period.

Occupational Ergonomics: Principles and Applications Amit Bhattacharya, Ph.D., Nancy Talbott, MS, PT, Laurel Kincl, MS 4 Common Upper Extremity Overuse Syndromes Space does not permit a detailed description of all impingements or entrapments, but common upper extremity conditions are described following. Summaries include common signs, symptoms, methods of diagnosis, and treatment. 4.1 Thoracic Outlet Syndrome Thoracic outlet syndrome (TOS) is a compressive neurovascular disorder of the upper extremity (78). Potential causes of this disorder include congenital abnormalities (cervical ribs), anatomic abnormalities of the anterior and middle scalene muscle, trauma, posture, tightness in the pectoralis minor muscle, and repetitive motion that involves continued abduction of the arms. Signs and symptoms are related to the compression of the nerves, arteries, and veins as they exit the cervical area and begin to transverse to the axilla (Fig. 104.10).

Figure 104.10. Thoracic outlet syndrome. The brachial plexus and related vascular structures can be compressed by the scalene muscles, the first rib, or the pectoralis minor muscle. Signs and symptoms include pain or paresthesia in the upper limb, especially in the medial arm, forearm, and fifth digit. Pain is nocturnal but, unlike carpal tunnel syndrome, radial digits are not affected in TOS. Elevation above the shoulder increases symptoms as do provocative tests that include hyperabduction of the shoulder. Diagnosis can be made through X ray (cervical ribs), vascular tests (venous and arterial obstructions), provocative tests, and ruling out peripheral entrapments. Treatment depends on cause. Conservatively, physical therapy may be initiated to normalize posture and muscle lengths. Work situations may be modified to lower work positions of arms. Surgery may be indicated for cervical ribs or other entrapments of the neurovascular bundle (104). 4.2 High Median Nerve Entrapment As the median nerve passes down the arm to the elbow, it travels anterior to the brachialis muscle and between the superficial and deep heads of the pronator teres muscle. It then traverses through the arch formed by the two heads of the flexor digitorum superficialis. Compression can occur as the nerve passes through the pronator teres or through the flexor digitorum superficialis. Signs and symptoms include pain in the proximal volar forearm and disturbances that may radiate proximally. Pain is increased with use of the upper extremity, especially forceful pronation and repeated pronation/supination. Unlike carpal tunnel syndrome, there is little nocturnal pain. Conservative treatment includes avoidance of aggravating activities, drugs, physical therapy, and splinting. Surgery may be indicated if motor and sensory symptoms persist (105). 4.3 Subacromial Impingement Subacromial impingement is a painful condition that results from contact between the rotator cuff, the subacromial bursa, and the undersurface of the anterior acromion. The supraspinatus tendon travels from the supraspinous fossa of the scapula underneath the coracoacromial arch to its attachment on the greater tuberosity of the humerus. In normal overhead elevation of the arm, the humerus must remain stable in a moving glenoid fossa. Kinematics involves complex dynamic stability of the rotators of the scapula, including a force couple that consists of the upper trapezius, the lower trapezius, and portions of the serratus anterior. These muscles contract throughout overhead movement of the humerus and cause upward rotation of the scapula without scapular elevation or depression. Stability is also needed to prevent superior movement of the

humeral head in the glenoid fossa. In a normal shoulder, the superior translatory force of the deltoid is opposed by the strong inferior and medial pull of the rotator cuff. The result is minimal superior movement of the humeral head as the arm flexes. In a patient who has impingement syndrome, there is likely to be an increase superior movement of the humeral head during elevation of the arm (Fig. 104.11). As the humeral head moves up, the supraspinatus is compressed against the acromion. Individuals who have this problem usually have a history of overhead activity in which the arm is repetitively abducted or flexed above the shoulder level.

Figure 104.11. A. At rest, a space exists between the humeral head and the acromion. The suprasinatus tendon occupies this space. B. With humeral elevation, the scapula upwardly rotates and the humerus externally rotates. If the upward rotation is accompanied by elevation, the suprahumeral space can decrease. Impingement of the supraspinatus tendon can result. Certain anatomical factors can also contribute to impingement. The presence of anterior acromial spurs, greater tuberosity spurs, inferior acromioclavicular osteophytes, or posteroglenoid rim spurs can narrow the outlet through which the supraspinatus tendon travels. It is expected that weakness in the rotator cuff that results in superior translation of the humeral head will be symptomatic earlier under these conditions. The clinical picture of impingement begins with a history of overhead movement and pain. Initially, pain is present only with elevation. Without relief of the stress, pain develops with activities of daily living and progresses to pain at rest and then pain at night. Adhesive capsulitis and rotator cuff muscle weakness may occur secondary to pain. Examination shows a loss of internal rotation and localized weakness of rotator cuff muscles. Scapular muscles may also be weak. Impingement signs such as forced shoulder flexion and cross-body adduction can be positive. Magnetic resonance is the most objective test for accurately assessing the status of the supraspinatus tendon. Conservative treatment of impingement includes modifying activities, physical therapy to restore rotator cuff and scapular strength, drugs, modifying the work position, and normalizing movement. If these are not successful, a range of surgical interventions can be considered.

4.4 Medial and Lateral Epicondylitis Repetitive tension overload of the wrist extensors, lateral epicondylitis, or the wrist flexors, medial epicondylitis, results in a degenerative condition rather than a typical inflammatory tendinitis. Unorganized fibrotic tissue found in the tendons of individuals who have these syndromes indicates a failed healing response to low-grade reinjury. Inflammatory cells are absent which supports the belief that the process is not acute and repair is not being attempted. Tendon arrangement is disorganized as illustrated by abnormal collagen orientation and abnormal maturation of collagen. Cellular affects include alteration in the size and shape of mitochondria, decreases in mitochondrial enzymes, differences in RNA transcription, and changes in calcium release and uptake. Intracytoplasmic calcifications, longitudinal collagen fiber splitting, and abnormal fiber cross-links have also been documented. Evidence suggests that mechanical, tensile, and vascular hypoxic injuries have occurred. As changes progress in the tendons, muscles become weak and inflexible and can no longer resist normal loads. As stresses persist, effects are cumulative, and degeneration continues (106). In lateral epicondylitis, the extensor carpi radialis brevis is involved in 100% of cases, the extensor digitorum in 30% (107). Medial epicondylitis usually involves the pronator teres and the flexor carpi radialis. Both result in aching pain in the tendon and muscle region and radiation of pain into the forearm. Symptoms increase with activity, with stretch, or with contraction of the involved muscles and decrease with rest. Lateral epicondylitis is accompanied by weak elbow extensors and posterior shoulder muscles. Medial epicondylitis is accompanied by weak elbow flexors and pronators. Treatment for epicondylitis aims to reduce load on the muscles by avoiding identified activities that stress the muscles. Physical therapy, drugs, splinting, work modification, and cortisone injections may be used. Surgical intervention is not frequent and depends on the cause determined. 4.5 High Radial Nerve Compression Compression of the radial nerve may occur proximal to the elbow as the nerve transverses the posterior aspect of the humerus. Trauma or pressure from crutches or support surfaces may be responsible. Strenuous muscular activity of elbow extensors may also contribute as the lateral head of the triceps constricts the radial nerve. Diagnosis is through EMG and nerve conduction studies. Therapy is conservative, although fractures may require surgical exploration. 4.6 Radial Tunnel Syndrome Compression of the posterior interosseous nerve, the deep branch of the radial nerve, can occur 6 to 8 cm distal to the lateral epicondyle. Etiology can include overuse of extensor carpi radialis brevis or the possible calcification of the origin of the extensor muscles. More often, compression occurs after unreduced anterior dislocation or after excision of the radial head. Symptoms include motor weakness of the extensors of the wrist and fingers and sparing of the extensor carpi radialis longus and brevis. Diagnosis is confirmed via EMG, and denervation changes are seen in the muscles supplied by the posterior interosseous nerve. Treatment is usually surgical to remove compressive bands or structures (78). 4.7 Ulnar Nerve Entrapment Ulnar nerve entrapment at the elbow is the second most frequently seen compression neuropathy. The ulnar nerve passes through the ulnar groove at the medial epicondyle and continues through the cubital tunnel. Compression can occur from hypertrophy of the origin of the flexor carpi ulnaris or from repeatedly resting the elbow on a flat surface. Fracture damage at the elbow and resultant scarring can also cause pressure on the ulnar nerve. Throwing can result in recurrent subluxation of the ulnar nerve over the medial epidoncyle and can also result in this type of neuropathy. Synovial cysts at the elbow and, more rarely, an abnormal insertion of the triceps brachii muscle may also cause symptoms in this part of the ulnar nerve. The cubital tunnel is 4 cm distal to medial epicondyle, and if the flexor-pronator aponeurosis tightens, symptoms may result. Common complaints that involve ulnar entrapment include symptoms of pain, numbness or tingling from elbow flexion, and weakness in finger abduction, thumb abduction, thumb and finger pinch, and power grip (78, 108). Diagnosis is based on motor and sensory nerve conduction studies. Conservative treatment should be

