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)     

Single administration toxicokinetic studies of decalin (decahydronaphthalene) in rats and mice.

Decalin (decahydronaphthalene) is an industrial solvent known to cause alpha2u-globulin nephropathy in male rats. Studies were conducted using decalin (mixture of cis and trans isomers) to (1) characterize systemic elimination of decalin in rats and mice and (2) evaluate disposition of decalin, its metabolites, and kidney alpha2u-globulin in young and old rats of both sexes following a single 6-h whole-body inhalation exposure at up to 400 ppm decalin. Additionally, a separate group of young male F344/N rats were administered either cis- or trans-decalin iv at doses up to 20 mg/kg to assess disposition of each isomer, its metabolites, and kidney alpha2u-globulin. Decalin was eliminated from blood in a dose-dependent manner, regardless of sex, age, or species. C0 and AUC infinity increased supra-proportionally with exposure concentration. Mice were more efficient in eliminating decalin than rats at lower exposure concentrations, but nonlinear elimination kinetics were more noticeable at 400 ppm. Sex differences in blood decalin elimination were observed in rats; females had a consistently higher AUC infinity at all exposure concentrations. There was a dose-dependent increase in kidney decalin, decalone, and alpha2u-globulin in male rats exposed to decalin. Kidney alpha2u-globulin and decalone concentrations in old male rats were substantially lower than those in young males, but were similar to those observed in all (young and old) females. Compared to old males and all females, young male rats had significantly lower urinary decalol concentrations, but higher kidney decalin, decalone, and alpha2u-globulin concentrations. Administration of decalin to male rats as either the cis or trans isomer revealed that more cis -decalone is produced per unit dose as compared to trans-decalone, and that more trans-decalin accumulated in the kidney (as alpha2u-globulin-ligand complexes) compared to cis-decalin. These patterns of isomer-specific metabolism were also reflected in the cis/trans ratios of decalin in blood, as well as urinary decalol metabolites. The ratio of alpha2u-globulin to the total amount of decalin plus decalone measured in the male rat kidney was approximately 1.0. Therefore, alpha2u-globulin was a key factor in the accumulation of decalin and decalone in kidneys of young male rats, decalin and decalone were practically absent in all females and in old males.     

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.     

Alpha 2u-globulin nephropathy and carcinogenicity following exposure to decalin (decahydronaphthalene) in F344/N rats.

Decalin (decahydronaphthalene) is a widely used industrial solvent known to cause male rat-specific alpha2u-globulin nephropathy. In this project, 13-week and two-year inhalation studies of decalin were conducted consecutively in both sexes of F344/N rats. The key objectives were to (1) characterize the 13-week toxicity of decalin in rats, with an emphasis on nephropathy in males; (2) compare the kidney concentrations of decalin, 2-decalone, and alpha2u-globulin in males over 2 to 13 weeks of decalin exposure; and (3) correlate male rat nephropathy observed in the 13-week study with renal carcinogenicity in the two-year study. F344 rats (M/F) were exposed via whole-body inhalation to 0, 25, 50, 100, 200, or 400 ppm decalin for 13 weeks. Urine was collected at weeks 2 and 6 for creatinine and decalol analyses and at week 12 for clinical urinalysis. Right kidneys were collected from male rats at weeks 2 and 6 and from both sexes at week 13, homogenates were prepared using the whole kidney, and these homogenates were analyzed for alpha2u-globulin, decalin, and 2-decalone. Left kidneys were evaluated for histopathology and cell proliferation utilizing a proliferating cell nuclear antigen technique and counting proximal renal tubular epithelial cells to determine cell labeling indices. Necropsies and histopathologic evaluations were performed at week 13. Decalin exposure caused increases in kidney weight, urinalysis parameters (protein, AST, LDH), kidney alpha2u-globulin concentration, and proximal convoluted renal tubular cell proliferation in males. These changes were accompanied by microscopic lesions (accumulation of hyaline droplets in cortical tubules, regeneration of proximal tubular epithelium, and granular casts in medullary tubules) clearly linked to alpha2u-globulin nephropathy. Both decalin and 2-decalone were related to increased alpha2u-globulin in male kidneys. Kidney concentrations of decalin, 2-decalone, and alpha2u-globulin in exposed females were negligible, while females excreted greater amounts of decalol metabolites in urine than males at weeks 2 and 6. There were no exposure-related microscopic lesions in females. For chronic exposure, F344 rats were exposed via whole-body inhalation to 0, 25, 50 (males only), 100, or 400 ppm decalin for two years. Chronic exposure induced a spectrum of nonneoplastic and neoplastic lesions in the renal cortex of males, ranging from regenerative lesions of chronic nephropathy to tubular carcinomas. Incidences of renal tubular adenoma, tubular carcinoma, combined tubular adenomas and carcinomas, cortical tubular hyperplasia, hyaline droplet accumulation, hyperplasia of pelvic epithelium, and mineralization in renal papilla were increased in exposed males compared to controls. There was a clear increase in the mean severity of chronic nephropathy in decalin-exposed males. It was concluded that the carcinogenic effect on the renal cortical epithelium of male rats exposed to decalin was related to increased turnover of this epithelium, resulting from the cytotoxic effects of alpha2u-globulin accumulation in the renal cortical tubular cell cytoplasm.     

