What is copper?
Copper is an essential element required by both plants and animals to live. Copper is also an industrial metal that possesses superior electrical and thermal conductivity, is easy to process and, through the incorporation of other metals, can deliver broad technical performance. This makes it a very important material in a wide range of consumer and industrial applications.
Copper is refined from ore that occurs naturally in many places around the world. The five largest mining countries are Chile, China, Peru, the United States and Australia.
Copper is one of the few materials that can be recycled, time and time again, without any loss in performance. Nearly one third of annual copper demand is met through recycling and, according to the Fraunhofer Institute, two thirds of the copper produced since 1900 is still in use today.
Copper is necessary in the human diet; the best sources for dietary copper include seafood, organ meats, whole grains, nuts, raisins, legumes and chocolate. An adult needs a daily intake of around 1mg per day to maintain good health.
An alloy is created when a metal is mixed with one or more elements. This mixture allows the combined elements to take on properties that they would not have individually in their pure states. The ratios of copper and added elements vary depending on what properties are required of the resulting alloy. Brass and bronze are common alloys of copper.
Yes. Brass is created by combining pure copper with zinc. Brass is strong, resistant to corrosion and easily worked without the use of heat. Bronze is created when tin and phosphorus are combined with copper. Bronze is harder than brass; it combines strength with fatigue resistance, machinability and high wear resistance. Both brass and bronze are available in a wide range of colors and finishes.
What is meant by 'antimicrobial'?
'Antimicrobial' is the ability of a substance to kill or inactivate microbes, such as bacteria, fungi (including moulds) and viruses.
Yes. humankind has exploited the inherent antimicrobial properties of copper since the dawn of civilization. It has been demonstrated clearly in many scientific studies conducted over several decades that copper has rapid, broad spectrum antimicrobial efficacy against some of the most toxic species of bacteria, fungi and viruses.
The scientific literature cites the efficacy of copper to inactivate many different types of harmful bacteria, fungi and viruses, including:
- Acinetobacter baumannii
- Candida albicans
- Campylobacter jejuni
- Carbapenem-resistant Enterobacteriaceae (CRE)
- Clostridium difficile (including spores)
- Coronavirus (Human 229E)
- Enterobacter aerogenes
- Escherichia coli O157:H7
- Helicobacter pylori
- Influenza A (H1N1)
- Klebsiella pneumoniae
- Legionella pneumophila
- Listeria monocytogenes
- Mycobacterium tuberculosis
- Norovirus or Norwalk-like virus
- Penicilliium chrysogenum
- Pseudomonas aeruginosa
- Salmonella enterica
- Staphylococcus aureus (MRSA, E-MRSA and MSSA)
- Tubercle bacillus
- Vancomycin-resistant enterococcus (VRE)
- Vibrio cholerae
A New England Journal of Medicine article authored by van Doremalen et al. reported that Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), the newly emerged strain of coronavirus that causes COVID-19 infections, retains infectivity in aerosols and on a variety of common surfaces for extended periods of time. Most significantly, while the virus remained infective on plastic and 304 stainless steel for up to 48-72 hours, inactivation was observed in 4 hours on a 99.9% copper alloy.
Another coronavirus, Human Coronavirus 229E (Hu-CoV-229E) causes a broad spectrum of lung disorders. An article published in 2015 authored by Warnes et al.3 showed that Hu-CoV-229E remained infectious following exposure to polytetrafluoroethylene (PTFE or Teflon), polyvinyl chloride (PVC), ceramic tile, glass, silicone rubber, and stainless steel, but was rapidly inactivated on copper and on a range of copper-zinc and copper-nickel alloys. Complete loss of infectious activity was reached after as little as a 5-minute exposure, depending on the particular alloy tested. Not only was the inactivation rapid but it was accompanied by the irreversible destruction of viral RNA and massive structural damages.
van Doremalen, N. T. et al., 2020. Aerosol and surface stability of SARS-CoV-2 as compared with SARS-CoV-1. N. Engl. Jour. Med. DOI: 10.1056/NEJMc2004973
Warnes, S.L., Z.R. Little, C.W. Keevil, 2015. Human coronavirus 229E remains infectious on common touch surface materials. mBio 6:e01697-15.
