Induction of tumours in rats by feeding nitrosatable amines together with sodium nitrite

Feed containing 0.2% allantoin or diphenhydramine (as the hydrochloride) or 0.1% chlorpheniramine (as the maleate), with or without 0.2% sodium nitrite, was given ad lib. to groups of 20 or 24 male and 20 or 24 female F344 rats for 106 wk. Groups of 24 male and 24 female F344 rats were given drinking-water that contained N,N-dimethyldodecylamine-N-oxide at a concentration of 0.1%, with or without 0.2% sodium nitrite, for 93 wk. Control rats were given untreated feed or drinking-water and nitrite-treated controls were given sodium nitrite at a concentration of 0.2% in feed or drinking-water. At the end of the treatment period the rats were given untreated feed and water and observed until death. There was little or no life-shortening effect in any treatment group. None of the four amines administered alone induced an increase in the incidence of any tumour in comparison with the untreated control groups. In the male rats given diphenhydramine, chlorpheniramine or N,N-dimethyldodecylamine-N-oxide concurrently with nitrite there was a significant increase in the incidence of liver neoplasms (hepatocellular carcinomas and neoplastic nodules). In the groups given untreated feed or drinking-water there were, respectively, five and three male rats that had liver tumours. In contrast the number of male rats with liver tumours was ten in the group given dimethyldodecylamine-N-oxide plus nitrite, 11 in that given diphenhydramine plus nitrite and 14 (eight with carcinomas) in the group given chlorpheniramine plus nitrite. These results suggest that the ingestion of dimethyldodecylamine-N-oxide, diphenhydramine hydrochloride or chlorpheniramine under conditions when they could be nitrosated with nitrite in the stomach might present an increased carcinogenic risk.     

Comparative toxicity of ethylene dichloride in F344/N, Sprague-Dawley and Osborne-Mendel rats

Studies were conducted to compare the toxicity of ethylene dichloride (EDC) in F344/N rats, Sprague-Dawley rats, and Osborne-Mendel rats. Ten rats/sex/group were exposed to EDC in drinking-water at 0, 500, 1000, 2000, 4000 and 8000 ppm for 13 wk. The highest concentration was limited by the maximum solubility of EDC in water (about 9000 ppm). In addition, F344/N rats (10/sex/group) were administered EDC in corn oil by gavage to compare toxicity resulting from bolus administration with that of continuous exposure in drinking-water. Gavage doses of EDC were within the range of total daily doses (in mg/kg body weight/day) resulting from exposure in drinking-water. EDC administered by gavage resulted in greater toxicity to F344/N rats than did administration of similar doses in drinking-water. All males receiving 240 and 480 mg/kg body weight and 9/10 females receiving 300 mg/kg body weight by gavage died before the end of the study. Necrosis of the cerebellum was observed in the brains of 3 males receiving 240 mg/kg body weight and 3 females receiving 300 mg/kg body weight. Hyperplasia and inflammation of the forestomach mucosa were observed in 8 male and 3 female rats that died or were killed in moribund condition. EDC caused minimal toxicity to F344/N, Sprague-Dawley and Osborne-Mendel rats at the drinking-water concentrations used in these studies; only female F344/N rats had EDC-related renal lesions. Based on mortality and EDC-related lesions, the no-effect levels for EDC administered by gavage to F344/N rats were 120 mg/kg body weight for males and 150 mg/kg body weight for females.     

Chronic Feeding Study of Pyrilamine in Fischer 344 Rats

The antihistamine, pyrilamine maleate, was fed for up to 2 yearsto groups of 57 Fischer 344 (F344) rats of each sex at dietarylevels of 0, 300,1500, or 3000 ppm (free base). Eight or nineof these rats per sex and dose group were killed at 65 weeksto analyze hematology and clinical chemistry in all groups andhistopathology of control and high-dose animals. Histopathologyalso was performed on all dead or moribund rats and on all thatsurvived for 2 years. Average daily exposures were 11 to 150mg/kg pyrilamine compared to human dosages up to 3 mg/kg. Pyrilaminetreatment did not reduce survival. Final body weights were reducedrelative to controls (mid-dose males, 93%, females, 82%: high-dosemales, 82%, females, 70%). The incidences of inflammation ofthe nasolacrimal duct (chronic in females; suppurative in males),liver cytoplasmic vacuolization (males), and the combinationof animals with either liver basophilic or clear cell foci (males)tended to significantly increase with dose. Adrenal pheochromocytomas,mammary gland fibroadenomas, and neoplasms of the clitoral gland,thyroid ccell, and pituitary gland all tended to decrease withincreasing dose in females. In males only preputial gland neoplasmsexhibited a similar negative trend. While two ovarian granulosathecacell benign tumors occurred in high-dose females, these werethought to be a random occurrence. There was no evidence forthe carcinogenicity of pyrilamine in F344 rats in the currentstudy.     

Carcinogenicity study of a commercial sodium oleate in Fischer rats

Sodium oleate was added to the drinking-water of groups of 50 male and 50 female F344 rats at levels of 2.5 and 5.0% for 108 wk. The mean liver weight in males given 5% oleate was lower than that of the males given 2.5% oleate or distilled water alone. The mean thymus weight of females given 5% oleate was higher than that of females given 2.5% oleate or distilled water. There were no statistically significant differences between treated and control rats in the results of the urine and serum analyses or haematological determinations or in the incidence of tumours, apart from pancreatic tumours. The latter, in the males, showed some increase over the concurrent controls but did not differ significantly from the reported spontaneous incidence in this strain. It was concluded that sodium oleate does not induce tumours when given orally to F344 rats.     

Toxicology and carcinogenesis studies of pentachlorophenol in rats.

Pentachlorophenol (PCP) has been used as an herbicide, algaecide, defoliant, wood preservative, germicide, fungicide, and molluscicide. A 28-day toxicity study of PCP in F344/N rats of both sexes was conducted to select dose levels for a carcinogenicity study. Groups of 10 male and 10 female rats were given 0, 200, 400, 800, 1600, or 3200 ppm PCP in feed for 28 days. The incidences of minimal to mild hepatocyte degeneration in males and females exposed to 400 ppm or greater and the incidences of centrilobular hepatocyte hypertrophy in the 3200-ppm groups were increased. For carcinogenicity studies, groups of 50 male and 50 female F344/N rats were fed diets containing 200, 400, or 600 PCP for 2 years. A stop-exposure group of 60 male and 60 female rats received 1000 ppm of PCP in feed for 52 weeks and control feed thereafter for the remainder of the 2-year studies; 10 male and 10 female rats were evaluated at 7 months. Survival of 600-ppm males was significantly greater than that of the controls; survival of all other exposed groups was similar to that of the control groups. Mean body weights of the 400- and 600-ppm groups were generally less than those of the controls throughout the studies. There was no evidence of carcinogenic activity of PCP in male or female rats fed diets containing 200, 400, or 600 ppm for 2 years. Stop-exposure study males and females regained a transitory body weight reduction by the end of the 2 year study, and males had better survival than the controls. At a 7-month interim evaluation, the incidences of centrilobular hypertrophy in stop-exposure males and females exceeded those in the controls. At 2 years, malignant mesothelioma originating from the tunica vaginalis was present in 9 1000-ppm males and 1 control male (p = 0.014). Nasal squamous cell carcinomas were present in five 1000-ppm males and 1 control male. This incidence was not significantly increased but exceeded the historical control range (0-4%). Based on the increased incidences of mesotheliomas and nasal tumors, there was some evidence of carcinogenic activity of PCP in male rats given a diet containing 1000 ppm for 1 year followed by control diet for 1 year. There was no evidence of PCP carcinogenic activity in stop-exposure female rats.     

