&EPA
United States
Environmental Protection
Agency
                                     Air Quality Index
                                     A Guide to
                                     Air Quality and
                                     Your Health
Recycled/Recyclable. Printed with
vegetable oil-based inks on 100%
postconsumer process, chlorine-free
recycled paper.

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"Local air quality is
 unhealthy today.''
          "It's a code red air
 quality  day for ozone."
 Increasingly, radio, TV, and newspapers
 are providing information like this to local
 communities. But what does it mean to you
 ...if you are planning outdoor activities that day?
 ...if you have children who play outdoors?
 ...if you are an older adult? ...if you have asthma?
 This booklet can help you understand what you
 can do to protect yourself from air pollution.
  Todays Air Quality
  Index  is  105,  which  is
  unhealthy for sensitive
 groups."
Air  Quality Index
A Guide to Air Quality
and  Your Health
Local air quality affects how you live and breathe. Like
the weather, it can change from day to day or even hour
to hour. The U.S. Environmental Protection Agency
(EPA) and others are working to make information
about outdoor air quality as easy to understand as the
weather forecast. A key tool in this effort is the Air
Quality Index, or AQI. EPA and local officials use the
AQI to provide you with simple information on local
air quality, the health concerns for different levels of air
pollution, and how you can protect your health when
pollutants reach unhealthy levels.

What is the AQI?
The AQI is an index for report-
ing daily air quality. It tells you
how clean or polluted your air
is, and what associated health
effects might be a concern for
you. The AQI focuses on health
effects you may experience
within a few hours or days after
breathing polluted air. EPA
calculates the AQI for five
major air pollutants regulated
by the Clean Air Act: ground-
level ozone, particle pollution
(also known as particulate
matter), carbon monoxide,
sulfur dioxide, and nitrogen dioxide. For each of these
pollutants,  EPA has established national air quality
standards to protect public health.
Air quality directly affects
our quality of life.

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      AIR   QUALITY
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How does the AQI work?
Think of the AQI as a yardstick that runs from 0 to 500.
The higher the AQI value, the greater the level of air
pollution and the greater the health concern. For exam-
ple, an AQI value of 50 represents good air quality with
little potential to affect public health, while an AQI value
over 300 represents hazardous air quality.
An AQI value of 100 generally corresponds to the
national air quality standard for the pollutant, which is
the level EPA has set to protect public health. AQI values
below 100 are generally thought of as satisfactory. When
AQI values are above 100, air quality is considered to be
unhealthy—at first for certain sensitive groups of people,
then for everyone as AQI  values get higher.

Understanding the AQI
The purpose of the AQI is to help you understand what
local air quality means to your health. To make it easier
to understand, the AQI is divided into six categories:
 Air Quality Index I Levels of Health Concern
 (AQI) Values    I
 When the AQI
 is in this range:
  .air quality conditions are:
...as symbolized
by this color:
 OtoSO
 51 to 100
 101 to 150
 151 to 200
 201 to 300
 301 to 500
 Good
 Moderate                 Yellow
 Unhealthy for Sensitive Groups  Orange
 Unhealthy
| Very Unhealthy
 Hazardous
Each category corresponds to a different level of health
concern. The six levels of health concern and what they
mean are:
• "Good" The AQI value for your community is between
  0 and 50. Air quality is considered satisfactory, and air
  pollution poses little or no risk.

• "Moderate" The AQI for your community is between
  51 and 100. Air quality is acceptable; however, for
  some pollutants there may be a moderate health
  concern for a very small number of people. For exam-
  ple, people who are unusually sensitive to ozone may
  experience respiratory symptoms.

• "Unhealthy for Sensitive Groups" When AQI values are
  between 101 and 150, members of sensitive groups
  may experience health effects. This means they are like-
  ly to be affected at lower levels than the general public.
  For example, people with lung disease are at greater risk
  from exposure to  ozone, while people with either lung
  disease or  heart disease are at greater risk from exposure
  to particle pollution. The general public is not likely to
  be affected when  the AQI is in this range.

