Working outside on hot and humid summer days or working in a hot building can cause heat stress. Heat stress occurs when the body overheats and is unable to effectively cool itself down. A rise in temperature of only a couple of degrees Celsius may cause ill effects as the body is very sensitive to temperature changes.
Heat is generated by muscles during work and working in hot conditions does not always allow the body to cool itself down.
The body copes with an increase in body temperature by releasing heat to the environment.
This is done by the body increasing the blood flow to the skin, which allows perspiration to occur. If the environment is cooler or if there is a breeze, the perspiration will evaporate which pulls heat away from the body. Problems begin to occur when these conditions do not occur.
It is actually a combination of high temperature and humidity that increases the risk of heat stress. This combination is known as the Humidex.
It is important to watch the temperature, humidity and workers to ensure there are no effects of heat stress.
If either the temperature or humidity climbs very high or workers seem to be having some difficulty, action needs to be taken immediately.
Workers should take a break. If anyone seems dizzy or unusually tired, loosen or remove their clothing and give them cool water to drink.
Early signs and symptoms
Some early signs and symptoms to watch for are: feeling tired, headache, dizziness, feeling faint and difficulty concentrating.
Mild symptoms include swelling of the hands or feet, heat rash and muscle cramps.
More serious symptoms include fainting, heat exhaustion, and the most serious effect of heat is heat stroke.
Early and mild symptoms can usually be controlled with an hour of removing the worker from the heat to a cool, shaded area, providing fluids to drink and allowing the worker to rest. If after one hour the symptoms persist, medical attention should be obtained.
The more serious symptoms require immediate medical attention. Emergency services should be contacted for transportation to a medical facility.
As well, more aggressive treatment of the condition should be initiated while waiting for the emergency response team.
This may include the above treatments as well as bathing the worker in cool water.
It is not advisable to provide fluids to a worker who has fainted or is in heat stroke as it could cause vomiting or choking to occur.
Four key elements
There are four key elements to preventing heat stress: water, acclimatization, rest breaks and monitoring. Anyone who will be out in the sun for long periods needs to have plenty of clean cool water available to drink regularly.
The human body has the ability to adapt to working in the heat through a gradual process known as acclimatization. This is usually achieved in about seven days.
A person becomes de-acclimatized when out of the heat in about seven days as well. So if a worker goes on vacation, he/she will have to re-acclimatize when returning to hot working conditions.
The Occupational Health Clinics for Ontario Workers (OHCOW), has developed a heat stress advisory system to help workplaces avoid heat stress and what actions need to be taken under variable Humidex measures.
The values obtained apply to employees wearing regular summer clothing who are working indoors and are not exposed to radiant heat (ovens, molten metal etc). Modifications can be made to the system by adding two degrees for radiant heat sources.
If the Humidex is:
30-33ºC: encourage workers to drink extra water and begin measuring temperatures and relative humidity hourly;
34-37ºC: notify employees that they need to drink more water and ensure workers have received appropriate heat stress
training in the last three months;
38-39ºC: provide employees with a 15-minute rest relief per hour; ensure adequate water is being supplied to each
employee (at least one cup or eight oz. of cool water every 20 minutes). Any employee with symptoms should seek
40-42ºC: employees should be provided with 30 minutes of rest relief per hour in addition to the previous provisions;
43-44ºC: provide employees with 45 minutes of rest relief per hour, in addition to the provisions listed for 38-39ºC. If relief is not feasible, then stop work until the Humidex is 42ºC or less;
45ºC or over: stop work until Humidex is 44ºC or less.
Workers should be taught the signs, symptoms and treatment of heat stress so they can look after themselves if working alone and look out for their co-workers when working in a group.
Workers who have health concerns should seek the advice of their doctor prior to working in hot conditions.
Another important issue to consider when working outside is to wear sunscreen with at least an SPF of 15. Hats should also be worn to provide shade. Working in hot conditions is possible and safe providing care and caution are exercised.
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Trevor Schell is a certified ergonomist with the Occupational Health Clinics for Ontario Workers Inc. (OHCOW). If you have an occupational health topic you would like addressed in a future column, contact OHCOW @ (705)-523-2330.