Toxic effects on bioaccumulation, hematological parameters, oxidative stress, immune responses and neurotoxicity in fish exposed to microplastics: A review

Investigating the toxicity of polylactic acid microplastics on the health and physiology of freshwater fish, Cirrhinus mrigala

The widespread presence of microplastics (MPs) in aquatic ecosystems has raised growing concerns among ecotoxicologists regarding their potential toxicity. This study explored the impacts of polylactic acid (PLA) MPs on the physiology and health of freshwater fish, Cirrhinus mrigala, by dietary exposure for 90 days. The experiment consisted of six groups: five treatment groups (0.5%, 1%, 1.5%, 2%, and 2.5% PLA-MP) and a control group (0% PLA-MP). Each group was comprised of fifteen fish, and the experiment was replicated three times. The exposure severity of PLA-MPs varied from low to high, with treatment levels ranging from 0.5% to 2.5% PLA-MPs, relative to the control group. This exposure significantly affected their growth performance. Additionally, the apparent digestibility of the SFM-based diet decreased with increasing PLA-MPs concentration. Exposure to PLA-MPs induced considerable changes in body composition, characterized by increased moisture and crude fat content and decreased ash content and crude protein. The blood profile, including MCHC, RBCs, Hb, PLT and PCV exhibited significant declines in the high treatment group (2.5% PLA-MPs), while MCH, WBCs and MCV showed notable increases. Furthermore, histopathological examination of the intestine revealed an increase in abnormalities in the intestine at 2.5% PLA-MPs level. The high treatment group (2.5% PLA-MPs) showed the lowest mineral content in the fish muscles. In summary, dietary exposure to PLA-MPs led to alterations in overall body performance across the treatment groups, ranging from low to high severity levels.

The effects of polystyrene microplastics on feeding, growth, and trophic upgrading of protozoan grazers

Microplastics have become ubiquitous in the global marine environment, posing substantial influences on marine organism health, food web function and marine ecosystem structure. Protozoan grazers are known for their ability to improve the biochemical constituents of poor-quality algae for subsequent use by higher trophic levels. However, the effects of microplastics on the trophic upgrading of protozoan grazers remain unknown. To address this knowledge gap, the ciliate Euplotes vannus and the heterotrophic dinoflagellate Oxyrrhis marina were exposed to microplastic particles (5 μm) for four days with various concentrations (1-20 mg/L). Both O. marina and E. vannus ingested microplastics. At the exposure level of 20 mg/L, the ingestion rate, growth rate, biovolume, and carbon biomass of E. vannus were significantly decreased by 28.18 %, 32.01 %, 30.46 %, and 82.27 %, respectively, while such effects were not observed for O. marina. The contents of highly unsaturated fatty acids in O. marina and E. vannus on a mixed diet of microplastic particles and green algae significantly reduced by 8.66 % and 41.49 % relative to feeding only on green algae, respectively. Besides, we also observed an increase in the composition of C18:3 (ω-3) and C20:3 (ω-3) concurrence with a significant decrease in C16:0 and C18:0 in E. vannus after 96 h exposure at 20 mg/L. These results indicate that microplastics can weaken trophic upgrading of the nutritional quality by protozoan grazers, which may consequently alter the function of food webs.

Accumulation and depuration of tire wear particles in zebrafish (Danio rerio) and toxic effects on gill, liver, and gut

The toxic effects of tire wear particles (TWPs) in the environment are a growing concern for a variety of aquatic organisms. However, studies about TWPs toxicity on aquatic organisms are limited. This study investigated the accumulation and depuration of TWPs in zebrafish at three different concentrations (5 mg/L, 10 mg/L, and 20 mg/L), as well as the toxic effects on the gill, liver, and gut. We found that TWPs could accumulate in the gill and gut for a long time, and the number of TWPs at the high-concentration (20 mg/L) was higher than at the low-concentration (5 mg/L). TWPs induced oxidative stress in the gill and liver. The liver transcriptome profiles indicated that the high concentration of TWPs tended to up-regulate metabolic processes, whereas the low concentration of TWPs was inclined to down-regulate cellular processes. The high-concentration treatment significantly increased xenobiotic biodegradation and metabolism, and lipid metabolism-related pathways, whereas the low-concentration treatment distinctly altered amino acid metabolism-related pathways. The expression of gstt1b, ugt1a1, mgst3b, miox, hsd17b3, and cyp8b1 gene was up-regulated in all TWPs treatments. In addition, Gemmobacter and Shinella enriched in the high-concentration treatment were closely correlated with the degradation of TWPs. These findings provided objective evidence for the toxicity evaluation of TWPs on zebrafish.

Organ-specific bioaccumulation of microplastics in market fish of Dhaka and size-dependent impacts of PVC microplastics on growth of Anabustestudineus

Microplastics (MPs), a growing environmental concern with potential ecotoxicological risks, are ubiquitous in aquatic environment. This study investigated the organ-specific distribution and variation of MPs in commercially caught fishes (7 species, 140 individuals) collected from Dhaka's two main fish distribution hubs (Uttara and Jatrabari). Additionally, the impact of different-sized MPs on fish growth (Anabas testudineus) was examined in a control experiment. Results revealed that kidneys of market fish bioaccumulated the highest concentration of MPs (average, 59.1 MPs/g), followed by liver (24.6 MPs/g) and intestine (18.6 MPs/g). On average, fish from Uttara had a higher MPs concentration (36 MPs/g) compared to Jatrabari (25 MPs/g). Among fish species, Glossogobius giuris showed the highest MPs bioaccumulation due to its feeding habits and morphology. Fiber-shaped MPs were most prevalent in all fishes (79-93%) except Glossogobius giuris (fragments, 51%). Fourier-transform infrared spectroscopy (FTIR) analysis identified 19 different polymer types, with high density polyethylene (HDPE), ethylene vinyl acetate (EVA) and polyamide (PA) being commonly found in all organs. The experimental study confirmed that large-sized PVC MPs (1.18 mm-300 μm) had a greater negative impact on fish growth (length) and caused more physical deformities (particularly intestinal injuries) compared to small-sized PVC MPs (150 μm-75 μm). Moreover, fish exposed to larger diameter MPs experienced highest physical weight and depth loss among exposed groups. Large-sized PVC MPs bioaccumulated highest in fish compared to small-sized PVC MPs. Similar to market fish, kidney in the experimental fish had the highest MPs bioaccumulation (6.5 MPs/g), followed by liver (5.2 MPs/g) and intestine (4.8 MPs/g), with a dominance of fibers despite the presence of high concentration of fragments in the food source. Statistical analysis also supported a clear correlation between increasing MPs size and adverse effects on fish growth and health. Urgent action is needed to curb microplastic pollution and protect ecosystems and human health.