While the efficacy of copper against Ebola has not been tested, copper has been shown to inactivate the two major types of viruses: those with a viral envelope covering their protective protein capsid and those without a viral envelope. Specifically, copper has been shown to inactivate both Influenza A (an enveloped virus) and norovirus (a non-enveloped virus). Testing of copper surfaces and other disinfectants with Ebola is difficult at this time due to limited access to laboratories with the required safety clearances (Biosafety Level 4).
The US Center for Disease Control and Prevention (CDC) has instructed hospitals to use disinfectants with proven efficacy against the following viruses: norovirus, rotavirus, adenovirus and poliovirus. Laboratory testing has demonstrated that copper alloys are effective against norovirus, rotavirus and adenovirus.
Based on CDC's recommendation, and proven efficacy against viruses with similar genetic structures, copper alloys are expected to inactivate Ebola virus. Strategically deployed copper surfaces within care facilities may reduce Ebola exposure from blood, urine, vomitus, stool, secretions and shed skin as it is encountered on common touch surfaces in the built environment.
The World Health Organization declared a global public health emergency in response to the rampant spread of the Zika virus, which is believed to cause serious birth defects. While no efficacy data is available, it is possible that antimicrobial copper surfaces inactivate this virus. Like Ebola, Zika is an enveloped virus. The U.S. Centers for Disease Control and Prevention (CDC) and other public health authorities consider enveloped viruses to be more sensitive than non-enveloped viruses such as norovirus. Antimicrobial copper rapidly inactivates norovirus and other non-enveloped viruses, including adenovirus and rotavirus. Thus the hierarchy of efficacy suggests antimicrobial copper may be effective against Zika.
However, Zika virus is a mosquito vector borne through bites, so the risk of transmission via touch surfaces is minimal. There have been two confirmed reports of sexual transmission, but no other routes of transmission have been identified. Even so, as the virus is carried in the blood, surface transmission could be possible if an uninfected person with an open wound came into contact with infected blood deposited on a surface. However, there has been little research on this. If Zika is eventually shown to be transmitted in other bodily fluids, then environmental surface transmission may become a factor.
Reference: Inactivation of Norovirus on Dry Copper Alloy Surfaces. Warnes, S.L., Keevil, C.W. PLOS One, September 2013, Vol. 8, Issue 9.
No, copper alloys also do. Tests have been performed on pure copper, high coppers, brasses, bronzes, copper-nickels and copper-nickel-zincs (sometimes referred to as nickel silvers because of their shiny white color, even though they contain no silver).
Alloys with higher copper content inactivate organisms faster but, as a general rule, alloys with >60% copper have good efficacy.
When choosing a copper alloy for a product it is important to balance the requirements for mechanical properties, manufacturing process and, of course, color. Copper alloys provide a palette of attractive colors from the yellow of brasses to the dark browns of bronzes and silver/white shades of nickel silvers.
Copper's rate of microbial inactivation can be affected by temperature, copper content of alloy, the type of microorganism with which it is in contact and the type of contamination event - be it a touch, sneeze or wipe. While some laboratory tests can differentiate the differences between alloys, no differences are discernible in the dynamic clinical environment. Clinical studies demonstrate the continuous and effective activity of both copper and copper alloys over many years.
No, the antimicrobial property of copper is intrinsic to the metal. This means the antimicrobial efficacy remains throughout the lifetime of a product - it never wears away or becomes depleted from the surface, unlike a coating. In order to maintain antimicrobial effectiveness, oils, waxes, glosses, paints and other coatings must NOT be applied.
While coatings and platings may initially display antimicrobial characteristics, they are susceptible to wear and any surface damage may not only remove the active copper coating but may introduce scratches, which can harbour germs. Surfaces made from solid copper or copper alloys are antimicrobial through and through. There are concerns over durability and long-term efficacy of platings and coatings.
Has copper been tested in clinical trials?
Yes, copper surfaces have been proven to harbour greater than 80% less bacterial contamination than conventional touch surfaces in hospital trials around the world.
