Polystyrene microplastic particles: In vitro pulmonary toxicity assessment

Recent advances on transport and transformation mechanism of nanoplastics in lung cells

Microplastics (MPs) are solid plastic particles less than or equal to 5 mm in size that are insoluble in water, and when the diameter is further reduced to <1 micrometer (μm), we call them nanoplastics (NPs). MPs and NPs are widely present in the atmosphere, and plastic particles have also been detected in the sputum of patients with respiratory diseases. This warns us that these tiny plastic particles are a potential threat to human respiratory health. The lungs, as the main organs of the respiratory system, are more likely to be adversely affected by inhaled NPs. However, the mechanism of transport and transformation of NPs in the lung is not clear, so our review mainly focuses on a series of effects and mechanisms of NPs on lung cells through absorption, distribution, metabolism, excretion (ADME) after inhalation into the human body. The most commonly used models in these experimental studies we focus on are A549 and BEAS-2B cells, which are used to model the lung cell response to plastic particles. In addition, we also summarize some shortcomings of these experiments and prospects for future studies, hoping to provide further clues for future studies and contribute to the prevention of related hazards and diseases.

Machine learning-driven QSAR models for predicting the cytotoxicity of five common microplastics

In the field of microplastics (MPs) toxicity prediction, machine learning (ML) computer simulation techniques are showing great potential. In this study, six ML algorithms were utilized to predict the toxicity of MPs on BEAS-2B cells based on quantitative structure-activity relationship (QSAR) models. Comparing the models of different algorithms, the extreme gradient boosting model showed the best fit and prediction performance (R2tra = 0.9876, R2test = 0.9286). Additionally, Williams plot analysis showed that the six models developed were able to predict stably within their applicability domain, with few outliers. Finally, the three feature importance methods-Embedded Feature Importance (EFI), Recursive Feature Elimination (RFE), and SHapley Additive exPlanations (SHAP)-consistently identified particle size as the most critical feature affecting toxicity prediction. The proposed QSAR model can be utilized for preliminary environmental exposure assessments of MPs and to better understand the associated health risks.

Polystyrene Microplastics Induce Injury to the Vascular Endothelial Through NLRP3-Mediated Pyroptosis

The health risks associated with microplastics have attracted widespread attention. Polystyrene microplastics (PS-MPs) can induce damage to cardiac tissue, while pyroptosis-mediated injury to the vascular endothelial plays a vital role in the pathogenesis of cardiovascular diseases. The study intended to explore the role and mechanism of NLR family pyrin domain containing 3 (NLRP3) mediated pyroptosis in PS-MPs causing the injury of vascular endothelial cells. In vivo, Wistar rats were exposed to 0.5, 5, and 50 mg/kg/d 0.5 μm PS-MPs. In vitro, the human vascular endothelial cells (HUVECs) were used for mechanistic studies. siRNA was used for silencing the NILRP3 gene. H&E staining and flow cytometry were performed to examine the vascular injury and cell membrane damage. The oxidative stress was detected by flow cytometry, immunofluorescence, and corresponding kits. ELISA were used to measure the levels of inflammatory factors. Real-time PCR and western blot were used to measure the expression of pyroptosis signaling pathway. In rats, PS-MPs could cause vascular damage, oxidative stress, and inflammatory response, and activated the pyroptosis signaling pathway. HUVECs exposure to PS-MPs, the vitality decreased in a dose-dependent manner, ROS and MDA were significantly increased while SOD was decreased. PS-MPs induced the onset of pyroptosis signaling pathway in HUVECs. Cell membrane damage and the levels of IL-Iβ and IL-18 in HUVECs significantly increased, those are symbols for the development of pyroptosis. Inhibition of NLRP3-mediated pyroptosis effectively protected HUVECs from PS-MPs-induced damage. Pyroptosis played a vital role in controlling the vascular endothelial injury caused by PS-MPs.

Polystyrene microplastics trigger testosterone decline via GPX1

As an emerging environmental endocrine disruptor, polystyrene microplastics (PS-MPs) are considered to have the anti-androgenic feature and impair male reproductive function. To explore the adverse effects of PS-MPs on testosterone synthesis and male reproduction and further elucidate underlying mechanisms, BALB/c mice and Leydig cells were employed in the present work. The results indicated that 50 μm PS-MPs accumulated in mouse testes and were internalized into the cytoplasm. This not only damaged the testicular histomorphology and ultrastructure, but also reduced the viability of Leydig cells and the serum level of GnRH, FSH, LH, and testosterone. After PS-MPs exposure, the ubiquitination degradation and miR-425-3p-targeted modulation synergistically contributed to the suppression of GPX1, which induced oxidative stress and subsequently activated the PERK-EIF2α-ATF4-CHOP pathway of endoplasmic reticulum (ER) stress. The transcription factor CHOP positively regulated the expression of SRD5A2 by directly binding to its promoter region, thereby accelerating testosterone metabolism and ultimately lowing testosterone levels. Besides, PS-MPs compromised testosterone homeostasis via interfering with the hypothalamic-pituitary-testis (HPT) axis. Taken together, PS-MPs possess an anti-androgenic characteristic and exert male reproductive damage effects. The antioxidant enzyme GPX1 plays a crucial role in the PS-MPs-mediated testosterone decline.

The alarming link between environmental microplastics and health hazards with special emphasis on cancer

Microplastic contamination is a burgeoning environmental issue that poses serious threats to animal and human health. Microplastics enter the human body through nasal, dermal, and oral routes to contaminate multiple organs. Studies have advocated the existence of microplastics in human breast milk, sputum, faeces, and blood. Microplastics can find their ways to the sub-cellular moiety via active and passive approaches. At cellular level, microplastics follow clathrin and caveolae-dependent pathways to invade the sub-cellular environment. These environmental contaminants modulate the epigenetic control of gene expression, status of inflammatory mediators, redox homeostasis, cell-cycle proteins, and mimic the endocrine mediators like estrogen and androgen to fuel carcinogenesis. Furthermore, epidemiological studies have suggested potential links between the exposure to microplastics and the onset of various chronic diseases. Microplastics trigger uncontrolled cell proliferation and ensue tissue growth leading to various cancers affecting the lungs, blood, breasts, prostate, and ovaries. Additionally, such contamination can potentially affect sub-cellular signaling and injure multiple organs. In essence, numerous reports have claimed microplastic-induced toxicity and tumorigenesis in human and model animals. Nonetheless, the underlying molecular mechanism is still elusive and warrants further investigations. This review provides a comprehensive analysis of microplastics, covering their sources, chemistry, human exposure routes, toxicity, and carcinogenic potential at the molecular level.

Inhaled polystyrene microplastics impaired lung function through pulmonary flora/TLR4-mediated iron homeostasis imbalance

Microplastics (MPs) have been found in the air, human nasal cavity, and lung, suggesting that the respiratory tract is one of the important exposure routes for MPs. The lung is a direct target organ for injury from inhaled MPs, but data on lung injury from longer-term exposure to environmental doses of MPs are limited, and the mechanisms remain unclear. Here, C57BL/6 J mice were treated with 5 μm polystyrene (PS)-MPs by intratracheal instillation (0.6, 3, and 15 mg/kg) for 60 days to establish MPs exposure model. We found that PS-MPs lead to increased collagen fibers and decreased lung barrier permeability and lung function in lung tissue. Mechanistically, the abundance of gram-negative bacteria in the pulmonary flora increased after inhalation of PS-MPs, causing lipopolysaccharide (LPS) release. The expression of Toll-like receptor 4 (TLR4), the key receptor of LPS, was increased, and ferroptosis occurred in lung tissue cells. Further in vitro intervention experiments were performed, pulmonary flora/TLR4-induced imbalance of lung iron homeostasis is an important mechanism of PS-MPs-induced lung injury. Our study provides new evidence for lung injury caused by environmental doses of MPs and strategies to prevent it through longer-term dynamic observation.

Production and characterisation of environmentally relevant microplastic test materials derived from agricultural plastics

Soil environments across the globe, particularly in agricultural settings, have now been shown to be contaminated with microplastics. Agricultural plastics - such as mulching films - are used in close or direct contact with soils and there is growing evidence demonstrating that they represent a potential source of microplastics. There is a demand to undertake fate and effects studies to understand the behaviour and potential long-term ecological risks of this contamination. Yet, there is a lack of test materials available for this purpose. This study describes the manufacture and characterisation of five large (1-40 kg) batches of microplastic test materials derived from agricultural mulching films. Batches were produced from either polyethylene-based conventional mulching films or starch-polybutadiene adipate terephthalate blend mulching films that are certified biodegradable in soil. Challenges encountered and overcome during the micronisation process provide valuable insights into the future of microplastic test material generation from these material types. This includes difficulties in micronising virgin polyethylene film materials. All five batches were subjected to a thorough physical and chemical characterisation - both of the original virgin films and the subsequent microplastic particles generated - including a screening for the presence of chemical additives. This is a critical step to provide essential information for interpreting particle fate or effects in scientific testing. Trade-offs between obtaining preferred particle typologies and time and cost constraints are elucidated. Several recommendations emerging from the experiences gained in this study are put forward to advance the research field towards greater harmonisation and utilisation of environmentally relevant test materials.

