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What is ultraviolet radiation (UV)?

The electromagnetic spectrum ranges from cosmic rays at one end, to radio waves at the other end. The ultraviolet (UV) region of the electromagnetic spectrum is situated between visible light and x-rays, with the wavelengths of the UV A radiation being shorter and more energetic than violet visible light and the wavelengths of vacuum UV radiation being slightly longer and less energetic than x-rays. The full UV radiation spectrum ranges from wavelengths of about 100 nanometers (nm) to 400 nanometers and the UV radiation spectrum is usually divided into 4 sections; vacuum UV radiation (also called far or very UV, from 100 nm to about 200 nm), UV C radiation (also called germicide or short-wave UV, from 200 to about 280 nm), UV B radiation (also called mid-wave or medium-wave UV, from 280 nm to about 320 nm), and UV A radiation (also called  poster lamp  , black-light, or long-wave UV, from 320 nm to 400 nm). Some sources (such as the US FDA), define the range of UB V as being from 260 nm to 320 nm, and other sources give the upper range only as high as 315 nm. In the figure below, the disputed region of the UV B (midwave) is in a shaded color.

Where does UV radiation come from and what is it used for?

In addition to sunlight, UV radiation can be emitted from a variety of sources such as light emitting diodes (LED s), lasers, electric arcs (especially as in arc welding), xenon bulbs, halogen bulbs, excimer bulbs, and mercury vapor lamps/tubes of low, medium and high pressures. UV C radiation is used extensively for sterilization, purifying, and deodorizing applications in food, air, water, and general surface sterilization processes because the UV C radiation not only deactivates micro-organisms such as: bacteria, molds, spores, fungi, and viruses (by direct irradiation which damages the DNA such that the micro-organisms cannot reproduce), but the UV C radiation also breaks down the chemical bonds of alcohols, pesticides, chloramines, and other contaminants such as NDMA or MTBE. UV B radiation is the agent that causes human skin to  sun-burn  and the UV B radiation is needed to start the suntanning process. The lamps/tubes used in suntanning booths usually emit a combination of UV B and UV A. UV B is also used extensively in various medical treatments  especially for skin diseases. UV A radiation is used for special effect lighting, suntanning, photo-lithotropy, and photo-chemistry.

Are Ultraviolet lamps dangerous?

Yes, there are several SAFETY CONCERNS about UV lamp fixtures to be considered when using the any UV lamp fixture. You must make sure that it is NEVER pointed at anyone including pets. A "sunburn" can occur to eyes or skin.

You should ALWAYS wear UV blocking safety glasses when looking at, or when collecting fluorescent minerals. We carry very inexpensive yet effective UV blocking glasses. (You can but them directly from harbor freight for $2.99). You can check to see that your glasses do block the UV, by putting the glasses close to a fluorescent rock and pointing the UV lamp toward the rock. The portion of the rock directly below the glasses will remain dark while the rest of the rock fluoresces. It is also a good idea to cover skin that is exposed to the UV and always wear sun block even under clothing as some fabrics can be penetrated by UV much like sun exposure.

For use in display cases,  I use UV blocking Plexiglas or UV blocking Lexan to make the "window" to be able to look in the display case while at the same time protecting people from the UV. You should always have a UV blocking transparent material for all cases.

How does UV radiation create a sun tan?

(Excerpted from US Patent 4967090)  Skin pigmentation and thickening of the upper layer of the skin called the corneum are the body's natural protective reactions to exposure to & .ultraviolet energy produced by the sun; these reactions are the skin's defense against further assault. Skin pigmentation, or tanning, is the result of a complex biological process, and to understand it, one most understand the skin's response to different wavelengths of ultraviolet radiation.

Deep down in the skin are special cells called melanocytes. Once these are stimulated with ultraviolet light, they will utilize substances which they have stored up to produce the pigment melanin. Because these substances only absorb & & .(UV B) ultraviolet light, these UV B rays must be present in order to achieve melanin production. Longer wavelength ultraviolet (UV A) can also formulate melanin but only when there exists enough sensitizing material in the skin to bring about a UV B-type reaction. However, this requires a very high radiation UV A intensity for a long period of time. On the other hand, UV B can induce the same desired melanin production utilizing very low levels of radiation with more frequent exposures. The pale pink colored melanin granules formed in the melanocytes will travel upward toward the horny layer or corneum. They are stored around the nuclei of the keratin cells there. In this manner, the pigment protects the UV B sensitive DNA located inside the nuclei without impeding the other positive effects of ultraviolet light.

