Identification and characterisation of individual nanoplastics by scanning transmission X-ray microscopy (STXM)

Microplastics and nanoplastics in tea: Sources, characteristics and potential impacts

Recent scientific studies have raised concerns about the presence and potential impacts of microplastics and nanoplastics (MNPs) in tea-based drinks. This review critically examines publications relating to MNPs in tea, with focus on the type of sample involved, methods and techniques employed to isolate and identify MNPs, and the main qualitative and quantitative findings. Sources of MNPs in tea include production water, plastic packaging and contaminated tea leaves but the most important source is teabags when steeped in boiling water. Here, more than 109 MNPs have been reported to be released per plastic teabag. However, significant quantities of MNPs are also released when plastic-cellulosic composite and biodegradable bags are steeped. Discrepancies among different studies partly reflect inter-brand and inter-material differences, but a more general cause is the adoption of different analytical protocols, including different size cutoffs used during isolation and constrained by identification. Some studies have also reported leaching of plastic additives and residues on steeping, although it is not clear whether these are released from the intact teabags or MNPs that are subsequently mobilised. As teabags generate concentrations of MNPs greater than other beverages or foodstuffs, potential impacts on human health and the environment are a concern and require further study.

Coarse microplastic accumulation patterns in agricultural soils during two decades of different urban composts application

Plastic pollution, a global threat to environmental and human health, is now ubiquitous in the environment, including agricultural soils receiving urban compost amendments. Yet, the accumulation pattern of microplastics in soils are still to be disentangled, with regards to their sources and/or their physical properties such as morphotypes. The aim of this study was to identify the accumulation patterns of coarse microplastics (CMP) resulting from the long-term amendment of soil with urban waste composts. To this end, we used a field experiment receiving three different urban composts derived from municipal solid waste, biowaste, and a mixture of sewage sludge and green waste. We isolated 1417 coarse microplastic particles from a 21-year archive of soil and compost samples, using density fractionation followed by oxidation, and used Py-GC/MS for polymer identification. Different compost types led to different coarse microplastics accumulation levels. The accumulation pattern showed increasing CMP contents in soils over time. After 21 years of experiment, the calculated number of CMP was in accordance with the estimated values for all three compost types but it was not the case for the CMP mass. No difference of evolution pattern was found between films and fragments. We proposed that biotic transport or abiotic weathering and fragmentation could explain such differences in CMP evolution pattern.

Adsorption behavior and mechanism of heavy metals onto microplastics: A meta-analysis assisted by machine learning

Microplastics (MPs) have the potential to adsorb heavy metals (HMs), resulting in a combined pollution threat in aquatic and terrestrial environments. However, due to the complexity of MP/HM properties and experimental conditions, research on the adsorption of HMs onto MPs often yields inconsistent findings. To address this issue, we conducted a comprehensive meta-analysis assisted with machine learning by analyzing a dataset comprising 3340 records from 134 references. The results indicated that polyamide (PA) (ES = -1.26) exhibited the highest adsorption capacity for commonly studied HMs (such as Pb, Cd, Cu, and Cr), which can be primarily attributed to the presence of C=O and N-H groups. In contrast, polyvinyl chloride (PVC) demonstrated a lower adsorption capacity, but the strongest adsorption strength resulting from the halogen atom on its surface. In terms of HMs, metal cations were more readily adsorbed by MPs compared with metalloids and metal oxyanions, with Pb (ES = -0.78) exhibiting the most significant adsorption. As the pH and temperature increased, the adsorption of HMs initially increased and subsequently decreased. Using a random forest model, we accurately predicted the adsorption capacity of MPs based on MP/HM properties and experimental conditions. The main factors affecting HM adsorption onto MPs were HM and MP concentrations, specific surface area of MP, and pH. Additionally, surface complexation and electrostatic interaction were the predominant mechanisms in the adsorption of Pb and Cd, with surface functional groups being the primary factors affecting the mechanism of MPs. These findings provide a quantitative summary of the interactions between MPs and HMs, contributing to our understanding of the environmental behavior and ecological risks associated with their correlation.

