Using Humidex to Prevent Heat Stress

1. Occupational Health Clinics for Ontario Workers Inc. Using Humidex to Prevent Heat Stress JH&SC information session John Oudyk MSc CIH ROH Occupational Hygienist May 26, 2009

2. Monthly average daily high temperatures (YYZ 2001-08)

3. Cooling evaporation of sweat H S S H H External Heat sources hot weather radiant heat sources Internal Heat sources muscle activity Heat Balance

4. Transient Heat Fatigue: Symptoms: General feeling of tiredness or fatigue. First Aid: Fluid replacement and rest.

5. 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.

6. Heat Syncope (fainting) 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.

7. 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.

8. 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.

9. 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!

10. 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!

11. 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

12. Predisposing 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 …

13. … with all these vulnerabilities who typically gets heat stroke? young physically fit males and sick older people

14. 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

15. NO YES keep monitoring above below above or no data 4. heat strain evaluation - heart rate - core temperature OK excessive 1. clothing OK/adjustment? 2/3a. WBGT screening/ detailed action limit below 2/3b. WBGT screening/ detailed TLV® general controls 2007 ACGIH Heat Stress/ Strain TLV® 5. job-specific controls

16. clothing adjustment changes

17. What is a WBGT? • normal thermometer (dry-bulb) • wet-bulb thermometer • humidity • globe temperature • radiant heat Wet Bulb Globe Temp.

18. WBGT Formulas: For indoor or shaded environments: WBGT = 70% Tnwb + 30% Tg Tnwb = natural wet-bulb temperature (70%) Tg = globe temperature (30%) For direct sunlight exposure: WBGT = 70% Tnwb + 20% Tg + 10% Tdb Tdb = dry-bulb temperature

19. Screening WBGT (in °C ): Action Level TLV®

20. Can we simply use the outside temperature to estimate WBGT? 4+ºC WBGT spread @ 30ºC

21. temperature lag (3ºC WBGT) in cooling down temperature lag (4ºC WBGT) in heating up Outside vs Inside (WBGT):

22. NO YES keep monitoring above below above or no data 4. heat strain evaluation - heart rate - core temperature OK excessive 1. clothing OK/adjustment? 2/3a. WBGT screening/ detailed action limit below 2/3b. WBGT screening/ detailed TLV® general controls 2007 ACGIH Heat Stress/ Strain TLV® 5. job-specific controls

23. Action limit vs. TLV® • Action limit triggers general controls for unacclimatized workers, general controls include: • providing annual heat stress training, • encouraging adequate fluid replacement, • permitting self-limitation of exposure, • encouraging watching out for symptoms in co-workers, and • adjusting expectations for workers coming back to work after an absence

24. Action limit vs. TLV® • The TLV® applies to healthy, acclimatized, well hydrated workers not on medication and triggers job-specific controls (in addition to general controls) which include: • engineering controls to reduce physical job demands, shielding of radiant heat, increased air movement, reduction of heat and moisture emissions at the source, • adjusting exposure times to allow sufficient recovery, and • personal protective equipment that provides for body cooling – in addition to general controls)

25. 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

26. When are you acclimatized? • acclimatization requires up to 3 weeks to be fully established and is noticeably decreased after 4 days: • the 2007 TLV® suggests as a criteria: exposed for 5 of last 7 days or 10 of the last 14 days • “Hot spells in Ontario seldom last long enough to allow acclimatization.” (taken from Ontario Ministry of Labour Heat Stress Guideline: http://www.gov.on.ca/LAB/english/hs/guidelines/gl_heat.html)

27. Pearson Airport (Jun-Sept/05)

28. 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!

29. Workload Descriptions (TLV Table 3): Light: Sitting with light manual work with hands or hands and arms, and driving. Standing with some light arm work and occasional walking. Moderate: Sustained moderate hand and arm work, moderate arm and leg work, moderate arm and trunk work, or light pushing and pulling. Normal walking. Heavy: Intense arm and trunk work, carrying, shoveling, manual sawing; pushing and pulling heavy loads; and walking at a fast pace. Very Heavy: Very intense activity at fast to maximum pace.

