Excess mortality associated with high ozone exposure: A national cohort study in China

Emerging epidemiological studies suggest that long-term ozone (O3) exposure may increase the risk of mortality, while pre-existing evidence is mixed and has been generated predominantly in North America and Europe. In this study, we investigated the impact of long-term O3 exposure on all-cause mortality in a national cohort in China. A dynamic cohort of 20882 participants aged ≥40 years was recruited between 2011 and 2018 from four waves of the China Health and Retirement Longitudinal Study. A Cox proportional hazard regression model with time-varying exposures on an annual scale was used to estimate the mortality risk associated with warm-season (April–September) O3 exposure. The annual average level of participant exposure to warm-season O3 concentrations was 100 μg m−3 (range: 61–142 μg m−3). An increase of 10 μg m−3 in O3 was associated with a hazard ratio (HR) of 1.18 (95% confidence interval [CI]: 1.13–1.23) for all-cause mortality. Compared with the first exposure quartile of O3, HRs of mortality associated with the second, third, and highest exposure quartiles were 1.09 (95% CI: 0.95–1.25), 1.02 (95% CI: 0.88–1.19), and 1.56 (95% CI: 1.34–1.82), respectively. A J-shaped concentration–response association was observed, revealing a non-significant increase in risk below a concentration of approximately 110 μg m−3. Low-temperature-exposure residents had a higher risk of mortality associated with long-term O3 exposure. This study expands current epidemiological evidence from China and reveals that high-concentration O3 exposure curtails the long-term survival of middle-aged and older adults.