December, 2000

Ensuring Employee Safety in Cold-Weather Working Environments
By Peter P. Greaney, MD
Board-Certified Occupational Physician
President, WorkCare
It’s a cold, blistery day and you are on a job site outdoors. Suddenly, you spot a worker who walks clumsily toward you. His speech is slurred and he is trying to tell you something about the job site, but he is not making any sense. He seems disoriented and he is shivering uncontrollably. Your first thought is that the worker is under the influence of drugs or alcohol. Is this a correct assumption? Is this your final answer?
The worker in this hypothetical situation is suffering from hypothermia—a medical emergency with a high fatality rate.
About 700 deaths a year are attributed to hypothermia, which results when the body’s internal temperature drops below 95°F.
Employees--especially those working in construction, commercial fishing and agriculture--should be aware of the physical hazards caused by cold working environments. Employees should also be familiar with treatment methods for cold-related disorders and understand how to protect against cold-weather hazards.
Recognizing Cold As A Potential Hazard
There are four factors that contribute to cold stress: cold temperature, high or cold wind, dampness and cold water. These factors, alone or in combination, draw heat away from the body. The wind chill factor can intensify the effects of cold stress. Wind chill is a combination of temperature and velocity and is a crucial factor to determine the risk of cold injury. For instance, if the actual air temperature of the wind is 400F and its velocity is 35 mph, this combination causes a still-air temperature effect of 110F for exposed skin.
Click here to access OSHA's Adobe Acrobat File on Wind Chill.
The Effects of Cold Stress
When body temperature drops, even a few degrees below its normal temperature of 98.60F, the body uses its defense mechanisms to help maintain its core temperature. Continuous exposure to cold will cause a person to shiver, which generates heat by speeding up the body’s metabolic rate. The body will also begin to shift blood flow away from the extremities (hands, feet, arms and legs) and outer skin to the core (chest and abdomen). This allows exposed skin and extremities to cool rapidly and increases the risk of frostbite and hypothermia. Combine this with cold water and trench foot may occur. Following is a description of cold-related injuries/illnesses, as well as symptoms and treatments.
Hypothermia
Hypothermia results when the body is unable to produce enough heat to replace the heat lost to the environment. It may occur at air temperatures up to 650F or at water temperatures up to 720F. Symptoms normally begin when the body temperature drops below 950F. The first symptoms are shivering and foot stomping, which helps generate heat. With continued exposure to frigid weather conditions, hypothermia becomes more severe. The individual falls into a state of dazed consciousness, failing to complete even simple motor functions. The victim's speech becomes slurred and his or her behavior may become irrational. When the body temperature is between 770F and 900F, shivering is diminished and the individual may be unable to walk or stand. Below 770F, there is failure of all heat regulatory and heat conservation mechanisms. The person becomes very sleepy or unconscious and death may occur at this stage.
Only conscious individuals with mild hypothermia (above 900F) should be rewarmed in the workplace. Their core temperature should be determined, and they should be insulated to prevent additional body heat loss. Use sleeping bags, blankets or a radiant heat source to rewarm them. Individuals with mild hypothermia should also be encouraged to stay active (walk around) to generate body heat. Warm, decaffeinated, non –alcoholic drinks should be provided to rewarm the body and replace lost fluids.
Severely hypothermic individuals (below 900F) and unconscious victims of hypothermia are in a life-threatening situation and should be transported to a medical facility for immediate treatment. They should be handled carefully and all extremities should be completely covered. Attempts to rewarm these hypothermia victims in the workplace should be avoided.
Frostnip and Frostbite
Frostbite is an irreversible condition in which the skin freezes, causing ice crystals to form between cells. The capillary walls of the frostbitten area are damaged, increasing cell wall permeability. Fluid is released into the tissues and is accompanied by local inflammation. The toes, fingers, nose, ears, and cheeks, are the most common sites of freezing cold injury.
Frostnip is a mild, reversible freezing of the top layers of skin tissue.
Frostbite can be superficial or deep. If there is superficial frostbite, the individual experiences a loss of sensation and the skin turns gray-white. Deep frostbite affects the skin and the subcutaneous tissues, as well as the muscle and bone. Deep frostbite will cause numbness. The affected area will be cold, hard and white. Frostnip and mild frostbite can be treated at the workplace by placing the injured body part (hands, fingers) in the armpits or groin. If there is absolutely no possibility of the tissue refreezing, the frozen tissue may be rewarmed and insulated until medical attention is received. Caution must be used to avoid applying excessive heat to rewarm frozen tissue, since this may produce a devastating secondary burn injury.
Trench/Immersion Foot
Trench/immersion foot is caused by continuous exposure to cold water. It may occur in wet, cold environments or through actual immersion in water. This injury generally occurs with commercial fisherman or workers who are immersed in cold water. Minor trench/immersion foot occurs after 3-12 hours of exposure. Severe exposure, which which lasts from 12 hours to 3 days, causes significant tissue damage.