Mechanisms underlying mitochondrial dysfunction and intestinal damage induced by ingestion of microplastics in Leuciscus waleckii: The role of the NF-κB/Nrf2 signaling pathway

This study investigates the impact of polystyrene microplastics (PS-MPs) on the growth, immunity, oxidative stress, mitochondrial function, and intestinal health of Leuciscus waleckii (3.00 ± 0.02 g) juveniles over 8 weeks. Our findings indicate that exposure to PS-MPs negatively affected the growth of Leuciscus waleckii, resulting in digestive disturbances. Furthermore, PS-MPs triggered immune dysfunction and oxidative stress through the activation of the NF-κB pathway and suppression of the Nrf2 signaling cascade. PS-MPs damaged intestinal tissue and compromised the intestinal barrier. Additionally, mitochondrial homeostasis was disrupted, activating endogenous mitochondrial apoptotic pathways, ultimately leading to cell apoptosis. High-throughput 16S rRNA sequencing disclosed that PS-MPs provoked shifts in the intestinal microbiota. Mantel analysis indicates significant correlations between growth parameters and the activities of enzymes related to antioxidant defense, immunity, apoptosis, and mitochondria, as well as with the gut microbiota. In summary, our study reveals that PS-MPs induce intestinal inflammation and oxidative stress in Leuciscus waleckii by activating the NF-κB pathway and the intrinsic mitochondrial apoptotic pathway while repressing the Nrf2 signaling, ultimately leading to cellular apoptosis, mitochondrial dysfunction, intestinal microbiota imbalance, and growth inhibition.

Microplastic assessment in aquaculture feeds: Analyzing polymer variability across commercial fishfeeds from three continents

This study analysed ten widely used commercial fishfeeds in aquaculture from six countries spanning three continents to assess microplastic (MP) contamination. MPs with an average abundance of 1130 ± 259.07 particles/kg and an average length of 2.64 ± 0.62 mm ( ± SE) were found in aquaculture feeds, with fibres (85 %) and fragments (15 %). The majority of these MPs were black. The abundance of MPs varied among the samples, with the highest in feed SP (26 %), followed by IF, GA, ELS, NT, EW, TB, GR, VR, and the least in HCF (3 %). Polymers identified consisted of Polyethylene terephthalates (PET, 20 %), Polyamide (PA, 30 %), Polymethyl methacrylate (PMMA), Polyurethane (PU), and Polystyrene (PS) with 15 % each, and Polypropylene (PP, 5 %). SEM-EDX analysis of fibres showed flakes, cracks, and pits and the presence of heavy metals Ni, Cu, Zn, Cr, Au, Hg, Cd, Ti, and Pb. Additionally, some fragments contained Nb (Niobium) alongside the naturally occurring elements. The Polymer Hazard Index (PHI) for the polymers in ten feeds was calculated, and nine were in the highly hazardous category (IV and V) with PHI values ranging from 400-394825. The work showcases the graveness of MPs in fishfeeds and advocates control measures to curtail MPs in fishfeeds for sustainable aquaculture production.

Genotoxic and neurotoxic potential of intracellular nanoplastics: A review

Plastic waste comprises polymers of different chemicals that disintegrate into nanoplastic particles (NPLs) of 1-100-nm size, thereby littering the environment and posing a threat to wildlife and human health. Research on NPL contamination has up to now focused on the ecotoxicology effects of the pollution rather than the health risks. This review aimed to speculate about the possible properties of carcinogenic and neurotoxic NPL as pollutants. Given their low-dimensional size and high surface size ratio, NPLs can easily penetrate biological membranes to cause functional and structural damage in cells. Once inside the cell, NPLs can interrupt the autophagy flux of cellular debris, alter proteostasis, provoke mitochondrial dysfunctions, and induce endoplasmic reticulum stress. Harmful metabolic and biological processes induced by NPLs include oxidative stress (OS), ROS generation, and pro-inflammatory reactions. Depending on the cell cycle status, NPLs may direct DNA damage, tumorigenesis, and lately carcinogenesis in tissues with high self-renewal capabilities like epithelia. In cells able to live the longest like neurons, NPLs could trigger neurodegeneration by promoting toxic proteinaceous aggregates, OS, and chronic inflammation. NPL genotoxicity and neurotoxicity are discussed based on the gathered evidence, when available, within the context of the intracellular uptake of these newcomer nanoparticles. In summary, this review explains how the risk evaluation of NPL pollution for human health may benefit from accurately monitoring NPL toxicokinetics and toxicodynamics at the intracellular resolution level.

The effects of acute ammonia stress on liver antioxidant, immune and metabolic responses of juvenile yellowfin tuna (Thunnus albacares)

The impact of acute ammonia nitrogen (NH3-N) stress on the antioxidant, immune, and metabolic capabilities of the liver in juvenile yellowfin tuna (Thunnus albacares) is not yet fully understood. This study set NH3-N concentrations at 0 (natural seawater, control group), 5, and 10 mg/L, and sampled the liver at 6, 24, and 36 h for analysis. As time progresses, NH3-N exposure leads to an increase in malondialdehyde (MDA) concentrations. The activity of superoxide dismutase (SOD) and the relative expression levels of related genes, as well as the activity of immune enzymes and ATPase, decrease. The levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), and interleukin-10 (IL-10) exhibit different fluctuation patterns. Low concentrations of NH3-N increase the activity of catalase (CAT) and glutathione peroxidase (GHS-PX) and the relative expression levels of the Na+K+-ATPase gene. The relative expression levels of the interleukin-6 receptor (IL-6r) gene show a decreasing trend. High concentrations of NH3-N decrease the activity of CAT, GSH-PX, and the relative expression levels of related genes. When the NH3-N concentration is below 5 mg/L, the stress duration should not exceed 36 h. When the NH3-N concentration is between 5 and 10 mg/L, the stress duration should not exceed 24 h, otherwise, it will have a negative impact on the liver of the juvenile yellowfin tuna. This study provides scientific data for the artificial breeding and recirculating aquaculture of juvenile yellowfin tuna.

Microplastics in faeces of European shags Gulosus aristotelis in central Norway

Plastic pollution is an increasing problem in the marine environment, and microplastics are frequently ingested by wildlife, including seabirds. Faeces are an increasingly used matrix to quantify egested microplastics. We investigated microplastics in 36 faeces samples from chicks of European shags (Gulosus aristotelis) sampled at Sklinna, central Norway in 2021. Small particles <300 μm (62 %) dominated the material. Out of 465 particles measured with Raman spectroscopy, 32 were identified as microplastics (21 fragments, 4 fibres). 69.4 % of faecal samples contained microplastics, with on average 17 microplastic particles per g faeces dry weight. Sixteen of the 36 samples originated from siblings sampled within the same hour, and plastic loads of these samples were more similar to each other compared to those from other individuals. This suggests that a sample from one chick is representative for all siblings at a given moment in time and proofs parental transfer of MP.

A critical review of microplastics in the shrimp farming environment: Incidence, characteristics, effects, and a first mass balance model

This review provides a critical overview of the sources, incidence, accumulation, effects, and interactions of microplastics (MPs) with other contaminants in the shrimp aquaculture environment, emphasizing this sector's challenges and future implications. A first and novel mass MPs balance model was developed to explore the fate and fluxes of MPs within shrimp farming systems. Two literature searches were conducted: one focused on MPs, crustaceans, and shrimp in aquaculture, and other on the effects of MPs in crustaceans, emphasizing shrimp. A total of 78 and 461 peer-reviewed papers were retrieved, respectively. This review details aspects of MPs in the shrimp farming environment, including water, sediments, food, zooplankton, and shrimp tissues. MPs can act as vectors for contaminants, including biological and chemical substances commonly used in shrimp aquaculture. A primary concern is the interaction between MPs and pathogens; thus MPs can facilitate the transport and retention of disease-causing agents. Key questions involve identifying which pathogen groups are most efficiently transported by MPs and how this may exacerbate disease outbreaks in aquaculture. This suggests that microorganisms can establish on MPs surfaces to disseminate an infection. Therefore, the possibility of disease outbreaks and epidemics is expected to rise as MP abundance increases. The mass balance shows that the primary source of MPs is associated with water during the filled (19.3 %) and water exchange (77.2 %) of shrimp ponds, indicating that MPs in the water input play a critical role in the MP dynamic in the shrimp farming environment. However, this initial mass balance model has several weaknesses, including liming, atmospheric deposition, and natural food, which must be addressed as other MPs suppliers. Macrofauna that incidentally enters shrimp ponds may also constitute a significant part of the MPs inventory. Future research should focus on the impact of polystyrene and polyethylene fibers commonly found in crustacean tissues.

