Are bathroom hand dryers really unsanitary?
August 30, 2007 9:37 AM   Subscribe

Are bathroom hand dryers REALLY unsanitary? A co-worker claims she doesn't use them because they blow contaminated air on your hands. I'm not finding a lot of evidence online. I'm specifically interested in scientific proof or a scientific argument either way.
posted by anonymous to Health & Fitness (16 answers total) 1 user marked this as a favorite
Contaminated air? As in, the same bathroom air you're breathing and moving through when in said bathroom? Your coworker is a freak. No science required.

/known to eat cookies off the floor
posted by Ambrosia Voyeur at 9:41 AM on August 30, 2007 [2 favorites]

I heard something about this on talk radio a couple of years ago, and therefore feel competent enough to answer this question.

The jury is out. Paper towel dispensers, which you have to touch, are home to harmful E. Coli and Staph bacteria. Hot air dryers spread all sorts of harmful gunk around the washroom as an aerosol.

Luckily, one company has set out to change all that (the article includes some interesting stats, and some amusing sales-y writing):
posted by KokuRyu at 9:44 AM on August 30, 2007

I'd have to agree that your co-worker is nutso-cuckoo. The air is being sucked in from either the bathroom itself, or from an outside area, served by a duct. (More likely from within the bathroom.) The act of blowing it through the dryer would not make the air any more dangerous.

Touching the buttom to start the dryer? That does expose you to germs. That's why new ones are sensor-driven.

Now the old-fashioned cloth towel on a recirculating roll? That's just gross.
posted by Futurehouse at 9:46 AM on August 30, 2007

I didn't really think there would be a difference, but I did some looking around, and it looks like your friend is correct.

Ngeow YF, Ong HW, Tan P. Dispersal of bacteria by an electric air hand dryer. Malays J Pathol. 1989 Aug;11:53-6.

The potential risk of an electric air hand dryer contributing to airborne infection in a hospital was investigated using a strain of Serratia marcescens and a strain of coagulase-negative, streptomycin-resistant Staphylococcus. Dispersal of marker bacteria by the air dryer was demonstrated within a radius of about 3 feet from the dryer and to the investigator's laboratory coat. When paper towels were used for hand drying, no dispersal of marker bacteria was demonstrated. It is suggested that air hand dryers are unsuitable for use in critical patient care areas as they may contribute to cross infection either via airborne dissemination or via contaminated personnel.

Rebecca Montville, Yuhuan Chen and Donald W. Schaffner, Risk assessment of hand washing efficacy using literature and experimental data, International Journal of Food Microbiology, Volume 73, Issues 2-3, 11 March 2002, Pages 305-313

Soap with an antimicrobial agent (in particular, CHG) was observed to be more effective than regular soap. Hot air drying had the capacity to increase the amount of bacterial contamination on hands, while paper towel drying caused a slight decrease in contamination. There was little difference in the efficacy of alcohol and alcohol-free sanitizers. Ring wearing caused a slight decrease in the efficacy of hand washing.


Personally, I don't use them because they don't dry my hands.
posted by Comrade_robot at 9:48 AM on August 30, 2007 [6 favorites]

I think that the reason that you're not finding a lot on this is that its, uh, crazy talk.

Why does she think that the air is contaminated?
posted by desuetude at 9:49 AM on August 30, 2007

Comrade robot, a critical-care facility, by definition, is populated by immuno-compromised patients and medical personnel who have been exposed to infectious disease. This isn't analogous to a garden-variety public washroom.
posted by desuetude at 9:56 AM on August 30, 2007

Actually, here's another one that says no difference:

Gustafson DR, Vetter EA, Larson DR, Ilstrup DM, Maker MD, Thompson RL, Cockerill FR 3rd., Effects of 4 hand-drying methods for removing bacteria from washed hands: a randomized trial, Mayo Clin Proc. 2000 Jul;75(7):705-8.

OBJECTIVE: To evaluate the effects of 4 different drying methods to remove bacteria from washed hands. SUBJECTS AND METHODS: One hundred adult volunteers participated in this randomized prospective study. All bacterial counts were determined using a modified glove-juice sampling procedure. The difference was determined between the amounts of bacteria on hands artificially contaminated with the bacterium Micrococcus luteus before washing with a nonantibacterial soap and after drying by 4 different methods (cloth towels accessed by a rotary dispenser, paper towels from a stack on the hand-washing sink, warm forced air from a mechanical hand-activated dryer, and spontaneous room air evaporation). The results were analyzed using a nonparametric analysis (the Friedman test). By this method, changes in bacterial colony-forming unit values for each drying method were ranked for each subject. RESULTS: The results for 99 subjects were evaluable. No statistically significant differences were noted in the numbers of colony-forming units for each drying method (P = .72). CONCLUSION: These data demonstrate no statistically significant differences in the efficiency of 4 different hand-drying methods for removing bacteria from washed hands.

