The aquatic toxicity and mutagenicity of azo and formazan dyes

The health of the environment is of paramount importance in today's textile and chemical industries. Growing regulations and public pressure have forced companies to be increasingly careful in every aspect of their production operations. For dyers and dye manufacturers, the disposal of dye effluent is of major concern. Colored wastewater is aesthetically unpleasing to the public and poses a potential health hazard to humans who consume it and to plants and animals that live in it. Though all dye classes present some concern, environmentally, dyes complexed with toxic metals are of special concern.; This dissertation is concerned with the mutagenicity and aquatic toxicity of metallized and unmetallized azo and formazan dyes. The Salmonella/Mammalian Microsome Assay and the Lemna Aquatic Toxicity Assay were used to assess the properties of 27 dyes.; The goals of this project were: (1) to determine structure/activity relationships; (2) to determine whether replacing chromium and cobalt with iron in metal complexes would lower mutagenicity and aquatic toxicity; and (3) to determine the effect of ozonolysis on the aquatic toxicity of metal-complex dyes. The results of this study suggest that: (1) The bacterial mutagenicity of the dyes examined was primarily due to nitro groups in the molecule. The mutagenic compounds were primarily frameshift mutagens and were both direct-acting and indirect-acting. (2) The mutagenicity of metal-complexes was dependent on the mutagenicity of the precursor. (3) In aquatic toxicity studies, iron-complexed azo dyes were less toxic to Lemna Minor than the corresponding chromium or cobalt complexes. (4) Ozonolysis of aqueous solutions of metal-complex dyes led to an increase in pH and to an increase in toxicity to Lemna Minor for most dyes.; It is apparent that iron-complex dyes have lower levels of aquatic toxicity than chromium or cobalt complexes, and that iron-complexation will generally decrease bacterial mutagenicity. The use of iron-complexes is therefore a viable alternative to complexes of chromium and cobalt and will reduce the genotoxicity of metallized dyes.