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Nitrogen Dioxide Standard Released by EPA

April 19th, 2010

Nitrogen-Dioxide-Public-Health EPA released a new National Ambient Air Quality Standard (NAAQS) for nitrogen dioxide (NO2) in January. This new one-hour standard is aimed to protect public health from peak short-term exposures, especially along busy city streets and highways where NO2 exposure is the most likely. According to the EPA, NO2 exposure has been linked to impaired lung function and increased respiratory infections, especially in people with asthma.

NO2 is one of a group of highly reactive gasses. It forms quickly from emissions from cars, trucks, buses, power plants, and off-road equipment. In addition, NO2 contributes to the development of ground-level ozone and fine particle pollution.

The EPA set the new one-hour standard for NO2 at a level of 100 parts per billion (ppb). This level defines the maximum allowable concentration anywhere in one area. However, the agency is also retaining, with no change, the current annual NO2 standard average of 53 ppb and states that this change does not affect the secondary NO2 standard, set to protect public welfare.

To determine compliance, EPA established the following standards for monitoring and reporting requirements for NO2:

  • At least one monitor must be located near a major road in any urban area with a population greater than or equal to 500,000 people. A second monitor is required near another major road in areas with either:
    • Population greater than or equal to 2.5 million people, or
    • One or more road segment with an annual average daily traffic (AADT) count greater than or equal to 250,000 vehicles.
  • A minimum of one monitor must be placed in any urban area with a population greater than or equal to 1 million people to assess community-wide concentrations.
  • An additional 53 monitoring sites will be required to assess community-wide levels in urban areas.
  • Working with the states, EPA will site at least 40 additional NO2 monitors to help protect communities that are susceptible and vulnerable to NO2 related health effects.

EPA estimates that the new NO2 monitoring requirements will result in a network of approximately 126 NO2 monitoring sites near major roads in 102 U.S. urban areas.

EPA expects to identify or designate NO2 monitoring areas and that they will be fully operational by January 1, 2013. EPA also intends to designate new areas, as appropriate, after three years of data have been collected from the NO2 monitoring network.


  1. as of March 22, 2010
  2. as of March 22, 2010

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