A nanogold sensor test for tire wear chemicals based on the plasmon ruler approach.

The release of tire wear substances in the environment is raising concerns about potential impacts on aquatic ecosystems. The purpose of this study was to develop a quick and inexpensive screening test for the following tire wear substances: 6-phenylphenyldiamine quinone (6-PPD quinone), hexamethoxymethylmelamine (HMMM), 1-3-diphenylguanidine (1,3-DPG), and melamine. A dual strategy consisting of nanogold (nAu) signal intensity and the plasmonic ruler principle was used based on the spectral shift from the unaggregated free-form nAu from 525 nm to aggregated nAu at higher wavelengths. The shift in resonance corresponded to the relative sizes of the tire wear substances at the surface of nAu: 6-PPD (560 nm), HMMM (590 nm), 1,3-DPG (620 nm), and melamine (660 nm) in a concentration-dependent manner. When present in mixtures, a large indiscriminate band between 550 and 660 nm with a maximum corresponding to the mean intermolecular distance of 0.43 nm from the tested individual substances suggests that all compounds indiscriminately interacted at the surface of nAu. An internal calibration methodology was developed for mixtures and biological extracts from mussels and biofilms and revealed a proportional increase in absorbance at the corresponding resonance line for each test compound. Application of this simple and quick methodology revealed the increased presence of melamine and HMMM compounds in mussels and biofilms collected at urban sites (downstream city, road runoffs), respectively. The data also showed that treated municipal effluent decreased somewhat melamine levels in mussels.

Assessment of the toxicity of a mixture of five rare earth elements found in aquatic ecosystems in Hydra vulgaris.

Rare earth elements (REEs) are considered critical elements for technology and their extraction through mining activities is expected to increase in the future. Due to their chemical similarities, they often co-occur in minerals and thus their ecotoxicity should be assessed as a group/family. However, the available ecotoxicological studies focused mainly on the evaluation of the potential toxicological impacts of individual REEs rather than their mixtures. The aim of this study was therefore to evaluate the toxicity of a representative mixture of five REEs (La, Ce, Pr, Nd and Sm) spanning environmentally relevant concentrations ranging from 0.05X (29 µg REEs L-1) to 5X (2926 µg REEs L-1) to the test organism, Hydra vulgaris, at the morphological, reproductive and regenerative levels. The data showed that lethality occurred at concentrations near (2.5 fold) to those inducing sublethal effects after chronic exposure of 7 days. The mixture affected reproduction and head regeneration and even lethality at concentrations even below those reported at environmental concentration (0.5X = 293 µg REEs L-1) in lakes. This suggests that REEs concentrations found in lakes near mining activities could disrupt regeneration and impair embryonic development. Our data also revealed that combining the 5 REEs results in an antagonistic effect, suggesting that those elements share the same receptor and that low molecular weight and high radius elements (approaching iron) were less toxic. Taken together, hydra could be used as a sensitive model organism for the assessment of aquatic ecotoxicological risks of REE mixtures but further analyses of biochemical and gene expressions should improve our understanding of the long-term effects of REEs mixtures.

Evaluation of general stress, detoxification pathways, and genotoxicity in rainbow trout exposed to rare earth elements dysprosium and lutetium.

Rare earth elements (REEs) have been recently identified as emergent contaminants because of their numerous and increasing applications in technology. The impact of REEs on downstream ecosystems, notably aquatic organisms, is of particular concern, but has to date been largely overlooked. The purpose of this study was thus to evaluate the toxicity of lanthanide metals, lutetium (Lu) and dysprosium (Dy) in rainbow trout after 96 h of exposure. The lethal concentration (LC50) was determined and the expression of 14 genes involved in different pathways such as oxidative stress, xenobiotic detoxification, mitochondrial respiration, DNA repair, protein folding and turnover, inflammation, calcium binding and ammonia metabolism were quantified in surviving fish. In parallel, lipid peroxidation (LPO), DNA damage (DSB), metallothionein level (MT) and cyclooxygenase activity (COX) were examined. The acute 96 h-LC50 data revealed that Lu was more toxic than Dy (1.9 and 11.0 mg/L, respectively) and was able to affect all investigated pathways by changing the expression of the studied genes, to the exception of superoxide dismutase (SOD), catalase (CAT) and glutathione-S-transferase (GST). It also induced a decrease in DNA repair at concentrations 29 times below the LC50. This suggests that Lu could trigger a general stress to disrupt the cell homeostasis leading to genotoxicity without promoting oxidative stress. However, Dy induced modulation in the expression of genes involved in the protection against oxidative stress, detoxification, mitochondrial respiration, immunomodulation, protein turnover and an increase in the DNA strand breaks at concentrations 170 times lower than LC50. Changes in mRNA level transcripts could represent an early signal to prevent against toxicity of Dy, which exhibited inflammatory and genotoxic effects. This study thus provides useful knowledge enhancing our understanding of survival strategies developed by rainbow trout to cope with the presence of lanthanides in the environment.

