Copper And Bacteria
in 1852, physician Victor Burq visited a copper smelter in Paris's 3rd arrondissement, where they used heat and chemicals to extract the reddish-brown metal. It was a dirty and dangerous job. Burq found the facility to be "in poor condition," along with the housing and the hygiene of the smelters. Normally, their mortality rates were "pitiful," he observed.
Yet, the 200 employees who worked there had all been spared from cholera outbreaks that hit the city in 1832, 1849, and 1852. When Burq learned that 400 to 500 copper workers on the same street had also mysteriously dodged cholera, he concluded that something about their professions—and copper—had made them immune to the highly infectious disease. He launched a detailed investigation into other people who worked with copper, in Paris and cities around the world.
In the 1854 to 1855 cholera epidemic, Burq could not find any deaths of jewellers, goldsmiths, or boilermakers—all those who worked with copper. In people in the army, he found that musicians who played brass instruments (brass is partly copper) were also protected. In the 1865 Paris epidemic, 6,176 people died of cholera, out of a population of 1,677,000 people—that’s 3.7 people out of every 1,000. But of the 30,000 who worked in different copper industries, only 45 died—an average of around 0.5 per 1,000.
After visiting 400 different businesses and factories in Paris, all of which used copper, and collecting reports from England, Sweden, and Russia on more than 200,000 people, he concluded to the French Academies of Science and Medicine in 1867 that “copper or its alloys, brass and bronze, applied literally and pregnantly to the skin in the cholera epidemic are effective means of prevention which should not be neglected.”
Today, we have insight into why a person handling copper day in and day out would have protection from a bacterial threat: Copper is antimicrobial. It kills bacteria and viruses, sometimes within minutes. In the 19th century, exposure to copper would have been an early version of constantly sanitizing one's hands.
Since then, studies have shown that copper is able to destroy the microbes that most threaten our lives. It has been shown to kill a long list of microbes, including norovirus, MRSA, a staph bacteria that has become resistant to antibiotics, virulent strains of E. coli that cause food-borne illness, and coronaviruses.
If copper were more frequently used in hospitals, where 1 in 31 people get healthcare-acquired infections (HAI), or in high-traffic areas, where many people touch surfaces teeming with microbial life—it could play an invaluable role in public health, said Michael Schmidt, a professor of microbiology and immunology at the Medical University of South Carolina, who studies copper. And yet, it is woefully absent from our public spaces, healthcare settings, and homes.
“What happened is our own arrogance and our love of plastic and other materials took over,” Schmidt said of the cheaper products more frequently used. “We moved away from copper beds, copper railings, and copper door knobs to stainless steel, plastic, and aluminium.”
Many of the microbes that make us sick can live on hard surfaces for up to four or five days. When we touch those surfaces, the microbes can make it into our bodies through our nose, mouth, or eyes, and infect us.
On copper surfaces, bacteria and viruses die. When a microbe lands on a copper surface, the copper releases ions, which are electrically charged particles. Those copper ions blast through the outer membranes and destroy the whole cell, including the DNA or RNA inside. Because their DNA and RNA are destroyed, it also means a bacteria or virus can’t mutate and become resistant to the copper, or pass on genes (like for antibiotic resistance) to other microbes.
Before people even knew what bacteria and viruses were, they knew that copper could—somehow—ward off infection. The of copper is from one of the oldest-known books, the Smith Papyrus, written between 2600 and 2200 B.C. It said that copper was used to sterilize chest wounds and drinking water. Egyptian and Babylonian soldiers would similarly put the shavings from their bronze swords (made from copper and tin) into their open wounds to reduce infections. A more contemporary use of copper: In New York City’s Grand Central Station, the grand staircase is flanked by copper handrails. “Those are actually anti-microbial,” Schmidt said.
The copper smelters were, ostensibly, exposed to less of the cholera bacterium because their surroundings included a lot of copper that bacteria couldn't live on. That and they potentially were covered in copper particles. If metallurgy doesn't call to you, there are now some products that are advertised as "copper hand sanitizers," but they work only if you can expose every surface of your hands to the copper for at least a full minute—essentially transferring any microbes to the copper surface to be killed. It could be difficult to get to every part of your skin's surface, so having copper surfaces in your environment paired with handwashing would be the ideal combination.
Schmidt said that using copper along with standard hygiene protocols has been shown to reduce bacteria in health care settings by 90 percent. A study from 1983 found that hospital door knobs made of brass, which is part copper, barely had any E. coli growth on them, compared to stainless steel knobs which were “heavily colonized.” This is significant because of how rampant healthcare-acquired infections are: In the U.S. alone, there are about 1.7 million infections and 99,000 deaths linked to HAIs per year, which cost between $35.7 and $45 billion annually, from the extra treatments people need when they get infected.
Microbes that live on surfaces in patient rooms and common spaces in hospitals play a role in getting a HAI—and this is where copper could help. And during this pandemic, when there is serious concern about the spread of the novel coronavirus via contaminated surfaces, a virus-killing substance seems worthwhile indeed.
