Theoretically it's conceivable that there is a separate, common factor in all the studies that causes the illness (e.g., people who are prone to cancer are somehow attracted to working with PFAS) but I think after the n-th human observational, plus experimental animal studies that at least show hormone disruption - we probably should on a go forwards basis operate with the assumption that PFAS are likely very toxic for humans, unless proven to be mostly safe.

That PFAS are very unreactive is meaningless. They still occupy volume and therefore affect kinematic rates and occupy reaction sites.

They're surfactants so they can interfere with basic processes in the intracellular matrix like cells sticking to each other and forming tissue. The long term epidemiological effects and in vitro studies are just getting started understanding the effects.

You know what else is a surfactant? Soap.

Literally every surfactant "interferes with basic processes in the intracellular matrix" -- they disrupt lipids (fats). That's how they work. They're not inherently dangerous as a category of chemicals. You slather yourself in them daily.

This discussion is veering into "the dangers of dihydrogen monoxide" territory now. You can make pretty much anything sound scary if you try hard enough.

Just because DHM is fairy will tolerated, I wouldn't go around drinking a pint of, say, methanol another polar solvent.

Yes, exactly: saying "it's a solvent, therefore it's dangerous" is equally dumb in both directions: you wouldn't drink a pint of methanol, and you wouldn't be scared of a pint of water. Likewise for "surfactant", and a ton of other terms you see on this comment thread.

In chemistry, details matter. The folks who run around parroting sciencey-sounding technical terms like "steric interference" to scare people are, unfortunately, often effective, because it takes ten times as many words to explain why they're talking gobbledygook as it does for them to make a ridiculous claim.

PFAS are a special set of surfactants because, being perfluorinated, evolution is unlikely to have endowed us with effective ways to neutralize them. Im not afraid of ingesting traditional fat soap because my bile will break it down. Dishwasher detergent freaks me out.

I think our (the anti PFAS crowd) concern stems from being able to identify many chemical pathways that can make these very dangerous and therefore believe that they should be proven safe by studies (including long term) as opposed to assumed safe of the common dismissal "no studies have demonstrated <insert noun here> are dangerous"

I mean...maybe? That's a huge statement without any evidence. There are tons of other organic fluorines in common use, so while I'm not rushing out to bathe in firefighting foam, if I got hit with some while escaping a burning building, I'd be OK with it.

> I think our (the anti PFAS crowd) concern stems from being able to identify many chemical pathways that can make these very dangerous and therefore believe that they should be proven safe by studies

That's not how empiricism works. You can't prove that something has no bad effects. That's called "proving a negative", and it's an infinitely high bar. Remember: millions of people die from dihydrogen monoxide exposure every year! We must ban it until proven safe!

Also, this:

> stems from being able to identify many chemical pathways that can make these very dangerous

...is pseudoscience. Everything is resting on the "can make" part of that sentence. There are so many "chemical pathways" (most of which we know nothing about) that any claim about a particular chemical triggering a particular pathway to negative human outcome absolutely must be backed by solid empirical evidence, and not just speculation or theory.

See also: "the dose makes the poison." Even completely innocuous -- or beneficial! -- chemicals are harmful if you consume too much of them. There are "chemical pathways" that can absolutely kill you if you take too much Tylenol, or drink too much alcohol, or eat grapefruit when taking certain statins, or a large number of other innocent things.

My current summary of the state of evidence around PFAS is that there's a constellation of weak/bad studies suggesting that the water-soluble variants might have bad effects in some animals. Bioaccumulation clearly occurs, and therefore caution is warranted (particular with certain manufacturing processes or pollution), but the people who are extending that to egg pans and sandwich wrappers are way out over their skis.

No, you don't need to deliberately expose people to toxins to do that. That's a straw man, when much of what passes for observational epidemiology is loaded with obvious uncontrolled confounders (like poverty).

More to the point, my ability (or lack) to come up with an experiment is not an excuse for you or anyone else to cite bad science with impunity. Likewise, if a study design is bad, it's bad regardless of my ability to correct it.

If you're going to fold like a cheap suit to a softball question (that isn't shifting the burden, it's trying to understand what you consider a good methodology) then kindly either shut the fuck up or fuck off and let the adults talk.

<https://news.ycombinator.com/item?id=38623345>

Specifically: "no matter how wrong someone else is or you feel they are": <https://news.ycombinator.com/item?id=12307773>

The question remains - what is “good science?”

You're slinging shade but parlous little illumination here. Adjusting that balance would make for a rather more substantive discussion.

If you want to think I'm "wrong" because I don't, then you're more than welcome to do so. But it doesn't change the fact that most observational epidemiology is riddled with bias, and is of low quality.

If, however, you do answer in good faith, credibly, and substantively to a specific question or request, you'll know, and fair-minded readers will generally recognise, that you've done so.

Or you could, say, contribute over a half-dozen responses within the thread with roughly a quarter of them explicitly withholding or defending the withholding of that substantive contribution.

Your call.

PFAS were released into environment in massive quantities. They are now, basically, impossibly expensive to remove. Same for microplastics.

Suppose tomorrow we come up with indisputable evidence that they are toxic. Now what? Will the companies that put them into environment be able to pay for a global cleanup effort that cost more than those companies are worth? Should we allow someone to make 1 million, knowing that remediation will cost $10 billion and they won't be able to pay for it?