A Pretreatment Method for GC–MS Determination of Endocrine Disrupting Chemicals in Mollusk Tissues

The impact of microplastics on bivalve mollusks: A bibliometric and scientific review

Bivalves are important members of the ecosystem and their populations are declining globally, making them a concern for their role in ecosystem services and the fishing industry. Bivalves are excellent bioindicators of MPs pollution due to their widespread distribution, filtering capabilities, and close association with human health. Microplastics (MPs) have direct and indirect impacts on bivalves, affecting their physiology, habitat structure, food sources, and persistence of organic pollutants. This review provides an extensive overview of the impact of MPs on bivalves, covering various aspects such as their economic significance, ecological roles, and importance in biomonitoring environmental quality. The article presents the current state of knowledge on the sources and pathways of MPs in aquatic environments and their effects on bivalves. The mechanisms underlying the effects of MPs on bivalves, including ingestion, filtration activity, feeding inhibition, accumulation, bioaccumulation, and reproduction, are also discussed. Additionally, a bibliometric analysis of research on MPs in bivalves is presented, highlighting the number of papers, geographical distribution, and keyword clusters relating to MPs. Finally, the review emphasizes the importance of ongoing research and the development of mitigation strategies to reduce the negative effects of MPs pollution on bivalves and their habitats in oceans and coastal waters.

The Relationship between Typical Environmental Endocrine Disruptors and Kidney Disease

Endocrine disrupting chemicals (EDCs) are exogenous substances that alter the endocrine function of an organism, to result in adverse effects on growth and development, metabolism, and reproductive function. The kidney is one of the most important organs in the urinary system and an accumulation point. Studies have shown that EDCs can cause proteinuria, affect glomeruli and renal tubules, and even lead to diabetes and renal fibrosis in animal and human studies. In this review, we discuss renal accumulation of select EDCs such as dioxins, per- and polyfluoroalkyl substances (PFAS), bisphenol A (BPA), and phthalates, and delineate how exposures to such EDCs cause renal lesions and diseases, including cancer. The regulation of typical EDCs with specific target genes and the activation of related pathways are summarized.

Determining the Properties that Govern Selective Ingestion and Egestion of Microplastics by the Blue Mussel (Mytilus edulis) and Eastern Oyster (Crassostrea virginica)

Suspension feeding bivalve molluscs interact with different types of microplastics (MP) suspended in the water column. Most bivalves are selective suspension feeders and, thus, do not consume all particles to which they are exposed. Selection depends upon the physicochemical properties and size of the particle. Recent work has provided evidence that blue mussels, Mytilus edulis, and eastern oysters, Crassostrea virginica, ingest and egest microspheres (polystyrene) and microfibers (nylon) differently, but whether other factors, such as polymer type and shape, mediate selection have not been explored. To investigate these factors, mussels and oysters were offered similar sized nylon (Ny) and polyester (PES) microfibers or polyethylene (PE) and polystyrene (PS) microspheres, or different sized PES microfibers during a 2 h exposure. Feces and pseudofeces were collected separately and analyzed for MPs, and the data were used to develop a linear regression model for selection. Results demonstrated clear species-specific differences in the efficiency of particle selection. Both mussels and oysters, however, exhibited size-based rejection of PES microfibers, ingesting a higher proportion of shorter fibers than longer fibers. Polymer type did not impact selection of fibers or spheres. The relative size of particles (area and perimeter) was found to be the most important factor in predicting whether a MP will be rejected or ingested.

An overview of the internalization and effects of microplastics and nanoplastics as pollutants of emerging concern in bivalves

Microplastic and nanoplastic pollution in aquatic environments is a topic of emerging concern due to the internalization, retention time and effects of these particles in aquatic biota. Bivalves are considered bioindicators due to their wide distribution, sessile behaviour, occupation of ecological niches and ability to filter a large water volume. The study of microplastics and nanoplastics in bivalves has revealed the uptake mechanisms, internalization, distribution and depuration of these particles as well as their effects on physiological parameters, morphological alterations, immunotoxicity and changes in gene expression and proteomic profiles. In this review, we examine the primary characteristics of microplastics and nanoplastics (type of material, size, coating, density, additives and shapes) involved in their possible toxicity in bivalves. Furthermore, secondary characteristics such as the suspension media, aggregation stage and adsorption of persistent pollutants were also recorded to assess the impact of these materials on bivalves. Here, we have highlighted the efforts exerted thus far and the remaining gaps in understanding the extent of microplastic and nanoplastic impacts on bivalves on the basis of laboratory experiments and mesocosm bioassays and in the field. Furthermore, further microplastic and nanoplastic toxicological studies are proposed to facilitate the realistic assessment of environmental risk.

