Washington — OSHA’s threshold for moderate occupational heat risks starts at a heat index of 91° F, but that “might not be sufficiently protective,” according to an analysis by the agency.
Together with researchers from NIOSH, OSHA reviewed 25 cases of outdoor work-related heat illnesses (14 fatal and 11 nonfatal) that OSHA investigated between 2011 and 2016. In each case, researchers examined the worker’s personal risk factors, heat acclimatization status, clothing and workload, along with environmental heat as measured by wet globe bulb temperature – which includes temperature, humidity, wind speed and sky conditions.
The heat index was below 91° F in 12 of the cases, including six of the fatalities. OSHA does not enforce a permissible exposure limit for heat, but recommends “basic heat safety and planning” at heat indexes below 91° F. With heat indexes of 91° F and above, the agency recommends implementing precautions.
The analysis suggests that when wet globe bulb temperature is unavailable, a heat index of 85° F could be used to screen for hazardous workplace environmental heat.
The agencies recommend a comprehensive heat stress prevention program that includes an acclimatization schedule, first aid training, provision of fluids, shady areas for rest breaks, and engineering and administrative controls to curb heat stress.
The analysis was published July 6 in the Centers for Disease Control and Prevention’s Morbidity and Mortality Weekly Report.
