title: [Environmental UV radiation levels for dosing PUVA-sol in 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/cm(2) and the highest 25.4 mW/cm(2) (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), (r(2) = 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.
authors.affiliation: Hospital Central "Dr. Ignacio Morones Prieto" y Universidad Autónoma de San Luis Potosí, San Luis Potosí, México. castanju@yahoo.com.
authors.forename: Juan Pablo
authors.initials: JP
authors.lastname: Castanedo-Cázares
authors.forename: Bertha
authors.initials: B
authors.lastname: Torres-Álvarez
authors.forename: Adriana
authors.initials: A
authors.lastname: Ehnis-Pérez
authors.forename: Isaura
authors.initials: I
authors.lastname: Alba-Barba
mesh_terms: D004777:Environment; D006801:Humans; D008800:Mexico; D011701:PUVA Therapy; D011829:Radiation Dosage; D011874:Radiometry; D013472:Sunlight; D014466:Ultraviolet Rays
keywords: Mexico; PUVA therapy; phototherapy; psoralens; radiation; ultraviolet rays