National Ambient Air Quality Standards for Criteria Air Pollutants, 1997
| Pollutant | Primary Standards* |
|---|---|
| Ozone | |
| 1-h average | 0.12 ppm (235 μg/m3) |
| 8-h average | 0.08 ppm (157 μg/m3) |
| PM10 | |
| Annual arithmetic mean | 50 μg/m3 |
| 24-h average | 150 μg/m3 |
| PM2.5 | |
| Annual arithmetic mean | 15 μg/m3 |
| 24-h average | 65 μg/m3 |
| Sulfur dioxide | |
| Annual arithmetic mean | 0.03 ppm (80 μg/m3) |
| 24-h average | 0.14 ppm (365 μg/m3) |
| Nitrogen dioxide | |
| Annual arithmetic mean | 0.053 ppm (100 μg/m3) |
| Carbon monoxide | |
| 8-h average | 9 ppm (10 mg/m3) |
| 1-h average | 35 ppm (40 mg/m3) |
| Lead | |
| Quarterly average | 1.5 μg/m3 |
Additional information on air quality standards are available at www.epa.gov/air/criteria.html.
↵* People residing in regions with pollutant concentrations above the primary standard may experience adverse health effects from poor air quality.