Sources of ultraviolet radiation
There are several categories of UV light, including UVA (U-V-A), UVB
(U-V-B), UVC (U- V-C), and Vacuum UV. Of these, only UVA and UVB reach
the earth from the sun, with the other types being absorbed by the
atmosphere. UV radiation is a concern because excessive amounts can
harm your skin and eyes.
In addition to the sun's natural radiation, UV
light is also generated by many artificial sources, including black
lights, mercury vapor street lamps, welding torches, and certain
lasers. Special devices called germicidal lamps emit UVC light to kill
bacteria. Phototherapy lamps that are used to treat skin diseases give
off primarily UVA light.
Tanning beds are a potent source, providing
three times the sun's UVA radiation during an average session.
Incandescent bulbs and halogen lamps emit low levels of UVA.
Fluorescent bulbs, however, give off traces of both UVA and UVB light.
While some researchers have speculated that fluorescent lights could
tire the eyes or age the skin, the long-term effects of such lights are