Air pollutants 

The U.S. Environmental Protection Agency (EPA) set national air quality standards for six common pollutants (also referred to as "criteria" pollutants. These standards, known as National Ambient Air Quality Standards (NAAQS) consist of:

Pollutant	Average Time	National Ambient Air Quality Standard (NAAQS) Violation Determination1	Federal Primary Health Standard (NAAQS) Exceedance Level	State Standard Exceedance Level
Carbon monoxide	1-hour	Not to be exceeded more than once/year	35 ppm	35 ppm
	8-hour	Not to be exceeded more than once/year	9 ppm	9 ppm
Lead	Calendar Quarter	Quarterly arithmetic mean	1.5 µg/m3	1.5 µg/m3
Nitrogen dioxide	Annual	Annual arithmetic mean	0.053 ppm	0.053 ppm
Ozone	8-hour	3-year average of the annual 4th highest daily maximum 8-hour average concentration	0.08 ppm	0.08 ppm
PM2.5	24 hour	98th percentile of the 24-hour values determined for each year. 3-year average of the 98th percentile values.	35 µg/m3
	Annual Average	3-year average of the annual arithmetic mean	15 µg/m3
PM10	24 hour	The expected number of days per calendar year with a 24-hour average concentrations above 150 µg/m3 is equal to or less than 1 over a 3-year period.	150 µg/m3	150 µg/m3
Sulfur dioxide	Annual Arithmetic Mean	Not to be exceeded more than once per calendar year.	0.03 ppm	0.02 ppm
	24 hour	Not to be exceeded more than once per calendar year	0.14 ppm	0.10 ppm
	3 hour	Not to be exceeded more than once per calendar year	*0.50 ppm secondary standard	0.50 ppm

*Secondary standards set limits to protect public welfare, including protection against decreased visibility, damage to animals, crops, vegetation, and buildings.

Maintenance and nonattainment areas in Oregon

Maintenance areas are those geographic areas that had a history of nonattainment, but are now consistently meeting the National Ambient Air Quality Standard (NAAQS). Maintenance areas have been re-designated by EPA from "nonattainment" to "attainment with a maintenance plan," or designated by the Environmental Quality Commission. Legal descriptions of these areas are listed in Oregon Administrative Rules, Chapter 340, Division 204-0010.

• Maintenance areas in Oregon

Nonattainment means that a geographic area has not consistently met the clean air levels set by the U.S. Environmental Protection Agency in the National Ambient Air Quality Standards (NAAQS). Legal descriptions of these areas are available in Oregon Administrative Rules, Chapter 340, Division 204-0010.

• Nonattainment areas in Oregon

New PM_2.5 Standards

• U.S. EPA Federal Register
• DEQ Pendleton Workshop, December 2006
• S. Oregon Meteorological Presentation - Nov. 4, 2008 PDF 2 MB

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