Guangzhou Merican Optoelectronic Technology Co., Ltd
UVB (from the sun or in a low pressure indoor tanning unit) stimulates the melanocytes in the upper skin layer (called the epidermis) which then produce melanin. The pale pink melanin granules formed in the melanocytes are stored around the core of the keratin cells. In this manner the pigment granula protects the sensitive DNA located inside the nuclei without impeding the other parts of the cell receiving ultraviolet light. UVA then darkens the melanin, thereby giving the skin a dark appearance. A tan gradually fades as the skin cells migrate to the surface.
Both the sun and low pressure indoor tanning equipment emit UVA and UVB, a combination of ultraviolet light which most efficiently produces pigmentation and darkening in the skin. The most prominent difference in exposure is the times in which the tanning process takes place and also the external factors existing in outside sunlight. Some examples include the time of year and day, altitude, cloud coverage, pollutants, proximity to the equator, reflective surface, etc. Indoor tanning is in a controlled environment while outdoor tanning is in an uncontrolled environment.
The “tan,” or pigmentation process, occurs in the epidermis, the top skin layer. The epidermis replaces all its skin cells every 28-30 days. Cells in the inner portion of the top skin layer divide themselves, migrate to the surface, gradu- ally die and slough off. Skin cells contain melanin, and as a result of UV exposure, rise to the surface and flake off.
Therefore, a tan can be maintained only by repeated exposure to UV light.
The exposure schedule imprinted on a unit or found in the unit’s user information booklet indicates the appropriate length of a tanning session for each skin type. It is derived as a result of testing performed on a unit equipped with a certain UV lamp product.
Testing is generally performed at an independent laboratory at the manufacturer’s request. The Food and Drug Administration requires such testing before a unit can be marketed in the United States.
An exposure schedule is based on a person’s Minimal Erythemal Dose. A MED is the least amount of UV exposure a person can receive and generate pigmentation while avoiding sunburn. Taking into account the spectral out- put of the bed and the tanning capabilities of a particular user, the dosage (in terms of length of session) is calculated and translated into the exposure schedules which comes with all indoor tanning equipment. Most exposure schedules reflect graduated exposure times: exposure starts slowly and increases carefully.
Since 1986, the Food and Drug Administration guidelines suggest that a 48 hour time interval should pass between tanning sessions. Pigmentation and/or erythema (sunburn) may not be fully visible for between 12-24 hours. Thus two tanning sessions within this 24 hour period could cause an unintentional burn. In general, maximum pigmentation can be built up gradually, following the exposure schedule, in 8-10 tanning sessions.
It is difficult to make a simple comparison between the sun and modern indoor tanning equipment. Just as vari- ous kinds of indoor tanning lamps and equipment differ in spectral output and energy emitted, the sun’s strength is dependent on several factors as well, such as the time of day or year, the latitude, cloud cover, pollution and reflection. Consequently, there is no formula for relating
indoor tanning exposure times to outdoor exposure times.
UVB irradiance is greatest between 10:00 am and 2:00 pm.
UVA continues throughout the day and can exceed that of UVB by 10 to 1,000 fold. In the northern hemisphere, UVB is most intense in summer months, but UVA is more consistent throughout the year.
The increased use of chlorofluorocarbons has resulted in a depletion of the ozone layer. A very thin level of ozone surrounds the earth and serves to filter a certain amount of UV light, particularly the shorter wavelengths.
Ozone depletion is the subject of some controversy, but it undoubtedly has a serious impact on the earth.
Moreover, some researchers have suggested that plant, animal and human life are well conditioned to adapt to new environmental circumstances. Still, should the trend continue, it could have ramifications for all forms of life. Without the filtering of UV light we will be exposed to more of the shorter wavelengths. Even though indoor tanning can help gradually build pigmentation (the body’s own way of avoiding excessive exposure to UV light), one should be aware of how much exposure is proper, and
take particular care when outdoors.
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