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

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

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

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

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

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

Toxicology and carcinogenesis studies of 1-bromopropane (CAS No. 106-94-5) in F344/N rats and B6C3F1 mice (inhalation studies)

In the early to mid 1990s, 1-bromopropane was used primarily as an intermediate in the production of pesticides, quaternary ammonium compounds, flavors and fragrances, pharmaceuticals, and other chemicals in well-controlled, closed processes. In the mid to late 1990s, it was introduced as a less toxic replacement for methylene chloride in emissive applications such as vapor and immersion degreasing operations and critical cleaning of electronics and metals. 1-Bromopropane was also introduced as a nonflammable, nontoxic, fast-drying, and inexpensive solvent for adhesive resins, and has been marketed as a replacement for ozone depleting refrigerants. 1-Bromopropane was nominated for study by the Occupational Safety and Health Administration based on the potential for widespread occupational and environmental exposure and a lack of toxicity and carcinogenicity data. Male and female F344/N rats and B6C3F1 mice were exposed to 1-bromopropane (99% or greater pure) by inhalation for 2 weeks, 3 months, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium and Escherichia coli and mouse peripheral blood. 2-WEEK STUDY IN RATS: Groups of five male and five female rats were exposed to 1-bromopropane vapor at concentrations of 0, 125, 250, 500, 1,000, or 2,000 ppm, 6 hours plus T90 (12 minutes) per day, 5 days per week for 16 days. All rats survived to the end of the study except one 500 ppm male. Mean body weights of 2,000 ppm rats were significantly less than those of the chamber controls. The absolute kidney weight of 1,000 ppm males, relative kidney weights of all exposed groups of males, and absolute and relative kidney weights of all exposed groups of females were significantly increased. The absolute and relative liver weights of 1,000 ppm males, relative liver weights of 500 and 2,000 ppm males, and absolute and relative liver weights of 500 ppm or greater females were significantly increased. Nasal lesions included suppurative inflammation in males exposed to 500 ppm or greater, respiratory epithelial necrosis in 1,000 and 2,000 ppm males, and respiratory epithelial regeneration in 1,000 and 2,000 ppm females. 2-WEEK STUDY IN MICE: Groups of five male and five female mice were exposed to 1-bromopropane vapor at concentrations of 0, 125, 250, 500, 1,000, or 2,000 ppm, 6 hours plus T90 (12 minutes) per day, 5 days per week for 17 days. All 2,000 ppm males, two 2,000 ppm females, four 500 ppm males, one 1,000 ppm male, and one 1,000 ppm female died early. The mean body weight gain of 1,000 ppm males was significantly less than that of the chamber controls. Abnormal breathing, lethargy, and eye discharge were observed primarily during week 1 in groups exposed to 500 ppm or greater. Liver weights of 1,000 ppm males and of females exposed to 500 ppm or greater were significantly increased. Kidney weights of 1,000 and 2,000 ppm females were significantly increased. Microscopic lesions related to 1-bromopropane exposure occurred in the lung, liver, and nose of males and females and were primarily seen in mice exposed to 500 ppm or greater. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats were exposed to 1-bromopropane vapor at concentrations of 0, 62.5, 125, 250, 500, or 1,000 ppm, 6 hours plus T90 (10 minutes) per day, 5 days per week for 14 weeks. Additional clinical pathology groups of 10 male and 10 female rats were exposed to the same concentrations for 23 days. All rats survived to the end of the study. Mean body weights of 1,000 ppm males were significantly less than those of the chamber controls. The increases in sorbitol dehydrogenase activities in 500 ppm males and 1,000 ppm males and females were consistent with the histopathologic evidence of mild hepatotoxicity caused by 1-bromopropane. Liver weights of males exposed to 250 ppm or greater and of females exposed to 125 ppm or greater were significantly increased. Spleen and kidney weights of 1,000 ppm females were significantly increased. Exposure concentration-related decreases of 28% in sperm motility and 37% in sperm counts were seen in the 1,000 ppm group of male rats. Female rats in all three exposure groups evaluated exhibited altered estrous cycles, spending significantly more time in extended estrus and less time in extended diestrus. The incidences of cytoplasmic vacuolization of the liver were significantly increased in males exposed to 250 ppm or greater and in females exposed to 500 ppm or greater. Hepatocyte degeneration was also observed in 1,000 ppm females. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice were exposed to 1-bromopropane vapor at concentrations of 0, 62.5, 125, 250, or 500 ppm, 6 hours plus T90 (10 minutes) per day, 5 days per week for 14 weeks. One 250 ppm male and four males and five females in the 500 ppm groups died early. Mean body weights of exposed groups were similar to those of the chamber controls. Lethargy was observed in males and females exposed to 500 ppm, and abnormal breathing was observed in moribund mice. The kidney, liver, and lung weights of 500 ppm females were significantly greater than those of the chamber controls. The kidney weights of 500 ppm males were significantly decreased. Sperm counts in the 500 ppm group of male mice were 28% less than that in the chamber controls. Female mice exhibited altered estrous cycles, with females in the 500 ppm group spending significantly more time in extended diestrus and those in the 250 ppm group spending significantly more time in extended estrus compared to the chamber controls. Nonneoplastic lesions were observed in the nose, larynx, trachea, lung, and liver of 500 ppm males and females and in the adrenal cortex of 500 ppm females. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were exposed to 1-bromopropane vapor at concentrations of 0, 125, 250, or 500 ppm, 6 hours plus T90 (10 minutes) per day, 5 days per week for 105 weeks. Survival of 500 ppm males was significantly less than that of the chamber control group. Mean body weights of exposed groups were similar to those of the chamber controls. Increased incidences of macroscopic, soft, pale-yellow to green, variably sized nodules were seen predominantly in the nose and skin of exposed rats. The number of animals with multiple masses was increased in the 500 ppm groups. In most cases, these lesions were microscopically shown to be suppurative inflammation, many with Splendore-Hoeppli material. The incidence of adenoma of the large intestine (colon or rectum) was significantly greater in 500 ppm females than in the chamber control group. The incidence of adenoma of the large intestine in 250 ppm males exceeded the historical control ranges for inhalation studies and all routes. The incidences of keratoacanthoma, basal cell adenoma, basal cell carcinoma, or squamous cell carcinoma (combined) were significantly greater in all exposed groups of males than in the chamber control group and exceeded the historical control range for inhalation studies. The incidences of keratoacanthoma and of keratoacanthoma or squamous cell carcinoma (combined) in 250 and 500 ppm males were also significantly increased and exceeded the historical control ranges for inhalation studies. In 500 ppm females, the incidence of squamous cell papilloma, keratoacanthoma, basal cell adenoma, or basal cell carcinoma (combined) exceeded the historical control range for inhalation studies. The incidence of malignant mesothelioma was significantly greater in 500 ppm males than in the chamber control group. The incidences of pancreatic islet adenoma in all exposed groups of males and of pancreatic islet adenoma or carcinoma (combined) in 125 and 250 ppm males were significantly increased. Treatment-related nonneoplastic lesions were observed in the respiratory system of exposed male and female rats. In the nose, the incidences of suppurative chronic inflammation, chronic active inflammation, glandular hyperplasia, respiratory epithelial hyperplasia (females), and respiratory metaplasia of the olfactory epithelium (females) were increased in all exposed groups. In the larynx, the incidences of chronic active inflammation and squamous metaplasia (except 125 ppm females) were increased in all exposed groups, and the incidences of suppurative chronic inflammation were increased in the 500 ppm groups. Also, chronic inflammation of the lung was observed in the 500 ppm females. In the trachea, there were increased incidences of chronic active inflammation in all exposed groups of females and 500 ppm males, and the incidence of epithelial hyperplasia was increased in 500 ppm females. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were exposed to 1-bromopropane vapor at concentrations of 0, 62.5, 125, or 250 ppm, 6 hours plus T90 (10 minutes) per day, 5 days per week for 105 weeks. Survival of exposed groups was similar to that of the chamber controls. Mean body weights of all exposed groups were similar to those of the chamber controls throughout the study. In the females, there were increased incidences of alveolar/bronchiolar adenoma, alveolar/bronchiolar carcinoma, and alveolar/bronchiolar adenoma or carcinoma (combined); the incidences of alveolar/bronchiolar adenoma or carcinoma (combined) were significantly increased in all exposed groups of females. There were significantly increased incidences of cytoplasmic vacuolization of the bronchiolar epithelium in all exposed male groups and regeneration of the bronchiolar epithelium in all exposed groups of males and females. In the nose, there were significantly increased incidences of cytoplasmic vacuolization of the respiratory epithelium in all exposed groups of males and in 125 and 250 ppm females. There were significantly increased incidences of respiratory epithelial hyperplasia in all exposed female groups and in 62.5 and 250 ppm males. (ABSTRACT TRUNCATED)     

Toxicology and carcinogenesis studies of pulegone (CAS No. 89-82-7) in F344/N rats and B6C3F1 mice (gavage studies)

