Environmental UV radiation levels for dosing PUVA-sol in Mexico
Main Article Content
Keywords
Phototherapy, PUVA therapy, Furocoumarins, Ultraviolet rays, Radiation, Mexico
Abstract
Background: PUVA-sol therapy has the advantage of its extensive availability and low cost. However, its use is empirical. The aim was to quantify the environmental UVA radiation and suggest a method for PUVA-sol administration.
Methods: we measured the UV radiation in the center of México (22 °N, 101 °W, 1877 m) by means of terrestrial radiometry from 2007 to 2011. We registered the variations according to hour, month, cloudiness and transmission through domestic silicate plates.
Results: more than 75 % of the UVA radiation is registered between the hours of 9:00 and 17:00. The annual lowest average intensity was 20 mW/cm2 and the highest 25.4 mW/cm2 (ANOVA, p < 0.001). The monthly UVA irradiation during the zenith for clear skies can be estimated by the following formula: 23.8 + 0.13 (month) – 0.13 (month – 6.5)2, (r2 = 0.95, p < 0.001). The commonly used silicate plate (3 mm) has a UVB absorbance of 0.93, and UVA transmittance of 0.58.
Conclusions: the rational use of PUVA-sol is possible on the basis of the obtained data. It is necessary to isolate UVB radiation, and to adjust exposure during cloudy days, as well as following the safety protocol to obtain benefit and to reduce the risk of adverse effects.
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