EPA proposes new one-hour NO2 standard in an effort to reduce respiratory illnesses

For the first time in more than 35 years, EPA has proposed to strengthen the nation’s nitrogen dioxide (NO2) air quality standard that protects public health.

EPA has proposed to toughen U.S. nitrogen dioxide (NO2) air quality standard in an effort to protect public health.

The revisions would establish a one-hour NO2 standard, in order to reduce people’s exposure to high, short-term concentrations of NO2. According to the EPA, there is scientific evidence linking these short-term NO2 exposures with increased respiratory problems.

The revisions would also maintain the current annual average NO2 standard; establish monitoring within 50 meters of major road in cities with a population of 350,000 or more; and continue "area-wide" monitoring in cities with a population of 1 million or more.

The standards were established based on recent scientific data regarding the health effects of exposure to NO2 from vehicle and industrial emissions.

"We’re updating these standards to build on the latest scientific data and meet changing health protection needs," said EPA Administrator Lisa P. Jackson. "In addition to limiting annual average concentrations, we’re preventing high NO2 levels for shorter periods of time and adding stronger monitoring in areas near roadways, where the highest levels of NO2 are often found. This will fill gaps in the current standard and provide important additional protections where they are needed most."


The National Ambient Air Quality Standard (NAAQS) for NO2 was first established in 1971 and has not been changed since then. The average annual standard for NO2 is 53 parts per billion (ppb). According to the EPA, annual NO2 concentrations have decreased across the U.S. by more than 40 percent in the past 30 years, averaging between 10 to 20 ppb.

A 60 public comment period in scheduled after the proposal is published in the Federal Register. A final decision will be issued by January 22, 2010. For more information visit http://www.epa.gov/air/nitrogenoxides.