The Human Intervertebral Disc as a Long-Term Repository for Micro/Nanoplastics: Tissue-Specific Accumulation and Risk Estimation

<title>Abstract</title> The presence of microplastics (MPs) and nanoplastics (NPs) in the human has raised health concerns, yet their tissue-specific accumulation in avascular environments remains unclear. Laser micro-Raman spectroscopy and pyrolysis-gas chromatography/mass spectrometry were employed to quantify MNPs from 21 donors undergoing spinal fusion. MPs showed a tissue-specific abundance gradient (blood: 6.74 ± 4.40 n/mL; bone: 13.55 ± 4.48 n/g; disc: 13.92 ± 4.69 n/g), predominantly composed of polyethylene terephthalate, polyethylene, and polystyrene fragments/fibers (1-100 μm). NPs (0.16-20.28 μg/g) were ubiquitously detected, with polyvinyl chloride and polyamide 66, accounting for 78.2% of the total mass, indicating distinct tissue-selective enrichment. A regulated accumulation pattern showed a dominant “disc-enriched” profile in nearly half the individuals. Fiber morphology, white color, larger size, and PET/PE polymers were identified as key drivers of tissue-selective retention. Although calculated chemical risks remain within safety limits, the substantial NPs sequestration in the avascular disc suggests an overlooked mechanism of long-term physical burden and potential tissue degradation. This study provides novel insights into the individualized MNPs accumulation and highlight the need to re-evaluate the health implications of plastic pollution in slow-metabolizing tissues.