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 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.     

Inhalation toxicology and carcinogenesis studies of propylene glycol mono-t-butyl ether in rats and mice

Propylene glycol mono-t-butyl ether (PGMBE) is used as a solvent in a variety of commercial applications. Male and female F344/N rats and B6C3F(1) mice were exposed to PGMBE by whole-body inhalation for 2 or 14 weeks (0, 75, 150, 300, 600, or 1200 ppm) or 2 years (0, 75, 300, or 1200 ppm); male NBR rats were exposed for 2 weeks. The kidney and the liver were targets of PGMBE toxicity in rats. Renal lesions suggestive of alpha(2u)-globulin nephropathy were observed in male F344/N, in the 2 and 14-week studies, no kidney lesions were seen in NBR rats. In the 2-year study, male rats displayed exposure-related nonneoplastic lesions in the kidney, and may have shown marginal increases in tubular neoplasms. In the liver, the incidences of hepatocellular adenomas occurred with a positive trend in male rats, and may have been related to PGMBE exposure. In mice of both sexes, the major target of PGMBE toxicity was the liver. In the 2-week study, liver weights and in the 14-week study, liver weights and the incidences of centrilobular hypertrophy were increased. In the 2-year study, the incidences of exposure-related hepatocellular adenoma, adenoma or carcinoma combined, and hepatoblastoma occurred with a positive trend, and were significantly increased in 1200 ppm groups. In summary, exposure to PGMBE resulted in nonneoplastic lesions of the kidney characteristic of alpha(2u)-globulin nephropathy, and may have increased renal tubular neoplasms in male rats. Exposure to PGMBE also produced increases in hepatic tumors in male and female mice.     

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

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

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

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

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

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

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

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

Toxicology and carcinogenesis studies of 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.     

NTP technical report on the toxicology and carcinogenesis studies of Stoddard Solvent IIC (Cas No. 64742-88-7) in F344/N rats and B6C3F1 mice (inhalation studies)

