Technical Assistance Document
for the Reporting of Daily Air Quality
the Air Quality Index (AQI)

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EPA-454/B-13-001
December 2013
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	23

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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. 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
0 to 50 	"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).
1

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Table 1: Pollutant Specific Sensitive Groups
When this pollutant has an index above 100...
Ozone
PM2.5
PM10
CO
N02
S02
Report these Sensitive Groups
People with lung disease, children, older adults, and
people who are active outdoors are the groups most
at risk
People with heart or lung disease, older adults,
children, and people of lower socioeconomic status
(SES) are the groups most at risk
People with heart or lung disease, older adults,
children, and people of lower socioeconomic status
are the groups most at risk
People with heart disease are the group most at risk
People with asthma, children, and older adults are
the groups most at risk
People with asthma, children, and older adults are
the groups 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.
2

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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: 66
Main pollutant: Particulate Matter
T
0-50
51-100
101-150
151-200
201-300
Good
Moderate
Unhealthy,
Unhealthy
Very


Sensitive

unhealthy


groups


~
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.
3
GOOD
MODERATE
UNHEALTHY for SENSITIVE
GROUPS
UNHEALTHY
VERY UNHEALTHY
HAZARDOUS

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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.
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
4

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Air Quality Index for St. Louis, MO
Time of this report:	1:00PM
Responsible pollutant: Ozone
AQI:
Category:
Example 9. A long form for a Web page- ozone
Air Quality Index for Chicago, IL for August 2
Report as of:
2:00PM
AQI:
162
Responsible pollutant:
Ozone
Code:
Red
Category:
Unhealthy

Sensitive groups:
Active children and adults, and people with lung disease, such as asthma,
should reduce prolonged or heavy outdoor exertion.
Health effects:
HEALTH
ADVISORY
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:
Orange

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Example 10. A long form for a Web page- particulate matter
Anchorage, Alaska
UnhoaHhy
Vmry Unhaaltny
Smoke Plume
Source: NOAA
ast, winds
Air Quality Outlook
for Aug 17-19, 2004
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.
6

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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 below for red, green, blue (RGB) and cyan, magenta, yellow,
and black (CMYK) color formulas:
Color
R
G
B
C
M
Y
K
Green
0
228
0
40
0
100
0
Yellow
255
255
0
0
0
100
0
Orange
255
126
0
0
52
100
0
Red
255
0
0
0
100
100
0
Purple
143
63
151
51
89
0
0
Maroon
126
0
35
30
100
100
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.
7

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Pollutant-Specific Sub-indices and Health Effects Statements
for Guidance on the Air Quality Index (AQI)
AQI
Categories:
Index Values
Ozone (ppm)
Particulate Matter (jjg/m3)
Carbon Monoxide (ppm)
[8-hour]
Sulfur Dioxide
(PPb)
[1-hour]
Nitrogen Dioxide
(PPb)
[1-hour]
[8-hour]
[1-hour]
PM [24-hour]
2.5
[24-hour]
PM10
Good
(Up to 50)
0 - 0.059
None
-
0-12.0
None
0-54
None
0-4.4
None
0-35
None
0-53
None
Moderate
(51 -100)
0.060 - 0.075
Unusually sensitive
individuals may
experience respiratory
symptoms.

