Without ozone, life on our planet would have no protection from the sun’s harmful radiation. Too much ozone, however, would blanket the earth in a cloak of dirty air. In recent years the double-edged nature of this colorless gas has fascinated and alarmed scientists. As a benefit, ozone in the stratosphere creates a shield that protects people form solar ultraviolet rays. As a hazard, ozone forms in the lower atmosphere as the main ingredient in the pollutant " smog". In this paper, I will analyze what exactly the ozone layer is; why it is vital to life on earth; why its destruction will cause a dramatic increase in cancer and other diseased, as well as a devastation of the would food supplies. I will also discuss what chemicals are destroying the ozone layer, how they are destroying it, and where they come from. Finally, I will talk about what can be dome to prevent further damage, why time is of the essence, and what we can do.

In 1839, the German-born scientist Christian Friederich Schonbein was a professor of chemistry at the University of Basel in Switzerland. During one of his experiments, Schonbein passed an electric charge through a flask of water. Each time he passed the electric charge through the water, he noticed a peculiar odor. Finally, he realized he had created a new substance. He named this new substance ozone, after the Greek work ozein, meaning "to smell"(Fisherman and Kalish, 1990)

Ozone is a bluish gas and is an unstable form of pure oxygen whose molecules consist of three atoms instead of two (O3). It is produced by electric discharges- naturally by lightning, and artificially by high voltage electrical equipment-and has a characteristic pungent odor. An ordinary molecule of oxygen contains two atoms while a molecule of ozone contains three atoms (O + O2 =O3). Because of ozone’s composition, it is reactive (Stille, 1990) That is, it readily combines with and oxidizes whatever materials it comes in contact with, including such biological substances as cells and tissues.

There are two general types of ozone: low-level and upper-level ozone. Low-level ozone exists near the earth’s surface in the lowest portion of the atmosphere. This is why scientists refer to it as low-level ozone. This lowest atmospheric layer, occupying the space between the earth’s surface and an altitude of about six to nine miles, it called the troposphere (Pearce, 1996). Scientists also refer to low-level ozone as tropospheric ozone. The gas forms in the troposphere when sunlight strikes nitrogen oxides (Nox) and hydrocarbons (HCs)-compounds of hydrogen and carbon-and other volatile organic compounds (VOCs) that come from a variety of industries, vehicle exhausts, and consumer products. As the nitrogen oxides and hydrocarbons "stew" in the sun the reaction that takes place produces ozone, the main ingredient in the pollutant commonly known as "smog" (Pearce, 1996). Biogenic or naturally produced hydrocarbons (NHCs) formed by trees and other vegetation in the presence of nitrogen oxides and sunlight also can produce ozone, but until recently it was generally believed that NHCs played only a small part in urban smog episodes. However, in a recent study of Atlanta’s air, a group of researchers from the school of Geophysical Sciences at the Georgia Institute of Technology found the "NHC emissions appear to be as large as, if not lager than" anthropogenic or human-produced hydrocarbons (AHCs). The scientific team also pointed out that NHCs react faster than AHCs, so they "can have a significant effect" even in low concentrations, and concluded tha NHCs must be considered when developing strategies to control smog (Pearce, 1996).

The second type of ozone exists in the upper portion of the earth’s atmosphere and is called upper-level ozone. This layer of the atmosphere, extending from about twelve to twenty-four miles above the planet’s surface, is known as the stratosphere. Most of the atmospheric ozone is concentrated not in the lower atmosphere where we breathe but some 7 to 15 miles above the earth’s surface in a layer of the upper atmosphere or stratosphere called the ozonosphere or the ozone layer (Stille, 1990). Most of the upper atmosphere ozone is formed where sunlight is strongest- over the tropics-and is circulated by global air patterns toward the North and South Poles. Ozone is destroyed and replenished by natural atmospheric chemistry in a dynamic and fairly stable balance. An average of only a few parts per million ozone has supported the evolution of life on land over millions of years. Oxygen-breathing life, such as us, could not survive in the thin upper atmosphere of the ozonosphere, but the ozone layer is, nonetheless, critical to earth’s life-support systems. Ozone is the only gas in the atmosphere that screens out much of the most harmful wavelengths of ultraviolet radiation from the sun by absorbing and converting that radiation to heat and chemical energy (Ko, Sze and Prather, 1994). The ozone layer can be imagined as a planetary umbrella, an invisible shield, and a diffuse, outer membrane that functions as our planet’s natural sunscreen.

