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Are you saying that the dozen studies listed in wikipedia about PFAS harm to humans are flawed? https://en.wikipedia.org/wiki/Per-_and_polyfluoroalkyl_substanc

Are you saying that the dozen studies listed in wikipedia about PFAS harm to humans are flawed? https://en.wikipedia.org/wiki/Per-_and_polyfluoroalkyl_substances#Health_and_environmental_effects https://en.wikipedia.org/wiki/Per-_and_polyfluoroalkyl_subst...

deleted 3y ago
[deleted]
timr 3y ago
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.
- thsksbd 3y ago
  Chronic toxins that affect us over decades are difficult to detect. For starters, few studies last the long. That PFAS are very unreactive is meaningless. They still occupy volume and therefore affect kinematic rates and occupy reaction sites.
  - throwup238 3y ago
    > 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.
    - timr 3y ago
      > 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.
      - voodoomagicman 3y ago
        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.
      - thsksbd 3y ago
        Funny how you speak of "dihydrogen monoxide" - a very polar solvent which is incredibly safe. Just because DHM is fairy will tolerated, I wouldn't go around drinking a pint of, say, methanol another polar solvent.
        timr 3y ago
        > 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.
        deleted 3y ago
        [deleted]
        thsksbd 3y ago
        Ok, I like this because we're converging. 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"
  - thfuran 3y ago
    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.
    - thsksbd 3y ago
      I think the concern is the endocrine system that does work on the high side of ppt
- crote 3y ago
  What's you suggested alternative? Deliberately exposing large groups of people to likely-harmful chemicals and seeing at what concentration they die?
  - timr 3y ago
    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).
    - phone8675309 3y ago
      Could you describe how you would design a "good, well-controlled science" study/experiment on the effects of PFAS in humans?
      - timr 3y ago
        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.
        spenczar5 3y ago
        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. The question remains - what is “good science?”
        phone8675309 3y ago
        [flagged]
        3y ago
- JoshTko 3y ago
  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.
  - mort96 3y ago
    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?
- ClumsyPilot 3y ago
  this is completely wrong approach. 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?
SkinTaco 3y ago
It might be more possible than you think https://en.wikipedia.org/wiki/Replication_crisis https://en.wikipedia.org/wiki/Replication_crisis

deleted 3y ago

[deleted]

timr 3y ago

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.

thsksbd 3y ago
Chronic toxins that affect us over decades are difficult to detect. For starters, few studies last the long. That PFAS are very unreactive is meaningless. They still occupy volume and therefore affect kinematic rates and occupy reaction sites.
- throwup238 3y ago
  > 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.
  - timr 3y ago
    > 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.
    - voodoomagicman 3y ago
      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.
    - thsksbd 3y ago
      Funny how you speak of "dihydrogen monoxide" - a very polar solvent which is incredibly safe. Just because DHM is fairy will tolerated, I wouldn't go around drinking a pint of, say, methanol another polar solvent.
      - timr 3y ago
        > 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.
        deleted 3y ago
        [deleted]
        thsksbd 3y ago
        Ok, I like this because we're converging. 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"
- thfuran 3y ago
  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.
  - thsksbd 3y ago
    I think the concern is the endocrine system that does work on the high side of ppt
crote 3y ago
What's you suggested alternative? Deliberately exposing large groups of people to likely-harmful chemicals and seeing at what concentration they die?
- timr 3y ago
  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).
  - phone8675309 3y ago
    Could you describe how you would design a "good, well-controlled science" study/experiment on the effects of PFAS in humans?
    - timr 3y ago
      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.
      - spenczar5 3y ago
        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. The question remains - what is “good science?”
      - phone8675309 3y ago
        [flagged]
        3y ago
JoshTko 3y ago
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.
- mort96 3y ago
  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?
ClumsyPilot 3y ago
this is completely wrong approach. 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?

SkinTaco 3y ago

It might be more possible than you think https://en.wikipedia.org/wiki/Replication_crisis https://en.wikipedia.org/wiki/Replication_crisis