Genotoxic hazards of long-term application of wastewater on agricultural soil.

In the city of Aligarh (India), wastewater coming from both industrial and domestic sources and without any treatment is used to irrigate the agricultural crops. This practice has been polluting the soil, and the pollutants could possibly reach the food chain. For the above reason, soil irrigated with wastewater was sampled and monitored for the presence of genotoxic agents using three biological assays namely Ames Salmonella/mammalian microsome test, survival of SOS defective E. coli K-12 mutants and bacteriophage lambda systems. Extracts from soils were prepared using different organic solvents, i.e. methanol, acetonitrile and acetone. TA98 was found to be most sensitive strain to all the soil extracts. A significant decline in the survival of DNA repair defective E. coli K-12 mutants as compared to their isogenic wild-type counterparts were observed when treated with soil extracts. PolA was found to be the most sensitive strain. A remarkable decline in the plaque forming units was also observed when tested with the soil extracts. Extracts of soil that has been irrigated with ground water were also tested by the above three biological assays to compare the results.