QUANTIFICATION OF THE BIOLOGICAL EFFECTIVENESS OF ENVIRONMENTAL UV-RADIATION

To determine the impact of environmental UV radiation on the critical processes of our biosphere demands accurate and reliable monitoring sy stems that weight the spectral irradiance according to the biological responses under consideration. The need for a biological weighting of solar UV irradiance derives from the highly wavelength-specific absorp tion characteristics of atmospheric ozone and the wavelength specifici ty of the biological action spectra in the UVB range. The degree to wh ich the biological effectiveness of solar UV radiation increases with stratospheric ozone depletion is determined by the shape of the action spectrum of the biological phenomenon under consideration. In princip le, three different approaches for quantifying biologically effective solar irradiance are available: (1) weighted spectroradiometry where t he biologically weighted radiometric quantities are derived from spect ral data by multiplication with an action spectrum of a relevant photo biological reaction, e.g. erythema formation, DNA damage, skin cancer or reduced productivity of terrestrial plants and aquatic ecosystems; (2) wavelength-integrating chemical or physical dosimetric systems wit h spectral sensitivities similar to a biological response curve; (3) b iological dosimeters that weight directly the incident UV components o f sunlight in relation to the effectiveness of the different wavelengt hs and the interactions between them. In most cases, simple biological dosimeters are applied, such as bacteria, bacteriophages or biomolecu les. Induction rates for lethality, mutagenesis or photoproduct format ion are used, which reflect directly the UV sensitivity of DNA. Biolog ical dosimeters are potentially reliable field dosimeters for measurin g the integrated biologically effective irradiance for key targets, pr ovided that a direct intercalibration with spectroradiometric-based me asurements is applied.