The mechanisms of nickel toxicity in aquatic environments: An adverse outcome pathway analysis

High-throughput transcriptomics: Insights into the pathways involved in (nano) nickel toxicity in a key invertebrate test species

Nickel nanoparticles (NiNPs) have an estimated production of ca. 20 tons per year in the US. Nickel has been risk-assessed for long in Europe, but not NiNPs, hence the concern for the environment. In the present study, we focused on investigating the mechanisms of toxicity of NiNPs and the comparison to NiNO₃. The high-throughput microarray for the soil ecotox model Enchytraeus crypticus (Oligochaeta) was used. To anchor gene to phenotype effect level, organisms were exposed to reproduction effect concentrations EC20 and EC50, for 3 and 7 days. Results showed commonly affected pathways between NiNPs and NiNO₃, including increase in proteolysis, apoptosis and inflammatory response, and interference with the nervous system. Mechanisms unique to NiNO₃ were also observed (e.g. glutathione synthesis). No specific mechanisms for NiNPs were found, which could indicate that longer exposure period (>7 days) is required to capture the peak response to NiNPs. A mechanisms scheme is assembled, showing both common and unique mechanisms to NiNO₃ and NiNPs, providing an important framework for further, more targeted, studies.

Nickel toxicity in wood frog tadpoles: Bioaccumulation and sublethal effects on body condition, food consumption, activity, and chemosensory function

Nickel (Ni) concentrations in aquatic ecosystems can be amplified by anthropogenic activities including resource extraction. Compared with fish and invertebrates, knowledge of Ni toxicity in amphibians is limited, especially for northern species. We examined the effect of Ni on wood frog (Lithobates sylvaticus) tadpoles, the species with the widest and most northern distribution of any anuran in North America. Wood frog tadpoles were exposed to a Ni concentration gradient (0.02-5.5 mg/L of Ni at 164 mg/L as CaCO₃ water hardness) for 8 d and examined for lethality, Ni bioaccumulation, and several sublethal endpoints including body condition, food consumption, activity, and chemosensory function. Nickel induced a sublethal effect on body condition (8-d 10 and 20% effect concentrations [EC10 and EC20] of 1.07 ± 0.38 and 2.44 ± 0.51 mg/L of Ni ± standard error [SE], respectively) but not on food consumption, activity, or chemosensory function. Nickel accumulation in tadpole tissues was positively related to an increase in aqueous Ni concentration but was not lethal. Both the acute and chronic US Environmental Protection Agency water quality guideline concentrations for Ni (0.71 and 0.08 mg/L at 164 mg/L as CaCO₃ water hardness, respectively) were protective against lethal and sublethal effects in wood frog tadpoles. In the present study, wood frog tadpoles were protected by current water quality guidelines for Ni and are likely not as useful as other taxa for environmental effects monitoring for this particular metal. Environ Toxicol Chem 2018;37:2458-2466. © 2018 SETAC.

Heavy metals in Yinma River sediment in a major Phaeozems zone, Northeast China: Distribution, chemical fraction, contamination assessment and source apportionment

Yinma River is a typical river in the major Phaeozems zone of Northeast China. It has been suffering an increasing environmental pressure from heavy metal contamination due to the rapid development of population, social-economy and urbanization as well as long term over cultivation. This study investigated the spatial distribution, chemical fraction of heavy metals (Cu, Pb, Zn, Cr, Cd, Ni, As, and Hg) in sediments of Yinma River based on BCR procedure, assessed the contamination level, and identified their sources via multivariate statistical analysis. The chemical fraction results indicated that Cd, Pb, Ni, and Zn exhibited higher mobility susceptibility and bioavailability with a significant and late anthropogenic origin. Hg and Cd might exert a potential hazardous influence on aquatic biota according to the geo-accumulation index (I_geo). The pollution load index (PLI) assessment suggested that all of the sediment samples have been contaminated. Multivariate statistical analysis revealed that Zn, Cu, Hg, Cd, and Pb reflected the anthropogenic sources with a close correlation with TOC and socio-economic development; Ni, As and Cr tended to represent the geochemical background. Furthermore, Changchun City and Shitoukoumen Reservoir as the major drinking water source may be hotspots of the heavy metal contamination in the watershed.

