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

Effects of polypropylene microparticles ingestion on the growth and physiology of Piaractus brachypomus, and its accumulation and tissue damage

The presence of microplastics in aquatic environments is a growing concern due to their impacts on fish health. This study aimed to investigate the effects of different concentrations of polypropylene microparticles (PPMs) added to the diet of juvenile Piaractus brachypomus, on their growth, survival, physiology and tissue health. A total of 280 juveniles weighing 13.45 ± 2.07 g were divided into five treatments (0, 10, 100, 1000 and 5000 mg PPMs per kg of feed) with four replicates each. The juveniles were cultivated for 60 days in recirculating aquaculture systems. Biometrics and blood and tissue collections were performed after 10 and 60 days of the experiment. Juvenile performance was affected by the presence of PPMs in the diet within 10 days, with a reduction in final weight for the different concentrations. No differences were observed in juvenile growth after 60 days compared to the control. Total protein, hematocrit, and the enzymes alanine aminotransferase (ALT) and aspartate aminotransferase (AST) changed significantly for the juveniles of the different treatments in both periods. No changes were observed in liver tissue histology; however, the presence of PPMs and damage to microvilli were verified in intestinal tissue. Although PPMs were observed in the intestine of juveniles in both periods, there was no migration of PPMs to the muscle. The addition of PPMs to juvenile diet caused growth disturbances within 10 days and blood and histological alterations in the intesine, without resulting in severe consequences leading to mortality in both periods.

Microplastics bioaccumulation in fish: Its potential toxic effects on hematology, immune response, neurotoxicity, oxidative stress, growth, and reproductive dysfunction

After being exposed, microplastics mostly bioaccumulated in guts and gills of fish, then, through circulation, spread and bioaccumulated in other tissues. Circulatory system of fish is impacted by the microplastic bioaccumulation in their tissues, influencing a number of hematological indices that are connected with immunity, osmotic pressure, blood clotting, molecular transport and fat metabolism. Variables like size, dose, duration, food consumption and species, all affect the bioaccumulation and toxicity of the microplastic, rather than the exposure routes. Microplastics lead to an imbalance in the generation of ROS and antioxidant defense of fish, which resulting in oxidative injury. Moreover, microplastics affect immunological responses through physico-chemical damage, hence produce neurotoxicity and modifies the activity of the acetylcholine esterase. Exposure to microplastics caused damage to the hepatic and gut tissue, affect intestinal barrier function and dysbiosis of microbial composition, altered the metabolism of host, affecting the activities of the digestive enzymes, eventually affecting the growth performance of fish. Microplastics exposure target the HPG axis and interfere with the process of steroidogenesis, apoptosis of the gonadal tissue, ultimately causing reproductive dysfunction. Fish exposed to microplastics have a range of toxic effects viz. alteration to immune, antioxidant and hematological indices, bioaccumulation, neurotoxicity, growth and reproductive dysfunction, all were examined in this present review by using different indicators.

Effect of microplastic binding capacity on antioxidant and immune responses of Korean rockfish Sebastes schlegeli in a co-exposure environment with microplastics and Streptococcusiniae

Korean rockfish (Sebastes schlegeli) aquaculture, which predominantly occurs in coastal regions, encounters challenges such as reduced productivity owing to microplastics and bacterial contamination. Microplastic adsorb bacteria and accumulates in fish, inducing alterations in antioxidant and immune responses. Numerous studies have examined the interaction between microplastics and external pollutants such as heavy metals and physiological changes in fish; however, studies on the effects of combined exposure to microplastics and bacteria on physiological changes in fish remain limited. Therefore, we investigated the effects of combined exposure to microbead (MB) and Streptococcus iniae (S. iniae) on the antioxidant and immune responses of Korean rockfish. Korean rockfish were exposed to single and combined environments of 0.2 μm MB at 5 and 50 beads/L and S. iniae at 1 × 105 and 1 × 107 CFU/mL for 5 days. MB accumulation in gill and intestine tissues was examined, and copy number changes of S. iniae in liver and spleen tissues were analyzed. The mRNA expression levels of antioxidant enzymes (SOD and CAT) and immune-related genes (IL-1β, IL-6, CCL25, and TNF-α) were analyzed in the liver tissue, while changes in plasma MDA and lysozyme levels were evaluated as an additional immune-related factor. Combined exposure to high concentrations of MB and S. iniae increased the accumulation of MB and the copy number of S. iniae than that of a single exposure. This also increased the mRNA expression of antioxidant enzymes and immune response genes. These results indicate that the accumulation of MB in Korean rockfish, depending on its concentration, can bind with S. iniae, inducing changes in the copy number of S. iniae and affecting antioxidant and immune responses. This study is expected to provide fundamental academic data for understanding the physiological and immunological responses of marine organisms exposed to the combined effects of MB and S. iniae.

Ecotoxicological assessment of microplastics and florfenicol on Acanthopagrus latus: mucus, humoral immune responses and DNA damage

This study evaluated the adverse effects of florfenicol (FLO) (15 mg/kg diet) and microplastics (MPs) (100 and 500 mg/kg diet) on yellowfin seabream, Acanthopagrus latus, over a 10-day exposure period. Fish were exposed to these substances individually and in combination. Tissue, blood, and skin mucus samples were collected on days 1, 4, 7, and 14 post-exposure. Results indicated that both MPs alone and combined with FLO elevated cholesterol, triglyceride, urea, creatinine, and glucose levels. The activities of aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase, alkaline phosphatase (ALP), and creatine kinase were also increased. Conversely, immunological markers such as complement 3, complement 4, immunoglobulin M, lysozyme activity, phagocytic activity, respiratory burst activity, and total protein concentrations decreased. Similar to blood results, the concentrations of alternative complement, total immunoglobulin, lysozyme, and total protein in the mucus were reduced, whereas ALP levels in the mucus increased. These biomarkers did not recover by day 14 in groups exposed to MPs alone or with the antibiotic. FLO concentration in muscle peaked on day 1 and declined by the end of the trial. The FLO alone affected creatinine, cholesterol, total protein, AST, ALT, ALP, and immunological markers, all of which returned to normal by the conclusion of the trial. FLO did not influence the total immunoglobulin in the mucus. MPs, individually and in combination, increased DNA damage in the liver, kidney, spleen, and intestinal tissues. The findings demonstrate that FLO and MPs detrimentally impact fish health, with a more pronounced effect when combined, indicating synergistic toxicity.

Effects of Hematological Parameters and Plasma Components of Starry Flounder, Platichthys stellatus, by Waterborne Copper Exposure

Starry flounder (Platichthys stellatus) (weight 96.42 ± 19.17 g, length 20.65 ± 1.04 cm) were exposed to waterborne copper at 0, 0.5, 1, 3, 6, 12, 24, and 48 mg Cu2+/L for 96 h. The lethal concentration 50 (LC50) of the P. stellatus exposed to waterborne copper was 15.644 mg Cu2+/L. Hemoglobin, hematocrit, and RBC count were significantly decreased by waterborne copper exposure. MCV (mean corpuscular volume) (µL) and MCHC (mean corpuscular hemoglobin concentration) (%) were also significantly decreased. The inorganic components, plasma calcium, and plasma magnesium were significantly increased. The organic components, such as plasma glucose, were significantly increased. In enzymatic components, the AST and ALT were also significantly increased by copper exposure. The results of this study indicate that exposure to copper may have effects on the survival rates and hematological parameters of the P. stellatus.

