Editing IPCC:AR6/WGII/Chapter-10 (section)

=== 10.4.7 Health and Well-Being ===

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Climate change is increasing risks to human health in Asia by increasing exposure and vulnerability to extreme weather events such as heatwaves, flooding and drought, and air pollutants, increasing vector- and water-borne diseases, undernutrition, mental disorders and allergic diseases ( ''high confidence'' ). Sub-regional diversity in socioeconomic and demographic contexts (e.g., ageing, urban compared with agrarian society, increasing population compared with reduced birth rate, high income compared with low to middle income), and geographic characteristics, largely define the differential vulnerabilities and impacts in Asia ( ''high confidence'' ).

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==== 10.4.7.1 Observed Impacts ====

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High temperatures affect mortality and morbidity in Asia ( ''high confidence'' ). In addition to all-cause mortality ( [[#Dang--2016|Dang et al., 2016]] ; [[#Chen--2018e|Chen et al., 2018e]] ), deaths related to circulatory, respiratory, diabetic ( [[#Li--2014b|Li et al., 2014b]] ) and infectious diseases ( [[#Ingole--2015|Ingole et al., 2015]] ), as well as infant mortality ( [[#Son--2017|Son et al., 2017]] ), are increased with high temperature ( ''high confidence'' ). Increased hospital admissions ( [[#Giang--2014|Giang et al., 2014]] ; [[#Lin--2019|Lin et al., 2019]] ) and ambulance transport ( [[#Onozuka--2015|Onozuka and Hagihara, 2015]] ) coincide with increased ambient temperature ( ''high confidence'' ). Heatwaves are particularly detrimental to all-cause and cause-specific mortality ( [[#Chen--2015a|Chen et al., 2015a]] ; [[#Lee--2016|Lee et al., 2016]] ; [[#Guo--2017b|Guo et al., 2017b]] ; [[#Yin--2018|Yin et al., 2018]] ). Both rural and urban populations are vulnerable to heat-related mortality ( [[#Ma--2015|Ma et al., 2015]] ; [[#Chen--2016a|Chen et al., 2016a]] ; [[#Wang--2018a|Wang et al., 2018a]] ). Individuals with lower degrees of education and socioeconomic status, older individuals and individuals living in communities with less green space are more susceptible to heat-related mortality ( ''high confidence'' ) ( [[#Yang--2012a|Yang et al., 2012a]] ; [[#Huang--2015b|Huang et al., 2015b]] ; [[#Seposo--2015|Seposo et al., 2015]] ; [[#Son--2016|Son et al., 2016]] ; [[#Kim--2017|Kim and]] [[#Kim--2017|Kim, 2017]] ). These heat effects have been attenuating over recent decades in East Asian countries, although the driving force behind this remains unknown ( ''high confidence'' ) ( [[#Chung--2017c|Chung et al., 2017c]] ; [[#Chung--2018|Chung et al., 2018]] ).

Rising ambient temperature accelerates pollutant formation reactions and may modify air-pollution-related health effects ( ''medium confidence'' ). Higher temperatures are associated with the increased effects of ozone on mortality ( [[#Shi--2020|Shi et al., 2020]] ). Climate change causes intensified droughts and greater wind erosion resulting in increased intensity and frequency of sand and dust storms ( [[#Akhtar--2018|Akhtar et al., 2018]] ). Mortality and hospital admissions for circulatory and respiratory diseases are increased after exposures to Asian dust events ( ''high confidence'' ) ( [[#Hashizume--2020|Hashizume et al., 2020]] ). El Niño has a major influence on weather patterns in various regions. For example, it causes dry conditions that sometimes result in forest fires and transboundary haze that increased all-cause mortality in children by 41% in Malaysia ( [[#Sahani--2014|Sahani et al., 2014]] ).

Ambient temperature is associated with the risk of an outbreak of mosquito-borne disease in South and Southeast Asia ( ''high confidence'' ) ( [[#Servadio--2018|Servadio et al., 2018]] ). Warmer climates are associated with a higher incidence of malaria ( [[#Xiang--2018|Xiang et al., 2018]] ). Moderate rainfall also promotes malaria infection, while excessive rainfall decreases the risk of malaria ( [[#Wu--2017b|Wu et al., 2017b]] ). El Niño intensity is positively associated with malaria incidence in a single year in India ( [[#Dhiman--2017|Dhiman and Sarkar, 2017]] ). The duration and survival rate of dengue mosquito development, mosquito density, mosquito biting activity, mosquito spatio-temporal range and distribution, and mosquito flying distance are all affected by temperature ( ''high confidence'' ) ( [[#Li--2018b|Li et al., 2018b]] ). Temperature, precipitation, humidity and air pressure are major weather factors associated with dengue fever transmission ( ''high confidence'' ) ( [[#Sang--2014|Sang et al., 2014]] ; [[#Choi--2016|Choi et al., 2016]] ; [[#Xu--2017|Xu et al., 2017]] ).

