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The National Ambient Air Quality Standards (NAAQS) for Particle Pollution 

EPA’S REVISED AIR QUALITY STANDARDS FOR PARTICLE POLLUTION: 

MONITORING, DESIGNATIONS AND PERMITTING REQUIREMENTS

On Dec. 14, 2012 the U.S. Environmental Protection Agency (EPA) strengthened the nation’s air 

quality standards for fine particle pollution to improve public health protection by revising the 

primary annual fine particle (PM2.5) standard to 12 micrograms per cubic meter (μg/m3) and 

retaining the 24-hour fine particle standard of 35 μg/m3. Exposure to particle pollution can 

cause premature death and harmful effects on the cardiovascular system (the heart, blood and 

blood vessels). Fine particle pollution also is linked to a variety of other significant health 

problems. In addition, particle pollution harms public welfare, including by causing haze in cities 

and some of our nation’s most treasured national parks. 

EPA and states have issued a number of rules that will help states meet the revised standards

by making significant strides toward reducing fine particle pollution.

CHANGES TO PM2.5 MONITORING REQUIREMENTS

As part of the revisions to the PM2.5 standards, EPA is updating monitoring requirements for 

fine particles, including adding a requirement for monitoring near heavily traveled roads in 

large urban areas. Particle pollution can be higher along these roads as a result of emissions 

from cars and heavy-duty diesel trucks and buses. 

EPA will require near-roadway PM2.5 monitoring at one location in each urban area (a corebased statistical area, or CBSA) with a population of 1 million or more. These monitors will 

likely be located at existing near-road monitoring sites also measuring nitrogen dioxide or 

carbon monoxide. The near-roadway monitoring will be phased in, beginning with the 

largest urban areas (population of 2.5 million or more) by Jan. 1, 2015; and extending to the 

remainder of the areas by Jan. 1, 2017. 

EPA is not increasing the size of the national PM2.5 monitoring network, which consists of 

about 900 monitors. Today’s rule minimizes the burden to state and local air agencies; EPA 

anticipates that states will be able to relocate existing monitors (about 52 total) to meet the 

near-roadway requirement at little or no additional cost.

Data from these monitors will not be available in time for use in making initial attainment 

and nonattainment designations for the revised primary annual PM2.5 standard.
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EPA also is making other updates to the monitoring and data handling requirements for 

PM2.5 monitoring to reflect the changes to the standards and to clarify existing 

requirements. 

EPA is not making any changes to monitoring requirements for the coarse particle standard.

DESIGNATING ATTAINMENT AND NONATTAINMENT AREAS

Improving air quality is a partnership between the federal government, states and tribes. 

EPA will work closely with states, local and tribal air agencies to implement the revised 

primary annual PM2.5 standard. 

Once EPA sets a new air quality standard, or revises an existing standard, the agency 

designates areas as meeting the standards (attainment areas), not meeting them 

(nonattainment areas), or there is not enough data to make a determination

(unclassifiable). EPA works closely with states as it determines initial attainment and 

nonattainment boundaries. 

States with nonattainment areas must then develop state implementation plans (SIPs)

showing how they will meet the new or revised standards. Tribes may, but are not required 

to, develop their own plans for nonattainment areas in Indian country. Where necessary, 

EPA will develop plans for any tribal area that chooses not to develop its own plans.

EPA anticipates the following schedule for designating areas and implementing the revised 

primary annual PM2.5 standard: 

o By December 2013, states (and any tribes that choose to do so), make 

recommendations for areas to be designated.

o By August 2014, EPA responds to states’ and tribes’ initial recommendations for 

attainment and nonattainment areas. States and tribes then will have the 

opportunity to comment on any modifications to their recommendations, and to 

provide new information and analyses to EPA if appropriate.

o By December 2014, EPA makes final designations; those designations would likely 

become effective in early 2015 (60 days after the designations are published in the 

Federal Register). 

o 2018: Implementation plans, outlining how states or tribes will reduce pollution to 

meet the standards, are due to EPA (three years after designations). State plans can 

include emission reductions from federal rules and programs, along with local 

measures to demonstrate that an area will meet the standards.
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o 2020: States are required to meet the standards. States must meet health standards 

“as expeditiously as practicable” but not later than five years after designations. A 

state may request a possible extension to 2025, depending on the severity of an 

area’s fine particle pollution problems and the availability of pollution controls. 

Recent Clean Air Act rules are projected to help states meet the revised standard by 

dramatically cutting pollution both regionally and across the country. These rules include 

rules to reduce pollution from power plants, clean diesel rules for vehicles and rules to 

reduce pollution from stationary diesel engines.

EPA intends to propose additional guidance and regulations related to state 

implementation requirements for the revised PM standards as necessary. These guidance 

documents or rules would address SIP requirements and permitting requirements related to 

the revised standards. The agency intends to issue a final implementation rule in late 2014 –

around the same time that the agency makes final designations. 

PERMITTING REQUIREMENTS

As part of this action, EPA is finalizing a grandfathering provision for preconstruction 

permitting to ensure that changes to the PM standards will not delay certain pending 

permits, and to reduce potential burdens to permit applicants and state, local and tribal air 

agencies. This provision applies to Prevention of Signification Deterioration (PSD) permits, 

which ensure that emissions from the addition of new or modified sources of pollution, 

such as factories, industrial boilers or power plants, do not significantly worsen air quality in 

areas with clean air.

To receive a PSD permit, a project must not cause or contribute to a violation of any NAAQS 

or any maximum allowable pollution increase in areas with clean air. These requirements 

generally apply to the air quality standards that are in place at the time the permit is issued. 

To ensure that certain pending permits are not unreasonably delayed because of the 

changes to the fine particle standards, EPA will grandfather permit applications if either: 

o The permitting agency has deemed the application complete. This must occur by

Dec. 14, 2012; or

o The public notice for a draft permit or preliminary determination has been published 

prior to the date the revised PM standards become effective (60 days after 

publication in the Federal Register). 

o Permit applications that have not met these criteria will have to demonstrate 

compliance with the revised standards. 
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The grandfathering provision does not apply to NAAQS for other pollutants.

o Permit applications that qualify for the grandfathering provisions will have to 

demonstrate compliance with the 2006 fine particle standards.

o The grandfathering provision will become part of EPA permitting regulations, but 

also may apply to permits issued by states with approved PSD programs.

EPA is updating its modeling guidance to assist with the implementation of the PSD 

requirements for sources of PM2.5. The agency anticipates issuing that guidance before the 

revised standard becomes effective. EPA will consider issuing additional guidance or rules 

related to permitting requirements for the revised standard as necessary.

MORE INFORMATION: 

To read the revised standards and additional summaries, visit 

http://www.epa.gov/airquality/particlepollution/actions.html

For information on the designation process for PM2.5 standards, visit 

http://www.epa.gov/pmdesignations/.

For information on EPA’s preconstruction permitting program, visit 

http://www.epa.gov/nsr/