Low level of polystyrene microplastics decreases early developmental toxicity of phenanthrene on marine medaka (Oryzias melastigma)

Micro/nano-plastics impacts in cardiovascular systems across species

The widespread presence of microplastics and nanoplastics (MPs/NPs) in the environment has become a critical public health issue due to their potential to infiltrate and affect various biological systems. Our review is crucial as it consolidates current data and provides a comprehensive analysis of the cardiovascular impacts of MPs/NPs across species, highlighting significant implications for human health. By synthesizing findings from studies on aquatic and terrestrial organisms, including humans, this review offers insights into the ubiquity of MPs/NPs and their pathophysiological roles in cardiovascular systems. We demonstrated that exposure to MPs/NPs is linked to various cardiovascular ailments such as thrombogenesis, vascular damage, and cardiac impairments in model organisms, which likely extrapolate to humans. Our review critically evaluated methods for detecting MPs/NPs in biological tissues, assessing their toxicity, and understanding their behaviour within the vasculature. These findings emphasise the urgent need for targeted public health strategies and enhanced regulatory measures to mitigate the impacts of MP/NP pollution. Furthermore, the review underlined the necessity of advancing research methodologies to explore long-term effects and potential intergenerational consequences of MP/NP exposure. By mapping out the intricate links between environmental exposure and cardiovascular risks, our work served as a pivotal reference for future research and policymaking aimed at curbing the burgeoning threat of plastic pollution.

Decoding the molecular concerto: Toxicotranscriptomic evaluation of microplastic and nanoplastic impacts on aquatic organisms

The pervasive and steadily increasing presence of microplastics/nanoplastics (MPs/NPs) in aquatic environments has raised significant concerns regarding their potential adverse effects on aquatic organisms and their integration into trophic dynamics. This emerging issue has garnered the attention of (eco)toxicologists, promoting the utilization of toxicotranscriptomics to unravel the responses of aquatic organisms not only to MPs/NPs but also to a wide spectrum of environmental pollutants. This review aims to systematically explore the broad repertoire of predicted molecular responses by aquatic organisms, providing valuable intuitions into complex interactions between plastic pollutants and aquatic biota. By synthesizing the latest literature, present analysis sheds light on transcriptomic signatures like gene expression, interconnected pathways and overall molecular mechanisms influenced by various plasticizers. Harmful effects of these contaminants on key genes/protein transcripts associated with crucial pathways lead to abnormal immune response, metabolic response, neural response, apoptosis and DNA damage, growth, development, reproductive abnormalities, detoxification, and oxidative stress in aquatic organisms. However, unique challenge lies in enhancing the fingerprint of MPs/NPs, presenting complicated enigma that requires decoding their specific impact at molecular levels. The exploration endeavors, not only to consolidate existing knowledge, but also to identify critical gaps in understanding, push forward the frontiers of knowledge about transcriptomic signatures of plastic contaminants. Moreover, this appraisal emphasizes the imperative to monitor and mitigate the contamination of commercially important aquatic species by MPs/NPs, highlighting the pivotal role that regulatory frameworks must play in protecting all aquatic ecosystems. This commitment aligns with the broader goal of ensuring the sustainability of aquatic resources and the resilience of ecosystems facing the growing threat of plastic pollutants.

Gender-specific effects of polystyrene nanoplastic exposure on triclosan-induced reproductive toxicity in zebrafish (Danio rerio)

Nanoplastics (NPs) and triclosan (TCS) are ubiquitous emerging environmental contaminants detected in human samples. While the reproductive toxicity of TCS alone has been studied, its combined effects with NPs remain unclear. Herein, we employed Fourier transform infrared spectroscopy and dynamic light scattering to characterize the coexposure of polystyrene nanoplastics (PS-NPs, 50 nm) with TCS. Then, adult zebrafish were exposed to TCS at environmentally relevant concentrations (0.361-48.2 μg/L), with or without PS-NPs (1.0 mg/L) for 21 days. TCS biodistribution in zebrafish tissues was investigated using ultra-performance liquid chromatography coupled with triple quadrupole mass spectrometry. Reproductive toxicity was assessed through gonadal histopathology, fertility tests, changes in steroid hormone synthesis and gene expression within the hypothalamus-pituitary-gonad-liver (HPGL) axis. Transcriptomics and proteomics were applied to explore the underlying mechanisms. The results showed that PS-NPs could adsorb TCS, thus altering the PS-NPs' physical characteristics. Our observations revealed that coexposure with PS-NPs reduced TCS levels in the ovaries, livers, and brains of female zebrafish. Conversely, in males, coexposure with PS-NPs increased TCS levels in the testes and livers, while decreasing them in the brain. We found that co-exposure mitigated TCS-induced ovary development inhibition while exacerbated TCS-induced spermatogenesis suppression, resulting in increased embryonic mortality and larval malformations. This co-exposure influenced the expression of genes linked to steroid hormone synthesis (cyp11a1, hsd17β, cyp19a1) and attenuated the TCS-decreased estradiol (E2) in females. Conversely, testosterone levels were suppressed, and E2 levels were elevated due to the upregulation of specific genes (cyp11a1, hsd3β, cyp19a1) in males. Finally, the integrated analysis of transcriptomics and proteomics suggested that the aqp12-dctn2 pathway was involved in PS-NPs' attenuation of TCS-induced reproductive toxicity in females, while the pck2-katnal1 pathway played a role in PS-NPs' exacerbation of TCS-induced reproductive toxicity in males. Collectively, PS-NPs altered TCS-induced reproductive toxicity by disrupting the HPGL axis, with gender-specific effects.

Chronic exposure to environmental concentrations of benzo[a]pyrene causes multifaceted toxic effects of developmental compromise, redox imbalance, and modulated transcriptional profiles in the early life stages of marine medaka (Oryzias melastigma)

Polycyclic aromatic hydrocarbons (PAHs) accumulate and integrate into aquatic environments, raising concerns about the well-being and safety of aquatic ecosystems. Benzo[a]pyrene (BaP), a persistent PAH commonly detected in the environment, has been extensively studied. However, the broader multifaceted toxicity potential of BaP on the early life stages of marine fish during chronic exposure to environmentally relevant concentrations needs further exploration. To fill these knowledge gaps, this study assessed the in vivo biotoxicity of BaP (1, 4, and 8 μg/L) in marine medaka (Oryzias melastigma) during early development over a 30-day exposure period. The investigation included morphological, biochemical, and molecular-level analyses to capture the broader potential of BaP toxicity. Morphological analyses showed that exposure to BaP resulted in skeletal curvatures, heart anomalies, growth retardation, elevated mortality, delayed and reduced hatching rates. Biochemical analyses revealed that BaP exposure not only created oxidative stress but also disrupted the activities of antioxidant enzymes. This disturbance in redox balance was further explored by molecular level investigation. The transcriptional profiles revealed impaired oxidative phosphorylation (OXPHOS) and tricarboxylic acid (TCA) cycle pathways, which potentially inhibited the oxidative respiratory chain in fish following exposure to BaP, and reduced the production of adenosine triphosphate (ATP) and succinate dehydrogenase (SDH). Furthermore, this investigation indicated a potential connection to apoptosis, as demonstrated by fluorescence microscopy and histological analyses, and supported by an increase in the expression levels of related genes via real-time quantitative PCR. This study enhances our understanding of the molecular-level impacts of BaP's multifaceted toxicity in the early life stages of marine medaka, and the associated risks.

Comparative effects of different metals on the Japanese medaka embryos and larvae

Rapid evaluation of the toxicity of metals using fish embryo acute toxicity is facilitative to ecological risk assessment of aquatic organisms. However, this approach has seldom been utilized for the comparative study on the effects of different metals to fish. In this study, acute and sub-chronic tests were used to compare the toxicity of Se(IV) and Cd in the embryos and larvae of Japanese medaka (Oryzias latipes). The embryos with different levels of dechorionation and/or pre-exposure were also exposed to Se(IV) and Cd at various concentrations. The results showed that the LC50-144 h of Cd was 1.3-5.2 folds higher than that of Se(IV) for the embryos. In contrast, LC50-96 h of Se(IV) were 200-400 folds higher than that of Cd for the larvae. Meanwhile, dechorionated embryos were more sensitive to both Se and Cd than the intact embryos. At elevated concentrations, both Se and Cd caused mortality and deformity in the embryos and larvae. In addition, pre-exposure to Cd at the embryonic stages enhanced the resistance to Cd in the larvae. However, pre-exposure to Se(IV) at the embryonic stages did not affect the toxicity of Se(IV) to the larvae. This study has distinguished the nuance differences in effects between Se(IV) and Cd after acute and sub-chronic exposures with/without chorion. The approach might have a potential in the comparative toxicology of metals (or other pollutants) and in the assessment of their risks to aquatic ecosystems.

