Space‐Based Observational Constraints on NO2 Air Pollution Inequality From Diesel Traffic in Major US Cities

Abstract Air pollution disproportionately burdens communities of color and lower‐income communities in US cities. We have generally lacked city‐wide concentration measurements that resolve the steep spatiotemporal gradients of primary pollutants required to describe intra‐urban air pollution inequality. Here, we use observations from the recently launched TROPospheric Ozone Monitoring Instrument (TROPOMI) satellite sensor and physics‐based oversampling to describe nitrogen dioxide (NO 2 ) disparities with race, ethnicity, and income in 52 US cities (June 2018–February 2020). We report average US‐urban census tract‐level NO 2 inequalities of 28 ± 2% (race‐ethnicity and income combined), with many populous cities experiencing even greater inequalities. Using observations and inventories, we find diesel traffic is the dominant source of NO 2 disparities, and that a 62% reduction in diesel emissions would decrease race‐ethnicity and income inequalities by 37%. We add evidence that TROPOMI resolves tract‐scale NO 2 differences using relationships with urban segregation patterns and spatial variability in column‐to‐surface correlations.