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EPA Issues Revised PM2.5 Ambient Air Quality Standards

On December 14, 2012, the United States Environmental Protection Agency (EPA) released a final rule revising the National Ambient Air Quality Standards (NAAQS) for particulate matter. These revisions stem from litigation that successfully challenged EPA’s 2006 final rule, EPA’s last set of revisions to the suite of particulate matter NAAQS. In that litigation, the United States Court of Appeals for the District of Columbia remanded the 2006 particulate matter NAAQS to EPA for further evaluation. On June 29, 2012, EPA published proposed revisions to these NAAQS. On December 14, 2012, EPA completed the reevaluation process by releasing the final rule. The final rule will soon be published in the Federal Register and in the interim can be found here, along with support documentation.

EPA Made Limited Changes in the 2006 NAAQS

Although EPA took six years to reevaluate the 2006 NAAQS, the final rule makes few revisions to these standards.

EPA chose to tighten the primary annual fine particulate matter (PM2.5) NAAQS from 15 micrograms per cubic meter (µg/m3) to 12 µg/m3. However, the primary 24-hour PM2.5 NAAQS remains unchanged at 35 µg/m3. EPA also retained the 24-hour NAAQS for coarse particulate matter (PM10) of 150 µg/m3 which was established in 1987. These primary NAAQS are designed to protect human health with an adequate margin of safety.

With respect to the secondary (i.e. welfare based) NAAQS for particulate matter, EPA made no changes. EPA had originally proposed replacing the current PM2.5 NAAQS standard of 35 µg/m3 with a new visibility based standard of 30 deciviews. The deciview metric expresses uniform changes in haziness in terms of common increments across a range of visibility conditions. EPA chose not to finalize this proposed revision, responding to comments that a visibility standard would be less protective and more difficult to implement than the current standards.

Impact of the Revised Standards in Wisconsin and Neighboring States

The vast majority of the United States already meets the revised annual PM2.5 NAAQS of 12 µg/m3 based on monitoring data. A listing of all counties in the United States with PM2.5 monitors can be found here.

Of the fourteen Wisconsin counties that have PM2.5 monitors, all have monitored concentrations exhibiting compliance with the revised NAAQS value of 12 µg/m3 (2009 through 2011 data). Milwaukee and Waukesha Counties are the closest to exceeding the NAAQS at 11.1 and 11.7 µg/m3, respectively.

In Illinois, Cook, Madison and St. Clair Counties, all have monitored concentrations above 12 µg/m3 (2009 through 2011 data).

In Iowa, Muscatine and Scott Counties’ monitoring concentrations are above the 12 µg/m3 standard (2009 through 2011 data).

Minnesota and Michigan have no counties exceeding the revised standard.

Implementation Schedule for the Revised Standards

EPA’s final rule includes an implementation plan with the following milestones:

  • 2013 – States issue attainment designation recommendations for counties within their jurisdiction.
  • August 2014 – EPA issues its response to the state and tribal attainment designation recommendations.
  • December 2014 – EPA makes its final attainment designations. These designations would likely become effective in early 2015 (i.e. within 60 days of EPA’s final designation decisions being published in the Federal Register).
  • 2018 – States must submit to EPA their implementation plans describing how particulate matter will be reduced or maintained within their borders to meet the revised NAAQS.
  • 2020 – States with non-attainment areas must meet the revised standards. EPA projects that by 2020, 99% of counties in the United States with monitors will attain the standards.
  • 2025 – States that have been granted an extension by EPA must meet the revised standards by this alternative attainment deadline.

Implementing NAAQS with the PSD Program

The final rule includes limited revisions to the federal Prevention of Significant Deterioration (PSD) permitting program to help implement the revised NAAQS in source-specific permitting decisions. For example, states must generally determine that a major source or major modification to a major source will "not cause or contribute to" the violation of a NAAQS prior to issuing a PSD permit. The final rule provides a limited grandfathering or exemption from this requirement for PSD permits that were first published in draft form for public notice prior to the effective date of the rule (i.e. the date 60 days after the final rule is published in the Federal Register). This grandfathering/exemption also extends to PSD permit applications that were deemed complete by the state or EPA prior to December 14, 2012.

PM2.5 Screening Tools Remain Unchanged

EPA made no changes to the PM2.5 screening tools that are often used in air permitting decisions. These tools are currently subject to a legal challenge in which EPA has conceded that several of the existing PM2.5screening tools need further evaluation. However, EPA did not use this as an opportunity to revise these three widely used screening tools:

  • Significant impact levels (SIL) used to determine the level of dispersion modeling that is required of a permit applicant.
  • Significant emission rate (SER) thresholds used for determining whether a project triggers PSD permitting obligations.
  • Significant monitoring concentrations (SMC) used to determine whether a source can be exempt from the requirement to collect preconstruction ambient air monitoring data which is otherwise required of PSD permit applicants.

Questions Still Remain

What remains unclear, particularly in Wisconsin, is how and when sources must demonstrate that a proposed modification will not cause or contribute to the violation of the revised PM2.5 NAAQS when obtaining air permits. The Wisconsin Department of Natural Resources (WDNR) issued a memorandum (seen here) dated April 15, 2011, which describes both WDNR’s interpretations of such requirements and its expectations for when that demonstration must be made through dispersion air modeling to support an air permitting decision. Wis. Admin. Code chs. NR 405 through 408 also include rules that set out the modeling obligations of permit applicants. However, environmental advocacy groups have been selectively challenging Wisconsin air permits arguing that WDNR’s April 2011 policy and implementation of its air rules have been inappropriate.

Sources seeking air pollution control permits should be aware of these revised standards and consider how they may impact WDNR’s permit issuance decisions.

©2020 MICHAEL BEST & FRIEDRICH LLPNational Law Review, Volume III, Number 3



About this Author

Todd Palmer, Michael Best Law Firm, Environment and Natural Resources Attorney
Partner, Practice Group Chair

For more than 25 years, Todd has helped numerous clients remain in compliance with all aspects of the complex and dynamic Clean Air Act regulatory program. His extensive knowledge of and experience with Clean Air Act matters includes obtaining air emission control permits, planning future activities to minimize the expense of regulation, and the defense of allegations that a company may have violated Clean Air Act requirements.