QUANTIFICATION OF BIOLOGICAL EFFECTIVENESS OF UV RADIATION - Environmental UV Radiation: Impact on Ecosystems and Human Health and Predictive Models - page 61

spectra for biologically adverse effects of sunlight decrease with increasing wavelength in the

UV-B and UV-A range, the rate of decline may vary considerably. Even when
considering the same endpoint, they may be different for different species or even
strains 23,42,59 . This phenomenon reflects the complex interplay of a variety of cellular
mechanisms for processing UV-induced damage.
Radiometric criteria . Besides the photobiological criteria, the general
requirements on radiometric systems should be met in biological dosimetry. These latter
criteria concern the reproducibility (standardized procedure, genetically defined
homogenous material, robust against unspecific environmental stress parameters, long
shelf life), the optical properties (identification curve, linearity of response, dynamic
range, dose rate effect, action spectra using both, mono- and polychromatic radiation,
additivity, dependence of response on temperature, relative humidity and angle of
incidence). Furthermore the agreement of predicted with observed spectral responses
(intercalibration with biologically weighted spectroradiometric data) should be verified.
For applications as field or personal dosimeters the availability, suitability for routine
measurements, easy handling, automatic registration, if possible, and low costs are
important requirements.

Applications of biological UV dosimeters

Long-term trends of biologically effective solar radiation . Daily and annual
profiles of biologically effective environmental UV radiation have been obtained using
the T7 dosimeter 46,47,70 , the spore dosimeter 35,50,64 , and the biofilm dosimeter 46,58,65 .
Using the spore dosimeter, Munakata showed in a 14 years study a trend of increase of
the BED of solar UV radiation in Tokyo from 1980 to 1993 35 . Using the biofilm
dosimeter in a more than 1 year lasting UV-monitoring campaign in Antarctica,
Quintern et al. provided experimental proof of an enhanced level of biologically
effective UV-B radiation during periods of stratospheric ozone depletion 58 . Figure 7
shows the annual profile of daily H eff values separately for the UV-B and UV-A range,
that were recorded at the Georg von Neumayer Station (70.4°S 80.3°W). Cut-off filters
were used, to separate the effects at different UV ranges. After the polar night, when
stratospheric ozone destruction led to values down to 150 DU, the BED for the UV-B
range was elevated to values as high as those that were measured later on in mid
summer. Figure 7 demonstrates that the enhancement in the UV-B dose coincided with
the so-called ozone hole.
Contribution of UV-B and UV-A to the biologically effective dose H eff . In order to
monitor the biological effectiveness of distinct wavebands of the solar spectrum, cut off
filters that largely remove the UV-B range of the solar spectrum have been used in
biological dosimetry. Using the E. coli biodosimeter, Karentz and Lutze for the first
time provided experimental proof of an enhanced UV-B/UV-A ratio during periods of
reduced stratospheric ozone concentrations over Antarctica in 1988 39 . During periods of
depleted stratospheric ozone the ratio UV-B/UV-A increased by a factor up to 10, from
0.3-0.4 to 2.5-3.4. This observation was subsequently confirmed with the spore
dosimeter for the ozone depletion period in 1990 57 and with the biofilm for the