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Heat Stress


									Heat Stress

What is it?
• Heat stress: is the buildup in the body of heat generated by the muscles during work and of heat coming from warm and hot environments. • Heat illnesses: result when the body is subjected to more heat than it can cope with.

Why worry about it?
• Heat can kill! • Work-related heat stroke fatalities: 1990: student, second day collecting garbage 2001: bakery worker in Barrie
– According to Environment Canada on August 9, 2001 outdoor temperature in Barrie is 33.4°C, and humidity was 30%; so the outdoor humidex was 36°C and the outdoor WBGT was 24.8°C – If temperature in the bakery was estimated to be 52°C and if the humidity inside was 10%, then humidex would have been 54°C for the workplace

True or False?
1. High internal temperature makes blood vessels expand and the heart rate quicken.

3. 4.

A heat stroke can be fatal.
Sweating cools the body. Operation of the body’s cooling system can result in: A. Rashes

B. Dizziness
C. Swelling D. Fainting E. Death


If you don’t feel thirsty, there is no need to drink water.
As long as you drink a sufficient amount, the timing of it doesn’t matter.

Physiology of Heat Stress
• During both rest and activity, the human body tries to maintain an internal temperature of • 37 °C or 98.6 °F. • (+/- 1 °C or 1.8 °F)

Physiology of Heat Stress
• Hot weather, heat sources, and hard work raise the body’s core temperature. • Heated blood is pumped to the skin’s surface, where body heat transfers to the environment, if cooler. • If heat has to be shed faster, sweat carries it outside skin and evaporates to aid cooling.

Physiology of Heat Stress
• During heavy work, a body can lose 1-2 liters of water per hour. • After 2-3 hours of fluid loss, a person is likely to: – Lose endurance – Become uncomfortable – Feel hot – Become thirsty

Physiology of Heat Stress
• The longer a body sweats, the less blood there is to carry excess heat to skin or oxygen and nutrients to muscles. • After 3 hours, a dehydrated worker may experience:
• • • • • • • Headaches Muscle fatigue Loss of strength Loss of accuracy and dexterity Heat cramps Reduced alertness Nausea

Physiology of Heat Stress
• Water is key to cooling body and combating heat stress. • Without fluid replacement during an extended period of work, the body is at risk of exhaustion. • Untreated heat exhaustion may lead to heat stroke.

Health Effects
When heat gain exceeds the ability of the body to compensate, heat illnesses can result:
– Heat rash, other skin ailments – Sunburn – Heat cramps – Fainting – Heat exhaustion – Heat stroke

Everyone’s Different
• People come in many shapes and sizes and with different tolerances for heat. • Personal factors affecting tolerance include:
– – – – – – – – Activity level (metabolic heat) Fluid intake and electrolyte replenishment Alcohol and drug use Acclimatization Age Physical fitness Body fat Diet

Controlling Heat Exposure
• • • • Acclimatization Engineering controls Administrative controls & work practices P.P.E.

Controlling Heat Exposure
Humidex 30-33 34-37 38-39 40-42 43-44 45+ Action alert, information & water warning, education & double water restrict activity 25% & actively monitor for signs of heat strain restrict activity 50% & actively monitor for signs of heat strain restrict activity 75% & actively monitor for signs of heat strain stop work

Fluid Replacement is extremely important!
• More than you want just to satisfy your thirst

• Sources of water are:
1. Fluids - 1 cup or 8 oz = 240 mL every 20 min 2. Foods - fruit & veggies are 90% water

• Maximize the amount you drink by ensuring the water is not too cold, but not lukewarm

Things You Can Check
• Look for typical heat strain symptoms; feeling over-heated, fatigue, headache, nausea, weakness, dark concentrated urine, etc. • Sweat that drips off your body no longer allows for cooling by evaporation; thus, unless there’s another medical reason for it, this is a sign that your body is heating up. • Check your pulse; heat stress is unlikely if your pulse rate is under 100 beats per minute after 1 minute rest.

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