UMLS:C0001430 - FACTA Search

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Nickel oxide (NiO) "sinters" are used in stainless steel and alloy steel production. Nickel oxide was nominated by the National Cancer Institute to the NTP for testing because exposure to this form of nickel is prevalent in the nickel industry. Increased incidences of lung and nasal sinus cancers have occurred among workers in certain nickel refining facilities, and nickel oxide was studied as part of a class study of nickel compounds. Male and female F344/N rats and B6C3F1 mice were exposed to nickel oxide (high temperature, green nickel oxide; mass median diameter 2.2 +/- 2.6 &mgr;m; at least 99% pure) by inhalation for 16 days, 13 weeks, or 2 years. Genetic toxicology studies were conducted in peripheral blood of B6C3F1 mice exposed to nickel oxide for 13 weeks. 16-DAY STUDY IN RATS: Groups of five male and five female F344/N rats were exposed to 0, 1.2, 2.5, 5, 10, or 30 mg nickel oxide/m(3)(equivalent to 0, 0.9, 2.0, 3.9, 7.9, or 23.6 mg nickel/m(3)) by inhalation for 6 hours per day, 5 days per week for a total of 12 exposure days during a 16-day period. Additional groups of five male and five female rats were exposed to 0, 1.2, 5, or 10 mg/m(3) for tissue burden studies. All core study rats survived until the end of the study, final mean body weights of exposed male and female rats were similar to those of the controls, and there were no clinical findings related to nickel oxide exposure. Absolute and relative lung weights of male and female rats exposed to 10 or 30 mg/m(3) were significantly greater than those of the controls. Pigment particles in alveolar macrophages or within the alveolar spaces were observed in the lungs of exposed groups of males and females. Chronic-active inflammation and accumulation of macrophages in alveolar spaces of the lungs and hyperplasia in the respiratory tract lymph nodes were most severe in 10 and 30 mg/m(3) males and females. Hyperplasia of bronchial lymph nodes occurred in 30 mg/m(3) rats. Atrophy of the olfactory epithelium was observed in one male and one female exposed to 30 mg/m(3). The concentrations of nickel oxide in the lungs of exposed groups of rats were greater than those in the lungs of control groups (males, 42 to 267 mg nickel/g lung; females, 54 to 340 mg/g lung). 16-DAY STUDY IN MICE: Groups of five male and five female B6C3F1 mice were exposed to 0, 1.2, 2.5, 5, 10, or 30 mg nickel oxide/m(3) by inhalation for 6 hours per day, 5 days per week for a total of 12 exposure days during a 16-day period. Additional groups of five male and five female mice were exposed to 0, 1.2, 2.5, or 5 mg/m(3) for tissue burden studies. No exposure-related deaths occurred among core study mice, and final mean body weights of exposed male and female mice were similar to those of the controls. There were no chemical-related clinical findings. Pigment particles were present in the lungs of mice exposed to 2.5 mg/m(3) or greater. Accumulation of macrophages in alveolar spaces was observed in the lungs of 10 and 30 mg/m(3)males and females. The concentrations of nickel oxide in the lungs of exposed groups of mice were significantly greater than those in the lungs of control animals (males, 32 to 84 mg nickel/g lung; females, 31 to 71 mg/g lung). 13-WEEK STUDY IN RATS: Groups of 10 male and 10 female F344/N rats were exposed to 0, 0.6, 1.2, 2.5, 5, or 10 mg nickel oxide/m(3) (equivalent to 0, 0.4, 0.9, 2.0, 3.9, or 7.9 mg nickel/m(3)) by inhalation for 6 hours per day, 5 days per week for 13 weeks. Additional groups of 18 male and 18 female rats were exposed to 0, 0.6, 2.5, or 10 mg/m(3) for tissue burden studies. No exposure-related deaths occurred among core study rats, final mean body weights of exposed male and female rats were similar to those of the controls, and no clinical findings in any group were related to nickel oxide exposure. Lymphocyte, neutrophil, monocyte, and erythrocyte counts; hematocrit values; and hemoglobin and mean cell hemoglobin concentrations in exposed rats were minimally to mildly greater than those of the controls; these differences were most pronounced ironounced in females. Mean cell volumes in exposed rats were generally less than those in the controls. Absolute and relative lung weights of exposed groups of males and females were generally significantly greater than those of controls. Chemical-related nonneoplastic lesions were observed in the lungs of male and female rats exposed to concentrations of 2.5 mg/m(3) or higher, and the severity of these lesions generally increased with exposure concentration. Accumulation of alveolar macrophages, many of which contained black, granular pigment, was generally observed in all exposed groups of males and females, and increased incidences of inflammation occurred in males and females exposed to 2.5 mg/m(3) or higher. In addition, lymphoid hyperplasia and pigment occurred in the bronchial and mediastinal lymph nodes of 2.5, 5, and 10 mg/m(3) males and females. The concentration of nickel oxide in the lungs of 0.6, 2.5, and 10 mg/m(3)males was greater than in the lungs of controls at 4, 9, and 13 weeks, and nickel continued to accumulate in the lung at the end of the 13-week exposures (4 weeks, 33 to 263 mg nickel/g lung; 9 weeks, 53 to 400 mg/g lung; 13 weeks, 80 to 524 mg/g lung). 13-WEEK STUDY IN MICE: Groups of 10 male and 10 female B6C3F1 mice were exposed to 0, 0.6, 1.2, 2.5, 5, or 10 mg nickel oxide/m(3) by inhalation for 6 hours per day, 5 days per week for 13 weeks. Additional groups of six male and six female mice were exposed to 0, 0.6, 2.5, or 10 mg/m(3) for tissue burden studies. No exposure-related deaths occurred among core study animals, final mean body weights of exposed male and female mice were similar to those of the controls, and no clinical findings in any group were related to nickel oxide exposure. Hematocrit values and erythrocyte counts in 5 and 10 mg/m(3) females were minimally greater than those of the controls, as was the hemoglobin concentration in 5 mg/m(3) females. Absolute and relative lung weights of 10 mg/m(3) males and females were significantly greater than those of controls, and absolute and relative liver weights of 10 mg/m(3) males were significantly less than those of controls. Accumulation of alveolar macrophages, many of which contained pigment particles, occurred in all groups of mice exposed to nickel oxide. Inflammation (chronic active perivascular infiltrates or granulomatous) occurred in 2.5, 5, and 10 mg/m(3) males and females. In addition, lymphoid hyperplasia and pigment occurred in the bronchial lymph nodes of males and females exposed to 2.5 mg/m(3) or higher. The concentration of nickel in the lung was greater than that of controls in 0.6, 2.5, and 10 mg/m(3) males at 13 weeks (42 to 736 mg nickel/g lung). 2-YEAR STUDY IN RATS: Survival, Body Weights, Clinical Findings, and Hematology Groups of 65 male and 65 female F344/N rats were exposed to 0, 0.62, 1.25, or 2.5 mg nickel oxide/m(3) (equivalent to 0, 0.5, 1.0, or 2.0 mg nickel/m(3)) by inhalation for 6 hours per day, 5 days per week for 104 weeks. Survival of exposed male and female rats was similar to that of the controls. Mean body weights of 1.25 mg/m(3) females and 2.5 mg/m(3) males and females were slightly lower than those of the controls during the second year of the study. No chemical-related clinical findings were observed in male or female rats during the 2-year study. No chemical-related differences in hematology parameters were observed in male or female rats at the 15-month interim evaluation. Pathology Findings: Absolute and relative lung weights of 1.25 and 2.5 mg/m(3) males and females were significantly greater than those of the controls at 7 and 15 months. At 2 years, there were exposure-related increased incidences of alveolar/bronchiolar adenomas alveolar/bronchiolar adenoma or carcinoma (combined) in males and females. Incidences of atypical alveolar epithelial hyperplasia in the lungs generally increased with increasing exposure concentration in male and female rats. Chronic inflammation of the lung was observed in most exposed rats at 7 and 15 months and at 2 years; the incidences in exposed males and females at 2 years were significantly greater than those in the controls, and the severity of the inflammation increased in exposed groups. The incidences of pigmentation in the alveolus of exposed groups of males and females were significantly greater than those of the controls at 7 and 15 months and at 2 years. Pigmentation in the bronchial lymph nodes similar to that in the lungs was observed in all exposure groups with the exception of 0.62 mg/m(3)males and females at 7 months. Lymphoid hyperplasia was observed in the bronchial lymph nodes of 1.25 and 2.5 mg/m(3) males and females at 7 and 15 months, and the incidence at 2 years generally increased with exposure concentration. At 2 years, there was an exposure-related increase in the incidence of benign pheochromocytoma in males and females. The incidences of benign pheochromocytoma and adrenal medulla hyperplasia in 2.5 mg/m(3) females and the incidence of benign or malignant pheochromocytoma (combined) in 2.5 mg/m(3) males were significantly greater than those in the controls. Tissue Burden Analyses: Nickel concentrations in the lungs of exposed rats were greater than those in the controls at 7 and 15 months (7 months, 173 to 713 mg nickel/g lung; 15 months, 262 to 1,116 mg/g lung), and nickel concentrations increased with increasing exposure concentration and with time. 2-YEAR STUDY IN MICE: Survival, Body Weights, Clinical Findings, and Hematology Groups of 74 to 79 B6C3F1 mice were exposed to 0, 1.25, 2.5, or 5 mg nickel oxide/m(3) by inhalation for 6 hours per day, 5 days per week for 104 weeks. Survival of exposed male and female mice was similar to that of the controls. Mean body weights of 5 mg/m(3) females were slightly lower than those of the controls during the second year of the study. No chemical-related clinical findings were observed in male or female mice during the 2-year study. No chemical-related differences in hematology parameters were observed in male or female mice at the 15-month interim evaluation. Pathology Findings: At 2 years, the incidence of alveolar/bronchiolar adenoma in 2.5 mg/m(3) females was significantly greater than that of the controls, as was the incidence of alveolar/bronchiolar adenoma or carcinoma (combined) in 1.25 mg/m(3) females. Generally, incidences of chronic inflammation increased with exposure concentration in males and females at 7 and 15 months. Bronchialization of minimal severity in exposed animals and proteinosis were first observed at 15 months. At 2 years, the incidences of chronic inflammation, alveolar epithelial hyperplasia, and proteinosis in exposed groups of males and females were significantly greater than those of the controls. The severity of chronic inflammation increased with exposure concentration in females, and proteinosis was most severe in 5 mg/m(3) males and females. Pigment occurred in the lungs of nearly all exposed mice at 7 and 15 months and at 2 years, and the severity increased with exposure concentration. Lymphoid hyperplasia occurred in two animals after 7 months; at 15 months, lymphoid hyperplasia occurred in males exposed to 2.5 and 5 mg/m(3) and in all exposed groups of females. At 2 years, lymphoid hyperplasia occurred in some control animals, but this lesion was still observed more often in exposed males and females and the incidence increased with exposure concentration. Pigmentation was observed in the bronchial lymph nodes of exposed males and females at 7 and 15 months and in nearly all exposed animals at 2 years. Tissue Burden Analyses: Nickel concentrations in the lungs of exposed mice were significantly greater than those in the controls at 7 and 15 months (7 months, 162 to 1,034 mg nickel/g lung; 15 months, 331 to 2,258 mg/g lung), and nickel concentrations increased with increasing exposure concentration and with time. GENETIC TOXICOLOGY: No increase in the frequency of micronucleated normochromatic erythrocytes was observed in peripheral blood samples from male or female mice exposed to nickel oxide. CONCLUSIONS: Under the conditions of these 2-year inhalation studies, there was some evidence of carcinogenic activity of nickel oxide in male F344/N rats based on increased incidences of alveolar/bronchiolar adenoma or carcinoma (combined) and increased incidences of benign or malignant pheochromocytoma (combined) of the adrenal medulla. There was some evidence of carcinogenic activity of nickel oxide in female F344/N rats based on increased incidences of alveolar/bronchiolar adenoma or carcinoma (combined) and increased incidences of benign pheochromocytoma of the adrenal medulla. There was no evidence of carcinogenic activity of nickel oxide in male B6C3F1 mice exposed to 1.25, 2.5, or 5 mg/m(3). There was equivocal evidence of carcinogenic activity of nickel oxide in female B6C3F1 mice based on marginally increased incidences of alveolar/bronchiolar adenoma in 2.5 mg/m(3) females and of alveolar/bronchiolar adenoma or carcinoma (combined) in 1.25 mg/m(3) females. Exposure of rats to nickel oxide by inhalation for 2 years resulted in inflammation and pigmentation in the lung, lymphoid hyperplasia and pigmentation in the bronchial lymph nodes, and hyperplasia of the adrenal medulla (females). Exposure of mice to nickel oxide by inhalation for 2 years resulted in bronchialization, proteinosis, inflammation, and pigmentation in the lung and lymphoid hyperplasia and pigmentation in the bronchial lymph nodes. Synonyms: Bunsenite; C.I. 77777; green nickel oxide; mononickel oxide; nickel monoxide; nickel oxide sinter 75; nickel protoxide; nickel (II) oxide; nickel (T+) oxide; nickelous oxide
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PMID:NTP Toxicology and Carcinogenesis Studies of Nickel Oxide (CAS No. 1313-99-1) in F344 Rats and B6C3F1 Mice (Inhalation Studies). 1259 24

