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BIOACCUMULATION, BIOTRANSFORMATION, AND METABOLITE FORMATION OF FIPRONIL AND CHIRAL LEGACY PESTICIDES IN RAINBOW TROUT
Citation:
KONWICK, B. J., A. W. GARRISON, M. C. BLACK, J. K. AVANTS, AND A. T. FISK. BIOACCUMULATION, BIOTRANSFORMATION, AND METABOLITE FORMATION OF FIPRONIL AND CHIRAL LEGACY PESTICIDES IN RAINBOW TROUT. ENVIRONMENTAL SCIENCE & TECHNOLOGY. American Chemical Society, Washington, DC, 40(9):2930-2936, (2006).
Impact/Purpose:
To determine the environmental occurrences, fate, and effects of the enantiomers of selected chiral pesticides and other chiral pollutants.
Description:
To assess the fate of current-use pesticides it is important to understand their bioaccumulation and biotransformation by aquatic biota. We examined the dietary accumulation and enantioselective biotransformation of the chiral current-use pesticide fipronil, along with a mixture of selected chiral [alpha-hexachlorocyclohexane (alpha-HCH), heptachlor epoxide (HEPX), polychlorinated biphenyls (PCBs) 84, 132, 174, o,p'-DDT, and o,p'-DDD], and non-chiral (p,p'-DDT, p,p'-DDD) organochlorine compounds in juvenile rainbow trout (Oncorhynchus mykiss). Fish rapidly accumulated all compounds, as measured in the carcass (whole body minus liver and GI tract) during the 32 d uptake phase, which was followed by varying elimination rates of the chemicals during the 96 d depuration period. No biotransformation was observed for alpha-HCH, HEPX, PCB 174, o,p'-DDT, or o,p'-DDD based on consistent enantiomeric fractions (EFs) in the fish and their t(1/2)s falling on a log Kow - log t(1/2) relationship established for recalcitrant contaminants in fish. p,p'-DDT and PCBs 84 and 132 were biotransformed based on the former's t(1/2) position below the log Kow - log t(1/2) relationship and the PCBs change in EF. Fipronil was rapidly biotransformed, based on a change in EF, a t(1/2) which fell below the log Kow - log t(1/2) relationship, which accounted for 88% of its elimination, and the rapid formation of fipronil sulfone, a known metabolite. Fipronil sulfone was found to persist longer than its parent compound fipronil and needs to be considered in fate studies of fipronil. This research demonstrates the utilities of the log Kow - log t(1/2) relationship as a mechanistic tool for quantifying biotransformation and of chiral analysis to measure biotransformation in fish.