Summer is coming! ☀ The sun is shining with might and main, someone is already planning a vacation, which means it's time to talk about sunscreen.

After a long winter and frosts, you especially want to soak up the sun. But the sun also has dark side”, which can cause significant harm to our skin and the whole body. To enjoy the sun safely, you need to study it from all angles.

In this post, we will talk in detail about the types of sun exposure, sunscreens, what SPF, PPD, PA, IPD are on sunscreen jars, and what SPF products are.

solar radiation

Sunlight is divided into 3 spectra:

ultraviolet;
visible light;
infrared radiation (heat).

From the point of view of the impact on the skin, we are interested in ultraviolet rays (ultraviolet), which, in turn, are divided into UVC, UVB and UVA.

UVC rays (ultraviolet C rays)

These are the strongest and most dangerous rays. But, fortunately for us, they are absorbed by the ozone layer and do not reach the Earth's surface. Therefore, UVC rays do not affect the skin in any way, and we will not talk about them further.

UVB rays (ultraviolet B rays)

They are also partially absorbed by the ozone layer, but the rest reaches the Earth's surface. These rays are most active during the period from spring to autumn, from 10 a.m. to 4 p.m.

They act on the surface of the skin, penetrate into its upper layer (epidermis), but do not reach the deep layers (dermis). It is these rays in small doses that cause sunburn, and in large doses - sunburn, are involved in photoaging, can cause skin cancer and eye damage.

UVA rays (ultraviolet A rays)

They are divided into long (UVA1) and short (UVA2).

They are not absorbed by the ozone layer at all and reach the Earth's surface. Equally active throughout the year, at any time of the day. Can penetrate glass and light clothing. The number of UVA rays is many times greater than the number of UVB rays.

These are the most insidious rays. They penetrate the epidermis and deep into the dermis, damaging the DNA of cells. They change their structure, increase the level of genetic mutations and can cause skin cancer.

UVA rays are responsible for hyperpigmentation, uneven skin tone, dryness and freckles. Much less likely than UVB, but they can also cause sunburn and sunburn. Actively participate in photoaging. Prolonged exposure to a large amount of UVA rays causes damage to collagen and elastin fibers. This leads to wrinkles and premature aging.

UVA are the main rays used in tanning beds.

Important nuances

All rays become stronger at altitude (for example, in the mountains). Each kilometer up increases the radiation intensity by as much as 12%. Therefore, in the mountains, sunscreen (or even a stick is better) is an absolute must-have.
All rays can be reflected to varying degrees from surfaces - snow, ice, water, and even asphalt, grass and sand. It also increases the intensity of radiation at times. Therefore, protection is always important - while swimming at the sea, in a ski resort and in the city.
Up to 80% of rays penetrate clouds. Therefore, protection from the "sun" is important even on cloudy days.

Sun protection

When it comes to the sun, the main thing is to know the measure. Not a large number of Ultraviolet radiation is good for the skin and the body and is necessary for the production of vitamin D.

Excessive UV radiation damages the skin and its immune system, thickens it, disrupts the blood supply, and causes photoaging. Skin aging is 70% dependent on ultraviolet radiation.

Moreover, any doses of UV radiation remain in the body and accumulate throughout life. Especially dangerous severe burns- to blisters and peeling skin. The body remembers every time you "fried".

Sunburn continues to develop (worse) for another 12-24 hours after it happened.

In order to protect our delicate skin from the negative effects of ultraviolet radiation, sunscreens are used in cosmetics.

Sun protection filters

There are various substances that selectively absorb, reflect and neutralize the action of UV rays. That is what they are called sunscreen or UV (UV) filters.

UV filters are also added to cosmetics to protect them from damage and degradation in the light.

Filters are physical, chemical and natural.

Physical filters

Reflect Sun rays. Distributed over the surface of the skin, forming a dense, impermeable film. They act as a mini-shell, shield or screen, from which the sun's rays "ricochet" like darts.

Means based only on physical filters, as a rule, give a basic and average protection factor.

Examples of physical filters (what to look for on the label): zinc oxide (zinc oxide); titanium dioxide (titanium dioxide).

"Pros +". These are "broad spectrum" filters - they protect against both UVB and UVA rays. They are not absorbed by the skin and do not react with it. They are effective even at low concentrations, non-toxic, photostable (do not decompose in the light) and have a low cost. They begin to act immediately after application to the skin.
"Minuses - ". At high concentrations, they create a white effect on the skin, they are dense, opaque, can dry out, are not waterproof, and do not combine well with many components of cosmetic formulas. Theoretically, they can clog pores (with a tendency).

The best choice for sensitive, hypersensitive, reactive skin, organics and children. Children's sun protection cosmetics should contain only physical filters.

Chemical filters

Absorb UV radiation and block its penetration into the skin. Some chemical filters also reflect and scatter the rays. Distributed over the surface of the skin and in the upper layer of the epidermis. Practically do not penetrate deeper. They do not enter the body, do not have any harmful effects on cells and the circulatory system, and do not cause hormonal imbalance.

Depending on the specific substance, they protect against either UVA or UVB, or both types of rays.

Examples of chemical filters (what to look for on the label): avobenzone (avobenzone); mexoryl (Mexoryl SX and XL); tinosorb (Tinosorb S and M); octocrylene (octocrylene); padimat O (padimate O); cinnamates (-cinnamate); oxybenzone, benzophenone-3 (oxybenzone, benzophenone-3); sulisobenzone (sulisobenzone); octylsalicylate (octyl salicylate).