Neurobehavioral toxicity induced by combined exposure of micro/nanoplastics and triphenyltin in marine medaka (Oryzias melastigma)

Microplastics/nanoplastics (MNPs) inevitably coexist with other pollutants in the natural environment, making it crucial to study the interactions between MNPs and other pollutants as well as their combined toxic effects. In this study, we investigated neurotoxicity in marine medaka (Oryzias melastigma) exposed to polystyrene micro/nanoplastics (PS-MNPs), triphenyltin (TPT), and PS-MNPs + TPT from physiological, behavioral, biochemical, and genetic perspectives. The results showed that marine medaka exposed to 200 ng/L TPT or 200 μg/L PS-NPs alone exhibited some degree of neurodevelopmental deficit, albeit with no significant behavioral abnormalities observed. However, in the PS-MP single exposure group, the average acceleration of short-term behavioral indices was significantly increased by 78.81%, indicating a highly stress-responsive locomotor pattern exhibited by marine medaka. After exposure to PS-MNPs + TPT, the swimming ability of marine medaka significantly decreased. In addition, PS-MNPs + TPT exposure disrupted normal neural excitability as well as activated detoxification processes in marine medaka larvae. Notably, changes in neural-related genes suggested that combined exposure to PS-MNPs and TPT significantly increased the neurotoxic effects observed with exposure to PS-MNPs or TPT alone. Furthermore, compared to the PS-MPs + TPT group, PS-NPs + TPT significantly inhibited swimming behavior and thus exacerbated the neurotoxicity. Interestingly, the neurotoxicity of PS-MPs was more pronounced than that of PS-NPs in the exposure group alone. However, the addition of TPT significantly enhanced the neurotoxicity of PS-NPs compared to PS-MPs + TPT. Overall, the study underscores the combined neurotoxic effects of MNPs and TPT, providing in-depth insights into the ecotoxicological implications of MNPs coexisting with pollutants and furnishing comprehensive data.

Microplastics weaken the digestion and absorption functions in the golden pompano (Trachinotus blochii) by affecting the intestinal structure, bacteria and metabolites

Microplastics are difficult to degrade and widespread environmental pollutants. Coastal areas are hardest hit of microplastic pollution as they receive significant amounts of microplastics discharged from inland sources. Golden pompano (Trachinotus blochii) is a high commercial valuable marine aquaculture fish species, most of the golden pompano are raised in coastal areas, which means they are at significant risk of exposure to microplastics. Therefore, we exposed golden pompano to 10 μg/L, 100 μg/L and 1000 μg/L of 5 μm spherical polystyrene microplastics and conducted a 14-day stress experiment. Histopathology results showed the intestinal villi shrank. The 16s sequencing analysis revealed that microplastics significantly impacted the abundance and community structure of intestinal microorganisms, which may affect the metabolic function of the gastrointestinal tract. Metabolomics sequencing of the intestinal contents showed that microplastics caused disruptions in lipid, glucose, and amino acid metabolism, thus compromising the normal digestion and absorption functions in the intestinal system. In addition, the activation of various pathways, including the intestinal endocrine system, proline metabolism, and signal transduction, which can lead to the occurrence of several diseases. This study combined various methods to investigate the adverse effects of microplastics on intestinal digestion and absorption, and provided new insights into the toxic mechanisms of microplastics.

Combined exposure with microplastics increases the toxic effects of PFOS and its alternative F-53B in adult zebrafish

Microplastics (MPs) can adsorb and desorb organic pollutants, which may alter their biotoxicities. Although the toxicity of perfluorooctane sulfonate (PFOS) and its alternative 6:2 chlorinated polyfluorinated ether sulfonate (F-53B) to organisms has been reported, the comparative study of their combined toxic effects with MPs on aquatic organisms is limited. In this study, adult female zebrafish were exposed to 10 μg/L PFOS/F-53B and 50 μg/L MPs alone or in combination for 14 days to investigate their single and combined toxicities. The results showed that the presence of MPs reduced the concentration of freely dissolved PFOS and F-53B in the exposure solution but did not affect their bioaccumulation in the zebrafish liver and gut. The combined exposure to PFOS and MPs had the greatest impact on liver oxidative stress, immunoinflammatory, and energy metabolism disorders. 16S rRNA gene sequencing analysis revealed that the combined exposure to F-53B and MPs had the greatest impact on gut microbiota. Functional enrichment analysis predicted that the alternations in the gut microbiome could interfere with signaling pathways related to immune and energy metabolic processes. Moreover, significant correlations were observed between changes in gut microbiota and immune and energy metabolism indicators, highlighting the role of gut microbiota in host health. Together, our findings demonstrate that combined exposure to PFOS/F-53B and MPs exacerbates liver immunotoxicity and disturbances in energy metabolism in adult zebrafish compared to single exposure, potentially through dysregulation of gut microbiota.

Trophic transfer of micro- and nanoplastics and toxicity induced by long-term exposure of nanoplastics along the rotifer (Brachionus plicatilis)-marine medaka (Oryzias melastigma) food chain

Microplastics (MPs) and nanoplastics (NPs) are emerging pollutants in the ocean, but their transfer and toxicity along the food chains are unclear. In this study, a marine rotifer (Brachionus plicatilis)-marine medaka (Oryzias melastigma) food chain was constructed to evaluate the transfer of polystyrene MPs and NPs (70 nm, 500 nm, and 2 μm, 2000 μg/L) and toxicity of 70 nm PS-NPs (0, 20, 200, and 2000 μg/L) on marine medaka after long-term food chain exposure. The results showed that the amount of 70 nm NPs accumulated in marine medaka was 1.24 μg/mg, which was significantly higher than that of 500 nm NPs (0.87 μg/mg) and 2 μm MP (0.69 μg/mg). Long-term food chain exposure to NPs caused microflora dysbiosis, resulting in activation of toll-like receptor 4 (TLR4) pathway, which induced liver inflammation. Moreover, NPs food chain exposure increased liver and muscle tissue triglyceride and lactate content, but decreased the protein, sugar, and glycogen content. NPs food chain exposure impaired reproductive function and inhibited offspring early development, which might pose a threat to the sustainability of marine medaka population. Overall, the study revealed the transfer of MPs and NPs and the effects of NPs on marine medaka along the food chain.

Size-dependent vector effect of microplastics on the bioaccumulation of polychlorinated biphenyls in tilapia: A tissue-specific study

Microplastics play a significant role in interactions between organisms and hydrophobic organic contaminants (HOCs), leading to a joint toxic effect on aquatic organisms. This study extensively investigated the tissue-specific accumulation of polychlorinated biphenyls (PCBs) resulting from different sized microplastics in tilapia (Oreochromis mossambicus) using a passive dosing device. Based on biological feeding behavior considerations, 1 mm and 2 μm polystyrene (PS) microplastics with concentrations of 2 and 5 mg L-1 were investigated. A physiologically based toxicokinetic (PBTK) model was applied to evaluate the exchange kinetics and fluxes among the tissues. Moreover, an in vitro simulation experiment was conducted to theoretically validate the vector effect. The findings demonstrated that the effects caused by HOCs and microplastics on organisms were influenced by multiple factors such as size and surface properties. The mass transfer kinetics of HOCs in specific tissues were closely related to their adsorption capacity and position microplastics could reach. Specifically, although 2 μm microplastics exhibited high adsorption capacity for PCBs, they were only retained in the intestines and did not significantly contribute to the bioaccumulation of PCBs in gills or muscle. While 1 mm microplastics were ingested but just paused in the mouth and subsequently flew through the gills with oral mucus. Their vector effects increased the desorption of microplastic-bound PCB-118 in the gill mucus microcosm, thereby facilitating the mass transfer and accumulation of PCB-118 in gills and muscle. This study sheds new light on how the size-dependent vector generated by microplastics affects the tissue-specific accumulation of HOCs in aquatic organisms.

Insight into microplastics in the aquatic ecosystem: Properties, sources, threats and mitigation strategies

Globally recognized as emergent contaminants, microplastics (MPs) are prevalent in aquaculture habitats and subject to intense management. Aquaculture systems are at risk of microplastic contamination due to various channels, which worsens the worldwide microplastic pollution problem. Organic contaminants in the environment can be absorbed by and interact with microplastic, increasing their toxicity and making treatment more challenging. There are two primary sources of microplastics: (1) the direct release of primary microplastics and (2) the fragmentation of plastic materials resulting in secondary microplastics. Freshwater, atmospheric and marine environments are also responsible for the successful migration of microplastics. Until now, microplastic pollution and its effects on aquaculture habitats remain insufficient. This article aims to provide a comprehensive review of the impact of microplastics on aquatic ecosystems. It highlights the sources and distribution of microplastics, their physical and chemical properties, and the potential ecological consequences they pose to marine and freshwater environments. The paper also examines the current scientific knowledge on the mechanisms by which microplastics affect aquatic organisms and ecosystems. By synthesizing existing research, this review underscores the urgent need for effective mitigation strategies and further investigation to safeguard the health and sustainability of aquatic ecosystems.

