Long-term effects of ambient air pollution on lung cancer and COPD mortalities in China: A systematic review and meta-analysis of cohort studies

The long-term effects of ambient air pollution on lung cancer (LC) and chronic obstructive pulmonary disease (COPD) mortalities in the more polluted regions in the world require a comprehensive analysis. In this study, a systematic literature search and meta-analysis using the updated Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) 2020 guideline were conducted to examine the association between long-term exposure to ambient air pollution for the LC and COPD mortalities in China. Two databases (PubMed and Scopus) were systematically searched and a total of eight research papers were finally included in this study with the risk of bias assessed by Newcastle-Ottawa Scale (NOS). A total of 409,945 participants were included in the analysis based on four individual Chinese cohorts during the follow-up periods between 1991 and 2011. The pooled risk ratios for LC and COPD mortalities were 1.08 (95% CI: 1.02–1.16) and 1.12 (95% CI: 1.11–1.13), respectively, for each 10 μg/m³ increase in the concentrations of PM_2.5. Furthermore, the results of the meta-analysis were examined using a case study in the Yangtze River Delta region in 2015. A comparison of the estimated LC and COPD mortality risks between the current study and the previous relative risk model demonstrated that the result of cohort studies could provide more accurate relative risk values and estimated mortalities for the population in China. Although only limited cohort studies have been conducted in China, they provide significant evidence of the long-term effects of ambient air pollution on LC and COPD mortalities in the population of the more polluted regions. It is also recommended to develop a more suitable relative risk model using the results of meta-analysis for the estimation of air pollution-related mortality in the more polluted regions.