On June 15, 2012, the United States Environmental Protection Agency (EPA) announced a proposed rule that would increase the stringency of the primary annual National Ambient Air Quality Standard (NAAQS) for fine particulate matter (PM_2.5) before the end of the year.¹  The proposal retains the 24-hour primary standard for PM_2.5 but would establish a new secondary PM_2.5 NAAQS to address visibility impacts. The agency did not propose revisions to the NAAQS for coarse particulate matter (PM₁₀), but will take public comment on the adequacy of the existing standard.

The new rulemaking was issued pursuant to a June 6, 2012, settlement with the American Lung Association (ALA) and the National Parks Conservation Association (NPCA). The settlement gave EPA an extra week to propose standards, compared to the deadline in a recent court order, in exchange for an EPA commitment to finalize standards by no later than December 14, 2012. The proposed rule would:

• Lower the annual primary PM_2.5 NAAQS from 15.0 µg/m³ to within a range of 12.0 to 13.0 µg/m³ and eliminate spatial averaging provisions from the form of the standard.²  The form would otherwise remain the same (an annual arithmetic mean averaged over three years).
• Retain the 24-hour primary PM_2.5 NAAQS at the current level of 35 µg/m³ and with the current form (98^th percentile, averaged over three years).
• Revise the secondary PM_2.5 NAAQS by adding a new 24-hour visibility index standard expressed as a light extinction level of either 30 deciviews (dv) or 28 dv and a 90^th percentile form averaged over three years.³
• Retain other secondary PM_2.5 NAAQS, but remove the option for spatial averaging in the annual standard to maintain consistency with the primary standards.

EPA's proposal would also revise the Prevention of Significant Deterioration (PSD) regulations to provide limited grandfathering from the revised NAAQS for PSD permit applications which have been noticed for public comment before the effective date of the revised PM_2.5 NAAQS and to allow a permit applicant to demonstrate compliance with the 24-hour primary PM_2.5 NAAQS as a surrogate method for demonstrating compliance with the secondary visibility index PM_2.5 NAAQS.⁴

If finalized, the proposed annual primary NAAQS would add an unknown number of additional areas to the 55 areas already designated as nonattainment for PM_2.5 and make attainment more difficult for existing areas. Proposed new and modified major stationary sources of PM_2.5 in these areas will be subject to the more stringent Nonattainment New Source Review (NNSR) requirements instead of PSD requirements. (It remains to be seen whether EPA would attempt to require NNSR for areas designated nonattainment with the 24-hour secondary PM_2.5 NAAQS for visibility impairment.)

Impacts would also be felt in attainment areas. First, existing regulations and statutes in many states would require most⁵ New Source Review (NSR) permit applicants to demonstrate compliance with the new NAAQS, even though nonattainment designations will not be finalized until late 2014. Second, demonstrations will become more difficult as EPA continues to drive the NAAQS closer to background concentrations.   

Statutory Background

Section 109 of the Clean Air Act (CAA) requires EPA to establish primary and secondary NAAQS for certain air contaminants, including PM.⁶  The primary NAAQS are set at levels to protect public health with an adequate margin of safety, whereas the secondary NAAQS are set at levels that are required to protect the public welfare. 

The EPA must conduct a review of each NAAQS every five years and make revisions in existing standards or promulgate such new standards as may be appropriate. The CAA also requires the EPA to appoint an independent scientific review committee, known as the Clean Air Scientific Advisory Committee (CASAC), to recommend new standards or revisions to existing standards.⁷

Procedural Background

EPA last revised the PM NAAQS in October 2006, establishing or retaining the following primary standards:  (a) a 24-hour PM₁₀ standard of 150 µg/m³; (b) a 24-hour PM_2.5 standard of 35 µg/m³; and (c) an annual PM_2.5 standard of 15 µg/m³. EPA set secondary standards equal to each of the primary standards.⁸

In 2009, the D.C. Circuit found that, in setting some of the 2006 NAAQS, EPA had departed from CASAC and internal staff recommendations without adequate justification. The court remanded the primary annual PM_2.5 standard, because EPA did not adequately explain how the standard would provide an "adequate margin of safety," and both secondary PM_2.5 standards, because EPA did not adequately explain how setting them equal to the primary standards would protect public welfare, including visibility impairment.⁹

EPA elected to respond to the partial remand through the statutorily required five-year review of the PM NAAQS. Although scientific and health assessments were completed by 2009 and 2010, respectively, and a policy assessment issued in April 2011, the agency missed the October 2011 deadline. 

In February 2012, the ALA and the NPCA filed suit in the U.S. District Court for the District of Columbia to force EPA to issue a final rule by October 2012.¹⁰  EPA requested an August 2013 deadline, but the court ordered the agency to issue proposed standards in only eight days, by June 7^th, due to concerns that EPA was not taking the D.C. Circuit remand seriously. EPA then entered an agreement with the ALA and NPCA to propose standards by June 14, 2012, and finalize standards by December 14, 2012.

Additional Discussion

The EPA has proposed NAAQS values which are toward the higher end of the level ranges recommended by CASAC. Where CASAC recommended a primary annual PM_2.5 NAAQS in the range of 13 to 11 µg/m³, EPA has proposed a range of 13 to 12 µg/m³. Where CASAC recommended a 24-hour PM_2.5 NAAQS in the range of the existing level (35 µg/m³) and 30 µg/m³, EPA has elected to retain the existing standard.¹¹   

The proposed secondary PM_2.5 visibility impairment NAAQS of 30 or 28 dv also skews toward the upper range of CASAC's recommendation of 20 to 30 dv.¹²  The standard has been proposed in a form that considers both speciated PM_2.5 mass concentrations and relative humidity because overall concentration alone does not fully reflect visibility impacts.¹³  The proposed standard is a significant departure from past practice for EPA, which generally sets secondary standards that are the same as primary standards.

EPA believes that most areas designated as attainment with the proposed primary PM_2.5 NAAQS will also be attainment for the new secondary visual impairment PM_2.5 NAAQS. However, the agency essentially acknowledges that there may be areas in attainment with the primary NAAQS, but nonattainment with the secondary NAAQS by requesting public comment on whether it is appropriate to apply NNSR requirements to areas designated nonattainment for only a secondary NAAQS.¹⁴

Although EPA may not consider cost when establishing a NAAQS, the agency did conduct a Regulatory Impact Analysis for informational purposes. If the primary annual PM_2.5 NAAQS is set at 12.0 µg/m³, the agency estimates costs of $69 million per year and health benefits of $2.3 to $5.9 billion per year.  At 13.0 µg/m³, EPA estimates costs of $2.9 million per year and benefits of $88 to $220 million per year.

EPA intends to promulgate the revised NAAQS in December 2012.  By December 2013, the states must submit to EPA recommendations for designating areas within each state as attainment, nonattainment, or unclassifiable with respect to the new/revised NAAQS. The EPA then intends to make initial nonattainment designations by December 2014, based on air quality data for 2011 to 2013.¹⁵

This article was prepared by Patricia Finn Braddock and Bob Greenslade (rgreenslade@fulbright.com or 512 536 5241) of Fulbright's Environmental Law Practice, Fulbright's Climate Change Practice and Fulbright's Energy Practice.