In the UK, Selly Oak Hospital, Birmingham—part of University Hospitals Birmingham NHS Trust—was selected to be the test center for this new approach to infection prevention.
The first paper from the trial reported that copper is antimicrobial in a busy ward situation and that copper-containing surfaces had >90% less bacterial contamination than controls made from conventional materials. The results have been confirmed in a subsequent, prolonged study at Selly Oak, published in Infection Control and Hospital Epidemiology. Furthermore, in order to assess for resistance, survival of isolates of VRE, MSSA, MRSA, and coliforms was assessed by a carrier test. No resistance to copper was observed.
Other trials have taken place, or are under way, in Chile, China, Finland, France, Germany, Greece, India, Japan, Poland, South Africa, Spain and the US.
In the Department of Defense-funded US trials, carried out in ICU rooms at three hospitals, the aim was to not only determine the efficacy of antimicrobial copper in reducing the level of pathogens, but whether such a reduction would translate into a lower rate of infection. Researchers at the three hospitals involved in the trial—Memorial Sloan Kettering Cancer Center in New York, the Medical University of South Caroline and the Ralph H Johnson VA Medical Center, both in Charleston, South Carolina—replaced commonly touched items such as bed rails, over-bed tray tables, nurse call buttons and IV poles, with antimicrobial copper versions.
Rooms with copper surfaces demonstrated an 83% reduction in average microbial bioburden compared to controls, better than the level achieved by 'terminal' cleaning: the regimen conducted after each patient vacates a room.
Furthermore, the initial results demonstrated that the use of antimicrobial copper surfaces in intensive care unit rooms resulted in a 58% reduction in the risk of acquiring a hospital infection.
Has any independent official body verified copper's antimicrobial efficacy?
Yes. On February 29, 2008, the US Environmental Protection Agency (EPA) registered 275 copper alloys with public health claims. Additional alloys have since been registered, bringing the total number of registered alloys to more than 450. Copper is the only solid metal to be granted this registration, which applies solely to the supply and marketing of products in the US.
Registration of copper and certain copper alloys such as brass and bronze means that the EPA recognises these solid materials' antimicrobial properties. Products made from any of the registered alloys are legally permitted to make public health claims in the US.
Under EPA guidelines a public health claim relates to the control of organisms that pose a threat to human health. Public health claims must be supported by extensive testing under EPA protocols in an independent laboratory that adheres to OECD (Organisation for Economic Cooperation and Development) Good Laboratory Practice guidelines.
Laboratory studies conducted under EPA-approved protocols have proven copper's ability to inactivate, within 2 hours of contact time, more than 99.9% of the following disease-causing bacteria: Staphylococcus aureus, Enterobacter aerogenes, Escherichia coli O157:H7 (E. coli O157:H7), Pseudomonas aeruginosa, Vancomycin-resistant Enterococcus faecalis (VRE) and methicillin-resistant Staphylococcus aureus (MRSA). MRSA is sometimes referred to as a 'superbug'.
When cleaned regularly...
- Antimicrobial copper, brass and bronze surfaces kill greater than 99.9% of bacteria within 2 hours of exposure.
- Antimicrobial copper, brass and bronze surfaces achieve continuous antibacterial action and remain effective in killing more than 99.9% of bacteria even after repeated contamination.
- Antimicrobial copper, brass and bronze surfaces remain effective in killing greater than 99.9% of bacteria within 2 hours, even after repeated wet and dry abrasion and re-contamination.
- Antimicrobial copper, brass and bronze surfaces help inhibit the buildup and growth of bacteria within 2 hours of exposure between routine cleanings.
Note: These claims apply only to uncoated copper and copper alloys. Copper alloys are a supplement to, not a substitute for, standard infection control practices.
How can copper improve patient safety?
The use of copper and copper alloys for frequently touched hospital surfaces such as door and furniture hardware, bed rails, IV poles, dispensers, taps, light switches and work stations can help reduce the amount of disease-causing microbes in hospitals. Copper alloy surfaces have been shown to reduce microbial contamination in between routine cleaning and disinfection, making them a useful additional measure to improve hygiene. Data from the US ICU study indicates an associated and significant reduced risk of infection.
