► Suspension-feeding by mussels can greatly alter mobility and fate of metal oxide nanoparticles. ► Bioprocessing of metal oxide nanoparticles by mussels removes large fraction from water column. ► ...Mussels repackage metal oxide nanoparticles in highly concentrated pseudofeces. ► Novel biological pathway between major compartments in marine systems. ► Very different outcome for ZnO and CeO2 nanoparticles based on their solubility.
A growing body of evidence indicates that some engineered nanoparticles (ENPs) are toxic to organisms that perform important ecosystem services in terrestrial and aquatic ecosystems. However, toxicity can be influenced by the biotransformation of contaminants, including ENPs, as it may alter the fate and transport of these substances. In turn, fate and transport can influence their bioavailability. To understand how biotransformation influences the fate and transport of ENPs in marine ecosystems, we exposed suspension-feeding mussels, Mytilus galloprovincialis, to two common nano-metal oxides, CeO2 and ZnO, over a range of concentrations from 1mgL−1 to 10mgL−1, in a laboratory experiment. Mussels exposed to 10mgL−1 accumulated 62μgg−1 of Ce and 880μgg−1 of Zn on a dry tissue basis but rejected 21,000μgg−1 for Ce and 63,000μgg−1 for Zn in pseudofeces. Scanning electron microscope evidence indicates CeO2 remained as ENPs but ZnO did not after being rejected by the mussels. Mussels filtered most of the CeO2 from the aqueous media, while a significant fraction of Zn remained in solution. Differences in ENP solubility affect ENP uptake, excretion, and accumulation in mussels. Our study highlights the potential role of marine suspension feeders in biotransformation of ENPs.
The unique or enhanced properties of manufactured nanomaterials (MNs) suggest that their use in nanoenabled products will continue to increase. This will result in increased potential for human and ...environmental exposure to MNs during manufacturing, use, and disposal of nanoenabled products. Scientifically based risk assessment for MNs necessitates the development of reproducible, standardized hazard testing methods such as those provided by the Organisation of Economic Cooperation and Development (OECD). Currently, there is no comprehensive guidance on how best to address testing issues specific to MN particulate, fibrous, or colloidal properties. This paper summarizes the findings from an expert workshop convened to develop a guidance document that addresses the difficulties encountered when testing MNs using OECD aquatic and sediment test guidelines. Critical components were identified by workshop participants that require specific guidance for MN testing: preparation of dispersions, dose metrics, the importance and challenges associated with maintaining and monitoring exposure levels, and the need for reliable methods to quantify MNs in complex media. To facilitate a scientific advance in the consistency of nanoecotoxicology test results, we identify and discuss critical considerations where expert consensus recommendations were and were not achieved and provide specific research recommendations to resolve issues for which consensus was not reached. This process will enable the development of prescriptive testing guidance for MNs. Critically, we highlight the need to quantify and properly interpret and express exposure during the bioassays used to determine hazard values.
Nanomedicine utilizes the remarkable properties of nanomaterials for the diagnosis, treatment, and prevention of disease. Many of these nanomaterials have been shown to have robust antioxidative ...properties, potentially functioning as strong scavengers of reactive oxygen species. Conversely, several nanomaterials have also been shown to promote the generation of reactive oxygen species, which may precipitate the onset of oxidative stress, a state that is thought to contribute to the development of a variety of adverse conditions. As such, the impacts of nanomaterials on biological entities are often associated with and influenced by their specific redox properties. In this review, we overview several classes of nanomaterials that have been or projected to be used across a wide range of biomedical applications, with discussion focusing on their unique redox properties. Nanomaterials examined include iron, cerium, and titanium metal oxide nanoparticles, gold, silver, and selenium nanoparticles, and various nanoscale carbon allotropes such as graphene, carbon nanotubes, fullerenes, and their derivatives/variations. Principal topics of discussion include the chemical mechanisms by which the nanomaterials directly interact with biological entities and the biological cascades that are thus indirectly impacted. Selected case studies highlighting the redox properties of nanomaterials and how they affect biological responses are used to exemplify the biologically-relevant redox mechanisms for each of the described nanomaterials.
Nanomedicine utilizes the remarkable properties of nanomaterials for the diagnosis, treatment, and prevention of disease.