Assessment of microplastic exposure in nasal lavage fluid and the influence of face masks

Microplastics (MPs) can enter the human body through respiration and pose a hazard to human health. Wearing masks has become a routine behavior during the COVID-19 pandemic. The level of respirational exposure and the influence of wearing masks are currently unknown. We recruited 113 college students and divided them into natural exposure (NE), surgical mask (SM), and cotton mask (CM) groups. Nasal lavage fluid (NLF) was collected and MPs characteristics were analyzed using polarized light microscopy and laser direct infrared system. We found a relatively high abundance of MPs in NLF in the SM group (41.24 ± 1.73 particles/g). The particle size distribution and fibrous MP percentage significantly differed among the three groups. The main components in the NE, SM, and CM groups were polypropylene (58.70 %)，polycarbonate (PC, 49.49 %)，and PC (54.29 %). Components such as polyamide, polyethylene and polyethylene terephthalate were also detected. Wearing surgical masks increased the MP abundance in NLF (β = 0.36, P < 0.01). As the wear time increased, the abundance of MPs also rose (β = 0.28, P < 0.05). However, those who used bedding containing synthetic fibers had lower MP abundance in their NLF. This study highlights the use of NLF to evaluate MP exposure, which is associated with potential health risks.

Microplastics, as a risk factor in the development of interstitial lung disease- a preliminary study

Microplastic (MPs) pollution is a global concern that affects all living organisms, yet research on MP-related disorders in humans, including incidence and symptoms, remains limited. In this study, the presence, composition, and characterization of MPs in bronchoalveolar lavage (BAL), which reflects lung tissue, and blood were examined. Fiberoptic bronchoscopy was performed to collect BAL samples from patients suspected of having interstitial lung disease (ILD) as well as from a control group. MPs were identified and measured using μ-Raman techniques. In BAL samples, the most common MPs color observed was grey/white, with sizes ranging from 4.19 to 792.00 μm. The particle shapes and polymer types identified included polyamide (PA), polyester (PET), polyvinyl chloride (PVC), and polyurethanes (PU). For blood samples, MPs were predominantly grey/white and blue, with sizes ranging from 13.14 to 20. 29 μm. The identified polymers in blood samples included polyamide (PA) and polyethylene (PE). MPs were detected in 10 out of 18 patients (55%) suspected of having ILD, with most of these patients presenting with the fibrotic type of the disease. In the control group, two patients whose BAL samples were positive for MPs were found to have chronic lung disease. This study is the first to explore the relationship between interstitial lung disease (ILD) and microplastics (MPs), revealing a tendency for the presence of MPs in the bronchoalveolar lavage (BAL) of ILD patients, particularly those with a fibrotic phenotype. Further research is needed to determine the cumulative effects of MPs on human health, especially concerning the respiratory system, which is highly exposed to environmental pollutants.

Accumulation of nanoplastics by wheat seedling roots: Both passive and energy-consuming processes

Nanoplastics can transfer from the environment to plants and potentially harm organisms. However, the mechanisms on how crop root systems absorb and transport nanoplastics are still unclear. Here, original and fluorescent labeled polystyrene and polyvinyl chloride nanoparticles (PS-NPs, PVC-NPs; 30 nm; 10 mg L-1) were employed to study the distribution and internalization pathways in wheat seedling roots. In the study, nanoplastics accumulated more in the root tip and surface, with PVC-NPs more prevalent than PS-NPs. After being treated with inhibitors (Na3VO4, chlorpromazine and amiloride), the nanoplastics mean fluorescence intensities were reduced by 4.0-51.1 %. During the uptake, both passive and energy-consuming pathways occurred. For the energy-consuming uptake pathway, macropinocytosis contributed more to cytoplasm than clathrin-mediated endocytosis. H+ influx was observed during nanoplastic transport into the cytoplasm, and the reduction in plasma membrane ATPase activity led to a decrease in nanoplastic internalization. These results elucidate the pathways of nanoplastics absorption and transport in wheat roots, provide crucial evidence for assessing nanoplastics' ecological risks and support the development of technologies to block nanoplastics absorption by crop roots, ensuring agricultural and ecosystem safety.

Biological effect of U(VI) exposure on lung epithelial BEAS-2B cells

In this study, the biological effects of U(VI) exposure on lung epithelial cells were investigated by MTT assay, immunofluorescence, flow cytometry, and Western blotting. U(VI)-induced stress triggers oxidative stress in cells, activates MAPK signaling pathways, and promotes inflammation. Additionally, U(VI) causes damage to the cell membrane structure and severe DNA injury, impacting the accuracy of transcription and translation. The results demonstrate that U(VI) exposure significantly inhibits cell proliferation and migration. This is attributed to the disruption of the PI3K/AKT/GSK-3β/β-catenin signaling pathway and the reduction in CyclinD1 expression, leading to a delayed cell cycle, decreased growth rate, mitochondrial damage, and reduced energy metabolism. This study provides a comprehensive understanding of the molecular mechanisms underlying uranium-induced cellular toxicity in lung epithelial cells.

A review on advancements in atmospheric microplastics research: The pivotal role of machine learning

Microplastics (MPs), recognized as emerging pollutants, pose significant potential impacts on the environment and human health. The investigation into atmospheric MPs is nascent due to the absence of effective characterization methods, leaving their concentration, distribution, sources, and impacts on human health largely undefined with evidence still emerging. This review compiles the latest literature on the sources, distribution, environmental behaviors, and toxicological effects of atmospheric MPs. It delves into the methodologies for source identification, distribution patterns, and the contemporary approaches to assess the toxicological effects of atmospheric MPs. Significantly, this review emphasizes the role of Machine Learning (ML) and Artificial Intelligence (AI) technologies as novel and promising tools in enhancing the precision and depth of research into atmospheric MPs, including but not limited to the spatiotemporal dynamics, source apportionment, and potential health impacts of atmospheric MPs. The integration of these advanced technologies facilitates a more nuanced understanding of MPs' behavior and effects, marking a pivotal advancement in the field. This review aims to deliver an in-depth view of atmospheric MPs, enhancing knowledge and awareness of their environmental and human health impacts. It calls upon scholars to focus on the research of atmospheric MPs based on new technologies of ML and AI, improving the database as well as offering fresh perspectives on this critical issue.

Polyethylene Micro/Nanoplastics Exposure Induces Epithelial-Mesenchymal Transition in Human Bronchial and Alveolar Epithelial Cells

Micro/nanoplastics (MNPs), which are widely spread in the environment, have gained attention because of their ability to enter the human body mainly through ingestion, inhalation, and skin contact, thus representing a serious health threat. Several studies have reported the presence of MNPs in lung tissue and the potential role of MNP inhalation in triggering lung fibrosis and tumorigenesis. However, there is a paucity of knowledge regarding the cellular response to MNPs composed of polyethylene (PE), one of the most common plastic pollutants in the biosphere. In this study, we investigated the effects of low/high concentrations of PE MNPs on respiratory epithelial cell viability and migration/invasion abilities, using MTT, scratch, and transwell assays. Morphological and molecular changes were assessed via immunofluorescence, Western blot, and qRT-PCR. We demonstrated that acute exposure to PE MNPs does not induce cellular toxicity. Instead, cells displayed visible morphological changes also involving actin cytoskeleton reorganization. Our data underlined the role of epithelial-mesenchymal transition (EMT) in triggering this process. Moreover, a remarkable increase in migration potential was noticed, in absence of a significant alteration of the cell's invasive capacity. The present study highlights the potential impact of PE MNPs inhalation on the human respiratory epithelium, suggesting a possible role in carcinogenesis.

