Eco-corona formation and associated ecotoxicological impacts of nanoplastics in the environment

Size dependent uptake and trophic transfer of polystyrene microplastics in unicellular freshwater eukaryotes

Microplastics (MP) have become a well-known and widely investigated environmental pollutant. Despite the huge amount of new studies investigating the potential threat posed by MP, the possible uptake and trophic transfer in lower trophic levels of freshwater ecosystems remains understudied. This study aims to investigate the internalization and potential trophic transfer of fluorescent polystyrene (PS) beads (0.5 μm, 3.6 × 108 particles/mL; 6 μm, 2.1 × 105 particles/mL) and fragments (<30 μm, 5 × 103 particles/mL) in three unicellular eukaryotes. This study focuses on the size-dependent uptake of MP by two freshwater Ciliophora, Tetrahymena pyriformis, Paramecium caudatum and one Amoebozoa, Amoeba proteus, serving also as predator for experiments on potential trophic transfer. Size-dependent uptake of MP in all three unicellular eukaryotes was shown. P. caudatum is able to take up MP fragments up to 27.7 μm, while T. pyriformis ingests particles up to 10 μm. In A. proteus, small MP (PS0.5μm and PS6μm) were taken up via pinocytosis and were detected in the cytoplasm for up to 14 days after exposure. Large PS-MP (PS<30μm) were detected in A. proteus only after predation on MP-fed Ciliophora. These results indicate that A. proteus ingests larger MP via predation on Ciliophora (PS<30μm), which would not be taken up otherwise. This study shows trophic transfer of MP at the base of the aquatic food web and serves as basis to study the impact of MP in freshwater ecosystems.

The short-term effect of microplastics in lettuce involves size- and dose-dependent coordinate shaping of root metabolome, exudation profile and rhizomicrobiome

Micro- and nano-plastics (MNPs) in the soil can impact the microbial diversity within rhizospheres and induce modifications in plants' morphological, physiological, and biochemical parameters. However, a significant knowledge gap still needs to be addressed regarding the specific effects of varying particle sizes and concentrations on the comprehensive interplay among soil dynamics, root exudation, and the overall plant system. In this sense, different omics techniques were employed to clarify the mechanisms of the action exerted by four different particle sizes of polyethylene plastics considering four different concentrations on the soil-roots exudates-plant system was studied using lettuce (Lactuca sativa L. var. capitata) as a model plant. The impact of MNPs was investigated using a multi-omics integrated approach, focusing on the tripartite interaction between the root metabolic process, exudation pattern, and rhizosphere microbial modulation. Our results showed that particle size and their concentrations significantly modulated the soil-roots exudates-plant system. Untargeted metabolomics highlighted that fatty acids, amino acids, and hormone biosynthesis pathways were significantly affected by MNPs. Additionally, they were associated with the reduction of rhizosphere bacterial α-diversity, following a size-dependent trend for specific taxa. The omics data integration highlighted a correlation between Pseudomonadata and Actinomycetota phyla and Bacillaceae family (Peribacillus simplex) and the exudation of flavonoids, phenolic acids, and lignans in lettuce exposed to increasing sizes of MNPs. This study provides a novel insight into the potential effects of different particle sizes and concentrations of MNPs on the soil-plant continuum, providing evidence about size- and concentration-dependent effects, suggesting the need for further investigation focused on medium- to long-term exposure.

The bioaccumulation and ecotoxicity of co-exposure of per(poly)fluoroalkyl substances and polystyrene microplastics to Eichhornia crassipes

