INTRODUCTION
Donna: What is the environment?
Martha: The environment is the earth, and you have to help the earth. Oh, and it�s the ozone layer.
Donna: And what is the ozone layer?
Martha: (shrugs her shoulders in a gesture of uncertainty) I think the ozone layer�s like the top of the air where we are right now and then the rest is empty of the ozone layer. I think it�s supposed to protect where we are right now from polluting and trash and stuff.
Donna: Where did you hear about the ozone layer?
Martha: Mostly on TV�.The news channels mostly�.Sometimes I want to see what there is, what I should wear, but they go into the ozone layer and stuff, and I watch that until they say what the weather�s going to be like. (King, 78)
In the book, Doing their Share to Save the Planet, author Donna Lee King interviewed numerous children to ask their opinions about environmental issues. The conversation above exhibits the innocence and naiveté of a young child, who will eventually inherit mother earth, in regards to the ozone layer. Although the adult reader may chuckle at this young girl�s lack of knowledge, the average adult is virtually as uneducated. With such a life affecting issue as the ozone layer, it is essential that society be well informed about the danger ozone depletion poses to earth.
There are many issues one must explore when educating himself/herself about the ozone layer. The goal of this paper is to provide the layman with a general knowledge of important components of ozone education. First, a general overview will be provided. Next, the reader will learn scientific aspects of the ozone layer such as factors responsible for ozone depletion, and then he/she will explore the ozone hole over Antarctica. To continue, societal aspects that will be addressed include health risks, crop/plant damage, and organism damage. Finally, actions that government has taken to attempt to solve the problem will be discussed. The paper will conclude with a discussion of the importance of ozone education.
SCIENTIFIC ASPECTS
The ozone layer: What is it?
The ozone layer is a portion of earth�s atmosphere that contains high levels of ozone. The atmosphere is divided into five layers: the troposphere, the stratosphere, the mesosphere, the thermosphere, and the exosphere. The troposphere is the layer closest to earth and is where all weather happenings occur. The stratosphere is located directly above the troposphere, about 10-50 kilometers above the planet, and houses the ozone layer at an altitude of 20-30 kilometers. The mesosphere is located approximately 50-80 kilometers above the earth, while the thermosphere rests at an altitude of approximately 100-200 kilometers above the earth�s surface. Finally, the boundary of the outermost layer, the exosphere, extends roughly to 960-1000 kilometers above the earth. For a visual of the lowermost three layers of our atmosphere, refer to Figure 1 below.
The ozone found in our atmosphere is formed by an interaction between oxygen molecules (composed of two oxygen atoms) and ultraviolet light. When ultraviolet light hits these oxygen molecules, the reaction causes the molecules to break apart into single atoms of oxygen (UV light + O2 --> O + O). These single atoms of oxygen are very reactive, and a single atom combines with a molecule of oxygen to form ozone (O3), which is composed of three atoms of oxygen (2O + 2O2 --> 2O3).
The ozone layer is essential for human life. It is able to absorb much harmful ultraviolet radiation, preventing penetration to the earth�s surface. Ultraviolet radiation (UV) is defined as radiation with wavelengths between 290-320 nanometers, which are harmful to life because this radiation can enter cells and destroy the deoxyribonucleic acid (DNA) of many life forms on planet earth. In a sense, the ozone layer can be thought of as a �UV filter� or our planet�s �built in sunscreen� (Geocities.com, 1998). Without the ozone layer, UV radiation would not be filtered as it reached the surface of the earth. If this happened, �cancer would break out and all of the living civilizations, and all species on earth would be in jeopardy� (Geocities.com, 1998). Thus, the ozone layer essentially allows life, as we know it, to exist.
In order for scientists to evaluate how much ozone is in the layer, a unit of measurement called the Dobson Unit is employed. A Dobson Unit is a measurement of how thick a specific portion of the ozone layer would be if it were compressed into a single layer at zero degrees Celsius with one unit of atmospheric pressure acting on it (standard temperature and pressure - STP). Thus, one Dobson Unit (DU) is defined as .01 mm thickness at standard temperature and pressure. Figure 2 shows a column of air over Labrador, Canada. Since the ozone layer over this area would form a 3 mm thick slab, the measurement of the ozone over Labrador is 300 DU.
