Sun’s ultraviolet radiation
Sun’s ultraviolet radiation
The sun's ultraviolet radiation (UV) is the most important source of UV radiation in the living environment. Exposure of the skin to large amounts of UV radiation and skin burn increase the risk of skin cancer.
About 95% of the sun's ultraviolet radiation reaching Earth’s surface is UVA radiation and
about 5% is UVB radiation. UVC doesn’t reach Earths’ surface.
UVB radiation burns the skin. It penetrates the surface layers of the skin and causes it to thicken and tan. The thickened layer of skin protects the tissues from the adverse effects of UV radiation together with tanning, i.e. increased pigmentation. However, exposure of the skin to large amounts of UV radiation and skin burn increases the risk of developing skin cancer.
UVA radiation penetrates the deepest layers of the skin and tans the pigment in the skin and causes premature skin aging. UVA radiation also promotes skin cancer.
UVC radiation is completely blocked in the upper layers of the atmosphere. UVC radiation is extremely burning and is used, for example, in germicidal lamps.
The UV index describes the intensity of ultraviolet radiation. The website of the Finnish Meteorological Institute provides UV index forecasts for the whole world. The higher the UV index, the greater the risk for sunburn.
In addition to the Finnish Meteorological Institute's web service, the UVI forecast is also available through the SMS service developed jointly by the Finnish Meteorological Institute and the Finnish Cancer Society. The SMS tells the UVI forecast for thousands of cities and resorts in Finland and around the world.
Has the UV radiation increased?
In the early 1980s, chlorine and bromine compounds released into the atmosphere were found to reduce ozone levels in the upper atmosphere (i.e., 10 to 50 kilometres). Atmospheric ozone is needed to attenuate relatively short-wave UVB radiation. It is UVB radiation that is most harmful to living nature.
UV-rays that burn the skin are estimated to have increased by about 12%. In the long run, this can increase skin cancer by 20 to 30 percent, if the lifestyle remains the same. For the time being, however, it is unclear whether UV radiation has increased permanently. It is difficult to make a reliable trend estimate because the natural variation in the thickness of the ozone layer and the variation in cloudiness affect the measured UV dose. In addition, it is very difficult to accurately measure UV radiation.
Ozone protection agreements are expected to halt atmospheric ozone depletion in the coming years. However, it is conditional on strict compliance with the agreements. If mankind had continued as before to destroy the ozone layer, recent estimates suggest that there would have been a major environmental disaster. Ozone protection paves the way for other measures to prevent atmospheric and climate change.