If you like to sweat it out in the gym, then make sure to dry your palms before you touch the door to leave because, according to new research, sweaty hands can reduce the anti-microbial properties of copper based objects (like door knobs) within an hour of contact. This discovery made by scientists at the University of Leicester especially applies to hospitals and schools where infections spread rapidly due to poor hand hygiene.

"The antimicrobial effect of copper has been known for hundreds of years. 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,” said Dr. John Bond OBE from the University of Leicester's Department of Chemistry, according to a press report.

Indeed, studies have found that bacteria, yeasts, and viruses are rapidly killed when in touch with antimicrobial touch surfaces made of copper. While copper is found in everyday brass items like door handles and water taps, scientists are now trying to expand its scope of application by using it in various places in hospitals to break the chain of infection that can spread from touching contaminated surfaces.  

But according to this new research, when copper comes in contact with human sweat, it starts to corrode within an hour of contact thus reducing its ability to kill a range of organisms that may be encountered in hospitals."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," said Dr. Bond.“We have shown that it is possible for sweat to produce an oxide layer on the metal within an hour of contact. While it is well known that sweat corrodes brass, this is the first study to quantitatively analyse the temporal corrosion of copper alloys such as brass in the first few hours after contact between fingerprint sweat concentrations of salt and the metal."

The research paper, published in the journal Applied Surface Science, was co-authored by Elaine Lieu as part of a third year Interdisciplinary Science project investigating how easily and quickly sweat can corrode brass at the University of Leicester. Hospital acquired infections are on the rise with an estimated 1.7 million infections and 99,000 associated deaths each year. But these can be reduced by following proper hygiene standards and using antimicrobial surfaces like copper to prevent infection through touch.

"My short-term advice is to keep the brass in public environments free from corrosion through regular and thorough cleaning. In the longer term, using copper alloys with corrosion inhibitors included in the alloy would be a good choice," said Dr. Bond. "While more research is needed in the study of sweat and brass corrosion, anywhere that needs to prevent the spread of bacteria, such as public buildings, schools and hospitals should be looking at using copper alloy on everyday items to help in avoiding the spread of disease."

Source: Bond J, Lieu E. Electrochemical behaviour of brass in chloride solution concentrations found in eccrine fingerprint sweat. Applied Surface Science.2014.