Heat Stress 1 18 March 2021

Home , Occupational heat stress

Heat Illness Response Guideline Presented in order of decreasing urgency. One or more indicators in a category indicate a positive determination for that category. Observations Determination and Action Severe Fatigue or Vomiting – Heat Stroke Watch for other signs of heat stroke Emergency Response while starting treatment for severe Begin aggressive cooling (cover in ice or place in cold/ice heat exhaustion. water bath). If ice is not available, other methods of cooling are flushing water over person from hose or shower; or Erratic / Irritable Behavior keep the skin wet and fanning. Confusion / Disorientation Garbled / Gibberish Speech Call emergency services and advise them that it is a heat Hysteria / Delirium / Apathy stroke case. Collapse Shivering Convulsions Unconscious

Wobbly Walking Severe Heat Exhaustion Slow Reaction Times Move to air-conditioned space, encourage water/electrolyte Severe Fatigue drink if able, and allow to lay down. Severe Muscle Cramps Vomiting or Collapse without Any Optional: Cover head and shoulders with a towel soaked in Signs of Heat Stroke ice water.

Person may say they have Watch for signs of heat stroke. Severe Fatigue Loss of Appetite If recovery is not progressing in 15 min, arrange for medical Nausea treatment and continue to watch for possible heat stroke. Headache Blurred Vision

Person may say they feel Mild Heat Exhaustion Tired / Fatigued Inform supervisor Thirsty Recovery in cool area Weak Drink water and/or electrolyte drink Dizzy Lightheaded If symptoms persist after 15 min, treat as severe heat Muscle cramps exhaustion

16 March 2021

Occupational Heat Stress 1 18 March 2021

Alternate Titles Occupational Heat Stress More than you could ever want to know Somethings Old about heat stress Somethings New or

Bernard – A one trick pony

Thomas E Bernard | 18 March 2021

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Special Thanks Fla AIHA

Those with whom I have worked • USF and sponsors of my work Heat-Related Illness Are Real • CDC/NIOSH and Sunshine Education and Research Center • ACGIH® and ISO Committees to which I contribute • Faculty, staff, students and the many study participants • Candi D. Ashley and Ximena P. Garzón

Notice: All opinions are mine

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NIOSH Case for Heat Stress Management Rate of Heat-Related Illness

CDC (2008) Occupation Incidence per 100,000 FTE • 423 deaths from 1992 through 2006 (28/y) Full Year Summer • Rate 20x higher for crop workers than all others Letter Carriers 81.3 176.5 Outdoors Fire Protection 80.8 158.8 BLS (2011) Roofers 59.0 161.2 • 4,190 lost time heat stress cases in 2010 Highway Construction 44.8 105.6 Increases with • Most fatalities among outdoor workers Underground Mining – Hard Rock 33.7 Hot Weather • Cases likely to be underreported Surface Mining – Stone 12.9 20 OSHA Citations in 2012 and 2013 Landscaping 11.6 25.6 Construction 6.8 21.3 • Most were deficient programs Surface Miners – Coal 5.3 • For fatalities: Usually no provisions for acclimatization All Other Industries 1.7 4.7

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Exertional Heat Illness Carry-Over Effect

Probability of exertional heat illness increases with environmental Previous Day heat and humidity • US Marine Training • Outdoor (mostly agriculture): 75% of heat disorders above 28°C- • Gulf Clean-up WBGT • Meta-analysis: Warm/Hot Work v Neutral: RR = 4) • Aluminum smelting (ORModHS = 20 and ORHighHS = 80) Multiple Day • Sports (OR = 7 between below and above 23 °C-WBGT) • Emergency Department Cases from Five States (3- to 4-day influence) • Outdoor work (Gulf Cleanup: OR = 1.4/°C-WBGT for >20°C) • Military training (OR = 4 between below and above 23 °C-WBGT) • Aluminum plants in Middle East (3-day weighted average)

That is, there is an exposure-response relationship

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Increased Accidents 150 Loss of Productivity Moderate Work Increase in Unsafe Behaviors Increase 100 1.8 50 1.7

Percent Light Work 1.6 0 Acute injuries in Aluminum Smelter 23 25 27 29 31 33 WBGT (ºC) 1.5 Speed (m/s) See also analysis of published papers 1.4 by June Spector, et al. (2019) that 1.3 demonstrates relationship between 0.1 1 10 100 1000 10000 ambient heat stress and frequency of Air Permeability severe injury

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Synthesis of Key Elements Heat Stress Management NIOSH Criteria Document ACGIH® TLV® for Heat stress and strain documentation Bernard Vision of Prof. Jacques Malchaire, Belgium Key Heat Stress Management Elements My personal experience and practice

A blend of old and new wine in new bottles

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Topics for Today

Written Policies

Basics of Heat Stress Written Policies

Heat Stress Exposure Assessment

Interventions

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Written Policies Program Context

Fundamental principle of occupational health and safety Part of your continuous improvement program programs

In the context of heat stress • Policies Specific to Heat Stress Management Program • Individual Discretion over Exposure • Discussed under heat stress hygiene practice • Part of administrative controls (See Tier 2 Interventions) • Acclimatization • Discussed under heat stress hygiene practices

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Heat Exchange

Biophysics of heat stress and job risk factors

The Basics

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Heat Flow Heat Balance Equation S = (M-W) + R + C + K – E

S Heat storage rate (M-W) Net rate of metabolic heat generation R Net rate of radiant heat exchange C Net rate of convective heat exchange K Net rate of conductive heat exchange E Rate of evaporative heat loss

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Metabolic Rate -- M Convection -- C Work demands are met by W Depends on converting chemical energy • Air to Skin Temperature Gradient (M) to mechanical energy (W) • Air Motion with a great deal of internal • Clothing heat generated in the process. M

0.6 C = hc vair (Tdb – Tsk) M >> W Clothing Effect, hc • Insulation (Inversely) H = M-W • Effective Porosity

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Radiant Heat -- R Maximum Evaporative Cooling

Depends on Depends on • Mean Radiant Temperature • Water Vapor Pressure (Humidity) Gradient • Clothing • Air Motion • Clothing Emax can be also limited by R = hr (Tr – Tsk) 0.6 Emax = vair (Psk – Pa) / Re sweating capacity

