Ozone Depletion Information Center

Health Effects of Overexposure to the Sun

Americans love the sun, and spend increasing amounts of time outside - working, playing, exercising - often in clothing that exposes a lot of skin to the sun. Most people are now aware that too much sun has been linked to skin cancer, but few know the degree of risk posed by overexposure, and fewer are aware that the risks go beyond skin cancer. Recent medical research has shown that overexposure to the sun's ultraviolet (UV) radiation can contribute to serious health problems.

This fact sheet provides a quick overview of the major problems linked to UV exposure: skin cancer (melanoma and non-melanoma), other skin problems, cataracts, and immune system suppression. Understanding these risks and taking a few sensible precautions (described in other UV Index fact sheets) will help you to enjoy the sun while lowering your chances of sun-related health problems later in life.

Skin Cancer

The incidence of skin cancer in the United States has reached epidemic proportions. One in five Americans will develop skin cancer in their lifetime, and one American dies every hour from this devastating disease. Medical research is helping us understand the causes and effects of skin cancer. Many health and education groups are working to reduce the incidence of this disease, of which 1.3 million cases have been predicted for 2000 alone, according to The American Cancer Society.


Melanoma, the most serious form of skin cancer, is also one of the fastest growing types of cancer in the U.S. Many dermatologists believe there may be a link between childhood sunburns and malignant melanoma later in life. Melanoma cases in the U.S. have almost doubled in the past two decades, with at least 32,000 new cases and 6,900 deaths estimated for 1994 alone. The rise in melanoma cases and deaths in America is expected to continue.
Cure Rate
Melanoma can spread to other parts of the body quickly, but when detected in its earliest stages it is almost always curable. If not caught early, melanoma is often fatal.

What to Watch For
Melanoma begins as an uncontrolled growth of pigment-producing cells in the skin. This growth leads to the formation of dark-pigmented malignant moles or tumors, called melanomas. Melanomas may suddenly appear without warning, but may also develop from or near a mole. For that reason, it is important to know the location and appearance of moles on the body so any change will be noticed. Melanomas are found most frequently on the upper backs of men and women, and the legs of women, but can occur anywhere on the body.

Be aware of any unusual skin condition, especially a change in the size or color of a mole or other darkly or irregularly pigmented growth or spot; scaliness, oozing, bleeding, or change in the appearance of a bump or nodule; spread of pigment from the border into surrounding skin; and change in sensation including itchiness, tenderness, or pain.

Non-Melanoma Skin Cancers

Unlike melanoma, non-melanoma skin cancers are rarely fatal. Nevertheless, they should not be taken lightly. Untreated, they can spread, causing more serious health problems. An estimated 900,000 Americans developed non-melanoma skin cancers in 1994, while 1,200 died from the disease.

There are two primary types of non-melanoma skin cancers:

Basal Cell Carcinomas are tumors of the skin which usually appear as small, fleshy bumps or nodules on the head and neck, but can occur on other skin areas as well. It is the most common skin cancer found among fair-skinned people. Basal cell carcinoma does not grow quickly, and rarely spreads to other parts of the body. However, it can penetrate below the skin to the bone and cause considerable local damage.

Squamous Cell Carcinomas are tumors which may appear as nodules or as red, scaly patches. The second most common skin cancer found in fair-skinned people, squamous cell carcinoma is rarely found in darker-skinned people. This cancer can develop into large masses, and unlike basal cell carcinoma, it can spread to other parts of the body.

Cure Rate
These two non-melanoma skin cancers have high cure rates - as high as 95 percent if detected and treated early. The key is to watch for signs and to detect the cancer in its early stages.

What to Watch For
Basal cell carcinoma tumors usually appear as slowly growing, raised, translucent, pearly nodules which, if untreated, discharge pus, and sometimes bleed. Squamous cell carcinomas usually are raised, red or pink scaly nodules or wart-like growths that form pus in the center. They typically develop on the edge of the ears, the face, lips, mouth, hands, and other exposed areas of the body.

