OAKLAND — California Attorney General Rob Bonta, alongside the California Air Resources Board, today led a multistate coalition in suing the U.S. Environmental Protection Agency (EPA) over its failure to implement a lifesaving 2024 Clean Air Act rule strengthening National Ambient Air Quality Standards (NAAQS) for fine particulate matter, commonly known as soot. Soot is a deadly air pollutant emitted from a variety of sources including combustion-engine vehicles, factories, and construction sites. Because of the particles’ small size, once inhaled, they can penetrate the lower parts of lungs, move out of the respiratory system, and affect other organs. As a result, soot exposure can lead to myriad health problems, including shortened lifespans, heart attacks, asthma attacks, and cancer. These health effects fall disproportionately on lower-income communities and communities of color. In their lawsuit, Attorney General Bonta and the coalition call for a court order to ensure EPA takes the key steps required by Congress to initiate the rule’s protections and kick off implementation planning.

“The science is clear: When air quality worsens, hospital visits rise. Children struggle to breathe. Lives are cut short. And these devastating impacts fall most heavily on lower-income communities and communities of color. This is the reality when this life-saving national soot standard is not implemented,” said Attorney General Rob Bonta. “The Trump Administration is once again failing to take action while communities across the country are left to deal with deadly and costly consequences on their own. The Trump EPA must comply with the law and take the actions that Congress mandated to help protect Americans from deadly soot pollution. Today, we are taking them to court to force them to do just that.” 

“By ignoring the legal responsibility to uphold its own rule, U.S. EPA is willfully abandoning the agency’s duties under the Clean Air Act and putting lives at risk,” said California Air Resources Board Chair Lauren Sanchez. “California will not stand by while federal protections are ignored. We are taking action to hold EPA accountable to ensure everyone — no matter your zip code — has the basic right to clean, healthy air.”

Under the Clean Air Act, EPA is required to set NAAQS for several pollutants, including fine particulate matter, at a level that protects public health and welfare. When NAAQS are updated, the Clean Air Act gives EPA a specific deadline to designate areas of the country that are in violation of the updated standard as “nonattainment.” This designation provides key support for State programs to reduce dangerous pollution levels to safer levels.

Reductions in soot are associated with decreases in the risk of mortality and increases in life expectancy. In 2024, in response to advocacy from California and others, EPA strengthened the soot NAAQS based on overwhelming scientific evidence. According to its own estimates, EPA has reported that the first year alone of full attainment of the 2024 NAAQS will result in significant public health benefits, including avoiding 4,500 premature deaths, 2,000 emergency room visits, 5,700 new cases of asthma, 800,000 cases of asthma symptoms, 290,000 lost workdays, and 1,000 hospital admissions for Alzheimer’s/Parkinson’s diseases. The value of these and other health benefits would outweigh the estimated costs of implementation by $46 billion. 

Shortly after EPA adopted the 2024 standard, a coalition of Republican states and chambers of commerce asked a federal court to strike down the updated soot standard. California led a lawsuit to defend the standard. Currently, the case is pending, and the 2024 standard remains in effect. In February 2025, the EPA missed its deadline for designating areas with soot levels that exceed the 2024 standard, denying California and other states important tools to reduce air pollution.  

California’s lawsuit, filed in the United States District Court for the Northern District of California, alleges that EPA violated the Clean Air Act by failing to designate areas in the United States as in or out of attainment with the 2024 standard. EPA’s failure undermines the ability of states and local governments to reduce levels of fine particulate pollution in the air—especially in low-income communities and communities of color, which are disproportionately impacted—and to achieve significant public health benefits including reduced premature deaths, mortality, and healthcare and administrative costs. The benefits of maintaining and implementing the 2024 standard are particularly important in California, due to the severity of its air pollution, especially in populous areas. Four of the areas of the country with the worst particulate matter pollution are all located in California — the Los Angeles-South Coast Air Basin, the San Joaquin Valley, Imperial County, and Plumas County. California and the coalition are seeking both declaratory and injunctive relief, asking the Court to declare EPA’s failure to implement the 2024 standard as unlawful and order it to carry out its responsibility to make attainment designations within 150 days of the court order. 

Attorney General Bonta leads the attorneys general of Connecticut, Hawaii, Maryland, Massachusetts, Minnesota, New York, Oregon, Rhode Island, Vermont, Wisconsin, and the District of Columbia, as well as Harris County and the City of New York, in challenging the Trump Administration’s failure to implement the soot standard.