Climate change alters the hydrological cycle by increasing the frequency of extreme weather events such as excess precipitation, storm surges, floods and droughts ( ''high confidence'' ). Water-borne diseases, such as diarrhoea, leptospirosis and typhoid fever, can increase in incidence following heavy rainfall, tropical cyclones and flooding events ( ''high confidence'' ) ( [[#Deng--2015|Deng et al., 2015]] ; [[#Levy--2016|Levy et al., 2016]] ; [[#Li--2018b|Li et al., 2018b]] ; [[#Matsushita--2018|Matsushita et al., 2018]] ; [[#Zhang--2019b|Zhang et al., 2019b]] ). Droughts can cause increased concentrations of pathogens, which overwhelm water-treatment plants and contaminate surface water. A positive association between ambient temperature and bacterial diarrhoea has been reported, compared with a negative association with viral diarrhoea ( [[#Carlton--2016|Carlton et al., 2016]] ; [[#Wang--2018c|Wang et al., 2018c]] ).

Asia has the highest prevalence of undernourishment in the world, which was 11.4% in 2017, representing more than 515 million people. Southeast Asia has been affected by adverse climate conditions such as floods and cyclones, with impacts on food availability and prices ( [[#FAO--2018d|FAO, 2018d]] ). Crop destruction due to tropical cyclones can include salt damage from tides blowing inland ( ''medium confidence'' ) ( [[#Iizumi--2015|Iizumi and Ramankutty, 2015]] ). Sea level rises result in intrusion of saline water into the coastal area of Bangladesh and people living in this area face an increased risk of hypertension resulting from high salt consumption ( [[#Scheelbeek--2016|Scheelbeek et al., 2016]] ).

Weather conditions have been linked to mental health. High temperatures increase the risk of mental problems including mental disorders, depression, distress and anxiety in Vietnam ( [[#Trang--2016|Trang et al., 2016]] ), Hong Kong SAR of China ( [[#Chan--2018|Chan et al., 2018]] ) and the Republic of Korea ( [[#Lee--2018d|Lee et al., 2018d]] ). In addition, high temperatures are reported to increase the risk of mortality from suicide in Japan, the Republic of Korea, Taiwan, Province of China ( [[#Kim--2016c|Kim et al., 2016c]] ), India ( [[#Carleton--2017|Carleton, 2017]] ) and China ( [[#Luan--2019|Luan et al., 2019]] ). Extreme weather events, such as storms, floods, hurricanes and cyclones, increase injuries and mental disorders (post-traumatic stress disorder and depressive disorders) ( [[#Rataj--2016|Rataj et al., 2016]] ), thereby negatively affecting well-being ( ''high confidence'' ).

Higher temperatures and increased CO 2 elevate the level of allergens such as pollen, which can result in increased allergic diseases, such as asthma and allergic rhinosinusitis. The association between variations in ambient temperature and the occurrence of asthma has been reported in several Asian countries/regions such as Japan ( [[#Yamazaki--2015|Yamazaki et al., 2015]] ), the Republic of Korea ( [[#Kwon--2016|Kwon et al., 2016]] ), China ( [[#Li--2016a|Li et al., 2016a]] ) and Hong Kong SAR of China ( ''medium confidence'' ) ( [[#Lam--2016|Lam et al., 2016]] ).

