Using a public restroom can be a stressful experience. People inevitably shake the flimsy stall doors to check for occupancy. Soap can be missing and gastrointestinal noises can be heard. Now, a new study has found that the perils of public voiding may not end at the sink. The wall-mounted hand dryers—often believed to be a sanitary solution—could be blasting fecal bacteria right back on your hands.
Published in Applied and Environmental Microbiology, the report looked at 36 bathrooms at the University of Connecticut School of Medicine. Samples of bacterial colonies were taken on plates. A typical bathroom air sample averaged less than one colony, while plates positioned underneath a hand dryer for 30 seconds averaged 18 to 60 colonies per plate.
Researchers aren’t yet sure whether the dryers are actually harboring bacteria or simply sucking it up and then blowing a concentrated amount back out: Swabs of dryer nozzles had only minimal bacteria levels. Researchers found that installing a HEPA filter in the dryers dramatically reduced their bacterial load.
Bacteria in a public bathroom are likely coming from nearby toilets, which don’t have lids and can release fecal particles when flushed. So what do you do if you don’t want weaponized poo on your freshly washed hands? Avoid the dryer and stick with paper towels. But for relatively healthy people who aren’t immunocompromised, a few blasts of contaminated air probably won’t harm you.