Sulfate-Dominated PM2.5 Constituents Are Associated with an Increased Risk of Acute Myocardial Infarction Mortality: A U.S. Nationwide Difference-in-Differences Study

Nationwide evidence on the relationship between the chemical constituents of PM2.5 and acute myocardial infarction (AMI) mortality remains limited. Based on county-level data on AMI mortality and the levels of PM2.5 and its major constituents─EC, OC, SO42–, and NO3–─we developed a causal mixture analysis method to estimate PM2.5 constituent effects on AMI mortality across the US. We observed a relative risk (RR) of 1.019 (95% CI: 1.013, 1.025) for AMI mortality per IQR increase in PM2.5 concentration. Each one-quartile increase in the constituent mixture was associated with an 11.6% higher risk of AMI mortality [RR = 1.116 (95% CI: 1.101, 1.130)], with SO42– contributing the most (weight: 0.762). Furthermore, each one-quartile increase in PM2.5 constituent mixture in eastern counties was linked to an excess of 1.545 (95% CI: 0.656, 2.437) AMI deaths per 100,000 population annually compared to the west, with SO42– displaying the largest contribution (weight: 0.707) in the east and OC (0.485) in the west. Long-term exposure to PM2.5 constituents, especially fine particulate matter enriched with SO42–, is associated with increased AMI mortality, with impacts varying by region, seasonal temperature, and sociodemographic disparities.