Toxicology and carcinogenesis studies of n-butyl chloride (greater than 99.5% pure), a solvent as well as an alkylating agent, were conducted by exposing groups of F344/N rats and B6C3F1 mice to n-butyl chloride in corn oil by gavage for 14 days, 13 weeks, and 2 years. In the 14-day studies, no compound-related gross pathologic effects were observed in groups of five male or female rats or mice administered doses of up to 3,000 mg/kg body weight. However, deaths occurred in the groups administered 750, 1,500, or 3,000 mg/kg. Tremors and convulsions following gavage administration were observed.
In the 13-week studies, groups of 10 male and 10 female rats were administered up to 500 mg/kg n-butyl chloride, and similar groups of mice received up to 1,000 mg/kg, Three of 10 male rats in the 500 mg/kg dose group and one female mouse in the 120 mg/kg dose group died before the end of the studies. Mild to moderate extramedullary hematopoiesis was observed in 3/10 male rats receiving 500 mg/kg. Mean body weights of male and female rats receiving 250 or 500 mg/kg were lower than those of the vehicle controls. Convulsions were observed in male and female rats receiving 250 mg/kg or higher and in 2/10 female mice receiving 1,000 mg/kg. Based on these results, 2-year toxicology and carcinogenesis studies of n-butyl chloride were conducted by administering doses of 0, 60, or 120 mg/kg in corn oil by gavage to groups of 50 male and 50 female rats and doses of 0, 500, or 1,000 mg/kg to groups of 50 male and 50 female mice.
In the 2-year studies, survival relative to that of vehicle controls was significantly lower in high dose male rats (40/50 vs 17/50) and high dose female rats (35/50 vs 11/50) and in male mice receiving 1,000 mg/kg (33/50 vs 10/50). Due to excessive mortality in the 1,000 mg/kg female mice, the group was terminated in the 45th week and a second series of 2-year studies in mice of each sex was started at concentrations of 0 and 250 mg/kg. Male mice in the 1,000 mg/kg group had 10% lower mean body weights than the vehicle control group. No adverse effects on survival or body weights in other dosed groups of rats and mice were observed. Convulsions were observed before or after gavage administration on several occasions during the rat studies. These observations were noted primarily in the high dose groups (male: vehicle control, 1/50; low dose, 3/50; high dose, 27/50; female: vehicle control, 0/50; low dose, 7/50; high dose, 45/50). Hemorrhage of the brain and alveoli were observed primarily in high dose male and female rats dying from convulsions. Lymphoid depletion of the spleen and splenic hemosiderosis were also observed inthese animals. In mice, convulsions were observed only in the first studies (in the high dose female mice that were terminated early and in 6/50 high dose male mice).
Pheochromocytomas of the adrenal gland occurred at marginally increased incidence in low dose female rats (1/50; 6/50; 1/49). Hyperplasia was observed in 3/50 vehicle controls, 7/50 low dose females, and 4/49 high dose females. The incidence of pheochromocytomas was low, not dose related, and not seen in males, and thus it was not considered to be compound related. Cytoplasmic vacuolization of the adrenal cortex occurred at increased incidences in males (5/50; 10/50; 20/50) but not in female rats. Nephropathy of the kidney occurred at increased incidences in female rats (13/50; 25/50; 20/50) but not in male rats. Additional nonneoplastic lesions such as congestion, inflammation, or nephrosis were not present to any degree in either vehicle control or dosed female rats.
An increased incidence of alveolar/bronchiolar adenomas or carcinomas (combined) was observed in the 500 mg/kg group of female mice (3/50 vs 9/50), but little effect was seen in the 250 mg/kg group (6/50 vs 8/50). The incidences of adenomas or carcinomas (combined) in dosed female mice were not significantly different from that in the pooled vehicle control group from the first and second studies (pooled controls, 9/100; 250 mg/kg, 8/50; 500 mg/kg, 9/50). The lack of hyperplasia in female mice and the negative trend in male mice suggest that these marginal effects were probably not related to the administration of n-butyl chloride.
An increased incidence of hepatocellular adenomas or carcinomas (combined) was observed in the 500 mg/kg dose group of female mice (3/50 vs 8/50) but not in the 250 mg/kg dose group (9/50 vs 7/50). An increased incidence of hemangiosarcomas was observed in male mice in the first study (1/50; 3/50; 4/50) but not in the second study (4/50 vs 2/50). Neither of these marginal effects was regarded as compound related.>n-Butyl chloride was not mutagenic in Salmonella typhimurium strains TA98, TA1535, or TA1537 in the presence or absence of Aroclor 1254-induced male Sprague-Dawley rat liver S9 or in the presence of male Syrian hamster liver S9. n-Butyl chloride was mutagenic in the mouse lymphoma L5178Y/TK+/- assay in the absence of Aroclor-induced male rat liver S9 and was not tested in the presence of S9. n-Butyl chloride did not induce sister-chromatid exchanges or chromosomal aberrations in Chinesehamster ovary cells in the presence or absence of Aroclor-induced male rat liver S9.
An audit of the experimental data was conducted for the 2-year studies of n-butyl chloride. 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 n-butyl chloride for male and female F344/N rats at daily doses of 60 or 120mg/kg, for male B6C3F1 mice at doses of 250, 500, or 1,000 mg/kg, or for female B6C3F1 mice at doses of 250 or 500 mg/kg. Chemical-induced toxicity in high dose rats (primarily females) reduced the sensitivity of the study for determining carcinogenicity.