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 be-tween 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 es-timate 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 mu g m3 (range: 61 -142 mu g m3). An increase of 10 mu g m3 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 mu g m3. Low-temperature-exposure residents had a higher risk of mortality associ-ated 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.(c) 2023 The Authors. Published by Elsevier B.V. on behalf of Chinese Society for Environmental Sciences, Harbin Institute of Technology, Chinese Research Academy of Environmental Sciences. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

Emerging evidence suggests that long-term exposure to ozone (O3) may increase the risk of mortality, but there is mixed evidence particularly from North America and Europe. This study investigated the impact of long-term O3 exposure on all-cause mortality in a national cohort in China. The results showed that an increase in O3 concentration was associated with a higher mortality risk, especially in high-concentration areas.