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Metabolism of pesticides after dermal exposure to amphibians
Citation:
Glinski, D., Matt Henderson, Tom Purucker, AND R. VanMeter. Metabolism of pesticides after dermal exposure to amphibians. Presented at 34th Annual SETAC North America, Nashville, TN, November 17 - 21, 2013.
Impact/Purpose:
Presentation given at SETAC North America 34th in Nashville, TN (Nov 17-21, 2013)
Description:
Understanding how pesticide exposure to non-target species influences toxicity is necessary to accurately assess the ecological risks these compounds pose. Aquatic, terrestrial, and arboreal amphibians are often exposed to pesticides during their agricultural application resulting in potential population disruption. To study these potential pathways, amphibians were exposed to three different classes of pesticides. Atrazine is one of the most commonly used herbicides, triadimefon is a fungicide and fipronil is an insecticide. In spring and summer 2012, southern leopard frogs (Rana sphenocephala), Fowler’s toads (Bufo fowleri), gray treefrogs (Hyla versicolor), green treefrogs (Hyla cinerea) and barking treefrogs (Hyla gratiosa) were collected from the University of Georgia’s Whitehall Forest and reared through 60-90 days post-metamorphosis at the USEPA in Athens, GA. Amphibians were exposed to active ingredients through indirect contact with pesticide contaminated soil. After an 8 hour dermal exposure experiment, body burdens (ppm) for both parents and metabolites were quantified using a liquid chromatographymass spectrometry. Atrazine metabolized into both desethyl atrazine and deisopropyl atrazine which consisted of 11-46% of the total atrazine body burden. The active ingredient triadimefon (TDN) was metabolized into triadimenol (TDL) which consists of two diastereomers a and b (a: 1S,2R; 1R,2S; b: 1S,2S; 1R,2R). All frog species analyzed for TDL exhibited higher body burdens for the less toxic TDL b diastereomer compared to the more toxic diastereomer TDL a. Analyses showed higher concentrations of TDL compared to TDN in the arboreal gray treefrog and the terrestrial toad, whereas all other species had higher concentrations of the parent compound. Although amphibian body burdens between fipronil enantiomers were not statistically significant, there were differences across species. The Fowler’s toad exhibited the highest body burdens for fipronil, while the three arboreal treefrog species accumulated the least. Gaining knowledge on species specific differences in metabolism of pesticides will be important in estimating risk to amphibians as non-target organisms considering pesticide metabolites can occasionally be more toxic than the parent compound.
