Traffic-related air pollution and lung cancer: A meta-analysis

Background: We conducted a meta-analysis to evaluate the association between traffic-related air pollution and lung cancer in order to provide evidence for control of traffic-related air pollution. Methods: Several databases were searched for relevant studies up to December 2013. The quality of articles obtained was evaluated by the Strengthening the Reporting of Observational Studies in Epidemiology checklist. Statistical analysis, including pooling effective sizes and confidential intervals, was performed. Results: A total of 1106 records were obtained through the database and 36 studies were included in our analysis. Among the studies included, 14 evaluated the association between ambient exposure to traffic-related air pollution and lung cancer and 22 studies involved occupational exposure to air pollution among professional drivers. Twenty-two studies were marked A level regarding quality, 13 were B level, and one was C level. Exposure to nitrogen dioxide (meta-odds ratio [OR]: 1.06, 95% confidence interval [CI]: 0.99-1.13), nitrogen oxide (meta-OR: 1.04, 95% CI: 1.01-1.07), sulfur dioxide (meta-OR: 1.03, 95% CI: 1.02-1.05), and fine particulate matter (meta-OR: 1.11, 95% CI: 1.00-1.22) were positively associated with a risk of lung cancer. Occupational exposure to air pollution among professional drivers significantly increased the incidence (meta-OR: 1.27, 95% CI: 1.19-1.36) and mortality of lung cancer (meta-OR: 1.14, 95% CI: 1.04-1.26). Conclusion: Exposure to traffic-related air pollution significantly increased the risk of lung cancer.