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USER MANUAL FOR EXPRESS, THE EXAMS-PRZM EXPOSURE SIMULATION SHELL
Citation:
BURNS, L. A. USER MANUAL FOR EXPRESS, THE EXAMS-PRZM EXPOSURE SIMULATION SHELL. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-06/095 (NTIS PB2007-100140), 2006.
Impact/Purpose:
Extend existing model technologies to accommodate the full range of transport, fate and food chain contamination pathways, and their biogeographical variants, present in agricultural landscapes and watersheds. Assemble the range of datasets needed to execute risk assessments with appropriate geographic specificity in support of pesticide safety evaluations. Develop software integration technologies, user interfaces, and reporting capabilities for direct application to the EPA risk assessment paradigm in a statistical and probabilistic decision framework.
Description:
The Environmental Fate and Effects Division (EFED) of EPA's Office of Pesticide Programs(OPP) uses a suite of ORD simulation models for the exposure analysis portion of regulatory risk assessments. These models (PRZM, EXAMS, AgDisp) are complex, process-based simulation codes that combine chemical and physical data required by EPA of industry with agronomic, physiographic , and limnological descriptions of the environmental settings into which pesticides are released. This complexity, while providing significant sophistication and specificity in analysis, has posed difficulties in maintaining a transparent, reproducible process clearly devoid of arbitrariness in parameter selections, exposure metrics, and interpretation of ecological and human health risks. This project was undertaken to develop a Graphical User Interface (GUI) to combine regulatory simulation models, their supporting databases, regulatory "scenarios" for major crops, and data input screens for chemical properties into a user-friendly "simulation shell" lending itself to consistent analytical practices and reproducible exposure and risk assessments. The resulting computer software "Express (the EXAMS - PRZM Exposure Simulation Shell)" is a joint project of EFED and ORD. EFED designed and funded an initial draft of the Express software, and retains responsibility for developing and maintaining crop-specific modeling scenarios for regulatory analyses. ORD is responsible for continuing development, quality control, maintenance, and public availability of the software and its constituent models and analytical modules. With the completion of Express, exposure metrics (peak, 4-day, 21-day, 60-day, annual) for ecological and human health risk assessments can be easily and conveniently and, as importantly, reproducibly, developed for any or all of the agronomic scenarios developed by EFED. Probabilistic analyses (Weibull distribution) of these exposure metrics are derived by coupling 30-year time-series of meteorological data to linked PRZM/EXAMS simulation studies. Express significantly reduces the variability, lack of reproducibility by external analysts, and perceived arbitrariness of EPA's regulatory processes for determining the safety and appropriate uses of registered pesticides.