Carcinogenicity of N-nitroso-3,4-dichloro- and n-nitroso-3,4-dibromopiperidine in rats.

The carcinogenic potencies of 3,4-dichloro- and 3,4-dibromonitrosopiperdine were compared with that of nitrosopiperidine by feeding to groups of 15 male rats in drinking water. A treatment of 15 weeks with a total of 0.5 mmole of the dichloro compound led to death of all animals before 24 weeks with tumors of the tongue, pharynx, esophagus, nonglandular stomach, nasal turbinates, trachea, bronchi, and bronchioles. Treatment of 27 weeks with the dibromo compound, a total of 1.0 mmole, caused death of all the animals by 41 weeks, with the same types of tumors. One-half of the rats treated with an almost 3-fold higher daily dose of nitrosopiperidine, 3.9 mmoles total, were alive at 40 weeks, and all were not dead until 55 weeks. Most of these animals died with tumors of the tongue, pharynx, esophagus, and nonglandular stomach and with squamous cell tumors and olfactory carcinomas of the nasal cavity, but there were no tumors of the respiratory tree. Substitution of chlorine or bromine in nitrosopiperidine greatly increased the carcinogenicity of the compound.