Ozone
Ozone (O3) is a gas composed of three oxygen atoms. It is not
usually emitted directly into the air, but at ground level is
created by a chemical reaction between oxides of nitrogen (NOx)
and volatile organic compounds (VOC) in the presence of heat and
sunlight. Ozone has the same chemical structure whether it occurs
miles above the earth or at ground level and can be "good"
or "bad," depending on its location in the atmosphere.
"Good" ozone occurs naturally in the stratosphere approximately
10 to 30 miles above the earth's surface and forms a layer that
protects life on earth from the sun's harmful rays. In the earth's
lower atmosphere, ground-level ozone is considered "bad."
VOC + NOx + Heat + Sunlight = Ozone
Motor vehicle exhaust and industrial emissions, gasoline vapors,
and chemical solvents are some of the major sources of NOx and
VOC, that help to form ozone. Sunlight and hot weather cause ground-level
ozone to form in harmful concentrations in the air. As a result,
it is known as a summertime air pollutant. Many urban areas tend
to have high levels of "bad" ozone, but even rural areas
are also subject to increased ozone levels because wind carries
ozone and pollutants that form it hundreds of miles away from
their original sources.
Ground-level ozone even at low levels can adversely affect everyone.
It can also have detrimental effects on plants and ecosystems.
| Health Problems |
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Ozone can irritate lung airways and cause inflammation
much like a sunburn. Other symptoms include wheezing, coughing,
pain when taking a deep breath, and breathing difficulties
during exercise or outdoor activities. People with respiratory
problems are most vulnerable, but even healthy people that
are active outdoors can be affected when ozone levels are
high. |
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Repeated exposure to ozone pollution for several months
may cause permanent lung damage. Anyone who spends time outdoors
in the summer is at risk, particularly children and other
people who are active outdoors. |
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Even at very low levels, ground-level ozone triggers a variety
of health problems including aggravated asthma, reduced lung
capacity, and increased susceptibility to respiratory illnesses
like pneumonia and bronchitis. |
| Plant and Ecosystem Damage |
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Ground-level ozone interferes with the ability of plants
to produce and store food, which makes them more susceptible
to disease, insects, other pollutants, and harsh weather. |
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Ozone damages the leaves of trees and other plants, ruining
the appearance of cities, national parks, and recreation areas. |
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Ozone reduces crop and forest yields and increases plant
vulnerability to disease, pests, and harsh weather |
Particulate matter,
or PM, is the term for particles found in the air, including
dust, dirt, soot, smoke, and liquid droplets. Particles
can be suspended in the air for long periods of time. Some
particles are large or dark enough to be seen as soot or
smoke. Others are so small that individually they can only
be detected with an electron microscope.
Some particles are directly emitted
into the air. They come from a variety of sources such as
cars, trucks, buses, factories, construction sites, tilled
fields, unpaved roads, stone crushing, and burning of wood.
Other particles may be formed in the
air from the chemical change of gases. They are indirectly
formed when gases from burning fuels react with sunlight
and water vapor. These can result from fuel combustion in
motor vehicles, at power plants, and in other industrial
processes. |
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Particulate Matter causes a wide variety
of health and environmental impacts.
Health effects
Many scientific studies have linked breathing PM to a series of
significant health problems, including:
- aggravated asthma
- increases in respiratory symptoms like coughing and difficult
or painful breathing
- chronic bronchitis
- decreased lung function
- premature death
Visibility impairment
PM is the major cause of reduced visibility (haze)
Carbon
monoxide, or CO, is a colorless,
odorless gas that is formed when carbon in fuel is not burned
completely. It is a component of motor vehicle exhaust,
which contributes about 56 percent of all CO emissions nationwide.
Other non-road engines and vehicles (such as construction
equipment and boats) contribute about 22 percent of all
CO emissions nationwide. Higher levels of CO generally occur
in areas with heavy traffic congestion. In cities, 85 to
95 percent of all CO emissions may come from motor vehicle
exhaust. Other sources of CO emissions include industrial
processes (such as metals processing and chemical manufacturing),
residential wood burning, and natural sources such as forest
fires. Woodstoves, gas stoves, cigarette smoke, and unvented
gas and kerosene space heaters are sources of CO indoors.
The highest levels of CO in the outside air typically occur
during the colder months of the year when inversion conditions
are more frequent. The air pollution becomes trapped near
the ground beneath a layer of warm air.
Chief Causes for Concern
CO is poisonous even to healthy people
at high levels in the air. Additionally, it can affect people with
heart diseasecan and the central nervous system.
Carbon monoxide can
cause harmful health effects by reducing oxygen delivery to the
body's organs (like the heart and brain) and tissues.
Cardiovascular Effects
The health threat from lower levels of CO is most serious
for those who suffer from heart disease, like angina, clogged
arteries, or congestive heart failure. For a person with heart
disease, a single exposure to CO at low levels may cause chest
pain and reduce that person's ability to exercise; repeated exposures
may contribute to other cardiovascular effects.
Central Nervous System Effects
Even healthy people can be affected by high levels of CO. People
who breathe high levels of CO can develop vision problems, reduced
ability to work or learn, reduced manual dexterity, and difficulty
performing complex tasks. At extremely high levels, CO is poisonous
and can cause death.
Smog
CO contributes to the formation of smog ground-level ozone, which
can trigger serious respiratory problems.
Nitrogen oxides, or
NOx, is the generic term for a group of highly reactive gases,
all of which contain nitrogen and oxygen in varying amounts. Many
of the nitrogen oxides are colorless and odorless. However, one
common pollutant, nitrogen dioxide (NO2) along with particles
in the air can often be seen as a reddish-brown layer over many
urban areas.
