Estimation of the uptake and gut retention of microplastics in juvenile marine fish: Mummichogs (Fundulus heteroclitus) and red seabreams (Pagrus major)

A Noninvasive Quantitative Method for Evaluating Intestinal Exposure to Microplastics Based on the Excretion and Metabolism Patterns of Microplastics and Their Additives

Microplastics (MPs) pose potential health risks to the intestinal tract and gut microbiota, a topic that has garnered significant attention. However, the absence of quantitative assessment methods for human gut MP exposure impedes related health risk assessments. Here, we performed long-term continuous exposure experiments on mice using MPs that mimic actual human exposure characteristics. The daily excretion of fecal MPs and the concentrations of phthalates (PAEs) and their metabolites (mPAEs) in serum and urine were detected. The cumulative excretion rate of fecal MPs remains stable at about 93%. A significant linear correlation was observed between MP exposure and concentration of mPAEs in urine for both low MP (LMP; 150 μg of MPs/d) (R2 = 0.90) and high MP (HMP; 360 μg of MPs/d) groups (R2 = 0.97). Moreover, a strong correlation was found between daily PAEs exposure and total MP-associated PAEs exposure in both LMP (R2 = 0.77) and HMP (R2 = 0.88) groups. Based on these findings, we established a noninvasive model and evaluated multiple MP exposure parameters in the human gut across 6 continents, 30 countries, and 133 individuals. This study offers novel insights for the quantitative assessment of in vivo MP exposure and provides technical support for assessing the health risks of MPs.

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

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

Effects Caused by the Ingestion of Microplastics: First Evidence in the Lambari Rosa (Astyanax altiparanae)

Microplastics are a class of contaminants that pose a threat to aquatic biota, as they are easily found in aquatic ecosystems and can be ingested by a wide variety of organisms, such as fish. The lambari rosa (Astyanax altiparanae) is a microphage fish, which feeds on microscopic beings and particles, making it potentially susceptible to ingesting MPs discarded in the environment. In addition, this fish is of great economic and food importance, as it is used for human consumption. This study aimed to evaluate the accumulation and possible toxicological effects caused to lambari rosa (n = 450) by the ingestion of polyethylene (PE) and polyethylene terephthalate (PET) MPs, since the MPs of these polymers in the form of granules, fragments, and fibers are the most commonly reported in the aquatic environment. The parameters investigated here were the quantitative analysis of ingested MPs using microscopic and staining techniques, as well as the mortality rate, malformations/injuries, and impaired weight gain. At the end of the experiment, it was concluded that MPs from both polymers accumulated in the gastrointestinal tract of the lambari rosa, and that dietary exposure, especially to the PET polymer, was responsible for increasing the mortality rate in this species.

Differential developmental and proinflammatory responses of zebrafish embryo to repetitive exposure of biodigested polyamide and polystyrene microplastics

Microplastics (MPs) have attracted global concern and are at the forefront of current research on environmental pollution, whereas, little is known about the degradation of ingested MPs in the gastrointestinal environment and repetitive exposure-associated risk of egested MPs to organisms. The present study revealed that polyamide (PA) and polystyrene (PS) MPs exhibited remarkably differential biodegradations in the gastric and intestinal fluids of a model fish (Siniperca chuatsi). Significant disintegration of the skeleton structure, size reduction (from 27.62 to 9.17 µm), benzene ring scission, and subsequent biogenic corona coating and surface oxidation occurred during in vitro digestion, thus increasing the hydrophilicity and agglomeration of PS. Conversely, PA MPs exhibited high resistance to enzymolysis with slight surface erosions and protein adsorption. Relative to the pristine form, the bioaccumulation of digested PS elevated and the musculoskeletal deformity and mortality of juvenile zebrafish were obviously enhanced, but these changes were unobservable for PA. Lipopolysaccharide-triggered inflammation and apoptosis via Toll-like receptor signaling pathways and reduction of extracellular matrix secretions driven by oxidative stress contributed to the aggravated inhibitory effects of digested PS on larval development. These findings emphasize the necessity of concerning the biota digestion in MP risk assessments in natural waters.