Effects of a polybrominated biphenyl mixture in the rat and mouse. II. Lifetime study

This study was undertaken to characterize the long-term toxic and carcinogenic potential of a polybrominated biphenyl (PBB) mixture in rats and mice of both sexes. Fischer 344 rats and B6C3F1 mice were given 125 po doses of PBB over a 6-month period at 0 (control), 0.1, 0.3, 1.0, 3.0, and 10.0 mg/kg body weight/day (5 days/week) and observed for an additional 23 months for rats and 24 months for mice (lifetime observation). The treatments (0.3 mg/kg or higher dosages) shortened the survival time in male rats whereas no such effect was observed in treated females. There was also evidence of shortened survival time in mice treated with 10.0 mg/kg PBB. As observed by uv light, hepatic porphyrin markedly increased at the 6-month observation, then tended to decrease, primarily in mice, following cessation of exposure. Significantly higher incidences of atypical hepatocellular foci, neoplastic nodules, hepatocellular carcinomas, and cholangiocarcinomas were observed in exposed rats. The incidence of hepatocellular carcinoma was also increased in both male (95%) and female (88%) mice (highest dose level) compared with control male (48%) and female (0%) mice. The incidence of hepatic neoplasms appeared to be dose dependent in both species. Liver tumors were observed primarily in those groups of animals to which PBB was given in doses sufficient to induce readily observable hepatic toxicity. Under the conditions of this experiment, polybrominated biphenyl mixture (Firemaster FF-1) was carcinogenic for Fischer 344 rats and B6C3F1 mice of both sexes. Lesions included neoplastic nodules, hepatocellular carcinomas, and cholangiocarcinomas in rats and hepatocellular carcinomas in mice. Other manifestations of toxicity included porphyrogenic effects and hepatotoxicity. A significantly higher incidence of chronic progressive nephropathy was observed in male rats of the 1.0, 3.0, and 10.0 mg/kg dosage groups when compared with control males. Gastric ulcers and hyperplastic gastropathy of the glandular portion of the stomach were observed more frequently in male rats, primarily in the high dosage groups.     

Carcinogenicity study of tetramethylthiuram disulfide (thiram) in F344 rats

The carcinogenic potential of tetramethylthiuram disulfide (thiram) was examined in F344 rats. Groups of 50 male and 50 female rats were given thiram in their diet at concentrations of 0.1% and 0.05% for 104 weeks. Similar numbers of male and female rats received the basal diet throughout the experiment. All surviving rats were sacrificed at week 112. The rats given the chemical at 0.1% showed reduced body weight gain, especially in females, and liver dysfunction in biochemical examination of blood in males. Histopathologically, however, no significant lesions or tumor induction attributable to the treatment were observed in any tissue except for dose-dependent reduction of spontaneous leukemia in both sexes and slightly reduced incidences of pituitary and thyroid adenomas in females. Under the present experimental conditions, thiram was not carcinogenic in F344 rats.     

NTP toxicology and carcinogenesis studies of trans-cinnamaldehyde (CAS No. 14371-10-9) in F344/N rats and B6C3F1 mice (feed studies)

Cinnamaldehyde is used in foods, beverages, medical products, perfumes, cosmetics, soaps, detergents, creams, and lotions. Cinnamaldehyde has been used as a filtering agent and a rubber reinforcing agent and is used as a brightener in electroplating processes, as an animal repellent, as an insect attractant, and as an antifungal agent. trans-cinnamaldehyde was nominated for study by the Food and Drug Administration based on its widespread use as a flavor and fragrance ingredient and its structural similarity to cinnamyl anthranilate and 3,4,5-trimethoxy cinnamaldehyde, two known rodent carcinogens. Male and female F344/N rats and B6C3F1 mice were exposed to trans-cinnamaldehyde (at least 95% pure) in feed for 3 months or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, cultured Chinese hamster ovary cells, Drosophila melanogaster, and mouse peripheral blood erythrocytes. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female F344/N rats were fed diets containing 4,100, 8,200, 16,500, or 33,000 ppm microencapsulated trans-cinnamaldehyde (equivalent to average daily doses of approximately 275, 625, 1,300, or 4,000 mg trans-cinnamaldehyde/kg body weight to males and 300, 570, 1,090, or 3,100 mg/kg to females) for 3 months. Additional groups of 10 male and 10 female rats received untreated feed (untreated controls) or feed containing placebo microcapsules (vehicle controls). All rats survived to the end of the study. Mean body weights of all exposed groups of males and 16,500 and 33,000 ppm females were significantly less than those of the vehicle controls, and 33,000 ppm males lost weight during the study. Feed consumption by exposed groups of males and females was less than that by the vehicle controls throughout the study. Clinical chemistry results of these studies indicated that trans-cinnamaldehyde administration, at the doses selected, induced an increase in serum bile acid concentration that suggests a hepatic effect in both male and female rats. Gross lesions observed at necropsy included multifocal to diffuse white nodules of the forestomach mucosa in 8,200 ppm or greater males and females. Increased incidences of nonneoplastic lesions of the forestomach included squamous epithelial hyperplasia in 8,200 ppm or greater males and females and chronic active inflammation in 33,000 ppm males and 16,500 and 33,000 ppm females. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female B6C3F1 mice were fed diets containing 4,100, 8,200, 16,500, or 33,000 ppm microencapsulated trans-cinnamaldehyde (equivalent to average daily doses of approximately 650, 1,320, 2,550, and 5,475 mg/kg to males and 625, 1,380, 2,680, and 5,200 mg/kg to females) for 3 months. Additional groups of 10 male and 10 female mice received untreated feed (untreated controls) or feed containing placebo microcapsules (vehicle controls). One vehicle control male, one 4,100 ppm male, and one 33,000 ppm male died during the first week of the study due to inanition that resulted from difficulty with the feeder. Five 16,500 ppm and eight 33,000 ppm male mice died during weeks 2 and 3 due to unpalatability of the dosed feed. Mean body weights of all exposed groups of males and of females exposed to 8,200 ppm or greater were significantly less than those of the vehicle controls. Feed consumption by 16,500 and 33,000 ppm mice was less than that by the vehicle controls during weeks 1 and 2. The incidence of squamous epithelial hyperplasia of the forestomach mucosa in 33,000 ppm females was significantly increased, and olfactory epithelial degeneration of the nasal cavity occurred in 16,500 and 33,000 ppm males and females. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female F344/N rats were fed diets containing 1,000, 2,100, or 4,100 ppm microencapsulated trans-cinnamaldehyde for 2 years. Additional groups of 50 male and 50 female rats received untreated feed (untreated controls) or feed containing placebo microcapsules (vehicle controls). Dietary concentrations of 1,000, 2,100, or 4,100 ppm delivered average daily doses of approximately 50, 100, or 200 mg/kg to males and females. Survival of 4,100 ppm males was greater than that of the vehicle controls. Mean body weights of 4,100 ppm males and females were generally less than those of the vehicle controls throughout the study. Feed consumption by 2,100 and 4,100 ppm males and 4,100 ppm females was less than that by the vehicle controls at the beginning and end of the study. There were no neoplasms or nonneoplastic lesions that were attributed to exposure to trans-cinnamaldehyde. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female B6C3F1 mice were fed diets containing 1,000, 2,100, or 4,100 ppm microencapsulated trans-cinnamaldehyde for 2 years. Additional groups of 50 male and 50 female mice received untreated feed (untreated controls) or feed containing placebo microcapsules (vehicle controls). Dietary concentrations of 1,000, 2,100, or 4,100 ppm delivered average daily doses of approximately 125, 270, or 550 mg/kg to males and females. Survival of males in the 2,100 ppm group was less than that of the vehicle control group. Mean body weights of 2,100 and 4,100 ppm males and females were generally less than those of the vehicle controls throughout the study, and mean body weights of 1,000 ppm males were less after week 74. Feed consumption by exposed mice was similar to that by the vehicle controls. The incidences of olfactory epithelial pigmentation in 4,100 ppm males and in 2,100 and 4,100 females were significantly greater than those in vehicle controls. There were no neoplasms that were attributed to exposure to trans-cinnamaldehyde. GENETIC TOXICOLOGY: trans-cinnamaldehyde was mutagenic in S. typhimurium strain TA100 in the presence of induced mouse liver S9 activation enzymes only. All other strain and activation combinations, including the standard rat and hamster derived liver S9 fractions yielded negative results. trans-cinnamaldehyde induced sister chromatid exchanges in Chinese hamster ovary cells with and without induced rat liver S9 activation. No significant increase in the frequency of chromosomal aberrations occurred in Chinese hamster ovary cells cultured with trans-cinnamaldehyde, with or without induced rat liver S9. In tests for induction of germ cell genetic damage in male Drosophila melanogaster, trans-cinnamaldehyde induced a significant increase in the frequency of sex-linked recessive lethal mutations when administered by abdominal injection; however, no induction of reciprocal translocations occurred in germ cells of treated males. No increase in the frequency of micronucleated erythrocytes was observed in peripheral blood of male or female mice administered trans-cinnamaldehyde in dosed feed for 3 months. CONCLUSIONS: Under the conditions of this 2-year feed study, there was no evidence of carcinogenic activity of transcinnamaldehyde in male or female F344/N rats exposed to 1,000, 2,100, or 4,100 ppm. There was no evidence of carcinogenic activity of trans-cinnamaldehyde in male or female B6C3F1 mice exposed to 1,000, 2,100, or 4,100 ppm. Exposure to trans-cinnamaldehyde resulted in olfactory epithelial pigmentation in male and female mice.     

