Don't confuse silicon oxide with a PFAS. It is quite the negligent and hazardous fallacy to put them in the same bucket. One has been around for billions of years. The other hardly has any research, and will take at least a decade more of data and research before we know what's it is capable of.
You are in no way smart enough to understand and consider all the pathways, uptake mechanisms, and consequences that are affected by the PFAS compound across all of biological life. Knowing just one or two over just a few years does not make you competent in it or qualified to make a broad safety comment.
PFAS is to my knowledge the only human-created unnatural class of compounds that does not deteriorate in the environment. So no, the argument applies exclusively to PFAS.
PFOA and PFOS have 8-member fluorinated chains. And they are dangerous, with clear dose-dependent effects.
PFHO has a 6-member fluorinated chain, and it has no known toxic effects.
> Even so, they all accumulate in the environment.
So does silicon oxide. Or a lot of other "terminal" compounds. The questions that need to be asked are:
1. Are they dangerous by themselves?
2. Do they bioaccumulate?
3. Do they stay mobile in the environment (i.e. don't get sequestered)?
In case of PFHO, it's not dangerous. It does not bioaccumulate because of its poor absorption. And it's also not mobile.
> The last I recall, it causes brain damage in children.
No, it doesn't.