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==== 10.4.7.2 Projected Impacts ====

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Climate change is associated with significantly increased mortality ( ''high confidence'' ). Figure 10.11 shows projected health impacts due to climate change in Asia. The global estimates of excess deaths due to malnutrition, malaria, diarrhoea and heat stress will be approximately 250,000 deaths per year in 2030–2050 under the medium-to-high emissions scenario, assuming no adaptation ( [[#World%20Health%20Organization--2014|World Health Organization, 2014]] ). The impacts are expected to be greatest in South, East and Southeast Asia. Another projection showed that the change in heat-related deaths is largest in Southeast Asia, which was a 12.7% increase at the end of the century under a high-emissions scenario ( [[#Gasparrini--2017|Gasparrini et al., 2017]] ). As the proportion of older individuals in the population rises, the number of years lost due to disability increases more steeply ( [[#Chung--2017b|Chung et al., 2017b]] ). In the 2080s, the number of annual temperature-related deaths is estimated to reach twice that in the 1980s in China ( [[#Li--2018c|Li et al., 2018c]] ). Over a 20-year period in the mid-21st century (2041–2060), the incidence of excess heat-related mortality in 51 cities in China is estimated to reach 37,800 (95% CI: 31,300–43,500) deaths per year under RCP8.5 ( [[#Bazaz--2018|Bazaz et al., 2018]] ).

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'''Figure 10.11 |''' '''Projected health impacts due to climate change in Asia.'''

Increased concentrations of fine particulate matter and ozone influenced by extreme events such as atmospheric stagnations and heatwaves are projected to result in an additional 12,100 and 8,900 deaths per year due to fine particulate matter and ozone exposure, respectively, in China in the mid-century under RCP4.5 ( [[#Hong--2019a|Hong et al., 2019a]] ). Excess ozone-related future premature deaths is noticeable in 2030 in East Asia and India for RCP8.5 (over 95% of global excess mortality) ( [[#Silva--2016|Silva et al., 2016]] ).

The global estimates for increases in malaria and dengue deaths (annual estimates) are approximately 32,700 and 280 additional deaths, respectively, in 2050 under the medium-to-high emissions scenario ( [[#World%20Health%20Organization--2014|World Health Organization, 2014]] ). Among these additional deaths, 9,300 and 200 deaths, respectively, are projected to occur in South Asia. The population at risk of malaria infection is estimated to increase by 134 million by 2030 in South Asia under the medium-to-high emissions scenario, considering socioeconomic development. If no actions are taken, malaria incidence in northern China is projected to increase by 69–182% by 2050 ( [[#Song--2016|Song et al., 2016]] ). Another study suggested a decrease in climate suitability for malaria in northern and eastern India, southern Myanmar, southern Thailand, the Malaysia border region, Cambodia, eastern Borneo and Indonesia by 2050 ( [[#Khormi--2016|Khormi and Kumar, 2016]] ). By contrast, climate suitability for malaria is projected to increase in the southern and southeast mainland of China and Taiwan, Province of China ( [[#Khormi--2016|Khormi and Kumar, 2016]] ).

Dengue incidence is projected to increase to 16,000 cases per year by 2100 in Dhaka, Bangladesh, if ambient temperatures increase by 3.3°C without any adaptation measures or changes in socioeconomic conditions ( [[#Banu--2014|Banu et al., 2014]] ). This would represent an increase in incidence of over fortyfold compared with 2010. Higher numbers of dengue fever cases are projected to occur under RCP8.5 than RCP2.6 in China ( [[#Song--2017|Song et al., 2017]] ). Compared with the average numbers in 1997–2012, the annual number of days suitable for dengue fever transmission in the 2020s, 2050s and 2080s will increase by 15, 25 and 40 d, respectively, in southern China under RCP8.5. In addition, areas in which year-round dengue fever epidemics occur will ''likely'' increase by 4500, 8800 and 20,700 km 2 in the 2020s, 2050s and 2080s, respectively, under RCP8.5 ( [[#Nahiduzzaman--2015|Nahiduzzaman et al., 2015]] ).

The global estimates for increases in deaths due to diarrhoeal disease (annual estimates) in children under 15 years in 2030 and 2050 are approximately 48,000 and 33,000 additional deaths, respectively, under the medium-to-high emissions scenario ( [[#World%20Health%20Organization--2014|World Health Organization, 2014]] ). Among these additional deaths, 14,900 and 7,700 deaths, respectively, are projected to occur in South Asia. An updated projection with a pathogen-specific approach estimated 25,000 additional annual diarrhoeal deaths in Asia in 2080–2095 under the high-emissions scenario ( [[#Chua--2021|Chua et al., 2021]] ), while in some countries, such as Japan, net reductions in temperature-induced infectious diarrhoeal cases were estimated, because viral infections are dominant in these countries during the cold season ( [[#Onozuka--2019|Onozuka et al., 2019]] ).

