Low hazard of silver nanoparticles and silver nitrate to the haematopoietic system of rainbow trout

Comparative toxicity of zinc oxide nanoparticles and zinc salts in male mice: Hematological, biochemical, and histopathological impacts

The aim of this study was to investigate the toxicity of zinc oxide nanoparticles (ZnO NPs) compared to different zinc salts (ZnSO4, Zn(NO3)2, and ZnCl2) in male mice. For this purpose, 45 male mice were divided into five groups of nine (one control group). Mice were exposed to ZnO NPs and various zinc salts for 28 days, while the control group remained unexposed. After the exposure period, the mice were euthanized, and hematological, biochemical, enzymatic, and histopathological changes were recorded. Most hematological (RBC, WBC, Hb, Ht counts), biochemical (cholesterol, triglyceride, glucose, total protein, and albumin), and enzymatic parameters alkaline phosphatase (ALP), aspartate transaminase (AST), alanine aminotransferase (ALT) were significantly different in exposed mice compared to the control group (p < 0.05). The number of erythrocytes in mice exposed to ZnCl2 for 28 days (7.84 ± 1.41 × 106 mm3) was significantly lower than in the control group (10.11 ± 1.14 ×106 mm3) (p < 0.05). Additionally, mice exposed to ZnCl2 had significantly lower white blood cell (WBC) counts, hemoglobin (Hb), and hematocrit (Ht) levels than the control group (p < 0.05). Zn-exposed mice developed deformed erythrocytes, including dacrocytes, keratocytes, and ovalocytes, likely due to cytogenetically damaged RBC precursors. ZnO NPs and its various salts caused degeneration in hepatocytes, thickening and inflammatory cell infiltration in the renal capsule, congestion in the blood vessels of the lungs, and swelling of goblet cells in the intestine. Adding to the wealth of literature on the toxicity of ZnO NPs and zinc salts, especially ZnCl2, our study highlights the ecotoxicity of these compounds in mice. Effective and timely measures should be taken to reduce the use of ZnO NPs and its various salts worldwide.

Investigating the toxic mechanism of iron oxide nanoparticles-induced oxidative stress in tadpole (Duttaphrynus melanostictus): A combined biochemical and molecular study

Metal oxide nanomaterials have toxicity towards aquatic organisms, especially microbes and invertebrates, but little is known about their impact on amphibians. We conducted a study on Duttaphrynus melanostictus (D. melanostictus) tadpoles to explore the chronic toxicity effects of iron oxide nanoparticles (IONPs) and the underlying mechanisms of IONPs-induced oxidative stress. IONPs exposure led to increased iron accumulation in the blood, liver, and kidneys of tadpoles, significantly affecting blood parameters and morphology. Higher IONPs concentrations (10 and 50 mg L-1) triggered reactive oxygen species generation, resulting in lipid peroxidation, oxidative stress, and pronounced toxicity in tadpoles. The activity levels of antioxidant enzymes/proteins (SOD, CAT, albumin, and lysozyme) decreased after IONPs exposure, and immunological measures in the blood serum were significantly reduced compared to the control group. Molecular docking analysis revealed that IONPs primarily attached to the surface of SOD/CAT/albumin/lysozyme through hydrogen bonding and hydrophobic forces. Overall, this study emphasizes the ability of IONPs to induce oxidative damage by decreasing immunological profiles such as ACH50 (34.58 ± 2.74 U mL-1), lysozyme (6.94 ± 0.82 U mL-1), total Ig (5.00 ± 0.35 g dL-1), total protein (1.20 ± 0.17 g dL-1), albumin (0.52 ± 0.01 g dL-1) and globulin (0.96 ± 0.01 g dL-1) and sheds light on their potential toxic effects on tadpoles.

