G'day, it's Dr Karl here.
Now we humans have long made use of the metal copper. More than 10,000 years ago, we used it to make tools, household items and weapons. By about 5,000 years ago, it was being used as a medicine. And now, with the COVID-19 pandemic, copper might be having its moment again to help fight the virus, SARS-CoV-2, the cause of COVID-19.
A recent study looked at how long this virus could survive on various surfaces.
The virus remained viable for three days on plastic, two days on stainless steel, one day on cardboard — but only four hours on copper. Copper won hands down.
You might remember from school, that an atom kind-of looks like a mini solar system — something heavy in the middle, lots of empty space, and various clouds of electrons orbiting around. Copper is a pretty special atom because it can "lose" varying numbers of electrons — one, two, three or even four. This means that it can be involved in very many different chemical reactions, especially those involving "life".
In fact, copper is an essential trace element for plants and animals. Our bodies need copper to turn glucose into energy, and to make the collagen that holds our flesh together and the melanin that colours our skin. Without it we'd be pale, floppy and dead.
But while copper is essential for some processes in living creatures, it also has the power to interfere with biological processes.
It's been used for centuries on ships to protect against mussels and barnacles. And French wineries still apply Bordeaux mixture (copper sulphate and slaked lime) to their vines to stop fungal attack.
In terms of human health, copper is mentioned in Smith's Papyrus, the oldest-known medical document, from 5,000 years ago.
The soldiers and sailors in the ancient Phoenician, Egyptian and Babylonian military forces would put copper into their battle wounds, to speed healing and to reduce infections. They actually used the metal shavings from sharpening their bronze swords (because bronze is mostly copper).
Fast forward to the cholera epidemic of 1832 in France, where it seemed that copper workers were relatively immune to the disease.
Professor Bill Keevil (of Southampton University in the UK) has been studying the effect of copper on bacteria and viruses for about a quarter of a century.
He has shown that mere contact with copper kills bacteria such as the one that causes Legionella disease, and even Methicillin-Resistant Staphylococcus Aureus. Copper would also inactivate viruses such as the coronavirus that caused MERS — the Middle Eastern Respiratory Syndrome, and the influenza virus that caused the H1N1 swine flu pandemic.
We still don't fully understand how copper kills viruses and bacteria. But copper's special chemistry is the key.
Suppose you put a single bacterium, or virus particle, on the surface of copper metal. It seems that atoms of copper physically drift, or diffuse, from the surface of the copper into the cell membrane of a bacterium, or into the outer coating of the virus particle.
The copper atoms then set off various chemical reactions, some of which manufacture hydrogen peroxide. The hydrogen peroxide blasts holes through the cell membrane of the bacterium, or disrupts the outer coating of the virus. And this destroys the germ's ability to infect us.
There are probably other chemical pathways of attack as well.
It's a bit controversial, but it seems copper can also damage the genetic material of the bacterium or virus — its DNA or RNA. This might stop the rise of mutations that could make the germs resistant to copper.
Now back to Professor Keevil. In one study, he checked out the copper hand railings inside Grand Central Station in New York, that had been installed over a century ago. Mechanically, the copper handrails are as good today as they were back then. But even better, that century-old copper is still killing bacteria and viruses.
Copper isn't so popular with architects and builders these days — a lot of our handrails, door knobs and lift buttons are made from stainless steel. Now I'm as big a fan of shiny, stainless steel as anyone — I'm a sucker for a mirror finish. But stainless steel has many micro-bumps and micro-valleys on its surface, which make a great home for bacteria and viruses to hide in. So while sparkly stainless steel looks reassuringly clean — it's all just shallow surface lustre.
Not so with copper.
Copper does not need electricity or chemicals to kill microbes — it does this by its own chemical structure that comes for free.
Maybe we should re-learn the lessons of the past, and use copper for all the surfaces we touch in all public transport, restaurants, kitchens, gyms and buildings — such as handrails, elevator buttons, taps, doorknobs and push panels on doors.
Now that's a grand design we could all get behind.
1. When did people start using copper as a medicine?
2. How long do viruses live on copper?
3. How would we look without copper?
4. How long ago was the first medical textbook written?
5. What are two viruses that copper can deactivate?
6. How does copper damage or destroy viruses and bacteria?
7. What is so special about Grand Central Station in New York?
8. What kind of help does copper need to kill microbes?
Explain the meaning of the following words and phrases as used in the passage.
In 300 – 500 words write a summary of Dr Karl’s talk