The “State of the Air” 2026 report finds that even after decades of successful efforts to reduce sources of air pollution, 44% of Americans—152.3 million people—are living in places that get failing grades for unhealthy levels of ozone or particle pollution. We found that nearly half of American children (46%, or 33.5 million people under the age of 18) live in counties that received a failing grade for at least one measure of air pollution. Ten percent of children (7.3 million people under age 18) live in counties with failing grades for all three measures. Infants, children and teens are especially vulnerable to the health harms of breathing air pollution. Their lungs are still developing, they breathe more air for their body size than adults, and they frequently spend more time outdoors.