Cytotoxic and genotoxic potential of tannery waste contaminated soils

Soil samples from agricultural fields in the vicinity of industrial area of Jajmau, Kanpur (India) were collected and found to be heavily contaminated with various toxic heavy metals. GC–MS analysis revealed the presence of organic compounds mainly phthalates in contaminated soils. Samples were extracted using dichloromethane (DCM) and hexane solvents, and the extracts were assayed for genotoxic potential using three different bioassays namely Ames Salmonella/mammalian microsome test, DNA repair defective Escherichia coli K-12 mutants and Allium cepa chromosomal aberration assay. TA98 was found to be the most sensitive strain to all the soil extracts tested. The highest mutagenic potential was observed in DCM extracts of soil as compared with hexane extracts for each strain of Salmonella typhimurium. DCM extracts of the soil exhibited maximum damage to the cells at a dose of 40 μl of soil extracts/ml of culture after a 6-h treatment. The survival was 23% in polA, 40% in lexA and 53% in recA mutants when treated with DCM extract of site I. In A. cepa assay, all the test concentrations of soil extracts (5–100%) affected mitotic index in a dose-dependent manner and several types of abnormalities were observed at different mitotic stages with the treatments: C-mitosis, anaphase bridges, laggards, binucleated cells, stickiness, broken and unequal distributions of chromosomes at anaphase stage of cell division. The soil is accumulating a large number of pollutants as a result of wastewater irrigation and this practice of accumulation has an adverse impact on soil health.

► Test soil samples showed maximum response with TA98 strain in the presence and absence of S9 microsomal fraction.
► Dichloromethane extracts of soil were more mutagenic compared to hexane extracts for each strain of S. typhimurium.
► polA mutant exhibited maximum decline in survival assay with the test samples.
► Soil samples were also found to be genotoxic and cytotoxic for Allium cepa root tip meristem cells.