Over the past few months, there has been a surge in the market for materials laced with copper—including face masks, bedsheets, and socks—with manufacturers touting the metal's germ-killing ability. But experts say consumers should be cautious, as copper isn't a cure-all against the new coronavirus.
How copper kills germs
Copper is known for killing microbes and has been shown to help limit the spread of E. coli, salmonella, and influenza.
According to Karrera Djoko, a biochemist and microbiologist at Durham University, when copper comes into contact with a germ, it has the ability to release reactive ions that puncture the exterior of the germ. The ions can then access the inside of the germ, affecting its genetic material.
Copper can also affect microbes in other ways. For instance, according to Michael Johnson, a microbiologist at the University of Arizona, metal ions are found in around 40% of proteins with known structures—and when copper works its way into a cell or a virus, it can displace other metal ions, which can inhibit or destroy proteins. "If 40% of your proteins don't work, you don't work," Johnson said.
The human immune system also utilizes copper to fight germs. Research suggests that certain immune cells, called macrophages, may be able to envelop and separate germs in an acidic "ball of death" chamber, which is then spiked with copper doses fatal to the germ, Johnson said.
According to Michael Schmidt, a professor of microbiology and immunology at the Medical University of South Carolina, copper's ability to fight viruses is like a "grenade." When the metal interacts with oxygen, it creates a very reactive molecule known as a free radical, which comes into contact with a virus and causes it to "literally explode," Schmidt said.
Should you use copper to fight the new coronavirus?
Research has shown that copper potentially could fight the new coronavirus, as well. A study published in the New England Journal of Medicine found that the virus lasted on copper for just a few hours, compared with days on stainless steel and plastic—although the New York Times notes that researchers do not think surfaces are the primary way the coronavirus transmits from person to person.
And copper masks have been shown to potentially be effective in stemming the spread of viruses. A study published in PLOS One determined copper masks "may significantly reduce the risk of hand or environmental contamination, and thereby subsequent infection, due to improper handling and disposal of the masks." (It's worth noting, however, that the study was authored by researchers who worked at Cupron, a manufacturer of copper masks.)
For copper masks to work properly, however, they need to be made with enough copper to fight viruses. "If your mask is only 1% copper, that means it's 99% not copper," Djoko said, adding that if the copper doesn't meet the microbe, the mask "won't confer any more benefit than just regular masks."
Djoko also expressed concerns about the durability of copper masks, especially if the masks are frequently being washed or disinfected, as many household cleaners contain compounds that could strip off copper ions.
Williams Schaffner, medical director of the National Foundation for Infectious Disease, said the idea that copper masks were better at protecting against viruses than regular masks was "dubious."
He added that he's "less concerned about the specific materials" in a mask and more concerned with getting people to wear them in general. "We wish to inhibit the spray of the virus from getting to other people, and it's actually the physical barrier that's the most important rather than any concept of inactivation of the virus," he said. "Even if you touch the surface of the mask and do some hand hygiene, that addresses the problem."
Schmidt, however, said copper masks could be a "game changer" for combating the new coronavirus. He added, "If we begin to incorporate copper masks into our strategy … we may be able to short-circuit a second wave that's coming."
And while Djoko was less enthused about masks per say, he did think the use of copper on hospital surfaces might help keep the virus in check—although experts cautioned that copper's effects aren't instantaneous, and therefore shouldn't replace handwashing, social distancing, and other strategies of avoidance to protect against the new coronavirus.
Johnson said he's fine with people wearing copper masks, but cautioned that people should have realistic expectations. "Copper is a fantastic fashion choice," he said. "You're going to look fabulous. It just might not work the way you think" (Wu, New York Times, 6/19; Hohman, TODAY, 5/28).