Fairly recent research claims that hobby (backyard) chickens tend to have higher PFAS contamination than factory farmed chickens because hobby chickens get the chance to eat (a lot of) rain worms whereas the factory farmed chickens only get commercial food, no live worms. I do agree that location is almost undoubtedly key to PFAS contamination rates.

Dutch source for the thing about rain worms: https://nos.nl/artikel/2539934-hoge-concentraties-pfas-via-r...