Non-ionizing radiation
From Wikipedia, the free encyclopedia
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 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, where 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)[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 photo-ageing; 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 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.
[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
-
- Occupational exposure standards
[edit] See also
[edit] External links
[edit] References
- ^ "Ionizing & Non-Ionizing Radiation". http://www.epa.gov/radiation/understand/ionize_nonionize.html.
- ^ a b Kwan-Hoong Ng (20th – 22nd October 2003). "[http://www.who.int/peh-emf/meetings/archive/en/keynote3ng.pdf Non-Ionizing Radiations – Sources, Biological Effects, Emissions and Exposures]" (PDF). Proceedings of the International Conference on Non-Ionizing Radiation at UNITEN ICNIR2003 Electromagnetic Fields and Our Health. http://www.who.int/peh-emf/meetings/archive/en/keynote3ng.pdf.
- ^ a b c d John E. Moulder. "Static Electric and Magnetic Fields and Human Health". http://www.mcw.edu/gcrc/cop/static-fields-cancer-FAQ/toc.html.
- ^ Helv. Chim. Acta vol. 83 (2000), pp. 1766. [1]
- ^ Photochem. Photobiol. Sci., 2004, 3, 337 - 340, DOI: 10.1039/b316210a [2]
- ^ a b "UW EH&S Hazards of Ultraviolet Light". http://www.ehs.washington.edu/rsononion/uvlight.shtm.
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