I'm using this thead to document what I learn about this chemical, which seems to be something of a solvent.

To start, it appears that propylene glycol (PG) is a preservative and can perhaps be injected (indirect reference). But at least one injectable medication still has 2% BA despite having 80% PG (and 18% PEG). Perhaps they added 2% BA because that's just so typical for injectables.

Of note, other data I've seen suggests that IV administration of PG can have devastating effects, so it isn't exactly harmless stuff.