This
page last reviewed November 29, 2007
The U.S. EPA has replaced its Pollutant Standards
Index (PSI) with its new Air Quality Index (AQI)
in order to incorporate the new Federal ozone and PM2.5 standards. The
index is designed to provide accurate, timely
and easily understandable information about daily levels of air
pollution.
The Air Quality Index (AQI), (formerly known as the
Pollutant Standards Index) was issued on July 23, 1999
by the U.S. EPA for daily air quality reporting to the public. This new
index reflects revisions to the primary
health-based national ambient air quality standards for ground-level
ozone and particulate matter issued by U.S.
EPA in 1997. For much more detailed information, about the AQI and AQI
levels in your area, please visit the U.S.
EPA's AirNow
website.
The intervals, color code assignment, and the terms describing
the AQI are as follows:
AQI
Index Values
|
Health Categories
|
Cautionary Statements for
8-Hour Ozone
|
0
to 50
|
Good
|
None |
51 to 100
|
Moderate
|
Unusually
sensitive people should consider limiting prolonged outdoor exertion. |
101 to 150
|
Unhealthy for Sensitive Groups
|
Active
children and adults, and people with respiratory disease, such as
asthma, should limit prolonged outdoor exertion. |
151 to 200
|
Unhealthy
|
Active children
and adults, and people with respiratory disease, such as asthma, should
avoid prolonged outdoor exertion; everyone else, especially children,
should limit prolonged outdoor exertion. |
201 to 300
|
Very Unhealthy
|
Active
children and adults, and people with respiratory disease, such as
asthma, should avoid all outdoor exertion; everyone else especially
children, should limit outdoor exertion. |
301
to 500
|
Hazardous
|
Everyone should avoid all outdoor exertion. |
The Pollutant Standards Index (PSI) is still
calculated daily for many major metropolitan areas of the United
States with populations exceeding 200,000. The PSI converts measured
pollutant concentration in a community's air
to a number on a scale from 0 to 500. The number of 100, corresponds to
the air quality standard established under
the federal Clean Air Act. According to the U.S. EPA, a PSI level in
excess of 100 means that a pollutant is in
the unhealthy range on a given day, a PSI level at or below 100 means
that a pollutant reading is in the satisfactory
range.
The intervals and the terms describing the federal PSI air
quality levels are as follows:
PSI
Index Values
|
Health Categories
|
Further Comment
|
From 0 to 50 |
Good |
|
From 51 to 100 |
Moderate |
100 = National Ozone Standard |
From 101 to 199 |
Unhealthful |
138 = Health Advisory - Athletes should avoid strenuous
outdoor activities |
From 200 to 299 |
Very Unhealthful |
200 = Stage I Alert - Everyone should avoid strenuous
outdoor activites
275 = Stage II Alert - Everyone should remain indoors |
Over 300 |
Hazardous |
|
See also these Recommendations
for Schools and
Others on Poor Air Quality Days.
Factsheets, FAQs &
Videos
|