Air pollution and air quality has been a topic of concern for decades
             in the United States. While great progress has been made toward cleaning
             up our air, there is still much left to do to make air quality healthful
             for the country's citizens. These experts note, "The United States has
             achieved remarkable progress in reducing air pollution since the Clean Air
             Act was established in 1970" (Mangun and Henning 229). However, most large
             cities still experience many days each year where air quality is
             unhealthful, and these days can lead to health and breathing problems for
             many residents.
             What causes air pollution' One of the major causes of unhealthy air
             is automobile emissions, and emissions from factories, power plants, and
             other industries. Fossil fuels are one of the biggest problems in
             controlling air pollution. Industries and homes that burn fossil fuels
             also contaminate the atmosphere, and these fuels must be replaced with
             cleaner technologies, such as solar and wind power, and other forms of
             power that are less costly in monetary and air pollution terms. The
             remainder of these dirty fuels accumulates in the atmosphere. Often they
             are invisible, but more often, when the accumulate in enough numbers; they
             become the glaze of smog that hangs over most large cities in the United
             States. In times of temperature inversion, when heat rises and traps
             colder air underneath, air pollution and ozone emissions can be trapped in
             valleys, creating a dangerous situation for the area's air quality. As the
             Utah Air Quality Web site notes, "Ozone is an invisible gas caused by
             vehicle emissions in the presence of sunlight and hot temperatures. [â€]
             Continued exposure to ozone can cause breathing problems, reduce lung
             function, irritate eyes and nasal passages and reduce resistance to colds
             and other infections" ("Air Quality"). Poor air quality can also
             exacerbate existing conditions such ...