Tetrafluoroethylene is used in the production of polytetrafluoroethylene (Teflon(R)) and other polymers. Tetrafluoroethylene was nominated by the National Cancer Institute for toxicity and carcinogenicity studies based on the potential for human exposure to the chemical due to the large production volume and on the lack of adequate data for tetrafluoroethylene in the literature. Male and female F344/N rats and B6C3F1 mice were exposed to tetrafluoroethylene (98% to 99% pure) by whole body inhalation exposure for 16 days, 13 weeks, or 2 years. Genetic toxicity studies were conducted in mouse peripheral blood erythrocytes. 16-DAY STUDY IN RATS: Groups of five male and five female F344/N rats were exposed to 0, 312, 625, 1,250, 2,500, or 5,000 ppm tetrafluoroethylene by inhalation for 6 hours per day, 5 days per week for a total of 12 exposures during a 16-day period. All rats survived to the end of the study. The final mean body weights and body weight gains of males and females exposed to 5,000 ppm were significantly less than those of the controls. The mean body weight gain of females exposed to 2,500 ppm was also significantly less than that of the controls. There were no exposure-related clinical findings in male or female rats. There were no significant differences in hematology parameters that were considered to be related to tetrafluoroethylene exposure. Absolute and relative kidney weights of all exposed groups of males were significantly greater than those of the controls, as were those of females in the 2,500 and 5,000 ppm groups. The absolute kidney weight of females exposed to 1,250 ppm was also significantly greater than that of the controls. The relative liver weights of all exposed groups of males and the absolute liver weights of males in the 625 and 2,500 ppm groups were significantly greater than those of the controls. Increased incidences of renal tubule degeneration occurred in males and females exposed to 625 ppm or greater; this lesion was located predominantly at the corticomedullary junction. The severity of degeneration increased with increasing exposure concentration and was slightly greater in males than females. 16-DAY STUDY IN MICE: Groups of five male and five female B6C3F1 mice were exposed to 0, 312, 625, 1,250, 2,500, or 5,000 ppm tetrafluoroethylene by inhalation for 6 hours per day, 5 days per week for a total of 12 exposures during a 16-day period. All mice survived to the end of the study. Final mean body weights and body weight gains of all exposed groups of mice were similar to those of the controls. There were no exposure-related clinical findings in male or female mice. There were no significant differences in hematology parameters that were considered to be related to tetrafluoroethylene exposure. The absolute and relative liver weights of females exposed to 5,000 ppm were significantly greater than those of the controls, as was the absolute kidney weight of females in that group and the absolute liver weight of females in the 2,500 ppm group. Renal tubule karyomegaly was observed in male and female mice in the 1,250, 2,500, and 5,000 ppm groups, and the severity of this lesion increased with increasing exposure concentration. Karyomegaly was located predominantly in the inner renal cortex. 13-WEEK STUDY IN RATS: Groups of 10 male and 9 or 10 female F344/N rats were exposed to 0, 312, 625, 1,250, 2,500, or 5,000 ppm tetrafluoroethylene by inhalation for 6 hours per day, 5 days per week, for 13 weeks. All rats survived to the end of the study. The final mean body weight and body weight gain of males exposed to 5,000 ppm were significantly less than those of the controls, as was the mean body weight gain of females in this exposure group. There were no clinical findings attributed to exposure to tetrafluoroethylene. Exposure of rats to tetrafluoroethylene resulted in a concentration-dependent normocytic, normochromic, nonresponsive anemia consistent with a secondary hypoproliferative anemia. An exposure concentration-dependent proteinuria also occurred, consistent with renal tubule th renal tubule degeneration observed histopathologically. The absolute and relative liver weights of all exposed groups of males and of females in the 5,000 ppm group were significantly greater than those of the controls. The absolute and relative right kidney weights of males and females exposed to 1,250 ppm or greater and of females in the 625 ppm group were also significantly greater than those of the controls. There were no differences in sperm morphology or vaginal cytology parameters between control and exposed groups of rats. Incidences of renal tubule degeneration in males exposed to 625 ppm or greater and in females exposed to 2,500 or 5,000 ppm were significantly greater than those in the controls. Renal lesions were similar to those observed in the 16-day study and were located predominantly at the corticomedullary junction. 13-WEEK STUDY IN MICE: Groups of 10 male and 10 female B6C3F1 mice were exposed to 0, 312, 625, 1,250, 2,500, or 5,000 ppm tetrafluoroethylene by inhalation for 6 hours per day, 5 days per week, for 13 weeks. All mice survived to the end of the study. Final mean body weights and body weight gains of all exposed groups of male and female mice were generally similar to those of the controls. There were no clinical findings that were considered to be related to tetrafluoroethylene exposure. Exposure of mice to tetrafluoroethylene resulted in a concentration-dependent normocytic, normochromic, nonresponsive anemia, consistent with a secondary hypoproliferative anemia, and in polyuria. Differences in sperm morphology parameters and estrous cycle lengths were not considered to be exposure related. Incidences of karyomegaly of the renal tubule epithelial cells in male and female mice exposed to 1,250 ppm or greater were significantly greater than those in the controls. Karyomegaly was similar to that observed in the 16-day study and was observed primarily in the inner renal cortex. 2-YEAR STUDY IN RATS: Groups of 60 male rats were exposed to 156, 312, or 625 ppm and groups of 60 female rats were exposed to 312, 625, or 1,250 ppm tetrafluoroethylene by inhalation for 6 hours per day, 5 days per week, for 104 weeks, with an observation period of 11 days following the final exposure. Ten male and ten female rats from each exposure group were evaluated at 15 months for organ weights and clinical pathology. Survival, Body Weights, and Clinical Findings: Survival rates of males in the 625 ppm group and of all exposed groups of females were significantly less than those of the controls. Mean body weights of males exposed to 625 ppm were lower than those of the controls from week 81 until the end of the study, and the mean body weight of 1,250 ppm females was slightly lower than that of the controls at the end of the study. The only clinical finding associated with exposure to tetrafluoroethylene was opacity of the eyes in exposed groups of female rats; this change was observed microscopically as cataracts. Hematology, Clinical Chemistry, and Urinalysis: At the 15-month interim evaluation, there were no differences in hematology, clinical chemistry, or urinalysis parameters that were considered to be related to tetrafluoroethylene exposure. Pathology Findings: The absolute and relative kidney weights of males exposed to 625 ppm and females exposed to 1,250 ppm and the absolute kidney weight of females exposed to 625 ppm were significantly greater than those of the controls at the 15-month interim evaluation. At 15 months, renal tubule hyperplasia was observed in one male exposed to 312 ppm and one male and one female exposed to 625 ppm; oncocytic hyperplasia was observed in one female exposed to 1,250 ppm. At the end of the study, incidences of renal tubule adenoma were greater in males and females exposed to 312 ppm or greater than those in the controls. This exposure-related increase was confirmed by examination of step sections (extended evaluations). At the end of the study, the incidences of renal tubule hyperplasia in males exposed to 625 ppm and females exposed to 1,250 ppm were significantly greater than those in the controls. The incidences of renal tubule adenoma and renal tubule adenoma or carcinoma (combined) in the extended evaluations and in the standard and extended evaluations (combined) in the 1,250 ppm female group and the 625 ppm male group were significantly greater than those in the controls, and the incidences occurred with significant positive trends. Oncocytic hyperplasia was observed at the end of the study in one male exposed to 312 ppm and in three females exposed to 1,250 ppm. At 15 months and at the end of the study, the incidences of renal tubule degeneration in all exposed groups of males and in females in the 625 and 1,250 ppm groups were greater than those in the controls. Renal tubule degeneration was similar to that observed in the 13-week study and was located predominantly at the corticomedullary junction. The severity of nephropathy generally increased with increasing exposure concentration in male rats at 15 months and 2 years. The absolute and relative liver weights of females in the 1,250 ppm group and the absolute liver weight of females exposed to 625 ppm were significantly greater than those of the controls at the 15-month interim evaluation. At 2 years, the incidences of hepatocellular carcinoma and hepatocellular adenoma or carcinoma (combined) in males exposed to 312 ppm, the incidences of hepatocellular adenoma and adenoma or carcinoma (combined) in females in all exposed groups, and the incidences of hepatocellular carcinoma in females exposed to 312 or 625 ppm were significantly greater than those in the controls. Also at 2 years, the incidence of hemangiosarcoma in females exposed to 625 ppm was significantly greater than that in the controls. In all exposed groups of males, the incidences of clear cell foci at 15 months were greater than those in the controls; at 2 years, the incidences of eosinophilic foci in all exposed groups of males and the incidences of basophilic and mixed cell foci in males in the 312 and 625 ppm groups were greater than those in the controls. The incidences of mixed cell foci at 15 months in females exposed to 625 or 1,250 ppm and at 2 years in females exposed to 1,250 ppm were also significantly greater than those in the controls. At the end of the 2-year study, increased incidences of cystic degeneration occurred in the liver of all exposed groups of males, and increased incidences of hepatic angiectasis were observed in exposed groups of females. Incidences of mononuclear cell leukemia in males exposed to 156 ppm and in all exposed groups of females were significantly greater than those in the controls. Incidences of cataracts in females exposed to 1,250 ppm were greater than those in the controls at the end of the 2-year study. At the end of the study, there were slight increases in the incidences of testicular interstitial cell adenoma in rats exposed to 312 or 625 ppm. 2-YEAR STUDY IN MICE: Groups of 58 male and 58 female B6C3F1 mice were exposed to 0, 312, 625, or 1,250 ppm tetrafluoroethylene by inhalation for 6 hours per day, 5 days per week, for 95 to 96 weeks. Ten male and ten female mice from each exposure group were evaluated at 15 months for organ weights. Survival, Body Weights, and Clinical Findings: The survival rates of all exposed groups of males and females were significantly less than those of the controls. Because of the reduced survival due to exposure-related liver neoplasms, the study was terminated during week 96. Mean body weights of exposed groups of males and females were generally similar to those of the controls, except at the end of the study, when they were somewhat less than those of the controls. There were no clinical findings related to tetrafluoroethylene exposure. Pathology Findings: At the 15-month interim evaluation, there were no differences in absolute or relative kidney, liver, or lung weights between exposed and control groups of mice. At the end of the study, the incidences of multifocal coagulative necrosis of the liver were increased in males in the 625 and 1,250 ppm groups. Also at the end of the study, females in all exposed groups had greater incidences of hematopoietic cell proliferation in the liver than the controls. Angiectasis occurred in all exposed groups of males and females at 15 months and at the end of the study. At the 15-month interim evaluation, hemangiosarcomas were observed in three males exposed to 1,250 ppm and in one female exposed to 312 ppm. The incidences of hemangiosarcoma in all exposed groups of males and females at the end of the study were significantly greater than those in the controls and exceeded the historical chamber control ranges. Also at the end of the study, the incidences of hemangioma in males and females exposed to 312 ppm and in males exposed to 625 ppm were also significantly greater than those in the controls and exceeded the range in historical chamber controls. At 15 months, hepatocellular adenomas and carcinomas occurred in control males and all exposed groups of males and females. Females exposed to 625 or 1,250 ppm had significantly greater incidences of eosinophilic foci than the controls at the 15-month interim evaluation. At the end of the study, the incidences of eosinophilic foci in males exposed to 625 or 1,250 ppm and in females exposed to 312 or 625 ppm were significantly greater than those in the controls. In male and female mice, increased incidences of a variety of hepatocellular neoplasms, including adenomas, multiple adenomas, carcinomas, and multiple carcinomas, were considered related to tetrafluoroethylene exposure. At the end of the study, the incidences of histiocytic sarcoma (all organs) in all exposed groups of males and females were significantly greater than those in the controls and exceeded the historical control ranges for all organs. The greatest incidences of histiocytic sarcomas were observed in the liver and lung, but these neoplasms were also observed in the spleen, lymph nodes, bone marrow, and kidney. Significantly increased incidences of renal tubule dilatation (males) and karyomegaly (males and females), located predominantly in the inner cortex, were observed in mice exposed to 625 or 1,250 ppm at 15 months. At the end of the study, the increased incidences of dilatation and karyomegaly in all exposed groups of males and of karyomegaly in 1,250 ppm females were generally significant. Incidences of hematopoietic cell proliferation in the spleen of all exposed groups of males and females were significantly greater than those in the controls at the end of the study. Additionally, the severity of this lesion increased with increasing exposure concentration. GENETIC TOXICOLOGY: No increases in the frequency of micronucleated erythrocytes were observed in peripheral blood samples obtained from male and female mice at the end of the 13-week inhalation study of tetrafluoroethylene. CONCLUSIONS: Under the conditions of these 2-year inhalation studies, there was clear evidence of carcinogenic activity of tetrafluoroethylene in male F344/N rats based on increased incidences of renal tubule neoplasms (mainly adenomas) and hepatocellular neoplasms. There was clear evidence of carcinogenic activity of tetrafluoroethylene in female F344/N rats based on increased incidences of renal tubule neoplasms, liver hemangiosarcomas, hepatocellular neoplasms, and mononuclear cell leukemia. There was clear evidence of carcinogenic activity of tetrafluoroethylene in male and female B6C3F1 mice based on increased incidences of liver hemangiomas and hemangiosarcomas, hepatocellular neoplasms, and histiocytic sarcomas. Slight increases in the incidences of mononuclear cell leukemia and testicular interstitial cell adenomas in male rats may have been related to exposure to tetrafluoroethylene. Exposure of rats to tetrafluoroethylene resulted in increased incidences of renal tubule hyperplasia and degeneration in males and females, increased severity of kidney nephropathy in males, and increased incidences of liver angiectasis and cataracts in females. Exposure of mice to tetrafluoroethylene resulted in increased incidences of hematopoietic cell proliferation of the liver in females, liver angiectasis in males and females, renal tubule dilatation in males, renal tubule karyomegaly in males and females, and splenic hematopoietic cell proliferation in males and females. Synonyms: Perfluoroethylene; tetrafluoroethene; 1,1,2,2-tetrafluoroethylene; TFE
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PMID:NTP Toxicology and Carcinogenesis Studies of Tetrafluoroethylene (CAS No. 116-14-3) in F344 Rats and B6C3F1 Mice (Inhalation Studies). 1259 25

