Ultraviolet radiation: types, lengths, action, and application
Ultraviolet radiation (UV, UV) occupies that part of the electromagnetic spectrum limited to 100 to 400 nanometers and is not perceived by the human eye. This is the gap between violet light and x-rays. Translated from Latin, the word ultraviolet means “beyond violet.” These are the shortest rays of the visible spectrum; infrared is adjacent to the longest (red light). Proximity to the limit of the visible range made it possible to detect ultraviolet at the beginning of the 19th century.
The German physicist Johann Ritter noticed that paper treated with silver chloride darkens faster under invisible rays below 400 nm. IR rays were then called thermal, and UV became oxidizing or chemical. Later, a classification of types of radiation appeared, which is still used today: 1) visible, 2) infrared, and 3) ultraviolet. Sources of the UV spectrum have opened up huge opportunities for various fields of activity. They are used in industry and technology, physical and biological research, printing, mineralogy, forensics, medicine, physiotherapy, cosmetology, and in everyday life.
Visible, ultraviolet radiation
Many are interested in the question: if the human eye does not perceive this spectrum, why do some people and other living beings see it? Light is at wavelengths from 380 nm (violet) to 650 nm (red). Above or below these values, our cornea and lens block But, for example, in young children, more than 70% of longwave ultraviolet radiation passes through them! By the age of 30, this percentage decreases to 10%. But closer to 380–400 nanometers, visible, ultraviolet radiation can be recognized as violet or bluish light. People with visual impairments also see it and describe it as white-purple or white-blue.
And insects and birds have a special receptor for the perception of UV rays and better orientation in space. It is on this ability that the principle of luring insects into insecticidal traps is based, emitting a long UV spectrum. As for the glow of various materials and paints under ultraviolet light, this is the effect of fluorescence. Depending on their structure and properties, they can glow with various colors (blue and orange). In diagnosing fungal diseases of the skin, the Voodoo black light UV lamp is also widely used, which illuminates the affected areas in different ways.
Types of ultraviolet radiation
Before proceeding to the division within the UV range, we present a general classification. Based on the type and length of the beams, their features, and applications, natural and artificial. The sun is the main source of natural UV rays passing through the atmosphere’s ozone layer and reaching the Earth. Although they account for only 10% of the total luminous flux, the sun’s ultraviolet radiation is quite powerful and capable of providing the necessary energy to all living things. But since it contains all the spectra, it can have beneficial and harmful effects. Artificial sources that generate UV rays of different lengths are lamps. They are established in stationary equipment, desktop devices, and manual irradiators.
Near and far, These types of ultraviolet radiation will be discussed in detail below, but for now, we will denote their general division. The near one includes energetically weak long rays of the A-spectrum (UVA). They occupy over 95% of the total solar ultraviolet energy and freely pass through the atmosphere. The far ultraviolet C-spectrum (UVC) is strong, harsh, and dangerous but is almost completely blocked by the ozone layer. Between them is the average B-band (UVB). There is also a far more extreme vacuum spectrum (VUV), completely absorbed by the atmosphere and artificially generated by instruments.
Bactericidal and curative. A short C-spectrum has a disinfecting effect, destroying bacteria, viruses, fungi, and other microorganisms. Thanks to this, UVC lamps are installed in industrial, medical, and domestic installations to disinfect air, surfaces, and water. The C-spectrum is also used to treat infectious or purulent diseases of the skin and mucous membranes. But other types of ultraviolet radiation, the A- and B-spectra, have received wider use in medicine. Their therapeutic effect formed the basis of physiotherapeutic methods such as skin phototherapy for dermatitis and dermatosis.
Technical and household The first type include all ultraviolet sources used in industry, science, and technology. For example, plants for curing plastics or paints. This category can include other professional areas of application of ultraviolet (criminology, expertise). Such sources of UV rays are intended only for specific tasks. Household devices are of different types and purposes. These are handheld UV flashlights, UV irradiators for skin treatment, devices for physiotherapy, and lamps for house plants and aquariums.
I. Shortwave UVC spectrum (100–280 nm). Thanks to its bactericidal action, it can disinfect not only air and surfaces but also the body’s living tissues. Although the upper stratum corneum of the epidermis transmits less than 1% of X-rays, they must be used with great care for the skin and mucous membranes. Irradiation helps with viral infections, purulent processes in the throat, nasopharynx, and oral cavity, and fungal diseases of the feet and nails.
II. medium-wave UVB spectrum (280–320 nm). Harmful to the eyes and may cause severe reddening of the skin. Penetrates through the upper barrier to the prickly layer of the epidermis. But this is therapeutic ultraviolet radiation that stimulates the production of vitamin D. Lamps emitting narrow beams at the peak of 311 nm are used for chronic skin diseases such as psoriasis, vitiligo, neurodermatitis, seborrhea, eczema, pityriasis versicolor, alopecia areata.
III. Longwave A-spectrum (320–400 nm) It forms a softer tan on the skin, often used in a solarium. But radiation has dangerous long-term effects in the form of early wrinkles and photoaging, persistent hyperpigmentation, and the risk of skin cancer. Together with an intensifying photoactive drug, it is used in PUVA therapy for advanced dermatoses. The rays penetrate through the upper and middle layers of the epidermis and reach the dermis.
