Tag Archives: dryer

It’s all in the friction: Hand dryers are germ-flinging BS

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The benefits of paper towels versus conventional blow dryers for drying after handwashing are well-documented.

handwash_south_park(2)But what about those high-tech – and expensive – Dyson thingies that seem to be popping up everywhere.

I say, show me the data.

Caroline Weinberg writes that a study published in the Journal of Applied Microbiology showed that Dyson jet air dryers can fling germs as far as 10 feet from the device.

For the experiment, researchers dipped their gloved hands in a suspension of the bacteriophage MS2 (similar in structure to the contagious enteric viruses transmitted in poop). The hands were then dried by one of three methods. First up were Dyson jet air dryers, which are designed to push water off of your hands in 10 seconds with roughly the force of a jet engine. Next were warm air dryers, which blow warm air downwards and supposedly remove water via evaporation. The final competitor was paper towels, which use absorbent paper to remove water from your hands (and actually leave them dry).

The first part of the experiment looked at how many bacteria are blown back on you during the drying process. Researchers erected a vertical board roughly 16 inches away from each dryer and counted the viral particles that landed on it. Overall, the jet dryer dispersed 60 times more particles than the warm air dryer and 1,300 more than the paper towel. 70 percent of particles hit the board between 2.5 and 4.5 feet—roughly chest or stomach level on an woman of average height, or right at the face level of a small child. At the highest density point, the jet air dryer dispersed 167 times as many viral particles as the warm air dryer and 8,340 times as many as a paper towel.

dyson.air-blade-thumb-468x369-147704For the second part of the experiment, researchers studied air dispersal, or how much of the bacteria is spread into the air around the machine or towel. Airborne virus counts were consistently higher around the jet dryer both over time and distance. The jet dryer dryer propelled the virus as far as 10 feet away, with high levels recorded a full 15 minutes after use. There was no significant difference in air dispersal between warm air dryers and paper towels.

This isn’t a perfect study: Because it was done in a lab setting, researchers could not account for individual behaviors or real world differences. They also only tested one example of each hand drying device (Dyson is taking the heat here, but they are not the only makers of jet air dryers) and did so over a small number of trials. Critics of the study also rightfully point out that most people don’t dip their hands in bacteria prior to using the hand dryers: they wash their hands first. And it’s true that if one were to stick perfectly clean hands into a dryer, there would not be germs to blow around.

Unfortunately, here in the real world, 95% of people using public restrooms fail to adequately wash their hands. Sure, a small percentage may use the scientifically vetted, 42-second-long, six-step hand washing process that most effectively rids your hands of all the filthy germs you’ve picked up in the bathroom and world at large. The rest of them (OK, us) are doing a quick scrub or, worse, simply passing their hands under a running faucet for a few seconds for the illusion of cleanliness. So while the hands most people place in the dryer aren’t drenched in germs, they are likely carrying, among other things, poop particles. Poop particles that the machine then proceeds to blow all over the room, including back on the very hands you just cleaned.

handwashing.blow.dryer.09This isn’t the first time a study has suggested that hand dryers are germ cannons, either. A 2014 study published in the Journal of Hospital Infection also supports this finding—but it was dismissed by Dyson as funded by Big Paper Towel (in their defense, that study was literally funded by Big Paper Towel, i.e. the European Tissue Symposium,). Dyson would direct us, instead, to 2011 study published in the Journal of Applied Microbiology that found their air dryers to be more effective at preventing the spread of germs than warm air dryers. Now it was Big Paper Towel’s turn to cry foul—that study was funded by Dyson Limited. The current study in question is funded independently by the researchers’ university (though the lead author has worked with the European Tissue Symposium in the past) lending it a hopefully uncontaminated air of legitimacy.

A few months ago, shortly after this study was published, Dyson posted an ominously narrated attack ad of sorts titled “Paper’s Dirty Secret.” Don’t listen to Big Jet Dryer’s propaganda (well, maybe listen to it, because the video is hilarious—but don’t believe it). It is true that a 2012 pilot study found unused paper towels to be contaminated with small amounts of bacteria. But paper towels have been repeatedly shown to be efficient, effective, and—perhaps most importantly—not responsible for flinging extra poop germs through the air.

