Histopathological Effects on Gills of Nile Tilapia (Oreochromis niloticus, Linnaeus, 1758) Exposed to Pb and Carbon Nanotubes

Carbon nanotubes and nanofibers seen as emerging threat to fish: Historical review and trends

Since the discovery of the third allotropic carbon form, carbon-based one-dimensional nanomaterials (1D-CNMs) became an attractive and new technology with different applications that range from electronics to biomedical and environmental technologies. Despite their broad application, data on environmental risks remain limited. Fish are widely used in ecotoxicological studies and biomonitoring programs. Thus, the aim of the current study was to summarize and critically analyze the literature focused on investigating the bioaccumulation and ecotoxicological impacts of 1D-CNMs (carbon nanotubes and nanofibers) on different fish species. In total, 93 articles were summarized and analyzed by taking into consideration the following aspects: bioaccumulation, trophic transfer, genotoxicity, mutagenicity, organ-specific toxicity, oxidative stress, neurotoxicity and behavioral changes. Results have evidenced that the analyzed studies were mainly carried out with multi-walled carbon nanotubes, which were followed by single-walled nanotubes and nanofibers. Zebrafish (Danio rerio) was the main fish species used as model system. CNMs' ecotoxicity in fish depends on their physicochemical features, functionalization, experimental design (e.g. exposure time, concentration, exposure type), as well as on fish species and developmental stage. CNMs' action mechanism and toxicity in fish are associated with oxidative stress, genotoxicity, hepatotoxicity and cardiotoxicity. Overall, fish are a suitable model system to assess the ecotoxicity of, and the environmental risk posed by, CNMs.

Multi-walled carbon nanotubes enhance the toxicity effects of dibutyl phthalate on early life stages of zebrafish (Danio rerio): Research in physiological, biochemical and molecular aspects

Phthalate esters (PAEs) are widely used as plasticizers. PAEs are ubiquitous in natural water bodies, with dibutyl phthalate (DBP) being one of the most common PAEs. DBP is prone to leaching or migration into the environment, posing serious health and environmental risks. Carbon nanotubes (CNTs) have been widely used in various fields with the rapid development of nanotechnology. CNTs could alter the environmental behavior and toxicity of co-existing pollutants. CNTs have been shown to rapidly adsorb PEAs. However, current knowledge about the effects of CNTs on DBP toxicity is limited. Here we show that the toxic effects of single and combined exposure to DBP (0.1, 0.5, 1.0 mg/L) and different CNTs (MWCNTs/MWCNTs-COOH, 0.5 mg/L) on the early growth stage of zebrafish. The results suggested that a significant increase in heart rate and heart malformation rate was observed after co-exposure of DBP and MWCNTs/MWCNTs-COOH (p < 0.05). Furthermore, combined exposure increased antioxidant enzyme activity during early developmental stages in zebrafish (p < 0.05). The qRT-PCR results revealed that DBP and MWCNTs/MWCNTs-COOH co-exposure significantly interfered with the expression of genes related to oxidative stress, energy metabolism, development of cardiac function, and apoptosis (p < 0.05). In addition, for oxidative stress and cardiotoxicity, MWCNTs/MWCNTs-COOH aggravated the toxic effects of 0.5 mg/L DBP on embryos/larvae. The metabolomics results showed that co-exposure mitigated the disturbance of amino acid metabolism mediated by single DBP exposure. In general, MWCNTs/MWCNTs-COOH increased the impact of DBP in the early developmental stages of zebrafish. This study provides new insights into the toxicology of early developmental stages of aquatic organisms exposed to co-exist pollutants of DBP and CNTs.

Ultrastructural characteristics of the accumulation of iron nanoparticles in the intestine of Cyprinus carpio (Linnaeus, 1758) under aquaculture