Ozone depletion: Who is responsible?
It is important to recognize the sources of ozone depletion before one can fully understand the problem. There are three main contributors to the ozone problem: human activity, natural sources, and volcanic eruptions (See Figure 3).
Natural sources also contribute to the depletion of the ozone layer, but not nearly as much as human activity. Natural sources can be blamed for approximately 15 to 20 percent of ozone damage. A common natural source of ozone damage is naturally occurring chlorine. Naturally occurring chlorine, like the chlorine released from the reaction between a CFC molecule and UV radiation, also has detrimental effects and poses danger to the earth.
Finally, volcanic eruptions are a small contributor to ozone damage, accounting for one to five percent. During large volcanic eruptions, chlorine, as a component of hydrochloric acid (HCl), is released directly into the stratosphere, along with sulfur dioxide. In this case, sulfur dioxide is more harmful than chlorine because it is converted into sulfuric acid aerosols. These aerosols accelerate damaging chemical reactions, which cause chlorine to destroy ozone.
The ozone hole: Why over Antarctica?
When the topic of the ozone layer arises, many people immediately think of the hole over Antarctica, but few know why the hole is actually there. In 1985, British scientists discovered this hole. A special condition exists in Antarctica that accelerates the depletion of the ozone layer. Every Arctic winter, a polar vortex forms over Antarctica. A polar vortex is �a swirling mass of very cold, stagnant air surrounded by strong westerly winds� (Roan, 126). Since there is an absence of sun during Arctic winters, the air becomes incredibly cold and the formation of ice clouds occurs. When the sun returns in the spring, the light shining on the nitrogen oxide filled ice particles activates the formation of chlorine. This excess of ozone destroying chlorine rapidly accelerates the depletion of the ozone layer. Finally, when the polar vortex breaks up, the rapid dissolution decreases. It is evident that the effects of the polar vortex are dramatic. �For about two month every southern spring, the total ozone declines by about 60% over most of Antarctica. In the core of the ozone hole, more than 75% of the ozone is lost and at some altitudes, the ozone virtually disappeared in October, 1993� (Nilsson, 19). The average size of the ozone hole is larger than most continents, including South America, Europe, Australia, and Antarctica, and the maximum size of the ozone hole in 1996 was larger than North America (See Figure 5). Finally, one must note that the �hole� over Antarctica is truly a �hole� only in the Antarctic spring, when the depletion is extremely severe due to the vortex.
At this time, due to the decreased number of photoplankton, the krill level was so low that it could not support the penguin population. Thus, some penguins were forced to travel up to two hundred miles in search of food, but most returned with none. Furthermore, when summer came, only approximately ten of the 1800 hatched penguin chicks survived. This tragedy illustrates the fact that even underwater creatures are not protected from harmful UV rays, and is a perfect example of the entire food chain being affected due to an increase in the UV radiation as a result of the thinning ozone layer.
SOCIETAL ASPECTS
The most obvious, and perhaps most important connection between society and the ozone layer is the fact that scientific research suggests depletion of the ozone layer directly and indirectly endangers the health of the population. Research has focused on connections between the depleting ozone layer and skin cancer, immuno-suppression, cataracts, and snowblindness.
Ozone depletion and skin cancer: What�s the connection?
Exposure to UV radiation increases the risk of skin cancer and causes damage to the DNA in the skin cells. DNA is extremely sensitive to UV radiation, especially UV-B radiation. UV radiation is located in the optical radiation portion of the electromagnetic spectrum, while UV-B radiation is a subdivision of the ultraviolet spectrum and consists of a wavelength of 280 to 315 nanometers. Thus, DNA is especially sensitive to radiation with a wavelength between 280 and 315 nanometers (See Figure 7).
