Sun and UV facts and evidence
Read the key facts about sun, UV and cancer risk, and find the supporting evidence to see why we say what we do.
There is sufficient evidence to show that overexposure to ultraviolet (UV) radiation is the main preventable cause of skin cancers – both melanoma skin cancer (the most serious type) and non- melanoma skin cancers (NMSC).[1,2] The sun is the principal source of natural UV radiation. Sunbeds produce artificial UV radiation.
An estimated 86% of melanomas in the UK (around 11,500 cases) every year are linked to too much exposure to sunlight and sunbed use.
The risk of melanoma is most strongly linked to intermittent sun exposure  – short, intense bursts of sun for people who generally spend most of their time indoors, for example sunbathers on holiday.
1. International Agency for Research on Cancer. Radiation. Vol 100.; 2012.
2. Parkin DM, Boyd L, Walker LC. The fraction of cancer attributable to lifestyle and environmental factors in the UK in 2010. Br J Cancer. 2011;105 Suppl(S2):S77-S81. doi:10.1038/bjc.2011.489.
3. Cancer Research UK. Preventable cancer stats. www.cancerresearchuk.org/health-professional/cancer-statistics/risk/prev.... Published 2014.
4. Gandini S, Sera F, Cattaruzza MS, et al. Meta-analysis of risk factors for cutaneous melanoma: II. Sun exposure. Eur J Cancer. 2005;41(1):45-60. doi:10.1016/j.ejca.2004.10.016.
Some people are more likely than others to develop skin cancer.
These people tend to have one or more of the following:
o fair skin
o skin that burns easily
o lots of moles or freckles
o a history of sunburn
o red or fair hair
o light-coloured eyes
o a personal[4,5] or family history of skin cancer.[1,6]
People with naturally dark brown/black skin burn less easily and have a lower risk of skin cancer. But people with darker skin can still develop skin cancers, especially types not related to UV for example on non-pigmented parts of the body like the soles of the feet.
1. Gandini S, Sera F, Cattaruzza MS, et al. Meta-analysis of risk factors for cutaneous melanoma: III. Family history, actinic damage and phenotypic factors. Eur J Cancer. 2005;41(14):2040-2059. doi:10.1016/j.ejca.2005.03.034.
2. Gandini S, Sera F, Cattaruzza MS, et al. Meta-analysis of risk factors for cutaneous melanoma: I. Common and atypical naevi. Eur J Cancer. 2005;41(1):28-44. doi:10.1016/j.ejca.2004.10.015.
3. Olsen CM, Zens MS, Green AC, et al. Biologic markers of sun exposure and melanoma risk in women: pooled case-control analysis. Int J Cancer. 2011;129(3):713-723. doi:10.1002/ijc.25691.
4. Balamurugan A, Rees JR, Kosary C, Rim SH, Li J, Stewart SL. Subsequent primary cancers among men and women with in situ and invasive melanoma of the skin. J Am Acad Dermatol. 2011;65(5 SUPPL. 1):S69.e1-S69.e9. doi:10.1016/j.jaad.2011.04.033.
5. Bradford PT, Freedman DM, Goldstein AM, Tucker M a. Increased risk of second primary cancers after a diagnosis of melanoma. Arch Dermatol. 2010;146(3):265-272. doi:10.1001/archdermatol.2010.2.
6. Olsen CM, Carroll HJ, Whiteman DC. Familial melanoma: A meta-analysis and estimates of attributable fraction. Cancer Epidemiol Biomarkers Prev. 2010;19(1):65-73. doi:10.1158/1055-9965.EPI-09-0928.
7. Wang Y, Zhao Y, Ma S. Racial differences in six major subtypes of melanoma: descriptive epidemiology. BMC Cancer. 2016;16(1):691. doi:10.1186/s12885-016-2747-6.
The World Health Organisation (WHO) developed an international UV index to reflect the strength of the sun’s rays (level of UV radiation) at the earth’s surface. There’s a guide to the UV Index available online at: http://www.who.int/uv/publications/en/UVIGuide.pdf . The greater the UV index value, the greater the potential for damage and the less time it takes for this damage to occur.[1,2]
The UV index can be used as an indication for how important it is to protect against UV radiation. It is widely accepted that people are unlikely to be harmed by UV levels below 3.[1,3]
The strength of UV radiation reaching the earth’s surface is affected by several factors including: [2,4,5]
o Time of day, being strongest at solar noon (around 1pm British Summer Time) when the sun is highest in the sky
o Time of year, being strongest in the summer months
o Latitude, being strongest in locations nearer the equator
o Altitude, being higher at higher altitudes
o Cloud cover – over 90% of UV can pass through light cloud
o Reflection – snow can reflect up to 80% of the UV radiation that hits it, increasing a person’s exposure. About 15% of rays are reflected back from sand, 10% from concrete and up to 30% from water (depending on choppiness)
1. World Health Organisation Intersun. UV Index. http://www.who.int/uv/intersunprogramme/activities/uv_index/en/.
2. World Health Organisation. GLOBAL SOLAR UV INDEX A Practical Guide.; 2002.
3. World Health Organisation Intersun. Workshop on Review of the UV Index. http://www.who.int/uv/UVI_workshop_Melbourne2015/en/. Published 2015.
