Mutagenicity of arylmethane dyes in Salmonella

22 arylmethane dyes which have been used as food colours, commercial dyes, laboratory stains and pH indicators were tested in the Salmonella/mammalian microsome mutagenicity assay. 8 mutagenic dyes were identified, including 5 food colours and 3 common laboratory strains; none of the 11 indicator dyes tested was mutagenic. The commercial and laboratory dyes Methyl Violet 2B C.I. 42535 and Crystal Violet C.I. 42555 were mutagenic in base-pair substitution mutation detector strain TA1535 in the absence of metabolic activation. By contrast, the food colours Benzyl Violet 4B C.I. 42640, Guinea Green B.C.I. 42085, Light Green SF C.I. 42095, Lissamine Green B C.I. 44090 and Violet BNP C.I. 42581 and the bacteriological stain, Basic Fuchsin C.I. 42500-42510, were all mutagenic in frameshift mutation detector strains TA98 and/or TA1538 and required metabolic activation. Most of these compounds gave weak mutagenic responses with Salmonella and were positive only within narrow dose ranges. Since conflicting results were obtained using dyes from different sources, minor dye components may have been responsible for their mutagenicity. This suggests the need to improve knowledge about impurities in arylmethane colours still used in food and to review the toxicological role of such impurities.