Silver

EPA Secondary Drinking Water Standard

0.1 mg/L

Silver, biologically, is neither essential nor beneficial to humans. When ingested, it is held indefinitely within tissue, especially in the eyes, skin and mucous membranes.

Some confusion exists in water treatment in regard to silver because silver has strong bacteriostatic properties and is sometimes used by filter makers to prevent the growth of bacteria in filter media. The EPA “certification” required for such devices is not a performance guarantee (as some vendors imply) but a guarantee that the silver content is within safe limits for human consumption.

Silver is not common in water supplies but when it is there it usually appears as Silver Fluoride or Silver Nitrate.

Health Effects of Silver

The effects of silver are typically aesthetic rather than health related. Exposure to large amounts can cause changes in skin and hair color, according to the World Health Organization:

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The only obvious sign of silver overload is argyria, a condition in which skin and hair are heavily discoloured by silver in the tissues. An oral NOAEL for argyria in humans for a total lifetime intake of 10 g of silver was estimated on the basis of human case reports and long-term animal experiments.

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Water Treatment for Silver

Reverse osmosis removes 90% plus of silver, and distillation about 98%. Strong Acid Cation Exchange is also effective at reducing silver.

Sources: WQA Technical Bulletin, World Health Organization, Photo: Jens Mohr