Toxicology and carcinogenesis study of styrene-acrylonitrile trimer in F344/N rats (perinatal and postnatal feed studies)

Styrene-acrylonitrile trimer (SAN Trimer) is a mixture of isomers formed by the condensation of two moles of acrylonitrile and one mole of styrene and has a molecular weight of 210. The mixture is composed of two structural forms: 4-cyano-1,2,3,4-tetrahydro-a-methyl-1-naphthaleneacetonitrile (THNA, CAS No. 57964-39-3) and 4-cyano-1,2,3,4-tetrahydro-1-naphthalenepropionitrile (THNP, CAS No. 57964-40-6). The THNA form consists of four stereoisomers. [Structure:see text]. The THNP form consists of two stereoisomers. [Structure:see text]. SAN Trimer is a by-product of the production of acrylonitrile styrene plastics and is created in specific manufacturing processes for polymers of acrylonitrile and styrene. In June 1998, due to community concerns about the toxicity of SAN Trimer, it was nominated to the NTP for carcinogenicity testing by a member of Congress. Male and female F344/N rats were exposed to SAN Trimer in feed in perinatal and postnatal studies for 7 weeks, 18 weeks, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium and Escherichia coli, and in rat reticulocytes, leukocytes, liver cells, and brain cells. In vivo comet and micronucleus assays were performed in the juvenile rats. 7-WEEK STUDY IN RATS: Groups of 10 male and 10 female rats were fed diets containing 0, 250, 500, 1,000, 2,000, or 4,000 ppm SAN Trimer (equivalent to average daily doses of approximately 50, 90, 175, 270, or 410 mg SAN Trimer/kg body weight to males and 45, 90, 185, 295, or 430 mg/kg to females) for 2 weeks postweaning; the dams of these rats were fed the same concentrations of SAN Trimer from gestation day 7 until the pups were weaned. One 4,000 ppm male rat died 3 days after weaning; all other rats that started the postweaning phase survived to the end of the study. Mean body weights of 1,000, 2,000, and 4,000 ppm males and 2,000 and 4,000 ppm females were significantly less than those of the controls; weaning mean body weights were reduced in 4,000 ppm males and females and in 2,000 ppm females. Feed consumption by 2,000 and 4,000 ppm males and females was less than that by the control groups. Thinness in 4,000 ppm male rats was the only clinical finding related to SAN Trimer exposure. Nonneoplastic lesions were observed in the brain, thymus, spleen, liver, kidney, and reproductive organs of males and females and were considered due to overt toxicity. 18-WEEK STUDY IN RATS: Groups of 10 male and 10 female rats were fed diets of 0, 100, 200, 400, 800, or 1,600 ppm SAN Trimer (equivalent to average daily doses of 10, 20, 40, 80, or 150 mg/kg to males and females) for 3 months postweaning; the dams of these rats were fed the same concentrations from gestation day 7 until the pups were weaned. All rats survived to the end of the study. Mean body weights of 1,600 ppm males and females exposed to 200 ppm or greater were significantly less than those of the controls. At termination, brown staining of the urogenital fur was observed in females exposed to 200 ppm or greater. The liver weights of all exposed groups of males and the spleen weights of 800 and 1,600 ppm males and 1,600 ppm females were significantly greater than those of the controls. There were no significant differences in sperm parameters of male rats or the estrous cyclicity of female rats administered 400, 800, or 1,600 ppm in the diet when compared to the control groups. No exposure-related histopathologic lesions were observed. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female core study rats were fed diets of 0, 400, 800, or 1,600 ppm SAN Trimer (equivalent to average daily doses of approximately 20, 40, or 75 mg/kg to males and 20, 40, or 85 mg/kg to females) for 2 years. Special study groups of 20 males and 20 females were fed the same exposure concentrations and were evaluated at 27, 52, and 78 weeks for hematology and clinical chemistry or at 26, 51, and 77 weeks for urinalysis. The dams of core and special study rats were fed the same concentrations from gestation day 7 until the pups were weaned. Mean body weights of 1,600 ppm males were less than 90% of the controls after week 1; mean body weights of 800 and 1,600 ppm females were less than 90% of the controls after weeks 41 and 13, respectively. Feed consumption by exposed groups of males and females was generally similar to that by the control groups. Brown staining of the urogenital fur was observed in all exposed groups, and the number of animals affected increased with increasing exposure concentration. Rare neoplasms were present in the central nervous system of male and female rats. In the original evaluation, the 800 and 1,600 ppm groups of male rats each had one astrocytoma and one granular cell tumor in the brain. Also in the brain, one 400 ppm female had a granular cell tumor and one control, one 400 ppm, and one 800 ppm female had a mixed cell glioma. In the spinal cord, one astrocytoma was noted in a 1,600 ppm male in the original evaluation. In the expanded review of the spinal cord, one granular cell tumor was found in a 400 ppm male and one meningioma was found in an 800 ppm female. There were statistically significant increases in the incidence of spinal nerve root degeneration in 1,600 ppm males and the incidences of sciatic nerve degeneration in 800 and 1,600 ppm females. More importantly, there were increases in the severities of both nerve lesions in males and in the severity of spinal nerve root degeneration in females. The incidences of bone marrow hyperplasia were significantly increased in 1,600 ppm males and females and 800 ppm females. Incidences of bone marrow granulomatous inflammation were increased in 1,600 ppm males and 800 and 1,600 ppm females, and the increase in the 800 ppm females was significant. Because this lesion is very rare and did not occur in control animals, it should be considered biologically significant. In the liver, the incidence of eosinophilic focus was significantly increased in 1,600 ppm males and the incidences of mixed cell focus were significantly increased in 400 and 1,600 ppm males. Incidences of mixed cell focus were increased in the liver of all exposed groups of females, and the increase was significant in the 1,600 ppm group. The incidence of transitional epithelial hyperplasia of the urinary bladder in 1,600 ppm females was significantly greater than that in the controls. There were significant decreases in the incidences of pituitary gland pars distalis adenoma in 1,600 ppm males and females, and the incidences in both sexes occurred with negative trends. The incidences of mammary gland fibroadenoma occurred in females with a negative trend, and the incidences in 800 and 1,600 ppm females were significantly less than that in the control group. The incidences of mononuclear cell leukemia in all exposed groups of males and females were significantly less than those in the controls. GENETIC TOXICOLOGY: SAN Trimer (Batch 3) was not mutagenic in Salmonella typhimurium strains TA98 or TA100 or in Escherichia coli strain WP2 uvrA/pKM101 in tests conducted with and without exogenous metabolic activation. In vivo, however, results of a comet assay indicated significantly increased levels of DNA damage in brain cells of male and female juvenile rats following administration of SAN Trimer (Batch 3) by oral gavage. Dose-related increases in DNA damage in liver cells of these rats were also observed, but the increases were smaller than those observed in brain cells and were judged to be equivocal in both males and females. Indications of DNA damage following exposure to SAN Trimer were also seen in leukocytes of male and female rats. Increases in male rats were significant, but in females, observed levels of DNA damage did not correlate with dose. Therefore, the results were judged to be positive in males and equivocal in females. In addition to the positive comet assay results, significant increases in the frequencies of micronucleated reticulocytes were observed in peripheral blood of male and female juvenile rats dosed with SAN Trimer. CONCLUSIONS: Under the conditions of this 2-year feed study preceded by perinatal exposure, there was no evidence of carcinogenic activity of SAN Trimer in male and female F344/N rats given feed containing 400, 800, or 1,600 ppm SAN Trimer. Exposure to SAN Trimer resulted in increased incidences and/or severities of peripheral nerve degeneration in male and female F344/N rats, increased incidences of nonneoplastic lesions of the bone marrow and liver in male and female F344/N rats, and of nonneoplastic urinary bladder lesions in female F344/N rats. The incidences of pituitary gland adenoma and mononuclear cell leukemia in male and female F344/N rats and mammary gland fibroadenoma in female F344/N rats were decreased.     

