The chemical industry took a page out of the tobacco playbook when they discovered and suppressed their knowledge of health harms caused by exposure to PFAS (per- and polyfluoroalkyl substances), according to an analysis of previously secret industry documents by UC San Francisco (UCSF) researchers.
I think that people in the industry have known for a while now that PFAS/PFOS are bad. I used to work at a company that made small amounts of fluoropolymers for their product lines (not consumer-facing stuff, voodoo RF electronics stuff) and I remember one of the workers there commenting on it once. This way maybe seven or eight years ago, and the hazards have also been listed on the SDSs for ages.
I think the contention was always that it doesn’t end up in the final fluoropolymer product so it’s not a concern for people not actively working in the plants. Time and experience has proved this to not really be true, however. The fluoropolymer industry should have switched to a different family of surfactants a long time ago in my opinion, but of course that would impact profits (other surfactants aren’t as stable / don’t work as well) and so corporate decided to bury it instead.