4. International Agency for Research on Cancer. Radiation. Vol 100.; 2012.
5. Met Office. UV Index. www.metoffice.gov.uk/uv.
Holloway’s rule is an easy way to know when the sun is strong: the sun’s UV rays are strongest when your shadow is shorter than you. So that’s when you’re more likely to burn.
1. Holloway L. Shadow method for sun protection. Lancet. 1990;335:484.
UV radiation from the sun damages the DNA in our skin cells which can lead to the development of cancer. Sunburn is a sign of DNA damage caused by too much UV. There are two main types of UV rays that damage skin and cause skin cancer:
• UVA penetrates deep into the skin. It ages the skin, but contributes much less towards sunburn.
• UVB is responsible for the majority of sunburns.
A third type of UV ray, UVC, could be the most dangerous of all, but it is completely blocked out by the ozone layer and doesn’t reach the earth's surface.
Getting a sunburn just once every two years can triple the risk of melanoma.
Sunburn during childhood or adolescence can increase the risk of skin cancer later on in life. But sunburn at any age increases the risk of malignant melanoma. [3,4]
1. International Agency for Research on Cancer. Radiation. Vol 100.; 2012.
2. Amano S. Characterization and mechanisms of photoageing-related changes in skin. Damages of basement membrane and dermal structures. Exp Dermatol. 2016;25(May):14-19. doi:10.1111/exd.13085.
3. Dennis LK, VanBeek MJ, Freeman LEB, Smith BJ, Dawson D V., Coughlin JA. Sunburns and risk of cutaneous melanoma, does age matter: a comprehensive meta-analysis. Ann Epidemiol. 2008;18(8):614-627. doi:10.1016/j.annepidem.2008.04.006.Sunburns.
4. Gandini S, Sera F, Cattaruzza MS, et al. Meta-analysis of risk factors for cutaneous melanoma: II. Sun exposure. Eur J Cancer. 2005;41(1):45-60. doi:10.1016/j.ejca.2004.10.016.
It is widely agreed that a combination of measures including using shade and clothing as the first lines of defence and sunscreen for the parts you can’t cover, offers the best protection against over-exposure to UV radiation from the sun.[1,2] Research suggests that shade and clothing offer better protection from UV rays than sunscreen. [3–6]
Shade structures can provide protection from the sun. Staying under shade, such as a tree or umbrella, can reduce your overall exposure to UV, but not completely protect you. Many shade structures are more likely to filter than to block UV radiation. Only very broad and thick shade such as thickly wooded areas and widely overhanging structures provide enough protection from strong sun.
Clothes, hats, sunglasses
Covering up with clothes, hats and sunglasses is an effective way of protecting yourself from UV rays.
Clothes tend to provide more protection if they:[1,2,9–12]
o Cover more skin – e.g. long-sleeved t-shirts and wide brim hats
o Are loose fitting
o Are deeper colours
o Are made of polyester preferably, or wool, silk or nylon. Cotton, rayon, linen and viscose fabrics tend to be less protective
o Are dry – for example cotton is less protective when wet
o Are thicker
o Have a close weave– check you can’t see through the fabric.
Wide-brimmed hats provide the most UV protection for the whole face and head.[1,2] Caps protect the nose and forehead but provide poor protection for other parts of the face.
Sunglasses can protect your eyes from too much UV exposure. Poorly-fitting sunglasses offer poor protection as sunlight can reflect off the back face of the lens back into the eye. Wraparounds are recommended. Because of the angle of the sun, eyes can be at risk of damage and need protection earlier in the morning and later in the afternoon than for the rest of your body.
Sunglasses should state that they block out 100% of UVA and UVB rays. Alternatively, look for the ‘CE Mark’ and British Standard, or a UV 400 label.
Many studies have shown that sunscreen can reflect or absorb harmful UV rays. However, whether or not using sunscreen reduces skin cancer risk remains unclear.[15–18] How sunscreen is applied and how using it affects someone’s subsequent behaviour, consciously or unconsciously, are important considerations.
