NTP technical report on the toxicology and carcinogenesis studies of Elmiron (Cas No. 37319-17-8) in F344/N rats and B6C3F1 mice (Gavage Studies)

[structure--see text] Elmiron, a white powder, is the sodium salt of pentosan polysulfate, a semisynthetic sulfated polyanion composed of beta-D-xylopyranose residues with biological properties similar to heparin. Elmiron is used in the United States for the relief of urinary bladder pain associated with interstitial cystitis. Because of its stimulating effect on fibrinolysis, Elmiron has been used clinically in the treatment and prevention of thrombotic disorders. The United States Food and Drug Administration nominated Elmiron for toxicology and carcinogenicity testing by the National Toxicology Program because of its orphan drug status. Male and female F344/N rats and B6C3F1 mice received Elmiron, which met product specifications provided by the manufacturer, in deionized water by gavage for 2 weeks, 3 months, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, rat and mouse bone marrow cells, and mouse peripheral blood erythrocytes. 2-WEEK STUDY IN RATS: Groups of five male and five female rats were administered 0, 33, 111, 333, 1,000, or 3,000 mg Elmiron/kg body weight in deionized water by gavage, 5 days per week, for 16 days. Elmiron administration had no effect on survival or body weight gain. Activated partial thromboplastin time was significantly increased in 3,000 mg/kg rats. Liver weights of 3,000 mg/kg rats were significantly greater than those of the vehicle controls. Hepatocellular cytoplasmic vacuolization occurred in all 3,000 mg/kg females. 2-WEEK STUDY IN MICE: Groups of five male and five female mice were administered Elmiron in deionized water by gavage at doses of 0, 33, 111, 333, 1,000, or 3,000 mg/kg, 5 days per week, for 16 days. All mice survived to the end of the study. Mean body weight gains of male mice administered 333 mg/kg or greater were significantly greater than that of the vehicle control group. Liver weights of 1,000 and 3,000 mg/kg males were significantly increased. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats were administered Elmiron in deionized water by gavage at doses of 0, 63, 125, 250, 500, or 1,000 mg/kg, 5 days per week, for 14 weeks. No deaths were attributed to administration of Elmiron. Mean body weights of 125 mg/kg males were less than those of vehicle controls and the mean body weights of all dosed groups of females were greater. Hematology results indicated that Elmiron, at the doses selected, induced a minimal erythron decrease and leukocyte and platelet count increases that may have been secondarily related to the inflammatory lesions observed in various tissues of rats. Liver and spleen weights of males administered 250 mg/kg or greater were significantly increased. Liver weights of all dosed groups of females, and kidney, lung, and spleen weights of 1,000 mg/kg females were significantly increased. Histiocytic cellular infiltration, chronic active inflammation, and ulcers of the rectum occurred in most 500 and 1,000 mg/kg rats. Administration of Elmiron was associated with the presence of vacuolated histiocytes in the mandibular and mesenteric lymph nodes, lung, kidney, and liver of male and female rats. Histochemical investigations of the vacuolated histiocytes indicated the presence of neutral and acidic mucins and lipid material within the vacuoles. Transmission electron microscopy identified these vacuoles as lysosomal structures that exhibited a variety of contents. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice were administered Elmiron in deionized water by gavage at doses of 0, 63, 125, 250, 500, or 1,000 mg/kg, 5 days per week, for 14 weeks. One 250 mg/kg female mouse was sacrificed moribund on day 84; all other mice survived to the end of the study. Mean body weights of dosed groups were similar to those of the vehicle control groups. Hematology results indicated that Elmiron, at the doses selected, induced a minimal erythron decrease and leukocyte and platelet count increases that may have been secondarily related to the inflammatory lesions observed in various tissues of mice. in various tissues of mice. Liver weights of 500 mg/kg males and 1,000 mg/kg males and females, and spleen weights of 1,000 mg/kg males were significantly increased. Histiocytic cellular infiltration and chronic active inflammation of the rectum occurred in most 1,000 mg/kg mice. Administration of Elmiron was associated with the presence of vacuolated histiocytes in the mandibular and mesenteric lymph nodes, liver, and spleen of males and females. Histochemical investigations of the vacuolated histiocytes indicated the presence of neutral and acidic mucins within the vacuoles. Transmission electron microscopy identified these vacuoles as lysosomal structures that exhibited a variety of contents. 2-YEAR STUDY IN RATS: Groups of 50 males and 50 females were administered Elmiron in deionized water by gavage at doses of 0, 14, 42, or 126 mg/kg to males and 0, 28, 84, or 252 mg/kg to females, 5 days per week, for 104 or 105 weeks. Survival of all dosed groups of rats was similar to that of the vehicle control groups. Mean body weights of all dosed groups were similar to those of the vehicle controls throughout the 2-year study. Microscopically, myxomatous changes were present in the rectum of 56% of 126 mg/kg males and 83% of 252 mg/kg females. The incidences of chronic active focal alveolar inflammation of the lung were increased in all dosed groups. The incidences of histiocytic cellular infiltration of the mesenteric lymph nodes were increased in 42 and 126 mg/kg males and in 84 and 252 mg/kg females, and lymphohistiocytic hyperplasia was present in the spleen of 126 mg/kg males and 252 mg/kg females. 2-YEAR STUDY IN MICE: Groups of 50 males and 50 females were administered Elmiron in deionized water by gavage at doses of 0, 56, 168, or 504 mg/kg, 5 days per week, for 104 or 105 weeks. Survival of all dosed groups of mice was similar to that of the vehicle control groups. Mean body weights of males were similar to those of vehicle controls. Mean body weights of 504 mg/kg females were progressively less than those of the vehicle controls during the second year of the study. Increased incidences of hemangiosarcomas of the liver and hepatocellular neoplasms were observed in male and female mice. The incidences of hemangiosarcomas in the 504 mg/kg groups exceeded the historical control ranges for males and females; both the trend and the incidence in the 504 mg/kg groups were significant for males. Hemangiosarcomas in males and females were attributed to Elmiron administration. The incidence of hepatocellular adenoma in 504 mg/kg females was significantly increased and exceeded the historical control range; the trends for hepatocellular adenoma and for hepatocellular adenoma or carcinoma (combined) were also significant in females and were attributed to Elmiron administration. There was also a marginal increase in the incidences of hepatocellular neoplasms in male mice, which may have been associated with Elmiron administration. Malignant lymphomas occurred with a positive trend in female mice; the incidence in the 504 mg/kg group was also significantly increased and matched the upper limit of the historical control range. These malignant lymphomas may have been associated with Elmiron administration. Nonneoplastic lesions related to the administration of Elmiron occurred in the liver, rectum, mesenteric lymph node, and spleen of 504 mg/kg mice and to a lesser extent in 168 mg/kg mice. These lesions were similar to those observed in the 3-month study. GENETIC TOXICOLOGY: Elmiron was not mutagenic in S. typhimurium strains TA97, TA98, TA100, or TA1535 with or without induced hamster or rat liver S9 enzymes. No increases in the frequency of micronucleated polychromatic erythrocytes were seen in bone marrow cells of rats or mice administered Elmiron by gavage three times at 24-hour intervals. No significant alterations in the frequency of micronucleated normochromatic erythrocytes were seen in peripheral blood samples from male or female mice administered Elmiron for 3 months by gavage. CONCLUSIONS: Under the conditions of these 2-year gavage studies, there was no evidence of carcinogenic activity of Elmiron in male F344/N rats administered 14, 42, or 126 mg/kg or in female F344/N rats administered 28, 84, or 252 mg/kg. There was some evidence of carcinogenic activity of Elmiron in male B6C3F1 mice based on increased incidences of liver hemangiosarcoma. The increased incidences of hepatocellular neoplasms in male mice may have been related to Elmiron administration. There was some evidence of carcinogenic activity of Elmiron in female B6C3F1 mice based on the increased incidences of liver hemangiosarcoma and hepatocellular neoplasms. The increased incidences of malignant lymphomas in female mice may have been related to Elmiron administration. Elmiron administration caused increased incidences of nonneoplastic lesions (presence of vacuolated histiocytes) of the rectum, lung, mesenteric lymph node, and spleen (males) in rats and of the liver, rectum, mesenteric lymph node, and spleen in mice.     

NTP technical report on the toxicology and carcinogenesis studies of beta-myrcene (CAS No. 123-35-3) in F344/N rats and B6C3F1 mice (Gavage studies)