• "Unhealthy" Everyone may begin to experience health
  effects when AQI values are between 151 and 200.
  Members of sensitive groups may experience more
  serious health effects.

• "Very Unhealthy" AQI values between 201 and  300
  trigger a health alert, meaning everyone may experience
  more serious health effects.

• "Hazardous" AQI  values over 300 trigger health warn-
  ings of emergency conditions. The entire population is
  more likely to be affected.

AQI colors
A specific color is assigned to each AQI category to
make it easier for you to understand quickly whether air
pollution is reaching unhealthy levels  in your community.
For example, the color orange means that conditions are
"unhealthy for sensitive groups," while red means that
conditions may be "unhealthy for everyone," and so on.

How is a community's AQI  calculated?
Air quality is measured by monitors that record the
concentrations of the major pollutants each day at more
than a thousand locations across the  country. These raw
measurements are then converted into AQI values using
standard formulas developed by EPA. An AQI value is
calculated for each pollutant in an area (ground-level
ozone, particle pollution, carbon monoxide, sulfur
dioxide, and nitrogen dioxide). The highest AQI value
for the individual pollutants is  the AQI value for that day.

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      AIR   QUALITY
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For example, if on July 12 a certain area had AQI values
of 90 for ozone and 88 for sulfur dioxide, the AQI value
would be 90 for the pollutant ozone on that day.

When and how is the AQI reported to the public?
In large cities (more than 350,000 people), state and local
agencies are required to report the AQI to the public daily.
When the AQI is above 100, agencies must also report
which groups, such as children or people with asthma  or
heart disease, may be sensitive to the specific pollutant. If
two or more pollutants have AQI values above 100 on a
given day, agencies must report all the groups  that are
sensitive to those pollutants. Many smaller communities
also report the AQI as a public health service.
Children active outdoors can be sensitive to some air pollutants.

Many cities also provide forecasts for the next day's AQI.
These forecasts help local residents protect their health
by alerting them to plan their strenuous activities for a
time when air quality is better.
The AQI is a national index, so the values and colors
used to show local air quality and the levels of health
concern will be the same everywhere you go in the
United States. Look for the AQI to be reported in your
local newspaper, on television and radio, on the Internet,
and on many state and local  telephone hotlines.
                                  • AQI in the Newspaper
                                  Newspapers in many U.S. cities, and some national news-
                                  papers, carry AQI reports each day. Here is one example:
                                      AIR QUALITY INDEX
                         Pollutant: Particles
                         Today's Forecast: 130
                         Quality: Unhealthy for
                               Sensitive Groups

                         People with heart or lung
                         disease, older adults,
                         and children are at risk.
                                  • AQI in Television and Radio Weather Reports
                                  Many local television or radio weathercasters use the AQI
                                  to provide air quality information in your area. Here's the
                                  type of report you might hear:

                                     Tomorrow will be a, code red air quality day for
                                     Center City. The cold winter air, morning traffic, and
                                     wood smoke are expected to cause particle pollution to
                                     rise to unhealthy levels. People with heart or lung dis-
                                     ease, older adults, and children should avoid strenuous
                                     activities.

                                  • AQI on the Internet
                                  EPA's AIRNow web site (www.epa.gov/airnow)
                                  contains general information about air pollution plus
                                  real-time and forecast air quality data. It also contains
                                  facts  about the health and environmental effects of air
                                  pollution,  steps you can take to  protect your health and
                                  to reduce pollution, and links to state and local air
                                  pollution agency web sites.

                                  What are typical AQI values in most communities?
                                  In many U.S. communities, AQI values are usually below
                                  100,  with values greater than 100 occurring just several
                                  times a year. Typically, larger cities have more severe air
                                  pollution problems, and the AQI in these areas may
                                  exceed  100 more often than in smaller  cities. AQI values
                                  higher than 200 are infrequent, and AQI values above
                                  300 are extremely rare.

