V1 contains diacetyl, known to cause a condition caused "popcorn lung" in high concentrations. It is used to give a buttery flavor to food items, ie popcorn, and to some flavoring used in some juices.
It is considered safe for eating but not for inhalation. What quantity crosses the
thresh hold between safe and unsafe is not known. Like anything else, the poison is in the dose.
In V2, the diacetyl has been replaced with other additives to achieve the buttery flavor. Whether these are any safer, any worse or about the same is not known. There is just not a long enough track record for our use to know for sure.