Evaluation of single and combined effects of cadmium and micro-plastic particles on biochemical and immunological parameters of common carp (Cyprinus carpio)

A review of the neurobehavioural, physiological, and reproductive toxicity of microplastics in fishes

Microplastics (MPs) have emerged as widespread environmental pollutants, causing significant threats to aquatic ecosystems and organisms. This review examines the toxic effects of MPs on fishes, with a focus on neurobehavioural, physiological, and reproductive impacts, as well as the underlying mechanisms of toxicity. Evidence indicates that MPs induce a range of neurobehavioural abnormalities in fishes, affecting social interactions and cognitive functions. Altered neurotransmitter levels are identified as a key mechanism driving behavioural alterations following MP exposure. Physiological abnormalities in fishes exposed to MPs are also reported, including neurotoxicity, immunotoxicity, and oxidative stress. These physiological disruptions can compromise the individual health of aquatic organisms. Furthermore, reproductive abnormalities linked to MP exposure are discussed, with a particular emphasis on disruptions in endocrine signaling pathways. These disruptions can impair reproductive success in fish species, impacting population numbers. Here we explore the critical role of endocrine disruptions in mediating reproductive effects after exposure to MPs, focusing primarily on the hypothalamic-pituitary-gonadal axis. Our review highlights the urgent need for interdisciplinary research efforts aimed at elucidating the full extent of MP toxicity and its implications for aquatic ecosystems. Lastly, we identify knowledge gaps for future research, including investigations into the transgenerational impacts, if any, of MP exposure and quantifying synergetic/antagonistic effects of MPs with other environmental pollutants. This expanded knowledge regarding the potential risks of MPs to aquatic wildlife is expected to aid policymakers in developing mitigation strategies to protect aquatic species.

Exploring adsorption dynamics of heavy metals onto varied commercial microplastic substrates: Isothermal models and kinetics analysis

The increasing presence of plastics in the environment has raised concerns about their potential impact, especially as carriers of heavy metals such as Cd, Ni, and Pb. However, the adsorption mechanism of heavy metals on microplastics remains poorly understood. In this study, we investigated the adsorption behavior of Cd, Ni, and Pb by polystyrene (PS) and polypropylene (PP) microplastics to better comprehend their interaction and potential environmental implications. Our results revealed that equilibrium adsorption of microplastics with different heavy metals was achieved within a 6-h contact time. The FTIR analysis findings, which suggest that physical interactions play a significant role in the adsorption of heavy metals onto microplastics, are further supported by the observed changes in surface morphology after adsorption. We explored the influence of solution pH, contact duration, and initial concentration on the adsorption capacity and found significant effects on the adsorption behavior. To model the adsorption process, we applied Langmuir and Freundlich adsorption isotherm models and observed that the Langmuir model better fit the experimental data. Furthermore, we compared the pseudo-first and pseudo-second-order kinetic models and found that the pseudo-second-order model provided a more accurate description of the adsorption kinetics. Notably, the adsorption percentages varied depending on the type of microplastic and experimental conditions. Overall, this study enhances our understanding of the adsorption mechanism of heavy metals on microplastics and provides valuable insights into their behavior in aquatic environments. These findings have implications for the development of effective strategies for mitigating pollution caused by microplastics and heavy metals in aquatic ecosystems.

Dissecting the mechanism of synergistic interactions between Aspergillus fumigatus and the microalgae Synechocystis sp. PCC6803 under Cd(II) exposure: insights from untargeted metabolomics

Co-culturing fungi and microalgae may effectively remediate wastewater containing Cd and harvest microalgae. Nevertheless, a detailed study of the mechanisms underlying the synergistic interactions between fungi and microalgae under Cd(II) exposure is lacking. In this study, Cd(II) exposure resulted in a significant enhancement of antioxidants, such as glutathione (GSH), malondialdehyde (MDA), hydrogen peroxide (H2O2) and superoxide dismutase (SOD) compared to the control group, suggesting that the cellular antioxidant defense response was activated. Extracellular proteins and extracellular polysaccharides of the symbiotic system were increased by 60.61 % and ,24.29 %, respectively, after Cd(II) exposure for 72 h. The adsorption behavior of Cd(II) was investigated using three-dimensional fluorescence excitation-emission matrix (3D-EEM), fourier transform infrared spectroscopy (FTIR), and scanning electron microscope (SEM). Metabolomics results showed that the TCA cycle provided effective material and energy supply for the symbiotic system to resist the toxicity of Cd(II); Proline, histidine, and glutamine strengthened the synergistic adsorption capacity of the fungus and microalgae. Overall, the theoretical foundation for a deep comprehension of the beneficial interactions between fungi and microalgae under Cd(II) exposure and the role of the fungal-algal symbiotic system in the management of heavy metal pollution is provided by this combined physiological and metabolomic investigation.

Impact of polyvinyl chloride microplastic and paraquat herbicide on the blood cells, biochemical parameters, liver enzymes and morphological changes of aqueduct fish

In recent years, the surge in plastic production has led to pervasive pollution across all environments, earning us the title of inhabiting a "plastic world." Consequently, this research endeavors to explore alterations in biochemical parameters, liver enzymes, and tissue integrity within the gills, intestines, and liver of black fish subjected to polyvinyl chloride (PVC) microplastics and paraquat herbicide, both individually and in combination. For this purpose, we allocated 90 blackfish specimens into 9 groups consisting of 10 individuals each through random selection. Following a period of 28 days, we carried out an assessment to investigate the toxic effects of PVC and paraquat, both separately and in combination. Subsequently, The results indicate that the number of red blood cells (RBCs, millions/mm3) in all studied groups (Group G: 3.6 ± 0.18; Group H: 3.5 ± 0.17; and Group I: 3.2 ± 0.16) is significanly lower than the control group (Pvalue<0.05). The glucose levels in all studied groups (Group B: 47 ± 5.12; Group C: 48 ± 3.79; Group D: 51 ± 4.14; Group E: 48 ± 5.37; Group F: 53 ± 7.48; Group G: 53 ± 9.24; Group H: 58 ± 10.43; and Group I: 61 ± 8.71) are higher than the control group (46 ± 3.71). The results indicate that the levels of AST enzyme in all studied groups (group B: 30 ± 0.17; group C: 32 ± 1.61; group D: 34 ± 1.92; group E: 33 ± 1.17; group F: 38 ± 2.27; group G: 38 ± 1.71; group H: 43 ± 2.15; and group I: 46 ± 2.33). Groups F, G, H, and I exhibit significantly higher levels of AST enzyme compared to the control group, with a p-value<0.05. Morphological changes observed in erythrocytes include deformation and cell vacuolation. The maximum amount of changes in the morphology of erythrocytes occurs when black fish is exposed to 2 mg/L of PVC and 0.4 mg/L of paraquat (group I). The histological harm caused by the combination of PVC and paraquat is significant. Findings indicate that increasing the concentration of both microplastics and paraquat enhances their toxicity when combined. Consequently, it's imperative to assess the toxic impact of microplastics (MPs) and paraquat individually, as well as in combination, on aquatic organisms to safeguard them from the detrimental effects of these substances.

Combined effect and mechanism of microplastic with different particle sizes and levofloxacin on developing Rana nigromaculata: Insights from thyroid axis regulation and immune system

Microplastics (MPs) usually appear in the aquatic environment as complex pollutants with other environmental pollutants, such as levofloxacin (LVFX). After 45-day exposure to LVFX and MPs with different particle sizes at environmental levels, we measured the weight, snout-to-vent length (SVL), and development stages of Rana nigromaculata. Furthermore, we analyzed proteins and genes related to immune system and thyroid axis regulation, intestinal histological, and bioaccumulation of LVFX and MPs in the intestine and brain to further explore the toxic mechanism of co-exposure. We found MPs exacerbated the effect of LVFX on growth and development, and the order of inhibitory effects is as follows: LVFX-MP3>LVFX-MP1>LVFX-MP2. 0.1 and 1 μm MP could penetrate the blood-brain barrier, interact with LVFX in the brain, and affect growth and development by regulating thyroid axis. Besides, LVFX with MPs caused severer interference on thyroid axis compared with LVFX alone. However, 10 μm MP was prone to accumulating in the intestine, causing severe histopathological changes, interfering with the intestinal immune system and influencing growth and development through immune enzyme activity. Thus, we concluded that MPs could regulate the thyroid axis by interfering with the intestinal immune system.

