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I have read that the Aura-specific thing was about the straps. I don't know if that's fact? I just haven't seen a source on it. I am assuming that it is, though, and that's part of why I'm attributing it to manufacturing contamination rather than intentionally making the mask, itself, waterproof with PFAs.
More in general, the study that included just 1 N95 alongside 6 cloth masks and a firefighting mask wasn't Aura specific, but, did give tenth of a microgram precision numbers. So I thought that would make a good test case for scale.
The fact that more or less random cloth tested higher for PFAs than the N95 tells me that it's likely manufacturing contamination with the N95. Manufacturing parts are a mess in that regard.
@BE @NilaJones
Most factories and plants have a good deal of teflon - it's in some roller bearings, it's some low-friction planar surfaces, etc. etc.