EPA Finalizes Tighter Nitrogen Dioxide Standards, Calls for New Roadside Monitoring Network

The U.S. Environmental Protection Agency (EPA) Jan. 22 finalized tighter air quality standards for nitrogen dioxide (NO2) gas.  The revision marks the first time EPA has updated the national ambient air quality standard (NAAQS) for NO2 in nearly four decades.  Significantly, EPA also chose to set new, first-time requirements calling on states to monitor and measure NO2 levels near major roads, despite AGC's objections. NAAQS define the maximum allowable level of pollutants and drive state air pollution cleanup programs.  NO2 serves as the indicator for the entire family of nitrogen oxides; diesel engines emit NOx (mono-nitrogen oxides).  The final rule introduces a new one-hour maximum standard for NO2 at 100 parts per billion (ppb). The agency is also retaining the existing annual standard of 53 ppb.  According to EPA Administrator Lisa Jackson, EPA is "for the first time ever... working to prevent short-term exposures in high-risk NO2 zones like urban communities and areas near roadways."  The standard establishes new monitoring requirements to measure NO2 levels near major roads. Cities with at least 500,000 residents must have monitors near roadways, and larger cities and areas with major roads will have additional monitors. Cities with at least 1 million residents will continue with communitywide monitoring.  All new NO2 monitors must begin operating no later than January 1, 2013.

AGC Comments

In a September 14, 2009, letter to EPA, AGC urged the Agency to remove the monitoring component from its NO2 NAAQS proposal and wait until the new air standard is finalized before proposing a subsequent rule for monitoring requirements.  AGC's comment letter also recommended that EPA consider a pilot study to determine how roadway monitoring of NO2 would function in the real world before imposing this costly new system.  AGC stressed that the more stringent NO2 requirements will be unnecessarily costly and burdensome on states and the regulated community. AGC urged EPA to let existing air emission/fuel regulations and voluntary programs work before tightening NAAQS rules, considering the continual phase-in of new federal engine standards and the recent switch-over to exclusively ultra-low-sulfur diesel fuel. EPA expects to identify areas not meeting the new NO2 standard, based on the existing monitoring network, by January 2012.  New monitors must begin operating no later than January 1, 2013.  When three years of air quality data are available from the new monitoring network, EPA intends to re-designate areas as appropriate. Currently there are no areas in the United States that are designated as nonattainment of the NO2 NAAQS. With the tighter NO2 NAAQS now on the books, however, some areas will be classified as non-attainment. (EPA's Web site provides a list of counties with the highest average 1-hour 99th percentile NO2 levels for 2005 to 2007, but these numbers are based on the current monitoring network that is focused on community-wide ambient levels of NO2, and not near-roadway levels, which may be significantly higher.)  States with non-attainment areas will be required to develop SIPs (state implementation "clean-up" plans) that identify and implement specific air pollution control measures to reduce ambient NO2 concentrations to attain and maintain the revised NO2 NAAQS, most likely by requiring air pollution controls on sources that emit oxides of nitrogen (NOx).  According to EPA, two of the top three categories of sources of NOx emissions are on-road and non-road mobile sources.


The Clean Air Act requires EPA to set national standards for six "criteria" pollutants, including NO2, and to periodically review those standards. (See related story in this issue of the Observer titled, "EPA Proposes Tougher Ozone Standard; 60-day Comment Period.")  EPA has reviewed the health-based NO2 standards twice since the standard was first proposed in 1971 but both times chose not to revise the standards.  EPA's final rule falls within recommendations by EPA's scientific advisers but does not go far enough for some environmentalists and public health advocates. The final rule will take effect 60 days after publication in the Federal Register.  More information, including a fact sheet and PowerPoint presentation, is available on EPA's Web site. AGC continues to analyze what the new NAAQS for NO2 may mean for future construction, including new stricter requirements and/or restrictions on diesel engines and their use (click here for an article from the August issue of AGC's Environmental Observer newsletter.  See also the "Editor's Note" in this issue of the Observer that provides a quick look at why tighter federal air standards may mean construction bans).

For more information, please contact Leah Pilconis at or (703) 837-5332.