Environmental Engineering Reference
In-Depth Information
MEDICAL AND ENVIRONMENTAL EFFECTS OF UV RADIATION
B. M. SUTHERLAND
Brookhaven National Laboratory
Upton, NY, 11973, USA
1. Introduction
Organisms living on the earth are exposed to solar radiation, including its ultraviolet
(UV) components (for general reviews, the reader is referred to Smith [1] and Young et
al. [2]). UV wavelength regions present in sunlight are frequently designated as UVB
(290-320 nm) and UVA (320-400 nm). In today's solar spectrum, UVA is the principal
UV component, with UVB present at much lower levels. Ozone depletion will increase
the levels of UVB reaching the biosphere, but the levels of UVA will not be changed
significantly [3]. Because of the high efficiency of UVB in producing damage in
biological organisms in the laboratory experiments, it has sometimes been assumed that
UVA has little or no adverse biological effects. However, accumulating data [4, 5],
including action spectra (efficiency of biological damage as a function of wavelength of
radiation; see Section 5) for DNA damage in alfalfa seedlings [6], in human skin [7],
and for a variety of plant damages (Caldwell, this volume) indicate that UVA can
induce damage in DNA in higher organisms. Thus, understanding the differential effects
of UVA and UVB wavebands is essential for estimating the biological consequences of
stratospheric ozone depletion.
2. Principles of Light Absorption
Underlying all the biological effects of UV radiation is the absorption of the UV
Figure 1 . Energy level diagram showing light absorption, radiative and non-radiative emissions and
photochemical reactions.
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