Understanding Wind Chill and Cold Stress Hazards

While physically taxing, freezing temperatures are also a serious hazard on the job. Cold stress has been called a “silent” killer as it often causes symptoms that quietly affect individuals, numbing them to the effects of worsening physical conditions, which may lead to frostbite, hypothermia, trench foot or death. Protect your workers by training them in recognition and prevention to reduce the risk of cold stress on the job.

Contributing Factors

Man is genetically engineered to adapt for many types of surroundings and environments. However, unlike adaption to warmer temperatures, human beings are quite limited in acclimating safely to the effects of cold weather.

While we can adjust for small variations in cooler temperature, cold environments force our bodies to work very hard to maintain a proper operating temperature. Eventually, given enough exposure to cold, the body becomes unable to warm itself and cold-related stress occurs. The most common cold-induced problems include hypothermia, frostbite, and trench foot.

There are four environmental factors that heighten the effects of cold stress on the body:

  1. Cold air temperatures
  2. High velocity air movement
  3. Dampness of the air
  4. Contact with cold water or surfaces

Combining any of these factors greatly increases the impact of cold on the body. As wind chill is the combination of air temperature and wind speed, it significantly affects the body’s heat loss, especially to exposed skin, often resulting in frostbite.

The National Weather Service Wind Chill Temperature Index identifies and charts the dangers of frostbite, based on the variables of temperature, wind speed and length of exposure. The index is formulated around the heat loss resultant from exposed skin.

The chart includes three shaded areas of frostbite danger. Each shaded area shows how long (30, 10 and 5 minutes) a person can be exposed before frostbite develops.

For example, a temperature of -15 degrees F and a wind speed of 30 mph will produce a wind chill temperature of -46 degrees F. Under these conditions, exposed skin can freeze in 10 minutes. Given the extreme temperatures in current weather patterns across the United States, one can see the dangers for workers. Image

Cold stress can also occur in other seasons or environments apart from wintery conditions. For example, damp weather combined with temperatures in the 50’s, can produce hypothermia. In fact, according to Princeton University, hypothermia occurs most frequently in the spring and fall when individuals are exposed to cooler wet conditions, not yet acclimated to the change in temperature and lacking adequate attire.

Other Risk Factors

While anyone working in cold conditions may be at risk, additional factors may also worsen the effects of chilly temperatures.

These factors include:

  • Medications including anti-depressants, sedatives, tranquilizers
  • Alcohol, caffeine and nicotine
  • Preexisting medical conditions such as diabetes, blood vessel disease, arthritis, infection, malnutrition.
  • Not being acclimated to the temperature difference.

In addition, older persons are not able to generate heat as well as younger individuals, which make seniors more prone to the effects of cold.

Preventive Measures

Like most hazards, the best method of protection is awareness and planning. Avoiding smoking, caffeine and alcohol prior to working in the cold reduce the risk.

Choosing the correct protective clothing and layering it appropriately is one of the most effective ways to avoid cold related stress. Select wool, synthetics or silk due to consistent insulating factors, as cotton loses heat retention qualities if it becomes wet.

Wear at least three layers of clothing. Start with an inner layer of wool, silk or synthetic material which wicks moisture away from the body. Choose a middle layer of synthetic or wool to insulate, followed by an outer layer that permits protection and ventilation to inhibit overheating. Other than the layer against your skin, keep the remaining layers loose.

The following are additional recommendations for working in cold environments:

•      Keep your head covered with a hat or a hood.

  • Schedule heavy work for the warmest parts of the day

•     Choose insulated boots or other insulated footwear.

•     Always have a dry change of clothing available (including gloves, socks and jacket).

•     Take frequent breaks from the cold

  • Work in pairs. Watch your partner for signs of cold stress, including shivering, slurred speech, lethargy, numb, red or pale cool skin, and loss of dexterity.
  • Stay hydrated. Drink water and hot (caffeine free) sugary drinks.
  • Consume warm high caloric content foods that cause the body to maintain energy and heat.
  • Use heat and foot warmers which can be inserted into gloves or boots.

Employers should also train supervisors to spot signs of cold stress and allow workers to take breaks from the cold if needed. Where possible, the employer should provide shelters, radiant heaters or other methods to reduce cold stress hazards. First aid training inclusive of treatment for frostbite, hypothermia and trench foot is necessary for workers and supervisors.


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