Join CSI in San Francisco at the ACS National Meeting: ENVR Division!

The 253rd ACS National Meeting (April 2-6, 2017) is rapidly approaching. Staff from Compliance Services International (CSI) will be in attendance and will be available for consultation throughout the meeting. Please plan to visit with our regulatory experts (Jeffrey Giddings and Kayla Campasino) at the ENVR: Division of Environmental Chemistry session, who will be presenting or are affiliated with the following:

Wednesday Afternoon – ENVR: Pesticides in Surface Water: Monitoring, Modeling, Mitigation, Risk Assessment & Regulation

  • 555 – Concentrations of synthetic pyrethroids in surface water and sediment from agricultural and urban land use areas.
  • Salons 10/11 – San Francisco Marriott Marquis
  • 2:55 pm – 3:15 pm
  • Abstract: The Pyrethroid Working Group (PWG) continues to compile all available data on the concentrations of 9 synthetic pyrethroids in US surface water and sediment. The database is very large (more than 8,000 samples through 2014) and more than 90% of the data are from regulatory monitoring programs in California. More than half of the sampling locations are on first- and second-order streams. Distributions of individual pyrethroid compounds in water and sediment samples are strongly skewed, with a very few samples containing concentrations much greater than all of the others. The highest concentrations are often associated with stormwater drains or agricultural drainage systems, not with receiving waters, and occur in localized areas of high pyrethroid use. Pyrethroids are detected in only 3% of filtered water samples. Detection frequencies are much greater in whole water samples, but a large fraction of the pyrethroid in whole water samples is bound to particulate or dissolved organic matter; only the freely dissolved fraction is bioavailable and able to cause toxicity. Sediment sampling protocols focus on depositional areas, which are where pyrethroid concentrations tend to be greatest but do not typically represent the majority of the wetted streambed. Despite these factors, the distributions of measured pyrethroid concentrations in water and sediment from urban and agricultural areas are lower, often much lower, than concentrations estimated by standard exposure models.

Thursday Morning – ENVR: Pesticides in Surface Water: Monitoring, Modeling, Mitigation, Risk Assessment & Regulation

  • 896 – Examination of the relative contributions of aqueous and dietary uptake to pyrethroid accumulation in organisms at different aquatic trophic levels.
  • 2007 – Moscone Center
  • 8:25 am – 8:45 am
  • 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.

Thursday Afternoon – ENVR: Pesticides in Surface Water: Monitoring, Modeling, Mitigation, Risk Assessment & Regulation

  • 976 – Why are real-world surface water exposure distribution much lower than US EPA FIFRA Tier II EECs?  An Evaluation based on pyrethroid insecticides.
  • 2007 – Moscone Center
  • 2:05 pm – 2:25 pm
  • 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.

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We look forward to seeing you at the meeting!

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