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The layer closest to the earth is called the troposphere. It extends up to ten miles above the surface of the earth. Over the troposphere is the stratosphere which extends from ten to forty miles above the earth ( Gutnick pg. 9). Ozone is a part of the stratosphere that blocks the sun’s harmful ultraviolet rays from reaching the earth. Over the stratosphere is the ionosphere which extends up to 400 miles ( Sandak pg. 37 ). In the ionosphere, the gases are broken into individual electrically charged particles called ions ( Gutnik pg. 9 ) Air, as we know, is the mixture of gases in the troposphere closest to the surface of the earth. It is mainly composed of nitrogen (78%), oxygen (21%), carbon dioxide (0.02%), argon and other rare gases (0.08%). Air pollution takes place when undesirable gases and particles mixes with the air to cause harmful effects on living and non-living things ( Becklake pg. 6 ). There are many types of air pollutants which can be put under three basic categories. These are - gaseous, particulates, and aerosol. Gaseous pollutants is any harmful gas that mixes into the air. Gaseous pollutants could be divided into four major groups. These are - carbon based gases, sulfur based gases, ozone, and nitrogen based gases ( Gutnik pg. 15 ). Carbon based gases include carbon dioxide (CO2), carbon monoxide (CO), and methane (CH4). Although carbon dioxide is found naturally in small quantity in the air, increased levels of this gas produced by the burning of fossil fuels will upset the temperature balance of the earth through the greenhouse effect. Carbon monoxide is a colorless, odorless, and tasteless gas which is emitted through the process of incomplete combustion of fossil fuel. Carbon monoxide is a deadly gas that, when inhaled, combines with the blood and renders them incapable of carrying oxygen. Methane occurs as a principal ingredient in natural gas, and is produced by the bacterial decomposition of plant and animal matters. Methane in the troposphere absorbs heat and causes greenhouse effect ( Gutnik pg. 15). A sulfur based gas occurs mostly as sulfur dioxide (SO2) which is a colorless, tasteless, foul smelling , heavier-than-air gas. Besides naturally produced from activities of the volcanoes or decomposition of organic material in swamps, it also is produced by the burning of sulfur containing fossil fuels. Sulfur dioxide combines with water vapor in the air, forming sulfurous acid (H2SO3), a major component of acid rain ( Gutnik pg. 15). Ozone is a form of oxygen (O3) and a major air pollutant in the troposphere. It is very harsh and irritant to the lungs, and can be a serious problem for people with lung disorders. Ozone in the stratosphere, on the other hand, is good and acts as a filter to the sun’s harmful rays which can reach the earth’s surface, causing skin cancer to the human and damaging plant tissues ( Gutnik pg. 15). Nitrogen based gases include nitrogen oxide (NO), nitrogen dioxide (NO2) and nitric oxide (NO3). These are mainly produced by the incomplete combustion of fuel in gasoline and diesel engines, and industrial and power plants. These gases in the presence of light energy and hydrocarbon form a group of compounds called PAN ( peroxyacetyl nitrate) through photochemical process which are responsible for causing smog. They also combine with water vapors in the air to form nitric acid (HNO3) which is also a component of acid rain ( Gutnik pg. 16). Particulates that pollute the air come mostly from natural sources such as soil dust, pollen grain, volcanic and forest fire ashes and dust. Human activities also contribute considerably to air pollution. These mainly come from dust, soot, and ashes from combustion and incineration. Industry, mining, power generation, transportation and construction are sources of particulates in air pollution. Burning of fuels alone adds close to a billion tons of particulates in the air ( Sandak pg. 90). Particulates can cause breathing problem and other respiratory diseases. It can also act as an effective sun block by reflecting light back into the stratosphere, and thus preventing photosynthesis ( Gutnik pg. 18). Aerosol are also particles, but they are so tiny that they stay afloat in the air and are not easily pulled by the gravity to settle down. Smoke and fog are common examples of aerosol that occurs in the nature. The most common solid aerosol are mineral dusts, fly ash ( including metal dusts), sodium