Skin cancer can be divided into two categories: melanoma and non-melanoma. The melanoma form of skin cancer is the more dangerous of the two. This type of cancer has the ability to spread quickly throughout the body and invade other cells. On the other hand, non-melanoma skin cancer is not to be taken lightly either, but is a less serious form of the disease. Non-melanoma skin cancers are not usually life threatening, and removal is relatively routine. However, treatment does include radiation therapy or surgery. The concern of many is that sunburn may lead to increased risk of acquiring skin cancer. Some forms of cancer are associated with sunburn, while other forms are not. Melanoma skin cancer is a form that sunburns may play a leading role in. Jan van der Leun, a Dutch scientist, explains that, �light hitting the outer layer of the skin, the epidermis, triggers the production of some substances which diffuse into the dermis below. The dermis is filled with blood vessels, and the chemical substances cause them to dilate, making the skin red and warm to the touch� (Nilsson, 83).
The bottom line is that UV ray exposure increases the risk of skin cancer. However, controversy lies around the question of whether or not the depletion of the ozone layer will lead to more sunburns, and in turn, more skin cancer. Some scientists suggest that the skin will gradually adapt to higher UV-B levels as the ozone gradually depletes (Nilsson, 83). The opponent to this theory would state that the thinning of the ozone layer would lead to more human UV-B exposure. This increased UV-B exposure would, in turn, increase the damage to the DNA making it difficult for the cell to correct the damage before it divides. This damage accumulates over time and increases the chances that a cell will turn cancerous. In addition, since UV-B radiation damages the immune system, it is much more likely that a cell will turn cancerous. �In animal studies, immunosuppressive effects caused by UV-B have indeed been shown to play an important role in the outcome of both melanoma and non-melanoma skin cancers� (Nilsson, 105). Furthermore, Nilsson (81) states that �for the non-melanoma skin cancers, the evidence is compelling and there are estimates that each percentage decrease in the stratospheric ozone will lead to a two percent increase in the incidence of these cancers.� Thus, if the ozone depletes by ten percent over a certain time period, 250,000 more people would be affected by these cancers each year (Nilsson, 81).
Due to controversy in the scientific community, it is difficult to clearly state whether or not ozone depletion will lead to an increased risk of skin cancers, but scientists agree on the fact that UV-B radiation plays a large role in the formation of cancer. Thus, it may very well be that as the �UV filter� we call the ozone layer thins, the increased amount of UV-B radiation posed on human skin may contribute to an increased amount of skin cancer. Yet, one can only weigh all the evidence and speculate, for science has yet to provide a �cut and dry� answer for society to base its judgments on.
Ozone depletion and immuno-suppression
Ozone depletion is also suggested to cause immuno-suppression. This theory was first explored in the 1960s when guinea-pigs, who were exposed to an allergen, showed a lowered immune system response after they had been irradiated with UV (Nilsson, 101). In addition, another study showed that UV radiation had the same effect on animals as X-ray treatment and chemical immuno-suppression. Logically, all three factors suppressed the immune system.
Scientists Edward de Fabo and Frances Noonan conducted a study to investigate exactly which portion of the UV spectrum has the power to suppress the immune system. In this experiment, de Fabo and Noonan employed filters that were able to separate UV radiation wavelength by wavelength. They subjected mice to UV rays and measured the effects at precise intervals on the UV range. �When de Fabo and Noonan started to match the parts of the spectrum that gave the most immuno-suppression with the absorption spectra of different compounds in the skin, they found an almost perfect match � UCA, the compound previously thought of as sunscreen (Nilsson, 102).� Nilsson (107) describes urocanic acid (UCA) as antenna-like because it attracts UV rays. When UV radiation hits the skin, it causes UCA within the skin to change molecular structure from trans-UCA to cis-UCA. This transformation interacts with a number of cells in the skin and sends a signal to the immune system, causing it to hinder its reaction. If the UVA has caused damage to the DNA, then the possibility exists for a cancer growth (See Figure 8).
What about other illnesses?
