Emerging evidence on micro- and nanoplastics carcinogenicity: mechanisms, models, and signaling networks

Abstract

Evidence of micro- and nanoplastics (MNPLs) presence in human tissues, cells, and biological fluids raises concerns about their potential role in hazardous diseases, including cancer. Higher concentrations of microplastics (MPLs) in cancerous tissues compared with adjacent healthy tissues, particularly in barrier organs such as the lungs, intestines, and reproductive system, suggest a potential association with tissue pathology and tumor-related processes. Extracted MNPLs from cancerous tissues exhibit diverse polymer compositions and morphologies, predominantly fibers and fragments larger than 1 μm, while smaller nanoplastics (NPLs) are likely underrepresented due to detection limitations. To investigate how MNPLs promote carcinogenesis depending on their physicochemical characteristics, various in vitro and in vivo studies have been analyzed. Most studies use pristine commercial spherical polystyrene (PS) MNPLs, which do not fully exhibit real-life MNPL characteristics but still provide valuable insights into their hazardous effects across a wide size range. Additional studies employing alternative polymers and environmentally relevant particle shapes further advance understanding of MNPL-associated health risks, as addressed in this review. Existing data indicates that smaller NPLs readily cross biological barriers and accumulate within cells due to their high surface area, whereas larger MPLs primarily interact at tissue surfaces, causing physical stress, tight junction disruption, and microbiota perturbation. Notably, MNPL exposure induces multiple hazardous effects and disrupts cellular homeostasis through coordinated and integrated signaling pathways. NF-κB signaling triggers pro-inflammatory and survival gene expression, while JNK-MAPK, ERK1/2-MAPK, and JAK–STAT pathways amplify inflammation, DNA damage responses, and apoptosis. MNPLs also induce ROS-driven ER stress, mitochondrial dysfunction, and dysregulation of AKT, TP53, caspases, and XIAP, activating apoptosis, necroptosis, and fibrosis. Compensatory antioxidant responses are activated via NRF2/HO-1 to counteract oxidative stress, while β-catenin/Wnt signaling is concurrently modulated, linking ROS-induced stress to tumorigenic reprogramming and cellular proliferation. Dysregulation of metabolic and growth regulators, including PI3K–AKT–mTOR, AMPK, mTORC1, and P70S6K, promotes cellular proliferation, survival, and metabolic adaptation. Simultaneously, modulation of ECM–receptor interactions, focal adhesion, Hippo, TGF-β, and cell-cycle regulators (CDK4/6, Cyclin D1, p-Rb) reshapes the tumor microenvironment, supporting potential malignant progression. All these interconnected events establish a tumor-permissive environment, promoting uncontrolled proliferation, metabolic reprogramming, and malignant transformation, thereby supporting the potential role of MNPLs in carcinogenesis.

Introduction

Micro/nanoplastics (MNPLs) are increasingly recognized as a significant environmental and public-health challenge [1]. Their occurrence is associated with a broad spectrum of anthropogenic activities, including industrial purposes [2], fiber release from synthetic textiles [3], tire abrasion during transportation [4], degradation of plastic packaging materials [5], and plastic-intensive agricultural practices [6]. Additional inputs arise from daily routine household activities during use, heating and washing plastic-based utensils [7]. In all cases, MNPLs ultimately reach various environmental compartments through the direct emission of particles [8] or through the progressive fragmentation of larger plastics [9], supporting their widespread distribution and environmental persistence. With ~ 359 million tons of plastics produced annually and 150–200 million tons accumulating in the environment, subsurface marine MNPLs concentrations reach up to 10⁴ particles/m³, based on measurements from 1,885 stations sampled between 2014 and 2024 [10]. Plastic degradation is a continuous process occurring over time, resulting in MPLs progressive fragmentation through physicochemical and environmental processes generating nanoplastics (NPLs), that represent a distinct and potentially more bioactive class of plastic pollutants. Environmental assessments estimate that the total mass of NPLs in the temperate–subtropical mixed layer of the North Atlantic reaches approximately 27 million tons, underscoring their vast and largely overlooked environmental burden [11]. When we discuss environmental exposures, we will use the term micro-nanoplastics (MNPLs) to show the complexity of such mix exposures. The terms microplastic (MPLs) and nanoplastics (NPLs) will be used when information about the exposure size is well known.

This diverse range of sources and the enormous volume of MNPLs have facilitated their infiltration into virtually all environments surrounding humans. They are widely distributed across marine systems [12], freshwater bodies [13], terrestrial ecosystems [14], and the atmosphere [15]. Consequently, drinking water [16], food [17], and air [18] are ubiquitously contaminated, rendering human exposure to MNPLs unavoidable. This exposure is facilitated by the small size of MPLs (1 μm–5 mm) and NPLs (< 1 μm), which enables their widespread dispersion and biological uptake. Although the European Food Safety Authority (EFSA) defines nanoplastics (NPLs) as particles < 100 nm, in line with criteria established for engineered nanomaterials, environmental MNPLs are not intentionally engineered and occur across a continuous and broad size distribution. Accordingly, several authors have proposed adapting the definitions of NPLs and MPLs to reflect their descriptive size ranges within the nano- and microscale domains. Under this framework, NPLs are considered to range from 1 to 1000 nm, whereas MPLs span from 1 to 1000 μm [11]. In this review, we adopt these size-based definitions.

The primary routes of exposure include ingestion of contaminated food and beverages [19], inhalation of airborne particles [20], and, to a lesser extent, dermal contact [21]. This widespread contamination highlights the urgent need to understand the extent and implications of human MNPL exposure. Human exposure is substantial, with annual intake estimated at 39,000–52,000 particles per person, rising to 74,000–121,000 particles when inhalation is included, while bottled water alone may contribute up to 90,000 particles annually [22]. Such exposure is unsurprising given the multiple sources of MNPLs in daily life; average daily intake is estimated at 382 ± 205 particles from drinking water, 594 ± 269 from air, and 1,036 ± 493 from food, highlighting the cumulative nature of human exposure [23]. A meta-analysis further revealed that MNPLs from polytetrafluoroethylene (PTFE), commonly used in cooking utensils, can contaminate human tissues at concentrations reaching 482.5 ± 554.1 particles/kg [7].

MNPLs have been documented in various human organs, including lungs [24], placenta [25], small intestine [26], testes [27], prostate [28], bone marrow [29], arteries [30], and in the brain, liver, and kidneys [31]. In addition, MNPLs have been identified in body fluids such as blood [32], semen [33], nasal fluids [34], and breast milk [35], along with feces and urine [36, 37]. This pervasive distribution of MNPLs in human tissues and fluids underscores their potential to contribute to systemic health hazards. Once inside the body, MNPLs can disrupt homeostasis, including gut dysbiosis [38] altering gut microbiota composition [39], epithelium damage [40], oxidative stress and inflammation [41], histopathology damages [42], metabolic disturbances [43], immunity [44], physical damage of cells [45], DNA damage [46], reproductive toxicity [47], mitochondrial dysfunction [48], endocrine disruption [49], apoptosis [50], and altering molecular pathway machinery [51]. Collectively, these disruptions may generate a microenvironment conducive to cellular transformation, potentially facilitating cancer initiation and progression. Notably, human studies have reported the broad presence of MNPLs in cancerous tissues and tumors, suggesting a possible association with carcinogenesis. However, the presence and impact of NPLs components remain largely underexplored due to current monitoring limitations.

Monitoring studies have detected MNPLs, particularly MPLs across multiple tumor tissues, with detection rates in lung, gastric, colorectal, and cervical cancers ranging from 17 to 80% and concentrations of 0.0071–0.546 µg/g, predominantly constituted by polyethylene (PE) and polyvinyl chloride (PVC) [52]. Colorectal tumors exhibit particularly high MPL burdens, with 702.68 ± 504.26 particles/g compared to 207.78 ± 154.12 particles/g in non-tumoral tissues, primarily composed of PE, poly(methyl methacrylate) (PMMA), and nylon (polyamide, PA), ranging from 1 to 1,299 μm [53]. Elevated MPLs in gastric cancer are linked to ingestion as a major entry route, especially via food and beverages [54]. Lung adenocarcinoma (LUAD) tissues similarly show high accumulation, with 5,476 particles detected versus 4,951 in adjacent normal tissue, reflecting deposition from environmental airborne MPLs [55]. Significant MPLs presence is also reported in reproductive cancers, including prostate [28], penile [56], cervical [57], and endometrial cancers [58]. These findings demonstrate that MPLs are highly prevalent across diverse cancer tissues, often surpassing levels observed in healthy counterparts, underscoring their potential role in carcinogenesis. Unfortunately, the lack of NPLs data underscores the role of these nanosized plastic particles. However, understanding the relationship between MNPL exposure and cancer development is extremely important and needs to be addressed. Addressing this complex issue requires a comprehensive, multidisciplinary approach that integrates material science, toxicology, clinical research, and advanced diagnostic modelling. Moving beyond isolated surveys of existing data, such coordinated efforts can identify key knowledge gaps, enable accurate tracking of MNPL exposure, and guide future studies to improve our understanding of their potential health impacts. Ultimately, this will inform strategies to mitigate risks and prioritize human health in the face of emerging plastic pollution, a focus that is explored in detail throughout this review.

Cancer progression and key molecular alterations

Cells can be conceptualized as intricately organized microcosms, wherein a multitude of molecular complexes and tightly coordinated processes operate concurrently to preserve structural integrity and functional stability. These processes maintain cellular homeostasis by directing physiological signaling pathways, ensuring precise intercellular communication, and facilitating coordinated interactions with neighboring cells, whether they perform analogous functions within the same tissue or complementary roles across disparate tissues and organs. Collectively, this orchestration underpins the proper function of the organism. Cells are constantly subjected to a spectrum of endogenous and exogenous stressors [59]. Under homeostatic conditions, cells detect these perturbations and mount adaptive responses, including activation of repair pathways and quality control mechanisms that rectify molecular errors, restore homeostasis, and enable the execution of essential cellular functions [60]. These regulatory networks are critical for maintaining controlled proliferation, genomic fidelity, and context-appropriate intercellular signaling [61]. However, when the magnitude or persistence of cellular stress surpasses the capacity of these protective mechanisms, homeostasis is compromised. Such conditions can induce aberrant cellular phenotypes characterized by dysregulated signaling, loss of growth control, and disorganization of intracellular processes. The cumulative effect of these maladaptive responses can drive oncogenic transformation, thereby initiating the complex multistep process of carcinogenesis [62].

Cancer is a devastating disease that imposes profound burdens not only in clinical settings but also across society, leaving lasting physical, psychological, and socioeconomic impacts on patients, families, and communities. It remains one of the most significant global health challenges and a leading cause of mortality worldwide, ranking as the primary cause of death in 57 countries and the second leading cause in 55 others among individuals under 70 years of age [63, 64]. Efforts to understand, diagnose, and treat cancer are not new; historical records indicate that cancer management dates to ancient civilizations, with seven Egyptian medical papyri from 3000 to 1600 BC documenting early descriptions and treatments of tumors [65].

Cancer is a multifactorial disease initiated by genetic mutations [66], epigenetic alterations affecting chromatin architecture and gene expression [67], and metabolic as well as physiological disturbances [68]. Environmental stressors may further contribute to cancer progression through mechanisms such as chronic inflammation, oxidative stress, and disruption of critical cellular pathways [69], these factors acting as surrogate biomarkers of cancer process. Inflammation is a major mediator of tumor development, with immune cells in the tumor microenvironment promoting proliferation, survival, migration, and metastasis of cancer cells [70]. Excessive reactive oxygen species (ROS) disturb cellular redox homeostasis, damaging lipids, proteins, and DNA, and triggering multiple forms of cell death, including ferroptosis, apoptosis, and necroptosis [71]. Together, these disruptions impair key signaling networks that maintain genomic stability, cellular identity, and homeostatic growth, thereby creating conditions favorable for malignant transformation [72].

Despite remarkable advances in molecular oncology, precision therapeutics, and early detection technologies, the global incidence and mortality of cancer continue to rise, partly associated by emerging environmental stressors. Among these, MNPLs have garnered increasing attention for their potential involvement in cancer development [73]. Elucidating the carcinogenic role of MNPLs requires systematic identification of their presence in human cancer tissues, including their distribution, abundance, polymer composition, and particle morphology. Furthermore, understanding MNPL-driven carcinogenesis necessitates an integrated evaluation of MNPL interactions with biological systems, including their bioavailability, cellular uptake, and persistence, as well as the molecular and cellular processes disrupted upon exposure, which may vary according to the intrinsic physicochemical properties of different MNPLs. These important aspects are comprehensively discussed in the following sections to delineate the mechanisms by which MNPLs may contribute to carcinogenesis.

Microplastic occurrence in human cancer tissues

As indicated, MNPLs have been increasingly detected across multiple compartments of the human body, including tissues, biological fluids, and excreta [33, 74]. Quantitative analyses have identified MNPLs in human blood (1.1 µg/mL), placenta (127 µg/g), and urine (7.4 µg/g) [75]. Other estimations have reported MNPL concentrations ranging from 0.0 to 0.3 particles/g (PS, PVC, PET) in colon and kidney; 0.4–2.2 particles/g (PS, PVC, PET) in spleen; 0.0–2.05 particles/g (PE, PVC, PP) in breast milk; 0.69 ± 0.84 particles/g (PP, PET, PS) in lung tissue; 0.0–1.5 particles/g (PS, PVC, PET) in liver; and 0.093–16.13 µg/g (PP, PET, PS) in fecal samples [76]. Zhu and coauthors detected MNPLs concentration in various organs such as lung, small intestine, large intestine, and tonsil (14.19 ± 14.57, 9.45 ± 13.13, 7.91 ± 7.00, and 6.03 ± 7.37 particles/g, respectively), sized 20–100 μm and predominantly PVC [26]. In skeletal system, MNPLs concentrations ranged from 22.9 ± 15.7–61.1 ± 44.2 particles/g, the largest average sizes in discs (159.5 μm) and bone (138.9 μm) compared to cartilage (87.5 μm), the most common polymers were PP (35%), ethylene vinyl acetate (30%), and PS (20%) [77]. Human exposure to MNPL extends to reproductive fluids, with PE and PVC detected in follicular fluid (1.21 µg/g and 1.85 µg/g, respectively) and seminal plasma (3.02 µg/g and 2.67 µg/g, respectively) in couples undergoing in vitro fertilization [78]. At the nanoscale, PVC and PMMA-NPLs (120–140 nm) are internalized by human lung fibroblasts, inducing cytotoxic effects including reduced cell viability and ATP, increased ROS and lactate dehydrogenase (LDH), cell cycle arrest, and apoptosis [79].

The occurrence of MNPLs is not restricted to healthy tissues; they have also been consistently detected in malignant tissues across respiratory, digestive, and reproductive systems, as summarized in Table 1; Fig. 1. Detection rates of MNPLs have been reported at 80% in lung tumors, 40% in gastric tumors, 50% in colorectal tumors, and 17% in cervical tumors, with concentrations ranging from 0.0071 to 0.546 µg/g. Among the identified polymers, PE was the most prevalent, exhibiting a mean concentration of 0.087 ± 0.117 µg/g, followed by PVC at 0.052 ± 0.082 µg/g [52]. As the lung represents a primary interface for airborne exposure, it is a key organ for reflecting the distribution and biological impacts of airborne MNPLs. To date, however, only a single study has directly reported the presence of MNPLs within lung adenocarcinoma (LUAD) tissues, despite demonstrating substantial accumulation. In a cohort of 15 LUAD patients, 34 distinct MNPL polymer types were identified, with PVC predominating; notably, 5,476 MNPL particles were detected in tumor tissues compared with 4,951 particles in adjacent normal lung tissues, with particle sizes ranging from 20 to 500 μm [55]. This limited yet compelling evidence underscores a critical knowledge gap regarding airborne MNPL deposition in lung cancers.

Table 1.

Microplastics extracted from human cancerous tissues. The table presents data on the concentration of various microplastic detected in various human tissues, including normal or cancerous. The table outlines the methodologies used to identify plastic polymer fragments, such as Laser Direct Infrared Imaging (LDIR); Pyrolysis Gas Chromatography–Mass Spectrometry (Py-GCMS), and Fourier transform infrared spectrometry (FTIR). Colorectal cancer (CRC), lung adenocarcinoma (LUAD). According to our calculation the mass of MPLs particles equivalent to 0.40 µg

Tissue Analyzed	Detection Methods	MPLs Type (Polymer)	Particle size	Concentration	Standardized Conc.	Ref.
Lung, gastric, colorectal, and cervical tumors (61 patients)	Py-GC-MS	PVC (0.052 ± 0.082 µg/g), PE (0.087 ± 0.117 µg/g), PS (0.06 ± 0.09 µg/g)	−	Lung, Gastric, Colorectal and Cervical (80%, 40%, 50% and 17%) with average (7.1–545.9 ng/g) PE (86.94 ± 116.84 ng/g) and PVC (51.98 ± 81.61 ng/g	MPLs (0.0071–0.546 µg/g) PE (0.087 ± 0.117 µg/g) and PVC (0.052 ± 0.082 µg/g)	[52]
Lung tissues (LUAD and adjacent normal, 15 LUAD patients)	LDIR; Py-GCMS	34 types, PVC, CPE, FKM, PU, PET dominant	20.34–499.25 μm	5,476 (LUAD tissues) and 4,951 particles (normal tissues)	LUAD tissues and normal tissues (329.8 and 298.2 µg/g, respectively) (The total wet weight of samples = 6.641 g)	[55]
Gastric tissues (tumor/para-tumor pairs, 52 samples)	Py-GC-MS and LDIR	PS, PE, PP, PMMA, PVC, PA66	< 100 μm	17.60–219.24 µg/g, PE, PVC, PA66, PS, PP, PMMA (32.35, 25.32, 17.09, 2.34, 2.33 and 0.30 µg/g, respectively)	Data are presented µg/g	[80]
Colon tissues (tumoral, non-tumoral, control)	FTIR; Raman spectroscopy	PE, PMMA, Nylon	1–1,299 μm	Tumoral tissues, non-tumoral and healthy control (702.68 ± 504.26, 207.78 ± 154.12 and 218.28 ± 213.05 particles/g, respectively)	Tumoral tissues, non-tumoral and healthy control ( 281.072 ± 201.704, 83.112± 61.648 and 87.312 ± 85.22 µg/g, respectively)	[53]
Colon tissues (tumoral, normal tissues,11 adults)	Stereo & FTIR microscopy	PC, PA, PP	Length 1.1 ± 0.3 mm	331 particles/specimen (28.1 ± 15.4 particles/g tissue); filaments/fibers (96.1%)	11.24 ± 6.16 µg/g	[54]
Colorectal cancer CRC (US & Malaysia)	Micro-FTIR	PE, PP, PA, PC; ABS only US	< 500 μm (Malaysia), 501–1000 μm (US)	Malaysia and USA (32.2 ± 48.1 and 25.0 ± 40.6 particles/g, respectively)	Malaysia and USA (12.88 ± 19.24 and 10 ± 16.24 µg/g, respectively)	[81]
Colon tissues (tumor peritumoral, 10 CRC patients)	SEM, LDIR	PP, PE, PVC, PS, PET, PA including particles, fibers, irregular shapes	< 100 μm	87.8 particles per tissue	-	[83]
Feces of CRC patients (n = 258), healthy controls (n = 493)	LDIR	17 types; PET, PA, PE, PP, PC (dominant)	< 200 μm	CRC (62 particles/g, range 30–177), Healthy controls (43 particles/g, range 33–141 particles/g); higher PET and PA in CRC	CRC (24.8 µg/g, range 12–70.8), Healthy controls (17.2 µg/g, range 13.2–56.4)	[82]
Cervical cancer, paracancerous tissue	Raman spectroscopy	13 types; mainly PE, PP, PE-co-PP	4.04–64.29 μm	Cancer and paracancerous tissue (1.67 ± 0.94 and 0.87 ± 0.72 particles /g, respectively)	Cancer and paracancerous tissue (0.67 ± 0.38 and 0.35 ± 0.29 µg/g, respectively)	[84]
Cervical cancer tissues (45 patients) & normal (n = 15)	Micro-Raman spectroscopy	12 types; PE and PP most abundant	> 20 μm	101 MPLs (2.24 ± 1.61 particles/g), PE 26.7%, PP 19.8%	0.90 ± 0.64 µg/g	[57]
Endometrial cancer & matched normal	Raman spectroscopy	PE, PP, EAA, PS	19.73 ± 9.72 μm	Endometrial and normal tissues (3.7 ± 2.5 and 2.0 ± 1.5 particles/g, respectively), PE (15.7%), PP (11.8%), EAA (10.8%), and PS (8.8%)	Endometrial and normal tissues (1.48 ± 1.0 and 0.8 ± 0.6 µg /g, respectively),	[58]
Penile cancer (17 patients)	LDIR	Nine types, mainly PE, PP, PVC	20–50 μm	6.42 particles/g	2.57 µg/g	[56]
Prostate tumor, para-tumor (22 patients)	LDIR; SEM; Py-GCMS	PS, PP, PE, PVC	20–100 μm (irregular shapes predominant)	Tumors (290.3 µg/g), para-tumor tissues (181.0 µg/g)	Data are presented µg/g	[28]

Fig. 1.

