Does UV radiation cause cancer?
Yes. In fact, most skin cancers are a direct 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 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 artificial sources of UV.
Studies in people
Basal and squamous cell skin cancer
Many observational studies have looked at the link between basal and squamous cell skin cancers and sun exposure. These 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:
- Spending time in the sun for recreation (including going to the beach)
- Spending a lot of time in the sun in a swim suit
- Living in an area with a high amount of sun
- Serious sunburns in the past (with more sunburns linked to a higher risk)
- Signs of sun damage to the skin, such as liver spots, actinic keratoses (rough skin patches that can be precancerous), and solar elastosis (thickened, dry, wrinkled skin caused by sun exposure) on the neck
Observational studies have also found links between certain behaviors and markers of sun exposure and melanoma of the skin, including:
- Activities that lead to “intermittent sun exposure,” like sunbathing, water sports, and taking vacations in sunny places
- Previous sunburn
- Signs of sun damage to the skin, such as liver spots, actinic keratoses, and solar elastosis
Melanoma of the eye has also been linked to sun exposure in some studies.
It is not clear if there is a link between cancer of the lip and sun exposure. One study found a link, but another did not.
A type of cancer affecting the eye, squamous cell of the conjunctiva, has been linked to sun exposure in some studies, but again the link is not clear.
Artificial sources of UV rays
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 20 or 25.
Some studies have also found a higher risk of melanoma of the eye in people who have used UV tanning beds.
Welding and metal work
Studies have found that welders and sheet metal workers have a higher risk of melanoma of the eye.
People exposed to UVA as a treatment for skin conditions such as psoriasis (as a part of PUVA therapy) have an increased risk of squamous cell skin cancers.
Treatment of skin conditions with UVB alone (not combined with PUVA) has not been linked to an increased risk of cancer.
Studies in the lab
Studies of cells
Studies of cells in lab dishes and test tubes have shown that sunlight and simulated sunlight (for example, from xenon or xenon-mercury arc lamps) can cause DNA damage (mutations).
One study compared a commercial tanning bed to natural sunlight, and found that the tanning bed was more likely to cause mutations than sunlight.
Studies in animals
Exposure of mice, rats, and some other lab animals to sunlight and artificial sources of UV rays has been shown to lead to skin cancers. Some exposed animals have also developed cancers of the eye (affecting the cornea and conjunctiva). No type of UV radiation has been shown to be safe – cancers have developed after exposure to UVA (alone), UVB (alone), and UVC (alone). Most of the cancers produced in these studies were squamous cell carcinomas.
What expert agencies say
Several national and international agencies study different substances in the environment to determine if they can cause cancer. (A substance that causes cancer or helps cancer grow is called a carcinogen.) The American Cancer Society looks to these organizations to evaluate the risks based on evidence from laboratory, animal, and human research studies.
Based on animal and human evidence like the examples above, 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). Its major goal is to identify causes of cancer. Based on the data available, IARC classifies UV radiation as “carcinogenic to humans.”
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 classified UV radiation as “known to be a human carcinogen.”
(For more information on the classification systems used by these agencies, see our document Known and Probable Human Carcinogens.)
What about tanning beds?
Some people think that getting UV rays from tanning beds is a safe way to get a tan, but this isn’t true.
IARC classifies the use of UV-emitting tanning devices as “carcinogenic to humans.” This includes sunlamps and sunbeds (tanning beds).
The NTP has stated that exposure to sunlamps or sunbeds is “known to be a human carcinogen.”
The US Food and Drug Administration (FDA) recently proposed that UV lamps used for tanning should be referred to as “sunlamps” and be required to carry a label that states, “repeated exposure may cause premature aging of the skin and skin cancer.” The FDA also proposed new labeling to warn users that those who are repeatedly exposed to sunlamp products should be regularly checked for skin cancer. The label would also “help to discourage use of sunlamp products by those populations that are especially susceptible to the risk of skin cancer—persons under the age of 18 and persons with a prior personal history or family history of skin cancer.” The new labeling that has been proposed is not final and currently up for public comment.
Last Medical Review: 07/02/2013
Last Revised: 07/12/2013