NCDENR - Division of Air Quality - Air Quality Standards Table



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Monitoring Data >> Air Quality Standards Table

The EPA Office of Air Quality Planning and Standards (OAQPS) 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 also adopted as State air quality standards. Units of measure for the standards are parts per million by volume(ppm), 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.

National and State (NC) Ambient Air Quality Standards
Pollutant	Threshold Level	Sample Aggregation	Statistical Summary⁽⁰⁾	Health Standard	Secondary Standard	State Standard
Carbon Monoxide	9 ppm-8 hr (10 mg/m³-8 hr)	Annual	Extreme⁽¹⁾	Yes	n/a	Yes
Carbon Monoxide	35 ppm-1 hr (40 mg/m³-1 hr)	Annual	Extreme⁽¹⁾	Yes	n/a	Yes
Lead	1.5 µg/m³-24 hr	Quarterly	Arith. Mean	Yes	Yes	Yes
Nitrogen Dioxide	0.053 ppm-1 hr (100 µg/m³-1 hr)	Annual	Arith. Mean	Yes	Yes	Yes
Total Suspended Particulates	75 µg/m³-24 hr	Annual	Geom. Mean	No	No	Yes
Total Suspended Particulates	150 µg/m³-24 hr	Annual	Extreme⁽²⁾	No	No	Yes
Particulate Matter (PM₁₀)	50 µg/m³-24 hr	Quarterly	Arith. Mean	Revoked⁽³⁾	Revoked⁽³⁾	Yes
Particulate Matter (PM₁₀)	150 µg/m³-24 hr	Annual	Extreme⁽²⁾	Yes	Yes	Yes
Particulate Matter (PM_2.5)	15.0 µg/m³-24 hr	Quarterly	Arith. Mean⁽⁴⁾	Yes	Yes	Yes
Particulate Matter (PM_2.5)	35 µg/m³-24 hr	Annual	Extreme⁽⁵⁾	Yes	Yes	Yes
Ozone	0.075 ppm-8 hr	Annual⁽⁶⁾	Extreme⁽⁷⁾	Yes	Yes	Yes
Ozone	0.12 ppm-1 hr	Annual⁽⁶⁾	Extreme⁽⁸⁾	In Limited Areas⁽⁹⁾	In Limited Areas⁽⁹⁾	No
Sulfur Oxides	0.03 ppm-1 hr	Annual	Arith. Mean	Yes	No	Yes
	0.14 ppm-24 hr	Annual	Extreme⁽¹⁾	Yes	No	Yes
	0.5 ppm-3 hr (1300 µg/m³-3 hr)	Annual	Extreme⁽¹⁾	No	Yes	Yes

⁽⁰⁾ Annual summary statistics, except as noted.

⁽¹⁾ Not to be exceeded more than once per year.

⁽²⁾ Not to be exceeded more than once per year on average for 3 years.

⁽³⁾ The USEPA revoked the standard in 2006 (effective December 17, 2006), because of a lack of evidence linking health problems to long-term exposure to coarse particle pollution.

⁽⁴⁾ The 3-year average from single or multiple community-oriented monitors must not exceed the threshold.

⁽⁵⁾ Ninety-eighth percentile. The 3-year average at each population-oriented monitor within an area must not exceed the threshold.

⁽⁶⁾ Certain months are exempted in many areas (specif., November through March in North Carolina).

⁽⁷⁾ Fourth-largest daily maximum. The 3-year average at each monitor within an area over each year must not exceed the threshold.

⁽⁸⁾ Largest daily maximum. The expected number of days per calendar year on which the statistic exceeds the threshold may not be greater than 1.

⁽⁹⁾ As of June 15, 2005 the USEPA revoked the standard in all areas except fourteen 8-hour ozone nonattainment Early Action Compact (EAC) Areas.