Several essential oils contain pulegone and are used for flavoring foods, drinks, and dental products, as fragrance agents, and in herbal medicines. Pulegone was nominated for study by the National Institute of Environmental Health Sciences based on the potential for human exposure and the absence of carcinogenicity data. Male and female F344/N rats and B6C3F1 mice received pulegone (approximately 96% pure) by gavage for 2 weeks, 3 months, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, Escherichia coli, and mouse peripheral blood erythrocytes. 2-WEEK STUDY IN RATS: Groups of five male and five female rats were administered 0, 37.5, 75, 150, 300, or 600 mg pulegone/kg body weight in corn oil by gavage, 5 days per week for 16 days. All male rats and nearly all female rats in the 300 and 600 mg/kg groups died prior to the end of the study. All moribund sacrifices and early deaths were attributed to liver toxicity. Mean body weight gains of males administered 37.5 or 150 mg/kg were significantly less than that of the vehicle controls. Clinical findings in 300 and 600 mg/kg rats included nasal/eye discharge, thinness, lethargy, and ruffled fur. Liver and kidney weights of dosed groups of females were generally significantly greater than those of the vehicle control group. The incidences of necrosis and cytoplasmic vacuolization of the liver in 300 and 600 mg/kg males and females were significantly greater than those in the vehicle control groups. 2-WEEK STUDY IN MICE: Groups of five male and five female mice were administered 0, 18.75, 37.5, 75, 150, or 300 mg pulegone/kg body weight in corn oil by gavage, 5 days per week for 16 days. Four females and one male in the 300 mg/kg groups died by study day 5. All early deaths were attributed to liver toxicity. Mean body weights of the dosed groups were similar to those of the vehicle controls. Clinical findings were observed only in 300 mg/kg mice and included thinness, lethargy, and ruffled fur. Liver weights of 300 mg/kg males were significantly greater than those of the vehicle controls. The incidences of cytoplasmic vacuolization and diffuse fatty change in 300 mg/kg females and necrosis in 300 mg/kg males were significantly greater than those in the vehicle controls. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats were administered 0, 9.375, 18.75, 37.5, 75, or 150 mg pulegone/kg body weight in corn oil by gavage, 5 days per week for 14 weeks. All rats survived until the end of the study except for one female in the 150 mg/kg group that died on day 9. Mean body weights of 75 and 150 mg/kg males and 150 mg/kg females were significantly less than those of the vehicle controls. At the end of the study, there was a small dose-related decrease in the erythron, evidenced by decreases in the hematocrit and hemoglobin values and the erythrocyte counts. An apparent erythroid response to the decreased erythron was evidenced by increased reticulocyte counts. Reduced and oxidized glutathione levels were generally increased in 75 and 150 mg/kg males and in 37.5 mg/kg or greater females. Absolute and relative liver weights of 75 and 150 mg/kg females and relative liver weights of males administered 18.75 mg/kg or greater were significantly greater than those of the vehicle controls. The absolute kidney weight of 150 mg/kg females and the relative kidney weights of all dosed groups, except 9.375 mg/kg males, were significantly greater than those of the vehicle controls. Absolute and relative thymus weights of 150 mg/kg males and females and the absolute thymus weight of 75 mg/kg males were significantly less than those of the vehicle controls. In the kidney, there was hyaline glomerulopathy in 75 mg/kg males and 150 mg/kg males and females. The incidence of renal tubule protein casts was significantly increased in the 150 mg/kg females. In the liver, incidences of bile duct hyperplasia and hepatocyte hypertrophy in 75 and 150 mg/kg males and 150 mg/kg females, hepatocyte focal necrosis in 150 mg/kg males, and oval cell hyperplasia and periportal fibrosis in 150 mg/kg males and females were increased. Incidences of bone marrow hyperplasia in 37.5 mg/kg males and 75 and 150 mg/kg males and females, heart mineralization in 150 mg/kg males, glandular stomach mineralization in 75 and 150 mg/kg females, and cellular histiocytic infiltration in the lung and ovarian cyst in 150 mg/kg females were significantly increased. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice were administered 0, 9.375, 18.75, 37.5, 75, or 150 mg pulegone/kg body weight in corn oil by gavage, 5 days per week for 14 weeks. All mice survived to the end of the study. Mean body weights of dosed mice were similar to those of the vehicle controls. Reduced and oxidized glutathione levels were generally greater than vehicle control levels in 150 mg/kg males and in 75 and 150 mg/kg females. Liver weights of 150 mg/kg males and 75 and 150 mg/kg females were significantly greater than those of the vehicle controls. No histopathologic lesions were observed that could be attributed to the administration of pulegone. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were administered 0, 18.75 (males only), 37.5, 75, or 150 (females only) mg pulegone/kg body weight in corn oil by gavage, 5 days per week for up to 104 weeks. Due to excessive morbidity and mortality, 75 mg/kg males and 150 mg/kg females were not administered pulegone after week 60 (stop-exposure); these groups were administered the corn oil vehicle until the end of the study. Survival of 37.5 mg/kg males was significantly less than that of the vehicle controls; only two 75 mg/kg stop-exposure males survived, and no 150 mg/kg stop-exposure females survived to the end of the study. Compared to those of the vehicle controls, mean body weights were less in 75 mg/kg stop-exposure males after week 13 and in 75 mg/kg and 150 mg/kg stop-exposure females after weeks 21 and 9, respectively. Clinical findings included thinness, lethargy, and ruffled fur in the 75 mg/kg stop-exposure males and 150 mg/kg stop-exposure females. The incidences of urinary bladder papilloma and of papilloma or carcinoma (combined) were significantly increased in 150 mg/kg stop-exposure females. In the kidney, incidences of hyaline glomerulopathy were significantly increased in 37.5 mg/kg and 75 mg/kg stop-exposure males and in all dosed groups of females. The severity of chronic progressive nephropathy was increased in 37.5 mg/kg and 75 mg/kg stop-exposure males and in 75 mg/kg and 150 mg/kg stop-exposure females; the incidences of nephropathy were significantly increased in 75 mg/kg and 150 mg/kg stop-exposure females. The incidence of renal cyst was significantly increased in 75 mg/kg stop-exposure males. In the liver, incidences of diffuse hepatocyte cellular alteration were significantly increased in 37.5 mg/kg and 75 mg/kg stop-exposure males and 75 mg/kg and 150 mg/kg stop-exposure females. There were significant increases in the incidences of other liver lesions including fatty change, bile duct cyst, hepatocyte necrosis, oval cell hyperplasia, bile duct hyperplasia, and portal fibrosis. In the nose, 37.5 mg/kg and 75 mg/kg stop-exposure males and all dosed groups of females had significantly increased incidences of olfactory epithelium degeneration. All dosed groups of females had significantly increased incidences of respiratory metaplasia of the olfactory epithelium and nasal inflammation. In the forestomach, incidences of inflammation and ulcer were significantly increased in 37.5 mg/kg and 75 mg/kg stop-exposure males, and incidences of epithelial hyperplasia and perforation were increased in 75 mg/kg stop-exposure males. In the glandular stomach, the incidence of inflammation was significantly increased in 75 mg/kg stop-exposure males. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were administered 0, 37.5, 75, or 150 mg pulegone/kg body weight in corn oil by gavage, 5 days per week for 105 weeks. Survival of all dosed groups was similar to that of the vehicle controls. Mean body weights of 150 mg/kg males and females were less than those of the vehicle controls after weeks 25 and 33, respectively. The incidences of multiple hepatocellular adenoma were significantly increased in all dosed groups of males, and the incidences of hepatocellular adenoma (includes multiple) and hepatoblastoma (includes multiple) were significantly increased in the 75 mg/kg males. The combined incidences of hepatocellular adenoma, hepatocellular carcinoma, or hepatoblastoma occurred with positive trends and were significantly increased in 75 mg/kg males and 150 mg/kg females. The incidence of hepatocellular adenoma was significantly increased in 150 mg/kg females. The incidences of several nonneoplastic liver lesions were significantly increased, primarily in the 75 and 150 mg/kg groups. These nonneoplastic lesions included clear cell, eosinophilic, and mixed cell foci; focal fatty change; centrilobular hepatocyte hypertrophy; intravascular hepatocyte; necrosis; pigmentation; bile duct cyst and hyperplasia; and oval cell hyperplasia. In the kidney, incidences of hyaline glomerulopathy were significantly increased in all dosed groups of males and 75 and 150 mg/kg females. The incidence of mineralization was significantly increased in 150 mg/kg females, and the incidence of nephropathy in 150 mg/kg females and severity of nephropathy in 150 mg/kg males were increased. Incidences of congestion of the glomerulus were increased in 150 mg/kg males and females. The incidence of osteoma or osteosarcoma (combined) in all organs of 75 mg/kg females exceeded the historical control ranges. One 150 mg/kg male and one 75 mg/kg female had nasal osteoma; no nasal osteomas have been observed in historical control mice. (ABSTRACT TRUNCATED)     

Toxicology and carcinogenesis studies of isoeugenol (CAS No. 97-54-1) in F344/N rats and B6C3F1 mice (gavage studies)

