Vinyl acetate (CAS No. 108-05-4) "is used in the production of a wide range of polymers, including polyvinyl acetate, polyvinyl alcohol, polyvinyl acetals, ethylene-vinyl acetate copolymers and polyvinyl chloride-vinyl acetate copolymers, which are widely used in the production of adhesives, paints and food packaging" (IARC, 1995). Vinyl acetate was reviewed by IARC in 1995. IARC concluded that the evidence of carcinogenicity was inadequate in humans and limited in animals, but classified the chemical as a group 2B carcinogen, based on "other relevant data". The studies reviewed by IARC are briefly described below.

Carcinogenicity Data available:

Epidemiological studies

One occupational cohort study of men exposed to numerous chemicals (Waxweiler et al., 1981) and one nested case-control study in a cohort of workers exposed to numerous chemicals (Ott et al., 1989) have found no association between vinyl acetate exposure and cancer. In reviewing these studies, IARC (1995) concluded that "the available data were too limited to form the basis for an evaluation of the carcinogenicity of vinyl acetate to humans."

Animal bioassays

Rat long-term drinking water studies (100 weeks + 30 weeks observation): Lijinsky and Reuber, 1983. A statistically significant increase in the incidence of liver neoplastic nodules was observed in high-dose females (0/20; 0/20; 6/20); a nonsignificant increase was observed in males (0/20; 4/20; 2/20). Statistically significant increases in the incidences of uterine polyps (0/20; 3/20; 5/20), uterine adenocarcinomas (0/20; 1/20; 5/20), and thyroid c-cell adenomas (0/20; 2/20; 5/20) were also observed in females. This study was considered inadequate by IARC (1995) due to small group sample size and degradation of the test chemical, leading to inaccurate dosing of the treated groups under the experimental conditions of the study.

Rat long-term inhalation studies (104 weeks): Bogdanffy et al., 1994a. A statistically significant increase in the incidence of nasal tumors (benign and malignant) was observed in high-dose males (0/59; 1/59; 7/59); a nonsignificant increase in squamous cell carcinoma of the nasal cavity was observed in high-dose females (0/60; 0/60; 4/59).

Mouse long-term inhalation studies (104 weeks): Bogdanffy et al., 1994a. No treatment-related tumors were observed in either male or female mice.

Rat in utero and long-term drinking water studies (in utero + 104 weeks): Bogdanffy et al., 1994b. No treatment-related tumors were observed in either male or female rats.

Other relevant data

"Vinyl acetate is rapidly metabolized by esterases in human blood and animal tissues to acetaldehyde and acetic acid. Vinyl acetate induced sperm abnormalities and sister chromatid exchange in rodents exposed in vivo; micronuclei were induced in bone marrow but not in meiotic cells. No DNA binding was seen in rat hepatocytes. In human lymphocytes in vitro, vinyl acetate produced chromosomal aberrations, micronuclei, sister chromatid exchange and DNA cross-links. It enhanced viral transformation and sister chromatid exchange in mammalian cells in vitro, and it induced DNA-protein cross-links in rat nasal epithelial cells in vitro. Vinyl acetate did not induce mutations in bacteria but induced DNA-protein cross-links in plasmid DNA. The primary metabolite of vinyl acetate, acetaldehyde, is genotoxic in a wide range of assays" (IARC, 1995).

Preliminary evaluation of carcinogenicity and exposure data:

There is a MEDIUM HIGH level of carcinogenicity concern over vinyl acetate. Although IARC (1995) determined that there was inadequate evidence in humans and limited evidence in experimental animals, the agency classified vinyl acetate as a Group 2B carcinogen based on "other relevant data." This classification is based on the following: "(1) Vinyl acetate is rapidly transformed into acetaldehyde in human blood and animal tissues. (2) There is sufficient evidence in experimental animals for the carcinogenicity of acetaldehyde (IARC, 1987). Both vinyl acetate and acetaldehyde induce nasal cancer in rats after administration by inhalation. (3) Vinyl acetate and acetaldehyde are genotoxic in human cells in vitro and in animals in vivo" (IARC, 1995). In the absence of the "other relevant data" IARC would have placed the chemical in Group 3.

There is a HIGH level of concern over the extent of exposure since vinyl acetate is a high volume industrial chemical with widespread uses (IARC, 1995). U.S. annual production was 2,800,000,000 lbs. in 1993. The Vinyl Acetate Toxicology Group, Inc. reports that vinyl acetate is not currently produced commercially in California (VATG, 1996), however, significant quantities are imported into the state. In 1987 16 facilities in California reported processing or otherwise using vinyl acetate; maximum amounts of vinyl acetate reported to be on site at each of these facilities ranged from 100 to 9,999,000 pounds (ATSDR, 1992). California TRI data indicate that approximately 50,000 pounds of vinyl acetate are released annually in the state (48,012 pounds released in 1994, including 30,358 pounds release to the air; 53,195 pounds released in 1993, including 33,261 pounds released to the air). NIOSH (1994) estimated that in 1983 129,024 workers were potentially exposed to vinyl acetate during production and operation by inhalation and dermal routes. The level of concern is supported by the detection of vinyl acetate in wastewater effluents, cigarette smoke, coal smoke, and emissions from new carpets, and its release from food packaging during heating in a microwave oven (IARC, 1995).

References

ATSDR (1992). Toxicological Profile for Vinyl Acetate. US Department of Health and Human Services, Public Health Service, Agency for Toxic Substances and Disease Registry.

Bogdanffy MS, Dreef-van der Meulen HC, Beems RB, Feron VJ, Cascieri TC, Tyler TR, Vinegar MB, Rickard RW (1994a). Chronic toxicity and oncogenicity inhalation study with vinyl acetate in the rat and mouse. Fund appl Toxicol 23:215-229.

Bogdanffy MS, Tyler TR, Vinegar MB, Rickard RW, Carpanini FMB, Cascieri TC (1994b). Chronic toxicity and oncogenicity study with vinyl acetate in the rat: in utero exposure in drinking-water. Fundam appl Toxicol 23:206-214.

International Agency for Research on Cancer (IARC, 1987). IARC Monographs on the evaluation of carcinogenic risks to humans, Suppl. 7, Overall evaluations of carcinogenicity: An updating of IARC Monographs volumes 1-42, Lyon, p. 64.

International Agency for Research on Cancer (IARC, 1995). IARC Monographs on the evaluation of carcinogenic risks to humans. Dry cleaning, some chlorinated solvents and other industrial chemicals. Volume 63. IARC, Lyon, pp. 443-465.

Lijinsky W, Reuber MD (1983). Chronic toxicity studies of vinyl acetate in Fischer rats. Toxicol appl Pharmacol 68:43-53.

National Institute for Occupational Safety and Health (NIOSH, 1994). National Occupational Exposure Survey (1981-83), Cincinnati, OH.

Ott MG, Teta MJ, Greenberg HL (1989). Lymphatic and hematopoietic tissue cancer in a chemical manufacturing environment. Am J Ind Med 16:631-643.

VATG (1996). Comments for Consideration by the California Environmental Protection Agency’s Office of Environmental Health Hazard Assessment/Carcinogen Identification Committee. Vinyl Acetate. Submitted July 5, 1996, Vinyl Acetate Toxicology Group, Inc.

Waxweiler RJ, Smith AH, Falk H, Tyroler HA (1981). Excess lung cancer risk in a synthetic chemicals plant. Environ Health Perspectives 41:159-165.

CARCINOGENICITY DATA SUMMARY: 5-Nitro-ortho-toluidine

5-Nitro-o-toluidine (2-amino-4-nitrotoluene; 2-methyl-5-nitroaniline; CAS No. 99-55-8) is used as a precursor for the synthesis of a number of dyes and pigments. It is also used in the textile industry for in situ dyeing. It is a metabolite of 2,4-dinitrotoluene. 5-Nitro-o-toluidine was reviewed by IARC in 1990. IARC concluded that there was no data available on the evidence of carcinogenicity in humans and that the evidence in animals was limited (group 3 carcinogen). Since the IARC (1990) review, IARC modified its criteria on the use of mechanistic data in evaluating carcinogenicity data (IARC, 1992). Mechanistic information that has become available since the IARC review in 1990 are described below.

Carcinogenicity Data available:

Epidemiological studies

IARC (1990) noted that no data on long-term effects of human exposure to 5-nitro-ortho-toluidine have been reported, and OEHHA did not find epidemiological data in a recent literature search.

Animal bioassays

Rat long-term feed studies (78 weeks + 30-31 weeks observation): NCI, 1978. Fischer 344 rats were fed 0.005% or 0.01% 5-nitro-ortho-toluidine in the diet. Increased incidences of hepatocellular carcinoma in male rats were not statistically significant relative to the control, but a significant positive dose-related trend in tumor incidence was found (control, 0/47; low-dose, 0/41; high-dose, 3/46). No increased tumor incidences were seen in the females.

Mouse long-term feed studies (78 weeks + 20 weeks observation): NCI, 1978. A statistically significant increase in the incidence of hepatocellular carcinoma was seen in both male and female B6C3F₁ mice (control, low-dose and high dose incidences: males - 12/50, 12/44, 29/45; females - 2/47, 7/46, 20/45). In addition, there was an increase in the combined incidence of hemangiomas and hemangiosarcomas in male mice and an increased incidence in hemangiosarcomas in female mice. NCI considered these tumors "to be associated with compound administration, since they rarely occur in untreated B6C3F₁ mice."

Mouse ip (16 week) screening studies: Maronpot et al., 1986. In a lung-tumor induction screening study in strain A mice, incidences of lung tumors were 11%, 18%, 30%, and 6% in vehicle control, low-dose, mid-dose and high-dose groups, respectively. In a similar study in A/J mice, a treatment- related effect was not seen among surviving animals.

Other relevant data

5-Nitro-ortho-toluidine was found to be mutagenic both with and without metabolic activation in the Salmonella reverse mutation assay (IARC, 1990). The chemical also formed hemoglobin adducts in vitro (Zwirner-Baier et al., 1994). The results of a computerized analysis of structure-activity relationships based on a set of rules generated by US EPA experts (Oncologic, version 1.0) finds that 5-nitro-o-toluidine is of high-to-moderate concern (i.e., the highest level of concern noted for chemicals which are not included in the database of carcinogenicity bioassay results from which the program rules are derived).

Preliminary evaluation of carcinogenicity and exposure data:

There is a MEDIUM HIGH level of carcinogenicity concern over 5-nitro-ortho-toluidine since evidence of carcinogenicity has been observed in both sexes of B6C3F₁ mice and a significant trend in the incidence of hepatocellular carcinomas was found in male rats. No tests in other species have been reported. On the basis of the bioassay data NCI concluded the substance was carcinogenic to male and female B6C3F₁ mice; IARC (1990) found limited evidence for carcinogenicity of the chemical in experimental animals; however, information on structure-activity relationships and hemoglobin binding were not included in this evaluation. The concern is reinforced by the observations of mutagenicity in short-term tests, hemoglobin binding activity, and structural similarity to known carcinogens, as indicated by the Oncologic computer program.

There is a MEDIUM level of concern over the extent of exposure. The compound is an intermediate in the production of pigments and azo dyes It is a metabolite of 2,4-dinitrotoluene. It is present in waste water effluent from munitions plants and sites, and dye and polyurethane manufacturing facilities. In 1990, use of greater than 25,000 lbs was reported to US EPA TSCA (Sherlock, 1995). There is the potential for occupational exposure.

References

International Agency for Research on Cancer (IARC, 1990). IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Volume 48. IARC, Lyon. pp. 169-177.

Maronpot RR, Shimkin MB, Witschi HP, Smith LH, Cline JM (1986). Strain A mouse pulmonary tumor test results for chemicals previously tested in the National Cancer Institute carcinogenicity tests. JNCI 76:1101-1112.

National Cancer Institute (NCI, 1978). Bioassay of 5-Nitro-o-toluidine for possible Carcinogenicity (CAS No, 99-55-8) (Technical Report No. 107: DHEW Publ. No. (NIH) 78-1357) Bethesda, MD, U.S. Department of Health, Education, and Welfare.

Sherlock, SM (1995). Facsimile letter dated May 11, 1995 from S.M. Sherlock, Attorney Advisor, Information Management Division, US Environmental Protection Agency, Washington, D.C. to S. Hoover, Reproductive Cancer Hazard Assessment Section, Office of Environmental Health Hazard Assessment.

Zwirner-Baier I, Kordowich FJ, Neumann HG (1994). Hydrolyzable hemoglobin adducts of polyfunctional monocyclic N-substituted arenes as dosimeters of exposure and markers of metabolism. Environ Health Perspect 102,Suppl 6:43-45.

CARCINOGENICITY DATA SUMMARY: ACROLEIN

Acrolein (2-propenal; CAS No. 107-02-8) is produced in the chemical industry by the oxidation of propylene. It is also produced as a photochemical oxidation product, and by the combustion of fossil fuels, wood, paper, cooking oils, and vegetable material such as tobacco. Acrolein has been identified as a natural product of certain plant species. The major use of acrolein is for the synthesis of acrylic acid for acrylate polymer products. It is used as an intermediate in the manufacture of glycerol, polyurethane, and methionine. It is used as an aquatic herbicide and as a rodenticide, and is also used for the control of algae and bacteria. The US EPA has classified acrolein as a group C carcinogen (US EPA, 1994). Acrolein was reviewed by IARC in 1995. IARC concluded that the evidence of carcinogenicity was inadequate in humans and inadequate in animals (group 3 carcinogen). The IARC review did not include the original data from the studies reported by Parent et al. (1991; 1992). These original study data, in addition to the data reviewed by IARC, are briefly described below.

Carcinogenicity Data available:

Epidemiological studies

One nested case-control study in a cohort of workers exposed to numerous chemicals reported two cases of non-Hodgkin’s lymphoma, one case of multiple myeloma and three cases of lymphatic leukemia in individuals exposed to acrolein (Ott et al., 1989). In reviewing this study, IARC (1995) concluded that "the available data were inadequate to form the basis for an evaluation of the carcinogenicity of acrolein to humans."

Animal bioassays

Rat long-term gavage studies (102 weeks): Submitted to CDPR in 1989 and published as Parent et al., 1992. Parent et al. (1992) reported that no treatment-related tumors were observed in either sex. Based on the published report, IARC (1995) reached an identical conclusion. Upon review of the data from this series of gavage studies submitted as a requirement for the continued use of acrolein as a pesticide in California, the California Department of Pesticide Regulation (CDPR, 1994) concluded that a dose-related increase in pancreatic acinar cell tumors (adenomas and carcinomas) was observed in treated males. CDPR (1994) further concluded that the increased incidences in pancreatic acinar cell tumors in acrolein-treated males was higher than that of the laboratory’s historical controls.

Mouse long-term gavage studies (18 months): Submitted to CDPR in 1989 and published as Parent et al., 1991. High early mortality was observed in all groups and attributed to gavage-related accidents. Parent et al. (1991) reported that no treatment-related tumors were observed in either sex. CDPR (1994) concluded that this study was unacceptable for evaluation, due to high early mortality and the late addition of mice to the study as replacements for those that succumbed to gavage-related accidents.

Rat long-term drinking water studies (104 weeks + 28 weeks additional observation): Lijinsky and Reuber, 1987; Lijinsky, 1988. The authors reported a nonsignificant increase in the incidence of adrenal cortical adenomas in female rats (controls 1/20; high-dose group 5/20). IARC (1995) noted the lack of a dose-related effect, and the small group size (n = 20).

Hamster long-term inhalation studies (52 weeks + 29 weeks additional observation): Feron and Kruysse, 1977. No treatment-related tumors were observed. IARC (1995) noted the short exposure period and the small group size (n = 18).

Other relevant data

"Acrolein induced both somatic and germinal mutations in insects and DNA mutation and DNA damage in bacteria. In cultured mammalian cells acrolein induced gene mutation, sister chromatid exchange and DNA damage; weak induction of chromosomal aberrations was observed in one study. In single studies, acrolein did not induce DNA damage in rats or dominant lethal mutations in mice treated in vivo" (IARC, 1995). Acrolein inhibits DNA synthesis in vivo and in vitro and forms DNA adducts in vitro and in vivo. A short-term initiation/promotion assay in rats indicates that acrolein initiates bladder carcinogenesis (Cohen et al., 1992). One of the metabolites of acrolein is glycidaldehyde, which is carcinogenic to mice after skin application and to mice and rats after subcutaneous injection (IARC, 1987). Acrolein is a potent irritant and cytotoxicant, causing intense eye and respiratory irritation in humans, which may serve to limit the amount of exposure.

