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How Does Copper Work?
How does copper kill 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 kills bacteria is still unknown, however several theories exist and are being studied. They include:
n Causing leakage of potassium or glutamate through the outer membrane of bacteria
n Disturbing osmotic balance
n Binding to proteins that do not require copper
n Causing oxidative stress by generating hydrogen peroxide.
How quickly do copper alloys kill MRSA?
Laboratory tests have demonstrated that copper alloys kill 99.9% of MRSA within two hours.
Does this mean that there is a delay in the antimicrobial effect?
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, e.g., MRSA, takes as little as 15 minutes.
Won't microorganisms develop resistance to copper?
This is highly unlikely for three reasons:
n 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.
n Copper kills microorganisms by multiple pathways rather than by acting in a specific way on one receptor.
n Microorganisms are killed before they can replicate, thus they cannot pass down genetic material which would ultimately allow it to evolve and develop resistance.


Copper vs Other Antimicrobial Materials
How is copper superior to other antimicrobial surfaces?
Copper and copper alloy products are antimicrobial through and through. Even when surfaces made of these materials are scratched, their antibacterial efficacy continues to work - they won't wear away like coatings or other treatments can. Copper alloys are the only solid surfaces with an EPA public health product registration.
Do aluminium, stainless steel and plastics have antimicrobial properties?
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 kill microbes quickly and effectively, there is no evidence that aluminium, stainless steel, PVC or polyethylene exhibit antimicrobial properties.
How does copper compare to silver in efficacy?
In 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 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 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 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 (20oC and 20-24% relative humidity). At 90% relative humidity and 35oC, all of the materials killed more than 99.9999% of MRSA. At 90% relative humidity and 20oC, similar results were obtained. At 20% relative humidity and 35oC, 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 20oC 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.
Cleaning
If copper kills 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 cleanings.
How should copper and copper alloy components and surfaces be cleaned?
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.
Aesthetics
Will copper and copper alloy surfaces change colour over time?
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 in Birmingham have not darkened in 36 months.
Does oxidation deter copper's antimicrobial effect?
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.
Cost
Will copper products be much more expensive than the products that they replace?
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.
Safety
If copper reduces microbes, 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 Sanita, 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.
Resources
Is there enough copper to equip all our hospitals?
Yes. 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.

Copper and Copper Alloys
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.
Where does copper come from?
Copper is refined from ore that naturally occurs in many places around the world. The five largest mining countries are Chile, the United States, Peru, Australia and Russia.
Is copper recyclable?
Copper is one of the few materials that can be recycled, time and time again, without any loss in performance. In 2008, 35% of the world's copper demand was met through recycling and it is estimated that most of the copper ever mined is still in circulation. Almost half of all recycled copper comes from building scrap and post-consumer waste, such as electric cables, plumbing installations, end of life vehicles and electronic and electrical equipment. The remainder is new scrap recovered from along the complex downstream value chain.
Is copper in food?
Copper is necessary in the human diet; the best sources for dietary copper include seafood, organ meats, whole grains, nuts, raisins, legumes and chocolate.
What are copper alloys?
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.
Are brass and bronze different?
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 colours and finishes.