Hand dryers in the loo spraying bacteria on your hands

By Dr. Ananya Mandal, MDApr 12 2018

One of the basic hygiene measures is to dry the hands under a hand dryer after using the washroom. New study finds that the measure of washing hands with soap to cleanse them may be undone by the hand dryer that is praying bacteria on the clean hands. The study by researchers at the University of Connecticut School of Medicine appeared in the latest issue of the journal Applied And Environmental Microbiology.

Image Credit: Focus and Blur / Shutterstock

The hand dryers were found to be sucking up the impure air inside the washrooms and spraying it back on the hands of the users. The flushing of toilets spreads tiny water droplets all over the room. These contain bacteria from excrement. The same droplets are sucked in by the hand dryers along with air. This is then dried and sprays on the hands of the user finds that study. Thus the air sprayed is teeming with bacteria like E. coli that is found in faeces. Hand and food contamination with these bugs can give a case of food poisoning or diarrhoea and vomiting. To be on the safe side, wiping hands with a paper towel after washing with soap is a better option.

E.Coli Bacteria. Image Credit: MichaelTaylor3d / Shutterstock

For this findings, the team of scientists turned on dryers in thirty six separate bathrooms at the University. They placed a sterile plate underneath the dryers for around 30 seconds. These sterile plates were then cultured and 18 to 60 colonies of bacteria were found to grow on them. They also exposed some of these sterile plates to the bathroom air under fans for 20 minutes. These other plates also showed growth of 15 to 20 colonies of bacteria. Another set of plates were exposed to the bathroom air for two minutes. They showed growth of just one or less bacterial colony.

The authors write, “These results indicate that many kinds of bacteria, including potential pathogens and spores, can be deposited on hands exposed to bathroom hand dryers... spores could be dispersed throughout buildings and deposited on hands by hand dryers.” They add that the dryers should be ideally fitted with a high-efficiency particulate air (HEPA) filter to filter out the bugs. But this study showed that adding the filters did not help. Authors write, “Potential human pathogens were recovered from plates exposed to hand dryer air whether or not a filter was present.”