FAQs

Q What is meant by 'antimicrobial'?

A 'Antimicrobial’ is the ability of a substance to kill or inactivate microbes, such as bacteria, fungi (including moulds) and viruses.

Q Does copper have antimicrobial properties?

A Yes. Man has exploited the natural antimicrobial properties of copper since the dawn of civilisation. It has been demonstrated clearly in many scientific studies conducted over several decades that copper inactivates some of the most toxic species of bacteria, fungi and viruses.

Q Which microbial pathogens can copper inactivate?

A The scientific literature cites the efficacy of copper to inactivate many different types of harmful microbes, bacteria, fungi and viruses, including:

• Aspergillus niger
• Candida albicans
• Campylobacter jejuni
• Clostridium difficile
• Escherichia coli O157:H7
• Enterobacter aerogenes
• Influenza A (H1N1)
• Legionella pneumophilia
• Listeria monocytogenes
• MRSA
• Poliovirus
• Pseudomonas aeruginosa
• Salmonella enteriditis
• Staphylococcus aureus
• Tubercle bacillus

Q How is copper currently used as an antimicrobial agent?

A 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.

Q Can copper metal and alloy surfaces inactivate microbes?

A Yes. Extensive experimental studies conducted over the past few years have confirmed that copper and certain copper alloys inactivate pathogenic microbes on contact, both at room and chill temperatures.

Q How does copper kill pathogens?

A 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 kills bacteria is still unknown, however several theories exist and are being studied. They include:

• Cause leakage of potassium or glutamate through the outer membrane of bacteria
• Disturb osmotic balance
• Bind to proteins that do not require copper
• Cause oxidative stress by generating hydrogen peroxide.

Q Is it just pure copper that has an antimicrobial effect?

A No, copper alloys do too. Tests have been performed on pure copper, high coppers, brasses, bronzes, copper-nickels and copper-nickel-zincs. The latter are sometimes referred to as nickel silvers because of their shiny white color, even though they contain no silver. In the US, the EPA has registered 282 antimicrobial copper alloys with nominal copper content down to 60%. Alloys with higher copper content kill organisms faster. When choosing a copper alloy for a product it is important to balance the requirements for mechanical properties, manufacturing process and, of course, colour. Copper alloys provide a palette of attractive colours from the yellow of brasses to the dark browns of bronzes.

Q Has copper been tested in clinical trials?

A Yes, clinical trials are currently under way at hospitals around the world where the impact of copper touch surfaces on the amount of microbes in the hospital environment is being assessed. In the UK, Selly Oak Hospital, Birmingham, which is part of University Hospitals Birmingham NHS Foundation Trust, was selected to be the test centre for this new approach to infection prevention as both Professors Tom Elliott and Peter Lambert have considerable expertise and an international reputation regarding the interaction between bacteria and surfaces in the clinical environment. The first results from the trial, presented at the Interscience Conference on Antimicrobial Agents and Chemotherapy in Washington, October 2008, showed conclusively that copper is antimicrobial in a real ward situation and that copper-containing surfaces had 90-100% less bacterial contamination than controls made from conventional materials. Other trials are under way in Germany, Chile, Japan and the US, where the Department of Defense is funding a three-centre trial.

Copper for Preventing Microbial Environmental Contamination
A L Casey, P A Lambert, L Miruszenko, T S J Elliott. Poster presented at the Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC), October 2008.

Q If copper inactivates pathogens, does that mean it doesn’t need cleaning?

A 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 sterilisation 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 to reduce microbial contamination between cleans.

Q How should copper and copper alloy components and surfaces be cleaned?

A 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.

Q Will copper and copper alloy surfaces change colour over time?

A Copper and copper alloy surfaces naturally oxidise and darken over time. The amount of time needed for a colour change to occur depends on the alloy and exposure conditions. In typical indoor exposure, appreciable colour changes can take many years to develop. The brass push plates on the main entrance to the Selly Oak test ward have not darkened in 12 months.

Q Does oxidation (darkening) deter copper’s antimicrobial effect?

A 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.

Q Different announcements state that copper inactivates MRSA in 45 minutes or 2 hours. Does this mean that there is a delay in the antimicrobial effect?

