Air pollution, especially exposure to fine particulate matter called PM2.5, is very harmful and leads to thousands of premature deaths every year. We already know that there are inequalities between race/ethnic groups regarding how much air pollution they’re exposed to. We wanted to look at whether health inequalities in premature mortality persist if communities are exposed to the same level of air pollution and in which areas such inequalities were more pronounced.

We found that there is a substantial contribution of PM2.5 to race/ethnic inequality in mortality in the U.S. Specifically, the Black population had the highest proportion of deaths attributable to PM2.5 in all years from 1990 to 2016. Even in areas where pollution levels are the same among other racial/ethnic groups, structural racism and social determinants of health contribute to higher rates of death for Black people. And though there has been some progress in limiting air pollution in the last two or three decades, these inequalities remain.

In February 2024, the Environmental Protection Agency set the PM2.5 standard at nine micrograms per cubic meter annually—a 25 percent decrease—meaning that this is the maximum amount of PM2.5 (whatever the source of emission and composition) that should be in the ambient air. This is a good start, but ultimately such thresholds should be modulated to consider existing structural inequalities and differences in sources of air pollution emission.