A Day-Night Population Exchange Model for Better Exposure and Consequence Management Assessments

In prior work, a day-night, indoor-outdoor population database was derived for the entire USA at 250 m grid resolution in order to improve exposure assessments for hazardous airborne contaminant releases. In order to enhance the utility of this database, we have recently derived algorithms for computing the “movement” of population between daytime and nighttime locations. This capability is useful for airborne contaminants that have a delayed health effect or could be spread from person to person (e.g., biological and infectious agents). For these cases, determining the population within the contaminant plume is just the first step; knowing where the dosed population ends up 12 hours later may be just as important from a consequence management perspective (e.g., for determining the impact on hospitals, how a disease will spread, or where to distribute medical supplies). In this presentation, we briefly describe the day-night and indoor-outdoor population databases and then explain the rationale for doing the day-night population “exchange” work. We then show the methodology and steps used in deriving the “exchange” database, algorithms, and tool. We will conclude with examples of targeted daytime (or nighttime) population and show where they end up at night (or during the day) and outline the limitations in the approach.