Elucidating the consequences of the co-exposure of microplastics jointly to other pollutants in bivalves: A review

Exposure to metoprolol and propranolol mixtures on biochemical, immunohistochemical, and molecular alterations in the American oyster, Crassostrea virginica

Pharmaceutical drugs, particularly beta-blockers (e.g., metoprolol, propranolol, etc.), are extensively used to treat human cardiovascular conditions, yet pose significant risks to non-target aquatic organisms when introduced into coastal and marine environments via wastewater effluent. This study aimed to investigate the effects of short-term exposure (one week) to environmentally relevant concentrations of metoprolol and propranolol (MP) mixtures (low-dose: 50 ng/L propranolol and 250 ng/L metoprolol, and high-dose: 250 ng/L propranolol and 650 ng/L metoprolol) in the American oyster (Crassostrea virginica, a commercially and ecologically important marine bivalve mollusk) under controlled laboratory conditions. Histopathological assessments revealed structural damage to gills, connective tissues, and digestive glands in both low- and high-dose MP treatment groups. Additionally, glucose concentration and pH of the extrapallial fluid significantly declined in the high-dose MP treatment groups. Hemocyte density in the connective tissues increased proportionally with MP dosages. MP mixtures significantly reduced mucous secretion in the gills and digestive glands. Immunohistochemical results showed significant (P < 0.05) upregulation of 3-nitrotyrosine protein (NTP, a biomarker of protein nitration) expression in tissues of oysters exposed to MP mixtures. Alongside, exposure to MP significantly (P < 0.05) decreased acetylcholinesterase (AChE, a cholinergic enzyme) expression in oyster tissues. Our findings suggest that beta-blockers induce protein nitration, leading to altered tissue morphology, disrupting extrapallial fluid homeostasis, and downregulating AChE expression that may impair physiological functions in oysters.

Effects of trace metals and microplastics on the gene expression of antioxidant and detoxification genes in Mytilus galloprovincialis from estuaries

In the present study, the effects of emerging and legacy pollutants such as hazardous microplastics (hMP) and toxic elements (As, Cd, Hg and Pb) were investigated in wild Mediterranean mussel Mytilus galloprovincialis (n = 40) from three estuaries with different anthropogenic uses in the Asturias region (SW Bay of Biscay). The expression levels of six candidate genes related with oxidative stress and/or heavy metal detoxification (sod1, sod2, cat, hsp70, mt10 & mt20) were measured using qPCR. The relationship between their expression levels, the Condition Index (CI), and the concentration of these concurrent pollutants was assessed through linear mixed models (LMM). PERMANOVA revealed significant differences between polluted and clean locations for both pollutants and gene expression levels in mussels. However, no differences were found between Nalón and Sella estuaries despite their distinct historical uses and pollution levels, suggesting recovery in post-mining times. Overall, the expression of the antioxidant gene sod2 and the detoxification genes mt10 and mt20 were upregulated in mussels from the most industrialized and heavy metal polluted estuary of Avilés, with Cd and Pb significantly predicting mt10 and mt20 increase. Hg and the hMP content significantly explained the expression patterns of sod1 and sod2 genes. To the best of our knowledge, this is the first study examining the combined molecular effects of legacy and emerging pollutants on wild populations of the bioindicator Mediterranean mussel. Additionally, it represents the first application of this molecular approach to monitor the ecological status of estuaries in the region that could be applied elsewhere.

Microplastics in the European native oyster, Ostrea edulis, to monitoring pollution-related patterns in the Solent region (United Kingdom)

Microplastics (MPs) are the most abundant type of debris in the marine environment, creating a significant threat to aquatic ecosystems due to their persistence, ability to absorb organic pollutants and potential ingestion by marine fauna. Shellfish are particularly vulnerable to MPs accumulation as they filter large volumes of seawater, and they become an important route for human exposure to these particles. This study, the first to examine MPs in European flat oyster (Ostrea edulis) populations, aimed to quantify these particles in the gill and digestive tissues of oysters from the Solent region (southern England). Enzymatic digestion using Proteinase-K was used in this study and MPs were identified in every oyster sampled to determine whether differences in abundance, type and size of MPs exist between locations. Oysters near urban areas contained significantly more MPs than those near rural areas. Fibres were the most prevalent type of MPs, with sizes varying across locations. The study found no significant differences in MPs presence between gills and digestive tissues, and an inverse correlation between the size of MPs and oyster size. The presence of MPs in wild O. edulis could be an additional threat to the survival of an already threatened species and may pose health risks for predatory species and human consumers of seafood. The use of O. edulis as a biomonitoring species for marine MPs pollution could help determine the extent, distribution and sources of MPs, potentially informing management strategies to reduce pollution.

