Redlining, Community Wealth, and Air Pollution: A Tale of Three Cities—Boston, Nashville, and Detroit

Despite US air quality improvements since the 1990 Clean Air Act Amendments, disparities in air pollution between communities persist. We studied whether persistent within-city geospatial disparities in pollution continued over time in historically minoritized and under-resourced areas codified as "redlined" in 1930's government mapping. We evaluated how longitudinal demographic patterns and disparities in community wealth and resources related to historical redlining score category in three US urban areas: Boston, MA, Nashville, TN, and Detroit, MI. We then examined longitudinal associations of redlining with changing levels of the air pollutants PM_2.5 and NO₂ between 2000 and 2016 in these cities. Our approach utilized daily estimates of air pollution levels from models with high spatiotemporal resolution, digitized redlining maps, and census data to evaluate temporal trends by redlining categories at the census tract level. Demographic and socioeconomic changes over time differed by city, but for each city, historically redlined areas continued to have a greater proportion of Black residents, higher poverty rates, lower income and home values, and a higher social vulnerability index (SVI). Over all areas, air pollution levels declined markedly over time, but for annual averaged NO₂, redlining-area-associated exposure disparities persisted in Boston and widened in Nashville. In contrast, by 2016, regardless of redlining history, areas in Detroit had similar NO₂ pollution levels. Our results highlight the lasting social, economic, and environmental effects of urban discriminatory practices, also showing that in some cities, areas may be equally exposed to specific criteria pollutants, regardless of area wealth.