Too much low-level ozone can be harmful to people, animals, and plants. Highly concentrated ozone is so lethal that it is used to kill germs on medical equipment. In lower concentrations, ozone can cause breathing difficulties for humans and other problems for plants. Scientists have known about the potential dangers of ozone for decades. But not until the 1970s and 1980s did ozone concentrations near the earth’s surface reach high levels often enough to cause much concern. Average low-level ozone concentrations rose steadily in the 1980s. The worst large-scale incident of tropospheric ozone pollution occurred during the summer of 1988. A huge mass of warm air hung over the eastern half of the United States for most of the summer. There was so little air movement in the lower atmosphere that ozone levels built up rapidly. The air was so bad in Detroit, Michigan, for example, that ozone levels exceeded that amount considered safe by the U.S. Environmental Protection Agency (EPA) sixteen times. Ozone levels in Philadelphia, Pennsylvania, exceeded EPA limits forty-two times that summer. And cities were not the only areas that suffered. Ozone levels broke records in the

Shenandoah Valley of Virginia. In Maine’s Acadia National Park, ozone concentrations were the highest ever, and park rangers warned people not to exert themselves. Because o f the rise in ozone pollution in the 1980s, scientists began paying more attention to ozone. Many studies were done. They revealed some new information about the harmful effects of low-level ozone (Shawn, 1987)

Some studies showed that ozone damages the lungs of animals and people. Inside the lungs are thousands of tiny air sacs through which oxygen and carbon dioxide pass when people breathe. Scientists have found that the thin walls of these air sacs suffer the most damage from ozone. Scientists are not completely sure how this occurs. One theory suggests ozone molecules combine with air sac molecules, creating scar tissue. The scar tissue eventually causes breathing problems. The other theory contends that the ozone reacts with fatty tissue in the air sacs, hardening the tissue and causing similar breathing problems (Stille, 1990). In either case, continued exposure to high concentrations of ozone can lead to emphysema.

If too much ozone can be dangerous to a person’s health, exactly how much ozone is too much? In 1981, the EPA set a national safety standard that allowed eight molecules of ozone for every billion-air molecule. This meant that exposure to less than this amount was considered safe. In 1987, the EPA upped the standard to twelve. Some later studies suggested that this new standard might be too high. For instance, scientists exposed baboons, rabbits, and dogs to various ozone levels. Exposures of one-third the EPA standard caused at least minor inflammation redness, and swelling of lung tissues. A 1994 study by researcher Richard Mann and other tested human being and found similar results (Mann, 1995)

Low-level ozone is also harmful to plants and crops. Recently, the tropospheric ozone levels did become high enough to cause problems. For instance, several forests in the state of Bavaria in Germany showed signs of "early autumn syndrome." Outbreaks of the syndrome also began to increase in the United States and other countries. The studies showed that when leaves are exposed to high concentrations of ozone, the stomata close, making it impossible for the plant to take in the gases and nutrients it needs to live (Karenlampi and Paakkonen, 1997). If trees experience this condition long enough, earl autumn syndrome sets in. Like trees and other forest plants, food crops can suffer from exposure to low-level ozone. The EPA estimates that crop losses form ozone in the United States total $2.5 billion to $3 billion per year. The World Resources Institute, an environmental research organization, believes that annual losses in the United States are as high as $5 billion. Studies showed that exposure to high levels of ozone increases the chances of some crops catching plant diseases (Khan, 1997). For example, potatoes and barley both become diseased more easily after contact with concentrated ozone.

One air pollutant that scientists have studied in combination with low-level ozone is sulfur dioxide, a by-product of burning coal. Even by itself, sulfur dioxide can be dangerous to life. In 1976, researchers H.A. Menser and H.E. Hoggestad exposed tobacco plants first to ozone alone, then to sulfur dioxide alone, each for a period of four hours. The plants did not appear to be hurt in either case. But, when the researchers exposed the plants to a mixture of the two pollutants of the two pollutants for four hours, nearly half of the leaves shriveled and died. Later studies, including one conducted at EPA labs, showed that the grapes, soybeans and some other crops suffered similarly from the combination of ozone and sulfur dioxide (Antonielli and Pasqualini, 1997).

Industrial smog mixes with pollution exhausts from cars and trucks and then with sunlight to create the ozone smog. The American city that has suffered the most from ozone smog is Los Angeles. In the late 1930s, the city began to expand, and by 1945, it was the fastest-growing city in the United States. By the early 1960s, there were more cars and trucks in southern California than in any other areas of similar size in the United States. Large amounts of car exhaust, unique terrain, and lots of sunlight- combine to produce serious ozone smog in Los Angeles. By the mid-1980s, ozone levels in the city often measured more than three times the level now regarded as safe by the EPA. Los Angeles eventually reduced its low-level ozone. Air pollution controls in the 1990s got rid of many of the pollutants released by cars and trucks. However, the ozone levels remain high, regularly violation the EPA standard. Los Angeles is not alone in failing to meet the EPA’s low-level ozone standard. During the summer of 1990, for instance, ninety-six cities and counties in the United States repeatedly went over the level considered safe by the EPA (Stille, 1990).

