The simple answer is that it isn't supposed be there. The more interesting one is: how much would you say is too much? Would a kilo of microplastics towards the end of your life do it?
A huge number of people have implements in their bodies (in their teeth, most often), and much more than seven grams of “foreign stuff” in their stomach and intestines all the time, so that by itself doesn’t seem anything to be terrified of.
https://www.theguardian.com/environment/article/2024/aug/21/...
That doesn't seem very complicated, does it?
It being in my brain is an adverse effect. Inert material in the brain is a problem itself.
Do you want inert rocks in your car engine? Taking up space, interfering with natural processes, etc?
The brain is incredibly complex; far, far, far beyond our current understanding. You don't want anything in there that isn't supposed to be, and plastic isn't fucking supposed to be there.
And, did you miss the part where this is up 50% from only 8 years ago?
... Tbh I'm aghast that anyone needs this explained to them.