![[logo] US EPA](https://webarchive.library.unt.edu/eot2008/20090830165023im_/http://www.epa.gov/epafiles/images/logo_epaseal.gif){kind=logo}
Announcements
July 31, 2009 – EPA posts current list of speakers for upcoming public hearings on the recently proposed rules for NO2
Learn More
July 15, 2009 - EPA announces hearing dates for national ambient air quality standards for NO2
Learn More
June 26, 2009 - EPA proposes changes to the national air quality standards for NO2 .
Learn More
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.
For more information about NO2:
Basic Information - Basics about NO2 air pollution.
Health - Effects of NO2 air pollution.
NO2 Standards - Links to technical information related to setting the national air quality standards for NO2.
NO2 Implementation - Programs and requirements for reducing NO2 air pollution.
Regulatory Actions - Links to proposed and final rules, fact sheets, and other rulemaking documents.
Air Quality Trends - Progress made in reducing NO2 in the air.
Air Emission Sources - Summarizes NOx air emissions by source at national, state and local levels.