Nanoplastics in Water: Artificial Intelligence-Assisted 4D Physicochemical Characterization and Rapid In Situ Detection

For the first time, we present a much-needed technology for the in situ and real-time detection of nanoplastics in aquatic systems. We show an artificial intelligence-assisted nanodigital in-line holographic microscopy (AI-assisted nano-DIHM) that automatically classifies nano- and microplastics simultaneously from nonplastic particles within milliseconds in stationary and dynamic natural waters, without sample preparation. AI-assisted nano-DIHM identifies 2 and 1% of waterborne particles as nano/microplastics in Lake Ontario and the Saint Lawrence River, respectively. Nano-DIHM provides physicochemical properties of single particles or clusters of nano/microplastics, including size, shape, optical phase, perimeter, surface area, roughness, and edge gradient. It distinguishes nano/microplastics from mixtures of organics, inorganics, biological particles, and coated heterogeneous clusters. This technology allows 4D tracking and 3D structural and spatial study of waterborne nano/microplastics. Independent transmission electron microscopy, mass spectrometry, and nanoparticle tracking analysis validates nano-DIHM data. Complementary modeling demonstrates nano- and microplastics have significantly distinct distribution patterns in water, which affect their transport and fate, rendering nano-DIHM a powerful tool for accurate nano/microplastic life-cycle analysis and hotspot remediation.

Rapid single-particle chemical imaging of nanoplastics by SRS microscopy

Plastics are now omnipresent in our daily lives. The existence of microplastics (1 µm to 5 mm in length) and possibly even nanoplastics (<1 μm) has recently raised health concerns. In particular, nanoplastics are believed to be more toxic since their smaller size renders them much more amenable, compared to microplastics, to enter the human body. However, detecting nanoplastics imposes tremendous analytical challenges on both the nano-level sensitivity and the plastic-identifying specificity, leading to a knowledge gap in this mysterious nanoworld surrounding us. To address these challenges, we developed a hyperspectral stimulated Raman scattering (SRS) imaging platform with an automated plastic identification algorithm that allows micro-nano plastic analysis at the single-particle level with high chemical specificity and throughput. We first validated the sensitivity enhancement of the narrow band of SRS to enable high-speed single nanoplastic detection below 100 nm. We then devised a data-driven spectral matching algorithm to address spectral identification challenges imposed by sensitive narrow-band hyperspectral imaging and achieve robust determination of common plastic polymers. With the established technique, we studied the micro-nano plastics from bottled water as a model system. We successfully detected and identified nanoplastics from major plastic types. Micro-nano plastics concentrations were estimated to be about 2.4 ± 1.3 × 105 particles per liter of bottled water, about 90% of which are nanoplastics. This is orders of magnitude more than the microplastic abundance reported previously in bottled water. High-throughput single-particle counting revealed extraordinary particle heterogeneity and nonorthogonality between plastic composition and morphologies; the resulting multidimensional profiling sheds light on the science of nanoplastics.

Research progress of nano-scale secondary ion mass spectrometry (NanoSIMS) in soil science: Evolution, applications, and challenges

Nano-scale secondary ion mass spectrometry (NanoSIMS) has emerged as a powerful analytical tool for investigating various aspects of soils. In recent decades, the widespread adoption of advanced instrumentation and methods has contributed significantly to our understanding of organic-mineral assemblages. However, few literature reviews have comprehensively summarized NanoSIMS and its evolution, applications, limitations, and integration with other analytical techniques. In this review, we addressed this gap by comprehensively overviewing the development of NanoSIMS as an analytical tool in soils. This review covers studies on soil organic matter (SOM) cycling, soil-root interactions, and the behavior of metals, discussing the capability and limitations related to the distribution, composition, and interactions of various soil components that occur at mineral-organic interfaces. Furthermore, we examine recent advancements in high-resolution imaging and mass spectrometry technologies and their impact on the utilization of NanoSIMS in soils, along with potential new applications such as utilizing multiple ion beams and integrating them with other analytical techniques. The review emphasizes the importance of employing advanced techniques and methods to explore micro-interfaces and provide in situ descriptions of organic-mineral assemblages in future research. The ongoing development and refinement of NanoSIMS may yield new insights and breakthroughs in soil science, deepening our understanding of the intricate relationships between soil components and the processes that govern soil health and fertility.

Worker studies suggest unique liver carcinogenicity potential of polyvinyl chloride microplastics

BACKGROUND

Plastic debris pervades our environment. Some breaks down into microplastics (MPs) that can enter and distribute in living organisms causing effects in multiple target organs. MPs have been demonstrated to harm animals through environmental exposure. Laboratory animal studies are still insufficient to evaluate human impact. And while MPs have been found in human tissues, the health effects at environmental exposure levels are unclear.

AIM

We reviewed and summarized existing evidence on health effects from occupational exposure to MPs. Additionally, the diverse effects documented for workers were organized by MP type and associated co-contaminants. Evidence of the unique effects of polyvinyl chloride (PVC) on liver was then highlighted.

METHODS

We conducted two stepwise online literature reviews of publications focused on the health risks associated with occupational MP exposures. This information was supplemented with findings from animal studies.

