GEM GUI – Stochastic Weather Model
The Stochastic Weather Model, GEM (Generation of Weather Elements for Multiple Applications) was developed by the USDA and is used by various federal, state, and private agencies. It is a free-ware program with its source code available on the Internet. The model is continually being tested and updated (latest development in research; allowing model to simulate weather conditions at smaller spatial and temporal scales). The purpose of the project is to develop a graphical user interface for the stochastic weather model, GEM, that allows the quick and easy implementation of GEM and produces a meteorological file formatted for direct use in PRZM or GLEAMS. This GEM GUI will also be developed so that it can be used in iterative simulations for probabilistic risk analysis.
GemPRO Home Page
Geospatial Exposure Modeling (GeoSEM)
Every risk assessment has spatial components associated with the distribution of the chemical in the environment, and the movement of the human or ecological populations that may be exposed to the chemicals. There is an increasing awareness among environmental scientists and regulators regarding the potential application of geographic information systems (GIS) and geospatial statistics in risk assessment. In 2002-2003, the PRA Center applied a software development process to SRC's exposure model called GeoSEM. This software combines a Visual Basic user interface with MapObjects mapping capability to provide a user-friendly tool for risk assessors to explore the impact that spatial information may have on risk management decisions. In Spring of FY03, a preliminary test version of GeoSEM was distributed to the modeling community. Future activities will focus on developing straightforward, reproducible examples to facilitate the use of geostatistical techniques in risk assessments and improve the cost effectiveness of sample designs.
GeoSEM Home Page
PBPK Model for 2-4D
A novel physiologically based pharmacokinetic (PB/PK) model was developed for 2-4D, an important herbicide in forestry applications that poses a potential health risk to pesticide applicators and the ecosystem. Few other PBPK models of weak organic acids have been developed, and none for 2-4D. In FY03, the software development was completed and a manuscript was submitted for publication in a scientific journal. Current activities are focusing on applying a probabilistic modeling capability. This will facilitate conducting a rigorous sensitivity analysis, which is critical to understanding the important assumptions and for guiding further scientific study of pesticides with toxicological properties similar to 2-4D. Reprints of the manuscript as well as more information can be obtained at pdurkin@twcny.rr.com
ISE Model
The Integrated Stochastic Exposure (ISE) Model is a probabilistic exposure model developed by SRC for use in childhood lead risk assessments. ISE uses the same exposure, uptake, and biokinetic variables as the U.S. EPA IEUBK Model for Lead in Children.
ISE Model Home Page
Generic PRA Model
SRC has developed a probabilistic model to quantify variability and uncertainty in exposures to lead. The model implements a variety of approaches that may be implemented in any chemical risk assessment, including one-dimensional and two-dimensional Monte Carlo simulation, as well as MicroExposure event simulation. Users can define input variables with either point estimates or probability distributions from a menu of options. This model can be revised to accommodate any exposure assessment scenario, and the biokinetic module for lead can be replaced with a series of toxicity variables relevant to cancer or non-cancer health endpoints. This effort has not yet been initiated, but will be a priority with future funding of the PRA Center.

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