Bacteria – including those with antibiotic-resistance – can survive on surfaces for hours, days, even months. From there, they can be transferred by touch, spreading to other surfaces, or to people, and causing infections. Surfaces can also serve as a pool of bacterial species between which genetic material can be transferred, including the genes for antibiotic resistance. The process by which this occurs is called horizontal gene transfer (HGT).
HGT in bacteria plays an important role in the evolution of antibiotic-resistance, which has led to an increasing number of difficult-to-treat healthcare-associated infections. Research shows that, while HGT can take place in the environment – on frequently-touched surfaces such as door handles, trolleys and tables from stainless steel – copper prevents this process from occurring by rapidly inactivating bacteria on contact and destroying plasmid and genomic nucleic acid. In this way, copper can help prevent the spread of infections caused by antibiotic-resistant bacteria and reduce the development of antibiotic resistance between bacterial species.
Copper is already an active ingredient in many different types of antimicrobial products, in agriculture, in marine environments, in healthcare environments and in the home. Copper is an active ingredient in antiplaque mouthwashes, toothpastes and medicines. Copper sink strainers and scourers for pots and pans can help prevent cross-contamination in the kitchen. Now copper and copper alloy touch surfaces have also been installed in hospitals across the world.
In addition to antimicrobial copper for frequently touched surfaces in hospitals, those materials may be used in other settings where transmission of infection could occur, such as care homes, ambulances, gyms, schools, public buildings, public transport, cruise ships and offices.
In today's modern buildings, the concern about exposure to toxic microorganisms has created a priority need to improve hygienic conditions of heating ventilation and air conditioning (HVAC) systems, which are believed to be factors in over 60% of all sick building situations (e.g. aluminium fins in HVAC systems have been demonstrated to be sources of significant microbial populations).
In immuno-compromised individuals, exposure to toxic microorganisms from HVAC systems can result in severe infections, possibly leading to death. Several papers indicate copper inactivates many pathogens commonly found in HVAC systems, and a US field study - in which heat exchangers were replaced in each of two near-identical army barracks - concluded that copper can be helpful in controlling the emission of fungi from HVAC systems and limiting contamination of system components.
The number of foodborne infections suggests that governmental hygiene programmes and industry self-monitoring are insufficient to protect the quality of the world's food supplies. An extensive body of academic research has shown that hygienic copper alloy contact surfaces can be used for dry food contact and touch surfaces to help reduce the incidence of cross-contamination of dangerous foodborne pathogens, such as E. coli O157:H7, Campylobacter jejuni, Listeria monocytogenes, Salmonella enteriditis, and MRSA, at food-processing facilities. Copper has an intrinsic ability to inactivate these dangerous microbes quickly at both refrigerated temperature (4°C) and at room temperature (20°C).
How does copper inactivate pathogens?
Copper is an essential nutrient for humans as well as bacteria but, in high doses, copper ions can cause a series of negative events in bacterial cells. The exact mechanism by which copper inactivates bacteria is still being studied, however several theories exist. These include:
- Causing leakage of potassium or glutamate through the outer membrane of bacteria
- Disturbing osmotic balance
- Binding to proteins that do not require copper
- Causing oxidative stress by generating hydrogen peroxide
Laboratory tests have demonstrated that copper alloys inactivate 99.9% of MRSA within two hours. This test simulates a wet contamination incident such as a sneeze or splash. The latest research shows that in a test which simulates a dry contamination event, such as a touch, 10 million colony forming units of Vancomycin Resistant-Enterococcus are eliminated in less than 10 minutes.
No, copper starts to have its antimicrobial effect immediately. The times stated are for scientific tests carried out under strictly controlled and reproducible conditions and therefore state the times for total elimination in a particular set of conditions. In these tests, an extremely high challenge of bacteria is used, many orders of magnitude higher than would be encountered in a real clinical situation. When the 'wet' tests are repeated using lower doses of contamination, total elimination of, e.g. MRSA, takes as little as 15 minutes. In laboratory tests closely simulating a dry touch, inactivation times have been demonstrated at under five minutes for typical levels of contamination.
