Health

Shocking discovery about bathroom hand dryers stuns scientists

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A new study has found that hand dryers may be just spreading around bacteria in the bathroom and are not hygenic at all.

An alarming new study claims that you are better off not using those hand dryers in public bathrooms, because they may actually be making your hands dirtier. The study, published in the journal Applied and Environmental Microbiology, determined that hot air hand dryers spread around all the bacteria that gathers in the bathroom despite the fact that they often advertise how hygenic they are.

The problem is that while hand dryers may indeed allow people to avoid touching more surfaces when drying their hands, it is negated by the fact that the air simply redeposits the bacteria all around the bathroom, scientists say. As a result, these hand dryers can cause disease and infections for some people, they warn.

The study examined 36 men’s and women’s bathrooms at the University of Connecticut School of Medicine and held up test plates to hand dryer air, where they found as many as 60 different colonies of bacteria while air drying for 30 seconds. The air itself that comes from the dryers is clean, it is the rest of the bathroom air that it pushes around that is not.

The abstract from the paper follows below.

Hot-air hand dryers in multiple men’s and women’s bathrooms in three basic science research areas in an academic health center were screened for their deposition on plates of (i) total bacteria, some of which were identified, and (ii) a kanamycin-resistant Bacillus subtilis strain, PS533, spores of which are produced in large amounts in one basic science research laboratory.

Plates exposed to hand dryer air for 30 s averaged 18 to 60 colonies/plate; but interior hand dryer nozzle surfaces had minimal bacterial levels, plates exposed to bathroom air for 2 min with hand dryers off averaged ≤1 colony, and plates exposed to bathroom air moved by a small fan for 20 min had averages of 15 and 12 colonies/plate in two buildings tested. Retrofitting hand dryers with HEPA filters reduced bacterial deposition by hand dryers ∼4-fold, and potential human pathogens were recovered from plates exposed to hand dryer air whether or not a HEPA filter was present and from bathroom air moved by a small fan.

Spore-forming colonies, identified as B. subtilis PS533, averaged ∼2.5 to 5% of bacteria deposited by hand dryers throughout the basic research areas examined regardless of distance from the spore-forming laboratory, and these were almost certainly deposited as spores. Comparable results were obtained when bathroom air was sampled for spores. These results indicate that many kinds of bacteria, including potential pathogens and spores, can be deposited on hands exposed to bathroom hand dryers and that spores could be dispersed throughout buildings and deposited on hands by hand dryers.

While there is evidence that bathroom hand dryers can disperse bacteria from hands or deposit bacteria on surfaces, including recently washed hands, there is less information on (i) the organisms dispersed by hand dryers, (ii) whether hand dryers provide a reservoir of bacteria or simply blow large amounts of bacterially contaminated air, and (iii) whether bacterial spores are deposited on surfaces by hand dryers.

Consequently, this study has implications for the control of opportunistic bacterial pathogens and spores in public environments including health care settings. Within a large building, potentially pathogenic bacteria, including bacterial spores, may travel between rooms, and subsequent bacterial/spore deposition by hand dryers is a possible mechanism for spread of infectious bacteria, including spores of potential pathogens if present.

The following is an excerpt from Wikipedia on the hygenics of hand dryers.

In 2009 a published study was conducted by the University of Westminster to compare the levels of hygiene offered by paper towels, warm air hand dryers and the more modern jet-air hand dryers. It found that after washing and drying hands with the warm air dryer, the total number of bacteria was found to increase on average on the finger pads by 194% and on the palms by 254%; drying with the jet air dryer resulted in an increase on average of the total number of bacteria on the finger pads by 42% and on the palms by 15%; and after washing and drying hands with a paper towel, the total number of bacteria was reduced on average on the finger pads by up to 76% and on the palms by up to 77%.

The scientists also carried out tests to establish whether there was the potential for cross contamination of other washroom users and the washroom environment as a result of each type of drying method. They found that:

the jet air dryer, which blows air out of the unit at claimed speeds of 400 mph (≈640 km/h), was capable of blowing micro-organisms from the hands and the unit and potentially contaminating other washroom users and the washroom environment up to 2 metres away
use of a warm air hand dryer spread micro-organisms up to 0.25 metres from the dryer paper towels showed no significant spread of micro-organisms.
In 2005, in a study conducted by TÜV Produkt und Umwelt, different hand drying methods were evaluated.

Another study found that hot air dryers had the capacity to increase the bacterial count on the skin, and that paper towel drying decreased skin bacterial count. This is corroborated by another study which found that the mechanical action of paper towel drying removed bacteria, something air dryers cannot do.

Doctors at the University of Ottawa claim that “the blowing of warm air may lead to an accelerated dehydration of the skin surface, thereby affecting the viability” of the microorganisms, and that the warm air may “penetrate all the crevices in the skin, whereas absorbent towels may not reach such areas, even though the skin appears dryer”.

The European Tissue Symposium, a trade body, has produced a position statement on the hygiene standards of different hand drying systems. This summarises some of the scientific research undertaken.

Dyson (creators of the Dyson Airblade dryer) have countered the claims presented, suggesting that the results were intentionally falsified.

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