Acute toxic effects of polyethylene microplastic on adult zebrafish

Exploring toxicological pathways of microplastics and nanoplastics: Insights from animal and cellular models

Microplastics (MPs) and nanoplastics (NPs) represent an emerging issue for human and animal health. This review critically examines in vitro and in vivo studies to elucidate their mechanisms of action and toxicological effects. Key objectives included: providing a comprehensive overview of MP-NPs studies in literature, assessing experimental conditions relative to real environmental scenarios, and identifying toxicological pathways at the molecular level. The findings revealed significant progress in understanding MP-NPs impacts. In particular, it has been observed the promotion of inflammation, oxidative stress, apoptosis, autophagy, and endoplasmic reticulum (ER) stress via specific signaling axes. Reproductive toxicity emerged as the primary research focus, particularly in male models, whereas effects on gastrointestinal, neurological, and cardiovascular systems were insufficiently studied, especially for the molecular pathways affected. Most studies disproportionately focused on polystyrene particles, neglecting other prevalent polymers such as polyethylene and polypropylene. Furthermore, reliance on synthetic microspheres and non-realistic experimental concentrations limits relevance to real-world conditions. Limited long-term exposure studies further constrain the understanding of MP-NPs persistence and risks. In view of this, future research should integrate environmentally relevant conditions for particles doses, size and composition, long-term exposure assessments, and advanced methodologies such as omics and computational modeling. In addition, therapeutic interventions targeting oxidative and ER stress, inflammation and apoptosis may be an excellent solution to mitigate MP-NPs toxicity. At the same time, a standardized global approach is needed to fully understand the risks posed by MP-NPs, attempting to safeguard public and environmental health.

Unveiling the toxicity of micro-nanoplastics: A systematic exploration of understanding environmental and health implications

The surge in plastic production has spurred a global crisis as plastic pollution intensifies, with microplastics and nanoplastics emerging as notable environmental threats. Due to their miniature size, these particles are ubiquitous across ecosystems and pose severe hazards as they are ingested and bioaccumulate within organisms. Although global plastic production has reached an alarming 400.3 MTs, recycling efforts remain limited, with only 18.5 MTs being recycled. Currently, out of the total plastic waste, 49.6 % is converted into energy, 27 % is recycled, and 23.5 % is recovered as material, indicating a need for better waste management practices to combat the escalating pollution levels. Research studies on micro-nanoplastics have primarily concentrated on their environmental presence and laboratory-based toxicity studies. This review critically examines the sources and detection methods for micro-nanoplastics, emphasising their toxicological effects and ecological impacts. Organisms like zebrafish and rats serve as key models for studying these particle's bioaccumulative potential, showcasing adverse effects that extend to DNA damage, oxidative stress, and cellular apoptosis. Studies reveal that micro-nanoplastics can permeate biological barriers, including the blood-brain barrier, neurological imbalance, cardiac, respiratory, and dermatological disorders. These health risks, particularly relevant for humans, underscore the urgency for broader, real-world studies beyond controlled laboratory conditions. Additionally, the review discusses innovative energy-harvesting technologies as sustainable alternatives for plastic waste utilisation, particularly valuable for energy-deficient regions. These strategies aim to simultaneously address energy demands and mitigate plastic waste. This approach aligns with global sustainability goals, providing a promising avenue for both pollution reduction and energy generation. The review calls for further research to enhance detection techniques, assess long-term environmental impacts, and explore sustainable solutions that integrate energy recovery with pollution mitigation, especially in regions most affected by both energy shortages and increased plastic waste.

Plastics and their derivatives are impacting animal ecophysiology: A review

Nowadays, plastic pollution is one of the most significant issues affecting the environment, posing a serious threat to marine biodiversity, ecosystem stability, and human health. Millions of tons of plastic waste enter the oceans every year, and the impact of microplastics (MPs) is much more worrying than visible contamination. The presence of these particles puts a strain on ecological dynamics, causing a significant impact on the health of marine organisms and affects humans due to the interconnection existing with the environment and the food chain. This review article examines the different ways in which MPs interact with marine life, the mechanisms that drive this pollution, and the cascading consequences for the health of organisms and ecosystems. It also highlights the critical links between plastic pollution and human health and underlines the urgency of a global and coordinated approach to address this growing crisis. Only through deeper understanding, increased awareness and collective action can we hope to mitigate the significant impacts of plastic pollution and ensure a sustainable future for oceans and our planet.

Microplastic pollution in urban drainage systems discharging into the alpine lakes of Como and Lugano, Italy

Urban stormwater outfalls and combined sewer overflows (CSOs) represent major sources of MPs pollution in receiving water bodies. This study presents an experimental and numerical investigation on MPs pollution from combined sewerage systems and wastewater treatment plants (WWTPs) discharging into two alpine lakes in northern Italy. Spatial and temporal trends of MPs concentrations and loads are investigated in the sewerage under dry-weather conditions and during representative rainfall events in the period September 2022-January 2023. The study allows the identification of key factors which contribute to higher MPs emissions. The acquired waste- and storm-water samples (2 L each) were dried and subjected to chemical oxidation with H2O2 before optical microscopy and infrared spectroscopy analysis. Dry-weather sewerage MPs concentration exhibits an average of 17.6 mg/L and standard deviation of 2.1 mg/L in dry-weather, with slightly higher values for the system with the lower per capita water supply. The daily mass of MPs directed to the treatment in the tourist season (i.e., September) is slightly above 50 % of the average daily mass characterizing the subsequent non-tourist months. Wet-weather MPs concentration is relatively lower (average of 12.9 mg/L, standard deviation of 2.0 mg/L), these values depending on the relative importance of the stormwater flow from the directly drained catchment compared to the flow contribution coming from the upstream pumping stations. The outcomes have implications for assessing spatial-temporal exposure of aquatic ecosystems to MPs pollution in urban areas, providing indications on effective management practices and control measures of urban drainage systems against environmental contamination.

Zebrafish and Drosophila as Model Systems for Studying the Impact of Microplastics and Nanoplastics ‐ A Systematic Review

Microplastics and nanoplastics (MNPs) are byproducts of plastics created to benefit humanity, but improper disposal and inadequate recycling have turned them into a global menace that we can no longer conceal. As they interact with all living organisms, including humans, their mechanism of interaction and their perilous impact must be meticulously investigated. To uncover the secrets of MNPs, there must be model systems that exist to interlink the two major scenarios: they must represent the environmental impact and be relevant to humans. Therefore, zebrafish and Drosophila are perfect to describe these two cases, as they are well studied and relatable to humans. In this review, 39% zebrafish studies reported higher mortality and hatching rates at greater MNP concentrations, severe oxidative stress as seen by raised malondialdehyde (MDA) levels, and reduced superoxide dismutase (SOD) activity. About 50% of studies showed severe neurotoxic behavior with drop of locomotor activity, suggesting neurotoxicity. MNPs have a significant impact on fertility rate of Drosophila. More than half of the studies revealed genotoxicity in Drosophila as observed by wing spot assays and modified genomic expressions associated with stress and detoxification processes. These findings emphasize the potential of MNPs to bioaccumulate, impair physiological systems, and cause oxidative and neurobehavioral damage. This study underscores the importance for thorough risk evaluations of MNPs and their environmental and health consequences.

Toxic effects of microplastics (polyethylene) exposure on acetylcholinesterase, stress indicators and immunity in Korean Bullhead, Pseudobagrus fulvidraco

Microplastics (MPs) in aquatic environments can have toxic effects on various organisms, including fish. This study exposed Pseudobagrus fulvidraco to polyethylene MPs at 0, 10 mg/L (approximately 9.50 ×108 particles/L), 20 mg/L (approximately 1.9 ×109 particles/L), 5000 mg/L (approximately 4.75 ×1011 particles/L), and 10,000 mg/L (approximately 9.50 ×1011 particles/L) concentrations for 96 h. At relatively lower MPs concentrations (0, 10 and 20 mg/L), no significant changes were observed in acetylcholinesterase (AChE) activity, stress indicators (heat shock protein 70 and cortisol), or immune responses (lysozyme activity and immunoglobulin M levels). However, at higher MPs concentrations (5000 and 10,000 mg/L), AChE activity was significantly inhibited, stress indicators were significantly increased, and immune responses were significantly decreased. Our results indicate that acute exposure of P. fulvidraco to MPs had negligible effects at concentrations below 20 mg/L, whereas significant toxic effects such as AChE activity inhibition, stress responses, and immune suppression were observed at concentrations above 5000 mg/L. Therefore, our study highlights the risks of severe MPs pollution on aquatic ecosystems and fish health.

