Differential toxicity of functionalized polystyrene microplastics to clams (Meretrix meretrix) at three key development stages of life history

Surface functionalization, particle size and pharmaceutical co-contaminant dependent impact of nanoplastics on marine crustacean - Artemia salina

Despite a significant amount of research on micronanoplastics (MNPs), there is still a gap in our understanding of their function as transporters of other environmental pollutants (known as the Trojan horse effect) and the combined effects of ingestion, bioaccumulation, and toxicity to organisms. This study examined the individual effects of polystyrene nanoplastics (PSNPs) with various surface functionalizations (plain (PS), carboxylated (PS-COOH), and aminated (PS-NH2)), particle sizes (100 nm and 500 nm), and a pharmaceutical co-contaminant (metformin hydrochloride (MH), an anti-diabetic drug) on the marine crustacean - Artemia salina. The study specifically aimed to determine if MH alters the detrimental effects of PSNPs on A. salina. The potential toxicity of these emerging pollutants was assessed by examining mortality, hatching rate, morphological changes, and biochemical changes. Smaller nanoparticles had a more significant impact than larger ones, and PS-NH2 was more harmful than PS and PS-COOH. Exposure to the nanoparticle complex with MH resulted in a decrease in hatching rate, an increase in mortality, developmental abnormalities, an increase in reactive oxygen species, catalase, and lipid peroxidase, and a decrease in total protein and superoxide dismutase, indicating a synergistic effect. There were no significant differences between the complex and the individual nanoparticles. However, accumulating these particles in organisms could contaminate the food chain. These results highlight the potential environmental risks associated with the simultaneous exposure of aquatic species to plastics, particularly smaller PS, aminated PS, and pharmaceutical complex PS.

Interactions between phenanthrene and polystyrene micro/nano plastics: Implications for rice (Oryza sativa L.) toxicity

Micro/nano plastics (MPs/NPs) are widely distributed and are one of the global pollutants of current concern. Micro/nano plastics can adsorb a variety of persistent organic pollutants, and different particle sizes and surface charges affect the biological effects of MPs/NPs. Therefore, how the compound pollution of MPs/NPs with different particle sizes and organic pollutants produces toxic effects on plants needs to be further studied. We investigated the toxic effects of phenanthrene (Phe) and amino-modified PS (PS-NH2) with two particle sizes (50 nm, 5 μm) on rice. The stress mechanism of PS-NH2 was different between the two particle sizes. Moreover, 50 nm PS-NH2 inhibited stomatal conductance and transpiration rate, reduced photosynthetic rate, significantly enriched GO functions such as "DNA repair" and "DNA double-strand break," and caused severe DNA damage in rice. Notably, 5 μm PS-NH2 affected the gene expression of "photosynthetic lighting" and "photosynthetic antenna protein" in rice, decreased chlorophyll content, and inhibited rice growth. The toxicity of 50 nm PS-NH2 was stronger. In addition, we found that Phe reduced the toxicity of PS-NH2 with different particle sizes, and the relief effect of 50 nm PS-NH2+Phe was more evident. Further, 50 nm PS-NH2+Phe alleviated the toxicity by stimulating the activities of antioxidant enzymes, reducing oxidative damage to chloroplasts, and inhibiting photosynthesis. However, 5 μm PS-NH2+Phe can reduce the stress by reducing the degree of membrane lipid peroxidation, activating metabolic pathways related to the cell wall and cell membrane formation, and plant antitoxin biosynthesis. The results contribute to the understanding of the mechanism of toxicity of MPs/NPs and polycyclic aromatic hydrocarbons (PAHs) to crops.

Sorption behaviour of tebuconazole on microplastics: kinetics, isotherms and influencing factors

Microplastics (MPs) and pesticides are two classes of environmental pollutants and have become global challenges. MPs could adsorb substantial environmental pollutants, which may affect their transportation, distribution and cause combination toxicity. Therefore, the study of sorption properties and mechanisms is the basis of the ecological risk assessment of co-exposure of pesticides and MPs. In this research, typical triazole fungicide tebuconazole (TEB) is selected as a model pollutant, and its sorption behaviour was investigated by kinetic and isotherm models. Meanwhile, a series of environmental influencing factors, like pH, salinity, and metals were conducted. Results showed that the sorption of TEB on MPs could reach equilibrium at 24 h, and the sorption capacity followed the order of PA (polyamide) > PS (polystyrene) > PP (polypropylene). The pseudo-second-order model was the most appropriate model to describe kinetic data, and the Freundlich model was well fit for PA sorption isotherms, in contrast the Langmuir model is better for PP and PS. Additionally, the pH of the solution, salinity, and metals have an important effect on sorption. Combined with Fourier Transform Infrared Spectroscopy and environmental influencing factors, the sorption mechanisms were mainly electrostatic interaction and hydrogen bond for PA and PP, and hydrophobic force, intermolecular force, and electrostatic force for PS, respectively.

A critical review on the evaluation of toxicity and ecological risk assessment of plastics in the marine environment

The increasing production of plastics together with the insufficient waste management has led to massive pollution by plastic debris in the marine environment. Contrary to other known pollutants, plastic has the potential to induce three types of toxic effects: physical (e.g intestinal injuries), chemical (e.g leaching of toxic additives) and biological (e.g transfer of pathogenic microorganisms). This critical review questions our capability to give an effective ecological risk assessment, based on an ever-growing number of scientific articles in the last two decades acknowledging toxic effects at all levels of biological integration, from the molecular to the population level. Numerous biases in terms of concentration, size, shape, composition and microbial colonization revealed how toxicity and ecotoxicity tests are still not adapted to this peculiar pollutant. Suggestions to improve the relevance of plastic toxicity studies and standards are disclosed with a view to support future appropriate legislation.

