Ultraviolet (UV) radiation is a form of electromagnetic radiation that comes from the sun and man-made sources like tanning beds and welding torches.
Radiation is the emission (sending out) of energy from any source. There are many types of radiation, ranging from very high-energy (high-frequency) radiation – like x-rays and gamma rays – to very low-energy (low-frequency) radiation – like radio waves. UV rays are in the middle of this spectrum. They have more energy than visible light, but not as much as x-rays.
There are also different types of UV rays, based on how much energy they have. Higher-energy UV rays are a form of ionizing radiation. This means they have enough energy to remove an electron from (ionize) an atom or molecule. Ionizing radiation can damage the DNA (genes) in cells, which in turn may lead to cancer. But even the highest-energy UV rays don’t have enough energy to penetrate deeply into the body, so their main effect is on the skin.
UV radiation is divided into 3 main groups:
Sunlight is the main source of UV radiation, even though UV rays make up only a small portion of the sun’s rays. Different types of UV rays reach the ground in different amounts. About 95% of the UV rays from the sun that reach the ground are UVA rays, with the remaining 5% being UVB rays.
The strength of the UV rays reaching the ground depends on a number of factors, such as:
The amount of UV exposure a person gets depends on the strength of the rays, the length of time the skin is exposed, and whether the skin is protected with clothing or sunscreen.
People can also be exposed to man-made sources of UV rays. These include:
Most skin cancers are a result of exposure to the UV rays in sunlight. Both basal cell and squamous cell cancers (the most common types of skin cancer) tend to be found on sun-exposed parts of the body, and their occurrence is typically related to lifetime sun exposure. The risk of melanoma, a more serious but less common type of skin cancer, is also related to sun exposure, although perhaps not as strongly. Skin cancer has also been linked to exposure to some man-made sources of UV rays.
Many studies have found that basal and squamous cell skin cancers are linked to certain behaviors that put people in the sun, as well as a number of markers of sun exposure, such as:
Studies have also found links between certain behaviors and markers of sun exposure and melanoma of the skin, including:
Because UV rays don’t penetrate deeply into the body, they wouldn’t be expected to cause cancer in internal organs, and most research has not found such links. However, some studies have shown possible links to some other cancers, including Merkel cell carcinoma (a less common type of skin cancer) and melanoma of the eye.
Studies have found that people who use tanning beds (or booths) have a higher risk of skin cancer, including melanoma and squamous and basal cell skin cancers. The risk of melanoma is higher if the person started indoor tanning before age 30 or 35, and the risk of basal and squamous cell skin cancer is higher if indoor tanning started before age 25.
In general, the American Cancer Society does not determine if something causes cancer (that is, if it is a carcinogen), but we do look to other respected organizations for help with this. Based on the available evidence, several expert agencies have evaluated the cancer-causing nature of UV radiation.
The International Agency for Research on Cancer (IARC) is part of the World Health Organization (WHO). One of its major goals is to identify causes of cancer. Based on the available data, IARC has made the following determinations:
The National Toxicology Program (NTP) is formed from parts of several different US government agencies, including the National Institutes of Health (NIH), the Centers for Disease Control and Prevention (CDC), and the Food and Drug Administration (FDA). The NTP has made the following determinations:
(For more information on the classification systems used by these agencies, see Determining if Something Is a Carcinogen.)
Some people think that getting UV rays from tanning beds is a safe way to get a tan, but this isn’t true.
Both IARC and NTP classify the use of UV-emitting tanning devices (including sunlamps and tanning beds) as carcinogenic to humans.
The US Food and Drug Administration (FDA), which refers to all UV lamps used for tanning as “sunlamps,” requires them to carry a label that states, “Attention: This sunlamp product should not be used on persons under the age of 18 years.”
The FDA also requires that user instructions and sales materials directed at consumers (including catalogs, specification sheets, descriptive brochures, and webpages) carry the following statements:
The FDA has also proposed a new rule to ban the use of indoor tanning devices by anyone under age 18, to require tanning facilities to inform adult users about the health risks of indoor tanning, and to require a signed risk acknowledgment from all users. Some US states have already banned indoor tanning by all people younger than 18, while others have banned use by younger teens and children.