Isoeugenol is one of several structurally similar phenylpropenoid compounds produced by plants. It has been extracted from calamus, savory, basil, ylang-ylang, clove, tuberose, jonquil, nutmeg, tobacco, sandalwood, dill seed, mace, gardenia, petunia, and other flowers. Isoeugenol can also be produced by isomerization of eugenol, which occurs naturally in clove, pimento, bay leaf, and cinnamon. As a fragrance with a spicy, carnation-like odor, isoeugenol is incorporated into numerous household and personal hygiene products, including perfumes, cream lotions, soaps, and detergents. As a flavoring agent, isoeugenol is added to nonalcoholic drinks, baked foods, and chewing gums. Isoeugenol was nominated by the National Cancer Institute and was selected for carcinogenicity testing because of widespread human exposure through its use as a flavoring and fragrance agent and because of its structural similarity to phenylpropenoids such as safrole, isosafrole, eugenol, methyleugenol, estragole, and anethole, most of which are known rodent carcinogens. Male and female F344/N rats and B6C3F1 mice were administered isoeugenol (99% or greater pure) in corn oil by gavage for 3 months or 2 years. Genetic toxicity tests were conducted in Salmonella typhimurium, Escherichia coli, cultured Chinese hamster ovary cells, and mouse peripheral blood erythrocytes. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats were exposed to isoeugenol in corn oil by gavage at doses of 0, 37.5, 75, 150, 300, or 600 mg/kg, 5 days per week for 14 weeks. All rats survived to the end of the study except one 600 mg/kg male and one 37.5 mg/kg female that were killed in dosing accidents. Mean body weights of all exposed groups of males were significantly less than that of the vehicle control group; however, only the decrease for the 600 mg/kg group exceeded 10% and was considered related to isoeugenol exposure. Liver weights were significantly increased in 300 and 600 mg/kg females. The incidences of minimal atrophy of the olfactory epithelium of the nose were significantly increased in 150 mg/kg or greater males and in 300 or 600 mg/kg females. The incidence of atrophy of olfactory nerve bundles was significantly increased in 600 mg/kg females. Minimal to mild periportal hepatocellular cytoplasmic alteration occurred in all 300 or 600 mg/kg females. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice were exposed to isoeugenol in corn oil by gavage at doses of 0, 37.5, 75, 150, 300, or 600 mg/kg, 5 days per week for 14 weeks. All mice survived to the end of the study. The mean body weight of 600 mg/kg males was significantly less (12%) than that of the vehicle controls. Liver weights of 300 and 600 mg/kg males were significantly greater than those of the vehicle controls. Minimal to moderate atrophy of olfactory epithelial tissue and nerve bundles was observed in 600 mg/kg males and females. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were exposed to isoeugenol in corn oil by gavage at doses of 0, 75, 150, or 300 mg/kg, 5 days per week for 105 weeks. Survival rates of exposed male and female rats were similar to those of vehicle controls. Mean body weights of 300 mg/kg male rats were 9% greater than the vehicle controls at the end of the study. The general lack of toxicity and nonneoplastic lesions indicates that rats might have been able to tolerate higher doses. Two male rats in the 300 mg/kg group had rare benign or malignant thymomas, while two other males in this group had rare mammary gland carcinomas. Low incidences of minimal atrophy and minimal to mild respiratory metaplasia of the olfactory epithelium were increased in 150 mg/kg males and 300 mg/kg males and females. Similar incidences of minimal to mild olfactory epithelial degeneration in 300 mg/kg males were also increased. Incidences of keratoacanthoma of the skin were decreased in 150 and 300 mg/kg males. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were exposed to isoeugenol in corn oil by gavage at doses of 0, 75, 150, or 300 mg/kg, 5 days per week for 104 (females) or 105 (males) weeks. Survival of 300 mg/kg males was significantly decreased compared to the vehicle controls. Mean body weights of 300 mg/kg male and female groups were less than those of vehicle controls at the end of the study, 10% and 15% less, respectively. In all groups of exposed males, the incidences of hepatocellular adenoma, hepatocellular carcinoma, and hepatocellular adenoma or carcinoma (combined) were significantly greater than those in the vehicle control group; incidences of multiple hepatocellular adenoma were also significantly increased. Incidences of clear cell focus were significantly increased in 75 and 150 mg/kg male mice. There was a significant positive trend in the incidences of histiocytic sarcoma in females, and this neoplasm occurred in multiple tissues. Incidences of respiratory metaplasia in olfactory epithelium in all exposed groups and of atrophy and hyaline droplet accumulation in all exposed groups except 75 mg/kg females were significantly greater than those in corresponding vehicle control groups. Incidences of minimal to marked hyperplasia of Bowman's gland were increased significantly in all exposed groups. Incidences of minimal to mild necrosis of renal papilla and mild to moderate necrosis of renal tubules were increased significantly in 300 mg/kg females. Incidences of forestomach squamous hyperplasia, inflammation, and ulceration (males only) increased with exposure and were significant in the 300 mg/kg groups. The incidence of glandular stomach ulcers was low but significantly increased in the 300 mg/kg groups. GENETIC TOXICOLOGY: Isoeugenol was not mutagenic in two independent assays in bacteria (S. typhimurium and E. coli) conducted with and without exogenous metabolic activation (S9 liver enzymes). Neither did it induce chromosomal aberrations in cultured Chinese hamster ovary cells, with or without S9 activation. Frequencies of micronucleated erythrocytes were not increased in peripheral blood of male mice exposed to isoeugenol by gavage for 3 months; however, an increasing trend and a threefold increase in the 600 mg/kg group indicate a positive result for this test in female mice. CONCLUSIONS: Under the conditions of these 2-year gavage studies, there was equivocal evidence of carcinogenic activity of isoeugenol in male F344/N rats based on increased incidences of rarely occurring thymoma and mammary gland carcinoma. There was no evidence of carcinogenic activity of isoeugenol in female F344/N rats administered 75, 150, or 300 mg/kg. There was clear evidence of carcinogenic activity of isoeugenol in male B6C3F1 mice based on increased incidences of hepatocellular adenoma, hepatocellular carcinoma, and hepatocellular adenoma or carcinoma (combined). There was equivocal evidence of carcinogenic activity of isoeugenol in female B6C3F1 mice based on increased incidences of histiocytic sarcoma. Exposure to isoeugenol resulted in nonneoplastic lesions of the nose in male and female rats; of the nose, forestomach, and glandular stomach in male and female mice; and of the kidney in female mice.     

Toxicology and carcinogenesis studies of benzophenone (CAS No. 119-61-9) in F344/N rats and B6C3F1 mice (feed studies)

Benzophenone is used as a photoinitiator, a fragrance enhancer, an ultraviolet curing agent, and occasionally as a flavor ingredient; it is also used in the manufacture of insecticides, agricultural chemicals, and hypnotics, antihistamines, and other pharmaceuticals; and it is used as an additive in plastics, coatings, and adhesive formulations. Benzophenone was nominated for study by the National Institute of Environmental Health Sciences based on its potential for occupational and consumer exposure and the lack of long-term toxicity data. Male and female F344/N rats and B6C3F1 mice were exposed to benzophenone (greater than 99% pure) in feed for 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, mouse bone marrow cells, and mouse peripheral blood erythrocytes. Results of 14-week toxicity studies in F344/N rats and B6C3F1 mice were reported earlier (NTP, 2000). 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were fed diets containing 0, 312, 625, or 1,250 ppm benzophenone (equivalent to average daily doses of approximately 15, 30, and 60 mg benzophenone/kg body weight to males and 15, 30, and 65 mg/kg to females) for 105 weeks. Survival of 1,250 ppm males was significantly less than that of controls. Mean body weights of 1,250 ppm males were markedly less than those of the controls during year 2 of the study, and weights of exposed females were consistently less than controls throughout the study. Feed consumption by 1,250 ppm males was less than that by the controls after week 70; feed consumption by 1,250 ppm females was generally less than that by the controls throughout the study. There was a positive trend in the incidences of renal tubule adenoma in males, and the incidences in 625 and 1,250 ppm males exceeded the historical control range for all routes; these neoplasms were accompanied by significantly increased incidences of renal tubule hyperplasia. Due to these findings, additional kidney sections were evaluated; results indicated additional renal tubule adenomas in all groups of males and renal tubule hyperplasia in all groups of males and females. The incidences of pelvic transitional epithelium hyperplasia and the severity of nephropathy were significantly increased in all exposed groups of male rats. Increased incidences of mononuclear cell leukemia in all exposed groups of females exceeded the historical control range from feed studies, and the incidence in 625 ppm females was significantly greater than that in the controls. Male rats exposed to 312 or 625 ppm had significantly increased incidences of mononuclear cell leukemia. One 625 ppm female and two 1,250 ppm females had histiocytic sarcomas, and the incidence in the 1,250 ppm group exceeded the range in the historical controls. Liver lesions included significantly increased incidences of hepatocytic centrilobular hypertrophy in all exposed groups of males and females, cystic degeneration in 625 and 1,250 ppm males, and bile duct hyperplasia in all exposed groups of females. Incidences of mammary gland fibroadenoma in females exposed to 625 or 1,250 ppm were lower than expected after adjusting for body weight. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were fed diets containing 0, 312, 625, or 1,250 ppm benzophenone (equivalent to average daily doses of approximately 40, 80, and 160 mg/kg body weight to males and 35, 70, and 150 mg/kg to females) for 105 weeks. Survival of all exposed groups of mice was generally similar to that of the control groups. Mean body weights of exposed females were less than vehicle controls. Feed consumption by exposed males and females was similar to that by the controls. In male mice, there were significantly increased incidences of hepatocellular adenoma in the 625 and 1,250 ppm groups, and these incidences exceeded the historical control range. All hepatocellular neoplasms combined occurred with a positive trend. In female mice, the incidences of hepatocellular adenoma in the 625 and 1,250 ppm groups were higher than expected after adjusting for the lower body weights in these groups. Incidences of centrilobular hepatocyte hypertrophy were significantly increased in all exposed groups of males and females. All exposed groups of male mice had significant increases in the incidences of multinucleated hepatocytes and chronic active inflammation. The incidences of cystic degeneration of hepatocytes in 625 and 1,250 ppm males were significantly increased. The incidence of histiocytic sarcoma in 625 ppm females was significantly increased and exceeded the historical control range. The incidences of kidney nephropathy and mineralization in exposed groups of females and the severity of nephropathy in exposed groups of males were significantly increased. The incidences of metaplasia of the olfactory epithelium were significantly increased in 1,250 ppm males and females. The incidences of hyperplasia of lymphoid follicles in the spleen were significantly increased in all exposed groups of males and in 312 and 625 ppm females. GENETIC TOXICOLOGY: Benzophenone was not mutagenic in Salmonella typhimurium strains TA98, TA100, TA1535, or TA1537, with or without hamster or rat liver activation enzymes. No significant increases in the frequencies of micronucleated polychromatic erythrocytes were seen in bone marrow samples from male mice administered benzophenone three times by intraperitoneal injection. In addition, no increases in micronucleated normochromatic erythrocytes were noted in peripheral blood of male or female mice administered benzophenone for 14 weeks in dosed feed. CONCLUSIONS: Under the conditions of these 2-year studies, there was some evidence of carcinogenic activity of benzophenone in male F344/N rats based on increased incidences of renal tubule adenoma; mononuclear cell leukemia in male F344/N rats may have been related to benzophenone exposure. There was equivocal evidence of carcinogenic activity of benzophenone in female F344/N rats based on the marginally increased incidences of mononuclear cell leukemia and histiocytic sarcoma. There was some evidence of carcinogenic activity of benzophenone in male B6C3F1 mice based on increased incidences of hepatocellular neoplasms, primarily adenoma. There was some evidence of carcinogenic activity of benzophenone in female B6C3F1 mice based on increased incidences of histiocytic sarcoma; the incidences of hepatocellular adenoma in female B6C3F1 mice may have been related to benzophenone exposure. Administration of benzophenone in feed resulted in increased incidences and/or severities of nonneoplastic lesions in the kidney and liver of male and female rats and in the liver, kidney, nose, and spleen of male and female mice. Decreased incidences of mammary gland fibroadenoma in female rats were related to benzophenone exposure.     