"Pros +". Very efficient. Water resistant. Provide high factor protection. Do not leave marks on the skin, usually liquid, colorless and odorless.
"Minuses - ". The mechanism of chemical filters is essentially a chemical reaction on the skin. They come into contact with radiation, absorb it and release heat. As a result, the temperature of the skin rises. They can cause allergies and provoke the development of rosacea. They may or may not be photostable. They begin to act only 20-30 minutes after application to the skin.

The inscription "sunblock" on the bottle usually implies the presence of physical filters, the inscription "sunscreen" - chemical. However, these are very arbitrary terms. The Americans, for example, banned the use of the inscription "sunblock", because no product can completely block the sun's rays.

natural filters

Natural, or natural, filters include many base oils. They can both reflect and absorb UV radiation.

Of course, you should not rely completely on natural filters for sun protection.
They are not enough. First, they create a film that is too thin and not effective enough. Secondly, the oils attract the sun's rays and enhance the tan. And third, the SPF values vary too much. But in combination with physical and chemical natural filters are wonderful.

Wear and photostability of filters

Physical and chemical filters tend to "wear out".

Physical ones are erased, for example, by contact with a towel. And each molecule of a chemical filter, when a photon of a solar beam hits it, dies and is converted into heat. Thus, it is consumed like, for example, gasoline for a car or food for the body.

That is why it is necessary to constantly update the protection. The more sun - the more often the repetition.

Some substances are more resistant to light (photostable), others die less and faster. Some filters can stabilize others (for example, mexoril stabilizes avobenzene), others, on the contrary, destroy each other (like octinoxate and avobenzene).

In addition, not all filters provide protection against both types of rays on their own. Therefore, a whole cocktail of filters is used in sunscreens (usually there are about 5 of them). The higher the protection - the more filters can be found in one jar.

A good sunscreen should provide protection from both UVB and UVA rays. The ideal ratio of UVB to UVA filters is 1:1.

What to look for on the label

SPF (UVB protection)

SPF stands for Sun Protection Factor, i.e. sun protection factor. This is an indicator that determines the ability of a cosmetic product to protect the skin from burns. It is calculated by smart uncles in white coats in laboratories.

The SPF calculation measures how much UV exposure it takes for our unprotected skin to start to burn compared to sunscreen-covered skin. The SPF value indicates what % of UV rays will be blocked. It is defined in numbers from 2 to 100. The higher the SPF, the more rays will be reflected (absorbed), and the higher the level of protection of the product from sunburn.

Probably many people know the formula: the amount of time that you can spend in the sun without sunburn without sunscreen (for example, 30 minutes) x the SPF value (for example, 10) = the amount of time that you can sunbathe serenely in the sun with this SPF smeared (in our case - 30x10 = 300 minutes, i.e. as much as 5 hours). It would seem that everything is right? And here it is not.

Why? Because SPF does not define duration sun exposure, and amount solar irradiation. Duration is just one of the factors. The intensity of the radiation is no less important. For example, 1 hour in the sun at 9 am is equal to 15 minutes at 1 pm in terms of the effect on the skin. Another important factor is geography. The closer to the equator, the more intense the solar radiation. Do not forget about the weather, you can get a burn under a cloudy sky. Therefore, it is impossible to be guided only by the above formula.

Important! SPF measures protection against sunburn (UVB rays) only, but it does not measure protection against the harmful effects of UVA rays.

SPF values

For clarity, SPF can be divided into protection levels.

SPF (2-10) - basic.
SPF (15-25) - medium.
SPF (30-100) - high.

But no cream, even with SPF 100, provides 100% protection from radiation. For total protection from the sun can only be given by a deaf bunker deep underground. Therefore, one should not think that having smeared himself with “weaving” you can “fry on the beach” all day without loss to health.

Another misconception is that, for example, SPF 30 gives 2 times more protection than SPF 15, and SPF 60 gives 2 times more protection than SPF 30. This is not true. The difference between SPF 15 and 100 is only 6%.

Let's see what % of the sun's rays reflect a particular SPF.

SPF 2 - 50%; SPF 6 - 83%; SPF 10 - 90%; SPF 15 - 93%; SPF 20 - 95%; SPF 25 - 96%; SPF 30 - 97%; SPF 45 - 97%; SPF 50 - 98%; SPF 60 - 98%; SPF 100 - 99%.

As you can see, smearing too much SPF does not make much sense. SPF 100 is more of a marketing ploy.

Moreover, the higher the SPF, the fatter and denser it feels on the skin. SPF 15 is much nicer to the touch than SPF 30. And SPF 100, uh… let's just say, it's phew. ☹

When choosing an SPF, be guided by the following factors:

phototype, skin color- red-haired owners of porcelain skin with freckles need a higher SPF (from 50);
season- in summer you need a higher SPF than in winter;
Times of Day- from 10 a.m. to 4 p.m. UVB rays are the most active;
cloudiness- cloudless skies require a higher SPF;
geography, climate and sun intensity- where you are - near the Equator or beyond the Arctic Circle - matters, the hot UAE and central Russia require a different degree of protection;
location- the sea and mountains require a higher SPF than a dacha in the suburbs.

PPD, PA and IPD (UVA protection)

The commonly accepted measure of protection against UVB rays is the SPF index. A measure of protection against UVA rays are the PPD, PA and IPD indices. The generally accepted, accurate and ideal measure of protection against UVA rays on this moment do not exist in nature. AT different countries different indexes are used.

Persistent Pigment Darkening (PPD)

Literally - a stable darkening of the pigment. Originally developed in Japan, adopted in Europe and the USA. You will find this icon on most European and American products.

Shows how much the product will reduce the penetration of UVA rays into the skin. The higher the number, the better, the minimum recommended index is 8, the maximum is 42. This means that 42% of the rays will be blocked.

It is the PPD index that is currently considered the most accurate in Europe and America.