Nickel toxicity in P. lividus embryos: Dose dependent effects and gene expression analysis

Many industrial activities release Nickel (Ni) in the environment with harmful effects for terrestrial and marine organisms. Despite many studies on the mechanisms of Ni toxicity are available, the understanding about its toxic effects on marine organisms is more limited. We used Paracentrotus lividus as a model to analyze the effects on the stress pathways in embryos continuously exposed to different Ni doses, ranging from 0.03 to 0.5 mM. We deeply examined the altered embryonic morphologies at 24 and 48 h after Ni exposure. Some different phenotypes have been classified, showing alterations at the expenses of the dorso-ventral axis as well as the skeleton and/or the pigment cells. At the lowest dose used, Ni mainly induced a multi-spicule phenotype observed at 24 h after treatment. On the contrary, at the highest dose of Ni (0.5 mM), 90% of embryos showed no skeleton and no pigment cells. Therefore, we focused on this dose to study protein and gene expression patterns at 24 and 48 h after exposure. Among the proteins analyzed, i.e. p38MAPK, Grp78 and Mn-SOD, only p38MAPK was induced by Ni treatment. Moreover, we analyzed the mRNA profiles of a pool of genes that are involved in stress response and in development mechanisms, i.e. the transcription factors Pl-NFkB and Pl-FOXO; a marker of DNA repair, Pl-XPB/ERCC3; a mitogen-activated protein kinase (MAPK), Pl-p38; an ER stress gene, Pl-grp78; an adapter protein, Pl-14-3-3ε; two markers of pigment cells, Pl-PKS1 and Pl-gcm. The spatial expression of mesenchymal marker genes has been evaluated in Ni-treated embryos at both 24 and 48 h after exposure. Our results indicated that Ni acts at several levels in P. lividus sea urchin, by affecting embryo development, influencing the embryonic immune response and activating stress response pathways to counteract the suffered injury and to promote embryos surviving.

30 Years of Lithium-Ion Batteries

Over the past 30 years, significant commercial and academic progress has been made on Li-based battery technologies. From the early Li-metal anode iterations to the current commercial Li-ion batteries (LIBs), the story of the Li-based battery is full of breakthroughs and back tracing steps. This review will discuss the main roles of material science in the development of LIBs. As LIB research progresses and the materials of interest change, different emphases on the different subdisciplines of material science are placed. Early works on LIBs focus more on solid state physics whereas near the end of the 20th century, researchers began to focus more on the morphological aspects (surface coating, porosity, size, and shape) of electrode materials. While it is easy to point out which specific cathode and anode materials are currently good candidates for the next-generation of batteries, it is difficult to explain exactly why those are chosen. In this review, for the reader a complete developmental story of LIB should be clearly drawn, along with an explanation of the reasons responsible for the various technological shifts. The review will end with a statement of caution for the current modern battery research along with a brief discussion on beyond lithium-ion battery chemistries.

A framework for ecological risk assessment of metal mixtures in aquatic systems

Although metal mixture toxicity has been studied relatively intensely, there is no general consensus yet on how to incorporate metal mixture toxicity into aquatic risk assessment. We combined existing data on chronic metal mixture toxicity at the species level with species sensitivity distribution (SSD)-based in silico metal mixture risk predictions at the community level for mixtures of Ni, Zn, Cu, Cd, and Pb, to develop a tiered risk assessment scheme for metal mixtures in freshwater. Generally, independent action (IA) predicts chronic metal mixture toxicity at the species level most accurately, whereas concentration addition (CA) is the most conservative model. Mixture effects are noninteractive in 69% (IA) and 44% (CA) and antagonistic in 15% (IA) and 51% (CA) of the experiments, whereas synergisms are only observed in 15% (IA) and 5% (CA) of the experiments. At low effect sizes (∼ 10% mixture effect), CA overestimates metal mixture toxicity at the species level by 1.2-fold (i.e., the mixture interaction factor [MIF]; median). Species, metal presence, or number of metals does not significantly affect the MIF. To predict metal mixture risk at the community level, bioavailability-normalization procedures were combined with CA or IA using SSD techniques in 4 different methods, which were compared using environmental monitoring data of a European river basin (the Dommel, The Netherlands). We found that the simplest method, in which CA is directly applied to the SSD (CA_SSD ), is also the most conservative method. The CA_SSD has median margins of safety (MoS) of 1.1 and 1.2 respectively for binary mixtures compared with the theoretically more consistent methods of applying CA or IA to the dose-response curve of each species individually prior to estimating the fraction of affected species (CA_DRC or IA_DRC ). The MoS increases linearly with an increasing number of metals, up to 1.4 and 1.7 for quinary mixtures (median) compared with CA_DRC and IA_DRC , respectively. When our methods were applied to a geochemical baseline database (Forum of European Geological Surveys [FOREGS]), we found that CA_SSD yielded a considerable number of mixture risk predictions, even when metals were at background levels (8% of the water samples). In contrast, metal mixture risks predicted with the theoretically more consistent methods (e.g., IA_DRC ) were very limited under natural background metal concentrations (<1% of the water samples). Based on the combined evidence of chronic mixture toxicity predictions at the species level and evidence of in silico risk predictions at the community level, a tiered risk assessment scheme for evaluating metal mixture risks is presented, with CA_SSD functioning as a first, simple conservative tier. The more complex, but theoretically more consistent and most accurate method, IA_DRC , can be used in higher tier assessments. Alternatively, the conservatism of CA_SSD can be accounted for deterministically by incorporating the MoS and MIF in the scheme. Finally, specific guidance is also given related to specific issues, such as how to deal with nondetect data and complex mixtures that include so-called data-poor metals. Environ Toxicol Chem 2018;37:623-642. © 2017 SETAC.

