Size Matters: Ingestion of Relatively Large Microplastics Contaminated with Environmental Pollutants Posed Little Risk for Fish Health and Fillet Quality

Effects of polystyrene nano- and microplastics and of microplastics with sorbed polycyclic aromatic hydrocarbons in adult zebrafish

The presence of nanoplastics (NPs) and microplastics (MPs) in the environment is recognised as a global-scale problem. Due to their hydrophobic nature and large specific surface, NPs and MPs can adsorb other contaminants, as polycyclic aromatic hydrocarbons (PAHs), and modulate their bioavailability and hazard. Adult zebrafish were exposed for 3 and 21 days to: (1) 0.07 mg/L NPs (50 nm), (2) 0.05 mg/L MPs (4.5 μm), (3) MPs with sorbed oil compounds of the water accommodated fraction (WAF) of a naphthenic crude oil (MPs-WAF), (4) MPs with sorbed benzo(a)pyrene (MPs-B(a)P), (5) 5 % WAF and (6) 21 μg/L B(a)P. Electrodense particles resembling NPs were seen in the intestine lumen close to microvilli. MPs were abundantly found in the intestine lumen, but not internalised into the tissues. After 21 days, NPs caused a significant downregulation of cat, and upregulation of gpx1a and sod1, while MPs upregulated cyp1a and increased the prevalence of liver vacuolisation. No histopathological alteration was observed in gills. In this study, contaminated MPs did not increase PAH levels in zebrafish but results highlight the potential differential impact of plastic particles depending on their size, making it necessary to urgently address the ecotoxicological impact of real environmental NPs and MPs.

Microplastics in aquaculture - Potential impacts on inflammatory processes in Nile tilapia

Aquaculture is essential for meeting the growing global demand for fish consumption. However, the widespread use of plastic and the presence of microplastics in aquaculture systems raise concerns about their impact on fish health and the safety of aquaculture products. This study focused on the Nile tilapia (Oreochromis niloticus), one of the most important aquaculture fish species globally. The aim of this study was to investigate the effects of dietary exposure to a mixture of four conventional fossil fuel-based polymers (microplastics) on the health of adult and juvenile Nile tilapia. Two experiments were conducted, with 36 juvenile tilapia (10-40 g weight) exposed for 30 days and 24 adult tilapia (600-1000 g) exposed for 7 days, the former including a natural particle (kaolin) treatment. In the adult tilapia experiment, no significant effects on intestinal health (Ussing chamber method), oxidative stress, or inflammatory pathways (enzymatic and genetic biomarkers) were observed after exposure to the microplastic mixture. However, in the juvenile tilapia experiment, significant alterations in inflammatory pathways were observed following 30 days of exposure to the microplastic mixture, indicating potential adverse effects on fish health. These results highlight the potential negative impacts of microplastics on fish health and the economics and safety of aquaculture.

Size effects of microplastics on antibiotic resistome and core microbiome in an urban river

Microplastics (MPs) in aquatic environments provide a new ecological niche that facilitates the attachment of antibiotic-resistance genes (ARGs) and pathogens. However, the effect of particle size on the colonization of antibiotic resistomes and pathogens remains poorly understood. To address this knowledge gap, this study explored the antibiotic resistome and core microbiome on three distinct types of MPs including polyethylene, polypropylene, and polystyrene (PS), with varying sizes of 30, 200, and 3000 μm by metagenomic sequencing. Our finding showed that the ARG abundances of the PS type increased by 4-folds with increasing particle size from 30 to 3000 μm, and significant differences in ARG profiles were found across the three MP types. In addition, the concentrations of ARGs and mobile genetic elements (MGEs) were markedly higher in the MPs than in the surrounding water, indicating their enrichment at these artificial interfaces. Notably, several pathogens such as Pseudomonas aeruginosa, Mycobacterium tuberculosis, and Legionella pneumophila were enriched in MP biofilms, and the co-occurrence of ARGs and virulence factor genes (VFGs)/MGEs suggested the presence of pathogenic antibiotic-resistant microbes with potential mobility. Both redundancy analysis (RDA) and structural equation modeling (SEM) demonstrated that physicochemical properties such as zeta potential, MP size, and contact angle were the most significant contributors to the antibiotic resistome. Strikingly, no significant differences were observed in the health risk scores of the ARG profiles among different sizes and types of MPs. This study expands our knowledge on the impact of MP size on microbial risks, thus enhancing our understanding of the potential health hazards they pose.

Chronic exposure to polystyrene microplastics increased the chemosensitivity of normal human liver cells via ABC transporter inhibition

Microplastics (MPs) are ubiquitous in environmental compartments and consumer products. Although liver is frequently reported to be a target organ of MP accumulation in mammals, few studies have focused on MP hepatoxicity in humans. In this study, we used normal human liver cells, THLE-2, to assess the acute and chronic toxicity of polystyrene (PS) MPs with sizes of 0.1 and 1 μm. The results showed that after 48 h of exposure, both kinds of PS MPs could enter THLE-2 cells and cause no obviously acute cytotoxicity at <20 μg/mL. In contrast, metabolomic analysis revealed that 90 days of PS MPs exposure at environmentally relevant dose (0.2 μg/mL) could significantly alter the metabolic profiles of the cells, especially the nanosized MPs. KEGG pathway analysis showed that the ATP-binding cassette (ABC) transporter pathway was the most significantly changed pathway. Cell functional tests confirmed that chronic PS MP treatment could inhibit the activity of the ABC efflux transporter and further increase the cytotoxicity of arsenic, indicating that the PS MPs had a chemosensitizing effect. These findings underline the chronic risk of MPs to human liver.

Carassius auratus as a bioindicator of the health status of Lake Trasimeno and risk assessment for consumers

Fish are good bio-indicators of the health status of the aquatic environment and can be used as biomarkers to assess the aquatic behavior of environmental pollutants, the exposure of aquatic organisms, and the health risk for consumers. Goldfish are a significant bioindicator in the Lake Trasimeno aquatic system (Umbria, Italy). This study aimed to characterize the health status and the chemical and biotic contamination of Lake Trasimeno to define its anthropogenic and natural pressures and the risk associated with consuming its fishery products. 114 determinations were performed on Carassius auratus samples from 2018 to 2020, and the occurrence of brominated flame retardants, non-dioxin-like polychlorinated biphenyls, heavy metals, and microplastics was analytically investigated. Dietary exposure assessment, risk characterization, and benefit-risk evaluation were performed for schoolchildren from 3 to 10 years old. Flame-retardants registered high levels of non-detects (99% for polybrominated diphenyl ether and 76% for hexabromocyclododecanes), while polychlorinated biphenyls were found in all samples with a maximum level of 56.3 ng/g. Traces of at least one heavy metal were found in all samples, though always below the regulatory limit. Microplastics were found with a 75% frequency of fish ingesting at least one particle. Dietary exposure and risk characterization reveal negligible contributions to the reference values of all contaminants, except for mercury, which reached up to 25% of admissible daily intake. The benefit- risk assessment highlighted that the benefits of freshwater fish intake outweigh the associated risks. The examination of goldfish as indicator fish reveals the quality of Lake Trasimeno's aquatic environment and the safety of its products.