Concentrations of MPLs extracted from human carcinogenic tissues. This figure shows the measured levels of MNPLs and their main polymer types in various tissues, including tumorous, nontumorous, and healthy tissues. The figure was created using BioRender

The gastrointestinal (GI) tract serves as a primary portal of entry for MNPLs via contaminated food and beverages, as reflected by their substantial accumulation in gastric and colorectal cancers (CRC) across multiple studies. In gastric cancer (GC) tissues, total MNPL loads ranged from 17.60 to 219.24 µg/g, with the highest concentrations detected for PE (32.35 µg/g), PVC (25.32 µg/g), and PA66 (17.09 µg/g), while PS (2.34 µg/g), PP (2.33 µg/g), and PMMA (0.30 µg/g) were comparatively lower [80]. In CRC tissues, MNPLs were markedly elevated, averaging 702.68 ± 504.26 particles/g, compared with 207.78 ± 154.12 particles/g in adjacent non-tumoral tissues and 218.28 ± 213.05 particles/g in healthy controls, with PE, PMMA, and Nylon being the predominant polymers [53]. Regarding polymer composition and morphology, filaments/fibers accounted for 96.1% of the detected MNPLs, primarily PC, PA, and PP, with a total of 331 particles per specimen (28.1 ± 15.4 particles/g tissue) in CRC and healthy colon samples [54]. Globally, MNPLs were also detected in CRC samples from USA (25.0 ± 40.6 particles/g) and Malaysia (32.2 ± 48.1 particles/g) patients, with PE, PP, PA, and PC being the most dominant [81]. Fecal samples from CRC patients further confirmed widespread exposure, with MNPLs significantly higher in 258 CRC patients (62 particles/g, range 30–177) compared to 493 healthy controls (43 particles/g, range 33–141, p < 0.05), predominantly PET, PA, PE, PP, and PC, and altered relative abundances observed in patients [82]. Peritumoral and tumor tissues from 10 CRC patients contained PP, PE, PVC, PS, PET, and PA MNPLs (< 100 μm; particles, fibers, irregular shapes) at an average of 87.8 particles per tissue, detected by SEM and LDIR [83].

MNPLs are also prevalent in reproductive organs, with consistently higher abundance reported in malignant tissues. Cervical cancer tissues show robust MNPL accumulation, identifying 13 MNPL types and significantly higher levels in tumors (1.67 ± 0.94 particles/g) compared with para-cancerous tissues (0.87 ± 0.72 particles/g), predominantly PE, PP, and PE-co-PP, and higher detection rates in tumors and blood (80%) than in adjacent tissues (66.7%) [84]. Similarly [57], detected 101 MNPLs representing 12 polymer types in cervical cancer tissues, averaging 2.24 ± 1.61 particles/g, dominated by PE (26.73%) and PP (19.80%), and associated with metabolomic disruptions in D-mannose, cis, cis-muconic acid, and amino- and nucleotide-sugar metabolism, suggesting a potential role of MNPLs in cervical cancer progression via metabolic reprogramming. Endometrial cancer tissues also contained significantly higher MNPL levels (3.7 ± 2.5 particles/g) than matched normal endometrium (2.0 ± 1.5 particles/g), with PE, PP, ethylene-acrylic acid (EAA), and PS as the predominant polymers [58]. In penile cancer, nine MNPL types of primarily PE, PP, and PVC were detected in 85.3% of samples, with an average abundance of 6.42 particles/g and particle sizes ranging from 20 to 50 μm [56]. Prostate cancer tissues further exhibited elevated MNPL loads (290.3 µg/g) compared with para-tumor tissues (181.0 µg/g), with PS, PP, PE, and PVC predominating, particle sizes of 20–100 μm, and irregular morphologies [28]. Considerable variability in the measurement units used to report MNPL concentrations across studies limits our ability to compare results and to draw generalized conclusions regarding MNPL accumulation in different human cancer tissues. To address this limitation, we applied a standardization approach to convert MNPL particle counts into mass-based units, based on an estimated average particle mass of 0.4 µg Sect. Micro/nanoplastics contaminate human food and beverages. Standardizing MNPL particle weight within this range facilitates conversion between particle number and mass, mitigates inconsistencies arising from non-uniform reporting units, and enables more reliable cross-study comparisons. Accordingly, based on this particle-to-mass standardization (Table 1), MNPL concentrations in human colon tissues differed among tumoral, non-tumoral, and healthy controls, with reported values of 281.07 ± 201.70, 83.11 ± 61.65, and 87.31 ± 85.22 µg/g, respectively.

Across multiple studies, the average MNPL concentration in CRC tissues was 86.7 ± 105.7 µg/g, with values ranging from 10 to 281.07 µg/g. Fecal samples from CRC patients also contained higher MNPL levels than those from healthy individuals, with median concentrations of 24.8 µg/g (range 12–70.8) and 17.2 µg/g (range 13.2–56.4), respectively. In LUAD, MNPL concentrations were reported at 329.8 µg/g in tumor tissues and 298.2 µg/g in adjacent normal tissues. Cervical cancer tissues contained MNPLs at levels ranging from 0.67 ± 0.38 to 0.90 ± 0.64 µg/g, compared with 0.35 ± 0.29 µg/g in para-cancerous tissues. Similarly, MNPL concentrations in endometrial cancer tissues were higher than in normal tissues, at 1.48 ± 1.0 µg/g and 0.8 ± 0.6 µg/g, respectively. In human prostate cancer, tumor tissues also exhibited higher MNPL levels (290.3 µg/g) compared with para-tumor tissues (181.0 µg/g). Figure 2 shows mean average of MNPLs in various cancer tissue.

Fig. 2.

Frequency of microplastics composed of different polymer types extracted from various human cancer tissues

The available evidence on MNPLs detected in human cancer tissues reveals several key findings. Higher levels of MNPLs in cancer tissues compared with para-tumor or normal tissues, suggesting a possible association with cancer proliferation. A broad spectrum of polymer types has been identified, with PE, PP, PVC, and PA predominating across multiple studies, whereas PS, despite being one of the most extensively investigated polymers, was reported in only four studies, which does not reflect its prevalence in broader literature. In terms of particle morphology, irregular shapes were most frequently observed [28], with filaments/fibers accounting for 96.1% of detected MNPLs in CRC and healthy colon samples [54]. Regarding particle size, all studies reported a lower detection threshold of approximately 1 μm, reflecting analytical limitations, as Fourier-transform infrared (FTIR) spectroscopy is generally unable to reliably detect particles smaller than ~ 10 μm [85], while Raman spectroscopy suffers from resolution interference at submicron scales, particularly below 1 μm [86]. These methodological constraints likely explain the limited detection of NPLs in existing studies, while the use of pyrolysis–gas chromatography–mass spectrometry (Py-GC–MS), although highly effective for polymer identification, destroys particle morphology and precludes size determination, thereby biasing results toward mass-based rather than particle-based analyses, which explains the absence of mention MNPLs sizes reporting in some studies [52, 78].

Micro/nanoplastics contaminate human food and beverages

Characterizing MNPLs from closely linked exposure sources such as food and beverages, particularly their size, shape, and polymer type, is essential because these properties largely determine their accumulation in healthy and cancerous human tissues. Fish represent a direct source of human MNPL exposure; for example, PP and PE particles ranging from 38 μm to 1 mm were detected in fish at 0.96 ± 0.08 particles per individual, predominantly fibers [87]. In shrimp, polyester (PES) and PA particles sized 157–2,785 μm were found at 0.39 ± 0.6 particle per shrimp (0.04 ± 0.07 particles/g), 83% of which were fibers [88]. Seaweed (nori) has also been reported to contain PES and PP particles measuring 0.11–4.97 mm at 1.8 ± 0.6 particles per gram, with fibers representing the most abundant form (18.9%) [89]. In addition, it must be stated that MNPLs can migrate from plastic packaging into human food [90]. Canned fish products also contain PET, PS, and PP particles ranging from 10 to 8000 μm, with concentrations of 1.28 ± 0.04 particles/g, fibers being the most abundant shapes [91]. MNPLs are also commonly present in vinegar bottles, where PE and HDPE particles ranging from 1 to 500 μm were detected at concentrations of 51.35 ± 20.73 particles/L, fragment (94%), while only a few was in the fiber shape (6%) [92]. Beer has been reported to contain MNPLs (28 ± 5.29 particles/L, 0.1–5 mm size), PET being dominant with fibers (93.42%) and fragments (6.58%) [93]; while bottled water commonly contains PET and HDPE particles larger than 3 μm, with concentrations of 148 ± 253 particles per liter (1.71 µg/L) [94]. These findings match the polymer types (e.g., PP, PE, and PET) and shapes (predominantly fibers, fragments, and irregular forms) observed in human cancer tissues, highlighting a clear link between environmental exposure and tissue accumulation.

MNPL concentrations vary substantially depending on the food or beverage source. For example, fish have been reported to contain 6.78 ± 2.73 particles per individual [95], while a single cup of tea may contain up to 11.6 billion particles resulting from the teabags [96, 97]. Estimates suggest that human intake of MPLs ranges from approximately 0.0002–1,531,524 particles/day from various sources [98], equivalent to 0.1–5 g per week (14–714 mg/day) [99]. To harmonize measurement units, we estimated the average weight of a single standard MNPL particle based on data from literature, aiming to improve comparability across studies. At the maximum intake, 1,531,524 particles per day correspond to roughly 714 mg, implying an average mass of ~ 0.47 µg per particle, or that 1 mg of MNPL contains ~ 2,145 particles. Considering that humans are exposed to a heterogeneous mixture of MNPLs composed of multiple polymer types, primarily PE, PP, PET, PS, PVC, PTFE, PMMA, and PA, with densities ranging from 0.9 to 2.2 g/cm³ (average 1.55 g/cm³) and particle sizes averaging ~ 75 μm (range 50–100 μm) [100]. Based on these parameters, the intake of 1,531,524 particles/day corresponds to approximately 525 mg (0.34 µg). Accordingly, two calculations yield an average MNPL particle mass of 0.34–0.47 µg (average ~ 0.4 µg). We acknowledge, however, that this conversion does not fully represent the wide range of heterogeneity of polymer types and particle sizes. Nevertheless, it provides a preliminary scheme to unify efforts and improve comparability across studies.

Most MNPLs in tissues are fragments or fibers, ranging from 1 to 2,500 μm, with concentrations varying from 0.7 ± 0.8 particles per gram in lung tissue to 702 ± 504 particles per gram in colorectal adenocarcinoma tissue [101]. In colorectal tumors, PA, PC, and PP predominate, existing as fibers, fragments, and films (0.1 μm–1.6 mm), at 25.9–32.2 particles per gram [102]. The abundance and shape of MNPLs in cancerous tissues appear to be directly related to dietary intake. For example, in a study of 40 fish samples, 92.5% contained MNPLs in the digestive tract (1.1–5.86 particles per individual) and 72.5% in the gills (1.2–4.00 particles per individual), with fibers, fragments, and films being the predominant shapes [103]. Across 32 fish samples, 875 MNPLs (478 marine and 397 freshwater) were recovered, primarily fibers (91%), with fragments (8%) and a small fraction of films, composed mainly of PVC (39.76%), PE (16.51%), methylcellulose (12.84%), and styrene (9.07%) [104]. The sources and characteristics of MNPLs with potential impacts on human health are schematized in Fig. 3. Collectively, polymer type, morphological shape, and particle size represent the key physicochemical properties of MNPLs that govern their biological interactions, tissue accumulation, and potential carcinogenic effects, which are discussed in detail in the following section.

Fig. 3.

Sources and characteristics of MNPLs with potential impacts on human health. This figure illustrates the major environmental and anthropogenic sources of MNPLs and their physicochemical characteristics, including size, shape, and chemical composition. It also highlights the primary human organs targeted by MNPL accumulation (e.g., lungs, skin, and gastrointestinal tract). The figure was created using BioRender

Physicochemical properties of microplastics that may drive cancer progression

The physicochemical properties of MNPLs critically govern their interactions with biological systems and form the basis of their potential involvement in carcinogenic processes. These properties may influence MNPL-induced chronic tissue injury, oxidative stress, inflammation, mitochondrial and DNA damage, as well as disturbances in cellular signaling pathways that maintain homeostasis. Comprehensive characterization of MNPLs is therefore essential to clarify the mechanisms through which they may exert biological and oncogenic effects and to enable accurate evaluation of their long-term health risks. Among the various physicochemical attributes, polymer composition, particle size, and shape represent key determinants influencing MNPL behavior in biological environments and their potential association with cancer initiation and progression, as discussed in the preceding sections. The specific roles of these individual characteristics in MNPL-induced pathophysiological and carcinogenic outcomes are addressed in the following sections.

Chemical properties

Polymer type

MNPLs derive from a wide range of synthetic polymers, each with distinct physicochemical characteristics that influence their biological behavior. The detection of diverse plastic polymers in carcinogenic tissues, often with varying dominance, raises the critical question of whether polymer composition may influence cancer progression pathways. Clarifying the role of MNPLs in cancer initiation requires understanding how different polymer types differentially disrupt oncogenic signaling pathways and whether cancer risk and progression are polymer specific. In human nasal epithelial cells exposure to PA fibers alter metabolic pathways and stimulate chemokine signaling, cell motility, and immune responses [105]. Cancer cell proliferation is enhanced by PE-MPLs, which also reduce chemotherapy efficacy by increasing mitochondrial ROS, releasing mtDNA, and activating NLRP3 [106, 107]. Irregular PTFE particles activate ERK/MAPK signaling and provoke oxidative and inflammatory responses in immune and lung cell lines [108], whereas PVC and PMMA particles induce oxidative stress, DNA damage, impair homologous recombination or NHEJ repair, and activate cGAS-STING–NF-κB signaling, promoting inflammation, genomic instability, and cellular senescence [109, 110]. Similarly, PP-MPLs trigger immune responses and cardiotoxicity through oxidative stress, MAPK–Nrf2 suppression, mitochondrial dysfunction, and activation of pro-apoptotic proteins [111, 112]. Genotoxic stress via p53 activation, endocrine-disrupting and inflammation in macrophages resulted in PA-MPLs exposure [113]. PET-MPLs further exacerbate cancer-related pathways by modulating immune genes (CCL19, KLRB1, CD40LG, IGLL5), elevating IL-6 and TNF-α, and disrupting lipid metabolism, affecting over 1,400 genes and nearly 3,000 metabolites in BEAS-2B cells [114, 115]. Despite these findings highlighting convergent mechanisms across polymer types, with MNPLs consistently activating pathways linked to early carcinogenesis, it remains unclear which polymers are more potent. To address this, it is necessary to examine studies that have performed comparable analyses across multiple polymer types.

Studies comparing the biological effects of different polymer types have shown that some polymers may have greater impactsthan others. PET-NPLs enter 3T3-L1 adipocytes, accumulate in lysosomes, and trigger triglyceride loss, increased fatty acids, and AMPK/HSL activation, unlike PLA-NPLs [116]. Similarly, in intestinal models, irregular PET-NPLs strongly impair Caco-2 cell energy metabolism, whereas spherical PS-NPLs produce milder effects [117]. While PET-MPLs show no acute effects in rainbow trout cell lines, whereas PVC-MPLs, particularly the 25 μm, induces ROS [118]. Cellular uptake of MPLs is strongly influenced by polymer type and particle size; for example, PE shows the highest transport in human Caco-2 intestinal cells, while PP, PET, and PVC exhibit minimal uptake and negligible toxicity unless tested at extremely high concentrations [119]. On the other hand, the impact of MNPLs also depends on the health status of the tissue. While PVC-MNPLs are largely harmless in a healthy intestine, they can exacerbate epithelial damage and inflammation when pre-existing intestinal inflammation exists. For instance, in a triple-culture model of healthy human intestine, both PS and PVC particles showed no acute toxicity. However, under inflammatory conditions, PVC exposure significantly increased IL-1β release and caused epithelial cell loss, suggesting that underlying inflammation amplifies the harmful effects of ingested MNPLs [120]. This phenomenon may help explain the widespread accumulation of microplastics in various polymers in cancerous tissues compared to healthy tissues.

Moreover, the degree of MNPLs-induced impacts depends on the exposed cell type. Fragmented PP- and PS-MPLs (~ 100 μm) do not affect Caco-2 or HepG2 cells, whereas THP-1 macrophages exhibit significant cytotoxicity and inflammatory responses (MIP-1β, IL-1β) driven by ROS [121]. MNPLs toxicity can be further amplified by co-exposure to other environmental contaminants. For example, human lung BEAS-2B cells exposed simultaneously to PET-NPLs and cigarette smoke condensate exhibited markedly increased oxidative stress (ROS), DNA damage, colony formation, migration, and invasion. This combined exposure also altered gene expression by upregulating stress-response genes (SLC7A11, NQO1, HSPA1A) and downregulating tumor-suppressor genes (LOX, FN1), demonstrating a synergistic enhancement of carcinogenic traits [122]. However, mechanistic studies showed that residual particles rather than leached compounds are responsible for mediated disorder like mitochondrial oxidative stress and reduce cell viability [123].

Despite the diversity of MNPL polymers, toxicological and oncological research remains heavily biased toward PS, which accounts for approximately 82% of experimental studies yet represent only ~ 2.2% of microplastics detected in human tissues [124, 125]. There is a critical mismatch between experimental studies, which focus largely on PS, and the polymers most found in human tissues, including PP, PE, PET, and PVC Sect. Microplastic occurrence in human cancer tissues, which are also prevalent in food and beverage sources. This highlights the need to prioritize exposure-relevant polymers and investigate how their physical properties, such as size and shape, along with chemical additives, influence cellular uptake, toxicity, and MNPL-driven carcinogenic mechanisms.

Plastic additives as potential carcinogens

Chemical additives incorporated into plastics to enhance their properties can pose significant hazards. Thus, plastics are complex systems containing plasticizers, flame retardants, stabilizers, pigments, and metals. While these additives enhance material performance, their release poses significant health risks. Among 2,712 identified plastic additives, over 150 are known carcinogens and nearly 90% lack carcinogenicity data, highlighting a substantial knowledge gap [126]. As plastics fragment into MNPLs, increased fragility and surface area accelerate additive release, facilitating their entry into the human body and disruption of cellular growth, immune regulation, and metabolic pathways, thereby enhancing carcinogenic potential. Plastic additives have shown to modulate genes involved in transcription, apoptosis, DNA damage, inflammation, and hormonal responses, with cancers ranking among the most strongly associated diseases and linked to phenotypes such as proliferation, oxidative stress, and detoxification [127]. Of particular concern are carcinogenic heavy metals, polycyclic aromatic hydrocarbons, and legacy flame retardants [128]. Notably, TiO₂ nanoparticles incorporated into PET milk bottles, providing the light protection that UHT milk requires and minimize gas permeability, induced gene expression changes, oxidative stress, and genotoxicity in Drosophila models [129].

Phthalates and bisphenols raise serious concern due to their widespread use and potent endocrine-disrupting activity linked to tumor initiation and progression [130]. Phthalate esters (PAEs), widely used as plasticizers in PVC and other polymers, are present in products ranging from construction materials and medical devices to pharmaceuticals and personal care items, leading to extensive human exposure [131]. Phthalate metabolites are detected in over 82% of women, with higher urinary monoethyl phthalate levels associated with increased breast cancer risk, particularly among premenopausal women [132]. A meta-analysis of 11 studies involving 3,101 cancer cases and 6,858 controls confirmed significant associations between urinary phthalates and increased cancer risk [133]. In in vitro studies, BBP, DBP, and DEHP induced MCF-7 cell proliferation and upregulated PCNA, PI3K, p-AKT, and estrogen receptor α at low concentrations, demonstrating estrogenic activity and PI3K/AKT pathway activation linked to cancer progression [134]. On the other side, bisphenol A (BPA), a widespread hormone-like compound, accumulates in human tissues, mimics estrogen, and modulates pathways such as STAT3, MAPK, and PI3K/AKT, contributing to breast, ovarian, and prostate cancers and potentially interacting with other steroid receptors [135].

