In 1801, I. Ritter (Germany) and W. Walaston (England), using a photographic plate, proved the presence of ultraviolet rays. Beyond the violet end of the spectrum, it turns black faster than under the influence of visible rays. Since the blackening of the plate occurs as a result of a photochemical reaction, scientists have concluded that ultraviolet rays are very active.
Ultraviolet rays cover a wide range of radiation: 400...20 nm. The radiation region of 180... 127 nm is called vacuum. Using artificial sources (mercury-quartz, hydrogen and arc lamps), providing both a line and a continuous spectrum, ultraviolet rays with a wavelength of up to 180 nm are obtained. In 1914, Lyman explored the range up to 50 nm.
Researchers have discovered the fact that the spectrum of ultraviolet rays from the sun reaching earth's surface, very narrow - 400...290 nm. Doesn't the sun emit light with a wavelength shorter than 290 nm?
The answer to this question was found by A. Cornu (France). He found that ozone absorbs ultraviolet rays shorter than 295 nm, after which he put forward the hypothesis: the Sun emits short-wave ultraviolet radiation, under its influence oxygen molecules disintegrate into individual atoms, forming ozone molecules, so in the upper layers of the atmosphere, ozone should cover the ground with a protective shield. Cornu's hypothesis was confirmed when people rose to the upper atmosphere. Thus, in terrestrial conditions The sun's spectrum is limited by the transmission of the ozone layer.
The amount of ultraviolet rays reaching the earth's surface depends on the height of the Sun above the horizon. During the period of normal illumination, the illumination changes by 20%, while the amount of ultraviolet rays reaching the earth's surface decreases by 20 times.
Special experiments have established that when rising upward for every 100 m, the intensity of ultraviolet radiation increases by 3...4%. The share of scattered ultraviolet radiation at summer noon accounts for 45...70% of the radiation, and that reaching the earth's surface - 30...55%. IN cloudy days When the disk of the Sun is covered with clouds, mainly scattered radiation reaches the Earth's surface. Therefore, you can tan well not only in direct sunlight, but also in the shade and on cloudy days.
When the Sun is at its zenith, rays with a length of 290...289 nm reach the earth's surface in the equatorial region. In mid-latitudes, the short-wave limit, during the summer months, is approximately 297 nm. During the period of effective lighting upper limit spectrum is about 300 nm. Beyond the Arctic Circle, rays with a wavelength of 350...380 nm reach the earth's surface.
The influence of ultraviolet radiation on the biosphere
Above the range of vacuum radiation, ultraviolet rays are easily absorbed by water, air, glass, quartz and do not reach the Earth's biosphere. In the range of 400... 180 nm, the effect on living organisms of rays of different wavelengths is not the same. The most energy-rich short-wave rays played a significant role in the formation of the first complex organic compounds on Earth. However, these rays contribute not only to the formation, but also to the decay organic matter. Therefore, the progress of life forms on Earth occurred only after, thanks to the activity of green plants, the atmosphere was enriched with oxygen and, under the influence of ultraviolet rays, a protective ozone layer was formed.Of interest to us are ultraviolet radiation from the Sun and artificial sources of ultraviolet radiation in the range of 400...180 nm. Within this range there are three areas:
A - 400...320 nm;
B - 320...275 nm;
C - 275...180 nm.
There are significant differences in the effect of each of these ranges on a living organism. Ultraviolet rays act on matter, including living matter, according to the same laws as visible light. Part of the absorbed energy is converted into heat, but the thermal effect of ultraviolet rays does not have a noticeable effect on the body. Another way of transmitting energy is luminescence.
Photochemical reactions under the influence of ultraviolet rays are most intense. The energy of ultraviolet light photons is very high, so when they are absorbed, the molecule ionizes and breaks into pieces. Sometimes a photon knocks an electron out of the atom. Most often, excitation of atoms and molecules occurs. When absorbing one quantum of light with a wavelength of 254 nm, the energy of the molecule increases to a level corresponding to the energy of thermal motion at a temperature of 38000°C.
Most of the solar energy reaches the earth as visible light and infrared radiation and only a small part - in the form of ultraviolet radiation. The UV flux reaches its maximum values in midsummer in the Southern Hemisphere (the Earth is 5% closer to the Sun) and 50% of the daily amount of UV arrives within 4 midday hours. Diffey found that for latitudes with temperatures of 20-60°, a person sunbathing from 10:30 to 11:30 and then from 16:30 to sunset will receive only 19% of the daily UV dose. At noon, the UV intensity (300 nm) is 10 times higher than three hours earlier or later: an untanned person needs 25 minutes to get a light tan at noon, but to achieve the same effect after 15:00, he will need to lie in the sun not less than 2 hours.
The ultraviolet spectrum, in turn, is divided into ultraviolet-A (UV-A) with a wavelength of 315-400 nm, ultraviolet-B (UV-B) -280-315 nm and ultraviolet-C (UV-C) - 100-280 nm which differ in penetrating ability and biological effects on the body.
UV-A does not linger ozone layer, passes through glass and the stratum corneum of the skin. The UV-A flux (mean value at noon) is twice as high at the Arctic Circle as at the equator, so its absolute value is greater at high latitudes. There are no significant fluctuations in UV-A intensity in different times year. Due to absorption, reflection and dispersion when passing through the epidermis, only 20-30% of UV-A penetrates into the dermis and about 1% of its total energy reaches the subcutaneous tissue.
Most UV-B is absorbed by the ozone layer, which is "transparent" to UV-A. So the share of UV-B in all ultraviolet radiation energy on a summer afternoon is only about 3%. It practically does not penetrate through glass, 70% is reflected by the stratum corneum, and is weakened by 20% when passing through the epidermis - less than 10% penetrates into the dermis.
However, for a long time it was believed that the share of UV-B in the damaging effects of ultraviolet radiation is 80%, since it is this spectrum that is responsible for the occurrence of sunburn erythema.
It is also necessary to take into account the fact that UV-B is scattered more strongly (shorter wavelength) than UV-A when passing through the atmosphere, which leads to a change in the ratio between these fractions with increasing geographical latitude(V northern countries) and time of day.
UV-C (200-280 nm) is absorbed by the ozone layer. If an artificial ultraviolet source is used, it is retained by the epidermis and does not penetrate the dermis.
The effect of ultraviolet radiation on the cell
In the effect of short-wave radiation on a living organism, the greatest interest is the effect of ultraviolet rays on biopolymers - proteins and nucleic acids. Biopolymer molecules contain ring groups of molecules containing carbon and nitrogen, which intensively absorb radiation with a wavelength of 260...280 nm. Absorbed energy can migrate along a chain of atoms within a molecule without significant loss until it reaches weak bonds between atoms and breaks the bond. During this process, called photolysis, fragments of molecules are formed that have a strong effect on the body. For example, histamine is formed from the amino acid histidine, a substance that dilates blood capillaries and increases their permeability. In addition to photolysis, denaturation occurs in biopolymers under the influence of ultraviolet rays. When irradiated with light of a certain wavelength electric charge molecules decrease, they stick together and lose their activity - enzymatic, hormonal, antigenic, etc.The processes of photolysis and denaturation of proteins occur in parallel and independently of each other. They are caused by different radiation ranges: rays of 280...302 nm cause mainly photolysis, and 250...265 nm - mainly denaturation. The combination of these processes determines the pattern of action of ultraviolet rays on the cell.
