Looking Fit 06/2003: Wolff Words: A Lesson In UV

UV ABCs
A Lesson In UV

Could you explain the difference between UVA, UVB and UVC and their uses in tanning?

Ultraviolet light is energy from the sun that cannot be seen; however, its effects can be observed upon all living things. UV light is organized into three distinct energy ranges: UVA, UVB and UVC. This spectrum of energy is measured in nanometers (nm), with one nanometer equaling one billionth of a meter. The relationship between the wavelength and the amount of energy it transports is the longer the wavelength, the lower the energy.

Ultraviolet light is organized from the shorter and higher-energy wavelength (UVC) to the longer and lower-energy wavelength (UVA), with each wave having its own location on the electromagnetic spectrum. The UVC energy range is 200-280 nm; UVB range is 280-320 nm; and UVA range is 320-400 nm. Visible light range is 400-780 nm.

Longer wavelengths typically are less harmful to humans exposed to its energy; shorter wavelengths are more intense. It is important to note that each has a beneficial purpose. For instance, while UVC is the most powerful of ultraviolet rays and considered harmful to humans, hospitals use germicidal lamps with UVC (253.7 nm) to sterilize surgical instruments, water and air in operating rooms because it can destroy bacteria and viruses.

People primarily are exposed to UVA and UVB light when spending time in the sun. UVC rays generally are filtered out by the earth's ozone layer. Some scientists hypothesize that erosion of the ozone layer may allow some UVC rays to reach the earth, but the research has not been conclusive.

UVA waves are longer than other ultraviolet waves and can penetrate deeper layers of the skin, called the dermis. While it is possible to darken only already existing pigment with UVA alone, this only can be accomplished by exposure to abnormally high amounts of UVA, which may have long-term effects.

UVB waves are shorter than UVA waves, principally affecting the upper layers of the skin, called the epidermis. UVB waves stimulate the upper layers of the skin to produce melanin, the pigment that forms a coating around other skin cells to protect them from overexposure to the sun. Although UVB cannot penetrate the skin as deeply as UVA, it is more likely than UVA to cause sunburn.

A quality tanning lamp needs a balance of UVA and UVB. UVB stimulates the melanin while UVA oxidizes the stimulated melanin and turns it brown. This combination results in a darkening of the pigmentation and a natural protection against damage from the sun.

If you have a specific lamp question you would like answered, please e-mail sales@wolffsys.com or visit www.wolffsystem.com.