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

The Human Intervertebral Disc as a Long-Term Repository for Micro/Nanoplastics: Tissue-Specific Accumulation and Risk Estimation | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Article The Human Intervertebral Disc as a Long-Term Repository for Micro/Nanoplastics: Tissue-Specific Accumulation and Risk Estimation Xuehua Li, Yanhua Wang, Zixian Feng, Jiawei Zhang, Baoshan Xing, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-9100391/v1 This work is licensed under a CC BY 4.0 License Status: Under Review Version 1 posted 11 You are reading this latest preprint version Abstract 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. Biological sciences/Biological techniques Physical sciences/Chemistry Earth and environmental sciences/Environmental sciences Physical sciences/Materials science Health sciences/Medical research Physical sciences/Nanoscience and technology Microplastics Nanoplastics Human tissues Accumulation patterns Health risks Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction Once released into the natural environment, plastics tend to degrade into Microplastics (MPs, < 5 mm 1 ) and Nanoplastics (NPs, <1 μm). These particles are widely detected in various environmental matrices, including oceans, rivers, lakes, sediments, soils, and the atmosphere 2-7 , as well as within aquatic organisms such as fish, shrimp, and mussels 8,9 . MPs and NPs (collectively MNPs) have also been identified in human-consumed food 10 and drinking water 11 . In recent years, MNPs were detected in an increasing number of human tissues and organs, ranging from feces, colon, and placenta to blood, lungs, respiratory tract, liver, and kidneys, and even in breast milk, testes, bone tissue, and the brain 12-18 . Marfella R et al. 19 were the first to demonstrate the direct association between MPs and human health, reporting that individuals with MNPs detected in carotid artery plaques had a 4.53-fold higher composite risk of myocardial infarction, stroke, or all-cause mortality compared to those without MNPs detection. Existing studies indicate that MNPs accumulation within blood vessels may damage the endothelial lining and even trigger thrombosis 20 . High levels of MNPs intake may exacerbate inflammation and disrupt distant organs, thereby elevating the risk of cancer, diabetes, cardiovascular disease, and chronic pulmonary disorders 21 . Although MNPs are known to penetrate multiple physiological barriers, existing studies have primarily focused on vascularized, metabolically active organs. Their long-term behavior and health implications in avascular, metabolically inert tissues remain underexplored. As the primary transport medium in the human body, blood can rapidly circulate MNPs to various tissues and organs 22 . It offers a transient window into recent systemic exposure. Previous studies employed pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) or micro-Fourier transform infrared spectroscopy (μ-FTIR) to detect MPs in blood samples 22,23 . However, Py-GC/MS does not provide information on particle size, morphology, or polymer type, while μ-FTIR is limited to characterizing MPs larger than 5 μm, and neither technique addresses the detection of NPs. In contrast, bone tissue has poor vascularization, resulting in a longer timescale for MNPs deposition. Thus, bone may serve as a mid-term retention compartment for MNPs. Animal studies confirmed that once NPs enter bone cells in mice, they can disrupt specific cellular functions and cause various adverse effects 24 , suggesting their potential for persistent retention in bone tissue. The intervertebral disc, the largest avascular tissue in the human body 25 , exhibits extremely slow metabolic activity, thereby, it is more likely to reflect long-term MNPs accumulation. To date, only one study reported the presence of MPs in intervertebral discs 26 , critical knowledge gaps remain regarding the simultaneous quantification of NPs and the comparative accumulation dynamics across the blood-bone-disc axis within the same individuals. Additionally, inter-individual differences such as lifestyle, occupation, age as well as variations in exposure routes and intake levels may jointly influence MNPs distribution in the body, yet relevant research remains limited. This study investigated MNPs in human blood, bone tissue, and intervertebral disc samples using laser micro-Raman spectroscopy and Py-GC/MS. We propose the following scientific hypothesis: due to the avascular nature and extremely slow metabolic rate of the intervertebral disc, it may exhibit a more significant retention effect for MNPs than bone tissue. The objectives are to: (1) systematically reveal, for the first time, the temporal deposition pattern of MNPs, from short-term exposure in blood to intermediate accumulation in bone tissue and long-term retention in the intervertebral disc; (2) perform detailed size-fraction analysis, covering NPs smaller than 1 μm and MPs ranging from 1 to 5000 μm, thereby enabling a comprehensive assessment of MNPs size distribution across human tissues; (3) explore the relationship between MNPs deposition patterns and potential health risks, offering an integrated evaluation of their implications for human health. The findings are expected to provide new momentum for the field of human MNPs exposure risk research and establish a robust data foundation for future investigations into long-term health effects. Results MPs abundance in blood, bone, and intervertebral disc MPs were detected in all blood, bone tissue, and intervertebral disc samples collected from 21 donors. The average MPs abundances were 6.74 ± 4.40 n/mL in blood, 13.26 ± 5.49 n/g in bone tissue, and 13.55 ± 4.48 n/g in intervertebral discs (Fig. 1a). Blood MPs concentrations varied considerably among individuals, ranging from 3.50 to 7.80 n/mL for most donors, whereas bone and disc levels were more consistent, with most values between 8.50 and 18.90 n/g. MPs were not detected in the bone tissue of donor No. 7. Donor No. 7 led a lifestyle with minimal plastic exposure and no underlying disease. Despite detectable MPs in blood and disc, none were found in bone. Notably, donor No. 8 exhibited the highest MPs abundances across all three tissues (blood: 19.16 n/mL; bone: 19.80 n/g; disc: 18.93 n/g). This individual suffered from lumbar disc herniation, and the MPs abundance in the intervertebral disc was lower than that in bone tissue. This individual’s lifestyle included frequent consumption of bottled beverages and takeout food (Fig. S1). Donors No. 3, 15, and 21 showed relatively higher MPs levels in blood compared to the rest of the cohort (Text S1). Statistical analysis revealed that MPs abundance in blood was significantly lower than in bone tissue and intervertebral discs (p<0.05). The MPs concentrations measured in this study exceeded those reported by Leonard et al. 23 for blood (2.47 ± 4.18 n/mL) but were considerably lower than the values documented by Yang et al. 26 for intervertebral discs (61.10 ± 44.20 n/g) and bone tissue (22.90 ± 15.70 n/g). Size, color, shapes and types of MPs The average particle sizes of MPs were 64.50 ± 38.20 μm in blood, 57.10 ± 33.80 μm in bone tissue, and 77.60 ± 53.40 μm in intervertebral discs (Fig. 1b). Overall, MPs sizes ranged from 9.79 to 193.29 μm, with the largest particles found in discs and the smallest in blood. The majority of MPs were below100 μm, accounting for 90.0% in blood, 92.5% in bone, and 62.5% in disc samples (Fig. 1c). Notably, 17.5% of MPs in intervertebral discs were larger than 100 μm, a proportion higher than in the other tissues. Clear distribution patterns of microplastic physical characteristics (color, shape) were observed across all three tissues. Across all tissues, fragments and fibers were the dominant morphotypes, with gray and transparent being the most common colors (Fig. S2a, S2b). Fragment-shaped PET particles were the dominant type in all three tissues, accounting for 58.60% of the total detected MPs. Nine polymer types were identified, including polyethylene terephthalate (PET), polyethylene (PE), ethylene-vinyl acetate copolymer (EVA), polystyrene (PS), polydimethylsiloxane (PDMS), polybutylene terephthalate (PBT), and polyvinyl chloride (PVC). PET was the predominant polymer in all three tissues, followed by PE and PS. Blood samples exhibited the greatest polymer diversity, containing trace amounts of PDMS, PBT, and PVC, whereas bone and disc showed more restricted polymer profiles (Fig. 2). PBT was detected exclusively in intervertebral discs. PET fibers were more abundant in intervertebral discs than in blood and bone tissue. NPs concentration and polymer distribution NPs were detected in all analyzed samples (15 donors), with mass concentrations ranging from 0.16 to 20.28 μg/g (Fig. 3a). The highest NPs concentration was observed in the bone tissue of donor No. 20 (PVC: 20.28 μg/g), while the intervertebral disc of donor No. 21 showed a high concentration of PA66 (18.75 μg/g), highlighting notable individual variability for specific NPs types. Tissue-specific distribution patterns were evident among polymer types (Fig. 3b). PVC exhibited the highest average concentration in bone tissue (7.74 μg/g), whereas PA66 was relatively enriched in intervertebral discs (6.28 μg/g). The average concentration of PVC in blood was 2.39 μg/g, remaining the dominant NPs type. PS concentrations were low in all three tissues. PMMA (0.56 μg/g) was detected only in the intervertebral disc of donor No. 8, who underwent bone graft fusion surgery. The polymer composition of NPs showed that PVC and PA66 accounted for 46.9% and 31.3% of the total mass, respectively, significantly higher than PS (18.8%) and PMMA (3.1%) (Fig. 3c). A size-dependent divergence in polymer composition was observed: PET and PE dominated the MPs fraction, whereas PVC and PA66 were predominant in the NPs fraction, with the two polymers together accounting for 78.2% of the total NPs mass. Health risk assessment Three exposure pathways (ingestion, inhalation, and dermal contact) were considered in the assessment, but the contributions to the hazard quotient (HQ) differed significantly among these pathways. HQ values for MPs in different tissues followed the order: intervertebral disc > bone tissue > blood. The highest HQ value was observed in intervertebral discs (9.0 × 10⁻⁴), which was mainly attributed to the sustained accumulation of MPs in intervertebral discs through blood circulation or local permeation, while the contributions of dermal and inhalation exposure pathways were limited. For all 21 donors, the HQ values remained below 1 (Fig. 4a). The hazard index (HI), calculated as the sum of HQs across exposure pathways, also followed the same tissue gradient (intervertebral disc > bone > blood), with an average HI of 3.8 × 10⁻³ across donors (Fig. 4b). Tissue-specific analysis showed that the intervertebral disc was the main contributor to health risk in most donors. Cancer risk (CR) values for all donors did not exceed 10⁻⁴ for any exposure pathway. The cumulative carcinogenic risk (CCR) averaged 9.7 × 10⁻⁶ across donors. Tissue-specific CCR values showed a gradient: intervertebral disc > bone tissue > blood. The maximum individual CCR reached 3.8 × 10⁻⁵, primarily contributed by intervertebral disc accumulation. Donors No. 2, 13, and 19 exhibited the highest CCR values in their intervertebral discs, and their CCR values were significantly higher than those in other tissues of the same individuals (Text S2). Correlation and multivariate analysis of MNPs accumulation patterns Correlation analysis revealed a significant positive correlation between MPs abundances in blood and bone tissue (p≤0.01). MP abundance in blood was significantly negatively correlated with donor age (p≤0.01; Fig. 5a). No significant correlations were found between MPs abundance and other demographic factors including gender, BMI, height and weight. Principal component analysis (PCA) showed distinct clustering patterns: blood and disc samples occupied separate areas in the score plot, with bone tissue samples positioned between them (Fig. 5b). Partial least squares-discriminant analysis (PLS-DA) classified the 21 donors into three accumulation phenotypes: disc-enriched (10/21), intermediate, and blood-enriched (Fig. 5c). Variable importance in projection (VIP) (presented here as “Total Importance” which corresponds to the normalized relative contribution of VIP values) analysis identified the top discriminatory features associated with disc/bone enrichment: fiber morphology, white color, larger particle size, and the polymers PET and PE. In contrast, transparent particles, polypropylene, and microspheres were more associated with blood samples (Fig. 5d). PLS-DA identified fiber morphology, white color, larger particle size, and PET/PE as key discriminatory features, with significant differences confirmed among tissue types and phenotype groups by one-way ANOVA (Fig. S3b, Text S3). The PLS-DA score plot (Fig. S3a) illustrates the distribution and separation of the three tissue types in the latent variable space. Nanoplastics also exhibited tissue-specific correlation patterns. Significant positive correlations were observed between blood and bone tissue for PVC and PA66 (p ≤ 0.01), suggesting systemic exposure and migration to bone. In contrast, correlations involving intervertebral discs were weaker, with only PVC and PA66 showing marginal significance with bone tissue (p ≤ 0.05). Principal component analysis further revealed distinct clustering: blood samples aligned with height (PC1), bone tissue correlated with BMI and PS-NPs (PC1), while intervertebral discs were closely associated with PVC and PA66 (PC2), identifying the disc as the primary accumulation site for these polymers (Fig. S4). Detailed correlation and principal component analysis of nanoplastic distribution across tissues are provided in Text S4 and Fig. S4. Discussion This study provides a simultaneous quantification of MPs and NPs in matched human blood, bone, and intervertebral disc samples from the same individuals. Our results reveal a clear tissue‑specific accumulation gradient: MPs abundance in blood was significantly lower than in bone and intervertebral discs, while NPs concentrations showed distinct polymer‑dependent distribution patterns. The intervertebral disc, being avascular and having a slow metabolic rate, can serve as a potential long-term repository for micro- and nanoplastics in the human circulatory system 25 , 27 . The observed MPs abundance gradient (blood < bone ≈ disc) aligns with the vascularization and metabolic activity of these tissues. Blood, as the primary transport medium, is directly exposed to circulating MPs but also possesses rapid clearance mechanisms 28 . In contrast, bone tissue has limited vascularization and undergoes continuous remodeling, which may allow intermediate‑term retention of particles 29 , 30 . Furthermore, MPs accumulation in bone has been associated with adverse effects on bone cells and bone homeostasis 31 . The intervertebral disc, being the largest avascular tissue in the human body, relies on diffusion for nutrient exchange and lacks efficient cellular clearance pathways 25 , 27 . This physiological feature likely contributes to the long‑term sequestration of MPs, as particles that enter the disc become trapped and cannot be readily removed. Consistent with previous reports by Zhu 17 and Guo 31 