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National Toxicology Program

Publications and source records attributed to National Toxicology Program.

At least 433 records · Page 24Linked to original sources

PubMed1987

NTP Toxicology and Carcinogenesis Studies of Methyl Carbamate (CAS No. 598-55-0) in F344/N Rats and B6C3F1 Mice (Gavage Studies).

Methyl carbamate is used as a chemical intermediate by the textile industry for the manufacture of dimethylol methyl carbamate-based resins that are applied on polyester/cotton blend fabrics as durable-press finishes. Experimental Design: Toxicology and carcinogenesis studies of methylyl carbamate (98% pure) were conducted by exposing groups of F344/N rats and B6C3F1 mice by gavage in water in a single dose and by repeated administration for 16 days, 13 weeks, 6 months, 12 months, 18 months, and 2 years. In addition, short-term mutagenicity studies in bacteria, mammalian cells, and Drosophila and of unscheduled DNA synthesis in rat liver cells were conducted. Single-Administration Studies: In the single-administration studies, 5/5 male and 5/5 female rats that received 8,000 mg/kg methyl carbamate and 2/5 male and 5/5 female that received 4,000 mg/kg died before the end of the 15-day observational period. Five of five male and 5/5 female mice that received 8,000 mg/kg and 1/5 females that received 4,000 mg/kg died before the end of the 15-day observational period. No compound-related morphologic effects were observed in rats or mice that received 2,000 mg/kg. Sixteen-Day Studies: In the 16-day studies, all rats dosed at 2,000 or 4,000 mg/kg died, and 3/5 male rats that received 1,000 mg/kg died. Male mice that received 2,000 or 4,000 mg/kg, female mice that received 4,000 mg/kg, and 1/5 female mice that received 2,000 mg/kg died. No compound-related gross pathologic or histopathologic effects were seen in male or female rats (groups of five each) that received 500 mg/kg or in mice that received 1,000 mg/kg. Thirteen-Week Studies: In the 13-week studies, groups of 10 male and 10 female rats and mice received up to 800 mg/kg (male rats), 1,000 mg/kg (female rats), 1,500 mg/kg (male mice), or 2,000 mg/kg (female mice). Four of 10 male rats that received 800 mg/kg and 1/10 female rats that received 1,000 mg/kg died of compound-related causes before the end of the studies. Toxic hepatitis, splenic pigmentation, bone marrow atrophy, and testicular atrophy were observed in the two highest dose groups of rats. One of the female mice that received 2,000 mg/kg died. The dosed female mice had significantly greater liver weights than did the vehicle controls. Experimental Design of Six-, Twelve-, and Eighteen-Month and Two-Year Studies: Based on the findings in the short-term studies, 2-year studies of methyl carbamate were conducted by administering 0, 100, or 200 mg/kg methyl carbamate in distilled water by gavage, 5 days per week for 103 weeks, to groups of 50 F344/N rats of each sex for 103 weeks. Groups of 50 B6C3F1 mice of each sex were administered 0, 500, or 1,000 mg/kg methyl carbamate on the same schedule. Additional groups of 30 rats of each sex were administered 0 or 400 mg/kg methyl carbamate, and additional groups of 30 mice of each sex were administered 0 or 1,000 mg/kg methyl carbamate in distilled water by gavage, 5 days per week. Ten animals from each group were killed at 6, 12, or 18 months so that the progression of lesions could be followed. Results of the Six-, Twelve-, and Eighteen-Month and Two-Year Studies: In the 6-month studies, all vehicle control and dosed (400 mg/kg) rats survived. Cytologic alterations and atypical proliferative changes were observed in the liver of all dosed male and female rats, and neoplastic nodules of the liver were observed in 6/10 dosed male and 5/10 dosed female rats. In the 12-month studies, all vehicle control male and female rats and dosed female rats survived. One of 10 dosed male rats died. Neoplastic nodules of the liver were observed in 7/10 dosed male and 9/10 dosed female rats, and hepatocellular carcinomas were observed in 8/10 dosed male and 6/10 dosed female rats. In the 18-month studies, 1/10 dosed male and 8/10 dosed female and all vehicle control rats survived. Hepatocellular carcinomas were observed in 9/10 dosed male and 8/10 dosed female rats. Compound-related neoplastic changes were not observed in mice in the 6-, 12-, or 18-month studies. In the 2-year studar studies, mean body weights of high dose (200 mg/kg) male rats were generally 5&percnt;-9&percnt; lower than those of the vehicle controls after week 20. Mean body weights of high dose female rats were 5&percnt;-8&percnt; lower than those of the vehicle controls after week 56. Survival of dosed and vehicle control rats was similar (male: vehicle control, 19/50; low dose, 26/50; high dose, 29/50; female: 29/50; 36/50; 35/50). The mean body weights of high dose (1,000 mg/kg) male mice were about 8&percnt;-18&percnt; lower than those of the vehicle controls after week 24. The mean body weights of high dose (1,000 mg/kg) female mice were about 16&percnt; lower than those of the vehicle controls after week 16 and 30&percnt; lower after week 64. Survival of dosed and vehicle control mice was similar (male: 28/50; 35/50; 28/50; female: 38/50; 36/50; 32/50). Chronic focal inflammation and cytologic alteration of the liver were observed at increased incidences in high dose rats of each sex. Hyperplasia of hepatocytes was observed atincreased incidences in dosed male and high dose female rats. Neoplastic nodules or hepatocellular carcinomas (combined) in female rats occurred with a significant positive trend (0/50; 0/50; 6/49; P<0.01); the incidence of neoplastic nodules or hepatocellular carcinomas (combined) in high dose female rats was greater (P<0.03) than that in the vehicle controls. Incidences of liver neoplasms in dosed male rats were not significantly increased (4/50; 0/50; 7/49). Inflammation of the harderian gland was observed at increased incidences in dosed rats (male: 4/50; 11/50; 16/50; female: 7/50; 16/50; 30/50). The lesions were considered to be chemically related. In the 2-year studies in rats, significant decreases in tumor incidences included the following: leukemia (both sexes), pituitary gland (male), adrenal gland (male), and mammary gland (female). In the 2-year mouse studies, multinucleate giant cells in the liver were observed at increased incidences in dosed male mice (14/50; 31/50; 31/49). Adenomatous hyperplasia and histiocytosis of the lung were observed at increased incidences in high dose mice (adenomatous hyperplasia--male: 13/50; 19/50; 24/49; female: 7/49; 10/50; 18/50; histiocytosis--male: 11/50; 7/50; 21/49; female: 9/49; 10/50; 21/50). Genetic Toxicology: Methyl carbamate was not mutagenic in Salmonella typhimurium strains TA97, TA98, TA100, or TA1535 when tested with or without metabolic activation in a preincubation protocol at doses up to 10 mg/plate. Methyl carbamate did not induce forward mutations in the mouse L5178Y/TK± lymphoma assay with or without metabolicactivation at doses up to 5 mg/ml. Unscheduled DNA synthesis was not detected in rat hepatocytes after in vitro treatment with methyl carbamate at concentrations of 1.0-1,000 ug/ml. When tested in Drosophila at doses of 25,000-50,000 ppm, methyl carbamate did not induce sex-linked recessive lethal mutations. Results of tests for induction of chromosomal aberrations and sister chromatid exchanges by methyl carbamate in cultured Chinese hamster ovary cells were also negative at doses up to 5 mg/ml. Data Audit: An audit of the experimental data was conducted for the 6-, 12-, and 18-month and 2-year studies of methyl carbamate. No data discrepancies were found that influenced the final interpretation. Conclusions: Under the conditions of these 6-, 12-, and 18-month and 2-year gavage studies, there was clear evidence of carcinogenic activity for male and female F344/N rats given methyl carbamate as indicated by increased incidences of hepatocellular neoplastic nodules and hepatocellular carcinomas. There was no evidence of carcinogenic activity for male and female B6C3F1 mice given methyl carbamate at doses of 500 or 1,000 mg/kg. Methyl carbamate also induced inflammation of the harderian gland in male and female rats and adenomatous hyperplasia and histiocytosis of the lung in male and female mice. Synonyms: carbamic acid, methyl ester; methylurethan; methylurethane; urethylane

Journal Article↗

PubMed1987

NTP Carcinogenesis Studies of Food Grade Geranyl Acetate (71% Geranyl Acetate, 29% Citronellyl Acetate) (CAS No. 105-87-3) in F344/N Rats and B6C3F1 Mice (Gavage Study).

Geranyl acetate (3,7-dimethyl-2,6-octadiene-1-ol acetate) is a colorless liquid prepared by fractional distillation of selected essential oils or by acetylation of geraniol. It is a natural constituent of more than 60 essential oils, including Ceylon citronella, palmarosa, lemon grass, petit grain, neroli bigarade, geranium, coriander, carrot, and sassafras. Geranyl acetate is used primarily as a component of perfumes for creams and soaps and as a flavoring ingredient. On the U.S. Food and Drug Administration's list of substances "generally recognized as safe," the Food Chemicals Codex (1972) specifies that geranyl acetate must contain at least 90% total esters. Carcinogenesis studies of food-grade geranyl acetate (containing approximately 29% citronellyl acetate) were conducted by administering the test chemical in corn oil by gavage to groups of 50 male and 50 female F344/N rats at doses of 1,000 or 2,000 mg/kg body weight and to groups of 50 male and 50 female B6C3F1 mice at doses of 500 or 1,000 mg/kg. Doses were administered five times per week for 103 weeks. Groups of 50 rats and 50 mice of each sex received corn oil by gavage on the same dosing schedule and served as vehicle controls. The cumulative toxicity of geranyl acetate in the 2-year study was indicated by the significantly shorter survival of high dose male rats (control, 34/50; low dose, 29/50; high dose, 18/50) and of high dose male mice (control, 31/50; low dose, 32/50; high dose, 0/50) and of dosed female mice (38/50; 15/50; 0/50) when compared with controls. Throughout most of the 2-year study, mean body weights of high dose rats and mice of each sex were lower than those of the controls. The occurrence of retinopathy or cataracts in the high dose male rats and low dose female rats as compared with the controls does not appear to be related to the administration of geranyl acetate but rather the proximity of the rats to fluorescent light. The incidence of retinopathy or cataracts (combined) was: males: control, 0/50, 0%; low dose, 1/50, 2%; high dose, 11/50, 22%; females: control, 1/50, 2%; low dose, 13/50, 26%; high dose, 2/50, 4%. Kidney tubular cell adenomas, an uncommon tumor type, were found in 2/50 (4%) low dose male rats. The historical incidence of male corn oil gavage control F344/N rats with kidney tumors is 1/250 (0.4%) at this laboratory and 4/998 (0.4%) in the program. Squamous cell papillomas in the skin were increased marginally in low dose male rats (control, 0/50; low dose, 4/50, 8%; high dose, 1/50, 2%). In addition, one low dose male rat had a squamous cell carcinoma of the skin. The incidence of low dose male rats with either squamous cell papillomas or carcinomas was greater (P<0.05) in comparison with the controls. The historical incidence of squamous cell papillomas or carcinomas (combined) in gavage control male F344/N rats is 3.6% (9/250) at this laboratory and 2.5% (25/999) throughout the program. The incidence of all epidermal tumors was not significantly elevated in dosed male rats relative to controls (control, 3/50, 6%; low dose, 6/50, 12%; high dose, 1/50, 2%). All high dose (1,000 mg/kg) male and female mice were dead by week 91 as a result of accidentally being administered 2,800 mg/kg for 3 days during week 91; survival of low dose and control male mice was comparable. Survival of high dose male and dosed female mice may have been inadequate for the detection of late-appearing tumors. No evidence of any carcinogenic effect was found in either low or high dose mice of either sex. An infection of the genital tract was probably responsible for the deaths of 14/22 control and 8/32 low dose female mice before the end of the study. Cytoplasmic vacuolization was increased in the liver and in the kidney of male and female mice and was considered to be compound related (liver-- male: control, 1/50, 2%; low dose, 7/50, 14%; high dose, 47/50, 94%; female: 1/50, 2%; 27/50, 54%; 46/50, 92%; kidney or kidney tubule--male: 0/50; 0/50; 41/50, 82%; female: 0/50; 24/49, 49%; 37/50, 74%). Under the conditions of these studies, geranyl 4&percnt;; 46/50, 92&percnt;; kidney or kidney tubule--male: 0/50; 0/50; 41/50, 82&percnt;; female: 0/50; 24/49, 49&percnt;; 37/50, 74&percnt;). Under the conditions of these studies, geranyl acetate was not carcinogenic for F344/N rats or B6C3F1 mice of either sex; however, the reduced survival observed in high dose male rats, high dose male mice, and high and low dose female mice lowered the sensitivity of these studies for detecting neoplastic responses in these groups. In male rats the marginal increases of squamous cell papillomas of the skin and tubular cell adenomas of the kidney may have been related to administration of geranyl acetate. Levels of Evidence of Carcinogenicity: Male Rats: Negative Female Rats: Negative Male Mice: Negative Female Mice: Negative

