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Does tanning cause skin cancer?
The truth about skin cancer, vitamin D, and sun exposure.
In this analysis of the relationship between tanning and skin cancer, three major topics emerge: Ultraviolet radiation and its effects, vitamin D intake from the sun and its benefits, and the development of skin cancer. The link between skin cancer and exposure to the sun has been raging for years. Here I will provide information that can be found on the Internet as well as in scientific literature addressing the controversy—does tanning cause skin cancer?. In looking at these sources, I hope to help you sort through the myths to find the truth about how dangerous tanning really is.
do we mean by “tanning”?
Tanning involves any exposure to the sun, and in particular ultraviolet radiation, including both outdoor and indoor exposure (such as tanning beds).
What are UV rays?
Ultraviolet (UV) radiation consists of waves with frequencies on the light spectrum between 295 and 400 nm. That is, this energy is shorter in wavelength than visible light. UV radiation comes directly from the sun. Three different types of UV rays are emitted—UV-A, UV-B, and UV-C radiation. UV-A radiation and UV-B radiation pass through the ozone layer, while the ozone absorbs UV-C radiation. When UV radiation goes through the ozone layer and comes in contact with the body, it can have potentially damaging effects. (http://www.epa.gov/SUNWISE/uvradiation.html).
UV-A rays have the longest wavelength of all UV rays and are most abundant. All UV-A radiation passes through the ozone layer, and thus is most commonly in contact with the human body. UV-A rays give skin its initial tan color, but prolonged exposure to UV-A can lead to damage to the immune system and the formation of cataracts, as well as wrinkles in the skin. (http://www.hps.org/hpspublications/articles/uv.html).
UV-B rays have the second longest wavelength and are primarily responsible for sunburn of the skin. When the skin comes in contact with UV-B radiation, the rays alter the DNA in the skin. While most of the time, the body can repair this damage to the DNA, in cases when the DNA cannot be fixed a problem develops. UV-B rays are also linked to cataracts and immune system problems, similarly as with UV-A radiation (http://www.nas.nasa.gov/About/Education/Ozone/radiation.html). However, as we will see in the next section, Ultraviolet Radiation also plays an important role in the production of vitamin D, which the human body needs.
Note: Tanning beds emit UV rays (usually UV-A) through UV light bulbs (artificial UV light like that of the sun) (http://www.hps.org/publicinformation/ate/faqs/tanningbooths.html). Therefore, indoor tanning is equally as much of a problem as direct sunlight exposure, if not more due to such concentrated doses.
What is vitamin D?
Vitamin D plays an important role in maintaining calcium levels in the blood by helping the body absorb calcium. This, in turn, helps strengthen bones in the body. Deficiency in vitamin D leads to a weakening of the bones. One of the primary ways the body receives vitamin D other than through food is through sunlight. Ultraviolet Radiation stimulates the body’s production of vitamin D (http://healthlink.mcw.edu/article/982088787.html). In fact, approximately 75% of the body’s vitamin D supply comes from UVB rays penetrating the skin (http://www.vvv.com/healthnews/dsunscre.html).
Furthermore, it is argued that the amount of vitamin D created by sun exposure is crucial in preventing other types of cancers, such as breast, colon, and prostate cancer, which outweighs the risk for skin cancer from sun exposure.
What is Skin Cancer?
Skin cancer is a result of damaged DNA that cannot repair itself. As a result, the damaged cells replicate at a rapid pace (more rapidly than normal skin cells), forming a tumor on the skin. Usually the tumor appears on the epidermis, or the uppermost layer of the skin, so it is visible to the human eye (http://www.skincarephysicians.com/SkinCancerNet/whatis.html). Skin cancer rates have risen drastically in the past several decades, placing skin cancer as the most common form of cancer in the United States today. Approximately 1.1 million Americans were diagnosed with skin cancer in 2007 alone (Coups, 2008). At this rate, one in five Americans will be diagnosed with some form of skin cancer in their lifetime.
