Heat Stress Hazards

If the dangers of heat stress are well known, why do workers keep getting hurt, or even killed, by the heat?

Heat stress is a common, yet it is an often ignored hazard in the workplace.  While it is widely recognized that heat stress can pose a serious health hazard to workers, employers may not realize that working in hot environments also increases safety risks.

Research shows that working in hot environments is linked with lower mental alertness and physical performance, and subsequently more injuries.  Factor in elevated body temperature and physical discomfort, and it’s easy to see how workers can divert their attention from hazardous tasks and overlook common safety procedures.

Sources of heat stress range from the hot summer sun to the body heat generated inside a hazardous material suit worn during the cleanup of a toxic chemical spill. While often considered a summer or southern states problem, many companies need to take precautions throughout the year regardless of where they are located.

Heat-Related Slips

The safety hazard of heat stress is overlooked partly because the “accidents” that result from it are often not properly recorded.  How many slips and falls does your company have during 100-degree days?  If a person trips or breaks an ankle, there may not be an emphasis on finding out if the person was heat-stressed, but there needs to be more awareness that the incident could have been caused by heat stress.

Monitoring the Heat

Medical screening of workers can help identify those who are more vulnerable to heat stress, such as workers who are older, overweight or taking medications that affect their ability to handle exertion in hot weather.

It is recommended that employers monitor hot environments by using a wet bulb thermometer, which will provide the wet bulb globe temperature (WBGT). Use of WBGT is essential, because it allows you to measure not just the air temperature, but humidity in the air, radiant heat and wind velocity.  All four factors are crucial in determining the risk of heat stress.  The level of work activity, plus the clothes and the condition of the employee, are additional factors that must be considered.  Research confirms that WBGT mirrors how hot a person will become in any given environment. But the critical missing piece from WBGT measurements is how hard a person is working. To determine if heat stress is a concern, you must know the time-weighted average of the metabolic demands and the time-weighted average of the WBGT, and compare that to the TLV table.

Cooler Climate Hazards

An additional reason heat stress may be overlooked is that many people living in regions that normally have a cooler climate think the issue does not affect them.  A person’s ability to withstand the heat is affected by whether the individual has acclimatized to high temperatures. That’s why sudden hot spells in traditionally cooler areas may pose more acute risks than heat in southern climates.

In addition, many employees are exposed to indoor high-heat environments and cooler climate regions may lack proper ventilation or air conditioning because such precautions are not normally needed.