UV Radiation 101

Sunlight, blue sky, green grass.
Though too much sun exposure is dangerous, people need some UV radiation to synthesize vitamin D.
© iStockphoto.com/Eric Gevaert

Everything about summer seems to suggest a carefree lifestyle. It's a time for beaches and barbeques, volleyball and vacations, swimming and sun. It's when we shrug off the rubber rain gear of spring and completely forget things like heavy winter coats and sweaters. With the sun shining, the chill of fall feels like a lifetime away.

However, there is danger that exists outdoors even during this happy season. The danger is strongest during those seemingly innocent sunny days of summer, and it's inescapable. It's there during every trip to the beach, every walk in the park, every picnic with the family. It goes on vacation with us. It even hides behind the clouds on rainy days.


It's the danger of ultraviolet, or UV, radiation.

If you're like a lot of people, you may find concerns about UV radiation easy to dismiss. You might think that you don't have to worry about wrinkles until you're older, or that getting a "base tan" is a must to prevent serious sunburn. It's possible you even believe that tanning in a tanning bed is perfectly safe, because you think it's the sun that does the worst damage [source: Gibson].

If any of those statements apply to you, the truth about UV radiation will probably come as a surprise. There's a difference between UV radiation and sun exposure, and many people still have yet to learn whether they are taking the right preventive measures to protect themselves against long-term damage. In fact, most don't even know what exactly they need to protect themselves from.

To dispel any uncertainty about what UV radiation is and isn't, read on to the next page, where you'll find out why UV radiation is both necessary and dangerous.


What Is UV Radiation?

The media has focused a lot on sun damage in recent years. On the news, they say that soaking up too much sun can cause cancer. Commercials for beauty products extol the virtues of creams and lotions that claim to reverse the signs of sun damage. Articles in magazines also link wrinkles and age spots to sun exposure. And while these messages may be grounded in scientific study, a lot them don't explain why UV radiation gets a bad rap or how the rays actually work.

To understand UV radiation, you have to look into the light, or more specifically, the spectrum. The electromagnetic spectrum consists of several types of electromagnetic radiation -- basically streams of photons (little bundles of energy or light) -- traveling in waves. This spectrum includes everything from radio waves to the visible light that we can see, and it ranks the various waves according to the degree of energy they emit and their wavelength. UV rays fall at the high energy/short wavelength end of the spectrum -- making them one of the more dangerous forms of radiation [source: NASA, Zeman].


There are two types of UV radiation that penetrate our atmosphere -- UVA and UVB radiation. UVA radiation is a longer wave than UVB radiation. People need UVA and UVB radiation to synthesize vitamin D; so essentially, you need sunlight to stay healthy. But too much exposure to UVA radiation can darken and toughen the skin. UVB radiation is more dangerous. Some UVB rays are captured by the ozone layer, but those that get through can cause photochemical changes to skin cell DNA; these changes manifest themselves as sunburns and skin cancer [source: Zeman].

Researchers once thought that UVA rays were "safe" compared to UVB rays. This was an understandable assumption to make, since UVB radiation is responsible for the most obvious damage to the surface of the skin, including many forms of skin cancer. But studies have shown that there is no truly safe form of UV radiation. UVA radiation, in addition to causing wrinkles, also causes permanent damage that can, in fact, lead to some types of skin cancer [source: American Cancer Society].

Since exposure to any UV rays can clearly lead to cancer, it's useful to know which skin growths you should remove and which ones do not spread. Read on to find out.


Dangers of UV Radiation

Though the sunburn you had in the summer may fade, your body doesn't forget that exposure to UV radiation. Changes in your skin's DNA due to UVA and UVB rays can cause serious, long-term skin damage.

One of the major downsides of UV radiation is that it advances the signs of aging. Premature wrinkling is common in people who have been exposed to the sun over long periods of time, as are age spots and uneven complexions. UV radiation can also cause cataracts and weaken the immune system [source: AAD: Exam].


But UV radiation is probably most notorious for causing various forms of skin cancer. Spending time in the sunlight affects melanocytes, the cells that produce melanin, a pigment that both gives skin its color and keeps it safe from UV rays. The rays cause melanocytes to produce more melanin. However, if the skin is overexposed to UV radiation, the melanocytes may change or experience abnormal growth, which causes cancer [source: Melanoma]. Melanoma is the most serious form of skin cancer, and it can spread quickly and appear anywhere on the body. Watch for pre-existing moles that become asymmetrical, vary in coloration or grow larger over time -- these are signs that you may have melanoma [source: AAD: Melanoma].