Occurrence, transport, and toxicity of microplastics in tropical food chains: perspectives view and way forward

Microplastics, which have a diameter of less than 5 mm, are becoming an increasingly prevalent contaminant in terrestrial and aquatic ecosystems due to the dramatic increase in plastic production to 390.7 million tonnes in 2021. Among all the plastics produced since 1950, nearly 80% ended up in the environment or landfills and eventually reached the oceans. Currently, 82-358 trillion plastic particles, equivalent to 1.1-4.9 million tonnes by weight, are floating on the ocean's surface. The interactions between microorganisms and microplastics have led to the transportation of other associated pollutants to higher trophic levels of the food chain, where microplastics eventually reach plants, animals, and top predators. This review paper focuses on the interactions and origins of microplastics in diverse environmental compartments that involve terrestrial and aquatic food chains. The present review study also critically discusses the toxicity potential of microplastics in the food chain. This systematic review critically identified 206 publications from 2010 to 2022, specifically reported on microplastic transport and ecotoxicological impact in aquatic and terrestrial food chains. Based on the ScienceDirect database, the total number of studies with "microplastic" as the keyword in their title increased from 75 to 4813 between 2010 and 2022. Furthermore, various contaminants are discussed, including how microplastics act as a vector to reach organisms after ingestion. This review paper would provide useful perspectives in comprehending the possible effects of microplastics and associated contaminants from primary producers to the highest trophic level (i.e. human health).

Micro(nano)plastics in marine medaka: Entry pathways and cardiotoxicity with triphenyltin

The simultaneous presence of micro(nano)plastics (MNPs) and pollutants represents a prevalent environmental challenge that necessitates understanding their combined impact on toxicity. This study examined the distribution of 5 μm (PS-MP5) and 50 nm (PS-NP50) polystyrene plastic particles during the early developmental stages of marine medaka (Oryzias melastigma) and assessed their combined toxicity with triphenyltin (TPT). Results showed that 2 mg/L PS-MP5 and PS-NP50 could adhere to the embryo surface. PS-NP50 can passively enter the larvae and accumulate predominantly in the intestine and head, while PS-MP5 cannot. Nonetheless, both types can be actively ingested by the larvae and distributed in the intestine. 2 mg/L PS-MNPs enhance the acute toxicity of TPT. Interestingly, high concentrations of PS-NP50 (20 mg/L) diminish the acute toxicity of TPT due to their sedimentation properties and interactions with TPT. 200 μg/L PS-MNPs and 200 ng/L TPT affect complement and coagulation cascade pathways and cardiac development of medaka larvae. PS-MNPs exacerbate TPT-induced cardiotoxicity, with PS-NP50 exhibiting stronger effects than PS-MP5, which may be related to the higher adsorption capacity of NPs to TPT and their ability to enter the embryos before hatching. This study elucidates the distribution of MNPs during the early developmental stages of marine medaka and their effects on TPT toxicity, offering a theoretical foundation for the ecological risk assessment of MNPs.

Aging of plastics in aquatic environments: Pathways, environmental behavior, ecological impacts, analyses and quantifications

The ubiquity of plastics in our environment has brought about pressing concerns, with their aging processes, photo-oxidation, mechanical abrasion, and biodegradation, being at the forefront. Microplastics (MPs), whether originating from plastic degradation or direct anthropogenic sources, further complicate this landscape. This review delves into the intricate aging dynamics of plastics in aquatic environments under various influential factors. We discuss the physicochemical changes that occur in aged plastics and the release of oxidation products during their degradation. Particular attention is given to their evolving environmental interactions and the resulting ecotoxicological implications. A rigorous evaluation is also conducted for methodologies in the analysis and quantification of plastics aging, identifying their merits and limitations and suggesting potential avenues for future research. This comprehensive review is able to illuminate the complexities of plastics aging, charting a path for future research and aiding in the formulation of informed policy decisions.

The combined effects of phenanthrene and micro-/nanoplastics mixtures on the cellular stress responses of the thick-shell mussel Mytilus coruscus

Pollution with complex mixtures of contaminants including micro- and nano-plastics (MNPs) and organic pollutants like polycyclic aromatic hydrocarbons (PAH) poses a major threat to coastal marine ecosystems. Toxic mechanisms of contaminant mixtures are not well understood in marine organisms. We studied the effects of single and combined exposures to polycyclic aromatic hydrocarbon phenanthrene (Phe) and MNPs mixture with sizes of 70 nm, 5 μm and 100 μm on the immune health and oxidative stress parameters in the thick-shell mussel Mytilus coruscus. Immune cells (hemocytes) were more sensitive to the pollutant-induced oxidative stress than the gills. In hemocytes of co-exposed mussels, elevated mortality, lower lysosomal content, high production of reactive oxygen species (ROS) and decrease mitochondrial were found. Disparate responses of antioxidant enzymes in the hemolymph (e.g. increased superoxide dismutase (SOD) activity without a corresponding increase in catalase (CAT) in Phe exposures and an increase in CAT without a change in SOD in MNPs exposures) suggests misbalance of the antioxidant defense in the pollutant-exposed mussels. Gill lacked pronounced oxidative stress response showing a decline in ROS and antioxidant levels. Tissue-specific single and combined effects of Phe and MNPs suggest variation in bioavailability and/or different sensitivity to these pollutants in the studied tissues. Notably, the combined effects of MNPs and Phe were additive or antagonistic, showing that MNPs do not enhance and occasionally mitigate the toxic effects of Phe on the hemocytes and the gills of the mussels. Overall, our study sheds light on the impact of long-term exposure to MNPs and Phe mixtures on mussels, showing high sensitivity of the immune system and modulation of the Phe toxicity by MNPs co-exposure. These findings that may have implications for understanding the impacts of combined PAH and MNPs pollution on the health of mussel populations from polluted coastal habitats.

Seawater Accelerated the Aging of Polystyrene and Enhanced Its Toxic Effects on Caenorhabditis elegans

Microplastics (MPs) are emerging pollutants and pose a significant threat to marine ecosystems. Although previous studies have documented the mechanisms and toxic effects of aging MPs in various environments, the impact of the marine environment on MPs remains unclear. In the present study, the aging process of polystyrene (PS) in seawater was simulated and the changes in its physicochemical properties were investigated. Our results showed that the surface of the PS eroded in the seawater, which was accompanied by the release of aged MPs with a smaller size. In situ optical photothermal infrared microspectroscopy revealed that the mechanism of PS aging was related to the opening of the carbonyl group and breaking of the bond between carbon and benzene removal. To verify the toxic effects of aged PS, Caenorhabditis elegans was exposed to PS. Aged PS resulted in a greater reduction in locomotion, vitality, and reproduction than virgin PS. Mechanistically, aged PS led to oxidative stress, high glutathione s-transferase activity, and high total glutathione in worms. Together, our findings provided novel information regarding the accelerated aging of PS in seawater and the increased toxicity of aged PS, which could improve our understanding of MPs' ecotoxicity in the marine environment.

A beaker method for determination of microplastic concentration by micro-Raman spectroscopy

Fourier-transform infrared (FT-IR) spectroscopy method for measuring small microplastic (SMP) concentration in marine environment is time-consuming and labor-intensive due to sample pre-treatment. In contrast, Raman spectroscopy is less influenced by water and can directly measure SMP samples in water, making it a more efficient method to measure SMP concentration. Therefore, a method that can directly estimate the concentration of SMPs in water was developed, and the relationship between SMP concentration and experimental Raman spectra were established by testing with standard polyethylene (PE) samples. It was found that average spectra acquired in water solution could reflect characteristic peaks of the plastic after baseline correction. Further investigation found that there is a significant functional relationship between correlation coefficient of sample spectra and the concentration of PE particles, and such relationship can be modelled by Langmuir model. The empirical functional relationships can be used to estimate SMP concentrations by measuring average Raman spectra. The developed methodology is helpful for developing rapid SMP identification and monitoring methods in a more complex manner.•A method of directly measuring MP concentration in water is proposed.•Experimental procedures are provided.•Data analysis methods are outlined.