Eco-toxicity of nano-plastics and its implication on human metabolism: Current and future perspective

In the current scenario, plastic pollution has become one of the serious environmental hazard problems due to its improper handling and insufficiency in degradation. Nanoplastics (NPs) are formed when plastic fragments are subjected to ultraviolet radiation, natural weathering, and biodegradation. This review paper focuses on the source of origin, bioaccumulation, potential nanoplastics toxicity impact towards environment and human system and management strategies towards plastic pollution. Moreover, this study demonstrates that nanoplastics interfere with metabolic pathways and cause organ dysfunction. A wide range of studies have documented the alteration of organism physiology and behavior, caused by NPs exposure. A major source of NPs exposure is via ingestion because these plastics are found in foods or food packaging, however, they can also enter the human body via inhalation but in a less well-defined form. In recent literature, the studies demonstrate the mechanisms for NP uptake, affecting factors that have been discussed followed by cytotoxic mechanisms of NPs. However, study on challenges regarding NPs toxicity for the risk assessment of human health is limited. It is important to perform and focus more on the possible impacts of NPs on human health to identify the key challenges and explore the potential impacts of their environmental accumulation and its toxicity impacts.

Occurrence of microplastics in freshwater gastropods from a tropical river U-Taphao, southern Thailand

Background

Microplastics (MPs) are pollutants in rivers and marine environments. Rivers can be sources and sinks of MPs that enter the biota. Previous studies focusing on freshwater species are quite limited, especially for gastropods. Freshwater gastropods are essential to aquatic ecosystems because they are food to other aquatic animals, such as fish, shrimp, and crabs. They are a crucial link in the food chain between water resources and human food. Therefore, this study aimed to investigate MP accumulation in freshwater gastropods, commonly known as snails (Filopaludina sumatrensis speciosa and Pomacea canaliculata), in a river flowing into a shallow coastal lagoon.

Method

In this study, snail tissue samples were digested with 30% hydrogen peroxide. The mixture was heated at 60 °C for 24 h. MP particles were identified, counted, and characterized (shape, size, and color) by visual identification under a stereomicroscope. Furthermore, polymer-type identification was performed using Fourier transform infrared spectroscopy (FTIR). Analysis of variance (ANOVA) was applied for the statistical analysis.

Results

The MPs found were as follows: 4.76 particles/individual were found in F. sumatrensis speciosa upstream, 5.20 particles/individual were found in F. sumatrensis speciosa downstream, 7.28 particles/individual were found in P. canaliculata upstream, and 4.00 particles/individual were found in P. canaliculata downstream. It was found in the two-way ANOVA that the accumulation of MPs in gastropods was affected by species and study sites (upstream and downstream). There was a significant difference in the amount of MPs in P. canaliculata between upstream and downstream sites (p = 0.003). Fibers were the most common MPs in both species. Moreover, P. canaliculata upstream had the most significant amount of MPs. The smallest amount of MPs was recorded for P. canaliculata downstream, but there was great diversity in shape, size, and polymer type. MPs sized 500 μm^-1 mm were the most common in both species. Fourier transform infrared spectroscopy revealed six polymers: poly (ethylene terephthalate), polypropylene, rayon, polyethyleneimine, polyamine, and poly (propylene: ethylene). The occurrence of MPs in gastropods is alarming for food security in Thailand. The results of this study can be used to support baseline data on MP accumulation among freshwater gastropods.

From marine to freshwater environment: A review of the ecotoxicological effects of microplastics

Microplastics (MPs) have been widely detected in the world's water, which may pose a significant threat to the ecosystem as a whole and have been a subject of much attention because their presence impacts seas, lakes, rivers, and even the Polar Regions. There have been numerous studies that report direct adverse effects on marine organisms, but only a few have explored their ecological effects on freshwater organisms. In this field, there is still a lack of a systematic overview of the toxic effects and mechanisms of MPs on aquatic organisms, as well as a consistent understanding of the potential ecological consequences. This review describes the fate and impact on marine and freshwater aquatic organisms. Further, we examine the toxicology of MPs in order to uncover the relationship between aquatic organism responses to MPs and ecological disorders. In addition, an overview of the factors that may affect the toxicity effects of MPs on aquatic organisms was presented along with a brief examination of their identification and characterization. MPs were discussed in terms of their physicochemical properties in relation to their toxicological concerns regarding their bioavailability and environmental impact. This paper focuses on the progress of the toxicological studies of MPs on aquatic organisms (bacteria, algae, Daphnia, and fish, etc.) of different trophic levels, and explores its toxic mechanism, such as behavioral alternations, metabolism disorders, immune response, and poses a threat to the composition and stability of the ecosystem. We also review the main factors affecting the toxicity of MPs to aquatic organisms, including direct factors (polymer types, sizes, shapes, surface chemistry, etc.) and indirect factors (persistent organic pollutants, heavy metal ions, additives, and monomer, etc.), and the future research trends of MPs ecotoxicology are also pointed out. The findings of this study will be helpful in guiding future marine and freshwater rubbish studies and management strategies.

A Comparative Systematic Analysis of The Influence of Microplastics on Colon Cells, Mouse and Colon Organoids

BACKGROUND

Microplastics (MPs) are small fragments from any type of plastic formed from various sources, including plastic waste and microfibers from clothing. MPs degrades slowly, resulting in a high probability of human inhalation, ingestion and accumulation in bodies and tissues. As its impact on humans is a prolonged event, the evaluation of its toxicity and influence on human health are critical. In particular, MPs can enter the human digestive system through food and beverage consumption, and its effect on the human colon needs to be carefully examined.

METHODS

We monitored the influence of small MPs (50 and 100 nm) on human colon cells, human colon organoids and also examined their toxicity and changes in gene expression in vivo in a mouse model.

RESULTS

The data suggested that 5 mg/mL concentrations of 50 and 100 nm MPs induced a > 20% decrease in colon organoid viability and an increase in the expression of inflammatory-, apoptosis- and immunity-related genes. In addition, in vivo data suggested that 50 nm MPs accumulate in various mouse organs, including the colon, liver, pancreas and testicles after 7 d of exposure.

CONCLUSION

Taken together, our data suggest that smaller MPs can induce more toxic effects in the human colon and that human colon organoids have the potential to be used as a predictive tool for colon toxicity.

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.

Recent Advances in Micro-/Nanoplastic (MNPs) Removal by Microalgae and Possible Integrated Routes of Energy Recovery

Reliance on plastic has resulted in the widespread occurrence of micro-/nanoplastics (MNPs) in aquatic ecosystems, threatening the food web and whole ecosystem functions. There is a tight interaction between MNPs and microalgae, as dominant living organisms and fundamental constituents at the base of the aquatic food web. Therefore, it is crucial to better understand the mechanisms underlying the interactions between plastic particles and microalgae, as well as the role of microalgae in removing MNPs from aquatic ecosystems. In addition, finding a suitable route for further utilization of MNP-contaminated algal biomass is of great importance. The present review article provides an interdisciplinary approach to elucidate microalgae-MNP interactions and subsequent impacts on microalgal physiology. The degradation of plastic in the environment and differences between micro- and nanoplastics are discussed. The possible toxic effects of MNPs on microalgal growth, photosynthetic activity, and morphology, due to physical or chemical interactions, are evaluated. In addition, the potential role of MNPs in microalgae cultivation and/or harvesting, together with further safe routes for biomass utilization in biofuel production, are suggested. Overall, the current article represents a state-of-the-art overview of MNP generation and the consequences of their accumulation in the environment, providing new insights into microalgae integrated routes of plastic removal and bioenergy production.

