Non-ionizing radiation or 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, and low-frequency RF (longwave) 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 varnishes or the breakdown of flavoring compounds in beer to produce the "lightstruck flavor". 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.
Non-ionizing radiation is less mutagenic than ionizing radiation. Non-ionizing radiation mostly causes the formation of pyrimidine dimers, while ionizing radiation can cause altered DNA bases, single strand breaks, and double strand breaks (see DNA repair). The pyrimidine dimers are much easier to repair and, thus, pose much lower health risk. Non-ionizing radiation can still be absorbed by the tissue and will produce a heating effect.
In terms of potential biological effects, the non-ionizing portion of the spectrum can be subdivided into:
|UVA||Black light, sunlight||318 nm - 400 nm||750 THz - 950 THz||Eye – photochemical cataract; skin – erythema, inc. pigmentation|
|Visible light||Lasers, sunlight, fire, LEDs, light bulbs||400 nm - 780 nm||385 THz - 750 THz||Skin photoaging; eye – photochemical & thermal retinal injury|
|IR-A||Lasers, remote controls||780 nm - 1.4 µm||215 THz - 385 THz||Eye – thermal retinal injury, thermal cataract; skin burn|
|IR-B||Lasers, long-distance telecommunications||1.4 µm - 3 µm||100 THz - 215 THz||Eye – corneal burn, cataract; skin burn|
|IR-C||Far-infrared laser||3 µm - 1 mm||300 GHz - 100 THz||Eye – corneal burn, cataract; heating of body surface|
|Microwave||PCS phones, some mobile/cell phones, microwave ovens, cordless phones, motion detectors, radar, Wi-Fi||1 mm - 33 cm||1 GHz - 300 GHz||Heating of body tissue|
|Radio-frequency radiation||Mobile/cell phones, television, FM, AM, shortwave, CB, cordless phones||33 cm - 3 km||100 kHz - 1 GHz||Heating of body tissue, raised body temperature|
|Low-frequency RF||Power lines||> 3 km||< 100 kHz||Cumulation of charge on body surface; disturbance of nerve & muscle responses|
|Static field||Strong magnets, MRI||Infinite||0 Hz||Magnetic – vertigo/nausea; electric – charge on body surface|
Ultraviolet 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.
Visible 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.
Visible light can also ionize DNA.
Non-ionizing radiation (or, esp. in British English, non-ionising radiation) means any type of electromagnetic radiation that does not carry enough energy to ionize atoms or molecules - that is, to completely remove an electron from an atom or molecule.
The composition of this radiation can vary depending on what may be ionized. Visible light, near ultraviolet, infrared, microwave and radio waves are all examples of non-ionizing radiation, though visible and near ultraviolet can also ionize some molecules. 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.