Bromodichloromethane, a trihalomethane that produces neoplasms in rodents.

Bromodichloromethane, a trihalomethane found in water supplies after chlorination, was administered by gavage in corn oil to male and female F344/N rats and B6C3F1 mice for up to 2 years at dose levels of 0, 50, or 100 mg/kg to rats, 0, 25, or 50 mg/kg to male mice, and 0, 75, or 150 mg/kg to female mice. Survival at 2 years in rats and in male mice was comparable among groups and was greater than 50% at the termination of the experiment. Survival in female mice was greater than 50% in all groups until week 84 but was reduced toward the end of the study because of ovarian abscesses in some female mice. There was clear evidence of carcinogenicity in males and females of both species as shown by increased incidences of tubular cell adenomas and adenocarcinomas in the kidney and adenocarcinomas and adenomatous polyps in the large intestine in male and female rats, increased incidences of tubular cell adenomas and adenocarcinomas in the kidney of male mice, and increased incidences of hepatocellular adenomas and carcinomas in female mice. Of the three trihalomethanes studied to date in the National Cancer Institute/National Toxicology Program (chloroform, chlorodibromomethane, or bromodichloromethane) bromodichloromethane caused the widest spectrum of neoplasms in rodents.