Influence of transboundary wildfire smoke on fine particulate matter concentrations at South Texas border schools

Exposure to air pollutants in indoor and outdoor school environments poses significant health risks to children due to their heightened vulnerability. Increasing wildfire frequency has intensified transboundary smoke transport, with border communities among the first to experience associated air quality impacts. While the impacts of wildfires on air quality are increasingly recognized through satellite observations and modeling, ground-based observations remain scarce in under-monitored regions. Low-cost air sensors were deployed across schools in the Roma and Rio Grande City areas of Starr County, along the U.S.–Mexico border, for 146-days from November 2023 to April 2024. The raw sensor measurements were corrected using a collocation-based calibration with a research-grade instrument and analyzed alongside meteorological data, back trajectories, and satellite-derived smoke and fire products. Daily average fine particulate matter concentrations were significantly higher during smoke-impacted days compared with non-smoke periods ( p < 0.001), with site-level increases ranging from 8.61% to 54.9%. Trajectory analysis integrated with these measurements indicate that the wildfire emissions from Mexico significantly influence fine particulate pollution in South Texas, during the wildfire seasons. These findings highlight the need for targeted mitigation strategies to decrease the exposure amongst border communities, especially that of children.