The environmental fate of nanoplastics: What we know and what we need to know about aggregation

Development of a simple SERS substrate for the detection of pollutants and nanoplastics

This study investigates the development and characterisation of Ag- and Au-coated silicon filter substrates developed for surface-enhanced Raman spectroscopy (SERS) applications. Silver nanoparticles were synthesised by immersing silicon filters in an AgNO3 solution, with the immersion time playing a crucial role in nanoparticle distribution and SERS efficiency. The highest performance was observed at an immersion time of 30-60 min and allowed the detection of 4-mercaptobenzoic acid (4-MBA) at nanomolar concentrations. To improve stability and tunability, gold was sputtered onto the Ag-coated substrates. Optimal performance was achieved with 6 min of Au sputtering, which allowed picomolar sensitivity for 4-MBA and micromolar detection of melamine. These substrates were further tested for the detection of polystyrene (PS) and polyethylene (PE) nanoplastic particles by Raman mapping with particles down to 50 nm. The successful identification showed great potential for the micro-Raman analysis of nanomaterials. The results emphasise the high sensitivity, versatility and ease of production of the SERS substrates and highlight their potential for applications in environmental and food monitoring, especially for the detection of nanoplastics.

Adsorption and desorption of phenanthrene and 1-hydroxyphenanthrene by goethite-coated polyvinyl chloride

Microplastics loaded with phenanthrene and derivatives are widely detected in aquatic environments, and the coating of natural minerals or organic macromolecules may change the environmental behavior of microplastics. In this study, three kinds of composites with different coverage were prepared by coating goethite on the surface of polyvinyl chloride microplastics to investigate the adsorption and desorption behavior of phenanthrene (PHE) and 1-hydroxyphenanthrene (1-OHPHE), and the effect of mucin on desorption was investigated. The results showed that goethite promoted the adsorption of PHE and 1-OHPHE by increasing the specific surface area of the composites. With the increase of the cover degree, the adsorption of PHE decreased because of the decrease in hydrophobicity; while the adsorption of 1-OHPHE initially increased and then decreased with the contributions of hydrophobic interaction and hydrogen bond. The adsorption of 1-OHPHE could be influenced by the pH and ionic strength primarily through electrostatic interactions and Ca2+ bridging. The goethite significantly increased the desorption hysteresis for two chemicals due to the complicated pore structures and increased adsorption affinity. Mucin promoted the desorption of PHE through competitive adsorption, and inhibit the desorption of 1-OHPHE through hydrophobic interaction, hydrogen bonding and Ca2+ bridging. This study elucidated the effects of natural minerals on the adsorption and desorption behavior of organic pollutants on microplastics, briefly discussed the effects of organic macromolecules on the desorption behavior of pollutants with different properties, and emphasized the different environmental behaviors of pollutants.

Eco-corona formation on aminated nanoplastics interacted with extracellular polymeric substances from bloom-forming cyanobacteria: Insightful mechanisms with DFT study

Nanoplastics (NPs) with amino functional groups have wide distribution and high toxicity; however, their environmental behaviors remain inadequately understood. This study investigated the mechanisms of eco-corona formation on pristine polystyrene NPs (PSNPs) and aminated PSNPs (PSNPs-NH2) by extracellular polymeric substances (EPS) from a bloom-forming cyanobacterium, Microcystis aeruginosa. Our results revealed that at the two tested concentrations of EPS (5.0 and 30.0 mg/L), the pristine PSNPs initially aggregated and subsequently repelled. In contrast, PSNPs-NH2 showed a more pronounced aggregation at the elevated EPS concentration of 30 mg/L. In addition, the elemental compositions and functional groups on both types of PSNPs were markedly altered after eco-corona formation. Combining with density functional theory, our findings indicated that electrostatic interaction, hydrogen bonding, and Van der Waals force served as the main binding forces between model EPS (polysaccharide) and PSNPs units. Furthermore, the binding energies of pristine PSNPs-, and PSNPs-NH2-polysaccharide were calculated to be -63.25 and -179.43 kJ/mol, respectively, suggesting a greater affinity of PSNPs-NH2 for polysaccharide. This outcome aligned with our experimental observation. Specifically, the xylose branch within polysaccharide was identified as an optimized binding site for interaction with PSNPs. Our research contributes to a deeper understanding of the environmental behaviors of aminated NPs in freshwater systems, particularly during periods of cyanobacterial blooms.

Interactions between Nanoplastics and Antibiotics: Implications for Nanoplastics Aggregation in Aquatic Environments

Nanoplastics and antibiotics frequently co-occur in aquatic environments, and their interactions could alter nanoplastics' surface properties, affecting nanoplastics aggregation, fate, and ecotoxicity. However, the mechanisms driving antibiotics-induced nanoplastics aggregation under environmentally relevant conditions remain unclear. This study investigated the effects of ciprofloxacin (CIP) and sulfamethoxazole (SMX) on the aggregation of four environmentally relevant nanoplastics (pristine and aged polystyrene, polyethylene, and polypropylene). At pH 5.0, both CIP and SMX significantly promoted nanoplastics aggregation, with CIP being more potent. CIP enhanced nanoplastics aggregation through charge shielding driven by electrostatic attraction, hydrogen bonding (HB), and charge-assisted HB (CAHB), whereas SMX promoted aggregation solely through molecular bridging involving HB and CAHB. At pH 7.0, only CIP facilitated aggregation, while neither antibiotic induced aggregation at pH 9.0. Aged polystyrene aggregated more readily than pristine polystyrene due to increased surface functional groups. Polyethylene and polypropylene showed weaker aggregation due to fewer surface functional groups. High organic matter (OM) levels (1.65 mg/L TOC) inhibited antibiotics-induced aggregation, whereas low OM levels (16.5 μg/L TOC) were more conducive. These findings highlight that antibiotic characteristics, pH, OM levels, plastic types, and environmental aging collectively influence nanoplastics aggregation, and improve the understanding of the fate and risk of nanoplastics in natural waters.

Total organic carbon (TOC): a simple tool for assessing micro(nano)plastics and nanocellulose recovery during size-based fractionation

The assessment of analyte recovery during sample preparation is a critical quality control parameter in method development. While elemental mass spectrometry techniques, such as ICP-MS, are very effective for assessing the recovery of particulate materials containing metallic elements, there is no equivalent applicable to metal-free carbon or CHNO-based particulate polymer materials. Vibrational spectro-microscopy or thermo-analytical techniques can be used to quantify polymer-based micro- and nanoparticles, but are typically expensive and time-consuming techniques that require higher levels of expertise. This study investigated the potential of a liquid-based total organic carbon (TOC) analyzer as a simple, cost-effective, and universal method for determining the recovery of polymer-based particulate micro- and nanomaterials following filtration, centrifugation, and asymmetric flow field flow fractionation (AF4) processes. A good correlation between solid contents and TOC analysis was demonstrated for standard polystyrene (PS) particle suspensions of various sizes, ranging from 50 nm to 90 μm (79.2 to 113.6% recovery), and other types of synthetic and natural polymeric particle suspensions, including polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polyethylene terephthalate (PET), and cellulose (86.2 to 126.2% recovery). Liquid-based TOC was then successfully applied to estimate particle recovery after various preparatory and fractionation steps, including the determination of filtration recoveries for nanocellulose suspensions (99.0 to 101.4% recovery) and PS micro- and nanoparticles spiked into environmental lake and river freshwater samples (70 to 96% recovery). The combination of TOC and single particle extinction and scattering (SPES) measurements allowed the tracking and quantification of three different populations of PS particles in a mixture (200, 500, and 1000 nm) during successive centrifugation steps (113.8 ± 13.9% cumulative recovery). Finally, this study demonstrated the suitability of TOC for determining both the absolute and relative recoveries of polymer-based particulate materials after AF4 fractionation in line with ISO standards. Liquid-based TOC proved to be a valuable tool for directly tracking, quantifying, and evaluating the recovery of polymer-based micro- and nanoparticles in model and environmental water samples before and after routine size-based fractionation steps.

The impact of micro- and nanoplastics on immune system development and functions: Current knowledge and future directions

The prevalence of microplastics (MPs)/ nanoplastics (NPs) in the environment has raised significant concerns regarding their potential toxicity, particularly their impact on biological systems. These particles, particularly NPs, possess unique properties due to their small size and high surface area, enabling them to more easily cross biological barriers and accumulate in tissues. Among various types of plastic materials, polystyrene (PS) is one of the most studied for its toxicological effects, given its widespread use and environmental persistence. This narrative review examines current research on the effects of MPs/NPs, on the immune system, with a focus on both the development of the immune system and its functional responses. Evidence from in vitro and in vivo studies suggests that MP/NP exposure can disrupt immune function, including hematopoiesis, immune cell activation, and the production of inflammatory cytokines. Although in vitro studies highlight cellular toxicity and altered immune cell behavior, in vivo studies reveal more complex outcomes, with some findings suggesting significant effects on organ systems such as the spleen and intestines, while others indicate minimal or no impact under environmentally relevant exposure conditions. Here, we aim to consolidate and summarize the current evidence on the topic, highlight key limitations in the field, and identify areas that warrant further investigation for immunotoxicologists. In addition, we emphasize the importance of using relevant exposure concentrations and complex in vitro or in vivo models to better understand the potential risks associated with MP/NP exposure and their long-term implications for immune health.