This is highly unlikely for three reasons:
- Copper is naturally present in the earth's crust and, to date, no resistant organisms have been demonstrated. Copper-tolerant organisms do exist but even these die on contact with copper surfaces. In comparison, resistance to penicillin by certain bacterial species began to appear within 30 years of its introduction.
- Copper inactivates microorganisms by multiple pathways rather than by acting in a specific way on one receptor like most antibiotics.
- Microorganisms are inactivated before they can replicate, thus they cannot pass on genetic material which could ultimately lead to the development of resistance.
Copper and copper alloy products are antimicrobial through and through. Even when surfaces made of these materials are scratched, their antimicrobial efficacy continues to work - they won't wear away like coatings or other treatments can. Copper alloys are the only solid metals with an EPA public health product registration.
No. Comparative antimicrobial efficacy studies have been conducted on copper, aluminium, stainless steel, PVC and polyethylene. While it has been clearly demonstrated that copper is able to inactivate microbes quickly and effectively, there is no evidence that aluminium, stainless steel, PVC or polyethylene exhibit antimicrobial properties.
In Professor Bill Keevil's Southampton tests, polymeric coatings impregnated with silver particles behave in the same way as the stainless steel control at ambient temperature and humidity i.e. they show no antimicrobial effect. Many silver-containing antimicrobial coatings use a Japanese Industrial Standard to test for antimicrobial efficacy. However, the test conditions of the Japanese standard are highly unrepresentative of conditions typically found in healthcare facilities.
The Japanese standard is a 24 hour test at 37°C and greater than 90% relative humidity. Additionally, a plastic film is pressed over the sample to retain humidity. Under these test conditions, silver-containing coatings do exhibit notable antimicrobial performance. This is largely influenced by the excess moisture available to participate in ion-exchange reactions required to release silver-ions to combat microorganisms. However, as Keevil demonstrated, when the temperature and humidity are decreased to typical indoor levels, the coatings have no antimicrobial effect and are indistinguishable from the stainless steel control. All copper alloys tested were effective under all tested conditions.
A separate study by Dr Harold Michels confirmed Professor Keevil's findings. Dr Michels tested the antimicrobial efficacy of various copper alloys and a silver-containing coating on stainless steel against MRSA under the temperature and humidity conditions prescribed by the Japanese Industrial Standard, and under temperature and humidity conditions typically found in indoor facilities (20°C and 20-24% relative humidity). At 90% relative humidity and 35°C, all the materials inactivated more than 99.9999% of MRSA. At 90% relative humidity and 20°C, similar results were obtained. At 20% relative humidity and 35°C, a reduction greater than 99.9999% is observed on all copper alloys; however, on the coated stainless steel no reduction of MRSA was achieved.
The results at 24% relative humidity and 20°C are very similar. A reduction greater than 99.9999% is achieved on all copper alloys, while the reduction on the stainless steel coated with a silver-containing antimicrobial coating is less than 20%. Sterling silver is an effective antimicrobial but lacks the mechanical properties and alloying capabilities for most touch surface applications and would, of course, be prohibitively expensive.
Yes, PROJ-NMX-W-163-SCFI-2013 COPPER AND COPPER ALLOY PRODUCTS - ANTIMICROBIAL CHARACTERISTICS - SPECIFICATIONS AND TEST METHODS is a Mexican Standard, published in January 2014. Other national standards bodies are working on the development of appropriate test standards. AFNOR is planning on publishing a dry-touch contamination simulation test standard in Q2 2019.
If copper inactivates pathogens, does that mean it doesn't need cleaning?
No, copper alloy products will need to be cleaned in the same way as other touch surfaces, to remove dirt and grime that can prevent contact with the copper surface. Prescribed hygienic practices for the cleaning of touch surfaces, along with hand-washing, are the first lines of defence and copper alloy surfaces are a supplement to, and not a substitute for, standard infection control and hygienic practices. Copper alloy products are active 24/7 and help reduce microbial contamination in between cleans.
The usual cleaning materials used in hospitals are fine for use on copper and even bleach-containing solutions can be used as long as items are washed down afterwards as described in the current NHS cleaning guidelines. Such cleaning is sufficient to maintain antimicrobial efficacy. Polishing with metal cleaners need only be considered if maintenance of a bright finish is required.
