Short-term molecular-level effects of silver nanoparticle exposure on the earthworm, Eisenia fetida

Combined toxicity of Cd and 2,4-dichlorophenoxyacetic acid on the earthworm Eisenia andrei under biochar amendment

Due to anthropogenic activities, various pollutants can be found in agricultural soil, such as cadmium (Cd) and 2,4-dichlorophenoxyacetic acid (2,4-D). They are highly toxic and can have a negative impact on soil fertility. For remediation strategies, biochar has acquired considerable attention due to its benefits for agriculture. However, we should recognize the ecological risk posed by biochar use. In addition, little is known about its non-desirable effects on soil organisms such as earthworms, especially in the case of soil remediation. In this study, earthworms (Eisenia andrei) were exposed to soil contaminated with Cd (0.7 mg/kg), (2,4-D) (7 mg/kg), and a mixture of the two in the presence and absence of biochar (2%). A 7- and 14-day incubation experiment was carried out for this purpose. Cd and 2,4-D uptakes in earthworms' tissues, oxidative stress, cytotoxic response, DNA damage, histopathological changes, and gene expression level were assessed. Results suggested that biochar increased the bioavailability of Cd and 2,4-D and the frequency of micronuclei (MNi) and decreased the lysosomal membrane stability (LMS) in earthworms. Also, histopathological examination detected numerous alterations in animals exposed to the contaminants without any amelioration when biochar was added. The biochemical response of earthworms in terms of oxidative stress demonstrates that in the presence of biochar, animals tend to alleviate the toxicity of Cd and 2,4-D. This was also supported by transcriptomic analyses where expression gene levels related to oxidative stress were upregulated in earthworms exposed to Cd and 2,4-D + biochar. The present investigation brought new insights concerning the use of biochar in agriculture.

Soil properties influence the toxicity and availability of Zn from ZnO nanoparticles to earthworms

To develop models that support site-specific risk assessment for nanoparticles (NPs), a better understanding of how NP transformation processes, bioavailability and toxicity are influenced by soil properties is needed. In this study, the influence of differing soil properties on the bioavailability and toxicity of zinc oxide (ZnO) NPs and ionic Zn to the earthworm Eisenia fetida was investigated. Earthworms were exposed to ZnO_NPs and ionic Zn, between 100 and 4400 mg Zn/kg, in four different natural soils (organic matter content: 1.8-16.7%, soil pH: 5.4-8.3, representing sandy loam to calcareous soils). Survival and reproduction were assessed after 28 and 56 days, respectively. Zn concentrations in soil pore waters were measured while labile concentrations of Zn were measured using an in-situ dynamic speciation technique (diffusive gradient in thin films, DGT). Earthworm Zn tissue concentrations were also measured. Soil properties influenced earthworm reproduction between soil controls, with highest reproductive output in soils with pH values of 6-7. Toxicity was also influenced by soil properties, with EC₅₀s based on total Zn in soil ranging from 694 to >2200 mg Zn/kg for ZnO_NP and 277-734 mg Zn/kg for ionic Zn. Soil pore water and DGT measurements showed good agreement in the relative amount of Zn extracted across the four soils. Earthworms exposed to ZnO_NPs survived higher Zn concentrations in the soils and had higher tissue concentrations compared with ionic Zn exposures, particularly in the high organic content calcareous soil. These higher tissue concentrations in ZnO_NP exposed earthworm could have consequences for the persistence and trophic mobility of Zn in terrestrial systems and need to be further investigated to elucidate if there any longer-term risks associated with sustained input of ZnO_NP to soil.