Flame retardants, especially organophosphate esters (OPEs), require priority studies because of their widespread use and emerging genotoxic and metabolic effects [136]. Gastrointestinal cancer patients exhibit higher OPE detection frequencies and concentrations than controls, with exposure effects varying by age and sex [137]. Exposure to OPEs like triphenyl phosphate (TPP) may promote prostate cancer progression by activating genes such as AR, mTOR, and DDIT3, which regulate steroid metabolism and hormones, enhancing cell proliferation and invasion and linking environmental OPEs to cancer risk [138]. Plastic additives may enter the human body through MNPLs, disrupt key cellular pathways, and contribute to cancers including breast, ovarian, prostate, and gastrointestinal. This highlights the urgent need for systematic research to understand the molecular mechanisms of plastic additive-induced carcinogenesis.

Beyond the chemical effects of plastics, the physical properties of MNPLs, such as polymer type, shape, and size, may contribute to health risks, including cancer, by influencing processes that drive cancer development and progression. The next section presents these physical characteristics in detail and explores their relationship with carcinogenesis.

Physical properties

Shape

The shape of polymeric MNPLs strongly influences their biological behavior, including tissue penetration and interactions with bio-interfaces [139, 140]. Particles, fibers, and irregular MNPLs have been detected at higher concentrations in human colon cancer tumors than in adjacent tissues [83]. Environmental MNPLs occur in diverse forms such as beads, fibers, fragments, films, spheres, pellets, and foams and their heterogeneity, often enhanced by environmental degradation, plays a pivotal role in exposure, uptake, and toxicity [141, 142]. Among these, irregular shaped fibers and fragments consistently emerge as the predominant shape, reflecting environmental contamination from sources such as the textile industry or natural degradation [125]. Textiles are a major source of microfiber pollution, releasing 210 to 72,000 MNPLs per gram of fabric per wash [143]. Laundry and clothing contribute substantially, with a single person releasing an estimated 2.98 × 10^8 PES fibers to water and 1.03 × 10^9 to air annually [144]. Accordingly, elongated MNPLs, which are widespread, can more readily translocate into human tissues than other shapes [145]. Fibers are also highly prevalent in human food sources, accounting for 59% of MPLs in seafood invertebrates, 68.8% in fish, 45.4% in meat, 49.2% in plant-based foods, and 41.9% in drinking water, with an estimated daily human intake of 63–232 microfibers [125, 146]. Reflecting this exposure, fibers have been reported in 87% of human lung specimens, including both cancerous and non-pathologic tissues [147], and in colorectal cancer tissues, with 331 MNPL particles per specimen (28.1 ± 15.4 particles/g tissue), of which 96.1% were filaments or fibers [54].

The predominance of specific MNPL shapes in human tissues likely mirrors their abundance in environmental matrices. A review of 55 water prevalence studies indicated that PE, PP, and PS are the most common polymer types, with fragments being the most frequently observed shape [148]. In the digestive tracts of 64 Japanese anchovy (Engraulis japonicus) from Tokyo Bay, most MPLs were PE (52%) or PP (43.3%), with fragments dominating (86%) [149]. In addition, fragments, film-shaped, and fibers were also detected in human stool samples [150]. Overall, MNPL toxicity is primarily governed by uptake and internalization, which depends on particle shape and the organism’s feeding mode [151]. These findings show the pivotal role of shape in determining MNPL distribution, uptake, and potential biological impacts across environmental and human contexts.

The shape of MNPLs strongly influences their toxicity by affecting interactions with cells and biological barriers. Irregular, fragmented MPLs smaller than 100 μm exhibit greater surface erosion than same-sized microbeads [152], and their dimensions and geometry determine whether they disperse via passive diffusion or are internalized through active phagocytosis [153]. Studies in grass shrimp showed that small fragments (< 34 μm) were preferentially ingested and caused the highest mortality, with fragments and fibers being more lethal than spheres [154]. Irregular sharp-edged MNPL fragments may cause more physical damage to tissues, and MPL fibers have been associated with a greater potential for cellular entanglement and respiratory issues digestive blockage [155, 156]. The impact of irregular MNPLs is attributed to their high curvature which can directly damage cell membranes upon contact [157]. Consistently, irregular shapes predominate in human paired tumors and para-tumor prostate tissues [28] and fibers, being resistant to mucociliary clearance, were more common in tumoral tissues [158].

Physical effects of MNPLs attributed to size and shape can be a major factor determining their toxicity [159]. Chronic dietary exposure to PE fibers in Lates calcarifer caused intestinal oxidative stress, microbiome disruption, and mild gut damage without affecting growth [160]. PES-MPL fibers induce mitochondrial damage, apoptosis and oxidative stress in Daphnia carinata, accompanied by changes in apoptotic and ferroptosis pathways [161]. Irregular MPLs released from PP infant feeding bottles triggered oxidative stress and inflammatory signaling in Caco-2 cells, marked by depleted glutathione, elevated ROS, lipid peroxidation, and increased IL-6/TNFα via the ROS–NLRP3–Caspase-1–IL-1β pathway [162].

Notably, the impacts of MNPL shape are attributed to their residence, bioaccumulation and degradation which can lead to inflammation and intestinal permeability. Bioaccumulation of PET fibers caused in zebrafish intestine and liver, increased ROS at high doses (100 mg/L), altered sex hormones, and disrupted gonadal development [163]. Gut retention amplifies MPL toxicity, with large fibers such as PES fibers causing greater intestinal effects than smaller spheres or fragments due to their longer residence time [154]. Degradation of PES fibers embedded in collagen matrices induce fibrotic scars in Wistar rats [164]. Fibers and irregular MPLs commonly cause gut damage by increasing intestinal permeability mediating physical stress [165]. Fragmented PP-MPLs disrupted cell-cycle gene expression in MDA-MB-231 breast cancer cells and, with longer exposure, increased IL-6 secretion, indicating activation of pro-inflammatory and metastasis-related pathways [166]. Despite the predominance of irregularly shaped plastic particles, including fibers and fragments, in both the environment and human tissues, particularly in cancerous tissues, and their potentially greater hazardous effects and stronger induction of carcinogenic pathways, most experimental studies rely predominantly on spherical PS-MNPLs. This discrepancy highlights a significant gap between experimental models and real-scenarios exposure conditions.

Micro-nanoplastic size

Cellular internalization is a key event following MNPL exposure, with particle size fundamentally determining uptake efficiency, intracellular interactions, distribution, and resulting toxicological effects [167, 168]. Larger particles (0.5–10 μm) are mainly internalized via phagocytosis in professional phagocytes [169]. Smaller particles exploit various forms of pinocytosis, including micropinocytosis (~ 5 μm), clathrin-mediated endocytosis (100–500 nm), caveolin-mediated endocytosis (50–100 nm), and clathrin/caveolin-independent pathways for particles < 50 nm, with vesicle size and associated proteins determining the uptake route [170, 171]. At the organismal level, PS- and PLA-NPLs in the midgut lumen of Drosophila larvae are internalized via intestinal vesicles and transported across the peritrophic membrane lining enterocytes [172, 173]. Nano scaled particles can also directly penetrate cellular membranes, by passing classical uptake pathways, a process influenced by particle shape [174, 175]. Furthermore, membrane pores provide direct routes for entry and exit, which can compromise cell viability and lead to cell death [176].

Size-dependent behaviors of MNPLs are decisive for understanding their health risks, including metabolic disruption, gut injury, oxidative stress, DNA damage, and tumor progression, highlighting the need to carefully assess particle size in environmental and human health studies [101]. In general, plastic particles with 10 μm may reach internal organs and cross cellular membranes [177], while only particles with 150 μm have been shown to traverse gastrointestinal epithelial cells in mammals [178]. In four colon cancer cell lines 0.25 and 1 μm PS particles internalized efficiently, whereas 10 μm particles were not internalized [179]. However, as the size becomes smaller their internalization and impact increases. For instance, 200 nm PS particles exhibit significantly higher uptake and blood-brain barrier permeability compared to 1 μm particles [180]. PS particles (0.08–0.5 μm) distribute more widely across organs in rodents, including the stomach, liver, and even the fetal brain, while larger particles (1–4.5 μm) accumulate mainly in the gastrointestinal tract, illustrating size-dependent systemic distribution and heightened organ toxicity [181, 182]. Notably, in humans, MPLs ranging from 2 to 200 μm have been detected in endometrial tissues, with smaller particles entering via circulation and larger particles accessing the uterus through the vaginal–uterine route [183].

Smaller-sized MNPLs exhibit more efficient cellular internalization and stronger biological effects due to increased barrier permeability, greater tissue bioaccumulation, higher surface area, enhanced interactions with cellular and nuclear components, and elevated chemokine release [184, 185]. Their easier passage across biological barriers also induces greater oxidative stress, DNA damage, and transcriptional disturbances [172, 186]. In diabetic mice, 100 nm PS-NPLs caused more severe liver damage than 5 μm MPLs, including higher MDA, lower SOD, lipid accumulation, tissue injury, elevated pro-inflammatory cytokines, and greater disruptions in energy and lipid metabolism and gut microbiota [187]. Although larger MPLs are more commonly detected in human cancer tissues, this does not contradict the stronger biological effects of smaller NPLs. The predominance of larger MPLs is mainly due to organ accumulation rather than efficient cellular internalization, particularly in barrier tissues such as the lungs, colorectal region, vaginal tract, and male reproductive organs, where particles tend to reside and persist. Monitoring studies in cancer tissues have generally focused on MNPLs larger than 1 μm, while smaller NPLs often remain undetected due to methodological limitations [74]. Nonetheless, smaller NPLs may have greater carcinogenic potential than larger MPLs, highlighting the need for further investigation using comprehensive in vivo and in vitro models.

Modelling and diagnostic approaches to MNPL-induced carcinogenesis

Understanding the role of MNPLs in cancer requires experimental studies, as direct investigation in humans is not feasible. In vitro studies reveal how MNPLs disrupt critical processes, and signaling pathways, while also showing how particle size, shape, and composition influence uptake and toxicity. In vivo studies are essential to capture tissue distribution, organ accumulation, and multi-organ effects, validating in vitro findings and demonstrating impacts on tissue structure, immune responses, and tumor-related pathways. Despite increasing research, mechanistic studies remain limited; of 4,705 screened articles since 2017, only 223 have examined the potential oncogenic effects of MNPLs, which may occur through mechanisms such as oxidative stress, DNA damage, chronic inflammation, and altered signaling, highlighting the urgent need for focused mechanistic investigations [188]. Therefore, in this review, a detailed analysis of the relevant literature has been conducted and integrated to provide general conclusions, emphasizing the role of MNPLs in carcinogenesis.

In vitro models

A wide range of in vitro and in vivo models (Table 2) has been employed to investigate the carcinogenic potential of MNPLs, with most studies focusing on PS-NPLs. Small spherical PS nanoplastics (20–100 nm) consistently disrupt cellular homeostasis across diverse mammalian cell types, even at concentrations as low as 10 µg/mL and following short exposures from 24 to168 h. In lung epithelial cells (BEAS-2B, HPAEpiC), 40 nm PS-NPLs induced dose- and cell-type-dependent inflammation, oxidative stress, apoptosis, and alveolar barrier disruption, accompanied by altered gene expression and activation of PI3K–Akt, TNF, Hippo, and ECM–receptor interaction pathways [189]. In renal and reproductive cell models, 20–50 nm PS nanoparticles triggered TNF-α signaling, apoptosis via Bcl-2/p53, tight-junction disruption (claudin-2), mitochondrial dysfunction, impaired glucose metabolism, and activation of MAPK and PI3K–Akt pathways [190, 191]. Similarly, 50 nm PS-NPLs in A549 cells promoted TNF-α, IL-6, IL-1β, and NF-κB1 expression, activated apoptosis and necroptosis through BCL2, caspase-3/9, BAX, MLKL, and RIPK3, increased ROS and MDA levels, stimulated antioxidant defenses (SOD, GST, Nrf2/Keap1), disrupted mitochondrial membrane potential and ATP production, and engaged cancer-related signaling pathways [192]. In ovarian cancer cells (SKOV3, A2780), same size (50 nm PS) promoted cell proliferation, associated with activation of CDK4/6–Cyclin D1–p-Rb signaling and clathrin-mediated endocytosis [193]. Other studies reported that exposure to 50 nm spherical PS reduced cell viability, induced G1-phase cell-cycle arrest, caused cytoskeletal remodeling with impaired migration, and elicited mitochondrial damage and metabolic alterations in HepG2 cells, involving dysregulation of FGFR2–Ras signaling, actin cytoskeleton dynamics, and ABC transporter activity [194].

Table 2.

In vitro diagnostic studies reporting major disorders and signaling pathways associated with exposure to micro- and nanoplastics of different physicochemical properties, polymer types, sizes, and shapes

MNPLs	Model / Treatment	Inflammation / Immune	Cell Death / Apoptosis	Fibrosis / Remodeling / Barrier	Oxidative Stress / DNA Damage	Mitochondria/ Metabolic	Signaling Pathways	Ref.
PS (40 nm, spherical)	BEAS-2B and HPAEpiC lung epithelial cells; 7.5–30 μg/cm² (24–96 μg/mL), 24 h	IL-6, MCP-1, ICAM-1 (cell-type & dose dependent)	Apoptosis   cleaved caspase-3/9; BCL2/BAX	Alveolar barrier disruption: TEER, ZO-1; MMP-9, SP-A	ROS, MDA; SOD, CAT, GSH-Px; HO-1, NQO1	Altered gene expression; oxidoreductase activity	PI3K-Akt; TNF; Hippo; ECM-receptor interaction (KEGG)	[189]
PS (50 nm, spherical)	Kidney–testis microphysiological chip (KTP); HK-2 & NTE; 200 µg/mL, 24 h	TNF-α upregulation; TNF-α-R activation	Bcl-2, apoptosis	Tight-junction disruption (claudin-2)	P53	Reduced glucose / Mitochondrial damage	MAPK (RTK, RAS, ERK, JNK, p38, NRF2); PI3K-AKT (PI3K, AKT, MDM2, BAD, P53)	[190]
PS (20–50 nm, spherical),	HK-2; 0–100 μg/mL, 12 h	IL-6, IL-8	BAX, Cyt C, caspase-3	–	ROS	ΔΨm, PGC-1α, TFAM	MAPK (p38, ERK1/2, JNK), CHOP, IRE-1α	[191]
PS (50 nm, spherical)	A549 (0.1–0.8 mg/mL, 24–48 h)	TNF-α, IL-6, IL-1β, IL6, TNF, NFKB1	Apoptosis & necroptosis; BCL2; caspase-3, caspase-3, BAX, MLKL, RIPK3		ROS, MDA; SOD & GST; activation of Nrf2/Keap1 pathway	Altered ATP, Mitochondrial depolarization	NF-κB, Nrf2/Keap1, apoptosis, necroptosis, cancer-related pathways (KEGG)	[192]
PS (50 nm, spherical)	SKOV3 & A2780 cells (20 μg/mL; 24 h	–	Proliferation	–	–	–	CDK4/6, Cyclin D1, p-Rb; clathrin-mediated endocytosis	[193]
PS (~50 nm, spherical)	Hep G2 cells, 10–500 μg/mL, 24 h	—	Cell cycle arrest (G1 phase), reduced viability	Cytoskeletal remodeling, impaired cell migration	—	Metabolic pathway alterations (RNA-seq KEGG enrichment)/ Mitochondrial damage,	FGFR2–Ras signaling; actin cytoskeleton regulation; ABC transporter inhibition	[194]
PS (~100 nm, spherical)	HET-1A & HEEC; 10–50 μg/mL, 1–72 h	TNFα, IL-6, IL-1β, MCP-1	caspase-3, Bax/Bcl-2, cytochrome c release. TUNEL+ cells (20–60%)	–	ROS, Fe²⁺ mediates ROS	Fe²⁺ accumulation; mitochondrial ROS contributes to apoptosis	NF-κB activation (implied)	[195]
PS (100 nm, spherical)	HepG2 cells (50 μg/mL; 24 h)	—	Apoptosis; chemoresistance		ROS, oxidized nucleotides, γ-H2AX (DNA DSBs)	—	NAT10, ac4C tRNA, NF-κB p65 phosphorylation	[196]
PS (100 nm, spherical)	HTR-8/SVneo human trophoblast cells; 10–100 µg/mL, 24–72 h	TNF-α, IFN-γ; IL-4, IL-10; pro-inflammatory shift	Apoptosis (late apoptosis); BAX/BCL2; G0/G1 arrest; proliferation	Migration and invasion; ECM structural changes	ROS	mitochondria damage	Hippo, TGF-β, FoxO, cAMP, Hedgehog, hormone signaling, ECM, cell adhesion	[197]
PS (100 nm)	IEC-6, A549, HepG2, RAW264.7, Neura2a, (10–200 μg/mL, 24–168 h)	—	Necroptosis via RIPK1/RIPK3/MLKL	—	ROS	altered fatty acid, ABC transporters, Mitochondrial stress	PI3K-Akt, ECM-receptor interaction, focal adhesion	[198]
PS (~280 nm, spherical)	A549 (2D & 3D, 25–100 µg/ml, 48 h); Calu-3 (1.5–45 µg/cm², 24–48 h)	IL-6; TGF-β; MUC5B; mild mucin secretion	—	Surface tension; lamellar bodies	—	Metabolic activity/ Altered mitochondrial structure	—	[199]
PS (800 nm)	A549; 10–500 µg/mL, 24–96 h	IL1A/B, IL6, IL8/CXCL8, SASP	BAX, caspase-3, BCL2	–	ROS, SOD1/2, CAT, GPX1, HMOX1	–	NRF2/HO-1	[200]
PS (90, 200, 300 nm, spherical)	MDA-MB-231, HFF-2 cells; (500–2000 µg/mL; 24–72 h)	—	Apoptosis and necrosis G1 and sub-G1 arrest	—	SOD and GPx; ROS modulation	Mitochondrial depolarization		[201]
PS (20, 50, 200, 500 nm, spherical)	HepG2 cells, 24 h exposure; PS20: 10 μg/mL, PS50/200/500: 100 μg/mL; ±30 μM arsenic	Apoptosis enhancement partly via XIAP (immune-related)	Apoptosis; LDH release, caspase-3/7, BCL2L1, MCL1		ROS / DNA damage	DEGs enriched in metabolic pathways/mitochondrial damage	AKT1, TP53, caspases, XIAP	[202]
PS (0.2–6 µm, mix)	Primary murine skin; 100 μg/mL, 24 h	TNFα, IL1β, IL6	Bcl-2	CLDN1, Cx43; KRT1, KRT14; αSMA, COL1A1, FN1/VIM	ROS, γH2AX, thiol	–	NRF2, HO-1, NQO1/CAT/SOD1/GPX2/GSR; β-catenin, Wnt1/Wnt7a, LEF1, c-JUN, PPARD	[203]
PS (80 nm & 2 μm, spherical)	A549; 2.5–400 µg/mL, 6–24 h	–	Cytotoxicity	–	ROS	–	–	[216]
PS (50–1000 nm, spherical)	IMR90, BEAS-2B, A549, NCI-H727, NCI-H1755, HCC1833 (20–80 µg/mL, 24–72 h)	—	Viability in cancer cells; migration in IMR90	Migration in IMR90	ROS, SOD1 (cancer cells)	—	—	[217]
PS (1.04 μm), PMMA MPLs (400 nm)	A549, HEK293, HeLa; 1–100 μg/mL, 24–72 h	IL-1β, IL-6, TNFα, IFN-α/γ, MCP-1	apoptosis/necrosis	–	Increase thiol; ROS	reduced metabolism	–	[204]
PMMA (50–5000 nm, spherical)	HepG2 cells; 0.1–100 µg/mL; 1–120 h	IL-8 increased (time-, size-, and concentration-dependent)	Apoptosis; caspase-3 modulation	—	—	—	—	[205]
PVC (1 µm, spherical)	Caco-2 cells; 0.5–40 µg/mL; 12–24 h; simulated GI digestion	inflammatory genes (CXCR4, CX3CL1, TNFSF9)	Reduced cell viability; LDH release; early apoptosis indicated	Increased membrane damage and permeability after digestion	ROS; oxidative stress genes (DDIT3, OXR1)	Altered metabolic / Mitochondrial membrane depolarization (JC-1 assay)	MAPK and PI3K-Akt signaling pathways enriched (t-PVC-MPs)	[206]
PA fibers (fibrous)	Human nasal epithelial cells; 200 µg/cm²	IL-1β, IL-6	–	–	–	Altered sterol/alcohol/acetyl-CoA metabolism,	Chemokine signaling, cell motility, immune response	[105]
PET (100 nm, spherical)	A549 (1.95–125 µg/mL; 3–24 h)	–	–	–	ROS; DNA breaks	–	–	[207]
PET (176 nm, irregular)	BEAS-2B cells (50 μg/mL, chronic 24 h → 30 weeks)	–	Anchorage-independent growth & invasiveness	Anchorage growth & invasiveness	DNA damage (30 weeks)	–	KRAS, MET, RET, EMT-; lung-cancer pathways	[208]
PE (spherical, 1 µm)	HaCaT & skin cancer cells (A431, SCL-1); 0–1 mg/mL	TNF-α, IL-6, IL-1β, NLRP3	proliferation, pyroptosis	–	ROS, mtDNA damage (8-oxo-dG)	Mitochondrial ROS, ΔΨm (MMP) altered	ROS-mtDNA-NLRP3, CyclinD1, c-Myc, Bcl-2, Ki67	[106]
PE (6.2-30.5 µm, irregular)	Caco-2, A549, HaCaT, THP-1, U937, Jurkat cells; 1–1000 µg/mL, 24–48 h	IL-6, TNFα	Minimal cytotoxicity	–	ROS: nitrosative stress increased	–	–	[209]
PE (irregular, ~35–45 µm)	A431 skin carcinoma; NHDFs (1 mg/mL, 6–96 h)	−	Apoptosis		ROS, LPO, CAT, SOD	Proliferation (A431); 5-FU efficacy	–	[107]
PTFE (~250 nm and ~2 µm, irregular & spherical)	Caco-2, HT29-MTX monocultures and Caco-2/HT29-MTX intestinal barrier; 0–200 µg/mL, 24–48 h	IL-8 secretion (48 h)	–	Tight-junction disruption	ROS and DNA damage	Mitochondrial damage	cGAS-STING; NLRP3 inflammasome; Caspase-1, IL-1β	[210]
PTFE (6 µm, 32 µm, irregular)	Caco-2, A549, HaCaT, THP-1, U937, Jurkat (1–1000 µg/mL. 0–48 h)	NO, TNF-α, IL-6 (cell-type & size dependent)	BCL-2; minimal apoptosis		ROS	–	MAPK (ERK, p38), NLRP3	[108]

Even with a slight increase in size to 100 nm, PS-NPLs remain highly effective in activating multiple carcinogenic pathways. In esophageal epithelial models, ~ 100 nm PS elicited dose-dependent inflammatory responses, Fe²⁺-mediated ROS generation, mitochondrial dysfunction, and apoptosis via caspase-3 and BAX/BCL-2 signaling, highlighting oxidative stress–driven cell death mechanisms [195]. In HepG2 cells, 100 nm PS induced apoptosis and chemoresistance, accompanied by elevated ROS, oxidized nucleotides, and DNA double-strand breaks (γ-H2AX), mediated through NAT10-dependent ac4C tRNA modification and NF-κB p65 phosphorylation [196]. Exposure of HTR-8/SVneo trophoblast cells to 100 nm PS triggered a pro-inflammatory cytokine shift, ROS-mediated mitochondrial damage, apoptosis with G0/G1 arrest, and impaired migration/invasion with ECM remodeling, involving Hippo, TGF-β, FoxO, and related signaling pathways [197]. Similarly, 100 nm PS-NPLs induced ROS-mediated necroptosis, mitochondrial stress, and metabolic dysregulation in IEC-6, A549, HepG2, RAW264.7, and Neura2a cells, engaging PI3K–Akt, ECM–receptor interaction, and focal adhesion signaling pathways [198].