A 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 tests are repeated using lower doses of contamination, total elimination of, eg, MRSA, takes as little as 15 minutes.

Q How does copper compare to silver in antimicrobial efficacy?

A In Professor 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 obtain efficacy data. 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 degrees Celsius 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 micro-organisms. 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 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 of the materials killed 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 99.999% 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 99.999% 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.

Q If copper reduces microbes, is it safe?

A Yes, copper, brass and bronze surfaces are safe and long lasting. In fact copper is 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.

Q Will copper products be much more expensive than the products that they replace?

A No. Material costs are only a small part of a product’s cost. Copper and copper alloys are easy and therefore cost-effective to form into components. No coatings or platings are required either and this saves costs too. Copper will be effective against microbes round the clock, 24/7. While coatings are fragile and wear out over time, the antimicrobial properties of copper, brass and bronze are integral to the metal and last the lifetime of the product. 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.

Q Are the antimicrobial copper surfaces coated?

A No, the antimicrobial property of copper is intrinsic to the metal. In order to maintain antimicrobial effectiveness, oils, waxes, glosses, paints and other coatings must NOT be applied.

Q Are copper platings and coatings effective too?

A Yes, in limited situations, but some words of caution: coatings are susceptible to wear and tear 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. Careful consideration should therefore be given to the intended use and likely abuse of a product. In the US, copper-coated surfaces are not registered by the EPA as antimicrobial public health products.

Q What is MRSA?

A MRSA is the acronym for meticillin-resistant Staphylococcus aureus. It is a virulent bacterium that is resistant to broad spectrum antibiotics and therefore very difficult to treat. It is a common source of infection in hospitals and is increasingly being found in the community as well. According to the United States Centers for Disease Control and Prevention (CDC), MRSA can cause serious, potentially life-threatening infections.

Q What is Clostridium difficile?

A Clostridium difficile infection ranges from mild to severe diarrhoea to, more unusually, severe inflammation of the bowel (known as pseudomembranous colitis). People who have been treated with broad spectrum antibiotics, people with serious underlying illnesses and the elderly are at greatest risk – over 80% of Clostridium difficile infections reported are in people aged over 65 years. Clostridium difficile infection is usually spread on the hands of healthcare staff and other people who come into contact with infected patients or with environmental surfaces (e.g. floors, bedpans, toilets) contaminated with the bacteria or its spores. Spores are produced when Clostridium difficile bacteria encounter unfavourable conditions, such as being outside the body. They are very hardy and can survive on clothes and environmental surfaces for long periods.

Q How can antimicrobial copper benefit the public?

A The use of copper and copper alloys for frequently touched hospital surfaces such as door and furniture hardware, bed rails, IV poles, nurses’ call buttons, dispensers, taps, sinks and work stations can help reduce the amount of disease-causing bacteria in patient rooms.

Q Where can antimicrobial copper be used?

A In addition to antimicrobial copper alloys for frequently touched surfaces in hospitals, those materials may be used in other settings such as care homes, ambulatory care facilities, offices, schools, gyms and public housing.

Q How can copper be used in air handling systems to improve indoor air quality by reducing airborne pathogens?

A 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., aluminum 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. There are several papers indicating that copper kills many pathogens commonly found in HVAC systems and clinical trials are underway in the U.S. to test the hypothesis that copper HVAC components will help improve indoor air quality.

Q How can copper be used in food processing operations to eliminate foodborne pathogens?

A 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. Hygienic contact surfaces, such as copper and copper alloys, can help to 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 operations. Copper has an intrinsic ability to kill these dangerous microbes quickly at both refrigerated temperature (4°C) and at room temperature (20°C).

Q Is there enough copper to equip all our hospitals?

A Copper extraction technology undergoes development to improve efficiency and so make even low concentration ores economic to mine. This, combined with increased recycling will ensure there is enough copper to meet demand.

Q Won’t microorganisms develop resistance to copper?

A 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.
• Copper kills microorganisms by multiple pathways rather than by acting in a specific way on one receptor.
• Microoganisms are killed before they can replicate, thus they cannot pass down genetic material which would ultimately allow it to evolve and develop resistance.