Brief reviews are presented on the occurrence of N-nitroso (NNO) compounds, the chemistry and kinetics of NNO compound formation from
nitrite and
amines or
amides, the in vivo formation of these compounds (as detected by
tumor induction) on feeding
nitrite with
amines or
amides to rodents, and the carcinogenicity for rats of some new
nitrosamides. The possible human hazard caused by exposure to specific readily nitrosated compounds is reviewed. Whether NNO compounds might be causing human
cancer of various organs (e.g., pancreatic, nasopharyngeal, and
esophageal cancer) is discussed. Some of our results in [3H]
thymidine incorporation in the rat esophageal epithelium are presented.
Nitrosamines that cause
esophageal cancer in rats were found to inhibit [3H]
thymidine incorporation, both in vivo and in vitro, when esophagi were incubated with
nitrosamines. With reference to the hypothesis that human
gastric cancer is caused by
nitrosamides (e.g., nitrosoureas), certain correlations were examined between
gastric cancer and environmental exposure to
nitrate,
nitrite, and nitrosatable
amides. In studies from our laboratory, dried, salted fish, which was treated with excess
nitrite at pH 1 and then "denitrosated" at pH O, yielded 16 mg methylurae/kh fish, possibly derived from
methylguanidine.