Clothing Effect, hr Clothing Effect, Re • Insulation (Inversely) • Water Vapor Permeability of Fabric (Inversely) • Effective Porosity (Inversely)

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Heat Balance Equation So, what makes the environment hot? S = (M-W) + R + C + K - E High If S = 0, W=0, and K=0, then Humidity High Air Ereq = M + R + C where Ereq < Emax Temperature Belding & Hatch Heat Stress Index: and Speed HSI = (Ereq/Emax)x100 Hot Surfaces S = Emax - Ereq (Increased Rate of Radiant Heat)

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Clothing Effects Job Risk Factors for Heat Stress Fabric Water Vapor Environment Permeability • Humidity (Water Vapor Pressure) Convective Fabric Permissibility Work (Metabolic) Demands Insulation • Fabric • Construction Clothing Requirements Thermal • Evaporative Resistance Characteristics of Clothing

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Measurement of Heat Stress Temperatures Psychrometric Natural Dry Bulb Wet Bulb Wet Bulb Globe Environment Tdb Tpwb Tnwb Tg Metabolic Rate Clothing

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Wet Bulb Globe Temperature Estimations from Weather Data

WBGT = 0.7 Tnwb + 0.3 Tg There are methods to estimate Tpwb, Tnwb and Tg from weather data. Except in direct sunlight,

WBGT = 0.7 Tnwb + 0.2 Tg + 0.1 Tdb

WBGT Index reflects effects of air temperature, humidity, hot surfaces and air motion. That is, C+R and Emax.

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Metabolic Rate Table Values

Tables Type of Work Metabolic Rate • Need to apply to the job of interest [Watts] • Most job descriptions and content are not current and thus the estimates are poor Passing the buck 125 Categories Dragging your heels 150 • Judgment about demands relative to descriptors Bending over backwards 200 Component Analysis Beating around the bush 250 Predictive Equations Jumping to conclusions 300 Heart Rate Running around in circles 350 Oxygen Consumption (called indirect calorimetry)

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Metabolic Rate Categories ISO Estimation Method

Light (Reference Rate: 180 W) Components of Metabolic Rate • < 235 W • Basal (Base) Metabolism (B) • sitting, standing, light hand/arm work Most Common • Posture (P) Moderate (Reference Rate: 300 W) • 235 - 350 W Approach • Type of Work (W) • walking, moderate lifting • Walking (D) Heavy (Reference Rate: 415 W) • Climbing (C) • 350 - 470 W • heavy materials handling Very Heavy (Reference Rate: 520 W) Potential Error • 470 - 800 W • Broad Range Total Metabolic Rate (M) = B + P + W + D + C • pick and shovel work • Over-Estimation

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Predictive Equations and Others Early Thought on Clothing Effects

Published equations that relate activity (or external work) to What WBGT metabolic rate. makes the heat stress Relationship between heart rate and metabolic demands the same? • Requires some care and no heat stress

28 °C-WBGT ?? °C-WBGT Assessment of oxygen consumption Moderate Work Moderate Work • Requires expertise and specialized equipment Work Clothes Protective Clothing

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Tc v WBGT and Clothing Clothing Adjustment Values

CAV Clothing Ensemble [°C-WBGT] Work Clothes 0 Cloth Coveralls 0 Double Layer Cloth Clothing 3 Shorts and Short-Sleeved Shirt -1 SMS Coveralls 0.5 Polyolefin Coveralls 1 Limited-Use Vapor-Barrier Coveralls 11 Note: Respirator Face Masks Have No Effect

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Effective WBGT Time-Weighted Average

WBGTeff1 x t1 + ••• + WBGTeffn x tn WBGTmeasured/estimated TWA-WBGTeff = t1 + ••• + tn + Clothing Adjustment Value M1 x t1 + ••• + Mn x tn TWA-M = WBGTeff t1 + ••• + tn

Over one- to two-hour time period.

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Biological Effects Physiological Systems in Heat Stress

Physiological Neurological responses to heat • Central Thermoregulatory Control stress and heat-related Cardiovascular disorders • Cardiac Output • Distribution of Blood Flow Skin and Sweating Water and Electrolyte Management • Renal (Kidney) Function • Sweat Glands • Gastrointestinal Track

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Cardiovascular Skin and Sweating

Muscular Activity Skin is the site of heat exchange between the body and the • Dictated by work demands environment. • Results in energy expenditure and heat generation Distribution of Blood Flow Peripheral blood flow is adjusted to meet the needs of heat • Support metabolic demands of muscles dissipation and is proportional to the gradient between the core • Convective movement of heat from core to skin and the skin temperatures. Work (Aerobic) Capacity • Marker of cardiovascular capacity Sweat rate adjusts to the needs for heat dissipation via • Interaction with thermal regulation evaporative cooling

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Water and Electrolyte Management Time Course of Acclimatization

Water Loss • Required for evaporative cooling • Replacement dictated by behavior • Difficult to replace more than 6 L during work Electrolyte Management • Physiological • Reduce diuresis (water conservation) • Conserve sodium (kidneys and sweat glands) Dilute fluids are best for water replacement (hypotonic and low solute concentrations)

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Benefits of Acclimatization Enhanced Cooling • Earlier onset of sweating • Greater rate of sweating • More dilute sweat Cost: Greater loss of body Heat Stress Exposure Assessment water content Lower Cardiovascular Strain • Increased fluid volume • Greater temperature gradient

Lower Core Temperature

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OSH Act of 1970 Heat Stress Assessment

2(b)7: criteria which will assure insofar as practicable Qualitative Judgment that no employee will suffer diminished health, functional capacity, or life expectancy as a result of his work experience Semi-Quantitative Analysis

Note: “… diminished … functional capacity” • Basis for heat stress limits Quantitative Analysis

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Qualitative Judgment Bernard Checklist

Simply accept that heat stress is possible (likely) • Obvious Sweating • Environment perceived to be warm Simple checklist-like approach • Work requires a break at least every 2 hours • Bernard • Wearing regular work clothes would be more comfortable • Malchaire • Reports of fatigue, weakness, loss of coordination, dizziness, headaches, nausea, heat exhaustion, cramps • Absenteeism, employee irritability or worsening employee relations • Increases in accidents and injuries and/or decreases in production and quality indices

