School of Forestry and Environmental Studies, Yale University, New Haven, United States.
J Expo Sci Environ Epidemiol. 2019 Oct;29(6):790-805. doi: 10.1038/s41370-018-0076-3. Epub 2018 Oct 3.
Heat wave warning systems and related research define heat waves using various indices and there exists no standard definition for a heat wave. Despite various weather forecast services for heat stress in South Korea, it is unclear how different thermal indices affect the designation of heat waves and health effect estimates. We aimed to analyze trends of heat wave characteristics and mortality associations using various criteria for the warm season (June-September) in 2011-5 for the most populated two cities in South Korea, Seoul and Busan. Hourly weather monitoring data and daily mortality data in each city were obtained. The following indices were estimated to define heat waves: air temperature, heat index (HI), humidex, apparent temperature (AT), effective temperature (ET), and wet-bulb globe temperature (WBGT). The thresholds of each index for heat wave definitions were obtained by statistical distribution (95th percentiles) and minimum mortality temperature (MMT). Thermal indices showed clustering of accumulation of excess heat above thresholds for northeast regions in the cities while air temperature showed it for central regions. Compared to 95th percentiles, the MMTs resulted 14 times longer heat wave days for thermal indices except for air temperature. When MMTs were used, nine times larger excess mortality from heat waves occurred for all indices compared to that from heat waves defined by the 95th percentiles. The thermal indices with the highest association between heat and mortality varied between the two cities: air temperature for Seoul and WBGT for Busan. Heat wave warnings should be based on a thorough comparison of how different heat wave criteria will affect the public health impact of heat wave warnings in terms of identifying a heat wave and degree of health impacts due to it.
热浪预警系统和相关研究使用各种指标来定义热浪，目前还没有热浪的标准定义。尽管韩国有各种针对热应激的天气预报服务，但不同的热指数如何影响热浪的划定和健康影响估计尚不清楚。我们旨在使用韩国两个人口最多的城市——首尔和釜山 2011-2015 年暖季（6 月至 9 月）的各种标准来分析热浪特征和死亡率相关性。我们获取了每个城市的逐小时天气监测数据和每日死亡率数据。为了定义热浪，我们估计了以下指标：气温、热指数（HI）、湿热指数、体感温度（AT）、有效温度（ET）和湿球黑球温度（WBGT）。通过统计分布（95%分位数）和最低死亡率温度（MMT）获得了每个指数的热浪定义阈值。热指数显示了城市东北部地区超过阈值的热量积累聚类，而气温则显示了城市中部地区的热量积累聚类。与 95%分位数相比，除气温外，所有热指数的 MMT 导致热浪日数延长了 14 倍。当使用 MMT 时，与使用 95%分位数定义的热浪相比，所有指数的热浪超额死亡人数增加了 9 倍。与死亡率关联度最高的热指数因城市而异：首尔为气温，釜山为 WBGT。热浪预警应基于对不同热浪标准如何影响热浪预警对公众健康的影响进行彻底比较，包括识别热浪和热浪对健康影响的程度。