carbonate, calcium sulfate from industrial process, and sodium chloride from sea salt. Another major aerosol product is the CFC (chlorofluorocarbon) gas that was used as a propellant gas from pressurized cans. CFC gases, when released, tend to go upward and reach the stratosphere where it destroys the ozone layer ( Sandak pg. 28 ). Air pollution has many impacts on earth’s ecosystem. Clouds containing sulfur and nitrogen oxides form acids as they mix with water vapor, and cause acid rain. Acid rain clouds may be carried by the winds hundreds of miles away from their sources. This causes a problem because no one knows where it came from, and we can not fix it unless we know the source. Acid rain that is between ten and seventy times more acidic than unpolluted rain is common in much of North America and Europe. Acid rain directly affects many aspects of life. It can damage entire forests. Acid river water may flow into lakes, making them acidic. Some fish can adapt to higher acidity, but finally only the strong survive. Even soil that absorbs acid rain affects life. The birds that are fed from acidic soil may die. Solutions to this problem is being tested in many parts of the world ( Sandak pg. 26 ). Global warming through greenhouse effect can have a major impact on earth’s ecology. The gases that cause greenhouse effects are: carbon dioxide, CFCs, nitrogen oxides, and methane. These are known as greenhouse gases. Of these four gases, carbon dioxide accounts for more then 50% of greenhouse effect ( Sandak pg. 63 ). With the steady build-up of the greenhouse gases, the average worldwide temperature has risen about 1 degree Fahrenheit over the past 100 years. If the greenhouse gases continue to accumulate at the present rate, including the earth’s natural increase of temperature, scientists predict that the average temperature will increase dramatically in a short time ( Gay pg. 45 ). Global warming may cause more drought in certain areas and increased precipitation in other areas. Alterations in precipitation patterns can effect water supply and distribution, changing where crops grown and animals raised. Another expected impact of global warming is a rise in sea level brought by ice and snow melting that run off into the ocean. Scientists believe that oceans could expand thermally and warming could reduce water density and increase volume. Warmer oceans could bring about more severe hurricanes and other violent storms. Higher sea levels would erode or inundate shorelines, destroying homes, businesses, roads, and ports worldwide. Rising sea levels would also force salt water into lakes, rivers, streams, and groundwater sources. This will affect our supply of drinking water ( Gay pg. 48 ). The impact of ozone depletion is of great concern to everyone. the ozone depletion process begins when CFCs and other ozone-depletion substances ( ODS ) are allowed to be released in the atmosphere. Winds mix them in the troposphere and evenly distributes the gases. After a period of several years, CFC and ODS molecules reach the stratosphere and are broken by the ultraviolet rays releasing chlorine and bromine that eventually breaks the ozone into oxygen molecules (O2). It is estimated that one chlorine atom destroys 100,000 ozone atoms before finally removed from the stratosphere. The ozone filters out harmful ultraviolet rays (UV). Less ozone means higher levels of UV on earth. More depletion of ozone can cause larger increase of incoming UVs. UV has been linked to skin cancer, cataracts, damage to plastics and harm to certain crops. Some UV reaches the earth even without ozone depletion. With the ozone depleting, even more UV is entering earth ( “Air Pollution / OAR” pg. 2). Smog, a combination of smoke and fog, is basically a mixture of fog and some air pollutants. These air pollutants are nitrogen oxides, sulfur dioxide, carbon monoxide, ozone, and volatile organic compounds. Majority of these pollutants come from automobile exhausts which is the cause of smog in large cities like, Los Angeles, Chicago, New York, etc. Smog destroys vegetation and forests. It also affects human health causing irritation in eyes and lungs ( Gay pg. 18 ). Some pollutants, collectively known as hazardous air pollutants (HAPs), can cause toxic effects on human and other living things. Most HAPs are released from man-made sources, such as factories and automobiles. Toxic pollutants can cause serious health problems. For example vapor from gasoline can cause