Preliminary evaluation of carcinogenicity and exposure data:

There is a MEDIUM level of carcinogenicity concern over acrolein since evidence of carcinogenicity has been observed only in male rats in one study (submitted to CDPR and published as Parent et al., 1992). Upon review of the original study data, which was not provided in Parent et al. (1992) or available to IARC (1995), CDPR (1994) concluded that acrolein induced a significant, dose-related increase in pancreatic acinar cell tumors in male rats. Three additional studies in mice, rats, and hamsters are considered either non-positive, or inadequate for evaluation due to one or more of the following: high early mortality, small numbers of animals tested, and short exposure period. There is a need for additional adequate long-term studies in animals; acrolein is scheduled to be tested in toxicity and carcinogenesis studies by the National Toxicology Program (NTP, 1995). The level of concern is reinforced by the observations of mutagenicity and genotoxicity in numerous short-term tests, and by the fact that it is metabolized to a known animal carcinogen. The level of concern is tempered by acrolein's potent irritant properties (IARC, 1995).

There is a HIGH level of concern over the extent of exposure since acrolein occurs naturally in foods and is formed during the combustion of fossil fuels, wood, and tobacco and during the heating of cooking oils (IARC, 1995). Acrolein is a widespread atmospheric pollutant which is listed by the California Air Resources Board as a Toxic Air Contaminant. Acrolein is also used extensively as a chemical intermediate and as an herbicide to control weeds in irrigation canals, a rodenticide to control squirrel populations, and as a slimicide to control algae and bacteria (IARC, 1995; CDPR, 1994). U.S. annual production in 1990 was estimated to be 60,000,000 lbs. (Cohen et al., 1992). In California, agricultural use was reported as 227,000 lbs. for 1992 and 300,000 lbs. for 1993 (CDPR, 1995).

References

California Department of Pesticide Regulation (CDPR, 1994). Summary of toxicological data: Acrolein.

California Department of Pesticide Regulation (DPR, 1995). Pesticide Use Report, Annual 1993. DPR, Information Systems Branch, Sacramento, CA.

Cohen SM, Garland, EM, St John M, Okamura T, Smith RA (1992). Acrolein initiates rat urinary bladder carcinogenesis. Cancer Res 52:3577-3581.

Feron VJ, Kruysse A (1977). Effects of exposure to acrolein vapor in hamsters simultaneously treated with benzo[a]pyrene or diethylnitrosamine. J Toxicol Environ Health 3:379-394.

International Agency for Research on Cancer (IARC, 1987). IARC Monographs on the evaluation of carcinogenic risks to humans. Suppl 7, Overall evaluations of carcinogenicity: An updating of IARC monographs Volumes 1-42. Lyon, p. 64.

International Agency for Research on Cancer (IARC, 1995). IARC Monographs on the evaluation of carcinogenic risks to humans. Dry cleaning, some chlorinated solvents and other industrial chemicals. Volume 63. IARC, Lyon, pp. 337-372.

Lijinsky W (1988). Chronic studies in rodents of vinyl acetate and compounds related to acrolein. Ann NY Acad Sci 554:246-254.

Lijinsky W, Reuber MD (1987). Chronic carcinogenesis studies of acrolein and related compounds. Toxicol ind Health 3:337-345.

National Toxicology Program (NTP, 1995). NTP Division of Toxicology Research and Testing. Management Status Report, 1/06/95.

Ott MG, Teta J, Greenberg HL (1989). Lymphatic and hematopoietic tissue cancer in a chemical manufacturing environment. Am J ind Med 16:631-643.

Parent RA, Caravello HE, Long JE (1991). Oncogenicity study of acrolein in mice. J Am Coll Toxicol 10:647-659.

Parent RA, Caravello HE, Long JE (1992). Two-year toxicity and carcinogenicity study of acrolein in rats. J appl Toxicol 12:131-139.

US Environmental Protection Agency (US EPA, 1994). Integrated Risk Information System (IRIS) February 1, 1994 update.

CARCINOGENICITY DATA SUMMARY: CHLOROACETALDEHYDE

Chloroacetaldehyde (CAS No. 107-20-0) is an intermediate in the manufacture of 2-aminothiazole and other chemicals. It is a by-product of drinking water chlorination and has also been used to facilitate bark removal from trees, and as a fungicide. The available data are briefly described below.

Carcinogenicity Data available:

Epidemiological studies

No data on long-term effects of human exposure to chloroacetaldehyde are available.

Animal bioassays

Long-term drinking water study in male B6C3F₁ mice: Daniel et al., 1992. Significantly increased incidences of hepatocellular tumors included 31% carcinoma and 8% adenoma compared to control incidences of 10% and 5% respectively. Preneoplastic lesions (hyperplastic nodules) were observed in 8% of the treated mice.

Other relevant data

Daniel et al. (1992) reported numerous measures of the genotoxicity of chloroacetaldehyde. These genotoxic effects include mutagenicity in Salmonella and mammalian cells, induction of aneuploidy in yeast, formation of DNA adducts and induction of DNA strand breaks in human lymphocytic cells. Chloroacetaldehyde was also observed to be a potent inhibitor of DNA synthesis.

Preliminary evaluation of carcinogenicity and exposure data:

There is a MEDIUM level of carcinogenicity concern regarding chloroacetaldehyde based on the carcinogenic effects observed in male B6C3F₁ mice as described above. Although only one sex of one species was tested, there is extensive genotoxicity data in both bacterial and mammalian cells that support the bioassay findings. In addition, chloroacetaldehyde is a major metabolite of vinyl chloride, a carcinogen listed under Proposition 65, and has been considered one of the likely proximate carcinogens involved in the carcinogenicity of vinyl chloride.

There is a HIGH level of concern over the extent of exposure to chloroacetaldehyde since there is the potential for widespread exposure to the general public as a result of formation of chloroacetaldehyde as a reaction product from chlorination of drinking water (Daniel et al., 1992). It has also been suggested that the reaction of vinyl chloride monomer and chlorine is a possible source of chloroacetaldehyde in drinking water (Ando and Sayato, 1984). There is further concern due to potential occupational exposure (NIOSH, 1974; RTECS, 1995) and its use as a fungicide (HSDB, 1995).

References

Bignami M, Conti G, Conti R, Crebelli F, Miscuraca Puglia A, Randazzo R, Sciandrello G, Carere A (1980). Mutagenicity of halogenated aliphatic hydrocarbons in Salmonella typhimurium, Streptomyces coelicolor and Aspergillus nidulans. Chem Biol Interact 30:9-23. (as cited in Daniel et al., 1992)

Chang LW, Daniel FB, DeAngelo AB (1991). Analysis of DNA strand breaks induced in rodent liver in vivo, primary rodent hepatocytes, and a human cell line by chlorinated acetic acid and chlorinated acetaldehydes. Environ Mol Mutagen 20(4):277-288. (abstract cited in Daniel et al., 1992)

Crebelli R, Conti G, Conti L, Carere A (1990). Chloroacetaldehyde is a powerful inducer of mitotic aneuploidy in Aspergillus nidulans. Mutagenesis 5:165-168. (abstract cited in Daniel et al., 1992)

Daniel FB, DeAngelo AB, Stober JA, Olson GR and Page NP (1992). Hepatocarcinogenicity of chloralhydrate,2-chloroacetaldehyde, and dichloroacetic acid in the male B6C3F1 mouse. Fund Appl Toxicol 19:159-168.

Hazardous Substances Data Bank (HSDB, 1995) National Library of Medicine.

Huberman E, Bartsch H, Sachs L (1975). Mutation induction in Chinese hamster V79 cells by two vinyl chloride metabolites, chloroethylene oxide and 2-chloroacetaldehyde. Int J Cancer 15:539. (as cited in Daniel et al., 1992)

Kandala JC, Mrema JEK, DeAngelo A, Daniel FB, Guntaka RV (1990). 2-Chloroacetaldehyde and 2-chloroacetal are potent inhibitors of DNA synthesis in animal cells. Biochem Biophys Res Comm 167:457-463. (as cited in Daniel et al., 1992)

Kopfler FC, Ringhand HP, Coleman WE, Meier JR (1985). Reactions of chlorine in drinking water with humic acids and in vivo. In Water Chlorination: Environmental Impact and Health Effects (RL Jolley et al., Eds.), Vol. 5, pp. 161-173. Lewis Publishing Co., Chelsea, Michigan. (as cited in Daniel et al., 1992)

CARCINOGENICITY DATA SUMMARY: C.I. DISPERSE YELLOW 3

C.I. Disperse Yellow 3 (N-(4-[(2-hydroxy-5-methylphenyl) azo] phenyl)-acetamide; CAS No. 2832-40-8) is a monoazo pigment dye used to color nylon, polyvinyl chloride and acrylic fibers, wools, furs, cellulose acetate, polystyrene and other thermoplastics. This compound was selected for evaluation as a result of a search of NCI/NTP summary data indicating positive bioassay findings, and information suggesting the potential for high exposures of some occupational subgroups. C.I. Disperse Yellow 3 was reviewed by IARC in 1990. IARC concluded that there was no data available on the evidence of carcinogenicity in humans and that the evidence in animals was limited (group 3 carcinogen). Literature searches did not identify any critical studies published subsequent to the IARC (1990) evaluation. The results of a structure-activity analysis performed by OEHHA, in addition to the studies reviewed by IARC, are briefly described below.

Carcinogenicity Data available:

Epidemiological studies

No data on long-term effects of human exposure to C.I. Disperse Yellow 3 were found by IARC (1990) or in subsequent literature searches by OEHHA.

Animal bioassays

Rat long-term feeding studies (103 weeks + 2 weeks observation): NTP, 1982. A significant increase in neoplastic liver nodules was observed in low- and high-dose males (1/49 controls; 15/50 low-dose group; 10/50 high-dose group). Five rare stomach tumors were observed in treated males (0/49; 4/50; 1/50); NTP noted that a relationship between the stomach tumors and treatment could not be clearly established, while IARC (1990) concluded that the stomach tumors were possibly related to treatment. No treatment-related tumors were observed in females.

Mouse long-term feeding studies (103 weeks + 2 weeks observation): NTP, 1982. A significant increase in hepatocellular adenomas was observed in low- and high-dose females (0/50 controls; 6/50 low-dose group; 12/50 high-dose group). A nonsignificant increase in hepatocellular carcinomas was observed in females (2/50; 4/50; 5/50). A significant increase in malignant lymphoma was observed in high-dose females, as was a significant dose-related trend (p < 0.05) (10/50; 16/50; 19/50). Due to the historical variability in the control incidence of malignant lymphoma in female mice, NTP concluded that the observed increase in malignant lymphoma was not clearly related to treatment; IARC (1990) concluded that this increase was possibly treatment-related. A significant increase in the incidence of alveolar/bronchiolar adenomas was observed in high-dose males (2/50; 6/49; 9/49), but neither NTP nor IARC (1990) considered these tumors to be treatment-related.

Other Relevant data

C.I. Disperse Yellow 3 was mutagenic in both the presence and absence of metabolic activation in the Salmonella reverse mutation assay and in cultured mouse lymphoma cells (IARC, 1990). C.I. Disperse Yellow 3 induced unscheduled DNA synthesis (UDS) in primary cultured rat hepatocytes and sister chromatid exchanges (SCEs) in Chinese hamster ovary (CHO) cells (IARC, 1990). C.I. Disperse Yellow 3 did not induce chromosomal aberrations in CHO cells (IARC, 1990). These positive results are in agreement with the observation that amino azo dyes are generally genotoxic. As an azo dye, C.I. Disperse Yellow 3 also has the potential to be metabolically transformed to aromatic amines, many of which have been shown to possess carcinogenic activity. A computer program that analyzes structure-activity relationships based on a set of rules generated by US EPA experts (Oncologic, version 1.0) predicts that C.I. Disperse Yellow 3 is of moderate concern.

Preliminary evaluation of carcinogenicity and exposure data:

There is a MEDIUM level of carcinogenicity concern over C.I. Disperse Yellow 3 since evidence of carcinogenicity has been observed in the male rat and the female mouse. The concern is tempered by the lack of a clear association between treatment with the chemical and the development of malignant tumors. IARC (1990) classified this chemical as a group 3 carcinogen. Evidence of genotoxic activity in short-term tests, combined with structural similarities to other genotoxicants, and with chemicals known to be metabolically transformed to carcinogenic aromatic amines support the level of concern.

There is a HIGH level of concern over the extent of exposure since there is potentially widespread exposure to C.I. Disperse Yellow 3 due to its widespread use in clothing, hosiery, carpets, and thermoplastics (NTP, 1982), although its availability for absorption from these materials would appear unlikely. C.I. Disperse Yellow 3 has been produced in significant quantities since the 1940’s. U.S. production in 1980 was 1,860,000 lbs. NIOSH estimated that 18,958 workers were potentially exposed in 359 U.S. facilities in 1983 (NIOSH, 1994). C.I. Disperse Yellow 3 has been found in wastewater and river mud samples taken from rivers that receive wastewater from carpet dyeing facilities (IARC, 1990).

References

International Agency for Research on Cancer (IARC, 1990). IARC Monographs on the evaluation of carcinogenic risks to humans. Some Flame Retardants and Textile Chemicals, and Exposures in the Textile Manufacturing Industry, Volume 48. IARC, Lyon, pp. 149-159.

National Institute for Occupational Safety and Health (NIOSH, 1994). National Occupational Exposure Survey (19981-83), Cincinnati, OH.

National Toxicology Program (NTP, 1982). NTP Technical Report on the Carcinogenesis Bioassay of C.I. Disperse Yellow 3 (CAS. No. 2832-40-8) in F344/N rats and B6C3F1/N mice (Feed Study). TR-222, NTP-81-80, NIH Publication No. 82-1778.

CARCINOGENICITY DATA SUMMARY: CLOMIPHENE AND ITS SALTS

Clomiphene (CAS No. 911-45-5) is a pharmaceutical agent used to treat infertility in women. Treatment with clomiphene stimulates ovulation, apparently as a result of increased concentrations of gonadotropins. Clomiphene has also been used in men to treat oligospermia. Clomiphene was reviewed by IARC in both 1979 and 1987. IARC concluded that the evidence of carcinogenicity was inadequate in humans and inadequate in animals (group 3 carcinogen). The IARC review did not include the epidemiology studies of Rossing et al. (1994), Whittemore et al. (1992), Harris et al., (1992), or the numerous case reports discussed by Spirtas et al. (1993). These results, in addition to the studies reviewed by IARC, are briefly described below.

Carcinogenicity Data available:

Epidemiological studies

A recent case-cohort study (Rossing et al., 1994) suggested that prolonged use of clomiphene may increase the risk of ovarian tumors. The study followed 3,837 women who had been evaluated for infertility. Eleven developed ovarian tumors classified as invasive or borderline malignant, compared with an expected number of 4.4 (standardized incidence ratio, 2.5; 95% CI, 1.3 - 4.5). Nine of the women in whom ovarian tumors developed took clomiphene. The study found that increased risk was associated with clomiphene treatment for one year or more (relative risk, 11.1; 95% CI 1.5 - 82.3).

An analysis of 12 case-control studies of ovarian cancer found that the risk of invasive epithelial tumors was increased among women who had used fertility drugs (Whittemore et al., 1992). In another study, risks were also increased for borderline epithelial ovarian tumors among women who had used fertility drugs (Harris et al., 1992). These studies were limited by small numbers and by the lack of information on specific fertility drugs prescribed.

A number of cases of ovarian cancer in women treated with fertility drugs have been reported in the literature and to the Food and Drug Administration (Spirtas et al., 1993).

Animal bioassays

Neonatal rat subcutaneous injection study: Clark and McCormack, 1977. Multiple reproductive tract abnormalities were noted in Sprague-Dawley rats treated with clomiphene citrate (10-500 m g, single s.c. injection at 1 day). These included hilus-cell tumors of the ovary and tumors of the uterus. The authors noted that although uterine tumors were observed in only a few animals, the observation period in the study was limited to a maximum of 100 days, and the incidence of these tumors may increase considerably in older rats. IARC (1979) noted the incomplete reporting of the experiment.

Other relevant data

No studies of short-term genetic toxicity tests of clomiphene were located in the literature. Epidemiological evidence suggests that any factor which reduces the number of times a woman ovulates (e.g. late menarche, use of oral contraceptives, number and duration of intervals without ovulation due to pregnancy and lactation, early menopause) reduces the risk of ovarian cancer (Spirtas et al., 1993). This is presumed to be because suppression of ovulation reduces the injury and repair of the ovarian epithelium. By analogy, any effect which promotes ovulation might be expected to increase the incidence of ovarian cancer. An alternative theory suggests that elevated levels of pituitary gonadotropins directly increases the risk of ovarian cancer.

Preliminary evaluation of carcinogenicity and exposure data:

There is a MEDIUM level of carcinogenicity concern over clomiphene since an association between exposure to clomiphene and ovarian cancer has been observed in a case-cohort study of women. This concern is reinforced by the findings of a meta-analysis of 12 case-control studies, which suggests that women treated with fertility drugs, including clomiphene, are at increased risk for ovarian cancer. Numerous case reports further support this. One limited animal bioassay in female rats provides additional support for this level of toxicological concern.

There is a HIGH level of concern over the extent of exposure since it is widely prescribed as a treatment for infertility in women, and since therapeutic dose levels are high (50-100 mg/day) (IARC, 1979). In 1991 there were an estimated 731,000 prescriptions for clomiphene citrate in the US, increased from 390,000 prescriptions in 1973 (Wysowski, 1993).