RESULTS

Our analysis focused on 34 published studies on occupational health effects from MP exposure with half involving exposure to PVC and the other half a variety of other MPs to compare. Liver effects following PVC exposure were reported for workers. While PVC exposure causes liver toxicity and increases the risk of liver cancers, including angiosarcomas and hepatocellular carcinomas, the carcinogenic effects of work-related exposure to other MPs, such as polystyrene and polyethylene, are not well understood.

CONCLUSION

The data supporting liver toxicity are strongest for PVC exposure. Overall, the evidence of liver toxicity from occupational exposure to MPs other than PVC is lacking. The PVC worker data summarized here can be useful in assisting clinicians evaluating exposure histories from PVC exposure and designing future cell, animal, and population exposure-effect research studies.

Preparation of Well-Defined Fluorescent Nanoplastic Particles by Confined Impinging Jet Mixing

Research on the origin, distribution, detection, identification, and quantification of polymer nanoparticles (NPs) in the environment and their possible impact on animal and human health is surging. For different types of studies in this field, well-defined reference materials or mimics are needed. While isolated reports on the preparation of such materials are available, a simple and broadly applicable method that allows for the production of different NP types with well-defined, tailorable characteristics is still missing. Here, we demonstrate that a confined impinging jet mixing process can be used to prepare colloidally stable NPs based on polystyrene, polyethylene, polypropylene, and poly(ethylene terephthalate) with diameters below < 100 nm. Different fluorophores were incorporated into the NPs, to allow their detection in complex environments. To demonstrate their utility and detectability, fluorescent NPs were exposed to J774A.1 macrophages and visualized using laser scanning microscopy. Furthermore, we modified the NPs in a postfabrication process and changed their shape from spherical to heterogeneous geometries, in order to mimic environmentally relevant morphologies. The methodology used here should be readily applicable to other polymers and payloads and thus a broad range of NPs that enable studies of their behavior, uptake, translocation, and biological end points in different systems.

A Novel Approach for Identifying Nanoplastics by Assessing Deformation Behavior with Scanning Electron Microscopy

As plastic production continues to increase globally, plastic waste accumulates and degrades into smaller plastic particles. Through chemical and biological processes, nanoscale plastic particles (nanoplastics) are formed and are expected to exist in quantities of several orders of magnitude greater than those found for microplastics. Due to their small size and low mass, nanoplastics remain challenging to detect in the environment using most standard analytical methods. The goal of this research is to adapt existing tools to address the analytical challenges posed by the identification of nanoplastics. Given the unique and well-documented properties of anthropogenic plastics, we hypothesized that nanoplastics could be differentiated by polymer type using spatiotemporal deformation data collected through irradiation with scanning electron microscopy (SEM). We selected polyvinyl chloride (PVC), polyethylene terephthalate (PET), and high-density polyethylene (HDPE) to capture a range of thermodynamic properties and molecular structures encompassed by commercially available plastics. Pristine samples of each polymer type were chosen and individually milled to generate micro and nanoscale particles for SEM analysis. To test the hypothesis that polymers could be differentiated from other constituents in complex samples, the polymers were compared against proxy materials common in environmental media, i.e., algae, kaolinite clay, and nanocellulose. Samples for SEM analysis were prepared uncoated to enable observation of polymer deformation under set electron beam parameters. For each sample type, particles approximately 1 µm in diameter were chosen, and videos of particle deformation were recorded and studied. Blinded samples were also prepared with mixtures of the aforementioned materials to test the viability of this method for identifying near-nanoscale plastic particles in environmental media. Based on the evidence collected, deformation patterns between plastic particles and particles present in common environmental media show significant differences. A computer vision algorithm was also developed and tested against manual measurements to improve the usefulness and efficiency of this method further.

Hydrophobicity-driven self-assembly of nanoplastics and silver nanoparticles for the detection of polystyrene microspheres using surface enhanced Raman spectroscopy

Microplastics (MPs) and Nanoplastics (NPs) accumulated in the environment have been identified as a major global issue due to their potential harm to wildlife. Current research in the detection of MPs is well established. However, the detection of NPs remains challenging. The aim of this paper is to investigate the detection of polystyrene (PS) NPs on a super-hydrophobic substrate using surface-enhanced Raman spectroscopy (SERS) technology after high-speed centrifugation of PS NPs and AgNPs. The hydrophobic substrate reduces the contact area of droplet, concentrating PS NPs and AgNPs on a small spot, which eliminates the random distribution of nano particles. The condensed PS NPs and AgNPs improve the SERS intensity, reproductivity and detection sensitivity. The results show that SERS measurement on a hydrophobic substrate could significantly improve the detection sensitivity of PS NPs, with the detection limits of PS NPs as low as 0.5 mg/L (500 nm PS NPs) and 1 mg/L (100 nm PS NPs). The study provides an effective and rapid method for the detection of NPs at trace concentration, demonstrating more possibility for the future detection of trace NPs in the aquatic environment.

