It's quite a mystery what "gum base" is actually made out of, but the investigators found it's usually a blend of elastomers, resins, plasticizers, and fillers. Most manufacturers do not reveal more specifics than this. After all, why would they want you to know that you're potentially chewing on petroleum-derived paraffin wax, polyvinyl acetate (carpenter's glue) and talc, all of which are linked to cancer.