Microplastics in aquaculture environments: Current occurrence, adverse effects, ecological risk, and nature-based mitigation solutions

Microplastics pose detrimental effects on the environment, aquatic products, and human health. This comprehensive analysis highlights the repercussions of microplastic contamination within aquaculture. Microplastics in aquaculture are primarily from land-based plastic waste, tourism-related disposal, shipping activities, fisheries/aquaculture, and atmospheric deposition. In aquaculture environments, microplastics have the potential to discharge harmful additives, attract pollutants, degrade the aquaculture setting, and induce toxicological effects. These particles pose ecological risks and can impact human health. Assessing the destiny of microplastics in aquaculture ecosystems is crucial to determining the role of aquaculture in contributing to microplastic contamination within the watershed. It particularly emphasizes the ecological consequences for aquaculture species and the subsequent health threats for humans. The review strongly supports strict regulations to control and limit microplastic presence within aquaculture ecosystems. Clear regulations are essential for reducing microplastics in aquaculture, thereby ensuring food safety. A novel nature-based solution is proposed using methods like microplastic biofilters, biodegradation, and wetlands. These innovations can be conducted in aquatic ecosystems to serve as microplastic biofilters, effectively eliminating waterborne microplastics. In the future, however, it is crucial to develop additional emergency treatment measures to avoid the potential negative impacts of microplastics on both aquaculture and human health.

Promotion of antibiotic-resistant genes dissemination by the micro/nanoplastics in the gut of snail Achatina fulica

Terrestrial animal intestines are hotspots for the enrichment of micro/nano plastics (M/NPs) and antibiotic-resistant genes (ARGs). However, little is known about the further impact of M/NPs on the spread of ARGs in animal guts. This study investigates the role of M/NPs (polystyrene) with varying particle sizes (0.082, 42, and 182 μm), concentrations (10 and 100 mg/L), and exposure durations (4 and 16 days) in the ARGs dissemination via conjugation in the edible snail (Achatina fulica) gut. Combination of qPCR with 16S rRNA-based sequencing, we found that PS exposure caused intestinal cell impairment and shifts in the gut microbial community of snails. Conjugation rate increased with PS particle sizes in the snail gut. After 4 days of exposure, significantly higher conjugation rates were observed in the gut exposed to 100 mg/L PS compared to 10 mg/L, however, this trend reversed after 16 days. Consistently, the abundances of conjugation relevant genes trfA and trbB shared similar trends to the conjugation ratios in the snail gut after PS exposure. Transconjugant diversity was much lower in 10 mg/L PS groups than in 100 mg/L PS treatments. Therefore, this study suggests that the presence of M/NPs would complicate management of ARG spread. The selection pressure exerted by M/NPs may sustain or even amplify the spread of ARGs in the gut of terrestrial animals even in the absence of antibiotics. It highlights the necessity of avoiding M/NPs intake as a part of comprehensive strategy for cubing ARG dissemination in the gut of animals.

Exploring the detrimental effects of microplastics on Asian seabass (Lates calcarifer) fingerlings survival and health

Microplastics (MPs) are widely used and disposed of indiscriminately, posing a potential threat to aquatic life. Herein, Asian seabass (Lates calcarifer) fingerlings were exposed to various concentrations (1, 10 and 100 ppt or g/kg) of dietary polyethylene MPs for 16 days. The results indicated a significant increase in mortality among the fish fed with dietary MPs compared to the control. Furthermore, histological analysis of the liver revealed moderate-to-severe morphological alterations, hepatocyte necrosis and vacuolisation as the concentration gradient of MPs increased. The severity of the alterations was highest at a concentration of 100 ppt, indicating a direct correlation between MP and liver damage. In addition, RNA sequencing and Gene Ontology term enrichment analysis revealed that a total of 4137 genes were significantly differentially expressed, with 1958 upregulated and 2179 downregulated genes. The significantly enriched terms included 'oxidoreductase activity', 'endocytosis', 'mitochondrial', 'immune system process' and 'lipid catabolic process'. Moreover, the Kyoto Encyclopaedia of Genes and Genomes enrichment analysis demonstrated that dietary MPs triggered oxidative stress, immune response and adaptive mechanism pathways in fish. Thus, MPs can induce metabolic disorders in L. calcarifer, highlighting their potential threat to aquatic organisms.

Polystyrene nanoparticles with different particle sizes cause autophagy by ROS/ERS/FOXO1 axis in the Cyprinus carpio kidney affecting immunological function

Microplastic pollution poses challenges for ecosystems worldwide, and nanoplastics (NPs, 1-1000 nm) have been identified as persistent pollutants. However, although some studies have described the hazards of NPs to aquatic organisms, the toxicological processes of NPs in the common carp kidney and the biotoxicity of differently sized NPs remain unclear. In this study, we used juvenile common carp as an in vivo model that were constantly exposed to freshwater at 1000 μg/L polystyrene nanoparticle (PSNP) concentrations (50, 100, and 400 nm) for 28 days. Simultaneously, we constructed an in vitro model utilizing grass fish kidney cells (CIK) to study the toxicological effects of PSNPs of various sizes. We performed RT-PCR and Western blot assays on the genes involved in FOXO1, HMGB1, HIF-1α, endoplasmic reticulum stress, autophagy, and immunoreaction. According to these results, exposure to PSNPs increased reactive oxygen species (ROS) levels, and the carp kidneys experienced endoplasmic reticulum stress. Additionally, PSNPs promoted renal autophagy by activating the ROS/ERS/FOXO1 (ERS: endoplasmic reticulum stress) pathway, and it affected immunological function by stimulating the ROS/HMGB1/HIF-1α signaling pathway. This study provides new insights into the contamination hazards of NPs in freshwater environments, as well as the harm they pose to the human living environments. The relationship between particle size and the degree of damage caused by PSNPs to organisms is a potential future research direction.