Plastic pollution in terrestrial ecosystems: Current knowledge on impacts of micro and nano fragments on invertebrates

The increasing accumulation of small plastic particles, in particular microplastics (>1 µm to 5 mm) and nanoplastics (< 1 µm), in the environment is a hot topic in our rapidly changing world. Recently, studies were initiated to better understand the behavior of micro- and nanoplastics (MNP) within complex matrices like soil, as well as their characterization, incorporation and potential toxicity to terrestrial biota. However, there remains significant knowledge gaps in our understanding of the wide-extent impacts of MNP on terrestrial invertebrates. We first summarized facts on global plastic pollution and the generation of MNP. Then, we focused on compiling the existing literature examining the consequences of MNP exposure in terrestrial invertebrates. The diversity of investigated biological endpoints (from molecular to individual levels) were compiled to get a better comprehension of the effects of MNP according to different factors such as the shape, the polymer type, the organism, the concentration and the exposure duration. The sublethal effects of MNP are acknowledged in the literature, yet no general conclusion was drawn as their impacts are highly dependent on their characteristic and experimental design. Finally, the synthesis highlighted some research gaps and remediation strategies, as well as a protocol to standardize ecotoxicological studies.

Spatial and seasonal variations of atmospheric microplastics in high and low population density areas at the intersection of tropical and subtropical regions

There is limited information regarding spatial and seasonal variations of atmospheric microplastics (MPs) and factors influencing MPs at the intersection of tropical and subtropical regions. A one-year study was conducted at sites in a high-population-density village (HPDV) and a low-population-density village (LPDV) in Taiwan to investigate the characteristics and influencing factors of airborne MPs. The predominant shapes, sizes, and polymer compositions of MPs were fragments, 3 to 25 and 26-50 μm, and polyamide at both sites. Seasonal variation in MP morphologies was not significant. Average MP concentrations were 2.20 ± 2.97 particles/m3 and 1.92 ± 2.35 particles/m3 at the HPDV and LPDV sites, respectively, and did not differ significantly. Higher concentrations and smaller sizes of MPs were found during the summer at both sites, while the predominant wind direction was southerly or southwesterly. In samples with temperatures exceeding 25 °C, the temperature was positively associated with MP concentrations at both the HPDV and LPDV sites. These results reflect that temperature influences the variations in the concentrations and sizes of MPs at our study site. Future research should consider the adverse risks of MP inhalation during the hot season. Moreover, when sites with different population densities and levels of human activity are closed, MP concentrations will not differ significantly between these areas since airflow can transport these particles from high-population-density areas into low-population-density areas in a short time.

Degradation of PET microplastic particles to monomers in human serum by PETase

More than 8 billion tons of plastic waste has been generated, posing severe environmental consequences and health risks. Due to prolonged exposure, microplastic particles are found in human blood and other bodily fluids. Despite a lack of toxicity studies regarding microplastics, harmful effects for humans seem plausible and cannot be excluded. As small plastic particles readily translocate from the gut to body fluids, enzyme-based treatment of serum could constitute a promising future avenue to clear synthetic polymers and their corresponding oligomers via their degradation into monomers of lower toxicity than the material they originate from. Still, whereas it is known that the enzymatic depolymerization rate of synthetic polymers varies by orders of magnitude depending on the buffer and media composition, the activity of plastic-degrading enzymes in serum was unknown. Here, we report how an engineered PETase, which we show to be generally trans-selective via induced fit docking, can depolymerize two different microplastic-like substrates of the commodity polymer polyethylene terephthalate (PET) into its non-toxic monomer terephthalic acid (TPA) alongside mono(2-hydroxyethyl)terephthalate (MHET) in human serum at 37 °C. We show that the application of PETase does not influence cell viability in vitro. Our work highlights the potential of applying biocatalysis in biomedicine and represents a first step towards finding a future solution to the problem that microplastics in the bloodstream may pose.

Understanding of environmental pollution and its anthropogenic impacts on biological resources during the COVID-19 period

The global outbreak of the COVID-19 pandemic has given rise to a significant health emergency to adverse impact on environment, and human society. The COVID-19 post-pandemic not only affects human beings but also creates pollution crisis in environment. The post-pandemic situation has shown a drastic change in nature due to biomedical waste load and other components. The inadequate segregation of untreated healthcare wastes, chemical disinfectants, and single-use plastics leads to contamination of the water, air, and agricultural fields. These materials allow the growth of disease-causing agents and transmission. Particularly, the COVID-19 outbreak has posed a severe environmental and health concern in many developing countries for infectious waste. In 2030, plastic enhances a transboundary menace to natural ecological communities and public health. This review provides a complete overview of the COVID-19 pandemic on environmental pollution and its anthropogenic impacts to public health and natural ecosystem considering short- and long-term scenarios. The review thoroughly assesses the impacts on ecosystem in the terrestrial, marine, and atmospheric realms. The information from this evaluation can be utilized to assess the short-term and long-term solutions for minimizing any unfavorable effects. Especially, this topic focuses on the excessive use of plastics and their products, subsequently with the involvement of the scientific community, and policymakers will develop the proper management plan for the upcoming generation. This article also provides crucial research gap knowledge to boost national disaster preparedness in future perspectives.

Type-specific inflammatory responses of vascular cells activated by interaction with virgin and aged microplastics

Microplastics (MPs) are recognized as a major environmental problem due to their ubiquitous presence in ecosystems and bioaccumulation in food chains. Not only humans are continuously exposed to these pollutants through ingestion and inhalation, but recent findings suggest they may trigger vascular inflammation and potentially worsen the clinical conditions of cardiovascular patients. Here we combine headspace analysis by needle trap microextraction-gas chromatography-mass spectrometry (HS-NTME-GC-MS) and biological assays to evaluate the effects of polystyrene, high- and low-density polyethylene MPs on phenotype, metabolic activity, and pro-inflammatory status of Vascular Smooth Muscle Cells (VSMCs) the most prominent cells in vascular walls. Virgin and artificially aged MPs (4 weeks at 40 °C and 750 W/m2 simulated solar irradiation) were comparatively tested at 1 mg/mL to simulate a realistic exposure scenario. Our results clearly show the activation of oxidative stress and inflammatory processes when VSMCs were cultured with aged polymers, with significant overexpression of IL-6 and TNF-α. In addition, volatile organic compounds (VOCs), including pentane, acrolein, propanal, and hexanal as the main components, were released by VSMCs into the headspace. Type-specific VOC response profiles were induced on vascular cells from different MPs.

The Potential Mechanisms Involved in the Disruption of Spermatogenesis in Mice by Nanoplastics and Microplastics

BACKGROUND

Plastic-based products are ubiquitous due to their tremendous utility in our daily lives. Nanoplastic (NP) and microplastic (MP) pollution has become a severe threat to the planet and is a growing concern. It has been widely reported that polystyrene (PS) MPs are severely toxic to the male reproduction system, with effects including decreased sperm parameters, impaired spermatogenesis, and damaged testicular structures. However, the molecular mechanisms for impaired spermatogenesis remain poorly understood.

METHODS

C57BL/6 male mice were treated with PS-NPs (80 nm) and PS-MPs (5 μm) by oral gavage every day for 60 days. A series of morphological analyses were completed to explore the influence of PS-NP and PS-MP exposure on the testes. Compared to other cell types in the seminiferous tubule, PS-NP and PS-MP exposure can lead to decreased spermatocytes. Then, more refined molecular typing was further performed based on gene expression profiles to better understand the common and specific molecular characteristics after exposure to PS-NPs and PS-MPs.

RESULTS

There were 1794 common DEGs across the PS-NP groups at three different doses and 1433 common DEGs across the PS-MP groups at three different doses. GO and KEGG analyses of the common DEGs in the PS-NP and PS-MP groups were performed to enrich the common and specific functional progress and signaling pathways, including 349 co-enriched GO entries and 13 co-enriched pathways. Moreover, 348 GO entries and 33 pathways were specifically enriched in the PS-NP group, while 526 GO entries and 15 pathways were specifically enriched in the PS-MPs group.

CONCLUSIONS

PS-NPs were predominantly involved in regulating retinoic acid metabolism, whereas PS-MPs primarily influenced pyruvate metabolism and thyroid hormone metabolism. Our results highlight the different molecular mechanisms of PS-NPs and PS-MPs in the impairment of spermatogenesis in male mammals for the first time, providing valuable insights into the precise mechanisms of PS-NPs and PS-MPs in male reproduction.

