Threshold for carcinogenicity of N-nitrosodiethylamine for esophageal tumors in rats.

In a study on 4080 rats by Peto et al. [Cancer Res. 51 (1991) 6415], esophageal neoplasms induced by N-nitrosodiethylamine (NDEA) were the tumors most clearly demonstrated to have a dose response from administration of the compound to male rats. However, they were unable to predict the shape of the dose-response curve at low doses. These data were reanalyzed in the present study for dose response on a logarithmic scale for dose. In contrast to the conclusion of Peto et al., the reanalysis shows a convincingly sharp threshold at 10(17.1) molecules/kg/day. This unequivocal threshold has substantial implications for risk assessment of chemical carcinogens.