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As the EPA studies show, the estimated amount of silver intake in order to be at risk for Argyria is 3.8 ( to six ) grams of silver.
One teaspoon of 50ppm colloidal silver contains 250 micrograms of silver, or 0.250 milligrams of silver. The EPA's critical dose for a 160 lb. adult is 1.09 milligrams daily. Taking one ounce of colloidal silver daily, according to EPA guidelines, is well below the critical daily intake for the development of Argyria. Four teaspoon daily would equal around 1 milligram.
However, all of this is dependent upon the body's actual retention of colloidal silver in body tissues. There is no existing data which addresses the very real differences between ionic silver (sized .0003 - .05 microns in diameter) and silver compounds ( Silver Nitrate, Silver arsphenamine , silver proteins, silver salts, silver acetate, ect ). However, there is accumulating evidence which strongly suggests that ionic silver does not build up in dermal tissues at all.
As an experimental baseline, hypothesize that 20% of ionic silver, through body processes, aggregates to form larger particles that are large enough to be treated by the body as silver, and a small percentage of these might be retained in the body for a period of time rather than be eliminated through urine/feces. That would mean that out of one ounce of 50ppm colloidal silver ( 0.250 milligrams ), only 0.50 milligrams would apply to the studies that the EPA has published. A four ounce solution ( often understood to be a therapeutic dose ) would then contain 0.50 milligrams of silver to be considered as applied to the EPA's guidelines. However, even THIS is an extremely conservative approach to colloidal silver toxicity, due to the fact that it would be a rare occurrence for this silver to bond with any substance in the body that would mimic the substances studied by the EPA, AND it is believed that the body would have to reach a level of toxic response in order to start to deposit silver in measurable quantities in body tissues.