Accumulation and Excretion of Permethrin by the Himedaka Oryzias latipes and Biological Significance of Accumulated Permethrin

Abstract

The toxicity of permethrin to the Himedaka Oryzias latipes was assessed with a formulated permethrin product, and cis- and trans-isomers of permethrin individually. LC₅₀ values obtained after 48h were 60ppb, 38ppb and 55ppb for the formulated product, cis-permethrin and trans-permethrin, respectively.
After 48h of rearing in test solutions, the amount of permethrin accumulated in the fish ranged from 1-6ppm. Most live fish contained permethrin from 1-4ppm and most dead fish contained permethrin from 3-6ppm. The biological concentration was more prominent with cis-permethrin than trans-permethrin. The excretion of accumulated permethrin was essentially completed in 4 days.
When the Himedaka were per-treated in a low concentration permethrin solution at 1/10 of LC50 for 48h and 168h, the fish developed tolerance to permethrin, and the mortality was substantially dropped in a LC₅₀ permethrin solutiohn at 60ppb; in one case no mortality was observed at all for the 48h period.
A gas chromatographic method with the use of a non-radioactive electron capture detector has been developed which gives complete resolution of cis- and trans-permethrin with more than 90% recovery and the lowest detectable limit of 0.1 ng.