Contamination of fresh water fish “Schizothorax niger” with chlorpyrifos from “Dal Lake” basins, India

Dal Lake a Sub-Himalyan urban Lake is one of the most beautiful lakes of India and second largest in Jammu & Kashmir. Intensive farming practiced in the surrounding area of Dal Lake and its floating gardens leads to an enhanced vulnerability of crops to pests and indiscriminate use of pesticides. Possible transfer of these hazardous molecules from vegetable fields to the aquatic environment of the Lake, poses a potential threat to the aquatic species and human health as well. In the present investigation conducted from 2008 to 2010, 135 samples of fish including 81 samples of schizothorax niger ( Algaad / Kasheer Gaad) and 54 samples of Cyprinus carpii (Punjab Gaad) were collected from three basins of Dal Lake namely Hazratbal, Nigeen and Cheshmashahi basin. The samples were analyzed for seven commonly used pesticides viz. Butachlor, γHCH, Chlorpyrifos, Hexaconazole, Endosulfan 1, Endosulfan 2 and Dichlorvas. Detection and quantification of pesticide residues was performed by GC-MS/MS (Thermofinnigan Polaris Q type) equipped with Ni ECD. It was found that 73 samples (54.07%) out of 135 were contaminated with chlorpyrifos an organophosphate pesticide with mean concentration of (0.0009 ± 0.0010ng/kg) with concentration ranging from undetected to 0.003ng/kg. The highest concentration was found in Hazratbal basin in 2009 (0.002 ± 0.001ng/kg). The results also reveal that level of pesticide was higher in pesticide use season than non use season except in 2009 when levels were same. With respect to basins the results show that mean concentration of chlorpyrifos level was higher in pesticide application season than non application season except in Nigeen basin in 2008 and 2009 where levels were same (0.001±0.001ng/kg) and in Hazratbal basin in 2010 where levels were same (0.001±0.001ng/kg). The results indicate a sub acute exposure of chlorpyrifos in a locally consumed Schizothorax niger and not in Cyprinus carpii. These findings suggest that low dose exposure to pesticides through food chain like fish can be a major contributor for presence of pesticide residual levels in human blood.