Melanin: Aging of the Skin and Skin Cancer by Diana Clarke

UV Radiation and Skin

UV-A has the longest wavelength, is not filtered by the ozone and passes through glass. It reaches the earth all year long and the amount is comparatively stable. It can penetrate the skin down to the dermis, beneath the four layers of epidermis. It is responsible for most of the visible signs of aging, due to damage to collagen and elastic fibers of the connective tissue of the dermis.

UV-A radiation also plays a role in the development of sunburns and skin cancer. Tanning salon lamps emit a large amount of UV-A rays to generate tans, so the American Academy of Dermatology does not recommend their use.

UV-B radiation, which is partially filtered by the ozone, penetrates the skin to the bottom layer of the epidermis where the basal cells are produced. UV-B can break the molecular bonds, disturbing the dividing cells and altering their structure. Compared with UV-A, UV-B is responsible for most of DNAs damage. It also causes most sunburns. During a sunburn the reddening of the skin, erythema, is caused by dilation of capillaries.

More UV-B is present during summer months between 10 a.m. and 4 p.m. and at latitudes closer to the equator. Furthermore, at high altitudes the air is thinner and cleaner, so UV-B radiation is more abundant.

UV-C, which is generally filtered by the ozone, has the shortest wavelength and the most energy, or intensity. It can sterilize hospital equipment and kill bacteria.

In addition, UV light that reaches the earth is scattered in all directions, and up to 85% is reflected from surfaces.

The Theory of Melanin for Environmental Adaptation

Originally, people of a particular race resided in a particular area. As time went on, their skin adapted to the environment. For instance, people who lived geographically close to the equator had darker skin, and people who lived far from the equator had lighter skin.

In Scotland, which lies at a northern latitude, descendants of the Britons have white skin. When their skin is exposed to the meager sunlight, the scant amount of melanin their skin produces is unable to block the sunlight. Therefore, their bodies are able to make Vitamin D with the help of sunlight. Vitamin D, a vitamin found in fish oil, is necessary to prevent rickets, a bone disease caused by too little calcium.

In contrast, in Africa, which is near the equator, blacks require intense sunlight to penetrate their dark skin to make Vitamin D. This is all well and good. However, when blacks lived in England during the Industrial Revolution, they were the first to develop symptoms of rickets, such as retarded growth, bowed legs and fractures because not enough sunlight was available.

Fortunately, in 1930, Vitamin D was discovered and dispensed as a supplement to add to the diet.

On the other hand, the skin of whites in Australia are in complete opposition to their climate. Consequently, intense UV radiation has been the major cause of skin damage and skin cancer Down Under.

Go to Page 1

BIO:

Diana Clarke is the editor of the Sun and Your Skin at http://yourskinandsun.com. She is a California credentialed teacher, freelance writer, and president of her own company, Clarke Communications and Technology. Her sun protection articles have appeared in publications, such as the San Jose Mercury News, Saratoga News and a high school health magazine, Listen Magazine.

Some Aditional Articles you may enjoy

SARS masks and repirators by cem

Overweight Gurus by Dr. Donald A. Miller

Mad Carb Disease! by Kim Beardsmore

Lumie Dawn Simulation Wake Up Clocks - The perfect Start To Your Day! by Tzaf

Hearing health resolutions for 2005 by Max Stein

Click a Number to go to an article index page
1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 | 21 | 22 | 23 | 24 | 25 | 26 | 27 | 28 | 29 | 30 | 31 | 32 | 33 | 34 | 35 | 36 | 37 | 38 | 39