SAN FRANCISCO— The U.S. District Court for the Northern District of California ruled on Friday that the Environmental Protection Agency must follow the law and implement the strengthened health-based 2024 National Ambient Air Quality Standard for particulate matter (PM2.5) air pollution, commonly known as soot.

The court rejected the EPA’s arguments for slow-walking implementation of the standard and ordered that the EPA officially identify the areas that violate the 2024 standard by Feb. 6, 2027. This court ruling follows on last month’s ruling from the U.S. Court of Appeals for the D.C. Circuit upholding the 2024 soot standard after the Trump administration’s EPA requested that the court strike it down.

The Clean Air Act requires the EPA to designate areas that violate the strengthened 2024 soot standard. Those designations are what put communities with unhealthy levels of soot pollution on a path to cleaner air, but the EPA missed its legal deadline earlier this year. In response, 17 health, community and environmental groups filed a lawsuit to compel the EPA to implement the lifesaving, strengthened soot standard, alongside 10 states, the District of Columbia, Harris County, Texas, and the city of New York.

“This is a huge victory for public health,” said Sage Lincoln, associate attorney at Earthjustice. “The science is clear that the strengthened soot standard will help reduce dangerous air pollution and prevent thousands of premature deaths and illnesses. The court’s order compelling EPA to follow the law and implement the standard puts people’s health where it belongs: first. As a result, millions of people, especially children, older adults and communities that bear that greatest pollution burdens, will breathe cleaner air.”

“As Judge Gilliam’s order makes clear, EPA’s failure to promulgate designations for the updated soot standard is unlawful, and the agency must expeditiously move forward with designations for the entire country,” said Hayden Hashimoto, attorney at Clean Air Task Force. “The science speaks for itself — soot leads to negative health outcomes, including heart attacks, asthma attacks, and premature death. EPA has an obligation under the Clean Air Act to protect public health, and it must now allocate the staff and resources required to publish designations in the Federal Register by the court-ordered deadline of Feb. 6, 2027.”

“EPA’s own scientists found that implementing the soot standard would save 4,500 lives each year while also preventing hundreds of thousands of asthma attacks and emergency room visits — as well as cases of lung cancer, heart disease, and dementia,” said Environmental Defense Fund attorney Richard Yates. “The court just set a firm deadline for EPA to designate which communities are breathing unsafe air, which is the first step toward cleaning it up. At a time when enormous swaths of the country are sheltering inside under red-alert levels of air pollution, this court order is especially welcome.”

“You can push back a deadline, but you cannot give families back the days they spent breathing unhealthy air,” said Kate Sinding Daly, senior vice president for law and policy at Conservation Law Foundation. “Every day Trump’s EPA delays these protections is another day polluters avoid stronger clean air rules and another day families are left exposed to dangerous soot. Those are days communities can never get back.”

“The court’s decision to ensure EPA implements the health-protective soot standard in a timely manner is critical to protecting the health of people across the country who are exposed to dangerous particulate pollution,” said Katie Huffling, executive director of the Alliance of Nurses for Healthy Environments. “The science shows stronger limits to reduce deadly soot pollution provide significant health benefits for Americans, especially for those most vulnerable and those exposed to higher levels of pollution. EPA must adhere to their mission of protecting health and the environment. We urge EPA to follow the law, designate the areas that violate the standards, and work with those locations to clean up dirty air.”

“We’re pleased the court confirmed that EPA cannot simply refuse to comply with its legal obligation to identify communities that are suffering from exposure to unhealthy levels of soot pollution,” said Caroline Cress, senior attorney at the Southern Environmental Law Center. “Issuing designations is a critical first step toward reducing one of the country’s deadliest forms of air pollution. At a time when many communities across the South continue to breathe unhealthy air, EPA must now move quickly to begin delivering the public health protections the Clean Air Act requires.”

