Causes of skin cancer

This page contains information about the links between sun exposure, sunbeds and cancer. It will also tell you about who is most at risk. Click on the links below to read about specific topics.

• Sun exposure and skin cancer
• Childhood exposure
• Melanoma risk factors
• Tanning
• Sunbeds

Too much sun exposure causes skin cancer

International health organisations agree that sun exposure is the main cause of skin cancers 1. Ultraviolet (UV) radiation from the sun damages DNA, which leads to the development of cancer 2.

Scientists estimate that heavy sun exposure causes at least two thirds (and probably more) of all malignant melanomas and up to 90% of all non-melanoma skin cancers (NMSCs) 3,4.

People who receive the highest exposures to the sun have about 20-35% higher risks of melanoma 5,6, but sunburn increases the risk of this disease even more. Two analyses of several studies showed that sunburn at any age nearly doubles the risk of malignant melanomas 5,6.

Recent studies have shown that intense, intermittent sun exposures, such as holiday sunbathing, pose the greatest risk of malignant melanomas 5,6. The recent increase in the numbers of people holidaying abroad may contribute to the rising numbers of melanoma cases 5,7,8.

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Sun exposure in childhood affects your skin cancer risk as an adult

Experts agree that a person’s lifetime skin cancer risk is strongly affected by sun exposure during the first 15 years of life 9,10. Studies indicate that sunburn during childhood can double a person’s risk of skin cancer 5,6. And migration studies have found that people who move to areas with higher UV exposures (like Australia) have higher melanoma risks if they arrive as children than as adults 11,12.

Some studies have found that sun protective behaviours during childhood can lead to fewer moles, a known risk factor for melanoma 13-16. For example, one study showed that regular sunscreen use during the first 18 years of life can reduce the risk of NMSC by 78% 17,18.

It is especially important to teach children sensible sun behaviours in the first few years of life when they are more likely to develop unhealthy attitudes to sun exposure 19-23.

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Some people have higher risks of melanoma and need to take extra care

Studies have shown that some people have a higher risk of melanoma than others. You should take extra care in the sun if you:

• have fair skin 24
• have red or blond hair 24
• have blue, green or hazel eyes 24
• have freckles 24
• tan poorly and burn easily 20,21
• have large numbers of moles 25,26
• have a family history of skin cancer; up to one in ten melanomas occur in people with inherited predispositions 24,27

Ethnic minorities with darker skins are up to 20 times less likely to develop melanoma than white Caucasians 28,29. They have higher levels of the pigment melanin, which provides some protection from UV-induced damage 22. But people with darker skin can still burn and develop skin cancers, especially on non-pigmented parts of the body like the soles of the feet, or the nail bed 30.

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Tanning is not a sign of health and offers little protection against burning

Far from being a sign of health, science tells us that a tan is a reaction to DNA damage in the skin. It is a sign that your body is trying to repair damage that has already happened 31,32. And pre-holiday tans or sunbed tans offer very little protection against the sun. Some studies have found that tans only offer protection equivalent to using factor 3 sunscreen 33,34.

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Sunbeds are not safe and can also increase your risk of skin cancer

Studies have linked sunbed use to both malignant melanoma and NMSCs 1,35. The International Agency for Research into Cancer (IARC) looked at 19 studies on sunbeds and cancer. They concluded that young people (under the age of 35) who use sunbeds have a 75% higher risk of melanoma.36 Another study estimated that sunbeds cause 100 deaths from melanomas every year in the UK 37. Sunbeds also cause eye damage and premature skin ageing 38.

IARC also concluded that sunbeds provide no positive health benefits. They do not protect against further damage from the sun and they do not help your skin to make enough vitamin D. 36

Sunbeds are marketed as a ‘controlled’ way of getting a ‘safer’ tan 39. But actually, sunbeds are no safer than exposure to the sun itself 40. It is a common misconception that sunbeds emit only UV-A radiation, and not UV-B, the type which causes most sunburns. But all sunbeds emit some measure of UVB, and even this tiny proportion is enough to cause substantial damage to our skin 41.

