Ozone, the main ingredient
of smog, presents a serious air quality problem in many parts of the
United States. Even at low levels, ozone can cause a number of respiratory
effects. You can take simple steps, described in this pamphlet, to
protect your health from ozone.
Ozone is the main ingredient
of smog.
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What
is ozone?
Ozone is a gas that occurs both in the Earth's upper atmosphere
and at ground level. Ozone can be good or bad, depending on where
it is found:
Good Ozone. Ozone occurs naturally in the Earth's upper
atmosphere-10 to 30 miles above the Earth's surface-where it
shields us from the sun's harmful ultraviolet rays.
Bad Ozone. In the Earth's lower atmosphere, near ground
level, ozone is formed when pollutants emitted by cars, power plants,
industrial boilers, refineries, chemical plants, and other sources
react chemically in the presence of sunlight. Ozone pollution
is a concern during the summer months when the weather conditions
needed to form ground-level ozone-lots of sun, hot temperatures-normally
occur.
Are
you at risk from ground-level ozone?
Several groups of people are particularly sensitive to ozone-especially
when they are active outdoors-because physical activity causes people
to breathe faster and more deeply.
Active children are the group at highest risk from ozone
exposure because they often spend a large part of the summer playing
outdoors. Children are also more likely to have asthma, which may
be aggravated by ozone exposure.
Active adults of all ages who exercise or work vigorously
outdoors have a higher level of exposure to ozone than people who
are less active.
People with asthma or other respiratory diseases that make
the lungs more vulnerable to the effects of ozone will generally
experience health effects earlier and at lower ozone levels than
less sensitive individuals.
People with unusual susceptibility to ozone. Scientists
don't yet know why, but some healthy people may experience health
effects at more moderate levels of outdoor exertion or at lower
ozone levels than the average person.
In general, as concentrations of ground-level ozone increase,
more and more people experience health effects, the effects become
more serious, and more people are admitted to the hospital for respiratory
problems. When ozone levels are very high, everyone should be concerned
about ozone exposure.
Children and adults of all
ages who are active outdoors
are at risk from ozone exposure.
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How
can ground-level ozone affect your health?
Ozone can irritate your respiratory system, causing you
to start coughing, feel an irritation in your throat and/or experience
an uncomfortable sensation in your chest.
Ozone can reduce lung function and make it more difficult
for you to breathe as deeply and vigorously as you normally would.
When this happens, you may notice that breathing starts to feel
uncomfortable. If you are exercising or working outdoors, you may
notice that you are taking more rapid and shallow breaths than normal.
Ozone can aggravate asthma. When ozone levels are high,
more people with asthma have attacks that require a doctor's attention
or the use of additional medication. One reason this happens is
that ozone makes people more sensitive to allergens, which are the
most common triggers for asthma attacks. Also, asthmatics are more
severely affected by the reduced lung function and irritation that
ozone causes in the respiratory system.
Ozone can inflame and damage cells that line your lungs.
Within a few days, the damaged cells are replaced and the old cells
are shed-much in the way your skin peels after a sunburn.
Ozone may aggravate chronic lung diseases such as emphysema
and bronchitis and reduce the immune system's ability to fight off
bacterial infections in the respiratory system.
Ozone may cause permanent lung damage. Repeated short-term
ozone damage to children's developing lungs may lead to reduced
lung function in adulthood. In adults, ozone exposure may accelerate
the natural decline in lung function that occurs as part of the
normal aging process.
Ozone can inflame the lung's
lining. These photos show a healthy lung air way (left)
and an inflamed lung air way (right).
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Are
there always symptoms?
Ozone damage also can occur without any noticeable signs. People
who live in areas where ozone levels are frequently high may find
that their initial symptoms go away over time-particularly when
exposure to high ozone levels continues for several days. Ozone
continues to cause lung damage even when the symptoms have disappeared.
The best way to protect your health is to find out when ozone levels
are elevated in your area and take simple precautions to minimize
exposure even when you don't feel obvious symptoms.
How
can you avoid unhealthy exposure to ozone?
Your chances of being affected by ozone increase the longer you
are active outdoors and the more strenuous the activity you engage
in. If you're involved in an activity that requires heavy exertion,
you can reduce the time you spend on this activity or substitute
another activity that requires more moderate exertion (e.g., go
for a walk rather than a jog). In addition, you can plan outdoor
activities when ozone levels are lower, usually in the morning or
evening.
Examples of activities that involve moderate exertion include
climbing stairs, playing tennis or baseball, simple garden or construction
work, and light jogging, cycling, or hiking. Activities that involve
heavy exertion include playing basketball or soccer, chopping
wood, heavy manual labor, and vigorous running, cycling, or hiking.
Because fitness levels vary widely among individuals, what is moderate
exertion for one person may be heavy exertion for another. No matter
how fit you are, cutting back on the level or duration of exertion
when ozone levels are high will help protect you from ozone's harmful
effects.
Air
Quality Index
The Air Quality Index, or AQI, is a scale used to report actual
levels of ozone and other common pollutants in the air. The higher
the AQI value, the greater the health concern. As shown in the table
below, the AQI scale has been divided into categories that correspond
to different levels of health concern.
AIR
QUALITY INDEX
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Index Values
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Descriptors
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Cautionary
Statements for Ozone
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0 to 50
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Good
|
None. |
51 to 100
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Moderate
|
Unusually
sensitive people should consider limiting prolonged outdoor
exertion. |
101 to 150
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Unhealthy
for Sensitive Groups
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Active
children and adults, and people with respiratory disease, such
as asthma, should limit prolonged outdoor exertion. |
151 to 200
|
Unhealthy
|
Active
children and adults, and people with respiratory disease, such
as asthma, should avoid prolonged outdoor exertion; everyone
else, especially children, should limit prolonged outdoor exertion.
|
201 to 300
|
Very
Unhealthy
|
Active
children and adults, and people with respiratory disease, such
as asthma, should avoid all outdoor exertion; everyone else,
especially children, should limit outdoor exertion. |
A specific color has been assigned to each AQI category. For example,
red means "unhealthy" conditions and purple means "very unhealthy"
conditions. This color scheme can help you quickly determine if
air pollutants are reaching unhealthy levels in your area.
You may see the AQI for ozone reported in your news paper or on
your local television or radio station. Here's the type of report
you might hear:
The Air Quality Index today was 160. Air quality was unhealthy
due to ozone. Hot, sunny weather and stagnant air caused ozone
in Center City to rise to unhealthy levels.
The illustration below shows how you might see the AQI used in
a newspaper. In this example, an AQI value of 130 is reported, which
means that ozone levels are unhealthy for sensitive groups.
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Pollutant:
Ozone
Today's Forecast: 130
Quality: Unhealthy for Sensitive Groups
Children and people with asthma are the groups most at risk.
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About AIRNow
AIRNow (htpp://www.epa.gov/airnow)
is an Internet site that gives daily information about
ozone and how it may affect you. AIRNow contains:
- Ozone maps that use contours based
on the AQI to show levels in local areas. You can
quickly determine if concentrations are reaching unhealthy
levels.
- Summertime ozone forecasts.
- Ideas about what you can do to reduce ozone levels,
such as driving less, making sure your car is well-tuned,
and participating in local energy conservation programs.
- Links to state and local air quality programs.
- SMOG-Who Does It Hurt?, a booklet that provides
more information about ozone health effects and how
you can protect yourself.
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Maps that provide daily information
about ozone levels are
available on the AIRNow web site.
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