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Non-ionizing radiation (or, esp. in British English, non-ionising radiation) refers to any type of electromagnetic radiation that does not carry enough energy per quantum to ionize atoms or molecules — that is, to completely remove an electron from an atom or molecule. Instead of producing charged ions when passing through matter, the electromagnetic radiation has sufficient energy only for excitation, the movement of an electron to a higher energy state. Nevertheless, different biological effects are observed for different types of non-ionizing radiation.Near ultraviolet, Visible light, infrared, microwave, radio waves, low frequency RF and static fields are all examples of non-ionizing radiation. Visible and near ultraviolet may induce photochemical reactions, ionize some molecules or accelerate radical reactions, such as photochemical aging of varnishesHelv. Chim. Acta vol. 83 (2000), pp. 1766. [http://www.zenobi.ethz.ch/publications/HelvChimActa_1766.pdf] or the breakdown of flavoring compounds in beer to produce the 'lightstruck flavor'.Photochem. Photobiol. Sci., 2004, 3, 337 - 340, DOI: 10.1039/b316210a [http://www.rsc.org/publishing/journals/PP/article.asp?doi=b316210a] The light from the Sun that reaches the earth is largely composed of non-ionizing radiation, with the notable exception of some ultraviolet rays. However, most ionizing radiation is filtered out by the atmosphere (see Earth's atmosphere). Static fields do not radiate.
Health risks Non-ionizing radiation is not mutagenic. The use of this type of radiation in medical fields and everyday life poses fewer health risks than ionizing radiation in forms such as X-rays. Strong non-ionizing radiation has a heating effect.In terms of potential biological effects, the non-ionizing portion of the spectrum can be subdivided into:
:#. The optical radiation portion, were electron excitation can occur (visible light, infrared light)
:#. The portion where the wavelength is smaller than the body, and heating via induced currents can occur (MW and higher-frequency RF).
:#. The portion where the wavelength is much larger than the body, and heating via induced currents seldom occurs (lower-frequency RF, power frequencies, static fields)
Ultraviolet radiationUltraviolet light can cause burns to skin and cataracts to the eyes. Ultraviolet is classified into near, medium and far UV according to energy, where near ultraviolet is non-ionizing. Ultraviolet light produces free radicals that induce cellular damage, which can be carcinogenic. Ultraviolet light also induces melanin production from melanocyte cells to cause sun tanning of skin. Vitamin D is produced on the skin by a radical reaction initiated by UV radiation. Plastic sunglasses (polycarbonate) generally absorb UV radiation. UV overexposure to the eyes causes snow blindness, which is a risk particularly on the sea or when there is snow on the ground.
Visible and infrared, lasersVisible light causes few effects to the human body. Bright visible light irritates the eyes. Visible-light lasers have much more powerful effects and may damage the eyes even at small powers. Very strong visible light is used for cauterizing hair follicles.
Microwave and radio frequency radiation:
Low frequency ELF
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