Exploring the ecotoxicological impacts of microplastics on freshwater fish: A critical review

Microplastics (MPs) have become ubiquitous in the environment, prompting significant concern among ecotoxicologists due to their potential toxic effects. These particles originate from various sources, including the fragmentation of larger plastic debris (secondary microplastics) and consumer products such as liquid soaps, exfoliants, and cleaning agents. The widespread use of plastics, coupled with inadequate waste management, poses a growing threat to ecosystem health worldwide. MPs are plastic particles composed of high-molecular-weight polymers that exhibit biochemical stability. Plastics break down into MPs and even smaller nanoplastics through various degradation mechanisms, such as exposure to UV radiation from sunlight and other environmental factors. Due to their resemblance to certain types of zooplankton and food particles, MPs are often ingested by fish, entering their digestive systems. Once inside, they do not remain solely in the gut; rather, they infiltrate the fish's circulatory and lymphatic systems, eventually distributing throughout various tissues and organs. Microplastics have been found in fish gills, muscles, liver, heart, swim bladders, ovaries, spinal cords, and even brains. The presence of MPs in these organs has been linked to significant adverse effects, including reproductive, neurological, hormonal, and immune system disruptions. This toxicity extends beyond fish, as bioaccumulation and biomagnification of MPs affect other organisms as well, marking MPs as a major anthropogenic stressor that impacts ecosystems at multiple levels. Research indicates that nearly all aquatic environments globally are at risk of MP contamination. Laboratory and field studies highlight fish as particularly susceptible to MP ingestion, though freshwater species have been less extensively studied than marine counterparts. After exposure, fish may suffer various health issues, either directly from MPs or from their interaction with other contaminants. The broader environmental implications of these laboratory findings and the specific role of MPs in increasing fish exposure to harmful chemicals remain topics of ongoing debate. This review aims to contribute to ecotoxicological insights on fish contamination by MPs and outline areas for future investigation.

Biotransport and toxic effects of micro- and nanoplastics in fish model and their potential risk to humans: A review

The growing body of scientific evidence suggests that micro- and nanoplastics (MPs/NPs) pose a significant threat to aquatic ecosystems and human health. These particles can enter organisms through ingestion, inhalation, dermal contact, and trophic transfer. Exposure can directly affect multiple organs and systems (respiratory, digestive, neurological, reproductive, urinary, cardiovascular) and activate extensive intracellular signaling, inducing cytotoxicity involving mechanisms such as membrane disruption, extracellular polymer degradation, reactive oxygen species (ROS) production, DNA damage, cellular pore blockage, lysosomal instability, and mitochondrial depolarization. This review focuses on current research examining the in vivo and in vitro toxic effects of MPs/NPs on aquatic organisms, particularly fish, in relation to particulate toxicity aspects (such as particle transport mechanisms and structural modifications). Meanwhile, from the perspectives of the food chain and environmental factors, it emphasizes the comprehensive threats of MPs/NPs to human health in terms of both direct and indirect toxicity. Additionally, future research needs and strategies are discussed to aid in mitigating the potential risks of particulate plastics as carriers of toxic trace elements to human health.

Phenotypic and Gene Expression Alterations in Aquatic Organisms Exposed to Microplastics

The use of plastics, valued for its affordability, durability, and convenience, has grown significantly with the advancement of industry. Paradoxically, these very properties of plastics have also led to significant environmental challenges. Plastics are highly resistant to decomposition, resulting in their accumulation on land, where they eventually enter aquatic environments, due to natural processes or human activities. Among these plastics, microplastics, which are tiny plastic particles, are particularly concerning when they enter aquatic ecosystems, including rivers and seas. Their small size makes them easily ingestible by aquatic organisms, either by mistake or through natural feeding behaviors, which poses serious risks. Moreover, microplastics readily adsorb other pollutants present in aquatic environments, creating pollutant complexes that can have a synergistic impact, magnifying their harmful effects compared to microplastics or pollutants acting alone. As a result, extensive research has focused on understanding the effects of microplastics on aquatic organisms. Numerous studies have demonstrated that aquatic organisms exposed to microplastics, either alone or in combination with other pollutants, exhibit abnormal hatching, development, and growth. Additionally, many genes, particularly those associated with the antioxidant system, display abnormal expression patterns in these conditions. In this review, we examine these impacts, by discussing specific studies that explore changes in phenotype and gene expression in aquatic organisms exposed to microplastics, both independently and in combination with adsorbed pollutants.

Osmoregulation affects elimination of microplastics in fish in freshwater and marine environments

In recent decades, microplastics (MPs) have emerged as one of the biggest environmental challenges in aquatic environments. Ingestion and toxicity of MPs in seawater (SW) and freshwater (FW) fish have been studied extensively both in field and laboratory settings. However, the basic mechanism of how fish deal with MPs in SW and FW remains unclear, although physiological conditions of fish differ significantly in the two environments. In this study, using Javanese medaka (Oryzias javanicus), a euryhaline fish that adapts readily to both SW and FW, we investigated elimination of MPs in fish in SW and FW environments. We exposed O. javanicus larvae (21 days post-hatching) to 0.25 mg/L of fluorescent polystyrene microspheres (1 μm) for 24 hours and then conducted an elimination test for up to 5 days. Results showed that the gut retention time of MPs is longer in FW than in SW, indicating that MP elimination occurs more quickly in SW than in FW. However, higher numbers of MPs tended to be retained longer in SW larvae than FW larvae. Subsequently, using a fluorescent marker, gastrointestinal fluid was found to move more rapidly in the SW group. This finding indicates that water drinking accelerates gastrointestinal fluid movement, which moves MPs through the gut in SW larvae. Beside the difference in physiological conditions, MP elimination was faster when food was available, suggesting that feeding also affects MP elimination in fish. Internal factors such as body size and intestine length were also examined, but indicated no significant difference. Therefore, osmoregulation and feeding both influence MP elimination in fish.

Female zebrafish are more affected than males under polystyrene microplastics exposure

Microplastics are ubiquitous in freshwater and can be absorbed into fish skin and gills, accumulate in the gut, and be transported to other tissues, thus posing a risk to fish health. Further studies are needed, however, to investigate effects such as endocrine disruption and multi-tissue toxicity. In this study, zebrafish were exposed to polystyrene (PS) microplastics and health-related indicators were measured, including skin mucus, gut damage, oxidative stress, stable isotope composition and reproduction as well as an assessment of changes to metabolites using a metabolomics approach. Results showed that concentrations of PS microplastics were higher in gills than those in the gut. Minimal impact to immunoglobulin M level and lysozyme activity in mucus indicated, however, that microplastic toxicity primarily stemmed from ingestion rather than disruption of skin mucus immunity. Female zebrafish were more affected by PS microplastics. Gut microbiota dysbiosis was induced, especially in females. Significant alterations in pathways associated with lipid and energy metabolism were observed in the liver of female fish. PS microplastics also induced sex steroid hormone disorder and reduced female egg production, possibly linked to the alteration of gut microbiota and hepatic metabolism. Combined, these results highlight the gender-specific toxicity of PS microplastics to zebrafish health, potentially harming their population.

Microplastics in freshwater ecosystems: probabilistic environmental risk assessment and current knowledge in occurrence and ecotoxicological studies

Ecotoxicological studies involving microplastics (MPs) conducted on a laboratory scale may not always accurately mirror real environmental conditions (types, sizes, shapes, and concentrations of MPs). This review primarily focused on examining studies that investigated the prevalence of MPs in freshwater environments and accumulation in organisms worldwide, considering important factors such as morphology, particle size, and the specific polymer types involved. This review also encompassed ecotoxicological studies related to MPs, and ecological risk analyses were carried out based on the obtained ecotoxicological data. Based on the extensive dataset collected, we determined the hazardous concentration for 5% of the tested organisms (HC5) and estimated for the first time a predicted noneffect concentration (PNEC) value for two distinct types of MPs polymers: polystyrene (PS) and polyethylene (PE), based on the species sensitive distribution (SSD) curves obtained from nonobserved concentration (NOEC) values, with 0.003 mg L-1 for PS and 0.011 mg L-1 for PE. Furthermore, another PNEC value for 7 types of MPs (PE, PS, polyvinyl chloride, PA6, polyester, polyethylene terephthalate, and ethylene acrylic acid copolymer (EEA copolymer)) was calculated (0.0027 mg L-1 or 2.61 particles L-1). Subsequently, the risk quotient (RQ) was computed utilizing data obtained from the measured environmental concentrations of 18 places. An RQ value of 0.094 was obtained, inferring that MPs have a low-risk potential globally. However, when the RQ values were examined for each country separately, they exhibited significant variability (RQ = 22.06 in Malaysia and 0.000008 in Australia). Overall, this review provides a comprehensive overview of the current knowledge on MP abundance in freshwater environments, the associated ecotoxicological research to reinforce the outcomes derived from the risk analysis, and their accumulation in biota.

