Determination of erythema-effective solar radiation in Japan and Germany with a spore monolayer film optimized for the detection of UVB and UVA - results of a field campaign

The available physical and biological broadband radiometers designed to det ermine erythema-effective radiation do not show any response or over/undere stimate the biologically effective radiation to a high extent in the ultrav iolet (UV)A spectral region. The data presented in this paper demonstrate t hat the biological system used in this study is the first one to make possi ble measurements of erythema-effective radiation in the sun in the UVA and WE spectral region. These measurements were performed with a spore-film fil ter system as well as with spectroradiometers. It was demonstrated that thi s biotechnological method could be used to determine exact values expressed as minimal erythemal dose (MED). The spore-film system was tested in vario us field campaigns performed in Germany and in Japan. The seasonal daily va riation of UV radiation in Germany determined in the period November 1995 t o December 1996 using the spore-film filter system in sunny conditions tall ied well with model calculations. The daily dose in Germany measured with t he spore-film system close to the summer solstice, in sunny conditions (20. 45 MED), was approximately 20 times higher than the lowest value measured c lose to the winter solstice (0.82 MED), a result which was in accordance wi th model calculations. The data determined with the spore-film filter syste m in Sapporo and Naha, Japan, fitted to the erythema-weighted data calculat ed from spectroradiometric measurements (Brewer), even at low solar radiati on angles in a solar spectrum with less UVB but significant UVA. The spore- film dosimeter values were about 103 +/- 8% of the integrated dose of the B rewer instrument. The standard deviation of the spore-film measurements obt ained in Japan was 12.8%. The responsivity of the spore-film system towards longer wavelengths within the UVA spectrum was tested with the Okasaki Lar ge Spectrograph with monochromatic radiation. At a wavelength of 365 nm - i n a spectral region which is dominant in many tanning lamps and with minor importance for solar radiation in summer conditions - the tested spore-film system gave results that were close (112% compared to the calibration dose ) to the calibration dose which was used for irradiation.