Long-Term Exposure to PM2.5 Components and Respiratory Disease Mortality in South China: The Pearl River Cohort Study

Evidence on the effects of fine particulate matter (PM2.5) components on respiratory mortality remains limited, especially in large cohorts. Using data from 182,009 participants, we examined the single-component and joint associations of six major PM2.5 components (NH4+, NO3–, BC, OM, SO42–, and Cl–) with respiratory mortality. Marginal structural Cox models were used to estimate single-component effects, while quantile g-computation assessed mixture effects and component contributions. All six components were associated with increased respiratory mortality, with hazard ratios (HRs) ranging from 1.42 to 2.75. Each quartile increase in the mixture index was associated with a 29% higher hazard of respiratory disease mortality (HR = 1.29, 95%; CI = 1.23–1.34). NO3– contributed most strongly to the overall mixture association (weight = 0.48), followed by OM and Cl–. Older adults, nonsmokers, and nonexercisers showed greater susceptibility, with HRs ranging from 1.25 to 2.02. These findings highlight the importance of targeted air pollution control and protection of vulnerable populations.