Impact of virgin and weathered microplastics on zebrafish: Bioaccumulation, developmental toxicity and molecular pathway disruptions

Microplastics (MPs) are ubiquitous environmental pollutants with significant ecological risks, particularly due to their potential for bioaccumulation and toxicity. This study examines the effects of virgin spherical MPs and environmentally weathered MPs, specifically polystyrene (PS) and polyethylene (PE), on zebrafish larvae to enhance the environmental relevance of the findings. MP concentrations used were 105-106 particles/L for the virgin MP group and 104 particles/L for the weathered MP group, reflecting levels commonly observed in natural environments. Weathered MPs were produced through mechanical grinding followed by one month of exposure to water and sunlight to simulate environmental aging. MP characterization was performed using advanced microscopy techniques, including Scanning Electron Microscopy (SEM) and Fourier-transform infrared spectroscopy (FTIR). The results indicated significantly higher mortality in the weathered MP group (80%) compared to the virgin MP group (20%). Zebrafish larvae ingested MPs and exhibited disruptions in key molecular pathways, including those involved in oxidative stress response, apoptosis, and DNA damage repair. Notably, this study is among the first to evaluate the impact of MPs on the complete homologous recombination (HR) and non-homologous end joining (NHEJ) DNA repair pathways. Our findings highlight the enhanced toxicity of weathered MPs and emphasize the importance of considering MP aging in toxicological assessments. These results contribute to a deeper understanding of MP pollution and provide valuable insights for the development of regulatory measures to protect aquatic ecosystems.

MAPK signaling pathway enhances tolerance of Mytilus galloprovincialis to co-exposure of sulfamethoxazole and polyethylene microplastics

Microplastics (MPs) and antibiotics often coexist in complex marine environments, yet their combined detrimental effects on marine organisms remain underexplored. This study evaluated the effects of polyethylene microplastics (PE, 200 μg/L) and sulfamethoxazole (SMX, 50 μg/L), both individually and in combination, on Mytilus galloprovincialis. The exposure lasted 6 days, followed by a 6-day recovery period. Bioaccumulation, DNA damage, pollutants transport/metabolism related responses and responding alterations of mitogen-activated protein kinase (MAPK) signaling pathway were detected in gills and digestive glands. Bioaccumulation of SMX/PE in mussels occurred in a tissue-specific manner, co-exposure altered SMX contents in investigated tissues. Co-exposure did not induce extra DNA damage, elevated DNA damage was alleviated during the recovery period in all treated groups. The exposure of SMX/PE exerted different alterations in pollutants transport/metabolism related responses, characterized by multixenobiotic resistance and relative expression of key genes (cytochrome P450 monooxygenase, glutathione S-transferase, ATP-binding cassette transporters). Key molecules (p38 MAPK, c-jun N-terminal kinase, extracellular regulated protein kinase, nuclear factor-κB and tumor protein p53) in MAPK signaling pathway were activated at transcriptional and translational levels after SMX/PE and co-exposure. Co-regulation between MAPK members and pollutants transport/metabolism related factors was revealed, suggesting MAPK signaling pathway served as a regulating hub in exposed mussels to conquer SMX/PE stress. Overall, this study provides new insights on SMX/PE induced health risks in marine mussels and potential mechanism through MAPK cascades regulation.

Towards microplastic hotspots detection: A comparative analysis of in-situ sampling and sea surface currents derived by HF radars

Marine plastic pollution is a global issue affecting ecosystems and various aspects of human life. The scientific community is exploring new monitoring and containment approaches. Because in-situ sampling campaigns are time and resource demanding, there is a focus on integrating different approaches for marine litter monitoring. Data of two in-situ surveys (using a manta net) were compared to sea surface currents data and derived products with the aim to find a proxy variable of the plastic occurrence. Sea surface currents data were provided by the CALYPSO HF network (operating in the Sicily Channel since 2012). Notably, the occurrence of fragment items is inversely correlated with the total kinetic energy (r2 ~ 0.85). This result was confirmed by a Lagrangian tracking model considering the deployment of virtual drifters around each in-situ measurement point. The proposed method applied to a wider domain using Copernicus Marine Service (CMS) data revealed that high plastic accumulation areas could be located at the centre of eddies often occurring in the winter period. However, uncertainties arise by the moderate-low correlation found between HF CALYPSO and CMS sea current data.

Adolescent exposure to tris(1,3-dichloro-2-propyl) phosphate (TCPP) induces reproductive toxicity in zebrafish through hypothalamic-pituitary-gonadal axis disruption

Tris(1,3-dichloro-2-propyl) phosphate (TCPP), a prevalent organophosphorus flame retardant in aquatic environments, has raised significant concerns regarding its ecological risks. This study aims to explore the impacts of TCPP on the reproductive functions of zebrafish and delineate its gender-related toxic mechanisms. By assessing the effects on zebrafish of 10 mg/L TCPP exposure from 30 to 120 days post-fertilization (dpf), we thoroughly evaluated the reproductive capability and endocrine system alterations. Our findings indicated that TCPP exposure disrupted gender differentiation in zebrafish and markedly impaired their reproductive capacity, resulting in decreased egg laying and offspring development quality. Histological analyses of gonadal tissues showed an abnormal increase in immature oocytes in females and a reduction in mature sperm count and spermatogonial structure integrity in males, collectively leading to compromised embryo quality. Additionally, molecular docking results indicated that TCPP showed a strong affinity for estrogen receptors, and TCPP-treated zebrafish exhibited imbalanced sex hormones and increased estrogen receptor expression. Alterations in genes associated with the hypothalamic-pituitary-gonadal (HPG) axis and activation of the steroidogenesis pathway suggested that TCPP targets the HPG axis to regulate sex hormone homeostasis. Tamoxifen (TAM), as a competitive inhibitor of estrogen, exhibited a biphasic effect, as evidenced by the counteraction of TCPP-induced effects in both male and female zebrafish after TAM addition. Overall, our study underscored the gender-dependent reproductive toxicity of TCPP exposure in zebrafish, characterized by diminished reproductive capacity and hormonal disturbances, likely due to interference in the HPG axis and steroidogenesis pathways. These findings emphasize the critical need to consider gender differences in chemical risk assessments for ecosystems and highlight the importance of understanding the mechanisms underlying the effects of chemical pollutants on the reproductive health of aquatic species.

Biodistribution of synthesized polyethylene terephthalate fibers in adult zebrafish, their sex hormone disruption effect, and mitigation using natural organic matter

Although polyethylene terephthalate (PET) fibers are a representative form of plastic pollutants, studies on their toxicity are currently limited compared to other plastic types. Moreover, the effect of natural organic matter (NOM) on their toxicity has not been investigated. In this study, female and male adult zebrafish were exposed to synthesized PET fibers at concentrations of 0.1, 1, 10, and 100 mg/L in the presence and absence of 10 mg/L of NOM for 10 d. Bioaccumulation of PET fibers in zebrafish intestine, liver, and gills was identified and expression levels of reactive oxygen species (ROS) generation, sex hormones, and oxidative stress and sex hormone-related genes were measured. In addition, the developmental stages of gonadal cells were examined through histological analysis. We found that PET fibers bioaccumulated in the intestine and liver of zebrafish. ROS generation significantly increased at 100 mg/L of PET fibers, the expression of oxidative stress-related genes decreased in female and increased in male zebrafish. Exposure to 100 mg/L of PET fibers did not affect 17-beta estradiol, but significantly decreased the testosterone levels in male zebrafish. Sex hormone-related genes significantly decreased in both female and male zebrafish, except for androgen receptor in female zebrafish. However, these changes were exacerbated by the removal of NOM, suggesting a protective effect of NOM against PET fibers toxicity. We demonstrated that the accumulated PET fibers may lead to oxidative stress and sex hormone alteration, and disrupt the development of gonadal cells. Additionally, the NOM coating did not alter bioaccumulation considerably, but mitigated the adverse effects at the hormone level in PET fiber-exposed zebrafish. Thus, this study provides a basis for further research on the toxicity assessment of PET fibers and interactions between NOM and PET fiber-related toxicity.

