The lawsuit centers on fine particulate matter, known as PM2.5 — a type of air pollution made up of tiny particles that can lodge deep in the lungs and bloodstream. Exposure has been linked to asthma, heart disease and premature death.
In 2024, the EPA strengthened national limits on PM2.5. Under the Clean Air Act, the agency was required to identify areas of the country that do not meet the updated standard within two years, a step that triggers deadlines for states to develop plans to reduce pollution.
Environmental groups say the EPA missed that deadline earlier this year.
"Delay at the designation step means delay in cleanup plans and delay in relief for people suffering from unhealthy levels of pollution," said Ryan Maher, a staff attorney with the Center for Biological Diversity, which is part of the coalition behind the lawsuit.
The group is asking a federal court to require the EPA to set a new deadline and move forward with the designations.
In northern Nevada, Washoe County is likely to be one of those designated areas. Based on federal monitoring data, it has recorded levels of fine particulate pollution that may exceed the updated standard, meaning it could be required to develop a cleanup plan. The American Lung Association has ranked the Reno area among the most polluted cities in the country for short-term particle pollution in recent years.
The issue could have broader implications across the Mountain West, where air quality is often affected by wildfire smoke, winter inversions and industrial emissions. States including Colorado, Utah, Wyoming, Nevada, New Mexico and Idaho could face stricter pollution controls under the updated standard.
Advocates say delays in implementing the rule could slow efforts to improve air quality in regions already dealing with elevated pollution levels.
If the court sides with the coalition, it would force the EPA to move forward with identifying areas that violate the standard — a key step in reducing pollution.
This story was produced by the Mountain West News Bureau, a collaboration between KUNR, Wyoming Public Media, Nevada Public Radio, Boise State Public Radio in Idaho, KUNC in Northern Colorado, KANW in New Mexico, Colorado Public Radio, KJZZ in Arizona and NPR, with additional support from affiliate newsrooms across the region. Funding for the Mountain West News Bureau is provided in part by the Corporation for Public Broadcasting and Eric and Wendy Schmidt.
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