The Emerging Threat of Micro- and Nanoplastics on the Maturation and Activity of Immune Cells

Abstract

With the increasing use of plastics worldwide, the amount of plastic waste being discarded has also risen. This plastic waste undergoes physical and chemical processes, breaking down into smaller particles known as microplastics (MPs) or nanoplastics (NPs). Advances in technology have enhanced our ability to detect these smaller particles, and it has been confirmed that plastics can be found in marine organisms as well as within the human body. However, research on the effects of MPs or NPs on living organisms has only recently been started, and our understanding remains limited. Studies on the immunological impacts are still ongoing, revealing that MPs and NPs can differentially affect various immune cells based on the material, size, and shape of the plastic particles. In this review, we aim to provide a comprehensive understanding of the effects of MPs and NPs on the immune system. We will also explore the methods for plastic removal through physicochemical, microbial, or biological means.

INTRODUCTION

Plastics have been manufactured and used in large amounts since the 1950s, and as of 2021, the global production of plastics exceeds 390 million tons and plastic waste disposal reaches 350 million tons annually (PlasticsEurope, 2020). However, only 5% of the plastic waste undergoes recycling, while the vast majority is discarded in landfills and the ocean (Hahladakis and Iacovidou, 2018). Upon entering ecosystems, the plastic wastes break down into smaller fragments through physical, chemical, and biological processes. Microplastics (MPs) are plastic particles less than 5 mm in length, and have emerged as a substantial environmental concern in recent years (Arthur et al., 2009). The sources of MPs are diverse from industrial processes to everyday consumer products. These tiny particles are ubiquitous in our environment, and are found in oceans, rivers, lakes, soil, air, and even in the food and water (Kunz et al., 2023). The prevalence of MPs in our environment is a direct consequence of negligent global plastic consumption, and the accumulation of plastic particles in our ecosystems has become a major environmental concern.

Plastic debris can be ingested by marine life and bioaccumulate in the food chain. In addition, humans are directly exposed to MPs through the use of plastic products and other sources, such as contaminated food and water. Notably, a recent study reported that 240,000 MP particles are present in bottled water and underscored their abundance in common items we consume daily (Qian et al., 2024). Once ingested, MPs are dispersed to various organs and affect their normal physiological functions. Although the primary routes of exposure are inhalation and ingestion, MPs can enter the bloodstream and lymphatic circulation, and reach other organs such as the liver, heart, and brain (Urban et al., 2000; Horvatits et al., 2022; Jenner et al., 2022; Leslie et al., 2022; Paing et al., 2024; Wang et al., 2024a). As the plastic particles present significant threats to both ecosystem and human health, the environmental and potential health impacts of MPs are major subjects of research.

This review aims to explore the effects of MPs on immune cells. Specifically, we will examine how MPs interact with the immune system, and the mechanisms by which they may trigger or modulate immune responses (Fig. 1). Furthermore, we will discuss various techniques to degrade or remove MPs from the environment through physicochemical methods and eco-friendly biological approaches. By integrating current research findings and identifying future research directions, we seek to provide a comprehensive understanding of the effects of MPs on the immune system, and emerging strategies in combating MP pollution, and contribute to the broader discourse on the health risks associated with MP exposure.

Fig. 1.

Graphical abstract.

CHARACTERISTICS AND CLASSIFICATION OF MICROPLASTICS

MPs are tiny plastic particles ranging from 1 μm to 5 mm in size, and particularly those smaller than 1 μm are often classified as nanoplastics (NPs) (Koelmans et al., 2015; Ghosh et al., 2023). MPs can be categorized into primary MPs and secondary MPs based on their origin. Primary MPs are directly generated for commercial use, such as microbeads found in personal care products and synthetic fibers released from fabrics during washing process. In contrast, secondary MPs are derived from the breakdown of larger plastic items due to environmental factors including UV radiation, mechanical abrasion, and weathering processes (Mepex for the Norwegian Environment Agency, 2014; GESAMP, 2016). The composition of MPs includes polyethylene terephthalate (PET), high-density polyethylene (HDPE), low-density polyethylene (LDPE), polypropylene (PP), polystyrene (PS), and polyvinyl chloride (PVC), polylactic acid (PLA), polyurethane (PU), etc. (Table 1). Among these, PLA, polybutylene succinate (PBS), poly-ε-caprolactone (PCL), polybutylene succinate-co-adipate (PBSA) are biodegradable (Tokiwa et al., 2009). These diverse polymer types contribute to the varied environmental fates and potential harmful effects on ecosystems.