Ecotoxic effects of microplastics and contaminated microplastics - Emerging evidence and perspective

The high prevalence and persistence of microplastics (MPs) in pristine habitats along with their accumulation across environmental compartments globally, has become a matter of grave concern. The resilience conferred to MPs using the material engineering approaches for outperforming other materials has become key to the challenge that they now represent. The characteristics that make MPs hazardous are their micro to nano scale dimensions, surface varied wettability and often hydrophobicity, leading to non-biodegradability. In addition, MPs exhibit a strong tendency to bind to other contaminants along with the ability to sustain extreme chemical conditions thus increasing their residence time in the environment. Adsorption of these co-contaminants leads to modification in toxicity varying from additive, synergistic, and sometimes antagonistic, having consequences on flora, fauna, and ultimately the end of the food chain, human health. The resulting environmental fate and associated risks of MPs, therefore greatly depend upon their complex interactions with the co-contaminants and the nature of the environment in which they reside. Net outcomes of such complex interactions vary with core characteristics of MPs, the properties of co-contaminants and the abiotic factors, and are required to be better understood to minimize the inherent risks. Toxicity assays addressing these concerns should be ecologically relevant, assessing the impacts at different levels of biological organization to develop an environmental perspective. This review analyzed and evaluated 171 studies to present research status on MP toxicity. This analysis supported the identification and development of research gaps and recommended priority areas of research, accounting for disproportionate risks faced by different countries. An ecological perspective is also developed on the environmental toxicity of contaminated MPs in the light of multi-variant stressors and directions are provided to conduct an ecologically relevant risk assessment. The presented analyses will also serve as a foundation for developing environmentally appropriate remediation methods and evaluation frameworks.

Microplastic ingestion from atmospheric deposition during dining/drinking activities

Human-health risks from microplastics have attracted considerable attention, but little is known about human-exposure pathways and intensities. Recent studies posited that inhalation of atmospheric microplastics was the dominant human-exposure pathway. Herein, our study identified that atmospheric microplastics ingested from deposition during routine dining/drinking activities represent another important exposure pathway. We measured abundances of atmospheric-deposited microplastics of up to 10⁵ items m^-2 d^-1 in dining/drinking venues, with 90% smaller than 100 µm and a dominance of amorphous fragments rather than fibers. Typical work-life scenarios projected an annual ingestion of 1.9 × 10⁵ to 1.3 × 10⁶ microplastics through atmospheric deposition on diet, with higher exposure rates for indoor versus outdoor dining/drinking settings. Ingestion of atmospheric-deposited microplastics through diet was similar in magnitude to presumed inhalation exposure, but 2-3 orders of magnitude greater than direct ingestion from food sources. Simple mitigation strategies (e.g., covering and rinsing dishware) can substantially reduce the exposure of atmospheric deposition microplastics through diet.

Accumulation of chiral pharmaceuticals (ofloxacin or levofloxacin) onto polyethylene microplastics from aqueous solutions

Drug chirality is attracting increasing attention because the enantiomers of the same chiral pharmaceutical usually exhibit different biological activities, metabolic pathways, and toxicities. The ubiquitous presence of microplastics (MPs) can enrich organic pollutants commonly found in the environment. However, knowledge about the enrichment of pharmaceutical enantiomers to MPs is relatively limited. We investigated the occurrence of enantioselectivity of ofloxacin (OFL) and levofloxacin (LEV) in the adsorption processes on polyethylene (PE) and the interactions influenced by environmental factors. The results showed that the adsorption efficiency of OFL was generally 3-5% (p < 0.05) higher than that of LEV, indicating the different affinities of the enantiomers to PE, but the adsorption process of OFL and LEV on PE was both well described by pseudo-first-order kinetics and liner isotherm models. The chirality of OFL and LEV was not affected by sizes of PE particles and solution salinity due to the identical physicochemical properties. An examination of pH effect indicated that OFL showed better acid-base adaptability than LEV. Moreover, the differences in enantiomeric enrichment between OFL and LEV on PE were promoted with increasing UV light exposure time and natural organic matter (NOM) concentrations. Using Fourier transform infrared spectroscopy (FTIR), we demonstrated that the constituents of the functional groups in chiral NOM were greatly related to the enantiomer stereoselectivity of OFL, subsequently affecting their adsorption in a chiral environment. The excitation-emission matrix (EEM) spectra confirmed the enantioselective behaviors of chiral pharmaceuticals under UV light due to the different optical activity and humic acid-like and fulvic acid-like molecular structure of the enantiomers. These findings imply that the enantioselectivity of drug enantiomers should be considered in presence of microplastics, leading to a more accurate environmental fate and risks assessments of chiral pharmaceuticals.

Occurrence of Microplastics in Tap and Bottled Water: Current Knowledge

A narrative review was carried out to describe the current knowledge related to the occurrence of MPs in drinking water. The reviewed studies (n = 21) showed the presence of microplastics (MPs) in tap (TW) and bottled (BW) water, increasing concerns for public health due to the possible toxicity associated with their polymeric composition, additives, and other compounds or microorganism adsorbed on their surface. The MP concentration increase by decreasing particles size and was higher in BW than in TW. Among BW, reusable PET and glass bottles showed a higher MP contamination than other packages. The lower MP abundance in TW than in natural sources indicates a high removal rate of MPs in drinking water treatment plants. This evidence should encourage the consumers to drink TW instead of BW, in order to limit their exposure to MPS and produce less plastic waste. The high variability in the results makes it difficult to compare the findings of different studies and build up a general hypothesis on human health risk. A globally shared protocol is needed to harmonize results also in view of the monitoring plans for the emerging contaminants, including MPs, introduced by the new European regulation.

Linking the physical and chemical characteristics of single small microplastics or nanoplastics via photolithographic silicon substrates

Small microplastics and nanoplastics are of growing concern as they pose more risks to ecological and human health than larger particles. However, characterization of the morphological and chemical features of single particles faces a major challenge if instrumental combination is not available. Here, we developed a marker system via computer aided design and crafted it on a silicon substrate (8 × 8 mm) via direct-write lithography. We dripped 20 μL of a solution containing tiny particles extracted from a highly weathered plastic fragment onto a silicon substrate. After the solution was oven-dried, the polymer composition of particles down to 895 nm was located via multiple markers and identified using micro-Raman. The lithographic substrate was then transferred to a scanning electron microscope with energy dispersive spectroscopy capability, and the surface morphology and element distribution were captured for the same particle. Similarly, the morphology and surface elevation were characterized using a scanning electron microscope and an atomic force microscope. The average retrieval rate for particles reached 86% if all characterization experiments were conducted within one week. Our results suggest that photolithographic silicon substrates provide a novel and economical way to link the physicochemical characteristics of small microplastics and parts of nanoplastics.