Here's another one that says your friend is right:

Gould D. The significance of hand-drying in the prevention of infection. Nurs Times. 1994 Nov 23-29;90(47):33-5

The original research linking poor hand hygiene to the development of infection was conducted by Semmelweis over 100 years ago. His experiments have never been replicated in the hospital setting, but over the years powerful circumstantial evidence has accumulated to suggest that hands are the main vectors of micro-organisms in both hospital and community and that hand-washing is the key to infection prevention. Nevertheless, many aspects of hand-washing remain under-researched. The area that has received least attention is hand-drying, despite early suggestions that when a quick, perfunctory hand-wash is performed by busy nurses in the clinical situation, the mechanical action of drying contributes to the efficient removal of pathogens. This paper explores evidence to show that the use of paper towels is safer than hot air hand-dryers in busy wards.

Here is another:
Importance of handwashing in the prevention of cross-infection.
Source: British journal of nursing [0966-0461] Parker yr:1999 vol:8 iss:11 pg:716 -20

Drying is as important as washing for good
hand hygiene and there are a variety' of methods
from which to choose. Cloth towels are rarely
used in healthcare settings because of concern
about contamination. If used the\ should be
strialy controlled — damp towels should bu
dried bet\veen use and changed daily (Horton
and Parker, 1997). Hot air dryers have been
shown to increase the bacterial count by over
500%, as well as increasing the baaerial contamination
of the local environment (Knight et al,
1993; Redway et al, 1994). They are also verynoisy
and should be discouraged from use in
patient areas. Paper towels are the most popular
choice. They are simple, quick, thorough and
effeaive at rubbing away transient organisms


On the balance, I'd say your friend is right.
posted by Comrade_robot at 9:57 AM on August 30, 2007

The question was if air hand dryers could spew bacteria all over the place. The answer seems to be yes -- air hand dryers do spread bacteria. If you are McDonald's and they have an air hand dryer, is it going to kill you? Probably not. But that wasn't the question.
posted by Comrade_robot at 9:59 AM on August 30, 2007

Waving your hands under the blower isn't going to contaminate them -- but wiping them on your pants to actually get them dry probably will.
posted by ottereroticist at 10:06 AM on August 30, 2007

Along with the hotel bedspread you ever think about the filth trapped in the holes of bowling balls? It's not like they're ever cleaned out. Not that anybody ever goes bowling anymore. I guess I just don't see much point of washing your hands at a bowling alley (but I do it anyway).

As far as bathrooms, I started a habit of dispensing a few sheets of paper towels BEFORE I wash my hands. When I'm done washing, I rip the hanging paper off (I don't have to touch the dirty dispenser knob with my bare hands) and dry my hands, and then wipe off the knob quickly (for the next person) and throw the paper towels away. Every once in a while there's some jackass who comes up and takes the paper towels I've so carefully rolled out for myself, but that's usually more amusing than annoying.

I personally hate the hand air blowers cause they're loud. So jarring after you've had a peaceful unburdening. Maybe your friend just doesn't like them for a variety of reasons, with the contaminated air theory sounding the most cogent.
posted by iamkimiam at 10:08 AM on August 30, 2007

Mod note: a few comments removed - this is not a referendum about germs, it's a pretty specific questin about bathroom hand dryers
posted by jessamyn (staff) at 12:25 PM on August 30, 2007

The Dyson Airblade may be the answer to your unsanitary and damp hands.
posted by arcticseal at 3:10 PM on August 30, 2007

#6 on this ppage says "Studies have shown that restroom automatic dryers inhibit the growth of bacteria on the skin by drying the skin more effectively than paper towels." I've also heard/read this. Unfortunately, I can't find the actual studies so far...
posted by edjusted at 4:54 PM on August 30, 2007

um...that should've read "page", not "ppage"
posted by edjusted at 4:54 PM on August 30, 2007

Have any of you guys actually gotten down and looked UP at a hand dryer? Lots of nasty gunk builds up there. IANAPHDI (professional hand drier inspector) but I think it's pretty plausible that some of that gunk could contain bacteria or fungus. Most hand driers don't seem to get hot enough to effectively kill much, but certainly warm enough to provide a nice breeding ground. They're also, as pointed out, sucking in the air around you, which being in a bathroom probably contains something--and then providing a place for that something to grow, so that instead of a tiny amount of something it is now a lot of something.

My preferred method of hand drying is the motion activated paper towel dispenser.
posted by anaelith at 6:14 PM on August 30, 2007

I don't buy the contaminated air thing. I mean, the only kind of contaimnated air I know about is if a sick person breathes on you.

My biggest worry with hand dryers is the fact that they rarely do a good job of drying your hands. I read somewhere that washing your hands and not drying them completely is worse then not washing them at all, since it promotes the growth of bacteria.

Don't really have a link to back that up, so take it with a grain of salt.
posted by Afroblanco at 9:00 AM on August 31, 2007

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