12.1 -35.4
55-154
4.4-9.4
None
36-75
None
54-100
None
Respiratory symptoms possible in unusually
sensitive individuals, possible aggravation of heart
or lung disease in people with cardiopulmonary
disease and older adults.
Unhealthy for
Sensitive Groups
(101 -150)
0.076 - 0.095
0.125-0.164
35.5 - 55.4
155-254
9.5-12.4
Increasing likelihood of
reduced exercise
tolerance due to increased
cardiovascular symptoms,
such as chest pain, in
people with heart disease.
76-185
Increasing likelihood of
respiratory symptoms,
such as chest tightness
and breathing discomfort,
in people with asthma.
101 -360
Increasing likelihood of
respiratory symptoms,
such as chest tightness
and breathing discomfort,
in people with asthma.
Increasing likelihood of respiratory symptoms
and breathing discomfort in people with lung
disease, such as asthma, children, older adults
and outdoor workers.
Increasing likelihood of respiratory symptoms in
sensitive individuals, aggravation of heart or lung
disease and premature mortality in people with
cardiopulmonary disease, older adults, and people
of lower SES.
Unhealthy
(151 -200)
0.096-0.115
0.165-0.204
55.5-150.4
254 - 354
12.5-15.4
Reduced exercise
tolerance due to increased
cardiovascular symptoms,
such as chest pain, in
people with heart disease.
186-304
Increased respiratory
symptoms, such as chest
tightness and wheezing in
people with asthma;
possible aggravation of
other lung diseases.
361 - 649
Increased respiratory
symptoms, such as chest
tightness and wheezing in
people with asthma;
possible aggravation of
other lung diseases.
Greater likelihood of respiratory symptoms and
breathing difficulty in people with lung disease,
such as asthma, children, older adults, and
outdoor workers; possible respiratory effects in
general population.
Increased aggravation of heart or lung disease and
premature mortality in people with cardiopulmonary
disease, older adults, and people of lower SES;
increased respiratory effects in general population.
8

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Very Unhealthy
(201 - 300)
0.116-0.374
0.205 - 0.404
150.5-250.4
355 - 424
15.5-30.4
Significant aggravation of
cardiovascular symptoms,
such as chest pain, in
people with heart disease.
305 - 604 [24-hour]
Significant increase in
respiratory symptoms,
such as wheezing and
shortness of breath, in
people with asthma;
aggravation of other lung
diseases.
650-1249
Significant increase in
respiratory symptoms,
such as wheezing and
shortness of breath, in
people with asthma;
aggravation of other lung
diseases.
Increasingly severe symptoms and impaired
breathing likely in people with lung disease,
such as asthma, children, older adults, and
outdoor workers; increasing likelihood of
respiratory effects in general population.
Significant aggravation of heart or lung disease and
premature mortality in people with cardiopulmonary
disease, older adults, and people of lower SES;
significant increase in respiratory effects in general
population.
Hazardous
(301 - 500)
-
0.405 - 0.604
250.5 - 500.4
425 - 604
30.5 - 50.4
Serious aggravation of
cardiovascular symptoms,
such as chest pain, in
people with heart disease;
impairment of strenuous
activities in general
population.
605-1004 [24-hour]
Severe respiratory
symptoms, such as
wheezing and shortness of
breath, in people with
asthma; increased
aggravation of other lung
diseases; possible
respiratory effects in
general population.
1249-2049
Severe respiratory
symptoms, such as
wheezing and shortness of
breath, in people with
asthma; increased
aggravation of other lung
diseases; possible
respiratory effects in
general population.
Severe respiratory effects and impaired
breathing likely in people with lung disease,
such as asthma, children, older adults and
outdoor workers; increasingly severe
respiratory effects likely in general population.
Serious aggravation of heart or lung disease and
premature mortality in people with cardiopulmonary
disease, older adults, and people of lower SES;
serious risk of respiratory effects in general
population.
9

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Pollutant-Specific Sub-indices and Cautionary Statements
for Guidance on the Air Quality Index (AQI)
AQI
Categories
(Index
Values)
Ozone (ppm)
Particulate Matter (jjg/m3)
Carbon Monoxide
(ppm)
[8-hour]
Sulfur Dioxide
(PPb)
[1-hour]
Nitrogen Dioxide
(PPb)
[1-hour]
[8-hour]
[1-hour]
PM [24-hour]
2.5
[24-hour]
PM10
Good
(Up to 50)
0 - 0.059
None

0-12.0
None
0-54
None
0-4.4
None
0-35
None
0-53
None
Moderate
(51 -100)
0.060 - 0.075