Actinic Keratoses

These sun-induced skin growths occur on body areas exposed to the sun. The face, hands, forearms, and the "V" of the neck are especially susceptible to this type of blemish. They are pre-malignant, but if left untreated, actinic keratoses can become malignant. Look for raised, reddish, rough-textured growths. See a dermatologist promptly if you notice these growths.

Cataracts and Other Eye Damage

Cataracts are a form of eye damage, a loss of transparency in the lens which clouds vision. Left untreated, cataracts can rob people of vision. Research has shown that UV radiation increases the likelihood of certain cataracts. Although curable with modern eye surgery, cataracts diminish the eyesight of millions of Americans, and necessitate millions of dollars of eye surgery each year. Other kinds of eye damage include: pterygium (tissue growth on the white of the eye that can block vision), skin cancer around the eyes, and degeneration of the macula (the part of the retina near the center, where visual perception is most acute). All of these problems could be lessened with proper eye protection from UV radiation.

Immune Suppression

Scientists have found that sunburn 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 exposure to UV radiation may cause more long-lasting 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.

About the UV Index

The UV Index, developed by the National Weather Service and the Environmental Protection Agency, provides a forecast of the expected risk of overexposure to the sun and indicates the degree of caution you should take when working, playing, or exercising outdoors. The UV Index predicts exposure levels on a 0-10+ scale, where 0 indicates a low risk of overexposure, and 10+ means a very high risk of overexposure. Calculated on a next-day basis for dozens of cities across the U.S. by the National Weather Service, the UV Index takes into account clouds and other local conditions that affect the amount of UV radiation reaching the ground in different parts of the country.

For More Information

To learn more about the UV Index and how to protect yourself from overexposure to the sun's UV rays, explore the UV Index Web site or call EPA's Stratospheric Ozone Hotline at (800) 296-1996. Hotline staff can supply you with other fact sheets in this series, as well as other useful information.

Information About UV Radiation for Meteorologists

March 1998; EPA430-K-98-004

This publication contains information about the health risks posed by ultraviolet (UV) radiation and describes the steps people can take to protect themselves from overexposure to the sun. This information is designed to help meteorologists when they broadcast a UV Index report.

In 1994, the U.S. Environmental Protection Agency (EPA) and the National Weather Service (NWS) introduced the UV Index as a daily report on the UV radiation levels people may experience. The Index predicts the next day's levels on a 0 to 10+ scale.

This information contains both general sun safety tips as well as specific health advisories for each UV Index level. These tips and advisories are the product of close cooperation between EPA,NWS, the American Academy of Dermatology, the American Meteorological Society, and representatives of the broadcast meteorology community who actively broadcast weather information to the public.

An Adobe Acrobat version of the brochure (558K) may also be downloaded for printing.

  • There has been an 1,800 percent rise in malignant melanoma since 1930.
  • One American dies of skin cancer every hour.
  • One in five Americans develops skin cancer.
  • People get 80 percent of their lifetime sun exposure by the age of 18.

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UV radiation from the sun can seriously threaten human health.

The most obvious result of too much sun is sunburn, which involves skin redness and sometimes tenderness, swelling, blistering, fever, and nausea. Although some skin types prevent individuals from burning, everyone is at risk for other UV-related health effects.

Premature wrinkling
In the long run, too much exposure to the sun can change your skin's texture, giving it a tough, leathery appearance. The sun also can cause discolorations in skin tone including red, yellow, gray, or brown spots.

Skin cancer
Over time, exposure to the sun and severe sunburns can lead to skin cancer. The most common places for skin cancer to develop are on those body parts exposed to the sun such as the face, neck, ears, forearms, and hands.

The three main types of skin cancer are basal cell carcinoma, squamous cell carcinoma, and malignant melanoma.

  • Basal cell carcinomas are tumors that usually appear as small, fleshy bumps or nodules.
  • Squamous cell carcinomas appear as nodules or as red, scaly patches.
  • Malignant melanomas may appear without warning as a dark mole or other dark spot in the skin.

All three types can be curable if you detect them in their early stages. To help recognize potential problems, conduct periodic self-examinations and watch for growths that meet one of the 'ABCDs' of melanoma.