Like immuno-suppression and skin cancer, science is not able to provide society with a confident answer to the question: Will the depletion of the ozone layer cause an increased number of cataract cases? Cataracts are a condition that begin with blurry vision and in some cases, develop into blindness. It has been proven that UV light can damage the DNA, membranes, and proteins in the eye, and in animal studies, this damage has resulted in scattered light and the formation of opaque areas in the eye. It was estimated by the Environmental Effects Panel of the United Nations Environment Programme that for each percent decrease in ozone, the number of people developing blindness would increase by approximately 100,000 to 150,000 people (Nilsson, 113). However, this estimation was contradicted by a team of Dutch scientists, who stated, �it is not scientifically justifiable to quantify the effects of UV radiation on the eye, if such effects are present under normal circumstances� (Nilsson, 113). The UNEP then published an updated statement and included information that poor diet and diseases, such as diabetes, also contribute to cataract development. Thus, it must be recognized that cataracts can result from poor nutrition, poor hygiene, and diabetes, and not solely from increased UV radiation.
Research has been conducted to investigate a link between cataracts and UV radiation. Some epidemiological studies have shown that UV-B radiation and formation of cataracts do have a positive relationship. For example, a study conducted with Chesapeake Bay fishermen asked these fishermen to disclose whether or not they wore sunglasses while working and during outdoor recreational activities. Then, radiation measurements were taken throughout the area to probe for a correlation. The results of this study showed a �weak positive dose-response relationship with UV-B exposure� (Nilsson, 117). Thus, in this study, one would argue that increased UV radiation would lead to increased rates of cataracts. Many other studies have been conducted to examine this phenomenon, and none have shown a strongly correlated causal relationship between UV-B and cataracts, but many suggest the possibility of a relationship. In summary, there is again no �cut and dry� answer explaining what will happen to the number of cases of cataracts as the ozone layer depletes, but when one examines the effects of UV-B radiation on the eyes, it is suggested that ozone depletion is likely to increase one�s risk of developing cataracts.
A short-term health problem that will increase as the level of ozone decreases is �snowblindness� or �welder�s arc flash.� This phenomenon is a result of sunburn of the conjunctiva and cornea and is �characterized by blurred vision, severe pain, photophobia, profuse tearing, and eyelid spasms� (Ozone.org, 1998). The condition occurs after exposure to UV-B radiation and does not result in permanent damage. The symptoms usually vanish after a few days.
It is obvious to recognize the controversy surrounding theories which state that depletion of the ozone layer causes health problems. While one resource may provide the reader with one answer, the next source may provide the opposite theory. It is evident that UV radiation causes various health problems, but what is not so clear is to what degree a depleting ozone layer will magnify the occurrence of these problems.
Ozone depletion: Not a farmer�s best friend.
Another common, yet, highly debated concern with regards to the depleting ozone layer is crop and plant damage. As it has been well stressed, depletion of the ozone layer results in higher UV-B radiation on the earth�s surface. Ironically, while plants use light as their main fuel for growth, a delicate balance must be achieved in order for the plant to survive. If a plant is exposed to too much UV radiation, the DNA of the plant may become damaged due to penetration of harmful UV radiation into sensitive areas of the plant. UV radiation also causes problems in the photosynthetic machinery by hampering the photosynthesis process, the cell membrane by altering the transportation of essential potassium, and the cell�s skeleton by affecting cell growth and morphology. With this information taken into account, it would seem logical that increased UV radiation from the depleting ozone layer would lead to plant damage. However, it is not that simple. Some plants actually employ a mechanism that allows them to protect themselves from UV damage. Thus, research suggests that if ozone depletion became serious enough, the plants without the protective mechanisms would die out, but the plants with these mechanisms would be able to replace the extinct plants, and not affect the level of productivity in the ecosystem (Nilsson, 54). Thus, much depends on which plants survive.
To further investigate the affect of UV radiation on plants, experiments have been done to study the effects of UV-B levels on crop yield (Nilsson, 52). The results concluded that in approximately 50% of the crops, an increased UV-B level lead to a decrease in crop yield. Specifically, the corn yield was reduced by 28 percent; and beans, squash, and various forms of peas were also found to be sensitive to UV-B radiation. One would logically conclude that the depletion of the ozone layer would lead to a reduction in the yield of crops. However, science may offer a solution by being able to breed crops that are resistant to UV radiation.
The answer to the question of decreased crop yield and existence of plants as a result of a thinning ozone layer is not scientifically definitive. However, it is important because if the ability of plants to intake carbon dioxide and regulate the amount of carbon dioxide in the air is altered, the consequences for society are detrimental.