The problem is even worse in many foreign countries. Ozone smog hangs over dozens of cities from Athens to Tokyo. Even some rural areas are threatened by ozone smog. In Thailand, Brazil, and some counties in eastern Africa, the burning of crops to enrich the soil and the burning of forests to clear land regularly produce high levels of ozone. The smog often becomes so thick that it reduces the brightness of the midday sun to a faded twilight glow (Sharon, 1989).

Many ways of creating low-level ozone exist in the modern industrial world. According to the EPA, in 1990 alone, cars, factories, fires, waste dumps, and other pollution sources in the United States poured more than ninety million tons of ozone-producing substances into the air. In addition, more than eighteen million tons of sulfur dioxide entered the atmosphere above the United States, creating the potential for a dangerous mixture of that gas and ozone (Sharon, 1989). Scientists estimate that trees produce at least several tens of millions of tons of hydrocarbons each year. Many of these hydrocarbons create ozone when they mix with car exhaust (Khan, 1997). The addition of huge amounts of sunlight to these substances makes the earth’s lower atmosphere, one big ozone-producing machine. The scientists are still unsure of just how much ozone is dangerous to animal and human. And there is still much disagreement about the size of crop losses due to ozone damage. But scientists do agree on two important points. First, highly concentrated low-level ozone is harmful to living things and alters or destroys many of the substances with which it comes in contact. Second, the world’s overall levels of tropospheric ozone are steadily rising.

While too much low-level ozone can be harmful, exactly the opposite is true for upper-level ozone. Because ozone high in the stratosphere absorbs incoming ultraviolet light from the sun, it keeps most of these destructive rays from reaching the earth’s surface. Ultraviolet radiation is so lethal that without the stratospheric ozone layer, the existence of life on earth would be nearly impossible. Until the 1970s and 1980s, most people- including scientists- took the ozone layer more or less for granted. They assumed it was one of the earth’s natural features and that it would always remain the same. This attitude changed in 1984 when scientists found a huge hole in the ozone layer over Antarctica, the continent covering the planet’s South Pole (Sharon, 1989). Since then, researchers have discovered that the stratospheric ozone shield is growing thinner and weaker. As this happens, more ultraviolet light reaches the earth’s surface. So, the scientists and government officials around the world are increasingly concerned about the possible health effects of upper-level ozone depletion. The concern over the decrease of stratospheric ozone is that it will eventually result in an increase in skin cancer and may lead to other threats to human health (Hu and Haines, 1993). The studies showed that the ozone layer in the stratosphere is slowly becoming thinner throughout the world, and that this effect is amplified by the existence of a "hole" in the ozone layer over Antarctica (see the figure on page 27).

Scientists and doctors have known for a long time that repeated exposure to ultraviolet radiation causes skin cancer. In general, light-skinned people have the highest risk, while dark-skinned people have a lower risk. This is because darker skins contain more of the pigment melanin, which blocks most ultraviolet light. About 90 percent of all skin cancers occur on the head and neck, mainly because these are the areas of the body that are most often left uncovered and exposed to sunlight. About 400,000 to 600,000 cases of skin cancer occur in the United States each year. Many of these cases are caused by too much exposure to ultraviolet rays from he sun. As the intensity of ultraviolet radiation increases, cancer rates and deaths may also increase. Many scientists expect that as upper-level ozone decreases, the intensity of ultraviolet radiation at the earth’s surface will increase. According to the EPA, for every 1 percent decrease in the ozone layer, ultraviolet ray reaching the earth’s surface will increase 2 percent. This, in turn, could cause an 8 percent rise in skin cancer rates or another 80,000 to 100,000 cases of skin cancer in the United States (Hu and Haines, 1993).

The most widely publicized examples are in Australia. That country is the closest heavily populated area to Antarctica, where upper-level ozone is disappearing. After the discovery of the Antarctic ozone hole, many scientists predicted that Australia would show the highest rates of skin cancer in the world. And this is exactly what happened. Studies have shown that the incidence of malignant melanoma, the most dangerous form of skin cancer, is four times higher in Australia than in the United States. About one out of every four Australians suffering form malignant melanoma dies from the disease (Hu and Haines, 1993).

Australia’s location near the Antarctic ozone hole, however, is a very real problem. On several occasions between 1990 andd1994, Australian scientists detected large patches of ozone-depleted air that had apparently traveled form the South Pole. When the patches were over Australia, ultraviolet radiation soared to levels more than twenty times higher than normal. In addition, studies show that skin cancer is increasing annually in Australia (Hu and Haines, 1993).