UVA can also damage the skin and the levels of UV-A from sunbeds can be over 10 times higher than that of the midday sun 42. Studies have shown that up to half of all sunbed users suffer from sunburns 43. And in people who are prone to burning, UV-A from sunbeds can burn the skin faster than the sun 44.

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References

1. IARC, Solar and ultraviolet radioation. Monographs on the evalutation of carcinogenic risks to humans. 1992, Lyon: IARCPress.Link
2. Gilchrest, B., et al., The pathogenesis of melanoma induced by ultraviolet radiation. N Engl J Med, 1999. 340: p. 1341-8.PubMed
3. Armstrong, B. and A. Kricker, How much melanoma is caused by sun exposure? Melanoma Res, 1993. 3: p. 395-401.PubMed
4. Fry, A. and J. Verne, Preventing skin cancer. BMJ, 2003. 326: p. 114-115.PubMed
5. Elwood, J. and J. Jopson, Melanoma and sun exposure: an overview of published studies. Int J Cancer, 1997. 73: p. 198-203.PubMed
6. Gandini, S., et al., Meta-analysis of risk factors for cutaneous melanoma: II. Sun exposure. Eur J Cancer, 2005. 41(1): p. 45-60.PubMed
7. Nelemans, P., et al., Effect of intermittent exposure to sunlight on melanoma risk among indoor workers and sun-sensitive individuals. Environ Health Perspect, 1993. 101: p. 252-5.PubMed
8. Elwood, J., Melanoma and sun exposure: contrasts between intermittent and chronic exposure. World J Surg, 1992. 16: p. 157-65.PubMed
9. Whiteman, D., C. Whiteman, and A. Green, Childhood sun exposure as a risk factor for melanoma: a systematic review of epidemiologic studies. Cancer Causes Control, 2001. 12: p. 69-82.PubMed
10. Autier, P. and J. Dore, Influence of sun exposures during childhood and during adulthood on melanoma risk. EPIMEL and EORTC Melanoma Cooperative Group. European Organisation for Research and Treatment of Cancer. Int J Cancer, 1998. 77: p. 533-7.PubMed
11. Khlat, M., et al., Mortality from melanoma in migrants to Australia: variation by age at arrival and duration of stay. Am J Epidemiol, 1992. 135(10): p. 1103-13.PubMed
12. Mack, T. and B. Floderus, Malignant melanoma risk by nativity, place of residence at diagnosis, and age at migration. Cancer Causes Control, 1991. 2: p. 401-11.PubMed
13. Gallagher, R., et al., Broad-spectrum sunscreen use and the development of new nevi in white children: A randomized controlled trial. JAMA, 2000. 283: p. 2955-60.PubMed
14. Haydon, A.M., et al., The effect of physical activity and body size on survival after diagnosis with colorectal cancer. Gut, 2005.PubMed
15. Autier, P., et al., Sunscreen use, wearing clothes, and number of nevi in 6- to 7-year-old European children. European Organization for Research and Treatment of Cancer Melanoma Cooperative Group. J Natl Cancer Inst, 1998. 90: p. 1873-80.PubMed
16. English, D.R., E. Milne, and J.A. Simpson, Sun protection and the development of melanocytic nevi in children. Cancer Epidemiol Biomarkers Prev, 2005. 14(12): p. 2873-6.PubMed
17. Severi, G., et al., Sun exposure and sun protection in young European children: an EORTC multicentric study. Eur J Cancer, 2002. 38: p. 820-6.PubMed
18. Jarrett, P., C. Sharp, and J. McLelland, Protection of children by their mothers against sunburn. BMJ, 1993. 306: p. 1448.PubMed
19. Holly, E., et al., Number of melanocytic nevi as a major risk factor for malignant melanoma. J Am Acad Dermatol, 1987. 17: p. 459-68.PubMed
20. Gallagher, R., et al., Sunlight exposure, pigmentation factors, and risk of nonmelanocytic skin cancer. II. Squamous cell carcinoma. Arch Dermatol, 1995. 131: p. 164-9.PubMed
21. Rhodes, A., et al., Risk factors for cutaneous melanoma. A practical method of recognizing predisposed individuals. JAMA, 1987. 258: p. 3146-54.PubMed