Stoddard solvent (white spirit/mineral spirit) is the most widely used solvent in the paint industry. It is used as a dry cleaning agent; as an extraction, cleaning, and degreasing solvent; and as a solvent in aerosols, paints, wood preservatives, asphalt products, lacquers, and varnishes. Stoddard solvent IIC was nominated by the International Union, United Auto Workers, for carcinogenicity testing because of the large volume used in industrial and other settings. Male and female F344/N rats and B6C3F1 mice were exposed to Stoddard solvent IIC (greater than 99% pure) by inhalation for 2 weeks, 3 months, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium and mouse peripheral blood erythrocytes. 2-WEEK STUDY IN RATS: Groups of five male and five female rats were exposed to Stoddard solvent IIC by inhalation at concentrations of 0, 138, 275, 550, 1,100, or 2,200 mg/m3, 6 hours per day, 5 days per week for 16 days. All rats survived to the end of the study, and mean body weights of all exposed groups were similar to those of the chamber controls. Liver weights of males exposed to 550 mg/m3 or greater and of females exposed to 275 mg/m3 or greater were increased. Minimal diffuse cytoplasmic vacuolization of hepatocytes of the liver occurred in all females exposed to 2,200 mg/m3. 2-WEEK STUDY IN MICE: Groups of five male and five female mice were exposed to Stoddard solvent IIC by inhalation at concentrations of 0, 138, 275, 550, 1,100, or 2,200 mg/m3, 6 hours per day, 5 days per week for 17 days. All mice survived to the end of the study, and mean body weights of all exposed groups were similar to those of the chamber controls. Liver weights of males and females exposed to 275 mg/m3 or greater were significantly increased. Cytomegaly of the liver occurred in all males and females exposed to 2,200 mg/m3. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats were exposed to Stoddard solvent IIC by inhalation at concentrations of 0, 138, 275, 550, 1,100, or 2,200 mg/m3, 6 hours per day, 5 days per week for 14 weeks. All rats survived to the end of the study, and the final mean body weight of females exposed to 275 mg/m3 was greater than that of the chamber controls. The relative kidney, liver, and testis weights of all exposed groups of males and the absolute kidney weights of males exposed to 550 mg/m3 or greater were increased. The sperm motility of 550 mg/m3 or greater males was significantly decreased. The incidences of renal tubule granular casts were significantly increased in males exposed to 550 mg/m3 or greater, and the severities of renal tubule hyaline droplet accumulation, granular casts, and regeneration increased with increasing exposure concentration in males. The incidences of goblet cell hypertrophy of the nasal respiratory epithelium in males and females exposed to 2,200 mg/m3 were significantly increased. Sperm motility was decreased in males exposed to 550 mg/m3 or greater. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice were exposed to Stoddard solvent IIC by inhalation at concentrations of 0, 138, 275, 550, 1,100, or 2,200 mg/m3, 6 hours per day, 5 days per week for 14 weeks. Mean body weights of exposed groups were similar to those of the chamber controls, but liver weights of males exposed to 2,200 mg/m3 were significantly increased. The sperm motility of 2,200 mg/m3 males was significantly decreased. This reduction in sperm motility, while statistically significant, is probably of modest importance as studies in mice have found that fertility is unaffected by motility decreases of less than 40%. The incidences of hematopoietic cell proliferation of the spleen in all exposed groups of females were greater than that in the chamber controls. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were exposed to Stoddard solvent IIC by inhalation at concentrations of 0, 138 (males), 550, 1,100, or 2,200 (females) mg/m3, 6 hours per day, 5 days per week for 104 to 105 weeks. Additional groups of 10 males and 10 females were exposed to the same concentrations for 3 months for renal toxicity analyses. Survival in the top exposure concentration groups of males and females was significantly less than that of the chamber controls. Mean body weights of exposed males and females were similar to those of the chamber controls. Cell proliferation analyses were performed in the left kidney of males and females after 3 months of exposure. The mean numbers of labeled cells and the labeling indices in males exposed to 550 and 1,100 mg/m3 were significantly increased. The amount of alpha2u-globulin in the right kidney of males increased with increasing exposure concentration. Also, the incidences of granular casts and cortical tubule degeneration and regeneration were generally increased in exposed males, as was the severity of hyaline droplets. These effects did not occur in females. At 2 years, the incidences of benign and benign or malignant pheochromocytoma (combined) of the adrenal medulla occurred with positive trends in males, and the incidences in the 550 and 1,100 mg/m3 groups were significantly increased. Due to increased incidences of renal tubule hyperplasia in males at 2 years, extended kidney evaluations were conducted; a slightly increased incidence of renal tubule adenoma occurred in the 1,100 mg/m3 group. Nonneoplastic lesions related to Stoddard solvent IIC exposure occurred in the kidney of males. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were exposed to Stoddard solvent IIC by inhalation at concentrations of 0, 550, 1,100, or 2,200 mg/m3, 6 hours per day, 5 days per week for 105 weeks. Survival of exposed mice was similar to that of the chamber controls. Mean body weights of exposed females were greater than those of the chamber controls. The incidences of hepatocellular adenoma occurred with a positive trend in females, and the incidence of multiple hepatocellular adenoma in females exposed to 2,200 mg/m3 was significantly increased. However, the incidences of hepatocellular adenoma or carcinoma (combined) and hepatocellular carcinoma alone in exposed males and females were not significantly increased. GENETIC TOXICOLOGY: Stoddard solvent IIC was tested for mutagenicity in Salmonella typhimurium strains TA97, TA98, TA100, and TA1535, with and without S9 metabolic activation enzymes; all results were negative. In vivo, the frequency of micronucleated erythrocytes was assessed in peripheral blood samples from male and female B6C3F1 mice after 3 months of inhalation exposure to Stoddard solvent IIC, and results were negative. CONCLUSIONS: Under the conditions of these 2-year inhalation studies, there was some evidence of carcinogenic activity of Stoddard solvent IIC in male F344/N rats based on increased incidences of adrenal medulla neoplasms; the slightly increased incidences of renal tubule adenoma may have been related to Stoddard solvent IIC exposure. There was no evidence of carcinogenic activity of Stoddard solvent IIC in female F344/N rats exposed to 550, 1,100, or 2,200 mg/m3. There was no evidence of carcinogenic activity of Stoddard solvent IIC in male B6C3F1 mice exposed to 550, 1,100, or 2,200 mg/m3. There was equivocal evidence of carcinogenic activity of Stoddard solvent IIC in female B6C3F1 mice based on increased incidences of hepatocellular adenoma; this slight increase was associated with increased body weight in exposed females. Exposure of male rats to Stoddard solvent IIC resulted in nonneoplastic lesions of the kidney characteristic of alpha2u-globulin accumulation.     