et al., microplastics smaller than 100 µm predominated in all tissues. The higher proportion of MPs > 100 µm in discs compared to blood and bone further supports this retention capacity, as larger particles are less likely to exit via diffusion 27 . This mechanism is consistent with the observation that fiber‑shaped and larger MPs were preferentially retained in discs and bone, as their morphology may facilitate entrapment within the extracellular matrix 32 , 33 . However, as an avascular tissue, the intervertebral disc requires an explanation for how circulating MNPs enter it. Based on available evidence, we propose the following potential pathways. (i) Degeneration-associated vascular ingrowth. Studies have shown that aberrant vascular proliferation accompanies disc degeneration 34 . These new blood vessels may serve as conduits for circulating MPs to enter the disc directly. (ii) Lymphatic involvement. Recent research has revealed the presence of lymphatic vessel structures within intervertebral discs 34 . The inter-endothelial gaps of these initial lymphatics could theoretically allow the passive transport of NPs and even micron-sized particles. (iii) Cell-mediated active transport. Immune cells such as macrophages can engulf particles and migrate between tissues 35 . This process may carry MNPs into the disc microenvironment. These pathways provide a mechanistic explanation for how MNPs enter and become deposited in the disc over the long term. The enrichment of MPs in discs may also be driven by physicochemical interactions with the tissue matrix. Considering that the nucleus pulposus has a mildly acidic environment and is rich in negatively charged aggregating proteoglycans 36 , its glycosaminoglycan side chains may adsorb positively charged MPs particles in acidic conditions via electrostatic interactions 37 , thus enhancing MPs retention. This electrostatic adsorption forms an initial “charge trap” The nucleus pulposus contains an anionic matrix, which is rich in negatively charged glycosaminoglycans (GAGs) 36 . This matrix can electrostatically bind to weathered MPs that may carry positive surface charges. Such an interaction is analogous to the cation-anion complementarity observed in targeted molecular interactions within intervertebral discs 38 . Crucially, long-term retention stems from the synergy between the capture and the tissue's lack of clearance. Bone undergoes active, cell-mediated remodeling that can potentially mobilize particles 30 . In contrast, the avascular disc lacks such clearance mechanisms, relying solely on slow diffusion 27 . Thus, electrostatic adsorption combined with absent biological clearance leads to the long-term sequestration and enrichment of MPs in discs. Additionally, the presence of macrophages in degenerated discs may modulate local MPs retention 25 , 39 , though their exact role requires further investigation. Beyond the physical retention, the polymer composition of MPs and NPs exhibited marked size‑dependent divergence. PET and PE dominated the MPs fraction across all tissues. This predominance reflects their widespread use in packaging and textiles 40 , 41 and their high prevalence in environmental samples 42 , 43 . PET emerged as the predominant polymer in all three tissues, aligning with prior findings from blood 22 and lung tissue 23 studies. PET is widely used in beverage bottles, food packaging films, synthetic fibers, and medical devices 40 . In urban indoor and outdoor dust in China, PET and polycarbonate (PC) were the main MPs components 41 . In contrast, PVC and PA66 accounted for nearly 80% of the NPs mass, with PVC enriched in bone and PA66 enriched in discs. This pattern may arise from the differential fragmentation and environmental persistence of these polymers. In the medical field, over one-quarter of polymer-based devices were made of PVC, including blood bags, infusion sets, and oxygen masks 44 , 45 . These devices directly contact the human body and serve as potential exposure sources. Widely used in textiles, personal care products, and fishing gear 46 , PA66 is frequently detected in wastewater treatment plants and widely distributed in marine and terrestrial environments, posing significant exposure risks to animals, plants, and humans 47 – 49 . The enrichment of PVC may be related to the high degree of mineralization and dense structure of bone tissue 50 , which facilitates its adsorption and retention. Meanwhile, the relative enrichment of PA66 was attributable to the high water content of intervertebral discs and its affinity for proteoglycans and other matrix constituents 51 , which jointly furnish a microenvironment for PA66 adsorption. At the molecular level, the dense polar amide groups on the PA66 chain can form hydrogen-bond networks and exhibit strong hydrogen bonding with hydrophilic groups such as hydroxyls 52 , 53 . The intervertebral disc possesses a highly hydrated and proteoglycan-rich microenvironment. In this setting, PA66 nanoparticles undergo selective adsorption. This process is mediated by intermolecular interactions, such as hydrogen bonding, between the amide groups of PA66 and the proteoglycan chains. These interactions facilitate the long-term retention of nanoparticles. The exclusive detection of PMMA in the disc of donor No. 8, who underwent spinal fusion with internal fixation, likely originates from surgical device wear 54 . This finding underscores the contribution of medical interventions to local NPs burden 44 , 45 . These observations indicate that both environmental sources and iatrogenic factors contribute to the complex mixture of MNPs in human tissues. Health risk assessment based on current chemical‑toxicity models indicates that both non‑carcinogenic and carcinogenic risks from MPs exposure fall within acceptable safety limits at the current exposure levels. Although the possibility of MPs entering the human body via the skin is minimal, they may still entry through wounds, sweat glands, or hair follicles 55 . Plastic products in medical supplies (e.g., surgical sutures) may also increase the risk for dermal exposure to MPs 56 . Existing animal and cell models consistently indicate that long-term or sub-chronic exposure to MNPs at low concentrations or doses can still compromise antioxidant defenses. The exposure levels in these studies range from µg/L to µg/mL or mg/kg·d, which are far below acute cytotoxic thresholds 57 , 58 . Nevertheless, such low-level exposure significantly increases oxidative stress markers, including reactive oxygen species (ROS) and malondialdehyde (MDA), and persistently upregulates various inflammatory factors. MPs’ biological persistence may drive long-term accumulation in slow-metabolism tissues like intervertebral discs 59 . Although current CR values (≤ 10⁻⁶) are substantially lower than the threshold of concern (10⁻⁴), chronic low-dose exposure could still induce pathological changes through oxidative stress or inflammation 60 . Therefore, reliance solely on chemical risk metrics may severely underestimate the true health burden, especially in tissues with slow turnover. Donors No. 2, 13, and 19 had the highest CCR values in their intervertebral discs. Although remaining within the currently accepted safety margins, these values were significantly higher than those in other tissues, likely reflecting the enhanced retention of MPs in slow-metabolizing tissues and their potential for injury 61 . Taking both the non-carcinogenic and carcinogenic risk assessments into account, the results for all 21 donors fall within safe limits. Nonetheless, from a long-term and population-wide perspective, continued vigilance regarding MPs pollution is necessary. A striking finding was the negative correlation between blood MPs abundance and donor age. This relationship was statistically significant (p ≤ 0.01) and suggested higher transient exposure in younger individuals. Lifestyle factors may contribute to this pattern, including greater consumption of bottled beverages, takeout food, and personal care products containing MPs 62 – 64 . However, no significant age correlation was observed in bone or disc tissues. This discrepancy implies that while younger individuals experience higher short‑term circulating loads, long‑term accumulation in deep tissues may depend on additional factors. The negative correlation in blood likely reflects immediate exposure from modern lifestyles, whereas its absence in deep tissues suggests that accumulation represents a long-term equilibrium between intake and clearance. This implies that as the current younger demographic ages, the cumulative load of MPs deposited in their intervertebral discs may ultimately surpass that observed in today's older generation. Using multivariate analysis, we identified three distinct individual accumulation phenotypes. Notably, the first principal component (PC1), which likely represents environmentally weathered MPs, showed a negative correlation with donor age, further supporting the link between lifestyle-related exposure and particle characteristics. Moreover, the disc-enriched phenotype exhibited a significant positive PC1 gradient from blood to intervertebral disc, indicating that particles with specific weathered characteristics are progressively sequestered in this avascular tissue. The predominance of the disc-enriched pattern, coupled with its marked positive blood-to-disc gradient, strongly corroborates the intervertebral disc as a key long-term reservoir for circulating MPs 65 . The key features identified by this Total Importance analysis (aligning with the core role of VIP in PLS-DA) suggest that both the physical morphology (e.g., fibers) and chemical nature (e.g., the biopersistence of PET) of the particles contribute to this tissue selectivity. The high detection frequency of PET in disc and bone tissues further supports its high biopersistence and mobility 66 . The age-dependent correlation observed here differs from a report on liver and brain tissues 67 , hinting at potential tissue- and population-specific deposition mechanisms 68 . This population-specific exposure pattern may be supported by consumption data: Exposure modelling estimates a considerable daily per capita intake of microplastics, with children and adults at 553 and 883 ng/capita/day, respectively 64 . The higher consumption of single-use packaged food, bottled beverages, and personal care products containing microbeads among younger demographics represents a significant and quantifiable source of their exposure. These results indicate that the distribution of MPs in vivo is an outcome of the complex interplay among exposure source characteristics, particle properties, and the tissue microenvironment. While this study offers preliminary datasets, it fails to elucidate the underlying toxicological mechanisms of MNPs exposure across diverse biological tissues. Moreover, Py-GC/MS technique used for NPs detection remains constrained by limited resolution and susceptibility to organic matrix interference. Future investigations should integrate analytical techniques (thermal desorption mass spectrometry, Raman imaging, and field-flow fractionation) to characterize MNPs occurrence across exposure pathways, polymers, and tissues, while combining cellular and animal models to elucidate their transport pathways and key toxicity mechanisms. Methods Sample collection and preservation This study was approved by the Medical Ethics Committee of the First Affiliated Hospital of Air Force Medical University (approval number: KY20242164-C-1). All procedures complied with the Declaration of Helsinki and Good Clinical Practice (GCP) guidelines, ensuring that participants' informed consent, rights, and safety were fully protected. This study included 21 participants who underwent spinal fusion with internal fixation between November 2024 and January 2025. The participants' ages ranged from 33 to 74 years (median 58 years), including 47.6% male and 52.4% female. The primary diagnoses were lumbar disc herniation and lumbar spondylolisthesis. The participants' body mass index (BMI) ranged from 19.5 to 30.2 kg/m², with approximately 57% of participants classified as overweight or obese according to Chinese adult BMI criteria. Detailed demographic and clinical characteristics are provided in Table S1 . Blood samples were collected before surgery. Bone tissue and intervertebral disc samples were collected intraoperatively by trained surgeons using sterile procedures. Blood was collected in EDTA anticoagulant tubes. All participants signed written informed consent before sample collection. To avoid external plastic contamination, all personnel wore 100% cotton lab coats, disposable nitrile gloves, and head coverings. Only plastic-free instruments were used during sampling and sample handling. Sample pretreatment and digestion All samples were vacuum freeze-dried before processing. Blood samples (2.5 mL) were transferred into 250 mL wide-mouth glass bottles, mixed with 50 mL nitric acid, pre-digested in a 50°C water bath for 30 min, followed by digestion at 70°C for 10 min. The digested solution was diluted with ultrapure water and filtered through membrane A (mixed cellulose membrane, 0.45 µm pore size, 50 mm diameter). The membrane was transferred to 100 mL anhydrous ethanol, sonicated for 15 min, rinsed three times with ethanol, and the rinse solutions were filtered again. Particles were retained on membrane A for MPs analysis. For bone tissue samples, visible muscle, fascia, and residual tissues were carefully scraped off using a scalpel. The bone was crushed using sterile bone forceps. Approximately 1.0 g of fragmented bone tissue was added to saturated ZnCl₂ solution to float MPs, left to stand for 24 hours, centrifuged, and the supernatant was collected into 250 mL amber glass bottles for digestion. For intervertebral disc samples, approximately 1.0 g of fragmented sample was placed directly into 250 mL amber glass bottles for digestion. The digestion process for both bone and intervertebral disc samples was as follows: (1) Fenton's reagent was added and digested in a water bath for 5 hours; (2) vacuum filtration through membrane A; (3) re-digestion with nitric acid (50 mL, 65%) for 30 minutes; (4) 50% dilution with ultrapure water and vacuum filtration through membrane B (PTFE membrane, 0.45 µm pore size, 50 mm diameter); (5) membrane transferred to 100 mL anhydrous ethanol, sonicated for 15 min, rinsed three times with ethanol, and vacuum filtered through a new membrane B. After freeze-drying, samples were ready for analysis. A sintered funnel (30 mm diameter) was used for filtration. To ensure repeatability and accuracy, three parallel samples were set for each tissue type. All samples were processed using the same procedure. Blank controls (with reagents only) were included in each batch and analyzed alongside real samples to identify potential background contamination. MPs analysis by laser micro-Raman spectroscopy The analysis of MPs in 21 blood, bone tissue, and intervertebral disc samples was primarily conducted using a laser micro-Raman spectroscopy (Thermo Scientific, DXR3xi). The main parameters were set as follows: laser source at 785 nm, laser power of 15 mW, exposure time of 0.5000 sec (2 Hz), and 50 scans. A five-point method was used for sample observation, in which the entire sample film was divided into nine regions. Five scanning points were set for each region (top, middle, bottom, left, and right), totaling 