Charles,

1) The patio process was invented in Spain about 1555 and introduced to Peru
about 1580..
2) I remember from my readings that the Spaniards (and the Amero-Indians),
the natives, were well aware of the deadly effects of mercury mining.  But
they, the Indians, were sent down into the Sta. Barbara mine in
Huancavelica, Peru (the only source of mercury in the Americas until this
century), and stayed there, many never coming back up (mind you, they had no
investigative reporters and other news seekers then, and the mercury mine
was a crown monopoly).  Life was worth little at the time, and a few less
....No, I am not aware that meaningful statistics were ever gathered or
published.
3) Mercury was transported from Almaden, Spain, to the Americas in
bags--leather bags- packed in boxes.  Mervyn Lang is the expert on that.
4) The amalgam, meaning the silver together with the mercury, was eventually
roasted which freed the mercury and left the silver. Yes, the fumes were
deadly. Yes, they knew it was bad. No, nothing was done about it.
(Curiously enough, go to the Madeira river in western-central Brazil, today,
or to Ouro Preto, near Belo Horizonte, in eastern Brazil, and you can find
the same roasting process still today. They also know it is deadly; they
also nod, but then say: "what else can we do, Senhor?"  We have no other
work. (I documented that 8-10 years ago and took academics to see it. I am
certain it continues unabated.
5) The Spaniards had no procedures in place to minimize it. I am certain
were you to go to the health authorities in Ouro Preto or Porto Velho, they
will have good records. Ten years ago, it was even dangerous to eat certain
types of fish in the Amazon as they had to have absorbed mercury.
Best
Helmut Waszkis