Genotoxicity studies on the azo dye Direct Red 2 using the in vivo mouse bone marrow micronucleus test

The clastogenicity of the azo dye Direct Red 2 (DR2) has been investigated using the murine bone marrow micronucleus assay. A potent dose-dependent response was observed following oral gavage of DR2 up to 4 mg/kg, after which significant toxicity to the erythroid compartment was observed. The route of administration had a significant effect on the frequency of micronucleus formation: intraperitoneal injection was approximately two-fold less clastogenic than the equivalent dose delivered orally (p<0.05). The requirement for activation of DR2 by intestinal microflora was indicated by the fact that mice given acid-treated water prior to administration of DR2 showed a significant reduction (40%; p<0.001) in micronucleated polychromatic erythrocyte formation. The implications of these findings for the health and safety of occupationally exposed workers are discussed.