45 scanning points. All particles in each scanning point were tested. The spectral range was set from 300 to 3500 cm − 1 . The collected spectra were compared with a custom-built standard spectral library (containing nearly 30 types of plastics, covering over 99% of plastic varieties) and the laser micro-Raman spectroscopy sample library to identify the composition of the plastic particles. Nano Measurer software (version 1.2) was used to statistically analyze the particle size, shape, and color of the MPs. NPs analysis through Py-GC/MS Fifteen samples of blood, bone tissue, and intervertebral disc were selected for nanoplastic analysis using Py-GC/MS. Nanoplastic detection was performed using a Multi-Shot Pyrolyzer EGA/PY-3030D (Frontier Laboratories, Japan) connected to a gas chromatograph-mass spectrometer (GCMS-QP2020, Shimadzu, Japan) equipped with an Rtx-5MS column (30 m × 0.25 mm × 0.25 µm). The pyrolysis temperature was set to 550°C. The gas chromatography settings were: temperature ramped from 40°C to 320°C at 20°C·min⁻¹, with a total runtime of 30 minutes, followed by 14 minutes at this temperature. Helium was used as the carrier gas, with a split ratio of 5:1. The mass-to-charge ratio (m/z) range was set from 29 to 600, with the ion source temperature fixed at 320°C. Sample preparation: Samples were accurately weighed (precision 0.001 g) into 100 mL beakers. Nitric acid was added at three times the sample weight and left at room temperature for 48 hours. After digestion, the solution was passed through a 1 µm steel membrane. The filtrate was concentrated at 110°C. An aliquot of the concentrated liquid was placed into the sample crucible and heated at 80°C until solvent evaporation, then analyzed by Py-GC/MS. Process blanks were performed, and the entire concentrated liquid was tested. Standard solutions with different concentrations were prepared and tested to establish a calibration curve. To eliminate the interference of complex organic matrices in biological samples on NPs detection, a series of strict sample pretreatment and instrumental quality control measures were adopted. Biological samples were subjected to acid digestion, membrane filtration and rotary concentration for targeted removal of endogenous organic matrices. The reagents used in this experiment were pre-filtered three times using a 0.45 µm PTFE membrane. Consumables were washed three times with filtered anhydrous ethanol before use. Health risk assessment The commonly used health risk assessment methods for non-cancer risks (HQ) and cancer risk values (CR) were proposed by the United States Environmental Protection Agency (USEPA) in 2000 as a way to evaluate human health risks 69 .We chose to use the HQ method and the CR method from human health risk assessment and combined the model parameters recommended in the “Technical Guidelines for Risk Assessment of Polluted Sites” issued by the Ministry of Ecology and Environment of China, along with the maximum weekly mass of MPs ingested by humans through various exposure pathways (food intake, inhalation, and dermal absorption) as estimated by Senathirajah et al. 70 , for the analysis and evaluation. The calculation formulas can be found in Text S5. The evaluation criteria and model parameters used in this study are listed in Table S2 and Table S3, respectively. Quality assurance and control To minimize background contamination and ensure data reliability, strict quality control measures were implemented throughout this study. During sample collection, all personnel wore sterile cotton garments, nitrile gloves, masks, and head coverings, with no contact permitted with plastic materials. Bone and disc samples were collected using stainless steel instruments and immediately transferred to foil‑sealed glass containers to limit air exposure. High‑speed power tools were avoided to prevent intraoperative plastic generation. A procedural blank accompanied each sampling session to monitor environmental contamination. All pretreatment and analytical steps were performed by the same operator in a laminar‑flow hood. Glassware was rinsed three times with ultrapure water and heat‑dried. Reagents were filtered through 0.45 µm PTFE membranes. Blank controls were included during the experiment, which consisted of air-exposed filter membrane blanks and reagent blanks that followed the same sample treatment process. These blanks followed the same preparation and filtration procedures yet yielded no detectable MPs particles. Finally, all data were calculated after subtracting the background from the procedural blanks. Statistical analysis In this study, the quantity of MNPs in samples was quantified by abundance, specifically the number of MPs per unit mass of sample (unit: n/kg) and the concentration of NPs (unit: mg/kg). Characterization data of MPs, including abundance, particle size, type, and morphology, were analyzed and summarized using Microsoft Excel 2024. Statistical charts were generated with Origin 2024. Statistical analyses were completed using IBM SPSS Statistics software. To classify individual accumulation patterns across tissues, partial least squares‑discriminant analysis (PLS‑DA) was performed. Significance was tested by non-parametric multivariate analyses Adonis and Anosim. Differences with p < 0.05 were considered statistically significant. Declarations Data availability Data will be made available on request. Acknowledgements This work was supported by the National Natural Science Foundation of China (42577468 and 42277207), the Fundamental Research Funds for the Central Universities (GK202401003), Shaanxi Province Key Industrial Innovation Chain under Grant (2023-ZDLSF-12) and FMMU special research project of cross-cooperation (2024JC044). Author contributions X.L.: data curation, formal analysis, investigation, methodology, writing-original draft; Y.W.: conceptualization, funding acquisition, project administration, supervision, writing-review & editing; Z.F.: data curation, formal analysis, software, validation; J.Z.: investigation, methodology, resources; B.X.: methodology, validation, writing-review & editing; and T.D.: conceptualization, methodology, supervision, validation, writing-review & editing. All authors reviewed and approved the final version. Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. References Arthur, C., Baker, J.E. & Bamford, H.A. Proceedings of the International Research Workshop on the Occurrence, Effects, and Fate of Microplastic Marine Debris, September 9-11, 2008, University of Washington Tacoma, Tacoma, WA, USA. (2009). Alfaro-Núñez, A. , et al. Microplastic pollution in seawater and marine organisms across the Tropical Eastern Pacific and Galápagos. Sci. Rep. 11 , 6424 (2021). Evangeliou, N. , et al. Atmospheric transport is a major pathway of microplastics to remote regions. Nat. Commun. 11 , 3381 (2020). He, L., Li, Z., Jia, Q. & Xu, Z. Soil microplastics pollution in agriculture. Science 379 , 547-547 (2023). Thompson, R.C. , et al. Lost at Sea: Where Is All the Plastic? Science 304 , 838-838 (2004). Wang, H., Zhu, T., Wang, J. & Liu, Y. Microplastic pollution in Pearl River networks: Characteristic, potential sources, and migration pathways. Water Res. 276 , 123261 (2025). Welsh, B., Paterson, A.M., Yao, H., McConnell, C. & Aherne, J. The Fate of Microplastics in Rural Headwater Lake Catchments. Environ. Sci. Technol. 58 , 16570-16577 (2024). Du, L. , et al. Enhanced ecological risk of microplastic ingestion by fish due to fragmentation and deposition in heavily sediment-laden river. Water Res. 278 , 123306 (2025). Li, Y. , et al. In situ imaging of microplastics in living organisms based on mass spectrometry technology. Eco-Environ. Health 3 , 412-417 (2024). Organization, W.H. Dietary and inhalation exposure to nano- and microplastic particles and potential implications for human health. (2022). Zhu, L. , et al. Insights into human exposure to microplastics through drinking water: Current state of the science. Crit Rev Environ Sci Technol 54 , 1875-1901 (2024). Kozlov, M. Your brain is full of microplastics: are they harming you? Nature 638 , 311-313 (2025). Thompson, R.C. , et al. Twenty years of microplastic pollution research—what have we learned? Science 386 , eadl2746 (2025). Yin, J. , et al. Nanoplastics and Microplastics May Be Damaging Our Livers. in Toxics , Vol. 10 586 (2022). Zhang, C. , et al. Association of mixed exposure to microplastics with sperm dysfunction: a multi-site study in China. EBioMedicine 108 , 105369 (2024). Zhao, Q. , et al. Detection and characterization of microplastics in the human testis and semen. Sci. Total Environ. 877 , 162713 (2023). Zhu, L. , et al. Tissue accumulation of microplastics and potential health risks in human. Sci. Total Environ. 915 , 170004 (2024). Zhu, L. , et al. Identification of microplastics in human placenta using laser direct infrared spectroscopy. Sci. Total Environ. 856 , 159060 (2023). Marfella, R. , et al. Microplastics and Nanoplastics in Atheromas and Cardiovascular Events. N. Engl. J. Med. 390 , 900-910 (2024). Kozlov, M. Landmark study links microplastics to serious health problems. Nature (2024). Krause, S. , et al. The potential of micro- and nanoplastics to exacerbate the health impacts and global burden of non-communicable diseases. Cell Rep. Med. 5 , 101581 (2024). Leslie, H.A. , et al. Discovery and quantification of plastic particle pollution in human blood. Environ. Int. 163 , 107199 (2022). V. L. Leonard, S. , et al. Microplastics in human blood: Polymer types, concentrations and characterisation using μFTIR. Environ. Int. 188 , 108751 (2024). Giannandrea, D. , et al. Nanoplastic impact on bone microenvironment: A snapshot from murine bone cells. J. Hazard. Mater. 462 , 132717 (2024). Wang, H. , et al. Preserving the Immune-Privileged Niche of the Nucleus Pulposus: Safeguarding Intervertebral Discs from Degeneration after Discectomy with Synthetic Mucin Hydrogel Injection. Adv Sci (Weinh) 11 , e2404496 (2024). Yang, Q. , et al. Microplastics in human skeletal tissues: Presence, distribution and health implications. Environ. Int. 196 , 109316 (2025). Johnson, Z.I., Shapiro, I.M. & Risbud, M.V. Extracellular osmolarity regulates matrix homeostasis in the intervertebral disc and articular cartilage: Evolving role of TonEBP. Matrix Biol. 40 , 10-16 (2014). Ali, S.S., Elsamahy, T., Al-Tohamy, R. & Sun, J. A critical review of microplastics in aquatic ecosystems: Degradation mechanisms and removing strategies. Environmental Science and Ecotechnology 21 , 100427 (2024). Zhao, H., Mu, S., Wang, W. & Li, X. Potential threats of environmental microplastics to the skeletal system: current insights and future directions. Front Endocrinol (Lausanne) 16 , 1658056 (2025). Ling, Z., Zeng, X., Luo, Q., Li, X. & Cui, L. Co-morbid mechanisms of intervertebral disc degeneration and osteoporosis: biomechanical coupling and molecular pathways synergistically driving degenerative lesions. Journal of Orthopaedic Surgery and Research 20 , 652 (2025). Pelepenko, L.E. , et al. Effects of microplastics on the bones: a comprehensive review. Osteoporos Int 36 , 1327-1345 (2025). Li, Z. , et al. Identification and analysis of microplastics in human lower limb joints. J. Hazard. Mater. 461 , 132640 (2024). Cao, Z. , et al. Mapping the hidden journey of microplastics: Multi-organ deposition patterns and organ-specific health risks revealed by AI-driven analysis. The Innovation , 101031 (2025). Zou, F. , et al. Revealing the presence of lymphatic vessels within intervertebral discs: Novel insights into disc degeneration. The Innovation 6 , 100865 (2025). Gustafson, H.H., Holt-Casper, D., Grainger, D.W. & Ghandehari, H. Nanoparticle uptake: The phagocyte problem. Nano Today 10 , 487-510 (2015). Wei, Q., Zhang, X., Zhou, C., Ren, Q. & Zhang, Y. Roles of large aggregating proteoglycans in human intervertebral disc degeneration. Connect. Tissue Res. 60 , 209-218 (2019). Yalan, C., Ke, S. & Bo, G. Sorption behavior, mechanisms, and models of organic pollutants and metals on microplastics: A review. Environ. Chem. 40 , 2271-2287 (2021). Wagner, E.K. , et al. Avidin grafted dextran nanostructure enables a month-long intra-discal retention. Sci. Rep. 10 , 12017 (2020). Jian, L. & Xiaoliang, Z. Research advances in the relationship between renal metabolism and hypertension. Journal of Clinical Nephrology 23 , 853-857 (2023). Cui, L. , et al. Insights into the effect of polyethylene terephthalate (PET) microplastics on HER2 signaling pathways. Toxicol. in Vitro 91 , 105632 (2023). Liu, C. , et al. Widespread distribution of PET and PC microplastics in dust in urban China and their estimated human exposure. Environ. Int. 128 , 116-124 (2019). Hossain, M. & Engelhardt, I. Global plastic footprint: unveiling property trends, environmental fate, and emerging threats of microplastic and nanoplastics pollution across ecosystems. Energy Ecol. Environ. 10 , 637-674 (2025). Kadac-Czapska, K., Knez, E. & Grembecka, M. Food and human safety: the impact of microplastics. Crit. Rev. Food Sci. Nutr. 64 , 3502-3521 (2024). Abdel‐Monem, R.A. , et al. Chitosan‐ PVC conjugates/metal nanoparticles for biomedical applications. Polym. Adv. Technol. 33 , 514-523 (2021). Zhong, R. , et al. In vitro investigation of the effect of plasticizers on the blood compatibility of medical grade plasticized poly (vinyl chloride). J Mater Sci Mater Med 24 , 1985-1992 (2013). Mofakhami, E. , et al. Microstructure-mechanical properties relationships in vibration welded glass-fiber-reinforced polyamide 66: A high-resolution X-ray microtomography study. Polym. Test. 85 , 106454 (2020). Murphy, F., Russell, M., Ewins, C. & Quinn, B. The uptake of macroplastic & microplastic by demersal & pelagic fish in the Northeast Atlantic around Scotland. Mar. Pollut. Bull. 122 , 353-359 (2017). Sun, J. , et al. Effects of polyamide microplastics on the adsorption of perfluoroalkyl substances in soil. J. Hazard. Mater. Adv. 13 , 100391 (2024). Tang, K.H.D., Li, R., Li, Z. & Wang, D. Health risk of human exposure to microplastics: a review. Environ. Chem. Lett. 22 , 1155-1183 (2024). Qiu, Y. , et al. Mesoporous Hydroxyapatite Nanoparticles Mediate the Release and Bioactivity of BMP-2 for Enhanced Bone Regeneration. ACS Biomater. Sci. Eng. 6 , 2323-2335 (2020). Pattappa, G. , et al. Diversity of intervertebral disc cells: phenotype and function. J. Anat. 221 , 480-496 (2012). Hartikainen, J. , et al. Structure and Morphology of Polyamide 66 and Oligomeric Phenolic Resin Blends: Molecular Modeling and Experimental Investigations. Chem. Mater. 16 , 3032-3039 (2004). Karimi-Varzaneh, H.A., Carbone, P. & Müller-Plathe, F. Hydrogen Bonding and Dynamic Crossover in Polyamide-66: A Molecular Dynamics Simulation Study. Macromolecules 41 , 7211-7218 (2008). Pituru, S.M. , et al. A Review on the Biocompatibility of PMMA-Based Dental Materials for Interim Prosthetic Restorations with a Glimpse into Their Modern Manufacturing Techniques. Materials 13 , 2894 (2020). Shahsavaripour, M., Abbasi, S., Mirzaee, M. & Amiri, H. Human occupational exposure to microplastics: A cross-sectional study in a plastic products manufacturing plant. Sci. Total Environ. 882 , 163576 (2023). Schmidt, A. , et al. Short- and long-term polystyrene nano- and microplastic exposure promotes oxidative stress and divergently affects skin cell architecture and Wnt/beta-catenin signaling. Part. Fibre Toxicol. 