Ambient PM Concentration Estimation and Population Exposure Assessment Over the Eastern United States
V.M. Vyas, V. Purushothaman, P.G. Georgopoulos (EOHSI, UMDNJ - R.W. Johnson Medical School and Rutgers University)
A Geographic Information System (GIS based exposure assessment tool has been developed to analyze the distribution and impact of spatiotemporal environmental variables such as ambient particulate matter concentrations. This tool can either be a stand-alone component in the MENTOR (Modeling ENvironment for TOtal Risk studies) framework, for estimating the distribution of pollutant concentrations and the subsequent assessment of outdoor population exposure, or it can be combined with other MENTOR components in order to estimate actual (affected by microenvironmental parameters) exposures (Isukapalli et al., PM 2000).
The population exposure component can use as input either monitoring data, or estimates of monitoring data obtained through spatiotemporal estimation (as in this study), or outputs from mechanistic photochemical/aerosol air pollution models (such as in Sun et al., PM 2000).
The spatiotemporal analysis component is based on the theory of Spatiotemporal Random Fields (STRF), and it is applied here to model the spatial and temporal evolution and the random fluctuations in the PM concentration distributions. The method uses simultaneously spatial as well as temporal data to provide more accurate estimates of the interpolated concentrations than purely spatial or purely temporal methods, thus reducing the uncertainty associated with the estimates. The input data can be at different time scales - hourly, weekly, or seasonal. The method also provides better treatment of missing values. The PM concentration maps so produced can be useful for evaluating compliance with ambient air quality standards. They can also provide the necessary inputs for region-wide potential population exposure analyses, conducted using the exposure assessment components of MENTOR. Selected case studies are presented to illustrate these methods and tools.