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Nitrogen Dioxide (NO2) Pollution

Setting and Reviewing Standards to Control NO2 Pollution

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What are NO2 standards?

National Ambient Air Quality Standards (NAAQS) for NO2 specify maximum amounts of NO2 to be present in outdoor air. Limiting NO2 in the air protects human health and the environment.
  • See primary NAAQS for NO2 for an in-depth explanation of the current NO2 primary (health-based) standards, including Federal Register citations and fact sheets.
  • See secondary NAAQS for NO2 for an in-depth explanation of the current NO2 secondary (welfare-based) standard and EPA’s most recent joint review of the secondary standards for NO2 and sulfur dioxide (SO2).

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How are the standards developed and reviewed?

The Clean Air Act requires EPA to set national ambient air quality standards for nitrogen oxides as one of the six criteria pollutants.  The NAAQS for nitrogen oxides are currently set using NO2 as the indicator of the larger group of nitrogen oxides. The law also requires EPA to periodically review the standards and revise them if appropriate to ensure that they provide the requisite amount of health and environmental protection and to update those standards as necessary.

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What scientific and technical information supports reviews?

The various documents published during the review process include multiple drafts of plans and assessments, reports from the Clean Air Scientific Advisory Committee (CASAC), and Federal Register notices.

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