Monitoring genotoxicity in the environment by using endemic organisms as sentinels requires sensitive assays. In this study the genotoxic properties of water and sediment collected from the Noyyal River, which is polluted with industrial effluent and sewage, was determined in fish (Cyprinus carpio) and earthworms (Eisenia foetida) using the alkaline comet assay. Upon electrophoresis, extensive DNA damage, measured as the DNA length:width ratio of the DNA mass, was observed in erythrocytes, liver, and kidney cells of fish exposed to polluted water samples and the amount of damage increased with the duration of exposure. Similarly, the mean DNA length:width ratio was significantly higher in the coelomocytes of earthworms placed in sediment samples. The highest levels of DNA damage were obtained with samples taken at and immediately downstream of urban centers. The results of this study indicate that the Noyyal River system is contaminated with substances that are genotoxic to fish and earthworms and that the comet assay has sufficient sensitivity to detect the genotoxicity.

This report presents the results of a genotoxicity study to evaluate the DNA damage caused by four sulfur dyes used in the textile and tannery industries. Alkaline single-cell gel electrophoresis assay (SCGE) was performed on erythrocytes from Rana hexadactyla tadpoles following whole-body exposure to increasing concentrations of the dyes. The dyes, along with their active ingredients, were Sandopel Basic Black BHLN, Negrosine, Dermapel Black FNI, and Turquoise Blue. The dye-treated tadpoles showed significant DNA damage, measured as mean DNA length:width ratio, when compared with unexposed control animals. Among the four tested dyes Sandopel Basic Black BHLN appears to be highly genotoxic, Dermapel Black FNI was least genotoxic, and Negrosine and Turquoise Blue were moderately toxic to R. hexadactyla tadpoles. The tadpoles showed a significant reduction in DNA damage when placed in dechlorinated tap water after exposure for a 24-hr period to the dye solutions.