PM2.5 annual average (μg/m3) over 5 years City markers indicating 2025 PM2.5 levels, size adjusted for population In 2025, the United States saw a 3% increase in annual average PM2.5 levels, reaching a concentration of 7.3 μg/m3. This rise was driven largely by extreme weather and fire events 8 μg/m3 throughout June and July. By September, wildfire activity shifted to Washington state, releasing over 1.5 megatonnes of carbon emissions and pushing monthly averages above 50 dropby an average of 9%while historic dust storms inEl Paso triggered a 46% increase in PM2.5 levels. On the West Coast, massive wildland-urban interface fires in Los Angeles exacerbated existing pollution in the city's Southeast region, including Cudahy, East Los Angeles, Huntington Park, and Florence-Graham, cementing it as the most PM2.5-polluted SeatlerindbiptsnstentinhWanalguideinwithavea below 5 μg/m3. The United States continued to face air quality challenges from PM2.5 emissions, driven by wildfires, dust storms, transportation emissions, power generation, and industrial sources. The Southern California wildfires in January 2025-fueled by Santa Ana winds and drought- burned over 40,000 acres. These fires caused 24 casualties and mass evacuations.83 Nationally, wildfires remained a key source of PM2.5, with 10,541 recorded fires.84 Al data centers are an emergent sourceofM5polutioncontributingindirectlythroughtheincreased powerlan emissions required to meet their massive energy demands, and directly through their reliance Caltech estimates that training a single large-scale generative Al model produces more PM2.5 pollution than 10,000 round trips between New York and Los Angeles by car.85.86 HIGHLIGHT: LEGAL CHALLENGE TO FEDERAL PM2.5 STANDARD In 2024, the U.S. EPA finalized a revision to the PM2.5 National Ambient Air Quality Standards (NAAQS), which lowered theanual limit from12μg/m3 to9 μg/m3,87 This codified rule followed Annual hours spent at different PM2.5 pollution levels