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

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

Microplastic exposure reduced the defecation rate, altered digestive enzyme activities, and caused histological and ultracellular changes in the midgut tissues of the ground beetle (Blaps polychresta)

Concerns about microplastic (MP) pollution in terrestrial systems are increasing. It is believed that the overall amount of MPs in the terrestrial system could be 4-23 times higher than that in the ocean. Agricultural ecosystems are among the most polluted areas with MPs. Terrestrial organisms such as ground beetles, will be more vulnerable to MPs in various agricultural soil types because they are common in garden and agricultural areas. Therefore, this work aims to assess for the first time the potential adverse effects of chronic exposure for 30 days of ground beetles to a field-realistic concentration of 2 % (w/w) of three different irregularly shaped MPs polymers: Polystyrene (PS), polyethylene terephthalate (PET), and polyamide 6 (PA; i.e., nylon 6) on their health. The results showed no effect on beetle survival; nevertheless, there was a decrease in beetle defecation rate, particularly in beetles exposed to PS-MPs, and a change in the activity of midgut digestive enzymes. The effects on digestive enzymes (amylase, protease, lipase, and α-glucosidase) were polymer and enzyme specific. Furthermore, histological and cytological studies demonstrated the decomposition of the midgut peritrophic membrane, as well as abnormally shaped nuclei, vacuolation, disordered microvilli, necrosis of goblet and columnar cells, and necrosis of mitochondria in midgut cells. Given the importance of ground beetles as predators in most agricultural and garden settings, the reported adverse impacts of MPs on their health may impact their existence and ecological functions.

The bio-accumulation and -magnification of microplastics under predator-prey isotopic relationships

Recent studies on microplastics (MPs) in marine ecosystems have focused on their bioaccumulation and biomagnification within food chains, emphasizing their potential health risks to humans. However, these bio-effects of MPs in marine ecosystems remain a contentious issue. Employing the "consumer-dietary source" tracking function in stable isotope analysis can enhance our comprehension of how MPs magnify in organisms. In our research conducted in the coastal waters of Haizhou Bay, Jiangsu, China, we examined two commercially important fish species, Larimichthys polyactis and Collichthys lucidus, through stable isotope analysis to investigate the accumulation of MPs in their dietary sources. Results revealed fiber, blue, and PET as the primary shapes, colors, and polymers of MPs in the region. C. lucidus displayed a broader isotopic niche and a higher propensity for MP accumulation than L. polyactis. Biomagnification analysis indicated that dominant MP shapes, colors, and polymers were magnified in both fish species, with MPs smaller than 3 mm exhibiting substantial biomagnification. Factors such as feeding strategies and habitat preferences may influence MP ingestion by fish. We conclude that a high proportion of dietary sources in fish does not necessarily equate to a high concentration of MPs. Neglecting the proportion of dietary sources might lead to underestimating MP biomagnification. Therefore, a multidimensional approach to exploring the biomagnification of MPs is essential to accurately grasp this unique pollutant's impact.

Toxic Effects of Cadmium Exposure on Hematological and Plasma Biochemical Parameters in Fish: A Review

Cadmium (Cd) is a non-essential trace element that poses significant toxic effects on fish. This review focuses on hematological and plasma biochemical parameters as key indicators of fish health under Cd exposure. Hematological parameters, such as red blood cell (RBC) count, hemoglobin (Hb) concentration, and hematocrit (Ht), were selected for their critical role in oxygen transport and their sensitivity to Cd-induced disruptions, which often result in anemia and impaired oxygen delivery to tissues. Mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), and mean corpuscular hemoglobin concentration (MCHC) provide further insights into erythropoiesis and hemoglobin synthesis, both of which are essential for assessing Cd toxicity. Plasma biochemical parameters, including calcium, magnesium, glucose, cholesterol, total protein, and liver enzymes such as aspartate aminotransferase (AST), alanine aminotransferase (ALT), and alkaline phosphatase (ALP), are crucial for understanding ionic balance, metabolic regulation, and organ function, especially in fish exposed to Cd. These biomarkers offer a comprehensive view of the physiological stress and organ damage caused by Cd toxicity. This review synthesizes literature findings on the toxic effects of Cd on these parameters. It also discusses potential mitigation strategies, including dietary supplementation with antioxidants and trace elements, to counteract the harmful effects of Cd exposure.

Environmental toxicology of microplastic particles on fish: A review

The increase in plastic debris and its environmental impact has been a major concern for scientists. Physical destruction, chemical reactions, and microbial activity can degrade plastic waste into particles smaller than 5 mm, known as microplastics (MPs). MPs may eventually enter aquatic ecosystems through surface runoff. The accumulation of MPs in aquatic environments poses a potential threat to finfish, shellfish, and the ecological balance. This study investigated the effect of MP exposure on freshwater and marine fish. MPs could cause significant harm to fish, including physical damage, death, inflammation, oxidative stress, disruption of cell signalling and cellular biochemical processes, immune system suppression, genetic damage, and reduction in fish growth and reproduction rates. The activation of the detoxification system of fish exposed to MPs may be associated with the toxicity of MPs and chemical additives to plastic polymers. Furthermore, MPs can enhance the bioavailability of other xenobiotics, allowing these harmful substances to more easily enter and accumulate in fish. Accumulation of MPs and associated chemicals in fish can have adverse effects on the fish and humans who consume them, with these toxic substances magnifying as they move up the food chain. Changes in migration and reproduction patterns and disruptions in predator-prey relationships in fish exposed to MPs can significantly affect ecological dynamics. These interconnected changes can lead to cascading effects throughout aquatic ecosystems. Thus, implementing solutions like reducing plastic production, enhancing recycling efforts, using biodegradable materials, and improving waste management is essential to minimize plastic waste and its environmental impact.

Visible Combined Near-Infrared in Situ Imaging Revealed Dynamic Effects of Microplastic Fibers and Beads in Zebrafish

Microplastics (MPs) as emerging contaminants are widely present in the environment and are ubiquitously ingested and accumulated by aquatic organisms. MPs may be quickly eliminated after a brief retention in aquatic animals (such as the digestive tract); thus, understanding the damage caused by MPs during this process and whether the damage can be recovered is important. Here, we proposed the use of visible light imaging to track MPs combined with near-infrared (NIR) imaging to reveal the in situ impacts of MPs. The combination of these two techniques allows for the simultaneous investigation of the localization and functionality of MPs in vivo. We investigated the effects of two types of MPs on zebrafish, microplastic fibers (MFs) and microplastic beads (MBs). The results showed that MPs larger than 10 μm primarily accumulated in the intestines of zebrafish. Both MFs and MBs disrupted the redox balance of the intestine, and the location of the damage was consistent with the heterogeneous accumulation of MPs. MFs caused greater and more difficult-to-recover damage compared to MBs, which was closely related to the slower elimination rate of MFs. Our study highlights the importance of capturing the dynamic toxicological effects of MPs on organisms. Fibrous MPs and spherical MPs clearly had distinct effects on their toxicokinetics and toxicodynamics in fish.

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.

Micro/nano-plastics impacts in cardiovascular systems across species

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

Effects of tire particles and associated-chemicals on the Pacific oyster (Magallana gigas) physiology, reproduction and next-generation

By 2040, tire particles (TP) are expected to dominate marine plastic contamination, raising concerns about their effects on marine animals. This study employed a multidisciplinary and multigenerational approach on the Pacific oyster Magallana gigas to investigate the effects of TP and their leachates (LEA). Effects were analyzed at the individual scale, from cellular, molecular, and microbiota changes to reproductive outputs and offspring performance. Microbiota characterization revealed potential dysbiosis in oysters treated with high concentration of both TP and LEA. RNA-seq analyses highlighted the activation of energy metabolism and stress responses in the LEA treatment. Additionally, transcriptional changes in oocytes and the reduction of motile spermatozoa suggested potential effects on gamete quality. Notably, possible oyster resilience was pointed out by the lack of significant ecophysiological modifications in adults and impacts on the growth and reproductive outputs of the offspring. Overall, the implications of the observed oyster resilience under our experimental setting are discussed in relation to available toxicity data and within a comprehensive view of coastal ecosystems, where a higher diversity of plastic/rubber materials and harsher environmental conditions occur.