Table 1.

Structure of plastics

Type	Chemical structure	Biodegradability	Density (g/cm3)	Reference
PBS (polybutylene succinate)		Biodegradable	1.26 ± 0.26	Saffian et al., 2021
PBSA (polybutylene succinate-co-adipate)		Biodegradable	1.25	Niang et al., 2022
PCL (poly-ε-caprolactone)		Biodegradable	1.14	Li et al., 2017
PLA (polylactic acid)		Biodegradable	1.25-1.49	Fredi and Dorigato, 2021
PU (polyurethane)		Biodegradable	1.20-1.26	Campanale et al., 2020
PE (polyethylene)		Non-biodegradable	0.94-0.96	Tong et al., 2024
PET (polyethylene terephthalate)		Non-biodegradable	1.35-1.39	Tong et al., 2024
PP (polypropylene)		Non-biodegradable	0.89-0.91	Tong et al., 2024
PS (polystyrene)		Non-biodegradable	1.04-1.09	Tong et al., 2024
PVC (polyvinyl chloride)		Non-biodegradable	1.38-1.48	Tong et al., 2024

One of the most problematic features of MPs is their resistance to degradation, which enables their long-term presence in the environment. In addition, their small size and large surface area-to-volume ratio allow them to interact with various environmental substances, and accumulate pollutants and toxic chemicals (Yang et al., 2023b). Understanding the characteristics of MPs is essential for assessing the harmful effects of MPs on ecosystems and human health, and developing effective strategies to manage MP pollution.

EFFECTS OF MICROPLASTICS ON THE IMMUNE SYSTEM

MPs have been shown to exert toxic effects on various cell types, particularly immune cells, through multiple mechanisms (Table 2) (Hwang et al., 2019; Banerjee and Shelver, 2021; Huang et al., 2021; Shengchen et al., 2021; Hua et al., 2022; Liu et al., 2022). Briefly, when macrophages are exposed to polystyrene MPs, they exhibit increased production of pro-inflammatory cytokines such as TNF-α and IL-1β, indicating an inflammatory response. Studies on human lymphocytes demonstrate that MPs can induce oxidative stress and DNA damage, potentially compromising immune function (Sangkham et al., 2022). In zebrafish, exposure to MPs has been found to alter the expression of genes related to oxidative stress and apoptosis in immune tissues, and marine organisms such as mussels exhibit changes in hemocyte counts and phagocytic activity following MP ingestion, suggesting impairment of innate immune responses (Yuan et al., 2023). In addition, ingestion of MPs can also alter the composition and diversity of gut microbiome (Yuan et al., 2023; Zhang et al., 2023). This dysbiosis can lead to inflammation, increased intestinal permeability, and other adverse health effects. These harmful effects of MPs are often size-dependent, and smaller particles generally elicit more pronounced immune reactions due to their ability to penetrate cellular membranes more easily. The toxicity of MPs on immune cells raises concerns about the potential long-term impacts on the overall function of immune system and susceptibility to diseases in both wildlife and humans (Li et al., 2022).

Table 2.

