National Ambient Air Quality Standards (NAAQS) for Particulate Matter (PM) – Environmental & Energy Law Program – Harvard Law School
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On this page we track EPA’s review and implementation of revised PM NAAQS. For information on EPA’s National Ambient Air Quality Standards (NAAQS) scientific review and approval process read our NAAQS Regulatory Tracker page here. To follow EPA’s work on the Ozone NAAQS, see our Ozone NAAQS Regulatory Tracker page here. Click here for our Air Transport – Cross-State Air Pollution Rule / Good Neighbor Rule, Section 126 Petitions, and Section 184 Ozone Transportation Commission Petition page.
Quick Take
EPA published a proposed rule for the particulate matter (PM) NAAQS on January 27, 2023, that would retain the primary 24-hour PM 2.5 standard without revision and revise the annual standard from 12 μg/m3 to 8-10 μg/m3. The Clean Air Science Advisory Committee (CASAC), an independent expert committee that assists EPA in reviewing the NAAQS, recommended tightening all PM standards based on its review of the science underlying the 2020 PM NAAQS, for both annual and 24-hour standards.
Why it Matters
EPA sets NAAQS for six common and harmful pollutants: carbon monoxide, lead, PM, ozone, nitrogen dioxide, and sulfur dioxide. The NAAQS are based solely on public health and welfare protection, meaning that the agency must not consider the cost of revising a standard if the current science demands a standard be tightened to protect public health or welfare. The NAAQS program is highly successful and is the cornerstone of EPA’s work to protect public health and the environment. EPA estimates that between 1980 and 2021, total emissions of these six pollutants dropped by 71% while the economy grew by 182%.
PM can vary in size but is so small that it can be inhaled and enter the bloodstream, which can increase overall mortality rates and is often linked to asthma and other respiratory impacts, cardiovascular disease, and cancer. It can be emitted by a wide range of sources such as vehicles, industrial sources (including power plants), construction sites, and fires.
The Clean Air Act requires that EPA review the NAAQS every five years to ensure their adequacy. The review process is a multi-stage, robust review of the current science that requires significant expert input. If a standard is tightened, there is a cascading effect on air quality policies and programs across the country. States and local regions must ensure that the sources of pollution in their jurisdiction decrease their emissions, so that the region can meet the new, more stringent national standard.
Current Status
In December 2020, the Trump EPA issued the 2020 PM NAAQS rule, retaining the 2015 NAAQS for PM despite significant scientific evidence that the 2015 standards were inadequate to protect public health. In June 2021, the Biden EPA then announced that it was beginning the process of reconsidering the 2020 PM NAAQS rule, following an Executive Order requiring EPA to review rules from the Trump EPA Administration.
On January 27, 2023, the Biden EPA published its proposed rule for PM NAAQS, opening it for public comment until March 28, 2023. Despite CASAC and EPA staff recommending the EPA consider tightening all of its PM standards, EPA proposes to retain the primary 24-hour PM 2.5 standards and lower only the primary annual PM 2.5 standards from 12 μg/m3 to 8-10 μg/m3.
OBAMA ADMINISTRATION
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Jan. 15, 2013 EPA concludes its 2012 review of the PM NAAQS and determines that the existing standards inadequately protect public health. EPA tightens annual health-based standards for fine particles (PM2.5) to 12.0 micrograms per cubic meter. EPA estimates that the benefits of the revised standards will be between $3.6 and $9 billion.
Dec. 3, 2014 EPA announces the beginning of its next review of the PM NAAQS by issuing a call for information to assist EPA in developing the Integrated Science Assessment.
Dec. 2016 EPA releases the final review plan for the PM NAAQS review. EPA projects that the scientific review will be completed in Fall 2020 and a final decision made on the NAAQS in 2022.
TRUMP ADMINISTRATION
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BIDEN ADMINISTRATION
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