There are two nonmelanoma cancers that you should keep an eye out for as well. Basal cell carcinoma is the most prevalent form of nonmelanoma cancer. Although it is treatable and is not likely to spread (metastasize), it's easy to overlook, because it can appear in areas not typically exposed to the sun. Basal cell carcinoma usually shows up as a small, pearly bump and often requires a biopsy to confirm whether or not it's cancerous [source: WebMD]. Squamous cell carcinoma is another nonmelanoma form of cancer that, unlike basal cell carcinoma, can metastasize. Squamous cell carcinoma typically appears on sun-exposed parts of the body as scaly bumps, growths or lesions [source: AAD: Squamous].

Now that you know what types of cancers you should be aware of, read on to learn how artificial tanning can affect your melanocytes, and why a base tan is a bad idea.


UV Radiation and Tanning

You may have already known about the dangers of UV radiation. But it's also important to be aware of some of the misconceptions.

One misconception is that tanning beds are safe. Many people think that their risk of getting skin cancer is not as high if they use tanning beds or tanning bulbs to achieve the look of golden-brown skin. This error stems from the belief that you can only get dangerous UV exposure from direct sunlight. The truth, however, is that tanning bulbs emit UV radiation just like the sun does, so getting your tan through "fake baking" is just as dangerous as laying outside in the sun.


The idea that a base tan will protect you from overexposure to the sun is another common misconception. The reasoning behind this concept is that, by visiting a tanning salon to acquire a base tan a few weeks prior to your vacation, you will reduce your risk of getting sunburned. But a base tan only prevents about 4 percent of UV rays from penetrating your skin, which just means that it may take you a little longer to burn. Add that to the UV rays you're exposed to in the tanning bed, and it's really not worth it at all [source: Gibson, AAD: Tanning].

When you go out in the sun, be smart. Know that UV rays can cause cancer and that you should take steps to protect your skin. To learn more about UV radiation and skin cancer prevention, visit the Web sites on the following page.


Lots More Information

Related HowStuffWorks Articles


  • American Academy of Dermatology. "Indoor Tanning: What You May Not Know." (Accessed 8/09/09)http://www.skincarephysicians.com/skincancernet/indoor_tanning.html
  • American Academy of Dermatology. "Melanoma: What it Looks Like." (Accessed 8/09/09)http://www.skincarephysicians.com/skincancernet/melanoma.html
  • American Academy of Dermatology. "More Young Patients Hearing "You Have Skin Cancer." (Accessed 8/09/09)http://www.skincarephysicians.com/skincancernet/young_patients_skin_cancer.html
  • American Academy of Dermatology. "Skin Cancer: Need for Skin Exam Increases with Age." (Accessed 8/09/09)http://www.skincarephysicians.com/agingskinnet/exam.html
  • American Academy of Dermatology. "Squamous Cell Carcinoma: What it Looks Like." (Accessed 8/09/09)http://www.skincarephysicians.com/skincancernet/squamous_cell_carcinoma.html
  • American Cancer Society. "What Are The Risk Factors for Squamous and Basal Cell Skin Cancer?" (Accessed 8/09/09)http://www.cancer.org/docroot/cri/content/cri_2_4_2x_what_are_the_risk_factors_for_skin_cancer_51.asp
  • Canadian Centre for Occupational Health and Safety. "Ultraviolet Radiation." July 24, 2005. (Accessed 8/15/2009)http://www.ccohs.ca/oshanswers/phys_agents/ultravioletradiation.html
  • Gibson, Lawrence E., M.D. "Sunburn." MayoClinic.com. (Accessed 8/09/09)http://www.mayoclinic.com/health/tanning/AN00589
  • HealthDay. "Tanning Beds Get Highest Carcinogen Rating." (Accessed 8/09/09)http://www.nlm.nih.gov/medlineplus/news/fullstory_87444.html
  • Melanoma. "What Is Melanoma?" (Accessed 8/16/2009)http://www.melanoma.com/whatis.html
  • National Cancer Institute. "Skin Cancer Prevention." (Accessed 8/09/09)http://www.cancer.gov/cancertopics/pdq/prevention/skin/Patient/page3
  • NASA. ""Electromagnetic Spectrum." Jan. 12, 2009. (Accessed 9/4/2009)http://imagine.gsfc.nasa.gov/docs/science/know_l1/emspectrum.html
  • WebMD. "Basal Cell Carcinoma." (Accessed 8/09/09)http://www.webmd.com/melanoma-skin-cancer/basal-cell-carcinoma
  • Zeman, Gary, Scd, CHP. "Ultraviolet Radiation." Health Physics Society. May 26, 2009. (Accessed 8/15/2009)http://www.hps.org/hpspublications/articles/uv.html