Tanning with sunscreens ends with cancer
WHAT ARE THE DANGERS OF SUNSCREENS?
Anna Margolina, PhD, G. Redmond (USA)
"Science and Life" No. 6-2010
Science has proved quite convincingly that excess ultraviolet radiation (UV) causes premature aging and skin cancer (including its most dangerous form – melanoma). Therefore, both in Europe and in the USA, people now rarely dare to go to the beach without smearing themselves from head to toe with sunscreen. Gradually, this custom is being instilled in Russia, which has recently been willingly picking up Western trends in the field of a healthy lifestyle.
Meanwhile, now there are more and more reasons to assert that sunbathing with sunscreens is sometimes no less, and sometimes more dangerous than roasting in the sun without any protection. After all, it is in the USA and Europe, where sunscreens have been used for quite a long time, over the past three decades there has been an increase in the incidence of all forms of skin cancer. If in the early 1970s the incidence of melanoma among the white population of the United States was six cases for every 10 thousand people, then by the early 2000s it had tripled. In Europe, the incidence of melanoma has increased almost fivefold over the same time period. Three hypotheses have been proposed to explain this sad fact. According to the first, the current increase in the incidence of skin cancer is a reckoning for the craze for the sun in the 1960s and 1970s, since more than a decade may pass between the primary DNA damage and the development of a tumor. Proponents of the second hypothesis blame sunscreens and the chemicals they contain. And finally, the third hypothesis is that it is not the sunscreens themselves, but the way we use them, that turns them from skin protectors into a risk factor.
Tan and vanityIt all started in the 1960s, when white-skinned Caucasians suddenly began to try their best to change the color of their skin, which until recently they were so proud of.
The driving force behind this aspiration was ordinary human vanity. Before the Industrial Revolution, a significant percentage of the population was engaged in agriculture, so labor and poverty were associated with sunburned skin, which speaks of long hours spent in the fields, under the open sky. However, in the post-war period (1950s), more and more people began to work in factories and factories where the sun's rays did not penetrate. Now it was the pale, pigment-free skin that became evidence of the need to earn a living by hard work, while the tan was associated with idleness, sun-drenched tennis courts and tropical beaches.
However, it turned out that changing the skin color, even temporarily, is not so easy. Someone did it pretty quickly, and someone had to put the skin to painful tests - it was worth spending a little more time in the sun, and you could get a sunburn, which negated all efforts to acquire the desired tan, as the skin peeled off after the burn.
It was to these sufferers that the cosmetic industry offered a novelty - cosmetics that protected from burns, but did not prevent tanning. Thanks to the new tools, even people who were endowed by nature with pale, poorly tanned skin could spend long hours on the beach, eventually achieving the desired tan. As it turned out, this was by no means the right thing to do.
The ABC of ultravioletUltraviolet radiation reaching the Earth with the sun's rays can be divided into two types – UV-A and UV-B.
The fundamental difference between them is the energy of radiation and the depth of penetration into the dermis. UV-B carries a lot of energy, so it causes a burn quickly enough. It was this type of radiation that was blocked by the first sunscreens, and it was it that was considered the most dangerous for a long time. However, it is now known that UV-B does not penetrate deeply and all the damage it causes to the skin usually does not have far-reaching consequences. The burned skin is first covered with blisters, then comes off in patches, and with it those cells that have dangerous breakdowns in DNA are removed.
Ultraviolet, visible light and infrared rays
they penetrate the skin to different depths.
The numbers on the arrows show what proportion of radiation
it reaches the epidermis, basal cell layer and dermis.
The situation is completely different with type A ultraviolet, which was initially considered useful because it causes a tan, but does not have enough energy to burn the skin. But it turned out that it is UV-A that can penetrate into the deep layers of the epidermis and dermis and damage biological molecules. If earlier people could not sunbathe for too long, as their skin burned, and usually received only temporary, superficial damage, then with the advent of the era of sunscreens that protected the skin from UV-B radiation, many began to lie on the beach for hours, being exposed to prolonged UV-A radiation.
What is the danger of ultravioletBoth UV-B and UV-A rays can be absorbed by biological molecules and cause photochemical reactions leading to the appearance of free radicals – unstable, highly reactive molecules that lack one electron and are very willing to enter into chemical reactions.
