Long-term exposure to ozone and incidence of lung cancer in China: data based on a national population cohort (ChinaHEART)

Objective Ozone (O 3 ) is recognized as a predominant and increasingly prevalent gaseous pollutant contributing to the Global Burden of Disease. However, its effect on the development of lung cancer has not been adequately acknowledged. Methods Based on Health Evaluation And risk Reduction through nationwide Teamwork (ChinaHEART), a nationwide, population-based cohort study, 2,006,878 participants living in 20,159 communities or villages were passively followed for the incidence of lung cancer through a linkage of data with the National Central Cancer Registry. The average O 3 levels over ten years from the year of enrolment in their respective localities were determined based on geographic coordinates. We conducted Cox proportional-hazards regression models to assess the independent hazard ratios (HRs) associated with O 3 exposure and the development of lung cancer. Results During the follow-up of 4.93 million person-years, 4,555 new cases of lung cancer were identified. After adjusting for participant characteristics and other environmental factors, we observed a significant positive association between ambient O 3 exposure and lung cancer. Compared with participants in the quartile 1 of O 3 , HRs and 95% confidence intervals (CI) for the other three quartiles were 1.09 (95% CI: 1.00–1.17), 1.17 (95% CI: 1.06–1.29) and 1.42 (95% CI: 1.26–1.59), respectively. Conclusions Long-term exposure to ambient O 3 is associated with a substantially higher risk of lung cancer. Further studies are needed to explore its pathogenic mechanisms, as well as to evaluate measures for exposure protection or harm mitigation at the individual or population level.