How safe is the patina layer on seasoned cast iron or carbon steel cookingware?

How safe are iron and carbonsteel pans? Or can they be misused making them unsafe?

For instance, have food safety authorities already reviewed this? Is there a regulation or at least a published opinion from an official body? For example, something like this opinion the European Food Safety Authority has published on PTFE (like Teflon) and PTFE coated cooking ware.

In order to have iron pans and carbonsteel to be non-stick one creates a patina layer on them by seasoning it. That is, burning fats and oils in thin layers onto the surface of the pan, creating a black layer of pyrolised and oxydized hydrocarbons (and probably all sorts of chemicals). (And it also changes the metal structure of the surface)

How is it with this 'burnt' patina layer? Is that layer safe? Or is it typically safe, but can it be unsafe when not properly done?

^{The specific section in the EFSA article is "3.1.3.1. Migration from food contact materials, including non-stick coatings used on cookware"}

^{The article is EFSA Panel on Contaminants in the Food Chain (CONTAM), et al. "Risk to human health related to the presence of perfluorooctane sulfonic acid and perfluorooctanoic acid in food." EFSA journal 16.12 (2018): e05194.}