The Surprising Antimicrobial Powers of Copper

Why modern hospitals are waking up to an ancient Egyptian secret.

You may think little would link smelly socks with the metallic element copper.

But since this post is brought to you by the team at uBiome, you’ll perhaps not be overly surprised to learn that, as ever, there’s a bacterial connection.

It’s bacteria’s interaction with sweat that causes foot odor, while copper has some pretty fascinating antimicrobial properties. More on this in a moment.

But first, an acknowledgement that socks and copper have indeed come together, with a little help from a company named Cupron that has developed odor-resistant socks, by incorporating antimicrobial copper in fabric.

These socks were even sent down to the trapped Chilean miners, who received them on Day 36 of their underground ordeal.

In fact, we were tipped off about copper’s extraordinary antimicrobial properties by a brief piece in The New York Times last week, which answered a reader’s question about the effectiveness of copper doorknobs at protecting patients from germs in hospitals.

Huh? Did you even know this was a thing?

Well, to be honest, we were surprised – and it set us off on a fascinating voyage of discovery.

According to The Wall Street Journal, more than 150 healthcare facilities in the US have installed various antimicrobial copper alloy fittings since 2011, largely as a reaction to the spread of antibiotic-resistant bacteria.

An informative review produced in 2011 by scientists at the University of Bern in Switzerland pointed out that, although the killing mechanism isn’t fully understood, a significant proportion of many pathogens die on copper services.

The phenomenon has come to be known as contact killing, which needs to be spelled carefully. Nothing to do with hitmen.

Going back centuries, copper was frequently used to store water after it was observed that water contained in copper vessels was of better quality than that held in containers made from other materials, developing little or no visible slime.

Actually, the use of copper for medicinal purposes goes way, way back, with a mention in what is considered to be one of the oldest-known books, the Smith Papyrus, written between 2600 and 2200 BCE.

It described the use of copper to sterilize chest wounds in ancient Egypt.

The Greeks, Romans, and Aztecs all used copper or copper compounds to treat conditions such as headaches, burns, ear infections, and – uh – intestinal worms.

Then, in 19th-century France, copper workers in Paris appeared to develop an immunity to cholera, an infection of the small intestine by certain strains of the bacterium Vibrio cholerae.

Jumping ahead to 1983, Dr. Phyllis Kuhn, now at Lake Erie Research Center at the University of Toledo, Ohio, conducted some remarkable (and, some may say, under-reported) research comparing brass and stainless steel door handles.

Brass is an alloy of copper and zinc, and stainless steel is an iron-chromium alloy.

Incredibly, the brass door handles inoculated with bacteria disinfected themselves in seven hours or less, while their stainless steel counterparts were still infected when the experiment ended three weeks later.

Even better, freshly scoured brass handles were bacteria-free in just an hour.

Dr. Kuhn urged healthcare facilities that were remodeling to retain their old brass door fittings rather than replace them with modern stainless steel ones.

It seems that while stainless steel can look clean, it’s actually pretty good at providing a long-term home for bacteria.

Copper, on the other hand, has some remarkable automatic antimicrobial properties, although, as a British study in 2013 pointed out, these can only be relied on when used alongside other methods of disinfection and overall hygiene.

One last, perhaps comforting, point about US coins.

Every single coin ever (well, apart from the 1943 Steel Wartime Penny) contains a certain amount of copper.

And we guess that may keep the microbes away from your moolah.


Further reading

Antimicrobial properties of copper

Copper Doors as Germ Assassins

Copper Socks May Have Helped Treat Chilean Miners’ Foot Infections

Cupron

Doors: A Source of Nosocomial Infection?

Doors: A Source of Nosocomial Infection? [paper]

Egyptian Pharaoh Had Copper Plumbing

Electrochemical behaviour of brass in chloride solution concentrations found in eccrine fingerprint sweat

Fingerprint Disinfection Test

Human sweat can reduce bacteria defenses of doors and taps

Metallic Copper as an Antimicrobial Surface

Paging Doctor Copper: Metal Wins Fans in Health Care

Which U.S. Coin Has Absolutely No Copper in it?