What Are Some Recent Findings On The Consequences And Mitigation Of Stratospheric Ozone Depletion?
Increases In UV Radiation Confirmed To Be An Important Public Health Problem One of the side-effects of depletion of the Earth's ozone layer is the increase in ultraviolet radiation (UV) reaching the Earth's surface. What then is the impact of UV radiation on skin cells? Scientists have recently discovered that the vast majority of grainy lesions that are often a precursor of skin cancer found on 1-exposed patients, had the kind of p53 gene mutations that are found in squamous cell carcinoma, a common form of skin cancer. By using animal studies, it was shown that UV radiation can act in two ways to cause the development of cancer. First, UV radiation mutates the p53 tumor-suppressing gene. Second, by stimulating cells with healthy p53 genes to kill themselves, UV radiation helps to select cells that have a greater chance of becoming cancerous. Thus, sunlight can act twice: as a tumor initiator and tumor enhancer.
Reference: Sunburn and p53 in the Onset of Cancer, Ziegler, A., A. S. Jonason, D. J. Leffell, J. A. Simon, H. W. Sharma, J. Kimmelman, L. Remington, T. Jacks, and D. E. Brash, Nature, Vol. 372, pp. 773-777, 1994.
Ice Cover In The Antarctic May Protect Phytoplankton From Adverse Impacts Of Increased Uvb It has previously been suggested that increased springtime UVB radiation caused by stratospheric ozone depletion is likely to reduce primary production and induce changes in the species composition of Antarctic marine phytoplankton. Experiments conducted in the Arctic revealed a reduction in primary productivity at present and increased levels of UVB. Laboratory studies have also shown that most plankton species under laboratory conditions are sensitive to high UVB levels, although the level at which growth or photosynthesis is inhibited is variable. Stratospheric ozone depletion, with resultant increased springtime UVB irradiance, has been occurring with increasing severity since the late 1970's. The phytoplankton community has therefore been exposed to increased levels of UVB for 20 years. Recent findings from assemblages of dead phytoplankton shells indicate that compositional changes in the diatom (phytoplankton with silicon shells) component of phytoplankton cannot be distinguished from long-term natural variability, although there is evidence of a decline in the production of some sea-ice diatoms. These results suggest that in places in the Antarctic coastal region where ice cover is thick, and the timing of the phytoplankton bloom does not coincide with increased levels of springtime UVB radiation, these phytoplankton are less affected by increased UVB radiation. These results do not suggest that increased UV is not a concern for phytoplankton outside these regions.
Reference: Minimal Effects of UVB Radiation on Antarctic Diatoms Over the Past 20 Years, McMinn, A. H. Heljnis, and D. Hodgson, Nature, Vol. 370, pp. 547-549, 1994.
Ozone Depletors And Their Substitutes Broken Down By Soil Microbes Potentially toxic by-products of ozone-destroying chlorofluorocarbons (CFCs), appear to be decomposed into harmless products by microbes found in some soils. The reactivity of the CFC alternatives has raised concerns that their degraded by-products might be harmful to the environment and life. The findings of this work indicate that certain bacteria found in some lakes and salt marsh bottoms can render some potentially dangerous CFC by-products harmless.
Reference: Degradation of Trifluoroacetate in Oxic and Anoxic Sediments, Visscher, P. T., Culbertson, C. W., and Oremland, R. S., McMinn, A., H. Heljnis, and D. Hodgson, Nature, Vol. 369, p. 729-731, 1994.
Some Fish Found To Be Especially Tolerant To Increases In Uv Radiation Certain fish are very tolerant of increased levels of UV-B radiation associated with the depletion of the ozone layer. Other fish, such as the endangered Lahontan cutthroat trout, are injured at current levels of UV-B solar radiation. Skin from UV-B tolerant fish has up to four times the amount of photo protective factor than that of sensitive species of fish. This factor may well serve as a bio-marker for susceptibility to UV-B radiation among diverse species from a variety of ecosystems.
Reference: Skin Component May Protect Fish from Ultraviolet- B Radiation, Fabacher, D. L., and E. E. Little, Environmental Science and Pollution Research, in press, 1995.
1994 Science Assessment On Ozone Depletion Published The latest science assessment on stratospheric ozone depletion prescribed under the provisions of Article 6 of the Montreal Protocol on Substances that Deplete the Ozone Layer has been published. This report, prepared under the international auspices of the World Meteorological Organization and the United Nations Environment Program, has chapters devoted to Ozone Measurement; Source Gases: Trends and Budgets; Polar Ozone; Tropical and Mid-Latitude Ozone; Tropospheric Ozone; Model Simulations of Stratospheric Ozone; Model Simulations of Global Tropospheric Ozone; Radiative Forcing and Temperature Trends; Surface UV Radiation; Methyl Bromide; Subsonic and Supersonic Aircraft Emission; Atmospheric Degradation of Halocarbon Substitutes; and Ozone Depletion Potentials, Global Warming Potentials and Future Chlorine-Bromine Loading.
Reference: Scientific Assessment of Ozone Depletion: 1994, World Meteorological Organization, Geneva, Report 37, 1995.