arbete och hälsa | vetenskaplig skriftserie isbn 91-7045-664-x issn 0346-7821 http://www.niwl.se/ nr 2002:19 Scientific Basis for Swedish Occupational Standards xxiii Ed. Johan Montelius Criteria Group for Occupational Standards National Institute for Working Life S-112 79 Stockholm, Sweden Translation: Frances Van Sant (Except for the consensus report on Toluene wich was written in English) National Institute for Working Life ARBETE OCH HÄLSA Editor-in-chief: Staffan Marklund Co-editors: Mikael Bergenheim, Anders Kjellberg, Birgitta Meding, Bo Melin, Gunnar Rosén and Ewa Wigaeus Tornqvist © National Institut for Working Life & authors 2002 National Institute for Working Life S-112 79 Stockholm Sweden ISBN 91–7045–664–X ISSN 0346–7821 http://www.niwl.se/ Printed at Elanders Gotab, Stockholm Arbete och Hälsa Arbete och Hälsa (Work and Health) is a scientific report series published by the National Institute for Working Life. The series presents research by the Institute’s own researchers as well as by others, both within and outside of Sweden. The series publishes scientific original works, disser- tations, criteria documents and literature surveys. Arbete och Hälsa has a broad target- group and welcomes articles in different areas. The language is most often English, but also Swedish manuscripts are welcome. Summaries in Swedish and English as well as the complete original text are available at www.niwl.se/ as from 1997. Preface The Criteria Group of the Swedish National Institute for Working Life (NIWL) has the task of gathering and evaluating data which can be used as a scientific basis for the proposal of occupational exposure limits given by the Swedish Work Environment Authority (SWEA). In most cases a scientific basis is written on request from the SWEA. The Criteria Group shall not propose a numerical occupational exposure limit value but, as far as possible, give a dose-response/dose-effect relationship and the critical effect of occupational exposure. In searching of the literature several databases are used, such as RTECS, Toxline, Medline, Cancerlit, Nioshtic and Riskline. Also information in existing criteria documents is used, e.g. documents from WHO, EU, US NIOSH, the Dutch Expert Committee for Occupational Standards (DECOS) and the Nordic Expert Group. In some cases criteria documents are produced within the Criteria Group, often in collaboration with DECOS or US NIOSH. Evaluations are made of all relevant published original papers found in the searches. In some cases information from handbooks and reports from e.g. US NIOSH and US EPA is used. A draft consensus report is written by the secretariat or by a scientist appointed by the secretariat. The author of the draft is indicated under Contents. A qualified evaluation is made of the information in the references. In some cases the information can be omitted if some criteria are not fulfilled. In some cases such information is included in the report but with a comment why the data are not included in the evaluation. After discussion in the Criteria Group the drafts are approved and accepted as a consensus report from the group. They are sent to the SWEA. This is the 23rd volume that is published and it contains consensus reports approved by the Criteria Group during the period July 2001 to June 2002. These and previously published consensus reports are listed in the Appendix (p 57). Johan Högberg Johan Montelius Chairman Secretary The Criteria Group has the following membership (as of June, 2002) Maria Albin Dept Environ Occup Medicine, University Hospital, Lund Olav Axelson Dept Environ Occup Medicine, University Hospital, Linköping Sture Bengtsson Swedish Industrial Workers Union Sven Bergström Swedish Trade Union Confederation Anders Boman Dept Environ Occup Dermatology, Norrbacka, Stockholm Christer Edling Dept Environ Occup Medicine, University Hospital, Uppsala Sten Flodström National Chemicals Inspectorate Lars Erik Folkesson Swedish Metal Workers' Union Johan Högberg chairman Dept Environmental Medicine, Karolinska Institutet and Natl Inst for Working Life Anders Iregren Dept for Work and Health, Natl Inst for Working Life Gunnar Johanson v. chairman Dept Environmental Medicine, Karolinska Institutet and Natl Inst for Working Life Bengt Järvholm Dept Environ Occup Medicine, University Hospital, Umeå Kjell Larsson Dept Environmental Medicine, Karolinska Institutet Carola Lidén Dept Environ Occup Dermatology, Norrbacka, Stockholm Johan Montelius secretary Dept for Work and Health, Natl Inst for Working Life Bengt Sjögren Dept Environmental Medicine, Karolinska Institutet Kerstin Wahlberg observer Swedish Work Environment Authority Olof Vesterberg Natl Inst for Working Life Robert Wålinder observer Swedish Work Environment Authority Contents Consensus report for: 4,4´-Methylenedianiline (MDA)1 1 Methylisocyanate (MIC) and Isocyanic Acid (ICA)2 15 Methylisoamylketone 3 29 Toluene4 34 Summary 56 Sammanfattning (in Swedish) 56 Appendix: Consensus reports in this and previous volumes 57 1 Drafted by Minna Tullberg, Karolinska Institutet, Department of Microbiology, Pathology and Immunology, Division of Pathology, Huddinge University Hospital, Sweden. 2 Drafted by Kerstin Engström, Turku Regional Institute of Occupational Health, Finland; Jyrki Liesivuori, Finnish Institute of Occupational Health, Kuopio, Finland. 3 Drafted by Birgitta Lindell, Department for Work and Health, National Institute for Working Life, Sweden. 4 Drafted by Grete Östergaard, Institute of Food Safety and Nutrition, Danish Veterinary and Food Agency, Søborg, Denmark. 1Consensus Report for 4,4´-Methylenedianiline (MDA) October 3, 2001 This work is an update of the Consensus Report published in 1987 (36). Chemical and physical data. Uses CAS No.: 101-77-9 Synonyms: 4,4´-diaminodiphenylmethane bis-(4-aminophenyl)-methane 4,4´-methylenebisaniline 4-(4-aminobenzyl)-aniline Formula: C13H14N2 Structure: Molecular weight: 198.27 Boiling point: 398 – 399 °C Melting point: 91.5 – 92 °C Vapor pressure: 1.2 kPa (9 mm Hg) at 232 °C; calculated 1.33 x 10-7 kPa (1 x 10-6 mm Hg) at 20 °C (16) Solubility: 0.1 g/100 g water Distribution coefficient: log Poctanol/water = 1.6 (22) Pure 4,4´-methylenedianiline at room temperature is a crystalline powder with a weak amine odor. It dissolves easily in alcohol, benzene and ether, but only slightly in water (1). Industrial grade MDA is a liquid, and typically has the following composition: 4,4´-MDA 60% MDA polymers 36% 2,4´-MDA 3.5% 2,2´-MDA < 0.1% water < 300 ppm aniline < 100 ppm. MDA is used in the production of various polymers and plastics. Most of it is used in closed systems to make methylenediphenyl diisocyanate (MDI) and CH2NH2 NH2 2polyisocyanates for use in production of polyurethane. MDA is also added to rubber as an antioxidant and to epoxy products and neoprene as a hardener. Smaller amounts are/were used in rust preventives and azo dyes for leather and hair (36). Occupational exposure occurs mostly during production of MDA or polymers. However, emissions of MDA and MDI have also been detected around use of finished products – heating polyurethane foam, for example (12, 25, 38). MDA and its metabolites have been found in hydrolyzed urine and plasma from workers exposed to MDI, and exposure to MDI thus implies potential exposure to MDA (50). To measure individual exposure to airborne MDA, samples are taken on acid-treated fiberglass filters and analyzed by liquid chromatography (16). Uptake, biotransformation, excretion Uptake At room temperature MDA occurs almost entirely in aerosol form, and it can be taken up via respiratory passages, skin and digestive tract. In occupational exposures, most MDA enters the body via skin and respiratory passages (9). Several reports describe skin uptake as the primary path of exposure (7, 8, 37). One study reviews several cases of MDA-induced hepatitis in a plastics factory during the years 1966 – 1972. The problems caused by the poor work environ- ment were addressed, and in 1971 the workers had begun using helmets with separate air intakes and the reported MDA concentrations in the air were low: in the range 1.6 to 4.4 µg/m3 outside the helmet and 0.6 µg/m3 inside the helmet. Despite these improvements, there were more cases of liver damage during 1971 – 72. All the workers who developed hepatitis had been kneading a paste of MDA plastic protected only by cotton gloves, and had worked with their hands in the plastic for several hours per day. Workers with other tasks at the workplace were unaffected (37). Skin uptake was quantified by Brunmark et al.: five volunteers were given patch tests with 0.75 – 2.25 µmol MDA in isopropanol. An average uptake of 28% was calculated from analysis of the MDA remaining in the patch test chamber after 1 hour of exposure (6). Calculations based on this result yield an uptake rate of 0.24 µg/cm2/hour. Biotransformation Biotransformation has been found to be an important factor in acute toxicity, genotoxicity and elimination of MDA (2, 6, 27, 31). Several metabolites and a few MDA-metabolizing enzymes have been identified, but mapping of MDA metabolism is far from complete. N-Acetyl MDA has been identified as the primary metabolite in the urine of exposed workers (8). MDA and acetyl-MDA have also been found as hemoglobin adducts (47). Valine adducts in hemoglobin were isolated in order to identify the genotoxic reactive intermediates of MDA. A valine adduct of hemoglobin was 3identified, and it was proposed that the reactive intermediate is 1-[(4-imino-2,5- cyclohexadiene-1-ylidene)-methyl]-4-aminobenzene (31). The cytochrome P450 system has been found to be involved, and several reactive intermediates have been identified (2, 27) (see Figure 1). MDA treatment of rats increases enzyme activity in their livers (57). CH2NH2 NH2 CHNH2 NH NH2 CH2CH3CONH NH2 CH2NH2 NO CH2N NH2 NH2CH2N CH2OCN NCO MDI MDA OH CH2 N H CH2N NH2 NH2 O CH2N Figure 1. Proposed metabolism of MDA. References are given within parentheses. cyt. P450 = cytochrome P450 monooxygenase; Hb = hemoglobin. Hb-adducts hydrolysis (50) peroxidase (31) O-glucuronidation N-glucuronidation N-sulfation oxidation O-, N-glucuronidation condensation oxidation cyt. P450 N-Acetyltransferase (27) (8) ? 4It is important to bear in mind that MDI may be hydrolyzed to MDA in vivo. Rats were exposed to an aerosol of MDI for 3 to 12 months, and although no MDA was detected in the exposure chamber both MDA and acetyl-MDA were identified in the rats’ urine and the corresponding hemoglobin adducts in their blood (50). MDA and acetyl-MDA have also been detected in urine and as hemoglobin adducts in blood from workers exposed only to MDI (47). The analysis method, however, involves hydrolysis of the plasma or urine, which means that MDI can be transformed to MDA during the sample processing. Figure 1 summarizes the proposed metabolic pathways for MDA. In a study of elimination and absorption kinetics, 5 volunteers were given 1 hour of epicutaneous exposure to 0.75 – 2.25 µmol MDA. It was found that the plasma concentration was highest 3 to 7 hours later, and the calculated half time for the elimination phase was 9 to 19 hours. The highest levels in urine were noted 6 to 11 hours after the exposure, and the half time in urine was 4 to 11 hours (6). A similar study of workers exposed to heated polyurethane foam showed con- siderably longer elimination times: the half times were determined to be 10 to 22 days in plasma and 59 to 73 hours in urine (13). The observation that in these two studies the half time for elimination was shorter in urine than in plasma can be explained by assuming that MDA probably exists in at least two compartments with different half times (free and protein-bound MDA, for example), or that the observation time was too brief. Excretion MDA is excreted in both urine and feces (16). The distribution between excretion pathways varies with species and method of administration (16). There are no complete data from human exposures. However, Brunmark et al. report that only 16% of absorbed MDA was excreted in urine within 50 hours of exposure and that MDA in urine was subsequently below the detection limit. They conclude that MDA is probably excreted and metabolized in other ways as well, and may be stored in the body (6). Biological measures of exposure Since skin uptake accounts for a large portion of total uptake, methods have been developed for biological exposure monitoring. These are gas-chromatographic- mass spectrophotometric analysis of MDA and acetyl-MDA in urine (7), in plasma (13), and as hemoglobin adducts in blood (50). Analysis of MDA con- centrations in urine is suitable for estimating exposures during a workshift, but several measurements both post-shift and pre-shift are required if the results are to be reliable (6, 12). For estimating exposures over longer periods, there is a method based on quantitative analysis of MDA and acetyl-MDA in hemoglobin adducts (47, 50). Workers exposed to low levels of MDA or MDI were examined, and acetyl-MDA and MDA were found (after hydrolysis) in the urine and blood of most of them, although in most cases the air concentration was below the de- tection limit. Biological exposure monitoring is proposed as a sensitive method of assessing exposure to MDA and MDI (47, 50). In order to identify high exposure 5during a single workshift, and for quantitative estimates of longer exposures, measurements of MDA in both blood and urine are recommended (47). However, this method can not differentiate between MDA exposure and MDI exposure. Toxic effects Human data Several incidents of MDA poisoning have been reported, after oral intake of contaminated bread or drink as well as after occupational exposure via skin or inhalation. In all cases the amount of MDA taken up is unknown. Regardless of whether the uptake was dermal, oral or via inhalation, the result was liver damage (3, 5, 32, 33, 37, 44, 53). A retrospective study reviews 12 cases of chemical hepatitis that occurred in the 1966-1972 period at a plastics factory where these workers made insulation containing MDA. They kneaded a plastic paste with their hands, and became ill after one to three weeks of work at the factory but one or two days after beginning work with the plastic. All 12 had jaundice and dark urine, and 5 also had skin rashes. In the report it is pointed out that other workers doing the same task did not become ill, and that differences in exposure or in sensitivity to MDA were possible reasons for the difference in risk (37). Another case report describes floorlayers who developed jaundice and stomach cramps. They used MDA as hardener in an epoxy glue that they mixed on site (3). A third study describes an occupational exposure in a chemical plant where large quantities of MDA were used. A young man was exposed to MDA when the air filtration system broke down, spraying MDA into the air as a yellow dust. While the system was being repaired he took a lunch break and removed the top part of his protective overalls, leaving his upper body covered only by a T-shirt. In addition to stomach pains he developed a skin rash and hepatitis, as well as acute myocardiopathy (5). Yet another study describes a man who drank an unknown amount of MDA dissolved in potassium carbonate and butyrolactone. His vision was affected, and he developed jaundice and temporary heart problems. Eighteen months later his vision had still not recovered (44). The most remarkable poisoning incident occurred in Epping, U.K, in 1965, when 84 persons developed jaundice and other symptoms after eating bread contaminated with MDA (32). The jaundice lasted for 1.5 to 4 months, and the patients felt unwell for several weeks after the symptoms of jaundice had disappeared. Liver biopsies revealed portal inflammation, eosinophil infiltration, bile duct inflammation, bile stasis and various degrees of cell damage (33). All the victims recovered without further complications within a year (33). A bit of the contaminated bread was analyzed, and the total dose was estimated to have been about 3 mg/kg body weight. It is emphasized, however, that this figure is highly speculative: only one slice of bread was analyzed, it is known that the MDA was unevenly distributed in the contaminated flour, the analysis method is presumably inaccurate, and the total bread intake of each individual is unknown (20, 32). 6Skin Direct contact with MDA colors the skin, nails and hair yellow (10), and several studies have demonstrated that MDA is a contact allergen. Several case reports describe positive reactions to patch tests with MDA, but it is uncertain whether MDA induced the hypersensitivity or the positive reactions are due to a cross- reaction with similar para-amino compounds (4, 16, 18, 28, 45). Studies by Von Gailhofer and Kanerva, however, indicate that MDA causes skin sensitization. Von Gailhofer and Ludvan (18) found that 39 of 202 patients had positive reactions to MDA only, and their data indicate that workers in chemical laboratories have an elevated risk of developing contact allergy to MDA. Kanerva et al. (28) found that MDA was the second most common contact allergen on patch tests given to patients with suspected occupational dermatosis after contact with plastic chemicals. They tested 174 patients with their ‘plastic and glue series no. 1,’ and 2.9% were positive to MDA. In a previous study the same group had examined 6 patients occupationally exposed to isocyanates: 5 of them had reactions to both MDA and MDI, 3 to an additional 5 isocyanates, and 1 to MDA alone. Primary sensitization to MDA and a cross-reaction to MDI is the most likely explanation, but primary sensitization to MDI is also a possibility (15). One case of photosensitization has been reported (34). Animal data MDA is acutely toxic to several animal species, including rats, mice, guinea pigs, rabbits and dogs, when given in oral doses of 100 to 800 mg/kg (23). Cats have been found to be more sensitive, with liver and kidney damage after a single dose of 10 mg/kg (16). Acute toxic effects in all species are liver and kidney damage, and cats also go blind. The LD50 for oral administration to Wistar rats was 830 mg MDA/kg body weight (43). Rats exposed to MDA for several weeks developed liver cirrhosis (39, 58) or liver fibrosis and inflammation in the portal area (46). In rats given 1000 ppm MDA in diet for 8 to 40 weeks, there was intraheptic bile duct proliferation in addition to a duration-dependent increase in the previously mentioned types of liver damage (17). Hypertrophy of adrenals, uterus and thyroid was observed in ovarectomized rats given MDA by gavage in doses of 150 mg/kg/day for two weeks (54). Other effects seen in rats given similar subchronic doses are degeneration of liver, kidneys and spleen (17, 19, 24). In a 13-week study by the National Toxicology Program (NTP), rats and mice were given MDA dihydrochloride (MDA-2HCl) in drinking water, 0 to 800 mg/liter. There were dose-dependent increases in the frequencies of hyperplasias in bile ducts and thyroids, and at the highest dose goiter as well. The highest dose having no observed effect was 100 mg/liter (≈ 6 - 7 mg/kg for rats, 13 - 16 mg/kg for mice) (40). For rats, the toxicity threshold for a single exposure is estimated to be between 25 and 75 mg/kg (2). Recent morphological studies have shown that bile duct epithelial cells are damaged first. Necrosis in intrahepatic bile ducts had become severe within 6 hours after oral administration of MDA (50 mg/kg), and less severe damage was seen in small 7peripheral bile ducts (30). Kanz et al. found toxic compounds in the bile of rats 4 hours after a single oral dose of 250 mg/kg (29). Effects on drug-metabolizing enzymes in rat liver were studied, and the lowest single dose that yielded a significant effect was 50 mg/kg (57). Dose-effect relationships observed in studies with rats and mice are summarized in Table 1. Mutagenicity Several experiments, both in vivo and in vitro, have shown that MDA is mutagenic and genotoxic. MDA was found to be mutagenic in Salmonella typhimurium strains TA98 and TA100 only after activation with S9. The N- acetylated metabolites were not mutagenic under the same conditions (41, 52). MDA induced DNA repair in rat hepatocytes (38). Exposure to MDA in vivo induced sister chromatid exchanges in bone marrow cells and DNA strand breaks in hepatic cells (41, 42). MDA-induced DNA adducts have been detected with the 32P-postlabeling method and by injection of radioactive MDA (48, 55). MDA is clearly mutagenic in vitro and genotoxic in vivo. Carcinogenicity The International Agency for Research on Cancer (IARC) has classified MDA as “possibly carcinogenic to humans” (Group 2B) (25, 26). The European Commission has placed MDA in Category 2, with the risk description “may cause cancer” (R45) (14). The results of cancer studies with rats and mice are summarized in Table 2 and below. Animal data The NTP conducted a well controlled cancer study in which Fischer-344 rats and B6C3F mice of both sexes, 50 animals per group, were given MDA in drinking water (two different dose levels) for two years. The study showed that MDA caused tumors in liver and thyroid (56). The rats received water containing 0, 150 or 300 mg MDA hydrochloride/liter, corresponding to a daily MDA intake of 0, 9- 10 or 16-19 mg/kg. There was no effect on survival. At the highest dose level, the incidences of thyroid carcinomas in male rats and of thyroid adenomas in female rats were significantly higher than in controls. A dose-related increase of hepato- cellular neoplastic noduli was also observed in the male rats (56). The same test protocol was followed with the mice. They were given drinking water containing 0, 150 or 300 mg MDA hydrochloride/liter, corresponding to a daily MDA intake of 0, 19-25, or 43-57 mg/kg. For males, survival was significantly lower in the high-dose group than in the low-dose or control groups. As with the rats, the greatest effects were on liver and thyroid. The incidences of hyperplasia and adenoma in thyroid were significantly higher in both males and females receiving the high dose. A dose-dependent increase in hepatocellular carcinomas was observed in both sexes, and of hepatocellular adenomas in females (56). Smaller 8or poorly documented studies also indicate that MDA has a carcinogenic effect (39, 46, 51). Using the results of the animal experiments made by the NTP, the Dutch Expert Committee on Occupational Standards (DECOS) made a linear extrapolation yielding a calculated increase of cancer risk for MDA exposure: 4 x 10-5 with 40 years of exposure to 0.009 mg MDA/m3 (21). Human data Seldén et al. studied 550 Swedish power plant workers probably exposed to MDA and found one case of bladder cancer (expected 0.6) (49). Cragle et al. compared 263 chemical process workers with 271 unexposed workers from the same factory and found five cases of bladder cancer among the exposed workers (expected 0.66), a significant increase (11). None of the five had worked with MDA, although there was indirect exposure. All five, however, had been exposed to trichloroethylene (11). Liss and Guirguis report one case of bladder cancer among 10 former workers in a factory that made epoxy paste, all of whom had been poisoned by MDA at some time during the 1967-1976 period (35). In a follow-up 24 years after the accident in Epping, where exposure consisted of high doses of MDA in contaminated bread consumed during a fairly short period, no chronic effect of the poisoning could be seen in the 68 victims (81%) that could be traced. This study unfortunately has little value, since the docu- mentation is poor and the investigation was incomplete (20). In summary, studies of occupational exposure are limited by the small number of cases and the prevalence of mixed exposures. Several aromatic amines similar to MDA can cause bladder cancer in humans. Reproduction toxicity A study of uncertain relevance reports that MDA injected into the yolks of fertile eggs reduces hatching frequency and has teratogenic effects (25). Dose-effect / dose-response relationships There are no data from which to derive a dose-effect or dose-response relationship for occupational exposure to MDA. An injection of 2-10 mg/kg given to rats resulted in enzyme induction, but no toxic effects (57). In the NTP study, the highest dose without toxic effect was 100 mg MDA-2HCl/liter (≈ 6-7 mg/kg for rats, 13-16 mg/kg for mice) for 13 weeks (40). Effects on rats and mice are summarized in Tables 1 and 2. 