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Research

There has been a great deal of research into the effects of copper-silver ionization of water on a variety of bacteria and other infectious agents. Progressive makes no medical or scientific claims, but provides the following data for informational purposes only.

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Microbiological Evaluation of Copper: Silver Disinfection Units

AUTHORS: Kutz SM, Landeen LK, Yahya MT, and Gerba CP

PUBLICATION: Proceedings of the Fourth Conference on Progress in Clinical Disinfection. State University of New York, Bighamton, New York, April 11-13, 1988

PURPOSE: Although chlorination is the traditional method of disinfecting swimming pools, hot tubs, and cooling towers to prevent outbreaks of illness due to pathogenic bacteria, viruses, and protozoa, high levels of chlorine can cause eye and skin irritation was well giving rise to a noticeable chlorine odor. The authors evaluated electrolytically generated copper: silver ions alone and in combination with low levels of free chlorine as an alternative method of reducing the bacterial population in water.

MATERIALS AND METHODS:
The test medium was local well water which was subjected to chemical analysis, filtering, and pH stabilization and used at room temperature. Suspensions of the following organisms were prepared: Escherichia coli, Legionella pneumophila, Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella TYPHII, Klebsiella terrigena, and Streptococcus faecalls. Approximately 1 ml of the selected bacterial suspension was added to 99 ml of test medium containing (1) copper: silver ions in a concentration of 400 ug/liter copper to 40 ug/liter silver, (2) free chlorine (0.2 mg/liter) alone, or (3) a combination of copper: silver ions and free chlorine (quantities as above). Cultures were incubated and the bacterial colonies enumerated, after which statistical analysis were performed.

RESULTS:
The bacteria tested were inactivated more rapidly in a solution in which electrolytically generated copper and silver ions were added to low levels of chlorine than where either method was used separately. Some organisms were more resistant to treatment than others. In the experiments with Salmonella typehi and Klebsiella terrigena no viable cells were recovered after 30 seconds of exposure to either chlorine alone or to the combined regimen, indicating equal effectiveness when resistance to disinfection is low. On the other hand, Legionella pneumophilia titers decreased more than 5 log 10 values after 7 minutes of exposure to free chlorine (0.2 mg/liters) alone for the same length of time. Similarly, E. coli numbers were reduced by 4.2 log 10 by the combination regimen but by less than 3 log 10 after extended exposure to the copper: silver method without chlorine.

CONCLUSIONS:
The use of electrolytically generated copper and silver ions in combination with low levels of free chlorine proved an effective method of killing a wide range of pathogenic bacteria under controlled test conditions. Such bacteria are of potential concern in swimming pools and cooling towers.

Inactivation of Poliovirus & Bacteriophage MS-2 by Copper/Silver and Reduced Levels of Free Chlorine

AUTHORS: Landeen LK, Yahya MT, and Gerba CP
PUBLICATION REF: Publication information not available

PURPOSE OF STUDY:
Viruses tend to be more resistant than bacteria to disinfection regimes. Although chlorination is widely used to control viral contamination, high levels of chlorine promote the formation of organic compounds in water that may be hazardous to human health. An alternative method, copper and silver ion treatment, is known to be effective against bacteria and algae. The authors tested electrolytically generated copper and silver ions, alone and in the presence of reduced levels of free chlorine, in treating water sample to which either bacteriophage MS-2 or poliovirus had been added to test effectiveness against viral contamination.

MATERIALS AND METHODS:
Purified bacteriophage MS-2 and poliovirus type I were prepared by standard methods in pellet form. The viral pellets were placed in samples of filtered well water. The virus-containing samples were then exposed to one of the following treatment regimens: (1) no added disinfectant, i.e. untreated control; (2) low levels of free chlorine; (3) a combination of copper: silver with free chlorine; (4) copper: silver ions without chlorine; or (5) either copper or silver without chlorine. Experiments were performed in duplicate at room temperature. Linear regression analysis was performed to calculate the viral inactivation rates for each treatment regimen.

RESULTS:
The bacteriophage MS-2 inactivation rate for copper alone was significantly higher when the concentration reached 400 ug/liter. The MS-2 inactivation rate for electrolytically generated copper and silver ions together was greater than for either metal alone, suggesting an additive effect. Although not significant for very low levels of chlorine, the addition of 0.3 mg/liter of free chlorine to a 400/40 ug/liter copper/silver regimen significantly enhanced MS-2 inactivation rates.

Similarly for poliovirus, the activation rates achieved with the 400/40 copper/silver regimen were significantly greater as compared with untreated controls. The number of poliovirus were reduced approximately 2.5 log 10 within 72 hours. The addition of 0.3 mg/liter of free chlorine again improved the inactivation rates achieved, although in this case the improvement did not reach statistical significance. Poliovirus showed greater resistance to inactivation by any means tested than did bacteriophage MS-2.