Impact of microplastics exposure on the reconfiguration of viral community structure and disruption of ecological functions in the digestive gland of Mytilus coruscus

Microplastics (MPs) pose ecological risks by serving as viral vectors and disrupting host microbiomes. This study investigated the impact of MPs on the digestive gland virome of Mytilus coruscus through an in situ exposure experiment on Xixuan Island, Zhoushan, China, using polyethylene MPs and metagenomic sequencing. MPs biofilms were dominated by lytic viruses (> 99 %) with low diversity (Shannon index = 4.10 ± 0.39), whereas digestive glands harbored a more diverse virome (Shannon index = 7.26 ± 1.26). MPs ingestion significantly reduced virome diversity and altered viral community composition. Functional analysis showed that MPs biofilms were enriched in genes related to genetic processing, carbohydrate metabolism and membrane biogenesis, while transcription- and replication-related genes declined (P < 0.05) in digestive glands post-ingestion. MPs biofilms carried abundant antibiotic resistance genes (ARGs) and virulence factors, selectively enriching multidrug resistance genes (efrA, patB) while reducing functional viral gene abundance. Metal (Zn, Hg, As) and biocide resistance genes were prevalent in MPs biofilms but declined post-ingestion. Additionally, MPs ingestion weakened microbial network stability, potentially impairing immune regulation and metabolic homeostasis. These findings underscore MPs' role in shaping viral communities and spreading resistance genes, heightening ecological risks in marine environments.

Interface adsorption characteristics of microplastics on multiple morphological arsenic compounds

Polystyrene (PS) and polyethylene terephthalate (PET) are commonly used materials that degrade into microplastics in the environment. These microplastics, possessing unique physical properties, can adsorb pollutants and contribute to composite pollution effects. This study examined the loading characteristics and toxic effects of PS and PET on six arsenic compounds, revealing that PS and PET displayed different adsorption capacities for these compounds, with PS demonstrating high adsorption for monomethylarsonic acid (MMA). The adsorption kinetics and isotherm analyses indicated that arsenic compounds quickly reached equilibrium on PS and PET. The kinetics were effectively described by pseudo-first-order models, and the isotherms aligned with the Langmuir and Freundlich models. Furthermore, simulated gastric fluid (SGF) and simulated intestinal fluid (SIF) were used to desorb arsenic compounds bound to PS and PET. The effects of aging, pH, salinity, anions, and humic acid (HA) on the ability of inorganic arsenic (iAs) to bind to PS and PET were analyzed. The results indicated that aging and HA increased the adsorption capacity of the microplastics, while salinity, anions, and elevated pH negatively affected this capacity. Additionally, the influence of microplastics and iAs on the clearance of free radicals by reduced glutathione (GSH) was explored. Microplastics inhibited the clearance of 1,1-diphenyl-2-picryl-hydrazyl (DPPH) by GSH, whereas iAs, especially arsenate, facilitated this process, likely due to synergistic effects with the oxidized form of GSH generated through GSH reactions. This study offers a theoretical foundation for understanding how microplastics transport various forms of arsenic compounds and their potential environmental risks.

Expression of antioxidant and stress-related genes in olive flounder, Paralichthys olivaceus exposed to high temperatures after pre-heating

The rising sea surface temperatures driven by climate change cause thermal stress, leading to oxidative stress, metabolic disorders, and increased disease susceptibility, thereby impairing the physiological functions of fish. Therefore, understanding the adaptation mechanisms of fish to high temperatures is essential for mitigating the negative impacts of thermal stress on aquaculture productivity and fish health. In this study, Paralichthys olivaceus were subjected to high temperatures following pre-heating to evaluate the advantages of pre-stimulation prior to exposure to the critical temperature. The P. olivaceus were exposed to four groups; Acute (subjected to acute heat shock at 32 °C), AH-S (exposed to acquired heat shock at 28 °C followed by short recovery of 2 h and subsequent heat shock at 32 °C), AH-L (exposed to acquired heat shock at 28 °C followed by long recovery of 2 days and subsequent heat shock at 32 °C) and AH-SL (combined of AH-S and AH-L protocols). In terms of antioxidant response, mRNA expression (caspase 10, thioredoxin (Trx), superoxide dismutase (SOD), peroxiredoxin (Prx), glutathione-S-transferase (GST), and transferrin (TF)) and enzyme activities (SOD, CAT, and GST) were significantly upregulated in P. olivaceus pre-heated prior to high-temperature exposure (AH-S, AH-L, and AH-SL groups). In addition, the stress gene expressions such as heat shock protein 70 (HSP70), HSP60, HSP90, warm-temperature-acclimation-associated 65-kDa protein (Wap65-1), and glucose-regulated protein 78 (GRP78) was significantly upregulated in AH-S, AH-L and AH-SL groups. Pre-heating has been found to be effective in mitigating thermal stress, with the efficacy varying according to the differences in pre-heating methods.

Effects of Polystyrene Nanoplastics on Oxidative Stress, Blood Biochemistry, and Digestive Enzyme Activity in Goldfish (Carassius auratus)

Plastic pollution in aquatic ecosystems has become a global concern, and nanoplastics, due to their small size and high penetration potential, pose significant risks to aquatic organisms. This study aimed to evaluate the effects of polystyrene nanoplastics (PS-NPs) on oxidative stress biomarkers, blood biochemical parameters, and digestive enzyme activities in Goldfish (Carassius auratus). The experiment was conducted over 21 days, exposing fish to four different dietary concentrations of PS-NPs (0, 1, 10, and 100 mg/Kg). The results showed that chronic exposure to 50 nm PS-NPs significantly increased the activity of antioxidant enzymes (CAT, SOD, and GPx) and MDA activity in the gill, kidney, and liver tissues, indicating the induction of oxidative stress. Furthermore, notable alterations were observed in blood biochemical enzymes (alkaline phosphatase [ALP], alanine aminotransferase [ALT], aspartate aminotransferase [AST], and lactate dehydrogenase [LDH]), suggesting cellular damage and physiological disturbances. Additionally, PS-NP exposure affected the activity of digestive enzymes (amylase, lipase, and protease), which may impact nutrient digestion and absorption. These findings highlight that PS-NPs can adversely affect aquatic animal health and may influence the nutritional quality of fish. Therefore, further research is necessary to assess the long-term ecological and toxicological impacts of nanoplastics in freshwater ecosystems.

Microplastics induce toxic effects in fish: Bioaccumulation, hematological parameters and antioxidant responses

This study investigates the toxic effects of microplastics by assessing bioaccumulation, hematological parameters, and antioxidant responses in juvenile Korean bullhead (Pseudobagrus fulvidraco) exposed to polyamide microplastics (PA-MPs). The increasing release of plastics into aquatic environments leads to their degradation into microplastics, which pose a significant threat to freshwater ecosystems. To evaluate these impacts, P. fulvidraco (mean length: 16.3 ± 1.1 cm, mean weight: 38.2 ± 6.6 g) were exposed to waterborne PA-MPs (white, spherical particles) at concentrations of 0, 10, 20, 5000 and 10,000 mg/L for 96 h. Bioaccumulation analysis revealed that PA-MPs primarily accumulated in the intestine, followed by the gills and liver. Hematological assessments showed significant reductions in hemoglobin and hematocrit levels at high PA-MP concentrations (5000 and 10,000 mg/L). Plasma biochemical analysis indicated significant alterations in calcium, magnesium, glucose, cholesterol, total protein, AST, ALT and ALP levels. In terms of antioxidant responses, superoxide dismutase (SOD) and catalase (CAT) activities increased significantly with PA-MP exposure, while glutathione S-transferase (GST) activity showed a marked decrease. These findings suggest that PA-MP exposure leads to bioaccumulation in key tissues and induces physiological stress in P. fulvidraco by altering hematological and antioxidant defense mechanisms, highlighting the potential toxicity of microplastics in freshwater fish.

