Mutagenicity evaluation of HC Blue No. 1 and HC Blue No. 2. III. Effects in the Salmonella typhimurium/Escherichia coli reversion assay and the mouse lymphoma L5178Y TK+/- forward mutation assay.

The hair-dye ingredients, HC Blue No. 1 (HCB1) and HC Blue No. 2 (HCB2), were tested for the induction of bacterial mutation using Salmonella typhimurium strains TA1535, TA1537, TA98 and TA100; and Escherichia coli strains WP2uvrA-. In addition, both dyes were evaluated in the mouse lymphoma L5178Y TK+/- assay (MLA) for the potential to induce forward mutation. A liver homogenate (S9) prepared from Aroclor 1254-induced male Fischer 344 rats was used to provide a means for metabolic activation. HCB1 was not mutagenic in the Ames assay, but was weakly mutagenic in the MLA only in the presence of metabolic activation. In contrast, HCB2 was a strong mutagen in the Ames assay in tester strain TA98 both in the presence and absence of metabolic activation. A positive response was also noted with HCB2 in the MLA, both in the presence and absence of metabolic activation. Negative findings from the Ames assay of this study agree with other published results where an identical lot of HCB1 was used. Using the same lot, a weak positive result was observed in the MLA, however, the activation requirements and magnitude of the response were different from that of a lot evaluated by the NTP. In contrast, HCB2 appears to be both a bacterial and mammalian cell mutagen independent of lot variability.