Single and combined toxicity of polystyrene nanoplastics and PCB-52 to the aquatic duckweed Spirodela polyrhiza

As nanoplastics and persistent organic pollutants are broadly distributed in aquatic ecosystems and pose a potential threat to ecosystem, most pertinent studies have focused on aquatic animals, while studies on freshwater plants have been rarely reported. Therefore, we analyzed the single and combined toxicological impacts of various concentrations of 80 nm polystyrene nanoplastics (PS-NPs) including 0.5, 5, 10, and 20 mg/L and polychlorinated biphenyl-52 (PCB-52, 2,2',5,5'- tetrachlorobiphenyl) at 0.1 mg/L on the aquatic plant Spirodela polyrhiza (S. polyrhiza) after a 10-day hydroponic experiment. Laser confocal scanning microscopy (LCSM) showed the accumulation of PS-NPs mainly in the root surface and the lower epidermis of leaves, and the enrichment of PS-NPs was aggravated by the presence of PCB-52. PS-NPs at 10 mg/L and 20 mg/L alone or in combination with PCB-52 notably inhibited the growth of S. polyrhiza, reduced the synthesis of chlorophylls a and b, and increased the activities of superoxide dismutase (SOD) and peroxidase (POD) as well as malondialdehyde (MDA) levels, and induced osmotic imbalance (soluble protein and soluble sugar contents) (p < 0.05). However, a single treatment with low levels of PS-NPs had positive effects on the growth (0.5 mg/L) and photosynthetic systems (0.5, 5 mg/L) of S. polyrhiza, while co-exposure exacerbated the damaging impacts of PS-NPs on the antioxidant defense system of S. polyrhiza, which was more pronounced in the roots. Furthermore, correlation analysis revealed that plant growth parameters were positively correlated with chlorophyll a and b content and negatively correlated with soluble sugars, antioxidant enzymes, lipid peroxidation, and carotenoid content (p < 0.05). These results provide data to improve the understanding of the single and combined ecotoxicological effects of nanoplastics and polychlorinated biphenyls (PCBs) in aquatic plants and their application in phytoremediation measures.

Nanoplastics enhance the intestinal damage and genotoxicity of sulfamethoxazole to medaka juveniles (Oryzias melastigma) in coastal environment

Antibiotics and nanoplastics are widely detected in the coastal ecosystem. However, the transcriptome mechanism elucidating the effect of antibiotics and nanoplastics co-exposure on the gene expression of aquatic organisms in coastal environment is still unclear. Here, single and joint effects of sulfamethoxazole (SMX) and polystyrene nanoplastics (PS-NPs) on the intestinal health and gene expression of medaka juveniles (Oryzias melastigma), which live in coastal environment, were investigated. The SMX and PS-NPs co-exposure decreased intestinal microbiota diversity compared to the PS-NPs, and caused more adverse effect on the intestinal microbiota composition and intestinal damage compared to the SMX, indicating that PS-NPs might enhance the toxicity of SMX on the medaka intestine. The increased abundance of Proteobacteria in the intestine was observed in the co-exposure group, which might induce the intestinal epithelium damage. In addition, the differentially expressed genes (DEGs) were mainly involved in the drug metabolism-other enzymes, drug metabolism-cytochrome P450, metabolism of xenobiotics by cytochrome P450 pathways in visceral tissue after the co-exposure. The expression of the host immune system genes (e.g., ifi30) could be associated with the increased pathogens in intestinal microbiota. This study is useful for understanding the toxicity effect of antibiotics and NPs on aquatic organisms in coastal ecosystem.

Toxicity of microplastics and nanoplastics: invisible killers of female fertility and offspring health

Microplastics (MPs) and nanoplastics (NPs) are emergent pollutants, which have sparked widespread concern. They can infiltrate the body via ingestion, inhalation, and cutaneous contact. As such, there is a general worry that MPs/NPs may have an impact on human health in addition to the environmental issues they engender. The threat of MPs/NPs to the liver, gastrointestinal system, and inflammatory levels have been thoroughly documented in the previous research. With the detection of MPs/NPs in fetal compartment and the prevalence of infertility, an increasing number of studies have put an emphasis on their reproductive toxicity in female. Moreover, MPs/NPs have the potential to interact with other contaminants, thus enhancing or diminishing the combined toxicity. This review summarizes the deleterious effects of MPs/NPs and co-exposure with other pollutants on female throughout the reproduction period of various species, spanning from reproductive failure to cross-generational developmental disorders in progenies. Although these impacts may not be directly extrapolated to humans, they do provide a framework for evaluating the potential mechanisms underlying the reproductive toxicity of MPs/NPs.

Microplastics in aquatic environments: A comprehensive review of toxicity, removal, and remediation strategies

The occurrence of microplastics (MPs) in aquatic environments has been a global concern because they are toxic and persistent and may serve as a vector for many legacies and emerging pollutants. MPs are discharged to aquatic environments from different sources, especially from wastewater plants (WWPs), causing severe impacts on aquatic organisms. This study mainly aims to review the Toxicity of MPs along with plastic additives in aquatic organisms at various trophic compartments and available remediation methods/strategies for MPs in aquatic environments. Occurrences of oxidative stress, neurotoxicity, and alterations in enzyme activity, growth, and feeding performance were identical in fish due to MPs toxicity. On the other hand, growth inhibition and ROS formation were observed in most of the microalgae species. In zooplankton, potential impacts were acceleration of premature molting, growth retardation, mortality increase, feeding behaviour, lipid accumulation, and decreased reproduction activity. MPs togather with additive contaminants could also exert some toxicological impacts on polychaete, including neurotoxicity, destabilization of the cytoskeleton, reduced feeding rate, growth, survivability and burrowing ability, weight loss, and high rate of mRNA transcription. Among different chemical and biological treatments for MPs, high removal rates have been reported for coagulation and filtration (>86.5 %), electrocoagulation (>90 %), advanced oxidation process (AOPs) (30 % to 95 %), primary sedimentation/Grit chamber (16.5 % to 58.84 %), adsorption removal technique (>95 %), magnetic filtration (78 % to 93 %), oil film extraction (>95 %), and density separation (95 % to 100 %). However, desirable extraction methods are required for large-scale research in MPs removal from aquatic environments.

Functional Trait-Based Evidence of Microplastic Effects on Aquatic Species

Microplastics represent an ever-increasing threat to aquatic organisms. We merged data from two global scale meta-analyses investigating the effect of microplastics on benthic organisms' and fishes' functional traits. Results were compared, allowing differences related to vertebrate and invertebrate habitat, life stage, trophic level, and experimental design to be explored. Functional traits of aquatic organisms were negatively affected. Metabolism, growth, and reproduction of benthic organisms were impacted, and fish behaviour was significantly affected. Responses differed by trophic level, suggesting negative effects on trophic interactions and energy transfer through the trophic web. The experimental design was found to have the most significant impact on results. As microplastics impact an organism's performance, this causes indirect repercussions further up the ecological hierarchy on the ecosystem's stability and functioning, and its associated goods and services are at risk. Standardized methods to generate salient targets and indicators are urgently needed to better inform policy makers and guide mitigation plans.

Ecotoxicological evaluation of functional carbon nanodots using zebrafish (Danio rerio) model at different developmental stages

Considering functional carbon nanodots (FCNs) are potential to be applied in many areas, their risk and toxicity to organisms are imperative to be evaluated. Thus, this study conducted acute toxicity test of zebrafish (Danio rerio) at embryonic and adult stage to estimate the toxicity of FCNs. Results show that the toxic effects of FCNs and nitrogen doped FCNs (N-FCNs) at their 10% lethal concentration (LC₁₀) values on zebrafish are expressed in developmental retardation, cardiovascular toxicity, renal damage and hepatotoxicity. There are interactive relationships between these effects, but the main reason should be ascribed to the undesirable oxidative damage induced by high doses of materials, as well as the biodistribution of FCNs and N-FCNs in vivo. Even so, FCNs and N-FCNs can promote the antioxidant activity in zebrafish tissues to cope with the oxidative stress. FCNs and N-FCNs are not easy to cross the physical barriers in zebrafish embryos or larvae, and can be excreted from intestine by adult fish, which proves their biosecurity to zebrafish. In addition, because of the differences in physicochemical properties, especially nano-size and surface chemical property, FCNs show higher biosecurity to zebrafish than N-FCNs. The effects of FCNs and N-FCNs on hatching rates, mortality rates and developmental malformations are dose-dependent and time-dependent. The LC₅₀ values of FCNs and N-FCNs on zebrafish embryo at 96 hpf are 1610 mg/L and 649 mg/L, respectively. According to the Acute Toxicity Rating Scale of the Fish and Wildlife Service, the toxicity grades of FCNs and N-FCNs are both defined as "practically nontoxic", and FCNs are "Relatively Harmless" to embryos because their LC₅₀ values are above 1000 mg/L. Our results prove the biosecurity of FCNs-based materials for future practical application.