In the preliminary stages of melanin production, very little protection is offered to the skin. In order to render the pigmentation process effective, the melanin granules must darken (oxidize). This requires a higher dosage of longer wave UV A. The dosage of UV A must be sufficiently high in order to provide enough energy to initiate the oxidation process. It must be remembered that UV A rays are not as energetic as UV B rays. Long-wave radiation is essential because high doses of short[er]-wave rays will activate substances in the body such as absorbic acid and cysteine which hinder the tanning process. These antioxidants not only inhibit oxidation of pigment but can even reverse the process.

Thus, UV B serves to synthesize the pigment granules while UV A ensure their oxidation. Together they form a light protection mechanism. UV B is also essential in developing the skin callosity in the horny layer or corneum. This light-induced thickening stabilizes the skin to guarantee protection from excessive radiation. After the skin has been exposed several times, this callosity will develop within one to three weeks and can remain for several months.

Most tanning lamps produce a spectrum of ultraviolet light which is similar to that of the sun. Most lamps provide the small amount of UV B necessary to initiate the tanning process while at the same time, providing the UVA needed to darken the pigment (melanin). Ultraviolet tanning lamps and tanning equipment used in the United States must comply with very specific regulations which are enforced by an agency of the Food and Drug Administration. These regulations restrict certain ultraviolet lamp characteristics and require extensive labeling of lamps and suntan equipment. The U.S. FDA defines UV A as the region of 320 nanometers (nm)-400 nm and UVB as the region of 260 nm -320 nm.

In the design of sun-tanning equipment and UV sources it is necessary to consider that tanning ability and tanning characteristics vary from one individual to another. In this regard there are two main factors which should be considered: 1. Skin Type this refers to the (genetic) capability of an individual to produce and maintain a pigmentation in the skin. It is determined by the histologic response of the skin to ultraviolet radiation and classified by the observable effects. 2. Present Skin Pigmentation - this refers to the relative pigmentation level of the skin at the time just prior to UV exposure. Previously well-tanned skin, exhibiting a high level of pigmentation is generally more resistant to erythema (sunburn) and hence may tolerate higher levels of UV B before the onset of Minimum Perceptible Erythema (MPE). Increased UV B will elicit, however, an increased melonogenic effect ultimately leading to a darker appearing skin. Previously, un-tanned skin will be more susceptible to UV B induced erythema and therefore UV B levels should be minimized in the early portion of an indoor tanning program.

Because of the factors mentioned above it is necessary in a commercial indoor tanning application or in the consumer tanning products marketplace to offer sunlamp products which are appropriate to the range of "tannable" skin types and skin conditions. This means that sunlamp product manufacturers, to be fully competitive, must offer products which produce the radiative characteristics necessary for safe and effective tanning of a range of skin types and conditions.

To this end many manufacturers offer a variety of ultraviolet sources which when used in conjunction with their tanning equipment give the desired ranges of UV A and UV B appropriate for the person(s) undergoing the tanning process. To cover the range of ultraviolet lamps to meet the needs of the market, equipment manufacturers and distributors generally make available three separate groups of lamps having the following characteristics:

1. Lamps with a relatively low proportion of UV B radiation approximately 1% UV B/UV A and lower,

2. Lamps with an intermediate proportion of UV B; approximately 1.0-3.0% UV B/UV A, and

3. Lamps with a relatively high proportion of UV B; 3% and above, usually to 5% maximum.

In all cases, UV A is defined [by the US FDA] as the region of 320 nm -400 nm, [and ] UV B is defined as the region of 260 nm-320 nm. 

How does a sun-tanning lamp differ from one used to make rocks and minerals fluoresce?

The tubes/lamps/bulbs used for rock collecting usually have a relatively narrow band of UV emission and they do not generally use blends of phosphors as the sun tanning lamps do.