We can say that a free radical is like a young reveller who has no moral obligations and does not miss an opportunity to start an affair. And if such an "immoral" radical comes into contact with a "respectable" molecule, then the latter will turn into a free radical and begin to bring confusion into the strict harmony of chemical reactions. In particular, UV-A radiation penetrating deep into the skin can turn collagen molecules into free radicals – a protein that provides smoothness and elasticity of the skin. As a result, collagen fibers bind to each other, forming clusters of defective inelastic collagen, which gradually leads to the appearance of characteristic skin irregularities and wrinkles. They, formed under the influence of UV radiation, appear with a noticeable advance of the "schedule", long before the skin begins to age for natural reasons. The consequences of the free radical transformation of DNA are even more serious: two parts of the DNA molecule that have become radicals can contact one another, thereby introducing confusion into the genetic code of the cell. From cells that have received DNA damage, malignant tumors can develop over time.
SPF is an unreliable indicator In the 1990s, broad-spectrum sunscreens finally appeared, that is, those that protected not only from UV-B, but also from UV-A radiation.
There was a problem here. People wanted to sunbathe, as tanned skin was still considered beautiful. But if a sunscreen is applied to the skin that does not pass either UV-A or UV-B, then no tanning will work. Beachgoers who dream of a "safe" tan began to especially appreciate sunscreens, which had reassuringly high values of the sun protection factor – SPF (sun protection factor). The fact that even with sunscreens having high SPF values, the tan appeared (albeit slower than without protection), for some reason did not alarm anyone. And in vain, because in fact the SPF value is a very unreliable indicator of the effectiveness of protection.
SPF allows you to assess how much this product slows down the appearance of the first redness of the skin under the influence of UV radiation. For example, if redness appears after 20 minutes without sunscreen, then with sunscreen having a protection factor of 10, redness will appear after 200 minutes. Since redness of the skin occurs only under the influence of UV-B radiation, the solar protection factor indicates only the effectiveness of UV-B protection.
Now many manufacturers of sunscreens indicate on packages the degree of protection against UV-A radiation according to a five-star system: the more stars, the better the protection. But so far, SPF remains the most well-known and popular performance indicator, which is why consumers pay attention to it. At the same time, few people realize that a sunscreen that has a high SPF, and therefore reliably protects the skin from sunburn, does not necessarily block the path of UV-A radiation as effectively. As a result, people can lull themselves to a sense of security and get the desired tan... with all the ensuing consequences.
Unsafe cocktailDecades of obsessive advertising of sunscreens have led to the fact that people, especially in the West, began to consider them as an obligatory component of a beach pastime.
However, let's think about what, strictly speaking, is being offered to us? And they offer us to smear ourselves with preparations containing a variety of chemicals and substitute this cocktail on our skin under the sun's rays. At the same time, it somehow goes without saying that these substances do not react with the skin or with solar radiation, they do not penetrate into the blood under any conditions and, in general, demonstrate complete inertia and reliability. But this is not the case.
Sunscreens contain UV filters (they are also called UV absorbers) - substances that reduce the amount of UV radiation entering the skin. Those UV filters that contain particles that reflect and scatter UV radiation are called physical or inorganic UV filters. These include zinc oxide and titanium dioxide. Physical UV filters do not cause allergies and do not irritate the skin, and also have a wide spectrum of action – they block both UV-A and UV-B radiation. Previously, physical UV filters contained large insoluble particles, so they stained the skin white. Now the particles of physical UV filters have become very small - in the micro– and even nano-range, so that they no longer stain the skin.
Another group of UV filters combines substances that can absorb UV radiation due to the peculiarities of their chemical structure. They are called organic or chemical UV filters. Organic UV filters allow you to create products with a protection factor of up to 100 and even higher, it is convenient to include them in a variety of cosmetic forms - creams, gels, sprays, lotions, etc., impregnate clothes with them, as well as add them to decorative cosmetics, shampoos and hair sprays. But not all of these substances are safe for the skin.
First of all, organic UV filters quite often cause allergies and skin irritation. In addition, some organic UV filters may exhibit photoreactivity. This means that if such UV filters are exposed to ultraviolet light for a long time, they begin to break down, sometimes releasing free radicals at the same time. This means that after a certain time of irradiation, more free radicals will form in the skin "protected" by such UV filters than in unprotected skin.
