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]

Standards

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

Pollutant	Type	Standard	Averaging Time^a	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-hour^b	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

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

• Air pollution
• Air Quality Index
• Asthma
• Atmospheric dispersion modeling
• Clean Air Act (1990)
• Portable Emissions Measurement System
• Toxic Substances Control Act of 1976

References

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

External links

• EPA summary of the National Ambient Air Quality Standards
• EPA summary for Air & Radiation
• EPA Green Book showing non-attainment, maintenance, and attainment areas
• Most Polluted Cities, 2005 – American Lung Association