considered for patients who have intermittent symptoms, mild neuropathy, or mild neuropathy that is from an occupational cause. Avoiding repetitive elbow extension and flexion, resting the elbow, splinting the elbow in extension, job modification, and patient education are included. Surgical techniques have mixed results. 4.8 Carpal Tunnel Carpal tunnel syndrome (CTS) is the most common entrapment neuropathy in the United States. In 1988, the National Center for Health Statistics estimated that 1.89 million workers were affected with CTS. By 1995, that figure had increased to more than 5 million. Incidence was highest in women between the ages 35 and 55. More than 450,000 surgeries, it is estimated, are performed annually, usually in women in the 45–55 age group and in men over 65. It is estimated that up to 15% of workers in the high-risk industries are affected annually (109). In 1994, the Bureau of Labor and Statistics attributed 8.5% of the carpal tunnel cases to repetitive typing or key entry, 5.5% to repetitive use of tools, and 12% to repetitively grasping or moving objects (not tools) (110). Costs, including those for surgery, compensation, and expenses, can exceed $15,000 per worker (109). 4.8.1 Normal Anatomy of the Carpal Tunnel The carpal tunnel is an anatomic space in the anterior wrist that contains the median nerve and nine flexor tendons that pass from the forearm to the palm (Fig. 104.12). The floor is made up of the concave arch formed from the carpal bones and covered by intercarpal ligaments. The roof consists of the transverse carpal ligament as it extends from the scaphoid and trapezium bones to the pisiform and the hook of the hamate. The median nerve and its thirty to thirty-five fascicles are in line with the longitudinal axis of the third digit and contain sensory and motor fibers. The median nerve relays sensation from the thumb, index, middle, and the radial half of the fourth digit. Its motor fibers innervate the superficial head of the flexor pollicis brevis, the abductor pollicis brevis, the opponens pollicis, and the lumbricals of fingers one and two. The diameter of the carpal tunnel varies in the normal population, and changes with normal wrist movements. Wrist flexion decreases the cross-sectional area of the tunnel in the pisiform and hamate areas. Wrist extension also decreases tunnel size and alteration is noted only in the pisiform area. Normal pressures in the tunnel are approximately 2.5 mmHg at rest, 31 mmHg for wrist flexion, and 30 mmHg for wrist extension (111).

Figure 104.12. Carpal tunnel. A transverse view of the carpal tunnel. Flexor tendons and the median nerve travel under the flexor retinaculum. 4.8.2 Etiology of Carpal Tunnel Syndrome The major signs and symptoms of carpal tunnel syndrome are pain, tingling, numbness, paresthesia, and later, muscle weakness in the distribution of median nerve. Typically, symptoms are worse at night. All of these findings are considered the result of compression on the median nerve. Theoretically, impingement on the median nerve could be due to any disorder that increases the volume of the contents of the carpal tunnel or that decreases the volume of the carpal tunnel. Rarely,

enlargement of the median nerve may result in compression. In addition, the prevalence of a decrease in the volume of the carpal tunnel due to rheumatic disease or bony deformities is unusual. The majority of symptoms are linked to increased content in the carpal tunnel that leads to tendonitis and/or tenosynovitis (89). 4.8.3 Risk Factors of Carpal Tunnel Syndrome Work factors are the most strongly associated risk factors of carpal tunnel syndrome. People who perform jobs with high repetition and high load have an increased risk of developing carpal tunnel (112). Risk is even higher if these high-repetition and high-load jobs also involve extreme wrist flexion, wrist extension, pinching, or ulnar deviation. Occupations that use high force and highly repetitive manual movements include meat packers, grocery store and assembly line workers, jackhammer operators, computer operators, and grinders. Vibration and awkward postures are additional stressors that increase the risk of carpal tunnel syndrome. Normal lumbrical muscle incursion into the tunnel may also contribute to work-related CTS (113, 114). Because the size of the tunnel may decrease, rheumatoid tenosynovitis, edema, pregnancy, and hypothyroidism have been identified as conditions that may contribute to the development of CTS. 4.8.4 Pathogenesis of Carpal Tunnel Syndrome The contents of the carpal tunnel, including the transverse ligament and the carpal bones are displaced against the walls of the carpal tunnel by flexion and extension. MRIs in normal persons have demonstrated changes in the size of the carpal tunnel, the shape of the tunnel, and the alignment of the contents with wrist flexion and extension (115, 116). The median nerve migrates during these movements, and the tendons slide over a curved surface. Friction occurs resulting in tendon edema and inflammation. As the tendon increases in size, it occupies a greater space in the carpal tunnel and increases the volume of the contents. The greater volume in the enclosed compartment results in more pressure on the median nerve. Signs and symptoms develop (90). Studies confirm the differences in the pressure in the carpal tunnel between patients who have median nerve symptomatology and that in normal subjects. Pressures are lowest for both groups in the neutral position, increase significantly with wrist flexion, and increase even more with extension. Symptomatic patients exhibit significantly increased pressures in all positions. They also experience a prolonged recovery of pressures to baseline (117–120). Normal resting pressure in individuals without carpal tunnel syndrome is 2.5 mmHg; it is 32 mmHg in those who have carpal tunnel syndrome. Values for flexion and extension in the individual who have CTS range from 94– 110 mmHg, significantly higher than normal range of 30–31 mmHg (111). This elevation of pressure leads to an ischemic compromise of the median nerve. The epineural venous blood flow is impaired and results in venous congestion, hyperemia, and circulatory slowing. Continued epineural edema leads to endoneural edema and alteration of the local ionic environment. Axonal transport is interrupted, and pathological changes occur. Ischemia and the presence of exudate promote fibroblastic activity and proliferation of fibroblasts. The epineurium and endoneurium are destroyed and replaced with dense, fibrous scar tissue that shows abnormal impulse generation and transmission, conduction delay, nerve block, and sheath enlargement (111). If repetitive flexion and extension continue, the coefficient of friction will increase and lead to further increases in the tenosynovitis. The volume of the content in the tunnel will become larger and lead to progressive entrapment. The unrelieved compression creates an initial neurapraxia and segmental demyelination of axons. Without relief, the pressure creates an axonotmesis in which axon continuity is lost and wallerian degeneration takes place. 4.8.5 Carpal Tunnel Syndrome, Clinical Manifestations Signs and symptoms reflect the median nerve distribution. Pain and paresthesia, especially nocturnal pain and numbness, are the hallmarks of carpal tunnel syndrome. Complaints usually involve the distal forearm and wrist and radiate into the thumb, index, and middle fingers. Symptomatic individuals are often awakened at night by painful numbness. Sensory complaints usually precede motor symptoms. Thenar weakness and atrophy can be seen in advanced cases. Half of the individuals who have carpal tunnel syndrome have bilateral symptoms. If untreated, pain will persist, the thenar musculature will atrophy, grip and

