Environmental Justice and Air Pollution in Metropolitan Regions Across the United States

Air pollution is a significant concern for metropolitan areas due to their high traffic density and proximity to industrial sources. However, air pollution does not impact all people equally. Environmental Justice (EJ) is defined by the Environmental Protection Agency (EPA) as the equal treatment of all people in the creation and enforcement of environmental policies. In support of the environmental justice movement, environmental observations are needed to document evidence for those which are unfairly impacted by environmental hazards due to factors such as race, socioeconomic status, and institutional marginalization. Satellite instruments provide continuous, long-term, full-coverage observations of air pollutants such as NO2, which are especially suitable for characterizing EJ. We use a newly developed block-group level satellite-based NO2 dataset to characterize NO2 pollution in different metropolitan regions and the corresponding environmental injustice among different ethnic and socioeconomic groups. The block-group level NO2 products are developed from TROPOspheric Monitoring Instrument (TROPOMI) retrievals of NO2, which are spatially oversampled to administrative units using a physics-based oversampling approach. Using the new dataset, we study the NO2 levels and their relationship with various EJ indexes such as traffic proximity and percentage of low-income populations in 10 metropolitan areas across the continental United States. People of color are more likely to be in regions with higher NO2 pollution and vehicular traffic. These findings shed light on how NO2 pollution and its sources vary among each metropolitan region, and underscore the need to protect vulnerable groups against air pollution and environmental hazards.