Gen X and F-53B have been popularized as alternatives to PFOA and PFOS, respectively. These per(poly)fluoroalkyl substances pervasively coexist with microplastics (MPs) in aquatic environments. However, there are knowledge gaps regarding their potential eco-environmental risks. In this study, a typical free-floating macrophyte, Eichhornia crassipes (E. crassipes), was selected for hydroponic simulation of a single exposure to PFOA, PFOS, Gen X, and F-53B, and co-exposure with polystyrene (PS) microspheres. F-53B exhibited the highest bioaccumulation followed by Gen X, PFOA, and PFOS. In the presence of PS MPs, the bioavailabilities of the four PFASs shifted and the whole plant bioconcentration factors improved. All four PFASs induced severe lipid peroxidation, which was exacerbated by PS MPs. The highest integrated biomarker response (IBR) was observed for E. crassipes (IBR of shoot: 30.01, IBR of root: 22.79, and IBR of whole plant: 34.96) co-exposed to PS MPs and F-53B. The effect addition index (EAI) model revealed that PS MPs showed antagonistic toxicity with PFOA and PFOS (EAI < 0) and synergistic toxicity with Gen X and F-53B (EAI > 0). These results are helpful to compare the eco-environmental impacts of legacy and alternative PFASs for renewal process of PFAS consumption and provide toxicological, botanical, and ecoengineering insights under co-contamination with MPs.

Suspension of micro- and nanoplastic test materials: Liquid compatibility, (bio)surfactants, toxicity and environmental relevance

Micro- and nanoplastics have been detected in environmental compartments from the highest mountains to the deepest seas. They have been shown to be present at almost all trophic levels, and within humans they have been detected in numerous organs and human stool. Whilst their ubiquitous nature is indisputable, little is known about the health risks they may present. Much current research is focussed on the production of test materials with which to perform the necessary health studies. An important aspect of this is the correct storage and suspension of the materials to ensure they remain stable both chemically and with regards to size and shape. In this review, we look at the chemical stability of nine common polymers in a range of liquids; first with the use of commercial compatibility charts and then with a more quantitative approach using Hansen solubility parameters. We then look at stability with regards to particle agglomeration, whether and how stable compositions can be predicted, and which dispersants can be added to increase stability. Finally, we discuss the role of bio-surfactants and the eco-corona and how these may offer a route to both better stability and environmental relevance.

An overview on dispersion procedures and testing methods for the ecotoxicity testing of nanomaterials in the marine environment

Considerable efforts have been devoted to develop or adapt existing guidelines and protocols, to obtain robust and reproducible results from (eco)toxicological assays on engineered nanomaterials (NMs). However, while many studies investigated adverse effects of NMs on freshwater species, less attention was posed to the marine environment, a major sink for these contaminants. This review discusses the procedures used to assess the ecotoxicity of NMs in the marine environment, focusing on the use of protocols and methods for preparing NMs dispersions and on the NMs physicochemical characterization in exposure media. To this purpose, a critical analysis of the literature since 2010 was carried out, based on the publication of the first NMs dispersion protocols. Among the 89 selected studies, only <5 % followed a standardized dispersion protocol combined with NMs characterization in ecotoxicological media, while more than half used a non-standardized dispersion method but performed NMs characterization. In the remaining studies, only partial or no information on dispersion procedures or on physicochemical characterization was provided. This literature review also highlighted that metal oxides NMs were the most studied (42 %), but with an increasing interest in last years towards nanoplastics (14 %) and multicomponent nanomaterials (MCNMs, 7 %), in line with the growing attention on these emerging contaminants. For all these NMs, primary producers as algae and bacteria were the most studied groups of marine species, in addition to mollusca, while organisms at higher trophic levels were less represented, likely due to challenges in evaluating adverse effects on more complex organisms. Thus, despite the wide use of NMs in different applications, standard dispersion protocols are not often used for ecotoxicity testing with marine species. However, the efforts to characterize NMs in ecotoxicological media recognize the importance of following conditions that are as standardized as possible to support the ecological hazard assessment of NMs.