12.1 -35.4
55-154
4.5-9.4
None
36-75
None
54-100
Unusually sensitive
individuals should
consider limiting
prolonged exertion
especially near busy
roads.
Unusually sensitive
people should
consider reducing
prolonged or heavy
outdoor exertion.
Unusually sensitive people should consider
reducing prolonged or heavy exertion.
Unhealthy for
Sensitive Groups
(101 -150)
0.076 - 0.095
0.125-0.164
35.5 - 55.4
155-254
9.5-12.4
People with heart disease,
such as angina, should
limit heavy exertion and
avoid sources of CO, such
as heavy traffic.
76-185
People with asthma
should consider limiting
outdoor exertion.
101 -360
People with asthma,
children and older adults
should limit prolonged
exertion especially near
busy roads.
People with lung disease, such as asthma,
children, older adults, and outdoor workers
should reduce prolonged or heavy outdoor
exertion.
People with heart or lung disease, older adults,
children, and people of lower SES should reduce
prolonged or heavy exertion.
10

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Unhealthy
0.096-0.115
0.165-0.204
55.5-150.4
255 - 354
12.5-15.4
186-304
361 - 649
(151 -200)








People with lung disease, such as asthma,
People with heart or lung disease, older adults,
People with heart disease,
Children, people with
People with asthma,

children, older adults, and outdoor workers
children, and people of lower SES should avoid
such as angina, should
asthma, or other lung
children and older adults

should avoid prolonged or heavy outdoor
prolonged or heavy exertion; everyone else should
limit moderate exertion
diseases, should limit
should avoid prolonged

exertion; everyone else should reduce
reduce prolonged or heavy exertion.
and avoid sources of CO,
outdoor exertion.
exertion near roadways;

prolonged or heavy outdoor exertion.


such as heavy traffic.

everyone else should







limit prolonged exertion







especially near busy







roads.
Very Unhealthy
0.116-0.374
0.205 - 0.404
150.5-250.4
355 - 424
15.5-30.4
305 - 604 [24-hour]
650- 1249
(201 - 300)




People with heart disease,
Children, people with
People with asthma,





such as angina, should
asthma, or other lung
children and older adults






People with lung disease, such as asthma,
People with heart or lung disease, older adults,
avoid exertion and
diseases should avoid
should avoid all outdoor

children, older adults, and outdoor workers
children, and people of lower SES should avoid all
sources of CO, such as
outdoor exertion; everyone
exertion; everyone else

should avoid all outdoor exertion; everyone
physical activity outdoors. Everyone else should
heavy traffic.
else should reduce
should avoid prolonged

else should reduce outdoor exertion.
avoid prolonged or heavy exertion.

outdoor exertion.
exertion especially near







busy roads.
Hazardous
_
0.405 - 0.604
250.5 - 500.4
425 - 604
30.5 - 50.4
604-1004 [24-hour]
1250-2049
(301 - 500)




People with heart disease,
Children, people with
People with asthma,

Everyone should avoid all outdoor exertion.
Everyone should avoid all physical activity outdoors;
people with heart or lung disease, older adults,
children, and people of lower SES should remain
indoors and keep activity levels low.
such as angina, should
avoid exertion and
sources of CO, such as
heavy traffic; everyone
else should limit heavy
asthma, or other lung
diseases, should remain
indoors; everyone else
should avoid outdoor
exertion.
children and older adults
should remain indoors;
everyone else should
avoid all outdoor
exertion.





exertion.


