Long chain like PTFE is fine. The issue is short chain fluorosurfactants (think PFOA and GenX) which contaminate the environment around the factories that make PTFE, harm the workers in those factories, and probably end up in trace amounts in the final products as well. These are very chemically stable in that they don't react well with most things, making them long lasting in the environment, but they do interact (but not react) with animal endocrine systems, which makes them so dangerous.