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Semi-Quantitative Malchaire Checklist ACGIH Screening Criteria for Action Limit

%Work L M H VH 75 to 100 28.1 25.0 -- -- 50 to 75 28.7 26.0 24.2 -- 25 to 50 29.3 27.2 25.7 24.6 0 to 25 30.0 28.8 27.8 27.0

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Semi-Quantitative ACGIH Screening Criteria TLV Quantitative Exposure Assessment WBGT-based Exposure Limits %Work L M H VH Rational Heat Stress Methods 75 to 100 30.8 28.2 -- -- • Predicted Heat Strain (PHS) 50 to 75 31.2 29.0 27.6 -- 25 to 50 31.8 30.1 28.8 27.9 0 to 25 32.3 31.3 30.5 29.8

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WBGT-Based Exposure Assessment Starting Point for Heat Stress Limits

ACGIH® TLV ® for Heat Stress and Strain (2021) WHO Report, 1969 • Core Temperature Limits • Sustained: 38 °C (100.4 °F) NIOSH Criteria Document (2016) • Peak: 39 °C (102.2 °F)

ISO 7243 (2017) Risk of Heat Stroke • Low at these core temperatures

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Lind’s Observation (1963) Implication for Using ULPZ

LIND AR. A physiological criterion for setting thermal environmental limits for everyday work. Journal of Applied Physiology 18:51-56, 1963 Using the ULPZ as the OEL means that the OEL is designed for sustainable heat stress exposures associated with the ability to maintain thermal equilibrium. Upper Limit of the Prescriptive Zone: Transition from Work-Driven to Environment-Driven Core Temperature In the framework of the OSH Act: “… diminished … functional capacity”

Note: No longer talking about limiting core temperature

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Second, Confirmation Exposures from Kuhlemeier, et al.

Starting with Lind’s ULPZ from 1963 35

Findings at 350 W 30 C]

• ULPZ at 28.4 ° • Confirmed in 1970 25 • 24 of 25 for 3 h: 27.4 >U LPZ • Thus lower 1963 ULPZ by 1 ºC [ WBGT 20

LIND AR. Effect of individual variation on upper limit of prescriptive zone of climates. Journal of 15 Applied Physiology 28:57-62, 1970 10 0 20 0 30 0 40 0 50 0 60 0 M [W]

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Overall Conclusions What about Unacclimatized?

Group-Based Outcomes from Lind and Kuhlemeier At a moderate/high rate of work (350 W), the difference is about • Below ULPZ: Sustainable 2 - 3 °C-WBGT. • Above ULPZ: Unsustainable

Professional Judgment Below ULPZ: Virtually all individuals exhibited a sustainable exposure • Less of a difference at lower work demands • Greater difference at higher work demands Above ULPZ: Many individuals exhibited a sustainable exposure

High Sensitivity and Good Specificity

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WBGT-Based OEL USF Data

NIOSH, ACGIH®, and ISO are OEL Validation the same heat stress exposure limit

Environment • Wet Bulb Globe Temperature (WBGT) Work Demands • Metabolic Rate (M) Adjustments for non-standard clothing

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Exposure-Response Curve Receiver Operator Characteristic (ROC) Curve 1.0 1.0 0.8 OEL 0.8 0.6 0.6 At ∆WBGT = 0 Sensitivity = 1.00 0.4 Specificity = 0.07 0.4 OEL Probability of

Unsustainable Sensitivity 0.2 0.2 0.0 0.0 0.0 0.2 0.4 0.6 0.8 1.0 -2 0 2 4 6 8 10 12 ∆OEL [°C-WBGT] 1 - Specificity

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Inter- and Intra-Individual Variation Sensitivity and Specificity Among Studies

Lind • Sensitivity: 0.95 Specificity: 0.69

Kuhlemeier • Sensitivity: 1.00 Specificity: 0.81

USF Progressive Heat Stress Studies • Sensitivity: 1.00 Specificity: 0.07

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Continuous v Intermittent Conclusions (Support for TWA) WBGT-based OEL LIND AR. Physiological effects of continuous or intermittent work in the heat. Journal of Applied Physiology 18:57-60, 1963 • High Sensitivity • Very Low Specificity • High Rate of False Positives

Public Health Model

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USF Review of Literature Heat Index as WBGT Surrogate

John Flach Steadman’s Sultry Index Intended to be an analog to Wind Chill Index Confirms that TWA works for acclimatized individuals Designed to approximate heat exchange to standard conditions • Sensitivity = 1.0; Specificity = 0.58 for various combinations of temperature and humidity Does not include radiant heat Less clarity for unacclimatized individuals Morphed from rational to empirical index • Also older workers (confounded data) • Sensitivity = 0.71; Specificity = 0.35 • Appears that TWA does not work well but needs more study

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Heat Index v WBGT – No Radiant Heat Heat Index v WBGT – High Radiant Heat

35 35 20% rh 30 20% rh 30 40% rh C)

C) 40% rh ° ° 60% rh 25 60% rh 25 80% rh 80% rh Cu rv e Fit

WBGT ( WBGT 20

WBGT ( WBGT 20 Cu rv e Fit Tg = Tdb + 10 °C

15 15 25 30 35 40 45 50 55 60 25 30 35 40 45 50 55 60 HI (°C) HI (°C)

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Adjustments for Radiant Heat Summary of Heat Index from WBGT

Factors HI [°F] = 0.24 WBGT2 − 9.3 WBGT + 170; for WBGT in °C • Low v High Radiant Heat • WBGTin v WBGTout • Absolute value of HI (Adjustments based on midrange slope) Effects of Radiant Heat on HI • Low Radiant Heat: HI + 4 °F

Low Radiant Heat (Tg = Tdb + 4 °C) • High Radiant Heat -- outside: HI + 6 °F • Add 4 °F to HI • High Radiant Heat -- inside: HI + 9 °F

High Radiant Heat (Tg = Tdb + 7 °C) • Direct Sun (WBGTout): Add 6 °F to HI • No Direct Sun (WBGTin): Add 9 °F to HI

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NIOSH OSHA Heat Index App Predicted Heat Strain

Good for getting local Heat Index (HI) ISO 7933 (2021)

Has useful intervention information Rational Model of Heat Stress Exposure

Bernard Caution: The specific level-based decisions may Visual Basic (VBA) Code underestimate level of heat stress • I can provide as Excel function on request

Best Treated as a Black Box for Ordinary Use

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What do we ask the Black Box? Extended Exposures

Is an exposure safe? Yes / No Compensable v. Uncompensable

How long can an exposure safely last?

