Workers exposed to cold temperatures and wind chill are at risk of cold stress. Cold stress occurs when skin temperature drops, lowering internal body temperatures and disabling the body’s ability to warm itself. The body shifts blood flow away from the extremities (hands, feet, arms, and legs) to keep the internal core (chest and abdomen) temperature warm, resulting in serious, sometimes fatal, cold-related illnesses and injuries that may cause permanent tissue damage. According to the U.S. Bureau of Labor Statistics, from 2003 to 2019, exposure to environmental cold resulted in 31 worker deaths (~3 per year) and 2,770 serious injuries and illnesses (~163 per year).

Cold-related illnesses are preventable with education and the appropriate prevention measures. Factors that may increase cold stress risk include physical fitness, dressing improperly, wet clothing, and health conditions such as hypertension, hypothyroidism, and diabetes.

Health Risks of Cold Stress

Hypothermia

Occurs when body heat is lost faster than replaced and the normal body temperature (98.6 °F) drops to less than 95 °F. Hypothermia is most likely at freezing temperatures, but it can occur when at cool temperatures (above 40 °F) if a person becomes chilled from rain, sweat, or submersion in cold water. Note, cold water immersion hypothermia develops more quickly because water conducts heat away from the body 25-times faster than air.

Signs & Symptoms

First Aid

• Call 911 immediately in an emergency.
• To prevent further heat loss:
  • Move the worker to a warm place as quickly as possible.
  • Remove any wet clothing, replace with dry garments.
  • Cover the body (including the head and neck) with dry clothing, towels, or blankets and with something to block the cold (e.g., tarp, garbage bag). Do not cover the face.
  • Give warm, sweetened drinks if alert (no alcohol) to help increase the body temperature. Never try to give a drink to an unconscious person.
  • Apply heat packs to the armpits, sides of chest, neck, and groin. Ask 911 operator for additional rewarming instructions.
  • If the worker is not breathing or has no pulse, begin cardiopulmonary resuscitation (CPR).

Frostbite

An injury to the body caused by freezing of the skin and underlying tissues, leading to a loss of feeling and color in the affected areas. Frostbite typically affects the extremities, particularly the nose, ears, fingers, or toes. It can permanently damage body tissues, and severe cases can lead to amputation. The lower the temperature, the more quickly frostbite will occur. It can also occur at temperatures above freezing due to wind chill.

Signs & Symptoms

First Aid

• Call 911 immediately in an emergency.
• Move the worker to a warm place as quickly as possible.
• Unless necessary, do not walk on frostbitten feet.
• Immerse affected area in warm (not hot) water or warm the affected area using body heat.
• Do not use a heating pad, heat lamp, stove, fireplace, or radiator for warming. Affected areas are numb and can be easily burned.
• Do not rub or massage the frostbitten area; doing so may cause more damage.
• Loosely cover and protect the area from contact.

Trench (Immersion) Foot

A non-freezing injury to the foot caused by prolonged exposure to a wet and cold environment. It can occur at temperatures as high as 60 °F if feet are constantly wet. Injury occurs because wet feet lose heat 25-times faster than dry feet. The body constricts the blood vessels to shut down circulation in the feet to prevent heat loss. The skin tissue begins to die because of a lack of oxygen and nutrients and the buildup of toxic products.

Signs & Symptoms

First Aid

• Seek medical assistance as soon as possible.
• Remove shoes/boots and wet socks.
• Air dry feet in a warm environment.
• Keep affected feet elevated and avoid walking, as this may cause tissue damage.

Chilblains

Chilblains are caused by the repeated exposure of skin to cold but not freezing air temperatures, resulting in damage to the capillary beds (groups of small blood vessels) in the skin. This damage is permanent, and the redness and itching will return with additional exposure, typically occurring on the cheeks, ears, fingers, and toes.

Signs & Symptoms

First Aid

• Avoid scratching.
• Slowly warm the skin.
• Use corticosteroid cream to relieve itching and swelling.
• Keep blisters and ulcers clean and covered.

Cold Stress Prevention

Engineering controls

• Shield work areas from drafts or winds to reduce wind chill.
• Use radiant heaters in outdoor work areas, if possible.

Administrative controls

• Pack extra clothing in case you get wet and need to change.
• Schedule heavy work during the warmer part of the day.
• Work in pairs to monitor each other for signs of cold stress.
• Take frequent breaks in warmer, protected areas.
• Drink warm, sweetened fluids (no alcohol). Sweetened drinks produce a quick release of sugar into the bloodstream that results in increased heat and energy.
• Acclimatize workers by gradually increasing their workload, as they build up a tolerance for working in a cold environment.
• When performing stationary tasks, move around occasionally to generate heat.
• Pack instant heat packs in your first aid kit.

Personal protective equipment (PPE)

• Wear layers of loose-fitting, insulating clothing. Do not wear cotton; it loses its insulation value when wet.
  • Inner layer should be wool, silk, or synthetic to keep moisture away from the body.
  • Middle layer should be wool or synthetic to provide insulation even when wet.
  • Outer layer should be wind and water-resistant.
• Wear a hat or hood to reduce the amount of body heat that escapes from your head.
• Use insulated, waterproof gloves to protect the hands.
• Wear insulated and waterproof footwear.
• Use a knit mask to cover the face and mouth.

Resources

1. CDC: https://www.cdc.gov/niosh/topics/coldstress/default.html
2. CDC-NIOSH Protecting Yourself from Cold Stress: https://www.cdc.gov/niosh/docs/2010-115/pdfs/2010-115.pdf
3. Mayo Clinic – Chilblains: https://www.mayoclinic.org/diseases-conditions/chilblains/symptoms-causes/syc-20351097
4. OSHA Protecting Workers from Cold Stress Quick Card: https://www.osha.gov/Publications/OSHA3156.pdf
5. U.S. Bureau of Labor Statistics
   1. Census of Fatal Occupational Injuries: https://www.bls.gov/iif/oshcfoi1.htm
   2. Work-related Injuries and Illnesses Involving Days Away from Work: https://www.bls.gov/iif/oshcdnew.htm