According to the Texas Commission on Environmental Quality (TCEQ), El Paso is the only border area in Texas that has violated national air quality standards. Mobile source emissions (including vehicle exhaust) contribute significantly to the problem, along with other sources including industrial, residential, and cross-border. CIITR researchers used multivariate receptor modeling—specifically positive matrix factorization (PMF)—to separate unobserved vehicle emissions from air-pollution mixtures indicated by ambient air quality data. They collected and analyzed two sets of multivariate air pollution data: 1) speciated PM2.5 (particulate matter with an aerodynamic diameter less than 2.5 microns) mass concentrations (measured every 3 days from 2006 to 2008) and 2) hydrocarbon hourly concentrations (measured in 2008) at El Paso’s Chamizal monitoring station. The team also used wind-direction analysis to estimate the contribution of sources from Mexico. Regression models were applied to relate traffic levels to vehicle emissions (taking the other sources into account). The findings of this project may interest local stakeholders—such as the El Paso Metropolitan Planning Organization, the Texas Department of Transportation, the City of El Paso, and TCEQ—in understanding source apportionment of pollutants measured in El Paso. It can potentially inform transportation planning strategies aimed at reducing emissions across the region or the development of more efficient traffic-management strategies. Other broader applications of this approach include supporting health impact analyses and risk analyses for border communities. For more information contact Eun Sug Park at (979) 317-2466 or [email protected].