Beta-myrcene, an acyclic unsubstituted monoterpene, and the essential oils which contain it are used as intermediates in the production of terpene alcohols (geraniol, nerol, and linalool), which, in turn, serve as intermediates in the production of aroma and flavor chemicals. Thus beta-myrcene is used widely in cosmetics, soaps, and detergents and as a flavoring additive in food and beverages. Beta-myrcene is also the major constituent of hop and bay oils, which are used in the manufacture of alcoholic beverages. Beta-myrcene was nominated for study by the National Institute of Environmental Health Sciences based on its high production volume, high level of human exposure, and structural relationship to d-limonene, which induced neoplasms in the kidneys of male rats in association with hyaline droplet nephropathy (NTP, 1990). Male and female F344/N rats and B6C3F1 mice were administered beta-myrcene (greater than 90% pure) by gavage for 3 months or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, Escherichia coli, and mouse peripheral blood erythrocytes. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats were administered 0, 0.25, 0.5, 1, 2, or 4 g beta-myrcene/kg body weight in corn oil by gavage, 5 days per week for 14 weeks. Additional groups of 10 male and 10 female special study rats were administered the same doses for 23 days. All core study rats in the 4 g/kg groups died during the first week of the study except one male that died on day 11. One to three rats in the 1 and 2 g/kg groups and one 0.5 g/kg male died by week 10 of the study. One 2 g/kg female died during the last week of the study. Except for lesion incidence data in groups administered 2 g/kg or less, data from rats that died early were excluded from the analysis and summary tables. Mean body weights were significantly decreased in male rats in the 0.5, 1, and 2 g/kg groups. Special study rats in the 4 g/kg groups died by the end of the first week. Dose-related clinical findings in animals that died early included thinness, lethargy, abnormal breathing, and ruffled fur. Right kidney and liver weights of dosed males and females were generally significantly greater than those of the vehicle controls. In special study rats evaluated on day 23, the incidences and severities of chronic progressive nephropathy (CPN) and renal tubule degeneration were increased in 2 g/kg males. At the end of the 3-month study, the incidences of renal tubule necrosis were significantly increased in all dosed groups of males and females. At 3 months, the incidences of olfactory epithelium degeneration in 2 g/kg males and females were significantly increased, and the severities were increased. The incidences of chronic inflammation in 1 and 2 g/kg males and females were significantly increased. All 2 g/kg males and females had splenic atrophy. In the mesenteric lymph node, significantly increased incidences of atrophy occurred in 2 g/kg males and 1 and 2 g/kg females. Acute inflammation of the forestomach occurred in four 2 g/kg females. The incidences of porphyrin pigmentation in the Harderian gland of males administered 0.5 g/kg or greater were significantly increased. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice were administered 0, 0.25, 0.5, 1, 2, or 4 g beta-myrcene/kg body weight in corn oil by gavage, 5 days per week for 14 weeks. All 4 g/kg male and female mice died during week 1; nine 2 g/kg males and eight 2 g/kg females died by week 4. The mean body weights of 1 g/kg males were significantly less than those of the vehicle controls. Clinical findings in animals that did not survive to the end of the study included thinness, lethargy, and abnormal breathing. The right kidney weights of 1 g/kg females and the liver weights of females administered 0.5 or 1 g/kg were significantly increased. No histopathology changes were observed in mice administered 1 g/kg or less. The 2 and 4 g/kg mice were not evaluated due to early deaths. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were administered 0, 0.25, 0.5, or 1 g beta-myrcene/kg body weight in corn oil by gavage, 5 days per week for 105 weeks. All 1 g/kg male rats died before the end of the study due to renal toxicity. Compared to vehicle controls, the mean body weights of 0.25 and 0.5 g/kg males were slightly greater, and mean body weights of 1 g/kg males and females were at least 8% less than those of vehicle controls after 11 weeks and 13 weeks, respectively. In the standard evaluation of the kidney, the incidence of renal tubule adenoma was significantly increased in 0.5 g/kg male rats, and the combined incidences of renal tubule adenoma or carcinoma were significantly increased in 0.25 and 0.5 g/kg males. In both the extended evaluation and the combined standard and extended evaluations, the incidences of renal tubule adenoma and the combined incidences of renal tubule adenoma or carcinoma were significantly increased in the 0.25 and 0.5 g/kg groups of males. The incidences of renal tubule nephrosis (nephrosis) were markedly increased in all dosed groups of both sexes except in 0.25 g/kg females. The incidences of papillary mineralization in 0.25 and 0.5 g/kg males were significantly increased. Significantly increased incidences of nephropathy occurred in dosed females, and the severity was increased in the 0.5 and 1 g/kg males and females. The incidences of hyperplasia of the transitional epithelium lining the pelvis and overlying the renal papilla were significantly increased in all dosed groups of males and females. In male rats, the incidences of focal suppurative inflammation were significantly increased in the 0.25 and 0.5 g/kg groups. A significantly increased incidence of chronic active inflammation of the nose occurred in 0.5 g/kg males. Also in 0.5 g/kg males, the incidence of chronic active inflammation of the forestomach was increased. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were administered 0, 0.25, 0.5, or 1 g beta-myrcene/kg body weight in corn oil by gavage, 5 days per week for 104 or 105 weeks. Survival of 1 g/kg mice was significantly less than that of the vehicle controls; the cause of the deaths was uncertain. Mean body weights of 1 g/kg males were at least 8% less than those of the vehicle controls between week 8 and week 56. Mean body weights of 0.5 g/kg females were at least 7% less than those of the vehicle controls after week 17, and those of 1 g/kg females were at least 8% less from week 11 to week 96. The incidences of liver neoplasms were significantly increased in 0.25 and/or 0.5 g/kg males and 0.25 g/kg females. Liver neoplasms included hepatocellular adenoma and hepatocellular carcinoma in males and females and hepatoblastoma in males. The incidences of hepatocellular hypertrophy were significantly increased in 0.5 g/kg males and females, as was the incidence of mixed cell focus in 0.5 g/kg females. The incidences of bone marrow atrophy and lymph node follicle atrophy in the spleen were significantly increased in 0.5 g/kg females. In the forestomach, there were significantly increased incidences of inflammation and epithelial hyperplasia in 0.5 g/kg females. GENETIC TOXICOLOGY: beta-myrcene did not show evidence of genotoxicity in assays conducted by the NTP. No mutagenicity was observed in any of several strains of Salmonella typhimurium or Escherichia coli in two independent Ames assays conducted with and without exogenous metabolic activation. In addition, no significant increase in frequency of micronucleated normochromatic erythrocytes, biomarkers of chromosomal damage, was observed in male or female mice administered beta-myrcene for 3 months by gavage. CONCLUSIONS: Under the conditions of these 2-year gavage studies, there was clear evidence of carcinogenic activity of beta-myrcene in male F344/N rats based on increased incidences of renal tubule neoplasms. There was equivocal evidence of carcinogenic activity of beta-myrcene in female F344/N rats based on increased incidences of renal tubule adenoma. There was clear evidence of carcinogenic activity of beta-myrcene in male B6C3F1 mice based on increased incidences of hepatocellular adenoma, hepatocellular carcinoma, and hepatoblastoma. There was equivocal evidence of carcinogenic activity of beta-myrcene in female B6C3F1 mice based on marginally increased incidences of hepatocellular adenoma and carcinoma. Administration of beta-myrcene induced nonneoplastic lesions in the kidney of male and female rats, nose of male rats, and liver of male and female mice. Synonyms: 2-Methyl-6-methylene-2,7-octadiene; 7-methyl-3-methylene-1,6-octadiene; myrcene.     

NTP toxicology and carcinogenesis studies of triethanolamine (Cas No. 102-71-6) in B6C3F1 mice (dermal studies)

[structure--see text] Triethanolamine is widely used in the manufacturing of household detergents and polishes, textiles, agricultural herbicides, mineral and vegetable oils, paraffin and waxes, pharmaceutical ointments, petroleum demulsifiers, synthetic resins, plasticizers, adhesives, and sealants. It is used as a chemical intermediate for anionic and nonionic surfactants, a vulcanization accelerator, a humectant and softening agent and in many other industrial applications. The National Cancer Institute nominated triethanolamine for study because of its widespread use in cosmetics and other consumer products, its high potential for worker exposure due to its many industrial uses, and its potential for conversion to the carcinogen N-nitrosodiethanolamine. Previous 3-month and 2-year studies of triethanolamine were conducted by the National Toxicology Program in F344/N rats and B6C3F1 mice; results from the 2-year rat study indicated equivocal evidence of carcinogenic activity based on a marginal increase in the incidence of renal tubule adenoma (NTP, 1991). Interpretation of the results from the 2-year study in mice was complicated by Helicobacter hepaticus infection, prompting a repeat 2-year study in mice. Male and female B6C3F1 mice received triethanolamine (greater than 99% pure) by dermal application for 2 years; a study of absorption, distribution, metabolism, and excretion was performed in additional mice. Genetic toxicology studies were conducted in Salmonella typhimurium, cultured Chinese hamster ovary cells, Drosophila melanogaster, and mouse peripheral blood erythrocytes. 2-YEAR STUDY: Groups of 50 male and 50 female mice received dermal applications of 0, 200, 630, or 2,000 mg/kg (males) and 0, 100, 300, or 1,000 mg/kg (females) triethanolamine in acetone, 5 days per week, for 104 (males) or 104 to 105 (females) weeks. Survival of all dosed groups was similar to that of the vehicle control groups. Body weights of 2,000 mg/kg males were less than those of the vehicle controls from weeks 17 to 37 and at the end of the study; body weights of dosed groups of females were similar to those of the vehicle controls throughout the study. Treatment-related clinical findings included skin irritation at the site of application, which increased with increasing dose and was more severe in males than in females. Gross lesions observed at necropsy included nodules and masses of the liver in dosed females. The incidences of hepatocellular adenoma and hepatocellular adenoma or carcinoma (combined) were significantly increased in all dosed groups of females. The incidence of hemangiosarcoma of the liver in 630 mg/kg males was marginally increased. The incidences of eosinophilic focus in all dosed groups of mice were greater than those in the vehicle controls. Gross lesions observed at necropsy included visible crusts at the site of application in all dosed groups of mice. Treatment-related epidermal hyperplasia, suppurative inflammation, ulceration, and dermal chronic inflammation occurred at the site of application in most dosed groups of mice, and the incidences and severities of these lesions generally increased with increasing dose. GENETIC TOXICOLOGY: Triethanolamine was not mutagenic in any of the in vitro or in vivo tests. It did not induce mutations in Salmonella typhimurium, and no induction of sister chromatid exchanges or chromosomal aberrations was noted in cultured Chinese hamster ovary cells exposed to triethanolamine. These in vitro tests were all conducted with and without S9 metabolic activation. Triethanolamine did not induce sex-linked recessive lethal mutations in germ cells of adult male Drosophila melanogaster exposed by feeding or injection. No increase in the frequency of micronucleated erythrocytes was observed in peripheral blood samples of male or female mice that received dermal applications of triethanolamine for 13 weeks. CONCLUSIONS: Under the conditions of this 2-year dermal study, there was equivocal evidence of carcinogenic activity of triethanolamine in male B6C3F1 mice based on the occurrence of liver hemangiosarcoma. There was some evidence of carcinogenic activity in female B6C3F1 mice based on increased incidences of hepatocellular adenoma. Exposure to triethanolamine by dermal application resulted in increased incidences of eosinophilic focus of the liver in males and females. Dosed mice developed treatment-related nonneoplastic lesions at the site of application.     

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 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.     

NTP toxicology and carcinogenesis studies of decalin (CAS No. 91-17-8) in F344/N rats and B6C3F(1) mice and a toxicology study of decalin in male NBR rats (inhalation studies)

