Although silver is not associated with any adverse health effects (only with cosmetic effects), the EPA establishes exposure limits for many materials based on various possible areas of concern. To our knowledge, silver is the only chemical or substance which has an RfD that is not based on an adverse health effect, but rather on a cosmetic effect called Argyria, an extremely rare phenomenon. While an RfD for silver still exists, in 1991 the EPA deleted the maximum contaminant level, or MCL for silver in drinking water (an enforceable value) and replaced it with a secondary maximum contaminant level (SMCL) goal (non-enforceable) of 0.1 ppm that is twice the previous level, an action that was probably driven by the recognized low toxicity associated with silver.
The EPA’s oral Reference Dose (RfD) for silver, which is “an estimate of a daily exposure to the human population that is likely to be without an appreciable risk of deleterious effects during a lifetime”. The RfD is expressed in units of mg/kg-day, which relates to an individual’s body weight. The RfD established for silver is .005mg/kg-day. This means that an individual who weighs 70 kilograms (160 pounds) could safely ingest .350 milligrams of silver per day for a lifetime. One 8 ounce bottle of Advanced Colloidal Silver contains 2.4 mg (or 2400 micrograms); one teaspoon (5 ml) of Advanced Colloidal Silver contains .1 mg or 100 micrograms of silver. The current EPA drinking water standards for silver state that in order to avoid possible skin discoloration, the maximum silver content in drinking water should not exceed .10 mg. per liter. This is equivalent to 100 micrograms of silver per liter.