The mechanism of the biological action of UV rays is very complex, ambiguous and not fully understood. This mechanism is based not on thermal effects, as with infrared irradiation, but on photochemical reactions occurring with biopolymers - proteins and nucleic acids. Under the influence of photons that knock electrons out of molecules, the charge of protein molecules changes, which ultimately causes the denaturation of proteins. Irradiation also leads to photolysis, i.e. the formation of “fragments” of large molecules with high biological activity (histamine, acetylcholine, etc.). Photolysis is caused by photons with wavelengths predominantly in the erythemal zone, and denaturation is caused by photons with wavelengths in the bactericidal zone.
Changes that occur with nucleic acids and DNA molecules affect the vital processes of cells, their growth and division, and can lead to the death of cells and single-celled organisms - bacteria. Depending on the wavelength and their structure, different bacteria have different sensitivity to radiation. Thus, the death of the largest number of staphylococci occurs at wavelengths of the order of 265 nm, E. coli - at 251 nm, etc. Ultraviolet rays also cause the destruction of viruses and bacteriophages, they neutralize some bacterial toxins (for example, cobra venom) and a number of other toxic substances. However, cell death requires a fairly large dose of radiation. Thus, for the death of one E. coli cell, an average of 2·106 photons is needed.
The bactericidal effect of UV irradiation is used to disinfect air in enclosed spaces. Such air sanitation is used in operating rooms and dressing rooms, which dramatically increases surgical asepsis. The bactericidal effect of UV irradiation is widely used in industrial poultry farming, since due to the high concentration of livestock, there is a danger of aerogenic infections due to microbial air pollution in poultry houses. Bactericidal irradiation for sanitizing the air environment when raising chickens showed that air irradiation 3 times a day for 5–25 minutes leads to a significant increase in the safety of chickens and an increase in live weight compared to chickens in control rooms. For disinfection purposes, the supply and exhaust air of isolators, quarantine and other premises in livestock farms is exposed to ultraviolet irradiation. In addition to the disinfecting effect, UV irradiation helps improve the ionic composition of the air (increases the concentration of light air ions), reduces the amount of hydrogen sulfide and carbon dioxide. When UV radiation sources operate, ozone is formed, which acts as an oxidizer of the gas components of the exhaust air of livestock buildings, which have a bad odor.
The effect of ultraviolet radiation begins with its absorption in the skin. In order for irradiation to cause biological effects, it must penetrate deeper than the stratum corneum of the skin, into the germinal layer of the epidermis adjacent to the skin itself (dermis), in which blood vessels and nerves pass. In humans, rays have a length; waves less than 300 nm do not penetrate deeper than the epidermis (~0.5 mm). It is in the germinal layer of the epidermis that a complex chain of biochemical reactions and physiological processes caused by ultraviolet radiation begins. One of the most important reactions is the formation of histamine during decarboxylation of the heterocyclic amino acid histidine.
Histamine, along with other “fragments” of molecules, is carried through the blood and lymphatic vessels. Histamine is a substance that dilates blood vessels, resulting in hyperemia, i.e., an increase in blood supply to the irradiated area of the organ. With active hyperemia, 1 erythema occurs, the formation of which requires a certain intensity of irradiation. Thus, the threshold value of ultraviolet intensity with a wavelength of 296.7 nm is 335 W/m2.
Skin response to irradiation - pigmentation (tanning). The skin pigment melanin is concentrated in the lowest layers of the epidermis. Rays with a wavelength of 200–250 nm penetrating the stratum corneum cause only erythema; radiation with a wavelength of 250–270 nm passes through the stratum corneum, causing pigmentation and erythema; Even more abundant pigmentation and erythema are caused by radiation with a wavelength of 270–320 nm, which penetrates to the vascular layer and stimulates the functioning of the fatty glands and nerve endings. Finally, radiation with a wavelength of 320–390 nm passes through the dermis, leading to pigmentation, often without prior erythema. The role of pigmentation, as well as the mechanism of pigmentation, has not yet been sufficiently studied. It is possible that melanin retains active fragments of destroyed molecules, preventing them from entering the blood. The effect of ultraviolet radiation is not limited to the skin, despite the fact that it itself does not penetrate deep into the body. Photolysis products, spreading through the capillaries, irritate the nerve endings of the skin and, through the central nervous system, affect all organs to one degree or another. It has been established that in the nerves extending from irradiated areas of the skin, the frequency of electrical impulses increases. The effect of irradiation is enhanced if the skin is pre-moistened with water, irradiated with a high-frequency electric field or ultrasound. This once again indicates that the primary effect of ultraviolet irradiation begins in the skin and is accompanied by a general increase in metabolism and an increase in the immunobiological state of the body, and this, in turn, leads to an acceleration of the processes of resorption of pathological products and tissue regeneration.