Effect of microplastics used in agronomic practices on agricultural soil properties and plant functions: Potential contribution to the circular economy of rural areas

The extensive use of plastic materials and their improper disposal results in high amounts of plastic waste in the environment. Aging of plastics leads to their breakdown into smaller particles, such as microplastics (MPs) and nanoplastics. This research investigates plastics used in agricultural practices as they contribute to MP pollution in agricultural soils. The distribution and characteristics of MPs in agricultural soils were evaluated. In addition, the effect of MPs on soil properties, the relationship between MPs and metals in soil, the effect of MPs on the fate of pesticides in agricultural soils and the influence of MPs on plant growth were analysed, discussing legume, cereal and vegetable crops. Finally, a brief description of the main methods of chemical analysis and identification of MPs is presented. This study will contribute to a better understanding of MPs in agricultural soils and their effect on the soil-plant system. The changes induced by MPs in soil parameters can lead to potential benefits as it is possible to increase the availability of micronutrients and reduce plant uptake of toxic elements. Furthermore, although plastic pollution remains an emerging threat to soil ecosystems, their presence may result in benefits to agricultural soils, highlighting the principles of the circular economy.

Unveiling population-specific outcomes: Examining life cycle traits of different strains of Chironomus riparius exposed to microplastics and cadmium questions generality of ecotoxicological results

Ecotoxicological tests used for risk assessment of toxicants and its mixtures rely both on classical life-cycle endpoints and bioindicator organisms usually derived from long-term laboratory cultures. While these cultures are thought to be comparable among laboratories and more sensitive than field organisms, it is not well investigated whether this assumption is met. Therefore, we aimed to investigate differential life-cycle endpoints response of two different strains of C. riparius, one originally from Spain and the other from Germany, kept under the same laboratory conditions for more than five years. To highlight any possible differences, the two populations were challenged with exposure to cadmium (Cd), polyvinyl chloride (PVC) microplastics and a co-exposure with both. Our results showed that significant differences between the strains became evident with the co-exposure of Cd and PVC MPs. The German strain showed attenuation of the deleterious Cd effects with microplastic co-exposure in survival and developmental time. Contrary to that, the Spanish strain showed no interaction between the substances. In conclusion, the toxicity-effects of contaminants may vary strongly among laboratory populations, which makes a universal risk assessment evaluation challenging.

Microplastic-stressor responses are rarely synergistic in freshwater fishes: A meta-analysis

Microplastic exposure can cause a range of negative effects on the biochemistry, condition and ecology of freshwater fishes depending on aspects of the exposure and the exposed fish. However, fishes are typically exposed to microplastics and additional multiple stressors simultaneously, for which the combined effects are poorly understood and may have important management consequences. Additive effects are those where the combined effect is equal to the sum, antagonistic where combined effects are less than the sum and for synergistic effects the combined effect is greater to the sum of the individual effects. Here, we performed a meta-analysis of studies recording freshwater fish responses to microplastic-stressor exposures to test if interactions were primarily non-additive (synergistic or antagonistic), and factors impacting the net response. Individual responses were classified (antagonistic/additive/synergistic) and the fit of net responses to a null additive model determined for 838 responses (36 studies) split by categorical variables for the microplastic exposure (environmental relevance, interacting stressor, microplastic morphology and response category measured), as well as the exposed fish (lifestage, ecology and family). Most responses were classified as antagonistic (48 %) and additive (34 %), with synergistic effects least frequent (17 %). Net responses fitted null additive models for all levels of interacting stressor, fish family and microplastic morphology. In contrast, net antagonism was present for biochemical responses, embryo lifestages, environmentally relevant microplastic exposures and fish with benthopelagic ecology, while synergism was identified for fishes with demersal ecology. While substantial knowledge gaps remain and are discussed, the data thus far suggest microplastic-stressor responses in freshwater fishes are rarely synergistic and, therefore, addressing either or both stressors will likely result in positive management and biological outcomes.

Combined toxicity of polyvinyl chloride microplastics and copper to marine jacopever (Sebastes schlegelii)

Marine organisms commonly encounter co-stress resulting from the coexistence of microplastics (MPs) and heavy metals pollution in marine environments. Nevertheless, the combined effects and toxicity mechanisms of MPs and heavy metals on marine organisms remain unclear. This study integrated growth, physiological, morphological, and biochemical markers to assess the individual and combined toxicity of polyvinyl chloride MPs (PVC MPs, 1 × 104 particles/L) and copper (Cu, 200 μg/L) on marine jacopever (Sebastes schlegelii). The results revealed that co-exposure to MPs and Cu had a more detrimental impact on jacopever compared to the single-exposure groups, as evidenced by the enhanced growth inhibition, respiratory stress, and hepatotoxicity. This phenomenon may be attributed to PVC MPs accelerating the accumulation of Cu in jacopever liver. Therefore, peroxidation damage occurred in the co-exposed liver and may result in liver dysfunction. These findings contribute valuable insights into the risks associated with the coexistence of MPs and heavy metal pollution in marine ecosystems.

Response and adaptation mechanisms of Apostichopus japonicus to single and combined anthropogenic stresses of polystyrene microplastics or cadmium

Microplastics (MPs) have become pervasive in marine ecosystems, exerting detrimental effects on marine life. The concurrent presence and interaction of MPs and heavy metals in aquatic environments could engender more insidious toxicological impacts. This study aimed to elucidate the potential impacts and underlying mechanisms of polystyrene microplastics (PS-MPs), cadmium (Cd), and their combined stress (MPs-Cd) on sea cucumbers (Apostichopus japonicus). It focused on the growth, Cd bioaccumulation, oxidative stress responses, immunoenzymatic activities, and metabolic profiles, specifically considering PS-MPs sizes preferentially ingested by these organisms. The high-dose MPs (MH) treatment group exhibited an increase in cadmium bioavailability within the sea cucumbers. Exposure to PS-MPs or Cd triggered the activation of antioxidant defenses and immune responses. PS-MPs and Cd exhibited a synergistic effect on lysozyme (LZM) activity. A total of 149, 316, 211, 197, 215, 619, 434, and 602 differentially expressed metabolites were identified, distinguishing the low-dose MPs (ML), high-dose MPs (MH), low-dose Cd (LCd), low-dose MPs and low-dose Cd (MLLCd), high-dose MPs and low-dose Cd (MHLCd), high-dose Cd (HCd), low-dose MPs and high-dose Cd (MLHCd), high-dose MPs and high-dose Cd (MHHCd) groups, respectively. Metabolomic analyses revealed disruptions in lipid metabolism, nervous system function, signal transduction, and transport and catabolism pathways following exposure to PS-MPs, Cd, and MPs-Cd. Correlation analyses among key differentially expressed metabolites (DEMs) underscored the interregulation among these metabolic pathways. These results offer new perspectives on the distinct and synergistic toxicological impacts of microplastics and cadmium on aquatic species, highlighting the complex interplay between environmental contaminants and their effects on marine life.

Immunotoxicity of microplastics in fish

Plastic waste degrades slowly in aquatic environments, transforming into microplastics (MPs) and nanoplastics (NPs), which are subsequently ingested by fish and other aquatic organisms, causing both physical blockages and chemical toxicity. The fish immune system serves as a crucial defense against viruses and pollutants present in water. It is imperative to comprehend the detrimental effects of MPs on the fish immune system and conduct further research on immunological assessments. In this paper, the immune response and immunotoxicity of MPs and its combination with environmental pollutants on fish were reviewed. MPs not only inflict physical harm on the natural defense barriers like fish gills and vital immune organs such as the liver and intestinal tract but also penetrate cells, disrupting intracellular signaling pathways, altering the levels of immune cytokines and gene expression, perturbing immune homeostasis, and ultimately compromising specific immunity. Initially, fish exposed to MPs recruit a significant number of macrophages and T cells while activating lysosomes. Over time, this exposure leads to apoptosis of immune cells, a decline in lysosomal degradation capacity, lysosomal activity, and complement levels. MPs possess a small specific surface area and can efficiently bind with heavy metals, organic pollutants, and viruses, enhancing immune responses. Hence, there is a need for comprehensive studies on the shape, size, additives released from MPs, along with their immunotoxic effects and mechanisms in conjunction with other pollutants and viruses. These studies aim to solidify existing knowledge and delineate future research directions concerning the immunotoxicity of MPs on fish, which has implications for human health.

