Sun exposure

Sunburn. From prolonged exposure to the sun on the human body, sunburns form on the skin, which can cause a painful condition for tourists.

Solar radiation is a stream of rays of the visible and invisible spectrum, having different biological activities. When exposed to the sun, there is simultaneous exposure to:

—direct solar radiation;

— scattered (arrived due to the scattering of part of the flow of direct solar radiation in the atmosphere or reflection from clouds);

— reflected (as a result of reflection of rays from surrounding objects).

The amount of solar energy flow falling on a particular area of ​​the earth's surface depends on the altitude of the sun, which, in turn, is determined by the geographical latitude of this area, the time of year and day.

If the sun is at its zenith, then its rays travel the shortest path through the atmosphere. At a sun altitude of 30°, this path doubles, and at sunset - 35.4 times more than with a vertical incidence of the rays. Passing through the atmosphere, especially through its lower layers, which contain suspended particles of dust, smoke and water vapor, the sun's rays are absorbed and scattered to a certain extent. Therefore, the longer the path of these rays through the atmosphere, the more polluted it is, the lower the intensity of solar radiation they have.

With increasing altitude, the thickness of the atmosphere through which the sun's rays pass decreases, and its most dense, moist and dusty lower layers are excluded. Due to the increase in atmospheric transparency, the intensity of direct solar radiation increases. The nature of the change in intensity is shown in the graph (Fig. 5).

Here the flow intensity at sea level is taken to be 100%. The graph shows that the amount of direct solar radiation in the mountains increases significantly: by 1-2% with an increase in every 100 meters.

The total intensity of the direct solar radiation flux, even at the same altitude of the sun, changes its value depending on the season. Thus, in summer, due to rising temperatures, increasing humidity and dust reduce the transparency of the atmosphere so much that the flow value at a sun altitude of 30° is 20% less than in winter.

However, not all components of the spectrum of sunlight change their intensity to the same extent. The intensity of ultraviolet rays, the most active in physiological terms, increases especially sharply: it increases by 5-10% with an increase in every 100 meters. The intensity of these rays has a pronounced maximum at a high position of the sun (at noon). It was found that precisely during this period, under the same weather conditions, the time required for skin redness at an altitude of 2200 m is 2.5 times less, and at an altitude of 5000 m, 6 times less than at an altitude of 500 meters (Fig. 6). As the altitude of the sun decreases, this intensity drops sharply. So, for an altitude of 1200 m, this dependence is expressed by the following table (the intensity of ultraviolet rays at a sun altitude of 65° is taken as 100%);

If the clouds of the upper level weaken the intensity of direct solar radiation, usually only within insignificant limits, then denser clouds of the middle and especially lower levels can reduce it to zero.

Scattered radiation plays a significant role in the total amount of incoming solar radiation. Scattered radiation illuminates places in the shade, and when the sun is obscured by dense clouds over an area, it creates general daylight illumination.

The nature, intensity and spectral composition of scattered radiation are related to the altitude of the sun, air transparency and cloud reflectivity.

Scattered radiation under a clear sky without clouds, caused mainly by molecules of atmospheric gases, is sharply different in its spectral composition from both other types of radiation and from scattered radiation under a cloudy sky; the maximum energy in its spectrum is shifted to the region of shorter waves. And although the intensity of scattered radiation under a cloudless sky is only 8-12% of the intensity of direct solar radiation, the abundance of ultraviolet rays in the spectral composition (up to 40-50% of the total number of scattered rays) indicates its significant physiological activity. The abundance of short-wavelength rays also explains the bright blue color of the sky, the bluer of which is more intense the cleaner the air.

In the lower layers of air, when solar rays are scattered from large suspended particles of dust, smoke and water vapor, the maximum intensity shifts to the region of longer waves, as a result of which the color of the sky becomes whitish. In a whitish sky or in the presence of light fog, the total intensity of scattered radiation increases by 1.5-2 times.

When clouds appear, the intensity of scattered radiation increases even more. Its magnitude is closely related to the number, shape and location of clouds. Thus, if, when the sun is high, the sky is covered by clouds by 50-60%, then the intensity of scattered solar radiation reaches values ​​equal to the flux of direct solar radiation. With further increase in cloudiness and especially as it thickens, the intensity decreases. With cumulonimbus clouds it can be even lower than with a cloudless sky.

