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What is UV Radiation?

What is UV Radiation?

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Effects of Sunlight

Sun Safety: Effects of Sunlight

The effect of sunlight is more dangerous than most people think.  Skin cancer is an obvious disease that is a direct affect of the sun.  In the United States, many organizations are targeting the reduction of skin cancer.  This has led to extensive efforts to raise awareness of the risks involved in overexposure to the sun and of the behavioral changes needed to avoid it.  Melanoma is one type of cancer that can strike people of any age, race, gender, and economic status.  It is the most common cancer for women ages 25 to 29.


A sunburn develops when the amount of UV exposure is greater than what can be protected against by the skin's melanin.   The lighter your skin, the less melanin it has to absorb UV and protect itself.   And all skin, no matter what color, responds to continued sun exposure by thickening and hardening, resulting in leathery skin and wrinkles later in life.

Unprotected sun exposure is even more dangerous if you have moles on your skin, very fair skin and hair, or a family history of skin cancer, including melanoma.  You should be especially careful about sun protection if you have one or more of these high-risk characteristics.

Not all sunlight is "equal" in UV concentration.  The intensity of the sun's rays depends upon the time of year, as well as the altitude and latitude of your location.

UV rays are strongest during summer.   Remember that the timing of this season varies by location; if you travel to a foreign country during its summer season, you'll need to pack the strongest sun protection you can find.

 Skin Cancer

According to the American Cancer Society (1999), skin cancer is the most common of all cancers.  The incidence of skin cancer is greater than the incidence of breast, lung, prostate, colorectal, and kidney cancers combined.  In the United States, about 1.3 million new cases of skin cancer are diagnosed each year.

Here are statistics from the American Cancer Society 2001:

  • More than one million new cases of basal cell and squamous cell carcinoma will be detected in 2001.
  • 47,700 new cases of malignant melanoma will be diagnosed in 2001.
  • In 2001, skin cancer will claim the lives of approximately 9,800 people, 7,800 of these from melanoma and 2,000 from other skin cancer.

Exposure to UV radiation appears to be the most important environmental factor in the development of skin cancer.  Scientists believe that the increase in skin cancer has resulted from:

  • Increased outdoor leisure time
  • Decrease in the amount of clothing worn outdoors
  • Decrease in atmospheric ozone levels

Skin cancer is a largely preventable disease.  Exposure to UV radiation may be the most important preventable factor in determining a person's risk for skin cancer (American Academy of Dermatology, 1998).  Skin color is the most important factor determining a person's risk for skin cancer.  There are three major types of skin cancers: basal cell carcinoma, squamous cell carcinoma, and melanoma.

Eye Damage

Sunlight is the primary source of UV radiation that can damage tissues of the eye.  Results from dozens of studies suggest that spending long hours in the sun without eye protection increases the chances of developing eye diseases, including cataracts.  The 1998 Journal of the American Medical Association reported that even low amounts of sunlight can increase the risk of developing eye disorders.

The American Academy of Ophthalmology has cautioned that excess exposure to UV radiation may increase the incidence of cataracts.  Cataracts are a form of eye damage that causes the loss of transparency in the lens, clouding vision.   Everyone is at risk for developing cataracts.  Another potential effect of UV radiation is a "burning" of the eye surface, called "snow blindness" or photokeratitis from sunlight.  The effects usually disappear within a couple of days, but may lead to further complications later in life.  UVB damage to the eyes is also cumulative, so it is never too late for people to start protecting their eyes.

Photo aging/Wrinkling

A very high percentage of age-associated cosmetic skin problems can be attributed to sun (Levine, 1997).   Chronic overexposure to the sun changes the texture and weakens the elastic properties of the skin.  The epidermis, which is the outer layer of the skin, thickens, becomes leathery, and wrinkles as a result of sun exposure.  The difference between skin tone, wrinkles, or pigmentation on the underside of a person's arm and the top side of the same arm illustrate the effects of sun exposure on skin.  In most cases, the top side of the arm has had more exposure to the sun and shows greater sun damage.  Sun-induced skin damage causes wrinkles and furrows, easy bruising, brown or "liver spots", precancerous lesions (actinic keratoses), and potentially skin cancer (Skin Cancer Foundation, 1992).  Because photo aging of the skin is cumulative, it is never too late for a person to start a sun protection program.

Immune System Suppression

Scientists believe sunburns can alter the distribution and function of disease-fighting white blood cells in humans for up to 24 hours after exposure to the sun.  Repeated overexposure to UV radiation can cause more damage to the body's immune system.  Mild sunburns can directly suppress the immune functions of human skin where the sunburn occurred, even in people with dark skin.

Repeated over-exposure to UV radiation can damage the body's immune system.

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