Using sunscreen for ‘non-intentional’ sun exposure, where the aim of the activity isn’t to expose skin to the sun but it may happen incidentally, such as walking, gardening, sport or other daily activities, may reduce the risk of sunburn. However, using sunscreen for ‘intentional’ sun exposure (e.g. sunbathing) has been linked with people spending longer in the sun overall and being no less likely, perhaps even more likely to get sunburnt. This was particularly seen when people used higher SPF sunscreens.
Because of this, we recommend that sunscreen should be used together with clothing and shade to protect the skin from sun damage, and should never be used to spend longer in the sun.
The SPF or ‘factor’ of a sunscreen is a measure of the amount of sun protection it provides. Experts have found that SPF 15 sunscreen provides sufficient protection when used appropriately, wherever you are in the world.[14,22] One study has found benefit for reduction in skin cancer risk for sunscreens of SPF15 or above, compared to below SPF 15. A minimum of SPF 15 is recommended by NICE (National Institute for Health and Care Excellence). No sunscreen is 100% effective and as SPF increases, sunscreens provide less and less extra protection.
SPF measurements are based on the assumption that people apply 2mg/cm2 of sunscreen on their body. But research has shown that people don’t apply enough. Studies have found the actual amount applied is less than half of the level SPF is tested at (0.39 to 1.0 m/cm2).
Sunscreen only works if you use enough. It should be applied evenly, thickly and regularly to be effective. As a guide, for an average adult, you should use:
o around two teaspoonfuls of sunscreen if you're just covering your head, arms and neck.
o around two and a half tablespoonfuls if you're covering your entire body, for example while wearing a swimming costume.
Sunscreens that provide UVA protection are recommended. The star rating system measures the balance between UVA and UVB protection and awards products a rating of 1-5 stars. It is not an absolute measure, but depends on the SPF rating of the sunscreen it is applied to. Sunscreen with at least 4 stars is recommended.
1. International Agency for Research on Cancer. How can I protect myself and my children from the sun in everyday life, during outdoor activities, or while on holiday? European Code Against Cancer. http://cancer-code-europe.iarc.fr/index.php/en/ecac-12-ways/sun-uv-expos....
2. National Institute for Health and Care Excellence. Sunlight exposure exposure : risks and benefits. 2016;(February).
3. Linos E, Keiser E, Fu T, Colditz G, Chen S, Tang JY. Hat, shade, long sleeves, or sunscreen? Rethinking US sun protection messages based on their relative effectiveness. Cancer Causes Control. 2011;22(7):1067-1071. doi:10.1007/s10552-011-9780-1.
4. Autier P, Doré JF, Cattaruzza MS, 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(24):1873-1880. doi:10.1093/jnci/90.24.1873.
5. Lazovich D, Vogel RI, Berwick M, Weinstock MA, Warshaw EM, Anderson KE. Melanoma risk in relation to use of sunscreen or other sun protection methods. Cancer Epidemiol Biomarkers Prev. 2011;20(12):2583-2593. doi:10.1158/1055-9965.EPI-11-0705.
6. Ackermann S, Vuadens A, Levi F, Bulliard J. Sun protective behaviour and sunburn prevalence in primary and secondary schoolchildren in western Switzerland. Swiss Med Wkly. 2016;(November). doi:10.4414/smw.2016.14370.
7. International Agency for Research on Cancer. Am I safe on a cloudy day or under a parasol? European Code Against Cancer. http://cancer-code-europe.iarc.fr/index.php/en/ecac-12-ways/sun-uv-expos....
8. Parisi A V, Turnbull DJ. Shade provision for UV minimization: a review. Photochem Photobiol. 2014;90(3):479-490. doi:10.1111/php.12237.
9. Hatch KL, Osterwalder U. Garments as solar ultraviolet radiation screening materials. Dermatol Clin. 2006;24(1):85-100. doi:10.1016/j.det.2005.09.005.
10. Davis S, Capjack L, Kerr N, Fedosejevs R. Clothing as protection from ultraviolet radiation: which fabric is most effective? Int J Dermatol. 1997;36(5):374-379.
11. Gambichler T, Rotterdam S, Altmeyer P, Hoffmann K. Protection against ultraviolet radiation by commercial summer clothing: need for standardised testing and labelling. BMC Dermatol. 2001;1:6. doi:10.1186/1471-5945-1-6.
12. Almutawa F, Buabbas H. Photoprotection: clothing and glass. Dermatol Clin. 2014;32(3):439-448.
13. Gies P. Effectiveness of Sunglasses. 2015;(December):1-13. http://www.who.int/uv/04_Gies_Effectiveness_of_Sunglasses.pdf?ua=1.
