Propylene Glycol is used as a stabilizer (to keep things held together, and keep them from evaporating), and to keep foods moist. It’s used in many of the foods that we eat, and the FDA deems it safe for human consumption.
Here is a list of the food items you may find PG in:
certain mustards, food coloring, artificial flavors, certain chips, certain soy sauce brands, fried onions, certain strawberry and chocolate syrups, certain icing, canned coconut milk, certain salad dressings, certain ice cream brands, maple flavored bacon, certain juices, certain sodas, certain cake mixes, certain chicken bullion brands, fast food burgers and dipping sauces, certain yogurts.
It's no different than any other chemical that we put in our bodies and possibly less harmful than others. Personally, other than the pellets I feed my birds, they get very little prepackaged foods for birds or humans...I'm trying very hard to go mostly fresh and raw, so no cooking either. Any time you feed them a prepackaged cereal, pasta, crackers, breads, anything...you are exposing them to chemicals such as PG...