Reviewing the role of microplastics as carriers for microorganisms in absorbing toxic trace elements

The pervasive presence of microplastics in various settings, such as freshwater and marine ecosystems, has sparked serious concerns. Microplastics can operate as possible transporters for hazardous trace elements or microbes, even though they are not naturally able to actively absorb these compounds. The binding sites on the plastic's surface or the complexes that are formed with the organic material on the plastic are how this adsorption process takes place. Microplastics' surfaces also seem to be attractive to microorganisms, such as bacteria and algae. Microorganisms can adhere to the rough surface of microplastics, which facilitates their colonization and formation of biofilms. Numerous bacteria, including ones that have the ability to absorb hazardous trace elements, can be found in these biofilms. Microplastics and microbes can interact in ways that are advantageous and detrimental. Microplastics have the ability to act as a substrate for microbial growth, which could lead to an increase in the quantity of microorganisms in the surrounding environment. On the other hand, microplastics may make it easier for microbes to spread to new areas, which could help dangerous or deadly species proliferate. Research is still ongoing to determine the degree to which microplastics serve as carriers of microbes and hazardous trace elements. Comprehending the implications of microplastics, pollutants, and microorganisms in a variety of environmental conditions is difficult due to their complex interplay. This review provides a detailed description of the complexity of the problem and used the examples related to microplastics, its environmental effects, and impacts on human health.

Role of UV radiation and oxidation on polyethylene micro- and nanoplastics: impacts on cadmium sorption, bioaccumulation, and toxicity in fish intestinal cells

This study investigated the role of ultraviolet (UV) radiation and oxidation in high-density polyethylene microplastics (2-15 μm) and nanoplastics (0.2-9.9 μm) (NMPs) on particle chemistry, morphology, and reactivity with cadmium (Cd). Additionally, toxicity of NMPs alone and with Cd was evaluated using RTgutGC cells, a model of the rainbow trout (Oncorhynchus mykiss) intestine. The role on NMPs on Cd bioaccumulation in RTgutGC cells was also evaluated. Dynamic light scattering indicated that after UV radiation NPs agglomerated size increased from 0.8 to 28 µm, and to 8 µm when Cd was added. Oxidized MPs agglomerated size increased from 11 and 7 to 46 and 27 µm in non-UV- and UV-aged oxidized MPs when adding Cd, respectively. Cd-coated particles exhibited generally significantly higher zeta potential than non-Cd-coated particles, while attenuated total reflectance-Fourier transform infrared spectroscopy showed that the functional chemistry of the particles was oxidized and modified after being exposed to UV radiation. Presence of NMPs resulted in a significant decrease in Cd bioaccumulation in RTgutGC cells (100.5-87.9 ng Cd/mg protein) compared to Cd alone (138.1 ng Cd/mg protein), although this was not quite significant for co-exposures with UV-aged NPs (105.7 ng Cd/mg protein). No toxicity was observed in RTgutGC cells exposed to NMPs alone for 24 h. Moreover, co-exposures with Cd indicated that NMPs reduce the toxicity of Cd. Altogether these results show that UV aging enhances NMP surface reactivity, increasing Cd absorption in solution, which resulted in a reduction in Cd bioavailability and toxicity.

Meta-analysis unravels the complex combined toxicity of microplastics and antibiotics in aquatic ecosystems

The aquatic ecosystem, a repository for various pollutants, has been identified as a crucial zone where microplastics (MPs) serve as vectors for antibiotics, facilitating their spread. Despite this, the influence of MPs on the toxicity of antibiotics remains a topic of debate. In this study, we conduct a global meta-analysis, examining 730 datasets from 29 laboratory studies. Our findings reveal that the impact of MPs on antibiotic toxicity is highly dependent on biological response pathways, microplastic concentration, antibiotic properties, and exposure time. We observed that MPs amplify the accumulation of antibiotics in aquatic organisms, significantly heightening their adverse effects on growth, development, and immune functions. Intriguingly, MPs appear to mitigate the reproductive toxicity caused by antibiotics. A notable inverse relationship was identified between antibiotic toxicity and microplastic concentration and exposure time. Furthermore, antibiotic concentration predominantly affects growth, development, and reproductive health, whereas exposure time is critical in determining antibiotic accumulation and immune-related toxicity. These insights underscore that microplastic co-exposure can modify the toxicological profile of antibiotics. The outcomes of this research enhance our comprehensive understanding of the intricate combined effects of MPs and antibiotics on aquatic life, emphasizing the necessity for informed scientific management of these emerging contaminants.

Deleterious effects of polypropylene released from paper cups on blood profile and liver tissue of Clarias gariepinus: bioremediation using Spirulina

Despite numerous studies on microplastics, the biological impacts of polypropylene microplastics (PP-MPs) and its toxicity on freshwater fish have yet to be fully revealed. The purpose of this research was to look at the potentially harmful effects of PP-MPs in freshwater African catfish Clarias gariepinus and bioremediation using Spirulina. After acclimatization to laboratory conditions, 108 fish (125 ± 3 gm and 27 ± 2 cm) were assigned into triplicate six experimental groups (12 fish/group), a control group, Spirulina group (SP), PP-MP-treated groups (0.14 and 0.28 mg/l PP-MPs), and PP-MP + Spirulina-treated groups (0.14 mg/l PP-MPs + 200 mg/L SP and 0.28 mg/l PP-MPs +200 mg/L SP) for 15-day exposure and 45-day recovery after that. The hematological parameters exhibiting significance (RBCs, Hct, Hb, and MCV) or non-significance (MCH and MCHC) either decreased with the increase in PP-MP doses from 0.0 in the control to 0.28 mg/L red blood cells (RBCs), hematocrit (Hct), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), hemoglobin (Hb) and platelets or increased with such an increase in doses (mean corpuscular volume (MCV)). The liver enzyme activity, aspartate aminotransferase (AST), alkaline phosphatase (ALP), and alanine aminotransferase (ALT) exhibited non-significant (p ≥ 0.05) or significant (p < 0.05) increases in (0.14 and 0.28 mg/L) PP-MP-exposed groups, respectively, except ALP. Furthermore, there was a significant (p < 0.05) or non-significant (p ≥ 0.05) increase in 0.14 and 0.28 mg/l PP-MP +200 mg/L-exposure groups, respectively, compared to the control group and the same exposure group without Spirulina. In comparison to the control group, PP-MPs (0.14 and 0.28 mg/L) induced a significant (p < 0.05) increase in the percentage of poikilocytosis and nuclear abnormalities of RBCs. The liver tissue from fish exposed to PP-MPs exhibited varying degrees of pathological changes. These results indicated that these pathological changes increased with PP-MP concentration, suggesting that the effect of PP-MPs was dose-dependent. After 45 days of recovery under normal conditions, it was obvious that there was a significant improvement in the percentage of poikilocytosis and nuclear abnormalities of RBCs, as well as a non-significant improvement in hemato-biochemical parameters and liver tissue.

Effect of microplastics on oxytetracycline trophic transfer: Immune, gut microbiota and antibiotic resistance gene responses

Microplastics and antibiotics are prevalent and emerging pollutants in aquatic ecosystems, but their interactions in aquatic food chains remain largely unexplored. This study investigated the impact of polypropylene microplastics (PP-MPs) on oxytetracycline (OTC) trophic transfer from the shrimp (Neocaridina denticulate) to crucian carp (Carassius auratus) by metagenomic sequencing. The carrier effects of PP-MPs promoted OTC bioaccumulation and trophic transfer, which exacerbated enterocyte vacuolation and hepatocyte eosinophilic necrosis. PP-MPs enhanced the inhibitory effect of OTC on intestinal lysozyme activities and complement C3 levels in shrimp and fish, and hepatic immunoglobulin M levels in fish (p < 0.05). Co-exposure of MPs and OTC markedly increased the abundance of Actinobacteria in shrimp and Firmicutes in fish, which caused disturbances in carbohydrate, amino acid, and energy metabolism. Moreover, OTC exacerbated the enrichment of antibiotic resistance genes (ARGs) in aquatic animals, and PP-MPs significantly increased the diversity and abundance of ARGs and facilitated the trophic transfer of teta and tetm. Our findings disclosed the impacts of PP-MPs on the mechanism of antibiotic toxicity in aquatic food chains and emphasized the importance of gut microbiota for ARGs trophic transfer, which contributed to a deeper understanding of potential risks posed by complex pollutants on aquatic ecosystems.

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.