Eco-friendly approaches for mitigating plastic pollution: advancements and implications for a greener future

Plastic pollution has become a global problem since the extensive use of plastic in industries such as packaging, electronics, manufacturing and construction, healthcare, transportation, and others. This has resulted in an environmental burden that is continually growing, which has inspired many scientists as well as environmentalists to come up with creative solutions to deal with this problem. Numerous studies have been reviewed to determine practical, affordable, and environmentally friendly solutions to regulate plastic waste by leveraging microbes' innate abilities to naturally decompose polymers. Enzymatic breakdown of plastics has been proposed to serve this goal since the discovery of enzymes from microbial sources that truly interact with plastic in its naturalistic environment and because it is a much faster and more effective method than others. The scope of diverse microbes and associated enzymes in polymer breakdown is highlighted in the current review. The use of co-cultures or microbial consortium-based techniques for the improved breakdown of plastic products and the generation of high-value end products that may be utilized as prototypes of bioenergy sources is highlighted. The review also offers a thorough overview of the developments in the microbiological and enzymatic biological degradation of plastics, as well as several elements that impact this process for the survival of our planet.

Polyethylene Terephthalate Microplastics Generated from Disposable Water Bottles Induce Interferon Signaling Pathways in Mouse Lung Epithelial Cells

Microplastics (MPs) are present in ambient air in a respirable size fraction; however, their potential impact on human health via inhalation routes is not well documented. In the present study, methods for a lab-scale generation of MPs from regularly used and littered plastic articles were optimized. The toxicity of 11 different types of MPs, both commercially purchased and in-lab prepared MPs, was investigated in lung epithelial cells using cell viability, immune and inflammatory response, and genotoxicity endpoints. The underlying mechanisms were identified by microarray analysis. Although laborious, the laboratory-scale methods generated a sufficient quantity of well characterized MPs for toxicity testing. Of the 11 MPs tested, the small sized polyethylene terephthalate (PETE) MPs prepared from disposable water bottles induced the maximum toxicity. Specifically, the smaller size PETE MPs induced a robust activation of the interferon signaling pathway, implying that PETE MPs are perceived by cells by similar mechanisms as those employed to recognize pathogens. The PETE MPs of heterogenous size and shapes induced cell injury, triggering cell death, inflammatory cascade, and DNA damage, hallmark in vitro events indicative of potential in vivo tissue injury. The study establishes toxicity of specific types of plastic materials in micron and nano size.

Polystyrene Microplastics Causes Diarrhea and Impairs Intestinal Angiogenesis through the ROS/METTL3 Pathway

Due to the immature intestinal digestion, immunity, and barrier functions, weaned infants are more susceptible to pathogens and develop diarrhea. Microplastics (MPs), pervasive contaminants in food, water, and air, have unknown effects on the intestinal development of weaned infants. This study explored the impact of polystyrene MPs on intestinal development using a weaned piglet model. Piglets in the control group received a basal diet, and those in the experimental groups received a basal diet contaminated with 150 mg/kg polystyrene MPs. The results showed that exposure to polystyrene MPs increased the diarrhea incidence and impaired the intestinal barrier function of weaned piglets. Notably, the exposure led to oxidative stress and inflammation in the intestine. Furthermore, polystyrene MPs-treated weaned piglets showed a reduced level of intestinal angiogenesis. Mechanistically, polystyrene MPs suppressed methyltransferase-like 3 (METTL3) expression by increasing reactive oxygen species (ROS) production, consequently destabilizing angiogenic factors' mRNA and hindering intestinal angiogenesis. In summary, polystyrene MPs contamination in the diet increases diarrhea and compromises intestinal angiogenesis through the ROS/METTL3 pathway, demonstrating their toxic effects on the intestine health of weaned infants.

Polystyrene nanoplastics of different particle sizes regulate the polarization of pro-inflammatory macrophages

Microplastics (MPs) are defined as plastic particles smaller than 5 mm in size, and nanoplastics (NPs) are those MPs with a particle size of less than 1000 nm or 100 nm. The prevalence of MPs in the environment and human tissues has raised concerns about their potential negative effects on human health. Macrophages are the major defence against foreign substances in the intestine, and can be polarized into two types: the M1 phenotype and the M2 phenotype. However, the effect of NPs on the polarization of macrophages remains unclear. Herein, we selected polystyrene, one of the most plastics in the environment and controlled the particle sizes at 50 nm and 500 nm respectively to study the effects on the polarization of macrophages. We used mouse RAW264.7 cell line models in this macrophage-associated study. Experiments on cell absorption showed that macrophages could quickly ingest polystyrene nanoplastics of both diameters with time-dependent uptake. Compared to the untreated group and 10 μg/mL treatment group, macrophages exposed to 50 μg/mL groups (50 nm and 500 nm) had considerably higher levels of CD86, iNOS, and TNF-α, but decreased levels of aCD206, IL-10, and Arg-1. According to these findings, macrophage M1 and M2 polarization can both be induced and inhibited by 50 μg/mL 50 nm and 500 nm polystyrene nanoplastics. This work provided the first evidence of a possible MPs mode of action with appropriate concentration and size through the production of polarized M1, providing dietary and environmental recommendations for people, particularly those with autoimmune and autoinflammatory illnesses.

Primary Microplastics in the Ecosystem: Ecological Effects, Risks, and Comprehensive Perspectives on Toxicology and Detection Methods

Recent discoveries of microplastics in cities, suburbs, and even remote locations, far from microplastic source regions, have raised the possibility of long-distance transmission of microplastics in many ecosystems. A little is known scientifically about the threat that it posed to the environment by microplastics. The problem's apparent size necessitates the rapid development of reliable scientific advice regarding the ecological risks of microplastics. These concerns are brought on by the lack of consistent sample and identification techniques, as well as the limited physical analysis and understanding of microplastic pollution. This review provides insight regarding some unaddressed issues about the occurrence, fate, movement, and impact of microplastics, in general, with special emphasis on primary microplastics. The approaches taken in the earlier investigations have been analyzed and different recommendations for future research have been suggested.

Reproductive toxicity and related mechanisms of micro(nano)plastics in terrestrial mammals: Review of current evidence

Micro(nano)plastics (MNPs) have been detected in various ecological environments and are widely used due to their stable properties, raising widespread concern about their potential human reproductive toxicity. Currently, infertility affects approximately 10-30% of couples of reproductive age globally. MNPs, as environmental pollutants, have been shown to exhibit reproductive toxicity through intrinsic mechanisms or as carriers of other hazardous substances. Numerous studies have established that MNPs of varying sizes and types can penetrate biological barriers, and enter tissues and even organelles of organisms through four main routes: dietary ingestion, inhalation, dermal contact, and medical interventions. However, historical research on the toxic effects of MNPs on reproduction mainly focused on lower and aquatic species. We conducted an inclusive review of studies involving terrestrial mammals, revealing that MNPs can induce reproductive toxicity via various mechanisms such as oxidative stress, inflammation, fibrosis, apoptosis, autophagy, disruption of intestinal flora, endocrine disruption, endoplasmic reticulum stress, and DNA damage. In terrestrial mammals, reproductive toxicity predominantly manifests as disruption in the blood-testis barrier (BTB), impaired spermatogenesis, sperm malformation, sperm DNA damage, reduced sperm fertilizing capacity, compromised oocyte maturation, impaired follicular growth, granulosa cell apoptosis, diminished ovarian reserve function, uterine and ovarian fibrosis, and endocrine disruption, among other effects. Furthermore, MNPs can traverse the maternal-fetal interface, potentially impacting offspring reproductive health. To gain a comprehensive understanding of the potential reproductive toxicity and underlying mechanisms of MNPs with different sizes, polymer types, shapes, and carried toxins, as well as to explore effective protective interventions for mitigating reproductive damage, further in-depth animal studies, clinical trials, and large-scale epidemiological studies are urgently required.

Beyond surface: Unveiling ecological and economic ramifications of microplastic pollution in the oceans

Every year, the global production of plastic waste reaches a staggering 400 million metric tons (Mt), precipitating adverse consequences for the environment, food safety, and biodiversity as it degrades into microplastics (MPs). The multifaceted nature of MP pollution, coupled with its intricate physiological impacts, underscores the pressing need for comprehensive policies and legislative frameworks. Such measures, alongside advancements in technology, hold promise in averting ecological catastrophe in the oceans. Mandated legislation represents a pivotal step towards restoring oceanic health and securing the well-being of the planet. This work offers an overview of the policy hurdles, legislative initiatives, and prospective strategies for addressing global pollution due to MP. Additionally, this work explores innovative approaches that yield fresh insights into combating plastic pollution across various sectors. Emphasizing the importance of a global plastics treaty, the article underscores its potential to galvanize collaborative efforts in mitigating MP pollution's deleterious effects on marine ecosystems. Successful implementation of such a treaty could revolutionize the plastics economy, steering it towards a circular, less polluting model operating within planetary boundaries. Failure to act decisively risks exacerbating the scourge of MP pollution and its attendant repercussions on both humanity and the environment. Central to this endeavor are the formulation, content, and execution of the treaty itself, which demand careful consideration. While recognizing that a global plastics treaty is not a panacea, it serves as a mechanism for enhancing plastics governance and elevating global ambitions towards achieving zero plastic pollution by 2040. Adopting a life cycle approach to plastic management allows for a nuanced understanding of possible trade-offs between environmental impact and economic growth, guiding the selection of optimal solutions with socio-economic implications in mind. By embracing a comprehensive strategy that integrates legislative measures and technological innovations, we can substantially reduce the influx of marine plastic litter at its sources, safeguarding the oceans for future generations.

