NTAA: Air Topics

NTAA Air Topics:

NAAQS - Nitrogen Oxides (NOx)

The Clean Air Act, which was last amended in 1990, requires EPA to set National Ambient Air Quality Standards (NAAQS) for wide-spread pollutants from numerous and diverse sources considered harmful to public health and the environment. The Clean Air Act established two types of national air quality standards. Primary standards set limits to protect public health, including the health of "sensitive" populations such as asthmatics, children, and the elderly. Secondary standards set limits to protect public welfare, including protection against visibility impairment, damage to animals, crops, vegetation, and buildings. The Clean Air Act requires periodic review of the science upon which the standards are based and the standards themselves.

EPA has set NAAQS for six principal pollutants, which are called "criteria" pollutants. They are listed below. For a summary table of the current NAAQS, click on the following link: NAAQS Table.

Nitrogen dioxide (NO2) is one of a group of highly reactive gasses known as "oxides of nitrogen," or "nitrogen oxides (NOx)." Other nitrogen oxides include nitrous acid and nitric acid. While EPA’s National Ambient Air Quality Standard covers this entire group of NOx, NO2 is the component of greatest interest and the indicator for the larger group of nitrogen oxides. NO2 forms quickly from emissions from cars, trucks and buses, power plants, and off-road equipment. In addition to contributing to the formation of ground-level ozone, and fine particle pollution, NO2 is linked with a number of adverse effects on the respiratory system.

EPA first set standards for NO2 in 1971, setting both a primary standard (to protect health) and a secondary standard (to protect the public welfare) at 0.053 parts per million (53 ppb), averaged annually. The Agency has reviewed the standards twice since that time, but chose not to revise the standards at the conclusion of each review. All areas in the U.S. meet the current (1971) NO2 standards.

Significance to Tribes
NTAA Documents

NTAA comments on Nitrogen Dioxide NAAQS - September 14, 2009

Related Documents

Primary NAAQS standards for Nitrogen Dioxide; Final Rule - Federal Register February 9, 2010

EPA Fact Sheet for Final Revisions to NAAQS Nitrogen Dioxide - February, 2010

EPA Presentation - Final Revisions to Primary NAAQS for Nitrogen Dioxide (NO2) - January 24, 2010

Related Links

American Lung Association - Nitrogen Dioxide website

EPA Nitrogen Dioxide website