"I'm going out for a breath of fresh air" seems to be a phrase we often hear throughout out lives. Unfortunately, in today's world, that "fresh air" isn't exactly fresh. As a result of increasing traffic, city size, economic development, and industrialization, we have more air pollution problems than ever before. A formal definition of air pollution is as follows:
             The presence in the atmosphere of one or more contaminants in such quality and for such duration as is injurious, or tends to be injurious, to human health or welfare, animal or plant life.
             Air pollution can cause health problems and can also damage the natural world. So, who are the main contributors to air pollution? In cities, where air pollution is the worst, transportation is one of the major causes. The combustion of gasoline in automobiles, trucks, and airplanes produces a number of major pollutants into the air. Some of these contaminants include carbon monoxide, nitrogen oxides, gaseous hydrocarbons, and lead. When exposed to sunlight, many of these chemicals combine to form additional pollutants that are very harmful. One of these contaminants, nitrogen dioxide, creates smog in the air.
             In addition to transportation, the burning of fossil fuels also play a role in the high amounts of air pollution in cities. Fossil fuels are burned in generating stations, factories, office buildings, and homes. This particular combustion produces large amounts of ash, soot, and other particulates responsible for much of the smog you see in cities. In addition to the smog, the burning of fossil fuels also produces large amounts of sulfur oxides that can be damaging for anything from plants to buildings.
             Consequently, there are more and more health problems arising from the increasing amounts of pollution. Small children and the elderly are most likely to feel the effects. Some of the short-term effects include irritat
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