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Health & Safety: Preventing heat-induced illnesses during outdoor summer work

Stay safe when temperatures soar

July 25, 2022  By CCOHS

Very hot environments can overwhelm the body’s natural cooling systems

Lana works at a golf course, where she spends most of her time outside. On hotter days, she finds it more challenging to perform her daily tasks. These are tasks she is used to doing, so why would they be harder to perform in the heat? Working outdoors in the summer months can be taxing on the body, and the exposure to heat can even be dangerous. Workers like Lana who are potentially exposed to extreme heat conditions may be at increased risk of heat stress.

Heat stress is a combination of body heat generated from the effort exerted while working, the clothing and equipment being worn, and the environment. Air temperature, humidity, air movement, radiation from the sun, and hot surfaces or sources can all affect the worker’s environment.

Most people feel comfortable when the air temperature is between 20°C and 27°C and when relative humidity ranges from 35 per cent to 60 per cent. When air temperature or humidity is higher, we may feel uncomfortable, but our bodies can cope with a little extra heat. However, very hot environments can overwhelm the body’s natural cooling systems, leading to serious and possibly fatal conditions.

Five illnesses caused by heat exposure
All workers are at risk of heat-related illness. However, workers at greater risk include those who have pre-existing health issues, are over 65 years old, or take medications that may affect how their body reacts to heat. Having skin diseases can also make people more susceptible to heat illness, as it might affect the body’s natural ability to regulate its temperature.


Heat puts workers at risk for illnesses such as heat edema, heat cramps, heat syncope, heat exhaustion, and heat stroke. Heat can also lead to incidents resulting from the slipperiness of sweaty palms or contact with hot surfaces. As a worker moves from a cold to a hot environment, fogging of eyeglasses can briefly obscure their vision, presenting a safety hazard. 

Heat edema is swelling which generally occurs among people who are not acclimatized to working in hot conditions. Swelling is often most noticeable in the ankles. Recovery occurs after a day or two in a cool environment. 


Heat cramps are sharp pains in the muscles that occur when there is a salt imbalance. Cramps occur most often when drinking large amounts of water without enough salt (electrolyte) replacement. 

Heat syncope occurs when people feel dizzy or lightheaded, or faint suddenly and lose consciousness. It can be caused by blood pooling in the legs (which lowers blood pressure), or by the loss of body fluids through sweating. It occurs mostly among unacclimatized people. Resting in a cool area usually brings about a quick recovery.

Heat exhaustion is caused when a worker loses body water and salt through excessive sweating. Signs and symptoms of heat exhaustion include heavy sweating, dizziness, intense thirst, nausea, headache, vomiting, diarrhea, and tingling and numbness of the hands and feet. People usually recover after resting in a cool area and drinking cool drinks, such as water, clear juice, or sports drinks.

Heat stroke is the most serious type of heat illnesses and requires immediate first aid and medical attention. Signs of heat stroke include body temperature of more than 41 degrees Celsius, and complete or partial loss of consciousness. Sweating is not a reliable symptom of heat stress because there are two types of heat stroke – “classical” heat stroke where there is little or no sweating (usually occurs in children, the chronically ill, and the elderly), and “exertional” heat stroke where body temperature rises because of strenuous exercise or work, and you do sweat.  Heat stroke can cause death if medical treatment is delayed.

Prevention tips for employers
Every year, Canadian workers are at risk because of heat-related issues. As an employer you must manage this risk – evaluate the situation and determine appropriate controls. A heat stress control program can help reduce the risk by managing work activities so that they match the employee’s physical condition and the environment.

Provide workers with training on the health risks of heat illness, how to avoid it, how to recognize the symptoms and what to do if it happens. Provide first aid attendants with training in heat stress response measures. 

Keep workers cool and hydrated and allow some flexibility in work arrangements during hot conditions. Schedule heavy tasks and work that requires personal protective equipment for cooler times such as early mornings or evenings. When working outside, take frequent rest breaks and provide at least a shaded, cool area, but air-conditioned rest areas are preferred where possible. Provide plenty of water and encourage workers to drink even if they don’t feel thirsty.

Heat illness is a serious but preventable health risk. Workers like Lana should be trained on the dangers of heat exposure and how to look out for signs and symptoms in themselves and others, and how to get first aid. And don’t forget to equip your crew with resources to help keep them safe while working outside this summer.

The Canadian Centre for Occupational Health and Safety (CCOHS) promotes the total well being of workers in Canada by providing information, training, education, systems and solutions that support health and safety programs and injury and illness prevention.

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