Transforming pollution into solutions: A bibliometric analysis and sustainable strategies for reducing indoor microplastics while converting to value-added products

Microplastics (MPs), as emerging indoor contaminants, have garnered attention due to their ubiquity and unresolved implications for human health. These tiny particles have permeated indoor air and water, leading to inevitable human exposure. Preliminary evidence suggests MP exposure could be linked to respiratory, gastrointestinal, and potentially other health issues, yet the full scope of their effects remains unclear. To map the overall landscape of this research field, a bibliometric analysis based on research articles retrieved from the Web of Science database was conducted. The study synthesizes the current state of knowledge and spotlights the innovative mitigation strategies proposed to curb indoor MP pollution. These strategies involve minimizing the MP emission from source, advancements in filtration technology, aimed at reducing the MP exposure. Furthermore, this research sheds light on cutting-edge methods for converting MP waste into value-added products. These innovative approaches not only promise to alleviate environmental burdens but also contribute to a more sustainable and circular economy by transforming waste into resources such as biofuels, construction materials, and batteries. Despite these strides, this study acknowledges the ongoing challenges, including the need for more efficient removal technologies and a deeper understanding of MPs' health impacts. Looking forward, the study underscores the necessity for further research to fill these knowledge gaps, particularly in the areas of long-term health outcomes and the development of standardized, reliable methodologies for MP detection and quantification in indoor settings. This comprehensive approach paves the way for future exploration and the development of robust solutions to the complex issue of microplastic pollution.

The potential of micro- and nanoplastics to exacerbate the health impacts and global burden of non-communicable diseases

Non-communicable diseases (NCD) constitute one of the highest burdens of disease globally and are associated with inflammatory responses in target organs. There is increasing evidence of significant human exposure to micro- and nanoplastics (MnPs). This review of environmental MnP exposure and health impacts indicates that MnP particles, directly and indirectly through their leachates, may exacerbate inflammation. Meanwhile, persistent inflammation associated with NCDs in gastrointestinal and respiratory systems potentially increases MnP uptake, thus influencing MnP access to distal organs. Consequently, a future increase in MnP exposure potentially augments the risk and severity of NCDs. There is a critical need for an integrated one-health approach to human health and environmental research for assessing the drivers of human MnP exposure and their bidirectional links with NCDs. Assessing these risks requires interdisciplinary efforts to identify and link drivers of environmental MnP exposure and organismal uptake to studies of impacted disease mechanisms and health outcomes.

Probing Long-Term Impacts: Low-Dose Polystyrene Nanoplastics Exacerbate Mitochondrial Health and Evoke Secondary Glycolysis via Repeated and Single Dosing

Nanoplastics (NPs) are omnipresent in the environment and contribute to human exposure. However, little is known regarding the long-term effects of NPs on human health. In this study, human intestinal Caco-2 cells were exposed to polystyrene nanoplastics (nanoPS) in an environmentally relevant concentration range (102-109 particles/mL) under two realistic exposure scenarios. In the first scenario, cells were repeatedly exposed to nanoPS every 2 days for 12 days to study the long-term effects. In the second scenario, only nanoPS was added once and Caco-2 cells were cultured for 12 days to study the duration of the initial effects of NPs. Under repeated dosing, initial subtle effects on mitochondria induced by low concentrations would accrue over consistent exposure to nanoPS and finally lead to significant impairment of mitochondrial respiration, mitochondrial mass, and cell differentiation process at the end of prolonged exposure, accompanied by significantly increased glycolysis over the whole exposure period. Single dosing of nanoPS elicited transient effects on mitochondrial and glycolytic functions, as well as increased reactive oxygen species (ROS) production in the early phase of exposure, but the self-recovery capacity of cells mitigated these effects at intermediate culture times. Notably, secondary effects on glycolysis and ROS production were observed during the late culture period, while the cell differentiation process and mitochondrial mass were not affected at the end. These long-term effects are of crucial importance for comprehensively evaluating the health hazards arising from lifetime exposure to NPs, complementing the extensively observed acute effects associated with prevalent short-term exposure to high concentrations. Our study underlines the need to study the toxicity of NPs in realistic long-term exposure scenarios such as repeated dosing.

Adverse effects and potential mechanisms of polystyrene microplastics (PS-MPs) on the blood-testis barrier

Microplastics (MPs) are defined as plastic particles or fragments with a diameter of less than 5 mm. These particles have been identified as causing male reproductive toxicity, although the precise mechanism behind this association is yet to be fully understood. Recent research has found that exposure to polystyrene microplastics (PS-MPs) can disrupt spermatogenesis by impacting the integrity of the blood-testis barrier (BTB), a formidable barrier within mammalian blood tissues. The BTB safeguards germ cells from harmful substances and infiltration by immune cells. However, the disruption of the BTB leads to the entry of environmental pollutants and immune cells into the seminiferous tubules, resulting in adverse reproductive effects. Additionally, PS-MPs induce reproductive damage by generating oxidative stress, inflammation, autophagy, and alterations in the composition of intestinal flora. Despite these findings, the precise mechanism by which PS-MPs disrupt the BTB remains inconclusive, necessitating further investigation into the underlying processes. This review aims to enhance our understanding of the pernicious effects of PS-MP exposure on the BTB and explore potential mechanisms to offer novel perspectives on BTB damage caused by PS-MPs.

Understanding microplastic pollution of marine ecosystem: a review

Microplastics are emerging as prominent pollutants across the globe. Oceans are becoming major sinks for these pollutants, and their presence is widespread in coastal regions, oceanic surface waters, water column, and sediments. Studies have revealed that microplastics cause serious threats to the marine ecosystem as well as human beings. In the past few years, many research efforts have focused on studying different aspects relating to microplastic pollution of the oceans. This review summarizes sources, migration routes, and ill effects of marine microplastic pollution along with various conventional as well as advanced methods for microplastics analysis and control. However, various knowledge gaps in detection and analysis require attention in order to understand the sources and transport of microplastics, which is critical to deploying mitigation strategies at appropriate locations. Advanced removal methods and an integrated approach are necessary, including government policies and stringent regulations to control the release of plastics.

Polystyrene microplastics induce male reproductive toxicity in mice by activating spermatogonium mitochondrial oxidative stress and apoptosis

Microplastics have emerged as environmental hazards in recent years. This study was intended to prove the toxic effects of microplastics on the male reproductive system and further elucidate its mechanism. C57bl/6 mice were exposed to ultrapure water or different doses (0.25, 0.5 and 1 mg/d) of 5 μm polystyrene microplastics (PS-MPs) for 4 weeks, and the GC-1 mouse spermatogonium was treated with different concentrations of PS-MPs. The results showed that sperm count and motility were decreased, and sperm deformity rate was increased after exposure to PS-MPs. The morphology of testes in PS-MPs groups exhibited pathological changes, such as abnormal development of spermatogenic tubules, and inhibited spermatogonium function. Furthermore, the fluorescence intensity of TUNEL staining and the BAX/BCL2 ratio were increased. Exposure to PS-MPs resulted in impaired mitochondrial morphology of spermatogonium, decreased activity of GSH-px and SOD, and increased the MDA level. In vitro, after treatment with PS-MPs, the cell apoptosis rate of spermatogonium was significantly increased, mitochondrial membrane potential was decreased, mitochondrial morphology was damaged, and exposure to PS-MPs increased mitochondrial reactive oxygen species, inducing an oxidative stress state in spermatogonia. In summary, PS-MPs induced a decrease in sperm quality by activating spermatogonium mitochondrial oxidative stress and apoptosis, offering novel insights into mitigating the reproductive toxicity of microplastics.

