Heatstroke of foreign visitors

Sweat rate and THI

Are those who live in the subarctic zones feel difficult to sweat?
Do foreign countries have more comfortable weather than Japan?

  The amount of perspiration is related to the risk of getting heatstroke. When the amount of perspiration is low, human beings cannot lower surface temperature of body and are easy to have heatstroke.

  According to the experiment “日本の真夏:訪日外国人の熱中症リスクの試算に成功~冷帯気候出身者のリスクは熱帯気候出身者に比べて顕著~” by Nagoya university, Kitami kogyo university, Tohoku university cyiber sciences center and the Japan Weather Association, the temperate zones and the torrid zones, people who live in the subarctic zones are the easiest to elevate of body temperature. Because a number of their perspiration gland is fewer than others, they are difficult to break a sweat.

What is Perspiratory gland?
… Perspiratory gland is the system of making sweat. There is in the skin of whole body and there are two types of gland, which are eccrine gland and apocrine gland. We have about three billion eccrine glands in our body. Hands and soles are most densely spots. As getting older, eccrine atrophy and the amount of perspiration is decreasing. (According to the explanation of perspiratory gland from JCA’s website)

  The website, Stop! Heatstroke (熱中症ゼロへ), indicates that those who live in the subarctic zones care heatstroke at lower humidity than other zone.

  Those who live in the subarctic zones do not adapt to Japan’s humidity. Therefore, it is easier for them than those who are from other areas to have heatstroke.
 Environment in childhood decides the number of perspiration gland.

  Next, we analyzed “Temperature Humid Index” (here after, THI). According to the Japan Weather Association, this index shows numerical number of sultriness by temperature and humidity.

  The following diagram shows THI in Paris, Los Angeles, Cairo, Sydney, and São Paulo. Based on:ダイキン『第20回現代人の空気感調査』

  According to this diagram, Tokyo has the highest THI of the six cities with THI exceed 85 almost every day. THI of other cities are usually between seventy and eighty. It can be inferred that Paris, Los Angeles, and Sydney could be more comfortable than Tokyo. THI is based on temperature and humidity. Those who come from low THI cities are more likely to have heatstroke.

  It is understandable that people may think “THI is subjective”. THI is the index based on temperature and humidity. If you cannot get the data of temperature or humidity difference between Japan and your country, you can compare them by altering THI to those data and imagine about the risk of heatstroke.
・Those who live in the subarctic zones do not adapt to Japan’s humidity and their risk of getting heatstroke is higher than those in other areas.
・Those who live in the land that THI is low should pay special attention to heatstroke!