Silver in drinking water can cause a discoloration of skin, eye, and mucous membranes known as argyria when ingested (Manual of Small Public Water Supply Systems; EPA570-9-91-003; May 1991). Silver is seldom found at significant levels in water supplies and drinking water has never been identified as the cause of argyria in the United States. EPA considers argyria a cosmetic effect since it does not impair body function and only causes a gray discoloration. Silver does not affect the taste, odor, color or appearance of the drinking water, nor is there evidence that the low level of silver that may be found in drinking water causes argyria. EPA has set a non-enforceable secondary maximum contaminant level of 0.1 mg/L to protect the welfare of the general public from the cosmetic effect of argyria (56 FR 3526, 3527; January 30, 1991).
To help determine the cause(s) of aesthetic or cosmetic effects from your drinking water, contact your local drinking water system. Additional guidance for household well owners is available at http://water.epa.gov/drink/info/well/index.cfm. General information on nuisance chemicals is available at http://water.epa.gov/drink/contaminants/secondarystandards.cfm .