Human sweat can corrode the protective qualities of brass door knobs and taps within just an hour of contact, according to new research from the University of Leicester in the UK, reducing these objects’ ability to prevent the spread of bacteria.
The copper found in brass objects such as door handles and water taps is known to have an antimicrobial effect on bacteria, and so these materials are routinely used in hospitals and schools to prevent disease from spreading.
“The antimicrobial effect of copper has been known for hundreds of years,” says Dr. John Bond OBE, co-author on the new study.
“It is thought to occur as a result of a charge exchange between copper and bacteria, which leads to a degradation of the bacteria DNA.”
However, Dr. Bond’s team has discovered that the antibacterial properties of the copper could be defeated by a substance as common as human sweat. This means that the microorganisms that might be present in hospitals can be more easily transferred by touch.
“We have discovered that the salt in sweat corrodes the metal, forming an oxide layer on its surface, which is the process of corrosion – and this corrosive layer is known to inhibit the effect of the copper. We have shown that it is possible for sweat to produce an oxide layer on the metal within an hour of contact.”
Bond claims that his is the first study to quantitatively analyze the temporal corrosion of copper alloys – of which brass is one – in the initial hours after contact between metal and salt administered at the concentration of fingerprint sweat. Similar experiments are sometimes used in criminal investigations.
The University of Leicester is currently investigating different methods of improving hospital hygiene, of which this research – part of a third year Interdisciplinary Science project, co-authored by Elaine Lieu – is just one.
Earlier this year, a study using video surveillance in the Kibera slum of Nairobi in Kenya proved the importance of hand hygiene in caregiving situations. The study – published in the journal PLOS One – showed that school students only washed their hands 48% of the time after using the toilet.
The video surveillance demonstrated, though, that if another person is present, hand washing rates increase to 71%. The study also found that girls were more likely to wash their hands than boys.
Also, students were not only 1.3 times more likely to wash their hands if the washroom was equipped with soap and water instead of sanitizer, but they would also clean their hands for longer when using soap.
However, as the participants consented to the video monitoring and were aware that they were being surveilled, this may have affected the results.
That study made the following recommendations for better hygiene:
- Placement of hand cleaning materials in public locations
- Scheduling specific times for bathroom breaks between classes
- Designating specific students to be hand hygiene “champions”
- Formation of student clubs to demonstrate and promote hand hygiene to classmates.
A similar study, conducted in a Rhode Island hospital during 2008-2012, measured an improvement of the staff’s hand hygiene from 60% compliance to 89%.