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MA6 Environmental Chemistry and Toxicology of Chiral Pollutants
() Enantioselective elimination of fipronil and selected organochlorines by rainbow trout (Oncorhynchus mykiss).
Konwick, B1, Fisk, A1, Garrison, A2, Avants, J2, Black, M1, 1 University of Georgia, Athens, GA, USA2 US Environmental Protection Agency, Athens, GA, USA
ABSTRACT- Fipronil is a phenylpyrazole pesticide widely used in applications such as rice culture, turf grass management, and residential pest control with a high probability to contaminate aquatic environments. Fipronil has moderate partitioning (log Kow = 4.01) for accumulation in biota; however, limited information exists on its toxicokinetics (i.e., uptake, elimination, biotransformation) in aquatic species. As a chiral molecule, fipronil is released into the environment as a racemic mixture, containing 50% of each enantiomer. Enantiomers have identical physical-chemical properties and abiotic degradation rates, but usually differ in their biological activities. Biological processes such as metabolism in aquatic species can therefore lead to enriched elimination of one enantiomer of a chiral pesticide. Here, laboratory experiments involved exposure (32 days) of rainbow trout (Oncorhynchus mykiss) to racemates of fipronil and selected organochlorine pesticides and PCBs followed by 128 days depuration to examine the enantiomer-specific biotransformation and elimination of these compounds. Bioaccumulation of each chemical, enantiomeric fractions (EFs), and log Kow - log half-life relationships will be measured over time. We expect residues to deviate from racemic (EF = 0.5), demonstrating that aquatic species can eliminate fipronil and other chiral compounds enantioselectively; this may indicate a greater metabolic capability of aquatic biota than previously recognized.
Key words: chiral, fipronil, biotransformation, enantioselective
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