Air quality modeling of PM and air toxics at neighborhood scales to improve human exposure assessments.

A methodology to link Eulerian-based air quality grid models with fixed site monitoring data to provide a capability for improving human exposure modeling and assessments of impacts of fine particles an toxics pollutants is described. Many causal mechanisms for PM and toxics have been proposed for adverse health including pollutants' concentration loading as well as their chemical constituents and physical properties. The distribution of pollutant concentration fields for different causal pollutants may be highly complex at neighborhood scales. Since urban areas introduce fresh sources of pollutants into a regional background, significant subgrid spatial variability of the concentration fields with corresponding impact on subsequent exposure levels may occur. This methodology being described is designed to bridge air quality dispersion modeling and monitoring approaches to determine concentration variation arising from the juxtaposition of concentration from the regional and urban sources. This methodology extends the Models-3 Community Multiscale Air Quality Modeling System (CMAQ) spatial resolution capability to model PM 2.5 and toxics pollutants from its current horizontal resolution ranging from regional (~36km) and urban scales (4km) to about 1 km. To illustrate its application to exposure modeling, a sensitivity study showing examples of human exposure to PM and air toxics as a function of grid resolution will be given.