Health and EJ benefits of reducing HDV NOx emissions

Heavy duty vehicles (HDVs) contribute about 43% of the transportation-related PM2.5 and ozone mortality burden in the U.S. (Anenberg et al. 2019). NO2 is estimated to contribute 200,000 cases of pediatric asthma development in U.S. cities each year (Anenberg et al. 2022). HDV-related air pollution is a high priority environmental justice issue, as race, ethnicity, and income are significant determinants of whether someone lives near a freight truck route in the U.S. Reducing HDV NOx emissions can substantially reduce air pollution-related premature mortality, NO2-attributable pediatric asthma incidence, and air pollution injustice for communities living near major roads. HDV NOx emissions can be reduced through emissions standards (for example, through the recently proposed standards to reduce NOx emissions from HDVs and engines), vehicle electrification, or other approaches. However, several key technical limitations preclude us from being able to fully characterize which communities could experience the greatest improvements in air quality and associated health benefits from the rule, an important consideration for the Biden Administration’s Justice40 initiative. The Regulatory Impact Analysis (RIA) for the EPA’s proposed HDV NOx emission standards provides an example of these technical limitations. First, the chemical transport model simulations used as inputs to this analysis were conducted at 12km x 12km spatial resolution, too coarse to capture neighborhood-scale impacts. Second, the RIA did not include a demographic analysis of the health benefits of the rule. Finally, the analysis focused only on ozone and PM2.5, and did not include NO2, the pollutant that is most inequitably distributed in U.S. cities that is also most affected by HDV NOx emissions standards. Thus, while this proposed rule could dramatically narrow inequities in air pollution-attributable health risks across the U.S., particularly for NO2, the demographic distribution of the rule’s air quality and health benefits is currently unknown. The same challenges apply to other approaches to reducing HDV NOx emissions, including vehicle electrification.