Journal Article↗

PubMed1987

NTP Toxicology and Carcinogenesis Studies of Tetrakis(hydroxymethyl)phosphonium sulfate (THPS) (CAS No. 55566-30-8) and Tetrakis(hydroxymethyl)phosphonium chloride (THPC) (CAS No. 124-64-1) in F344/N Rats and B6C3F1 Mice (Gavage Studies).

Toxicology and carcinogenesis studies of tetrakis(hydroxymethyl)phosphonium sulfate (THPS) and tetrakis(hydroxymethyl)phosphonium chloride (THPC) were conducted because of the widespread use of these chemicals as flame retardants in cotton fabrics. THPS was available as a 72% aqueous solution and THPC as a 75% aqueous solution. Short-term gavage studies with a range of doses were conducted first to identify toxic effects and affected sites and to determine doses for the 2-year studies. The doses selected for the 14-day studies ranged from 12.5 to 200 mg/kg THPS for rats and mice, 9.4 to 150 mg/kg THPC for rats, and 18.8 to 300 mg/kg THPC for mice. Mortality and reduction in body weight gain occurred at the two highest doses in the 14-day studies. There was hind limb paralysis in some rats and mice dosed at the highest concentrations of THPS and THPC. In the 13-week studies, doses of THPS ranged from 5 to 60 mg/kg in rats and from 2 to 180 mg/kg in mice; doses of THPC ranged from 3.75 to 60 mg/kg in rats and from 1.5 to 135 mg/kg in mice. Mortality and reduction in body weight gain occurred at the two higher doses for both sexes and species. Vascular degeneration of hepatocytes or hepatocellular necrosis was a common histopathologic finding. Hind limb paralysis was noted in rats and mice receiving the highest dose of THPC, and axonal degeneration, characterized by swollen axon sheaths, missing or fragmented axons, and some proliferation of neurolemma cells, was observed in rats. These lesions were found in the sciatic nerve, dorsal roots of the caudal spinal nerves, and the tracts of the spinal cord, particularly in the dorsal column of the lumbar cord. Two-year studies were conducted in F344/N rats by administering 0, 5, or 10 mg/kg THPS or 0, 3.75, or 7.5 mg/kg THPC in deionized water by gavage to groups of 49 or 50 animals of each sex, 5 days per week for 103 or 104 weeks. Groups of 49 or 50 B6C3F1 mice were administered 0, 5, or 10 mg/kg THPS (each sex), 0, 7.5, or 15 mg/kg THPC (males), or 0, 15, or 30 mg/kg THPC (females). Survival of male rats was reduced for the low dose (after week 102) and the high dose (after week 67) groups given THPS compared with that of the vehicle controls; survival at terminal kill was as follows: vehicle control, 28/50; low dose, 13/50; high dose, 16/50. Survival of the high dose group of female rats given THPC was lower after week 70 than that of the vehicle controls (survival at terminal kill: 37/50; 34/50; 21/50). Mean body weights of rats dosed with THPS or THPC were comparable to those of the vehicle controls. There was no difference in survival or mean body weights between the vehicle controls and mice dosed with either THPS or THPC. No neurotoxicity or any other signs of clinical toxicity were observed. A nonneoplastic effect common to 13-week and 2-year exposure to THPS or THPC was an increase in the incidence of hepatocellular lesions, primarily cytoplasmic vacuolization. The incidences of this lesion in the two-year studies were dose related for all studies except for the mice receiving THPS. Other lesions observed included focal hyperplasia of the adrenal medulla in high dose male mice given THPS and follicular cell hyperplasia of the thyroid gland in high dose female mice given THPC. The increased incidences of hematopoietic system lesions observed in these studies were not considered biologically related to chemical exposure because the increases were marginal, no dose-response relationship was observed, and the incidences of these lesions are highly variable in untreated rats and mice. The incidences of mononuclear cell leukemia in low dose male rats administered THPS or THPC were somewhat greater than those in the vehicle controls (THPS: 30/50; 36/50; 20/50; THPC: 19/50; 25/50; 16/50). Low dose male mice administered THPS had an increased incidence of malignant lymphomas when compared with vehicle controls (2/50; 9/50; 0/50). These marginal increases in the incidences of hematopoietic system tumors were not considered related to chemical exposure, since they were signific were significant only by the life table tests and were not dose related. THPC demonstrated no mutagenic activity in Salmonella typhimurium strains TA98, TA100, TA1535, or TA1537 with or without metabolic activation. Both THPS and THPC induced forward mutations in mouse lymphoma L5178Y cells without metabolic activation; neither was tested in the presence of S9. THPC increased the frequency of sister-chromatid exchanges and chromosomal aberrations in Chinese hamster ovary cells in the presence and absence of exogenous metabolic activation. An audit of the experimental data was conducted for the 2-year studies of THPS and THPC. No discrepancies were found that influenced the final interpretations. Under the conditions of these 2-year gavage studies, there was no evidence of carcinogenicity of THPS in either sex of F344/N rats or B6C3F1 mice given 5 or 10 mg/kg. There was no evidence of carcinogenicity of THPC in either sex of F344/N rats given 3.75 or 7.5 mg/kg, in male B6C3F1 mice given 7.5 or 15 mg/kg, or in female B6C3F1 mice given 15 or 30 mg/kg.

Journal Article↗

PubMed1987

NTP Toxicology and Carcinogenesis Studies of Chlorendic Acid (CAS No. 115-28-6) in F344/N Rats and B6C3F1 Mice (Feed Studies).

Chlorendic acid is a chemical intermediate used in the preparation of fire-retardant polyester resins and plasticizers. Toxicology and carcinogenesis studies of chlorendic acid (greater than 98% pure) were conducted by administering the chemical in feed to groups of 50 male and 50 female F344/N rats and B6C3F1 mice at concentrations of 0, 620, or 1,250 ppm for 103 weeks. The estimated mean daily consumption of chlorendic acid was 27 and 56 mg/kg body weight for low dose and high dose male rats and 39 and 66 mg/kg for low dose and high dose female rats. In mice, the estimated daily consumption was 89 and 185 mg/kg for low dose and high dose males and 100 and 207 mg/kg for low dose and high dose females. These concentrations were selected because higher levels in the 14-day and 13-week studies caused decreased mean body weights, more deaths, and increased incidences of liver lesions (rats: centrilobular cytomegaly, mitotic alterations, bile duct hyperplasia; mice: centrilobular cytomegaly, mitotic alterations, coagulative necrosis) relative to control groups. Survival and feed consumption of dosed male and female rats and mice in the 2-year studies were similar to those of controls. Mean body weights of high dose male and female rats and mice were lower than those of controls. Mean body weights of high dose female rats were 16%-24% lower than those of controls during the second half of the study. In the 2-year chlorendic acid feed studies, incidences of nonneoplastic lesions of the liver in dosed male rats (cystic degeneration) and dosed female rats (granulomatous inflammation, pigmentation, and bile duct hyperplasia) were increased. The incidences of neoplastic nodules of the liver were significantly increased in dosed male rats (control, 2/50; low dose, 21/50; high dose, 23/50) and high dose female rats (1/50; 3/39; 11/50). The incidence of hepatocellular carcinomas was also increased in high dose female rats (0/50; 3/49; 5/50). In mice, the incidences of nonneoplastic lesions of the liver were increased in dosed males (coagulative necrosis) and high dose females (mitotic alterations). The incidences of hepatocellular adenomas (5/50; 9/49; 10/50), hepatocellular carcinomas (9/50; 17/50; 20/50), and hepatocellular adenomas or carcinomas (combined) (13/50; 23/49; 27/50) were increased in dosed male mice. Hepatocellular carcinomas metastasized to the lung in 2/50 control, 4/49 low dose, and 7/50 high dose male mice. Hepatocellular adenomas or carcinomas (combined) were not significantly increased in female mice (3/50; 7/49; 7/50). The incidences of acinar cell hyperplasia (0/49; 4/50; 4/50) and acinar cell adenomas (0/49; 4/50; 6/50) of the pancreas were increased in dosed male rats relative to those of controls. Pancreatic acinar cell adenoma is an uncommonneoplasm in untreated control F344/N rats in NTP studies (3/1,667). In dosed male rats, incidences of alveolar/bronchiolar adenomas of the lung (0/50; 3/50; 5/50) were increased. The incidences of alveolar/bronchiolar adenomas or carcinomas (combined) in dosed female mice were also increased (1/50; 5/50; 6/50). Preputial gland carcinomas occurred at a greater incidence in low dose male rats (1/50; 8/50; 4/50) than in controls. An adenoma and a squamous cell papilloma were observed in two low dose male rats. The incidences of sarcomas, fibrosarcomas, or neurofibrosarcomas (combined) of the salivary gland (1/50; 2/49; 4/50) were increased in dosed male rats. The incidences in the dosed groups were not significantly different from that in the controls, but these tumors are uncommon in F344/N rats receiving no treatment (3/1,689). Chlorendic acid was not mutagenic in strains TA100, TA98, TA1535, or TA 1537 of Salmonella typhimurium in the presence or absence of Aroclor 1254-induced male Sprague-Dawley rat or male Syrian hamster liver activation when tested according to the preincubational protocol. Chlorendic acid was mutagenic in the L5178Y/TK+/- mouse lymphoma cell forward assay (in the absence of activation) at a dose resulting in toxicity. An audit of the experimental dudit of the experimental data was conducted for the 2-year studies of chlorendic acid. No data discrepancies were found that influenced the final interpretations. Under the conditions of these 2-year feed studies, there was clear evidence of carcinogenicity of chlorendic acid for male F344/N rats as shown by increased incidences of neoplastic nodules of the liver and acinar cell adenomas of the pancreas. Increased incidences of alveolar/bronchiolar adenomas and preputial gland carcinomas may also have been related to the administration of chlorendic acid. There was clear evidence of carcinogenicity of chlorendic acid for female F344/N rats as shown by increased incidences of neoplastic nodules and of carcinomas of the liver. There was clear evidence of carcinogenicity of chlorendic acid for male B6C3F1 mice as shown by increased incidences of hepatocellular adenomas and of hepatocellular carcinomas. There was no evidence of carcinogenicity of chlorendic acid for female B6C3F1 mice given chlorendic acid in the diet at concentrations of 620 or 1,250 ppm for 103 weeks.