11

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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
0 a 50
Buena
Ninguna.
51 a 100
Moderada
Las personas extraordinariamente sensitivas deben
considerar limitar los esfuerzos prolongados al aire
libre.
101 a 150
Danina a la Salud de
los Grupos
Sensitivos
Los ninos y adultos activos, y las personas con
enfermedades respiratorias, tales como el asthma,
deben limitar los esfuerzos prolongados al aire libre.
151 a 200
Danina a la Salud
Los ninos 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 ninos, deben limitar el
esfuerzo prolongado al aire libre.
201 a 300
Muy Danina a la
Salud
Los ninos y adultos activos, y las personas con
enfermedades respiratorias tales como el asthma,
deben evitar cualquier esfuerzo al aire libre; todos los
demas, especialmente los ninos, deben limitar los
esfuerzos al aire libre.
Se ha asignado un color especffico a cada categoria de AQI. Por ejemplo, el rojo significa
condiciones "daninas a la salud" y el purpura significa condiciones "muy daninas a la salud". Este
esquema de colores puede ayudarle a determinar rapidamente si los contaminantes del aire estan
alcanzando niveles muy daninos a la salud en su zona.
12

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How do I calculate the AQI from pollutant concentration data?
The AQI is the highest value calculated for each pollutant as follows:
a. Identify the highest concentration among all of the monitors within each reporting area and truncate
as follows:
Ozone - truncate to 3 decimal places
PM2.5 - truncate to 1 decimal place
PM10 - truncate to integer
CO - truncate to 1 decimal place
S02 - truncate to integer
N02 - truncate to integer
b.	Using Table 2, find the two breakpoints that contain the concentration.
c.	Using Equation 1, calculate the index.
d.	Round the index to the nearest integer.
Equation 1:
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
BPlo = the breakpoint that is less than or equal to Cp
BPHi = the breakpoint that is greater than or equal to Cp
lHi = the AQI value corresponding to BPHi
lLo = the AQI value corresponding to BPLo
I
13

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Table 2: Breakpoints for the AQI
These Breakpoints...
...equal
this AQI
...and this
category
o3
(ppm)
8-hour
o3
(ppm)
1-hour1
PM10
(|jg/m3)
24-hour
pm25
(|jg/m3)
24-hour
CO
(ppm)
8-hour
S02
(PPb)
1-hour
no2
(PPb)
1-hour
AQI

