Air
Quality Index Color Code Guide |
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Weather
Conditions |
Recommended
Actions |
Health
Effects |
Good |
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Moderate |
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Unhealthy
for Sensitive Groups |
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Unhealthy |
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Very
Unhealthy |
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AQI
refers to the Air Quality Index. An AQI of 100 is equivalent to the
National Ambient Air Quality Standard (NAAQS).
The
weather conditions listed above are common weather types associated
with the respective air quality levels. |
DAQ
is a division of the Department of Environment and Natural Resources (DENR)
Contact the Ozone
Forecast Center with questions or comments regarding this site.
The Air Quality Index and Your Health
You’ve
probably heard the words “code red” air quality, especially if you live in
or near an urban area. Knowing
what the color codes mean can help you protect your health and the health of
your loved ones.
The color-coded Air Quality Index (AQI) describes air
quality levels in a standard way all across the country.
In other words “code red," means the same thing in Los Angeles
as it does in Raleigh, NC or Washington, D.C.
Each color corresponds to a different level of health
concern. Below are the color
codes, from best to worst, with their corresponding health warnings.
Color |
Level of Health Concern |
AQI
Values |
Green |
Good |
0 to 50 |
Yellow |
Moderate |
51 to 100 |
Orange |
Unhealthy for sensitive groups |
101 to 150 |
Red |
Unhealthy |
151 to 200 |
Purple |
Very Unhealthy |
201 to 300 |
Maroon |
Hazardous |
301 to 500 |
As you can see, each color also corresponds to a range of Air Quality
Index Values. You can think of
the AQI as a yardstick that runs from 0 to 500. The higher the AQI value, the greater the level of air
pollution and the greater the health danger.
For example, an AQI value of 50 represents "good" air quality
and little danger to public health, while an AQI value of 250 represents
"very unhealthy" air quality.
The most important number on the scale is 100,
because 100 corresponds to the National Ambient Air Quality
Standard (NAAQS), which is set by the U.S. Environmental Protection
Agency (EPA) to protect public health. So,
AQI values below 100 are generally thought to be satisfactory.
When AQI values rise above 100, air quality is considered unhealthy –
at first for certain sensitive people, then for everyone as AQI values get
higher.
The AQI is most commonly used to describe
ground-level ozone levels*. However,
the AQI can be used to represent five pollutants that pose a threat to human
health. These pollutants are:
Ground-level
Ozone or O3
Particulate
Matter (soot and dust) or PM
Carbon
Monoxide or CO
Sulfur
Dioxide or SO2 and
Nitrogen
Dioxide or NO2
The EPA sets national standards for these five
pollutants under the Clean Air Act. The
EPA and other researchers have studied the health effects of different levels of
these pollutants to determine where to set the standards and health warnings.
For each pollutant, a color code represents a
specific range of concentrations. For
ground-level ozone, for example, the yellow level includes a concentration range
of 0.065 to 0.084 parts per million (ppm). For carbon monoxide, the yellow range represents a
concentration range of 4.5 to 9.4 ppm. For
both pollutants, the color yellow poses a “moderate” level of health
concern. And for both pollutants
the upper end of this range (0.84 ppm for ozone, 9.4 ppm for carbon monoxide) is
the national standard set by the EPA, so the upper end of both ranges is equal
to an AQI value of 100. As you can
see, the Air Quality Index provides a common reference for standardizing the
five pollutants in relation to their health impacts.
Air quality agencies measure all five pollutants with
a monitor network nationwide. For
major metropolitan areas, the measurements are converted to AQI values, and the
pollutant with the highest AQI is reported daily. In North Carolina, you can hear daily AQI reports by calling
1-888-AIRWISE (1-888- 247-9473). In
the Charlotte area, call (704) 333-7664.
Many state and local air quality agencies also issue
air quality forecasts using the AQI color code. You may have seen these forecasts on the evening news or in
the newspaper in your area. By
paying attention to these forecasts, you can protect your health by adjusting
your activities on days predicted to have poor air quality.
For nationwide ozone mapping and ozone forecasts,
visit US EPA AIRNOW at http://www.epa.gov/airnow/
For more information on ground-level ozone in
North Carolina, visit the NC Ozone Forecast Center at http://daq.state.nc.us/Ozone/
.
To learn more about the Air Quality Index and
all five pollutants, visit http://www.epa.gov/airnow/aqibroch/
.
* What is ground-level ozone?
First of all, it’s not the same thing as the “ozone layer”
or the “hole in the ozone"! Ozone
occurs naturally in the upper atmosphere and protects us from the sun’s
ultraviolet radiation. This
“ozone layer” is becoming thinner, especially in the Polar Regions.
However, “ozone pollution” or “ground-level ozone” occurs in the
lower atmosphere, where we live and breathe.
It’s created when various man-made pollutants combine in the heat of
the sun. Because heat and strong
sunlight are necessary for ground-level ozone formation, ozone is generally a
summertime problem. Small amounts of ozone do occur naturally because of
emissions from forest fires and even from trees.
However, most ground-level ozone is produced by human activities.
Ground-level ozone can damage lung tissues and the leaves of plants.
Remember - - ozone is “good up high, bad nearby”!