Protection Grade of UVA (PA)

Literally - the degree of protection against UVA. Appeared relatively recently and adopted in Japan and Korea. Similar to PPD. Denoted + from 1 to 4.

The ratio of PA and PPD indices: PA+ = PPD 2-4, PA++ = PPD 4-8, PA+++ = PPD 8-16, PA++++ = PPD 16 and above.

The more + PA and the higher the number and PPD - the better the protection.

Immediate Pigment Darkening (IPD)

Literally - instant darkening of the pigment.

The maximum index is 90. It means that the skin is 90% protected from UVA rays.

If neither PPD, nor PA, nor IPD are on the jar, look for UVA in a circle without numbers. It means protection from UVA rays, but without specifics. Also circled UVA means that the ratio of UVA to UVB filters is 1:3.

What else is added to sunscreen

Excessive solar exposure can lead to the appearance of free radicals in the body - unstable and highly reactive oxygen molecules that damage tissues at the molecular level, destroying and altering DNA.

Sunscreen Forms

Emulsions (creams and gels)- the most convenient, pleasant to use and effective.
Oils- less convenient and effective due to the thin layer, attract the sun's rays.
Sticks- Wax-based, generally the most water resistant and contain physical filters, ideal for local application, eg on the nose, on the whole body are inconvenient.
Powders- make-up with SPF, an option for additional protection.
Sprays, aerosols- for the body: a thin layer, they do not guarantee evenness, usually you can’t just pollinate and go - you still need to rub it, aerosols are dangerous when inhaled; for hair and head - sprays are ideal.

2 life hacks to keep in mind

If you forgot to put on an SPF cream before sticking your nose in the sun, use an oil-based product. They quickly create a protective film.
If you need "instant protection" before bathing - use the stick. They are the most water resistant and contain physical filters that start working immediately.

Daily and active remedies

According to the American Skin Cancer Foundation, all cosmetic products can be divided into "daily" and "active".

Daily.

Assume protection from episodic short-term UV radiation.

They must: contain an SPF of 15 or higher, provide full protection against the full spectrum of UVA rays, and not cause contact irritation and phototoxic reactions.

These are day creams, eye creams, lip balms, tonal foundations and other decorative cosmetics.

Active.

Assume protection from long-term UV radiation.

They must: contain an SPF of 30 or higher, provide full protection against the full spectrum of UVA rays, be waterproof (keep protection for 40 or 80 minutes of bathing), and not cause contact irritation and phototoxic reactions.

These are beach sunscreens, sports sunscreens, protective sticks with zinc and titanium, children's cosmetics.

Morality. The optimal SPF value for the city for every day is 15. If you are going to the sea, to the mountains or plan to be outdoors all day, choose SPF 30 (and higher). But again - if your city ended up in the Emirates or Africa - start with 30.

Summarize

Solar radiation that directly affects the skin is divided into 2 types: UVA and UVB. UVB rays cause sunburn and burns, UVA rays cause pigmentation, photoaging, and increase the risk of skin neoplasms. A moderate amount of sun is good, an excess is harmful.

To protect the skin from trouble, cosmetics manufacturers use sunscreens. They are divided into physical and chemical. The optimal cream contains both and provides protection from both UVA and UVB rays.

SPF is the UVB protection index. PPD, PA, IPD - indexes of protection against UVA rays. The higher their values, the stronger the protection.

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Stay with us, upgrade your cosmetic literacy and be beautiful.

See you on the air of LaraBarBlog. ♫

Ultraviolet radiation (UVR) is an electromagnetic radiation invisible to the eye with a wavelength of 200 to 400 nm, occupying an intermediate position in the electromagnetic spectrum between visible light and X-rays.

There are three areas of UFI: UVA - with a wavelength from 400 to 315 nm, has a relatively weak biological effect; UVB - with a wavelength of 315 to 280 nm, promotes sunburn; UVC - with a wavelength of 280 to 200 nm, acts on proteins and fats, has a pronounced bactericidal effect.

Ultraviolet radiation from the sun in the A range is not absorbed by ozone. If irradiation with beams of range A is accompanied by the action of certain chemical substances, it becomes harmful to human health.

UVC rays are the shortest wavelength, but no less dangerous than X-rays. They are completely dissipated by the Earth's atmosphere. If they reached us through the Earth's atmosphere, they would be absorbed in the upper layer of the skin, literally burning it.

UVB rays are the most dangerous. They are more carcinogenic than A-band rays. UVB radiation can cause skin cancer, leading to skin aging. But these rays are filtered out by the ozone layer of the Earth's atmosphere.

UV radiation in small doses has a beneficial stimulating effect on the body, activates the activity of the heart, metabolism, increases the activity of respiratory enzymes, improves blood formation, enhances oxidative processes in the body, which contributes to the rapid elimination of poisons.

Under the influence of U FI, the body's resistance to colds increases, fatigue decreases, and working capacity increases.

UV irradiation contributes to the production of vitamin D 3 in the body of humans, animals and birds, which regulates the process of calcium metabolism.

UV irradiation in high doses causes the disintegration of the most important parts of cells, in which substances arise that block the processes of DNA reproduction and RNA synthesis.

It has been established that ultraviolet rays strongly affect the body's immune system. UV rays activate many viruses, including the AIDS virus. UV radiation from an electric arc, a mercury-quartz torch, an autogenous flame can cause electrophthalmia - inflammation of the mucous membranes of the eyes, manifested by a sensation of a foreign body or sand in the eyes, photophobia, lacrimation, blepharospasm, erythema of the skin of the face and eyelids is often detected. The disease lasts 2-3 days.

