VIEWS: 90 PAGES: 15 POSTED ON: 4/21/2009
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. 2. 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 5. 6. 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 Hydration 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.