Dr. K. Venkata Krishna
Associate Professor of Chemistry, Government Degree College for Women (A), Nalgonda
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http://doi.org/10.37648/ijrst.v15i01.008
Synthetic dyes are chemically diverse contaminants whose effects on aquatic organisms depend on molecular structure, exposure conditions, environmental transformation and biological susceptibility. This narrative review examines azo, anthraquinone and triarylmethane dyes, distinguishing the hazards of parent compounds from those of their transformation products. Reductive cleavage of an azo linkage can produce aromatic amines, but the identities and toxicological properties of the products cannot be generalized across the entire dye class. The review distinguishes laboratory toxicity, human carcinogenic hazard and ecological risk, using selected literature published on or before 31 December 2022. An embryo–larval fathead minnow study reported LC₅₀ values based on measured aqueous concentrations of 25.4 μg/L for Disperse Yellow 7 and 16.7 μg/L for Sudan Red G in exposures extending to 14 days post-hatch; these laboratory values must not be described as demonstrated adverse concentrations in receiving waters. IARC classifications further demonstrate why malachite green and leucomalachite green require separate treatment. Practical assessment should combine parent and product measurements, relevant biological endpoints and wastewater-specific treatment evaluation. Colour removal alone does not establish mineralization or detoxification.
Keywords: azo dyes; aromatic amines; transformation products; aquatic ecotoxicology; genotoxicity; malachite green; textile wastewater.
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