Environmental impact of microplastic emissions from wastewater treatment plant through life cycle assessment

This study aimed to quantify the environmental impact of microplastic (MP) emissions from wastewater treatment plants (WWTPs) using life cycle assessment (LCA). The investigation comprehensively evaluated the contribution of MPs to overall WWTP midpoint and endpoint impacts, with a detailed analysis of the influence of particle size, shape, polymer type, and the environmental costs and benefits of individual wastewater treatment processes on MP removal. The LCA model was developed using SimaPro software, with impact assessments conducted via the USEtox framework and the IMPACT World+ methodology. Results showed that at the midpoint level, MPs accounted for 1.24E+05 CTUe (94 % of the total plant impact), representing the potential harm to aquatic species per cubic meter of discharged wastewater-surpassing the impacts of other contaminants (e.g., heavy metals, nutrients) by at least two orders of magnitude. At the endpoint level, the damage of 8.39E-02 PDF·m2·yr (1.7 % of the total) indicated the potential loss of species diversity, comparable to other pollutant contributions. Polyethylene, polystyrene, and polypropylene were identified as the most impactful polymer types. In terms of environmental costs and benefits, secondary, tertiary, and primary treatments demonstrated decreasing environmental benefits, directly correlated with their respective MP removal efficiencies. These findings underscore the critical role of MP emissions in WWTP life cycle inventories and highlight the urgent need for targeted environmental policies and advanced treatment technologies to address MP contamination in both natural and engineered aquatic systems.

Microplastics in Morocco's most consumed fisheries: Chemical characterization, ecological traits, and implications for human health

The pervasive presence of microplastics (MPs) in the environment is well established, yet many critical questions remain about their distribution and potential impacts on both ecological and human health. To assess the risks that MPs pose, especially through marine ecosystems and human consumption, monitoring their ingestion by fish in natural environments is essential. This study investigated the contamination of 12 fish species, the most commonly consumed in Morocco, collected from the Atlantic Ocean off the Moroccan coast. Analysis of 240 fish (20 individuals per species) revealed that 100 % of the samples contained microplastics. MPs were detected in the gills, gonads, and gastrointestinal tracts of all 12 species. The average abundance of microplastics per fish ranged from 20.6 to 133.2 MPs, with the forms identified as fragments (60 %), fibers (30 %), films (8 %), and pellets and foams (1 %). Additionally, omnivorous and demersal species presented the highest levels of MP contamination. Infrared spectroscopy (ATR-FTIR) analysis identified seven polymers, with high-density polyethylene (34 %), polyethylene terephthalate (30 %), and polypropylene (17.5 %) being the most prevalent. The microplastics were predominantly dark or light in color, with a notable presence of red and blue particles. Fish ingest various sizes of microplastics, primarily particles smaller than 1 mm. Scanning electron microscopy coupled with energy dispersive X-ray analysis (SEM/EDX) revealed that most MPs exhibited visible signs of weathering and contained inorganic components on their surfaces. The potential risk of MPs to fish, as assessed by the polymer hazard index (PHI), was categorized as level V, indicating that MPs may pose significant risks to human health. The highest estimated daily intake (EDI) of microplastics was found in children (1620 MPs/year), whereas the lowest intake was estimated in women (350 MPs/year) and men (337 MPs/year). Given the widespread presence of microplastics in commonly consumed fish species in Morocco, there is an urgent need for regulatory measures to ensure the safety of fisheries, both for domestic consumption and export. Policymakers should consider the development of guidelines for acceptable levels of microplastic contamination in fish to safeguard public health.

