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All around the earth there is a thick blanket of air called the atmosphere.
Air, like other gases, does not have a fixed shape. It spreads out to fill
any available space so nothing is really empty. But air cannot escape from
the atmosphere as the force of gravity keeps it from floating away from
Ever since people first gathered in settlements there has been pollution.
Pollution usually refers to the presence of substances that are either
present in the environment where it doesn't belong or at levels greater
than it should be.
Air pollution is caused by any undesirable substance, which enters the
atmosphere. Air pollution is a major problem in modern society. Even though
air pollution is usually a greater problem in cities, pollutants contaminate
air everywhere. These substances include various gases and tiny particles,
or particulates that can harm human health and damage the environment.
They may be gases, liquids, or solids. Many pollutants are given off into
the air as a result of human behavior. Pollution occurs on different levels:
personal, national, and global.
Some pollutants come from natural sources.
- Forest fires emit particulates, gases, and VOCs (substances that vaporize
into the atmosphere)
- Ultra-fine dust particles created by soil erosion when water and weather
loosen layers of soil, increase airborne particulate levels.
- Volcanoes spew out sulfur dioxide and large amounts of pulverized lava
rock known as volcanic ash.
The major types of air pollution are:
A different mix of vapors and
gaseous air pollutants is found in outdoor and indoor environments. The most
common gaseous pollutants are carbon dioxide, carbon monoxide, hydrocarbons,
nitrogen oxides, sulfur oxides and ozone. A number of sources produce these
chemical compounds but the major man-made source is the burning of fossil
fuel. Indoor air pollution is caused by cigarette smoking, the use of certain
construction materials, cleaning products, and home furnishings. Outdoor
gaseous pollutants come from volcanoes, fires, and industry, and in some
areas may be substantial. The most commonly recognized type of air pollution
is smog. Smog generally refers to a condition caused by the action of sunlight
on exhaust gases from motor vehicles and factories.
The Greenhouse effect prevents the sun's heat
from rising out of the atmosphere and flowing back into space. This warms
the earth's surface causing the green house effect. While a certain amount
of green house gases in the atmosphere are necessary to make the earth
warm, activities such as the burning of fossil fuels are creating a gaseous
layer that is too dense to allow the heat to escape. Many scientists believe
this is causing global warming. Other gases contributing to the problem
include chlorofluorocarbons (CFC), methane, nitrous oxides, and ozone.
Acid rain forms when moisture in the air interacts
with nitrogen oxide and sulfur dioxide released by factories, power plants,
and motor vehicles that burn coal or oil. This interaction of gases with
water vapor forms sulfuric acid and nitric acids. Eventually these chemicals
fall to earth as precipitation, or acid rain. Acid rain pollutants may
travel long distances, with winds carrying them thousands of miles before
they fall as dew, drizzle, fog, snow or rain.
Damage to the ozone layer is primarily caused
by the use of chlorofluorocarbons (CFCs). Ozone is a form of oxygen found
in the earth's upper atmosphere. The thin layer of ozone molecules in the
atmosphere absorb some of the sun's ultraviolet (UV) rays before it reaches
the earth's surface, making life on earth possible. The depletion of ozone
is causing higher levels of UV radiation on earth, endangering both plants
Particulate matter is the general term used
for a mixture of solid particles and liquid droplets found in the air.
Some particles are large or dark enough to be seen as soot or smoke. Others
are so small they can be detected only with an electron microscope. When
particulate matter is breathed in, it can irritate and damage the lungs
causing breathing problems. Fine particles are easily inhaled deeply into
the lungs where they can be absorbed into the blood stream or remain embedded
for long periods of time.
Climatic effects: Normally pollutants rise or
flow away from their sources without building up to unsafe levels. Wind
patterns, clouds, rain, and temperature can affect how quickly pollutants
move away from an area. Weather patterns that can trap air pollution in
valleys or move it across the globe may be able to damage pristine environments
far from the original sources.
The Air Quality Index
The Air Quality Index is a tool used by EPA and other agencies to provide
the public with timely and easy-to-understand information on local air
quality and whether air pollution levels pose a health concern. The AQI
tells the public how clean the air is and whether or not they should be
concerned for their health. The AQI is focused on health effects that can
happen within a few hours or days after breathing polluted air.
How does air pollution affect me?
Many studies have shown links between pollution and health effects. Increases
in air pollution have been linked to decreases in lung function and increases
in heart attacks. High levels of air pollution according to the EPA Air
Quality Index directly affect people with asthma and other types of lung
or heart disease. Overall air quality has improved in the last 20 years
but urban areas are still a concern. The elderly and children are especially
vulnerable to the effects of air pollution.
The level of risk depends on several factors:
- the amount of pollution in the air,
- the amount of air we breathe in a given time
- our overall health.
Other, less direct ways people are exposed to air pollutants are:
- eating food products contaminated by air toxins that have been deposited
where they grow,
- drinking water contaminated by air pollutants,
- ingesting contaminated soil, and
- touching contaminated soil, dust or water.