Bioaccumulation, elimination, and tissue distribution of chlorpyrifos by red hybrid Tilapia in fresh and brackish waters

Bioaccumulation, degradation, elimination and tissue partitioning of chlorpyrifos (Dursban 25E) was studied under static conditions for 3-4 days, in fresh (FW) and brackish (BW) waters by two methods: in the renewal method, fish were transferred every 24h to FW or BW aquaria containing 0.05 mg V of the insecticide; in the spiking method, the original concentration of 0.005 mg V was spiked every 8h. Samples of fish and water were collected at regular intervals and residues determined gas chromatographically. In the renewal experiments with 0.05 mg l(-1), bioconcentration reached its peak within 8h of exposure in FW (125 mg V) and within 1h in BW (0.95 mg g(-1)); in spiking experiments with 0.005 mg l(-1), these peaks were attained in 48 h in FW (3.8 mg g(-1)) and 8-24 h in BW (1.67 mg g(-1)) Thereafter, the concentrations declined. The concentrations of an unidentified metabolite were generally but not always correlated with that of the parent compound. Upon exposure of contaminated fish to uncontaminated waters, 72% was eliminated within the first 12 h and 4% later in 60 h in FW, and only 23% in I h and another 21% in the following 60 It in BW. Concentration of the metabolite was very high during the elimination. In the renewal experiment with 0.05 mg V of chlorpyrifos, tissue distribution was much higher in FW than in BW, while the reverse was true in spiking experiments with 0.005 mg V of the chemical. Testis, heart and brain had the highest levels of residues, followed by ovaries and other tissues.