Preliminary investigation on the impact of engineered PVP-capped and uncapped silver nanoparticles on Eudrilus eugeniae, a terrestrial ecosystem model

Recently, the production of silver nanoparticles and their commercial products has generated increased concern and caused a hazardous impact on the ecosystem. Therefore, the present study examines the toxic effect of chemically engineered silver nanoparticles (SNPs) and polyvinylpyrrolidone-capped silver nanoparticles (PVP-SNPs) on the earthworm Eudrilus eugeniae (E. eugeniae). The SNPs and PVP-SNPs were synthesized, and their characterization was determined by UV-vis spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and transmission electron microscopy. The toxicity of SNPs and PVP-SNPs was evaluated using E. eugeniae. The present result indicates that the lethal concentration (LC₅₀) of SNPs and PVP-SNPs were achieved at 22.66 and 43.27 μg/mL, respectively. The activity of antioxidant enzymes including superoxide dismutase (SOD) and catalase (CAT) was increased in SNPs compared to PVP-SNPs. Importantly, we have noticed that the E. eugeniae can amputate its body segments after exposure to SNPs and PVP-SNPs. This exciting phenomenon is named "autotomy," which describes a specific feature of E. eugeniae to escape from the toxic contaminants and predators. Accordingly, we have suggested this unique behavior may facilitate to assess the toxic effect of SNPs and PVP-SNPs in E. eugeniae.

nZVI-induced iron poisoning aggravated the toxicity of TCEP to earthworm in soil

Tris (2-chloroethyl) phosphate (TCEP) is a newly developed organophosphorus flame retardant that has been increasingly detected in soil as a contaminant. Nanoremediation is a potential solution for the control of TCEP, while the effectiveness and ecological risks are poorly understood. Here, we investigated the physicochemical interactions and joint toxicity of nano zero-valent iron (nZVI) (50-5000 mg/kg) and TCEP (50-5000 μg/kg) at environmental relevant concentrations to earthworms (Eisenia fetida) in soil. During a 28-d exposure, TCEP in soil was neither self-degraded nor removed by nZVI, and the individual toxicity of TCEP on the physiology of earthworms was significantly higher than that of nZVI. Notably, nZVI was found to synergize the toxicity of TCEP to earthworms without showing the classical "Trojan horse effect". Mechanically, TCEP mainly induced a typical neurotoxicity, and indirectly inhibited the food ingestion and growth performance of earthworms; nZVI induced iron poisoning aggravated the intestinal damage and directly inhibited the energy metabolism, therefore exacerbated the TCEP-induced malnutrition. Our findings provide new insights into the toxic mechanisms of nZVI-TCEP co-exposure to soil organisms, and emphasize the necessity of risk assessment and cautious usage of nanoremediation in newly emerged contaminations.

Effects of silver sulfide nanoparticles on the earthworm Eisenia andrei

The massive production and use of silver nanoparticles (Ag NPs) have led to their increasing release into the environment. Even though the antimicrobial and cytotoxic effects of native nanoparticles have been well studied, the environmental impacts of transformation products such as silver sulfide nanoparticles (Ag₂S NPs) have not been elucidated. In the present study, we assessed the toxicity of Ag₂S NPs and silver nitrate (AgNO₃), as a source of Ag, to the earthworm Eisenia andrei using a nominal concentration of 5 mg Ag kg^-1 soil. We used the OECD guidelines to assess effects on weight loss and mortality for 14 days. After exposure, we also extracted the immune effector cells (coelomocytes) and conducted a battery of biomarker tests. To ensure the quality of the toxicological results, the structural changes of NPs during the experiment and the uptake of silver by the earthworms were monitored. During the experiment, mortality effects were not detected, but a weight loss was observed in the earthworms exposed to Ag₂S NPs. Altough Ag₂S NPs were engulfed by E. andrei cells, neither phenoloxidase activity nor lipid peroxidation differed from the untreated control group. Cells from earthworms treated with Ag₂S NPs exerted very broad value range of nitric oxide (NO) generation, suggesting an imbalance in the NO metabolism. Overall, this study suggests minimal risks associated with Ag₂S NPs exposure to earthworms. However, further studies are needed to assure no immunotoxicological or chronic effects on a wider range of terrestrial organisms.