The effects of micro- and nanoplastics on immune cells

Cell type	The effects of MPs and NPs	Reference
Macrophage	Induction of apoptosis and cell cycle arrest (PS-NP) Oxidative stress (PS-MP, -NP) Production of pro-inflammatory cytokines (PS-MP, -NP, PE-MP) Activation of MAPK and NF-κB pathways (PS-NP) Mitochondrial damage and increased membrane potential (PS-MP, -NP) Lysosomal damage (PE-NP, PS-NP) Formation of extracellular traps (PS-MP)	Vlacil et al., 2021; Koner et al., 2023; Xuan et al., 2024 Collin-Faure et al., 2023 Busch et al., 2022; Alijagic et al., 2023 Tang et al., 2022; Chen et al., 2023a Chen et al., 2023b Florance et al., 2021; Yin et al., 2023 Yin et al., 2023
Dendritic Cell	Upregulation of genes associated with pDC activation (PE-MP) Decreased number of DCs in the small intestine after exposure (PE-MP) Production of pro-inflammatory cytokines after exposure (PVC-NP)	Yang et al., 2023a Djouina et al., 2022 Weber et al., 2022
Neutrophil	Formation of extracellular traps (PS-NP)	Zhu et al., 2022
T cell	Decreased number of CD4 and CD8 T cells in the small intestine after exposure (PE-NP) Reduction of intraepithelial T lymphocytes after exposure (PS-NP) Inhibition of T cell activation in mesenteric lymph node (MLN) after exposure (PS-MP) Activation of T cell in fatty liver (PS-MP) Th2, Th17, and Treg increased after exposure (PE-MP) Th2-dominant response after exposure (PP-MP)	Djouina et al., 2022 Li et al., 2024 Rawle et al., 2022 Liu et al., 2024 Yang et al., 2023a Kusma et al., 2024
B cell	Inhibition of B cell receptor signaling (PS-MP) Increased number in the mesenteric lymph nodes after exposure (PS-NP) Class switching favoring IgG1 over IgG2 due to IL-4 (PP-MP)	Huang et al., 2023 Li et al., 2024 Kusma et al., 2024
NK cell	Maturation of NK cells in the liver following exposure (PS-MP)	Zhao et al., 2021

IMMUNOTOXICITY OF MICROPLASTICS ON MYELOID CELLS

The immunotoxicity of MPs on myeloid cells, particularly macrophages, has been extensively studied. While macrophages are capable of phagocytosing MPs, exposure to these particles damages lysosomes and disrupts lipid metabolism, leading to lipid accumulation within the macrophages (Deng et al., 2017; Florance et al., 2022; Yin et al., 2023). This accumulation of lipids is linked to reactive oxygen species (ROS)-associated apoptosis. Both in vitro and in vivo research consistently show that MP-treated macrophages activate the MAPK and NF-κB pathways, leading to an elevation in ROS levels (Binatti et al., 2021; Tang et al., 2022; Chen et al., 2023a; Zhang et al., 2024). This activation is accompanied by increased expression of apoptotic proteins, including caspases-3, -7, and -9, along with an increase in mitochondrial transmembrane potential, ultimately causing cell death at higher MP concentrations (Koner et al., 2023; Yin et al., 2023). MP-treated macrophages also exhibit a pro-inflammatory response, marked by the increased production of pro-inflammatory cytokines, such as IL-1β, IL-6, and TNF-α, while anti-inflammatory cytokines including IL-10 are significantly reduced (Gautam et al., 2022; Chen et al., 2023a; Wang et al., 2024b). Moreover, MP exposure induces the formation of the NLRP3 inflammasome. Busch et al. reported that even in NLRP3^−/− THP-1 cells, neutrophil chemotactic factors such as IL-8 were released following treatment with polyester (PES), polyacrylonitrile (PAN), and polyamide 6 (PA6), underscoring the inflammatory potential of MPs (Busch et al., 2022; Alijagic et al., 2023). On the other hand, Huang et al. explored the gene profiles of LPS-challenged murine liver and suggested that MPs suppress the immune response by downregulating immune response genes and pathways (Huang et al., 2023).

According to Weber et al., dendritic cells as well as macrophages can internalize NPs (Weber et al., 2022). Interestingly, only irregular polydisperse PVC was found to trigger an inflammatory response in both monocytes and dendritic cells. This finding highlights an important case where the shape of the same plastic material can induce different immune responses. In a 10X genomics study by Yang et al., orally administered PE in mice led to the upregulation of genes linked to immune activation, such as Tnf, Cxcl2, Nlrp3, and Il1b, specifically within plasmacytoid dendritic cell (pDC) clusters (Yang et al., 2023a). Conversely, Djouina et al. observed a decrease in dendritic cells, inflammatory monocytes, and CD4⁺ and CD8⁺ T cells in the colons of mice treated with oral PE (Djouina et al., 2022).