Toxicology and carcinogenesis studies of riddelliine (CAS No. 23246-96-0) in F344/N rats and B6C3F1 mice (gavage studies)

Riddelliine belongs to a class of toxic pyrrolizidine alkaloids and is isolated from plants of the genera Crotalaria, Amsinckia, and Senecio that grow in the western United States. Cattle, horses, and sheep that ingest these plants succumb to their toxic effects. Riddelliine residues have been found in meat, milk, and honey, and the plants may contaminate human food sources. Riddelliine was nominated for study by the Food and Drug Administration because of its potential for human exposure and its economic impact on the livestock industry and because the toxicity of other pyrrolizidine alkaloids suggests riddelliine may be carcinogenic. Male and female F344/N rats and B6C3F1 mice received riddelliine (approximately 92% pure) by gavage. Female rats and male and female mice were dosed for 2 years; due to high mortality, the study in male rats was terminated at week 72. In vitro genetic toxicology studies were conducted in Salmonella typhimurium and in cultured Chinese hamster ovary (CHO) cells. In addition, riddelliine was evaluated in vivo for induction of micronuclei in mouse bone marrow and peripheral blood erythrocytes and for induction of S-phase DNA synthesis and unscheduled DNA synthesis in the liver of rats and mice. Riddelliine-induced DNA adduct levels were determined in liver tissue obtained from female rats admininstered riddelliine for 3 or 6 months. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were administered 0 or 1 mg riddelliine/kg body weight in sodium phosphate buffer by gavage 5 days per week; additional groups of 50 female rats received 0.01, 0.033, 0.1, or 0.33 mg/kg. A wide dose range was used in female rats to better characterize the dose-response curve. Females were dosed for 105 weeks; due to high mortality, male rats were terminated at week 72. All but three 1 mg/kg males died before week 70, and all 1 mg/kg females died before week 97. Mean body weights of 1 mg/kg males and females were less than those of the vehicle controls throughout most of the study. The only clinical finding related to riddelliine administration was a general debilitation of the animals prior to death. Hemangiosarcomas were present in the liver of 86% of males and 76% of females in the 1 mg/kg groups, and this neoplasm was considered the cause of the large number of early deaths in these groups. The incidences of hepatocellular adenoma and mononuclear cell leukemia in 1 mg/kg males and females were significantly increased. Nonneoplastic lesions related to riddelliine treatment occurred in the liver and kidney of males and females. Analyses of liver tissue from female rats treated with riddelliine for 3 or 6 months yielded eight DNA adducts; these were the same as DNA adducts formed in vitro by the metabolism of riddelliine by human liver microsomes in the presence of calf thymus DNA. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were administered riddelliine in sodium phosphate buffer by gavage at doses of 0 or 3 mg/kg, 5 days per week, for 105 weeks; additional groups of 50 male mice received 0.1, 0.3, or 1 mg/kg for 105 weeks. A wide dose range was used in male mice to better characterize the dose-response curve. Survival of males and females administered 3 mg/kg was significantly less than that of the vehicle controls. Mean body weights of 3 mg/kg mice were less than those of the vehicle controls throughout most of the study. Hemangiosarcomas of the liver were present in 62% of males in the 3 mg/kg group. The incidences of hepatocellular neoplasms occurred with negative trends in male mice and were significantly decreased in 3 mg/kg females. The incidences of alveolar/bronchiolar neoplasms in 3 mg/kg females were significantly increased. Nonneoplastic lesions related to riddelliine administration occurred in the liver and kidney of males and females and in the lung and arteries (multiple tissues) of females. GENETIC TOXICOLOGY: Riddelliine was mutagenic in S. typhimurium strain TA100 with, but not without, S9 activation; no significant mutagenic activity was detected in strain TA98 or TA1535,ed in strain TA98 or TA1535, with or without S9. A small, dose-related increase in mutant colonies seen in strain TA97 with S9 was judged to be equivocal. Riddelliine induced sister chromatid exchanges in cultured CHO cells with and without S9. Chromosomal aberrations were induced in CHO cells only in the presence of S9. Following 4 or 13 weeks of daily gavage treatment with riddelliine, no increases in the frequency of micronucleated erythrocytes were noted in the peripheral blood of male or female B6C3F1 mice. Use of a single intraperitoneal injection protocol, however, produced a small but significant increase in the frequency of micronucleated eryth-rocytes in peripheral blood of male Swiss mice 48 hours after injection; bone marrow analysis 24 hours after injection demonstrated a small but insignificant increase in the frequency of micronuclei. Unscheduled DNA synthesis was detected in cultured hepatocytes from male and female rats and mice following 5 or 30 days of riddelliine treatment by gavage. In addition, an S-phase DNA synthesis was observed in cultured hepatocytes of male and female rats treated for either time period. CONCLUSIONS: Under the conditions of these studies, there was clear evidence of carcinogenic activity of riddelliine in male and female F344/N rats based primarily on increased incidences of hemangiosarcoma in the liver. The increased incidences of hepatocellular adenoma and mononuclear cell leukemia in male and female rats were also considered to be treatment related. There was clear evidence of carcinogenic activity of riddelliine in male B6C3F1 mice based on increased incidences of hemangiosarcoma in the liver. There was clear evidence of carcinogenic activity in female B6C3F1 mice based on increased incidences of alveolar/bronchiolar neoplasms. Administration of riddelliine by gavage resulted in nonneoplastic lesions in the liver and kidney of male and female rats; the liver and kidney of male and female mice; and the lung and arteries (multiple tissues) of female mice. Decreased incidences of hepatocellular neoplasms in male and female mice were related to riddelliine administration.     

Toxicology and carcinogenesis studies of androstenedione (CAS No. 63-05-8) in F344/N rats and B6C3F1 mice (gavage studies)