The particle effect: comparative toxicity of chlorpyrifos in combination with microplastics and phytoplankton particles in mussel

Lately, the role of microplastics (MP) as vectors for dissolved contaminants and as vehicle for their transfer to aquatic organisms has received attention. Similarly to MP, other inorganic and organic particles may act as passive samplers. However, limited comparative knowledge exists at this respect. In the present study we have comparatively investigated the risk for mussel of MP and the pesticide chlorpyrifos (CPF) alone and in combination with MP and phytoplankton particles of microalgae (MP-CPF and MA-CPF, respectively). We selected MP and microalgae of similar size to expose mussel to the same volume of particles (≈1.5 mm3L-1 ≈ equivalent to 1.5 mg MP L-1) and the same concentration of contaminant (CPF, 7.6 μg L-1). MP were virgin HDPE microparticles (≤10 μm) while the microalgae species was Isochrisis galbana (4-8 μm). Mussels were exposed for 21 days to MP, CPF, MP-CPF and MA-CPF. Then, a suite of neurotoxicity, oxidative stress and oxidative damage biomarkers were measured in samples collected at day 7 and 21. Additionally, these biochemical markers were assessed in an integrated manner with others measured at physiological, immune and cell component level in the same organisms, previously published. Overall, MP did not elicit significant alterations on the majority of parameters measured. In contrast, mussels exposed to CPF, MA-CPF and MP-CPF showed evidence of neurotoxicity and oxidant imbalance at day 7, added to a detrimental physiological condition and immune imbalance at day 21. At the latter time MP-CPF mussels showed greater alterations than CPF or MA-CPF mussels. This suggested a synergistic toxicity of MP combined with CPF greater than that produced by the contaminants alone (MP or CPF) or by MA combined with CPF.

Ecotoxicological impact of naproxen on Eisenia fetida: Unraveling soil contamination risks and the modulating role of microplastics

Soils represent crucial sinks for pharmaceuticals and microplastics, making them hotspots for pharmaceuticals and plastic pollution. Despite extensive research on the toxicity of pharmaceuticals and microplastics individually, there is limited understanding of their combined effects on soil biota. This study focused on the earthworm Eisenia fetida as test organism to evaluate the biotoxicity and bioaccumulation of the typical pharmaceutical naproxen and microplastics in earthworms. Results demonstrated that high concentrations of naproxen (100 mg kg-1) significantly increased the malondialdehyde (MDA) content, inducing lipid peroxidation. Even though the low exposure of naproxen exhibits no significant influence to Eisenia fetida, the lipid peroxidation caused by higher concentration than environmental relevant concentrations necessitate attention due to temporal and spatial concentration variability found in the soil environment. Meanwhile, microplastics caused oxidative damage to antioxidant enzymes by reducing the superoxide dismutase (SOD) activity and MDA content in earthworms. Metabolome analysis revealed increased lipid metabolism in naproxen-treated group and reduced lipid metabolism in the microplastic-treated group. The co-exposure of naproxen and microplastics exhibited a similar changing trend to the microplastics-treated group, emphasizing the significant influence of microplastics. The detection of numerous including lipids like 17-Hydroxyandrostane-3-glucuronide, lubiprostone, morroniside, and phosphorylcholine, serves to identify potential biomarkers for naproxen and microplastics exposure. Additionally, microplastics increased the concentration of naproxen in earthworms at sub-organ and subcellular level. This study contributes valuable insights into the biotoxicity and distribution of naproxen and microplastics in earthworms, enhancing our understanding of their combined ecological risk to soil biota.

Screening of organic chemicals associated to virgin low-density polyethylene microplastic pellets exposed to the Mediterranean Sea environment by combining gas chromatography and liquid chromatography coupled to quadrupole-time-of-flight mass spectrometry

