The Spatial-Temporal Analysis Of Temperature And Air Pollution In China As Well As Their Influence On Mortality And Heat Vulnerability Assessment

Background:Global warming and air pollution are major environmental issues we are facing today, and studying the changing characteristics and distritubiton of high temperature and air pollution in China could contribute to adopting corresponding measures. Temperature and air pollution could bring harm to population, and the harm is not only immediate but also delayed. Studying temperature-mortality relationship and air pollution-mortality relationship could contribute to adopting corresponding measures to reduce their harm. In the context of global warming, there would be an increase in the duration, intensity and spatial extent of heat waves and warm spells during the next decade. In order to efficiently deal with high temperature disaster, it is important to highlight the areas where people are at the greatest risk of harm from heat, and this could be completed by taking heat vulnerability assessment.Objectives:(1) Finding out areas that facing serious high temperature disaster and air pollution through spatial-temporal analysis of temperature and air pollution in China; (2) Studing the influence of temperature and air pollution on human health; (3) Targeting the intervention of heat risk through heat vulnerability assessment.Methods:(1) Drewing line charts and histograms of the annual mean temperature and high temperature days, as well as line charts and histograms of air pollution index (API) and air quality index (AQI) of 31 capital cities and municipalities to research their distributions across different times and cities. Researching the spatial clustering of API and AQI through the software of GeoDa, the shift of gravity center of API and AQI in different years and months, as well as the reported primary pollutants and the correlation between different pollutants; (2) Taking four Chinese cities with different latitudes (Wuhan, Changsha, Guilin and Haikou) as examples, we studied the influence of temperature and air pollution on mortality and their lag effect adopting a Poisson regression model combined with a distributed lag nonlinear model; (3) We conducted heat vulnerability assessment taking Hainan province as example:first, drawing line charts and histograms to research the changing characteristics and distribution of high temperature days across different cities; then, after studying related articles and consulting relevant experts, we selected 10 heat-related indicators, and furtherly performed a principal component analysis of the 9 variables which belonged to socioeconomic indicators, the extraction of principal components was based on eigenvalues and explained variance; finally, HVI was calculated by synthesizing the extracted principal variables and high temperature days, and the HVT value of each city was present in the map by the software of ArcGIS.Results:(1) The annual mean temperature and high temperature days fluctuated regularly on a small scale in the studied period, and the adjacent areas present similar trends. The API values had a decreasing trend:the high values had a clustering trend in some northern cities, and the low values had a clustering trend in some southern cities. The AQI values were relatively low from 15:00 to 17:00 during the day. The gravity center of API had a trend of moving south from 2001-2003, then fluctuated in an unordered pattern, and moved north in the winter. The AQI gravity center did not have a regular shift during different months. The most reported primary pollutants were PM10 and PM2.5; the correlations between AQI, PM2.5 and PMio were relatively good, while the correlations between O3 and other air pollutants were weak, and the correlations were negative. The concentration of O3 was relatively high from 15:00 to 17:00; (2) we found that the cold months were December, January, February and March, whereas the hot months were June to September. The ratios of the deaths in the cold months to hot months were 1.43,1.54,1.37 and 1.12 for the cities of Wuhan, Changsha, Guilin and Haikou, respectively. The effects of extremely high temperatures were generally maintained for 3 days, whereas the risk of extremely low temperatures could persist for 21 days. Compared to the optimum temperature of each city, at a lag of 21 days, the relative risks (95% confidence interval) of extreme cold temperatures were 4.78 (3.63, 6.29),2.38 (1.35,4.19),2.62 (1.15,5.95) and 2.62 (1.44,4.79) for Wuhan, Changsha, Guilin and Haikou, while the risks were 1.35 (1.18,1.55),1.19 (0.96,1.48),1.22 (0.82, 1.82) and 2.47 (1.61,3.78) for extreme hot temperatures, respectively, at a lag of 3 days. As for Wuhan, the relative risks (95% confidence interval) of extreme cold temperatures were 5.62 (3.92,8.06),5.53 (2.87,10.69) and 5.80 (4.29,7.84) for circulation system disease, respiratory system disease and elderly population, while the risks were 1.39 (1.15,1.67),1.45 (0.98,2.16) and 1.32 (1.14,1.54) for extreme hot temperatures, respectively. The influence of API on non-accidental deaths didn’t show statistical significance; (3) the number of high temperature days of HaiKou, QiongHai, ChengMai, LinGao and BaiSha had increasing trends from 1971-2010, and the city of ChangJiang had the most number of high temperature days in this period, with 1864 hot days, an average of 46.6 days a year. There were significant correlations between the 9 socioeconomic indicators, and then 3 principal components were extracted. The city of BaiSha had the highest HVI scores, while SanYa had the lowest.Conclusions:the government should take more meatures to the areas facing more serious hazard of high temperature and air pollution, as well as taking meatures to mitigate air pollution during the winter. AQI could reflect the concentration of PM2.5 and PM10 to a certain extent, but it couldn’t reflect the pollution level of O3. Temperature-mortality relationships vary among cities with different latitudes, and local governments should establish regional prevention and protection measures to more effectively adapt to climate change. The effects of hot temperatures predominantly occur in the short term, whereas the effects of cold temperatures could persist for an extended number of days. Different cities of Hainan province have different numbers of high temperature days and different development levels of social economy, so they face with different degree of hot damage. Targeting high risk areas and protecting sensitive people could reduce the adverse effects of extreme heat more effectively.