A recent retrospective analysis found the evidence of significant microplastic and nanoplastic (MNP) bioaccumulation in the human brain, with concentrations seven to thirty times greater than those in the liver or kidney, as detailed in a recent study published in Nature Medicine in February 2025. Therefore, the retrospective analysis utilized Py-GC/MS to evaluate postmortem frontal cortex, liver, and kidney specimens from New Mexico and East Coast cohorts collected between 1997 and 2024, involving 20–28 participants per timepoint and 12 dementia cases. • Dementia Correlation: Brain samples from patients with diagnosed dementia showed strikingly higher levels of plastics, with a median of 26,076 µg/g compared to normal frontal cortex cohorts. The results suggest a significant and concerning trend of increasing MNP concentrations within the human brain and liver over the past several decades. This bioaccumulation, specifically of PE nanoplastic shards, is markedly more pronounced in the frontal cortex, where concentrations are substantially elevated compared to peripheral metabolic organs.