0.000 -
0.059
-
0-54
0.0-
12.0
0.0-4.4
0-35
0-53
0-50
Good
0.060 -
0.075
-
55- 154
12.1 -
35.4
4.5-9.4
36-75
54- 100
51 - 100
Moderate
0.076 -
0.095
0.125-
0.164
155-
254
35.5-
55.4
9.5-
12.4
76- 185
101 -
360
101 - 150
Unhealthy for
Sensitive Groups
0.096 -
0.115
0.165-
0.204
255-
354
(55.5 -
150.4)3
12.5-
15.4
(186-
304)4
361 -
649
151 -200
Unhealthy
0.116-
0.374
0.205 -
0.404
355-
424
(150.5-
(250.4)3
15.5-
30.4
(305-
604)4
650-
1249
201 - 300
Very unhealthy
(2)
0.405 -
0.504
425-
504
(250.5-
(350.4)3
30.5-
40.4
(605-
804)4
1250-
1649
301 - 400
Hazardous
(2)
0.505 -
0.604
505-
604
(350.5-
500.4)3
40.5-
50.4
(805-
1004)4
1650-
2049
401 - 500
Hazardous
1	Areas are generally required to report the AQI based on 8-hour ozone values. However, there are a small
number of areas where an AQI based on 1-hour ozone values would be more precautionary. In these cases, in
addition to calculating the 8-hour ozone index value, the 1-hour ozone value may be calculated, and the
maximum of the two values reported.
2	8-hour 03 values do not define higher AQI values (> 301). AQI values of 301 or higher are calculated with 1-
hour 03 concentrations.
3	If a different SHL for PM2.5 is promulgated, these numbers will change accordingly.
41-hour S02 values do not define higher AQI values (> 200). AQI values of 200 or greater are calculated with
24-hour S02 concentrations.
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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.
(150-101)	49
		-(.087-076) +101 =	.011 +101 = 129.368= 129
(.095-076)	7	.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 PM2.5 value of 35.9 |jg/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- —	-(35.9 —35 5)+ 101 =102
(55.4-35.5) V	J
(100-51)
CO: 		-(8.4 -4.5) + 51 = 90
(9.4-4.5)v	^
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:
x_hr (300 - 201) (162 155) + 2oi = 204
(.404-.155)v	7
8 - hr. (3QQ ~ 2Q1) (141-H6) + 201 = 211
(.374-.116)v	7
In this case, the index is 211 (the maximum of 204 and 211) and the responsible pollutant is ozone.
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How do I calculate AQI values for S02?
EPA strengthened the primary standard for S02 in 2010. Because there was not enough health
information to inform changing the upper end of the AQI for S02, the upper end continues to use the
24-hour average S02 concentration. The lower end of the AQI uses the new daily max 1-hour S02
concentration.
If you have a daily max 1-hour S02 concentration below 305 ppb, then use the breakpoints in Table 2
to calculate the AQI value.
If you have a 24-hour average S02 concentration greater than or equal to 305 ppb, then use the
breakpoints in Table 2 to calculate the AQI value. If you have a 24-hour value in this range, it will
always result in a higher AQI value than a 1-hour value would.
On rare occasions, you could have a day where the daily max 1-hour concentration is at or above 305
ppb but when you try to use the 24-hour average to calculate the AQI value, you find that the 24-hour
concentration is not above 305 ppb. If this happens, use 200 for the lower and upper AQI breakpoints
(ILo and I Hi) in Equation 1 to calculate the AQI value based on the daily max 1-hour value. This
effectively fixes the AQI value at 200 exactly, which ensures that you get the highest possible AQI
value associated with your 1-hour concentration on such days.
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 and an 8-hour ozone
value of 0.087ppm. First you disregard the 1-hour ozone value because it is less than 0.125ppm.
Then you calculate the index for the 8-hour ozone value as before:
(150-101)
		-(.087-076) +101 = 129.368
(.095-076)	7
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.
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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.
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
•	AQI calculator program
•	Forecasting guidance
•	Air quality guides for:
-Ozone
-Particle pollution
•	Pamphlets:
-Ozone Pollution and your Health
-Particle Pollution and your Health
-Smog: Who does it Hurt?
•	Medical poster
•	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:
upper. Y +tx_t
¦al 2, n —2