22. Saraiya, M., et al., Interventions to prevent skin cancer by reducing exposure to ultraviolet radiation: a systematic review. Am J Prev Med, 2004. 27: p. 422-66.PubMed
23. Marrett, L., et al., Use of host factors to identify people at high risk for cutaneous malignant melanoma. CMAJ, 1992. 147: p. 445-53.PubMed
24. Gandini, S., et al., Meta-analysis of risk factors for cutaneous melanoma: III. Family history, actinic damage and phenotypic factors. Eur J Cancer, 2005. 41(14): p. 2040-59.PubMed
25. Tucker, M.A. and A.M. Goldstein, Melanoma etiology: where are we? Oncogene, 2003. 22(20): p. 3042-52.PubMed
26. Gandini, S., et al., Meta-analysis of risk factors for cutaneous melanoma: I. Common and atypical naevi. Eur J Cancer, 2005. 41(1): p. 28-44.PubMed
27. Ford, D., et al., Risk of cutaneous melanoma associated with a family history of the disease. The International Melanoma Analysis Group (IMAGE). Int J Cancer, 1995. 62(4): p. 377-81.PubMed
28. NCI, SEER Cancer Statistics Review, 1998-2002.Link
29. Scotto, J., T. Fears, and J.J. Fraumeni, Incidence of nonmelanoma skin cancer in the United States. 1983, Bethseda, MD.: National Cancer Institute, National Institutes of Health.
30. Crombie, I.K., Racial differences in melanoma incidence. Br J Cancer, 1979. 40(2): p. 185-93.PubMed
31. Pedeux, R., et al., Thymidine dinucleotides induce S phase cell cycle arrest in addition to increased melanogenesis in human melanocytes. J Invest Dermatol, 1998. 111: p. 472-7.PubMed
32. Eller, M., et al., Enhancement of DNA repair in human skin cells by thymidine dinucleotides: evidence for a p53-mediated mammalian SOS response. Proc Natl Acad Sci U S A, 1997. 94: p. 12627-32.PubMed
33. Gange, R., et al., Comparative protection efficiency of UVA- and UVB-induced tans against erythema and formation of endonuclease-sensitive sites in DNA by UVB in human skin. J Invest Dermatol, 1985. 85: p. 362-4.PubMed
34. Bykov, V., J. Marcusson, and K. Hemminki, Protective effects of tanning on cutaneous DNA damage in situ. Dermatology, 2001. 202: p. 22-6.PubMed
35. Lazovich, D. and J. Forster, Indoor tanning by adolescents: prevalence, practices and policies. Eur J Cancer, 2005. 41: p. 20-27.PubMed
36. The association of use of sunbeds with cutaneous malignant melanoma and other skin cancers: A systematic review. Int J Cancer, 2006.PubMed
37. Diffey, B., A quantitative estimate of melanoma mortality from ultraviolet A sunbed use in the U.K. Br J Dermatol, 2003. 149: p. 578-81.PubMed
38. Wester, U., et al., Population UV-dose and skin area--do sunbeds rival the sun? Health Phys, 1999. 77: p. 436-40.PubMed
39. Gies, H., C. Roy, and G. Elliott, Artificial suntanning: spectral irradiance and hazard evaluation of ultraviolet sources. Health Phys, 1986. 50: p. 691-703.PubMed
40. Gerber, B., et al., Ultraviolet emission spectra of sunbeds. Photochem Photobiol, 2002. 76: p. 664-8.PubMed
41. Wright, A., et al., Survey of the variation in ultraviolet outputs from ultraviolet A sunbeds in Bradford. Photodermatol Photoimmunol Photomed, 1996. 12: p. 12-6.PubMed
42. Woollons, A., et al., The 0.8% ultraviolet B content of an ultraviolet A sunlamp induces 75% of cyclobutane pyrimidine dimers in human keratinocytes in vitro. Br J Dermatol, 1999. 140: p. 1023-30.PubMed
43. Autier, P., Perspectives in melanoma prevention: the case of sunbeds. Eur J Cancer, 2004. 40: p. 2367-2376.PubMed
44. Swerdlow, A. and M. Weinstock, Do tanning lamps cause melanoma? An epidemiologic assessment. J Am Acad Dermatol, 1998. 38: p. 89-98.PubMed

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