Human performance under hot thermal condition of work environment

Area of Science:

• Occupational Health
• Environmental Physiology
• Industrial Hygiene

Background:

• Workplace thermal conditions in Japanese industries were surveyed repeatedly from 1950 to 1973.
• Technical innovations led to reduced heat exposure and energy expenditure in hot industrial environments.

Purpose of the Study:

• To assess improvements in thermal conditions in major industries due to technological progress.
• To evaluate the adequacy of the 37°C permissible threshold limit for coal mines in Japan.
• To investigate the physiological and subjective responses of coal miners to heat stress.

Main Methods:

• Repeated surveys of thermal conditions in various industries across several decades.
• Experimental study on coal miners in a controlled hot and humid environment simulating mine conditions.
• Monitoring of physiological functions and subjective feelings during moderate work.

Main Results:

• Significant improvements in thermal conditions were observed in major industries from the 1950s to the 1970s, attributed to technological advancements.
• Experimental data suggested that 34°C dry bulb temperature, under high humidity and low air velocity, is a severe condition for coal miners.
• Physiological and subjective responses indicated heat stress even with intermittent work or frequent intervals.

Conclusions:

• Technological progress has positively impacted industrial thermal environments.
• The existing 37°C threshold limit for Japanese coal mines may not be sufficiently protective under specific conditions.
• Further research and potential revision of thermal stress limits for miners are warranted, considering humidity and work intensity.