Morphological and lipid metabolism alterations in macrophages exposed to model environmental nanoplastics traced by high-resolution synchrotron techniques

The release of nanoplastics (NPs) in the environment is a significant health concern for long-term exposed humans. Although their usage has certainly revolutionized several application fields, at nanometer size, NPs can easily interact at the cellular level, resulting in potential harmful effects. Micro/Nanoplastics (M/NPs) have a demonstrated impact on mammalian endocrine components, such as the thyroid, adrenal gland, testes, and ovaries, while more investigations on prenatal and postnatal exposure are urgently required. The number of literature studies on the NPs' presence in biological samples is increasing. However, only a few offer a close study on the model environmental NP-immune system interaction exploited by advanced microscopy techniques. The present study highlights substantial morphological and lipid metabolism alterations in human M1 macrophages exposed to labeled polypropylene and polyvinyl chloride nanoparticles (PP and PVC NPs) (20 μg/ml). The results are interpreted by advanced microscopy techniques combined with standard laboratory tests and fluorescence microscopy. We report the accurate detection of polymeric nanoparticles doped with cadmium selenide quantum dots (CdSe-QDs NPs) by following the Se (L line) X-ray fluorescence emission peak at higher sub-cellular resolution, compared to the supportive light fluorescence microscopy. In addition, scanning transmission X-ray microscopy (STXM) imaging successfully revealed morphological changes in NP-exposed macrophages, providing input for Fourier transform infrared (FTIR) spectroscopy analyses, which underlined the chemical modifications in macromolecular components, specifically in lipid response. The present evidence was confirmed by quantifying the lipid droplet (LD) contents in PP and PVC NPs-exposed macrophages (0-100 μg/ml) by Oil Red O staining. Hence, even at experimental NPs' concentrations and incubation time, they do not significantly affect cell viability; they cause an evident lipid metabolism impairment, a hallmark of phagocytosis and oxidative stress.

After the sun: a nanoscale comparison of the surface chemical composition of UV and soil weathered plastics

Once emitted into the environment, macro- (MaP), micro- (MP) and nanoplastics (NP) are exposed to environmental weathering. Yet, the effects of biogeochemical weathering factors occurring in the soil environment are unknown. As the transport, fate, and toxicity of MP and NP depend directly on their surface properties, it is crucial to characterize their transformation in soils to better predict their impact and interactions in this environment. Here, we used scanning transmission x-ray micro spectroscopy to characterize depth profiles of the surface alteration of environmental plastic debris retrieved from soil samples. Controlled weathering experiments in soil and with UV radiation were also performed to investigate the individual effect of these weathering factors on polymer surface alteration. The results revealed a weathered surface on a depth varying between 1 µm and 100 nm in PS, PET and PP environmental plastic fragments naturally weathered in soil. Moreover, the initial step of surface fragmentation was observed on a PS fragment, providing an insight on the factors and processes leading to the release of MP and NP in soils. The comparison of environmental, soil incubated (for 1 year) and UV weathered samples showed that the treatments led to different surface chemical modifications. While the environmental samples showed evidence of alteration involving oxidation processes, the UV weathered samples did not reveal oxidation signs at the surface but only decrease in peak intensities (indicating decrease of the number of chemical C bonds). After a one-year incubation of samples in soil no clear aging effects were observed, indicating that the aging of polymers can be slow in soils.

Supplementary Information

The online version contains supplementary material available at 10.1186/s43591-023-00066-2.

Microplastics in food - a critical approach to definition, sample preparation, and characterisation

The ubiquity of microplastics (MPs) is a more and more frequently brought up topic. The fact that such particles are present in food raises particular concern. Information regarding the described contamination is incoherent and difficult to interpret. Problems appear already at the level of the definition of MPs. This paper will discuss ways of explaining the concept of MPs and methods used for its analysis. Isolation of characterised particles is usually performed using filtration, etching and/or density separation. Spectroscopic techniques are commonly applied for analysis, whereas visual evaluation of the particles is possible thanks to microscopic analysis. Basic information about the sample can be obtained by the combination of Fourier Transform Infrared spectroscopy or Raman spectroscopy and microscopy or using the thermal method combined with spectroscopy or chromatography. The unification of the research methodology will allow a credible assessment of the influence of this pollution coming from food on health.

