Hand dryers may leave your hands significantly more dirty than before, according to a new study.
The study, the results of which were published in the journal Applied and Environmental Microbiology, found that plates exposed to 30 seconds of a bathroom hand dryer gained at least 18 to 60 colonies of bacteria, while plates exposed to bathroom air for two minutes had fewer than one.
The authors concluded that the “results indicate that many kinds of bacteria, including potential pathogens and spores, can be deposited on hands exposed to bathroom hand dryers, and that spores could be dispersed throughout buildings and deposited on hands by hand dryers.”
Still the study’s authors, who found that the nozzle of the dryers had minimal bacterial levels, said that more evidence was needed to determine if the dryers were bacteria harbors themselves or just blew large amounts of contaminated air.
It is known among those paying close attention to bathroom cleanliness — a hobby we probably wouldn’t recommend here — that bathroom air can contain fecal matter and droplets of urine.
“The more air you move? The more bacteria stick,” lead study author Peter Setlow told Business Insider. “And there are a lot of bacteria in bathrooms.”
The risk of this bacteria to the general public using shared restrooms is not entirely clear. Setlow, who is in his 70s, told the publication that he’s stopped using hand dryers.
“If I’m a person whose immune system is suppressed, I want to minimize my exposure to bacteria,” he said.
The study noted that hand dryers with certain types of filters, called HEPA filters, could reduce the bacteria fourfold.