Oftentimes, people go to a national park to clear their minds and get some fresh air, but a new study reveals that nearly all of the 399 key national park sites are experiencing high levels of human-caused ozone pollution.

Four parks right here in California take the top spots with the worst air in the nation. Joshua Tree, Sequoia and Kings Canyon National parks, and Mojave National Preserve experience poor air quality regularly. That exposure poses a great risk to visitors, employees, as well as plants and animals. 

For a closer look, KCBS Radio news anchors Bret Burkhart and Patti Reising spoke with Natalie Levine, National Parks Conservation Association’s Interim Campaigns Director of the Clean Air Program, which is the non-profit behind the report.