Environmental Fate Simulator Overview
EPA requires high throughput computational systems for conducting spatiotemporal exposure analyses. The ability requires an understanding of the processes controlling transport and transformation. More specifically, knowledge of the molecular descriptors (as a function of chemical structure), as well as the environmental descriptors (as a function of geographical location), is required for the prediction of reaction rates and pathways and partitioning behavior.
Although significant progress has been made over the past decade concerning scientific understanding of the processes controlling the transport and transformation of organic chemicals in natural systems, much of this process science has not been incorporated into existing environmental fate & transport tools and models currently used to assess risks from chemical exposures. This can be attributed to the lack of a systematic process that allows for the encoding of the process science as it becomes available through in-house research, publication in the peer-reviewed literature and data submitted under the chemical registration procedures of the Toxic Substance Control Act (TSCA) and Federal Insecticide, Fungicide and Rodenticide Act (FIFRA).
Cheminformatics tools are now available for the encoding of this process science through the storage and search of structural and non-structural data, and the encoding of transformation reactions and reaction rules for the generation of chemically feasible transformation products.
Development of the Environmental Fate Simulator
The design and development of the Environmental Fate Simulator represents an integrated effort involving process scientists, multi-media modelers and software engineers. The process scientists are focused on the application of the cheminformatics tools for the encoding of the process science underlying abiotic (i.e., reduction, hydrolysis, photolysis, and water disinfectant oxidation) and biotic (i.e., aerobic and anaerobic biodegradation) transformation processes. The process science for each of these transformation processes is being captured in reaction libraries that will be executed to provide the dominant transformation pathways and products for the chemical of interest as a function of environmental conditions. EPA multi-media modelers are focused on the design of the Environmental Fate Simulator to insure the development of a system that meets EPA’s various risk assessment needs. EPA software engineers are providing the necessary coding for the integration of the chemoinformatic tools with the required software technologies that will allow for development of both generic and user-defined exposure scenarios, as well as access to web-based databases and linkage to computational tools such as SPARC (SPARC Performs Automated Reasoning in Chemistry) and EPI Suite (Estimation Program Interface (EPI) Suite) for the calculation of molecular descriptors.
Integrating robust process science
The Environmental Fate Simulator will represent the integration of the most robust process science available with state-of-the-art chemoinformatic tools for the storage of process science relating to chemical structure and chemical processes, and the modeling software technologies developed through EPA’s Integrated Environmental Modeling (IEM) Program.
These modeling technologies will allow for the seamless access to databases and the parameritization of environmental fate and transport models necessary for the estimation of the environmental concentrations of chemical stressors in soil and aquatic ecosystems.
This computational tool will be used to screen for potential routes of exposure of humans and wildlife to organic chemicals for which the physicochemical and reactivity data is sparse. The anticipated impact of the Environmental Fate Simulator is to provide EPA with a computational system to conduct high-throughput screening level exposure assessments based on predefined or user-defined exposure scenarios.
Technical Team - Eric Weber (team contact), Caroline Stevens, Gene Whelan, Justin Babendreier, Kurt Wolfe, Rajbir Parmar, Mike Galvin, Said Hilal