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 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)     

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

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

Carcinogenesis studies of benzophenone in rats and mice.

Benzophenone, an aryl ketone, is used primarily as a photoinitiator and fragrance enhancer. Groups of 50 male and 50 female F344 rats and B6C3 F1 mice were fed diets containing 0, 312, 625, and 1250 ppm benzophenone for 105 weeks. Survival of males exposed to 1250 ppm benzophenone was significantly less than that of controls. There was a positive trend in the incidence of renal tubule adenoma in male rats; these neoplasms were accompanied by significantly increased incidences of renal tubule hyperplasia. Increased incidences of mononuclear cell leukemia were observed in male rats exposed to 312 or 625 ppm benzophenone and in female rats exposed to 625 ppm benzophenone. Liver lesions observed included significantly increased incidences of hepatocytic centrilobular hypertrophy in all exposed groups of rats. In mice, survival of all exposed groups was generally similar to that of the control groups. In male mice, there were significantly increased incidences of hepatocellular adenoma in the 625 and 1250 ppm groups. In female mice, the incidences of hepatocellular adenoma in the 625 and 1250 ppm groups were higher than expected after adjusting for the lower body weights in these groups. The incidences of kidney nephropathy in exposed groups of female mice, as well as the severity of nephropathy in exposed groups of males, were significantly increased. The incidences of metaplasia of the olfactory epithelium were significantly increased in 1250 ppm mice. Rare histiocytic sarcomas were observed in female rats and mice in the 625 and 1250 ppm groups. 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. There was equivocal evidence of carcinogenic activity of benzophenone in female F344/N rats based on the marginal increased incidences of mononuclear cell leukemia and histiocytic sarcoma. There was some evidence of carcinogenic activity of benzophenone in male B6C3F(1) mice based on increased incidences of hepatocellular neoplasms, primarily adenoma. There was some evidence of carcinogenic activity of benzophenone in female B6C3F(1) mice based on increased incidences of histiocytic sarcoma; the incidences of hepatocellular adenoma in female B6C3F(1) mice may have been related to benzophenone exposure.     

Toxicology and carcinogenesis studies of fumonisin B1 (cas no. 116355-83-0) in F344/N rats and B6C3F1 mice (feed studies)

