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Air Quality Program

Nitrogen Dioxide (NO2)

Nitrogen dioxide is a poisonous red-brown gas produced when fuel burns. Common sources include:

  • Fossil fuel power
  • Motor vehicles
  • Industrial combustion
  • Explosives manufacturing
  • Fertilizer manufacturing

Health Effects

It harms lungs, irritates bronchial and respiratory systems, and increases symptoms in people with asthma.

National Ambient Air Quality Standards (NAAQS) for Nitrogen Dioxide

EPA first established standards for nitrogen dioxide in 1971, setting both a primary standard (to protect health) and a secondary standard (to protect the public welfare) at 53 parts per billion (ppb), averaged yearly. Before 2010, EPA reviewed the standards twice, but chose not to revise them.

In 2010, EPA strengthened the standard by setting a new health-based 1-hour standard of 100 ppb. EPA also kept the current yearly average standard for nitrogen dioxide of 53 ppb.

Technical Table
Pollutant Averaging Time Level Remarks Measurement Method Interpretation Method
Nitrogen Dioxide Annual 53 ppbv Annual Mean 40 C.F.R. Part 50, Appendix F 40 C.F.R. Part 50, Appendix S
1-hour 100 ppbv 98th percentile of 1-hour daily maximum concentrations, averaged over 3 years

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