Air Pollution Causes and Effects
By Tom
Socha
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01/22/2007
History
Humans probably first
experienced harm from air pollution when they built fires in
poorly ventilated caves. Since then we have gone on to pollute
more of the earth's surface. Until recently, environmental
pollution problems have been local and minor because of the
Earth's own ability to absorb and purify minor quantities of
pollutants. The industrialization of society, the introduction
of motorized vehicles, and the explosion of the population, are
factors contributing toward the growing air pollution problem.
At this time it is urgent that we find methods to clean up the
air.
The primary air pollutants
found in most urban areas are carbon monoxide, nitrogen oxides,
sulfur oxides, hydrocarbons, and particulate matter (both solid
and liquid). These pollutants are dispersed throughout the
world's atmosphere in concentrations high enough to gradually
cause serious health problems. Serious health problems can occur
quickly when air pollutants are concentrated, such as when
massive injections of sulfur dioxide and suspended particulate
matter are emitted by a large volcanic eruption.
Air
Pollution in the Home
You cannot escape air
pollution, not even in your own home. "In 1985 the Environmental
Protection Agency (EPA) reported that toxic chemicals found in
the air of almost every American home are three times more
likely to cause some type of cancer than outdoor air
pollutants". (Miller 488) The health problems in these buildings
are called "sick building syndrome". "An estimated one-fifth to
one-third of all U.S. buildings are now considered "sick".
(Miller 489) The EPA has found that the air in some office
buildings is 100 times more polluted than the air outside. Poor
ventilation causes about half of the indoor air pollution
problems. The rest come from specific sources such as copying
machines, electrical and telephone cables,
mold and
microbe-harboring air conditioning systems and ducts, cleaning
fluids, cigarette smoke, carpet, latex caulk and paint, vinyl
molding, linoleum tile, and building materials and furniture
that emit air pollutants such as formaldehyde. A major indoor
air pollutant is radon-222, a colorless, odorless, tasteless,
naturally occurring radioactive gas produced by the radioactive
decay of uranium-238. "According to studies by the EPA and the
National Research Council, exposure to radon is second only to
smoking as a cause of lung cancer". (Miller 489) Radon enters
through pores and cracks in concrete when
indoor air pressure is less than the pressure of gasses in
the soil. Indoor air will be healthier than outdoor air if you
use an
energy recovery ventilator to provide a consistent supply of
fresh filtered air and then
seal air leaks in the shell of your home .
Sources of Pollutants
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The two main sources of
pollutants in urban areas are transportation (predominantly
automobiles) and fuel combustion in stationary sources,
including residential, commercial, and industrial heating and
cooling and
coal-burning power plants. Motor vehicles produce high
levels of carbon monoxides (CO) and a major source of
hydrocarbons (HC) and nitrogen oxides (NOx). Whereas, fuel
combustion in stationary sources is the dominant source of
sulfur dioxide (SO2).
Carbon Dioxide
Carbon dioxide (CO2) is one of
the major pollutants in the atmosphere. Major sources of CO2 are
fossil fuels burning and deforestation. "The concentrations of
CO2 in the air around 1860 before the effects of
industrialization were felt, is assumed to have been about 290
parts per million (ppm). In the hundred years and more since
then, the concentration has increased by about 30 to 35 ppm that
is by 10 percent". (Breuer 67) Industrial countries account for
65% of CO2 emissions with the United States and Soviet Union
responsible for 50%. Less developed countries (LDCs), with 80%
of the world's people, are responsible for 35% of CO2 emissions
but may contribute 50% by 2020. "Carbon dioxide emissions are
increasing by 4% a year". (Miller 450)
In 1975, 18 thousand million
tons of carbon dioxide (equivalent to 5 thousand million tons of
carbon) were released into the atmosphere, but the atmosphere
showed an increase of only 8 billion tons (equivalent to 2.2
billion tons of carbon". (Breuer 70) The ocean waters contain
about sixty times more CO2 than the atmosphere. If the
equilibrium is disturbed by externally increasing the
concentration of CO2 in the air, then the oceans would absorb
more and more CO2. If the oceans can no longer keep pace, then
more CO2 will remain into the atmosphere. As water warms, its
ability to absorb CO2 is reduced.
