Long-Term Exposure to PM2.5 Constituents and Coronary Heart Disease Risk in China.

BACKGROUND: In China, the associations between long-term fine particulate matter with aerodynamic diameter ≤2.5 μm (PM2.5) exposure and coronary heart disease appear to differ from those reported in high-income countries, thus potentially reflecting differences in PM2.5 composition. However, constituent-specific evidence from national cohort studies remains limited. OBJECTIVES: This study aimed to investigate the associations of long-term exposure to PM2.5 constituents with the incidence and mortality risks of coronary heart disease and its subtype, acute myocardial infarction (AMI). METHODS: This nationwide prospective cohort study was conducted in 101,906 adults from the China-PAR (Prediction for Atherosclerotic Cardiovascular Disease Risk in China) Project who were free of cardiovascular disease at baseline. Participants were followed up from 2003 to 2019. Annual residential exposures to PM2.5 constituents, including elemental carbon (EC), organic carbon (OC), nitrate, and sulfate, were estimated using validated satellite-based machine learning models. Cox proportional hazards models with time-varying exposures were used to estimate HRs and 95% CIs per IQR increase, adjusted for major demographic, behavioral, and clinical covariates. RESULTS: During a median follow-up of 11.08 years (1,230,732 person-years), 3,500 incident cases of coronary heart disease, including 1,771 AMI events, and 1,321 coronary heart disease deaths, including 808 AMI deaths, were recorded. Per IQR increase in EC, OC, nitrate, and sulfate exposure, HRs for coronary heart disease incidence were 1.10 (95% CI: 1.01-1.19), 1.60 (95% CI: 1.31-1.95), 1.43 (95% CI: 1.06-1.95), and 0.93 (95% CI: 0.82-1.06), respectively. Similar positive associations for EC, OC, and nitrate were observed for coronary heart disease mortality and AMI outcomes, whereas the health impacts of sulfate were weaker and less consistent across outcomes. Concentration-response curves indicated an overall increasing coronary heart disease risk for OC, EC, and nitrate exposure with a plateau or slight attenuation in the higher exposure range of EC and OC, whereas sulfate exposure showed nonlinear associations without a sustained increase in risk. CONCLUSIONS: Long-term exposure to specific PM2.5 constituents was associated with increased risks of coronary heart disease and AMI, thus highlighting the need for constituent-specific air pollution control beyond PM2.5 mass.