Despite decline, distribution of air pollution highlights socioeconomic disparities

While the level of fine particulate air pollution has declined considerably over the last several decades, a new study finds that its distribution has remained largely unchanged. According to the results, the most and least polluted U.S. neighborhoods in 1981 remained the most and least polluted more than 30 years later, with disadvantaged communities far more likely to have higher levels of particulate pollution at any given time. The findings reveal persistent socioeconomic disparities in access to clean air and highlight the perpetual problem of environmental inequality. Overall, the concentration of fine particulate air pollution (PM2.5) – airborne particulate matter less than 2.5 microns in diameter – has decreased by roughly 70% since 1981 in the U.S., leading to improvements in air quality and, by extension, human health and economic well-being. But air pollution is not evenly distributed. Like other types of pollution and environmental hazards, increased levels of air pollution are often associated with disparities between different racial, ethnic and economic groups. However, little is known about how the spatial distribution of PM2.5 has evolved over time. Jonathan Colmer and colleagues combined measurements of PM2.5 spanning 1981-2016 with geographic, economic, and demographic data from 65,000 neighborhoods across the U.S. Colmer et al. found that the differences in PM2.5 between more and less polluted areas declined over time. However, the neighborhoods and subpopulations most exposed to pollution in 1981 remained the most exposed in 2016. In contrast, areas that were less polluted in 1981 were still less polluted in 2016. “Colmer et al.’s findings highlight outstanding issues relevant to implementing environmental justice in practice,” writes Lala Ma in a related Perspective. “Further investigation to determine what caused the downward shift in the pollution distribution and the preservation of rankings over time could inform policies that avoid undesirable distributional consequences.”

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