Effects of microfiber and bead microplastic exposure in the goldfish Carassius auratus: Bioaccumulation, antioxidant responses, and cell damage

We confirmed antioxidant-related gene expression, bioaccumulation, and cell damage following exposure to various microplastics in vivo and in vitro in the goldfish Carassius auratus. Exposure of C. auratus to a 500 µm fiber-type microplastic environment (MF; 10 and 100 fibers/L) and two sizes (0.2 and 1.0 µm) of beads (MB; 10 and 100 beads/L) for 120 h increased superoxide dismutase (SOD) mRNA expression in the liver until 24 h followed by a decrease. Whereas, catalase (CAT) mRNA expression increased from 12 h to the end of the in vivo experiment. In vitro experiments were conducted with diluted microfibers (1 and 5 fibers/L) and microbeads (1 and 5 beads/L) using cultured liver cells. The results of SOD and CAT mRNA expression analysis conducted in vitro showed a tendency similar to those of experiments conducted in vivo. The H2O2 level increased in the high-concentration experimental groups compared with that in the low-concentration groups of 0.2-µm beads. In addition, the H2O2 level increased in both MF and MB groups from 12 h of exposure. Alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels in plasma were used as indicators of liver damage in fish. The ALT and AST levels increased up to 120 h after exposure. Caspase-3 (casp-3) mRNA expression was higher in the MB group than in the MF group. We visually confirmed liver casp-3 mRNA signals using in situ hybridization. The degree of DNA damage in the MF and MB high-concentration groups increased with the exposure time. The tail length and percent of DNA in the tail of the MB group were significantly higher than those of the MF group, confirming that DNA damage was greater in the MB group. Both fiber- and bead-type microplastics induced oxidative stress in C. auratus, but the bead-type induced greater stress than the fiber-type.

Microplastics in water, feed and tissues of European seabass reared in a recirculation aquaculture system (RAS)

Plastic particles (PLs) are ubiquitous in aquatic ecosystems and aquaculture production is susceptible to contamination from external or endogenous sources. This study investigated PL presence in water, fish feed and body sites of 55 European seabass produced in a recirculating aquaculture system (RAS). Fish morphometric parameters and health status biomarkers were determined. A total of 372 PLs were recovered from water (37.2 PL/L), 118 PLs from feed (3.9 PL/g), and 422 from seabass (0.7 PL/g fish; all body sites analysed). All 55 specimens had PLs in at least two of the four body sites analysed. Concentrations were higher in the gastrointestinal tract (GIT; 1.0 PL/g) and gills (0.8 PL/g) than in the liver (0.8 PL/g) and muscle (0.4 PL/g). PL concentration in GIT was significantly higher than in muscle. Black, blue, and transparent fibres made of man-made cellulose/rayon and polyethylene terephthalate were the most common PLs in water and seabass, while black fragments of phenoxy resin were the most common in feed. The levels of polymers linked to RAS components (polyethylene, polypropylene, and polyvinyl chloride) were low suggesting a limited contribution to the overall PL levels found in water and/or fish. The mean PL size recovered from GIT (930 μm) and gills (1047 μm) was significantly larger than those found in the liver (647 μm) and dorsal muscle (425 μm). Considering all body sites, PLs bioconcentrated in seabass (BCF_Fish >1) but their bioaccumulation did not occur (BAF_Fish <1). No significant differences were observed in oxidative stress biomarkers between fish with low (<7) and high (≥7) PL numbers. These findings suggest that fish produced in RAS are mainly exposed to MPs through water and feed. Further monitoring under commercial conditions and risk assessment are warranted to identify potential threats to fish and human health and define mitigating measures.

Euryhaline fish larvae ingest more microplastic particles in seawater than in freshwater

Microplastic (MP) pollution is a major concern in aquatic environments. Many studies have detected MPs in fishes; however, little is known about differences of microplastic uptake by fish in freshwater (FW) and those in seawater (SW), although physiological conditions of fish differ significantly in the two media. In this study, we exposed larvae (21 days post-hatching) of Oryzias javanicus (euryhaline SW) and Oryzias latipes (euryhaline FW), to 1-µm polystyrene microspheres in SW and FW for 1, 3, or 7 days, after which, microscopic observation was conducted. MPs were detected in the gastrointestinal tracts in both FW and SW groups, and MP numbers were higher in the SW group in both species. Vertical distribution of MPs in the water, and body sizes of both species exhibited no significant difference between SW and FW. Detection of water containing a fluorescent dye revealed that O. javanicus larvae swallowed more water in SW than in FW, as has also been reported for O. latipes. Therefore, MPs are thought to be ingested with water for osmoregulation. These results imply that SW fish ingest more MPs than FW fish when exposed to the same concentration of MPs.

