Comparative carcinogenicity of ring-halogenated 3-methyl-1-phenyltriazenes and their 3,3-dimethyl analogs at equimolar dose levels in male Sprague-Dawley rats.

The carcinogenic activity of 3-methyl-1-phenyltriazene and its four 4- and 2-ring halogenated derivatives was similar to the previously reported carcinogenicity of the corresponding 3,3-dimethyl-1-phenyltriazene analogs tested at equimolar dose levels in adult male Sprague-Dawley rats. The strongest carcinogens in each series were 3-methyl-1-phenyltriazene and 3,3-dimethyl-1-phenyltriazene, respectively. The carcinogenic potency of the individual test compounds decreased with progressive 4- and 2-halogenation of the phenyl ring. The administration of either 3-methyl-1-(2,4,6-trichlorophenyl)- or 3-methyl-1-(2,4,6-tribromophenyl)-triazene gave a negligible tumor yield not different from that observed in the control animals. Moreover, 3,5-dichloro-2-(3,3-dimethyl-1-triazeno)-benzoic acid or its ethyl ester, were found to be strong carcinogens that exclusively induced kidney tumors.