20 , 3 (2023). Wang, W. , et al. Polystyrene microplastics induced nephrotoxicity associated with oxidative stress, inflammation, and endoplasmic reticulum stress in juvenile rats. Front. Nutr. 9 , 1059660 (2022). Lafram, A., Krami, A.M., Akarid, K., Laadraoui, J. & Roky, R. Effects of exposure to micro/nanoplastics of polystyrene on neuronal oxidative stress, neuroinflammation, and anxiety-like behavior in mice: A Systematic Review. Emerging Contam. 11 , 100442 (2025). Chang, J. , et al. A critical review on interaction of microplastics with organic contaminants in soil and their ecological risks on soil organisms. Chemosphere 306 , 135573 (2022). Joseph, M.M., Nair, J.B. & Joseph, A.M. Microscopic menace: exploring the link between microplastics and cancer pathogenesis. Environ Sci Process Impacts 27 , 1768-1795 (2025). Cui, Y. , et al. Mitigating microplastic-induced organ Damage: Mechanistic insights from the microplastic-macrophage axes. Redox Biol. 84 , 103688 (2025). Qian, N. , et al. Rapid single-particle chemical imaging of nanoplastics by SRS microscopy. Proceedings of the National Academy of Sciences 121 , e2300582121 (2024). Du, F., Cai, H., Zhang, Q., Chen, Q. & Shi, H. Microplastics in take-out food containers. J. Hazard. Mater. 399 , 122969 (2020). Mohamed Nor, N.H., Kooi, M., Diepens, N.J. & Koelmans, A.A. Lifetime Accumulation of Microplastic in Children and Adults. Environ. Sci. Technol. 55 , 5084-5096 (2021). Tsou, T.-Y. , et al. Distribution and toxicity of submicron plastic particles in mice. Environ. Toxicol. Pharmacol. 97 , 104038 (2023). Liu, X.H. , et al. Perspectives on the microorganisms with the potentials of PET-degradation. Front. Microbiol. 16 , 1541913 (2025). Nihart, A.J. , et al. Bioaccumulation of microplastics in decedent human brains. Nat. Med. 31 , 1114-1119 (2025). Li, M. , et al. Quantitative source apportionment of groundwater pollution based on PCA-APCS-MLR. China Environmental Science 37 , 3773-3786 (2017). USEPA. Electronic Code of Federal Regulations, Risk Assessment Guidance for Superfund of Human health risk assessment method. (2019). Senathirajah, K. , et al. Estimation of the mass of microplastics ingested – A pivotal first step towards human health risk assessment. J. Hazard. Mater. 404 , 124004 (2021). Additional Declarations No competing interests reported. Supplementary Files SupportingInformation0314.docx Cite Share Download PDF Status: Under Review Version 1 posted Editorial decision: Revision requested 25 Mar, 2026 Reviews received at journal 25 Mar, 2026 Reviews received at journal 23 Mar, 2026 Reviewers agreed at journal 19 Mar, 2026 Reviews received at journal 17 Mar, 2026 Reviewers agreed at journal 17 Mar, 2026 Reviewers agreed at journal 16 Mar, 2026 Reviewers invited by journal 16 Mar, 2026 Editor assigned by journal 16 Mar, 2026 Submission checks completed at journal 16 Mar, 2026 First submitted to journal 12 Mar, 2026 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-9100391","acceptedTermsAndConditions":true,"allowDirectSubmit":false,"archivedVersions":[],"articleType":"Article","associatedPublications":[],"authors":[{"id":607510616,"identity":"6b14bc78-4738-4af5-9237-da41d89a7a1c","order_by":0,"name":"Xuehua Li","email":"","orcid":"","institution":"Shaanxi Normal University","correspondingAuthor":false,"prefix":"","firstName":"Xuehua","middleName":"","lastName":"Li","suffix":""},{"id":607510623,"identity":"b0b2e4a1-ab83-4bdf-ac92-304c490ec4a5","order_by":1,"name":"Yanhua Wang","email":"data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAAAZAAAAAyAQMAAABI0h/eAAAABlBMVEX///8AAABVwtN+AAAACXBIWXMAAA7EAAAOxAGVKw4bAAAA6ElEQVRIiWNgGAWjYDACCTBpY8fG3vgAxOLhI1JLWjI/z2EDsBY2IrUcZpw5IxmshYGgFoPbPYafC34dZja4+ZjxMW+OnQwbA/PDRzfwablzxlh6Zl86n8HtZGbDmduSgQ5jMzbOwaflRu4Gad4ea2aD2/nHJD5uYwZq4WGTJqBl82/eHmbGDTcPs0kkbqsnSss2aZ4fzkDvM7MBbTlMWIvkjfxv1rwNoEAG++U4DxszAb/w3UhLvs3zBxSVh4Ehtq3anp+9+eFjfFoUDgAJxjZkIWY8ykFAvgFE/iGgahSMglEwCkY2AAB90Ua/68XHHgAAAABJRU5ErkJggg==","orcid":"","institution":"Shaanxi Normal University","correspondingAuthor":true,"prefix":"","firstName":"Yanhua","middleName":"","lastName":"Wang","suffix":""},{"id":607510636,"identity":"0177680c-07c1-48c1-b206-c258200a3554","order_by":2,"name":"Zixian Feng","email":"","orcid":"","institution":"Shaanxi Normal University","correspondingAuthor":false,"prefix":"","firstName":"Zixian","middleName":"","lastName":"Feng","suffix":""},{"id":607510645,"identity":"e57962c6-4765-40b5-8ade-3ced23e76512","order_by":3,"name":"Jiawei Zhang","email":"","orcid":"","institution":"Xijing Hospital","correspondingAuthor":false,"prefix":"","firstName":"Jiawei","middleName":"","lastName":"Zhang","suffix":""},{"id":607510648,"identity":"e873cfbf-9b62-404f-b33a-3b8925764c96","order_by":4,"name":"Baoshan Xing","email":"","orcid":"","institution":"University of Massachusetts Amherst","correspondingAuthor":false,"prefix":"","firstName":"Baoshan","middleName":"","lastName":"Xing","suffix":""},{"id":607510652,"identity":"b843dd17-6413-4d6f-aebd-9628e18e7885","order_by":5,"name":"Tan Ding","email":"","orcid":"","institution":"Xijing Hospital","correspondingAuthor":false,"prefix":"","firstName":"Tan","middleName":"","lastName":"Ding","suffix":""}],"badges":[],"createdAt":"2026-03-12 05:38:17","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-9100391/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-9100391/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":104887955,"identity":"26f33249-4454-428b-802e-2e31391b7962","added_by":"auto","created_at":"2026-03-18 10:13:03","extension":"png","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":328321,"visible":true,"origin":"","legend":"\u003cp\u003eMPs abundance and size distribution in human blood, bone, and intervertebral discs. (a) MPs abundance in blood (n/mL), bone tissue (n/g), and intervertebral discs (n/g). (b) Average particle size of MPs in each tissue, presented as mean ± SD. (c) Size distribution of MPs across tissues, showing the proportion of particles in different size ranges (0-30 μm, 30-60 μm, 60-100 μm, 100-200 μm)\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-9100391/v1/73e911b985c670df11aca855.png"},{"id":104887689,"identity":"19081df6-5551-4071-b9d0-0e63ca615bd1","added_by":"auto","created_at":"2026-03-18 10:12:31","extension":"png","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":124936,"visible":true,"origin":"","legend":"\u003cp\u003eDistribution of polymer types and morphological characteristics of MPs in different human tissues.\u003c/p\u003e","description":"","filename":"2.png","url":"https://assets-eu.researchsquare.com/files/rs-9100391/v1/61588abcf3e8b53586c365dd.png"},{"id":104887904,"identity":"f43d17ea-a13c-4ac6-8942-e3827ee232f3","added_by":"auto","created_at":"2026-03-18 10:12:54","extension":"png","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":270215,"visible":true,"origin":"","legend":"\u003cp\u003eNPs concentration and polymer composition in human tissues. (a) NPs concentrations (μg/g) in blood, bone, and intervertebral discs from 5 donors. (b) Average NPs concentration for each polymer type across tissues, showing tissue-specific enrichment of PVC in bone and PA66 in discs. (c) Overall contribution of different polymer types to total NPs mass.\u003c/p\u003e","description":"","filename":"3.png","url":"https://assets-eu.researchsquare.com/files/rs-9100391/v1/6e829a9dc71d32635bb224a4.png"},{"id":104887713,"identity":"0f189a78-1cca-4776-bf53-1382940d15b8","added_by":"auto","created_at":"2026-03-18 10:12:36","extension":"png","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":37793,"visible":true,"origin":"","legend":"\u003cp\u003eHealth risk assessment of MPs exposure. (a) Hazard quotient (HQ) for non-carcinogenic risk and cancer risk (CR) values for each donor under ingestion, inhalation, and dermal exposure pathways. All HQ values remained below 1, and CR values did not exceed 10⁻⁴. (b) Hazard index (HI) and cumulative carcinogenic risk (CCR) across donors, showing a tissue gradient of intervertebral disc \u0026gt; bone \u0026gt; blood.\u003c/p\u003e","description":"","filename":"4.png","url":"https://assets-eu.researchsquare.com/files/rs-9100391/v1/5de4b08867adfae884a55e92.png"},{"id":104887676,"identity":"60f51446-1fe9-4478-ac6b-b71eb0d092e8","added_by":"auto","created_at":"2026-03-18 10:12:31","extension":"png","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":338346,"visible":true,"origin":"","legend":"\u003cp\u003eMultivariate analysis of MPs accumulation patterns. (a) Correlation heatmap showing relationships between MPs characteristics (abundance, size, shape, color, polymer type) and donor demographics (age, gender, BMI). Significant correlations are indicated by * (p ≤ 0.05) and ** (p ≤ 0.01). (b) Principal component analysis (PCA) score plot of MPs profiles in blood, bone, and disc samples, showing distinct clustering patterns. (c) Classification of individual donors into three accumulation phenotypes (disc-enriched, intermediate, blood-enriched) based on PC1 gradient. (d) Variable importance in projection (VIP) scores from PLS-DA, identifying the top 10 features driving tissue-specific accumulation.\u003c/p\u003e","description":"","filename":"5.png","url":"https://assets-eu.researchsquare.com/files/rs-9100391/v1/80bc4419769d4fb80b8679f5.png"},{"id":104888049,"identity":"56c30e88-0f38-4450-a7cb-dbef6e2ee59f","added_by":"auto","created_at":"2026-03-18 10:13:14","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1792621,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-9100391/v1/b2b8d5cd-3b1d-431a-a3cf-658994a5579b.pdf"},{"id":104887798,"identity":"54ee7ca8-b15c-4853-82d5-95f31887d266","added_by":"auto","created_at":"2026-03-18 10:12:39","extension":"docx","order_by":0,"title":"","display":"","copyAsset":false,"role":"supplement","size":233168,"visible":true,"origin":"","legend":"","description":"","filename":"SupportingInformation0314.docx","url":"https://assets-eu.researchsquare.com/files/rs-9100391/v1/abf5e11fa4094f73dae00e68.docx"}],"financialInterests":"No competing interests reported.","formattedTitle":"The Human Intervertebral Disc as a Long-Term Repository for Micro/Nanoplastics: Tissue-Specific Accumulation and Risk Estimation","fulltext":[{"header":"Introduction","content":"\u003cp\u003eOnce released into the natural environment, plastics tend to degrade into Microplastics (MPs, \u0026lt; 5 mm\u003csup\u003e1\u003c/sup\u003e) and Nanoplastics (NPs, \u0026lt;1 μm). These particles are widely detected in various environmental matrices, including oceans, rivers, lakes, sediments, soils, and the atmosphere\u003csup\u003e2-7\u003c/sup\u003e, as well as within aquatic organisms such as fish, shrimp, and mussels\u003csup\u003e8,9\u003c/sup\u003e. MPs and NPs (collectively MNPs) have also been identified in human-consumed food\u0026nbsp;\u003csup\u003e10\u003c/sup\u003e and drinking water\u003csup\u003e11\u003c/sup\u003e. In recent years, MNPs were detected in an increasing number of human tissues and organs, ranging from feces, colon, and placenta to blood, lungs, respiratory tract, liver, and kidneys, and even in breast milk, testes, bone tissue, and the brain\u003csup\u003e12-18\u003c/sup\u003e. Marfella R et al. \u003csup\u003e19\u003c/sup\u003ewere the first to demonstrate the direct association between MPs and human health, reporting that individuals with MNPs detected in carotid artery plaques had a 4.53-fold higher composite risk of myocardial infarction, stroke, or all-cause mortality compared to those without MNPs detection. Existing studies indicate that MNPs accumulation within blood vessels may damage the endothelial lining and even trigger thrombosis\u003csup\u003e20\u003c/sup\u003e. High levels of MNPs intake may exacerbate inflammation and disrupt distant organs, thereby elevating the risk of cancer, diabetes, cardiovascular disease, and chronic pulmonary disorders\u003csup\u003e21\u003c/sup\u003e. Although MNPs are known to penetrate multiple physiological barriers, existing studies have primarily focused on vascularized, metabolically active organs. Their long-term behavior and health implications in avascular, metabolically inert tissues remain underexplored.\u003c/p\u003e\n\u003cp\u003eAs the primary transport medium in the human body, blood can rapidly circulate MNPs to various tissues and organs\u003csup\u003e22\u003c/sup\u003e. It offers a transient window into recent systemic exposure. Previous studies employed pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) or micro-Fourier transform infrared spectroscopy (μ-FTIR) to detect MPs in blood samples\u003csup\u003e22,23\u003c/sup\u003e. However, Py-GC/MS does not provide information on particle size, morphology, or polymer type, while μ-FTIR is limited to characterizing MPs larger than 5 μm, and neither technique addresses the detection of NPs. In contrast, bone tissue has poor vascularization, resulting in a longer timescale for MNPs deposition. Thus, bone may serve as a mid-term retention compartment for MNPs. Animal studies confirmed that once NPs enter bone cells in mice, they can disrupt specific cellular functions and cause various adverse effects\u003csup\u003e24\u003c/sup\u003e, suggesting their potential for persistent retention in bone tissue. The intervertebral disc, the largest avascular tissue in the human body\u003csup\u003e25\u003c/sup\u003e, exhibits extremely slow metabolic activity, thereby, it is more likely to reflect long-term MNPs accumulation. To date, only one study reported the presence of MPs in intervertebral discs\u003csup\u003e26\u003c/sup\u003e, critical knowledge gaps remain regarding the simultaneous quantification of NPs and the comparative accumulation dynamics across the blood-bone-disc axis within the same individuals. Additionally, inter-individual differences such as lifestyle, occupation, age as well as variations in exposure routes and intake levels may jointly influence MNPs distribution in the body, yet relevant research remains limited.\u0026nbsp;\u003c/p\u003e\n\u003cp\u003eThis study investigated MNPs in human blood, bone tissue, and intervertebral disc samples using laser micro-Raman spectroscopy and Py-GC/MS. We propose the following scientific hypothesis: due to the avascular nature and extremely slow metabolic rate of the intervertebral disc, it may exhibit a more significant retention effect for MNPs than bone tissue. The objectives are to: (1) systematically reveal, for the first time, the temporal deposition pattern of MNPs, from short-term exposure in blood to intermediate accumulation in bone tissue and long-term retention in the intervertebral disc; (2) perform detailed size-fraction analysis, covering NPs smaller than 1 μm and MPs ranging from 1 to 5000 μm, thereby enabling a comprehensive assessment of MNPs size distribution across human tissues; (3) explore the relationship between MNPs deposition patterns and potential health risks, offering an integrated evaluation of their implications for human health. The findings are expected to provide new momentum for the field of human MNPs exposure risk research and establish a robust data foundation for future investigations into long-term health effects.