Ultraviolet 31990 225524505 2008-07-14T03:44:42Z Dbiel 2452011 Replaced {{pp-move|small=yes}} with {{pp-move-vandalism|small=yes}} {{pp-move-vandalism|small=yes}} {{otheruses}} {{redirect|UV|other uses of UV|UV (disambiguation)}} [[Image:SOHO EIT ultraviolet corona image.gif|thumb|right|300px|[[False-color]] image of the [[sun|solar]] [[corona]] as seen in deep ultraviolet light at 17.1 [[nanometer|nm]] by the [[Extreme ultraviolet Imaging Telescope]] instrument aboard the [[Solar and Heliospheric Observatory|SOHO]] spacecraft]] [[Image:AS16-123-19657.jpg|thumb|right|300px| An ultraviolet photograph of the Earth taken from the Moon by [[Apollo 16]] astronauts.]] '''Ultraviolet''' ('''UV''') light is [[electromagnetic radiation]] with a [[wavelength]] shorter than that of [[visible light]], but longer than soft [[X-ray]]s. It is so named because the spectrum consists of electromagnetic waves with frequencies higher than those that humans identify as the color [[Violet (color)|violet]]. UV light is typically found as part of the radiation received by the Earth from the Sun. Most humans are aware of the effects of UV through the painful condition of [[sunburn]]. The UV spectrum has many other effects, including both beneficial and damaging changes to human health. == Discovery == The discovery of UV radiation was intimately associated with the observation that silver salts darken when exposed to sunlight. In 1801 the German physicist [[Johann Wilhelm Ritter]] made the hallmark observation that invisible rays just beyond the violet end of the visible spectrum were especially effective at darkening [[silver chloride]]-soaked paper. He called them "de-oxidizing rays" to emphasize their chemical [[reactivity]] and to distinguish them from "heat rays" at the other end of the visible spectrum. The simpler term "chemical rays" was adopted shortly thereafter, and it remained popular throughout the 19th century. The terms chemical and heat rays were eventually dropped in favor of ultraviolet and [[infrared]] [[radiation]], respectively.<ref name="hockberger"> {{Citation | last = Hockberger | first = P. E. | title = A history of ultraviolet photobiology for humans, animals and microorganisms | journal = Photochem. Photobiol. | volume = 76 | issue = | pages = 561–579 | year = 2002 | url = http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=Retrieve%5C&db=pubmed%5C&dopt=Abstract%5C&list_uids=12511035 | doi = }} </ref> == Origin of term == The name means "beyond violet" (from [[Latin]] ''ultra'', "beyond"), [[violet (colour)|violet]] being the [[color]] of the shortest wavelengths of visible light. UV light has a shorter wavelength than that of violet light. == Subtypes == The electromagnetic spectrum of ultraviolet light can be subdivided in a number of ways. The draft ISO standard on determining solar irradiances (ISO-DIS-21348)<ref>{{cite web | title = ISO 21348 Process for Determining Solar Irradiances | url = http://www.spacewx.com/ISO_solar_standard.html}}</ref> describes the following ranges: {|class="wikitable" !Name !Abbreviation ![[Wavelength]] range in [[nanometers]] !Energy per photon |- |Ultraviolet A, long wave, or [[black light]] |UVA |400 nm &ndash; 315 nm |3.10 &ndash; 3.94 eV |- |'''Near''' |NUV |400 nm &ndash; 300 nm |3.10 &ndash; 4.13 eV |- |Ultraviolet B or medium wave |UVB |315 nm &ndash; 280 nm |3.94 &ndash; 4.43 eV |- |'''Middle''' |MUV |300 nm &ndash; 200 nm |4.13 &ndash; 6.20 eV |- |Ultraviolet C, short wave, or [[Ultraviolet germicidal irradiation|germicidal]] |UVC |280 nm &ndash; 100 nm |4.43 &ndash; 12.4 eV |- |'''Far''' |FUV |200 nm &ndash; 122 nm |6.20 &ndash; 10.2 eV |- |'''Vacuum''' |VUV |200 nm &ndash; 10 nm |6.20 &ndash; 124 eV |- |'''Extreme''' |[[EUV]] |121 nm &ndash; 10 nm |10.2 &ndash; 124 eV |} In [[photolithography]], in [[laser]] technology, etc., the term deep ultraviolet or DUV refers to wavelengths below 300 nm. "Vacuum UV" is so named because it is absorbed strongly by [[air]] and is therefore used in a vacuum. In the long-wave limit of this region, roughly 150&ndash;200 nm, the principal absorber is the [[oxygen]] in air. Work in this region can be performed in an oxygen free atmosphere, pure nitrogen being commonly used, which avoids the need for a vacuum chamber. See [[1 E-7 m]] for a list of objects of comparable sizes. ==Black light== {{main|Black light}} A black light, or Wood's light, is a lamp that emits long wave UV radiation and very little visible light. Commonly these are referred to as simply a "UV light". Fluorescent black lights are typically made in the same fashion as normal fluorescent lights except that only one phosphor is used and the normally clear glass envelope of the bulb may be replaced by a deep-bluish-purple glass called [[Wood's glass]], a nickel-oxide–doped glass, which blocks almost all visible light above 400 nanometers. The color of such lamps is often referred to in the trade as "blacklight blue" or "BLB." This is to distinguish these lamps from "bug zapper" blacklight ("BL") lamps that don't have the blue Wood's glass. The phosphor typically used for a near 368 to 371 nanometer emission peak is either europium-doped strontium fluoroborate (SrB4O7F:Eu2+) or europium-doped strontium borate (SrB4O7:Eu2+) while the phosphor used to produce a peak around 350 to 353 nanometers is lead-doped barium silicate (BaSi2O5:Pb+). "Blacklight Blue" lamps peak at 365 nm. While "black lights" do produce light in the UV range, their spectrum is confined to the longwave UVA region. Unlike UVB and UVC, which are responsible for the direct DNA damage that leads to skin cancer, black light is limited to lower energy, longer waves and does not cause sunburn. However, UVA is capable of causing damage to collagen fibers and destroying vitamin A in skin. A black light may also be formed by simply using Wood's glass instead of clear glass as the envelope for a common incandescent bulb. This was the method used to create the very first black light sources. Though it remains a cheaper alternative to the fluorescent method, it is exceptionally inefficient at producing UV light (a mere few lumens per watt) owing to the [[black body]] nature of the incandescent light source. Incandescent UV bulbs, due to their inefficiency, may also become dangerously hot during use. More rarely still, high power (hundreds of watts) mercury vapor black lights can be found which use a UV emitting phosphor and an envelope of Wood's glass. These lamps are used mainly for theatrical and concert displays and also become very hot during normal use. Some UV fluorescent bulbs specifically designed to attract insects for use in bug zappers use the same near-UV emitting phosphor as normal blacklights, but use plain glass instead of the more expensive Wood's glass. Plain glass blocks less of the visible mercury emission spectrum, making them appear light blue to the naked eye. These lamps are referred to as "blacklight" or "BL" in most lighting catalogs. Ultraviolet light can also be generated by some [[Light-emitting_diode#Ultraviolet_and_blue_LEDs|light-emitting diodes]]. == Natural sources of UV == The [[Sun]] emits ultraviolet radiation in the UVA, UVB, and UVC bands, but because of absorption in the [[Earth's atmosphere|atmosphere's]] [[ozone layer]], 98.7% of the ultraviolet radiation that reaches the Earth's surface is UVA. (Some of the UVB and UVC radiation is responsible for the generation of the ozone layer.) Ordinary [[glass]] is partially [[transparent]] to UVA but is [[opaque]] to shorter wavelengths while [[fused quartz|Silica or quartz glass]], depending on quality, can be transparent even to vacuum UV wavelengths. Ordinary window glass passes about 90% of the light above 350 nm, but blocks over 90% of the light below 300 nm.