Released December 04, 2025 | SUGAR LAND
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Written by John Egan for Industrial Info Resources (Sugar Land, Texas)
"Fine" particulate matter is classified as less than 2.5 micrometers in diameter (PM 2.5). A micrometer is about 1/30th the width of a human hair.
According to the U.S. Environmental Protection Agency (EPA) website, numerous scientific studies have linked particle pollution exposure to a variety of health problems, including:
The public health threat posed by particulate matter is why, when it wrote the Clean Air Act more than 50 years ago, Congress said the EPA has to rely solely on the best science and public health information when regulating those emissions. The Clean Air Act requires the agency to conduct a thorough review of the science every five years and to use that as the basis for any proposed change to the standards.
The potential costs and benefits of proposed changes must be estimated, but the EPA cannot use those costs to change the standard, even if those costs outweigh the benefits.
Last week, the Trump EPA asserted in a filing with the Federal Appeals Court for the D.C. Circuit that the Biden EPA failed to follow the procedure laid out in the statute, which called for a "thorough" review of the science and public health data to be conducted before trying to revise the standards.
"For the first time in nearly 50 years, EPA finalized a purported 'reconsideration' of a national ambient air quality standard, a central component of the Clean Air Act," the Trump administration filing asserted. "It did so based on a novel interpretation of the statute and without the 'thorough review' of the underlying air quality criteria and related standards required by the Clean Air Act.
"The result was an unlawful tightening of the annual standard for fine particulate matter (PM2.5) from 12 micrograms per cubic meter of air to 9 micrograms per cubic meter of air, without the rigorous, stepwise process that Congress required. EPA now confesses error and urges this Court to vacate the Rule before the area designation deadline of February 7, 2026."
At the time, the Biden EPA said the tougher standard would avoid 800,000 cases of asthma symptoms, 2,000 hospital visits and 4,500 premature deaths, adding up to about $46 billion in health benefits in 2032. It added that the tougher standard would especially benefit children, older adults and those with heart and lung conditions, as well as those living near highways, factories and power plants.
If granted by the court, the PM2.5 standard would revert to what it was in 2020: 12 micrograms per cubic meter of air.
"An abundance of scientific evidence shows that going back to the previous standard would fail to provide the level of protection for public health required under the Clean Air Act," he added.
Another source, Patrice Simms, vice-president of healthy communities at Earthjustice, a nonprofit law firm that represents environmental groups in the legal case, told AP, "Walking away from these clean-air standards doesn't power anything but disease."
Trump "has made it clear that his agenda is all about saving corporations money," Simms said, adding under Zeldin, the EPA "has nothing to do with protecting people's health, saving lives or serving children, families or communities."
Key Takeaways
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Summary
The EPA has asked a federal appeals court to vacate a 2024 rule governing emissions of particulate matter from power plants, refineries, vehicle tailpipes and other industrial sources, because the 2024 rule did not follow the review process set out in the Clean Air Act.Emissions of Particulate Matter and the Clean Air Act
The Clean Air Act, in its section on National Ambient Air Quality Standards (NAAQS), regulates the sizes and durations over which particulates that can be emitted from industrial facilities such as power plants, oil refineries and other smokestack industries. Vehicles emit particulate matter, which also is created by wildfires."Fine" particulate matter is classified as less than 2.5 micrometers in diameter (PM 2.5). A micrometer is about 1/30th the width of a human hair.
According to the U.S. Environmental Protection Agency (EPA) website, numerous scientific studies have linked particle pollution exposure to a variety of health problems, including:
- Premature death in people with heart or lung disease
- Nonfatal heart attacks
- Irregular heartbeat
- Aggravated asthma
- Decreased lung function
- Increased respiratory symptoms, such as irritation of the airways, coughing or difficulty breathing
The public health threat posed by particulate matter is why, when it wrote the Clean Air Act more than 50 years ago, Congress said the EPA has to rely solely on the best science and public health information when regulating those emissions. The Clean Air Act requires the agency to conduct a thorough review of the science every five years and to use that as the basis for any proposed change to the standards.