Rethinking the relevance of microplastics as vector for anthropogenic contaminants: Adsorption of toxicants to microplastics during exposure in a highly polluted stream - Analytical quantification and assessment of toxic effects in zebrafish (Danio rerio)

Given the increasing amounts of plastic debris entering marine and freshwater ecosystems, there is a growing demand for environmentally relevant exposure scenarios to improve the risk assessment of microplastic particles (MPs) in aquatic environments. So far, data on adverse effects in aquatic organisms induced by naturally exposed MPs are scarce and controversially discussed. As a consequence, we investigated the potential role of MPs regarding the sorption and transfer of environmental contaminants under natural conditions. For this end, a mixture of four common polymer types (polyethylene, polypropylene, polystyrene, polyvinyl chloride) was exposed to natural surface water in a polluted stream for three weeks. Samples of water, MP mixture, sediment, and suspended matter were target-screened for the presence of pollutants using GC/LC-MS, resulting in up to 94 different compounds. Possible adverse effects were investigated using several biomarkers in early developmental stages of zebrafish (Danio rerio). Exposure to natural stream water samples significantly inhibited acetylcholinesterase activity, altered CYP450 induction and modified behavioral patterns of zebrafish. In contrast, effects by samples of both non-exposed MPs and exposed MPs in zebrafish were less prominent than effects by water samples. In fact, the analytical target screening documented only few compounds sorbed to natural particles and MPs. Regarding acute toxic effects, no clear differentiation between different MPs and natural particles could be made, suggesting that - upon exposure in natural water bodies - MPs seem to approximate the sorption behavior of natural particles, presumably to a large extent due to biofilm formation. Thus, if compared to natural inorganic particles, MPs most likely do not transfer elevated amounts of environmental pollutants to biota and, therefore, do not pose a specific additional threat to aquatic organisms.

Biomarker responses in zebrafish (Danio rerio) following long-term exposure to microplastic-associated chlorpyrifos and benzo(k)fluoranthene

Continuously increasing plastic production causes a constant accumulation of microplastic particles (MPs) in the aquatic environment, especially in industrialized and urbanized areas with elevated wastewater discharges. This coincides with the release of persistent organic pollutants (polycyclic aromatic hydrocarbons (PAHs), pesticides) entering limnic ecosystems. Although the assessment of potential effects of environmental pollutants sorbed to MPs under chronic exposure scenarios seems vital, data on potential hazards and risk by combined exposure to pollutants and microplastics for aquatic vertebrates is still limited. Therefore, zebrafish (Danio rerio) were exposed over 21 days to the organophosphate insecticide chlorpyrifos (CPF; 10 and 100 ng/L) and the PAH benzo(k)fluoranthene (BkF; 0.78 and 50 µg/L) either dissolved directly in water or sorbed to different MPs (irregular polystyrene, spherical polymethyl methacrylate; ≤ 100 µm), where CPF was sorbed to polystyrene MPs and BkF was sorbed to polymethyl methacrylate MPs. Contaminant sorption to MPs and leaching were documented using GC-EI-MS; potential accumulation was studied in cryosections of the gastrointestinal tract. Enzymatic biomarkers and biotransformation were measured in liver and brain. Overall, exposure to non-contaminated MPs did not induce any adverse effects. Results of fluorescence tracking, CYP1A modulation by BkF as well as changes in acetylcholinesterase activity (AChE) by CPF were less pronounced when contaminants were sorbed to MPs, indicating reduced bioavailability of pollutants. Overall, following exposure to waterborne BkF, only minor amounts of parent BkF and biotransformation products were detected in zebrafish liver. Even high loads of MPs and sorbed contaminants did not induce adverse effects in zebrafish; thus, the potential threat of MPs as vectors for contaminant transfer in limnic ecosystems can be considered limited.

Toxicity mechanism of Nylon microplastics on Microcystis aeruginosa through three pathways: Photosynthesis, oxidative stress and energy metabolism

Nylon has been widely used all over the world, and most of it eventually enters the aquatic environment in the form of microplastics (MPs). However, the impact of Nylon MPs on aquatic ecosystem remains largely unknown. Thus, the long-term biological effects and toxicity mechanism of Nylon MPs on Microcystis aeruginosa (M. aeruginosa) were explored in this study. Results demonstrated that Nylon MPs had a dose-dependent growth inhibition of M. aeruginosa at the initial stage, and the maximum inhibition rate reached to 47.62% at the concentration of 100 mg/L. Meanwhile, Nylon MPs could obstruct photosynthesis electron transfer, reduce phycobiliproteins synthesis, destroy algal cell membrane, enhance the release of extracellular polymeric substances, and induce oxidative stress. Furthermore, transcriptomic analysis indicated that Nylon MPs dysregulated the expression of genes involved in tricarboxylic acid cycle, photosynthesis, photosynthesis-antenna proteins, oxidative phosphorylation, carbon fixation in photosynthetic organisms, and porphyrin and chlorophyll metabolism. According to the results of transcriptomic and biochemical analysis, the growth inhibition of M. aeruginosa is inferred to be regulated by three pathways: photosynthesis, oxidative stress, and energy metabolism. Our findings provide new insights into the toxicity mechanism of Nylon MPs on freshwater microalgae and valuable data for risk assessment of MPs.

The Pressing Issue of Micro- and Nanoplastic Contamination: Profiling the Reproductive Alterations Mediated by Oxidative Stress

Micro- and nanoplastics (MPs/NPs) are among the most widely distributed pollutants in the environment. It has been suggested that exposure to MPs/NPs can trigger toxicity pathways among which inflammation and oxidative stress (OS) play a pivotal role. Once absorbed, MPs/NPs may act locally or access the bloodstream and, following the translocation process, reach several organs and tissues, including the gonads. Notably, MPs/NPs can bioaccumulate in human and murine placenta, opening new scenarios for toxicological evaluations. We review recent studies on the effects of MPs/NPs on the reproductive health in aquatic and terrestrial organisms of both sexes, focusing on the role of OS and the antioxidant defence system failure as the main underlying mechanisms. Alterations in gametogenesis, embryonic and offspring development, and survival have been shown in most studies and often related to a broken redox balance. All these detrimental effects are inversely related to particle size, whereas they are closely linked to shape, plastic polymer type, superficial functionalization, concentration, and time of exposure. To date, the studies provide insights into the health impacts, but no conclusions can be drawn for reproduction toxicity. The main implication of the few studies on antioxidant substances reveals their potential role in mitigating MP-induced toxic effects.

Analysis of Microplastics in Human Feces Reveals a Correlation between Fecal Microplastics and Inflammatory Bowel Disease Status

Human ingestion of microplastics (MPs) is inevitable due to the ubiquity of MPs in various foods and drinking water. Whether the ingestion of MPs poses a substantial risk to human health is far from understood. Here, by analyzing the characteristics of MPs in the feces of patients with inflammatory bowel disease (IBD) and healthy people, for the first time, we found that the fecal MP concentration in IBD patients (41.8 items/g dm) was significantly higher than that in healthy people (28.0 items/g dm). In total, 15 types of MPs were detected in feces, with poly(ethylene terephthalate) (22.3-34.0%) and polyamide (8.9-12.4%) being dominant, and their primary shapes were sheets and fibers, respectively. We present evidence indicating that a positive correlation exists between the concentration of fecal MPs and the severity of IBD. Combining a questionnaire survey and the characteristics of fecal MPs, we conclude that the plastic packaging of drinking water and food and dust exposure are important sources of human exposure to MPs. Furthermore, the positive correlation between fecal MPs and IBD status suggests that MP exposure may be related to the disease process or that IBD exacerbates the retention of MPs. The relative mechanisms deserve further studies. Our results also highlight that fecal MPs are useful for assessing human MP exposure and potential health risks.

Do microplastics mediate the effects of chemicals on aquatic organisms?

