Attorney General Brown Sues EPA Over Failure to Implement 2024 Fine Particulate Matter NAAQS

Attorney General Brown Sues Trump Administration Over Failure to Implement Life-Saving Limits on Fine Particulate Matter Pollution

Published: 4/24/2026

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FOR IMMEDIATE RELEASE

Media Contacts press@oag.maryland.gov
410-576-7009​

BALTIMORE, MD – Attorney General Anthony G. Brown joined a coalition of 14 states and local governments in suing the United States Environmental Protection Agency (EPA). The lawsuit challenges the EPA's failure to implement a lifesaving 2024 Clean Air Act rule strengthening national ambient air quality standards (NAAQS) for fine particulate matter (PM2.5), a category of harmful airborne particles that includes soot, dust, and smoke. In the lawsuit, the coalition calls 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.

PM2.5 particles are deadly air pollutants 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, 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.

“Marylanders deserve clean air, and federal law requires EPA to protect it," said Attorney General Brown. “We will not stand by while the Trump Administration abandons standards that **** would save thousands of lives each year." ****

**** Under the Clean Air Act, the 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 fine particulate matter are associated with decreases in the risk of mortality and increases in life expectancy. In 2024, in response to advocacy from Maryland and others, EPA strengthened the fine particulate matter NAAQS based on overwhelming scientific evidence. According to its own estimates, the 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 standard. Maryland joined a lawsuit to defend the standard. The case is currently 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 Maryland and other states important tools to reduce air pollution.

Filed in the United States District Court for the Northern District of California, the lawsuit alleges that the 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, who are disproportionately impacted – and to achieve significant public health benefits including reduced premature deaths, mortality, and healthcare and administrative costs.  The lawsuit seeks 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.

Joining Attorney General Brown in filing the lawsuit are the attorneys general of California, Connecticut, Hawaii, 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.

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