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UV radiation

UV radiation exposure from tanning beds increases the risk of melanoma. The International Agency for Research on Cancer finds that tanning beds are "carcinogenic to humans" and that people who begin using tanning devices before the age of thirty years are 75% more likely to develop melanoma.

Those who work in airplanes also appear to have an increased risk, believed to be due to greater exposure to UV.

UVB light, emanating from the sun at wavelengths between 315 and 280 nm, is absorbed directly by DNA in skin cells. which results in a type of direct DNA damage called cyclobutane pyrimidine dimers. Thymine, cytosine, or cytosine-thymine dimers are formed by the joining of two adjacent pyrimidine bases within a strand of DNA. UVA light presents at wavelengths longer than UVB (between 400 and 315 nm); and it can also be absorbed directly by DNA in skin cells, but at lower efficiencies — about 1/100 to 1/1000 of UVB.

Exposure to radiation (UVA and UVB) is a major contributor to developing melanoma. Occasional extreme sun exposure that results in " sunburn " on areas of the human body is causally related to melanoma; and such areas of only intermittent exposure apparently explains why melanoma is more common on the back in men and on the legs in women. The risk appears to be strongly influenced by socioeconomic conditions rather than indoor versus outdoor occupations; it is more common in professional and administrative workers than unskilled workers. Other factors are mutations in (or total loss of) tumor suppressor genes. Using sunbeds with their deeply penetrating UVA rays has been linked to the development of skin cancers, including melanoma.

Possible significant elements in determining risk include the intensity and duration of sun exposure, the age at which sun exposure occurs, and the degree of skin pigmentation. Melanoma rates tend to be highest in countries settled by migrants from Northern Europe which have a large amount of direct, intense sunlight to which the skin of the settlers is not adapted, most notably Australia. Exposure during childhood is a more important risk factor than exposure in adulthood. This is seen in migration studies in Australia.

Incurring multiple severe sunburns increases the likelihood that future sunburns develop into melanoma due to cumulative damage. UV-high sunlight and tanning beds are the main sources of UV radiation that increase the risk for melanoma and living close to the equator increases exposure to UV radiation.