 

Handwashing studies offer conflicting results

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I’m confused with these conflicting handwashing studies.

And, as Les Nessman of WKRP in Cinncinatti said, when I get confused, I watch television. It somehow makes things simple. Television is never confusing.

This morning it was alcohol-based sanitizers didn’t do much to limit the spread of the H1N1 virus, but worked well against cold viruses (the sanitizers also sorta suck against norovirus).

Later today, it was the results of another of those creepy make-grad-students-hang –out-in-public-bathrooms studies, to see if people actually wash their hands, which found that 85 per cent of adults washed their hands in public restrooms, the highest number since the studies began in 1996.

But it’s a far cry from the 96% of adults who say they always wash their hands in public restrooms, based on a separate telephone survey conducted at the same time.

Men do a lot worse than women overall — just 77% scrubbed up, compared with 93% of women.

The study was sponsored by the American Society for Microbiology and the American Cleaning Institute (formerly the Soap and Detergent Association). It involved discreetly observing 6,028 adults in public restrooms in August to see whether they washed their hands.

Great. More people are attempting to wash their hands. But are they doing it correctly? Does any attempt count, or only if handwashing is done according to government prescriptions. What is the best way to wash hands? Can’t people with PhDs agree?

No.

A study by researchers at the University of Bradford and published in the current Journal of Applied Microbiology evaluated three kinds of hand drying and their effect on transfer of bacteria from the hands to other surfaces: paper towels, traditional hand dryers, which rely on evaporation, and a new model of hand dryer, which rapidly strips water off the hands using high velocity air jets.??

In this study the researchers quantified the effects of hand drying by measuring the number of bacteria on different parts of the hands before and after different drying methods. Volunteers were asked to wash their hands and place them onto contact plates that were then incubated to measure bacterial growth. The volunteers were then asked to dry their hands using either hand towels or one of three hand dryers, with or without rubbing their hands together, and levels of bacteria were re-measured.

The researchers found the most effective way of keeping bacterial counts low, when drying hands, was using paper towels. Amongst the electric dryers, the model that rapidly stripped the moisture off the hands was best for reducing transfer of bacteria to other surfaces.

Yet tomorrow’s N.Y. Times reports it’s a draw, and that “the best available evidence suggests that as far as germs go, the method of drying is less important than the amount of time invested: the longer the better.”

So my pants would be fine as long as I used them enough.

Dr. O. Peter Snyder at the St. Paul-based Hospitality Institute of Technology and Management summarized key aspects of handwashing and drying in a paper available at, http://www.hi-tm.com/Documents/Safehands.html. Snyder says that after hands are washed and rinsed, they must be thoroughly dried.

Blow dryers should not be used because they accumulate microorganisms from toilet aerosols, and can cause contamination of hands as they are dried by the drier (Knights, et al., 1993; Redway,et al., 1994).

Snyder notes that it is also apparent that many individuals do not dry their hands thoroughly when using a blow drier; hence, moisture, which is conducive to microbial growth, remains on hands, or people dry their hands on their clothing.

Proper handwashing requires access to the proper tools – and that means vigorously running water, soap and paper towel.

We’ve reviewed the literature on handwashing and how best to motivate people to wash hands, and conclude in a paper to be published shortly that,

“Although the role of hand hygiene in preventing infectious disease is well recognized, studies repeatedly show that compliance remains low. … Education and training have been cited often as essential to developing and maintaining hand hygiene compliance but, with few exceptions, this approach has not produced sustained improvement. … Hand hygiene was enhanced by provoking emotive sensations of discomfort, unpleasantness and disgust. Evidence suggests handwashing is a ritualized behavior mainly carried out as self-protection from infection and that patterns of handwashing behavior are likely established in childhood. Therefore, interventions that focus on culture, perception and behavior change may prove to be the most successful. How that success is measured must be carefully considered, as there is no standardized method for measuring hand hygiene compliance and current techniques have significant limitations.”