Comparative Toxicity and Carcinogenicity of Two Chlorinated Paraffins in F344/N Rats and B6C3F1 Mice

The toxicity and carcinogenicity of chlorinated paraffins containingC12 with 60% Cl, and C23 with 43% C1, were assessed in prechronicand 2-year gavage studies using F344/N rats and B6C3F1 miceof both sexes. Single administrations of chlorinated paraffinswere nonle thal in rats and mice, but repeated-dose and 2-yearstudies demonstrated toxic responses that differed with theparaffins. The C23,C143% paraffin produced a granulomatous inflammationin the liver of female rats in 13-week studies, while the C12,Cl60% paraffin caused deaths of rats and mice in 16-day studiesand marked liver enlargement in 13-week studies. In 2-year studies,the C23,C143% paraffin caused hepatic and lymphatic granulomatousinflammation and hyper plasia in both sexes of rats, and wasassociated with marginal increases in adrenal medullary pheochromocytomasin female rats and hepatocellular neoplasms in female mice andwith clear increases in malignant lymphomas in male mice. TheCl 2,Cl60% paraffin caused marked liver enlargement in ratsand increased the severity of nephropathy in male rats and theincidence of nephropathy in female rats. Cl2,Cl60% also causedhepatocellular neoplasms in both sexes of rats and mice: kidneytubular cell adenomas and adenocarcinomas in male rats, thyroidfollicular cell neoplasms in female rats and female mice, anda marginal increase in mononuclear cell leukemia in male rats.Thus, the short-chain, heavily chlorinated paraffin appearsto have a greater potential for chronic toxicity and carcinogenicitythan the longer-chain, lightly chlorinated paraffin. Both paraflinshave been reported to be nonmutagenic in bacteria. (NationalToxicology Program (1986) Technical Report, NIH Publications86-2561 and 86-2564).