Environmental Protection

EPA Proposes Updating Nitrogen Dioxide Standards

For the first time in more than 35 years, the U.S. Environmental Protection Agency has proposed to strengthen the nation's nitrogen dioxide (NO2) air quality standard, according to a June 29 press release.

"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."

EPA's proposed revisions apply to the primary NO2 standard and would:

  • Establish, for the first time, a one-hour NO2 standard at a level between 80 – 100 parts per billion (ppb),
  • Retain the current annual average NO2 standard of 53 ppb,
  • Add NO2 monitoring within 50 meters of major roads in cities with at least 350,000 residents, and
  • Continue monitoring "area-wide" NO2 concentrations in cities with at least 1 million residents.
Current scientific evidence links short-term NO2 exposures, ranging from 30 minutes to 24 hours, with increased respiratory effects, especially in people with asthma. These effects can lead to increased visits to emergency departments and hospital admissions for respiratory illnesses, particularly in at-risk populations such as children, the elderly, and asthmatics.

First set in 1971, standards for NO2 established both a primary standard to protect health and a secondary standard to protect the public welfare at 53 ppb, averaged annually. Annual average NO2 concentrations have decreased by more than 40 percent since 1980. All areas in the United States are well below the current (1971) NO2 standards with annual averages ranging from approximately 10 – 20 ppb.

EPA will accept public comments for 60 days after the proposal is published in the Federal Register. The agency will hold two public hearings in August 2009: one in Los Angeles and one in the Washington, D.C. area. The agency will provide details on the public hearings in a separate notice issued later this summer.

EPA must issue a final decision on the NO2 standard by Jan. 22, 2010.

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