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Source to Dose Modeling
Additional Information
Current Research Tasks
Model Development - Exposure Models
Exposure models predict concentrations of pollutants in environmental media as well as describing the activities that bring an individual into contact with the contaminated media. The goal of this research is to refine the Stochastic Human Exposure and Dose Simulation (SHEDS) Model to improve both ease of use and provide additional modeling capabilities to better understand aggregate exposures and cumulative risks. Under this task a user-friendly, documented aggregate SHEDS-Multimedia version will be evaluated, refined, peer reviewed and disseminated. An improved source-to-concentration module will be developed that use fugacity principals to predict fate and transport of primary pollutants and that incorporates indoor chemistry algorithms to predict formation of secondary pollutants. A refined dietary module will be incorporated into the model. Procedures for estimating exposures to mixtures of chemicals and longitudinal exposures over time will be developed to provide inputs for cumulative risk assessments. In conjunction with other tasks, SHEDs and its modules (e.g., dietary module, fugacity module) will also be evaluated against data from field measurement studies and against estimates from other models. The outcome of this research will be a state-of-the-science probabilistic modeling tool for assisting risk assessors and risk managers in regulatory decision-making when human exposure estimates are required beyond the screening level. Details of Model Development - Exposure Models
Dose Model Development
Dose models describe how pollutants are absorbed into the body, distributed to various organs what the may or may not be metabolized and contribute to health problem. The goal of this research is to refine the Exposure Related Dose Estimating Model (ERDEM) to improve both ease of use and provide additional modeling capabilities and to assess cumulative risk. The ERDEM is a physiologically based pharmacokinetic (PBPK) modeling system that describes internal doses resulting from human exposure to chemicals. In this research task, the ERDEM front end will be modified to include an exposure time history repository that will take inputs from various exposure models so that a Monte Carlo simulation can be run. The system will also be modified to provide the user with an uncertainty analysis interface that will enable researchers to perform sensitivity and Monte Carlo analyses including correlated parameters such as volumes and blood flows. ERDEM components will be modified or new ones added as necessary to meet the Agency’s needs. These include intracellular modeling approaches, multiple compartment organs, and the development of Quantitative Structure Activity Relationship (QSAR) databases to make predictions for chemicals where data are lacking. The outcome of this research will be a state-of-the science PBPK/PD modeling tool that can be used by risk assessor and risk managers to improve regulatory decision making. Details of Dose Model Development