Genotoxic and neurotoxic potential of intracellular nanoplastics: A review

Plastic waste comprises polymers of different chemicals that disintegrate into nanoplastic particles (NPLs) of 1-100-nm size, thereby littering the environment and posing a threat to wildlife and human health. Research on NPL contamination has up to now focused on the ecotoxicology effects of the pollution rather than the health risks. This review aimed to speculate about the possible properties of carcinogenic and neurotoxic NPL as pollutants. Given their low-dimensional size and high surface size ratio, NPLs can easily penetrate biological membranes to cause functional and structural damage in cells. Once inside the cell, NPLs can interrupt the autophagy flux of cellular debris, alter proteostasis, provoke mitochondrial dysfunctions, and induce endoplasmic reticulum stress. Harmful metabolic and biological processes induced by NPLs include oxidative stress (OS), ROS generation, and pro-inflammatory reactions. Depending on the cell cycle status, NPLs may direct DNA damage, tumorigenesis, and lately carcinogenesis in tissues with high self-renewal capabilities like epithelia. In cells able to live the longest like neurons, NPLs could trigger neurodegeneration by promoting toxic proteinaceous aggregates, OS, and chronic inflammation. NPL genotoxicity and neurotoxicity are discussed based on the gathered evidence, when available, within the context of the intracellular uptake of these newcomer nanoparticles. In summary, this review explains how the risk evaluation of NPL pollution for human health may benefit from accurately monitoring NPL toxicokinetics and toxicodynamics at the intracellular resolution level.

Amitriptyline ecotoxicity in Danio rerio (Hamilton, 1822) embryos - similar toxicity profile in the presence of nanoplastics

Interaction of nanoplastics (NPls) with other environmental contaminants could affect their uptake by the organisms and their toxicity. Thus, the present study aims to investigate the polystyrene NPls (44 nm) interaction with the antidepressant amitriptyline (AMI) and its toxicity to Danio rerio embryos. A similar toxicological profile for NPls + AMI exposure was found for most of the evaluated endpoints, comparing with AMI single exposure, showing that the presence of NPls did not modulate the AMI toxicity. However, the behavioral assessment showed a different pattern with hypoactivity for the NPls + AMI exposure (NPls - hyperactivity; AMI - no effect). Interaction effects between NPls and AMI were also found in the protein contents (antagonism) and in the total glutathione content (synergism). This study highlights the complexity and unpredictability of NPls interaction with pharmaceuticals, important for an accurate environmental risk assessment and for the developing of effective strategies and interventions against plastic pollution.

Influence of polystyrene nanoparticles on the toxicity of tetrabromobisphenol A in human intestinal cell lines

Research and regulatory efforts in toxicology are increasingly focused on the development of suitable non-animal methodologies for human health risk assessment. In this work we used human intestinal Caco-2 and HT29/MTX cell lines to address the potential risks of mixtures of the emerging contaminants tetrabromobisphenol A (TBBPA) and commercial polystyrene nanoparticles (PSNPs). We employed different in vitro settings to evaluate basal cytotoxicity through three complementary endpoints (metabolic activity, plasmatic, and lysosomal membrane integrity) and the induction of the oxidative stress and DNA damage responses with specific endpoints. Although no clear pattern was observed, our findings highlight the predominant impact of TBBPA in the combined exposures under subcytotoxic conditions and a differential behavior of the Caco-2 and HT29/MTX co-culture system. Distinctive outcomes detected with the mixture treatments include reactive oxygen species (ROS) increases, disturbances of mitochondrial inner membrane potential, generation of alkali-sensitive sites in DNA, as well as significant changes in the expression levels of relevant DNA and oxidative stress related genes.

Mechanistic Insights into Cellular and Molecular Basis of Protein-Nanoplastic Interactions

Plastic waste is ubiquitously present across the world, and its nano/sub-micron analogues (plastic nanoparticles, PNPs), raise severe environmental concerns affecting organisms' health. Considering the direct and indirect toxic implications of PNPs, their biological impacts are actively being studied; lately, with special emphasis on cellular and molecular mechanistic intricacies. Combinatorial OMICS studies identified proteins as major regulators of PNP mediated cellular toxicity via activation of oxidative enzymes and generation of ROS. Alteration of protein function by PNPs results in DNA damage, organellar dysfunction, and autophagy, thus resulting in inflammation/cell death. The molecular mechanistic basis of these cellular toxic endeavors is fine-tuned at the level of structural alterations in proteins of physiological relevance. Detailed biophysical studies on such protein-PNP interactions evidenced prominent modifications in their structural architecture and conformational energy landscape. Another essential aspect of the protein-PNP interactions includes bioenzymatic plastic degradation perspective, as the interactive units of plastics are essentially nano-sized. Combining all these attributes of protein-PNP interactions, the current review comprehensively documented the contemporary understanding of the concerned interactions in the light of cellular, molecular, kinetic/thermodynamic details. Additionally, the applicatory, economical facet of these interactions, PNP biogeochemical cycle and enzymatic advances pertaining to plastic degradation has also been discussed.