Impact of contaminant size and density on their incorporation into sea ice

Sea ice accumulates contaminants and redistributes them laterally as the ice drifts and vertically as it melts. Contaminant incorporation into sea ice must be better understood to resolve contaminant cycling and exposure to polar organisms. Here we develop an experimental method that mimics the formation of young sea ice and enables the quantification of model contaminants separately in the ice matrix and brine. Several limitations inherent in field studies are overcome using this approach. Results show that dissolved contaminants (<1 nm) and dispersed colloidal contaminants (1 nm-1 μm) follow the same behavior as sea salts. When colloids aggregate they follow a similar transport pathway to high-density particulate contaminants (>1 μm). While high-density particles are depleted in sea ice and low-density particles are enriched relative to their initial concentration in seawater, both are engulfed and can travel in wide brine channels. These results can also help to predict the incorporation of natural species in sea ice.

Short-term oral exposure to nanoplastics does not significantly impact the antiviral immune response of the mouse

The increasing prevalence of nanoplastics (NPs) in the environment, particularly polystyrene (PS) nanoparticles, raises concerns regarding their potential impact on human and animal health. Given their small size, NPs can cross biological barriers and accumulate in organs, including those critical for immune functions. This study investigates the effects of short-term oral exposure to 100 and 500 nm PS NPs on the adaptive immune responses during viral infections in vivo, using vesicular stomatitis virus (VSV) and lymphocytic choriomeningitis virus (LCMV) as models. Male and female C57BL/6 mice were orally exposed to PS NP for a period of 28 days, during which they were infected with either VSV or LCMV to study the humoral and cellular responses, respectively. The humoral responses were assessed by measuring total and VSV-specific antibody levels, and splenic immune populations. T cell phenotypes, activation, exhaustion and functionality towards LCMV epitopes were studied as readouts of the cellular responses. Our results demonstrate that short-term NP exposure does not significantly affect the generation or neutralizing capacity of antibodies against VSV, nor the cellular responses directed against LCMV. These findings indicate that, under these conditions, PS NP exposure does not significantly compromise the adaptive immune responses during viral infections, underscoring the value of in vivo models.

Machine learning-driven optical microfiltration device for improved nanoplastic sampling and detection in water systems

The rising presence of nanoplastics in water poses toxicity risks and long-term ecological and health impacts. Detecting nanoplastics remains challenging due to their small size, complex chemistry, and environmental interference. Traditional filtration combined with Raman spectroscopy is time-consuming, labor-intensive, and often lacks accuracy and sensitivity. This study presents an agarose-based microfiltration device integrated with machine learning-assisted Raman analysis for nanoplastic capture and identification. The 1 % agarose microfluidic channel features circular micropost arrays enabling dual filtration: nanoplastics diffuse into the porous matrix, while larger particles (>1000 nm) are blocked by the microposts. Unlike conventional systems, this design achieves both physical separation and preconcentration, enhancing nanoplastic detectability. Upon dehydration, the agarose forms a transparent film, significantly improving Raman compatibility by minimizing background interference. This transformation enables direct Raman analysis of retained nanoparticles with enhanced signal clarity and sensitivity. Using 100-nm polystyrene nanoparticles (PSNPs) as a model, we evaluated device performance in distilled water and seawater across concentrations (6.25-50 µg/mL) and flow rates (2.5-100 µL/min). Maximum capture efficiencies of 80 % (seawater) and 66 % (distilled water) were achieved at 2.5 µL/min. A convolutional neural network (CNN) further enhanced spectral analysis, reducing mapping time by 50 % and enabling PSNP detection in seawater at 6.25 µg/mL. This agarose-based system offers a scalable, cost-effective platform for nanoplastic sampling, demonstrating the potential of combining microfluidics with machine learning-assisted Raman spectroscopy to address critical environmental and public health challenges.

Importance of Attachment Efficiency in Determining the Fate of PS and PVC Nanoplastic Heteroaggregation with Natural Colloids Using a Multimedia Model

Here, we assessed the heteroaggregation of polystyrene (PS) and poly(vinyl chloride) (PVC) nanoplastics with SiO2 as a model of natural colloids. Homoaggregation and heteroaggregation were evaluated as a function of CaCl2 (0-100 mM) and natural organic matter (NOM) (50 mg L-1) at a designated concentration of nanoplastics (200 μg L-1). Critical coagulation concentrations (CCC) of nanoplastics were determined in homoaggregation and heteroaggregation experiments with SiO2 and CaCl2. The attachment efficiency (α) was calculated by quantifying the number of nanoplastics in the presence of CaCl2, NOM, and SiO2 using single-particle inductively coupled plasma mass spectrometry (spICP-MS) and pseudo-first-order kinetics. The calculated α was fed into the SimpleBox4Plastics model to predict the fate of nanoplastics across air, water, soil, and sediment compartments. Nanoplastics exhibited high stability against homoaggregation, while significant heteroaggregation with SiO2 occurred at CaCl2 concentrations above 100 mM. The influence of NOM was also evaluated, showing a reduction in heteroaggregation with SiO2 for both nanoplastic types. Sensitivity analysis indicated that the degradation half-life of the tested nanoplastics had a more significant impact on persistence than did α. The results emphasize the environmental stability of nanoplastics, particularly in freshwater and soil compartments, and the critical role of NOM and emission pathways in determining their fate.

Molecular modeling to elucidate the dynamic interaction process and aggregation mechanism between natural organic matters and nanoplastics

The interactions of nanoplastics (NPs) with natural organic matters (NOMs) dominate the environmental fate of both substances and the organic carbon cycle. Their binding and aggregation mechanisms at the molecular level remain elusive due to the high structural complexity of NOMs and aged NPs. Molecular modeling was used to understand the detailed dynamic interaction mechanism between NOMs and NPs. Advanced humic acid models were used, and three types of NPs, i.e., polyethylene (PE), polyvinyl chloride (PVC), and polystyrene (PS), were investigated. Molecular dynamics (MD) simulations revealed the geometrical change of the spontaneous formation of NOMs-NPs supramolecular assemblies. The results showed that pristine NPs initially tend to aggregate homogeneously due to their hydrophobic nature, and then NOM fragments are bound to the formed NP aggregates mainly by vdW interaction. Homo- and hetero-aggregation between NOMs and aged NPs occur simultaneously through various mechanisms, including intermolecular forces and Ca2+ bridging effect, eventually resulting in a mixture of supramolecular structures. Density functional theory calculations were employed to characterize the surface properties and reactivity of the NP monomers. The molecular polarity indices for unaged PE, PS, and PVC were 3.1, 8.5, and 22.2 kcal/mol, respectively, which increased to 43.2, 51.6, and 42.2 kcal/mol for aged NPs, respectively, indicating the increase in polarity after aging. The vdW and electrostatic potentials of NP monomers were visualized. These results clarified the fundamental aggregation processes, and mechanisms between NPs and NOMs, providing a complete molecular picture of the interactions of nanoparticles in the natural aquatic environment.

Colloidal stability of UV-aged and protein-coated nanoplastics in natural waters under warming

Nanoplastics, particles smaller than 1000 nm that are produced by degradation of plastic debris, pose an environmental threat and may endanger natural ecosystems and human health. In aquatic environments, the large surface area and high surface energy of NPs facilitate their interactions with the surroundings; thus, understanding their behavior, transport, and fate is essential. In this study, we investigated the individual and combined effects of UV aging and protein coating on the stability of NPs in aquatic environments under elevated temperatures. UV-aged NPs were created via indoor UV lamp exposure, and protein coating was achieved by introducing bovine serum albumin (BSA). Sequential processes produced UV + BSA and BSA + UV-coated NPs for comprehensive analysis. Aggregation kinetics and stability were examined in electrolyte solutions (NaCl and CaCl2) and natural waters. Results indicated that BSA coating improved the colloidal stability of NPs in electrolyte solutions by promoting steric repulsion, a trend observed in rivers, lakes, and seawater but not in groundwater. Sequential UV aging after BSA coating caused protein denaturation, reducing the stability of NPs. Additionally, increased temperatures led to a greater level of NP aggregation due to lower energy barriers. These findings highlight UV aging, protein coating, and temperature as critical factors influencing the behavior and fate of NPs in natural environments.