The odd couple: Caffeine and microplastics. Morphological and physiological changes in Mytilus galloprovincialis

In recent years, the presence of pharmaceuticals and microplastics (MPs) in aquatic ecosystems has raised concerns about their environmental impact. This study explores the combined effects of caffeine, a common pharmaceutical pollutant, and MPs on the marine mussel Mytilus galloprovincialis. Caffeine, at concentrations of 20.0 μg L-1, and MPs (1 mg L-1, 35-50 μm size range), was used to mimic real-world exposure scenarios. Two hundred M. galloprovincialis specimens were divided into four groups: caffeine, MPs, Mix (caffeine + MPs), and Control. After a two-week acclimation period, the mollusks were subjected to these pollutants in oxygen-aerated aquariums under controlled conditions for 14 days. Histopathological assessments were performed to evaluate gill morphology. Cellular volume regulation and digestive gland cell viability were also analyzed. Exposure to caffeine and MPs induced significant morphological changes in M. galloprovincialis gills, including cilia loss, ciliary disk damage, and cellular alterations. The chitinous rod supporting filaments also suffered damage, potentially due to MP interactions, leading to hemocyte infiltration and filament integrity compromise. Hemocytic aggregation suggested an inflammatory response to caffeine. In addition, viability assessments of digestive gland cells revealed potential damage to cell membranes and function, with impaired cell volume regulation, particularly in the Mix group, raising concerns about nutrient metabolism disruption and organ function compromise. These findings underscore the vulnerability of M. galloprovincialis to environmental pollutants and emphasize the need for monitoring and mitigation efforts. RESEARCH HIGHLIGHTS: The synergy of caffeine and microplastics (MPs) in aquatic ecosystems warrants investigation. MPs and caffeine could affect gill morphology of Mytilus galloprovincialis. Caffeine-exposed cells had lower viability than the control group in the NR retention test. MPs and mix-exposed cells struggled to recover their volume.

Hazards of microplastics exposure to liver function in fishes: A systematic review and meta-analysis

Microplastics (5 mm - 1 μm) have become one of the major pollutants in the environment. Numerous studies have shown that microplastics can have negative impacts on aquatic organisms, affecting their liver function levels. However, the extent of these effects and their potential toxicological mechanisms are largely unknown. In this study, a meta-analysis and systematic review were conducted to assess the effects of microplastics on fish liver function and summarize the potential toxicological mechanisms of microplastic-induced liver toxicity. The meta-analysis results indicate that compared to the control group, exposure to microplastics significantly affects fish liver indicators: aspartate aminotransferase (AST) (p < 0.001), alanine aminotransferase (ALT) (p < 0.001), alkaline phosphatase (ALP) (p < 0.001), total protein (TP) (p < 0.001), and lactate dehydrogenase (LDH) (p < 0.001), including oxidative stress indicators: superoxide dismutase (SOD) (p < 0.001), glutathione S-transferase (GST) (p < 0.001), glutathione (GSH) (p < 0.001), and malondialdehyde (MDA) (p < 0.001) in fish liver. For fish living in different environments, the potential toxicological mechanisms of microplastics exposure on fish liver may exhibit some differences. For freshwater fish, the mechanism may be that microplastics exposure causes overproduction of reactive oxygen species (ROS) in fish hepatocyte mitochondria. ROS promotes the expression of toll-like receptor 2 (TLR2) and activates downstream molecules myeloid differentiation factor 88 (MyD88) and tumor necrosis factor receptor-associated factor 6 (TRAF6) of the TLR2 signaling pathway, leading to phosphorylation of NF-κB p65. This leads to the release of inflammatory factors and oxidative stress and inflammation in fish liver. In addition, for seawater fish, the mechanism may be that microplastics exposure can cause damage or death of fish hepatocytes, leading to continuous pathological changes, inflammation, lipid and energy metabolism disorders, thereby causing significant changes in liver function indexes.

Micro(nano)plastics and Their Potential Impact on Human Gut Health: A Narrative Review

Microplastics and nanoplastics (MNPs) are becoming an increasingly severe global problem due to their widespread distribution and complex impact on living organisms. Apart from their environmental impact, the effects of MNPs on living organisms have also continued to attract attention. The harmful impact of MNPs has been extensively documented in marine invertebrates and larger marine vertebrates like fish. However, the research on the toxicity of these particles on mammals is still limited, and their possible effects on humans are poorly understood. Considering that MNPs are commonly found in food or food packaging, humans are primarily exposed to them through ingestion. It would be valuable to investigate the potential harmful effects of these particles on gut health. This review focuses on recent research exploring the toxicological impacts of micro- and nanoplastics on the gut, as observed in human cell lines and mammalian models. Available data from various studies indicate that the accumulation of MNPs in mammalian models and human cells may result in adverse consequences, in terms of epithelial toxicity, immune toxicity, and the disruption of the gut microbiota. The paper also discusses the current research limitations and prospects in this field, aiming to provide a scientific basis and reference for further studies on the toxic mechanisms of micro- and nanoplastics.

Individual and combined impact of microplastics and lead acetate on the freshwater shrimp (Caridina fossarum): Biochemical effects and physiological responses

Microplastics and heavy metals pollution is recognised as a major problem affecting aquatic ecosystems. For this reason, this study aims to assess the toxicity of different concentrations of polyethylene microplastics (PE-MPs) (0.0, 500, and 1000 μg L-1) with a mean size of 15-25 μm and lead acetate Pb(C2H3O2)2 (0.0, 2.5, and 5 mg L-1), both individually and in combination, through the exposure of the freshwater grass shrimp, Caridinia fossarum for 15 days, focusing on microplastic interaction with co-occurring contaminants. After being exposed to both contaminants, either individually or in combination, significant alterations in numerous biochemical markers were observed. Specifically, exposure to lead acetate alone resulted in significant changes across ALP, AST, ALT, LDH, GGT, and BChE enzyme activity levels indicating hepatotoxicity and neurotoxicity. Also, Pb exposure led to alterations in total antioxidant capacity, MDA, total lipids, and glycogen contents, signalling the onset of oxidative stress. Exposure to PE-MPs alone led to changes in ALP, LDH, GGT, and BChE enzyme levels, and in MDA, total lipids, and glycogen samples' contents. Remarkably, the study observed increased bioaccumulation of lead acetate in samples treated with the combination, emphasizing the synergistic impact of PE-MPs on the toxicity of lead acetate. This synergy was also evident in AST and ALT enzyme activity levels and MDA contents. This underscores the necessity for measures to address both microplastic pollution and heavy metal contamination, taking into account the synergistic behaviour of MPs in the presence of concurrent contaminants.

The potential toxicity of microplastics on human health

Microplastics are plastic particles, films, and fibers with a diameter of < 5 mm. Given their long-standing existence in the environment and terrible increase in annual emissions, concerns were raised about the potential health risk of microplastics on human beings. In particular, the increased consumption of masks during the COVID-19 pandemic has dramatically increased human contact with microplastics. To date, the emergence of microplastics in the human body, such as feces, blood, placenta, lower airway, and lungs, has been reported. Related toxicological investigations of microplastics were gradually increased. To comprehensively illuminate the interplay of microplastic exposure and human health, we systematically reviewed the updated toxicological data of microplastics and summarized their mode of action, adverse effects, and toxic mechanisms. The emerging critical issues in the current toxicological investigations were proposed and discussed. Our work would facilitate a better understanding of MPs-induced health hazards for toxicological evaluation and provide helpful information for regulatory decisions.

Immunotoxicological, histopathological, and ultrastructural effects of waterborne pyrogallol exposure on African catfish (Clariasgariepinus)

Pyrogallol is a naturally occurring polyphenol derived from natural plants, such as Acer rubrum and Eucalyptus sp. The current study was designed to evaluated pyrogallol-mediated toxicity at sublethal levels (1, 5, and 10 mg/L), derived from 96 h-LC50 values previously determined for African catfish (Clarias gariepinus). Immunotoxicological indices, histological, histochemical, and ultrastructural alterations in C. gariepinus were evaluated following a 15-day pyrogallol exposure. Pyrogallol decreased immune parameters [lysozyme activity (LYZ), immunoglobulin M (IgM), and phagocytic activity] and increased pro-inflammatory cytokines, interleukin-1 beta (IL-1β), interleukin-6 (IL-6) in the serum of C. gariepinus. In addition, histopathology analysis demonstrated that exposure to pyrogallol induced injury in the liver and spleen of fish. Cellular changes in the liver include hepatocyte hydropic degeneration, melanomacrophage, vacuolated hepatocytes, congested blood, severe structural deformation, and hemorrhage. In the spleen, ellipsoid structures, melanomacrophage centers, and infiltration of inflammatory cells were evident. Together, a high frequency of histopathological lesions was scored in both the liver and spleen of C. gariepinus, which showed a dose-dependent relationship between pyrogallol exposure and histopathological indices. Our data suggest that dysfunction in the immune system may be mediated by pyrogallol-induced changes in cytokines.

The impacts of synthetic and cellulose-based fibres and their associated dyes on fish hosts and parasite health

Plastic pollution is now a ubiquitous feature of freshwater systems and the majority of this is fibrous. Here, we test the effects of plastic and cellulose-based fibres (polyester, cotton, and bamboo from commercial clothing) on fish host-parasite interactions using a freshwater fish host-parasite model system (guppy Poecilia reticulata-Gyrodactylus turnbulli). For uninfected fish, polyester exposure was associated with significantly higher mortality rates compared with the other two fibre types. For infected fish, whilst polyester and cotton exposure were not associated with any significant changes to parasite burdens, fish exposed to bamboo fibres had significantly reduced maximum parasite burdens compared with fish not exposed to any fibres, indicating that the bamboo fibres and/or associated dyes conferred some degree of resistance or tolerance. Whilst unable to determine the exact nature of the chemical dyes, when testing off-host parasite survival on exposure to the fibre dyes, cotton and particularly polyester dyes were associated with higher parasite mortality compared to bamboo. Overall, we add to the growing body of evidence which shows that polyester microplastic fibres and their associated dyes can be detrimental for both fish and parasite survival, and we highlight the need for increased transparency from textile industries on the chemical identity of fabric dyes.

