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Nitrogen Dioxide


October 5, 2012 - EPA proposes revisions to NO2 monitoring requirements
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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. EPA’s National Ambient Air Quality Standard uses NO2 as 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 annual standards at the conclusion of each review.  In January 2010, EPA established an additional primary standard at 100 ppb, averaged over one hour. Together the primary standards protect public health, including the health of sensitive populations - people with asthma, children, and the elderly. No area of the country has been found to be out of compliance with the current NO2 standards.

For more information about NO2:

Basic Information - Basics about NO2 air pollution.

Health - Effects of NO2 air pollution.

NO2 Primary Standards - Links to technical information related to setting the national air quality standards for NO2 to protect public health.

NO2 Secondary Standards - Links to technical information related to setting the national air quality standards for NO2 to protect public welfare.

NO2 Designations - Regional, state and local information related to NO2 nonattainment..

NO2 Implementation - Programs and requirements for reducing NO2 air pollution.

Regulatory Actions - Links to proposed and final rules, fact sheets, and other rulemaking documents.

Nonattainment Areas - Status of nonattainment areas (the Green Book).

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.

SIP Status and Information - Identifies how states and EPA work together to ensure that the agency's National Ambient Air Quality Standards (NAAQS) are met and maintained.

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