At FI production sources, atmospheric air is ionized. At the same time, technogenic ozone and nitrogen oxides are formed in the air with concentrations exceeding the maximum permissible values, which can cause poisoning of the human body.

Hygienic standardization of UV radiation in industrial premises is carried out according to SN 4557-88 “Sanitary standards for ultraviolet radiation in industrial premises”, which establish the permissible radiation flux density depending on wavelengths, provided that the organs of vision and skin are protected.

Permissible UV radiation intensity for workers in the presence of unprotected areas of the skin surface - no more than 0.2 m 2 (face, neck, hands) with a total duration of exposure to 50% of the working shift and the duration of a single exposure over 5 minutes should not exceed 10 W / m 2 for the UVA area and 0.01 W/m 2 for the UVB area. UVC exposure under these conditions is not allowed. When using overalls and face and hand protection means, the permissible exposure intensity in the UVB and UVC areas should not exceed 1 W/m2.

To protect against ultraviolet radiation, collective and individual methods and means are used: shielding of radiation sources and workplaces; removal of service personnel from sources of ultraviolet radiation (protection by distance - remote control); rational placement of jobs; special coloring of premises; PPE and protective equipment (pastes and ointments).

To shield workplaces, screens, shields, or special cabins are used. Walls and screens are painted in light colors (gray, yellow, blue), zinc and titanium white are used to absorb ultraviolet radiation. PPE from ultraviolet radiation includes: thermal protective overalls; mittens; special shoes; protective helmets; goggles and shields with light filters.

You cannot see, hear, or feel ultraviolet radiation, but you can actually feel its effects on your body, including your eyes.

You probably know that excessive exposure to ultraviolet radiation increases the risk of skin cancer, and try to use protective creams. What do you know about protecting your eyes from UV radiation?
Many publications in professional journals are devoted to the study of the effects of ultraviolet radiation on the eye, and from them, in particular, it follows that prolonged exposure to it can cause a number of diseases. In the context of a decrease in the ozone layer of the atmosphere, the need for the correct selection of means of protecting the organs of vision from excessive solar radiation, including its ultraviolet component, is extremely relevant.

What is ultraviolet?

Ultraviolet radiation is electromagnetic radiation invisible to the eye, occupying the spectral region between visible and X-ray radiation within the wavelength range of 100-380 nanometers. The entire region of ultraviolet radiation (or UV) is conditionally divided into near (l = 200-380 nm) and far, or vacuum (l = 100-200 nm); moreover, the latter name is due to the fact that the radiation of this area is strongly absorbed by air and its study is carried out using vacuum spectral instruments.

Rice. 1. Full electromagnetic spectrum of solar radiation

The main source of ultraviolet radiation is the Sun, although some sources of artificial lighting also have an ultraviolet component in their spectrum, in addition, it also occurs during gas welding. The near range of UV rays, in turn, is divided into three components - UVA, UVB and UVC, which differ in their effect on the human body.

When exposed to living organisms, ultraviolet radiation is absorbed by the upper layers of plant tissues or the skin of humans and animals. Its biological action is based on chemical changes in biopolymer molecules caused both by their direct absorption of radiation quanta and, to a lesser extent, by interaction with water and other low molecular weight compounds formed during irradiation.

UVC is the shortest wavelength and highest energy ultraviolet radiation with a wavelength range of 200 to 280 nm. The regular impact of this radiation on living tissues can be quite destructive, but, fortunately, it is absorbed by the ozone layer of the atmosphere. It should be taken into account that it is this radiation that is generated by bactericidal ultraviolet radiation sources and occurs during welding.

UVB covers the wavelength range from 280 to 315 nm and is a medium energy radiation that poses a danger to the human eye. It is UVB rays that contribute to the occurrence of sunburn, photokeratitis, and in extreme cases - cause a number of skin diseases. UVB radiation is almost completely absorbed by the cornea, but part of it, in the range of 300-315 nm, can penetrate into the internal structures of the eye.

UVA is the longest wavelength and least energetic component of UV radiation with l = 315-380 nm. The cornea absorbs some UVA radiation, but most of it is absorbed by the lens. This component should be considered first of all by ophthalmologists and optometrists, because it is it that penetrates deeper than others into the eye and has a potential danger.

The eyes are exposed to the entire sufficiently wide UV range of radiation. Its short-wavelength part is absorbed by the cornea, which can be damaged by prolonged exposure to wave radiation with l = 290-310 nm. With increasing wavelengths of ultraviolet, the depth of its penetration into the eye increases, and the lens absorbs most of this radiation.

The lens of the human eye is a magnificent filter created by nature to protect the internal structures of the eye. It absorbs UV radiation in the range of 300 to 400 nm, protecting the retina from exposure to potentially harmful wavelengths. However, with long-term regular exposure to ultraviolet radiation, damage to the lens itself develops, over the years it becomes yellow-brown, cloudy and generally unsuitable for its intended function (that is, a cataract is formed). In this case, cataract surgery is indicated.

Light transmission of spectacle lens materials in the UV range.

Protection of the organs of vision is traditionally made with the use of sunglasses, clip-on earrings, shields, hats with visors. The ability of spectacle lenses to filter out the potentially dangerous component of the solar spectrum is associated with the phenomena of absorption, polarization or reflection of the radiation flux. Special organic or inorganic materials are introduced into the composition of the material of spectacle lenses or applied to their surface in the form of coatings. The degree of protection of spectacle lenses in the UV region cannot be visually determined based on the shade or color of the spectacle lens.

