Antimicrobial properties of copper, Brass/Bronze

Brass/bronze, copper are natural antimicrobial materials. Ancient civilizations were aware of these antimicrobial properties long before our research discoveries.

In 1852 Victor Burq discovered those working with copper had far fewer deaths to cholera than anyone else, and did extensive research confirming this. In 1867 he presented his findings to the French Academies of Science and Medicine, informing them that putting copper on the skin was effective at preventing someone from getting cholera.

In 1973, researchers at Battelle Columbus Laboratories conducted a comprehensive literature, technology, and patent search that traced the history of understanding the "bacteriostatic and sanitizing properties of copper and copper alloy surfaces", which demonstrated that copper, in very small quantities, has the power to control a wide range of molds, fungi, algae, and harmful microbes. It was observed for centuries that water contained in copper vessels was of better quality (i.e., no slime/contaminate formation) than water contained or transported in other materials.

Recent studies have shown that copper alloy surfaces kill E. coli O157:H7.   More than 99.9% of E. coli microbes are killed after just 1–2 hours on copper.

Too many recent studies to list have been conducted to examine bactericidal efficacies on different copper alloys to identify those alloys that provide the best combination of antimicrobial activity, corrosion/oxidation resistance, and fabrication properties.  Copper's antibacterial effect was found to be intrinsic in all of the copper alloys tested. For the most part, the bacterial kill rate of copper alloys increased with increasing copper content of the alloy.  This is further evidence of copper's intrinsic antibacterial properties.

Research on brasses also demonstrate bactericidal efficacies, but within a somewhat longer time frame than pure copper.  All nine brasses tested were almost completely bactericidal (more than 99.9% kill rate) at 20 °C within 60–270 minutes. Many brasses were almost completely bactericidal at 4 °C within 180–360 minutes.

Endless studies continue. The price of metals has increased drastically; if you noticed that your copper has tarnished, use a good metal polish to bring it back to its original shine. The best part, is that every couple of hours the brass/copper products and furniture is continually disinfected without any effort from cleaning chemicals. 

An antimicrobial surface contains an antimicrobial agent that inhibits the ability of microorganisms to grow on the surface of a material. Such surfaces are becoming more widely investigated for possible use in various settings including clinics, industry, and even the home. The most common and most important use of antimicrobial coatings has been in the healthcare setting for sterilization of medical devices to prevent hospital associated infections, which have accounted for almost 100,000 deaths in the United States. In addition to medical devices, linens and clothing can provide a suitable environment for many bacteria, fungi, and viruses to grow when in contact with the human body which allows for the transmission of infectious disease.

The host–pathogen interaction is defined as how microbes or viruses sustain themselves within host organisms on a molecular, cellular, organismal or population level. This term is most commonly used to refer to disease-causing microorganisms although they may not cause illness in all hosts. Because of this, the definition has been expanded to how known pathogens survive within their host, whether they cause disease or not.

EPA registrations

On February 29, 2008, the United States Environmental Protection Agency (EPA) approved the registrations of five different groups of copper alloys as "antimicrobial materials" with public health benefits. 

EPA test protocols for copper alloy surfaces

The registrations are based on studies supervised by EPA which found that copper alloys kill more than 99.9% of disease-causing bacteria within just two hours when cleaned regularly (i.e., the metals are free of dirt or grime that may impede the bacteria's contact with the copper surface).

To attain the EPA registrations, the copper alloy groups had to demonstrate strong antimicrobial efficacies according to all of the following rigorous tests:

• efficiency as a sanitizer : This test protocol measures surviving bacteria on alloy surfaces after two hours.
• Residual self-sanitizing activity: This test protocol measures surviving bacteria on alloy surfaces before and after six wet and dry wear cycles over 24 hours in a standard wear apparatus.
• Continuous reduction of bacterial contamination: This test protocol measures the number of bacteria that survive on a surface after it has been re-inoculated eight times over a 24-hour period without intermediate cleaning or wiping.