Reproductive and whole-body toxicity of Ag-doped and -undoped ZIF-8 nanoparticles and the building blocks: An Artemia-based comparative bioassay

The present research assessed, for the first time, toxicity of ZIF-8 (1 mg/L) and the building blocks (0.1 mg/L Zn2+ and 0.4 mg/L 2-methylimidazole (2-MIm)), besides that of AgNPs@ZIF-8 (0.25, 0.5, and 1 mg/L) and AgNO3 (0.1 mg/L) to aquatic organisms. Two consecutive generations (F0 & F1) of Artemia salina were exposed to these chemicals. All of the chemical treatments considerably caused mortality in F0, especially AgNPs@ZIF-8 and AgNO3, whereas F1 displayed notable tolerance and survived comparable to the control group, except in the case of AgNO3 treatment. Similarly, growth indices (weight, mainly in ZIF-8, Zn2+, and 2-MIm; length, in Ag-doped ZIF-8 and AgNO3) were significantly retarded in F0 and especially F1 of all treatments, and 2-MIm caused the greatest length retardation in F0. AgNPs@ZIF-8 (0.5 and 1 mg/L), 2-MIm, and AgNO3 postponed the ovary emergence in about 40%-60% of the exposed F0, and ZIF-8 delayed this phenomenon in some individuals of F0 and F1 up to 6 days. This temporal disturbance was also observed in time to first brood of almost all experimental F0 and F1 groups, with being over 80% of F1 exposed to ZIF-8, 2-MIm, and Zn2+, as well as about 50% of F0 treated with 2-MIm, and Zn2+. The highest neonate number was recorded for F0 and F1 exposed to AgNO3 and Zn2+, while ZIF-8 and, importantly, 2-MIm decreased the reproductivity to the lowest levels in both generations. Generally, the reproductive frequency was significantly decreased in all F0 and F1 treatments, especially 2-MIm, ZIF-8, AgNPs@ZIF-8 (0.25 & 1 mg/L). This study highlighted the neglected importance of 2-MIm in assessing overall toxicity of ZIF-8, and even other organic ligands of MOFs, and also filled a gap in the literature by investigating the potential effect of additives such as AgNPs on the toxicity of ZIF-8 and other MOFs.

Antibacterial and anticancer activities of green-synthesized silver nanoparticles using Photinia glabra fruit extract

Aims: We prepared Photinia glabra (PG) aqueous fruit extract, utilized it to synthesize silver nanoparticles (PG-Ag NPs) and evaluated the antibacterial and anticancer activities of the nanoparticles (NPs). Materials & methods: Silver nitrate aqueous solution was reduced to PG-Ag NPs using aqueous PG fruit extract. NP shape, size, composition and functionalization were determined using transmission electron microscopy, x-ray photoelectron spectroscopy, Fourier transform infrared and x-ray diffraction. Results & conclusions: PG-Ag NPs were spherical, approximately 39-77 nm-sized, functionalized surfaces with notable antibacterial activity against both Escherichia coli and Staphylococcus aureus, with an MIC <30 ug/ml and cytotoxicity toward esophageal cancer cells, with IC50 values less than 20 ug/ml. PG-Ag@rt NPs have been shown to be a potent antibacterial and anticancer agent, and their enriched particle surfaces can be conjugated with other compounds for multibiomedical applications.

Biological responses of whitefish (Coregonus lavaretus L.) to reduced toxic impact: Metal accumulation, haematological, immunological, and histopathological alterations

Bioaccumulation of the main pollutants in the organs of whitefish, as well as their haematological parameters, were examined dynamically over a 40-year period in historically contaminated Lake Imandra. A quantitative histological analysis was performed to assess the physiological state of whitefish and histopathologies of organs, as well as their physiological and biochemical functions in the current period of toxic load decline. Biological reactions of whitefish from the historically contaminated area have been greatly modified in contrast to those of whitefish from the never contaminated area of the lake, and this shift persisted even after approximately 20 years of toxic load decline. First, high antioxidant status supports the body's systems, smoothing over the negative consequences of metal toxicity, phagocytosis and inflammatory reactions. Moreover, the defence mechanism of whitefish from the historically contaminated area actively uses the oxidative systems of nonspecific immunity. Second, the adaptive strategy is aimed at improving gas exchange without compensatory proliferation of gill structure, which increases their functional surface and reduces the distance to the bloodstream, as well as increasing haemoglobin in maturing erythrocytes. Third, the higher efficiency of endo- and phagocytosis was confirmed by detecting increased monocytes and macrophages in the peripheral blood and decreased melano-macrophage centres in the fish kidney. Elevated accumulation of Fe, Cu, and Se may serve a sign of liver pathology, while elevated accumulation of Zn and Co already indicates kidney pathology, which is confirmed by histopathological alterations.

