Well it's certainly true that different yeast will produce
different profiles of the congeners, the things that produce
flavor (good and bad), as well as headaches in excess
quantities. Certainly lead is another possible source of bad
stuff leading to a short life span. I don't think there are
single answers, and the late 18th century probably had a number
of sources. But not all stills were made with solder. I have a
still from Portugal that simply riveted. And apparently this was
a very traditional still construction. And it didn't leak vapor
until I dropped it into the sink one day by accident. Now it's
all silver soldered. Verdigris is the green on copper, like when
exposed to the sea. It was used for a pigment in oil paints for
many years. But it's not something you want to eat or ingest.
The reason I asked about this, is I have all copper stills and
I've never had this green on the inside of my stills, nor have I
seen any discolored distillate. But a couple of these old books
definitely talk about this