pinch strength will be lost, and further sensory impairment will lead to clumsiness. 4.8.6 Carpal Tunnel Syndrome, Diagnosis Provocation tests for carpal tunnel include the tethered median-nerve stress test, Phalen's test, Tinel's sign, and carpal compression. The tethered mediannerve stress test positions the forearm in supination with hyperextension of the index finger. As the median nerve becomes ischemic, pain will increase. Phalen's test involves bilateral wrist flexion to 90° for one minute. Pain will increase within that period if the test is positive. Percussion over the carpal tunnel (Tinel's) or pressure applied over the flexor retinaculum (carpal compression) are also positive if pain increases during application. Diagnosis is confirmed by nerve conduction velocity studies of the median nerve. Changes in sensory conduction across the wrist are the most sensitive and most predictive (121). Magnetic resonance may be an aid, especially to rule out cervical radiculopathy. 4.8.7 Treatment of Carpal Tunnel Syndrome Early diagnosis and treatment are important because delay can result in irreversible median nerve damage, persistent symptoms, and permanent disability (78). Nonsurgical treatment is advised for patients who have mild symptoms, intermittent symptoms, or an acute flare-up from a specific condition. Conservative treatment includes steroid injection, oral steroids or nonsteroidal anti-inflammatory drugs, ergonomic measures, modification of occupation to avoid activities that precipitate the condition, wearing a splint that holds the wrist in the neutral position, patient education, and possible diuretics. Surgical treatment is indicated if there has been no relief after 2–3 months of conservative treatment, if the symptoms have been present for more than one year with motor and sensory NCV involvement, or if denervation as evidenced by fibrillation potentials on EMG is documented. The most common surgical technique is the release of the transverse carpal ligament. Approaches to the release may vary. Newer techniques are performed through limited incisions and involve less exposure and less manipulation of the nerve (122). Seventy-six percent of surgical patients experience return of normal two-point discrimination, and up to 70% have normal muscle strength return (123). Prognosis depends on the severity of the nerve entrapment, the cause, and the mode of treatment. Recovery of impaired sensation and motor function may take several months; full recovery is not always the end result.

Occupational Ergonomics: Principles and Applications Amit Bhattacharya, Ph.D., Nancy Talbott, MS, PT, Laurel Kincl, MS 5 Ergonomic Analysis of Low Back Loads and Pain 5.1 Specific Work-Related Injuries in the Low Back Region 5.1.1 Scope of Problem Low back pain and injuries among workers are major concerns of occupational safety and health personnel. Work-related back injuries continue to account for significant suffering, both physically and economically in the United States (124). Workers' compensation data support this. In the United States, approximately one-fourth of workers' compensation claims are filed for back injuries, and one-third of the costs are paid for back injury claims (125–127). The cost, however, is not only in the workers' compensation costs but in the loss of personal productivity, training of other workers to do the job, and medcal and supervisory time spent deciding the appropriateness of the injured worker's return to work and work restrictions (128). The Occupational Health Supplement to the 1988 National Health Interview Survey (129) provides data on back injuries in the United States. Guo analyzed some of these data and reported that back pain is a major cause of morbidity and lost production for U.S. workers. This article also identified the risk of back injury as the highest among construction workers for males and among nursing aides

for females. Some previously unidentified high-risk occupations include carpenters, automobile mechanics, maids, janitors, and hairdressers (130). The National Safety Council released a report in 1990 (131) identifying overexertion as the most common cause of occupational injury and the back as the body part most frequently injured and most costly to workers' compensation systems. Tables 104.3 and 104.4 show the incidence rates of nonfatal occupational injuries and illnesses according to industry and the number and percent distribution of days away from work for injuries to the neck, back, and shoulder (132). The transportation and public utilities industries have the highest incidence rates for neck, back, and shoulder injury. For the neck and back, 3–5 days away from work due to injury had the highest percentage distribution, and the shoulder had 31 days or more as the highest. Table 104.3. The Incidence Rates for Nonfatal Occupational Injuries and Illnesses Involving Days Away from Work per 10,000 Full-Time Workers by Industry and Body Part Affected by Injury or Illnessa

a

Industry

Neck Back Shoulder

Agriculture, forestry, and fishing Construction Manufacturing Mining Transportation and public utilities Wholesale and retail trade Finance, insurance, and real estate Services

3.8 5.0 3.7 5.9 10.1 3.7 1.4 3.8

71.9 89.7 56.8 56.5 108.2 78.6 14.8 55.1

14.8 15.7 13.6 10.3 25.3 9.4 2.8 9.7

Ref. 10.

