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
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.
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.
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.
What is UV Radiation?