<p>Global warming is associated with the co-occurrence of extreme heat and ozone pollution events, referred to as compound heatwave-ozone pollution events (CHOEs). However, the health risks associated with CHOEs remain poorly understood. Here, we estimate the spatiotemporal trends of CHOEs across China from 1995 to the end of the 21st century as well as the related health risks. CHOEs are defined as two consecutive days with a daily average temperature exceeding its 98th percentile, and two consecutive days with a daily maximum 8-hour ozone (O<sub>3</sub>) concentration surpassing 160μg/m<sup>3</sup> during summer. Days meeting only one of these criteria are classified as a heatwave-only (HW-only) or O<sub>3</sub> pollution-only (O₃-only) event. We employ a two-stage approach combining a generalized additive model (GAM) and multivariate meta-analysis to estimate exposure-response associations between HW-only, O<sub>3</sub>-only, and CHOEs and nonaccidental, cardiovascular, and respiratory mortality across 21 Chinese cities from 2010 to 2016. Leveraging these established associations, we further evaluate the national mortality burden attributable to CHOEs. Our findings indicate that, compared with HW-only events (relative risk [RR] = 1.20, 95% confidence interval [CI]: 1.17, 1.23) or O<sub>3</sub>-only events (RR = 1.03, 95% CI: 1.01, 1.05), CHOEs are significantly associated with a higher nonaccidental mortality risk (RR = 1.27, 95% CI: 1.24, 1.30). This pattern is also observed for cardiovascular and respiratory mortality, which are associated with synergistic interaction effects between HWs and O<sub>3</sub> pollution. Under the high-emission scenario (SSP5-8.5), CHOE occurrence shows a significant uptrend across China from 1995 to the end of the century, with the annual average CHOE days projected to increase by 27.49 days in the 2080s. The attributable excess deaths peak in the 2060s, reaching 164,599 annual nonaccidental deaths, including 91,088 cardiovascular and 20,437 respiratory deaths. Notably, regions with high population density are particularly vulnerable. These findings highlight the need for integrated early warning systems, targeted mitigation strategies, and climate-informed policies to address compound extreme event risks.</p>

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Mortality burden trends attributed to compound heatwave–ozone pollution events in China under global warming

  • Ying Zhang,
  • Jinyuan Xin,
  • Changjian Ni,
  • Chaoyong Tu,
  • Canjun Zheng

摘要

Global warming is associated with the co-occurrence of extreme heat and ozone pollution events, referred to as compound heatwave-ozone pollution events (CHOEs). However, the health risks associated with CHOEs remain poorly understood. Here, we estimate the spatiotemporal trends of CHOEs across China from 1995 to the end of the 21st century as well as the related health risks. CHOEs are defined as two consecutive days with a daily average temperature exceeding its 98th percentile, and two consecutive days with a daily maximum 8-hour ozone (O3) concentration surpassing 160μg/m3 during summer. Days meeting only one of these criteria are classified as a heatwave-only (HW-only) or O3 pollution-only (O₃-only) event. We employ a two-stage approach combining a generalized additive model (GAM) and multivariate meta-analysis to estimate exposure-response associations between HW-only, O3-only, and CHOEs and nonaccidental, cardiovascular, and respiratory mortality across 21 Chinese cities from 2010 to 2016. Leveraging these established associations, we further evaluate the national mortality burden attributable to CHOEs. Our findings indicate that, compared with HW-only events (relative risk [RR] = 1.20, 95% confidence interval [CI]: 1.17, 1.23) or O3-only events (RR = 1.03, 95% CI: 1.01, 1.05), CHOEs are significantly associated with a higher nonaccidental mortality risk (RR = 1.27, 95% CI: 1.24, 1.30). This pattern is also observed for cardiovascular and respiratory mortality, which are associated with synergistic interaction effects between HWs and O3 pollution. Under the high-emission scenario (SSP5-8.5), CHOE occurrence shows a significant uptrend across China from 1995 to the end of the century, with the annual average CHOE days projected to increase by 27.49 days in the 2080s. The attributable excess deaths peak in the 2060s, reaching 164,599 annual nonaccidental deaths, including 91,088 cardiovascular and 20,437 respiratory deaths. Notably, regions with high population density are particularly vulnerable. These findings highlight the need for integrated early warning systems, targeted mitigation strategies, and climate-informed policies to address compound extreme event risks.