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 disease. Secondary standards are designed to protect public welfare from any known or anticipated adverse effects of a pollutant (e.g. building facades, visibility, crops, and domestic animals).

A district meeting a given standard is known as an "attainment area" for that standard, and otherwise a "non-attainment area".^[1]

NAAQS requires the EPA to set standards on six criteria air contaminants:

1. Ozone (O₃)
2. Particulate Matter
   • PM₁₀, coarse particles: 2.5 micrometers (μm) to 10 μm in size (although current implementation includes all particles 10 μm or less in the standard)
   • PM_2.5, fine particles: 2.5 μm in size or less
3. Carbon monoxide (CO)
4. Sulfur dioxide (SO₂)
5. Nitrogen oxides (NO_x)
6. Lead (Pb)

[edit] Standards

The standards are listed in Title 40 of the Code of Federal Regulations Part 50.

Note a: Each standard has its own criteria for how many times it may be exceeded, in some cases using a three year average.

Note 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

[edit] See also

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

[edit] References

1. ^ Trans-Alaska Pipeline System Renewal Environmental Impact Statement article

[edit] 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