PHS Environment Metabolic Rate Decision / Clothing Recommendation Time Limit Personal Factors

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Woven Clothing: 2x2 Table Summary of Results by Clothing (PHS 2017)

Observed Outcome PHS 2017 Clothing Sensitivity Specificity State Uncompensable Compensable Total Woven Clothing 1.00 0.18 nSS 143 117 260 SS 0 26 26 Particle Barrier 0.95 0.60 Total 143 143 286 Water Barrier 0.91 0.83 Sensitivity Specificity Vapor Barrier 0.91 0.80 1.00 0.18 All Clothing 0.94 0.65

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Time Limited Exposures Reference for Viewing Data

Job Risk Factors The higher the PHS 2017 predicted Tre above the decision • Environment threshold (38.0 °C) means greater protection (protective • Metabolic Rate decision). • Clothing • Time

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Predicted Tre at USF Time Limit Predicted Tre at USF Time Limit Woven Clothing by Fixed Individual Factors All Clothing by Fixed Individual Factors

1.0 1.0

0.8 0.8

0.6 0.6

0.4 0.4

0.2 0.2 ProbabilityTransition of ProbabilityTransition of 0.0 0.0 36 .0 38 .0 40 .0 42 .0 44 .0 37 .0 38 .0 39 .0 40 .0 41 .0 42 .0 43 .0 Predicted Tre [°C] Predicted Tre [°C] 89 90

Observations on All Clothing Based on PHS Predicted Time Limit

The overall observations do not change from those for woven For each trial, the fixed personal factors method was used to clothing. predict safe exposure time. • Height = 1.8 m; Weight = 75 kg; Starting Core Temperature = 36.8 °C Work Clothes at highest Heat Stress Level provides most of the information to support a PHS Tre limit of 38°C. Comparing the predicted time to the observed time for all clothing, the range was from -5 min (observed time less than predicted to +100 (observed time greater than predicted). Represents general applicability across clothing evaporative Another way of saying that PHS 2021 is protective for time resistance; specifically, lower values of im than specified by ISO limited exposures. 7933.

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Risk Assessment Process

Risk = Severity x Probability

Two Methods to Assess Severity Severity Assessment • WBGT-based Exposure Response • PHS prediction of exposure time (called DLE) (Malchaire)

Probability is assigned by person doing the risk assessment

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WBGT-based Exposure-Response Curve Unacclimatized

1.0 Shifts curve to the left by about 3 °C-WBGT 0.8

0.6 Example for 9 healthy, young men and 9 healthy, 0.4 OEL young women Probability of Unsustainable 0.2

0.0 -2 0 2 4 6 8 10 12 ∆OEL [°C-WBGT]

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Rapid Rise in Core Temperature Suggested Severity Levels

Shifts the curve 3 °C-WBGT to the right Level ∆OEL Description Acceptable < -3 °C Low probability (< 1%) of unsustainable heat stress for anyone (baseline is unacclimatized) Caution < 0 °C Low probability (< 1%) of unsustainable heat stress for anyone who is acclimatized Moderate < +3 °C Low probability (< 1%) of rapid heat gain

High < +6°C Significant probability (up to10%) of rapid heat gain

Extremely High > +6 °C Likelihood (> 10%) of rapid heat gain

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Another Consideration Severity Levels for Moderate Work

The stages are in 3 °C-WBGT increments. Level WBGT Description Acceptable < 25 °C Low probability (< 1%) of unsustainable heat stress The odds or rate ratios for heat-related illness is about 1.4 per for anyone Caution 25 – 28 °C Low probability (< 1%) of unsustainable heat stress °C-WBGT. for anyone who is acclimatized Moderate 28 – 31 °C Low probability (< 1%) of rapid heat gain

This means that the 3 °C steps represent about a four times High 31 – 34 °C Significant probability (up to10%) of rapid heat gain increase in the probability of a heat-related illness from the previous severity stage. Extremely High > 34 °C Likelihood (> 10%) of rapid heat gain

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Severity Levels for Moderate Work Outside in the Sun Heat Index Chart Moderate work in the sun with regular clothing Level WBGT Heat Index Description Acceptable < 25 °C < 84 °F Low probability (< 1%) of unsustainable heat stress for anyone Caution 25 – 28 °C 84 – 94 °F Low probability (< 1%) of unsustainable heat stress for anyone who is acclimatized Moderate 28 – 31 °C 94 – 106 °F Low probability (< 1%) of rapid heat gain High 31 – 34 °C 106 – 130 °F Significant probability (up to10%) of rapid heat gain Extremely High > 34 °C > 130 °F Likelihood (> 10%) of rapid heat gain

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Notes on Heat Index Progressive Nature of Exposures

Criticisms • Does not account for radiant heat (sun) and air movement • The National Weather Service severity levels are not documented (and Thermal Thermal Health are arbitrary) Comfort Discomfort Risk

The severity levels here are at somewhat higher HIs than those posted by OSHA and NIOSH using NWS categories Occupational Exposure Limit (OEL) The criticisms are addressed Kodak

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Severity in PHS-based Assessment

Level Classes of Exposure• Description (Based on DLE)

Acceptable Possible thermal discomfort DLE > 480 min for unacclimatized Heat Stress Management Caution Possible thermal discomfort DLE > 480 min for acclimatized

Moderate Thermal constraint in the long term 120 < DLE ≤ 480 Bernard Vision of

High Thermal constraint in the short term 30 < DLE ≤ 120 Key Heat Stress Management Elements

Extremely High Immediate thermal constraint DLE ≤ 30

• Bernard adaptation of Malchaire’s classifications

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Intervention Categories Tier 1: Essential Interventions