Among other biological effects of ultraviolet irradiation, noteworthy is the formation of vitamin D, which promotes absorption from the intestines and assimilation of calcium, which is part of the bones and performs a number of essential physiological functions. With a lack of vitamin D, calcium in food is not absorbed and the need for it is met by bone calcium, and this leads to rickets. In children with rickets, the formation of the skeleton is disrupted, the bones become flexible, and the children stop walking and growing. Vitamin D can also be formed in the body itself under the influence of ultraviolet radiation with wavelengths from 280 to 315 nm. The most effective is combined irradiation with ultraviolet, infrared rays and visible light.
Photohemotherapy. For diseases accompanied by an increase in blood viscosity, the method of photohemotherapy is used to reduce blood viscosity. It consists of taking a small amount of blood from the patient (about 2 ml/kg of body weight), exposing it to UV irradiation and injecting it back into the bloodstream. Approximately 5 minutes after administering 100-200 ml of irradiated blood to patients, a significant decrease in viscosity is observed in the entire volume (about 5 l) of circulating blood. Studies of the dependence of viscosity on blood speed have shown that during photohemotherapy, viscosity decreases most strongly (by about 30%) in slow-moving blood and does not change at all in fast-moving blood. UV irradiation causes a decrease in the ability of red blood cells to aggregate and increases the deformability of red blood cells. In addition, there is a reduction in the formation of blood clots. All these phenomena lead to a significant improvement in both macro- and microcirculation.
Research in recent years has shown the promise of ultraviolet autohemotherapy, i.e. irradiation of blood in order to stimulate the protective properties of the body in various internal diseases, as well as in symptomatic infertility. Blood for irradiation is mixed with an anticoagulant, irradiated in quartz cuvettes and injected back into the blood vessel of the same person.
Therapeutic use of UV radiation. In rehabilitation physiotherapeutic methods, ultraviolet radiation of the long-wave (A), medium-wave (B), and short-wave (C) ranges is widely used. When ultraviolet radiation quanta are absorbed in tissues (skin), various photochemical and photobiological reactions occur.
Irradiation is created by artificial sources: lamps high pressure(mercury arc tubes), fluorescent lamps, low-pressure gas-discharge lamps, one of the varieties of which are bactericidal lamps. Sources are divided into integral, which emit all areas of the spectrum, and selective, which create radiation predominantly in one area.
Long wave irradiation(predominant erythema and tanning effect). It is used in the treatment of many dermatological diseases. Some chemical compounds of the furocoumarin series (for example, psoralen) can sensitize the skin of these patients to long-wave ultraviolet radiation and stimulate the formation of melanin pigment in melanocytes. The combined use of these drugs and subsequent irradiation with long-wave ultraviolet irradiation is the basis of a treatment method called photochemotherapy or PUVA therapy (PUVA: P – psoralen, UVA – ultraviolet radiation of zone A). In this case, part or the entire body is irradiated.
Medium wave irradiation(mainly vitamin-forming, anti-rickets effect).
Shortwave irradiation(mainly bactericidal effect). Under its influence, the structure of microorganisms and fungi is destroyed. It is created using mercury-quartz bactericidal lamps, Fig. 30.8a. Irradiators are used (Fig. 30.85) for local irradiation of the nasal mucosa and tonsils.
Some techniques use short-wave radiation to irradiate the blood.
Ultraviolet fasting. Many people are under-exposed to radiation. These are residents of the Far North, the Arctic, workers of the mining industry, metro, windowless industries, residents major cities. In cities, the lack of sunlight is associated with atmospheric air pollution with dust, smoke, and gases, which mainly retain the UV part of the solar spectrum. Indoors, window glass does not transmit UV rays with wavelength l< 310 нм. Резко снижают УФ поток загрязненные стекла, занавеси (тюлевые занавески снижают УФ излучение на 20%). Поэтому на многих производствах и в быту наблюдается так называемая «биологическая полутьма». В первую очередь страдают дети (возрастает вероятность заболевания рахитом). Поэтому для организации освещения всегда необходимо проводить санитарно-реабилитологические мероприятия.
The dangers of ultraviolet radiation. Along with the positive biological effects of this radiation on the body, the negative aspects of radiation should also be noted. First of all, this applies to the consequences of uncontrolled sunbathing: burns, age spots, eye damage - the development of photoophthalmia. The effect of ultraviolet radiation on the eye is similar to erythema, since it is associated with the decomposition of proteins in the cells of the cornea and mucous membranes of the eye. Living human skin cells are protected from the destructive effects of UV rays by “dead” cells of the stratum corneum of the skin. The eyes are deprived of this protection, therefore, with a significant dose of radiation to the eyes, after a latent period, inflammation of the cornea (keratitis) and the mucous membrane of the eye (conjunctivitis) develops. This effect is due to radiation with a wavelength shorter than 310 nm. The blastomogenic effect of UV radiation, leading to the development of skin cancer, deserves special consideration. Skin cancer is common among all peoples of the globe living in different climatic conditions.
It should also be noted that UV radiation has a harmful effect on the eyes, since the mucous membrane of the eye (conjunctiva) does not have a protective stratum corneum, and therefore the eye is more sensitive to ultraviolet radiation than the skin. Ultraviolet rays, reaching the lens, at certain doses, cause its clouding - cataracts. Therefore, all work with ultraviolet radiation must be carried out with protective glasses.