Exposure to polystyrene nanoplastics reduces bacterial and fungal biomass in microfabricated soil models

Nanoplastics have been proven to induce toxicity in diverse organisms, yet their effect on soil microbes like bacteria and fungi remains largely unexplored. In this paper, we used micro-engineered soil models to investigate the effect of polystyrene (PS) nanospheres on Pseudomonas putida and Coprinopsis cinerea. Specifically, we explored the effects of increasing concentrations of 60 nm carboxylated bovine serum albumin (BSA) coated nanospheres (0, 0.5, 2, and 10 mg/L) on these bacterial and fungal model organisms respectively, over time. We found that both microorganisms could disperse through the PS solution, but long-distance dispersal was reduced by high concentrations. Microbial biomass decreased in all treatments, in which bacteria showed a linear dose response with the strongest effect at 10 mg/L concentration, and fungi showed a non-linear response with the strongest effect at 2 mg/L concentration. At the highest nanoplastics concentration, the first colonizing fungal hyphae adsorbed most of the PS nanospheres present in their vicinity, in a process that we termed the 'vacuum cleaner effect'. As a result, the toxicity effect of the original treatment on subsequently growing fungal hyphae was reduced to a growth level indistinguishable from the control. We did not find evidence that nanoplastics are able to penetrate bacterial nor fungal cell walls. Overall, our findings provide evidence that nanoplastics can cause a direct negative effect on soil microbes and highlight the need for further studies that can explain how the microbial stress response might affect soil functions.

Assessing micro and nanoplastics toxicity using rodent models: Investigating potential mitochondrial implications

Mitochondria's role as a central hub in cellular metabolism and signaling cascades is well established in the scientific community, being a classic marker of organisms' response to toxicant exposure. Nonetheless, little is known concerning the effects of emerging contaminants, such as microplastics, on mitochondrial metabolism. Micro- and nanoplastics present one of the major problems faced by modern societies. What was once an environmental problem is now recognized as an one-health issue, but little is known concerning microplastic impact on human health. Indeed, only recently, human exposure to microplastics was acknowledged by the World Health Organization, resulting in a growing interest in this research topic. Nonetheless, the mechanisms behind micro- and nanoplastics toxicity are yet to be understood. Animal models, nowadays, are the most appropriate approach to uncovering this knowledge gap. In the present review article, we explore investigations from the last two years using rodent models and reach to find the molecular mechanism behind micro- and nanoplastics toxicity and if mitochondria can act as a target. Although no research article has addressed the effects of mitochondria yet, reports have highlighted molecular and biochemical alterations that could be linked to mitochondrial function. Furthermore, certain studies described the effects of disruptions in mitochondrial metabolism, such as oxidative stress. Micro- and nanoplastics may, directly and indirectly, affect this vital organelle. Investigations concerning this topic should be encouraged once they can bring us closer to understanding the mechanisms underlying these particles' harmful effects on human health.

