Technical Assistance Document
for the Reporting of Daily Air Quality
the Air Quality Index (AQI)
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EPA-454/B-09-001
February 2009
Technical Assistance Document
for the Reporting of Daily Air Quality
the Air Quality Index (AQI)
Contact:
David Mintz
U.S. Environmental Protection Agency
Research Triangle Park, North Carolina
U.S. Environmental Protection Agency
Office of Air Quality Planning and Standards
Research Triangle Park, North Carolina 27711
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TABLE OF CONTENTS
Reporting Guidance 1
Table 1: Pollutant-Specific Groups 2
Pollutant-Specific Health Effects Statements 8
Pollutant-Specific Sub-indices and
Cautionary Statements 10
Table 2: Breakpoints for the AQI 14
Table 3: Metropolitan Statistical Areas 20
Frequently Asked Questions 25
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This guidance is designed to aid local agencies in reporting the air quality using the Air Quality Index
(AQI) as required in Part 58.50 of 40 CFR and according to Appendix G to Part 58 of 40 CFR.
Do I have to report the AQI?
Part 58.50 states that Metropolitan Statistical Areas (MSAs) with a population of more than 350,000
are required to report the AQI daily to the general public. The U.S. Office of Management and Budget
defines MSAs according to the 2000 census. Table A-1 in the Appendix lists all metropolitan areas
with a population of more than 350,000.
How often do I report the AQI?
Appendix G states that MSAs must report the AQI on a daily basis. The appendix further defines daily
as at least five times each week. This definition allows for days when personnel are not available to
provide the AQI report or for equipment failures.
How do I provide the AQI report to the general public?
You may distribute the report to the local media (newspapers, radio, television), provide a recorded
telephone message, or publish the report on a publicly accessible Internet site. Other efforts,
including real-time data reporting and community action programs (e.g., ozone action day programs)
that provide timely air quality information to the public, may be used to meet reporting requirements.
What is in my AQI report?
Your AQI report must contain:
• The reporting area(s),
• The reporting period,
• The critical pollutant,
• The AQI,
• The category descriptor and, if reported in a color format, the associated color.1 Use
only the following names and colors for the six AQI categories:
For this AQI.... use this descriptor... and this color
Oto50 "Good" Green
51 to 100 "Moderate" Yellow
101 to 150 "Unhealthy for Sensitive Groups" Orange
151 to 200 "Unhealthy" Red
201 to 300 "Very Unhealthy" Purple
301 and above "Hazardous" Maroon
• Statements cautioning sensitive groups for all pollutants with an index value over 100.
Use Table 1 on page on the following page to caution sensitive groups. Statements
may be combined so that each group is mentioned only once.
Although a recorded phone message or a radio broadcast can't show colors, it can name a
color in the report (e.g. this is a "red" air quality day).
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Table 1: Pollutant Specific Sensitive Groups
When this pollutant has an index above 100... Report these Sensitive Groups
Ozone People with lung disease, children, older adults, and
people who are active outdoors are the groups most
at risk
PM2.5 People with heart or lung disease, older adults,
and children are the groups most at risk
PM10 People with heart or lung disease, older
adults, and children and the groups most at risk
CO People with heart disease are the group most at risk
SO2 People with asthma are the group most at risk
An AQI report may also contain, but does not require:
• The name and index value for other pollutants, particularly those with an index value
greater than 100,
• The index for sub-areas of the reporting area,
• Actual pollutant concentrations,
• Causes for unusual AQI values,
• Health effects and cautionary language,
• Statements that "blend" health effects and cautionary information for more than one
pollutant, if there is more than one pollutant with an index value greater than 100.
It is important to inform the public when the AQI is above 100. This is why EPA strengthened the
reporting provisions in section 6 of Appendix G in 1999. In particular, whenever the AQI exceeds 100,
reporting agencies should expand reporting to all major news media, and at a minimum, should
include notification to the media with the largest market coverage for the area in question.
What does an AQI report look like?
NEWSPAPER
Example 1. Newspaper short form in color
Air Quality for Raleigh, N.C.
Air Quality Index
Yesterday's report: 76
Main pollutant: Particulate Matter
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0-50
Good
51-100
Moderate
101-150
Unhealthy,
Sensitive
groups
151-200
Unhealthy
201-300
Very
unhealthy
Today's ozone forecast: 38
Example 2. Newspaper short form in black and white
Chicago Tribune
AIR QUALITY
Illinois EPA's air quality index (AQI):
0-50 is good; 51-100 moderate; 101-150 unhealthy
for sensitive groups; 151-200 unhealthy; 200+
very unhealthy
Tuesday's reading
na
Wednesday's forecast
Good
Critical pollutant
Particulate Matter
Example 3. Newspaper longer form
The Air Quality in Baltimore Yesterday
The AIR QUALITY yesterday in Northeast
Baltimore was Unhealthy for Sensitive
Groups due to ozone. Groups likely to be
sensitive to ozone include active children
and adults, and people with respiratory
disease such as asthma. The Air Quality
Index was 109 resulting from an ozone
concentration of 0.079 ppm. Elsewhere in
Baltimore, the air quality index was 87 or
Moderate. Since today's air quality is
expected to be much the same, sensitive
groups should consider limiting prolonged
or heavy outdoor exertion.
GOOD
MODERATE
UNHEALTHY for SENSITIVE
GROUPS
VERY UNHEALTHY
HAZARDOUS
TELEVISION
The following is a short script that could be used for a television evening news/weather report. The
graphics used in the report could be much the same as the graphics used in newspaper reports. The
weathercaster must use the descriptors and, if a color format is used, colors for the categories that
are listed above.
