Failure of short-term in vitro mutagenicity tests to predict the animal carcinogenicity of hair dyes.

A number of hair-dye chemicals that have given positive results in various short-term mutagenicity tests have shown no clear evidence of carcinogenicity in animal bioassays. Commercial HC Blue No. 1 and its analogues HC Red No. 3 and HC Blue No. 2 are all mutagenic in the Ames test but only the HC Blue No. 1 is carcinogenic in animals. A carcinogenicity study in mice was carried out on both a commercial sample of HC Blue No. 1 and a highly purified sample which was negative in a battery of short-term tests for mutagenic activity. Both samples, administered at 0.3% in the diet for up to 24 months, were carcinogenic to mice, inducing hepatocellular carcinomas in greater than or equal to 89% of the mice examined. Therefore the presence of mutagenic impurities is not responsible for the carcinogenicity of commercial HC Blue No. 1. Discrepancies between the results of mutagenicity and carcinogenicity tests on hair dyes and other chemicals are discussed, and the value of short-term mutagenicity tests for assessing chemical safety is questioned.