Yes. Specifcally, anything that is an observational epidemiology study (which is much of it) is extremely low credibility. Observational epidemiology is historically terrible, low-quality research that gets lots of hype but doesn't stand up to rigorous analysis.
> 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.
Aren't the concentrations of concern down in ppt range? Surely that can't be the explanation for why so low a concentration would affect much of anything.
So your argument is basically observational epidemiology study = low quality hence we cannot make conclusions? It would be a fair point if this were a single observational (non experimental) study. However when you look at a dozen studies on humans which all exhibit the same pattern where high PFAS in blood correlates with higher cancer rates then the burden of proof shifts to prove that PFAS is safe, not the other way around.
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.
I see this kind of argument so often from PFAS apologists - "we don't have conclusive proof yet that it's harmful so we should keep producing and using this substance which is known to bioaccumulate and never break down". Shouldn't the onus be on those who want to use it to prove that it's safe? If the studies we have are truly as inconclusive as they claim, doesn't that just mean that we don't have good evidence they're safe?
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?
My suggested alternative is doing good, well-controlled science.
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).
I could describe any number of study designs. But the burden is not on me, it's on the people who are in the research area to do good science.
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.
This line of questioning always goes to the same place: it's not about educating the OP of better ways to do science, but them attempting to argue with me about whatever suggestions I make. I'm not getting sucked into it. My ability to do a "better" study is not relevant here.
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.
You of course cannot determine how others will respond to you, as I cannot determine how you'll respond to me.
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.
I think the burden could be on the chemical producer: do “good science” to show this material is safe, or don’t use it at all. That conservative mindset seems very reasonable to me.