As PS-NPLs increase toward the microscale, their overall potency is reduced, yet exposure continues to induce a range of cellular disturbances. In A549 and Calu-3 cells, ~ 280 nm PS elicited IL-6 and TGF-β expression, mild mucin secretion, mitochondrial alterations, and disrupted metabolic activity [199]. In A549 cells, 800 nm PS promoted inflammatory cytokine release and senescence-associated secretory phenotype factors, accompanied by redox imbalance, NRF2/HO-1 activation, and apoptotic signaling [200]. Exposure of MDA-MB-231 and HFF-2 cells to 90–300 nm spherical PS-MPLs induced apoptosis and necrosis with G1 and sub-G1 cell-cycle arrest, mitochondrial depolarization, ROS modulation, and altered SOD and GPx activity [201]. In HepG2 cells, 24 h exposure to spherical PS-NPLs (20–500 nm), with or without 30 µM arsenic, enhanced apoptosis partly via XIAP, increased LDH release, caspase-3/7 activity, and BCL2L1/MCL1 regulation, induced DNA damage and ROS generation, and dysregulated metabolic pathways involving TP53, AKT1, caspases, and MMPs [202]. In primary murine skin cells, PS (0.2–6 μm) induced inflammatory cytokines, size-dependent oxidative stress, DNA damage, and activation of NRF2 and Wnt/β-catenin signaling, indicative of oxidative injury and tissue remodeling [203]. These findings demonstrate that PS-MNPLs, as a widely used MNPL model, can induce diverse cellular dysfunctions and disorders that may contribute to carcinogenesis, with the magnitude of effects inversely proportional to particle size.

PS-MNPLs, while widely used as a model for MNPL toxicity, do not fully highlight the diversity of MNPLs present in human cancer tissues or environmental sources, which are predominantly irregular in shape, including fibers and fragments. To address this limitation, recent studies have examined other polymeric MNPLs, including PMMA, PA, PVC, PET, PE, and PTFE, spanning a range of sizes and morphologies, which also induce significant cellular effects that may contribute to carcinogenesis. For example, exposure to 400 nm PMMA-NPLs and 1.04 μm PS-MPLs in A549, HEK293, and HeLa cells induced inflammatory cytokines, ROS production, and apoptosis/necrosis, with PS-MPLs additionally reducing metabolic activity and increasing thiol levels [204]. In another study, spherical PMMA-MNPLs (50–5000 nm) triggered time-, size-, and concentration-dependent IL-8 production and apoptosis via caspase-3 modulation in HepG2 cells [205]. Exposure of Caco-2 cells to pristine and digested 1 μm PVC-MPLs induced inflammatory gene expression, increased lactate dehydrogenase (LDH) release, early apoptosis, oxidative stress, mitochondrial depolarization, and activation of MAPK and PI3K–Akt signaling pathways, with stronger effects observed for digested particles [206]. Fibrous PA exposure in human nasal epithelial cells elevated IL-1β and IL-6, disrupted sterol, alcohol, and acetyl-CoA metabolism, and altered chemokine signaling, cell motility, and immune responses [105].

While short-term exposure to spherical PET nanoparticles induces oxidative stress and genotoxicity, the use of irregularly shaped particles and prolonged exposure further exacerbates cellular dysfunction and promotes persistent oncogenic signaling. For instance, 100 nm spherical PET-NPLs in A549 cells induced ROS production and DNA breaks, reflecting oxidative stress and genotoxic effects [207]. In contrast, chronic exposure of BEAS-2B cells to 176 nm irregular PET-NPLs (50 µg/mL, 30 weeks) promoted anchorage-independent growth and invasiveness, induced DNA damage, and dysregulated oncogenic pathways including KRAS, MET, RET, and EMT-related genes, implicating lung cancer–associated mechanisms [208].

Studies investigating PE-MPLs of varying shapes and sizes have demonstrated significant cellular effects. Exposure to 1 μm spherical PE-MPLs in HaCaT and skin cancer cells (A431, SCL-1) induced TNF-α, IL-6, IL-1β, and NLRP3 activation, ROS production, mitochondrial DNA damage, and altered mitochondrial function, promoting proliferation and pyroptosis via ROS–mtDNA–NLRP3 signaling, along with upregulation of Cyclin D1, c-Myc, Bcl-2, and Ki67 genes [106]. Larger PE particles predominantly trigger inflammation and oxidative stress. Irregular PE-MPLs (6.2–30.5 μm) induced IL-6 and TNF-α production, ROS and nitrosative stress in Caco-2, A549, HaCaT, THP-1, U937, and Jurkat cells, with minimal cytotoxicity [209]. Similarly, exposure to irregular PE-MPLs (~ 35–45 μm) in A431 skin carcinoma cells and normal human dermal fibroblasts (NHDFs) caused apoptosis, increased ROS and lipid peroxidation, activated antioxidant defenses (CAT, SOD), and affected A431 proliferation and 5-FU efficacy [107]. These findings indicate that particle size plays a critical role in modulating cancer-related cellular responses, with smaller PE-MPLs promoting proliferation and pyroptosis, while larger and irregular particles primarily induce inflammation, oxidative stress, and apoptosis, highlighting the importance of size in potential cancer complications.

Consistency, PTFE-NPLs (spherical) and -MPLs (irregular), also show that smaller particles generally induce stronger cellular effects regardless of shape. Exposure of Caco-2 and HT29-MTX monocultures, as well as Caco-2/HT29-MTX intestinal barrier models, to ~ 250 nm and ~ 2 μm PTFE-MNPLs (0–200 µg/mL, 24–48 h) induced IL-8 secretion, disrupted TEER and tight junctions, caused ROS generation and DNA damage, and elicited mitochondrial injury, accompanied by activation of cGAS–STING, NLRP3 inflammasome, Caspase-1, and IL-1β signaling, with small size has persistent severe impact [210]. Irregular PTFE-MPLs (6–32 μm) similarly induced NO, TNF-α, and IL-6 in a cell type- and size-dependent manner, increased ROS, activated MAPK (ERK, p38) and NLRP3 pathways, and showed minimal apoptosis with BCL-2 involvement [108], highlighting that irregular shapes can still produce severe cellular impacts.

In addition to the assays checking for effects associated to tumoral processes, cell transformation assays (CTAs) arise as in vitro alternative approaches to studying carcinogenicity, as the most advanced assays in terms of standardization and validation. Among the OECD (Organization for Economic Co-operation and Development) CTA test guidelines recommended, the Bhas 42 CTA stand out. This system was implemented to evaluate the tumor-initiating and promoting ability of the chemicals using the Bhas 42 cell line. A recent study [211] has compared the effects of PET-, PLA- and PS- NPLs in this assay to determining their ability to induce CTA. Results showed that the three NPLs present an efficient cellular internalization in Bhas 42 cells and cell growth was enhanced by PS-NPLs in the initiation assay, and by PET-NPLs in both conditions (initiation/promoting). Moreover, the number of transformed foci was significantly increased only by the highest PET concentration in the promotion assay, which also showed dose-dependency, indicating that PET-NPLs can act as a non-genotoxic tumor promoter. Together, these findings support the carcinogenic risk assessment of nanoplastics, raising concerns regarding whether real-life co-exposure of PET-MNPLs nanoplastics may result in synergistic transformation capacities.

Despite the expectations of the CTA assays, pre-validation efforts carried out by the European Center for Validation of Alternative Methods (ECVAM) have met important limitations that have hampered the extended use of such assays [212]. To overcome these limitations new approaches for human-cell-line-based CTAs has been proposed [213]. Authors propose a battery of alternative CTAs based on the hallmarks of carcinogenesis. These hallmarks describe distinctive events of cancer development, such as genomic instability and mutation, tumor-promoting inflammation, sustaining proliferative signaling, enabling replicative immortality, evading growth suppressors, resisting cell death, deregulating cellular energetics, avoiding immune destruction, inducing angiogenesis, and activating invasion and metastasis [214]. Interestingly, the different carcinogenic-related effects are analyzed under a long-term exposure scenario and low concentration exposures. Finally, the proposed biomarkers are grouped into early, intermediate, and advanced stages, as they were representative of different stages during the progression of the transformed phenotype. This proposal aims to improve the prediction ability of CTAs including mechanistic explanations [215]. Using such approaches, the long-term impact of true-to-life PET-NPLs generated from plastic water bottles and cigarette smoke condensate (CSC). Results show that co-exposure to PET-NPLs and CSC exacerbates oxidative stress, genotoxicity, and tumorigenic transformation, as evidenced by increased DNA damage, colony formation in soft agar, and enhanced cell migration and invasion. In addition, the transcriptomic analysis revealed a shift in cellular stress regulation including the upregulation of stress-response genes and key tumor-suppressor genes, which were significantly downregulated, promoting cellular transformation and invasiveness [122]). To assess the long-term effects of true-to-life PET-NPLs generated from plastic water bottles, BEAS-2B cells were exposed to PET-NPLs for 30 weeks. Genotoxicity, carcinogenic phenotypic hallmarks, and a panel of genes and pathways associated with cell transformation and lung cancer were examined and compared over time. Although no significant effects were observed after 24 h or 15 weeks of exposure. Exposure lasting for 30 weeks led to increased genotoxic damage, anchorage-independent growth, and invasive potential. From the transcriptomic analysis, the upregulation of several oncogenes and lung cancer-associated genes at the end of the exposure were detected. Increments in the number of differentially expressed genes over time, and a temporal gradient of lung cancer-related genes, were also observed [208]. It must be emphasized that true-to-life MNPLs contain the additives added during the plastic goods production, and some of them have been considered as potential carcinogens, as is the case of phthalates [126]. Consequently, those studies using such types of MNPLs are more relevant than those obtained using pristine polystyrene micro/nano beads.

Overall, in vitro studies demonstrate that MNPLs induce a wide range of size-, shape-, and polymer-dependent cellular disruptions, including inflammation, oxidative stress, apoptosis, necroptosis, mitochondrial dysfunction, cell transformation based on the hallmarks of carcinogenesis, and dysregulation of oncogenic pathways. Small NPLs, regardless of polymer type, generally elicit stronger and more diverse effects, while larger and irregular particles predominantly trigger inflammation and oxidative stress, though they can still cause DNA damage and disrupt cellular homeostasis. Additionally, these findings underscore the serious implications of MNPL exposure in potentially promoting carcinogenesis and highlight the critical role of particle characteristics. To fully address these perspectives, it is essential to advance in vivo models to investigate MNPL distribution in whole organisms, integrating functional assessments to reflect how MNPLs disrupt cellular pathways and potentially mediate carcinogenic processes.

In vivo models

Lower ranks in vivo models

Since cellular responses are conserved across a wide range of organisms and levels of biological complexity, and considering economic, logistical, and ethical constraints, lower-ranking organisms provide valuable models for studying MNPL-induced carcinogenicity. Exposure of Spodoptera frugiperda larvae to PE-MNPLs (0.5–50 μm; 1.25–20 g/L, 12 days) induced oxidative stress, inflammation, and altered midgut microbiota and metabolism [218]. In Caenorhabditis elegans, exposure to 1 μm PS-MPLs, both pristine (1.05 μm) and aged (0.98–0.996 μm) at 0.1–100 µg/L for 24 h, triggered DNA damage–mediated germline apoptosis through the hus-1–cep-1–egl-1–ced-9–ced-4–ced-3 or egl-1–cep-1–hus-1–ced-3–ced-4–ced-9 pathways [219].

In aquatic invertebrates, PS-MNPLs induce tissue-specific toxicity, oxidative stress, and histopathological damage. PS-NPLs (30 nm) caused DNA strand breaks, inhibited DNA repair genes (xrrc1, ATM, DECAY, NLK), disrupted oxidative and endocrine signaling, impaired development, and activated humoral immunity in Chironomus riparius larvae (0.1–3 mg/L, 24 h) [220]. In bivalves (Meretrix lyrata), 80 nm PS-NPLs (1 mg/L, 7 days) affected intestine, gill, mantle, foot, siphon, and digestive gland, inducing oxidative stress, microbiota disruption, and histopathological damage with increased SOD, CAT, GOT, GPT, and MDA expression [221]. Exposure to 1 μm PS beads (1000–5000 particles/mL, 30 days) in crustaceans (Procambarus clarkii and Leptuca pugilator) targeted the hepatopancreas, hemolymph, and gills, inducing lipid peroxidation, activating antioxidant enzymes, and causing tissue lesions [222]. Fibrous PES-MPLs (20 ± 4 μm diameter, 60 μm length) in Daphnia carinata (0–500 MPL fibers/mL, 7 days) impaired mitochondrial function, increased oxidative stress, and activated apoptosis and ferroptosis pathways [223].

Drosophila melanogaster has been widely employed to evaluate hazard-related disorders induced by MNPLs across different polymer types, origins, and particle sizes, providing mechanistic insight into pathways relevant to cancer progression. Ingestion of PS-NPLs (50, 200, 500 nm) by Drosophila larvae resulted in size-dependent uptake, ROS production, DNA damage, and altered expression of genes involved in antioxidant defense, genotoxicity, and intestinal injury, with the smallest 50 nm particles eliciting the strongest responses [172]. In adults, oral exposure to PMMA (5 μm; 0.1–20 g/L for 20 days) disrupted energy metabolism and oxidative-stress compensation, altered metabolic parameters including glucose, lipid, and protein levels [224]. Similarly, PA-MPLs (6.5 μm; 0.1–20 g/L for 20 days) induced oxidative stress, inflammation, and metabolic disruption [225]. Drosophila has also been used to assess MNPLs derived from real commercial products such as PET(Ti)-NPLs from milk bottles degradation (~ 112 nm; 0–500 µg/g food) [129] and PET-NPLs from water bottles degradation (40 nm; 0–500 µg/g food) [46] inducing oxidative stress, genotoxicity, dysregulated stress and DNA-repair gene expression, and intestinal barrier damage. In addition, bioplastics such as PLA-NPLs (~ 464 nm; 25–400 µg/mL for 4 days) resulted in intestinal damage, oxidative and DNA stress, inflammation, and cellular vacuolization [173]. In terrestrial soil invertebrates, earthworms (Eisenia fetida) exposed to PE (conventional) and PLA (biodegradable) MPLs (150 μm; 0.5–14% w/w, 28 days) showed oxidative stress and gut microbiota disruption [226].

Higher ranks in vivo models

Zebra fish

At higher-ranking vertebrate models, particularly in fish, which share conserved pathways and physiological scenarios with humans, studies can provide more relevant and reliable insights into MNPL-induced carcinogenicity, while balancing logistical and ethical considerations. At the larger microscale, PS-MPLs primarily exert their effects through chronic inflammation and disruption of gut microbiota, causing damage to the midgut lumen and intestinal tissues. For instance, exposure to 5 μm MPLs (50–500 µg/L, 21 days) induced oxidative stress, inflammation, and altered lipid metabolism in the gut of zebrafish [227]. PS-MPLs with size 1 μm triggered neuroinflammation (IL-6, IL-1β), microglial activation, circadian disturbances (per1b, per2, per3, cry1a, cry2), and altered neurotransmitter levels including dopamine, serotonin, norepinephrine, acetylcholine, tyrosine, and tryptophan in zebrafish (25–250 µg/L, 40 days) and microglia (0–250 µg/L, 12–48 h) [228].

As PS plastic particles decrease in size, their cellular penetration, toxicity, and mechanistic impact increase, even at lower concentrations or shorter exposure times. At the nanoscale, PS-NPLs disrupt cellular homeostasis in a size-, dose-, and exposure-dependent manner. In zebrafish larvae (4 dpf), 100 nm PS-NPLs (0–50 µg/mL, 48 h) caused intestinal apoptosis, barrier disruption, increased permeability, and altered gene expression, reflecting early tissue injury [229]. With prolonged or higher-concentration exposure to 100 nm PS-NPLs (100–1000 µg/mL, 8 hpf–12 dpf) in zebrafish larvae, or 500 µg/mL in ZF4 fibroblasts (2–24 h), intensified toxicity via NADPH oxidase–mediated ROS, resulting in mitochondrial dysfunction, apoptosis, and NF-κB–mediated inflammatory signaling, while ROS inhibition mitigated these effects, confirming oxidative stress as a central driver [230]. Prolonged exposure to slightly smaller PS-NPLs (80–100 nm; 1–100 µg/mL for 7 days) in zebrafish embryos further impaired development by suppressing antioxidant defenses (sod1, cat), promoting apoptosis (bcl-2, bax), inhibiting alkaline phosphatase activity, and downregulating skeletal development genes (sp7, sparc, smad1, runx2a, bmp2a, bmp4), ultimately resulting in pronounced skeletal deformities [231]. These effects were further exacerbated at smaller particle sizes: 50 nm NPLs (0.1–50 µg/mL, 5 days) caused systemic damage to liver, immune, and mitochondrial tissues, triggering oxidative stress, apoptosis, ferroptosis, and inflammation, which were partially attenuated by sodium nitroprusside, highlighting redox imbalance as a key mediator [232]. Similarly, exposure to 44 nm PS-NPLs (0.1–10 ppm, 96 h) in zebrafish (wildtype and transgenic lines Tg(MLS-EGFP) and Tg(EPRE: EGFP)) increased oxidative stress and reduced mitochondrial coupling efficiency, linking nanoparticle exposure to mitochondrial and ER dysfunction [233].

