The effects of PM2.5 on lung cancer-related mortality in different regions and races: A systematic review and meta-analysis of cohort studies.

Given the increasing environmental pollution around the world, air pollutants such as particulate matters (PM) have been becoming typical carcinogenic factors to cause lung cancer. The PM with aerodynamic diameter less than or equal to 2.5 μm (PM_2.5) plays an important role in lung cancer mortality. However, effects of PM_2.5 on the mortality of lung cancer patients have not been investigated well. The purpose of this study is to assess the associations between PM_2.5 exposure and lung cancer-related mortality, by regions and races. This systematic review was developed and conducted according to PRISMA protocol. A comprehensive literature search for peer-reviewed studies published up to October 2021 was conducted using the electronic databases PubMed, EMBASE, and Cochrane Library. The identified records were carefully evaluated following the PICOS criteria. Relative risks (RRs) and 95% confidence interval (CI) of lung cancer mortality associated with PM_2.5 were extracted and meta-analyzed. The Chi-squared test, Begg's test, and Eggerr analysis were performed to assess the heterogeneity and publication bias. Sensitivity analysis and subgroup analysis were also conducted to make sure the authenticity and stability of the present study. In total, 16 studies met the inclusion criteria. For the overall effects of PM_2.5 on lung cancer-related mortality, there was heterogeneity among the included studies (I² = 62.30%, P < 0.01); thus, the random effects model was chosen to conduct related analysis. The pooled adjusted RR of lung cancer mortality associated with PM_2.5 was 1.12 (95% CI: 1.09–1.15) for per 10 µg/m³ increase in PM_2.5 concentrations. For different continents, the RRs of subgroup analysis in North-America, Asia, and Europe were 1.16 (1.09–1.22), 1.08 (CI: 1.07–1.09), and 1.14 (CI: 1.04–1.23), respectively. Subgroup analysis by race showed that for Mongoloid RR = 1.08 (1.07–1.09), and for Caucasoid RR = 1.13 (CI: 1.11–1.15). With per 10 µg/m³ increase in PM_2.5, the mortality rate of Caucasoid lung cancer patients increased by 1.13 times, greater than that of the Mongoloid. Increase in PM_2.5 concentrations is associated positively with the mortality of lung cancer patients. For different regions and races, the adverse effects of PM_2.5 are discrepant. Our Findings can provide necessary evidence to protect public health further from air pollution. [ABSTRACT FROM AUTHOR]