With UV irradiation, even at the moment of receiving a dangerous dose, a person does not feel anything. There are no specialized UV receptors in the skin. This radiation is not perceived by the eye, the thermal effect is so small that a person practically does not feel it.
It has been established that the effect of UV radiation is the main factor causing skin cancer, as well as cataracts (clouding of the lens). For polar explorers and climbers, UV radiation is dangerous because due to the high intensity of this radiation, sunburns of the skin and eyes appear.
Lack of UV can lead to D-beri deficiency. UV can cause positive effects. Thus, in patients with skin dermatoses (for example, psoriasis), the diseases worsen in winter, and improvement occurs in summer. The reason is the therapeutic effect of UV, which is much greater in the spectrum of sunlight in summer than in winter.
Tanning is often recommended as a rehabilitation method for many diseases. The action of UV radiation causes hyperpigmentation of the skin, which causes tanning. Tanning is a “slow” photobiological process. It begins to develop 2-3 days after irradiation, reaches a maximum at 13-21 days and then fades away within several months. The spectrum of action of tanning is similar to the spectrum of action of erythema. Ultraviolet light triggers a complex chain of biosynthesis of the skin pigment melanin in specialized cells - melanocytes. The appearance of melanin is a protective reaction of the body.
Tanning should not be overused. Once on the beach in the spring, a person should not forget that our skin has lost its melanin protection over the winter. The minimum dose of ultraviolet radiation that triggers melanogenesis is approximately half the minimum erythemal dose. Therefore, in the first days you should sunbathe for a very short time, so that erythema does not yet appear, and the formation of pigment is already initiated. And only after a few days, having accumulated melanin in the skin, you can gradually increase the time you spend under the sun. After tanning, you should not overexpose yourself to sunlight. Ultraviolet radiation (especially UV-B) causes a number of undesirable effects: premature aging of the skin, the appearance of wrinkles on exposed areas of the body, and skin cancer may develop.
UV radiation initiates the suppression of cell-mediated immunity - immunosuppression.
In medicine, UV is widely used in the method of photohemotherapy, used for diseases associated with increased blood viscosity.
The large doses of UV (especially UV-B) that humans can receive are associated with the state of the atmosphere, in particular the ozone holes in the atmosphere. Stratospheric ozone defines the short-wavelength limit of solar ultraviolet radiation. Ozone destruction occurs, in particular, when fluorocarbon compounds, widely used in industrial and household refrigerators, as well as in the manufacture of aerosols, are released into the atmosphere. The diagram of the protective effect of the ozone layer and the process of its destruction by nitrogen oxide NO are shown in Fig..
Rice. Scheme of the protective effect of the ozone layer (a) and the process of its destruction by nitrogen oxide NO (b); dark arrows – thermal radiation, light arrows – UV radiation
Ozone destruction occurs because the nitrogen atoms in polluting gas molecules interact strongly with one of the oxygen atoms in the ozone molecule and tear it away from it. As a result, oxygen is formed, through which UV radiation passes unhindered.
General characteristics
Ultraviolet rays have the greatest biological activity. Under natural conditions, the sun is a powerful source of ultraviolet rays. However, only the long-wavelength part reaches earth's surface. Shorter wavelength radiation is absorbed by the atmosphere already at an altitude of 30-50 km from the earth's surface.
The highest intensity of ultraviolet radiation flux occurs shortly before noon with a maximum in the spring months.
As already indicated, ultraviolet rays have significant photochemical activity, which is widely used in practice. Ultraviolet irradiation is used in the synthesis of a number of substances, bleaching fabrics, making patent leather, photocopying drawings, obtaining vitamin D and other production processes.
An important property of ultraviolet rays is their ability to cause luminescence.
In some processes, workers are exposed to ultraviolet rays, for example, electric arc welding, autogenous cutting and welding, the production of radio tubes and mercury rectifiers, casting and smelting of metals and some minerals, photocopying, water sterilization, etc. Medical and technical personnel servicing mercury-quartz lamps.
Ultraviolet rays have the ability to change chemical structure tissues and cells.
Ultraviolet wavelength
The biological activity of ultraviolet rays of different wavelengths is not the same. Ultraviolet rays with a wavelength from 400 to 315 mμ. have a relatively weak biological effect. Rays with shorter wavelengths are more biologically active. Ultraviolet rays with a length of 315-280 mμ have a strong skin and antirachitic effect. Radiation with a wavelength of 280-200 mμ is especially active. (bactericidal effect, the ability to actively influence tissue proteins and lipoids, as well as cause hemolysis).
In industrial conditions, exposure to ultraviolet rays with a wavelength from 36 to 220 mμ occurs. i.e., having significant biological activity.
Unlike heat rays, the main property of which is the development of hyperemia in areas exposed to irradiation, the effect of ultraviolet rays on the body appears to be much more complex.
Ultraviolet rays penetrate the skin relatively little and their biological effect is associated with the development of many neurohumoral processes, which determine the complex nature of their influence on the body.