Considering particle size as a critical determinant of MNPL-induced carcinogenic effects, comparative zebrafish-based studies have been conducted across multiple exposure scenarios. Exposure to PS-MNPLs (25 nm NPLs and 2 μm MPLs; 10–100 µg/mL for 48 h) in zebrafish, as well as in 3T3-L1 preadipocytes (2.5–500 µg/mL for 8 days), promoted adipogenesis, pro-inflammatory responses, gluconeogenesis, and metabolic dysfunction, affecting adipocytes along with intestinal and pancreatic tissues [234]. Similarly, in zebrafish liver (ZFL) cells, PS-MNPLs (50 nm and 5 μm; 0–100 µg/mL, 24 h) induced oxidative stress, subcellular structural damage, and dysregulation of glycolipid metabolism, with nanosized particles eliciting more severe toxicity, likely due to their enhanced cellular internalization through multiple uptake pathways compared with MPLs [235]. Moreover, prolonged exposure of adult zebrafish to PS-MNPLs (80 nm NPLs and 8 μm MPLs; 10–1000 µg/L for 21 days) resulted in persistent gut microbiota alterations and intestinal tissue injury via activation of inflammatory pathways. Notably, nanosized particles selectively upregulated pro-inflammatory cytokine genes (il8, il10, il1β, tnfα), indicating a stronger capacity of NPLs than MPLs to induce gut inflammation and microbiota dysbiosis-processes closely linked to carcinogenesis [236].

Studies with polymers beyond PS demonstrate that particle composition, size, and shape critically influence toxicity. Zebrafish exposed to PE-MPLs (35.46 ± 18.17 μm, 1 × 10¹² particles/m³, 15 days) exhibited oxidative stress and redox imbalance in the brain, liver, gills, muscle, and erythrocytes, with elevated ROS and reactive nitrogen species and organ-specific changes in SOD and CAT activity, effects driven primarily by the particles themselves rather than co-exposure with pollutants [237]. Similarly, both larger and shaped fibers, such as PE (180 ± 210 μm) and PES (350 ± 220 μm) disrupted gut metabolomics, affecting pathways related to inflammation, immune signaling, and apoptosis, including leukotriene and arachidonic acid metabolism in adult zebrafish, administered at 200–1000 µg/L for 30 days, highlighting the role of polymer type, size, and morphology in systemic and tissue-specific toxicity [238].

Together, these findings underscore the pivotal role of polymer type, particle size, and morphology in promoting systemic and tissue-specific toxicity and in modulating carcinogenic progression, particularly through oxidative stress and inflammatory pathways.

Other fishes’ model

Cross various fish models, PS-MNPLs activate pathways linked to chronic oxidative stress, inflammation, ER stress, apoptosis, autophagy, and metabolic reprogramming, which are mechanistically associated with cancer susceptibility. Larger PS-MPLs (50–500 μm) in Crucian carp (200–3200 µg/L, 32 days) triggered hepatic detoxification responses (GST, CAT, GSTpi, GSTα), while 80 μm MPLs in Leuciscus waleckii (3.00 ± 0.02 g, 8 weeks) disrupted intestinal integrity, mitochondrial function, growth, and immunity [239]. Smaller MPLs produced stronger effects: 20 μm MPLs in goldfish (1 mg/L + 0.1 mg/L Cu²⁺, 7 days) induced hepatopancreatic oxidative stress, apoptosis, inflammation, and impaired autophagy [240]. Additionally, PS-MPLs (8 μm) in common carp (1000 ng/L, 21 days) activated ER-stress markers (GRP78, PERK, EIF2α, ATF4), NLRP3-mediated inflammation, autophagy, apoptosis, and TLR2–MyD88–TRAF6–NF-κB signaling [241, 242]. Wide-range MPLs (1–20 μm, 25–250 mg/kg/day, 21 days) in gilthead seabream altered hepatic lipid metabolism (PPARγ, Srebp1, Fasn), inflammation (CSF1R, TNF-α, IL-1β), oxidative stress (ROS, MDA, SOD, CAT, glutathione reductase), and detoxification (EROD, GST) [243].

Smaller particles of PS-NPLs (≤ 100 nm), induce pronounced systemic disorder across aquatic species. In carp, exposure to 50–400 nm PS-NPLs (1000 µg/L for 28 days) triggered ROS generation, suppression of antioxidant defenses (CAT, SOD1, Gpx1), activation of innate immune signaling (TLR4, NOX2), Th1/Th2 immune imbalance, and apoptosis-related pathways (IGFBP3, p53, ACHE), with the smallest particles inducing marked myocardial inflammation [244]. In medaka, chronic co-exposure to ~ 100 nm PS-NPLs and sulfamethoxazole (100 µg/L for 30 days) caused multi-organ toxicity, disrupting cytochrome P450 metabolism, immune signaling (ifi30), and intestinal microbiota composition [245]. Similarly, exposure of Larimichthys crocea to 100 nm PS-NPLs (10–10⁶ particles/L for 14 days) induced hepatic oxidative stress and lipid peroxidation, accompanied by elevated antioxidant enzyme activity (SOD, CAT, GPx) and increased MDA levels [246].

Beyond PS, other polymers such as PE-MPLs also exhibit pronounced size- and tissue-dependent severe implications. In European perch, dietary exposure to aged PE-MPLs (100–180 μm; 1 mg/g food for 15 days) resulted in greater DNA damage and hepatic stress compared with pristine particles [247]. Notably, smaller PE-MPLs (8 μm; 1000 ng/L for 21 days) in common carp induced severe structural damage, oxidative stress, inflammation, endoplasmic reticulum stress, and apoptosis through miR-21 downregulation, IRAK4 inhibition, and NF-κB activation [248]. These PE particles also impaired ovarian development via suppression of miR-132 and upregulation of CAPN, triggering mitochondrial dysfunction (Bax, AIF, cytochrome c, caspases-3/7/9) and TRAF6/NF-κB–mediated pro-inflammatory cytokine expression [249]. These findings reveal the broad hazardous impacts of MNPLs, which may ultimately contribute to carcinogenic processes, largely depending on the physical characteristics of the particles. Evidence spans diverse in vitro systems, lower-ranking organisms, and fish models, highlighting the need for confirmation in higher mammalian models that are more closely related to humans and share similar biological complexity.

Mammalian models

Across rodent models, commonly used as representative mammalian systems (Table 3), PS-MNPLs induce inflammation, oxidative stress, and cancer-associated signaling, with effects amplified by smaller particle size and prolonged exposure. Chronic exposure of mice to spherical PS-MPLs (5–200 μm) disrupted metabolic homeostasis via the IRS1/PI3K axis, elevated pro-inflammatory markers (TNF-α, IL-1β, LPS, NF-κB), and altered lipid metabolism genes, creating a pro-tumorigenic environment [250]. Several studies employed spherical 5 μm PS to evaluate MPLs impacts. In female SLE MRL/lpr mice, oral exposure promoted synovial pyroptosis through oxidative stress and NF-κB signaling, impairing joint structure [251]. In DSS-induced colitis mice, exposure elevated pro-inflammatory cytokines (IL-1β, IL-6, TNF-α, MCP-1, IL-17α, IL-22), upregulated TLR4, iNOS, COX2, and NF-κB signaling, and disrupted intestinal barrier integrity via TGF-β–mediated mechanisms [252]. In Sprague–Dawley rat pups, induced hepatic oxidative stress, evidenced by elevated MDA and altered GPx activity, and promoted lipid accumulation and fatty liver development [253]. Repeated injections in rats elicited skeletal inflammation and altered bone morphogenetic cytokines, indicating disruption of bone tissue homeostasis [77]. As PS-MPL size decreases within the microscale range, toxic effects persist. Rats exposed to 1 μm and 5 μm PS-MPLs exhibited hepatotoxicity accompanied by oxidative stress, activation of the Nrf2/HO-1 pathway, and pyroptosis mediated via NLRP3, caspase-1, and IL-1β, highlighting inflammation-driven cell death [254].

Table 3.

In vivo (mammalian model) diagnostic studies reportingmajor disorders and signaling pathways associated with exposure to micro- andnanoplastics of different physicochemical properties, polymer types, sizes, and shapes

MNPLs	Model / Treatment	Inflammation / Immune	Cell Death / Apoptosis	Fibrosis / Remodeling / Barrier	Oxidative Stress / DNA Damage	Mitochondria/ Metabolic	Signaling Pathways	Ref.
PS (5–200 μm, spherical)	Mice (80 mg/kg/day, 10 weeks)	TNF-α, IL-1β, LPS, NF-κB	–		–	Lipid metabolism genes	PI3K/AKT/mTOR (IRS1/PI3K axis)	[250]
PS (5 µm)	Female SLE MRLl/pr mice (0.5–5 mg/kg, 9 weeks)	IL-1β, IL-18, TNF-α, NF-κB	Pyroptosis (Caspase-1, GSDMD)	–	ROS increase	–	–	[251]
PS (5 µm, spherical)	DSS colitis mice (0.5–5 µg, acute or chronic)	IL-1β, IL-6, TNF-α, MCP-1, IL-17α, IL-22, TLR-4, iNOS, COX2, NF-κB	–	TGF-β/ Destroyed intestinal barrier	–	–	–	[252]
PS (5 µm)	Sprague–Dawley rat pups (100–1000 µg/L, 7 days)	–	–	–	MDA; GPx	Hepatic lipid; Fatty liver	–	[253]
PS (5 µm, spherical)	Rats: 1.3 mg/mL, 4 weeks)	TNF-α, alter morphogenetic protein	–	–	–		–	[77]
PS (1–5 µm, spherical)	Rats: 0.02 mg/kg, 6 weeks	iNOS, IL-1β, hepatic inflammation, NLRP3	Pyroptosis; caspase-1	Fibrosis and collagen deposition	MDA; Nrf2/HO-1 signaling	AST, ALT, LDH, total cholesterol, triglycerides/ Lipid droplet accumulation	–	[254]
PS: 1 μm	Juvenile rats: 2.0 mg/kg/day, 28 days	TNF-α, IL-6, NF-κB/p65, IRE1, ATF6	Bax, Bcl-2, GRP78, XBP1s, Caspase-3, 9, 12	Barrier destruction	GSH-Px, SOD, MDA	Reduce weight, alter organ index	JNK, CHOP	[255]
PS (500 nm, spherical)	Mdr2^-/- mice: 200 μg/day, 28 days	IL-1β, IL-6, TNF-α, NLRP3	Caspase-1, Gasdermin D	Damage (ZO-1, Occludin and Claudin-1)	–	–	–	[256]
PS (500 nm)	ICR mice: 4–16 μg/mL, 2 weeks	IL-1β, TNF-α, IL-4, IL-5, IL-10, IL-18	–	TGF-β1, Smad2/3, pro-collagen I, fibronectin, fibrosis	–	Fatty/nucleotide metabolism, altered related genes	–	[257]
PS (450–530 nm, spherical)	C57BL/6J mice: 1000–5000 µg/L, 6 weeks	TNF- α, Il6, Il1b; ILC1, ILC3, M1/M2 macrophages, NK cells	–	–	–	Altered metabolism: glucose, amino acid, fatty acid transporters; hepatic genes	Notch-related genes (Rbpj)	[258]
PS (100 nm)	SPF C57BL/6 mice: 1.7 µg/mL, 3 weeks	TNF-α, IL-6	Increased cell death in organoids	–	ROS	–	TGF-β1, p-Smad3; Smad7	[259]
PS (100 nm, spherical)	SPF ICR male mice: 30 mg/kg/day, 4 days, LPS: 5 mg/kg	IL-1β, IL-6, TNF-α, MCP-1	Reduced spermatogenesis	–	ROS; MDA; SOD	Testosterone; StAR, CYP11A1/ Functional impairment	Phosphorylation/activation NF-κB	[260]
PS (100 nm)	Female rats: 0.02–2 mg/day, 90 days	–	Caspase-9, Bax, Bcl-2	–	ROS, MDA, SOD, GSH, CAT; Keap1/Nrf2/HO-1	–	Keap1/Nrf2/HO-1 pathway	[261]
PS (50–90 nm)	Kunming mice, early pregnancy (GD1–GD8)1 mg/kg/day, 90 days)	Impaired decidualization immune environment	Cell cycle (CyclinE1, Cdk2, CyclinD1, CyclinB1)	impaired (BMP2, MMP9, HOXA11, LIF)	SOD, CAT, GSH-Px; LDH-x, γ-GGT, MDA	—	JNK-MAPK p-JNK; ERK1/2-MAPK, p-ERK1/2	[262]
PS (80 nm, spherical)	Male BALB/c mice: 0.015–1.5 mg/day, 21 days)	NLRP3 activation; IL-1β, IL-18	Bax, Bcl-2	Claudin-1, Occludin, ZO-1	–	–	TLR4/NF-κB/NLRP3/GSDMD pathways	[263]
PS (50 nm, spherical)	Adult male Wistar rats: 2.5 mg/kg/day, 15 days	TNF-α, IL-6, NRF-2	Bax/Bcl-2 imbalance; Caspase-9, Caspase-3	Fibrosis; collagen deposition, epithelial damage	Oxidative stress (MDA, NO), SOD, CAT, GPx, GSH, NPLSH)	Mitochondrial dysfunction	NF-κB activation	[264]
PS (25–50 nm, spherical)	Male Wistar rats (1–10 mg/kg/day, 5 weeks)	–	–	–	ROS; GSH; CAT/SOD altered	Disrupted metabolism/ Impaired mitochondria	–	[265]
PS (50, 250 nm, spherical)	Male C57B/L mice: 5–125 mg/kg, 28 days	–	Caspase 3, Bax, Bcl - 2	Damage gastric barrier	ROS; GPX4, HO-1, SOD2, GPX3, CATC, GCLC; p62/Keap1/Nrf2	Mitochondria dysfunction	P62/Keap1/Nrf2 pathway	[266]
PS (80 nm, 500 nm, 5 µm)	ICR male mice: 1 mg/L, 12 weeks	IL-1β, IL-6, TNF-α, CXCL2/12; CD68⁺	–	α-SMA; tubulointerstitial fibrosis	–	Acot3, Abcc3, Nr1i3; disrupted glucose / mitochondrial damage	–	[267]
PS (80–1000 nm, spherical)	Sprague–Dawley rats; 5 mg/L, 90 days	–	–	Gastric epithelial barrier disruption	ROS, MDA; SOD, GSH-Px, CAT/8-OhdG and γ-H2AX, DNA damage	Membrane rupture: cristae fracture	β-catenin/YAP	[186]
PS (100 nm, 5 µm, spherical)	C57BKS/Leprdb mice; 200 µg/L, 28 days	TNF-α, IL-1β; inflammatory infiltration	Hepatocyte apoptosis		SOD; MDA	Disrupted lipid & energy metabolism;	–	[187]
PMMA (25 nm)	ICR mice: 10–1000 µg/mL, 4.5–5.5 days	–	Apoptosis in blastocysts	–	ROS; Sod1/2, Gpx1/2, Cat; GSH	–	–	[268]
PE (1–10 µm, spherical)	Female ICR mice: 0–0.2 µg/g/day, 30 days	IL-8, IL-10, IL-1β	–	Colon mucus and mucin density decreased	–	Amino-acid metabolism changes	ERK1 and NF-κB mRNA	[272]
PP (8–70 µm, irregular shape)	Male C57BL/6 mice: 0.1–10 mg/mL, 28 days	TNF-α, IL-1β, IL-6; IL-10	Bax, cleaved caspase-3/9; Bcl-2	ZO-1, claudin-1, occludin; MUC1; CFTR, NKCC1, SLC26A6	MDA, GSSG; SOD, GSH, GSH-Px, CAT	Swelling, vacuolation, reduced matrix	TLR4–NF-κB activation (p50, p-p65, IκBα)	[269]
PE (10–90 µm, spherical)	Female C57BL/6J mice: 20 mg/kg/day, 4 weeks	Il10ra, Il1a, Il33, Tnfaip8l2, and Tnfrsf1b, Il17b	–	–	ROS in oocytes; GSH	Altered glycerophospholipid, fatty-acid metabolism	–	[270]
PE (10–150 µm, spherical	C57BL/6 mice: 6–600 µg/day, 5 weeks	Altered cytokines: IL-1α, IL-6, IL-9, IL-2, Th17	–	Histological intestinal disruption	–	–	TLR4, AP-1, and IRF5 signaling	[271]
PET: 1 µm	SPF male BALB/c mice: 0.01–1 mg/day, 42 days	–	Caspase-3/9	–	MDA and GSH	Mitochondria damage	p38 MAPK	[273]

At the nanoscale, spherical PS-NPLs induce size- and dose-dependent toxicity across multiple mammalian models. PS particles (1000 nm) administered to juvenile rats induced inflammation (TNF-α, IL-6, NF-κB/p65, IRE1, ATF6), ER stress and apoptosis (Bax, Bcl-2, GRP78, XBP1s, Caspase-3/9/12), intestinal barrier disruption, and altered body, renal, and cardiac indices, accompanied by oxidative stress (GSH-Px, SOD, MDA) and activation of JNK/CHOP signaling [255]. In Mdr2⁻/⁻ mice, 500 nm PS-NPLs triggered intestinal inflammation via elevated IL-1β, IL-6, TNF-α, and NLRP3 activation, leading to pyroptosis (caspase-1, gasdermin D) and disruption of tight-junction proteins (ZO-1, occludin, claudin-1) [256]. Similarly, 500 nm PS-NPLs in ICR mice induced strong systemic inflammation (IL-1β, TNF-α, IL-4, IL-5, IL-10, IL-18), activated profibrotic TGF-β1/Smad2/3 signaling, increased extracellular matrix markers (pro-collagen I, fibronectin), caused fibrosis, and disrupted fatty acid and nucleotide metabolism [257]. In C57BL/6J mice, 450–530 nm PS-NPLs elicited inflammatory cytokine responses (Tnfa, Il6, Il1b), altered immune cell populations (ILC1/3, macrophages, NK cells), impaired hepatic glucose, amino acid, and lipid metabolism, and activated Notch signaling (Rbpj) [258]. Smaller 100 nm PS-NPLs caused intestinal inflammation in SPF C57BL/6 mice, elevating TNF-α and IL-6, increasing ROS, reducing cellular proliferation, and promoting cell death via TGF-β1/p-Smad3 activation and Smad7 suppression [259]. Under LPS challenge, they triggered systemic inflammation, oxidative stress, and NF-κB activation, impairing spermatogenesis, reducing testosterone, and downregulating steroidogenic genes (StAR, CYP11A1), indicating reproductive toxicity [260]. In female rats, 100 nm PS-NPLs induced apoptosis (caspase-9, Bax, Bcl-2), oxidative stress (ROS, MDA, SOD, GSH, CAT), and activated the Keap1/Nrf2/HO-1 pathway [261]. PS (50–90 nm) administered to Kunming mice during early pregnancy (GD1–GD8) impaired decidualization and altered the immune environment, reduced proliferation and disrupted the cell cycle (CyclinE1, Cdk2, CyclinD1, CyclinB1), affected implantation-related genes (BMP2, MMP9, HOXA11, LIF) with uterine edema, increased oxidative stress markers (SOD, CAT, GSH-Px, LDH-x, γ-GGT, MDA), and activated JNK-MAPK/p-JNK and ERK1/2-MAPK/p-ERK1/2 pathways [262].

Exposure of male BALB/c mice to 80 nm PS-NPLs activated the NLRP3 inflammasome, increased IL-1β and IL-18, induced apoptosis via Bax/Bcl-2, and disrupted intestinal barrier integrity (claudin-1, occludin, ZO-1) through the TLR4/NF-κB/NLRP3/GSDMD axis [263]. In adult male Wistar rats, 50 nm PS-NPLs caused inflammation (TNF-α, IL-6, NRF-2), apoptosis (Bax/Bcl-2, caspase-9/3), fibrosis, tubular damage, oxidative stress (MDA, NO, SOD, CAT, GPx, GSH, NPLSH), mitochondrial dysfunction, and NF-κB activation [264]. These studies demonstrate that regardless of polymer type (PS-NPLs) toxicity is strongly size-dependent, with smaller particles inducing more severe oxidative stress, inflammatory signaling, apoptosis, and organ-specific damage across multiple mammalian systems.