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Example 4. A short form for television (morning)
"Yesterday the air quality was unhealthy due to ozone, and we expect similar air quality today - in the
red range or around an index of 160, which is unhealthy. Active adults and children and people with
asthma or other respiratory diseases should avoid prolonged physical exertion outside today. In fact,
everyone should consider limiting the time they spend on outdoor exercise or those outside jobs..."
Example 5. A short form for television (evening)
"The air quality index today was 156, a red air quality day. The air stagnation caused a buildup of
ozone to unhealthy levels."
Example 6. Two long forms for television (evening)
"Air quality today was unhealthy due to ozone, with an index value of 156. The cool front we expected
to come through here tomorrow and blow all this ozone away isn't going to make it, so the stagnant air
will still be here, making air quality unhealthy. Active children and adults and people with asthma or
other respiratory diseases should avoid prolonged exertion outside tomorrow. In fact, everyone
should consider limiting the time they spend on outdoor exercise or those outside jobs..."
"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 disease, older adults, and children should avoid strenuous activities."
TELEPHONE
Recorded telephone messages can be used to give more up-to-date information on the air quality. For
example, the following script has been used:
Example 7. A script for telephone
"As of 10:00 a.m., the air quality index is 45 which is a good or "green" air quality day. The
responsible pollutant is ozone."
INTERNET
Most State and local agencies report the AQI on their public Web sites. The data available on the
Web site are typically up to the most recent hour. Links to these sites can be found in the "Where I
Live" section of the AIRNow Web site, at www.airnow.gov.
Example 8. A short form for a Web page
Air Quality Index for St. Louis, MO
Time of this report: |l:OOPM | AQI: 1110 | Code:
Responsible pollutant: | Ozone | Category: | Unhealthy for Sensitive Groups
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Example 9. A long form for a Web page- ozone
Air Quality Index for Chicago, IL for August 2
Sensitive groups:
Health effects:
HEALTH
ADVISORY
AQI:
Category:
162 Responsible pollutant:
Unhealthy
Active children and adults, and people with lung disease, such as asthma,
should reduce prolonged or heavy outdoor exertion.
Greater likelihood of respiratory symptoms and breathing difficulty in
sensitive groups, possible respiratory effects in the general population.
Children and adults who are active outdoors, and people with lung
disease, such as asthma should avoid moderate exertion outdoors,
everyone else (especially children) should limit prolonged or heavy
outdoor exertion.
Air Quality in South Chicago - Gary, IL
AQI:
122
(Unhealthy for Sensitive Groups)
Tomorrow's air quality in Chicago is
predicted to be:
Unhealthy for Sensitive
Groups
Code:
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Example 10. A long form fora Web page- particulate matter
Anchorage, Alaska
Smoke Plume
Source: NO A A
as t wind
Fairbanks
Isolated Hazardous,
Anchorage
Juneau
Air Quality Outlook ;
forAug 17-19, 2OO4
www.epa.gov/airnow
Alaska Department of Environmental Conservation (DEC) Issues Statewide Air Quality
Advisory-
The AQI levels have been steadily increasing from Moderate to Unhealthy. Dense smoke advisory
has been issued by the National Weather Service for the Fairbanks area for today and tonight. Poor
air quality conditions are expected to persist for the next several days as a high pressure system to
the northeast drives easterly winds and smoke to the Fairbanks area.
Health Tip: Everyone should avoid any outdoor exertion; people with respiratory or heart disease, the
elderly, and children should remain indoors.
Source: Alaska Department of Environmental Conservation and United States Environmental
Protection Agency.
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What colors do I use in my AQI report?
If you report the Air Quality Index in a color format, the appropriate colors are specified in Appendix G
as the following:
For this category...
... use this color
Good Green
Moderate Yellow
Unhealthy for Sensitive Groups Orange
Unhealthy Red
Very Unhealthy Purple
Hazardous Maroon
Specific colors are defined in the table below2 for red, green, blue (RGB) and cyan, magenta, yellow,
and black (CMYK) color formulas:
Color
Green
Yellow
Orange
Red
Purple
Maroon
R
0
255
255
255
153
126
G
228
255
126
0
0
0
B
0
0
0
0
76
35
C
40
0
0
0
10
30
M
0
0
52
100
100
100
Y
100
100
100
100
40
100
K
0
0
0
0
30
30
Notes: The RGB model is traditionally used for screen colors, while CMYK is traditionally used for printing
processes. The color models are based on a 0 - 255 scale (e.g. 50% is 126).
What health effects and cautionary statements should I use in my report?
The most recent health effect information used with the AQI is pollutant-specific. The following table
lists the different health effects messages, sensitive groups, and cautionary statements for each
pollutant in the AQI.
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Pollutant-Specific Sub-indices and Health Effects Statements
for Guidance on the Air Quality Index (AQI)
AQI
Categories:
Index Values
Good
(Up to 50)
Moderate
(51 - 1 00)
Unhealthy for
Sensitive Groups
(101 -150)
Unhealthy
(151 -200)
Ozone (ppm)
[8 -hour]
0 - 0.059
None
0.060 - 0.075
Unusually sensitive
individuals may experience
respiratory symptoms.
0.076 - 0.095
[1-hour]
0.125-0.164
Increasing likelihood of respiratory symptoms and
breathing discomfort in active children and adults and
people with lung disease, such as asthma.
0.096-0.115
0.165-0.194
Greater likelihood of respiratory symptoms and breathing
difficulty in active children and adults and people with lung
disease, such as asthma; possible respiratory effects in
general population.
Particulate Matter (ug/m3)
PM [24-hour]
2.5
0-15
None
>15-40
[24-hour]
PM10
0-50
None
>50-150
Respiratory symptoms possible in unusually
sensitive individuals, possible aggravation of heart
or lung disease in people with cardiopulmonary
disease and older adults.