Toxicology and carcinogenesis studies of alpha-methylstyrene (Cas No. 98-83-9) in F344/N rats and B6C3F1 mice (inhalation studies)

alpha-Methylstyrene is used in the production of acrylonitrile-butadiene-styrene resins and copolymers, which improve the impact and heat-resistant properties of polymers, specialty grades of plastics, rubber, and protective coatings. alpha-Methylstyrene also moderates polymerization rates and improves product clarity in coatings and resins. Low molecular weight liquid polymers are used as plasticizers in paints, waxes, adhesives, and plastics. alpha-Methylstyrene was nominated by the U.S. Environmental Protection Agency for toxicologic evaluation and genotoxicity studies based on its high production volume and limited information available on its toxicity. Male and female F344/N rats and B6C3F1 mice were exposed to alpha-methylstyrene (99.5% pure) by inhalation for 3 months or 2 years. Inhalation studies were conducted because the primary route of human exposure is via inhalation. Genetic toxicology studies were conducted in Salmonella typhimurium, cultured Chinese hamster ovary cells, and mouse peripheral blood erythrocytes. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats were exposed by whole-body inhalation to alpha-methylstyrene at concentrations of 0, 75, 150, 300, 600, or 1,000 ppm for 6 hours per day, 5 days per week for 14 weeks. Additional clinical pathology groups of 10 male and 10 female rats were exposed to the same concentrations for 23 days. All rats survived to the end of the study, and mean body weights of all exposed groups were similar to those of the chamber controls. Kidney weights were significantly increased in 1,000 ppm males and 600 and 1,000 ppm females. Statistically significant increases in liver weights occurred in 150 ppm or greater males and 600 and 1,000 ppm females. The incidences of renal hyaline droplet accumulation were similar between exposed groups and chamber control groups, but the severity of hyaline droplet accumulation in 600 and 1,000 ppm males was greater than in chamber controls. Consistent with the hyaline droplet accumulation, an exposure-related increase in alpha2μ-globulin was detected in the kidneys of males exposed to alpha-methylstyrene. Morphologic changes were not detected in the liver. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice were exposed by whole-body inhalation to alpha-methylstyrene at concentrations of 0, 75, 150, 300, 600, or 1,000 ppm for 6 hours per day, 5 days per week for 14 weeks. Two female mice in the 1,000 ppm group died before exposure on day 3. Final mean body weights of 600 and 1,000 ppm males and 75, 300, and 1,000 ppm females were significantly less than those of the chamber controls; final mean body weight gains of mice exposed to 300 ppm or greater were also significantly less. Moderate to severe sedation (males only) and ataxia were observed in 1,000 ppm mice. The absolute liver weights of 600 and 1,000 ppm females and the relative liver weights of 300, 600, and 1,000 ppm males and females were significantly increased. The estrous cycle lengths of 600 and 1,000 ppm female mice were significantly longer than that of the chamber controls. Minimal to mild centrilobular hypertrophy was present in the livers of male and female mice exposed to 600 or 1,000 ppm alpha-methylstyrene. The incidences of exposure-related nasal lesions, including atrophy and hyperplasia of Bowman's glands and atrophy and metaplasia of the olfactory epithelium, were significantly increased in all exposed groups of males and females. The incidences of hyaline degeneration, characterized by the accumulation of eosinophilic globules in the cytoplasm of the respiratory epithelium, were significantly increased in females exposed to 150 ppm or greater. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were exposed by whole body inhalation to alpha-methylstyrene at concentrations of 0, 100, 300, or 1,000 ppm for 6 hours per day, 5 days per week, except holidays, for 105 weeks. Survival rates of exposed male and female rats were similar to those of the chamber controls. The mean body weights of 1,000 ppm males and females were less than those of the chamber control groups during year 2 of the study. Two 1,000 ppm males and one 300 ppm male had renal tubule carcinomas, and one 300 ppm male had a renal tubule adenoma. Because of the neoplasms observed in 300 and 1,000 ppm males at the end of the 2-year study and the finding of alpha2μ-globulin accumulation in the kidneys at 3 months, which is often associated with kidney neoplasms, additional step sections of kidney were prepared; additional males with focal hyperplasia or adenoma were identified. The incidences of renal tubule adenoma and carcinoma (combined) in the 1,000 ppm males were significantly greater than those in the chamber controls when the single and step sections were combined. The incidence of mineralization of the renal papilla was significantly increased in 1,000 ppm males. The incidence of mononuclear cell leukemia in 1,000 ppm males was significantly increased compared to the chamber controls. In the nose, the incidences of basal cell hyperplasia were significantly increased in all exposed groups of males and females, and the incidences of degeneration of the olfactory epithelium were increased in 1,000 ppm males and females and 300 ppm females. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were exposed by whole body inhalation to alpha-methylstyrene at concentrations of 0, 100, 300, or 600 ppm for 6 hours per day, 5 days per week, except holidays, for 105 weeks. Survival of all exposed male and female mice was similar to that of the chamber control groups. Mean body weights of 600 ppm males were less than those of the chamber control group throughout the study, and those of 600 ppm females were less after week 13. The mean body weights of 300 ppm males and females were less than those of the chamber controls during much of the study, but these groups recovered by the end of the study. The incidences of hepatocellular adenoma or carcinoma (combined) were significantly increased in the 100 and 600 ppm males and in all exposed groups of females. The incidences of hepatocellular adenoma were significantly increased in all exposed groups of females, and the incidences in all exposed groups of males and females exceeded the historical range for chamber controls. The incidences of hepatocellular carcinoma and eosinophilic foci of the liver were significantly increased in 600 ppm females. The incidences of olfactory epithelial metaplasia and hyperplasia of the glands overlying the olfactory epithelium were significantly increased in all exposed groups of males and females. In addition, atrophy of the olfactory epithelium was significantly increased in 300 and 600 ppm males. The incidence and severity of nephropathy were increased in 600 ppm females compared to chamber controls. Epithelial hyperplasia of the forestomach also was present in male mice. GENETIC TOXICOLOGY: alpha-Methylstyrene was not mutagenic in four strains of Salmonella typhimurium, with or without rat or hamster liver metabolic activation enzymes (S9). alpha-Methylstyrene did not induce chromosomal aberrations in cultured Chinese hamster ovary cells, with or without S9 activation, but did significantly increase the frequency of sister chromatid exchanges in cultures exposed in the presence of S9. In vivo, no significant increases in the frequencies of micronucleated erythrocytes were seen in blood samples of male mice obtained at the conclusion of the 3-month study. However, in female mice from the 3-month study, a significant increase in micronucleated erythrocytes was observed in the 1,000 ppm group. CONCLUSIONS: Under the conditions of this 2-year inhalation study, there was some evidence of carcinogenic activity of alpha-methylstyrene in male F344/N rats based on increased incidences of renal tubule adenomas and carcinomas (combined). The increased incidence of mononuclear cell leukemia in 1,000 ppm male F344/N rats may have been related to alpha-methylstyrene exposure. There was no evidence of carcinogenic activity of alpha-methylstyrene in female F344/N rats exposed to 100, 300, or 1,000 ppm. There was equivocal evidence of carcinogenic activity of alpha-methylstyrene in male B6C3F1 mice based on marginally increased incidences of hepatocellular adenoma or carcinoma (combined). There was clear evidence of carcinogenic activity of alpha-methylstyrene in female B6C3F1 mice based on increased incidences of hepatocellular adenomas and carcinomas. Exposure of rats to alpha-methylstyrene resulted in kidney toxicity, which in males exhibited some features of alpha2μ-globulin nephropathy. Exposure to alpha-methylstyrene resulted in nonneoplastic lesions of the nose in male and female rats and mice and of the liver and kidney in female mice.     