Androstenedione is an androgen steroid that is normally synthesized within men and women and may be metabolized to a more potent androgen or estrogen hormone. It was nominated to the National Toxicology Program for study due to concern for adverse health effects associated with its chronic use as a dietary supplement by athletes (prior to the banning of its over the counter sales). In order to evaluate its subchronic and chronic toxicity, male and female F344/N rats and B6C3F1 mice were administered androstenedione (98% pure) by gavage for 2 weeks, 3 months, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, Escherichia coli, rat bone marrow cells, and mouse peripheral blood erythrocytes. 2-WEEK STUDY IN RATS: groups of five male and five female rats were administered 0, 1, 5, 10, 20, or 50 mg androstenedione/kg body weight in a 0.5% aqueous methylcellulose solution by gavage, 5 days per week for 12 days. All rats survived to the end of the study, and the mean body weights of dosed groups were similar to those of the vehicle control groups. The development of cytoplasmic vacuoles within centrilobular hepatocytes in male rats was the only treatment-related effect observed. 2-WEEK STUDY IN MICE: groups of five male and five female mice were administered 0, 1, 5, 10, 20, or 50 mg androstenedione/kg body weight in a 0.5% aqueous methylcellulose solution by gavage, 5 days per week for 12 days. One vehicle control female, one 20 mg/kg female, and one 50 mg/kg female died early due to gavage accidents. There were no significant chemical-related histopathological or mean body weight changes. 3-MONTH STUDY IN RATS: groups of 10 male and 10 female core study rats were administered 0, 1, 5, 10, 20, or 50 mg androstenedione/kg body weight in a 0.5% aqueous methylcellulose solution by gavage, 5 days per week for 14 weeks; additional groups of 10 male and 10 female clinical pathology study rats received the same doses for 23 days. All rats survived to the end of the study. The mean body weights of the 20 mg/kg female group was significantly greater than those of the vehicle control group and there was significant increased weight gain in the 1, 20, and 50 mg/kg female groups. Female thymus weights were significantly increased in the 20 and 50 mg/kg groups, which may be related to the increase in mean body weight. The numbers of sperm per mg cauda epididymis in the 10, 20, and 50 mg/kg male groups and the total number of sperm per cauda epididymis in 50 mg/kg males were significantly less than those of the vehicle controls. No treatment-related histological lesions were observed in males or females. 3-MONTH STUDY IN MICE: groups of 10 male and 10 female mice were administered 0, 1, 5, 10, 20, or 50 mg androstenedione/kg body weight in a 0.5% aqueous methylcellulose solution by gavage, 5 days per week for 14 weeks. Except for one 10 mg/kg female that died early due to a dosing accident, all mice survived to the end of the study. The mean body weights of dosed groups were similar to those of the vehicle control groups. The number of spermatids per mg testis and the total number of spermatids per testis in 20 mg/kg males were significantly greater than those of the vehicle controls. Sperm motility in 50 mg/kg males was significantly lower than that in the vehicle controls. The incidences of x-zone atrophy of the adrenal cortex, an androgen-sensitive endpoint, were significantly increased in females administered 5 mg/kg or greater. There were also significant decreases in the incidences of x-zone cytoplasmic vacuolization in 20 and 50 mg/kg females. The incidences of bone marrow hyperplasia were significantly increased in 5 and 50 mg/kg males. 2-YEAR STUDY IN RATS: groups of 50 male and 50 female rats were administered 0, 10, 20, or 50 mg androstenedione/kg body weight in a 0.5% aqueous methylcellulose solution by gavage, 5 days per week for at least 104 weeks. Survival of 10 mg/kg males was significantly greater than that of the vehicle controls. The mean body weights of 20 and 50 mg/kg females were greater than those of the vehicle controls after weeks 17 and 9, respectively. The incidences of mononuclear cell leukemia were significantly increased in 20 and 50 mg/kg females and significantly decreased in 20 and 50 mg/kg males. Incidences of alveolar/bronchiolar adenoma and alveolar/bronchiolar adenoma or carcinoma (combined) were significantly increased in 20 mg/kg males. The incidence of testicular interstitial cell adenoma (including bilateral) was significantly decreased in 50 mg/kg males. In females, the incidences of mammary gland fibroadenoma were significantly decreased in the 20 and 50 mg/kg groups, the incidences of mammary gland hyperplasia were significantly decreased in all dosed groups, and the incidences of mammary gland cyst were significantly decreased in the 10 and 50 mg/kg groups. In the liver of males, the incidences of basophilic focus in all dosed groups, the incidence of clear cell focus in the 20 mg/kg group, and the incidence of eosinophilic focus in the 50 mg/kg group were significantly increased. The incidences of pancreatic islet hyperplasia and atrophy of the exocrine pancreas were significantly increased in 50 mg/kg females. 2-YEAR STUDY IN MICE: groups of 50 male and 50 female mice were administered 0, 2 (females only), 10, 20 (males only), or 50 mg androstenedione/kg body weight in a 0.5% aqueous methylcellulose solution by gavage, 5 days per week for at least 104 weeks. Survival of dosed groups was similar to that of the vehicle control groups. Mean body weights of 10 and 50 mg/kg females were generally less than those of the vehicle controls after weeks 81 and 17, respectively. The incidences of hepatocellular adenoma in males and females were significantly increased in the 50 mg/kg groups. In females, the incidences of hepatocellular carcinoma were significantly increased in all dosed groups. Incidences of hepatocellular adenoma or carcinoma (combined) in males and females were significantly increased in the 50 mg/kg groups. Incidences of hepatoblastoma were marginally increased in dosed males. Incidences of multiple hepatocellular adenomas and carcinomas were significantly increased in 10 and 50 mg/kg males, and there was an increased incidence of multiple hepatocellular adenomas in 50 mg/kg females. The incidence of eosinophilic focus was significantly increased in 50 mg/kg males, and the incidences of mixed cell focus and cytoplasmic vacuolization were significantly increased in 50 mg/kg females. There was a marginally increased incidence of pancreatic islet adenoma in 50 mg/kg males and in 10 and 50 mg/kg females, with an earlier day of first incidence in males. The incidences of clitoral gland hyperplasia and clitoral gland duct dilatation were significantly increased in 10 and 50 mg/kg females. The incidence of glomerular metaplasia of the kidney was significantly increased in 50 mg/kg females, and the incidences of cytoplasmic alteration of the submandibular salivary gland were significantly increased in all dosed female groups. The increased incidences of cytoplasmic alteration of the submandibular salivary gland and glomerular metaplasia of the kidney in female mice indicated a masculinizing effect from androstenedione treatment. In 50 mg/kg females, the incidence of malignant lymphoma was significantly decreased. GENETIC TOXICOLOGY: androstenedione was not mutagenic in either of two independent bacterial mutation assays conducted with and without exogenous metabolic activation. No significant increases in the frequencies of micronucleated polychromatic erythrocytes, indicators of chromosomal damage, were observed in bone marrow of male rats administered androstenedione by gavage once daily for 3 consecutive days. Results of a peripheral blood erythrocyte micronucleus test in mice, in which androstenedione was administered by gavage for 3 months, were negative in males but judged to be equivocal in females due to a small increase (twofold over background) in micronucleated normochromatic erythrocytes observed at the highest dose administered (50 mg/kg). CONCLUSIONS: under the conditions of these 2-year gavage studies, there was equivocal evidence of carcinogenic activity of androstenedione in male F344/N rats based on increased incidences of alveolar/bronchiolar adenoma and alveolar/bronchiolar adenoma or carcinoma (combined). There was equivocal evidence of carcinogenic activity of androstenedione in female F344/N rats based on increased incidences of mononuclear cell leukemia. There was clear evidence of carcinogenic activity of androstenedione in male B6C3F1 mice based on increased incidences of multiple hepatocellular adenoma and hepatocellular carcinoma and increased incidence of hepatoblastoma. There was clear evidence of carcinogenic activity of androstenedione in female B6C3F1 mice based on increased incidences of hepatocellular adenoma and hepatocellular carcinoma. Increased incidences of pancreatic islet adenoma in male and female mice were also considered chemical related. Androstenedione administration caused increased incidences in nonneoplastic lesions of the liver in male and female rats and mice; pancreatic islets and exocrine pancreas of female rats; and clitoral gland, kidney, and submandibular salivary gland of female mice. Decreases in the incidences of testicular interstitial cell adenoma in male rats, mammary gland fibroadenoma, cysts, and hyperplasia in female rats, and malignant lymphoma in female mice were considered related to androstenedione administration. Synonyms: Andro; androst-4-ene-3,17-dione; 4-androstene-3,17-dione; delta-4-androstene-3,17-dione; delta-4-androstenedione; 3,17-dioxoandrost-4-ene; 17-ketotestosterone; SKF 2170 Trade names: Androtex, Fecundin.     

Toxicology and carcinogenesis studies of ginseng (CAS No. 50647-08-0) in F344/N rats and B6C3F1 mice (gavage studies)

CHEMICAL AND PHYSICAL PROPERTIES: Ginseng is a perennial aromatic herb widely used in herbal remedies, dietary supplements, cosmetics, and as a food additive. Ginseng was nominated for study by the National Cancer Institute based on significant human exposure through the uses described above and the lack of information on its toxicity. Male and female F344/N rats and B6C3F1 mice were administered extracts of ginseng root by gavage for 2 weeks, 3 months, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, Escherichia coli, and mouse peripheral blood erythrocytes. 2-WEEK STUDY IN RATS: Groups of five male and five female rats were administered ginseng in 0.5% aqueous methylcellulose by gavage at doses of 0, 125, 250, 500, 1,000, or 2,000 mg/kg, 5 days per week for 16 days. All rats survived to the end of the study. Mean body weight gain of 2,000 mg/kg males was significantly greater than that of the vehicle controls. There were no chemical-related gross or microscopic findings attributed to the administration of ginseng. 2-WEEK STUDY IN MICE: Groups of five male and five female mice were administered ginseng in 0.5% aqueous methylcellulose by gavage at doses of 0, 125, 250, 500, 1,000, or 2,000 mg/kg, 5 days per week for 17 days. All mice survived to the end of the study. The final mean body weight of 1,000 mg/kg males was significantly less than that of the vehicle controls. There were no significant chemical-related gross or histopathologic changes in dosed mice. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats were administered ginseng in sterile water by gavage at doses of 0, 1,000, 2,000, 3,000, 4,000, or 5,000 mg/kg, 5 days per week for 14 weeks. All rats survived to the end of the study. Mean body weights of all dosed groups were similar to those of the vehicle control groups. No lesions that were observed by gross or histopathologic examination were attributed to the administration of ginseng. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice were administered ginseng in sterile water by gavage at doses of 0, 1,000, 2,000, 3,000, 4,000, or 5,000 mg/kg, 5 days per week for 14 weeks. All mice survived to the end of the study. Mean body weights of all dosed groups were similar to those of the vehicle control groups. Although sporadic incidences of lesions were observed in the vehicle control and 5,000 mg/kg groups, there were no chemical-related gross or microscopic findings in dosed mice. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were administered ginseng in sterile water by gavage at doses of 0, 1,250, 2,500, or 5,000 mg/kg, 5 days per week for 104 to 105 weeks. Survival of 5,000 mg/kg females was significantly less than that of the vehicle controls; however, the deaths were not attributed to the administration of ginseng because no histopathologic findings attributable to ginseng were found. Mean body weights of 5,000 mg/kg females were less than those of the vehicle controls after week 61 of the study, and mean body weights of other dosed groups of rats were similar to those of the vehicle controls throughout the study. No increases in the incidences of neoplasms or nonneoplastic lesions were attributed to the administration of ginseng. The incidence of mammary gland fibroadenoma was significantly decreased in 5,000 mg/kg females. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were administered ginseng in sterile water by gavage at doses of 0, 1,250, 2,500, or 5,000 mg/kg, 5 days per week for 105 weeks. Survival of dosed groups was similar to that of the vehicle control groups. Mean body weights of dosed mice were similar to those of the vehicle controls. No neoplasms or nonneoplastic lesions were attributed to the administration of ginseng. GENETIC TOXICOLOGY: Ginseng was not mutagenic in either of two independent bacterial mutagenicity assays, each conducted with or without exogenous metabolic activation enzymes. Bacterial strains tested included S. typhimurium strains TA97, TA98, TA100, TA102, TA104, and TA1535, as well as E. coli strain WP2 uvrA/pKM101. No significant increases were seen in the frequencies of micronucleated erythrocytes in the peripheral blood of male or female B6C3F1 mice exposed for 3 months to 1,000 to 5,000 mg/kg ginseng via gavage. CONCLUSIONS: Under the conditions of these 2-year gavage studies, there was no evidence of carcinogenic activity of ginseng in male or female F344/N rats or B6C3F1 mice administered 1,250, 2,500, or 5,000 mg/kg. The incidence of mammary gland fibroadenoma was significantly decreased in 5,000 mg/kg female rats.     

