OK, did some reading. I didn't realize at first that we were talking about PG metabolites. What are the amounts we're inhaling? How many mg of PG are there in one carto? The acceptable daily intake seems to be up to 25 mg per kg of body weight. But that is of course PG ingested or injected, not vaped. But still, I don't think we're anywhere near that amount. All the concerns about possible acidosis, hypoglycaemia, seizures, stupor and cardiac irregularities apply to much, much higher doses. Of course, we're mixing it with a rather powerful poison... As we agreed, all these things will eventually be studied, but for now we have to help ourselves and each other and keep our eyes wide open.
I also ran all those other metabolites by my resident pulmonologist--he didn't seem concerned. He says a sugar molecule is a sugar molecule, it falls apart, it comes together again. In his educated opinion all these metabolites will eventually find each other and form a big glucose molecule along the way. They are all innocuous and present in our bodies at all times, in one form or another. Compared to cigarette smoke...those are just as risky as sugared water (and vinegar-acetic acid).
I feel better. This is fascinating, isn't it?
Estimated acceptable daily intake: up to 25 mg propylene
glycol per kg body weight (Seventeeth Report of the FAO/WHO
Expert Committee, 1974).