Open Access Articles- Top Results for National Ambient Air Quality Standards

National Ambient Air Quality Standards

Counties in the United States where one or more National Ambient Air Quality Standards are not met, as of June 2007.

The National Ambient Air Quality Standards (NAAQS) 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. 50.4b
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 and Secondary 65 μg/m³ 24-hour 40 C.F.R. 50.7a
PM2.5 Primary and Secondary 15 μg/m³c annual 40 C.F.R. 50.7a
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 CFR 50.8(a)(1)
O3 Primary and Secondary 0.12 ppm (235 μg/m³) 1-hourb 40 CFR 50.9(a)
O3 Primary and Secondary 0.075 ppm (150 μg/m³) 8-hour 40 CFR 50.10(a)
NO2 Primary and Secondary 0.053 ppm (100 μg/m³) annual 40 CFR 50.11(a) and (b)
Pb Primary and Secondary 0.15 μg/m³ Rolling 3 months 40 CFR 50.12
  • ^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).
  • ^c As of December 2014, the primary fine particulate standard will be 12.0 μg/m³.[2]
  • Source: USEPA

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. [3]

See also


  1. ^ Trans-Alaska Pipeline System Renewal Environmental Impact Statement article
  2. ^
  3. ^ "EPA document". 

External links