Under the court ruling, the EPA must enforce stricter limits on soot, which is released from cars, factories and other industrial sites.

The greater Houston region will face stricter federal air quality standards following a recent court ruling.

A federal judge ruled in July that the U.S. Environmental Protection Agency (EPA) must enforce stricter air quality standards for PM 2.5 – fine particulate matter including dust, smoke and soot – that were adopted under the Biden administration. That type of pollution, emitted from sources such as vehicles, concrete batch plants and other industrial facilities, has been linked to respiratory and heart disease.

The ruling comes after several environmental groups and government agencies, including Harris County, sued the EPA.

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In an interview with Houston Public Media on Thursday, interim Harris County Attorney Abbie Kamin praised the ruling — which could force Texas’ environmental regulators to take action to reduce air pollution in the region.

"Under the Clean Air Act, EPA has to set certain standards for particles, including soot," she said. "And what was happening was EPA wasn’t enforcing its own rules."

In a statement, the EPA said it is reviewing the ruling.

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Under the Biden administration, the EPA decreased the regional PM 2.5 thresholds from 12 micrograms per cubic meter to 9 micrograms. Harris County’s air quality has not complied with either federal standard for soot pollution in recent years.

From 2023 to 2025, Harris County averaged 12.8 micrograms of PM 2.5 per cubic meter, according to the EPA. That amount of air pollution is in violation of both the new and old federal air quality standards, though the county has not yet been designated as a nonattainment zone.

The EPA previously was set to designate nonattainment zones for the stricter PM 2.5 standards by February of this year. It must now do so by February of 2027, according to the court ruling.

Kamin said it's likely that Harris County will be in violation of these air quality standards.

"We know that Houston and Harris County have some of the worst air quality in the nation," she said.

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If a region is out of compliance with federal air quality standards, its state government must come up with a plan to reduce pollution, Kamin said.

When the EPA adjusted its PM 2.5 air quality standards in 2024, the agency predicted the new standards could prevent as many as 4,500 deaths and 290,000 lost workdays, creating up to "$46 billion in net health benefits in 2032."