Effects of Diesel Engine Emission Controls on Environmental Equity and Justice

The air quality and environmental equity benefits for the accelerated use of diesel particle filter (DPF) and selective catalytic reduction (SCR) systems on heavy-duty diesel trucks are assessed in Oakland, California. The study focuses on communities adjacent to two major freeways: Brookfield Village and Sobrante Park along I-880, heavily affected by truck traffic; and Sequoyah along I-580, where heavy-duty trucks are prohibited. Brookfield-Sobrante has a higher proportion of nonwhite, low-income residents than Sequoyah (97% vs. 76%). We modeled concentrations of nitrogen oxides (NOx), diesel particulate matter (PM), and black carbon (BC) before widespread use of diesel emission controls (2009), after universal adoption of DPFs to control PM emissions (2018), and after universal adoption of SCR to control NOx emissions (2023). Reductions in near-roadway pollutant concentrations in Brookfield-Sobrante were 59% for NOx and 42%-43% for diesel PM and BC by 2018. In Sequoyah, reductions in NOx concentrations were smaller (52%), and diesel PM and BC concentrations increased by 19% and 13%, respectively. While estimated NOx concentrations remain higher in Brookfield-Sobrante compared with Sequoyah, diesel PM and BC concentrations will be similar in both neighborhoods by 2023. Reductions in diesel emissions also led to improvements in environmental equity when quantified by the difference in mean intakes for Brookfield-Sobrante versus Sequoyah. Maintaining these air quality and equity benefits requires that diesel emission control systems remain in good working order over time.