Response of the freshwater mussel, Dreissena polymorpha to sub-lethal concentrations of samarium and yttrium after chronic exposure.

Samarium (Sm) and yttrium (Y) are commonly used rare earth elements (REEs) but there is a scarcity of information concerning their biological effects in non-target aquatic organisms. The purpose of this study was to determine the bioavailability of those REEs and their toxicity on Dreissena polymorpha after exposure to increasing concentration of Sm and Y for 28 days at 15 °C. At the end of the exposure period, the gene expression of superoxide dismutase (SOD), catalase (CAT), metallothionein (MT), glutathione-S-transferase (GST), cytochrome c oxidase 1 (CO1) and cyclin D (Cyc D) were analysed. In addition, we examined lipid peroxidation (LPO), DNA strand breaks (DSB), GST and prostaglandin cyclooxygenase (COX) activities. Results showed a concentration dependent increase in the level of the REEs accumulated in the soft tissue of mussels. Both REEs decreased CAT but did not significantly modulated SOD and MT expressions. Furthermore, Sm3+ up-regulated GST, CO1 and Cyc D, while Y3+ increased and decreased GST and CO1 transcripts levels, respectively. Biomarker activities showed no oxidative damage as evidenced by LPO, while COX activity was decreased and DNA strand breaks levels were changed suggesting that Sm and Y exhibit anti-inflammatory and genotoxic effects. Factorial analysis revealed that the major impacted biomarkers by Sm were LPO, CAT, CO1 and COX, while GST gene expression, COX, Cyc D and CAT as the major biomarkers affected by Y. We conclude that these REEs display different mode of action but further investigations are required in order to define the exact mechanism involved in their toxicity.

Ecotoxicity responses of the freshwater cnidarian Hydra attenuata to 11 rare earth elements.

Lanthanides are the major family of rare earth elements (REEs) owing to the essential properties these metallic species provide in diverse fields of today's world economy. They are now being mined and produced as never before. This raises new environmental concerns in terms of their expected future discharges notably to aquatic systems. Interspecies studies of their ecotoxicity are sparse and effects on aquatic life are still poorly understood. Absence of such information for cnidarians, an ecologically relevant freshwater community, thus prompted the present research on REEs toxicity using Hydra attenuata as our animal model. Lethal and sublethal ecotoxicity data generated with the 11 REEs displayed LC50 values ranging from 0.21 to 0.77 mg L-1and EC50 values ranging from 0.02 to 0.27 mg L-1, thereby confirming the inherent sensitivity of Hydra to REE exposure at environmentally relevant concentrations. Additionally, two properties of REEs were shown to modulate Hydra (sub)lethal toxicity (LC50 and EC50) which decreases with increasing atomic number and with decreasing ionic radius. Compared to studies carried out with different taxonomic groups, Hydra toxicity responses to REEs proved to be among the most sensitive, along with those of other invertebrate species (i.e., Daphnia magna, Ceriodaphnia dubia, Hyalella azteca), suggesting that members of this community are likely more at risk to eventual REE discharges in aquatic environments. Demonstrated Hydra sensitivity to REE exposure strongly justifies their future use in toxicity testing battery approaches to evaluate liquid samples suspected of harbouring REEs.

In vitro immunotoxicology of quantum dots and comparison with dissolved cadmium and tellurium.

