Space‐Based Observational Constraints on NO 2 Air Pollution Inequality From Diesel Traffic in Major US Cities

• Published in: Geophysical research letters 2021-09, Vol.48 (17)
• Main Authors: Demetillo, Mary Angelique G., Harkins, Colin, McDonald, Brian C., Chodrow, Philip S., Sun, Kang, Pusede, Sally E.
• Format: Article
• Language: English
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2021GL094333

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. People of color and people with lower household incomes commonly experience higher levels of air pollution and worsened health burdens from poor air quality in US cities. We have lacked direct observations of air pollution across cities with which to describe, explain, and guide policymaking on air pollution disparities. Nitrogen dioxide is an important combustion pollutant that is co‐emitted with many other toxic pollutants, and its concentrations are highly variable between neighborhoods. Here, we use nitrogen dioxide measurements collected from space by the TROPospheric Ozone Monitoring Instrument (TROPOMI) to describe inequalities within 52 US cities. TROPOMI captures greater spatial detail than previously possible, and the near‐daily data collection allows for interpretation of the specific polluting sources causing nitrogen dioxide inequality, including diesel traffic emissions. Because satellite applications for air pollution inequality analyses are nascent, we build on our past work to advance understanding of the extent to which TROPOMI resolves inter‐neighborhood nitrogen dioxide differences. On average, urban NO 2 inequalities of ∼28% are observed with race‐ethnicity and income; disparities are much greater in many cities Diesel traffic is the dominant source of NO 2 disparities; a 62% reduction in diesel emissions would decrea