Besides destroying our quantities of oxygen, humans generate pollutants that reduce the quality of the atmosphere. People living in urban centers witness the daily flooding of the skies from smokestacks and automobiles. Since the industrial age began, pollution has become a by-product of our advancement. The most common effects of air pollution are poor visibility, irritated eyes, upper respiratory infections, unpleasant odors. Larger cities with a serious smog problem actually have daily alerts to instruct people considered at risk to stay indoors during peak times when the air is at its worst quality. ("Smog" was a word coined to describe the interaction of fog and smoke; but the increase of pollutants in the atmosphere is now such that fog is no longer necessary to the description of smog.)
Pollutant concentrates are reduced by atmospheric mixing, which depends on such weather conditions as temperature, wind speed, and the movement of high and low pressure systems and their interaction with the local topography. But sometimes a condition called an inversion occurs, in which a cold layer of air settles under a warm layer. This prevents an upward movement of air, atmospheric mixing is retarded and pollutants are trapped near the ground. It takes only three days of poor atmospheric mixing in high pollution areas to create life threatening conditions. An inversion over Donors, Pennsylvania in 1948 caused respiratory illnesses in over 6000 people and killed 20. In London in 1952, severe pollution took the lives of 5000 people. A disastrous combination of events occurred in Bhopal, India in December 1984. An industrial accident released methyl isocyanate into the air during an inversion. There were a reported 3300 deaths and at least 20,00 illnesses. Scientists are not sure of the long-term effects of low level exposure to pollution, but the experts have agreed that those at risk, which include the elderly, very young, smokers, workers whose jobs expose them to toxic materials, and individuals with heart or lung disease are the ones who end up in the hospitals with upper respiratory problems during days with poor atmospheric mixing or prolonged days of an inversion.
Like an inversion, acid rain is a natural phenomenon that is harmful to us only because of the pollutants we create. Rain and snow are naturally acidic. On the pH scale which measures acidity, 7 is considered neutral, while rain and snow have a pH balance of 5.6 and are considered slightly acidic. The "acid" in rain to which we refer is caused by the burning of fossil fuels, primarily by automobiles. The incomplete combustion of the fuel releases abundant quantities of sulfur into the air. Sulfur combines with oxygen to form sulfur dioxide, which in turn combines with water droplets in the air to become sulfuric acid, or "acid rain." This new combination of chemicls falls into our lakes, rivers, and soils. In the great chain of wilderness lakes that extends from northern Minnesota into Canada; in the Appalachians; and in much of Scandinavia, the precipitation of acid ice scoured right down to the bedrock, and new soil that has collected there is still quite thin. These regions are poor in the kind of natural alkaline rock, like limestone, that elsewhere helps to neutralize acid rain.
The incomplete combustion of fossil fuels also releases carbon dioxide into the atmosphere, and prevents radiation emitted by the earth from escaping into space. You will recall that the greenhouse effect, which acts as a blanket by returning terrestrial radiation to the surface, is essential to providing a livable temperature. But because of increased amounts of carbon dioxide, too much heat is being retained and a global warming is now taking place. Some scientists predict a melting of polar icecaps and an increase in the percentage of the earth covered by water (and conversely, a decrease in the land mass upon which humans, with an increasing population, habitate).
Similarly, air pollution has effected the stratosphere, specifically the ozone layer. Ozone, you remember, absorbs the shortwave, high energy ultraviolet radiation from the sun. Scientists in the 1970's discovered a "hole" in the ozone layer over Antarctica. In 1986 another hole was discovered over the Arctic. These areas allow ultraviolet radiation to pass through and into the troposphere. A marked increase in the incidence of skin cancer in humans is one of the results. Other possible effects are reduction of crop yields and of various forms of aquatic life found in the surface layer of oceans, streams and lakes. Scientists have agreed that the thinning of the atmosphere is a direct result of the use of freons, a synthetic compound containing carbon, fluorine, and chlorine atoms. When these compounds, otherwise known as chlorofluorocarbons (CFCs), are released into the atmosphere, the chlorine reacts with the ozone and destroys ozone molecules. CFCs are commonly found in refrigerants and aerosol spray cans.
It was projected that if the ultraviolet radiation increased at the observed rate over the neat 55 years, we would see a global warming of 4 degrees F. Although this may not seem like much to some, we know from our study that such a rise in temperature would have a great impact on every aspect of our environment. Understanding this, the United Nations Environmental Programme (UNEP) was established to have nations join forces to find solutions to the depletion of the ozone layer. The plan was to cut the consumption of CFCs by 50% by the year 1999. In 1988, the United States along with 31 other nations set a more ambitious goal. Fortunately, with the efforts of the two groups, UNEP and the Montreal Protocol, the organizations set a goal to reduce CFCs by 50% in 1995 and 85% by 1997. The National Aeronautics Science Academy (NASA) launched a 7-ton Upper Atmosphere Research Satellite whose purpose is to measure the ozone variations at different altitudes and provide a comprehensive picture of the upper atmosphere chemistry. Although a total ban of freons was called for, not all ozone-destroying chemicals have been eliminated. There are still some nitrous oxides in fertilizers and bromine halocarbons which can cause a breakdown in the ozone layer.
Pollution of the oceans is the result of sewage being drained directly into them. This pollution causes serious illnesses and even death to anyone who uses the oceans. Under-developed countries today don't have a proper waste disposal system and still use the oceans as a dumping ground for all types of wastes. This pollution can destroy all ocean life: plants, fish, mammals - virtually the entire food chain. Since the majority of precipitation originates as evaporated water from the oceans, rain water will be contaminated as it fill our lakes and rivers. Even when sewage is treated at a sewage treatment plant, a percentage, 10%-15%, is flushed into the oceans. This would equal about 24 trillion liters of partially contaminated waste that the United States dumps into the oceans each year. This is only the United States. What is the total world population dumping into the oceans each year? Not only are we polluting our atmosphere, we are depleting our oceans which support life.
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