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Ecosystems Research

SPARC Performs Automated Reasoning in Chemistry

Issue
EPA needs high throughput computational systems to predict the fate and transport of a myriad of chemicals for which environmental data are unavailable. A prerequisite for understanding how chemicals behave in the environment is knowing the chemical properties required for predicting reaction rates, pathways, transformation products and partitioning behaviors.

Physico-chemical properties have been experimentally measured for less than 1 percent of the approximately 84,000 chemicals on EPA’s Toxic Substances Control Act (TSCA) inventory and the 100,000 chemicals registered in Europe’s Registration, Evaluation, Authorization and Restriction of Chemical substances (REACH) Program.

Recent trends in environmental regulatory strategies rely on predictive modeling to carry out complex scientific assessments required for defensible regulations. New models used in these assessments will require huge arrays of input data, however many of these data inputs are currently unavailable or not easily measured.

Action
EPA ecosystems researchers in Athens, Ga., have developed a predictive modeling system known as SPARC (SPARC Performs Automated Reasoning in Chemistry) for estimating chemical reactivity parameters and physical properties for a wide range of organic molecules.

Although still under development, the SPARC modeling system is being designed to incorporate multiple mathematical approaches to estimate important chemical reactions and behavior. It will then interface directly with air, water, and land models to provide EPA with data that can inform risk assessments and prioritize toxicity-testing requirements for regulated chemicals.

SPARC is being designed to provide physical properties and chemical reactivity parameters describing factors for air, water and other environmental media needed to develop and apply models such as the Environmental Fate Simulator and Reaction Pathway Simulator. This will allow EPA scientists to use SPARC for characterizing complex processes that influence the reactivity and environmental fate and transport of chemicals as a function of environmental conditions. The fate and reaction pathway models and a chemical property database developed using SPARC will be made available online.

Results and Impact
Research is being conducted to test and refine SPARC’s physical and chemical process models, and to extend them to describe transport and fate of organic pollutants in the environment. Chemical and physical property estimation using SPARC will be used to provide data on the reaction rates, pathways and transformation products of chemicals. This data will be used by EPA in scientific assessments necessary to evaluate the safety of chemicals; and for prioritizing toxicity-testing requirements for regulated chemicals.

Technical Team: Said Hilal

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