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A POPULATION EXPOSURE MODEL FOR PARTICULATE MATTER: SHEDS-PM
Citation:
Burke, J M., R. Vedantham, T R. McCurdy, J Xue, AND A H. Ozkaynak. A POPULATION EXPOSURE MODEL FOR PARTICULATE MATTER: SHEDS-PM. Presented at American Association of Aerosol Research, Charlotte, NC, October 7-11, 2002.
Impact/Purpose:
The overall objective of this research is to develop, apply, and evaluate a human exposure model for predicting population exposures to the components of particulate matter (PM) identified as potential toxic agents contributing to adverse health effects.
Description:
The US EPA National Exposure Research Laboratory (NERL) has developed a population exposure and dose model for particulate matter (PM) that will be publicly available in Fall 2002. The Stochastic Human Exposure and Dose Simulation (SHEDS-PM) model uses a probabilistic approach to predict the distribution of PM exposures and deposited dose for a specified population. SHEDS-PM estimates the population distribution of PM exposures by sampling stochastically from various input distributions, and accounts for both ambient outdoor PM concentrations and emissions from indoor sources of PM (e.g., cigarette smoking, cooking). A steady-state mass-balance equation is used to calculate indoor PM concentrations for the residential microenvironment using ambient outdoor PM concentrations and distributions of available physical factor data (e.g., air exchange, penetration, deposition). PM concentrations in non-residential microenvironments are calculated based on distributions of the effective penetration of ambient outdoor PM, which were produced using regression analysis of available indoor-outdoor measurement data for vehicles, offices, restaurants/bars, schools and stores. SHEDS-PM generates a simulation population using demographic data for the specified population, and randomly assigns each simulated individual an appropriate activity diary from NERL's Consolidated Human Activity Database (CHAD). PM exposure for each individual is determined from the calculated microenvironmental PM concentrations and the time spent in each microenvironment. Activity-specific ventilation rates are used to determine the inhaled dose and a conventional pulmonary deposition model is used to estimate the deposited dose to three regions of the lung. Model outputs include distributions of PM exposure and dose in various microenvironments (indoors, in vehicles, outdoors) for the population, and the contributions from both PM of ambient origin and indoor sources of PM in these microenvironments. An executable version of the SHEDS-PM model with a graphical user interface (GUI) is being developed using the MATLAB software package. The GUI allows the user to define the modeling scenario of interest, to select input data files, and to modify various input parameters. The main input data requirements for the SHEDS-PM model include ambient outdoor PM concentrations that can be either measured or modeled data, and demographic data for population of interest from the US Census. The GUI also allows the user to select displays of the model results as tables or plots, and to save the data to an output file. Development of the SHEDS-PM model has identified the need for applicable data to use for model inputs, to further refine the model algorithms, and for evaluation of the model predictions.
This work has been partially funded by the United States Environmental Protection Agency under Contract No. 68-W-99-002 to Science Applications International Corporation. It has been subjected to Agency review and approved for publication. Mention of trade names or commercial products does not constitute endorsement or recommendation for use.