Acute Exposure to Biogenic Nanosilver Produced from Fusarium oxysporum in a Neotropical Fish

Biogenic nanosilver (bNAg) has emerged as a potentially less toxic alternative to synthetic nanosilver. However, no studies have evaluated its effects on a fish species from the Neotropical region. Thus, our aim was to evaluate the effects of a bNAg on the Neotropical fish Prochilodus lineatus. For this purpose, after 24 h of exposure to 100 µg L^-1 of bNAg, blood samples were collected to evaluate hematological, genotoxic, and plasma parameters. Gills and liver were sampled to evaluate biomarkers of oxidative stress and brain samples were used to assess neurotoxicity. The fish presented hyperglycemia, an increased number of erythrocytes, a reduction in antioxidant enzyme activity in both tissues evaluated, and a decrease in lipid peroxidation in the gills. We concluded that P. lineatus is a sensitive species to this nanoparticle, since it presented alterations in several biomarkers after an acute exposure.

Assessment of the potential threat of nickel(II) oxide nanoparticles to fish Heteropneustes fossilis associated with the changes in haematological, biochemical and enzymological parameters

The present study has been conducted to evaluate the potential threat of NiO nanoparticles (NiO NPs) on an edible fish Heteropneustes fossilis. Fishes selected for the study were exposed to four concentrations of NiO NPs (12, 24, 36 and 48 mg/l) for the period of 14 days, and various haematological, biochemical and enzymological changes in the exposed fishes were examined. Results revealed that maximum fluctuations were seen in 48-mg/l-exposed fishes when compared with the control in terms of the haematological parameters (RBC count, WBC count, Hb content, Ht% and O₂ carrying capacity of blood), enzymatic activities (AST, ALP, ALT and LDH) and biochemical parameters (level of cholesterol, triglycerides, glucose, total protein, albumin, globulin, bilirubin and creatinine). However, 12 mg/l treatment to the fishes showed its least impact on aforesaid parameters. Furthermore, Ni accumulation and changes in cortisol level in the blood were also noticed in all the treated fishes. Structural changes, such as membrane and nuclear disintegration, micronucleus, deformed and vacuolated cells, and enucleation were also observed in RBCs of NiO NP-treated fishes. Conclusively, our study provides useful information and insight for the possible ecotoxicity of NiO NPs on aquatic organisms and emphasizes upon the importance of treatment of effluents containing nanoparticles before their release into the aquatic system.

Toxicity, inflammatory and antioxidant genes expression, and physiological changes of green synthesis silver nanoparticles on Nile tilapia (Oreochromis niloticus) fingerlings

The rapid increase of incorporating silver nanoparticles (Ag-NPs) in different anthropogenic and industrial activities increased the discharge of these particles in the aquatic ecosystem. The environmental impact of Ag-NPs, especially the green synthesized is still not completely understood on fish. Therefore, this study aimed to investigate the effects of exposure to graded series of starch-mediated Ag-NPs at levels of 0, 3.31, 6.63, 13.25, and 26.50 mg L^-1 representing 0, 6.25, 12.5, 25, and 50% of LC₅₀ on Nile tilapia (O. niloticus), respectively. Fish with initial weight 37.63 ± 0.41 g were maintained in 70 L glass aquaria and exposed to starch-mediated Ag-NPs (average particle size 40 nm) for 28 days. The results revealed that starch-mediated Ag-NPs induced severe changes in the mRNA levels of toxicity (CYP1A and Hsp70) and inflammatory (TNF-α and TGF-β) genes. The expression of antioxidant genes (SOD and CAT) was significantly suppressed, and the activities of their enzymes were inhibited significantly upon exposure. Simultaneously, the malondialdehyde level increased significantly with increasing the exposure levels of starch-mediated Ag-NPs. The red blood cells, hemoglobin, hematocrit and white blood cell values were decreased significantly with doses over 3.31 mg L^-1 of Ag-NPs. In addition, the total protein and globulin decreased significantly with increasing Ag-NPs in a dose-dependent manner. The liver function enzymes and kidney function indicators revealed severe toxicity with Ag-NPs exposure. In conclusion, the effect of starch-mediated Ag-NPs in doses over 3.31 mg L^-1 induced obvious toxicity in the molecular and proteomic levels in Nile tilapia fingerlings.