Silica nanoparticle accumulation in plants: current state and future perspectives

With their excellent biocompatibility, adjustable size, and high specific surface area, silica nanoparticles (SiO2 NPs) offer an alternative to traditional bulk fertilizers as a means to promote sustainable agriculture. SiO2 NPs have been shown to promote the growth of plants and to reduce the negative effects of biotic and abiotic stresses, but their bioaccumulation is a crucial factor that has been overlooked in studies of their biological effects. In this review, the techniques to quantify and visualize SiO2 NPs in plants were examined first. We then provide a summary of the current state of knowledge on the accumulation, translocation, and transformation of SiO2 NPs in plants and of the factors (e.g., the physicochemical properties of SiO2 NPs, plant species, application mode, and environmental conditions) that influence SiO2 NP bioaccumulation. The challenges in analyzing NP-plant interactions are considered as well. We conclude by identifying areas for further research that will advance our understanding of NP-plant interactions and thus contribute to more sustainable, eco-friendly, nano-enabled approaches to improving crop nutrient supplies. The information presented herein is important to improve the delivery efficiency of SiO2 NPs for precision and sustainable agriculture and to assess the safety of SiO2 NPs during their application in agriculture.

Nanoplastics impacts on Thiobacillus denitrificans: Effects of size and dissolved organic matter

The widespread distribution of nanoplastics and dissolved organic matter (DOM) in sewage raises concerns about the potential impact of DOM on the bioavailability of nanoplastics. In this study, the effects of different sizes (100 nm and 350 nm) of polystyrene nanoplastics (PS-NPs, 50 mg/L) and combined with 10 mg/L or 50 mg/L DOMs (fulvic acid, humic acid and sodium alginate) on the growth and denitrification ability of Thiobacillus denitrificans were investigated. Results showed that 100 nm PS-NPs (50 mg/L) cause a longer delay in the nitrate reduction (3 days) of T. denitrificans than 350 nm PS-NPs (2 days). Furthermore, the presence of DOM exacerbated the adverse effect of 100 nm PS-NPs on denitrification, resulting in a delay of 1-4 days to complete denitrification. Fulvic acid (50 mg/L) and humic acid (50 mg/L) had the most significant adverse effect on increasing 100 nm PS-NPs (50 mg/L), causing a reduction of 20 mmol/L nitrate by T. denitrificans in nearly 7 days. It is noteworthy that the presence of DOM did not modify the adverse effect of 350 nm PS-NPs on denitrification. Further analysis of toxicity mechanism of PS-NPs revealed that they could induce reactive oxygen species (ROS) and suppressed denitrification gene expression. The results suggested that DOM may assist in the cellular internalization of PS-NPs by inhibiting PS-NPs aggregation, leading to the increased ROS levels and accelerated T. denitrificans death. This study highlights the potential risk of nanoplastics to autotrophic denitrifying bacteria in the presence of DOM and provides new insights for the treatment of nitrogen-containing wastewater by T. denitrificans.

The complexity of micro- and nanoplastic research in the genus Daphnia - A systematic review of study variability and a meta-analysis of immobilization rates

In recent years, the number of publications on nano- and microplastic particles (NMPs) effects on freshwater organisms has increased rapidly. Freshwater crustaceans of the genus Daphnia are widely used in ecotoxicological research as model organisms for assessing the impact of NMPs. However, the diversity of experimental designs in these studies makes conclusions about the general impact of NMPs on Daphnia challenging. To approach this, we systematically reviewed the literature on NMP effects on Daphnia and summarized the diversity of test organisms, experimental conditions, NMP properties and measured endpoints to identify gaps in our knowledge of NMP effects on Daphnia. We use a meta-analysis on mortality and immobilization rates extracted from the compiled literature to illustrate how NMP properties, study parameters and the biology of Daphnia can impact outcomes in toxicity bioassays. In addition, we investigate the extent to which the available data can be used to predict the toxicity of untested NMPs based on the extracted parameters. Based on our results, we argue that focusing on a more diverse set of NMP properties combined with a more detailed characterization of the particles in future studies will help to fill current research gaps, improve predictive models and allow the identification of NMP properties linked to toxicity.