Increased ingestion and toxicity of polyamide microplastics in Nile tilapia with increase of salinity

Microplastics pollution and salinity intrusion in freshwater ecosystem is one of the worldwide climate change consequences those have negative impacts on the physiology of aquatic organisms. Hence, a 15-day experiment was carried out where Nile tilapia (Oreochromis niloticus) was exposed to different salinity gradients i.e. 0 ‰, 3 ‰, 6 ‰, 9 ‰, and 12 ‰ alone and along with 10 mg/L polyamide microplastics (PA-MP) in order to measure its effects on the hematology, gill, and intestinal morphology. The results exhibited that all the fish treated with PA-MP ingested microplastics and the quantity of accumulation was significantly greater in higher salinity gradients (9 ‰ and 12 ‰). In addition, the PA-MP treated fish showed increased glucose level and at the same time reduced hemoglobin concentration with the increase of salinity. The percentages of abnormalities in erythrocytes both cellular (twin, teardrop and spindle shaped) and nuclear (notched nuclei, nuclear bridge and karyopyknosis) significantly enhanced with PA-MP exposure again in higher salinity treatments (9 ‰ and 12 ‰). The principal component analysis (PCA) exhibited that the addition of 10 mg/L PA-MP negatively affected the hematology of Nile tilapia than that of salinity treatments alone. Besides, the exposure of PA-MP in 9 ‰ and 12 ‰ salinity gradients escalated the severity of histological damages in gills and intestine. Overall, this experiment affirms that the increase of salinity enhanced the microplastics ingestion and toxicity in Nile tilapia, therefore, PA-MP possibly is addressed as additional physiological stressors along with increased salinity gradients in environment.

Selenium toxicity in fishes: A current perspective

Anthropogenic activities have led to increased levels of contaminants that pose significant threats to aquatic organisms, particularly fishes. One such contaminant is Selenium (Se), a metalloid which is released by various industrial activities including mining and fossil fuel combustion. Selenium is crucial for various physiological functions, however it can bioaccumulate and become toxic at elevated concentrations. Given that fishes are key predators in aquatic ecosystems and a major protein source for humans, Se accumulation raises considerable ecological and food safety concerns. Selenium induces toxicity at the cellular level by disrupting the balance between reactive oxygen species (ROS) production and antioxidant capacity leading to oxidative damage. Chronic exposure to elevated Se impairs a wide range of critical physiological functions including metabolism, growth and reproduction. Selenium is also a potent teratogen and induces various types of adverse developmental effects in fishes, mainly due to its maternal transfer to the eggs. Moreover, that can persist across generations. Furthermore, Se-induced oxidative stress in the brain is a major driver of its neurotoxicity, which leads to impairment of several ecologically important behaviours in fishes including cognition and memory functions, social preference and interactions, and anxiety response. Our review provides an up-to-date and in-depth analysis of the various adverse physiological effects of Se in fishes, while identifying knowledge gaps that need to be addressed in future research for greater insights into the impact of Se in aquatic ecosystems.

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.

Size-dependent deleterious effects of nano- and microplastics on sperm motility

INTRODUCTION

Growing concerns regarding the reproductive toxicity associated with daily life exposure to micro-/nano-plastics (abbreviated as MNPs) have become increasingly prevalent. In reality, MNPs exposure involves a heterogeneous mixture of MNPs of different sizes rather than a single size.

METHODS

In this study, an oral exposure mouse model was used to evaluate the effects of MNPs of four size ranges: 25-30 nm, 1-5 µm, 20-27 µm, and 125-150 µm. Adult male C57BL/6 J mice were administered environmentally relevant concentrations of 0.1 mg MNPs/day for 21 days. After that, open field test and computer assisted sperm assessment (CASA) were conducted. Immunohistochemical analyses of organ and cell type localization of MNPs were evaluated. Testicular transcriptome analysis was carried out to understand the molecular mechanisms.

RESULTS

Our result showed that MNPs of different size ranges all impaired sperm motility, with a decrease in progressive sperm motility, linearity and straight-line velocity of sperm movement. Alterations did not manifest in animal locomotion, body weight, or sperm count. Noteworthy effects were most pronounced in the smaller MNPs size ranges (25-30 nm and 1-5 µm). Linear regression analysis substantiated a negative correlation between the size of MNPs and sperm curvilinear activity. Immunohistochemical analysis unveiled the intrusions of 1-5 µm MNPs, but not 20-27 µm and 125-150 µm MNPs, into Leydig cells and testicular macrophages. Further testicular transcriptomic analysis revealed perturbations in pathways related to spermatogenesis, oxidative stress, and inflammation. Particularly within the 1-5 µm MNPs group, a heightened perturbation in pathways linked to spermatogenesis and oxidative stress was observed.

CONCLUSIONS

Our data support the size-dependent impairment of MNPs on sperm functionality, underscoring the pressing need for apprehensions about and interventions against the escalation of environmental micro-/nano-plastics contamination. This urgency is especially pertinent to small-sized MNPs.

Chronic Polystyrene Microplastic Exposure Reduces Testosterone Levels in Mice through Mitochondrial Oxidative Stress and BAX/BCL2-Mediated Apoptosis

Microplastics (MPs) have emerged as a major environmental issue. They have been found to cause significant reproductive toxicity and lower testosterone levels in adult males, though the exact mechanisms remain unclear. In this study, C57bl/6 mice were orally exposed to saline or varying doses (0.25, 0.5, and 1 mg/day) of 5 μm polystyrene MPs (PS-MPs) for 4 weeks, and TM3 mouse Leydig cells were treated with different concentrations of PS-MPs. Our results found that exposure to PS-MPs significantly reduced testosterone levels and impaired the synthesis function of testicular steroids. In vitro, PS-MPs reduced steroid synthesis in Leydig cells. Treatment with PS-MPs significantly increased the apoptosis rate and BAX/BCL2 ratio in Leydig cells. Additionally, GSH-px and SOD activities decreased, while MDA levels increased, along with a rise in mitochondrial ROS. In conclusion, chronic PS-MP exposure reduced testosterone levels in mice through mitochondrial oxidative stress and BAX/BCL2-mediated apoptosis. This study offers new insights into the health risks posed by MPs.

Occurrence, detection and ecotoxicity of microplastics in selected environments-a systematic appraisal

Microplastics (MPs) are being released into the environment in large quantities, especially in less developed parts of the world. This group of pollutants is mostly leached into the environment through heavy plastic dumpsites, pharmaceutical and personal care product containers, hospital wastes, plastic package accessories, and litter from food packaging. Consequently, these compounds are found in different compartments of the ecosystem, such as soils, sediments, biota, and, surprisingly, drinking water. The present study systematically appraised recent studies on MP pollution in the Asian and African environments. It also summarized the trends in the methods for the environmental monitoring of MPs and the removal strategies that have been employed. From the data gathered, the two key instrumentations involved are the microscopes for visualization and the Fourier transform-infra-red (FT-IR) spectrometer to classify or characterize the MPs. Based on the surveyed works of literature, China and South Africa have relatively more information on MP contamination of diverse matrices within their countries. Meanwhile, studies on the status of MP contamination should be conducted across all countries. Hence, this study becomes an eye-opener regarding the commencement of research works on the MP contamination of the environment, especially in other Asian and African countries with little or no information. Furthermore, the literature on ecotoxicity studies of MPs was investigated to ascertain the toxic nature of these compounds. This aspect of research is vital because it serves as a prerequisite for the remediation of these compounds. Microplastics have been declared lethal to biotic components, so all hands must be on deck to continuously remove them from the environment.

