Recent studies suggest that the transportation sector is a major contributor to fine particulate matter (PM2.5) in urban areas. A growing body of literature indicates PM2.5 exposure can lead to adverse health effects, and that PM2.5 concentrations are often elevated close to roadways. The transportation sector produces PM2.5 emissions from combustion, brake wear, tire wear, and resuspended dust. Traffic-related resuspended dust is particulate matter, previously deposited on the surface of roadways that becomes resuspended into the air by the movement of traffic. The objective of this study was to use regulatory guidelines to model the contribution of resuspended dust to near-road traffic-related PM2.5 concentrations. The U.S. Environmental Protection Agency (EPA) guidelines for quantitative hotspot analysis were used to predict traffic-related PM2.5 concentrations for a small network in Dallas, Texas. Results show that the inclusion of resuspended dust in the emission and dispersion modeling chain increases prediction of near-road PM2.5 concentrations by up to 74%. The results also suggest elevated PM2.5 concentrations near arterial roads. Our results are discussed in the context of human exposure to traffic-related air pollution.
Project-level particulate matter (PM) analysis, also known as hot-spot analysis, is required in non-attainment and maintenance areas for transportation projects that are identified as projects of air quality concern (POAQC). The only PM non-attainment area in Texas is El Paso which is currently designated as non-attainment for PM10. This paper presents an analytical methodology that was developed to determine the thresholds for highway activity parameters that would streamline the identification of projects that are not POAQCs, and minimize the risk that the project is misclassified. Researchers used the example provided by EPA, that is, 125,000 annual average daily traffic (AADT) and 8% heavy-duty trucks, as the baseline for the analysis. They then established combinations of AADT and truck percentage that would result in the same amount of PM10 emissions as the baseline scenario. Researchers used a set of conservative assumptions to achieve a very conservative/low-risk determination. The most important assumption among them was to not use a fixed baseline analysis year. Researchers used the proposed methodology to establish traffic activity thresholds for highway projects in El Paso, TX. Researchers established a baseline traffic activity (AADT and truck percentage) threshold curve which is a conservative representative of the lower boundary of POAQCs. Any combination of truck percentage and AADT that falls below this curve can be confidently excluded from POAQC consideration. Researchers developed an easy-to-use spreadsheet tool that would use user-provided AADT and truck percentages to identify whether a project could be confidently classified as not of air quality concern.
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