You are here:
INTEGRATED PROBABILISTIC AND DETERMINISTIC MODELING TECHNIQUES IN ESTIMATING EXPOSURE TO WATER-BORNE CONTAMINANTS: PART 1 EXPOSURE MODELING
Citation:
Wilkes, C. R., J N. Blancato, S C. Hern, F W. Power, AND S. S. Olin. INTEGRATED PROBABILISTIC AND DETERMINISTIC MODELING TECHNIQUES IN ESTIMATING EXPOSURE TO WATER-BORNE CONTAMINANTS: PART 1 EXPOSURE MODELING. Presented at Indoor Air 2002, Monterey, CA, June 30-July 5, 2002.
Impact/Purpose:
Research will be conducted to develop and apply integrated microenvironmental, and physiologically-based pharmacokinetic (PBPK) exposure-dose models and methods (that account for all media, routes, pathways and endpoints). Specific efforts will focus on the following areas:
1) Develop the Exposure Related Dose Estimating Model (ERDEM) System.
Includes: Updating the subsystems and compartments of the ERDEM models with those features needed for modeling chemicals of interest to risk assessors;
Designing and implementing the graphical user interface for added features.
Refining the exposure interface to handle various sources of exposure information;
Providing tools for post processing as well as for uncertainty and variability analyses;
Research on numerical and symbolic mathematical/statistical solution methods and computational algorithms/software for deterministic and stochastic systems analysis.
2) Apply ERDEM and other quantitative models to understand pharmacokinetics (PK) and significantly reduce the uncertainty in the dosimetry of specific compounds of regulatory interest.
Examples of the applications are:
exposure of children to pesticides
study design
route-to-route extrapolation
species extrapolation
experimental data analysis
relationship between parametric uncertainty and the distribution of model results
validity of scaling methods within species
validity of scaling methods from one species to another species
reduction of uncertainty factors for risk assessment
Description:
Exposure to contaminants originating in the domestic water supply is influenced by a number of factors, including human activities, water use behavior, and physical and chemical processes. The key role of human activities is very apparent in exposure related to volatile water-borne contaminants, since the release of a contaminant and resultant exposure is related to the activity of the exposed individual. Estimates of human exposure are often plagued by a poor understanding of many of the factors affecting the predictions. For example, existing activity pattern surveys do not contain integrated information about relevant water-using activities such as showers, and showering studies do not collect relevant information about the location, duration, and water temperature. Methods for integrating diverse data resources into a consistent modeling framework have been developed and implemented for prediction of exposure to water-borne contaminants. These methods are implemented in a computer model entitled the Total Exposure Model (TEM). TEM predicts the exposure and dose to an individual resulting from use of a contaminated water supply by modeling the fundamental physical and chemical processes that occur during interaction between the contaminated media (in this case water and air) and the exposed individual.
An application of the model to estimate inhalation, dermal and ingestion exposure to several common waterborne contaminants to several population groups will be presented. The exposure study considers the expected exposure of a population group to water-borne trichloethylene (TCE), dichloroacetic acid (DCA) and trichloroacetic acid (TCA). The distributions of exposures are estimated for several population groups to each compound as a function of route of exposure (inhalation, dermal and ingestion). The results are provided as inputs to a pharmacokinetic model, ERDEM (Exposure Related Dose Estimating Model) where target organ concentrations and doses are estimated across the population groups. This paper presents the results of the exposure modeling and analysis. A second, related paper will also be presented providing the methods and results of the pharmacokinetic modeling.
This work has been funded wholly or in part by the United States Environmental Protection Agency and has been approved for publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.