14. IARC. IARC Handbook on Cancer Prevention Vol 5 Sunscreens. Lyon, France; 2001.
15. Diffey BL. Sunscreens as a preventative measure in melanoma: An evidence-based approach or the precautionary principle? Br J Dermatol. 2009;161(SUPPL. 3):25-27. doi:10.1111/j.1365-2133.2009.09445.x.
16. Green AC, Williams GM, Logan V, Strutton GM. Reduced melanoma after regular sunscreen use: Randomized trial follow-up. J Clin Oncol. 2011;29(3):257-263. doi:10.1200/JCO.2010.28.7078.
17. Sánchez G, Nova J, Rodriguez-Hernandez AE, et al. Sun protection for preventing basal cell and squamous cell skin cancers. Cochrane Database Syst Rev. 2016;2016(7). doi:10.1002/14651858.CD011161.pub2.
18. Ghiasvand R, Weiderpass E, Green AC, Lund E, Veierod MB. Sunscreen Use and Subsequent Melanoma Risk: A Population-Based Cohort Study. J Clin Oncol. 2016. doi:10.1200/JCO.2016.67.5934.
19. IARC. IARC Handbooks of Cancer Prevention Volume 5 Sunscreens. Vol 5.; 2001.
20. Autier P, Boniol M, Doré JF. Sunscreen use and increased duration of intentional sun exposure: Still a burning issue. Int J Cancer. 2007;121(1):1-5. doi:10.1002/ijc.22745.
21. Autier P. Sunscreen abuse for intentional sun exposure. Br J Dermatol. 2009;161(SUPPL. 3):40-45. doi:10.1111/j.1365-2133.2009.09448.x.
22. Diffey B. Has the sun protection factor had its day? BMJ. 2000;320(7228):176-177. doi:10.1136/bmj.320.7228.176.
23. Petersen B, Wulf HC. Application of sunscreen - theory and reality. Photodermatol Photoimmunol Photomed. 2014;30(2-3):96-101. doi:10.1111/phpp.12099.
According to IARC there is sufficient evidence that sunbed use causes malignant melanoma, and limited evidence that sunbed use causes SCC .
According to a recent meta-analysis sunbed use at any age increases the risk of SCC by 67%, and increases BCC risk by 29% .
A comprehensive review published in 2012 of studies on sunbeds and cancer concluded that using a sunbed for the first time before the age of 35 increases the risk of malignant melanoma by 59%, and use at any age increases malignant melanoma risk by 20-25% .
A large study of Norwegian and Swedish women found that using sunbeds once a month or more increases the risk of melanoma by 55% in all age groups from 10-39 .
Sunbeds are marketed as a 'controlled' way of getting a 'safer' tan . But actually, sunbeds are no safer than exposure to the sun itself . It is a common misconception that sunbeds emit only UVA radiation, and not UVB, the type which causes more sunburns. But all sunbeds emit some measure of UVB, and even this tiny proportion is enough to cause substantial damage to our skin .
UVA can also damage the skin and the levels of UVA from sunbeds can be over 10 times higher than that of the midday sun . A recent study found that the average skin cancer risk from sunbeds can be more than double that of spending the same length of time in the Mediterranean midday summer sun .
Studies have shown that up to half of all sunbed users suffer from sunburn .
3. Cogliano VJ, Baan R, Straif K, et al. Preventable exposures associated with human cancers. J Natl Cancer Inst 2011;103:1827-39. View summary on PubMed
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87. Boniol M, Autier P, Boyle P, Gandini S. Correction to Cutaneous melanoma attributable to sunbed use: systematic review and meta-analysis. BMJ 2012;345:e8503. View Journal
88. Veierod MB, Weiderpass E, Thorn M, et al. A prospective study of pigmentation, sun exposure, and risk of cutaneous malignant melanoma in women. J Natl Cancer Inst 2003;95:1530–8.
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93. P Tierney et al, ‘Nine out of ten sunbeds in England emit UV radiation levels that exceed current safety limits’, DOI : 10.1111/bjd.12181
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In addition to carcinogenic effects, sunbeds can promote photoageing - UV-induced premature ageing of the skin - by destroying collagen and other large molecules. The consequences of UVA-induced damage in the skin include the formation of wrinkles, sagging, leathery appearance, fragility and impaired healing ability .
A French study found that women who frequently used sunbeds over the course of 5 years developed saggier skin with a loss of elasticity that resembled premature ageing . Another study of 59 people who used sunbeds over 3 months found that their skin cells showed a 2.4 fold increase in the levels of a common fault in mitochondrial DNA that is firmly associated with photoageing .