Characterization of inhaled alpha-methylstyrene vapor toxicity for B6C3F1 mice and F344 rats.

alpha-Methylstyrene (AMS) is a chemical intermediate used in the synthesis of specialty polymers and copolymers. Inhalation studies of AMS were conducted because of the lack of toxicity data and the structural similarity of AMS to styrene, a toxic and potentially carcinogenic chemical. Male and female B6C3F1 mice were exposed to 0, 600, 800, or 1000 ppm AMS 6 h/day, 5 days/week, for 12 days. After 1 exposure, 21% (5/24) of female mice were found dead in the 1000-ppm group, 56% (10/18) in the 800-ppm group, and 6% (1/18) in the 600-ppm concentration group. After 12 exposures, relative liver weights were significantly increased and relative spleen weights were significantly decreased in both male and female mice at all concentrations. No microscopic treatment-related lesions were observed. A decrease in hepatic glutathione (GSH) was associated with AMS exposure for 1 and 5 days. Male and female F344 rats were exposed to 0, 600 or 1000 ppm AMS for 12 days. No mortality or sedation occurred in AMS-exposed rats. Relative liver weights were significantly increased in both males and females after 12 exposures to 600 or 1000 ppm. An increased hyaline droplet accumulation was detected in male rats in both concentration groups; no significant microscopic lesions were observed in other tissues examined. Exposure of male and female F344 rats and male NBR rats to 0, 125, 250 or 500 ppm AMS, 6 h/day for 9 days resulted in increased accumulation of hyaline droplets in the renal tubules of male F344 rats in the 250 and 500 ppm concentration groups. Although AMS and styrene are structurally very similar, AMS was considerably less toxic for mice and more toxic for male rats than styrene.     

Chronic toxicology and carcinogenesis studies of Telone II by gavage in Fischer-344 rats and B6C3F1 mice

Telone II (technical grade, 1,3-dichloropropene), a soil fumigant, was evaluated in chronic toxicology/carcinogenicity studies using Fischer-344 (F344) rats and B6C3F1 mice of both sexes. Doses administered were 0, 25, or 50 mg/kg to rats and 0, 50, or 100 mg/kg to mice. Telone II was given in corn oil by gavage 3 times per week for 104 wk. Ancillary studies were conducted to determine time-related effects, in which dose groups containing 5 male and 5 females rats were killed after receiving Telone II for 9, 16, 21, 24, or 27 mo. The primary organs affected were the forestomach (rats and mice), urinary bladder (mice), lung (mice), and liver (rats). Compound-related non-neoplastic lesions included basal-cell or epithelial hyperplasia of the forestomach (rats and mice), epithelial hyperplasia of the urinary bladder (mice), and hydronephrosis (mice). Neoplastic lesions associated with administration of Telone II included squamous-cell papillomas of the forestomach (male and female rats, female mice), squamous-cell carcinomas of the forestomach (Male rats, female mice), transitional-cell carcinomas of the urinary bladder (female mice), alveolar/bronchiolar adenomas (female mice), and neoplastic nodules of the liver (male rats). Although cis- and trans-1,3-dichloropropene are the principal components of Telone II, the presence of 1% epichlorohydrin, a direct-acting mutagen and carcinogen added as stabilizer, may have influenced the development of forestomach lesions. The results of the ancillary studies supported the findings of the carcinogenesis studies and demonstrated the time-dependent development of lesions in the forestomach (basal-cell hyperplasia and squamous-cell papilloma). Under the conditions of these gavage studies, Telone II was shown to be carcinogenic in male and female F344 rats and female B6C3F1 mice. Although the study in male B6C3F1 mice was considered inadequate because of the low survival resulting from suppurative inflammation of the heart (myocarditis) in the control group, there was some indication of Telone II-related increases of transitional-cell carcinomas of the urinary bladder, squamous-cell papillomas of the forestomach, and alveolar/bronchiolar adenomas and carcinomas of the lung.     

Carcinogenicity study of sodium hypochlorite in F344 rats

The carcinogenic potential of sodium hypochlorite was examined in F344 rats. Groups of 50 males or 50 females were given sodium hypochlorite in their drinking-water, at concentrations of 0.1 and 0.05% for males and 0.2 and 0.1% for females, for 104 wk. Similar numbers of male and female rats received distilled water without supplement throughout the experiment. All surviving rats were killed at wk 112 (after 8 wk on untreated tap-water). Rats of both sexes given the chemical showed a reduction in body-weight gain, but haematological and biochemical examination of the blood showed no changes due to treatment, and no significant lesions attributable to the treatment were detected in any tissue in the histopathological investigation. Although a variety of tumours developed in all groups, no dose-related change in either the incidence or latent period of tumours was observed for any organ or tissue in either sex. Under the experimental conditions described, therefore, sodium hypochlorite was not carcinogenic in F344 rats.     

Toxicology and carcinogenesis studies of divinylbenzene-HP (Cas No. 1321-74-0) in F344/N rats and B6C3F1 mice (inhalation studies)