Ultraviolet erythema
Depending on the intensity of the light source and the content of infrared or ultraviolet rays in its spectrum, changes in the skin will be different.
Exposure to ultraviolet rays on the skin causes a characteristic reaction from the skin vessels - ultraviolet erythema. Ultraviolet erythema is significantly different from heat erythema caused by infrared radiation.
Usually when used infrared rays no pronounced changes in the skin are observed, since the resulting burning sensation and pain prevent prolonged exposure to these rays. Erythema, which develops as a result of the action of infrared rays, occurs immediately after irradiation, is unstable, does not last long (30-60 minutes) and is mainly nested in nature. After prolonged exposure to infrared rays, brown pigmentation of a spotted appearance appears.
Ultraviolet erythema appears after irradiation following a certain latent period. This period ranges from different people from 2 to 10 hours. The duration of the latent period of ultraviolet erythema is known to depend on the wavelength: erythema from long-wave ultraviolet rays appears later and lasts longer than from short-wave ultraviolet rays.
Erythema caused by ultraviolet rays has a bright red color with sharp boundaries that exactly correspond to the area of irradiation. The skin becomes somewhat swollen and painful. Erythema reaches its greatest development 6-12 hours after its appearance, lasts for 3-5 days and gradually turns pale, acquiring a brown tint, and a uniform and intense darkening of the skin occurs due to the formation of pigment in it. In some cases, slight peeling is observed during the period of disappearance of erythema.
The degree of development of erythema depends on the dose of ultraviolet rays and individual sensitivity. All other things being equal, the higher the dose of ultraviolet rays, the more intense the inflammatory reaction of the skin. The most pronounced erythema is caused by rays with wavelengths of about 290 mμ. With an overdose of ultraviolet irradiation, the erythema acquires a bluish tint, the edges of the erythema become blurred, and the irradiated area is swollen and painful. Intense radiation can cause a burn with the development of a blister.
Sensitivity of various areas of the skin to ultraviolet radiation
Skin of the abdomen, lower back, lateral surfaces chest have the greatest sensitivity to ultraviolet rays. The least sensitive skin is the hands and face.
Persons with delicate, weakly pigmented skin, children, as well as those suffering from Graves' disease and vegetative dystonia are more sensitive. Increased sensitivity of the skin to ultraviolet rays is observed in the spring.
It has been established that the sensitivity of the skin to ultraviolet rays can vary depending on the physiological state of the body. The development of an erythemal reaction depends primarily on the functional state nervous system.
In response to ultraviolet irradiation, a pigment is formed and deposited in the skin, which is a product of protein metabolism of the skin (organic coloring matter - melanin).
Long-wave ultraviolet rays cause a more intense tan than short-wave ultraviolet rays. With repeated ultraviolet irradiation, the skin becomes less susceptible to these rays. Skin pigmentation often develops without previously visible erythema. In pigmented skin, ultraviolet rays do not cause photoerythema.
Positive effects of ultraviolet radiation
Ultraviolet rays reduce the excitability of sensory nerves (analgesic effect) and also have an antispastic and antirachitic effect. Under the influence of ultraviolet rays, vitamin D, which is very important for phosphorus-calcium metabolism, is formed (ergosterol found in the skin is converted into vitamin D). Under the influence of ultraviolet rays, oxidative processes in the body intensify, the absorption of oxygen by tissues and the release of carbon dioxide increases, enzymes are activated, and protein and carbohydrate metabolism improves. The content of calcium and phosphates in the blood increases. Hematopoiesis, regenerative processes, blood supply and tissue trophism improve. Skin blood vessels dilate, blood pressure decreases, and the overall biotone of the body increases.
The beneficial effect of ultraviolet rays is expressed in a change in the immunobiological reactivity of the body. Irradiation stimulates the production of antibodies, increases phagocytosis, and tones the reticuloendothelial system. Thanks to this, the body's resistance to infections increases. Important radiation dosage has a role in this regard.
A number of substances of animal and plant origin (hematoporphyrin, chlorophyll, etc.), some chemicals (quinine, streptocide, sulfidine, etc.), especially fluorescent dyes (eosin, methylene blue, etc.), have the property increase the body's sensitivity to light. In industry, people working with coal tar experience skin diseases on exposed parts of the body (itching, burning, redness), and these phenomena disappear at night. This is due to the photosensitizing properties of acridine contained in coal tar. Sensitization occurs primarily in relation to visible rays and to a lesser extent in relation to ultraviolet rays.
Of great practical importance is the ability of ultraviolet rays to kill various bacteria (the so-called bactericidal effect). This effect is especially intense in ultraviolet rays with wavelengths shorter (265 - 200 mμ). The bactericidal effect of light is associated with the effect on the protoplasm of bacteria. It has been proven that after ultraviolet irradiation, mitogenetic radiation in cells and blood increases.
By modern ideas, the action of light on the body is based mainly on a reflex mechanism, although great value is also given to humoral factors. This especially applies to the action of ultraviolet rays. It is also necessary to keep in mind the possibility of visible rays acting through the organs of vision on the cortex and vegetative centers.