Exposure to polystyrene microplastics reduces sociality and brain oxytocin levels through the gut-brain axis in mice

The rising global prevalence of microplastics (MPs) has highlighted their diverse toxicological effects. The oxytocin (OT) system in mammals, deeply intertwined with social behaviors, is recognized to be vulnerable to environmental stressors. We hypothesized that MP exposure might disrupt this system, a topic not extensively studied. We investigated the effects of MPs on behavioral neuroendocrinology via the gut-brain axis by exposing adolescent male C57BL/6 mice to varied sizes (5 μm and 50 μm) and concentrations (100 μg/L and 1000 μg/L) of polystyrene MPs over 10 weeks. The results demonstrated that exposure to 50 μm MPs significantly reduced colonic mucin production and induced substantial alterations in gut microbiota. Notably, the 50 μm-100 μg/L group showed a significant reduction in OT content within the medial prefrontal cortex and associated deficits in sociality, along with damage to the blood-brain barrier. Importantly, blocking the vagal pathway ameliorated these behavioral impairments, emphasizing the pivotal role of the gut-brain axis in mediating neurobehavioral outcomes. Our findings confirm the toxicity of MPs on sociality and the corresponding neuroendocrine systems, shedding light on the potential hazards and adverse effects of environmental MPs exposure on social behavior and neuroendocrine frameworks in social mammals, including humans.

The impacts of microplastics on zebrafish behavior depend on initial personality state

Microplastic pollution is associated with inflammation, gut dysbiosis and behavioral changes in fish. Fish have distinct personality traits but the role of personality in behavioral toxicology is rarely considered. We classified zebrafish on four behavioral axes: boldness, anxiety, sociability and exploration tendency then exposed them to low- or high- concentrations of two types of polyethylene microplastics (low- and high-density) for 28 days. Behaviors, antioxidant enzymes (catalase and superoxide dismutase), and gut microbiome were then measured. There were direct effects of microplastics on boldness, anxiety and sociability. However, fish retained their initial behavioral tendencies. Exposure to all microplastic treatments reduced average swimming speed and decreased the time spent motionless. Microplastic exposure did not affect antioxidant enzymes but did cause significant changes in the composition of the gut microbiome. This study demonstrates that environmentally realistic concentrations of microplastics can alter fish behavior, but much of the variance in response can be explained by personality.

Ingestion of polyethylene terephthalate microplastic water contaminants by Xenopus laevis tadpoles negatively affects their resistance to ranavirus infection and antiviral immunity

Small plastic debris (0.1 μm-5 mm) or microplastics (MPs) have become major pollutants of aquatic ecosystems worldwide and studies suggest that MPs exposure can pose serious threats to human and wildlife health. However, to date the potential biological impacts of MPs accumulating in low amount in tissues during early life remains unclear. Here, for a more realistic assessment, we have used environmentally representative, mildly weathered, polyethylene terephthalate microplastics (PET MPs), cryomilled (1-100 μm) and fluorescently labelled. We leveraged the amphibian Xenopus laevis tadpoles as an animal model to define the biodistribution of PET MPs and determine whether exposure to PET MPs induce perturbations of antiviral immunity. Exposure to PET MPs for 1-14 days resulted in detectable PET MPs biodistribution in intestine, gills, liver, and kidney as determined by fluorescence microscopy on whole mount tissues. PET MPs accumulation rate in tissues was further evaluated via a novel in situ enzymatic digestion and subsequent filtration using silicon nanomembranes, which shows that PET MPs rapidly accumulate in tadpole intestine, liver and kidneys and persist over a week. Longer exposure (1 month) of tadpoles to relatively low concentration of PET MPs (25 μg/ml) significantly increased susceptibility to viral infection and altered innate antiviral immunity without inducing overt inflammation. This study provides evidence that exposure to MPs negatively impact immune defenses of aquatic vertebrates.

A systematic review on the impact of micro-nanoplastics on human health: Potential modulation of epigenetic mechanisms and identification of biomarkers

Epigenetic-mediated modifications, induced by adverse environmental conditions, significantly alter an organism's physiological mechanisms. Even after elimination of the stimulus, these epigenetic modifications can be inherited through mitosis, thereby triggering transgenerational epigenetics. Plastics, with their versatile properties, are indispensable in various aspects of daily life. However, due to mismanagement, plastics have become so ubiquitous in the environment that no ecosystem on Earth is free from micro-nanoplastics (MNPs). This situation has raised profound concerns regarding their potential impact on human health. Recently, both in vivo animal and in vitro human cellular models have shown the potential to identify the harmful effects of MNPs at the genome level. The emerging epigenetic impact of MNP exposure is characterized by short-term alterations in chromatin remodelling and miRNA modulation. However, to understand long-term epigenetic changes and potential transgenerational effects, substantial and more environmentally realistic exposure studies are needed. In the current review, the intricate epigenetic responses, including the NHL-2-EKL-1, NDK-1-KSR1/2, and WRT-3-ASP-2 cascades, wnt-signalling, and TGF- β signalling, established in model organisms such as C. elegans, mice, and human cell lines upon exposure to MNPs, were systematically examined. This comprehensive analysis aimed to predict human pathways by identifying human homologs using databases and algorithms. We are confident that various parallel miRNA pathways, specifically the KSR-ERK-MAPK pathway, FOXO-Insulin cascade, and GPX3-HIF-α in humans, may be influenced by MNP exposure. This influence may lead to disruptions in key metabolic and immune pathways, including glucose balance, apoptosis, cell proliferation, and angiogenesis. Therefore, we believe that these genes and pathways could serve as potential biomarkers for future studies. Additionally, this review emphasizes the origin, dispersion, and distribution of plastics, providing valuable insights into the complex relationship between plastics and human health while elaborating on the epigenetic impacts.

Multiomics analysis reveals a substantial decrease in nanoplastics uptake and associated impacts by nano zinc oxide in fragrant rice (Oryza sativa L.)

Nanoplastics (NPs) have emerged as global environmental pollutants with concerning implications for sustainable agriculture. Understanding the underlying mechanisms of NPs toxicity and devising strategies to mitigate their impact is crucial for crop growth and development. Here, we investigated the nanoparticles of zinc oxide (nZnO) to mitigate the adverse effects of 80 nm NPs on fragrant rice. Our results showed that optimized nZnO (25 mg L-1) concentration rescued root length and structural deficits by improving oxidative stress response, antioxidant defense mechanism and balanced nutrient levels, compared to seedlings subjected only to NPs stress (50 mg L-1). Consequently, microscopy observations, Zeta potential and Fourier transform infrared (FTIR) results revealed that NPs were mainly accumulated on the initiation joints of secondary roots and between cortical cells that blocks the nutrients uptake, while the supplementation of nZnO led to the formation of aggregates with NPs, which effectively impedes the uptake of NPs by the roots of fragrant rice. Transcriptomic analysis identified a total of 3973, 3513 and 3380 differentially expressed genes (DEGs) in response to NPs, nZnO and NPs+nZnO, respectively, compared to the control. Moreover, DEGs were significantly enriched in multiple pathways including biosynthesis of secondary metabolite, phenylpropanoid biosynthesis, amino sugar and nucleotide sugar metabolism, carotenoid biosynthesis, plant-pathogen interactions, MAPK signaling pathway, starch and sucrose metabolism, and plant hormone signal transduction. These pathways could play a significant role in alleviating NPs toxicity and restoring fragrant rice roots. Furthermore, metabolomic analysis demonstrated that nZnO application restored 2-acetyl-1-pyrroline (2-AP) pathways genes expression, enzymatic activities, and the content of essential precursors related to 2-AP biosynthesis under NPs toxicity, which ultimately led to the restoration of 2-AP content in the leaves. In conclusion, this study shows that optimized nZnO application effectively alleviates NPs toxic effects and restores both root structure and aroma production in fragrant rice leaves. This research offers a sustainable and practical strategy to enhance crop production under NPs toxicity while emphasizing the pivotal role of essential micronutrient nanomaterials in agriculture.

