Ultraviolet (UV) Radiation

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What is UV radiation?

Radiation is the emission (sending out) of energy from any source.

Ultraviolet (UV) radiation is a form of electromagnetic radiation. The main source of UV radiation (rays) is the sun, although it can also come from man-made sources such as tanning beds and welding torches.

Radiation exists across a spectrum from very high-energy (high-frequency) radiation – like x-rays and gamma rays – to very low-energy (low-frequency) radiation – like radio waves. In terms of energy, UV rays have more energy than visible light, but not as much as x-rays.

Higher energy UV rays often have enough energy to remove an electron from (ionize) an atom or molecule, making them a form of ionizing radiation. Ionizing radiation can damage the DNA in cells, which in turn may lead to cancer. But because UV rays don’t have enough energy to penetrate deeply into the body, their main effect is on the skin.

Scientists often divide UV radiation into 3 wavelength ranges:

  • UVA rays are the weakest of the UV rays. They can cause skin cells to age and can cause some indirect damage to cells’ DNA. UVA rays are mainly linked to long-term skin damage such as wrinkles, but are also thought to play a role in some skin cancers.
  • UVB rays are slightly stronger. They are mainly responsible for direct damage to the DNA, and are the rays that cause sunburns. They are also thought to cause most skin cancers.
  • UVC rays are the strongest UV rays. Fortunately, because of this, they react with ozone high in our atmosphere and do not reach the ground. Therefore UVC rays are not present in sunlight and are not normally a risk factor for skin cancer. But they can be found in some man-made sources, such as arc welding torches and mercury lamps. In the past, sunbeds were also a source of UVC rays.

Last Medical Review: 07/02/2013
Last Revised: 05/30/2014