Ultraviolet rays can cause other health problems besides skin cancer. High doses can impair the immune systems of mammals, including human beings. Ultraviolet light is also a major cause of eye cataracts. These are patches of opaque, or light-blocking, tissue that form in the eyes and can lead to partial or complete blindness. Laboratory experiments have shown that ultraviolet rays are 250 times more likely than regular light to cause cataracts. According to the EPA, if the present rate of ozone depletion continues for the next forty years, the increased ultraviolet radiation could cause as many as ten million extra cases of cataracts in the United States alone (Carassiti, 1996).

Animals and people are not the only creatures harmed by ultraviolet rays. Many microorganisms that produce nutrients in the soil die from over exposure to these rays. The microorganisms are extremely sensitive to changes in the intensity of the rays. So continued upper-level ozone depletion could potentially decrease soil fertility, especially in tropical regions where ultraviolet radiation is naturally more intense (Dickerson and Kondoagunta, 1997). Plants, too, can suffer from increased doses of ultraviolet rays. According to researcher Robert C. Worrest of the EPA, scientists have tested about two hundred species of land plants- mostly food crops- for sensitivity to ultraviolet light (Khan, 1997).

Ocean plants can also be damaged by too much exposure to ultraviolet rays. Some experiments suggest that tiny plants like algae and plankton, which move by the trillions through the seas, are extremely sensitive to ultraviolet light. These species are important for two reasons. Firstly, through the process of photosynthesis, they produce a significant amount of the oxygen in the earth’s atmosphere. Secondly, they occupy the base of nature’s food chain. Microscopic animals eat these tiny plants. Larger animals then eat these microscopic animals, and the process continued upward through the animal kingdom. Human beings are at the top of the food chain. Many scientists believe that increase in ultraviolet radiation caused by upper-level ozone depletion could significantly reduce algae and plankton found in the oceans. However, the same researchers admit that they still do not have enough information to predict how many species of these plants and animals might be lost. Some scientists think there might not be any loss at all. They point out that ozone depletion is happening gradually, over the course of years, while the life cycle of plankton spans only a few days. So the tiny plants might slowly be able to adapt themselves to higher ultraviolet levels. In that case, changes in the working of the food chain might be minimal (Miller and Heagle, 1995). All the researchers agree that long-term studies are needed before anyone can say with absolute certainty what ozone depletion will do to ocean plants and animals.

All these potentially harmful effects of ultraviolet radiation are a cause for concern to scientists and government leaders around the world. Researchers work to discover the reasons why this ozone depletion occurs. They also search for ways to slow and eventually halt the destruction of upper-level ozone. The discovery of ozone depletion came in the early 1970s. Before that, scientists paid little attention to the ozone layer. This was mainly because they did not yet thoroughly understand the chemistry of the upper atmosphere.

So, why did scientists become concerned about the ozone layer? A number of events prompted scientific research into the possibility that the ozone layer might be in danger. One was a debate that developed over a fleet of several hundred huge aircraft, called supersonic transports (SSTs). Congress planned to fund the manufacture of two U.S. prototype SSTs, modeled after the Concorde built in France, and congressional leaders wanted information on what impact the SSTs would have on the stratosphere where the aircraft would be flying. Scientific studies during the early 1970s showed that SSTs flying through the stratosphere released nitrogen oxides in exhaust gases. Ironically, nitrogen compounds that help produce ozone in the troposphere is part of a chemical process that destroys ozone in the stratosphere. Although the threat to the ozone layer was a consideration in whether or not SSTs should be manufactured, the project eventually was dropped because the production of SSTs became too costly (Russell, 1989).

About the same time that the SST debate was going on, teams of scientists at the University of Michigan, Harvard, and the Palo Alto research center were investigating the effects of the space shuttle on the environment. Researchers found that exhausts from the space shuttle’s engines released chlorine species into the atmosphere, but at first little was known about how chlorine compounds affected the stratosphere. As research continued, studies suggested that sixty shuttle launches a year would release only enough chemically active chlorine to reduce ozone concentrations by 0.2 percent. Nevertheless, the research on the stratospheric effects of shuttle launches alerted others in the scientific community and in government agencies to view chlorine compounds as possible threats to the ozone layer (Bittker, 1987).

Even before the research into environmental impacts of the SST and the space shuttle, a British chemist, James Lovelock, had invented an instrument that could detect chlorofluorocarbons (CFCs), gases consisting of chlorine, fluorine, and carbon that are produced by a variety of human activities and released into the atmosphere from many sources. Lovelock found traces of CFCs in remote areas far from their major sources, and theorized that CFCs stayed in the atmosphere and might have an impact on atmospheric chemistry (Bittker, 1987).