9Table 1. Dose-effect relationships observed in laboratory animals exposed to MDA. (i.p = intraperitoneal; p.o. = per os; d.w. = as MDA dihydrochloride in drinking water) Exposure method, dose (mg/kg b.w.) Effects Ref. Rats single dose, i.p. 2 or 10 No effect. 57 50 or 100 Increased enzyme activity in livers. 57 single dose, p.o. 25 Increased serum-alanine aminotransferase activity and liver weight. 2 50 Six hours after exposure: severe necrosis in intrahepatic bile ducts, moderate damage to smaller ducts. 30 75 or 125 or 225 Increased serum-alanine aminotransferase and γ -glutamyl transferase activity; dose-dependent increases in total serum bilirubin and liver weights; reduced bile flow. 2 100 Necrosis and neutrophil infiltration in bile ducts, hepato-cellular necrosis, neutrophil infiltration in parenchyme. 2 250 4 hours after exposure: severe cellular necrosis in main bile duct, minimal damage in peripheral ducts. 24 hours after exposure: hepatocellular necrosis, cytolysis of cortical thymocytes, bile stasis. 29 multiple doses, i.p. 2 (daily, 3 days) Increased enzyme activity in liver. 57 50 (daily, 3 days) Reduced cytochrome P450 activity, increased enzyme activity in liver. 57 multiple doses, p.o. 20 or 50 (daily, 3 days) DNA adducts. 55 8-600 (daily, 10 days) Necrotic inflammation in gall bladders and bile ducts. 19 150 or 2001 (daily, 14 days) Hypertrophy in adrenals, thyroids and uterus of ovarectomized females. 54 0.1% MDA in diet, (8 to 40 weeks) Time-dependent increase of proliferation, necrosis and fibrosis in bile duct epithelium and infiltration of oval cells. Reduced weight gain. 17 38 (daily, 5 days/week, 17 weeks) Cirrhosis. 39 50 or 1002 mg/l, d.w. (13 weeks) No effect. 40 200 mg/l, d.w. (13 weeks) Reduced water intake. 40 400 mg/l, d.w. (13 weeks) Some rats had hyperplasia in bile ducts, hypertrophy in pituitary, hyperplasia in thyroid. 40 800 mg/l, d.w. (13 weeks) All rats had hyperplasia in bile ducts, hypertrophy in pituitary, hyperplasia in thyroid and reduced weight gain. 40 Mice3 25 or 50 or 1004 mg/l (13 weeks) No effect. 40 200 mg/l (13 weeks) Reduced weight gain. 40 400 mg/l (13 weeks) Hyperplasia in bile ducts. 40 150-300 mg/l (104 weeks) Kidney damage with mineralization of renal papillae. 56 1the animals were given MDA dihydrochloride. 2 ≈ 6-7 mg/kg. 3All exposures in mice are to MDA dihydrochloride in drinking water. 4 ≈13-16 mg/kg b.w. 10 Table 2. Occurrence of tumors in rats and mice, 50 males or 50 females per group, exposed to MDA dihydrochloride in drinking water for 2 years (56). The numbers in the last two columns give the number of affected animals in the group of 50. Species, Tumors No. affected animals exposure males females Rats (Fischer-344) Unexposed controls Liver: hepatocellular neoplastic nodules 1 4 Thyroid: follicular hyperplasia adenoma carcinoma 1 1 0 1 0 0 150 mg/l (9-10 mg/kg/day) Liver: hepatocellular neoplastic nodules 12* 8 300 mg/l (16-19 mg/kg/day) Liver: hepatocellular neoplastic nodules 25* 8 Thyroid: follicular hyperplasia adenoma carcinoma 2 3 7* 3 17* 2 Mice (B6C3F) Unexposed controls Liver: hepatocellular adenoma carcinoma 7 10 3 1 Thyroid: follicular hyperplasia adenoma carcinoma 0 0 0 0 0 0 150 mg/l (19-25 mg/kg/day) Liver: hepatocellular adenoma carcinoma 10 33* 9 6 300 mg/l (43-57 mg/kg/day) Reduced survival Liver: hepatocellular adenoma carcinoma 8 29* 12* 11* Thyroid: follicular hyperplasia adenoma carcinoma 18* 16* 0 23* 13* 3 *significant difference from controls; p < 0.002. 11 Conclusions There are insufficient human data for establishing a critical effect of MDA. Occupational exposure to MDA, where skin absorption plays a major role, has caused liver damage. Judging from animal experiments, the critical effect is liver damage, including liver cancer. MDA is genotoxic in vitro and forms DNA adducts in vivo. MDA is carcinogenic to experimental animals and should be regarded as carcinogenic to humans. MDA in direct contact with the skin is readily absorbed, and the substance can cause contact allergy. References 1. ACGIH. Documentation of the Threshold Limit Values and Biological Exposure Indices. 6th ed. Cincinnati, Ohio: American Conference of Governmental Industrial Hygienists, 1992:998-1001. 2. Bailie MB, Mullaney TP, Roth RA. Characterization of acute 4,4´-methylene dianiline hepatotoxicity in the rat. Environ Health Perspect 1993;101:130-133. 3. Bastian PG. Occupational hepatitis caused by methylenedianiline. Med J Aust 1984;141:533- 535. 4. Baur X, Seemann U, Marcynski B, Chen Z, Raulf-Heimsoth M. Humoral and cellular immune responses in asthmatic isocyanate workers: report of two cases. Am J Ind Med 1996;29:467-473. 5. Brooks LJ, Neale JM, Pieroni DR. Acute myocardiopathy following tripathway exposure to methylenedianiline . JAMA 1979;242:1527-1528. 6. Brunmark P, Bruze M, Skerfving S, Skarping G. Biomonitoring of 4,4´-methylene dianiline by measurement in hydrolysed urine and plasma after epicutaneous exposure in humans. Int Arch Occup Health 1995;67:96-100. 7. Cocker J, Gristwood W, Wilson HK. Assessment of occupational exposure to 4,4´- diaminodiphenylmethane (methylene dianiline) by gas chromatography-mass spectrometry analysis of urine. Br J Ind Med 1986:43:620-625. 8. Cocker J, Boobis AR, Davies DS. Determination of the N-acetyl metabolites of 4,4´- methylene dianiline and 4,4´-methylene-bis(2-chloroaniline) in urine. Biomed Environ Mass Spec 1988;17:161-167. 9. Cocker J, Nutley BP, Wilson HK. A biological monitoring assessment of exposure to methylene dianiline in manufacturers and users. Occup Environ Med 1994;51:519-522. 10. Cohen SR. Yellow staining caused by 4,4´-methylenedianiline exposure: occurrence among molded plastic workers. Arch Dermatol 1985;121:1022-1027. 11. Cragle DL, Wells SM, Tankersley WG. An occupational morbidity study of a population potentially exposed to epoxy resins, hardeners and solvents. Appl Occup Environ Hyg 1992;7:826-834. 12. Dalene M, Jakobsson K, Rannug A, Skarping G, Hagmar L. MDA in plasma as a biomarker of exposure to pyrolysed MDI-based polyurethane: correlations with estimated cumulative dose and genotype for N-acetylation. Int Arch Occup Environ Health 1996;68:165-169. 13. Dalene M, Skarping G, Lind P. Workers exposed to thermal degradation products of TDI- and MDI-based polyurethane: biomonitoring of 2,4-TDA, 2,6-TDA and 4,4´-MDA in hydrolyzed urine and plasma. Am Ind Hyg Assoc J 1997;58:587-591. 14. EU 1967: Council directive 67/548/EEC on the approximation of laws, regulations and administrative provisions relating to the classification, packaging and labelling of dangerous substances. Annex 1. (most recent edition 010824). 12 15. Estlander T, Keskinen H, Jolanki R, Kanerva L. Occupational dermatitis from exposure to polyurethane chemicals. Contact Dermatitis 1992;27:161-165. 16. Fairhurst S, South D, Williams C, Cocker J, Brown R. 4,4´-Methylene dianiline. Criteria Document for an Occupational Exposure Limit. Health and Safety Executive, HSE Books, Sheffield, United Kingdom, 1993. 17. Fukushima S, Shibata M, Hibino T, Yoshimura T, Hirose M, Ito N. Intrahepatic bile duct proliferation induced by 4,4´-diaminodiphenylmethane in rats. Toxicol Appl Pharmacol 1979;48:145-155. 18. Von Gailhofer G, Ludvan M. The significance of patch test results to methylenedianiline. Dermatosen 1989;37:16-18. (in German, English summary) 19. Gohlke R, Schmidt P. 4,4´-Diaminodiphenylmethane: histological, enzyme-histochemical and autoradiographic investigation in acute and subacute experiments in rats with and without additional heat stress. Int Arch Arbeitsmed 1974;32:217-231. 20. Hall AJ, Harington JM, Waterhouse JAH. The Epping jaundice outbreak: a 24-year follow up. J Epidemiol Community Health 1992;46:327-328. 21. Health Council of the Netherlands: Dutch Expert Committee on Occupational Standards (DECOS). 4,4´-Methylene dianiline. Health-based Calculated Occupational Cancer Risk Values. The Hague: Health Council of the Netherlands, 2000, 2001/11OSH. 22. Hewitt PG, Hotchkiss SAM, Caldwell J. Decontamination procedures after in vitro topical exposure of human and rat skin to 4,4´-methylenebis(2-chloroaniline) and 4,4´methylenedianiline. Fundam Appl Toxicol 1995;26:91-98. 23. Hofman HT, Frohberg H, Meinecke KH, Oettel H, von Schilling B, Zeller H. Potential injuries by 4,4´-diaminodiphenylmethane: earlier recognition and prevention. Proceedings of the Fifteenth International Conference of Occupational Health. 1966;11-2:849-851. (in German) 24. Hofman HT, Frohberg H, Meinecke KH, Oettel H, von Schilling B, Zeller H. Zur Toxicität von 4,4´-Diaminodiphenylmethan. Naunyn Arch Pharmacol 1966;253:47. (in German) 25. IARC. Some chemicals used in plastic and elastomers. 4,4´-Methylenedianiline and its dihydrochloride. IARC Monographs on theEvaluation of Carcinogenic Risks to Humans. Lyon: International Agency for Research on Cancer 1986;39:347-365. 26. IARC. Overall evaluations of carcinogenicity: an updating of IARC Monographs volumes 1 to 42. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans. Lyon: International Agency for Research on Cancer 1987;suppl. 7:66. 27. Kajbaf M, Sepai O, Lamb JH, Naylor S. Identification of metabolites of 4,4´- diaminodiphenylmethane (methylene dianiline) using liquid chromatographic and mass spectrometric techniques. J Chromatogr 1992;583:63-76. 28. Kanerva L, Jolanki R, Estlander T. Allergic and irritant patch test reactions to plastic and glue allergens. Contact Dermatitis 1997;37:301-302. 29 Kanz MF, Wang A, Campbell GA. Infusion of bile from methylene dianiline-treated rats into the common bile duct injures biliary epithelial cells of recipient rats. Toxicol Lett 1995;78:165-171. 30. Kanz MF, Gunasena HG, Kaphalia L, Hammond KL, Syed YA. A minimally toxic dose of methylene dianiline injures biliary epithelial cells in rats. Toxicol Appl Pharmacol 1998;150:414-426. 31. Kautiainen A, Wachtmeister CA, Ehrenberg L. Characterization of hemoglobin adducts from a 4,4´-methylenedianiline metabolite evidently produced by peroxidative oxidation in vivo. Chem Res Toxicol 1998;11:614-621. 32. Kopelman H, Robertson MH, Sanders PG, Ash I. The Epping jaundice. Brit Med J 1966;1:514-516. 33. Kopelman H, Scheuer PJ, Williams R. The liver lesion of the Epping jaundice. Quarterl J Med, New series 1966;XXXV:553-564. 13 34. LeVine MJ. Occupational photosensitivity to diaminodiphenylmethane. Contact Dermatitis 1983;9:488-490. 35. Liss GM, Guirguis SS. Follow-up of a group of workers intoxicated with 4,4´- methylenedianiline. Am J Ind Med 1994;26:117-124. 36. Lundberg P (ed). Scientific Basis for Swedish Occupational Standards. VIII. 4,4´-Methylene dianiline and its dihydrochloride. Arbete och Hälsa 1987;39:165-172. National Institute of Occupational Health, Solna. 37. McGill DB, Motto JD. An industrial outbreak of toxic hepatitis due to methylenedianiline. N Engl J Med 1974;291:278-282. 38. McQueen CA, Williams GM. Review of the genotoxicity and carcinogenicity of 4,4´- methylene-dianiline and 4,4´-methylene-bis-2-chloroaniline. Mutat Res 1990;239:133-142. 39. Munn A. Occupational bladder tumors and carcinogens: recent developments in Britain. In: Deichmann W, Lampe K, eds. Bladder Cancer, A Symposium. Birmingham: AL, Aesculapius, 1967: 187-193. 40. NTP. Technical Report 248, on the carcinogenesis bioassay of 4,4´-methylenedianiline dihydrochloride in F344/N rats and B6C3F/N mice. Research Triangle Park, N.C.: National Toxicology Program, 1983. Report No. 83-2504. 41. Parodi S, Taningher M, Russo P, Pala M, Tamaro M, Monti-Bragadin C. DNA-damaging activity in vivo and bacterial mutagenicity of sixteen aromatic amines and azo-derivatives, as related quantitatively to their carcinogenicity. Carcinogenesis 1981;2:1317-1326. 42. Parodi S, Zunino A, Ottaggio L, De Ferrari M, Santi L. Lack of correlation between the capability of inducing sister-chromatid exchanges in vivo and carcinogenic potency, for 16 aromatic amines and azo derivatives. Mutat Res 1983;108:225-238. 43. Pludro G, Kartlowski K, Mankowska M, Woggon H, Uhde W-J. Toxicological and chemical studies of some epoxy resins and hardeners. I. Determination of acute and subacute toxicity of phthalic acid anhydride, 4,4´-diaminodiphenylmethane and of the epoxy resin: Epilox EG- 34. Acta Pol Pharmacol 1969;26:352-357. 44. Roy CW, McSorley PD, Syme JG. Methylene dianiline: a new toxic cause of visual failure with hepatitis. Human Toxicol 1985;4:61-66. 45. Rudzki E, Rebandel P, Zawadzka A. Sensitivity to diaminodiphenylmethane. Contact Dermatitis 1995;32:303-317. 46. Schoental R. Carcinogenic and chronic effects of 4,4´-diaminodiphenylmethane, an epoxy resin hardener. Nature 1968;219:1162-1163. 47. Schütze D, Sepai O, Lewalter J, Miksche L, Henschler D, Sabbioni G. Biomonitoring of workers exposed to 4,4´-methylenedianiline of 4,4´-methylenediphenyl diisocyanate. Carcinogenesis 1995;16:573-582. 48. Schütze D, Sagelsdorff P, Sepai O, Sabbioni G. Synthesis and quantification of DNA adducts of 4,4´-methylenedianiline. Chem Res Toxicol 1996;9:1103-1112. 49. Seldén A, Berg P, Jakobsson R, de Laval J. Methylene dianiline: assessment of exposure and cancer morbidity in power generator workers. Int Arch Occup Environ Health 1992;63:403- 408. 50. Sepai O, Schütze D, Heinrich U, Hoymann HG, Henschler D, Sabbioni G. Hemoglobin adducts and urine metabolites of 4,4´-methylenedianiline after 4,4´-methylenediphenyl diisocyanate exposure of rats. Chem Biol Interact 1995;97:185-198. 51. Steinhoff D, Grundmann E. Carcinogenic activity of 4,4´-diaminophenyl methane and 2,4´- diaminodiphenylmethane. Naturwissenschaften 1970;57:247-248. 52. Tanaka K, Ino T, Sawahata T, Marui S, Igaki H, Yashima H. Mutagenicity of N-actyl and N,N´-diacetyl derivatives of 3 aromatic amines used as epoxy-resin hardeners. Mutat Res 1985;143:11-15. 53. Tillman HL, van Pelt FNAM, Martz W, Luecke T, Welp H, Dörries F, Veuskens A, Fischer M, Manns MP. Accidental intoxication with methylene dianiline p,p´-diaminodiphenyl- 14 methane: acute liver damage after presumed ecstasy consumption. Clin Toxicol 1997;35:35- 40. 54. Tullner WW. Endocrine effects of methylenedianiline in the rat, rabbit and dog. Endocrinology 1959;66:470-474. 55. Vock EH, Hoymann HG, Heinrich U, Lutz WK. 32P-Postlabeling of a DNA adduct derived from 4,4´-methylenedianiline, in the olfactory epithelium of rats exposed by inhalation to 4,4´-methylenediphenyl diisocyanate. Carcinogenesis 1996;17:1069-1073. 56. Weisburger EK, Murthy ASK, Lilja HS, Lamb JC. Neoplastic response of F344 rats and B6C3F mice to the polymer and dyestuff intermediates 4,4´-methylenebis(N,N-dimethyl)- benzenamine, 4,4´-oxydianiline, and 4,4´methylenedianiline. J Natl Cancer Inst 1984;72:1457-1461. 57. Wu K, Leslie CL, Stacey NH. Effects of mutagenic and non-mutagenic aniline derivatives on rat liver drug-metabolizing enzymes. Xenobiotica 1989;19:1275-1283. 58. Zylbersac S. Action cirrhogène des diamino-diphényles insollubles sur le foie du rat. Cr Soc Biol 1951;145:136-138. (in French) 15 Consensus Report for Methylisocyanate (MIC) and Isocyanic Acid (ICA) December 5, 2001 Chemical and physical data. Occurrence methylisocyanate (MIC) isocyanic acid (ICA) CAS No.: 624-83-9 75-13-8 Synonyms: isocyanic acid methylester hydrogen isocyanate Structure: H3C-N=C=O HN=C=O Molecular weight: 57.06 43.02 Boiling point: 39 °C 23 °C Melting point: - 45 °C - 80 °C Vapor pressure: 46.4 kPa (20 °C) 13.3 kPa (- 19 °C) Conversion factors: 1 ppm = 2.4 mg/m3 1 ppm = 1.8 mg/m3 1 mg/m3 = 0.4 ppm 1 mg/m3 = 0.6 ppm Methylisocyanate (MIC) is a monoisocyanate. At room temperature it is a clear liquid. MIC is sparingly soluble in water, although on contact with water it reacts violently, producing a large amount of heat. The speed of the reaction depends a great deal on temperature, and is accelerated by acids, bases and amines (50). MIC has a sharp odor and an odor threshold above 2 ppm (13). Isocyanic acid (ICA) above 0 °C is an unstable liquid with a tendency to polymerize. The primary polymerization product – which is also generated in gas form – is the trimer, cyanuric acid. Isocyanic acid is soluble in water, but disintegrates both via ionization and by formation of ammonia and carbon dioxide (10). In gas form it has a sharp odor (54). Methylisocyanate occurs primarily as an intermediate in the production of carbamate pesticides. It has also been used in the production of polymers (32). Photolytic breakdown of N-methyldithiocarbamate releases some MIC, and it can therefore occur in the air around application of the pesticides (26). MIC is found in tobacco smoke: the measured content in the main stream ranges from 1.5 to 5 µg per cigarette (33). In the laboratory, MIC has also been identified in emissions from heating of core sand and mineral wool, where it results from breakdown or chemical transformation of the carbamide resin binder (42, 46). Exposure measurements made in foundries indicate that MIC occurs primarily where “hot box” cores are used in chill casting (47). MIC occurs in the isocyanate mixture created by thermal breakdown of TDI- or HDI-based polyurethane 16 lacquers during welding, cutting and grinding operations in automobile repair shops (7, 59). ICA is usually found along with MIC in welding plumes (and also around chill casting), often in concentrations as much as ten times as high. Most information on the occurrence of MIC and ICA is relatively new, since it has only recently become possible to analyze low-molecular monoisocyanates in mixed chemical exposures such as those resulting from thermal breakdown. A method based on sampling in dibutyl amine followed by analysis with liquid chroma- tography-mass spectrometry (LC-MS) (42) was published in 1998. Several laboratories have since developed methods for analyzing MIC. In another method that has been found applicable, samples are derivatized with 1-(2-methoxy- phenyl)piperazine and analyzed using GC-MS; LC and other detectors have also been used successfully (20). A recently published abstract presents a diffusion sampling method for MIC (48). These methods can also be used for analysis of ICA. Because of its instability, however, ICA is not commercially available – a circumstance that makes its quantification difficult. Uptake, biotransformation, excretion Massive exposure to MIC was one of the consequences of the disaster in Bhopal, India, in 1984, when about 27 tons of MIC dispersed into a populated area around a Union Carbide plant. There are no precise air measurements, but concentrations were later estimated to have been in the range 0.12 to 85 ppm (17). In subsequent assessments of the injuries, it has been debated whether they were caused in- directly as a result of reduced respiratory function or directly via respiratory uptake and distribution to other organs (13). The question arises from the fact that MIC is a powerful irritant: it is postulated that this may have inhibited normal respiratory uptake and systemic distribution. After Bhopal, animal experiments with radiocarbon-labeled MIC were conducted to clarify this point. Mice were exposed by inhalation to 0.5, 5 or 15 ppm 14C-MIC for 1 to 6 hours, and uptake and distribution were studied (24). The radioactivity appeared in the blood within a few minutes, but did not show a linear increase with concentration. This was attributed to the greater irritation of higher doses and the resulting formation of mucus in the respiratory passages, which was assumed to affect the respiratory rate and thus inhibit inhalation and uptake in the blood. The highest radioactivity in blood in relation to air concentration was measured after the exposure to 0.5 ppm. Radioactivity in blood dropped gradually after the exposures and was nearly gone within three days. Radioactivity fell more rapidly in urine than in bile. In male mice, the highest levels of radioactivity after 2 hours were found in the lungs, sternum, digestive tract, spleen and kidneys, and after 24 hours in blood and lungs. In female mice, the highest levels of radioactivity after 2 hours were in lungs, fetuses, spleen, uterus and kidneys, and after 24 hours in lungs, spleen and fetuses (24). The effective uptake and distribution is probably due to the in vivo binding of MIC to proteins in tissues, blood plasma and erythrocyte membranes. Protein binding has been experimentally verified in mice after both inhalation and intraperitoneal administration of 14C-labeled MIC (11, 12). 