Nanosilver and Silver Nitrate Toxicity in Ex Vivo-Exposed Gills of Fish and Mitigation by Humic Acids

Silver nanoparticles (AgNP) are unique because of their biocide properties. Once released to environment, AgNP interact with the natural organic matter which impact on their fate, dispersion, and ultimate toxicity. We carried out an ex vivo exposure of gill of Corydoras paleatus fish to 100 µg L^-1 of AgNP or AgNO₃, alone and in combination with 10 mg L^-1 of humic acids (HA), with the aim to evaluate the potential mitigation of HA on AgNP toxic effects. We analyzed Ag accumulation and oxidative stress biomarkers. The results showed high bioaccumulation after the AgNO₃+HA exposure. An inhibition of glutathione-S-transferase enzymatic activity and depletion of reduced glutathione levels were registered after the AgNO₃ exposure, and increased lipid peroxidation levels in the case of AgNP one. Oxidative responses were mitigated when the HA were present in the media. Overall, the knowledge about the fate of this emergent pollutant was deepened through this study.

Mitigation of silver nanoparticle toxicity by humic acids in gills of Piaractus mesopotamicus fish

Silver nanoparticles (AgNPs) are one of the most produced nanoproducts due to their unique biocide properties. The natural organic matter has an important impact on nanoparticle's dispersion as it may alter their fate and transport, as well as their bioavailability and toxicity. Therefore, this study aimed to evaluate the mitigatory effect of humic acids (HAs) on AgNP toxicity. For this purpose, we carried out an ex vivo exposure of gill of Piaractus mesopotamicus fish to 100 μg L^-1 of AgNPs or AgNO₃, alone and in combination with 10 mg L^-1 of HAs. In parallel, a complete AgNP characterization in the media, including the presence of HAs, was provided, and the Ag⁺ release was measured. We analyzed Ag bioaccumulation, antioxidant enzymes activities, lipid peroxidation, antioxidant capacity against peroxyl radicals, and reduced glutathione levels in fish tissue. Our results indicated the Ag⁺ release from AgNPs decreased 28% when the HAs were present in the media. The Ag accumulation in gill tissue exposed to AgNPs alone was higher than the AgNO₃ exposure, and sixfold higher than the treatment with the HA addition. Moreover, after both Ag forms, the catalase enzyme augmented its activity. However, those responses were mitigated when the HAs were present in the media. Then, our results suggested the mitigation by HAs under the exposure to both Ag forms, providing valuable information about the fate and behavior of this emergent pollutant.

Exploring the liver fibrosis induced by deltamethrin exposure in quails and elucidating the protective mechanism of resveratrol

Deltamethrin (DLM) is widely used in agriculture and the prevention of human insect-borne diseases. However, the molecular mechanism of DLM induced liver injury remains unclear to date. This study investigated the potential molecular mechanism that DLM induced liver fibrosis in quails. Japanese quails received resveratrol (500 mg/kg) daily with or without DLM (45 mg/kg) exposure for 12 weeks. Histopathology, transmission electron microscopy, biochemical indexes, TUNEL, quantitative real-time PCR, and western blot analysis were performed. DLM exposure induced hepatic steatosis, oxidative stress, inflammation, and apoptosis. Most importantly, the Nrf2/TGF-β1/Smad3 signaling pathway played an important role on DLM-induced liver fibrosis in quails. Interestingly, the addition of resveratrol, an Nrf2 activator, alleviates oxidative stress and inflammation response by activating Nrf2, thereby inhibits the liver fibrosis induced by DLM in quails. Collectively, these findings demonstrate that chronic exposure to DLM induces oxidative stress via the Nrf2 expression inhibition and apoptosis, and then results in liver fibrosis in quails by the activation of NF-κB/TNF-α and TGF-β1/Smad3 signaling pathway.