Decalin is used as an industrial solvent for naphthalene, fats, resins, oils, and waxes. It is also used as a substitute for turpentine in lacquers, paints, and varnishes; as a solvent and stabilizer for shoe polishes and floor waxes; and as a constituent of motor fuels and lubricants. Other applications include use as a paint thinner and remover, a patent fuel in stoves, a high-density fuel in submarine-launched cruise missile systems, and in stain removal and cleaning machinery. Decalin was nominated for study by the National Cancer Institute because of its chemical structure, its potential for consumer exposure, and a lack of adequate testing of the chemical. Male and female F344/N rats and B6C3F(1) mice were exposed to decalin (greater than 99% pure) by inhalation for 2 weeks, 3 months, or 2 years. Groups of male NBR rats were exposed to decalin for 2 weeks. Male NBR rats do not produce alpha2u-globulin; the NBR rats were included to study the relationship of alpha2u-globulin and renal lesion induction. Genetic toxicology studies were conducted in Salmonella typhimurium and mouse peripheral blood erythrocytes. 2-WEEK STUDIES IN RATS: Groups of five male and five female F344/N rats and five male NBR rats were exposed to 0, 25, 50, 100, 200, or 400 ppm decalin vapor 6 hours per day, 5 days per week for 16 days. All rats survived to the end of the study, and mean body weights of exposed groups were similar to those of the chamber controls. Renal toxicity studies were performed in male F344/N and NBR rats. The numbers of labeled cells and the labeling indices in the left kidney of 200 and 400 ppm F344/N male rats were significantly greater than those in the chamber controls. The alpha2u-globulin/soluble protein ratios were significantly increased in all exposed groups of F344/N rats. Liver weights of male F344/N and NBR rats exposed to 100 ppm or greater were significantly increased, as were those of all exposed groups of females. Kidney weights of male F344/N rats exposed to 50 ppm or greater were significantly increased. Exposure-related hyaline droplet accumulation, degeneration and regeneration of renal cortical tubules, and granular casts occurred in the kidney of exposed F344/N male rats. 2-WEEK STUDIES IN MICE: Groups of five male and five female B6C3F(1) mice were exposed to 0, 25, 50, 100, 200, or 400 ppm decalin vapor 6 hours per day, 5 days per week for 17 days. All mice survived to the end of the study, and mean body weights of exposed groups were similar to those of the chamber control groups. Liver weights of 200 and 400 ppm males and females and 100 ppm females were significantly increased. 3-MONTH STUDY IN RATS: Groups of 25 male and 20 female F344/N rats were exposed to 0, 25, 50, 100, 200, or 400 ppm decalin vapor 6 hours per day, 5 days per week for 2 (five male renal toxicity rats), 6 (10 male and 10 female clinical pathology rats), or 14 (10 core study rats) weeks. All rats survived to the end of the study, and mean body weights of exposed groups were similar to those of the chamber control groups. Urinalysis results indicated that decalin exposure caused increases in urine glucose and protein concentrations and enzyme activities that were consistent with the renal lesions observed microscopically. Renal toxicity studies were performed on rats sacrificed at 2 and 6 weeks and at the end of the study. In kidney tissue examined for cell proliferation, the numbers of PCNA-labeled cells and labeling indices were generally significantly greater than those of the chamber controls in exposed groups of rats at all three time points. Concentrations of alpha2u-globulin in the kidney as well as the alpha2u-globulin/soluble protein ratios were significantly increased at week 2 in all exposed groups and in the 200 and 400 ppm groups at week 6 and at the end of the study. Absolute and/or relative kidney and liver weights of male rats exposed to 50 ppm or greater were increased. Incidences of renal tubule regeneration and granular casts in the medulla of the kidney in exposed male rats were increased, and the severities of hyaline droplets generally increased with increasing exposure concentration. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female B6C3F(1) mice were exposed to 0, 25, 50, 100, 200, or 400 ppm decalin vapor 6 hours per day, 5 days per week for 14 weeks. All mice survived to the end of the study, and mean body weights of exposed groups were similar to those of the chamber control groups. Liver weights of 200 and 400 ppm males and females were significantly increased. There was a significant exposure concentration-related decrease in the absolute spermatid head count and a significant decrease in absolute head count of the 400 ppm group compared to the chamber controls. Incidences of centrilobular cytomegaly of the liver were increased in exposed male mice. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female F344/N rats were exposed to 0, 25, 50 (male rats only), 100, or 400 ppm (female rats only) decalin vapor 6 hours per day, 5 days per week for 105 weeks. A group of 20 male rats was exposed to 400 ppm. Survival of exposed groups was similar to that of the chamber control groups. Mean body weights of 400 ppm males were slightly less than those of the chamber controls during the second year of the study. Incidences of renal tubule adenoma and adenoma or carcinoma (combined) and of benign or malignant pheochromocytoma (combined) of the adrenal medulla in 100 and 400 ppm males were significantly increased. There was a significant association between nephropathy severity and adrenal pheochromocytoma incidence. Nonneoplastic lesions related to decalin exposure occurred in the kidney of male rats. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female B6C3F(1) mice were exposed to 0, 25, 100, or 400 ppm decalin vapor 6 hours per day, 5 days per week for 105 weeks. Survival of exposed mice was similar to that of the chamber controls. Mean body weights of exposed groups were generally similar to those of the chamber control groups throughout the study. Increased incidences of hepatocellular neoplasms occurred in 25 and 400 ppm female mice, and the incidences of centrilobular hypertrophy, necrosis, syncytial alteration, and erythrophagocytosis of the liver in 400 ppm males were significantly increased. The incidences of uterine stromal polyp and stromal polyp or stromal sarcoma (combined) occurred with positive trends in female mice. PHARMACOKINETIC MODEL: The rate of metabolism of decalin was the same for males and females in rats and mice. Also in rats and mice, decalin metabolism was saturated at less than 400 ppm. Increased labeling indices in male rats were likely due to changes related to alpha2u-globulin. GENETIC TOXICOLOGY: Decalin was not mutagenic in S. typhimurium strains TA97, TA98, TA100, or TA1535, with or without induced hamster or rat liver S9 enzymes. A small but significant increase in the frequency of micronucleated normochromatic erythrocytes was noted in male mice exposed to decalin for 3 months; however, no induction of micronuclei was observed in female mice. CONCLUSIONS: Under the conditions of these studies, there was clear evidence of carcinogenic activity of decalin in male F344/N rats based on increased incidences of renal tubule neoplasms. The increased incidences of benign or malignant pheochromocytoma (combined) of the adrenal medulla in male rats were also considered to be exposure related. There was no evidence of carcinogenic activity of decalin in female F344/N rats exposed to 25, 100, or 400 ppm. There was no evidence of carcinogenic activity of decalin in male B6C3F(1) mice exposed to 25, 100, or 400 ppm. There was equivocal evidence of carcinogenic activity of decalin in female B6C3F(1) mice based on marginally increased incidences of hepatocellular and uterine neoplasms. Exposure of male rats to decalin resulted in nonneoplastic lesions of the kidney characteristic of alpha2u-globulin accumulation. Nonneoplastic lesions of the liver were observed in male mice exposed to decalin.     

Toxicology and carcinogenesis studies of diethylamine (CAS No. 109-89-7) in F344/N rats and B6C3F1 mice (inhalation studies)

Diethylamine is used mainly as a chemical intermediate to produce the corrosion inhibitor N,N-diethylethanolamine and a lesser amount is used to produce pesticides and insect repellants and in rubber processing. Diethylamine was nominated for study by the National Institute of Environmental Health Sciences based upon its high production volume and ubiquitous natural occurrence in trace amounts and because of the lack of chronic toxicity and carcinogenicity data on the chemical. Male and female F344/N rats and B6C3F1 mice were exposed to diethylamine (approximately 99.9% pure) by inhalation for 2 weeks, 3 months, or 2 years. Genetic toxicology studies were conducted in bacterial mutagenicity tester strains and mouse peripheral blood erythrocytes. 2-WEEK STUDY IN RATS: Groups of five male and five female rats were exposed to diethylamine vapor at concentrations of 0, 31, 62.5, 125, 250, or 500 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. The mean body weights of 250 and 500 ppm males and females and 125 ppm males were significantly less than those of the chamber controls. Clinical findings included lethargy, nasal/eye discharge, abnormal breathing, thinness, eye abnormalities, and discolored urine. The thymus weights of males exposed to 125 ppm or greater and females exposed to 500 ppm were significantly less than those of the chamber controls. Focal eye lesions were noted at necropsy in four males and three females exposed to 500 ppm and one male exposed to 250 ppm. Crusty noses were observed in most 500 ppm males and females and in two 250 ppm males. Suppurative inflammation, necrosis of the turbinates (except in one 125 ppm female), and squamous metaplasia of the respiratory epithelium of the nose were present in all rats exposed to 125 ppm or greater. Ulcer of the respiratory epithelium and atrophy of the olfactory epithelium occurred in all rats exposed to 250 or 500 ppm, and ulcer of the nasopharyngeal duct was present in all 500 ppm rats. Suppurative inflammation of the cornea was present in most rats exposed to 500 ppm. 2-WEEK STUDY IN MICE: Groups of five male and five female mice were exposed to diethylamine vapor at concentrations of 0, 31, 62.5, 125, 250, or 500 ppm, 6 hours plus T90 (12 minutes) per day, 5 days per week for 17 days. Two males and three females exposed to 500 ppm died during the first week of the study. The mean body weights of males and females exposed to 125 ppm or greater were significantly less than those of the chamber controls. Males and females exposed to 250 or 500 ppm lost weight during the study. Lethargy, abnormal breathing, and thinness were observed in most mice exposed to 250 or 500 ppm. Eye irritation and discharge, nasal discharge, and low fecal and urine output were noted in 500 ppm mice. Thymus weights of 250 and 500 ppm males and 125 ppm or greater females were significantly less than those of the chamber controls. Suppurative inflammation of the nose occurred in all males exposed to 250 or 500 ppm and all females exposed to 125 ppm or greater, and most males exposed to 125 ppm. Turbinate necrosis occurred in all exposed mice except one 31 ppm female. Squamous metaplasia of the respiratory epithelium and olfactory epithelial atrophy were seen in mice exposed to 125 ppm or greater. In the lung, the incidence of minimal chronic active inflammation of mainstem bronchi was significantly increased in 500 ppm males. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats were exposed to diethylamine vapor at concentrations of 0, 8, 16, 32, 62, or 125 ppm, 6 hours plus T90 (12 minutes) per day, 5 days per week for 14 weeks. All rats survived to the end of the study. Mean body weights of all exposed groups were similar to those of the chamber control groups. There were significant exposure concentration-related decreases in sperm motility in 32, 62, and 125 ppm males; there were no significant differences in the lengths of estrous cycles between chamber control and exposed groups of females. Exposure-related nasal lesions were seen primarily in rats exposed to 62 or 125 ppm. These lesions included turbinate necrosis, suppurative inflammation, respiratory epithelial hyperplasia, squamous metaplasia of the respiratory epithelium, and olfactory epithelial atrophy. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice were exposed to diethylamine vapor at concentrations of 0, 8, 16, 32, 62, or 125 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. The mean body weights of 125 ppm males and females were significantly less than those of the chamber controls. There were significant exposure concentration-related decreases in sperm motility in males exposed to 32, 62, or 125 ppm; the estrous cycle of 125 ppm females was significantly longer than that of the chamber controls but only by half a day. Histopathologic changes were noted primarily in the nasal cavity and involved both the respiratory and olfactory epithelium of males and females principally in the 62 or 125 ppm groups. These lesions included suppurative inflammation, squamous metaplasia of the respiratory epithelium, olfactory epithelial atrophy, and necrosis of the turbinates. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were exposed to diethylamine vapor at concentrations of 0, 31, 62.5, or 125 ppm, 6 hours plus T90 (15 minutes) per day, 5 days per week for 105 weeks. Survival of exposed groups of rats was similar to that of the chamber control groups. Mean body weights of males and females exposed to 125 ppm were less than those of the chamber controls after week 57. Increased incidences of eye abnormality occurred in exposed males and females. A spectrum of nonneoplastic lesions was observed in the respiratory and olfactory epithelium of the nose in exposed rats. The lesions included suppurative inflammation, ulceration of the respiratory epithelium, hyaline droplet accumulation in the glands of the respiratory epithelium, necrosis of the turbinates, squamous metaplasia of the respiratory epithelium, hyperplasia of the respiratory epithelium, atrophy of the olfactory epithelium, hyaline droplet accumulation in the respiratory and olfactory epithelium, basal cell hyperplasia of the olfactory epithelium, respiratory metaplasia of the olfactory epithelium, and goblet cell hyperplasia. The incidence of chronic inflammation of the pleura was significantly increased in 125 ppm females. The incidences of histiocytic cellular infiltration of the alveolus of the lung were significantly increased in all exposed groups of females and the incidence of chronic inflammation was significantly increased in 125 ppm females. In 125 ppm males, the incidence of suppurative inflammation of the cornea was significantly increased. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were exposed to diethylamine vapor at concentrations of 0, 16, 31, or 62.5 ppm, 6 hours plus T90 (15 minutes) per day, 5 days per week for 105 weeks. Survival of exposed groups of mice was similar to that of the chamber control groups. Mean body weights of males and females were similar to those of the chamber controls. Eye abnormality was observed in greater incidence in exposed groups of males than in the chamber controls, and torso/ventral ulcer/abscess was observed in six 62.5 ppm males compared to none in the chamber controls. A similar spectrum of nonneoplastic lesions was seen in the nose of exposed mice as was seen in rats. GENETIC TOXICOLOGY: Diethylamine was not mutagenic in either of two independent bacterial mutagenicity assays, each conducted with and without exogenous metabolic activation enzymes. Bacterial strains tested included Salmonella typhimurium strains TA98, TA100, TA1535, and TA1537 and Escherichia coli strain WP2 uvrA/pKM101. In addition to the negative results in the two bacterial assays, no significant increases in the frequencies of micronucleated erythrocytes were seen in peripheral blood of male or female B6C3F1 mice from the 3-month study. CONCLUSIONS: Under the conditions of these 2-year inhalation studies, there was no evidence of carcinogenic activity of diethylamine in male or female F344/N rats exposed to 31, 62.5, or 125 ppm. There was no evidence of carcinogenic activity of diethylamine in male or female B6C3F1 mice exposed to 16, 31, or 62.5 ppm. Exposure to diethylamine resulted in increased incidences of nonneoplastic lesions of the nose in male and female rats and mice, of the cornea in male rats, and of the pleura and lung in female rats.     