Size-dependent toxicity of PS-MNPLs is closely associated with pro-carcinogenic pathways in mammalian models. At even smaller sizes (25–50 nm), PS-NPLs induced oxidative stress (ROS; GSH; altered CAT/SOD), metabolic disruption, and mitochondrial impairment in male Wistar rats [265]. In male C57B/L mice, spherical PS particles (50 and 250 nm) caused gastric barrier damage, induced apoptosis via caspase-3, Bax, and Bcl-2, triggered oxidative stress (ROS; GPX4, HO-1, SOD2, GPX3, CATC, GCLC; p62/Keap1/Nrf2), and led to mitochondrial dysfunction, and severe gastric damage induced by 50 nm PS caused than 250 nm [266]. Chronic exposure of ICR male mice to PS particles (80 nm, 500 nm, 5 μm) induced renal inflammation, characterized by elevated IL-1β, IL-6, TNF-α, CXCL2/12, and CD68⁺ macrophage infiltration, promoted tubulointerstitial fibrosis with increased α-SMA, and impaired glucose metabolism and mitochondrial function through dysregulation of Acot3, Abcc3, and Nr1i3 [267]. The authors noted that smaller NPLs (80 nm) primarily disrupt intracellular metabolic processes due to their high surface area, reactivity, and ability to penetrate cells and organelles such as mitochondria and the endoplasmic reticulum, whereas larger MPLs (5 μm) preferentially accumulate in organs like the liver, causing cellular compression, inflammation, and fibrosis through repeated tissue damage and repair. These findings underscore that microplastic toxicity is strongly size-dependent, with distinct mechanistic outcomes at different particle scales. In Sprague–Dawley rats, spherical PS particles (80–1000 nm) disrupted the gastric epithelial barrier, induced oxidative stress (ROS, MDA) with altered antioxidant defenses (SOD, GSH-Px, CAT), caused DNA damage (8-OHdG, γ-H2AX), mitochondrial membrane rupture, cristae fracture, and activated β-catenin/YAP signaling [186]. Notably, PS-NPLs smaller than 100 nm produced statistically significant effects across all endpoints, including increased ROS, reduced antioxidant enzyme activity, enhanced lipid peroxidation, and elevated DNA damage biomarkers, highlighting that NPLs pose a greater hazard than MPLs. Similarly, in diabetic C57BKS/Lepr^db mice, exposure to spherical PS particles (100 nm, 5 μm) induced hepatic inflammation with increased TNF-α and IL-1β, hepatocyte apoptosis, oxidative stress including MDA and altered SOD, and disrupted lipid and energy metabolism with broad metabolomic alterations [187]. Smaller PS particles (100 nm) induced greater liver lipid accumulation, tissue damage, oxidative stress, and pro-inflammatory cytokine expression (TNF-α, IL-1β) than larger MPLs (5 μm) in diabetic mice, while also disrupting liver metabolism and intestinal microbiome composition in both healthy and diabetic mice. Their higher toxicity is likely due to increased surface area, enhanced chemokine release, impaired macrophage migration, and elevated tissue permeability, promoting chronic inflammation [184].

Other MNPLs beyond PS, such as PMMA-NPLs (25 nm) administered to ICR mice induced apoptosis in blastocysts, triggered oxidative stress marked by elevated ROS, and altered antioxidant defenses (Sod1/2, Gpx1/2, Cat, GSH) [268]. Irregular PP particles (8–70 μm) administered to male C57BL/6 mice induced inflammation (TNF-α, IL-1β, IL-6, IL-10), apoptosis (TUNEL, Bax, cleaved caspase-3/9, Bcl-2), intestinal barrier disruption (ZO-1, claudin-1, occludin, MUC1, CFTR, NKCC1, SLC26A6), oxidative stress (MDA, GSSG, SOD, GSH, GSH-Px, CAT), tissue swelling and vacuolation, and activated TLR4–NF-κB signaling (p50, p-p65, IκBα) [269]. Spherical PE particles (10–90 μm) administered to female C57BL/6J mice induced inflammatory gene expression (Il10ra, Il1a, Il33, Tnfaip8l2, Tnfrsf1b, Il17b), increased ROS in oocytes, altered antioxidant levels (GSH), and disrupted glycerophospholipid, sphingolipid, and fatty-acid metabolism [270]. Wide range-sized PE-MPLs (10–150 μm) triggered gut dysbiosis, activated inflammatory signaling (TLR4, AP-1, IRF5), and reduced Th17 and Treg populations, indicating pro-inflammatory and immune-disruptive effects [271]. The smallest spherical PE particles (1–10 μm) administered to female ICR mice (0–0.2 µg/g/day, 30 days) elevated inflammatory cytokines (IL-8, IL-10, IL-1β), reduced colon mucus and mucin density, altered amino-acid metabolism, and upregulated ERK1 and NF-κB mRNA [272]. PET particles (1 μm) administered to SPF male BALB/c mice induced apoptosis via caspase-3 and caspase-9, triggered oxidative stress (MDA, GSH), caused mitochondrial damage, and activated the p38 MAPK pathway [273].

Studies on polymers beyond PS indicate that the carcinogenic potential of MNPLs is intrinsic and largely independent of polymer type, though often influenced by particle size and shape. For example, PMMA-NPLs (25 nm) administered to ICR mice induced blastocyst apoptosis and triggered oxidative stress, evidenced by elevated ROS and disrupted antioxidant defenses (Sod1/2, Gpx1/2, Cat, GSH) [268]. The smallest PE particles (1–10 μm) administered to female ICR mice elevated Il-8, Il-10, and Il-1β, reduced colon mucus and mucin density, disrupted amino-acid metabolism, and upregulated Erk1 and Nf-κB [272]. Irregular PP-MPLs (8–70 μm) given to male C57BL/6 mice caused systemic inflammation (Tnf-α, Il-1β, Il-6, Il-10), apoptosis (Bax, cleaved caspase-3/9, Bcl-2), intestinal barrier disruption (Zo-1, Claudin-1, Occludin, Muc1, Cftr, Nkcc1, Slc26a6), oxidative stress (MDA, GSSG, SOD, GSH, GSH-Px, CAT), tissue swelling and vacuolation, and activated Tlr4–Nf-κB signaling (p50, p-p65, IκBα) [269]. Spherical PE particles (10–90 μm) administered to female C57BL/6J mice upregulated inflammatory genes (Il10ra, Il1a, Il33, Tnfaip8l2, Tnfrsf1b, Il17b), increased ROS in oocytes, altered antioxidant defenses (GSH), and disrupted glycerophospholipid, sphingolipid, and fatty-acid metabolism [270]. Larger PE-MPLs (10–150 μm) induced gut dysbiosis, activated inflammatory pathways (Tlr4, Ap-1, Irf5), and decreased Th17 and Treg populations, reflecting pro-inflammatory and immune-disruptive effects [271]. Similarly, PET particles (1 μm) administered to SPF male BALB/c mice triggered apoptosis via caspase-3/9, induced oxidative stress (MDA, GSH), caused mitochondrial damage, and activated the p38 Mapk pathway [273]. Notably, most of these studies involved MPLs rather than NPLs, which are considered more hazardous, and the data remains limited. Nevertheless, they provide direct evidence that MNPLs of various sizes and polymer types, as detected in cancerous tissues, may contribute to carcinogenic processes. It is important to indicate the lack of studies using the standardized two-year carcinogenicity studies in rodents. This is consequence of the complexity of exposure (polymer type, size, and shape) and the elevated cost of such type of studies.

Both in vitro and in vivo studies

To comprehensively investigate the carcinogenic potential of MNPLs, various studies employed both in vitro and in vivo models, integrating mechanistic cellular insights with systemic and tissue-specific responses that more accurately reflect carcinogenesis in living organisms. As representative MPLs, several studies have commonly employed 5 μm spherical PS to evaluate systemic toxicity. These particles induced hepatotoxicity in mouse hepatocytes and ICR mice, characterized by elevated TNF-α, IL-1β, and NLRP3, caspase-1 activation, pronounced oxidative stress (increased ROS and MDA with altered SOD, CAT, and GSH), mitochondrial structural damage with dysregulated fusion–fission genes (MFN1, MFN2, DRP1, OPA1), lipid accumulation, and activation of the NF-κB/NLRP3 pathway [274]. Similarly, reproductive toxicity was observed in male C57BL/6 mice and TM3 Leydig cells, marked by oxidative stress (ROS, MDA, altered SOD and GSH-Px), mitochondrial ROS accumulation, apoptosis driven by Bax/Bcl2 imbalance, and impaired steroidogenesis with reduced testosterone production [275]. Moreover, chronic exposure to 5 μm PS-MPLs induced renal inflammation and fibrosis in BALB/c mice and HK-2/NRK-49 F renal cells, evidenced by increased TNF-α, IL-1β, IL-6, IL-10, IL-13, NF-κB activation, ferroptosis-associated fibroblast activation, elevated TGF-β1 secretion, ROS overproduction, metabolic stress, and mitochondrial damage [276].

At the nanoscale (~ 100 nm), spherical PS-NPL exerts broad, context-dependent effects across cellular and mammalian models, consistently perturbing inflammatory, metabolic, and oncogenic pathways. For example, this size of PS-NPLs administered to LPS-challenged male C57BL/6 mice and NCM460 cells induced robust inflammation, activated the NLRP3 inflammasome and caspase-1, increased IL-1β and IL-18 levels, disrupted tight-junction proteins (ZO-1, occludin, claudin-1), elevated oxidative stress, and activated NF-κB signaling [277]. Additionally, similar PS size in BALB/c and C57BL/6J mice and TNBC models mediated thrombosis, cancer stemness, gut microbiota dysbiosis, metabolic reprogramming, and activation of AMPK, HIF-1, NF-κB, TGF-β, and EMT pathways [278]. Similarly, in mice and liver cells activated NF-κB p65 and inflammatory cytokines (TNF, IL-6, GM-CSF, IFN-γ, IL-1β, IL-2, IL-4, IL-8, IL-12P70, TNF-α) via TLR4/MyD88, increased AST and LDH release, and triggered multiple signaling pathways including JAK1, STAT1/2/3, ERK1/2, p53, c-Fos, ATF2, AKT, AMPKα, mTOR, P70S6K, PDK1, GSK3α/β, PRAS40, PTEN, Raf-1, and RSK1/2 [279]. Moreover, inflammatory responses (IL6, TNF, TLR2, NF-κB), altered immune-cell infiltration, reduced cell viability, inhibited mitosis and migration, and remodeled tumor tissue, involving proteasome function, ER protein processing, O-glycan biosynthesis, and proteoglycan pathways via THBD-dependent NF-κB, TNF, and IL-17 signaling in HEY ovarian cancer cells and tumors in BALB/c mice were reported with 100 nm PS-NPLs [280]. As size reduced slightly to 80 nm, PS administered to male C57BL/6J mice and RAW264.7 macrophages induced macrophage polarization (CD86, CD206), increased pro-inflammatory cytokines (IL-1β, TNF-α), triggered apoptosis (Bax, Bcl-2), caused ROS bursts, and damaged mitochondria, disrupting glycolysis and TCA cycle metabolism, altering ATP and NADPH levels, and activating NF-κB signaling via PKM2-dependent pathways [281].

Ultra smaller size of spherical PS-NPLs (25 nm) administered to female KM mice and primary granulosa cells induced oxidative stress (HO-1), granulosa cell apoptosis (P53, BAX, BCL2), reduced oocyte quality, caused ovarian structural abnormalities, increased ROS, disrupted mitochondrial membrane potential, impaired estrogen (E2) synthesis, and dysregulated ovarian steroidogenesis via PI3K-AKT-mTOR signaling [282]. Additionally, spherical PS-NPLs (20 nm) induced inflammatory cell infiltration, strong ROS production, DNA damage, mitochondrial swelling, and lipid metabolism disorders in BALB/c mice and Caco-2 cells, activating the PI3K/AKT/mTOR pathway [283]. Similar PS size (20 nm) promoted tumor proliferation and immune infiltration in A549 and H520 cells and C57BL/6 mice, causing lung tumor growth, barrier disruption, ER stress via PERK-eIF2α-ATF4, mild ROS, and metabolic reprogramming through the ATF3 and PCK2 axis [284].

Using both mammalian in vivo models and employing various in vitro human cells (Table 4), several studies were conducted to reveal if MNPLs hazard impacts are size dependent. Al level of closely sized PS-MPLs (5–10 μm), it has been reported that both size activated TLR4 and NF-κB in female SPF mice and MEE cells, inducing fibrosis and collagen deposition via NOX2 and Notch signaling (Jagged1, Jagged2, Notch1/2/3) [285]. Wide variation in PS particles cross a size gradient from 100 nm to 10 μm, induced cytokine release and immune cell infiltration in NCM460 cells and BALB/c mice triggering ferroptosis and apoptosis, barrier disruption, cytoskeleton remodeling, ROS/ferroptosis, MMP loss, mitochondrial swelling, ATP depletion, and shifts in glycolysis/TCA via Fosl1-P53 and YAP-glycolysis signaling [286]. The authors noted that small-sized NPLs (100 nm) trigger ferroptosis-driven immune injury, while large-sized MPLs (10 μm) induce inflammation through mechanical disruption and metabolic reprogramming. Similar study administrated PS (0.2, 1, and 5 μm, spherical) to C57BL/6 mice and Caco-2 cells cause inflammation in elevating NF-κB, NLRP3, IL-6, IL-8, TNF-α, and IL-1β, causing barrier dysfunction (ZO-1, OCLN, CLDN-1), increased ROS, SOD, CAT, MDA, and activating the NF-κB/NLRP3/MLCK pathway [287]. However, 5-µm PS-MPLs induced more severe intestinal epithelial barrier dysfunction than 0.2- and 1-µm particles, significantly downregulating ZO-1, OCLN, and CLDN-1 at both mRNA and protein levels. Spherical PS (20 nm and 10 μm) induced lung inflammation in C57BL/6 mice and BEAS-2B cells, characterized by apoptosis, lung injury, oxidative stress, iron dysregulation, mitochondrial damage, and ROS-driven ER stress [288]. Notably, nanosized PS (20 nm) produced markedly greater cytotoxic and hazardous effects than the 10-µm particles. In a separate study, both in vitro (BEAS-2B) and in vivo (male C57BL/6 mice) exposure to PS-NPLs (200 nm) and MPLs (2.5 μm) increased IL-4, IL-5, IL-13, IL-6, and IL-1β, altered Bax/Bcl-2, induced tissue remodeling, hyperplasia, and barrier dysfunction, and activated p-PI3K, p-AKT, and p-mTOR signaling, with NPLs producing more severe asthma-like effects than MPLs [289].

Table 4.

In vitro and in vivo (mammalian model) diagnostic studies reporting major disorders and signaling pathways associated with exposure to micro- and nanoplastics of different physicochemical properties, polymer types, sizes, and shapes

MNPLs	Model / Treatment	Inflammation / Immune	Cell Death / Apoptosis	Fibrosis / Remodeling / Barrier	Oxidative Stress / DNA Damage	Mitochondria/ Metabolic	Signaling Pathways	Ref.
PS (5 µm, spherical)	Mouse hepatocytes (5–2000 µg/mL); ICR mice (0.1–10 mg/kg/d)	TNF-α, IL-1β, NLRP3	Caspase-1	–	ROS, MDA, SOD/CAT/GSH	Structural damage; genes: MFN1, MFN2, DRP1, OPA1/ lipid accumulation, altered fat	NF-κB, NLRP3	[274]
PS (5 µm, spherical)	Male C57BL/6 mice (0.25–1 mg/day, 4 weeks); TM3 Leydig cells (0–0.8 mg/mL, 24 h	–	BAX/BCL2	–	ROS; MDA, SOD, GSH-Px	Steroidogenesis / testosterone/ Dysfunction/mito ROS	–	[275]
PS (5 µm, spherical)	Male BALB/c mice (10 mg/L, 6 months); HK-2/NRK-49F cells (60 µg/mL, 96 h)	TNF-α, IL-1β, IL-6, IL-10, IL-13, NF-κB	Ferroptosis / fibroblast activation	TGF-β1 secretion	ROS increase	Metabolic stress/ mitochondrial damage	–	[276]
PS (102 nm, spherical)	Male C57BL/6 mice: 5 µg/g, 2 weeks + LPS (20 µg/g), NCM460 cells: 50 μg/mL and/or LPS (0.5 μg/mL), for 24 h	TNF-α, IL-6, IFN-γ, NLRP3, IL-1β, IL-18	Caspase-1	ZO-1, Occludin, Claudin-1; tight-junction disruption	ROS, MDA, SOD, CAT, GSH	–	NF-κB (p65, p-p65, IKKα/β)	[277]
PS (100 nm, spherical)	BALB/c, C57BL/6J mice; 4T1, Py8119 TNBC models; in vitro TNBC cells	Platelet activation, thrombus formation	Sorafenib-independent apoptosis; stemness	Gut microbiota dysbiosis	—	Lipid metabolic; glutamate (Alloprevotella-derived)	AMPK, HIF-1, NF-κB, TGF-β, EMT	[278]
PS (100 nm, spherical)	Mice (100 μL/day, 28 days); liver cells (0–2000 μg/cm², 24 h)	NF-κB p65; TNF, IL6; TLR4/MyD88; GM-CSF, IFN-γ, IL-1β, IL-2, IL-4, IL-8, IL-12P70, TNF-α	–	–	–	Aspartate aminotransferase increase, LDH release	JAK1, STAT1/2/3, Erk1/2, p53, c-Fos, ATF2; AKT, AMPKα, mTOR, P70S6K, PDK1, GSK3α/β, PRAS40, PTEN, Raf-1, RSK1/2	[279]
PS (100 nm, spherical)	HEY cells (0–40 mg/L, 48 h & 16 days); HEY tumors in Balb/C mice (10 mg/L, 27 days)	IL6, TNF, TLR2, NFκB; altered immune infiltration	Cell viability; mitosis; migration inhibited	Tumor tissue changes; migration inhibition		Proteasome; O-glycan biosynthesis; proteoglycans	THBD-mediated NFκB; TNF, IL-17, tumor microenvironment	[280]
PS (80 nm, spherical)	Male C57BL/6J mice: 200–1000 µg/L,RAW264.7: 50–400 µg/mL	CD86, CD206; IL-1β, TNF-α	Bax, Bcl-2	–	ROS burst	Mitochondrial damage / PKM2 signaling; glycolysis/TCA disturbance; ATP, NADPH,	Activate NF-κB signaling pathways	[281]
PS (25 nm, spherical)	Female KM mice 1 mg/day, 42 days; Primary granulosa cells 80–100 µg/mL	HO-1, oxidative stress in granulosa cells	Granulosa cell apoptosis (P53, BAX, BCL2); reduced oocyte quality	Ovarian structural abnormalities, fewer secondary/antral follicles	ROS in oocytes and granulosa cells	MMP in oocytes / E2 synthesis (ovarian steroidogenesis)	PI3K-AKT-mTOR signaling	[282]
PS (20 nm, spherical)	BALB/c mice: 0.1–10 mg/kg, Caco-2 cells: 125–500 µg/mL	Inflammatory cell infiltration	–	–	Strong ROS, DNA damage	Mitochondrial swelling and dysfunction/lipid metabolism disorders	PI3K/AKT/mTOR activation	[283]
PS (20 nm, spherical)	A549 & H520 cells (2.5 µg/mL); C57BL/6 mice, (2.5 mg/kg weekly ×5)	Tumor proliferation; Immune infiltration	—	Lung tumor growth; barrier disruption	ER stress (PERK-eIF2α-ATF4), mild ROS	ATF3→PCK2 axis, gluconeogenesis intermediates	PERK-eIF2α-ATF4 and ATF3; ATF3 and PCK2	[284]
PS (5–10 μm, spherical)	Female SPF mice (100 mg/L for 42 days); MEE cells (500 mg/L, 24 h)	TLR4 activation, NF-κB	–	Fibrosis, collagen	NOX2	–	Notch (Jagged1, Jagged2, Notch1/2/3)	[285]
PS (100 nm – 10 μm, spherical)	NCM460 cells (1 mg/mL, 24 h); BALB/c mice (1 mg/mL, 7 weeks)	Cytokines, immune cell infiltration	Ferroptosis; apoptosis	Barrier disruption, cytoskeleton remodeling	ROS/ferroptosis	MMP loss; swelling, ATP / Glycolysis/TCA shift	Fosl1-P53; YAP-glycolysis	[286]
PS (0.2, 1 and 5 µm, spherical)	C57BL/6 mice: 1 mg/kg/day, 28 days, Caco-2 cells: 100 µg/mL	NF-κB; NLRP3; IL-6, IL-8, TNF-α, and IL-1β	–	Barrier dysfunction, (Claudin-1, Occludin, ZO-1)	ROS increase, SOD, CAT, MDA	–	NF-κB/NLRP3/MLCK pathway	[287]
PS (20 nm), 10 μm. Spherical)	BEAS-2B cells, C57BL/6 mice; in vitro 0.2 mg/mL 24 h; in vivo 5–10 mg/kg intranasal for 15 days	Lung inflammatory infiltration in mice; H&E	Apoptosis (Annexin V/PI, TUNEL, Caspase-3)	Lung injury scoring, thickened alveolar walls	ROS, MDA, iron	Mitochondrial membrane rupture, cristae loss, swelling	ROS-driven ER stress:  p-IRE1α, p-PERK, XBP1S, CHOP, p-JNK	[288]
PS (200 nm and 2.5 μm, spherical)	Male C57BL/6 mice (300 µg/mL, 8 days), BEAS-2B cells (1–1000 μg/mL)	IL-4, IL-5, IL-13, IL-6, IL-1β	Bax, Bcl-2	Tissue remodeling; hyperplasia/ barrier dysfunction	–	–	p-PI3K, p-AKT, p-mTOR	[289]
PMMA (50 nm, spherical)	GES-1, NGEC, HEK293; 1–4 µg/mL, 72 h; C57BL/6 mice oral 5 mg/kg, 30 d	IL-6, IL-1, TNF-α, CCL5, CXCL10 (SASP)	(senescence-dominant)	−	ROS, γ-H2AX, DSBs, MN, genomic instability	Proliferation, G1 arrest, senescence (β-gal)	cGAS–STING → TBK1–IRF3; NHEJ (Ku70/Ku80)	[109]
PVC (50 nm)	HEEC, HET-1A, 293T (0–4 µg/mL, 72 h); C57BL/6 (25 mg/mL, 31 d)	IL-6, TNF-α, IFN-γ, CCL5, CXCL10	Senescence (p16, p21, LaminB1); apoptosis	Esophageal inflammation	ROS; γ-H2AX, DSBs, HDR (GRB2, BRCA2); chromosomal aberrations	−	cGAS–STING–TBK1–IRF3	[110]
PET (100–120 µm, irregular)	Male C57BL/6 mice: 50 µg/mL, 3 months, cardiomyocytes: 4.92 and 49.2 μg/mL, 24 h	IL-1β, IL-6, TNF-α, IL-18; NLRP3 inflammasome	Bax, Bcl-2; caspase-3	–	–	Altered amino-acid, purine, homocysteine metabolism	PI3K–AKT and HIF-1 pathways	[290]
PS, PE, PP (100 nm, 1 µm, spherical)	C57BL/6 mice: 10 mg/kg, days 1, 7, 13, 19BEAS-2B cells: 0–200 μg/mL, 24 h	IL-1β, IL-6, IL-1R1; macrophage (F4/80) and neutrophil (MPO) recruitment	Reduced cell viability (BEAS-2B)	Pulmonary fibrosis, collagen deposition, ECM imbalance (α-SMA, collagen I, TIMP-1/MMP13), EMT (Vimentin, N-cadherin; E-cadherin)	—	—	FXR / YAP1 axis dysregulation	[291]