Effects of metal nanoparticles on freshwater rotifers may persist across generations

Nanotechnology has become one of the fastest growing industries in the current century because nanomaterials (NMs) are present in an ever-expanding range of consumer products increasing the chance of their release into natural environments. In this study, the impacts of two metal nanoparticles (Ag-NPs and CuO-NPs) and their equivalent ionic forms (Ag⁺ and Cu²⁺) were assessed on the lentic freshwater rotifer Brachionus calyciflorus and on its ability to adapt and recover through generations. In our study, Ag-NPs and CuO-NPs inhibited the rotifer population growth rate and caused mortality at low concentrations (< 100 μg L^-1). Ag-NPs and CuO-NPs decreased in the medium when organisms were present (48 h exposure: 51.1 % and 66.9 %, respectively), similarly Ag⁺ and Cu²⁺ also decreased from medium in presence of the organisms (48 h: 35.2 % and 47.3 %, respectively); although the metal concentrations removed from the medium were higher for nanoparticles than metal ions, metal ions showed higher effects then their respective nanoparticle forms. Rotifer populations exposed for 4 generations to the toxicants were able to recover the population growth rate, but some rotifers showed developmental delay and inability to reproduce even after the removal of the toxicants. Intracellular accumulation of reactive oxygen species as well as plasma membrane damage were found in the rotifers at concentrations corresponding to EC₁₀ (Ag-NPs = 1.7 μg L^-1, Ag⁺ = 4.5 μg L^-1, CuO-NPs = 46.9 μg L^-1, Cu²⁺ = 35 μg L^-1) of the population growth rate. Our results showed, for the first time, that effects of metal nanoparticles and metal ions on rotifer populations may persist along several generations. This should be taken into account when assessing risks of metal nanoparticles in freshwaters.

c-Phycocyanin primed silver nano conjugates: Studies on red blood cell stress resilience mechanism

Green synthesis of metal-encased nutraceutical nano-hybrids has been a target for research over the last few years. In the present investigation, we have reported temperature dependent facile synthesis of silver nanoparticles using FDA approved c phycocyanin (cPC). The cPC conjugated silver nanoparticles (AgcPCNPs) were characterized by TEM, Zeta Potential, UV-vis, XPS, FTIR, and CD Spectroscopy. The temperature optimization studies suggested the synthesis of stable AgcPCNPs at 40 °C while at higher temperature system shows aggregated appearance. Molecular docking studies predicted the exclusive interaction of C, D, I, and J chains of cPC with the surface of AgNPs. Moreover, AgcPCNPs significantly (p < 0.1 %) counteract the toxic nature of AgNPs on red blood cell by measuring parameters like total RBC count, % hemolysis, % hematocrit, coagulation time, pH, electrolyte concentrations and degree of blood cell lipid peroxidation by the anti-oxidation mechanism. Skin fibroblast in vitro cell migration result suggeststhat AgcPCNPs enhanced the degree of cell movement towards the wound area. Data obtained collectively demonstrate that AgcPCNPs can be a better agent in the dermal wound healing with reduced toxicity with the bi-phasic advantage of cPC as a wound healer and Ag nano-metal as an anti-bacterial agent.