During the development of nanotechnology, the production of many substances containing nanoparticles leads to the release of various nanoparticles into the environment, including the water ecosystem. The main goal of the current research was to study the ultrastructural characteristics of the entry and bioaccumulation of Fe3O4 nanoparticles in the small intestine of Cyprinus carpio (Linnaeus, 1758), as well as the pathomorphological changes in the fish organism. Two different doses (10 and 100 mg) of Fe3O4 nanoparticles were fed to fingerlings for 7 days and then intestinal samples were taken and studied. It was found that the extent of damages was boosted within the increment of nanoparticle concentration. The sequence and bioaccumulation of Fe3O4 nanoparticles in the small intestine of fish occurred as below: firstly, the nanoparticles passed into microvilli located in the apical part of enterocytes in the mucosa layer, from there into the cytoplasm of the epithelial cells, including cytoplasmatic organelles (nucleus, mitochondria, lysosomes, fat granules), and then into a lamina propria of the mucosa of the small intestine and passed into the endothelium of the blood vessels and to the erythrocytes of the vessels which located in the lumen. It was determined that although the nanoparticles were up to 30 nm in size, only particles with a maximum size of 20 nm could penetrate the intestinal wall. Thus, the release of Fe3O4 nanoparticles into the environment in high doses has a negative effect on the living ecosystem, including the body of fish living in the water.

Comparative ecotoxicity of graphene, functionalized multi-walled CNTs, and their mixture in freshwater microalgae, Scenedesmus obliquus: analyzing the role of oxidative stress

Due to their remarkable properties, the applications of carbon-based nanomaterials (CNMs) such as graphene and functionalized multi-walled carbon nanotubes (f-MWCNTs) are increasing. These CNMs can enter the freshwater environment via numerous routes, potentially exposing various organisms. The current study assesses the effects of graphene, f-MWCNTs, and their binary mixture on the freshwater algal species Scenedesmus obliquus. The concentration for the individual materials was kept at 1 mg L^-1, while graphene and f-MWCNTs were taken at 0.5 mg L^-1 each for the combination. Both the CNMs caused a decrease in cell viability, esterase activity, and photosynthetic efficiency in the cells. The cytotoxic effects were accompanied by increased hydroxyl and superoxide radical generation, lipid peroxidation, antioxidant enzyme activity (catalase and superoxide dismutase), and mitochondrial membrane potential. Graphene was more toxic compared to f-MWCNTs. The binary mixture of the pollutants demonstrated a synergistic enhancement of the toxic potential. Oxidative stress generation played a critical role in toxicity responses, as noted by a strong correlation between the physiological parameters and the biomarkers of oxidative stress. The outcomes from this study emphasize the significance of considering the combined effects of various CNMs as part of a thorough evaluation of ecotoxicity in freshwater organisms.

Accumulation and human health risk assessment of trace elements in two fish species, Cirrhinus mrigala and Oreochromis niloticus, at Tarukri Drain, District Rahimyar Khan, Punjab, Pakistan

The toxic discharge of heavy metals into the water affects the aquatic ecosystem as well as the human population interacting with it because of their toxicity, bioaccumulation, long persistence, and transfer through the food chain. Thus, it is very important to conduct studies to determine the level of heavy metal pollution in order to better control, manage, and preserve the pollution of aquatic ecosystems. This study assessed heavy metal contamination in fish and its associated health risk to the population around the Tarukri Drain, Punjab, Pakistan. Two fish species (Oreochromis niloticus and Cirrhinus mrigala) were collected from three different sites in two different seasons. Collected fish were analyzed for cadmium (Cd), iron (Fe), lead (Pb), nickel (Ni), and zinc (Zn) accumulation using atomic absorption spectrometer (AAS). Furthermore, the human health risks associated with the consumption of affected fish were also assessed. Target hazardous quotient for seasonal consumers was between 0.12, - 1.58 × 10^-4, and 0.54 - 3.28 × 10^-4 (mg/kg) in O. niloticus and C. mrigala, respectively. While for regular consumers it was between 0.28-3.71 × 10^-4 and 1.27-7.68 × 10^-4 (mg/kg) in O. niloticus and C. mrigala respectively for the studied heavy metals. Fish sampled from Sadiqabad contained the highest concentration of heavy metals. The analysis of fish organs (kidney, liver, and muscles) showed heavy metal accumulation in the order of kidney > liver > muscles (p < 0.00). The obtained results showed that heavy metal contaminations in both fish species were within the permissible limits recommended by the World Health Organization (WHO). Both sampling seasons (i.e., summer and winter) showed a non-significant difference in heavy metal concentration. The calculated total target hazardous quotient across all heavy metals remained < 1 with only one exception. The carcinogenic risk assessment of heavy metals showed a non-significant effect in both fish species.