Biomineralization biomarkers to assess microplastics toxic effects in the freshwater snail Pomacea canaliculata

Microplastics (MPs) pollution has increased the number of reports on the toxic effects on biota, especially aquatic organisms. Recently, studies highlighted changes in ion transport and concentration, especially Ca²⁺, in organisms exposed to MPs. For calcifying organisms, such as mollusks, Ca²⁺ homeostasis is critical for their shells construction. We investigated the effects of polyethylene (PE) MPs at 20 μg/L on biomineralization biomarkers (Ca²⁺ATPase, carbonic anhydrase, hemolymph [Ca²⁺], and shell regeneration) of the freshwater gastropod Pomacea canaliculata. Two experimental sets were performed: (1) animals in physiological condition and (2) animals with their shells excised. The results of the first set showed that within 24 h, the hemolymph [Ca²⁺] decreased, and the Ca²⁺ATPase activity increased in the mantle edge. For carbonic anhydrase (CA), the activity decreased in the gland and increased in the mantle. By 72 h, the hemolymph [Ca²⁺] had not changed, whereas both enzymes had increased in both tissues. In the second set, the hemolymph [Ca²⁺] increased after 72 h, whereas Ca²⁺ATPase activity decreased in both tissues. For AC, the opposite results were observed. At 120 h, calcium pumping was still reduced and CA values increased in the digestive gland. Additionally, MPs exposure increased the capacity of the gastropods to recover their shells. Based on this, our work provides novel data associating PE microplastic exposures (at 20 μg/L) and their potential to stimulate biomineralization enzymes of P. canaliculata, as well as increase shell regeneration in excised animal; a good prerogative for further investigations on both subjects that still lacks of more robust evidence.

Antibiotic sorption onto microplastics in water: A critical review of the factors, mechanisms and implications

Microplastics as vectors for contaminants in the environment is becoming a topic of public interest. Microplastics have been found to actively adsorb heavy metals, per-fluorinated alkyl substances (PFAS), polychlorinated biphenyls (PCBs), polyaromatic hydrocarbons (PAHs), pharmaceuticals and personal care products (PPCPs) and polybrominated diethers (PBDs) onto their surface. Particular interest in microplastics capacity to adsorb antibiotics needs further attention due to the potential role this interaction plays on antibiotic resistance. Antibiotic sorption experiments have been documented in the literature, but the data has not yet been critically reviewed. This review aims to comprehensively assess the factors that affect antibiotic sorption onto microplastics. It is recognised that the physico- chemical properties of the polymers, the antibiotic chemical properties, and the properties of the solution all play a crucial role in the antibiotic sorption capacity of microplastics. Weathering of microplastics was found to increase the antibiotic sorption capacity by up to 171%. An increase in solution salinity was found to decrease the sorption of antibiotics onto microplastics, in some instances by 100%. pH also has a substantial effect on sorption capacity, illustrating the significance of electrostatic interactions on the sorption of antibiotics onto microplastics. The need for a uniform experimental design when testing antibiotic sorption is highlighted to remove inconsistencies in the data currently presented. Current literature examines the link between antibiotic sorption and antibiotic resistance, however, further studies are still required to fully understand this emerging global crisis.

Untangling the Interactions between Anionic Polystyrene Nanoparticles and Lipid Membranes Using Laurdan Fluorescence Spectroscopy and Molecular Simulations

Several classes of synthetic nanoparticles (NPs) induce rearrangements of cell membranes that can affect membrane function. This paper describes the investigation of the interactions between polystyrene nanoparticles and liposomes, which serve as model cell membranes, using a combination of laurdan fluorescence spectroscopy and coarse-grained molecular dynamics (MD) simulations. The relative intensities of the gel-like and fluid fluorescent peaks of laurdan, which is embedded in the liposome membranes, are quantified from the areas of deconvoluted lognormal laurdan fluorescence peaks. This provides significant advantages in understanding polymer-membrane interactions. Our study reveals that anionic polystyrene NPs, which are not cross-linked, induce significant membrane rearrangement compared to other cationic or anionic NPs. Coarse-grained MD simulations demonstrate that polymer chains from the anionic polystyrene NP penetrate the liposome membrane. The inner leaflet remains intact throughout this process, though both leaflets show a decrease in lipid packing that is indicative of significant local rearrangement of the liposome membrane. These results are attributed to the formation of a hybrid gel made up of a combination of polystyrene (PS) and lipids that forces water molecules away from laurdan. Our study concludes that a combination of negative surface charge to interact electrostatically with positive charges on the membrane, a hydrophobic core to provide a thermodynamic preference for membrane association, and the ability to extend non-cross linked polymer chains into the liposome membrane are necessary for NPs to cause a significant rearrangement in the liposomes.

