Project at a Glance

Title: A Tool to Prioritize Sources for Reducing High PM2.5 Exposures in Environmental Justice Communities in California

Principal Investigator / Author(s): Apte, Joshua

Contractor: The University of Texas at Austin

Contract Number: 17RD006

Research Program Area: Emissions Monitoring & Control, Health & Exposure

Topic Areas: Environmental Justice, Monitoring


This study developed and utilized a method based on intake fraction for evaluating inequality in exposure to fine particulate matter (PM2.5). The method utilizes a spatial database built from a reduced-complexity chemical transport model and census data for groups of different ages, income levels, and race/ethnicity. Given information on location and emission rates of PM2.5 or precursor emissions (NOX, SO2, NH3, or VOCs),
one can calculate, for a specific source, the amount of PM2.5 inhaled by the total population and exposure differences among demographic groups. Applying this method to an inventory of anthropogenic emissions sources in California shows differences in per-capita exposure concentration of up to 15% by income and 35% by race-ethnicity. The two top sources of exposure, on-road vehicles and industrial activity, contribute most to exposure concentration disparity by race-ethnicity in absolute terms. Some minor sources, such as petroleum refining and outdoor emissions from commercial cooking, result in higher percentages of exposure differences among demographic groups. Patterns in exposure disparity vary among population groups, with some source categories most severely affecting one particular group. This impact-oriented evaluation of emission sources can help decision makers to screen emission-reduction targets for further investigation in order to achieve environmental justice goals.

For questions regarding this research project, including available data and progress status, contact: Research Division staff at (916) 445-0753

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