Nitrogen Dioxide Pollution

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).

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.

• 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.