It should be taken into account that if the flux of scattered radiation is higher, the lower the transparency of the air, then the intensity of ultraviolet rays in this type of radiation is directly proportional to the transparency of the air. In the daily course of changes in illumination, the highest value of scattered ultraviolet radiation occurs in the middle of the day, and in the annual course - in winter.

The magnitude of the total flux of scattered radiation is also influenced by the energy of the rays reflected from the earth's surface. Thus, in the presence of clean snow cover, scattered radiation increases by 1.5–2 times.

The intensity of reflected solar radiation depends on the physical properties of the surface and the angle of incidence of the sun's rays. Wet black soil reflects only 5% of the rays falling on it. This is because reflectivity decreases significantly with increasing soil moisture and roughness. But alpine meadows reflect 26%, polluted glaciers - 30%, clean glaciers and snow surfaces - 60-70%, and freshly fallen snow - 80-90% of the incident rays. Thus, when moving in the highlands on snow-covered glaciers, a person is exposed to a reflected flux that is almost equal to direct solar radiation.

The reflectivity of individual rays included in the spectrum of sunlight is not the same and depends on the properties of the earth's surface. Thus, water practically does not reflect ultraviolet rays. The reflection of the latter from the grass is only 2-4%. At the same time, for freshly fallen snow, the reflection maximum is shifted to the short-wave range (ultraviolet rays). You should know that the lighter the surface, the greater the amount of ultraviolet rays reflected from the earth's surface. It is interesting to note that the reflectivity of human skin for ultraviolet rays is on average 1-3%, that is, 97-99% of these rays falling on the skin are absorbed by it.

Under normal conditions, a person is faced not with one of the listed types of radiation (direct, scattered or reflected), but with their total impact. On the plains, this total exposure under certain conditions can be more than twice the intensity of exposure to direct sunlight. When traveling in the mountains at medium altitudes, the intensity of radiation in general can be 3.5-4 times, and at an altitude of 5000-6000 m 5-5.5 times higher than normal plain conditions.

As has already been shown, with increasing altitude the total flux of ultraviolet rays especially increases. At high altitudes, their intensity can reach values ​​exceeding the intensity of ultraviolet irradiation under direct solar radiation in plain conditions by 8-10 times!

By affecting exposed areas of the human body, ultraviolet rays penetrate human skin to a depth of only 0.05 to 0.5 mm, causing redness and then darkening (tanning) of the skin at moderate doses of radiation. In the mountains, exposed areas of the body are exposed to solar radiation throughout the daylight hours. Therefore, if the necessary measures are not taken in advance to protect these areas, body burns can easily occur.

Externally, the first signs of burns associated with solar radiation do not correspond to the degree of damage. This degree is revealed somewhat later. Based on the nature of the injury, burns are generally divided into four degrees. For the sunburns under consideration, in which only the upper layers of the skin are affected, only the first two (lightest) degrees are inherent.

I is the mildest degree of burn, characterized by redness of the skin in the burn area, swelling, burning, pain and some development of skin inflammation. Inflammatory phenomena pass quickly (after 3-5 days). Pigmentation remains in the burn area, and sometimes peeling of the skin is observed. .

Stage II is characterized by a more pronounced inflammatory reaction: intense redness of the skin and detachment of the epidermis with the formation of blisters filled with clear or slightly cloudy liquid. Complete restoration of all layers of skin occurs in 8-12 days.

First degree burns are treated by tanning the skin: the burned areas are moistened with alcohol and a solution of potassium permanganate. When treating second-degree burns, primary treatment of the burn site is performed: wiping with gasoline or a 0.5% solution of ammonia, irrigating the burned area with antibiotic solutions. Considering the possibility of infection while traveling, it is better to cover the burn area with an aseptic bandage. Rarely changing the dressing promotes the rapid restoration of affected cells, since this does not damage the layer of delicate young skin.