In a study by Harusato et al., oral administration of 1μm-sized PET did not cause any histological damage to the colon, nor was neutrophil infiltration observed (Harusato et al., 2023). However, genes involved in immune regulation were downregulated. Another notable effect of MPs on neutrophils is the increased production of ROS, which induces the formation of neutrophil extracellular traps (NETs) (Zhu et al., 2022). Cytoplasmic ROS triggers the release of myeloperoxidase (MPO) from neutrophil granules, and MPO plays a crucial role in the formation of NETs. Similar findings were observed in the livers of mice, where macrophage extracellular traps were also detected (Yin et al., 2023).

IMMUNOTOXICITY OF MICROPLASTICS ON LYMPHOID CELLS

Recently, the immunotoxicity of MPs on lymphoid cells, including T cells and B cells, has gained significant attention, although the studies on lymphoid cells in relation to MP exposure are relatively scarce compared to those on myeloid cells.

Wolff et al. investigated how different sizes of MP affect T cells derived from peripheral blood mononuclear cells (PBMCs) (Wolff et al., 2023). After 24 h exposure, amino-modified PS treatment significantly decreased cell viability and downregulated CD25, CD62L, and PD-1 in CD4⁺ and CD8⁺ T cells, while poly methyl methacrylate (PMMA) and PS MPs showed minimal effects. When exposed for 72 h, PMMA MP led to changes in CD25 and CD62L expression. In addition, MP exposure altered cytokine secretion patterns with general downregulation of IL-1β and IFN-γ, and increases in CCL2, IL-17A, and IL-10. Corroborating these findings, Li et al. reported that PS-NP inhibits the activation of murine T cells and affects their immune function (Li et al., 2022). Upon stimulation with Staphylococcal endotoxin C2 (SEC2), PS-NP inhibited the expression of CD3⁺CD69⁺ and CD3⁺CD25⁺, as well as the secretion of IL-2 and IFN-γ from splenic T cells. Moreover, PS-NP suppressed the differentiation into CD8⁺ T cells, thereby impeding the development and function of cytotoxic T cells. Extending these findings, our recent unpublished observations have further revealed that PS-NPs significantly inhibit the proliferation of murine splenic CD4⁺ T cells and the differentiation of naïve CD4⁺ T cells into four CD4⁺ subsets (Th1, Th2, Th17, Treg cells). The effect of MPs on T cell function is not limited to in vitro studies. In the study with ICR mice, Kusma et al. showed that oral administration of PP-MPs causes an imbalance in immune homeostasis between Th1 and Th2 by lowering lFN-γ/IL-4 ratios (predominance of Th2) in the female mice (Kusma et al., 2024). Furthermore, Yang et al. reported an increase in Th2 (IL-4⁺CD4⁺), Th17 (IL-17a⁺CD4⁺), and Treg (FoxP3⁺CD4⁺) cells in the intestines of mice following oral ingestion of PE, further highlighting the role of MPs in disrupting immune homeostasis and creating an immunosuppressive environment (Yang et al., 2023a). In particular, in vivo studies suggest a close connection between macrophage inflammatory responses induced by MPs and T cell activation. Thus, if macrophages are hindered from responding to LPS stimulation, there is a possibility that T cell immune responses may also be reduced.

In addition to the effects of MP on T cells, MP can also interfere with B cell development and function. In primary cultures of rainbow trout (Oncorhynchus mykiss), PS-MP exposure affects B cell development by reducing the expression of Recombination Activating Gene-1 (RAG1) and the membrane form of immunoglobulin heavy chains μ and τ. As mentioned above, T cell immunomodulation by MPs promotes a Th2-dominant response that promotes B cell class switching to produce more IgG1 antibodies than IgG2 (Zwollo et al., 2021). In an in vivo study, exposure to PE-MPs inhibited B cell receptor signaling in the spleens of mice (Huang et al., 2023). Additionally, in vivo studies in mice administered with PS-NP-containing water revealed a decrease in B220⁺IgM⁺ B cells in the spleen (unpublished data).