Colloid and Interface Science for Understanding Microplastics and Developing Remediation Strategies

Microplastics (MPs) originate from industrial production of <1 mm polymeric particles and from the progressive breakdown of larger plastic debris. Their environmental behavior is governed by their interfacial properties, which dominate due to their small size. This Perspective highlights the complex surface chemistry of MPs under environmental stressors and discusses how physical attributes like shape and roughness could influence their fate. We further identify wastewater treatment plants (WWTPs) as critical hotspots for MP accumulation, where the MPs are inadvertently transferred to sewage sludge and reintroduced into the environment. We emphasize the potential of colloid and interfacial science not only to improve our fundamental understanding of MPs but also to advance mitigation strategies in hotspots such as WWTPs.

Primary astrocytes as a cellular depot of polystyrene nanoparticles

The continuous increase in plastic production has resulted in increased generation of microplastic particles (MPs), and nanoplastic particles (NPs). Recent evidence suggests that nanoplastics may be a potent neurotoxin because they are able to freely cross the blood-brain barrier and enter the brain. Therefore, the cytotoxic effects of polystyrene nanoparticles (PS-NPs) on cellular systems of cerebral origin should be thoroughly investigated. The aim of the current study is to evaluate the cytotoxic potential of 25 nm PS-NPs on in vitro cultured cells such as primary astrocytes, neurons and their co-cultures established from the cerebral cortex of Wistar pups. The results show that PS-NPs are internalized in both neurons and astrocytes, inducing time- and concentration-dependent cytotoxic effects. However, quantification of fluorescence intensity indicates cell type-dependent differences in the efficiency of PS-NPs uptake. Astrocytes are several times more efficient at accumulating PS-NPs than neurons, and this is a phagocytosis-dependent process. Moreover, the high rate of PS-NPs internalization during prolonged exposure (72 h) promotes astroglial activation, as assessed by analysis of GFAP expression and immunocytochemical imaging. The results show that astroglia act as a cellular depot of PS-NPs to protect neurons. However, once the critical threshold is exceeded, astroglia become overactivated and can lose their protective functions. These results highlight the importance of further research on the mechanisms underlying nanoplastic-induced cellular toxicity, which may have implications for understanding the broader impact of plastic pollution on neurological functions.

Uncovering layer by layer the risk of nanoplastics to the environment and human health

Nanoplastics (NPs), defined as plastic particles with dimensions less than 100 nm, have emerged as a persistent environmental contaminant with potential risk to both environment and human health. Nanoplastics might translocate across biological barriers and accumulate in vital organs, leading to inflammatory responses, oxidative stress, and genotoxicity, already reported in several organisms. Disruptions to cellular functions, hormonal balance, and immune responses were also linked to NPs exposure in in vitro assays. Further, NPs have been found to adsorb other pollutants, such as persistent organic pollutants (POPs), and leach additives potentially amplifying their advere impacts, increasing the threat to organisms greater than NPs alone. However, NPs toxic effects remain largely unexplored, requiring further research to elucidate potential risks to human health, especially their accumulation, degradation, migration, interactions with the biological systems and long-term consequences of chronic exposure to these compounds. This review provides an overview of the current state-of-art regarding NPs interactions with environmental pollutants and with biological mechanisms and toxicity within cells.

Polystyrene nanoplastics are unlikely to aggregate in freshwater bodies

The fate and toxicity of nanoplastics (NPs) in the environment is largely determined by their stability. We explored how water composition, nanoplastic size, and surface carboxyl group density influenced the aggregation of polystyrene (PS) NPs in fresh water. Unfunctionalized 200, 300, 500, and 1000 nm PS NPs and 310 nm carboxylated PS NPs with carboxyl group densities of 0.35 and 0.6 mmol g-1 were used to simulate pristine and aged NPs. Natural water matrices tested in this study include synthetic surface water (SSW), water from the Schie canal (Netherlands) and tap water. Suwannee River Natural Organic Matter (SRNOM) was included to mimic organic matter concentrations. In CaCl2, we found PS NPs are more stable as their size increases with the increase of the critical coagulation concentration (CCC) from 44 mM to 59 mM and 77 mM for NP sizes of 200 nm, 300 nm and 500 nm. Conversely, 1000 nm PS NPs remained stable even at 100 mM CaCl2. Increasing the carboxyl group density decreased the stability of NPs as a result of the interaction between Ca2+ and the carboxyl group. These results were consistent with the mass of Ca2+ adsorbed per mass of NPs. The presence of SRNOM decreased the stability of PS NPs via particle bridging facilitated by SRNOM. However, in SSW, Schie water and tap water with low divalent cation concentrations, the hydrodynamic size of PS NPs did not change, even at prolonged durations up to one week. We concluded that PS NPs are unlikely to aggregate in water with low divalent cation concentrations, like natural freshwater bodies. Ecotoxicologists and water treatment engineers will have to consider treating PS NPs as colloidally stable particles as the lack of aggregation in fresh surface water bodies will affect their ecotoxicity and may pose challenges to their removal in water treatment.

Natural Organic Matter Stabilizes Pristine Nanoplastics but Destabilizes Photochemical Weathered Nanoplastics in Monovalent Electrolyte Solutions

Photochemical weathering and eco-corona formation through natural organic matter (NOM) adsorption play vital roles in the aggregation tendencies of nanoplastics (NPs) in aquatic environments. However, it remains unclear how photochemical weathering alters the adsorption patterns of NOM and the conformation of the eco-corona, subsequently affecting the aggregation tendencies of NPs. This study examined the effect of Suwannee River NOM adsorption on the aggregation kinetics of pristine and photoaged polystyrene (PS) NPs in monovalent electrolyte solutions. The results showed that photochemical weathering influenced the conformation of the eco-corona, which, in turn, determined NP stability in the presence of NOM. Hydrophobic components of NOM predominantly bound to pristine NPs through hydrophobic and π-π interactions, and extended hydrophilic segments in water hindered NP aggregation via steric repulsion. Conversely, hydrogen bonding facilitated the binding of these hydrophilic segments to multiple photoaged NPs, thereby destabilizing them through polymer bridging. Additionally, the stabilization and destabilization capacities of NOM increased with its concentration and molecular weight. These findings shed light on the destabilizing role of NOM in weathered NPs, offering new perspectives on environmental colloidal chemistry and the fate of NPs in complex aquatic environments.

Differences in Nanoplastic Formation Behavior Between High-Density Polyethylene and Low-Density Polyethylene

High-Density Polyethylene (HDPE) and Low-Density Polyethylene (LDPE) films were used to create nanoplastic (NP) models, with the shape of delamination occurring during degradation. In the case of HDPE, selective degradation occurred not only in the amorphous part, but also in the crystalline part at the same time. Some of the lamellae that extend radially to form the spherulite structure were missing during the 30-day degradation. The length of these defects was less than 1 µm. HDPE disintegrated within units of spherulite structure by conformational defects in lamellae, and the size of the fragments obtained had a wide distribution. LDPE was synthesized by radical polymerization, so it contained a cross-linked part. The part was not sufficiently fused, and when it degraded, it delaminated and separated preferentially. The zeta potential reached a minimum value of approximately -20 mV at the degradation time of 21 days, and then increased. This complex dependence on degradation time was due to NP particle aggregation. The addition of 1% Triton(R) X-114 surfactant was effective in stabilizing the NP dispersion. The particle size remained constant at around 20 nm for degradation times of 15-30 days.

Exploring Nanoplastics Bioaccumulation in Freshwater Organisms: A Study Using Gold-Doped Polymeric Nanoparticles

The evaluation of nanoplastics bioaccumulation in living organisms is still considered an emerging challenge, especially as global plastic production continues to grow, posing a significant threat to humans, animals, and the environment. The goal of this work is to advance the development of standardized methods for reliable biomonitoring in the future. It is crucial to employ sensitive techniques that can detect and measure nanoplastics effectively, while ensuring minimal impact on the environment. To understand nanoplastics retention by freshwater organisms, phyto- and zooplankton, and mussels were exposed to gold-doped polymeric nanoparticles synthesized in our laboratory. The results demonstrated that measuring gold content using inductively coupled plasma mass spectrometry (ICP-MS), along with confirmation of its presence through electron microscopy in selected exposed samples provides insight into the accumulation and release of nanoplastics by organisms playing a relevant ecological role at the early levels of aquatic food webs.