Individual and combined effects of microplastics and diphenyl phthalate as plastic additives on male goldfish: A biochemical and physiological investigation

The development of the plastics industry worldwide has led to an increase in the rate of plastic waste and chemical additives such as microplastics (MPs) and diphenyl phthalate (DPP) in the environment. The penetration of these pollutants into aquatic ecosystems has also raised concerns about their toxic effects, individually and in combination. The present study investigated the individual and combined toxicity of MPs and DPP on the health of male goldfish. A 28-day exposure experiment was conducted using different concentrations of DPP (2.5, 5.0, 7.5 μL L-1) and MPs (20, 40 mg L-1), both individually and in combination. Biochemical markers, enzyme activities, and hormone levels were evaluated to ascertain the effects on metabolic, renal, and reproductive health. The findings revealed that concurrent exposure to DPP and MPs markedly elevated plasma glucose, creatinine, triglycerides, and cholesterol levels, accompanied by notable reductions in high-density lipoprotein and low-density lipoprotein. Moreover, combined exposures resulted in liver damage, as evidenced by elevated serum glutamic-oxaloacetic transaminase, serum glutamic-pyruvic transaminase, alkaline phosphatase, lactate dehydrogenase, and gamma-glutamyl transferase activities and disruptions in protein synthesis and immune response, with notable decreases in total protein, albumin, and globulin. Testosterone levels decreased, while estradiol levels increased, indicating endocrine disruption and potential reproductive impairment. These findings indicated the adverse synergistic effects of MPs and DPP on the physiology of goldfish. Therefore, further research must be conducted to increase our knowledge of their ecotoxicological risks.

Improved YOLOv5 s and transfer learning for floater detection

This study aims to address the detection and classification of floating objects on water surfaces, including items such as bottles, plastic bags, aquatic plants, and dead fish, which pose significant threats to water quality and ecosystems. Traditional detection methods rely on manual observation and cleanup, which are inefficient, costly, and risky. To tackle this challenge, this paper proposes a solution based on an improved YOLOv5 s model by collecting floating object image data and constructing and processing the dataset using manual photography and SAGAN data augmentation techniques. We optimized the YOLOv5 s model by integrating the EfficientNetv2 lightweight network, the content-aware reassembly of features lightweight upsampling module, the bidirectional feature pyramid network structure, and by introducing attention modules such as squeeze-and-excitation and efficient multi-scale attention, along with the scylla intersection over union (SIoU) loss function. Additionally, transfer learning techniques were employed to enhance the model's performance in detecting floating objects on water surfaces, and ablation experiments were conducted to validate the effectiveness of each improvement. The results show that the improved YOLOv5 s model exhibits better performance and generalization ability on the test set, with a 5.27 percentage point increase in model accuracy. The model's parameter count, computational load, and weight size are 53.9%, 21.3%, and 54% of the original YOLOv5 s model, respectively, providing an efficient, accurate, and real-time solution for detecting floating objects on water surfaces. The methodology presented in this paper holds significant importance for the monitoring of aquatic ecological environments and the management of floating debris, offering valuable insights for achieving precise and efficient detection and classification of floating objects on water surfaces.

Apoptosis, MAPK signaling pathway affected in tilapia liver following nano-microplastics and sulfamethoxazole acute co-exposure

Studies showed that toxicants that adhered to the surface of nano-microplastics (NPs) have toxicological effects. Juvenile tilapia were divided into four groups namely the control group (A), 100 ng·L-1 sulfamethoxazole (SMZ) group (B), 75 nm NPs group (C) and SMZ + 75 nm NPs group (D), and were exposed to an acute test for 2, 4 and 8 days. The hepatic histopathological changes, enzymatic activities, transcriptomics and proteomics analysis have been performed. The results showed that; the enzymatic activities of anti-oxidative enzymes (ROS, SOD, EROD), energy (ATP), lipid metabolism (TC, TG, FAS, LPL, ACC), pro-inflammatory factors (TNFα, IL-1β) and apoptosis (Caspase 3) have decreased significantly at 8 d. Hepatic histopathological results revealed the narrowed hepatic sinuses, displaced nucleus, and vacuoles under SMZ exposure. Transcriptome results demonstrated that endocytosis, MAPK signaling pathway, apoptosis, lysosome and herpes simplex infection were enriched in group C at 8 d. apaf1, casp3a, nfkbiaa (apoptosis, except for 8 d) were significantly increased, il1b and tgfb3, fgfr2 showed significant increase and decrease in group C/D. ctsd and ctsk associated with apoptosis have been especially significantly increased at 8 d, while MAPK signaling pathway, gadd45ga, gadd45gb/gadd45gg have been significantly decreased and increased, as well as map3k3/map3k2 significantly decreased at 8 d. Apoptosis and MAPK signaling pathway were affected and the synergistic effect was verified in tilapia liver following NPs and SMZ acute co-exposure.

Effects of Sub-Chronic Exposure to Polystyrene Nanoplastics on Lipid and Antioxidant Metabolism in Sparus aurata

Nanoplastics (NPs) can cross cellular membranes and affect cellular performance. This study aims to determine the effects of polystyrene NPs (PS-NPs, 44 nm) on gilthead seabream (Sparus aurata) exposed for 14 days to 100 μg/L PS-NPs. The results show that biometric indicators (weight, length, Fulton's condition factor, and hepatosomatic index) were not affected after the experimental exposures. No significant effects were observed on white blood cell count, red blood cell count, mean corpuscular hemoglobin, or platelets compared to the control group. However, there was a significant decrease in hemoglobin concentration, hematocrit values, and mean corpuscular cell volume in fish exposed to PS-NPs. There were no significant effects on plasmatic cholesterol, triglyceride, alkaline phosphatase, or aspartate aminotransferase levels. The histological anatomy of both the gills and the intestine revealed no obvious signs of cellular damage, excessive mucous, or inflammation in the PS-NP group. The expression of transcripts related to lipid metabolism (pparα, pparβ), growth and development (igf1), detoxification (bche), and oxidative stress (sod, gpx1) were significantly downregulated in animals exposed to PS-NPs, indicating a slight impairment in lipid homeostasis and antioxidant response.

Impact of microplastics exposure on liver health: A comprehensive meta-analysis

Microplastics (MPs) are significant concerns affecting liver health. This is the first comprehensive meta-analysis, evaluating the impact of MPs on liver functions across various animal models, including mice, fish, crabs, and shrimp. Five databases, including PubMed, Embase, Cochrane Central Register of Controlled Trials (CENTRAL), Ovid MEDLINE, and Web of Science, were used to select eligible studies. In all, 70 studies out of 1872 publications were included in the analysis, the impact of MPs on liver enzymes, oxidative stress markers, and inflammatory cytokines were evaluated. Our results revealed significant increases in liver enzymes ALT and AST, oxidative stress markers MDA, and pro-inflammatory cytokines IL-6 and TNF-α, along with a notable reduction in antioxidative enzymes like SOD, CAT, GSH, and GPx. These findings suggest that MPs exposure significantly disrupts liver function by inducing oxidative stress and inflammation. The results underscore the urgent need for targeted environmental policies and further research.

Microplastics influencing aquatic environment and human health: A review of source, determination, distribution, removal, degradation, management strategy and future perspective

Microplastics (MPs) are produced from various primary and secondary sources and pose multifaceted environmental problems. They are of non-biodegradable nature and may stay in aquatic environments for a long time period. The present review has covered novel aspects pertaining to MPs that were not covered in earlier studies. It has been observed that several methods are being employed for samples collection, extraction and identification of MPs and polymer types using various equipment, chemicals and instrumental techniques. Aquatic species mistakenly ingest MPs, considering them prey and through food-chain, and then suffer from various metabolic disorders. The consumption of seafood and fish may consequently cause health implications in humans. Certain plasticizers are added during manufacturing to provide colour, durability, flexibility, and strength to plastics, but they leach out during usage, storage, and transport, as well as after entering the bodies of aquatic species and human beings. The leached chemicals (bisphenol-A, triclosan, phthalates, etc.) act as endocrine disrupting chemicals (EDCs), which effect on homeostasis; thereby causing neurotoxicity, cytotoxicity, reproductive problems, adverse behaviour and autism. Negative influence of MPs on carbon sequestration potential of water bodies is also observed, however more studies are required to understand it with a detail mechanism under natural conditions. The wastewater treatment plants are found to remove a large amount of MPs, but in turn, also act as significant sources of their release in sludge and effluents. Further, it is covered that how advanced oxidation processes, thermal- and photo-oxidation, fungi, algae and microbes degrade the plastics and increase their numbers in the surrounding environment. The management strategy comprising recovery of energy and other valuable by-products from plastic wastes, recycling and regulatory framework; are also described in detail. The future perspectives can be of paramount importance to control MPs generation and their abundance in the aquatic and other types of environments. The studies in future need to focus on advanced filtration techniques, advanced oxidation processes, energy recovery from plastic wastes and influences of MPs on carbon sequestration in aquatic environment and human health.