Journal Article↗

PubMed1987

NTP Toxicology and Carcinogenesis Studies of Ethylene Oxide (CAS No. 75-21-8) in B6C3F1 Mice (Inhalation Studies).

Ethylene oxide is a major industrial chemical used primarily as an intermediate in the manufacture of other chemicals; e.g., ethylene glycol, a major component of automotive and other antifreeze products. Exposure to ethylene oxide is greatest in the health care industry, where an estimated 75,000 workers are potentially exposed. Ethylene oxide was nominated for toxicology and carcinogenesis studies in B6C3F1 mice because of its extensive production; the potential for human exposure in the workplace, from medical devices, or from food; the positive results of genetic toxicology assays; and the previous use of only F344/N rats in inhalation carcinogenicity studies. Two inhalation studies reported in 1984 by Snellings et al. and by Lynch et al. demonstrated carcinogenic responses in F344/N rats. Results were similar in both studies and consisted of increased incidences of mononuclear cell leukemia, peritoneal mesotheliomas, and primary brain tumors. Experimental Design: Toxicology and carcinogenesis studies of ethylene oxide (greater than 99% pure) were conducted by exposing groups of 50 B6C3F1 mice of each sex to air containing 0, 50, or 100 ppm ethylene oxide, 6 hours per day, 5 days per week for 102 weeks. These doses were selected because, in 14-week studies, all mice exposed at 600 ppm died within 1 week, and all mice exposed at 400 ppm died by week 4. Rhinitis was observed in both sexes exposed at 200, 400, and 600 ppm as was renal tubular degeneration in both sexes at 100, 200, and 400 ppm. The latter effects observed at 100 ppm were slight and deemed not to be life threatening in 2-year studies. Two-Year Studies: Survival of exposed and control mice was comparable in the 2-year studies (male: control, 28/50; low dose, 31/50; high dose, 34/50; female: 25/50; 24/50;31/50). Final mean body weights in exposed mice were 95%-102% of those of the controls. No compound-related clinical signs were observed. Those neoplastic lesions that occurred at elevated incidences in mice exposed to ethylene oxide are reported in the following table (see page 6 of the Technical Report). In male mice, alveolar/bronchiolar carcinomas, alveolar/bronchiolar adenomas, and papillary cystadenomas of the harderian gland occurred with positive trends. In female mice, alveolar/bronchiolar adenomas, alveolar/bronchiolar carcinomas, papillary cystadenomas of the harderian gland, malignant lymphomas, and uterine adenocarcinomas occurred with positive trends. Mammary gland tumors also were increased in exposed female mice. Data Audit: An audit of the experimental data was conducted for the 2-year studies of ethylene oxide. No data discrepancies were found that influenced the final interpretations. Conclusions: Under the conditions of these 2-year inhalation studies, there was clear evidence of carcinogenic activity for B6C3F1 mice as indicated by dose-related increased incidences of benign or malignant neoplasms of the lung and benign neoplasms of the harderian gland in both male and female B6C3F1 mice following exposure to ethylene oxide vapors at 50 and 100 ppm. In female mice, ethylene oxide caused additional malignant neoplasms of the uterus, mammary gland, and hematopoietic system (lymphoma). Synonyms: oxirane; EO; ETO; dihydrooxirene; dimethylene oxide; 1,2-epoxyethane; oxane; a,beta-oxidoethane

Journal Article↗

PubMed1987

NTP Toxicology and Carcinogenesis Studies of Pentachloronitrobenzene (CAS No. 82-68-8) in B6C3F1 Mice (Feed Studies).

Toxicology and carcinogenesis studies of pentachloronitrobenzene (99% pure), a fungicide, were conducted by administering diets containing 0, 2,500, or 5,000 ppm pentachloronitrobenzene to groups of 50 B6C3F1 mice of each sex for 103 weeks. These doses were selected because, in 13-week studies in which the chemical was administered in feed at doses up to 20,000 ppm in male mice and up to 40,000 ppm in female mice, body weight gain depression was observed at 10,000 ppm and above in males and female and deaths occurred at 40,000 ppm in females. The National Cancer Institute had conducted 2-year (diet) studies in B6C3F1 mice and Osborne-Mendel rats (See TR-61 reported in 1978). Survival among male mice was low, not all livers were examined from dosed female mice, and the size of the control group was considered to be small. For these reasons, the NCI decided to conduct additional 13-week and 2-year studies in B6C3F1 mice. Under the conditions of the NCI studies, pentachloronitrobenzene was not carcinogenic in either Osborne-Mendel rats or B6C3F1 mice. In the studies reported in this Technical Report, the survival of male mice was comparable among control and dosed groups (control, 35/50; low dose, 31/50; high dose, 32/50). Final mean body weights of low dose and high dose male mice were 96% and 90% that of the controls. All groups of female mice showed evidence of bacterial infection. At week 84, survival in dosed and control female mice was 38/50; 34/50; 30/50; after week 84, survival in dosed groups decreased, with the final survival being 30/50; 20/50; 15/50. The mean body weight of high dose female mice was more than 10% lower than that of the control group after week 20 and was 21% lower than controls at week 104. The mean body weight of low dose female mice was within 10% that of the control group until week 88 and was 18% lower than controls at week 104. No compound-related neoplastic lesions were seen in either male or female mice. The nonneoplastic lesions observed in female mice were considered to be secondary to bacterial infection (primarily Klebsiella) and included hematopoiesis of the liver (9/50; 21/50; 23/50) and spleen (14/50; 23/48; 27/50), plasma cell hyperplasia of the mediastinal lymph nodes (1/44; 4/47; 9/45), and ovarian abscesses (12/49; 22/50; 29/50). Pentachloronitrobenzene was not mutagenic in Salmonella typhimurium strains TA98, TA100, TA1535, or TA1537 in the presence or absence of Aroclor 1254-induced male Syrian hamster or male Sprague-Dawley rat liver S9 when tested according to the preincubational protocol. Pentachloronitrobenzene was not mutagenic at the TK+/- locus of L5178Y mouse lymphoma cells in the presence or absence of Aroclor 1254-induced F344/N rat liver S9. In cultured Chinese hamster ovary cells, pentachloronitrobenzene did not induce sister-chromatid exchanges but did induce chromosomal aberrations both with and without Aroclor 1254-induced male Sprague-Dawley rat liver S9. An audit of the experimental data was conducted for the 2-year studies of pentachloronitrobenzene. No data discrepancies were found that influenced the final interpretations. Under the conditions of these 2-year feed studies, there was no evidence of carcinogenicity for either male or female B6C3F1 mice receiving 2,500 or 5,000 ppm of pentachloronitrobenzene. Infection is considered to have decreased survival of the female mice and thus reduced the sensitivity for determining the presence or absence of a carcinogenic response. Synonyms or Trade Names: Avicolreg.; PCNB; quintozene; Botrilexreg.; Brassicolreg.;Folosanreg.; PKhNB; Tilcarexreg.; Terraclorreg.; Tritosanreg.

Journal Article↗

PubMed1987

NTP Toxicology and Carcinogenesis Studies of Boric Acid (CAS No. 10043-35-3) in B6C3F1 Mice (Feed Studies).

Boric acid is a component of cosmetics and pharmaceuticals and is also used in numerous industrial processes. Earlier long-term studies did not demonstrate a carcinogenic effect in Sprague-Dawley rats. Because of potential widespread human exposure, corroborative evidence was sought in a second species. Toxicology and carcinogenesis studies were conducted by feeding technical-grade boric acid (99.7% pure) to groups of male and female B6C3F1 mice for 14 days, 13 weeks, and 2 years. In the 14-day studies (five mice per group), mortality occurred in mice fed 25,000 ppm, 50,000 ppm, or 100,000 ppm boric acid; hyperplasia and/or dysplasia of the forestomach was also seen in these dose groups. No compound-related gross pathologic or histopathologic effects were seen in male or female mice exposed at concentrations up to 12,500 ppm in feed. In the 13-week studies, groups of 10 male and 10 female mice were fed boric acid at concentrations up to 20,000 ppm; 8 male mice and 1 female mouse receiving 20,000 ppm and 1 male receiving 10,000 ppm boric acid died before the end of the studies. Male and female mice receiving 20,000 ppm boric acid weighed 23% and 18% less, respectively, than did the controls at the end of the studies. Testicular atrophy in 8/10 male mice, hyperkeratosis and acanthosis of the stomach in 8/10 male and female mice, and extramedullary hematopoiesis of the spleen in all male and female mice receiving 20,000 ppm boric acid indicated that the testis, stomach, and spleen were potential target organs in the 2-year studies. Based on these results, 2-year toxicology and carcinogenesis studies were conducted by feeding diets containing boric acid at concentrations of 0, 2,500, or 5,000 ppm to groups of 50 male and 50 female mice. Survival of high dose male mice after week 63 and of low dose mice after week 84 was lower than that of the controls (final survival: control, 41; low dose, 30; high dose, 22), which may have reduced the sensitivity of the carcinogenicity study; the numbers of female mice (33; 33; 37) that survived to the end of the studies were considered adequate for toxicologic evaluation. Body weight gain was reduced in each sex after week 30; mean final body weights were 7% and 13% below control values for exposed male mice and 7% and 20% below those of controls for exposed female mice. No chemically related clinical signs were reported. At the top dose, boric acid caused an increased incidence of testicular atrophy (control, 3/49; low dose, 6/50; high dose, 27/47) and interstitial cell hyperplasia (0/49; 0/50; 7/47) inmale mice. The testicular atrophy was characterized by variable loss of spermatogonia, primary and secondary spermatocytes, spermatids, and spermatozoa from the seminiferous tubules. The seminiferous tubules contained primarily Sertoli cells and variable numbers of spermatogonia. In some mice, there were accumulations of interstitial cells, indicating hyperplasia. In low dose male mice, there were increased incidences of hepatocellular carcinomas (5/50; 12/50; 8/49) and hepatocellular adenomas or carcinomas (combined) (14/50; 19/50; 15/49) and an increased incidence of subcutaneous tissue fibromas, sarcomas, fibrosarcomas, or neurofibrosarcomas (combined) (2/50; 10/50; 2/50). No increased incidence of subcutaneous tissue neoplasms was seen in male mice receiving 5,000 ppm. Because the incidence of subcutaneous tissue tumors is variable in historical controls, because there was no corresponding increase in the high dose male mice, and because the incidence of hepatocellular tumors was not significant by the incidental tumor test and was within the historical control range, neither of these tumors was considered to be related to the administration of boric acid. Boric acid was not mutagenic in the Salmonella/microsome assay with Salmonella typhimurium strains TA98, TA100, TA1535, or TA1537. Boric acid was negative in the mouse lymphoma L5178Y/TK+/- assay and did not induce sister-chromatid exchanges or chromosomal aberrations in Chinese hamster ovary cells. All assays were preformed with anhamster ovary cells. All assays were preformed with and without metabolic activation. The data, documents, and pathology materials from the 2-year studies of boric acid were audited at the NTP Archives. The audit findings show that the conduct of the studies is documented adequately and support the data and results given in this Technical Report. Under the conditions of these 2--year feed studies, there was no evidence of carcinogenicity of boric acid at doses of 2,500 or 5,000 ppm for male or female B6C3F1 mice. Testicular atrophy and interstitial cell hyperplasia were observed in high dose male mice. The decrease in survival of dosed male mice may have reduced the sensitivity of this study. Synonyms: orthoboric acid; boracic acid

Journal Article↗

PubMed1987

NTP Toxicology and Carcinogenesis Studies of Dimethyl Methylphosphonate (CAS No. 756-79-6) in F344/N Rats and B6C3F1 Mice (Gavage Studies).

