“State of the Air” uses letter grades to measure unhealthy levels of ground-level ozone air pollution (also known as smog), and year-round and short-term spikes in particle pollution (also known as soot) over a three-year period. The 2025 report looks at the latest quality-assured air quality data, which was collected from 2021 to 2023.

Air pollution levels keep getting worse for more people in the US, according to a new report, and experts say the Trump administration’s proposed deregulation plans will make it even harder for people to get clean air.