Vanishing Sky: The Ozone Layer and The Tenous Battle Against its Obliviation
The ozone layer prevents the sun's worst effect from reaching us. To prevent its descent into obscurity we must first restore our canopies
Introduction: defining the problem
There is an inherent conflict between my interests and the interests of us all. The conflict is apparent in the degradation and decay of a shared resource, such as a public park. Each person using it seeks to utilize it to the best of their advantage often not caring about its preservation, replenishment, or the kind of management uniquely required for its sustenance. The resource relies on its beneficiaries for its continued existence and sustained value. This is what Garrett Hardin spoke of in his sharp essay written in 1968. Good collective living requires the mitigation and avoidance of ‘the tragedy of commons'. This challenge isn't limited to innocent things like a public park or spaces of agrarian idealism that are not relevant to modern city life like a common pasture, but also to critical resources. There are natural systems we all irreplaceably rely on that have been under threat for quite some time. One such system is subject of this piece: the 'ozone layer'. This is a region in the stratosphere of our atmosphere located 10 to 50 kilometers from the Earth's surface and it is primarily composed of ozone ( a molecule with three oxygen atoms ). When diatomic oxygen in the upper atmosphere interacts with ultraviolet radiation from the sun, ozone is formed. It is poisonous but harmless to us since we are not in contact with it. Its depletion, however, renders us vulnerable to U.V exposure. Ultraviolet radiation causes DNA damage resulting in skin cancer ( this is a consequence of its specific damage to the structure of skin cell DNA, preventing the cell from dividing ).
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The biological effects of ultraviolet exposure: a natural consequence of ozone layer depletion
Its terrible biological effects on organisms is of two broad categories: erythemal ( visible like sunburn ) and non-erythemal ( invisible like skin cancer, skin cell-DNA damage, and suppression of the immune system ). Erythemal effects are a consequence of epidermal ( the outermost layer of the skin) absorption of U.V radiation, leading to free radical formation consequently causing cellular damage and the beginning of inflammation. If we were exposed to it for prolonged periods of time we were likely to experience the premature aging of our skin and atleast three different kinds of skin cancer: squamous cell carcinoma, basal cell carcinoma, and melanoma. The more insidious effects are, however, non-erythemal like cancer causing mutations or the increased susceptibility to infections as a result of U.V induced immune suppression. Cataract ( clouding of the eye-lens) development that subsequently leads to blindness, is also accelerated by U.V. The non-urethymal biological effects of ultraviolet radiation are less apparent but more powerfully harmful. One such effect is the immunosuppression. U.V exposure weakens the immune system, reducing its ability to fight off infections and diseases caused as a result. An increasing infection susceptibility leads to a great number of health issues of various kinds ranging from simple flu-like symptoms to more egregious and potentially fatal syndromes. Autoimmune disorders like lupus and multiple sclerosis have been associated with U.V exposure, these disorders involve the mis-targetting of the body's own healthy cells by the immune system consequently causing inflammation and tissue damage. U.V exacerbates these conditions by putting the immune system is additional stress. These are direct effects but there are indirect effects too, like heart disease and hampered reprductive health causing infertility and deformities at birth.
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Threats to ozone layer and some measures to manage them
There are minor natural threats to the ozone layer. When high-energy particles from distant space collide with ozone in the stratosphere, they disintegrate the molecule. This results in some corrosion. Also, the solar emission of ultraviolet radiation is variable. We are not very deeply interested in the above, our interest is instead in the anthropogenic causes and threats. We are here to discuss them.
Let's start with CFCs or Chlorofluorocarbons and ODSs or Ozone Depleting Substances: these chemicals are involved in many important applications, such as in refrigeration and air-conditioning and as constituents in aerosol propellants, and solvents. When they reach the ozone layer, in the presence of U.V they are broken down releasing of Bromine and Chlorine which catalytically destroy ozone. Thanks to the signing of the Montreal Protocol in 1987, products containing these compounds have diminished in human usage and their concentration in the atmosphere has also gone down. As a result, the ozone layer is exhibiting signs of recovery.
A byproduct of burning fossil fuels, fertilizer breakdown, and some industrial processes, is Nitrous Oxide (N2O). It also originates as natural emissions from soils and oceans. It interacts with U.V to produce free radicals that can destroy ozone. While not as potent as CFCs and ODSs, its greater abundance compared to them makes its removal a priority.
Methy Bromide is a soil fumigation pesticide that has ozone depleting properties. Its usage is not as widespread as before ( due to increased knowledge of the harm caused ) but still continues in some parts of the world contributing to ozone corrosion.
Finally, Halons which are fire suppressants that find applications in computer server rooms and aircraft. There ability to persist longer in the stratosphere significantly worsening their ozone depleting effects.
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These direct effects coupled with the greenhouse gas emissions changing the stratospheric circulation for the worse and increasing temperatures. Consequently, ozone distribution across the stratosphere alters, becomes more uneven and less stable. In addition, as the Earth's surface temperatures rise due to greater atmospheric concentration of green house gases, U.V absorption at lower altitudes would increase significantly leading to greater exposure and potentially all the aforementioned health problems.