Dimethyl methylphosphonate (98% pure) is one of four chemicals nominated by the U.S. Army for toxicology and carcinogenesis studies because it was being considered for use to simulate the physical and spectroscopic (but not the biologic) properties of anticholinesterase (nerve) agents. Dimethyl methylphosphonate is also used as a flame retardant, a preignition additive for gasoline, an antifoam agent, a plasticizer and stabilizer, a textile conditioner and antistatic agent, and an additive for solvents and low-temperature hydraulic fluids. The United States produces 0.2-2 million pounds (91,000-910,000 kg) of per year. Gavage was chosen as the route of administration for all four candidate "simulants" to mimic potential exposure. Experimental Design: Dimethyl methylphosphonate was administered in corn oil by gavage to male and female F344/N rats and B6C3F1 mice in single-administration, 15-day, and 13-week studies to obtain toxicity data, to establish dose levels for the 2-year studies, and to identify target tissues. Additional studies were also performed to determine toxicity to the reproductive system of male F344/N rats and B6C3F1 mice and to study the potential for genetic damage in bacteria, mammalian cells, and Drosophila. Single-Administration Studies: In the single-administration studies, dimethyl methylphosphonate was given to rats and mice at doses up to 6,810 mg/kg body weight. No compound-related deaths were seen in male or female rats or male mice; two high dose female mice died. Rats exhibited inactivity, unsteady gait, and prostration after dosing; mice were inactive after dosing. Fifteen-Day Studies: Rats and mice received doses of 0, 1,250, 2,500, 5,000, 10,000, or 15,000 mg/kg dimethyl methylphosphonate per day. Compound-related deaths occurred in the three highest dose groups of rats and the two highest dose groups of mice. Rats receiving doses of 2,500 mg/kg or higher were inactive and at 5,000 or 10,000 mg/kg had an unsteady gait after dosing; mice exhibited inactivity, shallow breathing, and prostration at doses of 10,000 mg/kg or higher. No lesions were reported in rats. Nonneoplastic lesions of the stomach were seen in some male mice at doses of 1,250 mg/kg and higher and in some female mice at doses of 5,000 mg/kg and higher. Thirteen-Week Studies: Dimethyl methylphosphonate was given at doses up to 8,000 mg/kg per day. Compound-related deaths occurred at 2,000, 4,000, and 8,000 mg/kg in rats and at 4,000 and 8,000 mg/kg in mice. Mean body weights of rats at 1,000 mg/kg and mice at 2,000 mg/kg were similar to those of the vehicle controls; decreased weight gain was seen at higher doses. No compound-related clinical signs were reported. Minimal to mild renal and testicular lesions were seen at all doses in male rats, but the severity of these lesions did not increase with increasing dose of the chemical. No apparent target tissues were identified in female rats or male and female mice. Doses selected for the 2-year studies were based on body weight effects and mortality seen in the 13-week studies; the lesions seen in the kidney of male rats at the end of the 13-week studies were judged not to be life threatening. In the 2-year studies, dimethyl methylphosphonate was administered in corn oil by gavage at doses of 0, 500, or 1,000 mg/kg per day to groups of 50 F344/N rats of each sex and at 0, 1,000, or 2,000 mg/kg per day to groups of 50 B6C3F1 mice of each sex. All animals were dosed 5 days per week for 103 weeks. Body Weight and Survival in the Two-Year Studies: Mean body weights of high dose male rats were 5%-10% lower than those of the vehicle controls between weeks 28 and 76 and were 10%-24% lower between weeks 80 and 104. Mean body weights of high dose female rats were 8%-12% lower than those of the vehicle controls after week 80. Survival of male rats was greater than 50% in all groups until week 80, and after this time, survival decreased in both groups, with the survival at the end of the study being 27/50 in vehicle control, 17/50 in low dose, and 4/50 in high dose groups. Survival of in low dose, and 4/50 in high dose groups. Survival of low dose female rats was comparable to that of the vehicle controls, but the final survival of high dose female rats was decreased (vehicle control, 30/50; low dose, 33/50; high dose, 23/50). No other compound-related clinical signs were observed. Mean body weights of high dose male mice were 7&percnt;-16&percnt; lower than those of the vehicle control males between weeks 36 and 76, and those of high dose female mice were 6&percnt;-12&percnt; lower between weeks 88 and 103. Decreased survival between weeks 23 and 45 in high dose male mice was associated with fighting. Seventeen high dose male and 22 high dose female mice died during week 45; these deaths were associated with the accidental administration of a dose mixture that had a concentration 34&percnt; greater than the targeted amount. Eleven low dose male mice died on the same day during week 77. By the end of the study, 29/50 vehicle control, 12/50 low dose, and 0/50 high dose male mice were alive; 41/50, 30/50, and 2/50 female mice survived to the end of the study. Renal Effects in the Two-Year Studies: Administration of dimethyl methylphosphonate to male rats increased the average severity of nephropathy and caused mineralization (calcification) of the collecting tubules in the renal papilla (12/50; 41/50; 36/49), hyperplasia of the transitional epithelium lining the renal pelvis and overlying the renal papilla (0/50; 23/50; 21/49), and focal hyperplasia of the renal tubular epithelium (0/50; 8/50; 9/49). Administration of dimethyl methylphosphonate to male rats was also associated with the occurrence of rare renal tubular cell adenocarcinomas (0/50; 2/50; 3/49) and papillomas of the transitional epithelium lining of the renal pelvis (0/50; 2/50; 3/49); a transitional cell carcinoma occurred in a low dose male rat. There were no tubular cell or transitional cell neoplasms of the kidney in female rats. Hematopoietic System Effects in the Two-Year Studies: The incidence of mononuclear cell leukemia was increased in high dose male rats (10/50; 11/50; 17/50). Genetic Toxicity: Dimethyl methylphosphonate was not mutagenic when tested in the Salmonella typhimurium/microsome assay by the preincubational protocol with strains TA98, TA100, TA1535, or TA1537 with or without metabolic activation. The chemical did induce forward mutations in the mouse lymphoma L5178Y/TK± assay system in the absence of metabolic activation. Treatment of cultured Chinese hamster ovary cells with dimethyl methylphosphonate did not induce chromosomal aberrations; however, sister chromatid exchanges were induced after exposure to this chemical in both the presence and absence of metabolic activation. When fed to Drosophila, dimethyl methylphosphonate induced a significant increase in the frequency of sex-linked recessive lethal mutations but did not induce reciprocal translocations. Dimethyl methylphosphonate caused a dominant lethal effect in male rats and mice. Studies of Reproductive Effects: Dimethyl methylphosphonate caused a dose-related increase in the number of fetal resorptions in undosed female rats and mice mated with males that received the chemical by gavage in water 5 days per week for 13 weeks at doses of 0-2,000 mg/kg per day. After the 13-week dosing period, histopathologic changes were seen in the kidney and testis of male rats but not in male mice; dosed male rats sired fewer litters and fewer pups per litter. Dose-related decreases in sperm count and sperm motility occurred in male rats but not in male mice. Toxic effects to the reproductive system of male rats and mice were reversible after a 13-to 14-week recovery period. Data Audit: An audit of the experimental data was conducted for the 2-year studies on dimethyl methylphosphonate. No data discrepancies were found that influenced the final interpretations. Conclusions: Under the conditions of these 2-year gavage studies, there was some evidence of carcinogenic activity of dimethyl methylphosphonate for male F344/N rats as shown by increased incidences of tubular cell hyperplasia, tubular cell adenocarcinomas, hyperplasia of the transitional cell epithelium, and transitional cell papillomas of the kidney. There was an increased incidence of mononuclear cell leukemia in male rats at 1,000 mg/kg. Renal toxicity and decreased survival occurred in dosed male rats. There was no evidence of carcinogenic activity of dimethyl methylphosphonate for female F344/N rats given doses of 500 or 1,000 mg/kg. The study in male B6C3F1 mice was an inadequate study of carcinogenic activity because of decreased survival in both dosed groups. There was no evidence of carcinogenic activity for female B6C3F1 mice receiving dimethyl methylphosphonate at 1,000 mg/kg; decreased survival of female mice at 2,000 mg/kg made this group inadequate for determination of carcinogenic activity. Synonyms: fyrol DMMP; methyl phosphonic acid, dimethyl ester; DMMP; methanephosphonic acid dimethyl ester; dimethyl methanephosphonate

Journal Article↗

PubMed1987

NTP Toxicology and Carcinogenesis Studies of Phenylephrine Hydrochloride (CAS No. 61-76-7) in F344/N Rats and B6C3F1 Mice (Feed Studies).

Phenylephrine hydrochloride is a sympathomimetic amine recommended for use as a nasal decongestant and as a mydriatic in ophthalmic applications. In 1977, total U.S. human exposure was estimated at 1.9 x 107 g per year. Phenylephrine hydrochloride was nominated for toxicology and carcinogenesis studies because of a lack of previous long-term studies and because two other sympathomimetic agents (soterenol hydrochloride and mesuprine hydrochloride) produced mesovarial leiomyomas in Sprague-Dawley rats. Toxicology and carcinogenesis studies of USP-grade phenylephrine hydrochloride were conducted by administering diets containing the chemical (99% pure) to F344/N rats and B6C3F1 mice of each sex in studies of 14 days, 12 weeks, and 2 years. In the 14-day studies, no toxic effects were seen in rats or mice fed diets containing up to 2,000 ppm phenylephrine hydrochloride. Doses were increased in the 12-week studies, and deaths of male rats and male mice were observed in groups fed diets containing 10,000 or 20,000 ppm; 1/10 male rats in the 5,000-ppm group died. Other than inflammatory eye lesions (considered secondary to the pharmacologic drying action of the chemical), no specific organ toxicity was noted. Body weights decreased as concentrations of phenylephrine hydrochloride in the diet were increased, and feed consumption was lower in dosed rats. Doses of 0, 620, and 1,250 ppm for rats and 0, 1,250, and 2,500 ppm for mice were selected for the 2-year studies because of the decreased body weight gains in animals given higher doses in the 12-week studies. In the 2-year studies, the approximate amount of phenylephrine hydrochloride consumed per day was 24 mg/kg for low dose rats, 50 mg/kg for high dose rats, 133 mg/kg for low dose mice, and 270 mg/kg for high dose mice. Body weight differences in rats appeared to be dose related, and dosed animals were 3%-15% lighter than controls. Body weights of dosed mice averaged 3%-14% lower than those of controls throughout the 2-year studies. Survival of high dose male rats was greater than that of the controls (control, 30/50; low dose, 33/50; high dose, 42/50); differences in survival were not significant for female rats (42/50; 34/50; 36/50), male mice (35/50; 38/50; 43/50), or female mice (37/50; 34/50; 34/50). Few nonneoplastic lesions were related to phenylephrine hydrochloride dosing in rats or mice. Chronic focal inflammation of the liver was observed at increased incidences in dosed rats (male: 2/50; 13/50; 17/50; female:17/50; 28/50; 35/50). Inflammation of the prostate was seen more frequently in dosed than in control males (10/50; 24/50; 24/50). The incidence of focal cellular change in the liver was increased slightly in high dose male mice (0/50; 2/50; 7/50). In male rats, mononuclear cell leukemia (24/50; 9/50; 5/50) and pheochromocytomas of the adrenal gland (14/49; 11/50; 2/50) occurred with negative trends, and the incidences in the high dose group were lower than those in the controls. No increases in neoplasia were seen in dosed male or female rats or mice. Phenylephrine hydrochloride was not mutagenic in four strains of Salmonella typhimurium (TA100, TA1535, TA1537, and TA98) with or without Aroclor 1254-induced liver S9 from male Sprague-Dawley rats or male Syrian hamsters. The results of mutagenicity studies of phenylephrine hydrochloride were equivocal in the mouse lymphoma L5178Y/TK+/- assay in the absence of S9; it was not tested in the presence of S9. Phenylephrine hydrochloride induced sister-chromatid exchanges (SCEs) but not chromosomal aberrations in Chinese hamster ovary cells. The increase in SCEs was seen only in the absence of metabolic activation with S9. An audit of the experimental data was conducted for the 2-year studies of phenylephrine hydrochloride. No data discrepancies were found that influenced the final interpretations. Under the conditions of these 2-year studies, there was no evidence of carcinogenicity of phenylephrine hydrochloride for male B6C3F1 mice given 1,250 or 2,500 ppm in feed. Survival of high dose male rats was greater than of high dose male rats was greater than that of controls, and the incidences of mononuclear cell leukemia and pheochromocytomas were lower in dosed than in control male rats. Inflammation was observed more frequently in the liver and prostate gland of dosed male rats than in controls. Synonyms: benzene methanol,3-hydroxy-a[(methylamino)methyl]hydrochloride (R)-; (-)-meta-hydroxy-a-[(methylamino)methyl]benzyl alcohol hydrochloride; meta-Synephrine hydrochloride; Neo-synephrinereg.

