Page 10 - IAV Digital Magazine #448

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Restroom Hand Dryers Suck Up Feces Particles And Spray Them All Over Your Hands
By Katherine Hignett
Washing your hands is one of the easiest ways to stop the spread of germs, right? Well, your office hand dryer might actually be spreading fecal bacteria onto your hands and throughout your building.
Scientists com- paring normal bathroom air to that blasted from hand dryer noz- zles have found far more bacterial colonies develop in samples
exposed to
the latter. The results were pub- lished this month in the
journal Applied and Environmental Microbiology.
“Bacteria in bath- rooms will come from feces, which can be aerosolized a bit when toilets, especially lidless toilets, are flushed,” study author Peter Setlow
told Newsweek. The simple move- ment of lots of people in and out of the bathroom,
shedding microbes from their skin, he said, adds to the messy picture.
Hand dryers suck up bathroom air and spew it out at speed. So, in the brief moments your hands rest below the nozzle, they’ll be exposed to far more air than usual—and
far more bacteria.
In the study, researchers searched 36 bathrooms at the University of Connecticut School of
Medicine for a harmless, lab- engineered strain of bacteria Bacillus subtilis- called PS533. Unlike other types of B. sub- tilis often found in soil, this strain is only found in lab- oratory environ- ments.
The team found PS533 in every bathroom tested. Bacterial spores, Setlow explained, had probably traveled through- out the research building from a lab. Although these particular spores, which
can survive for years, are “mean- ingless”
for human health, their vast distribu- tion shows that bacteria had spread through the air of the entire building.
“Within a large building, poten- tially pathogenic bacteria including bacterial spores may travel between rooms,” the authors wrote in their research paper. Hand dry- ers, they added, could be one way such bacteria had seeped throu gh the building.
In theory, adding high-efficiency particulate air (HEPA) filters should stop bac- teria particles from spraying over your newly cleaned hands. However, when the team retrofit- ted some of their dryers with HEPA filters, they only blocked about 75 percent of bacte- ria. Although that's a lot, it cer- tainly isn't per- fect.
“Perhaps the fil- ters weren’t work- ing properly, or the large air col- umn below the hand dryers was sucking in bacte- ria from unfiltered air adjacent to the forced air col- umn,” Setlow, who is a profes- sor at the University of Connecticut, expl ained. Convection creat- edbyahand dryer's air streams, for example, might pull in unfiltered bathroom air.
The research adds to a growing body of evidence showing that hot- air hand dryers have a role in the spread of bacte- ria—safe and potentially dan- gerous.
For now, Setlow is sticking to paper towels—as is the University of Connecticut, which has added them to all 36 bathrooms sur- veyed in the study.
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