Collaborative Global Government Efforts
As a result of the many concerns that a thinning ozone layer poses to society and the environment, the U.S. government and many international agencies have been relatively active in attempting to monitor, regulate, and solve the problem. Perhaps the most well known acts to help control the depletion of the ozone layer were the Montreal Protocol, and the London Ozone amendment to the Montreal Protocol. On September 14, 1987, delegates from 43 countries met to discuss threats of the thinning ozone layer. After much discussion, the delegates agreed to halt production and consumption of CFCs at 1986 levels by the year 1990. In addition, nations also agreed to reduce CFCs 20 percent by January 1, 1994 and an additional 30 percent by January 1, 1999 (Roan, 208-9). This was known as the Montreal Protocol. Even though this protocol helped the state of the ozone layer, the results were not significant enough. Thus, shortly after the implementation of the protocol, in 1990, it was amended. This amendment recruited more countries, bringing the total number involved to almost 100. The new goals were to eliminate the use of all CFCs by the year 2000, and to help set up a fund so that developing countries may find alternates to using CFCs. The name of this amendment was the London Ozone Agreement. Thus, many nations recognized the need for rapid and dramatic action in fighting the war with CFC responsible ozone depletion.
DISCUSSION
Regardless of the details of the arguments, it is obvious that the depletion of the ozone layer is a serious problem that poses many consequences to society. Although scientific controversy exists, the possibility seems high that the depletion of the ozone layer will prove detrimental if action is not taken. For example, research shows the strong possibility of a number of health risks associated with increased UV-B exposure as a direct result of the thinning ozone layer. These health risks include skin cancer, immuno-suppression, cataracts, and �snowblindness.�
Furthermore, the possibility that increased UV-B radiation results in lower crop yields should provide a �wake up� call to those who feel the thinning ozone layer is not a problem. For if we are not able to breed UV-B resistant plants, the world�s food supply would become dramatically decreased, resulting in higher levels of famine and malnutrition.
Studies from Antarctica tell society that increased UV radiation can directly affect the food chain. Recall the decrease in food supply as a result of reduced levels of photoplankton in Antarctica. This may seem like an isolated, non-significant, and remote problem; however, this incident illustrates the dangers of reduced food supply and alteration of the food chain as a result of the thinning ozone layer. Even though the photoplankton were located at the bottom of the food chain, the whole chain was affected. In the future, problems like this could potentially affect the global food web and result in an overall decrease in food supply. Thus, realize that the dangers posed by ozone depletion are real now, and will be in the future, if action is not taken.
Take Action: Teamwork does the trick
Although the earth will be able to �heal� itself if the CFC level continues to stay as it is, the depletion of the ozone layer is still a problem that society should be concerned with. In order for earth to repair the damage humans have posed on the ozone layer, society must take an active role. There are many tasks individuals can involve themselves in to help combat the problem of ozone depletion. First of all, one can simply check product labels for ozone friendly status. Many companies have gone to great lengths to remove CFCs from their products. These products do not do as much damage to the ozone layer, and thus, are denoted as �ozone friendly.� A collaborative effort by society not using products with CFCs is a major step toward the healing of the ozone layer.
Unfortunately, many products still used in society are detrimental to the ozone layer. For example, CFCs marketed under the trade name �Freon� are used in appliances with refrigerants such as refrigerators and air conditioners. When individuals must dispose of products with refrigerants in them, certain actions must be taken in order to prevent the CFCs from escaping from the disposed product. For example, when an agency, such as a waste hauling company, comes to pick up the unwanted appliance, check to make sure refrigerant-recovery equipment is used by the agency. This equipment allows for the disposal of refrigerants without damage to the ozone layer.
Society can also help the problem of ozone depletion through education, as well as through various donations. If individuals contribute time or money to environmental agencies focused on healing the ozone layer, the agencies will be able to organize activities promoting the understanding of the ozone problem. If society is educated through these means, more individual efforts will be taken to make �ozone smart� decisions such as using �ozone friendly� products.
Although thinning ozone may not directly affect the generation growing up today, future generations depend on the actions taken now. Thus, it is important for society to recognize that the thinning ozone layer is a problem and to take action in order to ensure the safety and survival of future generations.
