Silver is used as a water bacteriostat in carbon containing water filters. The silver is deposited onto the carbon granules to potentially inhibit the growth of bacteria on the surfaces of these carbon particles. Such filters tend to leach out trace levels of silver into the effluent water. At these concentrations, the ingestion of silver has no detrimental effect on humans. When ingested and absorbed, silver is held indefinitely within tissue — particularly skin, eyes and mucous membranes. Skin discoloration is a cosmetic effect related to silver ingestion. This effect, called argyria, does not impair body function.


Contaminant  In Water As Maximum Contaminant Level

Silver (Ag)

AgO

US EPA SMCL* = 0.1 mg/L
WHO Guideline = 0.1 mg/L

Sources of Contaminant

Bacteriostat in carbon containing water filters

Potential Health Effects

Skin discoloration

Treatment Methods

Reverse osmosis
Distillation
Strong acid cation exchange (Na+)


*Secondary Maximum Contaminant Levels (SMCLs), or National Secondary Drinking Water Regulations (NSDWRs), are non-enforceable guidelines regulating contaminants that may cause cosmetic effects (such as skin or tooth discoloration) or aesthetic effects (such as taste, odor, or color) in drinking water. EPA recommends secondary standards to water systems but does not require systems to comply. However, states may choose to adopt them as enforceable standards.

**Operational Guidance Value (OG) established by Health Canada based on operational considerations.

WHO† - World Health Organization


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