The increasing use of products derived from nanotechnology has raised concerns about their potential toxicity, especially at the immunocompetence level in organisms. This study compared the immunotoxicity of cadmium sulfate/cadmium telluride (CdS/Cd-Te) mixture quantum dots (QDs) and their dissolved components, cadmium chloride (CdCl2 )/sodium telluride (NaTeO3 ) salts, and a CdCl2 /NaTeO3 mixture on four animal models commonly used in risk assessment studies: one bivalve (Mytilus edulis), one fish (Oncorhynchus mykiss), and two mammals (mice and humans). Our results of viability and phagocytosis biomarkers revealed that QDs were more toxic than dissolved metals for blue mussels. For other species, dissolved metals (Cd, Te, and Cd-Te mixture) were more toxic than the nanoparticles (NPs). The most sensitive species toward QDs, according to innate immune cells, was humans (inhibitory concentration [IC50 ] = 217 µg/mL). However, for adaptative immunity, lymphoblastic transformation in mice was decreased for small QD concentrations (EC50 = 4 µg/mL), and was more sensitive than other model species tested. Discriminant function analysis revealed that blue mussel hemocytes were able to discriminate the toxicity of QDs, Cd, Te, and Cd-Te mixture (Partial Wilk's λ = 0.021 and p < 0.0001). For rainbow trout and human cells, the immunotoxic effects of QDs were similar to those obtained with the dissolved fraction of Cd and Te mixture. For mice, the toxicity of QDs markedly differed from those observed with Cd, Te, and dissolved Cd-Te mixture. The results also suggest that aquatic species responded more differently than vertebrates to these compounds. The results lead to the recommendation that mussels and mice were most able to discriminate the effects of Cd-based NPs from the effects of dissolved Cd and Te at the immunocompetence level.

Effects of a major municipal effluent on the St. Lawrence River: A case study.

The St. Lawrence River (SLR) is the second largest waterway in North America. The discharge of the City of Montreal wastewater treatment plant (WWTP) represents the largest volume of treated wastewaters being released into the river. It also ranks as the largest sewage treatment plant of its kind in North America. Over the last decade, intensive multidisciplinary research has focused on assessing the impacts of Montreal wastewater effluents on the SLR. We describe the major findings of these investigations, including the determination of the fate of contaminants, bioaccumulation in fish and invertebrates, ecotoxicological measurements of aquatic animal health, evaluation of endocrine disruption, parasitism in fish, and combined effects of multiple stressors on the SLR. Impacts of the effluents from the WWTP on aquatic organisms from the SLR are both toxicological and ecological, demonstrating the need for an integrated view of the impacts of municipal effluents on aquatic ecosystems.

Responses of freshwater mussel (Elliptio complanata) hemocytes exposed in vitro to crude extracts of Microcystis aeruginosa and Lyngbya wollei.

Lyngbya wollei is a benthic filamentous cyanobacterium that produces a toxin analogous to the neurotoxic saxitoxin known as lyngbyatoxin (LYNGTX). Microcystis aeruginosa form blooms in the pelagic area of eutrophic lakes and produce a series of potent hepatotoxins-microcystins (MCYST). The aim of this study in vitro study was to examine the difference between the crude extracts of either M. aeruginosa or L. wollei toward the immune system of Elliptio complanata mussels. Freshly isolated hemolymph was plated and exposed to the crude extract of each species at LYNGTX or MCYST equivalent concentrations of 5, 10 and 25 µg/L for 18 h. Immunocompetence was characterized by following changes in hemocyte numbers, metabolic activity (viability), and phagocytosis. Hemocyte counts were not affected, indicating no turnover of hemocytes. Hemocyte metabolic activity was higher in cells exposed to crude extracts of L. wollei. Exposure to L. wollei extracts led to decreased pro-inflammatory precursors such as reactive oxygen species (ROS) and cyclooxygenase (COX) activities. Phagocytosis increased at 25 µg/L for both types of crude extracts. However, hemocytes exposed to crude extracts of M. aeruginosa produced more ROS and COX compared to hemocytes exposed to crude extracts of L. wollei. In conclusion, the data suggest that the crude extract of M. aeruginosa was more toxic than crude extract of L. wollei to mussel hemocytes.

Immunotoxic effects of an industrial waste incineration site on groundwater in rainbow trout (Oncorhynchus mykiss).

