Scientists have found that certain hand dryers are probably responsible for blowing bacteria all over bathrooms, scoring a point for the paper towel industry in an incessant war of cleanliness.
The study from the University of Connecticut was published in the journal Applied and Environmental Microbiology. While hand dryers are generally less expensive and more environmentally friendly than paper towels, they found that hot air dryers could be coating your hands with bacteria when you turn them on.
To make their finding, the team surveyed 36 bathrooms at the University of Connecticut using agar plates with gelled bacteria food. They used these to gather samples when the hot-air dryers were turned on and off.
“In the still bathrooms, the researchers caught an average of zero to one bacterial landings per plate,” noted Ars Technica. “When they left the plates open for 18 hours, that average leapt to six colonies per plate. But in the line of fire from the blowers for 30 seconds, the plates collected averages from 18 to 60, with a range as high as 254 depending on the bathroom.”
They even found that the dryers were spreading a bacterium called Bacillus subtilis (B. subtilis), strain PS533, from a nearby lab. The bacterium was dispersed as spores, which seemed to thrive in the high temperatures of the hand dryer’s air.
Somewhat worryingly, they also suggest that the bacterium Clostridium difficile (C. difficile), known for causing deadly bouts of diarrhea, could be spread in a similar way, simply by the flushing of a toilet.
“I don’t dry my hands on hand dryers anymore, especially if I go into bathrooms in airports or bus stations,” the senior author on the paper, Peter Setlow, told Connecticut Public Radio.
“The safety issue is very, very small. But it is there. I’d like to keep the bacteria that aren’t mine from getting on me. Simple as that.”
It’s the latest twist in the tale for the ongoing dryer vs. towels argument. Previously, the paper towels industry has come to blows with Dyson, known for its air blade dryers (which were not discussed in this study), and have even been accused of tainting studies.
There doesn’t seem to be any foul play here, but it does seem to score a point for paper towels, so who knows. Maybe the conspiracy goes deeper than you think.