Predicting azo dye toxicity

Abstract Literature regrading azo dye carcinogenicity was examined to establish, if possible, guidelines to predict the human health risks of new azo dyes. Three different mechanisms for azo dye carcinogenicity were identified, all involving metabolic activation to reactive electrophilic intermediates that covalently bind DNA. In the order of decreasing number of published references, these mechanisms are Azo dyes that are toxic only after reduction and cleavage of the azo linkage to give aromatic amines, mostly via intestinal anaerobic bacteria. The aromatic amines are met‐abolically oxidized to reactive electrophilic species that covalently bind DNA. Azo dyes with structures containing free aromatic amine groups that can be meta‐bolically oxidized without azo reduction. Azo dyes that may be activated via direct oxidation of the azo linkage to highly reactive electrophilic diazonium salts. Each mechanism may be compound specific, thus azo toxicity is probably caused by more than one mechanism. Although i...