Air quality monitoring at two major U.S.-Mexico border crossings drives the next phase of this funded project. Work focuses on the northbound Bridge of the Americas and the southbound Stanton Bridge, building on a completed year of uninterrupted fine particulate matter (PM2.5) monitoring and preliminary analysis of particulate composition. Findings from that earlier phase established annual and seasonal exposure patterns and informed the design of this expanded effort. Monitoring in the new phase adds nitrogen dioxide (NO2), ozone (O3), particulate matter (PM10), and ultrafine particles, with attention to occupational and pedestrian exposure in specific border-crossing settings. Multi-pollutant stations will be placed at passenger vehicle inspection booths and extended to commercial lanes, parking areas, and pedestrian waiting zones at the Bridge of the Americas, and, pending operator agreement, to toll booth and inspection areas at the southbound Stanton Bridge. Project activities integrate traffic, operations, and shift-based exposure data to support a more complete understanding of air quality risks and inform mitigation strategies at key border infrastructure sites.