The Pesticide Root Zone Model Groundwater (PRZM-GW) was developed as a regulatory model to estimate pesticide concentrations in vulnerable groundwater supplies. Input parameters include pesticide fate properties, environmental factors such as soil type, aquifer depth and weather, and agronomic practices, including application method, timing, and frequency of application.  PRZM-GW output data include peak and time weighted concentrations. The Office of Pesticide Programs implemented the use of PRZM-GW as an exposure model in 2012. As part of the implementation, data were collected from drinking water assessments completed in 2013 to support pesticide regulatory actions. These data were evaluated to determine 1) the effectiveness of PRZM-GW as a Tier 1 screen, 2) the impacts of the standard refinements, 3) a comparison of PRZM-GW estimated drinking water concentrations with Screening In GROund Water (SCI-GROW) estimated values, and 4) risk assessment and risk management outcomes.  Additional comparisons of PRZM-GW simulated pesticide concentrations to targeted and non-targeted data were conducted, including an analysis of the effects of pesticide properties and model input value selection criteria on predicted concentrations. The results of these analyses demonstrate that PRZM-GW is an effective and versatile model that can be used as a Tier 1 and Tier 2 risk assessment tool for estimating pesticide concentrations in groundwater.

Implementation of the Pesticide Root Zone Model Groundwater for use in EPA's pesticide exposure assessments

248th National Meeting (2014)

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