There are three types of skin cancer: Basal cell carcinoma (BCC), Squamous cell carcinoma (SCC), and Melanoma. Both BCC and SCC are non-melanoma skin cancers (commonly referred to as NMSC), and they occur most frequently. NMSC most often appear in areas highly exposed to UV radiation, such as the face, neck, head, arms, and hands (http://www.cancer.gov/cancertopics/wyntk/skin/page3).
While melanoma only accounts for approximately three percent of skin cancer diagnoses, it is by far the most dangerous. Melanoma causes three fourths of all skin cancer mortalities (http://www.skincancer.org/content/view/317/78/).
Common risk factors for cancer include fair skin, blonde or red hair, blue or green eyes, a history of cancer in the family, living in areas of high UV radiation, poor diet, and smoking. Melanoma mostly occurs in people of European descent, particularly in the United States. Melanoma rates are highest in fair-skinned people who are exposed to a great amount of ambient sunlight and are typically sensitive to the sun (English, 1997). Skin cancer usually appears after age 50 as a result of exposure to risk factors earlier in life (http://www.cancer.gov/cancertopics/wyntk/skin/page4).
What type of information supports or refutes the connection between skin cancer and tanning?
What the World Wide Web claims:
In searching for information regarding skin cancer and tanning on the Internet, arguments on both sides are in abundance. While some websites claim that there are far more benefits to tanning than costs, others argue that sun exposure can cause too many potential health problems. The following are examples from both pro-tanning and anti-tanning websites:
It’s okay to tan—sunlight is good for you:
Tanning salons are a major business in the United States, and thus, the claim that tanning (UV rays) cause skin cancer is dangerous to their business. The following link shows an add denying that tanning has any damaging effects on the skin: http://www.sunlightscam.com/HYPE_TanningAd_NYT.pdf. It is important to note that the message sent to these readers is published by the Indoor Tanning Association, which supports tanning for obvious reasons. Often times these websites encourage “healthy” tanning as opposed to sunburn. The Indoor Tanning Association’s website promotes not only the benefits of tanning for the skin and appearance, but also states that the tanning industry employs 160,000 people, generating 5 billion dollars each year for the economy (http://www.theita.com/).
The primary argument for healthy, moderate tanning relies on the importance of vitamin D in maintaining a healthy body. Many websites claim that there is no significant evidence linking sunlight to tanning, and choose the alternative—that sun in moderation is a good thing (http://www.suntanning.com/health.html). It has been shown that vitamin D received from sunlight is important in preventing other types of cancer, including breast and prostate cancers. Therefore, these claims state that the benefits of vitamin D in sunlight outweigh the risk of developing skin cancer (http://www.suntanning.com/tanning_myths_and_facts.html).
Protect your skin—stay out of the sun:
Other websites, on the contrary, argue that sunlight is dangerous for your health. Foundations such as the American Cancer Society (http://www.cancer.org/docroot/CRI/CRI_2_1x.asp?dt=39) and National Cancer Institute (http://www.cancer.gov/cancertopics/wyntk/skin) are interested not only in promoting healthy habits among individuals, but most importantly in preventing cancer (and most specifically, skin cancer). It is in their best interest to ensure that the public is aware of any possible danger to their health. Therefore, these sites are much more inclined to argue the idea that sunlight is, indeed, a main cause of skin cancer. For example, the following website run by the Food and Drug Administration promotes sun safety behaviors: http://www.fda.gov/opacom/lowlit/sunsafty.html. Rather than proving, however, that sun exposure causes skin cancer, such web pages focus mostly on prevention, which emphasizes avoiding prolonged periods in sunlight.
Furthermore, such organizations make a case against the use of tanning beds, which are popular among today’s youth and women in particular. Tanning beds emulate the sun in exposing the skin to UV-A rays to give the skin a bronze, or tan, tint. Because tanning beds emit the same UV radiation as the sun, they are a major contributor to sun exposure in youth today (http://www.hps.org/publicinformation/ate/faqs/tanningbooths.html).