>40 - 65
>150-250
Increasing likelihood of respiratory symptoms in
sensitive individuals, aggravation of heart or lung
disease and premature mortality in people with
cardiopulmonary disease and older adults.
>65-150
>250 - 350
Increased aggravation of heart or lung disease and
premature mortality in people with cardiopulmonary
disease and older adults; increased respiratory
effects in general population.
Carbon Monoxide
(ppm)
[8-hour]
0-4
None
>4-9
None
>9-12
Increasing likelihood of
reduced exercise
tolerance due to
increased cardiovascular
symptoms, such as
chest pain, in people
with heart disease.
>12-15
Reduced exercise
tolerance due to
increased cardiovascular
symptoms, such as
chest pain, in people
with heart disease.
Sulfur Dioxide
(ppm)
[24-hour]
0 - 0.03
None
>0.03-0.14
None
>0.14-0.22
Increasing likelihood of
respiratory symptoms, such as
chest tightness and breathing
discomfort, in people with
asthma.
>0.22-0.30
Increased respiratory
symptoms, such as chest
tightness and wheezing in
people with asthma; possible
aggravation of heart or lung
disease.
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Very Unhealthy
(201 - 300)
0.116 [8-hr]-0.404 [1-hr]
0.195-0.404
Increasingly severe symptoms and impaired breathing
likely in active children and adults and people with lung
disease, such as asthma; increasing likelihood of
respiratory effects in general population.
>150-250
>350 - 420
Significant aggravation of heart or lung disease and
premature mortality in people with cardiopulmonary
disease and older adults; significant increase in
respiratory effects in general population.
>15-30
Significant aggravation
of cardiovascular
symptoms, such as
chest pain, in people
with heart disease.
>0.30-0.60
Significant increase in
respiratory symptoms, such as
wheezing and shortness of
breath, in people with asthma;
aggravation of heart or lung
disease.
Hazardous
(301 - 500)
0.405 [1-hr]-0.60 [1-hr]
0.405 - 0.60
>250 - 500
>420 - 600
Severe respiratory effects and impaired breathing likely in
active children and adults and people with lung disease,
such as asthma; increasingly severe respiratory effects
likely in general population.
Serious aggravation of heart or lung disease and
premature mortality in people with cardiopulmonary
disease and older adults; serious risk of respiratory
effects in general population.
>30 - 50
Serious aggravation of
cardiovascular
symptoms, such as
chest pain, in people
with heart disease;
impairment of strenuous
activities in general
population.
>0.60-1.0
Severe respiratory symptoms,
such as wheezing and
shortness of breath, in people
with asthma; increased
aggravation of heart or lung
disease; possible respiratory
effects in general population.
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Pollutant-Specific Sub-indices and Cautionary Statements
for Guidance on the Air Quality Index (AQI)
AQI
Categories
(Index
Values)
Good
(Up to 50)
Moderate
(51 -100)
Unhealthy for
Sensitive Groups
(101 -150)
Ozone (ppm)
[8-hour]
0 - 0.059
None
0.060 - 0.075
Unusually sensitive people
should consider reducing
prolonged or heavy outdoor
exertion.
0.076 - 0.095
[1-hour]
0.125-0.164
Active children and adults, and people with lung disease,
such as asthma, should reduce prolonged or heavy
outdoor exertion.
Particulate Matter (ug/m3)
PM [24-hour]
2.5
0-15
None
>15-40
[24-hour]
PM10
0-50
None
>50-150
Unusually sensitive people should consider
reducing prolonged or heavy exertion.
>40 - 65
>150-250
People with heart or lung disease, older adults, and
children should reduce prolonged or heavy exertion.
Carbon Monoxide
(ppm)
[8-hour]
0-4
None
>4-9
None
>9-12
People with heart
disease, such as angina,
should limit heavy
exertion and avoid
sources of CO, such as
heavy traffic.
Sulfur Dioxide
(ppm)
[24-hour]
0 - 0.03
None
>0.03-0.14
None
>0. 14 -0.22
People with asthma
should consider limiting
outdoor exertion.
10
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Unhealthy
(151 -200)
Very Unhealthy
(201 - 300)
Hazardous
(301 - 500)
0.096-0.115
0.165-0.194
Active children and adults, and people with lung disease,
such as asthma, should avoid prolonged or heavy outdoor
exertion; everyone else, especially children, should reduce
prolonged or heavy outdoor exertion.
0.1 16 [8-hr]- 0.404 [1-hr]
0.195-0.404
Active children and adults, and people with lung disease,
such as asthma, should avoid all outdoor exertion;
everyone else, especially children, should reduce outdoor
exertion.
0.405 [1-hr]- 0.60 [1-hr]
0.405 - 0.60
Everyone should avoid all outdoor exertion.
>65-150
>250 - 350
People with heart or lung disease, older adults, and
children should avoid prolonged or heavy exertion;
everyone else should reduce prolonged or heavy
exertion.
>150-250
>350 - 420
People with heart or lung disease, older adults, and
children should avoid all physical activity outdoors.
Everyone else should avoid prolonged or heavy
exertion.
>250 - 500
>420 - 600
Everyone should avoid all physical activity outdoors;
people with heart or lung disease, older adults, and
children should remain indoors and keep activity
levels low.
>12-15
People with heart
disease, such as angina,
should limit moderate
exertion and avoid
sources of CO, such as
heavy traffic.
>15-30
People with heart
disease, such as angina,
should avoid exertion
and sources of CO, such
as heavy traffic.