Combined effects of microplastics and benz[a]anthracene on cardiotoxicity in zebrafish (Danio rerio) larvae: Size matters

The size of microplastics (MPs) plays an important role in combined toxic effects including synergistic or antagonistic effects. However, the influence of the size of MPs on the combined toxicity of contaminants remains unclear. In this study, we employed a zebrafish model to investigate the effects of MP size on the combined toxicity of benz[a]anthracene (BaA), a representative polyaromatic hydrocarbon, using three different sizes of polystyrene MPs (PSMPs) (0.2, 1.0, and 10 μm). Treatment of all groups did not result in any mortality of the zebrafish larvae. However, small-sized PSMPs (0.2 μm) enhanced the toxic effect of BaA in larvae such as cardiac defect and disruption of vessel formation. Medium-sized PSMPs (1.0 μm) were boundary in terms of the combined toxic effect; however, large-sized PSMPs (10 μm) alleviated the cardiotoxicity of BaA, including cardiac defect, ROS levels, and cell death. The combined effects showed a correlation with the body burden of MPs and BaA in larvae according to particle size (in the order of 0.2 μm > 1.0 μm > 10 μm). The synergistic effects occurred likely because the small PSMPs facilitated the body burden of BaA, induced excessive ROS by Ahr-mediated activity, and caused cell death in the heart, resulting in increased heart defects in the larvae. In contrast, large PSMPs abated the combined toxic effect through decreased body burden, whereas medium PSMPs form a boundary in combined effects. Therefore, the combined toxic effects of MPs are dependent on their size, which plays an important role in the transport and accumulation of environmental pollutants.

Acute and Chronic Effects of Crude Oil Water-Accommodated Fractions on the Early Life Stages of Marine Medaka (Oryzias melastigma, McClelland, 1839)

Oil spill is a major marine environmental pollution issue. Research regarding the long-term effects of oil spills on the early life stage of marine fish is still limited. In this study, the potential adverse impact of crude oil from one oil spill accident which occurred in the Bohai Sea on the early life stages of marine medaka (Oryzias melastigma, McClelland, 1839) was evaluated. A 96-h acute test (larvae) and a 21-d chronic test (embryo-larvae) of water-accommodated fractions (WAFs) from crude oil were conducted, respectively. The results of the acute test showed that only the highest concentration of WAFs (100.00%) significantly affected the mortality of larvae (p < 0.01) and that the 96 h-LC₅₀ was 68.92% (4.11 mg·L^-1 expressed as total petroleum hydrocarbons (TPHs)). Larval heart demonstrated histopathological alterations in all WAF-exposed groups. The chronic test results showed that, except for larval mortality, the total hatching success (%)/hatching time of embryos in WAF treatments was not significantly different from those of the control group (p > 0.05), and no malformation was found in surviving larvae after 21 d of exposure. Nevertheless, the exposed embryos and larvae in the highest concentration of WAFs (60.00%) demonstrated significantly reduced heart rate (p < 0.05) and increased mortality (p < 0.01), respectively. Overall, our results indicated that both acute and chronic WAF exposures had adverse impacts on the survival of marine medaka. In the early life stages, the heart of the marine medaka was the most sensitive organ which showed both structural alteration and cardiac dysfunction.

Presence of microplastics and microparticles in Oregon Black Rockfish sampled near marine reserve areas

Measuring the spatial distribution of microparticles which include synthetic, semi-synthetic, and anthropogenic particles is critical to understanding their potential negative impacts on species. This is particularly important in the context of microplastics, which are a form of microparticle that are prevalent in the marine environment. To facilitate a better understanding of microparticle occurrence, including microplastics, we sampled subadult and young juvenile Black Rockfish (Sebastes melanops) at multiple Oregon coast sites, and their gastrointestinal tracts were analyzed to identify ingested microparticles. Of the subadult rockfish, one or more microparticles were found in the GI tract of 93.1% of the fish and were present in fish from Newport, and near four of five marine reserves. In the juveniles, 92% of the fish had ingested one or more microparticles from the area of Cape Foulweather, a comparison area, and Otter Rock, a marine reserve. The subadults had an average of 7.31 (average background = 5) microparticles detected, while the juveniles had 4.21 (average background = 1.8). In both the subadult and juvenile fish, approximately 12% of the microparticles were identified as synthetic using micro-Fourier Infrared Spectroscopy (micro-FTIR). Fibers were the most prevalent morphology identified, and verified microparticle contamination was a complex mixture of synthetic (∼12% for subadults and juveniles), anthropogenic (∼87% for subadults and 85.5% for juveniles), and natural (e.g., fur) materials (∼0.7% for subadults and ∼2.4% for juveniles). Similarities in exposure types (particle morphology, particle number) across life stages, coupled with statistical differences in exposure levels at several locations for subadult fish, suggest the potential influence of nearshore oceanographic patterns on microparticle distribution. A deeper understanding of the impact microplastics have on an important fishery such as those for S. melanops, will contribute to our ability to accurately assess risk to both wildlife and humans.

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.

Reproductive toxicity and cross-generational effect of polyethylene microplastics in Paramisgurnus dabryanus

Pollution of microplastics (MPs) has become a global environmental issue due to the difficulty in its degradation and may cause unexpected ecological effects. Nevertheless, little is known about the potential effects of MPs on reproduction toxicity in aquatic species. In this study, adult loach (Paramisgurnus dabryanus, F0 generation) were exposed to two concentrations (1 and 10 mg/L) of polyethylene MPs (PE-MPs) for 15 or 30 days, and the toxic effects in parental loach and the offspring (F1 generation) were examined. Our results showed that PE-MPs exposure could change the indicators content of antioxidant system in the brain, liver, and gonad. PE-MPs can accumulate in the gonads, disrupt the transcription of HPG-axis related genes, alter sex hormone levels, increase cell apoptosis and gonadal pathological lesions, lead to the damage of biological characteristics of semen, and affect the reproduction in F0 generation. PE-MPs remaining in the parental gonads can be transferred to the F1 generation embryos and accumulated on the embryonic chorionic membrane, increasing mortality and malformation rates, accelerating hatching time, and decreasing hatching rate and body length. These results suggest that PE-MPs leads to a potential adverse influence on reproduction and serious impacts on population sustainability. This work provides a new perspective into the effects of MPs on reproductive damage and cross-generational effects in teleost fish, which have implications in fields of freshwater ecology and environmental toxicology.

Biotransformation as a tool for remediation of polycyclic aromatic hydrocarbons from polluted environment - review on toxicity and treatment technologies

Polycyclic aromatic hydrocarbons, a prominent family of persistent organic molecules produced by both anthropogenic and natural processes, are widespread in terrestrial and aquatic environments owing to their hydrophobicity, electrochemical stability and low aqueous solubility. Phenanthrene and naphthalene belong to the group of polycyclic aromatic hydrocarbons whose occurrence are reported to be relatively higher. The bioremediation mode of removing the toxicities of these two compounds has been reported to be promising than other methods. Most of the microbial classes of bacterial, fungal and algal origin are reported to degrade the target pollutants into non-toxic compounds effectively. The review aims to give an overview on toxicological studies, identification and enrichment techniques of phenanthrene and naphthalene degrading microbes and the bioremediation technologies (microbial assisted reactors, microbial fuel cells and microbial assisted constructed wetlands) reported by various researchers. All the three modes of bioremediation techniques were proved to be promising on different perspectives. In the treatment of phenanthrene, a maximum recovery of 96% and 98% was achieved in an aerobic membrane reactor with Bacillus species and single chamber air cathode microbial fuel cell with Acidovorax and Aquamicrobium respectively were reported. With the constructed wetland configuration, 95.5% of removal was attained with manganese oxide based microbial constructed wetland. The maximum degradation efficiency reported for naphthalene are 99% in a reverse membrane bioreactor, 98.5% in a marine sediment microbial fuel cell and 92.8% with a low-cost sandy soil constructed wetland.

Micro- and nanoplastics: A new cardiovascular risk factor?