Journal Article↗

PubMed1987

NTP Toxicology and Carcinogenesis Studies of Bromodichloromethane (CAS No. 75-27-4) in F344/N Rats and B6C3F1 Mice (Gavage Studies).

Bromodichloromethane (99% pure), one of several trihalomethanes commonly formed after chlorination of water, was selected for study because no carcinogenicity data were available for this compound and because chloroform, a related trihalomethane, had been found to cause tumors in rodents. The general population might be exposed to bromodichloromethane in drinking water supplies, in swimming pools, and in a variety of food substances. Single-administration, 14-day, 13-week, and 2-year studies were conducted in F344/N rats and B6C3F1 mice. The chemical was administered by gavage in corn oil because human exposure is primarily oral. Additional studies were performed to evaluate the potential for genetic damage in bacteria and mammalian cells. Results of the Short-Term Studies: In the single-administration studies, the chemical was administered at doses of 150-2,500 mg/kg per day. All rats and female mice at 1,250 and 2,500 mg/kg and all male mice at 600, 1,250, and 2,500 mg/kg died; 2/5 male rats, 1/5 female rats, and 2/5 female mice at 600 mg/kg died; all animals at lower dose levels survived. In the 14-day studies, rats received doses of 38-600 mg/kg, and mice received doses of 19-300 mg/kg per day. One female rat at 38 mg/kg and one female rat at 600 mg/kg died. Weight loss or decreased weight gain was seen at 300 and 600 mg/kg in male and female rats. All male mice at 150 and 300 mg/kg died, and one female mouse at 300 mg/kg died; no weight effects were observed in surviving mice. Dose-related necropsy findings included reddened renal medullae in male rats at 600 mg/kg and in male mice at 150 and 300 mg/kg. Clinical signs seen in high dose groups after dosing were hyperactivity in rats and lethargy in mice. In the 13-week studies, male and female rats received doses of 19-300 mg/kg per day, male mice received doses of 6.25-100 mg/kg per day, and female mice received doses of 25-400 mg/kg per day. Five of 10 male rats and 2/10 female rats at 300 mg/kg died. None of the mice died. Final body weights of male and female rats at 150 and 300 mg/kg were lower than those of vehicle controls (45%-88% of vehicle control weights); final body weights of male mice at 100 mg/kg and female mice at 400 mg/kg were 92% and 94% of those of the vehicle controls. Centrilobular degeneration in the liver and degeneration and necrosis of the kidney were seen in male rats at 300 mg/kg; centrilobular degeneration was seen in female rats at 300 mg/kg; degeneration andnecrosis of the kidney were seen in male mice at 100 mg/kg, and centrilobular degeneration of the liver was seen in female mice at 200 and 400 mg/kg. Experimental Design of the Two-Year Studies: The 2-year toxicology and carcinogenesis studies of bromodichloromethane were conducted by administering the chemical in corn oil by gavage, 5 days per week for 102 weeks, to groups of 50 male and female rats at doses of 0, 50, or 100 mg/kg per day; to groups of 50 male mice at doses of 0, 25, or 50 mg/kg per day; and to groups of 50 female mice at doses of 0, 75, or 150 mg/kg per day. The study in male rats was restarted because at 10.5 months into the original study, a temperature elevation killed 45/50 vehicle control male rats. Survival and Body Weight in the Two-Year Studies: Final survival of dosed rats was comparable to that of vehicle controls (male: vehicle control, 28/50; low dose, 36/50; high dose, 28/50; female: 34/50; 27/50; 41/50). Mean body weights of high dose male and female rats were decreased during the last 1.5 years of the study; final mean body weights of high dose male and female rats were 88% and 79% of the vehicle control mean weights. Final mean body weights of low dose male and female rats were comparable to those of the vehicle controls. Final survival of dosed male mice was comparable to that of the vehicle controls (34/50; 32/50; 42/50). At week 84, survival of female mice was greater than 50% in all dose groups. After week 84, survival of dosed and vehicle control female mice was reduced (final survival: 26/50; 13/50; 15/50), and this decreased survival was ass6/50; 13/50; 15/50), and this decreased survival was associated with ovarian abscesses (8/50; 19/47; 18/49). The final mean body weight of high dose male mice was 95&percnt; that of the vehicle controls; the final mean body weight of low dose male mice was comparable to that of the vehicle controls. Mean body weights of the high dose female mice were decreased during the last 1.5 years of the study; the final mean body weight was 75&percnt; that of the vehicle controls. The final mean body weight of the low dose female mice was 91&percnt; that of the vehicle controls. Nonneoplastic Effects in the Two-Year Studies: Compound-related nonneoplastic lesions included cytomegaly and tubular cell hyperplasia of the kidney and necrosis and fatty metamorphosis of the liver in male rats; eosinophilic cytoplasmic change, clear cell change, focal cellular change, and fatty metamorphosis of the liver and tubular cell hyperplasia of the kidney in female rats; fatty metamorphosisof the liver, renal cytomegaly, and follicular cell hyperplasia of the thyroid gland in male mice; and follicular cell hyperplasia of the thyroid gland in female mice. Neoplastic Effects in the Two-Year Studies: Bromodichloromethane caused compound-related increases in the incidences of neoplasms of the large intestine and kidney in male and female rats, the kidney in male mice, and the liver in female mice, as shown in the table (see page 5 of the Technical Report). The neoplasms of the large intestine and kidney are uncommon tumors in F344/N rats and B6C3F1 mice. Administration of bromodichloromethane was also associated with a decrease in the tumors of the adrenal glands in male rats, the pituitary and mammary glands in female rats, and the pituitary gland in female mice. Genetic Toxicology: Bromodichloromethane was not mutagenic in Salmonella typhimurium strains TA98, TA100, TA1535, or TA1537 when tested by the preincubational protocol at concentrations up to 1,000 ug/plate with or without metabolic activation. The compound was not mutagenic in the mouse lymphoma L5178Y/TK± assay in the presence of S9 but did induce forward mutations in the system in the presence of metabolic activation from rat liver S9. Cytogenetic tests with Chinese hamster ovary cells demonstrated no induction of chromosomal aberrations orsister chromatid exchanges following treatment with bromodichloromethane in either the presence or absence of metabolic activation. Data Audit: An audit of the experimental data was conducted for the 2-year toxicology and carcinogenesis studies of bromodichloromethane. No discrepancies were found that influenced the final interpretations of the results of these studies. Conclusions: Under the conditions of these 2-year gavage studies, there was clear evidence of carcinogenic activity for male and female F344/N rats and B6C3F1 mice as shown by increased incidences of tubular cell adenomas and adenocarcinomas in the kidney and adenocarcinomas and adenomatous polyps in the large intestine in male and female rats, increased incidences of tubular cell adenomas and adenocarcinomas in the kidney of male mice, and increased incidences of hepatocellular adenomas and carcinomas in female mice. Synonym: dichlorobromoethane

Journal Article↗

PubMed1987

NTP Toxicology and Carcinogenesis Studies of 1,4-Dichlorobenzene (CAS No. 106-46-7) in F344/N Rats and B6C3F1 Mice (Gavage Studies).