The legacy effect of microplastics on aquatic animals in the depuration phase: Kinetic characteristics and recovery potential

The prevalence of microplastics (MPs) in global aquatic environments has received considerable attention. Currently, concerns have been raised regarding reports that the adverse effect of MPs on aquatic animals in the exposure phase may not be (completely) reversed in the depuration phase. In order to provide insights into the legacy effect of MPs from the depuration phase, this study evaluated the kinetic characteristics and recovery potential of aquatic animals after the exposure to MPs. More specifically, a total of 68 depuration kinetic curves were highly fitted to estimate the retention time of MPs. It was shown that the retention time ranged from 1.26 to 3.01 days, corresponding to the egestion of 90 % to 99 % of ingested MPs. The retention time decreased with the increased retention rate. Furthermore, variables potentially affecting the retention time were ranked by the decision tree-based eXtreme Gradient Boosting (XGBoost) algorithm, suggesting that the particle size and tested species were of great importance for explaining the difference in retention time of MPs. Moreover, a biomarker profile was recompiled to determine the toxic changes. Results indicated that the MPs-induced toxicity significantly reduced in the depuration phase, evidenced by the recovery of energy reserves and metabolism, hepatotoxicity, immunotoxicity, hematological parameters, neurotoxicity and oxidative stress. However, the continuous detoxification and remarkable genotoxicity implied that the toxicity was not completely alleviated. In addition, the current knowledge gaps are also highlighted, with recommendations proposed for future research.

Desorption of polycyclic aromatic hydrocarbons from polyethylene microplastics in two morphologically different digestive tracts of marine teleosts: Gastric red seabream (Pagrus major) and agastric mummichog (Fundulus heteroclitus)

In this study, we elucidated the desorption potency of polycyclic aromatic hydrocarbons (PAHs) sorbed on microplastics (MP; polyethylene) in the digestive tract of two fish species: gastric red seabream and agastric mummichog. In our in vitro assay system using the real gut sample of unexposed fish, the digestive tract was firstly removed from the fish and divided into three parts. Then, MP that had previously been sorbed with 16 PAHs were incubated with extracts of the gut contents or tissue with buffer or only a buffer. The desorption potency of PAHs was individually assessed for gut contents and tissue, which revealed that PAH desorption from MP was elevated in extracts of the gut contents compared with that in the buffer alone for both fish species. PAH desorption potency was the highest in the midgut for gastric red seabream and in the foregut for agastric mummichog, which indicates that PAH desorption from MP varies among different parts of the digestive tract and among fish with distinct gut morphology. In the midgut contents of red seabream and foregut contents of mummichog, the desorption fraction was 5.6% and 8.1% of the total PAHs sorbed on MP, respectively. The desorption fraction enhancement achieved by adding gut contents extracts tended to be greater with an increase in the n-octanol/water partition ratio, suggesting that enhancement of the desorption fraction in the digestive tract depends on the physicochemical properties of PAHs. Thus, morphological differences in digestive tracts and PAH properties should be considered when evaluating the effect of MP vector on pollutant exposure in fish.

Review on alternatives for the reduction of textile microfibers emission to water

The microplastics (MPs) are considered one of the most threatening pollutants. One of the main concerns is their continuous and cumulative flow to water environments, as they are very difficult to be removed. Microfibers (MFs) are a significant type of MPs, with textile articles as one of the most renowned sources. This review aims to provide the current status of these MFs as pollutants, discussing possible alternatives from the manufacturing until the final disposition of MFs. There are many alternatives to reduce these pollutants from reaching the environment but also gaps that need to be further evaluated and addressed. Besides, it should be noticed that alternatives could be complementary between them. Some viable and non-contaminating solutions to reduce this pollution are currently on the market. Also, one relevant aspect is the final disposition or usage of the retained MFs to avoid them from reaching aquatic environments.

Color preferences and gastrointestinal-tract retention times of microplastics by freshwater and marine fishes

We examined ingestion and retention rates of microplastics (MPs) by two freshwater (Japanese medaka and zebrafish) and two marine fish species (Indian medaka and clown anemonefish) to determine their color preferences and gastrointestinal-tract retention times. In our ingestion experiments, clown anemonefish ingested the most MP particles, followed by zebrafish, and then Japanese and Indian medaka. Next, we investigated color preferences among five MP colors. Red, yellow, and green MP were ingested at higher rates than gray and blue MPs for all tested fish species. To test whether these differences truly reflect a recognition of and preference for certain colors based on color vision, we investigated the preferences of clown anemonefish for MP colors under light and dark conditions. Under dark conditions, ingestion of MP particles was reduced, and color preferences were not observed. Finally, we assessed gastrointestinal-tract retention times for all four fish species. Some individuals retained MP particles in their gastrointestinal tracts for over 24 h after ingestion. Our results show that fish rely on color vision to recognize and express preferences for certain MP colors. In addition, MP excretion times varied widely among individuals. Our results provide new insights into accidental MP ingestion by fishes.