Exposure to micro- and nanoplastics (MNPs) is inevitable due to their omnipresence in the environment. A growing body of studies has advanced our understanding of the potential toxicity of MNPs but knowledge gaps still exist regarding the adverse effects of MNPs on the cardiovascular system and underlying mechanisms, particularly in humans. Here, we reviewed up-to-date data published in the past 10 years on MNP-driven cardiovascular toxicity and mechanisms. Forty-six articles concerning ADME (absorption, distribution, and aggregation behaviors) and toxicity of MNPs in the circulatory system of animals and human cells were analyzed and summarized. The results showed that MNPs affected cardiac functions and caused toxicity on (micro)vascular sites. Direct cardiac toxicity of MNPs included abnormal heart rate, cardiac function impairment, pericardial edema, and myocardial fibrosis. On (micro)vascular sites, MNPs induced hemolysis, thrombosis, blood coagulation, and vascular endothelial damage. The main mechanisms included oxidative stress, inflammation, apoptosis, pyroptosis, and interaction between MNPs and multiple cellular components. Cardiovascular toxicity was determined by the properties (type, size, surface, and structure) of MNPs, exposure dose and duration, protein presence, the life stage, sex, and species of the tested organisms, as well as the interaction with other environmental contamination. The limited quantitative information on MNPs' ADME and the lack of guidelines for MNP cardiotoxicity testing makes risk assessment on cardiac health impossible. Furthermore, the future directions of cardiovascular research on MNPs are recommended to enable more realistic health risk assessment.

Different effects and mechanisms of polystyrene micro- and nano-plastics on the uptake of heavy metals (Cu, Zn, Pb and Cd) by lettuce (Lactuca sativa L.)

Heavy metals are widely distributed in soil ecosystems, posing a potential threat to soil biota. Micro- and nano-plastics (MNPs) can impact the accumulation of heavy metals in plants through changing soil microbial community and cause injury to plants. In this work, two concentrations (100 and 1000 mg/kg) polystyrene microplastics (PS-MPs) and nanoplastics (PS-NPs) were adopted to explore the effects and mechanisms of MNPs on the uptake of Cu, Zn, Pb and Cd in lettuce (Lactuca sativa L.). MPs increased the uptake of heavy metals in lettuce by increasing the relative abundance of the key metal-activation bacteria in rhizospheric soil. At the end of experiment, the contents of Cu, Zn, Pb and Cd in NP treatments were significantly (p < 0.05) higher than that of MPs, particularly in 1000 mg/kg of NPs, with concentrations of 52.6, 174, 10.3, and 33.2 mg/kg, respectively. Biomarkers and gene expression reveled that 1000 mg/kg of NPs caused more severe injuries to lettuce plant at the end. Moreover, metabolomic analysis demonstrated that NPs disturbed the metabolism of ATP-binding cassette transporter (ABC transporter) and plant hormone signal transduction of lettuce root, causing increased uptake of heavy metals by lettuce. This work reveals that MPs may increase accumulation of heavy metals by altering the rhizosphere microorganisms, whereas NPs increase accumulation of heavy metals by causing more severe injuries to lettuce plant.

Polystyrene microplastics mitigate the embryotoxic damage of metformin and guanylurea in Danio rerio

Microplastics (MPs) alone may endanger the health and fitness of aquatic species through different mechanisms. However, the harmful effects of these when mixed with other emerging contaminants require additional research. Herein, we aimed to determine whether a mixture of MPs with metformin (MET) or guanylurea (GUA) might induce embryotoxicity and oxidative stress in Danio rerio. Upon exposure to mixtures, our results showed MPs reduced the mortality rate of MET and GUA in embryos. Moreover, the severity and the rate of malformations were also decreased in all mixtures with MPs. Concerning oxidative stress, our findings indicated MET, GUA, MPs, and the mixtures increased the levels of lipoperoxidation, hydroperoxide content, and protein carbonyl content in D. rerio larvae. However, the oxidative damage induced in all mixtures was lower than that produced by both drugs alone. Thus, it is likely that the accumulation of MPs avoided the entrance of MET and GUA into the embryos. Once the embryo hatched, MPs did only remain accumulated in the yolk sac of larvae and did not translocate to other organs. Our risk assessment analysis confirmed that MPs shrunk the damage produced by MET and GUA. In a nutshell, MPs mitigate the embryotoxic damage of metformin and guanylurea in D. rerio by blocking their entrance.

Effects of the Antidepressant Amitriptyline on Juvenile Brown Trout and Their Modulation by Microplastics

Pharmaceuticals such as antidepressants are designed to be bioactive at low concentrations. According to their mode of action, they can also influence non-target organisms due to the phylogenetic conservation of molecular targets. In addition to the pollution by environmental chemicals, the topic of microplastics (MP) in the aquatic environment came into the focus of scientific and public interest. The aim of the present study was to investigate the influence of the antidepressant amitriptyline in the presence and absence of irregularly shaped polystyrene MP as well as the effects of MP alone on juvenile brown trout (Salmo trutta f. fario). Fish were exposed to different concentrations of amitriptyline (nominal concentrations between 1 and 1000 µg/L) and two concentrations of MP (104 and 105 particles/L; <50 µm) for three weeks. Tissue cortisol concentration, oxidative stress, and the activity of two carboxylesterases and of acetylcholinesterase were assessed. Furthermore, the swimming behavior was analyzed in situations with different stress levels. Exposure to amitriptyline altered the behavior and increased the activity of acetylcholinesterase. Moreover, nominal amitriptyline concentrations above 300 µg/L caused severe acute adverse effects in fish. MP alone did not affect any of the investigated endpoints. Co-exposure caused largely similar effects such as the exposure to solely amitriptyline. However, the effect of amitriptyline on the swimming behavior during the experiment was alleviated by the higher MP concentration.

Combined effects of copper oxide and nickel oxide coated chitosan nanoparticles adsorbed to styrofoam resin beads on hydrothermal vent bacteria

Microplastics are potential carriers of harmful contaminants but their combined effects are largely unknown. It needs intensive monitoring in order to achieve a better understanding of metal-oxide nanoparticles and their dispersion via microplastics such as styrofoam in the aquatic environment. In the present study, an effort was made to provide a preferable perception about the toxic effects of engineered nanoparticles (NPs), namely, copper oxide (CuO NPs), nickel oxide (NiO NPs), copper oxide/chitosan (CuO/CS NPs) and nickel oxide/chitosan (NiO/CS NPs). Characterizations of synthesized NPs included their morphology (SEM and EDX), functional groups (FT-IR) and crystallinity (XRD). Their combined toxic effect after adsorption to styrofoam (SF) was monitored using the hydrothermal vent bacterium Jeotgalicoccus huakuii as a model. This was done by determining MIC (minimum inhibitory concentration) through a resazurin assay measuring ELISA, growth, biofilm inhibition and making a live and dead assay. Results revealed that at high concentrations (60 mg/10 mL) of CuO, CuO/CS NPs and 60 mg of SF adsorbed CuO and CuO/CS NPs inhibited the growth of J. huakuii. However, NPs rather than SF inhibited the growth of bacteria. The toxicity of NPs adsorbed on plain SF was found to be less compared to NPs alone. This study revealed new dimensions regarding the positive impacts of SF at low concentrations. Synthesized NPs applied separately were found to affect the growth of bacteria substantially more than if coated to SF resin beads.

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.

Development of seawater quality criteria for phenanthrene based on toxicity data of native species in the Bohai Sea

Phenanthrene (Phe), one of the most commonly detected polycyclic aromatic hydrocarbons, poses a potential threat to marine ecosystems due to its strong toxicity to aquatic organisms. Developing marine water quality criteria (WQC) is critical to effectively control Phe pollution. This study conducted 10 acute toxicity tests and 4 chronic toxicity tests using native species in the Bohai Sea, China and found that the half-lethal/effective concentrations (LC₅₀/EC₅₀) of Phe for all tested organisms were in the range of 0.198-50.142 mg/L. Among them, the mysid Neomysis awatschensis was the most sensitive species, and the rotifer Brachionus plicatilis was the least sensitive. In terms of chronic toxicity, the range of no-observed-effect concentrations (NOECs) for the four tested organisms was 0.0156-4.00 mg/L. Based on the toxicity data and other data collected from existing databases and literature, the established species sensitivity distribution (SSD) model revealed that the marine WQC for Phe was 39.55 μg/L. Furthermore, the reliability of the derived criteria was verified by measuring multiple endpoints of Skeletonema costatum and Brachionus plicatilis after chronic exposure to Phe. Finally, the environmental concentrations of Phe in the Bohai Sea were determined to be 8.0-318 ng/L, and the joint probability curve (JPC) results showed that the ecological risk of Phe was acceptable. This study provides a reference for developing seawater quality standards for Phe.