<ref>{{cite web | title = Soda Lime Glass Transmission Curve | url = http://www.sinclairmfg.com/datasheets/sodalimecurve.htm}}</ref><ref>{{cite web | title = B270-Superwite Glass Transmission Curve | url = http://www.pgo-online.com/intl/katalog/curves/B270_kurve.html}}</ref><ref>{{cite web | title = Selected Float Glass Transmission Curve | url = http://www.pgo-online.com/intl/katalog/curves/whitefl_kurve.html}}</ref> The onset of vacuum UV, 200 nm, is defined by the fact that ordinary air is opaque below this wavelength. This opacity is due to the strong absorption of light of these wavelengths by oxygen in the air. Pure nitrogen (less than about 10 ppm oxygen) is transparent to wavelengths in the range of about 150&ndash;200 nm. This has wide practical significance now that semiconductor manufacturing processes are using wavelengths shorter than 200 nm. By working in oxygen-free gas, the equipment does not have to be built to withstand the pressure differences required to work in a vacuum. Some other scientific instruments, such as [[circular dichroism]] spectrometers, are also commonly nitrogen purged and operate in this spectral region. Extreme UV is characterized by a transition in the physics of interaction with matter: wavelengths longer than about 30 nm interact mainly with the chemical [[valence electrons]] of matter, while wavelengths shorter than that interact mainly with inner shell electrons and nuclei. The long end of the EUV/XUV spectrum is set by a prominent [[helium|He<sup>+</sup>]] [[spectral line]] at 30.4nm. XUV is strongly absorbed by most known materials, but it is possible to synthesize [[multilayer optics]] that reflect up to about 50% of XUV radiation at [[normal incidence]]. This technology has been used to make telescopes for [[Sun|solar imaging]]; it was pioneered by the [[NIXT]] and [[MSSTA]] sounding rockets in the 1990s; (current examples are [[Solar and Heliospheric Observatory|SOHO]]/EIT and [[TRACE]]) and for [[nanolithography]] (printing of traces and devices on [[microchips]]). == Human health-related effects of UV radiation == === Beneficial effects === The Earth's atmosphere blocks UV radiation from penetrating through the atmosphere by 98.7%. A positive effect of UVB exposure is that it induces the production of [[vitamin D]] in the skin. It has been estimated that tens of thousands of premature deaths occur in the United States annually from a range of cancers due to vitamin D deficiency.<ref>{{cite paper | title = An estimate of premature cancer mortality in the U.S. due to inadequate doses of solar ultraviolet-B radiation | author = Grant, W. B. | publisher = Cancer Volume 94, Issue 6, pp. 1867-1875 |date=2002 | url = http://www3.interscience.wiley.com/cgi-bin/abstract/91016211/ABSTRACT}}</ref> Another effect of vitamin D deficiency is [[osteomalacia]] (the adult equivalent of rickets), which can result in bone pain, difficulty in weight bearing and sometimes fractures. Other studies show most people get adequate Vitamin D through food and incidental exposure.<ref name="NPR" /> Many countries have [[fortified]] certain foods with Vitamin D to prevent deficiency. Eating fortified foods or taking a [[dietary supplement]] pill is usually preferred to UVB exposure, due to the increased risk of skin cancer from UV radiation.<ref name="NPR">[http://www.npr.org/templates/story/story.php?storyId=4717388 The Science of Sun Protection], Talk of the Nation Science Friday, 24 June 2005. Vitamin D pills recommended over sun exposure, but most people in Australia and Canada get enough Vitamin D by incidental exposure, studies show.</ref> Too little UVB radiation leads to a lack of Vitamin D. Too much UVB radiation leads to [[direct DNA damage]]s and sunburn. An appropriate amount of UVB (What is appropriate depends on your skin colour) leads to a limited amount of [[direct DNA damage]]. This is recognized and repaired by the body. Then the melanin production is increased which leads to a long lasting tan. This tan occurs with a 2 day lag phase after irradiation, but it is much less harmful and long lasting than the one obtained from UVA. Ultraviolet radiation has other medical applications, in the treatment of skin conditions such as [[psoriasis]] and [[vitiligo]]. UVA radiation can be used in conjunction with psoralens ([[PUVA]] treatment). UVB radiation is ''rarely'' used in conjunction with [[psoralens]]. In cases of [[psoriasis]] and [[vitiligo]], UV light with wavelength of 311 nm is most effective.{{Fact|date=April 2007}} === Harmful effects === An overexposure to UVB radiation can cause [[sunburn]] and some forms of skin cancer. In humans, prolonged exposure to solar UV radiation may result in acute and chronic [[health effect]]s on the [[skin]], eye, and [[immune system]].<ref>{{cite web | title = Health effects of UV radiation | url = http://www.who.int/uv/health/en/}}</ref> However the most deadly form - malignant melanoma - is mostly caused by the [[indirect DNA damage]] (free radicals and oxidative stress). This can be seen from the absence of a UV-signature mutation in 92% of all melanoma.<ref name=Davies> {{cite journal |author=Davies H.; Bignell G. R.; Cox C.; |year= 2002 |month=6 |title= Mutations of the BRAF gene in human cancer |journal= Nature |volume= 417 |issue= |pages=949–954 |id= |url= http://www.nature.com/nature/journal/v417/n6892/full/nature00766.html | doi = 10.1038/nature00766 <!