The human body is usually good at maintaining its ideal temperature of 37°C. At any time of year and in various circumstances, the body produces heat from muscle use and prevents overheating by sweating. In extreme temperatures however, when the air is as hot or hotter than the body, the cooling mechanisms don't work. When the body can no longer cool itself properly, a number of heat-related health problems may occur.
Heat stroke and heat exhaustion are the most serious health illnesses caused by hot environments, and a real danger to people who work outside in the summer. Without immediate medical attention, heat stroke can be fatal. In previous years, people have died at work of heat stroke in occupations ranging from agriculture workers to football players. Heat exhaustion and fainting are other less harmful heat-related health risks that can cause temporary illness.
Know the warning signs
Heat stroke victims usually don't recognize their own symptoms. Their survival therefore depends on their co-workers' abilities to detect symptoms and seek first aid and medical help immediately.
While the symptoms vary from person to person, they include dry, hot skin (due to failure to sweat), a body temperature often exceeding 41°C, and complete or partial loss of consciousness.
Signs of heat exhaustion (caused by loss of body water through excessive sweating) include heavy sweating, weakness, dizziness, visual disturbances, intense thirst, nausea, headache, vomiting, diarrhea, muscle cramps, breathlessness, palpitations, tingling and numbness of the hands and feet.
How to prevent health problems from overheating
Avoid sun exposure. Move some tasks indoors or into the shade. When that's not possible, erect a temporary shelter. Take frequent breaks in a cool or well-ventilated area to get out of the sun and heat.
Don't be afraid to sweat. Sweating is the body's most effective cooling mechanism. The cooling occurs as sweat evaporates. In some cases a fan can be used to move cool air into a room and help keep body temperatures down.
Become acclimatized. Don't take on strenuous activities too soon if you're not accustomed to the heat. It can take six to seven days for the body to fully adapt (or acclimatize) to a new thermal environment. Ease into your tasks gradually, taking frequent breaks from the heat as needed. It is advisable to assign about half of the normal workload to new employees or those back from vacations or illnesses on the first day of work and gradually increase day by day.
Stay hydrated. Drink plenty of water - frequently (equivalent of about one litre every hour) - in hot weather conditions whether you feel thirsty or not to replace the fluid loss. Avoid consuming caffeine and alcohol, which can dehydrate you.
Clothing. For protection from the sun and heat when working outside, cover up as much as possible with loose-fitting clothes made of a light fabric that "breathes". When you work in the sun without a shirt or hat, the sun dries your sweat too quickly and prevents it from cooling the body. Clothes give sweat a chance to cool the body, and help protect the skin from the sun's harmful rays.
Emergency Action Plan. An emergency plan should include procedures for providing affected workers with first aid and medical care. Workplaces where heat stress can occur should monitor conditions and ensure that workers get specified rest periods dependent on the measured heat levels. The Threshold Limit Values for Heat Stress and Strain, produced by the ACGIH (American Conference of Governmental Industrial Hygienists) offers guidelines to determine when the weather should have no effect on outdoor workers, when caution should be exercised and when work should be discontinued.
Health Effects of Hot Environments
Provincial regulations concerning heat
Working in Hot Environments: Health and Safety Guide
July 2006