\u003c/p\u003e"},{"header":"Results","content":"\u003cp\u003e\u003cstrong\u003eMPs abundance in blood, bone, and intervertebral disc\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eMPs were detected in all blood, bone tissue, and intervertebral disc samples collected from 21 donors. The average MPs abundances were 6.74 \u0026plusmn; 4.40 n/mL in blood, 13.26 \u0026plusmn; 5.49 n/g in bone tissue, and 13.55 \u0026plusmn; 4.48 n/g in intervertebral discs (Fig. 1a). Blood MPs concentrations varied considerably among individuals, ranging from 3.50 to 7.80 n/mL for most donors, whereas bone and disc levels were more consistent, with most values between 8.50 and 18.90 n/g. MPs were not detected in the bone tissue of donor No. 7. Donor No. 7 led a lifestyle with minimal plastic exposure and no underlying disease. Despite detectable MPs in blood and disc, none were found in bone. Notably, donor No. 8 exhibited the highest MPs abundances across all three tissues (blood: 19.16 n/mL; bone: 19.80 n/g; disc: 18.93 n/g). This individual suffered from lumbar disc herniation, and the MPs abundance in the intervertebral disc was lower than that in bone tissue. This individual\u0026rsquo;s lifestyle included frequent consumption of bottled beverages and takeout food (Fig. S1). Donors No. 3, 15, and 21 showed relatively higher MPs levels in blood compared to the rest of the cohort (Text S1).\u003c/p\u003e\n\u003cp\u003eStatistical analysis revealed that MPs abundance in blood was significantly lower than in bone tissue and intervertebral discs (p\u0026lt;0.05). The MPs concentrations measured in this study exceeded those reported by Leonard et al. \u003csup\u003e23\u003c/sup\u003e for blood (2.47 \u0026plusmn; 4.18 n/mL) but were considerably lower than the values documented by Yang et al. \u003csup\u003e26\u003c/sup\u003e for intervertebral discs (61.10 \u0026plusmn; 44.20 n/g) and bone tissue (22.90 \u0026plusmn; 15.70 n/g).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eSize, color, shapes and types of MPs\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe average particle sizes of MPs were 64.50 \u0026plusmn; 38.20 \u0026mu;m in blood, 57.10 \u0026plusmn; 33.80 \u0026mu;m in bone tissue, and 77.60 \u0026plusmn; 53.40 \u0026mu;m in intervertebral discs (Fig. 1b). Overall, MPs sizes ranged from 9.79 to 193.29 \u0026mu;m, with the largest particles found in discs and the smallest in blood. The majority of MPs were below100 \u0026mu;m, accounting for 90.0% in blood, 92.5% in bone, and 62.5% in disc samples (Fig. 1c). Notably, 17.5% of MPs in intervertebral discs were larger than 100 \u0026mu;m, a proportion higher than in the other tissues.\u003c/p\u003e\n\u003cp\u003eClear distribution patterns of microplastic physical characteristics (color, shape) were observed across all three tissues. Across all tissues, fragments and fibers were the dominant morphotypes, with gray and transparent being the most common colors (Fig. S2a, S2b). Fragment-shaped PET particles were the dominant type in all three tissues, accounting for 58.60% of the total detected MPs. Nine polymer types were identified, including polyethylene terephthalate (PET), polyethylene (PE), ethylene-vinyl acetate copolymer (EVA), polystyrene (PS), polydimethylsiloxane (PDMS), polybutylene terephthalate (PBT), and polyvinyl chloride (PVC). PET was the predominant polymer in all three tissues, followed by PE and PS. Blood samples exhibited the greatest polymer diversity, containing trace amounts of PDMS, PBT, and PVC, whereas bone and disc showed more restricted polymer profiles (Fig. 2). PBT was detected exclusively in intervertebral discs. PET fibers were more abundant in intervertebral discs than in blood and bone tissue.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eNPs concentration and polymer distribution\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNPs were detected in all analyzed samples (15 donors), with mass concentrations ranging from 0.16 to 20.28 \u0026mu;g/g (Fig. 3a). The highest NPs concentration was observed in the bone tissue of donor No. 20 (PVC: 20.28 \u0026mu;g/g), while the intervertebral disc of donor No. 21 showed a high concentration of PA66 (18.75 \u0026mu;g/g), highlighting notable individual variability for specific NPs types. Tissue-specific distribution patterns were evident among polymer types (Fig. 3b). PVC exhibited the highest average concentration in bone tissue (7.74 \u0026mu;g/g), whereas PA66 was relatively enriched in intervertebral discs (6.28 \u0026mu;g/g). The average concentration of PVC in blood was 2.39 \u0026mu;g/g, remaining the dominant NPs type. PS concentrations were low in all three tissues. PMMA (0.56 \u0026mu;g/g) was detected only in the intervertebral disc of donor No. 8, who underwent bone graft fusion surgery.\u003c/p\u003e\n\u003cp\u003eThe polymer composition of NPs showed that PVC and PA66 accounted for 46.9% and 31.3% of the total mass, respectively, significantly higher than PS (18.8%) and PMMA (3.1%) (Fig. 3c). A size-dependent divergence in polymer composition was observed: PET and PE dominated the MPs fraction, whereas PVC and PA66 were predominant in the NPs fraction, with the two polymers together accounting for 78.2% of the total NPs mass.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eHealth risk assessment\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThree exposure pathways (ingestion, inhalation, and dermal contact) were considered in the assessment, but the contributions to the hazard quotient (HQ) differed significantly among these pathways. HQ values for MPs in different tissues followed the order: intervertebral disc \u0026gt; bone tissue \u0026gt; blood. The highest HQ value was observed in intervertebral discs (9.0 \u0026times; 10⁻⁴), which was mainly attributed to the sustained accumulation of MPs in intervertebral discs through blood circulation or local permeation, while the contributions of dermal and inhalation exposure pathways were limited. For all 21 donors, the HQ values remained below 1 (Fig. 4a). The hazard index (HI), calculated as the sum of HQs across exposure pathways, also followed the same tissue gradient (intervertebral disc \u0026gt; bone \u0026gt; blood), with an average HI of 3.8 \u0026times; 10⁻\u0026sup3; across donors (Fig. 4b). Tissue-specific analysis showed that the intervertebral disc was the main contributor to health risk in most donors.\u003c/p\u003e\n\u003cp\u003eCancer risk (CR) values for all donors did not exceed 10⁻⁴ for any exposure pathway. The cumulative carcinogenic risk (CCR) averaged 9.7 \u0026times; 10⁻⁶ across donors. Tissue-specific CCR values showed a gradient: intervertebral disc \u0026gt; bone tissue \u0026gt; blood. The maximum individual CCR reached 3.8 \u0026times; 10⁻⁵, primarily contributed by intervertebral disc accumulation. Donors No. 2, 13, and 19 exhibited the highest CCR values in their intervertebral discs, and their CCR values were significantly higher than those in other tissues of the same individuals (Text S2).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCorrelation and multivariate analysis of MNPs accumulation patterns\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eCorrelation analysis revealed a significant positive correlation between MPs abundances in blood and bone tissue (p\u0026le;0.01). MP abundance in blood was significantly negatively correlated with donor age (p\u0026le;0.01; Fig. 5a). No significant correlations were found between MPs abundance and other demographic factors including gender, BMI, height and weight. Principal component analysis (PCA) showed distinct clustering patterns: blood and disc samples occupied separate areas in the score plot, with bone tissue samples positioned between them (Fig. 5b). Partial least squares-discriminant analysis (PLS-DA) classified the 21 donors into three accumulation phenotypes: disc-enriched (10/21), intermediate, and blood-enriched (Fig. 5c). Variable importance in projection (VIP) (presented here as \u0026ldquo;Total Importance\u0026rdquo; which corresponds to the normalized relative contribution of VIP values) analysis identified the top discriminatory features associated with disc/bone enrichment: fiber morphology, white color, larger particle size, and the polymers PET and PE. In contrast, transparent particles, polypropylene, and microspheres were more associated with blood samples (Fig. 5d). PLS-DA identified fiber morphology, white color, larger particle size, and PET/PE as key discriminatory features, with significant differences confirmed among tissue types and phenotype groups by one-way ANOVA (Fig. S3b, Text S3). The PLS-DA score plot (Fig. S3a) illustrates the distribution and separation of the three tissue types in the latent variable space. Nanoplastics also exhibited tissue-specific correlation patterns. Significant positive correlations were observed between blood and bone tissue for PVC and PA66 (p \u0026le; 0.01), suggesting systemic exposure and migration to bone. In contrast, correlations involving intervertebral discs were weaker, with only PVC and PA66 showing marginal significance with bone tissue (p \u0026le; 0.05). Principal component analysis further revealed distinct clustering: blood samples aligned with height (PC1), bone tissue correlated with BMI and PS-NPs (PC1), while intervertebral discs were closely associated with PVC and PA66 (PC2), identifying the disc as the primary accumulation site for these polymers (Fig. S4). Detailed correlation and principal component analysis of nanoplastic distribution across tissues are provided in Text S4 and Fig. S4.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003eThis study provides a simultaneous quantification of MPs and NPs in matched human blood, bone, and intervertebral disc samples from the same individuals. Our results reveal a clear tissue‑specific accumulation gradient: MPs abundance in blood was significantly lower than in bone and intervertebral discs, while NPs concentrations showed distinct polymer‑dependent distribution patterns. The intervertebral disc, being avascular and having a slow metabolic rate, can serve as a potential long-term repository for micro- and nanoplastics in the human circulatory system \u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e,\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e. The observed MPs abundance gradient (blood\u0026thinsp;\u0026lt;\u0026thinsp;bone\u0026thinsp;\u0026asymp;\u0026thinsp;disc) aligns with the vascularization and metabolic activity of these tissues. Blood, as the primary transport medium, is directly exposed to circulating MPs but also possesses rapid clearance mechanisms \u003csup\u003e\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e\u003c/sup\u003e. In contrast, bone tissue has limited vascularization and undergoes continuous remodeling, which may allow intermediate‑term retention of particles \u003csup\u003e\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e,\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e. Furthermore, MPs accumulation in bone has been associated with adverse effects on bone cells and bone homeostasis \u003csup\u003e\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e\u003c/sup\u003e. The intervertebral disc, being the largest avascular tissue in the human body, relies on diffusion for nutrient exchange and lacks efficient cellular clearance pathways \u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e,\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e. This physiological feature likely contributes to the long‑term sequestration of MPs, as particles that enter the disc become trapped and cannot be readily removed. Consistent with previous reports by Zhu 17 and Guo 31 et al., microplastics smaller than 100 \u0026micro;m predominated in all tissues. The higher proportion of MPs\u0026thinsp;\u0026gt;\u0026thinsp;100 \u0026micro;m in discs compared to blood and bone further supports this retention capacity, as larger particles are less likely to exit via diffusion \u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e. This mechanism is consistent with the observation that fiber‑shaped and larger MPs were preferentially retained in discs and bone, as their morphology may facilitate entrapment within the extracellular matrix \u003csup\u003e\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e,\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e\u003c/sup\u003e.\u003c/p\u003e \u003cp\u003eHowever, as an avascular tissue, the intervertebral disc requires an explanation for how circulating MNPs enter it. Based on available evidence, we propose the following potential pathways. (i) Degeneration-associated vascular ingrowth. Studies have shown that aberrant vascular proliferation accompanies disc degeneration \u003csup\u003e\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e. These new blood vessels may serve as conduits for circulating MPs to enter the disc directly. (ii) Lymphatic involvement. Recent research has revealed the presence of lymphatic vessel structures within intervertebral discs \u003csup\u003e\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e\u003c/sup\u003e. The inter-endothelial gaps of these initial lymphatics could theoretically allow the passive transport of NPs and even micron-sized particles. (iii) Cell-mediated active transport. Immune cells such as macrophages can engulf particles and migrate between tissues \u003csup\u003e\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e\u003c/sup\u003e. This process may carry MNPs into the disc microenvironment. These pathways provide a mechanistic explanation for how MNPs enter and become deposited in the disc over the long term. The enrichment of MPs in discs may also be driven by physicochemical interactions with the tissue matrix. Considering that the nucleus pulposus has a mildly acidic environment and is rich in negatively charged aggregating proteoglycans \u003csup\u003e\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u003c/sup\u003e, its glycosaminoglycan side chains may adsorb positively charged MPs particles in acidic conditions via electrostatic interactions \u003csup\u003e\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e\u003c/sup\u003e, thus enhancing MPs retention. This electrostatic adsorption forms an initial \u0026ldquo;charge trap\u0026rdquo; The nucleus pulposus contains an anionic matrix, which is rich in negatively charged glycosaminoglycans (GAGs) \u003csup\u003e\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e\u003c/sup\u003e. This matrix can electrostatically bind to weathered MPs that may carry positive surface charges. Such an interaction is analogous to the cation-anion complementarity observed in targeted molecular interactions within intervertebral discs \u003csup\u003e\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e\u003c/sup\u003e. Crucially, long-term retention stems from the synergy between the capture and the tissue's lack of clearance. Bone undergoes active, cell-mediated remodeling that can potentially mobilize particles \u003csup\u003e\u003cspan citationid=\"CR30\" class=\"CitationRef\"\u003e30\u003c/span\u003e\u003c/sup\u003e. In contrast, the avascular disc lacks such clearance mechanisms, relying solely on slow diffusion \u003csup\u003e\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e\u003c/sup\u003e. Thus, electrostatic adsorption combined with absent biological clearance leads to the long-term sequestration and enrichment of MPs in discs. Additionally, the presence of macrophages in degenerated discs may modulate local MPs retention \u003csup\u003e\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e,\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e\u003c/sup\u003e, though their exact role requires further investigation.