Triethanolamine is widely used as an ingredient in emulsifiers, thickeners, wetting agents, detergents, and alkalinizing agents in cosmetic products; as a chemical intermediate for anionic and nonionic surfactants and surface active agents in household cleaning agents, textiles, herbicides, pharmaceutical ointments, and other products; as a vulcanization accelerator in the manufacture of rubber; 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. Dermal application was chosen as the route of exposure to mimic the principal means of human exposure to triethanolamine and because considerable systemic exposure is achieved with this route. Male and female F344/N rats and B6C3F1 mice received triethanol amine (purity 98% or greater) by dermal application for 13 weeks or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, cultured Chinese hamster ovary cells, Drosophila melano gaster, and mouse peripheral blood erythrocytes. 13-WEEK STUDY IN RATS: Groups of 10 male and 10 female rats were topically administered 0, 125, 250, 500, or 1,000 mg triethanolamine per kilogram body weight in acetone or 2,000 mg/kg neat triethanolamine, 5 days per week, for 13 weeks. All rats survived to the end of the study. Final mean body weights and weight gains of males and females administered 2,000 mg/kg and the mean body weight gain of females administered 1,000 mg/kg were significantly less than those of the vehicle controls. Clinical observations included irritation, scaliness, and crustiness of the skin at the site of application for males and females. Males also had discoloration, and two males administered 2,000 mg/kg had ulceration at the site of application. Changes in clinical pathology parameters were minor and consistent with inflammation at the site of application. Kidney weights were generally greater in males and females administered 500, 1,000, or 2,000 mg/kg than in the vehicle controls. Microscopic lesions attributed to triethanolamine administration included acanthosis and inflammation at the site of application, nephropathy in females, and hypertrophy of the pituitary gland pars intermedia in males and females. These lesions generally occurred with dose-related increases in incidence and severity in males and females. 13-WEEK STUDY IN MICE: Groups of 10 male and 10 female mice were topically administered 0, 250, 500, 1,000, or 2,000 mg triethanolamine per kilogram body weight in acetone or 4,000 mg/kg neat triethanolamine, 5 days per week, for 13 weeks. All mice survived to the end of the study. The final mean body weight and weight gain of males in the 250 mg/kg group were less than those of the vehicle controls. Clinical findings were observed only in mice in the 4,000 mg/kg groups and included scaliness, irritation, and discoloration at the site of triethanolamine application for males and females and skin erosion at this site in one male. The absolute kidney and liver weights of males and females administered 4,000 mg/kg were greater than those of the vehicle controls; relative kidney weights of males administered 1,000 mg/kg or greater and females in all dosed groups were also greater than those of the vehicle controls. Microscopic examination of the skin of dosed mice indicated acanthosis and inflammation at the site of application. Acanthosis occurred in all dosed groups and in one vehicle control female; the severity increased with increasing dose in males and females. Inflammation was observed in males and females in the 4,000 mg/kg groups and in one female in the 2,000 mg/kg group. 2-YEAR STUDY IN RATS: Based on the presence of acanthosis and inflammation at the site of application at the higher doses in the 13-week study, triethanolamine doses selected for the 2-year study in rats were 32, 63, and 125 mg/kg for malesr males and 63, 125, and 250 mg/kg for females. Groups of 60 male and 60 female rats were topically administered triethanolamine in acetone 5 days per week for 103 weeks. Ten male and ten female rats from each group were evaluated at 15 months for organ weights and histopathology. Survival, Body Weights, Clinical Findings, and Organ Weights: The survival rate of females in the 250 mg/kg group was slightly less than that of the vehicle controls. The mean body weight of females administered 250 mg/kg ranged from 9&percnt; to 12&percnt; less than that of the vehicle controls between weeks 73 and 93. Male and female rats receiving triethanolamine had irritated skin at the site of application; in dosed females, the site of application also had a crusty appearance. The number of animals in which these findings were observed increased with increasing dose. At the 15-month interim evaluation, the absolute left and right kidney weights and relative right kidney weight of females administered 250 mg/kg were significantly greater than those of the vehicle controls. Pathology Findings: The incidence of acanthosis at the site of application in males administered 125 mg/kg and the incidences of acanthosis, inflammation, and ulceration in dosed females were greater than in the vehicle controls at the 15-month interim evaluation and at the end of the 2-year study. Males in the 125 mg/kg group also had greater incidences of inflammation and ulceration than the vehicle controls, and females receiving 125 or 250 mg/kg had greater incidences of epidermal erosion than the vehicle controls at 2 years. There were no skin neoplasms at or away from the site of application that were considered related to treatment with triethanolamine. At the end of the study, renal tubule adenomas were observed in seven dosed males and in one vehicle control female and one female in the 63 mg/kg group. One male in the 125 mg/kg group and one female in the 250 mg/kg group had renal tubule hyperplasia. Extended (step-section) evaluation of the kidneys of all male rats revealed additional renal tubule adenomas in one vehicle control male, one male in the 32 mg/kg group, two males in the 63 mg/kg group, and three males in the 125 mg/kg group (including one male from the 15-month interim evaluation). An oncocytoma was also identified in one male in the 32 mg/kg group. Hyperplasia was identified in eight additional vehicle control males and in 19 additional dosed males. The total incidences (combined standard and extended evaluations) of renal tubule adenoma in dosed male rats were slightly greater than the vehicle control incidence (vehicle control, 1/50; 32 mg/kg, 2/50; 63 mg/kg, 6/49; 125 mg/kg, 4/50). The total incidence of hyperplasia in dosed and vehicle control males was similar (9/50, 8/50, 7/49, 6/50). The severity of hyperplasia in males in the 32 and 125 mg/kg groups was greater than that in the vehicle controls. 2-YEAR STUDY IN MICE: Based on dose-related inflammation at the site of application in the 13-week study, triethanolamine doses selected for the 2-year study in mice were 200, 630, and 2,000 mg/kg for males and 100, 300, and 1,000 mg/kg for females. Groups of 60 male and 60 female mice were topically administered triethanolamine in acetone 5 days per week for 103 weeks. Ten male and ten female mice from each group were evaluated at 15 months for organ weights and histopathology. Survival, Body Weights, Clinical Findings, and Organ Weights: Survival rates of all dosed groups of males and females were similar to those of the vehicle controls. The mean body weight of males administered 2,000 mg/kg ranged from 8&percnt; to 10&percnt; less than that of the vehicle controls from week 69 through the end of the study. Clinical findings included irritation and discoloration of the skin at the site of application for most males in the 2,000 mg/kg group and a few females in the 1,000 mg/kg group; males administered 200 or 630 mg/kg also had skin irritation. At the 15-month interim evaluation, the right kidney weights of male mice that received 630 or 2,000 mg/kg and the left kidney weights of males that received 2,000 mg/kg were significantly greater than those of the vehicle controls. Pathology Findings: Acanthosis and inflammation of the skin were observed at the site of application in male and female mice at the 15-month interim evaluation and at the end of the 2-year study. In males in the 2,000 mg/kg group, the incidences of both lesions were significantly greater than those in the vehicle controls at both time points; however, the severities of acanthosis and inflammation did not increase with dose. At the end of the study, the incidence of inflammation in females in the 1,000 mg/kg group was significantly greater than that in the vehicle controls. One vehicle control male and two males in each of the 630 and 2,000 mg/kg groups had ulcers at the site of application. At the 15-month interim evaluation, hepatocellular carcinomas were observed in dosed and vehicle control males and hepatocellular adenomas in dosed and vehicle control males and females; however, the incidences were not dose related. Nonneoplastic lesions observed at 15 months included foci of cellular alteration in a few dosed males and females; eosinophilic foci were also observed in two vehicle control females. At the end of the 2-year study, females in the 1,000 mg/kg group had significantly greater incidences of hepatocellular adenoma and multiple adenomas and a greater combined incidence of hepatocellular adenoma and carcinoma than the vehicle controls (adenoma: vehicle control, 22/50; 100 mg/kg, 22/50; 300 mg/kg, 24/50; 1,000 mg/kg, 40/50; multiple adenomas: 11/50, 9/50, 13/50, 29/50; combined adenoma and carcinoma: 23/50, 26/50, 28/50, 41/50). Females in the 300 mg/kg group had significantly greater incidences of hepatocellular carcinoma (1/50, 4/50, 7/50, 5/50) and eosinophilic foci (9/50, 10/50, 18/50, 16/50) than the vehicle controls. Incidences of hepatocellular adenoma and multiple adenomas in males in the 2,000 mg/kg group were significantly greater than those in the vehicle controls (adenoma: vehicle control, 27/50; 200 mg/kg, 27/50; 630 mg/kg, 29/50; 2,000 mg/kg, 37/50; multiple adenomas: 17/50, 18/50, 17/50, 29/50). Three males in the 2,000 mg/kg group had hepatoblastomas, and males in this group also had significantly greater incidences of hepatocellular neoplasms (combined) (adenoma, carcinoma, and hepatoblastoma: 31/50, 34/50, 33/50, 42/50) and eosinophilic foci (10/50, 17/50, 11/50, 23/50) than the vehicle controls. Male mice had a pattern of nonneoplastic liver lesions along with silver-staining helical organisms within the liver which suggested an infection with Helicobacter hepaticus. With polymerase chain reaction-based assays and culture, the presence of an organism compatible with H. hepaticus was confirmed. An increased incidence of hepatocellular neoplasms in male mice has been shown to be associated with H. hepaticus infection when hepatitis is also present. Therefore, interpretation of the increased incidence of hepatocellular neoplasms in mice was confounded. GENETIC TOXICOLOGY: Triethanolamine was not mutagenic in any of the in vitro or in vivo short-term tests performed by the NTP. It did not induce mutations in Salmonella typhimurium, and no induction of sister chromatid exchanges or chromosomal aberrations in cultured Chinese hamster ovary cells exposed to triethanolamine was noted. These in vitro tests were 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 and female mice that received dermal applications of triethanolamine for 13 weeks. CONCLUSIONS: Under the conditions of these dermal studies, there was equivocal evidence of carcinogenic activity of triethanolamine in male F344/N rats based on a marginal increase in the incidence of renal tubule cell adenoma. There was no evidence of carcinogenic activity in female F344/N rats receiving 63, 125, or 250 mg triethanolamine per kilogram body weight. The study in male and female B6C3F1 mice was considered inadequate, because the presence of a Helicobacter hepaticus infection complicated inter pretation of the relationship between triethanolamine administration and liver neoplasms in these animals. Dosed rats and mice had varying degrees of acanthosis and inflammation, dosed rats had ulceration, and dosed female rats had epidermal erosion at the site of skin application. Synonyms: Nitrilo-2,2',2"-triethanol; 2,2',2"-nitrilotriethanol; 2,2',2"-nitrilotrisethanol; TEA; triaethanolamin-NG; triethanolamin; triethylolamine; tri(hydroxyethyl)amine; 2,2',2"-trihydroxytriethylamine; trihydroxytriethylamine; tris(hydroxyethyl)amine; tris(2-hydroxyethyl)amine; triethylolamine; trolamine Trade Names: Daltogen; Sterolamide; Thiofaco T-35
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PMID:NTP Toxicology and Carcinogenesis Studies of Triethanolamine (CAS No. 102-71-6) in F344 Rats and B6C3F1 Mice (Dermal Studies). 1259 26

Isobutyl nitrite is used to a limited extent as an intermediate in the syntheses of aliphatic nitrites. It is also an ingredient of various incenses or room odorizers and is used as a euphoric. The chemical has also been used as a jet propellant and in the preparation of fuels. Isobutyl nitrite was nominated by the Consumer Product Safety Commission to the NTP for toxicology and carcinogenicity studies because of its possible contribution to the high incidence of Kaposi's sarcoma among male homosexual acquired immune deficiency syndrome patients and because of the lack of available data on the potential carcinogenicity of isobutyl nitrite. Male and female F344/N rats and B6C3F1 mice were exposed to isobutyl nitrite (purity of 93% or greater) by inhalation for 16 days, 13 weeks, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, cultured Chinese hamster ovary cells, Drosophila melanogaster, and mouse peripheral blood. 16-DAY STUDY IN RATS: Groups of five male and five female F344/N rats were exposed to 0, 100, 200, 400, 600, or 800 ppm (approximately 420, 840, 1,700, 2,500, or 3,300 mg/m(3)) isobutyl nitrite by inhalation for 6 hours per day, 5 days per week for a total of 12 exposures during a 16-day period. All males and females exposed to 600 or 800 ppm and one 400 ppm female died on the first day of the study. Final mean body weights and mean body weight gains of 400 ppm males and females were significantly lower than those of the controls. Clinical findings observed in 400 ppm males and females included ocular discharge, lethargy, hunched posture, and rough coats. Absolute and relative lung weights of all exposed groups of males and of 200 and 400 ppm females were less than those of the controls. Chemical-related hyperplasia of the bronchial epithelium was observed in 200 and 400 ppm males and females and hyperplasia of the nasal turbinate epithelium was observed in rats exposed to 400 ppm or less. Hemosiderin pigmentation was observed in the spleen of 200 and 400 ppm males and females and bone marrow hematopoietic hyperplasia was observed in rats exposed to 400 ppm or less. 16-DAY STUDY IN MICE: Groups of five male and five female B6C3F1 mice were exposed to 0, 100, 200, 400, 600, or 800 ppm (approximately 420, 840, 1,700, 2,500, or 3,300 mg/m(3)) isobutyl nitrite by inhalation for 6 hours per day, 5 days per week for a total of 12 exposures during a 16-day period. Three males and four females exposed to 800 ppm died before the end of the study. Final mean body weights and mean body weight gains of 600 and 800 ppm males and females were significantly lower than those of the controls. Mice exposed to 400 ppm or greater were lethargic and exhibited hunched posture and rough coats. Absolute and relative lung weights of 600 and 800 ppm males and the relative lung weight of 600 ppm females were significantly greater than those of the controls. Chemical-related hyperplasia of the bronchiolar epithelium was observed in all exposed groups of males and females. Lymphocytic atrophy of the spleen and thymus was observed in males and females exposed to 400 ppm or greater. 