Audit, Compliance and Risk Blog

EPA reaffirms national particulate standards

Posted by Jon Elliott on Mon, Jan 18, 2021


The Environmental Protection Agency (EPA) has completed a long review, and reaffirmed the primary National Ambient Air Quality Standards (NAAQS) for particulate matter (PM), including those for PM-10 (particulates with an aerodynamic diameter less than or equal to 10 microns) and PM-2.5 (less than or equal to 2.5 microns; also call “fines”). On December 4, EPA announced it would retain the PM standards set in 2013, despite comments presenting recent scientific evidence – including evidence that higher pollution levels exacerbate harm from COVID-19 -- and seeking tighter standards.

What is EPA’s responsibility to establish and administer NAAQSs?

The Clean Air Act (CAA) requires EPA to identify and list “conventional” air pollutants that meet the following conditions:

  • emissions of the pollutant cause or contribute to air pollution, which may reasonably be anticipated to endanger public health or welfare; 

  • presence of the pollutant in ambient air results from “numerous or diverse mobile or stationary sources”; and

  • EPA intends to issue air quality criteria for the pollutant.

EPA evaluates atmospheric concentrations that would lead to unacceptable health and environmental impacts, and sets NAAQSs for atmospheric (ambient air) concentrations. EPA presently sets NAAQSs (primary and secondary standards) for oxides of sulfur (SOX), as well as for carbon monoxide (CO), lead, nitrogen dioxide, ozone, and particulates (PM-10 and PM-2.5). NAAQSs must “accurately reflect the latest scientific knowledge useful in indicating the kind and extent of all identifiable effects on public health or welfare….” CAA requires EPA to re-evaluate each NAAQS at least every 5 years, but EPA often misses these deadlines. For example, the latest PM review took seven years. EPA revises its review policies from time to time,  most recently when former Administrator Pruitt promulgated  “Back-to-Basics” Process for Reviewing [NAAQSs]” in May 2018 (I wrote about this policy HERE).

What are the national particulate standards?

EPA promulgated its first CAA particulate standards in 1971, and has slowly expanded and tightened PM regulations over the past fifty years. EPA initially set standards for PM-10, but added PM-2.5 requirements in in 1997. Since 2013, NAAQSs applicable to PM have been:  

  • PM-10

    • 24-hour average 150 micrograms per cubic meter (µg/m3)

  • PM-2.5

    • Annual average 12 µg/m3

    • 24-hour average 35 µg/m3

EPA is reaffirming these standards.

What now?

EPA’s decision became effective on December 18. Since EPA has reaffirmed the existing NAAQS, there are unlikely to be any incremental compliance requirements. However, it’s likely that environmental and public health advocates will sue to force EPA to reopen this rulemaking, and possible that the incoming Biden administration will choose to do so. 

However, readers should also note that states can and do promulgate stricter standards. For example, California has stricter standards for PM-10.

Self Assessment Checklist

Does the organization conduct activities that emit particulates from stationary sources?

- If so, are any of these activities characterized as “major sources” that are subject to the most extensive permit requirements?

- If so, are any of these activities in an area in which ambient concentrations are close to the NAAQS, where stricter standards may have led to stricter compliance requirements?

Where do I go for more information?

EPA PM decision (12/18/20 Federal Register)

EPA NAAQS/PM webpage 

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About the Author

Jon Elliott is President of Touchstone Environmental and has been a major contributor to STP’s product range for over 30 years. 

Mr. Elliott has a diverse educational background. In addition to his Juris Doctor (University of California, Boalt Hall School of Law, 1981), he holds a Master of Public Policy (Goldman School of Public Policy [GSPP], UC Berkeley, 1980), and a Bachelor of Science in Mechanical Engineering (Princeton University, 1977).

Mr. Elliott is active in professional and community organizations. In addition, he is a past chairman of the Board of Directors of the GSPP Alumni Association, and past member of the Executive Committee of the State Bar of California's Environmental Law Section (including past chair of its Legislative Committee).

You may contact Mr. Elliott directly at:

Tags: EPA, CAA, Environment, NAAQS