Microplastics are ubiquitous in both marine and freshwater ecosystems, where they can act as a physical contaminant, as well as interact with chemicals present in the environment. It has been suggested that chemical contaminants can sorb to microplastics, such that microplastics act as a vector for chemicals into aquatic biota and enhance their negative effects. It has been repeatedly suggested that the main factors underpinning the binding of chemicals to microplastics are hydrophobic partitioning and the size of microplastic particles. Therefore, we used the hydrophobicity of chemicals, as log K_ow, as well as the size of microplastic particles to conduct a quantitative analysis of published results to evaluate the influence of microplastics on chemical toxicity. We collated data from 39 laboratory studies that assessed the effects of microplastics, chemicals and their combination on several ecotoxicological responses of freshwater and marine organisms. Each chemical was assigned the relevant octanol / water partition coefficient (log K_OW) as a measure of its hydrophobicity, and the mean size of microplastics particles used in each study was recorded. We found no effect of log K_OW or the size of microplastic particles on the interaction between microplastics and chemicals with regards to any of the relevant ecotoxicological responses (behaviour, growth, survival and cellular) considered in this study. These findings are significant in showing that the effect of microplastics on the toxicity of chemicals is more complex than just considering hydrophobicity of chemicals and size of microplastics. We call for more mechanistic experiments to motivate a robust risk assessment and mitigation of microplastic toxicity in the environment.

Accumulation of chemical elements and occurrence of microplastics in small pelagic fish from a neritic environment

The assessment of contaminant exposure in marine organisms often focuses on the most toxic chemical elements from upper trophic level species. Information on mid-trophic level species and particularly on potentially less harmful elements is lacking. Additionally, microplastics have been considered emergent contaminants in aquatic environments which have not been extensively studied in species from mid-trophic levels in food chains. This study aims to contribute to an overall assessment of environmental impacts of such chemicals in a community of small pelagic fish in the North Atlantic. The concentrations of 16 chemical elements, rarely simultaneously quantified (including minerals, trace elements and heavy metals), and the presence of microplastics were analysed in sardines (Sardina pilchardus) and mackerels (Scomber spp. and Trachurus trachurus) sampled along the Portuguese coast. Biochemical stress assessments and stable isotope analyses were also performed. The chemical element concentrations in S. pilchardus, T. trachurus, and Scomber spp. were relatively low and lower than the levels reported for the same species in the North Atlantic and adjacent areas. No clear relationships were found between chemical elements and oxidative damage in fish. However, the concentration of several chemical elements showed differences among species, being related with the species' habitat use, trophic niches, and specific feeding strategies. The presence of plastic pieces in the stomachs of 29% of the sampled fishes is particularly concerning, as these small pelagic fish from mid-trophic levels compose a significant part of the diet of humans and other top predators. This study highlights the importance of multidisciplinary approaches focusing on the individual, including position data, stable isotopes, and oxidative stress biomarkers as complementary tools in contamination assessment of the marine mid-trophic levels in food chains.

What have we known so far about microplastics in drinking water treatment? A timely review

Microplastics (MPs) have been widely detected in drinking water sources and tap water, raising the concern of the effectiveness of drinking water treatment plants (DWTPs) in protecting the public from exposure to MPs through drinking water. We collected and analyzed the available research articles up to August 2021 on MPs in drinking water treatment (DWT), including laboratory- and full-scale studies. This article summarizes the major MP compositions (materials, sizes, shapes, and concentrations) in drinking water sources, and critically reviews the removal efficiency and impacts of MPs in various drinking water treatment processes. The discussed drinking water treatment processes include coagulation-flocculation (CF), membrane filtration, sand filtration, and granular activated carbon (GAC) filtration. Current DWT processes that are purposed for particle removal are generally effective in reducing MPs in water. Various influential factors to MP removal are discussed, such as coagulant type and dose, MP material, shape and size, and water quality. It is anticipated that better MP removal can be achieved by optimizing the treatment conditions. Moreover, the article framed the major challenges and future research directions on MPs and nanoplastics (NPs) in DWT.

Evaluation of different packaging methods and storage temperature on MPs abundance and fillet quality of rainbow trout

There are many studies on microplastics (MPs) about the aquatic ecosystems and its components. However, there is limited study on the MPs abundance, identification and sources in processed seafood products which are manufactured for direct human consumption. In this study, rainbow trout (Oncorhynchus mykiss) fillets were packed with different packaging techniques and stored at two different temperatures (+4 and -20°C) for 21 days. The presence, shape, size and polymer type of MPs were determined by ATR-FTIR on certain days (7, 14 and 21 days) in fillets during storage. The chemical quality changes in fillets [with pH, thiobarbituric acid reactive substrate (TBARS), and total volatile basic nitrogen (TVB-N) data] were monitored and the effect of MPs presence was evaluated. At the last step, the estimated MPs intake level in humans was determined with considering the presence of MPs (determined in fillets). The presence of MPs was determined the most in the Polystyrene plate + wrapped film (S) group and the least in the Chitosan film + Polystyrene plate + wrapped film (C) group. When evaluated in terms of chemical parameters, although good results were obtained in all samples stored at - 20°C, the presence of MPs was determined at a high level in fillets which stored at this temperature. As a result of the study, it was determined that the packaging type and storage temperature have significant effects on the presence of MPs and fillet quality.

Evidence from in vitro and in vivo studies on the potential health repercussions of micro- and nanoplastics

Plastic is a synthetic or semisynthetic polymer with numerous physicochemical properties, and its fragmentation can give rise to microplastics (MPs) and nanoplastics (NPs). These particles can enter our ecosystem, where a process of constant degradation facilitates their dispersion and absorption by different species, affecting multiple organs and systems. The objective of this review was to provide an update on the potential health effects of MPs and NPs indicated by in vitro and in vivo studies. In vitro studies have described the absorption of plastic particles of different sizes and have documented their proinflammatory effects and genotoxicity, which can lead to the structural alteration of cells. MPs and NPs have also been implicated in the development of antibiotic resistance. In vivo studies have demonstrated that MPs and NPs can access organisms via dietary and respiratory pathways and through the epidermis. Their reported effects include: changes in microbiota and digestive enzyme production; inflammatory processes at respiratory level; circulatory and reproductive system disorders; and neurotoxicity, inducing behavioral changes. In vitro and in vivo studies have evidenced detrimental effects in different organs and systems as a function of the dose, size, and chemical properties of plastic particles. Further research is warranted to determine the effects on human health of these particles at environmental doses.

Micro/nanoplastics effects on organisms: A review focusing on 'dose'

Microplastics have become predominant contaminants, attracting much political and scientific attention. Despite the massively-increasing research on microplastics effects on organisms, the debate of whether environmental concentrations pose hazard and risk continues. This study critically reviews published literatures of microplastics effects on organisms within the context of "dose". It provides substantial evidence of the common occurrence of threshold and hormesis dose responses of numerous aquatic and terrestrial organisms to microplastics. This finding along with accumulated evidence indicating the capacity of organisms for recovery suggests that the linear-no-threshold model is biologically irrelevant and should not serve as a default model for assessing the microplastics risks. The published literature does not provide sufficient evidence supporting the general conclusion that environmental doses of microplastics cause adverse effects on individual organisms. Instead, doses that are smaller than the dose of toxicological threshold and more likely to occur in the environment may even induce positive effects, although the ecological implications of these responses remain unknown. This study also shows that low doses of microplastics can reduce whereas high doses can increase the negative effects of other pollutants. The mechanisms explaining these findings are discussed, providing a novel perspective for evaluating the risks of microplastics in the environment.