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.     

Toxicology and carcinogenesis studies of propargyl alcohol (CAS No. 107-19-7) in F344/N rats and B6C3F1 mice (inhalation studies)

Propargyl alcohol is a commercially available acetylenic primary alcohol. It is also a by-product in the industrial synthesis of butynediol from acetylene and formaldehyde with copper acetylide as catalyst. Propargyl alcohol is used as a reactant/chemical intermediate, pharmaceutical intermediate, agricultural chemical intermediate, soil fumigant, corrosion inhibitor, solvent stabilizer, and polymer modifier. It has also been used to prevent the hydrogen embrittlement of steel. Propargyl alcohol was nominated by the National Cancer Institute for study because of the potential for human exposure in occupational settings through inhalation and dermal contact. Male and female F344/N rats and B6C3F1 mice were exposed to propargyl alcohol (greater than 99% pure) by inhalation for 2 weeks, 3 months, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium and mouse peripheral blood erythrocytes. 2-WEEK STUDY IN RATS: Groups of five male and five female rats were exposed to propargyl alcohol vapor at concentrations of 0, 31.3, 62.5, 125, 250, or 500 ppm, 6 hours plus T(90 )(12 minutes) per day, 5 days per week for 16 days. All males exposed to 125 ppm or greater and all females exposed to 250 or 500 ppm died by the end of day 3 of the study, and one 125 ppm female died on day 5. Mean body weights were significantly decreased in 62.5 ppm males and 125 ppm females. Clinical findings in the 125 and 250 ppm groups included lethargy, ataxia, abnormal breathing, and nasal/eye discharge. Right kidney weights of 62.5 and 125 ppm females and liver weights of 125 ppm females were significantly greater than those of the chamber controls. All 250 and 500 ppm males and females had moderate to marked periportal necrosis, congestion, and erythrophagocytosis of the liver. 2-WEEK STUDY IN MICE: Groups of five male and five female mice were exposed to propargyl alcohol vapor at concentrations of 0, 31.3, 62.5, 125, 250, or 500 ppm, 6 hours plus T(90) (12 minutes) per day, 5 days per week for 17 days. All mice exposed to 125 ppm or greater died by day 3 of the study. Mean body weights of mice exposed to 62.5 ppm were significantly less than those of the chamber controls. Clinical findings in the 62.5 and/or 125 ppm groups included abnormal breathing, nasal/eye discharge, thinness, and lethargy. Right kidney weights of 31.3 ppm mice were significantly greater, and thymus weights of 62.5 ppm males were significantly less than those of the chamber controls. The livers of all males and females exposed to 250 or 500 ppm exhibited marked periportal necrosis, congestion, and erythrophagocytosis; these lesions also occurred in all 125 ppm males with less severity. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats were exposed to propargyl alcohol vapor at concentrations of 0, 4, 8, 16, 32, or 64 ppm, 6 hours plus T(90) (12 minutes) per day, 5 days per week for 14 weeks. All rats survived to the end of the study. Mean body weights of all exposed groups were similar to those of the chamber control groups. The incidences of minimal to mild hyperplasia of respiratory epithelium of the nose were significantly increased in all exposed groups except 8 ppm males and 4 ppm females. Squamous metaplasia of the respiratory epithelium was noted in a few males and most females exposed to 64 ppm. Necrosis of olfactory epithelium was present in half of the males and females exposed to 64 ppm and in a few males and females exposed to 32 ppm. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice were exposed to propargyl alcohol vapor at concentrations of 0, 4, 8, 16, 32, or 64 ppm, 6 hours plus T(90) (12 minutes) per day, 5 days per week for 14 weeks. All mice survived to the end of the study. Mean body weights of males exposed to 8 ppm or greater and 32 and 64 ppm females were significantly less than those of the chamber control groups. Histopathologic changes occurred in the nasal cavity of mice and involved both the respiratory and olfactory epithelium in groups exposed to 16 ppm or greater. Lesions included minimal to moderate suppurative inflammation, minimal to moderate squamous metaplasia of the respiratory epithelium, minimal to mild hyaline degeneration (accumulation) in the respiratory epithelium, minimal to moderate olfactory epithelial atrophy, minimal to moderate hyperplasia of glands in the olfactory region, minimal necrosis of olfactory epithelium, and minimal to moderate turbinate atrophy. There were no biologically significant differences in organ weights between exposed and chamber control groups. Reproductive tissue parameters of exposed males were similar to those of the chamber controls. Only 2/9 female mice in the 64 ppm group exhibited regular estrous cyclicity compared to 6/10 in the controls. Females exposed to 16 ppm differed from chamber controls in the relative time in the estrous stages, and 64 ppm females had a significantly increased probability of extended estrus. No gross lesions were observed at necropsy. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were exposed to propargyl alcohol vapor at concentrations of 0, 16, 32, or 64 ppm, 6 hours plus T(90) (14 minutes) per day, 5 days per week for 105 weeks. Survival of 32 and 64 ppm males was significantly less than that of the chamber control group. Mean body weights of males exposed to 64 ppm were less than those of the chamber controls after week 24 of the study. Nasal respiratory epithelial adenomas were present in three 64 ppm males and one 32 ppm female; the incidence in 64 ppm males exceeded the historical control ranges. A spectrum of nonneoplastic lesions occurred in the respiratory and olfactory epithelium of rats at all exposure concentrations. The incidences of respiratory epithelial hyperplasia, respiratory glandular hyperplasia, and olfactory basal cell hyperplasia were significantly increased in all exposed groups of rats. The incidences of lesions of the olfactory epithelium including hyperplasia, glandular hyperplasia, atrophy, respiratory metaplasia, degeneration, necrosis, hyaline droplet accumulation, and chronic active inflammation were significantly increased in one or more exposed groups of males and/or females. The incidence of mononuclear cell leukemia was significantly increased in males exposed to 64 ppm, and the incidence exceeded the historical control ranges. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were exposed to propargyl alcohol vapor at concentrations of 0, 8, 16, or 32 ppm, 6 hours plus T(90) (14 minutes) per day, 5 days per week for 105 weeks. Survival of exposed groups was similar to that of the chamber control groups. Mean body weights of 16 and 32 ppm females were less than those of the chamber control group after weeks 73 and 21, respectively. Eye abnormality (unspecified) was observed after one full year of exposure with the incidence increasing in an exposure concentration-related manner. The incidences of nasal respiratory epithelial adenoma increased with a positive trend and were significantly increased in groups exposed to 32 ppm. A spectrum of nonneoplastic lesions occurred in the nasal respiratory and olfactory epithelium of mice at all exposure concentrations. The incidences of respiratory epithelial hyperplasia, respiratory glandular hyperplasia, and squamous metaplasia were significantly increased in most exposed groups of mice. Suppurative inflammation was often associated with the squamous metaplasia, and turbinate atrophy was present in all exposed mice (except one 16 ppm male). The incidences of olfactory epithelial atrophy and respiratory metaplasia were increased in the 16 and 32 ppm groups. Significantly increased incidences of Harderian gland adenoma occurred in 8 and 32 ppm males. GENETIC TOXICOLOGY: Propargyl alcohol was mutagenic in Salmonella typhimurium strain TA100 in the absence of liver S9 activation enzymes only; no mutagenicity was observed in TA100 in the presence of S9 enzymes, in TA1535 without S9, or in TA98 with or without S9. In vivo, no significant increases in the frequencies of micronucleated normochromatic erythrocytes were observed in peripheral blood samples from male mice exposed by inhalation to propargyl alcohol for 3 months. In female mice, propargyl alcohol exposure produced a small increase in micronucleated erythrocytes that was judged to be equivocal. No significant changes in the percentage of polychromatic erythrocytes were seen in either male or female mice after 3 months of exposure to propargyl alcohol. CONCLUSIONS: Under the conditions of these 2-year inhalation studies, there was some evidence of carcinogenetic activity of propargyl alcohol in male F344/N rats based on increased incidences of nasal respiratory epithelial adenoma and mononuclear cell leukemia. There was no evidence of carcinogenic activity of propargyl alcohol in female F344/N rats exposed to 16, 32, or 64 ppm. There was some evidence of carcinogenic activity of propargyl alcohol in male and female B6C3F1 mice based on increased incidences of nasal respiratory epithelial adenoma. The increased incidences of Harderian gland adenoma in male B6C3F1 mice may have been related to exposure to propargyl alcohol. Exposure to propargyl alcohol resulted in increased incidences of nonneoplastic nasal lesions in male and female rats and mice. Synonyms: Ethynylcarbinol; 1-hydroxy-2-propyne; 3-hydroxy-1-propyne; PA; 1-propyn-3-ol; 1-propyn-3-yl alcohol; 2-propynol; 3-propynol; propynyl alcohol; 2-propynyl alcohol.     

