SSEC Meetings

Presentation 1600-1630.  Nitrogen dioxide (NO2) is a gaseous air pollutant that causes a range of harmful effects on human health, and motor vehicles are a leading source of NO2. The Clean Air Act requires the U.S. Environmental Protection Agency (EPA) to monitor and regulate the ambient NO2 concentrations. In cooperation with state, local, and tribal air agencies, EPA has installed and tracked near-road NO2 monitoring stations across the country. In 2016, however, EPA removed the minimum near-road NO2 monitoring requirements in Core Based Statistical Areas (CBSAs) with populations between 500,000 and 1,000,000 persons (40 CFR 58). Although ambient NO2 concentrations are now below both the annual and 1-hour daily maximum NAAQS (National Ambient Air Quality Standards) levels, many studies and satellite measurements have demonstrated intra-urban variability of nitrogen dioxide. Given that policies and other decision-makings are primarily based on measurements, it is important to evaluate how adequately the current near-road NO2 monitoring stations can estimate population exposure. This study compared CMAQ predictions of NO2 concentrations with monitoring measurements in two urban areas in Texas. The model predictions demonstrated the variability of NO2 concentrations (higher concentrations near roads and areas with more people), but they did not show 1:1 agreement with monitor measurements. Further research is required, but this result concludes that current near-road NO2 monitoring stations in urban areas may not represent population exposure appropriately.