Several reports have suggested that particulate matter (PM) exposure increases the risk for atrial arrhythmias. However, data from large-scale epidemiologic studies supporting this hypothesis are lacking. We examined the association of PM <2.5 μm in diameter (PM2.5) concentration with premature atrial contractions (PACs) in 26,609 (mean age=65±9.4 years; 55% female; 41% black) participants from the REGARDS (REasons for Geographic And Racial Differences in Stroke) study. Estimates of short- (2 weeks) and long-term (1 year) PM2.5 exposure were computed before each participant's baseline visit using geographic information system data on the individual level at the coordinates of study participants' residences. PACs were identified from baseline electrocardiograms. A total of 2140 (8.2%) participants had evidence of PACs on the baseline electrocardiogram. Short-term PM2.5 (per 10 μg/m3) exposure was not associated with PACs (OR=1.09, 95% CI=0.98, 1.23). Increases in long-term PM2.5 (per 10 μg/m3) were associated with PACs (OR=1.40, 95% CI=1.10, 1.78). Interactions were not detected for short- and long-term PM2.5 exposure by age, sex, or race. Long- but not short-term PM2.5 exposure is associated with PACs. This suggests a role for long-term PM2.5 exposure in initiating supraventricular arrhythmias that are triggered by PACs.