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Meeting in China: Differential Toxicity and Accumulation of Fipronil Enantiomers in the Fathead Minnow (Pimephales promelas)
Citation:
Black, M. C., S. E. Baird, J. K. AVANTS, AND A. W. GARRISON. Meeting in China: Differential Toxicity and Accumulation of Fipronil Enantiomers in the Fathead Minnow (Pimephales promelas). Presented at SETAC Asia/Pacific Meeting, Guangzhou, CHINA, June 04 - 07, 2010.
Impact/Purpose:
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Description:
Fipronil is a chiral insecticide applied as a racemate with two enantiomers. Because of its high log KOC, fipronil will be found primarily in sediments of aquatic environments. Although a number of studies have examined toxicity in aquatic invertebrates, data on enantioselective toxicity and bioaccumulation in fish are limited. We characterized toxicity of fipronil racemate and enantiomers in acute and subchronic aquatic toxicity experiments (7 d) with larval fathead minnows (Pimephales promelas) and measured bioaccumulation of fipronil from spiked sediments in chronic exposures with fathead minnows. Enantioselective toxicity was observed in fathead minnows after 7 days, with higher toxicity of the racemate and (+) enantiomer compared to the (-) enantiomer. Fish growth was also reduced in fish exposed to the (+) enantiomer and racemate, compared to the (-) enantiomer. In the chronic exposure, fipronil was readily accumulated by fish, with peak concentrations measured at one week primarily as the metabolite fipronil sulfone. Enrichment of the (+) enantiomer likely resulted from increased biotransformation and/or excretion of the (-) enantiomer. These results concur with the interesting trend observed in the acute toxicity experiments in which the greatest toxicity (mortality and growth inhibition) was observed with exposures to the (+) enantiomer and racemate, both containing the enantiomer with the greatest accumulation. Results support application of fipronil enriched in the (-) enantiomer to protect nontarget organisms such as fish from toxicity, assuming adequate potency of that enantiomer to target species.