Nanoplastics in focus: Exploring interdisciplinary approaches and future directions

Nanoplastics (NPs) are gaining increasing attention due to their widespread distribution and potential environmental and biological impacts. Spanning a variety of ecosystems - from soils and rivers to oceans and polar ice - NPs interact with complex biological and geochemical processes, posing risks to organisms across multiple trophic levels. Despite their growing presence, understanding the behavior, transport, and toxicity of nanoplastics remains challenging due to their diverse physical and chemical properties as well as the heterogeneity of environmental matrices. Currently, nanoplastics are often studied alongside microplastics as a single, homogeneous group, which obscures the nuanced behavior of NPs, particularly in terms of their colloidal properties and interactions within ecosystems. This perspective aims to highlight the critical gaps in nanoplastics research, stressing the importance for field studies and advanced detection/quantification methods to better capture their behavior across environmental interfaces. We advocate for a more integrated approach that account for the dynamic interactions between nanoplastics and surrounding biological, chemical, and physical environments, especially across key ecological gradients. Furthermore, long-term and transgenerational studies are essential to assess the chronic impacts of low-concentration nanoplastics exposure. Innovative and appropriate methodologies are needed to explore NP fate, transport, and toxicity in realistic environmental conditions. By combining advanced experimental tools, field studies, and ecological modeling frameworks, this paper outlines provides a roadmap for advancing our understanding of nanoplastics and their broader ecological impacts, ultimately shaping more effective environmental monitoring and mitigation strategies.

Influence of micro- and nanoplastics on mitochondrial function in the cardiovascular system: a review of the current literature

Mitochondria represent pivotal cellular organelles endowed with multifaceted functionalities encompassing cellular respiration, metabolic processes, calcium turnover, and the regulation of apoptosis, primarily through the generation of reactive oxygen species (ROS). Perturbations in mitochondrial dynamics have been intricately linked to the etiology of numerous cardiovascular pathologies, such as heart failure, ischemic heart disease, and various cardiomyopathies. Notably, recent attention has been directed towards the detrimental impact of micro- and nanoplastic pollution on mitochondrial integrity, an area underscored by a paucity of comprehensive investigations. Given the escalating prevalence of plastic particle contamination and the concomitant burden of cardiovascular disease in aging populations, understanding the interplay between mitochondria within the cardiovascular system and micro- and nanoplastic pollution assumes paramount importance. This review endeavors to elucidate the current albeit limited comprehension surrounding this complex interplay. Key words Mitochondria, Nanoplastics, Microplastics, Cardiovascular system, Endothelial function, Oxidative phosphorylation.

Impact of electrolyte and natural organic matter characteristics on the aggregation and sedimentation of polystyrene nanoplastics

Nanoplastics are increasingly pervasive in ecosystems worldwide, raising concerns about their persistence and mobility in the environment. Our study focused on the interactions between polystyrene nanoplastics (PS NPs, Do:~200 nm) and Natural Organic Matter (NOM) uniquely isolated from water bodies under different electrolyte and temperature conditions (i.e., effectively mimicking a wide range of environmental scenarios). The selected dissolved NOM (DOM) fractions of varied physical chemical characteristics and geographical origins include: the hydrophobic acid (HPOA) fraction from the South Platte River (SPR HPOA, USA), the biopolymer/colloid fractions from Cazaux Lake (CL BIOP, France), and the dissolved fraction of the biofilm recovered from a nanofiltration-fouled module at the Méry-sur-Oise drinking water treatment plant (NF BIOP, France). The biopolymers (NF BIOP and CL BIOP) clearly hindered PS NPs aggregation through steric effects, forming a protective eco-corona, enhancing PS NPs stability, and inhibiting sedimentation in the long term, compared to HPOA. The temperature impacted the homo and hetero-aggregation of PS NPs differently, illustrating the complex interplay between thermal effects and NOMs stabilizing interactions. Furthermore, the seldom-explored aspect of the sequential introduction of reactants into the solution during aggregation experiments (i.e., which simulates a realistic scenario: the transport of PS NPs from one aquatic system to another of different compositions) was also investigated. This study provides essential insights into the dynamic behavior of PS NPs in environmental matrices and crucial knowledge for predicting nanoplastic interactions in complex ecosystems.

Effect of isomeric polysaccharides on heteroaggregation of nanoplastics in high ionic strength conditions: Synergies of morphology and molecular conformation

Polysaccharides with various molecular structures and morphology may influence the aggregation kinetics of nanoplastics. This study used various characterization methods to elucidate the heteroaggregation mechanism of polystyrene nanoplastics (PSNPs) in the presence of polysaccharides (ionic strength (IS) 1-800 mM NaCl and 0.01-60 mM CaCl2). The results showed that under high IS, cellulose (CL) accelerated the heteroaggregation of PSNPs, and the aggregation rate of PSNPs increased by approximately 62.05 %, while amylose (AM) had little effect (10.38 %). Compared with AM (43.2 nm), the morphology of the CL (78.4 nm) gully had improved surface roughness, leading to its decisive role in the heteroaggregation of PSNPs. Quantum chemistry calculations indicated that van der Waals forces of PSNPs-CL systems (-217.28 kJ mol-1) were stronger than those of PSNPs-AM systems (-184.62 kJ mol-1) based on the subtle molecular conformation differences between CL and AM (opposite and same sides of OH groups in CL and AM, respectively). The morphology and molecular conformation of polysaccharides collaboratively controlled the heteroaggregation of PSNPs. Because the morphology of polysaccharides was based on their molecular conformation, the latter is the most critical factor. These findings provide new insights into the effects of PSNPs stability in the environment.

A perspective on the algae-derived dissolved organic matter and its dynamic influence on the aggregation of nanoplastics in eutrophic waters

The aggregation behavior of nanoplastics (NPs) is crucial in determining their fate in aquatic environments. Dissolved organic matter (DOM), characterized by its complex molecular structure and diverse functional groups, can spontaneously absorb on the surface of NPs, thus altering their colloidal stability. In eutrophic waters, DOM primarily originates from metabolic byproducts released by phytoplankton, and its molecular composition and hydrophilic properties change dynamically as the progression of algal blooms. This perspective aims to summarize the heterogeneity of DOM during the initiation, outbreak and recession of algal blooms. And we investigate the influence of molecular-level variations in DOM composition on the aggregation behavior of NPs. Additionally, this study provides insights into the underlying mechanisms relating to the interactions between DOM and NPs. Ultimately, it tackles the challenges and future directions, highlighting the necessity for comprehensive studies to understand the fate of NPs in eutrophic waters.

Early-life polystyrene nanoplastics exposure impairs pathogen avoidance behavior associated with intestine-derived insulin-like neuropeptide (ins-11) and serotonin signaling in Caenorhabditis elegans

Nanoplastics (NPs) contamination is an emerging global concern due to the widespread use of plastic products and their potentially negative health impact on ecosystems. Despite their ubiquity, the effects of early-life NPs exposure on host-pathogen interactions remain largely unknown. In this study, we show that early-life exposure to polystyrene NPs (PS-NPs, 100-nm) at predicted environmentally relevant concentrations (10 µg/L) significantly impairs food preference and reduces avoidance of the pathogenic bacterium Bacillus thuringiensis in Caenorhabditis elegans. Exposure to PS-NPs led to a decrease in avoidance from 40.3 % in controls to 30.6 % at 10 µg/L and further to 23.1 % and 17.4 % at 50 and 100 µg/L, respectively. Mechanistic insights reveal that PS-NPs downregulate intestine-derived insulin-like neuropeptide (ins-11) via the transcription factor HLH-30 and the p38 MAPK signaling pathways, both are essential for avoidance behavior. Notably, acute serotonin treatment restored the avoidance behavior, indicating a role of serotonin signaling in this process. Our study indicates that early-life exposure to PS-NPs (100-nm) adversely affects the avoidance behavior of C. elegans, making them more vulnerable to harmful pathogens, thereby affecting their health. These findings highlight significant ecological and health hazards by early-life PS-NPs exposure.

Impacts of polystyrene nanoplastics on microgel formation from effluent organic matter

Municipal effluents discharged from wastewater treatment plants (WWTPs) are considered major contributors of nanoplastics (NPs) and dissolved effluent organic matter (dEfOM) to environments. Due to their small sizes, NPs can travel easily in waterways and evade wastewater treatment processes, and may directly interact with dEfOM, altering their environmental fates. However, although much research has examined the impact of natural organic matter on NPs, the interactions between NPs and dEfOM remain unexplored. This study investigated the influences of NPs on the behavior and capacity of dEfOM aggregation and surface granularity, and identified the possible aggregation mechanism. We also adjusted the salinity of water samples to simulate scenarios based on WWTP-sea continuums. Our data suggest that dEfOM can self-assemble with 55 nm polystyrene NPs to form microgels, particularly under high salinity conditions. NPs accelerates the formation speed and number of dEfOM aggregates, but the sizes of the aggregates remain largely unchanged. The relative particle counts at a salinity of 34 psu increased by 300 % compared to the control group. The potential mechanism behind NPs-microgels aggregation is likely driven by the synergistic effect of the divalent ion crosslinking and hydrophobic interactions between EfOM and NPs. Notably, NPs incorporation into microgels decreases the surface granularity, thereby possibly affecting settling velocity and colonization of aggregates, as well as microbial attachment and community diversity. Overall, our findings demonstrate the potential influence of NPs on dEfOM assembly and surface properties following effluent discharge, and can inspire further relevant studies on microorganism interactions, removal technologies, and the environmental transport of NPs.

