Recent occupational heat-related problems and national policies for occupational heat stress prevention in Japan

Introduction:  The objective of this paper is to report a recent trend in the incidence of death caused by occupational heat stress that has been officially registered by the Ministry of Health, Labour and Welfare (MHLW) in Japan. Also, the paper aims to present the national regulations and policies for heat stress prevention at work in Japan.    

Methods:  Cases of heat-related death included in the original reports of occupational diseases, which had been submitted to MHLW between 1989 and 2010, were made the subjects of the analysis in the study.    

Results:  Over the last 22 years, 350 workers had died due to occupational heat disorders. The annual incidence of heat-related deaths was closely correlated with the annual summer climate condition from July to September (r=0.694): the hotter the summer, the higher the incidence and vice versa.  In every year, consistently the higher incidence was found in outdoor works such as construction, transportation, patrol, forestry, etc. The higher incidence was also found in the afternoon (14:00-16:00) between July and August. More than 70% of the heat-related deaths occurred within a week from the beginning of hot work.    

Discussion:  To cope with such serious heat problems at work in Japan, a new guideline of prevention for occupational heat disorders (The Japanese Government MHLW Notice 2009) was released in 2009. Nevertheless, the heat wave in 2010 made the worst and highest record in the number of heat-related deaths since 1989. The present report will also refer to the main point of the new Japanese guideline 2009 and its base discussing why the occupational heat disorders increase in Japan despite the preventive effort of Japanese government.