Among other outdoor opportunities, many citizens of the United States get their annual dose of nature by visiting some of our country’s renowned national parks. However, not all national parks are perfect– especially when it comes to pollution.
Related: The 10 Most Popular National Parks
In fact, some national parks are making failing grades according to the National Parks Conservation Association. The NPCA recently got together to give all 48 national parks under the Clean Air Act grades based on variables such as air quality, visibility, and susceptibility to the onset of climate change.
Here are the 12 national parks with the worst overall grades
Find the entire NPCA post here: How Dirty Air is Harming America’s National Parks