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      AIR   QUALITY
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AQI values can vary from one season to another. In
winter, for example, carbon monoxide may be high in
some areas because the cold weather makes it difficult
for car emission control systems to operate effectively.
In summer, ozone may be a significant air pollutant
because it forms in the presence of heat and sunlight.
Particle pollution can be elevated at any time of the year.
AQI values also can vary depending on the time of day.
For example, ozone levels often peak in the afternoon,
while carbon monoxide is usually a problem during
morning  or evening rush hours. Particle pollution
can be high at any time of day.

How can I avoid being exposed to harmful air
pollutants?
The following AQI charts tell you how to protect your
health from air pollution.  Each chart contains cautionary
language to help you when air quality levels are unhealthy.
In general, you can reduce your risk by "reducing prolonged
or heavy exertion." Prolonged exertion is an activity that
occurs over several hours and makes you breathe slightly
harder than normal. Reducing prolonged exertion could
mean reducing the time you spend on this type of activity.
You can also reduce your risk by cutting back on heavy
exertion—more intense activities that cause you to breathe
hard. This might mean walking instead of jogging, or jog-
ging for half your usual time. Your breathing rate is a guide
to how hard you are exerting yourself. If you experience
any unusual coughing, chest discomfort, wheezing, or
breathing difficulty, you should reduce your activity level.
Charts are provided for four pollutants: ozone, particle
pollution, carbon monoxide, and sulfur dioxide. Another
common  pollutant, nitrogen dioxide, can cause respiratory
symptoms such as coughing, wheezing, and shortness of
breath in  children and adults who have respiratory diseases,
such as asthma. The AQI for nitrogen dioxide is not
included in this booklet because nitrogen dioxide levels
across  the country have been below the national air quality
standard for the past several years. Nitrogen dioxide levels
are usually so low that they pose little direct threat to
human health. Nitrogen dioxide,  however, is a concern
because it plays a significant role in the formation of
ozone, particle pollution, haze, and acid rain.
                                             Air Quality Index (AQI): Ozone

                                     0-50
                                                 Levels
                                                of Health
                                                Concern
    Good
                    Cautionary Statements
None
                                                              Unusually sensitive people should
                                    51 -100*     Moderate     consider reducing prolonged or heavy
                                                                    exertion outdoors.
                                                Unhealthy
                                    101-150    for Sensitive
                                                 Groups
                                    151 - 200 I   Unhealthy
                                    201 - 300   Very Unhealthy
                                    301 - 500 I   Hazardous
                 Active children and adults, and
                people with lung disease, such as
                asthma, should reduce prolonged or
                    heavy exertion outdoors.
                 Active children and adults, and
                people with lung disease, such as
                asthma, should avoid prolonged or
                heavy exertion outdoors. Everyone
                 else, especially children, should
                reduce prolonged or heavy exertion
                          outdoors.
                  Active children and adults, and
                people with lung disease, such as
                 asthma, should avoid all outdoor
                exertion. Everyone else, especially
                children, should avoid prolonged or
                    heavy exertion outdoors.
                    Everyone should avoid all
                    physical activity outdoors.
                                   *An AQI of 100 for ozone corresponds to an ozone level of 0.08 parts per million
                                    (averaged over 8 hours).
                                   What is ozone?
                                   Ozone is a gas composed of three atoms of oxygen.
                                   Ozone occurs both in the Earths 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—6 to 30 miles above the Earth's surface—
                                     where it forms a protective layer that shields us from
                                     the sun's harmful ultraviolet rays. This beneficial ozone
                                     is gradually being destroyed by manmade chemicals.

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8     AIR    QUALITY
D  E X
  An area where the protective "ozone layer" has been
  significantly depleted—for example, over the North or
  South pole—is sometimes called "the ozone hole."

 i Bad Ozone. In the Earths 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 at ground level is a
  harmful air pollutant.
The risk of exposure to unhealthy levels of ground-level ozone is greatest
during summer months.