Idea from Malchaire: Three tiers based on severity Training

Level Tier 1 Tier 2 Tier 3 Hygiene Practices Acceptable • Includes acclimatization Caution X Moderate X X Surveillance High X X X Extremely High X X X First Aid and Emergency Response

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Tier 2: Traditional Hierarchy of Controls Tier 3: Special Interventions

Based on NIOSH Medical Monitoring and many occupational health and safety Physiological Monitoring management systems (e.g., ANSI Z10 and ISO 45000)

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Tier 1 Training When Annually, in anticipation of heat stress Training Follow-up refresher(s) Training ties the Hygiene Practices How Typical training program format policy, science, and practice Heat Stress Alert Surveillance together. • Environmental What Heat stress and heat strain • Medical Heat-related disorders Heat stress hygiene practices Heat-Related Disorders: Recognition, First Aid and Emergency Policies on self-determination and acclimatization Response Discussion of site countermeasures

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Heat Stress Hygiene Practices Hygiene Practice: Self-Determination Self- Determination Interrupt heat stress exposure once excessive discomfort or the early symptoms of a heat-related disorder is felt Fluid Replacement Lifestyle Self-Pacing work and Diet Health Incentive payments and new workers make this difficult. Status Acclimatization / Expectations

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Hygiene Practice: Fluid Replacement Hygiene Practice: Lifestyle and Diet

Key Issues Lifestyle • Thirst versus Habit • Adequate sleep • Limited exposure to heat stress outside of work • No abuse of drugs or alcohol Water is the essential component but must be an acceptable drink. • People will drink more if the water is flavored and cool Diet • Well-balanced, perhaps extra salt • Weight-loss or salt-restricted – consult health care provider Some caffeine is acceptable.

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Hygiene Practice: Health Status Acclimatization Notes

Chronic Disease Physiological Improvement in Heat Stress Tolerance • Consult with health care provider • Clearly inform health care provider of heat stress exposure • See Medical Review handout Policy: Make allowances for acclimatization of new or returning workers Acute Illness • Consider anything that may cause fever, dehydration or the use of any prescription or OTC medication (e.g., flu, vomiting, allergies, etc.) • Stay home or report it to supervisor (presenteeism problem) • Restricted exposures may be prudent course • Some sort of “readiness for work” query (e.g., sleep and appetite)

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OSHA Citations Acclimatization Schedule

84 heat-related citations in 2012 and 2013 • Only one employer had an acclimatization program Day New* Experienced 1 20% 50% 31 citations with heat-illness between 2011 and 2016 • No employer had an acclimatization program 2 40% 60% 3 60% 80% • New to a job that 4 80% 100% requires demanding 5 100% 100% skills training

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Re-Acclimatization Schedule Alternative Acclimatization Schedule Plus-Up on Observed WBGT Routine Exposure Day 1 Day 2 Day3 Day 4 Absence Illness Sequence Unacclimatized New employee; +2.5 °C +1.5 °C +1.0 °C Acclimatized Day 1 Day 2 Day 3 Day 4 Away for a week or more due to < 4 –– 100% illness; Absent for 3 weeks 4 – 5 1 – 3 R/E† 100% Mostly Away for less than +1.5 °C +1.0 °C Acclimatized Acclimatized Unacclimatized a week due to 6 – 12 4 – 5 80% 100% illness; Absent for 2 weeks 12 – 20 6 – 8 60% 80% 100% Somewhat Absent for 1 week +1.0 °C Acclimatized Acclimatized Acclimatized > 20 > 8 50% 60% 80% 100% Unacclimatized † Reduce expectations, some loss of capacity Some Caution Absent less than 1 Reduce Acclimatized Acclimatized Acclimatized week Expec- tations

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Alternative Acclimatization Schedule Plus-Up on Observed HI Who Benefits? Day 1 Day 2 Day3 Day 4 Ayub Odera Unacclimatized New employee; +10°F +8°F +4°F Acclimatized Away for a week or more due to Pre-Acclimatization Post-Acclimatization illness; Absent for Condition 50°C/20% 40°C/30% 50°C/20% 40°C/30% 3 weeks Mostly Away for less than +8°F +4°F Acclimatized Acclimatized ΔWBGT [°C] ∆AL = 10.5 ∆AL = 4.5 ∆OEL = 8 ∆OEL = 2 Unacclimatized a week due to illness; Absent for Observed (%) 14 75 34 75 2 weeks Expected (%) 2 80 20 95 Somewhat Absent for 1 week +4°F Acclimatized Acclimatized Acclimatized Unacclimatized Based on heat tolerance projections, about 90% of exposures for Some Caution Absent less than 1 Reduce Acclimatized Acclimatized Acclimatized unacclimatized people are already above the OEL for acclimatized week Expec- tations

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Comments on Acclimatization Surveillance

Acclimatization is an important physiological adaptation to Environmental increase heat tolerance. • Provide some guidance on trigger points for different actions

In practice, about 10% of the healthy, unacclimatized population will have insufficient tolerance to work at the OEL. This is Medical reduced to about 1% after acclimatization • Chronic Disease: At least advice to seek counselling from health care provider (see handout) • Acute Illness: Report it to supervisor who may restrict exposures It is important in heat stress management but is a limited intervention applicable to a smaller group of workers who are not easily knowable

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Trigger Points Medical Surveillance

For those wearing work clothes, a suggest trigger point to have a Review Illness and Injury Logs heat stress management program is 27 °C (80 °F). Acute Illness: Have a plan to deal with presenteeism Triggers for specific actions should be based on an assessment • Good public health practice of the exposures. Chronic • Individuals advise their personal healthcare provider of exposure to heat stress as part of the job

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Personal Risk Factors Heat Stroke – Predisposing Factors

Inter- (and Intra-) Individual Variations Administrative Acquired Fitness / Aerobic Capacity • Overtime • Not acclimatized Age • Illness (acute or chronic) • Changes in aerobic capacity • Machine pacing • Skin disease Sex • Piece-work • Differences in aerobic capacity • New worker • Immunization Obesity • Convalescence • Larger metabolic costs to do the same work • Obesity Disease / Illness • Consider the pathophysiology and the physiological systems needed to manage thermal Circumstantial • Lack of sleep regulation • Heat wave • Drugs / Alcohol Drugs: Prescription, OTC and Recreational • Preceding exposure • Consider the site of action and the physiological systems needed to manage thermal • Dehydration regulation • After a meal

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What you may see in first aid records Monitoring for Signs and Symptoms

Excessive fatigue Bernard: Many reported cases of heat-related illness may be a Nausea mix of job and personal risk factors. • Someone has to be the least tolerant of heat stress in your workforce; Headache and it may not be the same person each day. Skin rashes Muscle cramps Monitoring of signs and symptoms is the essential backstop. Elevated temperature Never work without a buddy; and both must be able to easily communicate with the other.