Single and combined effects of CuSO4 and polyethylene microplastics on biochemical endpoints and physiological impacts on the narrow-clawed crayfish Pontastacusleptodactylus

This study investigated the toxicity of polyethylene microplastics (MPs; <0.02 mm) and CuSO4, alone and in combination, on the freshwater crayfish Pontastacus leptodactylus. In this study, the crayfish were exposed to PE-MPs (0.0, 0.5, and 1 mg L-1) and CuSO4·5H2O (0.0, 0.5, and 1 mg L-1) for a period of 28 days. Next, multi-biomarkers, including biochemical, immunological, and oxidative stress indicators were analyzed. Results showed that co-exposure to PE-MPs and CuSO4 resulted in increased aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH), and decreased alkaline phosphatase (ALP), butyrylcholinesterase (BChE), and gamma-glutamyl-transferase (GGT). Triglycerides, cholesterol, glucose, and albumin content also increased. Although no significant change was observed in lysozyme and phenoloxidase activities in crayfish co-exposed to 0.5 mg L-1 MPs and 0.5 mg L-1 CuSO4, their activities were significantly decreased in other experimental groups. Oxidative stress parameters in hepatopancreas indicated increased superoxide dismutase (SOD), glutathione peroxidase (GPx), and in malondialdehyde (MDA) levels, but decreased catalase (CAT), glucose 6-phosphate dehydrogenase (G6PDH), and cellular total antioxidant (TAC). Results showed that the sub-chronic toxicity of CuSO4 was confirmed. The study confirmed the toxicity of CuSO4 and found that higher concentrations led to more severe effects. Co-exposure to PE-MPs and CuSO4 primarily compromised the endpoints, showing increased toxicity when both pollutants were present in higher concentrations. The activities of POX, LYZ, ALP, GGT, LDH, and CAT were suppressed by both CuSO4 and MPs. However, a synergistic increase was observed in other measured biomarkers in crayfish co-exposed to CuSO4 and MPs.

Exploring the combined interplays: Effects of cypermethrin and microplastic exposure on the survival and antioxidant physiology of Astacus leptodactylus

Plastic waste and micro/nanoplastic particles pose a significant global environmental challenge, along with concerns surrounding certain pesticides' impact on aquatic organisms. This study investigated the effects of microplastic particles (MPPs) and cypermethrin (CYP) on crayfish, focusing on biochemical indices, lipid peroxidation, oxidative stress, hematological changes, and histopathological damage. After determining the LC50-96 h value (4.162 μg/L), crayfish were exposed to sub-lethal concentrations of CYP (1.00 ppb (20%) and 2.00 ppb (50%)) and fed a diet containing 100 mg/kg MPPs for 60 days. Hemolymph transfusion and histopathological examinations of the hepatopancreas were conducted. The results showed significant alterations in crayfish. Total protein levels decreased, indicating protein breakdown to counteract contaminants, while total cholesterol and triglyceride levels declined, suggesting impaired metabolism. Glucose levels increased in response to chemical stress. The decline in total antioxidant capacity highlighted the impact of prolonged xenobiotic exposure and oxidative stress, while increased CAT, SOD, and MDA activities helped mitigate oxidative stress and maintain cellular homeostasis. The elevated total hemocyte count, particularly in semi-granular cells, suggests their active involvement in the detoxification process. Further research is needed to fully understand the implications of these effects.

Review of cadmium toxicity effects on fish: Oxidative stress and immune responses

Cadmium (Cd) in aquatic environments can cause environmental toxicity to fish and induce oxidative stress owing to an excessive production of reactive oxygen species in fish bodies. Fish have developed various antioxidant systems to protect themselves from reactive oxygen species; thus, a change in antioxidant responses in fish can be a criterion for evaluating oxidative stress resulting from Cd exposure. Because Cd exposure may be recognized as an exogenous substance by a fish body, it may lead to the stimulation or suppression of its immune system. Various immune responses can be assessed to evaluate Cd toxicity in fish. This review aimed to identify the impacts of Cd exposure on oxidative stress and immunotoxicity in fish as well as identify accurate indicators of Cd toxicity in aquatic ecosystems.

Microplastic polyamide toxicity: Neurotoxicity, stress indicators and immune responses in crucian carp, Carassius carassius

This study aimed to determine the toxicity standard and potential risks and effects of polyamide (PA) exposure on neurotoxicity, stress indicators, and immune responses in juvenile crucian carp Carassius carassius. Numerous microplastics (MPs) exists within aquatic environments, leading to diverse detrimental impacts on aquatic organisms. The C. carassius (mean weight, 23.7 ± 1.6 g; mean length, 13.9 ± 1.4 cm) were exposed to PA concentrations of 0, 4, 8, 16, 32 and 64 mg/L for 2 weeks. Among the neurotransmitters, the acetylcholinesterase (AChE) activity in the liver, gill, and intestine of C. carassius was significantly inhibited by PA exposure. Stress indicators such as cortisol and heat shock protein 70 (HSP70) in the liver, gill, and intestine of C. carassius were significantly increased, while immune responses to lysozyme and immunoglobulin M (IgM) were significantly decreased. Our study demonstrates the toxic effects of MP exposure on crucian carp's neurotoxicity, stress indicators, and immune responses.

Toxicity of co-exposure of microplastics and lead in African catfish (Clarias gariepinus)

Microplastics (MPs) are an emerging threat to freshwater ecosystems with several ecotoxicological ramifications for fish. Microplastics (MPs) can adsorb heavy metals on their surfaces and increase their availability to aquatic organisms. The combined impact of lead and microplastics on fish has only been studied seldom utilizing a variety of markers. The present study aimed to evaluate the hematological, biochemical, and inflammatory signals (cytokines), as well as antioxidant enzymes in African catfish (Clarias gariepinus) exposed to lead (Pb) and MPs individually and combined for 15 days (acute toxicity experiment). The fish were split into four groups, the first of which was the control group. The second group received exposure to 1 mg/L of lead nitrate [Pb(NO3)2]. The third group was given 100 mg/L of MPs. A solution containing 100 mg/L of MPs and 1 mg/L of lead nitrate [Pb(NO3)2] was administered to the fourth group (the combination group). According to the findings, when MPs and Pb were combined for 15 days, the red blood cells (RBCs), thrombocytes, and lymphocytes were significantly reduced in comparison to the control fish. When compared to the control fish, the fish exposed to MPs and Pb alone or together showed a significant rise in blood interleukin-1β (IL-1β) and interleukin-6 (IL-6) cytokines. Both MPs and Pb exposure in catfish resulted in significant changes in the plasma electrolytes. The fish treated with MPs and Pb individually or in combination showed significant reduction in superoxide dismutase (SOD) and total antioxidant capacity (TAC) levels compared to the control group. The fish exposed to the combined action of MPs and Pb showed a considerable modification in all biochemical markers. The difference in the mean concentration of Pb (mg/L) between the fish exposed to Pb alone and the fish subjected to Pb and MPs combination was not statistically significant. In conclusion, according to this investigation, exposure to Pb caused an insignificant increase in Pb accumulation when MPs were present. However, co-exposure may result in anemia, cellular harm, extremely high levels of oxidative stress, and an inflammatory reaction.

Co-exposure to environmentally relevant concentrations of cadmium and polystyrene nanoplastics induced oxidative stress, ferroptosis and excessive mitophagy in mice kidney

Nanoplastics (NPs) are defined as a group of emerging pollutants. However, the adverse effect of NPs and/or heavy metals on mammals is still largely unclear. Therefore, we performed a 35-day chronic toxicity experiment with mice to observe the impacts of exposure to Cadmium (Cd) and/or polystyrene nanoplastics (PSNPs). This study revealed that combined exposure to Cd and PSNPs added to the mice's growth toxicity and kidney damage. Moreover, Cd and PSNPs co-exposure obviously increased the MDA level and expressions of 4-HNE and 8-OHDG while decreasing the activity of antioxidase in kidneys via inhibiting the Nrf2 pathway and its downstream genes and proteins expression. More importantly, the results suggested for the first time that Cd and PSNPs co-exposure synergistically increased iron concentration in kidneys, and induced ferroptosis through regulating expression levels of SLC7A11, GPX4, PTGS2, HMGB1, FTH1 and FTL. Simultaneously, Cd and PSNPs co-exposure further increased the expression levels of Pink, Parkin, ATG5, Beclin1, and LC3 while significantly reducing the P62 expression level. In brief, this study found that combined exposure to Cd and PSNPs synergistically caused oxidative stress, ferroptosis and excessive mitophagy ultimately aggravating kidney damage in mice, which provided new insight into the combined toxic effect between heavy metals and PSNPs on mammals.

