Ultraviolet light comes from the sun's rays but is invisible to humans. Two of the three forms of ultraviolet light, UVA and UVB rays, reach the earth and can damage a person's skin and eyes.
UVA and UVB rays are reaching the earth at greater intensities with the thinning of the ozone layer.
A person may look tan soon after being exposed to UVA and UVB rays. Long-term effects of exposure include premature aging, wrinkling, skin damage, and sometimes skin cancer.
Tanning booths also use and transmit ultraviolet light.
WebMD Medical Reference from Healthwise