Then, in 1974, F. Sherwook Rowland and Mario J. Molina, both in the chemistry department of the University of California at Irvine, released a study proposing that CFCs percolated through the troposphere into the stratosphere, altering the chemistry of the protective ozone layer (Bittker, 1987). That proposal sounded an alarm. Atmospheric scientists in many nations followed up with studied that confirmed the findings of Rowland and Molina. At the same time, the possible threat to the ozone layer caught the attention of the general public.

Since CFCs were used in aerosol sprays for hundreds of different kinds of consumer products, worried consumers, environmentalists, and other groups called for bans on CFCs in aerosol spray. In 1978, the U.S. Congress passed legislation that outlawed the manufacture of CFC aerosols. Canadian, Swiss, and Scandinavian governments took similar actions. However, CFSs still are used widely in aerosol products manufactured on other nations and in a variety of U.S. products, including refrigerators, air conditioners, and foam packaging and in solvents for cleaning computer circuit boards (Russell, 1989).

It is not surprising that industrial users for many years have fought a total ban on CFCs. When the gases were first developed by chemists at General Motors Corporation in the early 1930s, they were thought to be almost perfect chemicals because they are stable and do not react easily with other substances. In fact, CFCs replaced toxic and flammable gases once used as coolants in refrigerators. Since CFCs are nonflammable, nontoxic, and noncorrosive, they can be used in a variety of products without the worry of drastic changes in their properties or the threat of fire and other hazards. But the great stability of CFCs also allows them to survive for many years and "pile up" in the troposphere. As a result, some CFCs eventually move into the stratosphere, where they can destroy ozone (Thiele and Podda, 1985).

Recently, public attention again has focused on the damaging effects of CFCs on the ozone layer. British atmospheric scientists had been collecting data for decades. They found that almost half of the vertical column of ozone over the South Pole failed to appear every season (Russell, 1989). The phenomenon, which later was dubbed a "hole", occurred repeatedly, with increasing amounts of ozone loss each season.

Since 1986, a number of expeditions to the South Pole have provided strong evidence to support the theory that chlorine compounds are responsible for much of the ozone loss over Antarctica. There was debate over how chlorine compounds destroy ozone, but most atmospheric chemists now theorize that chlorine monoxide from human-produced CFCs accumulate in the stratosphere. Reactive chlorine then comes in contact with clouds of microscopic ice particles formed from water vapor and chemical compounds. These polar stratospheric clouds (PSCs), as they are called, provide a surface for the catalytic process to take place when the sun appears over Antarctica in early September. Basically, chlorine nitrate and hydrogen chloride, which are relatively inert, are converted to active chlorine compounds that can attack ozone. Atmospheric chemist F.Sherwood Rowland, who firs presented the idea that chlorine destroy 100,000 molecules of ozone before its chain reaction has been completed. Elevated amounts of chlorine dioxide, a by-product of the chemical reaction, and chlorine monoxide which actually destroys ozone, are considered signs that CFCs are responsible for stratospheric ozone loss. Other chemicals may also be involved in the reactions that take place in the stratosphere, and research is continuing on the chemistry of PSCs (Bittker, 1987).

The large amounts of chlorine compounds that have been found in the Antarctic ozone hole, some chlorine comes from such natural sources as the oceans. But, according to a NOAA report, four times more chlorine comes from a type of human-produced hydrocarbons. In this class of hydrocarbons, hydrogen atoms have been replaced by a halogen- chlorine, bromine or fluorine atom. When some of the hydrogen atoms are replaced by a halogen, the resulting compound is known as a partially halogened compound; when all of the hydrogen atoms are replaced by halogens, the compound is fully halogenated. Some scientists determine whether the halogenatd hydrocarbons, called halogens or halocarbons, will deplete ozone. Using the properties of chemical compounds, scientists estimate the ozone depleting potential (ODP) of halogens. One variety of fully halogenated hydrocarbons are the CFCs, known by such names as CFC 11, CFC12, and CFC13, which are the largest contributors to the predicted depletion of ozone, according to the NOAA report. Halogenated bromine compounds, called halons, are even more effective in destroying ozone. For example, a molecule of the compound halon 1301 (the compound used in fire extinguishers) is ten times more effective in destroying ozone than a molecule of the compound CFC11, a gas used in refrigeration and the manufacture o foam products. Overall, much smaller amounts of halons than CFCs are used, but worldwide a total of many hundreds of millions of kilograms of halons and CFCs are produced each year. Because of their long lifetimes, CFCs and halons are expected to increase in the stratosphere even if emissions of these compounds stay the same or drop in the next few decades. In other words, the compounds have been accumulation and move slowly from the troposphere into the stratospheres (Thiele and Podda, 1985).

