Published on March 16, 2014
Heat StressHeat Stress EssentialsEssentials Occupational Health Clinics for Ontario Workers Inc. Prevention in Action
OutlineOutline • Heat stress/strain health effects • What you can do to prevent them • What the law says • Simple ways to monitor the heat
Symptoms: General feeling of tiredness or fatigue. First Aid: Fluid replacement and rest. Transient Heat Fatigue:Transient Heat Fatigue:
First Aid: Practice good personal hygiene; keep the skin clean and the pores unclogged, allow skin to dry, wear loose clothing, see doctor if rash persists. Heat Rash (prickly heat)Heat Rash (prickly heat) Symptoms: Skin becomes reddened and may itch, feel prickly or hurt.
Symptoms: Syncope means “fainting.” First signs are dizziness, feeling light-headed and perhaps nauseous, then the person may faint. Usually occurs in the beginning of heat stress season before the circulation system is adapted. First Aid: Lay victim in a cool location horizontally with feet elevated. If conscious, give fluids. Treatment the same as shock. HeatHeat SyncopeSyncope (fainting)(fainting)
Symptoms: Cramping of either active muscles (arms, legs) or involuntary (usually abdominal) muscles (or both). First Aid: Replenish electrolytes through drinking of fluids such as Gator-Ade, Squincher, PowerAde, etc-Ade. Rest in a cool environment. Heat Cramps:Heat Cramps:
Symptoms: Nausea, dizziness, weakness headache, blurred vision, profuse sweating, cold/wet (clammy) grayish skin, unconsciousness, coma and death. First Aid: Place victim in a prone position in a cool location, administer fluids if the victim is conscious. If unconscious, seek medical care or transport to a medical emergency room. Heat Exhaustion:Heat Exhaustion:
Symptoms: Chills, restlessness, irritability, euphoria, red face and skin, disorientation, hot/dry skin (not always), collapse, unconsciousness, convulsions and death. First Aid: Immediate, aggressive cooling of the victim’s body using wet cloths, immersion into cold water or alcohol wipes. Transport to emergency medical facility ASAP! Heat Stroke:Heat Stroke:
Watch out for each other!Watch out for each other! • A worker heading into a heat stroke will no longer realize what’s happening to him/her • It is vital that co-workers be able to recognize what’s happening and intervene • Without quick attention, the co-worker may die!
Indirect Health Effects:Indirect Health Effects: Reduced Work Performance: tired, fatigued workers perform with reduced accuracy, efficiency Increased Accidents: tired, fatigued workers are more susceptible to accident and injury Reproductive Problems: heat has been shown to reduce both male and female fertility and can be a problem for the fetus Heart/Lung Strain: if you already have heart, lung, kidney or circulatory problems; heat stress is an added strain on your body which in severe situation may precipitate serious episodes of acute problems
PredisposingPredisposing Factors:Factors: very small body size overweight over 40 years old (the older the more sensitive) previous heat illness heart disease high blood pressure diabetes inactivity physical activity …sooner or later we’re all vulnerable …
…… with all thesewith all these vulnerabilities who typicallyvulnerabilities who typically gets heat stroke?gets heat stroke? young physically fit males and sick older people
S S Cooling evaporation of sweat Heat Balance H H Internal Heat sources muscle activity H External Heat sources hot weather radiant heat sources
External heatExternal heat source controlssource controls • At the source – Replace/isolate heat producing processes – Block radiant heat with barriers (shade) • Along the path – Isolate worker from heat – Air condition workplace (booth) – Capture hot air with exhaust ventilation External Heat sources hot weather radiant heat sources H
Internal sourceInternal source controls:controls: • At the source – Reduce workload • improve ergonomics, • provide assistance, • increase relief time • slow down – Provide adequate water – Actively cool body – Gradually acclimatize – Ensure good nutrition and rest Internal Heat sources muscle activity H H
Promoting CoolingPromoting Cooling • Wear loose clothes that allow sweat to evaporate easily (cotton) • Take internal heat sources into account when using any personal protective clothing that prevents sweat from evaporating • Wash clothes regularly and maintain good personal hygiene S S Cooling evaporation of sweat
Body Changes due toBody Changes due to Acclimatization:Acclimatization: • Gradually build up your ability to handle heat (increase exposure time by an hour/day) • When your body gets used to the heat (acclimatized) your sweating becomes more “efficient” (more sweat, quicker but with less salt in sweat) • blood flow to skin is reduced; more blood is available to muscles • heart rate more stable, heart stoke volume increases and blood volume increases
See your doctorSee your doctor • If you are having trouble getting used to the heat or • If you have questions about how heat may affect a medical condition you have … see your doctor!
