Heat stress

					Occupational Health Clinics
for Ontario Workers Inc.




        Heat Stress
        Essentials

    Prevention in Action
              Outline

•   Heat stress/strain health effects
•   What you can do to prevent them
•   What the law says
•   Simple ways to monitor the heat
 Transient Heat Fatigue:

Symptoms: General
 feeling of tiredness or
 fatigue.
First Aid: Fluid
  replacement and rest.
    Heat Rash (prickly heat)
Symptoms: Skin becomes
  reddened and may itch,
  feel prickly or hurt.


                  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.
             Symptoms: Syncope means
   Heat        “fainting.” First signs are
               dizziness, feeling light-headed
 Syncope       and perhaps nauseous, then
(fainting)     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.
           Heat Cramps:
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 Exhaustion:
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 Stroke:
   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!
 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:
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
                very small body size
                overweight
                over 40 years old (the older
Predisposing     the more sensitive)
  Factors:      previous heat illness
                heart disease
                high blood pressure
                diabetes
                inactivity
                physical activity

                …sooner or later we’re
                 all vulnerable …
… with all these vulnerabilities
who typically gets heat stroke?




 young physically fit males
 and sick older people
      Heat
                                     Cooling
      Balance              H
                                    evaporation
                                      of sweat
                       S       S
  H
                           H
   External
 Heat sources
    hot weather
radiant heat sources
                                     Internal
                                   Heat sources
                                   muscle activity
                                      H
  External heat
                                   External
 source controls                 Heat sources
                                   hot weather
• At the source                radiant heat sources

  – 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
  Internal source
     controls:
• At the source                                H


  – Reduce workload
                               Internal
    • improve ergonomics,                      H
                             Heat sources
    • provide assistance,    muscle activity
    • increase relief time
    • slow down
  – Provide adequate water
  – Actively cool body
  – Gradually acclimatize
  – Ensure good nutrition and rest
       Promoting Cooling
• Wear loose clothes that allow
  sweat to evaporate easily                     S
  (cotton)                         Cooling
                                                S
• Take internal heat sources      evaporation
                                    of sweat
  into account when using any
  personal protective clothing
  that prevents sweat from
  evaporating
• Wash clothes regularly and
  maintain good personal
  hygiene
     Body Changes due to
       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 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:
• 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 Water
      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 …
                         Dehydration
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
  3L                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
         Eat Healthy
You can and should replace
essential elements lost during
sweating;

Eat a balanced diet
rather than taking salt
tablets or drinking
expensive sports
drinks.
         Cooler 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 Fans (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 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?

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
 NO    1. clothing OK/adjustment?

              YES
                                      keep monitoring
2/3a. WBGT screening/         below
detailed action limit
            above
2/3b. WBGT screening/         below
detailed TLV®                         general controls
            above or no data
                                             2007
  4. heat strain evaluation                  ACGIH
      - heart rate              OK
      - core temperature
                                             Heat
                                             Stress/
              excessive
                                             Strain
5. job-specific controls                     TLV®
           What is a WBGT?
1. normal thermometer (dry-bulb)
2. wet-bulb thermometer
  •   humidity
3. globe temperature
  •   radiant heat

Wet Bulb Globe Temp.
      Screening WBGT (in °C ):
   work          light moderate heavy           very
 demands:                                      heavy
100% work;       28.0      25.0           not     not
(breaks incl.)   31.0      28.0        allowed allowed
75% work;        28.5      26.0          24.0     not
25% rest         31.0      29.0          27.5  allowed
50% work;        29.5      27.0          25.5    24.5
50% rest         32.0      30.0          29.0    28.0
25% work;        29.0      29.0          28.0    27.0
75% rest         32.5      31.0          30.5    30.0
                        Action Level
                            TLV®
      How to measure heat stress
     using 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 Response Plan
Temp RH = 100% 95% 90% 85% 80% 75%                70% 65% 60% 55% 50% 45% 40% 35% 30%
 47   Moderate                                     Moderate
 46  Unacclimati                                  Acclimatiz
 45    zed &                                      ed & Light
 44    Heavy                 Action               Unacclimat
 43     45+      only medically supervised work      50+        Humidex = 37°C
 42    42-44               75% relief               47-49                          50
 41    40-41               50% relief               45-46                          48
 40    38-39               25% relief               43-44                      49  47
 39    34-37        warning & double water          40-42                  49  47  45
 38    30-33             alert & water              36-39              49  47  45  43
 37    25-29            water as needed             32-35          49  47  45  44  42
 36                                                          50 49 47  45  44  42  40
 35              Temperature = 29°C                      50  48 47 45  43  42  40  39
 34                                                49    48  46 45 43  42  40  39  37
 33              Relative Humidity = 60%
                                     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
CAVEAT (warning)!

never ignore symptoms
       even if
   measurements meet
      standards!
      Why Worry About
        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 Douglas
  Warner 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 -
        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:

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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