Carboxyl-modified polystyrene microplastics induces neurotoxicity by affecting dopamine, glutamate, serotonin, and GABA neurotransmission in Caenorhabditis elegans

Microplastics (MPs) are ubiquitous in various environmental media and have potential toxicity. However, the neurotoxicity of carboxyl-modified polystyrene microplastics (PS-COOH) and their mechanisms remain unclear. In this study, Caenorhabditis elegans was used as a model to examine the neurotoxicity of polystyrene microplastic (PS) and PS-COOH concentrations ranging from 0.1 to 100 μg/L. Locomotion behavior, neuron development, neurotransmitter level, and neurotransmitter-related gene expression were selected as assessment endpoints. Exposure to low concentrations (1 μg/L) of PS-COOH caused more severe neurotoxicity than exposure to pristine PS. In transgenic nematodes, exposure to PS-COOH at 10-100 μg/L significantly increased the fluorescence intensity of dopaminergic, glutamatergic, serotonergic, and aminobutyric acid (GABA)ergic neurons compared to that of the control. Further studies showed that exposure to 100 μg/L PS-COOH can significantly affect the levels of glutamate, serotonin, dopamine, and GABA in nematodes. Likewise, in the present study, the expression of genes involved in neurotransmission was altered in worms. These results suggest that PS-COOH exerts neurotoxicity by affecting neurotransmission of dopamine, glutamate, serotonin, and GABA. This study provides new insights into the underlying mechanisms and potential risks associated with PS-COOH.

Bioaccumulation of functionalized polystyrene nanoplastics in sea cucumber Apostichopus japonicus (Selenka, 1867) and their toxic effects on oxidative stress, energy metabolism and mitochondrial pathway

Micro/nano-plastics (M/NPs) are emerging contaminants in aquatic environment, however, little knowledge regarding the adverse effects of functionalized NPs has been documented so far. This study investigated the accumulation of different polystyrene nanoplastics (PS-NPs, i.e., plain PS, carboxyl-functional PS-COOH and amino-functional PS-NH₂) at two particle sizes of 100 nm and 200 nm, and evaluated the impacts on oxidative stress, energy metabolism and mitochondrial pathway responses in intestine and respiratory tree of Apostichopus japonicus during the 20-d exposure experiment. The results showed that there were significant interactions of particle size and nanoplastic type on the accumulation of different PS-NPs. Exposure to NPs significantly increased the production of malondialdehyde, glutathione and reactive oxygen species, as well as the activities of antioxidant enzymes including glutathione reductase, superoxide dismutase and catalase, resulting in various degrees of oxidative damage in sea cucumber. The significant decrease in adenosine triphosphate content and increases in alkaline phosphatase and lactate dehydrogenase activities suggested that NPs impaired energy metabolism and modified their energy allocation. After 20-d exposure, the complex I, II and III activities in mitochondrial respiratory chain were significantly inhibited. Meanwhile, the Bax and Caspase-3 gene expression were significantly up-regulated, and Bacl-2 was down-regulated, indicating the toxicity on mitochondrial pathway of A. japonicus. The calculated IBR values elucidated the greater detriment to mitochondrial pathway than oxidative stress and energy metabolism. For 100 nm particle size, plain PS has stronger influence on all the biomarkers compared to PS-COOH/NH₂, however, the opposite trends were observed in 200 nm PS-NPs. Furthermore, 100 nm PS-NPs were recognized to be more hazardous to sea cucumber than 200 nm microbeads. These findings provide new insights for understanding the differentiated toxic effects of functionalized NPs in marine invertebrates.

Transport behavior of nanoplastics in activated carbon column

Nanoplastics can be produced directly from some artificial products, such as cosmetics, or indirectly from the breakup of large pieces of plastic waste. They have a small particle size, large specific surface area, and stable structure and can concentrate toxic compounds in water. The discharge of nanoplastics into the water environment through urban piping systems or surface runoff may lead to the contamination of surface water resources, which poses a great threat to the safety of drinking water. As a common adsorbent, granular activated carbon (GAC) is widely used in the advanced treatment of drinking water. However, most of the studies focused on the transport ability of nanoplastics in quartz sand, and there is a lack of research on the migration behavior of nanoplastics in activated carbon media. In this study, the stability and pore characteristics of GAC were studied, and its regeneration efficiency was investigated. The transport curves of PSNPs, which have a particle size of 98 ± 9 nm and specific surface area of about 67 m²/g, were compared under different ionic strengths, ionic species, flow rates, pH, and humic acid (HA) concentrations. And DLVO theory was used to analyze the transport behavior of nanoplastics in activated carbon column. All experiments were performed at room temperature to make the results generalizable. The results showed that GAC had stable pore structure and excellent adsorption capacity. The surface area and pore volume of GAC are 759 m²/g and 0.357 cm³/g, respectively. And the regeneration rate of GAC can reach 90% and 83.3% after the first two regeneration cycles. On the other hand, at high ionic strength and low pH, the repulsive barrier between PSNPs and activated carbon gradually disappeared; then, more PSNPs were deposited in the activated carbon media, and the concentration of PSNPs in the effluent water was lower. Both the flow rate and HA promoted the transport of PSNPs, but the breakthrough curves of PSNPs did not change significantly when the HA concentration was further increased. At the same ion concentration, PSNPs tend to deposit on the surface of activated carbon in the background solution of Ca²⁺ compared with Na⁺. This study reveals the migration mechanism of PSNPs in the activated carbon filter column, which is of great importance to ensure the safety of drinking water and human health.

Hazard of polystyrene micro-and nanospheres to selected aquatic and terrestrial organisms

Plastics contamination in the environment is a major concern. Risk assessment of micro- and nanoplastics (MPL and NPL) poses significant challenges due to MPL and NPL heterogeneity regarding compositional polymers, particle sizes and morphologies in the environment. Yet, there exists considerable toxicological literature on commercial polystyrene (PS) micro- and nanospheres. Although such particles do not directly represent the environmental MPL and NPL, their toxicity data should be used to advance the hazard assessment of plastics. Here, toxicity data of PS micro- and nanospheres for microorganisms, aquatic and terrestrial invertebrates, fish, and higher plants was collected and analyzed. The evaluation of 294 papers revealed that aquatic invertebrates were the most studied organisms, nanosized PS was studied more often than microsized PS, acute exposures prevailed over chronic exposures, the toxicity of PS suspension additives was rarely addressed, and ∼40 % of data indicated no organismal effects of PS. Toxicity mechanisms were mainly studied in fish and nematode Caenorhabditis elegans, providing guidance for relevant studies in higher organisms. Future studies should focus on environmentally relevant plastics concentrations, wide range of organisms, co-exposures with other pollutants, and method development for plastics identification and quantification to fill the gap of bioaccumulation assessment of plastics.

