Causes and Effects of Stratospheric Ozone Reduction An Update (1982) / Chapter Skim
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2 INTRODUCTION
2 INTRODUCTION
Pages 37-46
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From page 37... ...
The ozone layer provides protection from W by absorbing the most harmful wavelengths. The spectrum of solar radiation reaching the surface of the earth for the current atmospheric distribution of ozone is shown schematically in Figure 2.1.
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From page 38... ...
Changes in ozone abundance resulting from the release of chlorofluorocarbons, and other human activities, would take place only over a long period of time, probably decades. It is conceivable that many living creatures with relatively fast reproductive cycles could adapt biologically to a slow increase in the average intensity of W
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From page 39... ...
A long-term commitment to research designed to answer the remaining critical questions is needed to facilitate predictions about the effects of enhanced W on biological systems. With new knowledge comes the possibility of reduced or increased concerns about ozone reduction, either from changes in understanding of the effects currently recognized or from previously unknown effects.
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From page 40... ...
0.1 en in UJ 0.01 Z J z en 0.001 > J LL 0.0001 FIGURE 2.2 The relative intensity of sunlight (solar elevation of 60°) reaching the surface of the earth for different amounts of stratospheric ozone (the normal amount is close to 3.4 atmosphere mm)
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From page 41... ...
Without data from many more locations that differ widely in the variables that might affect skin cancer incidence, it is not possible to use epidemiological data alone to determine the important variables or the action spectrum responsible for skin cancer. Thus we must draw inferences about the action spectrum for human skin cancer from animal experiments and molecular theories.
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From page 42... ...
Predictions about the effects of ozone depletion on complex biological systems, such as humans and ecosystems, can then be made from fundamental principles. THE UNDERLYING BIOLOGICAL QUESTIONS Part II of this report builds on the large amount of photobiological data accumulated in the U.S.
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From page 43... ...
If the dose-response curve were a straight line, a 10 percent change in dose would give a 10 percent increase in effect. If, on the other hand, it were curved sharply upward, as in curve _ (c)
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From page 44... ...
For example, in simple cellular systems, a given effect usually requires a higher dose at low intensities than at high intensities, presumably because during low-intensity irradiation repair processes take place and little damage accumulates (Harm 1980b)
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From page 45... ...
It is clear from descriptions given above that the specific biological effects resulting from a change in amount of ozone depends critically on the action spectra. If these curves are not known from direct experiment or cogent theory, there is no theoretical basis for making a prediction of the effects of ozone depletion.
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From page 46... ...
As will be discussed in Chapter 3, there are large synergistic effects between W -B and longer wavelengths in many simple photobiological systems. Despite the present uncertainties in understanding, there has been impressive progress in the extent of knowledge and in the delineation of the types of questions that can be answered easily.
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