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HP7 Pyrethroids, Chemistry, Toxicity, and TIE Methods
(614) Preliminary Identification of Bifenthrin Toxicity to Hyalella azteca in Sediment from the Central Valley, California.
Phillips, B1, Anderson, B1, Hunt, J1, Nicely, P1, Tjeerdema, R1, Rowan, J2, Miller, J3, Crane, D4, Mekebri, A4, 1 University of California, Davis, Monterey, CA, USA2 Central Valley Regional Water Quality Control Board, Sacramento, CA, USA3 Aquascience, Davis, CA, USA4 California Department of Fish and Game, Rancho Cordova, CA, USA
ABSTRACT- As organophosphate pesticide use declines, increased use of synthetic pyrethroid pesticides is expected. Synthetic pyrethroids are highly insoluble and are primarily associated with sediments in the environment. In addition to US EPA procedures, toxicity identification evaluation (TIE) methods specifically designed to indicate pyrethroid toxicity are being developed. The results of several TIE methods suggest bifenthrin was the cause of toxicity to Hyalella azteca in sediment from an agricultural drainage stream. After determining that interstitial water extracted from the sediment was highly toxic to amphipods, we subjected two samples to TIE treatments. The first TIE used US EPA Phase I techniques to characterize the sample. Toxicity of the sample was 2.5 times greater with the addition of piperonyl butoxide (PBO), a pyrethroid synergist. In the second TIE, toxicity was increased 4.3 times with the addition of PBO. Toxicity increased 11.2 times when the sample was tested at 15°C instead of 23°C. Increased toxicity at lower temperatures is characteristic of Type I pyrethroids. Toxicity was also reduced with addition of carboxylesterase, an enzyme that has been demonstrated to degrade pyrethroids. Interstitial water contained relatively low concentrations of pesticides except bifenthrin (48 ng/L). This concentration was in the range toxic to other crustacea. Dose response experiments with bifenthrin and other synthetic pyrethroids are being conducted.
Key words: TIE, Hyalella azteca, Bifenthrin, Sediment
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