Health Impact Of Heat And Ozone Pollution Under A Changing Climate

Global warming of our climate system has been found to be ’unequivocal’.Climate change has been identified as "the biggest global health threat of the 21 st century",and tackling it could be "the greatest global health opportunity of the 21 st century".Climate change threatens human health in many ways,including both direct impacts from changes in temperatures and indirect impacts mediated through air pollution.Numerous epidemiologic studies have shown that short-term exposure to heat and ambient ozone pollution have devastating impacts on human health by increasing the mortality and morbidity of the population.To date,due to a combination of data limitations and discipline barriers,far few studies have examined the climate change effects on human health via changes in regional temperature extremes and air pollution concentrations in China.This research investigates the mortality impact of short-term heat and ozone exposures under both current and future climates in Jiangsu Province,China.This study first analyzed heat-related mortality risk in each of 102 counties in Jiangsu Province,China during 2009 to 2013 using a distributed lag non-linear model.The county-specific estimates were then pooled for more urban and less urban counties using a Bayesian hierarchical model.The overall mortality risk comparing the 99th vs.75th percentiles of temperature was 1.43[95%Posterior Intervals(PI):1.36-1.50]in less urban counties and 1.26(95%PI:1.23,1.30)in more urban counties.The heat effects on cardiorespiratory mortality followed a similar pattern.Higher education level and prevalence of air conditioning were significantly associated with counties having lower risks,while percentage of elderly people was significantly associated with increased risks.These findings reveal that nonurban areas have significant heat-related mortality risks in Jiangsu,China.These results suggest the need for enhanced adaptation planning in Chinese nonurban areas under a changing climate.Based on the estimated heat-related mortality risks and statistical downscaled temperature projections from 21 global climate models at a high spatial resolution of 0.25° ×0.25°,this study then assessed the impact of climate change on heat-related total and cause-specific mortality in both urban and rural counties of Jiangsu Province,China.Under both Representative Concentration Pathway(RCP)scenarios,projected warmer temperature in 2016-2040 and 2041-2065 will lead to higher heat-related mortality for total non-accidental,cardiovascular,respiratory,stroke,ischemic heart disease(IHD),and chronic obstructive pulmonary disease(COPD)causes occurring annually during May to September in Jiangsu Province,China.Compared with a constant population,projected future population will cause heat-related cause-specific mortality to increase in 2016-2040 and to decrease in 2041-2065.Nonurban residents in Jiangsu will suffer from more excess heat-related cause-specific mortality in 2016-2065 than urban residents.Targeted climate change mitigation and adaptation measures should also be taken in both urban and nonurban areas of Jiangsu Province.Specific public health interventions should be focused on the leading causes of death,whose health burden will be amplified by a warming climate.Using a generalized additive model and a univariate random-effects meta-analysis,this research evaluated the relationship between short-term ozone exposure and daily total mortality in nine cities of Jiangsu Province,China during 2013-2014.This study found strong evidence that short-term ozone exposure is significantly associated with premature total mortality.This finding is robust when considering the confounding effect of PM2.5,PM10,NO2,and SO2.Higher risks were observed during the warm season(Apr.-Sept.)than the cold season(Oct.-Mar.)in Jiangsu Province.No strong evidence was found to support an obvious threshold in the ozone-mortality concentration-response relationship.Finally,this study estimated the impact of climate change on ozone-related premature mortality in urban areas of Jiangsu Province,China by statistical downscaling ozone projections from a coarse-scale(2.5°×2.0°,longitude × latitude)Geophysical Fluid Dynamics Laboratory(GFDL)chemistry-climate model CM3(GFDL-CM3),and by using the newly available ground level ozone monitoring data across China.Under all RCP scenarios,future ozone concentrations and ozone-related total mortality will increase from 2010s to 2030s.From 2030s to 2050s,emission changes would greatly influence ozone concentrations and associated health burden,as positive changes were found under the high emission scenario RCP8.5 whereas negative changes were found under the low emission scenario RCP4.5.An increasing trend was found for climate change driven ozone concentrations and ozone-related premature mortality in Jiangsu Province from 2010s to 2050s under the RCP8.5_WMGG scenario(climate only scenario),demonstrating the existence of ’climate penalty’ phenomenon in Jiangsu Province.Population growth would influence the impact of climate change on ozone-related premature mortality in Jiangsu Province.Urban residents in Jiangsu Province will experience more ozone attributable deaths in cold season than in warm season,suggesting that climate change-induced ozone-related mortality is not limited to the warm months in China.Addressing the effects of climate change on human health via heat and ozone exposure is especially challenging due to the complicated relationships between climate change,atmospheric environment,and human health.There are still gaps and limitations in this study quantifying the health effects of heat and ozone pollution under a changing climate in Jiangsu Province,including the interactive effect between temperature and ozone pollution on population health risk,the variation of heat-related mortality effects across time periods,population acclimatization and adaptation,and the future changes in demographic structure such as population ageing.Future research can benefit from the following aspects:(1)interactive effects between temperature and air pollution on daily mortality;(2)Long-term variation of temperature-mortality relationship;(3)Population adaptation to temperature/air pollution;and(4)Projections of future heat-and ozone-related health impacts under both climate and demographic structure changes.Our findings could provide valuable information to aid policy makers in understanding and reducing the amount of health burdens attributable to heat and ambient ozone pollution in the context of climate change in Jiangsu Province,China.First of all,adaptation and intervention strategies to reduce heat-related vulnerability are urgently needed in rural areas of China.In addition,ozone concentrations below the current Chinese Ambient Air Quality Standard(CAAQS)level 2 standard(160 μg/m3)could still induce increased mortality risks in China,suggesting that continuous air pollution control measures could yield important health benefits in China,even if future ozone air quality meets the current CAAQS level 2 standard.Moreover,the ’climate penalty’ found in this research reveals that more stringent climate mitigation and air pollution reduction measures are needed to prevent the potential health impacts of future ambient ozone pollution in Jiangsu Province,China.