Uptake of endocrine-disrupting chemicals by quagga mussels (Dreissena bugensis) in an urban-impacted aquatic ecosystem

Untreated organic contaminants in municipal wastewater, such as endocrine-disrupting chemicals (EDCs), have become a significant issue in aquatic ecosystems, particularly in freshwater bodies that receive wastewater discharge. This has raised concerns about the accumulation of EDCs in aquatic species via continuous exposure. This study evaluated the uptake of EDCs by quagga mussels (Dreissena bugensis), an invasive species in a water supply reservoir. The field sampling results showed that steroid hormones were not detected in the water samples, and only pharmaceuticals and personal care products were present (0.49 to 36 ng/L). Additionally, testosterone was the most abundant steroid in the mussel tissue (6.3 to 20 ng/g dry weight), and other synthetic chemicals (i.e., bisphenol A, triclosan, and salicylic acid) were also detected in the mussel tissue (24 to 47 ng/g dry weight). After being exposed to exogenous EDCs for 7, 21, and 42 days under controlled laboratory conditions, testosterone was not detected in the mussel anymore, but bisphenol A, triclosan, and salicylic acid were found at relatively high levels in the mussel tissue, although the concentrations did not increase over time. Overall, the study demonstrated the uptake of EDCs in quagga mussels, which suggests that this species can be used to reflect water quality deterioration in aquatic ecosystems.

Analysis and Occurrence of Bisphenol A in Mediterranean Mussels (Mytilus galloprovincialis) Sampled from the Slovenian Coastal Waters of the North Adriatic Sea

During 2015, a selection of Mediterranean mussels (Mytilus galloprovincialis) and seawater were sampled along the Slovenian coast, which is part of the North Adriatic Sea, in order to test for the presence of bisphenol A (BPA). The concentration of the BPA in the tissues of mussels sampled from the farms and open sea was from < 0.03 to 0.55 µg kg^-1 of w.w. and from < 0.03 to 0.46 µg kg^-1 of w.w., respectively. The mussel shells from the farms and open sea contained from 0.01 to 0.3 µg BPA kg^-1 of w.w. and from 0.04 to 0.27 µg BPA kg^-1 of w.w., respectively. In a harbour, mussel tissue and shell concentration of BPA was 0.21 and 0.18 µg BPA kg^-1 of w.w., respectively. The seawater in the shellfish farms and the open sea was contaminated with an average of 0.007 µg l^-1 of BPA.

Rapid uptake, biotransformation, esterification and lack of depuration of testosterone and its metabolites by the common mussel, Mytilus spp

The presence of the vertebrate steroids, testosterone (T) and 17β-estradiol in mollusks is often cited as evidence that they are involved in the control of their reproduction. In this paper, we show that a likely source of T in at least one species, the common mussel (Mytilus spp.), is from uptake from water. When mussels were exposed to waterborne tritiated T ([³H]-T) in a closed container, the radioactivity decreased rapidly and exponentially until, by 24h, approximately 35% remained in the water. The rate of uptake of radiolabel could not be saturated by concentrations as high as 16.5μgL^-1 (mean measured) of non-radiolabeled T, showing that the animals have a very high capacity for uptake of T. At least 30% of the applied radioactivity could be extracted from the tissues of the animals with organic solvents and most of this (26% of the total applied radioactivity) was in the fatty acid ester fraction. Following alkaline hydrolysis, reverse phase HPLC and TLC, this fraction was shown to consist predominantly of 5α-dihydrotestosterone and 5α-androstane-3β,17β-diol, while T was a minor component. These steroids were definitively identified in the fatty acid ester fraction by mass spectrometry. Overall, less than 5% of the [³H]-T applied to the system remained untransformed at the end of exposure. After ten days of depuration there was no reduction in the total amount of radioactivity in the tissues, nor any changes in the ratio of the metabolites in the ester fraction. These findings show that any association between T presence and reproductive status or sex is confounded by their significant capacity for uptake, and that T undergoes extensive metabolism in mussels in vivo and therefore may not be representative of the androgenic burden of the animals. Consequently, measurements of T in mussel tissue offer little utility as an indicator of reproductive status or sex.