>30 - 50
People with heart
disease, such as angina,
should avoid exertion
and sources of CO, such
as heavy traffic;
everyone else should
limit heavy exertion
>0.22-0.30
Children, asthmatics,
and people with heart or
lung disease should limit
outdoor exertion.
>0.30-0.60
Children, asthmatics,
and people with heart or
lung disease should
avoid outdoor exertion;
everyone else should
reduce outdoor exertion.
>0.60- 1.0
Children, asthmatics,
and people with heart or
lung disease should
remain indoors;
everyone else should
avoid outdoor exertion.
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Classifications and cautionary statements in Spanish:
Use estas tarjetas para entender los efectos de la contamination del aire cuando escuche las noticias
del Indice de la Calidad del Aire.
Valores del
Indice
Clasificacion
Precauciones para Protegerse del Ozono
Oa50
Buena
Ninguna.
51 a 100
Moderada
Las personas extraordinariamente sensitivas deben
considerar limitar los esfuerzos prolongados al aire
libre.
101 a 150
DaZina a la Salud de
los Grupos
Sensitives
Los niZos y adultos activos, y las personas con
enfermedades respiratorias, tales como el asthma,
deben limitar los esfuerzos prolongados al aire libre.
151 a 200
DaZina a la Salud
Los niZos y adultos activos, y las personas con
enfermedades respiratorias, tales como el asthma,
deben evitar el esfuerzo prolongado al aire libre; todos
los demas, especialmente los niZos, deben limitar el
esfuerzo prolongado al aire libre.
201 a 300
niZos y adultos activos, y las personas uui
irmedades respiratorias tales como el asthm
ien evitar cualquier esfuerzo al aire libre; todos los
iias, especialmente los niZos, deben limitar los
lerzos al aire libre.
Se ha asignado un color especffico a cada categorfa de AQI. Por ejemplo, el rojo significa
condiciones "daZinas a la salud" y el purpura significa condiciones "muy daZinas a la salud". Este
esquema de colores puede ayudarle a determinar rapidamente si los contaminantes del aire estan
alcanzando niveles muy daZinos a la salud en su zona.
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How do I calculate the AQI from pollutant concentration data?
You calculate the AQI by using your pollutant concentration data, the following table, and the
following equation (linear interpolation):
Where lp = the index for pollutant p
Cp = the rounded concentration of pollutant p
BPHi = the breakpoint that is greater than or equal to Cp
BP|_0 = the breakpoint that is less than or equal to Cp
BPHi = the breakpoint that is greater than or equal to Cp
IHI = the AQI value corresponding to BPHi
lLo = the AQI value corresponding to BPLo
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Table 2: Breakpoints for the AQI
This Breakpoint...
o3 (ppm)
8-hour
0.000 -
0.059
0.060 -
0.075
0.076 -
0.095
0.096 -
0.115
0.116-
0.374
(0.155-
0.404)4
(3)
(3)
O3 (ppm)
1-hour1
-
-
0.125-
0.164
0.165-
0.204
0.205 -
0.404
0.405 -
0.504
0.505 -
0.604
PM10
(ljg/m3)
0-54
55-
154
155-
254
255-
354
355-
424
425-
504
505-
604
PM2.5
(ljg/m3)
0.0- 15.4
15.5-40.4
40.5-65.4
65.5-
150.4
150.5-
250.4
250.5-
350.4
350.5 -
500.4
CO
(ppm)
0.0-4.4
4.5-9.4
9.5-
12.4
12.5-
15.4
15.5-
30.4
30.5-
40.4
40.5-
50.4
SO2 (ppm)
0.000 -
0.034
0.035 -
0.144
0.145-
0.224
0.225 -
0.304
0.305 -
0.604
0.605 -
0.804
0.805 -
1.004
...equal this AQI
NO2
(ppm)
(2)
(2)
(2)
(2)
0.65-
1.24
1.25-
1.64
1.65-
2.04
AQI
0-50
51 - 100
101 - 150
151 -200
201 - 300
301 - 400
401 - 500
...and this
category
Good
Moderate
Unhealthy for
Sensitive Groups
Unhealthy
Very unhealthy
Hazardous
Hazardous
1 Areas are required to report the AQI based on 8-hour ozone values. However, there are areas where an AQI
based on 1-hour ozone values would be more protective. In these cases the index for both the 8-hour and the
1-hour ozone values may be calculated and the maximum AQI reported.
2 NO2 has no short-term NAAQS and can generate an AQI only above a value of 200.
3 8-hour O3 values do not define higher AQI values (> 301). AQI values of 301 or higher are calculated with 1-
hour O3 concentrations.
4 The numbers in parentheses are associated 1-hour values to be used in this overlapping category only.
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How do I use the table and the equation and my concentration data to calculate the AQI?
Suppose you have an 8-hour ozone value of 0.08753333. First, round off the value to 0.087. Then
refer to the 8-hour ozone in table 2 for the values that fall above and below your value (0.076-0.095).
In this case, the 0.087 value falls within the index values of 101 to 150. Now you have all the
numbers needed to use the equation.
^150~101Vo87-.076) +101 = —.011+101 = 129.368=129
(.095-076)v } .019
So an 8-hour value of 0.08753333 corresponds to an index value of 129.
What if I have values for more pollutants?
Suppose you have an 8-hour ozone value of 0.077 ppm, a PM2.s value of 40.9 ug/m3, and a CO value
of 8.4 ppm. You apply the equation 3-times:
(150-101)
a: - - -(.077-076) +101= 104
3 (.095-076) v '
(150-101)
PM: — - -(40.9 -40.5) +101 =102
(65.4- 40.5) V '
C0:
The AQI is 104, with ozone as the responsible pollutant.
How do I use both ozone 1-hour and 8-hour values?