References

Clark JH, McCormack S (1977). Clomid or nafoxidine administered to neonatal rats causes reproductive tract abnormalities. Science 197:164-165.

Harris R, Whittemore AS, Itnyre J and the Collaborative Ovarian Cancer Group (1992). Characteristics relating to ovarian cancer risk: Collaborative analysis of 12 US case-control studies. III. Epithelial tumors of low malignant potential in white women. Am J Epidemiol 136:1204-1211.

International Agency for Research on Cancer (IARC, 1979). IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Humans. Volume 21. IARC, Lyon, France.

International Agency for Research on Cancer (IARC, 1987). IARC Monographs on the evaluation of carcinogenic risks to humans. Suppl 7, Overall evaluations of carcinogenicity: An updating of IARC monographs Volumes 1-42. Lyon, p. 64.

Rossing MA, Daling JR, Weiss NS, Moore DE, Self SG (1994). Ovarian tumors in a cohort of infertile women. N Engl J Med 331:771-776.

Spirtas R, Kaufman SC, Alexander NJ (1993). Fertility drugs and ovarian cancer: red alert or red herring? Fertility and Sterility 59(2):291-293.

Whittemore AS, Harris R, Itnyre J and the Collaborative Ovarian Cancer Group (1992). Characteristics relating to ovarian cancer risk: Collaborative analysis of 12 US case-control studies. II. Invasive epithelial ovarian cancers in white women. Am J Epidemiol 136:1184-1203.

Wysowski DK (1993). Use of fertility drugs in the United States, 1973 through 1991. Fertility and Sterility 60(6):1096-1098.

CARCINOGENICITY DATA SUMMARY: COUMARIN

Coumarin (CAS No. 91-64-5) is a member of a large class of naturally occurring compounds. It is widely used in perfumes and cosmetics as a fragrance and has potential application as a flavor-enhancer in food and tobacco. IARC reviewed this compound in 1976 and concluded that the evidence of carcinogenicity was limited in animals (group 3 carcinogen). The Food and Drug Administration and the National Cancer Institute nominated coumarin for testing by the National Toxicology Program (NTP) because of its widespread use. The results of this NTP bioassay are described below.

Carcinogenicity Data available:

Epidemiological studies

No data on long-term effects of human exposure to coumarin are available.

Animal bioassays

Long-term gavage studies in F344/N rats: NTP, 1993. NTP found some evidence of the carcinogenic activity of coumarin based on increased incidences of renal tubule adenomas in male rats. Marginal increases in these tumors were seen in female rats.

Long-term gavage studies in B6C3F₁ mice: NTP, 1993. NTP reported clear evidence of the carcinogenic activity of coumarin in female mice based on increased incidences of alveolar/bronchiolar adenomas, alveolar/bronchiolar carcinomas, and hepatocellular adenomas. In male mice, there were increased incidences of alveolar/bronchiolar adenomas which NTP considered to provide some evidence of carcinogenic activity. Marginal increases in the incidences of squamous cell papillomas of the forestomach in both males and females were also observed.

Other relevant data

Coumarin was shown to be mutagenic in Salmonella TA100 with S9 (NTP, 1993). It was also found to induce SCEs in CHO cells (without S9), as well as chromosomal aberrations in CHO cells (with S9). NTP has also tested 3,4-dihydrocoumarin, a metabolite of coumarin and reported kidney tumors in male rats and liver tumors in female mice.

Preliminary evaluation of carcinogenicity and exposure data:

There is a MEDIUM level of carcinogenicity concern regarding coumarin based on carcinogenic effects observed in male F344/N rats and B6C3F₁ mice as described above. The NTP concluded that there was clear evidence of the carcinogenic activity of coumarin in female mice based on neoplasms in the lung and the liver. The incidences of pulmonary neoplasms (benign or malignant combined) in high-dose male and female mice were well above the highest incidence observed in NTP historical controls. Further, focal renal hyperplasia (a lesion considered to be preneoplastic) was observed in dosed rats with incidences generally paralleling the incidences of renal neoplasms. The level of concern is also supported by the positive results in short-term tests for mutagenicity and genotoxicity, and by the observation that a metabolite of coumarin induced neoplasms in the male rat kidney and the female mouse liver.

There is a HIGH level of concern over the extent of exposure to coumarin. In addition to being widely used in perfumes, soap, other related household products, coumarin is also used as an odor-masking agent that may be found in paints, insecticides, and plastics (NTP, 1993). In 1990, NIOSH (NTP, 1993) estimated that approximately 240,000 workers are potentially exposed. The annual production of coumarin in the US is reported to be over 1 million lbs/yr (TSCA, 1990).

References

National Toxicology Program (1993). Toxicology and Carcinogenesis Studies of Coumarin (CAS No. 91-64-5) in F344/N Rats and B6C3F1 Mice (Gavage Studies). Technical Report Series No. 422. NIH Publication No. 93-3153. US Department of Health and Human Services, Public Health Service, National Institutes of Health.

US Environmental Protection Agency (1990). Toxic Substances Control Act (TSCA) Chemical Substance Inventory.

CARCINOGENICITY DATA SUMMARY: nitrofurantoin

Nitrofurantoin (CAS No. 67-20-9) is used extensively to treat and to prevent lower urinary-tract infections in humans. This compound was evaluated by the IARC in 1990. IARC concluded that evidence of carcinogenicity was inadequate in humans and limited in animals (group 3 carcinogen). No additional information was identified by OEHHA since the IARC review. Studies reviewed by IARC are briefly described below.

Carcinogenicity Data available:

Epidemiological studies

One study found an association between nitrofurantoin use and the incidence of cancers of the female genital tract and nervous system (IARC, 1990). A recent literature search by OEHHA did not identify any additional epidemiologic studies.

Animal bioassays

Rat long-term feed studies: NTP, 1989. A statistically significant increase in the incidence of renal tubular cell adenomas was seen in males (control, 3/50; 1,300 ppm, 11/50; 2,500 ppm, 19/50). Also, uncommon osteosarcomas of the bone and neoplasms of the subcutaneous tissue were observed in high-dose male rats. On the basis of these findings NTP concluded that this provided some evidence of carcinogenicity in the male F344 rat. No significant increases in tumor incidence were found in treated female Fischer 344 rats.

Female rat long-term feeding study: Wang et al., 1984. Female Sprague Dawley rats received 1880 ppm nitrofurantoin in the diet for 104 weeks. Mammary fibroadenomas were observed in 9/12 treated animals compared to 2/11 controls.

Mouse long-term feed studies: NTP, 1989. Statistically significant increases in the incidences of ovarian tubular adenomas, benign mixed cell tumors, and granulosa cell tumors were observed in female mice, and NTP consequently concluded that there was clear evidence for carcinogenicity in the female. No significant increases in tumor incidence were seen in male B6C3F₁ mice given nitrofurantoin. Feed concentrations were 0, 1300 or 2500 ppm for both male and female studies.

Mouse long-term feed studies: Ito et al., 1983. No increases in tumor incidence were seen in groups of male and female BDF₁ mice given 750 or 3,000 ppm nitrofurantoin in feed for 104 weeks.

Mouse long-term feed studies: Butler et al., 1990. A significant increase in the incidence of malignant lymphomas was seen in male Swiss mice given 200 ppm nitrofurantoin in the diet for 22 months (p=0.014). A non-statistically significant decrease in the incidence of these tumors was seen in females receiving this dose.

Female mouse intermediate-term feed study: Stitzel et al., 1989. The incidence of reproductive tract tumors was not elevated in female mice fed nitrofurantoin at 0, 350 or 500 ppm in the diet for 64 weeks. This experiment was too short in duration to observe late occurring tumors.

Other relevant data

Nitrofurantoin was mutagenic to Salmonella typhimurium and Escherichia coli and induced DNA strand breaks, unscheduled DNA synthesis, and sister chromatid exchanges in mice (IARC, 1990).

Preliminary evaluation of carcinogenicity and exposure data:

There is a MEDIUM level of carcinogenicity concern over nitrofurantoin based on the findings by the NTP of renal tubular cell adenomas in the male rat and ovarian tumors in female mice, malignant lymphomas in male mice (Butler et al., 1990), and mammary fibroadenomas in female rats (Wang et al., 1984). The level of concern is reinforced by the observations of mutagenicity and genotoxicity in short-term tests. On the basis of the bioassay data, IARC (1990) found the evidence for carcinogenicity of the chemical in experimental animals was limited. OEHHA did not identify information in recent literature searches that indicate this evaluation should be reconsidered.

There is a HIGH level of concern over the extent of exposure based on the extensive use of this drug to treat and prevent lower urinary tract infections. The recommended dosage is 200-400 mg per day by mouth for the treatment of infections. When administered chronically as a preventive for urinary tract infections, the recommended dosage is 50-100 mg/day. Sales in the U.S. of nitrofurantoin were 9,300 kg in 1986 (NTP, 1989).

References

Butler WH, Graham TC, Sutton ML (1990). Oncogenicity study of macrodantin in Swiss mice. Food Chem Toxicol 28: 49-54.

International Agency for Research on Cancer (IARC, 1990). IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Volume 50. IARC, Lyon. pp. 211-231.

Ito A, Naito M, Naito Y, Watsanabe H (1983). Tumorigenicity test of N-(5-nitro-2-furanylydine)-1-aminohydantoin by dietary administration in BDF₁ mice. Hiroshima J Med Sci 32:99.

National Toxicology Program (NTP, 1989). Bioassay of Nitrofurantoin for possible Carcinogenicity (CAS No, 67-20-9 (Technical Report No. 341: DHEW Publ. No. (NIH) 89-2597) Bethesda, MD, U.S. Department of Health, Education, and Welfare.

Stitzel KA, RF McConnell, Kierckman TA (1989). Effects of nitrofurantoin on the primary and secondary reproductive organs of female B6C3F1 mice. Toxicol Pathol 17:774-781.

Wang CY, Croft WA, Bryan WT (1984). Tumor production in germ-free rats fed 5-nitrofurans. Cancer Letters 21:303-308.

CARCINOGENICITY DATA SUMMARY: OZONE

Ozone (CAS No. 10028-15-6) is formed naturally in the stratosphere by photodissociation of oxygen. It is also formed in the lower atmosphere as a result of interaction between ultraviolet radiation and atmospheric pollutants, and it is produced in welding arcs and by electrical discharges in general. Ozone is used as a disinfectant for air and water; for bleaching textiles, oils, and waxes, and in organic syntheses (NTP, 1994).

Carcinogenicity Data available:

Epidemiological studies

No studies of the long-term effects of human exposure to ozone have been reported which provide an adequate assessment of the potential for carcinogenic effects.

Animal bioassays

Mouse long-term inhalation studies (105 weeks): NTP, 1994. The "incidences of alveolar/bronchiolar adenoma or carcinoma (combined) were marginally increased in 0.5 and 1.0 ppm males (0 ppm 14/50; 0.12 ppm 13/50; 0.5 ppm 18/50; 1.0 ppm 19/50) and were increased in 1.0 ppm females (6/50; 7/50; 9/49; 16/50)."

Mouse long-term inhalation studies (130 weeks): NTP, 1994. The "incidences of alveolar/bronchiolar adenoma or carcinoma (combined) were marginally increased in exposed males (0 ppm 16/49; 0.5 ppm 22/49; 1.0 ppm 21/50) and in exposed females (6/50; 8/49; 12/50)."

Rat long-term inhalation studies (105 weeks): NTP, 1994. No treatment-related tumors were observed in either male or female rats.

Rat long-term inhalation studies (125 weeks): NTP, 1994. No treatment-related tumors were observed in either male or female rats.

Rat long-term inhalation study (105 weeks ozone + NNK for the first 20 weeks): NTP, 1994. Male rats were exposed to ozone for 105 weeks and injected 3 times weekly for the first 20 weeks with 4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone (NNK). "The administration of ozone did not affect the occurrence of pulmonary neoplasms or nonneoplastic lesions in rats administered NNK."

Rat long-term inhalation studies (13 months): Ichinose and Sagai, 1992. Rats were exposed to low levels of ozone (i.e., 0.05 ppm). No treatment-related tumors were observed in either male or female rats.

Hamster long-term inhalation studies: Witschi et al., 1993. No ozone treatment-related effects were observed in hamster lungs.

Mouse lung adenoma inhalation study (103 hr/wk for 6 months + additional observation for 5 months): Hassett et al., 1985. Female strain A/J mice were exposed to ozone starting in week 8 of life. Other treatment groups, in addition to untreated controls, include animals treated with a single i.p. injection of urethane in week 7 of life, and animals treated with a single i.p. injection of urethane plus ozone exposure. A statistically significant increase in the mean number of lung tumors per animal was observed in the ozone-treated group (0.85) as compared with the untreated controls (0.60) (Chi square analysis, p < 0.005). No significant difference in the mean number of lung tumors per animal was observed in the urethane + ozone group (2.68) vs. the urethane only group (2.95).

Mouse lung adenoma inhalation study (102 hr/wk for the first week of 6 consecutive months + additional observation for 3 months): Hassett et al., 1985. Female strain A/J mice were exposed to ozone starting in week 8 of life. Other treatment groups, in addition to untreated controls, include animals treated with six i.p. injections of urethane (once a month for 6 months), and animals treated with (six) i.p. injections of urethane immediately following each week of exposure to ozone for 6 months. A statistically significant increase in the mean number of lung tumors per animal was observed in the ozone-treated group (0.64) as compared with the untreated controls (0.20) (Chi square analysis, p < 0.005), and in the urethane + ozone group (10.30) vs. the urethane only group (7.91) (p < 0.005).

Other relevant data

Ozone is genotoxic in a variety of in vitro and in vivo tests. In vitro, ozone induced gene mutations in E. coli and S. typhimurium, dominant lethal mutations in D. melanogaster, chromosomal aberrations in cultured human lymphocytes and fibroblasts, and sister chromatid exchanges in Chinese hamster V79 cells and human lymphocytes. In vivo, ozone induced chromosomal aberrations in lymphocytes of Chinese hamsters and in pulmonary macrophages of F344 rats (NTP, 1994).

In the long-term inhalation studies conducted in rats by NTP (1994), increased incidences of ozone-induced metaplasia occurred in the nose and lung of rats exposed to 0.5 or 1.0 ppm ozone for two years, and in the nose, larynx, and lung of rats exposed to 0.5 or 1.0 ppm ozone for an additional six months in the lifetime studies. Metaplasia is thought to be one step in the continuum of pathologic changes which lead to neoplasia, although no increases in the incidences of neoplasms of the nose, larynx or lung were observed in these studies (see above, NTP, 1994). Similar increases in the incidence of ozone-induced metaplasia were observed in the long-term inhalation studies conducted in mice by NTP (1994). As noted above, these increases in metaplasia observed in the mouse studies were accompanied by marginal increases in the incidences of alveolar/bronchiolar adenomas and carcinomas (NTP, 1994).

Preliminary evaluation of carcinogenicity and exposure data:

There is a MEDIUM level of carcinogenicity concern over ozone since there is "some evidence of carcinogenic activity in female mice", "equivocal evidence of carcinogenic activity in male mice", and "no evidence of carcinogenic activity for male and female rats" (NTP, 1994). This level of concern is reinforced by the evidence of carcinogenic activity in strain A/J mice (Hassett et al., 1985) and by the observations of genotoxicity in a variety of in vitro systems and in two in vivo test systems. The observations of metaplasia, but not dysplasia in both rats and mice in long-term inhalation studies (NTP, 1994) provide additional support for this level of concern.

There is a HIGH level of concern over the extent of exposure since ozone is a widespread air contaminant; the US EPA (1986) estimates that greater than 115 million people in the U.S. are exposed to concentrations higher than the current standard (i.e., 0.12 ppm) each year. Concentrations in large cities such as Los Angeles typically range from 0.2 - 0.5 ppm during the summer, and have reached as high as 1.0 ppm (US EPA, 1986).

References

Hassett C, Mustafa MG, Coulson WF, Elashoff RM. (1985). Murine lung carcinogenesis following exposure to ambient ozone concentrations. J Natl Cancer Institute 75:771-777.

Ichinose T, Sagai M. (1992). Combined exposure to NO_2, O₃, and H₂SO₄-aerosol and lung tumor formation in rats. Toxicology 74:173-184.

National Toxicology Program (NTP, 1994). Toxicology and carcinogenesis studies of ozone (CAS No. 10028-15-6) and ozone/NNK (CAS No. 10028-15-6/64091-91-4) in F344/N rats and B6C3F₁ mice (Inhalation studies). NTP Technical Report Series No. 440, NIH Publication No. 95-3371.

U. S. Environmental Protection Agency (US EPA, 1986). Air quality criteria for ozone and other photochemical oxidants. Office of Health and Environmental Assessment. Research Triangle Park, NC.

Witschi H, Wilson DW, Plopper CG. (1993). Modulation of N-nitrosodiethylamine-induced hamster lung tumors by ozone. Toxicology 77:193-202.

