Hand dryers are a seemingly fantastic green alternative to paper towels, but a study from January 2018 finds that, in fact, they’re actually pretty gross.
Hand Dryers Suck In Fecal Bacteria
When you flush a toilet without a lid, fecal bacteria shoots into the air. This phenomenon is called the toilet plume. So what happens in a public restroom where toilets flush constantly? The bacteria get sucked into the hand dryer, and then, well, you can guess where it goes from there.
To find out just how much of this bacteria transfers from the dryer to your hands during use, researchers exposed a set of plates to 30 seconds of hand dryer air and another set to 2 minutes of restroom air with dryers off. The hand dryer air plates average 18 to 60 colonies/plate whereas the plates from regular restroom air had an average of less than 1 colony/plate. They also exposed plates to restroom air being circulated by a small fan and found an average of 12 to 15 colonies/plate. Of that bacteria, 2 to 5% were spore-forming colonies called Bacillus subtilis PS533. (1)
B. subtilis naturally exists in soil, water, air and in decomposing plants and can survive even in high heat. The bacteria is relatively benign and is not pathogenic or toxigenic to humans, animals, or plants. For this reason, fermentation facilities and laboratories regularly use this type of bacteria. The PS533 strain specifically, however, is resistant to the kanamycin antibiotic. (1, 2)
Dryers Spread Bacteria
B. subtilis bacteria isn’t concerning for human health, but the spread of bacteria is. Even in large buildings, bacteria, including spores, may travel between rooms. If potentially pathogenic bacteria makes its way to the restrooms, hand dryers may be a possible way for infectious bacteria to spread. This is especially concerning in public spaces and health care environments. (1)
“These results indicate that many kinds of bacteria, including potential pathogens and spores, can be deposited on hands exposed to bathroom hand dryers, ” the authors told Newsweek. “And that spores could be dispersed throughout buildings and deposited on hands by hand dryers.” (3)
The authors say they’re not clear exactly why the plates had so many more spores. It could be the dryers weren’t working properly. Dryers retrofitted with HEPA filters show a four-fold decrease in the deposit of bacteria. It could be that they act as a reservoir for bacteria, or that the strong blast of air gives more exposure to already contaminated air. (1)
Peter Setlow, the study author, said, “Bacteria in bathrooms will come from feces, which can be aerosolized a bit when toilets, especially lidless toilets, are flushed.” (3)
Dryers Or Paper Towel
The move to hand dryers came from a desire to reduce paper waste. But is it a good move? We find bacteria on so many public surfaces like grocery cart handles, fast food touch screens, doorknobs, elevator pushbuttons, etc. It’s partly because humans are walking microbes, and not all of the bacteria are harmful to human health. But it does make you think twice about using a hot-air hand dryer in a public restroom!
Setlow is still opting for paper towels. In fact, they’ve fully stocked all the bathrooms tested in the study.
Bottom line: it’s not anything a little proper hygiene can’t fix. Wash your hands regularly, use a paper towel if possible, use a paper towel or sleeve to open the bathroom door, and practice common sense.
