Here's a WS article from 2013.
In addition to the additives, there may be bugs, bird shit, spiders, spider webs, moths, caterpillars, insect eggs, toe cheese if the grapes were foot stomped, and various other proteinaceous treats.
As with all foods as well, contamination with teeny amounts of unmentionables occurs. Given what Greg T has written, I wonder if vegetarians should eschew wine due to the bugs, etc.
Personally, if a label said "Contains trace amounts of bugs, bird shit, spiders, etc." I would pass on the purchase of that wine. I'd rather not know.