Air Pollution

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CFish

Mr. Nollen

Biology 2B

8 May, 1996

Air Pollution

The Problem

Contamination of the atmosphere by gaseous, liquid, or solid wastes

or by-products that can endanger human health and the health and welfare

of plants and animals, or can attack materials, reduce visibility, or produce

undesirable odors. Among air pollutants emitted by natural sources, only

the radioactive gas radon is recognized as a major health threat. A

byproduct of the radioactive decay of uranium minerals in certain kinds of

rock, radon seeps into the basements of homes built on these rocks.

According to recent estimates by the U.S. government, 20 percent of the

homes in the U.S. harbor radon concentrations that are high enough to pose

a risk of lung cancer.





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Each year industrially developed countries generate billions of tons of

pollutants. The level is usually given in terms of atmospheric

concentrations or, for gases in terms of parts per million, that is, number of

pollutant molecules per million air molecules. Many come from directly

identifiable sources; sulfur dioxide, for example, comes from electric power

plants burning coal or oil. Others are formed through the action of sunlight

on previously emitted reactive materials. For example, ozone, a dangerous

pollutant in smog, is produced by the interaction of hydrocarbons and

nitrogen oxides under the influence of sunlight. Ozone has also caused

serious crop damage. On the other hand, the discovery in the 1980s that air

pollutants such as fluorocarbons are causing a loss of ozone from the earth's

protective ozone layer has caused the phasing out of these materials.


Current information about the problem

The tall smokestacks used by industries an utilities do not remove

pollutants but simply boost them higher into the atmosphere, thereby

reducing their concentration at the site. These pollutants may then be

transported over large distances and produce adverse effects in areas far

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from the site of the original emission. Sulfur dioxide and nitrogen oxide

emissions from the central and eastern U.S. are causing acid rain in New

York State, New England, and eastern Canada. The pH level, or relative

acidity, of many freshwater lakes in that region has been altered so

dramatically by this rain that entire fish populations have been destroyed.

Similar effects have been observed in Europe. Sulfur dioxide emissions and

the subsequent formation of sulfuric acid can also be responsible for the

attack on limestone and marble at large distances from the source.

The worldwide increase in the burning of coal and oil since the late

1940s has led to ever increasing concentrations of carbon dioxide. The

resulting "greenhouse effect", which allows solar energy to enter the

atmosphere but reduces the remission of infrared radiation from the earth,

could conceivably lead to a warning trend that might affect the global

climate and lead to a partial melting of the polar ice caps. Possibly an

increase in cloud cover or absorption of excess carbon dioxide by the
oceans

would check the greenhouse effect before it reached the stage of polar

melting. Nevertheless, research reports released in the U.S. in the 1980s


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indicate that the greenhouse effect is definitely under way and that the


nations of the world should be taking immediate steps to deal with it.

History

In the U.S. the Clean Air Act of 1967 as amended in 1970, 1977, and

1990 is the legal basis for air-pollution control throughout the U.S. The

Environmental Protection Agency has primary responsibility for carrying

out the requirements of the act, which specifies that air-quality standards be

established for hazardous substances. These standards are in the form of

concentration levels that are believed to be low enough to protect public

health. Source emission standards are also specified to limit the discharge

of pollutants into the air so that air-quality standards will be achieved. The

act was also designed to prevent significant deterioration of air quality in

areas where the air is currently cleaner than the standards require. The

amendments of 1990 identify ozone, carbon monoxide, particulate matter,

acid rain, and air toxins as major air pollution problems. On the

international scene, 49 countries agreed in March 1985 on a United Nations

convention to protect the ozone layer. This "Montreal Protocol," which was


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renegotiated in 1990, calls for the phaseout of certain chlorocarbons and

fluorocarbons by the year 2000 and provides aid to developing countries in

making this transition.





References

Encarta 95, New Groilers Encyclopedia,

Comptons, ABC News (magazine), Chicago Tribune

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