Transcript THERMAL STRESS - Indiana University of Pennsylvania

THERMAL STRESS
…..A DISCUSSION OF THE
HEALTH HAZARDS
ASSOCIATED WITH
TEMPERATURE/HUMIDITY EXTREMES
Overview
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Sources of heat
– High air
temperatures
– Radiant heat sources
– High humidity
– Direct physical
contact with hot
objects
– Strenuous physical
activities
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Sources of cold
– Low air temperatures
– Wet and windy
environments
– Direct physical
contact with cold
objects
Industries
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Iron and steel foundries
Brick-firing plant
Ceramic plants
Glass products facilities
Rubber products
factories
Electrical utilities
Bakeries
Commercial kitchens
Laundries
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Food canneries
Chemical plants
Mining sites*
Smelters
Steam tunnels
Construction sites*
Asbestos removal
Hazardous waste site
activities*
* cold or heat exposure
Key Definitions
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Heat – a measure of energy
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Metabolism - the system of chemical activities by which a living thing gets
power (energy) from other things, such as food
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Conduction- the transfer of heat between materials that contact each other
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Convection- the transfer of heat in a moving fluid
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Radiation - the transfer of heat energy through space
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Evaporative cooling- takes place when sweat evaporates from the skin
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Hypothermia – systematic effect of cold stress; reduced body temperature
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Hyperthermia – systematic effect of heat stress; increase in core body
temperature
Causal Factors
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Primary:
– Environment/climatic
conditions
– Clothing
– Work Demands
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Secondary
– Age
– Weight
– Degree of physical
fitness
– Degree of acclimatization
– Use of alcohol or drugs
– Medical conditions
– Prior heat/cold injuries
Responses of Humans to Heat
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Increased flow of
blood
Sweating
Illnesses/disorders
Acclimatization to
heat
Susceptibility to
diseases
Signs and Symptoms
Heat Stress
 Markedly raised temperature of about 40°C (104°F) or more.
 Headache, nausea, vomiting; loss of appetite
 Fast heart rate (tachycardia); fast breathing
 Red skin; skin may feel hot to touch
 Profuse sweating which eventually leads to an absence of sweating
 Chills and shivering is possible
 Confusion; dizziness; fainting; convulsions; coma/unconsciousness
 Temporary Blindness is possible
Cold Stress
 Dry, cold skin
 Shivering, but only during the early stages
 Slow pulse; slow breathing
 Drowsiness, which can lapse into coma.
Metabolic Expenditures
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sleeping
desk work
light machine work
moderate
assembly work
lifting, manual
handling
pick & shovel work
Activities Within Metabolic Rate
Categories
Category
Example Activities
Resting
Sitting quietly; sitting with moderate arm movements
Light
Sitting with moderate arm and leg movements; standing
with light work at machine; using table saw, some walking
about
Moderate
Scrubbing in a standing position; walking with moderate
lifting or pushing or carrying 3 kg load
Heavy
Sawing by hand; shoveling dry sand; heavy assembly work
on a non-continuous basis; intermittent heavy lifting with
pushing or pulling (pick-and-shovel work)
Very Heavy
Shoveling wet sand
Heat-Related Illnesses
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Heat stroke
Heat exhaustion
Heat cramps
Heat collapse
Heat rash
Heat fatigue
Standards…
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OSHA General Duty
Clause
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ACGIH –
100.4°F/96.8°F
Ways to reduce heat stress
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Engineering controls
– Ventilation
– Shielding
– Cooling fans, etc.
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Work practices
– Drinking plenty of water
– Training
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Move to cooler place
Reduce work pace or work load
Removing or loosening clothing
Acclimate
Ways to reduce cold stress
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Engineering controls
– Heating
– Shielding (from wind)
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Work practices
– Training
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Move to warmer place; avoid winds and wet
environments
Clothing
– Adequate insulating dry clothing
– Protect extremities
Summary of Identification
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Is the environment recognized as being
hot/cold, is protective clothing required, or are
work demands high (in a hot environment)?
Are worker behaviors indicative of attempts to
reduce heat or cold stress, is morale low or
absenteeism high, or are people making
mistakes or getting hurt?
Do medical records show a pattern of the
symptoms of exposure?
Are body temperatures (or in the case of heat
stress- heart rate or sweat losses high) on a
sample of workers?