The most sensitive cell function to ultraviolet rays is division. Irradiation at a dose of 10(-19) J/m2 causes the division of about 90% of bacterial cells to stop. But the growth and vital activity of cells does not stop. Over time, their division is restored. To cause the death of 90% of cells, suppression of the synthesis of nucleic acids and proteins, and the formation of mutations, it is necessary to increase the radiation dose to 10 (-18) J/m2. Ultraviolet rays cause changes in nucleic acids that affect the growth, division, and heredity of cells, i.e. on the main manifestations of life.
The importance of the mechanism of action on nucleic acid is explained by the fact that each DNA (deoxyribonucleic acid) molecule is unique. DNA is the cell's hereditary memory. Its structure encrypts information about the structure and properties of all cellular proteins. If any protein is present in a living cell in the form of tens or hundreds of identical molecules, then DNA stores information about the structure of the cell as a whole, about the nature and direction of metabolic processes in it. Therefore, disturbances in the DNA structure may be irreparable or lead to serious disruption of life.
The effect of ultraviolet radiation on the skin
Exposure to ultraviolet radiation on the skin significantly affects our body's metabolism. It is well known that it is UV rays that initiate the process of formation of ergocalciferol (vitamin D), which is necessary for the absorption of calcium in the intestine and ensuring the normal development of the bone skeleton. In addition, ultraviolet light actively affects the synthesis of melatonin and serotonin - hormones responsible for the circadian (daily) biological rhythm. Research by German scientists showed that when blood serum was irradiated with UV rays, the content of serotonin, the “hormone of vivacity” involved in the regulation of emotional state. Its deficiency can lead to depression, mood swings, and seasonal functional disorders. At the same time, the amount of melatonin, which has an inhibitory effect on the endocrine and central nervous systems, decreased by 28%. It is this double effect that explains the invigorating effect of the spring sun, which lifts your mood and vitality.The effect of radiation on the epidermis - the outer surface layer of the skin of vertebrates and humans, consisting of human stratified squamous epithelium, is an inflammatory reaction called erythema. First scientific description gave erythema in 1889 by A.N. Maklanov (Russia), who also studied the effect of ultraviolet rays on the eye (photoophthalmia) and found that they are based on common causes.
There are caloric and ultraviolet erythema. Caloric erythema is caused by the effect of visible and infrared rays on the skin and the flow of blood to it. It disappears almost immediately after the irradiation ceases.
After the cessation of exposure to UV radiation, after 2..8 hours, redness of the skin (ultraviolet erythema) appears simultaneously with a burning sensation. Erythema appears after a latent period, within the irradiated area of the skin, and is replaced by tanning and peeling. The duration of erythema ranges from 10...12 hours to 3...4 days. The reddened skin is hot to the touch, slightly painful and appears swollen and slightly swollen.
Essentially, erythema is an inflammatory reaction, a burn of the skin. This is a special, aseptic (Aseptic - putrefactive) inflammation. If the radiation dose is too high or the skin is especially sensitive to it, the edematous fluid accumulates, peels off the outer layer of the skin in places, and forms blisters. In severe cases, areas of necrosis (death) of the epidermis appear. A few days after the erythema disappears, the skin darkens and begins to peel. As peeling occurs, some of the cells containing melanin are exfoliated (Melanin is the main pigment of the human body; it gives color to the skin, hair, and iris of the eye. It is also contained in the pigment layer of the retina and is involved in the perception of light), the tan fades. The thickness of human skin varies depending on gender, age (in children and the elderly - thinner) and location - on average 1..2 mm. Its purpose is to protect the body from damage, temperature fluctuations, and pressure.
The main layer of the epidermis is adjacent to the skin itself (dermis), which contains blood vessels and nerves. In the main layer there is a continuous process of cell division; older ones are forced out by young cells and die. Layers of dead and dying cells form the outer stratum corneum of the epidermis with a thickness of 0.07...2.5 mm (On the palms and soles, mainly due to the stratum corneum, the epidermis is thicker than in other parts of the body), which is continuously exfoliated from the outside and restored from the inside.
If the rays falling on the skin are absorbed by dead cells of the stratum corneum, they have no effect on the body. The effect of irradiation depends on the penetrating ability of the rays and the thickness of the stratum corneum. The shorter the radiation wavelength, the lower their penetrating ability. Rays shorter than 310 nm do not penetrate deeper than the epidermis. Rays with a longer wavelength reach the papillary layer of the dermis, in which blood vessels pass. Thus, the interaction of ultraviolet rays with the substance occurs exclusively in the skin, mainly in the epidermis.
The main amount of ultraviolet rays is absorbed in the germinal (basic) layer of the epidermis. The processes of photolysis and denaturation lead to the death of styloid cells of the germ layer. Active protein photolysis products cause vasodilation, skin swelling, release of leukocytes and other typical signs of erythema.
Photolysis products, spreading through the bloodstream, also irritate the nerve endings of the skin and, through the central nervous system, reflexively affect all organs. It has been established that in the nerve extending from the irradiated area of the skin, the frequency of electrical impulses increases.
Erythema is considered as complex reflex, the formation of which involves active products of photolysis. The severity of erythema and the possibility of its formation depends on the condition nervous system. On affected areas of the skin, with frostbite, or inflammation of the nerves, erythema either does not appear at all or is very weakly expressed, despite the action of ultraviolet rays. The formation of erythema is inhibited by sleep, alcohol, physical and mental fatigue.
N. Finsen (Denmark) first used ultraviolet radiation to treat a number of diseases in 1899. Currently, the manifestations of the effects of different areas of ultraviolet radiation on the body have been studied in detail. Of the ultraviolet rays contained in sunlight, erythema is caused by rays with a wavelength of 297 nm. To rays with longer or shorter wavelengths, the erythemal sensitivity of the skin decreases.
With the help of artificial radiation sources, erythema was caused by rays in the range of 250...255 nm. Rays with a wavelength of 255 nm are produced by the resonant emission line of mercury vapor used in mercury-quartz lamps.
Thus, the curve of erythemal sensitivity of the skin has two maxima. The depression between the two maxima is provided by the shielding effect of the stratum corneum of the skin.
Protective functions of the body
Under natural conditions, after erythema, skin pigmentation develops - tanning. The spectral maximum of pigmentation (340 nm) does not coincide with any of the peaks of erythemal sensitivity. Therefore, by selecting a radiation source, you can cause pigmentation without erythema and vice versa.Erythema and pigmentation are not stages of the same process, although they follow one another. This is a manifestation of different processes related to each other. The skin pigment melanin is formed in the cells of the lowest layer of the epidermis - melanoblasts. The starting material for the formation of melanin are amino acids and adrenaline breakdown products.
