Working in Cold Temperatures

The Issue

As we approach the first day of winter in the N. hemisphere, it is important to remember that workers are more likely to be exposed to cold and wet conditions in the winter months.  A cold environment challenges workers by: 

• Air temperature; 
• Air movement (wind speed); and 
• Humidity (wetness). 

In order to work safely, these challenges have to be countered with proper clothing, physical activity levels and by controlling exposure to cold. Our bodies work best when we maintain a core temperature of 37°C.  This temperature is necessary for our vital organs to function normally.  By sweating, shivering, and changing the rate of blood flow, the body can adapt to a wide range of temperatures. Nevertheless, there are limits to what the body can adapt to and its ability to maintain its core temperature can fail.

Context – Harmful Cold Exposure at Work 

Many workers are potentially exposed to harmful cold at work. Municipal work, electric power distribution, construction, oil and gas extraction, trucking and delivery, law enforcement, mining, fishing and logging are some examples of jobs which may expose workers to cold stress.

Health problems that can result from cold exposure:

• Frostnip: Is the mildest form of a freezing cold injury. It occurs when ear lobes, noses, cheeks, fingers, or toes are exposed to the cold and the top layers of the skin freeze. The skin of the affected area turns white and it may feel numb. The top layer of skin sometimes peels off the affected area.
• Frostbite: Is caused by exposure to extreme cold or contact with extremely cold objects or materials (cooled and compressed gases).  Frostbite occurs when tissues fall below freezing or when blood flow is obstructed under cold conditions. Frostbitten skin is very susceptible to infection and gangrene.
• Hypothermia: If the body continues to cool without recovery or warming periods the core temperature drops.  Hypothermia results when the core temperature drops below 33°C.  Shivering stops and affected persons may experience muscular weakness, an inability to think clearly and drowsiness.  At a core temperature of 27°C coma sets in.  It is important to remember that hypothermia can result at temperatures of 10°C or more in wet conditions. Body heat is lost at a rate 25 times higher in water than in air.  In the United States 1,500 people die from hypothermia every year. 

Factors Affecting Cold Adaptation

Factors which will negatively affect how well you adapt to cold conditions include:

• Poor general health, being overweight
• Older than 45 years of age
• Medical conditions such as Raynaud’s disease, chronic skin conditions
• Use of alcohol, anti-depressants, and many illicit drugs

How Harmful Cold is Encountered at Work

The potential of exposure to harmful cold at work increases according to following combined factors:

Cold Air Temperature: Air temperature as measured by a thermometer in degrees Celsius (°C) or degrees Fahrenheit (°F).

Higher Wind Speeds: Wind speed can be obtained from weather reports, measured with an anemometer or estimated in the following manner:

• 8 km/h (5 mph): light flag moves,
• 16 km/h (10 mph): light flag fully extended,
• 24 km/h (15 mph): raises newspaper sheet,
• 32 km/h (20 mph): causes blowing dust and drifting snow.

In calm conditions our body is insulated by a thin layer of warm air which is stripped away by the wind.  Wind chill is a measure of increased heat loss as a combination of temperature and wind speed, expressed as an equivalent temperature.  Wind chill warnings are issued by the weather service and often cite how long it will take for frostbite to occur on exposed skin.

Higher Humidity (Wetness): Cold air with high humidity conducts heat more quickly to the surrounding air.  Being wet in cool conditions results in high rates of heat loss.

Low Physical Activity: Body heat is produced by physical activity (metabolic rate). Metabolic heat production is measured in kilo-calories (kcal) per hour. 

Longer Exposures: Cold stress increases with increased exposure.

Less Protective Clothing: Properly designed clothing insulates the body reducing heat loss.  Wet clothing may make you colder due to accelerated heat loss.

Controlling the Hazards

A hazard assessment should be performed for routine cold work job positions.  The risks can be assessed using the factors cited above to develop a standard set of response procedures and control measures.  Control measures must be instituted as a function of the conditions which are likely to be encountered or if conditions change (worsen).

Engineering Controls

• Enclosures, shelters, shields and heating systems
• Heat sources for extremities and exposed skin (contact heating pads, radiant heaters)

Administrative Controls

• Establish a warm-up schedule according to the cold conditions.  The American Conference of Governmental Industrial Hygienists (ACGIH) has adopted guidelines developed by Saskatchewan Labour for working outdoors in cold weather conditions. The recommended exposure times are based on the wind chill factor and assume workers are wearing dry clothing. This can be used as a guideline to control worker exposure.
• Review medical conditions which might affect a worker’s reaction to cold.
• Institute a monitoring system for hypothermia and frostbite when working in cold conditions.

PPE

• Wear layered clothing designed for wind, rain and cold weather protection according to the results of your hazard assessment and the weather conditions.
• Protect your head and extremities
• Wear appropriate footwear 

Best Practices and Training

If workers may routinely be exposed to cold temperatures or hypothermia risks you should develop a Cold Stress policy which requires:

• High risk jobs or activities to be identified through hazard and risk assessments
• Job specific safe work procedures to be developed which include recommendations for specific working conditions according to published guidelines
• Training for workers and supervisors on the risks of cold stress, the warning signs of frostbite and hypothermia and the control methods to be used.
• Treats clothing as PPE and enforces cold weather clothing standards.

Control cold exposure hazards and give winter the “cold shoulder”!