What are artificial Christmas trees made out of?

Most are made from polyvinyl chloride, commonly known as PVC. There are some made with a combo of polyethylene and pvc. There is a concern about lead in pvc tree and in the lights, and incidentally other electrical cords.

The ones we've always had are silk, easy to tell since the needles are bendable, short, well made and look fairly real when placed correctly. I've not seen a PVC tree in about 20 years, but I know they use to make plastic (pvc?) trees when PVC was being used for outdoor furniture so much. I love my silk one and the garland that matches. Easy to store and