T9 PM Pyrethroid Insecticides in Urban and Agricultural Environments
Tuesday, 15 November 2005: 1:50 PM - 5:30 PM in 339-340

(SHA-1117-664582) Risk Assessment Approach to Evaluate Exposure and Risk from Agricultural and Urban Uses of Pyrethroids.

Shamim, M¹, Rexrode, M¹, Melendez, J¹, Parker, R¹, ¹ Environmental Protection Agency, Washington, DC, USA

ABSTRACT- The Environmental Protection Agency has completed its screening-level ecological risk assessments for a number of synthetic pyrethroids relative to their use on agricultural crops (e.g., cotton, corn, wheat) and urban settings (e.g., mosquito abatement use). These assessments show that pyrethroids pose a potential risk to aquatic species, including fish, invertebrates, and sediment-dwelling organisms. Furthermore, pyrethroid bioavailability is not expected to be completely mitigated through adsorption to sediments and particulate matter. Because of the toxicity, mode of action, high partition coefficients (K_ocs), and moderate to high persistence of this class of compounds, the Agency considered pyrethroid bound sediments as an important aquatic exposure component. In the absence of data, the Agency estimated sediment toxicity values by using the equilibrium partitioning method (EqP) for extrapolating sediment/pore water exposure values. This method is based on the assumption that partitioning of pyrethroids between sediment organic carbon and pore water is at equilibrium. The estimated toxicity values in conjunction with model generated sediment/pore water exposure values were used to calculate the Risk Quotients (RQs). In its assessment of this class of compounds, the Agency also used an innovative modeling approach involving the spray drift model AGDISP coupled with the surface water model PRZM/EXAMS to predict potential exposure and risk to aquatic ecosystems from pyrethroid mosquito abatement uses. The effect of spray drift and the use of buffer zones in reducing exposure to bodies of water adjacent to treated areas was also investigated. This abstract has been subjected to review by EPA's Office of Pesticide Programs and was approved for submission. Approval does not signify the contents reflect the views of EPA, nor does mention of trade names or commercial products constitute endorsement or recommendation for use.

Key words: invertebrates, sediment-dwelling organisms, mosquito abatement use, risk quotients