This document is intended to provide:
- guidance in the development of job-specific safe work procedures for the prevention of cold-stress related injuries, and
- assistance to supervisors and health and safety staff in addressing health and safety concerns related to cold stress.
The management of cold stress requires an understanding of how the body regulates temperature, the contributing factors to cold stress and how cold stress may affect a worker.
How the body responds to cold.
The body is designed to work best at a constant core temperature of 38-39oC. The body maintains this temperature by gaining heat from food and muscular work or by losing it through convection, conduction, radiation and sweating.
Cold first affects the skin, cooling the blood in the peripheral capillaries. Then a complex signal is sent to brain, which initiates two processes: one to conserve heat already in body and the other to generate new heat. Heat conservation is accomplished by causing the blood vessels to the skin to constrict to reduce heat loss. Involuntary shivering, which raises the body’s metabolic rate, also begins in attempt to produce heat.
Factors contributing to cold-stress related injuries.
Cold-stress related injuries are caused by a combination of these factors:
- low temperature;
- cool high winds;
- cold water; and
- contact with cold objects, such as metal.
Wind chill, which is cooling effect of the combination of temperature and air velocity, is an important factor in the evaluation of the outdoor environment. For example, when the actual air temperature of the wind is 5oC and its velocity is 55 km/h, the exposed skin would perceive these conditions as if the equivalent still air temperature were -2oC. The Wind Chill Temperature Index (Appendix A) is the best known and the most used of the cold stress indices.
Other major factors contributing to cold stress include inadequate or wet clothing, worker’s age, health, physical condition, use of medication and level of acclimatization.
Cold-stress related injuries
Cold-stress related injury is classified as either localized, as in frostbite; or generalized, as in hypothermia. The key concern in the work environment is frostbite. The attached “Cold Stress Hazards Information Sheet” defines the primary types of cold-stress related injuries and provides information on their causes, signs and symptoms, treatment and prevention.
Managing Cold Stress
Various types of control measures in different combinations can be used to prevent or minimize cold-stress related injuries.
Engineering controls change the conditions so that the level of cold stress is reduced. They are the most effective, but sometimes the most difficult to achieve in the outdoor environment. They include:
- Redesign and/or mechanize the task. This reduces the work time in cold environments and thus exposure to cold. When temperatures drop below -17.5°C, machine controls and tools should be designed so they can be handled without removing mittens.
- Shield work areas from drafty or windy conditions.
- where practical, provide a heated shelter for employees who experience prolonged exposure to low wind-chill temperatures.
- Thermal insulating material on equipment. When in direct contact with skin, metal handles conduct heat away from the body and should be insulated, where practicable, when temperatures drop below –1o This reduces the risk of frostbite.
Administrative controls attempt to minimize the risks through work practices. They are relatively easy to implement. Administrative controls include the following:
- Limit exposure time that worker is required to work in a cold environment.
Some examples for reducing exposure time include:
- perform partial components of a task indoors/sheltered, where feasible;
- increase task variation and rotation;
- assign additional relief workers;
- routine maintenance and repair work in cold exposed environments may be scheduled for warmer days/seasons of the year, where practicable;
- activities that minimize blood circulation such as static, cramped positions should be reduced/eliminated, where feasible.
Allow recovery time. It is important to provide adequate recovery time from cold stress exposures. Appropriate rest breaks should be determined based on environmental conditions (i.e. temperature and wind speed). If work is performed continuously in the cold at or below a wind chill temperature of -7°C, heated warming shelters (tents, cabins, rest rooms, etc.) should be made available nearby.
Initiate a Buddy System.Since individuals are less likely to notice their own symptoms, a buddy system approach would allow for earlier recognition of the risk of signs and symptoms, such as frostbite to the ears, cheeks and nose.
Acclimatization. Some degree of acclimatization may be possible in cold environments. With enough exposure to cold, the body does undergo some changes that increase comfort and reduce the risk of cold-stress related injuries. People who are physically unfit, older, obese, or taking medications may not acclimatize as readily.
- Supervisors should encourage workers to wear multiple layers of light, loose-fitting clothing consisting of:
- a waterproof/water-resistant outer layer to break the wind and allow some ventilation;
- a middle layer of wool or synthetic fabric to absorb sweat and retain insulation in a damp environment; and
- an inner layer of synthetic weave to allow ventilation.
- When temperatures drop below -17.5°C, hands should be protected by mittens.
- Workers should keep a change of clothing available in case work garments become wet.
- If a worker becomes immersed in water, the worker should immediately change to dry clothing.
- Workers should avoid wearing down-filled garments in wet environments.
- Workers should be aware that wearing dirty or greasy clothing have poor insulating properties.
- Workers should pay special attention to protecting feet, hands, face and especially head. Up to 50% of body heat can be lost when the head is exposed.
- A wool knit cap with ear protection provides the best protection.
- For employees required to wear a hard hat, provide a liner for protection from the cold.
- Face protection that does not restrict vision should be worn.
- Workers should not wear scarves when the work performed may result in the scarves getting caught in moving parts of machinery.
- Footgear should be insulated and water-resistant to protect against cold and dampness.
Personal Prevention Strategies
Personal prevention strategies are those actions that individuals can take to lower their risk of cold-stress related injuries. Although they are the responsibility of the individual workers, management should minimize, to the extent possible, any barriers to the use of personal prevention strategies. Workers should be advised that the following actions would be helpful in preventing cold-stress related injuries.
- Self-monitoring. Individual workers should interrupt cold stress exposure once extreme discomfort or the initial symptoms of a cold-stress related injury are detected. Individuals should be required to report to their supervisor cold stress-related symptoms in themselves or their co-workers.
- Fluid Replacement. Warm, non-caffeinated, non-alcoholic drinks should be consumed frequently. Caffeine is a diuretic and causes dehydration, which is linked to heat loss. Alcohol causes dilation of the blood vessels near the skin causing heat loss to the body’s core and its consumption at work is prohibited, however, this should be kept in mind for off-work activities.
- Lifestyle and Diet. Practicing a generally accepted healthy lifestyle greatly reduces the risk of cold-stress related injuries. This includes getting adequate sleep, limiting non-work exposure to cold, exercising, not using alcohol or drugs, and eating a well-balanced diet. Nicotine should be avoided because it increases constriction of peripheral blood vessels and can increase the risk of frostbite.
- Health Status. Many conditions predispose individuals to cold-stress related injuries. It is suggested that employees discuss their medical history and have a physical examination with their physician in order recognize their risk factor(s) and thereby help prevent cold-stress related injuries. People taking certain medications may have inhibited circulation and should consult their physician.
- Warm-up Stretches. Working in cold environments may increase the risk of back injuries and other musculoskeletal injuries. Workers should perform warm-up stretching exercises before handling heavy equipment and material. Workers should consult with their family physician to determine appropriate exercises.
Education and Training
Education and training is a fundamental health and safety practice for those who may be exposed to a hazard such as cold stress. A training program should include the following components:
- knowledge of the hazards and potential health effects of cold stress;
- recognition of predisposing factors, danger signs and symptoms;
- awareness of first-aid procedures for cold-stress related injuries;
- employee responsibilities in minimizing cold stress;
- safe work practices;
- use of protective clothing and equipment; and
- documentation of employees who have received education and training.
Occupational Health and Safety Act (R.S.O. 1990, c.0.1)
November 28, 2000 (Occupational Health & Safety Coordinating Committee)
February 23, 2001 (Executive Management Team)
April 26, 2016
October 15, 2019
Policy on Climate-Related Hazards – (ii) Cold Stress Policy