Other studies have demonstrated that MNPLs composed of polymers other than PS also exert deleterious effects. PMMA-NPLs (50 nm) induced senescence-dominant toxicity in multiple cell types and C57BL/6 mice, marked by elevated SASP cytokines (IL-6, IL-1, TNF-α, CCL5, CXCL10), oxidative stress, DNA damage (γ-H2AX foci, double-strand breaks, micronuclei) and genomic instability, G1 arrest, β-gal–positive senescence, and activation of the cGAS–STING–TBK1–IRF3 pathway and NHEJ repair [109]. PVC-NPLs (50 nm) exposure in HEEC, HET-1 A, and 293T cells and C57BL/6 mice induced IL-6, TNF-α, IFN-γ, CCL5, and CXCL10, triggered senescence (p16, p21, LaminB1) and apoptosis, caused esophageal inflammation, generated ROS, γ-H2AX, double-strand breaks (DSBs), HDR (GRB2, BRCA2) and chromosomal aberrations, and activated the cGAS–STING–TBK1–IRF3 pathway [110]. PET (100–120 μm, irregular) exposure in male C57BL/6 mice and cardiomyocytes induced IL-1β, IL-6, TNF-α, IL-18, and NLRP3 inflammasome activation; triggered Bax, Bcl-2, and caspase-3 changes; altered amino acid, purine, and homocysteine metabolism; and activated PI3K–AKT and HIF-1 pathways [290]. Additionally, a multipolymer study using PS-, PE-, and PP-NPLs (100 nm–1 μm) in C57BL/6 mice and BEAS-2B cells demonstrated pronounced inflammatory signaling (IL-1β, IL-6, IL-1R1), increased immune-cell recruitment, reduced epithelial cell viability, pulmonary fibrosis characterized by extracellular matrix (ECM) remodeling, progression of epithelial–mesenchymal transition (EMT), and dysregulation of the FXR/YAP1 axis [291]. Notably, NPLs exposure resulted in greater immune-cell infiltration in mouse lung tissue than MPLs, indicating that NPLs more effectively activate the innate immune system and amplify local inflammatory responses. Although PS-, PE-, and PP-NPLs all induced pulmonary fibrosis, PS-NPLs elicited substantially more severe effects, including enhanced ECM deposition, EMT activation, inflammation, and cytotoxicity, attributable to its chemical composition. These findings indicate that polymer type is the primary determinant of plastic impacts at equivalent particle sizes, while decreasing particle size further exacerbates hazardous biological effects that may contribute to the development of a carcinogenic microenvironment.

Carcinogenic risk assessment in humans

Despite growing concern about MNPLs as environmental contaminants, direct epidemiological evidence linking MNPL exposure to cancer in humans is currently lacking. Experimental studies provide strong biological plausibility: MNPLs may induce oxidative stress, chronic inflammation, genotoxicity, and epigenetic alterations, all of which are recognized as potential mechanisms of carcinogenesis. Yet, translating these mechanistic findings into population-level risk remains challenging due to ubiquitous exposure, long latency periods of cancer, and the multifactorial nature of the disease [292]. To investigate MNPL-induced carcinogenesis epidemiologically, researchers would need to study populations with varying levels of exposure, measure MNPL presence in tissues, blood, urine, or feces, and correlate these findings with cancer incidence or progression. Appropriate study designs include prospective cohort studies, case–control studies, and cross-sectional surveys, with careful control for confounders such as age, lifestyle, and co-exposure to other pollutants. Emerging evidence from case–control studies highlight potential associations: MNPLs accumulation in colorectal cancer tissue has been reported to be significantly higher than in controls, suggesting that MNPLs, may contribute to colorectal carcinogenesis [102]. However, these studies are limited, and further research is needed to determine whether MNPL exposure contributes to cancer initiation or progression.

A recent meta-analysis of 43 studies encompassing over 1 million patients (32 case–control and 11 cohort studies) found that MNPL exposure was modestly associated with increased cancer risk in case–control studies (OR = 1.10, 95% CI 1.01–1.19) but not in cohort studies (OR = 1.04, 95% CI 0.96–1.12). Subgroup analyses suggested that phthalates (OR = 1.28) and bisphenol A (OR = 1.038) may contribute to risk, highlighting the role of chemical additives carried by microplastics [293]. Nevertheless, methodological limitations including small sample sizes, indirect exposure measures, and lack of precise quantification mean these associations must be interpreted cautiously. Occupational studies provide additional, though limited, evidence: workers exposed to airborne plastic dust in manufacturing and recycling settings show increased occurrences of lung diseases, including cancer, yet these studies often lack rigorous exposure assessment and rely on indirect indicators. Similarly, MNPLs and their chemical additives, including bisphenol A and phthalates, have been implicated in the rising incidence of metabolic syndrome and early-onset colorectal cancer, further supporting the need for systematic investigation [294]. The evidence is multi-faceted, as plastic additives are epidemiologically associated with elevated cancer risk, while MNPL particles independently may exert pro-carcinogenic effects Notably, recent studies have directly detected MNPLs in human gynecological tumor tissues, often at higher concentrations than in adjacent normal tissue, underscoring their clinical relevance [295]. Together, mechanistic, chemical, and clinical findings establish a compelling rationale for MNPLs as emerging environmental risk factors that may contribute to cancer initiation. A critical barrier in epidemiological research is accurate exposure assessment. Unlike classical carcinogens such as tobacco smoke or asbestos, MNPL exposure is diffuse, multifactorial, and occurs via ingestion, inhalation, and dermal contact. Standardized and validated exposure metrics are therefore essential, integrating dietary data, occupational histories, environmental monitoring, and lifestyle questionnaires. Without quantitative measurements, risk estimation and dose–response relationships remain uncertain.

Human biomonitoring offers a more direct approach. By measuring MNPLs and associated chemical additives in blood, urine, feces, lung tissue, placenta, or tumor samples, and combining these data with biomarkers of effect (oxidative stress, inflammation, DNA damage, epigenetic changes), researchers could begin to identify early carcinogenic mechanisms before disease develops. Therefore, integrating biomonitoring into large-scale epidemiological cohorts represents the most promising strategy to establish causality. Such studies could quantify internal MNPL burden, track long-term cancer incidence, and help define exposure thresholds and dose–response relationships. Using this approach allows for the examination of the probability that MNPLs contribute to cancer in humans and supports public health and safety decisions.

Mechanisms of micro- and nanoplastics–induced carcinogenesis

From various studies, it is observed that small NPLs are efficiently internalized into cells and penetrate tissues efficiently, reaching hepatic, intestinal, pulmonary, and reproductive cells (among others) being readily internalized by intestinal cells via endocytosis. This facilitates their accumulation within cells and tissues, making them difficult to be metabolized and degraded [276]. As primary contact points for MNPL exposure, body barriers retain these particles, leading to hazardous effects through physical stress. In the gastrointestinal tract, MNPL accumulation disrupts epithelial barrier integrity by altering tight junction proteins (Claudin-1, Occludin, ZO-1), increasing circulating lipopolysaccharide levels, and reshaping gut microbiota. Irregular sharp-edged MPL fragments may cause more physical damage to tissues, and MPL fibers have been associated with a greater potential for cellular entanglement and respiratory issues digestive blockage [155, 156]. These changes promote immune cell infiltration, including dendritic cells, macrophages, and neutrophils, and may trigger type 2 immune responses characterized by elevated Th2 cells and IL-4 [244, 262, 287]. MNPL retention in the gut impairs epithelial barrier integrity through MLCK-dependent tight junction disruption. This effect is driven by excessive ROS and redox imbalance, which activate the NF-κB/NLRP3 pathway and elevate pro-inflammatory cytokines (IL-1β, IL-6, IL-8, TNF-α) and can be mitigated by NLRP3 inhibitors or MLCK blockade [287].

The presence of MNPLs in cells induces oxidative stress, characterized by increased reactive oxygen species (ROS) and disruption of redox homeostasis through dysregulation of antioxidant enzymes such as SOD1/2, CAT, GPX1/3/4, HO-1, CATC, and GCLC, along with altered levels of MDA and GSH [264, 266]. Excess ROS led to widespread homeostasis disruption that could further make hazardous impacts including inflammation, mitochondrial dysfunction and DNA damage. At the cellular level, MNPL-induced oxidative stress activates inflammatory signaling pathways, most prominently NF-κB. Elevated ROS enhances NF-κB phosphorylation and transcriptional activity, driving the expression of pro-inflammatory mediators such as IL-1β, IL-6, TNF-α, and (Monocyte Chemoattractant Protein-1) MCP1. Notably, MNPLs can also activate NF-κB through oxidative stress–independent mechanisms, indicating convergence of multiple upstream signals on inflammatory pathways [260]. Excessive ROS amplify inflammation by promoting M1 macrophage polarization and mitochondrial dysfunction, which increases macrophage migration inhibitory factor (MIF) expression via a ROS–NF-κB–M1/MIF axis. MIF reinforces NF-κB signaling and apoptosis, establishing a positive feedback loop that intensifies oxidative stress and inflammatory injury, while MIF inhibition mitigates these effects [281]. In parallel, MNPLs activate innate immune sensing pathways, particularly the TLR4–NF-κB–NLRP3 inflammasome axis. This activation leads to NF-κB phosphorylation, upregulation of inflammasome components (NLRP3, ASC, caspase-1), GSDMD-mediated pyroptosis, and increased release of IL-1β and IL-18, collectively driving systemic inflammation and multi-organ injury [251, 262]. However, greater tissue deposition of MNPLs, along with enhanced cellular uptake and larger surface area, contributes to amplified inflammatory and fibrotic signaling [291].

MNPL exposure damages structurally and functionally, key cellular organelles, particularly mitochondria, and disrupts metabolic homeostasis at both cellular and systemic levels. Structurally, mitochondria exhibit membrane rupture, cristae loss, and swelling [288]. Functionally, dysregulation of genes such as Acot3, Abcc3, and Nr1i3 impairs glucose metabolism, alters mitochondrial membrane potential (MMP), and disrupts energy processing [267]. These changes lead to reduced glucose levels, altered lipid metabolism, lipid droplet accumulation, and altered serum biomarkers including AST, ALT, LDH, total cholesterol, and triglycerides [254]. Mitochondrial dysfunction may inhibit plasma membrane ATP-binding cassette transporter activity through ATP depletion [296]. Systemically, MNPL-induced metabolic disturbances are associated with reduced body weight, altered organ indices, and widespread pathway dysregulation, collectively contributing to tissue dysfunction and potentially promoting tumorigenesis [255]. MNPLs target the endoplasmic reticulum (ER), inducing ER stress primarily via the PERK–eIF2α–ATF4 signaling pathway. This activates downstream effectors, including ATF3 and PCK2, leading to dysregulation of gluconeogenesis intermediates and other metabolic pathways [284]. ER stress disrupts protein folding, exacerbates oxidative stress, and promotes apoptosis, collectively contributing to tumorigenic processes. ROS further amplifies ER stress, reinforcing cellular dysfunction and metabolic disturbances [288].

Smaller MNPLs can directly interact with DNA or cause damage indirectly via ROS. DNA damage manifests as single- and double-strand breaks (DSBs), oxidative lesions such as 8-OHdG, increased γ-H2AX foci, chromosomal aberrations, and activation of repair pathways including homologous recombination mediated by BRCA2 and GRB2 [110, 186, 196, 297]. Mitochondrial DNA (mtDNA) is also affected, evidenced by elevated 8-oxo-dG levels [106]. These genotoxic effects, combined with oxidative stress and mitochondrial dysfunction, promote genomic instability and may drive carcinogenesis, particularly when DNA repair mechanisms, such as those mediated by p53, are disrupted [190]. MNPL exposure triggers cell death pathways that contribute to tissue injury and potentially carcinogenesis. Apoptotic signaling is activated, evidenced by increased cleaved caspase-3 and caspase-9, upregulation of pro-apoptotic BAX, and downregulation of anti-apoptotic BCL2 [264]. Simultaneously, necroptotic pathways are engaged through MLKL and RIPK3 activation, amplifying cell death [192]. The combined activation of apoptosis and necroptosis disrupts tissue homeostasis, promotes chronic inflammation, and may create a tumor-permissive microenvironment, linking MNPL exposure to potential cancer development. However, the impact is widely related to physicochemical properties of MNPLs including polymer type, size and shape.

The hazardous mechanisms of MNPLs are strongly size dependent, with MPLs and NPLs eliciting distinct biological effects. Smaller particles are more readily internalized and accumulate within cells; accordingly, 100 nm PS particles induce greater epithelial barrier disruption and inflammatory responses than larger particles due to higher cellular uptake [298]. Immune cells such as macrophages also preferentially engulf NPLs over MPLs, leading to increased intracellular accumulation [299]. NPL exposure is further associated with upregulation of Fosl1 and activation of ferroptosis and p53 pathways, and inhibition of ferroptosis or Fosl1 knockdown alleviates cellular and tissue damage, identifying ferroptosis as a key mechanism of small MNPL-induced intestinal toxicity [286]. However, exposure of mice to PS particles of 70 nm and 5 μm showed that both sizes induced gut damage, but the larger 5 μm particles exerted a more pronounced disruptive effect on the gut microbiota [300]. MPLs (10 μm) induce injury mainly through physical stress and YAP-mediated inflammation, whereas smaller particles are more toxic due to higher surface area and cellular uptake [301]. 5 μm PS particles were more cytotoxic than 0.1 μm particles inducing greater mitochondrial depolarization via a mass effect on organelles causing physical damage to internalized cells [287, 302]. Supporting this, PS-MPLs (5 μm) reduced the expression of tight junction proteins in the blood–brain barrier [303]. Thereby, MNPLs exhibit size-dependent toxicity, with smaller particles inducing cellular uptake, oxidative stress, ferroptosis, and inflammation, and larger particles causing physical stress, mitochondrial dysfunction, and microbiota disruption.

Polymer composition is a key determinant of MNPL toxicity, often outweighing particle size. Although PS-, PE-, and PP-NPLs all induce pulmonary fibrosis, PS exerts more severe effects, including EMT activation, inflammation, and cytotoxicity, due to its aromatic structure that enhances interactions with cellular membranes and biomolecules [291, 304, 305]. In contrast, the chemically inert backbones of PE and PP confer lower toxicity. While most studies rely on spherical MNPLs, they still provide important insights, as smaller particles are readily translocated, cross biological barriers, and accumulate in tissues, increasing toxicological risk [306, 307]. Figure 4 summarizes experimental approaches used to investigate MNPL uptake, biodistribution, cellular internalization, and biological effects.

Fig. 4.

Diagnostic studies of MNPLs using in vitro and in vivo models. This figure summarizes experimental approaches used to investigate MNPL uptake, biodistribution, cellular internalization, and biological effects. In vitro and in vivo studies include cell-based and animal assays to evaluate cytotoxicity, oxidative stress, inflammation, organ-specific targeting, systemic toxicity, and signaling pathway activation, which may contribute to cancer progression. The figure was created using BioRender

Main signaling pathways induced by MNPLs

Inflammation fibrosis and cellular stress

MNPLs strongly activate inflammatory and stress-response pathways, disrupting cellular homeostasis and promoting a tumor-supportive microenvironment. Central to this is NF-κB signaling, where phosphorylation of p65 and upstream IKKα/β drives expression of pro-inflammatory and survival genes, including TNF-α, IL-4, IL-6, IFN-γ, NLRP3, IL-1β, IL-18, CD86, CD206, IL-1β and IL-12P70 [277, 279, 281]. MNPLs also stimulate chemokine signaling, enhance cell motility, and modulate immune responses [105], while TLR4–NF-κB activation further amplifies cytokine production and tissue injury [269]. Stress-responsive pathways such as JNK-MAPK and ERK1/2-MAPK are concurrently activated, reinforcing inflammation and cancer-related cellular responses [262]. Additionally, MNPLs induce apoptosis and fibrosis via TGF-β1/Smad signaling, ROS-driven ER stress (p-IRE1α, p-PERK, XBP1s, CHOP, p-JNK), and dysregulation of AKT1, TP53, caspases, and XIAP, while simultaneously engaging NF-κB, Nrf2/Keap1, and necroptotic pathways. Simultaneously, MNPLs trigger cellular stress and inflammatory responses through JAK1–STAT1/2/3, Erk1/2, and transcription factors p53, c-Fos, and ATF2, coordinating cytokine production, DNA damage responses, and apoptosis [279]. These combined effects drive cell death, extracellular matrix remodeling, and tissue alterations that collectively facilitate tumor progression [192, 202, 259, 288]. Most of these events are driven by the physical stress of MNPLs and their capacity to induce oxidative damage, which together trigger inflammation, cellular dysfunction, and tissue remodeling.

DNA damage and oxidative stress

Concurrently, MNPL exposure disrupts redox balance through activation of the p62/Keap1/Nrf2 pathway, leading to excessive oxidative stress that amplifies inflammation, DNA damage, and potentially cancer-related signaling [266]. ROS-induced mitochondrial dysfunction and activation of the NLRP3 inflammasome subsequently enhance the expression of proliferation and survival markers, including Cyclin D1, c-Myc, Bcl-2, and Ki67 [106]. In parallel, compensatory activation of the NRF2/HO-1 antioxidant response (NQO1, CAT, SOD1, GPX2, GSR) occurs alongside oncogenic β-catenin/Wnt signaling (Wnt1/Wnt7a, LEF1, c-JUN, PPARD), directly coupling oxidative stress to tumorigenic cellular reprogramming [186, 203]. These cellular disruptions and pathway alterations induce cytosolic DNA stress, activating the cGAS–STING pathway, which triggers downstream TBK1–IRF3 signaling and engages the NHEJ DNA repair machinery (Ku70/Ku80), linking DNA sensing to genotoxic stress and potential initiation of carcinogenesis [109]. As cellular stress escalates, MNPLs also target the endoplasmic reticulum, inducing ER stress predominantly through the PERK–eIF2α–ATF4 pathway. This response upregulates ATF3 and downstream metabolic regulators such as PCK2, leading to metabolic dysregulation, impaired cellular homeostasis, and further enhancement of tumorigenic potential [284].

Proliferation and tumor-permissive microenvironment

Exposure to MNPLs drives tumorigenic processes by activating interconnected signaling pathways that promote cell proliferation, metabolic reprogramming, and survival. Metabolic and growth regulators, including AKT, AMPKα, mTOR, P70S6K, PDK1, GSK3α/β, PRAS40, PTEN, Raf-1, and RSK1/2, are dysregulated, further promoting proliferation and survival [279]. Additionally, the PI3K-AKT-mTOR pathway is upregulated, enhancing growth, inhibiting apoptosis, and supporting tumor progression [282, 283]. MNPLs also dysregulate the Notch pathway (Jagged1/2, Notch1/2/3), the Fosl1–p53 axis, YAP-mediated glycolysis, and the FXR/YAP1 axis, further reinforcing proliferative and metabolic changes [285, 286, 291]. Concurrently, oncogenic drivers such as KRAS, MET, RET, and epithelial–mesenchymal transition (EMT) are activated, increasing invasiveness and metastatic potential [208]. MNPLs additionally modulate ECM–receptor interactions, focal adhesion, Hippo, TGF-β, FoxO, cAMP, Hedgehog, and hormone signaling, reshaping the tumor microenvironment and promoting uncontrolled proliferation [197, 198]. Other effects include FGFR2–Ras activation, cytoskeleton disruption, ABC transporter inhibition, and dysregulation of cell-cycle regulators (CDK4/6, Cyclin D1, p-Rb), collectively driving malignant transformation and cancer progression [193, 194].

