U.S. EPA is poised to propose an updated standard for airborne nitrogen dioxide (NO2) after the White House Office of Management and Budget cleared the agency's draft rule Friday.

EPA was under a court deadline to propose by Friday whether to revise the primary health-based air quality standard for NO2, a gaseous air pollutant that contributes to the formation of particle pollution and ozone.

The agency's staff and scientific advisers have recommended that the agency establish a new one-hour daily maximum standard to prevent spikes of NO2 concentrations, which have been linked to asthma attacks and other adverse health effects. The current standard -- set in 1971 -- is an annual average of 53 parts per billion (ppb).

EPA has reviewed the health-based NO2 limit twice since the standard was set nearly four decades ago, but both times chose not to revise the regulation.

Observers expect the agency to release its proposal, likely recommending a range of allowable NO2 concentrations, as early as today.

EPA staff scientists have recommended a one-hour maximum standard between 50 ppb and 200 ppb, with strong support for a level at or below 100 ppb. The staff also suggested that a standard based on annual average NO2 concentrations would not likely be an effective or efficient approach to evaluating short-term NO2 exposures.

The agency's Clean Air Scientific Advisory Committee, or CASAC, recommended setting one-hour limits at or below 100 ppb and suggested retaining the annual average standard.

The American Lung Association is calling for the agency to set a one-hour daily maximum standard of 50 ppb or below to protect vulnerable groups. The group also supports strengthening the annual average standards to protect against long-term damage caused by NO2 exposure.

"We have strong scientific research that tells us that the current NO2 standard fails to protect public health," said Janice Nolen, assistant vice president for policy and advocacy at the American Lung Association. "It is time for EPA to follow the science and adopt tighter standards to protect the health of all of our communities."

The consent decree requires the agency to issue a final rule by Jan. 22, 2010.

Reprinted from Greenwire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500