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.^[1] 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.^[2][3]

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^[4] or the breakdown of flavoring compounds in beer to produce the "lightstruck flavor".^[5] 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.^[3]

[edit] Health risks

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:

1. The optical radiation portion, where electron excitation can occur (visible light, infrared light)
2. The portion where the wavelength is smaller than the body, and heating via induced currents can occur (MW and higher-frequency RF)
3. 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)^[3]

[2]	Source	Wavelength	Frequency	Biological effects
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[3]	Strong magnets, MRI	Infinite	0 Hz	Magnetic – vertigo/nausea; electric – charge on body surface

[edit] Ultraviolet radiation

Ultraviolet light can cause burns to skin^[6] and cataracts to the eyes.^[6] 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 (polycarbonate) sunglasses 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.

[edit] Visible and infrared, lasers

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.

[edit] Microwave and radio-frequency radiation

• Biological effects
  • Effects on the skin
  • Effects on the eyes
  • Other hazards
• Occupational exposure standards

[edit] Low-frequency ELF

• Biological effects
  • Effects on the skin
  • Effects on the eyes
  • Other hazards
• Occupational exposure standards

[edit] Static fields

• Biological effects
  • Effects on the skin
  • Effects on the eyes
  • Other hazards

    cf. Electric power transmission

• Occupational exposure standards

[edit] See also

• Ionizing radiation
• Mobile phone radiation and health

[edit] External links

• Health Physics Society Public Education website

[edit] References

v • d • e Radiation (Physics & Health) Main articles Non-ionizing radiation Ultraviolet light · Near ultraviolet · Visible light · Infrared light · Microwave · Radio waves · Acoustic Radiation Ionizing radiation X-ray · Cosmic radiation · Gamma ray · Background radiation · Nuclear fission · Nuclear fusion · Particle accelerators · Nuclear radiation (nuclear weapons · Nuclear reactors) · Radioactive materials (Radioactive decay) Thermal radiation · Electromagnetic radiation · Earth's radiation balance Radiation health effects Radiation therapy · Radiation poisoning · Skin depth · Radioactivity in biological research · List of civilian radiation accidents Mobile phone radiation and health · Wireless electronic devices and health · Health physics Related articles Radiation hardening · Half-life · Radiobiology · Nuclear physics See also: Category:Radiation effects · Category:Radioactivity · Category:Radiation health effects · Category:Radiobiology