Everywhere that is never tested. How do you know for sure you are on good soil, and that no contaminated soil was used under your house and garden, which no doubt were levelled before construction started?

This includes feed. Commercial animal foods literally contains waste, such as plastic, due to waste food recycling not being required to be unpacked.

Sure, you _can_ control these things, but more often than not, people don't. Semi commercial hobbyists don't have the money.

Purportedly the Netherlands, but the research was badly performed.

KNOWN PFAS contamination was around heavy industry, and yeah, if you live near those regions, maybe don't. Otherwise proceed with scepticism and/or some testing.