Impacts of microplastic accumulation in aquatic environment: Physiological, eco-toxicological, immunological, and neurotoxic effects

The presence of microplastics (MPs) in aquatic ecosystem has become a pressing global concern. MPs pose a significant threat to aquatic ecosystems, with devastating consequences for both aquatic life and human health. Notably, freshwater ecosystems are particularly vulnerable to MPs pollution. MPs, characterized by their small size (< 5 mm), have emerged as a ubiquitous environmental pollutant. They exhibit diverse characteristics, including varying sizes, forms, polymer types, and colors. Two distinct categories of MPs exist: primary and secondary. Primary MPs are incorporated into industrial hard materials, cosmetics, and hand cleaners, whereas secondary MPs result from the breakdown of larger plastic products in both terrestrial and marine environments. They enter the environment through various sources, such as household products, clothing, industrial activities, sewage waste and plastic degradation. Aquatic organisms ingest these contaminants, facilitating the transfer of MPs into the food chain and potentially causing severe health problems. This review delves into the bioaccumulation of MPs in fish, highlighting the eco-toxicological, neurological and immunological effects. This review provides an in-depth analysis of innovative solutions for MPs removal and reduction. Finally, we delineate evidence-based strategies to mitigate impacts of MPs, offering valuable insights to inform policy formulations and accelerate the development of sustainable plastic technologies.

Impact of polyvinyl chloride nano-plastics on the biochemical status of Oreochromis niloticus under a predicted global warming scenario

Plastic pollution and global warming are widespread issues that lead to several impacts on aquatic organisms. Despite harmful studies on both subjects, there are few studies on how temperature increases plastics' adverse effects on aquatic animals, mainly freshwater species. So, this study aims to clarify the potential impact of temperature increases on the toxicological properties of polyvinyl chloride nano-plastics (PVC-NPs) in Nile tilapia (Oreochromis niloticus) by measuring biochemical and oxidative biomarkers. The fish groups were subjected to three distinct temperatures (30, 32, and 34 °C) and subsequently separated into two groups: 0 and 10 mg/L of PVC-NPs, as it is expected that these temperatures may modify their chemical properties, which can influence their absorption and toxicity in fish. After 4 days, the biochemical response of fish exposed to PVC-NPs and elevated temperatures showed a significant increase in the levels of plasma total proteins, albumin, globulin, aspartate aminotransferase (AST), alanine aminotransferase (ALT), alkaline phosphatase (ALP), creatinine, and uric acid. Additionally, the level of oxidative stress biomarkers in the liver, gills, and brain was found to have a significant increase in malondialdehyde (MDA) concentration and a decrease in glutathione reduced (GSH) concentration and catalase (CAT) activity in all studied groups. Finally, the current findings revealed a synergistic cytotoxic effect of PVC-NPs and temperatures on the metabolic and oxidative stress indices of O. niloticus.

Biotransformation and oxidative stress markers in yellowfin seabream (Acanthopagrus latus): Interactive impacts of microplastics and florfenicol

This study investigates the combined toxicity of microplastics (MPs) and florfenicol (FLO) on biotransformation enzymes and oxidative stress biomarkers in the liver and kidney of yellowfin seabream (Acanthopagrus latus). Fish were fed 15 mg kg-1 of FLO and 100 or 500 mg kg-1 of MPs for 10 days. Biomarkers, including ethoxyresorufin-O-deethylase, glutathione-S-transferase, superoxide dismutase, catalase, glutathione peroxidase, malondialdehyde (MDA), and protein carbonylation (PC), were measured in both organs at 1, 7, and 14 days post-exposure. FLO levels peaked on day 1 and declined after that. Liver biomarkers were more responsive to pollutants, with the combined exposure of FLO and MPs leading to more pronounced toxicity. By day 14, only the FLO group showed a return to baseline biomarker levels, while MDA and PC levels remained elevated in MPs and co-exposed groups. These findings highlight the importance of considering the interactive effects of multiple pollutants in addressing marine environmental stressors.

Toxicity assessment of Oreochromis mossambicus exposed to carbamazepine and selenium: Physiological and genotoxic approach

Although the toxicity of selenium (Se) and carbamazepine (CBZ) has already been demonstrated, the possible effects of freshwater fish co-exposure to these pollutants have not been explored. Thus, we aimed to evaluate the potential impact of Se and CBZ (alone and combined) exposure (both 5 µg/L) in Oreochromis mossambicus after 28 days. Exposure to CBZ, alone or combined with Se, significantly increases the "red blood cells" and "mean corpuscular volume." In the gills, malondialdehyde levels in the "CBZ" and "Se + CBZ" groups were lower than in the control group. Furthermore, the exposure to treatments induced a significant increase in protein carbonyl formation in gills and DNA damage in gill and liver cells. Still, acetylcholinesterase activity in the brain was not changed. Thus, our study provides insight into the toxicity of metals and pharmaceutical drugs and warns about the ecotoxicological risk posed by such mixtures.

Are microplastics a new cardiac threat? A pilot study with wild fish from the North East Atlantic Ocean

Global environmental contamination by microplastics (MPs) is a growing problem with potential One Health impacts. The presence of MPs in vital organs, such as the heart, is of particular concern, but the knowledge is still limited. The goal of the present pilot study was to investigate the potential presence of MPs in the heart of wild specimens of three commercial fish species (Merluccius merluccius, Sardina pilchardus, and Trisopterus luscus) from the North East Atlantic Ocean. Heart samples from 154 fish were analysed for MP content (one heart sample per fish). A total of 44 MPs were recovered from heart samples from the three species. MPs had varied chemical composition (5 polymers), shapes (4) and colours (5). Differences in the profile of the MPs among species was observed (p ≤ 0.05). Thirty fish (19%) had MPs in their hearts, with a total mean (±SD) concentration of 0.286 ± 0.644 MPs/fish. S. pilchardus had the highest heart contamination (p ≤ 0.05). There were no significant (p > 0.05) differences between M. merluccius and T. luscus. These findings in fish with different biological and ecological traits together with literature data suggest that heart contamination likely is a disseminated phenomenon. Therefore, further research on the presence of MPs in the cardiovascular system and its potential health effects is very much needed.

The use of chitosan as an antioxidant in the feed of cultivated P. vannamei shrimp against oxidative stress induced by exposure to microplastics

Microplastics (MP) are omnipresent in aquaculture and can induce several toxic effects, mainly oxidative stress. Therefore, alternatives to minimize these effects are welcome. In this study, chitosan (1 and 3 g/kg) was supplemented through the feed of farmed shrimp P. vannamei for 30 days. After this period, the shrimp were exposed to MP (0.5 mg/L) for 7 days. The results showed the presence of MP in hepatopancreas, gills and muscle. Hepatopancreas morphological alterations, as well as lipid peroxidation, a decrease in GSH level, and an increase in SOD activity indicated an oxidative stress that was reversed by chitosan. The muscle was also affected by MP, showing decreased CAT activity and increased SOD activity, though no lipid peroxidation was observed. In muscle, chitosan reversed the SOD increase to basal activity. The results obtained showed that chitosan was more effective against oxidative stress than in preventing accumulation and histological damage.

