| Samenvatting: | On-road vehicular emissions contribute to the formation of fine particulate matter and ozone which can lead to increased adverse health outcomes near the emission source and downwind. In this study, we present a transportation-specific modeling platform utilizing the community multiscale air quality model (CMAQ) with the decoupled direct method (DDM) to estimate the air quality and health impacts of on-road vehicular emissions from five vehicles classes; light-duty autos, light-duty trucks (LDT), medium-duty trucks, heavy-duty trucks (HDT), and buses (BUS), on PM _2.5 and O _3 concentrations at a 12 × 12 kilometer scale for 12 states and Washington D.C. as well as four large metropolitan statistical areas in the Northeast and Mid-Atlantic U.S. in 2016. CMAQ-DDM allows for the quantification of sensitivities from individual precursor emissions (NO ${}_\mathrm{X}$ , SO _2 , NH _3 , volatile organic compounds, and PM _2.5 ) in each state to pollution levels and health effects in downwind states. In the region we considered, LDT are responsible for the most PM _2.5 -attributable premature mortalities at 1234 with 46% and 26% of those mortalities from directly emitted primary particulate matter and NH _3 , respectively; and O _3 -attributable premature mortalities at 1129 with 80% of those mortalities from NO ${}_\mathrm{X}$ emissions. Based on a detailed source-receptor matrix of sensitivities with subsequent monetization of damages that we computed, we find that the largest damages-per-ton estimate is approximately $4 million per ton of directly emitted primary particulate matter from BUS in the New York-Newark-Jersey City metropolitan statistical area. We find that on-road vehicular NH _3 emissions are the second largest contributor to PM _2.5 concentrations and health impacts in the study region, and that reducing 1 ton of NH _3 emissions from LDT is ∼75 times and from HDT is ∼90 times greater in terms of damages reductions than a 1 ton reduction of NO ${}_\mathrm{X}$ . By quantifying the impacts by each combination of source region, vehicle class, and emissions precursor this study allows for a comprehensive understanding of the largest vehicular sources of air quality-related premature mortalities in a heavily populated part of the U.S. and can inform future policies aimed at reducing those impacts.
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