Assessing the bioavailability and biotoxicity of spiromesifen and its main metabolite spiromesifen-enol (M01) reveals the defense mechanisms of earthworms (Eisenia fetida)

As a promising acaricide and potentially hazardous material, the defense mechanisms of non-target organisms to its exposure are unknown. This study investigates the bioavailability and biotoxicity of spiromesifen and spiromesifen-enol (M01), its main metabolite, in Eisenia fetida. The results showed that M01 was more persistent in the soil environment and E. fetida than spiromesifen. Transcriptome analysis indicated that the spiromesifen- and M01-induced differentially expressed genes (DEGs) were mainly enriched in lysosomal and phagosomal pathways. Analysis of the key common DEGs showed that both spiromesifen and M01 significantly influenced the lysosomes, phagosomes, antioxidant systems, and detoxification systems. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed that spiromesifen and M01 damaged E. fetida epidermis and enhanced lysosomal and phagosomal activities. Significant oxidative stress effects were observed at the end of exposure. The hydroxyl free radical (·OH^-) content and neutral red retention time (NRRT) could serve as sensitive early biomarkers to predict their pollution. These results revealed the synergistic effects of the epidermis, lysosomes, phagosomes, antioxidant systems, and detoxification system in resisting spiromesifen- and M01-induced damage, which could contribute to the defense mechanisms of non-target organisms against these pollutants.

Interactive effects of environmental microplastics and 2,4-dichlorophenoxyacetic acid (2,4-D) on the earthworm Eisenia andrei

Given the wide use of plastic and pesticides in agriculture, microplastics (MP) and the herbicide 2,4 dichloro-phenoxy-acetic acid (2-4-D) can be present simultaneously in soil. Nevertheless, little is known about their combined toxicity. In this study, Eisenia andrei was exposed to environmental MP (100 µg kg^-1 soil) and 2,4-D (7 mg kg^-1 soil) for 7 and 14 days. Bioaccumulation, genotoxicity, oxidative stress and gene expression level were assessed. Results revealed that MP increased 2,4-D bioaccumulation in earthworms. Simultaneous exposure to both these pollutants caused a significant reduction in lysosomal membrane stability (LMS) and an increase in micronuclei (MNi) frequency. Biochemical analysis revealed oxidative alterations in earthworms exposed to all treatments; being very pronounced in earthworms exposed to the mixture in terms of increase in glutathione-S-Transferase (GST), catalase (CAT) and malondialdehydes accumulation (MDA). Furthermore, an up-regulation in cat and gst expression level was recorded in worms exposed to single or mixture treatment, except MP in case of gst. Our data highlight the toxicity of the combined exposure to MP and 2,4-D and afford new insights into the potential ecological risks posed by MP in terrestrial ecosystems.

A critical review of the environmental impacts of manufactured nano-objects on earthworm species

The presence of manufactured nano-objects (MNOs) in various consumer or their (future large-scale) use as nanoagrochemical have increased with the rapid development of nanotechnology and therefore, concerns associated with its possible ecotoxicological effects are also arising. MNOs are releasing along the product life cycle, consequently accumulating in soils and other environmental matrices, and potentially leading to adverse effects on soil biota and their associated processes. Earthworms, of the group of Oligochaetes, are an ecologically significant group of organisms and play an important role in soil remediation, as well as acting as a potential vector for trophic transfer of MNOs through the food chain. This review presents a comprehensive and critical overview of toxic effects of MNOs on earthworms in soil system. We reviewed pathways of MNOs in agriculture soil environment with its expected production, release, and bioaccumulation. Furthermore, we thoroughly examined scientific literature from last ten years and critically evaluated the potential ecotoxicity of 16 different metal oxide or carbon-based MNO types. Various adverse effects on the different earthworm life stages have been reported, including reduction in growth rate, changes in biochemical and molecular markers, reproduction and survival rate. Importantly, this literature review reveals the scarcity of long-term toxicological data needed to actually characterize MNOs risks, as well as an understanding of mechanisms causing toxicity to earthworm species. This review sheds light on this knowledge gap as investigating bio-nano interplay in soil environment improves our major understanding for safer applications of MNOs in the agriculture environment.

