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 56 km/h, the exposed skin would perceive these conditions as if the equivalent still air temperature were -12oC. The equivalent chill chart (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.