Developmental and reproductive toxic effects of exposure to microplastics: A review of associated signaling pathways

Microplastics (MPs), small pieces of plastic (∼5 mm), are released into the environment not only as a result of the decomposition of large-sized plastics but also from day-to-day use of plastic products. Chronic exposure to MPs has been attributed to harmful effects on aquatic organisms and rodents. Effects include gastrointestinal toxicity, hepatotoxicity, neurotoxicity, and reproductive and developmental toxicities. Exposure to MPs may also potentially affect human health. Herein, we reviewed the impact of MPs on male and female reproductive systems and the associated mechanisms involved in the reproductive and developmental toxicities of MPs. We performed a literature search in Google Scholar and PubMed using the following keywords: MPs and reproductive toxicity; MPs and developmental studies; MPs and infertility; MPs and aquatics; and MPs and rodents. Evidence of MPs accumulation has been reported in many organs of humans and experimental models. The harmful effects of MPs have been manifested in male and female reproductive systems of mammalian and aquatic animals, including developmental effects on gametes, embryos, and their offspring. This review describes various signaling pathways involved in MPs-associated male and female reproductive and developmental toxicities.

Promotion of the biodegradation of phenanthrene adsorbed on microplastics by the functional bacterial consortium QY1 in the presence of humic acid: Bioavailability and toxicity evaluation

The adsorption of hydrophobic organic compounds (HOCs) by microplastics (MPs) has attracted great attention in recent years. However, the ultimate environmental fate of the HOCs sorbed on MPs (HOCs-MPs) is poorly understood. In this work, we investigated the potential influence of the biotransformation process on the environmental fate of phenanthrene (PHE, a model HOC) sorbed on MPs (PHE-MPs) under the existence of humic acid (HA, the main ingredient of dissolved organic matter (DOM)) in the aquatic environment. The results indicated that the adsorption behavior of PHE on MPs decreased its bioavailability and thus inhibited its biotransformation efficiency. However, HA significantly promoted the biodegradation rate and percentage of PHE-MPs. This was probably because HA improved the desorption of PHE from MPs, which promoted the acquisition of PHE by bacteria from the aqueous phase. Further, HA dramatically increased the bacterial community diversity and richness and altered the community composition. The richness of some PHE-degrading bacteria, such as Methylobacillus and Sphingomonas, significantly increased, which may also be an important factor for promoting PHE biodegradation. Molecular ecological network analysis implied that HA enhanced the modularity and complexity of bacterial interaction networks, which was beneficial to maintaining the functional stability of the consortium QY1. Besides, HA decreased the cytotoxicity of functional microbes induced by HOCs-MPs. This work broadens our knowledge of the environmental fate of HOCs-MPs and interactions of MPs, HOCs, DOMs and functional microbial consortiums in aqueous environments.

A review of interactions of microplastics and typical pollutants from toxicokinetics and toxicodynamics perspective

The widespread microplastics (MPs) pollution has become a concerning environmental issue. The interactions between MPs and typical pollutants may change the bioaccumulation, and toxicity of pollutants, leading to high uncertainty in risk assessment. Still, significant gaps remain in the knowledge available to integrate these interactions in the perspectives of toxicokinetics (TK) and toxicodynamics (TD), which is also an essential part of quantitative toxicological research. This review systematically summarizes the interaction between MPs and typical pollutants in TK and TD processes. MPs can be acted as the vector or sink of pollutants to increase or decrease their bioaccumulation, and also may not affect their bioaccumulation due to no interaction. The adverse outcome pathway (AOP) framework enables novel approaches for determining the interaction between MPs and pollutants in the TD process. MPs can directly or indirectly enhance, reduce and not affect the toxicity of pollutants. A series of factors influencing the interaction in TK and TD processes are summarized, including MPs characteristics and exposure scenarios. TK-TD approach can quantitatively understand the interaction between MPs and pollutants based on the mechanism. Given the current knowledge gap in TK and TD processes, future perspectives on combined exposure research are proposed.

Reduction in Toxicity of Polystyrene Nanoplastics Combined with Phenanthrene through Binding of Jellyfish Mucin with Nanoplastics

Mucin (Mu), a biological substance extracted from jellyfish (Aurelia aurita), was used to reduce the toxic effect of polystyrene nanoplastics (PS-NP) combined with phenanthrene (Phe) in the aquatic environment of zebrafish (Danio rerio), among other aquatic organisms. Mu showed a high binding capacity, as it bound to 92.84% and 92.87% of the PS-NPs (concentration of 2.0 mg/L) after 0.5 h and 8 h, respectively. A zebrafish embryo development test was conducted to check for any reduction in toxicity by Mu. When exposed to PS-NP + Mu and PS-NP + Phe + Mu, respectively, the hatching rates were 88.33 ± 20.21% and 93.33 ± 2.89%, respectively; these results were not significantly different from those of the control group. However, the hatching rate with the addition of Mu increased, compared to that of the PS-NP (71.83 ± 13.36%) and Phe (37.50 ± 19.83%) treatments, and the morphological abnormality rate decreased. The presence of Mu was also found to obstruct the absorption of PS-NP and PS-NP + Phe by the zebrafish. When zebrafish embryos were exposed to PS-NP at a concentration of 5.0 mg/L, the hatching rate differed significantly from that of the control group, and the expression of CAT and p53 genes increased significantly, but the expression of Bcl-2 decreased significantly. An mRNA sequence analysis revealed that the gene expression levels of the test group containing Mu were similar to those of the control group. These results infer that Mu can be used as a biological material to collect and remove PS-NPs from aquatic environments and reduce toxicity.

The hormetic response of heart rate of fish embryos to contaminants - Implications for research and policy

Evidence of contaminant-induced hormesis is rapidly accumulating, while the underlying mechanisms of hormesis are becoming increasingly understood. Recent developments in this research area, and especially the emergence of the nuclear factor-erythroid factor 2-related factor 2 (Nrf2) as the master mechanism, suggest that contaminants can induce cardiac hormetic responses. This paper collates significant evidence of hormetic response of the heart rate of fish embryos to contaminants, in particular antibiotics, microplastics, and herbicides, characterized by a low-dose increase (tachycardia) and a high-dose decrease (bradycardia). The increase often occurs at doses about 100-800 times smaller than the no-observed-adverse-effect-level (NOAEL). There are also indications for even triphasic responses, which include a sub-hormetic decrease of the heart rate by doses over 10⁶ times smaller than the NOAEL. Such sub-NOAEL effects cannot be captured by linear-no-threshold (LNT) and threshold models, raising concerns about environmental health and highlighting the pressing need to consider hormetic responses in the ecological risk assessment. A visionary way forward is proposed, but addressing this research bottleneck would require improved research designs with enhanced ability and statistical power to study diphasic and triphasic responses of heart rate.

Combined toxicity of polystyrene microplastics and sulfamethoxazole on zebrafish embryos

Despite extensive investigation on the toxicity of microplastics (MPs), an emerging global concern, little is known about the combined toxicity of MPs and co-occurring pollutants in aquatic environments. In this study, the combined toxicity of polystyrene MPs and sulfamethoxazole (SMZ) antibiotics was explored in zebrafish embryos in terms of the developmental, physiological, and endocrine toxicities. Exposure to PS and SMZ induced mortality (rate: 25.0 ± 7.5%) and malformation (rate: 20~35%) at multiple regions and stages of zebrafish development. Physiological toxicity was also induced as shown by the significant decrease in fetal movement (by 31.1~37.0%) and swimming frequency (by 26.9~36.8%) and the increase in heartbeat rate (by 19.0~20.9%). Finally, PS and SMZ exposure also induced extensive endocrine toxicities in zebrafish as confirmed by increases in various biomarkers including vitellogenin, 17β-estradiol, testosterone, and triiodothyronine. The combination index showed that antagonistic effects were present between PS and SMZ toxicity, which slightly decreased their combined toxicity. This study aims to further understand the combined toxicity of MPs and co-occurring pollutants in aquatic environments.

Effects of different types of primary microplastics on early life stages of rainbow trout (Oncorhynchus mykiss)

Plastic pollution is recognized as serious threat to aquatic organisms. The aim of this research was to determine the effect of environmentally realistic concentrations of various microplastics (MPs) on survival, growth, development and induction of endocrine, geno- and cytotoxic responses in the early life stages of rainbow trout Oncorhynchus mykiss. Fish were exposed for 69-days, from embryos at eyed-stage to mobile yolk-sac larvae, to pre-production pellets (3000 μm; polystyrene - PS and polyethylene terephthalate - PET). Additionally, since salmonid larvae are particularly exposed to light polymers after swimming up from the bottom, fish were also treated with PE microspheres (150-180 μm; polyethylene - PE) for both long (69-days, from embryos at eyed-stage) and short period (29 days, from larvae 3 weeks after hatching) to test the development stage-related effect on the growth parameters and fitness. Hatching success, rate and the survival of larvae did not differ among treatments. Although some alterations were found in the length gain after the long-term exposure and in the yolk-sac exhaustion rate in all PE treatments, the final size of larvae did not differ from the respective controls. PE-treated larvae have shown elevated corticosterone concentrations being significantly higher in fish exposed from the embryo stage. It was indicated for the first time that mobile yolk-sac larvae ingested MPs (up to 24% of larvae contained microspheres). No changes were recorded in cytotoxicity endpoints in any of the treatments, but exposure to PS pellets resulted in significantly higher frequencies of genotoxicity endpoints compared to the control treatment. This effect and aforementioned alterations in PE-treated larvae might result from the exposure to toxic MPs leaches. The fact that selected PAHs' levels reached the highest values in PS pellets and PE microspheres must be underlined.

