Fact Sheet – Air Quality Designations for the 

2010 Primary Nitrogen Dioxide (NO2) National 

Ambient Air Quality Standards 

ACTION 

• On January 20, 2012, based on the most recent air quality monitoring 

data (2008-2010), the U.S. Environmental Protection Agency has 

determined that no area in the country is violating the 2010 national 

air quality standards for nitrogen dioxide (NO2). 

• These areas have been designated as “unclassifiable/attainment.” 

• EPA will work with states, tribes and local air quality agencies to 

ensure that air quality is maintained and public health is protected. 

• Areas that are designated unclassifiable/attainment do not have to 

take steps to improve air quality but they must prevent their air 

quality from deteriorating to unhealthy levels. For example, Prevention 

of Significant Deterioration (PSD), a permitting program for industrial 

facilities, applies in these areas to ensure that new and modified 

sources of pollution do not cause or contribute to violations of air 

quality standards. 

• EPA is working with state, tribal and local air agencies to put in place 

additional NO2 monitors that were required along with the 2010 

standard. EPA expects this network to be deployed in 2013. 

BACKGROUND

• On January 22, 2010, EPA strengthened the health-based standard for 

NO2 by setting a new 1-hour standard of 100 parts per billion (ppb).  

The new standard will protect public health, including the health of 

sensitive populations – people with asthma, children and the elderly. 

• To determine compliance with the new standard, EPA established new 

ambient air monitoring and reporting requirements for NO2. 

In urban areas, monitors are required near major roads as well 

as in other locations where maximum concentrations are 

expected. 

Additional monitors are required in large urban areas to measure 

the highest concentrations of NO2 that occur more broadly 

across communities. 
Working with the states, EPA will site a subset of monitors in 

locations to help protect communities that are susceptible and 

vulnerable to NO2-related health effects. 

• EPA and State and Tribal agencies are currently working to establish 

an expanded network of NO2 monitors, expected to be deployed in 

2013. Once three years of air quality data have been collected from 

the expanded network EPA will be better able to determine NO2 air 

quality in additional locations. 

• Within two years of setting a new NAAQS or revising an existing 

standard, the Clean Air Act directs EPA to formally identify or 

“designate” areas as “unclassifiable/attainment” (meeting the standard 

or no evidence indicating a violation), “nonattainment” (not meeting 

the standard), or “unclassifiable” (insufficient information to designate 

as attainment or nonattainment, but likely to be violating). 

ABOUT DESIGNATIONS 

• EPA is designating all areas in the country, both state lands and Indian 

country. Unlike states, tribes are not obligated to submit designation 

recommendations but are invited to participate in the designations 

process by submitting a recommendation for Indian country and/or by 

engaging in formal or informal consultation with EPA and states. 

• Once designations take effect, they become an important component 

of state, local and tribal governments’ efforts to manage NO2 pollution. 

The designations govern what subsequent regulatory actions states 

and EPA must take in order to improve or preserve air quality in each 

area. 

FOR MORE INFORMATION 

• For more information on the designation process for the NO2

standards, and to view individual letters from EPA to states and tribes, 

go to EPA’s Web site at www.epa.gov/air/nitrogenoxides/designations/