Abstract
By-products of mobile source combustion processes, such as those associated with gasoline- and diesel-powered engines, include direct emissions of particulate matter as well as precursors to particulate matter and ground-level ozone. Human exposure to fine particulate matter with an aerodynamic diameter smaller than 2.5 μm (PM2.5) is associated with increased incidence of premature mortality and morbidity outcomes. This study builds upon recent, detailed source-apportionment air quality modeling to project the health-related benefits of reducing PM2.5 from mobile sources across the contiguous U.S. in 2025. Updating a previously published benefits analysis approach, we develop national-level benefit per ton estimates for directly emitted PM2.5, SO2/pSO4, and NOX for 16 mobile source sectors spanning onroad vehicles, nonroad engines and equipment, trains, marine vessels, and aircraft. These benefit per ton estimates provide a reduced-form tool for estimating and comparing benefits across multiple mobile source emission scenarios and can be applied to assess the benefits of mobile source policies designed to improve air quality. We found the benefit per ton of directly emitted PM2.5 in 2025 ranges from $110,000 for nonroad agriculture sources to $700,000 for onroad light duty gas cars and motorcycles (in 2015 dollars and based on an estimate of PM-related mortality derived from the American Cancer Society cohort study). Benefit per ton values for SO2/pSO4 range from $52,000 for aircraft sources (including emissions from ground support vehicles) to $300,000 for onroad light duty diesel emissions. Benefit per ton values for NOX range from $2100 for C1 and C2 marine vessels to $7500 for “nonroad all other” mobile sources, including industrial, logging, and oil field sources. Benefit per ton estimates increase approximately 2.26-fold when using an alternative concentration response function to derive PM2.5-related mortality. We also report benefit per ton values for the eastern and western U.S. to account for broad spatial heterogeneity patterns in emissions reductions, population exposure and air quality benefits.
Highlights
The transportation sector, which includes on-road vehicles, non-road vehicles, aircraft, trains, and marine vessels, emits pollutants that degrade air quality (Dallman and Harley, 2010; Zawacki et al, 2018)
Updating a previous benefits analysis approach presented in Fann et al (2012), we develop benefit per ton estimates of directly emitted PM2.5, SO2+SO4, and NOX for 16 specific mobile source sectors spanning onroad vehicles, nonroad engines and equipment, trains, marine vessels, and aircraft
Because the relationship between emissions reductions and human exposure to atmospheric pollution is dependent on background atmospheric composition, meteorological conditions, and proximity to population sources, the marginal benefits of reducing emissions show significant spatial heterogeneity (Fann et al, 2009; Heo et al, 2016)
Summary
The transportation sector, which includes on-road vehicles, non-road vehicles, aircraft, trains, and marine vessels, emits pollutants that degrade air quality (Dallman and Harley, 2010; Zawacki et al, 2018). Monetizing the health impacts of changes in pollutant concentrations requires integrated benefits mapping tools that account for population distribution, baseline incidence rates of health endpoints, mortality and morbidity effect estimates, and incidence cost estimates associated with these health endpoints or detailed economic data (Davidson et al, 2007; Saari et al, 2015). The complexity of these models can make full-scale benefits assessments time and resource prohibitive
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