The intake of PS-MPs for a month also led to an increase in natural killer cells in the liver (Zhao et al., 2021). When the liver was damaged, the presence of MPs enhanced the infiltration of DX5⁺ natural killer cells and M1 macrophages, while simultaneously reducing the numbers of PD-1⁺ B cells and T cells. This indicates that PS promotes the maturation of natural killer cells and suggests a decrease in anti-inflammatory responses, accompanied by an increase in inflammatory responses. These findings collectively underscore the detrimental effects of MPs on lymphoid cell functionality.

PHYSICOCHEMICAL METHODS FOR MICROPLASTIC ELIMINATION

Various advanced techniques have been developed to resolve MP pollution through degradation and removal processes (Tong et al., 2024). The polymer chains and chemical bonds in the plastics can be destroyed through various methods, resulting in the decomposition into smaller substances or complete degradation into CO₂ and H₂O. Chemical treatments typically involve oxidation processes using reagents including Fenton’s reagent, hydrogen peroxide, or persulfate (Hu et al., 2022). Oxidation produces oxygen-containing functional groups that trigger chain breakage and cross-linking reactions within the internal long-chain structure of MPs. These processes contribute to the continued aging and breakdown of MPs. Advanced oxidation processes (AOPs) such as UV/H₂O₂ and ozonation have also shown promise in degrading MPs (Bule Možar et al., 2024). The degradation process and efficiency of MPs in aquatic environments are significantly influenced by the variety and content of reactive oxygen species produced during oxidative degradation. Thermal methods utilize high temperatures (300 to 900°C) to decompose polymer chains in the absence (pyrolysis) or presence of oxygen (thermal oxidation) (Cui et al., 2023). The intense heat causes chain scission and leads to the formation of smaller molecules including monomers and other volatile compounds. For improved efficiency, thermal methods can be combined with other methods such as Fenton oxidation. This technique is particularly useful for mixed plastic contamination, but high energy operation and release of toxic and hazardous substances are substantial drawbacks. Photodegradation, primarily driven by UV radiation, is the main degradation process of plastics in natural environments. This method often employs photocatalysts such as TiO₂, ZnO, and organic-inorganic hybrid composites to enhance degradation efficiency under UV or visible light irradiation (Kamalian et al., 2020; Kaewkam et al., 2022). Photocatalytic processes can effectively break down various types of MPs, and potentially achieve complete conversion to CO₂ and H₂O. The combination of these approaches offers versatile strategies for addressing MP pollution, with ongoing research focused on improving efficiency and applicability in diverse environmental conditions.

MICROBIAL DEGRADATION OF MICROPLASTICS

Microbial degradation has become a promising approach to manage the increasing environmental concern of plastic pollution. The microbes, including bacteria and fungi, utilize degrading enzymes to attack the polymer chains and gradually depolymerize them into smaller molecules that can be assimilated as carbon and energy sources.

Bacteria constitute the majority (more than half) of species capable of biodegrading plastics. They break down plastics into low molecular weight compounds that cells can utilize through biofilm formation and a sequence of enzymatic processes. Ideonella sakaiensis, Enterobacter asburiae, Paenibacillus amylolyticus, Pseudomonas, Rhodococcus, and Bacillus spp. including B. subtilis and B. gottheilii have shown to degrade common plastics including PLA, PET, or PE (Table 3) (Auta et al., 2017). Fungal species including Fusarium solani, Penicillium simplicissimum, Zalerion maritimum, and Aspergillus spp. have demonstrated the ability to degrade various plastics such as PE, PS, and PVC (Sowmya et al., 2015; Paco et al., 2017; Sarkhel et al., 2019; Tournier et al., 2020; Zhang et al., 2020; Nasrabadi et al., 2023). Especially, Aspergillus spp. and Penicillium spp., are well-documented fungal species capable of degrading plastic polymers. The fungal mycelia can effectively penetrate and extend the plastic surface, spread into the substrate to absorb nutrients, and allow them to attach to the plastic surface. In addition, fungi can produce surface proteins called hydrophobins for adhesion to hydrophobic plastic surfaces as well as extracellular enzymes including peroxidase, laccases, cutinase, lipase, and protease. Some algae found in oceans with high plastic abundance are also capable of degrading plastic. Cyanobacteria Spirulina sp. could degrade PET, while cyanobacteria Phormidium and Oscillatoria subbrevis degraded PE (Sarmah and Rout, 2018; Khoironi et al., 2019). The diatom Navicula pupula, the blue-green algae Anabaena spiroides, and the green microalga Scenedesmus dimorphus can also colonize and biodegrade PE (Kumar et al., 2017).

