Association between a Rapid Reduction in Air Particle Pollution and Improved Lung Function in Adults

Rationale: Lung function impairment is reportedly associated with elevated exposure to ambient fine particles (particulate matter ≤2.5 μm in aerodynamic diameter [PM_2.5]). However, whether improvement of air quality prevents respiratory diseases is unclear.Objectives: To examine whether the policy-driven reduction in PM_2.5 concentration after 2013 was associated with improved lung function among Chinese adults.Methods: We compared the longitudinal measurements of peak expiratory flow (PEF) before (2011) and after (2013 and 2015) China's clean air actions. Long-term exposure to ambient pollution was assessed using a state-of-the-art estimator of historical PM_2.5 concentration, and its association with PEF was examined using a linear mixed-effects model. The robustness and homogeneity of the association were examined via sensitivity analyses.Results: We analyzed 35,055 repeated measurements from 13,959 adults. Mean of age at survey was 60.5 years (standard deviation = 9.7 yr). Compared with the reference in 2011, after the policy was implemented, the mean PEF was elevated by 9.19 (6.79-11.59) L/min and 36.64 (33.53-39.75) L/min in 2013 and 2015, respectively. According to the regression results, each 10-μg/m³ reduction of PM_2.5 was associated with a 14.95 (12.62-17.28) L/min improvement of PEF. The significance of the association was not affected by adjustments for covariates, inclusion criteria, or the approach to control for the effects of age. Adults of lower socioeconomic status (e.g., those with an educational level of below middle school or rural residents) were more susceptible to the adverse effects of PM_2.5 on PEF.Conclusions: We found a robust association between a reduction in PM_2.5 and an increase in PEF among Chinese adults. The findings suggest that mitigation of air pollution can promote respiratory health.