> 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.
> They're surfactants so they can interfere with basic processes in the intracellular matrix like cells sticking to each other and forming tissue.
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.
PFAS are different from soap in that your body can't break them down or excrete them well, so they bioaccumulate. Eating soap is absolutely not good for you, and if it also built up in your body people would be really worried about small exposures to it.
> 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"
> PFAS are a special set of surfactants because, being perfluorinated, evolution is unlikely to have endowed us with effective ways to neutralize them.
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.
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.