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Comment by Mistletoe | Hacker News Reader

80 micromolar is a ridiculously high level to test at. I’m really tired of studies doing this. The public doesn’t understand molarity and that the concentration of almost anything is toxic at 80 uM.

https://www.sciencedirect.com/science/article/pii/S143846392...

The highest concentration of PFOS type substances we could expect in blood is 6 ng/mL.

The molecular weight of PFOS is 538 g/mol. Use the molarity calculator at https://www.graphpad.com/quickcalcs/molarityform/ to see that that is 11 nanomolar.

The 80 uM amount used in this study is 7272x higher than the highest amount we would expect in the blood.

This isn’t to say that PFOS isn’t bad, it is bad but this looks like the standard university PR department nonsense and researchers using ultra high concentrations looking for a positive result. Honestly this looks like something I would expect an undergrad to do that doesn’t understand concentration.

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Not exactly the same, but reminds me of the saccharin rat studies. Massive dosing (the human equivalent of ~800 diet sodas per day!) plus a physiology that highly concentrates urine led to bladder cancer in rats. Turned out to be completely irrelevant to humans (and now ironically saccharin may be somewhat cancer fighting?).

For expedience many of these studies are done at the Maximum Tolerated Dose, which is the amount that does not otherwise outright kill the subjects. It’s understandable that this is useful for magnifying sensitivity but it also leaves them with a tinge of doubt. That compounds with the career benefit for publishing sensational results to generate some bad science (especially frustrating when there are tinfoilers looking to distrust science as it is).

Glad to see this comment here.

You see that a lot in studies - models that bear no resemblance to actual exposure.

All you can say is “at levels that will never occur in the human body, X happens”

Ok?

I believe that the concentration of the solution they were suspended in was 80 uM, but the concentration in their blood isn't mentioned (and probably wasn't measured) in their work. I'm not a zebrafish expert so I have no idea how much PFAS would a zebrafish absorb from its surrounding solution into its bloodstream.

It says the embryos and cells were put in 80 uM.

>The embryos and cells were exposed to 80 micromolar solutions of each chemical:

Yes, but your original comment talks about a concentration of 6 ng/mL in human blood, while the researchers only point out the concentration of the surrounding medium. Perhaps I'm missing something, but you can't compare these two values since you didn't measure the actual concentration of PFAS in the blood stream of the larvae. For all we know it could be lower than 6 ng/mL, right?

They are also doing studies on human neutrophil cells etc. at 80 uM. The fluid above the cells at 80 uM is a model for cells in blood.

You can see in Figure 5 here that the effects are really only seen at the highest non physiological doses. Even their lowest dose of GenX is 2.6 uM which is 2600 nM. I don’t have data for blood levels of GenX but if it is like PFOA that would be 260x higher than any concentration we would expect a neutrophil to ever see. And there is no effect on respiratory burst.

https://www.tandfonline.com/doi/epdf/10.1080/1547691X.2023.2...

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