Chronic effects of wastewater-borne silver and titanium dioxide nanoparticles on the rainbow trout (Oncorhynchus mykiss)

Even though nanoparticles (NPs) are mostly removed by wastewater treatment plants, wastewater-borne NPs may show an altered toxicity to aquatic organisms. The main objectives of this work were: i) to assess the chronic (28 days) effects of wastewater-borne NPs of silver (AgNPs, 1.4-36.2 μg L^-1) and titanium dioxide (TiO₂NPs, 3.1-50.2 μg L^-1) at the individual (growth) and biochemical (biomarkers of neurotoxicity, oxidative stress and energy metabolism) levels in rainbow trout Oncorhynchus mykiss; and ii) to compare them with their effluent-supplemented and water-dispersed counterparts. The total Ag and Ti levels were determined in several fish organs. The growth of O. mykiss was not affected by the NPs in any treatment, except a 29% increase at 5.5 μg L^-1 of total Ag supplemented to effluents. The Ag level in organs of O. mykiss was significantly higher after exposure to water-dispersed AgNPs than their wastewater-borne or effluent-supplemented counterparts. No significant Ti uptake could be observed. Effluent-supplemented TiO₂NPs (50.1 μg L^-1 Ti) potentially induced neurotoxic effects, indicated by a 24% increase in acetylcholinesterase activity comparatively to controls. Energy reserves were unaffected by TiO₂ treatments, while nearly all AgNP-containing treatments caused a depletion of total lipids, proteins and carbohydrates in the muscle, suggesting an increased energy demand for detoxification processes to cope with AgNPs. Besides NPs, the effluent matrix and dispersing agent (for AgNPs) induced significant effects on energetic reserves and oxidative stress, indicating background toxicity of both treatments at the biochemical level. Our study is the first to assess chronic effects of wastewater-borne NPs on rainbow trout. While no effects were found at the individual level, several biochemical markers were changed by the NPs exposure. Our results highlight the importance of using complex matrices for a reliable risk assessment of NPs in the aquatic environment.

The effects of silver nanoparticles (Ag-NPs) sublethal concentrations on common carp (Cyprinus carpio): Bioaccumulation, hematology, serum biochemistry and immunology, antioxidant enzymes, and skin mucosal responses

The present study aimed to evaluate the effects of different waterborne sublethal concentrations of Ag-NPs LC₅₀ (96h) on common carp Cyprinus carpio using a multi-biomarker approach. Fish (9.22 ± 0.12 g) were stocked in fiberglass tanks and exposed to concentrations of 0 (control), 12.5%, 25% and 50% of Ag-NPs LC₅₀ (96h) or Ag-NO₃ LC₅₀ (96h), as the source of Ag⁺ ion, for a period of 21 days. At the end of study, tissue Ag contents were significantly (P < 0.05) higher and different in fish exposed to concentrations of 25% and 50% compared to the control. The numbers of RBCs, hematocrit, and MCHC values at these concentrations differed significantly in respect to the control. No significant effects were observed for hemoglobin, MCH, and MCV values. The number of WBCs was significantly higher at concentrations of 12.5% and 25% compared to the control. Meanwhile, the percentage of neutrophils significantly elevated at concentrations of 25% and 50%. Serum total protein at concentration of 50% detected significantly lower than that of 12.5% or the control. The serum albumin and globulin levels significantly declined in Ag-NPs-exposed groups versus the control. The serum ACH50 and total immunoglobulins showed significantly lower values in the treatments of 25% and 50% compared to the control. The serum glucose, cortisol, ALT, and ALP values significantly escalated upon Ag-NPs exposure. The serum SOD and CAT showed enhanced activity in the treatment of 12.5% vice versa significantly diminished at concentrations of 25% and 50% compared to the control. The exposure to the concentrations of 25% and 50% significantly dwindled the lysozyme activity and total immunoglobulin levels in skin mucus. In conclusion, sublethal concentrations of Ag-NPs LC₅₀ (96h) impaired fish health status at higher concentrations and 12.5% of Ag-NPs LC₅₀ (96h) was presumably safe for common carp aquaculture.