In this work, organic chemicals associated with microplastics (MPs) exposed to a coastal anthropogenized environment for up to eight weeks have been screened for, in order to discern the (de)sorption dynamics of chemicals in the marine ecosystem. Low-density polyethylene (LDPE) pellets were studied since they represent primary MPs used by the plastic industry and a relevant input of MPs into the oceans. To maximize the coverage of chemicals that could be detected, both liquid and gas chromatography coupled to quadrupole-time-of-flight (GC-QTOF and LC-QTOF, respectively) were used. In the case of LC-QTOF, an electrospray ionization source was employed, and the compounds were investigated by combining suspect and non-target screening workflows. The GC-QTOF was equipped with an electron ionization source and compounds were screened in raw and derivatized (silylated) extracts by deconvolution and contrast to high- and low-resolution libraries. A total of 50 compounds of multifarious classes were tentatively identified. Among them, melamine and 2-ethylhexyl salicylate (EHS) were detected in the original MPs but were rapidly desorbed. Melamine was completely released into the marine environment, while EHS was partly released but a portion remained bound to the MPs. On the other hand, many other chemicals of both anthropogenic (e.g. phenanthrene or benzophenone) and natural origin (e.g. betaine and several fatty acids) accumulated onto MPs over time. Quantification of 12 unequivocally identified chemicals resulted into a total concentration of 810 μg/kg after MPs exposure for 8 weeks.

The combined effects of phenanthrene and micro-/nanoplastics mixtures on the cellular stress responses of the thick-shell mussel Mytilus coruscus

Pollution with complex mixtures of contaminants including micro- and nano-plastics (MNPs) and organic pollutants like polycyclic aromatic hydrocarbons (PAH) poses a major threat to coastal marine ecosystems. Toxic mechanisms of contaminant mixtures are not well understood in marine organisms. We studied the effects of single and combined exposures to polycyclic aromatic hydrocarbon phenanthrene (Phe) and MNPs mixture with sizes of 70 nm, 5 μm and 100 μm on the immune health and oxidative stress parameters in the thick-shell mussel Mytilus coruscus. Immune cells (hemocytes) were more sensitive to the pollutant-induced oxidative stress than the gills. In hemocytes of co-exposed mussels, elevated mortality, lower lysosomal content, high production of reactive oxygen species (ROS) and decrease mitochondrial were found. Disparate responses of antioxidant enzymes in the hemolymph (e.g. increased superoxide dismutase (SOD) activity without a corresponding increase in catalase (CAT) in Phe exposures and an increase in CAT without a change in SOD in MNPs exposures) suggests misbalance of the antioxidant defense in the pollutant-exposed mussels. Gill lacked pronounced oxidative stress response showing a decline in ROS and antioxidant levels. Tissue-specific single and combined effects of Phe and MNPs suggest variation in bioavailability and/or different sensitivity to these pollutants in the studied tissues. Notably, the combined effects of MNPs and Phe were additive or antagonistic, showing that MNPs do not enhance and occasionally mitigate the toxic effects of Phe on the hemocytes and the gills of the mussels. Overall, our study sheds light on the impact of long-term exposure to MNPs and Phe mixtures on mussels, showing high sensitivity of the immune system and modulation of the Phe toxicity by MNPs co-exposure. These findings that may have implications for understanding the impacts of combined PAH and MNPs pollution on the health of mussel populations from polluted coastal habitats.

Exposure to polystyrene nanoplastics and PCB77 induced oxidative stress, histopathological damage and intestinal microbiota disruption in white hard clam Meretrix lyrata

The toxic effects of organic pollutants and nanoplastics on fish have been extensively studied, but there is limited research available on their combined toxicity to bivalves. This research aimed to investigate the accumulation and ecotoxicological impacts such as antioxidant capacity, histopathology and intestinal microbiota in white hard clam Meretrix lyrata, resulting from 7 days of single and mixture exposure to 3,3',4,4'-tetrachlorobiphenyl (PCB77, 0.1 mg/L) and polystyrene nanoplastics (PS-NPs, 80 nm, 1 mg/L). Our findings revealed that PS-NPs accumulated in various tissues such as the intestine, gill, mantle, foot, and siphon. And when compared to the PCB-PSNPs (PP) co-exposure group, the intestinal fluorescence intensity mediated by plastic particles in the PS-NPs (PS group) was significantly higher. The gill, digestive gland, and intestine were all damaged to varying extent by single exposure to PS-NPs or PCB77, according to histopathological analysis, which was aggravated by PP group. Moreover, the co-exposure induced a higher level of oxidative stress, which reflected by increase of activities of superoxide dismutase, catalase, glutamate oxaloacetate transaminase and glutamic-pyruvic transaminase and malondialdehyde content. In addition, the intestine microbial composition was dramatically altered by the combined exposure, reducing the abundance of probiotics such as Firmicutes, thereby posing a great threat to the health and metabolism of M. lyrata. In conclusion, our findings showed that PS-NPs and PCB77 co-exposure induced a higher toxicity to M. lyrata, including histopathological changes, altered antioxidant capacity and intestinal microbiota disruption. This study provides novel insights into PCB77 and PS-NPs' combined toxicity to marine organisms and its underlying molecular mechanisms of ecotoxicological effects.