CONCLUSIONS:
Electrolytically generated copper and silver ions demonstrate efficacy against bacteriophage MS-2; further improvement occurs with the addition of reduced levels of free chlorine. The same regimen is capable of inactivating an enteric virus such as poliovirus in the presence or absence of free chlorine. The same regimen is capable of inactivating an enteric virus such as poliovirus in the presence or absence of free chlorine. Therefore, a regimen in which copper: silver ion treatment is combined with low levels of chlorine should prove useful as a method of disinfecting water against viral contamination.

US SURVEY OF HOSPITALS USING COPPER-SILVER IONIZATION FOR THE CONTROL OF LEGIONELLA

September 26-29, 2000,
Janet E. Stout, Y.E. Lin, V.L. Yu
VA Medical Center, Pittsburgh, PA
and the University of Pittsburgh, Pittsburgh, PA

Despite documentation of its efficacy in numerous hospitals, the long term efficacy of copper-silver ionization for controlling Legionella pneumophila in hospital water distribution systems has not been well documented. We conducted a survey of the first 13 hospitals in the U.S. that had implemented copper-silver ionization systems on their hot water systems for Legionella control. The mean bed size was 434 (range 150-700), 61% (8/13) performed transplant operations. 100% (13/13) had diagnosed cases of nosocomial Legionnaires' disease (LD). 30% of the hospitals installed copper-silver ionization because of problems and expense associated with the prior use of hyperchlorination. 50% had previously used thermal eradication. The average number of ionization flow cells installed per hospital was 3.4 (range 1-7), and the average start-up cost was $86,432. 46% (6/13) of hospitals had >30% of distal outlets positive before using ionization, and 0% had > 30% positive after installation. For 46% (6/13) of the hospitals, distal site positivity decreased to 0% positivity. When we conducted the survey, the ionization systems had been in place from 1 to 4 years. Ionization requires regular maintenance and the pH of water should be < 8.0 for optimal performance. Ionization is a viable option for controlling Legionella in hospital water distribution systems.

5th International Conference on Legionella
September 26-29, 2000, Ulm, Germany

Janet E. Stout
Infectious Disease Section,
University Drive C
Pittsburgh PA 15240USA

Disinfection of Bacteria In Water Systems by Using Electrolytically Generated Copper: Silver & Reduced Levels of Free Chlorine

AUTHORS: Yahya MT, Landeen LK, Mesina MC, Kutz SM, Schultze R, & Gerba CP
PUBLICATION REF: Canadian Journal of Microbiology 36: 109-116, 1990

PURPOSE:
The recommended minimum level of free chlorine for disinfection of public swimming pools is 1 mg/liter. This level is difficult to maintain due to the chlorine-demanding organic material introduced by bathers themselves as well as the environment. Eye and skin irritation may also occur at the minimum chlorine level needed for effective disinfection. Electrolytically generated copper/silver ions are also microbiocidal and are much less subject to degradation but are slower acting than chlorine. Therefore, the authors tested the hypothesis that using the two methods together would accomplish effective disinfection while reducing the level of free chlorine required.

MATERIALS AND METHODS:
Two 32-gallon plastic containers, one indoors (temperature range 22 to 25) and the second outdoors exposed to sunlight (temperature range 18 to 36) were filled with tap water. After chemical analysis and adjustment of pH and test levels of disinfectants, bath water and urine were added to stimulate typical swimming conditions. Four treatment regimens were tested: (1) No added disinfectants (2) Free chlorine alone at the generally recommended level of 1 mg/liter (3) Free chlorine at 0.3 mg/liter combined with copper and silver ions at a ration of 400 ug/liter of copper to 40 ug/liter of silver (4) Copper and silver ions alone at the same ratio as above. An isolate of Staphylococcus sp was employed for bacterial challenge testing since previous work had shown that staphylococci are more resistant to disinfection than are coli form bacteria. The experiment was continued for 12 weeks.

RESULTS:
In the test of free chlorine alone, location proved to be critical. In the outdoor setting subject to strong sunlight and high temperatures, no residual chlorine could be detected 3 to 4 hours after optimization. Indoor, where environmental factors were much less extreme, a residual level of 0.1 to 0.3 mg/liter was found after 24 hours.
Bacterial counts were kept within drinking water standards (as recommended for swimming pools) by either high levels of chlorine alone or by the combination regimen of copper and silver ions with low levels of chlorine: the difference in total bacterial numbers was not significant. Hen challenged with Staphylococcus sp isolate, the combination of copper and silver ions with low levels of chlorine achieved a 2.4 log 10 reduction in bacterial numbers within 2 minutes, while the single-agent regimes (free chlorine alone, or copper/silver alone) showed only 1.5 & 0.03 log 10 reductions respectively. Under Staphylococcus sp challenge, the combined copper/silver and free chlorine had a faster log 10 reduction of microbial numbers than did treatment with a high level of chlorine alone.

CONCLUSIONS:
The addition of electrolytically generated copper/silver ions in the radio tested (400 ug/liter copper to 40 ug/liter silver) allowed reduction in the concentration of free chlorine to one third of the level customarily recommended. The use of copper/silver may provide resisting protection in swimming pools after chlorine has been rendered ineffective due to contamination from swimmers and the natural environment.