Microplastics (MNP) and nanoplastics (MNPs) are increasingly present in the environment, raising concerns about human exposure and health impacts. This study used pyrolysis gas chromatography-mass spectrometry (Py-GC/MS) to analyze MNP accumulation in human organs, specifically brains, livers, and kidneys, from autopsy samples collected in 2016 and 2024. Results showed that brains had significantly higher MNP concentrations than livers and kidneys, with concentrations increasing over time. Polyethylene was the most prevalent polymer, with a higher proportion in brain samples compared to liver and kidney. Transmission electron microscopy confirmed the nanoscale nature of the particles, which were largely aged, shard-like plastics. The study highlights the selective accumulation of MNPs in the brain, with concentrations rising over time. The findings suggest that MNPs may contribute to neurological health issues, particularly given the brain's high lipid content and the potential role of anionic nanoplastics in protein aggregation. The study also notes that while liver and kidney concentrations were lower than in the brain, they are still significant, and the lipophilic nature of plastics may facilitate their uptake and accumulation. The study underscores the need for further research to link MNP concentrations to health outcomes, given the rising environmental presence of microplastics and the increasing global rates of age-corrected Alzheimer's disease and related dementia. The study's limitations include the use of novel analytical methods and the potential for contamination, though these were minimized through quality control measures. Overall, the study provides important insights into the accumulation of MNPs in human tissues and their potential health implications.Microplastics (MNP) and nanoplastics (MNPs) are increasingly present in the environment, raising concerns about human exposure and health impacts. This study used pyrolysis gas chromatography-mass spectrometry (Py-GC/MS) to analyze MNP accumulation in human organs, specifically brains, livers, and kidneys, from autopsy samples collected in 2016 and 2024. Results showed that brains had significantly higher MNP concentrations than livers and kidneys, with concentrations increasing over time. Polyethylene was the most prevalent polymer, with a higher proportion in brain samples compared to liver and kidney. Transmission electron microscopy confirmed the nanoscale nature of the particles, which were largely aged, shard-like plastics. The study highlights the selective accumulation of MNPs in the brain, with concentrations rising over time. The findings suggest that MNPs may contribute to neurological health issues, particularly given the brain's high lipid content and the potential role of anionic nanoplastics in protein aggregation. The study also notes that while liver and kidney concentrations were lower than in the brain, they are still significant, and the lipophilic nature of plastics may facilitate their uptake and accumulation. The study underscores the need for further research to link MNP concentrations to health outcomes, given the rising environmental presence of microplastics and the increasing global rates of age-corrected Alzheimer's disease and related dementia. The study's limitations include the use of novel analytical methods and the potential for contamination, though these were minimized through quality control measures. Overall, the study provides important insights into the accumulation of MNPs in human tissues and their potential health implications.