CO2 is a good transmitter of
sunlight, but partially restricts infrared radiation going back
from the earth into space. This produces the so-called
greenhouse effect that prevents a drastic cooling of the Earth
during the night. Increasing the amount of CO2 in the atmosphere
reinforces this effect and is expected to result in a warming of
the Earth's surface. Currently carbon dioxide is responsible for
57% of the global warming trend. Nitrogen oxides contribute most
of the atmospheric contaminants.
N0X
- nitric oxide (N0) and nitrogen dioxide (N02)
- Natural component of the
Earth's atmosphere.
- Important in the
formation of both acid precipitation and photochemical smog
(ozone), and causes nitrogen loading.
- Comes from the burning of
biomass and fossil fuels.
- 30 to 50 million tons per
year from human activities, and natural 10 to 20 million
tons per year.
- Average residence time in
the atmosphere is days.
- Has a role in reducing
stratospheric ozone.
N20
- nitrous oxide
- Natural component of the
Earth's atmosphere.
- Important in the
greenhouse effect and causes nitrogen loading.
- Human inputs 6 million
tons per year, and 19 million tons per year by nature.
- Residence time in the
atmosphere about 170 years.
- 1700 (285 parts per
billion), 1990 (310 parts per billion), 2030 (340 parts per
billion).
- Comes from nitrogen based
fertilizers, deforestation, and biomass burning.
Sulfur and chlorofluorocarbons (CFCs)
Sulfur dioxide is produced by
combustion of sulfur-containing fuels, such as coal and fuel
oils. Also, in the process of producing sulfuric acid and in
metallurgical process involving ores that contain sulfur. Sulfur
oxides can injure man, plants and materials. At sufficiently
high concentrations, sulfur dioxide irritates the upper
respiratory tract of human beings because potential effect of
sulfur dioxide is to make breathing more difficult by causing
the finer air tubes of the lung to constrict. "Power plants and
factories emit 90% to 95% of the sulfur dioxide and 57% of the
nitrogen oxides in the United States. Almost 60% of the SO2
emissions are released by tall smoke stakes, enabling the
emissions to travel long distances". (Miller 494) As emissions
of sulfur dioxide and nitric oxide from stationary sources are
transported long distances by winds, they form secondary
pollutants such as nitrogen dioxide, nitric acid vapor, and
droplets containing solutions of sulfuric acid, sulfate, and
nitrate salts. These chemicals descend to the earth's surface in
wet form as rain or snow and in dry form as a gases fog, dew, or
solid particles. This is known as acid deposition or acid rain.
Chlorofluorocarbons (CFCs)
CFCs are lowering the average
concentration of ozone in the stratosphere. "Since 1978 the use
of CFCs in aerosol cans has been banned in the United States,
Canada, and most Scandinavian countries. Aerosols are still the
largest use, accounting for 25% of global CFC use". (Miller 448)
Spray cans, discarded or leaking refrigeration and air
conditioning equipment, and the burning plastic foam products
release the CFCs into the atmosphere. Depending on the type,
CFCs stay in the atmosphere from 22 to 111 years.
Chlorofluorocarbons move up to the stratosphere gradually over
several decades. Under high energy ultra violet (UV) radiation,
they break down and release chlorine atoms, which speed up the
breakdown of ozone (O3) into oxygen gas (O2).
Chlorofluorocarbons, also
known as Freons, are greenhouse gases that contribute to global
warming. Photochemical air pollution is commonly referred to as
"smog". Smog, a contraction of the words smoke and fog, has been
caused throughout recorded history by water condensing on smoke
particles, usually from burning coal. With the introduction of
petroleum to replace coal economies in countries, photochemical
smog has become predominant in many cities, which are located in
sunny, warm, and dry climates with many motor vehicles. The
worst episodes of photochemical smog tend to occur in summer.