Divinylbenzene-HP is used for producing vinyl polymers. Divinylbenzene-HP was nominated for study by the National Cancer Institute because of the potential for worker exposure and the structural similarity of divinylbenzene to styrene, a potential human carcinogen. Male and female F344/N rats and B6C3F1 mice were exposed to divinylbenzene-HP (80%) by inhalation for 2 weeks, 3 months, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, Escherichia coli, and mouse peripheral blood erythrocytes. 2-WEEK STUDY IN RATS: Groups of five male and five female rats were exposed by whole body inhalation to divinylbenzene-HP at target concentrations of 0, 25, 50, 100, 200, or 400 ppm 6 hours plus T90 (12 minutes) per day, 5 days per week for 16 days. All rats survived to the end of the study. Significant decreases in mean body weights occurred in both male and female rats in the 400 ppm groups. Relative kidney weights of 50 ppm or greater males and relative liver weights of 200 and 400 ppm males were significantly greater than those of the chamber controls. A clear serous nasal/eye discharge was observed in groups of males exposed to 100 ppm or greater and females exposed to 50 ppm or greater. Minimal or mild rhinitis occurred in 400 ppm rats of both sexes. 2-WEEK STUDY IN MICE: Groups of five male and five female mice were exposed by whole body inhalation to divinylbenzene-HP at target concentrations of 0, 25, 50, 100, 200, or 400 ppm for 6 hours plus T90 (12 minutes) per day, 5 days per week for 17 days. All 400 ppm males and females died on or before the second day of the study, and two male and two female 200 ppm mice died early. Mean body weights of 100 and 200 ppm males were significantly less than those of the chamber controls. Thymus weights of exposed groups of males were significantly less than those of the chamber controls, and relative liver weights of 100 and 200 ppm males were significantly increased. Kidney and liver weights of exposed groups of females were significantly greater than those of the chamber controls. Mice exposed to 200 and 400 ppm had liver lesions including degeneration, necrosis, hemorrhage or cytomegaly. Renal tubule necrosis and regeneration occurred at 200 ppm. Necrosis or metaplasia of nasal epithelium and glands occurred in the nose in all exposure groups. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats were exposed to divinylbenzene-HP at concentrations of 0, 25, 50, 100, 200, or 400 ppm for 6 hours plus T90 (12 minutes) per day, 5 days per week for 14 weeks. All rats survived to the end of the study. There were no biologically significant changes in body weight in either sex. Nasal/eye discharge was noted in 400 ppm males and 100 ppm females. Kidney and liver weights of exposed groups of males and of 400 ppm females were generally greater than those of the chamber controls. In addition, the relative weights of the heart and testis were significantly increased in 200 and 400 ppm males. Incidences of degeneration of the olfactory epithelium in 200 and 400 ppm rats and basal cell hyperplasia of the olfactory epithelium in rats exposed to 100 ppm or greater were significantly increased. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice were exposed to divinylbenzene-HP at concentrations of 0, 12.5, 25, 50, 100, or 200 ppm for 6 hours plus T90 (12 minutes) per day, 5 days per week for 14 weeks. All 200 ppm males and nine 200 ppm females died early. Final mean body weights were significantly lower in males and females exposed to 25, 50, or 100 ppm when compared with chamber controls. Lethargy or hypoactivity was observed in the higher exposure concentration groups. Exposure to divinylbenzene was associated with necrosis of the liver and kidney in 200 ppm males and females dying early. In all exposed groups of male and female mice, there was necrosis of nasal cavity lateral walls, olfactory epithelium, and glands with resultant atrophy of olfactory epithelium and glands in females. A lower number of animals had necrotic or degenerative changes of the upper respiratory tract. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were exposed to divinylbenzene-HP at concentrations of 0, 100, 200, or 400 ppm for 6 hours plus T90 (12 minutes) per day, 5 days per week for up to 105 weeks. Survival of 400 ppm females was significantly less than that of the chamber control group. Survival of all exposed groups of males was similar to that of the chamber control group. Mean body weights of 400 ppm males and females were significantly less than those of the controls during the second half of the study. Renal tubule carcinomas occurred in two of 50 males exposed to 400 ppm in the original kidney sections, an incidence that exceeded the historical control range. In 400 ppm males, the incidence of renal tubule hyperplasia was increased, and the incidence of nephropathy was significantly increased. Following combined analysis of single and step-section data, the incidences of renal tubule adenoma and adenoma or carcinoma (combined) were marginally higher in 200 and 400 ppm males, and the incidence of renal tubule hyperplasia was significantly increased in 400 ppm males. The incidences of malignant glial cell tumors (malignant astrocytoma and oligodendroglioma) in the brain were slightly increased in 100 and 200 ppm males, and the incidence in the 200 ppm group exceeded the historical range for chamber controls. There were increased incidences of degenerative and regenerative changes in the olfactory epithelium in the nose of all exposed groups of rats. The incidence of focal chronic inflammation in the lung of 400 ppm males was significantly greater than in the chamber control group. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were exposed to divinylbenzene-HP at concentrations of 0, 10, 30, or 100 ppm for 6 hours plus T90 (12 minutes) per day, 5 days per week for up to 105 weeks. Survival of all exposed groups of male and female mice was similar to that of the chamber controls. Mean body weights were lower relative to chamber controls in 100 ppm males and in 30 and 100 ppm females. The incidences of alveolar/bronchiolar adenoma and alveolar/bronchiolar adenoma or carcinoma (combined) in 100 ppm males were greater than chamber control incidences, but the incidences of adenoma or carcinoma (combined) were within the historical control range. The incidences of alveolar/bronchiolar adenoma and alveolar/bronchiolar adenoma or carcinoma (combined) in all exposed groups of females were generally greater than those of the chamber controls; the incidences were at the upper end or exceeded the historical control ranges. There was a greater incidence and severity of alveolar epithelial hyperplasia in 100 ppm females and a greater severity of this lesion in 30 ppm females, when compared to chamber controls. The incidences and/or severities of atypical bronchiole hyperplasia were significantly increased in all exposed groups of mice. Nonneoplastic nasal lesions occurred in most exposed mice. GENETIC TOXICOLOGY: Divinylbenzene-HP was not mutagenic in any of three independent gene mutation assays using Salmonella typhimurium strains TA97, TA98, TA100, TA1535, or TA1537 or Escherichia coli tester strain WP2 uvrA with or without induced hamster or rat liver enzymes. No increases in the frequencies of micronucleated normochromatic erythrocytes or alterations in the percentages of polychromatic erythrocytes were seen in peripheral blood of male or female B6C3F1 mice exposed to divinylbenzene-HP by inhalation for 3 months. CONCLUSIONS: Under the conditions of this 2-year inhalation study, there was equivocal evidence of carcinogenic activity of divinylbenzene-HP in male F344/N rats based upon the occurrence of carcinomas in the kidney and glial tumors in the brain. There was no evidence of carcinogenic activity in female F344/N rats exposed to 100, 200, or 400 ppm divinylbenzene-HP. There was no evidence of carcinogenic activity in male B6C3F1 mice exposed to 10, 30, or 100 ppm divinylbenzene-HP. There was equivocal evidence of carcinogenic activity of divinylbenzene-HP in female B6C3F1 mice based on the incidences of alveolar/bronchiolar adenoma or carcinoma (combined) in the lung. Exposure to divinylbenzene-HP caused nonneoplastic lesions of the nasal cavity in male and female rats and of the lung and nasal cavity in male and female mice.     

Toxicology and carcinogenesis studies of tetralin (CAS No. 119-64-2) in F344/N rats and B6C3F1 mice (inhalation studies)