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

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

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

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

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

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

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

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

Toxicology and carcinogenesis studies of milk thistle extract (CAS No. 84604-20-6) in F344/N rats and B6C3F1 mice (Feed Studies)

Milk thistle extracts have been used as medicinal herbs in the treatment of liver cirrhosis, chronic hepatitis (liver inflammation), and gallbladder disorders. Treatment claims also include lowering cholesterol levels; reducing insulin resistance; reducing the growth of cancer cells in breast, cervical, and prostate gland cancers; and antiviral activity. Other reported uses of milk thistle in folk medicine include as a treatment for malarial fever, bronchitis, gallstones, jaundice, peritonitis, uterine congestion, varicose veins, and as a milk production stimulant for nursing mothers. The roots soaked in water overnight are used in food, and the despined leaves are added to salads. Roasted milk thistle fruit has been used as a coffee substitute. Milk thistle extract was nominated for study by the National Institute of Environmental Health Sciences because it is one of the most widely used herbs in the United States. Male and female F344/N rats and B6C3F1 mice were exposed to an ethanol/water extract of milk thistle fruit (milk thistle extract) containing approximately 65% silymarin in feed for 3 months or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium and Escherichia coli and mouse peripheral blood erythrocytes. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats were fed diets containing 0, 3,125, 6,250, 12,500, 25,000, or 50,000 ppm milk thistle extract (equivalent to average daily doses of approximately 260, 525, 1,050, 2,180, or 4,500 mg milk thistle extract/kilogram body weight to males and 260, 510, 1,050, 2,150, or 4,550 mg/kg to females) for 14 weeks. All rats survived to the end of the study. Mean body weights of exposed groups were within 10% of those of the controls. Feed consumption by exposed and control groups was similar. The sperm motility in 12,500, 25,000, and 50,000 ppm males was decreased by 5%, 11%, and 9%, respectively, relative to that of the controls; the total number of spermatid heads per testis decreased by 11%, 21%, and 9% in 12,500, 25,000, and 50,000 ppm males. No significant differences in estrous cyclicity were observed between exposed and control groups of female rats. No exposure-related histopathologic lesions were observed. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice were fed diets containing 0, 3,125, 6,250, 12,500, 25,000, or 50,000 ppm milk thistle extract (equivalent to average daily doses of approximately 640, 1,340, 2,500, 5,280, or 11,620 mg/kg to males and 580, 1,180, 2,335, 4,800, or 9,680 mg/kg to females) for 14 weeks. All mice survived to the end of the study. Mean body weights and feed consumption of all exposed groups were similar to those of the controls. Absolute and relative thymus weights were significantly decreased in 25,000 and 50,000 ppm males. No significant differences were observed between exposed and control groups, for sperm parameters of male mice, for estrous cyclicity of female mice, or for reproductive organ weights of male or female mice, when mice were administered milk thistle extract in feed at 12,500, 25,000, or 50,000 ppm. No exposure-related histopathologic lesions were observed. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were fed diets containing 0, 12,500, 25,000, or 50,000 ppm milk thistle extract (equivalent to average daily doses of approximately 570, 1,180, or 2,520 mg/kg to males and 630, 1,300, or 2,750 mg/kg to females) for 105 to 106 weeks. Exposure to milk thistle extract had no effect on survival of male or female rats. Mean body weights of all exposed groups were similar to those of the controls throughout the study. Feed consumption by exposed groups of males and females was generally similar to that by the controls throughout the study. Significantly decreased incidences of mammary gland fibroadenoma, adenoma, or carcinoma (combined) occurred in females exposed to 25,000 or 50,000 ppm. Significantly increased incidences of clear cell and mixed cell focus of the liver occurred in 25,000 and 50,000 ppm females. The incidences of bile duct hyperplasia were significantly decreased in 50,000 ppm males and in all exposed groups of females, and the incidence of mixed inflammatory cell infiltration was significantly decreased in 50,000 ppm males. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were fed diets containing 0, 12,500, 25,000, or 50,000 ppm milk thistle extract (equivalent to average daily doses of approximately 1,610, 3,530, or 7,770 mg/kg to males and 1,500, 3,175, or 7,180 mg/kg to females) for 105 to 106 weeks. Exposure to milk thistle extract had no effect on survival of male or female mice. The mean body weights of the 25,000 ppm groups were less than those of controls after week 25; mean body weights of 50,000 ppm groups were less than those of controls after week 12. Feed consumption by exposed groups of males and females was generally similar to that by the controls throughout the study. Significantly decreased incidences of hepatocellular adenoma and hepatocellular carcinoma occurred in 50,000 ppm males, and decreased incidences of hepatocellular adenoma or carcinoma (combined) occurred in 25,000 and 50,000 ppm males. GENETIC TOXICOLOGY: Five milk thistle extracts were tested independently in bacterial mutagenicity studies using a variety of S. typhimurium tester strains and one E. coli strain. Results were negative in three of the five studies, with and without exogenous metabolic activation. In two studies, milk thistle extract was mutagenic in S. typhimurium strain TA98 in the presence of exogenous metabolic activation enzymes. Silymarin, a major constituent of milk thistle extract, was positive in S. typhimurium strains TA98 and TA100, when testing occurred in the presence of exogenous metabolic activation enzymes. Silybin, another component of milk thistle extract, was negative in a S. typhimurium gene mutation assay, with and without liver S9 activation enzymes. Administration of milk thistle extract in feed for 3 months did not increase the frequencies of micronucleated normochromatic erythrocytes, an indication of chromosomal abnormalities, in the peripheral blood of male or female B6C3F1 mice. CONCLUSIONS: Under the conditions of these 2-year feed studies, there was no evidence of carcinogenic activity of milk thistle extract in male or female F344/N rats or B6C3F1 mice exposed to 12,500, 25,000, or 50,000 ppm. Exposure to milk thistle extract resulted in increased incidences of clear cell and mixed cell foci in the liver of female rats and decreases in body weights of exposed groups of male and female mice. Decreased incidences of mammary gland neoplasms occurred in exposed groups of female rats, and decreased incidences of hepatocellular neoplasms occurred in exposed groups of male mice.     

Toxicology and carcinogenesis studies of bis(2-chloroethoxy)methane (CAS No. 111-91-1) in F344/N rats and B6C3F1 mice (dermal studies)

