In the 30 years since the National Institute for Occupational Safety and Health (NIOSH) made major recommendations to prevent work-related heat stress, recent events have raised questions about working safely in hot environments. For example, during the Deepwater Horizon response and cleanup of 2010, crews worked through the hot Gulf of Mexico summer. That event, and the evaluation of accumulated research and literature characterizing effects of working with heat stress, prompted NIOSH to revise its guidance document Criteria for a Recommended Standard: Occupational Exposure to Heat and Hot Environments after an extensive scientific review. Although the recommended alert and exposure limits still protect workers in hot environments and remain unchanged, the revised document includes updated research findings, training, and intervention tools.

Working in hot environments—both outdoors and indoors—increases the risk of heat stress, which can cause injuries, disease, reduced productivity, and even death. To continue to protect workers from this serious work-related hazard, NIOSH investigators collaborated with other scientific experts, partners, and the public, through a request for comments and peer review, to revise the criteria document.

The finalized document includes guidance for safety and health professionals and employers, describing methods to protect workers from heat stress. These methods include medical monitoring; acclimatization; a recommendation of drinking 1 cup (8 oz.) of water or other fluids every 15–20 minutes; and differentiating between the symptoms of classic and exertional heat stroke. In classic heat stroke, sweating is usually absent, but in exertional heat stroke, sweating often occurs. Exertional heat stroke is more likely to occur in workers, so it is particularly important to re-educate workers who may have incorrectly learned that heat stroke occurs only without sweating. New training tools include a urine color chart, which is a good indicator of hydration status, and occupation-related case studies. As NIOSH continues to study this evolving area of workplace safety and health, possible subjects for future research are the effects of climate change on workers and of heat stress on chemical absorption in the body.

For more information, click the titles below:

NIOSH Criteria for a Recommended Standard: Occupational Exposure to Heat and Hot Environments

Heat Stress