Sequential exposures of single walled carbon nanotubes and heavy metal ions to macrophages induce different cytotoxicity

The probability of occupational exposure rises with the increasing production and biomedical application of carbon nanotubes (CNTs). Thus, the risk of co-exposure of nanomaterials with environmental pollutants is also increasing. Although many studies have focused on the combined toxicity of nanomaterials and pollutants, more attention has been paid to the toxicity of nanomaterials after adsorbing pollutants or the toxicity of nanomaterials and pollutants exposed simultaneously. Few studies have been conducted on the toxicity and toxicity mechanisms of nanomaterials and environmental pollutants following sequential exposure. In this study, we employed THP-1 cells to investigate how pristine single walled CNTs (p-SWCNTs) and oxidized single walled CNTs (SWCNT-COOHs) pretreatments at a non-lethal dose of 10 μg/mL affect cell responses to metal ions (i. e., Pb²⁺, Cu²⁺, and Cr(VI)). We found that p-SWCNTs caused more significant damage to cell membrane integrity than SWCNT-COOHs, which led to higher metallothionein (MT) levels and increased transport of metal ions into cells. Pretreatment of p-SWCNTs in cells significantly increased the cytotoxicity of Pb²⁺, Cu²⁺, and Cr(VI) by 2-4-fold, whereas SWCNT-COOHs pretreated cells showed no noteworthy changes in response to heavy metals, which were further confirmed by the cellular reactive oxygen species (ROS) assays. These findings indicate that understanding the effects of the exposure sequence of engineered nanomaterials and environmental pollutants on their toxicity provides an excellent complement to combined toxicity evaluation.

Aquatic pollutants are associated with reproductive alterations and genotoxicity in estuarine fish (Sciades herzbergii - Bloch, 1794) from the Amazon Equatorial Coast

Estuaries are constantly subject to continuous environmental impacts of human activities, such as fisheries, port or industry, and domestic sewage, with fish being one of the most affected aquatic animals, reflecting the impacts directly on their bodies. Thus, the aim of this study was to carry out the biomonitoring of an estuary located on the Amazonian Equatorial Coast through analysis of PAHs (Polycyclic Aromatic Hydrocarbons) in the water, in addition to trace metals, histopathological alterations and analysis of erythrocyte micronuclei in Sciades herzbergii. S. herzbergii was used as a model species, due to its estuarine-resident behavior. Gonad and gill samples were subjected to histopathological evaluations. The quantification of trace metals was performed in samples of skeletal muscles of the animals collected, where concentrations of Lead (Pb), Copper (Cu), Zinc (Zn), Cadmium (Cd), Magnesium (Mg), Iron (Fe) and Aluminum (Al) were found. Except for Cadmium (Cd), all the concentrations were above the recommended limits. The PAHs analysis revealed the presence of Naphthalene and Acenaphthene in the water samples Histopathological and genotoxic analyses revealed of lesions in 100% of the study specimens. Thus, the histological and genotoxic alterations found in 100% of S. herzbergii specimens captured in São José Bay-MA are potentially associated with PAH concentrations present in the water. These results are potentially associated with the presence of PAH and trace metals, both in water and in animal tissues, inferring a general scenario of environmental contamination which directly implies a risk to the health and survival of the local biota. This study shows the relevance of continuous biomonitoring of estuarine ecosystems, in order to guide authorities regarding sewage management and ensure the evolutionary development of estuarine species, especially fishes of importance in the local cuisine, therefore related to human food security.

Assessment of Lead (Pb) Toxicity in Juvenile Nile Tilapia, Oreochromis niloticus-Growth, Behaviour, Erythrocytes Abnormalities, and Histological Alterations in Vital Organs

Lead (Pb) is one of the toxins responsible for the deterioration of ecological health in aquatic environments. The present study investigated the effects of Pb(NO₃)₂ toxicity on growth, blood cell morphology, and the histopathology of gills, liver, and intestine of juvenile Nile tilapia, Oreochromis niloticus. A 30-day long aquarium trial was conducted by assigning three treatment groups T₁ 5.20 mg L^-1, T₂ 10.40 mg L^-1, and T₃ 20.80 mg L^-1, and a control 0 mg L^-1 following the 96 h LC₅₀ of 51.96 mg L^-1 from acute toxicity test. Overall growth performance significantly declined in all the Pb(NO₃)₂ treated groups and the highest mortality was recorded in T₃. Behavioural abnormalities were intense in all the treatment groups compared to the control. Hepatosomatic index (HSI) values were reported as higher in treatment groups. Reduced nucleus diameter and nuclei size in erythrocytes were reported for T₂ and T₃ groups. Dose-dependent histological alterations were visible in the gills, liver, and intestine of all the Pb(NO₃)₂ treated groups. The width of the intestinal villi was highly extended in T₃ showing signs of severe histological alterations. In conclusion, Pb toxicity causes a negative effect on growth performance, erythrocyte morphology, and affected the vital organs histomorphology of juvenile O. niloticus.