CARCINOGENICITY DATA SUMMARY: PENTACHLOROANISOLE

Pentachloroanisole (CAS No. 1825-21-4) is a widespread environmental contaminant from the breakdown of chlorinated aromatic compounds. The Food and Drug Administration and the National Institute of Environmental Health Sciences nominated pentachloroanisole for testing by the NTP because of its wide distribution in the environment and in human foods. The results of this NTP bioassay are briefly described below.

Carcinogenicity Data available:

Epidemiological studies

No data on long-term effects of human exposure to pentachloroanisole are available.

Animal bioassays

Long-term gavage studies in F344/N rats: NTP, 1993. Significantly increased incidences of benign pheochromocytomas of the adrenal medulla were observed in male rats. Marginally increased incidences of benign pheochromocytomas of the adrenal medulla were reported in female rats. On the basis of these findings NTP concluded that there was some evidence of carcinogenicity in the male rat and equivocal evidence of carcinogenicity in the female rat.

Long-term gavage studies in B6C3F₁ mice: NTP, 1993. Significantly increased incidences of benign pheochromocytomas of the adrenal medulla and hemangiosarcomas of the liver were observed in male mice, and NTP consequently concluded that there was some evidence of carcinogenic activity in these animals. No evidence of carcinogenicity was reported in female mice.

Other relevant data

Pentachloroanisole was found to be mutagenic in Salmonella typhimurium strains TA98 and TA1537 in the absence of S9. It was also found to be positive in the mouse lymphoma assay in the presence of S9 and induced SCEs in CHO cells in vitro (with and without S9) (NTP, 1993). NTP reported that some species can metabolize pentachloroanisole to pentachlorophenol in assays in vitro and in vivo. In NTP diet studies with pentachlorophenol, adrenal gland medullary pheochromocytomas and hepatocellular carcinomas or carcinomas/adenomas were observed in male and female B6C3F₁ mice. Also in the pentachlorophenol studies, circulatory system hemangiosarcomas were observed in female mice. (Pentachlorophenol is listed as a carcinogen under Proposition 65.)

Preliminary evaluation of carcinogenicity and exposure data:

There is a MEDIUM level of carcinogenicity concern regarding pentachloroanisole based on the increased incidence of benign pheochromocytomas of the adrenal medulla in male F344/N rats and male B6C3F₁ mice, hemangiosarcomas in male mice and no evidence of carcinogenicity in female mice, as described above. Concern is strengthened by the observations of bacterial mutagenicity and by the metabolism of pentachloroanisole to pentachlorophenol, a known carcinogen which induces pheochromocytomas of the adrenal medulla, hepatocellular adenomas and carcinomas, and hemangiosarcomas in mice.

There is a HIGH level of concern over the extent of exposure. Although pentachloroanisole is not manufactured commercially, it occurs as a result of environmental degradation of structurally related, ubiquitous chlorinated aromatic compounds such as pentachlorophenol, a known carcinogen currently listed under Proposition 65 (NTP, 1993). NTP (1993) states that "its presence as an environmental contaminant is widespread" and that it "is probably derived from ubiquitous related chlorinated aromatic compounds, especially pentachlorophenol". NTP also notes that "Pentachloroanisole was nominated for toxicity and carcinogenicity testing by the Food and Drug Administration and NIEHS because its wide distribution in the environment and in human foods presents a potential for low-level human exposure through drinking water and through food."

References

National Toxicology Program (1993). Toxicology and Carcinogenesis Studies of Pentachloroanisole (CAS No. 1825-21-4) in F344/N Rats and B6C3F1 Mice (Gavage Studies). Technical Report Series No. 414. NIH Publication No. 93-3145. US Department of Health and Human Services, Public Health Service, National Institutes of Health.

CARCINOGENICITY DATA SUMMARY: TRIFLURALIN

Trifluralin (CAS No. 1582-09-8) is an herbicide for grasses and broadleaf weeds. Trifluralin was reviewed by IARC in 1991. IARC concluded that the evidence of carcinogenicity was inadequate in humans and limited in animals (group 3 carcinogen). However, their review included only the NCI (1978) rat and mouse studies and the mouse studies by Francis et al. (1991). The studies by Emmerson et al. (1980) and Eli Lilly (1966) were not considered. US EPA has posted a series of reviews and actions relating to trifluralin (USEPA, Federal Register) and IRIS currently lists trifluralin as a Class C - possible human carcinogen.

Carcinogenicity data available:

Epidemiological studies

Population-based case-control study: Hoar, 1986. This study of white males in an agricultural setting found an elevated odds ratio for non-Hodgkin’s lymphoma among farmers exposed to trifluralin, among other herbicides (OR 12.5, 95% CI 1.6-116.1). However, these other significant chemical exposures confound the analysis with respect to trifluralin.

Animal bioassays

Mouse long-term diet studies (treated 78 weeks + additional 12 weeks observation): NCI, 1978. Significant increases in hepatocellular carcinomas and alveolar and bronchial adenomas were seen in female mice receiving 0, 2740 or 5192 ppm in the diet. A small increase in relatively rare forestomach carcinomas seen in low-dose female mice (4/45 versus 0/60 in pooled controls) was also considered treatment-related. Increased tumor incidences in male mice were not significant. The NCI concluded that "technical grade trifluralin is a carcinogen in female B6C3F₁ mice…" This study used technical grade trifluralin, later found to be contaminated with N-nitroso-n-propylamine (NDPA).

Rat long term diet studies (treated 78 weeks + additional 33 weeks observation): NCI, 1978. No increase in tumors was observed in male or female rats.

Rat diet studies: Emmerson et al., 1980 (This series of studies has not been published in the open literature, but was submitted to and reviewed by CDFA [1990], and is cited by US EPA, with a summary in IRIS). Technical grade trifluralin with <0.01 ppm of NDPA was administered to both sexes of Fischer 344 rats at 0, 813, 3250 or 6500 ppm in diet. Uncommon transitional cell carcinomas of the renal pelvis epithelium were increased in all treated groups of males, reaching significance in the high-dose group. Dose-dependent increases in tumors of the bladder or renal pelvis transitional epithelium were observed in both sexes (males: 0/60, 3/59, 4/60, 7/60; females: 0/60, 0/60, 1/60, 5/60). In addition, thyroid follicular adenomas and carcinomas were significantly increased in high-dose male rats.

Mouse long-term diet studies (2 years): Francis et al., 1991. Technical grade trifluralin with < 0.01 NDPA was administered at 0, 563, 2250, or 4450 in diet to males and female B6C3F₁ mice. No evidence of oncogenicity was observed, although the high dose resulted in significantly decreased body weight gains.

Rat long-term diet studies (2 years): Eli Lilly, 1966, as reported in US EPA 1986 Peer Review of Trifluralin. In groups of 25 of each sex, Sprague-Dawley rats were administered 0, 200, 1000, or 2000 ppm trifluralin in the diet. "The CAG concluded that this study showed no evidence of carcinogenicity and that the study was an adequate basis for safety evaluation."

IARC (1991) reviewed the published data on trifluralin and concluded that there was limited evidence of carcinogenicity in animals (group 3). However, since they do not, as a matter of policy, review studies which have only been submitted for product registration purposes and not otherwise published, their review included only the NCI (1978) rat and mouse studies and the mouse studies by Francis et al. (1991). Neither the positive study by Emmerson et al. (1980), nor the non-positive result obtained by Eli Lilly (1966) was considered. US EPA currently classifies trifluralin as a Class C - possible human carcinogen.

Other relevant data

Trifluralin was negative in the dominant lethal test in rats and in assays for SCEs and induction of reverse mutations in Salmonella (CDFA, 1990), however, it induced aneuploidy in Neurospora crassa, and yielded mixed results in aneuploidy tests in Drosophila (IARC, 1991). Trifluralin is structurally related to ethalfluralin, which produces mammary gland fibroadenomas in female rats (IRIS).

Preliminary evaluation of carcinogenicity and exposure data:

There is a MEDIUM level of carcinogenicity concern over trifluralin. Concern is due to dose-dependent increases in the incidences of tumors of the transitional epithelium of the bladder and renal pelvis in male and female F344 rats, and significant increases in thyroid follicular tumors in males. Similar observations were not made in studies in other strains of rats. It is noteworthy that in the positive study, the number of animals observed with renal calculi increased substantially with increasing dose; they were found in the majority of high-dose animals. There was a positive bioassay in female mice at three tumor sites, but the study is compromised by contamination with N-nitroso-n-propylamine and was considered unacceptable by CDFA (1990). A follow-up study with a sample of greater purity did not find an effect under similar circumstances. The level of concern is reinforced by the possible (but unproven) association with lymphoma among exposed farmers and the structural similarity to the animal tumorigen ethalfluralin. The single positive observation of genotoxicity in short-term tests neither adds nor detracts from the level of concern.

There is a HIGH level of concern over the extent of exposure to trifluralin. It is used on a large number of California crops; 1,404,088 lbs were applied in 1993 (DPR, 1995). Most usage is on cotton and alfalfa, indicating that, like other agricultural chemicals, occupational exposures are possible. The general public may consume food crops treated with trifluralin, especially tomatoes, carrots and grapes, and could be additionally exposed by dermal and inhalation routes from lawn products (HSDB). Trifluralin may also bioaccumulate in fish (HSDB).

References

California Department of Pesticide Regulation (DPR, 1995). Pesticide Use Report, Annual 1993. DPR, Information Systems Branch, Cal/EPA, Sacramento, CA.

California Department of Food and Agriculture (1990). Summary of toxicology data, trifluralin. CDFA, Medical Toxicology Branch, Sacramento, CA.

Emmerson JL, Pierce EC, McGrath JP et al. (1980). The chronic toxicity of compound 36352 (trifluralin) given as a component of the diet to Fischer 344 rats for two years. Studies R-87 and R97, submitted by Elanco Products Co., division of Eli Lilly Co.) as cited in IRIS and discussed in Peer Review of Trifluralin by the Toxicology Branch Peer Review Committee (April 11, 1986 memorandum from R. Bruce Jaeger).

Francis PC, Emmerson JL, Adams ER, Owen NV (1991). Oncogenicity study of trifluralin in B6C3F1 mice. Food Chemical Tox 29(8):549-555.

Hazardous Substances Data Bank (HSDB, 1995). National Library of Medicine.

Hoar SK, Blair A, Holmes FF, Boysen CD, Robel RJ, Hoover R, Faumeni JF (1986). Agricultural herbicide use and risk of lymphoma and soft-tissue sarcoma. JAMA 256(9):1141-1147.

Integrated Risk Information System (IRIS). US EPA.

International Agency for Research on Cancer (IARC, 1991). IARC monographs on the evaluation of carcinogenic risks to humans, Volume 53. Occupational exposures in insecticide application, and some pesticides. IARC, Lyon.

National Cancer Institute (NCI) (1978). Bioassay of trifluralin for possible carcinogenicity. CAS No. 1582-09-8. NCI Technical Report Series No. 34. DHEW Publication No. (NIH) 78-834, Bethesda, MD.

USEPA, Federal Register. 55 FR 17560, April 25 1990: other notices 1988-1992.

CARCINOGENICITY DATA SUMMARY: ACETOXIME

Acetoxime (acetone oxime; 2-propanone oxime; CAS No. 127-06-0) is widely used as a starting material for organic synthesis. It is also used in oil paints and coatings as an anti-skinning agent.

Carcinogenicity Data available:

Epidemiological studies

No data on long-term effects of human exposure to acetoxime have been reported.

Animal bioassays

Rat long-term drinking water studies (18 months + observation until death): Mirvish et al., 1982. Acetoxime was administered at a concentration of 1,000 ppm in drinking water to groups of male and female MRC-Wistar rats for 18 months. Surviving animals were then observed without further exposure until death occurred. For male rats, the incidence of hepatocellular neoplasms was 12/15 in treated animals as compared with 0/23 in controls. For females, the incidences were 3/16 and 0/20 in treatment and control groups, respectively. All of the hepatocellular tumors were classified as adenomas with the exception of a carcinoma found in a dosed male. In addition, acetoxime produced a significant increase in the number of hyperplastic liver nodules in Wistar and MRC-Wistar rats.

Other relevant data

In short-term studies, acetoxime was not mutagenic in Salmonella typhimurium strains TA98, TA100 or TA2637 and it was not mutagenic in E. coli strain WP2 uvrA/pKM101 either with or without metabolic activation (Araki et al., 1986). Acetoxime produced 8-hydroxyguanine in hepatic DNA following oral or i.p. administration to male Sprague-Dawley and F344 rats (Hussain et al., 1990). The pattern of modified nucleosides produced in rat liver is qualitatively similar to the pattern produced by the known rat liver carcinogen 2-nitropropane. Both acetoxime and 2-nitropropane are metabolized in the liver to propane 2-nitronate, the proximate carcinogenic metabolite of 2-nitropropane (Kohl et al., 1992). A computer program that analyzes structure-activity relationships based on a set of rules generated by US EPA experts (Oncologic, version 1.0) finds that acetoxime is of moderate carcinogenicity concern.

Preliminary evaluation of carcinogenicity and exposure data:

There is a MEDIUM level of carcinogenicity concern over acetoxime since it produces liver tumors in male rats and it is metabolized to propane 2-nitronate, the active metabolite of the animal liver carcinogen 2-nitropropane. No tests in other species have been reported. A computer program that analyzes structure- activity relationships based on a set of rules generated by US EPA experts (Oncologic, version 1.0) predicts that acetoxime is of moderate concern.

There is a MEDIUM level of concern over the extent of exposure to acetoxime. It is used in oil paints, with many containing 0.1-0.4% acetoxime and other similar oximes (Mirvish et al., 1982; Kohl et al., 1992); therefore artists are likely to represent a highly exposed subpopulation. It is used as starting material in organic syntheses and as an anti-skinning agent in oil paints and coatings. Exposure to acetoxime is likely to occur by inhalation due to its high volatility (Mirvish et al., 1982). The reported level of U.S. production in 1990 is 70,000 lbs. (Sherlock, 1995).

References

Araki A, Takahashi F, Matsushima T (1986). Mutagenicities of oxime compounds in S. typhimurium TA98, TA100, TA2637 and E. coli WP2 uvrA/pKM101. Mutation Research 164:263.

Hussan NS, Conaway CC, Guo N, Asaad W, Fiala ES (1990). Oxidative DNA and RNA damage in rat liver due to acetoxime: similarity to effects of 2-nitropropane. Carcinogenesis 11: 1013-1016.

Kohl C, Schiller ED, Gescher A, Farmer PB, Bailey E (1992). Acetoxime is metabolized by human and rodent hepatic P450 enzymes to the genotoxicant and carcinogen propane 2-nitronate. Carcinogenesis 15: 1901-1094.

Mirvish SS, Salmasi S, Runge RG (1982). Carcinogenicity test of acetoxime in MRC-wistar rats. J Natl Cancer Inst 69: 961-962.

Sherlock, SM (1995). Facsimile letter dated May 11, 1995 from S.M. Sherlock, Attorney Advisor, Information Management Division, US Environmental Protection Agency, Washington, D.C. to S. Hoover, Reproductive Cancer Hazard Assessment Section, Office of Environmental Health Hazard Assessment.

CARCINOGENICITY DATA SUMMARY: 2,6-DICHLORO-p-PHENYLENEDIAMINE

2,6-Dichloro-p-phenylenediamine (CAS No. 609-20-1) is a chemical intermediate in dye and resin manufacture. It is also a metabolite of the fungicide 2,5-dichloronitroaniline. The compound was identified as being of potential concern because of the suggestive findings in bioassays by the NTP published in the early 1980's. IARC (1985) reviewed 2,6-dichloro-p-phenylenediamine and concluded that there was limited evidence of carcinogenicity in animals (group 3). Literature searches were performed to identify additional data which have become available since the IARC review. These new findings include a structure-activity analysis and several tests for mutagenicity which are briefly described below.

Carcinogenicity data available:

Epidemiological Studies

No studies of the effects of long-term human exposure have been reported.

Animal Bioassays

Mouse diet studies (treated 103 weeks + additional 8 weeks observation): NTP, 1982. Increased incidences of liver tumors were observed in both male and female mice. There was a statistically significant trend in the incidence of hepatocellular adenomas with increasing dose in males; the increase in the high-dose group was also significant (4/50, 7/50, 15/50). In female mice, incidence of liver carcinomas exhibited a significant dose-related trend, although no single dose group had a significant increase. When the incidences of carcinomas and adenomas in females were taken together, the trend with dose was again significant as was the increase in the high-dose group (6/50, 6/50, 16/50).

Rat diet studies (103 weeks): NTP, 1982. No evidence of carcinogenicity in rats of either sex was observed.

Other relevant data

2,6-Dichloro-p-phenylenediamine was positive in the mouse lymphoma forward mutation assay (McGregor et al., 1988), and showed equivocal results in a mammalian cell transformation assay (Hatch et al., 1986; Tu et al., 1986). Mutagenicity in 3 strains of Salmonella typhimurium has also been reported (HSDB). A computer program that analyzes structure activity relationships based on a set of rules generated by US EPA experts (Oncologic, version 1.0) finds 2,6-dichloro-p-phenylenediamine to be of high-moderate carcinogenicity concern, the highest predictive level of concern possible. Only known carcinogens will be reported as having a high level of concern.

