Handwashing studies offer conflicting results

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?


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.”

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About Douglas Powell

A former professor of food safety and the publisher of barfblog.com, Powell is passionate about food, has five daughters, and is an OK goaltender in pickup hockey. Download Doug’s CV here. Dr. Douglas Powell editor, barfblog.com retired professor, food safety 3/289 Annerley Rd Annerley, Queensland 4103 dpowell29@gmail.com 61478222221 I am based in Brisbane, Australia, 15 hours ahead of Eastern Standard Time