95. Ma W et al. Chronological ageing and photoageing of the fibroblasts and the dermal connective tissue. Clin Exp Dermatol. 2001 Oct;26(7):592-9. View summary on PubMed
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97. Reimann V et al. Sunbed use induces the photoaging-associated mitochondrial common deletion. J Invest Dermatol. 2008 May;128(5):1294-7. View summary on PubMed
Far from being a sign of health, 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 [98, 99]. 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 [100, 101].
98. 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. View summary on PubMed
99. 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. View summary on PubMed
100. 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. View summary on PubMed
101. Bykov, V., J. Marcusson, and K. Hemminki, Protective effects of tanning on cutaneous DNA damage in situ. Dermatology, 2001. 202: p. 22-6. View summary on PubMed
'Fake tan' lotions, sprays, creams and mousses are topical products containing the active ingredient dihydroxyacetone (DHA), typically in concentrations of between three and five per cent [102, 103]. DHA is a type of carbohydrate which reacts with the amino acids in the top layer of the skin, to form brown-black compounds called melanoidins [102, 104]. The depth of the colour change is related to DHA concentration . DHA-containing 'fake tan' products are considered to be non-toxic [103, 104].
Bronzers do not contain the active ingredient DHA and so the colour delivered through these products, for example in the form of tinted moisturisers and powders, can be removed with the aid of soap and water .
The FDA (Food and Drug Administration) in the US has approved the use of DHA-containing products for the pigmentation of skin where the products are applied by hand for this allows control over the application process, and the avoidance of the mucous membranes and the area of the eye .
Some DHA-containing products also contain sunscreen, but at most a fake tan will only provide the same protection as an SPF4 sunscreen [106, 107]. And the protection they offer will last for hours and not for the duration of the colour pigmentation, so regular application of sunscreen is still needed .
102. Fu JM et al. Sunless tanning. J Am Acad Dermatol. 2004 May;50(5):706-13. View summary on PubMed
103. Levy SB. Tanning preparations. Dermatol Clin. 2000 Oct;18(4):591-6. View summary on PubMed
104. Draelos ZD. Self-tanning lotions: are they a healthy way to achieve a tan? Am J Clin Dermatol. 2002;3(5):317-8. View summary on PubMed
105. FDA: Sunless tanners and bronzers.
106. Faurschou, A., Wulf, H.C., Durability of the sun protection factor provided by dihydroxyacetone. Photodermatology, Photoimmunology and Photomedicine, 2004. 20: p. 239-242. View summary on PubMed
107. Faurschou, A., Janjua, N.R., Wulf, H.C., Sun protection effect of dihydroxyacetone. Archives of Dermatology, 2004. 140: p. 886-887. View summary on PubMed
Our bodies produce vitamin D when our skin is exposed to UV rays from the sun. This is the main source of this vitamin . We all need vitamin D to build and maintain strong bones. If you are lacking in vitamin D for a long time then your bones may soften. In serious cases this leads to rickets in children and a condition called osteomalacia in adults .
Most people in the UK only need to spend a short amount of time in the sun to make enough vitamin D [109-111]. This is typically less that the time taken to lead to sunburn . It should be possible for most people to find a balance between enjoying the beneficial effects of the sun while not increasing the risk of skin cancer.
Once a person makes enough vitamin D, any extra is turned into inactive substances . So heavy sun exposure does not improve vitamin D levels beyond a maximum threshold, but it can increase the risk of skin cancer . Even leading vitamin D researchers advise using sun protection, such as SPF sunscreens, during long or heavy exposures .
Vitamin D synthesis is much lower in winter months in countries at higher latitudes like the UK . But as long as normal vitamin D level has been built up in the summer, studies show that this will combine with stored vitamin D in fatty tissue to prevent deficiency in the winter [115, 116].
Some groups have a higher risk of vitamin D deficiency, including:
- People with naturally brown or black skin, who need more UV radiation to increase their vitamin D levels than Caucasians [117-120].
- People who wear clothing that fully conceals them [120, 121].
- Older people who don't go outside much, since they have a reduced ability to make vitamin D through their skin [109, 117].
- Pregnant women and breast-feeding babies with vitamin D-deficient mothers .
The Government recommends that people at risk of vitamin D deficiency should take vitamin D supplements of 10µg a day for adults and 7µg a day for children .
In 2010 Cancer Research UK teamed up with other health organisations to bring together evidence on the important but controversial topic of vitamin D. It is endorsed by the British Association of Dermatologists, Cancer Research UK, Diabetes UK, the Multiple Sclerosis Society, the National Heart Forum, the National Osteoporosis Society and the Primary Care Dermatology Society.
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