A peer-reviewed Nature Health study found microplastics and nanoplastics in the brains of all 35 healthy people sampled and 99.4% of 156 people with brain tumors, with significantly higher concentrations in tumor tissue. The finding is important because it's the first large-scale confirmation that microplastics accumulate in living human brains, and the elevated levels near tumors suggest a possible connection—though the study notes this is correlation, not proven causation and more research is needed. What matters: microplastics are now detected in virtually every human brain examined, raising urgent questions about long-term neurological effects, but scientists emphasize the causal relationship between microplastic exposure and disease remains unknown and requires further investigation.