why did not they got flushed by our digestive system,yes micro plastics are tiny,still they are too large to get into arteries and veins thus no way to reach the brain?
Nanoplastics can be so small that they can get inside most cells even blood cell so could pass through gut lining and blood brain barrier and sometimes are shaped like the key/lock our body already uses for certain intracellular chemical interactions and interferes with the correct molecules doing work, so they can be both inert for the most part and harmful because our cells just don’t just eject them automatically - though there also appears to be some max amount based on exposure level. The vast majority we might eat is excreted in bowel movements and urine and it still accumulates in tissue due to ubiquity.
article for laypeople
https://www.npr.org/sections/shots-health-news/2024/12/18/nx...