Rice. 2. Ultraviolet spectrum

Although the spectral properties of spectacle lens materials are regularly discussed in professional publications, including Veko magazine, there are still persistent misconceptions about their transparency in the UV range. These misjudgments and ideas find their expression in the opinions of some ophthalmologists and even splash out on the pages of mass publications. So, in the article “Sunglasses can provoke aggressiveness” by ophthalmologist-consultant Galina Orlova, published in the newspaper “St. Therefore, any glasses with glass spectacle lenses will protect the eyes from ultraviolet radiation. It should be noted that this is absolutely wrong, since quartz is one of the most transparent materials in the UV range, and quartz cuvettes are widely used to study the spectral properties of substances in the ultraviolet region of the spectrum. Ibid: "Not all plastic spectacle lenses will protect against ultraviolet radiation." Here we can agree with this statement.

In order to finally clarify this issue, let us consider the light transmission of the main optical materials in the ultraviolet region. It is known that the optical properties of substances in the UV region of the spectrum differ significantly from those in the visible region. A characteristic feature is the decrease in transparency with decreasing wavelength, that is, the increase in the absorption coefficient of most materials that are transparent in the visible region. For example, ordinary (non-spectacle) mineral glass is transparent at wavelengths above 320 nm, while materials such as uviol glass, sapphire, magnesium fluoride, quartz, fluorite, lithium fluoride are transparent in the shorter wavelength region [TSB].

Rice. 3. Light transmission of spectacle lenses made of various materials
1 - crown glass; 2, 4 - polycarbonate; 3 - CR-39 with light stabilizer; 5 - CR-39 with UV absorber in bulk polymer

In order to understand the effectiveness of UV protection of various optical materials, let us turn to the spectral light transmission curves of some of them. On fig. light transmission in the wavelength range from 200 to 400 nm of five spectacle lenses made of various materials: mineral (crown) glass, CR-39 and polycarbonate is presented. As can be seen from the graph (curve 1), most mineral spectacle lenses made of crown glass, depending on the thickness in the center, begin to transmit ultraviolet from wavelengths of 280-295 nm, reaching 80-90% light transmission at a wavelength of 340 nm. At the border of the UV range (380 nm), the light absorption of mineral spectacle lenses is only 9% (see table).

Material	Indicator refraction	Absorption UV radiation, %
CR-39 - traditional plastics
CR-39 - with UV absorber
crown glass
Trivex
Spectralite
Polyurethane
Polycarbonate
Hyper 1.60
Hyper 1.66

This means that mineral spectacle lenses made from ordinary crown glass are unsuitable for reliable protection from UV radiation, if special additives are not introduced into the mixture for glass production. Crown glass spectacle lenses can only be used as sunscreens after quality vacuum coatings have been applied.

The light transmission of CR-39 (curve 3) corresponds to the characteristics of traditional plastics that have been used for many years in the production of eyeglass lenses. Such spectacle lenses contain a small amount of a light stabilizer that prevents photodegradation of the polymer under the influence of ultraviolet radiation and atmospheric oxygen. Traditional spectacle lenses made of CR-39 are transparent to UV radiation from 350 nm (curve 3), and their light absorption at the border of the UV range is 55% (see table).

We draw the attention of our readers to how much better traditional plastics are compared to mineral glass in terms of UV protection.

If a special UV absorber is added to the reaction mixture, then the spectacle lens transmits radiation with a wavelength of 400 nm and is an excellent means of UV protection (curve 5). Spectacle lenses made of polycarbonate have high physical and mechanical properties, but in the absence of UV absorbers they begin to transmit ultraviolet at 290 nm (that is, similar to crown glass), reaching 86% light transmission at the border of the UV region (curve 2), which makes them unsuitable for use as a UV protection agent. With the introduction of a UV absorber, spectacle lenses cut off ultraviolet radiation up to 380 nm (curve 4). In table. Table 1 also shows the light transmission values of modern organic spectacle lenses made of various materials - highly refractive and with average refractive index values. All of these spectacle lenses transmit light radiation starting only from the border of the UV range - 380 nm, and reach 90% light transmission at 400 nm.

It should be taken into account that a number of characteristics of spectacle lenses and design features of frames affect the effectiveness of their use as means of UV protection. The degree of protection increases with an increase in the area of spectacle lenses - for example, a 13 cm2 spectacle lens provides 60-65% protection, and a 20 cm2 lens provides 96% or even more. This is due to the reduction of side illumination and the possibility of UV radiation entering the eye due to diffraction at the edges of spectacle lenses. The presence of side shields and wide temples, as well as the choice of a more curved shape of the frame, corresponding to the curvature of the face, also contribute to the increase in the protective properties of glasses. You should be aware that the degree of protection decreases with increasing vertex distance, since the possibility of rays penetrating under the frame and, accordingly, getting into the eyes increases.

Cut off limit

If the boundary of the ultraviolet region corresponds to a wavelength of 380 nm (that is, light transmission at this wavelength is not more than 1%), then why on many vintage sunglasses and spectacle lenses cut off up to 400 nm? Some experts argue that this is a marketing technique, since buyers like to provide protection beyond the minimum requirements, besides, the “round” number 400 is remembered better than 380. At the same time, data have appeared in the literature about the potentially dangerous effects of blue light in the visible region. spectrum on the eye, so some manufacturers have set a slightly larger limit of 400 nm. However, you can be sure that 380nm-blocking protection will provide you with sufficient UV protection by today's standards.

I would like to believe that we have finally convinced everyone that ordinary mineral spectacle lenses, and even more so quartz glass, are significantly inferior to organic lenses in terms of UV cutting efficiency.

Prepared by Olga Shcherbakova, Veko 7/2002

UV radiation and skin aging

A woman covering her face with a veil in our enlightened age seems to be a relic of the past. Therefore, many women of the East have already thrown off the veil and ... fully experienced the effect of the merciless sun on their skin. The fact that the sun ages the skin was also confirmed by Russian repatriates in Israel, whose skin quickly becomes covered with wrinkles in a hot, dry climate.

