National Ambient Air Quality Standards

Counties in the United States where one or more National Ambient Air Quality Standards are not met, as of October 2015

The US National Ambient Air Quality Standards (NAAQS, pronounced \'naks\) are standards established by the United States Environmental Protection Agency 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 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

Air quality control region

An air quality control region is an area, designated by the federal government, where communities share a common air pollution problem. [2]

See also


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