Smog
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Photochemical smog is also
appearing in regions of the tropics and subtropics where savanna
grasses are periodically burned. Smog's unpleasant properties
result from the irradiation by sunlight of hydrocarbons caused
primarily by unburned gasoline emitted by automobiles and other
combustion sources. The products of photochemical reactions
includes organic particles, ozone, aldehydes, ketones,
peroxyacetyl nitrate, organic acids, and other oxidants. Ozone
is a gas created by nitrogen dioxide or nitric oxide when
exposed to sunlight. Ozone causes eye irritation, impaired lung
function, and damage to trees and crops. Another form of smog is
called industrial smog.
This smog is created by
burning coal and heavy oil that contain sulfur impurities in
power plants, industrial plants, etc... The smog consists mostly
of a mixture of sulfur dioxide and fog. Suspended droplets of
sulfuric acid are formed from some of the sulfur dioxide, and a
variety of suspended solid particles. This smog is common during
the winter in cities such as London, Chicago, Pittsburgh. When
these cities burned large amounts of coal and heavy oil without
control of the output, large-scale problems were witnessed. In
1952 London, England, 4,000 people died as a result of this form
of fog. Today coal and heavy oil are burned only in large
boilers and with reasonably good control or tall smokestacks so
that industrial smog is less of a problem. However, some
countries such as China, Poland, Czechoslovakia, and some other
eastern European countries, still burn large quantities of coal
without using adequate controls.
Pollution Damage to Plants
With the destruction and
burning of the rain forests more and more CO2 is being released
into the atmosphere. Trees play an important role in producing
oxygen from carbon dioxide. "A 115 year old Beech tree exposes
about 200,000 leaves with a total surface to 1200 square meters.
During the course of one sunny day such a tree inhales 9,400
liters of carbon dioxide to produce 12 kilograms of
carbohydrate, thus liberating 9,400 liters of oxygen. Through
this mechanism about 45,000 liters of air are regenerated which
is sufficient for the respiration of 2 to 3 people". (Breuer 1)
This process is called photosynthesis which all plants go though
but some yield more and some less oxygen. As long as no more
wood is burnt than is reproduced by the forests, no change in
atmospheric CO2 concentration will result.
Pollutants such as sulfur
dioxide, nitrogen oxides, ozone and peroxyacl nitrates (PANs),
cause direct damage to leaves of crop plants and trees when they
enter leaf pores (stomates). Chronic exposure of leaves and
needles to air pollutants can also break down the waxy coating
that helps prevent excessive water loss and damage from
diseases, pests, drought and frost. "In the midwestern United
States crop losses of wheat, corn, soybeans, and peanuts from
damage by ozone and acid deposition amount to about $5 billion a
year". (Miller 498)
Reducing Pollution
You can help to reduce global
air pollution and
climate
change by
driving a car that gets at least 35 miles a gallon, walking,
bicycling, and using mass transit when possible. Replace
incandescent light bulbs with compact fluorescent bulbs,
make your home more energy efficient, and buy only energy
efficient appliances. Recycle newspapers, aluminum, and other
materials. Plant trees and avoid purchasing products such as
Styrofoam that contain CFCs. Support much stricter clean air
laws and enforcement of international treaties to reduce ozone
depletion and slow global warming.
Earth is everybody's home and
nobody likes living in a dirty home. Together, we can make the
earth a cleaner, healthier and more pleasant place to live.
Works
Cited:
- Breuer, Georg, Air in
Danger: Ecological Perspectives of the Atmosphere. New
York: Cambridge University Press, 1980
- Stewart, T. Charles,
Air Pollution, Human Health and Public Policy. New York:
Lexington Books, 1979
- Miller, G. Tyler,
Living in the Environment: an introduction to environmental
science. Belmont: Wadsworth, 1990.
Additional
Sources of Information:
NOTE: You can
help to reduce air pollution by improving energy efficiency so
that less fossil fuel is burned. This will help you to endure
the oil
shortages and
natural gas shortages. |
