A dangerous haze is creeping across parts of the US, threatening to turn ordinary summer activities into a health risk.
Millions of Americans across 10 states are under air quality alerts as a combination of ground-level ozone, wildfire smoke and harmful particle pollution degrades conditions from the Northeast to the Southwest.
Officials in New York, New Jersey, Connecticut, Rhode Island, Pennsylvania, Maine, New Hampshire, Colorado, Arizona and California have issued advisories warning that the air could become unhealthy, particularly for sensitive groups.
Many of the alerts remain in effect through Wednesday evening, though some wildfire smoke advisories in Colorado began Tuesday and continue into Wednesday morning.
