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Sun & Skin Damage

Tuesday, June 20, 2006

Additional Resources

Sun & Skin Damage - Tuesday, June 20, 2006The energy from the sun makes life possible. It supplies the light for plants to grow, via the process of photosynthesis, and oxygen is produced as a by-product of this process. The sun keeps our planet heated, allowing for a temperature range that supports life and permits metabolic reactions to occur. In our bodies, sunlight facilitates the production of vitamin D, necessary for calcium metabolism and proper bone health. While the radiation from the sun is essential to life, too much sun exposure can be detrimental.

Electromagnetic radiation from the sun (solar radiation) comes in different frequencies. (Incidentally, all electromagnetic waves travel at the speed of light, making the trip from the sun to the earth in approximately 8 minutes.) There is a whole spectrum of energy that is produced by the nuclear reactions that occur in the sun. Visible light represents only one range of all of the energies from the sun - accounting for slightly greater than 40% of solar electromagnetic emissions. Visible light includes all of the colors of the rainbow, which vary in wavelength. Ultraviolet (UV) radiation is also produced by the sun. It accounts for about 3% of solar radiation reaching earth. This type of radiation is more energetic than visible light; that is, it has a shorter wavelength and a higher frequency. UV radiation can damage the DNA, the genetic blueprint material, inside the cells of the body.

There are three types of radiation: UVA, UVB, and UVC. Ultraviolet A rays are the most abundant type of solar ultraviolet radiation at the earth's surface. Ultraviolet A radiation consists of wavelengths that are roughly 400-320 nanometers in length. (A nanometer is one billionth of a meter.) Ultraviolet A radiation can pass through the atmosphere, even on a cloudy day. This type of ultraviolet radiation penetrates the top layer of human skin. It can damage connective tissue and increase a person's risk of skin cancer. Ultraviolet B rays are less abundant at the earth's surface than ultraviolet A radiation. Ultraviolet B radiation consists of wavelengths that are approximately 320-290 nanometers in length. Less UVB rays reach the earth's surface than UVA rays because a significant portion of the UVB rays are absorbed by the ozone layer of the atmosphere.

Ultraviolet C radiation has the shortest wavelength of the three types of ultraviolet energy. Ultraviolet C radiation consists wavelengths of 290-200 nanometers. A shorter wavelength corresponds to a higher degree of energy, so that UVC rays are more energetic than UVA rays, but the ultraviolet C radiation is less penetrating. It is completely absorbed by gases in the atmosphere before it reaches the ground. It is good that this is the case because ultraviolet C radiation can be extremely hazardous to the skin. The ozone layer is important to our protection from ultraviolet C radiation.

Both UVA and UVB radiation are damaging to the skin. UVB radiation is responsible for sunburn. The longer wavelength ultraviolet A rays penetrate the skin more deeply and damage the underlying connective tissue. Ultraviolet A radiation is felt to be an important factor in accelerated aging of the skin produced by the sun (photo aging) and the development of skin cancers. UVA rays lead to premature wrinkling of the skin and toughening of the texture of the skin. To appreciate the difference in skin texture between sun-exposed and -unexposed areas, feel the difference in softness between the outside of the upper arm and the inner aspect of the arm (the side facing the armpit). It is important to reduce skin exposure to both ultraviolet A and ultraviolet B rays.

Avoidance of the sun during the time when the sunrays are most intense is advised. This is, roughly speaking, between the hours of 10:00 a.m. and 4:00 p.m. during daylight savings time in the continental United States. UV radiation from the sun is the greatest during late spring and early summer.

When you are in the sun during peak hours, it is a good idea to wear a wide-brimmed hat to shade the face, scalp, ears, and neck from ultraviolet radiation. Sunglasses that afford protection from both UVA and UVB are advised. Such sunshades protect the eyes and help to prevent the development of cataracts. Cataracts are a form of aging damage to the collagen in the front of the eye and produce cloudy vision.

Wearing loose fitting, but tightly-weaved clothing protects against damaging radiation from the sun. The more skin that is covered, the better. During mid-day, when radiation is the strongest, it is helpful to seek shade from an umbrella, a tree, or a tent. Sunscreen is also important in preventing skin damage from solar radiation. It is a supplemental measure beyond limiting time outdoors, not the primary method of preventing skin damage. Look for sunscreen that provides both UVA and UVB protection. Choose a sunscreen with a sun protection factor (SPF) of 15 or greater. Remember to apply the sunscreen before going outdoors, preferably 15-30 minutes before sun exposure. For most adults, this means a full ounce of lotion to cover sun-exposed parts of the body. Reapply sunscreen frequently, especially after spending time in the pool or after sweating. Lip balm with UVA and UVB protection is also advised to protect the lips against skin damage produced by sun exposure. Lip balm can also protect against the drying effects of the wind.

For more information about sunscreens, sun safety, and ultraviolet radiation, please see the following links:

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