Exposure to nanopolystyrene and its 4 chemically modified derivatives at predicted environmental concentrations causes differently regulatory mechanisms in nematode Caenorhabditis elegans

Nanoplastics represented by nanopolystyrene (NPS) and its chemically modified derivatives are environmentally ecotoxicological hotpots in recent years, but their toxicity and underlying mechanisms have not been fully identified. Here we employed Caenorhabditis elegans as an animal model to systematically compare the toxicity between nanopolystyrene and its 4 chemically modified derivatives (PS-PEG, PS-COOH, PS-SOOOH and PS-NH₂) at predicted environmental concentrations. Our study demonstrated that compared with PS exposed group, PS-NH₂ exposure (15 μg/L) caused a significant decline in lifespan by suppressed DAF-16/insulin signaling and shortened body length by inhibiting DBL-1/TGF β signaling. Different from PS-NH₂ exposed group, PS-SOOOH exposure (15 μg/L) could not cause changes in lifespan, but shortened body length by inhibiting DBL-1/TGF β signaling. In addition, PS-COOH, PS-SOOOH or PS-NH₂ exposure (1 μg/L or 15 μg/L) caused more serious toxicity in reducing locomotion behavior and causing gut barrier deficit. Hence the rank order in toxicity of PS-NH₂＞PS-SOOOH＞PS-COOH＞PS＞PS-PEG was identified. Furthermore, we also presented evidence to support the contention that the observed toxic effects on nematodes were linked to oxide stress and activation of anti-oxidative molecules for reversing the adverse effects induced by nanopolystyrene and its 4 chemically modified derivatives. Our data highlighted nanoplastics may be charge-dependently toxic to environmental organisms, and the screened low toxic modification may support polystyrene nanoparticles continued application for daily consumer goods and biomedicine.

Microplastics, both non-biodegradable and biodegradable, do not affect the whole organism functioning of a marine mussel

Microplastics are ubiquitous in the marine environment, and their uptake by many organisms has been well documented. Concern about increasing plastic waste in ecosystems and organisms has led to the production of biodegradable alternatives. However, long breakdown times of biodegradable plastics in natural environments mean they still have the potential to induce ecological impacts. The impacts of microplastics on organisms remain unclear, especially as many experimental microplastic exposures employ particle concentrations orders of magnitude greater than those found in natural ecosystems. Here, we exposed the ecosystem engineer, the Asian green mussel Perna viridis, to non-biodegradable and biodegradable microplastics at two environmentally relevant concentrations (~17-20 particles L^-1 and ~ 135-140 particles L^-1). After four weeks of exposure, there were no significant effects of microplastic type or concentration on the mortality, oxygen consumption rate, clearance rate, or condition index of P. viridis. With the increasing body of microplastic literature, future exposure studies considering biotic effects should make efforts to employ environmentally relevant concentrations. Further, we suggest that, while a high-profile threat to ecosystems, investigating the effects of microplastics on ecosystems should be conducted alongside, and not draw focus away from, other major threats such as climate change.

Biokinetics of fluorophore-conjugated polystyrene microplastics in marine mussels

Biokinetic information on microplastics in bivalves is required to reduce the human exposure, but little is known about the time-course and size effect on tissue absorption and clearance. The biokinetics of fluorophore-labeled polystyrene microbeads with diameters 10 µm (PL10) and 90 µm (PL90) in Mytilus galloprovincialis marine mussels was investigated in the present study. It was found that both PL10 and PL90 showed a biphasic tissue distribution pattern in digestive and non-digestive tissues, highlighting the significant tissue distribution starting from 48 h post-treatment. The differential size effect on tissue distribution was observed only in the gills, which suggests that PL10 accumulates more than PL90. The depuration kinetics show that particles of both sizes can be cleared in any tissue, but non-digestive tissue requires a longer duration for depuration than digestive tissue. The differential size effect on depuration was observed for both digestive and non-digestive tissues, suggesting that PL10 needed a longer duration for depuration than PL90. More than seven days were needed for depuration of microplastics in mussels, which is an exceptionally longer period compared to conventional depuration of bivalves. The most significant improvement of this study is providing the biokinetics of two different-sized microplastics in mussels and the differential time for purging microplastics from mussels.

Toxicological impacts of micro(nano)plastics in the benthic environment

Micro(nano)plastics (MNPs) have sparked growing public and scientific concerns as emerging pollutants in recent decades, due to their small size and potential for significant ecological and human health impacts. Understanding the toxicological effects of MNPs on aquatic organisms is of great importance; however, most of the available research on aquatic organisms has focused on the pelagic organisms, and studies on benthic organisms are lacking yet. Being bottom-dwelling creatures, benthos perhaps confronts more extreme pressure from MNPs. Therefore, this review summarizes the current literature on the impacts of MNPs on benthic organisms to reveal their toxicity on the survival, growth, development and reproductive systems. MNPs can accumulate in various tissues of benthos and probably cause tissue-specific damage, resulting in genotoxicity and reproductive toxicity to benthic organisms. And, in severe cases, they may also pass on the adverse effects to the next generations. The complexity of co-exposure to MNPs with other aquatic contaminants is also highlighted. Furthermore, we have comprehensively discussed the internal and external factors affecting the toxicity of MNPs in benthic organisms. Additionally, we also presented the current research gaps and potential future challenges, providing overall background information for a thorough understanding of the toxic effects of MNPs in the benthic aquatic ecosystem.