1,4-Dichlorobenzene is commonly used as a space deodorant in toilets and for moth control. Because of its extensive production and use and the absence of carcinogenicity data, carcinogenesis studies were conducted by administering 1,4-dichlorobenzene (greater than 99% pure) in corn oil by gavage (5 days per week) to male F344/N rats at doses of 0, 150, or 300 mg/kg and to female F344/N rats and male and female B6C3F1 mice at doses of 0, 300, or 600 mg/kg per day for 2 years (50 animals per group). Fourteen-day and 13-week studies were performed to characterize the toxicity, identify affected sites, and set doses for the 2-year studies. Clinical chemistry and hematologic studies were performed during the 13-week studies to assess the effects of 1,4-dichlorobenzene on the liver, kidney, and hematopoietic system and to assess whether the compound produced hepatic porphyria. Two 13-week studies were performed in rats. In the first study, rats were dosed with 300-1,500 mg/kg 1,4-dichlorobenzene. Because histologic changes were observed in the kidney of male rats at all doses, a second 13-week study was performed at doses of 38-600 mg/kg. In the 13-week studies, survival was decreased in groups of male rats given 1,200 or 1,500 mg/kg and in female rats given 1,500 mg/kg. Weight gain was decreased in male rats receiving doses of 300 mg/kg or more and in female rats given doses of 1,200 or 1,500 mg/kg. Doses of 1,200 or 1,500 mg/kg produced degeneration and necrosis of hepatocytes, hypoplasia of the bone marrow, lymphoid depletion of the spleen and thymus, and epithelial necrosis of the nasal turbinates in male and female rats. Renal tubular cell degeneration was observed in male rats receiving 300 mg/kg or more in the first study, but only slight changes were seen at 300 mg/kg in the second study. Liver weight to brain weight ratios were increased at 900 mg/kg or more for both male and female rats. The kidney weight to brain weight ratio was increased in male rats receiving doses of 600 mg/kg or more. Administration of 1,4-dichlorobenzene to rats for 13 weeks produced slight but statistically significant decreases in the hematocrit, red blood cell count, and hemoglobin level in all males receiving doses of 300-1,200 mg/kg. No clear hematologic changes were observed in female rats. 1,4-Dichlorobenzene produced minimal changes in clinical chemistry parameters in the 13-week studies. Serum cholesterol levels were increased by doses of 600 mg/kg or more in male rats and 900 mg/kg or more in female rats. Serum triglycerides were reduced by doses of 300 mg/kg or more in male rats. The blood urea nitrogen level was increased slightly in male rats dosed with 900 mg/kg or more. Urinary porphyrins were increased slightly in male rats administered 1,200 or 1,500 mg/kg and female rats receiving 1,200 mg/kg. However, these increases were modest and indicative of a mild porphyrinuria rather than hepatic porphyria. Liver porphyrins were not increased at any dose. Two 13-week studies were performed in mice. The doses selected for the first study were 600-1,800 mg/kg. Survival was decreased in male and female mice receiving doses of 1,500 mg/kg or more, and body weight gain was decreased at all doses. Hepatocellular degeneration was observed in both sexes at all doses, and the liver weight to brain weight ratio was increased at doses of 900 mg/kg or more. Serum cholesterol levels were increased in male mice at doses of 900 mg/kg or more, whereas serum protein and triglycerides were increased at doses of 1,500 mg/kg or more. These relatively modest clinical chemistry changes probably reflect the hepatic effects of this compound. The white blood cell count was reduced significantly in male mice receiving doses of 600 mg/kg or more and female mice receiving 1,000 mg/kg or more, but this effect was not dramatic. Hepatic porphyria was not found in mice at any dose in the 13-week study. Because hepatic effects were seen in all dose groups in the first study, a second 13-week study was performed at doses of 85-900 mg/kg. In this study, hepatocellularellular cytomegaly was observed im male and female mice at doses of 675 mg/kg or more but not at 338 mg/kg. Renal damage was not observed in mice in either 13-week study. Based on the histopathologic findings in the kidney of male rats and in the liver of both sexes of rats and mice in the 13-week studies, the doses selected for the 2-year studies were 150 and 300 mg/kg for male rats and 300 and 600 mg/kg for female rats and male and female mice. In the 2-year studies, survival of female rats and of both sexes of mice was comparable to that of the vehicle controls; survival of high dose male rats was significantly lower than that of the vehicle controls (vehicle control, 32/50; low dose, 31/50; high dose, 20/50). Mean body weights of high dose male rats were 5&percnt;-8&percnt; lower than those of vehicle controls after week 38, and those of high dose female rats were 5&percnt;-7&percnt; lower than those of vehicle controls after week 55. Mean body weights of mice dosed with 1,4-dichlorobenzene were comparable to those of vehicle controls throughout the studies. Administration of 1,4-dichlorobenzene to male rats increased the average seveity of nephropathy and caused epithelial hyperplasia of the renal pelvis (1/50; 30/50; 31/50), mineralization of the collecting tubules in the renal medulla (4/50; 46/50; 47/50), and focal hyperplasia of renal tubular epithelium (0/50; 1/50; 9/50). There were increased incidences of nephropathy in both low and high dose female rats compared with vehicle controls (21/49; 32/50; 41/49). 1,4-Dichlorobenzene produced a dose-related increase in the incidence of tubular cell adenocarcinomas of the kidney in male rats (1/50; 3/50; 7/50); one tubular cell adenoma was observed in a high dose male rat. These malignant tumors are uncommon in male F344/N rats. They have been diagnosed in only 4/1,098 (0.4&percnt;) corn oil gavage controls in previous NTP studies. There were no tubular cell tumors in dosed or vehicle control female rats. There was a marginal increase in the incidence of mononuclear cell leukemia in dosed male rats compared with that in vehicle controls (5/50; 7/50; 11/50). 1,4-Dichlorobenzene increased the incidences of nonneoplastic liver lesions in male and female mice, including alteration in cell size (cytomegaly and karyomegaly), hepatocellular degeneration, and individual cell necrosis. 1,4-Dichlorobenzene also increased the incidences of nephropathy in male mice and renal tubular regeneration in female mice. 1,4-Dichlorobenzene increased the incidences of hepatocellular carcinomas in high dose male (14/50; 11/49; 32/50) and female (5/50; 5/48; 19/50) mice and hepatocellular adenomas in dosed male (5/50; 13/49; 16/50) and high dose female (10/50; 6/48; 21/50) mice. Hepatoblastomas were observed in four high dose male mice but not in vehicle controls. This rare tumor has not occurred in 1,091 male vehicle control mice in NTP studies. An increase in thyroid gland follicular cell hyperplasia was observed in dosed male mice (1/47; 4/48; 10/47), and there was a marginal positive trend in the incidence of follicular cell adenomas of the thyroid gland in female mice (0/48; 0/45; 3/46). Pheochromocytomas (benign or malignant, combined) of the adrenal gland occurred with a positive trend in dosed male mice, and the incidence in the high dose group was significantly greater than in vehicle controls (0/47; 2/48; 4/49). The incidence of adrenal gland medullary hyperplasia in male mice was 2/47; 4/48; and 4/49. Focal hyperplasia of the adrenal gland capsule was also observed in dosed male mice (11/47;21/48; 28/49). 1,4-Dichlorobenzene was not mutagenic in Salmonella typhimurium strains TA98, TA100, TA1535, or TA1537 with or without activation by Aroclor 1254-induced male Sprague-Dawley rat or male Syrian hamster liver S9 when tested according to a preincubational protocol at concentrations up to 100 ug/plate. 1,4-Dichlorobenzene did not induce forward mutations in the mouse lymphoma L5178Y/TK± assay in the absence of exogenous metabolic activation; however, the results were equivocal in this system in the presence of metabolic activation. 1,4-Dichlorobenzene did not produce an increase in sister-chromatid exchanges or chromosomal aberrations in Chinese hamster ovary cells in culture with or without exogenous metabolic activation. No increase in micronucleated cells was seen in erythrocytes of mice from the first 13-week studies. An audit of the experimental data was conducted for the 2-year studies of 1,4-dichlorobenzene. No data discrepancies were found that influenced the final interpretations. Under the conditions of these 2-year gavage studies, 1,4-dichlorobenzene produced clear evidence of carcinogenicity for male F344/N rats, as shown by an increased incidence of renal tubular cell adenocarcinomas. There was no evidence of carcinogenicity for female F344/N rats receiving doses of 300 or 600 mg/kg. There was clear evidence of carcinogenicity for both male and female B6C3F1 mice, as shown by increased incidences of hepatocellular carcinomas and hepatocellular adenomas. Marginal increases were observed in the incidences of pheochromocytomas of the adrenal gland in male mice. Nonneoplastic effects in the kidney of male and female rats, in the liver of male and female mice, and in the thyroid gland and adrenal gland of male mice were also associated with the administration of 1,4-dichlorobenzene. Synonyms: p-dichlorobenzene; para-dichlorobenzene; para-chlorophenyl chloride

Journal Article↗

PubMed1987

NTP Toxicology and Carcinogenesis Studies of Ampicillin Trihydrate (CAS No. 7177-48-2) in F344/N Rats and B6C3F1 Mice (Gavage Studies).

Ampicillin trihydrate is a broad-spectrum semi-synthetic penicillin that is effective in the treatment of gram-positive and gram-negative bacterial infections produced by Streptococcus, Bacillus anthracis, Haemophilus influenzae, Neisseria gonorrhoeae, and Escherichia coli. This antibiotic is used in the treatment of upper respiratory tract infections, genital and urinary tract infections, and otitis media in children. Toxicology and carcinogenesis studies of ampicillin trihydrate (97%-99% pure) were conducted by administering the chemical in corn oil by gavage to groups of 50 F344/N rats and 50 B6C3F1 mice of each sex, 5 days per week for 103 weeks. Male and female rats received doses of 0, 750, or 1,500 mg/kg, and male and female mice received doses of 0, 1,500, or 3,000 mg/kg. Doses selected for the 2-year studies were based on the lack of body weight effects and histopathologic effects at 2,400 mg/kg in the 14-day studies and 3,000 mg/kg in the 13-week studies. Clinical signs in the 13-week studies included diarrhea at 3,000 mg/kg in male and female rats and male mice. Corn oil suspensions containing more than 300 mg ampicillin trihydrate/ml were too viscous to be administered by gavage; therefore, a high dose of 1,500 mg/kg was selected for rats and a high dose of 3,000 mg/kg was selected for mice. During the 2-year studies, mean body weights of male and female rats were similar to or slightly increased over those of the corresponding vehicle control groups. Mean body weights of low dose and high dose male mice were similar to those of the corresponding vehicle group during year 1 of the study but were slightly below those of the vehicle control group during the last half of the study. Mean body weights of low dose and high dose female mice were greater than those of the vehicle controls throughout most of the study. No significant differences in survival were observed in groups of rats or mice of either sex. Clinical signs observed in dosed rats included diarrhea, excessive urination, and chromodacryorrhea and in dosed mice included increased salivation and decreased activity. In male rats, administration of ampicillin trihydrate was associated with an increased incidence of mononuclear cell leukemia (vehicle control, 5/50; low dose, 14/50; high dose, 13/50). Malignant lymphomas were observed in one additional vehicle control male rat and two low dose male rats. Lymphocytic leukemia was seen in one high dose rat. High dose male rats showed increased incidences of pheochromocytomas of the adrenal gland medulla (13/50; 12/50; 23/49). Malignant pheochromocytomas were observed in 1/50 vehicle control, 5/50 low dose, and 1/49 high dose male rats. The incidence of adrenal gland medullary hyperplasia was not increased in male rats (14/50; 10/50; 8/49). There were increased incidences of C-cellhyperplasia of the thyroid gland in low dose male and high dose female rats. High dose male rats showed increased incidences of hyperkeratosis and acanthosis of the forestomach. In male and female mice, ampicillin trihydrate administration was associated with increased incidences of forestomach lesions, including ulcers, inflammation, hyperkeratosis, acanthosis, and evidence of fungal infection. Ampicillin trihydrate was not mutagenic in Salmonella typhimurium strains TA98, TA100, TA1535, or TA1537 in the presence or absence of Aroclor 1254-induced male Syrian hamster or male Sprague-Dawley rat liver S9 when tested according to preincubation protocol. Ampicillin trihydrate was not mutagenic in L5178Y mouse lymphoma cells with or without metabolic activation. Ampicillin trihydrate did not cause chromosomal aberrations or sister-chromatid exchanges in Chinese hamster ovary cells with or without metabolic activation. An audit was conducted for these 2-year studies. Animal/carcass identification discrepancies were observed in rats and mice. The most common findings were the failure to clip some toes in rats and opened ear holes in mice. A review of the inlife data (including body weights, clinical observations, and dosing records) indicrecords) indicated that animals had not been interchanged among groups. The data are considered adequate to support the conclusions. Under the conditions of these 2-year gavage studies, there was equivocal evidence of carcinogenicity of ampicillin trihydrate for male F344/N rats as shown by increased incidences of pheochromocytomas of the adrenal medulla and by marginally increased incidences of mononuclear cell leukemia. There was no evidence of carcinogenicity for female F344/N rats receiving 750 or 1,500 mg/kg or for male and female B6C3F1 mice receiving 1,500 or 3,000 mg/kg per day. Nonneoplastic lesions of the forestomach were seen in male rats and male and female mice. Synonyms and trade names: Acillin; Amcap; Amcill; Aminobenzylpencillin trihydrate; a-Aminobenzylpencillin trihydrate; Amperil; Ampichel; Ampikel; Ampinova; Amplin; Cymbi; Divercillin; Liffampil; Morepen; Pen A; Pensyn; Polycillin; Princillin; Principen; Ro-ampen; Trafarbiot

Journal Article↗

PubMed1987

NTP Toxicology and Carcinogenesis Studies of Oxytetracycline Hydrochloride (CAS No. 2058-46-0) in F344/N Rats and B6C3F1 Mice (Feed Studies).