Preliminary evaluation of carcinogenicity and exposure data:

There is a MEDIUM level of carcinogencity concern over 2,6-dichloro-p-phenylenediamine due to the observed liver tumors in mice of both sexes. NTP found that the compound "was carcinogenic for male and female B6C3F₁ mice". Based on the NTP bioassay results, IARC (1985) concluded that there is limited evidence of carcinogenicity in animals. The level of concern of medium is reinforced by the structure-activity analysis results of the Oncologic computer program, and mutagenic activity in vitro.

There is a MEDIUM level of concern over the extent of exposure to 2,6-dichloro-p-phenylenediamine. The major potential for exposure is as a metabolite of the fungicide 2,6-dichloro-4-nitroaniline, also called dicloran. In 1993, 42,922 lbs of dicloran were used on a variety of California crops (DPR, 1995). The USFDA Total Diet Studies estimated an adult ADI of 0.047 ug/kg-day in 1982 (HSDB). Dicloran is listed on the EPA TSCA inventory (1993). In addition to exposure to dicloran as a food residue, NIOSH estimated 3,580 workers were potentially exposed in 1972-1974. Although IARC and HSDB report that 2,6-dichloro-p-phenylenediamine is no longer produced in the US, one manufacturer of the compound was found listed in a 1996 chemical manufacturers directory.

References

California Environmental Protection Agency, Department of Pesticide Regulation (DPR, 1995). Pesticide Use Report, Annual 1993. DPR Information Systems Branch, Sacramento, CA.

Hatch GG, Anderson TM, Lubet RA, Kouri RE, Putman DL, Cameron JW, Nims RW, Most B, Spalding JW, Tennant RW, et al. (1986). Chemical enhancement of SA7 virus transformation of hamster embryo cells: evaluation by interlaboratory testing of diverse chemicals. Environmental Mutagenesis, 8(4):515-31.

Hazardous Substances Data Bank (HSDB, 1995). National Library of Medicine.

International Agency for Research on Cancer (IARC, 1985). IARC monographs on the evaluation of the carcinogenic risk of chemicals to humans; Some chemicals used in plastics and elastomers. Volume 39. IARC, Lyon.

McGregor DB, Brown A, Cattanach P, Edwards I, McBride D, Riach C, Caspary WJ (1988). Responses of the L5178Y tk+/tk- mouse lymphoma cell forward mutation assay: III. 72 coded chemicals. Environmental and Molecular Mutagenesis, 12(1):85-154

National Toxicology Program (NTP, 1982). NTP technical report on the carcinogenesis bioassay of 2,6-dichloro-p-phenylenediamine (CAS no. 609-20-1) in F344 rats and B6C3F1 mice (feed study). NTP-80-36, NIH Publication No. 82-1775, USDHHS, NTP, Bethesda MD.

Tu A, Hallowell W, Pallotta S, Sivak A, Lubet RA, Curren RD, Avery MD, Jones C, Sedita BA, Huberman E, et al. (1986). An interlaboratory comparison of transformation in Syrian hamster embryo cells with model and coded chemicals. Environmental Mutagenesis 8(1):77-98.

US Environmental Protection Agency (US EPA, 1993) US EPA TSCA Inventory.

CARCINOGENICITY DATA SUMMARY: Chlorofluoromethane

Chlorofluoromethane (Halocarbon 31; CAS number 593-70-4) occurs as an impurity in commercial grades of dichlorofluoromethane (Halocarbon 21). This compound was identified for review because of positive bioassay data. Chlorofluoromethane was reviewed by IARC in 1986. IARC concluded that the evidence of carcinogenicity was inadequate in humans and limited in animals (group 3 carcinogen). No more recent information on the evidence for carcinogenicity of the agent identified by the literature searches conducted. However, a new structure-activity analysis is now available. These results, in addition to the study reviewed by IARC, are briefly described below.

Carcinogenicity Data available:

Epidemiological studies

No data on long-term effects of human exposure to chlorofluoromethane were available to IARC (1986) or identified in subsequent literature searches by OEHHA.

Animal bioassays

Rat long-term gavage study: Longstaff et al., 1984. Squamous cell carcinoma and fibrosarcoma of the stomach were reported in 92% of exposed males and 94% of exposed females: Background incidence of these lesions in both sexes was 1%. The study authors were unable to determine whether the sites of origin of the tumors were in the forestomach only or in both forestomach and glandular stomach.

Other relevant data

Chlorofluoromethane was found to be a highly active mutagen in the Salmonella reverse mutation assay, and to induce transformation of BHK21 cells in vitro (Longstaff et al., 1984). A computerized analysis of structure-activity relationships based on a set of rules generated by US EPA experts (Oncologic, version 1.0) finds that chlorofluoromethane is of high-to-moderate concern. (This is the highest level of concern noted for chemicals which are not included in the database of carcinogenicity bioassay results from which the program rules are derived.)

Preliminary evaluation of carcinogenicity and exposure data:

There is a MEDIUM level of carcinogenicity concern over chlorofluoromethane since evidence of carcinogenicity has been observed in both sexes of the rat in the one available study. In this single dose-level study, carcinogenic effects were observed at the site of application. Although the study was smaller and more limited in design than the standard bioassay, the extremely high level of incidence relative to controls of a relatively uncommon tumor is noteworthy. No tests in other species have been reported. The concern is reinforced by the observations of mutagenicity and cell transforming ability in short-term tests, and by the results of a computerized analysis of structure-activity relationships based on rules generated by US EPA experts (Oncologic, version 1.0), which predicts that chlorofluoromethane is of high-to-moderate concern (i.e., the highest level of concern possible on chemicals which have not been included in the program’s database).

There is a LOW level of concern over the extent of exposure since chlorofluoromethane is not manufactured in bulk or naturally abundant, although it occurs as an impurity in a commodity chemical (IARC, 1986). NIOSH (1983) estimated that 2,703 workers were potentially exposed to chlorofluoromethane, but levels were probably low since this compound is only present as an impurity. IARC (1986) characterized the exposure potential as limited.

References

International Agency for Research on Cancer (IARC,1986). IARC Monographs on the evaluation of carcinogenic risks to humans, Volume 41. IARC, Lyon. pp. 229-235, Chlorofluoromethane.

Longstaff E, Robinson M, Bradbrook C, Styles JA, Purchase IFH (1984). Genotoxicity and carcinogenicity of fluorocarbons: Assessment by short-term in vitro tests and chronic exposure in rats. Toxicol Appl Pharmacol 72:15-31.

National Institute for Occupational Safety and Health (NIOSH, 1983). National Occupational Exposure Survey for 1983, cited in the NIOSH database RTECS (Registry of Toxicological Effects of Chemical Substances).

CARCINOGENICITY DATA SUMMARY: mercuric chloride

Mercuric chloride (CAS No. 7487-94-7) is used in the production of other mercury compounds. It is also used as a catalyst in the production of vinyl chloride and as a fungicide. Mercuric chloride was reviewed by IARC in 1993. IARC concluded that the evidence for carcinogenicity was inadequate in humans and limited in animals (group 3). A literature search by OEHHA did not reveal critical studies not reviewed by IARC.

Carcinogenicity Data available:

Epidemiological studies

IARC (1993) concluded "There is inadequate evidence in humans for the carcinogenicity of mercury and mercury compounds." A recent literature search by OEHHA did not find additional recent epidemiological studies not reviewed by IARC.

Animal bioassays

Mouse drinking water study (lifetime): Schroeder and Mitchner, 1975. Groups of 54 male and 54 female Swiss mice were given drinking water containing either 0 or 5 ppm of mercuric chloride starting at 20 days of age. No significant increase in the incidence of tumors was found in treated animals of either sex, but there was a non-significant increase in the incidence of lymphoma and leukemia (combined) in treated females.

Mouse gavage study (two years): NTP, 1993. Groups of 60 male and 60 female B6C3F₁ mice were given mercuric chloride at a rate of 0, 5, or 10 mg/kg body weight by gavage on 5 days per week for 103-104 weeks. No statistically significant increases in tumor incidence were seen in treated animals, but 2 of 49 high-dose males were found with renal tubular-cell adenomas, and one with adenocarcinomas. No renal adenomas or carcinomas were seen in controls or dosed females. The NTP concluded that there was equivocal evidence of carcinogenic activity in mice and no evidence in females based on these findings.

Rat gavage study (two years): NTP, 1993. Groups of 60 male and 60 female Fischer 344/N rats were given mercuric chloride by gavage at a rate of 0, 2.5, or 5 mg/kg body weight on 5 days per week for 103-104 weeks. In treated males, there was a dose-related increase in the incidence of squamous-cell papillomas of the forestomach (controls, 0/50; low dose, 3/50; high dose, 12/50) and of follicular-cell carcinomas of the thyroid (controls, 1/50; low dose, 2/50; high dose, 6/50). The NTP concluded that there was some evidence of carcinogenicity in the male and equivocal evidence in the females based on these findings.

Following review of the above studies, IARC (1993) concluded that "There is limited evidence in experimental animals for the carcinogenicity of mercuric chloride."

Other relevant data

IARC (1993) stated that mercuric chloride induced DNA damage, chromosomal aberrations, and sister chromatid exchange.

Preliminary evaluation of carcinogenicity and exposure data:

There is a MEDIUM level of carcinogenicity concern for human exposure to mercuric chloride based on the observations of thyroid tumors in rats and DNA damage in short-term tests.

There is a LOW level of concern over the extent of exposure. The compound is used in the production of other mercury compounds, and is used as a catalyst in the production of vinyl chloride and as a fungicide and wood preservative. There is not widespread exposure to the general population, although it is expected that small numbers of people may be occupationally exposed. In 1990, use of 11,840 pounds was reported to US EPA TSCA (Sherlock, 1995).

References

International Agency for Research on Cancer (IARC, 1993). IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Volume 58 IARC, Lyon. pp. 239-330

National Toxicology Program (NTP, 1993). Bioassay of Mercuric Chloride (CAS No. 7487-94-7) for Possible Carcinogenicity (Gavage Study) (Technical Report No. 408: DHEW Publ. No. (NIH) 91-3139) Bethesda, MD, U.S.

Sherlock, SM (1995). Facsimile letter dated May 11, 1995 from S.M. Sherlock, Attorney Advisor, Information Management Division, US Environmental Protection Agency, Washington, D.C. to S. Hoover, Reproductive Cancer Hazard Assessment Section, Office of Environmental Health Hazard Assessment.

Schroeder HA, Mitchener M (1975). Life-term effects of mercury, methyl mercury and nine other trace metals on mice. J Nutr 105: 452-458.

CARCINOGENICITY DATA SUMMARY: 2-nitro-p-phenylenediamine

2-Nitro-p-diphenylamine (1,4-diamino-2-nitrobenzene, CAS No. 5307-14-2) is used as an ingredient in cosmetic products for dyeing hair. This compound was identified for review because of positive findings in the early bioassay by the National Cancer Institute (NCI) and the potential for direct and repeated exposures through its use as a hair dye. IARC (1993) reviewed 2-nitro-p-phenylenediamine and concluded that the evidence for carcinogenicity was inadequate in humans and limited in animals (group 3).

Carcinogenicity Data available:

Epidemiological studies

No data on carcinogenic effects of human exposure to 2-nitro-p-diphenylamine were available to IARC (1993) or discovered in a more recent literature search by OEHHA.

Animal bioassays

Rat long-term feed studies: NCI, 1979. No statistically significant increases in tumor incidence were seen in male or female Fischer 344/N rats fed 2-nitro-p-diphenylamine at 550 or 1,100 ppm for 78 weeks and then observed for an additional 27 weeks (NCI, 1979).

Mouse long-term feed studies: NCI, 1979. A statistically significant increase in the incidence of hepatocellular adenomas or carcinomas was seen in female but not in male B6C3F₁ mice fed a diet containing 2-nitro-p-diphenylamine (control 1/20, low-dose 10/49, high-dose 17/48).

Other relevant data

2-Nitro-p-diphenylamine was found to be mutagenic both with and without metabolic activation in Salmonella typhimurium, Escherichia coli, and L5178Y cells, but not in Neurospora crassa (IARC, 1993). A computerized analysis of structure-activity relationships using rules generated by US EPA experts (Oncologic, version 1.0) predicts that the level of carcinogenicity concern is moderate for this compound.

Preliminary evaluation of carcinogenicity and exposure data:

There is a MEDIUM level of carcinogenicity concern over 2-nitro-p-diphenylamine since evidence of carcinogenicity has been observed in female B6C3F₁ mice. The concern is reinforced by the observations of mutagenicity in short-term tests. On the basis of the NCI oral carcinogenicity studies IARC (1993) found limited evidence in experimental animals for the carcinogenicity of the compound. A computerized analysis of structure-activity relationships (Oncologic) predicts that 2-nitro-p-diphenylamine is of moderate concern.

There is a LOW level of concern over the extent of exposure based on the use of this lipid soluble compound in hair dyes (brunette shades) which may be used continuously for several years (possibly even decades). A large segment of the US population over 40 years of age uses hair dyes: approximately half of all women in the US dye their hair (Seligson, 1993) and consumer sales of men’s hair dyes have increased 4-fold between 1986 and 1995 (Wallenstein, 1995). The reported U.S. annual usage of 2-nitro-p-diphenylamine is only 150 kilograms (IARC, 1993).

References

International Agency for Research on Cancer (IARC, 1993). IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Volume 57. IARC, Lyon. pp. 185-200.

National Cancer Institute (NCI, 1979). Bioassay of 1,4-diamino-2-nitrobenzene for possible Carcinogenicity (CAS No. 5307-14-2) (Technical Report No. 169) Bethesda, MD, U.S. Department of Health, Education, and Welfare.

Seligson SV (1993). Dyeing for a change. Health 7:34-36.

Wallenstein A (1995). Boomers put new life in hair dye for men. Advertising Age 66:1-3.

CARCINOGENICITY DATA SUMMARY: SEMICARBAZIDE HYDROCHLORIDE

Semicarbazide hydrochloride (carbamylhydrazine hydrochloride, CAS No. 563-41-7) is used as a chemical reagent and is synthesized and available commercially in the US. IARC reviewed this compound in 1976, and found that there was limited evidence of carcinogenicity in animals (group 3). A literature review was conducted to identify studies not evaluated by IARC. The results of these studies are briefly described below.

Carcinogenicity data available:

Epidemiological studies

No studies of long term exposure in humans have been reported.

Animal bioassays

Drinking water studies in female Swiss mice ("lifetime"): Toth et al., 1975. 0.0625% semicarbazide hydrochloride was administered in drinking water for life resulting in increased incidence of lung and vascular tumors in treated females. 50% of treated females developed lung adenomas and adenocarcinomas, compared with 21 % of controls. The incidence of vascular tumors, including angiomas of the liver and angiosarcomas, rose from a control incidence of 5% to 18% in the treated group. 0.0625% semicarbazide hydrochloride administered in drinking water for life was also associated with an increase in lung tumors in male mice. The incidence rose from 23% in controls to 30% in the treated group

Diet study in mice (7 months): Mori et al., 1960. Female mice were fed 0.1% semicarbazide hydrochloride in diet. Six of 8 survivors had lung tumors, compared with 1 of 20 controls.

Diet study in rats (104 week): Weisburger et al., 1981. Male and female Charles River CD rats were fed diets containing 500 ppm for 78 weeks or 1000 ppm for 32 weeks. Treatment-related increases in tumor incidences were not observed. However, the authors noted that "In males, the number of survivors was so small that induction of any late occurring tumors could have gone undetected."

Other relevant data

This compound is a hydrazine derivative; hydrazines have been found to induce lung and/or vascular tumors in animal studies. Semicarbazide hydrochloride is mutagenic in Drosophila (cited in TOMES), and induced chromosome aberrations and non-disjunction in cultured grasshopper cells (cited in RTECS).

Preliminary evaluation of carcinogenicity and exposure data:

There is a MEDIUM level of carcinogenicity concern regarding semicarbazide hydrochloride. Two tumor sites were seen, and for lung tumors an increased incidence was observed in both sexes. Both target sites for semicarbazide hydrochloride are consistent with results from studies of other hydrazines; this consistency lends support to the level of concern. This concern is reinforced by the observation of mutagenicity in vitro.

There is a LOW level of concern over the extent of exposure to semicarbazide hydrochloride. Current information on exposure was not available. IARC (1974) notes that the compound has been used as a chemical reagent in the qualitative determination of aldehydes and ketones, and in the isolation of hormones and certain fractions of essential oils. NIOSH (1983) estimated that 2815 employees in 41 US facilities were exposed in 1983. The identification of a low level of concern is based on the presumption that, as in the past, there is likely to be very little exposure to the general public.

References

Toth B, Shimizu H, Erickson J (1975). Carbamylhydrazine hydrochloride as a lung and blood vessel tumor inducer in Swiss mice. Europ J Cancer 11: 17-22.

