Geography Reference
In-Depth Information
One of the other nasty little chemicals we have been spewing out into the atmosphere is a compund called
a
chlorofluorocarbon,
or CFC, and it is also considered a greenhouse gas along with carbon dioxide and
methane. But another proven effect of CFCs is the “Antarctic donut,” a huge hole in the atmosphere's
ozone layer over the South Pole. This ozone hole opens over Antarctica every southern spring. It is as wide
as the United States and as deep as Mount Everest is tall. The discovery of the Antarctic donut in October
1982 caught many scientists by surprise. Computers on a satellite measured the hole, but scientists rejected
the data as too unlikely. Recent data also suggest that another tear in the ozone fabric may be taking place
in the Northern Hemisphere.
At first glance, the ozone layer doesn't sound very appealing. In fact, it is a shroud of poison enveloping
the earth. A form of oxygen, ozone is highly toxic; less than one part per million of the blue-tinged gas
in air is poisonous to humans. Near ground level, it is a pollutant that helps form smog. But far above, in
the stratosphere, it forms a lifesaving screen on which all life depends. Ozone is the only gas in the atmo-
sphere that can screen out the lethal ultraviolet rays of the sun. If it were not for this thin screen of ozone,
ultraviolet radiation would kill all terrestrial life.
Small amounts of ultraviolet radiation do get through this fragile filter. It is the main cause of skin can-
cer, a rapidly increasing disease that already kills some twelve thousand people a year in the United States
alone. Dermatologists in the United States are already seeing many more cases of skin cancers among
teenaged and adolescent patients. Ultraviolet radiation suppresses the immune system, helping cancers to
become established and grow, and increases susceptibility to other diseases. It is a major cause of cataracts,
which blind at least 12 million people worldwide and damage the sight of at least another 18 million. This
radiation also diminishes crop yields and kills ocean microorganisms that serve as food for other species.
There is no question that damaging the ozone layer even slightly will increase the toll on human health.
The greatest danger to the ozone layer comes from CFCs—outstandingly useful and versatile chemic-
als. They were first developed as coolants and played an essential role in the implementation of air condi-
tioning and refrigeration. They were then introduced as aerosol propellants. But every CFC molecule lives
on to destroy thousands of molecules of ozone.
It will be a long time before the ozone returns. U.S. Environmental Protection Agency analyses suggest
that, even if all ozone-depleting chemicals are phased out, it will take a century for conditions in the atmo-
sphere to return to what they were in 1986. But the world did move quickly to agree to phase out the chem-
icals once their dangers were demonstrated. The DuPont Company, the largest producer of CFCs, voluntar-
ily pledged to phase out CFC production, probably an unprecedented example of corporate responsibility.
Action on CFCs offers one of the first hopeful precedents for international action on other environmental
threats.
We are just left to wonder if it is too little, too late.
What Is Acid Rain?
First described in 1872 by an English chemist, acid rain stands as one of the industrialized world's nastiest
problems, the most controversial form of air pollution in the developed world. It is bitterly ironic that
something we think of as so generally positive—gently falling rain—is like taking a shower in battery acid.
Seemingly simple “rainfall” is degrading and destroying both nature and the achievements of humanity.
Acid rain, including acid sleet and snow, is produced primarily by the release of sulfur oxides into the
atmosphere. The chief sources of such emissions are electrical generating plants, industrial boilers, and
large smelters. Gases that are vented into the air by tall smokestacks get caught up in prevailing winds
where, in the course of transport over land, they are transformed into dilute solutions of sulfuric acid and