Drink Water Acclimatization does not decrease your body’s need for water. Drink plenty of water!
What to drink:What to drink: • Electrolyte drinks (e.g. Gatorade) are usually not needed for typical North American diet (can be used for first aid for cramps). • Stay away from caffeinated carbonated, diet drinks and alcohol as they take water out of your body. • Water is the best; juices and/or noncaffeine sport drinks are also good (juices contain energy restoring glucose).
Dehydration To prevent dehydration, take advantage of scheduled water breaks!
How Much WaterHow Much Water is Enough?is Enough? • 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 • Why 10-15°C? … to maximize the amount you drink (not too cold, not luke warm) • Does it need to be delivered to the work station? … depends on workplace logistics …
DehydrationDehydration fluid loss time* effect & symptoms (* timing may vary based on intensity of work and heat/humidity) 0.75 L 1 hr unnoticed (at 1.5% weight loss you are considered dehydrated) 1.5 L 2-3 hrs loss of endurance, start to feel thirsty, feel hot, uncomfortable 2.25 L 3-4 hrs loss of strength, loss of energy, moderate discomfort 3 L 4-5 hrs cramps, headaches, extreme discomfort 3.5-4 L 5-6 hrs heat exhaustion, nausea, faint 5+ L 7+ hrs heat stroke, collapse, unconsciousness taken from: OH&S Canada Volume 69, Number 5, page 52, May 2000
You can and should replace essential elements lost during sweating; Eat a balanced diet rather than taking salt tablets or drinking expensive sports drinks. Eat Healthy
Cooler FansCooler Fans • Purpose of a cooling fan is primarily to increase the rate of sweat evaporation but it also cools by convection if the air is cooler than the skin • Fan coolers may interfere with local exhaust ventilation for contaminant control, therefore be careful in where they are placed and how they are pointed
Cooler FansCooler Fans (limitations)(limitations) • If the relative humidity is over 75-80% the fan will no longer increase evaporation of sweat • The closer the air temperature is to skin temperature (35- 36°C) the less effective the cooling – if the air temperature exceeds skin temperature then the fan may even heat up the body (like a convection oven)!
Personal Protective EquipmentPersonal Protective Equipment Special cooling vests or ice vests have been developed to wear under chemical–resistant suits (use on a case by case basis – they may not work for everyone)
What’s the Law?What’s the Law? General Duty Clause: – 25(2)(h) “… an employer shall, … take every precaution reasonable in the circumstances for the protection of a worker;” taken from: OH&S Act MOL Heath and Safety Guidelines: Heat Stress: – “The MOL uses the TLVs® for Heat Stress published by the ACGIH”. taken from: http://www.gov.on.ca/LAB/english/hs/guidelines/gl_heat.html
1. clothing OK/adjustment? 2/3a. WBGT screening/ detailed action limit 2/3b. WBGT screening/ detailed TLV® 5. job-specific controls NONO 4. heat strain evaluation - heart rate - core temperature YESYES aboveabove belowbelow above or no dataabove or no data excessiveexcessive OKOK belowbelow 2007 ACGIH Heat Stress/ Strain TLV® keep monitoring general controls
What is a WBGT?What is a WBGT? 1. normal thermometer (dry-bulb) 2. wet-bulb thermometer • humidity 3. globe temperature • radiant heat WWet BBulb GGlobe TTemp.