The wedge clam Donax trunculus L., 1758 as a bioindicator of microplastic pollution

This study describes the use of D. trunculus as a bioindicator of microplastic (MPs) pollution due to beach urbanization related to the development of the Taghazout Bay tourist resort in Morocco. In six sites located on the coast, MPs densities ranged from 1.75 to 5.93 items per gram of D. trunculus wet weight. MPs contamination was significantly influenced spatiotemporally by the urbanization degree in the area. The shapes found were fibers (90.5%) and fragments (9.5%). The Fourier Transform Infrared Spectroscopy (FTIR) analysis reported two polymers: polyethylene (65%) and polypropylene (35%). MPs colors were dark and light, with a predominance of light blue (23.8%). The species ingested different sizes of MPs, mainly the 0.1 and 0.5 mm fractions. Scanning Electron Microscope coupled with an energy dispersive X-ray analyzer (SEM/EDX) revealed weathered MPs with chemical elements adhered to their surface (Cu, Fe, Mg, S, Cl, etc.). The results of this study recommend the use of D. trunculus as a new bioindicator of MPs pollution following an urban change in the coastal scenery. Also, a sustainable coastal management must be implemented in the study area.

Immunotoxicity responses to polystyrene nanoplastics and their related mechanisms in the liver of zebrafish (Danio rerio) larvae

Nanoplastics in aquatic environments may induce adverse immunotoxicity effects in fish. However, there is insufficient evidence on the visible immunotoxicity endpoints in the larval stages of fish. The liver plays an important role in systemic and local innate immunity in the fish. In this study, the hepatic inflammatory effects of polystyrene (PS) nanoplastic particles (NPs: 100 and 50 nm) and micron PS particles on transgenic zebrafish (Danio rerio) larvae were estimated using fluorescent-labeled neutrophils, macrophages, and liver-type inflammatory binding protein (fabp10a). Particles with smaller size induced higher aggregations of neutrophils and apoptosis of macrophages in the abdomen of the larvae, corresponding to greater hepatic inflammation in the larvae. NPs increased the expression of fabp10a in the larval livers in a dose- and size-dependent manner. PS particles of 50 nm at a concentration of 0.1 mg·L^-1 increased the expression of fabp10a in the larval liver by 21.90% (P < 0.05). The plausible mechanisms of these effects depend on their distribution and the generation of reactive oxygen species in the larvae. Metabonomic analysis revealed that the metabolic pathways of catabolic processes, amino acids, and purines were highly promoted by NPs, compared to micron PS particles. NPs also activate steroid hormone biosynthesis in zebrafish larvae, which may lead to the occurrence of immune-related diseases. For the first time, the liver was identified as the target organ for the immunotoxicity effects of NPs in the larval stage of fish.

Biodegradable and re-usable sponge materials made from chitin for efficient removal of microplastics

Microplastics have attracted widespread attention due to their detrimental effects on organisms, and their efficient removal poses great challenges, especially those smaller than 3 µm that are more harmful for aquatic biota. Herein, the chitin based sponges with interconnected pores, excellent elasticity and mechanical durability were fabricated and composed with graphene oxide (GO) and oxygen-doped carbon nitride (O-C₃N₄). The chitin based sponges could effectively remove different functionalized microplastics (~1 µm) at pH 6-8, including carboxylate-modified polystyrene (PS-COOH), amine-modified polystyrene (PS-NH₂), and polystyrene (PS). Notably, the removal efficiency of three microplastics by the chitin based sponges reached up to 71.6-92.1% at an environmentally relevant concentration of 1 mg L^-1 in water system. The potential driving forces of the adsorption were electrostatic interactions, hydrogen bond interactions, and π-π interactions. In addition, the chitin based sponges are reusable and after re-used for 3 cycles due to their excellent compressibility. The algae toxicity test demonstrated good biocompatibility of the chitin based sponges and they are also biodegradable in a natural soil. This study provides a green and promising method for fabricating environmentally friendly adsorbents for small-size microplastics removal, and expands the insights into the mechanisms of microplastic adsorption onto the sponge materials.

Microplastic contamination in Indian edible mussels (Perna perna and Perna viridis) and their environs

This study investigated the microplastic (MPs) contamination of the mussels, P. viridis and P. perna of different sizes, and their environment viz. water and sediment. MPs were recovered from the soft tissues of both species. The mean abundance of MPs ranges from 0.87 ± 0.55 to 10.02 ± 4.15 items/individual; 0.1 ± 0.03 to 2.05 ± 0.33 items/g; 31.57 ± 7.63 to 59.25 ± 14.32 items/l in water, and 79.54 ± 18.66 to 108 ± 40.36 items/kg in sediment. Smaller mussels (3-6 cm) are capable of ingesting higher quantities of MPs per gram of tissue weight, and the rate of MP uptake decreases when the mussels grow in size. These might be due to the faster filtration rate in smaller mussels. MPs of fiber type and blue color in the size range of 500 μm to 1 mm are predominant in mussels. Eleven different polymeric groups were identified, of which PE is the most common, followed by PP. The distribution patterns of MP abundance, shape, size, color, and polymer in mussels more closely resemble those in water. There is no significant difference in MP quantities between P. perna and P. viridis (p > 0.05). FTIR-ATR spectroscopy and SEM analysis show that most of the MPs have been strongly weathered. EDAX analysis detects heavy metals like As, Ni, Fe, Zn, and Cd associated with MPs. This study shows that the MPs contents of both the mussel species are transferred from seawater to their edible meat. This study again proved that mussels can act as bio indicator of MPs pollution.