A study from 2015 found that a different coronavirus, human coronavirus 229E, which causes respiratory tract infections, could still infect a human lung cell after five days of being on materials like teflon, ceramic, glass, silicone rubber, and stainless steel. But on copper alloys, the coronavirus was “rapidly inactivated.”
In a new preprint on SARS-CoV2, the strain that causes COVID-19, researchers at the National Institutes of Health virology laboratory in Montana sprayed the virus onto seven different common materials, reported MIT Technology Review. They found that it survived the longest—up to three days—on plastic and stainless steel, suggesting that surfaces in hospitals or steel poles on public transit could be places where people pick up the illness. Just a single droplet from a cough or sneeze can carry an infectious dose of a virus.
Bill Keevil, a professor of environmental healthcare at the University of Southampton in England who has previously received funding from the Copper Development Association, said that if copper surfaces were put in communal areas where many people gather, it could help reduce the transmission of respiratory viruses, like coronavirus 229E and also SARS-CoV2. Other than hospitals, he thinks the ideal locations for copper are public transportation systems, like buses, airports, subways. But he doesn't stop there: He would also like to see copper used in sports equipment in gyms, like weights, along with other everyday objects, including shared office supplies, like pens.
In the preprint, SARS-CoV2 "liked copper least," Antonio Regalado wrote in MIT Technology Review. "The virus was gone after just four hours."
In 2012, Schmidt and his colleagues ran a clinical trial in three hospitals, Memorial Sloan Kettering Cancer Centre in New York City, Medical University of South Carolina, in Charleston, and Ralph H. Johnson Veterans Administration Medical Centre, also in Charleston.
First, they figured out which items closest to a patient were the most contaminated with microbes—those were the bed rails, the nurse call button, the arm of the visitor chair, the tray tables, and the IV pole. Enveloping these items in copper reduced the presence of microbes by 83 percent. As a result, HAIs were reduced by 58 percent, even though the researchers had introduced copper to less than 10 percent of the surface area of the room.
We have other methods of killing bacteria and viruses to mitigate HAIs, including ultraviolet light and hydrogen peroxide gas. But both require a hospital room to be empty, and once sick people re-enter rooms, surfaces can easily be contaminated again. “Copper is continuously working 24/7 without supervision, without any need to intervene, and it never runs out,” Schmidt said. “As long as the metal's there, it's good to go."
So given how well it could work, for hospital infections and for health more generally, why isn’t copper everywhere? Why isn’t every door knob, every subway rail, every ICU room, made of copper? Why can we easily buy stainless steel water bottles, but not copper? Where are the copper iPhone cases?
It doesn't seem like we'll run out of copper in the near future, according to the World Copper Factbook from 2019. Copper is one of the most recycled of all metals—nearly all copper can be recycled and not lose any of its properties.
Doctors and healthcare workers might not be aware of its properties, as Keevil wrote in The Conversation: “When doctors are asked to name an antimicrobial metal used in healthcare, the most common reply is silver—but little do they know that silver does not work as an antimicrobial surface when dry—moisture needs to be present."
There might also be a perception that copper is too expensive, Schmidt said, despite the fact that the numbers indicate it would ultimately save money. One of Keevil and Schmidt's studies from 2015 did the math: The cost of treating an HAI ranges from $28,400 to $33,800 per patient. Installing copper on 10 percent of surfaces cost $52,000 and prevented 14 infections over the course of the 338-day study. If you take the lower end of the HAI treatment cost ($28,400), then those 14 prevented infections saved a total of $397,600, or $1,176 a day.
Even when factoring in how much the copper cost initially, you'd make that money back in savings within two months, Schmidt said. And considering that the copper never loses its microbial killing abilities—hospitals would quickly be saving money (and lives).
"Your payback is literally in less than two [prevented] infections,” he said. “I really struggle with this. Since 2013, I have been literally begging, groveling, pleading, with any and all concerned to make a completely copper encapsulated [hospital] bed."
He recently did convince a company to invest, and said they’re in the process of testing it to show that it could reduce infections even further than 58 percent.
Another reason copper may have been passed over for steel, plastic, or glass is that it can easily tarnish and requires a lot of cleaning to remain shiny. “But copper is antimicrobial regardless of how grody it looks, if it turns green on you, it still has the ability to kill bacteria and viruses and fungi,” he said.
Some places around the world have started to use copper. In Chile, a theme park called Fantasilandia, replaced a lot of its commonly touched surfaces with copper. At the Atlanta airport, 50 water bottle filling stations are now made with copper. But Schmidt believes it should be more widespread.
He said that one of the reasons scientists are worried about the current coronavirus is how infectious it is, and a major way people might be getting it is from touching contaminated surfaces. He thinks it's possible that the pandemic could raise awareness for copper—if it motivates anyone to start using it. Imagine, he said, if our hospitals and public spaces already had copper in place—it’s impossible to say for sure, but it’s likely that transmission would have been affected.
“I have great confidence that it would work because bacteria or viruses are the ones causing the infection," he said. "If their numbers go down, common sense would tell you: you should have fewer infections.”