Not only is it easier to look in someone balls than someone's brain, the fact that it can cross the blood brain barrier is pretty fucking crazy.
It's not like someone said "we gotta find out if this can get inside testicles stat!" It's that between cancer and fertility issues balls are looked at pretty frequently, and we found micro plastics there.
The reason we found it in the brain. Is someone asked if it was possible and that's a big enough deal to go out and look.
It's much easier to get tissue from testicles than a brain sample. About 10,000 men develop testicular cancer annually in the US. Plenty of test can still be ran on those testicles if the patient consents. Getting a aample of brain tissue usually requires the donor to be dead, and there is a long list of scientists that would loke to stidy brain matter for one reason or another.
The amount of people who donated theor body to science is overwhelming. So much, that lots of bodies can't be used. Some niche ectomy doesn't increase the samples here.
Any foreign objects made up of substance that are non-reactive can end up embedded in our bodies. Most obviously, there are medical devices that might permanently be left there: screws, prosthetics, artificial meshes and valves and membranes, etc. There are also some foreign objects that come from trauma, like shrapnel. Even tattoos are foreign pigments placed in a particular layer of skin that the body doesn't have a mechanism for clearing out.
But generally speaking, if our body doesn't have the enzymes to break down a substance into constituent compounds small enough to transport out, or if that foreign substance sits in a place where our body doesn't have a mechanism to actually get to, it stays in the body.
The reason why we're talking about microplastics, though, is that these compounds might actually be more reactive than previously assumed. If the plastics don't break down at all, then there's no chemical reaction byproducts to worry about. But if they break down very slowly, and the products of those reactions interfere with our biological processes in those tiny quantities, then we have a problem.
Because Steel and Wool degrade into their chemical components by chemical reactions (like oxidation or mold). Plastic wont, it gets smaller and smaller but it stays plastic. So Steel and Wool "skip" being really small, they become other chemicals nature can work with.
I just put the small pieces up my nose. No need to grind. Those hand pieces from the little people are ideal. Pull them out the arm and right up the nose. Then a 1x1 block to push it all the way up there.
When your victim complex is so strong that you have to invent new microaggressions to continue feeling persecuted instead of thinking logically for 5 seconds.