Causes and Effects of Stratospheric Ozone Reduction An Update (1982) / Chapter Skim
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SUMMARY
SUMMARY
Pages 1-12
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According to current understanding, the most important photochemical reactions regulating ozone involve molecular and atomic oxygen and various radicals containing nitrogen, hydrogen, and chlorine. All of these compounds have natural sources, but their concentrations in the stratosphere can be significantly altered by human activities.
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Current scientific understanding, expressed in both 1and 2-dimensional models, indicates that if production of two CFCs, CF2C12 and CFC13, were to continue into the future at the rate prevalent in 1977, the steady state reduction in total global ozone, in the absence of other perturbations, could be between 5 percent and 9 percent. Comparable results from models prevalent in 1979 ranged from 15 percent to 18 percent.
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Because data on total global ozone cannot be analyzed to distinguish among causes of ozone changes, total ozone data alone cannot be relied upon for early detection of an anthropogenic change. Measurement of the spatial and
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2. The global monitoring effort should include both ground-based and satellite observations of total ozone and concentrations of ozone above 35 km, where theory indicates the largest reductions might occur.
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about the effects of inter=~ ; an c amine ~ i nays wavelengths in a broad band, such as an ~ ~ w~= ALVIN -_~ _~ ,, 7 _ in the ultraviolet of sunlight, in producing antagonistic or synergistic effects. Moreover, it has been learned only recently that rapid repair of sunlight damage to human skin takes place during irradiation.
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is probably the primary target in animal cells for most deleterious effects of UV-B, especially effects involving mutagenesis and neoplastic transformation. Other targets of possible biological significance for UV-B effects include membranes, ribonucleic acid (RNA)
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8. From limited field experiments on terrestrial plants and laboratory experiments with captured or cultured aquatic organisms, it appears that different species of both plants and animals have different sensitivities to increases in UV-B above current levels.
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Allergic contact dermatitis, skin graft rejection, tumor susceptibility, and function and viability of individual circulating and noncirculating cells of the immune system can be altered, primarily by W-B. Skin Cancer Other Than Melanoma 14.
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Epidemiological data suggest that a 2 percent increase in UV-B would give a 2 percent to 5 percent increase in basal cell skin cancers. For squamous cell skin cancers the increase would be about twice these values (4 percent to 10 percent)
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to study individuals who are exposed to high levels of UV-B as part of phototherapy for psoriasis. The aim of such experiments would be to determine whether the kinetics of dark repair of damage from pyrimidine dimers in human skin show two components, a slow one and a fast one, as is true for human cells irradiated in vitro.
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the underwater spectral irradiances are integrated over the varying positions of organisms in water columns to obtain the exposures that simulate spectral intensities in the natural systems, and (b) damage to individuals can be related to population dynamics in the natural ecosystem.
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6. Animal studies of UV-induced skin cancers other than melanoma are needed to understand interactions among parameters such as intermittent exposures, different wavelengths, dose rates, chemical carcinogens and promoters, and agents that modify cellular responses to irradiation.
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