The Performing Party shall hire a contractor to measure PM2.5 concentration at different hours of the day and locations within selected international border crossings (IBCs) to understand the potential for human respiratory exposure to such air pollutant of users waiting to cross the border in private vehicles or as pedestrians, as well as with CBP officials manning inspection booths. Furthermore, the project will research correlations between these PM2.5 measurements and other variables, such as motorized traffic volume/congestion and its distance to the monitor locations, as well as ambient conditions. These correlations can potentially help predict the spatial concentration of PM2.5 within an IBC, and even help foresee mitigation strategies.