Cytotoxicity of amine-modified polystyrene MPs and NPs on neural stem cells cultured from mouse subventricular zone

Microplastics (MPs) and nanoplastics (NPs) are found in various environments such as aquatic, terrestrial, and aerial areas. Once ingested and inhaled, these tiny plastic debris damaged the digestive and respiratory organ systems in animals. In humans, the possible connection between MPs and various diseases such as lung diseases has been raised. Yet, the impact of MPs on the human nervous system has been unclear. Previous research using animals and cultured cells showed possible neurotoxicity of MPs and NPs. In this study, we used neural stem cells cultured from mouse subventricular zone to examine the effects of polystyrene (PS) NPs and MPs with sizes of 0.1 μm, 1 μm, and 2 μm on the cell proliferation and differentiation. We observed that only positively charged NPs and MPs, but not negatively charged ones, decreased cell viability and proliferation. These amine-modified NPs and MPs decreased both neurogenesis and oligodendrogenesis. Finally, fully differentiated neurons and oligodendrocytes were damaged and removed by the application of NPs and MPs. All these effects varied among different sizes of NPs and MPs, with the greatest effects from 1 μm and the least effects from 2 μm. These results clearly demonstrate the cytotoxicity and neurotoxicity of PS-NPs and MPs.

Multi-Omics Analysis Reveals the Toxicity of Polyvinyl Chloride Microplastics toward BEAS-2B Cells

Polyvinyl chloride microplastics (PVC-MPs) are microplastic pollutants widely present in the environment, but their potential risks to human lung health and underlying toxicity mechanisms remain unknown. In this study, we systematically analyzed the effects of PVC-MPs on the transcriptome and metabolome of BEAS-2B cells using high-throughput RNA sequencing and untargeted metabolomics technologies. The results showed that exposure to PVC-MPs significantly reduced the viability of BEAS-2B cells, leading to the differential expression of 530 genes and 3768 metabolites. Further bioinformatics analyses showed that PVC-MP exposure influenced the expression of genes associated with fluid shear stress, the MAPK and TGF-β signaling pathways, and the levels of metabolites associated with amino acid metabolism. In particular, integrated pathway analysis showed that lipid metabolic pathways (including glycerophospholipid metabolism, glycerolipid metabolism, and sphingolipid metabolism) were significantly perturbed in BEAS-2B cells following PVC-MPs exposure. This study provides new insights and targets for a deeper understanding of the toxicity mechanism of PVC-MPs and for the prevention and treatment of PVC-MP-associated lung diseases.

Emissions from plastic incineration induce inflammation, oxidative stress, and impaired bioenergetics in primary human respiratory epithelial cells

Inhalation exposure to plastic incineration emissions (PIEs) is a problem of increasing human relevance, as plastic production and waste creation have drastically increased since mainstream integration during the 20th century. We investigated the effects of PIEs on human nasal epithelial cells (HNECs) to understand if such exposures cause damage and dysfunction to respiratory epithelia. Primary HNECs from male and female donors were cultured at air-liquid interface (ALI), and 16HBE cells were cultured on coverslips. Smoke condensates were generated from incineration of plastic at flaming (640°C) and smoldering (500°C) temperatures, and cells were subsequently exposed to these materials at 5-50 μg/cm2 concentrations. HNECs were assessed for mitochondrial dysfunction and 16HBE cells for glutathione oxidation in real-time analyses. HNEC culture supernatants and total RNA were collected at 4-h postexposure for cytokine and gene expression analysis, and results show that PIEs can acutely induce inflammation, oxidative stress, and mitochondrial dysfunction in HNECs, and that incineration temperature modifies biological responses. Specifically, condensates from flaming and smoldering PIEs significantly increased HNEC secretion of cytokines IL-8, IL-1β, and IL-13, as well as expression of xenobiotic metabolism pathways and genes such as CYP1A1 and CYP1B1 at 5 and 20 μg/cm2 concentrations. Only 50 μg/cm2 flaming PIEs significantly increased glutathione oxidation in 16HBEs, and decreased respiration and ATP production in HNEC mitochondria. Impact Statement: Our data reveal the impact of incineration temperatures on biological outcomes associated with PIE exposures, emphasizing the importance of temperature as a factor when evaluating respiratory disease associated with PIEs exposure.

Probabilistic Estimation of Airborne Micro- and Nanoplastic Intake in Humans

Little research exists on the magnitude, variability, and uncertainty of human exposure to airborne micro- and nanoplastics (AMNPs), despite their critical role in human exposure to MNPs. We probabilistically estimate the global intake of AMNPs through three main pathways: indoor inhalation, outdoor inhalation, and ingestion during indoor meals, for both children and adults. The median inhalation of AMPs is 1,207.7 (90% CI, 42.5-8.48 × 104) and 1,354.7 (90% CI, 47.4-9.55 × 104) N/capita/day for children and adults, respectively. The annual intake of AMPs is 13.18 mg/capita/a for children and 19.10 mg/capita/a for adults, which is approximately one-fifth and one-third of the mass of a standard stamp, assuming a consistent daily intake of medians. The majority of AMP number intake occurs through inhalation, while the ingestion of deposited AMPs during meals contributes the most in terms of mass. Furthermore, the median ANP intake through outdoor inhalation is 9,638.1 N/day (8.23 × 10-6 μg/d) and 5,410.6 N/day (4.62 × 10-6 μg/d) for children and adults, respectively, compared to 5.30 × 105 N/day (5.79 × 10-4 μg/d) and 6.00 × 105 N/day (6.55 × 10-4 μg/d) via indoor inhalation. Considering the increased toxicity of smaller MNPs, the significant number of ANPs inhaled warrants great attention. Collaborative efforts are imperative to further elucidate and combat the current MPN risks.

Polystyrene microplastics disturb maternal glucose homeostasis and induce adverse pregnancy outcomes

Pregnant women are a special group that is sensitive to adverse external stimuli, causing metabolic abnormalities and adverse pregnancy outcomes. Microplastics (MPs), an environmental pollutant widely used in various fields, can induce a variety of toxic responses in mammals. Recent studies verified an association between MPs and metabolic disorders. Our research built a gestational mouse model in which polystyrene microplastics (PS-MPs) of 1 μm size were consumed at concentrations of 0.1, 1, and 10 mg/L during pregnancy. Results indicated that PS-MPs induced placental malfunction and fetal growth retardation. Significant glucose disorders, decreased liver function, hepatic inflammation, and oxidative stress were also observed after PS-MPs exposure. The hepatic SIRT1/IRS1/PI3K pathway was inhibited in the 10 mg/L PS-MPs exposure group. Our study found that PS-MPs activated inflammatory response and oxidative stress by increasing hepatic lipopolysaccharide (LPS) that inhibited the hepatic SIRT1/IRS1/PI3K pathway, ultimately leading to insulin resistance, glucose metabolism disorders, and adverse pregnancy outcomes. This study provides a basis for preventing environment-related gestational diabetes and concomitant adverse pregnancy outcomes.

Reproductive cytotoxic and genotoxic impact of polystyrene microplastic on Paracentrotus lividus spermatozoa

In recent decades, industrialization, intensive agriculture, and urban development have severely impacted marine environments, compromising the health of aquatic and terrestrial organisms. Inadequate disposal results in hundreds of tons of plastic products released annually into the environment, which degrade into microplastics (MPs), posing health risks due to their ability to biomagnify and bioaccumulate. Among these, polystyrene MPs (PS-MPs) are significant pollutants in marine ecosystems, widely studied for their reproductive toxicological effects. This research aimed to evaluate the reproductive cytotoxic and genotoxic effects of PS-MPs on sea urchin (Paracentrotus lividus) spermatozoa in vitro. Results showed that PS-MPs significantly reduced sperm viability and motility without altering morphology, and induced sperm DNA fragmentation mediated by reactive oxygen species production. Furthermore, head-to-head agglutination of the spermatozoa was observed exclusively in the sample treated with the plastic agents, indicating the ability of microplastics to adhere to the surface of sperm cells and form aggregates with microplastics on other sperm cells, thereby impeding movement and reducing reproductive potential. These findings suggest that PS-MPs can adversely affect the quality of sea urchin sperm, potentially impacting reproductive events.

Application of organoid technology in the human health risk assessment of microplastics: A review of progresses and challenges

Microplastic (MP) pollution has become a global environmental issue, and increasing concern has been raised about its impact on human health. Current studies on the toxic effects and mechanisms of MPs have mostly been conducted in animal models or in vitro cell cultures, which have limitations regarding inter-species differences or stimulation of cellular functions. Organoid technology derived from human pluripotent or adult stem cells has broader prospects for predicting the potential health risks of MPs to humans. Herein, we reviewed the current application advancements and opportunities for different organoids, including brain, retinal, intestinal, liver, and lung organoids, to assess the human health risks of MPs. Organoid techniques accurately simulate the complex processes of MPs and reflect phenotypes related to diseases caused by MPs such as liver fibrosis, neurodegeneration, impaired intestinal barrier and cardiac hypertrophy. Future perspectives were also proposed for technological innovation in human risk assessment of MPs using organoids, including extending the lifespan of organoids to assess the chronic toxicity of MPs, and reconstructing multi-organ interactions to explore their potential in studying the microbiome-gut-brainaxis effect of MPs.