Bis(2-chloroethoxy)methane is used as a solvent and the starting agent in the production of fungicides and polysulfide polymers. Bis(2-chloroethoxy)methane was nominated for study by the National Institute of Environmental Health Sciences because of its widespread use as a starting material to produce polysulfide elastomers, and because there were no 2-year carcinogenicity studies reported in the literature. Male and female F344/N rats and B6C3F1 mice received dermal applications of bis(2-chloroethoxy)-methane in ethanol (greater than 98% pure) for 2 weeks, 3 months, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium and Escherichia coli, rat bone marrow cells, and mouse peripheral blood erythrocytes. 2-WEEK STUDY IN RATS: Groups of five male and five female rats were dermally administered 0, 12.5, 25, 50, 100, or 200 mg bis(2-chloroethoxy)methane/kg body weight in ethanol, 5 days per week for 16 days. All rats survived to the end of the study. Mean body weights of dosed rats were similar to those of the vehicle control groups. There were no histopathologic lesions related to bis(2-chloroethoxy)methane administration. 2-WEEK STUDY IN MICE: Groups of five male and five female mice were dermally administered 0, 12.5, 25, 50, 100, or 200 mg bis(2-chloroethoxy)methane/kg body weight in ethanol, 5 days per week for 17 days. All mice survived to the end of the study. Mean body weights of dosed mice were similar to those of the vehicle control groups. There were no histopathologic lesions related to bis(2-chloroethoxy)methane administration. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats were dermally administered 0, 50, 100, 200, 400, or 600 mg bis(2-chloroethoxy)methane/kg body weight in ethanol, 5 days per week for 14 weeks. Additional clinical pathology groups of 10 male and 10 female rats were administered the same doses for 23 days. All core study 600 mg/kg males and females and two 400 mg/kg females died before the end of the study. The cause of death was considered to be related to the cardiotoxic effect of bis(2-chloroethoxy)methane. There were no significant differences between final mean body weights of dosed rats and those of the vehicle control groups; the mean body weight gain of 400 mg/kg males was significantly less than that of the vehicle controls. Clinical findings included prostration and ataxia in 600 mg/kg rats during the first week of the study and nasal/eye discharge, lethargy, ataxia, and abnormal breathing in 400 and 600 mg/kg females beginning week 5. An enlarged heart was noted in one 100 mg/kg female rat. Relative kidney weights of 100, 200, and 400 mg/kg males were significantly greater than that of the vehicle control group. Increased incidences and severities of myofiber cytoplasmic vacuolization and interstitial mononuclear cell infiltration in the heart occurred in 400 and 600 mg/kg male and female rats and in 200 mg/kg females. Increased incidences and severities of myofiber necrosis occurred in 600 mg/kg males and females; one female each in the 200 and 400 mg/kg groups also had this lesion. Three 600 mg/kg males had atrial thrombosis. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice were dermally administered 0, 50, 100, 200, 400, or 600 mg bis(2-chloroethoxy)methane/kg body weight in ethanol, 5 days per week for 14 weeks. Except for three 600 mg/kg females, all mice survived to the end of the study. Mean body weights of dosed and vehicle control mice were similar. One 600 mg/kg female that died early exhibited lethargy, abnormal breathing, and tremors, and one animal had clonic seizures. One 600 mg/kg female that died early had focal erosion of the glandular stomach and a focus in the duodenum found to consist of acute suppurative inflammation and thrombosis. Absolute and relative kidney weights of 400 and 600 mg/kg males and 600 mg/kg females were significantly greater than those of the vehicle control groups. Absolute liver weights of 400 and 600 mg/kg females were also significantly increased. Significantly increased incidences of myofiber cytoplasmic vacuolization occurred in 400 and 600 mg/kg females. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were dermally administered 0, 75, 150, or 300 mg bis(2-chloroethoxy)methane/kg body weight in ethanol, 5 days per week for 105 weeks. Survival of all dosed groups of rats was generally similar to that of the vehicle controls. Mean body weights of dosed rats were similar to those of the vehicle controls throughout the study. Clinical findings in 300 mg/kg females that died during the first year of the study included abnormal breathing, lethargy, thinness, nasal discharge, and ataxia. Significantly increased incidences of degeneration of the olfactory epithelium in the nose occurred in all dosed groups of males and in 150 and 300 mg/kg females. The incidences of inflammation of the forestomach were significantly increased in 150 and 300 mg/kg males, and the incidence of ulcers was significantly increased in 300 mg/kg males. Increased incidences of cystic degeneration of the liver occurred in 150 and 300 mg/kg male rats; the incidence was significantly increased in the 300 mg/kg group. 2-YEAR STUDY IN MICE: Groups of 50 male mice were dermally administered 0, 150, 300, or 600 mg bis(2-chloroethoxy)methane/kg body weight in ethanol, 5 days per week for 105 weeks. Groups of 50 female mice were dermally administered 0, 100, 200, or 400 mg/kg in ethanol, 5 days per week for 104 weeks. Survival of 600 mg/kg male mice was significantly less than that of the vehicle control group. Mean body weights of dosed mice were generally similar to those of the vehicle controls throughout the study. Clinical findings observed in 600 mg/kg male mice that died during the first year of the study included lethargy and thinness. Myocardial heart changes were recorded according to the characteristic lesions of cardiomyopathy syndrome (necrosis, mononuclear cell infiltration, myocardial cell vacuolization, and interstitial fibrosis) separately, and in addition, where appropriate, they were also categorized as cardiomyopathy. Increased incidences of cardiomyopathy and mononuclear cell infiltration occurred in 600 mg/kg males and 400 mg/kg females; the incidences were significantly increased in 600 mg/kg males compared to the vehicle controls. Significantly increased incidences of cardiomyocyte vacuolization and interstitial fibrosis occurred in 600 mg/kg males. A few early deaths in the 600 mg/kg males were considered to be due, at least in part and probably exclusively, to bis(2-chloroethoxy)methane-induced cardiotoxicity. The incidence of ulceration of the forestomach was significantly increased in 600 mg/kg males. Significantly increased incidences of dermal inflammation and fibrosis and epidermal hyperplasia at the site of application occurred in 600 mg/kg male mice. GENETIC TOXICOLOGY: Bis(2-chloroethoxy)methane was mutagenic in S. typhimurium strains TA100 and TA1535 in the presence of exogenous metabolic activation enzymes (S9) in one study; results from a second bacterial mutagenicity test were judged to be equivocal based on responses observed in TA100 and in E. coli strain WP2 uvrA/pKM101 in the presence of S9. No mutagenicity was observed in other tester strains or in the absence of S9. Bis(2-chloroethoxy)methane did not increase the frequency of micronucleated reticulocytes in bone marrow of male F344/N rats following three daily treatments by gavage or micronucleated erythrocytes in peripheral blood of male or female mice after 3 months of dermal exposure. CONCLUSIONS: Under the conditions of these 2-year dermal studies, there was no evidence of carcinogenic activity of bis(2-chloroethoxy)methane in male or female F344/N rats administered 75, 150, or 300 mg/kg. There was no evidence of carcinogenic activity of bis(2-chloroethoxy)methane in male B6C3F1 mice administered 150, 300, or 600 mg/kg or in female B6C3F1 mice administered 100, 200, or 400 mg/kg. The administration of bis(2-chloroethoxy)methane for 2 years resulted in increased incidences of nonneoplastic lesions in the nose of male and female rats, the forestomach of male rats, the heart of male and female mice, and the forestomach and skin of male mice.     

Toxicology and carcinogenesis studies of p,p'-dichlorophenyl sulfone (CAS No. 80-07-9) in F344/N rats and B6C3F1 mice (feed studies)

p,pN-Dichlorodiphenyl sulfone is used as a starting material in the production of polysulfones and polyethersulfones and as a component in reactive dyes in the textile industry; it is also a by-product of pesticide production. p,pN-Dichlorodiphenyl sulfone was nominated for study by the National Cancer Institute because of its history of high production and use, the prospect of increased production and use, and the absence of adequate toxicity testing. Male and female F344/N rats and B6C3F1 mice were exposed top,pN-dichlorodiphenyl sulfone (greater than 99% pure)in feed for 14 weeks or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium,cultured Chinese hamster ovary cells, and mouse bone marrow. 14-WEEK STUDY IN RATS: Groups of 10 male and 10 female F344/N rats were fed diets containing 0, 30, 100, 300, 1,000, or 3,000 ppm p,pN-dichlorodiphenyl sulfone (equivalent to average daily doses of approximately 2, 6, 19, 65, or 200 mgp,pN-dichlorodiphenyl sulfone/kg body weight) for 14 weeks. All rats survived until the end of the study. Mean body weights of groups exposed to 300 ppm or greater were significantly less than those of the controls. Liver weights of groups exposed to 100 ppm or greater and kidney weights of 1,000 and 3,000 ppm male rats were significantly greater than those of the controls. Centrilobular hepatocyte hypertrophy of the liver was observed in most male rats exposed to 100 ppm or greater and in all female rats exposed to 300 ppm or greater, and the severities were increased in 300 ppm males and 1,000 and 3,000 ppm males and females. The incidences of nephropathy in 1,000 and 3,000 ppm female rats were significantly increased. Dose-related increases in severity of nephropathy were observed in male rats. 14-WEEK STUDY IN MICE: Groups of 10 male and 10 female B6C3F1 mice were fed diets containing 0, 30, 100, 300, 1,000, or 3,000 ppm p,pN-dichlorodiphenyl sulfone (equivalent to average daily doses of approximately 3.5, 15, 50, 165,or 480 mg/kg) for 14 weeks. All mice survived until the end of the study. Mean body weights of groups exposed to 300 ppm or greater were significantly less than those of the controls. Liver weights of groups exposed to 300 ppm or greater were significantly increased. Centrilobular hypertrophy of the liver was observed in most males exposed to 100 ppm or greater and in all females exposed to 1,000 or 3,000 ppm, and the severities generally increased with increasing exposure concentration. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were fed diets containing 0, 10 (males), 30, 100, or 300 (females) ppm p,pN-dichlorodiphenyl sulfone for 105 weeks. Dietary concentrations of 10, 30, and 100 ppm resulted in average daily doses of approximately 0.5, 1.5, and 5.0 mg/kg to males. Dietary concentrations of 30, 100,and 300 ppm resulted in average daily doses of approximately 1.6, 5.4, and 17 mg/kg to females. Additional groups of 10 male and 10 female rats were fed the same p,pN-dichlorodiphenyl sulfone-containing diets for 18 months and bled for plasma determinations of p,pN-dichlorodiphenyl sulfone at approximately 2 weeks and 3, 12, and 18 months. Survival of all exposed groups of male and female rats was similar to that of the control groups. Mean body weights of 30 and 100 ppm males were generally less than those of the controls during the latter part of the study, and mean body weights of 100 and 300 ppm female rats were less from weeks 30 and 18,respectively. Feed consumption by the exposed groups was similar to that by the controls throughout the study. The incidences of centrilobular hepatocyte hypertrophy in 100 ppm male and 100 and 300 ppm female rats were significantly greater than those in the controls. The incidences of bile duct hyperplasia and centrilobular degeneration were also significantly increased in 100 and 300 ppm females. No neoplasms were related to chemical exposure. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were fed diets containing 0, 30, 100, or 300 ppm p,pN-dichlorodiphenyl sulfone for 105 to 106 weeks. Dietary concentrations of 30, 100, and 300 ppm delivered average daily doses of approximately 4, 13, and 40 mg/kg to males and approximately 3, 10, and 33 mg/kg to females. Additional groups of 10 male and 10 female mice were fed the same p,pN-dichlorodiphenyl sulfone-containing diets for up to 12 months;three mice in each group were bled for plasma determinations of p,pN-dichloro-diphenyl sulfone at approximately 2 weeks or 3 or 12 months. Survival of all exposed groups of male and female mice was similar to that of the control groups. Mean body weights of 300 ppm mice were less than those of the controls throughout most of the study. Feed consumption by the exposed groups was similar to that by the controls throughout the study. The incidences of centrilobular hepatocyte hypertrophy in all exposed groups of male mice and in 100 and 300 ppm females were significantly greater than those in the controls. The incidence of eosinophilic foci in 300 ppm females was significantly increased. No neoplasms were related to chemical exposure. PHARMACOKINETICS OF p,pN-DICHLORODIPHENYL SULFONE: p,pN-Dichlorodiphenyl sulfone is rapidly absorbed from the gut and metabolized by a saturable process. Although some p,pN-dichlorodiphenyl sulfone is eliminated unchanged in feces and urine, most of the elimination is via metabolism. Mathematical modeling of the toxicokinetics supports the view that p,pN-dichlorodiphenyl sulfone induces enzymes involved in its metabolism. GENETIC TOXICOLOGY: p,pN-Dichlorodiphenyl sulfone was not mutagenic in any of several strains of Salmonella typhimurium, with or without metabolic activation enzymes (S9). Results of the sister chromatid exchange test in cultured Chinese hamster ovary cells were judged to be negative in the presence of S9 and equivocal in the absence of S9, but no induction of chromosomal aberrations was noted, with or without S9. In contrast to the in vitro results, positive results were obtained in an acute in vivo mouse bone marrow micronucleus assay with p,pN-dichlorodiphenyl sulfone administered by intraperitoneal injection three times over a dose range of 200 to 800 mg/kg. CONCLUSIONS: Under the conditions of these 2-year feed studies, there was no evidence of carcinogenic activity* of p,pN-dichlorodiphenyl sulfone in male F344/N rats exposed to 10, 30, or 100 ppm or in female F344/N rats exposed to 30, 100, or 300 ppm. There was no evidence of carcinogenic activity of p,pN-dichlorodiphenyl sulfone in male or female B6C3F1 mice exposed to 30,100, or 300 ppm. Exposure to p,pN-dichlorodiphenyl sulfone for 2 years caused increased incidences of nonneoplastic lesions of the liver in male and female rats and mice.     