Global hotspots and trends in interactions of microplastics and heavy metals: a bibliometric analysis and literature review

Microplastics (MPs) are identified as emerging contaminants; however, their interactions with heavy metals in the environment have not been well elucidated. Here, the research progress, hotspots, and trends in the interactions of MPs and heavy metals were analyzed at a global scale using a bibliometric analysis combined with a literature review. We comprehensively searched the Web of Science Core Collection database from 2008 to July 5, 2022. A total of 552 articles published in 124 journals were selected, which came from 70 countries and 841 institutions. The most contributing journals, countries, institutions, and authors were identified. Visualization methods were used to identify high co-citation references and hot keywords in the 552 articles. Evolutionary and cluster analyses of hot keywords suggested several research hotspots in the co-contamination of MPs and heavy metals, including their toxicity and bioaccumulation, the adsorption and desorption behaviors, the environmental pollution and risk assessment, and their detection and characterization. Based on the current research status, several directions of priority are recommended to understand the interactions between MPs and heavy metals and their potential risks. This article can help recognize the current research status and future directions in this field.

Toxic effects of sub-acute microplastic (polyamide) exposure on the accumulation, hematological, and antioxidant responses in crucian carp, Carassius carassius

The purpose of this study is to investigate the impact of microplastics (MPs) on fish and to confirm the toxic effects of MPs on fish, as well as to clarify the standard indicators. MPs are present in a large amount in the aquatic environment and can have various adverse effects on aquatic animals. Crucian carp, Carassius carassius (mean weight, 23.7 ± 1.6 g; mean length, 13.9 ± 1.4 cm), were exposed to PA (Polyamide) concentrations of 0, 4, 8, 16, 32 and 64 mg/L for 2 weeks. The PA accumulation profile in C. carassius decreased from the intestine to the gill to the liver. Hematological parameters such as red blood cell (RBC) counts, hemoglobin (Hb), and hematocrit (Ht) notably decreased at high levels of PA exposure. Plasma components such as calcium, magnesium, glucose, cholesterol, total protein, aspartate aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphatase (ALP) were significantly altered by PA exposure. The activities of superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST) and glutathione (GSH) of liver, gill and intestine significantly increased following PA exposure. The results of this study suggest that MP exposure affects the hematological physiology and antioxidant responses in C. carassius as well as accumulation in specific tissues.

Species-specific effects of microplastics on juvenile fishes

Microplastics contamination have been extensively reported in aquatic ecosystem and organisms. It is wildly acknowledged that the ingestion, accumulation and elimination of microplastics in fishes are species-specific, which mainly depending on the feeding behavior. This study aimed to investigate the effects of microplastics on the morphology and inflammatory response in intestines of fishes with different feeding types. Largemouth bass (carnivorous fish), grass carp (herbivorous fish) and Jian carp (omnivorous fish) were used as organism model. The contributing concentration and size of microplastics were explored as well as the response time and legacy effect in fishes. Two different sizes of polystyrene microplastics (80 nm and 8 μm) were set at three concentrations. And samples were analyzed at different exposure times and depuration times. Histological analysis indicated that multiple abnormalities in intestines were presented in three species fishes after acute exposure microplastics. The mRNA abundance of immune-related genes in the intestine tissues of fishes were significantly fluctuant. There were differential expressions of genes coping with differential sizes and concentrations of microplastics exposure in different fishes. The reason for the difference effects of microplastics on fishes was still unclear but could be due to the difference in the structure and function of the digestive system. These results provided a theoretical basis to further analysis of the mechanism of fish intestinal pathology caused by microplastics.

Effects of Dietary Medlar (Mespilus germanica L.) Extract on Growth Performance, Innate Immune Characteristics, Antioxidant Status, and Responses to Crowding Stress in Rainbow Trout (Oncorhynchus mykiss)

High stocking density is a stress factor that potentially affects physiological and immune responses. In this study, the effects of medlar (Mespilus germanica) extract (ME) supplementation on growth performance, antioxidant, immune status, and stress responses in rainbow trout (Oncorhynchus mykiss) were studied. Six hundred fish (40.19 ± 1.09 g; average fish weight ± standard error) were distributed randomly into five experimental groups (assayed in triplicates). The experimental diets were formulated as follows: 0 (T1, control), 0.5% (T2), 1% (T3), 1.5% (T4), and 2% (T4). After 60 days feeding trial, the fish were confined, and the density increased (60 kg/m3) for further 14 days. Results showed significant increases in final weight (FW), weight gain (WG), specific growth rate, and feed intake in the T4 compared to the control (P < 0.05). The feed conversion ratio (FCR) in T4 significantly decreased compared to the control (P < 0.05). Also, the treated groups showed significant improvements in catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), lysozyme (LYZ), total immunoglobulin (total Ig), respiratory burst activity (RBA), total protein, and phagocytosis (PHA) (P < 0.05). Moreover, compared with the control group, supplementation could significantly decrease glucose (GLU) and cortisol (CORT), alanine transaminase (ALT), lactate dehydrogenase (LDH), aspartate transaminase (AST), and alkaline phosphatase (ALP) (P < 0.05). After the challenge, FW and WG in all treated challenge groups were significantly improved compared to the control group (P < 0.05). FCR showed a significant decrease in all treated challenged groups compared to the control group (P < 0.05). However, malondialdehyde, CAT, GPx, SOD, LYZ, complement activity (C3 and C4), total Ig, RBA, peroxidase, and PHA in challenged treated groups were significantly increased compared to the control group (P < 0.05). All treated challenged groups showed lower ALT, LDH, AST, ALP, GLU, and CORT levels than the control group (P < 0.05). The experiment herein successfully demonstrated that dietary ME stimulated fish growth, antioxidant status, and immune responses in crowding conditions and can be recommended as beneficial feed additives for rainbow trout.

Joint cadmium and polypropylene microparticle action in cadmium tolerant model insect

Microplastic enlisted as a contaminant of emerging concerns in polluted environments interact with "traditional" contaminants such as metals, causing, among others, their increased accumulation in the body. Harmful effects depend on the exposed animals' possible preadaptation and/or cross-tolerance. The project aimed to assess the role of this phenomenon in the limited toxicity of polypropylene fibers (PPf) in 0%, 0.02%, 0.06, 0.18%, 0.54%, and 1.6% of Cd-supplemented food of larvae of Spodoptera exigua multigenerationally selected to cadmium tolerance. The activity of 20 digestive enzymes (API-ZYM test), defensins, and heat shock proteins, HSP70 levels in the exposed groups were used as biomarkers. PPfs caused the increase of Cd accumulation in the body, while intake of polypropylene microfibers did not change the biomarker levels. Moreover, multigenerational Cd pre-exposure, due to increased tolerance of Cd and, possibly, cross-tolerance, prepares the insects for an additional stressor (PPf) alone and in interaction with cadmium.

Rainbow trout (Oncorhynchus mykiss) physiological response to microplastics and enrofloxacin: Novel pathways to investigate microplastic synergistic effects on pharmaceuticals

Enrofloxacin (ENR) is a broad-spectrum antibiotic widely used due to its efficacy against pathogens. Microplastics (MPs) may bind to ENR and reduce its efficiency, whereas there would be an increase in its toxicity, bioavailability, and bio-accumulation rates. Therefore, the hypothesis is that the interaction between MPs and ENR can alter their toxicity and bioavailability. The subjective of this study is to examine the toxicity of various concentrations of ENR (0, 1.35, and 2.7 ml Kg^-1 diet) and MPs (0, 1000, and 2000 mg Kg^-1 diet) alone and in combination for 21 days. The rainbow trout (Oncorhynchus mykiss) is an economic aquaculture species used as an experimental model in ecotoxicology studies. Blood biochemical analytes indicated that ENR and MPs combination led to increasing enzymatic activity of each biomarker, except for gamma-glutamyl-transferase (GGT). Alterations related to triglycerides, cholesterol, glucose, urea, creatinine, total protein, and albumin blood contents were observed. An elevation in the levels of superoxide dismutase (SOD), malondialdehyde (MDA), and glucose 6-phosphate dehydrogenase (G6PDH) was found in the liver. In contrast, catalase (CAT) and glutathione peroxidase (GPx) levels decreased. Furthermore, a decline was observed in the cellular total antioxidant (ANT) levels. These findings suggested that ENR and MPs could affect fish health both independently and together. Consequently, the study determined that when both ENR and MPs were present in high concentrations, the toxicity of ENR was amplified, providing further evidence of the synergistic impact of MPs on ENR toxicity.