Inhalation of Microplastics-A Toxicological Complexity

Humans are chronically exposed to airborne microplastics (MPs) by inhalation. Various types of polymer particles have been detected in lung samples, which could pose a threat to human health. Inhalation toxicological studies are crucial for assessing the effects of airborne MPs and for exposure-reduction measures. This communication paper addresses important health concerns related to MPs, taking into consideration three levels of complexity, i.e., the particles themselves, the additives present in the plastics, and the exogenous substances adsorbed onto them. This approach aims to obtain a comprehensive toxicological profile of deposited MPs in the lungs, encompassing local and systemic effects. The physicochemical characteristics of MPs may play a pivotal role in lung toxicity. Although evidence suggests toxic effects of MPs in animal and cell models, no established causal link with pulmonary or systemic diseases in humans has been established. The transfer of MPs and associated chemicals from the lungs into the bloodstream and/or pulmonary circulation remains to be confirmed in humans. Understanding the toxicity of MPs requires a multidisciplinary investigation using a One Health approach.

Polystyrene nanoplastics mediate oxidative stress, senescence, and apoptosis in a human alveolar epithelial cell line

Background

Nanoplastics, an emerging form of pollution, are easily consumed by organisms and pose a significant threat to biological functions due to their size, expansive surface area, and potent ability to penetrate biological systems. Recent findings indicate an increasing presence of airborne nanoplastics in atmospheric samples, such as polystyrene (PS), raising concerns about potential risks to the human respiratory system.

Methods

This study investigates the impact of 800 nm diameter-PS nanoparticles (PS-NPs) on A549, a human lung adenocarcinoma cell line, examining cell viability, redox balance, senescence, apoptosis, and internalization. We also analyzed the expression of hallmark genes of these processes.

Results

We demonstrated that PS-NPs of 800 nm in diameter significantly affected cell viability, inducing oxidative stress, cellular senescence, and apoptosis. PS-NPs also penetrated the cytoplasm of A549 cells. These nanoparticles triggered the transcription of genes comprised in the antioxidant network [SOD1 (protein name: superoxide dismutase 1, soluble), SOD2 (protein name: superoxide dismutase 2, mitochondrial), CAT (protein name: catalase), Gpx1 (protein name: glutathione peroxidase 1), and HMOX1 (protein name: heme oxygenase 1)], senescence-associated secretory phenotype [Cdkn1a (protein name: cyclin-dependent kinase inhibitor 1A), IL1A (protein name: interleukin 1 alpha), IL1B (protein name: interleukin 1 beta), IL6 (protein name: interleukin 6), and CXCL8 (protein name: C-X-C motif chemokine ligand 8)], and others involved in the apoptosis modulation [BAX (protein name: Bcl2 associated X, apoptosis regulator), CASP3 (protein name: caspase 3), and BCL2 (protein name: Bcl2, apoptosis regulator)].

Conclusion

Collectively, this investigation underscores the importance of concentration (dose-dependent effect) and exposure duration as pivotal factors in assessing the toxic effects of PS-NPs on alveolar epithelial cells. Greater attention needs to be directed toward comprehending the risks of cancer development associated with air pollution and the ensuing environmental toxicological impacts on humans and other terrestrial mammals.

The triple exposure nexus of microplastic particles, plastic-associated chemicals, and environmental pollutants from a human health perspective

The presence of microplastics (MPs) is increasing at a dramatic rate globally, posing risks for exposure and subsequent potential adverse effects on human health. Apart from being physical objects, MP particles contain thousands of plastic-associated chemicals (i.e., monomers, chemical additives, and non-intentionally added substances) captured within the polymer matrix. These chemicals are often migrating from MPs and can be found in various environmental matrices and human food chains; increasing the risks for exposure and health effects. In addition to the physical and chemical attributes of MPs, plastic surfaces effectively bind exogenous chemicals, including environmental pollutants (e.g., heavy metals, persistent organic pollutants). Therefore, MPs can act as vectors of environmental pollution across air, drinking water, and food, further amplifying health risks posed by MP exposure. Critically, fragmentation of plastics in the environment increases the risk for interactions with cells, increases the presence of available surfaces to leach plastic-associated chemicals, and adsorb and transfer environmental pollutants. Hence, this review proposes the so-called triple exposure nexus approach to comprehensively map existing knowledge on interconnected health effects of MP particles, plastic-associated chemicals, and environmental pollutants. Based on the available data, there is a large knowledge gap in regard to the interactions and cumulative health effects of the triple exposure nexus. Each component of the triple nexus is known to induce genotoxicity, inflammation, and endocrine disruption, but knowledge about long-term and inter-individual health effects is lacking. Furthermore, MPs are not readily excreted from organisms after ingestion and they have been found accumulated in human blood, cardiac tissue, placenta, etc. Even though the number of studies on MPs-associated health impacts is increasing rapidly, this review underscores that there is a pressing necessity to achieve an integrated assessment of MPs' effects on human health in order to address existing and future knowledge gaps.

Environmental toxicants and nephrotoxicity: Implications on mechanisms and therapeutic strategies

Kidneys are one of the most important organs in the human body. In addition to filtering 200 liters of fluid every 24 hours, the kidney also regulates acid-base balance, maintains electrolyte balance, and removes waste and toxicants from the body. Nephrotoxicity is the term used to describe the deterioration of kidney function caused by the harmful effects of medications and various types of environmental toxicants. Exposure to environmental toxicants is an inevitable side effect in the world's increasing industrialization and even more prevalent in underdeveloped nations. Growing data over the past few years has illuminated the probable connection between environmental toxicants and nephrotoxicity. Phthalates, microplastics, acrylamide and bisphenol A are environmental toxicants of particular concern, which are known to have nephrotoxic effects. Such toxicants may accumulate in the kidneys of humans after being consumed, inhaled, or come into contact with the skin. They can enter cells through endocytosis and accumulate in the cytoplasm. Small-sized nephrotoxicants can cause a variety of ailments including inflammation with increased production of pro-inflammatory cytokines, oxidative stress, mitochondrial dysfunction, autophagy, and apoptosis. This study uncovers the potential for new insights concerning the relationship between various environmental toxicants and kidney health. The objectives of this review is to establish information gaps, assess and identify the toxicity mechanisms of different nephrotoxicants, identify innovative pharmacological therapies that demonstrate promising therapeutic benefits/ relevance, and discuss the predictions for the future based on the analysis of the literature.

Mechanism of circRNA_SMG6 mediating lung macrophage ECM degradation via miR-570-3p in microplastics-induced emphysema

Microplastics (MPs) are plastic particles < 5 mm in diameter, of which polystyrene microplastics (PS-MPs) are representative type. The extracellular matrix (ECM) degradation of macrophages is associated with the development of emphysema. Additionally, circular RNAs (circRNAs) have a regulatory role in epigenetic mechanisms related to lung disease. However, the mechanisms of the ECM degradation and circRNAs in MPs-induced emphysema are still unclear. In our study, Sprague-Dawley (SD) rats were treated with 0, 0.5, 1.0 and 2.0 mg/m3 100 nm PS-MPs for 90 days in an inhalation experiment. PS-MPs-exposed rats showed elevated airway resistance and pulmonary dysfunction. Lung histopathology exhibited inflammatory cell infiltration, septal thickening and alveolar dilatation. Exposure to PS-MPs was able to induce elevated levels of ECM degradation-related markers MMP9 and MMP12, as well as reduced levels of elastin in rat lung tissues. CircRNA_SMG6 is a non-coding RNA (ncRNA) with a homologous circular structure in human, rat and mouse. The expression level of circRNA_SMG6 was decreased in both rat lung tissues exposed to PS-MPs and PS-MPs-treated THP-1 cells. The luciferase reporter gene demonstrated that circRNA_SMG6 combined with miR-570-3p and co-regulated PTEN, the target gene of miR-570-3p. Moreover, overexpression of circRNA_SMG6 or inhibition of miR-570-3p attenuated PS-MPs-induced ECM degradation in THP-1 cells. Taken together, circRNA_SMG6 may have a significant function in the deterioration of emphysema caused by PS-MPs-induced macrophage ECM degradation by regulating miR-570-3p. Our findings reveal a novel mechanism of emphysema caused by PS-MPs and provide valuable information for assessing the health risks of MPs.

