Strategies for keeping core temperatures from rising into the danger zone.
By David Miller
There are many strategies for enduring the worst summer has to offer. To get the most work done on a hot day, it pays to use all of the tricks at our disposal. Our bodies run best at an internal temperature of about 98.6° F. When the ambient temperature becomes too hot, the body is designed to regulate the internal temperature to prevent damage to organs. Some of the amazing mechanisms we are born with are detailed, but there are limits to their effectiveness as conditions grow more inhospitable. When pushed beyond the limit, core temperatures exceeding 103° F can do lasting damage.
Factors That Contribute to the Problem
The danger of overheating is determined by a combination of
factors:
1. Temperature
2. Humidity
3. Level of exertion
4. Type of clothing/gear being worn
5. Acclimatization/fitness of individual
There is a temperature/humidity matrix known as the heat index that determines the level of caution required. There is a phone app offered by OSHA/NIOSH1 that calculates the risk of your environment using local heat and humidity readings. If the temperature and humidity combine to render a “feels like” rating of 105° F or higher, a healthy worker is considered to be at high risk and should be afforded plenty of rest breaks in the shade or air conditioning, if available.
Although you may assume that a heat index of 105° would only occur on the hottest days in August, it is not that rare, especially when the humidity approaches saturation levels. At 95 percent humidity, the temperature needs to be no higher than 85° to reach this high-risk level.
The other factors listed above can significantly contribute to the danger. If you are working hard or have to wear bulky equipment or clothing, your risk goes up. If you have new team members unaccustomed to the heat, it is going to take them two or three weeks before they are fully acclimated and ready to work as hard as the others.
There are any number of individual factors affecting a worker’s resistance to heat illness. Certain medications or injuries, prior incidence of heat stroke, or pregnancy can all make a team member more vulnerable to heat illness.
Strategies to Regulate Sustainable Core Temperature
The human body has a variety of systems in place to regulate core temperatures. The most obvious system to counteract high temperatures is through perspiration. The sweat moistening your skin quickly evaporates, causing evaporative cooling. This process allows a significant amount of heat to transfer away from your body.
In order to perspire adequately on a hot day, hydration is critical. Drinking plenty of water the night before gives you a great head start going into a hot day. You will have more success if you plan ahead, because once you become dehydrated, it is a struggle to catch up when you are supposed to be working. A good way to determine if you are maintaining enough fluid in your body is to observe the color of your urine. The darker the pee, the more you need to correct your hydration situation.
Our sweat is composed of more than just water. If you perspire a lot, you are going to lose trace minerals and salts, which need to be replaced as well as the water. This is why it is important to consume an isotonic drink like Sqwincher or Gatorade to replace the lost electrolytes.
Besides evaporative cooling, which happens more or less automatically, what proactive methods are there to cool down core temperatures? What about lowering body temperature using chilled fluids? If your body is struggling to cool down internally on a blistering hot day, what is the effect of downing an ice-cold beverage or chewing on ice?
This turns out to be a rather complicated subject. According to research from the Gatorade Sports Science Institute, this can be an effective way of reducing core body temperature, but the benefits can be cancelled out by the suspension of evaporative cooling while your body puts your sweat glands on “pause.”
It turns out we have receptors in our stomach lining that automatically moderate perspiration as soon as something cold is introduced. So as soon as you drink cold water, there is an immediate reduction in your rate of perspiration pending the equalization of stomach temperature with the rest of the body.
Armed with this understanding, we have to develop an optimal strategy. In a situation where a worker is getting the full benefit of the cooling effect of perspiration, it would be counterproductive to use slushy drinks that will suppress that cooling effect. It is hard to improve on the cooling capability of sweat unless the conditions are less than ideal. On the other hand, if your situation is not conducive to evaporative cooling, then ingestion of icy drinks is going to be more effective. Some of the conditions that impede evaporative cooling are:
1. Lack of air movement
2. Humidity levels close to 100 percent
3. Bulky, unventilated safety clothing
4. Problems producing sweat due to injury, medication or other factors
It is a judgment call to know when natural cooling should be
assisted by a direct shot of slush or a popsicle.
Other tools in your arsenal to fight rising core temperature have their place as well. Some of these are:
1. Shade
2. Cooling clothing
3. Fans and swamp coolers
4. Strategic breaks
Win the Battle
Heat-related illness is a serious business that can have lasting effects on those who experience it. We need to be respectful of hazardous conditions and use all the tools at our disposal to win the battle. | WA
David Miller is the Waste Industry Manager for HUB Industrial Supply (Lake City, FL). He is a Certified Safety Professional and works with managers to effectively implement and manage PPE and MRO programs in the waste industry. He may be reached at [email protected]. HUB Industrial Supply is an Applied MSSSM company.
Note
1. Phone app for calculating risk: www.cdc.gov/niosh/topics/heatstress/heatapp.html Gatorade Sports Science Institute article: www.gssiweb.org/sports-science-exchange/article/cold-water-and-ice-slurry-ingestion-for-reducing-body-temperature-during-exercise-in-the-heat#articleTopic_4