Table 3.

Microplastic-degrading microorganisms

Types	Bacteria		Fungi		Algae
PET (polyethylene terephthalate)	Bacillus cereus Bacillus gottheilii Ideonella sakaiensis Marinobacter gudaonensis Marinobacter sedimimum Nocardioides marinus Rhodococcus pyridinivorans Thalassospira xiamenensis	Auta et al., 2017 Auta et al., 2017 Yoshida et al., 2016 Zhao et al., 2023 Zhao et al., 2023 Zhao et al., 2023 Guo et al., 2023 Zhao et al., 2023	Fusarium solani Penicillium citrinum Penicillium funiculosum	Tournier et al., 2020 Liebminger et al., 2007 Nowak et al., 2011	Spirulina	Khoironi et al., 2019
PE (polyethylene)	Bacillus cereus Bacillus gottheilii Enterobacter asburiae Kocuria palustris Meyerozyma guilliermondii Pseudomonas aeruginosa Serratia marcescens	Auta et al., 2017 Auta et al., 2017 Yang et al., 2014 Harshvardhan and Jha, 2013 Lou et al., 2022 Lee et al., 2020 Lou et al., 2022	Aspergillus glaucus Penicillium simplicissimum Rhodotorula mucilaginosa Zalerion maritimum	Kathiresan, 2003 Sowmya et al., 2015 Vaksmaa et al., 2023 Paco et al., 2017
HDPE (high-density polyethylene)	Alcaligenes faecalis Bacillus cereus Bacillus sphaericus	Tareen et al., 2022 Sudhakar et al., 2008 Sudhakar et al., 2008	Aspergillus flavus Penicillium chrysogenum Penicillium oxalicum	Sangeetha Devi et al., 2015 Ojha et al., 2017 Ojha et al., 2017
LDPE (low-density polyethylene)	Achromobacter denitrificans Alcanivorax borkumensis Bacillus amyloliquefaciens Bacillus cereus Bacillus sphaericus Bacillus subtilis Chelatococcus daeguensis Micromonospora matsumotoense Nocardiopsis prasine Pseudomonas putida Pseudomonas stutzeri Streptomyces gougerotti	Maleki Rad et al., 2022 Delacuvellerie et al., 2019 Das and Kumar, 2015 Sudhakar et al., 2008 Sudhakar et al., 2008 Harshvardhan and Jha, 2013 Jeon and Kim, 2013 Oliveira et al., 2022 Oliveira et al., 2022 Skariyachan et al., 2015 Skariyachan et al., 2015 Oliveira et al., 2022	Aspergillus clavatus Aspergillus niger Aspergillus nomius Penicillium chrysogenum Penicillium oxalicum	Gajendiran et al., 2016 Volke-Sepúlveda et al., 2001 Munir et al., 2018 Ojha et al., 2017 Ojha et al., 2017	Uronema africanum Phormidium lucidum Oscillatoria subbrevis	Sanniyasi et al., 2021 Sarmah and Rout, 2018 Sarmah and Rout, 2018
PP (polypropylene)	Bacillus gottheilii Pseudomonas aeruginosa Rhodococcus ruber	Auta et al., 2017 Lee et al., 2020 Auta et al., 2017	Phanerochaete chrysosporium	Artham and Doble, 2010	Spirulina	Khoironi et al., 2019
PS (polystyrene)	Acinetobacter bacterium Alcanivorax xenomutans Bacillus cereus Bacillus gottheilii Bacillus paralicheniformis Gordonia bronchialis Gordonia mangrove Gordonia sihwensis Micromonospora matsumotoense Nocardiopsis prasine Pseudomonas aeruginosa Streptomyces gougerotti	Wang et al., 2020 Liu et al., 2023 Lee et al., 2020 Lee et al., 2020 Ganesh Kumar et al., 2021 Liu et al., 2023 Liu et al., 2023 Liu et al., 2023 Oliveira et al., 2022 Oliveira et al., 2022 Liu et al., 2023 Oliveira et al., 2022	Aspergillus flavus Aspergillus niger Curvularia sp. Penicillium sp. Pullularia pullulans Trichoderma sp.	Galgali et al., 2004 Galgali et al., 2004 Motta et al., 2009 Motta et al., 2009 Galgali et al., 2004 Galgali et al., 2004
PVC (polyvinyl chloride)	Achromobacter denitrificans	Maleki Rad et al., 2022

