At the very least, significantly more microplastics were found in corpses of people who had dementia and the volume has increased between 2016 and 2024.

Correlation vs causation will require more research but it surely can't be harmful begin to reduce exposure where we can as we didn't have microplastics resident in our body for most of human history. I'd hazard an educated guess that accumulating any inorganic material inside your body isn't good for you.

There are hints about them having carcinogen properties and promoting cerebral disorders (they do cross the blood-brain-barrier). But since human health is complex, not much evidence yet.

Yess, as they accumulate in the body at least.