Melanin is not just a pigment or passive protective screen fencing off living tissue. Melanin molecules are huge molecules with a network structure. In the links of these molecules, fragments of molecules destroyed by ultraviolet light are bound and neutralized, preventing them from entering the blood and internal environment body.
The function of tanning is to protect the cells of the dermis, the vessels and nerves located in it from long-wave ultraviolet, visible and infrared rays, which cause overheating and heat stroke. Near-infrared rays and visible light, especially its long-wave, “red” part, can penetrate tissue much deeper than ultraviolet rays - to a depth of 3...4 mm. Melanin granules - a dark brown, almost black pigment - absorb radiation in a wide range of the spectrum, protecting delicate internal organs, accustomed to a constant temperature, from overheating.
The body's operational mechanism to protect itself from overheating is a rush of blood to the skin and dilation of blood vessels. This leads to an increase in heat transfer through radiation and convection ( Total surface The skin area of an adult is 1.6 m2). If the air and surrounding objects have high temperature, another cooling mechanism comes into play - evaporation due to sweating. These thermoregulatory mechanisms are designed to protect against exposure to visible and infrared rays from the Sun.
Sweating, along with the function of thermoregulation, prevents the effects of ultraviolet radiation on humans. Sweat contains urocanic acid, which absorbs short-wave radiation due to the presence of a benzene ring in its molecules.
Light starvation (deficiency of natural UV radiation)
Ultraviolet radiation supplies energy for photochemical reactions in the body. Under normal conditions, sunlight causes the formation small quantity active products photolysis, which have a beneficial effect on the body. Ultraviolet rays in doses that cause the formation of erythema enhance the functioning of the hematopoietic organs and the reticuloendothelial system ( Physiological system connective tissue, which produces antibodies that destroy bodies and microbes foreign to the body), the barrier properties of the skin, eliminate allergies.Under the influence of ultraviolet radiation in human skin, fat-soluble vitamin D is formed from steroid substances. Unlike other vitamins, it can enter the body not only with food, but also be formed in it from provitamins. Under the influence of ultraviolet rays with a wavelength of 280...313 nm, provitamins contained in the skin lubricant secreted by the sebaceous glands are converted into vitamin D and absorbed into the body.
The physiological role of vitamin D is that it promotes the absorption of calcium. Calcium is part of bones, participates in blood clotting, compacts cell and tissue membranes, and regulates enzyme activity. A disease that occurs due to a lack of vitamin D in children in the first years of life, whom caring parents hide from the Sun, is called rickets.
In addition to natural sources of vitamin D, artificial ones are also used, irradiating provitamins with ultraviolet rays. When using artificial sources of ultraviolet radiation, it should be remembered that rays shorter than 270 nm destroy vitamin D. Therefore, using filters in the light flux of ultraviolet lamps, the short-wave part of the spectrum is suppressed. Solar starvation manifests itself in irritability, insomnia, and rapid fatigue of a person. In large cities, where the air is polluted with dust, ultraviolet rays that cause erythema almost do not reach the surface of the Earth. Long-term work in mines, engine rooms and closed factory workshops, work at night, and sleep during the daytime lead to light starvation. Light starvation is facilitated by window glass, which absorbs 90...95% of ultraviolet rays and does not transmit rays in the range of 310...340 nm. The color of the walls is also significant. For example, yellow color completely absorbs ultraviolet rays. Lack of light, especially ultraviolet radiation, is felt by people, pets, birds and indoor plants in the autumn, winter and spring periods.
Lamps that, along with visible light, emit ultraviolet rays in the wavelength range 300...340 nm can compensate for the lack of ultraviolet rays. It should be borne in mind that errors in prescribing the radiation dose, inattention to issues such as spectral composition ultraviolet lamps, the direction of radiation and the height of the lamps, the duration of lamp burning, can cause harm instead of benefit.
Bactericidal effect of ultraviolet radiation
It is impossible not to note the bactericidal function of UV rays. In medical institutions, this property is actively used to prevent nosocomial infections and ensure the sterility of operating rooms and dressing rooms. The impact of ultraviolet radiation on bacterial cells, namely DNA molecules, and the development of further chemical reactions in them leads to the death of microorganisms.Air pollution with dust, gases, and water vapor has harmful influence on the body. The ultraviolet rays of the Sun enhance the process of natural self-purification of the atmosphere from pollution, promoting the rapid oxidation of dust, smoke particles and soot, destroying microorganisms on dust particles. The natural ability to self-purify has limits and is insufficient when the air is very polluted.
Ultraviolet radiation with a wavelength of 253...267 nm most effectively destroys microorganisms. If we take the maximum effect as 100%, then the activity of rays with a wavelength of 290 nm will be 30%, 300 nm - 6%, and rays lying on the border of visible light 400 nm - 0.01% of the maximum.
Microorganisms have varying sensitivity to ultraviolet rays. Yeasts, molds and bacterial spores are much more resistant to their action than vegetative forms of bacteria. Spores of individual fungi, surrounded by a thick and dense shell, thrive in high layers of the atmosphere and it is possible that they can travel even in space.
The sensitivity of microorganisms to ultraviolet rays is especially great during the period of division and immediately before it. The curves for the bactericidal effect, inhibition and cell growth practically coincide with the absorption curve for nucleic acids. Consequently, denaturation and photolysis of nucleic acids leads to the cessation of division and growth of microorganism cells, and in large doses to their death.
The bactericidal properties of ultraviolet rays are used to disinfect air, tools, and dishes; with their help, they increase the shelf life of food products, disinfect drinking water, and inactivate viruses when preparing vaccines.
Negative effects of ultraviolet radiation
A number of negative effects that occur when exposed to UV radiation on the human body are also well known, which can lead to a number of serious structural and functional damage to the skin. As is known, these damages can be divided into:The role of UV-A rays in the etiology of photoaging has been proven by the work of many foreign and Russian scientists, but nevertheless, the mechanisms of photoaging continue to be studied using modern scientific and technical base, cell engineering, biochemistry and methods of cellular functional diagnostics.
The mucous membrane of the eye - the conjunctiva - does not have a protective stratum corneum, so it is more sensitive to UV radiation than the skin. Pain in the eye, redness, lacrimation, and partial blindness occur as a result of degeneration and death of cells of the conjunctiva and cornea. The cells become opaque. Long-wave ultraviolet rays, reaching the lens in large doses, can cause clouding - cataracts.
Artificial sources of UV radiation in medicine
Germicidal lampsDischarge lamps are used as sources of UV radiation, in which, during the process of electrical discharge, radiation is generated containing a wavelength range of 205-315 nm (the rest of the radiation spectrum plays a secondary role). These lamps include low and low mercury lamps. high pressure, as well as xenon flash lamps.