South and Southeast Asia are projected to be among the highest-risk regions for reduced dietary iron intake among women of childbearing age and children under five years due to elevated CO 2 concentrations ( ''medium confidence'' ) ( [[#Smith--2018|Smith and Myers, 2018]] ). The estimated number of additional deaths due to climate change in children aged under five years attributable to moderate and severe stunting in 2030 and 2050 are approximately 20,700 and 16,500, respectively, in South Asia, under the medium-to-high emissions scenario ( [[#World%20Health%20Organization--2014|World Health Organization, 2014]] ). In Bangladesh, due to climate change, river salinity is projected to be increased in coastal and freshwater fishery communities leading to significant shortages of drinking water in the coastal urban areas ( [[#Dasgupta--2014c|Dasgupta et al., 2014c]] ).

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==== 10.4.7.3 Adaptation Options/Co-benefits ====

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The health co-benefits of GHG mitigation measures in energy generation have been reported to reduce disease burden. In China, the implementation of GHG policies would reduce the air-pollution-associated disease burden by 44% in 2020 under the Integrate Carbon Reduction scenario compared with the business-as-usual scenario ( [[#Liu--2017b|Liu et al., 2017b]] ). Transition to a half-decarbonised power supply for the residential and transport sectors would prevent 55,000–69,000 deaths in 2030 compared with the business-as-usual scenario ( [[#Peng--2018|Peng et al., 2018]] ). A shift in travel modes from private motor vehicles to the use of mass rapid-transit lines is estimated to reduce CO 2 -equivalent emissions by 6% in greater Kuala Lumpur and bring important health co-benefits to the population ( [[#Kwan--2017|Kwan et al., 2017]] ). The 25 measures developed for reducing air pollution levels in Asia and the Asia–Pacific in general would reduce CO 2 emissions in 2030 by almost 20% relative to baseline projections and decrease warming by 0.3°C by 2050, which could eventually reduce heat-related excess deaths in the region ( [[#UNEP--2019|UNEP, 2019]] ). The 25 measures include conventional emissions controls focusing on emissions that lead to the formation of fine particulate matter (PM2.5), next-stage air-quality measures for reducing emissions that lead to the formation of PM2.5 and are not yet major components of clean-air policies in many parts of the region, and measures contributing to development-priority goals with benefits for air quality. Health co-benefits outweigh mitigation costs in the Republic of Korea up to 2050 ( [[#Kim--2020|Kim et al., 2020]] ). Low-carbon pathways consistent with the 2°C and 1.5°C long-term climate targets defined in the Paris Agreement are associated with the largest health co-benefits when coordinated with stringent air pollution controls in Asia followed by Africa and Middle East ( [[#Rafaj--2021|Rafaj et al., 2021]] ).

Strategies to increase energy efficiency in urban environments by compact urban design and circular-economy policies can reduce GHG emissions and reap ancillary health benefits; for example, compared with conventional single-sector strategies, national CO 2 emissions can be reduced by 15–36%, and the annual deaths from 25,500 to 57,500 are avoidable from air pollution reduction in 637 Chinese cities ( [[#Ramaswami--2017|Ramaswami et al., 2017]] ). In a city in China, the existing mitigation policies (e.g., promotion of tertiary and high-tech industry) and the one-adaptation policy (increasing resilience) increased the co-benefits for well-being ( [[#Liu--2016a|Liu et al., 2016a]] ).

Changing dietary patterns, particularly reducing red meat consumption and increasing fruit and vegetable consumption, contributes to reduced GHG emissions as well as reduced premature deaths. The adoption of global dietary guidelines was estimated to prevent 5.1 million deaths per year relative to the reference scenario in which the largest number of avoidable deaths occurred in East Asia and South Asia, and GHG emissions would be reduced most in East Asia ( [[#Springmann--2016|Springmann et al., 2016]] ). In China, dietary shifts to meet national dietary reference intakes reduced the daily carbon footprint by 5–28% depending on the scenario ( [[#Song--2017|Song et al., 2017]] ). In India, the optimised healthy diets (e.g., lower amounts of wheat and increased amounts of legumes) could help reduce up to 30% water use per person for irrigation and reduce diet-related GHG emissions. This would result in 6800 life-years gained per 100,000 population in 2050 ( [[#Milner--2017|Milner et al., 2017]] ).

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