Toxicology and carcinogenesis studies were conducted on oxytetracycline hydrochloride (greater than 98.8% pure), a broad-spectrum antibiotic. Groups of F344/N rats and B6C3F1 mice were fed diets containing oxytetracycline hydrochloride for a series of 14-day, 13-week, and 2-year studies. In the 14-day studies, no compound-related gross pathologic effects were seen in rats or mice (groups of five animals per sex per species) given up to 100,000 ppm in their feed. The final mean body weight of male rats receiving in feed was 27% lower than that of the controls. Final mean body weights of mice that received 25,000, 50,000, or 100,000 ppm were lower (male: 11%; 16%; 17%; female: 6%; 5%; 17%) than those of the controls. In the 13-week studies, groups of 10 male and 10 female rats and mice were fed diets containing up to 50,000 ppm in feed, and no chemically related gross or histopathologic effects were observed in mice of either sex or in female rats. In male rats, fatty metamorphosis of minimal severity was diagnosed in the liver of 5/10 animals at 6,300, 12,500, and 50,000 ppm and in 2/10 animals at 3,100 and 25,000 ppm. None was seen in the controls. Oxytetracycline levels in bones of rats and mice (as determined fluorometrically) at the end of the 13-week studies increased with dose, the highest levels (3-10 times background levels) being observed at 50,000 ppm. The 2-year toxicology and carcinogenesis studies were conducted by administering diets containing 0, 25,000, or 50,000 ppm oxytetracycline hydrochloride to groups of 50 male and 50 female rats and diets containing 0, 6,300, or 12,500 ppm oxytetracycline hydrochloride to groups of 50 male and 50 female mice for 103 weeks. The highest dose selected for rats was considered to be the maximum level that would not affect the nutritional value of dosed feed. The dietary concentrations correspond to the following approximate doses: rats-- 0, 1,000, or 2,000 mg/kg body weight per day; mice-- 0, 650, or 1,400 mg/kg per day. Mean body weights were approximately 5%-8% lower than those of controls in high dose male rats during weeks 4-47, in high dose male mice after week 31, and in high dose female mice after week 26. The mean body weights of dosed female rats and low dose male and female mice were comparable to those of controls. The survival of control male rats was lower than that of the high dose group (22/50 vs 38/50). No significant differences in survival were observed between the remaining groups of rats or between any groups of mice. Pheochromocytomas of the adrenal gland occurred with positive trends in male rats (control, 10/50; low dose, 18/50; high dose, 24/50), and the incidence in the high dose group was greater than that in the controls. Two additional control males and one additional low dose male had malignant pheochromocytomas. The incidence of adrenalgland medullary hyperplasia was elevated slightly but not significantly in dosed male rats (7/50; 14/50; 9/50). Adenomas and adenomas and adenocarcinomas (combined) of the pituitary gland in female rats occurred with positive trends, and the incidences in the high dose group were greater than that in the controls (adenomas: 19/50; 17/50; 30/50; adenomas or adenocarcinomas [combined]: 20/50; 24/50; 32/50). The incidence of pituitary gland hyperplasia was slightly decreased in dosed female rats (16/50; 10/50; 11/50). No compound-related increases in nonneoplastic or neoplastic lesions were observed in male or female mice. Oxytetracycline hydrochloride was not mutagenic in Salmonella typhimurium strains TA100, TA1535, TA1537, or TA98 in the presence or absence of Aroclor 1254-induced male Sprague-Dawley rat or male Syrian hamster liver S9 when assayed according to the preincubational protocol. Oxytetracycline hydrochloride was mutagenic in L5178Y/TK+/- mouse lymphoma cells in the presence but not in the absence of Aroclor 1254-induced male rat liver S9. In cultured Chinese hamster ovary cells, oxytetracycline was weakly positive in inducing sister-chromatid exchanges both with and without Aroclor 1254-induced mang sister-chromatid exchanges both with and without Aroclor 1254-induced male Sprague-Dawley rat liver S9 but did not induce chromosomal aberrations. An audit of the experimental data was conducted for these 2-year carcinogenesis studies of oxytetracycline hydrochloride. No data discrepancies were found that influenced the final interpretations. Under the conditions of these 2-year feed studies of oxytetracycline hydrochloride, there was equivocal evidence of carcinogenicity for male F344/N rats, as indicated by increased incidences of pheochromocytomas of the adrenal gland. There was equivocal evidence of carcinogenicity for female F344/N rats fed diets containing oxytetracycline hydrochloride, as indicated by increased incidences of adenomas of the pituitary gland. There was no evidence of carcinogenicity for male or female B6C3F1 mice fed diets containing 6,300 or 12,500 ppm oxytetracycline hydrochloride for 2 years. Synonyms: 2-naphthacenecarboxamide,4(dimethylamino)-1,4,4a,5,5a,6,11,12a-octahydro-3,6-10,2,12a-pentahydroxy-6-methyl-1,11-dioxo-monohydrochloride; Biosolvmycin; Hydrocyclin; Liquamycin; Otetryn; Oxlopar; 5-hydroxytetracycline hydrochloride; Terramycin Hydrochloride; Tetramine; Tetran Hydrochloride

Journal Article↗

PubMed1987

Carcinogenesis Studies of C.I. Acid Orange 10 (CAS No. 1936-15-8) in F344 Rats and B6C3F1 Mice (Feed Studies).

Carcinogenesis studies of 80% pure C.I. Acid Orange 10 (a monoazo textile dye) were conducted by feeding to groups of 50 male and 50 female F344/N rats diets containing 1,000 or 3,000 ppm C.I. Acid Orange 10 for 103 weeks. Groups of 50 male and 50 female B6C3F1 mice were fed diets containing 3,000 or 6,000 ppm for 103 weeks. Groups of 90 male and 90 female untreated rats and 50 male and 50 female untreated mice served as controls. Mean body weights and clinical signs of control and dosed rats and mice were comparable. Because no toxic effects or consistent weight differences were observed, the rats and mice may have been able to tolerate higher doses. In male rats with neoplastic nodules of the liver, the dose response trend was positive (P<0.05) and the incidence in the 3,000 ppm group was increased (P<0.05) compared to controls (control, 5/90, 6%; low dose, 3/50, 6%; high dose, 8/50, 16%). One male rat in the high dose group had both a neoplastic nodule and a carcinoma of the liver. This marginal increase in liver cell neoplasms may have been associated with the dietary administration of C.I. Acid Orange 10. For both dose groups of male and female rats, leukemia was significantly (P<0.05) decreased in a dose related (P<0.005) trend (male: 22/90, 24%; 4/50, 8%; 3/50, 6%; female: 16/88, 18%; 2/50, 4%; 0/50). No compound-related nonneoplastic or neoplastic lesions were observed in the female rats or in mice of either sex. For 103 weeks C.I. Acid Orange 10 was given in the diets of male and female F344/N rats (0, 0.1, or 0.3%) and of male and female B6C3F1 mice (0, 0.3%, or 0.6%). Under these conditions, there was no evidence of carcinogenicity for male and female F344/N rats or for male and female B6C3F1 mice. Levels of Evidence of Carcinogenicity: Male Rats: Negative Female Rats: Negative Male Mice: Negative Female Mice: Negative Synonym: 7-hydroxy-8-(phenylazo)-1,3-naphthalenedisulfonic acid, disodium salt

Journal Article↗

PubMed1986

NTP Toxicology and Carcinogenesis Studies of Xylenes (Mixed) (60% m-Xylene, 14% p-Xylene, 9% o-Xylene, and 17% Ethylbenzene) (CAS No. 1330-20-7) in F344/N Rats and B6C3F1 Mice (Gavage Studies).

The technical grade of xylenes (mixed) (hereafter termed xylenes) contains the three isomeric forms and ethylbenzene (percentage composition shown above). The annual production for 1985 was approximately 7.4 x 108 gallons. Xylenes is used as a solvent and a cleaning agent and as a degreaser and is a constituent of aviation and automobile fuels. Xylenes is also used in the production of benzoic acid, phthalate anhydride, and isophthalic and terephthalic acids as well as their dimethyl esters. Toxicology and carcinogenesis studies of xylenes were conducted in laboratory animals because a large number of workers are exposed and because the long- term effects of exposure to xylenes were not known. Exposure for the present studies was by gavage in corn oil. In single-administration studies, groups of five F344/N rats and B6C3F1 mice of each sex received 500, 1,000, 2,000, 4,000, or 6,000 mg/kg. Administration of xylenes caused deaths at 6,000 mg/kg in rats and mice of each sex and at 4,000 mg/kg in male rats. In rats, clinical signs observed within 24 hours of dosing at 4,000 mg/kg included prostration, muscular incoordination, and loss of hind limb movement; these effects continued through the second week of observation. Tremors, prone position, and slowed breathing were recorded for mice on day 3, but all mice appeared normal by the end of the 2- week observation period. In 14- day studies, groups of five rats of each sex were administered 0, 125, 250, 500, 1,000, or 2,000 mg/kg, and groups of five mice of each sex received 0, 250, 500, 1,000, 2,000, or 4,000 mg/kg. Chemical- related mortality occurred only at 2,000 mg/kg in rats and at 4,000 mg/kg in mice. Rats and mice exhibited shallow breathing and prostration within 48 hours following dosing at 2,000 mg/kg. These signs persisted until day 12 for rats, but no clinical signs were noted during the second week for mice. In 13- week studies, groups of 10 rats of each sex received 0, 62.5, 125, 250, 500, or 1,000 mg/kg, and groups of 10 mice of each sex received 0, 125, 250, 500, 1,000, or 2,000 mg/kg. No deaths or clinical signs of toxicity were recorded in rats. However, high dose male rats gained 15% less weight and females 8% less weight than did the vehicle controls. Two female mice died at the 2,000 mg/kg dose. Lethargy, short and shallow breathing, unsteadiness, tremors, and paresis were observed for both sexes in the 2,000 mg/kg group within 5- 10 minutes after dosing and lasted for 15- 60 minutes. Two- year toxicology and carcinogenesis studies were conducted by administering 0, 250, or 500 mg/kg xylenes in corn oil by gavage to groups of 50 F344/N rats of each sex, 5 days per week for 103 weeks. Groups of 50 B6C3F1 mice of each sex were administered 0, 500, or 1,000 mg/kg xylenes on the same schedule. Although the mortality was dose related in male rats (final survival: vehicle control, 36/50; low dose, 26/50; high dose, 20/50), many of the early deaths in the dosed males were gavage related. Body weights of the high dose male rats were 5%- 8% lower than those of the vehicle controls after week 59. The mean body weights of low dose and vehicle control male rats and those of dosed and vehicle control female rats were comparable. Survival rates of female rats and both sexes of dosed mice were not significantly different from those of the vehicle controls. The mean weights of dosed male and female mice were comparable to those of the vehicle controls. Hyperactivity lasting 5- 30 minutes was observed in high dose mice after dosing, beginning after week 4 and continuing through week 103. At no site was the incidence of nonneoplastic or neoplastic lesions in dosed rats or mice of either sex considered to be related to the administration of xylenes. Neither xylenes nor any of its components (o- xylene, m-xylene, p- xylene, or ethylbenzene) were mutagenic when tested with or without metabolic activation in Salmonella typhimurium strains TA100, TA1535, TA97, or TA98 with the preincubation protocol. In addition, ethylbenzene was tested in cytogenetic assays using cultured Cetic assays using cultured Chinese hamster ovary cells both with and without metabolic activation; neither sister- chromatid exchanges nor chromosomal aberrations were induced by ethylbenzene. An audit of the experimental data was conducted for the 2-year studies of xylenes. No data discrepancies were found that influenced the final interpretations. Under the conditions of these 2-year gavage studies, there was no evidence of carcinogenicity of xylenes (mixed) for male or female F344/N rats given 250 or 500 mg/kg or for male or female B6C3F1 mice given 500 or 1,000 mg/kg.

Journal Article↗

PubMed1986

NTP Toxicology and Carcinogenesis Studies of Benzyl Acetate (CAS No. 140-11-4) in F344/N Rats and B6C3F1 Mice (Gavage Studies).