17 Sax (55) mentions, without going into detail, that MIC is absorbed by the skin. No other data on skin uptake were found. MIC has been observed to cause carbamoylation of N-terminal valine in the hemoglobin of rats and rabbits both in vivo and in vitro (53), and 3-methyl-5- isopropyl hydantoin (MIH), the cyclic transformation product of MIC and valine, could then be identified in blood. MIH has also been identified in blood from the Bhopal victims (61). S-(N-methylcarbamoyl)glutathione, another reactive conjugate, has been identified in bile from rats given MIC via a catheter in the portal vein (52). In another experiment, the glutathione conjugate in the form of S-(N-methylcarbamoyl)-N-acetylcysteine was identified in urine of rats given MIC intraperitoneally (60). MIC reacts readily with water, forming methylamine, which further reacts to dimethylurea (72). It is quite likely that some MIC is also transformed in vivo to methylamine. No studies were found in which methylamine or dimethyl urea were measured in blood or urine, however. There is no information on uptake, biotransformation or excretion of ICA. Patients with uremia have elevated concentrations of carbamoylated hemoglobin, which is the reaction product of hemoglobin and isocyanic acid (45, 73). The isocyanic acid is assumed to result from the endogenous breakdown of urea occurring in cases of acute kidney failure. Toxic effects Human data A study made at an industry producing and using MIC presents an examination of lung function data in employee medical records covering a 10-year period (the dates are not given) (8). The employees were divided by their supervisors into four categories based on their estimated exposure to MIC: none (N = 123), low (N = 103), moderate (N = 138) and high (N = 67). The records also contained in- formation on smoking habits. About 800 monitoring measurements of MIC (the method used is not reported) had been made in the 1977 – 1990 period. In 1977 more than 80% of the measurements had exceeded 0.02 ppm, whereas only one of 33 measurements made in 1990 were above this level. The groups were compared, using lung function values from the most recent examination and taking smoking habits into account, and no effect of MIC on lung function could be discerned. Nor was any effect seen when a worker’s first examination was compared with his most recent one. Conclusions should be drawn with caution, however, since individuals who developed health problems may have quit (and thus not been examined after the problem arose) and also because there is considerable room for error in the exposure classifications. The medical records also contained information on exposures due to spills or leakage. The authors do not give the number of these cases, but report that the most common symptoms were eye and skin irritation, and in a few cases respiratory problems. No clear effect on lung function was seen in these cases. 18 Four volunteers were briefly exposed (1 to 5 minutes) to MIC (44) (see Table 1). No effect was noted at an exposure level of 0.4 ppm, but 2 ppm caused irritation of eyes (notably tear flow) and mucous membranes in nose and throat, although no odor was perceived. At 4 ppm the symptoms of irritation were more pronounced, and at 21 ppm they were unbearable. There are several studies providing information on the 1984 disaster in Bhopal. About 200,000 persons were acutely exposed to high (> 27 ppm) concentrations of MIC, as well as to other substances including phosgene, methylamine and hydrogen cyanide (50). There is thus some doubt as to whether all the observed effects can be attributed to MIC. Because of the nature of the exposure conditions, and because effects on the lungs may have produced secondary effects on other organs, most of the toxicological information from the disaster is of little value in establishing an occupational exposure limit. A brief review of some of the studies is nevertheless presented below. The acute effects of the Bhopal disaster have been compiled. It is estimated that about 2000 people died within the first few hours. The reported cause of death is alveolar necroses combined with ulcerations in bronchial mucosa and pulmonary edema (71). In one study, 379 survivors were divided into eight groups on the basis of their degree of exposure, as estimated from the numbers of dead (both humans and animals) near their homes and the hypothetical spread of the toxic cloud. There were 119 controls with similar socioeconomic backgrounds. The number of dead was estimated to be 1850 in an area that was assumed to represent 70% of the total area contaminated by the gas. The symptom most commonly reported on the questionnaire given to the surviving victims was smarting eyes, followed by coughing, persistent tear flow and nausea. The prevalence of eye symptoms showed no correlation to the proportion of deaths nearby, but the reports of coughing did show such a correlation. Redness and superficial sores on corneas and conjunctiva were observed in eye examinations (5). Since amines can cause eye damage (35), the relevance of MIC here can not be assessed with certainty. Kamat et al. (41) followed 113 patients who had been referred to their pulmonary medicine and psychiatric clinics for persistent respiratory symptoms in the three months following the disaster. The patients (with 23 - 50% attrition from the original cohort) were followed up at 3, 6, 12, 18 and 24 months, using a standardized questionnaire, physical examinations, lung x-rays, spirometry etc. The report is difficult to interpret, but it appears that a patient’s condition was initially classified on the basis of the number and severity of respiratory symptoms: mild for 30 patients, moderate for 57, and severe for 26. The respira- tory symptoms had regressed somewhat at 3, 6, and 12 months, but increased again at 18 and 24 months. Shortness of breath with physical exertion was the most persistent. Neurological symptoms such as muscular weakness and forget- fulness increased. The proportion of patients with depression had increased at 6 months and the proportion with anxiety at 12 months. Other symptoms, such as irritability and concentration difficulty, showed declining trends. Only 2 to 4 percent of the lung x-rays were judged to be completely normal. The others 19 showed changes in interstitial lung tissue and in the pleural sac. Lung function tests revealed possible reductions in lung function, primarily of a restrictive type. The above study also presents an analysis of antibodies in serum samples from 99 cases (41). These results are more fully described in an earlier report from the same study (43). The initial samples were taken a few months after the disaster, and MIC-specific antibodies were found in 11 subjects: IgM in 7, IgG in 6 and IgE in 4. The antibody titers of some of the subjects were followed for up to a year after the disaster. The rises in antibodies were small, and in most cases later samples were negative. The small elevations in IgE antibodies were seen only on the first sampling occasion (41, 43). The data on antibodies are difficult to assess, since the documentation is poor and the articles contain inconsistencies. Another research group made similar examinations of lung function in Bhopal victims one to seven years after the disaster (70). The material consisted of 60 persons, 6 of whom were judged to have had low exposure (slight irritation of eyes and respiratory passages on the day of the disaster), 13 moderate exposure (respiratory symptoms, eye irritation that did not require hospitalization), and 41 high exposure (respiratory and eye symptoms severe enough to require hospitalization and/or death of a family member as a result of the exposure). There was also an unexposed control group. The most commonly reported symptoms were shortness of breath on physical exertion and coughs. BAL samples taken one to seven years (average 2.8 years) after the disaster showed elevations of total cell counts, macrophages and lymphocytes in the high-exposure group, statistically significant when compared with the low-exposure group and controls. Permanent damage to the respiratory passages was reported in a follow-up study made 10 years after the disaster (16). Questionnaires were distributed to 454 persons chosen on the basis of residence within a radius of 2, 4, 6, 8 or 10 kilo- meters from the plant. The control group comprised persons of the same socio- economic background who lived in an area outside the city. From the cohort, 20% were randomly chosen for spirometry tests; this group ultimately contained 74 persons. The occurrence of specific respiratory symptoms – mucus formation, cough, rales etc. – could be clearly related to the exposure level derived from the distance between the victim’s home and the site of the disaster (from 0-2 km to >10 km). The symptoms were equally prevalent among men and women, and more common among persons below 35 years of age (median value for the entire group) and among smokers than non-smokers. The same trend could be discerned in the results of lung function tests, which showed mild obstructive reductions in lung function that increased with proximity to the plant. This trend became a bit less clear when smoking habits and socioeconomic factors were included in the calculations. In a follow-up study of effects on eyes, no cases of blindness or impaired vision were found 2 months after the event (6). Of a total of 131 examined cases, six had unilateral scars on the cornea, three had corneal edema and one complained of constantly running eyes. After 3 years, 463 were examined, 99 of whom were controls. Compared with controls, the victims of the Bhopal disaster had higher 20 frequencies of eye irritation, eyelid infections, cataracts, trachoma and loss of visual acuity, which increased with increasing exposure (4). One year after the disaster, a study of cognitive function was made on a group of 52 victims (51). They were grouped into three exposure classes on the basis of symptoms and distance from the plant. Compared with controls, normal per- formance values were seen in the least-exposed group, whereas in the other two groups the values deviated significantly for “associate learning” and motor ability. In the most exposed group there were also lower values on the Standard Progressive Matrix (SPM), a test that measures ability to think logically. Clinical indications of central, peripheral and vestibular neurological damage, as well as impaired short-term memory, were also seen in another study of the Bhopal victims (15). In interviews, they reported more psychological symptoms such as headaches, fatigue, concentration difficulty and irritability than controls. The symptoms did not always increase with exposure. The exposure estimates can be questioned in both these studies of CNS effects, and in the latter article there is some discussion of the difficulty of taking socioeconomic differences into account in assessing the results. The authors also suggest that persistent depressions may be a factor contributing to the other symptoms. Asthma resulting from exposure to MIC has not been reported. For ICA, there are no data regarding toxic effects on humans. Animal data The calculated LD50 for rats given MIC subcutaneously is 329 mg/kg body weight. The LC 50 for 30 minutes of exposure was 465 ppm (1080 mg/m3) (38). The LC50 for 15 minutes of exposure to MIC has been reported to be 171 ppm for rats and 112 ppm for guinea pigs (19). The reported LC50 for 3 hours of exposure is 26.8 ppm for mice (68). The RD50 for mice (the dose that causes a 50% decline in respiratory rate), a measure of sensory irritation (effects on the trigeminus nerve via the upper respiratory passages), was estimated to be 1.3 ppm in one study (23), and 2.9 ppm in another (34). The RD50 for pulmonary irritation (stimulation of the vagus nerve cells via type J receptors in the alveoli) was 1.9 ppm for mice exposed via tracheal catheters (23). Irritation of the upper and lower respiratory passages is the most commonly reported effect in all animal experiments. When rats were exposed to 0, 3, 10 or 30 ppm MIC for 2 hours, effects on lung function increased with concentration. No abnormal changes of lung function were observed at exposure to 3 ppm MIC, but exposure to 10 ppm caused obstructive changes in respiratory passages which did not regress during the following 13 weeks (62). Lung damage was seen in rats exposed to 3 or 10 ppm MIC for 2 hours and examined 4 and 6 months later. At 4 months there were ECG changes in both dose groups, and right ventricular hyper- trophy was also seen in the high-dose group (not examined at 6 months). The authors suggest that the hypertrophy and the ECG changes were probably secondary effects of the lung damage with pulmonary hypertension (63). A LOAEL (Lowest Observed Adverse Effect Level) of 3.1 ppm for damage to 21 respiratory epithelium was reported in a study in which rats were exposed by inhalation to 0, 0.15, 0.6 or 3.1 ppm MIC 6 hours/day for 4 + 4 days. The NOAEL (No Observed Adverse Effect Level) in this study was 0.6 ppm (18). Six hours of high exposure – above 4.4 ppm for guinea pigs, above 4.6 ppm for rats and above 8.4 ppm for mice – resulted in damage to the upper respiratory passages of all three species: necrosis and erosion of epithelial cells in the larynx and trachea, and alveolitis, hemorrhages and inflammation in lungs (25). The changes disappeared within a week. When rats were exposed to 128 ppm (320 mg/m3) MIC 8 minutes/day for 10 days, the exposure induced progressive cellular inflammation with increase of eosinophils, neutrophils and mononuclear cells (28). Guinea pigs exposed for 3 hours to 19 or 37 ppm MIC had lung changes of the same types reported earlier in the victims at Bhopal (22). In one study (14), F344 rats and B6C3F1 mice were exposed by inhalation to 0, 1, 3 or 10 ppm MIC for 2 hours, and then observed for 2 years. Survival and weight gain were normal in all exposure groups. Definite effects on the lungs, particularly proliferation of the connective tissue layer below the respiratory epithelium and connective tissue invasion in the lumen of the respiratory passages, were observed in the rats exposed to 10 ppm. Similar damage was seen in another group of rats exposed to 10 ppm MIC and examined one year later. Rats and mice exposed to 10 or 30 ppm MIC for 2 hours had severe necrosis and damage on most of the nasal mucosa, including the olfactory cells. Both epithelial and olfactory cells regenerated rapidly, however, and had returned to normal within 3 months (66). In a National Toxicology Program (NTP) study (31), mice were exposed to 1 or 3 ppm MIC 6 hours/day for 4 days. Histopathological examination after the exposure to 3 ppm revealed pronounced fibrosis in bronchi, with intraluminal fibrosis and damage to olfactory epithelium. The 1 ppm exposure caused damage to respiratory epithelium (not more fully described). Myelotoxic effects on stem cells were also observed at both exposure levels, but they were judged to be a secondary effect of the damage to the respiratory system. Immunological effects of MIC have been examined in some studies (43, 65). A slight increase of immunoglobulin levels was measured in rats after exposure to MIC (56). MIC demonstrated a slight immunosuppressive effect in an NTP study with mice (65). Mice were exposed to 1 or 3 ppm MIC 6 hours/day for 4 days, and slightly reduced mitogen-stimulated lymphocyte proliferation was observed at both doses; at the higher dose there was also a significantly lower response on MLR (Mixed Leukocyte Response) tests. The reduction was temporary and had disappeared after 120 days. The authors regard these effects as secondary, resulting from toxic effects on the lungs or general toxicity, rather than a direct effect of MIC on the immune system. Systemic effects of MIC observed in exposed rats are severe hyperglycemia, metabolic acidosis and uremia (11, 36, 38). Exposure of mice or rats to MIC concentrations in the range 3 to 30 ppm, either intraperitoneally or via inhalation, has caused temporary degenerative changes in blood cells and cells in liver parenchyma (29). In a study with mice, intraperitoneal injections of 293-1170 mg 22 MIC/kg body weight had effects on amino acid concentrations (stimulating on glutamate and aspartate, inhibiting on GABA) in the brain and plasma. This was regarded as an indication of neurotoxic and systemic effects (30). In vitro studies have shown that MIC affects both brain and muscle cells, but the clinical rele- vance of this finding is not clear (2, 3). There are only a few studies of the toxic mechanisms of MIC. In vitro and in vivo studies with cells from hepatic and nervous tissue of rats indicate that MIC can inhibit the respiratory chain in mitochondria, and thus induce histotoxic hy- poxia (39, 40). This effect was also observed in another study, in which guinea pigs were exposed to 25, 125 or 225 ppm and rats to 100, 600 or 1000 ppm MIC for 15 minutes (64). MIC also exerts a dose-dependent inhibition of acetyl- cholinesterase activity in vitro in erythrocytes from humans, rats and guinea pigs (37, 64). There are no data from animal studies on toxic effects of ICA. Mutagenicity, carcinogenicity, teratogenicity MIC showed no mutagenic activity in standard Ames’ tests (58). Negative results were also obtained in Ames’ tests with urine from rats exposed to MIC (1) and in a sex-linked recessive lethal test with Drosophila (58). In the same study, positive results were obtained for point mutations in the mouse lymphoma test. The authors conclude that MIC may be genotoxic by binding to nuclear proteins. MIC has induced chromosome aberrations and polyploidy in hamster fibroblasts both with and without metabolizing systems (49). Persons exposed to MIC and other substances during the Bhopal disaster had higher frequencies of chromosome aberrations than unexposed controls (27). No neoplastic changes in respiratory organs were observed in a study (14) in which F344 rats and B6C3F1 mice were exposed by inhalation to 0, 1, 3 or 10 ppm MIC for 2 hours and subsequently observed for up to 2 years. In the male rats exposed to 3 or 10 ppm there were elevated incidences of pheochromocytomas in adrenal cortex and acinous tumors in pancreas. This study is not a conventional cancer study, and the authors point out that the correlation to exposure is weak and that no conclusions should be drawn on the basis of their observations. Judging from structure-activity correlations, the carcinogenic potency of MIC should be low (21). There are no mutagenicity, carcinogenicity or teratogenicity studies with long-term exposures to MIC. A dose-dependent absorption of fetuses was observed in mice exposed to 2, 6, 9 or 15 ppm MIC for 3 hours on the eighth day of gestation. There was total resorp- tion in more than 75% of the females exposed to the two highest doses, and reduced fetus and placenta weights were observed at all dose levels. The authors suggest that the maternal toxicity (weight loss, reduced weight gain) may have caused the observed effects (67). In a later study it was shown that treatment with hormones that counteract certain effects of the maternal toxicity (but not e.g. weight loss) did not counteract the effects on the fetuses (69). In another study, mice were exposed to 1 or 3 ppm MIC 6 hours/day on days 14 to 17 of gestation. 