After the publication of our article on clay water filters (EDN 71-4), we were questioned about the safety of colloidal silver. First of all, you might be wondering what exactly colloidal silver is. Peter Campbell, a professor at the University of Quebec in Canada, studies the effects of metals on living organisms. He told us that the term “colloidal” refers only to the size range of the particles. Thus it might refer to metallic elemental silver suspended in a solvent. It also might refer to any solid silver precipitate such as a silver salt, in which case the silver would be in an ionic form. According to our reading, it is better to use silver in elemental form than silver in ionic form. Ingestion of some silver salts can lead to a condition called argyrosis, which is not dangerous but is characterized by a darkening of the skin and the whites of the eyes.
We wrote to Potters for Peace to ask if they knew of any concerns with the use of colloidal silver. We asked if the whole solution mentioned in the article is painted on the inside of the filter. We also wanted to know if tests had been done to see how much silver goes through the filter.
Barbara Donachy wrote back to say that Potters for Peace uses colloidal silver in elemental form. The whole amount of silver is painted inside the filter. Potters for Peace is currently using a slightly more concentrated suspension (3.2% silver preparation with 1 cc per 250 cc of water), than the one we mentioned in our article (0.32% silver preparation with 7 cc added to 250 cc of water).
Although she didn’t know of any tests being done to see how much silver goes through a filter and ends up in the drinking water, Ms. Donachy said that filters had been tested after seven years of use and still worked, which would indicate that silver was still present in the filter.
According to a paper titled “The Development and Functions of Silver in Water Purification and Disease Control” by Richard L. Davies and Samuel F. Etris, “a 2500-year history of the use of silver for water purification…has been established with no reports of toxic reactions to the hundreds of millions of children and adults exposed to it.” Silver vessels were used in ancient times to keep liquids from spoiling, and two well-known water purification systems (the Katadyn system and the Ionics system) incorporate metallic silver into their designs. The authors discuss silver’s ability to sanitize water by several different mechanisms. First of all, silver catalyzes (i.e. speeds up) a process called oxidation that destroys microorganisms. Silver is not used up at all in this process.
[Here is a bit more detail for those who know a little chemistry. Because of silver’s structure, oxygen atoms (not molecules) are adsorbed by silver but do not react with it. These oxygen atoms can remove hydrogen atoms from sulfhydryl (-S-H) groups on the surface of bacteria and viruses. The sulfur atoms then join together, blocking both respiration and electron transfer. Monovalent silver (silver with a +1 charge) can also effectively kill bacteria and viruses. The silver ions can replace hydrogen ions on the sulfhydryl groups, disrupting electron transfer in bacteria and preventing the unwinding of DNA in viruses. The authors write “mammalian cells are not affected by silver because the protective cell walls block entry of large ions such as silver.”]
In addition to its use in water purification, colloidal silver is often used to treat infections. However, it is not a substance regulated by the U.S. Food and Drug Administration (FDA). In fact, the FDA has stated that it “is issuing a final rule establishing that all over-the-counter (OTC) drug products containing colloidal silver ingredients or salts for internal or external use are not generally recognized as safe and effective and are misbranded. FDA is issuing this final rule because many over the counter (OTC) drug products containing colloidal silver ingredients or silver salts are being marketed for numerous serious disease conditions and FDA is not aware of any substantial scientific evidence that supports the use of OTC colloidal silver ingredients or silver salts for these disease conditions” (Federal Register 64(158), pp. 44653-44658). The regulation became effective September 16, 1999.
A web search of the term “colloidal silver” will lead to numerous links to web sites stating the benefits of colloidal silver. The sites I have looked at all report no negative side effects from the use of colloidal silver. Ms. Donachy also told us of a study done in Mexico by a chemist named Michael Owens; the study showed no negative health effects from colloidal silver used over a 30-year period.
Once again, note that the colloidal silver used and advocated by Potters for Peace is pure, elemental silver, NOT silver salts of any kind. Before you buy colloidal silver, make sure you know that it contains elemental silver. This silver remains in the filter and acts by catalyzing reactions that destroy bacteria, in contrast to water purification by chlorine compounds that are actually additives dissolved in the water.
Berkelaar, D. 2001. Colloidal Silver for Clay Water Filters. ECHO Development Notes no. 72