“Over recent days millions of Americans felt, with every breath, the damage soot can do to our lungs. Climate change is creating a new normal, worsening wildfire smoke and making it unsafe to breathe outside,” said Dr. Vijay Limaye, a climate and health scientist at NRDC. “In this new reality, science-based safeguards like the strengthened soot standard aren’t bureaucratic paperwork, they’re one of the most effective tools we have to prevent heart attacks, asthma attacks, and premature deaths. The court was right to insist the agency stop stalling and start protecting the people it’s supposed to serve.”

“We commend the court for ensuring that EPA fulfills its legal duty to protect the public from a dangerous pollutant that causes thousands of premature deaths each year, contributes to cardiovascular disease and dementia, and condemns children to a lifetime of asthma and other health injuries,” said Annie Fox, a staff attorney with Clean Air Council. “In addition to improving public health, enforcing this scientifically supported soot standard will strengthen the economy by reducing missed days of school and work from pollution-induced illnesses and will help restore the public’s faith in our government.”

“The court’s decision to hold EPA accountable for meeting its statutory requirement to identify areas of the country that are not meeting the 2024 standards for particulate matter is a victory for public health,” said Dr. Georges C. Benjamin, chief executive officer of the American Public Health Association. “Particulate matter pollution can cause asthma attacks, COPD exacerbations, heart attacks, strokes, lung cancer and premature death. This decision will especially benefit the health of low-income and minority communities who often live near polluting sources, putting their health at the greatest risk.”

“The court affirmed what we’ve long known to be true: The EPA has a responsibility to protect people from dangerous soot pollution, and communities have every right to hold the agency accountable when it falls short,” said Marqus Cole, organizing director with Georgia Interfaith Power & Light. “For the thousands of Georgians living in the eight counties that currently violate the federal standard, this ruling moves us closer to the cleaner, healthier air they deserve.”

“Fortunately Trump’s EPA can’t stop losing when it tries to undermine these lifesaving soot standards,” said Ryan Maher, staff attorney at the Center for Biological Diversity. “This ruling is the only just result when the agency blatantly disregards clean air law and sacrifices lives and public health in favor of corporate polluters.”

“Today’s ruling is a victory for Americans’ quality of life, our public health, and our environment,” said Sierra Club beyond coal campaign director Laurie Williams. “As the mom of a child who has asthma, I know firsthand how these preventable diseases caused by pollution can upend lives. We are glad to see the court uphold the law in directing Trump’s EPA to implement soot standards in order to improve the health of Americans. The Trump administration has launched dangerous and reckless attacks on public health by attempting to dismantle lifesaving environmental guardrails, but we will continue to fight back and defend our communities from preventable pollution.”

Background

Soot, made up of tiny toxic particles that lodge deep in the lungs, causes severe health harms including cancer, asthma and premature deaths. National Ambient Air Quality Standards are baseline air-quality standards for six common, harmful pollutants, including soot. In February of this year the EPA missed a key deadline for designating areas with soot pollution levels in violation of the 2024 standard.

These designations are the first step toward bringing dangerous soot pollution levels down to safer levels and making sure areas across the United States comply with that health-based standard. The EPA projected that implementation of the 2024 standard will save 4,500 lives in 2032 alone. A December 2025 Earthjustice analysis of EPA data revealed that 75 million people — 22% of the U.S. population — were living in counties whose air violated the standard under the then-most current data.

The coalition members in the case that was decided on Friday are Alliance of Nurses for Healthy Environments, American Lung Association, American Public Health Association, American Thoracic Society, the Center for Biological Diversity, Citizens for Pennsylvania’s Future, Clean Air Council, CleanAIRE NC, Conservation Law Foundation, Environmental Defense Fund, Georgia Interfaith Power & Light, Michigan Environmental Council, Natural Resources Defense Council, Northeast Ohio Community Resilience Centre, Rio Grande International Study Center, Savannah Riverkeeper and Sierra Club. Clean Air Task Force, Earthjustice and Southern Environmental Law Center served as legal counsel representing many of these organizations.