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Assessment of SHEDS model for air sample placement based on population exposure estimates following a Bacillus anthracis outdoor release
Citation:
Burke, J. Assessment of SHEDS model for air sample placement based on population exposure estimates following a Bacillus anthracis outdoor release. U.S. Environmental Protection Agency, Washington, DC, EPA/600/R-18/281, 2018.
Impact/Purpose:
Strategies for emergency response following a wide-area release of a biological agent may utilize modeling tools to prioritize air sample placement for guiding decontamination activities. These models estimate air concentrations, but don't account for people's behaviors and activities which could result in some populations having greater risk of exposure. A case study application of the previously developed Stochastic Human Exposure and Dose Simulation (SHEDS) model for particulate air pollutants was performed for a hypothetical Bacillus anthracis outdoor release scenario to demonstrate and assess how the model output could be used for providing estimates of human exposures and dose for biological agents. Incorporating the potential risk of exposure in air sampling strategies for biological agents following an outdoor release may help decontamination efforts reduce risks to the population.
Description:
As part of EPA/ORD's Homeland Security research program, there is a need to improve strategies for emergency response following a wide-area release of a biological agent. Modeling tools that simulate the dispersion of biological agents for a wide-area release may be used to prioritize air sample placement based on estimated concentrations. However, dispersion models don't account for people's behaviors and activities which could result in some populations having greater risk of exposure. Human exposure models that account for variability in population demographics, human activity patterns, and the factors influencing infiltration of outdoor air indoors have previously been developed, and could be used to better guide decontamination efforts by incorporating potential risk of exposure in air sampling strategies. To explore this, a case study application was performed to assess the utility of the Stochastic Human Exposure and Dose Simulation for Particulate Matter (SHEDS-PM) model that provides estimates of human exposures by simulating representative individuals for a specific geographic location. The individuals time series of exposure and dose are estimated using human activity pattern data matched to each individual and the concentrations for each location they spend time in such as outdoors, indoors, and in vehicles. Results from the case study highlighted the impact that demographics and other factors such as day of week have on model estimates of exposure and dose due to their influence on activity patterns, as well as the importance of accounting for population mobility. Key advantages of the SHEDS model and its output identified through this case study are summarized, as well as current limitations and options for addressing them.