DEEP DIVE: U.S. EPA Finalizes Ambient Air Quality Standards for Particulate Matter

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February 13, 2024Stefan Modrich, Reporter, 3E News TeamBlog

(Editor’s Note: 3E is expanding news coverage to provide customers with insights into topics that enable a safer, more sustainable world by protecting people, safeguarding products, and helping businesses grow. Deep Dive articles, produced by reporters, feature interviews with subject matter experts and influencers as well as exclusive analysis provided by 3E researchers and consultants.)

The U.S. Environmental Protection Agency (EPA) is updating its air quality standards to reduce exposure to particle or soot pollution, which the EPA regards as one of the most dangerous forms of air pollution. The agency announced on 7 February 2024 that it had finalized its new, stronger standards for the National Ambient Air Quality Standards for Particulate Matter (PM NAAQS).

The EPA set the threshold of the primary (health-based) annual PM2.5 standard at 9.0 micrograms per cubic meter. The agency said that, moving forward, it is going to account for the proximity of populations at increased risk of PM2.5-related health effects to sources of air pollution, which will ensure localized data collection in overburdened areas to inform future NAAQS reviews.

The EPA is also revising its Air Quality Index (AQI) to improve public communications about the health risks from PM2.5 exposures.

“This final air quality standard will save lives and make all people healthier, especially within America’s most vulnerable and overburdened communities,” said EPA Administrator Michael S. Regan in a news release. “Cleaner air means that our children have brighter futures, and people can live more productive and active lives, improving our ability to grow and develop as a nation. EPA looks forward to continuing our decades of success in working with states, counties, Tribes, and industry to ensure this critical health standard is implemented effectively to improve the long-term health and productivity of our nation.”


The EPA sets NAAQS for six common and harmful pollutants: carbon monoxide, lead, PM, ozone, nitrogen dioxide, and sulfur dioxide. Those at greatest risk for particle pollution include children and older adults, as well as people with asthma or other respiratory conditions.

In June 2021, the agency announced that it would reconsider the December 2020 decision to retain its 2012 standards because the available scientific evidence and technical information indicated that the standards may not be adequate to protect public health and welfare.

Industry experts have been supportive of more stringent EPA air quality guidelines going back several years.

The Clean Air Science Advisory Committee (CASAC), an independent expert committee that assists the EPA in reviewing the NAAQS, recommended tightening all PM standards based on its review of the science underlying the 2020 PM NAAQS and research from Harvard University’s Environmental & Energy Law Program

The nonprofit Clean Air Task Force (CATF) previously argued that the Trump Administration undermined the NAAQS review process and welcomed the EPA’s renewed focus on tightening its current standards.

The NAAQS has also drawn support from advocacy groups, such as Earthjustice, the Climate Action Campaign, Mom’s Clean Air Force, and the National Medical Association, for its efforts to combat environmental injustices that have disproportionately impacted communities of color.

“Administrator Regan and President Biden deserve thanks for taking this vital step to curb soot pollution — a dangerous and even deadly pollutant that has taken an oversized toll on underrepresented and overburdened communities less equipped to deal with its severe health impacts,” said Dr. Doris Browne, former president of the National Medical Association, while adding, “this new standard of 9 micrograms per cubic meter will save lives based on scientific evidence. As a physician and an advocate for clean air, our ultimate goal is health equity.”


The industries most likely to be affected by the new NAAQS are cement and concrete product manufacturing, iron and steel mills, glass makers, and natural gas pipeline transportation.

In some cases, PM is emitted directly from combustion sources, construction sites, and older diesel engines. Emissions from power plants, gasoline and diesel engines, and certain industrial processes can contain sulfur dioxide and nitrogen oxide.

Some industry groups, among them the American Petroleum Institute (API) and the American Forest & Paper Association (AFPA), are opposed to the new standards because they “add red tape” and “defy common sense.” 

The EPA said its more robust air pollution regulations will yield up to $46 billion in net health benefits, preventing up to 4,500 premature deaths and 290,000 lost workdays by 2032. For every $1 spent from this action, there could be as much as $77 in human health benefits in 2032, according to an agency estimate.

Nearly all, or 99% of U.S. counties, are projected to meet the more protective standard in 2032, likely the earliest year that states would be required to meet the revised standard, according to the EPA data. Of the 52 that are not expected to meet the new PM standard, most contain densely populated urban and suburban areas with highly concentrated industrial centers and manufacturing districts.

  • Arizona: Maricopa
  • California: Alameda, Calaveras, Contra Costa, Fresno, Imperial, Kern, Kings, Los Angeles, Madera, Merced, Orange, Plumas, Riverside, Sacramento, San Bernardino, San Diego, San Joaquin, Santa Clara, Solano, Stanislaus, Sutter, Tulare, Ventura
  • Colorado: Adams, Denver
  • Florida: Broward
  • Georgia: Richmond
  • Idaho: Lemhi, Shoshone
  • Illinois: Cook, Madison
  • Indiana: Lake, Marion
  • Louisiana: Caddo
  • Michigan: Wayne
  • Montana: Lincoln, Missoula
  • New Jersey: Bergen, Camden
  • Ohio: Butler, Cuyahoga, Hamilton
  • Oregon: Harney, Jackson, Klamath
  • Pennsylvania: Allegheny, Delaware
  • Texas: Cameron, Harris, Hidalgo, Travis

The EPA said it received more than 700,000 written comments and held a public hearing prior to finalizing its updated air quality standards.

(About the author: Stefan Modrich is a Washington, D.C.-based reporter for 3E. He covers the latest developments in environmental health and safety policy and regulation. Modrich previously wrote for S&P Global Market Intelligence, The Arizona Republic, and the Chicago Tribune. He is an alumnus of Arizona State University and the University of Zagreb.)