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Cfcs Cause Deterioration of the Ozone Layer
The earth’s atmosphere is a blanket of air that surrounds the planet. This atmospheric air is made up of many different gases, 78% nitrogen, 21% oxygen, and 1% of a dozen or more other gases like carbon dioxide, helium, and ozone.
This atmosphere extends many miles out from the earth’s surface. However, this layer is not a uniform layer, from top to bottom. As one moves out from the planet’s surface the atmosphere becomes progressively dense. This atmosphere can be divide into four major regions.
The first region is the troposphere which extends about 6.5 miles above the planet’s surface. The troposphere contains the oxygen that we breath and is where a majority of our weather takes place.
Beyond the troposphere is the second region of the atmosphere, the stratosphere. The stratosphere extends from roughly 6.5-30 miles from the earth’s’ surface. The air on this region is much less dense than in the troposphere, and it’s a lot drier. The stratosphere is the area that contains the majority of the ozone layer.
Past the stratosphere is the mesosphere which extends to 50 miles above the planet. The last region is the thermosphere. The thermosphere’s outermost edge is roughly 600 miles above the surface of the earth. Beyond it, the airless vacuum of space begins.
Oxygen is made up of two oxygen atoms that are bonded together. In the periodic table it is represented by O2.
Like oxygen, ozone is a gas that is made up of oxygen atoms. However, a molecule of ozone is made up of three atoms of oxygen bonded together, therefore, O3, represents ozone. The ozone makes up only .01% of the atmosphere. Furthermore, 90% of the ozone is found in the stratosphere. It is concentrated in a layer between 7 and 22 miles above the earth’s surface.
The massive depth of the ozone in the stratosphere would lead you to believe that it is very thick, it is not. If it were condensed, the ozone layer would only be a few millimeters thick (Rowland and Molina 1994. p.23).
The ozone is made in the stratosphere. It is continuously being formed, broken down, and reformed, over and over again. Furthermore, the three key elements of the cycle are: oxygen, ozone, and the energy from the sun.
The ultimate source of energy for our planet is the sun. This energy travels through space in the form of Electromagnetic Radiation. Furthermore, this electromagnetic radiation is often referred to as waves and their length, therefore, wavelengths. The sun has a wide range of wavelengths. This range is known as the Electromagnetic Spectrum. In this spectrum there is Gamma, Ultraviolet, Visible, Infrared, and Radio waves.
It is the ultraviolet (UV) radiation coming from the sun that drives the ozone cycle in the stratosphere. When a oxygen molecule is hit by a high-energy UV ray, the O2 molecule absorbs the ray’s energy. As a result, the bond holding the oxygen molecule together breaks. This break separates the molecule, O2=O+O. These separate molecules quickly join with nearby oxygen molecules to form a ozone molecule, O3=O2+O. Simultaneously, ozone molecules are being hit, they absorb the ray’s energy and break apart, leaving behind an oxygen molecule and a single oxygen molecule, O3>O2-O. At this time, the entire process repeats itself making new molecules that are separated which combine to make new molecules, over and again (Rowland and Molin 1991 p. 42).
As a result of this cycle, about the same amount of ozone is produced as is broken down in the stratosphere. Therefore, the amount of ozone stays the same under normal circumstances (Rowland and Molina 1991 p.43).
A constant and stable ozone layer are important for life on earth because the high-energy UV rays that are absorbed in the ozone layer are extremely dangerous. These rays can kill some things while seriously damaging others. For example, some bacteria exposed to UV rays will die. Plants, on land and in oceans, can be seriously damaged or even destroyed by UV rays. When humans are exposed to the powerful rays, their skin can burn, damage to the eyes , and permanent changes in cells that can lead to cancer and other problems can occur. By absorbing the UV rays, the ozone molecules in the ozone layer form a shield that protects life on earth from the dangerous and even deadly UV rays. Cfcs affect this process.
