High-resolution modeling of air quality and health benefits of transportation policies in the Boston Metropolitan area

Onroad vehicular emissions can adversely affect the health of people both near-road and regionally through contributions to O3, NO2 and PM2.5. While multiple studies have characterized the overall air quality and health benefits of emissions from the transportation sector, fewer studies have modeled the benefits of transportation policies at higher geographic resolution relevant to communities. We use a multi-scale nested (12/4/1.33km) application of EPA's Community Multiscale Air Quality (CMAQ) model with the Carbon Bond 6 revision 3 mechanism (cb6r3) version with aero6 treatment for standard cloud chemistry. We use CMAQ Version 5.2.1 coupled with the decoupled direct method (DDM) simulations for January and July of 2017 with spin up of 15 days using Northern Hemisphere 108-km domain initial and boundary conditions, meteorology derived from WRF model, and updated emissions inventory from the EPA's National Emissions Inventories for the year 2017 processed through SMOKE. Outer domain runs are done without DDM (12/4km), while the innermost nest at 1.33 km resolution focuses on Boston neighborhoods and surrounding communities. We instrumented CMAQ-DDM to compute sensitivities of predicted O3, NO2 and PM2.5 to a large matrix of input parameters including five vehicular classes (light-duty autos, light-duty trucks, medium-duty trucks, heavy-duty trucks, and buses), five precursor emissions (PM2.5, NOX, SO2, NH3 and volatile organic compounds (VOC)), and eight Metropolitan Area Planning Council inner core sub-regions. Health benefits from emissions and air quality changes are estimated using the Environmental Benefits Mapping and Analysis Program in R (BenMAPR). Our findings will emphasize the air quality and health impacts from the sensitivity matrix, with consideration of variability in impact per ton of precursor emissions by individual vehicle class and source location. Results from our modeling platform will help in assessing both the public health benefits and the equity implications of local-scale transportation policies in the Boston metropolitan area.