Mutagenicity evaluation of the commercial product CI Disperse Blue 291 using different protocols of the Salmonella assay

Textile dyes can enter the water ecosystem through wastewater discharges potentially exposing humans through the consumption of water and food. The commercial disperse dye product CI Disperse Blue 291 containing the aminoazobenzene 2-[(2-bromo-4,6-dinitrophenyl)azo]-5-(diethylamino)-4-methoxyacetanilide (CAS registry no. 56548-64-2) was tested for mutagenic activity in the Salmonella assay. We used strains with different levels of nitroreductase and O-acetyltransferase (i.e., TA98DNP6, YG1024, and YG1041) that are relevant enzymes in the activation of nitrocompounds by the intestinal microflora. The commercial product tested also was mutagenic for TA1537, TA1538, TA98 and TA100. Presence of the pKM101 plasmid and the addition of S9 enhanced the mutagenic response. Specialized strains showed that both nitroreductase and O-acetyltransferase are important in activation of the product. The highest potency obtained was 240 revertants per microgram for YG1041 in the presence of S9. Besides being able to cause frameshift mutations (hisd3052), the dye was able to cause all types of base pair substitution with a preference for TA to AT; CG to TA and CG to AT changes. With these results clearly showing that the bacterial nitroreductase and O-acetyltransferase metabolites of this compound are mutagenic, there is a need to test this dye using in vivo systems to verify possible adverse effects of this product in mammalian tissues.