Mori K, Yasuno A, Matusumoto K (1960). Induction of pulmonary tumors in mice with isonicotinic acid hydrazide. Gann 51: 83-89.

International Agency for Research on Cancer (IARC, 1976). IARC monographs on the evaluation of the carcinogenic risk of chemicals to man: Some carbamates, thiocarbamates and carbazides. Volume 12. IARC, Lyon.

National Institute for Occupational Safety and Health (NIOSH, 1983). National Occupational Exposure Survey for 1983, cited in RTECS (Registry of Toxicological Effects of Chemical Substances).

Weisburger EK, Ulland BM, Nam J, Gart JJ, Weisburger JH (1981) Carcinogenicity tests of certain environmental and industrial chemicals. JNCI 67:75-88.

CARCINOGENICITY DATA SUMMARY: ACETAMINOPHEN

Acetaminophen (CAS No. 103-90-2) (otherwise known as Paracetamol; systematic name N-(4-hydroxyphenyl)-acetamide) is a widely used analgesic and antipyretic drug. It is available without prescription and commonly used by a large number of people, including children (since it is considered preferable to aspirin in view of the latter compound’s rare induction of Reye’s syndrome in febrile children and adolescents). Acetaminophen was reviewed by IARC in 1990, and was tested by the National Toxicology Program in 1993. IARC concluded that the evidence of carcinogenicity was inadequate in humans and limited in animals (group 3 carcinogen). The IARC review did not include the non-positive results of the NTP bioassays in rats and mice. These results, in addition to the studies reviewed by IARC, are briefly described below.

Carcinogenicity Data available:

Epidemiological studies

A series of three case-control studies examined possible associations between urinary tract cancer and acetaminophen use. In these studies, cases were classified as controls (no acetaminophen use), regular use (cumulative consumption of at least 0.1 kg) or higher exposure (cumulative consumption of at least 1 kg). A significantly increased risk of ureteral cancer was observed in regular acetaminophen users, but there was no further increase in this risk for the subgroup with higher exposure. Three other studies found no association between acetaminophen use and cancer at any urinary tract site. Results were adjusted for smoking, but not for exposure to phenacetin, a known carcinogen formerly used as an analgesic. IARC (1990) found the human evidence for carcinogenicity of acetaminophen to be inadequate.

Animal bioassays

Rat long-term diet studies: NTP, 1993. No evidence of carcinogenicity was found in male F344/N rats given 0, 600, 3000 or 6000 ppm acetaminophen in the diet for 103 weeks. An increased incidence of mononuclear cell leukemia was observed in female rats. The incidence in the highest dose group (48%, compared to 18% in the control group) and the positive dose-related trend were statistically significant. NTP (1993) noted however that the spontaneous incidence of mononuclear cell leukemia in rats is high and variable, and that the increased incidence was not associated with increased mortality. In view of these considerations, and the lack of response in male rats, they concluded that this result provided equivocal evidence of carcinogenicity in the female rat.

Mouse long-term diet studies: NTP, 1993. No evidence of carcinogenicity was found in male or female B6C3F₁ mice given 0, 600, 3000 or 6000 ppm acetaminophen in the diet for 103 weeks.

Rat long-term diet studies: Flaks et al., 1985. Male and female Leeds rats were fed 0, 5000 or 10000 ppm acetaminophen in the diet. Incidences of liver neoplastic nodules (characterized by IARC as benign) and bladder tumors (papillomas and a few carcinomas) were increased in rats of both sexes. The incidences of liver neoplastic nodules were: males, control 0/40, low-dose 1/48, high-dose 9/45; females, control 0/40, low-dose 0/49, high-dose 10/49. The incidences of bladder tumors were: males, control 0/40, low-dose 0/48, high-dose 5/45 papillomas and 1/49 carcinoma; females, control 0/40, low-dose 4/49 papillomas and 1/49 carcinoma, high-dose 0/49. Hyperplasia and calculi were also noted in the bladders of treated rats, but there was no relationship between the presence of calculi and the appearance of either tumors or hyperplasia.

Rat long-term diet study: Johansson, 1981. Groups of 30 male SPF Sprague-Dawley rats were fed 0 or 5350 ppm acetaminophen in the diet for 117 weeks. No significant differences in tumor incidences or survival rates were noted, although bladder papillomas or tumors were observed in 4/30 exposed rats, vs. 2/30 controls.

Rat long-term diet study: Hiraga and Fujii, 1985. Groups of 50 Fischer 344 rats were fed acetaminophen in the diet for 104 weeks, then observed for a further 26 weeks. Males received 0, 4500 or 9000 ppm, while females received 0, 6500 or 13000 ppm. Survival at 104 weeks was 86-90% in males and 80-82% in females. No significant increases in tumor incidences were seen in any group.

Rat Short-term diet study: Maruyama et al., 1990. Groups of 13 Fischer 344 rats were fed 0, 4500 ppm or 9000 ppm acetaminophen in the diet for a period of 25 weeks following feeding of choline supplemented, basal or choline-deficient diets for 27 weeks. Non-neoplastic lesions were observed in the liver associated with both choline deficiency and acetaminophen treatment, but no significant increase in tumor incidence was associated with acetaminophen treatment.

Mouse long-term diet studies: Flaks and Flaks, 1983. Groups of 60 male and 60 female IF strain mice were fed 0, 5000 or 10000 ppm acetaminophen in the diet for 18 months. Significant increases of liver tumors (including carcinomas) were observed in male and female IF mice. Severe toxicity, including liver necrosis, body weight depression and early mortality, was observed in animals receiving 10000 ppm acetaminophen in the diet. This dose caused hepatotoxicity in hale the males, as well as early lethality. A group receiving 5000 ppm acetaminophen showed neither the carcinogenic nor the toxic effects. The incidences of liver adenomas and carcinomas (combined) were: males, control 1/50, low-dose 1/54, high-dose 20/23; females, control 0/48, low-dose 0/57, high-dose 9/47.

Mouse long-term diet studies: Amo and Matsuyama, 1985. Groups of 50 - 55 male and female B6C3F₁ mice were fed 3000 or 6000 ppm acetaminophen in the diet for 134 weeks. No differences were observed between incidences of tumors at any site in control vs. exposed mice.

Mouse long-term diet study: Hagiwara and Ward, 1986. Groups of 60 and 120 male B6C3F₁ mice were fed 5000 or 10000 ppm acetaminophen in the diet for 70 weeks. Survival was poor in the high- dose group, with severe hepatotoxicity commonly found in mice that died. No increases in the incidences of neoplasms were found.

Other relevant data

Some studies of co-administration of acetaminophen with known carcinogens were reviewed by IARC (1990). One study (Tsuda et al., 1984) showed an increased incidence of preneoplastic renal lesions in Fischer 344 rats treated with a single injection of N-nitrosoethyl-N-hydroxyethylamine followed by up to 70 weeks exposure to diet containing 5000 or 10000 ppm acetaminophen. Five other series of studies examining promotion of tumors or preneoplastic lesions in liver, kidney and other tissues of rats, mice or hamsters were negative.

Acetaminophen at high doses causes liver and kidney toxicity in animals and humans. Liver damage is a potentially fatal side-effect of severe accidental or suicidal overdose with acetaminophen. It is exacerbated by concurrent exposure to alcohol. Initial signs of liver and/or kidney toxicity such as elevated serum transaminase levels may appear after use at therapeutic doses or moderate over-use, especially when this is combined with alcohol consumption (IARC, 1990). The liver and kidney damage are considered to be the result of a minor (5-10%) metabolic pathway involving cytochrome P-450 activation. This generates a reactive intermediate (postulated to be a quinoneimine), which interacts with tissue proteins and undergoes glutathione conjugation (IARC, 1990).

Acetaminophen does not induce gene mutations in the standard Salmonella reverse mutation assay, in Escherichia coli or in Chinese hamster V79 cells in vitro, or in vivo in Drosophila. Sister chromatid exchanges and chromosomal effects (aberrations, micronuclei) were observed in several mammalian cell test systems in vitro, including one study with human lymphocytes. Studies of chromosomal effects in mammals in vivo were negative apart from one report (Tsuruzaki et al., 1982) of aneuploidy induction in 12-day rat embryos after maternal treatment with acetaminophen. Another study reported no embryo or fetotoxic effects after oral treatment of rats.

Preliminary evaluation of carcinogenicity and exposure data:

There is a LOW level of carcinogencity concern over acetaminophen. Although carcinogenic effects were observed in two studies (Flaks et al., 1985; Flaks and Flaks, 1983), these effects occurred only at high doses at which significant toxicity was also noted. Several other studies had non-positive outcomes. IARC (1990) determined that the evidence for carcinogenicity in experimental animals was limited, and the evidence in humans was inadequate. This judgment preceded the non-positive results of the NTP bioassays in rats and mice. It is plausible that high dose hepatotoxicity is the mode of action for the observation of liver tumorigenicity. Acetaminophen is metabolized to a reactive intermediate that is detoxified by conjugation with glutathione. High dose levels may lead to the depletion of hepatic glutathione, resulting in hepatotoxicity.

There is a HIGH level of concern over the extent of exposure since acetaminophen is a widely used over-the counter medication. (IARC, 1990; NTP, 1993).

References

Amo H, Matsuyama (1985). Subchronic and chronic effects of feeding large amounts of acetaminophen in B6C3F₁ mice. Jpn J Hyg 40:567-574.

Flaks A, Flaks B (1983). Induction of liver cell tumors in IF mice by paracetamol. Carcinogenesis 4:363-368.

Flaks B, Flaks A, Shaw APW (1985). Induction of bladder and liver tumors in the rat. Acta Path Microbiol Immunol Scand. Sect A 93:367-377.

Hagiwara A, Ward JM (1986). The chronic hepatotoxic, tumor-promoting and carcinogenic effects of acetaminophen in male B6C3F₁ mice. Fundam Appl Toxicol 7:376-368.

Hiraga K, Fujii T (1985). Carcinogenicity testing of acetaminophen in F344 rats. Jpn J Cancer Res (Gann) 76:79-85.

International Agency for Research on Cancer (1990). IARC Monographs on the Evaluation of the Carcinogenic Risk of Chemicals to Man. Volume 50. IARC, Lyon, France. pp 307-332.

Johansson SL (1981). Carcinogenicity of analgesics: long-term treatment of Sprague-Dawley rats with phenacetin, phenazone, caffeine and paracetamol (acetaminophen). Int J Cancer 27:521-529.

Maruyama H et al., 1990. Carcinogenesis 11(6):895-901.

National Toxicology Program (1993). Toxicology and Carcinogenesis Studies of Acetaminophen (CAS No. 103-90-2) in F344/N Rats and B6C3F1 Mice (Feed Studies). Technical Report Series No. 394. NIH Publication No. 93-2849. US Department of Health and Human Services, Public Health Service, National Institutes of Health.

Tsuruzaki T, Yamamoto M, Watanabe G (1982). Maternal consumption of antipyretic analgesics produces chromosome anomalies in F₁ rat embryos. Teratology 26:42A.

Tsuda H, Sakata T, Masui T Imaida K, Ito N (1984). Modifying effects of butylated hydroxyanisole, ethoxygquin and acetaminophen on induction of neoplastic lesions in rat liver and kidney initiated by N-ethyl-N-hydroxyethylnitrosamine. Carcinogenesis 5:525-531.

CARCINOGENICITY DATA SUMMARY: BENZYL ACETATE

Benzyl acetate (acetic acid phenylmethyl ester; CAS No. 140-11-4) occurs naturally in some flowers, fruits, and essential oils. It is used as a fragrance in soaps, perfumes and cosmetics, as a synthetic flavoring agent in food (e.g., gum, candy, gelatin, ice cream, beverages, baked goods), as a solvent for cellulose acetate and nitrate, resins, oils, lacquers, polishes and printing inks, and in varnish removers. Benzyl acetate was reviewed by IARC in 1986. IARC concluded that there was no data available on the evidence of carcinogenicity in humans and that the evidence was limited in animals (group 3 carcinogen). The IARC review did not include the mouse studies of NTP (1993), the rat studies of NTP (1993) and Longnecker et al. (1990), or the short-term genotoxicity studies reported by NTP (1993). These results, in addition to the studies reviewed by IARC, are briefly described below.

Carcinogenicity Data available:

Epidemiological studies

No data on long-term effects of human exposure to benzyl acetate have been reported (IARC, 1986).

Animal bioassays

Mouse long-term gavage studies (103 weeks): Abdo et al., 1985; NTP, 1986. Early mortality was observed in all female groups, and was due to the occurrence of genital tract infections. A statistically significant dose-related increase in the incidence of hepatocellular adenomas was observed in both males (0/50; 5/49; 13/50, test for trend p < 0.001) and females (0/50/; 0/50; 6/50, test for trend p = 0.002) after adjusting for age. A statistically significant increase in the incidence of hepatocellular adenomas and carcinomas (combined) was observed in high-dose males (10/50; 18/49; 23/50) and high-dose females (1/50; 0/50; 10/50) after adjusting for age, as well as significant positive trends with increasing doses in both sexes. A statistically significant increase in the incidence of squamous-cell papillomas of the forestomach was observed in high-dose males (3/49; 3/48; 9/49) and high-dose females (0/50; 0/50; 4/48) after adjusting for age. The incidences of these tumors in the high-dose animals were higher than the historical corn oil gavage control rates in this laboratory. A significant positive trend for squamous-cell papillomas and carcinomas (combined) of the forestomach was also observed in males.

Rat long-term gavage studies (103 weeks): Abdo et al., 1985; NTP, 1986. A statistically significant increase in acinar-cell adenomas of the pancreas was observed in both low- and high-dose males, after adjusting for age (22/50; 27/50; 37/49). Significant positive trends in preputial gland cystadenocarcinomas (0/50; 0/50; 3/50), all adenocarcinomas (0/50; 1/50; 4/50) and adenocarcinomas and carcinomas (combined) (1/50; 1/50; 6/50) were observed in males, at p < 0.05. A nonsignificant increase in the incidence of clitoral gland tumors (adenomas and carcinomas combined) was observed (2/50; 0/50; 5/50) in females.

Mouse long-term feeding studies (103 weeks): NTP, 1993. No treatment-related increases in tumors were observed. NTP (1993) noted the contrast in these results with those of the gavage study in mice (NTP, 1986), and suggested that the difference in the dose levels used (highest dose: gavage, 1,000 mg/kg/day; feed, 360 mg/kg/day) might have played a role in the different study outcomes.

Rat long-term feeding studies (103 weeks): NTP, 1993. No treatment-related increases in tumors were observed. The highest dose administered was similar to that used in the earlier gavage study (feed - 510 and 575 mg/kg/day were received by high-dose male and female groups, respectively, as compared to gavage - 500 mg/kg/day).

Rat long-term feeding study (104 weeks, males only): Longnecker et al., 1990. A low, but statistically significant increase in the incidence of carcinoma in situ of the pancreas (p = 0.04) was observed in the high-dose group (3/25) vs. the control group (0/25). No increase in the incidence of pancreatic adenomas was observed (controls 10/50; 11/50 high-dose group). The authors concluded that benzyl acetate had no initiating activity, but might have had a weak promoting effect on the growth of spontaneous pre-neoplastic foci in the male rat pancreas. [The small size of the treatment groups (n = 25) and the histopathological examination of only pancreatic tissue is noted.]

Other relevant data

Benzyl acetate was negative in several short-term tests for mutagenicity and genotoxicity (e.g., Salmonella reverse mutation assay, Bacillus subtilis assay, sister chromatid exchanges and chromosomal aberrations in Chinese hamster ovary cells, unscheduled DNA synthesis in rat liver primary cell cultures following in vitro or in vivo administration) (IARC, 1986). Benzyl acetate was mutagenic in the mouse lymphoma assay in the presence of metabolic activation (IARC, 1986). IARC (1986) concluded that there was inadequate evidence of the genotoxicity of benzyl acetate. Additional short-term tests have also been negative (e.g., sister chromatid exchanges and chromosomal aberrations in mouse bone marrow cells, sex-linked recessive lethal germ cell mutations in D. melanogaster, micronuclei in mouse bone marrow and peripheral blood) (NTP, 1993).

Preliminary evaluation of carcinogenicity and exposure data:

There is a LOW level of carcinogenicity concern over benzyl acetate. In gavage studies (NTP, 1986) an increased incidence of acinar cell adenomas of the pancreas was observed in male rats, but well-conducted follow-up feeding studies by NTP (1993) did not confirm this finding. There was "some evidence of carcinogenicity in mice" since increased incidences of hepatocellular adenomas and squamous cell neoplasms of the forestomach were observed in males and females (NTP, 1986). Evaluating the gavage studies, IARC (1986) found this evidence suggestive and concluded that "there is limited evidence of carcinogenicity" in experimental animals. Feeding studies in rats by Longnecker et al. (1990) provide additional support for IARC’s conclusion. NTP more recently conducted long-term feeding studies in rats and mice and concluded that under the conditions present in the feeding studies, there was "no evidence of carcinogenic activity" (NTP, 1993). Failure to observe tumors in the same species/strains in the later NTP studies reduces the overall toxicological concern. The low level of concern is reinforced by the lack of mutagenic and genotoxic activity in the majority of short-term tests conducted to date.