Environmental Implications Associated with the Development of Nanotechnology: From Synthesis to Disposal

Nanotechnology remains under continuous development. The unique, fascinating, and tunable properties of nanomaterials make them interesting for diverse applications in different fields such as medicine, agriculture, and remediation. However, knowledge about the risks associated with nanomaterials is still poorly known and presents variable results. Furthermore, the interaction of nanomaterials with biological systems and the environment still needs to be clarified. Moreover, some issues such as toxicity, bioaccumulation, and physicochemical transformations are found to be dependent on several factors such as size, capping agent, and shape, making the comparisons even more complex. This review presents a comprehensive discussion about the consequences of the use and development of nanomaterials regarding their potential risks to the environment as well as human and animal health. For this purpose, we reviewed the entire production chain from manufacturing, product development, applications, and even product disposal to raise the important implications at each stage. In addition, we present the recent developments in terms of risk management and the recycling of nanomaterials. Furthermore, the advances and limitations in the legislation and characterization of nanomaterials are also discussed.

Exposure of carbon nanotubes affects testis and brain of common carp

Carbon nanotubes production has been rapidly increasing for many potential applications, however, the environmental impact of this nanomaterial needs to be comprehended. The present work focused on unraveling the effects of single-walled carbon nanotubes (SWCNT) in the common carp, Cyprinus carpio. The physicochemical properties of SWCNT were analyzed with X-ray diffraction, Fourier transforms infra-red, UV-Vis absorption, transmission electron microscopy (TEM), and Raman spectroscopy before testing for exposure impact. The effects of SWCNT, were investigated by exposing to two doses viz., 10 and 50 μg/L, for 7 days in adult common carp, in vivo. Expression of key steroidogenic and transcription factor genes related to testis and brain were downregulated after the treatment. The concomitant decreases in serum testosterone and 11-ketotestosterone levels revealed the impact of SWCNT after exposure. Further, SWCNT exposure induced antioxidant enzymes namely glutathione-S-transferases, superoxide dismutase, and catalase in both testis and brain. Concurrently, histological and TEM analysis of testis revealed structural disarray. In addition, SWCNT treatment, in testicular and brain primary cell cultures decreased cell viability with an increase of reactive oxygen species levels, leading to a significant elevation of apoptotic cells. In line with this, low mitochondrial membrane potential and DNA damage were also observed during post SWCNT treatment. Taken together, transient exposure of SWCNT causes toxic effects and alters testicular and brain function in the common carp. Thus, the discharge of carbon nanotubes poses a greater risk to the aquatic environment warranting regulatory measures.

Morphological and Functional Alterations Induced by Two Ecologically Relevant Concentrations of Lead on Danio rerio Gills

Lead (Pb), due to its high toxicity and bioaccumulation tendency, is one of the top three pollutants of concern for both humans and wildlife and occupies second place in the Priority List of Hazardous Substances. In freshwater fish, Pb is mainly absorbed through the gills, where the greatest accumulation occurs. Despite the crucial role of gills in several physiological functions such as gas exchange, water balance, and osmoregulation, no studies evaluated the effects of environmentally relevant concentrations of Pb on this organ, and existing literature only refers to high levels of exposure. Herein we investigated for the first time the molecular and morphological effects induced by two low and environmentally relevant concentrations of Pb (2.5 and 5 μg/L) on the gills of Danio rerio, a model species with a high translational value for human toxicity. It was demonstrated that Pb administration at even low doses induces osmoregulatory dysfunctions by affecting Na⁺/K⁺-ATPase and AQP3 expression. It was also shown that Pb upregulates MTs as a protective response to prevent cell damage. Modulation of SOD confirms that the production of reactive oxygen species is an important toxicity mechanism of Pb. Histological and morphometric analysis revealed conspicuous pathological changes, both dose- and time-dependent.