Low-pressure mercury lamps are structurally and electrically no different from conventional fluorescent lighting lamps, except that their bulb is made of special quartz or uviol glass with a high transmittance of UV radiation, inner surface which does not have a layer of phosphor applied. These lamps are available in a wide range of wattages from 8 to 60 W. The main advantage of low-pressure mercury lamps is that more than 60% of the radiation falls on the line with a wavelength of 254 nm, which lies in the spectral region of maximum bactericidal action. They have a long service life of 5,000-10,000 hours and instantaneous ability to work after they are ignited.
The bulb of high-pressure mercury-quartz lamps is made of quartz glass. The advantage of these lamps is that, despite their small dimensions, they have a large unit power from 100 to 1,000 W, which makes it possible to reduce the number of lamps in the room, but they have low bactericidal efficiency and a short service life of 500-1,000 hours. In addition, normal combustion mode occurs 5-10 minutes after they are ignited.
A significant disadvantage of continuous radiant lamps is the risk of contamination of the environment with mercury vapor if the lamp is destroyed. If the integrity of bactericidal lamps is damaged and mercury enters the room, thorough demercurization of the contaminated room must be carried out.
In recent years, a new generation of emitters has appeared - short-pulse ones, which have much greater biocidal activity. The principle of their operation is based on high-intensity pulsed irradiation of air and surfaces with continuous-spectrum UV radiation. Pulsed radiation is produced using xenon lamps, as well as lasers. There is currently no data on the difference between the biocidal effect of pulsed UV radiation and that of traditional UV radiation.
The advantage of xenon flash lamps is due to their higher bactericidal activity and shorter exposure time. Another advantage of xenon lamps is that if they accidentally break, environment not contaminated by mercury vapor. The main disadvantages of these lamps, which hinder their widespread use, are the need to use high-voltage, complex and expensive equipment for their operation, as well as the limited life of the emitter (on average 1-1.5 years).
Germicidal lamps are divided into ozone and non-ozone.
Ozone lamps have a spectral line with a wavelength of 185 nm in their emission spectrum, which, as a result of interaction with oxygen molecules, forms ozone in the air. High concentrations of ozone can have adverse effects on human health. The use of these lamps requires monitoring of the ozone content in the air and careful ventilation of the room.
To eliminate the possibility of ozone generation, so-called bactericidal “ozone-free” lamps have been developed. For such lamps, due to the manufacture of the bulb from a special material (coated quartz glass) or its design, the output of the 185 nm line radiation is eliminated.
Germicidal lamps that have reached the end of their service life or are out of order must be stored packed in a separate room and require special disposal in accordance with the requirements of the relevant regulatory documents.
Bactericidal irradiators.
A bactericidal irradiator is an electrical device that contains: a bactericidal lamp, a reflector and other auxiliary elements, as well as devices for its fastening. Germicidal irradiators redistribute the radiation flux into the surrounding space in a given direction and are divided into two groups - open and closed.
Open irradiators use a direct germicidal flow from lamps and a reflector (or without it), which covers a wide area of \u200b\u200bthe space around them. Installed on the ceiling or wall. Irradiators installed in doorways are called barrier irradiators or ultraviolet curtains, in which the bactericidal flow is limited to a small solid angle.
A special place is occupied by open combined irradiators. In these irradiators, due to the rotating screen, the bactericidal flow from the lamps can be directed to the upper or lower zone of the space. However, the efficiency of such devices is much lower due to changes in wavelength upon reflection and some other factors. When using combined irradiators, the bactericidal flow from shielded lamps must be directed to the upper zone of the room in such a way as to prevent direct flow from the lamp or reflector from escaping into the lower zone. In this case, the irradiance from reflected fluxes from the ceiling and walls on a conventional surface at a height of 1.5 m from the floor should not exceed 0.001 W/m2.
In closed irradiators (recirculators), the bactericidal flow from the lamps is distributed in a limited, small area confined space and has no exit to the outside, while air disinfection is carried out in the process of pumping it through the ventilation holes of the recirculator. When using supply and exhaust ventilation, bactericidal lamps are placed in the exit chamber. The air flow speed is provided either by natural convection or forced by a fan. Irradiators closed type(recirculators) should be placed indoors on the walls along the main air flows (in particular, near heating devices) at a height of at least 2 m from the floor.
According to the list of typical premises divided into categories (GOST), it is recommended that rooms of categories I and II be equipped with both closed irradiators (or supply and exhaust ventilation) and open or combined ones - when they are turned on in the absence of people.
In rooms for children and pulmonary patients, it is recommended to use irradiators with ozone-free lamps. Artificial ultraviolet irradiation, even indirect, is contraindicated for children with active form tuberculosis, nephroso-nephritis, feverish condition and severe exhaustion.
The use of ultraviolet bactericidal installations requires strict implementation of safety measures that exclude possible harmful effects on humans of ultraviolet bactericidal radiation, ozone and mercury vapor.
Basic safety precautions and contraindications for the use of therapeutic UV irradiation.
Before using UV irradiation from artificial sources, it is necessary to visit a doctor in order to select and establish the minimum erythemal dose (MED), which is a purely individual parameter for each person.Since individual sensitivity varies widely, it is recommended that the duration of the first session be halved from the recommended time in order to establish skin reaction user. If any adverse reaction is detected after the first session, further use of UV irradiation is not recommended.
Regular irradiation over a long period of time (a year or more) should not exceed 2 sessions per week, and there can be no more than 30 sessions or 30 minimum erythemal doses (MED) per year, no matter how small the erythemal-effective irradiation may be. It is recommended to occasionally interrupt regular radiation sessions.
Therapeutic irradiation must be carried out with the mandatory use of reliable eye protection.
The skin and eyes of any person can become a “target” for ultraviolet radiation. It is believed that people with fair skin are more susceptible to damage, but dark-skinned people may not feel completely safe either.
Very careful with natural and artificial UV exposure whole body should be the following categories of people:
I remember disinfection with UV lamps from childhood - in kindergartens, sanatoriums and even in summer camps there were somewhat frightening structures that glowed with a beautiful purple light in the dark and from which teachers drove us away. So what exactly is ultraviolet radiation and why does a person need it?
Perhaps the first question that needs to be answered is what ultraviolet rays are and how they work. This is usually the name for electromagnetic radiation, which is in the range between visible and x-ray radiation. Ultraviolet is characterized by a wavelength from 10 to 400 nanometers.
It was discovered back in the 19th century, and this happened thanks to the discovery of infrared radiation. Having discovered the IR spectrum, in 1801 I.V. Ritter turned his attention to the opposite end of the light spectrum during experiments with silver chloride. And then several scientists immediately came to the conclusion about the heterogeneity of ultraviolet radiation.
Today it is divided into three groups:
- UVA radiation – near ultraviolet;
- UV-B – medium;
- UV-C - far.
This division is largely due to the impact of rays on humans. The natural and main source of ultraviolet radiation on Earth is the Sun. In fact, it is this radiation that we protect ourselves from with sunscreens. At the same time, far ultraviolet radiation is completely absorbed by the Earth's atmosphere, and UVA just reaches the surface, causing a pleasant tan. And on average, 10% of UV-B provokes those same sunburns, and can also lead to the formation of mutations and skin diseases.