Role sunlight in the process of early aging is so significant that scientists began to call this type of aging photoaging. Signs of photoaging are thickening of the stratum corneum (solar keratosis), the appearance of age spots (lentigines), the accumulation of abnormal collagen fibers in the skin (elastosis), and degradation of collagen.

The deeply wrinkled faces of South American Indians or Australian farmers are a vivid illustration of photoaging. So, sunlight is the main culprit of early wilting. The sun emits light in a wide range of wavelengths (from 200 nm and above). The solar spectrum is divided into several areas: the UKF range (200-400 nm), visible light (400-700) and infrared radiation (more than 700 nm).

Visible light is the electromagnetic radiation that our eyes perceive. At a wavelength of more than 700 nm, the infrared spectrum begins, the rays of which are perceived by us as heat; and at a wavelength of less than 400 nm, there is a range of ultraviolet radiation, which plays an exceptional role in the life of many living organisms on our planet. According to modern ideas, the first wrinkles appear precisely because of ultraviolet radiation.

The UV spectrum is divided into 3 regions - UV-A, UV-B and UV-C. UV-C, the shortest wavelengths (200-290 nm), are the most dangerous because they have the highest energy. Luckily for us, all UV-C rays are trapped in the stratosphere.

UV-B rays have a range of 290 - 320 nm. They reach the Earth's surface by passing through the ozone layer. In human skin, UV-B rays penetrate the epidermis but do not reach the dermis. These rays are highly damaging and are responsible for many of the acute and chronic side effects associated with sunlight exposure. Waves of 297 nm have the greatest ability to cause erythema. UV-A wavelengths range from 320 to 400 nm. Of the entire UV spectrum, these rays have the lowest energy, but at the same time have the highest penetrating power. Reaching the surface of the Earth, they pass through the water column into the depths of the sea.

In human skin, UV-A rays reach the middle layers of the dermis. It is with them that the processes underlying photoaging of the skin are associated. It is known that in the mountains and southern regions, solar radiation is higher - you can tan and burn much faster here. This is because the intensity of UV radiation depends not only on the path traveled from the Sun, but also on the distance traveled in the atmosphere: the greater the distance, the lower the intensity of the radiation.

When UV rays pass through the atmosphere, their intensity drops by about 20% every 1000 m of travel. This is not only due to absorption in the atmosphere, but also due to additional scattering due to dust and clouds. So, on a cloudy day, the intensity of UV radiation can be reduced by almost half compared to clear days. On the sea and in the mountains, a large amount of UV rays are reflected from water or snow, and then the effect of direct radiation is supplemented by the effect of indirect, reflected light. As a result, the risk of getting sunburn is significantly increased.

In the middle lane, people usually suffer from a lack of sun, so they like to lie on the beach and gladly expose their faces to the sun's rays. Photoaging, which is a very real threat in hot countries, remains a scary tale in which they do not really believe in the inhabitants of a temperate climate.

And, apparently, in vain. Scientists believe that over the past 10 years, due to the thinning of the ozone layer, the intensity of UV radiation has increased by 3-10%. This forced doctors to take a closer look at the effect of sunlight on the skin and reconsider their attitude towards a "healthy tan".

The effect of UV rays on the skin

Small doses of UV radiation are essential for human life. Their exceptional role in the synthesis of vitamin D and calcium metabolism has been proven. In the winter months, with a lack of UV radiation, an exacerbation of some skin diseases is observed.

The psycho-emotional state of a person also largely depends on UV radiation: in cloudy weather and at night, many people become depressed. Excessive UV exposure has a damaging effect on the skin, which can be divided into acute and chronic. Acute effects are associated with damage to the skin and the reaction of the skin to damage. To sharp side effects include sunburn, thickening of the skin, and sunburn.

UV-A rays with a wavelength of more than 340 nm are mainly responsible for premature skin aging. UV-B (280-320 nm) radiation is more responsible for sunburn. Both UV-A and UV-B rays can cause malignant degeneration of cells. In modern society, a tan is considered a sign of health, but from a medical point of view, this is not entirely true. The fact is that sunburn is a protective reaction of the skin to damage.

The main goal of tanning is to prevent further damage that can lead to dangerous changes in the skin. Immediate tanning is caused by long wavelength UV-A rays and is the result of photo-oxidative darkening and redistribution of melanin pigment in epidermal cells, which they receive from melanocytes.

An immediate tan appears within 2 hours of UV exposure and has no protective effect against sunburn. A number of experimental data suggest that it may provide some protection for the DNA of cells in the basal layer of the epidermis.

Slow tanning occurs hours or days after exposure to predominantly UVB rays. The exact mechanism of tanning is still not entirely clear. It is assumed that as a result of UV damage to certain parts of the genome responsible for melanin metabolism, the enzyme tyrosinase is activated.

This leads to an increase in melanin production, an increase in the size of melanocytes, an elongation of processes (dendrites) and an increase in their degree of branching. In addition, UV radiation affects the enzymatic processes in other skin cells and intercellular space, which entails the transition of the cellular community to a different level of physiological activity. Slow tan stays for weeks and even months after UV exposure.

Thickening of the skin is not only the result of damage, but also a protective reaction that appears hours or days after UV-B exposure and persists for months. Increased division of basal cells and increased adhesion of corneocytes leads to thickening of the stratum corneum of the epidermis, which is the first barrier to UV rays and protects underlying cells and, most importantly, basal keratinocytes from damage.

