Mapping Health Vulnerability To Heat-related Exposure Based On A Directional Interaction Network In China

Background:Global warming has become the most significant global health threat of the 21st Century.Under the background of global warming,the frequency,intensity,and duration of extreme temperature events are expected to rise in the future.Studies have shown that the effects of hot temperatures predominantly occur over the short term and have acute effects on mortality and morbidity.In addition,the health risks caused by global warming have systematic characteristics that further increase the difficulty of coping with health threats of global warming.Accurate assessment of systemic health risks caused by global warming is a prerequisite for better managing global warming trends.Therefore,Intergovernmental Panel on Climate Change(IPCC)proposed a vulnerability assessment framework for climate change.A series of studies used multi-criteria decision making methods to build composite indexes to assess heat-related health vulnerability based on the IPCC vulnerability framework.Previous studies have recognized interactions between and among system components but have left open the question of indicator directional interaction.Therefore,it is difficult to identify specific intervention steps and develop actionable strategies to address global warming risks.Objective:Our study aimed to build a heat-related health vulnerability assessment index system based on a directional interaction network to assess heat-related health vulnerability in China.The results from health vulnerability assessments were then used to explore hotspots,priority indicators,and potential coping strategies,providing policy guidance for the government to implement intervention measures and allocate resources rationally.Methods:Our study combined individual data with city-level social development,meteorological and pollution data,constructing an indicators pool of heat-related health vulnerability based on the IPCC vulnerability framework and previous literature.Exploratory Factor Analysis was used to determine the specific evaluation indicators.Afterward,Bayesian network model(BN)and network analysis were proposed to estimate the directional associations between indicators.Using indicator directional associations as weights,a weighted technique for the order of preference by similarity to ideal solution method(TOPSIS)was proposed to assess heat-related health vulnerability.The results from the directional interaction network and health vulnerability assessments were then used to explore hotspots,priority indicators,and coping strategies for northern and southern China,respectively.Results:1.The proposed heat-related health vulnerability framework included 33 indicators covering exposure,adaptive capacity and sensitivity.2.Exposure to heavy fine particles(PM2.5)pollution,Exposure to PM2.5 pollution,and Exposure to inhalable particles(PM10)pollution were the top three contributing indicators for heat-related health vulnerability in northern China.Standard deviation of humidex in one month,Standard deviation of average temperature in one month,and Monthly average humidex were the top three contributing indicators for heat-related health vulnerability in southern China.3.The cities in northern China with the five worst vulnerabilities were Liaocheng,Puyang,Cangzhou,Dezhou,and Tianjin.According to the growth rate,heat-related health vulnerability of these cities showed a positive growth trend.Spatial autocorrelation analysis implied that heat-related health vulnerability experienced external regional spillover effects.For southern China,the cities with the worst vulnerability were located in the Yangtze River Basin.Meanwhile,spatial correlation was also documented in some cities(such as Ningbo and Taizhou)along the Yangtze River Basin.The deterioration of health vulnerability in the Yangtze River Basin was more concerning,judging from the negative growth rate.4.Air pollution and temperature exposure were recognized as priority indicators in the most vulnerable cities of northern and southern China,respectively.With the same exposure level,improving adaptive capacity could alter the risk of health vulnerability caused by high temperatures.Conclusion:1.The directional interaction network differed in northern and southern China.Air pollution and temperature exposure were the most influential indicator of heat-related health vulnerability for northern and southern cities,respectively.2.China revealed a dramatic spatial imbalance in terms of heat-related health vulnerability levels.In northern China,hotspots were concentrated in the Beijing-Tianjin-Hebei Region and Shandong and Henan Provinces.In southern China,the majority of hotspots were along the Yangtze River Basin.Air pollution and temperature exposure were recognized as priority indicators in the most vulnerable cities of northern and southern China,respectively.These two indicators were prioritized because they have high levels of air pollution or temperature exposure and also contributed most to heat-related health vulnerability.3.Even though exposure contributed most to the health vulnerability issue,our results indicate that adaptive capacity could alter the extent of risk.Thus,mitigation and adaptation are the two primary policy responses to temperature change and should be implemented in an integrated way.Meanwhile,interregional cooperation should be strengthened under the circumstances of spatial correlation.