Copper-silver ionization is an industrial control and prevention process, approved by the U.S. Environmental Protection Agency (as per its Safe Water Drinking Act Lead and Copper Rule limits), against infections of Legionella, the bacteria responsible for legionellosis (Legionnaires' disease).
Copper-silver ionization is a dispersive process that introduces long-lived, stable, positively charged copper and silver ions into the water system. The ions bond electrostatically with negative sites on bacterial cell walls and denature proteins. Over the long term, ionization thus disperses and destroys biofilms and slimes that can harbor Legionella, the bacteria responsible for legionellosis (Legionnaires' disease). Complete control of a water system can take 30 to 45 days. Flow cells should be cleaned periodically to maintain the system; in a hospital, this task can be delegated to the facility's utility engineers.
Forensic scientist Randy Fornshell of the Sedgwick County Regional Forensic Science Center explains that copper-silver ionization is a modern implementation of the ancient Greek practice of reducing bacteria in wine vessels by lining them with silver, and controlling algae and fungi with copper. Fornshell notes that copper-silver ionization has been effective in swimming pools (it is an alternative to chlorine) and is becoming adopted by larger municipalities.
Replacing chlorination with copper-silver ionization to keep water safe was one response of Frederick Memorial Hospital, Frederick, Maryland, to new requirements in the 2001 Guidelines for Design and Construction of Hospital and Healthcare Facilities, issued by the American Institute of Architects. Ionization is in many cases installed because more convenient and cost-effective than other approaches.
Ionization is an effective industrial control and prevention process to eradicate Legionella in potable water distribution systems found in health facilities, hotels, nursing homes and most large buildings. In 2003, ionization became the first such hospital disinfection process to have fulfilled a proposed four-step modality evaluation; by then it had been adopted by over 100 hospitals. Additional studies indicate ionization is superior to thermal eradication.
A 2011 study by Lin, Stout and Yu  evaluating 79 research papers found Copper-Silver ionization to be the only Legionella control technology which has been validated through a proposed four-step modality evaluation.
Copper silver ionization technology is recognized by the WHO, the U.S. Environmental Protection Agency (EPA) to control Legionella within potable water distribution networks found in hospitals, hotels and other large type facilities. The level of ions generated has been reported to be usually below EPA Safe Water Drinking Act Lead and Copper Rule limits. EPA-approved levels of copper or silver in potable water are 1.3 ppm (Cu) and 0.1 ppm (Ag). Suboptimal timing of specimen shipment for testing at reference laboratories may contribute to silver concentration above recommendations. Industry leaders who manufacture copper silver ionization technology recommends copper concentration of 0.4 to 0.8 ppm and silver at 40 to 60 ppb, as compliant with EPA drinking water standards.
The British Health and Safety Commission regulates U.K. ionization, advising regular system monitoring to ensure ions reach all water circuits. Also, copper in drinking water is limited to 2 ppm (mg/L) by the European Community whereas Legionella control only requires 0.4 to 0.8 ppm in concentration...well below the permissible limits. Headquarters (ECH) in Brussels, Belgium, and silver is not prescribed by the ECH.
USA maximum copper limits for potable water is set at 1.3 ppm whereas EU limitations is 1.0 ppm. Silver limits in the USA is set at 0.1 ppm (100 ppb) yet the EU does not have any guidelines for ionic silver concentrations.
The European Commission in February 2012 issued a non-inclusion decision regarding the use of Copper as a biocide in Europe. This decision was based on a failure of industry to supply the commission with required information regarding Copper and was not based on health or efficacy concerns. In response to this decision 5 member states to date,Spain, the UK, Norway, Poland and the Netherlands have applied to the Commission to allow for the continued use of Copper as a biocide in their respective nations. In addition the UK authourity, the HSE has issued a statement stating that the derogation applicaiton for the UK has been informally granted. Industry has responded by forming a Taskforce to ensure full and long term compliance with the regulatory issues facing Copper in the EU.
- Hayes 2001.
- Stout & Yu 2003 "(1) Demonstrated efficacy of Legionella eradication in vitro using laboratory assays, (2) anecdotal experiences in preventing legionnaires’ disease in individual hospitals, (3) controlled studies in individual hospitals, and (4) validation in confirmatory reports from multiple hospitals during a prolonged time."
- Shields 2002.
- Knapp 2008.
- Sheerin 2003.
- Block 2001.
- Lin, Stout & Yu 2011.
- Yusen E. Lin, PhD, MBA; Janet E. Stout, PhD; Victor L. Yu, MD (2011-2). "Controlling Legionella in Hospital Drinking Water: An Evidence-Based Review of Disinfection Methods". Infection Control and Hospital Epidemiology. 32, no.2 (2).
- Hayes, John (December 2001). "Copper/silver ionization gaining approval". Professional Carwashing & Detailing 25 (12). Retrieved 2009-03-02.
- Stout, Janet E., PhD; Yu, Victor L., MD (August 2003). "Experiences of the First 16 Hospitals Using Copper-Silver Ionization for Legionella Control: Implications for the Evaluation of Other Disinfection Modalities". Infection Control and Hospital Epidemiology 24 (8): 563–568.
- Knapp, Adam (2008-01-25). "Chemist claims water purifying system can save money, health problems". Wichita Business Journal. Retrieved 2009-03-06.
- Shields, Todd (2002-03-01). "Hospitals turn to ionization method for controlling Legionella infections (What Works)". Healthcare Purchasing News. Retrieved 2009-03-06.
- Sheerin, Michael, PE (2003-09-01). [tt_news=20399 "Go with the Flow: Midstream Design Changes"]. Consulting-Specifying Engineer. Retrieved 2009-03-02. "Note about link: URL uses improper characters."
- Block, Seymour Stanton (2001). Disinfection, Sterilization, and Preservation (5th ed.). Lippincott Williams & Wilkins. pp. 423–424. ISBN 978-0-683-30740-5. Retrieved 2009-03-02.
- Beoordelingsrichtlijn: Kiwa Netherlands National Guideline BRL. blr-k14010-2/10. 2009-02-24.