Sunburn- this is a reaction of the skin to damage, as well as a kind of protective reaction: a burnt person no longer wants to sit under the sun and thus damage the skin more. The exact mechanism of sunburn formation is not well understood, but it has already been proven that it involves the formation and release of cytokines and inflammatory mediators from the cells of the epidermis and dermis. Redness, pain, swelling and even blistering can occur within hours or even days after exposure to 300 nm UV rays. Sunburn is familiar to anyone who has sunburned on the beach. This is redness of the skin, accompanied by pain, swelling, in some cases, fever and blistering.

Skin pigmentation or sunburn appears 2-3 days after irradiation, and on the 6th-10th day the tan "comes off" - the skin begins to peel off. The ability to sunbathe in all people is different.

According to the reaction to UV radiation, human skin is divided into 6 types (Fitzpatrick skin types):

1st type - never sunbathe, always burn (often have very white skin, blond hair, light eyes);

2nd type - sometimes they manage to tan, but more often they burn (fair skin, blond or brown hair);

3rd type - they tan well, sometimes they burn;

4th type - always tan, never burn (olive skin, dark hair);

5th-6th types - never burn (dark skin, black hair).

The fact that skin color can predict its sensitivity to sunlight suggests that melanin is the skin's main protector against UV radiation. Blacks, whose skin contains a lot of melanin, never get melanoma, but melanoma inevitably affects albino blacks living in Africa.

The skin of people suffering from vitiligo (white spots on the skin) has different sensitivity to the sun in pigmented and non-pigmented areas. Melanin absorbs UV radiation and acts as a natural UV filter. Keratinocytes receive melanin granules from melanocytes, cells that produce melanin and are located in the basal layer of the epidermis. The more intense the UV radiation, the more melanin the melanocytes produce.

Skin damaged by UV rays ages. However, this aging has some distinctive features. With true aging, all layers of the skin become thinner. With photoaging, thickening of the epidermis and the stratum corneum occurs. Changes in the intercellular substance of the dermis during photoaging are uneven - along with normal collagen fibers, accumulations of amorphous atypical material consisting of elastin are found in it.

The ability to synthesize collagen and other components of the intercellular substance of the dermis in photodamaged skin is preserved, so many signs of photoaging are reversible. A characteristic sign of photoaging are spider veins (spiders, reticulum) and age spots (lentigo). Together, all these symptoms give a characteristic picture of photoaging, which gave scientists reason to distinguish it as an independent form of aging.

Another negative consequence of UV radiation is photodermatitis - a violent inflammatory reaction of the skin with the formation of blisters. The causes of photodermatitis are different.

Sensitivity to the sun can be caused by any disease, or it can appear as a result of cosmetic procedures (dermabrasion, laser resurfacing, peeling, epilation). Sometimes photodermatitis appears after certain drugs (sulfonamides, tetracyclines, psoralens, some antidepressants).

A substance that makes the skin more sensitive to UV radiation is called a photosensitizer. The role of a photosensitizer can be played by components of cosmetics - some preservatives, a number essential oils and even UV filters. Therefore, if after going outside the skin suddenly blistered and inflamed, then the first thing to do is remember if you have taken any medications and have not applied a new day cream to your skin.

And if you have had laser resurfacing, dermabrasion, epilation, etc., you must use sunscreens with 100% UV absorption (for example, based on titanium dioxide).

Photoaging, unlike normal aging, is treatable. Of course, it is not possible to completely rejuvenate the skin, however, to a large extent, changes in the skin caused by UV radiation are reversible. For the treatment of photodamaged skin, peeling with alpha-hydroxy acids (ANA) is used, which stimulate increased peeling of the upper layer of the skin, accelerate the renewal of the epidermis and enhance collagen synthesis, as well as preparations containing retinoic acid.

How to protect yourself from UV radiation

It is impossible to constantly hide from the sun, and it is not necessary. However, precautions should be taken to protect against excessive UV radiation.

There are three main ways to protect:

If possible, avoid direct sunlight;

Wear clothing that protects the skin from the sun;

Use sunscreens containing UV filters.

The first method seems at first glance the simplest, but in reality it is not always feasible. As for clothing, materials such as silk and polyester provide the best protection. In general, the thicker the fabric, the better it protects the skin from UV rays. But there are also difficulties with clothes, especially on a hot sunny day or on the beach. Therefore, the most reliable and “convenient” protection are sunscreens containing UV filters.

Sunscreens fall into several categories.

Sun creams are needed in order to sunbathe without burning. They contain UV filters that absorb UV-B rays. This is, for example, Firstan Cream SPF 8, manufactured by INTEGRE (Heliosystem line). However, it should be remembered that the cause of photoaging is mainly UV-A radiation, from which sunscreens do not protect.

Creams "anti-sun" contain broad-spectrum UV filters that block the entire UV range. Such a remedy, for example, is Firstan Milcream SPF15 cream, manufactured by INTEGRE (Heliosystems line). This hypoallergenic cream contains micronized titanium dioxide - a physical filter with a high degree of protection and tyrosine - a substance that activates melanogenesis. Flax seed extract - a natural antioxidant - enhances the protective effect of the cream.

It is these remedies that are the best protection against photoaging and reduce the risk of malignant neoplasms. They are also used in case of increased skin sensitivity to sunlight. Under the influence of UV radiation, free radicals form in the skin. The entire antioxidant system of the skin rises to fight them. This fight is often unequal, because. Intense solar radiation damages the skin's antioxidant enzymes.

To help your skin fight off free radicals, boost your antioxidant defenses before hitting the beach. To do this, use cosmetic oils containing natural antioxidants, vitamin E and carotenoids: for example, carrot oil, palm oil or linseed oil. At the same time, cosmetics should not contain unsaturated fatty acids, because. Under the influence of UV radiation, they will oxidize and become a source of free radicals on the skin.