\u003c/p\u003e \u003cp\u003eBeyond the physical retention, the polymer composition of MPs and NPs exhibited marked size‑dependent divergence. PET and PE dominated the MPs fraction across all tissues. This predominance reflects their widespread use in packaging and textiles \u003csup\u003e\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e,\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e\u003c/sup\u003e and their high prevalence in environmental samples \u003csup\u003e\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e,\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e\u003c/sup\u003e. PET emerged as the predominant polymer in all three tissues, aligning with prior findings from blood \u003csup\u003e\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e\u003c/sup\u003e and lung tissue \u003csup\u003e\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e\u003c/sup\u003e studies. PET is widely used in beverage bottles, food packaging films, synthetic fibers, and medical devices \u003csup\u003e\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e\u003c/sup\u003e. In urban indoor and outdoor dust in China, PET and polycarbonate (PC) were the main MPs components \u003csup\u003e\u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e\u003c/sup\u003e. In contrast, PVC and PA66 accounted for nearly 80% of the NPs mass, with PVC enriched in bone and PA66 enriched in discs. This pattern may arise from the differential fragmentation and environmental persistence of these polymers. In the medical field, over one-quarter of polymer-based devices were made of PVC, including blood bags, infusion sets, and oxygen masks \u003csup\u003e\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e,\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e\u003c/sup\u003e. These devices directly contact the human body and serve as potential exposure sources. Widely used in textiles, personal care products, and fishing gear \u003csup\u003e\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e\u003c/sup\u003e, PA66 is frequently detected in wastewater treatment plants and widely distributed in marine and terrestrial environments, posing significant exposure risks to animals, plants, and humans \u003csup\u003e\u003cspan additionalcitationids=\"CR48\" citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e\u003c/sup\u003e. The enrichment of PVC may be related to the high degree of mineralization and dense structure of bone tissue \u003csup\u003e\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e\u003c/sup\u003e, which facilitates its adsorption and retention. Meanwhile, the relative enrichment of PA66 was attributable to the high water content of intervertebral discs and its affinity for proteoglycans and other matrix constituents \u003csup\u003e\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e\u003c/sup\u003e, which jointly furnish a microenvironment for PA66 adsorption. At the molecular level, the dense polar amide groups on the PA66 chain can form hydrogen-bond networks and exhibit strong hydrogen bonding with hydrophilic groups such as hydroxyls \u003csup\u003e\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e,\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e\u003c/sup\u003e. The intervertebral disc possesses a highly hydrated and proteoglycan-rich microenvironment. In this setting, PA66 nanoparticles undergo selective adsorption. This process is mediated by intermolecular interactions, such as hydrogen bonding, between the amide groups of PA66 and the proteoglycan chains. These interactions facilitate the long-term retention of nanoparticles. The exclusive detection of PMMA in the disc of donor No. 8, who underwent spinal fusion with internal fixation, likely originates from surgical device wear \u003csup\u003e\u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e54\u003c/span\u003e\u003c/sup\u003e. This finding underscores the contribution of medical interventions to local NPs burden \u003csup\u003e\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e,\u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e\u003c/sup\u003e. These observations indicate that both environmental sources and iatrogenic factors contribute to the complex mixture of MNPs in human tissues.\u003c/p\u003e \u003cp\u003eHealth risk assessment based on current chemical‑toxicity models indicates that both non‑carcinogenic and carcinogenic risks from MPs exposure fall within acceptable safety limits at the current exposure levels. Although the possibility of MPs entering the human body via the skin is minimal, they may still entry through wounds, sweat glands, or hair follicles \u003csup\u003e\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e\u003c/sup\u003e. Plastic products in medical supplies (e.g., surgical sutures) may also increase the risk for dermal exposure to MPs \u003csup\u003e\u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e\u003c/sup\u003e. Existing animal and cell models consistently indicate that long-term or sub-chronic exposure to MNPs at low concentrations or doses can still compromise antioxidant defenses. The exposure levels in these studies range from \u0026micro;g/L to \u0026micro;g/mL or mg/kg\u0026middot;d, which are far below acute cytotoxic thresholds \u003csup\u003e\u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e57\u003c/span\u003e,\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e\u003c/sup\u003e. Nevertheless, such low-level exposure significantly increases oxidative stress markers, including reactive oxygen species (ROS) and malondialdehyde (MDA), and persistently upregulates various inflammatory factors. MPs\u0026rsquo; biological persistence may drive long-term accumulation in slow-metabolism tissues like intervertebral discs \u003csup\u003e\u003cspan citationid=\"CR59\" class=\"CitationRef\"\u003e59\u003c/span\u003e\u003c/sup\u003e. Although current CR values (\u0026le;\u0026thinsp;10⁻⁶) are substantially lower than the threshold of concern (10⁻⁴), chronic low-dose exposure could still induce pathological changes through oxidative stress or inflammation \u003csup\u003e\u003cspan citationid=\"CR60\" class=\"CitationRef\"\u003e60\u003c/span\u003e\u003c/sup\u003e. Therefore, reliance solely on chemical risk metrics may severely underestimate the true health burden, especially in tissues with slow turnover. Donors No. 2, 13, and 19 had the highest CCR values in their intervertebral discs. Although remaining within the currently accepted safety margins, these values were significantly higher than those in other tissues, likely reflecting the enhanced retention of MPs in slow-metabolizing tissues and their potential for injury \u003csup\u003e\u003cspan citationid=\"CR61\" class=\"CitationRef\"\u003e61\u003c/span\u003e\u003c/sup\u003e. Taking both the non-carcinogenic and carcinogenic risk assessments into account, the results for all 21 donors fall within safe limits. Nonetheless, from a long-term and population-wide perspective, continued vigilance regarding MPs pollution is necessary.\u003c/p\u003e \u003cp\u003eA striking finding was the negative correlation between blood MPs abundance and donor age. This relationship was statistically significant (p\u0026thinsp;\u0026le;\u0026thinsp;0.01) and suggested higher transient exposure in younger individuals. Lifestyle factors may contribute to this pattern, including greater consumption of bottled beverages, takeout food, and personal care products containing MPs \u003csup\u003e\u003cspan additionalcitationids=\"CR63\" citationid=\"CR62\" class=\"CitationRef\"\u003e62\u003c/span\u003e\u0026ndash;\u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e64\u003c/span\u003e\u003c/sup\u003e. However, no significant age correlation was observed in bone or disc tissues. This discrepancy implies that while younger individuals experience higher short‑term circulating loads, long‑term accumulation in deep tissues may depend on additional factors. The negative correlation in blood likely reflects immediate exposure from modern lifestyles, whereas its absence in deep tissues suggests that accumulation represents a long-term equilibrium between intake and clearance. This implies that as the current younger demographic ages, the cumulative load of MPs deposited in their intervertebral discs may ultimately surpass that observed in today's older generation. Using multivariate analysis, we identified three distinct individual accumulation phenotypes. Notably, the first principal component (PC1), which likely represents environmentally weathered MPs, showed a negative correlation with donor age, further supporting the link between lifestyle-related exposure and particle characteristics. Moreover, the disc-enriched phenotype exhibited a significant positive PC1 gradient from blood to intervertebral disc, indicating that particles with specific weathered characteristics are progressively sequestered in this avascular tissue. The predominance of the disc-enriched pattern, coupled with its marked positive blood-to-disc gradient, strongly corroborates the intervertebral disc as a key long-term reservoir for circulating MPs \u003csup\u003e\u003cspan citationid=\"CR65\" class=\"CitationRef\"\u003e65\u003c/span\u003e\u003c/sup\u003e. The key features identified by this Total Importance analysis (aligning with the core role of VIP in PLS-DA) suggest that both the physical morphology (e.g., fibers) and chemical nature (e.g., the biopersistence of PET) of the particles contribute to this tissue selectivity. The high detection frequency of PET in disc and bone tissues further supports its high biopersistence and mobility \u003csup\u003e\u003cspan citationid=\"CR66\" class=\"CitationRef\"\u003e66\u003c/span\u003e\u003c/sup\u003e. The age-dependent correlation observed here differs from a report on liver and brain tissues \u003csup\u003e\u003cspan citationid=\"CR67\" class=\"CitationRef\"\u003e67\u003c/span\u003e\u003c/sup\u003e, hinting at potential tissue- and population-specific deposition mechanisms \u003csup\u003e\u003cspan citationid=\"CR68\" class=\"CitationRef\"\u003e68\u003c/span\u003e\u003c/sup\u003e. This population-specific exposure pattern may be supported by consumption data: Exposure modelling estimates a considerable daily per capita intake of microplastics, with children and adults at 553 and 883 ng/capita/day, respectively \u003csup\u003e\u003cspan citationid=\"CR64\" class=\"CitationRef\"\u003e64\u003c/span\u003e\u003c/sup\u003e. The higher consumption of single-use packaged food, bottled beverages, and personal care products containing microbeads among younger demographics represents a significant and quantifiable source of their exposure. These results indicate that the distribution of MPs in vivo is an outcome of the complex interplay among exposure source characteristics, particle properties, and the tissue microenvironment.\u003c/p\u003e \u003cp\u003eWhile this study offers preliminary datasets, it fails to elucidate the underlying toxicological mechanisms of MNPs exposure across diverse biological tissues. Moreover, Py-GC/MS technique used for NPs detection remains constrained by limited resolution and susceptibility to organic matrix interference. Future investigations should integrate analytical techniques (thermal desorption mass spectrometry, Raman imaging, and field-flow fractionation) to characterize MNPs occurrence across exposure pathways, polymers, and tissues, while combining cellular and animal models to elucidate their transport pathways and key toxicity mechanisms.\u003c/p\u003e"},{"header":"Methods","content":"\u003cdiv id=\"Sec8\" class=\"Section2\"\u003e\n \u003ch2\u003eSample collection and preservation\u003c/h2\u003e\n \u003cp\u003eThis study was approved by the Medical Ethics Committee of the First Affiliated Hospital of Air Force Medical University (approval number: KY20242164-C-1). All procedures complied with the Declaration of Helsinki and Good Clinical Practice (GCP) guidelines, ensuring that participants\u0026apos; informed consent, rights, and safety were fully protected. This study included 21 participants who underwent spinal fusion with internal fixation between November 2024 and January 2025. The participants\u0026apos; ages ranged from 33 to 74 years (median 58 years), including 47.6% male and 52.4% female. The primary diagnoses were lumbar disc herniation and lumbar spondylolisthesis. The participants\u0026apos; body mass index (BMI) ranged from 19.5 to 30.2 kg/m\u0026sup2;, with approximately 57% of participants classified as overweight or obese according to Chinese adult BMI criteria. Detailed demographic and clinical characteristics are provided in Table \u003cspan class=\"InternalRef\"\u003eS1\u003c/span\u003e. Blood samples were collected before surgery. Bone tissue and intervertebral disc samples were collected intraoperatively by trained surgeons using sterile procedures. Blood was collected in EDTA anticoagulant tubes. All participants signed written informed consent before sample collection. To avoid external plastic contamination, all personnel wore 100% cotton lab coats, disposable nitrile gloves, and head coverings. Only plastic-free instruments were used during sampling and sample handling.\u003c/p\u003e\n\u003c/div\u003e\n\u003ch3\u003eSample pretreatment and digestion\u003c/h3\u003e\n\u003cp\u003eAll samples were vacuum freeze-dried before processing. Blood samples (2.5 mL) were transferred into 250 mL wide-mouth glass bottles, mixed with 50 mL nitric acid, pre-digested in a 50\u0026deg;C water bath for 30 min, followed by digestion at 70\u0026deg;C for 10 min. The digested solution was diluted with ultrapure water and filtered through membrane A (mixed cellulose membrane, 0.45 \u0026micro;m pore size, 50 mm diameter). The membrane was transferred to 100 mL anhydrous ethanol, sonicated for 15 min, rinsed three times with ethanol, and the rinse solutions were filtered again. Particles were retained on membrane A for MPs analysis.\u003c/p\u003e\n\u003cp\u003eFor bone tissue samples, visible muscle, fascia, and residual tissues were carefully scraped off using a scalpel. The bone was crushed using sterile bone forceps. Approximately 1.0 g of fragmented bone tissue was added to saturated ZnCl₂ solution to float MPs, left to stand for 24 hours, centrifuged, and the supernatant was collected into 250 mL amber glass bottles for digestion. For intervertebral disc samples, approximately 1.0 g of fragmented sample was placed directly into 250 mL amber glass bottles for digestion.\u003c/p\u003e\n\u003cp\u003eThe digestion process for both bone and intervertebral disc samples was as follows: (1) Fenton\u0026apos;s reagent was added and digested in a water bath for 5 hours; (2) vacuum filtration through membrane A; (3) re-digestion with nitric acid (50 mL, 65%) for 30 minutes; (4) 50% dilution with ultrapure water and vacuum filtration through membrane B (PTFE membrane, 0.45 \u0026micro;m pore size, 50 mm diameter); (5) membrane transferred to 100 mL anhydrous ethanol, sonicated for 15 min, rinsed three times with ethanol, and vacuum filtered through a new membrane B. After freeze-drying, samples were ready for analysis. A sintered funnel (30 mm diameter) was used for filtration. To ensure repeatability and accuracy, three parallel samples were set for each tissue type. All samples were processed using the same procedure. Blank controls (with reagents only) were included in each batch and analyzed alongside real samples to identify potential background contamination.