Risk Assessment of Heat Stroke during the Marathon of the Tokyo 2020 Olympics in Sapporo, Hokkaido

A marathon is a grueling endurance race, and runners are at risk of heatstroke. Therefore, the thermal environment of the marathon course should be accurately assessed. Solar radiation, a factor in the thermal environment, is particularly affected by the surrounding environment. In this study, we proposed a method to calculate wet-bulb globe temperature (WBGT) in a short period of time using geographic information system (GIS) data, considering changes in solar radiation. WBGT is used as an indicator of heat stroke. This method was used to assess the risk of heat stroke due to weather conditions, span of time, and location on the marathon course of the Tokyo 2020 Olympics. According to the analysis results, in Sapporo, trees and buildings can suppress WBGT by about 2 degrees C, but on days when the average temperature exceeded 26 degrees C, WBGT exceeded 21 degrees C from 5:00 to 13:00. On the contrary, even in August, the hottest month of the year, there were days when WBGT was almost always below 21 degrees C from 5:00 to 13:00. In other words, it is concluded that the risk of heat stroke can be reduced if the marathon is held in accordance with the weather conditions of the day. In addition, by mapping and identifying locations where there is little change in attenuated WBGT, it is possible to identify locations where the thermal environment should be improved.