The discharge of organic waste from the petrochemical industry into the Mercier lagoons caused major groundwater contamination. The objective of this study was to determine the immunotoxic potential of three groundwater wells at increasing distance from the incinerator dumping site (1.17, 2.74 and 5.40 km). Rainbow Trout were exposed to increasing concentrations of water from three groundwater wells for 14 days. Immunocompetence was characterized by phagocytosis, mitogen-stimulated proliferation of lymphocytes, cell cycle analysis and apoptosis. A significant increase in innate (phagocytosis) and specific immune response (B lymphocyte proliferation) was observed in trout exposed to water collected from the well at 2.74 km. However, phagocytosis activity was suppressed in groups at 1.17 and 5.40 km. The proportion of lymphocytes in S phase was significantly increased in groups at 2.74 and 5.40 km, while lymphocytes in G0/G1 phase were decreased in all three exposure groups. Additionally, dexamethasone (DEX)-induced apoptosis of lymphocytes was significantly reduced in the group at 2.74 km, which suggests decreased lymphocyte turnover. Furthermore, the ratio of DEX-induced apoptosis/apoptosis was lower in the groups at 2.74 and 5.40 km. In summary, our experiments have shown that exposure to the mixture of organic compounds present in Mercier groundwater modulates phagocytosis and cell proliferation, disrupts the cell cycle and reduces the ratio of DEX-induced apoptosis/apoptosis. It is concluded that groundwater collected in the vicinity of an incinerator containment field could impact immunocompetence in fish.

Plastic Analysis with a Plasmonic Nano-Gold Sensor Coated with Plastic-Binding Peptides.

Contamination with plastics of small dimensions (<1 µm) represents a health concern for many terrestrial and aquatic organisms. This study examined the use of plastic-binding peptides as a coating probe to detect various types of plastic using a plasmon nano-gold sensor. Plastic-binding peptides were selected for polyethylene (PE), polyethylene terephthalate (PET), polypropylene (PP), and polystyrene (PS) based on the reported literature. Using nAu with each of these peptides to test the target plastics revealed high signal, at 525/630 nm, suggesting that the target plastic limited HCl-induced nAu aggregation. Testing with other plastics revealed some lack of specificity but the signal was always lower than that of the target plastic. This suggests that these peptides, although reacting mainly with their target plastic, show partial reactivity with the other target plastics. By using a multiple regression model, the relative levels of a given plastic could be corrected by the presence of other plastics. This approach was tested in freshwater mussels caged for 3 months at sites suspected to release plastic materials: in rainfall overflow discharges, downstream a largely populated city, and in a municipal effluent dispersion plume. The data revealed that the digestive glands of the mussels contained higher levels of PP, PE, and PET plastic particles at the rainfall overflow and downstream city sites compared to the treated municipal effluent site. This corroborated earlier findings that wastewater treatment could remove nanoparticles, at least in part. A quick and inexpensive screening test for plastic nanoparticles in biological samples with plasmonic nAu-peptides is proposed.

Nanoplastic Contamination in Freshwater Biofilms Using Gel Permeation Chromatography and Plasmonic Nanogold Sensor Approaches.

The worldwide contamination of aquatic ecosystems by plastics is raising concern, including their potential impacts on the base of the food chain, which has been poorly documented. This study sought to examine, for the first time, the presence of nanoplastics (NPs) in biofilms from freshwater streams/rivers. They were collected at selected polluted sites, such as the industrial sector for plastic recycling and production, miscellaneous industries, agriculture, municipal wastewaters/effluents and road runoffs. In parallel, the functional properties of sampled biofilms were determined by proteins, lipids, esterase (lipase), viscosity and oxidative stress. The results revealed that biofilms collected at the plastic industries and road runoffs contained the highest NP levels based on size exclusion chromatography, fluorescence detection and a new nanogold sensor visualization method. Examination of the chromatographic elution profiles showed increased abundance and size of NPs in the 10-150 nm size range at the polluted sites. Biofilms from the plastic industry site had elevated levels of aldehydes (oxidative stress) and lipids compared to the other sites. Biofilms collected at the municipal sites had elevated levels of proteins and esterases/lipases, with a decrease in total lipids. Biofilms collected at agriculture sites had the lowest levels of NPs in this campaign, but more samples would be needed to confirm these trends. In conclusion, biofilms represent an important sink for plastics in freshwater environments and display signs of distress upon oxidative stress.

