I don't know the chemistry of this but find it difficult to believe we could be inhaling significant amounts of propylene glycol. The average amount of eliquid to use is 2ml per day, even if that was all pg that's not a lot plus some is also being exhaled.
Not that I'm saying it's not important to take pg into account and to be aware of possible adverse reactions, just that I'm not sure how big a problem it could be for people who are not sensitive/allergic.
Not that I'm saying it's not important to take pg into account and to be aware of possible adverse reactions, just that I'm not sure how big a problem it could be for people who are not sensitive/allergic.