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Research | Atmosphere | Ozone shield - The right protection against UV radiation
The right protection against UV radiation
The Sun is a source of warmth, light and pleasure, especially in northern countries where summer is short. In the middle of winter, summer is often sought on southern beaches, and the Sun in solariums.
Radiation from the Sun includes not only light but also, for example, invisible UV (ultraviolet) radiation. UV radiation affects melanosythes, cells producing the skin's pigment. The skin tans when exposed to UV radiation, but may also burn, if it gets too much radiation. The amount of ozone in the upper atmosphere has been declining over the last few years above Finland and Scandinavia, particularly in late winter. This somewhat increases the UV radiation reaching the ground. This increase of exposure will not become evident as health damage until years have passed by.
The risk of skin cancer increases because of radiation entering the skin. Skin cancers have indeed rapidly become more common in Finland. There are three different forms of skin cancer: basal cell carcinoma, squamous cell carcinoma and melanoma. Basal cell carcinoma is cured by a local operation, but squamous cell carcinoma and melanoma are more dangerous, as they metastasise to other parts of body. Melanoma is probably connected with frequent sun-burning especially in childhood. Every year about 600 melanoma cases are diagnosed in Finland.
Despite its bad reputation, melanoma can usually be cured. Nowadays about 20 % of melanoma patients in Finland die of this cancer. Mortality has declined, because treatment methods have improved and, unlike earlier, people go for treatment in time.
Differences between different skin types affect the skin's capability of reacting to the Sun's radiation and tanning. Each skin type has its own self-protection time, during which one can stay in strong sunlight without any shelter and still avoid skin damage.
| Skin |
Burning and |
Self-protection time in |
| type |
tanning in the sun |
strong sunlight |
| I |
always burns, never tans |
5-10 minutes |
| II |
usually burns, sometimes tans |
10-20 minutes |
| III |
sometimes burns, usually tans |
20-30 minutes |
| IV |
rarely burns, always tans |
40 minutes |
About one third of Finnish people fall into categories I and II. Most are of type III, every tenth belonging to group IV. Dark skin responds slower to sunlight, light skin being more sensitive. Individuals having red hair and very light skin usually tolerate sun poorly. Tanning will not give a perfect protection against sunburn. Tanning obtained in a solarium is not as protective a shield as that obtained in sun, because the UV-A radiation in solariums does not cause thickening of the skin. Beta carotene obtained from carrots, for example, and the consequential yellowish skin colour also have only a minor protective impact. Excessive UV radiation ages skin prematurely. The skin becomes dry and coarse and will develop irregular pigmentation.
In southern countries about half of the overall UV radiation exposure is obtained during the hours around noon. If you stay in the shade during these hours, you can reduce your burning risk considerably. The siesta is healthy in many ways.
Near the Equator UV radiation is abundant, weakening towards the north and south. In northern parts of Australia, the amount of radiation reaching the ground is 3-4 times greater than in Finland.
Enhanced awareness of the disadvantages of excessive sunbathing has created a need for getting information about changes in UV radiation. For this purpose a UV index in conformance with the recommendations of the UN has also been introduced in Finland. The UV index is being used in the same way all over the world. Factors affecting variations in the UV index are mainly the location on the globe together with season and time of day. The ozone amount and the weather have an influence, too.
The UV index is a number indicating the amount of harmful UV radiation. A value of 0 means that there is no radiation at all. Values of 10 and greater indicate very strong radiation obtained when approaching latitudes near the Equator. The Finnish midsummer UV index varies between values of 4 and 6 at noon.
It is also obvious that a light skin in spring tolerates UV radiation much worse than one already naturally tanned in sunlight, later in summer. The tan obtained in a solarium does not give too good a basic protection. If the given protection time is exceeded by a factor of three, slight burning will result. A five-fold excess exposure will lead to painful burning and a ten-fold one to blisters appearing on the skin.
The Finnish Centre for Radiation and Nuclear Safety recommends an annual limit of 10-30 times for the use of a solarium. Usage, however, also depends on skin type: individuals with the most sensitive skin (of type I) are advised not to use a solarium at all. If the skin begins to get reddish after a session in the solarium, the exposure has been excessive. If the skin has been sensitised as a consequence of medication or sickness, it is no use going into a solarium or into sunlight.
Having over 50 moles of different shapes and sizes indicates an increased risk for getting skin cancer. It is important to follow changes in the moles and their number. If a mole on your skin begins to grow, itch, darken or become broken, or other unusual changes in the skin appear, consult your doctor.
Without any special protection, children with blond hair burn easily in the sun. Repeated sunburn increases children's risk of getting skin cancer in the future. It is therefore a good practice to protect children against the harmful effects of UV radiation. Short-term staying in the sun at the beginning and a gradual familiarisation to warmth and radiation are the simple and well-known methods. A shirt and hat may be used for protecting those areas of skin most susceptible to sunburn: the shoulders, neck and arms. Sun lotions are often necessary for children. During a holiday in the sun, the recommended sun protection factor (SPF) for children is 8.
UV radiation enhances a dimming of the eye's lens, which means that potential cataracts begin to evolve at earlier ages. Part of the UV radiation reaches the back of the eye, causing cells in the retina to slowly begin to deteriorate. Damage will in time especially affect near vision. Radiation is partly absorbed in the lens of an adult, but will go right through the lens of a child, reaching the back of the eye. This is the reason why children's eyes in particular should be protected against strong sunlight.
UV radiation is reflected from different surfaces, increasing the amount of radiation. Particularly good reflectors are snow and white sand - fresh snow reflects over 80 % of UV radiation and sand may also reflect as much as 20 % of the rays. On the other hand, water reflects much less. Being under water will not therefore protect against sunburn, at least while swimming in surface water, because radiation penetrates a thin water layer. At a depth of half a metre, 40 % of the radiation is still present. One can tan and theoretically even burn in cloudy weather - 90 % of UV radiation may be transmitted by thin cloud. A sunbather in a horizontal position receives 4 times more radiation than in a vertical position.
Sun lotions take the form of emulsions, creams or oils. Their effect is based on chemical substances and physical protection. The chemical substances of a sun lotion are absorbed into the skin. Some of them also have so-called micro-pigments that remain on the skin. They both absorb and reflect rays. Sun lotions are especially useful when the overall exposure time is not too long.
The SPF (Sun Protection Factor) indicates how much longer a time than the actual self-protection time one can stay in sun after applying the sunscreen. If e.g. your self-protection time is 20 and the SPF of your sun lotion is 4, you can stay in the sun for a maximum of 80 minutes. A fully protective sun lotion has an SPF of over 20. In the United States one should bear in mind that the SPF indicated on the sun lotion container is about one third higher than that for European ones.
The more effective substances a sun lotion has, the higher the SPF. At the same time, the risk of becoming allergic to these substances increases. Crucial factors affecting the choice of a sun lotion are skin type and the extent of UV exposure. At the beginning it is sensible to use sunscreens with a high SPF. After a week or so it is possible to start using a sun lotion having a lower SPF. In the south, the SPF should be at least 8 for blond individuals and children.
The eyes may be best protected against UV radiation by wearing sunglasses. Currently-available sunglasses almost always protect 99 -100 %. Consult an optician for further information. Ordinary glasses also protect eyes against UV-B radiation, but transmit the longer-wave UV-A radiation. Because the eye lens of a child is clear and transmits UV radiation effectively, protecting children's eyes is important especially on springtime snow and on southern beaches.
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