What are the health effects of exposure to cold?
Exposure to cold working conditions may result in a variety of cold injuries and illnesses - with hypothermia and frostbite being the most serious. Other types of cold stress injuries include chilblain, immersion foot or trench foot, windburn, frostnip, and frostbite.
Generally, toes, fingers, ears, and nose are at greatest risk because these areas do not have major muscles to produce heat. The body preserves heat by keeping the internal organs warm, reducing the flow of blood to the extremities under cold conditions. In addition, hands and feet tend to get cold more quickly than the body (torso) because:
If the eyes are not protected with goggles in high wind chill conditions, the corneas of the eyes may freeze.
The most severe cold injury is hypothermia, which occurs from excessive loss of body heat and the consequent lowering of the inner core temperature (internal temperature of the body). Hypothermia can be fatal.
For more information on the general effects of working in the cold, please see Cold Environments - Overview.
For information on exposure limits and injury prevention while working in the cold, please see Cold Environments - Control Measures.
- general they lose heat more rapidly since they have a higher surface area-to-volume ratio, and
- physical they are more likely to be in contact with colder surfaces than other parts of the body.
Evaporation
Evaporation is the loss of heat due to the conversion of water from a liquid to a gas. In terms of human physiology, it is:
It is important to recognize the strong connection between fluid levels, fluid loss, and heat loss. As body moisture is lost through the various processes, the overall circulating volume is reduced which can lead to dehydration. This decrease in fluid level makes the body more susceptible to hypothermia and other cold injuries and illnesses.
- context Perspiration or sweating – evaporation of water to remove excess heat.
- context "Insensible" perspiration – body sweats to maintain a humidity level next to the skin. Particularly in a cold, dry environment, you can lose a great deal of moisture this way and not notice that you have been sweating.
- context Respiration – air is heated as it enters the lungs and is exhaled with an extremely high moisture content.
How do we produce and retain heat within the body?
In order to survive and stay active in the cold, the constant heat loss has to be counterbalanced by the production of an equal amount of heat. Heat is both required and produced at the cellular level as a result of complex metabolic processes that convert food – a primary source of energy – into glycogen. Glycogen is a substance (biochemical compound) that is the “fuel” for biochemical processes underlying all life functions, heat production included.
Factors important for heat production include:
Heat retention and tolerance to cold also depend on the body’s structure, certain reflexes and behavioural mechanisms that retain heat within the body, as well as what you are wearing. They are:
- context Food intake.
- context “Fuel” (glycogen) store.
- context Fluid balance.
- context Physical activity.
- context Shivering – a reflex reaction, which increases the body’s heat production when necessary. This reaction is limited to a few hours because of the depletion of muscle glycogen and the onset of fatigue.
- context Size and shape of the body (surface-to-volume ratio).
- context The layer of fat under the skin (Subcutaneous adipose tissue).
- context Decreased the blood flow through the skin and outer parts of the body.
- context Insulation (layering and type of clothing).
What first aid can I do for frostnip?
First aid for frostnip include:
- context Gentle rewarming (e.g., holding the affected tissue next to the unaffected skin of the victim or of another person).
- context For all cold-induced injuries, never rub the affected parts—ice crystals in the tissue could damage the skin if the skin is rubbed.
- context Do not use very hot objects such as hot water bottles to warm the area or person.
What first aid is appropriate for frostbite or immersion foot?
First aid for frostbite, as well as immersion or trench foot, includes:
- context Never ignore numbness. If the area feels numb or tingly, take steps to warm the area immediately. (e.g., put hands under armpits, or pull arms into the inside of a jacket for more direct contact with the body)
- context If possible, move the victim to a warm area.
- context Remove wet clothing, and gently loosen or remove constricting clothing or jewellery that may restrict circulation.
- context Warm the person by wrapping them in blankets or by putting them in dry clothing. Cover the head and neck. Warm the person slowly. Avoid direct heat which can burn the skin.
- context Loosely cover the affected area with a sterile dressing. Place some gauze between fingers and toes to absorb moisture and prevent them from sticking together.
- context If the person is alert, give them warm liquids to drink to rehydrate.
- context Check for signs of hypothermia and seek medical attention. If necessary, quickly transport the victim to an emergency care facility.