[formula: see text] Fumonisin B1 is a mycotoxin produced by the fungus Fusarium moniliforme, one of the major species found in corn. There are no known commercial or medical uses of fumonisin B1. Fumonisin B1 was nominated by the FDA Center for Food Safety and Applied Nutrition for study because of its occurrence in corn and corn-based products in the United States and its toxicity in field exposure of horses and pigs. Male and female F344/N Nctr BR rats and B6C3F1/Nctr BR (C57BL/6N x C3H/HeN MTV-) mice were exposed to fumonisin B1 (92% pure) in feed for 28 days or (greater than 96% pure) for 2 years. 28-DAY STUDY IN RATS: Groups of 10 male and 10 female rats were fed diets containing 0, 99, 163, 234, or 484 ppm fumonisin B1 for 28 days. There were no exposure-related deaths in rats. The mean body weights of the 484 ppm groups were significantly less (-16%) than those of the controls. Dietary concentrations of 99, 163, 234, and 484 ppm fumonisin B1 resulted in average daily doses of 12, 20, 28, and 56 mg fumonisin B1/kg body weight for males and females. Additional groups of male and female rats were exposed to the same concentrations of fumonisin B1 for 28 days for clinical pathology studies. The concentrations of creatinine, cholesterol, triglycerides, and total bile acids, as well as activities of the enzymes alanine aminotransferase, alkaline phosphatase, aspartate aminotransferase, and gamma-glutamyltransferase, were generally significantly greater in the 484 ppm groups than in the control groups at all time points, indicating hyperlipidemia and a hepatic effect. Fumonisin B1 is an inhibitor of ceramide synthase, resulting in an interruption of de novo sphingolipid synthesis. This enzyme inhibition results in increased levels of sphinganine (or increased sphinganine:sphingosine ratio) in tissues and urine. Urinary sphinganine was increased in groups of males exposed to 163 ppm or greater, while urinary sphinganine was increased in all exposed groups of females. The kidney weights, relative to body weight, of all exposed groups of rats were less than those of the control groups, decreasing by approximately 11% in the females and 20% in the males. Apoptosis and degeneration of the kidney were observed in all exposed males and in most females exposed to 163 ppm or greater. The incidences of minimal to mild apoptosis, degeneration, and mitotic alteration of the liver were significantly increased in 234 and 484 ppm males and in females exposed to 163 ppm or greater. The incidences of bile duct hyperplasia were significantly increased in males and females in the 484 ppm groups. In the core study, male rats in all exposed groups and females exposed to 163 ppm or greater had significantly increased percentages of hepatocytes in one or more proliferative (non-G0) states. 28-DAY STUDY IN MICE: Groups of 12 male and 12 female mice were fed diets containing 0, 99, 163, 234, or 484 ppm fumonisin B1 for 28 days. There were no exposure-related deaths in mice. The mean body weights of the 484 ppm groups of males were significantly less than those of the controls. Feed consumption by males exposed to 484 ppm was less than that by the controls; dietary concentrations of 99, 163, 234, and 484 ppm fumonisin B1 resulted in average daily doses of approximately 19, 31, 44, and 93 mg/kg for males and 24, 41, 62, and 105 mg/kg for females. Additional groups of male and female mice were exposed to the same concentrations of fumonisin B1 for 28 days for clinical pathology studies. Cholesterol and total bile acid concentrations and alanine aminotransferase and alkaline phosphatase activities were increased at 484 ppm, indicating hyperlipidemia and a hepatic effect. Urinary sphinganine concentrations and sphinganine/sphingosine ratios were increased in 484 ppm male mice. In 484 ppm males and all exposed groups of females, the incidences of hepatocellular necrosis, diffuse periportal hypertrophy, and diffuse centrilobular hyperplasia, as well as hyperplasia of the bile canaliculi and Kupffer cells, were generally significantly greater than those in the controls. Core study males exposed to 99, 163, or 234 ppm had significantly increased incidences of hepatocellular cytoplasmic alteration. Hepatocytes of 484 ppm male mice and all exposed groups of female mice were induced into proliferative (non-G0) states. 