On February 7 of this year, after receiving nearly 700,000 written comments,² the EPA finalized updates to their NAAQS as it relates to PM_2.5.³ Such standards have been in place for approximately 20 years without change.⁴

The updates strengthen the annual health-based NAAQS for PM2.5 from a level of 12 micrograms per cubic meter (µg/m3) to 9 µg/m^3.5 Scientific evidence encouraged this change, which revealed that the previous standard of 12 µg/m³ was insufficient to protect public health with an adequate margin of safety as required by the CAA.⁶ Other particulate matter standards, like those for PM₁₀, will remain unchanged under the final rule.⁷

The final rule becomes effective 60 days after publication in the Federal Register.⁸ See the unpublished final rule here: https://www.epa.gov/system/files/documents/2024-02/pm-naaqs-final-frn-pre-publication.pdf.

The EPA will support states and Tribes in implementing the new clean air standard, and they expect that 99% of U.S. counties will be able to meet the revised PM_2.5 annual standard with actions already in place as of 2032—likely the earliest possible year that states would need to demonstrate attainment of the standards.⁹

Further, and in support of this ruling, the EPA is revising its Air Quality Index to improve public communications about the risks from PM_2.5 exposures, as well as making changes to their monitoring network to enhance the protection of communities already overburdened by air pollution.¹⁰

For those who are unfamiliar with particulate matter, it is a pollutant made up of hundreds of different chemicals and comes in many shapes and sizes.¹¹ Some particles are emitted directly from a source like construction sites and smokestacks, and others form in the atmosphere as a result of complex chemical reactions when pollutants are emitted into the ambient air from power plants, industrial sites, and automobiles.¹²

Those particles 10 micrometers in diameter or smaller are known as PM₁₀, and those particles 2.5 micrometers or smaller are known as PM_2.5, and it is the latter of the two that pose the greatest health risks to humans and the environment.¹³

PM_2.5 is generally so small that long- and short-term exposure can cause it to be inhaled and enter the bloodstream, potentially leading to serious health impacts like respiratory infections, lung disease, heart disease, cancer, and in some cases, premature death.¹⁴ The most at-risk members of the population include children, older adults, people with pre-existing respiratory or cardiovascular disease, and those living in already overburdened communities.¹⁵

In relation to environmental impacts, particulate matter is the main cause of reduced visibility (haze) in the U.S. and also causes acidification in lakes and streams, depletion of nutrients in the soil, alteration of the nutrient cycle in bodies of water, and impacts to biodiversity, among others.¹⁶

These updated standards are essential to the protection of human health and the environment. In fact, according to the EPA, this stronger standard will yield up to $46 billion in net health benefits in 2032.¹⁷ Be on the lookout for the final rule to be published in the Federal Register this year.

Adam Scheckman is a law clerk at McGregor Legere Stevens PC

FOOTNOTES
¹ EPA, National Ambient Air Quality Standards (NAAQS) for PM (Feb. 15, 2024), www.epa.gov/pm-pollution/national-ambient-air-quality-standards-naaqs-pm; McNees Wallace & Nurick LLC, EPA Significantly Lowers the National Ambient Air Quality Standard for Fine Particulate Matter, Westlaw NewsRoom (Feb. 13, 2024), https://today.westlaw.com/Document/I495fffa0caba11eeac10a65a15dd61af/View/FullText.html.
² EPA, Final Rule to Strengthen the National Air Quality Health Standard for Particulate Matter: Fact Sheet (Feb. 7, 2024), https://www.epa.gov/system/files/documents/2024-02/pm-naaqs-overview.pdf.
³ McNees Wallace & Nurick LLC, EPA Significantly Lowers the National Ambient Air Quality Standard for Fine Particulate Matter, Westlaw NewsRoom (Feb. 13, 2024), https://today.westlaw.com/Document/I495fffa0caba11eeac10a65a15dd61af/View/FullText.html.
⁴ EPA, Final Rule to Strengthen the National Ambient Air Quality Standards for Particulate Matter (Feb. 7, 2024), https://www.epa.gov/system/files/documents/2024-02/2024-pm-naaqs-final-overview-presentation.pdf.
⁵ McNees Wallace & Nurick LLC, EPA Significantly Lowers the National Ambient Air Quality Standard for Fine Particulate Matter, Westlaw NewsRoom (Feb. 13, 2024), https://today.westlaw.com/Document/I495fffa0caba11eeac10a65a15dd61af/View/FullText.html.
⁶ EPA, Final Rule to Strengthen the National Air Quality Health Standard for Particulate Matter: Fact Sheet (Feb. 7, 2024), https://www.epa.gov/system/files/documents/2024-02/pm-naaqs-overview.pdf.
⁷ EPA, Final Reconsideration of the National Ambient Air Quality Standards for Particulate Matter (PM) (Feb. 7, 2024), https://www.epa.gov/pm-pollution/final-reconsideration-national-ambient-air-quality-standards-particulate-matter-pm.
⁸ McNees Wallace & Nurick LLC, EPA Significantly Lowers the National Ambient Air Quality Standard for Fine Particulate Matter, Westlaw NewsRoom (Feb. 13, 2024), https://today.westlaw.com/Document/I495fffa0caba11eeac10a65a15dd61af/View/FullText.html.
⁹ EPA, Final Rule to Strengthen the National Air Quality Health Standard for Particulate Matter: Fact Sheet (Feb. 7, 2024), https://www.epa.gov/system/files/documents/2024-02/pm-naaqs-overview.pdf.
¹⁰ EPA, Final Rule to Strengthen the National Ambient Air Quality Standards for Particulate Matter (Feb. 7, 2024), https://www.epa.gov/system/files/documents/2024-02/2024-pm-naaqs-final-overview-presentation.pdf.
¹¹ EPA, Particulate Matter (PM) Basics (Jul. 11, 2023), https://www.epa.gov/pm-pollution/particulate-matter-pm-basics.
¹² Id.
¹³ Id.
¹⁴ EPA, Health and Environmental Effects of Particulate Matter (PM) (Aug. 23, 2023), https://www.epa.gov/pm-pollution/health-and-environmental-effects-particulate-matter-pm.
¹⁵ EPA, Final Rule to Strengthen the National Ambient Air Quality Standards for Particulate Matter (Feb. 7, 2024), https://www.epa.gov/system/files/documents/2024-02/2024-pm-naaqs-final-overview-presentation.pdf.
¹⁶ EPA, Health and Environmental Effects of Particulate Matter (PM) (Aug. 23, 2023), https://www.epa.gov/pm-pollution/health-and-environmental-effects-particulate-matter-pm.
¹⁷ EPA, EPA finalizes stronger standards for harmful soot pollution, significantly increasing health and clean air protections for families, workers, and communities (Feb. 7, 2024), https://www.epa.gov/newsreleases/epa-finalizes-stronger-standards-harmful-soot-pollution-significantly-increasing.