Female zebrafish (Danio rerio) exposure to polystyrene nanoplastics induces reproductive toxicity in mother and their offspring

Nanoplastics (NPs) have been commonly detected in aquatic ecosystems, and their negative effects on aquatic organisms have raised concerns in the scientific community and general public. The acute toxicity, neurotoxicity, and metabolic toxicity induced by NPs on fishes have been reported by many studies, although less attention has been focused on how mother exposed to NPs affected their offspring in aquatic organisms. Here, female zebrafish (F0) were exposed to 0, 200 and 2000 μg/L polystyrene nanoplastics (PS-NPs) for 42 d, with their offspring (F1) reared in clear water until sexual maturity. The results showed that PS-NPs were detected in various organs of F0 and F1. PS-NPs exposure significantly decreased gonadal 17-estradiol (E2), while increasing testosterone (T) contents. Lower levels of cyp19a1a, lhr and erα expressions in the 2000 μg/L group were consistent with a reduced number of mature oocytes (MO), but an increase in perinucleolar oocytes (PO). Interestingly, the expression of vtg was only up-regulated by 200 μg/L PS-NPs. After exposure, the egg production was dramatically reduced, but the hatching rate and heartbeat of F1 embryos from treated females were significantly higher than those observed in females from the control group. Maternal PS-NPs exposure significantly decreased the E2 and T levels in F1 adults, while PS-NPs exposure significantly up-regulated the sox9a but down-regulated the foxl2a in F1 larvae of 30 days post fertilization (dpf). This study showed that PS-NPs caused reproductive toxicity by changing the hypothalamic-pituitary-gonadal (HPG) axis-related genes, impairing the reproductive capacity of female zebrafish, affecting the development and disrupting the endocrine function of F1. These results suggested that PS-NPs had adverse effects on fish reproductive system both in the directly exposed generation and in their unexposed offspring.

Detection of microplastics in zebrafish housing systems: Can microplastic background contamination affect the final results of microplastic-related toxicological tests?

Concentrations of microplastics (MPs) were determined in three commonly used zebrafish housing systems to see if their levels could affect the final results of laboratory microplastic-related toxicology tests. MPs have received notable attention in the last few years, and their toxicology tests have also come to the fore. Zebrafish (Danio rerio), kept in fish housing systems, are widely used as models for MPs studies. Most of these systems contain a significant number of parts made of different polymers. As usage and amortization can erode these parts, MPs might appear in the keeping water or the fish body, which may represent a background load and possibly influence the results of microplastic-related toxicological tests. To take representative water samples from systems, two in-situ filtration techniques, a newly developed peristaltic pump-, and a jet pump-driven method were applied. The collected MP particles were analyzed with a Fourier-transform infrared microscope (detection limit 50 μm), and their possible origin was also investigated. The newly developed technique was more sufficient for sampling as it had a higher MPs recovery, especially in the smaller size range. Polyester, polyethylene and polypropylene were the most frequently detected polymers in the examined fish housing systems, the highest detected concentration was 0.31±0.12 particles/liter (0.22±0.16 μg/liter). These values are negligible compared to the literature data reporting enormously high applied MPs concentrations (104 - 2.21 × 108 particles/liter) during toxicology tests. The results also show that some detected MPs did not originate from the systems, their origin was presumed to be external.

Genotoxicity and metabolic changes induced via ingestion of virgin and UV-aged polyethylene microplastics by the freshwater fish Perca fluviatilis

The present study aims to compare and assess the toxicity induced by aged (irradiated with ultraviolet radiation for 120 days) polyethylene microplastics (PE-MPs) in comparison to virgin (non-irradiated) ones, after feeding the freshwater fish Perca fluviatilis. To this end, MPs mediated genotoxicity was assessed by the investigation of micronucleus nuclear abnormalities frequency in fish blood, and the degree of DNA damage in the liver and muscle tissues, while metabolic alterations were also recorded in both tissues. Results showed that both virgin and aged PE-MPs induced signaling pathways leading to DNA damage and nuclear abnormalities, as well as metabolites changes in all tissues studied. Metabolic changes revealed that the metabolism of nucleic acids, energy, amino acids, and neurotransmitters was more disrupted in the liver and by aged PE-MPs compared to muscles. Fish fed with aged PE-MPs exhibited greater DNA damage, while blood cells of fish fed with virgin PE-MPs seemed to be more vulnerable to nuclear abnormalities in relation to those fed with aged PE-MPs. Moreover, aged PE-MPs induced more acute overall effects on the metabolic profiles of fish tissues, and initiated stronger stress responses, inflammation, and cellular damages in fish tissues in relation to virgin ones. Characterization of both virgin and aged MPs revealed that the latter exhibited lower crystallinity and melting point, more irregular shapes and higher moiety of oxygen and carbonyl groups, which could be attributed for their observed higher toxicity. The research outcomes provide significant insights for advancing toxicological investigations in this field.

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.

Advances of microplastics ingestion on the morphological and behavioral conditions of model zebrafish: A review

Concerns have been conveyed regarding the availability and hazards of microplastics (MPs) in aquatic biota due to their widespread presence in aquatic habitats. Zebrafish (Danio rerio) are widely used as a model organism to study the adverse impacts of MPs due to their several compelling advantages, such as their small size, ease of breeding, inexpensive maintenance, short life cycle, year-round spawning, high fecundity, fewer legal restrictions, and genetic resemblances to humans. Exposure of organisms to MPs produces physical and chemical toxic effects, including abnormal behavior, oxidative stress, neurotoxicity, genotoxicity, immune toxicity, reproductive imbalance, and histopathological effects. But the severity of the effects is size and concentration-dependent. It has been demonstrated that smaller particles could reach the gut and liver, while larger particles are only confined to the gill, the digestive tract of adult zebrafish. This thorough review encapsulates the current body of literature concerning research on MPs in zebrafish and demonstrates an overview of MPs size and concentration effects on the physiological, morphological, and behavioral characteristics of zebrafish. Finding gaps in the literature paves the way for further investigation.

Effect of ultra-high-density polyethylene microplastic on the sorption and biodegradation of organic micropollutants

Microplastics and organic micropollutants are two emerging contaminants that interact with each other in environmental and engineered systems. Sorption of organic micropollutants, such as pharmaceuticals, pesticides and industrial compounds, to microplastics can modify their bioavailability and biodegradation. The present study investigated the capacity of ultra-high density polyethylene particles (125 µm in diameter), before and after aging, to sorb 21 organic micropollutants at different environmentally relevant concentration. Furthermore, the biodegradation of these organic micropollutants by a biofilm microbial community growing on the microplastic surface was compared with the biodegradation by a microbial community originating from activated sludge. Among all tested organic micropollutants, propranolol (70%), trimethoprim (25%) and sotalol (15%) were sorbed in the presence of polyethylene particles. Growth of a biofilm on the polyethylene particles had a beneficial effect on the sorption of bromoxynil, caffeine and chloridazon and on the biodegradation of irbesartan, atenolol and benzotriazole. On the other hand, the biofilm limited the sorption of trimethoprim, propranolol, sotalol and benzotriazole and the biodegradation of 2,4-D. These results showed that ultra-high density polyethylene particles can affect both in a positive and negative way for the abiotic and biotic removal of organic micropollutants in wastewater. This project highlights the need for further investigation regarding the interaction between microplastics and organic micropollutants in the aquatic environment.

Neurotoxicity of Some Environmental Pollutants to Zebrafish

The aquatic environment encompasses a wide variety of pollutants, from plastics to drug residues, pesticides, food compounds, and other food by-products, and improper disposal of waste is the main cause of the accumulation of toxic substances in water. Monitoring, assessing, and attempting to control the effects of contaminants in the aquatic environment are necessary and essential to protect the environment and thus human and animal health, and the study of aquatic ecotoxicology has become topical. In this respect, zebrafish are used as model organisms to study the bioaccumulation, toxicity, and influence of environmental pollutants due to their structural, functional, and material advantages. There are many similarities between the metabolism and physiological structures of zebrafish and humans, and the nervous system structure, blood-brain barrier function, and social behavior of zebrafish are characteristics that make them an ideal animal model for studying neurotoxicity. The aim of the study was to highlight the neurotoxicity of nanoplastics, microplastics, fipronil, deltamethrin, and rotenone and to highlight the main behavioral, histological, and oxidative status changes produced in zebrafish exposed to them.

Neurotoxicities induced by micro/nanoplastics: A review focusing on the risks of neurological diseases

Pollution of micro/nano-plastics (MPs/NPs) is ubiquitously prevalent in the environment, leading to an unavoidable exposure of the human body. Despite the protection of the blood-brain barrier, MPs/NPs can be transferred and accumulated in the brain, which subsequently exert negative effects on the brain. Nevertheless, the potential neurodevelopmental and/or neurodegenerative risks of MPs/NPs remain largely unexplored. In this review, we provide a systematic overview of recent studies related to the neurotoxicity of MPs/NPs. It covers the environmental hazards and human exposure pathways, translocation and distribution into the brain, the neurotoxic effects, and the possible mechanisms of environmental MPs/NPs. MPs/NPs are widely found in different environment matrices, including air, water, soil, and human food. Ambient MPs/NPs can enter the human body by ingestion, inhalation and dermal contact, then be transferred into the brain via the blood circulation and nerve pathways. When MPs/NPs are present in the brain, they can initiate a series of molecular or cellular reactions that may harm the blood-brain barrier, cause oxidative stress, trigger inflammatory responses, affect acetylcholinesterase activity, lead to mitochondrial dysfunction, and impair autophagy. This can result in abnormal protein folding, loss of neurons, disruptions in neurotransmitters, and unusual behaviours, ultimately contributing to the initiation and progression of neurodegenerative changes and neurodevelopmental abnormalities. Key challenges and further research directions are also proposed in this review as more studies are needed to focus on the potential neurotoxicity of MPs/NPs under realistic conditions.

