EPA Revises NAAQS Ground-Level Ozone Standards

March 24, 2008 // Published as a news service by IHS

The revised primary 8-hour standard is 0.075 ppm and the revised secondary standard is set at a form and level identical to the primary standard.

The previous primary and secondary standards were identical 8-hour standards set at 0.08 ppm.

In addition to changing the level of the standards from 0.08 pm to 0.075 ppm, the EPA specified the level of the standard to the third decimal.

An area will meet the revised standards if the three-year average of the annual fourth-highest daily maximum 8-hour average at every ozone monitor is less than or equal to the level of the standard, said the EPA. In addition, the EPA changed the Air Quality Index (AQI) to reflect the revised primary standard.

Implementing the standards
The Clean Air Act requires the EPA to designate areas as attainment (meeting the standards), nonattainment (not meeting the standards) or unclassifiable (insufficient data to classify) after the agency sets a new standard or revises an existing standard.

The following schedule will apply to the revised ozone standards:

• States must make recommendations to the EPA no later than March 2009 for areas to be designated attainment, nonattainment and unclassifiable.
• The EPA will issue final designations of attainment, nonattainment and unclassifiable areas no later than March 2010 unless there is insufficient information to make these designation decisions. In that case, the EPA will issue designations no later than March 2011.
• States must submit state implementation plans outlining how they will reduce pollution to meet the standards by a date that the EPA will establish in a separate rule. That date will be no later than three years after the EPA’s final designations. If the EPA issues designations in 2010, then these plans would be due no later than 2013.
• States are required to meet the standards by deadlines that may vary based on the severity of the problem in the area.
• The EPA will issue a separate rule to address monitoring requirements necessary to implement the revised standards. The EPA intends to propose a monitoring rule in June 2008 and issue a final rule by March 2009.

Review of the ozone standards
The ozone review process began with an assessment of scientific studies on ozone by the EPA's National Center for Environmental Assessment. This assessment was published as an air quality criteria document for ozone, which explored the scientific data pertaining to the health and environmental effects associated with ozone.

The EPA's Office of Air Quality Planning & Standards then prepared a "staff paper" document, which presented policy-relevant scientific information, the results of quantitative exposure and risk assessments with associated uncertainties and a policy assessment that identified policy options including ranges of standards for consideration.

The criteria document and staff paper underwent scientific and public review including review by the Clean Air Scientific Advisory Committee (CASAC). As part of its mandate, the CASAC makes recommendations to the EPA on the adequacy of the existing standards and revisions it believes would be appropriate.

Before making a final decision on whether to revise the ozone NAAQS, the EPA undertook a public review and comment process on its proposed decision of June 20, 2007. The EPA said it considered and analyzed issues raised in public comments during the public comment period on the proposed rule, which ended Oct. 9, 2007. The EPA claims that the final standards will yield health benefits valued between $2 billion and $19 billion.

The EPA's Regulatory Impact analysis claims that benefits are likely greater than the cost of implementing the standards. Cost estimates range from $7.6 billion to $8.5 billion, said the EPA.

Source: U.S. Environmental Protection Agency (EPA).