Combined toxic effects of cadmium and environmental microplastics in Aphanius fasciatus (Pisces, Cyprinodontidae)

Microplastics (MPs), plastic particles smaller than 5 mm in diameter, have received extensive attention as new environmental pollutants with still unexplored potential ecological risks. The main objective of the present study is to see if the concomitant exposure to MPs and Cd is more toxic than that to MPs or Cd separately in Aphanius fasciatus. Immature female were exposed to Cd and/or MPs for 21 days, and the subsequent effects were monitored by a combination of biochemical, histological and molecular toxicity markers. Exposure to Cd, but not to MPs, increased metallothioneins content and mRNA levels of the metallothioneins gene MTA both in liver and gills. In addition, we observed a significant oxidative stress response at histological, enzymatic (Catalase and Superoxide dismutase), non-enzymatic (proteins sulfhydryl and malondialdehyde) and gene expression levels to both toxicants in both tissues, particularly in gills, but no clear evidence for interaction between the two factors. Our results indicate a major effect of MPs on gills at different organizational levels. Finally, exposure to both MPs and Cd induced spinal deformities, although bone composition was only altered by the latter, whereas MTA mRNA bone levels were only increased realtive to controls in doubly-exposed samples. Interestingly, the simultaneous use of both pollutants produced the same effects as Cd and MPs alone, probably due to reduced bioavailability of this heavy metal.

Sub-chronic exposure of Oreochromis niloticus to environmentally relevant concentrations of smaller microplastics: Accumulation and toxico-physiological responses

This study assesses the accumulation and toxic effects of environmentally relevant concentrations (0.01, 0.1 and 1 mg/L) of polystyrene MPs (1 µm) in Oreochromis niloticus (Nile tilapia) for 14 days. The results showed that 1 µm PS-MPs accumulated in the intestine, gills, liver, spleen, muscle, gonad and brain. RBC, Hb and HCT showed a significant decline, while WBC and PLT showed a significant increase after the exposure. Glucose, total protein, A/G ratio, SGOT, SGPT and ALP showed significant increments in 0.1 and 1 mg/L of PS-MPs treated groups. The increase in cortisol level and upregulation of HSP70 gene expression in response to MPs exposure indicate MPs-mediated stress in tilapia. MPs-induced oxidative stress is evident from reduced SOD activity, increased MDA levels and upregulated P53 gene expression. The immune response was enhanced by inducing respiratory burst activity, MPO activity and serum TNF-α and IgM levels. MPs exposure also led to down-regulation of CYP1A gene and decreased AChE activity, GNRH and vitellogenin levels, indicating the toxicity of MPs on the cellular detoxification mechanism, nervous and reproductive systems. The present study highlights the tissue accumulation of PS-MP and its effects on hematological, biochemical, immunological and physiological responses in tilapia with low environmentally relevant concentrations.

Toxic effects of microplastic (Polyethylene) on fish: Accumulation, hematological parameters and antioxidant responses in Korean Bullhead, Pseudobagrus fulvidraco

Plastic waste discharged into the aquatic environment decomposes into microplastics (MP), which have toxic effects on fish species. Korean bullhead, Pseudobagrus fulvidraco is widely distributed in freshwater ecosystems in Korea, and it is important as an ecological indicator species to evaluate MP toxicity in Korea. In this study, the accumulation and physiological effects of juvenile P. fulvidraco exposed to microplastics (Polyethylene: PE-MPs with white surface and spherical shape) at control (0 mg/L), 100, 200, 5000 and 10,000 mg/L for 96 h were confirmed. Exposure to PE-MPs showed significant bioaccumulation of P. fulvidraco, and the accumulation profile was in the order of gut > gills > liver. Hematological parameters such as the red blood cell (RBC), hemoglobin (Hb) and hematocrit (Ht) were significantly decreased over 5000 mg/L In plasma components, calcium, magnesium and total protein were significantly decreased over 5000 mg/L, whereas glucose, cholesterol, aspartate aminotransferase (AST), alanine transaminase (ALT) and alkaline phosphatase (ALP) were significantly increased over 5000 mg/L or at 10,000 mg/L In antioxidant responses, superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST) were significantly increased over 5000 mg/L, whereas glutathione (GSH) was significantly decreased over 5000 mg/L. The results of this study suggest that acute exposure to PE-MPs induced all physiological changes in a concentration-dependent manner, and it affects the hematological parameters, plasma components and antioxidant response of juvenile P. fulvidraco after accumulation in specific tissues.

Combined impacts of microplastics and cadmium on the liver function, immune response, and intestinal microbiota of crucian carp (Carassius carassius)

Microplastics (MPs) and the heavy metal cadmium (Cd) have attracted global attention for their toxicological interactions in aquatic organisms. The purpose of this investigation was evaluating the effect of MPs (1 mg L^-1) and Cd (5 mg L^-1) on the liver function, immune response of crucian carp (Carassius carassius) after 96 h exposure, and intestinal microbiota after 21 days, respectively. Co-exposure to MPs and Cd significantly enhanced MP accumulation in the liver of the crucian carp compared to the accumulation with exposure to MPs alone. Co-exposure to MPs and Cd triggered notable histopathological alterations accompanied by increased hepatic cell necrosis and inflammation, and was associated with higher aspartate aminotransferase and alanine aminotransferase levels, lower superoxide dismutase and catalase activity levels, but higher malondialdehyde content and total antioxidant capacity in the liver. Moreover, the combined treatment of MPs and Cd led to the up-regulated transcription of genes related to immune response, such as interleukin 8 (il-8), il-10, il-1β, tumor necrosis factor-α, and heat shock protein 70, both in the liver and spleen. Co-exposure to MPs and Cd reduced the variety and abundance of the intestinal microbiota in the crucian carp. Our research indicates that the combined exposure to MPs and Cd may exert synergistic toxic effects on crucian carp, which could impede the sustainable growth of the aquaculture industry and pose potential risks to food safety.

Exposure to polypropylene microplastics via diet and water induces oxidative stress in Cyprinus carpio

The occurrence of accumulation of microplastics in humans and wildlife has become a serious concern on a global scale, especially in the last decade. Although there are many studies on microplastics, their biological effects and toxicity on freshwater fish have not been fully revealed. In order to evaluate the potential toxic effects of PP (polypropylene) microplastics in freshwater fish, we performed 1-day, 2-day, 3-day, 4-day, 5-day, 6-day, and 7-day microplastic exposure to different concentrations of the microplastics through water and diet on Cyprinus carpio. Fish samples were divided into 3 groups; Group-A with different PP microplastic concentrations in their water (A_Low:1.0 g/L and A_High:2.5 g/L), Group-B with different PP microplastic concentrations in their diet (B_Low:100 mg/g and B_High:250 mg/g), and Group-C (Control group) free of PP microplastics in their diet and water. The results showed that although microplastics did not cause death in C. carpio, they caused oxidative stress in comparing the MP exposed groups to the control groups. When indices of oxidative stress of fish individuals in all treatment groups were compared with the control group, it was determined that MDA (malondialdehyde) and GSH (glutathione) levels increased, while TPC (total protein content) and CAT (catalase) levels decreased depending on the concentrations and exposure times. Significant differences were observed between the control and treatment groups in the indices of oxidative stress (P<0.05). This study provided basic toxicological data to elucidate and quantify the effects of PP microplastics on freshwater fish. In addition, this study is the first study to indicate that microplastic exposure of carp via diet and water causes oxidative stress in gill tissues and causes changes in CAT, MDA, GSH, and TPC levels. The findings also provide useful reference data for improving knowledge of the effects of microplastics on organisms in freshwater systems.

Factors Affecting the Adsorption of Heavy Metals by Microplastics and Their Toxic Effects on Fish

Fish not only constitute an important trophic level in aquatic ecosystems but also serve as an important source of protein for human beings. The health of fish is related to the sustained and healthy development of their entire aquatic ecosystem. Due to the widespread use, mass production, high disposal frequency, and degradation resistance of plastics, these pollutants are released into aquatic environments on a large scale. They have become one of the fastest growing pollutants and have a substantial toxic effect on fish. Microplastics have intrinsic toxicity and can absorb heavy metals discharged into water. The adsorption of heavy metals onto microplastics in aquatic environments is affected by many factors and serves as a convenient way for heavy metals to migrate from the environment to organisms. Fish are exposed to both microplastics and heavy metals. In this paper, the toxic effects of heavy metal adsorption by microplastics on fish are reviewed, and the focus is on the toxic effects at the individual (survival, feeding activity and swimming, energy reserves and respiration, intestinal microorganisms, development and growth, and reproduction), cellular (cytotoxicity, oxidative damage, inflammatory response, neurotoxicity, and metabolism) and molecular (gene expression) levels. This facilitates an assessment of the pollutants' impact on ecotoxicity and contributes to the regulation of these pollutants in the environment.