Microplastic pollution in the Chapora River, Goa, Southwest India: spatial distribution and risk assessment

The amount of information available on the microplastic (MP) contamination in Goa's riverine water systems is currently limited. The abundance, size, colour, and polymer composition of microplastics in Chapora River surface water were investigated in this study. MPs in Chapora River surface water ranged from 0.1 particles/L (station 13) to 0.47 particles/L (station 5). The mean (± standard deviation) MP concentration was 0.25 (± 0.13) particles/L. Fibre was the dominant shape (77.15%), followed by fragments (12.36%), films (9.36%), and foam (1.12%). Most MPs were found in the 0.1-0.3 mm size range, then in the 0.3-1 mm and 1-5 mm. The dominant type of polymer studied was polyethylene terephthalate (PET; 46%), followed by high-density polyethylene (HDPE; 14%), polypropylene (PP; 5%), and polystyrene (PS; 1%). The risk assessment study indicated high risk with respect to PHI, while PLI shows low risk in the area. The source of MPs was mostly anthropogenic in nature in the region. When compared with other tropical rivers, MP pollution was relatively lower in the Chapora River. Nevertheless, the baseline data will help the local administration take mitigation measures to reduce the impact of MP pollution in the region.

Leakage of plastics and other debris from landfills to a highly protected lake by wintering gulls

GENERAL CONTEXT

Gulls ingest plastic and other litter while foraging in open landfills, because organic matter is mixed with other debris. Therefore, gulls are potential biovectors of plastic pollution into natural habitats, especially when they concentrate in wetlands for roosting.

NOVELTY

We quantified, for the first time, the flow of plastic and other anthropogenic debris from open landfills to a natural lake via the movement of gulls. We focused on Fuente de Piedra, an inland closed-basin lake in Spain that is internationally important for biodiversity.

METHODOLOGY

In 2022, we sampled gull pellets regurgitated in the lake by lesser black-backed gulls Larus fuscus that feed on landfills, as well as their faeces, then characterized and quantified debris particles of ≥0.5 mm. By combining GPS and census data from 2010 to 2022, together with plastic quantification based on FTIR-ATR analysis, we estimated the average annual deposition of plastic and other debris by the wintering gull population into the lake.

MAIN RESULTS

86 % of pellets contained plastics, and 94 % contained other debris such as glass and textiles. Polyethylene (54 %), polypropylene (11.5 %) and polystyrene (11.5 %) were the main plastic polymers. An estimated annual mean of 400 kg of plastics were moved by gulls into the lake. Only 1 % of plastic mass was imported in faeces.

DISCUSSION

Incorporating the biovectoring role of birds can provide a more holistic view of the plastic cycle and waste management. Biovectoring is predictable in sites worldwide where gulls and other waterbirds feed in landfills and roost in wetlands. We discuss bird deterrence and other ways of mitigating debris leakage into aquatic ecosystems.

Assessment of dietary polyvinylchloride, polypropylene and polyethylene terephthalate exposure in Nile tilapia, Oreochromis niloticus: Bioaccumulation, and effects on behaviour, growth, hematology and histology

Microplastics (MPs) have been recognized as emerging aquatic pollutants receiving major concern due to their detrimental effects on aquatic life. Nile Tilapia, Oreochromis niloticus is a model species considered in toxicological studies to address the effects of pollutants in freshwater animals. However, comprehensive knowledge comparing the impacts on fish across various MPs polymers is scarce. Therefore, the overarching aim of the current study was to examine the bioconcentration of MPs polymers: polyvinylchloride (PVC), polypropylene (PP), and polyethylene terephthalate (PET), and their toxic effects on growth, and behavioral responses, hematology, and histology of gills, liver, and intestine in O. niloticus. Fishes were subjected to a 21-day dietary exposure to MPs by assigning them into six treatment groups: T1 (4% of PVC), T2 (4% of PP), T3 (4% of PET), T4 (8% of PVC), T5 (8% of PP), T6 (8% of PET), and control (0% of MPs), to assess the effects on fish across the polymers and dosage. Results showed several abnormalities in anatomical and behavioral parameters, lower growth, and high mortality in MPs-exposed fish, indicating a dose-dependent relationship. The elevated dosage of polymers raised the bioavailability of PVC, PP, and PET in gills and gut tissues. Noteworthy erythrocyte degeneration referred to cytotoxicity and stress imposed by MPs, whereas the alterations in hematological parameters were possibly due to blood cell damage, also indicating mechanisms of defense against MPs toxicity. Histopathological changes in the gills, liver, and intestine confirmed the degree of toxicity and associated dysfunctions in fish. A higher sensitivity of O. niloticus to PET-MPs compared to other polymers is likely due to its chemical properties and species-specific morphological and physiological characteristics. Overall, the present study reveals valuable insights into the emerging threat of MPs toxicity in freshwater species, which could be supportive of future toxicological research.

Incidence of microplastic translocation in freshwater fish eggs

The issue of microplastic contamination in seafood is progressively recognised as a significant global issue. This study presents novel findings regarding the detection of microplastics within the eggs of commercially available fish intended for consumption by humans. Eggs of Ompok bimaculatus, Heteropneustes fossilis, Mystus vittatus and Anabas testudineus collected from the Periyar River, Kerala, India were subjected to analysis for the potential presence of microplastics. Out of the 91 fishes (containing eggs) examined, microplastics were observed in the eggs of 2 species, i.e., Ompok bimaculatus and Mystus vittatus. The polymers recorded were polyethylene and polypropylene. Fish eggs are commonly consumed by humans and are highly esteemed as a delectable food. Considering the widespread consumption of fish eggs as a delicacy among humans, there exists a potential route for human exposure to microplastics, which raises concerns regarding public health.

Distribution and risk assessment of microplastic pollution in a rural river system near a wastewater treatment plant, hydro-dam, and river confluence

Rivers are the natural drainage system, transporting anthropogenic wastes and pollution, including microplastics (plastic < 5 mm). In a riverine system, microplastics can enter from different sources, and have spatial variance in concentration, physical and chemical properties, and imposed risk to the ecosystem. This pilot study presents an examination of microplastics in water and sediment samples using a single sample collection from the rural Raquette River, NY to evaluate a hypothesis that distinct locations of the river, such as downstream of a wastewater treatment plant, upstream of a hydro-dam, and river confluence, may be locations of higher microplastics concentration. In general, our results revealed the presence of high microplastic concentrations downstream of the wastewater treatment plant (in sediments), upstream of the hydro dam (both water and sediment), and in the river confluence (water sample), compared to other study sites. Moreover, the risk assessment indicates that even in a rural river with most of its drainage basin comprising forested and agricultural land, water, and sediment samples at all three locations are polluted with microplastics (pollution load index, PLI > 1; PLIzone = 1.87 and 1.68 for water and sediment samples respectively), with risk categories between Levels I and IV ("minor" to "danger"). Overall, the river stands in a "considerable" risk category (PRIzone = 134 and 113 for water and sediment samples respectively). The overall objective of this pilot study was to evaluate our hypothesis and advance our understanding of microplastic dynamics in rural river systems, elucidating their introduction from a point source (wastewater treatment plant), transit through an impediment (hydro-dam), and release into a vital transboundary river (confluence of Raquette-St. Lawrence Rivers).

Co-exposure to polystyrene microplastics and cypermethrin enhanced the effects on hepatic phospholipid metabolism and gut microbes in adult zebrafish

Microplastics (MPs) can absorb environmental pollutants from the aquatic environment to cause mixed toxicity, which has received widespread attention. However, studies on the joint effects of MPs and insecticides are limited. As one of the most widely used pyrethroids, there was a large amount of residual cypermethrin (CYP) in water due to insufficient decomposition. Here, adult female zebrafish were exposed to MPs, CYP, and their mixtures for 21 days, respectively. After exposures, the MPs and CYP caused tissue damage to the liver. Hepatic triglyceride (TG) level increased significantly after MPs + CYP exposure, and the expression of genes about glycolipids metabolism was significantly altered. Furthermore, metabolome results suggested that MPs + CYP exposure resulted in increased content of some glycerophospholipid, affecting phospholipid metabolism-related pathways. In addition, through 16 s rDNA sequencing, it was found that MPs + CYP led to significant changes in the proportion of dominant phyla. Interestingly, Cetobacterium which increased in CYP and the co-exposure group was positively correlated with most lipid metabolites. Our results suggested that co-exposure to MPs and CYP enhanced the disturbances in hepatic phospholipid metabolism by affecting the gut microbial composition, while these changes were not observed in separate treatment groups. These results emphasized the importance of studying the joint toxicity of MPs and insecticides.