Studying microplastics: Lessons from evaluated literature on animal model organisms and experimental approaches

Although we are witnesses of an increase in the number of studies examining the exposure/effects of microplastics (MPs) on different organisms, there are many unknowns. This review aims to: (i) analyze current studies devoted to investigating the exposure/effects of MPs on animals; (ii) provide some basic knowledge about different model organisms and experimental approaches used in studying MPs; and to (iii) convey directions for future studies. We have summarized data from 500 studies published from January 2011 to May 2020, about different aspects of model organisms (taxonomic group of organisms, type of ecosystem they inhabit, life-stage, sex, tissue and/or organ) and experimental design (laboratory/field, ingestion/bioaccumulation/effect). We also discuss and try to encourage investigation of some less studied organisms (terrestrial and freshwater species, among groups including Annelida, Nematoda, Echinodermata, Cnidaria, Rotifera, birds, amphibians, reptiles), and aspects of MP pollution (long-term field studies, comparative studies examining life stages, sexes, laboratory and field work). We hope that the information presented in this review will serve as a good starting point and will provide useful guidelines for researchers during the process of deciding on the model organism and study designs for investigating MPs.

Current Progress on Marine Microplastics Pollution Research: A Review on Pollution Occurrence, Detection, and Environmental Effects

Recently, microplastics pollution has attracted much attention in the environmental field, as researchers have found traces of microplastics in both marine and terrestrial ecological environments. Here, we reviewed and discussed the current progress on microplastics pollution in the marine environment from three main aspects including their identification and qualification methods, source and distribution, and fate and toxicity in a marine ecosystem. Microplastics in the marine environment originate from a variety of sources and distribute broadly all around the world, but their quantitative information is still lacking. Up to now, there have been no adequate and standard methods to identify and quantify the various types of microplastics, which need to be developed and unified. The fate of microplastics in the environment is particularly important as they may be transferred or accumulated in the biological chain. Meanwhile, microplastics may have a high adsorption capacity to pollutants, which is the basic research to further study their fate and joint toxicity in the environment. Therefore, all the findings are expected to fill the knowledge gaps in microplastics pollution and promote the development of relative regulations.

Microplastic accumulation via trophic transfer: Can a predatory crab counter the adverse effects of microplastics by body defence?

Microplastics are considered detrimental to aquatic organisms due to their potential accumulation along food chains. Thus, it is puzzling why some of them appear unaffected by microplastics. Here, we assessed the contribution of water filtration and food consumption to microplastic accumulation in a predatory marine crab (Charybdis japonica) and examined the associated impacts of microplastics (particle size: 5 μm) following ingestion for one week. Results showed that water filtration and food consumption contributed similarly to the accumulation of microplastics, which were distributed among organs in this order: hepatopancreas > guts > gills > muscles. Yet, biomagnification (i.e. accumulation through consumption of microplastic-contaminated mussels) did not occur possibly due to egestion of microplastics. The crabs upregulated detoxification capacity (EROD) and antioxidant defence (GST) in response to the microplastics accumulated in their tissues. However, these defence mechanisms collapsed when the microplastic concentration in hepatopancreas exceeded ~3 mg g^-1, leading to severe hepatic injury (elevated AST and ALT) and impaired neural activity (reduced AChE). Our results suggest that marine organisms have an innate capacity to counter the acute effects of microplastics, but there is a limit beyond which the defence mechanisms fail and hence physiological functions are impaired. As microplastic pollution will deteriorate in the future, the fitness and survival of marine organisms may be undermined by microplastics, affecting the stability and functioning of marine ecosystems.

An overview of the internalization and effects of microplastics and nanoplastics as pollutants of emerging concern in bivalves

Microplastic and nanoplastic pollution in aquatic environments is a topic of emerging concern due to the internalization, retention time and effects of these particles in aquatic biota. Bivalves are considered bioindicators due to their wide distribution, sessile behaviour, occupation of ecological niches and ability to filter a large water volume. The study of microplastics and nanoplastics in bivalves has revealed the uptake mechanisms, internalization, distribution and depuration of these particles as well as their effects on physiological parameters, morphological alterations, immunotoxicity and changes in gene expression and proteomic profiles. In this review, we examine the primary characteristics of microplastics and nanoplastics (type of material, size, coating, density, additives and shapes) involved in their possible toxicity in bivalves. Furthermore, secondary characteristics such as the suspension media, aggregation stage and adsorption of persistent pollutants were also recorded to assess the impact of these materials on bivalves. Here, we have highlighted the efforts exerted thus far and the remaining gaps in understanding the extent of microplastic and nanoplastic impacts on bivalves on the basis of laboratory experiments and mesocosm bioassays and in the field. Furthermore, further microplastic and nanoplastic toxicological studies are proposed to facilitate the realistic assessment of environmental risk.

Characteristics of microplastics in shoreline sediments from a tropical and urbanized beach (Da Nang, Vietnam)

Microplastics in shoreline sediments were investigated from Da Nang beach for the first time. Sediment samples at the two depth strata (0-5 cm and 5-10 cm) at eight sites along the entire coast were collected for identifying the characteristics of microplastics, including their concentration, size, shape, color, and nature. The synthetic fiber was the predominant type of microplastics, accounting for 99.2% of the total items. Blue (59.9%) and white (22.9%) were the most common colors of the fibers. Synthetic fibers showed a homogenous distribution at all sampling sites with a mean concentration of 9238 ± 2097 items kg^-1 d.w. Meanwhile, the fibers tended to concentrate much more at the surface stratum than the deeper stratum. A large number of synthetic fibers (81.9%) were in the size range of 300-2600 μm, which might pose a threat to marine biota and human health.