Chloroflourocarbons (Cfcs) are man-made chemicals that were invented in 1928. However, they were not used on a large scale until the 1950’s. There are many different types of Cfcs, but they all contain the same basic elements: chlorine, flourine, and carbon. Furthermore, different Cfcs contain different amounts of these elements. Some of the more commonly used Cfcs are: Cfc 11, also known as R-11, Cfc 13, and Trichloroflouromethane; Cfc 12, also known as freon, R-12, Cfc 12, and Dichlorodiflouromethane; and the third common type is Cfc13, also known as R-113, CF2CICFC12, and 1,1,2 Trichlorotrifluroethane. Moreover, Cfcs are considered to be chemically unreactive, or stable.
Due to their stability, Cfcs have been used for many different tasks. For example, Cfc 12 is the most popular liquid coolants for refrigerators and air conditioners. Several other Cfcs work well as aerosol propellants, in manufacturing foam, and in making Styrofoam containers. Furthermore, others are being used for cleaning delicate electronic equipment, such as computer chips and circuit boards. Moreover, these Cfcs appeared to be the perfect industrial chemical because they were, seemingly, completely safe for people and the environment.
However, two scientists, F. Sherwood Rowland and J. Molina became curious if they were as stable high in the atmosphere as they were on earth. In 1974 they published a paper which outlines their concerns and findings on Cfcs.
In their paper, Rowland and Molina explain how Cfcs would damage the ozone layer. After evaporation, due to their stability, Rowland and Molina reasoned, the Cfcs would not combine with other molecules in the air. Therefore, they wouldn’t be involved in the natural process that removes most foreign chemicals from the lower region of the atmosphere. Instead, they would remain there for a long period of time, “50-200 years”(Rowland 1991 p. 32), gradually rising through the troposphere into the stratosphere(Rowland and Molina 1974 p.39).
In the stratosphere, Cfcs would be exposed to UV radiation. Once exposed to the UV radiation the bond that holds the chlorine containing compounds together would be broken by the rays. When a molecule of a Cfc breaks apart, chlorine atoms (CL) are released. Furthermore, individual chlorine atoms are very reactive. Rowland and Molina knew from laboratory experiments that chlorine atoms react with ozone molecules on a way that destroys the ozone. Therefore, the two hypothesized that Cfcs would indeed harm the ozone layer in the same way they affected Cfcs in experiments on earth. They warned society of the dangers, however, they were not taken seriously until the 1980s when British scientists, working at Halley Bay, using a Dobson spectrometer, discovered the whole in the ozone layer over the Anartic coast(Farman, Gardiner, and Shaklin, p.207). In 1985, the British scientists told the world about their findings, subsequently in 1995 Rowland and Molina were awarded the Nobel Peace prize. Furthermore, currently scientists are certain of the damage done by Cfcs. However, Cfcs themselves do not destroy the ozone, their decay products do.
After Cfcs reach the stratosphere and come into contact[photolyze] with UV radiation, the chlorine atoms are released. Furthermore, due to their high reactivity, the chlorine does not remain single for very long, they rapidly join nearby molecules. Since these reactions are occurring in the ozone layer, many of these nearby molecules are ozone molecules.
When a chlorine atom and a ozone molecule come together, the chlorine atom binds to one of the oxygen atoms on the ozone molecule. “As a result of the reaction, the ozone molecule is destroyed and a molecule of oxygen and chlorine monoxide (CIO) are left over”(Rowland 1989 p.71).
The ozone-destroying process does not stop there. Each one of the CIO molecules go on to react with other molecules nearby. When two CIO molecules come together, they briefly combine. This molecule breaks apart very quickly, leaving oxygen gas (O2) and chlorine atoms (CL). These chlorine atoms are now free again to destroy more ozone molecules. With the destruction of ozone molecules, comes more destructive UV rays.
The type of UV rays absorbed by the ozone layer are the same ones that are most harmful to humans; skin cancer and cataracts. Furthermore, depletion of the ozone layer results in increased UV radiation exposure.
