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.
Zou et al. (Tue,) studied this question.