This past few weeks has been a challenge to the populace as they grapple with the intense heat from the present hot weather. It is even more challenging to the workers who have to work outdoors, and to a certain extent are also not protected even though they may work in the shade or indoors without air-conditioning. Humans are by nature warm blooded and the biochemical processes that occur in the body takes place within a very narrow operating temperature range, much like the engine of the car; that is why any deviation in the operating temperature triggers a signal to the driver and we respond accordingly by stopping the car. But, in workers/people, do we have a ‘signal’ to tell us that we are operating out of range? The answer is when the body temperature goes down, we shiver and when it goes up, we know it as fever. As in the example of the car, high temperatures can cause the engine to fail or even burn up; it is about the same for people. So, a difference of a few degrees can have very serious consequences on our health. The body at all times must maintain this core body temperature of 36.8 degrees Celsius and for workers and people who work outdoors or are exposed to high temperatures must understand and control those factors which may change the body temperature.
Heat stress
Heat stress is when a worker is subjected to a combination of the type of work, environmental factors like the air movement and temperature, humidity and the surrounding heat or radiant heat and finally the amount of clothing or personal protective equipment that a worker has to use while working. The response towards this is known as heat strain which is the body’s reaction to the above. In principle, the higher the heat stress, the greater is the strain; meaning that it will affect the health and work. The body therefore works tirelessly to keep the temperature ‘stable’ for optimal function and health through various means. At 39oC, we feel ‘warm’ or develop fever, by 41oC, we may lose our ability to sweat which is one of the important physiological function of stabilizing the body temperature and at 43oC, develop tissue damage in various organs of the body.
How the body regulates temperature is called thermoregulation.
Methods of thermoregulation is by vasodilatation where there is increase blood flow to the skin and hence heat loss through skin. 2 to 4 million sweat glands also help to regulate body temperature via evaporation (sweating) and is a major method of regulating temperature in hot conditions. Along with the sweat, there is loss of water and electrolytes (salt) which is why sweat is salty. This ‘salt’ is important for many functions in the body. Muscle cramps is one of the effect of the loss of salt from the body. So, how much sweat can be loss working on hot days? Up to 15 litres! And that’s a lot of bottled water. As a result of the loss of water (dehydration), our body functions and productivity will begin to fail. Reduced mental and physical performance, increased risk of heat related illness like heat stress and heat stroke. Increase loss of fluids from the body can cause reduced blood volume and consequently heart problems and organ failure.
So, can we work or continue to work in hot environments?
It should be possible if the following can be carried out. Acclimatization which is a combination of behavioural and physiological changes that can reduce the strain brought about by changes in the natural environment. These workers are able to adapt to hot surroundings and increase their tolerance to higher temperatures. For example, an office worker who have to supervise or their job requires them to work for a time in hot environments. These workers are first exposed to the hot environment for increasing periods of time until they are used to it or acclimatized. 7 to 10 days would be an average period taken for acclimatization to a workplace. Needless to say, a healthy worker adapts faster than one with pre-existing health problems.
Heat stroke
Heat stroke is the most dangerous health effect of working in hot environments. It happens when the body loses its ability to maintain its core temperature. This is life threatening and it occurs when the body temperature exceed 40oC. At this point, the worker is in imminent danger of heat stroke. Hot dry skin, rapidly rising body temperature, loss of consciousness and the person may also fit are the signs to watch out for in a victim of heat stroke.
In the workplace, needless to say, all workers should be trained in first aid and be able to take quick action to avoid death. Move the victim to a cool shaded area and loosen all clothing. Immediate cooling by spraying/wetting the victim’s body with cool water and fan to evaporate; or ice packs can be placed on limbs. If the person can tolerate, give sips of cool water. Call for help and monitor the vital signs.
Heat exhaustion
Heat exhaustion while it is serious is less severe than heat stroke and primarily due to lack of adequate water intake (fluid replacement). In this case, if not well managed will progress to heat stroke. The skin is moist and sticky, the person is weak/fatigue, nausea and vomiting might be present and they may have headache. First aid action as in heat stroke with adequate fluid replacement. Observe and refer to the hospital.
Heat syncope
Heat syncope or fainting is the mildest form and is caused also by inadequate fluid intake. It is due to the diversion of blood supply to the skin for cooling resulting in sudden drop of blood supply to the brain and consequent fainting. It happens suddenly and without warning. First aid is usually sufficient.
Heat cramps
Heat cramps is the result of doing heavy work in hot environment and is due to electrolyte (salt) imbalance caused by excessive sweating. Painful muscle contractions usually of the lower limb occurs. Water should be taken every 15 – 20 minutes in such an environment and workers must be advised not to rely on their thirst alone. Last but not least is a condition called prickly heat (heat rash). In a hot humid environment, sweat produced cannot evaporate easily and made worse by clogged pores. Skin hygiene would be the best way to avoid this condition.
Thermal surveys should be carried out when workers are required to work in hot environments because in this condition it can affect productivity and quality of work as explained above. Thermal work limits should be applied to protect the workers from ill health due to heat.
What can we do when faced with work in hot environments?
The general health should be looked into during the medical surveillance. Factors to be taken into consideration are obesity, medication, age and the state of acclimatization because it can affect the health of the workers. Adequate ventilation either natural or mechanical should be used whenever possible. Worker training hot environment should carried out especially the health effects of heat. And finally, not forgetting adequate supply of drinking water on site and freely available.
[This article belongs to The Malaysian Medical Gazette. Any republication (online or offline) without written permission from The Malaysian Medical Gazette is prohibited.]