Toxicology and carcinogenesis studies of indium phosphide (CAS No. 22398-90-7) in F344/N rats and B6C3F1 mice (inhalation studies)

Indium phosphide is used to make semiconductors,injection lasers, solar cells, photodiodes, and light-emittingdiodes. Indium phosphide was nominated for study because of its widespread use in the microelectronics industry, the potential for worker exposure,and the absence of chronic toxicity data. Male and female F344/N rats and B6C3F1 mice were exposed to indium phosphide (greater than 99% pure) by inhalation for 14 weeks or 2 years. The frequency of micronuclei was determined in the peripheral blood of mice exposed to indium phosphide for 14 weeks. 14-WEEK STUDY IN RATS: Groups of 10 male and 10 female rats were exposed to particulate aerosols of indium phosphide with amass median aerodynamic diameter of approximately 1.2 microm at concentrations of 0, 1, 3, 10, 30, or 100 mg/m3 by inhalation, 6 hours per day, 5 days per week (weeks 1 through 4 and weeks 10 through 14) or 7 days per week (weeks 5 through 9) to accommodate a concurrent teratology study. One male in the 100 mg/m3 group died before the end of the study. Body weight gains of all males and females exposed to 100 mg/m3 were less than those of the chamber controls. As a result of indium phosphide exposure, the lungs of all exposed rats had a gray to black discoloration and were significantly enlarged, weighing 2.7- to 4.4-fold more than those of the chamber controls. Indium phosphide particles were observed throughout the respiratory tract and in the lung-associated lymph nodes. A spectrum of inflammatory and proliferative lesions generally occurred in the lungs of all exposed groups of rats and consisted of alveolar proteinosis, chronic inflammation, interstitial fibrosis, and alveolar epithelial hyperplasia. Pulmonary inflammation was attended by increased leukocyte and neutrophil counts in the blood. The alveolar proteinosis was the principal apparent reason for the increase in lung weights. Indium phosphide caused inflammation at the base of the epiglottis of the larynx and hyperplasia of the bronchial and mediastinal lymph nodes. Exposure to indium phosphide affected the circulating erythroid mass. It induced a microcytic erythrocytosis consistent with bone marrow hyperplasia and hematopoietic cell proliferation of the spleen. Hepatocellular necrosis was suggested by increased serum activities of alanine aminotransferase and sorbitol dehydrogenase in all exposed groups of males and in 10 mg/m3 or greater females and was confirmed microscopically in 100 mg/m3 males and females. 14-WEEK STUDY IN MICE: Groups of 10 male and 10 female mice were exposed to particulate aerosols of indium phosphide with a mass median aerodynamic diameter of approximately 1.2 microm at concentrations of 0, 1, 3, 10, 30, or 100 mg/m3 by inhalation, 6 hours per day, 5 days per week (weeks 1 through 4 and weeks 10 through 14)or 7 days per week (weeks 5 through 9). Although the effects of indium phosphide exposure were similar in rats and mice, mice were more severely affected in that all males and females in the 100 mg/m3 groups either died or were removed moribund during the study. One male and three females in the 30 mg/m3 group were also removed before the end of the study. In general, body weight gains were significantly less in males and females exposed to 3 mg/m3 or greater compared to those of the chamber controls. Mice exposed to 30 or 100 mg/m3 were lethargic and experienced rapid, shallow breathing. As in rats, lungs were discolored and enlarged 2.6- to 4.1-fold greater than those of chamber controls due to the exposure-induced alveolar proteinosis. Indium phosphide particles were observed in the nose, trachea,larynx, and lymph nodes of some exposed males and females. Alveolar proteinosis, chronic active inflammation,interstitial fibrosis, and alveolar epithelial hyperplasia were observed; these effects were more severe than in rats. Hyperplasia in the bronchial lymph nodes and squamous metaplasia, necrosis, and suppurative inflammation of the larynx were observed in some exposed males and females. Exposure to indium phosphide induced a microcytic erythrocytosis which was consistent with the observed hematopoietic cell proliferation of the spleen.2-YEAR STUDY IN RATS Groups of 60 male and 60 female rats were exposed to particulate aerosols of indium phosphide at concentrations of 0, 0.03, 0.1, or 0.3 mg/m3, 6 hours per day,5 days per week, for 22 weeks (0.1 and 0.3 mg/m3 groups) or 105 weeks (0 and 0.03 mg/m3 groups). Animals in the 0.1 and 0.3 mg/m3 group were maintained on filtered air from exposure termination at week 22 until the end of the studies. Ten males and 10 females per group were evaluated at 3 months. 3-Month Interim Evaluation: Exposure to indium phosphide for 3 months caused a microcytic erythrocytosis and also caused enlarged lungs and lesions in the respiratory tract and lung associated lymph nodes. Although qualitatively similar to those observed in the 14-week studies, these effects were considerably less severe. However, the lesions in the lungs of rats exposed to 0.1 or 0.3 mg/m3 were considered sufficiently severe that exposure was discontinued in these groups, and the groups were allowed to continue unexposed for the remainder of the study. Survival, Body Weights, and Clinical Findings: Exposure to indium phosphide had no effect on survival or body weight gain. During the last 6 months of the study, rats in the 0.03 and 0.3 mg/m3 groups became lethargic and males breathed abnormally. Pathology Findings: At 2 years, exposure to indium phosphide caused increased incidences of alveolar/bronchiolar adenomas and carcinomas in rats. Squamous cell carcinoma of the lung occurred in four male rats exposed to 0.3 mg/m3. As observed in the 14-week study and at the 3-month interim evaluation, a spectrum of inflammatory and proliferative lesions of the lung were observed in all exposed groups of males and females;however, the extent and severity of the lesions were generally greater and included atypical hyperplasia,chronic inflammation, alveolar epithelial hyperplasia and metaplasia, alveolar proteinosis, and interstitial fibrosis. Exposure to indium phosphide also caused increased incidences of benign and malignant pheochromocytomas of the adrenal gland in males and females. Marginal increases in the incidences of mononuclear cell leukemia in males and females, fibroma of the skin in males, and carcinoma of the mammary gland in females may have been related to exposure to indium phosphide. 2-YEAR STUDY IN MICE: Groups of 60 male and 60 female mice were exposed to particulate aerosols of indium phosphide at concentrations of 0, 0.03, 0.1, or 0.3 mg/m3, 6 hours per day,5 days per week, for 21 weeks (0.1 and 0.3 mg/m3 groups) or 105 weeks (0 and 0.03 mg/m3 groups). Animals in the 0.1 and 0.3 mg/m3 groups were maintained on filtered air from exposure termination at week 21 until the end of the studies. Ten males and 10 females per group were evaluated at 3 months. 3-Month Interim Evaluation:Exposure to indium phosphide for 3 months affected the circulating erythroid mass and caused enlarged lungs and lesions in the respiratory tract and lung associated lymph nodes. These effects, although qualitatively similar to those observed in the 14-week studies, were considerably less severe. However, the lesions in the lungs of mice exposed to 0.1 mg/m3 and greater were considered sufficiently severe that exposure was discontinued in these groups and the groups were allowed to continue unexposed for the remainder of the study. Survival and Body Weights: In general, exposure to indium phosphide for 2 years reduced survival and body weight gain in exposed males and females. Pathology Findings:At 2 years, exposure to indium phosphide caused increased incidences of alveolar/bronchiolar carcinomas in males and alveolar/bronchiolar adenomas and carcinomas in females. In addition to the alveolar proteinosis and chronic active inflammation seen at earlier time points, serosa fibrosis and pleural mesothelial hyperplasia were also present. The incidences of hepatocellular neoplasms were also significantly increased in exposed males and females. Exposed groups of males and females had increased incidences of eosinophilic foci of the liver at 2 years. Marginal increases in the incidences of neoplasms of the small intestines in male mice may have been related to exposure to indium phosphide. Exposure to indium phosphide also caused inflammation of the arteries of the heart, primarily the coronary arteries and the proximal aorta, and to a lesser extent the lung-associated lymph nodes in males and in females. TISSUE BURDEN ANALYSES: Deposition and clearance studies of indium following long term exposure of rats and mice to indium phosphide by inhalation were performed. Although there were quantitative differences in lung burden and kinetic parameters for rats and mice, qualitatively they were similar. Deposition of indium in the lungs appeared to follow a zero-order (constant rate) process. Retained lung burdens throughout the studies were proportional to exposure concentration and duration. No differences in elimination rates of indium from the lungs were observed as a function of exposure concentration in either rats or mice. These studies indicated that elimination of indium was quite slow. Mice exhibited clearance half-times of 144 and 163 days for the 0.1 and 0.3 mg/m3 groups, respectively, as compared to 262 and 291 days for rats exposed to the same concentrations. The lung deposition and clearance model was used to estimate the total amount of indium deposited in the lungs of rats and mice after exposure to 0.03 mg/m3 for 2 years or to 0.1 or 0.3 mg/m3 for 21 or 22 weeks, the lung burdens at the end of the 2-year study, and the area under lung burden curves (AUC). For both species, estimates at the end of 2 years indicated that the lung burdens in the continuously exposed 0.03 mg/m3 groups were greater than those in the 0.1 or 0.3 mg/m3 groups. (ABSTRACT TRUNCATED)     

NTP toxicology and carcinogensis studies of vanadium pentoxide (CAS No. 1314-62-1) in F344/N rats and B6C3F1 mice (inhalation)