--Retrieved from CrossRef by DOI bot-->}}</ref> UVC rays are the highest energy, most dangerous type of ultraviolet light. Little attention has been given to UVC rays in the past since they are filtered out by the atmosphere. However, their use in equipment such as pond [[Sterilization (microbiology)|sterilization]] units may pose an exposure risk, if the lamp is switched on outside of its enclosed pond sterilization unit. [[Image:DNA UV mutation.gif|thumb|right|350px|Ultraviolet photons harm the [[DNA]] molecules of living organisms in different ways. In one common damage event, adjacent [[Thymine]] bases bond with each other, instead of across the "ladder". This makes a bulge, and the distorted DNA molecule does not function properly.]] ====Skin==== {{cquote2 | Ultraviolet (UV) irradiation present in sunlight is an environmental human carcinogen. The toxic effects of UV from natural sunlight and therapeutic artificial lamps are a major concern for human health. The major acute effects of UV irradiation on normal human skin comprise sunburn inflammation [[erythema]], [[sun tanning|tanning]], and local or systemic [[immunosuppression]]. | Matsumura and Ananthaswamy | (2004)<ref> {{citation | title = Toxic effects of ultraviolet radiation on the skin | last = Matsumu | first = Y. | last2 = Ananthaswamy | first2 = H. N. | year = 2004 | journal = Toxicology and Applied Pharmacology | volume = 195 | issue = 3 | pages = 298–308 | url = http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=pubmed&dopt=Abstract&list_uids=15020192 | doi = 10.1016/j.taap.2003.08.019 }}</ref> }} UVA, UVB and UVC can all damage [[collagen]] fibers and thereby accelerate aging of the skin. Both UVA and UVB destroy vitamin A in skin which may cause further damage.<ref> {{citation |last = Torma |first = H |last2 = Berne |first2 = B |last3 = Vahlquist |first3 = A |journal = Acta Derm. Venereol. |date=1988 |volume = 68 |issue = 4 |pages = 291--299 |title = UV irradiation and topical vitamin A modulate retinol esterification in hairless mouse epidermis |url = http://www.ncbi.nlm.nih.gov/sites/entrez?cmd=Retrieve&db=PubMed&list_uids=2459873&dopt=AbstractPlus}} </ref> In the past UVA was considered less harmful, but today it is known, that it can contribute to skin cancer via the [[indirect DNA damage]] (free radicals and reactive oxygen species). It penetrates deeply but it does not cause [[sunburn]]. UVA does not damage DNA directly like UVB and UVC, but it can generate highly reactive chemical intermediates, such as hydroxyl and oxygen radicals, which in turn can damage DNA. Because it does not cause reddening of the skin (erythema) it cannot be measured in the [[Sunscreen#Sun protection factor|SPF]] testing. There is no good clinical measurement of the blocking of UVA radiation, but it is important that [[sunscreen]] block both UVA and UVB. Some scientists blame the absence of UVA filters in [[sunscreen]]s for the higher melanoma-risk that was found for sunscreen users. <ref name=Autier> {{cite journal |author=Autier P; Dore J F; Schifflers E; et al |title=Melanoma and use of sunscreens: An EORTC case control study in Germany, Belgium and France |url= |journal=Int. J. Cancer |volume=61 |issue= |pages=749–755 |year=1995| doi = 10.1002/ijc.2910610602 <!--Retrieved from CrossRef by DOI bot-->}}</ref> [[Image:Erythemal action spectrum.svg|thumb|right|350px|The reddening of the skin due to the action of sunlight depends both on the amount of sunlight as well as the sensitivity of the skin ("erythemal action spectrum") over the UV spectrum.]] UVB light can cause [[direct DNA damage]]. The radiation [[excited state|excites]] DNA molecules in skin cells, causing aberrant [[covalent bond]]s to form between adjacent [[cytosine]] bases, producing a dimer. When DNA polymerase comes along to replicate this strand of DNA, it reads the dimer as "AA" and not the original "CC". This causes the DNA replication mechanism to add a "TT" on the growing strand. This is a [[mutation]], which can result in [[cancer]]ous growths and is known as a "classical C-T mutation". The mutations that are caused by the direct DNA damage carry a UV signature mutation that is commonly seen in skin [[cancer]]s. The [[mutagen]]icity of UV radiation can be easily observed in [[bacterium|bacteria]] cultures. This cancer connection is one reason for concern about [[ozone depletion]] and the ozone hole. UVB causes some damage to collagen but at a very much slower rate than UVA. As a defense against UV radiation, the body tans when exposed to moderate (depending on [[human skin color|skin type]]) levels of radiation. UVA gives a quick tan that last for days by oxidizing melanin that was already present and it triggers the release of the [[melanin]] from melanocytes. UVB yields a tan that takes roughly 2 days to develop because it stimulates the body to produce more melanin. The purpose of melanin is to block UV radiation and to dissipate the energy as harmless heat. Thereby the potential damage to the skin tissues is prevented. The photochemical properties of melanin make it an excellent [[photoprotection|photoprotectant]]. However, sunscreen chemicals can not dissipate the energy of the excited state as efficiently as melanin and therefore the penetration of sunscreen ingredients into the lower layers of the skin is increasing the amount of [[free radical]]s and [[ROS]].<ref name="Hanson">{{cite journal |author=Hanson Kerry M.; Gratton Enrico; Bardeen Christopher J. |title=Sunscreen enhancement of UV-induced reactive oxygen species in the skin |doi=10.1016/j.freeradbiomed.2006.06.011| journal=Free Radical Biology and Medicine |volume=41 |issue=8 |pages=1205–1212 |year=2006 }}</ref> [[Sunscreen]] prevents the [[direct DNA damage]] which causes sunburn. Most of these products contain an [[sunscreen#sun protection factor|SPF rating]] to show how well they block '''''UVB''''' rays. The SPF rating, however, offers no data about '''''UVA''''' protection. In the US, the [[FDA]] is considering adding a star rating system to show UVA protection. A similar system is already used in some European countries. Some sunscreen lotions now include compounds such as [[titanium dioxide]] which helps protect against UVA rays. Other UVA blocking compounds found in sunscreen include [[zinc oxide]] and [[avobenzone]]. [[Cantaloupe]] extract, rich in the compound [[superoxide dismutase]] (SOD), can be bound with [[gliadin]] to form [[glisodin]], an orally-effective protectant against UVB radiation. There are also naturally occurring compounds found in rainforest plants that have been known to protect the skin from UV radiation damage, such as the fern ''[[Phlebodium aureum]]''. =====Sunscreen safety debate===== {{main|Sunscreen controversy}} Medical organizations recommend that patients protect themselves from UV radiation using sunscreen. Five sunscreen ingredients have been shown to protect mice against skin tumors (see [[sunscreen]]). However, some sunscreen chemicals produce potentially harmful substances if they are illuminated while in contact with living cells.