ABSTRACT
The natural thickness of the ozone layer varies substantially. Ultraviolet (UV) radiation is known to be biologically damaging at sufficiently high doses, but it is apparently fairly well-tolerated at current solar irradiance levels. For assessment purposes, the value of interest is not the biologically effective irradiance, but the biologically effective dose. Lesions of the types shown if unrepaired or misrepaired can interfere with DNA replication, can delay cell division and thus growth, can lead to changes in the sequence of nucleotide bases thereby causing a mutation, and can kill cells. As protection against the solar UV-B radiation to which exposed organisms are subjected, there are a variety of organismal screening agents. Perturbations of non-agricultural ecosystems could ultimately be as important as more direct effects on human health or human food supplies, but there is almost no information with which to assess the consequences of increased solar UV-B radiation on such ecosystems.