23 There were significant increases in the numbers of dead fetuses in both groups, and lower neonatal survival in the high-dose group. The authors caution against drawing conclusions on whether the fetotoxicity was a direct effect of MIC or was secondary to the effects on the lungs of the mothers (57). Studies of victims of the Bhopal disaster revealed that mothers exposed to MIC had higher numbers of miscarriages, but not stillbirths, than unexposed controls (9). In a controlled study, Cullinan et al. (15) reported an increase in stillbirths (exposed 9%, unexposed 4%) and miscarriages (year of disaster 7%, later years 1%), but the study covered few cases. There are no data on mutagenicity, carcinogenicity or teratogenicity for ICA. Dose-effect / dose-response relationships Despite the Bhopal disaster and the facts that MIC is chemically related to more thoroughly studied substances such as toluene diisocyanate and is an extremely toxic substance, the literature on which to base a critical effect or a dose-response relationship is scanty. No reliable studies on the relationship between occupational exposure to MIC and effects on health were found. There is only one study on dose-response relationships for humans. Results from animal studies suggest that dose-effect and dose-response curves are steep. Irritation of eyes and mucous membranes has been described in human subjects after short-term exposures to MIC. In one study, volunteers were exposed to MIC for 1 to 5 minutes: at 0.4 ppm no irritation was reported, but irritation of eyes and mucous membranes increased markedly at 2 and 4 ppm, and was unacceptable at 21 ppm (see Table 1). Irritation of upper and lower respiratory passages has been described in studies with rats, mice and guinea pigs. Permanent lung damage has been reported at higher doses (Table 2). The exposure-effect relationships observed in laboratory animals exposed by inhalation to MIC are summarized in Table 2. There are no data on which to base an estimate of dose-effect or dose-response relationships for ICA. Table 1. Effects on four volunteers exposed to MIC in an exposure chamber for 1 to 5 minutes (44). MIC concentration Effects 21 ppm Unendurable irritation 4 ppm Severe irritation of mucous membranes 2 ppm Tear flow, irritation of eyes, nose and throat 0.4 ppm No irritation 24 Table 2. Effects on laboratory animals exposed by inhalation to MIC. Exposure Species Effect Ref. 171 ppm, 15 min. rat LC50 19 121 ppm, 15 min. guinea pig LC50 19 12.2 ppm, 6 hours mouse LC50 25 10 ppm, 2 hours rat Proliferation of connective tissue below respiratory epithelium with intrusion into respiratory lumen 14 10 ppm, 2 hours rat Right ventricular hypertrophy, ECG changes secondary to lung damage 63 9 ppm, 3 hours day 8 or 9 of gestation mouse, rat Over 80% of fetuses resorbed, reduced placenta weights 67 6.1 ppm, 6 hours rat LC50 25 5.4 ppm, 6 hours guinea pig LC50 25 3.1 ppm, 6 hours/day, 4 + 4 days rat Damage to respiratory epithelium, weight loss, pulmonary edema, increase in hemoglobin (males) 18 3 ppm, 6 hours/day, 4 days mouse Bronchial fibrosis, damage to olfactory epithelium 31 3 ppm, 2 hours rat ECG changes due to lung damage 63 3 ppm, 2 hours rat No changes in lung function 62 2.9 ppm, 30 min. mouse RD50 (sensory irritation) 34 2.4 ppm, 6 hours mouse, rat, guinea pig Retarded weight gain 25 1.9 ppm, 90 min. (via tracheal catheter) mouse RD50 (pulmonary irritation) 23 1.3 ppm, 90 min. mouse RD50 (sensory irritation) 23 1 ppm, 6 hours/day 4 days mouse Damage to respiratory epithelium 31 0.6 ppm, 6 hours/day 4 + 4 days rat No effect on respiratory passages, weight or hemoglobin levels 18 25 Conclusions Judging from the data from brief exposures of human subjects, the critical effect of exposure to MIC is irritation of eyes and mucous membranes, which occurs at 2 ppm. In animal experiments exposure to similar levels for up to 6 hours results in severe damage to mucous membranes in respiratory passages. At somewhat higher levels there is a steep increase in mortality. There are no data which would serve to establish a critical effect for ICA. References 1. Andersson D, Blowers S, Nemery B. Investigation of the Ames test of urine samples from rats exposed to methyl isocyanate. Br J Ind Med 1986;43:566-567. 2. Andersson D, Goyle S, Phillips B, Tee A, Beech L, Butler W. Effects of methyl isocyanate on rat muscle cells in culture. Br J Ind Med 1988;45:269-274. 3. Andersson D, Goyle S, Phillips B, Tee A, Beech L, Butler W. Effects of methyl isocyanate on rat brain cells in culture. Br J Ind Med 1990;47:596-601. 4. Andersson N, Ajwani M, Mahashabde S, Tiwari M, Muir M, Mehra V, Ashiru K, Mackenzie C. Delayed eye and other consequences from exposure to methyl isocyanate. 93% follow up of exposed and unexposed cohorts in Bhopal. Br J Ind Med 1990;47:553-558. 5. Andersson N, Muir M, Mehra V, Salmon A. Exposure and response to methyl isocyanate: results of a community based survey in Bhopal. Br J Ind Med 1988;45:469-475. 6. Andersson N, Muir M, Salmon A, Wells C, Brown R, Purnell C, Mittal P, Mehra V. Bhopal disaster: Eye follow-up and analytical chemistry. Lancet 1985;30:761-762. 7. Antonsson A-B, Ancker K, Veibäck T. Isocyanater från heta arbeten i skadereparationsverkstäder. IVL Rapport 2000, B 1389. IVL Swedish Environmental Research Institute. (in Swedish) 8. Avashia B, Battigelli M, Morgan W, Reger R. Effects of prolonged low exposure to methyl isocyanate. J Occup Environ Med 1996;38:625-630. 9. Bajaj JS, Misra A, Rajalakshmi M, Madan R. Environmental release of chemicals and reproductive ecology. Environ Health Perspect 1993;101 Suppl. 2:125-130. 10. Belson DJ, Strachan AN. Preparation and properties of isocyanic acid. Chem Soc Reviews 1982;11:41-56. 11. Bhattacharya B, Sharma S, Jaiswal D. Binding of [1-14C] methylisocyanate to erythrocyte membrane proteins. J Appl Toxicol 1996;16:137-138. 12. Bhattacharya B, Sharma S, Jaiswal D. In vivo binding of [1-14C]methylisocyanate to various tissue proteins. Biochem Pharmacol 1988;37:2489-2493. 13. Bucher J. Methyl isocyanate: A review of health effects research since Bhopal. Fund Appl Toxicol 1987;9:367-369. 14. Bucher J, Uraih L. Carcinogenicity and pulmonary pathology associated with a single 2-hour inhalation exposure of laboratory rodents to methyl isocyanate. J Natl Cancer Inst 1989;81:1586-1587. 15. Cullinan P, Acquilla S, Dhara V. Long term morbidity in survivors of the 1984 Bhopal gas leak. Natl Med J India 1996;9:5-10. 16. Cullinan P, Acquilla S, Dhara V. Respiratory morbidity 10 years after the Union Carbide gas leak at Bhopal: a cross sectional survey. Br Med J 1997;314:338-343. 17. Dhara R, Dhara VR. Bhopal – A case study of international disaster. Int J Occup Environ Med 1995;1:58-69. 26 18. Dodd D, Fowler E, Snellings W, Pritts I. Methyl isocyanate eight-day vapor inhalation study with Fischer 344 rats. Environ Health Perspect 1987;72:117-123. 19. Dodd D, Frank F, Fowler E, Troup C, Milton R. Biological effects of short-term, high- concentration exposure to methyl isocyanate. 1. Study objectives and inhalation exposure design. Environ Health Perspect 1987;72:13-19. 20. Eckerman M-L, Välimaa J, Rosenberg C. Determination of airborne methyl isocyanate as dibutylamine or 1-(2-methoxyphenyl)piperazine derivatives by liquid and gas chromatography. Analyst 2000;125:1949-1954. 21. Ennever F, Rosenkranz H. Evaluating the potential for genotoxic carcinogenicity of methyl isocyanate. Toxicol Appl Pharmacol 1987;91:502-505. 22. Ferguson J, Alarie Y. Long term pulmonary impairment following a single exposure to methyl isocyanate. Toxicol Appl Pharmacol 1991;107:253-268. 23. Ferguson J, Schaper M, Stock M, Weyel D, Alarie Y. Sensory and pulmonary irritation with exposure to methyl isocyanate. Toxicol Appl Pharmacol 1986;82:329-335. 24. Ferguson J, Stock K, Brown W, Alarie Y. Uptake and distribution of 14C during and following exposure to [14C]methyl isocyanate. Toxicol Appl Pharmacol 1988;94:104-117. 25. Fowler EH, Dodd DE. Respiratory tract changes in guinea pigs, rats and mice following a single six-hour exposure to methyl isocyanate vapor. Environ Health Perspect 1987;72:109- 116. 26. Geddes J, Miller G, Taylor G. Gas phase photolysis of methyl isothiocyanate. Environ Sci Technol 1995;29:2590-2594. 27. Ghosh B, Sengupta S, Roy A, Maity S, Ghosh S, Talukder G, Sharma A. Cytogenetic studies in human populations exposed to gas leak at Bhopal, India. Environ Health Perspect 1990;86:323-326. 28. Gupta G, Baipai J, Kaw J, Dutta K, Ray P. Modulation of biochemical and cytological profile of bronchoalveolar constituents in rats following split-dose multiple inhalation exposure to methyl isocyanate. Hum Exp Toxicol 1993;12:253-257. 29. Gupta M, Amma M. Alterations in hepatic biochemistry of mice intoxicated with MIC, carbaryl and thiram. J Appl Toxicol 1993;13:33-37. 30. Gupta M, Prabha V. Changes in brain and plasma amino acids of mice intoxicated with methyl isocyanate. J Appl Toxicol 1996;16:469-473. 31. Hong HL, Bucher JR, Canipe J, Boorman GA. Myelotoxicity induced in female B6C3F1 mice by inhalation of methyl isocyanate. Environ Health Perspect 1987;72:143-148. 32. Hrhyhorczuk D, Aks S, Turk J. Unusual occupational toxins. Occup Med 1992;3:567-586. 33. IARC. Tobacco smoking. IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Lyon, International Agency for Research on Cancer, 1986;38:97-98. 34. James J, Buettner L, Hsu S. Sensory irritation of methyl isocyanate vapor. J Appl Toxicol 1987;7:147-148. 35. Järvinen P, Engström K, Riihimäki V, Ruusuvaara P, Setälä K. Effects of experimental exposure to triethylamine on vision and the eye. Occup Environ Med 1999;56:1-5. 36. Jeevaratnam K, Sugendran K, Vaidynathan C. Influence of methylamine and N,N- dimethylurea, the hydrolysis products of methyl isocyanate, on its systemic toxicity. J Appl Toxicol 1993;13:15-18. 37. Jeevaratnam K, Vaidynathan C. Acute toxicity of methyl isocyanate in rabbit: In vitro and in vivo effects on rabbit erythrocyte membrane. Arch Environ Contam Toxicol 1992;22:300- 304. 38. Jeevaratnam K, Vijayaraghavan R, Kaushik M, Vaidynathan C. Acute toxicity of methyl isocyanate in mammals. II. Induction of hyperglycemia, lactic acidosis, uraemia, and hypothermia in rats. Arch Environ Contam Toxicol 1990;19:314-318. 27 39. Jeevaratnam K, Vidya S. In vivo and in vitro effects of methyl isocyanate on rat brain mitochondrial respiration. Arch Environ Contam Toxicol 1994;27:272-275. 40. Jeevaratnam K, Vidya S, Vaidynathan C. In vitro and in vivo effect of methyl isocyanate on rat liver mitochondrial respiration. Toxicol Appl Pharmacol 1992;117:172-179. 41. Kamat S, Patel M, Pradhan P, Taskar S, Vaidya P, Kolhatkar V, Gopalani J, Chandarana J, Dalal N, Naik N. Sequential respiratory, psychologic and immunologic studies in relation to methyl isocyanate exposure over two years with model development. Environ Health Perspect 1992;97:241-253. 42. Karlsson D, Dalene M, Skarping G. Determination of complex mixtures of airborne isocyanates and amines. Part 5. Determination of low molecular weight aliphatic isocyanates as dibutylamine derivatives. Analyst 1998;123:1507-1512. 43. Karol MH, Kamat SR. The antibody response to methyl isocyanate: experimental and clinical findings. Bull Eur Physiopathol Respir 1988;23:591-597. 44. Kimmerle G, Eben A. Zur Toxicität von Methylisocyanat und dessen quantitativer Bestimmung in der Luft. Arch Toxicol 1964;20:235-241. (in German) 45. Kraus L, Kraus A. The search for the uremic toxin: the case for carbamoylation of amino acids and proteins. Wien Klin Wochenschr 1998;110:521-530. 46. Lilja B-G, Westberg H, Nayström P. Kartläggning av isocyanater i gjuterier. Etapp 1 – Emissionsmätningar. Jönköping, Svenska Gjuteriföreningen, 1999. (in Swedish) 47. Lilja B-G. Westberg H, Nayström P. Kartläggning av isocyanater i gjuterier. Etapp 2 – Exponeringsmätningar. Jönköping, Svenska Gjuteriförening, 2000. (in Swedish) 48. Lindahl R, Zweigbergk P, Östin A, Levin J-O. Diffusive sampling of low-molecular isocyanates. International conference - Measuring Air Pollutants by Diffusive Sampling, 26- 28 September, 2001, Montpellier, France. 49. McConnell E, Bucher J, Schwetz B, Gupta B, Shelby M, Luster M, Brody A, Boorman G, Richter C, Stevens M, Adkins B. Toxicity of methyl isocyanate. Environ Sci Technol 1987;21:188-193. 50. Mehta P, Mehta A, Mehta S, Makhijani A. Bhopal tragedy’s health effects – a review of methyl isocyanate toxicity. J Am Med Assoc 1990;264:2781-2787. 51. Misra U, Kalita J. A study of cognitive functions in methyl isocyanate victims one year after Bhopal accident. Neurotoxicology 1997;18:381-386. 52. Pearson P, Slatter J, Rashed M, Han D-H, Grillo M, Baillie T. S-(N- methylcarbamoyl)glutathione: A reactive S-linked metabolite of methyl isocyanate. Biochem Biophys Res Commun 1990;166:245-250. 53. Ramachandran P, Gandhe B, Venkateswaran K, Kaushik M, Vijayaraghavan R, Agarwal G, Gopalan N, Surynarayana M, Shinde S, Srimachari S. Gas chromatographic studies of the carbamylation of haemoglobin by methylisocyanate in rats and rabbits. J Chromat 1988;426:239-247. 54. Römpp H, Falbe J, eds. Römpp-Lexicon Chemie. 10th ed. Stuttgart: Georg Thieme Verlag 1997:2000. (in German) 55. Sax N. Dangerous Properties of Industrial Materials. 6th ed. New York, NY: Van Nostrand 1984:1864. 56. Saxena AK, Paul BN, Sinha M, Dutta KK, Das SN, Ray PK. A study on the B cell activity in protein deficient rats exposed to methyl isocyanate vapour. Immunopharmacol Immunotoxicol 1991;13:413-424. 57 Schwetz B, Adkins B, Harris M, Moorman M, Sloane R. Methyl isocyanate: Reproductive and developmental toxicology studies in Swiss mice. Environ Health Perspect 1987;72:149- 152. 58. Shelby M, Allen J, Caspary W. Haworth S, Ivett J, Kligerman A, Luke C, Mason J, Myhr B, Tice R, Valencia R, Zeiger E. Results of in vitro and in vivo genetic toxicity tests on methyl isocyanate. Environ Health Perspect 1987;72:183-187. 28 59 Skarping G, Dalene M, Lind P, Karlsson D, Adamsson M, Spanne M. Rapport Isocyanater. Department of Occupational and Environmental Medicine, Lund 2001. ISBN:91-630-8237-3. (in Swedish) 60. Slatter J, Rashed M, Pearson P, Han D-H, Baillie T. Biotransformation of methylisocyanate in the rat. Evidence for glutathione conjugation as a major pathway of metabolism and implications for isocyanate mediated toxicities. Chem Res Toxicol 1991;4:157-161. 61. Srimachari S, Chandra H. The lessons of Bhopal (toxic) MIC gas disaster scope for expanding global biomonitoring and environmental specimen ranking. Chemosphere 1997;34:2237-2250. 62. Stevens M, Fitzgerald S, Ménache M, Costa D, Bucher J. Functional evidence of persistent airway obstruction in rats following a two-hour inhalation exposure to methyl isocyanate. Environ Health Perspect 1987;72:89-94. 63. Tepper JS, Wiester MJ, Costa DL, Watkinson WP, Weber MF. Cardiopulmonary effects in awake rats four and six months after exposure to methyl isocyanate. Environ Health Perspect 1987;72:95-103. 64. Troup CM, Dodd DE, Fowler EH, Frank FR. Biological effects of short-term, high- concentration exposure to methyl isocyanate. II. Blood chemistry and hematologic evaluations. Environ Health Perspect 1987;72:21-28. 65. Tucker A, Bucher J, Germolec D, Silver M, Vore S, Luster M. Immunological studies on mice exposed subacutely to methyl isocyanate. Environ Health Perspect 1987;72:139-141. 66. Uraih LC, Talley FA, Mitsumori K, Gupta BN, Bucher JR, Boorman GA. Ultrastructural changes in the nasal mucosa of Fischer 344 rats and B6C3F1 mice following an acute exposure to methyl isocyanate. Environ Health Perspect 1987;72:77-88. 67. Varma DR. Epidemiological and experimental studies on the effects of methyl isocyanate on the course of pregnancy. Environ Health Perspect 1987;72:153-157. 68. Varma DR, Ferguson J, Alarie Y. Inhibition of methyl isocyanate toxicity in mice by starvation and dexamethasone but not by sodium thiosulfate, atropine, and ethanol. J Toxicol Environ Health 1988;24:93-101. 69. Varma DR, Guest I, Smith S. Dissociation between maternal and fetal toxicity of methyl isocyanate in mice and rats. J Toxicol Environ Health 1990;30:1-14. 70. Vijayan V. Sankaran K. Relationship between lung inflammation, changes in lung function and severity of exposure in victims of Bhopal tragedy. Eur Respir J 1996;9:1977-1982. 71. Weill H. Disaster at Bhopal: The accident, early findings and respiratory health outlook in those injured. Bull Eur Physiopathol Respir 1988;23:587-590. 72. Worthy W. Methyl isocyanate: the chemistry of hazard. Chemical & Engineering News 1985:27-33. 73. Wynckel A, Randoux C, Millart H, Desroches C, Gillery P, Canivet E, Chanard J. Kinetics of carbamylated haemoglobin in acute renal failure. Nephrol Dial Transplant 2000;15:1183- 1188. 29 Consensus Report for Methylisoamylketone February 6, 2002 This report is an update of the Consensus Report published in 1992 (6). Chemical and physical data. Uses CAS No.: 110-12-3 Synonyms: 5-methylhexane-2-one 5-methyl-2-hexanone isoamylmethylketone isopentylmethylketone methyl isoamyl ketone MIAK Formula: CH3COCH2CH2CH(CH3)2 Molecular weight: 114.19 Boiling point: 144 °C Melting point: - 73.9 °C Flash point (closed cup): 43 °C Density: 0.813 g/ml Vapor pressure (20 °C): 0.2 kPa (6); 0.6 kPa (10) Saturation concentration: 5900 ppm (20 °C) Solubility in water: 5.4 g/liter Conversion factors (20 °C): 1 mg/m3 = 0.211 ppm 1 ppm = 4.74 mg/m3 MIAK is a clear, flammable liquid with a sharp, sweetish odor. The odor threshold has been reported to be 0.01 (11) and 0.18 ppm (3). The latter value was calculated with QSAR (Quantitative Structure-Activity Relationship). The substance is soluble in alcohol and ether and somewhat soluble in water (10). It is used as a solvent for nitrocellulose, cellulose acetate, and acrylic and vinyl copolymers (11). Uptake, biotransformation, excretion Uptake of MIAK via inhalation and oral administration has been studied in rats. With six hours of inhalation exposure to 1950 ppm, the highest concentration in blood (138 µg/ml) was measured after 4 hours, and with single oral doses of 1830 mg/kg body weight (b.w.) the highest blood concentration (94 µg/ml) was seen 30 after 1 hour. The half time in blood was 0.7 hours after the inhalation exposure and 5.3 hours after the oral dose (5). Skin uptake is indicated by an LD50 for dermal exposure (8), but this study provides no uptake data. The water/air distribution coefficient for MIAK is reported to be 240 (1) and that for octanol/water is given as 52.5 in one work (3) and as 75.9 in another (9). Toxic effects MIAK has fairly low acute toxicity. The reported LD50 for oral administration to rats and mice is in the range 2542 – 4760 mg/kg b.w. (8, 9, 11), and the reported LD50 for skin application to rabbits is 8130 mg/kg b.w. (8). An LC50 somewhere between 2000 and 4000 ppm is reported in an inhalation study with rats (4 hours of exposure: 0/6 rats died at 2000 ppm; 6/6 died at 4000 ppm) (8). An unpublished study with rats (cited in Reference 10) gives a calculated LC50 of 3813 ppm for 6- hours of exposure. The same study reports that 6-hour exposures resulted in eye irritation, narcosis, reduced respiratory rates and a death (1/4) at 3200 ppm, effects on the central nervous system (reduced response to noise) at 1600 ppm, and no discernible effects at 800 ppm (10). The RD50 (50% reduction of respiratory rate due to sensory irritation in the upper respiratory passages) for mice exposed to MIAK by inhalation is reported in one study to be 1232 ppm for 5 minutes (Muller & Greff 1984, cited in Reference 7). In another study, inhalation of 416 to 1515 ppm MIAK for 15 minutes was found to reduce the respiratory rates of mice by 27 to 61%, and the RD50 was calculated to be 1222 ppm (2). The reported nasal irritation threshold for people exposed to MIAK, calculated with QSAR, is 2042 ppm (3). Effects on the nervous system, measured as reduction in total duration of inactivity during 3 minutes of swimming (the“behavioral despair swimming test”), were reported in mice after 4 hours of whole-body exposure to 270 – 637 ppm MIAK. The lowest exposure level (270 ppm) yielded a 26% reduction in the total duration of inactivity, and the ID50 (the air concentration causing a 50% deterioration in test performance) was calculated to be 446 ppm (2). The relevance of this swimming test in assessing toxicity, however, is unclear (11). In an inhalation experiment, rats were exposed 6 hours/day, 5 days/week (12 exposures in 16 days) to 970 or 2090 ppm MIAK. CNS effects – slight lethargy and lower aural response – were observed during the higher exposure. There were also dose-dependent increases in absolute (not significant in males) and relative liver weights, higher relative kidney weights (not significant in females at 2090 ppm), and, in males, histopathological changes (hyalin degeneration or hyalin droplet formation) in epithelial cells in renal ducts. No indications of liver or kidney damage were seen in clinical/chemical analysis, however (5). When rats were exposed on the same schedule to 210, 1030 or 2080 ppm MIAK for 96 days (69 exposures) a dose-dependent CNS effect was initially seen at the two higher dose levels. Slight lethargy and lower aural response were observed later, but only at the highest air concentration. Porphyrin-like discolorations around the eyes, nose and mouth (regarded as indications of slight irritation), as well as significant, 31 dose-dependent increases of absolute and relative liver weights, were also seen at the two higher dose levels. Histopathological examinations revealed dose- dependent liver changes, including minimal to moderate hypertrophy of hepato- cytes and, in males, also minimal to mild necrosis. Effects on kidneys were seen primarily in males. Indications of mild/moderate regeneration of epithelium in renal tubules were seen at the two higher dose levels, though at 1030 ppm only in males. Males in the highest dose group also showed indications of possible in- crease in hyalin drop degeneration in the proximal convoluted tubules. Signifi- cantly higher absolute and relative kidney weights were reported in males at the two higher doses, and increased relative kidney weights in females at the highest dose, although clinical-chemical examination revealed no indications of liver or kidney damage. The NOEL in this study was 210 ppm (5). An unpublished inhalation study reports that no exposure-related effects were seen in rats after exposure to 400 ppm MIAK 6 hours/day, 5 days/week (12 exposures). The same report describes effects observed when the animals were given MIAK by gavage in doses of 1000, 2000 or 4000 mg/kg body weight, 5 days/week for 3 weeks. The highest dose resulted in CNS depression and all the animals died within 1.5 hours. Effects seen at 2000 mg/kg included chronic irritation of stomach lining, hypertrophy of hepatic cells and hyalin drop forma- tion in kidneys. The only observed effect at 1000 mg/kg was slight irritation of the stomach lining. It is also reported that oral administration of 2000 mg/kg b.w./day to rats 5 days/week for 13 weeks resulted in somewhat elevated levels of hepatic enzymes, increased absolute and relative liver and adrenal weights, higher relative kidney weights and histopathological changes in the liver (degeneration, hypertrophy, hyperplasia) and stomach lining (chronic irritation) (10). Undiluted MIAK applied to the skin of rabbits caused no irritation within 24 hours: changes were ranked 1 on a 10-point scale. In the same study, MIAK applied to eyes of rabbits was ranked 2 (8). Mutagenicity, carcinogenicity, effects on reproduction No data were found in the literature. Dose-effect / dose-response relationships Kane et al. (4), in a study of various irritating substances (not including MIAK), found that the RD50 levels for mice often produce intolerable irritation in the eyes and upper respiratory passages of humans, and that an air concentration equivalent to 10% of the RD50 for mice usually causes some irritation in humans. A good agreement has also been shown between the ACGIH threshold limit values (1991) based on sensory irritation and air concentrations equivalent to 3% of the RD50, i.e. the value midway between 1% and 10% of the RD50 on a logarithmic scale (7). Dose-effect relationships documented in experimental animals exposed to MIAK by inhalation are summarized in Table 1. The RD50 for mice is reported to be about 1200 ppm, and a 27% reduction in respiratory rate is observed at about 32 Table 1. Effects observed in experimental animals exposed to MIAK by inhalation. Exposure Species Effects Ref. 2090 ppm, 6 hours/day, 5 days/week (12 exposures) Rat Slight lethargy, reduced aural response; somewhat elevated liver and kidney weights; histopathological changes in kidneys of males. 