Why is there an EPA exposure limit (Reference Dose, RfD) for silver if it has no associated adverse effects?
Even though silver is not associated with adverse health effects, the EPA establishes exposure limits for many materials based on various endpoints 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 (argyria). 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 (nonenforceable) of 0.1 ppm (100 µg/L) that is twice the previous level, an action that was driven by the recognized low toxicity associated with silver.
