Air pollution in the United States

Air pollution is the introduction of chemicals, particulate matter, or biological materials into the atmosphere that cause harm or discomfort to humans or other living organisms, or damage ecosystems. Health problems attributed to air pollution include premature death, cancer, organ failure, infections, behavioral changes, and other diseases. These health effects are not equally distributed across the U.S. population; there are demographic disparities by race, ethnicity, socioeconomic status, and education. Air pollution can derive from natural sources, such as wildfires and volcanoes, or from anthropogenic sources. Anthropogenic air pollution has affected the United States since the beginning of the Industrial Revolution.

According to a 2024 report: "39% of people living in America—131.2 million people—still live in places with failing grades for unhealthy levels of ozone or particle pollution." Analyzing data from 2020 to 2022, the American Lung Association found the number of people living in counties with a failing grade for ozone declined, this year by 2.4 million people.

A 2016 study reported that levels of nitrogen oxides, which contribute to smog and acid rain, had plummeted over the previous decade, due to better regulations, economic shifts, and technological innovations. The National Aeronautics and Space Administration (NASA) reported a 32% decrease of nitrogen dioxide in New York City and a 42% decrease in Atlanta between the periods of 2005–2007 and 2009–2011.

During June 2023, due to early season wildfires in Canada, cities like New York and Washington D.C. suffered from dangerous levels of air pollution. It was the worst regional air quality in decades for the Northeast.