Table 104.4. Number and Percentage Distribution of Nonfatal Occupational Injuries and Illnesses Involving Days Away from Work by Part of Body Affected by Injury or Illness and Number of Days Away from Work, 1996. Neck

Back

Shoulder

Days away from work Number Percent Number Percent Number Percent 1 day 2 days 3–5 days 6–10 days 11–20 days 21–30 days 31 days or more

5,740 5,106 7,877 4,115 3,118 1,651 6,902

16.6 14.8 22.8 11.9 9.0 4.8 20.0

63,494 60,770 117,052 72,369 58,973 29,044 88,905

12.9 12.4 23.9 14.8 12.0 5.9 18.1

12,862 9,938 18,435 12,549 11,112 6,049 25,567

13.3 10.3 19.1 13.0 11.5 6.3 26.5

median days away

5

6

8

5.1.2 Biomechanics of Spinal (Vertebral) Column and Low Back Region The spinal unit is a complex structure that allows humans to perform a range of physiological motions such as flexion, extension, lateral bending, and rotation around its long axis. The spinal unit supports the attachments of internal organs, the head, and the extremities. It also provides mobility via a series of motion segments that consist of vertebral bodies (bony structure), intervertebral discs (soft tissue structures) sandwiched between each vertebra, and the surrounding ligaments (Fig. 104.13). This series of motion segments constitutes the entire spinal unit. The movement of the motion segment is controlled by active contraction of muscles and passive support provided by ligaments. This anatomical structure consists of thirty-three vertebrae. The major muscle groups that support the lower back are erector spinae muscles, hip flexor and extensor muscles, and abdominal muscles. Because of the short lever arm (2.5 cm) of the erectores spinae muscles, it has to generate a very high force to keep the body from falling forward during lifting or holding weight in the sagittal plane. The hip flexors and extensors are instrumental during forward, backward, and lateral bending. The abdominal muscles are instrumental in providing stabilizing force to the spine and because they are located anterior to the spinal unit, they provide an assistive torque that reduces the force needed by the erectores spinae muscle. The action of the trunk muscles converts the thoracic and abdominal cavities (chambers) into nearly rigid-walled cylinders of (1) air (thoracic cavity) and (2) liquid and semisolid material (abdominal cavity). Both of these cylinders can resist part of the force generated in loading the trunk and, thereby, relieve the load on the spine itself.

Figure 104.13. Spinal column. The spinal unit also houses and protects the spinal cord and nerves along its entire length. The range of motion of the motion segments varies depending on their location in the spinal column and the mode of motion. The range of motion in the lumbosacral region is the largest for flexion/extension and the least for axial rotation. The range of motion in the lower thoracic region (T-10 to T-12) is the largest for flexion/extension and the least in axial rotation. Axial rotation in the cervical region is much larger than that available in the lumbar region (133, 134).

The literature provides data about the compressive strength of vertebrae at various levels of the spinal unit ranging from the cervical to the lumbar region (135, 136). In general, compressive strength is the smallest at the cervical level, and values increase for the thoracic and lumbar regions. Vertebral strength also decreases with age especially beyond 40 years. The rib cage provides strength and overall stability to the spinal column (137). 5.1.3 Intervertebral Disc About 20–30% of the entire height of the spinal column is made up of intervertebral discs. The disc has three components called nucleus pulposus, annulus fibrosus, and cartilaginous end plates. The intervertebral discs do not have a direct blood supply and do not carry any nerve endings. Upon the application of a load due to body segment weight associated with postures assumed, the fluid pressure within the nucleus pulposus (in a young healthy person, the inside of the disc is moist) pushes the surrounding annulus fibrosus and the end plates (Fig. 104.14). The orientations of the annulus fibers and the nucleus pulposus play a significant role in load transmission from one vertebra to the next.

Figure 104.14. Spinal disc loading (Adapted from Ref. 133). During normal physiological upright posture, the intervertebral disc along with facet joints is exposed primarily to compressive forces. However, during dynamic motions such as jumping and jogging, the disc loading may be severalfold higher than that observed in the static case. The types of stresses produced within the disc depend on the nature of physiological motion performed. For example, during bending (flexion, extension, and lateral bending), one side of the disc is subjected to compression and the opposite side experiences tensile load (Fig. 104.14). The compressive loading causes bulging of disc material which in the pathological case may impinge on the spinal nerve to cause back pain. Figures 104.15 and 104.16 show relative intradiscal pressure during various postures and the effect of various lumbar support on intradiscal pressure, respectively (138) (Fig. 106.17).

Figure 104.15. Effect of seat back inclinations on relative spinal disc pressure taken from Ref. 6.

Figure 104.16. Effect of body postures on relative spinal disc pressure taken from Ref. 6.

Figure 104.17. Potential pinching of spinal nerve during lifting weight taken from Ref. 6.

Axial rotation of the torso with respect to the pelvis causes torsional loads that result in shear stresses in the discs. Research studies have shown that bending and torsional loadings are more dangerous than compressive loads. Intervertebral discs have time-dependent properties such as fatigue and viscoelasticity characterized by hysteresis, creep, and relaxation. These properties determine disc failure due either to short-duration (high-amplitude load, i.e., jerk lifting) or longduration (low-amplitude load) application of forces (11). 5.1.4 Biomechanical Aspects of Low Back Pain Low back pain symptoms can result from one of the following: disc degeneration, injuries and tumors of the spine, disc inflammation due to arthritis, and referred pain from abdominal or pelvic organs. A majority of low back pain cases (68%) fall into the category of disc degeneration (5). A variety of factors such as physical, psychosomatic, biochemical, and anatomical can cause back pain. The biomechanical reason for back pain is explained in the following: Because disc materials do not have any nerve endings, simple compression forces do not create pain. Rather, during compression, the disc material can protrude outside and impinge upon the spinal nerves that surround the disc and the vertebral units. In the static spine, an increase in the lumbosacral angle can cause an increase in lumbar lordosis. This is called “swayback.” About 75% of all postural low back pain is due to excessive lordosis. Pain caused is possibly due to facet impingement and irritation. See Fig. 104.17 (16, 139). Kinetic low back pain is caused by abnormal body movement such as sudden movement or nonsymmetrical bending. Standing in a forward-flexed posture of 10–15° causes high loading of lumbar discs. This type of loading can also occur in a seated forward position. These are common postures used in many industrial occupations that are responsible for occupational low back pain (5) (Table 104.5). Table 104.5. List of Aggravators of Low Back Paina Descriptions of Tasks/Postures That Aggravate Low Back Pain Constant standing and sitting Low working height that makes worker bend Extended reach to perform a task continuously for more than one minute Turning and twisting of the trunk, such as lifting weights from the front to the side Crouching posture for more than 1 minute Repeated sustained work above the shoulder Seats with improper low back support Handling of loads with shifting weights of > 25 lb, such as liquids Fixed work place height; frequent (one or more per minute) lifting or lowering of objects that weigh > 25 pounds Handling of bulky loads whose physical dimensions are > 20 inches on any side of the box Sustained (> 30-second period) pushing or pulling of loads in excess of 40 lb Bending trunk below the waist for > 1 minute a

Ref. 5.

5.1.5 Analysis of Holding Weight in Hand and Its Effect on the Low Back Lumber-Sacral Joint The most common forces that determine the effect on the lower back during lifting in the sagittal plane are (1) gravity (BW, weight carried by the body) [external], (2) tension in the deep muscles of the back and in the muscles of the abdominal wall [internal], (3) pressure in the internal cavities of the trunk (intra-abdominal and intrathoracic) [internal], and (4) force transmitted by the spinal column [internal]. To determine the forces on the spine at a given level, say the L5/S1 point, it is necessary to consider the external (gravity) forces on the body above the L5/S1 level and the internal forces that resist or support the external forces. The stability of the spine depends largely on the action of the extrinsic support provided by the trunk muscles. The portion of the trunk above the L5/S1 is about 30% of body weight. The force of a weight lifted by the arms is transmitted to the spinal column by the shoulder-girdle muscles, principally the trapezius, and then to the abdominal cylinder and to the pelvis, partly through the spinal column but also through the rigid rib cage. Example: The following data (Fig. 104.18) are given for a sagittal lifting activity (140). Calculate the back muscle force F(B) and the magnitude and direction of reaction force R at the L5/S1 joint. The person weighs 170 lb. Assume that F(B) is at an angle a = 40° to the vertical. Assume the right horizontal as the positive x-axis and vertical down as the positive y-axis (adapted from Ref. 18).