Predator traits influence uptake and trophic transfer of nanoplastics in aquatic systems-a mechanistic study

Predicting the response of aquatic species to environmental contaminants is challenging, in part because of the diverse biological traits within communities that influence their uptake and transfer of contaminants. Nanoplastics are a contaminant of growing concern, and previous research has documented their uptake and transfer in aquatic food webs. Employing an established method of nanoplastic tracking using metal-doped plastics, we studied the influence of biological traits on the uptake of nanoplastic from water and diet in freshwater predators through two exposure assays. We focused on backswimmers (Anisops wakefieldi) and damselfly larvae (Xanthocnemis zealandica) - two freshwater macroinvertebrates with contrasting physiological and morphological traits related to feeding and respiration strategies. Our findings reveal striking differences in nanoplastic transfer dynamics: damselfly larvae accumulated nanoplastics from water and diet and then efficiently eliminated 92% of nanoplastic after five days of depuration. In contrast, backswimmers did not accumulate nanoplastic from either source. Differences in nanoplastic transfer dynamics may be explained by the contrasting physiological and morphological traits of these organisms. Overall, our results highlight the importance and potential of considering biological traits in predicting transfer of nanoplastics through aquatic food webs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s43591-024-00096-4.

Leveraging nanoparticle environmental health and safety research in the study of micro- and nano-plastics

Lessons learned, methodologies, and application of tools that have been developed within the context of research on the environmental impacts, health, and safety of nanomaterials (nano-EHS) provide a solid foundation for research on nano/microplastics. In this communication, we summarize key discoveries obtained through major research efforts over the last two decades in the area of nano-EHS that are applicable for the study of micro- and nano-plastics (referred to here more generally as particulate plastics). We focus on how non-equilibrium particle transport processes affect: 1) bio-physico-chemical mechanisms of particle toxicity and determining dose-response relationships; 2) the potential for biouptake, bioaccumulation, translocation, trophic transfer and intergenerational effects of particulate contaminants; 3) extrapolations from laboratory experiments to complex systems and the impact of environmental transformations; 4) the formulation of functional assays as a basis for predicting the impacts of particulate contaminants in complex environments; 5) the relative importance of incidental particles compared with engineered particles and, 6) experience with data platforms, curation, and experimental design.

Addressing the relevance of polystyrene nano- and microplastic particles used to support exposure, toxicity and risk assessment: implications and recommendations

BACKGROUND

There has been an exponential increase in the number of studies reporting on the toxicological effects associated with exposure to nano and microplastic particles (NMPs). The majority of these studies, however, have used monodispersed polystyrene microspheres (PSMs) as 'model' particles. Here we review the differences between the manufacture and resulting physicochemical properties of polystyrene used in commerce and the PSMs most commonly used in toxicity studies.

MAIN BODY

In general, we demonstrate that significant complexity exists as to the properties of polystyrene particles. Differences in chemical composition, size, shape, surface functionalities and other aspects raise doubt as to whether PSMs are fit-for-purpose for the study of potential adverse effects of naturally occurring NMPs. A realistic assessment of potential health implications of the exposure to environmental NMPs requires better characterisation of the particles, a robust mechanistic understanding of their interactions and effects in biological systems as well as standardised protocols to generate relevant model particles. It is proposed that multidisciplinary engagement is necessary for the development of a timely and effective strategy towards this end. We suggest a holistic framework, which must be supported by a multidisciplinary group of experts to work towards either providing access to a suite of environmentally relevant NMPs and/or developing guidance with respect to best practices that can be adopted by research groups to generate and reliably use NMPs. It is emphasized that there is a need for this group to agree to a consensus regarding what might best represent a model NMP that is consistent with environmental exposure for human health, and which can be used to support a variety of ongoing research needs, including those associated with exposure and hazard assessment, mechanistic toxicity studies, toxicokinetics and guidance regarding the prioritization of plastic and NMPs that likely represent the greatest risk to human health. It is important to acknowledge, however, that establishing a multidisciplinary group, or an expert community of practice, represents a non-trivial recommendation, and will require significant resources in terms of expertise and funding.

CONCLUSION

There is currently an opportunity to bring together a multidisciplinary group of experts, including polymer chemists, material scientists, mechanical engineers, exposure and life-cycle assessment scientists, toxicologists, microbiologists and analytical chemists, to provide leadership and guidance regarding a consensus on defining what best represents environmentally relevant NMPs. We suggest that given the various complex issues surrounding the environmental and human health implications that exposure to NMPs represents, that a multidisciplinary group of experts are thus critical towards helping to progress the harmonization and standardization of methods.

Influence of macromolecules and electrolytes on heteroaggregation kinetics of polystyrene nanoplastics and goethite nanoparticles in aquatic environments

Fate and transport of nanoplastics in aquatic environments are affected by their heteroaggregation with minerals in the presence of macromolecules. This study investigated the heteroaggregation of polystyrene nanoplastics (PSNPs) with goethite nanoparticles (GNPs) under the influence of macromolecules [humic acid (HA), bovine serum albumin (BSA), and DNA] and electrolytes. Under 1 mg C/L macromolecule, raising electrolyte concentration promoted heteroaggregation via charge screening, except that calcium bridging with HA also enhanced heteroaggregation at CaCl2 concentration above 5 mM. At all NaCl concentrations and CaCl2 concentration below 5 mM, 1 mg C/L macromolecules strongly retarded heteroaggregation, ranking BSA > DNA > HA. Raising macromolecule concentration strengthened such stabilization effect of all macromolecules in NaCl solution and that of DNA and BSA in CaCl2 solution by enhancing steric hindrance. However, 0.1 mg C/L BSA slightly promoted heteroaggregation in CaCl2 solution due to stronger electrostatic attraction than steric hindrance. In CaCl2 solution, raising HA concentration strengthened its destabilization effect via calcium bridging. Macromolecules having more compact globular structure and higher molecular weight may exert greater steric hindrance to inhibit heteroaggregation more effectively. This study provides new insights on the effects of macromolecules and electrolytes on heteroaggregation between nanoplastics and iron minerals in aquatic environments.

Heteroaggregation kinetics of oppositely charged nanoplastics in aquatic environments: Effects of particle ratio, solution chemistry, and interaction sequence

Interactions between positively charged amino-modified (APS) and negatively charged bare (BPS) polystyrene nanoplastics may cause heteroaggregation in aquatic environments. This study investigated the effects of particle concentration ratio, solution chemistry [electrolytes, pH, and natural organic matter (NOM)], and interaction sequence on their heteroaggregation kinetics. In the absence of electrolytes and NOM, the APS/BPS ratio for attaining maximum heteroaggregation rate (khetero) increased from APS/BPS= 3/7 to APS/BPS= 1/1 as pH increased from 4 to 10, indicating that electrostatic interactions dominated heteroaggregation. In the absence of NOM, khetero ranked APS/BPS= 2/3 > APS/BPS= 1/1 > APS/BPS= 3/2. Colloidal stability decreased linearly as pH increased from 4 to 8 at APS/BPS= 1/1, while diffusion-limited heteroaggregation persisted at pH 10. In NaCl solution, humic acid (HA) retarded heteroaggregation more effectively than sodium alginate (SA) via steric hindrance and weakening electrostatic interactions, following the modified Derjaguin-Landau-Verwey-Overbeek (MDLVO) theory. Compared with simultaneous interactions among APS, BPS, NaCl, and NOM, the NOM retardation effects on heteroaggregation weakened if delaying its interaction with others. In CaCl2 solution, the effects of NOM on heteroaggregation depended on counterbalance among charge screening, steric hindrance, and calcium bridging. These findings highlight the important role of heteroaggregation between oppositely charged nanoplastics on their fate and transport in aquatic environments.