Artificial sources ultraviolet radiation is created and used in medicine, agriculture, cosmetology and various sanitary institutions. Ultraviolet radiation can be generated in several ways: by temperature (incandescent lamps), by the movement of gases (gas lamps) or metal vapors (mercury lamps). Moreover, the power of such sources varies from several watts, usually small mobile emitters, to kilowatts. The latter are mounted in large stationary installations. The areas of application of UV rays are determined by their properties: the ability to accelerate chemical and biological processes, the bactericidal effect and the luminescence of certain substances.
Ultraviolet is widely used to solve a wide variety of problems. In cosmetology, the use of artificial UV radiation is used primarily for tanning. Solariums create fairly mild ultraviolet-A according to the introduced standards, and the share of UV-B in tanning lamps is no more than 5%. Modern psychologists recommend solariums for the treatment of “winter depression,” which is mainly caused by a deficiency of vitamin D, as it is formed under the influence of UV rays. UV lamps are also used in manicure, since it is in this spectrum that especially resistant gel polishes, shellac and the like dry.
Ultraviolet lamps are used to create photographs in non-standard situations, for example, to capture space objects, which are invisible in a regular telescope.
Ultraviolet light is widely used in expert activities. With its help, the authenticity of paintings is verified, since fresher paints and varnishes look darker in such rays, which means the real age of the work can be established. Forensic scientists also use UV rays to detect traces of blood on objects. In addition, ultraviolet light is widely used for the development of hidden seals, security elements and threads confirming the authenticity of documents, as well as in the lighting design of shows, signs of establishments or decorations.
In medical institutions, ultraviolet lamps are used to sterilize surgical instruments. In addition, air disinfection using UV rays is still widespread. There are several types of such equipment.
This is the name given to high- and low-pressure mercury lamps, as well as xenon flash lamps. The bulb of such a lamp is made of quartz glass. The main advantage of bactericidal lamps is their long service life and immediate ability to work. Approximately 60% of their rays are in the bactericidal spectrum. Mercury lamps are quite dangerous to operate; if the housing is accidentally damaged, thorough cleaning and demercurization of the room is necessary. Xenon lamps are less dangerous if damaged and have higher bactericidal activity. Germicidal lamps are also divided into ozone and ozone-free. The former are characterized by the presence in their spectrum of a wave with a length of 185 nanometers, which interacts with oxygen in the air and turns it into ozone. High concentrations of ozone are dangerous to humans, and the use of such lamps is strictly limited in time and recommended only in a ventilated area. All this led to the creation of ozone-free lamps, the bulb of which was coated with a special coating that did not transmit a wave of 185 nm to the outside.
Regardless of the type, bactericidal lamps have common disadvantages: they operate in complex and expensive equipment, average resource The life of the emitter is 1.5 years, and the lamps themselves after burnout must be stored packaged in a separate room and disposed of in a special way in accordance with current regulations.
Consist of a lamp, reflectors and other auxiliary elements. There are two types of such devices - open and closed, depending on whether UV rays pass out or not. Open ones release ultraviolet radiation, amplified by reflectors, into the space around, capturing almost the entire room at once if installed on the ceiling or wall. It is strictly prohibited to treat a room with such an irradiator in the presence of people.
Closed irradiators operate on the principle of a recirculator, inside of which a lamp is installed, and a fan draws air into the device and releases the already irradiated air outside. They are placed on the walls at a height of at least 2 m from the floor. They can be used in the presence of people, but long-term exposure is not recommended by the manufacturer, since some of the UV rays may pass out.
The disadvantages of such devices include immunity to mold spores, as well as all the difficulties of recycling lamps and strict regulations for use depending on the type of emitter.
Bactericidal installations
A group of irradiators combined into one device used in one room is called a bactericidal installation. They are usually quite large and have high energy consumption. Air treatment with bactericidal installations is carried out strictly in the absence of people in the room and is monitored according to the Commissioning Certificate and the Registration and Control Log. Used only in medical and hygienic institutions to disinfect both air and water.
Disadvantages of ultraviolet air disinfection
In addition to what has already been listed, the use of UV emitters has other disadvantages. First of all, ultraviolet radiation itself is dangerous for the human body; it can not only cause skin burns, but also affect work cardiovascular system, is dangerous for the retina. In addition, it can cause the appearance of ozone, and with it the unpleasant symptoms inherent in this gas: irritation of the respiratory tract, stimulation of atherosclerosis, exacerbation of allergies.
The effectiveness of UV lamps is quite controversial: inactivation of pathogens in the air by permitted doses of ultraviolet radiation occurs only when these pests are static. If microorganisms move and interact with dust and air, then the required radiation dose increases by 4 times, which a conventional UV lamp cannot create. Therefore, the efficiency of the irradiator is calculated separately, taking into account all parameters, and it is extremely difficult to select those suitable for influencing all types of microorganisms at once.
The penetration of UV rays is relatively shallow, and even if immobile viruses are under a layer of dust, the upper layers protect the lower ones by reflecting ultraviolet radiation from themselves. This means that after cleaning, disinfection must be carried out again.
UV irradiators cannot filter the air; they only fight microorganisms, keeping all mechanical pollutants and allergens in their original form.
Ultraviolet radiation (ultraviolet, UV, UV) is electromagnetic radiation, occupying the range between the violet boundary of visible radiation and x-ray radiation (380 - 10 nm, 7.9 1014 - 3 1016 Hertz).
The concept of ultraviolet rays was first encountered by an Indian philosopher of the 13th century in his work. The atmosphere of the Bhootakasha area he described contained violet rays that cannot be seen with the naked eye.
Soon after infrared radiation was discovered, the German physicist Johann Wilhelm Ritter began searching for radiation at the opposite end of the spectrum, with a wavelength shorter than that of violet. In 1801, he discovered that silver chloride, which decomposes faster when exposed to light decomposes under the influence of invisible radiation outside the violet region of the spectrum. Silver chloride white within a few minutes it darkens in the light. Different parts of the spectrum have different effects on the rate of darkening. This happens most quickly in front of the violet region of the spectrum. Many scientists, including Ritter, then agreed that light consists of three distinct components: an oxidative or thermal (infrared) component, an illuminant (visible light) component, and a reducing (ultraviolet) component. At that time, ultraviolet radiation was also called actinic radiation. Ideas about the unity of three different parts of the spectrum were first voiced only in 1842 in the works of Alexander Becquerel, Macedonio Melloni and others.