Defence mechanisms: the role of physiology in current and future environmental protection paradigms

Ecological risk assessments principally rely on simplified metrics of organismal sensitivity that do not consider mechanism or biological traits. As such, they are unable to adequately extrapolate from standard laboratory tests to real-world settings, and largely fail to account for the diversity of organisms and environmental variables that occur in natural environments. However, an understanding of how stressors influence organism health can compensate for these limitations. Mechanistic knowledge can be used to account for species differences in basal biological function and variability in environmental factors, including spatial and temporal changes in the chemical, physical and biological milieu. Consequently, physiological understanding of biological function, and how this is altered by stressor exposure, can facilitate proactive, predictive risk assessment. In this perspective article, existing frameworks that utilize physiological knowledge (e.g. biotic ligand models, adverse outcomes pathways and mechanistic effect models), are outlined, and specific examples of how mechanistic understanding has been used to predict risk are highlighted. Future research approaches and data needs for extending the incorporation of physiological information into ecological risk assessments are discussed. Although the review focuses on chemical toxicants in aquatic systems, physical and biological stressors and terrestrial environments are also briefly considered.

Characterization of the effects of binary metal mixtures on short-term uptake of Cd, Pb, and Zn by rainbow trout (Oncorhynchus mykiss)

Biotic Ligand Models (BLMs) for individual metals improve our ability to regulate metals in the aquatic environment by considering the effects of water quality parameters (ionic composition, pH, DOC) on metal bioavailability. However, in natural aquatic systems, organisms are often simultaneously exposed to multiple metals and these interactions are not currently considered in BLMs or most environmental regulations. Recently, several different mixture BLMs (mBLMs) have been developed to begin assessing this issue. Some of these models assume competitive interactions between all metals, while others assume only metals with similar modes of action (e.g., Na⁺ or Ca²⁺ antagonists) will competitively interact. In this study, we used standard in vivo 3-h gill metal binding assays to characterize the uptake of Cd, Pb, and Zn individually and in binary mixtures with Ag, Cd, Cu, Pb, Ni, and Zn across a range of concentrations that encompassed the 96-h LC50 for each metal. Inhibition of Cd, Pb, and Zn uptake at the gill by introduction of a second metal was consistent with mode of action in some cases, but not others. Further, contrary to expectations, inhibition was always either non-competitive or could not be defined statistically. We also observed one example of stimulated metal uptake (Ni stimulated Zn uptake). Consistent with our previous experiments on Ag, Cu, and Ni, these studies suggest that current mBLM frameworks will need revision to better reflect the mechanisms underlying metal mixture interactions.

Systematic Evaluation of Chronic Metal-Mixture Toxicity to Three Species and Implications for Risk Assessment

Metal contamination generally occurs as mixtures. However, it is yet unresolved how to address metal mixtures in risk assessment. Therefore, using consistent methodologies, we have set up experiments to identify which mixture model applies best at low-level effects, i.e., the independent action (IA) or concentration addition (CA) reference model. The toxicity of metal mixtures (Ni, Zn, Cu, Cd, and Pb) to Daphnia magna, Ceriodaphnia dubia, and Hordeum vulgare was investigated in different waters or soils, totaling 30 different experiments. Some mixtures of different metals, each individually causing <10% inhibition, yielded much larger inhibition (up to 66%) when dosed in combination. In general, IA was most accurate in predicting mixture toxicity, while CA was the most conservative. At low-effect levels important in risk assessments, CA overestimated mixture toxicity to daphnids and H. vulgare, on average, with a factor 1.4 to 3.6. Observed mixture interactions could be related to bioavailability or by competition interactions, either for binding sites of dissolved organic carbon or for biotic ligand sites. Our study suggests that the current metal-by-metal approach in risk evaluations may not be conservative enough for metal mixtures.