Figure 104.18. Example of a biomechanical analysis of a lifting weight problem. Solution:

(2) From Equations (1) and (2),

Conclusion: The back muscle force F(B) needed to sustain the posture and the 200-lb weight in the hand is about nine times that of the weight held because the body's lever system works at a

mechanical disadvantage.

Occupational Ergonomics: Principles and Applications Amit Bhattacharya, Ph.D., Nancy Talbott, MS, PT, Laurel Kincl, MS 6 Job Analysis Ergonomic job analysis is used to identify and measure potential hazards. From such an analysis, solutions for reducing or eliminating ergonomic risk factors can be developed. Potential ergonomic hazards include work conditions that cause fatigue, overexertion, injuries, and chronic musculoskeletal disorders (141). Physical, mental, and perceptual demands due to these hazards can be measured during a job analysis (142). The type of job analysis can vary according to the purpose and scope of the investigation but generally involves the following elements: (1) identifying the potential hazards, (2) preparing to conduct a job analysis, (3) conducting the job analysis, (4) interpreting the results, (5) developing solutions, and (6) documentation (143). 6.1 Identifying Potential Hazards First a review of injury data should be completed. Statistics on injury, absenteeism, or a high turnover rate on specific jobs can be obtained from plant records and/or employee surveys. These jobs can then be ranked according to their severity. After this has been completed, jobs of the highest severity should be investigated further. Walk-through surveys can then be conducted for the selected jobs. Background information about the job, employee and supervisor interviews, checklists, and surveys can be used to collect information (143). Various checklists (144) that have been developed can be modified to analyze specific jobs as needed. 6.2 Preparing to Conduct a Job Analysis Observation and direct measurements can be used to evaluate the ergonomic hazards identified. The equipment required will depend on the type of hazard and the specific type of job analysis to be evaluated. Table 104.6 displays some examples of measurements that may be quantified for physical, physiological, and mental work. Some items that are generally useful for job analysis are video cameras, tape measures, force gauges, and stopwatches. More sophisticated, equipment and techniques such as electromyography, accelerometers, finger force sensors, and electrogoniometers are available and have been applied in the field (143). Table 104.6. Measurements for a Job Analysisa Type of Measurement Biomechanical

Motions

Timed activity analysis

Environmental

Example of Measurement Reach height and distance Weight and dimension of material handled Forces and torques Frequency Degree of rotation Duration Dexterity/coordination requirements Pattern of activities during shift Time to perform a task Frequency of more demanding tasks Temperature, humidity, air movement

Noise Illumination Shift schedule Other physical or chemical factors (odors, work surface) Use of protective clothing or equipment Mental and perceptual Visual and auditory requirements Complexity Information handling/decision making requirements External pacing Productivity during shift (units/hour, interruptions, etc.) Quality of output (defects, incomplete work, etc) Physiological Heart rate Blood pressure Oxygen consumption Surface electromyography Psychophysical scaling (perceived exertion, comfort, stress) Minute ventilation Body temperature a

Ref. 142.

Methods and tools have been developed for analyzing a specific risk factor for some job tasks. For example, Waters et al. recently studied some methods for assessing manual materials handling (MMH) tasks (145). The review article provides information for selecting appropriate methods for a particular job/task and included the following: 1. The revised National of Institute for Occupational Safety and Health (NIOSH) lifting equation (146) 2. The University of Michigan 3D Static Strength Prediction Program (147) 3. The Oxylog portable consumption meter (148) 4. The Polar portable heart rate monitor 5. The University of Michigan Energy Expenditure Program (149) 6. The Chattanooga Corporation Lumbar Motion Monitor 7. The Ohio State University risk assessment model (150) 8. The Snook and Ciriello psychophysical approach for assessing manual lifting demands (151) After equipment and/or an analysis tool are selected, a sampling strategy must be developed. A typical work period should be observed under normal conditions. At least three workers who perform the job and the entire work cycle should be observed at least three times. If the job does not have repetitive cycles or is an irregular task, the workers may need to be observed randomly during an extended period to capture all tasks. 6.3 Conducting the Job Analysis For accuracy, the job should be disrupted as little as possible. A large part of the job analysis will be direct observation of the work tasks. Discussion with workers to obtain information on specific elements of the job and supervisors to obtain information on the broader view of the operations and the feasibility of future proposed changes can also be conducted. Finally, preliminary measurements of the worksite should be recorded, including a dimensioned sketch of the layout of the workstation

and tools. The specific measurements would depend on the type of analysis performed and the equipment used. 6.4 Interpreting the Results To analyze the results, the job must be broken down in tasks or subtasks. Then, each task can be evaluated for such factors as force required, posture assumed, repetitiveness, duration of work and recovery periods, and other physical exposures such as vibration or cold temperatures. Factors such as these increase the risk of cumulative trauma disorders. However currently, there are no known limits for force and repetition that are safe for the working population. Estimates can be made from strength data, anthropometry, physiological data, psychosocial data, and integrated models. 6.5 Developing Solutions The results from the ergonomic job analysis should include methods to eliminate, reduce, or control the ergonomic hazards identified. This can involve modifying equipment, workstation layout, work practices, and raw material packaging and administrative changes such as employee rotation, longer rest breaks, and reduced production rates. A follow-up job analysis should be conducted after the interventions are in place to ensure the feasibility and effectiveness of any changes made to the job. 6.6 Documentation Finally, a report of the entire job analysis process should be written. It can include the reason that the analysis was done, what risk factors were identified, how they were evaluated, and recommendations for correcting the problem (143).

Occupational Ergonomics: Principles and Applications Amit Bhattacharya, Ph.D., Nancy Talbott, MS, PT, Laurel Kincl, MS 7 Regulations and Recommendations The Occupational Safety and Health Administration (OSHA) has issued guidelines for controlling ergonomic hazards in the meatpacking industry (152). OSHA is also developing a general ergonomic standard and will soon issue a draft of the proposed standard (153). California has a standard that regulates repetitive motion injuries (154). In addition, the American National Standards Institute's (ANSI) Z-365 (155) is another proposed general ergonomic standard for cumulative trauma disorders. 7.1 Occupational Safety and Health Administration's Meatpacking and Proposed Ergonomics Standards The Occupational Safety and Health Act of 1970 states that it is the general duty of all employers to provide a workplace free of serious hazards. These hazards include ergonomic hazards. The management of worker safety and health protection includes all hazards even if they are not specified by a U.S. federal regulation. In 1990, OSHA issued general guidelines (OSHA 3123) for ergonomic management programs, specifically for the meatpacking industry. OSHA's proposed ergonomics standard, if passed, will be an enforceable regulation in the United States. A draft of the national standard is expected to become public in the near future. 7.1.1 Ergonomic Program Management Guidelines for Meatpacking Plants These guidelines are neither a standard nor a regulation but provide information on the approach that employers should take to determine if ergonomically-related problems exist in their workplaces, to identify the nature and location of these problems, and to implement measures to reduce or eliminate these problems. The guidelines are divided into three sections (1) management commitment and employee involvement, (2) program elements, and (3) detailed guidance and examples. The management commitment and employee involvement section stresses the importance of management's commitment and a team approach to a successful program. It states that a written program should be developed and communicated to all employees. The importance of employee involvement in the program and in decision making is also stressed in this section. Finally, regular review and evaluation of the program by managers, supervisors, and employees is recommended.