SUMMARY
The ozone layer is essential for protecting society from harmful UV radiation by acting as a filter. However, this protective layer has been thinning due to three main sources: human activity, natural sources, and volcanoes. Human activity is responsible for the most damage to the ozone layer, thus, society should recognize that much can be done to prevent ozone layer damage.
In 1985, in a region over Antarctica, the yearly polar vortex had caused the ozone layer to deplete so greatly, that it could be classified as a hole. In 1996, this hole was large enough to cover Antarctica.
The depletion of the ozone layer does not come without problems. Scientific research has suggested the probability that increased UV-B radiation as a result of the thinning ozone layer leads to increased cases of skin cancer, immuno-suppression, cataracts, and �snowblindness� due to radiation damage of the DNA. Additionally, experiments have shown a correlation between increased UV radiation and crop damage due to UV radiation damaging the plants� DNA. Some scientists, however, feel that this will not be a problem in the future due to the possibility of breeding UV resistant crops and plants.
Many national governments and agencies recognized the problem of ozone depletion, and therefore, united in 1987 to sign the Montreal Protocol. This agreement was implemented to decrease CFC levels in order to help protect the thinning ozone layer.
Clearly, ozone depletion is a dangerous problem due to possible disease outbreaks and famine as a result of increased UV-B radiation. However, society can collectively attempt to combat this problem by relatively simple means such as education and the practice of �ozone smart� behavior. For if society acts now, future generations will be handed a safe and healthy planet.
Aerosol: A gas bearing another substance.
Allergen: An overreaction to an antigen in amounts that do not affect most people; often involves IgE antibodies
Chlorofluorocarbon (CFC): A chemical compound of one fluorine atom, one carbon atom, and three chlorine atoms. These molecules are very stable and contribute to ozone depletion.
Conjunctiva: The mucous membrane covering the exposed portion of the eyeball.
Cornea: Portion of the eye located at the front of the eyeball, through which light enters the eye.
Deoxyribonucleic acid (DNA): The fundamental hereditary material of all living organisms.
Dermis: The thick layer of skin below the epidermis.
Dobson Unit: Unit of measurement used to measure thickness of ozone layer at STP.
Electromagnetic Spectrum: Visible light that fits between ultraviolet and infrared radiation in the spectrum.
Epidermis: In plants and animals, the epidermis is the outermost cell layer. (Only one cell layer thick in plants.)
Malaria: A disease caused by a parasitic protozoan transferred to the human bloodstream by a mosquito.
Malignant: Another term for cancerous.
Montreal Protocol: This agreement between many foreign nations aims to reduce and eventually eliminate the emissions of man-made ozone depleting substances.
Ozone: This molecule, consisting of three oxygen atoms, is formed in the stratosphere when sunlight hits an oxygen molecule.
Ozone Hole: The extreme thinning of the ozone layer over Antarctica. The ozone hole is unique to Antarctica because of the polar vortex.
Ozone Layer: The area in the stratosphere where most of the earth's ozone is located which is usually between 20 and 30 kilometers above the earth's surface.
Photosynthesis: Metabolic processes, carried out by green plants, by which visible light is trapped and energy is used to synthesize compounds such as ATP and glucose.
Polar Vortex: Field measurements in and theoretical studies of the Antarctic stratosphere have demonstrated that processes that occur in the wintertime engender chemical transformations that lead to the formation of the springtime ozone hole over the Antarctic continent.
Radiation: The process by which energy is emitted as particles or waves.
Standard Temperature and Pressure (STP): The reference conditions for gases chosen by convention to be 0 degrees Celsius and 1 unit of atmospheric pressure.
Stratosphere: The area of the earth's atmosphere directly above the troposphere. The stratosphere makes up about 10% of the atmospheric mass.
Urocanic acid: A compound in the skin that changes forms when it comes in contact with UV radiation. This transformation can lead to immuno-suppression.
UV-B Radiation: A harmful form of ultraviolet radiation with a wavelength of between 280 and 320 nanometers that is usually filtered out by the ozone layer. UV-B is the main cause of skin cancer.
Wavelength: The distance between any two adjacent identical points of a wave.
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