Ultraviolet radiation from the sun
Recall that the natural range contains all the spectra (A, B, and C), which are difficult to filter. Therefore, the impact can be both positive and negative. It ensures that the atmosphere delays the most dangerous and strong rays; otherwise, life on Earth would be impossible. The surface reaches 95–97% of the longwave A-rays; the rest are medium-wave B-rays. The strength of the ultraviolet radiation from the sun depends on several factors.
The greatest activity occurs during the spring-summer season and during the daytime between 12:00 and 15:00 hours. The higher the area above sea level, the stronger the ultraviolet. It can pass freely through clouds, but smoke and dust in the air reduce its strength. It also decreases as you dive into the water, so only the upper part of the human body tans during swimming. But UV rays can be reflected from the surface of the water, as well as from snow cover and sand. Window panes absorb the B-spectrum almost completely but do not hinder A-rays. Therefore, certain types of glass in cars, institutions, and residential buildings additionally protect against them.
Exposure to ultraviolet radiation
The effect of UV rays on the eyes, skin, and body depends on several fundamental conditions: the spectrum (length) of the rays, their duration, and the area of their exposure. A-rays are responsible for tanning, while B-rays can cause temporary, intense redness (erythema). But any regular or prolonged exposure to even soft A-ultraviolet is inevitably fraught with consequences!
Eyes are very vulnerable and should always be protected with goggles. The skin of the body has different levels of sensitivity. For example, redness is always more pronounced on the abdomen and back than on the arms or legs. The most stable are the palms and feet. UV rays affect children and light-skinned people more than dark-skinned people. But if we take the correct spectrum choice and exposure time as our basis, then this will only bring benefits. Penetrating through the skin and tissues,
General and direct action of ultraviolet radiation:
- Strengthening immunity and increasing overall bio tonus due to the synthesis of vitamin D
- Elimination of vitamin D deficiency found in half of the country’s population.
- Normalization of bone tissue mineralization due to the balance of calcium and phosphorus
- Development of bioactive elements necessary for health (melatonin, serotonin).
- Activation of cell regeneration, blood circulation, nutrition, and oxygen uptake
- Lowering blood pressure, cholesterol levels, and the risk of heart disease.
- Detoxification effect, for example, through the procedure of UV irradiation of the blood.
- Suppression of the local immune response (immunosuppression) in skin inflammations.
- Decreased production of inflammatory modulators in dermatitis, psoriasis, and eczema.
- Restoration of pigment cells (vitiligo) and hair follicles (alopecia).
Sources of ultraviolet radiation
Natural solar energy has also found its practical application, for example, in the form of reflex concentrators, batteries, and panels. But the widest prospects are provided by artificial ultraviolet generators of the required range and length. They allow for filtering out dangerous or unnecessary rays for specific purposes, enhancing the effect of one selected spectrum. These are massive installations for professional use and portable household appliances for various purposes. Both their beneficial effect and possible risks depend on the sources established in them.
They are straight glass tubes with metal electrodes sealed at the ends. Inside, they are filled with an inert gas (argon, xenon) and a small amount of mercury. When turned on, they heat up, and an arc discharge occurs in mercury vapor. One part of the lamp’s radiation is visible light, and the other is UV rays, which easily pass through quartz glass.
They are used in open disinfection units intended to disinfect medical and laboratory premises. The formation of ozone, which is dangerous for humans, occurs in the air; therefore, sterilization is carried out only in the absence of people. A variety of quartz is used in xenon flash lamps for disinfection. But they are very expensive and increase the concentration of ozone.
These gas-discharge lamps produce ultraviolet radiation by passing an electric arc through mercury vapor. In addition to UV rays, white light with a blue tint is also generated. The most common type is low-pressure mercury lamps that emit short-wavelength C-rays. For example, bactericidal ones generate ultraviolet light at the peak of 253.7 nm. These rays are the most destructive for most bacteria and viruses. For disinfection of premises in the presence of people, lamps are made of ultraviolet glass, which blocks ozone-forming radiation. For safety, they are installed in closed-type irradiators and recirculation. High-pressure mercury lamps are used, for example, as powerful sources of white light.
Lamps of high power and enhanced bactericidal flow. In addition to mercury, they also contain bismuth and indium for greater safety. The name “amalgam” itself means an alloy of mercury with metals. Traditional mercury technologies are limited to 100 W due to unstable vapor pressure, while amalgam technologies allow this limit to be exceeded. In addition, mercury can be contained in the granules, so it does not settle on the walls.
This prevents fouling of the flask, greatly extends the service life, and maintains stable operation. But, compared to conventional mercury lamps, their cost is much higher. Such sources of ultraviolet radiation are used in industrial water purification systems, for the disinfection of swimming pools and water parks, and in various technical devices.
4) Light-emitting diode (LED)
Ultraviolet radiation lamps of low and medium power, which are most widely used in UV identification and in everyday life, To generate rays; they provide special additives (gallium or aluminum nitride). LEDs are inferior to gas-discharge mercury lamps in terms of efficiency. But they provide stable radiation in the 100–400 nm range and have an almost unlimited service life. They are installed in handheld devices for forensics, UV examination, and mineralogy.
