10.4.5 Human health
Climate change poses substantial risks to human health in Asia. Global burden (mortality and morbidity) of climate-change attributable diarrhoea and malnutrition are already the largest in South-East Asian countries including Bangladesh, Bhutan, India, Maldives, Myanmar and Nepal in 2000, and the relative risks for these conditions for 2030 is expected to be also the largest (McMichael et al., 2004), although in some areas, such as southern states in India, there will be a reduction in the transmission season by 2080 (Mitra et al., 2004). An empirical model projected that the population at risk of dengue fever (the estimated risk of dengue transmission is greater than 50%) will be larger in India and China (Hales et al., 2002). Also in India and China, the excess mortality due to heat stress is projected to be very high (Takahashi et al., 2007), although this projection did not take into account possible adaptation and population change. There is already evidence of widespread damage to human health by urban air quality and enhanced climate variability in Asia. Throughout newly industrialised areas in Asia, such as Chongqing, China, and Jakarta, Indonesia, air quality has deteriorated significantly and will likely contribute to widespread heat stress and smog induced cardiovascular and respiratory illnesses in the region (Patz et al., 2000). Also, the number of patients of Japanese cedar pollen disease is likely to increase when the summer temperature rises (Takahashi and Kawashima, 1999; Teranishi et al., 2000).
The negative influence of temperature anomalies on public health has been established in Russia (Izmerov et al., 2004) and in the semi-arid city, Beirut (El-Zein et al., 2004). Exposure to higher temperatures appears to be a significant risk factor for cerebral infarction and cerebral ischemia during the summer months (Honda et al., 1995). Natural habitats of vector-borne diseases are reported to be expanding (Izmerov et al., 2004). Prevalence of malaria and tick-borne encephalitis has also increased over time in Russia (Yasukevich and Semenov, 2004). The distribution of vector-borne infectious diseases such as malaria is influenced by the spread of vectors and the climate dependence of the infectious pathogens. There are reports on the possible effects of pesticide resistance of a certain type of mosquito on the transition of malaria type (Singh et al., 2004). The insect-borne infectious diseases strongly modulated by future climate change include malaria, schistosomiasis, dengue fever and other viral diseases (Kovats et al., 2003). Oncomelania is strongly influenced by climate and the infection rate of schistosomiasis is the highest in the temperature range of 24°C to 27°C. Temperature can directly influence the breeding of malaria protozoa and suitable climate conditions can intensify the invasiveness of mosquito (Tong and Ying, 2000). A warmer and more humid climate would be favourable for propagation and invasiveness of infectious insect vector. Serious problems are connected with the impact of air pollution due to Siberian forest fires on human health (Rachmanin et al., 2004).
Warmer sea-surface temperatures along coastlines of South and South-East Asia would support higher phytoplankton blooms. These phytoplankton blooms are excellent habitats for survival and spread of infectious bacterial diseases such as cholera (Pascual et al., 2002). Water-borne diseases including cholera and the suite of diarrhoeal diseases caused by organisms such as Giardia, Salmonella and Cryptosporidium could also become common with the contamination of drinking water. Precipitation increase and frequent floods, and sea-level rise in the future will degrade the surface water quality owing to more pollution and, hence, lead to more water-borne infectious diseases such as dermatosis, cardiovascular disease and gastrointestinal disease. For preventive actions, assessment of climate change impacts on nutritional situation, drinking water supply, water salinity and ecosystem damage will be necessary. The risk factor of climate-related diseases will depend on improved environmental sanitation, the hygienic practice and medical treatment facilities.