The Romans even knew about asbestos, there were recommendations to not buy slaves from the asbestos mines because of the poor health associated.
Oddly enough, they still wiped their faces with the stuff because those napkins and towels could be cleaned by throwing them in fire.
Everything that the FDA doesn’t declare as “known” or “proven” safe within defined limits are “considered” safe or may be allowable to a defined limit. It is their cute little scapegoat should a substance they allow be proven unsafe and then they would face a greater risk of lawsuit had they determined it was known or proven safe.