Toxicity of two heavy rare earth elements to freshwater mussels Dreissena polymorpha.

Rare earth elements (REE) are essential components of many electronic devices that could end-up in solid waste disposal sites and inadvertently released in the environment. The purpose of this study was to examine the toxicity of two heavy REEs, erbium (Er) and lutetium (Lu), in freshwater mussels Dreissena polymorpha. Mussels were exposed to 14 days to increasing concentration (10, 50, 250, and 1250 µg/L) of either Er and Lu at 15 °C and analyzed for gene expression in catalase (CAT), superoxide dismutase (SOD), metallothionein (MT), cytochrome c oxidase (CO1), and cyclin D for cell cycle. In addition, lipid peroxidation (LPO), DNA damage (DNAd), and arachidonate cyclooxygenase were also determined. The data revealed that mussels accumulated Er and Lu similarly and both REEs induced changes in mitochondrial COI activity. Er increased cell division, MT, and LPO, while Lu increased DNAd and decreased cell division. Tissue levels of Er were related to changes in MT (r = 0.7), LPO (r = 0.42), CO1 (r = 0.69), and CycD (r = 0.31). Lu tissue levels were related to changes in CO1 (r = 0.73), CycD (r = - 0.61), CAT (r = 0.31), DNAd (r = 0.43), and SOD (r = 0.34). Although the lethal threshold was similar between Er and Lu, the threshold response for LPO revealed that Er produced toxicity at concentrations 25 times lower than Lu suggesting that Er was more harmful than Lu in mussels. In conclusions, the data supports that the toxicity pattern differed between Er and Lu although they are accumulated in the same fashion.

Burrowing in the freshwater mussel Elliptio complanata is sexually dimorphic and feminized by low levels of atrazine.

The widely used herbicide atrazine (ATR) may have endocrine-associated adverse effects, including on behavior. In this study, 120 adult freshwater mussels, Elliptio complanata, were exposed to ATR at the environmentally relevant concentrations of 1.5, 15, or 150 µg/L. Burrowing depth was evaluated hourly for 6 h and at sacrifice animals were sexed by gonad smear. Female controls burrowed overall approximately 30% less than males, the first report of sexual dimorphism in this behavior. Atrazine at 15 µg/L feminized burrowing in both sexes, in that exposed animals burrowed 20% less than their same-sex controls. Males treated with 1.5 µg /L ATR displayed approximately 20-fold higher vitellogenin (VTG) levels than same-sex controls. Higher concentrations of ATR were not associated with increasing effects. A scatterplot showed a weak binomial curve associating low burrowing with high VTG levels. Taken together, these data suggest a nonlinear dose response in behavioral and physiological feminization produced by ATR and support the need to reconsider the widespread use of this compound.

Temporal and seasonal variation in acetylcholinesterase activity and glutathione-S-transferase in amphipods collected in mats of Lyngbya wollei in the St-Lawrence River (Canada).

Mats of filamentous algae Lyngbya wollei cover large areas on top of the sediments along the St-Lawrence River. Like most cyanobacteria, L. wollei produce toxins, named lyngbyatoxin (LYNGTX), an analog of saxitoxin. In order to verify the neurotoxic potential of these filamentous cyanobacteria, we collected amphipods within local vegetation at three sites in summer months: a site rich in L. wollei (Lake St-Louis [LSL]) and two urban sites composed of macrophytes but devoid of L. wollei mats (Richelieu River [RICH] and L'Assomption River [ASSO] outlets). The body weight of each amphipod was measured, and the neurotoxicity was estimated with the measurement of acetylcholinesterase (AChE) and glutathione-s-transferase (GST) activities. Levels of protein-bound phosphates were also evaluated, to rule out contamination by Microcystis sp. The results showed that the activity of acetylcholinesterase measured in amphipods in ASSO and RICH was lower than the activity found in amphipods collected in L. wollei mats in LSL. In addition, amphipods found in L. wollei mats at the LSL site have significantly higher GST activity than those located at the two devoid sites, RICH and ASSO. No significant change was observed for protein-bound phosphate levels. This study suggests that the presence of L. wollei triggers potential toxicity.