Information on the toxicity of environmentally relevant concentrations of nanoparticles in marine ecosystems is needed for informed regulation of these emerging materials. We tested the effects of ...two types of metal oxide nanoparticles, TiO2 and ZnO, on population growth rates of four species of marine phytoplankton representing three major coastal groups (diatoms, chlorophytes, and prymnesiophytes). These metal oxide nanoparticles (NPs) are becoming common components in many industrial, household, and cosmetic products that are released into coastal ecosystems. Titania NPs showed no measurable effect on growth rates of any species, while ZnO NPs significantly depressed growth rate of all four species. ZnO NPs aggregated rapidly in seawater, forming particles >400 nm hydrodynamic diameter within 30 min, and dissolved quickly, reaching equilibrium concentrations within 12 h. Toxicity of ZnO NPs to phytoplankton was likely due to dissolution, release, and uptake of free zinc ions, but specific nanoparticulate effects may be difficult to disentangle from effects due to free zinc ions. A modeling approach based on a Dynamic Energy Budget (DEB) framework was used to estimate sublethal effects of the two NPs on phytoplankton populations. Concentrations that were estimated to have no effect on population growth (NEC) were (one standard error in parentheses) 428 (58) μg L−1 ZnO for the diatom Skeletonema marinoi and 223 (56) μg L−1 for Thalassiosira pseudonana. NEC could not be estimated for the other taxa but were within the range of 500−1000 μg L−1. Our results suggest that effects of metal oxide NPs on marine organisms is likely to vary with particle type and organism taxonomy.
Background/MethodsIncreased use and sales of e-cigarettes raises concerns about the potential environmental impacts throughout their life-cycle. However, few available research studies focus on the ...environmental impacts and ecotoxicity of e-cigarettes. In this study, we short-list e-liquid chemicals from published literature that should be considered in future environmental impact and risk assessments. We used a combination of available laboratory bioassays-based data and predictive methods (eg, Structure-Activity Relationships) to characterise the hazards of the e-liquid chemicals (environmental persistence, bioaccumulation, and aquatic toxicity including hazardous concentration values (concentration affecting specific proportion of species)) for short-listing.ResultsOf the 421 unique e-liquid chemicals compiled from literature, 35 are US Environmental Protection Agency’s hazardous constituents, 42 are US Food and Drug Administration’s harmful or potentially harmful constituents in tobacco products and smoke, and 20 are listed as both. Per hazard characteristics, we short-listed 81 chemicals that should be considered for future environmental impact and risk assessments, including tobacco-specific compounds (eg, nicotine, N'-nitrosonornicotine), polycyclic aromatic hydrocarbons (eg, chrysene), flavours (eg, (-)caryophyllene oxide), metals (eg, lead), phthalates (eg, di(2-ethylhexyl)phthalate) and flame retardants (eg, tris(4-methylphenyl)phosphate).ImplicationsOur findings documenting various hazardous chemicals in the e-liquids underscore the importance of awareness and education when handling or disposing of e-liquids/e-cigarettes and aim to inform strategies to prevent and reduce hazards from e-cigarettes. This includes any scenario where e-liquids can come into contact with people or the environment during e-liquid storage, manufacturing, use, and disposal practices. Overall, our study characterises the environmental hazards of e-liquid chemicals and provides regulators and researchers a readily available list for future ecological and health risk assessments.
The increased use and incorporation of engineered nanoparticles (ENPs) in consumer products requires a robust assessment of their potential environmental implications. However, a lack of standardized ...methods for nanotoxicity testing has yielded results that are sometimes contradictory. Standard ecotoxicity assays may work appropriately for some ENPs with minimal modification but produce artifactual results for others. Therefore, understanding the robustness of assays for a range of ENPs is critical. In this study, we evaluated the performance of a standard Caenorhabditis elegans (C. elegans) toxicity assay containing an Escherichia coli (E. coli) food supply with silicon, polystyrene, and gold ENPs with different charged coatings and sizes. Of all the ENPs tested, only those with a positively charged coating caused growth inhibition. However, the positively charged ENPs were observed to heteroagglomerate with E. coli cells, suggesting that the ENPs impacted the ability of nematodes to feed, leading to a false positive toxic effect on C. elegans growth and reproduction. When the ENPs were tested in two alternate C. elegans assays that did not contain E. coli, we found greatly reduced toxicity of ENPs. This study illustrates a key unexpected artifact that may occur during nanotoxicity assays.
•ZnO nanoparticles dissolve within days while CuO and NiO nanoparticles take months.•ZnO and CuO nanoparticles are toxic to amphipods at similar concentrations.•NiO nanoparticles are not toxic to ...amphipods up to 2000μgg−1.•Metal concentration in amphipods increased with nanoparticle exposure, making trophic transfer possible.•ZnO toxicity is due mainly to dissolved Zn while CuO toxicity is due to particulate CuO.
