Transcript Thermoregulation and Heat Injury A/Prof Lim Chin Leong

Heat Injury Prevention
MOM WSH Guidelines 2010
A/Prof Lim Chin Leong Fabian
BSc(PE), MSc(PE), MBA, PhD,
Heat Intolerance
Incidence of Heat Stroke in Construction Industry
April 2007
• One construction worker died
Jan to May 2009 (6 cases of heat stroke)
• One construction worker had permanent brain damage
• Two construction workers died
• 3 construction workers recovered
Common factors
• Males
• 31 to 49 yrs
• Construction workers
• Working under hot sun
• Collapsed in the afternoon at about 1 to 3pm
• All were from countries with colder climates
• All except one occurred from day 1 to day 4 of starting work
K.
4 Choy, Ministry of Manpower, Singapore
Types of Heat Injury
Heat cramps
• Muscle cramps while working in the heat
• Not life threatening
Heat Syncope
• Collapsed while standing still in the heat
• Usually not life threatening
Heat Exhaustion
• Hyperthermia (> 40 oC)
• Drowsy, headache and nausea
• Collapsed
Heat stroke
• Hyperthermia, mental disorientation
• Collapsed
• Loses brain functions (e.g., bladder / bowels)
• Brain damage, coma, death
Heat Injury Prevention Measures
WSH Guidelines 2010
Monitor Environmental
heat stress
• Risk awareness
Shades
• Rest and recover
Education / Training
• Take responsibility
Fitness to work
• Medical examination
• On-site observation
Heat acclimatisation
• Physical conditioning
• Heat tolerance
Reporting
• Risk management
Water intake
• Lower heat stress
• Preserve body functions
Work Schedule
• Rest and recover
Clothing
• Lower heat stress
Environmental Conditions
• Rh 60% - 75% in the noon time (32 oC – 35 oC)
• Beware of environmental heat and high
relative humidity
Environmental heat
• Rh 80% - 95% in the night and early morning
(26 oC – 30 oC).
• Beware of high relative humidity
Sweat
production
Body
produces
heat
during
exertion
Sweat evaporation
(80% of heat loss)
Dry air
Heat
dissipation
Moist air
Low humidity
High humidity
Sweat evaporates
Sweat drips off
Heat is removed
from the body
Heat is trapped
in the body
Heat Acclimatisation
• Enhances the ability of the
body to dissipate heat
• Daily heat exposure to heat
stress over 10 – 14 days
• Gradual increase in heat
exposure and duration of
work
• Newly arrived workers and
return to duty
• Extended period of absence
Example of acclimatization schedule
Hours worked under the
sun
• Conditioning the body to
work in the heat
9
8
7
6
5
4
3
2
1
0
11am to 3pm*
8am to 11am; 3pm to
5pm
Day 1 Day 2 Day 3 Day 4 Day 5 Day 6 Day 7
Day of work
Water Intake during Physical Exertion
• Regular water intake helps to:
– Maintain blood circulation
– Control body temperature
• Different requirements
between individuals
For the Employer
• Make drinking water freely
available to workers
• Provide opportunity to
refilled water bottle and to
drink
• About 0.5L/h – 1L/h
• Drink enough water to:
– Quench thirst
– Maintain clear urine
• Ice water whenever practical
• Reinforce the importance
of water intake e.g.,
posters and signage
• Do not enforce a fixed
volume of water to drink
during water parades
Beware of Water Intoxication
Education
Environmental
heat stress
Shades
Reporting
Heat
acclimatisation
Water intake
Work schedule
Clothing
Fitness to work
Stay in Good State of Health
Adequate Rest
Adequate Sleep Good Nutrition
Foundation for Effective Heat Injury Prevention