Claims granted by EPA in antimicrobial copper alloy registrations

The following claims are now legally permitted when marketing EPA-registered antimicrobial copper alloys in the U.S.:

Laboratory testing has shown that when cleaned regularly:

• Antimicrobial Copper Alloys continuously reduce bacterial contamination, achieving 99.9% reduction within two hours of exposure.
• Antimicrobial Copper Alloy surfaces kill greater than 99.9% of Gram-negative and Gram-positive bacteria within two hours of exposure.
• Antimicrobial Copper Alloy surfaces deliver continuous and ongoing antibacterial action, remaining effective in killing greater than 99% of bacteria within two hours.
• Antimicrobial Copper Alloys surfaces kill greater than 99.9% of bacteria within two hours, and continue to kill 99% of bacteria even after repeated contamination.
• Antimicrobial Copper Alloys surfaces help inhibit the buildup and growth of bacteria within two hours of exposure between routine cleaning and sanitizing steps.
• Testing demonstrates effective antibacterial activity against Staphylococcus aureus, Enterobacter aerogenes,Methicillin-resistant Staphylococcus aureus (MRSA), Escherichia coli O157:H7, and Pseudomonas aeruginosa

The registrations state that “antimicrobial copper alloys may be used in hospitals, other healthcare facilities, and various public, commercial and residential buildings.”

Product stewardship requirements of EPA

EPA warranty statement

The EPA warranty statement is worded as follows:

If used as intended, ANTIMICROBIAL COPPER ALLOYS are wear-resistant and the durable antibacterial properties will remain effective for as long as the product remains in place and is used as directed.

Note: With the exception of the product name and the percentage of active ingredient, the EPA-approved Master Labels for the six groups of registered alloys are identical.

Antimicrobial copper products

Many antimicrobial copper alloy products have been approved for registration in healthcare facilities, public and commercial buildings, residences, mass transit facilities, laboratories, and play area equipment in the US. A complete list of registered products is available from EPA.

See also

• Antimicrobial properties of copper
• Copper alloys in aquaculture

References

1. ↑ Zaleski, Andrew, As hospitals look to prevent infections, a chorus of researchers make a case for copper surfaces, STAT, September 24, 2020
2. ↑ Cassandra D. Salgado, Kent A. Sepkowitz, Joseph F. John, J. Robert Cantey, Hubert H. Attaway, Katherine D. Freeman, Peter A. Sharpe, Harold T. Michels, Michael G. Schmidt (2013); "Copper Surfaces Reduce the Rate of Healthcare-Acquired Infections in the Intensive Care Unit"; Infection Control and Hospital Epidemiology, May 2013
3. ↑ "Copper Surfaces Reduce the Rate of Health Care-Acquired Infections in the ICU", April 9, 2013; Science News, https://www.sciencedaily.com/releases/2013/04/130409110014.htm
4. ↑ Arendsen, LP; Thakar, R; Sultan, AH (September 18, 2019). "The Use of Copper as an Antimicrobial Agent in Health Care, Including Obstetrics and Gynecology". Clinical Microbiology Reviews. 32(4). doi:1128/CMR.00125-18. PMC   6730497 . PMID   31413046.
5. ↑ Michels, H. T. (2006), "Anti-Microbial Characteristics of Copper", ASTM Standardization News, October, pp. 28–31
6. ↑ Kramer A.; et al. (2006). "How long do nosocomial pathogens persist on inanimate surfaces? A systematic review". BMC Infectious Diseases. 6: 130. doi:1186/1471-2334-6-130. PMC   1564025. PMID   16914034.
7. ↑ Boyce J. M. (2007). "Environmental contamination makes an important contribution to hospital infection". Journal of Hospital Infection. 65(S2): 50–54. doi:1016/s0195-6701(07)60015-2. PMID   17540242.
8. 1 2 "EPA registers copper-containing alloy products". May 2008. Archived from the originalon July 14, 2008.
9. ↑ Collery, Ph., Maymard, I., Theophanides, T., Khassanova, L., and Collery, T., Editors, Metal Ions in Biology and Medicine: Vol. 10., John Libbey Eurotext, Paris, 2008; Antimicrobial regulatory efficiency testing of solid copper alloy surfaces in the U.S., by Michels, Harold T. and Anderson, Douglas G. (2008), pp. 185–190.
10. ↑ "Test Method for efficiency of Copper Alloy Surfaces as a Sanitizer", EPA
11. ↑ "Test Method for Residual Self-Sanitizing Activity of Copper Alloy Surfaces", EPA
12. ↑ "Test Method for the Continuous Reduction of Bacterial Contamination on Copper Alloy Surfaces", EPA
13. ↑ EPA databaseArchived January 10, 2010, at the Wayback Machine (To read the registrations, insert 82012 in the Company Number box.)
14. ↑ "Antimicrobial Copper Site -". www.antimicrobialcopper.com. Archived from the originalon October 17, 2012. Retrieved December 23, 2012.
15. ↑ EPA Office of Pesticide Programs; Antimicrobial Copper Alloys; List of Approved Fabricated Products; pp. 5–10; http://www.epa.gov/pesticides/chem_search/ppls/082012-00001-20130322.pdfArchived March 11, 2020, at the Wayback Machine