There is a war going on in your nearest restroom. Paper towel producers are head to head with hand dryer manufacturers in the battle over who can kill the most bacteria on wet hands. The science, funded largely by the warring parties, remains unsettled.
The conflict kicked off in 2008 with a study by Westminster University, which said that electric hand dryers increase the amount of bacteria on the hands of users and contaminate the restroom.
The bacteria
The most common microbes found in public toilets are streptococcus, E. coli , shigella bacteria and staphylococcus. These critters are linked to severe infections of the throat and skin, and cause gastroenteritis and MRSA.
According to many studies, hand washing can prevent contamination from these microbes and protect people from coming into contact with them. However, the consequences of washing your hands seem to be more complicated than meets the eye.
Dr. Keith Redway, who conducted the Westminster research, says that hand dryers are so unhygeinic that if you are going to use one, it would be better not to have washed your hands at all.
The study
Researchers selected 20 men and women, and asked them to use public toilets and return to the lab without washing their hands. Bacteria was removed from the subjects’ hands and transferred onto agar plates, where they were grown to allow for colony counting. Three hand-drying methods were compared: paper towels, warm air dryer and the Dyson Airblade dryer.
The results
The London-based research project found that people who dry their hands using a Dyson dryer are contributing to bacteria spread. The air that comes out of the jet air dryer transports germs found on hands, and on the hand dryer itself, up to two metres away. The warm air hand dryer also scatters the bacteria, but only up to 0.25 metres away. Paper towel use, however, did not contribute to any significant bacterial spread.
Perhaps most unexpectedly was the finding that using a warm air dryer increased bacteria on palms by up to 254 percent. The Dyson dryer increased bacteria by up to 42 percent on fingertips.
Conversely, using paper towels resulted in a decrease of bacterial incidence by up to 77 percent on palms and 76 percent on finger pads.
The results suggest that anyone using a public toilet is at risk of being contaminated with some types of bacteria. If correct, people that have weaker immune systems, such as children and the elderly, would be most at risk of suffering the consequences of bacterial infection spread. This research shows that places like hospitals, schools, nurseries and homes should take a special account of this issue.
Paper towels cost more than maintaining air dryers systems, which may explain the widespread adoption of hand dryers.
Reactions to the study
This study was funded by the European Tissue Symposium (ETS), which represents European manufacturers of tissue paper. Also, the number of individuals used in the study was relatively small and this might have affected the results by not representing well the population. Critics also pointed out that this study wasn’t peer-reviewed.
Other, more recent studies, such as the one carried out at Bradford University and funded by Dyson, support different theories that confirm that paper towels and jet air dryers produce similar results and changes in bacterial incidence are only related to the time spent using a hand drying.
This study also found that rubbing hands when drying them would increase bacteria and using a cold air hand dryer, like the Dyson hand dryer, would be better than using a warm air hand dryer as the cold air hand dryers dry the hands faster and this is crucial to bacterial removal.
This last study helped the Dyson Airblade to be recognised by the new accreditation scheme of the Royal Society of Public Health, which supports products and technologies that are beneficial for health, hygiene and safety.
While some questions are answered by these various studies, their conflicts of interest are clear for all to see, so some independent research in this field would be welcome.
Further reading
Hand Hygiene and you
Research highlights importance of hand drying
Are air dryers hygienic?
European tissue symposium