2-YEAR STUDY IN RATS: Groups of 48 male and 48 female rats (40 for 5 ppm groups) were fed diets containing 0, 5, 15, 50, or 150 ppm fumonisin B1 (males) or 0, 5, 15, 50, or 100 ppm fumonisin B1 (females) (equivalent to average daily doses of approximately 0.25, 0.76, 2.5, or 7.5 mg/kg to males and 0.31, 0.91, 3.0, or 6.1 mg/kg to females) for 105 weeks. Additional groups of four male and four female rats were exposed to the same concentrations as the core study animals and were evaluated at 6, 10, 14 or 26 weeks. Survival, Body Weights, and Feed Consumption Survival, mean body weights, and feed consumption of exposed male and female rats were generally similar to the controls throughout the study. Clinical Pathology Findings Sphinganine/sphingosine ratios were increased in the urine of 15, 50 and 150 ppm males and 50 and 100 ppm females exposed to fumonisin B1 for up to 26 weeks. The sphinganine/sphingosine ratios were also increased in kidney tissue of 50 and 150 ppm males (85- and 119-fold) and 50 and 100 ppm females (7.8- and 22-fold) at 2 years. Cell Proliferation Analyses Renal tubule epithelial cell proliferation was increased in 50 and 150 ppm male rats exposed to fumonisin B1 for up to 26 weeks. Renal tubule epithelial cell proliferation was marginally increased in 100 ppm females. Organ Weights and Pathology Findings Kidney weights of 50 and 150 ppm males were less than those of the controls at 6, 10, 14, and 26 weeks and at 2 years. Kidney weights of 100 ppm females were less than those of the controls at 26 weeks, and kidney weights of 15, 50, and 100 ppm females were less than those of the controls at 2 years. At 2 years, there was a significant increase in the incidences of renal tubule adenoma from none in the groups receiving 15 ppm or less to five of 48 in 150 ppm males. Renal tubule carcinomas were not present in male rats receiving 15 ppm or less and occurred in seven of 48 and 10 of 48 male rats in the 50 and 150 ppm groups, respectively. Incidences of apoptosis of the renal tubule epithelium were generally significantly increased in males exposed to 15 ppm or greater for up to 26 weeks. The incidences of focal renal tubule epithelial hyperplasia were significantly increased in 50 and 150 ppm males at 2 years. 2-YEAR STUDY IN MICE: Groups of 48 male and 48 female mice were fed diets containing 0, 5, 15, 80, or 150 ppm (males) or 0, 5, 15, 50, or 80 ppm (females) fumonisin B1 (equivalent to average daily doses of approximately 0.6, 1.7, 9.7, or 17.1 mg/kg to males or 0.7, 2.1, 7.1, or 12.4 mg/kg to females) for 105 weeks. Additional groups of four male and four female mice were exposed to the same concentrations as the core study animals and were evaluated at 3, 7, 9, or 24 weeks. Survival, Body Weights, and Feed Consumption Survival of males and females in the 15 ppm groups and of 5 ppm females was significantly greater and survival of 80 ppm males and females was significantly less than that of the control groups. Mean body weights and feed consumption of exposed mice were generally similar to the controls. Organ Weights and Pathology Findings Liver weights, relative to body weight, were increased 1.3- and 2.9-fold in 50 and 80 ppm females at 2 years. At 2 years, the incidences of hepatocellular adenoma in 50 and 80 ppm females were significantly greater than those in the controls and occurred with a positive trend. Similarly, the incidences of hepatocellular carcinoma increased from none in the groups receiving 0, 5, or 15 ppm fumonisin B1 to 10 of 47 females at 50 ppm and nine of 45 females at 80 ppm. The incidences of hepatocellular hypertrophy were significantly increased in 15, 80, and 150 ppm males and in 50 and 80 ppm females at 2 years. The incidences of hepatocellular apoptosis were significantly increased in 50 and 80 ppm females at 2 years. CONCLUSIONS: Under the conditions of these 2-year feed studies, there was clear evidence of carcinogenic activity of fumonisin B1 in male F344/N rats based on the increased incidences of renal tubule neoplasms. There was no evidence of carcinogenic activity of fumonisin B1 in female F344/N rats exposed to 5, 15, 50, or 100 ppm. There was no evidence of carcinogenic activity of fumonisin B1 in male B6C3F1 mice exposed to 5, 15, 80, or 150 ppm. There was clear evidence of carcinogenic activity of fumonisin B1 in female B6C3F1 mice based on the increased incidences of hepatocellular neoplasms. The sphinganine/sphingosine ratios were increased in the urine and the kidney tissue of rats receiving diets containing fumonisin B1. There was evidence of apoptosis and increased cell proliferation of the renal tubule epithelium in exposed rats, particularly in those groups of males that developed renal tubule neoplasms. Increased incidences of hyperplasia of the renal tubule epithelium also occurred in these groups of male rats. In mice exposed to the higher concentrations of fumonisin B1, males and females had increased incidences of hepatocellular hypertrophy and females had increased incidences of hepatocellular apoptosis.     

