Relative Energy Requirements for an Erythemal Response of Skin to Monochromatic Wave Lengths of Ultraviolet Present in the Solar Spectrum**From the Departments of Dermatology and Pathology, Baylor University College of Medicine, Houston, Texas.
1966; Elsevier BV; Volume: 47; Issue: 6 Linguagem: Inglês
10.1038/jid.1966.189
ISSN1523-1747
AutoresRobert G. Freeman, Donald W. Owens, John M. Knox, H.T. Hudson,
Tópico(s)Skin Protection and Aging
ResumoThe production of erythema has been the endpoint most often used to evaluate the biological effects of ultraviolet. Finsen first demonstrated that erythema was caused by ultraviolet (1). The specific wavelengths responsible were studied, and an erythema action curve was derived by Hausser and Vahle (2, 3). This curve is widely accepted as standard (4, 5) and is characterized by having the greatest erythemal effectiveness at 297 m/x, rapid loss of effectiveness at 310 and 280 m/x, and a second maximum at 250 m/x (Fig. 1). Data supporting this curve were reported by Coblentz and Stair (6), Hauser (7), and Luckiesh, Holladay and Taylor (8).Blum and Terus (9), Magnus (10), and Rottier (11) have presented quantitative data on energy requirements for erythema production by different parts of the spectrum. In each instance less energy was required at shorter wavelengths of 250-260 mit than at longer wavelengths. Both Rottier and Magnus observed erythema at 280 m/x with doses comparable to those effective at adjacent wavelengths. In 1965 Everett, Olsen and Sayre (12), using a xenon arc grating monochromator, found that, in contrast to the “standard,” 250 m/x was the most effective wavelengths and that 280 m/x was just as effective as adjacent wavelengths. They stated that their results agreed with other quantitative data on erythema energy (Fig. 2).Knowledge of energy requirements for producing erythema at different wavelengths is essential to further understanding of light injury. Since sunlight is the major source of light injury in man, greatest interest is in the ery-thema-producing ability of the sun's rays at the earth's surface, those longer than 290 m/x in wavelength.Using a high intensity xenon arc grating monochromator, we have extended previous observations on erythema production and have compared these energy requirements with the available data on solar radiation intensity. In this way the erythemal effectiveness of ultraviolet in sunlight has been determined for human skin and for albino rabbit skin.METHODSSkin of the lower abdomen of human subjects and of albino rabbits was exposed to serially increasing amounts of ultraviolet emitted from a high pressure xenon arc grating monochromator. The minimal erythemal dose (M.E.D.), the smallest amount of energy that would produce a barely perceptible erythema within 24 hours, was determined. The human volunteers were adult males who did not have known photosensitivity and who had lightly pigmented skin on the lower abdomen which had not been recently exposed to sunlight nor altered by skin disease. Male and female adult albino rabbits were depilated* 24 hours before being irradiated while under barbital anesthesia. The irradiated sites were examined for erythema at 24 hours. Sites exposed to shorter wavelengths were examined at 8 and 24 hours, according to the data of Everett (13).The energy values required to produce erythema were determined on human and albino rabbit skin for wavelengths between 220 and 330 m t at intervals of 10 m/t. At least 100 determinations were made at each point between 250 and 318 mfi. Fewer endpoints were obtained above and below these points because of the inefficiency of these wavelengths and the time required to find an endpoint. These energy values are represented in Figures 3 and 4 by the mean values and 1 standard deviation. In order to fix more precisely the erythema-producing capabilities of the wavelengths in sunlight (above 290 m/0 the M.E.D. was determined at 2 mfi intervals from 290-320 mu in both humans and albino rabbits.The M.E.D. was not significantly altered when infra-red energy was applied immediately before* Surgex depilatory, Crookes-Barnes Laboratories, Inc., Wayne, N. J.586REQUIREMENTS FOR AN ERYTHEMAL RESPONSE 587or after ultraviolet exposure. A G.E. 250-watt infra-red lamp was used 12 inches from the skin surface for a time sufficient to produce a 10°F. rise in skin temperature.Monochromatic Light SourceThe light source used in these experiments is a high pressure xenon arc grating monochromator consisting of three Bausch&Lomb monochromator units with their outputs superimposed on a test site 1.1 cm in diameter (14). In each monochromator a 150-watt xenon arc light source is housed in a standard housing attached to a Bausch&Lomb diffraction grating. The output of one of the monochromators passes directly to the test site while the other two monochromators are perpendicularly arranged, their output being focused by convex lenses and reflected onto the test site by right angle mirrors. Where appropriate in these experiments, a filter is inserted in the beam to reduce scatter radiation and second-order effects.A reflective prism which serves as a shutter mechanism is lowered during exposure by an electronically-controlled solenoid so that the beamstandard” curve for erythemal effectivenessERYTHEMA ACTION SPECTUM (Everett, Olson, and Sayre )250 260300 310 mu280 290 WAVELENGTH Fig. 1. “Standard” curve for erythemal effective-270 280 WAVELENGTH300 310 mjjness.Fig. 2. Erythema action spectrum (Everett, Olsen and Sayre).impinges directly on the test site. Between exposures the prism covers the test site and diverts the beam into a detector connected to a Bausch&Lomb laboratory recorder. The total energy output of all three units and the duration of exposure is permanently recorded.When the entrance and exit slits are set to provide a 50 Â bandwidth at V -power output, the intensity of output in the ultraviolet and visible ranges approximates twice that of the sun outside the earth's atmosphere. Specifically, at 300 m//. and 50 Â bandwidth the calibrated output is 0.66 nw/cm2 of the dial setting. An erythema can be produced in human skin with 4-6 seconds of exposure to effective wavelengths.RESULTSThe major erythema-producing capability of ultraviolet was found in the range of 250-310 m/x, (Figs. 3, 4). Much more energy was required above and below this range to produce erythema. The least energy was required at 260588THE JOURNAL OF INVESTIGATIVE DERMATOLOGYENERGY VALUES FOR MINIMAL ERYTHEMA DOSE (HUMAN) ( mean values and I std. dev. )M.E.D. mW- sec.10220 240 260300 320Fig. 3. Energy values for erythema production on human abdominal skin.m/x for man and at 250 m/x for rabbits. Somewhat more energy was required at 280 m/x than at 260 and 290 m/x, but not to the extent indicated by the “standard” erythema curve.Energy requirements rapidly increased for wavelengths longer than 300 m/x. It took approximately ten times as much energy to produce erythema at 310 m/x than at 300 and 100 times as much energy to produce erythema at 320 m/x than at 300. Erythema did not occur at 330 m/x even with massive amounts of energy (over 10,000 mW. sec/cm2 I-O LJ b_ U. UJLJ >-I UJceo.o J220 240 260 280 300 320 X
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