Traffic-related air pollutants are especially prevalent in border cities with multiple ports of entry (POEs). Excessive emissions due to long delays of idling commercial and passenger vehicles at the POEs could exacerbate various types of respiratory health conditions for the POE users and workers. We conducted a 1-month in-traffic air monitoring campaign at a POE in El Paso, Texas using three continuous FEM instruments for three criteria pollutants (PM, O₃, and NO₂). Concurrent monitoring of PM in the nearby community was performed using a number of low-cost PM sensors. The 1-month average PM_2.5 concentration at the POE was found below 11.6 µg/m³, while the 5-min average of in-traffic PM_2.5 concentration could be as high as 450 µg/m³. The in-traffic PM_2.5 concentrations were comparable to the data concurrently measured in a state-operated community monitoring site approximately 0.4 km away from the POE. Ozone (O₃) concentrations remained low in the region. The in-traffic 1-h NO₂ concentrations were below the 1-h NAAQS of 100 ppb, except for only two 5-min intervals. Our results suggest that traffic emissions do not result in elevated levels of pollutant concentrations at this POE compared to the concentration levels observed in the nearby community. In addition, the performance and accuracy of the low-cost sensors appear to be less reliable during our study, although the devices were capable of detecting the trends and variability in pollutant concentrations in real time.

This project assesses the feasibility of employing mobile air pollutant concentration monitoring along fixed routes within an urban community to evaluate near-road exposure. Continuous mobile air monitoring measurements of four pollutants (PM_2.5, PM₁₀, NO₂, and O₃) were collected using high-quality air monitors paired with a GPS device to track coordinates and vehicle speed. Simultaneous near-road measurements of the same pollutants were taken at two stationary sites to establish correlations with the mobile air monitoring data. The results indicate that pollutant concentrations recorded by mobile air monitors align closely with those from near-road stationary sites. This study demonstrated strong concordance between mobile and stationary monitoring for particulate matter concentrations, with PM_2.5 and PM₁₀ showing high correlation coefficients (R² = 0.74 and 0.75, respectively). Ozone (O₃) exhibited particularly consistent spatial distributions across all measurement platforms—mobile, near-road, and community stationary sites—as reflected in even stronger correlations (R² = 0.93 and 0.89 for the two near-road sites). These robust associations suggest that mobile monitoring could serve as a viable alternative to stationary approaches for O₃ assessment. In contrast, nitrogen dioxide (NO₂) measurements displayed greater variability, with mobile concentrations consistently exceeding near-road stationary values and demonstrating weaker correlation (R² = 0.19), indicating potential limitations in mobile NO₂ monitoring reliability. This study highlights that mobile air pollutant monitoring in less congested communities can effectively capture exposure concentrations representative of both the community and near-road receptors represented by stationary air monitoring sites. Future research should explore how mobile air monitoring data can be utilized in exposure and health assessments, as well as how this technique can be applied in areas where stationary monitoring is impractical or prohibited due to cost or access limitations.

Queueing-driven transportation emissions at international ports of entry create localized air pollution hotspots affecting commuters, pedestrians, and facility workers. This study examines the Bridge of the Americas, a U.S.-Mexico port of entry in El Paso, Texas, using continuous Federal Equivalent Method monitoring and AERMOD dispersion modeling to assess traffic-related air pollutants. Monitored PM2.5 and NO2 concentrations were elevated at the port compared to a nearby reference site. Modeling showed that concentrations plateau once vehicle queues exceed 270 meters, with levels declining tenfold within 200 meters of the traffic lanes. Pedestrians experienced 75% of in-lane pollutant concentrations, and toll booth workers 66%. Modeled contributions accounted for 51% of PM2.5, 147% of PM10, and 7% of NO2 relative to monitored averages. Findings demonstrate how queue length, traffic mix, and weather impact exposure and support strategies, such as queue management, lane design, and walkway placement, to reduce emissions at border crossings.