Are long-term exposure studies needed? Short-term toxicokinetic model predicts the uptake of metal nanoparticles in earthworms after nine months

Uptake of most metal nanoparticles (NPs) in organisms is assumed to be mainly driven by the bioavailability of the released ions, as has been verified in controlled and short-term exposure tests. However, the changeability of NPs and the dynamic processes which NPs undergo in the soil environment, bring uncertainty regarding their interactions with soil organisms over a long period of time. To assess the potential impacts of long-term exposure scenarios on the toxicokinetic of metal NPs, earthworms Eisenia fetida were exposed to soils spiked with pristine Ag-NP, aged Ag-NP (Ag₂S-NP) and ionic Ag for nine months, and results were compared to those from a similar short-term (28 days) experiment, conducted under similar conditions. Overall, there were no statistical differences between long-term accumulation patterns in earthworms exposed to pristine Ag-NP and AgNO₃, while for Ag₂S-NP, the amount of Ag internalized after 9 months was five times lower than for the other treatments. Average Ag concentrations in soil pore water in all treatments did not change over time, however the soil pH decreased and electrical conductivity increased in all treatments. Metallothionein concentrations in exposed earthworms were not statistically different from levels in untreated earthworms. Finally, the short-term toxicokinetic models predicted the bioaccumulation in earthworms exposed to Ag-NP, AgNO₃ after nine months on the whole. Although the bioaccumulation for Ag₂S-NPs was somewhat under-predicted, the rate of accumulation of Ag₂S-NPs is much lower than that of Ag-NPs or AgNO₃ and thus potentially of lower concern. Nevertheless, better understanding about the exposure kinetics of Ag₂S-NP would help to address potential nano-specific toxicokinetic and toxicodynamics, also of other sulfidized metal NPs.

Bio-interaction of nano and bulk lanthanum and ytterbium oxides in soil system: Biochemical, genetic, and histopathological effects on Eisenia fetida

The massive application of rare earth elements (REEs) in electronic industries cause their inevitable release into the environment; however, its effects on soil biota remain largely unaddressed. We investigated the E. fetida detoxification potential of nano and bulk La₂O₃ and Yb₂O₃ and their potential impact on biochemical and genetic markers at 50, 100, 200, 500 and 1000 mg kg^-1 concentration. We found that earthworms bioremediate 3-15% La₂O₃ and Yb₂O₃ contaminated soil at low and medium levels, while this potential was limited at higher levels. Nano and bulk La₂O₃ and Yb₂O₃ treatment induced neurotoxicity in earthworm by inhibiting acetylcholinesterase by 49-65% and 22-36% at 500 and 1000 mg kg^-1, respectively. Nano La₂O₃ proved to be highly detrimental, mainly through oxidative stress and subsequent failure of antioxidant system. Nano La₂O₃ and Yb₂O₃ at 100 mg kg^-1 significantly down-regulated the expression of annetocin mRNA in the parental and progeny earthworms by 50% and 20%, which is crucial for earthworm reproduction. Similarly, expression level of heat shock protein 70 (HSP70) and metallothionein was significantly upregulated in both generations at medium exposure level. Histological observations showed that nano REEs at 200 mg kg^-1 induced drastic changes in the intestinal epithelium and typhlosole of E. fetida. To date, our results enhance the understanding of interaction between REEs and earthworms.

