2. Heat stress
• The net heat load to which a worker is exposed
• Climatic (temp,humidity,radiant temp,
air velocity)
• non climatic(metabolic heat ,physical fitness,clothing,age,sex etc.
• ET,CET
• WBGT
• OXFORD INDEX
• P4SR
• Balding Hatch Index{HIS}
The Wet Bulb Globe Temperature (WBGT) screening criteria is the most
commonly used method of monitoring of potential heat stress
3. CASE STUDY
• On dd/mm/yyyy at 4pm a 40/M lawn mover collapsed and
died of heat stroke. As per co worker the victim was of
feeling light headedness and SOB 2 hrs before his death.
• The worker was wearing two pairs of pants on the day he
died
• ER team treated the victim at the site, and then
transported to hospital where he was pronounced dead
with an internal temperature of 42degree.
Given and Assumptions
Date of Incident: dd/mm/yyyy
Air Temperature: 77°F (25°C) – From
Cloud Cover: Clear
Wind Speed: 4.6 mph –
Relative Humidity: 56% -
Time: 2 pm The worker's symptoms began two hours
before his death at 4:00 pm barometric pressure: 30.13
in Hg
Clothing Adjustment Factor (CAF): 3 – From Table 3
4. Step 1: Determine WBGT
Table 1, solar irradiance for clear/sunny may be estimated as 990 W/m2
5. Step 2: Determine WBGTeff
WBGTeff = WBGTout + Clothing Adjustment Factor (CAF)
The worker's two pairs of work pants fall under the double layer woven clothing in
Table 2; therefore, the Clothing Adjustment Factor (CAF) is 3.
Clothing Worn CAF
Work clothes (long sleeves and pants). Examples: Standard cotton shirt/pants. 0
Coveralls (w/only underwear underneath). Examples: Cotton or light polyester material. 0
Double-layer woven clothing. 3
SMS Polypropylene Coveralls 0.5
Polyolefin coveralls. Examples: Micro-porous fabric (e.g., TyvekTM). 1
Limited-use vapor-barrier coveralls. Examples: Encapsulating suits, whole-body chemical protective suites, firefighter turn-
out gear.
11
WBGTeff = 25.5°C + 3
WBGTeff = 28.5°C
Step 3: Determine the metabolic work rate
Lawn care falls under "Heavy work" on Table 3, as it requires
intensive, repetitive work and heavy material/equipment
handling.
Using Table 3, Metabolic Rate = 415 Watts
6. Work Category Metabolic Rate (Watts) Examples
Rest 115 Sitting
Light 180 Sitting, standing, light arm/hand work and
occasional walking
Moderate 300 Normal walking, moderate lifting
Heavy 415 Heavy material handling, walking at a fast pace
Very Heavy 520 Pick and shovel work
Step 4: Determine if exposure was above the Threshold Limit Values
Using Table 3, metabolic rate at 415 and 28.5°C WBGTeff in Figure 4, the TLV (27°C) was
exceeded indicating that the worker was exposed to excessive heat stress at the time of
death. . The worker’s core temperature at death was 42°C
7. % Work Workload
Light Moderate Heavy* Very Heavy*
75 to 100%
(Continuous)
31.0°C 28.0°C N/A N/A
50 to 75% 31.0°C 29.0°C 27.5°C N/A
25 to 50% 32.0°C 30.0°C 29.0°C 28.0°C
0 to 25% 32.5°C 31.5°C 30.5°C 30.0°C
8. What could have prevented his death
Perform hot jobs in the cooler part of the day or cooler season of the year.
• Increase water intake.
• Distribute heart rate wristwatches to at-risk individuals to allow them to
monitor their heart rate throughout the day.
• Schedule hot operations to minimize the number of exposed
Finish the hot work in early part of the day ,or during night time
Workers must be given awareness on heat and related disorders.
Provide lime juice or ORS for people working in hot conditions.
9. P4SR
This works best if converted into kilograms (kg) and milliliters (mL)
• A. Body Weight pre-exercise ___________________ [lb/2.2 = kg]
• B. Body Weight post-exercise ___________________ [lb/2.2 = kg]
• C. Change in Body Weight ___________________ grams [kg x 1000
= g] (A-B)
• D. Volume of fluid consumed ___________________ mL [oz x 30 =
mL]
• E. Sweat Loss ___________________ mL [oz x 30 = mL] (C + D)
• F. Exercise time ___________________ [min or hr] G. Sweat Rate
___________________ [mL/min or mL/hr]
• G. Sweat Rate ___________________ [mL/min or mL/hr]
