Last updated: 12:36 PM ET, Mon July 23 2018

Ozone Levels at America's National Parks Match Those of Big Cities

Impacting Travel Monica Poling July 20, 2018

El Capitan in Yosemite National Park.
PHOTO: El Capitan in Yosemite National Park. (photo courtesy of Joehendricks/iStock/Getty Images Plus)

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