Nitrogen Dioxide (NO2)
Nitrogen dioxide is a poisonous red-brown gas produced when fuel burns. Common sources include:
It harms lungs, irritates bronchial and respiratory systems, and increases symptoms in people with asthma.
National Ambient Air Quality Standards (NAAQS) for Nitrogen Dioxide
EPA first established standards for nitrogen dioxide in 1971, setting both a primary standard (to protect health) and a secondary standard (to protect the public welfare) at 53 parts per billion (ppb), averaged yearly. Before 2010, EPA reviewed the standards twice, but chose not to revise them.
In 2010, EPA strengthened the standard by setting a new health-based 1-hour standard of 100 ppb. EPA also kept the current yearly average standard for nitrogen dioxide of 53 ppb.Technical Table
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