4. Cold-related injuries

occupational activities that require cold exposure. Different industries like construction industry, fishery, farming, reindeer breeding, mining, metallurgy, forestry, horticulture, etc. involve work in outdoor conditions with low temperatures. In Sweden over 30% of the employed persons, for example, work in cold conditions repeatedly, for shorter or longer time [13].

The artificial cold workplaces can be found mainly in the food industry and fishery. Fresh food is usually preserved at a temperature below 6°C; frozen food is handled and stored at a temperature around −25°C. The work in food processing departments of big supermarkets is also related to cold exposure. It is reported that cold-related diseases and discomfort complaints are more frequently observed among workers, exposed to artificial than to outdoor

In any case, to protect the human body from the cold-related hazards, workers must be provided with protective clothing during their cold exposure. The comparison between the occupational activities in natural and artificial cold shows, however, some differences, which

On the first place, the indoor, artificial cold, is more stable in temperature, air velocity, and humidity fluctuations, which is preconditioned by the application of systems for chilling and air conditioning. This helps the proper selection of protective clothing, which does not need changing during the exposure. In the natural cold environment, the air temperature changes during the 24-hour period. This requires the use of clothing, which allows adding or removing of layers within some limits, in order to protect the worker from overheating or freezing.

In addition, the climate conditions have to be considered together with the geographical features: activities in mountain regions (road construction, logging, tourism) increase the negative effect of the low temperatures and the solar load; activities in the flatlands or seas

In the food processing industry, static work is frequently observed. Some outdoor activities (transportation or work with heavy machinery) also require a sitting posture of the worker, but it is performed in the protective indoor environment of the vehicle (track, bulldozer, etc.). In any case the immobility of the body in cold environment is harmful and has to be avoided. Protective gloves and boots must be used, but they cannot replace the need of blood circulation in the extremities. At the same time, indoor cold work may require fine motor skills activities,

Another difference between the occupational activities in artificial and natural cold is that workers in an artificial cold environment move more frequently between colder and warmer environment. The temperature difference provokes higher strain on the thermoregulatory system of the body. At the same time, continuous cold air flows in the artificial cold facilities lead to appearance of body temperature asymmetry (asymmetric cooling), which adds to the

Last but not least, the protective clothing in an artificial cold environment may need to combine different protective abilities, i.e., against chemical or mechanical hazards, because of

which is in contradiction with the application of heavy protective gloves and mittens.

(agriculture, fishing, oil platforms) increase the severity of the wind effect.

influence the thermophysiological comfort of the workers.

thermal discomfort of the workers.

the occupational safety regulations.

cold [14, 15].

228 Occupational Health

Cold-related injuries may occur in any environment, which temperature is around the freezing temperature. However, the thermoregulatory reactions to cold start at any air temperature, which is below the temperature of the body, and signals for cold are received by the cold sensors in the skin. Hypothermia may occur even in deserts if it is preconditioned by the body state and environmental conditions.

The major injuries, related to cold exposure, are frostbite, trench foot, immersion foot, hypothermia, and cold allergy. The reactions of the thermoregulatory system against the cold start when the core body temperature decreases below 37°C (Figure 5). The shivering, which is a way for heat production, reaches its peak at 35°C [16]. Below this temperature the body starts to demonstrate signs of hypothermia. At a temperature of 34°C, muscle rigidity appears, and the person is not anymore able to perform manual operations due to a loss of manual dexterity [17]. At 32°C the consciousness is clouded and around 30°C it is lost. If the core body temperature decreases below 30°C, the risk of death becomes extremely high if the cold exposure continues. The data from [16] show that cardiac arrhythmia appears at 29°C, and at 27°C the person appears dead. The drop of the core body temperature to 24°C leads to the development of pulmonary edema, and around 20°C the heart stops beating. However, it has to be mentioned that the lowest core body temperature, from which a person has been recovered, is 18°C [16].

Figure 5. Effect of the time of cold exposure on core body temperature and hypothermia.

Frostbite is an injury that affects mainly the extremities in the cold, especially fingers and toes, as well as unprotected parts of the face (nose, lips, ears). It appears due to the crystallization of the liquids in the cells of the skin and deeper tissues of the body shell. The severity of the injury depends on the speed of freezing. Temperatures below 0°C and low relative humidity of the air precondition the appearance of frostbite.

Trench foot and immersion foot are classified as a nonfreezing cold injury [16]. Trench foot may appear at temperatures above 0°C and high relative humidity of the air. Its severity depends on the time of cold exposure. Immersion foot occurs as a result of prolonged static work in upright posture or as a consequence of immobilization of the extremities. It is related with wet environment, including cold water exposure.

Hypothermia appears after prolonged cold stimulus, but other environmental factors like wind, contact with cold objects, or immersion in water can favor it. Three types of hypothermia are classified in [18]: primary, secondary, and clinically induced (the last being out of the scope of cold-related injuries).

Primary hypothermia is diagnosed when the thermoregulation responses to the cold exist, but they cannot beat the symptoms of hypothermia. Primary hypothermia can appear in any cold environment, when the low temperature overwhelms the body thermoregulatory system.

Secondary hypothermia differs from the primary as the thermoregulatory reactions of the body are impaired [17]. Symptoms of hypothermia appear again, but their severity is not proportional to the cold induced. Secondary hypothermia is due to additional peculiarities of human physical or physiological state: fatigue, illness, or injury. Insufficient clothing insulation, poor nutrition or dehydration, and short sleep are also reasons for secondary hypothermia. The onset of the secondary hypothermia can hardly be predicted, being dependent of several factors: clothing insulation, metabolic rate, body size, nutrition status, hydration, and physiological and even psychological status.

Cold allergy, expressed in red and itchy pimples on uncovered skin, exposed to cold air, is also frequently observed as cold injury. It usually disappears after warming. Severe cases of cold allergy are associated with fever, seizures, fever, increment of the heartbeat, and swelling of the torso or extremities.
