3. How can different types of ultraviolet radiation affect health?
- 3.1 Do natural and artificial UV radiation present different health risks?
- 3.2 What are the health risks of UVA, UVB and UVC radiation?
3.1 Do natural and artificial UV radiation present different health risks?
UV radiation from sunbeds and from the sun is essentially the same
There are no physical differences in UV radiation generated by the sun or by UV lamps. However, there are three types of UV radiation – UVA, UVB, and UVC – which have different wavelength ranges, and the intensity at each wavelength is distributed differently for the sun and for various artificial sources. Solar UV radiation at ground level, for instance, is primarily made up of UVA, with some UVB and no UVC, and varies with the season, latitude, and time of day.
The short-term risks of exposure to UV radiation are similar for natural and artificial sources. However, it is much more difficult to compare long-term effects which, in the sun, also depend on patterns of exposure. There are few data on the risk of skin cancer associated with artificial UV radiation sources compared with those related to sun exposure, and the existing studies often do not provide useful information because they involve few cases, and cannot estimate exposure doses accurately. In addition, people who use sunbeds often sunbathe frequently which may seriously affect the reliability of the data.
Artificially generated UV radiation is used to treat some skin diseases such as psoriasis, and the risk of developing cancer following treatment seems to be small, except when combined with the use of psoralen. However, the data are few and the doses of UV radiation to which patients are exposed are significantly smaller than those used in commercial sunbeds. More...
3.2 What are the health risks of UVA, UVB and UVC radiation?
UV radiation covers a range of wavelengths and is divided into three bands: UVA (315-400nm), UVB (280-315nm) and UVC (<280nm). More recently, the terms UVA-I and UVA-II have been introduced because UVA-I (340-400nm) and UVA-II (315-340nm) cause different biological effects.
In general, it takes much less UVB than UVA to produce short-term effects on the skin such as sunburn, delayed pigmentation (tanning) and damage to DNA. UVB reduces the immune response of the body but the role of UVA remains unclear.
Because it is completely absorbed by the ozone layer, UVC from solar UV radiation is not a health issue. UVC from artificial sources is unlikely to present a short or long-term hazard to human skin, but it is likely to cause a temporary inflammation of the cornea.
Sunburn, a marker for excessive UV radiation exposure, is a risk factor for melanoma. UVB is the main cause of sunburn but this does not necessarily mean that it is the prime cause of melanoma. Indeed, the relative roles that UVA and UVB play in causing melanoma are still not well known and, at present, it is advisable to restrict both UVB and UVA exposure in susceptible individuals.