What are the health effects and who is most at risk?
Roughly one out of every three people in the United
States is at a higher risk of experiencing problems from
ground-level ozone.
• One group at high risk is active children because they
 often spend a large part  of the summer playing outdoors.
• People of all ages who are active outdoors are at
 increased risk because, during physical activity, ozone
 penetrates deeper into the parts of the lungs that are
 more vulnerable to injury.
AIR   QUALITY
D  E X
                                  1 People with respiratory diseases, including asthma, that
                                   make their lungs more vulnerable to ozone may experi-
                                   ence health effects earlier and at lower ozone
                                   levels than other people.

                                  i Though scientists don't yet know why, some healthy
                                   people are unusually sensitive to ozone. They may
                                   experience health effects at more moderate levels of
                                   outdoor exertion or at lower ozone levels than the
                                   average person.

                                  1 Ozone can irritate the respiratory system, causing
                                   coughing, throat irritation, and/or an uncomfortable
                                   sensation in the chest.

                                  1 Ozone can reduce lung function and make it more dif-
                                   ficult to breathe deeply and vigorously. Breathing may
                                   become more rapid and shallow than normal. This may
                                   limit a person's ability to engage in vigorous activities.

                                  i Ozone can aggravate  asthma. When ozone levels
                                   are high, more people with asthma have attacks that
                                   require a doctor's attention or use of medication. One
                                   reason this happens is that ozone makes people more
                                   sensitive to allergens such as pets, pollen, and dust
                                   mites, which are common triggers of asthma attacks.

                                  1 Ozone can increase susceptibility to respiratory
                                   infections.

                                  1 Ozone can inflame and damage the lining of the
                                   lungs. Within a few days, the damaged cells are shed
                                   and replaced—much like the skin peels after a sun-
                                   burn. Studies suggest that if this type of inflammation
                                   happens repeatedly over a long time period (months,
                                   years, a lifetime), lung tissue may become permanently
                                   scarred, resulting in permanent loss of lung function
                                   and a lower quality of life.

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     10    AIR   QUALITY   INDEX
                                                           AIR    QUALITY
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»JI:«.llMHi-JI,'l.li>:«
         Air Quality Index (AQI): Particle Pollution

                    Levels
                   of Health
                   Concern
       0 - 50        Good
      51 -100*      Moderate
    Cautionary Statements
            None

   Unusually sensitive people
    should consider reducing
   prolonged or heavy exertion.
                   Unhealthy      People with heart or lung disease,
      101  -150    for Sensitive      older adults, and children should
                    Groups       reduce prolonged or heavy exertion.
      151 - 200  I   Unhealthy
      201 - 300 | Very Unhealthy
      301 - 500 |   Hazardous
People with heart or lung disease,
 older adults, and children should
avoid prolonged or heavy exertion.
  Everyone else should reduce
  prolonged or heavy exertion.
People with heart or lung disease,
 older adults, and children should
avoid all physical activity outdoors.
   Everyone else should avoid
   prolonged or heavy exertion.
People with heart or lung disease,
 older adults, and children should
 remain indoors and keep activity
 levels low. Everyone else should
avoid all physical activity outdoors.

     *An AQI of 100 for particles up to 2.5 micrometers in diameter corresponds to a level of 40
      micrograms per cubic meter (averaged over 24 hours). An AQI of 100 for particles up to 10
      micrometers in diameter corresponds to a level of 150 micrograms per cubic meter
      (averaged over 24 hours).
     What is particle pollution?
     Particle pollution (also known as "particulate matter")
     in the air includes a mixture of solids and liquid droplets.
     Some particles are emitted directly; others are formed in
     the atmosphere when other pollutants react. Particles come
     in a wide range of sizes. Those less than 10 micrometers in
     diameter are so small that they can get into the lungs,
     potentially causing serious health problems. Ten microme-
     ters is smaller than the width of a single human hair.
• Fine particles. Particles less than 2.5 micrometers in
  diameter are called "fine" particles. These particles are
  so small they can be detected only with an electron
  microscope. Sources of fine particles include all types
  of combustion, including motor vehicles, power plants,
  residential wood burning, forest fires, agricultural
  burning, and some industrial processes.