Inhalation exposure to polystyrene nanoplastics induces chronic obstructive pulmonary disease-like lung injury in mice through multi-dimensional assessment

Nanoplastics are widely distributed in indoor and outdoor air and can be easily inhaled into human lungs. However, limited studies have investigated the impact of nanoplastics on inhalation toxicities, especially on the initiation and progression of chronic obstructive pulmonary disease (COPD). To fill the gap, the present study used oronasal aspiration to develop mice models. Mice were exposed to polystyrene nanoplastics (PS-NPs) at three concentrations, as well as the corresponding controls, for acute, subacute, and subchronic exposure. As a result, PS-NPs could accumulate in exposed mice lungs and influence lung organ coefficient. Besides, PS-NPs induced local and systemic oxidative stress, inflammation, and protease-antiprotease imbalance, resulting in decreased respiratory function and COPD-like lesions. Meanwhile, PS-NPs could trigger the subcellular mechanism to promote COPD development by causing mitochondrial dysfunctions and endoplasmic reticulum (ER) stress. Mechanistically, ferroptosis played an important role in the COPD-like lung injury induced by PS-NPs. In summary, the present study comprehensively and systematically indicates that PS-NPs can damage human respiratory health and increase the risk for COPD.

Exploring the potential and challenges of developing physiologically-based toxicokinetic models to support human health risk assessment of microplastic and nanoplastic particles

Microplastics (MPs) and nanoplastics (NPs) pollution has emerged as a significant and widespread environmental issue. Humans are inevitably exposed to MPs and NPs via ingestion, inhalation, and dermal contacts from various sources. However, mechanistic knowledge of their distribution, interaction, and potency in the body is still lacking. To address this knowledge gap, we have undertaken the task of elucidating the toxicokinetic (TK) behaviors of MPs and NPs, aiming to provide mechanistic information for constructing a conceptual physiologically based toxicokinetic (PBTK) model to support in silico modeling approaches. Our effort involved a thorough examination of the existing literature and data collation on the presence of MPs in the human body and in vitro/ex vivo/in vivo biodistribution across various cells and tissues. By comprehending the absorption, distribution, metabolism, and excretion mechanisms of MPs and NPs in relation to their physicochemical attributes, we established a foundational understanding of the link between external exposure and internal tissue dosimetry. We observed that particle size and surface chemistry have been thoroughly explored in previous experimental studies. However, certain attributes, such as polymer type, shape, and biofilm/biocorona, warrant attention and further examination. We discussed the fundamental disparities in TK properties of MPs/NPs from those of engineered nanoparticles. We proposed a preliminary PBTK framework with several possible modeling approaches and discussed existing challenges for further investigation. Overall, this article provides a comprehensive compilation of existing TK data of MPs/NPs, a critical overview of TK processes and mechanisms, and proposes potential PBTK modeling approaches, particularly regarding their applicability to the human system, and outlines future perspectives for developing PBTK models and their integration into human health risk assessment of MPs and NPs.

Microplastic and plastic pollution: impact on respiratory disease and health

Throughout their lifecycle, from production to use and upon disposal, plastics release chemicals and particles known as micro- and nanoplastics (MNPs) that can accumulate in the environment. MNPs have been detected in different locations of the human body, including in our lungs. This is likely a consequence of MNP exposure through the air we breathe. Yet, we still lack a comprehensive understanding of the impact that MNP exposure may have on respiratory disease and health. In this review, we have collated the current body of evidence on the implications of MNP inhalation on human lung health from in vitro, in vivo and occupational exposure studies. We focused on interactions between MNP pollution and different specific lung-resident cells and respiratory diseases. We conclude that it is evident that MNPs possess the capacity to affect lung tissue in disease and health. Yet, it remains unclear to which extent this occurs upon exposure to ambient levels of MNPs, emphasising the need for a more comprehensive evaluation of environmental MNP exposure levels in everyday life.

Interactions between inhalable aged microplastics and lung surfactant: Potential pulmonary health risks

The relationship between microplastics (MPs) and human respiratory health has garnered significant attention since inhalation constitutes the primary pathway for atmospheric MP exposure. While recent studies have revealed respiratory risks associated with MPs, virgin MPs used as plastic surrogates in these experiments did not represent the MPs that occur naturally and that undergo aging effects. Thus, the effects of aged MPs on respiratory health remain unknown. We herein analyzed the interaction between inhalable aged MPs with lung surfactant (LS) extracted from porcine lungs vis-à-vis interfacial chemistry employing in-vitro experiments, and explored oxidative damage induced by aged MPs in simulated lung fluid (SLF) and the underlying mechanisms of action. Our results showed that aged MPs significantly increased the surface tension of the LS, accompanied by a diminution in its foaming ability. The stronger adsorptive capacity of the aged MPs toward the phospholipids of LS appeared to produce increased surface tension, while the change in foaming ability might have resulted from a variation in the protein secondary structure and the adsorption of proteins onto MPs. The adsorption of phospholipid and protein components then led to the aggregation of MPs in SLF, where the aged MPs exhibited smaller hydrodynamic diameters in comparison with the unaged MPs, likely interacting with biomolecules in bodily fluids to exacerbate health hazards. Persistent free radicals were also formed on aged MPs, inducing the formation of reactive oxygen species such as superoxide radicals (O2•-), hydrogen peroxide (HOOH), and hydroxyl radicals (•OH); this would lead to LS lipid peroxidation and protein damage and increase the risk of respiratory disease. Our investigation was the first-ever to reveal a potential toxic effect of aged MPs and their actions on the human respiratory system, of great significance in understanding the risk of inhaled MPs on lung health.

Long-term polystyrene nanoplastic exposure disrupt hepatic lipid metabolism and cause atherosclerosis in ApoE-/- mice

Nanoplastics (NPs) exposure is usually linked with abnormal inflammation and oxidative stress, which are high-risk triggers of atherosclerosis; however, whether this exposure causes the development of atherosclerosis is vague. Here, we found that PS NPs co-exposure with ox-LDL induces significant accumulation of lipid, as well as oxidative stress and inflammation in RAW264.7 macrophages. Using an ultrasound biomicroscope (UBM), we observed the emergence of atherosclerotic plaques at the aortic arch of apolipoprotein knockout (ApoE-/-) mice after being exposed to PS NPs for three months. Oil-red O and hematoxylin-eosin (H&E) staining at the mice's aortic root also observed the deposition of lipids with plaque formation. Moreover, the development of atherosclerotic disease is associated with disturbances in lipid metabolism and oxidative stress damage in the mice liver. In conclusion, this study provides additional evidence to further understand the possible cardiovascular damage caused by NPs exposure.

PS-MPs promotes the progression of inflammation and fibrosis in diabetic nephropathy through NLRP3/Caspase-1 and TGF-β1/Smad2/3 signaling pathways

BACKGROUND

Diabetic nephropathy (DN) is a prevalent chronic microvascular complication of diabetes and the leading cause of end-stage renal disease (ESRD). Understanding the progressive etiology of DN is critical for the development of effective health policies and interventions. Recent research indicated that polystyrene microplastics (PS-MPs) contaminate our diets and accumulate in various organs, including the liver, kidneys, and muscles.

METHODS

In this study, ten-week-old db/db mice and db/m mice were fed. Besides, db/db mice were divided into two groups: PS-MPs group (oral administration of 0.5 µm PS-MPs) and an H2O group, and they were fed for three months. A type II diabetes model was established using db/db mice to investigate the effects of PS-MPs on body weight, blood glucose level, renal function, and renal fibrosis.

RESULTS

The results demonstrated that PS-MPs significantly exacerbated various biochemical indicators of renal tissue damage, including fasting blood glucose, serum creatinine, blood urea nitrogen, and blood uric acid. Additionally, PS-MPs worsened the pathological alterations and degree of fibrosis in renal tissue. An increased oxidative stress state and elevated levels of inflammatory cytokines, such as tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), and monocyte chemoattractant protein-1 (MCP-1) were identified. Furthermore, PS-MPs significantly enhanced renal fibrosis by inhibiting the transition from epithelial cells to mesenchymal cells, specifically through the inhibition of the TGF-β/Smad signaling pathway. The expression levels of NOD-like receptor protein 3 (NLRP3), apoptosis-associated speck-like protein containing a CARD (ASC), Caspase-1, and cleaved Caspase-1, which are inflammasome proteins, were significantly elevated in the PS-MPs group.

CONCLUSION

The findings suggested that PS-MPs could aggravate kidney injury and renal fibrosis in db/db mice by promoting NLRP3/Caspase-1 and TGF-β1/Smads signaling pathways. These findings had implications for elucidating the role of PS-MPs in DN progression, underscoring the necessity for additional research and public health interventions.