Asymmetry: One half of the growth doesn't match the other half.

Border irregularity: The edges of the growth are ragged, notched, or blurred.

Color: The pigmentation of the growth is not uniform. Shades of tan, brown, and black are present. Dashes of red, white, and blue also may appear.

Diameter: Any growth greater than 6 millimeters (about the size of a pencil eraser) is cause for concern.

If you notice any changes in the appearance of moles or freckles, contact a dermatologist.

Sun sensitivity
Some people may develop bumps, hives, blisters, or red blotchy areas as an allergic reaction to sun exposure. Certain drugs, perfumes, and cosmetics also can make some people sensitive to the sun.

Immune system suppression and disease
No matter what your skin type or susceptibility to burns, sun exposure can damage your immune system and make your body more vulnerable to infections and cancers. Diseases, such as herpes simplex (cold sores), chicken pox, and lupus, can become worse with sun exposure.

Eye damage
The American Academy of Ophthalmology has cautioned that excess exposure to UV radiation can cause a painful burn of the cornea. Chronic eye exposure to UV radiation may increase the incidence of 'cataract,' which is a clouding of the eye lens; 'pterygium,' in which a fleshy membrane covers the eye; and possibly 'macular degeneration,' or the development of spots that could result in blindness.

There are two types of UV radiation, UVA and UVB. UVB is usually associated with sunburn while UVA is recognized as a deeper penetrating radiation.

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You can use the following general messages to help educate your viewers about how they can avoid overexposure to the sun on any day. The remainder of the booklet contains messages that apply directly to each UV Index level.

  • Minimize exposure to the sun during the hours when exposure could be most damaging, from 10 a.m. to 4 p.m. Typically, exposure at 8 a.m. or 4 p.m. is only one third that at midday. Try getting outdoor activities accomplished during minimum exposure hours. Remember, however, you can still get a sunburn even in the mid-afternoon.

  • Remember that incidental time in the sun can add up to long-term sun damage, including the time spent walking the dog, window shopping, performing outdoor chores, or jogging at lunch. Even on overcast days, 30 to 60 percent of the sun's rays can penetrate to the Earth's surface.

  • Wear a hat and other protective clothing, as well as sunglasses, to protect your body from too much sun.

  • Use 'broad spectrum sunscreens,' which are those that contain active ingredients that absorb at least 85 percent of the UVA and UVB rays of the sun. Read labels carefully and choose a broad spectrum sunscreen with a Sun Protection Factor (SPF) of at least 15, which filters out both UVA and UVB radiation.

  • Apply sunscreen liberally to all exposed skin, about 20 minutes before exposure, especially to easily overlooked areas like the rims of the ears, the back of the neck, and the tops of the feet. For an average adult, the recommended dose is 1 ounce, or one quarter of a 4-ounce bottle, per application. Reapply every 2 hours, after being in the water, or after exercising and sweating.

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The UV Index can help the public be aware of the level of UV radiation exposure expected on a given day. As a result, people can use simple sun protective behaviors to reduce their lifetime risk of developing skin cancer and other sun-related illnesses. What follows is a description of each UV Index level and tips you can give to help people prepare.

0 to 2: Minimal

A UV Index reading of 0 to 2 means minimal danger from the sun's UV rays for the average person:
  • Most people can stay in the sun for up to 1 hour during the hours of peak sun strength, 10 a.m. to 4 p.m., without burning.
  • People with very sensitive skin and infants should always be protected from prolonged sun exposure.

Look Out Below
Snow and water can reflect the sun's rays. Skiers and swimmers should take special care. Wear sunglasses or goggles, and apply sunscreen with an SPF of at least 15. Remember to protect areas that could be exposed to UV rays by the sun's reflection, including under the chin and nose.

3 to 4: Low

A UV Index reading of 3 to 4 means low risk of harm from unprotected sun exposure. Fair-skinned people, however, might burn in less than 20 minutes:
  • Wear a hat with a wide brim and sunglasses to protect your eyes.
  • Use a sunscreen with an SPF of at least 15 and wear long-sleeved shirts and long pants when outdoors.