13-WEEK STUDY IN RATS: Groups of 10 male and 10 female F344/N rats were exposed to 0, 10, 25, 75, 150, or 300 ppm (approximately 42, 105, 315, 630, or 1,260 mg/m(3)) isobutyl nitrite by inhalation for 6 hours per day, 5 days per week for 13 weeks. All rats survived to the end of the study. Final mean body weights and mean body weight gains of 300 ppm males and females were significantly lower than those of the controls, as was the mean body weight gain of 150 ppm females. Clinical findings observed during the study included ruffled fur in 300 ppm males and females, hypoactivity in 300 ppm males, and hyperactivity in 150 and 300 ppm females. A very mild chemical-related methemoglobinemia and anemia occurred in male and female rats in the 75, 150, and 300 ppm groups. Hematopoietic hyperplasia occurred in the bone marrow of all exposed groups of males and females and was considered to be a secondary response to the anemia and methed methemoglobinemia. There was minimal hemosiderin pigment accumulation in the spleens of males and females exposed to 75 ppm or greater, mild to moderate epithelial cell hyperplasia of the nasal mucosa was observed in 300 ppm males and females, and minimal hyperplasia occurred in 150 ppm males and females. Hyperplasia of the bronchial epithelium was observed in 300 ppm males and females. 13-WEEK STUDY IN MICE: Groups of 10 male and 10 female B6C3F1 mice were exposed to 0, 10, 25, 75, 150, or 300 ppm (approximately 42, 105, 315, 630, or 1,260 mg/m(3)) isobutyl nitrite by inhalation for 6 hours per day, 5 days per week for 13 weeks. There were no chemical-related deaths. Final mean body weights and mean body weight gains of 150 and 300 ppm females were significantly less than those of the controls. Final mean body weights and mean body weight gains of exposed groups of males were similar to those of the controls. There were no chemical-related clinical findings. A very mild chemical-related methemoglobinemia occurred in male and female mice in the 150 and 300 ppm groups. A very mild anemia occurred in the 300 ppm groups. In the lung, increased incidences of mild to moderate hyperplasia of the bronchiolar epithelium occurred in males and females exposed to 300 ppm. Minimal hyperplasia occurred in males exposed to 75 ppm or greater and in females exposed to 150 ppm. Minimal epithelial cell hyperplasia of the nasal mucosa was observed in 300 ppm males. Increased hematopoiesis of the spleen, secondary to the hematotoxicity, occurred in males exposed to 75 ppm or greater and in females exposed to 150 or 300 ppm. Increased hemosiderosis of the spleen occurred in males exposed to 300 ppm and in females exposed to 75 ppm or greater. 2-YEAR STUDY IN RATS: Based on the low final mean body weights, anemia, and the mild to moderate nasal mucosal lesions and the hyperplastic bronchial lesions observed in 300 ppm males and females, isobutyl nitrite exposure concentrations selected for the 2-year inhalation study in rats were 37.5, 75, and 150 ppm. Groups of 56 male and 56 female rats were exposed to 0, 37.5, 75, or 150 ppm (equivalent to 0, 158, 315, or 630 mg/m(3)) isobutyl nitrite by inhalation for 6 hours per day, 5 days per week, for 103 weeks. Ten male and 10 female rats from each group were evaluated at 15 months for clinical pathology and histopathology. Survival, Body Weights, Clinical Findings, Hematology, and Clinical Chemistry: Survival rates of exposed groups of rats were greater than those of the controls, and the survival rates of 75 and 150 ppm males were significantly greater than that of the control. Mean body weights of 150 ppm males and females were 3&percnt; to 11&percnt; lower than those of the controls throughout the course of the study. There were no clinical findings considered to be related to isobutyl nitrite exposure. A very mild methemoglobinemia and anemia occurred in male and female rats exposed to 75 or 150 ppm. Pathology Findings: Incidences of alveolar/bronchiolar adenoma and alveolar/bronchiolar adenoma or carcinoma (combined) occurred with significant positive trends in exposed males and females, and the incidences of these neoplasms in 75 ppm males and in 150 ppm males and females were significantly greater than those in the controls. The incidence of alveolar/bronchiolar carcinoma was significantly greater in 150 ppm male rats than that in the controls. The incidences of alveolar epithelial hyperplasia were also increased in 75 and 150 ppm males and in all exposed groups of females. The incidences of mononuclear cell leukemia in exposed groups of males and females were significantly less than those in the controls. 2-YEAR STUDY IN MICE: Based on the low final mean body weight of 300 ppm females and the mild to moderate bronchiolar hyperplasia observed in 300 ppm males and females, isobutyl nitrite exposure concentrations selected for the 2-year inhalation study in mice were 37.5, 75, and 150 ppm. Groups of 60 male and 60 female mice were exposed to 0, 37.5, 75, or 150 ppm (equivalent to 0, 158, 315, or 630 mg/m(3)) isobutyl nitrite by inhalation for 6 hours per day, 5 days per week, for 103 weeks. As many as 10 male and 10 female mice from each group were evaluated at 15 months for clinical pathology and histopathology. Survival, Body Weights, Clinical Findings, and Hematology and Clinical Chemistry: Survival rates of exposed groups of males were similar to those of the controls. Survival rates of exposed groups of females were greater than those of the controls, and the survival rate in 37.5 ppm females was significantly greater than that of the controls. Mean body weights of exposed groups of males and of 37.5 and 75 ppm females were similar to those of the controls throughout the study. Mean body weights of 150 ppm females were lower than those of the controls from week 20 until the end of the study. There were no biologically significant clinical findings noted in the 2-year study in mice. A very mild methemoglobinemia and anemia occurred in male and female mice exposed to 75 or 150 ppm. Pathology Findings: Incidences of alveolar/bronchiolar adenoma and alveolar/bronchiolar adenoma or carcinoma (combined) occurred with significant positive trends in exposed males and females, and the incidences of these neoplasms were significantly greater than those in the controls in 75 ppm males and in 150 ppm males and females. Incidences of alveolar epithelial hyperplasia were significantly increased in 75 and 150 ppm male and female mice. Thyroid gland follicular cell adenoma occurred with a significant positive trend in male mice; the incidences of thyroid gland follicular cell hyperplasia were increased in all exposed groups of males, and the incidences in males exposed to 37.5 or 150 ppm were significantly greater than those in the controls. Incidences of serous exudate and olfactory epithelium atrophy in the nose of 150 ppm females were significantly greater than those in the controls. Incidences of minimal to mild hemosiderin pigment in the spleen of 75 and 150 ppm male mice were significantly greater than those in the controls. GENETIC TOXICOLOGY: Isobutyl nitrite was found to be mutagenic in vitro and in vivo. It induced base-pair substitution mutations in Salmonella typhimurim strains TA100 and TA1535 and sister chromatid exchanges and chromosomal aberrations in cultured Chinese hamster ovary cells. Positive responses in the S. typhimurium tests required S9 activation, but isobutyl nitrite induced chromosomal effects in cultured Chinese hamster ovary cells with and without S9. In vivo, no induction of sex-linked recessive lethal mutations was noted in the germ cells of male Drosophila melanogaster exposed to isobutyl nitrite via feeding or injection. However, significant increases in micronucleated normochromatic erythrocytes were observed in the peripheral blood of male and female mice treated with isobutyl nitrite for 90 days by inhalation. CONCLUSIONS: Under the conditions of these 2-year inhalation studies, there was clear evidence of carcinogenic activity of isobutyl nitrite in male and female F344/N rats based on the increased incidences of alveolar/bronchiolar adenoma and alveolar/bronchiolar adenoma or carcinoma (combined). There was some evidence of carcinogenic activity of isobutyl nitrite in male and female B6C3F1 mice based on the increased incidences of alveolar/bronchiolar adenoma and alveolar/bronchiolar adenoma or carcinoma (combined) in males and females. The increased incidence of thyroid gland follicular cell adenoma in male mice may have been related to isobutyl nitrite exposure. Exposure of rats and mice to isobutyl nitrite by inhalation for 2 years resulted in increased incidences of alveolar epithelial hyperplasia (male and female rats and mice), thyroid gland follicular cell hyperplasia and splenic hemosiderin pigmentation (male mice), and serous exudate and atrophy of the olfactory epithelium of the nose (female mice). Exposure of rats to isobutyl nitrite by inhalation for 2 years resulted in decreased incidences of mononuclear cell leukemia in males and females.
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PMID:NTP Toxicology and Carcinogenesis Studies of Isobutyl Nitrite (CAS No. 542-56-3) in F344 Rats and B6C3F1 Mice (Inhalation Studies). 1259 27

Acetonitrile is used primarily as a solvent in extractive distillation and crystallization of pharmaceutical and agricultural products and as a catalyst in chemical reactions. It was nominated for testing by the National Cancer Institute due to its presence in drinking water supplies and the environment, due to lack of information on the carcinogenicity of alkyl cyanides, and because of widespread worker exposure. Male and female F344/N rats and B6C3F1 mice were exposed to acetonitrile (at least 99% pure) by inhalation for 13 weeks or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, cultured Chinese hamster ovary cells, and peripheral blood of B6C3F1 mice exposed to acetonitrile for 13 weeks. 13-WEEK STUDY IN RATS: Groups of 10 male and 10 female F344/N rats were exposed to 0, 100, 200, 400, 800, or 1,600 ppm (equivalent to 0, 168, 335, 670, 1,340, or 2,681 mg/m(3)) acetonitrile by inhalation for 6 hours per day, 5 days per week for 13 weeks. Six male and three female rats that received 1,600 ppm and one male that received 800 ppm died during the study. At exposure concentrations up to and including 800 ppm, the final mean body weights and body weight gains were generally similar to those of the controls. At 1,600 ppm, body weight gain was lower and the final mean body weights of both males and females were significantly lower than those of the controls. Hypoactivity and ruffled fur were observed during the first week of the study in males receiving 800 ppm and males and females receiving 1,600 ppm. Additional clinical findings in 1,600 ppm males that died during week 1 were ataxia, abnormal posture, and clonic convulsions. Clinical pathology findings included nonresponsive, normocytic, normochromic anemia in 1,600 ppm males and females and in 800 ppm females, and decreased triiodothyronine (T3) concentrations in 1,600 ppm females. Absolute and relative thymus weights were significantly lower than those of the controls in the 800 and 1,600 ppm males and females. Females exposed to 1,600 ppm had significantly greater absolute and relative heart, kidney, and liver weights than those of the controls. There were no clear exposure-related histopathologic effects, although pulmonary congestion and edema and hemorrhage in the lung and brain were seen in some rats that died early. These lesions are consistent with cyanide-induced anoxia. 13-WEEK STUDY IN MICE: Groups of 10 male and 10 female B6C3F1 mice were exposed to 0, 100, 200, 400, 800, or 1,600 ppm (equivalent to 0, 168, 335, 670, 1,340, or 2,681 mg/m(3)) acetonitrile by inhalation for 6 hours per day, 5 days per week for 13 weeks. All mice exposed to 1,600 ppm died during the first 3 weeks of the study. In addition, one 400 ppm female and one male and four females from the 800 ppm groups also died before the end of the study. Body weight gains were similar to those of controls for all surviving groups of mice except the 800 ppm males, for which the final mean body weight was slightly lower than that of the controls. Clinical findings observed during the first week in 800 and 1,600 ppm mice were hypoactivity and a hunched, rigid posture. In males that received 200 ppm and above, absolute liver weights were greater than that of the controls and relative liver weights were greater in all exposed groups. In 800 ppm females, the absolute liver weight was greater than that of the controls and relative liver weights of females that received 400 ppm and above were greater than that of the controls. Lesions clearly associated with acetonitrile exposure were observed in the stomach, predominantly the forestomach, of males that received 400 ppm and above and of females that received 200 ppm and above. Histologically, these focal or multifocal pale to dark raised lesions consisted of areas of focal epithelial hyperplasia and ulceration, sometimes associated with hemosiderin deposition. An increased incidence of cytoplasmic vacuolation occurred in the liver of males and females exposed to 400 or 800 ppm. A lack of fatty degenerative change was observed inrved in the X-zone of the adrenal cortex of 800 and 1,600 ppm female mice. 2-YEAR STUDY IN RATS: The doses selected for the 2-year study of acetonitrile were based on reduced survival of 800 ppm males and 1,600 ppm males and females in the 13-week study. Groups of up to 56 male and 56 female rats were exposed to 0, 100, 200, or 400 ppm (equivalent to 0, 168, 335, or 670 mg/m(3)) acetonitrile by inhalation for 6 hours per day, 5 days per week for 2 years. Eight male and eight female rats from each exposure group were evaluated at 15 months for histopathology and hematology parameters. Survival, Body Weights, Clinical Findings, and Hematology: Two-year survival, mean body weights, organ weights, behavior, general health, and appearance of exposed male and female rats were similar to those of the controls. The hematologic effects observed were minor and of no biological significance. Pathology Findings: The incidences of hepatocellular adenoma (3/48), hepatocellular carcinoma (3/48), and hepatocellular adenoma or carcinoma (combined; 5/48) were greater in male rats exposed to 400 ppm than in the controls (one carcinoma). The incidences of hepatocellular adenoma and hepatocellular carcinoma were within the range of historical controls. However, the incidence of hepatocellular adenoma or carcinoma (combined) slightly exceeded the range of historical controls (2&percnt;-8&percnt;). In addition, the incidences of basophilic, eosinophilic, and mixed cell foci in 400 ppm males were marginally greater than in controls, suggesting hepatotoxicity of acetonitrile. There were no exposure-related liver lesions in female rats. 2-YEAR STUDY IN MICE: The exposure concentrations selected for the 2-year study were based on reduced survival and gross and histopathologic lesions in 400, 800, and 1,600 ppm groups of male and female mice in the 13-week study. Groups of 60 male and 60 female mice were exposed to 0, 50, 100, or 200 ppm (equivalent to 0, 84, 168, or 335 mg/m(3)) acetonitrile by inhalation for 6 hours per day, 5 days per week for 2 years. Ten male and 10 female mice from each exposure group were evaluated at 15 months for