What the scientific literature claims:
In the study by Moan et. al (2007), “Addressing the health benefits and risks, involving vitamin D or skin cancer, of sun exposure,” the major issues regarding tanning and skin cancer are discussed. The study looks to answer the question of whether sun exposure’s benefits outweigh its costs by calculating the annual yield of vitamin D photosynthesis in regard to latitude and the annual incidence rates of skin cancers and internal cancers in regard to latitude. That is, the researchers looked at both vitamin D photosynthesis and cancer incidence in people from the UK and Scandanavia in comparison to countries below the equator, such as Australia. Interestingly, the data finds that “increased sun exposure may lead to improved cancer prognosis and, possibly, give more positive than adverse health effects” (Moan 2007). Ultimately, the study shows that vitamin D is an important deterrent of internal cancers; however, it does not refute the idea that melanoma and nonmelanoma skin cancers are related to sun exposure. Thus, this study is important in understanding the benefits of sun exposure on one’s health and overall vitamin D intake.
English, Armstrong, Kricker and Fleming (1997) review the evidence of the relationship between sunlight and cancer, specifically evidence that shows sunlight has a strong connection to the cause of skin cancer. In order to do so, the paper examines ethnic origin (light skin is more susceptible to sunlight), place of residence (closer versus farther from the equator), sensitivity of sunlight, occupation, and total exposure to sunlight in relation to the incidence and mortality rate of skin cancer. The study found that “all three cancers are related to sunburn (particularly melanoma) and all are related also to other indicators of sunlight-induced skin damage” (English, 1997, 279).
Suarez-Varela, et. al (1992) performed a retrospective study on subjects who had been diagnosed with non-melanoma skin cancer (which includes both BCC and SCC). They looked at the person’s exposure to ultraviolet radiation in order to examine the relationship between non-melanoma skin cancer (NMSC) and UV rays. The study found that there was “a significant relationship…between occupational UV exposure and individuals with more than one NMSC” (Suarez-Varela,1992, 838). Furthermore, subjects who were blue-eyes and had frequent exposure to UV radiation tended to have more than one NMSC, and most subjects did not apply sunscreen or wear protective clothing. Therefore, this study revealed a link between extended sun exposure and the appearance of skin cancer later in life.
It is important to note that in researching scientific journals regarding skin cancer and its link to sun exposure, the majority of articles you will find focus on preventing skin cancer through moderating sun exposure. Therefore, it is safe to assume that in the scientific world, the causal connection between prolonged periods of sunlight on the skin and the development of skin cancer later in life is well established. The studies previously mentioned show both the importance of vitamin D to the body and of understanding the risks of sun exposure to the skin.
And the verdict is…
Tanning does have a negative impact on skin, and often times can lead to skin cancers. While sun exposure is most certainly a risk factor for developing skin cancers, there are also some benefits to moderate sun exposure. That is, it is important to receive an adequate amount of vitamin D in order to maintain healthy bones and prevent internal cancers, as shown in Moan, et al. However, as other studies have shown, first and foremost it is crucial to protect one’s skin through sunscreen and protective clothing; skin cancer is “the most important avoidable cause of non-melanoma skin cancer and melanoma” (Weinstock, 1995). That being said, be safe and be smart—remember that one in five people will develop skin cancer, so perhaps that attractive dark bronze glow is not so important after all.
Coups, E. J., Manne, S. L., and Heckman, C. J. (2008). Multiple Skin Cancer Risk Behaviors in the U.S. Population. American Journal of Preventive Medicine, 34(2), 87-93.
English, D.R., Armstrong, B. K., Kricker, A., and Fleming, C. (1997). Sunlight and Cancer. Cancer Causes and Control, 8(3), 271-283.
Suarez-Varela, M., Gonzalez, A., and Caraco, E. (1992). Non-melanoma Skin Cancer: An evaluation of risk in terms of Ultraviolet exposure. European Journal of Epidemiology, 8(6), 838-844.
Moan, J., Porojnicu, A. C., Dahlback, A. and Setlow, R. B. (2007). Addressing the health benefits and risks, involving vitamin D or skin cancer, of increased sun exposure. Proceedings of the National Academy of Science of the United States of America, 105(2), 668-673.
Wienstock, M. A. (1995). Overview of Ultraviolet Radiation and Cancer: What is the Link? How are we doing? Environmental Health Perspectives, 103(8), 251-254.
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