You must calculate the 8-hour values, and you may also calculate the 1-hour values. If you calculate
both, you must report the higher AQI value.
Suppose you had a 1-hour value of 0.162ppm and an 8-hour value of 0.141 ppm. Then you apply the
equation twice:
l~hr:
In this case, the index is 21 1 (the maximum of 204 and 211) and the responsible pollutant is ozone.
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What do I do with concentrations for pollutants that have blank places in the table for
Breakpoints for the AQI?
Disregard those numbers. Suppose you had a 1-hour ozone value of 0.104ppm, an 8-hour ozone
value of 0.087ppm and an NO2 value of 0.54ppm. First you disregard the 1-hour ozone value
because it is less than 0.125ppm and the NO2 value because it is less than 0.65ppm. Then you
calculate the index for the 8-hour ozone value as before:
(150-101)
-(.087-.076) +101 = 129.368
(.095-076)v }
This value rounds to 129.
Are there exceptions to these reporting requirements?
Yes. When you have low index values that meet the following criteria, you do not have to meet all the
requirements. If the index for a specific pollutant remains below 50 for an extended period of time (for
example, for that particular season), then you are not required to include this pollutant in the
calculation of the AQI.
The final rule allows agencies to discontinue reporting for any pollutant if index values for that
pollutant have been below 50 for an entire season or a year. However, this does not hold if in
subsequent years' pollutant levels rise so that index values for that pollutant would be above 50 and
the criteria for an exemption are no longer met. In these cases, section 8 of appendix G now requires
that the responsible agency must again report the AQI.
Do I have to forecast pollutant concentrations for the AQI report?
Although not required, you are encouraged to forecast values at least 24 hours in advance. The AQI
is designed to inform members of sensitive groups and the general population so that they may
choose to reduce or avoid exposure to certain levels and types of air pollution. If the information is
not timely, the public cannot make this choice. However, good forecasts may require data,
computational resources and expertise that may be unavailable to you. The EPA provides guidance if
you are interested in starting a forecasting program for AQI reporting in your Metropolitan Statistical
Area (MSA).
Since ozone is a dominant pollutant in AQI reporting and the form of the ozone standard is an 8-hour
average, the timing of how the public is informed is an important issue, even if you have decided not
to forecast 24 hours in advance. In order for potentially affected people to take advantage of this
information, it is necessary to consider at least a short term forecast or prediction of 8-hour ozone
levels for the purposes of reporting the AQI. You can do this with very little additional resources; the
method you can use relies on the high correlation between daily maximum of 8-hour ozone and 1-
hour ozone values. A simple linear regression can be calculated on daily max data at any site. From
this regression, you can predict that the 8-hour ozone maximum for a day will be at least the
corresponding maximum 8-hour value, given the present 1-hour value. From this information, you can
estimate the AQI without having to wait for the full 8-hour maximum to be observed.
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What if the correlation at my site is low- can I still forecast the AQI?
The lowest observed correlation at any site reporting to AIRS data was 0.86, which is adequate to
predict the maximum 8-hour values from the maximum 1-hour for reporting the AQI. However, if you
feel uncomfortable from either a public health or cost viewpoint, you may want to use a confidence
interval for the decision you make based on the predicted 8-hour maximum. For example, if your
ozone action day is declared when you reach the unhealthy category and you predict an unhealthy
day but are unsure whether or not you should call an "ozone action day" based on this prediction, you
can use the confidence interval of the predicted value to trigger your decision. If you are concerned
about public health, you might consider calling an "ozone action day" as soon as the upper bound of
the confidence interval is greater than the AQI cut-point for the unhealthy category. If you are
concerned with the cost of calling an "ozone action day" unnecessarily, then you might consider
calling an ozone action day only when the lower bound of the confidence interval is above the cut-
point for the unhealthy category.
Is there anything else I should know about reporting the AQI?
For further information, go to www.epa.gov/airnow. Under "Publications," there are several
informative documents to help you report the AQI, including the ones listed:
• AQI brochure • Pamphlets:
• AQI calculator program -Ozone Pollution and your Health
• Forecasting guidance -Particle Pollution and your Health
• Air quality guides for: -Smog: Who does it Hurt?
-Ozone • Medical poster
-Particle pollution • Ozone web course for health care
providers
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How do I calculate the upper and lower bounds of the confidence interval for the predicted
maximum 8-hour ozone value?
Most computer regression programs include the error variance, or the residual variance, or the
variance of "Y given X" as part of the output. Call this Se2. Then you calculate the upper and lower
bounds of the predicted value as:
I (x' -x~)2
upper. r+^/2w_2J^|l+- + '
(n-l)S
lower. 7-^/2,_2
Where:
is the predicted 8-hour ozone maximum,
ti-a/2,n-2 is a tabulated Student's-T value corresponding to a two sided (1- a) 100% confidence
interval with n-2 degrees of freedom,
Se2 is the error variance described above,
x! is the 1-hour value used to predict the 8-hour value,
x is the average of the 1-hour values, and
Sx2 is the variance of the 1-hour values.
The value a is arbitrary, but conventionally it is set to 0.05 corresponding to a 95% confidence
interval.