histopathology. Survival, Body Weights, and Clinical Findings: Two-year survival of exposed male and female mice was similar to that of the controls, except that the survival of male mice in the 200 ppm group was significantly greater than that of the controls. Mean body weights and organ weights of exposed groups of male and female mice were similar to those of the controls, and no clinical observations in any group were clearly related to acetonitrile exposure. Pathology Findings: There were no increases in the incidences of neoplasms that were considered related to acetonitrile exposure in mice. The incidence of squamous hyperplasia of the epithelium of the forestomach was significantly increased at 15 months in 200 ppm females. At 2 years, the increased incidence of this lesion was dose related in all exposed groups of males and females. GENETIC TOXICOLOGY: Acetonitrile was not mutagenic in Salmonella typhimurium strain TA97, TA98, TA100, TA1535, or TA1537, with or without S9 metabolic activation. In cultured Chinese hamster ovary cells, acetonitrile produced a weakly positive response in the sister chromatid exchange test without, but not with, S9. A small increase in chromosomal aberrations was observed in cultured Chinese hamster ovary cells treated with acetonitrile in the presence, but not in the absence, of S9. A significant increase in micronucleated normochromatic erythrocytes was observed in peripheral blood samples from male mice treated with acetonitrile for 13 weeks; the frequency of micronucleated erythrocytes in female mice was not affected by exposure to acetonitrile. CONCLUSIONS: Under the conditions of these 2-year inhalation studies, there was equivocal evidence of carcinogenic activity of acetonitrile in male F344/N rats based on marginally increased incidences of hepatocellular adenoma and carcinoma. There was no evidence of carcinogenic activity of acetonitrile in female F344/N rats exposed to 100, 200, or 400 ppm. There was no evidence of carcinogenic activity of acetonitrile in male or female B6C3F1 mice exposed to 50, 100, or 200 ppm. Exposure to acetonitrile by inhalation resulted in increased incidences of hepatic basophilic foci in male rats and of squamous hyperplasia of the forestomach in male and female mice. Synonyms: Cyanomethane, ethanenitrile, ethyl nitrile, methanecarbonitrile, methyl cyanide, nitrile of acetic acid
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PMID:NTP Toxicology and Carcinogenesis Studies of Acetonitrile (CAS No. 75-05-8) in F344/N Rats and B6C3F1 Mice (Inhalation Studies). 1259 28

1-Trans-delta(9)-tetrahydrocannabinol (THC) was nominated by the National Cancer Institute to the NTP for study because it is the major psychoactive component of marijuana and a widely used Schedule I substance. Male and female F344/N rats and B6C3F1 mice received THC (97% pure) in corn oil by gavage for 13 weeks, 13 weeks with a 9-week recovery period, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, cultured Chinese hamster ovary cells, and mouse peripheral blood cells. 13-WEEK STUDY IN RATS: Groups of 10 male and 10 female rats received 0, 5, 15, 50, 150, or 500 mg THC/kg body weight in corn oil by gavage, 5 days per week for 13 weeks. Six male and six female rats receiving 500 mg/kg died before the end of the study. The final mean body weights and weight gains of all dosed groups of males and females, except 5 mg/kg females, were significantly lower than those of the controls. Feed consumption by dosed groups was similar to that by controls. Clinical findings observed during the study included lethargy, sensitivity to touch, convulsions, tremors, and aggressiveness. There were no clinical pathology differences considered to be directly related to the administration of THC. The absolute and relative uterus weights of 50, 150, and 500 mg/kg females were significantly lower than those of the controls. Treatment-related multifocal atrophy was observed in the testes of 150 and 500 mg/kg males; uterine and ovarian hypoplasia observed in 150 and 500 mg/kg females was also considered to be related to THC administration. Based on final mean body weights and mortality observed in the 13-week study, doses selected for the 2-year rat study were 12.5, 25, and 50 mg/kg. 13-WEEK STUDY IN MICE: Groups of 10 male and 10 female mice received 0, 5, 15, 50, 150, or 500 mg THC/kg body weight in corn oil by gavage, 5 days per week for 13 weeks. There were no treatment-related deaths. The final mean body weight and weight gain of 500 mg/kg males were significantly lower than those of the controls. Clinical findings included lethargy and aggressiveness, and both male and female mice in all dosed groups were easily startled. There were no absolute or relative organ weight differences, clinical pathology differences, or microscopic changes observed that were considered to be related to the administration of THC. Due to the minimal THC-related effects observed in the 13-week study, doses selected for the 2-year mouse study were 125, 250, and 500 mg/kg. 13-WEEK WITH 9-WEEK RECOVERY STUDY IN RATS: Groups of 10 male and 10 female rats received 0, 5, 15, 50, 150, or 500 mg THC/kg body weight in corn oil by gavage, 5 days per week for 13 weeks, and then were allowed to recover during a 9-week treatment-free period. Five male and eight female 500 mg/kg rats, five male and two female 150 mg/kg rats, and three male and two female 50 mg/kg rats died before the end of the study. During the 13-week dosing period, mean body weight gains of all dosed groups of rats were lower than those of the controls but returned to normal during the recovery period. Final mean body weights of all dosed groups were similar to those of the controls. Clinical findings observed during the recovery period included sensitivity to touch, convulsions, and aggressiveness. The absolute right testis weight of 500 mg/kg males was significantly lower than that of the controls. Treatment-related multifocal atrophy of the testis was observed in 150 and 500 mg/kg males. There were no treatment-related lesions observed in females administered THC. 13-WEEK WITH 9-WEEK RECOVERY STUDY IN MICE: Groups of 10 male and 10 female mice received 0, 5, 15, 50, 150, or 500 mg THC/kg body weight in corn oil by gavage, 5 days per week for 13 weeks, and then were allowed to recover during a 9-week treatment-free period. The final mean body weights of all dosed groups were similar to those of the controls. Clinical findings observed during the study included lethargy and aggressiveness, and both male and female mice in all dosed groups were easily startled. The absolutebsolute and relative uterus weights of 150 and 500 mg/kg female mice were significantly lower than those of the controls, as was the absolute uterus weight of 50 mg/kg females. 2-YEAR STUDY IN RATS: Groups of 62 vehicle control male rats, 60 low-dose male rats, 70 mid- and high-dose male rats, and 60 female rats were administered 0, 12.5, 25, or 50 mg THC/kg body weight in corn oil by gavage for 104 to 105 weeks. Nine or ten animals from each group were evaluated at 15 months. Survival, Body Weights, and Clinical Findings: Survival of all dosed groups was generally significantly greater than that of the controls. Mean body weights of dosed groups of males and females were lower than those of the controls throughout the study. Convulsions and seizures were observed in all dosed groups of male and female rats, usually following dosing or handling. Hematology and Clinical Chemistry: At the 15-month interim evaluation, total leukocyte and lymphocyte counts in all dosed groups of females were greater than those of the controls, and platelet counts in these groups were lower than that of the controls. Levels of follicle stimulating and luteinizing hormones in all dosed groups of males were significantly greater than those of the controls, as was the serum corticosterone level of 25 mg/kg females. Pathology Findings: No increased incidences of neoplasms were considered related to administration of THC. The incidences of mammary gland fibroadenoma and uterine stromal polyps were decreased in dosed groups of females, as were the incidences of pituitary gland adenomas, interstitial cell adenomas of the testis, and pancreatic adenomas in dosed males. 2-YEAR STUDY IN MICE: Groups of 62 vehicle control male mice, 60 low-dose male mice, 61 mid-dose male mice, and 60 high-dose male mice and 60 female mice were administered 0, 125, 250, or 500 mg THC/kg body weight in corn oil by gavage for 104 to 105 weeks (males) or 105 to 106 weeks (females). Survival, Body Weights, and Clinical Findings: Survival of 500 mg/kg males was significantly less than that of the controls; survival of all other groups of males and of all dosed groups of females was similar to that of the controls. Mean body weights of all dosed groups were markedly lower than those of the controls throughout the study. Clinical findings in dosed groups included hyperactivity, convulsions, and seizures which occurred following dosing or handling. Hematology: At the 15-month interim evaluation, total leukocyte and lymphocyte counts in all dosed groups of males were significantly lower than those of the controls. Pathology Findings: Increased incidences of thyroid gland follicular cell adenoma occurred in 125 mg/kg males and females, but the increase was not dose-related. Increased incidences of thyroid gland follicular cell hyperplasia occurred in all dosed groups of males and females. Increased incidences of forestomach hyperplasia and ulcers occurred in all groups of males administered THC. Incidences of hepatocellular adenoma and of hepatocellular adenoma or carcinoma (combined) occurred with a significant negative trend in male and female mice, as did incidences of eosinophilic foci and fatty change in the liver. GENETIC TOXICOLOGY: THC was not mutagenic in Salmonella typhimurium strains TA97, TA98, TA100, or TA1535 with or without rat and hamster liver S9 fractions. In cultured Chinese hamster ovary cells, THC induced sister chromatid exchanges at the highest dose tested in the presence of S9; at this dose level, cell cycle delay indicative of toxicity was observed. THC did not induce chromosomal aberrations in cultured Chinese hamster ovary cells with or without S9 metabolic activation enzymes. In vivo, no increase in the frequency of micronucleated erythrocytes was observed in the peripheral blood of male or female mice administered THC by gavage for 13 weeks. CONCLUSIONS: Under the conditions of these 2-year gavage studies, there was no evidence of carcinogenic activity of 1-trans-delta(9)-tetrahydrocannabinol in male or female F344/N rats administered 12.5, 25, or 50 mg/kg. There was equivocal evidence of carcinogenic activity of THC in male and female B6C3F1 mice based on the increased incidences of thyroid gland follicular cell adenomas in 125 mg/kg groups. Increased incidences of thyroid gland follicular cell hyperplasia occurred in male and female mice, and increased incidences of hyperplasia and ulcers of the forestomach were observed in male mice. The incidences of mammary gland fibroadenomas and uterine stromal polyps were decreased in dosed groups of female rats, as were the incidences of pancreatic adenomas, pituitary gland adenomas, and interstitial cell adenomas of the testis in dosed male rats and liver neoplasms in dosed mice. These decreases were likely related to lower body weights in dosed animals. Synonyms: 3-Pentyl-6,6,9-trimethyl-6a,7,8,10a-tetrahydro-6h-dibenzo(b,d)pyran-1-ol; delta1-tetrahydrocannabinol; (-)-delta1-3,4-trans- tetrahydrocannabinol; delta(9)-tetrahydrocannabinon; THC; delta1-THC; delta(9)-THC
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PMID:NTP Toxicology and Carcinogenesis Studies of 1-Trans-Delta(9)-Tetrahydrocannabinol (CAS No. 1972-08-3) in F344 Rats and B6C3F1 Mice (Gavage Studies). 1259 29

Scopolamine hydrobromide trihydrate is used in ophthalmic preparations and as a preanesthetic sedative. Its major use is in transdermal patches for the treatment of motion sickness. Scopolamine hydrobromide trihydrate was selected for study because of considerable human exposure resulting from its use in prescription and over-the-counter preparations. Scopolamine was a suspect carcinogen because it contains an aliphatic epoxide moiety which may act as a biological alkylating agent. Male and female F344/N rats and B6C3F1 mice received scopolamine hydrobromide trihydrate (89% pure) in distilled water by gavage for 16 days, 14 weeks, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, cultured Chinese hamster ovary cells, and mouse peripheral blood erythrocytes. 16-DAY STUDY IN RATS: Groups of five male and five female rats were administered 0, 75, 150, 300, 600, or 1,200 mg scopolamine hydrobromide trihydrate/kg body weight in distilled water by gavage for 16 days. All rats survived to the end of the study. The final mean body weights and body weight gains of males receiving 600 and 1,200 mg/kg and the mean body weight gain of males receiving 300 mg/kg were significantly lower than those of the control group. Clinical findings included bilateral pupillary dilation in all dosed animals and red eyelids in males and females receiving 1,200 mg/kg. There were no significant treatment-related gross or microscopic lesions. 16-DAY STUDY IN MICE: Groups of five male and five female mice were administered 0, 150, 250, 450, 900, or 1,800 mg scopolamine hydrobromide trihydrate/kg body weight in distilled water by gavage for 16 days. One male and two females receiving 1,800 mg/kg and one female receiving 150 mg/kg died during the study. The final mean body weights and body weight gains of dosed mice were similar to those of the control groups. Clinical findings related to scopolamine hydrobromide trihydrate administration included bilateral pupillary dilation and squinting in all dosed males and females. The relative liver weights of males receiving 1,800 mg/kg and of females in all dosed groups were significantly greater than those of the control groups. There were no significant treatment-related gross or microscopic lesions. 14-WEEK STUDY IN RATS: Groups of 10 male and 10 female rats were administered 0, 15, 45, 135, 400, or 1,200 mg scopolamine hydrobromide trihydrate/kg body weight in distilled water by gavage for 14 weeks. One female receiving 45 mg/kg, one male and one female receiving 135 mg/kg, six males and one female receiving 400 mg/kg, and eight males and seven females receiving 1,200 mg/kg died during the study. The final mean body weights and mean body weight gains of all dosed males and females were significantly lower than those of the control groups. Clinical findings included bilateral pupillary dilation in all dosed males and females and reddening of the eyes in 15 mg/kg males and 135, 400, and 1,200 mg/kg males and females. Hematocrit, hemoglobin concentration, and/or erythrocyte count in male and female rats receiving 45 mg/kg or greater were slightly higher than those of the control groups. In general, these changes were most prominent in rats in the 400 and 1,200 mg/kg groups. Higher hematocrit, hemoglobin concentration, and erythrocyte count were likely due to hemoconcentration from dehydration (relative erythrocytosis). A minimal to mild mature neutrophilia, evidenced by higher segmented neutrophil numbers than in the control group, occurred in all dosed male rats. Sperm morphology and vaginal cytology parameters in dosed rats were similar to those in the control groups. Nine male and five female dosed rats died from esophageal obstructions consisting of feed and bedding material in the posterior pharynx. Tracheal obstruction occurred concurrently with esophageal obstruction as a result of food build-up in the oropharyngeal region. This condition is considered to be secondary to the inhibitory effects of scopolamine hydrobromide trihydrate on salivary gland secretions and on esopon esophageal smooth muscle involved in swallowing. There were no other significant treatment-related gross or microscopic findings. 