Will copper and copper alloy surfaces change color over time?
Copper and copper alloy surfaces naturally oxidise and darken over time. The amount of time needed for a color change to occur depends on the alloy and exposure conditions. In typical indoor exposure, appreciable color changes can take many years to develop. The brass push plates on the main entrance to the Selly Oak test ward in Birmingham did not darken in 36 months. A range of color stable copper alloys with antimicrobial efficacy is available with a palette of colors from which to select, including those with a silver appearance.
No. In fact, studies show that as uncoated copper, brass and bronze surfaces oxidise, or darken, they become more effective at eliminating disease-causing bacteria.
No. Material costs are only a small part of a product's price, so only equipment with high material cost or high labour input will be more expensive. No coatings or platings are required and this saves costs and the environment too. Specifiers should also consider that antimicrobial copper components will be effective against microbes around the clock, providing potentially life-saving protection 24/7. Copper products also help to deliver eco-design in that they can be fully recycled at the end of their long and useful lives, without any loss of properties.
Professor Tom Elliott, leader of the Selly Oak research, has stated that 'the one-off cost of fitting out the trial ward (a 20-bed general medical ward) was equivalent to the cost of just one-and-a-half infections.'
Based upon data on reduction in HAI risk from the multi-site US copper clinical trial, component cost data from recent antimicrobial copper installations in European hospitals, and published cost of care figures for the UK, upgrading an ICU as part of a new build or planned refurbishment achieves payback in less than two months. Ongoing cost savings of an antimicrobial copper installation will also accrue from the reduction in blocked beds and better-directed staff resources.
If microbes die on copper, is it safe?
Yes, copper, brass and bronze surfaces are safe and long lasting. The copper industry initiated a Voluntary Risk Assessment for copper. The assessment process was agreed with the Italian Government's Istituto Superiore di Sanità, acting as the review country on behalf of the European Commission and the EU Member States. The risk assessment has now been completed and one of the main conclusions, accepted by the European Commission and EU Member State experts, is 'the use of copper products is in general safe for Europe's environment and the health of its citizens.'
Copper is also an essential micronutrient in the human diet, along with zinc and iron. An adult needs 1mg of copper every day. Foods rich in copper include chocolate, nuts and seeds. A balanced diet should provide enough copper to avoid a copper deficiency.
No. Copper has been used for coinage - which is regularly handled - for centuries. In fact, copper plays an important role in maintaining and improving skin health and dermatologists have developed numerous skin creams that use copper as an anti-ageing or anti-oxidant agent.
Some individuals can become sensitised to nickel and develop allergic contact dermatitis (ACD) when their skin comes into direct and prolonged contact with nickel or chrome-plated articles or some alloys in consumer applications such as jewellery, watches and eyeglasses. In the European Union, there is a nickel release limit for such items in close contact with the skin. This does not apply to nickel used in copper alloys for coins or touch surfaces, which are only handled transiently.
Is there enough copper to equip all our hospitals?
Yes. Based on the latest knowledge on geological availability and continuous industry innovation, there are good reasons to believe that copper will continue to be a vital and positive contributor to society well into the future. Since 1950, according to US Geological Survey data, there has always been, on average, around 40 years of copper reserves and over 200 years of resources left. This reflects the timeframes, technological advances and evolving economics of mining. In addition, 35% of global demand is met from recycling.
* Laboratory testing shows that, when cleaned regularly, Antimicrobial CopperTM kills greater than 99.9% of the following bacteria within 2 hours of exposure: VRE, MRSA,Staphylococcus aureus, Enterobacter aerogenes,Pseudomonas aeruginosa, and E. coli O157:H7. Antimicrobial Copper surfaces are a supplement to and not a substitute for standard infection control practices and have been shown to reduce microbial contamination, but do not necessarily prevent cross contamination; users must continue to follow all current infection control practices. Michels et al, Lett Appl Microbiol, 49 (2009) 191-195 demonstrated that Antimicrobial CopperTM outperforms two commercially available silver-containing coatings under typical indoor conditions.