Efficient removal of 17α-ethinylestradiol (EE2) from water using freshly formed Fe–Mn binary oxide

The removal mechanism of EE2: adsorption onto FMBO through hydrogen bonding and then oxidation by MnO₂.

Mussels (Mytilus spp.) display an ability for rapid and high capacity uptake of the vertebrate steroid, estradiol-17β from water

Six experiments were carried out to define the optimum conditions for investigating the dynamics of uptake and metabolism of tritiated E₂ from water by adult blue mussels, Mytilus spp. Optimum uptake was achieved using 400mL aerated sea water animal^-1 and an incubation period of no more than 24h. The pattern of disappearance conformed closest to an inverse hyperbolic curve with the percentage of radiolabel that could be measured in the water reaching an asymptote that was on average 50% of the original. This apparent inability of the animals to absorb all the radiolabel was investigated further. Solvent partition and chromatography revealed that, after 24h, c. 60% of the radiolabel still present in the water was composed of water soluble conjugates, c. 25% was composed of tritiated water and only 15% ran on and around the chromatographic position of E₂. The major water soluble constituent was identified by chromatography and mass-spectrometry as 1,3,5(10)-estratriene-3,17β-diol 3-sulfate (estradiol 3-S). The clearance rate of radiolabel was 46.9±1.8mLanimal^-1h^-1. This was not significantly affected by the addition of as much as 25μgL^-1 cold E₂ to the water, demonstrating that mussels have a large capacity for E₂ uptake. A new procedure involving solvent partition was developed for separating the free, esterified and sulfated forms of E₂ present in the flesh of mussels. This involved extracting the soft tissue with organic solvents and then treating a portion of dried extract with a combination of heptane (dissolved fatty acid esters of E₂) and 80% ethanol (dissolved free and sulfated E₂). The latter fraction was further partitioned between water (sulfate) and diethyl ether (free steroid). This procedure was much cheaper and less time-consuming than chromatography. Approximately 80% of the radioactivity that was taken up by the animals was present in the form of ester. Moreover, E₂ was the only steroid identified after saponification of these esters. Of the remaining radioactivity, c. 10% was in the form of unidentified free steroids and c. 10% was estradiol 3-S. In order to determine how rapidly mussels were able to depurate tritiated E₂ and its metabolites, two experiments were carried out. Animals from the first experiment purged up to 63% of radioactivity in 20days under flow-through conditions; whereas animals from the second experiment released only 16% of radioactivity in 10days under semi-static conditions. The ratios of the different forms of E₂ did not change substantially during the course of depuration.

β-Estradiol and ethinyl-estradiol contamination in the rivers of the Carpathian Basin

17β-Estradiol (E2) and 17α-ethinyl estradiol (EE2), which are environmental estrogens, have been determined with LC-MS in freshwater. Their sensitive analysis needs derivatization and therefore is very hard to achieve in multiresidue screening. We analyzed samples from all the large and some small rivers (River Danube, Drava, Mur, Sava, Tisza, and Zala) of the Carpathian Basin and from Lake Balaton. Freshwater was extracted on solid phase and derivatized using dansyl chloride. Separation was performed on a Kinetex XB-C18 column. Detection was achieved with a benchtop orbitrap mass spectrometer using targeted MS analysis for quantification. Limits of quantification were 0.05 ng/L (MS1) and 0.1 ng/L (MS/MS) for E2, and 0.001 ng/L (MS1) and 0.2 ng/L (MS/MS) for EE2. River samples contained n.d.-5.2 ng/L E2 and n.d.-0.68 ng/L EE2. Average levels of E2 and EE2 were 0.61 and 0.084 ng/L, respectively, in rivers, water courses, and Lake Balaton together, but not counting city canal water. EE2 was less abundant, but it was still present in almost all of the samples. In beach water samples from Lake Balaton, we measured 0.076-0.233 E2 and n.d.-0.133 EE2. A relative high amount of EE2 was found in river Zala (0.68 ng/L) and in Hévíz-Páhoki canal (0.52 ng/L), which are both in the catchment area of Lake Balaton (Hungary).

