FACT SHEET

Final Rule to Implement the 1997 8-Hour Ozone National Ambient Air Quality Standard: 

Classification of Areas That Were Initially Classified as Subpart 1; Revision of the AntiBacksliding Provisions to Address 1-Hour Contingency Measure Requirements; Deletion of 

Obsolete 1-Hour Ozone Standard Provision

ACTION

On April 27, 2012, the U.S. Environmental Protection Agency finalized revisions to the 2004 

rule that specified the first phase of requirements that state, tribal and local air pollution control 

agencies would follow to meet the 1997 8-hour Ozone National Ambient Air Quality Standards.

As a result of this action, the Clean Air Act classifications for 16 areas of the U.S. will be revised 

for the 1997 8-hour ozone standard. The areas were originally classified under the more general 

Subpart 1 provisions of the CAA as shown in the table below. The areas will be classified as 

marginal or moderate under the ozone-specific Subpart 2 provisions of the CAA.

The revisions are EPA’s response to a December 22, 2006 decision by the U.S. Circuit Court of 

Appeals for the District of Columbia Circuit Court. (South Coast Air Quality Management Dist. 

v. EPA, 472 F.3d 882 (D.C. Cir. 2006)).

EPA is reclassifying the following areas under Subpart 2 as shown in the table below.

State Area

Original 

Subpart 1 

Classification

New Subpart 2 

Classification

Arizona Phoenix-Mesa Marginal Marginal

California Amador and Calaveras Counties (Central Mountain)

Chico

Kern County (Eastern Kern)

Mariposa and Tuolumne Counties (Southern Mountain)

Nevada County

San Diego

Sutter County (Sutter Buttes)

Marginal

Marginal

Moderate

Marginal

Moderate

Moderate

Marginal

Moderate

Marginal

Moderate

Moderate

Moderate

Moderate

Marginal

Colorado Denver, Boulder, Greeley, Ft. Collins & Love Marginal Marginal

Nevada Las Vegas Marginal Marginal

New York Albany-Schenectady-Troy

Buffalo-Niagara Falls

Essex County (Whiteface Mtn.)

Jamestown 

Rochester

Marginal

Moderate

Marginal

Moderate

Marginal

Marginal

Moderate

Marginal

Moderate

Marginal

Pennsylvania Pittsburgh-Beaver Valley Moderate Moderate

Subpart 2 of the Clean Air Act contains additional requirements that areas need to follow to 

implement the standards for ground-level ozone. EPA is aware that many of the areas listed in 

the table above have already satisfied certain Subpart 2 requirements in their state air plans.
The final action addresses how contingency measures for the 1-hour ozone standards should 

apply under the anti-backsliding provisions of the 1997 8-hour ozone implementation rule. 

The contingency measures include emissions control requirements designed to maintain air 

quality that meets the level of the 1-hour ozone standard. The provisions must remain in state 

implementation plans to assure that air quality does not deteriorate or back-slide

If areas have current air quality data that meets the 1997 8-hour ozone standards and Clean 

Data Determinations, they may be able to suspend planning obligations as long as the air 

quality meets the standard.

This action removes the provisions that exempted areas from the requirements of 

nonattainment new source review and CAA section 185 penalty fees under the 1-hour 

standards.

This action deletes an obsolete provision that stayed the EPA’s authority to revoke the 1-hour 

ozone standard pending judicial review and certain rulemaking activities that have now been 

completed.

BACKGROUND 

The EPA set the 1997 ground-level ozone standard at 0.08 parts per million - ppm. Even 

though the ozone standard was subsequently revised in 2008, the 1997 standard remains in 

effect. Many areas throughout the country continue to work towards attaining it. 

On March 12, 2008, the EPA strengthened the 1997 8-hour primary ozone standard, designed 

to protect public health, to a level of 0.075 ppm. EPA also strengthened the secondary 8-hour 

ozone standard to the level of 0.075 ppm making it identical to the revised primary standard.

On April 30, 2004 (69 FR 23951), the EPA published the final Phase 1 implementation rule 

that addressed the following key elements related to implementation of the 1997 8-hour 

ozone national ambient air quality standards: 

o Classifications for the 8-hour NAAQS; revocation of the 1-hour NAAQS (i.e., when 

the 1-hour NAAQS will no longer apply); 

o How anti-backsliding principles will ensure continued progress toward attainment of 

the 8-hour ozone NAAQS; 

o Attainment dates; and 

o The timing of emissions reductions needed for attainment. 

On December 22, 2006, the U.S. Circuit Court of Appeals for the District of Columbia 

Circuit issued a decision, ruling against EPA on several of the issues raised and rejecting 

other challenges to the rule. (South Coast Air Quality Management Dist. v. EPA, 472 F.3d 

882 (DC Cir. 2006)). 

In response to this court action, the EPA proposed revisions to this rule in January 2009 to 

address the provisions vacated by the court. Today’s rulemaking finalizes these revisions.
HEALTH AND ENVIRONMENTAL EFFECTS OF OZONE POLLUTION

Ground-level ozone is not emitted directly into the air, but forms through a reaction of 

nitrogen oxides (NOx) and volatile organic compounds (VOC) in the presence of sunlight. 

Emissions from industrial facilities and electric utilities, motor vehicle exhaust, gasoline

vapors, and chemical solvents are the major man-made sources of NOx and VOC. 

Exposures to ozone can:

o Reduce lung function, making it more difficult for people to breathe as deeply and

o vigorously as normal,

o Irritate the airways, causing coughing, sore or scratchy throat, pain when taking a

o deep breath and shortness of breath,

o Inflame and damage the airways,

o Increase frequency of asthma attacks,

o Increase susceptibility to respiratory infection, and

o Aggravate chronic lung diseases such as asthma, emphysema and bronchitis.

In some people, these effects can lead to:

o Increased medication use among asthmatics,

o More frequent doctors visits,

o School absences,

o Increased emergency room visits and hospital admissions, and

o Increased risk of premature death in people with heart and lung disease.

Groups that are at greater risk from ozone include:

o People with lung disease, especially children with asthma,

o Children and older adults, and

o People who are active outside, especially children and people who work outdoors.

Ground-level ozone can have harmful effects on sensitive vegetation and ecosystems. When 

sufficient ozone enters the leaves of a plant, it can:

o Interfere with the ability of sensitive plants to produce and store food, leading to

reduced growth, making them more susceptible to certain diseases, insects, other 

pollutants, competition and harsh weather.

o Visibly damage the leaves of trees and other plants, harming the appearance of 

vegetation in urban areas, national parks, and recreation areas. These effects can have 

adverse impacts on ecosystems, including loss of species and changes to habitat 

quality, and water and nutrient cycles.

FOR MORE INFORMATION

To download the action from EPA’s website, please visit: 

http://www.epa.gov/air/ozonepollution/actions.html#stand.

Today’s final rule and other background information are also available either electronically at 

http://www.regulations.gov, the EPA’s electronic public docket, and comment system, or in 

hardcopy at the EPA Docket Center’s Public Reading Room.
o The Public Reading Room is located in the EPA Headquarters Library, Room Number 

3334 in the EPA West Building, located at 1301 Constitution Ave., NW, Washington, 

D.C. Hours of operation are 8:30 a.m. to 4:30 p.m. eastern standard time, Monday 

through Friday, excluding Federal holidays.

o Visitors are required to show photographic identification, pass through a metal detector,

and sign the EPA visitor log. All visitor materials will be processed through an X-ray 

machine as well. Visitors will be provided a badge that must be visible at all times.