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ACUTE AND CHRONIC EFFECTS OF FIPRONIL AND ITS ENANTIOMERS TO AQUATIC ORGANISMS
Citation:
OVERMYER, J., W. A. WILSON, D. ROUSE, A. W. GARRISON, J. K. AVANTS, M. DELORENZO, P. KEY, K. CHUNG, B. KONWICK, AND M. BLACK. ACUTE AND CHRONIC EFFECTS OF FIPRONIL AND ITS ENANTIOMERS TO AQUATIC ORGANISMS. Presented at Society of Environmental Toxicology and Chemistry Annual Meeting, Montreal, QC, CANADA, November 05 - 09, 2006.
Impact/Purpose:
To determine the environmental occurrences, fate, and effects of the enantiomers of selected chiral pesticides and other chiral pollutants.
Description:
Fipronil is a phenylpyrazole insecticide used in agriculture and domestic settings for controlling various insect pests in crops, lawns and residential structures. Fipronil is chiral; however, it is released into the environment as a racemic mixture of two enantiomers. In this study, the acute toxicity of the (+) and (-) enantiomers and the racemic mixture of fipronil were assessed using Ceriodaphnia dubia (water flea), Simulium vittatum IS-7 (black fly), Xenopus laevis (African clawed frog), Procambarus clarkii (crayfish), Palaemonetes pugio (grass shrimp), Mercenaria mercenaria (hardshell clam), and Dunaliella tertiolecta (phytoplankton). Chronic effects were also assessed using C. dubia. Results of the acute study showed that S. vittatum IS-7 was the most sensitive freshwater species while P. pugio was the most sensitive marine species. Ceriodaphnia dubia, S. vittatum IS-7, P. clarkii and P. pugio showed greater sensitivity to either a specific isomer or the racemate of fipronil. The (+) enantiomer was significantly more toxic to C. dubia and P. clarkii than the (-) enantiomer or the racemate; the racemate was significantly more toxic to S. vittatum IS-7 than either of the individual enantiomers. The (-) enantiomer was significantly more toxic to larval P. pugio than the (+) or the racemate; however, this was not observed with the adults. Increased mortality and minimal recovery was observed in all species tested for recovery from fipronil exposure. Ceriodaphnia dubia exposed in an 8-day chronic test showed significant decreases in reproduction and fitness indicators at lower concentrations of the (+) enantiomer compared to the racemic mixture or the (-) enantiomer. Neonates born during this time period showed a significant increase in mortality and decrease in fitness when exposed the (+) compared to the racemate or the (-) enantiomer. These results indicate that the most toxic isomer or racemate of fipronil is organism specific and that acute and chronic exposures can result in isomer specific toxicity.