Energy status and immune system alterations in Elliptio complanata after ingestion of cyanobacteria Anabaena flos-aquae.

Cyanobacteria have often been described as nutritionally poor for herbivorous organisms. To gain additional information on the potential impacts of invertebrates feeding on cyanobacteria, we fed Elliptio complanata mussels with two types of algae: Anabaena flos-aquae (cyanobacteria) and Pseudokirchneriella subcapitata (green algae). Physiological parameters were examined at the energy status, immune system and oxidative stress levels. Energy status was examined by following the rate of electron transport activity in mitochondria (a measure of cellular energy expense) and lipid/sugar stores in the visceral mass. The cyanobacteria were not actively producing toxins. Based on the digestive gland index, the mussels fed equally on either regime. However, the energy status in mussels fed A. flos-aquae revealed that the total sugar was lower in the digestive gland, whereas mitochondrial electron transport activity (MET), once corrected against the digestive gland somatic index, showed increased energy expenses. Acetylcholinesterase activity and lipid peroxidation (LPO) were also higher in mussels fed with A. flos-aquae compared with mussels fed with P. subcapitata. LPO was correlated by mitochondrial activity in both the digestive gland and gills, suggesting that oxidative stress resulted from metabolic respiration. Immunocompetence (phagocytic activity, natural killer cell-like activity, haemocyte count and viability) and humoral level of lysozyme were not affected in mussels by the algae or cyanobacteria regime. Moreover, the xenobiotic conjugating enzyme, glutathione S-transferase, hemoprotein oxidase and vitellogenin-like proteins were not affected in mussel organs via ingestion of A. flos-aquae. Our study suggests that ingestion of cyanobacteria leads to increased energy expenses, oxidative stress and increased acetylcholine turnover in mussels.

In vitro immunotoxicity of untreated and treated urban wastewaters using various treatment processes to rainbow trout leucocytes.

Municipal effluents are known to impede the immune system of aquatic organisms. The purpose of this study was to examine the immunotoxicity of urban wastewaters before and after 6 treatment processes from 12 cities toward trout leucocytes. Freshly prepared trout leucocytes were exposed to increasing concentrations of solid phase (C18) extracts of wastewaters for 24 hr at 150C. Immunocompetence was determined by following changes in leucocyte viability and the proportion of cells able to ingest at least one (immunoactivity) and at least three (immunoefficiency) fluorescent beads. The influents were treated by six different treatment strategies consisting of facultative aerated lagoons, activated sludge, biological aerated filter, biological nutrient removal, chemically-assisted physical treatment and trickling filter/solid contact. Water quality parameters of the wastewaters revealed that the plants effectively removed total suspended solids and reduced the chemical oxygen demand. The results revealed that the effluents' immunotoxic properties were generally more influenced by the properties of the untreated wastewaters than by the treatment processes. About half of the incoming influents decreased leucocyte viability while 4 treatment plants were able to reduce toxicity. The influents readily increased phagocytosis activity for 8/12 influents while it was decreased in 4/12 influents. This increase was abolished for 4/12 of the effluents using treatments involving biological and oxidative processes. In conclusion, municipal effluents have the potential to alter the immune system in fish and more research will be needed to improve the treatments of wastewaters to better protect the quality of the aquatic environment.

Micro and Nanoplastic Contamination and Its Effects on Freshwater Mussels Caged in an Urban Area.

Plastic-based contamination has become a major cause of concern as it pervades many environments such as air, water, sediments, and soils. This study sought to examine the presence of microplastics (MPs) and nanoplastics (NPs) in freshwater mussels placed at rainfall/street runoff overflows, downstream (15 km) of the city centre of Montréal, and 8 km downstream of a municipal effluent dispersion plume. MPs and NPs were determined using flow cytometry and size exclusion chromatography using fluorescence detection. Following 3 months of exposure during the summer season, mussels contained elevated amounts of both MPs and NPs. The rainfall overflow and downstream of the city centre were the most contaminated sites. Lipid peroxidation, metallothioneins, and protein aggregates (amyloids) were significantly increased at the most contaminated sites and were significantly correlated with NPs in tissues. Based on the levels of MPs and NPs in mussels exposed to municipal effluent, wastewater treatment plants appear to mitigate plastic contamination albeit not completely. In conclusion, the data support the hypothesis that mussels placed in urbanized areas are more contaminated by plastics, which are associated with oxidative damage. The highest responses observed at the overflow site suggest that tire wear and/or asphalt (road) erosion MPs/NPs represent important sources of contamination for the aquatic biota.

