TOXICITY OF CHLORPYRIFOS TECHNICAL GRADE AND 20% EC TO THE FRESHWATER FISH, CHANNA PUNCTATA (BLOCH)

The toxicity studies of chlorpyrifos technical grade (TG) and 20% EC are conducted in the prevailing laboratory conditions of the fish Channa punctata in vivo to determine the median lethal concentrations i.e., LC50 values for 24, 48, 72 and 96 hrs duration by employing both static renewal and continuous flowthrough systems. The most preferred and palatable fish and mostly used pesticide the organophosphate are selected for study. The static renewal values are 6.02 µg/L, 5.82 µg/L, 5.62 µg/L, 5.38 µg/L for technical grade and for 20% EC 3.01 µg/L, 2.71 µg/L, 2.61 µg/L, and 2.51 µg/L for 24, 48, 72 and 96 hrs respectively. Similarly, for the continuous flow through system (CFTS) the values are 3.11 µg/L, 2.87 µg/L, 2.81 µg/L and 1.61 µg/L for technical grade and for 20% EC 1.91 µg/L, 1.81 µg/L, 1.61 µg/L and 1.41 µg/L respectively for 24, 48, 72 and 96 hrs. The toxicity is the concentration and duration dependent and the LC50 values in both methods decreased as well as concentrations also. The static renewal values are higher to CFTS and 20% EC is sufficiently toxic, which had synergistic effect on target and tested organism. The values are useful for data base and also in prescribing the permissible limits.