Long-Term Ambient Ozone Exposure and Nonaccidental Mortality among Chinese Adults: A Nationwide Cohort Study

Existing evidence on long-term ozone exposure and total mortality was mainly from Europe and the United States, with inconsistent findings. In China, there is a critical lack of localized cohort-based evidence on this association to inform air quality standard revisions. In this nationwide cohort study of 96,955 adults across 31 Chinese provinces, peak-season and warm-season ozone exposure were estimated using a previously developed random forest model. Stratified Cox proportional hazards models were employed to examine the associations between long-term ozone exposure and nonaccidental mortality and to characterize their exposure-response relationships. In the fully adjusted model, each 10 μg/m³ increase in peak-season and warm-season average ozone concentrations was associated with increased nonaccidental mortality risks of 3.0% (hazard ratio [HR] = 1.030; 95% CI: 1.010, 1.050) and 2.9% (HR = 1.029; 1.010, 1.048), respectively. The exposure-response curves provided weak evidence for a threshold effect of long-term ozone exposure. We estimated that 487,207 (95% UI: 168,705, 786,351) deaths could be attributed to long-term ozone exposure in China in 2019. These findings underscore an urgent need to establish standards for semiannual average ozone concentrations and to strengthen ozone air pollution control.