Effect on Serum Parameters and Immune Responses of Carassius auratus gibelio Exposed to Dietary Lead and Bacillus subtilis

Lead (Pb), a heavy metal and an environmental stressor, may affect many physiological processes, including the serum index and the immune response. The aim of this study was to explore the toxic effects of Pb on the serum index and the immune response of Carassius auratus gibelio (C. gibelio) fed 0, 120, or 240 mg/kg Pb, and 10⁹ cfu/g Bacillus subtilis (B. subtilis). After 15 and 30 days of dietary exposure, the serum indices and the immune responses of the fish were assessed. Dietary Pb exposure significantly affected various components of the serum index, including calcium, magnesium, glucose, cholesterol, total protein, glutamic-pyruvic transaminase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP), and lactate dehydrogenase (LDH). However, sIgA activity in the gut increased significantly following B. subtilis supplementation. Notable changes were also observed in the expression levels of immune-related genes, including HSP70, IgM, HSP90, IL-1β, IL-6, and TNF-α. B. subtilis supplementation effectively attenuated the effects of dietary Pb exposure.

Mercury, silver, selenium and other trace elements in three cyprinid fish species from the Vaal Dam, South Africa, including implications for fish consumers

The levels of Cr, Cu, Zn, Se, Ag, Cd, Hg, and Pb were determined in muscle and liver samples from 30 specimens of fish belonging to the species Labeobarbus aeneus, Labeobarbus kimberleyensis, and Labeo umbratus from the Vaal Dam. Health risks for human fish consumers were estimated using the target hazard quotient (THQ), the Se:Hg-ratio, and Se health benefit value (Se HBV). This is the first comprehensive report on Hg levels in fish from this lake. Mean concentrations ranging from 0.247-0.481 mg/kg dw in muscle and from 0.170-0.363 mg/kg dw in liver clearly show a contamination with this element. Although levels in muscle did not exceed maximum allowances for human consumption, a calculated THQ of 0.12 and 0.14 for the two Labeobarbus species, respectively, showed a potential risk due to additive effects. All Se:Hg-ratios as well as Se HBVs clearly suggested positive effects for fish consumers. Levels of Cu were remarkably high in the liver of L. umbratus, calling for further investigation on this species. Cadmium levels were above the maximum allowances for fish consumption in the liver of all three species (means between 0.190 and 0.460 mg/kg dw), but below the LOD in all muscle and intestine samples. This is also the first report of Ag in fish from South Africa. Levels were below the LOD in muscle, but well detectable in liver; they varied significantly between the two Labeobarbus species (0.054 ± 0.030 and 0.037 ± 0.016 mg/kg dw) compared to L. umbratus (1.92 ± 0.83 mg/kg dw) and showed a positive correlation with Cu levels (63.7 ± 17.0; 70.3 ± 9.0 and 1300 ± 823 mg/kg dw), possibly due to similar chemical affinities to metallothioneins. The detected Ag levels can serve as a basis to monitor the development of this new pollutant in aquatic environments in South Africa and worldwide.

The nanotechnology among US: are metal and metal oxides nanoparticles a nano or mega risk for soil microbial communities?

Metal nanoparticles and metal oxides nanoparticles (MNPs/MONPs) have been widely included in a great diversity of products and industrial applications and they are already a part of our everyday life. According to estimation studies, their production is expected to increase exponentially in the next few years. Consequently, soil has been suggested as the main sink of MNPs/MONPs once they are deliberately or accidentally released into the environment. The potential negative perturbations that may result on soil microbial communities and ecological processes are resulting in concerns. Several nano-toxicological studies of MNPs/MONPs, reported so far, have focused on aquatic organisms, animals, and soil invertebrates. However, during recent years, the studies have been oriented to understand the effects of MNPs/MONPs on microbial communities and their interaction with soil components. The studies have suggested that MNPs/MONPs are one of the most toxic type to soil biota, amongst different types of nanomaterials. This may threaten soil health and fertility, since microbial communities are known to support important biological processes and ecosystem services such as the nutrient cycling, whereby their protection against the environmental pollution is imperative. Therefore, in this review we summarize the actual knowledge available from the last five years (2013-2018) and gaps about the potential negative, positive or neutral effects produced on soil by different classes of MNPs/MONPs. A particular emphasis has been placed on the associated soil microorganisms and biological processes. Finally, perspectives about future research are discussed.