2025.06.01
🔔【Important】Provision of Information in Response to the Mandatory Heatstroke Prevention Measures
As of June 1, 2025, the revised Industrial Safety and Health Regulations have come into effect, making heatstroke prevention measures mandatory in workplaces.
Employers are now responsible for properly assessing heatstroke risks and implementing appropriate countermeasures during work in high-temperature environments.
According to documentation from the Ministry of Health, Labour and Welfare (Kumamoto Labour Bureau PDF)002215755.pdf
the following work conditions are subject to this regulation:
Work conducted under environmental conditions where the WBGT (Wet Bulb Globe Temperature) index is 28°C or higher or the air temperature is 31°C or higher,
and is expected to be carried out for more than one continuous hour or more than four hours per day.
Under such conditions, employers are legally required to:
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Establish organizational systems
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Develop procedures
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Communicate measures to all relevant personnel
Non-compliance may result in penalties.
For details, refer to document 002215755.pdf (Ministry of Health, Labour and Welfare).
To help address the risks of heatstroke, Ima-Tetsu provides:
▶ A Real-Time Map of Air Temperature and WBGT (Heatstroke Index)
The WBGT index on this map is calculated using the formula proposed by Ono et al. (2014)*1.
It estimates real-time values based on air temperature, relative humidity, average wind speed, and global solar radiation:
WBGT =
0.735 × Ta + 0.0374 × RH + 0.00292 × Ta × RH + 7.619 × SR − 4.557 × SR² − 0.0572 × WS − 4.064
Where:
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Ta = Air Temperature [°C]
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RH = Relative Humidity [%]
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SR = Global Solar Radiation [kW/m²]
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WS = Average Wind Speed [m/s]
The estimation of these parameters is based on our proprietary network of observational data combined with JMA (Japan Meteorological Agency) AMeDAS data, utilizing spatial interpolation technology.
▼ You can view the Ima-Tetsu Temperature & Heatstroke Map here:
https://imatetsu.earth/ja/heatmap
▶ We also encourage you to use it alongside the Ministry of the Environment’s Heat Illness Prevention Information Site:
https://www.wbgt.env.go.jp/
“Ima-Tetsu” remains committed to providing useful information from the perspectives of weather and safety.
*1 Ono, M. et al. (2014): Estimation of WBGT Using Common Meteorological Observation Elements. Journal of Human and Environmental Studies, Vol. 50(4), pp.147-157.
