Texas may have to curb soot pollution after major federal court rulings

Texas could soon face federal enforcement for the first time over its high levels of fine particulate matter, also known as soot, after two courts upheld stricter Biden-era pollution standards this summer.

Harris County is one of 14 Texas counties whose air pollution exceeds the annual limit introduced during the Biden administration, according to recent U.S. Environmental Protection Agency data. Seven of the county’s nine official air monitoring sites measured average soot levels that violated the new health standards. The federal rules cap annual averages at 9 micrograms per cubic meter, down from the previous limit of 12 micrograms. 

Fine particulate matter consists of tiny particles, small enough to reach deep into people’s lungs and enter their bloodstream. The pollutant kills tens of thousands of people in the United States each year, contributing to cancers and heart attacks while exacerbating chronic conditions like asthma.  

After President Donald Trump took office, the EPA targeted the Biden administration’s new health standard for soot, saying it hurt businesses. Agency administrator Lee Zeldin said in March 2025 that the update had “shut down opportunities for American manufacturing and small businesses” and announced plans to roll it back. 

Zeldin’s statements came one month after Gov. Greg Abbott wrote his own letter to the EPA refusing to report any Texas counties that are out of attainment, saying the revision to the health standard was “unlawful.” 

This summer, two key court rulings sided with the previous administration’s efforts to strengthen the health standard.

On June 26, the U.S. Court of Appeals in Washington denied the EPA’s effort to undo the Biden-era rule, saying Zeldin’s predecessor “adequately explained his reasons” for the update. Then, a July 17 decision by a U.S. District Court in California ordered the EPA to implement the new standard nationally, giving the agency until Feb. 6, 2027 to identify violators.

At least three counties – Harris, El Paso, and Cameron – have such high levels of fine particle pollution that they are on track to violate older rules for the pollutant, also known as PM2.5, in addition to the Biden-era update. Still, Texas has never been held to account for exceeding health standards, and will now have another opportunity to argue against enforcement.

“If that changes, the state would need to develop attainment plans for Houston and other regions. That would mean finding ways to reduce emissions of the pollutant,” said Daniel Cohan, a Rice professor whose research models air quality.

“Particulate matter is the world’s deadliest air pollutant, and high levels expose us to a wide range of health risks,” he said.

Advocates and public officials from the Houston area celebrated the courts’ decisions.

“This ruling confirms the Trump Administration cannot keep ignoring the law,” said Harris County Attorney Abbie Kamin. The county joined a nationwide group of plaintiffs that sued the EPA when it did not enforce the rule. 

“The EPA had a legal obligation to protect communities like ours from dangerous soot pollution,” Kamin said.

In 2025, a Houston Chronicle investigation found that both official air monitors and community-installed sensors across the region were picking up risky levels of particle pollution. The state had not yet taken any measures to lower the area’s soot pollution levels and cited a number of technicalities, including the EPA’s resistance to the Biden-era rule.

Jennifer Hadayia, the executive director of environmental group Air Alliance Houston, said she would welcome county noncompliance designations that could force Texas to create stricter rules for polluters.  

“This is a win for public health,” she said, but added that the decision marked “the very beginning of a process.”

Harris County is not the only Houston-area county that could be impacted, according to the latest averages reported to the EPA. 

Montgomery County, which has a single official air monitor, is also measuring soot levels that exceed the federal threshold. Its three-year average was 11 micrograms per cubic meter between 2023 and 2025. 

Still, the judicial decisions would not automatically throw Harris and Montgomery counties out of compliance with federal rules. States have a chance to analyze their own data and propose exceptions to the federal government if they feel they need not reduce emissions. 

Hadayia also pointed to the data gaps that will prevent many counties, including the booming Houston-area suburbs of Fort Bend and Chambers, from getting their own pollution plan. Neither county has any official TCEQ air monitors, so they do not factor into the calculations.

“Without data, there’s an assumption of good air quality,” she said. “We think that assumption is false.”