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Evaluation of
UV-induced tan vs. time - considerations for development of exposure
schedules
Miller, Sharon1,
Lao, Nelson1, Zmudzka, Barbara1
and Beer, Janusz1
Food and Drug Administration, Rockville, MD1
Abstract-
The FDA Performance Standard for sunlamp products and the International
Electrotechnical Commission (IEC) standard for UV-emitting appliances
are currently under revision. An important element of these standards
is the recommended exposure schedule that is to be provided by the sunlamp
manufacturer to the user. The current FDA standard recommends exposures
at 48-hr intervals with doses that correspond to up to 4 minimal erythema
doses (MED). Since this schedule was published (1986), there have been
a few reports that the desired effect can be produced with less frequent
and possibly lower exposures. This view is supported by data from our
current study on the effects of UV on human skin of different racial/ethnic
origins. We evaluated the color of the skin both visually and instrumentally.
Instrumental measurements are particularly useful for erythema evaluation
in dark skin and for exploring the dynamics of erythema/melanin production.
Measurements with both the Diastron Erythema/Melanin Meter and the Minolta
CM-2002 spectrophotometer provide comparable quantitative information
regarding the dose dependence and time course of changes in skin color.
However, the Minolta instrument measures diffuse reflectance at 10-nm
intervals, which allows for more complex analysis of the skin color.
Our data confirm that the development of a tan requires approximately
one week. UV doses needed to produce a tan depend on UV sensitivity
(MED). However, the ratio of minimal tanning dose to minimal erythema
dose (MTD/MED) varies with UV sensitivity. This ratio may be >1 for
sensitive skin and <1 for resistant skin. The return to baseline skin
color occurs more rapidly in those individuals with higher UV sensitivity.
These observations indicate that quantification of the production and
the persistence of UV-induced tan is necessary for determining the optimum
exposure schedules for individuals of varying UV sensitivity.
Keywords: tanning,
exposure schedules, sunlamps
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