One affect of UV on humans is skin cancer. “Most skin cancers fall into three classes: basal cell carcinomas, squamous cell carcinomas, and melanomas. In the US there were 500,000 cases of the first, 100,.000 cases of the second, and 27,000 of the third type, in 1990”(Wayne p. 47). Furthermore, cases of melanoma have been estimated to be increasing at an average of 10% from 1979 to 1993 and even larger increases are believed to be occurring in the southern hemisphere. Also, studies suggest that a 1% decrease in stratospheric ozone will result in a 2% increase of skin cancers (Wayne p.49). Moreover, some of these skin cancers can result in death. Malignant melanoma is much more dangerous, however, they are the least common. Malignant melanoma effects the pigment cell in the skin which can spread rapidly to the blood and lymphatic system. Furthermore, Wayne says, these have become increasingly frequent throughout the world, especially in areas of higher latitudes. Moreover, “there is a correlation between melanomas and exposure to UV. Melanoma incidence is correlated with latitude, with twice as many deaths (relative to state population) in Florida or Texas as in Wisconsin or Montana”(Wayne p.50). Furthermore, melanomas can take up too 20 years to develop, therefore, time will give us a better example of the effects of increased UV rays have on the skin. The eyes are also affected by UV rays.
An increase in UV rays results in an increase of UV absorption by the eye. Chronic UV exposure has been shown to be a factor in eye disease, says Roach. Moreover, “blindness from cataracts is the number one preventable cause of cataracts” (Roach p.119).
The latest findings indicate that “for every 1% decrease in ozone levels results in a .6-.8% increase in eye cataracts, or annually approximately 100,000 to 150,000 additional cases of cataract-induced blindness worldwide” (Roach p.122-3).
Moreover, UV rays cause other eye injures including photokeratitis, also known as sun blindness or snow blindness, damage to the retina, and intraocular melanoma tumors. Roach’s predictions suggest a substantial future increase in eye cancer rates. However, some, object to the effects Cfcs have on the ozone and on humans.
Two of the more common objections are: Cfcs are two heavy to reach the stratosphere and we should not be concerned about Cfcs because the majority of chlorine in the atmosphere is created by the acidification if salt spray.
However, for the first objection, atmospheric gases do not segregate by weight in the troposphere and the stratosphere. This is because vertical transport in the troposphere takes place by convection and turbulent mixing, says Wayne. Furthermore Wayne says, in the stratosphere and in the mesosphere, it takes place by “eddy diffusion”, the gradual mechanical mixing of gas by motions on smaller scales, these mechanisms due not distinguish molecular masses (Wayne Ch. 4).
As for the second objection, it is an assumption that is not correct at all. “Eighty percent of the chlorine found is from Cfcs and other man made organic chlorine compounds (Rowland 1989 p.77).
In conclusion, despite the increasing list of negative affects of UV radiation, we continue to release ozone depleting chemicals into the atmosphere. Despite the availability of safer alternatives, we continue to promote technologies that are only slightly safer than the ones they replaced. Despite all of the current information on the destructive affects of Cfcs, we still continue to use them on a mass scale.
Scientific research has only began to discover the impacts of UV radiation, however, what we do know should be enough for action. We cannot afford to sit around and wait for the damage to reach a point that makes us react, by then it will be too late.
The time to act is now because even with an immediate and complete end to production and release of ozone-depleting substances to the environment, we are still left with many decades of decreasing ozone and increased UV exposure. We must think long term and act now.
Works Cited
Farman, J.C., B.G. Gardiner, and J.D. Shankin. “Large losses of total ozone in Antartica
reveal seasonal CIOx/NOx interaction.” Nature v.230 (Aug.4,1985): p.205-215.
Roach, M. “Sun Track.” Health v.201 (May/June 1992): p.119-125.
Rowland, F.S. “Chloroflourocarbons and the depletion of stratospheric ozone.”
American Scientist v.128 (Nov. 4,1989): p. 70-78.
Rowland, F.S. and M.J. Molina. “Ozone depletion: 20 years after the alarm.” Chemical
Engineering News v.20 (Jan.11,1994): p. 20-34.
Rowland, F.S. and M.J. Molina. “Chloroflourocarbons in the environment.”
Rev.Geophys. and Space Phys. v.7 (Mar.1975): p. 13-73
Wayne, R.P. Chemistry of Atmosphere. New York: Oxford Univ.,1991.