Toxicology and carcinogenesis studies of goldenseal root powder (Hydrastis Canadensis) in F344/N rats and B6C3F1 mice (feed studies)

Goldenseal root powder is used in folk medicine for the treatment of gastrointestinal disturbances, urinary disorders, hemorrhage, skin, mouth, and eye infections, and inflammation. The major alkaloids in goldenseal are berberine, hydrastine, and canadine. Goldenseal root powder was nominated for study by the National Institute of Environmental Health Sciences based on the potential for human exposure and the lack of carcinogenicity data, and 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 ground goldenseal root powder in feed for 2 weeks, 3 months, or 2 years. Genetic toxicology studies were conducted in Salmonella typhimurium, Escherichia coli, mouse bone marrow cells, and mouse peripheral blood erythrocytes. 2-WEEK STUDY IN RATS: Groups of five male and five female rats were fed diets containing 0, 1,560, 3,121, 6,250, 12,500, 25,000, or 50,000 ppm goldenseal root powder (equivalent to average daily doses of approximately 155, 315, 630, 1,190, 2,465, and 4,815 mg goldenseal root powder/kg body weight for males and 150, 290, 640, 1,240, 2,370, and 4,870 mg/kg for females) for 15 days. All rats survived to the end of the study. Mean body weights and feed consumption of all exposed groups of males and females were similar to those of the control groups throughout the study. Liver weights of males exposed to 6,250 ppm or greater and females exposed to 12,500 ppm or greater were significantly greater than those of the controls. Minimal to moderate hepatocellular hypertrophy occurred in three males and all females exposed to 25,000 ppm and in all 50,000 ppm males and females. 2-WEEK STUDY IN MICE: Groups of five male and five female mice were fed diets containing 0, 1,560, 3,121, 6,250, 12,500, 25,000, or 50,000 ppm goldenseal root powder (equivalent to average daily doses of approximately 380, 840, 1,760, 3,435, 6,700, and 15,170 mg/kg body weight for males and 330, 670, 1,240, 2,375, 4,760, and 8,475 mg/kg for females) for 15 days. All mice survived to the end of the study. Mean body weights and feed consumption of all exposed groups of males and females were similar to those of the control groups throughout the study. Significant increases in liver weights occurred in males exposed to 25,000 and 50,000 ppm and in females exposed to 50,000 ppm. Absolute and relative thymus weights of 12,500 and 50,000 ppm males were significantly decreased. Minimal hypertrophy of centrilobular hepatocytes occurred in all males and females exposed to 50,000 ppm. 3-MONTH STUDY IN RATS: Groups of 10 male and 10 female rats were fed diets containing 0, 3,121, 6,250, 12,500, 25,000, or 50,000 ppm goldenseal root powder (equivalent to average daily doses of approximately 255, 500, 1,000, 2,020, and 4,060 mg/kg for males and 260, 500, 1,030, 2,070, and 4,100 mg/kg for females) for 14 weeks. Additional groups of 10 male and 10 female clinical pathology study rats were given the same concentrations for 23 days. All rats survived to the end of the study. None of the body weights or mean body weight gains were significantly different from those of the controls. Feed consumption by exposed groups was generally similar to that by controls throughout the study. Liver weights were significantly increased in males exposed to 6,250 ppm or greater and in all exposed groups of females. The incidences of hepatocyte hypertrophy were significantly increased in the liver of males and females exposed to 12,500 ppm or greater; cytoplasmic vacuolization of hepatocytes occurred in all exposed males. 3-MONTH STUDY IN MICE: Groups of 10 male and 10 female mice were fed diets containing 0, 3,121, 6,250, 12,500, 25,000, or 50,000 ppm goldenseal root powder (equivalent to average daily doses of approximately 680, 1,360, 2,260, 5,370, and 10,550 mg/kg for males and 590, 1,250, 2,345, 4,790, and 10,740 mg/kg for females) for 14 weeks. All mice survived to the end of the study. Mean body weights of males exposed to 50,000 ppm and females exposed to 25,000 or 50,000 ppm were significantly less than those of the controls. Feed consumption by 3,121, 6,250, 12,500, 25,000, and 50,000 ppm males was similar to that by controls. Liver weights were significantly increased in males exposed to 12,500 ppm or greater and in females exposed to 25,000 or 50,000 ppm. The left epidydimal weight in male mice was significantly decreased relative to controls. The incidences of hepatocyte hypertrophy were significantly increased in males and females exposed to 12,500 ppm or greater. 