Now it has become known that a number of organic UV filters also have hormonal effects. It has been revealed that they can cause sex change and disorders of the development of sexual organs in fish, shellfish and other aquatic inhabitants. It is not yet clear how hormonal effects of UV filters are manifested in the human body, but it is already obvious that these substances cannot be called safe and inert.
Perhaps the most shocking fact is that UV filters can penetrate into the blood and accumulate in the body. For example, according to a recent study conducted in the United States, a common UV filter benzophenone-3 (oxybenzone), which is part of many sunscreens, was found in 96% of more than 2,000 urine samples taken from Americans of different ethnic origin, age and gender. At the same time, in the body of women, especially young people, the content of oxybenzone was on average three times higher than in the body of men, and in the blood of white Americans seven times higher than that of African Americans.
Natural protectionIf not sunscreens, then what?
Let's start with the fact that human skin is not at all as defenseless against UV radiation as manufacturers of sunscreens are trying to imagine. We just need to treat this protection reasonably and not make exorbitant demands on it. For example, if a construction helmet withstood the impact of a fallen brick, this does not mean that it is impenetrable. Therefore, if you have a whim to put on a helmet and beat yourself on the head with a crowbar, you only have yourself to blame for the consequences. It's the same with skin protection systems. Don't overexert them.
The main protector of the skin is the dark pigment melanin. At the same time, the darker the original (genetically predetermined) pigmentation of the skin, the more effective the protection. People with dark skin, as a rule, tan well and rarely get burned. With insufficient production of melanin, a person easily burns and hardly achieves at least some kind of tan. Therefore, if you have light, easily scorching skin, then you need to be careful with the sun's rays, regardless of whether you are smeared with sunscreen or not. If you have dark skin, then you can rely on the protective effect of your own skin pigment. However, too long and intense UV radiation can damage and cover with wrinkles and age spots even the skin of Negroids. And even negroids have melanoma. However, much less often than in white people.
The skin is damaged the more, the thinner it is. Therefore, as a rule, women's and children's skin suffer more from UV radiation. It is especially dangerous to expose the skin of infants under a year to excessive UV radiation. However, short sun baths in the morning will not hurt and, on the contrary, will help to develop the necessary vitamin D.
Another line of defense is antioxidants – substances that neutralize free radicals. They are contained in the stratum corneum of the skin, and also stand out on its surface with sebum. It should be remembered that many antioxidants are vitamins that are not produced in the body and must come with food. An excellent source of antioxidants – vegetables, fruits and berries, green tea.
If the protection did not work and the skin cells suffered from the sun, then all is not lost, since the skin is able to correct a significant part of the damage. One of these life–saving reactions is the well-known "peeling" of the skin after a sunburn. This "skin change" helps the body get rid of cells with damaged DNA, which otherwise could give rise to a malignant tumor.
Who is to blame and what to do?As we can see, there are many reasons that the era of sunscreens has become at the same time an era of an unprecedented increase in the incidence of skin cancer.
A certain role was played by the fact that in the period from the 1970s to the 1990s, most sun lovers either did not use sunscreens at all, or used UV-V protection, which only contributed to a longer stay on the beach, without reducing the risk of skin damage at all. Along with this, a certain role is played by the presence of substances in sunscreens that are potentially capable of increasing skin damage. But most importantly, this is still the paradoxical behavior of people who continue to strive for the desired tan, despite all the warnings of scientists and doctors.
Of course, a person needs sunlight. Ultraviolet provides the synthesis of vitamin D, which is not only important for the proper formation of bones and muscles, but also plays a significant role in preventing malignant tumors, maintaining the health of the heart, liver and kidneys, as well as endocrine balance. Sunlight falling on the retina of the eye causes the formation of the natural antidepressant melatonin. Moderate UV radiation stimulates skin immunity (excess UV suppresses it), facilitates the course of many skin diseases.
But excess sunlight can prematurely age the skin and cause other adverse changes. Our great-grandmothers knew about this without any research, they just saw the dark wrinkled faces of peasant women working in the open air. Shady trees, wide-brimmed hats and gloves covering the hands up to the elbows served as protection from the sun at that time. Nowadays, it is quite possible to use sunscreens with low SPF values for the same purpose. However, if you certainly want to get a little tan, exercise reasonable caution – avoid the sun at noon, increase the time spent on the beach gradually, starting from 5-10 minutes a day, and with or without sunscreen, do not irradiate the skin for too long.
Portal "Eternal youth" http://vechnayamolodost.ru25.06.2010