The section on program elements includes four major elements: worksite analysis, hazard prevention and control, medical management, and training and education. The worksite analysis objectives described are to recognize, identify, and correct ergonomic hazards. The hazard prevention and control element includes guidelines for using engineering controls, work practice controls, personal protective equipment, and administrative controls. The third major element involves guidelines for implementing a medical management system that identifies, evaluates, treats signs and symptoms, and aids in preventing ergonomically related injuries and illnesses. Finally, the element that involves training and education presents information to inform employees about the ergonomic hazards to which they are exposed and their role in the ergonomics program. The last section on detailed guidance and examples gives more specific information on an ergonomics program related to the meatpacking industry. A recommended worksite analysis for ergonomics is described in detail. It provides information on gathering information from available resources, conducting baseline screening surveys, performing ergonomic job hazard analyses both before and after controls are in place, and conducting periodic surveys and follow-ups to evaluate changes. This section also includes specific examples of engineering controls for hazard prevention and control and medical management programs to prevent and cumulative trauma disorders in the meatpacking industry (152). 7.1.2 OSHA's Ergonomics Standard The proposed standard includes the following sections: introduction, purpose, scope and application, identification of problem jobs, control of workplace risk factor exposures, ergonomic design and controls for new or changed jobs, training, medical management, recordkeeping, effective date and definitions. The standard can be found in 29 CFR 1910.500 or the OSHA homepage (http://www.OSHA.gov) on the internet. This standard is scheduled to go into effect, January 2001. The purpose of this standard is to prevent and reduce the severity of musculoskeletal disorders by controlling the exposure to risk factors, medical management, information dissemination, technology, and management and employee participation in ergonomic programs. The scope covers employees who are exposed to risk factors that are measured in hours and employees who have recorded work-related musculoskeletal disorders. The application of this standard depends on the extent of workplace risk factors and work-related musculoskeletal disorders. The identification of problem jobs includes sections on employee information, a workplace risk factor checklist, and start-up dates. An OSHA workplace risk factor checklist would be provided in an appendix. The control of workplace risk factor exposures describes the requirements for determining and implementing an appropriate strategy to control problem jobs by reducing or preventing employee exposure to workplace ergonomic risk factors. The ergonomic design and controls for new or changed jobs section includes ways to prevent or control problem jobs when changes are made in the workplace in the future. This includes information on eliminating workplace risk factors in job design and the employer's responsibilities when job changes introduce signal risk factors. The training section describes the training requirements for the employee. The medical management section describes the requirements for plans to assess and manage musculoskeletal disorders among employees. Such plans are proposed to provide for early assessment and treatment of work-related musculoskeletal disorders and to reduce their severity and prevent progression. The recordkeeping section details the maintenance of records according to the requirements of 29 CFR 1910.20. Finally, the effective date and definitions for the standard will be provided (153). 7.2 California's Repetitive Motion Injury Standard This standard, Title 8, General Industry Safety Orders, Article 106, Ergonomics, Section 5110, Repetitive Motion Injuries, went into effect on July 3, 1997 in California. This standard is comprised of three sections, including scope and application, a repetitive motion injury program, and satisfaction of an employer's obligation. The Scope and Application states that the standard applies to a job, process, or operation where at

least one employee has a repetitive motion injury (RMI) diagnosed by a licensed physician. This RMI must be work-related and must be reported by the employee within 12 months. Employers are exempt from this standard if they have fewer than nine employees. The employer is required to develop an RMI program. This program is required to include a worksite evaluation, control of exposures that have caused RMIs and training of employees. The worksite evaluation involves evaluating jobs, processes, or operation for exposures that may cause RMIs. Control of exposures may include engineering controls and administrative controls and must eliminate the exposure or at least minimize it. The training must include an explanation of the employer's program, potential exposures, symptoms and consequences of injuries caused by repetitive motion, the importance of reporting RMIs and finally, the methods that are being implemented to minimize exposures. Finally, the section on satisfaction of an employer's obligation states that the employer is obligated to take measures that would greatly reduce RMIs as long as they do not impose excessive costs (154). 7.3 ANSI Z-365 The ANSI Z-365 draft consensus standard for cumulative trauma disorders (CTDs) is a proposed voluntary standard, which means that it is not regulated and not enforceable. It is comprised of four sections, including purpose and scope, definitions, conformance, and the process. The Purpose and Scope of the standard is divided into three sections. The Purpose and Intended Audience states the standard and describes the processes and principles for controlling work-related CTDs. A definition of CTDs is given, including their causes and their characteristics. The Scope states that the aim of the standard is to control work-related CTDs that arise from manual lifting, assembly, manipulation of tools, machinery and other devices, and other stresses on muscles, nerves, tendons, and associated soft tissues of the body. The Scope also describes the ergonomic considerations such as work postures, work layout, force requirements, vibration, work rates, tool design, and flexibility of workstations to accommodate individual variations. Finally, the Standard Content describes that the scope will be addressed through surveillance, job analysis and design, management of CTD cases, and training sections. The definition section contains words relevant to understanding the standard. The section on conformance explains that the standards/guidelines in this document would be voluntary and, would be established by consensus. This section also discusses the wording used in the document. A section on the process includes background to explain how and why the standard came about. The CTD Control Process proposes a CTD control program that includes management responsibilities, training, employee involvement, surveillance, evaluation and management of CTD cases, job analysis and job design, and intervention. Finally the Program Implementation states that priorities will have to be established by individual employers to determine which component should be addressed first. This section also states that regular evaluations are required to determine if the evaluation and reduction of CTD risk factors is beneficial. Occupational Ergonomics: Principles and Applications Bibliography

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Occupational Vibration Donald E. Wasserman, MSEE, MBA 1 Vibration Defined 1.1 Vibratory Motion Vibration (2), by definition, is a vector quantity, consisting of both a magnitude (or intensity) and direction. Vibration motion measured at any one point is defined by a total of six vectors: three mutually perpendicular “linear vectors” and three corresponding “rotational vectors” called “pitch,” “yaw,” and “roll.” Most occupational vibration measurements use only the three mutually linear vectors, ignoring the rotational vectors. Hand–arm vibration measurements use a special vector coordinate system, as shown in Figure 105.1. Whole-body vibration measurements use another special vector coordinate system, as shown in Figure 105.2.

Figure 105.1. Coordinate system directions used to measure hand–arm vibration acceleration for use with ANSI S3.34 and ACGIH standards.

