Nitrogen Dioxide Pollution
Nitrogen Dioxide Pollution

What is Nitrogen Dioxide?
Nitrogen Dioxide (NO2) is a reddish-brown, highly reactive gas formed when another pollutant (nitric oxide) combines with oxygen in the atmosphere. Once it has formed, NO2 reacts with other pollutants, such as volatile organic compounds. Eventually these reactions result in the formation of ground level ozone. Major sources of NO2 include vehicles, waste disposal systems, and power plants.

The Environmental Protection Agency uses its Air Quality Index to provide general information to the public about air quality and associated health effects. An Air Quality Index (AQI) of 100 for any pollutant corresponds to the level needed to violate the federal health standard for that pollutant. For nitrogen dioxide, an AQI of 100 corresponds .053 parts per million (averaged over 24 hours) -- the current federal standard. Short-term health effects for NO2 do not occur until index values are above 200; therefore, an AQI value is not calculated below 201 for NO2. An index value of 201 for NO2 corresponds to an NO2 level of 0.65 parts per million (averaged over 24 hours).

Nitrogen Dioxide Health Hazards

EPA Air Quality Index Levels
of Health
Concern		 Cautionary
Statements
0 - 50 Good None
51 - 100 Moderate None
101 - 150 Unhealthy for
Sensitive Groups		 None
151 - 200 Unhealthy None
201 - 300 Very Unhealthy Children and people with respiratory disease, such as asthma, should limit heavy outdoor exertion.
301 - 500 Hazardous Children and people with respiratory disease, such as asthma, should limit moderate or heavy outdoor exertion.

What are the health effects from Nitrogen Dioxide?

  • In children and adults with respiratory disease, such as asthma, NO2 can cause respiratory symptoms such as coughing, wheezing, and shortness of breath. Even short exposures to NO2 affect the lung function.
  • In children, short-term exposure can increase the risk of respiratory illness.
  • Animal studies show that long-term exposure to NO2 may increase susceptibility to respiratory infection and may cause permanent structural changes in the lungs.

For detailed information about real-time pollution levels in the U.S., visit the Environmental Protection Agency's Website.


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