- context Treat the person gently and monitor breathing
- context DO NOT attempt to rewarm a frostbitten area on site (but do try to stop the area from becoming any colder). Without the proper medical care, the tissue that has been warmed may refreeze and cause more damage.
- context DO NOT thaw the area if it may freeze again.
- context DO NOT rub the area or apply snow.
- context DO NOT allow the victim to drink alcohol or smoke.
What are the signs of hypothermia?
The levels of cold stress and hypothermia include:
Cold stress (not hypothermic)
Mild hypothermia
Moderate hypothermia
Severe hypothermia
- context Shivering
- context Normal mental status
- context Able to care for self
- context Shivering
- context Increased blood pressure
- context Poor judgement and behaviour changes
- context Difficulty forming or pronouncing words
- context Loss of coordination
- context Fatigue
- context Weak and intermittent shivering, or shivering that later stops
- context Dilated pupils
- context Unconsciousness
- context Irregular heartbeat
- context Shivering has stopped
- context Unresponsiveness; breathing has slowed down or stopped
- context Loss of reflexes
- context No response to pain
- context Dilated pupils
- context Blue skin
What first aid is appropriate for hypothermia?
Hypothermia is a medical emergency. At the first sign, find medical help immediately. The survival of the victim depends on the co-worker's ability to recognize the symptoms of hypothermia. The victim is generally not able to notice his or her own condition.
First aid for hypothermia includes the following :
- context Seek medical help immediately. Hypothermia is a medical emergency.
- context Move the person out of the cold, and/or insulate the person (e.g., by applying a hypothermia wrap or layers of dry blankets or coats).
- context Check for ABC - Airway, breathing, and circulation.
- context Handle the person gently. Do not massage or rub the skin.
- context Allow them to lay down. No standing or walking.
- context Warm by carefully applying warm water bottles, heating pads, or electric blankets to the upper body (such as the armpits, chest, groin and upper back). Wrap items in towels or clothing if available. Body heat from another person can also help in an emergency.
- context DO NOT massage or rub the skin.
- context DO NOT rewarm the person too quickly (e.g., do not use a heating lamp or stove, or soak in a hot bath/shower).
- context Give food or warm drinks (caffeine-free, non-alcoholic) ONLY if the individual has mild hypothermia (e.g., when the person is conscious and responsive).
- context Perform CPR (cardiopulmonary resuscitation) if the victim stops breathing. Continue providing CPR until medical aid is available. The body slows when it is very cold and in some cases, hypothermia victims that have appeared "dead" have been successfully resuscitated.
What is meant by a hypothermia wrap?
Supplies to make a hypothermia wrap include:
When the person has dry or damp clothing, leave the clothing on.
When the person has very wet clothing:
To apply a hypothermia wrap:
- context a tarp or plastic sheet to act as a vapour barrier
- context an insulated ground pad
- context a hooded sleeping bag (or equivalent) to act as the insulation wrap
- context another plastic or foil sheet (2x3 metres) to act as a vapour barrier inside the sleeping bag
- context source of heat (e.g., warm water in a bottle or hydration bladder, chemical heating pads)
- context wrap the person immediately if shelter and transport are less than 30 minutes away
- context if shelter and transport are more than 30 minutes away, protect the person from the environment, remove wet clothing, and apply wrap
- context Place an insulation pad (or pads) between the person and the ground.
- context Apply as much insulation as possible. Add extra clothing and wrap the person in blankets or sleeping bags.
- context Add heat sources to the person's upper body inside the wrapping.
- context Cover the person's head and neck with a toque, heavy hat, or hood, but leave their face exposed enough for breathing.
- context If the person is dry, place a vapour barrier (plastic or foil) outside the insulation wrap. If the person is wet, place the vapour barrier inside the insulation wrap. If you have two vapour barriers, place one inside and one outside the insulation wrap.
Predisposing Conditions
Susceptibility to cold injury varies from person to person. In general, people in good physical health are less susceptible to cold injury. While anyone working in a cold environment may be at risk, the following conditions may make the risk of cold injury greater:
- context Age (infants less than one year, and older adults are more susceptible).
- context Diseases of the blood circulation system.
- context Injuries resulting in blood loss or altered blood flow.
- context Previous cold injury or illness.
- context Certain medical conditions, such as hypothyroidism and Raynaud's Phenomenon.
- context Fatigue.
- context Consumption of alcohol or nicotine (smoking).
- context Use of certain drugs or medications.