Investigation on the Toxicity of Nanoparticle Mixture in Rainbow Trout Juveniles.

The environmental impacts of nanoparticle mixtures in the aquatic environment is not well understood. The purpose of this study examined the sub-lethal toxicity of low concentrations (ug/L range) of selected nanoparticles alone and in mixtures in juvenile trout. Fish were exposed to to individual and two environmentally relevant mixtures of silver (nAg), copper oxide (nCuO) and cerium oxide (nCeO) nanoparticles for 96 h at 15 °C. After the exposure period, fish were depurated overnight and tissue levels in Ag, Ce, Cu and Zn were determined along with a suite of effects biomarkers such as oxidative stress/inflammation, denatured protein tagging (ubiquitin), DNA strand breaks (genotoxicity) and acetylcholinesterase (AChE) activity. The data showed that these nanoparticles behaved as suspended matter but were nevertheless bioavailable for fish with bioconcentration factors of 6, 8 and 2 for nAg, nCeO and nCuO respectively. Only nCuO alone increased malonaldehyde (lipid peroxidation) contents but all nanoparticles increased DNA damage, protein-ubiquitin labeling, and decreased AChE activity. Globally, the toxicity of nCeO and nCuO was generally stronger than nAg, and antagonist effects were found in the mixtures. The interactions involved in these antagonisms are not well understood but do not involve the liberation of free ions and labile zinc in tissues. In conclusion, the bioavailability and toxicity of these nanoparticles are influenced by mixtures of nanoparticles, which is likely to occur in contaminated environments.

Comparative toxicity of micro and nanopolystyrene particles in Mya arenaria clams.

The contamination of coastal marine environments by plastics of sizes ranging from mm down to the nanoscale (nm) could pose a threat to aquatic organisms. The purpose of this study was to examine the toxicity of polystyrene nanoparticles (PsNP) of various sizes (50, 100 and 1000 nm) to the marine clams Mya arenaria. Clams were exposed to concentrations of PsPP for 7 days at 15 °C and analyzed for uptake/transformation, changes in energy metabolism, oxidative stress, genotoxicity and circadian neural activity. The results revealed that PsNP accumulated in the digestive gland was 50 nm > 100 nm > 1000 nm. All sized increased oxidative stress as follows: 50 nm (peroxidase, antioxidant potential and LPO), 100 nm (LPO and antioxidant potential) and 1000 nm (LPO). Tissue damage was also size dependent by increasing genotoxicity. The 100 nm PsPP altered the levels of the circadian metabolite melatonin. We conclude that the toxicity of plastics is size dependent in clams.

Form-Dependent Toxicity of Silver Nanomaterials in Rainbow Trout Gills.

The toxicity of the form of nanoparticles is presently not well understood. The purpose of this study consists in comparing the toxicity of various forms of silver nanoparticles (nAg) in juvenile rainbow trout Oncorhynchus mykiss. Juveniles were exposed to various forms of polyvinyl-coated nAg of similar size for 96 h at 15 °C. After the exposure period, the gills were isolated and analyzed for Ag uptake/distribution, oxidative stress, glucose metabolism, and genotoxicity. Higher levels of Ag were detected in gills in fish exposed to dissolved Ag followed by spherical, cubic, and prismatic nAg. Size-exclusion chromatography of gill fractions revealed that the dissolution of nAg was observed for all forms of nAg where prismatic nAg released more important levels of Ag in the protein pool as in fish exposed to dissolved Ag as well. The aggregation of nAg was more important for cubic nAg in respect of the other forms of nAg. The data revealed that lipid peroxidation was closely associated with protein aggregation and viscosity. Biomarkers revealed changes in lipid/oxidative stress and genotoxicity, which were related to the loss of protein aggregation and inflammation (NO2 levels), respectively. In general, the observed effects were found for all forms of nAg where the effects from prismatic nAg were generally higher than for spherical and cubic nAg. The strong relationship between genotoxicity and inflammation response suggests the participation of the immune system in the observed responses of juvenile fish gills.