In the development of light-induced erythema, significant importance is attached to the influence of rays on the receptor apparatus of the skin. When exposed to ultraviolet rays, as a result of the breakdown of proteins in the skin, histamine and histamine-like products are formed, which dilate skin vessels and increase their permeability, which leads to hyperemia and swelling. The products formed in the skin when exposed to ultraviolet rays (histamine, vitamin D, etc.) enter the blood and cause those general changes in the body that occur during irradiation.
Thus, the processes developing in the irradiated area lead through a neurohumoral pathway to the development of a general reaction of the body. This reaction is determined mainly by the state of the higher regulatory parts of the central nervous system, which, as is known, can change under the influence of various factors.
It is impossible to talk about the biological effect of ultraviolet irradiation in general, regardless of the wavelength. Short-wave ultraviolet radiation causes denaturation of protein substances, long-wave radiation causes photolytic decomposition. The specific effect of different parts of the ultraviolet radiation spectrum is revealed mainly in the initial stage.
Application of ultraviolet radiation
The broad biological effect of ultraviolet rays makes it possible to use them in certain doses for preventive and therapeutic purposes.
For ultraviolet irradiation, sunlight is used, as well as artificial irradiation sources: mercury-quartz and argon-mercury-quartz lamps. The emission spectrum of mercury-quartz lamps is characterized by the presence of shorter ultraviolet rays than in the solar spectrum.
Ultraviolet irradiation can be general or local. The dosage of procedures is carried out according to the principle of biodoses.
Currently, ultraviolet irradiation is widely used, primarily for prevention. various diseases. For this purpose, ultraviolet irradiation is used to improve the health of the external environment around a person and change his reactivity (primarily to increase his immunobiological properties).
With the help of special bactericidal lamps, air can be sterilized in medical institutions and residential premises, milk, water, etc. can be sterilized. Ultraviolet irradiation is widely used to prevent rickets, influenza, and for the general strengthening of the body in medical and children's institutions, schools, and gyms , fotariums in coal mines, when training athletes, for acclimatization to northern conditions, when working in hot shops (ultraviolet irradiation gives a greater effect in combination with exposure to infrared radiation).
Ultraviolet rays are especially widely used to expose children to radiation. First of all, such irradiation is indicated for weakened, often ill children living in northern and middle latitudes. At the same time it improves general condition children, sleep, weight increases, morbidity decreases, the frequency of catarrhal phenomena and the duration of diseases decreases. General improvement physical development, blood and vascular permeability are normalized.
Ultraviolet irradiation of miners in fotariums, which are organized in large numbers at mining enterprises, has also become widespread. With systematic mass exposure of miners engaged in underground work, there is an improvement in well-being, increased ability to work, reduced fatigue, and a decrease in morbidity with temporary loss of ability to work. After irradiation of miners, the percentage of hemoglobin increases, monocytosis appears, the number of cases of influenza decreases, the incidence of the musculoskeletal system and peripheral nervous system decreases, pustular skin diseases and catarrhs of the upper respiratory tract and sore throats, vital capacity and lung readings improve.
Application of ultraviolet radiation in medicine
The use of ultraviolet rays for therapeutic purposes is based mainly on the anti-inflammatory, antineuralgic and desensitizing effects of this type of radiant energy.
In combination with others therapeutic measures ultraviolet irradiation is carried out:
1) in the treatment of rickets;
2) after suffering infectious diseases;
3) for tuberculous diseases of bones, joints, lymph nodes;
4) with fibrous pulmonary tuberculosis without phenomena indicating activation of the process;
5) for diseases of the peripheral nervous system, muscles and joints;
6) for skin diseases;
7) for burns and frostbite;
8) for purulent complications of wounds;
9) during resorption of infiltrates;
10) in order to accelerate regenerative processes in case of injuries to bones and soft tissues.
Contraindications to irradiation are:
1) malignant neoplasms (since irradiation accelerates their growth);
2) severe exhaustion;
3) increased thyroid function;
4) severe cardiovascular diseases;
5) active pulmonary tuberculosis;
6) kidney diseases;
7) pronounced changes in the central nervous system.
It should be remembered that obtaining pigmentation, especially in short term, should not be the goal of treatment. In some cases, a good therapeutic effect is observed even with weak pigmentation.
Negative effects of ultraviolet radiation
Prolonged and intense ultraviolet irradiation can have an adverse effect on the body and cause pathological changes. With significant exposure, fatigue, headaches, drowsiness, memory loss, irritability, palpitations, and decreased appetite are observed. Excessive radiation can cause hypercalcemia, hemolysis, growth retardation, and decreased resistance to infection. With strong irradiation, burns and dermatitis develop (burning and itching of the skin, diffuse erythema, swelling). At the same time, there is an increase in body temperature, headache, brokenness. Burns and dermatitis that occur under the influence of solar radiation are associated primarily with the influence of ultraviolet rays. Those working at outdoors under the influence of solar radiation, long-term and severe dermatitis can occur. It is necessary to remember about the possibility of the described dermatitis turning into cancer.
