Incidence of heat stroke in Hokkaido and research trends on the effectiveness of ventilated working wear at construction sites

Abstract

We analyzed the occurrence of heat stroke in workplace in Hokkaido, using heat stroke cases from the Hokkaido Labor Bureau from 2017 to 2024. During this period, 510 cases of heat stroke occurred in workplaces in Hokkaido, 63% of which occurred outdoors. Since there are two peaks in the number of heatstroke cases outdoors, at 11:00 and between 14:00 and 15:00, taking a short rest around 14:00 is suggested as a countermeasure. When the outside temperature exceeds 26°C, several people may suffer heat stroke in a single day. The most frequently mentioned terms in the text on the occurrence of heat stroke during work were terms related to "mowing" outdoors and "factory" and "plastic greenhouse" indoors. It is necessary to raise awareness of heat stroke prevention among construction and manufacturing workers, and among those working in agriculture and forestry. We also reviewed research on fan-equipped work clothes and summarized findings to date on their efficacy. In an experiment with 12 construction workers in a standardized thermal environment in an artificial climate room, physiological and psychological responses were compared between conditions in which ventilated working-jacket (VWJ) was worn over a long-sleeved T-shirt and those in which only a long-sleeved T-shirt was worn. At 34°C, mean skin temperature and clothing sweat content were significantly lower when VWJ were worn. In an outdoor field test of seven construction workers at a construction site in Tokyo, mean skin temperature was significantly lower for workers wearing VWJ than for those who wore only long-sleeved T-shirts in the same air temperature. The relationship between thermal and comfort sensations was significantly stronger among those wearing VWJ. These studies revealed that drinking water intake among construction workers was much lower than that among athletes during sports and that wearing VWJs at construction sites effectively reduced the dehydration rate. Provision of an appropriate volume of drinking water and mandating VWJ use effectively reduces the risk of heatstroke. These results suggest that wearing VWJs may be effective in WBGTs within 23–28 °C.