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Nitrogen Dioxide Pollution Standards Debated

Monitoring along highways will be key



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U.S. EPA's planned toughening of health standards for nitrogen dioxide (NO2) emissions is not tough enough for some advocacy groups.

The EPA proposal would set a new one-hour maximum NO2 limit to prevent spikes in air pollution. The proposal also involves setting up new monitors in locations with the highest concentrations, like major roads in urban areas. The agency is proposing to retain the current annual average standard of 53 parts per billion (ppb).

The proposal's range -- between 80 and 100 ppb -- falls within EPA's scientific advisers' recommendations, but some environmentalists and public-health advocates want more.

"The standard needs to be much, much tighter," said Janice Nolen, assistant vice president for policy and advocacy at the American Lung Association.

The association and some environmentalists are calling for the agency to set a one-hour daily maximum standard of 50 ppb or lower to protect vulnerable groups. The groups have welcomed EPA's proposal to place monitors near areas known to have the highest NO2 concentrations.

The agency's Clean Air Scientific Advisory Committee, or CASAC, recommended setting one-hour limits at or below 100 ppb. EPA's staff scientists recommended a one-hour maximum standard between 50 and 200 ppb, with strong support for a level at or below 100 ppb.

An alternative approach offered in the EPA proposal would set a communitywide one-hour NO2 standard at a lower range -- between 50 and 75 ppb -- but that alternative would not require monitoring near major roads.

"That, to me, is a Catch-22 choice," said Frank O'Donnell, president of Clean Air Watch.

"We think that the level that they're talking about in the alternative is closer to what we think would be appropriate, but we also ought to have a much more robust monitoring system," O'Donnell said. "I don't think that it ought to be an either-or situation."

Clean Air Watch and the American Lung Association are planning to voice their concerns to EPA next week as the agency holds public hearings Monday in Arlington, Va., and next Thursday in Los Angeles.

"We're going to comment to EPA that the [roadway] monitoring is needed, period, and that much tighter standards are needed, period," Nolen said.

The agency has proposed and intends to finalize a system that would monitor peak concentrations of NO2 near roadways, said an EPA air official. However, that person said, the agency offered the alternative in order to have the flexibility to consider other options.

Because NO2 concentrations are between 30 and 100 percent higher within 50 meters of major roads, the limit should be adjusted to be somewhat higher if the monitors are placed near roadways, the EPA official said.

For example, a standard level of 50 ppb under the alternative approach could limit near-road concentrations to between 65 and 100 ppb, according to the proposal. The level of health protection and the stringency of both the proposed and the alternative one-hour standards would be identical, the official said.

EPA's proposal to place more monitors near roadways would offer more certainty that the agency was catching peak concentrations, the rule says, while the alternative would provide more confidence that area-wide concentrations were being met.


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

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