Non-ionizing radiation
Non-ionizing 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 Earth's atmosphere. Static fields do not radiate.[3]
Health risks
Non-ionizing radiation can produce non-mutagenic effects such as inciting thermal energy in biological tissue that can lead to burns.
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 | 318–400 nm | 750–950 THz | Eye – photochemical cataract; skin – erythema, inc. pigmentation |
| Visible light | Lasers, sunlight, fire, LEDs, light bulbs | 400–780 nm | 385–750 THz | Skin photoaging; eye – photochemical & thermal retinal injury |
| IR-A | Lasers, remote controls | 780 nm – 1.4 µm | 215–385 THz | Eye – thermal retinal injury, thermal cataract; skin burn |
| IR-B | Lasers, long-distance telecommunications | 1.4–3 µm | 100–215 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 | 1–300 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 |
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.
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.
See also
- Ionizing radiation
- Electromagnetic hypersensitivity
- Mobile phone radiation and health
- Electromagnetic radiation and health
- Wireless electronic devices and health
- Electronic harassment
References
- ^ "Ionizing & Non-Ionizing Radiation".
- ^ a b Kwan-Hoong Ng (20 – 22 October 2003). "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.
{{cite journal}}: Check date values in:|date=(help) - ^ a b c d John E. Moulder. "Static Electric and Magnetic Fields and Human Health".
- ^ Helv. Chim. Acta vol. 83 (2000), pp. 1766
- ^ Photochemical & Photobiological Sciences, 2004, 3, 337-340, DOI: 10.1039/b316210a
- ^ a b "UW EH&S Hazards of Ultraviolet Light".