This paper documents novel evidence on the relationship between fine particulate matter in micrograms per cubic meter (PM2.5) (μg/m³) and sufficient physical activity prevalence in U.S. counties. The rest of the explanatory variables include: ambient temperature, precipitation (mm), sunlight (KJ/m²), income per capita, and poverty rate. The beta regression results indicate that an increase in PM2.5 by one μg/m³ is associated with a decrease in male (female) SPAP by 2.58 (4.15) percentage points.