This is not self-evident. Biology is extremely complex and we have a lot left to learn before we can make definitive statements about safety. This idea of 'you can be sure we'd hear about it' places too much of the burden on journalists, random medical researchers, and eventually regulators to suss out what is going on.

As it stands in our system today any awareness we may have about dangers will come far after the danger to us, and then we'll all say a collective 'oops' as we've had to do the last hundred times. Look no further than all the 'I [live near the plant/play on the field/drink the water] and have [cancer/autoimmune/rare disease/etc]' stories that keep coming out year after year.

> you can be sure we’d hear from it

If it’s widely used and profitable to many, you can be sure you won’t hear from it.

https://en.m.wikipedia.org/wiki/Choice-supportive_bias

Or you just need to be a fetus.

Yes, did you know, fetuses start as single cells?

There's lots of evidence that long-chain PFAS can bioaccumulate across generations. You don't need to live a millennium personally. (Also the effects are disproportionately bad on infants, so you don't need 1000 years of generations either.)

Also we didn't really stop putting them in the water yet...

We are in the stone ages of medicinal and biological understanding. We have no idea what levels or forms of exposure are "safe", not only for humans but the ecosystem as a whole.