Long-term improvement of air quality associated with lung function benefits in Chinese young adults: A quasi-experiment cohort study

Introduction: Long-term exposure to air pollution is associated with lung function impairment. However, whether long-term improvements in air quality could improve lung function is unclear. Objectives: To examine whether the reduction of long-term air pollution was associated with lung function improvement among Chinese young adults. Methods: We conducted a prospective quasi-experiment cohort study with 1731 college students in Shandong, China from September 2019 to September 2020, covering COVID-19 lockdown period. Data on air pollution concentrations were obtained from China Environmental Monitoring Station. Lung function indicators included forced vital capacity (FVC), forced expiratory volume in 1st second (FEV₁) and forced expiratory flow at 50 % of FVC (FEF50%). We used linear mixed-effects model to examine the associations between the change of air pollutants concentrations and the change of lung function, and additional adjustments for indoor air pollution (IAP) source. We also conducted stratified analysis by sex. Results: Compared with 2019, the mean FVC, FEV₁ and FEF50% were elevated by 414.4 ml, 321.5 ml, and 28.4 ml/s respectively in 2020. Every 5 μg/m³ decrease in annual average PM_2.5 concentrations was associated with 36.0 ml [95 % confidence interval (CI):6.0, 66.0 ml], 46.1 ml (95 % CI:16.7, 75.5 ml), and 124.2 ml/s (95 % CI:69.5, 178.9 ml/s) increment in the FVC, FEV₁, and FEF50%, respectively. Similar associations were found for PM₁₀. The estimated impact was almost unchanged after adjusting for IAP source. There was no significant effect difference between males and females. Conclusion: Long-term improvement of air quality can improve lung function among young adults. Stricter policies on improving air quality are needed to protect human health.