and 124 national parks have no air monitors within or outside of park boundaries. Most air pollution affecting our 428 national parks originates beyond their borders, sometimes traveling hundreds of ...

The three main qualities they look at are ground-level ozone, particle pollution, and nitrogen dioxide. At Crater Lake National Park, the air is so clear on some days that it may be possible to ...

While most air pollution doesn’t originate in national parks, it can travel hundreds of miles from its source, affecting even remote parks and communities. Places like Rocky Mountain National Park ...