Resolving the effects of environmental micro- and nanoplastics exposure in biota: A knowledge gap analysis

The pervasive spread of microplastics (MPs) and nanoplastics (NPs) has raised significant concerns on their toxicity in both aquatic and terrestrial environments. These polymer-based materials have implications for plants, wildlife and human health, threatening food chain integrity and ultimate ecosystem resilience. An extensive - and growing - body of literature is available on MP- and NP-associated effects, including in a number of aquatic biota, with as yet limited reports in terrestrial environments. Effects range from no detectable, or very low level, biological effects to more severe outcomes such as (but not limited to) increased mortality rates, altered immune and inflammatory responses, oxidative stress, genetic damage and dysmetabolic changes. A well-established exposure route to MPs and NPs involves ingestion with subsequent incorporation into tissues. MP and NP exposures have also been found to lead to genetic damage, including effects related to mitotic anomalies, or to transmissible damage from sperm cells to their offspring, especially in echinoderms. Effects on the proteome, transcriptome and metabolome warrant ad hoc investigations as these integrated "omics" workflows could provide greater insight into molecular pathways of effect. Given their different physical structures, chemical identity and presumably different modes of action, exposure to different types of MPs and NPs may result in different biological effects in biota, thus comparative investigations of different MPs and NPs are required to ascertain the respective effects. Furthermore, research on MP and NP should also consider their ability to act as vectors for other toxicants, and possible outcomes of exposure may even include effects at the community level, thus requiring investigations in mesocosm models.

Microplastic ingestion in reared aquaculture fish: Biological responses to low-density polyethylene controlled diets in Sparus aurata

During the last years, ingestion of microplastics (MPs) has been quantified in marine species both with an ecological and commercial interest at sea and under experimental conditions, highlighting the importance to assess MP ingestion in commercially and aquaculture important species such as gilthead seabream (Sparus aurata) fish. In order to study the ingestion of MPs in a commercially valuable species, gilthead seabreams were exposed to an enriched diet with virgin and weathered low-density polyethylene (LDPE) pellets for three months followed by a detoxification period of one month of no exposure to MP enriched diets. Our results indicate that MP ingestion in these fishes increased with exposure time, and differences were found between treatments, showing the highest ingestion values after three months of exposure to MP enriched diets and in the weathered treatment. However, after one month of detoxification, no MPs were found in the gastrointestinal tracts of fish, reflecting no long-term retention of MPs in Sparus aurata digestive system. According to results from this study, exposure of fish to MP enriched diets does not affect fish size neither the Fulton's condition index as both parameters increased with time in all treatments (control, virgin and weathered). Both carbon and nitrogen isotopic signatures decreased with fish size in all treatments which could be related to an increase of nitrogen deposition efficiency in fish muscle with a high protein assimilation during the first months of Sparus aurata.

Micro and Nano Plastics Distribution in Fish as Model Organisms: Histopathology, Blood Response and Bioaccumulation in Different Organs

Micro- and nano-plastic (MP/NP) pollution represents a threat not only to marine organisms and ecosystems, but also a danger for humans. The effects of these small particles resulting from the fragmentation of waste of various types have been well documented in mammals, although the consequences of acute and chronic exposure are not fully known yet. In this review, we summarize the recent results related to effects of MPs/NPs in different species of fish, both saltwater and freshwater, including zebrafish, used as model organisms for the evaluation of human health risk posed by MNPs. The expectation is that discoveries made in the model will provide insight regarding the risks of plastic particle toxicity to human health, with a focus on the effect of long-term exposure at different levels of biological complexity in various tissues and organs, including the brain. The current scientific evidence shows that plastic particle toxicity depends not only on factors such as particle size, concentration, exposure time, shape, and polymer type, but also on co-factors, which make the issue extremely complex. We describe and discuss the possible entry pathways of these particles into the fish body, as well as their uptake mechanisms and bioaccumulation in different organs and the role of blood response (hematochemical and hematological parameters) as biomarkers of micro- and nano-plastic water pollution.

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.

Microplastics and associated contaminants in the aquatic environment: A review on their ecotoxicological effects, trophic transfer, and potential impacts to human health

The microplastic pollution and related ecological impacts in the aquatic environment have attracted global attention over the past decade. Microplastics can be ingested by aquatic organisms from different trophic levels either directly or indirectly, and transferred along aquatic food chains, causing different impacts on life activities of aquatic organisms. In addition, microplastics can adsorb various environmental chemical contaminants and release toxic plastic additives, thereby serving as a sink and source of these associated chemical contaminants and potentially changing their toxicity, bioavailability, and fate. However, knowledge regarding the potential risks of microplastics and associated chemical contaminants (e.g., hydrophobic organic contaminants, heavy metals, plastic additives) on diverse organisms, especially top predators, remains to be explored. Herein, this review describes the effects of microplastics on typical aquatic organisms from different trophic levels, and systematically summarizes the combined effects of microplastics and associated contaminants on aquatic biota. Furthermore, we highlight the research progress on trophic transfer of microplastics and associated contaminants along aquatic food chain. Finally, potential human health concerns about microplastics via the food chain and dietary exposure are discussed. This work is expected to provide a meaningful perspective for better understanding the potential impacts of microplastics and associated contaminants on aquatic ecology and human health.

Interactive effects of micro/nanoplastics and nanomaterials/pharmaceuticals: Their ecotoxicological consequences in the aquatic systems

Micro/nanoplastics are ubiquitous in the environment and cause pollution of the aquatic ecosystem, in particular, which is a serious concern worldwide. Micro/nanoplastics can act as a vector for multiple co-contaminants that co-exist in the aquatic environment. Apart from micro/nanoplastics, nanomaterials and pharmaceuticals are other emerging contaminants that can also raise severe problems. Thus, in this review, the physicochemical interactions occurring between micro/nanoplastics and nanomaterials and pharmaceuticals and the factors (chemical and environmental) affecting the sorption efficiency of nanomaterials and pharmaceuticals have been addressed. Furthermore, the influence of micro/nanoplastics on the bioavailability and toxic effects of nanomaterials and pharmaceuticals on both freshwater and marine species has been highlighted. Additional focus has also been given to study the mechanism of toxicity of the micro/nanoplastics-nanomaterials and pharmaceuticals complex on the different species of different trophic levels. Finally, this review addresses the knowledge gaps and provides insights into the future research strategies to better understand the interactive mechanisms between the binary contaminants and also the toxicity mechanisms of micro/nanoplastics and nanomaterials and pharmaceuticals.

The need to investigate continuums of plastic particle diversity, brackish environments and trophic transfer to assess the risk of micro and nanoplastics on aquatic organisms

Plastic particles are ubiquitous in marine and freshwater environments. While many studies have focused on the toxicity of microplastics (MPs) and nanoplastics (NPs) in aquatic environments there is no clear conclusion on their environmental risk, which can be attributed to a lack of standardization of protocols for in situ sampling, laboratory experiments and analyzes. There are also far more studies concerning marine environments than fresh or brackish waters despite their role in the transfer of plastics from continents to oceansWe systematically reviewed the literature for studies: (1) using plastics representative of those found in the environment in laboratory experiments, (2) on the contamination of plastic particles in the continuum between fresh and marine waters, focusing in particular on estuaries and (3) on the continuum of contamination of plastic particles between species through trophic transfer in aquatic environments. We found that the exposure of aquatic organisms in the laboratory to plastic particles collected in the environment are very scarce. Moreover, plastic exposures of estuarine species in the laboratory are generally carried out for a single salinity and a single temperature that do not reflect the fluctuating environmental conditions of estuaries. Finally, the trophic transfer of plastic particles is mainly studied in the laboratory through simple food chains which are not representative of the complexity of the trophic networks observed in the aquatic environment. We pointed out that future studies in the laboratory should include both MPs and NPs sampled in the environment and focus on the precise characterization of the composition and surface of these plastics as well as on their absorbed pollutants, additives or biofilms. Moreover, investigations must be continued concerning the toxicity of plastic particles in brackish water environments such as estuaries and the trophic transfer of plastic particles in complex food chains.