Tetralin is used as an industrial solvent primarily for naphthalene, fats, resins, oils, and waxes; as a solvent and stabilizer for shoe polishes and floor waxes; as a solvent for pesticides, rubber, asphalt, and aromatic hydrocarbons (e.g., anthracene); as a dye solvent carrier in the textile industry; as a substitute for turpentine in lacquers, paints, and varnishes; in paint thinners and as a paint remover; in alkali-resistant lacquers for cleaning printing ink from rollers and type; as a constituent of motor fuels and lubricants; for the removal of naphthalene in gas distribution systems; and as an insecticide for clothes moths. Tetralin was nominated by the National Cancer Institute for carcinogenicity and disposition studies because of its structure, high production volume, and high potential for worker and consumer exposure. Male and female F344/N rats and B6C3F1 mice were exposed to tetralin (at least 97% pure) by inhalation for 2 weeks, 3 months, or 2 years; male NCI Black Reiter (NBR) rats were exposed to tetralin by inhalation for 2 weeks. Male NBR rats do not produce 2u-globulin; the NBR rats were included to study the relationship of 2u-globulin and renal lesion induction. Genetic toxicology studies were conducted in Salmonella typhimurium, Escherichia coli, and mouse peripheral blood erythrocytes. 2-WEEK STUDY IN RATS: Groups of five male (F344/N and NBR) and five female (F344/N) rats were exposed to tetralin at air concentrations of 0, 7.5, 15, 30, 60, or 120 ppm, 6 hours plus T90 (12 minutes) per day, 5 days per week for 12 exposures. All rats survived to the end of the studies. The final mean body weight of female rats exposed to 120 ppm and mean body weight gains of female rats exposed to 30 ppm or greater were significantly less than those of the chamber controls. Final mean body weights of exposed groups of male NBR rats and mean body weight gains of all exposed groups of male rats were significantly less than those of the chamber controls. Dark-stained urine was observed in all 120 ppm rats. Squinting, weeping, or matted fur around the eyes were noted in the majority of F344/N rats exposed to 120 ppm. The 2u-globulin concentrations in the kidney of male F344/N rats were significantly greater in all exposed groups than in the chamber control group. The absolute kidney weight of 60 ppm females and the relative kidney weights of male F344/N rats exposed to 30 ppm or greater and female rats exposed to 15 ppm or greater were significantly increased. The absolute liver weight of 120 ppm NBR male rats and the relative liver weights of male and female rats exposed to 60 or 120 ppm were significantly increased. In the nose, the incidences of mononuclear cell cellular infiltration were generally significantly increased in all exposed groups of rats, and incidences of olfactory epithelium degeneration and glandular hypertrophy occurred in all male F344/N rats exposed to 120 ppm. 2-WEEK STUDY IN MICE: Groups of five male and five female mice were exposed to tetralin at air concentrations of 0, 7.5, 15, 30, 60, or 120 ppm, 6 hours plus T90 (12 minutes) per day, 5 days per week for 13 exposures. All mice survived to the end of the study. Mean body weights of male and female mice were similar to those of the chamber controls. Dark-stained urine was observed in most of the exposed mice. The absolute and relative liver weights of 60 and 120 ppm males and 30 and 120 ppm females and the relative liver weights of 60 ppm females were significantly greater than those of the chamber controls. In the nose, the incidences of olfactory epithelium atrophy were significantly increased in 60 and 120 ppm males and females. Glandular dilatation occurred in all 120 ppm females, and glandular hyperplasia occurred in all 120 ppm males and females. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats were exposed to tetralin at air concentrations of 0, 7.5, 15, 30, 60, or 120 ppm, 6 hours plus T90 (12 minutes) per day, 5 days per week for 14 weeks. The same exposure concentrations were given to additional groups of 10 male and 10 female clinical pathology study rats for up to 6 weeks and five male renal toxicity rats for 2 weeks. All rats survived to the end of the study. During the first 4 weeks of exposure, dark-stained urine was observed in the catch pans of rats exposed to 30, 60, or 120 ppm. Tetralin induced a minimal decrease in the erythron in both sexes that resulted in a hematopoietic response. Tetralin increased urine aspartate aminotransferase and urine lactate dehydrogenase activities (males and females) and glucose/creatinine ratio (males), suggestive of renal injury. The absolute kidney weights of 60 and 120 ppm females and the relative kidney weights of males and females exposed to 15 ppm or greater were significantly greater than those of the chamber controls. Concentrations of 2u-globulin in the kidney of exposed male rats were generally greater than those of the chamber controls at all time points and greater at 6 and 14 weeks than at 2 weeks. There were significantly increased incidences of olfactory epithelium necrosis in rats exposed to 30 ppm or greater and of olfactory epithelium regeneration in 60 and 120 ppm rats. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice were exposed to tetralin at air concentrations of 0, 7.5, 15, 30, 60, or 120 ppm, 6 hours plus T90 (12 minutes) per day, 5 days per week for 14 weeks. All mice survived to the end of the study. Mean body weights of 120 ppm males were significantly less than those of the chamber controls. Dark-stained urine was observed in the catch pans of mice exposed to 30, 60, or 120 ppm during the first month of the study. Tetralin induced a minimal decrease in the erythron in both sexes that resulted in a hematopoietic response. The relative liver weights of 120 ppm males and 30 ppm or greater females were significantly greater than those of the chamber controls. Incidences of olfactory epithelium metaplasia in 60 and 120 ppm males and females, respiratory epithelium hyaline droplet accumulation in 120 ppm males and 60 and 120 ppm females, cytoplasmic eosinophilic granules within the transitional epithelium lining the urinary bladder in all exposed groups of males and females, and ovarian atrophy and uterine atrophy in 60 and 120 ppm females were significantly increased. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were exposed to tetralin at air concentrations of 0, 30, 60, or 120 ppm, 6 hours plus T90 (12 minutes) per day, 5 days per week for 105 weeks. Additional groups of five male and five female rats were exposed to the same concentrations for 12 months. Survival of all exposed groups of rats was similar to that of the chamber controls. Mean body weights of 120 ppm females were 6% less than those of the chamber controls after week 29. Dark-stained urine was observed in all exposed groups of rats. Creatinine-adjusted levels of all urinary metabolites increased with increasing exposure concentration in males and females. In the standard evaluation of the kidney, there were slightly increased incidences of cortical renal tubule adenoma in male rats. In the combined analysis of single and step sections, the incidence of cortical renal tubule adenoma was significantly increased in the 120 ppm group. In the combined analysis, there was also a significantly increased incidence of renal tubule hyperplasia in the 120 ppm group. In 120 ppm males in the standard evaluation, the severity of chronic nephropathy was increased and the incidence of transitional epithelial hyperplasia in the renal pelvis was significantly increased. Three hepatocellular adenomas occurred in 120 ppm females, and one hepatocellular carcinoma each was observed in the 60 and 120 ppm groups. The incidences of uterine stromal polyp and endometrium hyperplasia were significantly increased in 120 ppm females. Incidences of interstitial cell adenoma and germinal epithelium atrophy of the testis in 30 and 120 ppm males were significantly greater than those in the chamber controls. The incidences of olfactory epithelium degeneration, metaplasia, basal cell hyperplasia, suppurative inflammation, and mineralization (except 30 ppm females) in the nose were significantly increased in all exposed groups of rats. The incidences of glandular dilatation were significantly increased in 120 ppm males and all exposed groups of females. The incidences of respiratory epithelium chronic inflammation were significantly increased in males exposed to 60 or 120 ppm and all exposed groups of females. The incidences of lens cataract in 120 ppm females were significantly increased. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were exposed to tetralin at air concentrations of 0, 30, 60, or 120 ppm, 6 hours plus T90 (12 minutes) per day, 5 days per week for 105 weeks. Additional groups of five male and five female mice were exposed to the same concentrations for 12 months. Survival of 60 and 120 ppm female mice was significantly greater than that of the chamber controls. The mean body weights of all exposed groups of male and female mice were similar to those of the chamber controls by the end of the study. Dark-stained urine was observed in all exposed groups of male mice and in females exposed to 60 or 120 ppm. Creatinine-adjusted levels of all urinary metabolites increased with increasing exposure concentration in males and females. The incidence of hemangiosarcoma of the spleen was increased in 120 ppm females and exceeded the historical control range for inhalation studies. The incidences of olfactory epithelium atrophy, respiratory metaplasia, glandular hyperplasia, and suppurative inflammation in exposed groups of mice were significantly greater than those in the chamber controls. Transitional epithelium cytoplasmic eosinophilic granules were present in the urinary bladder of all exposed mice. (ABSTRACT TRUNCATED)     

Toxicology and carcinogenesis studies of dipropylene glycol in rats and mice

Dipropylene glycol (DPG) is a component of many commercial products such as antifreeze, air fresheners, cosmetic products, solvents, and plastics. Male and female F344/N rats and B6C3F1 mice were exposed to DPG in the drinking water for 2 weeks, 3 months, or 2 years. In the 2-week and 3-month studies, rats and mice were exposed to 0, 5000, 10,000, 20,000, 40,000, or 80,000 ppm DPG. There was no mortality in the 2-week studies. In the 3-month rat study, all animals survived to the end of the study. Liver weights of rats exposed to 10,000 ppm or greater and kidney weights of rats exposed to 40,000 and 80,000 ppm were greater than those of the controls. The incidences of liver and kidney lesions were significantly increased in males exposed to 20,000 ppm or greater and females exposed to 80,000 ppm. Focal olfactory epithelial degeneration was present in all rats exposed to 80,000 ppm. In males, the incidences of testicular atrophy, epididymal hypospermia, and preputial gland atrophy were significantly increased in the 80,000 ppm group. In the 3-month mouse study, three males and one female exposed to 80,000 ppm died. Liver weights were increased, as was the incidence of centrilobular hypertrophy in males exposed to 40,000 ppm and males and females exposed to 80,000 ppm. In the 2-year studies, exposure groups were 0, 2500 (rats only), 10,000, 20,000 (mice only) or 40,000 ppm DPG. Survival of male rats exposed to 40,000 ppm and mean body weights of males and females exposed to 40,000 ppm were significantly less than controls. In male rats, exposure to DPG resulted in increased incidences and severities of nephropathy and secondary lesions in the parathyroid and forestomach. Increased incidences of focal histiocytic and focal granulomatous inflammation of the liver were also observed. In male and female rats, there were increased incidences of bile duct hyperplasia and changes in the olfactory epithelium of the nose. In mice, survival of males and females was similar to controls. Mean body weights and water consumption of males exposed to 40,000 ppm were less than that of the controls. Treatment-related nonneoplastic lesions did not occur in mice. Treatment-related neoplastic lesions did not occur in rats or mice.     