<ref name=Parsons> {{cite journal |author=Xu, C.; Green, Adele; Parisi, Alfio; Parsons, Peter G |year= 2001 |month= |title= Photosensitization of the Sunscreen Octyl p-Dimethylaminobenzoate b UVA in Human Melanocytes but not in Keratinocytes. |journal= Photochemistry and Photobiology |volume= 73 |issue= 6 |pages=600–604 |id= |url=|doi= 10.1562/0031-8655(2001)073<0600:POTSOP>2.0.CO;2}}</ref><ref name=Knowland1993>{{cite journal |author=Knowland, John; McKenzie, Edward A.; McHugh, Peter J.; Cridland, Nigel A. |title= Sunlight-induced mutagenicity of a common sunscreen ingredient. | journal= FEBS Letters |volume= 324(3) |pages=309–313 |year=1993 |doi= 10.1016/0014-5793(93)80141-G }}</ref><ref name=Damiani1999> {{cite journal |author=Damiani, E.; Greci, L.; Parsons, R.; Knowland |title= Nitroxide radicals protect DNA from damage when illuminated in vitro in the presence of dibenzoylmethane and a common sunscreen ingredient. |journal= Free Radic. Biol. Med. |volume= 26 |issue= |pages=809 – 816 |year=1999 |doi= 10.1016/S0891-5849(98)00292-5 }}</ref> The amount of sunscreen which penetrates through the [[stratum corneum]] may or may not be large enough to cause damage. The Authors Chatelain et al. criticize (page 34)[http://content.karger.com/ProdukteDB/produkte.asp?Aktion=ShowPDF&ArtikelNr=68291&ProduktNr=224219&Ausgabe=228903&filename=68291.pdf|pdf file]: <blockquote>The question whether UV filters acts on or in the skin has so far not been fully answered. Despite the fact that an answer would be a key to improve formulations of sun protection products, many publications carefully avoid addressing this question.</blockquote> In an experiment that was published in 2006 by Hanson et al, the amount of harmful [[reactive oxygen species]] (ROS) had been measured in untreated and in sunscreen treated skin. In the first 20 minutes the film of sunscreen had a protective effect and the number of ROS species was smaller. After 60 minutes however the amount of absorbed sunscreen was so high, that the amount of ROS was higher in the sunscreen treated skin than in the untreated skin.<ref name="Hanson">{{cite journal |author=Hanson Kerry M.; Gratton Enrico; Bardeen Christopher J. |title=Sunscreen enhancement of UV-induced reactive oxygen species in the skin |doi=10.1016/j.freeradbiomed.2006.06.011| journal=Free Radical Biology and Medicine |volume=41 |issue=8 |pages=1205–1212 |year=2006 }}</ref> ==== Eye ==== High intensities of UVB light are hazardous to the eyes, and exposure can cause ''[[welder's flash]]'' ([[photokeratitis]] or [[arc eye]]) and may lead to [[cataract]]s, [[pterygium]],<ref>{{cite paper | author = Nolan, T. M. et al. | title = The Role of Ultraviolet Irradiation and Heparin-Binding Epidermal Growth Factor-Like Growth Factor in the Pathogenesis of Pterygium |date=2003 | publisher = American Journal of Pathology | url = http://ajp.amjpathol.org/cgi/content/abstract/162/2/567}}</ref><ref>{{cite paper | author = Di Girolamo, N. et al. | title = Epidermal Growth Factor Receptor Signaling Is Partially Responsible for the Increased Matrix Metalloproteinase-1 Expression in Ocular Epithelial Cells after UVB Radiation |date=2005 | publisher = American Journal of Pathology | url = http://ajp.amjpathol.org/cgi/content/abstract/167/2/489}}</ref> and [[pinguecula]] formation. [[Protective eyewear]] is beneficial to those who are working with or those who might be exposed to ultraviolet radiation, particularly short wave UV. Given that light may reach the eye from the sides, full coverage eye protection is usually warranted if there is an increased risk of exposure, as in high altitude mountaineering. Mountaineers are exposed to higher than ordinary levels of UV radiation, both because there is less atmospheric filtering and because of reflection from snow and ice. Ordinary, untreated [[eyeglasses]] give some protection. Most plastic lenses give more protection than glass lenses, because, as noted above, glass is transparent to UVA and the common acrylic plastic used for lenses is less so. Some plastic lens materials, such as [[polycarbonate]], inherently block most UV. There are protective treatments available for eyeglass lenses that need it which will give better protection. But even a treatment that ''completely'' blocks UV will not protect the eye from light that arrives around the lens. ==Degradation of polymers, pigments and dyes== Many [[polymers]] used in consumer products are degraded by UV light, and need addition of UV absorbers to inhibit attack, especially if the products are used externally and so exposed to [[sunlight]]. The problem appears as discoloration or fading, [[cracking]] and sometimes, total product disintegration if cracking has proceeded far enough. The rate of attack increases with exposure time and sunlight intensity. It is known as [[UV degradation]], and is one form of [[polymer degradation]]. Sensitive polymers include thermoplastics, such as [[polypropylene]] and [[polyethylene]] as well as speciality fibres like [[aramid]]s. UV absorption leads to chain degradation and loss of strength at sensitive points in the chain structure. They include [[tertiary carbon]] atoms, which in [[polypropylene]] occur in every [[repeat unit]]. In addition, many [[pigments]] and [[dyes]] absorb UV and change colour, so [[paintings]] and [[textiles]] may need extra protection both from sunlight and [[fluorescent lamp]]s, two common sources of UV radiation. Old and [[antique]] paintings such as [[watercolour painting]]s for example, usually need to be placed away from direct sunlight. Common window [[glass]] provides some protection by absorbing some of the harmful UV, but valuable artifacts need shielding. ==Blockers and absorbers== Ultraviolet Light Absorbers (UVAs) are molecules used in organic materials ([[polymers]], [[paints]], etc.) to absorb UV light in order to reduce the [[UV degradation]] (photo-oxidation) of a material. A number of different UVAs exist with different absorption properties. UVAs can disappear over time, so monitoring of UVA levels in weathered materials is necessary. In [[sunscreen]], ingredients which absorb UVA/UVB rays, such as avobenzone and octyl methoxycinnamate, are known as absorbers. They are contrasted with physical "blockers" of UV radiation such as [[titanium dioxide]] and [[zinc oxide]]. (See [[sunscreen]] for a more complete list.) ==Applications of UV == ===Security=== [[Image:RBC Visa UV.jpg|right|thumb|250px|A bird appears on many Visa credit cards when held under a UV light source.]] To help thwart [[counterfeiting|counterfeiters]], sensitive documents (e.g. [[credit card]]s, [[driver's license]]s, [[passport]]s) may also include a UV watermark that can only be seen when viewed under a UV-emitting light. Passports issued by most countries usually contain UV sensitive inks and security threads. [[Visa (document)|Visa]] stamps