Vanadium pentoxide, commercially the most important compound of vanadium, presents a potential occupational hazard during the cleaning of oil-fired boilers and furnaces, the handling of catalysts, and during the refining, processing, or burning of vanadium-rich mineral ores or fossil fuels. Vanadium pentoxide was nominated for study by the National Cancer Institute as a representative of the metals class study. Male and female F344/N rats and B6C3F1 mice were exposed to vanadium pentoxide (99% pure) by inhalation for 16 days, 14 weeks, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium and mouse peripheral blood. 16-DAY STUDY IN RATS: Groups of five male and five female rats were exposed to particulate aerosols of vanadium pentoxide at concentrations of 0, 2, 4, 8, 16, or 32 mg/m(3) by inhalation, 6 hours per day, 5 days per week for 16 days. Three males in the 32 mg/m(3) group died before the end of the study. Mean body weights of males and females exposed to 8 mg/m(3) or greater were less than those of the chamber controls. Clinical findings included rapid respiration and hypoactivity in rats exposed to 16 or 32 mg/m(3). Relative lung weights of 4 mg/m(3) or greater males and 2 mg/m(3) or greater females were significantly greater than those of the chamber controls. Lavage fluid analysis indicated an inflammatory response in the lung that was either directly mediated by vanadium pentoxide or was secondary to lung damage induced by vanadium pentoxide exposure. 16-DAY STUDY IN MICE: Groups of five male and five female mice were exposed to particulate aerosols of vanadium pentoxide at concentrations of 0, 2, 4, 8, 16, or 32 mg/m(3) by inhalation, 6 hours per day, 5 days per week for 16 days. All males exposed to 32 mg/m(3) and one 8 mg/m(3) male died or were killed moribund before the end of the study. Mean body weights of 16 mg/m(3) males and 8 mg/m(3) or greater females were significantly less than those of the chamber controls, and the 32 mg/m(3) females lost weight during the study. Absolute and relative lung weights of 4 mg/m(3) or greater males and all exposed groups of females and liver weights of 16 mg/m(3) males were significantly greater than those of the chamber controls. The mediastinal lymph nodes were enlarged in 4, 8, and 16 mg/m(3) males and females, and lymphoid hyperplasia was confirmed histologically. Lavage fluid analysis indicated an inflammatory response in the lung that was either directly mediated by vanadium pentoxide or was secondary to lung damage induced by vanadium pentoxide exposure. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats were exposed to particulate aerosols of vanadium pentoxide at concentrations of 0, 1, 2, 4, 8, or 16 mg/m(3) by inhalation, 6 hours per day, 5 days per week for 3 months. Seven males and three females exposed to 16 mg/m(3) died during the study. Mean body weights were significantly less in males exposed to 4 mg/m(3) or greater and in females exposed to 16 mg/m(3). Abnormal breathing, thinness, lethargy, abnormal posture, and ruffled fur were observed in rats exposed to 16 mg/m(3). Hematology results indicated that exposure of rats to vanadium pentoxide induced a microcytic erythrocytosis in males and females. Absolute and relative lung weights were significantly greater for 4 mg/m(3) or greater males and females than for the chamber controls as were the relative lung weights of 2 mg/m(3) males. The estrous cycle of females exposed to 8 mg/m(3) was significantly longer than that of the chamber control group, and the number of cycling females in the 16 mg/m(3) group was reduced. The incidences of several nonneoplastic lesions of the lung and nose were significantly increased in males and females exposed to 2 mg/m(3) or greater. Data from pulmonary function analyses indicated that a restrictive lung disease was present in male and female rats exposed to 4 mg/m(3) or greater, while an obstructive lung disease was present only in the 16 mg/m(3) groups. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice were exposed to particulate aerosols of vanadium pentoxide at concentrations of 0, 1, 2, 4, 8, or 16 mg/m(3) by inhalation, 6 hours per day, 5 days per week for 3 months. One male exposed to 16 mg/m(3) died before the end of the study. Mean body weights of 8 and 16 mg/m(3) males and 4 mg/m(3) or greater females were significantly less than those of the chamber controls. Absolute and relative lung weights of males and females exposed to 4 mg/m(3) or greater were significantly greater than those of the chamber controls. The epididymal spermatozoal motility of males exposed to 8 or 16 mg/m(3) was significantly decreased. Some mice exposed to 2 or 4 mg/m(3) had inflammation of the lung, and all mice exposed to 8 or 16 mg/m(3) had inflammation and epithelial hyperplasia of the lung. 16-DAY SPECIAL STUDY IN RATS: Groups of 60 female rats were exposed to particulate aerosols of vanadium pentoxide at concentrations of 0, 1, or 2 mg/m(3) and groups of 40 female rats were exposed to 4 mg/m(3) by inhalation, 6 hours per day, 5 days per week for 16 days. Alveolar and bronchiolar epithelial hyperplasia was observed in most rats exposed to 2 or 4 mg/m(3) on days 6 and 13. Histiocytic infiltration and inflammation occurred in a time- and concentration-related manner. Cell turnover rates were increased in the terminal bronchioles on days 6 and 13 and in the alveoli in the 4 mg/m(3) group on day 6 and in all exposed groups on day 13. Assessment of lung vanadium concentrations suggested deposition and clearance exhibited linear kinetics over the exposure range studied. Lung clearance half-times ranged from 4.42 to 4.96 days. 16-DAY SPECIAL STUDY IN MICE: Groups of 60 female mice were exposed to particulate aerosols of vanadium pentoxide at concentrations of 0, 2, or 4 mg/m(3) and groups of 40 female mice were exposed to 8 mg/m(3) by inhalation, 6 hours per day, 5 days per week for 16 days. Alveolar and bronchiolar epithelial hyperplasia occurred with similar incidences and severities among the exposed groups on days 6 and 13, and time- and concentration-related increases in the incidences of interstitial inflammation and histiocytic infiltration also occurred in these groups. Cell turnover rates were increased in the terminal bronchioles on day 6 and remained greater than those of the chamber controls on day 13. In the alveoli, cell turnover rates were increased in an exposure concentration-related manner on day 13; cell turnover rates were increased only in the 8 mg/m(3) group on day 6. Assessment of lung vanadium concentrations suggested deposition and clearance exhibited linear kinetics over the exposure range studied. Lung clearance half-times ranged from 2.40 to 2.55 days. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were exposed to particulate aerosols of vanadium pentoxide at concentrations of 0, 0.5, 1, or 2 mg/m(3) by inhalation, 6 hours per day, 5 days per week for 104 weeks. Survival and body weights of males and females were generally similar to those of the chamber controls. Mean body weights of females exposed to 2 mg/m(3) were less than those of the chamber controls throughout the study. Alveolar/bronchiolar neoplasms were present in exposed groups of male rats, and the incidences often exceeded the historical control ranges. Alveolar/bronchiolar adenomas were present in 0.5 and 1 mg/m(3) females; one 2 mg/m(3) female also had an alveolar/bronchiolar carcinoma. The incidence of alveolar/bronchiolar adenoma in the 0.5 mg/m(3) group was at the upper end of the historical control ranges. Nonneoplastic lesions related to vanadium pentoxide exposure occurred in the respiratory system (lung, larynx, and nose) of male and female rats, and the severities of these lesions generally increased with increasing exposure concentration. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were exposed to particulate aerosols of vanadium pentoxide at concentrations of 0, 1, 2, or 4 mg/m(3) by inhalation, 6 hours per day, 5 days per week for 104 weeks. Survival of 4 mg/m(3) males was significantly less than that of the chamber controls. Mean body weights of 4 mg/m(3) males and all exposed groups of females were generally less than those of the chamber controls throughout the study, and those of males exposed to 2 mg/m(3) were less from week 85 to the end of the study. Many mice exposed to vanadium pentoxide were thin, and abnormal breathing was observed in some mice, particularly those exposed to 2 or 4 mg/m(3). The incidences of alveolar/bronchiolar neoplasms were significantly increased in all groups of exposed males and females. Nonneoplastic lesions related to vanadium pentoxide exposure occurred in the respiratory system (lung, larynx, and nose) of male and female mice, and the severities of these lesions generally increased with increasing exposure concentration. Bronchial lymph node hyperplasia was present in many exposed females. MOLECULAR ONCOLOGY STUDIES: K-ras codon 12 mutation and loss of heterozygosity on chromosome 6 were detected in vanadium pentoxide-induced alveolar/bronchiolar carcinomas from mice. GENETIC TOXICOLOGY: Vanadium pentoxide was not mutagenic in Salmonella typhimurium strain TA97, TA98, TA100, TA102, or TA1535, with or without induced rat or hamster liver S9 enzymes. CONCLUSIONS: Under the conditions of this 2-year inhalation study, there was some evidence of carcinogenic activity of vanadium pentoxide in male F344/N rats and equivocal evidence of carcinogenic activity of vanadium pentoxide in female F344/Nrats based on the occurrence of alveolar/bronchiolar neoplasms. There was clear evidence of carcinogenic activity of vanadium pentoxide in male and female B6C3F1 mice based on increased incidences of alveolar/bronchiolar neoplasms. (ABSTRACT TRUNCATED)     

Toxicology and carcinogenesis studies of 4-methylimidazole (Cas No. 822-36-6) in F344/N rats and B6C3F1 mice (feed studies)

4-Methylimidazole is used in the manufacture of pharmaceuticals, photographic chemicals, dyes and pigments, cleaning and agricultural chemicals, and rubber. It has been identified as a by-product of fermentation in foods and has been detected in mainstream and sidestream tobacco smoke. 4-Methylimidazole was nominated by the National Cancer Institute for a long-term study because of the high potential for human exposure. Male and female F344/N rats and B6C3F1 mice were exposed to 4-methylimidazole (99.5% pure) in feed for 2 years. Fifteen-day and 14-week toxicity studies of 4-methylimidazole in F344/N rats and B6C3F1 mice are reported in NTP Toxicity Report No. 67. Genetic toxicology studies were conducted in Salmonella typhimurium, rat and mouse bone marrow cells, and mouse peripheral blood. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were fed diets containing 0, 625, 1,250, or 2,500 ppm 4-methylimidazole (males) or 0, 1,250, 2,500, or 5,000 ppm 4-methylimidazole (females) (equivalent to average daily doses of approximately 30, 55, or 115 mg 4-methylimidazole/kg body weight to males and 60, 120, or 260 mg/kg to females) for 106 weeks. Survival of all exposed groups of male and female rats was similar to that of the control groups. Mean body weights of males in the 1,250 and 2,500 ppm groups and females in the 2,500 and 5,000 ppm groups were less than those of the control groups throughout the study; mean body weights of 1,250 ppm females were less after week 41. Feed consumption by 5,000 ppm females was less than that by the controls. Clonic seizures, excitability, hyperactivity, and impaired gait were observed primarily in 2,500 and 5,000 ppm females. The incidence of mononuclear cell leukemia in 5,000 ppm females was significantly greater than that in the controls, and the incidence exceeded the historical range in feed study controls. The incidences of hepatic histiocytosis, chronic inflammation, and focal fatty change were generally significantly increased in all exposed groups of male and female rats. The incidences of hepatocellular eosinophilic and mixed cell focus were significantly increased in 2,500 ppm males and 5,000 ppm females. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were fed diets containing 0, 312, 625, or 1,250 ppm 4-methylimidazole (equivalent to average daily doses of approximately 40, 80, and 170 mg 4-methylimidazole/kg body weight to males and females) for 106 weeks. Survival of all exposed groups of male and female mice was similar to that of the control groups. Mean body weights of males and females in the 1,250 ppm groups were less than those of the control groups after weeks 17 and 12, respectively. Mean body weights of 312 and 625 ppm females were less after weeks 85 and 65, respectively. Feed consumption by exposed groups of male and female mice was generally similar to that by the controls. The incidences of alveolar/bronchiolar adenoma in all exposed groups of females, alveolar/bronchiolar carcinoma in 1,250 ppm males, and alveolar/bronchiolar adenoma or carcinoma (combined) in 1,250 ppm males and 625 and 1,250 ppm females were significantly greater than those in the control groups. The incidence of alveolar epithelium hyperplasia was significantly increased in 1,250 ppm females. GENETIC TOXICOLOGY: 4-Methylimidazole was not mutagenic in the S. typhimurium mutation assay when tested in strains TA97, TA98, TA100, and TA1535, with and without hamster or rat liver metabolic activation enzymes. No consistent or significant increases in the frequencies of micronucleated erythrocytes were seen in the bone marrow of male rats or mice treated with 4-methylimidazole by intraperitoneal injection, or in peripheral blood samples from male and female mice administered the compound in dosed feed for 14 weeks. CONCLUSIONS: Under the conditions of these 2-year studies, there was no evidence of carcinogenic activity of 4-methylimidazole in male F344/N rats exposed to 625, 1,250, or 2,500 ppm. There was equivocal evidence of carcinogenic activity of 4-methylimidazole in female F344/N rats based on increased incidences of mononuclear cell leukemia. There was clear evidence of carcinogenic activity of 4-methylimidazole in male and female B6C3F1 mice based on increased incidences of alveolar/bronchiolar neoplasms. Exposure to 4-methylimidazole resulted in nonneoplastic lesions in the liver of male and female rats and the lung of female mice and in clinical findings of neurotoxicity in female rats.     