Dietary Moringa oleifera mitigates Fluconazole-Induced immunological and spleen-histological alterations in Catfish (Clarias gariepinus)

Fluconazole (FCZ), an antifungal from the azole family, causes several detrimental effects in fish. In recent times, there has been a notable surge in interest regarding the utilization of Moringa oleifera (Mo) as a dietary antioxidant. This research aimed to evaluate the potential protective effects of dietary Moringa oleifera (MO) against the adverse impacts of fluconazole in the African catfish (Clarias gariepinus). The fish were allocated into four groups as follows: a control group fed a basal diet, an FCZ - exposed (200 ng/L) fed basal diet, 1% MO fed through basal diet, and an FCZ-exposed (200 ng/L) and 1% MO fed through basal diet fed group. The results showed that FCZ exposure decreased superoxide dismutase, total antioxidant capacity, and acetylcholine esterase levels. On the other hand, FCZ exposure increased malonaldehyde and cortisol levels as compared to control (P < 0.05). FCZ caused immunosuppressive effects in C. gariepinus as revealed by lower immunity indices (lysozyme and phagocytic activity and immunoglobulin level) and increased cytokine levels (IL-6 IL-1β). Histological examination of the spleen from fish exposed to FCZ showed several splenic changes. We conclude that dietary MO supplementation has the potential to alleviate the oxidative stress, restore immune response balance, and mitigate histological damage induced by FCZ exposure, thus positioning MO as an immunostimulant in C. gariepinus when administered alongside FCZ.

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.

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.

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.

Micro-and nano-plastics induce kidney damage and suppression of innate immune function in zebrafish (Danio rerio) larvae

Aquatic environments serve as critical repositories for pollutants and have significantly accumulated micro- and nanoplastics (MNPs) due to the extensive production and application of plastic products. While the disease resistance and immunity of fish are closely linked to the condition of their aquatic habitats, the specific effects of nanoplastics (NPs) and microplastics (MPs) within these environments on fish immune functions are still not fully understood. The present study utilized zebrafish (Danio rerio) embryos and larvae as model organisms to examine the impacts of polystyrene NPs (100 nm) and MPs (5 μm) on fish immune responses. Our findings reveal that NPs and MPs tend to accumulate on the surfaces of embryos and within the intestines of larvae, triggering oxidative stress and significantly increasing susceptibility to Edwardsiella piscicida infection in zebrafish larvae. Transmission electron microscopy examined that both NPs and MPs inflicted damage to the kidney, an essential immune organ, with NPs predominantly inducing endoplasmic reticulum stress and MPs causing lipid accumulation. Transcriptomic analysis further demonstrated that both NPs and MPs significantly suppress the expression of key innate immune pathways, notably the C-type lectin receptor signaling pathway and the cytosolic DNA-sensing pathway. Within these pathways, the immune factor interleukin-1 beta (il1b) was consistently downregulated in both exposure groups. Furthermore, exposure to E. piscicida resulted in restricted upregulation of il1b mRNA and protein levels, likely contributing to diminished disease resistance in zebrafish larvae exposed to MNPs. Our findings suggest that NPs and MPs similarly impair the innate immune function of zebrafish larvae and weaken their disease resistance, highlighting the significant environmental threat posed by these pollutants.

Single and combined toxicity of tadalafil (Cilais) and microplastic in Tilapia fish (Oreochromis niloticus)

The joint impact of tadalafil (Cilais) as a pharmaceutical residue and microplastics on fish is not well comprehended. The current study examined haematological, biochemical, and antioxidant parameters, along with immunohistochemical and histological indications in tilapia (Oreochromis niloticus) after being exposed to tadalafil, polyethylene microplastics (PE-MPs), and their mixtures for 15 days. The fish were distributed into 1st group control group (The fish was maintained in untreated water without any supplements); 2nd group exposed to 10 mg/L PE-MPs;3rd group exposed to 20 mg/l tadalafil (Cilais); 4th group exposed to 20 mg/l tadalafil (Cilais) + 10 mg/LPE-MPs (in triplicate). The levels of creatinine, uric acid, glucose, AST, ALT, and albumin in fish treated with tadalafil alone or in combination with PE-MPs were significantly higher than those in the control group. Fish exposed to PE-MPs, tadalafil, and tadalafil plus PE-MPs showed significantly lower levels of RBCs, Hb, Ht, neutrophils, and lymphocytes compared to the control group. Serum levels of total antioxidant capacity and reduced glutathione (GSH) were notably lowered in fish groups subjected to PE-MPs, tadalafil, and tadalafil + PE-MPs combinations in comparison to the control group. Malondialdehyde (MDA) serum levels were notably elevated in fish groups subjected to PE-MPs, tadalafil, and tadalafil + PE-MPs combinations compared to the control group. The most severe impact was observed in the tadalafil + PE-MPs combination group. Interleukin-6 (IL-6) levels were significantly increased in liver tissues following exposure to both tadalafil and microplastics compared to tissues exposed to only one substance or the control group. Changes in the gills, liver, and renal tissues were seen following exposure to PE-MPs, tadalafil, and tadalafil + PE-MPs combination in comparison to the control group of fish. Ultimately, the mixture of tadalafil and PE-MPs resulted in the most detrimental outcomes. Tadalafil and PE-MPs exhibited showed greater adverse effects, likely due to tadalafil being absorbed onto PE-MPs.

Toxicological review of micro- and nano-plastics in aquatic environments: Risks to ecosystems, food web dynamics and human health

The increase of micro- and nano-plastics (MNPs) in aquatic environments has become a significant concern due to their potential toxicological effects on ecosystems, food web dynamics, and human health. These plastic particles emerge from a range of sources, such as the breakdown of larger plastic waste, consumer products, and industrial outputs. This review provides a detailed report of the transmission and dangers of MNPs in aquatic ecosystems, environmental behavior, and interactions within aquatic food webs, emphasizing their toxic impact on marine life. It explores the relationship between particle size and toxicity, their distribution in different tissues, and the process of trophic transfer through the food web. MNPs, once consumed, can be found in various organs, including the digestive system, gills, and liver. Their consumption by lower trophic level organisms facilitates their progression up the food chain, potentially leading to bioaccumulation and biomagnification, thereby posing substantial risks to the health, reproduction, and behavior of aquatic species. This work also explores how MNPs, through their persistence and bioaccumulation, pose risks to aquatic biodiversity and disrupt trophic relationships. The review also addresses the implications of MNPs for human health, particularly through the consumption of contaminated seafood, highlighting the direct and indirect pathways through which humans are exposed to these pollutants. Furthermore, the review highlights the recommendations for future research directions, emphasizing the integration of ecological, toxicological, and human health studies to inform risk assessments and develop mitigation strategies to address the global challenge of plastic pollution in aquatic environments.