To protect against excess UV radiation, sunscreens are used, which can be chemical (chemicals and cover creams containing ingredients that absorb UV radiation) and physical (various barriers that reflect, absorb or scatter rays). A good means of protection is special clothing made from fabrics that are the least permeable to UV radiation (for example, poplin). To protect the eyes in production conditions, light filters (glasses, helmets) made of dark green glass are used. Full protection against UV radiation of all wavelengths is provided by a 2 mm thick flint eye (glass containing lead oxide).

When arranging rooms, it must be taken into account that the reflectivity of various finishing materials for UV radiation is different than for visible light. Highly polished aluminum and honey white reflect UV radiation well, while zinc and titanium oxides, oil-based paints do not.

3.4 Ionizing radiation

3.4.1 Sources and scope of ionizing radiation

The rapid development of nuclear energy and the widespread use of ionizing radiation sources (IRS) in various fields of science, technology and the national economy have created a potential threat of radiation hazard to humans and environmental pollution with radioactive substances. Therefore, the issues of protection against ionizing radiation (radiation safety) are becoming one of the most important problems.

Radiation (from the Latin radiatio - radiation) is characterized by radiant energy. Ionizing radiation (IR) is the name given to the streams of particles and electromagnetic quanta formed during nuclear transformations, i.e. as a result of radioactive decay. The most common types of ionizing radiation are X-rays and gamma rays, fluxes of alpha particles, electrons, neutrons and protons. Ionizing radiation directly or indirectly causes ionization of the medium, i.e. the formation of charged atoms or molecules - ions.

Sources of IR can be natural and artificial radioactive substances, various types of nuclear installations, medicines, numerous control and measuring devices (defectoscopy of metals, quality control of welded joints). They are also used in agriculture, geological exploration, in the fight against static electricity, etc.

Some characteristics of the main radioactive elements are presented in Table. 3.2.

Table 3.2

Characteristics of the main radioactive elements

Name element	Element Specification and Precautions	Half-life

	A gas that emits alpha particles. Constantly formed in rocks. Dangerous when accumulated in mines, basements, on the 1st floor. Ventilation (ventilation) is required.
Xenon-133	gaseous isotopes. Constantly formed and decay during the operation of a nuclear reactor. Insulation is used as protection.
	Emits beta particles and gamma rays. Formed during the operation of a nuclear reactor. Together with greens, it is absorbed by ruminants and passes into milk. Accumulates in the human thyroid gland. As protection against internal exposure, an "iodine diet" is used, i. introduce stable iodine into the human diet.
Krypton-85	A heavy gas that emits beta particles and gamma rays. Included in the spent fuel element of the reactor. Released during storage. Protection - an isolated room.
Strontium-90	A metal that emits beta particles. Major fission product in radioactive waste. Accumulates in human bones.
	A metal that emits beta particles and gamma rays. Accumulates in muscle cells.
	A metal that emits gamma radiation, alpha and beta particles. Protection - shelters and shelters.
Carbon-14	Emits beta particles. Natural natural isotope of carbon. Used to determine the age of archaeological material.
Plutonium-239	Emits alpha particles. Contained in radioactive waste. Protection - high-quality disposal of radioactive waste.
	Emits beta particles and gamma rays. It is contained and replaced (excreted) in all plants and animals.	1.3 billion years

Surveyors may encounter ionizing radiation when performing work on charged particle accelerators (synchrophasotrons, synchrotrons, cyclotrons), as well as at nuclear power plants, uranium mines, etc.

Alpha particles are the positively charged nuclei of helium atoms. These particles are emitted during the radioactive decay of some elements with a large atomic number, mainly transuranium elements with atomic numbers over 92. Alpha particles propagate in media in a straight line at a speed of about 20 thousand km / s, creating high-density ionization on their way. Alpha particles, having a large mass, quickly lose their energy and therefore have an insignificant range: in air -20-110mm , in biological tissues - 30-150mm , in aluminum -10-69 mm.

Beta particles are a stream of electrons or positrons that have a greater penetrating and less ionizing power than alpha particles. They arise in the nuclei of atoms during radioactive decay and are immediately emitted from there at a speed close to the speed of light. At medium energies, the range of beta particles in air is several meters, in water - 1-2 cm, in human tissues - about 1 cm, in metals - 1 mm.

X-ray radiation is electromagnetic radiation of high frequency and short wavelength, which occurs when a substance is bombarded by a stream of electrons. The most important property of X-ray radiation is its high penetrating power. X-rays can occur in X-ray tubes, electron microscopes, powerful generators, rectifier lamps, cathode ray tubes, etc.

Gamma radiation refers to electromagnetic radiation and is a stream of energy quanta propagating at the speed of light. They have shorter wavelengths than X-rays. Gamma radiation freely passes through the human body and other materials without noticeable attenuation and can create secondary and scattered radiation in the media through which it passes. The intensity of exposure to gamma rays decreases inversely with the square of the distance from a point source.

Neutron radiation is a stream of neutral particles. These particles fly out of the nuclei of atoms in some nuclear reactions, in particular, in the reactions of fission of uranium and plutonium nuclei. Due to the fact that neutrons do not have an electric charge, neutron radiation has a high penetrating power. Depending on the kinetic energy, neutrons are conditionally divided into fast, ultrafast, intermediate, slow and thermal. Neutron radiation arises during the operation of charged particle accelerators and reactors, which form powerful fluxes of fast and thermal neutrons. A distinctive feature of neutron radiation is the ability to convert atoms of stable elements into their radioactive isotopes, which dramatically increases the danger of neutron exposure.

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