5 2080 ppm, 6 hours/day, 5 days/week (69 exposures) Rat Lethargy, reduced aural response; somewhat elevated liver and kidney weights; histopathological changes in liver and kidneys; slight irritation of eyes and respiratory passages. 5 1232 ppm, 5 minutes Mouse RD50 7 1222 ppm, 15 minutes Mouse RD50 2 1030 ppm, 6 hours/day, 5 days/week (69 exposures) Rat Slight lethargy, initially reduced aural response; somewhat elevated liver and kidney weights; histopathological changes in liver, and in males also in kidneys. Slight irritation of eyes and respiratory passages. 5 970 ppm, 6 hours/day, 5 days/week (12 exposures) Rat Somewhat elevated liver and kidney weights; histopathological changes in kidneys of males. 5 416 ppm, 15 minutes Mouse 27% reduction in respiratory rate. 2 210 ppm, 6 hours/day, 5 days/week (69 exposures) Rat No exposure-related effects. 5 400 ppm (2, 7). In a relatively large study with effects on liver, kidneys and CNS as well as irritation, the NOEL was reported to be 210 ppm (5). Conclusions There are no data for human exposures on which to base a critical effect for occupational exposure to MIAK. Limited data from animal experiments indicate that the critical effect of short-term exposure is irritation of mucous membranes in respiratory passages. 33 References 1. Amoore JE, Hautala E. Odor as an aid to chemical safety: odor thresholds compared with threshold limit values and volatilities for 214 industrial chemicals in air and water dilution. J Appl Toxicol 1983;3:272-290. 2. De Ceaurriz J, Micillino JC, Marignac B, Bonnet P, Muller J, Guenier JP. Quantitative evaluation of sensory irritating and neurobehavioural properties of aliphatic ketones in mice. Food Chem Toxicol 1984;22:545-549. 3. Hau KM, Connell DW, Richardson BJ. Use of partition models in setting health guidelines for volatile organic compounds. Regul Toxicol Pharmacol 2000;31:22-29. 4. Kane LE, Barrow CS, Alarie Y. A short-term test to predict acceptable levels of exposure to airborne sensory irritants. Am Ind Hyg Assoc J 1979;40:207-229. 5. Katz GV, Renner ER, Terhaar CJ. Subchronic inhalation toxicity of methyl isoamyl ketone in rats. Fund Appl Toxicol 1986;6:498-505. 6. Lundberg P (ed). Scientific Basis for Swedish Occupational Standards. IX. Arbete och Hälsa 1992;6:7-12. Swedish National Institute for Working Life, Solna. 7. Schaper M. Development of a database for sensory irritants and its use in establishing occupational exposure limits. Am Ind Hyg Assoc J 1993;54:488-544. 8. Smyth HF, Carpenter CP, Weil CS, Pozzani UC, Striegel JA. Range-finding toxicity data: list VI. Am Ind Hyg Assoc J 1962;23:95-107. 9. Tanii H, Tsuji H, Hashimoto K. Structure-toxicity relationship of monoketones. Toxicology Letters 1986;30:13-17. 10. Topping DC, Morgott DA, David RM, O’Donoghue JL. Ketones. In: Clayton GD, Clayton FE, eds. Patty’s Industrial Hygiene and Toxicology, 4th ed. New York: John Wiley & Sons, 1994:1739-1878. 11. Wibowo AAE. DEC and NEG basis for an occupational health standard. 7/8 carbon chain aliphatic monoketones (2-heptanone, 3-heptanone, ethylamylketone and methylisoamylketone). Arbete och Hälsa 1990;2:1-44. Swedish National Institute of Occupational Health, Solna. 34 Consensus Report for Toluene February 6, 2002 This report is based primarily on a criteria document from the Nordic Expert Group (162). The Criteria Group has previously published a consensus report for toluene in 1981 (137). Chemical and physical data. Uses. CAS No.: 108-88-3 Synonyms: methyl benzene, phenyl methane, toluol, methyl benzol, methacide Molecular formula: C7H8 Structure: Molecular weight: 92.13 Boiling point: 110.6 °C Melting point: -95 °C Density: 0.876 g/ml (20 °C) Vapour pressure: 3.73 kPa (20 °C) Saturation concentration: 142,000 mg/m3 (25 °C) Conversion factors (25 °C): 1 ppm = 3.75 mg/m3 1 mg/m3 = 0.267 ppm Toluene is a high production volume substance, and millions of tonnes are used yearly. Toluene at room temperature is a clear colourless liquid with unpleasant aromatic odour. The odour thresholds reported in various studies range from 1.5 to 262.5 mg/m3 (2, 43, 121). The reason for the variability in the reported odour threshold is unknown. However, toluene can be detected in air in concentrations at the lower end of the reported odour threshold range. In a volunteer study, in- creased odour level was perceived at the lowest concentration tested, 37.5 mg/m3 (3). Toluene is only slightly soluble in water, approximately 6.5 mmol/l at 20 °C. Toluene is soluble in acetone and carbon disulphide, and miscible with most ethers, ketones, alcohols, esters, and aliphatic and aromatic hydrocarbons. Toluene forms azeotropic mixtures with many of the solvents mentioned above. Toluene is used as a solvent in a number of products such as bitumen, tar, paints, lacquers, greases, and natural and synthetic resins. Workers in the chemical industry and paint industry, and workers using products containing toluene (e.g. CH3 35 painters) may be occupationally exposed. The main exposure to toluene occurs by inhalation of vapours and liquid aerosols and via dermal exposure to liquids. Within production of toluene in the chemical industry, a reasonable worst case short term exposure level is 100 mg/m3, while the typical full shift exposure level is low, 3 mg/m3. For production of toluene-containing products, a reasonable worst case short term exposure level is 200 mg/m3, while the typical full shift exposure level is low, 4 mg/m3. Occupational use of toluene-containing products can lead to high exposure levels. For use of toluene-containing adhesives and inks the typical full shift exposure level is 75 mg/m3. These values derive from the EU risk assessment of toluene (24). Uptake, biotransformation, excretion The major route of exposure to toluene is inhalation of vapour. Data from experimental exposure of voluntary study subjects show that physical work results in increased toluene uptake (16, 146). Using a 50 W work load, exposure to 300 mg/m3 (80 ppm) toluene for 2 hours did not result in steady state of the blood concentration of toluene in 12 study subjects. The toluene uptake was 2.4 times higher than the uptake at rest. During the work, lung ventilation increased 2.8 times. Concentrations of toluene in alveolar air and blood increased with increasing work loads (0-150 W in periods of 30 minutes) (16). However, at higher workloads the proportion of toluene taken up decreased (only 29% at 150 W compared with 52% at rest), indicating that the uptake is limited by the rate of removal of toluene from the lungs via blood (77). The amount of toluene absorbed increased with larger amounts of body fat (17). In nine male volunteers exposed to 200 mg/m3 (53 ppm) toluene for 2 hours during a workload of 50 W the total uptake of toluene was 50% of that inhaled (78). The steady state dermal penetration rate of neat toluene has been reported to be 14.5 nmol/cm2/min (80 µg/cm2/h) (145) using human skin in vitro. Similar values of 8.5 and 12.5 nmol/cm2/min have been reported from animal experiments (140, 141). Applying the ECETOC criteria for skin notation (26), i.e. exposure of 2,000 cm2 of skin (approximately corresponding to the skin of the hands and forearms) for 1 hour (equivalent to exposure of 250 cm2 skin or 70% of one hand for 8 h) and using the above human data a dermally absorbed dose of 1.7 mmol toluene is obtained. This corresponds to 16% of the amount absorbed during 8-h inhalatory exposure at 50 ppm (10.8 mmol). The inhalation uptake was calculated assuming exposure at the present Swedish OEL (50 ppm, 8-h TWA), 10 m3 inhaled air during 8 hours and a pulmonary retention of 50%. In conclusion, dermal exposure to liquid toluene may result in significant systemic exposure. Experiments with volunteers indicate that upon whole body exposure to toluene vapour, the dermal route contributes to about 1-2% of the systemic exposure (10, 103, 116). Toluene appears to be well absorbed after oral exposure (162). 36 Toluene is widely distributed in body tissues, including the placenta, and has high affinity to adipose tissue. In humans the adipose tissue/blood partition coefficient of toluene is 81-83 (123, 124). Biotransformation of toluene occurs mainly by oxidation in the liver. About 20% of the absorbed toluene is eliminated unchanged in the expired air. Of the remaining 80%, approximately 99% is oxidised via benzyl alcohol and benz- aldehyde to benzoic acid. The remaining 1% is oxidised in the aromatic ring, forming ortho-, meta- and para-cresol (157, 158). Benzoic acid is linked to glycine forming hippuric acid, which is excreted in the urine. Elimination curves for toluene in blood from exposed workers was found to contain at least three exponential components with median half-lives of 9 minutes, 2 hours, and 90 hours, the latter value reflecting the decline of toluene in adipose tissue (94). The half-life of toluene in human adipose tissue is about 3 days (17). The time period during which accumulation occurs can be calculated by multi- plying the half-life by 5, i.e. about 15 days, after which steady-state is reached. The conclusion therefore is that although there is some accumulation of toluene it is not an accumulative substance as such compared with, e.g. PCBs, which have a half-life of several years. Biological measures of exposure Measurement of toluene in blood, urine and exhaled air provide reliable markers of exposure to toluene. Measurement of toluene metabolites is also utilised for monitoring toluene exposure in humans. Hippuric acid is formed in the body when toluene is metabolised. High performance liquid chromatography (HPLC) with ultraviolet detection is usually used for detection of hippuric acid in urine. Other metabolites such as o-cresol, benzylmercapturic acid, or S-p-toluylmercapturic acid may also be measured (143). A good correlation was found between toluene exposure (air concentration multiplied by time) and concentration of hippuric acid in post exposure urine. However, a background level of hippuric acid is present in human urine, as a product of endogenous metabolism, and of metabolism of substances present in food. In the Western part of the world, at exposure levels below 100 ppm (375 mg/m3) hippuric acid in post exposure urine cannot be used to separate an exposed person from an unexposed one because the difference between the background level and the toluene-generated level is too small (74). However, hippuric acid background levels in urine vary geographically. In some countries (e.g. Taiwan and Croatia) a low urinary hippuric acid background level is found. Thus, in these parts of the world it is possible to use this metabolite as a biological marker for toluene exposure even at exposure levels lower than 100 ppm (19, 143, 147, 149). 37 Toxic effects Human data Toluene has a degreasing effect on the skin. After repeated exposures, irritative contact dermatitis may develop (11, 38, 153). A five-minute exposure to 1.5 ml toluene on a skin surface area of 3.1 cm2 caused marked erythema and increased blood flow measured by laser Doppler flowmetry (151). Studies in human volun- teers exposed at rest show that deterioration in the air quality and increased odour level is perceived around 10 ppm (37.5 mg/m3), while complaints of eye irritation start at air concentrations around 100 ppm (375 mg/m3) (3, 27). Kidney damage has been described as a consequence of high exposure levels in relation to work- place accidents or abuse (114, 120, 143). Three older occupational studies did not show a relation between toluene exposure and kidney damage (4, 34, 93). In a recent longitudinal study of 92 photogravure printers and 74 referents, it was concluded that toluene at 50 ppm (187.5 mg/m3) was not related to detectable renal dysfunction assessed on the basis of various markers in blood and urine (131). Acute neuropsychological effects of toluene has been investigated in a number of studies in volunteers (3, 12, 13, 20, 27, 28, 53, 58, 112, 154). Headache, diz- ziness, feeling of intoxication, irritation and sleepiness were reported in several of the studies at toluene concentrations in the range of 75-150 ppm (281 mg/m3- 562.5 mg/m3). In one study, headache, eye irritation and increased number of sleeping episodes occurred at 75 ppm (281 mg/m3) and above (27). At 150 ppm in the same study, function in performance tests was impaired. As concentrations below 75 ppm were not tested, this study does not provide a NOAEL (no observed adverse effect level). Because of various limitations and uncertainties in design and reporting, this study is not considered for further use. Another study (3) reports that concentrations up to 40 ppm did not result in any adverse effects. In this study, 100 ppm was a LOAEL (lowest observed adverse effect level) for irritation of the eye and nose, headache, dizziness, feeling of intoxication, and a feeling that performance tests were more strenuous. Six out of 16 subjects did not report any irritation during the 100 ppm exposure, i.e. 10 subjects did experience irritation. The highest individual estimation was 64 on a scale with a maximum value called strong irritation (=100). The irritation was felt just after the exposure began and was constant throughout the exposure day. Disruption of performance of complex tests and increased response time in simple tests following exposure to 100 ppm for 6 hours (mostly at rest, 30 minutes of moderate exercise during the exposure) was found in six healthy adults in a two-period cross-over experiment where each subject served as his/her own control (112). Effects of lower exposure levels were not studied. The subjective experience and performance effects of a 6 h toluene-exposure were studied in 43 printers and 43 subjects without previous history of chemical exposure (12). Half of each group of subjects were exposed to air, half were exposed to 100 ppm toluene at rest. Fatigue, irritation of eyes, nose and throat was increased by toluene. Manual dexterity, colour discrimination and visual perception were impaired. 38 Humans exposed to very high levels of toluene as a result of toluene abuse or industrial accidents may experience serious nervous system effects including fatal CNS depression. Other effects include cerebellar, pyramidal and cognitive dys- function such as tremor, ataxia and memory impairment. Brain atrophy attributed to toluene exposure has been identified in heavy abusers (8, 32, 74, 75, 122, 143). A number of cross-sectional studies, in which a toluene-exposed group of workers have been compared with a matched control group, have been published. Unfortunately, exposure data covering the subjects’ entire exposure history are generally lacking in these studies, with only recent exposure being reasonably well documented. As the effects observed in these cross-sectional studies may be viewed as the accumulation of effects induced during the entire period of occupa- tional exposure, which is often many years, it is necessary to have information about the whole period in order to identify LOAELs and NOAELs for the effects. It must be assumed that the exposure levels have changed during the years because of changes in industrial operations and hygiene measures. These studies have reported increased prevalence of subjective complaints (fatigue, recent memory failure, concentration difficulty, mood lability, depressive feelings, irritability, headache, dizziness, sleep disturbances, paresthesia, chest oppression, sexual problems) (75, 161), neuropsychological impairments (6, 30, 35, 57), electrophysiological changes (1, 148), and increased prevalence of neurasthenic complaints, short-term memory complaints, and chronic toxic encephalopathy (CTE) (72, 161) in the toluene-exposed group. In the latter study (161), exposure levels in the two rotogravure plants concerned were estimated retrospectively based on personal interviews, previous hygienic measurements and other written reports concerning the working environment (Table 1). These estimates show that irreversible effects may be induced at exposure during many years at concentra- tions ranging from 40 to 1700 mg/m3. Even higher concentrations may have been present in previous years. Table 1. Estimated retrospective exposure levels for toluene at two Swedish rotogravure plants, from Ørbæk and Nise (161). Year Retrospective exposure level (mg/m 3 ) Company A Company B -1955 570a 1,710 1956-57 1,710 1,710 1958-68 1,710 1,710 1969 950 1,710 1970-72 950 950 1973-74 610 950 1975-76 610 380 1977 610 250 1978-79 300 250 1980- 43 157 aMixed Stoddard solvent exposure in letterpress printing 39 Two cross-sectional studies in workers indicate that occupational exposure to toluene increases the risk of developing occupational noise-related high-frequency hearing loss (83, 84). In the first study (83) four groups of workers were studied: unexposed (noise level <85 dB(A) and no toluene), noise exposed (noise level 88- 97 dB(A) and no toluene); noise plus toluene exposed (noise level 88-98 dB(A) and toluene concentration 281-2250 mg/m3), and organic solvent mixture exposed (noise level <85 dB(A) and exposure to four solvents). In the second study (84), a group of workers exposed to varying levels of noise and a mixture of toluene, ethyl acetate, and ethanol were studied. The toluene concentration was 0.14 to 919 mg/m3, and noise levels were in the range of 71-93 dB(A). In two cross-sectional studies of workers occupationally exposed to toluene the leukocyte count in peripheral blood has been measured (56, 142). A slight positive correlation to toluene exposure was found in one of the studies (142), however, the leukocyte count in the exposed group was within the range of normal values. The other study did not show an association between increased number of leuko- cytes and toluene exposure. Animal data Toluene was found slightly irritating to the skin in rabbits (41), and moderately to severely irritating to the eyes, also in rabbits (42, 132). Toluene-induced skin oedema following repeated topical administration has been measured in rabbits and guinea pigs (150). The mean increase in guinea pig skin-fold thickness was 225% after 10 daily applications. The response in rabbits was similar. No published data have been found regarding skin sensitisation by toluene. Data from mice suggest that toluene can cause irritation to the respiratory tract at high concentrations (25, 85, 92). Toluene has low acute toxicity via inhalation and the oral route. In rats, in- halatory LC50 values in the range of 20,000-50,000 mg/m3/6 h (7, 14) and oral LD50 values of 5.5-7.5 g/kg have been reported (65, 128, 144, 156, 159). A dermal LD50 of 12.4 g/kg has been determined in the rabbit (128). Via the intraperitoneal route LD50 values were found to be approximately 2 g/kg for rats and mice (29, 55, 67, 76). The effect of repeated inhalation has been examined in a number of studies in rats and mice with exposure durations ranging from 15 weeks to 2 years (40, 51). The most relevant studies for the prediction of effects of long-term exposure in man are the 2-year studies. The major effect of toluene identified in rats exposed for 2 years to 600 or 1200 ppm (2250 or 4500 mg/m3), was toxicity to the olfactory and respiratory epithelium and was found in both males and females at both exposure levels (51). In other studies specifically examining the effects on the nervous system after inhalation exposure in rats, various changes were found, including brain region volume changes and neurochemical changes. The dose levels varied between 100 and 1500 ppm (375-5625 mg/m3) (49, 68, 70, 126, 127). Auditory impairment of toluene-exposed rats has been demonstrated in a number of studies as behavioural and electrophysiological changes at inhalatory 40 exposure concentrations between 900 and 1400 ppm 14 h/day, 7 days/week, for 5- 14 weeks (109, 110, 111, 113). A LOAEL of 1000 ppm (14 h/day, 2 weeks) and a NOAEL of 700 ppm (14 h/day, 16 weeks) was found. Studies on combined exposure to toluene and noise strongly indicate that a synergistic toxic effect of toluene and noise (1000 ppm toluene + 100 dB Leq (62); or 2000 ppm toluene + 92 dB SPL (73)) on auditory functions may exist (62). In rats exposed to toluene plus hexane, each solvent in a concentration of 1000 ppm (3750 mg/m3 toluene), a synergistic loss of auditory sensitivity was observed after 3 months (97). Toluene exposure causes a progressive severe loss of hair cells in the cochlea (15, 60, 61, 73, 133). Repeated oral dosing by gavage for 13 weeks caused neurone cell death in the brain in rats that received 2500 or 1250 mg/kg/day (51). Mutagenicity Carcinogenicity Toluene is not mutagenic in Salmonella typhimurium (9, 21, 47, 52, 59, 88, 89, 130). Toluene has not been found to induce DNA repair mediated toxicity to any of several bacteria strain tested, gene conversion in the yeast Saccharomyces cerevisiae or genotoxic effects in Drosophila melanogaster (59, 79, 80, 81, 87, 88, 117, 118, 155). Toluene does not appear to induce biologically significant increases in mutations, sister chromatid exchanges, micronuclei or DNA damage in vitro in mammalian cells at non-cytotoxic doses (18, 39, 59, 115, 125, 129, 160). Positive results have been obtained in three cytogenetic studies performed in the former USSR in the 1970’s (54). It has, however, been implied that these significant cytogenetic responses might be due to benzene contamination. In more recent studies, toluene has not induced biologically significant increases in micronuclei and chromosomal aberrations in the bone marrow of mice and rats or DNA damage in peripheral blood cells, bone marrow, and liver of mice (37, 59, 81, 82, 105, 119). Toluene can be considered to be adequately tested and is considered non-genotoxic in vivo. Equivocal results were obtained in a multitude of studies with biological monitoring of various genotoxic effects in peripheral blood lymphocytes from workers exposed to toluene in the occupational environment (5, 33, 36, 44, 45, 64, 71, 86, 95, 102, 104, 107). In most cases confounding due to coexposure to ink, other solvents and various genotoxic substances in the environment cannot be excluded. Smoking, estimated to increase chromosomal aberrations by 10-20% and sister chromatid exchange by 5-8% (96), was not considered in some older studies (33, 36), and matching for this confounding factor was inadequate in other studies (95, 102). A clear synergistic effect between toluene exposure and smoking was demonstrated in one study, that is, the genotoxic effect of smoking was enhanced by toluene (45). Toluene was not carcinogenic in rats or mice exposed via inhalation for two years (40, 51). 