Heat Stress Indicators to Watch For During the Hot Summer Ahead

Humans can adapt to varying environments, but acclimatization to heat takes time. Smart PPEs monitor heat stress and indicators such as heart and sweat rate and activity levels.
By Michael Prewitt
May 26, 2021

The warming months are bringing heat safety to mind for anyone who works outside or in a challenging hot environment. How bad is it going to get? And what can be done to make it easier on everyone? These are common questions that arise this time of year.

Humans have an incredible ability to adapt to varying environments, but adaptation to heat takes time and varies by individual. Acclimatization to heat can take from two to three weeks when done properly and risks the worker’s health and work site safety if not done properly.

Appropriate heat acclimatization is accomplished by increasing one’s core body temperature 1°C for an hour each day during the work period. If the job requires PPE, as most do, workers need to slowly add PPE each day to balance acclimatization – adding 20% of clothing and equipment each day until the full worksite PPE can be worn. It’s not easy to put a worker that is used to cooler climates into a hot environment and have productivity and well-being stay the same. While it takes time and understanding of proper techniques, simple acclimatization steps make for a better, more productive jobsite in hot conditions.

Beyond acclimatization, dealing with heat during work is a complex problem. That’s because heat adaptability depends on how efficient a person is at cooling him or herself, via sweat, and there are several things that can contribute to that:

  • being older than 35;
  • psoriasis, cardiovascular disease or diabetes;
  • prescription drugs for a variety of illnesses;
  • over-the-counter drugs; and
  • nicotine and alcohol use.

Including all of that information in protective strategies can be a logistical challenge. Understanding the physiological functions can help inform what metrics to use for recognizing heat stress.

As a worker’s core body temperature rises, the primary mode of cooling off is through sweating. Blood flow is increased to the skin, water and electrolytes are expelled by the sweat glands, and the evaporation of sweat cools the body down. This process is very efficient, as long as evaporation can occur while activity level does not increase and adequate hydration occurs.

Once a worker starts sweating on the job site in the heat, she needs to be monitored to track her health vitals. Heart rate needs to increase during sweating in order to pump blood fast enough to get it to the skin to cool down. But muscles also require blood to get oxygen and other nutrients for proper function during work in the heat. This means the cardiovascular system has added strain because it must get blood everywhere it is needed.

If a worker is sweating and maintaining a steady workload, eventually that fluid loss from the sweat is going to be felt. Sweat loss will result in lower blood volume and pressure. In order to maintain physical activity for work and continue sweating to keep the body cool, the heart once again needs to beat faster.

Being able to monitor a worker’s heart rate, body temperature, sweat rate and knowing the intensity of their daily labor can provide the best insights to the individual’s health at any given time during warm working conditions for the onsite supervisor or health and safety officer. Allowing managers to give each worker breaks at the right time (when their individual body needs them), with water and shade, can keep everyone safe in the heat.

The cardiovascular system is not the only vital function that’s disrupted during hot work. The nervous system is also impacted, decreasing a worker’s ability to complete tasks as well as affecting cognitive ability. Similar to the cardiovascular system having to work harder in the heat, the nervous system also needs to work harder in order to accomplish the same muscle movement that happened without the added heat. An overtasked nervous system makes work-related tasks harder as well as making cognitive decision-making more difficult. A worker experiencing heat stress is forcing their heart to work harder while his muscles are challenged to continue work and their cognitive functions are dropping, which add up to a significant risk to the individual, the team, the project and the company.

Worker heat stress is a serious and complex problem. Current heat safety strategies, without the use of today’s new smart PPE health monitors, may be well intentioned but not as effective as they could be. Today, advanced monitoring of personal heat stress indicators is possible, helping workers and their supervisors more closely watch individual physiological indicators of heat stress such as heart rate, sweat rate and activity levels, making summertime jobsites safer and more productive.

by Michael Prewitt
Michael Prewitt onboards companies and their employees to the Kenzen smart PPE heat prevention system.

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