A common belief says workers get used to extreme heat with the passage of time. Now a new study reveals whether that’s really true and what that means to employees and employers.
What better group to test than firefighters? They perform strenuous work in hot environments wearing protective clothing that can lead to dehydration.
Dehydration speeds up the rate of increase in core body temperature, increases cardiovascular strain, impairs attention and working memory, thereby increasing the risk for incidents that lead to injuries.
So researchers at the School of Human Kinetics at the University of Ottawa, Canada, compared response rates of firefighters and non-firefighters (both physically fit and with average ages of around 50) to exercise.
The researchers wanted to determine whether repeated occupational heat stress of firefighters led to partial heat acclimation and reduction in cardiovascular strain during subsequent heat exposures.
The two groups had similar thermal, cardiovascular and hydration responses during exercise.
However, the non-firefighters reported greater perceptual strain compared to the firefighters during exercise and recovery periods.
What this means: These older (middle age) firefighters had some evidence of heat resilience adaptation through repeated occupational heat exposure when compared to the non-firefighters.
The firefighters are in a better position than their counterparts to handle working in heat, and therefore they can perform more challenging tasks without putting themselves at a greater risk for injuries.
But their resilience to heat also means they are likely to stay in those conditions longer. And that’s not necessarily a good thing.
This “may actually put firefighters at increased risk for heat-related injuries and illnesses in real firefighting,” according to the study. That’s because the actual cardiovascular strain the two groups experienced was similar, but the firefighters didn’t perceive the strain to be as bad as the non-firefighters did.
This phenomenon isn’t limited to firefighters. Giving workers one to two weeks to get acclimated to extreme heat before giving them a full workload is common advice from a number of occupational safety and health sources, including OSHA.
But this research shows another message must accompany the one about heat acclimation. Workers need to know that acclimation doesn’t equal immunity from the effects of extreme heat.
Since acclimated workers don’t mind the heat as much and therefore are more likely to continue working in it, they need to know how to protect themselves.
Workers exposed to high temperatures should know the signs of heat stress. They also need to understand it’s OK to let a supervisor know they need relief if they believe they exhibit any of the symptoms.
The research was published in the December issue of the Journal of Occupational and Environmental Hygiene, a publication of the American Industrial Hygiene Association and the American Conference of Governmental and Industrial Hygienists.
How do you educate workers about heat stress? Let us know in the comments below.