CSI Principal Consultant, John Frew presented the following presentations at the 2016 American Chemistry Society (ACS) Fall National Meeting – AGRO Division in Philadelphia, PA – August 21-25, 2016. Please find the abstracts and presentations below:
Abstract: In vivo time-course studies were conducted with rainbow trout to characterize the disposition and elimination of imidacloprid, a neonicotinoid insecticide. Animals confined to respirometer-metabolism chambers were injected with a low (47.6 µg/kg), medium (117.5 µg/kg), or high (232.7 µg/kg) dose of imidacloprid and then allowed to depurate for 36 to 48 h. Plasma and water expired over the gills were sampled from all 3 groups at multiple intervals throughout the depuration period. Urine was collected at these same intervals from the medium dose group. The brain, kidney, liver, white muscle and bile were sampled from each animal at the end of the test. Biotransformation of imidacloprid was evaluated in liver S9 fractions using an in vitro substrate depletion approach. The plasma time-course data indicated a brief (4–6 h) distributional phase followed by a log-linear terminal elimination phase. These data were subsequently evaluated by non-compartmental kinetic analysis. Mean fitted values for the steady-state volume of distribution (VD) were 1.72, 1.81 and 2.23 L/kg, and mean whole-body clearance (CLWB) values were 0.0217, 0.0195 and 0.0270 L/h/kg for the low, medium and high dose groups, respectively. Estimated whole-body half-lives for the same groups were 67.0, 68.4 and 68.1 h, respectively. The two-fold greater VD over that predicted for relatively polar compounds indicated some distribution of imidacloprid outside of total body water. Tissue:plasma concentration ratios reflected the relative affinity of imidacloprid for individual tissues under near-equilibrium conditions and were consistent with modeled VD values. A mass balance analysis of expired water data revealed that branchial clearance accounted for approximately 50% of CLWB, while an initial analysis of urine data suggested that renal clearance could account for 25–30% of CLWB. A lack of measurable substrate depletion from the S9 fractions suggested that hepatic metabolism did not contribute to overall clearance. These data provide information required to model uptake, accumulation, and clearance of imidacloprid by fish in known or hypothetical environmental exposures.
Abstract: The Pyrethroid Working Group has compiled data from all available pyrethroid monitoring programs in surface water and sediment across the U.S. Many of the monitoring programs targeted agricultural and urban sampling locations where pyrethroid concentrations were expected to be high (e.g., irrigation channels and residential storm drain outlets), and included event-driven sampling intended to capture peak pyrethroid concentrations associated with storm events. The database currently contains more than 65,000 analytical results for nine key pyrethroids from approximately 5,000 whole water samples, 2,500 filtered water samples, and 2,400 sediment samples collected from 1992 to 2014. Nearly 90% of these records, including most of the highest measured concentrations, are from California. The goal of this analysis was to identify the factors that contributed to the highest measured concentrations at agricultural and urban monitoring sites. Monitoring reports were reviewed for information on site characteristics, co-occurrence of storm events, and other factors associated with sample collections. Site locations, drainage areas and surrounding features were examined using GIS software. Pyrethroid use in agricultural drainage areas was estimated using data from the CA Pesticide Use Reporting (PUR) database. Pyrethroid use in urban drainage areas was estimated based on population and housing density data from the US Census. Many of the highest measured pyrethroid concentrations were reported from agricultural drainage channels and urban stormwater outfalls, and most were associated with wet season sampling. The highest concentrations for most pyrethroids were 10-fold greater, and in some cases more than 100-fold greater, than 99% of all measured concentrations. Even the 99th percentiles of the measured concentrations were below nearly all of the 90th percentile concentrations predicted by standard pesticide exposure modeling, indicating the extreme conservatism of modeling assumptions.
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For a list of other events that CSI will be attending in 2016, visit our Events page.