Depending on the depth of penetration of rays from different parts of the solar spectrum, eye changes may develop. Acute retinitis occurs under the influence of infrared and visible rays. The so-called glassblower's cataract, which develops as a result of prolonged absorption of infrared rays by the lens, is well known. Clouding of the lens occurs slowly, mainly among workers in hot shops with work experience of 20-25 years or more. Currently, occupational cataracts in hot shops are rare due to significant improvements in working conditions. The cornea and conjunctiva react mainly to ultraviolet rays. These rays (especially with a wavelength of less than 320 mμ.) cause in some cases an eye disease known as photoophthalmia or electroophthalmia. This disease is most common among electric welders. In such cases, acute keratoconjunctivitis is often observed, which usually occurs 6-8 hours after work, often at night.
With electroophthalmia, hyperemia and swelling of the mucous membrane, blepharospasm, photophobia, and lacrimation are noted. Corneal lesions are often found. The duration of the acute period of the disease is 1-2 days. In people who work outdoors in bright sunlight in wide spaces covered with snow, photoophthalmia sometimes occurs in the form of so-called snow blindness. Treatment of photoophthalmia consists of staying in the dark, using novocaine and cold lotions.
UV protection products
To protect the eyes from the adverse effects of ultraviolet rays in production, they use shields or helmets with special dark glasses, safety glasses, and to protect other parts of the body and surrounding persons - insulating screens, portable screens, and special clothing.
Ultraviolet rays have the greatest biological activity. Under natural conditions, the sun is a powerful source of ultraviolet rays. However, only the long-wave part of it reaches the earth's surface. Shorter wavelength radiation is absorbed by the atmosphere already at an altitude of 30-50 km from the earth's surface.
The highest intensity of ultraviolet radiation flux occurs shortly before noon with a maximum in the spring months.
As already indicated, ultraviolet rays have significant photochemical activity, which is widely used in practice. Ultraviolet irradiation is used in the synthesis of a number of substances, bleaching fabrics, making patent leather, photocopying drawings, obtaining vitamin D and other production processes.
An important property of ultraviolet rays is their ability to cause luminescence.
In some processes, workers are exposed to ultraviolet rays, for example, electric arc welding, autogenous cutting and welding, the production of radio tubes and mercury rectifiers, casting and smelting of metals and some minerals, photocopying, water sterilization, etc. Medical and technical personnel servicing mercury-quartz lamps.
Ultraviolet rays have the ability to change the chemical structure of tissues and cells.
Ultraviolet wavelength
The biological activity of ultraviolet rays of different wavelengths is not the same. Ultraviolet rays with a wavelength from 400 to 315 mμ. have a relatively weak biological effect. Rays with shorter wavelengths are more biologically active. Ultraviolet rays with a length of 315-280 mμ have a strong skin and antirachitic effect. Radiation with a wavelength of 280-200 mμ is especially active. (bactericidal effect, the ability to actively influence tissue proteins and lipoids, as well as cause hemolysis).
In industrial conditions, exposure to ultraviolet rays with a wavelength from 36 to 220 mμ occurs, i.e., having significant biological activity.
Unlike heat rays, the main property of which is the development of hyperemia in areas exposed to irradiation, the effect of ultraviolet rays on the body appears to be much more complex.
Ultraviolet rays penetrate the skin relatively little and their biological effect is associated with the development of many neurohumoral processes, which determine the complex nature of their influence on the body.
Ultraviolet erythema
Depending on the intensity of the light source and the content of infrared or ultraviolet rays in its spectrum, changes in the skin will be different.
Exposure to ultraviolet rays on the skin causes a characteristic reaction from the skin vessels - ultraviolet erythema. Ultraviolet erythema is significantly different from heat erythema caused by infrared radiation.
Usually, when using infrared rays, no pronounced changes in the skin are observed, since the resulting burning sensation and pain prevent prolonged exposure to these rays. Erythema, which develops as a result of the action of infrared rays, occurs immediately after irradiation, is unstable, does not last long (30-60 minutes) and is mainly nested in nature. After prolonged exposure to infrared rays, brown pigmentation of a spotted appearance appears.
Ultraviolet erythema appears after irradiation following a certain latent period. This period varies among different people from 2 to 10 hours. The duration of the latent period of ultraviolet erythema is known to depend on the wavelength: erythema from long-wave ultraviolet rays appears later and lasts longer than from short-wave ultraviolet rays.
Erythema caused by ultraviolet rays has a bright red color with sharp boundaries that exactly correspond to the area of irradiation. The skin becomes somewhat swollen and painful. Erythema reaches its greatest development 6-12 hours after its appearance, lasts for 3-5 days and gradually turns pale, acquiring a brown tint, and a uniform and intense darkening of the skin occurs due to the formation of pigment in it. In some cases, slight peeling is observed during the period of disappearance of erythema.