Impact of sub-chronic polystyrene nanoplastics exposure on hematology, histology, and endoplasmic reticulum stress-related protein expression in Nile tilapia (Oreochromis niloticus)

Nanoplastics (NPs) are one of the most hazardous marine litters, having the potential to cause far-reaching impacts on the environment and humankind. The effect of NPs on fish health has been studied, but their impact on the subcellular organelles remains unexplored. The present investigation studied the possible implications of polystyrene-nanoplastics (PS-NPs) on the hematology, tissue organization, and endoplasmic reticulum (ER) stress-related proteins in Nile tilapia (Oreochromis niloticus). Fish were exposed to ∼100 nm PS-NPs at environmentally relevant (0.1 mg/L), and sublethal (1, 10 mg/L) concentrations for 14 days through water exposure. The growth performance and hematological parameters such as erythrocytes, hemoglobin, hematocrit, and leucocytes decreased, while thrombocytes increased with PS-NPs dose-dependently. The gills, liver, kidney, and heart tissues displayed increasing degrees of pathology with increased concentrations of PS-NPs. The gills showed severe epithelial hyperplasia and lamellar fusion. The liver had an abstruse cellular framework, membrane breakage, and vacuolation. While glomerular and tubular atrophy was the most prominent pathology in the kidney tissue, the heart displayed extensive myofibrillar loss and disorderly arranged cardiac cells. The ER-stress-related genes such as bip, atf6, ire1, xbp1, pkr, and apoptotic genes such as casp3a, and bax were over-expressed, while, the anti-apoptotic bcl2 was under-expressed with increasing concentrations of PS-NPs. Immunohistochemistry and blotting results of GRP78, CHOP, EIF2S, and ATF6 in gills, liver, kidney, and heart tissues affirmed the translation to ER stress proteins. The results revealed the sub-lethal adverse effects and the activation of the ER-stress pathway in fish with sub-chronic exposure to PS-NPs.

Correlative Effects on Nanoplastic Aggregation in Model Extracellular Biofilm Substances Investigated with Fluorescence Correlation Spectroscopy

Recent studies show that biofilm substances in contact with nanoplastics play an important role in the aggregation and sedimentation of nanoplastics. Consequences of these processes are changes in biofilm formation and stability and changes in the transport and fate of pollutants in the environment. Having a deeper understanding of the nanoplastics-biofilm interaction would help to evaluate the risks posed by uncontrolled nanoplastic pollution. These interactions are impacted by environmental changes due to climate change, such as, e.g., the acidification of surface waters. We apply fluorescence correlation spectroscopy (FCS) to investigate the pH-dependent aggregation tendency of non-functionalized polystyrene (PS) nanoparticles (NPs) due to intermolecular forces with model extracellular biofilm substances. Our biofilm model consists of bovine serum albumin (BSA), which serves as a representative for globular proteins, and the polysaccharide alginate, which is a main component in many biofilms, in solutions containing Na+ with an ionic strength being realistic for fresh-water conditions. Biomolecule concentrations ranging from 0.5 g/L up to at maximum 21 g/L are considered. We use non-functionalized PS NPs as representative for mostly negatively charged nanoplastics. BSA promotes NP aggregation through adsorption onto the NPs and BSA-mediated bridging. In BSA-alginate mixtures, the alginate hampers this interaction, most likely due to alginate-BSA complex formation. In most BSA-alginate mixtures as in alginate alone, NP aggregation is predominantly driven by weaker, pH-independent depletion forces. The stabilizing effect of alginate is only weakened at high BSA contents, when the electrostatic BSA-BSA attraction is not sufficiently screened by the alginate. This study clearly shows that it is crucial to consider correlative effects between multiple biofilm components to better understand the NP aggregation in the presence of complex biofilm substances. Single-component biofilm model systems based on comparing the total organic carbon (TOC) content of the extracellular biofilm substances, as usually considered, would have led to a misjudgment of the stability towards aggregation.

Hazard assessment of nanoplastics is driven by their surface-functionalization. Effects in human-derived primary endothelial cells

During plastic waste degradation into micro/nanoplastics (MNPLs) their physicochemical characteristics including surface properties (charge, functionalization, biocorona, etc.) can change, potentially affecting their biological effects. This paper focuses on the surface functionalization of MNPLs to determine if it has a direct impact on the toxicokinetic and toxicodynamic interactions in human umbilical vein endothelial cells (HUVECs), at different exposure times. Pristine polystyrene nanoplastics (PS-NPLs), as well as their carboxylated (PS-C-NPLs) and aminated (PS-A-NPLs) forms, all around 50 nm, were used in a wide battery of toxicological assays. These assays encompassed evaluations on cell viability, cell internalization, induction of intracellular reactive oxygen species (iROS), and genotoxicity. The experiments were conducted at a concentration of 100 μg/mL, chosen to ensure a high internalization rate across all treatments while maintaining a sub-toxic concentration. Our results show that all PS-NPLs are internalized by HUVECs, but the internalization dynamic depends on the particle's functionalization. PS-NPLs and PS-C-NPLs internalization modify the morphology of the cell increasing its inner complexity/granularity. Regarding cell toxicity, only PS-A-NPLs reduced cell viability. Intracellular ROS was induced by the three different PS-NPLs but at different time points. Genotoxic damage was induced by the three PS-NPLs at short exposures (2 h), but not for PS-C-NPLs at 24 h. Overall, this study suggests that the toxicological effects of PSNPLs on HUVEC cells are surface-dependent, highlighting the relevance of using human-derived primary cells as a target.

Heteroaggregation kinetics of nanoplastics and soot nanoparticles in aquatic environments

Heteroaggregation between polystyrene nanoplastics (PSNPs) and soot nanoparticles (STNPs) in aquatic environments may affect their fate and transport. This study investigated the effects of particle concentration ratio, electrolytes, pH, and humic acid on their heteroaggregation kinetics. The critical coagulation concentration (CCC) ranked CCCPSNPs > CCCPSNPs-STNPs > CCCSTNPs, indicating that heteroaggregation rates fell between homoaggregation rates. In NaCl solution, as the PSNPs/STNPs ratio decreased from 9/1 to 3/7, heteroaggregation rate decreased and CCCPSNPs-STNPs increased from 200 to 220 mM due to enhanced electrostatic repulsion. Outlier was observed at PSNPs/STNPs= 1/9, where CCCPSNPs-STNPs= 170 mM and homoaggregation of STNPs dominated. However, in CaCl2 solution where calcium bridged with STNPs, heteroaggregation rate increased and CCCPSNPs-STNPs decreased from 26 to 5 mM as the PSNPs/STNPs ratio decreasing from 9/1 to 1/9. In composite water samples, heteroaggregation occurred only at estuarine and marine salinities. Acidic condition promoted heteroaggregation via charge screening. Humic acid retarded or promoted heteroaggregation in NaCl or CaCl2 solutions by steric hindrance or calcium bridging, respectively. Other than van der Waals attraction and electrostatic repulsion, heteroaggregation was affected by steric hindrance, hydrophobic interactions, π - π interactions, and calcium bridging. The results highlight the role of black carbon on colloidal stability of PSNPs in aquatic environments.

Transgenerational Response of Germline Nuclear Hormone Receptor Genes to Nanoplastics at Predicted Environmental Doses in Caenorhabditis elegans

Transgenerational nanoplastic toxicity could be detected in Caenorhabditis elegans after exposure at the parental generation (P0-G); however, the underlying mechanisms remain largely unclear. We aimed to examine the role of germline nuclear hormone receptors (NHRs) in controlling the transgenerational toxicity of polystyrene nanoparticles (PS-NPs) based on gene expression screening and functional analysis. Among germline NHR genes, daf-12, nhr-14, and nhr-47 expressions were increased and nhr-12 expression was decreased by PS-NPs (1 and 10 μg/L). Transgenerational alterations in expressions of these four NHR genes were also induced by PS-NPs (1 and 10 μg/L). RNAi of daf-12, nhr-14, and nhr-47 caused resistance, whereas RNAi of nhr-12 conferred susceptibility to transgenerational PS-NP toxicity. After PS-NP exposure, expressions of ins-3, daf-28, and ins-39 encoding insulin ligands, efn-3 encoding Ephrin ligand, and lin-44 encoding Wnt ligand, as well as expressions of their receptor genes (daf-2, vab-1, and/or mig-1), were dysregulated by the RNAi of daf-12, nhr-14, nhr-47, and nhr-12. Therefore, alteration in certain germline NHRs could mediate the induction of transgenerational nanoplastic toxicity by affecting secreted ligands and their receptors in the offspring of exposed organisms.