and stickers on passports of visitors contain large and detailed seals invisible to the [[naked eye]] under normal lights, but strongly visible under UV illumination. Passports issued by many nations have UV sensitive watermarks on all pages of the passport. Currencies of various countries' [[Banknotes of the Canadian dollar|banknotes]] have an image, as well as many multicolored fibers, that are visible only under ultraviolet light. Some brands of [[pepper spray]] will leave an invisible chemical (UV Dye) that is not easily washed off on a pepper sprayed attacker, which would help police identify them later. <ref>{{cite web | title = Pepper Spray FAQ | url = http://www.worthprotectionsecurity.com/how-to-use-pepper-spray.htm}}</ref> ===Fluorescent lamps=== [[Fluorescent lamp]]s produce UV radiation by ionising low-pressure [[mercury (element)|mercury]] vapour. A phosphorescent coating on the inside of the tubes absorbs the UV and converts it to visible light. The main mercury emission wavelength is in the UVC range. Unshielded exposure of the skin or eyes to mercury arc lamps that do not have a conversion phosphor is quite dangerous. The light from a mercury lamp is predominantly at discrete wavelengths. Other practical UV sources with more continuous emission spectra include [[Xenon flash lamp|xenon arc lamps]] (commonly used as sunlight simulators), deuterium arc lamps, [[mercury-xenon arc lamp]]s, metal-halide arc lamps, and tungsten-halogen incandescent lamps. ===Astronomy=== [[Image:Satellite Footprints Seen in Jupiter Aurora.jpg|thumb|right|300px|[[Aurora (phenomenon)|Aurora]] at [[Jupiter]]'s north pole as seen in ultraviolet light by the Hubble Space Telescope.]] In [[astronomy]], very hot objects preferentially emit UV radiation (see [[Wien's law]]). Because the ozone layer blocks many UV frequencies from reaching telescopes on the surface of the Earth, most UV observations are made from space. (See ''[[UV astronomy]]'', ''[[space observatory]]''.) ===Biological surveys and pest control=== Some animals, including [[bird]]s, [[reptile]]s, and [[insect]]s such as [[bee]]s, can see into the near ultraviolet. Many fruits, flowers, and seeds stand out more strongly from the background in ultraviolet wavelengths as compared to human color vision. [[Scorpion]]s glow or take on a yellow to green color under UV illumination. Many birds have patterns in their plumage that are invisible at usual wavelengths but observable in ultraviolet, and the urine and other secretions of some animals, including dogs, cats, and human beings, is much easier to spot with ultraviolet. Many insects use the ultraviolet wavelength emissions from celestial objects as references for flight navigation. A local ultraviolet emissor will normally disrupt the navigation process and would eventually attract to itself the flying insect. [[Image:ultraviolet trap entomologist.jpg|thumb|right|Entomologist using a UV light for collecting [[beetles]] in the [[Paraguay]]an [[Chaco]].]] Ultraviolet traps are used to eliminate various small flying insects. They are attracted to the UV light, and are killed using an electric shock, or trapped once they come into contact with the device. Different designs of ultraviolet light traps are also used by [[entomologists]] for [[collect]]ing [[nocturnal]] insects during [[faunistic]] survey studies. ===Spectrophotometry=== [[UV/VIS spectroscopy]] is widely used as a technique in [[chemistry]], to analyze [[chemical structure]], most notably [[conjugated system]]s. UV radiation is often used in visible [[spectrophotometry]] to determine the existence of fluorescence in a given sample. ===Analyzing minerals=== [[Image:Fluorescent minerals hg.jpg|thumb|right|350px|A collection of [[mineral]] samples brilliantly fluorescing at various wavelengths as seen while being irradiated by UV light.]] Ultraviolet lamps are also used in analyzing [[minerals]], [[gemstone|gems]], and in other detective work including authentication of various [[collectible]]s. Materials may look the same under visible light, but [[fluorescence|fluoresce]] to different degrees under ultraviolet light; or may fluoresce differently under short wave ultraviolet versus long wave ultraviolet. ===Chemical markers=== UV fluorescent [[dye]]s are used in many applications (for example, [[biochemistry]] and [[Forensic science|forensics]]). The [[Green Fluorescent Protein]] (GFP) is often used in [[genetics]] as a marker. Many substances, such as proteins, have significant light absorption bands in the ultraviolet that are of use and interest in biochemistry and related fields. UV-capable spectrophotometers are common in such laboratories. ===Photochemotherapy=== Exposure to UVA light while the skin is hyper-photosensitive by taking [[psoralen]]s is an effective treatment for [[psoriasis]] called [[PUVA]]. Due to [[psoralens]] potentially causing damage to the [[liver]], [[PUVA]] may only be used a limited number of times over a patient's lifetime ===Phototherapy=== {{Refimprove|date=April 2007}} {{Expert-subject|health|date=March 2008}} Exposure to UVB light, particularly the 310 nm narrowband UVB range, is an effective long-term treatment for many skin conditions like [[psoriasis]], [[vitiligo]], [[eczema]], and many others. UVB phototherapy does not require additional medications or topical preparations for the therapeutic benefit; only the light exposure is needed. However, phototherapy can be effective when used in conjunction with certain topical treatments such as anthralin, coal tar, and Vitamin A and D derivatives, or systemic treatments such as methotrexate and soriatane.<ref> {{cite web |title = UVB Phototherapy |url = http://www.psoriasis.org/treatment/psoriasis/phototherapy/uvb.php |archiveurl=http://web.archive.org/web/20070622180124/http://www.psoriasis.org/treatment/psoriasis/phototherapy/uvb.php |archivedate=2007-06-22 |format=php |accessdate=2007-09-23 |publisher=National Psoriasis Foundation, USA}}</ref> Typical treatment regimes involve short exposure to UVB rays 3 to 5 times a week at a hospital or clinic, and for the best results, up to 30 or more sessions may be required. Side effects may include itching and redness of the skin due to UVB exposure, and possibly sunburn, if patients do not minimize exposure to natural UV rays during treatment days. ===Photolithography=== Ultraviolet radiation is used for very fine resolution [[photolithography]], a procedure where a chemical known as a photoresist is exposed to UV radiation which has passed through a mask. The light allows chemical reactions to take place in the photoresist, and after development (a step that either removes the exposed or unexposed photoresist), a geometric pattern which is determined by the mask remains on the sample. Further