Antimicrobial. is the ability to inactivate microbes, such as bacteria, fungi and viruses.

Yes. It has been demonstrated clearly in many studies conducted over several decades that copper inactivates some of the most toxic species of bacteria, fungi and viruses.

No. Comparative antimicrobial efficacy studies have been conducted on copper, aluminum, stainless steel, PVC and polyethylene. While it has been clearly demonstrated that copper is able to eradicate microbes quickly and effectively, there is no evidence at all that aluminum, stainless steel, PVC or polyethylene exhibit any antimicrobial properties.

The scientific literature cites the efficacy of copper to kill many different types of harmful microbes, including

• Actinomucor elegans,
• Aspergillus niger,
• Bacterium linens,
• Bacillus megaterium,
• Bacillus subtilis,
• Brevibacterium erythrogenes,
• Candida utilis,
• Candida albicans,
• Penicillium chrysogenum,
• Rhizopus niveus,
• Saccharomyces mandshuricus,
• Saccharomyces cerevisiae,
• Torulopsis utilis,
• Tubercle bacillus,
• Achromobacter fischeri,
• Photobacterium phosphoreum,
• Paramecium caudatum,
• Poliovirus,
• Proteus,
• Escherichia coli,
• Staphylococcus aureus and Streptococcus Group D.

In recent years, antimicrobial efficacy studies on various contact surfaces have clearly demonstrated that copper and certain copper alloys can readily eradicate several of the most potent types of microbes, including

• Escherichia coli O157:H7,
• Listeria monocytogenes,
• Campylobacter jejuni,
• Salmonella enteriditis,
• Legionella pneumophilia,
• Methicillin-resistant Staphylococcus aureus (MRSA) the antibioticresistant superbug, Enterobacter aerogenes,
• Pseudomonas aeruginosa,
• Influenza A (H1N1).

The exact mechanisms for copper.s antimicrobial effect are still unknown and the subject of on-going research. Several distinct mechanisms are hypothesised and believed to act simultaneously. A critical factor believed to be responsible for copper's antimicrobial properties is copper's ability to readily accept or donate electrons. This electro-chemical property enables copper to participate in chemical reactions (Fenton-like reactions) that cause oxidative damage to the cell. Further, excess copper ions bind to intracellular proteins and inhibit their function or cause protein degradation. It has also been observed that copper is responsible for lesions in the cell wall, causing leakage of essential cellular components. These and other mechanisms are hypothesised to be why copper inactivates many types of bacteria, fungi and viruses and are the subject of ongoing studies.

Under specific conditions, copper can inactivate microbes or prevent their further growth. Its efficacy and rate of microbial inactivation are dependent on temperature, copper ion concentration and the type of microorganism with which it is in contact. Under optimal conditions, survival rates of 0% have been achieved for certain microbes when they have been in contact with copper. Scientific investigations have proven the efficacy of copper and copper alloys as hygienic, antimicrobial materials capable of controlling pathogenic microbes in various environments.

Copper is an active ingredient in many different types of antimicrobial products. In agriculture, copper sulphate, copper-8-quinolate, copper octoate, nanocopper oxide, alkaline copper quat and copper azole are used to fight fungi in crops, textiles and wood. In marine environments, copper-based paints and copper sheathing on boats and offshore platforms exhibit potent antifouling properties. In healthcare environments, copper incubators resist microbial growth, and copper chloride solutions have antimicrobial efficacies similar to disinfection and sterilization chemicals used in the medical-devices industry. For consumers, 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.

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.

For example, the Keevil (2000) study and others show that at 20°C (room temperature) E. coli O157 perish completely on copper in just 4 hours. On stainless steel, these toxic bacteria remained viable for 34 days. At 4°C (chill temperature), E.coli O157 are completely inactivated on copper in just 14 hours. On stainless steel, however, the bacteria continue to be viable for several months. The antimicrobial efficacy and rate of inactivation of microbes by contact with copper alloys generally increases with the copper content of the alloy.

For example, at room temperature, MRSA are completely eliminated within 1½ hours on a 99% copper alloy and within 3 hours on an 80% copper alloy. They are significantly reduced within 4½ hours on a 55% copper alloy. On stainless steel, however, MRSA are able to persist and remain viable in dried deposits for up to 72 hours (three days). Survival rates of Listeria monocytogenes on copper, brass and high-silicon bronze are limited to 60 minutes at room temperatures. Alloys of lower copper content, such as copper-nickel and nickel silver, are able to eliminate Listeria monocytogenes in 70 to 85 minutes. On stainless steel, Listeria monocytogenes can survive for several days. Salmonella enterica and Campylobacter jejuni populations are also inactivated when in contact with copper. Populations of both these microbes are reduced by 99% within 4 hours of contact at 25°C. This research holds promise also for the potential role of copper in helping to reduce the incidence of infection from airborne pathogens in Hospital air conditioning systems, as well as the incidence of cross-contamination from dangerous foodborne, hospital-borne and community-borne pathogens.

In today's modern buildings, there is strong concern about indoor air quality and exposure to toxic microorganisms. This has created a dire need to improve hygienic conditions of HVAC systems, which are believed to be factors in over 60% of all sickbuilding situations (for example, aluminium fins in HVAC systems have been identified as sources of significant microbial populations). In immunocompromised individuals, exposure to potent microorganisms from HVAC systems can result in severe and sometimes fatal infections. The use of antimicrobial copper instead of biologically inert materials in heat exchanger tube, fins, condensate drip pans and filters is a viable and cost-effective means to help control the growth of bacteria and fungi that thrive in dark, damp HVAC systems.

Hygiene regulations 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, Campylobacter, Listeria monocytogenes and Salmonella at food-processing operations. Copper has an intrinsic ability to quickly inactivate these dangerous microbes at both refrigerated temperature (4°C) and at room temperature (20°C).

Despite enormous advances in understanding how pathogenic microbes cause illnesses and death, inadequate hygienic practices at health-related facilities have contributed towards a dramatic number of hospital-borne infections, some 300,000 each year in the UK, alone. Copper has an intrinsic ability to kill:-

• E. coli O157,
• Legionella pneumophilia,
• Staphylococcus aureus,
• Streptococcus Group D,
• Enterobacter aerogenes
• Pseudomonas aeruginosa,
• MRSA.(the deadly pathogen that has become a primary concern of healthcare administrators around the world). This strongly suggests that the replacement of touch surfaces with copper alloys at healthcare facilities can help to reduce the incidence of microbial infection due to contaminated surfaces.

Examples of products that would benefit from hygienic copper alloy touch surfaces include door handles, push plates, bedrails, bed trays, remote controls, grab rails, taps, towel bars, dispensers (soap, paper towel, alcohol gel, apron), chairs, instrument handles, equipment trolleys, intravenous poles and exercise and rehabilitation equipment.

Yes. Copper and copper alloy surfaces naturally develop a tarnish film and change colour 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.

No. Tarnishing does not deter copper's antimicrobial effect. In fact, studies show that the antimicrobial efficacy of copper and its alloys is enhanced with the development of a tarnish layer.