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Monitoring Data >> Air Quality Standards Table

National and State (NC) Ambient Air Quality Standards (2006-2012)

The EPA Office of Air Quality Planning and Standards has set National Ambient Air Quality Standards for six principal pollutants, referred to as "criteria" pollutants. (This table identifies eight pollutants, because we have divided "Particulate Matter" into three categories.) The federal air quality standards are usually also adopted as State air quality standards. Units of measure for the standards are parts per million by volume (ppm), parts per billion by volume (ppb), milligrams per cubic meter of air (mg/m3), or micrograms per cubic meter of air (µg/m3), exposed for durations of between 1 hour and 24 hours. Statistical Summary entries are calendar-year annual statistics, except as noted. Historical standards discontinued before 2006 by both EPA and NC are not included.

Pollutant Threshold Level Sample Aggregation Statistical Summary Effective Date Health Standard Secondary Standard State Standard
Carbon Monoxide 9 ppm-8 hr
(10 mg/m3-8 hr)
Annual Extreme(1) 1971 Yes n/a Yes
35 ppm-1 hr
(40 mg/m3-1 hr)
Annual Extreme(1) 1971 Yes n/a Yes
Lead 0.15 µg/m3-24 hr Monthly Extreme(2) 2009 Yes Yes Yes
1.5 µg/m3-24 hr Quarterly Arith. Mean 1978 Yes Yes No
Nitrogen Dioxide 0.053 ppm-1 hr
(100 µg/m3-1 hr)
Annual Arith. Mean 1971 Yes Yes Yes
100 ppb-1 hr Annual Extreme(3) 2010 Yes No Yes
Total Suspended Particulates 75 µg/m3-24 hr Annual Geom. Mean 1971 No(4) No(4) Yes
150 µg/m3-24 hr Annual Extreme(5) 1971 No(4) No(4) Yes
Particulate Matter (PM10) 150 µg/m3-24 hr Annual Extreme(5) 2006 Yes Yes Yes
Particulate Matter (PM2.5) 12.0 µg/m3-24 hr
Quarterly Arith. Mean(6) 2013 Yes No Yes
15.0 µg/m3-24 hr
Quarterly Arith. Mean(6) 2006 No Yes No
35 µg/m3-24 hr Annual Extreme(7) 2006 Yes Yes Yes
Ozone 0.075 ppm-8 hr Annual(8) Extreme(9) 2008 Yes Yes Yes
0.12 ppm-1 hr Annual(8) Extreme(10) 2005 No(11) No(11) No
Sulfur Dioxide 75 ppb-1 hr Annual Extreme(12) 2010 Yes No Yes
0.03 ppm-1 hr Annual Arith. Mean 1971 No(13) No Yes
0.14 ppm-24 hr Annual Extreme(1) 1971 No(13) No Yes
0.5 ppm-3 hr
(1300 µg/m3-3 hr)
Annual Extreme(1) 1971 No Yes Yes


  1. Not to be exceeded more than once per year.
  2. The 3-year average of annual maximum 3-month moving averages must not exceed the threshold.
  3. The 3-year average of ninety-eighth percentile daily maximums must not exceed the threshold.
  4. The USEPA discontinued the TSP standard in 1987 and replaced it with a like standard for PM10.
  5. Not to be exceeded more than once per year on average for 3 years.
  6. The 3-year average from single or multiple community-oriented monitors must not exceed the threshold.
  7. Ninety-eighth percentile. The 3-year average at each population-oriented monitor within an area must not     exceed the threshold.
  8. Certain months are exempted in many areas (specif., November through March in North Carolina).
  9. Fourth-largest daily maximum. The 3-year average at each monitor within an area over each year must not       exceed the threshold.
  10. Largest daily maximum. The 3-year average at each monitor within an area over each year must not       exceed the threshold.
  11. As of June 15, 2005 the USEPA revoked the standard in all areas except fourteen 8-hour ozone       nonattainment Early Action Compact (EAC) Areas. The standard was revoked for the various EAC areas       piecemeal on either Nov. 20, 2007; Nov. 20, 2008; or April 15, 2009.
  12. The 3-year average of ninety-ninth percentile daily maximums must not exceed the threshold.
  13. The USEPA revoked this standard in 2010 in acknowledgement that the new primary standard is generally       sufficient to protect the 1971 primary standards from being violated.

     


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Last Modified: Wed March 20 11:12:42 2013
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