steps may then be taken to "etch" away parts of the sample with no photoresist remaining. UV radiation is used extensively in the electronics industry because photolithography is used in the manufacture of [[semiconductor]]s, [[integrated circuit]] components<ref>{{cite web | title = Deep UV Photoresists | url = http://www.almaden.ibm.com/st/chemistry/lithography/deep_uv/}}</ref> and [[printed circuit board]]s. ===Checking electrical insulation=== A new application of UV is to detect [[corona discharge]] (often simply called "corona") on electrical apparatus. Degradation of insulation of electrical apparatus or pollution causes corona, wherein a strong electric field ionizes the air and excites nitrogen molecules, causing the emission of ultraviolet radiation. The corona degrades the insulation level of the apparatus. Corona produces [[ozone]] and to a lesser extent [[nitrogen oxide]] which may subsequently react with water in the air to form [[nitrous acid]] and [[nitric acid]] vapour in the surrounding air.<ref>{{cite web | title = Corona - The Daytime UV Inspection Magazine | url = http://www.seeing-corona.com/}}</ref> ===Sterilization=== {{main|Ultraviolet germicidal irradiation}} [[Image:UV-ontsmetting laminaire-vloeikast.JPG|thumb|right|300px|A low pressure mercury vapor discharge tube floods the inside of a [[Fume hood|hood]] with shortwave UV light when not in use, sterilizing microbiological contaminants from irradiated surfaces.]] Ultraviolet lamps are used to [[sterilization (microbiology)|sterilize]] workspaces and tools used in biology laboratories and medical facilities. Commercially-available low pressure [[mercury-vapor lamps]] emit about 86% of their light at 254 nanometers (nm) which coincides very well with one of the two peaks of the germicidal effectiveness curve (i.e., effectiveness for UV absorption by DNA). One of these peaks is at about 265 nm and the other is at about 185 nm. Although 185 nm is better absorbed by DNA, the [[quartz glass]] used in commercially-available lamps, as well as environmental media such as water, are more opaque to 185 nm than 254 nm (C. von Sonntag et al., 1992). UV light at these germicidal wavelengths causes adjacent [[thymine]] molecules on DNA to [[dimer]]ize, if enough of these defects accumulate on a microorganism's DNA its replication is inhibited, thereby rendering it harmless (even though the organism may not be killed outright). However, since microorganisms can be shielded from ultraviolet light in small cracks and other shaded areas, these lamps are used only as a supplement to other sterilization techniques. ===Disinfecting drinking water=== UV radiation can be an effective [[viricide]] and [[bactericide]]. Disinfection using UV radiation is commonly used in wastewater treatment applications and is finding an increased usage in drinking water treatment. Many bottlers of spring water use UV disinfection equipment to sterilize their water. [[Solar water disinfection]] is the process of using [[PET]] bottles and sunlight to disinfect water. New York City has approved the construction of a 2 billion gallon per day ultraviolet drinking water disinfection facility<ref>{{cite paper | title = UV Disinfection for New York City: Bridging Design with Operational Strategies | author = Donna Portoti et al. | publisher = American Water Works Association | format = [[PDF]] | url = http://www.cdm.com/NR/rdonlyres/EB81DD91-38EC-48AA-A993-2F08A81917B3/0/StrategiesforNYCUVDinsfectionProject.pdf}}</ref>. There are also several facilities under construction and several in operation that treat waste water with several stages of filters, hydrogen peroxide and UV light to bring the water up to drinking standards. One such facility exists in Orange County California. <ref>[http://www.latimes.com/news/local/la-me-reclaim2jan02,0,7789563.story?coll=la-home-center Sewage in O.C. goes full circle - Los Angeles Times<!-- Bot generated title -->]</ref> <ref>[http://www.wired.com/science/planetearth/multimedia/2008/01/gallery_sewage_plant New Purification Plant Answers California's Water Crisis<!-- Bot generated title -->]</ref> It used to be thought that UV disinfection was more effective for bacteria and viruses, which have more exposed genetic material, than for larger pathogens which have outer coatings or that form cyst states (e.g., [[Giardia]]) that shield their DNA from the UV light. However, it was recently discovered that ultraviolet radiation can be somewhat effective for treating the microorganism [[Cryptosporidium]]. The findings resulted in two [http://www.calgoncarbon.com/company/news/index.cfm?mode=detail&id=DF8B2807-AB22-705E-D9769AEA0B6A744E US patents] and the use of UV radiation as a viable method to treat drinking water. Giardia in turn has been shown to be very susceptible to UV-C when the tests were based on infectivity rather than excystation.<ref>{{cite paper | title = Inactivation of Giardia muris by Low Pressure Ultraviolet Light | author = Ware, M. W. et al. | publisher = United States Environmental Protection Agency | format = [[PDF]] | url = http://www.epa.gov/nerl/news/forum2003/water/ware_poster.pdf}}</ref> It has been found that [[protists]] are able to survive high UV-C doses but are sterilized at low doses. A process named SODIS [http://www.sodis.ch/index.htm] has been extensively researched in Switzerland and has proven ideal to treat small quantities of water using natural sunlight. Contaminated water is poured into transparent plastic bottles and exposed to full sunlight for six hours. The sunlight treats the contaminated water through two synergetic mechanisms: Radiation in the spectrum of UV-A (wavelength 320-400 nm) and increased water temperature. If the water temperatures rises above 50 °C, the disinfection process is three times faster. === Food processing === As consumer demand for fresh and "fresh-like" food products increases, the demand for nonthermal methods of [[food processing]] is likewise on the rise. In addition, public awareness regarding the dangers of [[food poisoning]] is also raising demand for improved food processing methods. Ultraviolet radiation is used in several food processes to kill unwanted [[microorganisms]]. UV light can be used to [[pasteurization|pasteurize]] fruit juices by flowing the juice over a high intensity ultraviolet light source. The effectiveness of such a process depends on the UV [[absorbance]] of the juice (see [[Beer's law]]). ===Fire detection=== Ultraviolet detectors generally use either a solid-state device, such as one based on [[silicon carbide]] or [[aluminium nitride]], or a gas-filled tube as the sensing element. UV detectors which are sensitive to UV light in any part of the spectrum respond to irradiation by [[sunlight]] and [[artificial light]]. A burning