Characterization and spatial distribution of microplastics in two wild captured economic freshwater fish from north and west rivers of Guangdong province

As a new type of pollutant, microplastics are of emerging widespread concern, while amount of research done in freshwater environments and organisms is litter compared to that in marine. Following this reality, the categories of MPs in two economic freshwater fish at 25 sites from 11 cities in the north and west rivers of Guangdong province were documented. Here, 76 individuals belong Oreochromis niloticus and Cirrhinus molitorella were investigated and microplastics were found in the GITs of 43.4% and gills of 25%. The average abundances of microplastics have significant difference between Oreochromis niloticus (0.015 items/ g) and Cirrhinus molitorella (0.031 items/g), while no difference by individual (~1.9 items). The plastics were dominated by white in color (61%), fragment in shape (67%), and lass than 1 mm in size (74%). The spatial distribution of microplastics revealed that there are significant differences between different cities in average abundances, and the highest average abundances of MPs were found in Zhanjiang city (4.25 items/individual) and Guangzhou city (0.044 items/g), respectively. Our results fully proved that the microplastics was widely ingested by wild fish species and suggested that the abundance and distribution of microplastics are positively related with the development of economy, tourism, industry, agriculture, and fishery.

Global trends and prospects in microplastics research: A bibliometric analysis

Microplastic pollution is a global enviromental issues. This is the first time in recent decades that quantitative and qualitative evidence from bibliometrics and Altmetric has been used to conduct an in-depth statistical analysis of global microplastics research knowledge and demonstrate research progress, trends and hotspots. We comprehensively searched the Web of Science Core Collection scientific database from its inception (1986) to September 21, 2019. The study shown that the number of papers on microplastics has increased significantly since 2011. Worldwide, researchers in the field come mostly from Western Europe, mainly spread in the UK, Netherlands and Belgium. With the exception of China, the contribution of developing countries was very limited. Moreover, this study systematically elaborated the hotspots in this field (especially in ecological toxicity and human health risks). The results shown that research on marine systems and marine plankton is still dominant. Since human beings are the ultimate consumers of the food chain, microplastics may have potential effects on the human respiratory system and gastrointestinal tract. Towards that end, some topics and perspectives are noted that could indicate the current scientific hotspots and guide future research directions.

Microplastics as a Vector for HOC Bioaccumulation in Earthworm Eisenia fetida in Soil: Importance of Chemical Diffusion and Particle Size

The role of microplastics as a carrier in the bioaccumulation of hydrophobic organic contaminants (HOCs) in soil organisms is poorly understood. Two environmentally relevant scenarios, including earthworm Eisenia fetida exposed to contaminated soil amended with clean microplastics (S1) and clean soil introduced with precontaminated microplastics (S2), were simulated to estimate the importance of microplastics in bioaccumulation. Three polychlorinated biphenyls and polyethylene particles with different sizes were employed. The microplastics under the S1 scenario significantly decreased the polychlorinated biphenyl congener (PCB) bioaccumulation, whereas for the S2 scenario, the PCBs on the microplastics can be assimilated by earthworms. Compared to plastic-free treatments, the freely dissolved concentrations (C_free) of PCBs were consistently lower in the soils amended with microplastics. Biodynamic model analysis suggested that the contribution of microplastic ingestion to bioaccumulation under the S2 scenario (mean 26.1%) was higher than that under S1 (8.7%), likely because of the slow chemical transfer between plastics and ambient media. These results indicated whether microplastics act as a source or a sink of HOCs depended strongly on the diffusion gradients between microplastics and soils. As ingestion of smallest particles (50-150 μm) showed the greatest contribution to bioaccumulation under S1 and S2 scenarios, the gradual breakdown of microplastics may increase their relative importance in contaminant transfer.

Toxicological effects of nano- and micro-polystyrene plastics on red tilapia: Are larger plastic particles more harmless?

Nanoplastics (NPs) and microplastics (MPs) are a heterogeneous class of pollutants with diverse sizes in aquatic environments. To evaluate the hazardous effects of N/MPs with different sizes, the accumulation, oxidative stress, cytochrome P450 (CYP) enzymes, neurotoxicity, and metabolomics changes were investigated in the red tilapia exposed to three sizes of polystyrene (PS) N/MPs (0.3, 5, and 70 - 90 μm). After 14-d exposures, the largest particles (70 - 90 μm) showed the highest accumulation levels in most cases. Exposures to PS-MPs (5 and 70 - 90 μm) caused a more severe oxidative stress in red tilapia than PS-NPs. The activity of CYP3A-related enzyme was obviously inhibited by PS-NPs, whereas the CYP enzymes in the liver may not be sensitive to MP exposures. In the brain, only 5 μm PS-MPs significantly inhibited the acetylcholinesterase activity. After exposures, the treatments with 0.3, 5, and 70 - 90 μm N/MPs resulted in 31, 40, and 23 significantly differentially expressed metabolites, respectively, in which the pathway of tyrosine metabolism was significantly affected by all the three PS-N/MP exposures. Overall, the PS particles within the μm size posed more severe stress to red tilapia. Our results suggest that the toxicity of N/MPs may not show a simply monotonic negative correlation with their sizes.

Assessing microplastic uptake and impact on omnivorous juvenile white seabream Diplodus sargus (Linnaeus, 1758) under laboratory conditions

Previous laboratory feeding experiments, representing the state-of-the-art methodology to investigate microplastic (MP) ingestion and its impact for fish, tend to disregard both the significance of applying realistic MP densities and the potential relevance of biofilm-coating for ingestion probability. This experiment assessed the uptake of either pristine or biofilm-coated MP particles and the physiological impacts for juvenile white seabream for MP concentrations consistent with those found in the field along with natural prey over a course of 3.5 weeks. Results indicate the ability of juvenile D. sargus to discriminate between edible and non-edible prey. A distinct preference for biofilm-coated over pristine particles could not be verified. No significant impact on growth and condition was found except for high levels of MP ingestion. The outcomes highlight the importance of performing MP feeding experiments mimicking natural conditions to reliably assess the impact of MP on early life stages of fish.

Microplastics in subsurface coastal waters along the southern coast of Viti Levu in Fiji, South Pacific

Microplastics (MPs) remain largely understudied in Small Island Developing States. This study is aimed at comparing the abundance and characteristics of MPs in rural and urban marine coastal sites located along the southern coast of Fiji's main inhabited island, Viti Levu. Collection of subsurface waters (at depth of ca. 0.6 m) was performed at seven sites via Niskin bottle. Samples were filtered over a membrane filter to extract MPs and to allow visual analysis and polymer identification by using attenuated total reflectance in Fourier transform infrared spectroscopy. Findings from this study depict widespread presence of MPs in both urban and rural sites, and show no significant differences in the four parameters studied, i.e. abundance of MP pieces (2.0 vs 1.6 MP/L, respectively), form types (dominance of fibers), size (0.5-0.9 and 1.0-1.4 mm totaling 48% of the samples), and color (blue contributing 30%, and red and black contributing 25% each). These findings challenge the common expectation of a higher MPs pollution in urban areas compared to rural areas.