Figure 105.2. Coordinate system directions used to measure whole-body vibration acceleration for use with ANSI S3.18 and ACGIH standards. 1.1.1 Types of Vibratory Motion Vibratory motion can be: periodic or nonperiodic; continuous, impact, or random. The motion can be purely single sinusoidal (or pure tone, if it were audible) or a complex mixture containing many sinusoids. If sinusoidal motion is completed in one second, then the vibration frequency is one cycle/second or 1 hertz (Hz). If five complete cycles of sinusoidal motion occur in one second, then 5 Hz is the frequency; 1000 complete cycles in one second is 1 kHz (kilohertz), and so on. 1.2 Measures of Intensity There are three interrelated descriptors of motion, which can be used as measures of intensity: displacement, velocity, or acceleration. Displacement is motion measured away from some reference point. The units of displacement can be meters, feet, centimeters, inches, and so on. Velocity is the time rate of change of displacement, or the speed of a moving object. The units of velocity are distance divided by time; feet per second, meters per second, and so forth. Acceleration is the time rate of change of velocity. The units of acceleration are usually either in meters per second per second or in gravity g units, where 1 g = 9.81 meters per second per second. Acceleration is usually the measurement quantity of choice as the “intensity” descriptor for human vibration measurements. Since displacement, velocity, and acceleration are all related mathematically, it is necessary to measure only one of these parameters, and the remaining two parameters can be mathematically obtained; for example, if acceleration is measured, mathematically integrating the acceleration function will yield velocity. Repeating the integration process on the velocity function will yield displacement. 1.3 Vibration Acceleration Intensity Characterizing vibration acceleration intensity, as measured in the workplace, necessitates that the following issues be addressed: • What is needed is a typical measure of the vibration acceleration intensity or “dose” impinging on the worker's body without collecting data over the entire workday. • Workplace vibration is usually complex and time-varying and thus contains a mixture of vibration frequencies. What parameter of acceleration intensity represents vibration dose? If we choose to measure only the “peak,” or the largest value of acceleration occuring in a specific direction over a specific measurement time period, does this represent the vibration dose impinging on the worker? Probably not, since there is no guarantee that this motion will be repeated. The answer to these questions is to use a type of average vibration acceleration intensity measurement called root-mean-squared (rms) acceleration, which is more desirable than using peak measurements. If varying peak acceleration values do occur during measurements, then the rms mathematical process can account for these values. The Following equation defines RMS acceleration: (1) where: a = measured acceleration (m/s2 or g value) t = time (s)T = measurement time period, (s) In equation (1), acceleration values are first squared; thus negative values become positive. All such

values are summed or integrated over the measurement period; the sum is then divided by the total measurement time T; the square root of the resulting value yields the rms value. For pure sinusoidal motion the rms acceleration value is (2) where A = peak acceleration, (m/s2 or g values). 1.4 Using Fourier Spectrum Analysis to Calculate Workplace Vibration Workplace vibration is rarely a single sinusoid, but is usually complex motion containing several vibration frequencies. A frequency separation method for data analysis known as Fourier spectrum analysis is needed and is used to • Convert time-domain data to corresponding frequency domain data, thus forming a spectrum • Determine the acceleration intensity contribution to the overall vibration spectrum for each frequency in the spectrum Fourier spectrum analysis is analogus to chemical spectrophotometry, where the concentration of each element forming a compound is separated into its elements and graphically displayed as a line spectrum, in which position of each vertical spectral line denotes an element's wavelength in the spectrum and the corresponding height of each line represents the concentration that element contributes to the compound. In the 1800s a French mathematician, Jean-Baptiste Fourier (1768– 1830), showed that a linear, complex waveform was composed of a mathematical series of sines and cosines of differing frequencies and amplitudes as given by equation 3: (3) where the a and b terms are intensity values for each sinusoid frequency that constitutes the spectrum. The a0 term is the zero hertz [or DC] component and is seldom used. The Fourier spectrum computer's output is a graphical line spectrum; the graph's abscissa is vibration frequency in hertz; the graph's ordinate is intensity in rms acceleration in m/s2 or g units. Spectrum analysis is a very powerful analytical method for identifying the frequency/intensity characteristics of different vibration sources. 1.5 Vibration Transmissibility Often many times it is necessary to determine how vibration entering and then exiting a structure is modified. An often used descriptive term is called vibration transmissibility, which is defined as the ratio of output acceleration exiting the structure divided by input acceleration entering the structure, as a function of vibration frequency, with both input and output vibration moving in the same direction. Transmissibility is a “transfer function” and is a dimensionless number; a transmissibility ratio equaling unity (one) means that there is no change between input and output; a ratio less than one (< 1) means that the structure internally reduces the input vibration; a ratio greater than one (> 1) means that the structure is internally amplifying the original vibration and may be “resonating,” which is an undesirable phenomenon, discussed next. 1.6 Resonance Virtually all physical structures vibrate when mechanically excited, this is also true of the human body. There are certain preferred vibration frequencies (known as “natural” or resonance frequencies) where a structure will naturally vibrate with very little externally applied input excitation. Simply stated, resonance is the tendency of a mechanical system (or the human body) to act in concert with externally generated vibration and to internally amplify the input vibration and exacerbate its effects. Maximum vibration energy is transmitted from the source to the receiver at resonance. Resonance is undesirable, is uncontrollable, and can be very destructive (This is one reason why soldiers never march across a bridge); in rare instances, resonance can be managed and

controlled, and can even be desirable, such as in the construction of certain musical instruments (3). Undeniably, in the workplace situation, resonance is totally undesirable, because if a vibrating source such as a vehicle or powered handtool should emit frequencies corresponding to human resonances, and a worker's body comes in physical contact with that source, most likely the emitted vibration would be internally amplified by the worker's body. Resonance is the Achilles heal of human vulnerability to vibration and must be avoided. 1.7 Damping and Isolation Finally, there are two main engineering methods for minimizing vibration: damping and isolation. Vibration damping is the conversion of mechanical vibratory motion into a corresponding small amount of heat, due to the deformation of the damping material as in a glove containing viscoelastic materials. Vibration isolation is the intentional design mismatch or alteration of the pathway(s) between the vibration source and the receiver; as, for example, in an automotive shock absorber.