Both nanoplastic and iron mineral types determine their heteroaggregation: Aggregation kinetics and interface process

Nanoplastics (NPs) inevitably interact with iron minerals (IMs) after being released into aquatic environments, changing their transport and fate. In this study, batch heteroaggregation kinetics of four types of NPs, i.e., polymethyl methacrylate (PMMA), polystyrene (PS-Bare), amino-polystyrene (PS-NH2), and carboxyl-polystyrene (PS-COOH), with two different IMs (hematite and magnetite) were conducted. We found that the heteroaggregation of NPs and IMs and the associated interfacial interaction mechanisms are both NPs-dependent and IMs-dependent. Specifically, the NPs had stronger heteroaggregation with hematite than magnetite; the heteroaggregation order of two IMs with NPs was PMMA > PS-NH2 > PS-Bare > PS-COOH. Moreover, hydrogen bond, complexation, hydrophobic, cation-π, and electrostatic interaction were involved in the interfacial reaction between NPs and hematite, and electrons were transferred from the NPs to the hematite, causing the reduction of Fe3+ into Fe2+. Furthermore, we first revealed that both pre-homoaggregation of NPs and IMs could affect their subsequent heteroaggregation, and the homoaggregates of IMs could be interrupted by PMMA or PS-COOH NPs introduction. Therefore, the emerging NPs pollution is likely to generate an ecological effect in terms of elemental cycles such as iron cycle. This work provides new insights into assessing the environmental transfer and ecological effects of NPs in aquatic environments.

Assessment of Ingested Micro- and Nanoplastic (MNP)-Mediated Genotoxicity in an In Vitro Model of the Small Intestinal Epithelium (SIE)

Micro- and nanoplastics (MNPs) have become ubiquitous contaminants of water and foods, resulting in high levels of human ingestion exposure. MNPs have been found in human blood and multiple tissues, suggesting that they are readily absorbed by the gastrointestinal tract (GIT) and widely distributed. Growing toxicological evidence suggests that ingested MNPs may pose a serious health threat. The potential genotoxicity of MNPs, however, remains largely unknown. In this study, genotoxicity of primary and environmentally relevant secondary MNPs was assessed in a triculture small intestinal epithelium (SIE) model using the CometChip assay. Aqueous suspensions of 25 and 1000 nm carboxylated polystyrene spheres (PS25C and PS1KC), and incinerated polyethylene (PEI PM0.1) were subjected to simulated GIT digestion to create physiologically relevant exposures (digestas), which were applied to the SIE model at final MNP concentrations of 1, 5, and 20 μg/mL for 24 or 48 h. PS25C and PS1KC induced DNA damage in a time- and concentration-dependent manner. To our knowledge, this is one of the first assessment of MNP genotoxicity in an integrated in vitro ingestion platform including simulated GIT digestion and a triculture SIE model. These findings suggest that ingestion of high concentrations of carboxylated PS MNPs could have serious genotoxic consequences in the SIE.

Microplastics in drinking water: A review on methods, occurrence, sources, and potential risks assessment

Microplastics in drinking water captured widespread attention following reports of widespread detection around the world. Concerns have been raised about the potential adverse effects of microplastics in drinking water on human health. Given the widespread interest in this research topic, there is an urgent need to compile existing data and assess current knowledge. This paper provides a systematic review of studies on microplastics in drinking water, their evidence, key findings, knowledge gaps, and research needs. The data collected show that microplastics are widespread in drinking water, with large variations in reported concentrations. Standardized methodologies of sampling and analysis are urgently needed. There were more fibrous and fragmented microplastics, with the majority being <10 μm in size and composed of polyester, polyethylene, polypropylene, and polystyrene. Little attention has been paid to the color of microplastics. More research is needed to understand the occurrence and transfer of microplastics throughout the water supply chain and the treatment efficiency of drinking water treatment plants (DWTPs). Methods capable of analyzing microplastics <10 μm and nanoplastics are urgently needed. Potential ecological assessment models for microplastics currently in use need to be improved to take into account the complexity and specificity of microplastics.

Comparing the effects and mechanisms of exposure to polystyrene nanoplastics with different functional groups on the male reproductive system

After aging in the environment, some nanoplastics will carry different charges and functional groups, thereby altering their toxicological effects. To evaluate the potential impact of aging of nanoplastics on the mammalian reproductive system, we exposed C57BL/6 male mice to a dose of 5 mg/kg/d polystyrene nanoparticles (PS-NPs) with different functional groups (unmodified, carboxyl functionalized and amino functionalized) for 45 days for this study. The results suggest that PS-NPs with different functional groups triggered oxidative stress, a decreased in the testis index, disruption of the outer wall of the seminiferous tubules, reduction in the number of spermatogonia cells and sperm counts, and an increased in sperm malformations. We performed GO and KEGG enrichment analysis on the differentially expressed proteins, and found they were mainly enriched in protein transport, RNA splicing and mTOR signaling. We confirmed that the PI3K-AKT-mTOR pathway is over activated, which may lead to reduction of spermatogonia stem cells by over differentiation. Strikingly, PS-NPs with functional group modifications are more toxic than those of unmodified polystyrene, and that PS-NPs with positively charged amino modifications are the most toxic. This study provides a new understanding for correctly evaluating the toxicological effects of plastic aging, and of the mechanism responsible for the reproductive toxicity caused by nanoplastics.

Tracking the micro- and nanoplastics in the terrestrial-freshwater food webs. Bivalves as sentinel species

Micro- (MPs) and nanoplastics (NPs) are currently ubiquitous in the ecosystems, and freshwater biota is still insufficiently studied to understand the global fate, transport paths, and consequences of their presence. Thus, in this study, we investigated the role of bivalves and a trophic transfer of MPs and NPs in an experimental food chain. The food chain consisted of terrestrial non-selective detritivore Dendrobaena (Eisenia) sp., freshwater benthic filter feeder Unio tumidus, and freshwater benthic detritivore-collectors Asellus aquaticus or Gammarus sp. Animals were exposed to different fluorescently labeled micro- and nanoplastics (PMMA 20 μm, nanoPS 15-18 nm, and 100 nm, PS 1 μm and 20 μm, PE from cosmetics) as well as to the faeces of animals exposed to plastics to assess their influence on the environmental transportation, availability to biota, and bioaccumulation of supplied particles. Damaged and intact fluorescent particles were observed in the faeces of terrestrial detritivores and in the droppings of aquatic filter feeders, respectively. They were also present in the guts of bivalves and of crustaceans which were fed with bivalve droppings. Bivalves (Unio tumidus, and additionally Unio pictorum, and Sphaerium corneum) produced droppings containing micro- and nanoparticles filtered from suspension and deposited them onto the tank bottom, making them available for broader feeding guilds of animals (e.g. collectors, like crustaceans). Finally, the natural ageing of PS and its morphological changes, leakage of the fluorescent labelling, and agglomeration of particles were demonstrated. That supports our hypothesis of the crucial role of the characterization of physical and chemical materials in adequately understanding the mechanisms of their interaction with biota. Microscopical methods (confocal, fluorescent, scanning electron) and Raman and FT-IR spectroscopy were used to track the particles' passage in a food web and monitor structural changes of the MPs' and NPs' surface.

Sunscreens and micro(nano)plastics: Are we aware of these threats to the Egyptian coral reefs?

During a snorkeling trip to Marsa Alam and Hamata (southern Red Sea Riviera, Egypt) I explored the coral reefs and the diverse marine habitats of fish and invertebrate species. The area invites recreational diving and snorkeling, but the beaches are littered with all sorts of solid waste (mainly fragmented plastics). Also, there are no local restrictions on sunscreen use. The development of tourism to the area raises questions about the environmental impact and how its further growth will have on coral reefs. Every year, 1.2 million tourists visit the Red Sea coast (about 3287 tourists per day) and release about 1.7 tons/month of sunscreen into the Red Sea. As an ecologist and editorial board member of Science of the Total Environment, I ask myself how we as scientists can increase public awareness and call for prompt actions to protect the coral reefs. The discussion underlines two major threats to the Egyptian coral reefs: sunscreen use and micro(nano)plastics waste. The discussion closes with possible solutions, future perspectives, and recommendations to protect the coral reefs ecosystem of the Egyptian Red Sea.

Two plant-growth-promoting Bacillus species can utilize nanoplastics

Plastics in agricultural soils pose a potential risk to humans because environmental plastics can enter our foods. Here, we present a first step toward developing bacteria that can both flourish in agricultural settings and bioremediate nanoplastics. We exposed two species known to promote plant growth in agricultural settings, Bacillus inaquosorum and B. velezensis, to polystyrene nanoplastic beads at various dosages. When grown in a medium with a low dosage of plastic as the only carbon source, the bacteria could oxidize the plastic, indicating the possibility of utilizing the plastic in their growth. When plastic was added to a rich medium, low and high dosages brought immediate death or inhibition to about a third of B. inaquosorum cells during 1 h. Despite the immediate harm, over the course of 24 h, the bacteria from one strain each of B. inaquosorum and B. velezensis reached higher densities at low plastic doses than with no plastic, although they reached lower densities at high plastic doses (a toxicological phenomenon known as hormesis). Microscopic studies demonstrated that the bacteria are shielded from excessive accumulation of nanoplastic particles. Because these plant-growth-promoting species can utilize polystyrene nanoplastics, strains of these species might be developed to bioremediate environmental plastic in agricultural settings. SYNOPSIS: Plastic fragments on farmlands accumulate on produce, creating a need for bioremediation. We identify bacteria that can flourish on agricultural land and utilize nanoplastics, a first step toward developing agricultural bioremediators.

