Compound toxicity and accumulation of permethrin and mercury in the himedaka Oryzias latipes.

Abstract

The 48h mortality of the Himedaka was examined in a solution containing 60μg/ml (LC50) permethrin and variable concentrations of mercuric chloride, HgCl2 (200-800μg/ml), or methyl mercuric chloride, MeHgCl (50-200μg/ml). The additive effect of these chemicals was proven by the increase in the fish mortality and the change in concentrations of chemicals accumulated in the fish. Concentrations permethrin accumulated in the fish decreased substantially, and concen-trations of mercury accumulated (total mercury, T-Hg) increased as the concentrations of HgCl2 test solution increased with the presence of 60μg/ml permethrin.A similar additive effect was observed when the Himedaka were exposed stepwise to LC50 permethrin and mercury solutions for two successive 48h periods; more than 50% of the survived fish after the initial 48h exposure died during the second 48h exposure. In contrast, when the fish were exposed to the same chemical for successive two 48h periods, no further death was observed during the second exposure period, indicating the development of tolerance to the chemical during the initial 48h period.Permethrin and mercury can be accumulated up to 8μg/g and more than 45μg/g, respectively, if these two are present individually. If both are present in the same solution, individual concentrations are lower than the above values and the proportions of the two chemicals vary depending on the exposure conditions.