Propyline Glycol is approved as a food additive, so I don't think I would consider it "toxic".

However, once exposed to the radiator and engine, all coolants pick up various metal deposits and other nasty stuff that makes them unfit for human or animal consumption.

Used propylene glycol antifreeze is considered toxic, but you can drink it when fresh (and you do it you consume "artificial" milkshakes like McDonald's, etc... Prop glycol is used as a thickening agent...)

-David