People who work outdoors or in cold indoor environments such as walk-in freezers are frequently subject to cold, wet working conditions. Working in wet or cold environments can take a heavy toll on workers’ bodies and be hazardous to their health. It’s important for workers and supervisors to recognize signs of cold stress, factors that can contribute to cold stress, and how they can protect themselves from cold stress.
Cold Stress Factors
A healthy human body regulates its core temperature to approximately 98.6 °F (37 °C). When we eat, move or perform other physical activity, our bodies generate heat. Most of our body heat dissipates through the skin (with the help of sweat when it’s hot or we’re engaging in strenuous physical activity) and through the lungs as we breathe. When it’s cold outside, our bodies minimize heat loss by constricting blood vessels close to the skin’s surface and in our arms and legs. This helps protect internal organs in the head and torso, but reduced blood flow to the skin, arms and legs causes them to get cold faster, increasing the risk of frostbite in those areas. The risk of hypothermia is also increased, because while the body is trying to retain as much heat in its core as possible, it is still being lost more quickly than it can be replaced.
Cold stress can happen even when temperatures are above freezing. Wind and moisture can make the skin colder and conduct heat out of the body. Sweat from heavy exertion can also saturate underclothes and conduct heat out of the body, even if workers are dressed for cold conditions. Illnesses and medical conditions can affect the body’s ability to retain heat. Workers who have conditions that can reduce blood flow, such as diabetes or thyroid problems, should consult a doctor before working in cold environments.
Cold Stress Symptoms and Illnesses
- Frostnip and frostbite: If body parts are left exposed to the cold long enough to freeze the skin, frostnip can occur. Frostnip occurs when blood vessels constrict and reduce blood flow to the point where the skin’s outer layers become dehydrated and freeze. Untreated frostnip can turn into frostbite if the skin’s inner layers and tissues begin to freeze. Frostbitten skin feels cold or hard to the touch. Move any frostbite victims to a warm area and call 911 immediately. To help treat frostnip and protect frostbite victims until emergency responders arrive:
- Wrap the affected area in a warm, dry cloth
- Do not break blisters or rub frostbitten skin
- If instructed to by emergency responders, soak frostbitten skin in warm (not hot) water
- Don’t warm the skin if there’s a chance it could refreeze and cause more tissue damage
- Hypothermia: Hypothermia is a life-threatening condition that happens when body heat is lost faster than it can be replaced. Mild hypothermia can begin to set in when the body’s core temperature drops below 95 °F. Symptoms of mild hypothermia can include shivering, loss of coordination and motor skills in the hands, slurred speech, and pale, cold skin. You should seek medical attention for hypothermia, but you can help treat mild hypothermia by:
- Moving the victim to a warm area (indoors if possible)
- Replacing wet clothes and covering uncovered skin or extremities
- Keeping the victim active and moving as much as possible
- Giving the victim a warm, sweetened drink
- Providing heat packs or warm water bottles for the head, neck, chest and groin
If the victim’s body temperature continues dropping, the victim may become confused or impaired, breathing and heart rate will slow, and shivering will slow down and eventually stop. Breathing may become shallow or stop, and the victim will likely lose consciousness. Severe hypothermia is an emergency and must be treated in a hospital setting. Call 911 immediately and ask for instructions to keep the victim alive until emergency responders arrive.
- Trench foot: Trench foot can occur when feet stay damp inside tight shoes or boots, or when feet stay immersed in cold water. Trench foot can occur outdoors in wet weather, but it can also occur in wet indoor environments such as refrigerators or butcher shops. Trench foot symptoms can range from tingling, burning and swelling, to blisters and even infection. If left untreated, the affected foot can contract gangrene and may require amputation. To treat trench foot:
- Move the victim to a warm, dry area and remove footware and socks
- Keep feet elevated and avoid walking if possible
- Get medical attention ASAP
Preventing Cold Stress
In order to help workers stay safe in the cold, employers can implement controls and policies designed to protect them from cold stress injuries. Some engineering controls can include:
- Installing insulated covers on metal equipment handles
- Providing radiant heaters for workers to use during work
- Using heavy machinery, vehicles or other barriers to give workers cover from wind and weather
- Your workplace can also establish policies to protect your workers from extreme cold:
- Scheduling outdoor work during the warmest parts of the day
- Providing heated, sheltered break areas
- Using the buddy system to watch for signs of cold stress
- Acclimating new or returning workers to the cold before beginning their full job duties
All workers exposed to cold conditions should dress in multiple layers of loose clothing, which can include:
- Warm socks and long undergarments
- Heavy shirt and long pants
- Insulated, waterproof coat
- Weather-proof gloves
- Ear and face protection (ear muffs, balaclava, ski mask, etc.)
Finally, there are some good general practices that anyone working in the cold should take:
- Get plenty of rest before and after work, including a full night of sleep
- Eat healthy, high-calorie and high-carb foods such as pasta, and drink warm, sweet beverages
- Stay active while working and keep moving to generate heat
- Avoid alcohol, nicotine and other drugs, and limit caffeine intake
- Ask your doctor if any medications you take can affect your body’s ability to retain heat
Working in cold conditions can be challenging, especially when workers aren’t acclimated to the cold. When workers are properly trained over the conditions they’ll face and the precautions they’ll need to protect themselves, they’ll be able to work safely and more effectively in freezing conditions.
The Occupational Safety and Health Administration (OSHA) and the National Institute of Occupational Safety and Health (NIOSH) provide free information and materials designed to help employers and workers stay safe in cold conditions. SafetySkills also offers training for employees over cold stress symptoms, hazards and controls.