Near-Road Emission Monitors Not a Must Near Small Populations

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By Rachel Leven

Certain areas with populations between 500,000 and 1 million will no longer have to install near-road nitrogen dioxide monitors under a recent Environmental Protection Agency final rule.

These areas were supposed to have monitors in place by Jan. 1, 2017, under the 2010 National Ambient Air Quality Standards for nitrogen dioxide (75 Fed. Reg. 6,474). The requirement for these population areas was rescinded, however, after the EPA found that nitrogen dioxide levels in near-road areas with populations of more than 1 million people are significantly below the levels required under the 2010 standards.

“In light of this information, and the relationship between population, traffic, and expected NO2 concentrations in the near-road environment, EPA expects measured near-road NO2 concentrations in relatively smaller [population centers] would exhibit similar and, more likely, lower concentrations than what is being measured in larger urban areas,” said the fact sheet accompanying the rule (RIN:2060–AS71) that EPA Administrator Gina McCarthy signed Dec. 22.

The move drew praise from entities such as the Association of Air Pollution Control Agencies, which asserted that data collected by near-road monitors in larger population centers show there isn’t a need for such monitoring in lesser populated areas and that those resources could be more effectively used elsewhere. But at least one environmental group found the EPA’s step disappointing and worried about the consequences of not looking at nitrogen dioxide more aggressively.

“It goes to show that the EPA and the current administration have put all of its chips on dealing with climate and carbon and has really given short-shrift to nitrogen dioxide,” Frank O’Donnell, president of Clean Air Watch, told Bloomberg BNA, adding that his group believes the 2010 nitrogen dioxide standards aren’t stringent enough. “I think from a public health standpoint that’s going to be [detrimental] in the long run.”

Looking Forward

Clint Woods, executive director of the air agencies association, told Bloomberg BNA that the next step will be for state agencies and the EPA to look at how air agencies are efficiently using monitoring—what is working—and to decide about how to most effectively use these freed resources to protect the environment.

The change doesn’t affect other monitoring requirements under the 2010 standards, including near-road monitoring of nitrogen dioxide in more populated areas.

The rule could be judicially reviewable by filing a petition for review in the U.S. Court of Appeals for the District of Columbia Circuit within 60 days of the final rule’s publication in the Federal Register.

Exposure to high concentrations of nitrogen dioxide emissions can harm the human respiratory system and aggravate diseases such as asthma. Nitrogen dioxide also interacts with water and other chemicals in the air to form acid rain and particulate matter, among other environmental and health effects.

To contact the reporter on this story: Rachel Leven in Washington, D.C., at

To contact the editor responsible for this story: Larry Pearl at

For More Information

The final rule is available at

The fact sheet is available at

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