Nitrogen oxides form when fuel is burned at high temperatures,
as in a combustion process. The primary sources of NOx are motor
vehicles, electric utilities, and other industrial, commercial,
and residential sources that burn fuels.
| Nox |
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is one of the main ingredients involved in the formation
of ground-level ozone, which can trigger serious respiratory
problems |
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reacts to form nitrate particles, acid aerosols, as well
as NO2, which also cause respiratory problems |
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contributes to formation of acid rain |
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contributes to nutrient overload that deteriorates water
quality |
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contributes to atmospheric particles, that cause visibility
impairment most noticeable in national parks |
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reacts to form toxic chemicals |
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contributes to global warming |
NOx and the pollutants formed from
NOx can be transported
NOx causes a wide variety
of health and environmental impacts because of various compounds
and derivatives in the family of nitrogen oxides, including nitrogen
dioxide, nitric acid, nitrous oxide, nitrates, and nitric oxide.
Ground-level Ozone (Smog)
- is formed when NOx and volatile organic compounds (VOCs) react
in the presence of heat and sunlight. Children, people with lung
diseases such as asthma, and people who work or exercise outside
are susceptible to adverse effects such as damage to lung tissue
and reduction in lung function. Ozone can be transported by wind
currents and cause health impacts far from original sources.
Particles - NOx reacts with
ammonia, moisture, and other compounds to form nitric acid and
related particles. Human health concerns include effects on breathing
and the respiratory system, damage to lung tissue, and premature
death. Small particles penetrate deeply into sensitive parts of
the lungs and can cause or worsen respiratory disease such as
emphysema and bronchitis, and aggravate existing heart disease.
Toxic Chemicals - In the
air, NOx reacts readily with common organic chemicals and even
ozone, to form a wide variety of toxic products, some of which
may cause biological mutations. Examples of these chemicals include
the nitrate radical, nitroarenes, and nitrosamines
Sulfur dioxide, or
SO2, belongs to the family of sulfur oxide gases (SOx). These
gases dissolve easily in water. Sulfur is prevalent in all raw
materials, including crude oil, coal, and ore that contains common
metals like aluminum, copper, zinc, lead, and iron. SOx gases
are formed when fuel containing sulfur, such as coal and oil,
is burned, and when gasoline is extracted from oil, or metals
are extracted from ore. SO2 dissolves in water vapor to form acid,
and interacts with other gases and particles in the air to form
sulfates and other products that can be harmful to people and
their environment.
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SO2 contributes to respiratory illness, particularly in
children and the elderly, and aggravates existing heart and
lung diseases |
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SO2 contributes to the formation of acid rain, which damages
trees, crops, historic buildings, and monuments and makes
soils, lakes, and streams acidic |
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SO2 contributes to the formation of atmospheric particles
that cause visibility impairment, most noticeably in national
parks |
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SO2 can be transported over long distances.
SO2 and the pollutants formed from SO2, such as sulfate particles,
can be transported over long distances and deposited far from
the point of origin. This means that problems with SO2 are
not confined to areas where it is emitted |
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Short-term Peak Levels
High levels of SO2emitted over a short period, such as a day,
can be particularly problematic for people with asthma. EPA
encourages communities to learn about the types of industries
in their communities and to work with local industrial facilities
to address pollution control equipment failures or process
upsets that could result in peak levels of SO2. |
SO2 causes a wide variety
of health and environmental impacts because of the way it reacts
with other substances in the air. Particularly sensitive groups
include people with asthma who are active outdoors and children,
the elderly, and people with heart or lung disease.
Respiratory Effects from Gaseous
SO2
Peak levels of SO2 in the air can cause temporary breathing difficulty
for people with asthma who are active outdoors. Longer-term exposures
to high levels of SO2 gas and particles cause respiratory illness
and aggravate existing heart disease.
Respiratory Effects from Sulfate Particles
SO2 reacts with other chemicals in the air to form tiny sulfate
particles. When these are breathed, they gather in the lungs and
are associated with increased respiratory symptoms and disease,
difficulty in breathing, and premature death.
Lead is a metal found
naturally in the environment as well as in manufactured products.
The major sources of lead emissions have historically been motor
vehicles (such as cars and trucks) and industrial sources. Due
to the phase out of leaded gasoline, metals processing is the
major source of lead emissions to the air today. The highest levels
of lead in air are generally found near lead smelters. Other stationary
sources are waste incinerators, utilities, and lead-acid battery
manufacturers.
| Lead |
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particularly affects young children and infants |
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is still found at high levels in urban and industrial areas |
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deposits on soil and water and harms animals and fish |
Children are at greatest risk
Although overall blood lead levels have decreased since 1976,
infants and young children still have the highest blood lead levels.
Children and others can be exposed to lead not only through the
air, but also through accidentally or intentionally eating soil
or paint chips, as well as food or water contaminated with lead
People, animals, and fish are mainly
exposed to lead by breathing and ingesting it in food, water,
soil, or dust. Lead accumulates in the blood, bones, muscles,
and fat. Infants and young children are especially sensitive to
even low levels of lead.
Damages organs - Lead causes
damage to the kidneys, liver, brain and nerves, and other organs.
Exposure to lead may also lead to osteoporosis (brittle bone disease)
and reproductive disorders.
Affects the brain and nerves
- Excessive exposure to lead causes seizures, mental retardation,
behavioral disorders, memory problems, and mood changes. Low levels
of lead damage the brain and nerves in fetuses and young children,
resulting in learning deficits and lowered IQ.
Affects the heart and blood
- Lead exposure causes high blood pressure and increases heart
disease, especially in men. Lead exposure may also lead to anemia,
or weak blood.