hydrogen flame, for instance, radiates strongly in the 185 to 260 nanometer range and only very weakly in the [[IR]] region, while a [[coal]] fire emits very weakly in the UV band yet very strongly at IR wavelengths; thus a fire detector which operates using both UV and IR detectors is more reliable than one with a UV detector alone. Virtually all fires emit some [[thermal radiation|radiation]] in the UVB band, while the [[Sun]]'s radiation at this band is absorbed by the [[Earth's atmosphere]]. The result is that the UV detector is "solar blind", meaning it will not cause an alarm in response to radiation from the Sun, so it can easily be used both indoors and outdoors. UV detectors are sensitive to most fires, including [[hydrocarbon]]s, [[metal]]s, [[sulfur]], [[hydrogen]], [[hydrazine]], and [[ammonia]]. [[Arc welding]], electrical arcs, [[lightning]], [[X-ray]]s used in nondestructive metal testing equipment (though this is highly unlikely), and radioactive materials can produce levels that will activate a UV detection system. The presence of UV-absorbing gases and vapors will attenuate the UV radiation from a fire, adversely affecting the ability of the detector to detect flames. Likewise, the presence of an oil mist in the air or an oil film on the detector window will have the same effect. ===Curing of inks, adhesives, varnishes and coatings=== Certain inks, coatings and [[adhesives]] are formulated with photoinitiators and resins. When exposed to the correct energy and irradiance in the required band of UV light, polymerization occurs, and so the adhesives harden or cure. Usually, this reaction is very quick, a matter of a few seconds. Applications include glass and plastic bonding, [[optical fiber]] coatings, the coating of flooring, [[UV Coating]] and paper finishes in offset [[printing]], and dental fillings. An industry has developed around the manufacture of [[UV lamps]] sourced for UV curing applictions. Fast processes such as flexo or offset printing require high intensity light focused via reflectors onto a moving substrate and medium and high pressure [[Mercury (element)|Hg]] (mercury) or [[Fe]] (iron) based bulbs are used which can be energised with electric arc or microwaves. Lower power fluorescent lamps can be used for static applications and in some cases, small high pressure lamps can have light focused and transmitted to the work area via liquid filled or fibre optic light guides. Radtech is a trade association dedicated to the promotion of this technology. ===Deterring substance abuse in public places=== {{Refimprove|date=April 2007}} UV lights have been installed in some parts of the world in public restrooms, and on public transport, for the purpose of deterring substance abuse. The blue color of these lights, combined with the fluorescence of the skin, make it harder for intravenous drug users to find a vein.<ref>[http://iccoventry.icnetwork.co.uk/0100news/0150swarksnews/tm_objectid=14644486&method=full&siteid=50003&headline=public-toilets--lighting-has-wrong-effect-name_page.html Public toilets' lighting has wrong effect] from Coventry Telegraph</ref> The efficacy of these lights for that purpose has been questioned, with some suggesting that drug users simply find a vein outside the public restroom and mark the spot with a marker for accessibility when inside the restroom. There is currently no published evidence supporting the idea of a deterrent effect. ===Sun tanning=== [[Sun tanning]] describes a darkening of the skin in a natural physiological response stimulated by exposure to [[ultraviolet radiation]] from [[sunlight|sunshine]] (or a [[sunbed]]). With excess exposure to the sun, a suntanned area can also develop sunburn. The increased production of melanin is triggered by the [[direct DNA damage]].<ref name=Agar2005> {{cite journal |author=Nita Agar; Antony R. Young |title=Review: Melanogenesis: a photoprotective response to DNA damage? |journal=Mutation Research/Fundamental and Molecular Mechanisms of Mutagenesis |volume=571 |issue=1-2 |pages=121–132 |year=2005 |pmid=10.1016/j.mrfmmm.2004.11.016 |url=http://www.ncbi.nlm.nih.gov/pubmed/15748643 |doi=10.1016/j.mrfmmm.2004.11.016 |url=http://www.ncbi.nlm.nih.gov/pubmed/15748643 |issn=}}</ref> This kind of damage is recognized by the body and as a defense against UV radiation the skin produces more melanin. Melanin dissipates the UV energy as harmless heat, and therefore it is an excellent [[photoprotection|photoprotectant]]. Melanin protects against the direct DNA damage and against the [[indirect DNA damage]]. Sunscreen protects only against the direct DNA damage, but increases the indirect DNA damage<ref name=Parsons> {{cite journal |author=Xu, C.; Green, Adele; Parisi, Alfio; Parsons, Peter G |year= 2001 |month= |title= Photosensitization of the Sunscreen Octyl p-Dimethylaminobenzoate b UVA in Human Melanocytes but not in Keratinocytes. |journal= Photochemistry and Photobiology |volume= 73 |issue= 6 |pages=600–604 |id= |url=|doi= 10.1562/0031-8655(2001)073<0600:POTSOP>2.0.CO;2}}</ref><ref name=Knowland1993>{{cite journal |author=Knowland, John; McKenzie, Edward A.; McHugh, Peter J.; Cridland, Nigel A. |title= Sunlight-induced mutagenicity of a common sunscreen ingredient. | journal= FEBS Letters |volume= 324(3) |pages=309–313 |year=1993 |doi= 10.1016/0014-5793(93)80141-G }}</ref><ref name=Damiani1999> {{cite journal |author=Damiani, E.; Greci, L.; Parsons, R.; Knowland |title= Nitroxide radicals protect DNA from damage when illuminated in vitro in the presence of dibenzoylmethane and a common sunscreen ingredient. |journal= Free Radic. Biol. Med. |volume= 26 |issue= |pages=809 – 816 |year=1999 |doi= 10.1016/S0891-5849(98)00292-5 }}</ref> - this causes the higher amount of melanoma that had been found repeatedly in sunscreen users compared to non-users.<ref name=Garland> {{cite journal |author=Garland C, Garland F, Gorham E |title=Could sunscreens increase melanoma risk? |url= http://www.ajph.org/cgi/reprint/82/4/614 |journal=Am J Public Health |volume=82 |issue=4 |pages=614–5 |year=1992 |pmid=1546792 |issn=}}</ref><ref name=Westerdahl2000> {{cite journal |author=Westerdahl J; Ingvar C; Masback A; Olsson H |title= Sunscreen use and malignant melanoma. | journal= International journal of cancer. Journal international du cancer |volume=87 |pages=145–50 |year=2000 |doi= 10.1002/1097-0215(20000701)87:1<145::AID-IJC22>3.0.CO;2-3 }}</ref><ref name=Autier> {{cite journal |author=Autier P; Dore J F; Schifflers E; et al |title=Melanoma and use of sunscreens: An EORTC case control study in Germany, Belgium and France |url= |journal=Int. J. Cancer |volume=61 |issue= |pages=749–755 |year=1995 |doi=10.1002/ijc.2910610602}}</ref><ref name=Weinstock> {{cite journal |author=Weinstock, M. A. |title=Do sunscreens increase or decrease melanoma risk: An epidemiologic evaluation. |url= |journal=Journal of Investigative Dermatology Symposium Proceedings |volume=4 |issue= |pages= 97–100 |year=1999 |doi=10.1038/sj.jidsp.