Si
r 1 (jc' -x)2^
l+-+v ;
V
n (W-1)S;
J
lower Y -1
1 —a!2,n—2 ¦
S:
f 1 (jc' - j)2^
l+-+v ;
V
n (n-l)S^
y
Where:
Y is the predicted 8-hour ozone maximum,
ti-o/2,n-2 is a tabulated Student's-T value corresponding to a two sided (1- a) 100% confidence
Se2
x!
X
Sx2
interval with n-2 degrees of freedom,
is the error variance described above,
is the 1-hour value used to predict the 8-hour value,
is the average of the 1-hour values, and
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 (2010 Census)
CBSA code
Geographic Area
2010 Census
10420
Akron, OH
703,200
10580
Albany-Schenectady-Troy, NY
870,716
10740
Albuquerque, NM
887,077
10900
Allentown-Bethlehem-Easton, PA-NJ
821,173
11260
Anchorage, AK
380,821
11700
Asheville, NC
424,858
12060
Atlanta-Sandy Springs-Marietta, GA
5,268,860
12260
Augusta-Richmond County, GA-SC
556,877
12420
Austin-Round Rock-San Marcos, TX
1,716,289
12540
Bakersfield-Delano, CA
839,631
12580
Baltimore-Towson, MD
2,710,489
12940
Baton Rouge, LA
802,484
13140
Beaumont-Port Arthur, TX
388,745
13820
Birmingham-Hoover, AL
1,128,047
14260
Boise City-Nampa, ID
616,561
14460
Boston-Cambridge-Quincy, MA-NH
4,552,402
14860
Bridgeport-Stamford-Norwalk, CT
916,829
15180
Brownsville-Harlingen, TX
406,220
15380
Buffalo-Niagara Falls, NY
1,135,509
15940
Canton-Massillon, OH
404,422
15980
Cape Coral-Fort Myers, FL
618,754
16700
Charleston-North Charleston-Summerville, SC
664,607
16740
Charlotte-Gastonia-Rock Hill, NC-SC
1,758,038
16860
Chattanooga, TN-GA
528,143
16980
Chicago-Joliet-Naperville, IL-IN-WI
9,461,105
17140
Cincinnati-Middletown, OH-KY-IN
2,130,151
17460
Cleveland-Elyria-Mentor, OH
2,077,240
17820
Colorado Springs, CO
645,613
17900
Columbia, SC
767,598
18140
Columbus, OH
1,836,536
18580
Corpus Christi, TX
428,185
19100
Dallas-Fort Worth-Arlington, TX
6,371,773
19340
Davenport-Moline-Rock Island, IA-IL
379,690
19380
Dayton, OH
841,502
19660
Deltona-Daytona Beach-Ormond Beach, FL
494,593
19740
Denver-Aurora-Broomfield, CO
2,543,482
19780
Des Moines-West Des Moines, IA
569,633
19820
Detroit-Warren-Livonia, Ml
4,296,250
20500
Durham-Chapel Hill, NC
504,357
21340
El Paso, TX
800,647
21660
Eugene-Springfield, OR
351,715
21780
Evansville, IN-KY
358,676
22180
Fayetteville, NC
366,383
22220
Fayetteville-Springdale-Rogers, AR-MO
463,204
22420
Flint, Ml
425,790
23060
Fort Wayne, IN
416,257
23420
Fresno, CA
930,450
24340
Grand Rapids-Wyoming, Ml
774,160