41 Toluene has been used as vehicle control in a number of dermal cancer studies in mice. No clear increase of skin tumours attributable to toluene was noted (54). The carcinogenic potential of toluene has been evaluated by IARC (54). IARC has evaluated toluene as not classifiable as to its carcinogenicity to humans (IARC Group 3). In the evaluation, four case-control studies involving several anatomical sites of cancer are mentioned. The results could not be evaluated with regard to toluene itself, because the exposure was to mixtures of solvents and not to pure toluene. A cohort of 1020 rotogravure printers exposed to toluene and employed for a minimum period of three months in eight plants during 1925-85 was studied. Based on the measurements in the 1940’s and 1950’s the maximum toluene concentration was about 450 ppm, but it was only about 30 ppm in the mid 1980’s. Exposure to benzene occurred until the beginning of the 1960’s. Compared with the regional rates, total mortality was not increased during the observation period 1952-86. There was no increase in mortality from non- malignant diseases of the lungs, nervous system, or gastrointestinal and urinary tracts. There was no overall excess of tumours in the years 1958-85. Among the specific cancers, those of the respiratory tract increased significantly. However, statistical significance was not attained, when only subjects with an exposure period of at least five years and a latency period of at least 10 years were considered, and no dose-response relationship could be established (135). The mortality from various cancer forms in a cohort of 6830 male and 751 female workers in the German rotogravure industry has been investigated. Mortality causes were based on death certificates. Because death certificates are removed after five years in many German federal states, the true number of cause- specific deaths was estimated mathematically based on the information on available causes of death. The number of deaths was 466. Total mortality from cancer (100 deaths observed, resulting in 122.7 estimated deaths) did not differ substantially from the expected level of 127.7 deaths. A significantly higher mortality due to bone and connective tissue tumours was identified, based on a low number of cases (7 deaths observed, resulting in 7.9 estimated deaths versus 4.2 deaths expected). Also mortality due to lung+trachea+bronchus tumours (35 deaths observed, resulting in 43.6 estimated deaths versus 35.4 expected deaths), and brain tumours and tumours of the nervous system was increased (6 deaths observed, resulting in 9.1 estimated deaths versus 4.1 deaths expected), but not to a level reaching statistical significance. Exposure information was very limited and based on work area (152). Reproductive effects Human data In two independent studies in rotogravure printers, effects on male hormones were studied. The observed effects were rather small with most hormone levels being within the reference limit. A correlation with present exposure concentrations was found for the levels of some hormones. Although the effects cannot be regarded as 42 directly adverse, the studies do give evidence that toluene might interfere with endocrine mechanisms (134, 136). The possible influence of toluene exposure on fertility was examined by retrospective interviews in a German cross sectional study of 150 male and 90 female workers. The findings of the study indicate reduced female fecundity in relation to low-level toluene exposure. The women worked exclusively in the stacking and bookbinding process, and their estimated overall exposure (based on measurements in previous years) was classified as low (<10 ppm) (106). However, due to various limitations, clear conclusions cannot be drawn from this study. Limitations in the study include potential for recall bias, i.e. persons with undesirable outcome may have recall of exposure, which is different from those who do not experience the outcome. More than one pregnancy per woman could be included in the study, and such pregnancies cannot be regarded as independent observations. Furthermore, the study suffered from an unvalidated low participa- tion rate (39% for women). Reasons for non-participation were not investigated. No evidence of menstrual disorders were found in female workers exposed to toluene at a mean concentration of 88 ppm (330 mg/m3), range 50-150 ppm, in a factory manufacturing audio speakers compared with an internal (exposed to 0-25 ppm toluene) and an external control group (90). There have been several case reports of mothers giving birth to children with so-called toluene embryopathy as a result of toluene sniffing during pregnancy. Microcephaly, narrow bifrontal diameter, short palpebral fissures, deep-set eyes, small midface, low-set prominent ears, micrognathia, spatulate fingertips, small fingernails, hypotonia, and hyperreflexia were found in the children. In total about 45 cases have been described in the literature (101). These cases all very much resemble the foetal alcohol syndrome, and there might be a common mechanism. Among women working in laboratories, spontaneous abortions and congenital malformations and birth weights of the children were examined in a retrospective case-referent study (138). Significant associations with spontaneous abortions were found for frequent exposure to toluene. No association with congenital malformation was found, however, the number of persons in the malformation study was too small for drawing final conclusions. Rates of spontaneous abortions were determined using a reproductive questionnaire in 55 women with 105 pregnancies exposed to toluene as the only solvent (mean 88 ppm, range 50-150 ppm). 31 women (68 pregnancies) working in the same factory in departments where little or no exposure to toluene occurred (0-25 ppm) answered the same questionnaire. An external community control group of 190 working class women who were receiving routine antenatal and postnatal care in public maternal health clinics with 444 pregnancies were also studied. The workers were exposed to fairly constant concentrations of toluene during the workshift. Exposure to toluene was assessed by passive personal sampling (31, 91). Only abortions from curettage after a diagnosis by a medical practitioner were determined, and spontaneous and induced abortions were clearly distinguished by probing questions as to the reasons for the curettage. Spontaneous abortion was defined by its occurrence after 12 weeks and before 28 43 weeks of pregnancy. Significantly higher rates for spontaneous abortions were noted in the toluene exposed women compared with those in the internal and external control groups (12.9% vs. 2.9-4.5%). The rate differences between groups were not likely to be confounded by classical risk factors such as maternal age, order of gravidity, smoking, or alcohol, which were taken into account both in the study design and the analysis (91). A weakness in the study is that a few women contributed with a large fraction of all spontaneous abortions (four women contributed with 9 out of 13 spontaneous abortions in the high toluene exposure group), but the employed (fixed effect) statistical models do not account for this dependence between the observations. Use of a fixed effect model leads to an underestimation of the uncertainty of the effect estimates in this context. A more feasible approach would be to use a random effect logistic regression model. However, the difference in spontaneous abortion rates between the high toluene exposure group and the women receiving care at the maternal health clinic is likely to stay significant with the random effect model. Animal data In a 15-week inhalation study no toluene-related effects on sperm morphology and vaginal cytology in rats exposed to 100, 625, and 1250 ppm toluene 6.5 h/day, 5 d/week, were found. Significantly and dose-related decreased sperm count and reduced epididymal weight was found in rats exposed via inhalation to a concen- tration of 2000 ppm (7500 mg/m3) during 6 h/day for 90 days. The NOAEL was 600 ppm (2250 mg/m3) (99). Inhalation of high concentrations of toluene (4000- 6000 ppm) for 2 h/day for 5 weeks caused reduced sperm count and quality, and reduced in vitro egg penetration ability. The exposure was also associated with narcotic effect, lacrimation, ataxia and tremor and reductions in body weight gain (98). Lower foetal weight, lower birth weight and delayed postnatal development have been reported in a number of studies (23, 46, 48, 50, 100, 139). The LOAELs are in the range of 1000-2000 ppm (3750-7500 mg/m3). The NOAELs are in the range of 400-750 ppm (1500-2812 mg/m3). A NOAEL for effects on birth weight and postnatal development of 600 ppm (2250 mg/m3) can reasonably be set. Increased spontaneous activity and impairments of cognitive functions (learning and memory) after exposure to toluene during brain development have been found in two studies in rats. In one study, the dams were exposed at 0 or 1200 ppm (4500 mg/m3) from gestational day 7 to postnatal day 18 (46). In the other study, the dams were exposed to 0 or 1800 ppm (6750 mg/m3 on gestational day 7-20 (48, 100, 139). In both studies, the behaviour of the offspring was studied. The LOAEL for the behavioural effects is 1200 ppm (4500 mg/m3) and a NOAEL cannot be established since lower exposure levels were not investigated. In mice, Courtney et al. (22) found some signs of foetotoxicity of toluene at 400 ppm (1500 mg/m3), the only dose level in this study. Jones and Balster (63) exposed pregnant mice to air, 200, 400, or 2000 ppm toluene on gestational days 12-17 and found lower birth weight, decreased postnatal weight gain, and delayed 44 reflex development in the absence of maternal toxicity at 2000 ppm toluene (7500 mg/m3). The NOAEL was 400 ppm (1500 mg/m3), but the daily exposure periods were limited to 3 hours. Effects on behaviour in the absence of maternal or general toxicity have been reported in mice after perinatal dosing via drinking water with approximately 60 mg toluene/kg/day (69). In rabbits equivocal effects were found in a study comprising two teratology tests (66). In the first part of the study (n=14) slight delays in skeletal develop- ment were registered at 500 ppm (1875 mg/m3). No effect was observed in the second part of the study at the same exposure level (n=20). Dose-effect / dose-response relationships The effects of toluene have been extensively studied in humans and laboratory animals. The key studies for evaluation of the important effects of toluene are listed in Table 2 (human data) and Table 3 (animal data). Liquid toluene is irritating to the skin and eyes in animals, while toluene vapours in concentrations at and above 100 ppm causes complaints of the eye, and nose and throat irritation in humans. In the rat, a NOAEL for clinical and morphological signs of toxicity of 300 ppm for repeated exposure via inhalation was identified in a 2-year study. In another 2- year study higher exposure levels (600 ppm) resulted in nasal toxicity and in- creased incidence of stomach ulcers. For the dermal route, no data on clinical and morphological signs of toxicity have been found. Toluene has been shown to affect the central nervous system and the inner ear. In humans exposed at rest under experimental conditions to 100 ppm toluene (375 mg/m3) headache, dizziness, feeling of intoxication, and irritation were recorded to occur with significantly increased frequency. At 150 mg/m3 (40 ppm) and below the effects have not been recorded to occur with increased frequency. For these subjective symptoms a LOAEL of 375 mg/m3 (100 ppm) and a NOAEL of 150 mg/m3 (40 ppm) can be established. Experimental chamber inhalation of 375 mg/m3 (100 ppm) toluene for 6 hours at rest has in two studies been shown to cause disruption of performance of psychological performance tests, and in another study a feeling of tests being more difficult and strenuous. In the latter study, a NOAEL of 40 ppm was found. For acute neuropsychological effects, 100 ppm can be regarded as a LOAEL. Chronic toxic encephalopathy (CTE) may be induced by toluene exposure during many years at concentrations ranging from 40-1700 mg/m3. In the study concerned, it is possible that even higher levels were present in earlier years. Toluene is ototoxic in the rat and causes a progressive severe loss of hair cells in the cochlea accompanied by hearing loss. The LOAEL in rats is around 1000 ppm (3750 mg/m3), and the NOAEL around 700 ppm (2625 mg/m3). In humans, occupational exposure to toluene increases the risk of developing noise-related hearing loss. The exposure concentrations in the studies where this has been 45 Table 2. LOAELs (lowest observed adverse effect levels) and NOAELs (no observed adverse effect levels) from human studies. Concentration Exposure duration Effects Ref. 40-1700 mg/m3 10-450 ppm possibly even higher concentrations in years preceding exposure estimation workplace, > 4-43 years, median 29 years fatigue, recent short-term memory problems, concentration difficulties, mood lability, reduced psychometric performance (161) 375-1125 mg/m3 average exposure levels 1978-1980: 140-600 ppm 1990: 75-365 ppm Workplace Increased incidence of high-frequency bilateral hearing loss (in the presence of noise) (51 noise+toluene-exposed, 50 unexposed, 50 noise-exposed, 39 organic solvent mixture exposed) (83) 375 mg/m3 100 ppm 6h LOAEL for impaired function performance of psychological performance tests (12, 112) 375 mg/m3 100 ppm 6h LOAEL for irritation of eyes, nose and throat (12) 375 mg/m3 100 ppm 6h LOAEL for irritation of the eyes and nose, headache, dizziness, and feeling of intoxication NOAEL for psychometric performance (however tests felt more difficult and strenuous) (16 experimentally exposed subjects, serving as their own control) (3) 300 mg/m3 range 50-150 ppm (mean 88 ppm) workplace Increased rate of spontaneous abortion (55 exposed, 31 internal controls, 190 external controls) (91) 150 mg/m3 40 ppm 6h NOAEL for irritation of the eyes and nose, headache, dizziness, and feeling of intoxikation (16 experimentally exposed subjects, serving as their own control) (3) 37,5 mg/m3 10 ppm 6h LOAEL for deterioration in the perceived air quality and increased odour level (16 experimentally exposed subjects, serving as their own control) (3) 46 Table 3. LOAELs (lowest observed adverse effect levels) and NOAELs (no observed adverse effect levels) from animal studies. Concentraion Exposure duration Species and effects Ref. 30 mg/m3 8000 ppm 4-6.5h Rat, lethal (LD50) (7, 14, 108, 128) 3750 mg/m3 1000 ppm 2 weeks Rat, LOAEL for auditory toxicity (111) 3750 mg/m3 1000 ppm gestation day 9-21 Rat, LOAEL for reduced birth weight and retarded postnatal development (139) 2625 mg/m3 700 ppm 16 weeks Rat, NOAEL for auditory toxicity (111) 2250 mg/m3 600 ppm 2 years Rat, LOAEL for nasal toxicity and clinical and morphological signs of toxicity (nasal toxicity and stomach ulcers) (51) 2250 mg/m3 600 ppm gestation day 9-21 Rat, NOAEL for reduced birth weight and retarded postnatal development (139) 1125 mg/m3 300 ppm 2 years Rat, NOAEL for clinical and morphological signs of toxicity (40) shown were relatively high (in the first study 281-2250 mg/m3; in the second study up to 919 mg/m3). The data cannot be used to identify a human NOAEL. In toluene-exposed female workers a significantly higher rate of spontaneous abortions was found. The mean toluene concentration was 88 ppm (333 mg/m3) with a range of 50-150 ppm (188-563 mg/m3). At higher concentrations in animal studies, toluene has been found to cause lower foetal and birth weight with a LOAEL of around 1000 ppm (3800 mg/m3), and NOAEL around 600 ppm (2280 mg/m3). Long-lasting developmental neurotoxicity (impairment of learning ability) has been demonstrated in offspring exposed prenatally or pre- and postnatally with a LOAEL of 1200 ppm (4560 mg/m3). In male rats exposed to 2000 ppm (7600 mg/m3), reduced sperm count was found with a NOAEL of 600 ppm (2250 mg/m3). Conclusions The critical effects of toluene exposure are acute CNS effects, irritation and spontaneous abortions. Headache, dizziness, feeling of intoxication, irritation of the eyes, nose and throat and impaired function in neuropsychological tests have been reported after experimental exposure of volunteers at rest for 6 h at 100 ppm (LOAEL). A NOAEL of 40 ppm (irritation) has been reported in healthy volunteers. For spontaneous abortion (studied epidemiologically) the dose- response relationship is not well known in terms of concentrations and duration 47 of exposure. In one study an increased risk for spontaneous abortion was found at concentrations varying between 50-150 ppm (average 88 ppm). Other effects of concern are ototoxicity and chronic toxic encephalopathy. Ototoxicity has been studied epidemiologically, and the dose-response relation is not well known. However, ototoxicity has been thoroughly investigated in experi- mental animals, and a LOAEL of 1000 ppm and a NOAEL of 700 ppm has been identified. Chronic toxic encephalopathy has been studied epidemiologically, and the dose-response relation is not well known. However, it is believed that an individual must be exposed for many years before chronic toxic encephalopathy occurs. In the study concerned, exposure concentrations ranged from 40-1700 mg/m3 (10-500 ppm), and it is possible that even higher levels were present in earlier years. Dermal exposure to liquid toluene may result in significant systemic exposure. References 1. Abbate C, Giorgianni C, Munaò F, Brecciaroli R. Neurotoxicity induced by exposure to toluene. Int Arch Occup Environ Health 1993;64:389-392. 2. Amoore JE, Hautala E. Odor as an aid to chemical safety: Odor thresholds compard with threshold limit values and volatilities for 214 industrial chemicals in air and water dilution. J Appl Toxicol 1983;3:272-289. 3. Andersen I, Lundqvist GR, Molhave L, Pedersen OF, Proctor DF, Vaeth M, Wyon DP. Human response to controlled levels of toluene in six-hour exposures. Scand J Work Environ Health 1983;9:405-418. 4. Askergren A. Organic solvents and kidney function. Adv Mod Environ Toxicol 1982;2:157- 172. 5. Bauchinger M, Schmid E, Dresp J, Kolin-Gerresheim J, Hauf R, Suhr E. Chromosome changes in lymphocytes after occupational exposure to toluene. Mutat Res 1982;102:439- 445. 6. Boey KW, Foo SC, Jeyaratnam J. Effects of occupational exposure to toluene: a neuropsychological study on workers in Singapore. Ann Acad Med Singapore 1997;26:184- 187. 