Toxicology and carcinogenesis studies of kava kava extract (CAS No. 9000-38-8) in F344/N rats and B6C3F1 mice (Gavage Studies)

Kava beverages, made from dried roots of the shrub Piper methysticum, have been used ceremonially and socially in the South Pacific and in Europe since the 1700s. The drink is reported to have pleasant mild psychoactive effects, similar to alcoholic beverages. In the United States, kava kava is an herbal product used extensively as an alternative to anti-anxiety drugs such as Xanax and Valium. It has also been reported as being used to help children with hyperactivity and as a skin-conditioning agent in cosmetics. Kava kava was nominated by the National Cancer Institute for study because of its increasing use as a dietary supplement in the mainstream United States market and reports of liver toxicity among humans. Male and female F344/N rats and B6C3F1 mice received kava kava extract in corn oil by gavage for 2 weeks, 3 months, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, Escherichia coli, and mouse peripheral blood erythrocytes. 2-WEEK STUDY IN RATS: Groups of five male and five female rats were administered kava kava extract in corn oil by gavage at doses of 0, 0.125, 0.25, 0.5, 1.0, or 2.0 g/kg body weight, 5 days per week for 16 days. One female rat administered 2.0 g/kg kava kava extract died on day 3 of the study. Mean body weights of all dosed groups of rats were similar to those of the vehicle controls. Clinical findings included abnormal breathing, ataxia, and lethargy in the 2.0 g/kg groups of males and females and ataxia and lethargy in the 1.0 g/kg group of females. Liver weights were significantly increased in 1.0 and 2.0 g/kg males and in 0.5 g/kg or greater females compared to the vehicle controls. Minimal hepatocellular hypertrophy occurred in all 2.0 g/kg males and in all females administered 0.25 g/kg or greater. 2-WEEK STUDY IN MICE: Groups of five male and five female mice were administered kava kava extract in corn oil by gavage at doses of 0, 0.125, 0.25, 0.5, 1.0, or 2.0 g/kg body weight, 5 days per week for 17 days. In the 2.0 g/kg group of males, one died on day 2 and one died on day 3. Mean body weights of all dosed groups of mice were similar to those of the vehicle controls. Clinical findings included abnormal breathing, ataxia, and lethargy in males and females in the 1.0 and 2.0 g/kg groups. Liver weights of 2.0 g/kg males and females were significantly increased. The incidence of hepatocellular hypertrophy in 2.0 g/kg female mice was significantly greater than that in the vehicle control group. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats were administered kava kava extract in corn oil by gavage at doses of 0, 0.125, 0.25, 0.5, 1.0, or 2.0 g/kg, 5 days per week for 14 weeks. Deaths attributed to kava kava extract administration included three males and four females in the 2.0 g/kg groups and one female in the 1.0 g/kg group. One 0.25 g/kg male and one vehicle control female also died before the end of the study. The mean body weights of males in the 1.0 and 2.0 g/kg groups and females in the 2.0 g/kg group were significantly less than those of the vehicle controls. Ataxia and lethargy were observed in males and females in the 1.0 g/kg groups during week 1 and in the 2.0 g/kg groups throughout the study. Increased -glutamyltransferase activity in 1.0 g/kg females and 2.0 g/kg males and females may represent enzyme induction. However, the hepatocellular hypertrophy observed in the 2.0 g/kg females may have contributed to the increased -glutamyltransferase activity. The liver weights of 0.25 g/kg or greater males and 0.5 g/kg or greater females were significantly increased compared to the vehicle controls. The kidney weights of 0.5 g/kg or greater males and females were significantly increased compared to the vehicle controls. The incidence of hepatocellular hypertrophy in 2.0 g/kg females was significantly greater than that in the vehicle controls. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice were administered kava kava extract in corn oil by gavage at doses of 0, 0.125, 0.25, 0.5, 1.0, or 2.0 g/kg, 5 days per week for 14 weeks. Four male and three female 2.0 g/kg mice died during week 1; these deaths were attributed to kava kava extract administration. One additional 2.0 g/kg female died during week 6 due to a gavage accident. The mean body weights of dosed males and females were similar to those of the vehicle controls. Ataxia and lethargy occurred in males and females in the 1.0 and 2.0 g/kg groups during week 1. The liver weights of 2.0 g/kg males and 1.0 and 2.0 g/kg females were significantly increased compared to those of the vehicle control groups. The incidences of centrilobular hypertrophy in the liver of 0.5 g/kg or greater males and 1.0 and 2.0 g/kg females were significantly greater than those in the vehicle controls. 2-YEAR STUDY IN RATS: Groups of 49 or 50 male and 50 female rats were administered kava kava extract in corn oil by gavage at doses of 0, 0.1, 0.3, or 1.0 g/kg, 5 days per week for 104 (males) or 105 (females) weeks. Survival of dosed groups of males and females was similar to that of the vehicle controls. Mean body weights of males administered 1.0 g/kg were less than those of the vehicle controls after week 65, and those of the 1.0 g/kg females were less than those of the vehicle controls after week 41. Clinical findings included ataxia and lethargy that occurred in 21 males and 14 females in the 1.0 g/kg groups during the first 4 weeks of the study. After week 5, ataxia and lethargy were noted in 10 males and eight females in the 1.0 g/kg groups and these findings were observed randomly and intermittently throughout the study. At approximately 1 year into the study, twitching and seizures were observed in males and females in all dosed groups but mainly in the 1.0 g/kg groups. There was a dose-related increase in the incidences of interstitial cell adenoma in the testis with increased incidences of bilateral neoplasms. The incidences of hepatocellular hypertrophy in 1.0 g/kg males and females were significantly greater than those in the vehicle controls. Increased -glutamyltransferase activity and/or bile salt concentrations in males and females may represent a cholestatic event related to the hepatocellular hypertrophy observed in rats. Enzyme induction may have played a role in the increased -glutamyltransferase activity. Significantly increased incidences of centrilobular fatty change occurred in 0.1 and 1.0 g/kg males. The incidences of inflammation, ulcer, and epithelial hyperplasia in the forestomach were significantly increased in 1.0 g/kg males and females. The severity of nephropathy was increased in 1.0 g/kg male rats, and the incidence of nephropathy was significantly increased in 1.0 g/kg females. Incidences of transitional epithelial hyperplasia of the pelvis of the kidney were significantly increased in 1.0 g/kg males and 0.3 and 1.0 g/kg females. The incidences of retinal degeneration in the eye were significantly increased in 1.0 g/kg males and females. The incidences of metaplasia of pancreatic acinar cells to a hepatocytic morphology increased in 1.0 g/kg males and females, and the increase in males was significant. Significantly decreased incidences of pars distalis adenoma in the pituitary gland occurred in 1.0 g/kg males and in 0.1 and 1.0 g/kg females. The incidence of fibroadenoma of the mammary gland in 1.0 g/kg females was significantly less than that in the vehicle control group. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice received kava kava extract in corn oil by gavage at doses of 0, 0.25, 0.5, or 1.0 g/kg, 5 days per week for 105 weeks. Survival of dosed groups of males and females was similar to that of the vehicle controls. Mean body weights of males administered 1.0 g/kg were generally similar to those of the vehicle controls until the end of the study; however, those of 1.0 g/kg females were less than those of the vehicle controls after week 21. Clinical findings included ataxia and lethargy that occurred in 13 males and 31 females in the 1.0 g/kg groups during the first week of the study. Decreasing numbers of animals exhibited ataxia or lethargy during the remainder of the study, but these findings were observed in 1.0 g/kg females as late as week 101. The incidences of hepatoblastoma in 0.5 and 1.0 g/kg males were significantly increased compared to the vehicle controls. The incidences of hepatocellular carcinoma or hepatoblastoma (combined) were significantly increased in 0.5 g/kg males. Incidences of hepatocellular carcinoma were increased in all dosed groups of females, and the increase was significant in the 0.25 g/kg group. The incidences of hepatocellular adenoma or carcinoma (combined) were significantly increased in 0.25 and 0.5 g/kg females. In the liver, the incidences of centrilobular hypertrophy in all dosed groups of males and females were significantly greater than those in the vehicle control groups. Significantly increased incidences of eosinophilic foci occurred in 0.5 g/kg males and in 1.0 g/kg males and females, and the incidence of angiectasis was significantly increased in the 1.0 g/kg males. The incidences of hepatocellular necrosis were significantly increased in 0.25 and 1.0 g/kg males. In the forestomach, the incidences of chronic inflammation, epithelial hyperplasia, and erosion were significantly increased in 0.5 and 1.0 g/kg females, and the incidence of ulceration was significantly increased in 1.0 g/kg females. GENETIC TOXICOLOGY: Kava kava extract was tested for bacterial mutagenicity over a broad range of concentrations in two independent assays using several strains of bacteria (S. typhimurium tester strains TA97, TA98, TA100, and TA1535 and E. coli strain WP2 uvrA/pKM101), with and without exogenous metabolic activation. No increase in mutant colonies was seen in any of the tester strains, under any activation condition. (ABSTRACT TRUNCATED)