There is a HIGH level of concern over the extent of exposure since there is widespread human exposure by ingestion, skin application, and inhalation through the wide use of benzyl acetate in foods, perfumes, and other consumer goods (NTP, 1986; 1993). NIOSH estimated that 161,626 U.S. workers were exposed to benzyl acetate in 1983 (NIOSH, 1994). U.S. annual production in 1990 was estimated to be 3,000,000 lbs.

References

Abdo KM, Huff JE, Haseman JK, Boorman GA, Eustis SL, Matthews HB, Burka LT, Prejean JD, Thompson RB (1985). Benzyl acetate carcinogenicity, metabolism, and disposition in Fischer 344 rats and B6C3F1 mice. Toxicology 37:159-170.

Longnecker DS, Roebuck BD, Curphey TJ, MacMillan DL (1990). Evaluation of promotion of pancreatic carcinogenesis in rats by benzyl acetate. Fd Chem Toxic 28:665-668.

National Institute for Occupational Safety and Health (NIOSH, 1994). National Occupational Exposure Survey (1981-83), Cincinnati, OH.

National Toxicology Program (NTP, 1986). NTP Technical report on the toxicology and carcinogenesis studies of benzyl acetate (CAS No. 140-11-4) in F344/N rats and B6C3F1 mice (Gavage studies). NTP TR-250, NIH Publication No. 86-2506.

National Toxicology Program (NTP, 1993). NTP Technical report on the toxicology and carcinogenesis studies of benzyl acetate (CAS No. 140-11-4) in F344/N rats and B6C3F1 mice (Feed Studies). NTP TR-431, NIH Publication No. 93-3162.

International Agency for Research on Cancer (IARC, 1986). IARC Monographs on the evaluation of the carcinogenic risk of chemicals to humans. Some naturally occurring and synthetic food components, furocoumarins and ultraviolet radiation. Volume 40. IARC, Lyon, pp. 109-122.

CARCINOGENICITY DATA SUMMARY: Butyl Benzyl Phthalate

Butyl benzyl phthalate (CAS number 85-68-7) is a synthetic substance used as a plasticizer for plastics (in particular, polyvinyl chloride). It is also used as a dispersant and carrier. Butyl benzyl phthalate was reviewed by IARC in 1982, and was tested by the National Toxicology Program in 1995. IARC found inadequate evidence of carcinogenicity in animals and insufficient evidence for evaluation in humans. The more recent NTP study found some evidence of carcinogenic activity of butyl benzyl phthalate in the male F344 rat and equivocal evidence of carcinogenic activity in the female rat These results, in addition to the studies reviewed by IARC, are briefly described below.

Carcinogenicity Data available:

Epidemiological studies

Although there are some occupational studies of irritation, neurotoxicity and reproductive effects, no data on possible carcinogenic effects of human exposure to butyl benzyl phthalate have been reported (NTP, 1995; IARC, 1982).

Animal bioassays

Rat long-term diet studies: NTP, 1995. Fischer 344/N rats were fed diets containing butyl benzyl phthalate for 103 weeks. Males received 0, 3,000, 6,000 or 12,000 ppm while females received 0, 6,000, 12,000 or 24,000 ppm. The incidence of pancreatic acinar cell adenoma or carcinoma was increased in the 12,000 ppm males only (3/50 in controls, 2/49 low-dose, 3/50 mid-dose, 11/50 high-dose). Focal hyperplasia of the pancreatic acinar cells was also increased in this group. Transitional cell papillomas were observed in the urinary bladders of two high-dose females, and one control female, but in no other groups. Transitional epithelial cell hyperplasia of the kidney and urinary bladder were also observed in high-dose females. NTP (1995) determined that these results showed some evidence of carcinogenicity in male rats, and equivocal evidence in female rats.

Rat long-term diet studies: NTP, 1982. Fischer 344/N rats were fed diets containing 0, 6,000 or 12,000 ppm butyl benzyl phthalate for 103 weeks. Severe early mortality occurred in both dosed groups of male rats, and this section of the study was abandoned without further examination. In the exposed females, an increased incidence of mononuclear cell leukemia was noted in the high-dose group only (7/49 in controls, 7/49 low-dose, 18/49 high-dose). This increase was statistically significant and also larger (at 37%) than the incidence of this tumor in historical controls, although this historical incidence is high and somewhat variable (females, mean 11%, range 8-15%; males, mean 17%, range 9-24%). NTP (1982) concluded from these data that butyl benzyl phthalate was "probably" carcinogenic to female rats, but was unable to reach a conclusion about its effects in male rats.

Mouse long-term diet studies: NTP, 1982. Male and female B6C3F₁ mice were fed diets containing 0, 6,000 or 12,000 ppm butyl benzyl phthalate for 103 weeks. No carcinogenic effects were observed.

Mouse intraperitoneal injection study: Theiss et al., 1977. In this study, which used the mouse lung adenoma "accelerated bioassay" protocol, no increases in lung adenomas were observed in male Strain A mice receiving 24 intraperitoneal doses of up to 800 mg/kg butyl benzyl phthalate.

Other relevant data

Butyl benzyl phthalate has been tested in various genetic toxicity assays, including the Salmonella reverse mutation assay, other assays in bacteria and Saccharomyces cerevisiae, and various mutation or cytogenetic tests in mammalian cells. In all the tests in vitro, the results were negative (IARC, 1982; NTP, 1995). A recessive lethal test in vivo in Drosophila melanogaster was negative, but weak induction of sister chromatid exchanges, and chromosome aberrations at a single time point only, were reported in vivo in mice (NTP, 1995).

A related compound, di(2-ethylhexyl)phthalate, is a rodent hepatocarcinogen and is listed as a carcinogen under Proposition 65. There is an ongoing debate over the extent to which observations of hepatocarcinogenicity in rodents by phthalates and other peroxisome-proliferation inducing agents are applicable to non-rodent species such as humans. Butyl benzyl phthalate appears to have only weak peroxisome proliferation inducing activity (NTP, 1995). It causes thymic and testicular atrophy in rodents.

Preliminary evaluation of carcinogenicity and exposure data:

There is a LOW level of carcinogenicity concern over butyl benzyl phthalate, based on the equivocal carcinogenic responses in the female rat and the suggestive evidence in the male rat observed in the recent NTP (1995) studies. The observations in the male rat involved tumors with variable background incidence, and results statistically above background were obtained only at the highest dose level. Mononuclear cell leukemia was noted in the high-dose male rats in an earlier NTP (1982) study. The sites of tumor appearance in the male rat were not concordant in the two NTP studies. Available studies in the mouse were nonpositive. There are no clear observations of mutagenicity, cytogenetic effects or cell transforming ability in short-term tests. IARC (1982) found inadequate evidence of carcinogenicity in animals.

There is a HIGH level of concern over the extent of exposure since butyl benzyl phthalate is manufactured in bulk and occurs ubiquitously as an ingredient in consumer products and as an environmental contaminant (IARC, 1982; NTP, 1995). Butyl benzyl phthalate has been commercially produced in the United States since 1946, and annual production was estimated at 80 million pounds per year in 1978. U.S. FDA has approved butyl benzyl phthalate as a plasticizer in food contact materials. As a result of this use, food product levels of butyl benzyl phthalate between 0.5 and 53 mg/kg have been reported. Occupational exposure studies indicated that 68,488 workers were potentially exposed to benzyl butyl phthalate in 1972-74, and 331,840 in 1981-1983. (Production and exposure statistics are quoted from NTP [1995], who cite a variety of primary sources.) Persistence in the environment appears to be moderate: Although subject to biodegradation, the rate of input appears to be sufficient to produce measurable levels in many surface water bodies and drinking water supplies (IARC, 1982; NTP, 1995). According to reports cited by NTP (1995), water samples from a range of US sources showed a mean level of 9 µg/l, and one study in New Orleans found 0.08 to 1.8 µg/l in drinking water. NTP (1995) estimates that all consumers are exposed to butyl benzyl phthalate to some extent.

References

International Agency for Research on Cancer (IARC, 1982). IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, Volume 29. IARC, Lyon. pp. 193-201, Butyl Benzyl Phthalate.

National Toxicology Program (1995). Toxicology and Carcinogenesis Studies of Butyl Benzyl Phthalate (CAS No. 85-68-7) in F344/N Rats (Feed Studies). Technical Report Series No. 458. NIH Publication No. 95-3374. US Department of Health and Human Services, Public Health Service, National Institutes of Health.

National Toxicology Program (1982). Carcinogenesis Bioassay of Butyl Benzyl Phthalate (CAS No. 85-68-7) in F344/N Rats and B6C3F₁ Mice (Feed Study). Technical Report Series No. 213. NIH Publication No. 82-1769. US Department of Health and Human Services, Public Health Service, National Institutes of Health.

CARCINOGENICITY DATA SUMMARY: DECABROMOBIPHENYL OXIDE

Decabromobiphenyl oxide (CAS No. 1163-19-5) is a widely used flame retardant for plastics (e.g., components in electrical and electronic equipment) and other materials (e.g., textiles) for which long-term flame retardant properties are desirable. This compound was identified as a result of a CCRIS (Chemical Carcinogenesis Research Information System) database search, and information suggesting a potential for high exposure concern. IARC reviewed this compound in 1990 and found that there was limited evidence of carcinogenicity in animals (group 3). The results of the studies reviewed, as well as from a new structure-activity analysis are briefly described below.

Carcinogenicity Data available:

Epidemiological studies

No data on long-term effects of human exposure to decabromobiphenyl oxide were identified by IARC (1990) or in a more recent literature search by OEHHA.

Animal bioassays

Long-term diet study in F344/N rats: NTP, 1986. Significantly increased incidences of neoplastic nodules of the liver were observed in male and female rats. However, the incidence of hepatocellular carcinomas was low in all groups and characterized by NTP as not compound-related. Since benign rather than malignant tumors were observed, NTP considered these results to indicate some, rather than clear, evidence of carcinogenicity.

Long-term diet study in B6C3F₁ mice: NTP, 1986. Increased incidences of hepatocellular adenomas/carcinomas, and thyroid follicular cell adenomas/carcinomas were observed in male mice. NTP considered this to be equivocal evidence of carcinogenicity due to the early loss of control animals and the lack of a statistically significant effect at the high dose. No evidence of carcinogenicity was reported in female mice. Increased incidences of several nonneoplastic lesions were observed, most notably thyroid gland follicular cell hyperplasia in male mice.

Long-term diet study in Sprague-Dawley rats: Kociba et al., 1975. No significant differences in the number of rats developing tumors (total number of tumors or specific type of tumors) were observed between control and treated animals.

Other relevant data

Decabromobiphenyl oxide was not found to be mutagenic in several strains of Salmonella (with or without S9), or mouse lymphoma assays. It also did not induce SCEs or chromosomal aberrations in CHO cells in vitro. (NTP, 1986) A computerized analysis of structure-activity relationships (Oncologic) based on rules generated by US EPA experts predicts decabromobiphenyl oxide to be of "moderate" concern.

Preliminary evaluation of carcinogenicity and exposure data:

There is a LOW level of carcinogenicity concern regarding decabromobiphenyl oxide. NTP concluded that there was "some evidence" of carcinogenicity in rats due to increases in the same tumor type in both males and females. Oncologic, a computer analysis of structure-activity relationships generated by US EPA experts, predicts that decabromobiphenyl oxide is of moderate concern. IARC (1990) concluded that there was limited evidence of carcinogenicity in animals.

There is a HIGH level of concern over the extent of exposure to decabromobiphenyl oxide. This is a widely used, high production volume flame retardant. US annual production is estimated to be up to 50 million pounds (TSCA, 1990) and TRI release data reports over 170,000 pounds were released in the U.S. in 1993. Human exposure occurs in the course of manufacture and use; the Brominated Flame Retardants Industry Panel estimates that "the greatest potential for occupational exposure or dispersive types of releases (to air or water) occurs at the site of polymer formulation, and not at the level of the persons using the formulation or finished article" (Spurlock, 1996). According to the Panel, decabromobiphenyl oxide is produced in only two locations within the U.S., neither of which is in California (Spurlock, 1996). The Panel reports that decabromobiphenyl oxide typically enters California in either formulated resin systems (e.g., thermoplastics, thermosets, or coatings/adhesives) or as finished articles; a lesser amount enters the state as the pure chemical (Spurlock, 1996). The 1994 TRI data for California reported releases of decabromobiphenyl oxide at four separate locations; 350 pounds were reported as released to the air and 250 pounds were reported as released to publicly operated treatment works (Spurlock, 1996). The Panel was not aware of any uses of decabromobiphenyl oxide in polymer formulations for making food contact articles or in components (pipes, valves, etc.) of drinking water systems, nor was the Panel aware of any uses in its commercial form by the general public (Spurlock, 1996).

References

International Agency for Research on Cancer (IARC, 1990). IARC Monographs on the evaluation of carcinogenic risks to humans. Some Flame Retardants and Textile Chemicals, and Exposures in the Textile Manufacturing Industry. Volume 48. IARC, Lyon.

Kociba RJ, Frauson LO, Humiston CG, Norris JM, Wade CE, Lisowe RW, Quast JF, Jersey GC and Jewett GL (1975). Results of a two-year dietary feeding study with decabromobiphenyl oxide (DBDPO) in rats. J Combust Toxicol, 2:267-285

National Toxicology Program (1986). Toxicology and Carcinogenesis Studies of Decabromobiphenyl Oxide (CAS No. 1163-19-5) in F344/N Rats and B6C3F1 Mice (Feed Studies). Technical Report Series No. 309. NIH Publication No. 86-2565. US Department of Health and Human Services, Public Health Service, National Institutes of Health.

Spurlock LA (1996). Letter dated December 4, 1996 from L.A. Spurlock, Vice President, CHEMSTAR, RE: Carcinogen Identification Committee Review of Decabromodiphenyl oxide (CAS RN 1163-19-5) to C. Oshita, Office of Environmental Health Hazard Assessment.

CARCINOGENICITY DATA SUMMARY: EUGENOL

Eugenol (2-methoxy-4-(2-propenyl)-phenol; CAS No. 97-53-0) occurs naturally and is widely distributed in plants as a component of essential oils (e.g., cloves, cinnamon, fennel, jasmine, basil, tobacco leaf phenol). It is widely used as a flavoring agent in foods and as a fragrance, an analgesic in dental materials and nonprescription drugs, an insect attractant and a chemical intermediate. The concern over the chemical arose because of the potential for high exposure. Eugenol was reviewed by IARC in 1985 and 1987. IARC concluded that there was no data available on the evidence of carcinogenicity in humans and that the evidence was limited in animals (group 3 carcinogen). The IARC review did not include the promotion study of Imaida et al. (1990), or the genotoxicity data of Allavena et al. (1992) and Howes et al. (1991). These results, in addition to the studies reviewed by IARC, are briefly described below.

Carcinogenicity Data available:

Epidemiological studies

IARC (1987) noted that no data on long-term effects of human exposure to eugenol have been reported; also, a more recent literature search by OEHHA did not identify epidemiological studies.

Animal bioassays

Mouse long-term feeding studies (103 weeks): NTP, 1983. A nonsignificant increase in hepatocellular adenomas was seen in males (4/50; 13/50; 10/49) and females (0/50; 4/49; 3/49). A nonsignificant increase in hepatocellular carcinomas was seen in males (10/50; 20/50; 9/49) and females (2/50; 3/49; 6/49). No dose-related trend in the incidence of combined hepatocellular adenomas and carcinomas was observed in males, although a statistically significant increase was observed in the low-dose group compared to controls (p = 0.004). A dose-related trend (p = 0.02) in the incidence of combined hepatocellular adenomas and carcinomas was observed in females, and a statistically significant increase was observed in the high-dose group compared to controls (p = 0.02). NTP (1983) concluded that the evidence of carcinogenicity in these studies was equivocal.

Rat long-term feeding studies (103 weeks): NTP, 1983. A positive trend in the incidence of (benign) endometrial stromal polyps was observed with increasing dose (p = 0.02) in females (6/40; 6/50; 16/50). No other treatment-related tumors were observed in males or females. NTP (1983) concluded, based on these results, that eugenol was not carcinogenic in F344 rats of either sex.

Mouse long-term feeding studies (12 months + 8 months additional observation): Miller et al., 1983. No treatment-related tumors were observed. IARC (1985) noted the short duration of the experiment.

Mouse long-term gavage studies (5 weeks + 13 months additional observation): Miller et al., 1983. No treatment-related tumors were observed. IARC (1985) noted the short treatment and the short duration of the experiment.

Mouse long-term topical application study (3x/week for 63 weeks): Van Duuren et al., 1966. No treatment-related tumors were observed. IARC (1985) noted the small number of animals per group (n = 20) and the short duration of the experiment.

