UVA Vs UVB Rays

The sun emits an invisible form of energy known as ultraviolet (UV) radiation. Two distinct types of ultraviolet radiation - UVA rays and UVB rays -- can pierce Earth's protective ozone layer and cause harmful effects such as premature aging, sunburn, skin cancer and cataracts in humans. Due to the dangers posed by UVA and UVB rays, many weather forecasts now include a UV index that predicts the peak intensity of ultraviolet radiation at noontime in a particular place.

History

A German physicist named Johann Wilhelm Ritter discovered ultraviolet radiation in 1801. During an experiment, Ritter found that sodium chloride rapidly oxidized and darkened when exposed to light rays past the visible spectrum's violet end.

Throughout the 20th century, researchers gained a better understanding of long-wave UVA rays and shorter UVB rays and the role that each plays in causing skin cancer and other health problems. At the same time, they have documented a troubling rise in the number of skin cancer cases.

Three Canadian scientists developed the UV index in 1992. The United States created its own index in 1994. A decade later the World Health Organization established a worldwide UV index to replace inconsistent regional indices. The WHO index measures UV radiation on a scale of 1 to 11+.

Significance

UVA and UVB rays can both cause skin cancer. Each year more than 1 million Americans are diagnosed with skin cancer. That total surpasses the combined annual number of breast, colon, lung, ovarian, pancreas, prostate and uterine cancers.

Function

UVA rays make up more than 90 percent of the ultraviolet radiation that penetrates the atmosphere. Long-term exposure to UVA rays can harm deeper layers of the skin, contributing to signs of premature aging like wrinkling and a loss of elasticity. UVA rays also have been linked to melanoma, the most dangerous form of skin cancer.

UVB rays affect the skin's surface. They are the primary cause of sun burns and most skin cancers.

Effects

Painful sunburns, skin cancers and wrinkles aren't the only potential consequences of getting too much sun. UV radiation also can cause cataracts and other eye problems, as well as weakening the immune system.

Prevention/Solution

The following tips will help individuals avoid the harmful effects of UVA and UVB rays:
* Stay out of the sun between 10 a.m. and 4 p.m.
* Wear a hat and sunglasses when outside during the day.
* Use a broad spectrum sunscreen with a Sun Protection Factor (SPF) of at least 15. These products provide protection from both UVA and UVB rays.

Resources

• UVA-UVB Sun Rays