Effects of microplastics on the properties of different types of sewage sludge and strategies to overcome the inhibition: A review

Microplastics have been identified as an emerging pollutant. When microplastics enter wastewater treatment plants, the plant traps most of the microplastics in the sludge during sewage treatment. Therefore, the effects of microplastics on sludge removal performance, and on the physical and chemical properties and microbial communities in sludge, have attracted extensive attention. This review mainly describes the presence of microplastics in wastewater treatment plants, and the effects of microplastics on the decontamination efficiency and physicochemical properties of activated sludge, aerobic granular sludge, anaerobic granular sludge and anaerobic ammonium oxidation sludge. Further, the review summarizes the effects of microplastics on microbial activity and microbial community dynamics in various sludges in terms of type, concentration, and contact time. The mechanisms used to strengthen the reduction of microplastics, such as biochar and hydrochar, are also discussed. This review summarizes the mechanism by which microplastics influence the performance of different types of sludge, and proposes effective strategies to mitigate the inhibitive effect of microplastics on sludge and discusses removal technologies of microplastics in sewage. Biochar and hydrochar are one of the effective measures to overcome the inhibition of microplastics on sludge. Meanwhile, constructed wetland may be one of the important choice for the future removal of microplastics from sewage. The goal is to provide theoretical support and insights for ensuring the stable operation of wastewater treatment plants and reducing the impact of microplastics on the environment.

Effects of polymethylmethacrylate nanoplastics on the polychaete Hediste diversicolor: Behavioural, regenerative, and biochemical responses

Plastics, particularly microplastics (MPs) and nanoplastics (NPs), have been regarded as pollutants of emerging concern due to their effects on organisms and ecosystems, especially considering marine environments. However, in terms of NPs, there is still a knowledge gap regarding the effects of size and polymer on marine invertebrates, such as benthic organisms. Therefore, this study aimed to understand, regarding behavioural, physiological, and biochemical endpoints (neurotransmission, energy metabolism, antioxidant status, and oxidative damage), the effects of 50 nm waterborne polymethylmethacrylate (PMMA) NPs (0.5 to 500 µg/L) on the marine benthic polychaete Hediste diversicolor, a key species in estuarine and coastal ecosystems. Results demonstrated that worms exposed to PMMA NPs had a shorter burrowing time than control organisms. Nevertheless, worms exposed to PMMA NPs (0.5 and 500 µg/L) decreased cholinesterase activity. Energy metabolism was decreased at 50 and 500 µg/L, and glycogen content decreased at all concentrations of PMMA NPs. Enzymes related to the antioxidant defence system (superoxide dismutase and glutathione peroxidase) displayed increased activities in H. diversicolor specimens exposed to concentrations between 0.5 and 500 µg/L, which led to no damage at the cell membrane and protein levels. In this study, polychaetes also displayed a lower regenerative capacity when exposed to PMMA NPs. Overall, the data obtained in this study emphasize the potential consequences of PMMA NPs to benthic worms, particularly between 0.5 and 50 µg/L, with polychaetes exposed to 50 µg/L being the most impacted by the analysed NPs. However, since sediments are considered to be sinks and sources of plastics, further studies are needed to better understand the impacts of different sizes and polymers on marine organisms, particularly benthic species.

Formation, behavior, properties and impact of micro- and nanoplastics on agricultural soil ecosystems (A Review)

Micro and nanoplastics (MPs and NPs, respectively) in agricultural soil ecosystems represent a pervasive global environmental concern, posing risks to soil biota, hence soil health and food security. This review provides a comprehensive and current summary of the literature on sources and properties of MNPs in agricultural ecosystems, methodology for the isolation and characterization of MNPs recovered from soil, MNP surrogate materials that mimic the size and properties of soil-borne MNPs, and transport of MNPs through the soil matrix. Furthermore, this review elucidates the impacts and risks of agricultural MNPs on crops and soil microorganisms and fauna. A significant source of MPs in soil is plasticulture, involving the use of mulch films and other plastic-based implements to provide several agronomic benefits for specialty crop production, while other sources of MPs include irrigation water and fertilizer. Long-term studies are needed to address current knowledge gaps of formation, soil surface and subsurface transport, and environmental impacts of MNPs, including for MNPs derived from biodegradable mulch films, which, although ultimately undergoing complete mineralization, will reside in soil for several months. Because of the complexity and variability of agricultural soil ecosystems and the difficulty in recovering MNPs from soil, a deeper understanding is needed for the fundamental relationships between MPs, NPs, soil biota and microbiota, including ecotoxicological effects of MNPs on earthworms, soil-dwelling invertebrates, and beneficial soil microorganisms, and soil geochemical attributes. In addition, the geometry, size distribution, fundamental and chemical properties, and concentration of MNPs contained in soils are required to develop surrogate MNP reference materials that can be used across laboratories for conducting fundamental laboratory studies.

Two genes related to apoptosis in the hepatopancreas of juvenile prawn, Macrobrachium nipponense: Molecular characterization and transcriptional response to nanoplastic exposure

Nanoplastics have been widely found in the global water environment, causing plastic pollution and affecting human beings and numerous organisms. Studies involving freshwater crustacean exposure to nanoplastics, however, are limited. In this study, juvenile prawns (Macrobrachium nipponense) were exposed to 75 nm polystyrene nanoplastics at different concentrations (0, 5, 10, 20, or 40 mg/L) for a 28-d chronic exposure experiment. To study the effects of exposure to nanoplastics on hepatopancreas cell apoptosis, C-Jun N-terminal kinase (JNK) and phosphatidylinositol-4,5-bisphosphate 3-kinase, catalytic subunit alpha (PIK3CA) genes were selected, and hepatotoxic enzyme activities and Toll pathway- and apoptosis-related gene expression were determined. For the first time, full-length Mn-JNK and Mn-PIK3CA cDNAs were cloned from M. nipponense. Homologous comparisons showed that JNK and PIK3CA had conserved functional sequences. The apoptosis rate in the high-concentration nanoplastic group (40 mg/L) was significantly higher than in the low-concentration nanoplastic (5 mg/L) and control groups (0 mg/L). The alanine aminotransferase (ALT), aspartate aminotransferase (AST), glutamyl transpeptidase (GGT) and xanthine oxidase (XOD) enzyme activities in the hepatopancreas increased with exposure to higher concentrations of nanoplastics. In addition, the levels of apoptosis- and Toll pathway-related gene expression and JNK and PIK3CA gene expression were initially increased, then decreased with exposure to higher concentrations of nanoplastics. This study showed that polystyrene nanoplastics activate toll-related pathways leading to apoptosis and hepatopancreas damage, which provides theoretical support for future aquatic toxicological research.

Intertwined synergistic abiotic and biotic degradation of polypropylene pellets in marine mesocosms

The accumulation of plastic waste in the oceans has caused growing concern for its effects on marine life. The interactions of plastics with environmental factors have been linked to fragmentation to micro- and nanoparticles with different properties and consequences, but the mechanism of fragmentation has not been fully understood yet. In this work, we investigate the combined effect of marine communities and ultraviolet (UV) radiation towards the degradation of virgin and artificially weathered polypropylene (PP) pellets after a long-term incubation period in marine mesocosms. The surface chemical alterations and deterioration of the polymer, in conjunction with the attachment and evolution of marine bacterial communities, the development of biofilm and exopolymeric substances (EPS), as well as the colloidal properties (zeta-potential and hydrodynamic diameter) of the mesocosms were studied. The surface area of both types of pellets decreased over time, despite no concrete weight change being observed. Cell growth, EPS production and colloid particle size were correlated to the loss of area. Therefore, we propose that surface area could be effectively monitored, instead of weight loss, as an alternative indicator of polymer degradation in biodegradation experiments. Changes in the chemical structure of the polymer, in addition to the evolution of the biological factors, implied that a complex degradation process alternated between two phases: an abiotic phase, when UV irradiation contributes to the deterioration of the polymer surface layers and a biotic phase, when marine communities degrade the weathered polymer surface to reveal the underlying layer of virgin polymer. Finally, microscopic particles, produced as a result of the decrease in pellet area, promoted the aggregation of colloidal particles. The role and impacts of these colloidal particles in marine ecosystems are yet as unidentified as that of micro- and nano-sized plastic particles and call for further investigation.