Effect of Co-exposure to Additional Substances on the Bioconcentration of Per(poly)fluoroalkyl Substances: A Meta-Analysis Based on Hydroponic Experimental Evidence

A consensus has yet to emerge regarding the bioconcentration responses of per(poly)fluoroalkyl substances under co-exposure with other additional substances in aqueous environments. This study employed a meta-analysis to systematically investigate the aforementioned issues on the basis of 1,085 published datasets of indoor hydroponic simulation experiments. A hierarchical meta-analysis model with an embedded variance covariance matrix was constructed to eliminate the non-independence and shared controls of the data. Overall, the co-exposure resulted in a notable reduction in PFAS bioaccumulation (cumulative effect size, CES =  - 0.4287, p < 0.05) and bioconcentration factor (R2 = 0.9507, k < 1, b < 0) in hydroponics. In particular, the inhibition of PFAS bioconcentration induced by dissolved organic matter (percentage form of the effect size, ESP =  - 48.98%) was more pronounced than that induced by metal ions (ESP =  - 35.54%), particulate matter (ESP =  - 24.70%) and persistent organic pollutants (ESP =  - 18.66%). A lower AS concentration and a lower concentration ratio of ASs to PFASs significantly promote PFAS bioaccumulation (p < 0.05). The bioaccumulation of PFASs with long chains or high fluoride contents tended to be exacerbated in the presence of ASs. Furthermore, the effect on PFAS bioaccumulation was also significantly dependent on the duration of co-exposure (p < 0.05). The findings of this study provide novel insights into the fate and bioconcentration of PFAS in aquatic environments under co-exposure conditions.

Aged polystyrene microplastics exposure affects apoptosis via inducing mitochondrial dysfunction and oxidative stress in early life of zebrafish

In recent years, the toxic effects of microplastics (MPs) on aquatic organisms have been increasingly recognized. However, the developmental toxicity and underlying mechanisms of photoaged MPs at environmental concentrations remain unclear. Therefore, the photodegradation of pristine polystyrene (P-PS) under UV irradiation was used to investigate, as well as the developmental toxicity and underlying mechanisms of zebrafish (Danio rerio) exposed to P-PS and aged polystyrene (A-PS) at environmentally relevant concentrations (0.1-100 μg/L). Mortality, heart rate, body length, and tail coiling frequency of zebrafish larvae were the developmental toxicity endpoints. A-PS had increased crystallinity, the introduction of new functional groups, and higher oxygen content after UV-photoaging. The toxicity results showed that exposure to A-PS resulted in more adverse developmental toxicity than exposure to P-PS. Exposure to A-PS induced oxidative damage, as evidenced by elevated production of reactive oxygen species (ROS) and DNA damage, and led to decreased mitochondrial membrane potential (MMP) and causes the release of cytochrome c (cyt c) from the mitochondria. The caspase-3/-9 activation signaling pathways may cause developmental toxicity via mitochondrial apoptosis. Significant changes in the expression of genes were further explored linking with oxidative stress, mitochondria dysfunctions and apoptosis pathways following A-PS exposure. These findings underscore the importance of addressing the environmental applications of aged MPs and call for further research to mitigate their potential risks on aquatic ecosystems and human health.

Ecotoxicological effects of polystyrene nanoplastics on common carp: Insights into blood parameters, DNA damage, and gene expression

Plastics are ubiquitous in modern society due to their cost-effectiveness, lightweight nature, and versatility. However, their extensive use and inadequate recycling have led to a significant environmental challenge, with plastic waste accumulating rapidly and causing ecological and health problems, especially in aquatic environments. Nanoplastics, particles ranging from 1 to 100 nm, have emerged as a particularly concerning subset due to their ability to easily penetrate biological barriers and accumulate in tissues. In this study, we investigated the toxicity of carboxylate-modified polystyrene nanoplastics (PS-NPs) on common carp (Cyprinus carpio), a species often used in ecotoxicology research due to its ability to accumulate pollutants. The PS-NPs were characterized, and their effects on DNA damage gene expression related to oxidative stress and immunity were examined. PS-NPs with a diameter of 20-30 nm were found to possess a spherical shape and negatively charged surfaces. Exposure to PS-NPs led to significant DNA damage in the blood and brain cells of common carp, with higher concentrations resulting in more severe damage. Additionally, PS-NP exposure influenced the expression of genes related to antioxidative defense and stress response in the liver. Specifically, genes encoding superoxide dismutase (SOD), catalase (CAT), and heat shock protein 70 (Hsp70) showed upregulation, while glutathione peroxidase (GPx) and glutathione S-transferase (GST) exhibited downregulation at higher PS-NP concentrations. Furthermore, the immune-related genes interleukin-1ß (IL-1ß), interleukin-8 (IL-8), and tumor necrosis factor-α (TNF-α) displayed dose-dependent downregulation in the liver tissue. These findings suggest that exposure to PS-NPs induces oxidative stress, disrupts immune responses, and causes DNA damage in common carp. The results highlight the need for further research on the environmental impacts of PS-NPs and underscore the importance of proper waste management and recycling practices to mitigate plastic pollution.

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.

Polystyrene nanoplastics at predicted environmental concentrations enhance the toxicity of copper on Caenorhabditis elegans

Excessive nanoplastics not only pose a direct threat to the environment but also have the propensity to adsorb and interact with other pollutants, exacerbating their impact. The coexistence of nanoplastics and heavy metals in soils is a prevalent phenomenon. However, limited research existed about the joint effects of the two contaminants on soil organisms. In this paper, we ascertained the combined toxicity of polystyrene nanoplastics (PS-NPs) and copper (Cu2+) on soil organisms (Caenorhabditis elegans) at quantities that were present in the environment, further exploring whether the two toxicants were synergistic or antagonistic. The outcomes manifested that single exposure to low-dose PS-NPs (1 μg/L) would not cause significant damage to nematodes. After treatment with PS-NPs and Cu2+, the locomotion ability of nematode was impaired, accompanied by an elevation in reactive oxygen species (ROS) level and a biphasic response in antioxidant enzyme activity. Moreover, combined exposure to PS-NPs and Cu2+ induced the mRNA up-regulation of vit-6, cyp-35a2, hsp-16.2, age-1, and cep-1, both of which were stress-related genes. The comparative analysis between groups (with or without PS-NPs) revealed that the combined exposure group resulted in significantly greater toxic effects on nematodes compared with Cu2+ exposure alone. Furthermore, the addition of PS-NPs influenced the metabolic profiles of Caenorhabditis elegans under Cu2+ stress, with numerous differential metabolites associated with oxidative damage or defense mechanism. Overall, these findings manifested that PS-NPs at the expected environmental concentration elevated Cu2+ toxicity on nematodes.

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.

Impact of sub-chronic polystyrene nanoplastics exposure on hematology, histology, and endoplasmic reticulum stress-related protein expression in Nile tilapia (Oreochromis niloticus)

Nanoplastics (NPs) are one of the most hazardous marine litters, having the potential to cause far-reaching impacts on the environment and humankind. The effect of NPs on fish health has been studied, but their impact on the subcellular organelles remains unexplored. The present investigation studied the possible implications of polystyrene-nanoplastics (PS-NPs) on the hematology, tissue organization, and endoplasmic reticulum (ER) stress-related proteins in Nile tilapia (Oreochromis niloticus). Fish were exposed to ∼100 nm PS-NPs at environmentally relevant (0.1 mg/L), and sublethal (1, 10 mg/L) concentrations for 14 days through water exposure. The growth performance and hematological parameters such as erythrocytes, hemoglobin, hematocrit, and leucocytes decreased, while thrombocytes increased with PS-NPs dose-dependently. The gills, liver, kidney, and heart tissues displayed increasing degrees of pathology with increased concentrations of PS-NPs. The gills showed severe epithelial hyperplasia and lamellar fusion. The liver had an abstruse cellular framework, membrane breakage, and vacuolation. While glomerular and tubular atrophy was the most prominent pathology in the kidney tissue, the heart displayed extensive myofibrillar loss and disorderly arranged cardiac cells. The ER-stress-related genes such as bip, atf6, ire1, xbp1, pkr, and apoptotic genes such as casp3a, and bax were over-expressed, while, the anti-apoptotic bcl2 was under-expressed with increasing concentrations of PS-NPs. Immunohistochemistry and blotting results of GRP78, CHOP, EIF2S, and ATF6 in gills, liver, kidney, and heart tissues affirmed the translation to ER stress proteins. The results revealed the sub-lethal adverse effects and the activation of the ER-stress pathway in fish with sub-chronic exposure to PS-NPs.