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Mild Heat Exhaustion

Signs and Symptoms Actions Person may say they feel • Inform supervisor • Tired / Fatigued • Recovery in cool area • Thirsty • Drink water and/or electrolyte drink Recognition of and First Aid for • Weak • Dizzy Exertional Heat-Related Disorders Note: If symptoms persist after 15 • Lightheaded min, treat as severe heat • Faintness with change in exhaustion posture or prolonged standing • Muscle cramps

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Severe Heat Exhaustion Heat Stroke

Signs and Symptoms Actions Signs Actions You may see one or more of the following • Move to air-conditioned space, • Severe Fatigue or Nausea/Vomiting – • Emergency Response • Wobbly Walking encourage water/electrolyte drink if Watch for other signs of heat stroke able, and allow to lay down. • Begin aggressive cooling (cover in ice • Slow Reaction Times while starting treatment for severe • Severe Fatigue or place in cold/ice water bath). If ice is heat exhaustion. not available, other methods of cooling • Severe Muscle Cramps • Optional: Cover head and shoulders are flushing water over person from • Vomiting or Collapse without Any Signs with a towel soaked in ice water. You may see one or more of the hose or shower; or keep the skin wet of Heat Stroke following and fanning. Person may say they have • Watch for signs of heat stroke. • Erratic / Irritable Behavior • Severe Fatigue • Confusion / Disorientation • Garbled / Gibberish Speech • Loss of Appetite • If there is little improvement in 15 min, • Call emergency services and advise • Nausea arrange for medical treatment and • Hysteria / Delirium / Apathy them that it is a heat stroke case. • Headache continue to watch for possible heat • Collapse • Blurred Vision stroke. • Shivering • Convulsions or Unconscious Note: You need to know where you are

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Other Heat-Related Disorders Notes on Recognition and Treatment

Heat Syncope Act early and error to the side of thinking there is a problem where none exists. Heat Cramps Heat stroke depends on early recognition of signs. • The person will not come up to you and say they have heat stroke. Heat Rash

Any time a worker experiences a fainting spell or other form of collapse, medical approval for return to work is advised.

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Tier 2 Recall Heat Balance

Heat stress levels exceed the OEL for acclimatized workers Evaporation

For those workers who are exposed to heat stress Radiation M What • Eliminate the hazard • Substitute methods or process Convection Ereq = M + R + C • Engineering controls and re-organization of work • Administrative Controls • Personal protective equipment and methods

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Elimination and Substitution Engineering Controls

Change the processes or environment so that heat stress is Change the conditions so that heat stress is reduced. reduced, ideally below the OEL. Methods • Reduce metabolic rate (greatest contributor) • Change clothing requirements • Reduce air temperature and humidity • Increase air motion (limited value) • Radiant heat control

Temporary or Permanent Controls

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Metabolic Rate Clothing: Balance Requirements

Reduce External Work -- Opportunities • Application of force through a distance Chemicals Heat Stress • Lifting the body against gravity • Walking and carrying on the level

Reduce External Work First: Then: • Eliminate or reduce the opportunities Acceptable Lowest • Add powered assists Contaminate Evaporative • Sharing the work Hold Out Resistance

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Air Permeability and Productivity Reduce Evaporative Resistance

1.8

1.7

1.6

1.5 Speed (m/s) 1.4

1.3 0.1 1 10 100 1000 10000 Air Permeability

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Reduce Humidity and Air Temperature Air Movement and Radiant Heat

Ventilation Fans • Enhance evaporative cooling Air Conditioning • Work Area Force air through/under clothing • General and spot cooling • Recovery Area (e.g., tent) Radiant Heat Management • Insulation, surface emissivity, shields Temporary or Permanent

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Administrative Controls Work and Recovery Cycles

Manage the risk by controlling the exposure Based on TWA-M and 35 TWA-WBGT between the Methods two conditions. • Recovery Allowances (Work/Rest Cycles) 30

• Planned Time (Time Limit) C] OEL • Self-determination ° 25 • Set the pace of work Work and recovery • Limit the exposure schedules assume a 20 • Scheduling fixed metabolic rate for [ WBGT • Buddy System work and for rest and a 15 resulting TWA. 100 200 300 400 500 600 Most easily implemented Metabolic Rate [W]

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Time-Weighted Averages Move Down and Left

Remember that TWA works for at least acclimatized individuals Heat Stress Level Work Demands

V Light Light Moderate 60/0 124 112 98 45/15 125 113 103 30/30 126 119 110 15/45 128 125 119 Caution 131 131 131

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Work and Recovery in the Shade Work and Recovery in Cooled Area

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Cool Recovery Area Planned Time

The TWA is also favored by a larger difference between the Adds time to the other job 55 WBGTs in the work and recovery areas. risk factors. 155 W 50 200 W C)

° 45 260 W Recovery areas should not be less than about 20 °C-WBGT PHS is a useful method to 40 prescribe a time limit.

WBGT ( WBGT 35

30 0 1 2 3 4 5 6 Exposure Time (h)

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Self-Limitation Heat Exhaustion and Core Temperature

Why Use Self-Limitation? • Planned Time limits productivity • Extends work time beyond protective limits • Implication: More productivity and greater risk

Criteria to Stop • Fatigue or untoward symptoms • Decision to stop • Active query versus passive decision

For High and Extremely High Heat Stress, see Teir 3.

