Evaluation of new direct dyes for mutagenicity using the salmonella mammalian mutagenicity assay

A series of new direct dyes based on benzidine congeners, 2,2′-dimethyl-5,5′-dipropoxybenzidine and 5,5′- dipropoxybenzidine, were evaluated for mutagenicity in Salmonella typhimurium strains TA98 and TA 100. All of the dyes examined were judged to be non-mutagenic with and without metabolic activation while toxicity was seen in some dyes at high doses. The study also suggested that the standard Salmonella mutagenicity plate-incorporated assay was an excellent method for evaluation of direct dyes for mutagenicity.