The electromagnetic spectrum of ultraviolet radiation can be divided into subgroups in various ways. The ISO standard for the definition of solar radiation (ISO-DIS-21348) gives the following definitions:
|
Name |
Abbreviation |
Wavelength in nanometers |
Amount of energy per photon |
|
Near |
400 nm - 300 nm |
3.10 - 4.13 eV |
|
|
Average |
300 nm - 200 nm |
4.13 - 6.20 eV |
|
|
Further |
200 nm - 122 nm |
6.20 - 10.2 eV |
|
|
Extreme |
121 nm - 10 nm |
10.2 - 124 eV |
|
|
Ultraviolet A, long wave range |
400 nm - 315 nm |
3.10 - 3.94 eV |
|
|
Ultraviolet B, midwave |
315 nm - 280 nm |
3.94 - 4.43 eV |
|
|
Ultraviolet C, shortwave |
280 nm - 100 nm |
4.43 - 12.4 eV |
The near ultraviolet range is often called “black light” because it is not recognized by the human eye, but when reflected from some materials, the spectrum moves into the visible region.
For the far and extreme range, the term "vacuum" (VUV) is often used, due to the fact that waves in this range are strongly absorbed by the Earth's atmosphere.
Biological effects of ultraviolet radiation in three spectral areas are significantly different, so biologists sometimes identify the following ranges as the most important in their work:
Near ultraviolet, UV-A rays (UVA, 315-400 nm)
UV-B rays (UVB, 280-315 nm)
Far ultraviolet, UV-C rays (UVC, 100-280 nm)
Almost all UVC and approximately 90% of UVB are absorbed by ozone, as well as water vapor, oxygen and carbon dioxide when passing sunlight through the earth's atmosphere. Radiation from the UVA range is rather weakly absorbed by the atmosphere. Therefore, the radiation reaching the Earth's surface largely contains near-ultraviolet UVA and a small proportion - UVB.
Somewhat later, in the works of (O. G. Gazenko, Yu. E. Nefedov, E. A. Shepelev, S. N. Zaloguev, N. E. Panferova, I. V. Anisimova), this specific effect of radiation was confirmed in space medicine . Preventive UV irradiation was introduced into space flight practice along with the 1989 Methodological Instructions (MU) “Preventive ultraviolet irradiation of people (using artificial sources of UV radiation).” Both documents are a reliable basis for further improvement of UV prevention.
Exposure of the skin to ultraviolet radiation in excess of the skin's natural protective ability to tan results in burns.
Long-term exposure to ultraviolet radiation can contribute to the development of melanoma and premature aging.
Ultraviolet radiation is imperceptible to the human eye, but with intense irradiation it causes typical radiation damage (retinal burn).
Natural springs
The main source of ultraviolet radiation on Earth is the Sun. Intensity ratio UV-A radiation and UV-B, the total amount of ultraviolet rays reaching the Earth's surface depends on the following factors:
on the concentration of atmospheric ozone above the earth's surface (see ozone holes)
from the height of the Sun above the horizon
from altitude above sea level
from atmospheric dispersion
on the state of the cloud cover
on the degree of reflection of UV rays from the surface (water, soil)
Thanks to the creation and improvement of artificial sources of UV radiation, which went in parallel with the development of electrical sources of visible light, today specialists working with UV radiation in medicine, preventive, sanitary and hygienic institutions, agriculture, etc., are provided with significantly great opportunities than when using natural UV radiation.
There are a number of lasers operating in the ultraviolet region. The laser produces high-intensity coherent radiation. However, the ultraviolet region is difficult for laser generation, so there are no sources as powerful as in the visible and infrared ranges. Ultraviolet lasers are used in mass spectrometry, laser microdissection, biotechnology and other scientific research.
Many polymers used in consumer products degrade when exposed to UV light. To prevent degradation, special substances that can absorb UV are added to such polymers, which is especially important in cases where the product is directly exposed to sunlight. The problem manifests itself in color fading, surface tarnishing, cracking, and sometimes complete destruction of the product itself. The rate of destruction increases with increasing exposure time and sunlight intensity.
The described effect is known as UV aging and is one of the types of aging of polymers. Sensitive polymers include thermoplastics such as polypropylene, polyethylene, polymethyl methacrylate (plexiglass), as well as special fibers such as aramid fiber. UV absorption leads to destruction of the polymer chain and loss of strength at a number of points in the structure. The effect of UV on polymers is used in nanotechnology, transplantology, X-ray lithography and other fields to modify the properties (roughness, hydrophobicity) of the polymer surface. For example, the smoothing effect of vacuum ultraviolet (VUV) on the surface of polymethyl methacrylate is known.
Application: Disinfection with ultraviolet (UV) radiation, Sterilization of air and hard surfaces, Disinfection of drinking water, Chemical analysis, UV spectrometry, Mineral analysis, Qualitative chromatographic analysis, Insect catching, Artificial tanning and “Mountain sun”, restoration.
Ultraviolet radiation is a form of optical radiation not visible to the human eye, characterized by shorter length and higher energy photons compared to light. Ultraviolet rays cover the spectrum between visible and x-ray radiation, in the wavelength range 400-10 nm. In this case, the radiation region in the range of 200-10 nm is called far or vacuum, and the region in the range of 400-200 nm is called near.
UV sources
1 Natural sources (stars, Sun, etc.)
Only the long-wave part of ultraviolet radiation from space objects (290-400 nm) is capable of reaching the Earth's surface. At the same time, short-wave radiation is completely absorbed by oxygen and other substances in the atmosphere at an altitude of 30-200 km from the earth's surface. UV radiation from stars in the wavelength range 90-20 nm is almost completely absorbed.
2. Artificial sources
Radiation solids, heated to a temperature of 3 thousand kelvins includes a certain proportion of UV radiation, the intensity of which increases noticeably with increasing temperature.
A powerful source of UV radiation is gas-discharge plasma.
IN various industries production (food, chemical and other industries) and medicine use gas-discharge, xenon, mercury-quartz and other lamps, the cylinders of which are made of transparent materials - usually quartz. Significant UV radiation is emitted by electrons in the accelerator and special lasers in the nickel-like ion.
Basic properties of ultraviolet radiation
The practical use of ultraviolet is due to its basic properties:
— significant chemical activity (helps accelerate the flow of chemical and biological processes);
- bactericidal effect;
- the ability to cause luminescence of substances - glow with different colors of emitted light.
Research on modern equipment emission/absorption/reflection spectra in the UV range makes it possible to set electronic structure atoms, molecules, ions.
UV spectra of the Sun, stars and various nebulae make it possible to obtain reliable information about the processes occurring in these objects.
Ultraviolet light is also capable of disrupting and changing chemical bonds in molecules, as a result of which various reactions can occur (reduction, oxidation, polymerization, etc.), which serves as the basis for such a science as photochemistry.
UV radiation can destroy bacteria and microorganisms. Thus, ultraviolet lamps are widely used for disinfection in crowded places ( medical institutions, kindergartens, metro, train stations, etc.).
Certain doses of UV radiation contribute to the formation of vitamin D, serotonin and other substances on the surface of human skin that affect the tone and activity of the body. Excessive exposure to ultraviolet radiation leads to burns and accelerates the aging process of the skin.
Ultraviolet radiation is also actively used in the cultural and entertainment sphere - to create a series of unique lighting effects in discos, stages of bars, theaters, etc.
Today, the question very often arises about the potential danger of ultraviolet radiation and the most effective ways to protect the organ of vision.
