Fascinating. So it seems to have been used for parasitic and fungal skin treatments, angina, and to induce miscarriage. With no doubt a very narrow band of error.
But you also don't touch it, eat it, or stand under it when it rains, so the opportunity to burn it by mistake is limited.
You remind me of Episode 2 of the Apothecary Diaries: several Chinese troops were poisoned after eating local food. The food was fine, the wood used for fire and eating utensils was the source. I wonder if something like that ever actually happened?
That is such a good show.
I would think any poisonous campfire would be quickly noticeable (who the hell likes to breathe campfire smoke?) and you would have to actually ingest the toxin like the guys who drank poisoned coffee.