PM_2.5 chemical constituents and chronic obstructive pulmonary disease mortality risk: The Pearl River Cohort study

Chronic obstructive pulmonary disease (COPD) imposes a major burden on global health, yet evidence on the prolonged health effects of individual PM_2.5 constituents remains limited. Previous research has primarily employed traditional models, which may struggle to capture the complex correlations among the PM_2.5 components and be less effective in confounding adjustment. We conducted a prospective cohort study involving 182,009 participants from the Pearl River Cohort (2013-2015) followed through 2020, applying inverse probability-weighted marginal structural Cox models and quantile g-computation (QGC) to assess the associations of individual PM_2.5 components and their mixtures with COPD mortality, followed by stratified analyses for effect modification. Over 1.18 million person-years of follow-up, 422 COPD deaths were documented. Long-term exposure to ammonium (NH₄⁺), black carbon (BC), nitrate (NO₃^-), organic matter (OM) and chloride (Cl^-) was associated with higher COPD mortality, with HRs (95% CI) of 2.75 (1.86-4.05), 2.41 (1.64-3.55), 1.86 (1.45-2.39), 1.85 (1.33-2.57) and 1.45 (1.15-1.82), respectively. Mixture analysis showed that each one-quartile increase in the PM_2.5 component mixture was associated with a 39% (29%-50%) higher risk of COPD mortality, primarily driven by OM, Cl^-, and NO₃^- (weights = 0.34, 0.34, 0.32). Stratified analyses indicated greater associations among older adults, suggesting increased susceptibility in this group. Our findings underscore the potential contribution of individual PM_2.5 constituents and their mixtures in COPD mortality, while suggesting actionable source-control priorities and coordinated precursor-reduction strategies, as well as population-specific prevention approaches.