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National Ambient Air Quality Standards
(NAAQS)
The Clean Air Act, which was last amended
in 1990, requires EPA to set National Ambient Air Quality Standards
for pollutants considered harmful to public health and the environment.
The Clean Air Act established two types of national air quality standards.
Primary standards set limits to protect public health,
including the health of "sensitive" populations such as asthmatics,
children, and the elderly. Secondary standards set
limits to protect public welfare, including protection against decreased
visibility, damage to animals, crops, vegetation, and buildings.
The EPA Office of Air Quality Planning and Standards (OAQPS) has set
national Ambient Air Quality Standards for six principal pollutants,
which are called "criteria" pollutants. They are listed below. Units
of measure for the standards are parts per million (ppm) by volume,
milligrams per cubic meter of air (mg/m3), and micrograms
per cubic meter of air (mg/m3).
Click here for description
of pollutants listed below.
| National Ambient Air
Quality Standards |
| POLLUTANT |
STANDARD VALUE* |
STANDARD TYPE |
| Carbon Monoxide (CO) |
|
| 8-hour Average |
9 ppm (10
mg/m3) |
Primary |
| 1-hour Average |
35 ppm (40 mg/m3) |
Primary |
| Nitrogen Dioxide (NO2) |
|
| Annual Arithmetic Mean |
0.053 ppm (100 µg/m3) |
Primary & Secondary |
| Ozone (O3) |
|
| 1-hour Average |
0.12 ppm (235 µg/m3) |
Primary & Secondary |
| 8-Hour Average |
0.075 ppm (150 µg/m3) |
Primary & Secondary |
| Lead (Pb) |
|
| Rolling Three Month
Average |
0.15 µg/m3 |
Primary & Secondary |
| Fine Particulate (PM2.5) |
|
| Annual Arithmetic Mean |
15 µg/m3 |
Primary & Secondary |
| 24-hour Average |
35 µg/m3 |
Primary & Secondary |
| Particulate (PM10) |
|
| Annual Arithmetic Mean |
50 µg/m3 |
Primary & Secondary |
| 24-hour Average |
150 µg/m3 |
Primary & Secondary |
| Sulfur Dioxide (SO2) |
|
| Annual Arithmetic Mean |
0.03 ppm (80 µg/m3)
| Primary |
| 24-hour Average |
0.14 ppm (365 µg/m3)
| Primary |
| 3-hour Average |
0.50 ppm (1300 µg/m3)
| Secondary |
*Parenthetical
value is approximately equivalent concentration.
|
Air Pollution Control Division 
dec calendar 