The researchers further concluded that there had been an overall 2 percent drop in upper-level ozone in the Northern Hemisphere between 1978 and 1987. The ozone depletion in the Southern Hemisphere during that same period was 3 percent. Depletion within the Antarctic hole itself varied from about 60 percent to 70 percent. And the rate of depletion appeared to be increasing. During a six-week period in 1987, 90 percent of the ozone in the center of the hole disappeared. The scientists also used computers to build "models" of ozone depletion to help predict future losses of the gags. The models suggested that the losses would continue (Russell, 1989).

To make matter worse, in 1989, NASA scientists discovered a similar, though much smaller, area of ozone depletion over the Arctic, the North Polar region, and researchers began to detect patches of ozone-depleted air floating over Australia and other areas of the Southern Hemisphere.

Scientists had found that, apparently, there was too little ozone where it was needed most. And, according to some researchers, there is even more to worry about. Ozone might be involved in a trend that may be causing global temperatures to increase. The effects of these higher temperatures could be disastrous.

Many scientists believe that low-level ozone is presently contributing to a slow but steady increase in the temperature of the earth’s atmosphere. These scientists say that this global warming could eventually lead to significant and harmful changes in the planet’s climate. Ozone may contribute to global warming by trapping heat in the lower atmosphere. It does this in the same way that a glass greenhouse captures and holds heat. When sunlight shines on a greenhouse, the rays pass straight through the transparent glass. The air molecules inside the closed structure absorb the heat from the solar rays. The warmed air, unable to pass back through the glass, remains trapped inside (Schneider, 1989). So as long as the sun is shining, the air inside the greenhouse gets warmer and warmer.

Low-level ozone in the atmosphere works similarly. The ozone molecules absorb heat from incoming sunlight. They then push the heat back toward the earth’s surface, causing heat to build up in the lower atmosphere. This process is known as the greenhouse effect. Because ozone molecules absorb heat, helping to create this effect, scientists refer to ozone as a "greenhouse gas." It is not the only greenhouse gas. There are several others, including water vapor, carbon dioxide, methane, nitrogen oxides, and CFCs. When all of these gases are present in the atmosphere, the warming trend increases, according to some scientists. This is because ozone and these other gases trap heat very efficiently (Schneider, 1989).

The amount of low-level ozone in the atmosphere has been increasing since the 1950s. Scientists have shown that there is presently 100 to 200 percent more tropospheric ozone in the atmosphere than there was a century ago (Puckrin, 1987). Considering ozone’s strong heat-trapping powers and its increased concentration in the troposphere, many researchers believe that ozone may play an even larger role in the warming of the earth’s atmosphere in the next century. Some scientists believe this warming has already begun and that it is likely to get worse. One such scientist is James Hansen of NASA’s Goddard Institute for Space Studies in New York. In 1988, Hansen told a group of U.S. senators, " With 99 percent confidence, the greenhouse effect has been detected and is changing our climate now."

Some scientists have tried to predict what global warming could mean to the earth and its in habitants. These scientists say the climate changes that would accompany global warming would transform life as we know it today. The EPA conducted a serious of studies in the late 1980s on the subject of global warming. The aim of these studies was to help both the government and the public understand the environmental changes that could result if global warming occurred. One EPA study examined what would happen if average global temperatures rose five degrees. The conclusion was that less rain and snow would fall in many parts of the United States. This, in turn, would mean less water for growing crops. Corn, for example, needs a minimum amount of rain at a certain time in its growing season, and wheat requires a lot of groundwater from melting snow. In addition, the EPA report stated that a five-degree temperature increase would lead to greater evaporation of lake and water. Colorado River runoff, for example, would fall by at least 10 percent. This would, in turn, affect food production in large sections of the Southwest that rely on the river’s runoff for irrigation (Schneider, 1989).

Another EPA study looked at possible changes in sea level. If global temperatures rise, this study said, at least part of the polar ice caps would melt. This would cause sea levels around the world to rise. According to the EPA, a rise of just three feet would flood most U.S. coastlines. A five-foot rise in sea levels would mean severe flooding for coastal cities like New York and Los Angeles, the EPA predicted. Some parts of the world would fare even worse.

Although global warming is still being debated, many experts and organizations, including the EPA, have called for action now. They propose steps toward reducing human production of greenhouse gases, especially ozone, carbon dioxide, and CFCs. They urge that these steps be part of an overall environmental strategy.

So, what people are doing about ozone? Efforts by various governments and organizations to do something about ozone-related problem are already underway. These efforts fall into two general categories-attempts to eliminate low-level ozone pollution and attempts to slow the depletion of the upper ozone layer.

