Particulate matter and respiratory health in middle-aged and older adults: disentangling size-fractionated and constituent-specific effects under China’s clean-air policies

Particulate matter (PM) with distinct physicochemical properties may drive differential respiratory health risks. We investigated associations of long-term exposure to size- and constituent-specific PM with chronic respiratory diseases (CRDs) and evaluated respiratory benefits linked to PM composition changes under China’s air control policies. A prospective cohort of 2100 adults (baseline mean age, 57.2 years) in Guangzhou, China, was followed between 2008 and 2021. Residential exposure to size-fractionated PM (PM 1 , PM 2.5 , PM 10 ) and six PM 2.5 chemical constituents were estimated with 1-km spatiotemporal models. Structured questionnaires collected diagnoses of incident CRDs every 3 years, including chronic bronchitis, asthma, and emphysema. Cough and wheezing were assessed during policy intervention periods (2013–2017). A time-varying Cox model examined PM-CRD associations, while a logistic regression analyzed PM reduction-associated respiratory symptoms. Variance decomposition and quantile g-computation assessed PM size-specific and constituent mixture effects. Approximately, 7.7% ( n = 162/2100) of participants developed any CRD during a median follow-up of 9.0 years. Increased exposure to PM 1 , PM 2.5 , and PM 10 was associated with elevated hazard ratios ( HRs : 1.40–1.80 per 1 μg/m 3 increase) for CRDs, with associations primarily driven by PM’s shared variances. In mixture analyses, sulfate, chloride, and organic matter positively contributed to the joint effects of PM 2.5 constituents on CRDs ( HRs : 4.42–6.42). Notably, sulfate reduction was consistently associated with decreased wheezing odds, preventing an estimated 107 cases ( n = 107/1905, 95% CI 12–241). PM-associated CRD risks were largely attributed to shared variances of PM across size fractions and toxic effects of constituents, particularly sulfate. Targeted emission controls for toxic PM sources may mitigate respiratory health risks.