Nearly Half of Americans Live in Areas With Unhealthy Ozone or Particle Pollution

Ozone and particle pollution rank among the most dangerous air pollutants because they can enter the lungs and bloodstream. Long-term exposure is linked to respiratory and cardiovascular problems. The assessment draws on monitoring from official air quality networks that track daily readings against federal health standards.

Areas exceeding those standards for either pollutant count toward the total population figure.

The 152.3 million residents represent a substantial share of the national population living with elevated exposure risks. Both urban and some rural counties register readings that trigger health advisories on high-pollution days. Public health guidance recommends limiting outdoor activity during episodes when either ozone or fine particles exceed safe thresholds.

Children, older adults and individuals with preexisting conditions face higher risks during such periods. Further regional breakdowns typically appear in the full underlying assessment from air quality monitoring programs.

Federal standards set allowable concentrations for ground-level ozone and for particles 2.5 microns or smaller. Readings above those levels trigger air quality alerts in affected communities. The current figures reflect conditions measured across recent monitoring periods. Officials use the data to identify regions needing additional emission controls from vehicles, industry and other sources.