Mitigating Dietary Microplastic Accumulation and Oxidative Stress Response in European Seabass (Dicentrarchus labrax) Juveniles Using a Natural Microencapsulated Antioxidant

Aquafeed's contamination by microplastics can pose a risk to fish health and quality since they can be absorbed by the gastrointestinal tract and translocate to different tissues. The liver acts as a retaining organ with the consequent triggering of oxidative stress response. The present study aimed to combine the use of natural astaxanthin with natural-based microcapsules to counteract these negative side effects. European seabass juveniles were fed diets containing commercially available fluorescent microplastic microbeads (1-5 μm; 50 mg/kg feed) alone or combined with microencapsulated astaxanthin (AX) (7 g/kg feed; tested for half or whole feeding trial-30 or 60 days, respectively). Fish from the different dietary treatments did not evidence variations in survival and growth performance and did not show pathological alterations at the intestinal level. However, the microplastics were absorbed at the intestinal level with a consequent translocation to the liver, leading, when provided solely, to sod1, sod2, and cat upregulation. Interestingly, the dietary implementation of microencapsulated AX led to a mitigation of oxidative stress. In addition, the microcapsules, due to their composition, promoted microplastic coagulation in the fish gut, limiting their absorption and accumulation in all the tissues analyzed. These results were supported by in vitro tests, which demonstrated that the microcapsules promoted microplastic coagula formation too large to be absorbed at the intestinal level and by the fact that the coagulated microplastics were released through the fish feces.

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.

Microplastics have additive effects on cadmium accumulation and toxicity in Rice flower carp (Procypris merus)

Procypris merus, a local fish species found in Guangxi, China is often exposed to both microplastics (MPs) and Cd. However, it remains unclear how these two pollutants affect P. merus. Therefore, we investigated the effects of MPs on Cd accumulation in P. merus. To this end, P. merus was separately exposed to Cd and MPs (500 μg/L) or their combination for 14 days. We found that MPs enhanced Cd accumulation in liver and gills of P. merus. Further, both the single-contaminant (MP and Cd) and combined treatments resulted in lesions in these two tissues, with more severe damage associated with the combined treatment. Even though the effect of MP on the antioxidant defense system of P. merus was limited, the Cd-only and combined treatments considerably affected the antioxidant parameters of P. merus, with the combined treatment showing a stronger effect. GO and KEGG analyses revealed that the differentially expressed genes (DEGs; TNF-related apoptosis-inducing ligand receptor, trail-r) in the Cd-only treatment group were enriched for immune-related GO terms and cell growth and death related pathways, indicating that Cd toxicity affected immune defense in P. merus. The MP-only treatment downregulated DEGs (acyl-CoA synthetase long chain family member 1a, acsl1a) related to lipid metabolism, possibly leading to lipid accumulation in the liver. The combined treatment also upregulated DEGs (aspartate aminotransferase 1, ast 1) associated with immune-related GO terms and amino acid metabolism pathways, suggesting that it affected immune function in P. merus, thereby negatively impacting its health. Results indicated that MPs have additive effects on Cd accumulation and toxicity in rice flower carp. Consequently, MPs ingested by P. merus can promote Cd accumulation, more adverse effects on the health may occur after combined exposure, which can eventually reach humans through the food chain and pose potential risks to human health.

Ecotoxicological evaluation of chitosan biopolymer films particles in adult zebrafish (Danio rerio): A comparative study with polystyrene microplastics

To mitigate the environmental impact of microplastics (MPs), the scientific community has innovated sustainable and biodegradable polymers as viable alternatives to traditional plastics. Chitosan, the deacetylated form of chitin, stands as one of the most thoroughly investigated biopolymers and has garnered significant interest due to its versatile applications in both medical and cosmetic fields. Nevertheless, there is still a knowledge gap regarding the impact that chitosan biopolymer films (CBPF) may generate in aquatic organisms. In light of the foregoing, this study aimed to assess and compare the potential effects of CBPF on the gastrointestinal tract, gills, brain, and liver of Danio rerio against those induced by MPs. The findings revealed that both CBPF and MPs induced changes in the levels of oxidative stress biomarkers across all organs. However, it is essential to note that our star plots illustrate a tendency for CBPF to activate antioxidant enzymes and for MPs to produce oxidative damage. Regarding gene expression, our findings indicate that MPs led to an up-regulation in the expression of genes associated with apoptotic response (p53, casp3, cas9, bax, and bcl2) in all fish organs. Meanwhile, CBPF produced the same effect in genes related to antioxidant response (nrf1 and nrf2). Overall, our histological observations substantiated these effects, revealing the presence of plastic particles and tissue alterations in the gills and gastrointestinal tract of fish subjected to MPs. From these results, it can be concluded that CBPF does not represent a risk to fish after long exposure.

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.

Subchronic oral exposure to polystyrene microplastics affects hepatic lipid metabolism, inflammation, and oxidative balance in gilthead seabream (Sparus aurata)

Microplastics (MPs) pose a clear threat to aquatic organisms affecting their health. Their impact on liver homeostasis, as well as on the potential onset of nonalcoholic fatty liver disease (NAFLD), is still poorly investigated and remains almost unknown. The aim of this study was to evaluate the outcomes of subchronic exposure to polystyrene MPs (PS-MPs; 1-20 μm; 0, 25, or 250 mg/kg b.w./day) on lipid metabolism, inflammation, and oxidative balance in the liver of gilthead seabreams (Sparus aurata Linnaeus, 1758) exposed for 21 days via contaminated food. PS-MPs induced an up-regulation of mRNA levels of crucial genes associated with lipid synthesis and storage (i.e., PPARy, Srebp1, Fasn) without modifications of genes involved in lipid catabolism (i.e., PPARα, HL, Pla2) or transport and metabolism (Fabp1) in the liver. The increase of CSF1R and pro-inflammatory cytokines gene expression (i.e., TNF-α and IL-1β) was also observed in exposed fish in a dose-dependent manner. These findings were confirmed by hepatic histological evaluations reporting evidence of lipid accumulation, inflammation, and necrosis. Moreover, PS-MPs caused the impairment of the hepatic antioxidant defense system through the alteration of its enzymatic (catalase, superoxide dismutase, and glutathione reductase) and non-enzymatic (glutathione) components, resulting in the increased production of reactive oxygen species (ROS) and malondialdehyde (MDA), as biomarkers of oxidative damage. The alteration of detoxifying enzymes was inferred by the decreased Ethoxyresorufin-O-deethylase (EROD) activity and the increased activity of glutathione-S-transferase (GST) at the highest PS-MP dose. The study suggests that PS-MPs affect the liver health of gilthead seabream. The liver dysfunction and damage caused by exposure to PS-MPs result from a detrimental interplay of inflammation, oxidative damage, and antioxidant and detoxifying enzymatic systems modifications, altering the gut-liver axis homeostasis. This scenario is suggestive of the involvement of MP-induced effects in the onset and progression of hepatic lipid dysfunction in gilthead seabream.

