11.2.5.1. Thermal Stress and Air Pollution-Related Diseases

Figure 11-12: Heat stroke morbidity (cases per million; Tokyo, July-August, 1980-1995, males >65 years) (Piver et al., 1999).

A remarkable increase in the number of heatstroke patients and mortality was observed when maximum daily temperatures in Nanjing, China, exceeded 36°C for 17 days during July 1988 (Ando et al., 1996). In Japan as well, intense heat in summer is now becoming more common in large cities. The numbers of heatstroke patients are reported to have increased exponentially with temperatures of more than 31°C in Tokyo, Japan, and 35°C in Nanjing, China. Beyond a maximum daily temperature of 36°C, a remarkable increase in the number of heatstroke patients and deaths caused by heatstroke has been observed (Honda et al., 1995; Ando, 1998). Typical hyperthermia occurs during hot days and during physical exercise in the summer (Nylen et al., 1997).

Climate change will have a wide range of health impacts all across Asia (see Chapter 9). Although a reduction in health stresses and wintertime deaths is anticipated as a result of less frequent occurrence of extreme cold temperatures in boreal and temperate Asia, an increase in the frequency and duration of severe heat waves and humid conditions during the summer will increase the risk of mortality and morbidity, principally in older age groups and urban poor populations of temperate and tropical Asia (Epstein et al., 1995). Heat stress-related chronic health damages also are likely for physiological functions, metabolic processes, and immune systems (Bouchama et al., 1991; Ando, 1998).

Adverse health impacts also result from the build-up of high concentrations of air pollutants such as nitrogen dioxide (NO₂), ozone, and air-borne particulates in large urban areas. Combined exposures to higher temperatures and air pollutants appear to be critical risk factors for cerebral infarction and cerebral ischemia during the summer months (Piver et al., 1999). As summarized in Figure 11-12, the heat index (a combination of daily mean temperature and relative humidity) and the concentration of NO₂ are shown to be significant risk factors for heatstroke in males age 65 years and older residing in Tokyo, Japan (Piver et al., 1999). The number of heatstroke emergency cases per million residents is found to be greater in males than in females in the same age groups. Global warming also will increase the incidences of some diseases, such as respiratory and cardiovascular diseases, in arid and semi-arid, temperate, and tropical Asia.

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