Graphene oxide promoted chromium uptake by zebrafish embryos with multiple effects: Adsorption, bioenergetic flux and metabolism

The increasing production and application of graphene oxide (GO, a popular carbon nanomaterial), makes their release into aqueous environment inevitably. The capability of GO to enhance the toxicity of background contaminants has been widely concerned. However, the effect of GO on heavy metal accumulation in fish embryos remains unclear. Here, we show that GO-promoted chromium (Cr) uptake by zebrafish embryos with multiple effects. The adsorption accelerated the aggregation and settlement of Cr⁶⁺-adsorbed GO and decreased the Cr⁶⁺ concentration in the upper water, which enhanced the interaction of chorions and contaminants (Cr⁶⁺, GO and Cr⁶⁺-adsorbed GO). In the presence of GO, the Cr content in chorions and intra-chorion embryos was increased by four times and 57% respectively, compared to that of the single Cr⁶⁺ exposure. Furthermore, GO+Cr⁶⁺ increased the oxygen consumption rates, embryonic acid extrusion rates and ATP production, induced more serious oxidative stress, and disturbed amino acid metabolism, fatty acid metabolism and TCA cycle. These findings provide new insights into the effect of GO on heavy metal bioaccumulation and toxicity during embryogenesis.

Nanoparticles as vectors of other contaminants in estuarine suspended sediments: Natural and real conditions

Studding the behaviour and danger of nanoparticles (NPs, minerals and amorphous phases) in the estuarine ecosystem is presently incomplete by the lack of measureable description of NPs in the ecological conditions, such as suspended-sediments (SS). In the last years, several works have revealed the toxic consequences of ultra-fine and nanoparticulate compounds on diverse systems, raising apprehensions over the nanocontaminants behaviour and destiny in the numerous ecological partitions. The general objective of the manuscript is to explain the geochemical conditions of the LES (Laguna estuarine system, southern Brazil) suspended sediments covering an area around the main South American coal plant, enhancing the creation of future public policies for environmental recovery projects. Subsequently the discharge of nanoparticles and toxic element (TE) in the ecosystem, NPs react with several constituents of the nature and suffers active alteration progressions. Contamination coming from engineering actions, wastewater, are something identifiable, however when these contaminations are accompanied by other contamination sources (e.g. mining and farming) the work gets defaulted. By combining material about the concentration of TE contaminants and NPs occurrences, this work offers novel visions into contaminant contact and the possible effects of such exposure on estuarine systems in Brazil. The results presented here will be useful for different areas of estuaries around the world.

Histological and molecular changes in gill and liver of fish (Astyanax lacustris Lütken, 1875) exposed to water from the Doce basin after the rupture of a mining tailings dam in Mariana, MG, Brazil

The effects of the rupture of a mining tailings dam were investigated using the gills and liver of Astyanax lacustris as a proxy for environmental quality. The fish were exposed for seven days to water sampled forming four groups: upstream of the dam rupture (P1), and 22 km (P2); 48 km (P3); and 70 km (P4) downstream from the dam rupture in the Doce River basin. The control group received dechlorinated tap water. The dissolved concentrations of metals were determined by Inductively Coupled Plasma Mass Spectrometry (ICP-MS). We evaluated the histology of the gills and liver, as well as, immunohistochemistry for HSP70 and Na⁺/K⁺ ATPase (NKA) in the gills, and for P-gp in liver. In all sites we observed a mix of metals, with higher concentrations of Mn, Cd, As, and Cu/Cr in P1, P2, P3, and P4, respectively. All treatments groups showed histological changes in gills and liver, with the highest amount of these alterations found in the P2 group. Disorganization of the secondary lamellae, epithelial lifting, and mitochondria-rich cells (MRC) were observed in the gills. The parenchyma of the liver was rather disorganized, and hepatocytes and nuclei showed hypertrophy, vacuolization and cytoplasmic degeneration. A higher immunoreaction of HSP70 in P2 when compared with the other groups and lower labeling of HSP70 in the P4 was registered. In P2 and P3, NKA-positive cells were observed with hypertrophy and disorganization. Morphometric analyses of the liver revealed that all treatment groups presented a lower immunolabeling of P-gp when compared with the control group. Thus, the experimental approach revealed that the water from Doce basin can promote histological alterations in fish's liver and gills, as well as modulation of disruption of ionic balance, cellular responses to stress, and cell detoxification pathways.

