A Public Health Initiative for Action on Early Warning of Heat Health Risks

Heatwaves, also known as extreme heat events, represent periods of excessively hot weather and rank among the most perilous natural hazards worldwide due to their increased mortality risk, especially among vulnerable populations.The frequency, intensity, and geographical spread of heatwaves are noticeably increasing in the setting of climate change (1).In 2019, there were a reported 475 million global heatwave events, an increase of 160 million per capita days in comparison to 2016 (2).Disturbingly, in 2003 there were approximately 25,000-70,000 premature heat-related deaths in Western Europe (3), and in the summer of 2010 around 55,000 excess deaths in Russia were linked to heatwaves (4).A similar pattern was observed in 2019 with approximately 26,800 deaths in China being attributed to heatwaves (5).Furthermore, in the same year, nearly half (46.2%) of the total global heatrelated deaths were elderly individuals, with the majority of these deaths occurring in Japan, Eastern China, Northern India, and Central Europe (6).Given the relentless trends in population aging and urbanization, heatwaves could pose a significantly bigger health hazard in future years.Projections from the World Health Organization (WHO) predict over 92,000 premature deaths from high temperatures globally by 2030, with over 19,000 premature deaths expected in Eastern Asia (inclusive of China and the Republic of Korea) alone ( 7).Hence, the development and implementation of effective strategies to combat heatwaves, as well as improving public safeguards, are and will continue to be pivotal challenges across the intersecting fields of climate change and public health.In an effort to mitigate the health consequences of heat, the United States pioneered the establishment of the Hot Weather-Health Watch/Warning System during the 1990s.This was not only based on traditional hightemperature forecast warnings, but also focused on the premature mortality risk (8).The devastating heatwave of 2003 spurred many European countries into active research about health risks associated with such heatwaves.This resulted in the development of a more comprehensive heat health warning system (9).In 2015, to further global public health protection, the World Meteorological Organization and WHO collaboratively published the guidance document "Heatwaves and Health: Guidance on Warning-System Development".This aimed to influence the development of similar early warning systems worldwide (10).In China, the reaction to heatwaves primarily depends on the early heat wave warnings disseminated by the China Meteorological Administration, which consist of three classifications: yellow, orange, and red.However, this system exclusively considers temperature intensity, neglecting the correlation between heatwaves and health ramifications.Consequently, its effectiveness in safeguarding public health remains limited.Over the past two decades, Chinese researchers have endeavored to develop a more efficient heatwave health risk early warning system.Despite pieces of related research, the full-scale implementation of this system across the country has not yet materialized.In 2001, the Shanghai Meteorological Bureau, in conjunction with the Shanghai Health Commission, launched the pioneering "Heatwave/Health Warning System" in Shanghai Municipality (11).Subsequently, in 2013, led by the National Institute of Environmental Health, Chinese Center for Disease Control and Prevention (NIEH, China CDC), a heatwave health early warning system was set up in Shenzhen, Nanjing, Chongqing, and Harbin, which are located in various climatic zones with different climatic characteristics (12)(13)(14).Researchers gathered historical data related to meteorology, air quality, mortality, and morbidity, and established models to identify the relationships between heatwaves and mortality and morbidity rates for various diseases in each city.The warning levels encompass red, orange, yellow, and blue.Depending on the risk reaching the corresponding warning level, the system generates an alert indicating the disease risk level, appropriate response measures, and recommendations for mitigation for diverse population groups.However, this system only operated on a trial basis and was not expanded nationwide.