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24660
24860
25420
25540
25860
26180
26420
26620
26900
27140
27260
28140
28660
28940
29460
29540
29620
29820
30460
30780
31100
31140
31540
31700
32580
32820
33100
33340
33460
33660
33700
33860
34980
35300
35380
35620
35840
36260
36420
36540
36740
37100
37340
37860
37900
37980
38060
38300
38860
38900
Greensboro-High Point, NC	723,801
Greenville-Mauldin-Easley, SC	636,986
Harrisburg-Carlisle, PA	549,475
Hartford-West Hartford-East Hartford, CT	1,212,381
Hickory-Lenoir-Morganton, NC	365,497
Honolulu, HI	953,207
Houston-Sugar Land-Baytown, TX	5,946,800
Huntsville, AL	417,593
Indianapolis-Carmel, IN	1,756,241
Jackson, MS	539,057
Jacksonville, FL	1,345,596
Kansas City, MO-KS	2,035,334
Killeen-Temple-Fort Hood, TX	405,300
Knoxville, TN	698,030
Lakeland-Winter Haven, FL	602,095
Lancaster, PA	519,445
Lansing-East Lansing, Ml	464,036
Las Vegas-Paradise, NV	1,951,269
Lexington-Fayette, KY	472,099
Little Rock-North Little Rock-Conway, AR	699,757
Los Angeles-Long Beach-Santa Ana, CA	12,828,837
Louisville/Jefferson County, KY-IN	1,283,566
Madison, Wl	568,593
Manchester-Nashua, NH	400,721
McAllen-Edinburg-Mission, TX	774,769
Memphis, TN-MS-AR	1,316,100
Miami-Fort Lauderdale-Pompano Beach, FL	5,564,635
Milwaukee-Waukesha-West Allis, Wl	1,555,908
Minneapolis-St. Paul-Bloomington, MN-WI	3,279,833
Mobile, AL	412,992
Modesto, CA	514,453
Montgomery, AL	374,536
Nashville-Davidson-Murfreesboro-Franklin, TN	1,589,934
New Haven-Milford, CT	862,477
New Orleans-Metairie-Kenner, LA	1,167,764
New York-Northern New Jersey-Long Island, NY-NJ-
PA	18,897,109
North Port-Bradenton-Sarasota, FL	702,281
Ogden-Clearfield, UT	547,184
Oklahoma City, OK	1,252,987
Omaha-Council Bluffs, NE-IA	865,350
Orlando-Kissimmee-Sanford, FL	2,134,411
Oxnard-Thousand Oaks-Ventura, CA	823,318
Palm Bay-Melbourne-Titusville, FL	543,376
Pensacola-Ferry Pass-Brent, FL	448,991
Peoria, IL	379,186
Philadelphia-Camden-Wilmington, PA-NJ-DE-MD	5,965,343
Phoenix-Mesa-Glendale, AZ	4,192,887
Pittsburgh, PA	2,356,285
Portland-South Portland-Biddeford, ME	514,098
Portland-Vancouver-Hillsboro, OR-WA	2,226,009
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38940
Port St. Lucie, FL
424,107
39100
Poughkeepsie-Newburgh-Middletown, NY
670,301
39300
Providence-New Bedford-Fall River, RI-MA
1,600,852
39340
Provo-Orem, UT
526,810
39580
Raleigh-Cary, NC
1,130,490
39740
Reading, PA
411,442
39900
Reno-Sparks, NV
425,417
40060
Richmond, VA
1,258,251
40140
Riverside-San Bernardino-Ontario, CA
4,224,851
40380
Rochester, NY
1,054,323
40900
Sacramento-Arden-Arcade-Roseville, CA
2,149,127
41180
St. Louis, MO-IL
2,812,896
41420
Salem, OR
390,738
41500
Salinas, CA
415,057
41620
Salt Lake City, UT
1,124,197
41700
San Antonio-New Braunfels, TX
2,142,508
41740
San Diego-Carlsbad-San Marcos, CA
3,095,313
41860
San Francisco-Oakland-Fremont, CA
4,335,391
41940
San Jose-Sunnyvale-Santa Clara, CA
1,836,911
42060
Santa Barbara-Santa Maria-Goleta, CA
423,895
42220
Santa Rosa-Petaluma, CA
483,878
42340
Savannah, GA
347,611
42540
Scranton-Wilkes-Barre, PA
563,631
42660
Seattle-Tacoma-Bellevue, WA
3,439,809
43340
Shreveport-Bossier City, LA
398,604
44060
Spokane, WA
471,221
44140
Springfield, MA
692,942
44180
Springfield, MO
436,712
44700
Stockton, CA
685,306
45060
Syracuse, NY
662,577
45220
Tallahassee, FL
367,413
45300
Tampa-St. Petersburg-Clearwater, FL
2,783,243
45780
Toledo, OH
651,429
45940
Trenton-Ewing, NJ
366,513
46060
Tucson, AZ
980,263
46140
Tulsa, OK
937,478
46700
Vallejo-Fairfield, CA
413,344
47260
Virginia Beach-Norfolk-Newport News, VA-NC
1,671,683
47300
Visalia-Porterville, CA
442,179
47900
Washington-Arlington-Alexandria, DC-VA-MD-WV
5,582,170
48620
Wichita, KS
623,061
48900
Wilmington, NC
362,315
49180
Winston-Salem, NC
477,717
49340
Worcester, MA
798,552
49620
York-Hanover, PA
434,972
49660
Youngstown-Warren-Boardman, OH-PA
565,773
Source: U.S. Census Bureau, Population Division, Annual Estimates of the Population of Metropolitan and
Micropolitan Statistical Areas: April 1, 2010 to July 1, 2011 (CBSA-EST2011-01), Release Date: April 2012,
http://www.census.gov/popest/data/metro/totals/2011/
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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 decision
makers 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 other
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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-13-001
Agency	Research Triangle Park, NC 27711	December2013
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