The degree of development of erythema depends on the dose of ultraviolet rays and individual sensitivity. All other things being equal, the higher the dose of ultraviolet rays, the more intense the inflammatory reaction of the skin. The most pronounced erythema is caused by rays with wavelengths of about 290 mμ. With an overdose of ultraviolet irradiation, the erythema acquires a bluish tint, the edges of the erythema become blurred, and the irradiated area is swollen and painful. Intense radiation can cause a burn with the development of a blister.
Sensitivity of various areas of the skin to ultraviolet radiation
The skin of the abdomen, lower back, and lateral surfaces of the chest is most sensitive to ultraviolet rays. The least sensitive skin is the hands and face.
Persons with delicate, weakly pigmented skin, children, as well as those suffering from Graves' disease and vegetative dystonia are more sensitive. Increased sensitivity of the skin to ultraviolet rays is observed in the spring.
It has been established that the sensitivity of the skin to ultraviolet rays can vary depending on the physiological state of the body. The development of an erythema reaction depends primarily on the functional state of the nervous system.
In response to ultraviolet irradiation, a pigment is formed and deposited in the skin, which is a product of protein metabolism of the skin (organic coloring matter - melanin).
Long-wave ultraviolet rays cause a more intense tan than short-wave ultraviolet rays. With repeated ultraviolet irradiation, the skin becomes less susceptible to these rays. Skin pigmentation often develops without previously visible erythema. In pigmented skin, ultraviolet rays do not cause photoerythema.
Positive effects of ultraviolet radiation
Ultraviolet rays reduce the excitability of sensory nerves (analgesic effect) and also have an antispastic and antirachitic effect. Under the influence of ultraviolet rays, vitamin D, which is very important for phosphorus-calcium metabolism, is formed (ergosterol found in the skin is converted into vitamin D). Under the influence of ultraviolet rays, oxidative processes in the body intensify, the absorption of oxygen by tissues and the release of carbon dioxide increases, enzymes are activated, and protein and carbohydrate metabolism improves. The content of calcium and phosphates in the blood increases. Hematopoiesis, regenerative processes, blood supply and tissue trophism improve. Skin blood vessels dilate, blood pressure decreases, and the overall biotone of the body increases.
The beneficial effect of ultraviolet rays is expressed in a change in the immunobiological reactivity of the body. Irradiation stimulates the production of antibodies, increases phagocytosis, and tones the reticuloendothelial system. Thanks to this, the body's resistance to infections increases. The dose of radiation is important in this regard.
A number of substances of animal and plant origin (hematoporphyrin, chlorophyll, etc.), some chemicals (quinine, streptocide, sulfidine, etc.), especially fluorescent dyes (eosin, methylene blue, etc.), have the property increase the body's sensitivity to light. In industry, people working with coal tar experience skin diseases on exposed parts of the body (itching, burning, redness), and these phenomena disappear at night. This is due to the photosensitizing properties of acridine contained in coal tar. Sensitization occurs predominantly to visible rays and to a lesser extent to ultraviolet rays.
Of great practical importance is the ability of ultraviolet rays to kill various bacteria (the so-called bactericidal effect). This effect is especially intense in ultraviolet rays with wavelengths shorter (265 - 200 mμ). The bactericidal effect of light is associated with the effect on the protoplasm of bacteria. It has been proven that after ultraviolet irradiation, mitogenetic radiation in cells and blood increases.
According to modern ideas, the action of light on the body is based mainly on the reflex mechanism, although great importance is also attached to humoral factors. This especially applies to the action of ultraviolet rays. It is also necessary to keep in mind the possibility of visible rays acting through the organs of vision on the cortex and vegetative centers.
In the development of light-induced erythema, significant importance is attached to the influence of rays on the receptor apparatus of the skin. When exposed to ultraviolet rays, as a result of the breakdown of proteins in the skin, histamine and histamine-like products are formed, which dilate skin vessels and increase their permeability, which leads to hyperemia and swelling. The products formed in the skin when exposed to ultraviolet rays (histamine, vitamin D, etc.) enter the blood and cause those general changes in the body that occur during irradiation.
Thus, the processes developing in the irradiated area lead through a neurohumoral pathway to the development of a general reaction of the body. This reaction is determined mainly by the state of the higher regulatory parts of the central nervous system, which, as is known, can change under the influence of various factors.
It is impossible to talk about the biological effect of ultraviolet irradiation in general, regardless of the wavelength. Short-wave ultraviolet radiation causes denaturation of protein substances, long-wave radiation causes photolytic decomposition. The specific effect of different parts of the ultraviolet radiation spectrum is revealed mainly in the initial stage.
Application of ultraviolet radiation
The broad biological effect of ultraviolet rays makes it possible to use them in certain doses for preventive and therapeutic purposes.
For ultraviolet irradiation, sunlight is used, as well as artificial irradiation sources: mercury-quartz and argon-mercury-quartz lamps. The emission spectrum of mercury-quartz lamps is characterized by the presence of shorter ultraviolet rays than in the solar spectrum.
Ultraviolet irradiation can be general or local. The dosage of procedures is carried out according to the principle of biodoses.