Assessing the impact of COVID-19 era drug combinations on hepatic functionality: A thorough investigation in adult Danio rerio

Current and thorough information on the ecotoxicological consequences of pharmaceuticals is accessible globally. However, there remains a substantial gap in knowledge concerning the potentially toxic effects of COVID-19 used drugs, individually and combined, on aquatic organisms. Given the factors above, our investigation assumes pivotal importance in elucidating whether or not paracetamol, dexamethasone, metformin, and their tertiary mixtures might prompt histological impairment, oxidative stress, and apoptosis in the liver of zebrafish. The findings indicated that all treatments, except paracetamol, augmented the antioxidant activity of superoxide dismutase (SOD) and catalase (CAD), along with elevating the levels of oxidative biomarkers such as lipid peroxidation (LPX), hydroperoxides (HPC), and protein carbonyl content (PCC). Paracetamol prompted a reduction in the activities SOD and CAT and exhibited the most pronounced toxic response when compared to the other treatments. The gene expression patterns paralleled those of oxidative stress, with all treatments demonstrating overexpression of bax, bcl2, and p53. The above suggested a probable apoptotic response in the liver of the fish. Nevertheless, our histological examinations revealed that none of the treatments induced an apoptotic or inflammatory response in the hepatocytes. Instead, the observed tissue alterations encompassed leukocyte infiltration, sinusoidal dilatation, pyknosis, fatty degeneration, diffuse congestion, and vacuolization. In summary, the hepatic toxicity elicited by COVID-19 drugs in zebrafish was less pronounced than anticipated. This attenuation could be attributed to metformin's antioxidant and hormetic effects.

Microplastics induced endoplasmic reticulum stress to format an inflammation and cell death in hepatocytes of carp (Cyprinus carpio)

Microplastics (MPs) are a serious threat to the living environment of aquatic organisms. However, there are fewer studies on the toxicity of microplastics to freshwater organisms. This study aimed to establish a polystyrene microplastics (PS-MPs) model by feeding carp (Cyprinus carpio) PS-MP (1000 ng/L) particles 8 μm in size. HE staining revealed a mass of inflammatory cells infiltrated in the carp hepatopancreas. The activities of alkaline phosphatase (AKP), aspartate transaminase (AST), lactate dehydrogenase (LDH), and alanine transaminase (ALT) were strengthened considerably, suggesting that PS-MPs cause injury to the hepatopancreas of carp. Real-Time polymerase chain reaction and western blotting results indicated increased levels of glucose-regulated protein 78 (GRP78), (PKR)-like ER kinase (PERK), eukaryotic translation initiation Factor 2α (EIF2α) and activating transcription Factor 4 (ATF4) genes and increased levels of inflammatory factors downstream of endoplasmic reticulum stress (ERs) thioredoxin-interacting protein (TXNIP), NOD-like receptor protein 3 (NLRP3), interleukin-18 (IL-18), interleukin-1β (IL-1β), and caspase 1. Increased expression of microtubule-associated protein-2 (LC3II), autophagy-related 5 (ATG5) and autophagy-related 12 (ATG12) genes revealed that PS-MPs promoted autophagy in carp hepatocytes. The enhanced expression of the Caspase 12, Caspase 3, and Bax genes suggested that PS-MPs led to the apoptosis of carp hepatocytes. These results suggest that PS-MPs result in serious injury to the hepatopancreas of carp. The present study of PS-MPs in freshwater fish from the aspect of endoplasmic reticulum stress was conducted to provide references and suggestions for toxicological studies of PS-MPs in freshwater environments.

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.

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

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

Accumulation and elimination properties and comparative toxicity of fluxapyroxad in juvenile and adult large yellow croaker (Larimichthys crocea)

Fluxapyroxad (FX), a succinate dehydrogenase inhibitor fungicide, has been detected in global marine and aquatic organisms. However, as a new pollutant, its biotoxicity and ecological risks to marine aquatic organisms are unclear. The accumulation and elimination processes and toxic effects of FX on Larimichthys crocea (L. crocea) at environmental concentrations were assessed. FX (1.0 μg/L) was rapidly enriched and persisted prolonged in L. crocea muscle and FX is highly toxic to juvenile L. crocea with the 96 h LC50 of 245.0 μg/L. Furthermore, the toxic effects of FX on juvenile L. crocea and adults L. crocea were compared and analyzed. In contrast to those of adult L. crocea, juvenile L. crocea showed a stronger oxidative stress response and rescued liver damage in terms of antioxidant enzyme activity, energy supply, and liver damage to FX. Transcriptomic analysis also showed that drug metabolism was activated. In the adult L. crocea, the disturbance of the energy metabolism, oxidative respiration, TCA cycle, and lipid metabolism genes were firstly found. The results revealed the accumulation and elimination pattern and ecotoxicological hazards of FX to L. crocea, which provided important theoretical basis for the study of environmental risks caused by new pollutants to marine organisms.

Environmentally persistent free radicals on photoaged microplastics from disposable plastic cups induce the oxidative stress-associated toxicity

Microplastics (MPs) are ubiquitous environmental contaminants that exerting multiple toxicological effects. Most studies have focused primarily on the models of unaged MPs and lack environmental relevance. The generation and toxicity of environmentally persistent free radicals (EPFRs) on photoaging MPs from disposable plastic cups (DPC-MPs) have not been well studied. Here, the formation of EPFRs on photoaged DPC-MPs and their toxic effects in nematodes were investigated. UV irradiation generated EPFRs, which influenced the characterization of DPC-MPs. Exposure to photoaged DPC-MPs at environmentally relevant concentrations （100-1000 μg/L） reduced the locomotion behavior, body length, and brood size. The Reactive oxygen species (ROS) production, lipofuscin accumulation, malondialdehyde (MDA), and 8-hydroxy-2'-deoxyguanosine (8-OHdG) levels were increased along with the downregulation of the expression levels of associated genes, such as clk-1, clt-1, and gst-4，in nematodes. Moreover, the toxicity and oxidative stress response of nematodes were significantly inhibited due to N-acetyl-l-cysteine (NAC). Pearson's correlation analysis revealed that the oxidative stress was significantly associated with adverse physiological effects. Therefore, EPFRs on photoaged DPC-MPs cause toxicity in nematodes, and oxidative stress is important for regulating toxicity. This study offers novel insights into the potential risks of DPC-MPs under UV irradiation, highlighting the need to consider the role of EPFRs in toxicity assessments of DPC-MPs.

Effect of polypropylene microplastics on virus resistance in spotted sea bass (Lateolabrax maculatus)

Microplastics (MPs) pollution is a hot issue of global concern. Polypropylene microplastics (PP-MPs) age quickly in the marine environment and break down into smaller particles because of their relatively low temperature resistance, poor ultraviolet resistance, and poor antioxidant capacity, making them one of the major pollutants in the ocean. We assessed whether long-term exposure to micron-sized PP-MPs influences fish susceptibility to viral diseases. We found that exposure to PP-MPs (1-6 μm and 10-30 μm) at concentrations of 500 and 5000 μg/L resulted in uptake into spleen and kidney tissues of Lateolabrax maculatus. Increased activation of melanomacrophage centers was visible in histopathological sections of spleen from fish exposed to PP-MPs, and greater deterioration was observed in the spleen of fish infected by largemouth bass ulcerative syndrome virus after PP-MPs exposure. Additionally, exposure to PP-MPs led to significant cytotoxicity and a negative impact on the antiviral ability of cells. PP-MPs exposure had inhibitory or toxic effects on the immune system in spotted sea bass, which accelerated virus replication in vivo and decreased the expression of the innate immune- and acquired immune related genes in spleen and kidney tissues, thus increasing fish susceptibility to viral diseases. These results indicate that the long-term presence of micron-sized PP-MPs might impact fish resistance to disease, thereby posing a far-reaching problem for marine organisms.

