Rolling Back Clean Air: How Relaxed PM₂.₅ Standards Threaten Health Gains, Widen Inequities, and Strain Care

This Grand Rounds explains how regulation of fine particulate matter (PM2.5) has produced substantial public‑health improvements in the United States and why weakening those standards risks reversing those gains. The session briefly reviews PM2.5 sources, health effects, and the regulatory history behind observed declines in pollution and disease. Evidence projecting the consequences of relaxed standards is then discussed with respect to widened exposure and health inequities in historically marginalized communities, and higher health‑care utilization and costs that disproportionately strain safety‑net providers. The presentation concludes with potential policy actions to prevent harm, mitigate inequities, and support evidence‑based air‑quality protections.