Secondary PVC microplastics are more toxic than primary PVC microplastics to Oryzias melastigma embryos

Irregular-shaped and partially degraded secondary microplastics (SMP) account for the majority of MPs in marine environments, yet little is known about their effects on marine organisms. In this study, we investigated the embryotoxicity of polyvinyl chloride SMP and primary microplastics (PMP) to the marine medaka Oryzias melastigma. This study aimed to determine the physical impacts of MPs and, for the first time, elucidate the underlying mechanisms of physical toxicity. SMP shortened hatching time and induced higher teratogenic effects on larvae relative to PMP, indicating a higher toxicity from SMP. Physical damage from SMP to the chorion surface appears to be the main toxicity mechanism, caused by their irregular shape and reduced aggregation relative to PMP. In contrast, real-time changes in oxygen demonstrated that hypoxia caused by greater PMP adsorption to the chorion surface contributes to the toxicological responses of this material relative to SMP. Modulation of genes involved in hypoxia-response, cardiac development and hatching confirmed the toxicity mechanisms of PMP and SMP. The chemical contribution to observed toxicity was negligible, confirming impacts derived from physical toxicity. Our findings highlight the negative effects of environmentally relevant SMP on the marine ecosystems.

Microplastics increase the accumulation of phenanthrene in the ovaries of marine medaka (Oryzias melastigma) and its transgenerational toxicity

Microplastics (MPs) are considered to exacerbate the impacts of hydrophobic organic pollutants on aquatic organisms through the carrier function, but whether MPs affect the transgenerational toxicity of pollutants is unclear. This study exposed adult female marine medaka to phenanthrene (Phe)-adsorbed MPs for 60 days to investigate the effects of MPs on the bioaccumulation, reproductive and transgenerational toxicity of Phe. Compared to Phe alone, co-exposure to Phe and 200 μg/L MPs significantly increased Phe bioaccumulation in the intestines and ovaries. Phe alone and Phe combined with MPs disrupted the regulation of the hypothalamus-pituitary-gonadal axis, and reduced vitellogenin levels and reproductive capacity of female fish. In particular, co-exposure to 200 μg/L MPs and Phe increased the rate of follicular atresia, inhibited ovarian maturity, and aggravated reproductive toxicity. Notably, maternal uptake of Phe could be transferred to the offspring, and embryonic accumulation increased with the concentrations of MPs. Moreover, MPs aggravated Phe-induced bradycardia in embryos, suggesting that MPs exacerbated the transgenerational toxicity of Phe. These findings reveal that the growing number of MPs in the ocean might amplify the adverse effects of organic pollutants on the health and population stability of marine fishes, and this problem merits more attention.

Microplastics aggravate the bioaccumulation and toxicity of coexisting contaminants in aquatic organisms: A synergistic health hazard

There are ongoing controversies regarding the effects of microplastics (MPs) on the bioaccumulation and toxicity of coexisting contaminants in aquatic organisms. This study aims to quantitatively evaluate this issue based on 870 endpoints from 40 publications. It was shown that the presence of MPs significantly increased the bioaccumulation of co-contaminants by 31%, with high statistical power and without obvious publication bias. The aggravated bioaccumulation was also revealed by the strongly positive correlation between bioconcentration factors in the presence and the absence of MPs. Furthermore, the subgroup/regression analyses indicated that the vector effect of MPs on other chemicals was affected by multiple factors and their interactions, such as particle size and exposure time. In addition, a relatively comprehensive biomarker profile was recompiled from included studies to assess the changes in toxicity caused by combined exposure. Results confirmed that the presence of MPs obviously exacerbated the toxicity of co-contaminants by 18%, manifested by the potentiated cytotoxicity, endocrine disruption, immunotoxicity and oxidative stress, implying a synergistic health hazard. Ultimately, the mismatches between laboratory and field conditions were discussed, and the recommendations for future research were offered.

Seeking for a perfect (non-spherical) microplastic particle - The most comprehensive review on microplastic laboratory research

In recent decades, much attention has been paid to microplastic pollution, and research on microplastics has begun to grow exponentially. However, microplastics research still suffers from the lack of standardized protocols and methods for investigation of microplastics under laboratory conditions. Therefore, in this review, we summarize and critically discuss the results of 715 laboratory studies published on microplastics in the last five years to provide recommendations for future laboratory research. Analysis of the data revealed that the majority of microplastic particles used in laboratory studies are manufactured spheres of polystyrene ranging in size from 1 to 50 µm, that half of the studies did not characterize the particles used, and that a minority of studies used aged particles, investigated leaching of chemicals from microplastics, or used natural particles as a control. There is a large discrepancy between microplastics used in laboratory research and those found in the environment, and many laboratory studies suffer from a lack of environmental relevance and provide incomplete information on the microplastics used. We have summarized and discussed these issues and provided recommendations for future laboratory research on microplastics focusing on (i) microplastic selection, (ii) microplastic characterization, and (iii) test design of laboratory research on microplastics.

Thyroid disruption and growth inhibition of zebrafish embryos/larvae by phenanthrene treatment at environmentally relevant concentrations

Phenanthrene induces reproductive and developmental toxicity in fish, but whether it can disrupt the thyroid hormone balance and inhibit growth had not been determined to date. In this study, zebrafish embryos were exposed to phenanthrene (0, 0.1, 1, 10 and 100 μg/L) for 7 days. The results of this experiment demonstrated that phenanthrene induced thyroid disruption and growth inhibition in zebrafish larvae. Phenanthrene significantly decreased the concentration of l-thyroxine (T4) but increased that of 3,5,3'-l-triiodothyronine (T3). The expression of genes related to the hypothalamic-pituitary-thyroid (HPT) axis was altered in zebrafish larvae exposed to phenanthrene. Moreover, phenanthrene exposure significantly increased the malformation rate and significantly reduced the survival rate and the body length of zebrafish larvae. Furthermore, phenanthrene significantly decreased the concentrations of growth hormone (GH) and insulin-like growth factor-1 (IGF-1). Changes observed in gene expression patterns further support the hypothesis that these effects may be related to alterations along the GH/IGF-1 axis. In conclusion, our study indicated that exposure to phenanthrene at concentrations as low as 0.1 μg/L resulted in thyroid disruption and growth inhibition in zebrafish larvae. Therefore, the estimation of phenanthrene levels in the aquatic environment needs to be revisited.

Polystyrene microplastics increase estrogenic effects of 17α-ethynylestradiol on male marine medaka (Oryzias melastigma)

Microplastics (MPs) and endocrine disrupting chemicals are ubiquitous pollutants in marine environments, but their combined ecological risk is unclear. This study exposed male marine medaka (Oryzias melastigma) to 10 ng/L 17α-ethynylestradiol (EE₂) alone or EE₂ plus 2, 20, and 200 μg/L polystyrene MPs for 28 days to investigate the impacts of MPs on the reproductive disruption of EE₂. The results showed that 10 ng/L EE₂ alone did not affect biometric parameters, while co-exposure to EE₂ and 20, 200 μg/L MPs suppressed the growth and decreased gonadosomatic and hepatosomatic indices. Compared to EE₂ alone, EE₂ plus MPs exposure significantly increased plasma 17β-estradiol (E₂) levels in a dose-dependent manner, and co-exposure to EE₂ and 20, 200 μg/L MPs significantly increased the ratios of E₂/testosterone (T). Moreover, EE₂ plus MPs exposure elevated the transcription levels of estrogen biomarker genes vitellogenin and choriogenin, and estrogen receptor (ERα and ERβ). Morphological analysis also showed that co-exposure to EE₂ and MPs induced more severe damage to the testes and livers, indicating that MPs increased the toxicity of EE₂. The actual EE₂ concentrations in the solution increased with the exposure concentrations of MPs, suggesting that MPs changed the fate and behavior of EE₂ in the seawater. These findings demonstrate that MPs could increase the estrogenic effects of EE₂ on marine fish, suggesting that the combined health risk of MPs and endocrine disrupting chemicals on marine organisms should be paid great attention.