2-YEAR STUDY IN RATS: Groups of 50 male and 50 female rats were fed diets containing 0, 3,000, 9,000, or 25,000 ppm goldenseal root powder (equivalent to average daily doses of approximately 135, 400, and 1,175 mg/kg for males and 150, 470, and 1,340 mg/kg for females) for 105 to 106 weeks. Survival of 9,000 ppm females was significantly greater than that of the controls. Mean body weights of females exposed to 9,000 ppm were 6% less than those of the controls after week 37, and those of 25,000 ppm females were 6% less than those of the controls after week 8. Feed consumption by exposed groups of males and females was generally similar to that by the controls throughout the study. The incidences of hepatocellular adenoma were significantly increased in males and females exposed to 25,000 ppm, and the incidence of hepatocellular adenoma or carcinoma (combined) was significantly increased in 25,000 ppm males. All exposed groups of males and females had significantly increased incidences of hepatocyte hypertrophy. The incidences of hepatocyte degeneration were significantly increased in all exposed groups of males and in 9,000 and 25,000 ppm females. The incidences of eosinophilic focus were significantly increased in 9,000 and 25,000 ppm males and all exposed groups of females. The incidences of cardiomyopathy were significantly decreased in all exposed groups of males and in 25,000 ppm females. 2-YEAR STUDY IN MICE: Groups of 50 male and 50 female mice were fed diets containing 0, 3,000, 9,000, or 25,000 ppm goldenseal root powder (equivalent to average daily doses of approximately 375, 1,120, and 3,275 mg/kg for males and 330, 1,000, and 2,875 mg/kg for females) for 105 to 106 weeks. Survival of 9,000 ppm females was significantly less than that of the controls. Mean body weights of females exposed to 25,000 ppm were 3% to 9% less than those of the controls after week 13, 6% less for weeks 14 to 52, and 5% less for weeks 53 to 101. Feed consumption by exposed groups of males and females was generally similar to that of the controls throughout the study. The incidences of hepatocellular adenoma occurred with a positive trend in males, and the incidences of multiple hepatocellular adenoma were significantly increased in 9,000 and 25,000 ppm males. The incidences of hepatoblastoma occurred with a positive trend in males with a marginal increase in the 25,000 ppm group. Significantly increased incidences of eosinophilic focus or mixed cell focus occurred in all exposed groups of males. GENETIC TOXICOLOGY: Goldenseal root powder was not mutagenic in Salmonella typhimurium or Escherichia coli tester strains, with or without liver S9 metabolic activation enzymes. In addition, no increases in the frequencies of micronucleated erythrocytes were observed in peripheral blood samples from mice exposed to goldenseal root powder in feed for 3 months. Berberine chloride was also tested for mutagenicity in standard screening assays. No mutagenicity was observed in several tester strains of Salmonella typhimurium, with or without rat or hamster liver S9 metabolic activation enzymes. In an acute exposure assay, no increase in the frequency of micronucleated polychromatic erythrocytes was seen in bone marrow of male mice administered three intraperitoneal injections of berberine chloride at 24-hour intervals. CONCLUSIONS: Under the conditions of these 2-year feed studies, there was clear evidence of carcinogenic activity of goldenseal root powder in male F344/N rats based on the increased incidences of hepatocellular adenoma and hepatocellular adenoma or carcinoma (combined). There was clear evidence of carcinogenic activity of goldenseal root powder in female F344/N rats based on the increased incidence of hepatocellular adenoma. There was some evidence of carcinogenic activity of goldenseal root powder in male B6C3F1 mice based on the increased incidences of hepatoblastoma and multiple hepatocellular adenoma. There was no evidence of carcinogenic activity of goldenseal root powder in female B6C3F1 mice exposed to 3,000, 9,000, or 25,000 ppm goldenseal root powder in feed for 2 years. Administration of goldenseal root powder resulted in increased incidences of nonneoplastic lesions in the liver of male and female rats and male mice.