The chapter began with a survey of
major air pollutants, which include sulfur compounds, nitrogen
oxides, ozone, carbon monoxide, volatile organic compounds, heavy
metals, and particulate matter. Air quality indoors may be compromised
by a number of pollutants contained in building materials, furniture,
paint, cleaning materials and insecticides, as well as second-hand
smoke.
Temperature, in particular the atmosphere's
vertical temperature profile at a locale, greatly affects the
dispersion of pollutants from their sources. When the environmental
air temperature increases upward, a condition known as a temperature
inversion, the air is stable and little vertical mixing occurs.
In contrast, when the environmental air temperature cools rapidly
with height, vertical mixing is vigorous. Winds are important dispersers of
air pollutants. However, while winds may bring relief to locales
close to the pollution source, they may cause pollution problems
elsewhere. The transport of sulfur compounds from sources in the
Midwest to the Northeast and eastern Canada is an example. Topography also shapes the dispersal
of air pollutants. The pollution-prone Los Angeles basin, flanked
by mountains to the east and cool water to the west, is a prime
example.
The Clean Air Act, enacted in 1970 and updated in 1990, has served
as an important tool in the struggle to improve air quality in
the U.S. The EPA, which was created in 1970, sets air quality
standards, monitors pollution levels, and seeks compliance of
violators. Acid deposition, mainly the result
of SO2 and NOx emissions, is a serious environmental
and health problem in many cities and over much of the eastern
United States and Canada. Some slight improvement has been noted
recently, but the problem is far from solved.
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