The battle against low-level ozone pollution in the United States began as a battle against air pollution in general. When Congress established the EPA in 1970, the new organization immediately tackled the problem of air pollution. EPA officials set standards for various pollutants, including ozone. The goal was to have all parts of the country meet these standards by 1976. Many areas of the United States did not comply with the EPA’s standards by 1976. So Congress extended the deadline to 1982 for most areas and to 1987 fir areas with the worst levels of ozone and other pollution (Russell, 1989).

These efforts to control air pollution centered on reducing ozone-producing waste materials emitted into the air by factories and motor vehicles. The idea was to "scrub" the pollutants from the exhausts by using filtering device. The most familiar example is the catalytic converter, used to convert automobile exhaust into mostly harmless substances. As exhaust pass through the converter, chemical reactions remove many of the pollutants. Larger, more complex versions of these converters are found in the smokestacks of factories and oil refineries. Each year, the devices absorb millions of tons of pollutants that would otherwise flow into the atmosphere and produce ozone. The use of catalytic converters and other filtering devices seemed to help for a while. Levels of some pollutants fell in the late 1970s and early 1980s.

While low-level ozone in the cities decreased, ozone levels increased in many rural areas. This situation at first surprised and confused scientists. But they soon found that nitrogen oxides were causing the problem. The catalytic converters in use did not remove nitrogen oxides from the exhausts, and winds carried these chemicals far out into the countryside. There, the gases mixed with hydrocarbons given of by trees. The addition of sunlight created plenty of ozone. What people needed were catalytic converters that also removed nitrogen oxides from exhausts. Actually, such converters have existed for many years. But they are much more expensive than standard converters. The auto industry was reluctant to install the more costly devices. Industry spokespeople argued that regular converters had already substantially reduce air pollution, making the nitrogen oxide converters unnecessary (Chan, 1982).

In the 1980s, despite the widespread use of catalytic converters and other antipollution measures, air pollution increased again. And concentrations of low-level ozone grew faster than those of other pollutants. This was mainly because of a huge increase in the number of cars and trucks in the United States. The number of these vehicles increased by more than twenty-five million between 1980 and 1989. More vehicles burn more fuel. U.S. cars and trucks burned about three billion more gallons of gasoline per year in the mid-1980s than in the mid-1970s (Chan, 1982). All this extra fuel burning caused a rise in air contamination, including ozone pollution. On June 12,1989, President George Bush spoke to the nation’s governors about a new attack on air pollution. "Too many Americans breathe dirty air," he stated, urging every citizen to join the fight against air pollution (Baines, 1990). The president’s plan, a version of a bill debated in Congress for several years, called for stricter controls on exhausts from factory smokestacks and car tailpipes. He also proposed that more gas stations use pumps that prevent gasoline fumes from floating into the atmosphere. The plan called on gasoline companies to make a product that would be less likely to evaporate into the air. In addition, the president talked about the possibilities of alcohol fuels for cars and trucks.

This new plan also set goals for meeting ozone standards. All cities would have to meet the existing EPA low-level ozone standard by the year 2000. The exceptions would be the three cities with the worst smog problems- Los Angeles, New York, and Houston. These cities would have until the year 2010 to comply with the ozone standards. President Bush and Congress finally agreed on the plan in 1990. On November 15, 1990, Bush signed into law what has been hailed as the most comprehensive air pollution measure introduced so far in the United States. The new Clean Air Act gives industry until the turn of the century to cut emissions of pollutants that cause smog and deplete the protective ozone layer. This includes complete phaseout of CFCs. The bill also requires manufactures to produce cars and fuels that pollute less or not at all.

Some officials feel the bill is not tough enough on ozone. California officials, for example, said they had hoped for even stricter standards on pollution created by cars, small construction equipment, and farm equipment. But other people praised the bill, saying it was a step in the right direction. Those concerned about low-level ozone were especially pleased that the bill required car manufactures to design vehicles that burn fuels other than gasoline. One of the most frequently mentioned for these alternative fuels is alcohol. The idea of using alcohol as a furl is not new. Alcohol-burning cars were designed by several companies in the 1960s. Brazil began large-scale use of such cars more than ten years ago. As a result of these practices, low-level ozone and smog caused by cars in many Brazilian cities significantly decreased in the 1980s. In the United States, some peopled have been using alcohol fuels since the 1970s. They buy a product called gasohol, a mixture of ethanol and gasoline. Gasohol can be used in most car and truck engines, but it presently available at only a limited number of service stations. American vehicles that run strictly on alcohol are even harder to find. However, using alcohol as a fuel does have its drawbacks. Although alcohol fuels like ethanol burn cleaner than gasoline and therefore causes less ozone pollution, they release formaldehyde into the air. Formaldehyde is a chemical known to cause cancer. So, the car designers are trying to eliminate these drawbacks of alcohol fuels (Baines, 1990).

