TABLE 1.

National Ambient Air Quality Standards for Criteria Air Pollutants, 1997

PollutantPrimary Standards*
Ozone
    1-h average0.12 ppm (235 μg/m3)
    8-h average0.08 ppm (157 μg/m3)
PM10
    Annual arithmetic mean50 μg/m3
    24-h average150 μg/m3
PM2.5
    Annual arithmetic mean15 μg/m3
    24-h average65 μg/m3
Sulfur dioxide
    Annual arithmetic mean0.03 ppm (80 μg/m3)
    24-h average0.14 ppm (365 μg/m3)
Nitrogen dioxide
    Annual arithmetic mean0.053 ppm (100 μg/m3)
Carbon monoxide
    8-h average9 ppm (10 mg/m3)
    1-h average35 ppm (40 mg/m3)
Lead
    Quarterly average1.5 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.