• Coarse dust particles. Particles between 2.5 and
  10 micrometers in diameter are referred to as "coarse."
  Sources of coarse particles include crushing or
  grinding operations, and dust stirred up by vehicles
  traveling on roads.

What are the health effects and who is most at risk?
Particles smaller than 10  micrometers in diameter can cause
or aggravate a number of health problems and have been
linked with illnesses and  deaths from heart or lung diseases.
These effects have been associated with both short-term
exposures (usually over a  24-hour period, but possibly as
short as one hour) and long-term exposures (years).
• Sensitive groups for particle pollution include people
  with heart or lung disease, older adults (who may have
  undiagnosed heart or lung disease), and children.

• People with heart or lung diseases—such as congestive
  heart failure, coronary artery  disease,  asthma, or chron-
  ic obstructive pulmonary disease—and older adults are
  more likely to visit emergency rooms, be admitted to
  hospitals, or in some cases, even die. When exposed to
  particle pollution, people with heart disease may expe-
  rience chest pain, palpitations, shortness of breath, and
  fatigue. Particle pollution has also been associated with
  cardiac arrhythmias and heart attacks.

• When exposed to particles, people with existing lung
  disease may not be able to breathe as deeply or vigorous-
  ly as they normally would. They may experience symp-
  toms such as coughing and shortness of breath. Healthy
  people also may experience these effects, although they
  are unlikely to experience more serious effects.

• Particle pollution also  can increase susceptibility to
  respiratory infections and can aggravate existing respira-
  tory diseases, such as asthma and chronic bronchitis,
  causing more use of medication and more doctor visits.

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12   AIR   QUALITY
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                                                                AIR   QUALITY
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 Air Quality Index (AQI): Carbon Monoxide (CO)
  Index Values
                  Levels of
               Health Concern
                    Cautionary
                    Statements
                       Good

                     Moderate
                    Unhealthy for
                  Sensitive Groups
    151 - 200
                 Unhealthy
    201 - 300
               Very Unhealthy
                                        None

                                        None

                                   People with heart
                                   disease, such as
                                 angina, should reduce
                                  heavy exertion and
                                 avoid sources of CO,
                                 such as heavy traffic.
                  People with heart
               disease, such as angina,
               should reduce moderate
                  exertion and avoid
               sources of CO, such as
                   heavy traffic.
                  People with heart
               disease, such as angina,
               should avoid exertion and
                sources of CO, such as
                    heavy traffic.
                                       People with heart
                                    disease, such as angina,
                                     should avoid exertion
                                    and sources of CO, such
                                       as heavy traffic.
                                     Everyone else should
                                     reduce heavy exertion.
* An AQI of 100 for carbon monoxide corresponds to a CO level of 9 parts per million
 (averaged over 8 hours).
What is carbon monoxide?

Carbon monoxide (CO) is an odorless, colorless gas.
It forms when the  carbon in fuels does not completely
burn. Vehicle exhaust contributes roughly 60 percent of
all carbon monoxide emissions nationwide, and up to
95 percent in cities. Other sources include fuel combus-
tion in industrial processes and natural sources such as
wildfires.  Carbon monoxide levels typically are highest
during cold weather, because cold temperatures make
combustion less complete and cause inversions that
trap pollutants close to the ground.
301 - 500
Hazardous
What are the health effects and who is most at risk?

Carbon monoxide enters the bloodstream through the
lungs and binds to hemoglobin, the substance in blood
that carries oxygen to cells. It actually reduces the amount
of oxygen reaching the body's organs and tissues.

• People with cardiovascular disease, such as angina, are
  most at risk. They may experience chest pain and other
  cardiovascular symptoms if they are exposed to carbon
  monoxide, particularly while  exercising.

