Your clodhoppers track in dirt, yes, but also fecal germs and diarrhea-inducing bacteria, studies show, and the shoes themselves can get dirtier than a toilet seat. And science has shown just what makes up that filth, too.

Even Charles Gerba, a University of Arizona microbiologist who conducted a seminal study on the subject, was surprised.

“I’m starting to make myself paranoid,” Gerba told the Baltimore Sun when his study debuted in 2008. “It seems like we step in a lot more poop than I thought.”