Integrating aggregate exposure pathway and adverse outcome pathway for micro/nanoplastics: A review on exposure, toxicokinetics, and toxicity studies

Micro/nanoplastics (MNPs) have emerged as a significant environmental concern due to their widespread distribution and potential adverse effects on human health and the environment. In this study, to integrate exposure and toxicity pathways of MNPs, a comprehensive review of the occurrence, toxicokinetics (absorption, distribution, and excretion [ADE]), and toxicity of MNPs were investigated using the aggregate exposure pathway (AEP) and adverse outcome pathway (AOP) frameworks. Eighty-five papers were selected: 34 papers were on detecting MNPs in environmental samples, 38 papers were on the ADE of MNPs in humans and fish, and 36 papers were related to MNPs toxicity using experimental models. This review not only summarizes individual studies but also presents a preliminary AEP-AOP framework. This framework offers a comprehensive overview of pathways, enabling a clearer visualization of intricate processes spanning from environmental media, absorption, distribution, and molecular effects to adverse outcomes. Overall, this review emphasizes the importance of integrating exposure and toxicity pathways of MNPs by utilizing AEP-AOP to comprehensively understand their impacts on human and ecological organisms. The findings contribute to highlighting the need for further research to fill the existing knowledge gaps in this field and the development of more effective strategies for the safe management of MNPs.

Toxicological Response of Zebrafish Exposed to Cocktails of Polymeric Materials and Valproic Acid

Microplastic pollution represents an emerging problem of great interest in the public domain in the last decade; in addition, it overlaps with another delicate problem—pollution with pharmaceutical products that can have negative effects on the environment and people, even in small amounts. The main purpose of this study was to assess the biochemical and behavioral effects of exposure of adult zebrafish (Danio rerio) to polyethylene (PE), polypropylene (PP) and valproic acid (VPA), respectively to their mixtures—possible situations in natural aquatic environments. In terms of behavioral responses, sociability appears to be more impaired in the PP group after 5 days of exposure. The mechanisms affected are more those of swimming performance than of sociability. Even more, VPA increases presence in the arm with conspecifics but decreases mobility and locomotion, indicating a possible anxiety mechanism. The mixtures decrease the aggressiveness, especially in the case of the PE+VPA group, where it reaches a super low level compared to the control, which could endanger the species in nature. Regarding the anxiogenic effect, PP and PE act differently: if PE has an anxiogenic effect, on the opposite side is the PP group, which shows a bolder and more agitated behavior. All four variants showed behavioral changes indicative of toxicity from the first dose.

Chronic exposure to low concentrations of microplastics causing gut tissue damage but non-significant changes in the microbiota of marine medaka larvae (Oryzias melastigma)

Microplastics (MPs) have become a popular research topic due to their potential ramifications on aquatic organisms. To evaluate the ecotoxicological impacts of chronic exposure to different microplastics on marine medaka larvae, we exposed medaka larvae to 200 μg/L of polyethylene (PE-200) and polylactic acid (PLA-200) microplastics for 60 days, respectively. The results indicated that both exposures had no significant effect on fish length/weight and did not result in fish mortality. Notably, the structure of intestinal microbiota was not disrupted either. However, microscopy observations of intestinal tissue suggested that exposure to MPs resulted in inflammation of the intestinal tract of fish and significant atrophy and shedding of small intestinal villus. Linear discriminant analysis Effect Size (LEfSe) showed that intestinal enrichment of Streptomyces occurred in marine medaka larvae in both MPs treatments, while the PE-200 treatment exhibited a significant enrichment. In addition, the PICRUSt2 prediction indicated significant upregulation of the Novobiocin biosynthesis function in gut microbiota in the PE-200 treatment. Overall, multi-level assessment is necessary to determine the risk of exposure of aquatic organisms to MPs.

A new approach to explore the correlation between declarative memory and anxiety in animal models of schizophrenia and microplastic pollution

The discovery of new detrimental effects associated with microplastic pollution is ever-growing and reaching alarming rates worldwide, as it is linked to numerous disorders such as lung diseases, gastrointestinal problems, and cancer. However, a less explored issue is their impact on mental health, more precisely schizophrenia, even though several studies have shown the presence of microplastics in air, water, soil, and even food, thus making them a significant part of our daily dietary intake. It is also well known that declarative memory and anxiety levels are impaired in schizophrenia. However, apart from the novel object recognition test, the possibilities for testing memory in zebrafish are quite limited. For these reasons, we designed a novel memory test based on rewards, a learning period, and zebrafish's natural preference for certain colors. Among the results, our fish preferred the color yellow over red, and we illustrated that ketamine and its combination with methionine provide a robust model that seems to better represent the aspects of schizophrenia in animal models. Moreover, surprisingly, we observed that microplastics (more precisely, polypropylene fibers) ingested by animals through the diet seem to act as a buffer against ketamine toxicity and as an enhancer for methionine exposure. Moreover, according to our results, groups with higher anxiety levels seem to perform better on the memory test.

Studies on the transfer effect of aged polyethylene microplastics in soil-plant system

The widespread use of polyethylene (PE) agricultural films has led to a large accumulation of microplastics in soil, and the environmental effects of microplastics on soil-plants have received increasing attention. In the actual soil environment, microplastics undergo significant changes in their physicochemical properties due to aging, accompanied by complex ecological and environmental effects. However, the quantitative understanding of the environmental effects of microplastic aging in soil-plant systems is still unclear. Therefore, this study investigated the effects of aged and unaged PE microplastics on ecological functions and microplastic transfer mechanisms in soil-plant system, and confirmed the transport behavior of micrometer-sized microplastics (26 μm) within maize plants, expanding the upper size limit of existing studies on microplastic transport within plants. The accumulation of microplastics in maize was also quantitatively assessed in combination with the self-established method of Eu marked PE. The mobility ratio of microplastics from soil to roots, roots to stems, and stems to leaves was 1.07%, 0.76%, and 103.28%, respectively. This study provides a scientific understanding for the environmental effects of microplastics in soil-plants systems quantitatively.

Long-term sublethal exposure to polyethylene and tire wear particles: Effects on risk-taking behaviour in invasive and native fish

Anthropogenic polymeric particles pollute even the most remote ecosystems and may compromise organisms' behaviour and movement skills. It is expected that invasive species cope better with pollutants than native species (i.e., pollution resistance hypothesis). In this study, invasive gibel carp (Carassius gibelio) and native crucian carp (Carassius carassius) were used as model organisms. Specimens were fed daily with food pellets (1 % body weight) added with 0.1 % polyethylene (PE), tire wear particles (TWPs) and control. Their behavioural parameters were compared before and after 14 and 60 days of exposure. Additionally, we evaluated burst swimming capacity after 60 days of exposure to the treatments. The fishes exposed to the PE and TWPs treatments showed significant trends toward increased boldness scores and, in the PE treatment, higher utilization of the open field, and both behavioural changes are associated with higher risk-taking. Invasive gibel carp had substantially better swimming performance than crucian carp, but the expected trend in relation to the treatments was not found. Fish exposed to sublethal doses of PE and TWPs showed signs of behavioural changes after two months of exposure that may affect risk-taking behaviour, which might impact species interactions with predators.

The potential impacts of micro-and-nano plastics on various organ systems in humans

Humans are exposed to micro-and-nano plastics (MNPs) through various routes, but the adverse health effects of MNPs on different organ systems are not yet fully understood. This review aims to provide an overview of the potential impacts of MNPs on various organ systems and identify knowledge gaps in current research. The summarized results suggest that exposure to MNPs can lead to health effects through oxidative stress, inflammation, immune dysfunction, altered biochemical and energy metabolism, impaired cell proliferation, disrupted microbial metabolic pathways, abnormal organ development, and carcinogenicity. There is limited human data on the health effects of MNPs, despite evidence from animal and cellular studies. Most of the published research has focused on specific types of MNPs to assess their toxicity, while other types of plastic particles commonly found in the environment remain unstudied. Future studies should investigate MNPs exposure by considering realistic concentrations, dose-dependent effects, individual susceptibility, and confounding factors.