Monitoring of microplastics in the clam Donax cuneatus and its habitat in Tuticorin coast of Gulf of Mannar (GoM), India

Microplastics (MPs) in the marine environment are ubiquitous. The ingestion of these pollutants by marine organisms has drawn global attention. This work studies the distribution pattern and characteristics of MPs found in the body of the clam Donax cuneatus and its environment in order to understand the possible relationship between the MP concentration in the environment (water and sediment) and that in the clam's body. Samples of D. cuneatus were collected from the coast between Vembar and Periyathazhai in Tuticorin district along GoM. MP concentrations range from 0.6 to 1.3 items/g (wet weight) in clams, 10-30 items/l in water, and 24-235 items/kg in sediment. Small-sized clams contain the highest concentration of MPs. Hence it is hypothesised that allometric relationship exists between body size and MP concentration, depending on the surface-area to volume ratio. MP abundance in clam body has a clear, positive, significant correlation with MP abundance in sediment but not with abundance of MP in water. Microplastics of fiber type with size 100-250 μm have a predominant presence in clams. The study identified ten types of polymers, of which polyethylene is the most common polymer in all sample types. FTIR-ATR spectra and surface morphology indicate that most of the microplastics have been strongly weathered. Energy dispersive X-ray spectroscopy analysis detected heavy metals associated with MPs like Cd, Pb, Cu, Zn, Ni and Fe. Filter-feeding clams like Donax sp. can provide valuable information on the spatial patterns of MP distribution, and so can act as bio-indicators in monitoring MP pollution in coastal areas.

Synthetic microfibers: Pollution toxicity and remediation

The ever-increasing use of domestic washing machine by urban population is playing a major role in synthetic microfibers (SMFs) pollution via entering the ecosystem. Although many of the sources of fragmented plastic pollution in oceanic environments have been well known, urban areas are playing a major contributor due to huge populations. Thousands of scientific investigations are now reporting the adverse effect of these micro pollutants on aquatic and terrestrial environment, food chain and human health. Microfiber particles along with washing machine grey waters are emitted into urban drainage adjoining the lakes and river which ultimately mix in ocean water and after emission these tiny particles dispersed though out the ocean water by currents due to their low density. Environmental pollution cause by domestic laundering processes of synthetic clothes has been reported as the major cause of primary microplastics in the marine system. While community awareness and improved education will be successful in making public conscious of this problem, there needs to be more research on global scale to mitigate the ecological consequences of microfiber pollution by urban habitats through environmental friendly approach. This paper focuses to improve the understanding of urban population influence on microfiber pollution, their ecological toxicity to aquatic organism and humans, detection and characterization techniques with an emphasis on future research for prevention and control of microfiber pollution.

Sedimentation of nanoplastics from water with Ca/Al dual flocculants: Characterization, interface reaction, effects of pH and ion ratios

Nanoplastics (NPs), which are broken down from large pieces of plastics and caused water environment pollution, are becoming an emerging environmental problem due to their stable structure, high mobility, and easy interactions with ambient organic compounds. Separation of NPs by flocculation may be an effective approach for remediation of NPs contaminated-water. Aluminum ion has been used as a highly efficient flocculant in sewage treatment, and calcium ion also shows excellent sedimentation performance for impurities under high pH conditions. In this study, composite metal calcium-aluminum (Ca/Al) ions were used as flocculants, achieving a settling efficiency of NPs almost as high as 80%. The effects of pH and Ca/Al flocculant ratios on the zeta potentials, solution stability, as well as sedimentation efficiency of NPs were investigated. Results showed that the crystal formation of Ca/Al flocs increased with pH. The contact and adsorption mechanism of NPs by Ca/Al flocs were confirmed by X-ray diffraction, scanning electron microscope, Fourier Transform Infrared Spectrometer, and X-ray photoelectron spectroscopy. The capture of NPs by Ca/Al flocculants could provide a new insight for the treatment of NPs from aqueous environment.

Effects of polystyrene microplastics on larval development, settlement, and metamorphosis of the intertidal barnacle Amphibalanus amphitrite

The effects of microplastic on mortality and sublethal responses on larval development of meroplankton are still largely unknown. Present study investigated the effects of four sizes of virgin spherical polystyrene microplastics (diameter 1.7, 6.8, 10.4, 19.0 μm) on naupliar (stage II-VI) and cypris larvae of barnacle Amphibalanus amphitrite at environmentally relevant concentrations (1, 10, 100, 1000 beads mL^-1). Essential life-history traits, including mortality, development time and rates of growth, settling, and metamorphosis were measured throughout the entire larval development. Feeding experiments were conducted to evaluate if microplastics decreased naupliar feeding due to physical impacts or selective feeding of nauplii. The results showed that A. amphitrite stage II nauplii were able to ingest and efficiently egest all sizes of microplastics. All the life-history endpoints measured were not significantly affected by all sizes of microplastics at any concentration tested. Presence of all sizes of microplastics did not cause physical interference on naupliar feeding and all stages of nauplius larvae (stage III-VI) did not selectively feed on microplastics. However, the feeding ability of stage III nauplius appeared to be affected by 1.7 μm at 1000 beads mL^-1 which was possibly due to individual variations rather than microplastics' impacts. Overall, the full larval development of barnacle A. amphitrite was not affected by microplastics at environmentally relevant concentrations under laboratory condition.

