Undiseased and diseased abdominal aortas contain environmentally relevant micronanoplastics

Background

Plastics production has accelerated, with most products ultimately residing in the environment. Plastics degrade into micro- (<5 mm) and nano- (<1000 nm) plastic particles (MNPs) that can be ingested or inhaled by humans. In the literature, MNPs have been found in higher concentrations in diseased arteries, but the mechanisms remain unclear. Studies have found MNPs in tissue from ascending aortic dissections, but data on infrarenal aortic aneurysms, occlusive plaques, and cadaveric aortas have not been reported.

Methods

MNPs from aortic aneurysmal walls, aortic occlusive plaques, and fresh cadaveric aortas were measured using pyrolysis-gas chromatography/mass spectroscopy; the MNPs assessed included polyethylene (PE), polypropylene (PP), polystyrene, acrylonitrile butadiene styrene, styrene-butadiene (SBR), poly(methyl methacrylate), polycarbonate, polyvinylchloride (PVC), polyurethane, polyethylene terephthalate, nylon 6, and nylon 66. Scanning electron microscopy/energy dispersive X ray spectroscopy was used to visualize MNPs and characterize the milieu of a single aortic plaque for hypothesis generation.

Results

Nine aneurysms (n = 9 male; mean age, 71 years), six occlusive plaques (n = 4 male; mean age, 67 years), and twelve cadaveric aortas (n = 4 male; mean age, 35 years) were collected. In non-atherosclerotic, cadaveric aortas, the most prevalent polymers were PE (33.7 μg/g tissue), PVC (33.5 μg/g), and PP (21.3 μg/g). In atherosclerotic cadaveric aortas, the most prevalent polymers were PE (99.5 μg/g), PP (66.7 μg/g), and PVC (58 μg/g). In aneurysms, the most prevalent polymers were PE (115.8 μg/g), SBR (114.7 μg/g), and PVC (67.3 μg/g). In plaques, the most prevalent polymers were PE (745.5 μg/g), PVC (47.5 μg/g), and SBR (40.3 μg/g). Numerous within-group differences between polymers were noted, often following a common theme of which was the most prevalent. Single plaque scanning electron microscopy/energy dispersive X ray spectroscopy revealed shard-like MNPs surrounded by calcium/phosphorus, suggesting that MNPs accumulate within plaque calcifications in occlusive disease.

Conclusions

Detectable levels of MNPs were found in aortic atherosclerotic occlusive plaques, aortic aneurysms, and both normal and diseased cadaveric aortas. Nanoplastics were visualized within plaque calcifications in occlusive disease. Further study is needed to elucidate the mechanisms through which MNPs play a role in atherosclerotic and degenerative vascular disease development.

Clinical relevance

This work examines the levels of micronanoplastics in human aortic aneurysms and aortoiliac atherosclerotic plaques and reports the levels in healthy and diseased cadaveric aortic tissues. No clear associations between age and micronanoplastic levels were demonstrated among patients. Of the polymers measured, polyethene, polyvinyl chloride, and polypropylene were the most common. These data not only add to the growing literature suggesting that micronanoplastic particles accumulate in atherosclerotic lesions but also provide valuable insights regarding the micronanoplastic content of healthy arteries. Future work should investigate the mechanistic role, if any, of micronanoplastics in the pathophysiology of vascular atherosclerotic disease.