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Personal Protection Tier 3: Special Interventions

Provide a microclimate to promote cooling (or reduce heat gain) Medical Monitoring

Methods Physiological Monitoring • Circulating Air Systems • Liquid Cooling Systems • Ice Cooling Garments • Arm/Hand Immersion Cooling

• Evaporative Cooling • Reflective Clothing for radiant heat

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Medically Qualified Physiological Monitoring

Those working at severity levels of High or Extremely High are Subjective Judgment Criterion: Onset of symptoms working under conditions that are physiologically demanding. • Implication: Passive decision • Decision Outcome: Unreliable (<10%?) A health care provider should review each person and explicitly offer a written opinion that the individual is medically qualified to Personal Monitoring perform the work. • Criteria: HR and/or Tcore plus onset of symptoms • Implication: Better informed self-assessment • Decision Outcome: More reliable

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Physiological Measures Comments on Monitoring Heat Strain

Heart Rate Temperature is the primary indicator. • Recovery • Fixed Threshold • Selected Averages Preceding indicator is heart rate.

Core Temperature (via surrogates) • Oral Significant dehydration indicates high compensable stress or • Ear canal poor water replacement. • Other

Better to Assess Both

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Body Temperature Rectal Temperature

Principal Concern is Core Temperature Slower Responding than Esophageal and Tympanic • Direct Measures Temperatures • Rectal (Tre)

• Tympanic (Tt) • Esophageal (Te) Indicative of Total Heat Content of Body • Indirect (Surrogate) Measures

• Oral (To)

• Ear Canal (Tec) Radio-pills are available. • Tympanic via Infrared (Tti)

• Surface-mounted Disk (Td) Skin Temperature

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Core Temperature Criteria Oral Temperature

Chronic Exposures (WHO and others) Method • 38 °C • Sublingual • No eating or drinking for 15 minutes prior • No talking or mouth breathing Acute, Monitored Exposures (WHO) • 39 °C Somewhat Influenced by Environment

Acute, Monitored Exposures with Margin Clinical Thermometer • 38.5 °C • Electronic • Thermal Strips

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Ear Canal Temperature Alternative Methods

Method There are other methods are emerging to assess body • Placed Carefully, usually by individual temperature to make decisions on exposure limits. The methods • Insulated should be validated and the validation data available for critical review. Sensitive to External Environment

Commercial and Adaptable Devices Available

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Heart Rate Recovery Heart Rate

Indicative of Cardiovascular Response Method • Metabolic Demands • Stop Work and Sit • Heat Transfer • Note HR at 1 minute (HR@1) • Secondary Measure of Heat Strain • Measure by Electronic Device

Techniques Interpretation • Recovery Pattern • HR@1 < 110: No excessive strain • Average • HR@1 > 110: Increased risk • Peak • HR@1 > 120: Significant strain and risk

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Rough Outcomes for HR@1 Peak Heart Rate

Moderate Heat Strain Method • Sensitivity = 1.0 • Monitor or Log Heart Rate • Specificity < 0.1 • Criterion for 1 min Sustained HR is 90% HRmax • HRmax = 195 – 0.67 (age – 25) ± 10 • ACGIH® (Sustained Peak)

High Heat Strain • HRpeak = 180 – Age • Sensitivity = 0.9 • Bernard Suggestion: 140 • Specificity = 1.0 Better indicator of acute health risk than overall strain. That is, sustained peak HR criterion is a ceiling limit.

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Average Heart Rate Thresholds for Selected Averaging Periods

Method • Log HR for Work Shift Time Period • Average the Rate for the Shift Threshold HRave for Average • Loggers are Commercially Available 5 min 156 20 min 141 Interpretation 45 min 133 • HRave < 115: No excessive strain 90 min 128 • HRave > 115: Increased risk

Bernard and Kenney, AIHAJ (pg 505) 1994

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Exposure Assessment

When the exposures are below the WBGT-based OEL or PHS > 480, the severity level is low enough the the risk over 8 hours should be considered acceptable. In Conclusion Nonetheless, most data to support exposure limits assume healthy workers. Provisions should be made to recognize when a worker with low heat tolerance may experience a heat-related disorder and act accordingly.

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Interventions Comments on Tier 3 Interventions

Tier 1 interventions are essential features of heat stress Some organizations may wish to establish a stop-work level of management. exposure when engineering and administrative controls are not sufficient to stay at the OEL. Tier 2 interventions are best considered in the actual manifestation of the work. That is, the selection and implementation consider the technical and economic feasibility of There are extraordinary work conditions that will require candidate interventions. heightened vigilance with an appreciation of the increased risk.

Tier 3 interventions are for high and extremely high severity, which should be undertaken with care.

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Final Comments It was a pleasure spending some time with you

Heat stress management must fit into your overall safety and health practices • Where does the risk fall in the workplace hazards you face?

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Thanks from USF, UCF and Embry-Riddle University Together, we’re making a difference

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Screening for Heat Stress – Checklist *

Job Analyst Date Description of Climate, Work Demands, Clothing Special Conditions

Complete the following checklist for each potential heat stress situation. Job Factor Yes No Obvious sweating

Environment perceived to be warm

Work requires a break at least every 2 hours

Wearing regular work clothes would be more comfortable

Reports of fatigue, weakness, loss of coordination, dizziness, headaches, nausea, heat exhaustion, cramps Absenteeism, employee irritability or worsening employee relations can be associated with these work conditions Increases in accidents and injuries and/or decreases in production and quality indices can be associated with these work conditions

A “Yes” to the presence of any of these job factors would indicate that a further investigation and controls are appropriate.

* This checklist is a prototype based on the professional judgment of the author.

Screening for Thermal Stress -- Observational Analysis *

Job Analyst Date Description of Climate, Work Demands, Clothing Special Conditions

Complete the following matrix by consensus of observers very familiar with the workplace and possible exposure situations. Table of scores and qualitative descriptors for each of the categories follows on the next page. Scores -3 -2 -1 0 +1 +2 +3 Ideal Zone Air Temperature

Humidity Thermal Radiation Air Movement

Work Load

Clothing

Worker Opinion

Actions should be taken to bring scores outside of the ±1 range into this range.

* This observational method is adapted from J. Malchaire, H. J. Gebhardt and A. Piette: Strategy for evaluation and prevention of risk due to work in thermal environments. Annals of Occupational Hygiene 43:367-376, 1999.