Combined exposure to polyvinyl chloride and polystyrene microplastics induces liver injury and perturbs gut microbial and serum metabolic homeostasis in mice

A variety of microplastics (MPs) have become ubiquitous environmental pollutants, leading to inevitable human contact and health impacts. Most previous research has explored the toxic effects of a single type of MPs exposure. However, the effects of co-exposure to both common types of MPs, polyvinyl chloride (PVC) and polystyrene (PS) MPs on mammals have not been explored. Here, adult mice were exposed to PS-PVC (1.0 µm PS and 2.0 µm PVC both at the concentration of 0.5 mg/day) for 60 days. The results showed that PS-PVC co-exposure-induced hepatotoxicity was evidenced by liver histopathological changes, the release of inflammatory cytokines, and the activation of oxidative stress. Moreover, the intestinal mucosal barrier was damaged after PS-PVC treatment. The results of 16S rRNA gene sequencing reported there was a marked shift in the gut microbial structure accompanied by decreased relative abundances of probiotics, such as Clostridium, Lachnospiraceae_UCG-006, Desulfovibrio, Clostridiales_unclassified and Ruminococcaceae_unclassified and increased the conditional pathogen abundances, such as Erysipelatoclostridium. Furthermore, the triglyceride (TG) and total cholesterol (TCH) expression levels in the serum and liver were increased after PS-PVC co-exposure. Serum metabolomics analysis showed that there were 717 differential expression metabolites found in the positive- and negative-ion modes, including 476 up-regulated and 241 down-regulated, mainly enriched in butyrate metabolism, thiamine metabolism, and phenylacetate metabolism. In addition, remarked changes in the gut microbiota and serum metabolic profiles were closely related to hepatic and intestinal injuries after PS-PVC co-exposure. These results have provided new insights into the toxic effects of PS and PVC MPs co-exposure through the gut-liver axis and the health risks of PS and PVC MPs should be paid more attention to humans.

Binational survey using Mytilus galloprovincialis as a bioindicator of microplastic pollution: Insights into chemical analysis and potential risk on humans

Microplastic (MP) contamination in edible mussels has raised concerns due to their potential risk to human health. Aiming to provide valuable insights regarding the occurrence, physicochemical characteristics, and human health implications of MP contamination, in the present study, two nationwide surveys of MP contamination in mussels (Mytilus galloprovincialis) were conducted in Morocco and Tunisia. The results indicated that MP frequency ranged from 79 % to 100 % in all the analyzed samples. The highest MP density was detected in mussels from Morocco (gills "GI": 1.88 MPs/g ww^-1; digestive glands "DG": 0.92 MPs/g ww^-1) compared to mussels of Tunisia (GI: 1.47 MPs g^{- 1}; DG: 0.79 MPs g^{- 1}). No significant differences in MP density were found between the two organs (GI and DG) for both countries. MPs were predominantly blue and black fibers, and smaller than 1000 μm. Seven polymeric types were identified, of which PET, PP, and PE were the most abundant, accounting for >87 % of all samples. Scanning Electron Microscopy (SEM) coupled with Energy dispersive X-ray (EDX) showed that most MPs have noticeable signs of weathering and inorganic components on their surface. The highest MP daily intake was found in children, while the lowest was estimated in women and men. Moreover, the annual dietary exposure of MPs through mussel consumption was estimated to be 1262.17 MPs/year in Morocco and 78.18 MPs/year in Tunisia. The potential risk assessment of MPs in mussels based on the polymer hazard index (PHI) was estimated in the high-risk levels, implying that MPs may pose health risks to humans. Overall, this research suggests that the consumption of mussels represents a considerable MP exposure route for the Moroccan and Tunisian populations.