National Ambient Air Quality Standards

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US counties that are designated "nonattainment" for the Clean Air Act's NAAQS. Valid 6/20/2017.

The US National Ambient Air Quality Standards (NAAQS, pronounced \'naks\) are standards established by the United States Environmental Protection Agency (EPA) under authority of the Clean Air Act (42 U.S.C. 7401 et seq.) that apply for outdoor air throughout the country. Primary standards are designed to protect human health, with an adequate margin of safety, including sensitive populations such as children, the elderly, and individuals suffering from respiratory diseases. Secondary standards are designed to protect public welfare (including effects on soils, water, crops, vegetation, man-made materials, animals, wildlife, weather, visibility, and climate), damage to property, transportation hazards, economic values, and personal comfort and well-being from any known or anticipated adverse effects of a pollutant. A district meeting a given standard is known as an "attainment area" for that standard, and otherwise a "non-attainment area".[1]


The standards are listed in 40 C.F.R. 50.

Pollutant Type Standard Averaging Timea Regulatory Citation
SO2 Primary 75 ppb 1-hour 40 C.F.R. 50.17a
SO2 Secondary 0.5 ppm (1,300 μg/m³) 3-hour 40 C.F.R. 50.5a
PM10 Primary and Secondary 150 μg/m³ 24-hour 40 C.F.R. 50.6a
PM2.5 Primary 12 μg/m³ annual 40 C.F.R. 50.18a
PM2.5 Secondary 15 μg/m³ annual 40 C.F.R. 50.7a
PM2.5 Primary and Secondary 35 μg/m³ 24-hour 40 C.F.R. 50.18a
CO Primary 35 ppm (40 mg/m³) 1-hour 40 C.F.R. 50.8a(2)
CO Primary 9 ppm (10 mg/m³) 8-hour 40 C.F.R. 50.8a(1)
O3 Primary and Secondary 0.12 ppm (235 μg/m³) 1-hourb 40 C.F.R. 50.9a
O3 Primary and Secondary 0.070 ppm (140 μg/m³) 8-hour 40 C.F.R. 50.19a
NOx Primary and Secondary 0.053 ppm (100 μg/m³) annual 40 C.F.R. 50.11ab
Pb Primary and Secondary 0.15 μg/m³ Rolling 3 months 40 C.F.R. 50.12a
  • ^a Each standard has its own criteria for how many times it may be exceeded, in some cases using a three-year average.
  • ^b As of June 15, 2005, the 1-hour ozone standard no longer applies to areas designated with respect to the 8-hour ozone standard (which includes most of the United States, except for portions of 10 states).
  • Source: USEPA

Detection methods[edit]

The EPA National Exposure Research Laboratory can designate a measurement device using an established technological basis as a Federal Reference Method (FRM) to certify that the device has undergone a testing and analysis protocol, and can be used to monitor NAAQS compliance. Devices based on new technologies can be designated as a Federal Equivalent Method (FEM).[2] FEMs are based on different sampling and/or analyzing technologies than FRMs, but are required to provide the same decision making quality when making NAAQS attainment determinations. Approved new methods are formally announced through publication in the Federal Register.[3] A complete list of FRMs and FEMs is available.[4]

Air quality control region[edit]

An air quality control region is an area, designated by the federal government, where communities share a common air pollution problem. [5]

See also[edit]


  1. ^ Trans-Alaska Pipeline System Renewal Environmental Impact Statement article
  2. ^ Hall, Eric S.; Kaushik, Surender M.; Vanderpool, Robert W.; Duvall, Rachelle M.; Beaver, Melinda R.; Long, Russell W.; Solomon, Paul A.; Hall, Eric S.; Kaushik, Surender M. (2014). "Integrating Sensor Monitoring Technology into the Current Air Pollution Regulatory Support Paradigm: Practical Considerations". American Journal of Environmental Engineering. 4 (6). ISSN 2166-465X. doi:10.5923/j.ajee.20140406.02 (inactive 2017-06-27). 
  3. ^ "EPA scientists develop Federal Reference & Equivalent Methods for measuring key air pollutants". U.S. Environmental Protection Agency. 2016-12-29. Retrieved 2017-06-28. 
  4. ^ Gilliam, Joseph H.; Hall, Eric S. (2016-07-13). "Reference and Equivalent Methods Used to Measure National Ambient Air Quality Standards (NAAQS) Criteria Air Pollutants - Volume I". U.S. Environmental Protection Agency. Retrieved 2017-06-28. 
  5. ^ "EPA document". 

External links[edit]