The symptoms include a tingling and/or itching sensation, with redness, swelling and blistering in some cases. Avoidance of trench/immersion foot is important because treatment—moving the individual to a warm dry area and using rewarming techniques—is only minimally effective.
Risk Factors
Individuals who work in a cold environment are at greatest risk for cold-induced injuries/illnesses. T he United States Occupational Safety and Health Administration has listed the following as major risk factors for cold-related stresses:
- Wearing inadequate or wet clothing increases the effects of cold on the body
- Taking certain drugs or medications such as alcohol, nicotine, caffeine, and medication that inhibits the body's response to the cold or impairs judgment
- Having a cold or certain diseases, such as diabetes, heart, vascular, and thyroid problems, may make a person more susceptible to the winter elements.
- Being a male increases a person's risk to cold-related stresses. Men experience far greater death rates due to cold exposure than women, perhaps due to inherent risk-taking activities, body-fat composition or other physiological differences.
- Becoming exhausted or immobilized, especially due to injury or entrapment, may speed up the effects of cold weather.
- Aging -- the elderly are more vulnerable to the effects of harsh winter weather.
Work Precautions
Employers with cold work environments should use the following guidelines as a defense against cold-induced injuries/illnesses.
Workplace Controls
A wind chill calculator (see link below) may be used to determine still-air temperature. In outdoor work situations, wind speed should be measured and recorded, together with air temperature, whenever the air temperature is below 30.20F. The equivalent chill temperature should be recorded with these data whenever the equivalent chill temperature is 19.40F.
- Use heat sources, such as air jets, radiant heaters and contact warm plates, which provide effective spot heating.
- Warming shelters, such as heated tents, cabins and break rooms should be provided to employees who experience prolonged exposure to equivalent wind-chill temperatures of 200F or less.
- Provide wind shields to reduce drafts or windy conditions
- When the temperature falls below 300F, use thermal insulating material on equipment handles.
Employee Guidelines
Employees should wear personal protective clothing to prevent cold-related disorders. This is the most significant precaution an employee can take to reduce cold stress. Wearing appropriate clothes for cold weather requires using three layers of clothing.
The inner layer of clothing should be made of materials, such as polypropylene, that draws moisture (perspiration) to the outside. The middle layers should be made of material like wool or Thinsulate that provides insulation without adding significant weight. The outer layer of clothing is used for wind and water protection and should be water repellent. These fabrics, such as Gore-Tex, are breathable, allowing body heat to be released and providing easy evaporation of moisture.
Use this system of layering to also protect the head, hands and feet. Gloves should be worn to prevent injury while not hindering dexterity. Glove liners, gloves and mittens can be layered for maximum protection. If manual dexterity is required, the outer glove and mitten may be removed as needed. The head should also be protected, as 30 percent of body heat is lost through the head. Hats, hoods and facemasks will help prevent frostbite and conserve heat loss.
Employees should ensure that a complete change of clothing is available in case clothes get wet or there is excessive sweating.
A person’s thirst is suppressed in a cold environment and dehydration may occur when fluid intake is reduced. Since the body requires a large amount of fluids in cold weather, employees are encouraged to drink plenty of fluids, preferably warm, sweet beverages. Alcohol and caffeine drinks should be avoided.
Workers in cold environments who wear heavy, protective clothing expend more heat than those working in moderate climates. As a result, these workers require 10-15 percent more calories. Employees should ensure that caloric intake is higher when working in cold, outdoor environments.
Cold-Weather Working Precautions
- Provisions should be made to allow new employees to adjust to cold weather working conditions.
- Employees should be educated on proper re-warming techniques, first-aid treatment, appropriate clothing practices, eating and drinking requirements and recognition of cold-related injuries/illnesses.
- Employees should work in a buddy system when temperatures are at or below 10.40F. as a protective observation measure.
- The workload should not be so intense that it causes heavy sweating.
- When possible, employers should schedule work during the warmest hours of the day and allow employees to set their own work pace and take breaks as needed.
- Eye protection should be provided to employees who may be exposed to blowing snow and ice crystals.
Protect Yourself Against A Silent, Deadly Work Hazard
The above precautions will enable employers and employees to protect themselves against cold stress ailments. Keep in mind that injuries due to cold stress often creep up on a person. The symptoms are insidious and often go undetected until a worker’s health is endangered. By understanding cold stress protective measures and recognizing cold-induced injuries/illnesses, you can enjoy the winter season in a safe and healthful way.
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References:
Physical and Biological Hazards of the Workplace, Peter H. Wald M.D. and Greg M. Stave, M.D.
Reference Links:
http://www.osha-slc.gov/OshDoc/Fact_data/FSNO98-55.html
http://www.princeton.edu/~ehs/coldstress.htm