Estuarine and marine sediments are a probable end point for many engineered nanoparticles (ENPs) due to enhanced aggregation and sedimentation in marine waters, as well as uptake and deposition by suspension-feeding organisms on the seafloor. Benthic infaunal organisms living in sediments encounter relatively high concentrations of pollutants and may also suffer toxic effects of ENPs. We tested whether three heavily used metal oxide ENPs, zinc oxide (ZnO), copper oxide (CuO), and nickel oxide (NiO) were toxic to an estuarine amphipod, Leptocheirus plumulosus. We used results from 10-day laboratory bioassays to estimate potential demographic impacts of ENP exposure. We also evaluated fate and transport pathways of the ENPs in the experiments to elucidate routes of uptake and exposure. Dissolved Zn was found in sediment pore water and overlying water samples at 10 fold the concentrations of Cu or Ni, a pattern indicative of the relatively high dissolution rate of ZnO ENPs compared with CuO and NiO ENPs. Accumulation of metals in amphipod tissues increased with exposure concentrations for all three ENPs, suggesting possible exposure pathways to higher taxa. Amphipods accumulated ≤600μg Zn and Cug−1 and 1000μgNig−1. Amphipod mortality increased with ZnO and CuO concentrations, but showed no significant increase with NiO to concentrations as high as 2000μgg−1. The median lethal concentration in sediment (LC50) of ZnO was 763μgg−1 and 868μgg−1 for CuO ENPs. Our results indicate that ZnO and CuO ENPs, but not NiO ENPs, are toxic to L. plumulosus and that ZnO toxicity primarily results from Zn ion exposure while CuO toxicity is due to nanoparticle exposure.
Bivalves are hypothesized to be key organisms in the fate and transport of engineered nanomaterials (ENMs) in aquatic environments due to their ability to filter and concentrate particles from water, ...but how different exposure pathways influence their interactions with ENMs is not well understood. In a five-week experiment, we tested how interactions between CeO2 ENMs and a marine mussel, Mytilus galloprovincialis, are affected through two exposure methods, direct and through sorption to phytoplankton. We found that phytoplankton sorbed ENMs in <1 h. The exposure methods used did not result in significantly different mussel tissue or pseudofeces Ce concentrations. Approximately 99% of CeO2 was captured and excreted in pseudofeces and average pseudofeces mass doubled in response to CeO2 exposure. Final mean dry tissue Ce concentration (±SE) for treatments exposed to 3 mg L–1 CeO2 directly was 33 ± 9 μg g–1 Ce, and 0 ± 0, 19 ± 4, 21 ± 3, and 28 ± 5 μg g–1 for treatments exposed to 0, 1, 2, and 3 mg L–1 CeO2 sorbed to phytoplankton. Clearance rates increased with CeO2 concentration but decreased over time in groups exposed to CeO2 directly, indicating stress. These results show the feedback between ENM toxicity and transport and the likelihood of biological mediation in the fate and transport of ENMs in aquatic environments.
•Water suspended pristine MWCNT were efficiently degraded in an electrochemical reactor.•Up to 99% of the initially suspended carbon mass completely mineralized.•The residual solid particles are ...mostly amorphous carbon.•A major reduction in the effluent water toxicity as tested with C. Elegans.
As the production mass of multiwall carbon nanotubes (MWCNT) increases, the potential for human and environmental exposure to MWCNTs may also increase. We have shown that exposing an aqueous suspension of pristine MWCNTs to an intense oxidative treatment in an electrochemical reactor, equipped with an efficient hydroxyl radical generating Boron Doped Diamond (BDD) anode, leads to their almost complete mineralization. Thermal optical transmittance analysis showed a total carbon mass loss of over two orders of magnitude due to the electrochemical treatment, a result consistent with measurements of the degraded MWCNT suspensions using UV–vis absorbance. Liquid chromatography data excludes substantial accumulation of the low molecular weight reaction products. Therefore, up to 99% of the initially suspended MWCNT mass is completely mineralized into gaseous products such as CO2 and volatile organic carbon. Scanning electron microscopy (SEM) images show sporadic opaque carbon clusters suggesting the remaining nanotubes are transformed into structure-less carbon during their electrochemical mineralization. Environmental toxicity of pristine and degraded MWCNTs was assessed using Caenorhabditis elegans nematodes and revealed a major reduction in the MWCNT toxicity after treatment in the electrochemical flow-by reactor.
Analytical techniques capable of determining the spatial distribution and quantity (mass and/or particle number) of engineered nanomaterials in organisms are essential for characterizing nano-bio ...interactions and for nanomaterial risk assessments. Here, we combine the use of dynamic secondary ion mass spectrometry (dynamic SIMS) and single particle inductively coupled mass spectrometry (spICP-MS) techniques to determine the biodistribution and quantity of gold nanoparticles (AuNPs) ingested by Caenorhabditis elegans. We report the application of SIMS in image depth profiling mode for visualizing, identifying, and characterizing the biodistribution of AuNPs ingested by nematodes in both the lateral and z (depth) dimensions. In parallel, conventional- and sp-ICP-MS quantified the mean number of AuNPs within the nematode, ranging from 2 to 36 NPs depending on the size of AuNP. The complementary data from both SIMS image depth profiling and spICP-MS provides a complete view of the uptake, translocation, and size distribution of ingested NPs within Caenorhabditis elegans.
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•SIMS rapidly displays biodistribution of nanomaterials in C. elegans.•Ingested AuNPs located in pharynx and intestinal tract.•spICP-MS determined the number and size distribution of bioaccumulated AuNPs.•Taken together, the data better inform nanomaterial risk assessment.
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