About Ultraviolet Radiation
The sun emits energy in the form of heat and light. Sunlight is the visible form of the sun's energy. Ultraviolet (UV) radiation, or ultraviolet light, is invisible to the human eye. Some wavelengths of UV radiation filter through the earth's atmosphere and enter the body through the skin and eyes.
Overexposure to UV radiation causes sunburn, premature aging of the skin, cataracts, and, in some cases, skin cancer. In fact, frequent and intense exposure to UV radiation is one of the major risk factors for melanoma.
There are three types of UV rays:
- UVA rays are long wavelength UV rays (320 to 400 nm) given off by tanning beds and sunlamps, as well as the sun. They are less intense than UVB rays but penetrate the skin more deeply, causing premature wrinkling and leathering of the skin. Current studies show that UVA intensifies the damage caused by UVB, and may directly stimulate the development of some skin cancers, including melanomas.
- UVB rays are the medium wavelength (290 to 320 nm) "burning rays" that are the primary cause of sunburn. They are considered the main cause of basal and squamous cell carcinoma, as well as a significant cause of melanoma.
- UVC rays are short wavelength rays (200 to 290 nm) absorbed by the earth's ozone layer, and so never reach the earth.