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APPENDIX
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Table 3: Metropolitan Statistical Areas with over 350,000 population (2000 Census)
MSA NAME
1000 Birmingham, AL MSA
5160 Mobile, AL MSA
4400 Little Rock-North Little Rock, AR MSA
6200 Phoenix-Mesa, AZ MSA
8520 Tucson, AZ MSA
680 Bakersfield, CA MSA
2840 Fresno, CA MSA
4480 Los Angeles-Long Beach, CA PMSA
5170 Modesto, CA MSA
5775 Oakland, CA PMSA
5945 Orange County, CA PMSA
6780 Riverside-San Bernardino, CA PMSA
6920 Sacramento, CA PMSA
7120 Salinas, CA MSA
7320 San Diego, CA MSA
7360 San Francisco, CA PMSA
7400 San Jose, CA PMSA
7480 Santa Barbara-Santa Maria-Lompoc, CA MSA
7500 Santa Rosa, CA PMSA
8120 Stockton-Lodi, CA MSA
8720 Vallejo-Fairfield-Napa, CA PMSA
8735 Ventura, CA PMSA
8780 Visalia-Tulare-Porterville, CA MSA
1720 Colorado Springs, CO MSA
2080 Denver, CO PMSA
1160 Bridgeport, CT PMSA
3280 Hartford, CT MSA
5480 New Haven-Meriden, CT PMSA
8040 Stamford-Norwalk, CT PMSA
8840 Washington, DC-MD-VA-WV PMSA
9160 Wilmington-Newark, DE-MD PMSA
2020 Daytona Beach, FL MSA
2680 Fort Lauderdale, FL PMSA
2700 Fort Myers-Cape Coral, FL MSA
STATE
AL
AL
AR
AZ
AZ
CA
CA
CA
CA
CA
CA
CA
CA
CA
CA
CA
CA
CA
CA
CA
CA
CA
CA
CO
CO
CT
CT
CT
CT
DC/MDA/A/WV
DE/MD
FL
FL
FL
POPULATION
921,106
540,258
583,845
3,251,876
843,746
661,645
922,516
9,519,338
446,997
2,392,557
2,846,289
3,254,821
1,628,197
401,762
2,813,833
1,731,183
1,682,585
399,347
458,614
563,598
518,821
753,197
368,021
516,929
2,109,282
459,479
1,183,110
542,149
353,556
4,923,153
586,216
493,175
1,623,018
440,888
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3600 Jacksonville, FL MSA FL 1,100,491
3980 Lakeland-Winter Haven, FL MSA FL 483,924
4900 Melbourne-Titusville-Palm Bay, FL MSA FL 476,230
5000 Miami, FL PMSA FL 2,253,362
5960 Orlando, FL MSA FL 1,644,561
6080 Pensacola, FL MSA FL 412,153
7510 Sarasota-Bradenton, FL MSA FL 589,959
8280 Tampa-St. Petersburg-Clearwater, FL MSA FL 2,395,997
8960 West Palm Beach-Boca Raton, FL MSA FL 1,131,184
520 Atlanta, GA MSA GA 4,112,198
600 Augusta-Aiken, GA-SC MSA GA/SC 477,441
3320 Honolulu, HI MSA HI 876,156
2120 Des Moines, IA MSA IA 456,022
1960 Davenport-Moline-Rock Island, IA-IL MSA IA/IL 359,062
1080 Boise City, ID MSA ID 432,345
1600 Chicago, IL PMSA IL 8,272,768
6880 Rockford, ILMSA IL 371,236
2760 Fort Wayne, IN MSA IN 502,141
2960 Gary, IN PMSA IN 631,362
3480 Indianapolis, IN MSA IN 1,607,486
9040 Wichita, KS MSA KS 545,220
4280 Lexington, KY MSA KY 479,198
4520 Louisville, KY-IN MSA KY 1,025,598
760 Baton Rouge, LA MSA LA 602,894
3880 Lafayette, LA MSA LA 385,647
5560 New Orleans, LA MSA LA 1,337,726
7680 Shreveport-Bossier City, LA MSA LA 392,302
1120 Boston, MA-NH PMSA MA 3,406,829
8000 Springfield, MA MSA MA 591,932
9240 Worcester, MA-CT PMSA MA/CT 511,389
4160 Lawrence, MA-NH PMSA MA/NH 396,230
720 Baltimore, MD PMSA MD 2,552,994
440 Ann Arbor, Ml PMSA Ml 578,736
2160 Detroit, Ml PMSA Ml 4,441,551
2640 Flint, Ml PMSA Ml 436,141
3000 Grand Rapids-Muskegon-Holland, Ml MSA Ml 1,088,514
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3720 Kalamazoo-Battle Creek, Ml MSA
4040 Lansing-East Lansing, Ml MSA
6960 Saginaw--Bay City-Midland, Ml MSA
5120 Minneapolis-St. Paul, MN-WI MSA
7040 St. Louis, MO-IL MSA
3760 Kansas City, MO-KS MSA
920 Biloxi-Gulfport-Pascagoula, MS MSA
3560 Jackson, MS MSA
3120 Greensboro-Winston-Salem-High Point, NC MSA
6640 Raleigh-Durham-Chapel Hill, NC MSA
1520 Charlotte-Gastonia-Rock Hill, NC-SC MSA
5920 Omaha, NE-IA MSA
560 Atlantic-Cape May, NJ PMSA
875 Bergen-Passaic, NJ PMSA
3640 Jersey City, NJ PMSA
5015 Middlesex-Somerset-Hunterdon, NJ PMSA
5190 Monmouth-Ocean, NJ PMSA
5640 Newark, NJ PMSA
8480 Trenton, NJ PMSA
200 Albuquerque, NM MSA
4120 Las Vegas, NV-AZ MSA
160 Albany-Schenectady-Troy, NY MSA
1280 Buffalo-Niagara Falls, NY MSA
5380 Nassau-Suffolk, NY PMSA
5600 New York, NY PMSA
6840 Rochester, NY MSA
8160 Syracuse, NY MSA
5660 Newburgh, NY-PA PMSA
80 Akron, OH PMSA
1320 Canton-Massillon, OH MSA
1680 Cleveland-Lorain-Elyria, OH PMSA
1840 Columbus, OH MSA
2000 Dayton-Springfield, OH MSA
8400 Toledo, OH MSA
9320 Youngstown-Warren, OH MSA
1640 Cincinnati, OH-KY-IN PMSA
Ml
Ml
Ml
MN/WI
MO/IL
MO/KS
MS
MS
NC
NC
NC/SC
NE/IA
NJ
NJ
NJ
NJ
NJ
NJ
NJ
NM
NV/AZ
NY
NY
NY
NY