Other relevant data

Eugenol was not mutagenic in E. coli, equivocal in the Bacillus subtilis DNA repair assay, negative for mutations and gene conversion in Saccharomyces cerevisiae, and tested both positive and negative in various Salmonella reverse mutation assays. Eugenol induced chromosomal aberrations and sister chromatid exchanges in Chinese hamster ovary cells in vitro. IARC (1985) concluded that the evidence for the genetic activity of eugenol in short-term tests was inadequate. More recent short-term test data contribute to the overall evidence that eugenol is unlikely to have significant carcinogenic activity (Allavena et al., 1992; Howes et al., 1990). However, eugenol is structurally similar to the animal liver carcinogen safrole. Eugenol is metabolized by rat liver epithelial cell cultures to 2’,3’-epoxyeugenol, which is mutagenic in the Salmonella reverse mutation assay and induces benign skin tumors in mice following topical application. In a study of the effect of treatment of eugenol during the promotional phase of tumor development in rats pretreated with 1,2-dimethylhydrazine and 1-methyl-1-nitrosourea, eugenol enhanced the development of forestomach hyperplasia and papilloma but decreased the incidence kidney nephroblastomas (although the results were not statistically significant) (Imaida et al., 1990).

Preliminary evaluation of carcinogenicity and exposure data:

There is a LOW level of carcinogenicity concern over eugenol since long-term feeding studies have reported equivocal results in mice, and no evidence of carcinogenicity in rats. Specifically, a dose-response relationship was not observed for the induction of tumors (liver adenomas and carcinomas) in male mice, and in females, the induction of tumors (liver adenomas and carcinomas) was only observed in the high-dose group. Consideration of other relevant information, including that published since the IARC review, does not add to this concern.

There is a HIGH level of concern over the extent of exposure since eugenol is a naturally occurring substance, with widespread distribution in plants and widespread use in foods (e.g., sweets, baked goods), alcoholic beverages, chewing gum, and mouthwashes (IARC, 1985). NIOSH (1994) estimated that 72,961 U.S. workers in 53 industries were exposed to eugenol in 1983. U.S. annual production in 1984 was estimated to be 360,000 lbs. Eugenol has been detected in U.S. municipal wastewater treatment effluent (IARC, 1985).

References

Allavena A, Martelli A, Robbiano L, Brambilla G (1992). Evaluation in a battery of in vivo assays of four in vitro genotoxins proved to be noncarcinogens in rodents. Teratogenesis, Carcinogenesis and Mutagenesis 12:31-41.

Howes AJ, Chan VS, Caldwell J (1990). Structure specificity of the genotoxicity of some naturally occurring alkenylbenzenes determined by the unscheduled DNA synthesis assay in rat hepatocytes. Fd Chem Toxicol 28:537-542.

Imaida K, Hirose M, Yamaguchi S, Takahashi S, Ito N (1990). Effects of naturally occurring antioxidants on combined 1,2-dimethylhydrazine- and 1-methyl-1-nitrosourea initiated carcinogenesis in F344 male rats. Cancer Letters 55:53-59.

International Agency for Research on Cancer (IARC, 1985). IARC Monographs on the evaluation of carcinogenic risks to humans. Volume 36, IARC, Lyon, pp. 75-97.

International Agency for Research on Cancer (IARC, 1987). IARC Monographs on the evaluation of carcinogenic risks to humans. Suppl 7, Overall evaluations of carcinogenicity: An updating of IARC Monographs volumes 1-42. IARC, Lyon, p.63.

Miller EC, Swanson AB, Phillips DH, Fletcher TL, Liem A, Miller JA (1983). Structure-activity studies of the carcinogenicities in the mouse and rat of some naturally occurring and synthetic alkenylbenzene derivatives related to safrole and estragole. Cancer Res 43:1124-1134.

National Institute for Occupational Safety and Health (NIOSH, 1994). National Occupational Exposure Survey (1981-83), Cincinnati, OH.

National Toxicology Program (NTP, 1983). NTP Technical Report on the Carcinogenesis Bioassay of Eugenol (CAS No. 97-53-0) in F344/N rats and B6C3F1 Mice (Feed Studies). TR-223, NTP-80-068, NIH Publication No. 84-1779.

Van Duuren BL, Sivak, A, Orris L, Langseth L (1966). The tumor-promoting agents of tobacco leaf and tobacco smoke condensate. J Natl Cancer Inst 37, 519-526.

CARCINOGENICITY DATA SUMMARY: ISOPHORONE

Isophorone (CAS No. 78-59-1) is used as a solvent for vinylic resins, printing inks, lacquers, adhesives, nitrocellulose resins, finishes, and a variety of fats, oils and gums. It is used in the formulation of pesticides and herbicides, and as a chemical intermediate. It occurs naturally in cranberries in trace amounts. Isophorone was reviewed by US EPA in 1992. US EPA concluded that there was no data available on the evidence of carcinogenicity in humans and that the evidence in animals was limited (group C, possible human carcinogen). Literature searches did not identify any critical studies published subsequent to the US EPA (1992) evaluation. The studies reviewed by US EPA are briefly described below.

Carcinogenicity Data available:

Epidemiological studies

US EPA (1992) found no data on long-term effects of human exposure to isophorone, and neither did OEHHA in a more recent literature search.

Animal bioassays

Rat long-term gavage studies: NTP, 1986; Bucher et al., 1986. A statistically significant increase in renal tubular cell adenomas and adenocarcinomas was observed in the high-dose males by life table analysis (0/50 controls; 3/50 low-dose group; 3/50 high-dose group). A statistically significant increase in carcinoma of the preputial gland was also seen in high-dose males (0/49; 0/46; 5/44). NTP concluded that the findings of renal tubular cell and preputial gland tumors provide some evidence of carcinogenicity in the male rat. The US EPA (1992) considered this as equivocal evidence of carcinogenicity, after concluding that the increased incidence of renal tumors in the male rat were the result of an interaction between isophorone and the male rat specific protein a -2m -globulin. No treatment-related tumors were observed in female rats.

Mouse long-term gavage studies: NTP, 1986; Bucher et al., 1986. A statistically significant increase in the incidence of liver adenomas and carcinomas combined (18/48 controls; 18/50 low-dose group; 29/50 high-dose group) and mesenchymal tumors of the integumentary system (6/48; 8/50; 14/50) was observed in high-dose males. A nonsignificant increase in the incidence of malignant lymphomas was observed in low-dose males (8/48; 18/50; 5/50). Survival was so low in both the treated and control groups that both the NTP and the US EPA consider the results in male mice to be equivocal (NTP, 1986; US EPA, 1992). No treatment-related tumors were observed in female mice.

Other relevant data

Isophorone tested positive in the mouse lymphoma assay and induced sister chromatid exchanges in cultured Chinese hamster ovary cells (CHO) in the absence of metabolic activation. Isophorone was negative in the Salmonella reverse mutation assay (+ metabolic activation) and did not induce chromosomal aberrations in cultured CHO cells, nor did it induce unscheduled DNA synthesis in primary cultures of rat hepatocytes.

Preliminary evaluation of carcinogenicity and exposure data:

There is a LOW level of carcinogenicity concern over isophorone. There are no data in humans. There are some suggestive findings of carcinogenicity in animals, primarily from small increases in the incidence of preputial gland tumors in the male rat in one study. The kidney tumors observed in male rats in this study may be associated with a -2m -globulin, and the US EPA concluded that they were of questionable relevance to humans.

There is a HIGH level of concern over the extent of exposure since isophorone is a widely used solvent and chemical intermediate (NTP, 1986). U.S. annual production was 6,891,540 lbs. in 1990. In 1991, 327 lbs. were reported to be released into the atmosphere in California. Isophorone has been detected in U.S. municipal water supplies, and in oysters and fish (ATSDR, 1989). In 1988, NIOSH estimated that 37,469 workers were exposed to isophorone. Inhalation and dermal contact are the most likely routes for occupational exposures, while drinking isophorone-contaminated water is the most probable route of exposure for the general population (ATSDR, 1989).

References

Agency for Toxic Substances and Disease Registry (ATSDR, 1989). Toxicological profile for isophorone.

Bucher JR, Huff J, Kluwe WM. (1986). Toxicology and carcinogenesis studies of isophorone in F344 rats and B6C3F1 mice. Toxicology 39:207-219.

National Toxicology Program (NTP, 1986). NTP Technical Report on the Toxicology and Carcinogenesis Studies of Isophorone (CAS No. 78-59-1) in F344/N rats and B6C3F1 mice (gavage studies). NTP TR 291, NIH Publication No. 86-2547.

US Environmental Protection Agency (US EPA, 1992). Integrated Risk Information System.

CARCINOGENICITY DATA SUMMARY: NAPHTHALENE

Naphthalene (CAS number 91-20-3) occurs naturally in crude oil, and is also manufactured from coal tar. It is also formed as a combustion product, particularly from combustion of fuel oil and gasoline. It is used in chemical manufacturing, as an insecticide and insect repellent, vermicide, and antiseptic; some of these uses result in its appearance in consumer products. It has been reported as a contaminant of tap water and fresh water fish. Naphthalene was tested by the National Toxicology Program in 1992. The NTP studies found some evidence for carcinogenicity via inhalation in female mice, but no evidence in male mice. These results are briefly described below.

Carcinogenicity Data available:

Epidemiological studies

An unexpectedly high incidence of laryngeal and other cancers was noted in two reports on workers exposed to naphthalene, and naphthalene exposure was found for some cases in a small case-control study (studies cited by NTP, 1992). It is not clear whether these studies have any relevance to possible human carcinogenic effects of naphthalene since there may have been substantial confounding effects from other carcinogens in the workplace and from cigarette smoking.

Animal bioassays

Mouse long-term inhalation studies: NTP, 1992. Mice of both sexes were exposed to 0, 10 or 30 ppm naphthalene vapor for 6 h daily, 5 days per week for 104 weeks. No increase in tumor incidence was observed in males. A significantly increased incidence of alveolar/bronchiolar adenomas, and a single alveolar/bronchiolar carcinoma, were observed in the high-dose females. On the basis of these findings the NTP concluded that there was some evidence of carcinogenic activity in females, and no evidence in males.

Studies in rats: Schmähl, 1955. Three small long-term (>1000 days) studies in BD I, II or III rats using subcutaneous or intraperitoneal injection with, or dietary incorporation of, naphthalene in oil did not result in any increase in tumors. The study is seriously limited: Small numbers of animals were used and the study was without controls.

Short term A/J mouse inhalation study: Adkins et al., 1986. Daily 6-h exposures of Strain A/J mice to 30 ppm naphthalene for 6 months caused a statistically significant increase in the number of adenomas per mouse lung.

Rabbit dermal study: Bogdat’eva and Bid, 1955. No carcinogenic activity was observed at levels which induced systemic toxicity.

Mouse bladder implantation study: Boyland et al., 1964. Carcinoma incidence was similar to that caused by implantation of inert materials.

Several early studies using various routes of exposure were non-positive: Bloch, 1922 (mice, skin painting); Kennaway, 1930 (mice, skin painting); Kennaway and Heiger, 1930 (mice, skin painting); Fitzhugh and Buschke, 1949 (rats, diet). However, a study in rats by Knake (1956) using subcutaneous injection found some sarcomas, as did a study by the same author using skin painting of mice with naphthalene dissolved in benzene. These studies are described in PHS 149 (DHHS, 1994 and earlier).

Other relevant data

Naphthalene has been found to be negative in the Salmonella reverse mutation assay by numerous investigators. Various studies of gene mutation potential in other systems in vivo and in vivo have also found negative results with naphthalene. NTP (1992) examined the genetic toxicity of naphthalene and found negative results in the Salmonella reverse mutation assay but significant increases in sister chromatid exchanges and chromosome aberrations in Chinese hamster ovary cells in vitro. Metabolism of naphthalene in various species is postulated to occur via an epoxide intermediate: the observed metabolites include naphthol, various diols and quinones and conjugates of these products. Some of the metabolites have been observed to react with cellular macromolecules and cause DNA damage in vitro. One metabolite, 1,4-naphthoquinone, was reported to induce skin tumors in a skin-painting assay (Takizawa, 1940).

Preliminary evaluation of carcinogenicity and exposure data:

There is a LOW level of carcinogenicity concern over naphthalene. No clear evidence of carcinogenicity has been observed in rats or mice. Some evidence for carcinogenicity was found in female mice, but no evidence in similarly treated male mice. Most of the other studies did not find significant carcinogenic activity, although it is hard to draw any definite conclusion from the early studies which were limited by number of animals, duration of treatment, survival and in some cases, lack of control groups.

There is a HIGH level of concern over the extent of exposure since naphthalene appears to be widely distributed in the environment. Although it does not appear to be very environmentally persistent, there are sufficient natural and artificial sources to result in its presence as a contaminant in many media, including drinking water with a range of reported concentrations from 1 ng/l to 1 µg/l. Some residues in freshwater fish have been noted, including a range of 0.1- 3.4 µg/kg in Boston. U.S. production of naphthalene in 1984 was 280 million pounds. [Environmental levels and production data are taken from NTP (1992), who cite a number of primary sources]. Occupational exposures are reported to be significant, affecting an estimated 112,696 workers in 1981-83, especially in the petroleum and coal products industries (NIOSH, 1990). It is also a component of various consumer products (NTP, 1992).

References

Adkins B Jr, Van Stee EW, Simmons JE, Eustis SL (1986). Oncogenic response of strain A/J mice to inhaled chemicals. J Toxicol Environ Health 17:311-322.

Bogdat’eva AG, Bid DY (1955). Effect of high molecular weight products of pyrolysis of petroleum on the animal organism. Gig Sanit 7:21.

Boyland E, Busby ER, Dukes CE, Grover PL, Manson D (1964). Further experiments on implantation of materials into the urinary bladder of mice. Br J Cancer 18:575-581.

National Toxicology Program (1992). Toxicology and Carcinogenesis Studies of Naphthalene (CAS No. 91-20-3) in B6C3F1 Mice (Inhalation Studies). Technical Report Series No. 410. NIH Publication No. 92-3141. US Department of Health and Human Services, Public Health Service, National Institutes of Health.

National Institute for Occupational Safety and Health (NIOSH, 1990). National Occupational Exposure Survey for 1981-1983, cited by NTP (1992).

US Department of Health, Education and Welfare (1994 and earlier). Public Health Service Publication No. 149 ("PHS 149"). Survey of compounds which have been tested for carcinogenicity. US Department of Health, Education and Welfare, National Institutes of Health; various dates. Bethesda, MD.

Schmähl, D (1955). Prüfung von Napthalin und anthracen auf cancerogene Wikiung an Ratten. Zeit Krebsforsch 60:697-710.

CARCINOGENICITY DATA SUMMARY: PROPYL GALLATE

Propyl gallate (CAS No. 121-79-9) is used as an antioxidant to stabilize cosmetics, food-packaging material, and foods containing fats. It is also found in hair grooming products, pressure-sensitive adhesives, lubricating oil additives, and transforming oils. This compound was selected for testing by NTP because of widespread human exposure through its use as a food additive and because the available carcinogenicity data was considered to be inadequate. Propyl gallate is regulated as Generally Recognized as Safe (GRAS) by the US FDA (see 21 CFR 184.1660 for use in human foods and 21 CFR 582.1660 for use in animal feed).

Carcinogenicity Data available:

Epidemiological studies

No data on long-term effects of human exposure to propyl gallate are available.

Animal bioassays

Long-term diet study in F344/N rats: NTP, 1982. Significantly increased incidences of preputial gland tumors, pancreatic islet-cell tumors, and adrenal gland pheochromocytomas were observed in low-dose (6000 ppm) male rats. Rare brain tumors were found in two low-dose (6000 ppm) female rats. NTP concluded that the compound "was not considered to be carcinogenic for F344/N rats, although there was evidence of an increased proportion of low-dose male rats with preputial gland tumors, islet-cell tumors of the pancreas, and pheochromocytomas of the adrenal glands; rare tumors of the brain occurred in two low dose females".

Long-term diet study in B6C3F₁ mice: NTP, 1982. Significantly increased incidences of malignant lymphoma were observed in male mice in the high-dose group (12000 ppm) as compared to concurrent controls, as well as a positive trend with increasing dose (p<0.014). However, the high-dose incidence was not statistically significant when compared to the historical rate. Liver adenomas in female mice occurred with a statistically significant positive trend, with the incidence in the high-dose group being significantly higher than that in controls. However, since the incidences of hepatocellular adenomas or carcinomas (combined) were similar in control and dosed groups, the increased incidence of hepatocellular adenomas in the high-dose group was not considered to be related to propyl gallate administration. NTP concluded that the compound "was not considered to be carcinogenic for B6C3F₁ mice of either sex, although the increased incidence of malignant lymphoma in male mice may have been related to dietary administration of propyl gallate".

Other relevant data

Propyl gallate was not found to be mutagenic in Salmonella strains TA98, 100, 1535 or 1537 (with or without metabolic activation).

Preliminary evaluation of carcinogenicity and exposure data: