29.12.2014
Antony Young, an expert in the effect of sunlight on the skin, spoke out after studying the damage two types of ultraviolet rays a€“ A (longwave) and B (shortwave) a€“ caused to the skin of healthy young men and women.'Tanning salons still tend to claim that UVA is safe but that's nonsense,' he said, adding that it 'may be more carcinogenic than previously thought'. The views expressed in the contents above are those of our users and do not necessarily reflect the views of MailOnline. It is a general perception that people look better with a tan skin.  This is the reason use of tanning salons has become a common practice among teenagers, especially females. Tanning is caused by harmful ultraviolet (UV) radiation from the sunlamps and tanning beds. Pediatricians should incorporate advice about ultraviolet exposure into health-supervision practices, including advice to avoid sunburning and suntanning, wearing clothing and hats with brims, and applying sunscreen. Pediatricians should discuss about sun protection with children and parents together beginning at 9 or 10 years of age. Infants younger than 6 months of age should be kept out of direct sunlight and covered with appropriate protective clothing and hats. Guidelines for vitamin D supplementation should be followed and all infants, children, and adolescents should receive at least 400 international units of vitamin D daily. Note: Many of our articles have direct quotes from sources you can cite, within the Wikipedia article! Ultraviolet (UV) light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than x-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV.
UV light is found in sunlight and is emitted by electric arcs and specialized lights such as black lights.
The discovery of UV radiation was intimately associated with the observation that silver salts darken when exposed to sunlight. The name means "beyond violet" (from Latin ultra, "beyond"), violet being the color of the shortest wavelengths of visible light.
In photolithography and laser technology, the term deep ultraviolet or DUV refers to wavelengths below 300 nm. Ordinary glass is partially transparent to UVA but is opaque to shorter wavelengths while Silica or quartz glass, depending on quality, can be transparent even to vacuum UV wavelengths.
The onset of vacuum UV, 200 nm, is defined by the fact that ordinary air is opaque at shorter wavelengths.
A black light, or Wood's light, is a lamp that emits long wave UV radiation and very little visible light. While "black lights" do produce light in the UV range, their spectrum is confined to the longwave UVA region. 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. Some UV fluorescent bulbs specifically designed to attract insects use the same near-UV emitting phosphor as normal blacklights, but use plain glass instead of the more expensive Wood's glass. Fluorescent lamps without a phosphorescent coating to convert UV to visible light emit ultraviolet light peaking at 254 nm due to the peak emission of the mercury within the bulb. Such low pressure mercury lamps are used extensively for disinfection and in standard form have an optimum operating temperature of approx 30 degrees Celsius. Light-emitting diodes (LEDs) can be manufactured to emit light in the ultraviolet range, although practical LED arrays are very limited below 365 nm.
UV laser diodes and UV solid-state lasers can be manufactured to emit light in the ultraviolet range. Ultraviolet detection and measurement technology can vary with the part of the spectrum under consideration. Technology for VUV instrumentation has been largely driven by solar physics for many decades and more recently some lithographic applications. Ultraviolet radiation has other medical applications, in the treatment of skin conditions such as psoriasis and vitiligo.
It has also been scientifically proven that UV rays can help people with certain sleeping disorders.[citation needed] The gamma rays emitted by a UV bulb are powerful enough to travel through the body. The reddening of the skin due to the action of sunlight depends both on the amount of sunlight and on the sensitivity of the skin ("erythemal action spectrum") over the UV spectrum.
As a defense against UV radiation, the amount of the brown pigment melanin in the skin increases when exposed to moderate (depending on skin type) levels of radiation; this is commonly known as a sun tan. Some sunscreen lotions now include compounds such as titanium dioxide which helps protect against UVA rays. Medical organizations recommend that patients protect themselves from UV radiation using sunscreen.
However, some sunscreen chemicals produce potentially harmful substances if they are illuminated while in contact with living cells.[20][21][22] The amount of sunscreen which penetrates through the stratum corneum may or may not be large enough to cause damage. Such effects can be avoided by using newer generations of filter substances or combinations that maintain their UV protective properties even after several hours of solar exposure. 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 cataracts, pterygium,[24][25] and pinguecula formation.
UV light is absorbed by molecules known as chromophores, which are present in the eye cells and tissues. Protective eyewear is beneficial to those who are working with or those who might be exposed to ultraviolet radiation, particularly short wave UV. 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 exposed to sunlight. In addition, many pigments and dyes absorb UV and change colour, so paintings and textiles may need extra protection both from sunlight and fluorescent bulbs, two common sources of UV radiation. Ultraviolet Light Absorbers (UVAs) are molecules used in organic materials (polymers, paints, etc.) to absorb UV light to reduce the UV degradation (photo-oxidation) of a material. UV is an investigative tool at the crime scene helpful in locating and identifying bodily fluids (semen, blood, bile etc.). Some animals, including birds, reptiles, and insects such as bees, can see near-ultraviolet light. Butterflies use ultraviolet as a communication system for sex recognition and mating behavior.
Many insects use the ultraviolet wavelength emissions from celestial objects as references for flight navigation. UV lamps including newer LEDs (light emitting diode) aid in the detection of organic mineral deposits that remain on surfaces where periodic cleaning and sanitizing may not be properly accomplished. Using a catalytic reaction from titanium dioxide and UV light exposure, a strong oxidative effect occurs on any organic objects that pass through the media converting otherwise irritating pathogens, pollens, and mold spores into harmless inert byproducts. 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, gems, and in other detective work including authentication of various collectibles. In other detective work including authentication of various collectibles and art, and detecting counterfeit currency absent of marker dyes. UV fluorescent dyes are used in many applications (for example, biochemistry and forensics). Exposure to UVA light while the skin is hyper-photosensitive by taking psoralens is an effective treatment for psoriasis called PUVA.
Typical treatment regimes involve short exposure to UVB rays 3 to 5 times a week at a hospital or clinic, and up to 30 or more sessions may be required before results are noticeable. 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. Certain fungal growths under the toenail can be treated using a specific wavelength of UV delivered from a high power LED (light emitting diode) and can be safer than traditional systemic drugs.
These original EMS pages will be available until May 31, 2011 at which point you'll automatically be redirected to the new pages. We can study stars and galaxies by studying the UV light they give off - but did you know we can even study the Earth?


The researcher, of King's College London, also warned that it is not just the midday sun that is dangerous, with UVA levels still high in the morning and in the late afternoon.
However, the outer cells are renewed and replaced every four weeks or so.In contrast, UVA, which is associated with wrinkles, did more harm deeper down. The finding is particularly worrying because, unlike UVB light, UVA rarely burns the skin, leaving people unaware of the harm that is being caused. In a national survey, 24% teenagers, aged 13 to 19 years found to use a tanning facility at least once.
It is so named because the spectrum consists of electromagnetic waves with frequencies higher than those that humans identify as the color violet.
As an ionizing radiation it can cause chemical reactions, and causes many substances to glow or fluoresce. 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. The Earth's ozone layer blocks 98.7% of this UV radiation from penetrating through the atmosphere.
This opacity is due to the strong absorption of light of these wavelengths by oxygen in the air. 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. Plain glass blocks less of the visible mercury emission spectrum, making them appear light blue to the naked eye. With the addition of a suitable phosphorescent coating, they can be modified to produce a UVA, UVB, or visible light spectrum (all fluorescent tubes used for domestic and commercial lighting are mercury (Hg) UV emission bulbs at heart). Use of a mercury amalgam allows operating temperature to rise to 100 degrees Celsius and UVC emission to approx double or triple.
While some silicon detectors are used across the spectrum, and in fact the US NIST has characterized simple silicon diodes[9] that work with visible light too, many specializations are possible for different applications.
While optics can be used to remove unwanted visible light that contaminates the VUV, generally detectors can be limited by their response to non-VUV radiation and the development of "solar-blind" devices has been an important area of research.
UVA radiation has been much used in conjunction with psoralens (PUVA treatment) for psoriasis, although this treatment is less used now because the combination produces dramatic increases in skin cancer, and because treatment with UVB radiation by itself is more effective. This means the rays can easily pass through the eye lids of a human allowing them to be received by the Retina at the back of the eye.
In humans, prolonged exposure to solar UV radiation may result in acute and chronic health effects on the skin, eye, and immune system.[13] However the most deadly form - malignant melanoma - is mostly caused by the indirect DNA damage (free radicals and oxidative stress). Little attention has been given to UVC rays in the past since they are filtered out by the atmosphere. In one common damage event, adjacent thymine bases bond with each other, instead of across the "ladder". The toxic effects of UV from natural sunlight and therapeutic artificial lamps are a major concern for human health. Both UVA and UVB destroy vitamin A in skin which may cause further damage.[16] In the past, UVA was considered less harmful, but today it is known that it can contribute to skin cancer via indirect DNA damage (free radicals and reactive oxygen species). The radiation excites DNA molecules in skin cells, causing aberrant covalent bonds to form between adjacent cytosine bases, producing a dimer. The purpose of melanin is to absorb UV radiation and dissipate the energy as harmless heat, blocking the UV from damaging skin tissue. Five sunscreen ingredients have been shown to protect mice against skin tumors (see sunscreen). Despite the fact that an answer would be a key to improve formulations of sun protection products, many publications carefully avoid addressing this question.
Chromophores absorb light energy from the various wavelengths at different rates - a pattern known as absorption spectrum. 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. 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.
The problem appears as discoloration or fading, cracking and sometimes, total product disintegration if cracking has proceeded sufficiently. Sensitive polymers include thermoplastics, such as polypropylene and polyethylene as well as speciality fibres like aramids. Old and antique paintings such as watercolour paintings for example, usually need to be placed away from direct sunlight. They are contrasted with physical "blockers" of UV radiation such as titanium dioxide and zinc oxide. A phosphorescent coating on the inside of the tubes absorbs the UV and converts it to visible light. Unshielded exposure of the skin or eyes to mercury arc lamps that do not have a conversion phosphor is quite dangerous.
Other practical UV sources with more continuous emission spectra include xenon arc lamps (commonly used as sunlight simulators), deuterium arc lamps, mercury-xenon arc lamps, metal-halide arc lamps, and tungsten-halogen incandescent lamps.
Because the ozone layer blocks many UV frequencies from reaching telescopes on the surface of the Earth, most UV observations are made from space. Many fruits, flowers, and seeds stand out more strongly from the background in ultraviolet wavelengths as compared to human color vision. A local ultraviolet emissor will normally disrupt the navigation process and will eventually attract the flying insect.
They are attracted to the UV light, and are killed using an electric shock, or trapped once they come into contact with the device. UV radiation is often used in visible spectrophotometry to determine the existence of fluorescence in a given sample. Materials may look the same under visible light, but fluoresce to different degrees under ultraviolet light; or may fluoresce differently under short wave ultraviolet versus long wave ultraviolet.
Almost all of the conditions that respond to UVB light are chronic problems, so continual treatment is required to keep those problems in check.
Professor Michael Kimlin, an Australian expert in sun and health, said: 'What the researchers are saying is that we may have been looking at the wrong wavelength of light for years. Most people are aware of the effects of UV through the painful condition of sunburn, but the UV spectrum has many other effects, both beneficial and damaging, on human health.
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. In the long-wave limit of this region, roughly 150–200 nm, the principal absorber is the oxygen in air.
Pure nitrogen (less than about 10 ppm oxygen) is transparent to wavelengths in the range of about 150–200 nm.
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.
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 nanometres. However, UVA is capable of causing damage to collagen fibers and destroying vitamin A in skin. Though it remains a cheaper alternative to the fluorescent method, it is exceptionally inefficient at producing UV light (less than 0.1% of the input power) owing to the black body nature of the incandescent light source. Such LED arrays are beginning to be used for UV curing applications and are already successful in digital print applications and inerted UV curing environments.
Ultraviolet lasers have applications in industry (laser engraving), medicine (dermatology and keratectomy), secure communications and computing (optical storage). Many approaches seek to adapt visible light sensing technologies but these can suffer from unwanted response to visible light and various instabilities. Wide-gap solid state devices or vacuum devices with high cutoff photocathodes can be attractive compared to silicon diodes.


An appropriate amount of UVB (which varies according to skin color) leads to a limited amount of direct DNA damage. Gamma rays received by the retina are sent directly to a part of the brain called the Cingulate Sulcus that controls most of the muscles in the body. However, their use in equipment such as pond sterilization units may pose an exposure risk, if the lamp is switched on outside of its enclosed pond sterilization unit. The major acute effects of UV irradiation on normal human skin comprise sunburn inflammation erythema, tanning, and local or systemic immunosuppression.