Molecular assembly of extracellular polymeric substances regulating aggregation of differently charged nanoplastics and subsequent interactions with bacterial membrane

Extracellular polymeric substances (EPS) represent an interface between microbial cells and aquatic environment, where nanoplastics acquire coatings to alter their fate and toxicity. However, little is known about molecular interactions governing modification of nanoplastics at biological interfaces. Molecular dynamics simulations combining experiments were conducted to investigate assembly of EPS and its regulatory roles in the aggregation of differently charged nanoplastics and interactions with bacterial membrane. Driven by hydrophobic and electrostatic interactions, EPS formed micelle-like supramolecular structures with hydrophobic core and amphiphilic exterior. Different components, depending on their hydrophobicity and charge, were found to promote or suppress EPS assembly. Neutral and hydrophobic nanoplastics showed unbiased adsorption of EPS species, while cationic and anionic nanoplastics were distinct and attracted specific molecules of opposite charges. Compared with isolated EPS, assembled EPS concealed hydrophobic groups to be less adsorbed by nanoplastics. Aggregation of nanoplastics was alleviated by EPS due to electrostatic repulsion plus steric hindrance. ESP suppressed binding of cationic nanoplastics to the bacterial membrane through reducing the surface charge. Neutral and anionic nanoplastics showed weak membrane association, but their binding interactions were promoted by EPS. The structural details revealed here provided molecular level insights into modifications of nanoplastics at the eco-environment interface.

Systematic Review of Nano- and Microplastics' (NMP) Influence on the Bioaccumulation of Environmental Contaminants: Part II-Freshwater Organisms

Nano- and microplastic fragments (NMPs) exist ubiquitously in all environmental compartments. The literature-based evidence suggests that NMPs interact with other environmental contaminants in freshwater ecosystems through sorption mechanisms, thereby playing a vector role. Chemically bound NMPs can translocate throughout the environment, reaching long distances from the contaminant discharge site. In addition, they can be ab/adsorbed by freshwater organisms. Although many studies show that NMPs can increase toxicity towards freshwater biota through the carrier role, little is known regarding their potential to influence the bioaccumulation of environmental contaminants (EC) in freshwater species. This review is part II of a systematic literature review regarding the influence of NMPs on bioaccumulation. Part I deals with terrestrial organisms and part II is devoted to freshwater organisms. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses Extension for Scoping Reviews (PRISMA ScR) was used for the literature search and selection. Only studies that assessed the bioaccumulation of EC in the presence of NMPs and compared this with the bioaccumulation of the isolated EC were considered. Here, we discuss the outcome of 46 papers, considering NMPs that induced an increase, induced a decrease, or caused no effect on bioaccumulation. Lastly, knowledge gaps are identified, and future directives for this area of research are discussed.

Direct Measurement of Microplastics by Carbon Detection via Single Particle ICP-TOFMS in Complex Aqueous Suspensions

Multiple analytical techniques to measure microplastics (MPs) in complex environmental matrices are currently under development, and which is most suited often depends on the aim(s) of the research question and the experimental design. Here, we further broaden the suite of possible techniques which can directly detect MPs in suspension while differentiating the carbon contained in MPs from other natural particles and dissolved organic carbon (DOC). Single particle inductively coupled plasma mass spectrometry (sp-ICP-MS) is well suited to measuring particles at trace concentrations, and the use of ICP time-of-flight-MS (ICP-TOFMS) allows one to simultaneously monitor the entire elemental spectrum to assess the full elemental composition of individual particles through developing elemental fingerprints. Because carbon is not detected in a standard operation mode with icp TOF, a dedicated optimization was necessary. Subsequently, to assess the feasibility of monitoring ¹²C particle pulses for the detection of MPs in more complex natural waters, two proof-of-principle studies were performed to measure MPs in waters with environmentally relevant DOC backgrounds (≤20 mg/L) and in the presence of other carbon containing particles, here, algae. Elevated DOC concentrations did not impact the enumeration of particles in suspension, and individual MPs, single algae, and aggregates of MPs and algae were clearly distinguished. The simultaneous identification of different analytes of interest allows for multiplexed sp-ICP-TOFMS experiments utilizing elemental fingerprinting of particles and is a step forward in quantifying MPs in aqueous environmental samples.

