A new study at Columbia University Mailman School of Public Health highlights disparities in fine particulate matter (PM2.5) trends between American Indian (AI) and non-AI populated counties of the U.S. PM2.5 is one of several air pollutants regulated by the U.S. Environmental Protection Agency (EPA), with the current annual standard set at 12μg/m3. Downward trends in PM2.5 concentrations were steeper among the non-AI populated compared to AI-populated counties. Although AI-populated counties had lower PM2.5 concentrations than non- AI populated counties in 2000, by 2018, their levels were higher. With most U.S. air pollution research conducted in urban settings, this is the first study to detail the extent of particulate air pollution levels and its potential health consequences among rural AI communities. The findings are published in the American Journal of Public Health.