Effects of carbon nanotubes on the toxicities of copper, cadmium and zinc toward the freshwater microalgae Scenedesmus obliquus

Due to their unique structure and properties, carbon nanotubes (CNTs) released into the aquatic environment can potentially influence the behavior of other coexisting pollutants, thereby altering their toxicity to aquatic organisms. In this study, the toxicities of multi-walled CNTs and three heavy metals, copper (Cu), cadmium (Cd) and zinc (Zn) were determined individually. Following this, CNTs with low concentrations (1 and 5 mg/L) were co-exposed with Cu, Cd or Zn to the microalgae Scenedesmus obliquus, to investigate the effects and underlying mechanisms of CNTs on metal toxicity. Results showed that CNTs, especially at a concentration of 5 mg/L, promoted algae growth and enhanced photosynthetic efficiency via increasing exciton trap efficiency and quantum yield for electron transport. Introduction of CNTs appeared to alleviate the adverse effects of Cu, Cd or Zn on microalgae, indicated by algae growth, total chlorophyll content and photosynthetic indices. However, these effects differed greatly for different metals, depending on both the toxicity of each metal and the exposure period (4 day and 8 day). Enhancement of photosynthesis and interference of metal uptake by CNTs, have a crucial role in the effects of CNTs on metal toxicity.

Effects of nanomaterials on metal toxicity: Case study of graphene family on Cd

The risk of heavy metal cadmium (Cd) on aquatic organisms has drawn widespread attentions, but the effects of nanomaterials (e.g. graphene (G)) on Cd toxicity are rarely clarified. It was known that mixture of contaminants may exhibit more severe impact than the individual metal. Here, we conducted a study systematically on the effects of nanomaterials on the toxicity of Cd to Scenedesmus Obliquus (S. obliquus) with or without the presence of graphene family materials (GFMs) derived from G, such as graphene oxide (GO) and amine-modified graphene (GNH). Our results showed that the influence of GFMs on the acute toxicity of Cd to S. obliquus is in the order of GO > G > GNH based on their EC₅₀ of Cd-GFMs. The effects of GFMs on the cytotoxicity and oxidative damage of Cd to S. obliquus are varied with the concentrations of GFMs. The differences between the effects of GFMs on Cd toxicity may attribute to their different surface oxygen-containing functional groups contained in the nanomaterials. The adsorption capacity of nanomaterials on metal ions, their dispersibility in water and their interaction mode with organisms, may dominate main contributions to their effects on Cd toxicity. Our study aids to clarify the interference of nanoparticles on the ecotoxicity of metals, to avoid the misunderstanding of the potential risk of metals in the complicate water environments.

Transformation pathways and fate of engineered nanoparticles (ENPs) in distinct interactive environmental compartments: A review

The ever increasing production and use of nano-enabled commercial products release the massive amount of engineered nanoparticles (ENPs) in the environment. An increasing number of recent studies have shown the toxic effects of ENPs on different organisms, raising concerns over the nano-pollutants behavior and fate in the various environmental compartments. After the release of ENPs in the environment, ENPs interact with various components of the environment and undergoes dynamic transformation processes. This review focus on ENPs transformations in the various environmental compartments. The transformation processes of ENPs are interrelated to multiple environmental aspects. Physical, chemical and biological processes such as the homo- or hetero-agglomeration, dissolution/sedimentation, adsorption, oxidation, reduction, sulfidation, photochemically and biologically mediated reactions mainly occur in the environment consequently changes the mobility and bioavailability of ENPs. Physico-chemical characteristics of ENPs (particle size, surface area, zeta potential/surface charge, colloidal stability, and core-shell composition) and environmental conditions (pH, ionic strength, organic and inorganic colloids, temperature, etc.) are the most important parameters which regulated the ENPs environmental transformations. Meanwhile, in the environment, organisms encountered multiple transformed ENPs rather than the pristine nanomaterials due to their interactions with various environmental materials and other pollutants. Thus it is the utmost importance to study the behavior of transformed ENPs to understand their environmental fate, bioavailability, and mode of toxicity.

Metabolic effects in the freshwater fish Geophagus iporangensis in response to single and combined exposure to graphene oxide and trace elements