Source, transport, and toxicity of emerging contaminants in aquatic environments: A review on recent studies

Emerging contaminants (ECs) are gaining global attention owing to their widespread presence and adverse effects on human health. ECs comprise numerous composite types and pose a potential threat to the growth and functional traits of species and ecosystems. Although the occurrence and fate of ECs has been extensively studied, little is known about their long-term biological effects. This review attempts to gain insights into the unhindered connections and overlaps in aquatic ecosystems. Microplastics (MPs), one of the most representative ECs, are carriers of other pollutants because of their strong adsorption capacity. They form a complex of pollutants that can be transmitted to aquatic organisms and humans through the extended food chain, increasing the concentration of pollutants by tens of thousands of times. Adsorption, interaction and transport effects of emerging contaminants in the aquatic environment are also discussed. Furthermore, the current state of knowledge on the ecotoxicity of single- and two-pollutant models is presented. Herein, we discuss how aquatic organisms within complex food networks may be particularly vulnerable to harm from ECs in the presence of perturbations. This review provides an advanced understanding of the interactions and potential toxic effects of ECs on aquatic organisms.

Combined effects of a high-fat diet and polyethylene microplastic exposure induce impaired lipid metabolism and locomotor behavior in larvae and adult zebrafish

Microplastics (MP), tiny plastic particles, can be ingested by fish through their habitat or contaminated food sources. When combined with a high-fat diet (HFD), MP exposure may lead to increased MP accumulation in fish and negative impacts on their health. However, the underlying mechanisms of how MP and HFD interact to promote fat accumulation in fish remain poorly understood. In this study, we aimed to evaluate the combined effect of HFD and polyethylene MP (PE-MP) in the zebrafish model (Danio rerio) and decipher its molecular mechanisms. Adult zebrafish exposed to the combined HFD and PE-MP showed elevated lipid accumulation, total cholesterol, triglycerides, and abnormal swimming behavior compared to HFD-fed fish. Histological and gene expression analysis revealed severe hepatic inflammation and injury, resembling nonalcoholic fatty liver disease (NAFLD) in the HFD + PE-MP exposed zebrafish. Moreover, HFD and PE-MP exposure upregulated genes related to lipogenesis (SREBP1, FAS, and C/EBPα) and inflammation (tnfα, il1β, and il-6) in the liver. These findings underscore the interactive effect of environmental pollutants and fish diet, emphasizing the importance of improving fish culture practices to safeguard fish health and human consumers from microplastic contamination through the food chain. This research sheds light on the complex interactions between microplastics and diet, providing valuable insights into the potential risks of microplastic pollution in aquatic ecosystems and the implications for human health. Understanding the underlying molecular mechanisms will contribute to international research efforts to mitigate the adverse effects of microplastics on both environmental and public health.

Journey of micronanoplastics with blood components

The entry of micro- and nanoplastics (MNPs) into the human body is inevitable. They enter blood circulation through ingestion, inhalation, and dermal contact by crossing the gut-lung-skin barrier (the epithelium of the digestive tract, the respiratory tract, and the cutaneous layer). There are many reports on their toxicities to organs and tissues. This paper presents the first thorough assessment of MNP-driven bloodstream toxicity and the mechanism of toxicity from the viewpoint of both MNP and environmental co-pollutant complexes. Toxic impacts include plasma protein denaturation, hemolysis, reduced immunity, thrombosis, blood coagulation, and vascular endothelial damage, among others, which can lead to life-threatening diseases. Protein corona formation, oxidative stress, cytokine alterations, inflammation, and cyto- and genotoxicity are the key mechanisms involved in toxicity. MNPs change the secondary structure of plasma proteins, thereby preventing their transport functions (for nutrients, drugs, oxygen, etc.). MNPs inhibit erythropoiesis by influencing hematopoietic stem cell proliferation and differentiation. They cause red blood cell and platelet aggregation, as well as increased adherence to endothelial cells, which can lead to thrombosis and cardiovascular disease. White blood cells and immune cells phagocytose MNPs, provoking inflammation. However, research gaps still exist, including gaps regarding the combined toxicity of MNPs and co-pollutants, toxicological studies in human models, advanced methodologies for toxicity analysis, bioaccumulation studies, inflammation and immunological responses, dose-response relationships of MNPs, and the effect of different physiochemical characteristics of MNPs. Furthermore, most studies have analyzed toxicity using prepared MNPs; hence, studies must be undertaken using true-to-life MNPs to determine the real-world scenario. Additionally, nanoplastics may further degrade into monomers, whose toxic effects have not yet been explored. The research gaps highlighted in this review will inspire future studies on the toxicity of MNPs in the vascular/circulatory systems utilizing in vivo models to enable more reliable health risk assessment.

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.

Toxic effect of chronic exposure to polyethylene nano/microplastics on oxidative stress, neurotoxicity and gut microbiota of adult zebrafish (Danio rerio)

The rapid development of aquaculture industry has provided a large amount of high-quality animal protein, while the food safety caused by microplastics and nanoplastics (MP/NPs) has become a major concern. In addition, recent evidence has shown the potential toxic effect of PE-MP/NPs, highlighting the need for further research into their environmental and health impacts. Chronic exposure of polyethylene microplastics (PE-MPs) and nanoplastics (PE-NPs) on adult zebrafish were conducted in the present study for 21 d. Organ-dependent oxidative damage induced by MP/NPs was observed. Insignificant differences in neurotoxicity and dysbiosis of gut microbiota were found between MPs and NPs. Changes in glutathione S-transferase (GST), glutathione (GSH), catalase (CAT), lipid peroxidation (LPO), and superoxide dismutase (SOD) showed that MP/NPs induced oxidative damage in gill and intestinal cells of zebrafish. The inhibited AChE activity suggested the potential neurotoxicity of microplastics and nanoplastics (MP/NPs). In addition, chronic exposure increased the alpha-diversity of intestinal microbiota. At the phylum level, the average relative abundance of Proteobacteria increased from 29.73% (control group) to 66.10% (microplastics), 54.84% (nanoplastics) and 60.03% (combined exposure), respectively. Tenericutes decreased from 55.43% (control group) to 20.02% (microplastics), 22.44% (nanoplastics) and 31.77% (combined exposure), respectively. Overall, this study provides new insights and objective evidence for the toxicity assessment of PE-MPs.

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.

Effects of microplastics, pesticides and nano-materials on fish health, oxidative stress and antioxidant defense mechanism

Microplastics and pesticides are emerging contaminants in the marine biota, which cause many harmful effects on aquatic organisms, especially on fish. Fish is a staple and affordable food source, rich in animal protein, along with various vitamins, essential amino acids, and minerals. Exposure of fish to microplastics, pesticides, and various nanoparticles generates ROS and induces oxidative stress, inflammation, immunotoxicity, genotoxicity, and DNA damage and alters gut microbiota, thus reducing the growth and quality of fish. Changes in fish behavioral patterns, swimming, and feeding habits were also observed under exposures to the above contaminants. These contaminants also affect the Nrf-2, JNK, ERK, NF-κB, and MAPK signaling pathways. And Nrf2-KEAP1 signalling modulates redox status marinating enzymes in fish. Effects of pesticides, microplastics, and nanoparticles found to modulate many antioxidant enzymes, including superoxide dismutase, catalase, and glutathione system. So, to protect fish health from stress, the contribution of nano-technology or nano-formulations was researched. A decrease in fish nutritional quality and population significantly impacts on the human diet, influencing traditions and economics worldwide. On the other hand, traces of microplastics and pesticides in the habitat water can enter humans by consuming contaminated fish which may result in serious health hazards. This review summarizes the oxidative stress caused due to microplastics, pesticides and nano-particle contamination or exposure in fish habitat water and their impact on human health. As a rescue mechanism, the use of nano-technology in the management of fish health and disease was discussed.

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.