At home, they are used, for example, for the polymerization of nail polish or as photo lamps for plants. Due to the wide spectrum of light emitted, including UVC, they can also perform a disinfecting function. But the effectiveness of LED disinfection remains in question.
Application of ultraviolet radiation
Using different spectra and lengths makes it possible to solve diverse tasks in professional fields and everyday life. A narrow application is available only to specialists. For example, in the field of UV printing and lithography, a new technology is being mastered with radiation at the extreme lower end of the spectrum (13.5 nm). The resistance of varnishes, paints, plastics, and textiles to UV continues to be tested in the 315–380 nm range. Under the rays of 300–365 nm, polymers are cured.
Detection of individual minerals, biological traces, and UV identification of banknotes or works of art is performed by detectors and flashlights emitting in the 365–390 nm range. 380–400 nm lamps provide specific illumination of dance floors and nightclubs. But most people are interested in these sources’ opportunities in everyday life.
Use of ultraviolet radiation
- General strengthening lamps for rickets and vitamin D deficiency (UVB spectrum)
- Home narrow-band skin phototherapy with therapeutic UV irradiators (UVB, 311 nm).
- Irradiators and recirculation for indoor air disinfection (UVC, 253.7 nm)
- Quartz disinfectants for skin and mucous membranes (UVC, 180 nm)
- Tanning lamps, cosmetic devices, nail polish, and nail dryers (UVA spectrum)
- LED lights for the home and UV lights for illumination (UVA, 365–400 nm)
- Aquarium lamps and house plant growth promoters (UVB, UVA).
- UV traps and repellents for midges, mosquitoes, flies, wasps, and other insects (UVA, 350–370 nm).
Recirculators: ultraviolet bactericidal action
In enclosed spaces with the constant presence of people, the air environment is polluted by bacteria and viruses. These microorganisms are transmitted by airborne droplets and cause respiratory diseases (influenza, SARS, coronavirus, measles, chickenpox, and mumps). Antiseptics can be used to clean surfaces, but how do you eliminate airborne pathogens?
And so that during the disinfection, every time does not leave the room. For this purpose, closed-type irradiators and recirculation are used. They are equipped with a mercury lamp made of uv-glass, which does not cause ozone formation in the air. Ultraviolet radiation of bactericidal action is shortwave rays with a peak of 253.7 nanometers. The most destructive length for most microorganisms. The devices also have a fan that draws air from the room into the case, runs it through the lamp, and returns it clean. UV rays are absorbed by the DNA of viruses and deactivate them at the molecular level, depriving them of the ability to divide further and spread.
For various purposes, bactericidal recirculation Ultramig of our production and Khronos are intended for disinfection of the air environment in rooms for various purposes. They have a germicidal efficiency of 99.9%, a powerful fan, a replaceable filter, and a high-quality ozone-free lamp. Younger models are used at home to protect family members from viruses. Safe for people and pets. They operate quietly and can be installed in nurseries, bedrooms, and living rooms.
These are Ultramig floor recirculation that can be moved from room to room. Available in a metal case in white and black. Air disinfection in offices, preschools, and educational institutions is always relevant. The flow of people and their long stays on the premises greatly increase the accumulation of pathogens in the air. If there is at least one sick person among those present, then he can infect several people. For offices, salons, kindergartens, and schools, Khronos produces powerful wall-mounted recirculation.
Curative ultraviolet irradiators
UV irradiation has been used to treat chronic skin diseases for over half a century. The first method was the general body PUVA therapy: a combination of A-rays and psoralen that enhances them. After two hours, a person takes the drug and is placed in a booth like a vertical solarium. In its therapeutic action, ultraviolet radiation, in combination with the drug, causes early and delayed side effects.
To ensure safety while maintaining high efficiency, narrow-band phototherapy is allowed. It appeared later than other methods after the invention of the 311-nm UVB treatment lamp. It has an anti-inflammatory and immunosuppressive effect and accelerates the restoration of the skin and the functions of its main cells (keratinocytes and melanocytes). Recognized as first-line therapy for psoriasis, parapsoriasis, and vitiligo. It is also used for eczema of various types.
For phototherapy in medical institutions, an ultraviolet irradiator, Ultramig-302, manufactured by Khronos, is offered. It has eight lamps of type PL-S 9W/1,2P 1CT and is distinguished by its high power and the large perimeter of the emitting window. It can be mounted on a static horizontal surface or attached to a mobile medical stand.
The therapeutic effect of ultraviolet radiation is available at home. For irradiation of the chest, abdomen, back, waist, and lower extremities, using the Ultramig-311 irradiator with two lamps is convenient. Installed on a table or the floor. For local irradiation of the scalp, palms, hands, flexion surfaces, and other areas, a manual ultraviolet comb (Ultramig-311R) is used. Has a built-in comb to help part the hair on the head and not bring the lamp too close to the skin. Ultramig therapeutic ultraviolet irradiators are delivered to all regions of the country, complete with goggles and instructions for use.