Issue Date: July 6, 2009
Strengthened NO₂ Limit Proposed
EPA is proposing to strengthen the national air quality standard for nitrogen dioxide, a limit that has not been changed since it was established in 1971. Under a proposal released last week, the agency would, for the first time, set a short-term standard for NO2 concentrations in outdoor air. EPA is considering a limit of between 80 and 100 ppb for a one-hour period. Meanwhile, the agency would retain the current NO2 standard of 53 ppb, which is a yearlong average. EPA says a one-hour standard for NO2 is needed because scientific studies link short-term exposures of between 30 minutes and 24 hours with increased adverse effects. "Breathing NO2 can irritate the lungs, trigger asthma attacks, and lower the body's natural resistance to respiratory infections," says Norman H. Edelman, chief medical officer for the American Lung Association, a group favoring a short-term standard for the pollutant. Sources of NO2 include vehicles, fossil-fuel-burning power plants, and industrial facilities.
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