NTP Toxicology and Carcinogenesis Studies of Chlorinated Paraffins (C23, 43% Chlorine) (CAS No. 108171-27-3) in F344/N Rats and B6C3F1 Mice (Gavage Studies).

Toxicology and carcinogenesis studies of chlorinated paraffins (C23, 43% chlorine), an extreme-pressure lubricant and flame retardant, 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. Additional groups of 10 rats per sex and dose were examined at 6 and at 12 months. Male rats received doses of 0, 1,875, or 3,750 mg/kg body weight; female rats were given 0, 100, 300, or 900 mg/kg. Male and female mice received 0, 2,500, or 5,000 mg/kg. Doses selected for the 2-year studies were based on the results from 13-week studies in which rats of each sex received 0 to 3,750 mg/kg, and mice of each sex, 0 to 7,500 mg/kg. No toxicity of chlorinated paraffins (C23, 43% chlorine) was observed in male rats or in male or female mice in the 13-week studies. A dose-related inflammation of the liver was observed in female rats in the 13-week studies and in male and female rats in the 13-week studies and in male and female rats at 6 and 12 months in the 2-year studies. Chlorinated paraffins (C23, 43% chlorine) administration did not influence mean body weights of rats during the 2-year studies, but both male and female low dose mice gained less weight than did vehicle controls or the high dose groups. Survival of dosed and vehicle control groups was similar for each sex and species (male rats: vehicle control, 30/50; low dose, 32/50; high dose, 27/50; female rats: 34/50; 30/50; 33/50; 31/50; male mice: 29/50; 36/50; 28/50; female mice: 21/50; 22/50; 20/50). For female mice, 60%-70% of the early deaths in each group were attributed to utero-ovarian infection. The lower survival for female mice may have decreased the sensitivity of this study to detect a carcinogenic effect. Pheochromocytomas of the adrenal gland medulla occurred with an increased incidence in female rats exposed to chlorinated paraffins (C23, 43% chlorine) (vehicle control, 1/50; low dose, 4/50; mid dose, 6/50; high dose, 7/50). However, adrenal gland medullary hyperplasia was not increased (6/50; 3/50; 1/50; 6/50). Malignant lymphomas were increased in dosed male mice (6/50; 12/50; 16/50). High dose female mice showed a marginal increase in the incidence of hepatocellular carcinomas (1/50; 1/49; 6/50) and in the incidence of adenomas or carcinomas (combined) (4/50; 3/49; 10/50). The primary nonneoplastic lesion associated with chlorinated paraffins (C23, 43% chlorine) administration was a diffuse lymphohistiocytic inflammation in the liver and in the pancreatic and mesenteric lymph nodes of male and female rats. Splenic congestion was a secondary effect. These lesions occurred earlier and at lower doses in female rats than in male rats. No significant nonneoplastic lesions were considered compound related in mice. Chlorinated paraffins (C23, 43% chlorine) was not mutagenic in strains TA100, TA1535, TA97, or TA98 of Salmonella typhimurium in the presence or absence of Aroclor 1254-induced male Sprague-Dawley rat or male Syrian hamster liver S9 when assayed according to the preincubation protocol. An audit of the experimental data was conducted for these 2-year studies of chlorinated paraffins (C23, 43% chlorine). 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 chlorinated paraffins (C23, 43% chlorine) for male F344/N rats given 1,875 or 3,750 mg/kg per day. There was equivocal evidence of carcinogenicity of chlorinated paraffins (C23, 43% chlorine) for female F344/N rats as shown by an increased incidence of adrenal gland medullary pheochromocytomas. There was clear evidence of carcinogenicity of chlorinated paraffins (C23, 43% chlorine) for male B6C3F1 mice as shown by an increase in the incidence of malignant lymphomas. There was equivocal evidence of carcinogenicity of chlorinated paraffins (C23, 43% chlorine) for female B6C3F1 mice as shown by a marginal increase in the incidence of hepatocellular neoplasms. *The Chemical Abstract Service Seal increase in the incidence of hepatocellular neoplasms. *The Chemical Abstract Service Service (CAS) number that appeared on this technical report at the time of publication (63449-39-8) reflects the generic CAS number for chlorinated paraffins. This number has been replaced in the NTP Chemtrack chemical tracking system with the more appropriate number.