46 % of Americans—156 M—Now Breathe Hazardous Smog and Soot: State of the Air Report Exposes Decade-High Pollution

American Lung Association’s 2025 “State of the Air” report reveals 156 million Americans—46% of the population—now breathe unhealthy air, a troubling increase of nearly 25 million people compared to last year’s findings. The 26th annual assessment, released April 23, 2025, shows exposure to dangerous air pollution has reached its highest level in a decade, with climate change effects like extreme heat and wildfires significantly worsening air quality nationwide.

The report analyzes EPA monitoring data from 2021-2023 for ground-level ozone (smog) and fine particulate matter (PM2.5 or soot), finding 42.5 million people live in areas receiving failing grades for all three major pollution measures. “Families across the U.S. are dealing with the health impacts of air pollution every day, and extreme heat and wildfires are making it worse,” said Harold Wimmer, President and CEO of the American Lung Association. “Air pollution is causing kids to have asthma attacks, making people who work outdoors sick, and leading to low birth weight in babies.”

A notable shift has occurred in pollution patterns. While western states dominated recent years’ pollution rankings, 2023 saw improved conditions on the west coast but devastating air quality problems in central and eastern regions. This eastward movement resulted largely from Canadian wildfires that sent unprecedented smoke plumes across midwestern and eastern states. During summer 2023, smoke from these fires not only produced harmful PM2.5 but also created conditions that generated ground-level ozone in regions typically free from such problems. Nine states experienced uniform degradation, with worsening ozone levels in all monitored counties—including all 27 counties in Indiana, all 23 in Illinois, and all 17 in Missouri.

Bakersfield, California, continues its unfortunate distinction as America’s most polluted city, topping the list for worst short-term particle pollution for the third consecutive year and maintaining a six-year streak as the metropolitan area with the worst year-round particle pollution. Los Angeles remains the city with the worst ozone pollution—a position it has held for 25 of the 26 years the report has been published. Only two cities—Bangor, Maine, and San Juan, Puerto Rico—earned places on all three “cleanest cities” lists, down from five cities last year, reflecting broadly deteriorating air quality. 

The pollution burden falls disproportionately across racial and ethnic lines. While people of color constitute 41.2% of the U.S. population, they represent 50.2% of people living in counties with at least one failing grade. Hispanic individuals face nearly three times the risk of white individuals living in areas with failing grades across all three pollution measures.

Both ozone and particle pollution can trigger serious health effects. Short-term particle pollution reached 77.2 million people—the highest number in 16 years. The report documents the highest recorded number of days with unhealthy (red) and very unhealthy (purple) particle pollution levels in 26 years of reporting. Year-round particle pollution affects 85 million people, while ozone pollution impacts 125 million Americans (37% of the population)—an increase of 24.6 million from last year.

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These pollutants cause premature death and health problems, including asthma attacks, heart attacks, strokes, and preterm births. PM2.5 is particularly dangerous because its microscopic size allows it to penetrate deep into the lungs and even enter the bloodstream, reaching other organs. Long-term exposure is linked to diminished lung development in children, increased risk of diabetes, and cognitive decline later in life. Particle pollution also causes lung cancer.

A critical gap exists in air quality surveillance: the report explicitly states that “more than 72.8 million people live in counties where neither their ozone nor their particle pollution levels are being monitored.” Out of 3,221 counties in the U.S., only 922 monitor for at least one pollutant, creating significant blind spots in understanding air quality risks, particularly in rural areas.

The health burden falls heaviest on vulnerable populations: 34.6 million children under 18 and 25.2 million adults over 65 live in counties with at least one failing grade. People with underlying conditions face particular risks— 2.5 million children and 11.8 million adults with asthma, 6.8 million with COPD, and 9.7 million with cardiovascular disease live in counties with failing air quality. Low-income populations are also disproportionately affected, with 19 million people living in poverty exposed to unhealthy air.

The report expresses concern about environmental protection challenges: “Even as more people are breathing unhealthy air, the federal staff, programs and policies that are supposed to be cleaning up pollution are facing rollbacks, restructuring and funding challenges,” Wimmer warned. “For decades, the U.S. Environmental Protection Agency has worked to ensure people have clean air to breathe, from providing trustworthy air quality forecasts to making sure polluters who violate the law clean up. Efforts to slash staff, funding, and programs at EPA are leaving families even more vulnerable to harmful air pollution. We need to protect EPA.”

Beyond federal action, the Lung Association recommends interventions at state, city, community, and individual levels, including adopting cleaner vehicle standards, investing in renewable energy, and implementing “smart surfaces” solutions like cool roofs and more green space to reduce urban heat. Individuals can protect themselves by checking daily pollution forecasts at AirNow.gov and preparing for extreme weather events.

The full “State of the Air” 2025 report, with detailed data on specific locations and at-risk populations, is available at Lung.org/sota.

Frequently Asked Questions About Air Pollution in America