14-WEEK STUDY IN MICE: Groups of 10 male and 10 female mice were administered 0, 15, 45, 135, 400, or 1,200 mg scopolamine hydrobromide trihydrate/kg body weight in distilled water by gavage for 14 weeks. One male receiving 135 mg/kg and two males and one female receiving 1,200 mg/kg died during the study. The final mean body weights and mean body weight gains of all dosed male groups and females receiving 45 mg/kg and above were significantly lower than those of the control groups. Clinical observations included bilateral pupillary dilation, hyperactivity, and hypoactivity. A minimal to mild mature neutrophilia, similar to that which occurred in the 14-week rat study, occurred in male mice receiving 45 mg/kg or greater. As in the rat study, there was no microscopic evidence of inflammation that could account for the neutrophilia. The estrous cycle length of 1,200 mg/kg females was significantly greater than that in the control group. There were no significant treatment-related gross or microscopic lesions. 2-YEAR STUDY IN RATS: Groups of 60 male and 60 female rats were administered 0, 1, 5, or 25 mg scopolamine hydrobromide trihydrate/kg body weight in distilled water by gavage for 104 weeks. Ten males and ten females from each dose group, excluding the 1 mg/kg female group, were evaluated at 15 months. Survival, Body Weights, Clinical Findings, and Ophthalmic Examination Findings: The survival rates of female rats receiving 1 and 25 mg/kg were significantly lower than that of the control group. Mean body weights of 1 and 5 mg/kg males and females were similar to those of the controls throughout the study. However, mean body weights of 25 mg/kg males and females were generally lower than those of the control groups after about week 25. Clinical findings included bilateral pupillary dilation in all dosed males and females. Ophthalmic examination revealed no significant findings. Hematology: Compared to controls, hematocrit was slightly higher in the 25 mg/kg male rats, similar to the effects observed in the 14-week study; this is consistent with dehydration resulting in hemoconcentration. Reticulocyte numbers in the 25 mg/kg female rats were slightly lower than those in the controls. This result is consistent with the lower body weights, and thus a decreased nutritional status, exhibited by these animals. Plasma Scopolamine Determinations: The serum scopolamine concentrations were 6 ng scopolamine/mL serum for the 5 mg/kg female sample and 12 and 28 ng/mL for the 25 mg/kg male and female samples, respectively. The amounts of scopolamine in the other serum samples were below the minimum detection limit (4 ng/mL) of the analysis method. Neurobehavioral Findings: Horizontal motor activity of 25 mg/kg females was significantly greater than that of the control group on days 90, 180, and 360. Startle response of 5 and 25 mg/kg females was significantly lower than that of the control group on day 90. On day 180, passive avoidance of 25 mg/kg males was significantly lower than that of the control group. Pathology Findings: The incidences of adenoma of the pituitary gland pars distalis decreased with increasing dose in both male and female rats; however, this trend was only significant in males (males: vehicle control, 19/49; 1 mg/kg, 17/49; 5 mg/kg, 13/50; 25 mg/kg, 10/50; females: 20/50, 13/60, 14/50, 10/50). The incidences of adenoma of the pituitary gland pars distalis in 25 mg/kg males and all groups of dosed females were below the NTP historical control range. The incidences of hyperplasia were not significantly different from those in the control groups. The incidences of mononuclear cell leukemia in 25 mg/kg males and females were significantly lower than those of the control groups (males: 33/50, 21/50, 26/50, 24/50; females: 20/50, 6/60, 13/50, 4/50). The incidence of mononuclear cell leukemia in females receiving 25 mg/kg was well below the NTP historical range. 2-YEAR STUDY IN MICE: Groups of 70 male and 70 female mice were administered 0, 1, 5, or 25 mg scopolamine hydrobromide trihydrate/kg body weight in distilled water by gavage for 104 to 105 weeks. Ten control animals and ten animals from each dose level were evaluated at 15 months. Survival, Body Weights, Clinical Findings, and Ophthalmic Examination Findings Survival of dosed males and females was similar to that of the controls. The mean body weights of males and females receiving 1 mg/kg were similar to those of the control groups throughout the majority of the study. The mean body weights of 5 mg/kg males and females were slightly lower than those of the controls. The mean body weights of males and females receiving 25 mg/kg were lower than those of the control groups after week 13. Clinical findings included bilateral pupillary dilation in all dosed male and female groups. Ophthalmic examination revealed no significant findings. Hematology: Hematocrit, hemoglobin concentration, and erythrocyte count in 25 mg/kg female mice were slightly lower than those in the control group. These results are consistent with development of a minimal normocytic, normochromic nonresponsive anemia. The anemia may be related to the lower body weights exhibited by these animals and are presumed to be due to a decreased nutritional status. Pathology Findings: The combined incidences of hepatocellular neoplasms (adenoma or carcinoma) occurred with a significant negative trend in males and females (males: vehicle control, 30/50; 1 mg/kg, 33/50; 5 mg/kg, 14/50; 25 mg/kg, 15/50; females: 22/51, 21/50, 16/50, 9/51). The combined incidences of hepatocellular neoplasms in 5 and 25 mg/kg males were within the NTP historical control range. The incidences of clear cell foci and eosinophilic foci in dosed male groups, and eosinophilic foci in 25 mg/kg females, were significantly lower than those of the control groups. The incidences of many spontaneously occurring nonneoplastic lesions were significantly lower in dosed mice than in the control groups and usually decreased with increasing dose. These included kidney nephropathy, alveolar epithelial hyperplasia, hyperplasia of the pancreatic islets, bone marrow myelofibrosis, hyperplasia of the pituitary gland pars distalis, cystic hyperplasia of the uterus, and hematopoietic cell proliferation of the spleen. The decreased incidences of these spontaneous lesions were most likely a result of lower body weights in dosed animals. GENETIC TOXICOLOGY: Scopolamine hydrobromide trihydrate did not induce mutations in any of five strains of Salmonella typhi murium, with or without S9 metabolic activation enzymes, nor did it induce sister chromatid exchanges in cultured Chinese hamster ovary cells, with or without S9. A weakly positive response was obtained, however, in a chromosomal aberrations test conducted in cultured Chinese hamster ovary cells with very high doses of scopolamine hydrobromide trihydrate in the presence of S9; without S9, no increase in aberrations was noted. Despite the evidence for chromosomal damage observed in vitro, no increase in the frequencies of micronucleated normochromatic erythrocytes was observed in peripheral blood samples of male or female mice exposed to scopolamine hydrobromide trihydrate for 14 weeks by gavage. CONCLUSIONS: Under the conditions of these 2-year gavage studies, there was no evidence of carcinogenic activity of scopolamine hydrobromide trihydrate in male or female F344/N rats or B6C3F1 mice administered 1, 5, or 25 mg/kg. Synonyms: Scopolamine hydrobromide, 6,7-epoxytropan-3-yl, euscopol, hydroscine hydrobromide, hyoscine bromide, (-)-hyoscine hydrobromide, hysco, isoscopil, scopolammonium bromide, (s)-tropate hydrobromide trihydrate, lα-tropyl-a-scopine
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PMID:NTP Toxicology and Carcinogenesis Studies of Scopolamine Hydrobromide Trihydrate (CAS No. 6533-68-2) in F344 Rats and B6C3F1 Mice (Gavage Studies). 1259 30

Oxazepam is one of a number of benzodiazepines used therapeutically as a sedative-hypnotic and antianxiety agent. Toxicology and carcinogenesis studies were performed by administering oxazepam (greater than 99% pure) in feed to male and female Swiss-Webster and B6C3F1 mice for 14 weeks, 57 weeks (Swiss-Webster), or 2 years (B6C3F1). Neurobehavioral assessments were performed during the studies. Genetic toxicology studies were conducted in Salmonella typhimurium and cultured Chinese hamster ovary cells, and peripheral blood samples were analyzed for frequency of micronucleated normochromatic erythrocytes. Supplemental studies were performed to compare the metabolism and toxicokinetics of oxazepam in the two mouse strains, to evaluate the effect on liver cell replication rates, to perform clinical pathology assessments, and to examine the mutation spectrum and frequency of activated H-ras oncogenes in liver neoplasms from the 2-year study with B6C3F1 mice. 14-WEEK STUDY IN SWISS-WEBSTER MICE: Groups of 10 male and 10 female Swiss-Webster mice received oxazepam in feed at concentrations of 0, 625, 1,250, 5,000, 10,000 ppm for 14 weeks. One 625 ppm male and one 10,000 female were killed moribund before the end of the study, and the condition of the female mouse was attributed to oxazepam exposure. Mean body weight gains of exposed groups were similar to those of the controls. Exposed mice displayed chemical-related sedation and lethargy during the first study week, but appeared normal thereafter. In the neurobehavioral studies, reductions in grip strength were evident in both male and female mice at week 2 and persisted in males through week 11. An antianxiety effect was detected in exposed mice in measures of motor activity, startle response, and reactions to thermal stimulus. At necropsy, absolute and relative liver weights were increased in an exposure-related manner and were approximately two-fold greater in 10,000 ppm mice than in controls. Centrilobular hepatocellular hypertrophy was present only in exposed mice, and the severity increased with dose. 14-WEEK STUDY IN B6C3F1 MICE: Groups of 10 male and 10 female B6C3F1 mice received oxazepam in feed at concentrations of 0, Groups of 10 male and 10 female Swiss-Webster mice 625, 1,250, 2,500, 5,000, or 10,000 ppm for 14 weeks. received oxazepam in feed at concentrations of 0, There were no deaths that were clearly related to 625,1,250, 2,500, 5,000, or 10,000 ppm for 14 weeks. oxazepam exposure. Mean body weight gains of One 625 ppm male and one 10,000 ppm female were exposed groups were similar to those of the controls. Exposed mice displayed chemical-related sedation and lethargy during only the first study week. In neurobehavioral studies, reductions in grip strength were evident in males at week 2 but were no longer observed at week 12. An antianxiety effect was noted in exposed mice in measures of motor activity, startle response, and reactions to a thermal stimulus (females). At necropsy, absolute and relative liver weights were increased in an exposure-related manner and were approximately two-fold greater in 10,000 ppm mice than in controls. Centrilobular hepatocellular hypertrophy was present only in exposed mice, and the severity increased with dose. CHRONIC STUDIES: Groups of 60 male and 60 female Swiss-Webster and B6C3F1 mice received oxazepam in feed at concentrations of 0, 2,500, or 5,000 ppm. Additional groups of 60 male and 60 female B6C3F1 mice received 125 ppm in feed to allow for study of a group with projected serum concentrations of oxazepam similar to those achieved in humans taking a therapeutic dose. Ten male and 10 female B6C3F1 mice per group were evaluated at 15 months. Average daily oxazepam consumption varied throughout the studies, and the overall daily average ranged from 10 to 29 mg/kg body weight for the 125 ppm groups, 234 to 512 mg/kg for the 2,500 ppm groups, and 444 to 1,085 mg/kg for the 5,000 ppm groups. Serum oxazepam concentrations determined at 57 weeks in Swiss-Webster mice and at the 15-month interim evaluation of B6C3F1 mice 1 mice were approximately 1 ug/mL in the 125 ppm groups, 4 to 7 μg/mL in the 2,500 ppm groups, and 7 to 10 μg/mL in the 5,000 ppm groups. Neurobehavioral assessments during the chronic studies of each strain of mice were confounded by the poor survival and deteriorating condition of mice with hepatic neoplasia. However, within the limitations of the studies, there were no notable changes in the types of behaviors observed compared to those observed in the 14-week studies, nor was there an enhancement in the degree to which they were exhibited. 57-Week Study in Swiss-Webster Mice: Survival, Body Weights, Feed and Compound Consumption, and Clinical Findings: At 57 weeks, survival of exposed mice was significantly lower than that of controls (males: O ppm, 45/60; 2,500 ppm, 19/60; 5,000 ppm, 10/60; females: 47/60, 28/59, 17/59), causing the study to be terminated. Mean body weights of exposed males were similar to controls until week 17; afterwards, mean body weights of exposed male groups were lower than those of controls. Final mean body weights of exposed males were 9% lower than that of the controls. The mean body weight of 2,500 ppm females was greater than that of the controls throughout the study. Females receiving 5,000 ppm had a mean body weight greater than that of the controls early in the study; after week 29, the mean body weight of this group was similar to that of the controls. Feed consumption by exposed males and females was slightly lower than that by the controls, and females in all groups, including controls, consumed slightly more feed than males throughout the study. Dietary levels of 2,500 and 5,000 ppm oxazepam resulted in average daily compound consumption levels of 270 and 570 mg/kg for males and 320 and 670 mg/kg for females. Hypoactivity and sedation were observed in exposed mice during the first week of the study. There were no other clinical findings associated with oxazepam exposure. Pathology Findings: Systemic amyloidosis was the principal cause of death in mice dying before the study was terminated. The lower survival of mice receiving oxazepam was attributed to an increase in the extent and severity of amyloid deposits in many organs, including the heart and kidney. Atrial thrombosis and pulmonary lesions consistent with chronic heart failure occurred at higher incidences and with greater severity in exposed mice. The incidence of hepatocellular adenomas (males: 1/60, 35/60, 50/60; females: 0/60, 22/59, 47/59) and carcinomas (males: 0/60, 5/60,19/60; females: 1/60, 1/59, 11/59) were increased in exposed mice. The incidences of eosinophilic foci were also increased in exposed mice (males: 0/60, 22/60, 22/60; females: 0/60, 20/59, 14/59), and there was evidence of increased centrilobular hepatocyte hypertrophy (males: 12/60, 46/60, 47/60; females: 3/60, 51/59, 53/59). 