7. Bonnet P, Morele Y, Raoult G, Zissu D, Gradiski D. Détermination de la concentration léthale50 des principaux hydrocarbures aromatiques chez le rat. Arch Mal Prof 1982;34:261- 265. 8. Boor JW, Hurtig HI. Persistent cerebellar ataxia after exposure to toluene. Ann Neurol 1977;2:440-442. 9. Bos RP, Brouns RME, Doorn Rv, Theuws JLG, Henderson PT. Non-mutagenicity of toluene, o-, m- and p-xylene, o-methylbenzylalcohol and o-methylbenzylsulfate in the Ames assay. Mutat Res 1981;88:273-279. 10. Brooke I, Cocker J, Delic JI, Payne M, Jones K, Gregg NC, Dyne D. Dermal uptake of solvents from the vapour phase: an experimental study in humans. Ann Occup Hyg 1998;42:531-540. 11. Browning E. Toxicity and metabolism of industrial solvents. Amsterdam: Elsevier Publishing Company 1965:66-76. 12. Bælum J, Andersen IB, Lundqvist GR, Mølhave L, Pedersen OF, Væth M, Wyon DP. Response of solvent-exposed printers and unexposed controls to six-hour toluene exposure. Scand J Work Environ Health 1985;11:271-280. 48 13. Bælum J, Lundqvist GR, Mølhave L, Andersen NT. Human response to varying concentrations of toluene. Int Arch Occup Environ Health 1990;62:65-71. 14. Cameron GR, Paterson JLH, De Saram GSW, Thomas JC. The toxicity of some methyl derivatives of benzene with special reference to pseudocumene and heavy coal tar naphtha. J Path Bact 1938;46:95-107. 15. Campo P, Lataye R, Cossec B, Placidi V. Toluene-induced hearing loss: a mid-frequency location of the cochlear lesions. Neurotoxicol Teratol 1997;19:129-140. 16. Carlsson A. Exposure to toluene. Uptake, distribution and elimination in man. Scand J Work Environ Health 1982;8:43-55. 17. Carlsson A, Ljungquist E. Exposure to toluene. Concentration in subcutaneous adipose tissue. Scand J Work Environ Health 1982;8:56-62. 18. Casto BC. Detection of chemical carcinogens and mutagens in hamster cells by enhancement of adenovirus transformation. In: Mishra N, Dunkel V, Mehlman I (eds.) Advances in modern environmental toxicology. Vol.1. Princeton NJ: Senate Press, 1981:241-271. 19. Chang MJW, Hsu KH, Chen YC, Hsieh LL, Luo JJ. Biological monitoring of urinary hippuric acid in a Taiwanese semiconductor company. International symposium on biological monitoring in occupational and environmental health. Finnish Institute of Occupational Health, 1996:94-95. 20. Cherry N, Johnston JD, Venables H, Waldron HA, Buck L, MacKay CJ. The effects of toluene and alcohol on psychomotor performance. Ergonomics 1983;26:1081-1087. 21. Connor TH, Theiss JC, Hanna HA, Monteith DK, Matney TS. Genotoxicity of organic chemicals frequently found in the air of mobile homes. Toxicol Lett 1985;25:33-40. 22. Courtney KD, Andrews JE, Springer J, Menache M, Williams T, Dalley L, Graham JA. A perinatal study of toluene in CD-1 mice. Fundam Appl Toxicol 1986;6:145-154. 23. da Silva V, Malheiros LR, Paumgartten FJ, Sa-Rego Mde M, Riul TR, Golovattei MA. Developmental toxicity of in utero exposure to toluene on malnourished and well nourished rats. Toxicology 1990;64:155-168. 24. Danish EPA. Risk Assessment. Toluene. Final report. EU Existing Substances Risk Assessment Programme 2001. 25. de-Ceaurriz JC, Micillino JC, Bonnet P, Guenier JP. Sensory irritation caused by various industrial airborne chemicals. Toxicol Lett 1981;9:137-143. 26. ECETOC. Strategy for skin notation. ECETOC Document 1993;31. 27. Echeverria D, Fine L, Langolf G, Schork A, Sampaio C. Acute neurobehavioural effects of toluene. Br J Ind Med 1989;46:483-495. 28. Echeverria D, Fine L, Langolf G, Schork T, Sampaio C. Acute behavioural comparisons of toluene and ethanol in human subjects. Br J Ind Med 1991;48:750-761. 29. Fodor GG. Schädliche Dämpfe. Düsseldorf: VDI Verlag, 1972. 30. Foo SC, Jeyaratnam J, Koh D. Chronic neurobehavioural effects of toluene. British J Ind Med 1990;47:480-484. 31. Foo SC, Phoon WO, Khoo NY. Toluene in blood after exposure to toluene. Am Ind Hyg Assoc J 1988;49:255-258. 32. Fornazzari L, Wilkinson DA, Kapur BM, Carlen PL. Cerebellar, cortical and functional impairment in toluene abusers. Acta Neurol Scand 1983;67:319-329. 33. Forni A, Pacifico E, Limonta A. Chromosome studies in workers exposed to benzene or toluene or both. Arch Environ Health 1971;22:373-378. 34. Franchini I, Cavatorta A, Falzoi M, Lucertini S, Mutti A. Early indicators of renal damage in workers exposed to organic solvents. Int Arch Occup Environ Health 1983;52:1-9. 35. Freie Universität Berlin UBFIfT. Feldstudie Toluol (Tiefdruck). 1996. 36. Funes-Cravioto F, Zapata-Gayon C, Kolmodin-Hedman B, Lambert B, Lindsten J, Norberg E, Nordenskjöld M, Olin R, Swensson Å. Chromosome aberrations and sister-chromatid 49 exchange in workers in chemical laboratories and a rotoprinting factory and in children of women laboratory workers. Lancet 1977;2:322-325. 37. Gad-El KM, Harper BL, Legator MS. Modifications in the myeloclastogenic effect of benzene in mice with toluene, phenobarbital, 3-methylcholanthrene, Aroclor 1254 and SKF- 525A. Mutat Res 1984;135:225-243. 38. Gerarde HW. Toxicology and biochemistry of aromatic hydrocarbons. Amsterdam: Elsevier Publishing Company, 1960:141-150. 39. Gerner-Smidt P, Friedrich U. The mutagenic effect of benzene, toluene and xylene studied by the SCE technique. Mutat Res 1978;58:313-316. 40. Gibson JE, Hardisty JF. Chronic toxicity and oncogenicity bioassay of inhaled toluene in Fischer-344 rats. Fundam Appl Toxicol 1983;3:315-319. 41. Guillot JP, Gonnet JF, Clement C, Caillard L, Truhaut R. Evaluation of the cutaneous- irritation potential of 56 compounds. Food Chem Toxicol 1982;20:563-572. 42. Guillot JP, Gonnet JF, Clement C, Caillard L, Truhaut R. Evaluation of the ocular-irritation potential of 56 compounds. Food Chem Toxicol 1982;20:573-582. 43. Gusev IS. The reflex action of microconcentrations of benzene, toluol, xylol and their comparative assessment. Gig Sanit 1965;30:6-11. (in Russian, with summary in English) 44. Haglund U, Lundberg I, Zech L. Chromosome aberrations and sister chromatid exchanges in Swedish paint industry workers. Scand J Work Environ 1980;6:291-298. 45. Hammer KD, Mayer N, Pfeiffer EH. Sister chromatid exchange in rotogravure printing plant workers. Int Arch Occup Environ Health 1998;71:138-142. 46. Hass U, Lund SP, Hougaard KS, Simonsen L. Developmental neurotoxicity after toluene inhalation exposure in rats. Neurotoxicol Teratol 1999;21:349-357. 47. Haworth S, Lawlor T, Mortelmans K, Speck W, Zeiger E. Salmonella mutagenicity test results for 250 chemicals. Environ Mutagen 1983;5 Suppl. 1:3-142. 48. Hougaard KS, Lund SP, Simonsen L. Effects of prenatal exposure to toluene on postnatal development and behaviour in rats. Neurotoxicol Teratol 1999;21:241-250. 49. Huang J, Asaeda N, Takeuchi Y, Shibata E, Hisanaga N, Ono Y, Kato K. Dose dependent effects of chronic exposure to toluene on neuronal and glial cell marker proteins in the central nervous system of rats. Br J Ind Med 1992;49:282-286. 50. Hudák A, Ungváry G. Embryotoxic effects of benzene and its methyl derivatives: toluene, xylene. Toxicology 1978;11:55-63. 51. Huff J. Toxicology and carcinogenesis studies of toluene (Cas No. 108-88-3) in F344/N rats and B6C3F1 mice (Inhalation Studies). US Department of Health and Human Services. National Institute of Health, 1990. 52. Hughes TJ, Simmons DM, Monteith LG, Claxton LD. Vaporization technique to measure mutagenic activity of volatiles organic chemicals in the Ames/Salmonella assay. Environ Mutagen 1987;9:421-441. 53. Hydén D, Larsby B, Andersson H, Ödkvist LM, Liedgren SR, Tham R. Impairment of visuo- vestibular interaction in humans exposed to toluene. ORL J Otorhinolaryngol Relat Spec 1983;45:262-269. 54. IARC. Re-evaluation of some organic chemicals, hydrazine and hydrogen peroxide (Part two). In: IARC monographs on the evaluation of carcinogenic risks to humans. Lyon: International Agency for Research on Cancer, 1999. 55. Ikeda M, Othsuji H. Phenobarbital-induced protection against toxicity of toluene and benzene in the rat. Toxicol Appl Pharmacol 1971;20:30-43. 56. Inoue O, Seiji K, Takahashi M, Kudo K, Nakatsuka H, Watanabe T, Uchida Y, Ikeda M. Subtle increase in leukocyte counts in association with drinking and smoking habits. Int Arch Occup Environ Health 1995;66:383-388. 50 57. Iregren A. Effects on psychological test performance of workers exposed to a single solvent (toluene)--a comparison with effects of exposure to a mixture of organic solvents. Neurobehav Toxicol Teratol 1982;4:695-701. 58. Iregren A, Akerstedt T, Anshelm OB, Gamberale F. Experimental exposure to toluene in combination with ethanol intake. Psychophysiological functions. Scand J Work Environ Health 1986;12:128-136. 59. Jagannath DR, Matheson D, Brusick D. Mutagenicity evaluation of toluene. Litton Bionetics Inc., Kensington, Maryland, 1978. 60. Johnson AC, Canlon B. Progressive hair cell loss induced by toluene exposure. Hear Res 1994;75:201-208. 61. Johnson AC, Canlon B. Toluene exposure affects the functional activity of the outer hair cells. Hear Res 1994;72:189-196. 62. Johnson AC, Juntunen L, Nylen P, Borg E, Hoglund G. Effect of interaction between noise and toluene on auditory function in the rat. Acta Otolaryngol Stockh 1988;105:56-63. 63. Jones HE, Balster RL. Neurobehavioral consequences of intermittent prenatal exposure to high concentrations of toluene. Neurotoxicol Teratol 1997;19:305-313. 64. Karacic V, Skender L, Bosner-Cucancic B, Bogadi-Sare A. Possible genotoxicity in low level benzene exposure. Am J Ind Med 1995;27:379-388. 65. Kimura ET, Ebert DM, Dodge PW. Acute toxicity and limits of solvent residue for sixteen organic solvents. Toxicol Appl Pharmacol 1971;19:699-704. 66. Klimisch HJ, Hellwig J, Hofmann A. Studies on the prenatal toxicity of toluene in rabbits following inhalation exposure and proposal of a pregnancy guidance value. Arch Toxicol 1992;66:373-381. 67. Koga K, Ohmiya Y. Potentiation of toluene toxicity by hepatic enzyme inhibition in mice. J Toxicol Sci 1978;3:25-30. 68. Korbo L, Ladefoged O, Lam HR, Ostergaard G, West MJ, Arlien SP. Neuronal loss in hippocampus in rats exposed to toluene. Neurotoxicology 1996;17:359-366. 69. Kostas J, Hotchin J. Behavioral effects of low-level perinatal exposure to toluene in mice. Neurobehav Toxicol Teratol 1981;3:467-469. 70. Ladefoged O, Strange P, Moller A, Lam HR, Ostergaard G, Larsen JJ, Arlien SP. Irreversible effects in rats of toluene (inhalation) exposure for six months. Pharmacol Toxicol 1991;68:384-390. 71. Lagorio S, Tagesson C, Forastiere F, Iavarone I, Axelson O, Carere A. Exposure to benzene and urinary concentrations of 8-hydroxydeoxyguanosine, a biological marker of oxidative damage to DNA. Occup Environ Med 1994;51:739-743. 72. Larsen F, Leira HL. Organic brain syndrome and long-term exposure to toluene: a clinical, psychiatric study of vocationally active printing workers. J Occup Med 1988;30:875-878. 73. Lataye R, Campo P. Combined effects of a simultaneous exposure to noise and toluene on hearing function. Neurotoxicol Teratol 1997;19:373-382. 74. Lauwerys R. Human biological monitoring of industrial chemicals series. Toluene. Industrial health and safety. Ispra, 1983:1-175. 75. Lazar RB, Ho SU, Melen O, Daghestani AN. Multifocal central nervous system damage caused by toluene abuse. Neurology 1983;33:1337-1340. 76. Lundberg I, Håkansson M, Gustavsson P. Relative hepatotoxic effect of 14 industrial solvents after intraperitoneal injection in rats. Arbete och Hälsa 1983;22:1-20. Arbetarskyddsverket, Solna. (in Swedish with English summary) 77. Löf A, Johanson G. Toxicokinetics of organic solvents: A review of modifying factors. Crit Rev Toxicol 1998;28:571-650. 78. Löf A, Wallen M, Wigaeus HE. Influence of paracetamol and acetylsalicylic acid on the toxicokinetics of toluene. Pharmacol Toxicol 1990;66:138-141. 51 79. Matsushita T, Arimatsu Y, Ueda A, Satoh K, Nomura S. Hematological and neuro-muscular response of workers exposed to low concentration of toluene vapor. Ind Health 1975;13:115- 121. 80. McCarrol NE, Keech BH, Piper CE. A microsuspension adaptation of the Bacillus subtilis 'rec' assay. Environ Mutagenesis 1981;3:607-616. 81. McCarrol NE, Piper CE, Keech BH. An E. coli microsuspension assay for the detection of DNA damage induced by direct-acting agents and promutagens. Environ Mutagenesis 1981;3:429-444. 82. Mohtashamipur E, Norpoth K, Woelke U, Huber P. Effects of ethylbenzene, toluene, and xylene on the induction of micronuclei in bone marrow polychromatic erythrocytes of mice. Arch Toxicol 1985;58:106-109. 83. Morata TC, Dunn DE, Kretschmer LW, Lemasters GK, Keith RW. Effects of occupational exposure to organic solvents and noise on hearing. Scand J Work Environ Health 1993;19:245-254. 84. Morata TC, Fiorini AC, Fischer FM, Colacioppo S, Wallingford KM, Krieg EF, Dunn DE, Gozzoli L, Padrao MA, Cesar CL. Toluene-induced hearing loss among rotogravure printing workers. Scand J Work Environ Health 1997;23:289-298. 85. Muller J, Greff G. Relation between the toxicity of molecules of industrial value and their physico-chemical properties: test of upper airway irritation applied to 4 chemical groups. Food Chem Toxicol 1984;22:661-664. 86. Mäki-Paakkanen J, Husgafvel-Pursiainen K, Kalliomäki P-L, Tuominen J, Sorsa M. Toluene- exposed workers and chromosome aberrations. J Toxicol Environ Health 1980;6:775-781. 87. Mørck HI, Winkel P, Gyntelberg F. Helbredseffekter af toluenudsættelse. Arbejdsmiljøfondet, København, 1985:1-54. (in Danish, with English summary) 88. Nakamura S, Oda Y, Shimada T, Oki I, Sugimoto K. SOS-inducing activity of chemical carcinogens and mutagens in Salmonella typhimurium TA1535/pSK 1002: examination with 151 chemicals. Mutat Res 1987;192:239-246. 89. Nestmann ER, Lee EGH, Matula TI, Douglas GR, Mueller JC. Mutagenicity of constituents identified in pulp and paper mill effluents using the Salmonella/mammalian-microsome assay. Mutat Res 1980;79:203-212. 90. Ng TP, Foo SC, Yoong T. Menstrual function in workers exposed to toluene. Brit J Ind Med 1992;49:799-803. 91. Ng TP, Foo SC, Yoong T. Risk of spontaneous abortion in workers exposed to toluene. Br J Ind Med 1992;49:804-808. 92. Nielsen GD, Alarie Y. Sensory irritation, pulmonary irritation, and respiratory stimulation by airborne benzene and alkylbenzenes: prediction of safe industrial exposure levels and correlation with their thermodynamic properties. Toxicol Appl Pharmacol 1982;65:459-477. 93. Nielsen HK, Krusell L, Bælum J, Lundqvist G, Omland Ø, Væth M, Husted SE, Mogensen CE, Geday E. Renal effects of acute exposure to toluene. A controlled clinical trial. Acta Med Scand 1985;218:317-321. 94. Nise G, Attewell R, Skerfving S, Ørbæk P. Elimination of toluene from venous blood and adipose tissue after occupational exposure. Br J Ind Med 1989;46:407-411. 95. Nise G, Högstedt B, Bratt I, Skerfving S. Cytogenetic effects in rotogravure workers exposed to toluene (and benzene). Mutat Res 1991;261:217-223. 96. Nordic Study Group on the Health Risk of Chromosome Damage. A Nordic data base on somatic chromosome damage. Mutat Res 1990;241:325-337. 97. Nylén P, Hagman M, Johnson AC. Function of the auditory and visual systems, and of peripheral nerve, in rats after long-term combined exposure to n-hexane and methylated benzene derivatives. I. Pharmacol Toxicol 1994;74:116-123. 52 98. Ono A, Kawashima K, Sekita K, Hirose A, Ogawa Y, Saito M, Naito K, Yasuhara K, Kaneko T, Furuya T, Inoue T, Kurokawa Y. Toluene inhalation induced epididymal sperm dysfunction in rats. Toxicology 1999;139:193-205. 99. Ono A, Sekita K, Ogawa Y, Hirose A, Suzuki S, Saito M, Naito K, Kaneko T, Furuya T, Kawashima K, Yasuhara K, Matsumoto K, Tanaka S, Inoue T, Kurokawa Y. Reproductive and developmental toxicity studies of toluene. II. Effects of inhalation exposure on fertility in rats. J Environ Pathol Toxicol Oncol 1996;15:9-20. 100. Ono A, Sekita K, Ohno K, Hirose A, Ogawa Y, Saito M, Naito K, Kaneko T, Furuya T, Matsumoto K, Tanaka S, Kurokawa Y. Reproductive and developmental toxicity of toluene I. Teratogenicity study of inhalation exposure in pregnant rats. J Toxicol Sci 1995;20:109-134. 101. Pearson MA, Hoyme HE, Seaver LH, Rimeza ME. Toluene embryopathy: Delineation of the phenotype and comparison with fetal alcohol syndrome. Pediatrics 1994;93:211-215. 102. Pelclová D, Rössner P, Picková J. Chromosome aberrations in rotogravure printing plant workers. Mutat Res 1990;245:299-303. 103. Piotrowski J. Quantitative estimate of the absorption of toluene in people. Med Pracy 1967;18:213-223. (in Polish, with English summary) 104. Pitarque M, Vaglenov A, Nosko M, Hirvonen A, Norrpa H, Creus A, Marcos R. Evaluation of DNA damage by the Comet assay in shoe workers exposed to toluene and other organic solvents. Mutat Res 1999;441:115-127. 105. Plappert U, Barthel E, Seidel HJ. Reduction of benzene toxicity by toluene. Environ Mol Mutagen 1994;24:283-292. 106. Plenge-Bönig A, Karmaus W. Exposure to toluene in the printing industry is associated with subfecundity in women but not in men. Occup Environ Med 1999;56:443-448. 107. Popp W, Vahrenholz C, Yaman S, Müller C, Müller G, Schmeiding W, Norpoth K, Fahnert R. Investigation of the frequency of DNA strand breakage and cross-linking and of sister chromatid exchange frequency in the lymphocytes of female workers exposed to benzene and toluene. Carcinogenesis 1992;13:57-61. 108. Pozzani UC, Weil CS, Carpenter CP. The toxicological basis of threshold limit values: 5. The experimental inhalation of vapor mixtures by rats, with notes upon the relationship between single dose inhalation and single dose oral data. Am Ind Hyg Assoc J 1959;20:364-369. 109. Pryor GT, Dickinson J, Howd RA, Rebert CS. Neurobehavioral effects of subchronic exposure of weanling rats to toluene or hexane. Neurobehav Toxicol Teratol 1983;5:47-52. 110. Pryor GT, Dickinson J, Howd RA, Rebert CS. Transient cognitive deficits and high- frequency hearing loss in weanling rats exposed to toluene. Neurobehav Toxicol Teratol 1983;5:53-57. 111. Pryor GT, Rebert CS, Dickinson J, Feeney EM. Factors affecting toluene-induced ototoxicity in rats. Neurobehav Toxicol Teratol 1984;6:223-238. 112. Rahill AA, Weiss B, Morrow PE, Frampton MW, Cox C, Gibb R, Gelein R, Speers D, Utell MJ. Human performance during exposure to toluene. Aviat Space Environ Med 1996;67:640- 647. 113. Rebert CS, Sorenson SS, Howd RA, Pryor GT. Toluene-induced hearing loss in rats evidenced by the brainstem auditory-evoked response. Neurobehav Toxicol Teratol 1983;5:59-62. 114. Reisin E, Teicher A, Jaffe R, Eliahou HE. Myoglobinuria and renal failure in toluene poisoning. Br J Ind Med 1975;32:163-168. 115. Richer CL, Chakrabarti S, Senécal-Quevillon M, Duhr MA, Zhang XX, Tardif R. Cytogenetic effects of low-level exposure to toluene, xylene, and their mixture on human blood lymphocytes. Int Arch Occup Environ Health 1993;64:581-585. 116. Riihimäki V, Pfäffli P. Percutaneous absorption of solvent vapors in man. Scand J Work Environ Health 1978;4:73-85. 53 117. Rodrigue-Arnaiz R, Villalobos-Pietrini R. Genetic effects of thinner, benzene and toluene in Drosophila melanogaster. 1. Sex chromosome loss and non-dis-junction. Contam Ambiental 1985;1:35-43. 118. Rodrigue-Arnaiz R, Villalobos-Pietrini R. Genetic effects of thinner, benzene and toluene in Drosophila melanogaster. 2. Sex linked recessive lethal mutations and translocations II-III. Contam Amb 1985;1:45-49. 119. Roh J, Moon YH, Kirr K-Y. The cytogenetic effects of benzene and toluene on bone marrow cells in rats. Yonsei Medical Journal 1987;28:297-309. 120. Russ G, Clarkson AR, Woodroffe AJ, Seymour AE, Cheng IKP. Renal failure from glue sniffing. Med J Aust 1981;2:121-123. 121. Ruth JH. Odor thresholds and irritation levels of several chemical substances: A review. Am Ind Hyg Assoc J 1986;47:142-151. 122. Sasa M, Igarashi S, Miyazaki T, Miyazaki K, Nakano S, Matsuoka I. Equilibrium disorders with diffuse brain atrophy in long-term toluene sniffing. Arch Otorhinolaryngol 1978;221:163-169. 123. Sato A, Nakajima T, Fujwara Y, Hirosawa K. Pharmakokinetics of benzene and toluene. Int Arch Arbeitsmed 1974;33:169-182. 124. Sherwood RJ. Ostwald solubility coefficients of some industrially important substances. Brit J Ind Med 1976;33:106-107. 125. Sina JF, Bean CL, Dysart GR, Taylor VI, Bradley BO. Evaluation of the alkaline elution/rat hepatocyte as a predictor of carcinogenic/mutagenic potential. Mutat Res 1983;113:357-391. 126. Slomianka L, Edelfors S, Ravn-Jonsen A, Rungby J, Danscher G, West MJ. The effect of low-level toluene exposure on the developing hippocampal region of the rat: Histological evidence and volumetric findings. Toxicology 1990;62:189-202. 127. Slomianka L, Rungby J, Edelfors S, Ravn-Jonsen A. Late postnatal growth in the dentate area of the rat hippocampus compensates for volumetric changes caused by early postnatal toluene exposure. Toxicology 1992;94:203-208. 128. Smyth HF, Carpenter CP, Weil CS, Pozzani UC, Striegel JA, Nycum JS. Range-finding toxicity data: List VII. Am Ind Hyg Assoc J 1969;30:470-476. 129. Snyder RD, Matheson DW. Nick translation – a new assay for monitoring DNA damage and repair in cultured human fibroblasts. Env Mutagen 1985;7:267-279. 130. Spanggord RJ, Mortelmans KE, Griffin AF, Simmon VF. Mutagenicity in Salmonella typhimurium and structure-activity relationships of wastewater components emanating from the manufacture of trinitrotoluene. Environ Mutagen 1982;4:163-179. 131. Stengel B, Cenee S, Limasset JC, Diebold F, Michard D, Druet P, Hemon D. Immunologic and renal markers among photogravure printers exposed to toluene. Scand J Work Environ Health 1998;24:276-284. 132. Sugai S, Murata K, Kitagaki T, Tomita I. Studies on the eye irritation caused by chemicals in rabbits - 1. A quantitative structure-activity relationships approach to primary eye irritation of chemicals in rabbits. J Toxicol Sci 1990;15:245-262. 