Score Qualitative Descriptors Air Temperature -3 Generally Freezing (Below 0 °C / 32 °F) -2 Generally between 0 and 10 °C (32 and 50 °F) -1 Generally between 10 and 18 °C (50 and 64 °F) 0 Generally between 18 and 25 °C (64 and 77 °F) +1 Generally between 25 and 32 °C (77 and 90 °F) +2 Generally between 32 and 40 °C (90 and 104 °F) +3 Generally greater than 40 °C (104 °F) Humidity -1 Dry Throat and/or Eyes after 2-3 hours 0 Normal +1 Moist Skin +2 Skin Completely Wet Thermal Radiation -1 Cold on the Face after 2-3 minutes 0 No Discernable Radiation +1 Warm on the Face after 2-3 minutes +2 Unbearable on the Face after more than 2 minutes +3 Immediate Burning Sensation Air Movement -2 Cold, Strong Air Movement -1 Cold, Light Air Movement 0 No Noticeable Air Movement +1 Warm, Light Air Movement +2 Warm, Strong Air Movement Work Load 0 Office Work; Easy, Low Muscular contractions; Occasional Movement at Normal Speed +1 Moderate Work with Arms and Legs; Use of Heavy Machines; Steadily Walking +2 Intense Work with Arms and Truck; Handling of Heavy Objects; Shoveling; Walking Rapidly; Carrying Heavy Loads +3 Very Intense Work at High Speed; Climbing Stairs or Ladders Clothing 0 Light, Flexible, No Interference with Work +1 Long, Heavier, Slight Interference with Work +2 Clumsy, Heavy, Specially-Designed Barrier for Radiation, Water Vapor, Cold +3 Special Coveralls with Gloves, Hoods, Shoes Worker Opinion -3 Shivering, Strong Discomfort for the Whole Body -2 Strong Local Discomfort; Overall Sensation of Coolness -1 Slight, Local Cool Discomfort 0 No Thermal Discomfort +1 Slight Sweating and Discomfort; Thirst +2 Heavy Sweating; Strong Thirst; Modified Work Pace +3 Excessive Sweating; Very Tiring Work; Special Clothing

During the medical and physical examination, specific concerns related to heat tolerance are  water and electrolyte management (renal, endocrine and gastrointestinal functions)  cardiac output and distribution to musculature and skin  sweating (skin integrity and sweat gland function)  thermal regulation (CNS and peripheral nervous system)  previous episodes of heat-related disorders

Health History  Cardiac  Vascular  Respiratory  Neurologic  Renal  Hemologic  Gastrointenstianal  Endocrine  Skin (e.g., chronic damage, anhydrosis)  Heat-related disorders (based on follow-up questions: single case of heat stroke (some people will report experiencing heat stroke when it is heat exhaustion), repeated episodes of heat exhaustion, or general reports of not tolerating heat well)

Prescription Medications (see annex for possible mechanism)  Psychotropics o Phenothiazines o Tricyclic antidepressants (e.g., imipramine, amitriptyline, protriptyline) o Lithium o Amphetamines, cocaine, ecstasy o Haloperidol o Anticonvulsants o Others (e.g., MAOIs, benzodiazepines)  Anticholinergics (e.g., benzotropine, trihexyphenidyl)  Antispasmodics  Antihistamines  Diuretics  Laxatives  Calcium channel blockers (e.g., amlodipine, verapamil)  Beta blockers (atenolol, betaxolol)  Levothyroxine  Anticholinergics (e.g., benzotropine, trihexyphenidyl)  Narcotics  Barbiturates  Ergogenic stimulants (e.g., ephedrine/ephedra)  NSAIDs (long term and/or high dose)

OTC Medications and Supplements  Antihistamines  Analgesics (high dose and/or long-term use) (e.g., acetaminophen (impaired liver function); aspirin and NSAIDs (impaired renal function))  Laxatives  Ergogenic stimulants (e.g., ephedrine/ephedra)

Drugs of Abuse  Ethanol  CNS stimulants such as amphetamines, cocaine, ecstasy  CNS depressants such as barbiturates

Drug Annex

Prescription Drugs Drug Effect on Heat Tolerance Phenothiazines Impaired sweating, (possibly) disturbed hypothalamic temperature regulation Tricyclic antidepressants (e.g., imipramine, Impaired sweating, increased motor activity amitriptyline, protriptyline) and heat production Lithium Nephrogenic diabetes insipidus and water loss Amphetamines, cocaine, ecstasy Increased psychomotor activity, activated vascular endothelium Haloperidol Tachycardia, altered central temperature regulation, and hyponatremia Other psychotropics as a general class (e.g., Impaired thermoregulation anticonvulsants, MAOIs, benzodiazepines) Antispasmodics Impaired sweating Anticholinergics (e.g., benzotropine, Impaired sweating trihexyphenidyl) Antihistamines Impaired sweating Analgesics (e.g., acetaminophen, aspirin, Liver or kidney damage NSAIDs) (long term use) Diuretics Salt (sodium and/or potassium) depletion and dehydration Laxatives Dehydration Calcium channel blockers (e.g., amlodipine, Reduced skin blood flow and reduced blood verapamil) pressure Beta blockers (atenolol, betaxolol) Reduced skin blood flow, reduced blood pressure, and impaired sweating Levothyroxine Excessive sweating, salt depletion and dehydration Anticholinergics (e.g., benzotropine, Impaired sweating trihexyphenidyl) Narcotics Excessive sweating, salt depletion and dehydration Barbiturates Reduced blood pressure Ergogenic stimulants (e.g., Increased heat production ephedrine/ephedra)

Other-the-Counter Medications and Supplements Drug Effect on Heat Tolerance Antihistamines Impaired sweating Analgesics (e.g., acetaminophen, aspirin, Liver or kidney damage NSAIDs) Laxatives Dehydration Ergogenic stimulants (e.g., Increased heat production ephedrine/ephedra)

Other Drugs and Drugs of Abuse Drug Effect on Heat Tolerance Ethanol Diuresis, possible effects on intestinal permeability, impaired thermoregulation CNS stimulants such as amphetamines, Increased psychomotor activity, activated cocaine, ecstasy vascular endothelium, impaired thermoregulation Central nervous system depressants such as Reduced blood pressure, impaired barbiturates thermoregulation