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Cold Stress



Introduction (top)

Your mother was right. Remember when our parents insisted that we wear warm clothes and a hat when we play outside? The colder weather is here, and those of us that must work outside must be aware of the effects of cold stress, including hypothermia, trench foot and frostbite.

How cold is too cold? (top)

When most people think of hypothermia, they think of frigid temperatures or blizzard-like conditions. Actually, hypothermia occurs most often in the spring and fall, rather than winter.

Four factors contribute to cold stress: cold temperatures, high or cold wind, dampness and cold water. A cold environment forces the body to work harder to maintain it's temperature. Cold air, water, and snow all draw heat from the body. Wind chill is the combination of air temperature and wind speed. For example, when the air temperature is 40°F, and the wind speed is 35 mph, your exposed skin receives conditions equivalent to the air temperature being 11° F.

So, while it is obvious that below freezing conditions combined with inadequate clothing could bring about cold stress, it is important to understand that it can also be brought about by temperatures in the 50's coupled with some rain and wind.

How your body reacts to cold conditions (top)

When in a cold environment, most of your body's energy is used to keep your internal temperature warm. Over time, your body will begin to shift blood flow from your extremities (hands, feet, arms, and legs) and outer skin to the core (chest and abdomen). This allows exposed skin and the extremities to cool rapidly and increases the risk of frostbite and hypothermia. Combine this with cold water, and trench foot may also be a problem.


Hypothermia means "low heat" and is a potentially serious health condition. This occurs when body heat is lost from being in a cold environment faster than it can be replaced. When the body temperature drops below the normal 98.6° F to around 95° F, the onset of symptoms normally begins. The person begins to shiver and stomp feet in order to generate heat. As the body temperature continues to fall, slurred speech, lack of coordination and memory loss develop and the person will stop shivering. Once the body temperature falls to around 85° F, the person may become unconscious, and at 78°, the person could die.

Who is at risk:

Anyone working in a cold environment may be at risk for cold stress. However, older people may be at more risk than younger adults, since older people are not able to generate heat as quickly.

Certain medications may prevent the body from generating heat normally. These include anti-depressants, sedatives, tranquilizers and some heart medications.

Signs and symptoms:

  • Mild hypothermia (98 - 90° F)
    • Shivering
    • Lack of coordination, stumbling, fumbling hands
    • Slurred speech
    • Memory loss
    • Pale, cold skin
  • Moderate hypothermia (90 - 86° F)
    • Shivering stops
    • Unable to walk or stand
    • Confused and irrational
  • Severe hypothermia (86 - 78° F)
    • Severe muscle stiffness
    • Very sleepy or unconscious
    • Ice cold skin
    • Death

What to do:

(Proper treatment depends on the severity of the hypothermia.)

  • Mild hypothermia
    • move to warm area
    • stay active
    • remove wet clothes and replace with dry clothes or blankets, cover the head
    • drink warm (not hot) sugary drink
  • Moderate hypothermia
    All of the above, plus:
    • Call 911 for an ambulance
    • Cover all extremities completely
    • Place very warm objects, such as hot packs or water bottles on the victim's head, neck, chest and groin
  • Severe hypothermia
    • Call 911 for an ambulance
    • Treat the victim very gently.
    • Do not attempt to re-warm -- the victim should receive treatment in a hospital


Frostbite occurs when the skin actually freezes and loses water. In severe cases, amputation of the frostbitten area may be required. While frostbite usually occurs when the temperatures are 30° F or lower, wind chill factors can allow frostbite to occur in above freezing temperatures. Frostbite typically affects the extremities, particularly the feet and hands.

Signs and symptoms

  • Cold, tingling, stinging or aching feeling in the frostbitten area, followed by numbness
  • Skin color turns red, then purple, then white or very pale skin, cold to the touch
  • Blisters in severe cases

What to do:

  • Call Public Safety at 911
  • Do not rub the area
  • Wrap in soft cloth
  • If help is delayed, immerse in warm, not hot, water

Trench Foot

Trench foot or immersion foot is caused by having feet immersed in cold water for long periods of time. It is similar to frostbite, but considered less severe.

Signs and symptoms:

  • Tingling, itching or burning sensation
  • Blisters
What to do:
  • Soak feet in warm water, then wrap with dry cloth bandages
  • Drink a warm, sugary drink

Preventing Cold Stress (top)

Planning for work in cold weather is the most important defense. Wearing appropriate clothing and being aware of how your body is reacting to the cold are important to preventing cold stress. Avoiding alcohol, certain medications and smoking can also help to minimize the risk.

Protective Clothing

Wearing the right clothing is the most important way to avoid cold stress. The type of fabric also makes a difference. Cotton loses its insulation value when it becomes wet. Wool, on the other hand, retains its insulation even when wet. The following are recommendations for working in cold environments:

  • Wear at least three layers of clothing:
    • An outer layer to break the wind and allow some ventilation (like Gortex® or nylon)
    • A middle layer of down or wool to absorb sweat and provide insulation even when wet
    • An inner layer of cotton or synthetic weave to allow ventilation
  • Wear a hat. Up to 40% of body heat can be lost when the head is left exposed.
  • Wear insulated boots or other footwear.
  • Keep a change of dry clothing available in case work clothes become wet.
  • Do not wear tight clothing. Loose clothing allows better ventilation.

Work Practices

  • Drinking: Drink plenty of liquids, avoiding caffeine and alcohol. It is easy to become dehydrated in cold weather.
  • Work Schedule: If possible, heavy work should be scheduled during the warmer parts of the day. Take breaks out of the cold.
  • Buddy System: Try to work in pairs to keep an eye on each other and watch for signs of cold stress

Engineering Controls

Some engineering controls are available to reduce the risk of cold stress:

  • Radiant heaters may be used to warm workers
  • Shield work areas from drafts or wind
  • Use insulating material on equipment handles when temperatures drop below 30° F.


Employees and supervisors need to be trained to be able to detect early signs of cold stress.

Supervisors should watch for signs of cold stress and allow workers to interrupt their work if they are extremely uncomfortable. Supervisors should also ensure that work schedules allow appropriate rest periods and ensure liquids are available. They should use appropriate engineering controls, personal protective equipment and work practices to reduce the risk of cold stress.

For more information (top)

Contact Environmental Health and Safety at 258-5294 or Employee Health at McCosh Health Center at 258-5068 for more information.

In an emergency, call Public Safety at 9-1-1.



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