2-Year Study in B6C3F1 Mice: Survival, Body Weights, Feed and Compound Consumption, and Clinical Findings: Survival of mice receiving 2,500 and 5,000 ppm was significantly lower than that of controls (males: O ppm, 45/50; 125 ppm, 44/50; 2,500 ppm, 15/50; 5,000 ppm, 0/50; females: 39/50, 41/50, 2/50, 0/50). Mean body weight gains of exposed male and female mice were similar to controls until about week 15 when weight gains for mice exposed to 2,500 or 5,000 ppm slowed in relation to controls, resulting in weight gains approximately 30&percnt; to 40&percnt; lower than those of the controls throughout the remainder of the study. Mean body weight gain of male mice exposed to 125 ppm was similar to that of the controls, while that of female mice receiving 125 ppm was 10&percnt; to 15&percnt; lower than that of the controls after about week 45. Feed consumption by exposed males and females was similar to that by controls. Dietary levels of 125, 2,500, and 5,000 ppm resulted in average daily oxazepam consumption levels of 12, 310, and 690 mg/kg body weight for males and 15, 350, and 780 mg/kg for females. In the 5,000 ppm groups, lethargy and sedation were observed in a few mice during the first week of study. Pathology Findings: The early deaths of many of the B6C3F1 mice exposed to oxazepam were attributed to a marked increase in the incidences of hepatoblastoma (males: 0/49, 2/50, 21/50, 13/50; females: 0/50, 1/50, 8/50, 8/50), hepatocellular adenoma (males: 17/49,18/50, 34/50, 32/50; females: 25/50, 35/50, 35/50, 36/50), and hepatocellular carcinoma (males: 9/49, 5/50, 45/50, 50/50; females: 9/50, 5/50, 49/50, 44/50). Moderate hypertrophy of centrilobular hepatocytes occurred in mice receiving 2,500 and 5,000 ppm (males: 0/49, 2/50, 26/50, 43/50; females: 0/50, 2/50,11/50, 29/50). An increase in the incidence of follicular cell hyperplasia of the thyroid gland occurred in all exposed groups of mice (males: 4/49, 22/50, 49/50, 47/50; females: 16/50, 34/50, 49/50, 44/50), and thyroid gland follicular cell adenoma was increased in exposed females (0/50, 4/50, 5/50, 6/50). Testicular atrophy occurred in the 2,500 and 5,000 ppm groups (1/50, 0/50, 25/50, 38/50), and the incidence of epididymal Iymphocyte infiltration was increased in all exposed groups (2/50,14/50, 33/50, 21/50). The frequency of hepatocellular neoplasms with an activated H-ras oncogene in the B6C3F1 mice and the mutation spectrum of the H-ras gene were determined. The mutation spectrum of the H-ras genes in the relatively few neoplasms from exposed mice that did have an activated H-ras did not differ from the spectrum of mutations observed in neoplasms from controls, but the proportion of neoplasms with an activated H-ras gene decreased with increasing oxazepam dose. While 11 of 19 (58&percnt;) neoplasms from control mice had an activated H-ras gene, only 1 of 40 neoplasms from mice receiving 2,500 or 5,000 ppm oxazepam exhibited a similar molecular lesion. Thirteen of 37 (35&percnt;) neoplasms from mice in the 125 ppm group had an activated H-ras oncogene, suggesting that, although the incidence of all liver neoplasms was not statistically increased compared to controls, there was an increase in a similar subset of neoplasms (lacking an activated H-ras) that occurred with increased incidence at higher doses. SUPPLEMENTAL STUDIES: Because exposure to oxazepam caused increased incidences of liver neoplasms, supplemental short-term studies were performed. Oxazepam given in feed to male B6C3F1 mice at 25, 125, 2,500, or 5,000 ppm for up to 13 weeks was found to cause a dose-related increase in nuclear labeling index in studies measuring the incorporation of bromodeoxyuridine into replicating liver cells. This increase was statistically significant at all but the 25 ppm exposure level and was limited to mice evaluated at 15 days. Cell replication rates in most groups evaluated at 30 days and after were similar to control rates. There was minimal evidence suggestive of hepatocyte necrosis either by light microscopy or in clinical chemistry measures. There was, however, evidence of cholestasis, likely due to physical obstruction of bile canaliculi by swollen hepatocytes. The metabolic fate and toxicokinetics of oxazepam were evaluated in each strain of mice and were compared to published data from human studies. Both mice and humans form glucuronides of oxazepam and form 3- and 4-hydroxy and methoxy derivatives of the phenyl group. Oxidative metabolism of the phenyl group appears to be more prevalent in mice than is reported for humans. Elimination half-lives of parent compound do not differ between Swiss-Webster and B6C3F1 mice and are similar to values reported for humans. GENETIC TOXICOLOGY: Oxazepam was not mutagenic in any of several strains of Salmonella typhimurium, nor did it induce sister chromatid exchanges or chromosomal aberrations in cultured Chinese hamster ovary cells. These in vitro tests were performed with and without S9 metabolic activation. Results from an in vivo mouse peripheral blood micronucleus test performed on the B6C3F1 mice used in the 14-week study were also negative. CONCLUSIONS: Under the conditions of these feed studies, there was clear evidence of carcinogenic activity of oxazepam in male and female Swiss-Webster mice based on increased incidences of hepatocellular adenoma and carcinoma. There was clear evidence of carcinogenic activity of oxazepam in male and female B6C3F1 mice based on increased incidences of hepatoblastoma and hepatocellular adenoma and carcinoma. Increased incidences of hyperplasia of thyroid gland follicular cells in male and female B6C3F1 mice and of follicular cell adenomas in female B6C3F1 mice were also related to oxazepam exposure. Administration of oxazepam to Swiss-Webster mice resulted in centrilobular hepatocellular hypertrophy and increased incidences and severity of systemic amyloidosis. Administration of oxazepam to B6C3F1 mice also resulted in centrilobular hepatocellular hypertrophy. Synonyms: 7-Chloro-1,3-dihydro-3-hydroxy-5-phenyl-2 H - 1,4-benzodiazepin-2-one Trade Names: Tazepam, Wy-3498, Serax
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PMID:NTP Toxicology and Carcinogenesis Studies of Oxazepam (CAS No. 604-75-1) in Swiss-Webster and B6C3F1 Mice (Feed Studies). 1259 20

p-Nitrobenzoic acid is produced in large volumes for organic synthesis and as an intermediate in the manufacture of pesticides, dyes, and industrial solvents. Groups of male and female F344/N rats and B6C3F1 mice were exposed to p-nitrobenzoic acid (>99% pure) in feed for 14 days, 13 weeks, or 2 years for toxicity and carcinogenicity studies. Genetic toxicology studies were conducted in in vitro assays with Salmonella typhimurium and cultured Chinese hamster ovary cells, and in studies of erythrocyte micronucleus formation in mice in the 13-week study. 14-DAY STUDY IN RATS: Groups of five male and five female rats were given 0, 2,500, 5,000, 10,000, 20,000, or 40,000 ppm p-nitrobenzoic acid in feed for 14 days. All rats survived until the end of the study. Male and female rats given 20,000 and 40,000 ppm lost weight. The final mean body weights of 10,000, 20,000, and 40,000 ppm males were 82%, 60%, or 52% that of the controls, and the final mean body weights of 10,000, 20,000, and 40,000 ppm females were 87%, 68%, and 65% that of the controls. There were no clinical findings that were characteristic of organ-specific toxicity. Absolute and relative spleen weights were significantly increased in rats exposed to 10,000, 20,000, and 40,000 ppm. There were decreases in erythrocyte count and hemoglobin and hematocrit values and increases in reticulocyte count, nucleated erythrocytes, and methemoglobin concentration that were most pronounced in the 20,000 and 40,000 ppm groups. Congestion of the spleen occurred in 10,000 ppm males and in 20,000 and 40,000 ppm females. Hypertrophy of the follicular epithelium of the thyroid gland was present in male and female rats exposed to 10,000, 20,000, or 40,000 ppm p-nitrobenzoic acid, while follicular hyperplasia was observed in the 40,000 ppm males and females. Atrophy of the testis was observed in 20,000 and 40,000 ppm males. Other lesions observed in 20,000 and 40,000 ppm rats included atrophy of the thymus in males and atrophy of the ovary, bone marrow, and thymus in females. 14-DAY STUDY IN MICE: Groups of five male and five female mice were given 0, 2,500, 5,000, 10,000, 20,000, or 40,000 ppm p-nitrobenzoic acid in feed for 14 days. Three males and two females given 40,000 ppm died during the study. All other animals survived until the end of the study. Male mice given 20,000 and 40,000 ppm and females given 20,000 ppm lost weight. Mean body weight gains of 20,000 and 40,000 ppm males and 10,000, 20,000, and 40,000 ppm females were significantly lower than those of the controls. There were no clinical findings related to organ-specific toxicity although lethargy and ataxia were observed in 40,000 ppm mice. Relative liver weights were significantly increased in 20,000 and 40,000 ppm males and females and in 10,000 ppm females. Absolute and relative thymus weights of 20,000 and 40,000 ppm males and of 10,000, 20,000, and 40,000 ppm females were reduced. No significant differences in hematology parameters occurred in exposed mice. Testicular degeneration was observed in three 20,000 ppm and two 40,000 ppm males. Bone marrow hemorrhage and atrophy occurred in 40,000 ppm females. 13-WEEK STUDY IN RATS: Groups of 10 male and 10 female rats were given 0, 630, 1,250, 2,500, 5,000, or 10,000 ppm pnitrobenzoic acid in feed for 13 weeks resulting in approximate daily doses of 40, 70, 160, 310, or 660 mg/kg to males and 40, 80, 170, 340, or 680 mg/kg to females. All rats survived until the end of the study. Mean body weight gains and final mean body weights were significantly less than those of the controls in 2,500, 5,000, and 10,000 ppm males and in 5,000 and 10,000 ppm females. There were no clinical findings related to organ-specific toxicity. Differences in spleen weights and hematology parameters characteristic of regenerative anemia were observed in males and females, primarily in groups given 10,000 ppm. The absolute and relative spleen weights were significantly increased in 10,000 ppm males and females and the relative spleen weights were significantly increased in 5,000 ppm males hts were significantly increased in 5,000 ppm males and females. Methemoglobin, Heinz bodies, and reticulocyte counts were increased and erythrocyte counts, hemoglobin, and hematocrit values were decreased in 10,000 ppm males and females. Congestion, pigmentation, and accumulation of macrophages in the spleen and pigmentation in the kidney occurred in 2,500, 5,000, and 10,000 ppm males. Congestion and pigmentation of the spleen occurred in 10,000 ppm females. A yellowish brown pigment (hemosiderin) in the spleen and kidney was associated with hemolytic anemia. Mild cytoplasmic hyaline droplet accumulation was present in renal tubule epithelial cells in 10,000 ppm males while karyomegaly was present in male and female rats exposed to 2,500, 5,000, and 10,000 ppm p-nitrobenzoic acid. A chemical-related testicular lesion, consisting of atrophy of the seminiferous tubules, occurred in 10,000 ppm males. 13-WEEK STUDY IN MICE: Groups of 10 male and 10 female mice were given 0, 1,250, 5,000, 10,000, or 20,000 ppm pnitrobenzoic acid in feed for 13 weeks resulting in approximate daily doses of 170, 330, 670, 1,900, or 4,000 mg/kg body weight to males and 240, 460, 970, 2,500, or 4,900 mg/kg to females. All mice survived until the end of the study, except one 1,250 ppm female that was killed accidentally. Final mean body weights and mean body weight gains of all exposed males and of 5,000, 10,000, and 20,000 ppm females were significantly lower than those of the controls. No clinical findings or differences in organ weights or histopathology related to organ-specific toxicity were observed in exposed mice. 2-YEAR STUDY IN RATS: Groups of 60 male and 60 female rats were given 0, 1,250, 2,500, or 5,000 ppm p-nitrobenzoic acid in feed for 2 years. Ten males and 10 females from each exposure group were evaluated at 15 months. Survival, Body Weights, Feed Consumption, and Clinical Findings: Two-year survival rates of 1,250 and 2,500 ppm males were similar to that of the controls. Two-year survival of 5,000 ppm males was marginally greater than that of the controls and was attributed in part to a decrease in the severity of nephropathy and a decrease in the incidence of mononuclear cell leukemia. Survival of exposed females was similar to that of the controls. Mean body weights of 5,000 ppm males were 2&percnt; to 8&percnt; lower than those of the controls through week 80. Final mean body weights of exposed males were similar to that of the controls. Mean body weights of 5,000 ppm females were 2&percnt; to 9&percnt; lower than those of the controls during the first year of the study and were 10&percnt; to 16&percnt; lower during the second year of the study. Final mean body weights of exposed females were 97&percnt; (1,250 ppm), 92&percnt; (2;500 ppm), and 84&percnt; (5,000 ppm) that of the controls. Feed consumption by exposed males and females was similar to that by the controls. Dietary levels of 1,250, 2,500, or 5,000 ppm p-nitrobenzoic acid delivered approximately 50, 100, or 210 mg/kg body weight per day to males and 60, 125, or 250 mg/kg per day to females. There were no clinical findings attributable to organ-specific toxicity. Pathology Findings: There were increases in the incidences of clitoral gland adenoma and of clitoral gland adenoma or carcinoma (combined) (4/50, 14/49, 15/49, 15/50) in exposed females. The incidences of clitoral gland adenoma or carcinoma (combined) in the exposed groups (29&percnt; to 31&percnt;) exceeded the historical control mean incidence (11&percnt;) and range (2&percnt; to 21&percnt;) in female F344/N rats in recent 2-year NTP feed studies. The increased incidences of clitoral gland neoplasms were considered to be some evidence of carcinogenic activity in female rats exposed to p-nitrobenzoic acid. The incidences of hyperplasia of the clitoral gland in exposed females were marginally lower than that of the controls (10/50, 6/49, 6/ 49, 7/50). There was a chemical-related decrease in the severity of nephropathy in male rats. Male rat kidneys were examined using both single and step-section analyses, and the incidences of renal tubule neoplasms were not statistically greater than those of the controls. Mild hyaline droplet accumulation was observed in renal tubule epithelial cells in 10,000 ppm males in the 13-week study, but this effect was not severe enough to lead to a chemical-related neoplastic response in the 2-year study as has been observed with other chemicals. At the 15-month interim evaluation, hematologic parameters characteristic of a mild regenerative anemia and significant differences in spleen weights were noted in 5,000 ppm females. These differences included decreases in erythrocyte count, hemoglobin, and hematocrit, increases in spleen weights, and hemosiderin accumulation in splenic macrophages. At 2 years, significant decreases in the incidences of mononuclear cell leukemia were observed in 5,000 ppm males and 2,500 and 5,000 ppm females (males: 29/50, 35/50, 26/50, 2/50; females: 17/50, 11/50, 3/50, 0/50). While the mechanism for this decrease is unknown, decreases in the incidence of mononuclear cell leukemia have also been observed in 2year studies with other amine/nitro compounds. 