Screening WBGTScreening WBGT (in °C )(in °C ):: work demands: light moderate heavy very heavy 100% work; (breaks incl.) 28.0 31.0 25.0 28.0 not allowed not allowed 75% work; 25% rest 28.5 31.0 26.0 29.0 24.0 27.5 not allowed 50% work; 50% rest 29.5 32.0 27.0 30.0 25.5 29.0 24.5 28.0 25% work; 75% rest 29.0 32.5 29.0 31.0 28.0 30.5 27.0 30.0 Action Level TLV®
How to measure heat stressHow to measure heat stress using temperature & humidityusing temperature & humidity 1. Find a representative place 2. Find temperature and humidity on chart and read off the Humidex 3. Take into account radiant heat (add 2° Humidex to measurement for full sun) 4. Need to take clothing into account (add 5° Humidex for overalls on top of summer clothes)
Humidex Heat Stress ResponseHumidex Heat Stress Response PlanPlan Temp RH = 100% 95% 90% 85% 80% 75% 70% 65% 60% 55% 50% 45% 40% 35% 30% 47 46 45 44 43 45+ 42 42-44 50 41 40-41 48 40 38-39 49 47 39 34-37 49 47 45 38 30-33 49 47 45 43 37 25-29 49 47 45 44 42 36 50 49 47 45 44 42 40 35 50 48 47 45 43 42 40 39 34 49 48 46 45 43 42 40 39 37 33 50 48 47 46 44 43 41 40 39 37 36 32 50 49 48 46 45 44 42 41 40 38 37 36 34 31 50 49 48 47 45 44 43 42 40 39 38 37 35 34 33 30 48 47 46 44 43 42 41 40 39 37 36 35 34 33 31 29 46 45 43 42 41 40 39 38 37 36 35 33 32 31 30 28 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29 27 41 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 39 38 37 36 35 34 33 33 32 31 30 29 28 27 26 25 37 36 35 34 33 33 32 31 30 29 28 27 26 26 25 24 35 34 33 33 32 31 30 29 28 28 27 26 25 23 33 32 31 31 30 29 28 28 27 26 25 w at er as needed 32-35 warning & double w at er 40-42 alert & w at er 36-39 50% relief 45-46 25% relief 43-44 only medically supervised work 75% relief 47-49 Moderat e Unacclimat i zed & Heavy Moderat e Acclimat iz ed & Light UnacclimatAct ion 50+ Temperature = 29°C Relative Humidity = 60% Humidex = 37°C
CAVEAT (warning)!CAVEAT (warning)! never ignore symptoms even if measurements meet standards!
Why Worry AboutWhy Worry About Heat Stress?Heat Stress? • Heat can kill! • Work-related heat stroke fatalities: 1990: student, second day collecting garbage 2001: bakery worker in Barrie • If global warming is happening, heat stress will become more important
August 9, 2001: Kim DouglasAugust 9, 2001: Kim Douglas Warner Died of Heat StrokeWarner Died of Heat Stroke • bakery worker was near the end of a 12 hour shift on the 5th day of a heat waver • 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 • 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
Heat stress death 1990 -Heat stress death 1990 - Inquest Findings:Inquest Findings: • Brian Freeman, arts student, on the second day on a summer job as a garbage collector experienced a heat stroke; died 17 days later • He had received no training to recognize symptoms • Heat stress measurements are too difficult to apply and don’t take into account vulnerabilities • Rather than relying on measurements, train workers to enable them to self-regulate (recognize symptoms and know how to reduce heat stress with breaks and fluid intake) • issues around malignant hyperthermia, a genetic condition (1 in 200) which makes people more susceptible to heat strain
Remember, when it’s hot:Remember, when it’s hot: Heed your body! watch for symptoms! Ensure you’re drinking enough! Adjust your activity level – slow down! Take clothing/PPE into account!
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