Induction of liver tumors in rats by nitrosodiethanolamine at low doses.

Nitrosodiethanolamine was given to male and female F344 rats in drinking water at three concentrations, 160, 64 and 28 mg/l. The highest dose was given for 50 weeks, the middle dose for 50 weeks and for 100 weeks, and the lowest dose for 100 weeks, the last to a group of 39 rats of each sex. The principal neoplasms that could be attributed to the treatment were hepatocellular carcinomas and neoplastic nodules in the liver. All of the female rats and 70% of male rats drinking 160 mg/l had hepatocellular neoplasms. At 64 mg/l the incidence of hepatocellular neoplasms was higher after 100 weeks administration than after 50 weeks, and was significantly higher than in controls after 100 weeks in both sexes. At 28 mg/ml there was a greater incidence of hepatocellular neoplasms than among controls only in the female rats. Nitrosodiethanolamine appears to be carcinogenic to F344 rats at quite low concentrations.