Ultraviolet Radiation

The presence of an upper layer of atmospheric ozone shields the earth's surface from incoming solar ultraviolet radiation and protects us from its effects. Many epidemiological studies have recognized that UV radiation is harmful to animals and plants. The UV rays have been linked to skin cancer, cataracts, and probably macular degeneration an important cause of blindness in America. There are 2 types of UV radiation: A and B, both are dangerous. UV-A is in the 320 - 400 nanometers band, and UV-B is in the 290-320 nanometers band action spectra. UV-B in sunlight is the most biologically significant wavelength. The measure of outdoor UV exposure is difficult. The fraction of UV-A and UV-B is constantly changing due to solar elevation, angle, varying hourly and seasonally and also varies with the ozone level. Sunburn is the result of overexposure to the sun's ultraviolet radiation. Long-term cumulative sun exposure increases the risk of melanoma and non-melanoma skin cancer. Melanoma is a kind of skin cancer, sometimes called malignant melanoma. It arises from the melanocytes, the cells where pigment is synthesized. This is a very serious kind of skin cancer that can cause death. If melanoma is caught early, when still very small, it can be cured. Melanoma can have many different shapes and appearances and can occur any place on the body.

Non-melanoma skin cancers are: Basal cell cancers and squamous cell cancers. Basal cells are usually seen in exposed areas of the body, they are slow growing and rarely spread internally. Squamous cells also appear in sun exposed areas, but is more aggressive than Basal cell. About 3% of them spread to distant parts of the body. Both cancers are more prevalent in men due to greater sun exposure.

Prevention:

• Avoid the strongest UV sunlight, between 10AM-3PM
• Avoid tanning parlors and sunlamps. They emit UV-A.
• Use sunscreens with an SPF of 15 or higher on areas exposed to the sun. Use water resistant sunscreens often when swimming or sweating.
• When buying sunglasses, look for a pair that blocks 99-100% of UV-A and UV-B. The safest material for use in sunglasses is polycarbonate since it is the most impact resistant material available.
• Make sure that children's eyes are not overexposed to the sun. They may develop photokeretitis, also known as corneal sunburn. This condition is very painful and may cause temporary vision loss.
• Lifeguards and skiers are at increased risk of UV eye damage since UV reflects off water, sand, snow, and other bright surfaces. For this reason it is advised that these individuals should wear UV coated sunglasses. Lifeguards should also wear brimmed hats for maximum protection.
• Be aware that there is more exposure to UV radiation in higher elevations. Cloud cover decreases UV radiation, but dangerous amounts of UV radiation can still be present on cloudy days.

Sun Sensitivity:

Some people experience a skin reaction to the sun rays after even a brief sun exposure. The skin will be red, itchy, or swollen or will blister. These individuals are called photosensitive or "sun sensitive". The skin reaction will last longer than sunburn and be more painful. It is important to check with your physician about medications that can make your skin more sensitive to sun exposure.

The best known products to cause increased sensitivity are:

• antibiotics like tetracycline, quinolones, and sulfas
• diuretics like thiazide
• some cancer drugs
• tricyclic antidepressents
• oral diabetic medications
• some blood pressure controlling drugs
• some creams and acne medication
• ibuprofen like products

Very Important: Contact your physician for proper diagnosis and treatment of your condition.

Beneficial Effects of UV Radiation

UV Radiation is beneficial in vitamin D formation. Vitamin D deficiency can be corrected by sunlight exposure. Also, sunlight is beneficial in Seasonal Affective Disorder.

References:

1. Research workshop on risks and benefits of exposure to ultraviolet radiation and tanning National Institute of Arthritis and Musculoskeletal and Skin Diseases
2. Global Climate Change: Beyond Sunburn Environmental Health Perspectives
3. Non-Melanoma Skin Cancer
4. Polymorphous Light Eruption Mayo Clinic Health Oasis