Toxicology and carcinogenesis studies of formamide (Cas No. 75-12-7) in F344/N rats and B6C3F1 mice (gavage studies)

Formamide is used as a softener for paper, gums, and animal glues; as an ionizing solvent; and in the manufacture of formic esters and hydrocyanic acid. Formamide was nominated for reproductive and genetic toxicity evaluation by the Environmental Defense Fund and for carcinogenicity evaluation by the National Cancer Institute because of the potential for human exposure associated with its widespread industrial use, the absence of data adequately characterizing its potential for reproductive and genetic toxicity, and the fact that acetamide, a compound structurally related to form-amide, is hepatocarcinogenic in rats when administered in feed. Male and female F344/N rats and B6C3F1 mice were administered formamide (approximately 100% pure) in deionized water by gavage for 2 weeks, 3 months, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium and Escherichia coli, Drosophila melanogaster, and mouse peripheral blood erythrocytes. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats were administered 0, 10, 20, 40, 80, or 160 mg formamide/kg body weight in deionized water by gavage, 5 days per week for 14 weeks. Additional groups of 10 male and 10 female rats (clinical pathology study) and five male and five female rats (plasma concentration study) were administered the same doses, 5 days per week for up to 14 weeks. All core study rats survived to the end of the study. Mean body weights of females in the 40 mg/kg group and males and females in the 80 and 160 mg/kg groups were significantly less than those of the vehicle controls. On day 23 and at week 14, there was a dose-related increase in the erythron, evidenced by increases in hematocrit values, hemoglobin concentrations, and erythrocyte counts. The incidences of degeneration of the germinal epithelium of the testes and epididymis were significantly increased in 160 mg/kg males. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice were administered 0, 10, 20, 40, 80, or 160 mg formamide/kg body weight in deionized water by gavage, 5 days per week for 14 weeks. Additional groups of five male and five female mice (plasma concentration study) were administered the same doses, 5 days per week for 14 weeks. All mice survived to the end of the study. Final mean body weights of the 80 and 160 mg/kg males and mean body weight gains of 40, 80, and 160 mg/kg males were significantly less than those of the vehicle controls. Dosed females differed significantly from vehicle controls in the relative amount of time spent in the estrous stages. All 160 mg/kg males had abnormal residual bodies in the testes. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were administered 0, 20, 40, or 80 mg formamide/kg body weight, 5 days per week for 104 to 105 weeks in deionized water by gavage. Survival of all dosed groups of rats was similar to that of the vehicle controls. Mean body weights of 80 mg/kg males were less than those of the vehicle controls throughout most of the study. Mean body weights of 40 and 80 mg/kg females were somewhat less than those of the vehicle controls during the second year of the study. A significant increase in the incidence of bone marrow hyperplasia occurred in 80 mg/kg males. No neoplasms were attributed to exposure to formamide. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were administered 0, 20, 40, or 80 mg formamide/kg body weight, 5 days per week for 104 to 105 weeks in deionized water by gavage. Survival of all dosed groups of mice was similar to that of the vehicle controls. Mean body weights of 80 mg/kg males and females were generally less than those of the vehicle controls throughout the study; mean body weights of 40 mg/kg females were generally less after week 13 of the study. The incidences of hemangiosarcoma of the liver occurred with a positive trend in males, and the incidences were significantly increased in the 40 and 80 mg/kg groups. The incidence of hepatocellular adenoma or carcinoma (combined) in 80 mg/kg females was significantly increased. The incidences of mineralization of the testicular arteries and testicular tunic were significantly increased in 80 mg/kg males. The incidence of hematopoietic cell proliferation of the spleen was significantly increased in 80 mg/kg males. GENETIC TOXICOLOGY: Formamide gave no evidence for mutagenicity in a series of short-term assays. In three independent Ames assays, formamide was not mutagenic in any of several strains of S. typhimurium tested with and without rat or hamster liver S9 activation enzymes or in E. coli strain WP uvrA pKM101 tested with and without 10% rat liver S9. Negative results were obtained in a test for induction of sex-linked recessive lethal mutations in germ cells of male D. melanogaster treated with formamide either by feeding or injection. Formamide did not induce increases in micronucleated erythrocytes in male or female mice treated by gavage for 3 months. CONCLUSIONS: Under the conditions of these 2-year gavage studies, there was no evidence of carcinogenic activity of form-amide in male or female F344/N rats administered 20, 40, or 80 mg/kg. There was clear evidence of carcinogenic activity of formamide in male B6C3F1 mice based on increased incidences of hemangiosarcoma of the liver. There was equivocal evidence of carcinogenic activity of formamide in female B6C3F1 mice based on increased incidences of hepatocellular adenoma or carcinoma (combined). An increased incidence of bone marrow hyperplasia occurred in male rats. Mineralization of the testicular arteries and tunic and hematopoietic cell proliferation of the spleen in male mice were also associated with administration of formamide.     

Toxicology and carcinogenesis studies of diisopropylcarbodiimide (Cas No. 693-13-0) in F344/N rats and B6C3F1 mice (dermal studies)

Diisopropylcarbodiimide is used as a reagent for peptide syntheses and as a chemical intermediate. The National Cancer Institute nominated diisopropylcarbodiimide for study as a representative chemical in the alkylcarbodiimide class because of its acute toxicity; its use in chemical, pharmaceutical, and recombinant DNA industries; and the absence of data on potential health effects. Male and female F344/N rats and B6C3F1 mice were administered diisopropylcarbodiimide (greater than 99% pure) dermally for 2 weeks, 3 months, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, rat and mouse bone marrow cells, and mouse peripheral blood erythrocytes. 2-WEEK STUDY IN RATS: Groups of five male and five female F344/N rats were dermally administered 0.3 mL ethanol containing 0, 3, 9, 27, or 81 mg diisopropylcarbodiimide or 0.3 mL of the neat chemical containing 242 mg per animal, 5 days a week for 2 weeks. All rats in the 27, 81, and 242 mg groups died before the end of the study. Of the surviving groups, final body weights were similar to those of the vehicle controls. Clinical findings included convulsions/seizures, nasal/eye discharge, tremors, and comatose conditions in 81 and 242 mg rats and lethargy, ataxia, and abnormal breathing in 27 mg rats. The incidences of epidermal hyperplasia at the site of application in 9 and 27 mg males and 27 mg females were significantly greater than those in the vehicle controls; the incidences of hyperkeratosis in 3 and 9 mg males and 9 mg females were also significantly increased. 2-WEEK STUDY IN MICE: Groups of five male and five female B6C3F1 mice were dermally administered 0.1 mL ethanol containing 0, 1, 3, 9, or 27 mg diisopropylcarbodiimide or 0.1 mL of the neat chemical containing 81 mg per animal, 5 days a week for 2 weeks. All 9, 27, and 81 mg mice died before the end of the study. Final body weights of the surviving groups were similar to those of the vehicle controls. Clinical findings in 9, 27, and 81 mg mice included comatose conditions, convulsions/seizures, tremors, abnormal breathing, nasal/eye discharge, lethargy, and irritation at the site of application. Incidences of chronic active inflammation at the site of application in 9 mg males and females were significantly greater than those in the vehicle control groups. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female core study F344/N rats were dermally administered 0, 10, 20, 40, 80, or 160 mg diisopropylcarbodiimide/kg body weight in ethanol, 5 days per week for 3 months. Groups of 10 male and 10 female clinical pathology rats were administered the same doses for 22 days. All 160 mg/kg core study rats were sacrificed moribund or died within the first week of the study. All 80 mg/kg rats died or were found moribund by day 59. Significant decreases in body weight gain occurred in 40 mg/kg males and females, and a significant decrease in final mean body weight occurred in 40 mg/kg females. Clinical findings in groups administered 40 mg/kg or more generally included irritation of the skin at the site of application, seizures, ataxia, abnormal breathing, ruffled fur, thinness, and lethargy. Significantly increased incidences of skin lesions at the site of application included epidermal hyperplasia in all dosed groups of males (except 160 mg/kg) and 40 mg/kg or greater females, epidermal necrosis in 160 mg/kg males and females, and chronic active inflammation in 80 and 160 mg/kg males and females. Significantly increased incidences of nonneoplastic lesions occurred in the brain, lung, and liver (males only) of rats administered 80 or 160 mg/kg. 3-MONTH STUDY IN MICE Groups of 10 male and 10 female B6C3F1 mice were dermally administered 0, 17.5, 35, 70, 140, or 280 mg/kg diisopropylcarbodiimide in ethanol, 5 days per week for 3 months. All mice in the 280 mg/kg group and nine males and nine females in the 140 mg/kg group died before the end of the study. The final mean body weight gain of 70 mg/kg males was significantly less than that of the vehicle control group. Clinical findings observed in 140 and 280 mg/kg mice included abnormal breathing, ataxia, comatose conditions, convulsions/seizures, irritation at the site of application, lethargy, ruffled fur, and thinness. Significant increases in kidney weights occurred in 17.5 and 35 mg/kg males. Significant decreases in total spermatid heads per testis and average spermatid count occurred in 17.5 mg/kg males. At the site of application, the incidences of epidermal hyperplasia in males and females administered 70 mg/kg or greater, chronic inflammation in 140 and 280 mg/kg males and 70 mg/kg or greater females, and sebaceous gland hyperplasia in 140 mg/kg males were significantly increased. Thymic atrophy was significantly increased in 140 and 280 mg/kg males and females. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female F344/N rats were dermally administered 0, 10, 20, or 40 mg/kg diisopropylcarbodiimide in anhydrous ethanol 5 days per week for 2 years. Survival of 20 mg/kg males was significantly greater than that of the vehicle controls; survival of all dosed groups of females was similar to that of the vehicle controls. Body weights of 40 mg/kg rats were generally less than those of the vehicle controls after week 13. Clinical findings frequently observed in 40 mg/kg males included ataxia, excitability, impaired gait, low muscle tone, abnormal breathing, lethargy, vocalization, and seizures. Because of severe neurological signs exhibited by the 40 mg/kg males, a neuropathological review of these animals was performed. The principal pathological findings of the brain included neuronal necrosis, hemorrhage, and/or fibrinoid arteriole necrosis. Incidences of hemorrhage in the lung of 40 mg/kg males, chronic lung inflammation in 10 and 20 mg/kg females, and alveolar epithelium hyperplasia in 20 mg/kg females were significantly greater than those of the vehicle controls. At the site of application, the incidences of epidermal hyperplasia in all dosed groups of males and 20 and 40 mg/kg females and chronic inflammation in all dosed groups of males and 40 mg/kg females were significantly increased. There was no increased incidences of neoplasms related to diisopropylcarbodiimide administration. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female B6C3F1 mice were dermally administered 0, 10, 20, or 40 mg/kg diisopropylcarbodiimide in anhydrous ethanol, 5 days per week for 2 years. Survival of all dosed groups was similar to that of the vehicle control groups. Mean body weights of dosed groups of mice were generally similar to those of the vehicle control groups throughout the study. There were no increased incidences of neoplasms that were attributed to the administration of diisopropylcarbodiimide. Significantly increased incidences of epidermal hyperplasia and focal dermal inflammation of the skin at the site of application occurred in 20 mg/kg male mice. GENETIC TOXICOLOGY: Diisopropylcarbodiimide was not mutagenic in Salmonella typhimurium strains TA97, TA98, TA100, or TA1535 with or without liver S9 activation enzymes. In vivo, the frequency of micronucleated normochromatic erythrocytes was significantly increased in male and female mice after 3 months of dermal exposure to diisopropylcarbodiimide. In addition, significantly elevated frequencies of micronucleated polychromatic erythrocytes (reticulocytes) and micronucleated normochromatic erythrocytes were seen in male mice during a 4-month dermal exposure to diisopropylcarbodiimide. Negative results were obtained, however, in an acute three-injection rat bone marrow micronucleus study. A three-treatment acute micronucleus test in male mice also showed no increase in micronucleated erythrocytes, but results of a single injection micronucleus test in male mice were concluded to be equivocal, due to an increase in micronucleated erythrocytes seen in peripheral blood but not in bone marrow preparations. CONCLUSIONS: Under the conditions of these 2-year dermal studies, there was no evidence of carcinogenic activity of diisopropylcarbodiimide in male or female F344/N rats or B6C3F1 mice administered 10, 20, or 40 mg/kg. Clinical and histological signs of neurotoxicity in male rats were associated with diisopropylcarbodiimide administration.     