2-YEAR STUDY IN MICE: Groups of 60 male and 60 female mice were given 0, 1,250, 2,500, or 5,000 ppm p-nitrobenzoic acid in feed for 2 years. Ten males and 10 females from each exposure group were evaluated at 15 months. Survival, Body Weights, Feed Consumption, and Clinical Findings: Two-year survival rates of exposed mice were similar to those of the controls. Mean body weights of 5,000 ppm males were 6&percnt; to 12&percnt; lower than those of the controls after week 17, and mean body weights of 5,000 ppm females were 12&percnt; to 24&percnt; lower than those of the controls after week 16. The final mean body weight of 5,000 ppm females was 19&percnt; less than that of the controls; final mean body weights of males were similar to that of the controls. Feed consumption by exposed mice was similar to that by the controls. Dietary levels of 1,250, 2,500, or 5,000 ppm p-nitrobenzoic acid delivered approximately 150, 300, or 675 mg/kg per day to males and 170, 365, or 905 mg/kg per day to females. There were no clinical findings of organ-specific toxicity. No chemical-related effects on hematology parameters were noted at the 15-month interim evaluation. Pathology Findings: There were no increases or decreases in neoplasms in male or female mice that were considered to be related to chemical administration. GENETIC TOXICOLOGY: p-Nitrobenzoic acid was mutagenic in Salmonella typhimurium strain TA100 with and without S9. No mutagenic activity was noted in strains TA98, TA1535, or TA1537, with or without S9. p-Nitrobenzoic acid induced sister chromatid exchanges and chromosomal aberrations in cultured Chinese hamster ovary cells in the absence of S9; with S9, results of both tests were negative. In vivo, no increase in micronuclei was observed in peripheral blood erythrocytes of male or female mice administered p-nitrobenzoic acid in dosed feed for 13 weeks. CONCLUSIONS: Under the conditions of these 2-year feed studies, there was no evidence of carcinogenic activity of p-nitrobenzoic acid in male F344/N rats exposed to 1,250, 2,500, or 5,000 ppm. There was some evidence of carcinogenic activity of p-nitrobenzoic acid in female F344/N rats based on increases in the incidences of clitoral gland adenoma and of clitoral gland adenoma or carcinoma (combined). There was no evidence of carcinogenic activity of p-nitrobenzoic acid in male or female B6C3F1 mice exposed to 1,250, 2,500, or 5,000 ppm. There were chemical-related decreases in the incidences of mononuclear cell leukemia in exposed male and female rats. p-Nitrobenzoic acid caused mild hematologic toxicity in female rats. Synonyms: 4-Nitrobenzoic acid; nitrodracylic acid; p-nitrobenzenecarboxylic acid; p-carboxynitrobenzene
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PMID:NTP Toxicology and Carcinogenesis Studies of p-Nitrobenzoic Acid (CAS No. 62-23-7) in F344/N Rats and B6C3F1 Mice (Feed Studies). 1259 21

There is widespread concern over the health effects of oxidant air pollutants. The state of California and the Health Effects Institute (HEI) (a nonprofit research institute funded jointly by the U.S. Environmental Protection Agency [USEPA] and combustion engine manufacturers) nominated ozone for evaluation in long-term animal studies. The NTP study designs were a result of a series of meetings at the NIEHS with scientists from NIEHS, USEPA, and HEI, as well as experts from academic institutions working in the area of air pollutants. Male and female F344/N rats and B6C3F1 mice were exposed to ozone by inhalation for 4 weeks, 2 years, or for 124 weeks (rats) or 130 weeks (mice). The oxygen used to generate the ozone was greater than 99.9% pure. Additional groups of male F344/N rats were administered injections of 4-(N-methyl-Nnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) (~99% pure) 3 times per week for 20 weeks and exposed to ozone by inhalation for 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium. 4-WEEK OZONE STUDY IN RATS: Groups of five male and five female F344/N rats were exposed to 0, 0.5, or 1.0 ppm ozone by inhalation 6 hours per day, 5 days per week, for a total of 20 days. All rats survived to the end of the study. The final mean body weights and mean body weight gains of 0.5 ppm males and females and of 1.0 ppm females were similar to those of the controls. The final mean body weight of 1.0 ppm males was 7% lower than that of the controls. Clinical findings included hypoactivity in 1.0 ppm males and females and ruffled fur in exposed groups of males. Male and female rats exposed to 0.5 or 1.0 ppm developed multifocal lesions of the lung, which consisted of infiltration of granulocytes and macrophages with extension of the bronchial epithelium into the alveolar ducts. Female rats exposed to ozone developed minimal squamous metaplasia of the laryngeal epithelium at the base of the epiglottis. Absolute and relative lung weights of all exposed groups of males and females were greater than those of the controls, and absolute and relative thymus weights of all exposed groups were generally lower than those of the controls. 4-WEEK OZONE STUDY IN MICE: Groups of five male and five female B6C3F1 mice were exposed to 0, 0.5, or 1.0 ppm ozone by inhalation 6 hours per day, 5 days per week, for a total of 20 days. All mice survived to the end of the study. The final mean body weights and body weight gains of all exposed groups of mice were less than those of the controls. Hypoactivity was observed in 1.0 ppm mice. Male and female mice exposed to 0.5 or 1.0 ppm ozone developed patchy, multifocal lesions of the lung, which consisted of infiltration of granulocytes and macrophages with extension of the bronchial epithelium into the alveolar ducts. The relative lung weight of 1.0 ppm males was significantly greater than that of the controls. There were no other statistically significant differences in absolute or relative organ weights in males or females. 2-YEAR OZONE STUDY IN RATS: The 2-year study was designed to include the present USEPA standard (0.12 ppm), the maximum concentration believed compatible with long-term survival (1.0 ppm), and an intermediate concentration (0.5 ppm). Groups of 50 male and 50 female F344/N rats were exposed to 0, 0.12, 0.5, or 1.0 ppm ozone by inhalation for 6 hours per day, 5 days per week, for 105 weeks. Survival, Body Weights, and Clinical Findings: Survival of exposed groups of rats was similar to that of the controls at the end of the study. The mean body weights of 0.12 and 0.5 ppm males and females were similar to those of the controls throughout the study. The mean body weights of 1.0 ppm males and females were slightly lower than those of the controls throughout the study. Hypoactivity was observed in male and female rats exposed to ozone. Pathology Findings: Increased incidences of ozone-induced metaplasia occurred in the nose and lung of rats exposed to 0.5 or 1.0 ppm ozone. The lesions in the nose were characterized by an increase in the number of goblin the number of goblet cells in the respiratory epithelium with mild squamous metaplasia of the cuboidal epithelium on the lateral wall. The increase in the number of goblet cells was found primarily in level I and II epithelium occurring along the lateral wall and on the maxilloturbinates and nasoturbinates. The metaplasia in the lung was a patchy multifocal lesion consisting of extension of the bronchial epithelium into the alveoli of the centriacinar region. This may represent more an extension of the bronchial epithelium into the pulmonary parenchyma than an actual transition of one epithelial cell type into another. There were increased incidences of squamous metaplasia at the base of the epiglottis characterized by one or more layers of flattened epithelial cells where low cuboidal cells are normally found. There were no increases in the incidences of alveolar/bronchiolar adenoma or carcinoma in either males or females exposed to ozone. LIFETIME OZONE STUDY IN RATS: For this study, rats were exposed to 0.5 and 1.0 ppm ozone for an additional 6 months to determine the effect of extended exposure on neoplasm incidence. Groups of 50 male and 50 female F344/N rats were exposed to 0, 0.5, or 1.0 ppm ozone by inhalation for 6 hours per day, 5 days per week, for 125 weeks. Survival, Body Weights, and Clinical Findings: Survival rates of exposed rats were similar to those of the controls. The mean body weights of 0.5 ppm males and females were similar to those of the controls throughout the study. The mean body weights of 1.0 ppm males and females were slightly lower than those of the controls for the first two years of the study. Hypoactivity was observed in exposed groups of males and females. Pathology Findings: Increased incidences of metaplasia occurred in the nose, larynx, and lung of rats exposed to 0.5 or 1.0 ppm ozone. The lung lesions were multifocal, centriacinar and were characterized by the presence of cuboidal epithelium (ciliated and nonciliated) along the alveolar ducts where type I epithelium is normally present. Inflammation (histiocytic infiltration) and interstitial fibrosis were observed in the lung of exposed males and females, and hyperplasia was observed in the nose of exposed male and female groups. There were no ozone-related increased incidences of neoplasms. 2-YEAR OZONE/NNK STUDY IN MALE RATS: An intermediate concentration of 0.5 ppm ozone was combined with exposure to two levels of a known carcinogen (0.1 and 1.0 mg NNK/kg body weight) in order to determine if ozone promotes the carcinogenic process or acts as a cocarcinogen. Groups of 48 male F344/N rats were exposed to 0 or 0.5 ppm ozone by inhalation, 6 hours per day, 5 days per week for 105 weeks. During the first 20 weeks of the study, these rats were subcutaneously injected with 0, 0.1, or 1.0 mg NNK per kg body weight in trioctanoin three times weekly. Survival and Body Weights: Two-year survival rates of male rats were similar in all groups. Final mean body weights of all males exposed to NNK alone or NNK and ozone were similar to that of the controls, with the exception of rats exposed to 1.0 mg NNK/kg body weight and 0.5 ppm ozone. Hypoactivity was observed in males exposed to NNK and ozone, in those exposed to NNK without ozone, and in those exposed to ozone only. Pathology Findings: Alveolar epithelial metaplasia and interstitial fibrosis occurred in all groups of rats exposed to ozone or to NNK and ozone, but not in those exposed to NNK without ozone. Increased incidences of hyperplasia occurred in groups of rats exposed to NNK or to ozone and NNK. Incidences of hyperplasia were similar among groups of rats exposed to NNK only. An increased incidence of alveolar/bronchiolar adenoma or carcinoma (combined) occurred in rats administered 1.0 mg/kg NNK, with or without ozone. The administration of ozone did not affect the occurrence of pulmonary neoplasms or nonneoplastic lesions in rats administered NNK. 2-YEAR OZONE STUDY IN MICE: The 2-year study was designed to include the present USEPA standard (0.12 ppm), the maximum concentration believed compatible with long-term survival (1.0 ppm), and an intermediate concentration (0.5 ppm). Groups of 50 male and 50 female B6C3F1 mice were exposed to 0, 0.12, 0.5, or 1.0 ppm ozone by inhalation for 6 hours per day, 5 days per week, for 105 weeks. Survival, Body Weights, and Clinical Findings: Survival rates of exposed mice were generally similar to those of the controls; the 2-year survival rate of 1.0 ppm females was greater than that of the controls. The mean body weights of 0.12 and 0.5 ppm males were similar to that of the controls throughout the study; the mean body weights of 1.0 ppm males and of all exposed groups of females were generally lower than those of the controls throughout the study. Hypoactivity was observed in male and female mice exposed to ozone. Pathology Findings: Increased incidences of metaplasia occurred in the nose and lung of mice exposed to 0.5 or 1.0 ppm ozone. The metaplasia in the nose consisted of increased thickening and extension of the squamous epithelium in the anterior portion of the nasal passage. The metaplasia in the lung consisted of extension of the bronchial epithelium into the alveoli of the centriacinar region. There were increased incidences of hyperplasia in the nose characterized by thickening of the noncuboidal (transitional) epithelium. There were increased incidences of hyperplasia in the epiglottis of female mice, a change that was characterized by a minimal increase in the thickness of the epithelium. Incidences of alveolar/bronchiolar adenoma or carcinoma (combined) were marginally increased in 0.5 and 1.0 ppm males (0 ppm, 14/50; 0.12 ppm, 13/50; 0.5 ppm, 18/50; 1.0 ppm, 19/50) and were increased in 1.0 ppm females (6/50, 7/50, 9/49, 16/50). LIFETIME OZONE STUDY IN MICE: For this study, mice were exposed to 0.5 and 1.0 ppm ozone for 30 months to determine the effect of extended exposure on neoplasm incidence. Groups of 50 male and 50 female B6C3F1 mice were exposed to 0, 0.5, or 1.0 ppm ozone by inhalation for 6 hours per day, 5 days per week, for 130 weeks. Survival and Body Weights: Survival rates of exposed mice were similar to those of the controls. The mean body weights of 0.5 ppm males and females were similar to those of the controls throughout the study. The mean body weights of 1.0 ppm males and females were generally lower than those of the controls throughout the study. Hypoactivity was observed in male and female mice exposed to ozone. Pathology Findings: The incidences of alveolar/bronchiolar adenoma and carcinoma (combined) were marginally increased in exposed males (0 ppm, 16/49; 0.5 ppm, 22/49; 1.0 ppm, 21/50) and in exposed females (6/50, 8/49, 12/50). Increased incidences of metaplasia occurred in the nose, larynx, and lung of exposed groups of males and females, and the incidences of hyperplasia were increased in the larynx and nose of exposed mice. The morphology of the lesions was similar to that seen in the 2-year study. There were no ozone-related increases in alveolar epithelial hyperplasia. GENETIC TOXICOLOGY: Ozone was mutagenic in Salmonella typhimurium strain TA102, with and without S9 metabolic activation. CONCLUSIONS: Under the conditions of these 2-year and lifetime inhalation studies, there was no evidence of carcinogenic activity of ozone in male or female F344/N rats exposed to 0.12, 0.5, or 1.0 ppm. There was equivocal evidence of carcinogenic activity of ozone in male B6C3F1 mice based on increased incidences of alveolar/bronchiolar adenoma or carcinoma. There was some evidence of carcinogenic activity of ozone in female B6C3F1 mice based on increased incidences of alveolar/bronchiolar adenoma or carcinoma. There was no evidence that exposure to 0.5 ppm ozone enhanced the incidence of NNK-induced pulmonary neoplasms in male rats. Exposure of male and female rats to ozone for 2 years or 125 weeks was associated with goblet cell hyperplasia and squamous metaplasia in the nose, squamous metaplasia in the larynx, and metaplasia (extension of bronchial epithelium into the centriacinar alveolar ducts) and interstitial fibrosis in the lung. Exposure of male and female mice to ozone for 2 years or 130 weeks was associated with hyperplasia and squamous metaplasia in the nose and inflammation (histiocytic infiltration) and metaplasia (extension of bronchial epithelium into the centriacinar alveolar ducts) of the lung.
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PMID:NTP Toxicology and Carcinogenesis Studies of Ozone (CAS No. 10028-15-6) and Ozone/NNK (CAS No. 10028-15-6/ 64091-91-4) in F344/N Rats and B6C3F1 Mice (Inhalation Studies). 1259 23

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