Benzyl acetate, a water-white liquid with a pear-like odor, is a natural constituent of several essential oils and flower absolutes extracted from jasmine, hyacinth, gardenia, tuberose, ylang-ylang, cananga, and neroli. Commercial benzyl acetate, a liquid prepared synthetically from benzyl chloride, acetic acid, and triethylamine is used primarily as a component of perfumes for soaps and as a flavoring ingredient. This compound is practically insoluble in water but is miscible in alcohol and ether and soluble in benzene and chloroform. Toxicology and carcinogenesis studies of benzyl acetate (>99% pure) were conducted by administering benzyl acetate in corn oil gavage to groups of 50 male and 50 female F344/N rats at doses of 0, 250, or 500 mg/kg body weight and to groups of 50 male and 50 female B6C3F1 mice at doses of 0, 500, or 1,000 mg/kg once daily five days per week for 103 weeks. Dose selection for the 2-year study was based on mean body weight gain depression and decreased survival observed at higher doses in 13 week studies. The absence of any observable adverse effect of benzyl acetate on the survival or mean body weight gains of the rats or mice in the 2-year studies suggests that both the rats and the mice of each sex could have tolerated higher doses. An infection in the genital tract was probably responsible for the deaths of 26/35 control, 14/32 low-dose, and 8/20 high-dose female mice before the end of the study. Acinar-cell adenomas in the pancreas of male rats occurred with a positive trend (P<0.01), and the incidence in the high-dose group (37/49, 76%) was significantly (P<0.01) higher than in the vehicle controls (22/50, 40%). The incidence of these tumors in the low-dose group (27/50, 54%) was comparable to that in the gavage controls. Acinar-cell hyperplasia of the pancreas was observed in 37/50 control, 34/50 low-dose, and 36/49 high-dose male rats. No acinar-cell hyperplasia or adenoma of the pancreas was observed in female rats. The incidence of retinopathy and cataracts in the high-dose male rats was increased compared with the controls (retinopathy: 1/50; 0/50; 20/50; cataracts: 0/50; 0/50; 13/50). Low-dose female rats had an increased incidence of retinopathy (18/50). Retinopathy and cataracts in rats have been associated with proximity to fluorescent light in this and previous studies. Preputial gland neoplasms occurred with a positive trend (P<0.05) in male rats (cystadenocarcinoma: 0/50; 0/50; 3/50; all adenocarcinoma: 0/50; 1/50; 4/50; adenocarcinoma or carcinoma combined: 1/50; 1/50; 6/50). However, the incidence of all preputial gland tumors was not significantly elevated (2/50; 1/50; 6/50). For female rats the incidence of clitoral gland neoplasms was marginally increased (2/50; 0/50; 5/50). Hepatocellular adenomas occurred in mice of each sex with statistically positive trends (males: 0/50; 5/49; 13/50; females: 0/50; 0/50; 6/50), and the incidences in the high-dose groups were greater than those in the controls (males: P<0.001; females: P<0.05). Hepatocellular carcinomas were marginally elevated in dosed male and high-dose female mice (males: 10/50; 14/49; 12/50; females: 1/50; 0/50; 4/50). Squamous cell papillomas or carcinomas of the forestomach (uncommon neoplasms) occurred with a positive trend (P<0.05) in male mice (4/49; 4/48; 11/49). The incidence of these tumors was also marginally (P=0.054) increased in the high-dose female mice (0/50; 0/50; 4/48). The incidences of these tumors in both the high-dose male and the high-dose female mice were considerably higher than the historical corn oil gavage control rates at this laboratory (males, 2/296, 0.7%; females, 2/297, 0.7%) and throughout the program (males, 14/1,070, 1.3%; females, 3/1,073, 0.3%). Forestomach hyperplasia occurred at increased incidences in dosed mice of either sex (males: 1/49, 7/48, 22/49; females: 1/50, 6/50, 17/48). The neoplasms and hyperplasia of the forestomach were probably related to administration of benzyl acetate. In a separate metabolism study, benzyl acetate was absorbed from the gastrointestinal traolism study, benzyl acetate was absorbed from the gastrointestinal tract of rats and mice, with approximately 90&percnt; of the administered dose recovered as various metabolites in the urine within 24 hr. The primary metabolite was hippuric acid, with minor amounts of a mercapturic acid, and one or more unidentified metabolites. This capacity for absorption, metabolism, and disposition was unaffected by the amount or number of doses administered. Benzyl acetate was not mutagenic in strains TA100, TA98, TA135, or TA137 of Salmonella typhimurium in the presence or absence of Aroclor 1254-induced Sprague-Dawley rat or Syrian hamster S9 when tested according to the preincubation protocol. Benzyl acetate did not induce sister-chromatid exchanges or chromosomal aberrations in Chinese hamster ovary cells in the presence or absence of Aroclor 1254-induced Sprague-Dawley rat liver S9. Benzyl acetate was mutagenic in the mouse lymphoma L5178Y/TK± assay in the presence, but not in the absence, of Aroclor 1254-induced Fisher 344 rat liver S9. An audit was conducted on the experimental data and the draft technical report for these 2-year studies on benzyl acetate. Based on the results of this audit additional pathology examinations were conducted on all target organs in male rats and male and female mice. The Technical Report reflects these final pathology evaluations. The overall conclusions regarding the toxicology and carcinogenicity of benzyl acetate did not change as a result of this evaluation. Under the conditions of these gavage studies, benzyl acetate increased the incidence of acinar-cell adenomas of the exocrine pancreas in male F344/N rats; the gavage vehicle may have been a contributing factor. There was no evidence of carcinogenicity for female F344/N rats. For male and female B6C3F1 mice there was some evidence of carcinogenicity in that benzyl acetate caused increased incidences of hepatocellular adenomas and squamous cell neoplasms of the forestomach. Synonyms: alpha-acetoxytoluene; benzyl ethanoate; acetic acid, benzyl ester

Journal Article↗

PubMed1986

NTP Toxicology and Carcinogenesis Studies of 1,2-Dichloropropane (Propylene Dichloride) (CAS No. 78-87-5) in F344/N Rats and B6C3F1 Mice (Gavage Studies).

1,2-Dichloropropane is a chemical intermediate widely used in the production of tetrachloroethylene and carbon tetrachloride. It is an oil and fat solvent in certain furniture finishes, dry cleaning fluids, and paint removers and has been used to fumigate grain and soil and to control peach tree borers. Approximately 77 million pounds of 1,2-dichloropropane were produced in the United States in 1980. The current 8-hour time-weighted-average concentration to which workers may be exposed to is 75 ppm. Carcinogenesis studies of 1,2-dichloropropane (<99% pure) were conducted by administering the chemical in corn oil by gavage to groups of 50 female F344/N rats and 50 male and 50 female B6C3F1 mice at doses of 125 or 250 mg/kg body weight and to groups of 50 male F344/N rats at doses of 62 or 125 mg/kg body weight. Doses were administered five times per week for 103 weeks. Vehicle control groups of 50 rats and 50 mice of each sex received an equivalent amount of corn oil by gavage on the same dosing schedule. Survival was reduced for high dose female rats (P<0.001) and for high dose female mice (P<0.05) relative to controls; 16/50 high dose female rats and 26/50 high dose female mice survived to the end of the experiment. Survival in the other groups was comparable to the control groups. In female mice, ovarian, uterine, or multiple organ infections may have contributed to the deaths of 5/11 vehicle control, 9/14 low dose, and 14/22 high dose animals that died before the end of the study. There was no evidence of an adverse effect on survival in male rats or in male mice. Mean body weights of high dose male (-14%) and high dose female (-24%) rats were lower than those of the controls. Low dose rats and all groups of mice had mean body weights comparable to the controls. High dose female rats had increased incidences of both clear-cell changes and necrosis of the liver; but there was no increase in the incidence of liver tumors in the female rats. There was no treatment-related effects observed in the male rats, other than decreased body weights. Dose-related increases were observed for adenomas of the liver in both male (control, 7/50; low dose, 10/50; high dose 17/50) and female (1/50, 5/50, 5/50) mice. The increase in the frequency of liver carcinomas supported the evidence that there was a neoplastic response in the mouse liver for both sexes (males: 11/50, 17/50, 16/50, females: 1/50, 3/50, 4/50). Hepatocytomegaly and hepatic necrosis were increased in male mice, but not in female mice. A dose related increase in adenocarcinomas of the mammary gland was observed in female rats (control, 1/50; low dose, 2/50; high dose, 5/50) with the majority of these tumors being found at the end of the study (1/37, 3%; 2/43, 5%; 4/16, 25%). The incidence of mammary adenocarcinomas was increased when compared to the historical controls for this laboratory (3/150, 2.0%) and for all laboratories combined (11/895, 1.2%). Mammary fibroadenomas were decreased in the high dose treated female rats (15/50, 20/50, 7/50). The mutagenic activity of 1,2-dichloropropane was marginal. The compound was tested in strains TA100, TA98, TA1537, and TA1535 of Salmonella typhimurium in the presence or absence of S9 and no clearly positive response was obtained. Chromosomal aberration and sister chromatid exchange data showed that 1,2-dichloropropane caused increases in both in the absence or presence of S9. Under the conditions of these 2-year gavage studies, there was no evidence of carcinogenicity for male F344/N rats receiving 62 or 125 mg/kg. For female rats there was equivocal evidence of carcinogenicity in that 250 mg/kg 1,2-dichloropropane caused a marginally increased incidence of adenocarcinomas in the mammary gland; these borderline malignant lesions occurred concurrent with decreased survival and reduced body weight gain. There was some evidence of carcinogenicity for male and female B6C3F1 mice exposed to 1,2-dichloropropane, as indicated by increased incidences of hepatocellular neoplasms, primarily adenomas. Synonym: propylene dichloride

Journal Article↗

PubMed1986

NTP Carcinogenesis Studies of Ethyl Acrylate (CAS No. 140-88-5) in F344/N Rats and B6C3F1 Mice (Gavage Studies).

Ethyl acrylate is a monomer used to produce polymers and copolymers for use in latex paints, textiles, paper coatings, fabric finishes, dirt release agents, and specialty plastics. In 1980, 268 million pounds of ethyl acrylate were produced in the United States of which 209 million pounds were used by the producers and 59 million pounds sold. Carcinogenesis studies of ethyl acrylate were conducted by administering this test chemical in corn oil by gavage to groups of 50 male and 50 female F344/N rats and B6C3F1 mice at doses of 100 or 200 mg/kg. Ethyl acrylate was administered five times per week for 103 weeks. Groups of 50 rats and 50 mice of each sex received corn oil by gavage on the same schedule and served as vehicle controls. Survival of dosed male and female rats and mice was comparable with that of the corresponding vehicle controls. There was no evidence of systemic toxicity in the prechronic or in the 2-year studies. Compound-related increased incidences of hyperkeratosis, inflammation, and hyperplasia of the forestomach were observed in rats and mice in the prechronic as well as 2-year studies. In the 2-year studies, squamous cell papillomas and squamous cell carcinomas of the forestomach occurred at the site of chemical deposition with significant positive trends and increased incidences in dosed groups versus vehicle controls for both sexes of rats and mice. Nonneoplastic and neoplastic forestomach lesion frequencies were related to the concentration of ethyl acrylate in dosing solutions used. Significant negative trends for several common rodent tumors were found in treated animals in the 2-year studies. Under the conditions of these studies, ethyl acrylate was carcinogenic for the forestomach of F344/N rats and B6C3F1 mice, causing squamous cell carcinomas in male rats and male mice, squamous cell papillomas in male and female rats and male mice, and squamous cell papillomas or carcinomas (combined) in male and female rats and mice. Evidence for carcinogenicity was greater in males than in females. Ethyl acrylate also caused irritation of the forestomach mucosa in male and female rats and mice. Levels of Evidence of Carcinogenicity: Male Rats: Positive Female Rats: Positive Male Mice: Positive Female Mice: Positive Synonym: 2-propanoic acid, ethyl ester

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