Microplastics in Ghana: An in-depth review of research, environmental threats, sources, and impacts on ecosystems and human health

Microplastics pose significant challenges on a global scale. In Ghana, these tiny pollutants infiltrate diverse ecosystems such as coastal areas, rivers, lakes, and forests, vital to the nation's economy and social well-being. This review examines the current depth of knowledge in research and the escalating concern of microplastics, identifying significant gaps in research and understanding. The findings highlight the limited understanding of the extent and distribution of microplastic pollution across different environmental compartments, primarily focusing on coastal environments. Additionally, detection and quantification techniques for microplastics face several complexities and limitations in the Ghanaian context due to constraints such as infrastructure, resources, and expertise. Despite some research efforts, particularly along the coastline, there is still a distinct lack of attention in various regions and ecosystems within Ghana. This imbalance in research focus hinders the understanding and effective mitigation of microplastics in the country. This therefore necessitates the implementation of systematic policy frameworks, emphasizing the importance of recycling and upcycling as effective strategies to address the challenges of microplastics in Ghana with more targeted research and public engagement. This review serves as a call to action for a strategic approach to research and policy-making on microplastic research and pollution in Ghana.

Unraveling the nexus: Microplastics, antibiotics, and ARGs interactions, threats and control in aquaculture - A review

In recent years, aquaculture has expanded rapidly to address food scarcity and provides high-quality aquatic products. However, this growth has led to the release of significant effluents, containing emerging contaminants like antibiotics, microplastics (MPs), and antibiotic resistance genes (ARGs). This study investigated the occurrence and interactions of these pollutants in aquaculture environment. Combined pollutants, such as MPs and coexisting adsorbents, were widespread and could include antibiotics, heavy metals, resistance genes, and pathogens. Elevated levels of chemical pollutants on MPs could lead to the emergence of resistance genes under selective pressure, facilitated by bacterial communities and horizontal gene transfer (HGT). MPs acted as vectors, transferring pollutants into the food web. Various technologies, including membrane technology, coagulation, and advanced oxidation, have been trialed for pollutants removal, each with its benefits and drawbacks. Future research should focus on ecologically friendly treatment technologies for emerging contaminants in aquaculture wastewater. This review provided insights into understanding and addressing newly developing toxins, aiming to develop integrated systems for effective aquaculture wastewater treatment.

Investigating the metabolic and oxidative stress induced by biofouled microplastics exposure in Seriola lalandi (yellowtail kingfish)

Microorganisms quickly colonise microplastics entering the ocean, forming a biofilm that, if ingested, is consumed with the microplastics. Past research often neglects to expose fish to biofouled microplastics, opting only for clean microplastics despite the low likelihood that fish will encounter clean microplastics. Here, we investigate the physiological impacts of biofouled polyethylene microplastic (300-335 μm) exposure in juvenile fish. Intermittent flow respirometry, antioxidant enzyme activity, and lipid peroxidation were investigated after fish were exposed to clean, biofouled, or no microplastic beads. Fish exposed to biofouled microplastics had a wider aerobic scope than those exposed to clean microplastics while antioxidant enzyme and lipid peroxidation levels were higher in clean microplastics. Clean microplastic exposure indicated higher fitness costs, potentially due to a nutritional advantage of the biofilm or varying bioavailability. These findings highlight the importance of replicating natural factors in exposure experiments when predicting the impacts of increasing pollutants in marine systems.

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.

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

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

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.

Size dependent ingestion and effects of microplastics on survivability, hematology and intestinal histopathology of juvenile striped catfish (Pangasianodon hypophthalmus)

Microplastic pollution is drastically increasing in aquatic ecosystems and it is assumed that different sizes of microplastics have diverse impacts on the physiology of aquatic organisms. Therefore, this study was intended to examine the ingestion and size specific effects of polyamide microplastic (PA-MP) on different physiological aspects such as growth, feed utilization, survivability, blood parameters and intestinal histopathology of juvenile striped catfish (Pangasianodon hypophthalmus). In a 28-day exposure, the fish were fed with different sized PA-MP with a concentration of 500 mg per kg of feed in order to simulate highly microplastic contaminated environment. Three different treatments were set for this experiment i.e. T1, 25-50 μm (smaller microplastic); T2, 300 μm-2 mm (larger microplastic); T3, (mixed) including a control (C); each had three replicates. The highest ingestion was recorded in the gastrointestinal tract (GIT) of fish exposed to smaller PA-MP treatments (T1 followed by T3). The results also showed compromised weight gain (WG; g), specific growth rate (SGR; %/day) and feed conversion ratio (FCR) with the exposure of PA-MP. Besides, survivability significantly reduced among treatments with the ingestion of smaller sized microplastic and found lowest in T1 (65.0 ± 5.0). In addition, the presence of PA-MP in feed negatively affected the concentration of hemoglobin and blood glucose. Similarly, smaller PA-MP caused most erythrocytic cellular and nuclear abnormalities; found highest in T1 that significantly different from other treatments (p < 0.05). Various histopathological deformities were observed in fish fed with PA-MP incorporated feed. The principal component analysis (PCA) showed that the toxicity and stress imparted by smaller PA-MP affected the survivability and blood parameters where larger PA-MP caused mild to severe abnormalities. Based on eigenvector values, the major abnormalities in intestine included occurrence of epithelium columnar degeneration (ECD: 0.402; PC1), hyperplasia of internal mucosa (HISM: 0.411; PC1), beheading of villi (BV: 0.323; PC1), atrophy of mucosa (AM: 0.322; PC1), tiny vacuoles in apical villi (TV: 0.438. PC2), crypt degeneration (CD: 0.375: PC2) and atrophy of goblet cell (AGC: 0.375; PC2). Therefore, it has been speculated that the size based PA-MP ingestion in the GIT interfered with the digestion and absorption as well as caused deformities that reflected negatively in survivability and hemato-biochemical parameters of juvenile striped catfish.

Microplastic-induced oxidative stress response in turbot and potential intake by humans

Microplastic (MP) pollution has become a health concern subject in recent years. Althoughann increasing number of studies about the ingestion of microplastics by fish, research on the oxidative stress response to MPs in natural environments is quite limited. In this study, the identification and characterization of MPs in gill (G), muscle tissues (M), and gastrointestinal tract (GI) of turbot (Scophthalmus maximus) were evaluated. Oxidative damage of MPs on the brain (B), liver (L), gill (G), and muscle (M) tissues as well as their effect on superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), paraoxonase (PON), arylesterase (AR) myeloperoxidase (MPO), and malondialdehyde (MDA) biomarkers were evaluated. The potential transmission of MPs from muscle tissues to humans was examined. Results showed that gills contain the highest amounts of MPs, ethylene propylene is the most dominant polymer type, black and blue are the most common MP color, fiber is the most common shape, and 50-200 µm is the most common MP size. Results showed that MPs cause oxidative stress of tissues with inhibiting effect on enzyme activities and promoting impact on lipid peroxidation. The oxidative damage mostly affected the liver (detoxification organ) followed by gill tissue. The intake of MPS in the European Union was estimated by EFSA as 119 items/year, while in Turkey it is 47.88 items/year. This study shows that more research is needed in terms of ecosystem health and food chain safety. The risk assessment of MPs in living organisms and environmental matrices including food safety and human health should be considered a public health issue.