Occupational Vibration Donald E. Wasserman, MSEE, MBA 2 Hand-Arm Vibration 2.1 Health Effects and Epidemiology There are some 2 million workers (1) in the United States alone exposed to hand–arm vibration (HAV). These include workers using vibrating pneumatic, electric, and gasoline-powered handtools such as chippers, grinders, impact hammers, rachet hammers, jack-leg-type drills, demolition tools, jackhammers, chain saws, and brush removers. The negative health effects (4, 5) of this HAV exposure have been recognized since the very early 1900s. In 1911, Loriga in Italy reported white fingers in workers using pneumatic tools in mining (6). During 1918, in a study of cutters and carvers using vibrating pneumatic tools in the Oolitic limestone mines of Bedford, Indiana, the famous occupational physician, Dr. Alice Hamilton, first reported some 80% prevalence of a disease of their hands called white finger or Raynaud's phenomenon (7). Since those early times there have been numerous studies causally linking HAV exposure with disease of the fingers and hands (4, 5). Typically this condition's initial symptoms are attacks of tingling and/or numbness (paresthesia) in the fingers, followed by an initial attack of finger whitening (or blanching), usually of one finger, lasting a few minutes. As the vibration exposure continues, blanching attacks increase in number and severity, and include multiple fingers; cold temperatures often trigger these blanching attacks (4, 5), and smoking exacerbates this condition (8). Often the thumbs are the very last of the fingers to be affected. A small percentage of the population (mostly women) have naturally occurring Raynaud's disease, which is not an occupationally induced condition, but the symptoms of which are similar to the condition described above. Through the years occupationally induced Raynaud's has undergone several name changes from “dead fingers” to “white fingers,” to Raynaud's phenomenon, to “vibration white fingers” (VWF), and currently hand–arm vibration syndrome (HAVS). For the most part HAVS is an irreversible condition of the fingers and hands after the blanching process is well under way. Calcium channel blockers are the current medications used to relieve some signs and symptoms of HAVS; however, these agents are palliative and not a cure. The timespan from when a worker begins using a vibrating handtool to the appearance of the first white fingertip is called the latent period and has been used as the HAVS peripheral vascular time marker for many years. Depending on the type of tool used, worker exposure time and conditions, and attendent tool acceleration levels, the latent period can vary from as little as a few months to several years. Generally, higher tool acceleration levels result in shorter latent periods (4, 5, 9–11). Patient diagnosis of HAVS consists of a vibrating toolwork and hobby history and a specialized battery of medical tests (4, 5), which include finger plethysmography and Doppler blood flow tests, finger systolic blood pressure, two-point discrimination, finger depth sense, vibrometry/frequency threshold measurements, and thermal hot/cold perception of the fingers.

In 1968 the Taylor–Pelmear medical classification system for scaling HAVS (11) was introduced and used successfully until 1986. Table 105.1 describes the Taylor–Pelmear system. The initial stages of tingling and/or whitening are noted as OT, ON, TN, followed by the initial blanching Stage 1, whose timespan is defined as the aforementioned latent period. With increased vibration exposure, overall finger blanching progresses, more fingers become involved, and the person's ability to perform work and overall quality of life steadily deteriorate in Stage 2, 3, and 4. If vibration exposure is allowed to continue beyond Stage 4, finger gangrene (tissue necrosis) can occur. In reality, in most cases the pain and suffering from HAVS is so extensive in these latter Stages that the worker is essentially forced to change jobs, thus avoiding any finger gangrene. Sadly, the white finger condition will persist despite removal of the vibration source. In 1986 the Taylor–Pelmear system was modified by the Stockholm scale, which separately grades each hand for peripheral vascular loss (Table 105.2) and sensorineural loss (Table 105.3). This modified system was requested by the international medical community because it was found that some HAVS patients never advanced to the finger blanching stages and only the early neurological stages occured with vibration exposure (12). Table 105.1. Taylor–Pelmear Medical Classification System for HAV Syndromea Stage

Condition of Digits

0 No blanching of digits OT, ON Intermittent tingling, or TN numbness, or both Blanching of one or more 1 fingertips with or without tingling and numbness Blanching of one or more 2 fingers with numbness; usually confined to winter Extensive blanching; frequent 3 episodes, summer as well as winter Extensive blanching; most 4 fingers; frequent episodes, summer and winter a

Work and Social Interference No complaints No interference with activities No interference with activities Slight interference with home and social activities; no interference at work Definite interference at work, at home, and with social activities; restriction of hobbies Occupation changed to avoid further vibration exposure because of severity of symptoms and signs

Adapted from Ref. 9.

Table 105.2. Stockholm (Modified Taylor–Pelmear) Peripheral Vascular Classification System for HAV Syndromea Stage 0 1 2

Grade

Description

No attacks Occasional attacks affecting only the tips of one or more Mild fingers Occasional attacks affecting distal and middle (rarely also Moderate proximal) phalanges of one or more fingers

3

Severe Very severe

4

a

Frequent attacks affecting all phalanges of most fingers As in stage 3, with trophic skin changes in the fingertips

Adapted from Ref. 4.

Table 105.3. Stockholm (Modified Taylor–Pelmear) Sensorineural Classification System for HAV Syndromea Stagesa 0SN 1SN 2SN 3SN

a

Symptoms Exposed to vibration but no symptoms Intermittent numbness, with or without tingling Intermittent or persistent numbness, reduced sensory perception Intermittent or persistent numbness, reduced tactile discrimination and/or manipulative dexterity

Adapted from Ref. 4.

Although the major components of HAVS are neurological and peripheral vascular, there are other conditions related to HAV exposure which are suspect but less documentated; these include some prevalence of elbow and wrist osteoarthritis and some damage to the articular cartilage due to impact tool vibration exposure (13) and a tonic vibration reflex that reduces tactile sensibility because the hand muscles are involuntarily contracting (14). The occurence of HAV-induced carpal tunnel syndrome (CTS), a compression syndrome, with or without HAVS (4, 5) can also occur. A combined medical treatment is needed for both CTS and HAVS. Worldwide there have been numerous epidemiology studies of vibration-induced HAVS over the years. It is common to discover about a 50% prevalence of HAVS with relatively short latent periods of 1–2.5 years in foundry workers, for example, using vibrating pneumatic handtools (4, 5, 9–11, 15). 2.2 Hand–Arm Vibration Measurements (2, 4, 5) Only the salient aspects of measuring both HAV and WBV in the workplace are discussed here. It is beyond the scope of this chapter to present the numerous details of this process, which are available elsewhere (2). 2.2.1 Premeasurement First, it is not advisable to attempt vibration measurements without careful planning; it is advisable to initially perform a “walk through” visit before conducting any vibration measurements, preferably with a portable videocamcorder, recording those vibration processes that are to be measured together with personal taped narration. Try to observe both new and experienced workers performing the same or similar vibration tasks. Later replay the video at normal speed and then in slow motion to observe how the worker(s) interact with the vibration process. Recognize that many work processes can be divided into a series of work, rest, vibration, and nonvibration steps; these steps and the vibration work cycle form the basis of the required measurements. Finally, plan how, when, and where the vibration measurements will be made for minimal disruption of production lines, and so on. When possible, test adjacent to, but not directly in, the actual production line area using experienced workers performing their regular tasks in a normal manner. Sometimes off-hour testing can be done, using experienced workers to avoid work disruptions. During testing it is advisable to maintain both written test logs and a videotape of the actual vibration measurements. 2.2.2 Workplace Vibration Testing Occupational vibration testing consists of the basic elements

shown in Figure 105.3. For a single HAV measurement, three axes (viz., triaxial), mutually perpendicular, linear, rms acceleration measurements are required to quantify, record, and analyze the vibration impinging on a worker's hand. When both hands operate a tool, two triaxial simultaneous measurements are needed.

Figure 105.3. Typical equipment setup used to measure occupational hand–arm or whole-body vibration (adapted from Ref. 2). All accelerometers used should be identical, very lightweight (