NY
NY
NY/PA
OH
OH
OH
OH
OH
OH
OH
OH/KY/IN
452,851
447,728
403,070
2,968,806
2,603,607
1
1
1
1
1
1
1
,776,062
363,988
440,801
,251,509
,187,941
,499,293
716,998
354,878
,373,167
608,975
,169,641
,126,217
2,032,989
1
1
350,761
712,738
,563,282
875,583
,170,111
2,753,913
9,314,235
1
,098,201
732,117
387,669
694,960
406,934
2,250,871
1
1
,540,157
950,558
618,203
594,746
,646,395
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5880 Oklahoma City, OK MSA
8560 Tulsa, OK MSA
6440 Portland-Vancouver, OR-WA PMSA
240 Allentown-Bethlehem-Easton, PA MSA
3240 Harrisburg-Lebanon-Carlisle, PA MSA
4000 Lancaster, PA MSA
6280 Pittsburgh, PA MSA
6680 Reading, PA MSA
7560 Scranton-Wilkes-Barre-Hazleton, PA MSA
9280 York, PA MSA
6160 Philadelphia, PA--NJ PMSA
6360 Ponce, PR MSA
7440 San Juan-Bayamon, PR PMSA
6480 Providence-Fall River-Warwick, RI-MA MSA
1440 Charleston-North Charleston, SC MSA
1760 Columbia, SC MSA
3160 Greenville-Spartanburg-Anderson, SC MSA
3840 Knoxville, TN MSA
5360 Nashville, TN MSA
4920 Memphis, TN-AR-MS MSA
1560 Chattanooga, TN-GA MSA
3660 Johnson City-Kingsport-Bristol, TN-VA MSA
640 Austin-San Marcos, TX MSA
840 Beaumont-Port Arthur, TX MSA
1880 Corpus Christi, TX MSA
1920 Dallas, TX PMSA
2320 El Paso, TX MSA
2800 Fort Worth-Arlington, TX PMSA
3360 Houston, TX PMSA
4880 McAllen-Edinburg-Mission, TX MSA
7240 San Antonio, TX MSA
6520 Provo-Orem, UT MSA
7160 Salt Lake City-Ogden, UT MSA
5720 Norfolk-Virginia Beach-Newport News, VA--NC
MSA
6760 Richmond-Petersburg, VA MSA
7600 Seattle-Bellevue-Everett, WA PMSA
OK
OK
OR/WA
PA
PA
PA
PA
PA
PA
PA
PA/NJ
PR
PR
RI/MA
SC
SC
SC
TN
TN
TN/AR/MS
TN/GA
TN/VA
TX
TX
TX
TX
TX
TX
TX
TX
TX
UT
UT
VA/NC
VA/NC
WA
1
1
,083,346
803,235
,918,009
637,958
629,401
470,658
2,358,695
373,638
624,776
381,751
5,100,931
1
1
1
1
1
361,094
,967,627
,188,613
549,033
536,691
962,441
687,249
,231,311
,135,614
465,161
480,091
,249,763
385,090
380,783
3,519,176
1
679,622
,702,625
4,177,646
1
1
1
569,463
,592,383
368,536
,333,914
,569,541
996,512
2,414,616
23
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7840 Spokane, WA MSA WA 417,939
8200 Tacoma, WA PMSA WA 700,820
460 Appleton-Oshkosh-Neenah, Wl Wl 358,365
4720 Madison, Wl MSA Wl 426,526
5080 Milwaukee-Waukesha, Wl PMSA Wl 1,500,741
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FREQUENTLY ASKED QUESTIONS
I want to buy an air purifier. Are the purifiers that produce ozone helpful to my indoor air
quality?
Some air cleaning devices, such as ozone generators and ionic air purifiers, can generate significant
levels of ozone. Even at low levels, ozone triggers a variety of health problems, including aggravated
asthma and increased susceptibility to respiratory illnesses. Additional information on the assessment
of the effectiveness and health consequences of ozone generators that are sold as air cleaners can
be found at http://www.epa.gov/iaq/pubs/ozonegen.html, and also at the California Air Resources
Board Web site at http://www.arb.ca.gov/research/indoor/ozone gen fact sheet-a.pdf.
If you're having issues with mold and moisture, solutions and preventative tips are offered at
http://www.epa.gov/mold/index.html. For additional questions about indoor air quality, please use
the EPA Office of Indoor Air Quality hotline at 1-800-438-4318.
Why is my area not covered in the Air Quality Index?
Towns and cities with 350,000 or fewer inhabitants are not required to report the AQI. Also, AIRNow is
a voluntary program based upon state and local air quality monitoring networks. Some networks don't
submit their data, or don't have any monitors in the area.
The other day, the air quality in my area was reported as green, or good air quality. However,
it was pretty hazy outside. Why didn't the AQI report this accurately?
There are a couple of reasons why this may have occurred, depending on what was "reported." If this
was an AQI forecast, there are still some parts of the United States that only forecast for ozone and
not particle pollution. It is possible that the forecast ozone AQI was "GOOD" and the hazy conditions
experienced were due to particle pollution. In this instance, the "reported" AQI forecast may have only
represented ozone. As more and more areas begin forecasting for PM2.5 and ozone together, this
discrepancy should diminish.
