Assessment of Heat Stress−Related Mortality in Major Korean Cities

Heat is now recognized as the most deadly among all atmospheric hazards in terms of mortality impacts. Even if affected by the same intensity of heat, the damage from the heat depends on the age structure and regional climate. Therefore, it is necessary to regionally assess the heat-related mortality in order to issue heat warnings effectively. This study quantifies heat-related mortality in 6 major cities (Seoul, Incheon, Daejeon, Gwangju, Daegu, and Busan) in South Korea for relative risk assessment by heat-stress. We used daily maximum of perceived temperature (PTmax) and air temperature (Tamax) and daily mortality over a 17-year period from 2000 to 2016. The PT considers not only meteorological element such as air temperature, dew point temperature, wind speed, and solar radiation but also heat exchange processes of human body (Jendritzky et al. 2000, Staiger et al. 2012). Heat-related mortality was estimated based on an event-based heat-stress risk analysis (Scherer et al. 2013). A heat-stress event is defined as sequence days (N≥3days) which PTmax or Tmax exceeds a certain threshold temperature(Tth, 21~50℃). A magnitude of heat-stress events (Mevt) represents cumulative temperature exceeding the threshold (Tth) for each day of the event. The mean total mortality rate of each event was computed considering the period as well as lag days(0~14day). Tth for regions was selected based on high coefficient of determination in relationship of the mean total mortality rate and Mevt.
The results showed that Tth during heat-stress events for PTmax was as high as 41℃ in Daejeon and 39℃ in Seoul, Daegu, and Busan. The base mortality rates of PTmax by region was highest in Busan (11.7 persons/10-6) and lowest in Seoul (7.92 persons/10-6). A Mevt of 2.0 would increase the mean total mortality rate of Daegu by a factor of almost 1.6 than base mortality rate. However the increasing effect would be small and weakly correlated to the Mevt in Busan, Incheon, Gwangju and Daejeon. Tth for Tamax was 32℃ in Gwangju and 31℃ in Seoul, Daejeon and Daegu. Base mortality rate of Tamax was as high as 11.8 (persons/10-6) in Busan. Deagu, which had the highest heat stress, showed highest increasing rate of total daily mortality by heat-stress.
These results can be used to establish regional heat wave policies and to improve the heat-wave forecast information in Korea.