US EPA finalizes stronger air quality standards for particulate matter

7 February 2024

The US Environmental Protection Agency (EPA) issued a final rule that strengthens the national ambient air quality standard (NAAQS) for fine particulate matter (PM_2.5) from a level of 12 μg/m³ to 9 μg/m³.

In June 2021, the Biden-Harris EPA announced it would reconsider the December 2020 decision of the Trump-Pence EPA to retain the 2012 standards for particulate matter. The EPA said it considered the available science and technical information, the recommendations of the agency’s Clean Air Scientific Advisory Committee (CASAC), as well as public comments on the 2023 proposed standards when making the decision on whether to strengthen the PM standards.

The EPA has strengthened the annual average PM_2.5 standard, while retaining all other PM standards. These NAAQS standards for particulate matter include:

• Primary (health) standards for fine particles (PM_2.5):
  • An annual average standard of 9.0 μg/m³ (strengthened from the prior 12 μg/m³).
  • A 24-hour standard of 35 μg/m³.
• Primary (health) standard for coarse particles (PM₁₀)—A 24-hour standard of 150 μg/m³.
• Secondary (welfare) standards for particle pollution—EPA’s secondary standards for particle pollution are identical to the primary standards for PM_2.5 and PM₁₀, except for the secondary annual PM_2.5 standard of 15.0 μg/m³.

Along with strengthening the primary annual PM_2.5 standard, the EPA has modified the PM_2.5 monitoring network design criteria to include a factor that accounts for proximity of populations at increased risk of PM_2.5-related health effects to sources of air pollution. The agency has also revised the Air Quality Index (AQI) to improve public communications about the health risks from PM_2.5 exposures.

The EPA predicts that due to already implemented pollution control measures, 99% of US counties will meet the more protective standard in 2032—likely the earliest year that states would need to meet the revised standard.

Source: US EPA