Graphene oxide (GO) is part of a new set of nanomaterials with particular characteristics related to its nanoscale size. Due to this feature, it presents high reactivity and other contaminants present in the environment could bind to them and affect its intrinsic toxicity. The metabolic effects of such nanomaterials and their combination with two common pollutants, zinc and cadmium, on the freshwater fish Geophagus iporangensis are analyzed. Moreover, metabolic rate and ammonia excretion were used as bioindicators to measure metabolic changes. Fishes were exposed for 24 h in filtered tap water to different concentrations of GO (0.5; 1.0; 2.0 and 4.0 mg L^-1), Zn (0.5; 1.0; 2.0; 4.0 and 10.0 mg L^-1) and Cd (0.1; 0.5; 1.0; 2.0 and 4.0 mg L^-1). Combined effects were verified using the same concentrations of trace elements added to 1.0 mg L^-1 of GO. Exposure to GO and Cd resulted in a decrease of metabolic rate in G. iporangensis, by about 30% compared to control means, in the highest concentration tested (4.0 mg L^-1). However, zinc exposure in the highest concentration (10 mg L^-1) raised metabolic rate to around three times that of the control group. Ammonia excretion was not affected by exposure to GO and Cd. In contrast, exposure to Zn at 10 mg L^-1 raised the rate to around 47%. The combined exposure of GO and Zn intensified the effects of the trace element, inducing responses in both biomarkers at lower concentrations and demonstrating that the interaction between elements increases zinc's effects. The combination Cd + GO only affects metabolic rate. Thus, this metabolic rate alone reveals that combined exposure potentiates effects of trace elements on fish metabolism.

Effects of multiwalled carbon nanotubes and carbofuran on metabolism in Astyanax ribeirae, a native species

The study of the toxic effect of carbofuran and multiwalled carbon nanotubes (MWCNTs) on Astyanax ribeirae metabolism is of paramount importance due to the increasing use of this pesticide in agriculture and in the production of nanotubes within the material industry. This study aimed to evaluate the effects of carbofuran, MWCNT, and the combination of these compounds on specific oxygen consumption and excretion of ammonia in A. ribeirae. Therefore, 65 fish were divided into three groups of treatments at varying concentrations: carbofuran (0.01, 0.05, 0.1, and 0.5 mg/L), MWCNT (0.1, 0.25, 0.5, and 1.0 mg/L), and 0.5 mg/L of MWCNT added to carbofuran concentrations (0.01, 0.05, 0.1, and 0.5 mg/L). The average specific oxygen consumption in the groups exposed to carbofuran, compared to the control, increased 73.49% at the 0.01 mg/L concentration and decreased 63.86% and 91.57% with treatments of 0.1 and 0.5 mg/L, respectively. For groups exposed to the MWCNT, there was an 83.91% drop with the 1.0 mg/L treatment, and the carbofuran + MWCNT groups recorded a decrease of 71.09%, 92.77%, and 93.98% at concentrations of 0.05, 0.1, and 0.5 mg/L, respectively. In relation to specific ammonia excretion, in groups exposed to carbofuran compared to the control, there was an increase of 134.37% and 200% with the 0.1 and 0.5 mg/L treatments, respectively. The group exposed to carbofuran + MWCNT experienced a decrease of 60% and 80% with treatments of 0.1 mg/L carbofuran + 0.5 mg/L MWCNT and 0.5 mg/L carbofuran + 0.5 mg/L MWCNT, respectively. Therefore, it was concluded that carbofuran + MWCNT interact, increasing the effects in Astyanax sp.

A Gill Histopathology Study in two Native Fish Species from the Hydrographic Douro Basin

Gill histopathology is a valuable tool to evaluate ecosystems health, because the gill is a key site of waterborne pollutant uptake and the first target organ to their toxicity. Consequently, this makes it important in biomonitoring programs. This study aims to evaluate gill histopathological differences in Douro basin native fish species and determine possible associations with water quality and the ecological status classifications. Two native fish species (Pseudochondrostoma duriense and Luciobarbus bocagei) were sampled in four points of the Douro basin: two reference points, Ameixiosa (Paiva River) and Covelas (Bestança River), both classified with an excellent ecological status; and two disturbed points, Castro Daire (Paiva River) and Alvações do Corgo (Corgo River), categorized with a good and a moderate ecological status, respectively. Gill histopathological differences were qualitative and quantitatively analyzed. The histological analysis showed that, in all sampling locations, both species presented some degree of gill differences, such as epithelial lifting, lamellar fusion, and/or necrosis. The histopathological differences evaluation emphasized some variances in the responses between the two species. In nase, the filament and lamellar epithelium proliferation were the histopathological differences that better reflected the river ecological status classification, proving their usefulness in biomonitoring programs.

