There’s no way poop can make its way onto your toothbrush, right? A new study presented to attendees of a meeting of the American Society for Microbiology offered some startling evidence that our toothbrushes may not be as clean as we think. According to the Chicago Tribune, up to 60 percent of the toothbrushes sampled in a communal bathroom at Connecticut’s Quinnipiac University tested positive for fecal coliform bacteria.

What’s even worse is that up to 80 of the fecal coliforms found on toothbrushes originated from people other than the brush’s owner. This is likely the result of violent toilet flushes spraying fecal particles throughout the air.

Study author and Quinnipiac graduate student Lauren Aber noted, “The main concern is not with the presence of your own fecal matter on your toothbrush, but rather when a toothbrush is contaminated with fecal matter from someone else, which contains bacteria, viruses or parasites that are not part of your normal flora.”

While there is no medical evidence that fecal coliforms from communal bathrooms can cause specific illnesses by way of toothbrushes, it’s still a good idea to take steps to protect yourself as you brush your teeth.

The American Dental Association recommends not sharing your toothbrush with others, rinsing and drying the toothbrush upright, and avoiding the use of toothbrush covers, which provide a damp, protected environment for bacterial colonies to flourish. In general, better hygiene practices will result in cleaner toothbrushes, which should be replaced once every three to four months, according to the ADA.