However, the switch to alcohol is welcomed by environmentalists as a way of slowing global warming. Such fuels produce fewer greenhouse gases. Therefore, they could help reverse the warming trend that some scientists believe is steadily worsening. The use of alternative fuels is one of the steps proposed by the EPA to slow the greenhouse effect. The agency also proposed increasing the price of oil and other fossil fuels. The agency hopes this will encourages people to use less of these polluting substances and change to cleaner alternatives. The EPA has also suggested expanding the use of energy alternatives like solar and nuclear power. Neither produces low-level ozone or any other greenhouse gases.

Mnay chemical companies work on research and development of new products that will replace halons and CFCs. One example is a new type of technology for refrigeration. According to a report in Business Week, research scientists in the United and Japan are developing devices that rely on hydrogen and nickel-alloy "sponges". The units work because the sponges release and reabsorb hydrogen. When hydrogen is released, the metal cools off, chilling air that flows over it.

In other efforts, manufacturers are seeking ways to redesign mobile air conditioners so that there are fewer joints and tighter seals and valves, which would cut back on CFC emissions. CFCs also escape from mobile air conditioners during servicing, but if the coolant is recycled rather than allowed to evaporate, leakage of CFCs can be prevented (Baines, 1990). Removing the coolant from refrigerators and air conditioners before they are scrapped is another way to prevent the release of CFCs.

Also, a variety of businesses that use products manufactured with CFCs, such as foam packaging for foods, have begun to cut back on their purchases of CFC containers. One well-publicized example is McDonald’s. In August 1987, the company announced that it would phase out CFC-produced styrofoam packaging and use another type of container manufactured without the use of ozone-depleting chemicals (Baines, 1990).

Reducing levels of CFCs is also part of the worldwide effort to deal with the other major ozone-related problem-depletion of the upper ozone layer. After the discovery of the Antarctic ozone hole, people began to seriously consider limiting CFC production. In 1985, The United Nations brought together representatives from twenty-one countries to talk about CFC restrictions. Along with the United States, Japan and Western European countries, including Britain, West Germany, and France, are major producers and consumers of CFCs. The representatives of twenty-one nations, signed a agreement that essentially set up a framework for cooperative research on ozone depletion. The next step would be convincing the participation nations to sign a protocol, that would regulate use of CFCs and halons on a global scale (Baines, 1990).

Discussion

Individuals can begin by learning how human activities in a part of the world can have a global impact. Supporting environmental protection policies is one form of action you can take. Since dry-cleaning solvents release CFCs into the atmosphere, we could buy and wear clothing that is made form washable fabrics. You can also buy furniture products and food in containers that are not made with CFC foam. A home fire extinguisher does not have to contain halon-buy the type filled with a more environmentally safe chemical. All nations are responsible for contributing to recent changes in our atmosphere.

If the air conditioner in the family car needs service, ask the mechanic to check the hoses and replace them if they leak and to drain the coolant into a container that can be sealed so CFCs are not released by evaporation. When a refrigerator or home air conditioner needs to be discarded, find out if there is a safe way to remove the coolant before the appliance is smashed in a scrap metal yard or landfill.

Energy conservation is one action that almost everyone can undertake. During times of oil shortages, people have been well aware of the need to conserve fuel, whether used to operate motor vehicles or machinery of for heating or cooling. But it is more difficult to reduce the use of an air conditioner, cut back on home heating or use of the family car if there is little understanding about the need for such measures. On the other hand, if you could join with millions of people across the nation in conservation efforts designed to protect the environment from atmospheric pollutants, fossil fuel consumption- and the release of hazardous chemical substances-would certainly decrease.

Whatever each of us can do to protect our global commons, it seems crucial to begin those efforts now. No one can say how long it will take to bring ozone back into the balance it once maintained in nature. It will be a huge job. No single scientific breakthrough or legislative action will be enough. Large industries, small businesses, and individual citizens must all share in the task. This will sometimes involve throwing out old products and learning to use new, safer ones. Many people will have to alter their life- styles by conserving fuel and switching to cleaner and more efficient technologies.

Most important, ordinary people everywhere will need to become more conscious of the environment, more aware of how it can be damaged, and more educated about what is required to repair the damage already done. As Jack Fishman and Robert Kalish, authors of Global Alert: The ozone Pollution Crisis, put it, "Despite national borders and differences among peoples, we are all residents of the same smoke-filled room-the planet earth…and its continued existence is everyone’s responsibility".

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