Toxicological effects of transition metal-doped titanium dioxide nanoparticles on goldfish (Carassius auratus) and common carp (Cyprinus carpio)

The aim of present study was to assess the toxicological effects of transition metal-doped titanium dioxide nanoparticles (TiO₂ NPs) on histopathological changes, behavioral patterns, and antioxidant responses of goldfish (Carassius auratus) and common carp (Cyprinus carpio). The synthesized nanoparticles were confirmed by Transmission Electron Microscopy, Field Emission Scanning Electron Microscopy, X-ray diffraction, UV-visible, and Vibration Sample Magnetometer. Fish in four experimental groups exposed to sub-lethal concentrations of pure TiO₂ NPs (10 mg L^-1), chromium (Cr), iron (Fe), and nickel (Ni) doped TiO₂ NPs for seven days. Statistical analysis of oxidative stress responses in gills showed significant differences in superoxide dismutase, total antioxidant capacity, and malondialdehyde parameters between two species and in all parameters than glutathione peroxidase between experimental groups and control group. In intestine, no significant difference was observed among groups, but oxidative responses were markedly different in all parameters among fish species. The histopathological analysis showed hyperplasia, fusion, and aneurism in the gills as well as degeneration, integration of villi, necrosis and erosion of the intestine. Our findings indicated that compare to pure TiO₂ NPs, exposure to transition metals-doped TiO₂ NPs induced oxidative stress and histopathological changes in both fish species.

Mechanisms involved in the impact of engineered nanomaterials on the joint toxicity with environmental pollutants

Emerging nanoscience and nanotechnology inevitably facilitate discharge of engineered nanomaterials (ENMs) into the environment. Owing to their versatile physicochemical properties, ENMs invariably come across and interact with various pollutants already existing in the environment, leading to considerable uncertainty regarding the risk assessment of pollutants. Nevertheless, the underlying mechanisms of the complicated joint toxicity are still largely unexplored. This review aims to aid in understanding the interaction of ENMs and pollutants from the perspective of ecological and environmental health risk assessment. Based on related research published from 2005 to 2018, this review focuses on summarizing the effect of ENMs on the toxicity of pollutants both in vivo and in vitro. Physicochemical interaction appears as a main factor affecting ENMs-pollutants joint toxicity, with the mechanisms and the resultants for ENM-pollutant adsorption been illustrated. Cellular and molecular mechanisms involved in the joint toxicity of ENMs and pollutants are discussed, including the effect of ENMs on the bioaccumulation, biodistribution, and metabolism of pollutants, as well as the defense responses of organisms against such pollutants. Future in-depth investigation are suggested to focus on further exploring biological mechanisms (especially for the antagonized effect of ENMs against pollutants), using more advanced mammalian models, and paying more attention to the realistic exposure scenarios.

Al2O3 nanoparticle impact on the toxic effect of Pb on the marine microalga Isochrysis galbana

The rapid development and application of nanotechnology have led to increasing concern about the environmental implications of released nanomaterials and potential risks to public health and aquatic ecosystems. Information on the joint effect of nanomaterials and co-existing contaminants such as heavy metals is still inadequate. Our work investigated the effect of Al₂O₃ nanoparticles (NPs; nano-Al₂O₃) on the toxic effect of Pb in the unicellular marine phytoplankton Isochrysis galbana. Results showed that a dose-response effect of nano-Al₂O₃ was found. Significant enhancement of fluorescence in cell cytoplasm rather than cell membrane occurred in the presence of nano-Al₂O₃, indicating that nano-Al₂O₃ can penetrate cells and affect the fluorescence emitted from the chloropigments inside them. The presence of nano-Al₂O₃ has no impact on the toxic effect of Pb at an NP concentration of 1 mg/L but increased that at NP concentrations of 10 mg/L and 100 mg/L. A synergistic effect was also found for the toxic effect of Pb in the presence of 10 mg/L nano-Al₂O₃. The presence of 100 mg/L nano-Al₂O₃ significantly increased the bio-uptake of Pb in the range of 0.25 mg/L to 2.0 mg/L Pb, and the maximum accumulated Pb in algae can reach up to 18.22 ng/10⁵ cells with 100 mg/L nano-Al₂O₃ compared with Pb alone at 2.0 mg/L(12.53 ng/10⁵ cells). Inside cells, Pb loaded onto nano-Al₂O₃ can be more toxic than the same amount of free Pb species. The results of toxicity tests and accumulated Pb in algae imply that, in addition to the total Pb cell content, the bioavailability of Pb inside algae should be taken into consideration in evaluating the joint toxicity effect. Our work enhances understanding of the combined toxicity of NPs and co-existing heavy metals and is of practical significance in the natural environment.