Source: economist
Silver is a toxic heavy metal just like lead, mercury and arsenic. Which has anti-microbial properties hence was used earlier to treat wounds, prolong food life and prevent infection. However later on scientists found that silver causes argyria.
It turns the skin grey or blue. It, like other toxic metals gets accumulated in the body organs. Some of the silver compounds are poisonous and some are even carcinogenic.
One of the reasons of the decline of Roman Civilization was that they drank wine in Lead Goblets. The metal leached from the containers and slowly poisoned them. Many kids are being born with silver spoon. Their parents are realizing that they can afford silverware (and having the same effects)
Most nanotechnologists are using silver ions to purify water, Samsung uses them in washing machine etc. Nanosilver is found in bandages, food-storage containers, shoe-liners and sportswear. The size of these ions/nano particles make the deep absorption much more easy and effects much more deadly.
History repeats itself. And maybe NanoSilver is going to be the next asbestos.