A critical viewpoint on current issues, limitations, and future research needs on micro- and nanoplastic studies: From the detection to the toxicological assessment

Increasing scientific attention on the presence of micro- and nanoplastics (MNPs) in the environments and their potential toxic effects on humans and the ecosystems is evident. Accordingly, the number of publications on this topic has increased substantially from only 5 in 2010 to more than 850 in 2019. Thus, this critical review aimed at providing state-of-the-art information on the existing methods for characterization and detection of MNPs in various matrices, as well as the reported toxic effects of MNPs in both in vivo and in vitro systems, anticipating challenges and providing future needs to improve the current scientific knowledge. We performed a systematic search of recent literature on available methodologies for the characterization/detection of MNPs in different samples, and the summary of such protocols is provided. Also, the existing procedures for in vitro and in vivo toxicity evaluation of MNPs were critically described. The results of our search revealed that quite a great deal of effort had been made to detect, characterize, and quantify the fate and effect of MNPs. However, we are still far from a complete understanding of behaviors of MNPs in the environments and biological systems. Thus, there is a need to advance the existing protocols to improve data accuracy. Besides, more studies that focus on uptake kinetics, accumulation, and biodistribution of MNPs in biological systems are required.

Aquatic toxicity of iron-oxide-doped microplastics to Chlorella pyrenoidosa and Daphnia magna

Novel metal-oxide-doped microplastic particles (MMPs) have become emerging particulate plastics. The toxicity of MMPs in the aquatic environment remains unknown yet. In this study, toxicological effects of a representative MMP (iron-oxide core) with the nominal diameter of 1 μm and two different surface functional groups, amine-modified (MPS (Fe)-NH₂) and carboxyl-modified (MPS (Fe)-COOH) polystyrene, were investigated by toxicity testing using Chlorella pyrenoidosa and Daphnia magna. The aquatic toxicity of two microplastic particles (MPS-NH₂ and MPS-COOH) with the same particle size and surface modification in the absence of iron-oxide core was also observed and compared. Results show that the toxicity of MPS (Fe)-NH₂ to the studied organisms (in terms of median effective concentration) was greater than the MPS (Fe)-COOH and non-iron-oxide-doped microplastic particles. Moreover, the MMPs mainly contributed to the toxicity rather than their dissolved fraction. The accumulation (based on total Fe) of MPS (Fe)-NH₂ in C. pyrenoidosa was higher than the MPS (Fe)-COOH at low effect concentrations. The observations by optical microscopy indicated that the MPS (Fe)-NH₂ was heavily adsorbed on the surface and distributed over the antennae, carapace, and apical spine of D. magna body whereas the MPS (Fe)-COOH was mainly accumulated inside the digestive tract of the daphnia. Furthermore, the analysis of intracellular reactive oxygen species level and antioxidant capacity confirmed that the intensities of the toxic effects cannot be linked to oxidative stress induced by the particles in the algae and daphnids. This work provides valuable insights into the ecological effects of MMPs, which is helpful for the quantitative assessment of food chain transfer of microplastics.

Polystyrene microplastics impaired the feeding and swimming behavior of mysid shrimp Neomysis japonica

Growing evidences revealed the deleterious impacts of microplastics (MPs) on marine organisms. However, the effects of MPs on the movement behavior of marine crustacean is poorly understood. Therefore, this study aims to evaluate the physiological and behavioral responses of mysid shrimp (Neomysis japonica) larvae to polystyrene (PS) and carboxylated polystyrene (PS-COOH). PS-COOH presented a greater physiological toxicity to shrimp larvae compared to PS, causing significant lethal and growth inhibition effect, owing to bioaccumulation of MPs inside stomach. Both two MPs decreased the feeding efficiency of larvae, showing weakened predation competence. Moreover, reduced hunting and/or explorative ability of shrimps caused by MPs was also identified, which was evidenced by an overall decrease in swimming activity, range and frequency after exposure. Our study firstly highlighted that micron-sized polystyrene particles had the negative effects on the movement behavior of mysid shrimp larvae, thus posing potential hazard to population dynamics and ecological function of marine crustacean.

Adsorption behavior of three triazole fungicides on polystyrene microplastics

Environmental pollution caused by microplastics (MPs) and pesticides has become a global challenge, and increasing evidence shows that MPs can adsorb organic pollutants which may affect their distribution and bioavailability. As widely used pesticides, triazole fungicides with potential environmental and human safety risks often coexist with MPs in the environment. Understanding the adsorption behavior is the basis of risk assessment of co-exposure of MPs and triazole fungicides. In this study, the adsorption behavior of three commonly used triazole fungicides on polystyrene (PS) was studied using adsorption test. The influences of PS particle size and environmental factors on adsorption capacity were evaluated, and the adsorption mechanisms were discussed. Results suggested that the adsorption kinetics and isotherm conformed to the Pseudo-second-order and Freundlich model, respectively. The order of adsorption and desorption capacity was hexaconazole (HEX) > myclobutanil (MYC) > triadimenol (TRI), which was positively correlated with LogKow of pesticides. To a certain extent, the decrease in PS particle size and change in solution pH value and increase in salt ion strength all contribute to increasing adsorption capacity. The main mechanisms of adsorption were hydrophobic and electrostatic interactions. MPs can adsorb and may become the source and sink of triazole fungicides in aqueous environments. Our results demonstrate that more attention should be given to the combined water pollution risk of MPs and triazoles fungicides.