• People with marginal or compromised cardiovascular
  and respiratory systems (for example, individuals with
  congestive heart failure, cerebrovascular disease, anemia,
  chronic obstructive lung disease), and possibly young
  infants and fetuses, also may be at greater risk from
  carbon monoxide pollution.

• In healthy individuals, exposure to higher levels of
  carbon monoxide can affect mental alertness and vision.
                                                                                                                                 '•'
                                                                                IIIMIMUIlillliilMiiiJiniiiifiiiMi
                                                                      Vehicle exhaust contributes roughly 60 percent of all carbon monoxide
                                                                      emissions nationwide.

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     14    AIR    QUALITY   INDEX
                                                                                  AIR   QUALITY
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»JI:«.llMHi-JI,'l.li>:«
       Air Quality Index (AQI): Sulfur Dioxide (SO?)
       Index Values
                  Levels of
               Health Concern
 0 - 50             Good

51-100*          Moderate
     Cautionary
     Statements
                                                 None
         101 -150
                Unhealthy for       People with asthma
               Sensitive Groups    snould consider reducin9
                                   exertion outdoors.
         151 - 200
         201 - 300
                 Unhealthy
               Very Unhealthy
         301 - 500
                 Hazardous
Children, asthmatics, and
people with heart or lung
 disease should reduce
   exertion outdoors.
Children, asthmatics, and
people with heart or lung
  disease should avoid
   outdoor exertion.
  Everyone else should
reduce exertion outdoors.
 Children, asthmatics,
and people with heart or
  lung disease should
    remain indoors.
 Everyone else should
avoid exertion outdoors.
     * An AQI of 100 for sulfur dioxide corresponds to an S02 level of 0.14 parts per million
      (averaged over 24 hours).
     What is sulfur dioxide?
     Sulfur dioxide (SO2), a colorless, reactive gas, is pro-
     duced when sulfur-containing fuels such as coal and
     oil are burned.  Major sources include power plants and
     industrial boilers. Generally, the highest levels of sulfur
     dioxide are near large industrial complexes.

     What are the health effects and who is  most at risk?
     Sulfur dioxide is an irritant gas that is removed by
     the nasal passages. Moderate activity levels that trigger
     mouth breathing, such as a brisk walk,  are needed for
     sulfur dioxide to cause health effects.
i People with asthma who are physically active outdoors
 are most likely to experience the health effects of sulfur
 dioxide. The main effect, even with brief exposure, is a
 narrowing of the airways (called bronchoconstriction).
 This may cause wheezing,  chest tightness, and short-
 ness of breath. Symptoms increase as sulfur dioxide
 levels and/or breathing rates increase. When exposure
 to sulfur dioxide ceases, lung function  typically returns
 to normal within an hour.
1 At very high levels, sulfur dioxide may cause wheezing,
 chest tightness, and shortness of breath even in healthy
 people who do not have asthma.
                                                                       Children and adults with asthma who are active outdoors are most
                                                                       vulnerable to the health effects of sulfur dioxide.

                                                                       • Long-term exposure to sulfur dioxide can cause respi-
                                                                         ratory illness, alter the lung's defense mechanisms, and
                                                                         aggravate existing cardiovascular disease. People with
                                                                         cardiovascular disease or chronic lung disease, as well
                                                                         as children and older adults, may be most susceptible
                                                                         to these effects.

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16   AIR   QUALITY   INDEX
Where can I get more information?
For information on air quality in your area, visit
EPA's AIRNow web site at www.epa.gov/airnow.
For information on programs under way to improve
air quality, visit www.epa.gov/air.
The AQI focuses on outdoor air quality. For informa-
tion on indoor air quality, contact EPA's Indoor Air
Quality Information Hotline at (800) 438-4318 or
visit www.epa.gov/iaq.
                                                                                      Air and Radiation
                                                                                      EPA-454/K-03-002
                                                                                      http://www.epa.gov
                                                                                        August 2003

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