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Oregon Department of Environmental Quality

Air Quality

Maintenance and nonattainment areas 

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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 0.15 µg/m3 0.15 µg/m3
Nitrogen dioxide Annual Annual arithmetic mean 53 ppb 53 ppb
1-hour 3-year average of the maximum daily 98th percentile one hour average 100 ppb NA
Ozone 8-hour 3-year average of the annual 4th highest daily maximum 8-hour average concentration 75 ppb 75 ppb
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 35 µg/m3
Annual Average 3-year average of the annual arithmetic mean 15 µg/m3 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 1 hour 3-year average of the maximum daily 99th percentile one hour average 75 ppb NA

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.

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.

New PM2.5 Standards

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For more information about Air Quality call 503-229-5359 or email.

Oregon Department of Environmental Quality
Headquarters: 811 SW Sixth Ave., Portland, OR 97204-1390
Phone: 503-229-5696 or toll free in Oregon 1-800-452-4011
Oregon Telecommunications Relay Service: 1-800-735-2900  FAX: 503-229-6124

The Oregon Department of Environmental Quality is a regulatory agency authorized to protect Oregon's environment by
the State of Oregon and the Environmental Protection Agency.

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