Information about Nitrogen Dioxide (NO2)

Current conditions

Condensed from Measuring Air Quality: The Pollutant Standards Index; Office of Air Quality Planning and Standards, US EPA; EPA 451/K-94-001; February 1994.

Sources

Nitrogen dioxide (NO2) is a light brown gas that can become an important component of urban haze. Nitrogen oxides usually enter the air as the result of high-temperature combustion processes, such as those occurring in automobiles and power plants. NO2 plays an important role in the atmospheric reactions that generate ozone. Home heaters and gas stoves also produce substantial amounts of NO2.

Health effects

Healthy individuals experience respiratory problems when exposed to high levels of NO2 for short durations (less than three hours). Asthmatics are especially sensitive, and changes in airway responsiveness have been observed in some studies of exercising asthmatics exposed to relatively low levels of NO2. Studies also indicate a relationship between indoor NO2 exposures and increased respiratory illness rates in young children, but definitive results are still lacking. Many animal studies suggest that NO2 impairs respiratory defense mechanisms and increases susceptibility to infection.

Several studies also show that chronic exposure to relatively low NO2 pollution levels may cause structural changes in the lungs of animals. These studies suggest that chronic exposure to NO2 could lead to adverse health effects in humans, but specific levels and durations likely to cause such effects have not yet been determined.

Air quality levels

The air quality standard for NO2, which is designed to protect public health with an adequate margin of safety, is 0.053 ppm, annual average. EPA is required to issue a public alert when NO2 reaches 0.6 ppm on a one hour average, a public warning when NO2 reaches 1.2 ppm, and a declaration of public emergency at the level of 1.6 ppm. The significant harm level, at which serious and widespread health effects occur to the general population, is 2.0 ppm of NO2.
[ mail questions to: Susan Zimmer-Dauphinee, Ambient Monitoring Program | Back to AMP Homepage ]