Today, the question very often arises about the potential danger of ultraviolet radiation and the most effective ways to protect the organ of vision. We have prepared a list of the most frequently asked questions about ultraviolet radiation and the answers to them.
What is ultraviolet radiation?
The spectrum of electromagnetic radiation is quite broad, but the human eye is sensitive only to a certain region called the visible spectrum, which covers the wavelength range from 400 to 700 nm. Radiations that are beyond the visible range are potentially hazardous and include infrared (wavelengths greater than 700 nm) and ultraviolet (less than 400 nm). Radiations that have a shorter wavelength than ultraviolet are called x-rays and γ-rays. If the wavelength is longer than that of infrared radiation, then these are radio waves. Thus, ultraviolet (UV) radiation is electromagnetic radiation invisible to the eye, occupying spectral region between visible and x-ray radiation within the wavelength range 100-380 nm.
What ranges does ultraviolet radiation have?
How visible light can be divided into components different colors, which we observe when a rainbow appears, and the UV range, in turn, has three components: UV-A, UV-B and UV-C, the latter being the shortest wavelength and highest energy ultraviolet radiation with a wavelength range of 200-280 nm, however it is mainly absorbed top layers atmosphere. UVB radiation has a wavelength of 280 to 315 nm and is considered medium energy radiation that is hazardous to the human eye. UV-A radiation is the longest wavelength component of ultraviolet with a wavelength range of 315-380 nm, which has maximum intensity when it reaches the Earth's surface. UV-A radiation penetrates biological tissues most deeply, although its damaging effect is less than that of UV-B rays.
What does the name “ultraviolet” mean?
This word means "above (above) violet" and comes from Latin word ultra (“over”) and the names of the shortest radiation in the visible range - violet. Although UV radiation is not detectable by the human eye, some animals - birds, reptiles, and insects such as bees - can see in this light. Many birds have plumage colors that are invisible under visible light conditions, but clearly visible under ultraviolet light. Some animals are also easier to spot in ultraviolet light. Many fruits, flowers and seeds are perceived more clearly by the eye in this light.
Where does ultraviolet radiation come from?
On outdoors The main source of UV radiation is the sun. As already mentioned, it is partially absorbed by the upper layers of the atmosphere. Since a person rarely looks directly at the sun, the main damage to the organ of vision occurs as a result of exposure to scattered and reflected ultraviolet radiation. Indoors, UV radiation occurs when using sterilizers for medical and cosmetic instruments, in tanning salons, during the use of various medical diagnostic and therapeutic devices, as well as when curing filling compositions in dentistry.
In solariums, UV radiation occurs to form a tan.
In industry, UV radiation is generated during welding operations at levels so high that they can cause serious damage to the eyes and skin, which is why the use of protective equipment is mandated for welders. Fluorescent lamps, widely used for lighting at work and at home, also produce UV radiation, but the level of UV radiation is very low and does not pose a serious danger. Halogen lamps, which are also used for lighting, produce light with a UV component. If a person is close to a halogen lamp without a protective cover or shield, the level of UV radiation can cause serious eye problems.
In industry, UV radiation is generated during welding operations at levels so high that they can cause serious damage to the eyes and skin.
What determines the intensity of exposure to ultraviolet radiation?
Its intensity depends on many factors. Firstly, the height of the sun above the horizon varies depending on the time of year and day. During the daytime in summer, the intensity of UV-B radiation is highest. There is a simple rule: when your shadow is shorter than your height, you risk receiving 50% more of this radiation.
Secondly, the intensity depends on the geographic latitude: in equatorial regions (latitude close to 0°) the intensity of UV radiation is the highest - 2-3 times higher than in northern Europe.
Third, intensity increases with increasing altitude because the layer of atmosphere capable of absorbing ultraviolet light is correspondingly reduced, so more of the highest-energy short-wave UV radiation reaches the Earth's surface.
Fourthly, the intensity of radiation is affected by the scattering ability of the atmosphere: the sky appears blue to us due to the scattering of short-wavelength blue radiation in the visible range, and even shorter-wavelength ultraviolet radiation is scattered much more strongly.
Fifthly, the intensity of radiation depends on the presence of clouds and fog. When the sky is cloudless, UV radiation is at its maximum; dense clouds reduce its level. However, clear and sparse clouds have little effect on UV radiation levels; water vapor from fog can lead to increased ultraviolet scattering. A person may feel cloudy and foggy weather as colder, but the intensity of UV radiation remains almost the same as on a clear day.
When the sky is cloudless, UV radiation is at its maximum
Sixth, the amount of reflected ultraviolet radiation varies depending on the type of reflective surface. Thus, for snow, reflection is 90 % of the incident UV radiation, for water, soil and grass - approximately 10 %, and for sand - from 10 to 25 %. You need to remember this while on the beach.
What is the effect of ultraviolet radiation on the human body?
Prolonged and intense exposure to UV radiation can be harmful to living organisms - animals, plants and humans. Note that some insects see in the UV-A range, and they are an integral part of ecological system and in some way benefit the person. Most known result The impact of ultraviolet radiation on the human body is tanning, which is still a symbol of beauty and a healthy lifestyle. However, prolonged and intense exposure to UV radiation can lead to the development of skin cancer. It is important to remember that clouds do not block ultraviolet light, so a lack of bright sunlight does not mean that UV protection is not needed. The most harmful component of this radiation is absorbed by the ozone layer of the atmosphere. The fact that the thickness of the latter has decreased means that UV protection will become even more important in the future. Scientists estimate that a decrease in the amount of ozone in the Earth's atmosphere by just 1% will lead to an increase in skin cancer by 2-3%.
What danger does ultraviolet radiation pose to the organ of vision?
There are serious laboratory and epidemiological data linking the duration of exposure to ultraviolet radiation with eye diseases: pterygium, etc. Compared to the lens of an adult, the child’s lens is significantly more permeable to solar radiation, and 80 % of the cumulative effects of exposure to ultraviolet waves accumulate in the human body before the person reaches 18 years of age. The lens is most exposed to radiation immediately after the baby is born: it transmits up to 95 % of incident UV radiation. With age, the lens begins to acquire a yellow tint and becomes less transparent. By age 25, less than 25 % of incident ultraviolet rays reach the retina. In aphakia, the eye is deprived of the natural protection of the lens, so in this situation it is important to use UV-absorbing lenses or filters.
It should be borne in mind that a number of medications have photosensitizing properties, that is, they increase the consequences of exposure to ultraviolet radiation. Optometrists and optometrists must have an understanding of a person's general condition and medications in order to make recommendations regarding the use of protective equipment.
What eye protection products are there?
