EPA Advances PM Rule It Calls Unlawful

LINCOLN, Neb. (DTN) -- Even as the U.S. Environmental Protection Agency opposes the implementation of tighter 2024 National Ambient Air Quality Standards for fine particulate matter, the agency notified all 50 states on Friday of its plans to implement the Biden-era rule.

The EPA last week also filed a brief with the U.S. Supreme Court in support of an appeal seeking to overturn the rule, joining 25 states in a legal fight.

The long-standing saga of PM 2.5 standards has featured a ping-pong, back-and-forth regulatory approach, often framed by Republican politicians as an attempt by the feds to regulate farm dust and by Democratic politicians as needed to improve air quality.

The EPA is racing forward on implementing the rule because of a Feb. 6, 2027, deadline imposed by the U.S. District Court for the Northern District of California to designate areas of attainment, non-attainment and unclassifiable.

The EPA said in a news release last week that it continues to hold that the 2024 rule is "unlawful on multiple grounds."

The agency joins the states of Kentucky, West Virginia, Alabama, Alaska, Arkansas, Florida, Georgia, Idaho, Indiana, Iowa, Kansas, Louisiana, Mississippi, Missouri, Montana, Nebraska, New Hampshire, North Dakota, Ohio, Oklahoma, South Carolina, South Dakota, Texas, Utah, Virginia and Wyoming in seeking Supreme Court review.

In 2020, the agency concluded after a review of available science that the 2012 PM 2.5 standard protects public health. In 2021, the EPA reconsidered and revised the standard.

"The resulting 2024 PM 2.5 NAAQS -- which were set without fully considering the available science or taking into account the severe consequences a rushed revision would have on Americans -- is the most stringent in history and approaching natural levels," the agency said on Friday.

On Aug. 21, 2023, the EPA announced a new scientific review of the standards.

Agriculture groups and rural interests responded by asking the agency in a letter to maintain existing NAAQS at PM 2.5.

Ag groups argued that many ranching counties, particularly in the Southwest, face a difficult task in staying within the PM 2.5 standard and that further tightening standards makes compliance nearly impossible.

What's more, ag groups have told the EPA that most PM 2.5 emissions come from nonpoint sources, including fires and unpaved roads, yet ranches would be swept up by tighter standards.

In the Supreme Court brief filed last week, the EPA said the agency in 2024 did not conduct a thorough review that's required to revise the NAAQ standards.

"EPA acknowledged that the supplement did not 'represent a full multidisciplinary evaluation of evidence' for the underlying air quality criteria and did not 'satisfy the EPA's obligation to periodically complete a thorough review of the air quality criteria,'" the EPA told the Supreme Court.

In November 2025, EPA told the U.S. Court of Appeals for the District of Columbia Circuit that the agency had erred and that the 2024 standard was unlawful. The court denied EPA's motion to withdraw the rule.

In addition, the agency told the high court last week that the EPA should have considered the costs of implementing more stringent 2024 PM 2.5 standards.

"Nothing in the Clean Air Act compelled the agency to do so or prohibited the agency from considering costs in deciding whether a discretionary midcycle review was advisable," the EPA said in its brief.

"Bedrock principles of administrative law required EPA to consider the disruptive effect of a midcycle revision as an important aspect of the decision before it. The costs of an agency's action typically are an important aspect that warrants consideration."

The EPA told the Supreme Court that the rule should be reviewed because it will have "sweeping effects" on nearly every segment of the U.S. economy.

"The rule sets in motion a years-long implementation process that will culminate in tighter particulate-matter controls over a variety of sources affecting energy-production, manufacturing, transportation and consumer sectors," the agency said.

Last month, the EPA appealed the district court order imposing the Feb. 6, 2027, deadline. The U.S. Court of Appeals for the Ninth Circuit granted expedited consideration of the case.

Read more on DTN:

"Rural Groups Want Air Regs Untouched," https://www.dtnpf.com/…

"Pruitt Targets 'Farm Dust' Regulation," https://www.dtnpf.com/…

Todd Neeley can be reached at todd.neeley@dtn.com

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