\u003c/p\u003e\n\u003ch3\u003eMPs analysis by laser micro-Raman spectroscopy\u003c/h3\u003e\n\u003cp\u003eThe analysis of MPs in 21 blood, bone tissue, and intervertebral disc samples was primarily conducted using a laser micro-Raman spectroscopy (Thermo Scientific, DXR3xi). The main parameters were set as follows: laser source at 785 nm, laser power of 15 mW, exposure time of 0.5000 sec (2 Hz), and 50 scans. A five-point method was used for sample observation, in which the entire sample film was divided into nine regions. Five scanning points were set for each region (top, middle, bottom, left, and right), totaling 45 scanning points. All particles in each scanning point were tested. The spectral range was set from 300 to 3500 cm\u003csup\u003e\u0026minus;\u0026thinsp;1\u003c/sup\u003e. The collected spectra were compared with a custom-built standard spectral library (containing nearly 30 types of plastics, covering over 99% of plastic varieties) and the laser micro-Raman spectroscopy sample library to identify the composition of the plastic particles. Nano Measurer software (version 1.2) was used to statistically analyze the particle size, shape, and color of the MPs.\u003c/p\u003e\n\u003cdiv id=\"Sec11\" class=\"Section2\"\u003e\n \u003ch2\u003eNPs analysis through Py-GC/MS\u003c/h2\u003e\n \u003cp\u003eFifteen samples of blood, bone tissue, and intervertebral disc were selected for nanoplastic analysis using Py-GC/MS. Nanoplastic detection was performed using a Multi-Shot Pyrolyzer EGA/PY-3030D (Frontier Laboratories, Japan) connected to a gas chromatograph-mass spectrometer (GCMS-QP2020, Shimadzu, Japan) equipped with an Rtx-5MS column (30 m \u0026times; 0.25 mm \u0026times; 0.25 \u0026micro;m). The pyrolysis temperature was set to 550\u0026deg;C. The gas chromatography settings were: temperature ramped from 40\u0026deg;C to 320\u0026deg;C at 20\u0026deg;C\u0026middot;min⁻\u0026sup1;, with a total runtime of 30 minutes, followed by 14 minutes at this temperature. Helium was used as the carrier gas, with a split ratio of 5:1. The mass-to-charge ratio (m/z) range was set from 29 to 600, with the ion source temperature fixed at 320\u0026deg;C.\u003c/p\u003e\n \u003cp\u003eSample preparation: Samples were accurately weighed (precision 0.001 g) into 100 mL beakers. Nitric acid was added at three times the sample weight and left at room temperature for 48 hours. After digestion, the solution was passed through a 1 \u0026micro;m steel membrane. The filtrate was concentrated at 110\u0026deg;C. An aliquot of the concentrated liquid was placed into the sample crucible and heated at 80\u0026deg;C until solvent evaporation, then analyzed by Py-GC/MS. Process blanks were performed, and the entire concentrated liquid was tested. Standard solutions with different concentrations were prepared and tested to establish a calibration curve. To eliminate the interference of complex organic matrices in biological samples on NPs detection, a series of strict sample pretreatment and instrumental quality control measures were adopted. Biological samples were subjected to acid digestion, membrane filtration and rotary concentration for targeted removal of endogenous organic matrices. The reagents used in this experiment were pre-filtered three times using a 0.45 \u0026micro;m PTFE membrane. Consumables were washed three times with filtered anhydrous ethanol before use.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec12\" class=\"Section2\"\u003e\n \u003ch2\u003eHealth risk assessment\u003c/h2\u003e\n \u003cp\u003eThe commonly used health risk assessment methods for non-cancer risks (HQ) and cancer risk values (CR) were proposed by the United States Environmental Protection Agency (USEPA) in 2000 as a way to evaluate human health risks \u003csup\u003e\u003cspan class=\"CitationRef\"\u003e69\u003c/span\u003e\u003c/sup\u003e.We chose to use the HQ method and the CR method from human health risk assessment and combined the model parameters recommended in the \u0026ldquo;Technical Guidelines for Risk Assessment of Polluted Sites\u0026rdquo; issued by the Ministry of Ecology and Environment of China, along with the maximum weekly mass of MPs ingested by humans through various exposure pathways (food intake, inhalation, and dermal absorption) as estimated by Senathirajah et al. \u003csup\u003e70\u003c/sup\u003e, for the analysis and evaluation. The calculation formulas can be found in Text S5. The evaluation criteria and model parameters used in this study are listed in Table S2 and Table S3, respectively.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec13\" class=\"Section2\"\u003e\n \u003ch2\u003eQuality assurance and control\u003c/h2\u003e\n \u003cp\u003eTo minimize background contamination and ensure data reliability, strict quality control measures were implemented throughout this study. During sample collection, all personnel wore sterile cotton garments, nitrile gloves, masks, and head coverings, with no contact permitted with plastic materials. Bone and disc samples were collected using stainless steel instruments and immediately transferred to foil‑sealed glass containers to limit air exposure. High‑speed power tools were avoided to prevent intraoperative plastic generation. A procedural blank accompanied each sampling session to monitor environmental contamination. All pretreatment and analytical steps were performed by the same operator in a laminar‑flow hood. Glassware was rinsed three times with ultrapure water and heat‑dried. Reagents were filtered through 0.45 \u0026micro;m PTFE membranes. Blank controls were included during the experiment, which consisted of air-exposed filter membrane blanks and reagent blanks that followed the same sample treatment process. These blanks followed the same preparation and filtration procedures yet yielded no detectable MPs particles. Finally, all data were calculated after subtracting the background from the procedural blanks.\u003c/p\u003e\n\u003c/div\u003e\n\u003cdiv id=\"Sec14\" class=\"Section2\"\u003e\n \u003ch2\u003eStatistical analysis\u003c/h2\u003e\n \u003cp\u003eIn this study, the quantity of MNPs in samples was quantified by abundance, specifically the number of MPs per unit mass of sample (unit: n/kg) and the concentration of NPs (unit: mg/kg). Characterization data of MPs, including abundance, particle size, type, and morphology, were analyzed and summarized using Microsoft Excel 2024. Statistical charts were generated with Origin 2024. Statistical analyses were completed using IBM SPSS Statistics software. To classify individual accumulation patterns across tissues, partial least squares‑discriminant analysis (PLS‑DA) was performed. Significance was tested by non-parametric multivariate analyses Adonis and Anosim. Differences with p\u0026thinsp;\u0026lt;\u0026thinsp;0.05 were considered statistically significant.\u003c/p\u003e\n\u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eData availability\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eData will be made available on request.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis work was supported by the National Natural Science Foundation of China (42577468 and 42277207), the Fundamental Research Funds for the Central Universities (GK202401003), Shaanxi Province Key Industrial Innovation Chain under Grant (2023-ZDLSF-12) and FMMU special research project of cross-cooperation (2024JC044).\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthor contributions\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eX.L.: data curation, formal analysis, investigation, methodology, writing-original draft; Y.W.: conceptualization, funding acquisition, project administration, supervision, writing-review \u0026amp; editing; Z.F.: data curation, formal analysis, software, validation; J.Z.: investigation, methodology, resources; B.X.: methodology, validation, writing-review \u0026amp; editing; and T.D.: conceptualization, methodology, supervision, validation, writing-review \u0026amp; editing. All authors reviewed and approved the final version.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDeclaration of competing interest\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n \u003cli\u003eArthur, C., Baker, J.E. \u0026amp; Bamford, H.A. Proceedings of the International Research Workshop on the Occurrence, Effects, and Fate of Microplastic Marine Debris, September 9-11, 2008, University of Washington Tacoma, Tacoma, WA, USA. (2009).\u003c/li\u003e\n \u003cli\u003eAlfaro-N\u0026uacute;\u0026ntilde;ez, A.\u003cem\u003e, et al.\u003c/em\u003e Microplastic pollution in seawater and marine organisms across the Tropical Eastern Pacific and Gal\u0026aacute;pagos. \u003cem\u003eSci. Rep.\u003c/em\u003e \u003cstrong\u003e11\u003c/strong\u003e, 6424 (2021).\u003c/li\u003e\n \u003cli\u003eEvangeliou, N.\u003cem\u003e, et al.\u003c/em\u003e Atmospheric transport is a major pathway of microplastics to remote regions. \u003cem\u003eNat. Commun.\u003c/em\u003e \u003cstrong\u003e11\u003c/strong\u003e, 3381 (2020).\u003c/li\u003e\n \u003cli\u003eHe, L., Li, Z., Jia, Q. \u0026amp; Xu, Z. Soil microplastics pollution in agriculture. \u003cem\u003eScience\u003c/em\u003e \u003cstrong\u003e379\u003c/strong\u003e, 547-547 (2023).\u003c/li\u003e\n \u003cli\u003eThompson, R.C.\u003cem\u003e, et al.\u003c/em\u003e Lost at Sea: Where Is All the Plastic? \u003cem\u003eScience\u003c/em\u003e \u003cstrong\u003e304\u003c/strong\u003e, 838-838 (2004).\u003c/li\u003e\n \u003cli\u003eWang, H., Zhu, T., Wang, J. \u0026amp; Liu, Y. Microplastic pollution in Pearl River networks: Characteristic, potential sources, and migration pathways. \u003cem\u003eWater Res.\u003c/em\u003e \u003cstrong\u003e276\u003c/strong\u003e, 123261 (2025).\u003c/li\u003e\n \u003cli\u003eWelsh, B., Paterson, A.M., Yao, H., McConnell, C. \u0026amp; Aherne, J. The Fate of Microplastics in Rural Headwater Lake Catchments. \u003cem\u003eEnviron. Sci. Technol.\u003c/em\u003e \u003cstrong\u003e58\u003c/strong\u003e, 16570-16577 (2024).\u003c/li\u003e\n \u003cli\u003eDu, L.\u003cem\u003e, et al.\u003c/em\u003e Enhanced ecological risk of microplastic ingestion by fish due to fragmentation and deposition in heavily sediment-laden river. \u003cem\u003eWater Res.\u003c/em\u003e \u003cstrong\u003e278\u003c/strong\u003e, 123306 (2025).\u003c/li\u003e\n \u003cli\u003eLi, Y.\u003cem\u003e, et al.\u003c/em\u003e In situ imaging of microplastics in living organisms based on mass spectrometry technology. \u003cem\u003eEco-Environ. Health\u003c/em\u003e \u003cstrong\u003e3\u003c/strong\u003e, 412-417 (2024).\u003c/li\u003e\n \u003cli\u003eOrganization, W.H. Dietary and inhalation exposure to nano- and microplastic particles and potential implications for human health. (2022).\u003c/li\u003e\n \u003cli\u003eZhu, L.\u003cem\u003e, et al.\u003c/em\u003e Insights into human exposure to microplastics through drinking water: Current state of the science. \u003cem\u003eCrit Rev Environ Sci Technol\u003c/em\u003e \u003cstrong\u003e54\u003c/strong\u003e, 1875-1901 (2024).\u003c/li\u003e\n \u003cli\u003eKozlov, M. Your brain is full of microplastics: are they harming you? \u003cem\u003eNature\u003c/em\u003e \u003cstrong\u003e638\u003c/strong\u003e, 311-313 (2025).\u003c/li\u003e\n \u003cli\u003eThompson, R.C.\u003cem\u003e, et al.\u003c/em\u003e Twenty years of microplastic pollution research\u0026mdash;what have we learned? \u003cem\u003eScience\u003c/em\u003e \u003cstrong\u003e386\u003c/strong\u003e, eadl2746 (2025).\u003c/li\u003e\n \u003cli\u003eYin, J.\u003cem\u003e, et al.\u003c/em\u003e Nanoplastics and Microplastics May Be Damaging Our Livers. in \u003cem\u003eToxics\u003c/em\u003e, Vol. 10 586 (2022).\u003c/li\u003e\n \u003cli\u003eZhang, C.\u003cem\u003e, et al.\u003c/em\u003e Association of mixed exposure to microplastics with sperm dysfunction: a multi-site study in China. \u003cem\u003eEBioMedicine\u003c/em\u003e \u003cstrong\u003e108\u003c/strong\u003e, 105369 (2024).\u003c/li\u003e\n \u003cli\u003eZhao, Q.\u003cem\u003e, et al.\u003c/em\u003e Detection and characterization of microplastics in the human testis and semen. \u003cem\u003eSci. Total Environ.\u003c/em\u003e \u003cstrong\u003e877\u003c/strong\u003e, 162713 (2023).\u003c/li\u003e\n \u003cli\u003eZhu, L.\u003cem\u003e, et al.\u003c/em\u003e Tissue accumulation of microplastics and potential health risks in human. \u003cem\u003eSci. Total Environ.\u003c/em\u003e \u003cstrong\u003e915\u003c/strong\u003e, 170004 (2024).\u003c/li\u003e\n \u003cli\u003eZhu, L.\u003cem\u003e, et al.\u003c/em\u003e Identification of microplastics in human placenta using laser direct infrared spectroscopy. \u003cem\u003eSci. Total Environ.\u003c/em\u003e \u003cstrong\u003e856\u003c/strong\u003e, 159060 (2023).\u003c/li\u003e\n \u003cli\u003eMarfella, R.\u003cem\u003e, et al.\u003c/em\u003e Microplastics and Nanoplastics in Atheromas and Cardiovascular Events. \u003cem\u003eN. Engl. J. Med.\u003c/em\u003e \u003cstrong\u003e390\u003c/strong\u003e, 900-910 (2024).\u003c/li\u003e\n \u003cli\u003eKozlov, M. Landmark study links microplastics to serious health problems. \u003cem\u003eNature\u003c/em\u003e (2024).\u003c/li\u003e\n \u003cli\u003eKrause, S.\u003cem\u003e, et al.\u003c/em\u003e The potential of micro- and nanoplastics to exacerbate the health impacts and global burden of non-communicable diseases. \u003cem\u003eCell Rep. Med.\u003c/em\u003e \u003cstrong\u003e5\u003c/strong\u003e, 101581 (2024).\u003c/li\u003e\n \u003cli\u003eLeslie, H.A.\u003cem\u003e, et al.\u003c/em\u003e Discovery and quantification of plastic particle pollution in human blood. \u003cem\u003eEnviron. Int.\u003c/em\u003e \u003cstrong\u003e163\u003c/strong\u003e, 107199 (2022).\u003c/li\u003e\n \u003cli\u003eV. L. Leonard, S.\u003cem\u003e, et al.\u003c/em\u003e Microplastics in human blood: Polymer types, concentrations and characterisation using \u0026mu;FTIR. \u003cem\u003eEnviron. Int.\u003c/em\u003e \u003cstrong\u003e188\u003c/strong\u003e, 108751 (2024).\u003c/li\u003e\n \u003cli\u003eGiannandrea, D.\u003cem\u003e, et al.\u003c/em\u003e Nanoplastic impact on bone microenvironment: A snapshot from murine bone cells. \u003cem\u003eJ. Hazard. Mater.\u003c/em\u003e \u003cstrong\u003e462\u003c/strong\u003e, 132717 (2024).\u003c/li\u003e\n \u003cli\u003eWang, H.\u003cem\u003e, et al.\u003c/em\u003e Preserving the Immune-Privileged Niche of the Nucleus Pulposus: Safeguarding Intervertebral Discs from Degeneration after Discectomy with Synthetic Mucin Hydrogel Injection. \u003cem\u003eAdv Sci (Weinh)\u003c/em\u003e \u003cstrong\u003e11\u003c/strong\u003e, e2404496 (2024).\u003c/li\u003e\n \u003cli\u003eYang, Q.\u003cem\u003e, et al.\u003c/em\u003e Microplastics in human skeletal tissues: Presence, distribution and health implications. \u003cem\u003eEnviron. Int.\u003c/em\u003e \u003cstrong\u003e196\u003c/strong\u003e, 109316 (2025).\u003c/li\u003e\n \u003cli\u003eJohnson, Z.I., Shapiro, I.M. \u0026amp; Risbud, M.V. Extracellular osmolarity regulates matrix homeostasis in the intervertebral disc and articular cartilage: Evolving role of TonEBP. \u003cem\u003eMatrix Biol.\u003c/em\u003e \u003cstrong\u003e40\u003c/strong\u003e, 10-16 (2014).\u003c/li\u003e\n \u003cli\u003eAli, S.S., Elsamahy, T., Al-Tohamy, R. \u0026amp; Sun, J. A critical review of microplastics in aquatic ecosystems: Degradation mechanisms and removing strategies. \u003cem\u003eEnvironmental Science and Ecotechnology\u003c/em\u003e \u003cstrong\u003e21\u003c/strong\u003e, 100427 (2024).