Pollutant
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Sources
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Effects
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Ozone. A gas that can be found in two places. Near the
ground (the troposphere), it is a major part of smog. The harmful ozone in
the lower atmosphere should not be confused with the protective layer of
ozone in the upper atmosphere (stratosphere), which screens out harmful
ultraviolet rays.
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Ozone is not created directly, but is formed when nitrogen
oxides and volatile organic compounds mix in sunlight. That is why ozone is
mostly found in the summer. Nitrogen oxides come from burning gasoline, coal,
or other fossil fuels. There are many types of volatile organic compounds,
and they come from sources ranging from factories to trees.
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Ozone near the ground can cause a number of health problems.
Ozone can lead to more frequent asthma attacks in people who have asthma and
can cause sore throats, coughs, and breathing difficulty. It may even lead to
premature death. Ozone can also hurt plants and crops.
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Carbon monoxide. A gas that comes from the burning of
fossil fuels, mostly in cars. It cannot be seen or smelled.
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Carbon monoxide is released when engines burn fossil fuels.
Emissions are higher when engines are not tuned properly, and when fuel is
not completely burned. Cars emit a lot of the carbon monoxide found outdoors.
Furnaces and heaters in the home can emit high concentrations of carbon
monoxide, too, if they are not properly maintained.
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Carbon monoxide makes it hard for body parts to get the oxygen
they need to run correctly. Exposure to carbon monoxide makes people feel
dizzy and tired and gives them headaches. In high concentrations it is fatal.
Elderly people with heart disease are hospitalized more often when they are
exposed to higher amounts of carbon monoxide.
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Nitrogen dioxide. A reddish-brown gas that comes from
the burning of fossil fuels. It has a strong smell at high levels.
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Nitrogen dioxide mostly comes from power plants and cars.
Nitrogen dioxide is formed in two ways—when nitrogen in the fuel is
burned, or when nitrogen in the air reacts with oxygen at very high
temperatures. Nitrogen dioxide can also react in the atmosphere to form
ozone, acid rain, and particles.
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High levels of nitrogen dioxide exposure can give people
coughs and can make them feel short of breath. People who are exposed to
nitrogen dioxide for a long time have a higher chance of getting respiratory
infections. Nitrogen dioxide reacts in the atmosphere to form acid rain,
which can harm plants and animals.
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Particulate matter. Solid or liquid
matter that is suspended in the air. To remain in the air, particles usually
must be less than 0.1-mm wide and can be as small as 0.00005 mm.
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Particulate matter can be divided into two types—coarse
particles and fine particles. Coarse particles are formed from sources like
road dust, sea spray, and construction. Fine particles are formed when fuel
is burned in automobiles and power plants.
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Particulate matter that is small enough can enter the lungs
and cause health problems. Some of these problems include more frequent
asthma attacks, respiratory problems, and premature death.
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Sulfur dioxide. A corrosive gas that cannot be seen or
smelled at low levels but can have a “rotten egg” smell at high levels.
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Sulfur dioxide mostly comes from the burning of coal or oil in
power plants. It also comes from factories that make chemicals, paper, or
fuel. Like nitrogen dioxide, sulfur dioxide reacts in the atmosphere to form
acid rain and particles.
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Sulfur dioxide exposure can affect people who have asthma or
emphysema by making it more difficult for them to breathe. It can also
irritate people's eyes, noses, and throats. Sulfur dioxide can harm trees and
crops, damage buildings, and make it harder for people to see long distances.
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Lead. A blue-gray metal that is very toxic and is found
in a number of forms and locations.
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Outside, lead comes from cars in areas where unleaded gasoline
is not used. Lead can also come from power plants and other industrial
sources. Inside, lead paint is an important source of lead, especially in
houses where paint is peeling. Lead in old pipes can also be a source of lead
in drinking water.
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High amounts of lead can be dangerous for small children and
can lead to lower IQs and kidney problems. For adults, exposure to lead can
increase the chance of having heart attacks or strokes.
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Toxic air pollutants. A large number of chemicals that are
known or suspected to cause cancer. Some important pollutants in this
category include arsenic, asbestos, benzene, and dioxin.
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Each toxic air pollutant comes from a slightly different
source, but many are created in chemical plants or are emitted when fossil
fuels are burned. Some toxic air pollutants, like asbestos and formaldehyde,
can be found in building materials and can lead to indoor air problems. Many
toxic air pollutants can also enter the food and water supplies.
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Toxic air pollutants can cause cancer. Some toxic air
pollutants can also cause birth defects. Other effects depend on the
pollutant, but can include skin and eye irritation and breathing problems.
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Stratospheric ozone depleters. Chemicals that
can destroy the ozone in the stratosphere. These chemicals include
chlorofluorocarbons (CFCs), halons, and other
compounds that include chlorine or bromine.
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CFCs are used in air conditioners and refrigerators, since
they work well as coolants. They can also be found in aerosol cans and fire extinguishers.
Other stratospheric ozone depleters are used as
solvents in industry.
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If the ozone in the stratosphere is destroyed, people are
exposed to more radiation from the sun (ultraviolet radiation). This can lead
to skin cancer and eye problems. Higher ultraviolet radiation can also harm
plants and animals.
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Greenhouse gases.Gases that stay in the
air for a long time and warm up the planet by trapping sunlight. This is
called the “greenhouse effect” because the gases act like the glass in a
greenhouse. Some of the important greenhouse gases are carbon dioxide,
methane, and nitrous oxide.
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Carbon dioxide is the most important greenhouse gas. It comes
from the burning of fossil fuels in cars, power plants, houses, and industry.
Methane is released during the processing of fossil fuels, and also comes
from natural sources like cows and rice paddies. Nitrous oxide comes from
industrial sources and decaying plants.
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The greenhouse effect can lead to changes in the climate of
the planet. Some of these changes might include more temperature extremes,
higher sea levels, changes in forest composition,
and damage to land near the coast. Human health might be affected by diseases
that are related to temperature or by damage to land and water.
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