Bioaccumulation, biotransformation, and toxicity of fipronil
Konwick, Brad Joseph
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Fipronil is an increasingly used phenylpyrazole insecticide with a high probability to contaminate aquatic ecosystems, and is released into the environment as a racemic mixture (equal amounts of optical isomers called enantiomers) due to its chirality. Enantiomers can have different toxicological and biological activity; however, information on these differences, which is necessary for accurate risk assessment of chiral pesticides, is limited. We examined the acute toxicity of fipronil to the crustacean, Ceriodaphnia dubia, and indicated toxicity was significantly greater for the (+) enantiomer. In assessing the bioaccumulation potential of fipronil in rainbow trout (Oncorhynchus mykiss), rapid elimination via biotransformation was shown to be the dominant pathway, with a greater biotransformation rate of the (+) enantiomer, as indicated by changes in the enantiomeric composition of the fish. This thesis highlights the utility of chiral compounds to provide insights into biotransformation and toxicity processes with additional research needed on fipronil’s enantiomer-specific activity.