Microplastic uptake and gut retention time in Japanese anchovy (Engraulis japonicus) under laboratory conditions

To explore the impact of microplastic (MP) pollution on planktivorous fish, we examined the uptake and retention of MPs by Japanese anchovy (Engraulis japonicus) under laboratory conditions. MP uptake was size selective in adult anchovy-0.3-mm MPs were taken up in significantly larger amounts than 0.85-mm MPs-but not in juveniles. There were no significant differences in the uptake of MPs of three different colors, suggesting that anchovy do not select for MP coloration. More than 90% of the MPs were excreted within 20 h of ingestion, indicating that MP retention time is similar to the processing time of food items. Our findings suggest that Japanese anchovy tend to take up MPs that are equivalent in size to prey items, but that the impacts of MP ingestion are likely to be limited under the current state of oceanic MP contamination.

Can the toxicity of polyethylene microplastics and engineered nanoclays on flatfish (Solea senegalensis) be influenced by the presence of each other?

Microplastics and nanomaterials are applied in a myriad of commercial and industrial applications. When leaked to natural environments, such small particles might threaten living organisms' health, particularly when considering their potential combination that remains poorly investigated. This study investigated the physiological and biochemical effects of polyethylene (PE; 64-125 μm in size, 0.1, 1.0, and 10.0 mg·L^-1) single and combined with an engineered nanomaterial applied in antifouling coatings, the copper-aluminium layered double hydroxides (Cu-Al LDH; 0.33, 1.0, and 3.33 mg·L^-1) in the flatfish Solea senegalensis larvae (8 dph) after 3 h exposure, in a full factorial design. Particles ingestion, histopathology, and biochemical biomarkers were assessed. Fish larvae presented <1 PE particles in their gut, independently of their concentration in the medium. The histological health index showed minimal pathological alterations at PE combined exposure, with a higher value observed at 1 mg LDH·L^-1 × 0.1 mg PE·L^-1. Gut deformity and increased antioxidant defences (catalase), neurotransmission (acetylcholinesterase), and aerobic energy production (electron transport system) were observed at PE ≥ 1.0 mg·L^-1. No oxidative damage (lipid peroxidation) or alterations in the detoxification capacity (glutathione-S-transferase) was observed on single and combined exposures. PE, combined or not with Cu-Al LDH, does not seem to compromise larvae's homeostasis considering levels reported so far in the marine and aquaculture environments. However, harsh effects are expected with MP contamination rise, as projections suggest.

Minimal meso-plastics detected in Australian coastal reef fish

Recording plastic ingestion across various species and spatial scales is key to elucidating the impact of plastic pollution on coastal and marine ecosystems. The effect of plastic ingestion on the diets, physiologies, and behaviors of selected fish species are well documented under laboratory settings. However, prevalence of plastic ingestion in wild fish across latitudinal gradients is yet to be widely documented; with a substantial lack of research in the Southern Hemisphere. We analyzed the gut content of reef fish across ~30^o latitude of the east coast of Australia. Of 876 fish examined from 140 species (83 genera and 37 families), 12 individuals had visible (meso-plastics detectable to the naked eye) plastics present in the gut. Here, we present a first-look at plastic ingestion for coastal species with this region.

Seasonal distributions of microplastics and estimation of the microplastic load ingested by wild caught fish in the East China Sea

Microplastic (MP) pollution in marine environments and organisms has received substantial international attention. However, long-term field studies of MPs are scarce. Here, we assessed the seasonal variation in MP abundance in the Zhoushan fishing ground (ZFG), one of the most abundant and productive fishing grounds worldwide, and analyzed the long-term MP accumulation in fish gastrointestinal tracts from September 2017 to June 2018. The most common MP particles in the ZFG were polyethylene terephthalate and polypropylene. After four seasons of continuous monitoring, we did not find accumulation of MPs in the fish after 10% KOH digestion. In total, 254 MP particles were removed from the gastrointestinal tracts of all fish. The average number of particles per fish was lower than that reported in previous global marine studies. There were significant differences among species. Moreover, this study provides the calculation of the weight of MPs ingested by fish and an estimate of the load of accumulated MPs in fish. According to the estimation, the load of MPs ingested by fish annually was approximately 3 kg in ZFG. These findings provide the long-term evidence of MP contamination in biota from the ZFG. The amounts of MPs ingested by fish require more detailed and improved investigation and estimation in further studies.