When DNA polymerase comes along to replicate this strand of DNA, it reads the dimer as "AA" and not the original "CC". UVA gives a quick tan that lasts for days by oxidizing melanin that was already present and triggers the release of the melanin from melanocytes. Cantaloupe extract, rich in the compound superoxide dismutase (SOD), can be bound with gliadin to form glisodin, an orally-effective protectant against UVB radiation. In the first 20 minutes the film of sunscreen had a protective effect and the number of ROS species was smaller.
If too much UV light is absorbed, eye structures such as the cornea, the lens and the retina can be damaged. 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.
UV absorption leads to chain degradation and loss of strength at sensitive points in the chain structure. Common window glass provides some protection by absorbing some of the harmful UV, but valuable artifacts need extra shielding. UVAs can disappear over time, so monitoring of UVA levels in weathered materials is necessary.
Scorpions glow or take on a yellow to green color under UV illumination, thus assisting in the control of these arachnids. Different designs of ultraviolet light traps are also used by entomologists for collecting nocturnal insects during faunistic survey studies. Pet urine deposits in carpeting or other hard surfaces can be detected for accurate treatment and removal of mineral tracers and the odor causing bacteria that feeds on proteins within. The contaminants that pollute the indoor environment are almost entirely based upon organic or carbon-based compounds.
Many substances, such as proteins, have significant light absorption bands in the ultraviolet that are of use and interest in biochemistry and related fields. There is no link between an increase in the patient's risk for skin cancer and the proper use of UVB phototherapy. However, UV-A rays penetrate to the deeper layers of the skin and are often associated with allergic reactions, such as a rash. The simpler term "chemical rays" was adopted shortly thereafter, and it remained popular throughout the 19th century. 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. This has wide practical significance now that semiconductor manufacturing processes are using wavelengths shorter than 200 nm. 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. Incandescent UV bulbs, due to their inefficiency, may also become dangerously hot during use.
A variety of solid-state and vacuum devices have been explored for use in the different part of the UV spectrum.
These muscles then relax, which helps the the brain into a deep sleep and can often cure snoring. 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. UVB yields a tan that takes roughly 2 days to develop because it stimulates the body to produce more melanin.[citation needed] The photochemical properties of melanin make it an excellent photoprotectant.
In the US, the Food and Drug Administration is considering adding a star rating system to show UVA protection. 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. There are protective treatments available for eyeglass lenses that need it which will give better protection. Many museums place black curtains over watercolour paintings and ancient textiles, for example.
Visa stamps and stickers on passports of visitors contain large detailed seals invisible under normal light, but strongly visible 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 hospitality industries use UV lamps to inspect for unsanitary bedding to determine life cycle for mattress restoration as well as general performance of the cleaning staff.
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. 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.
Ultraviolet light can be detected by suitable photodiodes and photocathodes which can be tailored to be sensitive in different parts of the UV spectrum. Because it does not cause reddening of the skin (erythema) it cannot be measured in SPF testing.[citation needed] There is no good clinical measurement for blockage of UVA radiation, but it is important that sunscreen block both UVA and UVB. This is a mutation, which can result in cancerous growths and is known as a "classical C-T mutation". But even a treatment that completely blocks UV will not protect the eye from light that arrives around the lens.
Aramid rope must be shielded with a sheath of thermoplastic if it is to retain its strength. Since watercolours can have very low pigment levels, they need extra protection from UV light. Urine trails of rodents can be detected by pest control technicians for proper treatment of infested dwellings. A perennial news feature for many television news organizations involves an investigative reporter using a similar device to reveal unsanitary conditions in hotels, public toilets, hand rails, and such.
Short-wave ultraviolet light can destroy DNA in living microorganisms and breakdown organic material found in indoor air. Some other scientific instruments, such as circular dichroism spectrometers, are also commonly nitrogen purged and operate in this spectral region.
These lamps are used mainly for theatrical and concert displays and also become very hot during normal use. This tan occurs with a 2-day lag phase after irradiation, but it is much less harmful and is longer lasting than the one obtained from UVA.
The mutations that are caused by the direct DNA damage carry a UV signature mutation that is commonly seen in skin cancers. Currencies of various countries' banknotes have an image, as well as many multicolored fibers, that are visible only under ultraviolet light.



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