It began in mid-March. Every time Michael D. L. Johnson checked his email, the University of Arizona microbiologist would find a new batch of messages, all asking the same question: Will products made with copper keep the coronavirus at bay?
“I was getting three to four emails about it a day,” Dr. Johnson said. Some asked if he recommended ingesting copper as a cure. Others wondered if it was a good idea to outfit their homes with it. A few inquisitive citizens even wanted to know whether wearing copper accessories, such as bracelets, would stave off disease.
“It was kind of a wild ride,” Dr. Johnson said.
The flood of missives in his inbox eventually waned. But in many ways, the Covid-19 copper craze has not. In recent months, there’s been a surge of interest in materials laced with the metal, including socks, bedsheets and coatings that can be sprayed onto surfaces. Multiple companies are marketing face coverings and masks with built-in copper linings, touting their germ-killing properties. One company even offers a “nasal wand” designed to apply “the touch of solid copper” to the hands, face and nostrils at the first sign of illness.
But while copper does have antimicrobial qualities, Dr. Johnson and others said you should think twice before buying into many of these products’ claims.
What copper might do to pathogens
People have been aware of copper’s sanitizing abilities at least as far back as ancient Egypt, said Karrera Djoko, a biochemist and microbiologist at Durham University in England.
“Even before we had a concept of what a germ is,” Dr. Djoko said, “we were using copper to contain water” and keep it safe to drink.
Scientists today know the mighty metal as a swift slayer of microbes, capable of limiting the spread of E. coli, salmonella, influenza virus and more. In certain settings, it may stifle the coronavirus, too. In a study in the New England Journal of Medicine, researchers reported that, under controlled laboratory conditions, the coronavirus couldn’t last more than a few hours on copper surfaces, compared with a couple days on stainless steel or plastic. (Though scientists don’t think surfaces are the main way the virus spreads between people.)
For humans, copper is an essential nutrient, which you easily get enough of in a typical diet. But Dr. Djoko said many microbes don’t take to copper so kindly. When copper physically contacts a germ like coronavirus, it can release reactive ions that pummel and puncture the bug’s exterior. That gives the ions access to the microbe’s innards, where they wreak similar havoc on its genetic material.
Copper can be calamitous for microbes in other ways as well, Dr. Johnson said. Metal ions, like iron or zinc, are found in about 40 percent of proteins with known structures, and most likely play essential roles in their function. But in a vicious game of musical chairs, copper that finds its way into a cell or a virus can swoop in and displace other metals, impairing or even destroying the proteins it commandeers.
“If 40 percent of your proteins don’t work, you don’t work,” Dr. Johnson said. Copper may even be capable of jamming up proteins that typically run metal-free by simply glomming onto their surfaces.
Even our own immune systems appear to exploit copper’s protective perks. Some evidence suggests that immune cells like macrophages — which gobble up and destroy bacteria, viruses and other microbes — may be capable of engulfing and sequestering germs in an acidic “ball of death” chamber that’s then spiked with lethal doses of copper, Dr. Johnson said. “Our bodies have been using this for warfare” long before copper masks hit the market, he added.
But it remains to be seen which of these scenarios will play out with the coronavirus, and to what extent. Dr. Johnson is one of several scientists currently on the case, tinkering with copper to suss out exactly how it exerts its apparently potent effects on this dangerous germ.
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Steer clear of the copper nose picker
What works well in the lab, however, won’t necessarily pass muster in the real world. Both Dr. Johnson and Dr. Djoko have held off on recommending copper-infused accessories, including face coverings and masks, to their friends, family and colleagues as a way to reduce transmission. (Overingesting copper is also a bad idea, and probably wouldn’t do much to boost immunity, Dr. Johnson said. And Dr. Djoko isn’t keen on the idea of sticking copper wands up your nose.)
Loosefitting face coverings, like cloth or surgical masks, aren’t air tight and don’t make the wearer impervious to infection. But if the wearer is infected, masks can do a great deal to protect others from virus-laden droplets spewed by coughs, sneezes and speech. A 2010 study found that the metal-laced accessories could curb the amount of active influenza virus lingering on contaminated masks. (The analysis was conducted by Cupron Scientific, one of several companies now selling copper-lined face coverings.)
If copper face coverings also curtail the coronavirus, that could come in handy for people who mishandle their masks, said Linsey Marr, an aerosol scientist at Virginia Tech. A hefty dose of copper could diminish the chances of viable virus making it into the eyes, nose or mouth via a wayward hand that’s touched the front of a mask.
Still, not all metal-infused masks are created equal. Manufacturers would need to design them with enough copper — ideally near the product’s surface — to actually do the job.
“If your mask is only 1 percent copper, that means it’s 99 percent not copper,” Dr. Djoko said. If the metal and microbe don’t physically meet, the mask “won’t confer any more benefit than just regular masks.”
Durability could also be an issue, especially if copper masks are getting repeatedly washed or disinfected. Many common household cleaners are formulated with compounds that could strip copper ions off a protective surface, Dr. Djoko said.
Still, copper may yet have a role to play in the pandemic. Installing copper-based surfaces in hospitals has been shown to cut down on transmission rates of certain pathogens, including antibiotic-resistant strains of bacteria. Dr. Djoko thinks it could keep coronavirus in check in such settings, too.
But all experts emphasize that having the metal around doesn’t let anyone off the hygiene hook. Copper on its own is no cure-all — and its effects aren’t instantaneous. It takes about 45 minutes for copper to reduce the amount of virus on a surface by half.
“It’s not like it hits the copper and poof, it’s gone,” said Dr. Marr. So you might want to keep that in mind before you buy a copper or brass tool for using touch screens and opening doors. To minimize transmission risk, people should still wash their hands, avoid crowds and maintain a safe distance from one another.
More copper-containing accouterments — coronavirus-related or not — may yet be headed our way. Dr. Johnson has nothing against that.
“Copper is a fantastic fashion choice,” he said. “You’re going to look fabulous. It just might not work the way you think.”