A novel framework-based meta-analysis for in-depth characterization of microplastic pollution and associated ecological risks in Chinese Bays

Among aquatic ecosystems, bays are ubiquitously contaminated with microplastics (MPs, size <5 mm), but a comprehensive understanding of their pollution characterization in Chinese Bays is largely elusive. The current study aims to systematically highlight factors intricating MP contamination as well as their geographic distribution, interactions, risk evaluation, and abundance prediction in bays. MPs' abundance was varied in different bays, at concentrations ranging between 0.26 ± 0.14-89, 500 ± 20, 600 items/m³ in water, 15 ± 6-6433.5 items/kg dry weight in sediment and 0.21 ± 0.10-103.5 items/individual in biota. Redundancy analysis, Permannova, and GeoDetector model revealed that the sampling and extraction/identification methods, and geographical locations were the major drivers affecting MP distribution and characteristics. The Mantel test highlighted that the MP characteristics changed with geographic distance, higher in water than that in sediment and biota. ANOSIM results showed that the different environmental media exhibit significant differences in MP characteristics (e.g., color, shape, and polymer). The ARIMA model predicted that Sanggou Bay and Hangzhou Bay have a higher potential for significantly increasing MP contamination in the future. The highest hazard index (HI) values for water, sediment, and biota were respectively reported at Jiaozhou Bay (18,844.16), Bohai Bay (11,485.37), and Dongshan Bay (48,485.11). The highest values for the ecological risk index (RI) in water, sediment, and biota were detected at Beibu Gulf (6,129,559.02), Haikou Bay (2229.14), and Dongshan Bay (561,563.05), respectively. Overall, this framework can be used at different scales and in different environments, which makes it useful for understanding and controlling MP pollution in the ecosystem.

Toxicity of nanoplastics to aquatic organisms: Genotoxicity, cytotoxicity, individual level and beyond individual level

Due to the small size, high mobility and large surface area, nanoplastics (NPs) showed high potential risks to aquatic organisms. This paper reviews the toxicity of NPs to aquatic organism at various trophic levels including bacteria, plankton (algae), zooplankton, benthos, and nekton (fish). The effects at individual level caused by NPs were explained and proved by cytotoxicity and genotoxicity, and the toxicity of NPs beyond individual level was also illustrated. The toxicity of NPs is determined by the size, dosage, and surface property of NPs, as well as environmental factors, the presence of co-contaminants and the sensitivity of tested organisms. Furthermore, the joint effects of NPs with other commonly detected pollutants such as organic pollutants, metals, and nanoparticles etc. were summarized. In order to reflect the toxicity of NPs in the real natural environment, studies on toxicity assessment of NPs with the coexistence of various environmental factors and contaminants, particularly under the concentrations in natural environment are suggested.

Aging of colloidal contaminants and pathogens in the soil environment: Implications for nanoplastic and COVID-19 risk mitigation

Colloidal contaminants and pathogens are widely distributed in soil, whose tiny sizes and distinct surface properties render unique environmental behaviours. Because of aging, colloids can undergo dramatic changes in their physicochemical properties once in the soil environment, thus leading to diverse or even unpredictable environmental behaviour and fate. Herein, we provide a state-of-art review of colloid aging mechanisms and characteristics and implications for risk mitigation. First, we review aging-induced formation of colloidal contaminants and aging-associated changes. We place a special focus on emerging nanoplastic (NP) contaminants and associated physical, chemical, and biological aging processes in soil environments. Second, we assess aging and survival features of colloidal pathogens, especially viruses. Viruses in soils may survive from several days to months, or even several years in groundwater, depending on their rates of inactivation and the reversibility of attachment. Furthermore, we identify implications for risk mitigation based on aging mechanisms. Hotspots of (photo)chemical aging of NPs, including plastic gauzes at construction sites and randomly discarded plastic waste in rural areas, are identified as area requiring greater research attention. For COVID-19, we suggest taking greater care in regions where viruses are persist for long periods, such as cold climate regions. Soil amendment with quicklime (CaO) may act as an effective means for pathogen disinfection. Future risk mitigation of colloidal contaminants and pathogens relies on a better understanding of aging mechanisms and more sophisticated models accurately depicting processes in real soil environments.