Lower NAAQS for PM2.5 Takes Effect May 6, 2024

On February 7, the United States Environmental Protection Agency (USEPA) announced a final rule lowering the primary annual National Ambient Air Quality Standard (NAAQS) for fine particulate matter (PM2.5) from 12 micrograms per cubic meter (µg/m³) to 9.0 µg/m³. While 99 percent of U.S. counties are expected to meet this lower standard by 2032 due to steps already taken by States, Tribes, industry, and local communities, USEPA does expect that new nonattainment areas will be designated. USEPA is required to set NAAQS for six “criteria pollutants”—carbon monoxide, particulate matter, nitrogen dioxide, lead, ozone, and sulfur dioxide—and is lowering the PM2.5 standard to address fine particle pollution known as soot.[1] Sources of soot include coal burning, internal-combustion engines, boilers, waste incineration, and furnaces.

Here is what we know about the new rule:

  • The secondary 24-hour (daily) PM5 standards and the secondary annual PM2.5 standard remain unchanged.
  • The final rule was published in the Federal Register on March 6, 2024.
  • The effective date of this rule is 60 days after publication in the Federal Register, or May 6, 2024.
  • States will need to come into attainment by 2032, at the earliest.
  • USEPA will determine attainment/nonattainment designations within approximately 2 years after issuing new standards, but it is expected that new nonattainment areas will be designated.
  • States must develop and submit attainment plans for areas designated as nonattainment within 18 months after USEPA finalizes designations.
  • For areas in moderate nonattainment, these plans must ensure attainment by the end of the sixth calendar year after nonattainment designations.
  • Areas with severe nonattainment will have longer periods to achieve attainment of the new standards.

Additionally, applicants for permits to construct new major sources or modify existing major stationary sources must consider the revised PM2.5 NAAQS in their ambient air quality analyses after the effective date of this rule.

Additional information is available at https://www.epa.gov/pm-pollution/final-reconsideration-national-ambient-air-quality-standards-particulate-matter-pm

For further information or questions on how this change may affect your facility, please contact Andy Sheppard at 540-580-1540 or andy.sheppard@ehs-support.com.

[1] USEPA, “Reviewing National Ambient Air Quality Standards (NAAQS): Scientific and Technical Information.” Updated March 12, 2024. Available at https://www.epa.gov/naaqs



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