The release of polylactic acid nanoplastics (PLA-NPLs) from commercial teabags. Obtention, characterization, and hazard effects of true-to-life PLA-NPLs

This study investigates MNPLs release from commercially available teabags and their effects on both undifferentiated monocultures of Caco-2 and HT29 and in the in vitro model of the intestinal Caco-2/HT29 barrier. Teabags were subjected to mechanical and thermodynamic forces simulating the preparation of a cup of tea. The obtained dispersions were characterized using TEM, SEM, DLS, LDV, NTA, and FTIR. Results confirmed that particles were in the nano-range, constituted by polylactic acid (PLA-NPLs), and about one million of PLA-NPLs per teabag were quantified. PLA-NPLs internalization, cytotoxicity, intracellular reactive oxygen species induction, as well as structural and functional changes in the barrier were assessed. Results show that PLA-NPLs present high uptake rates, especially in mucus-secretor cells, and bio-persisted in the tissue after 72 h of exposure. Although no significant cytotoxicity was observed after the exposure to 100 µg/mL PLA-NPLs during 48 h, a slight barrier disruption could be detected at short-time periods. The present work reveals new insights into the safety of polymer-based teabags, the behavior of true-to-life MNPLs in the human body, as well as new questions on how repeated and prolonged exposures could affect the structure and function of the human intestinal epithelium.

Method for nanoparticles uptake evaluation based on double labeled fluorescent cells scanned in enhanced darkfield microscopy

We present a method that integrates the standard imaging tools for locating and detecting unlabeled nanoparticles (NPs) with computational tools for partitioning cell volumes and NPs counting within specified regions to evaluate their internal traffic. The method uses enhanced dark field CytoViva optical system and combines 3D reconstructions of double fluorescently labeled cells with hyperspectral images. The method allows the partitioning of each cell image into four regions: nucleus, cytoplasm, and two neighboring shells, as well as investigations across thin layers adjacent to the plasma membrane. MATLAB scripts were developed to process the images and to localize NPs in each region. Specific parameters were computed to assess the uptake efficiency: regional densities of NPs, flow densities, relative accumulation indices, and uptake ratios. The results of the method are in line with biochemical analyses. It was shown that a sort of saturation limit for intracellular NPs density is reached at high extracellular NPs concentrations. Higher NPs densities were found in the proximity of the plasma membranes. A decrease of the cell viability with increasing extracellular NPs concentration was observed and explained the negative correlation of the cell eccentricity with NPs number.

Spectro-Microscopic Techniques for Studying Nanoplastics in the Environment and in Organisms

Nanoplastics (NPs), small (<1 μm) polymer particles formed from bulk plastics, are a potential threat to human health and the environment. Orders of magnitude smaller than microplastics (MPs), they might behave differently due to their larger surface area and small size, which allows them to diffuse through organic barriers. However, detecting NPs in the environment and organic matrices has proven to be difficult, as their chemical nature is similar to these matrices. Furthermore, as their size is smaller than the (spatial) detection limit of common analytical tools, they are hard to find and quantify. We highlight different micro-spectroscopic techniques utilized for NP detection and argue that an analysis procedure should involve both particle imaging and correlative or direct chemical characterization of the same particles or samples. Finally, we highlight methods that can do both simultaneously, but with the downside that large particle numbers and statistics cannot be obtained.

Unraveling the potential human health risks from used disposable face mask-derived micro/nanoplastics during the COVID-19 pandemic scenario: A critical review

With the global spread of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), disposable face masks (DFMs) have caused negative environmental impacts. DFMs will release microplastics (MPs) and nanoplastics (NPs) during environmental degradation. However, few studies reveal the release process of MPs/NPs from masks in the natural environment. This review presents the current knowledge on the abiotic and biotic degradation of DFMs. Though MPs and NPs have raised serious concerns about their potentially detrimental effects on human health, little attention was paid to their impacts on human health from DFM-derived MPs and NPs. The potential toxicity of mask-derived MPs/NPs, such as gastrointestinal toxicity, pneumotoxicity, neurotoxicity, hepatotoxicity, reproductive and transgenerational toxicity, and the underlying mechanism will be discussed in the present study. MPs/NPs serve as carriers of toxic chemicals and pathogens, leading to their bioaccumulation and adverse effects of biomagnification by food chains. Given human experiments are facing ethical issues and animal studies cannot completely reveal human characteristics, advanced human organoids will provide promising models for MP/NP risk assessment. Moreover, in-depth investigations are required to identify the release of MPs/NPs from discarded face masks and characterize their transportation through the food chains. More importantly, innovative approaches and eco-friendly strategies are urgently demanded to reduce DFM-derived MP/NP pollution.