||Pathology Associates, Inc., West Chester, OH. ;Page Associates, Gaithersburg, MD.;Health Effects Research Lab., Research Triangle Park, NC.
Chloral hydrate (CH) and 2-chloroacetaldehyde (CAA) have been identified as chlorination by-products in drinking water. Both chemicals are genotoxic, but their carcinogenic potential had not been adequately tested. These bioassays were conducted using male B6C3F1 mice exposed to 1 g/L CH and 0.1 g/L CAA in the drinking water for 104 weeks. Distilled water served as the control; dichloroacetic acid (DCA; 0.5 g/L) was included. Mean daily doses of 166 mg/kg/day for CH, 17 mg/kg/day for CAA and 88 mg/kg/day for DCA were measured. Mortality, body weight, organ weights, gross pathology, and histopathology were examined. The primary target organ was the liver since the organ weights and pathologic changes in other organs were comparable between treated and untreated groups. Liver weights were increased for all chemicals at the terminal sacrifice with the greatest increases seen in the CH and DCA groups. Liver necrosis was induced by all test chemicals, but was most severe in the CH and DCA groups. A significant increase in the prevalence of liver tumors was seen for all chemicals. For DCA 63% of the mice had carcinomas and 43% had adenomas. The combined prevalence for both neoplasms was 75%. For CH, the prevalence for carcinomas, adenomas, and combined tumors was 46%, 29%, and 71% respectively.