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#2) Enantiomer Specific Measurements of Current-use Pesticides in Aquatic Systems
Citation:
Ulrich, E., L. McMillan, Q. Wang, T. Albertson, G. Cho, K. Kuivila, W. Lao, S. Peoples, R. Reif Lopez, AND P. TenBrook. #2) Enantiomer Specific Measurements of Current-use Pesticides in Aquatic Systems. IUPAC International Congress of Pesticide Chemistry, San Francisco, CA, August 10 - 14, 2014.
Impact/Purpose:
The National Exposure Research Laboratory (NERL) Human Exposure and Atmospheric Sciences Division (HEASD) conducts research in support of EPA mission to protect human health and the environment. HEASD research program supports Goal 1 (Clean Air) and Goal 4 (Healthy People) of EPA strategic plan. More specifically, our division conducts research to characterize the movement of pollutants from the source to contact with humans. Our multidisciplinary research program produces Methods, Measurements, and Models to identify relationships between and characterize processes that link source emissions, environmental concentrations, human exposures, and target-tissue dose. The impact of these tools is improved regulatory programs and policies for EPA.
Description:
Research has shown that current-use pesticides can enter urban and agricultural watersheds and adversely affect aquatic organisms. A potential cause may be higher concentrations of the more toxic pesticide enantiomer present in the pesticide mixture. The presence of pesticide enantiomers is dictated by the formulation (e.g., racemic or enriched), transport and degradation rates (usually stereoselective if biotic, non-selective if abiotic) which can vary between the mirror images. We developed a new GC/MS method for stereoisomer-specific analysis of the current-use pesticides fipronil, cis-bifenthrin, cis-permethrin, cypermethrin, and cyfluthrin. Single enantiomer standards were obtained for the first four compounds to allow a direct link to enantiomer toxicity. The method was applied to several different sets of extracts including lab dosed salmon and various environmental media (concrete runoff, sediment, river-, surface-, storm-, and waste- water) that were collected from California aquatic systems. Enantiomer fractions (EFs) for racemic standards ranged from 0.351 to 0.592 for fipronil, 0.457 to 0.521 for bifenthrin, and 0.429 to 0.525 for cis-permethrin. At least in part due to the wide range, EFs for most environmental samples were the same as racemic standards. An interesting exception was for permethrin washed off of concrete, which had EFs ranging from 0.094 to 0.502. As expected, the biological fish samples (dosed with bifenthrin) were also non-racemic, ranging from 0.378 to 0.499. Enantioselective processes can easily occur in this matrix