The DLR-Biofilm as Personal UV Dosimeter

Abstract

In general the biological efficiency of UV radiation increases with decreasing wavelengths. This has to be taken into account by calculation if solar UV radiation is measured with physical methods. UV dosimetry with biological UV dosimeters utilize biological objects as UV sensitive targets which per se weight the incident UV radiation according to its biological effectiveness thereby integrating over the UV wavelengths and the exposure time. The wavelength sensitivity of a biological UV dosimeter is described by the so-called action spectrum. The biological UV dosimeter biofilm’ uses dry spores of the bacterium Bacillus subtilis immobilized on the surface of a plastic sheet as UV sensor. It weights the UV radiation according to its DNA damaging potential. Measurement areas on a biofilm in an exposure housing adapted to the measurement purpose are exposed to the UV source which can be the sun but also artificial UV lamps. Unexposed areas on each biofilm are used afterwards for calibration with 254 nm UV-C. The inhibition of biological activity by the biologically effective UV radiation is determined as relative optical density after development and staining of the biomass formed inside the biofilm. The biologically effective dose of each measurement area is determined with the help of the calibration curve. Now the biofilm is also adapted to its application as personal UV dosimeter. For the personal UV dosimetry different groups of persons were selected according to their UV exposures during their work or leisure activities. In measurement periods at different seasons volunteers carried a personal biofilm UV dosimeter during the whole day and made a protocol of their activities. First results of these measurement campaigns are shown.