Toxicity and Carcinogenicity Studies of Oxazepam in the Fischer 344 Rat

Oxazepam and related benzodiazepines are used in the treatmentof anxiety. Carcinogenicity studies of oxazepam were performedwith the F344 rat because of marked differences in tumor responsesobserved in NTP studies with B6C3F1 and Swiss-Webster mice comparedto the results of Sprague-Dawley rat studies submitted to theFDA by a manufacturer to support registration of the drug. Groupsof 50 male and 50 female F344/N rats were fed diets containing0, 625, 2500, or 5000 ppm oxazepam for up to 105 weeks. A stop-exposuregroup of 50 males and 50 females received 10,000 ppm oxazepamin diet for 26 weeks, after which animals received control diet.All 5000- and 10,000-ppm stop-exposure males died before theend of the study. Survival of 2500-ppm males and females waslower than that of controls. Body weight gains of 2500- and5000-ppm males and females were less than those of controls.Male rats exposed to 2500 ppm had an increased incidence ofrenal tubule adenoma and hyperplasia. In addition, the incidencesof renal tubule adenoma and hyperplasia were increased in the10,000-ppm stop-exposure group. The incidences of nephropathyin exposed females were greater than those in controls, andthe severity of nephropathy increased in exposed males. Epithelialhyperplasia and chronic inflammation of the nonglandular stomachwere increased in males given 2500 and 5000 ppm and the incidenceof ulcers of the nonglandular stomach in 2500-ppm males wasalso greater than that in controls. In males exposed to 5000ppm, mineralization of the glandular stomach and erosion ofthe duodenum were observed. In females exposed to 2500 ppm,the incidences of epithelial hyperplasia, chronic inflammation,and ulcers of the nonglandular stomach and the incidence oferosion in the glandular stomach were increased. The incidencesof centri-lobular hepatocyte hypertrophy in males and femalesgiven 2500 and 5000 ppm were greater than those in controls.In summary, there was equivocal evidence of carcinogenicityin males based on increased renal tubule adenomas in groupswhich also had significantly enhanced nephropathy. There wasno evidence of carcinogenicity of oxazepam in females givena diet containing 625, 2500, or 5000 ppm for 2 years or 10,000ppm for 6 months.     

Dimethylarsinic acid: results of chronic toxicity/oncogenicity studies in F344 rats and in B6C3F1 mice

Dimethylarsinic acid (DMA(V), cacodylic acid), a foliar herbicide, was administered in the diet to B6C3F1 mice (at dose levels of 0, 8, 40, 200, and 500 ppm) and to F344 rats (at dose levels of 0, 2, 10, 40, and 100 ppm) for 2 years, according to US EPA guidelines. In mice, there were no treatment-related tumors observed at any site. Treatment-related progressive glomerulonephropathy and nephrocalcinosis were observed in the kidneys in both sexes. The incidence of vacuolation of the epithelium in the urinary bladder was increased in both sexes, but was not associated with cytotoxicity, necrosis or hyperplasia. Based on non-neoplastic lesions found in the urinary bladder, the NOEL for mice was assessed to be 40 ppm in males and 8 ppm in females. In rats, treatment-related mortality occurred early in the study in five males in the 100 ppm group and in one male in the 40 ppm group. Papillomas and carcinomas with degeneration of the urothelium, necrosis and urothelial cell hyperplasia, were found in the urinary bladders of both sexes. In male rats, one papilloma was found in each of the 10 and 40 ppm groups; one urothelial cell carcinoma was found in the 2 ppm group and two in the 100 ppm group. Four papillomas and six urothelial cell carcinomas were found in the female 100 ppm group. Non-neoplastic treatment-related kidney lesions were confined to the 40 and 100 ppm levels and included necrosis, pyelonephritis, medullary nephrocalcinosis and tubular cystic dilation, hyperplasia of the epithelial lining of the papilla, and pelvic urothelial cell hyperplasia. All of these kidney changes appear to be related to an increase in the aging nephropathy of the rat. Dose-related increases in the height of the thyroid follicular epithelium were also noted in males and females, however, such changes reflect an adaptive response of the thyroid to decreased levels of circulating thyroid hormone, rather than an adverse effect. Based on the kidney and bladder lesions, the NOEL for non-neoplastic and neoplastic lesions was considered to be 10 ppm in males and females. Based on these studies, DMA(V) is carcinogenic only in rats and only at relatively high doses, with the urinary bladder as the target organ. Female rats appear to be more sensitive to the effects of DMA(V) than male rats. DMA(V) is not carcinogenic in mice.     

Lesions of the Urinary Tract Produced in Fischer 344 Rats and B6C3F1 Mice After Chronic Administration of 11-Aminoundecanoic Acid

Lesions of the Urinary Tract Produced in Fischer 344 Rats andB6C3F₁ Mice After Chronic Administration of 11-AminoundecanoicAcid. Dunnick, J.K., Huff, James E., Haseman, J.K. and Boorman,G.A. (1983). Fundam. Appl. Toxicol. 3:614–618. 11-Aminoundecanoicacid, the monomer of nylon 11, was toxic to the urinary tractof both male and female B6C3F₁ mice and Fischer 344 rats, whenadministered in the diet at 7500 or 15 000 ppm for 103–104weeks. Dose-related effects included a decrease in mean bodyweight gain and in survival for male rats and for mice of eachsex; increased incidence of hyperplasia of the transitionalepithelium of the kidney in rats of each sex; increased incidenceof calcification of the kidney in the female rats; increasedincidence of hyperplasia of the urinary bladder in male rats;and mineralization of the kidney in mice of each sex. Transitionalcell carcinomas of the urinary bladder of the male rat occurredwith increased frequency in the high-dose group (control, 0/48;low-dose, 0/48; high-dose, 7/49). Additional evidence for carcinogenicityin the male rat was seen in the liver, where an increased frequencyof neoplastic nodules was found in the treated animals (controls,1/50; low-dose, 9/50; high-dose, 8/50). Therefore, under theconditions of these studies, 11-aminoundecanoic acid was carcinogenicfor male Fischer 344 rats, inducing transitional cell carcinomasin the urinary bladder and neoplastic nodules in the liver.The test chemical was not demonstrated to be carcinogenic forfemale Fischer 344 rats or for B6C3F₁ mice of either sex.     

Lack of carcinogenicity and increased survival in F344 rats treated with 5-fluorouracil for two years.

The carcinogenicity of 5-fluorouracil (5-FU), a compound employed as an antineoplastic drug, was investigated in F344 rats of both sexes. 5-FU was administered to groups of 50 male and 50 female rats ad lib. for 104 weeks, added to drinking water at concentrations of 0 (control), 62 and 125 ppm, these dose levels being selected on the basis of results of a 13-week subchronic toxicity study. Body weight gains were slightly depressed in the 125 ppm group of both sexes. While not statistically significant in females, final survival rates at week 111 in the 125 ppm group of both sexes were higher than those in the control group, suggesting an ability of 5-FU to prolong the lifespan. Histopathologically, a decreased incidence of islet cell adenomas in males and increased incidences of pituitary gland adenomas and pheochromocytomas in females were observed in the 62 ppm group without dose dependence. There was no significant induction of any other neoplastic or non-neoplastic lesions. These results indicate a lack of carcinogenicity of 5-FU under the present experimental conditions using rats.