CSI’s Risk Assessment Team made the following technical presentations at the 253rd American Chemical Society (ACS) National Meeting – ENVR Division in San Francisco, CA (April, 2017).
Concentrations of Synthetic Pyrethroids in Surface Water and Sediment from Agricultural and Urban Land Use Areas – Thoughts About Interpretations of Monitoring Data, Jeffrey Giddings, David Campana, Jeffrey Wirtz. Presentation at the 253rd ACS National Meeting, San Francisco, CA, April 2017.
Abstract: Aquatic organisms can be exposed to pyrethroid insecticides present in the water column and pore water, and sorbed to the food and sediment particles they consume. Accumulation in organisms is dependent not only on the concentrations present in the environment, but also on chemical bioavailability. Pyrethroids are highly hydrophobic compounds with log KOW >6. Within aquatic systems, these compounds associate strongly with aquatic plants, sediments, and dissolved organic carbon (DOC) in the water column and sediment pore water. The partitioning of pyrethroids to DOC and organic materials dramatically reduces the fraction of freely dissolved, bioavailable chemical. Equilibrium partitioning (EqP) relationships between bioavailable concentrations in water and sediment pore water and organism lipid content are used to estimate chemical accumulation in organisms, independent of the exposure route. EqP theory has been applied to pyrethroids to relate aqueous uptake and toxicity to freely dissolved pyrethroids in water and sediment pore water. Ingestion of pyrethroids sorbed to sediment particles or food represents another potential route of exposure. An examination is being conducted to determine the relative contributions of aqueous and dietary uptake to pyrethroid accumulation at aquatic trophic levels ranging from primary consumers such as benthic invertebrates, to predatory fish trophic groups such as benthivores and piscivores. Regardless of the route of exposure, studies have shown that aquatic organisms do not accumulate pyrethroids significantly because metabolic transformation to nontoxic degradates rapidly reduces concentrations within the body.
Bioconcentration, Biotransformation, and Biomagnification of Pyrethroids, Jeffrey Giddings, Kayla Campasino. Presentation at the 253rd ACS National Meeting, San Francisco, CA, April 2017.
Abstract: Once sufficient credible real-world monitoring data has been accumulated for a pesticide (class), the resulting distribution of concentrations/detection frequencies provides a perspective on real world surface water exposure to provide context for Estimated Environmental Concentrations (EECs) generated using standard FIFRA Tier II models/scenarios. For pyrethroids, the monitoring data from agricultural catchments reflect worst-case ranges of exposure settings; the high percentile concentrations from these distributions are lower than the corresponding simulated Tier II EECs by several orders of magnitude for agricultural use patterns. Development of a pyrethroid-specific conceptual model of potential aquatic behavior indicates that some chemical class-specific environmental fate factors account for a portion of these discrepancies. However, detailed analyses of over 30 sources of potential uncertainty inherent in standard Tier II agricultural crop scenarios (including the percent of crops grown at the catchment scale, the density of crops treated and the intrinsic erosion/runoff vulnerability of scenarios) can be shown to contribute substantially to the over-prediction by Tier II exposure modeling approach. For agricultural uses, it can be shown that, when even a few of these factors co-occur in a catchment, even refined EECs will exaggerate real-world exposures by 5 to 20-fold and often by a much greater margin while still retaining considerable conservatism. A similar analysis was performed for potential sources of uncertainty in residential exposure assessments. One key finding is that the current modeled EECs are not incorrect, they simply reflect concentrations with a much lower probability of occurrence than the standard FIFRA protection goal of a return frequency of 1 year in 10 in a 90th percentile vulnerability use area for a particular crop. This highlights the importance of developing clear regulatory protection goals for surface water and ensuring that the standard models and scenarios reflect those goals. Equally, it is critical for risk managers to appreciate the real-world relevance of EECs generated using current Tier II scenarios.
For a complete list of events that CSI will be attending in 2017, please visit our Events page.