A critical review on male-female reproductive and developmental toxicity induced by micro-plastics and nano-plastics through different signaling pathways

It is widely accepted that humans are constantly exposed to micro-plastics and nano-plastics through various routes, including inhalation of airborne particles, exposure to dust, and consumption of food and water. It is estimated that humans may consume thousand to millions of micro-plastic particles, equating to several milligrams per day. Prolonged exposure to micro-plastics and nano-plastics has been linked to negative effects on different living organisms, including neurotoxicity, gastrointestinal toxicity, nephrotoxicity, and hepatotoxicity, and developmental toxicities. The main purpose of this review is to explore the effect of micro-plastics and nano-plastics on the male and female reproductive system, as well as their offspring, and the associated mechanism implicated in the reproductive and developmental toxicities. Micro-plastics and nano-plastics have been shown to exert negative effects on the reproductive system of both male and female mammals and aquatic animals, including developmental impacts on gonads, gametes, embryo, and their subsequent generation. In addition, micro-plastics and nano-plastics impact the hypothalamic-pituitary axes, leading to oxidative stress, reproductive toxicity, neurotoxicity, cytotoxicity, developmental abnormalities, poor sperm quality, diminishes ovarian ovulation and immune toxicity. This study discusses the so many different signaling pathways associated in the male and female reproductive and developmental toxicity induced by micro-plastics and nano-plastics.

Polystyrene exposure induces lamb gastrointestinal injury, digestive disorders and inflammation, decreasing daily gain, and meat quality

Microplastics (MPs), recognized as an emerging environmental menace, have been extensively investigated in both marine and terrestrial fauna. This study is comprehensive to investigate how polystyrene (PS) affects ruminant animals. The experimental design comprised 24 individually housed lambs, divided into a CON group (diet without PS) and three PS-exposed (25 μm, 50 μm, 100 μm) groups, each with six lambs, the exposure of PS was 100 mg/day, and the duration of exposure was 60 days. The study yielded noteworthy results: (ⅰ) PS leads to a decrease in average daily gain along with an increase in feed conversion rate. (ⅱ) PS decreases rumen ammonia nitrogen. The rumen microbiota diversity remains consistent. However, the relative abundance of Bacteroidetes and Actinobacteria increased in the PS-exposed groups, while the relative abundance of Coriobacteriales_incertae_Sedis and Prevotellaceae_YAB2003_group decreased. (ⅲ) PS leads to decrease in hemoglobin, thrombocytocrit, and albumin levels in lamb blood, thus triggering oxidative stress accumulation, along with swelling of the kidneys and liver. (ⅳ) PS inflicts severe damage to jejunum, consequently impacting digestion and absorption. (ⅴ) PS reduces meat quality and the nutritional value. In conclusion, PS-exposure inhibited lambs' digestive function, adversely affects blood and organs' health status, reducing average daily gain and negatively influencing meat quality. PS particles of 50-100 μm bring worse damage to lambs. This research aims to fill the knowledge void concerning MPs' influences on ruminant animals, with a specific focus on the meat quality of fattening lambs.

Aged polystyrene microplastics exacerbate alopecia associated with tight junction injuries and apoptosis via oxidative stress pathway in skin

Microplastics (MPs) are pervasive pollutants in the natural environment and contribute to increased levels of illness in both animals and humans. However, thespecific impacts of MPs on skin damage and alopeciaare not yet well understood. In this study, we have examined the effects of two types of polystyrene MPs (pristine and aged) on skin and hair follicle damage in mice. UV irradiation changed the chemical and physical properties of the aged MPs, including functional groups, surface roughness, and contact angles. In both in vivo and in vitro experiments, skin and cell injuries related to oxidative stress, apoptosis, tight junctions (TJs), alopecia, mitochondrial dysfunction, and other damages were observed. Mechanistically, MPs and aged MPs can induce TJs damage via the oxidative stress pathway and inhibition of antioxidant-related proteins, and this can lead to alopecia. The regulation of cell apoptosis was also observed, and this is involved in the ROS-mediated mitochondrial signaling pathway. Importantly, aged MPs showed exacerbated toxicity, which may be due to their elevated surface irregularities and altered chemical compositions. Collectively, this study suggests a potential therapeutic approach for alopecia and hair follicle damage caused by MPs pollution.

A Systematic Review on Microplastic Contamination in Fishes of Asia: Polymeric Risk Assessment and Future Prospectives

Microplastics (MPs) have attracted global concern because of their harmful effects on marine biota; their toxic properties can negatively impact aquatic ecosystems. Fish is an essential source of protein for humans, playing a crucial role in daily food intake. Until recently, MPs were addressed primarily as environmental pollutants, but they are now increasingly recognized as contaminants in the food supply. The present review has comprehended the current knowledge of MP contamination in freshwater and marine fishes of Asia, including 112 peer-reviewed sources from 2016 to 2023. The review recorded 422 Asian fishes (345 marine and 77 freshwater) to be contaminated with MPs. Clarias gariepinus and Selaroides leptolepi have shown maximum MP contamination in the freshwater and marine environments of Asia, respectively. Omnivorous and carnivorous fishes exhibited higher susceptibility to ingesting MPs. Benthopelagic, demersal, and reef-associated habitats were identified as more prone to MP accumulation. In both freshwater and marine environments, China has the highest number of contaminated species among all the countries. Pollution indices indicated high MP contamination in both freshwater and marine environments. A prevalence of fibers was recorded in all fishes. Black- and blue-colored MPs of <500 µm-1 mm size were found dominantly. Polyethylene terephthalate and polyethylene were recorded as the prevalent plastic polymers in freshwater and marine fish, respectively. Overall, the review served as a comprehensive understanding of MP concentrations and variations between species, between feeding habits, and between geographic locations, which can be pivotal for addressing pressing environmental challenges, protecting human health, and fostering global sustainability efforts in the face of escalating plastic pollution. Environ Toxicol Chem 2024;43:671-685. © 2024 SETAC.

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.

Abundance and risk assessment of microplastics in water, sediment, and aquatic insects of the Nile River

Microplastics (MPs) are a serious threat in freshwater environments. The ecological risk and abundance level of MPs in abiotic and biotic compartments of the Nile River haven't been systematically reported. Thus, these issues were highlighted in the present study during different seasons of the sampling year. The results showed that MP concentrations in the river ranged from 2.24 ± 0.6 to 3.76 ± 1.1 particles/L, 298 ± 63 to 520 ± 80 particles/kg dry weight, and 0.081 ± 0.051 to 4.95 ± 2.6 particles/individual in surface water, sediment, and different species of aquatic insects, respectively. All the extracted MPs are colored blue, red, and black. Fiber-shaped polyesters (<500-1500 μm) were the most common MPs in all the river compartments. MPs' dominance was observed during the summer in comparison with that in the other seasons. Environmental risk indicators indicate the high ecological risk of MPs, which are widely distributed in the Nile River. In conclusion, MP consumption by aquatic insects may not only be related to levels of environmental contamination, since other variables, such as taxon size, weight, and particular feeding behavior, may also be significant. Additionally, the presence of MPs in insects (at lower trophic levels) creates the potential for predation-based inter-trophic level transmission. Thus, higher trophic-level investigations of various feeding groups should be carried out to identify any possible harm that MPs cause to various aquatic organisms.