In addition to skin cancer, exposure to UV rays can cause other health problems:
Some people are more sensitive to the damaging effects of UV radiation. Some medications can also make you more sensitive to UV radiation, making you more likely to get sunburned. And certain medical conditions can be made worse by UV radiation.
Your skin makes vitamin D naturally when it is exposed to UV rays from the sun. How much vitamin D you make depends on many things, including how old you are, how dark your skin is, and how strong the sunlight is where you live.
Vitamin D has many health benefits. It might even help lower the risk of some cancers. At this time, doctors aren’t sure what the optimal level of vitamin D is, but a lot of research is being done in this area.
Whenever possible, it’s better to get vitamin D from your diet or vitamin supplements rather than from exposure to UV rays. Dietary sources and vitamin supplements do not increase skin cancer risk, and are typically more reliable ways to get the amount you need.
It’s not possible (or healthy) to avoid sunlight completely, but there are ways to help ensure you’re not getting too much sun:
For more information, see How Do I Protect Myself from Ultraviolet (UV) Rays?
The US Centers for Disease Control and Prevention (CDC) has also recommended ways for communities to help prevent skin cancer by reducing sun exposure, including educational interventions in schools and providing shade at schools, recreational sites, and work sites.
Many people believe the UV rays of tanning beds are harmless. This is not true. The best thing to do is to not use tanning beds (or booths).
People who may be exposed to artificial sources of UV at their job should follow appropriate safety precautions, including using protective clothing and UV shields and filters.
The American Cancer Society medical and editorial content team
Our team is made up of doctors and oncology certified nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.
Along with the American Cancer Society, other sources of information include:
American Academy of Dermatology
Toll-free number: 1-888-462-3376 (1-888-462-DERM)
Environmental Protection Agency
National Cancer Institute
Toll-free number: 1-800-422-6237 (1-800-4-CANCER); TYY: 1-800-332-8615
Skin Cancer Foundation
Toll-free number: 1-800-754-6490 (1-800-SKIN-490)
*Inclusion on this list does not imply endorsement by the American Cancer Society.
Boniol M, Autier P, Boyle P, Gandini S. Cutaneous melanoma attributable to sunbed use: Systematic review and meta-analysis. BMJ. 2012;345:e4757.
Centers for Disease Control and Prevention. Skin Cancer Prevention Progress Report. Atlanta, GA: Centers for Disease Control and Prevention, US Department of Health and Human Services; 2017.
International Agency for Research on Cancer (IARC). IARC Monographs on the Evaluation of Carcinogenic Risks to Humans. Vol. 100D: Solar and Ultraviolet Radiation. 2012. Accessed at: https://monographs.iarc.fr/wp-content/uploads/2018/06/mono100D-6.pdf on June 7, 2019.
US Food and Drug Administration. Sec. 878.4635 Sunlamp products and ultraviolet lamps intended for use in sunlamp products. 2018. Accessed at https://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr=878.4635 on June 7, 2019.
US Food and Drug Administration. The Risks of Tanning. 2019. Accessed at https://www.fda.gov/radiation-emitting-products/tanning/risks-tanning on June 7, 2019.
US National Toxicology Program (NTP). Report on Carcinogens, Fourteenth Edition: Ultraviolet-Radiation-Related Exposures. 2016. Research Triangle Park, NC: US Department of Health and Human Services, Public Health Service. Accessed at https://ntp.niehs.nih.gov/ntp/roc/content/profiles/ultravioletradiationrelatedexposures.pdf on June 7, 2019.
Wehner MR, Shive ML, Chren MM, et al. Indoor tanning and non-melanoma skin cancer: Systematic review and meta-analysis. BMJ. 2012;345:e5909.
World Health Organization (WHO). Ultraviolet radiation (UV): The known health effects of UV. Accessed at https://www.who.int/uv/faq/uvhealtfac/en/index1.html on June 7, 2019.
Last Revised: July 10, 2019
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