What is Silver?
Silver is a transitional metal that is very soft, malleable, and white that has excellent properties for electric transmission and heat or thermal capacity. Silver has a high luster and is considered a precious metal. Silver has been used in the water treatment process and other industries as a means of controlling and inhabiting bacterial growth. Naturally occurring silver is typically associated with the presence of gold, copper, sulfide mineral deposits, quartz deposits, and arsendies, i.e., compounds that contain arsenic deposits, but may also be associated with mercury and antimony. With respect to geology, this transitional metal is typically associated with igneous and metamorphic rock. The main sources of silver are mined as an ore of copper, copper-nickel, lead, and lead-zinc. The majority of the world’s silver mines are located in Peru, Bolivia, Mexico, China, Australia, Chile, Poland, and Serbia. (Source).
Silver minerals can be sulfides (S=), halides (Cl–), sulfates (SO4=), silicates (SiO4==), bromates, carbonates (CO3=), nitrates (NO3-), oxides, hydroxides (OH-) and others. Metallic silver has been used for surgical prosthesis and splints, fungicides, and coinage. Soluble silver compounds, such as silver salts, have been used in treating mental illness, epilepsy, nicotine addiction, gastroenteritis, and infectious diseases, including syphilis and gonorrhea. (Source) Currently, colloidal silver is used to fight colds and as a dietary supplement. Silver is typically associated with the mining, metal and chemical industries, photographic processes (to develop film, now largely obsolete), soldering, effluents from coal fired power plants, and battery production. Some point-of-use and whole-house water systems use a silver-impregnated carbon filter with silver to acting as a biocide, i.e., bactericide.
How Does Silver Become a problem?
When silver is ingested or absorbed into the human body the silver is not flushed from the body, but held in the tissue. The primary target areas are the mucous membranes, and the eyes. Long-term exposure can cause the skin to discolor. It is critical to note that silver may be present in hair treatments such as permanents, dyes, and bleaches.
What are the Health Risks for Silver?
When the skin becomes discolored, this is known as argyria or argyrosis, which causes the skin to turn a purple to purple gray color. Argyria is also known as "Blue Man Syndrome". At this time, there are no specific health impacts associated with the ingestion of low levels of silver via drinking water.
What are the Standards for Silver?
The EPA has recommended a secondary drinking water standard of 0.1 mg/L and some state agencies and the World Health Organization use this as a maximum drinking water standard. The 2018 EPA Health Advisory on drinking water has a DWEL, i.e., Drinking Water Equivalent Level, for silver of 0.2 mg/L.
(Drinking Water Equivalent Level. A DWEL is a drinking water lifetime exposure level, assuming 100% exposure from that medium, at which adverse, non-carcinogenic health effects would not be expected to occur. DrinkingWater Standards and HealthAdvisories Tables)
