A chronic toxicity and oncogenicity study in rats and subchronic toxicity study in dogs on ingested vinylidene chloride

The chronic toxicity and oncogenic potential of ingested vinylidene chloride (VDC) was evaluated in a 2-year study on Sprague-Dawley rats and the subchronic toxicity was evaluated in beagle dogs in a 97-day study. The vinylidene chloride was incorporated in the drinking water of the rats at nominal concentrations of 50, 100 or 200 ppm. The time weighted average mg/kg body weight/day dosages of vinylidene chloride administered to the male and female rats over the 2-year period at the various mean analyzed concentrations were 7, 10 or 20 for the males and 9, 14 or 30 for the females. Dogs were administered vinylidene chloride in peanut oil incorporated in a gelatin capsule at concentrations which provided 6.25, 12.5 or 25 mg vinylidene chloride/kg body weight/day. There were no significant differences between the groups of rats or dogs ingesting vinylidene chloride and their corresponding control groups in the following parameters: appearance and demeanor, mortality, body weight, food consumption, hematology, urinalysis, clinical chemistry determinations, organ weights and organ to body weight ratios. There were no significant differences in water consumption of the groups of rats ingesting vinylidene chloride and the controls. The sole treatment-related observation in the rats, evident only upon microscopic examination, was in the liver. The observation was characterized by a minimal amount of hepatocellular swelling with midzonal fatty change which occurred in the females at all dose levels and in the males only at the 200 ppm level. No exposure-related neoplastic changes occurred in the rats in any of the test groups. No exposure-related gross or histopathological changes were present in the tissues taken from the dogs at the termination of the 97-day study.