PLASTAMINATION: Outcomes on the Central Nervous System and Reproduction

BACKGROUND

Environmental exposures to non-biodegradable and biodegradable plastics are unavoidable. Microplastics (MPs) and nanoplastics (NPs) from the manufacturing of plastics (primary sources) and the degradation of plastic waste (secondary sources) can enter the food chain directly or indirectly and, passing biological barriers, could target both the brain and the gonads. Hence, the worldwide diffusion of environmental plastic contamination (PLASTAMINATION) in daily life may represent a possible and potentially serious risk to human health.

OBJECTIVE

This review provides an overview of the effects of non-biodegradable and the more recently introduced biodegradable MPs and NPs on the brain and brain-dependent reproductive functions, summarizing the molecular mechanisms and outcomes on nervous and reproductive organs. Data from in vitro, ex vivo, non-mammalian and mammalian animal models and epidemiological studies have been reviewed and discussed.

RESULTS

MPs and NPs from non-biodegradable plastics affect organs, tissues and cells from sensitive systems such as the brain and reproductive organs. Both MPs and NPs induce oxidative stress, chronic inflammation, energy metabolism disorders, mitochondrial dysfunction and cytotoxicity, which in turn are responsible for neuroinflammation, dysregulation of synaptic functions, metabolic dysbiosis, poor gamete quality, and neuronal and reproductive toxicity. In spite of this mechanistic knowledge gained from studies of non-biodegradable plastics, relatively little is known about the adverse effects or molecular mechanisms of MPs and NPs from biodegradable plastics.

CONCLUSION

The neurological and reproductive health risks of MPs/NPs exposure warrant serious consideration, and further studies on biodegradable plastics are recommended.

Exposure to petroleum-derived and biopolymer microplastics affect fast start escape performance and aerobic metabolism in a marine fish

Evidence suggests that petroleum-derived polymers can impact marine organisms however, little is understood about whether biopolymers affect the behaviour and physiology of marine teleost fish. The aim of this research was to examine the potential effects of microplastics from a petroleum-derived polymer, (polyethylene, PE), and a biopolymer, (edible food coating EFC) on the escape performance, routine swimming, and aerobic metabolism of Forsterygion capito (the mottled triplefin). PE exposure negatively affected fish through longer latencies (∼25 % slower to respond), slower maximum speeds and higher responsiveness in escape performance compared to control fish. Furthermore, fish exposed to PE displayed slower mean speeds and reduced the distance travelled by ∼25 %. After an exhaustive challenge, PE-exposed fish showed higher excess post-exercise oxygen consumption during recovery, compared to control fish. By contrast, EFC exposure only negatively affected maximum speed during an escape. Directionality and mean speed in escape performance, metabolic rate and recovery time were unaffected by biopolymer exposure. With the ever-increasing number of microplastics in the ocean, a shift to biodegradable polymers may be beneficial to marine organisms due to the smaller effect found when compared to petroleum-derived polymers in this study. As a central tool for conservation, this study represents a significant advance to predict the impact of microplastics on wild fish populations.

Combined effects of microplastics and antibiotic-resistant bacteria on Daphnia magna growth and expression of functional genes

Microplastics could act as vectors for the transport of harmful bacteria, such as pathogens and antibiotic resistance bacteria (ARB), but their combined effects have not been reported yet. Here, ARB Shigella flexneri with sulfonamides resistance and micro-polystyrene (micro-PS) were used to investigate their possible combined effects on the growth and expression of functional genes in Daphnia magna. Results showed that micro-PS colonized with S. flexneri were ingested by D. magna and blocked in their intestine after 24 h exposure. Changes were observed in the life history and morphology of D. magna, as well as the expression of functional genes in all treatments, but with no difference in the survival rate. We also determined the expression of six functional genes involved in energy and metabolism (arginine kinase, AK) and oxidative stress response (thioredoxin reductase, TRxR, catalase, CAT, and glutathione S-transferases, GSTs), as well as in growth, development and reproduction (vitellogenin, Vtg1 and ecdysone receptor, EcR). AK and Vtg1 did not show significant differences, however, EcR was down-regulated and the other three genes (TRxR, CAT, GSTs) were up-regulated in the combined-treated group. Antibiotic resistance gene (ARGs) sul1 was detected when exposed to micro-PS colonized with S. flexneri., suggesting that D. magna could acquire resistance genes through microplastic biofilms. These results indicated that MPs could act as a carrier of ARB to transfer ARGs into D. magna, and affect the life history, morphology, and the expression of related functional genes of D. magna, to adapt to the stress caused by MPs and ARB.

Is 5 mm still a good upper size boundary for microplastics in aquatic environments? Perspectives on size distribution and toxicological effects

Plastic is everywhere as an essential component of industries' products, but accumulation and degradation of plastics into microplastics occurs continuously in aquatic environments. Despite numerous studies investigating the influence of microplastics, challenges remain when comparing comprehensive results due to the lack of agreement regarding microplastics sizes. Over 80 studies and reports were reviewed, revealing the inconsistencies in defining the upper size limit for microplastics, and are the basis of this exploration of the need to redefine the latter by focusing on pragmatic factors such as size distribution and toxicity endpoints in aquatic environments. Reviewed articles indicate a gap between recommendations for microplastics definitions and the current status of microplastics. We suggest initiating a discussion regarding downscaling the broadly accepted 5 mm upper limit to 1000 μm, considering environmentally realistic conditions and SI nomenclature. We encourage continued international discussion of redefining the upper size limit defining microplastics from this pragmatic view.

Comprehensive analysis of nanoplastic effects on growth phenotype, nanoplastic accumulation, oxidative stress response, gene expression, and metabolite accumulation in multiple strawberry cultivars

Nanoplastics (NPs) have emerged as a novel environmental threat due to their potential impacts on both animals and plants. Currently, research on the ecotoxicity of NPs has mainly focused on marine aquatic organisms and freshwater algae, with very limited investigations conducted on horticultural plants. This study examined the effects of varying concentrations (0, 1, 10, 50 mg·L-1) of polystyrene NPs (PS-NPs) on strawberry growth. The findings revealed that low concentrations of PS-NPs stimulated strawberry growth, whereas high concentrations impeded it. Notably, diverse strawberry cultivars displayed considerable differences in their sensitivity to PS-NP exposure. Laser scanning confocal microscopy confirmed the absorption of PS-NPs by strawberry roots, with variations in PS-NP accumulation observed across different cultivars. Comparative transcriptomics analysis suggested that the differential expression of genes responsible for calcium ion transport played a significant role in the observed intervarietal differences in PS-NP accumulation among strawberry cultivars. Furthermore, distinct variations in endogenous oxidative responses were observed in different strawberry cultivars under PS-NP treatment. Further analysis indicated that the down-regulation of peroxidase (POD) gene expression and terpenoid compounds accumulation were responsible for heightened endogenous oxidative stress observed in certain strawberry cultivars under PS-NP treatment. Transcriptomic and metabolomic analyses were performed on six strawberry cultivars to investigate their response to PS-NPs in terms of endogenous gene expression and metabolite accumulation. The results identified one commonly up-regulated gene (wall-associated receptor kinase-like) and sixteen commonly down-regulated genes associated with lipid metabolism and carbohydrate metabolism. In addition, a significant reduction in fatty acid metabolite accumulation was observed in the six strawberry cultivars under PS-NP treatment. These findings have significant implications for understanding the effects of NPs on strawberry growth, metabolism, and antioxidant responses, as well as identifying marker genes for monitoring and evaluating the impact of NP pollution on strawberry.

Microplastics in Cetaceans Stranded on the Portuguese Coast

This study characterises microplastics in small cetaceans on the coast of Portugal and assesses the relationship between several biological variables and the amount of detected microplastics. The intestines of 38 stranded dead cetaceans were processed in the laboratory, with digestion methods adapted to the amount of organic matter in each sample. The influence of several biological and health variables (e.g., species, sex, body condition) on the amount of microplastics was tested in all analysed species and particularly in common dolphins, due to the larger number of available samples. Most of the analysed individuals had microplastics in the intestine (92.11%), with harbour porpoises revealing a significantly higher median number of microplastics than common dolphins, probably due to their different diets, use of habitat and feeding strategies. None of the other tested variables significantly influenced the number of microplastics. Moreover, the microplastics found should not be enough to cause physical or chemical sublethal effects, although the correlation between microplastic ingestion and plastic additive bioaccumulation in cetacean tissues requires further investigation. Future monitoring in biota should rely on improved and standardised protocols for microplastic analyses in complex samples to allow for accurate analyses of larger samples and spatio-temporal comparisons.

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.