Visualizing micro- nanoplastics in the human brain: Early evidence for roles in microvascular pathology

Our environment has become progressively contaminated with non-biological materials, especially synthetic carbon polymers, plastics. Unsurprisingly some of these make it into the human body as detected by chemical analyses, yet it is unknown whether they cause harm or are innocent bystanders. Building on our observations of glossy deposits and unusual non-biological fluorescent particles in blood vessels, we aimed to determine whether these objects represented plastics. To do this we prepared plastics-enriched pellets from brain and subjected them to pyrolysis gas-chromatography/mass spectroscopy (py-GC/MS), electron microscopy and confocal laser scanning microscopy. Py-GC/MS confirmed the presence of 10 different plastics. Contents of pellets were examined by thin-section EM. We then used laser scanning confocal microscopy to acquire hyperspectral profiles of each type of plastic in suspensions. We found fluorescent particles in all pellets from brains. All 12 plastics in the calibration standard fluoresced. We obtained hyperspectral profiles of single species plastics from industry: Polyethylene, polypropylene and polystyrene. Controls included chemical analysis of brain storage buffer, which had no detectable plastics; and imaging water only and areas on slides lacking tissue. Abundant particles with emission profiles similar to polyethylene and polypropylene decorated the walls of both arterioles and venules. These particles were coincident with glossy deposits we first observed in white matter, suggesting that both features represent plastics. In summary our results demonstrate that synthetic polymers exhibit detectable fluorescence, and particles with similar spectral properties are visible in histologic sections. This opens the door to investigating correlations between plastics and pathology.