This may be old news...

Yesterday I told my sister (who has never smoked) about my new, healthier habit (and sent her a link to DonDaBoomVape's Wonderful World of Vaping so she could read all about it.)

She sent me back a MSDS document on PG which basically said it's fine. And that was for industrial PG. So I searched a database. It's not letting me link to the results, but "propylene glycol" results included one for a USP Kosher one from JLM Marketing. You can't search for vegetable glycerin, but "glycerin, usp" comes up with 3 documents.