\u003c/li\u003e\n \u003cli\u003eZhao, H., Mu, S., Wang, W. \u0026amp; Li, X. Potential threats of environmental microplastics to the skeletal system: current insights and future directions. \u003cem\u003eFront Endocrinol (Lausanne)\u003c/em\u003e \u003cstrong\u003e16\u003c/strong\u003e, 1658056 (2025).\u003c/li\u003e\n \u003cli\u003eLing, Z., Zeng, X., Luo, Q., Li, X. \u0026amp; Cui, L. Co-morbid mechanisms of intervertebral disc degeneration and osteoporosis: biomechanical coupling and molecular pathways synergistically driving degenerative lesions. \u003cem\u003eJournal of Orthopaedic Surgery and Research\u003c/em\u003e \u003cstrong\u003e20\u003c/strong\u003e, 652 (2025).\u003c/li\u003e\n \u003cli\u003ePelepenko, L.E.\u003cem\u003e, et al.\u003c/em\u003e Effects of microplastics on the bones: a comprehensive review. \u003cem\u003eOsteoporos Int\u003c/em\u003e \u003cstrong\u003e36\u003c/strong\u003e, 1327-1345 (2025).\u003c/li\u003e\n \u003cli\u003eLi, Z.\u003cem\u003e, et al.\u003c/em\u003e Identification and analysis of microplastics in human lower limb joints. \u003cem\u003eJ. Hazard. Mater.\u003c/em\u003e \u003cstrong\u003e461\u003c/strong\u003e, 132640 (2024).\u003c/li\u003e\n \u003cli\u003eCao, Z.\u003cem\u003e, et al.\u003c/em\u003e Mapping the hidden journey of microplastics: Multi-organ deposition patterns and organ-specific health risks revealed by AI-driven analysis. \u003cem\u003eThe Innovation\u003c/em\u003e, 101031 (2025).\u003c/li\u003e\n \u003cli\u003eZou, F.\u003cem\u003e, et al.\u003c/em\u003e Revealing the presence of lymphatic vessels within intervertebral discs: Novel insights into disc degeneration. \u003cem\u003eThe Innovation\u003c/em\u003e \u003cstrong\u003e6\u003c/strong\u003e, 100865 (2025).\u003c/li\u003e\n \u003cli\u003eGustafson, H.H., Holt-Casper, D., Grainger, D.W. \u0026amp; Ghandehari, H. Nanoparticle uptake: The phagocyte problem. \u003cem\u003eNano Today\u003c/em\u003e \u003cstrong\u003e10\u003c/strong\u003e, 487-510 (2015).\u003c/li\u003e\n \u003cli\u003eWei, Q., Zhang, X., Zhou, C., Ren, Q. \u0026amp; Zhang, Y. Roles of large aggregating proteoglycans in human intervertebral disc degeneration. \u003cem\u003eConnect. Tissue Res.\u003c/em\u003e \u003cstrong\u003e60\u003c/strong\u003e, 209-218 (2019).\u003c/li\u003e\n \u003cli\u003eYalan, C., Ke, S. \u0026amp; Bo, G. Sorption behavior, mechanisms, and models of organic pollutants and metals on microplastics: A review. \u003cem\u003eEnviron. Chem.\u003c/em\u003e \u003cstrong\u003e40\u003c/strong\u003e, 2271-2287 (2021).\u003c/li\u003e\n \u003cli\u003eWagner, E.K.\u003cem\u003e, et al.\u003c/em\u003e Avidin grafted dextran nanostructure enables a month-long intra-discal retention. \u003cem\u003eSci. Rep.\u003c/em\u003e \u003cstrong\u003e10\u003c/strong\u003e, 12017 (2020).\u003c/li\u003e\n \u003cli\u003eJian, L. \u0026amp; Xiaoliang, Z. Research advances in the relationship between renal metabolism and hypertension. \u003cem\u003eJournal of Clinical Nephrology\u003c/em\u003e \u003cstrong\u003e23\u003c/strong\u003e, 853-857 (2023).\u003c/li\u003e\n \u003cli\u003eCui, L.\u003cem\u003e, et al.\u003c/em\u003e Insights into the effect of polyethylene terephthalate (PET) microplastics on HER2 signaling pathways. \u003cem\u003eToxicol. in Vitro\u003c/em\u003e \u003cstrong\u003e91\u003c/strong\u003e, 105632 (2023).\u003c/li\u003e\n \u003cli\u003eLiu, C.\u003cem\u003e, et al.\u003c/em\u003e Widespread distribution of PET and PC microplastics in dust in urban China and their estimated human exposure. \u003cem\u003eEnviron. Int.\u003c/em\u003e \u003cstrong\u003e128\u003c/strong\u003e, 116-124 (2019).\u003c/li\u003e\n \u003cli\u003eHossain, M. \u0026amp; Engelhardt, I. Global plastic footprint: unveiling property trends, environmental fate, and emerging threats of microplastic and nanoplastics pollution across ecosystems. \u003cem\u003eEnergy Ecol. Environ.\u003c/em\u003e \u003cstrong\u003e10\u003c/strong\u003e, 637-674 (2025).\u003c/li\u003e\n \u003cli\u003eKadac-Czapska, K., Knez, E. \u0026amp; Grembecka, M. Food and human safety: the impact of microplastics. \u003cem\u003eCrit. Rev. Food Sci. Nutr.\u003c/em\u003e \u003cstrong\u003e64\u003c/strong\u003e, 3502-3521 (2024).\u003c/li\u003e\n \u003cli\u003eAbdel‐Monem, R.A.\u003cem\u003e, et al.\u003c/em\u003e Chitosan‐ PVC conjugates/metal nanoparticles for biomedical applications. \u003cem\u003ePolym. Adv. Technol.\u003c/em\u003e \u003cstrong\u003e33\u003c/strong\u003e, 514-523 (2021).\u003c/li\u003e\n \u003cli\u003eZhong, R.\u003cem\u003e, et al.\u003c/em\u003e In vitro investigation of the effect of plasticizers on the blood compatibility of medical grade plasticized poly (vinyl chloride). \u003cem\u003eJ Mater Sci Mater Med\u003c/em\u003e \u003cstrong\u003e24\u003c/strong\u003e, 1985-1992 (2013).\u003c/li\u003e\n \u003cli\u003eMofakhami, E.\u003cem\u003e, et al.\u003c/em\u003e Microstructure-mechanical properties relationships in vibration welded glass-fiber-reinforced polyamide 66: A high-resolution X-ray microtomography study. \u003cem\u003ePolym. Test.\u003c/em\u003e \u003cstrong\u003e85\u003c/strong\u003e, 106454 (2020).\u003c/li\u003e\n \u003cli\u003eMurphy, F., Russell, M., Ewins, C. \u0026amp; Quinn, B. The uptake of macroplastic \u0026amp; microplastic by demersal \u0026amp; pelagic fish in the Northeast Atlantic around Scotland. \u003cem\u003eMar. Pollut. Bull.\u003c/em\u003e \u003cstrong\u003e122\u003c/strong\u003e, 353-359 (2017).\u003c/li\u003e\n \u003cli\u003eSun, J.\u003cem\u003e, et al.\u003c/em\u003e Effects of polyamide microplastics on the adsorption of perfluoroalkyl substances in soil. \u003cem\u003eJ. Hazard. Mater. Adv.\u003c/em\u003e \u003cstrong\u003e13\u003c/strong\u003e, 100391 (2024).\u003c/li\u003e\n \u003cli\u003eTang, K.H.D., Li, R., Li, Z. \u0026amp; Wang, D. Health risk of human exposure to microplastics: a review. \u003cem\u003eEnviron. Chem. Lett.\u003c/em\u003e \u003cstrong\u003e22\u003c/strong\u003e, 1155-1183 (2024).\u003c/li\u003e\n \u003cli\u003eQiu, Y.\u003cem\u003e, et al.\u003c/em\u003e Mesoporous Hydroxyapatite Nanoparticles Mediate the Release and Bioactivity of BMP-2 for Enhanced Bone Regeneration. \u003cem\u003eACS Biomater. Sci. Eng.\u003c/em\u003e \u003cstrong\u003e6\u003c/strong\u003e, 2323-2335 (2020).\u003c/li\u003e\n \u003cli\u003ePattappa, G.\u003cem\u003e, et al.\u003c/em\u003e Diversity of intervertebral disc cells: phenotype and function. \u003cem\u003eJ. Anat.\u003c/em\u003e \u003cstrong\u003e221\u003c/strong\u003e, 480-496 (2012).\u003c/li\u003e\n \u003cli\u003eHartikainen, J.\u003cem\u003e, et al.\u003c/em\u003e Structure and Morphology of Polyamide 66 and Oligomeric Phenolic Resin Blends:\u0026thinsp; Molecular Modeling and Experimental Investigations. \u003cem\u003eChem. Mater.\u003c/em\u003e \u003cstrong\u003e16\u003c/strong\u003e, 3032-3039 (2004).\u003c/li\u003e\n \u003cli\u003eKarimi-Varzaneh, H.A., Carbone, P. \u0026amp; M\u0026uuml;ller-Plathe, F. Hydrogen Bonding and Dynamic Crossover in Polyamide-66: A Molecular Dynamics Simulation Study. \u003cem\u003eMacromolecules\u003c/em\u003e \u003cstrong\u003e41\u003c/strong\u003e, 7211-7218 (2008).\u003c/li\u003e\n \u003cli\u003ePituru, S.M.\u003cem\u003e, et al.\u003c/em\u003e A Review on the Biocompatibility of PMMA-Based Dental Materials for Interim Prosthetic Restorations with a Glimpse into Their Modern Manufacturing Techniques. \u003cem\u003eMaterials\u003c/em\u003e \u003cstrong\u003e13\u003c/strong\u003e, 2894 (2020).\u003c/li\u003e\n \u003cli\u003eShahsavaripour, M., Abbasi, S., Mirzaee, M. \u0026amp; Amiri, H. Human occupational exposure to microplastics: A cross-sectional study in a plastic products manufacturing plant. \u003cem\u003eSci. Total Environ.\u003c/em\u003e \u003cstrong\u003e882\u003c/strong\u003e, 163576 (2023).\u003c/li\u003e\n \u003cli\u003eSchmidt, A.\u003cem\u003e, et al.\u003c/em\u003e Short- and long-term polystyrene nano- and microplastic exposure promotes oxidative stress and divergently affects skin cell architecture and Wnt/beta-catenin signaling. \u003cem\u003ePart. Fibre Toxicol.\u003c/em\u003e \u003cstrong\u003e20\u003c/strong\u003e, 3 (2023).\u003c/li\u003e\n \u003cli\u003eWang, W.\u003cem\u003e, et al.\u003c/em\u003e Polystyrene microplastics induced nephrotoxicity associated with oxidative stress, inflammation, and endoplasmic reticulum stress in juvenile rats. \u003cem\u003eFront. Nutr.\u003c/em\u003e \u003cstrong\u003e9\u003c/strong\u003e, 1059660 (2022).\u003c/li\u003e\n \u003cli\u003eLafram, A., Krami, A.M., Akarid, K., Laadraoui, J. \u0026amp; Roky, R. Effects of exposure to micro/nanoplastics of polystyrene on neuronal oxidative stress, neuroinflammation, and anxiety-like behavior in mice: A Systematic Review. \u003cem\u003eEmerging Contam.\u003c/em\u003e \u003cstrong\u003e11\u003c/strong\u003e, 100442 (2025).\u003c/li\u003e\n \u003cli\u003eChang, J.\u003cem\u003e, et al.\u003c/em\u003e A critical review on interaction of microplastics with organic contaminants in soil and their ecological risks on soil organisms. \u003cem\u003eChemosphere\u003c/em\u003e \u003cstrong\u003e306\u003c/strong\u003e, 135573 (2022).\u003c/li\u003e\n \u003cli\u003eJoseph, M.M., Nair, J.B. \u0026amp; Joseph, A.M. Microscopic menace: exploring the link between microplastics and cancer pathogenesis. \u003cem\u003eEnviron Sci Process Impacts\u003c/em\u003e \u003cstrong\u003e27\u003c/strong\u003e, 1768-1795 (2025).\u003c/li\u003e\n \u003cli\u003eCui, Y.\u003cem\u003e, et al.\u003c/em\u003e Mitigating microplastic-induced organ Damage: Mechanistic insights from the microplastic-macrophage axes. \u003cem\u003eRedox Biol.\u003c/em\u003e \u003cstrong\u003e84\u003c/strong\u003e, 103688 (2025).\u003c/li\u003e\n \u003cli\u003eQian, N.\u003cem\u003e, et al.\u003c/em\u003e Rapid single-particle chemical imaging of nanoplastics by SRS microscopy. \u003cem\u003eProceedings of the National Academy of Sciences\u003c/em\u003e \u003cstrong\u003e121\u003c/strong\u003e, e2300582121 (2024).\u003c/li\u003e\n \u003cli\u003eDu, F., Cai, H., Zhang, Q., Chen, Q. \u0026amp; Shi, H. Microplastics in take-out food containers. \u003cem\u003eJ. Hazard. Mater.\u003c/em\u003e \u003cstrong\u003e399\u003c/strong\u003e, 122969 (2020).\u003c/li\u003e\n \u003cli\u003eMohamed Nor, N.H., Kooi, M., Diepens, N.J. \u0026amp; Koelmans, A.A. Lifetime Accumulation of Microplastic in Children and Adults. \u003cem\u003eEnviron. Sci. Technol.\u003c/em\u003e \u003cstrong\u003e55\u003c/strong\u003e, 5084-5096 (2021).\u003c/li\u003e\n \u003cli\u003eTsou, T.-Y.\u003cem\u003e, et al.\u003c/em\u003e Distribution and toxicity of submicron plastic particles in mice. \u003cem\u003eEnviron. Toxicol. Pharmacol.\u003c/em\u003e \u003cstrong\u003e97\u003c/strong\u003e, 104038 (2023).\u003c/li\u003e\n \u003cli\u003eLiu, X.H.\u003cem\u003e, et al.\u003c/em\u003e Perspectives on the microorganisms with the potentials of PET-degradation. \u003cem\u003eFront. Microbiol.\u003c/em\u003e \u003cstrong\u003e16\u003c/strong\u003e, 1541913 (2025).\u003c/li\u003e\n \u003cli\u003eNihart, A.J.\u003cem\u003e, et al.\u003c/em\u003e Bioaccumulation of microplastics in decedent human brains. \u003cem\u003eNat. Med.\u003c/em\u003e \u003cstrong\u003e31\u003c/strong\u003e, 1114-1119 (2025).\u003c/li\u003e\n \u003cli\u003eLi, M.\u003cem\u003e, et al.\u003c/em\u003e Quantitative source apportionment of groundwater pollution based on PCA-APCS-MLR. \u003cem\u003eChina Environmental Science\u003c/em\u003e \u003cstrong\u003e37\u003c/strong\u003e, 3773-3786 (2017).\u003c/li\u003e\n \u003cli\u003eUSEPA. Electronic Code of Federal Regulations, Risk Assessment Guidance for Superfund of Human health risk assessment method. (2019).\u003c/li\u003e\n \u003cli\u003eSenathirajah, K.\u003cem\u003e, et al.\u003c/em\u003e Estimation of the mass of microplastics ingested \u0026ndash; A pivotal first step towards human health risk assessment. \u003cem\u003eJ. Hazard. Mater.\u003c/em\u003e \u003cstrong\u003e404\u003c/strong\u003e, 124004 (2021).\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"npj-emerging-contaminants","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [npj Emerging Contaminants](https://www.nature.com/npjemergcontam/)","snPcode":"44454","submissionUrl":"https://submission.springernature.com/new-submission/44454/3","title":"npj Emerging Contaminants","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Unsupported Journal","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"Microplastics, Nanoplastics, Human tissues, Accumulation patterns, Health risks","lastPublishedDoi":"10.21203/rs.3.rs-9100391/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-9100391/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eThe 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.\u003c/p\u003e","manuscriptTitle":"The Human Intervertebral Disc as a Long-Term Repository for Micro/Nanoplastics: Tissue-Specific Accumulation and Risk Estimation","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2026-03-18 10:09:53","doi":"10.21203/rs.3.rs-9100391/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Revision requested","date":"2026-03-25T15:21:52+00:00","index":"","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-03-25T06:01:31+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-03-23T14:15:33+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"78061968276776103244067684661792707355","date":"2026-03-19T07:39:40+00:00","index":"hide","fulltext":""},{"type":"editorInvitedReview","content":"","date":"2026-03-17T10:07:35+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"49856835327684254461964949599104215773","date":"2026-03-17T06:47:12+00:00","index":"hide","fulltext":""},{"type":"reviewerAgreed","content":"92698987293633104852546445232214187182","date":"2026-03-16T14:25:41+00:00","index":"hide","fulltext":""},{"type":"reviewersInvited","content":"","date":"2026-03-16T13:41:31+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2026-03-16T09:00:50+00:00","index":"","fulltext":""},{"type":"checksComplete","content":"","date":"2026-03-16T07:46:11+00:00","index":"","fulltext":""},{"type":"submitted","content":"npj Emerging Contaminants","date":"2026-03-12T05:22:18+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"npj-emerging-contaminants","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"","sideBox":"Learn more about [npj Emerging Contaminants](https://www.nature.com/npjemergcontam/)","snPcode":"44454","submissionUrl":"https://submission.springernature.com/new-submission/44454/3","title":"npj Emerging Contaminants","twitterHandle":"","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"stoa","reportingPortfolio":"Unsupported Journal","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"f87de48d-a386-4047-b4e9-b53262d34300","owner":[],"postedDate":"March 18th, 2026","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"under-review","subjectAreas":[{"id":64643833,"name":"Biological sciences/Biological techniques"},{"id":64643834,"name":"Physical sciences/Chemistry"},{"id":64643835,"name":"Earth and environmental sciences/Environmental sciences"},{"id":64643836,"name":"Physical sciences/Materials science"},{"id":64643837,"name":"Health sciences/Medical research"},{"id":64643838,"name":"Physical sciences/Nanoscience and technology"}],"tags":[],"updatedAt":"2026-05-07T15:39:30+00:00","versionOfRecord":[],"versionCreatedAt":"2026-03-18 10:09:53","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-9100391","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-9100391","identity":"rs-9100391","version":["v1"]},"buildId":"XKTyCvWXoU3ODBz1xrDgd","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}