Pesticide toxicokinetics in fish: accumulation and elimination

Bioaccumulation of fenitrothion in the European eel (Anguilla anguilla) was studied using two sublethal concentrations of this pesticide in a flow-through test system. The pesticide concentrations used were one-tenth (0.002 ppm) and one-fifth (0.04 ppm) the 96-h LC50 of fenitrothion in this species. Steady state was reached early (2 h) when the animals were exposed to 0.02 ppm of toxicant, and after 48 h when the animals were exposed to 0.04 ppm. Toxicokinetic parameters for fenitrothion in eel muscle (K1, K2, and T1/2) were calculated for both experiments. The highest bioconcentration factor was calculated for animals exposed to 0.04 ppm of toxicant, indicating the relationship between the bioconcentration in muscle tissue and the disposition of fenitrothion in the medium. After transfer to clean water (depuration phase), the animals rapidly eliminated the pesticide accumulated. Excretion rate constants (K2) were 0.06 and 0.04 h-1 in both experiments and the half-lives of fenitrothion in muscle tissue were less than 24 h. After 24 h of the recovery period, fenitrothion was not detected in eel muscle of those animals exposed to 0.02 ppm, and in eels exposed to 0.04 ppm of toxicant, a reduction of 91% was reached by the end of the period.