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Nitrogen Dioxide Designations


June 29, 2011 - EPA responds to state recommendations on areas meeting the 2010 NO2 standards.
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January 20, 2012 - EPA finalized designations for the 2010 NO2 NAAQS.
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This web site provides information on the process EPA, the states, and the tribes follow to determine whether or not an area is meeting the revised national air quality standards for nitrogen dioxide (NO2) established in 2010. After EPA establishes or revises a primary and/or secondary National Ambient Air Quality Standard (NAAQS), the Clean Air Act requires EPA to designate areas as “attainment” (meeting), “nonattainment” (not meeting), or “unclassifiable” (insufficient data) after monitoring data is collected by state, local and tribal governments.

Current scientific evidence links short-term NO2 exposures, ranging from 30 minutes to 24 hours, with an array of adverse respiratory effects including increased asthma symptoms, more difficulty controlling asthma, and an increase in respiratory illnesses and symptoms. Reducing levels of NO2 pollution is an important part of EPA’s commitment to a clean, healthy environment.

A designation is the term EPA uses to describe the air quality in a given area for any of six common air pollutants known as criteria pollutants. One of these pollutants is NO2. (The other criteria pollutants are particulate matter, lead, carbon monoxide, sulfur dioxide, and ozone.)

Once nonattainment designations take effect, the state and local governments have three years to develop implementation plans outlining how areas will attain and maintain the standards by reducing air pollutant emissions contributing to NO2 concentrations.

EPA strengthened the air quality standards for NO2 in 2010.
Learn more about the 2010 standards

This Web site contains the following information:

State Designations: State area designations for the 2010 NO2 air quality standards are summarized here.

Tribal Designations: Tribal area designations for the 2010 NO2 air quality standards are summarized here.

Frequent Questions: Answers to common questions regarding NO2 in air and the designations process.

Related Links: Related sites offering further information and assistance.

Glossary: Explanations of the technical terms and acronyms used throughout the site.

EPA has similar sets of web pages for ozone designations, fine particle (PM2.5) designations, sulfur dioxide (SO2) designations, and lead (Pb) designations.


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