Single-Cell RNA Sequencing Reveals Size-Dependent Effects of Polystyrene Microplastics on Immune and Secretory Cell Populations from Zebrafish Intestines

Microplastics (MPs) as widespread contamination pose a high risk for aquatic organisms. However, the current understanding of MP toxicity is based on cell population-averaged measurements. Our aim was to gain a comprehensive understanding of the size-dependent effects of polystyrene MPs (PS-MPs) on intestinal cell populations in zebrafish and characterize the interplay of MPs, intestinal cells, and intestinal microbiota. Here, we used single-cell RNA sequencing to determine the transcriptome heterogeneity of 12 000 intestinal cells obtained from zebrafish exposed to 100 nm, 5 μm, and 200 μm PS-MPs for 21 days. Eight intestinal cell populations were identified. Combined with changes in intestinal microbiota, our findings highlight a previously unrecognized end point that all three sizes of PS-MPs induced dysfunction of intestinal immune cells (including effects on phagosomes and the regulation of immune system processes) and increased the abundance of pathogenic bacteria. However, only 100 nm PS-MPs altered the expression of genes related to phagocyte-produced reactive oxygen species (ROS) generation and increased mucus secretion by secretory cells. Microsize PS-MPs specifically changed the lysosome (5 μm) and cell surface receptor signaling (200 μm) processes of the macrophages. Our findings pinpoint to cell-specific and size-dependent responses to PS-MPs in fish intestine, which can provide a reference for future study directions.

Microplastics and seafood: lower trophic organisms at highest risk of contamination

Microplastic debris is a prevalent global pollutant that poses a risk to marine organisms and ecological processes. It is also suspected to pose a risk to marine food security; however, these risks are currently poorly understood. In this review, we seek to understand the current knowledge pertaining to the contamination of commercially important fished and farmed marine organisms with microplastics, with the aim of answering the question "Does microplastic pollution pose a risk to marine food security?". A semi-systematic review of studies investigating the number of microplastics found in commercially important organisms of different trophic levels suggests that microplastics do not biomagnify, and that organisms at lower trophic levels are more likely to contaminated by microplastic pollution than apex predators. We address the factors that influence microplastic consumption and retention by organisms. This research has implications for food safety and highlights the risks of microplastics to fisheries and aquaculture, and identifies current knowledge gaps within this research field.

Toxicity of Microplastics and Nanoplastics in Mammalian Systems

Fragmented or otherwise miniaturized plastic materials in the form of micro- or nanoplastics have been of nagging environmental concern. Perturbation of organismal physiology and behavior by micro- and nanoplastics have been widely documented for marine invertebrates. Some of these effects are also manifested by larger marine vertebrates such as fishes. More recently, possible effects of micro- and nanoplastics on mammalian gut microbiota as well as host cellular and metabolic toxicity have been reported in mouse models. Human exposure to micro- and nanoplastics occurs largely through ingestion, as these are found in food or derived from food packaging, but also in a less well-defined manner though inhalation. The pathophysiological consequences of acute and chronic micro- and nanoplastics exposure in the mammalian system, particularly humans, are yet unclear. In this review, we focus on the recent findings related to the potential toxicity and detrimental effects of micro- and nanoplastics as demonstrated in mouse models as well as human cell lines. The prevailing data suggest that micro- and nanoplastics accumulation in mammalian and human tissues would likely have negative, yet unclear long-term consequences. There is a need for cellular and systemic toxicity due to micro- and nanoplastics to be better illuminated, and the underlying mechanisms defined by further work.

Microplastic (1 and 5 μm) exposure disturbs lifespan and intestine function in the nematode Caenorhabditis elegans

As an emerging environmental pollutant, microplastics (MPs) are increasingly viewed as a serious health concern to terrestrial and aquatic ecosystems. However, previous toxicological studies examining MPs on freshwater and terrestrial organisms provide contradictory results, possibly due to few investigations at environmentally relevant concentrations. Here, the nematode Caenorhabditis elegans (C. elegans), a model organisms with both aquatic and terrestrial free-living forms, was employed to investigate the effects of 1 and 5 μm MPs (10⁷-10¹⁰ particles/m²) on the intake, lifespan, defecation rhythm, defecation-related neurons and transcriptional expression of related genes (skn-1, mkk-4, pmk-1, cpr-1 and itr-1). We demonstrated that the percentage of MP-contaminated nematodes increased with increasing exposure concentrations and duration. The lifespan of nematodes in the lower concentration exposure groups (2.4 × 10⁷ and 2.4 × 10⁸ particles/m²) decreased more prominently than that of higher concentration groups (2.4 × 10⁹ and 2.4 × 10¹⁰ particles/m²) after a 72-h exposure period. Concomitantly, expression of the skn-1 gene, involved in detoxification and lifespan regulation, was significantly altered at lower MP concentrations. Physiologically, the defecation rhythm after a 72-h exposure period was most strongly affected by 1 μm MPs at 2.4 × 10⁸ particles/m². The significant up-regulation of related genes by 1 μm MPs appears responsible for the shortened defecation interval. Results of this study identified a potential toxicity threat to C. elegans from exposure to MPs at environmentally relevant concentrations and provide novel evidence for MP risks to freshwater and terrestrial organisms. Capsule. After exposure to 1 and 5 μm MPs (10⁷-10¹⁰ particles/m²), the lifespan of C. elegans decreased more rapidly at lower concentrations.

Effect of nanoplastics on fish health and performance: A review

Small plastic particles are considered emerging pollutants, and this has motivated a considerable number of studies to establish their environmental consequences. At present, the study of the effects of nanoplastics (NPs) on aquatic organisms is still scarce, especially in organisms from higher trophic levels such as fish. This review describes the effects reported in different fish species after exposure to plastic particles smaller than 100 nm. Studies show that NPs can adversely affect fish at different stages of development, with reported accumulation in tissues, decreased locomotor and foraging activities, effects on growth and the immune system and alterations on lipid metabolism and neurotoxicity. However, mortality, effects on hatching success or malformations related to NPs have not been reported to this date.

Accumulation of polybrominated diphenyl ethers and microbiome response in the great pond snail Lymnaea stagnalis with exposure to nylon (polyamide) microplastics

Microplastics attract widespread attention, including for their potential to transport toxic chemicals in the form of plasticisers and associated hydrophobic organic chemicals, such as polybrominated diphenyl ethers (PBDEs). The aims of this study were to investigate how nylon (polyamide) microplastics may affect PBDE accumulation in snails, and the acute effects of nylon particles and PBDEs on survival, weight change and inherent microbiome diversity and community composition of the pond snail Lymnaea stagnalis. Snails were exposed for 96 h to BDEs-47, 99, 100 and 153 in the presence and absence of 1% w/w nylon microplastics in quartz sand sediment. No mortality was observed over the exposure period. Snails not exposed to microplastics lost significantly more weight compared to those exposed to microplastics. Increasing PBDE concentration in the sediment resulted in an increased PBDE body burden in the snails, however microplastics did not significantly influence total PBDE uptake. Based on individual congeners, uptake of BDE 47 by snails was significantly reduced in the presence of microplastics. The diversity and composition of the snail microbiome was not significantly altered by the presence of PBDEs nor by the microplastics, singly or combined. Significant effects on a few individual operational taxonomic units (OTUs) occurred when comparing the highest PBDE concentration with the control treatment, but in the absence of microplastics only. Overall within these acute experiments, only subtle effects on weight loss and slight microbiome alterations occurred. These results therefore highlight that L. stagnalis are resilient to acute exposures to microplastics and PBDEs, and that microplastics are unlikely to influence HOC accumulation or the microbiome of this species over short timescales.