Development and application of individual and population-level human exposure models for fine particles and other vehicle-related air pollutants in Southern California

In this study, spatial accuracy issues in roadway data and geocoding process were investigated to provide the most accurate data for exposure and epidemiological studies concerned with vehicle-related air pollution. Large discrepancies, up to hundreds of meters, were found between two widely used roadway networks. Inaccurate roadway geometry and geocoding errors can lead to serious exposure misclassifications, on the order of factors of three to ten in assigned pollutant concentrations. A GIS-based algorithm we developed was effective in transferring vehicle activity information from a less accurate USGS roadway network to a GPS-accurate road network.; An individual exposure model was developed to quantify exposures to vehicle-related pollutants for the children in the Southern California Children's Health Study by taking into account time-activity patterns, local emissions, and regional pollution effects. Local traffic significantly increased within-community variability of exposure to vehiclerelated pollutants. The overall within-community variability of personal exposures was highest for NO2, followed by EC, PM10, PM2.5, and CO. Between-community exposure differences were affected by community location, traffic density, and locations of residences and schools in each community.; Besides the individual level exposure assessment, the population exposure to naphthalene was quantified for the first time for the California South Coast Air Basin by linking the Surface Meteorology and Ozone Generation airshed model and the Regional Human Exposure model. Average hourly naphthalene exposures in the SoCAB under summer and winter conditions were 270 ng m-3 and 430 ng m-3, respectively. More than one million and one thousand individuals were estimated to experience naphthalene exposure greater than 1000 and 3000 ng m-3, respectively.; The environmental justice issue was also investigated with respect to disproportionate exposure to vehicle-generated pollutants. Minority and high-poverty neighborhoods were found to have a higher population density, lower housing value, higher density of highways and major roads, and older and more multifamily housing. These neighborhoods bear over two times the level of traffic density compared to the rest of the Southern California region, which may associate them with a higher risk of exposure to vehicle-related pollutants.