The problem of marine litters for cultured teleost

Here, characteristics of marine litter ingested by Pacific bluefin tuna (PBF, Thunnus orientalis) juveniles under captive conditions were investigated. Swimming speeds of PBF juveniles with pseud-ingested polystyrene chips were compared, and mortality due to polystyrene chip ingestion in cultured teleosts (red sea bream, greater amberjack, and white trevally) was examined in the laboratory. Marine litter ingested by the PBF juveniles included mainly microplastics. The body size of dead specimens with ingested marine litter was significantly smaller than that of other dead fish. We suggest that when the PBF juveniles ingested the marine litter, they died due to energy exhaustion within a few days. All the examined species ingested polystyrene chips, but no related mortality was confirmed. These results suggest that only the PBF could not vomit or excrete the ingested marine litter. This study indicates that the marine litter problem significantly affects the aquaculture industry, especially tuna aquaculture.

Influence of the co-exposure of microplastics and tetrabromobisphenol A on human gut: Simulation in vitro with human cell Caco-2 and gut microbiota

Microplastics (MPs) pollution becomes an emergent threat to the ecosystem, and its joint effect with organic contaminants will cause more severe consequences. Recently, MPs has been observed in human feces, suggesting that we are exposed to an uncertain danger. In this study, the joint effect of polyethylene microplastics particles (PEMPs) and Tetrabromobisphenol A (TBBPA) on human gut was explored through the simulation experiment in vitro with human cell Caco-2 and gut microbiota. The toxicity of TBBPA and PEMPs on Caco-2 human cells was considered by physiological and biochemical indexes such as cell proliferation, cell cycle, reactive oxygen species, lactate dehydrogenase release, and mitochondrial membrane potential. Besides, microbial community diversity, community structure, and function changes of gut microbiota were investigated using Illumina 16S rRNA gene MiSeq sequencing to reveal the influence of TBBPA and PEMPs on human gut microbiota. The results indicated that both PEMPs and TBBPA would deteriorate the status of Caco-2 cells, and TBBPA played a major role in it; meanwhile, PEMPs affected Caco-2 cells at high concentrations. Particularly, TBBPA and PEMPs exhibited a joint effect on Caco-2 cells to a certain degree. TBBPA selectivity inhibited the growth of gram-positive bacteria such as Enterococcus and Lactobacillus, contributing to the thriving of gram-negative bacteria such as Escherichia and Bacteroides. The existence of PEMPs would enhance the proportion of Clostridium, Bacteroides, and Escherichia. Community composition changed dramatically with the interference of PEMPs and TBBPA; this was undesirable to the healthy homeostasis of the human gut. PICRUSt analysis determined both PEMPs and TBBPA interfered with the metabolism pathways of gut microbiota. Hence, the threat of MPs and TBBPA to humans should arouse vigilance.

Micro and Nano Plastics Distribution in Fish as Model Organisms: Histopathology, Blood Response and Bioaccumulation in Different Organs

Micro- and nano-plastic (MP/NP) pollution represents a threat not only to marine organisms and ecosystems, but also a danger for humans. The effects of these small particles resulting from the fragmentation of waste of various types have been well documented in mammals, although the consequences of acute and chronic exposure are not fully known yet. In this review, we summarize the recent results related to effects of MPs/NPs in different species of fish, both saltwater and freshwater, including zebrafish, used as model organisms for the evaluation of human health risk posed by MNPs. The expectation is that discoveries made in the model will provide insight regarding the risks of plastic particle toxicity to human health, with a focus on the effect of long-term exposure at different levels of biological complexity in various tissues and organs, including the brain. The current scientific evidence shows that plastic particle toxicity depends not only on factors such as particle size, concentration, exposure time, shape, and polymer type, but also on co-factors, which make the issue extremely complex. We describe and discuss the possible entry pathways of these particles into the fish body, as well as their uptake mechanisms and bioaccumulation in different organs and the role of blood response (hematochemical and hematological parameters) as biomarkers of micro- and nano-plastic water pollution.