Effects of microplastics on the toxicity of co-existing pollutants to fish: A meta-analysis

Aquatic ecosystems are among the main destination for microplastics (MPs) in the environment. MPs that enter aquatic ecosystems can contribute to pollution together with other co-existing pollutants. However, whether such pollution results in higher or lower toxicity to fish than that caused by co-existing pollutants alone remains controversial. This study aimed at closing this research gap based on 1380 biological endpoints under the background of environmental MP concentrations collected from 55 laboratory studies. Overall, MPs in co-existing pollutant solutions significantly increased the toxicity to fish. Specifically, MPs elevated negative effects on the immune system, metabolism, and oxidative damage. Subgroup analysis indicated that changes in toxicity were related to fish life stage and MP size, but not to co-existing pollutant or MP type. Meta-regression analysis indicated that changes in toxicity were not related to the logarithm of the octanol-water partition coefficient (logKow) or exposure time. Finally, the differences between laboratory research and the actual aquatic environment were discussed from four aspects: MPs, co-existing pollutants, environmental factors, and experimental objects. Our study provides a basis for further understanding the potential impact of MPs on aquatic organisms from a combined pollution perspective. Moreover, our results can provide a reference for the conservation and management of aquatic ecosystems.

Potential ecotoxicity of substrate-enriched zinc oxide nanoparticles to Physalaemus cuvieri tadpoles

Although the ecotoxicological effects of ZnO nanoparticles (ZnO NPs) have already been reported in different taxa, little is known about their impacts on amphibians. Thus, we aimed to evaluate the potential effects of exposure of Physalaemus cuvieri tadpoles to substrates enriched with ZnO NPs (and with its ionic counterpart, Zn+2, ZnCl2 - both at 100 mg/kg) previously used in the cultivation of Panicum maximum (Guinea grass). We showed that although exposure for 21 days did not impact the survival, growth, and development of tadpoles, we noted an increase in the frequency of erythrocyte nuclear abnormalities in the "ZnCl2" and "ZnONP" groups, which was associated with suppression of antioxidant activity in the animals (inferred by SOD and CAT activity and DPPH free radical scavenging capacity). In the tadpoles of the "ZnONP" group, we also noticed a reduction in creatinine and bilirubin levels, alpha-amylase activity, and an increase in alkaline phosphatase activity. But the treatments did not alter the activity of the enzymes lactate dehydrogenase and gamma-glutamyl-transferase and total protein and carbohydrate levels. On the other hand, we report a cholinesterase and hypotriglyceridemic effect in the "ZnCl2" and "ZnONP" groups. Zn bioaccumulation in animals, from ZnO NPs, from Zn+2 released from them, or both, has been associated with causing these changes. Finally, principal component analysis (PCA) and the values of the "Integrated Biomarker Response" index revealed that the exposure of animals to substrates enriched with ZnO NPs caused more pronounced effects than those attributed to its ionic counterpart. Therefore, our study reinforces the need to consider the environmental risks of using these nanomaterials for agricultural purposes for amphibians.

Toxic effects of microplastic (polyethylene) exposure: Bioaccumulation, hematological parameters and antioxidant responses in crucian carp, Carassius carassius

The purpose of this study was to evaluate the toxic effects of polyethylene microplastics (PE-MPs) by measuring the bioaccumulation, hematological parameters, and antioxidant responses in crucian carp (Carassius Carassius) exposed to waterborne 22-71 μm PE-MPs. C. carassius (mean weight, 24.0 ± 2.1 g; mean length, 13.1 ± 1.2 cm) were exposed to PE-MPs at concentration of 0, 4, 8, 16, 32, and 64 mg/L for 2 weeks. The accumulation of PE-MPs in each tissue of C. carassius was significantly increased in proportion to the PE-MPs concentration; the highest accumulation was observed in the intestine, followed by the gills and liver. Hematological parameters, plasma components and antioxidants responses were significantly affected by PE-MPs in a concentration-dependent manner. Exposure to ≥32 mg/L PE-MPs induced a significant decrease in red blood cells (RBCs), hemoglobin (Hb) content, and hematocrit values. However, exposure to ≥32 mg/L PE-MPs induced oxidative stress in the liver, gill, and intestine of C. carassius, thereby resulting in a significant increase in the levels of superoxide dismutase (SOD), catalase (CAT), and glutathione S-transferase (GST) and a decrease in glutathione (GSH) levels. The effects of interaction between the PE-MPs and exposure periods showed no significant changes in bioaccumulation, hematological parameters, plasma components and antioxidant responses. These finding indicate that the exposure to ≥32 mg/L PE-MPs could cause a significant accumulation in specific tissues of C. carassius, resulting in changes in hematological parameters, plasma components, and antioxidant responses. However, the interaction between PE-MPs and exposure periods had no significant effects, thereby suggesting the lack of toxicological interactions between PE-MPs and exposure periods in C. carassius.

Cadmium effects on the freshwater teleost Prochilodus lineatus: Accumulation and biochemical, genotoxic, and behavioural biomarkers

In order to evaluate the effects of Cd, juveniles of the Neotropical fish Prochilodus lineatus were exposed to 1 and 10 μg L^-1 Cd, for 24 and 96 h. Fish exposed to Cd showed metal accumulation in the gills, kidney, and liver, an increase in DNA damage in erythrocytes, and an increase in lipid peroxidation (LPO) in the kidney. Cd exposure also caused a reduction in catalase activity, metallothionein induction, and LPO in the liver. Cd stimulated the swimming activity of exposed fish, resulting in longer swimming times and distances travelled, especially for the shortest exposure time. Changes in acetylcholinesterase activity (AChE) in the muscle and brain are probably related to these behavioural responses. These results show that Cd affects the functioning of several organs in P. lineatus, which is indicated by the genotoxic damage and changes in the AChE and swimming pattern of the exposed fish.

Biochemical, Genotoxic and Histological Implications of Polypropylene Microplastics on Freshwater Fish Oreochromis mossambicus: An Aquatic Eco-Toxicological Assessment

In recent years, polypropylene microplastic has persisted in freshwater ecosystems and biota, forming ever-growing threats. This research aimed to prepare polypropylene microplastics and evaluate their toxicity to the filter feeder Oreochromis mossambicus. In this research, fish were given a dietary supplement of polypropylene microplastics at 100, 500, and 1000 mg/kg for acute (96 h) and sub-acute (14 days) durations to assess toxic effects on liver tissues. FTIR results revealed the presence of polypropylene microplastic in their digestion matter. The ingestion of microplastics in O. mossambicus led to fluctuations in homeostasis, an upsurge in reactive oxygen species (ROS) levels, an alteration in antioxidant parameters, including superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST), and glutathione peroxidase (GPx); a promotion in the oxidation of lipid molecules; and a denaturation in the neurotransmitter enzyme acetylcholinesterase (AChE). Our data indicated that sustained exposure to microplastics (14 days) produced a more severe threat than acute exposure (96 h). In addition, higher apoptosis, DNA damage (genotoxicity), and histological changes were found in the liver tissues of the sub-acute (14 days) microplastics-treated groups. This research indicated that the constant ingestion of polypropylene microplastics is detrimental to freshwater environments and leads to ecological threats.

Microplastic and oil pollutant agglomerates synergistically intensify toxicity in the marine fish, Asian seabass, Lates calcalifer

Asian seabass, Lates calcarifer frys were exposed to polystyrene (MP: 0.5 mg/l), oil (0.83 ml/l) and agglomerates (MP + oil + Corexit) as eight treatments in three replicates, and fresh synthetic marine water (control) for 15 days. The synergistic effect was confirmed (P ˂ 0.05) by bio-indicators including RBC count, total plasma protein, aspartate aminotransferase (AST), catalase (CAT), glutathione S-transferase (GST), basophils, thrombocyte and eosinophils percentages. Most of the significant and synergistic effects were observed in the highest doses (5 mg/l MP and 5 mg/l MP-oil-dispersant). Exposure to MP and a combination of MP+ oil caused tissue lesions in gill, liver and intestine. Our results suggest there are no critical health issues for Asian seabass in natural environments. However, the bioaccumulation of MPs, oil, and their agglomerates in consumers' bodies may remain a concern.

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

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

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.