}}</ref><ref name=Vainio> {{cite journal |author=Vainio, H., Bianchini, F. |title=Cancer-preventive effects of sunscreens are uncertain. |url= |journal=Scandinavian Journal of Work Environment and Health |volume=26 |issue= |pages=529–31 |year=2000 |issn=}}</ref> ===Erasing EPROM modules=== Some [[EPROM]] (electronically programmable read-only memory) modules are erased by exposure to UV radiation. These modules often have a transparent glass ([[quartz]]) window on the top of the chip that allows the UV radiation in. These have been largely superseded by [[EEPROM]] and [[flash memory]] chips in most devices. ===Preparing low surface energy polymers=== UV radiation is useful in preparing low surface energy polymers for adhesives. Polymers exposed to UV light will oxidize thus raising the surface energy of the polymer. Once the surface energy of the polymer has been raised, the bond between the adhesive and the polymer will not be smaller. ===Reading otherwise illegible papyruses=== Using multi-spectral imaging it is possible to read illegible [[papyrus]]es, such as the burned papyruses of the [[Villa of the Papyri]] or of [[Oxyrhynchus]]. The technique involves taking pictures of the illegible papyruses using different filters in the infrared or ultraviolet range, finely tuned to capture certain wavelengths of light. Thus, the optimum spectral portion can be found for distinguishing ink from paper on the papyrus surface. ===Lasers=== Ultraviolet [[lasers]] have applications in industry ([[laser engraving]]), medicine ([[dermatology]] and [[keratectomy]]), [[Free Space Optics|free air secure communications]] and computing ([[optical storage]]). They can be made by applying [[frequency conversion]] to lower-frequency lasers, or from Ce:LiSAF crystals ([[cerium]] [[Dopant|doped]] with lithium strontium aluminum fluoride), a process developed in the 1990s at [[Lawrence Livermore National Laboratory]].<ref>{{cite web | last = Marshall | first = Chris | authorlink = | coauthors = | title = A simple, reliable ultraviolet laser: the Ce:LiSAF | work = | publisher = Lawrence Livermore National Laboratory | date = 1996 | url = https://www.llnl.gov/str/Marshall.html | format = | doi = | accessdate = 2008-01-11}}</ref> == Evolutionary significance == Evolution of early reproductive [[proteins]] and [[enzymes]] is attributed in modern models of [[evolutionary theory]] to ultraviolet light. UVB light causes [[thymine]] base pairs next to each other in genetic sequences to bond together into [[thymine dimers]], a disruption in the strand which reproductive enzymes cannot copy (see picture above). This leads to [[frameshifting]] during genetic replication and [[protein synthesis]], usually killing the organism. As early prokaryotes began to approach the surface of the ancient oceans, before the protective ozone layer had formed, blocking out most wavelengths of UV light, they almost invariably died out. The few that survived had developed enzymes which verified the genetic material and broke up [[thymine dimer]] bonds, known as [[excision repair]] enzymes. Many enzymes and proteins involved in modern [[mitosis]] and [[meiosis]] are extremely similar to excision repair enzymes, and are believed to be evolved modifications of the enzymes originally used to overcome UV light.<ref>{{cite paper | author = Margulis, Lynn and Sagan, Dorion | title = Origins of Sex: Three Billion Years of Genetic Recombination | version = 1 | publisher = Yale University Press |date=1986 | url = http://books.google.com/books?vid=ISBN0300046197&id=3hDVTEk3ioIC&pg=PP1&lpg=PP1&ots=IG3gUOrVBQ&dq=origins+of+sex:+three&sig=kcL3cFKL0NqFQoSXXlsFzQ9mh-8 | format = book }}</ref> == See also == * [[UV index]] * [[High-energy visible light]] * [[Sun tanning]] * [[Black light]] * [[Wood's lamp]] * [[Tanning lamp]] * [[UV degradation]] * [[UV Stabilizers in plastics]] * [[Ultraviolet photography]] ==References== {{reflist}} ==External links== *[http://www.mmmp.org/MMMP/public/biomap/viewBioMapImage.mmmp Ultraviolet radiation biology] == Further reading == {{Wiktionary}} *{{Citation | last = Hu | first = S | last2 = Ma | first2 = F | last3 = Collado-Mesa | first3 = F | last4 = Kirsner | first4 = R. S. | title = UV radiation, latitude, and melanoma in US Hispanics and blacks | journal = Arch. Dermatol. | volume = 140 | issue = 7 | pages = 819–824 | month = Jul | year = 2004 | url = http://archderm.ama-assn.org/cgi/content/full/140/7/819 | doi = 10.1001/archderm.140.7.819 | id = | pmid = 15262692 }} *{{Citation | last = Hockberger | first = Philip E. | title = A History of Ultraviolet Photobiology for Humans, Animals and Microorganisms | journal =Photochemisty and Photobiology | volume =76 | issue =6 | pages =561–569 | date = | year =2002 | url =http://www.bioone.org/archive/0031-8655/76/6/pdf/i0031-8655-76-6-561.pdf | doi = 10.1562/0031-8655(2002)076<0561:AHOUPF>2.0.CO;2|label=10.1562/0031-8655(2002)076<0561:AHOUPF>2.0.CO;2 }} *{{Citation | last = Allen | first = Jeannie | title = Ultraviolet Radiation: How it Affects Life on Earth | url = http://earthobservatory.nasa.gov/Library/UVB/ |date=2001-09-06 | series = Earth Observatory | publisher = NASA, USA }} {{EMSpectrum}} [[Category:Electromagnetic spectrum]] [[Category:Printing]] [[ar:أشعة فوق بنفسجية]] [[zh-min-nan:Chí-goā-soàⁿ]] [[bs:Ultraljubičasto zračenje]] [[br:Uslimestra]] [[bg:Ултравиолетови лъчи]] [[ca:Ultraviolat]] [[cs:Ultrafialové záření]] [[da:Ultraviolet lys]] [[de:Ultraviolettstrahlung]] [[et:Ultraviolettkiirgus]] [[es:Radiación ultravioleta]] [[eo:Ultraviola radiado]] [[eu:Ultramore]] [[fa:فرابنفش]] [[fr:Ultraviolet]] [[gl:Ultravioleta]] [[ko:자외선]] [[hi:पराबैंगनी]] [[hr:Ultraljubičasto zračenje]] [[io:Ultreviolea]] [[id:Ultraungu]] [[is:Útfjólublátt ljós]] [[it:Radiazione ultravioletta]] [[he:על-סגול]] [[kn:ಅತಿನೇರಳೆ ವಿಕಿರಣ]] [[lv:Ultravioletais starojums]] [[lt:Ultravioletiniai spinduliai]] [[hu:Ultraibolya sugárzás]] [[mk:Ултравиолетова светлина]] [[mr:अतीनील किरणे]] [[ms:Sinar ultraungu]] [[nl:Ultraviolet]] [[ja:紫外線]] [[no:Ultrafiolett stråling]] [[om:Ultraviolet]] [[nds:Ultravigelett]] [[pl:Ultrafiolet]] [[pt:Radiação ultravioleta]] [[ksh:Shwatzleesh]] [[ro:Raze ultraviolete]] [[ru:Ультрафиолетовое излучение]] [[sq:Rrezet ultravioletë]] [[simple:Ultraviolet]] [[sk:Ultrafialové žiarenie]] [[sl:Ultravijolično valovanje]] [[sr:Ултраљубичасто зрачење]] [[sh:Ultraljubičasto zračenje]] [[fi:Ultraviolettisäteily]] [[sv:Ultraviolett strålning]] [[ta:புற ஊதா கதிர்]] [[th:รังสีอัลตราไวโอเลต]] [[vi:Tia cực tím]] [[tr:Morötesi]] [[uk:Випромінювання ультрафіолетове]] [[zh:紫外线]]