Toxicology and carcinogenesis studies of methyl isobutyl ketone (Cas No. 108-10-1) in F344/N rats and B6C3F1 mice (inhalation studies)

Methyl isobutyl ketone is used as a denaturant for rubbing alcohol; as a solvent for paints, varnishes, nitrocellulose, lacquers, and protective coatings; in industrial extraction processes; in dry-cleaning preparations; and in the synthesis of methyl isobutyl carbinol. Methyl isobutyl ketone was nominated for study by the National Cancer Institute and the United States Environmental Protection Agency because of its widespread use, the high potential for worker exposure due to its many industrial applications, and its high production volume. Male and female F344/N rats and B6C3F1 mice were exposed to methyl isobutyl ketone (greater than 99% pure) by inhalation for 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium. 2-YEAR STUDY IN RATS: Groups of 50 males and 50 females were exposed to methyl isobutyl ketone at concentrations of 0, 450, 900, or 1,800 ppm by inhalation, 6 hours plus T(90) (12 minutes) per day, 5 days per week for 104 weeks. Survival of males exposed to 1,800 ppm was significantly less than that of the chamber controls. The mean body weights of the 900 and 1,800 ppm males were less than those of the chamber controls after weeks 97 and 89, respectively. In the standard evaluation of the kidney, there were slightly increased incidences of renal tubule adenoma and renal tubule adenoma or carcinoma (combined) in males exposed to 900 or 1,800 ppm, and renal tubule carcinoma in males exposed to 1,800 ppm. The incidences of renal tubule hyperplasia were also significantly increased in the 450 and 1,800 ppm males, and the severities were greater than in the chamber controls. Chronic nephropathy occurred in all males exposed to 1,800 ppm and in 70% to 88% of exposed females, and the severity was increased in 1,800 ppm males. The incidences of transitional epithelial hyperplasia of the renal pelvis in males exposed to 900 or 1,800 ppm and mineralization of the renal papilla in all groups of exposed males were significantly increased. In addition, two female rats exposed to 1,800 ppm had renal mesenchymal tumors. In the extended evaluation of the kidney, renal tubule adenomas and renal tubule hyperplasia occurred in all groups of exposed male rats. In the combined single and step section analysis, the incidences of renal tubule adenoma and renal tubule adenoma or carcinoma (combined) were significantly increased in males exposed to 1,800 ppm. The incidences of renal tubule hyperplasia were also significantly increased in all exposed groups of males. There was a positive trend in the incidences of mononuclear cell leukemia in males, and the incidence in the 1,800 ppm group was significantly increased. The incidence of adrenal medulla hyperplasia in the 1,800 ppm males was significantly increased. 2-YEAR STUDY IN MICE: Groups of 50 males and 50 females were exposed to methyl isobutyl ketone at concentrations of 0, 450, 900, or 1,800 ppm by inhalation, 6 hours plus T(90) (12 minutes) per day, 5 days per week for 105 weeks. Survival of males and females was similar to that of the chamber controls. The mean body weights of females exposed to 1,800 ppm were less than those of the chamber controls after week 17. The incidences of hepatocellular adenoma and hepatocellular adenoma or carcinoma (combined) were significantly increased in males and females exposed to 1,800 ppm. The incidences of eosinophilic foci were significantly increased in 450 and 1,800 ppm females. GENETIC TOXICOLOGY: Methyl isobutyl ketone was not mutagenic in Salmonella typhimurium strains TA97, TA98, TA100, or TA1535 when tested with and without hamster or rat liver metabolic activation enzymes. CONCLUSIONS: Under the conditions of these 2-year studies, there was some evidence of carcinogenic activity of methyl isobutyl ketone in male F344/N rats based on increased incidences of renal tubule neoplasms. Increased incidences of mononuclear cell leukemia in 1,800 ppm male F344/N rats may have been related to methyl isobutyl ketone exposure. There was equivocal evidence of carcinogenic activity of methyl isobutyl ketone in female F344/N rats based on the occurrence of renal mesenchymal tumors in the 1,800 ppm group. There was some evidence of carcinogenic activity of methyl isobutyl ketone in male and female B6C3F1 mice based on increased incidences of liver neoplasms. Exposure to methyl isobutyl ketone resulted in nonneoplastic lesions of the kidney characteristic of alpha2u-globulin accumulation in male rats and nephropathy in female rats.     

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)     

NTP toxicology and carcinogenesiss studies of citral (microencapsulated) (CAS No. 5392-40-5) in F344/N rats and B6C3F1 mice (feed studies)

Citral is used primarily as lemon flavoring in foods, beverages, and candies. It is also used as a lemon fragrance in detergents, perfumes, and other toiletries. Citral was nominated by the National Cancer Institute for study because of its widespread use in foods, beverages, cosmetics, and other consumer products and its structure as a representative beta-substituted vinyl aldehyde. Male and female F344/N rats and B6C3F1 mice were exposed to microencapsulated citral (greater than 96% pure) in feed for 14 weeks or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, cultured Chinese hamster ovary cells, mouse bone marrow cells, and mouse peripheral blood erythrocytes. 14-WEEK STUDY IN RATS: Groups of 10 male and 10 female F344/N rats were fed diets containing starch microcapsules with a load of 31.3% citral. The concentration of citral in the diet was 3,900, 7,800, 15,600, or 31,300 ppm microencapsulated citral (equivalent to average daily doses of approximately 345, 820, 1,785, and 1,585 mg citral/kg body weight to males and 335, 675, 1,330, and 2,125 mg/kg to females) for 14 weeks. Additional groups of 10 male and 10 female rats received untreated feed (untreated controls) or feed containing placebo microcapsules (vehicle controls). In the second week of the study, all rats in the 31,300 ppm groups were killed moribund. Mean body weights of exposed males and females that survived to the end of the study were generally significantly less than those of the vehicle controls. Feed consumption by 15,600 and 31,300 ppm males and females was less than that by the vehicle controls during the first week of the study. Males and females in the 31,300 ppm groups exhibited listlessness, hunched posture, absent or slow paw reflex, and dull eyes. Exposure of rats to citral may have been associated with forestomach epithelial hyperplasia and hyperkeratosis, bone marrow atrophy and hemorrhage, and nephrotoxicity. 14-WEEK STUDY IN MICE: Groups of 10 male and 10 female B6C3F1 mice were fed diets containing 3,900, 7,800, 15,600, or 31,300 ppm microencapsulated citral (equivalent to average daily doses of approximately 745, 1,840, 3,915, and 8,110 mg/kg to males and 790, 1,820, 3,870, and 7,550 mg/kg to females) for 14 weeks. Additional groups of 10 male and 10 female mice received untreated feed (untreated controls) or feed containing placebo microcapsules (vehicle controls). In the second week of the study, four males in the 31,300 ppm group were killed moribund. Mean body weights of all exposed groups of males and females were significantly less than those of the vehicle controls. Feed consumption by females exposed to 7,800 ppm or greater was less than that by the vehicle controls during the first week of the study. By the end of the study, feed consumption by all exposed groups was greater than that by the vehicle controls. Mice in the 15,600 and 31,300 ppm groups were generally thin and lethargic; a few males in the 7,800 ppm group were also thin. The incidences of ovarian atrophy were significantly increased in females exposed to 15,600 or 31,300 ppm. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female F344/N rats were fed diets containing 1,000, 2,000, or 4,000 ppm microencapsulated citral 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, 2,000, and 4,000 ppm delivered average daily doses of approximately 50, 100, and 210 mg/kg to males and females. Survival of all exposed groups of males was significantly greater than that of the vehicle control group. Mean body weights of rats exposed to 4,000 ppm were generally less than those of the vehicle controls from week 49 (males) or 25 (females) to the end of the study. Feed consumption by exposed groups was similar to that by the vehicle controls. No neoplasms or nonneoplastic lesions were attributed to exposure to citral. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female B6C3F1 mice were fed diets containing 500, 1,000, or 2,000 ppm microencapsulated citral 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 500, 1,000, and 2,000 ppm delivered average daily doses of approximately 60, 120, and 260 mg/kg to males and females. Survival of exposed males and females was similar to that of the vehicle control groups. Mean body weights of mice exposed to 1,000 or 2,000 ppm were generally less than those of the vehicle controls throughout the study, and mean body weights of 500 ppm females were less from week 30 to the end of the study. Feed consumption by the exposed groups was similar to that by the vehicle controls. The incidences of malignant lymphoma occurred with a positive trend in female mice, and the incidence in 2,000 ppm females was significantly greater than that in the vehicle control group. Tissues most commonly affected by malignant lymphoma were the spleen, mesenteric lymph node, thymus, and, to a lesser extent, the ovary. GENETIC TOXICOLOGY: Citral was not mutagenic in S. typhimurium strain TA98, TA100, TA1535, or TA1537 with or without induced rat or hamster liver S9 enzymes. In cytogenetic tests with cultured Chinese hamster ovary cells, citral induced sister chromatid exchanges with and without S9, but chromosomal aberrations were not significantly increased after exposure to citral, with or without S9. Negative results were obtained in an in vivo bone marrow micronucleus test in male B6C3F1 mice treated by intraperitoneal injection with 250 to 750 mg/kg daily for 3 days. Likewise, no increases in the frequencies of micronucleated erythrocytes were observed in peripheral blood samples collected from male and female mice within 24 hours of the final exposure in the 14-week study. In conclusion, citral gave negative results in in vitro and in vivo tests for genotoxicity, with the exception of the in vitro mammalian cell test for sister chromatid exchange induction CONCLUSIONS: Under the conditions of these 2-year feed studies, there was no evidence of carcinogenic activity of citral in male or female F344/N rats exposed to 1,000, 2,000, or 4,000 ppm. There was no evidence of carcinogenic activity of citral in male B6C3F1 mice exposed to 500, 1,000, or 2,000 ppm. There was equivocal evidence of carcinogenic activity in female B6C3F1 mice based on increased incidences of malignant lymphoma.