Air Pollution from Nitrogen Dioxide
- What is nitrogen dioxide?
- Latest air quality planning to address the standard for nitrogen dioxide
- Related Web pages and publications
- Get more information on the Texas SIP and contact the TCEQ
What is nitrogen dioxide?
The sum of nitric oxide (NO) and nitrogen dioxide (NO2) is commonly called nitrogen oxides (NOx). Other compounds, including nitrous acid and nitric acid, are part of the NOx family. NO2 is the component of greatest interest and the indicator for the larger group of NOx. NO2 forms quickly from emissions from cars, trucks and buses; power plants; and off-road equipment. In addition to contributing to the formation of ground-level ozone and fine-particle pollution, NO2 is linked with a number of adverse effects on the respiratory system.
Latest air quality planning that addresses the standard for nitrogen dioxide
Last updated: 2/21/2012
2010 One-Hour NO2 National Ambient Air Quality Standard (NAAQS)
On February 9, 2010, the United States Environmental Protection Agency (EPA) published a final rule in the Federal Register to strengthen the primary NAAQS for nitrogen dioxide, establishing a new one-hour standard at 100 parts per billion (ppb). The new standard focuses on short-term exposures to NO2, which are generally highest on and near major roads. Currently, no area in Texas monitors above the 100 ppb standard. The EPA is retaining the current annual average NO2 standard of 53 ppb. The EPA is changing the monitoring network to capture both peak NO2 concentrations that occur near roadways and community-wide NO2 concentrations.
The EPA expects to decrease the number of new monitoring sites from the estimate provided in the 2010 rule. Texas near-road monitors will likely be reduced from eight to four and be located in the Dallas-Fort Worth (DFW), Houston-Galveston-Brazoria (HGB), San Antonio, and Austin-Round Rock areas. Two near-road NO2 monitors in DFW and HGB must begin operating no later than January 1, 2013. Two near-road NO2 monitors in San Antonio and Austin-Round Rock must begin operating no later than January 1, 2014. In 2016 or 2017, once the expanded network of NO2 monitors is fully deployed and three years of air quality data have been collected, the EPA intends to redesignate areas based on data from the new monitoring network. The 2010 NO2 NAAQS attainment date is January 2021 or 2022, approximately five years after the date of nonattainment designations.
On February 17, 2012, the EPA published the final NO2 designations identifying all areas in the United States as unclassifiable/attainment (77 FR 9532) 
. The EPA administrator signed the initial designations on January 20, 2012 and sent a letter to the governor with the announcement.
Related Web pages and publications
- EPA General Page on Nitrogen Dioxide
- Primary NAAQS for Nitrogen Dioxide
- Secondary NAAQS for Nitrogen Dioxide
- Complete List of Texas SIP Revisions