The potential costs and benefits of proposed changes must be estimated, but the EPA cannot use those costs to change the standard, even if those costs outweigh the benefits.
Allowable Standards Get Smaller
As of 2020, the annual primary standard for fine particulate matter was 12 micrograms per cubic meter of air. But in March 2024, the EPA under the Biden administration moved to tighten that standard to 9 micrograms per cubic meter of air, according to testimony filed that year in litigation that challenged the move. The case is Commonwealth Of Kentucky, Et Al., v. U.S. Environmental Protection Agency, Et Al. The litigation was paused in late 2024 following the election of Donald Trump to a second presidential term.Last week, the Trump EPA asserted in a filing with the Federal Appeals Court for the D.C. Circuit that the Biden EPA failed to follow the procedure laid out in the statute, which called for a "thorough" review of the science and public health data to be conducted before trying to revise the standards.
"For the first time in nearly 50 years, EPA finalized a purported 'reconsideration' of a national ambient air quality standard, a central component of the Clean Air Act," the Trump administration filing asserted. "It did so based on a novel interpretation of the statute and without the 'thorough review' of the underlying air quality criteria and related standards required by the Clean Air Act.
"The result was an unlawful tightening of the annual standard for fine particulate matter (PM2.5) from 12 micrograms per cubic meter of air to 9 micrograms per cubic meter of air, without the rigorous, stepwise process that Congress required. EPA now confesses error and urges this Court to vacate the Rule before the area designation deadline of February 7, 2026."
Costs and Benefits of Tougher Standards
Even though the EPA is prohibited from using the potential cost of a NAAQS rule as a reason to support or oppose it, the estimated costs and benefits of the tighter Biden-era standards were considerable. The final rule estimated costs would be $590 million (in 2017 dollars) and the benefits would range from $22 billion to $46 billion.At the time, the Biden EPA said the tougher standard would avoid 800,000 cases of asthma symptoms, 2,000 hospital visits and 4,500 premature deaths, adding up to about $46 billion in health benefits in 2032. It added that the tougher standard would especially benefit children, older adults and those with heart and lung conditions, as well as those living near highways, factories and power plants.
What the EPA Seeks
The agency told the appeals court it "no longer seeks to defend the 2024 Rule and has asked the Department of Justice to file a motion confessing error and seeking vacatur of the 2024 Rule."If granted by the court, the PM2.5 standard would revert to what it was in 2020: 12 micrograms per cubic meter of air.
Public Health Groups Cry 'Foul'
"[The] EPA's motion is a blatant attempt to avoid legal requirements for a rollback, in this case for one of the most impactful actions the agency has taken in recent years to protect public health," said Hayden Hashimoto, an attorney at the nonprofit Clean Air Task Force, to the Associated Press (AP)."An abundance of scientific evidence shows that going back to the previous standard would fail to provide the level of protection for public health required under the Clean Air Act," he added.
Another source, Patrice Simms, vice-president of healthy communities at Earthjustice, a nonprofit law firm that represents environmental groups in the legal case, told AP, "Walking away from these clean-air standards doesn't power anything but disease."
Trump "has made it clear that his agenda is all about saving corporations money," Simms said, adding under Zeldin, the EPA "has nothing to do with protecting people's health, saving lives or serving children, families or communities."
Key Takeaways
- The Trump administration has asked a court to vacate a Biden-era rule that would tighten particulate matter standards.
- The rule being challenged would tighten standards to 9 micrograms per cubic foot of air from 12 micrograms.
- The Trump administration says the EPA did not follow the law when it moved to tighten the standards to benefit public health.
About Industrial Info Resources
Industrial Info Resources (IIR) is the leading provider of industrial market intelligence. Since 1983, IIR has provided comprehensive research, news and analysis on the industrial process, manufacturing and energy related industries. IIR's Global Market Intelligence (GMI) platform helps companies identify and pursue trends across multiple markets with access to real, qualified and validated plant and project opportunities. Across the world, IIR is tracking more than 200,000 current and future projects worth $17.8 trillion (USD).
