Genotoxicity of the Yamuna River water at Okhla (Delhi), India

Water samples from the Yamuna River at Okhla (Delhi), India, were concentrated using XAD resins (XAD-4 and XAD-8) and liquid–liquid extraction procedures. Gas chromatographic analysis of liquid–liquid extracted water samples revealed the presence of the pesticides DDT, BHC, dieldrin, endosulfan, aldrin, 2,4-D, dimethoate, methyl parathion, and malathion at concentrations of 14, 25, 2.1, 114, 0.9, 0.6, 0.9, 1.7, and 1.9 ng/L, respectively. The genotoxicity of the extracted water samples was evaluated with the Ames Salmonella/mammalian microsome test, DNA repair-defective mutants, and bacteriophage λ systems. The results of the Salmonella test demonstrated that the XAD-concentrated water samples had maximum mutagenicity with the TA98 strain both with and without metabolic activation. However, the liquid–liquid-extracted water samples were also found to be mutagenic with one or more of the Ames tester strains, but to a lesser extent as compared with XAD extracts. The damage brought about in the DNA repair-defective mutants in the presence of XAD-concentrated water samples was found to be markedly high as compared with that liquid–liquid-extracted water samples at the dose level of 20 μl/mL culture. All mutants invariably exhibited significant declines in their colony-forming units as compared with their isogenic wild-type counterparts. Survival decreased by 86.3 and 75.5% in the polA− strain after 6 h of treatment with XAD-concentrated and liquid–liquid-extracted water samples, respectively. A significant decrease was also observed in the survival of bacteriophage λ when treated with the test samples. Mutagenic responses of the liquid–liquid-extracted water samples may not necessarily reflect the mutagenicity of existing pesticides in the test water, because some other organic pollutants might accompany the pesticides in the extract.