133. Sullivan MJ, Rarey KE, Conolly RB. Ototoxicity of toluene in rats. Neurotoxicol Teratol 1989;10:525-530. 134. Svensson BG, Erfurth EM, Nise G, Nilsson A, Skerfving S. Hormone status in occupational toluene exposure. Am J Ind Med 1992;22:99-107. 135. Svensson BG, Nise G, Englander V, Attewell R, Skerfving S, Möller T. Deaths and tumours among rotogravure printers exposed to toluene. Br J Ind Med 1990;47:372-379. 136. Svensson BG, Nise G, Erfurth EM, Olsson H. Neuroendocrine effects in printing workers exposed to toluene. Br J Ind Med 1992;49:402-408. 137. Swedish Criteria Group for Occupational Standards. Scientific Basis for Swedish Occupational Standards. Toluene. Arbete och Hälsa 1981;21:40-45. Arbetarskyddsverket, Solna. 54 138. Taskinen H, Kyyrönen P, Hemminki K, Hoikkala M, Lajunen K, Lindbohm M-L. Laboratory work and pregnancy outcome. J Occup Med 1994;36:311-319. 139. Thiel R, Chahoud I. Postnatal development and behaviour of Wistar rats after prenatal toluene exposure. Arch Toxicol 1997;71:258-265. 140. Tsuruta H. Percutaneous absorption of organic solvents. III. On the penetration rates of hydrophobic solvents through the excised rat skin. Ind Health 1982;20:335-345. 141. Tsuruta H. Skin absorption of solvent mixtures - effect of vehicles on skin absorption of toluene. Ind Health 1996;34:369-378. 142. Tähti H, Kärkkäinen S, Pyykkö K, Rintala E, Kataja M, Vapaatalo H. Chronic occupational exposure to toluene. Int Arch Occup Environ Health 1981;48:61-69. 143. U.S. Department of Health & Human Services. Public Health Service. Agency for Toxic Substances and Disease Registry (ATSDR). Toxicological profile for toluene (Update). Draft for public comment. 1998. 144. Ungváry G, Tátrai E, Szeberényi S, Rodics K, Lörincz M, Barcza G. Effect of toluene exposure on the liver under different experimental conditions. Exp Mol Pathol 1982;36:347- 360. 145. Ursin C, Hansen CM, van Dyk JW, Jensen PO, Christensen IJ, Ebbehoej J. Permeability of commercial solvents through living human skin. Am Ind Hyg Assoc J 1995;56:651-660. 146. Veulemans H, Masschelein R. Experimental human exposure to toluene. II. Toluene in venous blood during and after exposure. Int Arch Occup Environ Health 1978;42:105-117. 147. Vrca A, Bozicevic D, Bozikov V, Fuchs R, Malinar M. Brain stem evoked potentials and visual evoked potentials in relation to the length of occupational exposure to low levels of toluene. Acta Med Croatica 1997;51:215-219. 148. Vrca A, Bozicevic D, Karacic V, Fuchs R, Prpic-Majic D, Malinar M. Visual evoked potentials in individuals exposed to long-term low concentrations of toluene. Arch Toxicol 1995;69:337-340. 149. Vrca A, Karacic V, Bozicevic D, Fuchs R, Malinar M. Cognitive evoked potentials VEP P300 in persons occupationally exposed to low concentrations of toluene. Arh hig rada toksikol 1997;48:277-285. 150. Wahlberg JE. Edema-inducing effects of solvents following topical administration. Dermatosen 1984;32:91-94. 151. Wahlberg JE. Erythema-inducing effects of solvents following epicutaneous administration to man - Studied by laser Doppler flowmetry. Scand J Work Environ Health 1984;10:159-162. 152. Wiebelt H, Becker N, Holzmeier S. Kohortenstudie zur Mortalität in einer toluolexponierten Berufsgruppe (Tiefdrucker) und einer Vergleichsgruppe aus der papierverarbeitenden Industrie (Hygieneartikel). Abschlussbericht. Deutsches Krebsforschungszentrum, Abteilung Epidemiologie, Heidelberg, 1996. 153. Wigger-Alberti W, Krebs A, Elsner P. Experimental irritant contact dermatitis due to cumulative epicutaneous exposure to sodium lauryl sulphate and toluene: single and concurrent application. Br J Dermatol 2000;143:551-556. 154. Winneke G, Krämer U, Kastka J. Zur Beeinflussung psychomotorischer Leistungen durch Alkohol und durch verschiedene Lösungsmitteldämpfe. In: Horváth M, ed. Adverse effects of environmental chemical and psychotropic drugs. Vol. 2. Amsterdam: Elsevier Scientific Publishing Company, 1976. 155. Winston S, Matsuhita T. Permanent loss of chromosome initiation in toluene-treated Bacillus subtilis cells. J Bacteriol 1975;123:921-927. 156. Withey RJ, Hall JW. The joint toxic action of perchloroethylene with benzene or toluene in rats. Toxicology 1975;4:5-15. 157. Woiwode W, Drysch K. Experimental exposure to toluene: further consideration of cresol formation in man. Br J Ind Med 1981;38:194-197. 55 158. Woiwode W, Wodarz R, Drysch K, Weichardt H. Metabolism of toluene in man: Gas- chromatographic determination of o-, m- and p-cresol in urine. Arch Toxicol 1979;43:93-98. 159. Wolf MA, Rowe VK, McCollister DD, Hollingsworth RL, Oyen F. Toxicological studies of certain alkylated benzenes and benzene. Arch Ind Health 1956;14:387-398. 160. Zarani F, Papazafiri P, Kappas A. Induction of micronuclei in human lymphocytes by organic solvents in vitro. J Environ Pathol Toxicol Oncol 1999;18:21-28. 161. Ørbæk P, Nise G. Neurasthenic complaints and psychometric function of toluene-exposed rotogravure printers. Am J Ind Med 1989;16:67-77. 162. Østergaard G. Nordic Expert Group for Documentation of Occupational Exposure Limits 125. Toluene. Arbete och Hälsa 2000;19:1-45. Arbetslivsinstitutet, Solna. 56 Summary Montelius J (ed). Scientific Basis for Swedish Occupational Standards. XXIII. Arbete och Hälsa 2002:19, pp 1-63. National Institute for Working Life, Solna. Critical review and evaluation of those scientific data which are relevant as a background for discussion of Swedish occupational exposure limits. This volume consists of the consensus reports given by the Criteria Group at the Swedish National Institute for Working Life from July, 2001 through June, 2002. Key Words: Isocyanic Acid (ICA), 4,4´-Methylenedianiline (MDA), Methylisoamylketone, Methylisocyanate (MIC), Occupational exposure limit (OEL), Risk assessment, Scientific basis, Toluene, Toxicology. Sammanfattning Montelius J (ed). Vetenskapligt underlag för hygieniska gränsvärden. XXIII. Arbete och Hälsa 2002:19, s 1-63. Arbetslivsinstitutet, Solna. Sammanställningar baserade på kritisk genomgång och värdering av de vetenskapliga fakta, vilka är relevanta som underlag för fastställande av hygieniskt gränsvärde. Volymen omfattar de underlag som avgivits från Kriteriegruppen för hygieniska gränsvärden under perioden juli 2001 - juni 2002. Nyckelord: Hygieniskt gränsvärde, Isocyansyra (ICA), 4,4´-Metylendianilin (MDA), Metylisoamylketon, Metylisocyanat (MIC), Riskvärdering, Toluen, Toxikologi, Vetenskapligt underlag. En svensk version av dessa vetenskapliga underlag finns publicerad i Arbete och Hälsa 2002:18. 57 APPENDIX Consensus reports in this and previous volumes Substance Consensus date Volume in Arbete och Hälsa (No.) Acetaldehyde February 17, 1987 1987:39 (VIII) Acetamide December 11, 1991 1992:47 (XIII) Acetic acid June15, 1988 1988:32 (IX) Acetone October 20, 1987 1988:32 (IX) Acetonitrile September 12, 1989 1991:8 (XI) Acrylamide April 17, 1991 1992:6 (XII) Acrylates December 9, 1984 1985:32 (VI) Acrylonitrile April 28, 1987 1987:39 (VIII) Aliphatic amines August 25, 1982 1983:36 (IV) Aliphatic hydrocarbons, C10-C15 June 1, 1983 1983:36 (IV) Aliphatic monoketons September 5, 1990 1992:6 (XII) Allyl alcohol September 9, 1986 1987:39 (VIII) Allylamine August 25, 1982 1983:36 (IV) Allyl chloride June 6, 1989 1989:32 (X) Aluminum April 21, 1982 1982:24 (III) revised September 14, 1994 1995:19 (XVI) p-Aminoazobenzene February 29, 1980 1981:21 (I) Ammonia April 28, 1987 1987:39 (VIII) Amylacetate March 23, 1983 1983:36 (IV) revised June 14, 2000 2000:22 (XXI) Aniline October 26, 1988 1989:32 (X) Anthraquinone November 26,1987 1988:32 (IX) Antimony + compounds December 8, 1999 2000:22 (XXI) Arsenic, inorganic December 9, 1980 1982:9 (II) revised February 15, 1984 1984:44 (V) Arsine October 20, 1987 1988:32 (IX) Asbestos October 21, 1981 1982:24 (III) Barium June 16, 1987 1987:39 (VIII) revised January 26, 1994 1994:30 (XV) Benzene March 4, 1981 1982:9 (II) revised February 24, 1988 1988:32 (IX) Benzoyl peroxide February 13, 1985 1985:32 (VI) Beryllium April 25, 1984 1984:44 (V) Borax October 6, 1982 1983:36 (IV) Boric acid October 6, 1982 1983:36 (IV) Boron Nitride January 27 1993 1993:37 (XIV) Butadiene October 23, 1985 1986:35 (VII) 1-Butanol June 17, 1981 1982:24 (III) Butanols June 6, 1984 1984:44 (V) Butyl acetate June 6, 1984 1984:44 (V) Butyl acetates February 11, 1998 1998:25 (XIX) Butylamine August 25, 1982 1983:36 (IV) Butyl glycol October 6, 1982 1983:36 (IV) Cadmium January 18, 1980 1981:21 (I) revised February 15, 1984 1984:44 (V) revised May 13, 1992 1992:47 (XIII) Calcium hydroxide February 24, 1999 1999:26 (XX) 58 Calcium nitride January 27, 1993 1993:37 (XIV) Calcium oxide February 24, 1999 1999:26 (XX) Caprolactam October 31, 1989 1991:8 (XI) Carbon monoxide December 9, 1981 1982:24 (III) Cathecol September 4, 1991 1992:47 (XIII) Chlorine December 9, 1980 1982:9 (II) Chlorine dioxide December 9, 1980 1982:9 (II) o-Chlorobenzylidene malononitrile June 1, 1994 1994:30 (XV) Chlorocresol December 12, 1990 1992:6 (XII) Chlorodifluoromethane June 2, 1982 1982: 24 (III) Chlorophenols September 4, 1985 1986:35 (VII) Chloroprene April 16, 1986 1986:35 (VII) Chromium December 14, 1979 1981:21 (I) revised May 26, 1993 1993:37 (XIV) revised May 24, 2000 2000:22 (XXI) Chromium trioxide May 24, 2000 2000:22 (XXI) Coal dust September 9, 1986 1987:39 (VIII) Cobalt October 27, 1982 1983:36 (IV) Copper October 21, 1981 1982:24 (III) Cotton dust February14, 1986 1986:35 (VII) Creosote October 26, 1988 1989:32 (X) Cresols February 11, 1998 1998:25 (XIX) Cumene June 2, 1982 1982:24 (III) Cyanamid September 30, 1998 1999:26 (XX) Cyanoacrylates March 5, 1997 1997:25 (XVIII) Cycloalkanes, C5-C15 April 25, 1984 1984:44 (V) Cyclohexanone March 10, 1982 1982:24 (III) revised February 24 1999 1999:26 (XX) Cyclohexanone peroxide February 13, 1985 1985:32 (VI) Cyclohexylamine February 7, 1990 1991:8 (XI) Desflurane May 27, 1998 1998:25 (XIX) Diacetone alcohol December 14, 1988 1989:32 (X) Dichlorobenzenes February 11, 1998 1998:25 (XIX) 1,2-Dibromo-3-chloropropane May 30, 1979 1981:21 (I) Dichlorodifluoromethane June 2, 1982 1982:24 (III) 1,2-Dichloroethane February 29, 1980 1981:21 (I) Dichloromethane February 29, 1980 1981:21 (I) Dicumyl peroxide February 13, 1985 1985:32 (VI) Dicyclopentadiene March 23, 1994 1994:30 (XV) Diethanolamine September 4, 1991 1992:47 (XIII) Diethylamine August 25, 1982 1983:36 (IV) 2-Diethylaminoethanol January 25, 1995 1995:19 (XVI) Diethylene glycol September 16, 1992 1993:37 (XIV) Diethyleneglycol ethylether + acetate December 11, 1996 1997:25 (XVIII) Diethyleneglycol methylether + acetate March 13, 1996 1996:25 (XVII) Diethyleneglycol monobutylether January 25, 1995 1995:19 (XVI) Diethylenetriamine August 25, 1982 1983:36 (IV) revised January 25, 1995 1995:19 (XVI) Diisocyanates April 8, 1981 1982:9 (II) revised April 27, 1988 1988:32 (IX) Diisopropylamine February 7, 1990 1991:8 (XI) N,N-Dimethylacetamide March 23, 1994 1994:30 (XV) Dimethyl adipate December 9, 1998 1999:26 (XX) Dimethylamine December 10, 1997 1998:25 (XIX) N,N-Dimethylaniline December 12, 1989 1991:8 (XI) Dimethyldisulfide September 9, 1986 1987:39 (VIII) Dimethylether September 14, 1994 1995:19 (XVI) 59 Dimethylethylamine June 12, 1991 1992:6 (XII) Dimethylformamide March 23, 1983 1983:36 (IV) Dimethyl glutarate December 9, 1998 1999:26 (XX) Dimethylhydrazine January 27, 1993 1993:37 (XIV) Dimethyl succinate December 9, 1998 1999:26 (XX) Dimethylsulfide September 9, 1986 1987:39 (VIII) Dimethylsulfoxide, DMSO December 11, 1991 1992:47 (XIII) Dioxane August 25, 1982 1983:36 (IV) revised March 4, 1992 1992:47 (XIII) Diphenylamine January 25, 1995 1995:19 (XVI) 4,4'-Diphenylmethanediisocyanate (MDI) April 8, 1981 1982:9 (II) reviderat May 30 2001 2001:20 (XXII) Dipropylene glycol May 26, 1993 1993:37 (XIV) Dipropyleneglycol monomethylether December 12, 1990 1992:6 (XII) Disulfiram October 31, 1989 1991:8 (XI) Enzymes, industrial June 5, 1996 1996:25 (XVII) Ethanol May 30, 1990 1991:8 (XI) Ethanolamine September 4, 1991 1992:47 (XIII) Ethylacetate March 28, 1990 1991:8 (XI) Ethylamine August 25, 1982 1983:36 (IV) Ethylamylketone September 5, 1990 1992:6 (XII) Ethylbenzene December 16, 1986 1987:39 (VIII) Ethylchloride December 11, 1991 1992:47 (XIII) Ethylene December 11, 1996 1997:25 (XVIII) Ethylene chloride February 29, 1980 1981:21 (I) Ethylene diamine August 25, 1982 1983:36 (IV) Ethylene glycol October 21, 1981 1982:24 (III) Ethylene glycol methylether + acetate June 2, 1999 1999:26 (XX) Ethyleneglycol monoisopropylether November 16, 1994 1995:19 (XVI) Ethyleneglycol monopropylether + acetate September 15, 1993 1994:30 (XV) Ethylene oxide December 9, 1981 1982:24 (III) Ethylenethiourea September 27, 2000 2001:20 (XXII) Ethylether January 27, 1993 1993:37 (XIV) Ethylglycol October 6, 1982 1983:36 (IV) Ferbam September 12, 1989 1991:8 (XI) Ferric dimethyldithiocarbamate September 12, 1989 1991:8 (XI) Flour dust December 10, 1997 1998:25 (XIX) Formaldehyde June 30, 1979 1981:21 (I) revised August 25, 1982 1983:36 (IV) Formamide December 12, 1989 1991:8 (XI) Formic acid June 15, 1988 1988:32 (IX) Furfural April 25, 1984 1984:44 (V) Furfuryl alcohol February 13, 1985 1985:32 (VI) Gallium + Gallium compounds January 25, 1995 1995:19 (XVI) Glutaraldehyde September 30 1998 1999:26 (XX) Glycol ethers October 6, 1982 1983:36 (IV) Glyoxal September 13, 1996 1996:25 (XVII) Grain dust December 14, 1988 1989:32 (X) Graphite December 10, 1997 1998:25 (XIX) Halothane April 25, 1985 1985:32 (VI) 2-Heptanone September 5, 1990 1992:6 (XII) 3-Heptanone September 5, 1990 1992:6 (XII) Hexachloroethane September 15, 1993 1994:30 (XV) Hexamethylenediisocyanate (HDI) April 8, 1981 1982:9 (II) 60 revised May 30, 2001 2001:20 (XXII) Hexamethylenetetramine August 25, 1982 1983:36 (IV) n-Hexane January 27, 1982 1982:24 (III) 2-Hexanone September 5, 1990 1992:6 (XII) Hexyleneglycol November 17, 1993 1994:30 (XV) Hydrazine May 13, 1992 1992:47 (XIII) Hydrogen bromide February 11, 1998 1998:25 (XIX) Hydrogen cyanide February 7 2001 2001:20 (XXII) Hydrogen fluoride April 25, 1984 1984:44 (V) Hydrogen peroxide April 4, 1989 1989:32 (X) Hydrogen sulfide May 4, 1983 1983:36 (IV) Hydroquinone October 21, 1989 1991:8 (XI) Indium March 23, 1994 1994:30 (XV) Industrial enzymes June 5, 1996 1996:25 (XVII) Isocyanic Acid (ICA) December 5 2001 2002:19 (XXIII) Isophorone February 20, 1991 1992:6 (XII) Isopropanol December 9, 1981 1982:24 (III) Isopropylamine February 7, 1990 1991:8 (XI) Isopropylbenzene June 2, 1982 1982:24 (III) Lactates March 29, 1995 1995:19 (XVI) Lactate esters June 2, 1999 1999:26 (XX) Lead, inorganic February 29, 1980 1981:21 (I) revised September 5, 1990 1992:6 (XII) Lithium boron nitride January 27, 1993 1993:37 (XIV) Lithium nitride January 27, 1993 1993:37 (XIV) Maleic anhydride September 12, 1989 1991:8 (XI) Manganese February 15, 1983 1983:36 (IV) revised April 17, 1991 1992:6 (XII) revised June 4, 1997 1997:25 (XVIII) Man made mineral fibers March 4, 1981 1982:9 (II) revised December 1, 1987 1988:32 (IX) Mercury, inorganic April 25, 1984 1984:44 (V) Mesityl oxide May 4, 1983 1983:36 (IV) Metal stearates, some September 15, 1993 1994:30 (XV) Methacrylates September 12, 1984 1985:32 (VI) Methanol April 25, 1985 1985:32 (VI) Methyl acetate March 28 1990 1991:8 (XI) Methylamine August 25, 1982 1983:36 (IV) Methylamyl alcohol March 17, 1993 1993:37 (XIV) Methyl bromide April 27, 1988 1988:32 (IX) Methyl chloride March 4, 1992 1992:47 (XIII) Methyl chloroform March 4, 1981 1982:9 (II) Methylene chloride February 29, 1980 1981:21 (I) 4,4'-Methylene dianiline June 16, 1987 1987:39 (VIII) revised October 3 2001 2002:19 (XXIII) Methyl ethyl ketone February 13, 1985 1985:32 (VI) Methyl ethyl ketone peroxide February 13, 1985 1985:32 (VI) Methyl formate December 12, 1989 1991:8 (XI) Methyl glycol October 6, 1982 1983:36 (IV) Methyl iodide June 30, 1979 1981:21 (I) Methylisoamylamine September 5, 1990 1992:6 (XII) Methylisoamylketone February 6 2002 2002:19 (XXIII) Methylisocyanate (MIC) December 5 2001 2002:19 (XXIII) Methyl mercaptane September 9, 1986 1987:39 (VIII) Methyl methacrylate March 17, 1993 1993:37 (XIV) 61 Methyl pyrrolidone June 16, 1987 1987:39 (VIII) α-Methylstyrene November 1 2000 2001:20 (XXII) Methyl-t-butyl ether November 26, 1987 1988:32 (IX) revised September 30, 1998 1999:26 (XX) Mixed solvents, neurotoxicity April 25, 1985 1985:32 (VI) Molybdenum October 27, 1982 1983:36 (IV) Monochloroacetic acid February 20, 1991 1992:6 (XII) Monochlorobenzene September 16,1993 1993:37 (XIV) Monomethylhydrazine March 4, 1992 1992:47 (XIII) Mononitrotoluene February 20, 1991 1992:6 (XII) Monoterpenes February 17, 1987 1987:39 (VIII) Morpholine December 8, 1982 1983:36 (IV) revised June 5, 1996 1996:25 (XVII) Naphthalene May 27, 1998 1998:25 (XIX) Natural crystallinic fibers (except asbestos) June 12, 1991 1992:6 (XII) Nickel April 21, 1982 1982:24 (III) Nitroethane April 4, 1989 1989:32 (X) Nitrogen oxides December 11, 1985 1986:35 (VII) Nitroglycerin February 13, 1985 1985:32 (VI) Nitroglycol February 13, 1985 1985:32 (VI) Nitromethane January 6, 1989 1989:32 (X) Nitropropane October 28, 1986 1987:39 (VIII) 2-Nitropropane March 29, 1995 1995:19 (XVI) Nitroso compounds December 12, 1990 1992:6 (XII) Nitrosomorpholine December 8, 1982 1983:36 (IV) Nitrotoluene February 20, 1991 1992:6 (XII) Nitrous oxide December 9, 1981 1982:24 (III) Oil mist April 8, 1981 1982:9 (II) Organic acid anhydrides, some September 12, 1989 1991:8 (XI) Oxalic acid February 24, 1988 1988:32 (IX) Ozone April 28, 1987 1987:39 (VIII) Paper dust February 7, 1990 1991:8 (XI) Pentaerythritol November 16, 1994 1995:19 (XVI) 1,1,1,2,2-Pentafluoroethane February 24, 1999 1999:26 (XX) Pentyl acetate June 14, 2000 2000:22 (XXI) Peroxides, organic February 13, 1985 1985:32 (VI) Phenol February 13, 1985 1985:32 (VI) Phosphorous chlorides September 30, 1998 1999:26 (XX) Phosphorous oxides February 11, 1998 1998:25 (XIX) Phthalates December 8, 1982 1983:36 (IV) Phthalic anhydride September 12, 1989 1991:8 (XI) Piperazine September 12, 1984 1985:32 (VI) Plastic dusts December 16, 1986 1987:39 (VIII) Platinum June 4, 1997 1997:25 (XVIII) Polyaromatic hydrocarbons February 15, 1984 1984:44 (V) Polyisocyanates April 27, 1988 1988:32 (IX) Potassium aluminium fluoride June 4, 1997 1997:25 (XVIII) Potassium cyanide February 7 2001 2001:20 (XXII) Potassium dichromate May 24, 2000 2000:22 (XXI) Potassium hydroxide Marsh 15, 2000 2000:22 (XXI) 2-Propanol December 9, 1981 1982:24 (III) Propene September 13, 1996 1996:25 (XVII) Propionic acid November 26, 1987 1988:32 (IX) Propylacetate September 14, 1994 1995:19 (XVI) Propylene glycol June 6, 1984 1984:44 (V) 62 Propylene glycol-1,2-dinitrate May 4, 1983 1983:36 (IV) Propylene glycol monomethylether October 28, 1986 1987:39 (VIII) Propylene oxide June 11, 1986 1986:35 (VII) Pyridine May 13, 1992 1992:47 (XIII) Quartz March 13, 1996 1996:25 (XVII) Resorcinol September 4, 1991 1992:47 (XIII) Selenium December 11, 1985 1986:35 (VII) revised February 22, 1993 1993:37 (XIV) Sevoflurane May 27, 1998 1998:25 (XIX) Silica March 13, 1996 1996:25 (XVII) Silver October 28, 1986 1987:39 (VIII) Sodium cyanide February 7 2001 2001:20 (XXII) Sodium hydroxide August 24, 2000 2000:22 (XXI) Stearates, metallic, some September 15, 1993 1994:30 (XV) Stearates, non-metallic, some November 17, 1993 1994:30 (XV) Strontium January 26, 1994 1994:30 (XV) Styrene February 29, 1980 1981:21 (I) revised October 31, 1989 1991:8 (XI) Sulfur dioxide April 25, 1985 1985:32 (VI) Sulfur fluorides March 28, 1990 1991:8 (XI) Synthetic inorganic fibers March 4, 1981 1982:9 (II) revised December 1, 1987 1988:32 (IX) Synthetic organic and inorganic fibers May 30, 1990 1991:8 (XI) Talc dust June 12, 1991 1992:6 (XII) Terpenes, mono- February 17, 1987 1987:39 (VIII) Tetrabromoethane May 30, 1990 1991:8 (XI) Tetrachloroethane June 4, 1997 1997:25 (XVIII) Tetrachloroethylene February 29, 1980 1981:21 (I) 1,1,1,2-Tetrafluoroethane March 29, 1995 1995:19 (XVI) Tetrahydrofuran October 31, 1989 1991:8 (XI) Tetranitromethane April 4, 1989 1989:32 (X) Thioglycolic acid June 1, 1994 1994:30 (XV) Thiourea December 1, 1987 1988:32 (IX) revised June 2, 1999 1999:26 (XX) Thiram October 31, 1989 1991:8 (XI) Thiurams, some October 31, 1989 1991:8 (XI) Titanium dioxide February 21, 1989 1989:32 (X) Toluene February 29, 1980 1981:21 (I) revised February 6 2002 2002:19 (XXIII) Toluene-2,4-diamine November 1, 2000 2001:20 (XXII) Toluene-2,6-diamine November 1, 2000 2001:20 (XXII) Toluene-2,4-diisocyanate April 8, 1981 1982:9 (II) revised May 30, 2001 2001:20 (XXII) Toluene-2,6-diisocyanate April 8, 1981 1982:9 (II) revised May 30, 2001 2001:20 (XXII) 1,1,1-Trifluoroethane February 24, 1999 1999:26 (XX) Trichlorobenzene September 16, 1993 1993:37 (XIV) 1,1,1-Trichloroethane March 4, 1981 1982:9 (II) Trichloroethylene December 14, 1979 1981:21 (I) Trichlorofluoromethane June 2, 1982 1982:24 (III) 1,1,2-Trichloro-1,2,2-trifluoroethane June 2, 1982 1982:24 (III) Triethanolamine August 25, 1982 1983:36 (IV) Triethylamine December 5, 1984 1985:32 (VI) Trimellitic anhydride September 12, 1989 1991:8 (XI) 63 Trimethylolpropane November 16, 1994 1995:19 (XVI) Trinitrotoluene April 17, 1991 1992:6 (XII) Vanadium March 15, 1983 1983:36 (IV) Vinyl acetate June 6, 1989 1989:32 (X) Vinyl toluene December 12, 1990 1992:6 (XII) White spirit December 16, 1986 1987:39 (VIII) Wood dust June 17, 1981 1982:9 (II) revised June 25, 2000 2000:22 (XXI) Xylene February 29, 1980 1981:21 (I) Zinc April 21, 1982 1982:24 (III) Zinc chromate May 24, 2000 2000:22 (XXI) Zinc dimethyl dithiocarbamate September 12, 1989 1991:8 (XI) Ziram September 12, 1989 1991:8 (XI) Sent for publication December 2002