Studies on the carcinogenicity of pentachloroethane in rats and mice.

Studies on the Carcinogenicity of Pentachloroethane in Rats and Mice. Mennear, J.H., Haseman, J.K., Sullivan, D.J., Bernal, E. and Hildebrandt, P.K. (1982). Fundam. Appl. Toxicol 2:82-81. The carcinogenicity of chronically administered (41 to 103 weeks) technical-grade pentachloroethane (PCE) was assessed in groups of 50 male and female Fischer 344 rats and B6C3Ft mice. The major contaminant in the PCE sample used for the chronic study was hexachloroethane (4.2%). Prechronic studies (two and 13 weeks repeated dose) employing gavage doses offrom 5.0 to 1000 mg/kg/day of PCE failed to reveal specific target organ toxicity in these species. In the absence of treatmentrelated pathological changes during the prechronic tests, the doses for the chronic studies were set on the basis of survival and body weight gains during the 13-week repeated dose study. During the chronic studies dose levels of 75 and 150 mg/ kg for rats and 250 and 500 mg/ kg for mice were administered, by gavage, five days per week. The survival of highdose rats (both sexes) was significantly reduced as compared to the survival of control animals and that of the low-dose males was slightly, but not significantly, reduced. Although the administration of PCE to rats did not increase the incidence of primary tumors, it did produce a significant doserelated increase in the incidence of chronic renal inflammation among males. The survival times of all treated groups of mice were significantly shortened by PCE administration. Despite this reduced survival time, the incidence of hepatocellular carcinoma was significantly increased in all treated groups. With the exception of a dose-related increase in the incidence of hepatocellular adenoma among females, there were no other significant increases in primary tumor incidence in mice. Neither renal lesions in rats nor hepatocellular carcinoma in mice were considered to be adequate explanations for the decreased survivals. Complete histopathological examinations failed to reveal the cause of decreased survival. The results of the study show that technical-grade PCE,like numerous other chlorinated ethanes, is an hepatocarcinogen for B6C3FJ mice. This interpretation for PCE The qudie~ v.~re conducted at Gulf South R~search Institute under a ~ubcontract w Tracor-JitCl'.l nc.. the pnme comractor for the Carcinogenesis Testing Program. The chronic stud' v.as inuia«d in December. 1977 and completed in December. 19"9. To whom requests for reprints should be addressed. ~ational Toxicologv Program ~IEHS. P.O. Box l~c33. Research Triangle Park. ~C 27709. ~ational ToX<colog,· Program 'Gulf South Research Institute