Me and My Shadow
An easy way to tell how much UV exposure you are getting is to look for your shadow:

  • If your shadow is taller than you are (in the early morning and late afternoon), your UV exposure is likely to be low.
  • If your shadow is shorter than you are (around midday), you are being exposed to high levels of UV radiation. Seek shade and protect your skin and eyes.

5 to 6: Moderate

A UV Index reading of 5 to 6 means moderate risk of harm from unprotected sun exposure. Fair-skinned people might burn in less than 15 minutes. Apply a sunscreen with an SPF of at least 15. Wear a wide-brim hat and sunglasses to protect your eyes:
  • Use sunscreen if you work outdoors and remember to protect sensitive areas like the nose and the rims of the ears. Sunscreen prevents sunburn and some of the sun's damaging effects on the immune system.
  • Use a lip balm or lip cream containing a sunscreen. Lip balms can help protect some people from getting cold sores.

Made in the Shades
Wearing sunglasses protects the lids of your eyes as well as the lens.

7 to 9: High

A UV Index reading of 7 to 9 means high risk of harm from unprotected sun exposure. Fair-skinned people might burn in less than 10 minutes. Minimize sun exposure during midday hours, from 10 a.m. to 4 p.m. Protect yourself by liberally applying a sunscreen with an SPF of at least 15. Wear protective clothing and sunglasses to protect the eyes:
  • When outside, seek shade. Don't forget that water, sand, pavement, and grass reflect UV rays even under a tree, near a building, or beneath a shady umbrella.
  • Wear long-sleeved shirts and trousers made from tightly woven fabrics. UV rays can pass through the holes and spaces of loosely knit fabrics.
Stay in the Game
Be careful during routine outdoor activities such as gardening or playing sports. Remember that UV exposure is especially strong if you are working or playing between the peak hours of 10 a.m. and 4 p.m. Don't forget that spectators, as well as participants, need to wear sunscreen and eye protection to avoid too much sun.

10+ Very High

A UV Index reading of 10+ means very high risk of harm from unprotected sun exposure. Fair-skinned people might burn in less than 5 minutes. Outdoor workers are especially at risk as are vacationers who can receive very intense sun exposure. Minimize sun exposure during midday hours, from 10 a.m. to 4 p.m. Apply sunscreen with an SPF of at least 15 liberally every 2 hours:
  • Avoid being in the sun as much as possible.
  • Wear sunglasses that block 99 to 100 percent of all UV rays (both UVA and UVB). Some reduction in blue light also might be beneficial but colors should not be severely distorted.
  • Wear a cap or hat with a wide brim, which will block roughly 50 percent of UV radiation from reaching the eyes. Wearing sunglasses as well can block the remainder of UV rays.
Beat the Heat
If possible, stay indoors on days when the UV Index is very high. Take the opportunity to relax with a good book rather than risk dangerous levels of sun exposure. Try not to pursue outdoor activities, whether at work or at play, unless protected with sunscreen, hat, and sunglasses.

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For more information about the UV Index, contact EPA's Stratospheric Protection Hotline at 800 296-1996 or explore the rest of the UV Index web site. In addition, an Adobe Acrobat version of the brochure (558K) may be downloaded for printing.

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This publication is based largely on results of a workgroup on UV health effects, with participants including:

Kevin D. Cooper, Professor and Chairman, Department of Dermatology, Case Western Reserve University/Director, Department of Dermatology, University Hospitals of Cleveland;
Allan Eustis, Chief, Office of Industrial Meteorology, National Weather Service (NWS), National Oceanic and Atmospheric Administration (NOAA);
Sandra Gordon, Communications Director, American Academy of Dermatology;
Paul Gross,Consulting Meteorologist;
Drusilla Hufford, Director, Stratospheric Protection Division, U.S. EPA;
Howard H. Koh, MD, MPH, Commissioner, Massachusetts Department of Public Health;
Craig Long, Meteorologist, Climate Prediction Center, NWS, NOAA;
Alvin J. Miller, Chief, Climate Operations Branch, Climate Prediction Center, NWS,NOAA.

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