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 1017.1 molecules/kg/day. This unequivocal threshold has substantial implications for risk assessment of chemical carcinogens.