In the case of real-time data, the AIRNow program provides separate maps for ozone and PM2.5 AQI.
It is possible that the ozone AQI maps were showing "GOOD" conditions and the PM2.5 maps
showing "MODERATE" or above conditions. It is important to check both maps for a specific
geographical area to cover both primary pollutants. In the future, AIRNow plans to have combined
AQI maps of both ozone and PM2.5 that will eliminate this problem, but will continue to provide the
separate pollutant AQI maps to allow for people to identify the pollutant of concern.
Finally, it should be noted that there are occasions where hazy conditions may be due primarily to
high humidity and not pollution. On these days, it is still good to check the AQI maps and forecasts to
make sure that pollution is not the primary cause of the haze.
How do I get my newspaper to publish the AQI?
Most newspaper weather pages and graphics are developed and produced by private weather service
providers. We recommend that you direct your initial approach to the newspaper editors, since they
are the customers of the weather provider company. In general, newspapers want to provide more
health-based information to their readers. However, it may take some effort to educate
decisionmakers about the importance of providing air quality information to the public. When you
meet with the newspaper staff, bring along this guidance document or several examples showing how
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other newspapers publish the AQI. In addition, most weather service providers already have access
to the air quality data through AIRNow, which makes it easier for them to acquire and publish the
information. Space on weather pages is limited, so a small, compact graphic might be a better choice
for a crowded weather page.
If the AQI reported in the newspaper is incorrect, what should I do?
Common problems with AQI reporting in newspapers include either reporting data values that are
wrong or reporting pollutant concentrations instead of the AQI. Another frequent mistake is to report
inconsistent AQI colors or terminology, as well as incorrect pollutant names. Establishing a good
working relationship with the newspaper and educating them about how misleading or erroneous AQI
information can impact their readers could help minimize potential problems. We recommend that
you first notify the newspaper directly about any error so they can relay discrepancies to their weather
service provider as a paying customer. If you have difficulty getting the newspaper to correct the
issue, you could team with other health and nongovernmental organizations to approach the
newspaper editor with a united message and request.
Should I report yesterday's observed value, today's forecast, or tomorrow's forecast to the
newspaper?
Let's assume that today is Monday, and you are submitting data for Tuesday morning's paper. Let's
also assume that the paper is willing to carry both the observed AQI and the forecast. In such a case:
• Send the paper the most recent observed AQI. If it's midnight to midnight, that means
Sunday's data.
• Send the Tuesday forecast so there is a "day-of" forecast in the Tuesday paper.
• If you have the Wednesday forecast and they're willing to carry that, include it too.
My local newspaper has a deadline of 2 pm for the next day's paper. Should I report the AQI
value through 1 pm, or report the forecast?
Again, since the true AQI is a midnight to midnight calculation, we recommend that you report
tomorrow's forecast. If this is not possible, then report the AQI value through a certain time, but make
sure the newspaper includes the reporting period to avoid confusion.
How do I get my local TV station to show the AQI?
Similar to the newspaper industry, television reporting reflects the culture of the local community and
what competing stations show. Television stations use weather service providers to provide graphics
and data support for their weathercasts. All of the weather service companies have access to the air
quality data through AIRNow, which makes it easy for them to acquire and provide these data to their
television station customers. There are several questions that need to be addressed: Does the
station want to show air quality information? Do other stations in your market show air quality
information? Is the station news director on board with providing this information? Does the station
have the proper software to access the air quality data?
For stations that have never shown these data on the air, you will need to establish a relationship and
educate them about the benefits of providing air quality information to their viewers. Air quality is
weather, news and health all in one. Once a station in your market begins to provide air quality
information, chances are good that other stations will follow suit. However, even if the weathercasters
want to provide this information in their weathercasts, the station news director controls the content of
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what goes on the air. In addition, if the station wants to show the AQI on the air, they need to have
the proper software version of weather graphics products to access and display the AQI. Keep in
mind that air quality information could be displayed only during periods of high pollution levels, when it
is considered more "newsworthy."
Can we still use the Pollutant Standards Index?
No. The Air Quality Index is required by law.
Does providing our data and forecasts to AIRNow meet the AQI reporting requirements?
No. Even though the air quality information that you provide to AIRNow is distributed on a national
basis to the media and weather service provider companies, there is no guarantee that this
information ends up within the media (newspaper, radio, or web site) in your local community as
required.
Why doesn't the AQI cover toxic air pollutants or air toxics?
While the AQI is an excellent indicator of the air quality resulting from ozone and particulate matter, it
does not directly include health implications from air pollutants such as air toxics. Adverse health
effects from air toxics are generally not believed to be episodic in nature like ozone and particulate
matter, and are usually evaluated on a longer term, or chronic, basis. For information on
concentrations of air toxics, refer to EPA's National Air Toxics Assessment (NATA) Website at:
http://www.epa.gov/ttn/atw/nata/.
Why does EPA issue AQI forecasts only for ozone and particle pollution?
AQI reporting is required for all criteria pollutants when they have an index value of 50 or above. Most
cities forecast for ozone and particle pollution as these pollutants are the major sources of unhealthy
air quality around 99% of the time. However, several cities forecast for all five pollutants- ground-level
ozone, particle pollution, carbon monoxide, sulfur dioxide, and nitrogen dioxide.
Should I use particulate matter or particle pollution when speaking with the public?
Based on focus group testing by EPA, people better understand and prefer the term "particle
pollution" than "particulate matter."
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United States Office of Air Quality Planning and Publication No. EPA-
Environmental Protection Standards 454/B-09-001
Agency Research Triangle Park, NC 27711 February 2009
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