In reply to BRILLBRUM:
Teflon has several disparate issues that give it its bad rep. Yes, the PTFE itself – (C2F4)n – is very stable and harmless at normal temperatures. But that's not the whole picture.
First is the manufacturing, which used to release lots of PFASs in its waste stream (DuPont and others used to dump it directly into rivers for decades). PFOA and PFOS salts were used as part of the PTFE making process.
After massive multi‑billion lawsuits and public backlash, they changed that to other PFAS formulations free of PFOA and PFOS only. Which doesn't mean that it's now PFAS‑free, only that they changed the formula to lesser known PFASs ("Gen‑X"), which might be less persistent. Or so they say. Sure. Gen‑X compounds were still found in the rivers, go figure...
Second is outgassing, as some smaller emissions of PFASs were sometimes found even at normal cooking temperatures over 180C, perhaps from left‑over emulsifier residues or PTFE degradation during the high temperature coating process degrading into PFASs and trapping them in the coating.
Third is thermal degradation of PTFE, which happens at higher temperatures, mostly above 260C. The more you heat it, the more PTFE degrades into potentially harmful PFASs, and not linearly. Overheating an empty teflon pan over 360C released 2500x more PFASs than at normal use at 230C in one study.
Post edited at 16:17