I'd hope you are right about the higher plastic concentrations in the AD brains being a result ofblood brain barrier breakdown. The BBB is quite complex, but we do know that in some types of dementia the capillary 'tight' epitheilial bonds break down similarly to what happens in 'leaky gut'. It's unlear whether this is cause or effect (or coincidental) - and I'm now curious as to whether the two conditions are more likely found in the same individuals.
That said, we've somewhat inadvertently reduced the nanoplastics we're inhaling as I've always had seasonal allergies and HEPA filters offered some relief. And a few years ago, our state health organization dropped the acceptable levels of 'forever chemicals' (per/poly fluoroalkyls) in municipal drinking water to well below national EPA requirements. Our town was over. Major wakeup call. We went with reverse osmosis. If it can reduce/remove chemicals in solution, then it's making a bigger reduction on particle (even nanoparticle) matter.
I'm still making coffee in an Aeropress, which is plastic. It's supposedly BPA-free, but it's probably another of the bisphenols - just one that has yet to be 'found to be harmful'. I could make the same comment about anything 'BPA-free' (e.g. 'nalgene').
BTW/FWIW as someone with a background in data communications I'm struck with the similarity between "white lists" (only let through known-good) and the way nephrites work (dump everything, pull back "known good") - but apparently this doesn't work with some substances? I would have expected more of a concentration in both the kidneys and liver so...?