During a mountain or ski trip, the neck, earlobes, face and skin on the outside of the hands suffer the most from exposure to direct sunlight. As a result of exposure to scattered, and when moving through the snow and reflected rays, the chin, lower part of the nose, lips, and skin under the knees are subject to burns. Thus, almost any open area of ​​the human body is susceptible to burns. On warm spring days when driving in the highlands, especially in the first period, when the body does not yet have a tan, under no circumstances should you be allowed to remain in the sun for a long time (more than 30 minutes) without a shirt. The delicate skin of the abdomen, lower back and sides of the chest is most sensitive to ultraviolet rays. We must strive to ensure that in sunny weather, especially in the middle of the day, all parts of the body are protected from exposure to all types of sunlight. Subsequently, with repeated repeated exposure to ultraviolet radiation, the skin becomes tanned and becomes less sensitive to these rays.

The skin of the hands and face is the least susceptible to ultraviolet rays. But due to the fact that the face and hands are the most exposed areas of the body, they suffer most from sunburn. Therefore, on sunny days, the face should be protected with a gauze bandage. To prevent the gauze from getting into your mouth when breathing deeply, it is advisable to use a piece of wire (length 20-25 cm, diameter 3 mm) as a weight to pull the gauze, passed through the lower part of the bandage and bent in an arc (Fig. 7).

In the absence of a mask, the parts of the face most susceptible to burns can be covered with a protective cream such as “Ray” or “Nivea”, and the lips with colorless lipstick. To protect the neck, it is recommended to sew double-folded gauze to the headdress from the back of the head. You should especially take care of your shoulders and hands. If, with a burn on the shoulders, the injured participant cannot carry a backpack and all of its additional weight falls on other comrades, then with a burn on the hands, the victim will not be able to provide reliable insurance. Therefore, on sunny days, wearing a long-sleeved shirt is mandatory. The backs of the hands (when moving without gloves) must be covered with a layer of protective cream.

Snow blindness (eye burn) occurs during relatively short (1-2 hours) movement in the snow on a sunny day without protective glasses as a result of the significant intensity of ultraviolet rays in the mountains. These rays affect the cornea and conjunctiva of the eyes, causing them to burn. Within a few hours, pain (“sand”) and lacrimation appear in the eyes. The victim cannot look at light, even a lit match (photophobia). There is some swelling of the mucous membrane, and later blindness may occur, which, if measures are taken in a timely manner, disappears without a trace in 4-7 days.

To protect your eyes from burns, it is necessary to use safety glasses, the dark glasses of which (orange, dark purple, dark green or brown) significantly absorb ultraviolet rays and reduce the overall illumination of the area, preventing eye fatigue. It is useful to know that orange color improves the sense of relief in conditions of snowfall or light fog and creates the illusion of sunlight. Green color brightens up the contrasts between brightly lit and shadowy areas of the area. Since bright sunlight reflected from the white snow surface has a strong stimulating effect on the nervous system through the eyes, wearing safety glasses with green lenses has a calming effect.

The use of safety glasses made of organic glass in high-altitude and ski trips is not recommended, since the spectrum of the absorbed part of ultraviolet rays in such glass is much narrower, and some of these rays, which have the shortest wavelength and have the greatest physiological impact, still reach the eyes. Prolonged exposure to such, even reduced amounts of ultraviolet rays, can eventually lead to eye burns.

It is also not recommended to take canned glasses on a hike that fit tightly to your face. Not only the glass, but also the skin of the area of ​​the face covered by it fogs up heavily, causing an unpleasant sensation. Much better is the use of ordinary glasses with sides made of wide adhesive plaster (Fig. 8).

Participants of long hikes in the mountains must have spare glasses at the rate of one pair for three people. If you don’t have spare glasses, you can temporarily use a gauze blindfold or put cardboard tape over your eyes, making narrow slits in it first in order to see only a limited area of ​​​​the terrain.

First aid for snow blindness is rest for the eyes (dark bandage), washing the eyes with a 2% solution of boric acid, cold lotions from tea broth.

Sunstroke is a severe painful condition that suddenly occurs during long marches as a result of many hours of exposure to the infrared rays of direct solar flow on an uncovered head. At the same time, during a hike, the back of the head is exposed to the greatest impact of rays. The resulting outflow of arterial blood and a sharp stagnation of venous blood in the veins of the brain lead to swelling and loss of consciousness.

The symptoms of this disease, as well as the actions of the team when providing first aid, are the same as for heat stroke.

A headgear that protects the head from exposure to sunlight and, in addition, maintains the possibility of heat exchange with the surrounding air (ventilation) thanks to a mesh or a series of holes, is a mandatory accessory for a participant in a mountain trip.