Currently, ultraviolet irradiation is widely used, primarily for the prevention of various diseases. For this purpose, ultraviolet irradiation is used to improve the health of the external environment around a person and change his reactivity (primarily to increase his immunobiological properties).
With the help of special bactericidal lamps, air can be sterilized in medical institutions and residential premises, milk, water, etc. can be sterilized. Ultraviolet irradiation is widely used to prevent rickets, influenza, and for the general strengthening of the body in medical and children's institutions, schools, and gyms , fotariums in coal mines, when training athletes, for acclimatization to northern conditions, when working in hot shops (ultraviolet irradiation gives a greater effect in combination with exposure to infrared radiation).
Ultraviolet rays are especially widely used to expose children to radiation. First of all, such irradiation is indicated for weakened, often ill children living in northern and middle latitudes. At the same time, the general condition of children, sleep, weight increases, morbidity decreases, the frequency of catarrhal phenomena and the duration of diseases decreases. General physical development improves, blood and vascular permeability are normalized.
Ultraviolet irradiation of miners in fotariums, which are organized in large numbers at mining enterprises, has also become widespread. With systematic mass exposure of miners engaged in underground work, there is an improvement in well-being, increased ability to work, reduced fatigue, and a decrease in morbidity with temporary loss of ability to work. After irradiation of miners, the percentage of hemoglobin increases, monocytosis appears, the number of cases of influenza decreases, the incidence of the musculoskeletal system and peripheral nervous system decreases, pustular skin diseases, catarrh of the upper respiratory tract and tonsillitis are observed less frequently, and vital capacity and lung readings improve.
Application of ultraviolet radiation in medicine
The use of ultraviolet rays for therapeutic purposes is based mainly on the anti-inflammatory, antineuralgic and desensitizing effects of this type of radiant energy.
In combination with other therapeutic measures, ultraviolet irradiation is carried out:
1) in the treatment of rickets;
2) after suffering infectious diseases;
3) for tuberculous diseases of bones, joints, lymph nodes;
4) with fibrous pulmonary tuberculosis without phenomena indicating activation of the process;
5) for diseases of the peripheral nervous system, muscles and joints;
6) for skin diseases;
7) for burns and frostbite;
8) for purulent complications of wounds;
9) during resorption of infiltrates;
10) in order to accelerate regenerative processes in case of injuries to bones and soft tissues.
Contraindications to irradiation are:
1) malignant neoplasms (since irradiation accelerates their growth);
2) severe exhaustion;
3) increased thyroid function;
4) severe cardiovascular diseases;
5) active pulmonary tuberculosis;
6) kidney diseases;
7) pronounced changes in the central nervous system.
It should be remembered that obtaining pigmentation, especially in a short time, should not be the goal of treatment. In some cases, a good therapeutic effect is observed even with weak pigmentation.
Negative effects of ultraviolet radiation
Prolonged and intense ultraviolet irradiation can have an adverse effect on the body and cause pathological changes. With significant exposure, fatigue, headaches, drowsiness, memory loss, irritability, palpitations, and decreased appetite are observed. Excessive radiation can cause hypercalcemia, hemolysis, growth retardation, and decreased resistance to infection. With strong irradiation, burns and dermatitis develop (burning and itching of the skin, diffuse erythema, swelling). In this case, there is an increase in body temperature, headache, and fatigue. Burns and dermatitis that occur under the influence of solar radiation are associated primarily with the influence of ultraviolet rays. People who work outdoors under the influence of solar radiation may develop long-term and severe dermatitis. It is necessary to remember about the possibility of the described dermatitis turning into cancer.
Depending on the depth of penetration of rays from different parts of the solar spectrum, eye changes may develop. Acute retinitis occurs under the influence of infrared and visible rays. The so-called glassblower's cataract, which develops as a result of prolonged absorption of infrared rays by the lens, is well known. Clouding of the lens occurs slowly, mainly among workers in hot shops with work experience of 20-25 years or more. Currently, occupational cataracts in hot shops are rare due to significant improvements in working conditions. The cornea and conjunctiva react mainly to ultraviolet rays. These rays (especially with a wavelength of less than 320 mμ.) cause in some cases an eye disease known as photoophthalmia or electroophthalmia. This disease is most common among electric welders. In such cases, acute keratoconjunctivitis is often observed, which usually occurs 6-8 hours after work, often at night.
With electroophthalmia, hyperemia and swelling of the mucous membrane, blepharospasm, photophobia, and lacrimation are noted. Corneal lesions are often found. The duration of the acute period of the disease is 1-2 days. In people who work outdoors in bright sunlight in wide spaces covered with snow, photoophthalmia sometimes occurs in the form of so-called snow blindness. Treatment of photoophthalmia consists of staying in the dark, using novocaine and cold lotions.
UV protection products
To protect the eyes from the adverse effects of ultraviolet rays in production, they use shields or helmets with special dark glasses, safety glasses, and to protect other parts of the body and surrounding persons - insulating screens, portable screens, and special clothing.