Environmental fate and ecological risks of nonylphenols and bisphenol A in the Cape D'Aguilar Marine Reserve, Hong Kong

Nonylphenols (NPs) and bisphenol A (BPA) are the most common endocrine disruptors detected in the coastal waters of Hong Kong. The Cape D'Aguilar Marine Reserve (CAMR), the only marine reserve in Hong Kong is close to urbanized areas, thus the resident marine organisms are inevitably influenced by partially treated wastewater from adjacent sewage treatment plants (STPs). Elevated levels of NPs and BPA were detected in all seawater, sediment and biota samples collected from the CAMR. Estrogenic activities of seawater from the CAMR, and sludge and sewage from a nearby STP were assessed using yeast estrogen screen assay. We found aromatase, estrogen receptor and vitellogenin genes in the marine medaka fish Oryzias melastigma were significantly up-regulated after exposure to the reserve's seawater. According to a tissue-residue-based probabilistic risk assessment, the marine species living in the CAMR are having 35% and 21% of chance to be at risk due to exposure to NPs and BPA, respectively.

Do mollusks use vertebrate sex steroids as reproductive hormones? Part I: Critical appraisal of the evidence for the presence, biosynthesis and uptake of steroids

The consensus view is that vertebrate-type steroids are present in mollusks and perform hormonal roles which are similar to those that they play in vertebrates. Although vertebrate steroids can be measured in molluscan tissues, a key question is 'Are they formed endogenously or they are picked up from their environment?'. The present review concludes that there is no convincing evidence for biosynthesis of vertebrate steroids by mollusks. Furthermore, the 'mollusk' genome does not contain the genes for key enzymes that are necessary to transform cholesterol in progressive steps into vertebrate-type steroids; nor does the mollusk genome contain genes for functioning classical nuclear steroid receptors. On the other hand, there is very strong evidence that mollusks are able to absorb vertebrate steroids from the environment; and are able to store some of them (by conjugating them to fatty acids) for weeks to months. It is notable that the three steroids that have been proposed as functional hormones in mollusks (i.e. progesterone, testosterone and 17β-estradiol) are the same as those of humans. Since humans (and indeed all vertebrates) continuously excrete steroids not just via urine and feces, but via their body surface (and, in fish, via the gills), it is impossible to rule out contamination as the sole reason for the presence of vertebrate steroids in mollusks (even in animals kept under supposedly 'clean laboratory conditions'). Essentially, the presence of vertebrate steroids in mollusks cannot be taken as reliable evidence of either endogenous biosynthesis or of an endocrine role.

Distribution and bioaccumulation of steroidal and phenolic endocrine disrupting chemicals in wild fish species from Dianchi Lake, China

The distribution and bioaccumulation of steroidal and phenolic endocrine disrupting chemicals (EDCs) were studied in various tissues of wild fish species from Dianchi Lake, China. In muscle tissue, 4-tert-octylphenol, 4-cumylphenol, 4-nonlyphenol and bisphenol A were detected in fish from each sampling site, with maximal concentrations of 4.6, 4.4, 18.9 and 83.5 ng/g dry weight (dw), respectively. Steroids (estrone, 17β-estradiol 17α-ethynylestradiol and estriol) were found at lower levels (<11.3 ng/g dw) and less frequently in muscle samples. The highest concentrations of steroids and phenols were found in liver, followed by those in gill and the lowest concentration was found in muscle. The field bioconcentration factors (BCFs) of phenols were calculated in fish species ranged from 18 to 97. Moreover, the measured tissue concentrations were utilized in order to estimate water concentration of steroids (4.4-18.0 ng/L). These results showed that steroidal and phenolic EDCs were likely ubiquitous contaminants in wild fish.