Impacts of Outdoor Particulate Matter Exposure on the Incidence of Lung Cancer and Mortality

Background and objectives: Long-term exposure to air pollution has been associated with lung cancer. This study aimed to evaluate the relative risk (RR) and hazard ratio (HR) of lung cancers and the prognostic implication of outdoor particulate matter (PM) pollution using a meta-analysis. Materials and Methods: We performed the meta-analysis using 19 eligible studies and evaluated the PMs, dividing into PM smaller than 2.5 µm (PM(2.5)) and PM smaller than 10 µm (PM(10)). In addition, subgroup analyses, based on the increment of PM exposure, location, sex, smoking history, and tumor histology, were performed. Results: Lung cancer was significantly increased by exposure to PM(2.5) (RR 1.172, 95% confidence interval (CI) 1.002–1.371), but not PM(10) exposure. However, there was no significant correlation between PM(10) exposure and the incidence of lung cancers (RR 1.062, 95% CI 0.932–1.210). The all-cause and lung-cancer-specific mortalities were significantly increased by PM(2.5) exposure (HR 1.1.43, 95% CI 1.011–1.291 and HR 1.144, 95% CI 1.002–1.307, respectively). However, PM(10) exposure significantly increased the all-cause mortality, but not the lung-cancer-specific mortality. The lung-cancer-specific mortality was significantly increased by PM10 per 12.1 μg/m(3) increment and in the Europe area. Conclusions: PM(2.5) significantly increased lung cancer and the all-cause and lung-cancer-specific mortalities, whereas PM(10) did not increase lung cancer or lung-cancer-specific mortality. However, PM(10) increased the all-cause mortality and the PM(10) per 12.1 μg/m(3) increment and PM(10) in the Europe area may increase the lung-cancer-specific mortality.