QUANTIFICATION OF BIOLOGICAL EFFECTIVENESS OF UV RADIATION - Environmental UV Radiation: Impact on Ecosystems and Human Health and Predictive Models - page 49

QUANTIFICATION OF BIOLOGICAL EFFECTIVENESS OF UV RADIATION
G. HORNECK, P. RETTBERG, R. FACIUS AND K. SCHERER
German Aerospace Center, Institute of Aerospace Medicine, Radiation
Biology, D-51170 Cologne, Germany
1. Introduction
The problem of a progressive depletion of stratospheric ozone, particular in both
polar regions, and now identified globally outside the tropics during all seasons of the
year 1,2 , points at a potentially threat to the biosphere of an increase in solar
ultraviolet-B-radiation (UV-B: 280-315 nm) reaching the Earth's surface. There is
serious concern on the consequences of an increased UV-B radiation on human health 3 ,
on ecosystem balance 4 and on crop productivity 5,6 . To determine the implications of
increased levels of solar UV-B radiation for critical processes of our biosphere in
quantitative terms, an instrumentation for UV-measurement is required that weights the
spectral irradiance according to the biological responses under consideration.
This chapter gives a brief description of the different approaches available to
quantify the biological effectiveness of solar radiation followed by a discussion on the
biological dosimeters available and the criteria for their applicability. Then, examples
are given for the use of biological UV dosimeters in field and personal monitoring.
2. Approaches to quantify the biological effectiveness of environmental UV
Any electromagnetic radiation can be quantified using radiometric units. These
units describe the energy or power that is either emitted from a source or that arrives at a
surface. The recommended SI units concerning target incidence units are W/m² for
irradiance, i.e. flux per unit area incident on a small plane surface, and J/m² for the
exposure or dose, i.e. energy per unit area incident on one side of a small plane surface.
To determine the impact of environmental UV-radiation on critical processes of our
biosphere or on human health requires weighting of the spectral irradiance according to
the biological spectral responses under consideration, such as erythema, skin cancer,
suppression of immune functions, virus induction, ocular damage, reduced productivity
of agricultural crops, effects on ecosystem balance and/or biodiversity 7 .
Biological effectiveness spectra of environmental UV radiation
The spectrum of extraterrestrial solar UV radiation has been measured during
several space missions 8,9 (Figure 1). It contributes to the whole solar electromagnetic