30. Adjusting for Weight: Sample calculation: standing = 42 watts*(55 min/60min) = 38.5 watts walking = 174 watts*(5 min/60min) = 14.5 watts light work, two arms = 105 watts basal metabolism = 70 watts total metabolic rate = 228 watts (light) … but this applies to a 154 lb person, for an 200 lbs person we need a correction factor: 228 watts * (200/154)= 296 watts(moderate) … for an 245 lb person we need a correction factor: 228 watts * (245/154)= 362 watts(heavy) … and, what if the worker isfemale, or dehydrated, or etc.? …

31. NO YES keep monitoring above below above or no data 4. heat strain evaluation - heart rate - core temperature OK excessive 1. clothing OK/adjustment? 2/3a. WBGT screening/ detailed action limit below 2/3b. WBGT screening/ detailed TLV® general controls 2007 ACGIH Heat Stress/ Strain TLV® 5. job-specific controls

32. Physiological Monitoring? • check heart rate • check body temperature • is this medical monitoring? (MOL opinions split) • should data collected be treated as medical information? (i.e. confidential) • who is qualified to collect info, store it, interpret? • what happens if exceed limits? • personal vital signs monitoring equipment (e.g. swallow monitoring pill, ear temperature monitor, heart rate monitor) – who sets alarms on machines? • issues need to be addressed before it happens

33. 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 • No training to recognize symptoms • WBGT too difficult to apply and doesn’t take into account vulnerabilities • Rather than relying on the TLV, 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

34. Response to a Heat Stroke Death • the hazard of heat stress was tragically illustrated by a fatal incident in Barrie in 2001 • soon after the incident, the CAW approached OHCOW to find a simpler way of evaluating heat stress (e.g. Humidex), than the WBGT (wet bulb globe temperature) • the Oshawa GM assembly plant was used for the pilot study & GM management had input into the development

35. WBGT-Humidex correlation • a mid-sized manufacturing firm (350 workers) with some heated presses (400 °F) • during summer of 2002 three students hired to take WBGT/Humidex measurements continuously on 3 shifts (>7000 measurements taken) • based on 3773 measurements (all measurements above 22°C WBGT) resulting regression equation: Humidex = 1.9392*WBGT - 11.338

36. WBGT table converted to Humidex by correlation Action Level TLV®

37. 2007 Humidex Response Plan:

38. WBGT/Humidex Category Assignment Comparison:

39. acclimatized version:

40. How to measure heat stress using temperature & humidity • Find a representative place • Find temperature and humidity on chart and read Humidex • Take into account radiant heat (add 2-3° to Humidex for full sun) • Need to take clothing into account (add 5° for overalls on top of clothes) • Measurements should be when the ambient temperature is above 26°C and then be taken hourly • Compare to chart

41. CAVEAT (warning)! never ignore symptoms even if measurements meet standards!

42. temperature lag (6ºC Humidex) in cooling down temperature lag (5ºC Humidex) in heating up Outside vs Inside (Humidex):

43. Where do breaks fit in? • General controls (action limit triggered) do not specifically mention breaks although the categories are ordered by % work • Specific controls (TLV triggered) specifically mention adjusting work/rest schedules (administrative controls) • However, general controls do specify permitting “self-limitation of exposures” – what if this cannot be done (line work) … situation is ambiguous …

44. Calculators: • Humidex calculator (http://www.ohcow.on.ca/menuweb/calculator.htm) • WBGT estimate calculator (under development) (http://www.csao.org/heat_stress/WBGT%20Estimate%20Calculator.htm)

45. Adjustments for Radiant Heat: • Outside measurements taken over 2002 show the radiant heat load (globe temperature - Tg) between 10 am- 3 pm was 0-16°C above dry bulb temperature (Tdb) with an average 7.5°C • The difference this makes to the WBGT (using the formula WBGT = 0.7 x Tnwb + 0.2 x Tg + 0.1 x Tdb) is 0-3.2°C WBGT (average 1.5°C which is equivalent to 2-3°C Humidex on average)

47. Adjustments for Air Velocity: • For the issue of the difference air velocity makes, the difference between natural wet bulb and psychrometric wet bulb is 1°C • Thus the maximum WBGT difference between dead air and high velocity air would be (using the formula WBGT = 0.7 x Tnwb + 0.3 x Tg) about 1°C or 1.5-2°C Humidex

48. General Controls (1)Humidex 1 • Provide accurate verbal and written instructions, frequent training programs, and other information about heat stress and strain • Encourage drinking small volumes (approximately 1 cup) of cool, palatable water (or other acceptable fluid replacement drink) about every 20 minutes • Permit self-limitation of exposures and encourage co-worker observation to detect signs and symptoms of heat strain in others • Adjust expectations of those returning to work after absence from hot exposure situations • Monitor heat stress conditions and reports of heat-related disorders

49. General Controls (2)Humidex 1 • Counsel and monitor those who take medications that may compromise normal cardiovascular, blood pressure, body temperature regulation, renal, or sweat gland functions; and those who abuse or are recovering from the abuse of alcohol or other intoxicants • Encourage consumption of salty foods (with approval of physician if on a salt-restricted diet) • Consider pre-placement medical screening to identify those susceptible to systemic heat injury

50. H External heat source controls External Heat sources hot weather radiant heat sources • 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