I have a background in chemistry and molecular biology and everything is about amounts. Those who developed "Popcorn lung" (what an idiotic name for a disease) were microwave popcorn factory workers who inhaled massive doses of powdered diacetyl. Cigarettes contain this chemical as well and I've never heard of anyone getting popcorn lung from smoking. It does not appear that the quantity of this chemical in
juice is sufficient to cause adverse health effects.
If you knew the high dosage health effects of the chemicals you are inhaling everytime you clean your ba
throom or spray for bugs, you'd likely never do either without a hazmat suit ever again.