damage to brain and nervous systems ( “Air Pollution / OAR” pg. 4 ). To control air pollution in the United States, Congress passed the nation’s first Clean Air Act in 1963, which provided funds for state and local agencies to establish regulations for air quality. But the regulations were not adequate. By the end of the 1960s, it was clear that the national standards were needed. The Clean Air Act of 1970 addressed that need. One part of the federal law set standards for emissions of various chemical compounds from mobile and stationary sources like cars, aircrafts, industries and powerplants. In 1990, the Clean Air Act was changed further restricting release of a broader range of HAPs with lower limits ( “Air Pollution / OAR” pg. 4). The U.S. Environment Protection Agency ( EPA ) has the authority to identify HAPs and set standards for the amounts of these pollutants that may be emitted without endangering public health ( Gay pg. 12). The Clean Air Act also provided framework for ideas of alternate fuels to be used in cars and airplanes. It promotes the use of clean low sulfur coals and natural gas as well as technologies to clean high sulfur coal. The act also encourages to reduce energy waste and create market for clean fuel. The new law gives states more time to meet the air quality standard, for example up to 20 years for ozone in L.A. It requires states to make constant formidable progress reducing emissions. The act requires the Federal government to reduce emissions from all automobiles, consumer products, and from ships and barges during loading and unloading of petroleum. The new law also establishes a clean fuel car pilot program in California, requiring the phase-in of tighter emission limit for 150,000 vehicles in models 1996 and 300,000 by the model year 1999. These standards can be met with any combination of vehicle technology and cleaner fuels. The standards become stricter in the year 2001 ( “Air Pollution / OAR” pg. 5 ). With each year passing, the quality of earth’s air both improves and worsens. While science and technology makes some advances in the war against pollution, they also create and discover other air pollution problems that the world was unaware of previously. The growth of population is also a major factor for the increase of air pollution ( Gutnik pg. 49 ). To control the global air pollution, a joint effort by the national government of all the countries is necessary. As a step towards achieving this objective, an international agreement was signed in December, 1997, in Kyoto, Japan, for voluntary emission control of greenhouse gases. Under this agreement the United States is required to reduce greenhouse gas emission 7% below the 1990 level by the year 2012 ( Kyoto Conference pg. 1 ). Some people think that this will not only reduce air pollution, but also open up the opportunities for the U.S. companies to take a lead in developing environmental improvement technology and give them a competitive advantage in world market. Some, on the other hand, think that this will create a burden on the U.S. economy raising the prices of goods and services, when some of the countries like China, India, and Mexico might not even follow the voluntary restriction of greenhouse gas emission (Passacantando pg. A22 ). In the end, we must realize that though government regulation is one of the important ways of controlling and monitoring air pollution, a lot could be achieved by our own individual actions, such as walking or biking to go short distances, taking mass transit for commuting to and from work, practicing energy conservation, encouraging use of renewable energy, recycling wastes, planting and preserving trees, and last but not the least by taking birth control measures to reduce population growth, particularly, in developing countries. Bibliography: 1. Becklake, John Green Issues - Thinking for the Future: Pollution Gloucester Press, New York, 1990 2. Earth Negotiations Bulletin Kyoto Conference http:// www.iisd.ca/linkage/vollz/enb1276e.html, 1997 3. EPA Administrators Air Pollution / OAR http://www.epa.gov/oar/, 1996 4. Gay, Kathlyn Air Pollution Franklin Watts, New York, 1991 5. Gutnik, Martin The Challenge of Clean Air Enslow Publishers, Inc., New Jersey, 1990 6. Passacantando, John “A Pothole in the Ozone Layer” Washington Post March 1998: A22 7. Sandak, Cass A Reference Guide to Clean Air Enslow Publishers, Inc., New Jersey, 1990 Word Count: 2300
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