Winter Woes

Be aware that certain workers are at increased risk for a cold injury.

IT was one of the coldest, snowiest Decembers that Scott Knowlen could remember. Even after 40 years enduring Maine's heavy snowfall and average winter temperatures of around 20 degrees, the then-site safety specialist was not prepared for the 90 inches of snow this month would bring.

Working within strict time constraints, Knowlen's crew found itself trying to pour a concrete slab for a client in very harsh conditions. After overcoming the obstacle of curing the concrete in the cold temperatures, Knowlen was soon knee-deep in snow and faced with a fall hazard created by slick walking surfaces. "At times we had to stop all work and put all hands on the job to clearing snow from the walkways and work areas," Knowlen said. "On a job where time is so critical, a move like this could have cost us a lot of money. But, in the end, it was probably profitable because we were making it easier and safer for everyone to do their work."

Slips and falls are not the only hazards winter weather conditions create for construction workers. Knowlen and his crew were working long hours in extreme cold with low visibility, prime conditions for cold injury and accidents.

Our minds may be dreaming of warmer spring weather, but we're not out of the cold yet.

How Cold is too Cold?
"There is no single, exact temperature that presents a threat to the health of a person because there are a variety of factors that affect the risk of cold injury," said Dr. Peter Wald, an occupational physician. In addition to air temperature, Wald said the wind chill factor, individual health risk factors, and the use of protective equipment and engineering controls affect the threat level to an individual.

"The two most significant factors for evaluating cold exposures are core body temperature and wind chill index," he said. The wind chill index estimates the relative cooling ability of a combination of air temperature and wind velocity; it is used to determine the risk of cold injury. It is measured as the equivalent chill temperature. For example, the wind chill index would be minus 22 if the temperature were 15 and the wind were blowing at 22 mph. For a wind chill index, visit the National Weather Service at

While the air temperature plays a major part in cold weather injuries, the body's ability to react to colder temperatures and maintain its own temperature can ultimately determine how an individual will be affected by the cold. " The core body temperature is just as important as the wind chill index in evaluating the effects of cold weather exposure," Wald said.

The use of cold stress Threshold Limit Values (TLVs) provides guidelines to protect workers from the severest effects of cold stress. The TLV's goal is to prevent the core body temperature from falling below 96.8 degrees, a point that increases the risk of hypothermia and cold injury. Workers with predisposing health conditions, such as cardiovascular disease, diabetes, and hypertension, along with workers taking certain medications, those in poor physical condition, those that have a poor diet, and older workers, are at increased risk for cold injury.

Cold Injury: Signs and Symptoms
Injuries from cold exposure are divided into two types: non-freezing and freezing. Non-freezing injuries include hypothermia, chilblains, pernio, and trench/immersion foot. Frostnip and frostbite are considered freezing injuries.

Non-freezing injuries
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 65 degrees or at water temperatures up to 72 degrees. Symptoms normally begin when the body temperature drops below 95 degrees. At first, individuals may shiver or stomp their feet to help generate heat. With continued exposure, they may fall into a state of dazed consciousness, unable to complete even simple motor functions. The victim's speech becomes slurred and his or her behavior may become irrational.

Chiblains involve the hands and feet. After prolonged exposure to wet cold, they will usually cause a red or purple swelling on a toe or a finger and an itchy feeling. A severe form of chiblains, pernio is characterized by black eschars on the hands and feet and can be very painful.

Freezing Injuries
Frostnip is a mild, reversible freezing of the outer layers of skin tissue, but frostbite is an irreversible freezing in the layers of the skin and deeper tissue. The capillary walls of the frostbitten area are damaged, increasing cell wall permeability and causing local inflammation.

Frostbite can be superficial or deep. An individual with superficial frostbite will experience a loss of sensation and have gray-white skin in the affected area. The skin and tissues, as well as the muscle and bone, are affected by deep frostbite. Individuals with deep frostbite will experience numbness. The affected area will be cold, hard, and white. According to Wald, "The toes, fingers, nose, ears, and cheeks are the most common sites of freezing cold injury."

Trench/immersion foot is caused by continuous exposure to cold water, with symptoms occurring after three to 12 hours of continuous exposure. While treatment is only minimally effective, this injury generally occurs among commercial fisherman or other workers who are continually immersed in cold water.

In its 1998 Cold Stress Card, OSHA recommended that all employees exhibiting cold injury symptoms receive emergency assistance by calling 911.

While waiting for emergency personnel, Wald said, "Only conscious individuals with mild hypothermia should be rewarmed in the workplace."

Move the victim to a warm, dry area, remove any wet clothing, and wrap the person in blankets or warm him or her with a radiant heat source. Have the person drink warm, decaffeinated, non-alcoholic sweet drinks, such as sugar water or sports-type drinks, to rewarm the body and replace lost fluids. "Because the body requires a large amount of fluids in cold weather," Wald explained, "dehydration is also more likely in a cold working environment."

Like OSHA, Wald recommends that individuals with mild hypothermia be encouraged to stay active and move their arms and legs to create muscle heat. If they are unable to do so, place warm bottles or hot packs in the armpits, groin, neck, and head areas. Hypothermia victims should not be rubbed or placed in a warm water bath because it may stop their hearts.

Employees exhibiting the signs of severe hypothermia and unconscious victims are in a life-threatening situation and should be transported to a medical facility immediately. These individuals should be handled carefully, keeping all extremities completely covered.

Workers who are exposed to cold water temperatures face an even greater danger because body heat is lost up to 25 times faster in the water. Employees should get or be helped out of the water immediately, if possible, or climb on anything floating. Swimming only uses the body's heat and can reduce survival time by about 50 percent. "The possibility of exposure to and falls into cold water must be taken into account during the emergency planning process," Knowlen stressed. He recalled a job in Portland, Maine, where workers were required to set steel on a bridge in shifts around the clock. "The nighttime air made it even colder and slip hazards took on a new meaning over that cold water. You've only got about two or three minutes to work with if someone falls in the cold water up here."

