If I am remembering correctly, they have been shown to contain some level of PFAs. Which have also been found in a lot of the trendy mineral water drinks like Topo Chico and La Croix. The ultimate problem is that there is not much that is actually understood or even known about PFAs, including what levels are safe to consume. So far it's mostly just forewarning in the sense of "hey these things are in this stuff, and it might be bad maybe".