The most effective way to protect against ultraviolet radiation is to cover your eyes with special safety glasses, masks, and shields that completely absorb UV radiation. In production where UV radiation sources are used, the use of such products is mandatory. When outdoors on a bright sunny day, it is recommended to wear sunglasses with special lenses that reliably protect against UV radiation. Such glasses should have wide temples or a close-fitting shape to prevent radiation from penetrating from the side. Clear spectacle lenses can also perform this function if absorbent additives are added to their composition or special surface treatment is carried out. Well-fitting sunglasses protect against both direct incident radiation and scattered and reflected radiation from various surfaces. The effectiveness of using sunglasses and recommendations for their use are determined by indicating the category of filter whose light transmission corresponds to the spectacle lenses.
The most effective way to protect against ultraviolet radiation is to cover your eyes with special safety glasses and masks that completely absorb UV radiation.
What standards regulate the light transmission of sunglasses lenses?
Currently, in our country and abroad, regulatory documents have been developed that regulate the light transmission of sun lenses according to the categories of filters and the rules for their use. In Russia this is GOST R 51831-2001 “Sunglasses. General technical requirements", and in Europe - EN 1836: 2005 "Personal eye protection - Sunglasses for general use and filters for direct observation of the sun".
Each type of sun lens is designed for specific lighting conditions and can be classified into one of the filter categories. There are five of them in total, and they are numbered from 0 to 4. According to GOST R 51831-2001, the light transmittance T, %, of sunscreen lenses in the visible region of the spectrum can range from 80 to 3-8 % depending on the category of the filter. For the UV-B range (280-315 nm) this figure should not be more than 0.1 T (depending on the category of the filter it can be from 8.0 to 0.3-0.8 %), and for UV-A - radiation (315-380 nm) - no more than 0.5 T (depending on the filter category - from 40.0 to 1.5-4.0 %). At the same time, manufacturers of high-quality lenses and glasses set more stringent requirements and guarantee the consumer complete cutting of ultraviolet radiation to a wavelength of 380 nm or even up to 400 nm, as evidenced by special markings on glasses lenses, their packaging or accompanying documentation. It should be noted that for sunglasses lenses, the effectiveness of ultraviolet protection cannot be clearly determined by the degree of their darkening or the cost of the glasses.
Is it true that ultraviolet radiation is more dangerous if a person wears low-quality sunglasses?
This is true. Under natural conditions, when a person does not wear glasses, his eyes automatically react to the excessive brightness of sunlight by changing the size of the pupil. How brighter light, the smaller the pupil, and with the proportional ratio of visible and ultraviolet radiation, this protective mechanism works very effectively. If a darkened lens is used, the lighting appears less bright and the pupils become larger, allowing more light reaches the eyes. When the lens does not provide adequate UV protection (the amount of visible radiation is reduced more than UV radiation), the total amount of ultraviolet radiation entering the eye is greater than without sunglasses. This is why tinted and light-absorbing lenses must contain UV absorbers that reduce the amount of UV radiation in proportion to the reduction in visible light. According to international and domestic standards, the light transmission of sun lenses in the UV region is regulated as being proportionally dependent on light transmission in the visible part of the spectrum.
What optical material for spectacle lenses provides UV protection?
Some eyeglass lens materials provide UV absorption due to their chemical structure. It activates photochromic lenses, which, under appropriate conditions, block its access to the eye. Polycarbonate contains groups that absorb radiation in the ultraviolet region, so it protects the eyes from ultraviolet radiation. CR-39 and other organic materials for spectacle lenses in their pure form (without additives) transmit a certain amount of UV radiation, and special absorbers are introduced into their composition for reliable eye protection. These components not only protect users' eyes by cutting off ultraviolet radiation up to 380 nm, but also prevent photo-oxidative destruction of organic lenses and their yellowing. Mineral spectacle lenses made from ordinary crown glass are unsuitable for reliable protection against UV radiation unless special additives are added to the mixture for its production. Such lenses can be used as sun filters only after applying high-quality vacuum coatings.
Is it true that the effectiveness of UV protection for photochromic lenses is determined by their light absorption in the activated stage?
Some glasses users ask a similar question because they are worried about whether they will be reliably protected from ultraviolet radiation on a cloudy day when there is no bright sunlight. It should be noted that modern photochromic lenses absorb from 98 to 100 % of UV radiation at all light levels, that is, regardless of whether they are currently clear, medium or dark colored. This feature makes photochromic lenses suitable for outdoor glasses wearers in a variety of environments. weather conditions. With a growing number of people now becoming aware of the dangers long-term exposure to UV radiation poses to eye health, many are choosing photochromic lenses. The latter are characterized by high protective properties combined with the special advantage of automatically changing light transmission depending on the light level.
Does dark lens color guarantee UV protection?
The intense coloring of sun lenses alone does not guarantee UV protection. It should be noted that cheap organic sun lenses produced in large-scale production can have a fairly high level of protection. Typically, a special UV absorber is first mixed with lens raw materials to make colorless lenses, and then dyeing is carried out. It is more difficult to achieve UV protection for mineral sunglasses because their glass transmits more radiation than many types of polymer materials. To guarantee protection, it is necessary to introduce a number of additives into the composition of the charge for producing lens blanks and the use of additional optical coatings.
Tinted prescription lenses are made from matching clear lenses, which may or may not have sufficient quantity UV absorber for reliable cutting off of the corresponding radiation range. If you need lenses with 100% ultraviolet protection, the task of monitoring and ensuring this indicator (up to 380-400 nm) is assigned to the optical consultant and the master glasses collector. In this case, the introduction of UV absorbers into the surface layers of organic spectacle lenses is carried out using a technology similar to coloring lenses in dye solutions. The only exception is that UV protection cannot be seen with the eye and to check it you need special devices - UV testers. Manufacturers and suppliers of equipment and dyes for coloring organic lenses include in their range various compositions for surface treatment, providing different levels protection from ultraviolet and short-wave visible radiation. It is not possible to control the light transmission of the ultraviolet component in a standard optical workshop.
Should UV absorber be added to clear lenses?
Many experts believe that the introduction of a UV absorber into clear lenses will only be beneficial, as it will protect the users’ eyes and prevent the deterioration of the properties of lenses under the influence of UV radiation and atmospheric oxygen. In some countries where there is a high level of solar radiation, such as Australia, this is mandatory. As a rule, they try to cut off radiation up to 400 nm. Thus, the most dangerous and high-energy components are excluded, and the remaining radiation is sufficient for the correct perception of the color of objects in the surrounding reality. If the cutoff boundary is shifted into the visible region (up to 450 nm), then the lenses will appear yellow, and when magnified to 500 nm, orange will appear.
How can you make sure your lenses provide UV protection?
There are many different UV testers on the optical market that allow you to check the light transmission of spectacle lenses in the ultraviolet range. They show what level of transmission a given lens has in the UV range. However, it should also be taken into account that the optical power of the corrective lens can affect the measurement data. More accurate data can be obtained with the help of complex instruments - spectrophotometers, which not only show light transmission at a certain wavelength, but also take into account when measuring optical power corrective lens.
UV protection is an important aspect to consider when selecting new eyeglass lenses. We hope that the answers to questions about ultraviolet radiation and methods of protection from it provided in this article will help you choose spectacle lenses that will make it possible to maintain the health of your eyes for many years.
