The spectral irradiance and spectral transmittance of UVA radiation. (a) The spectral irradiance of a Philips HB 171/A facial tanner is indicated with a thin line. The irradiance with a glass plate filter, cutting off the UVB portion, is indicated with thick line. (b) The transmittance of three mice skins, measured ex vivo, is shown with 3 thin lines, respectively. The average transmittance is indicated by a thick line. (c) The actual spectral irradiance transmitted through mice skin (thick line) was determined by multiplying the measured spectral irradiance of Philips facial solarium (thin line) with the average transmittance (thick line in Figure 1b).