Ultraviolet (UV) Radiation, Broad Spectrum and UVA, UVB, and UVC
- Primary Uses or Exposures: Of the band within the optical radiation spectrum, broad-spectrum ultraviolet radiation (UVR) is the strongest and most damaging to living things. UVR is divided into wavelength ranges identified as UVA (315 to 400 nm), UVB (280 to 315 nm), and UVC (100 to 280 nm). Of the solar UV energy reaching the equator, 95% is UVA and 5% is UVB. No measurable UVC from solar radiation reaches the earth's surface, because the shortest UV wavelengths are completely absorbed by ozone, molecular oxygen, and water vapor in the upper atmosphere. Sunlamps and sunbeds emit broad-spectrum UVR. Sunbeds now chiefly emit UVA; however, before the mid 1970s, they more commonly emitted UVB and UVC. The greatest source of human exposure to broad-spectrum UVR is solar radiation; however, the exposure varies with geographical location. Approximately 25 million people in the United States use sunbeds each year, and one to two million people visit tanning facilities as often as 100 times a year.
- Nominated by: NTP Executive Committee Interagency Working Group
- Basis for Nomination: Previous RoC review of solar radiation
- Current Status: Broad SpectrumListed in the RoC as known to be a human carcinogen; UVA Radiation, UVB Radiation and UVC Radiation each listed as a reasonably anticipated to be human carcinogen since the 10th RoC (2002): See Ultraviolet Radiation Related Exposures
Web page last updated on January 05, 2009