Together, MNPLs may induce cancer through a complex interplay of interrelated signaling pathways that disrupt cellular and tissue homeostasis. MNPLs generate oxidative stress, which activates inflammatory pathways and mitochondrial dysfunction, while also triggering ER stress and apoptosis/necroptosis. These disturbances lead to DNA damage, genomic instability, and activation of stress-response pathways such as cGAS–STING and Nrf2/Keap1, linking cellular stress to oncogenic signaling. Simultaneously, MNPLs stimulate proliferative and survival pathways, including PI3K-AKT-mTOR, Notch, Hippo, YAP-mediated glycolysis, and EMT, while reshaping the extracellular matrix, focal adhesions, and cell-cycle regulators. The combined effect of these interconnected pathways potentially creates a tumor-permissive microenvironment characterized by chronic inflammation, impaired tissue integrity, metabolic reprogramming, and enhanced cellular proliferation, collectively may promoting malignant transformation, tumor progression, and metastasis.

Future perspectives

The oncogenic potential of MNPLs is determined by multiple interdependent factors, including polymer composition, particle size and shape, dose, exposure duration, and the presence of intrinsic or adsorbed contaminants. However, most current studies predominantly employ pristine spherical PS-MNPLs, which poorly reflect real-exposure conditions. Evidence from environmental samples and human tissues whether tumorous, peritumoral, or healthy, indicates that MNPLs are largely composed of diverse polymer types and predominantly occur as irregular fragments and fibers rather than uniform spheres. Because these parameters interact in complex and often non-linear ways, realistic experimental designs are essential. Systematic studies should therefore be guided by empirical environmental and human tissue data, incorporating representative MNPL sizes, polymer compositions, and morphologies. Prioritizing environmentally relevant MNPL characteristics will be pivotal for accurately assessing exposure scenarios and elucidating the true oncogenic potential of MNPLs. Consequently, the future challenges must move to use real-life MNPLs resulting from the degradation of plastic goods. This is the most realistic way to describe the biological effects (including cancer) of environmental MNPLs.

Almost all monitoring studies, whether conducted in environmental matrices, biological samples, or human tissues, have predominantly identified MPLs, with NPLs rarely reported. This systematic underrepresentation of NPLs remains a major concern, despite strong biological plausibility that their small size, high surface reactivity, and enhanced tissue penetration make them the dominant and potentially more toxic fraction of plastic debris. The apparent absence of NPLs in most studies is likely reflecting analytical blind spots rather than true biological scarcity. Widely used analytical methods are limited by inadequate size resolution, high detection thresholds, and, in some cases, destructive sample preparation procedures. Notably, pyrolysis–gas chromatography–mass spectrometry (Py-GC–MS), while highly effective for polymer identification, inherently destroys particle morphology, thereby precluding size determination and biasing datasets toward mass-based rather than particle-based interpretations [52, 78]. Together, these limitations highlight critical methodological/ detections gaps, including the need for harmonized extraction and reporting protocols, the integration of non-destructive, high-resolution techniques capable of capturing the full nano-micro scaled particles. Addressing these gaps is essential for accurately quantifying plastic burdens in cancer tissues and for strengthening mechanistic and epidemiological links between plastic exposure and carcinogenesis.

An important methodological shortage in current research examining MNPLs in human cancer tissues is the profound lack of standardization in particle extraction, quantification, and particularly reporting. Existing studies report MNPL burdens using heterogeneous metrics such as particle number per sample, particle number per tissue weight, or polymer mass per gram limiting cross-study comparability and precluding robust conclusions regarding true MNPLs burdens in tumors. This inconsistency undermines meta-analytical efforts and weakens causal inference in cancer risk assessment. Comprehensive harmonization remains challenging because many studies rely exclusively on particle-number–based metrics rather than mass-based units. This disparity highlights the urgent need for unified analytical and reporting frameworks in MNPL-related cancer research to enable meaningful comparisons and to strengthen conclusions regarding MNPL concentrations in tumor tissues. However, in this review, we attempted to address this limitation as far as possible by relying on available literature data to calculate an average plastic particle mass of approximately 0.4 µg (see Table 1 and Sect.  Micro/nanoplastics contaminate human food and beverages, thereby enabling more comparable estimates of microplastic burdens identified across different human tissues. On the other hand, most diagnostic and monitoring studies, whether in vitro or in vivo, use MNPL concentrations in the µg/mL range, which do not directly reflect human exposure, as human studies often report MNPLs in different units. This scenario complicates the contextualization of experimental doses relative to estimated human exposure. To address this gap, more human monitoring studies are needed to quantify actual MNPL exposure, considering different routes, exposure levels, and potential bioaccumulation. Diagnostic studies should use measurement units comparable to human exposure assessments and account not only for the administered dose but also for the fraction of particles effectively internalized.

Despite increasing interest in the carcinogenic potential of MNPLs, major knowledge gaps persist. Moreover, only a small fraction of studies has systematically linked MNPL physicochemical properties, such as size, shape, surface chemistry, and polymer composition, to these biological effects, limiting mechanistic interpretation. Notably, of the 4,705 articles screened since 2017, only 223 explicitly investigated oncogenic mechanisms associated with MNPL exposure, underscoring the urgent need for focused, property-driven mechanistic research [188]. Consequently, current evidence supports MNPLs as potential cancer risk indicators rather than confirmed causal drivers of carcinogenesis.

The absence of tumor formation in short-term exposure studies underscores the need for long-term experiments, environmentally realistic exposure scenarios, and human-relevant models to adequately assess MNPL-induced gastric toxicity and carcinogenic risk [186, 213]. Current adverse outcome pathway (AOP) frameworks primarily identify oxidative stress and mitochondrial dysfunction as central mechanisms of microplastic-induced gastric toxicity, providing a valuable conceptual foundation for risk assessment and management. Within these AOPs, increased ROS production is proposed as the molecular initiating event, triggering oxidative stress, mitochondrial damage, apoptosis, and subsequent tissue injury. While antioxidant-based interventions, such as N-acetylcysteine (NAC), have demonstrated efficacy in suppressing ROS overproduction and reducing apoptosis in vitro, existing AOP models largely focus on intracellular ROS. This narrow focus overlooks additional ROS sources, including extracellular radicals generated through environmental weathering, photooxidation, or reactions with salivary nitrates and nitrites, which may substantially amplify MNPL toxicity [308, 309]. Importantly, inflammation, a hallmark consistently reported across MNPL exposure studies, remains insufficiently integrated into current AOP frameworks despite its well-established role in linking chronic tissue injury to carcinogenesis. Persistent inflammatory signaling may promote genomic instability, dysregulated cell proliferation, and tumor-promoting microenvironments, positioning inflammation as a critical intermediate key event between MNPL exposure and cancer development. Expanding AOP models to explicitly incorporate inflammatory pathways, alongside comprehensive evaluation of all ROS and radical species, will be essential for identifying effective intervention targets and for strengthening mechanistic links between MNPL-induced toxicity and carcinogenesis [266].

Although numerous in vitro and in vivo studies have reported carcinogenesis-related responses, including oxidative stress, genotoxicity, chronic inflammation, and disrupted signaling pathways, this evidence remains largely indirect. Direct demonstrations of tumor initiation or promotion following MNPL exposure in cancer-relevant tissues are still lacking. To fill this critical gap, greater use of genetically engineered and disease-relevant models is required. Such models can provide mechanistic insights into direct interactions between MNPL exposure and tumor development. However, only a limited number of studies have exploited these powerful systems. For example, Aloisi et al. [310] employed warts-defective D. melanogaster mutants to assess the carcinogenic potential of PS-NPLs, demonstrating enhanced tumor-like phenotypes in exposed flies. Given the extensive availability of genetically tractable D. melanogaster models, comprising tens of thousands of strains worldwide, with approximately 88,000 readily accessible through the Bloomington Drosophila Stock Center, this organism and other similar models with different species represent an underutilized yet highly powerful experimental platform. These resources enable systematic interrogation of MNPL effects at the level of individual cancer-related genes, signaling pathways, and tumor suppressor networks. Leveraging such models could substantially advance causal inference, identify susceptible molecular targets, and strengthen mechanistic understanding of MNPL-induced carcinogenesis.

Many limitations in current studies arise from variability in monitoring, diagnostic approaches, and the lack of methodological standardization. As a result, traditional experimental methods alone are insufficient to capture the complexity of MNPL-induced carcinogenesis that encourage to fully leverage recent advances in artificial intelligence (AI). Computational and AI-based modelling offer powerful complementary tools by integrating large-scale toxicological, molecular, and exposure datasets to predict carcinogenic risk, identify high-risk particle properties, and prioritize experimental targets. Additionally, AI-driven technologies could enhance MNPLs monitoring by improving particle detection, characterization, and exposure assessment, thereby reducing methodological discrepancies and promoting standardization. However, these advances are employed to mechanistic understanding of the MNPL-cancer relationship and informing effective risk mitigation strategies [311, 312]. Integrated experimental and computational frameworks therefore provide a comprehensive strategy to address current gaps in detection, exposure assessment, and mechanistic insight, highlighting the need to leverage these smart tools in future studies.

Conclusion

Micro- and nanoplastics (MNPLs) are widely detected in human tissues, including cancerous tissues, where their concentrations are generally higher than in adjacent pre-tumor or healthy tissues, suggesting a potential link to MNPL-associated carcinogenicity. The highest concentrations are observed in lung and intestinal tissues, likely reflecting their role as primary contact points for environmental exposure. Predominant polymers include PE, PP, PVC, and PA, with particles mainly appearing as fiber or fragments ranging from 1 μm to several millimeters, mirroring the types, sizes, and shapes found in direct exposure sources such as food, beverages, and the atmosphere. These findings underscore the critical role of MNPL physicochemical properties, including polymer composition, size, shape, and surface chemistry, in governing tissue accumulation, cellular uptake, and biological impacts, a relationship further confirmed by various diagnostic studies. Most of the literature primarily focuses on pristine spherical PS-MNPLs, which provide valuable insights but cannot fully represent the diversity of polymer types and shapes found in real-world exposures. Furthermore, methodological limitations, including detection thresholds and challenges in standardized reporting, hinder the accurate characterization of MNPLs, particularly NPLs, and their mechanistic contributions to carcinogenesis. Addressing these gaps should be a priority to enhance our understanding of how MNPLs contribute to cancer development.

In vitro and in vivo diagnostic models have provided valuable insights into the mechanistic impacts of MNPLs and their potential role in increasing cancer risk. The distribution and retention of MNPLs in the gastrointestinal tract are strongly influenced by particle size and shape. MNPL accumulation in the gastrointestinal tract disrupts epithelial barrier integrity, alters tight junction proteins (ZO-1, OCLN, CLDN-1, CLDN-2), and reshapes the gut microbiota, promoting immune cell infiltration and type 2 immune responses, including increased Th2 cells and IL-4. Spherical smaller particles are more readily able to cross biological barriers, disseminate throughout the body, penetrate deep tissues, and interact closely with cellular components, including lipids and DNA, potentially causing molecular damage that may contributes to carcinogenesis. MNPLs, whether they retain in gastric or those crossing barriers, induce physical stress which is reflected with direct inflammation as reflected by IL-1β, IL-6, TNF-α, MCP-1, IL-17α, IL-22, TLR-4, iNOS, COX2, and NF-κB biomarkers that almost is the shared respond in most of diagnostic studies. Another important scenario associated with MNPLs is the oxidative stress whether detect from increase free radical as ROS or disruption redox homeostasis by deregulation various antioxidant enzymes as SOD1/2, CAT, GPX1/3/4, HO-1, CATC, GCLC MDA, and GSH among others.

MNPLs also attack one of the govern cellular as mitochondria whether physically or at functional issues mediating dysfunction, damage, swelling, vacuolation, reduced matrix and alter mitochondrial membrane potential (MMP). Furthermore, MNPL exposure disrupts metabolic homeostasis at both cellular and systemic levels, affecting glucose, lipid, and nucleotide metabolism. Dysregulation of key genes such as Acot3, Abcc3, and Nr1i3 impairs glucose metabolism and mitochondrial function. Functional outcomes include reduced glucose levels, altered lipid metabolism, lipid droplet accumulation, and changes in serum biomarkers including AST, ALT, LDH, total cholesterol, and triglycerides. These metabolic disturbances are accompanied by reduced body weight, altered organ indices, and widespread pathway dysregulation, collectively reflecting systemic metabolic stress that may contribute to tissue dysfunction and tumorigenesis. MNPLs induce endoplasmic reticulum (ER) stress, primarily via activation of the PERK–eIF2α–ATF4 signaling pathway. Moreover, MNPL exposure triggers programmed cell death through both apoptosis and necroptosis. MNPL exposure may induce extensive DNA damage, including double-strand breaks (DSBs) and oxidative lesions such as 8-OHdG. This is reflected by increased γ-H2AX foci, activation of DNA repair pathways including homologous recombination mediated by BRCA2 and GRB2, and chromosomal aberrations. These genotoxic effects, combined with oxidative stress and mitochondrial dysfunction, contribute to genomic instability and may promote carcinogenesis. Apoptotic pathways are activated via increased cleaved caspase-3 and caspase-9, upregulation of pro-apoptotic BAX, and downregulation of anti-apoptotic BCL2. Concurrently, necroptotic signaling involves MLKL and RIPK3 activation, further promoting cell death and tissue injury. These processes, combined with oxidative stress, mitochondrial dysfunction, and DNA damage, contribute to a pro-tumorigenic microenvironment and may facilitate cancer development. Since the serious impact in not happen in separated response but occurred via integrated and coordinated networks govern by various cellular and molecular signals.

Exposure to MNPLs initiates a cascade of cellular disturbances that could collectively promote carcinogenesis. They trigger DNA damage and oxidative stress through activation of cGAS–STING, β-catenin/YAP, and p62/Keap1/Nrf2 pathways, causing mitochondrial dysfunction, ROS accumulation, and NLRP3 inflammasome activation, which upregulate proliferation and survival markers. ER stress is induced via the PERK–eIF2α–ATF4 pathway, while inflammatory signaling is driven by NF-κB, TLR4, JNK-MAPK, ERK1/2-MAPK, and chemokine pathways, amplifying chronic inflammation, immune modulation, and tissue injury. MNPLs further promote apoptosis dysregulation and fibrosis through TGF-β1/Smad signaling, ROS-mediated ER stress, and modulation of AKT1, TP53, caspases, XIAP, NF-κB, and Nrf2/Keap1, remodeling the extracellular matrix and sustaining survival of damaged cells. Proliferation and tumorigenic reprogramming are enhanced via PI3K-AKT-mTOR, Notch, Fosl1–p53, YAP/FXR, KRAS/MET/RET, EMT, Hippo, TGF-β, FoxO, Hedgehog, ECM–receptor interactions, FGFR2–Ras, and cell-cycle regulators including CDK4/6, Cyclin D1, and p-Rb. By sequentially disrupting genomic integrity, redox balance, metabolic homeostasis, inflammatory control, apoptosis, and proliferation, MNPLs create a microenvironment conducive to tumor initiation, progression, and metastasis. Accordingly, the hazardous impacts of MNPL exposure raise serious concerns, as these particles could trigger irreversible and unrepaired cellular damage, potentially leading to cancer and posing a significant threat to human health. Figure 5 illustrates how MNPLs may influence multiple cellular pathways, including NRF2/HO-1 (oxidative stress response), β-catenin/Wnt (cell proliferation and survival), JAK–STAT (inflammation and immune regulation), and PI3K–AKT–mTOR (cell growth, metabolism, and anti-apoptosis), leading to potential impacts on mitochondrial function, oxidative stress, inflammation, and carcinogenesis.

Fig. 5.

Key signaling pathways modulated by MNPLs. This figure illustrates how MNPLs can influence multiple cellular pathways, including NRF2/HO-1 (oxidative stress response), β-catenin/Wnt (cell proliferation and survival), JAK–STAT (inflammation and immune regulation), and PI3K–AKT–mTOR (cell growth, metabolism, and anti-apoptosis), leading to potential impacts on mitochondrial function, oxidative stress, inflammation, and carcinogenesis. The figure was created using BioRender

Abbreviations

AKT1 / p-AKT

AKT serine/threonine kinase 1 / Phosphorylated protein kinase B

AMPKα

AMP-activated protein kinase alpha

ATF3,4

Activating transcription factor 3,4

Bax

Pro-apoptotic protein

BCL-2 / Bcl-2

B-cell lymphoma 2

CDK4

Cyclin-dependent kinase 4

CHOP

C/EBP homologous protein

CLDN-1

Claudin-1

Cyclin D1

G1/S-specific cyclin D1

ECM

Extracellular matrix

Fosl1

Fos-like antigen 1

GSK3α/β

Glycogen synthase kinase 3 alpha/beta

GSH-Px / GSH-PX

Glutathione peroxidase

GSSG

Glutathione disulfide

HIF-1

Hypoxia-inducible factor 1

HO-1 / HMOX1

Heme oxygenase-1

ICAM-1

Intercellular adhesion molecule-1

IL- / IL-1β

Interleukin / Interleukin-1 beta

IRF5

Interferon regulatory factor 5

JNK / p-JNK

c-Jun N-terminal kinase / Phosphorylated JNK

Ki67

Cell proliferation marker

LDH

Lactate dehydrogenase

MLCK

Myosin light chain kinase

MDA

Malondialdehyde

MAPK

Mitogen-activated protein kinase

MMP-9

Matrix metalloproteinase-9

NF-κB

Nuclear factor kappa B

NHEJ (Ku70/Ku80)

Non-homologous end joining (Ku70/Ku80)

NQO1

NAD(P)H: quinone oxidoreductase 1

Nrf2

Nuclear factor erythroid 2–related factor 2

NLRP3

Nucleotide-binding domain and leucine-rich repeat protein 3

NKCC1

Sodium-potassium-chloride cotransporter 1

OCLN

Occludin

PA

Polyamide (Nylon 88)

PC

Polycarbonate

PE

Polyethylene

PET

Polyethylene terephthalate

PM

Polyoxymethylene

PMMA

Polymethyl methacrylate

PP

Polypropylene

PRAS40

Proline-rich AKT substrate 40 kDa

PCK2

Phosphoenolpyruvate carboxykinase 2

PTEN

Phosphatase and tensin homolog

PTFE

Polytetrafluoroethylene

PVDF

Polyvinylidene fluoride

PLA

Polylactic acid

PU

Polyurethane

P70S6K

70 kDa ribosomal protein S6 kinase

PDK1

3-phosphoinositide-dependent protein kinase-1

RSK1/2

Ribosomal S6 kinases 1 and 2

PS

Polystyrene

p-Rb

Phosphorylated retinoblastoma protein

PPAR-γ

Peroxisome proliferator-activated receptor gamma

PRAS40

Proline-rich AKT substrate 40 kDa

ROS

Reactive oxygen species

SOD

Superoxide dismutase

TGF-β

Transforming growth factor β

TLR4/NOX2

Toll-like receptor 4 / NADPH oxidase 2

ΔΨm (MMP)

Mitochondrial membrane potential

XIAP

X-linked inhibitor of apoptosis protein

YAP

Yes-associated protein

γ-H2AX

Phosphorylated H2AX

Authors’ contributions

Mohamed Alaraby and Ricard Marcos provided the framework and direction for this review. Mohamed Alaraby and Doaa Abass collect and organize the literature. The manuscript was written by Mohamed Alaraby and Doaa Abass and revised by Alba Hernández and Ricard Marcos. All authors read and approved of the final manuscript.

Funding

Funding M. Alaraby holds a Beatriu de Pinós contract at the UAB (Departament de Recerca i Universitats de la Generalitat de Catalunya, expedient: 2022-BP-00026). A. Hernández was granted an ICREA ACADEMIA award. The PlasticHeal project has received funding from the European Union’s Horizon 2020 research and innovation program under grant agreement No 965196. This study was supported by the Spanish Ministry of Science and Innovation (PID2020-116789RB-C43) and the Generalitat de Catalunya (2021-SGR-00731).

Data availability

No datasets were generated or analysed during the current study.

Declarations

Ethics approval and consent to participate

Not applicable.

Consent for publication

All authors have reviewed and approved the publication of this manuscript.

Competing interests

The authors declare no competing interests.