Frostnip and mild frostbite can be treated in the workplace by placing the injured body part in the armpits or groin area for warmth. "If there is absolutely no possibility of the tissue refreezing, the frozen tissue may be rewarmed and insulated until medical attention is received," Wald said. "However, caution must be used to avoid applying excessive heat to rewarm frozen tissue, since this may produce a devastating secondary burn injury."

Frostbitten tissue should be warmed slowly, over a time period of 25 to 40 minutes, to avoid tissue damage. When normal feeling, movement, and skin color have returned, the affected area should be dried and wrapped to keep it warm.

Other Cold Weather Hazards
Cold weather not only brings new hazards to the workplace; it also increases the likelihood of workplace accidents. Snow, ice, and reduced visibility increase the incidence of accidents in the cold. "It's really hard to hold onto a tool or small piece of equipment when your hands start going numb," Knowlen said. "Workers have to be especially careful."

Cold weather also can adversely affect equipment. In addition to longer warm-up periods, most equipment will become more brittle in freezing conditions. In particular, nylon slings will experience reduced capacities, which should be accounted for before use.

Aside from the obvious slip hazards, the build-up of ice and snow on scaffolding can increase the weight being supported to a level that exceeds maximum capacity. Knowlen said OSHA requires that scaffolding be cleared of ice and snow prior to employee use, at 1926.451(a)(17).

Even the engineering controls put into place to control other workplace hazards during warmer seasons can become hazards during winter conditions. "We often use saws to cut concrete, but these saws use water to control dust," Knowlen explained. "The water can create an additional ice hazard, which has to be taken into account. Cold weather typically amounts to more work." The very heaters used to provide employees with warmth and prevent cold-weather injuries can increase the risk of fire, burns, and carbon monoxide poisoning in confined spaces.

Dressing for Warmth
"The principles of using a layered clothing system provide flexibility and protection when working in cold weather," Wald emphasized. "Proper clothing for cold environments should include a system of insulation, layering, and ventilation."

He recommended that the inner layer of clothing be made of a material, such as polypropylene, that pulls moisture away from the skin to the outer layers of clothing. The middle layers of clothing should be made of materials such as wool or ThinsulateTM that provide insulation without adding significant weight that might inhibit task performance. The outer layer should repel wind and water but allow water vapor and moisture from perspiration to pass through. Fabrics such as Gor-TexTM are breathable.

The same layering principle applies to protection of the head, hands, and feet. Facemasks will help prevent frostbite and conserve heat loss. Employees should ensure that a complete change of clothes is available in case their clothes get wet or they sweat excessively; to ensure maximum insulation, all clothing should be kept clean.

When providing or recommending cold weather apparel, employers should consider the demands of each employee's tasks. "In construction, workers are on their hands and knees throughout the day--they're using power tools, and they're operating heavy equipment," Knowlen said. "The clothes they wear need to be not only warm, but also durable."

Working Precautions
While there is no particular standard for cold working environments, OSHA does require employers to provide or require PPE wherever employees are exposed to hazardous conditions, at 1926.28(a) and 1926.95(a). While important, warm-weather apparel is only one of the precautions an employer can take to protect his workforce from cold weather injuries and related accidents.

Shielding work areas from the wind and snow or providing safe heating equipment can reduce the stresses of cold weather. In the interest of worker safety and staying on schedule, Knowlen's client eventually erected a large, heated dome over the construction site to protect the crew from the unusually harsh December weather described earlier.

When possible, employers should schedule work during the warmest hours of the day and allow employees to set their own work pace and take frequent breaks in a heated area. New employees should be allowed time to adjust to the cold-weather conditions and to working with the added clothing and protective equipment. The work activity level should be moderate to avoid heavy sweating that could result in wet clothing, and the employer should consider the weight and bulkiness of winter clothing in determining the work activity output. The workflow should be designed to minimize prolonged sitting and standing; unprotected metal chairs should not be used.

Still, just as with any work safety program, Knowlen said, "Pre-planning is the most effective tool."

Wald recommends that all employees be trained in proper rewarming techniques, appropriate first aid treatment, proper cold-weather apparel, eating and drinking requirements, the signs and symptoms of cold injury, and safe work practices.

"Construction is tough," Knowlen said, "and cold weather just makes it that much harder."


  • Scott Knowlen is the Manager of Health and Environmental Hazards for Cianbro, located in Pittsfield, Maine. With a bachelor's degree in Chemical Engineering, he is responsible for company environmental issues, industrial hygiene, and employee training. Cianbro works on a wide variety of projects throughout the eastern United States.
  • Peter H. Wald, M.D., M.P.H., FACP, FACOEM, is the Medical Director and Principal for WorkCareTM, located in Orange, Calif. Board-certified in occupational medicine, Wald has more than 13 years' experience in corporate medicine. WorkCare provides a variety of outsource business services, including occupational health audits.
  • "Cold Weather Work: OSHA Offers Tips to Protect Workers in Cold Environments." 4 Safety. (Nov. 5, 2002).
  • Greaney, Peter P. "Ensuring Employee Safety in Cold-Weather Working Environments." WorkCare Whitepaper Article. December 2000. (Nov. 5, 2002).
  • U.S. Department of Labor Occupational Health and Safety Administration, Cold Stress Card, 1998.
  • "What You Can Do to Prevent Cold Stress Injuries." Tailgate Safety Meeting Topics. (Nov. 5, 2002).

This article originally appeared in the February 2003 issue of Occupational Health & Safety.

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