The microbial degrading process often involves biofilm formation on the plastic surface, followed by enzymatic degradation, and factors such as temperature, pH, salinity, and the presence of oxygen and other nutrients can significantly influence the efficiency of microbial degradation (De Tender et al., 2015). The discovery of numerous plastic-degrading microorganisms across aquatic and terrestrial environment has expanded our understanding of natural biodegradation processes. Further research is required to identify more effective microbial strains and to understand degradation mechanisms for developing strategies to enhance the rate of biodegradation in a sustainable and practically applicable manner.

BIOLOGICAL AND BIOCHEMICAL INTERVENTIONS TO REDUCE MICROPLASTIC TOXICITY

Recent studies have reported biological and biochemical approaches to alleviate the toxic effects of MPs and NPs in the environment. Geum and Yeo demonstrated that jellyfish (Aurelia aurita) mucin can bind to PS-NPs and decrease their uptake and combined toxicity with organic pollutant phenanthrene in zebrafish embryos (Geum and Yeo, 2022). The study also revealed that mucin reduced the expression of oxidative stress and apoptosis-related genes, suggesting a protective effect of jellyfish mucin against PS-NP at the molecular level. Chitosan, a natural biopolymer, has also been investigated for its ability to interact with and remove NPs from water. Djajadi et al. found that chitosan effectively induces aggregation of NPs, and facilitates their removal from aquatic systems (Djajadi et al., 2024). This interaction is influenced by environmental factors such as pH, salinity, and dissolved organic matter content. Furthermore, a comprehensive review by Mashayekhi-Sardoo et al. focused on curcumin as a protective agent against MP and NP toxicity (Mashayekhi-Sardoo et al., 2024). The review highlighted the effect of curcumin on mitigating various forms of MP and NP-induced toxicity, including osteolysis, immunotoxicity, thyroid disturbances, and toxicity in multiple organ systems. The antioxidant, antiapoptotic, anti-inflammatory, and anti-proliferative properties of curcumin were found to restore oxidative and histopathological damage caused by MPs and NPs to normal levels in most studies reviewed.

These studies demonstrate the potential of natural substances in addressing MP pollution collectively. Jellyfish mucin and chitosan provide eco-friendly methods for reducing NP toxicity and facilitating their removal from water, respectively. Curcumin offers a broad-spectrum protection against MP and NP-induced toxicity across various biological systems. While these findings are promising, further research is needed to fully understand the long-term efficacy, potential side effects, and scalability of these interventions. As the field progresses, these biological and biochemical approaches may provide valuable tools to combat the growing challenge of MP pollution in ecosystems and human health.

CONCLUDING REMARKS

The universal presence of MPs in our environment has become a significant challenge to human health, particularly to the immune system. This review highlighted the complex impacts of these particles on various immune cell types, from myeloid to lymphoid lineages. The cytotoxic effects and immunomodulatory potential of MPs underscore the urgent need to develop intervention strategies to cope with such harmful effects. As our understanding of the interactions between MPs and the immune system expands, a multidisciplinary approach to combine environmental science, immunology and materials engineering is crucial to address this global issue. Future research should focus on elucidating the long-term consequences of chronic exposure of MPs on immune function and on developing innovative strategies to protect and restore immune homeostasis from this persistent environmental challenge. More importantly, the concerted efforts from researchers, policymakers, and the public to reduce plastic use, improve waste management, and develop safer and biodegradable alternatives will be required to mitigate the adverse effects of plastic pollution on human health and the environment.