Microplastic fibers influence Ag toxicity and bioaccumulation in Eisenia andrei but not in Enchytraeus crypticus

Microplastic fibers (MF) are released from synthetic textiles during washing and end up in the wastewater. Similarly, silver nanoparticles (AgNP), incorporated in textiles as antimicrobial agents, are released in washing machines, also reaching the wastewater treatment plants. Therefore, both MF and AgNP co-exist in the environment and enter the soil compartment mainly via the application of biosolids. Yet, the combined effect of MF and AgNP has not been studied. Here, we assessed the effects of polyester MF on the toxicity of AgNP and AgNO₃ to the earthworm Eisenia andrei and the enchytraeid Enchytraeus crypticus. The organisms were exposed to a range of concentration of AgNP (32, 100, 320, 1000, 3200 mg Ag/kg) and AgNO₃ (12.8, 32, 80, 200, 500 mg Ag/kg) in LUFA 2.2 soil in the absence or presence of MF (0.01% DW). Reproduction tests were conducted and the toxicity outcomes compared between soils with and without MF. The exposure to MF caused a decrease in the number of juveniles and changed the biochemical composition of earthworms. Moreover, the presence of MF increased the toxicity of AgNP to earthworm reproduction (EC50 = 165 mg Ag/kg) when compared to AgNP exposure alone (EC50 = 450 mg Ag/kg), but did not alter the toxicity of AgNO₃ (EC50 = 40 mg Ag/kg). For enchytraeids, no significant difference in Ag toxicity could be detected when MF was added to the soil for both AgNP and AgNO₃. Overall, Ag bioaccumulation was not affected by MF, except for a decrease in earthworm body concentration at the highest Ag soil concentration (3200 mg Ag/kg). Our results suggest that the presence of MF in the soil compartment may be a cause of concern, and that the joint exposure to Ag may be deleterious depending on the Ag form, organism, and endpoint. The present work provides the first evidence that a realistic MF concentration in soil lowers AgNP concentration necessary to provoke reproductive impairment in earthworms. The influence of MF on the risk assessment of AgNP should be considered.

FEAST of biosensors: Food, environmental and agricultural sensing technologies (FEAST) in North America

We review the challenges and opportunities for biosensor research in North America aimed to accelerate translational research. We call for platform approaches based on: i) tools that can support interoperability between food, environment and agriculture, ii) open-source tools for analytics, iii) algorithms used for data and information arbitrage, and iv) use-inspired sensor design. We summarize select mobile devices and phone-based biosensors that couple analytical systems with biosensors for improving decision support. Over 100 biosensors developed by labs in North America were analyzed, including lab-based and portable devices. The results of this literature review show that nearly one quarter of the manuscripts focused on fundamental platform development or material characterization. Among the biosensors analyzed for food (post-harvest) or environmental applications, most devices were based on optical transduction (whether a lab assay or portable device). Most biosensors for agricultural applications were based on electrochemical transduction and few utilized a mobile platform. Presently, the FEAST of biosensors has produced a wealth of opportunity but faces a famine of actionable information without a platform for analytics.

Embryotoxicity of silver nanomaterials (Ag NM300k) in the soil invertebrate Enchytraeus crypticus - Functional assay detects Ca channels shutdown

Despite that silver (Ag) is among the most studied nanomaterials (NM) in environmental species and Ag's embryotoxicity is well known, there are no studies on Ag NMs embryotoxicity in soil invertebrates. Previous Full Life Cycle (FLC) studies in Enchytraeus crypticus, a standard soil invertebrate, showed that Ag materials decreased hatching success, which was confirmed to be a hatching delay effect for silver nitrate (AgNO₃) and mortality for Ag NM300K. In the present study, we aimed to investigate if the impact of Ag takes place during the embryonic development, using histology and immunohistochemistry. E. crypticus cocoons were exposed to a range of concentrations of Ag NM300K (0-10-20-60-115 mg Ag/kg) and AgNO₃ (0-20-45-60-96 mg Ag/kg) in LUFA 2.2 soil, in an embryotoxicity test, being sampled at days 1, 2, 3 and 6 (3, 4, 5 and 7 days after cocoon laying). Measured endpoints included the number of embryonic structures, expression of transferrin receptor (TfR) and L type calcium channels (LTCC) through histological and immunohistochemistry analysis, respectively. Results confirmed that Ag materials affected the embryonic development, specifically at the blastula stage (day 3). The expression and localization of TfR in E. crypticus was shown in the teloblasts cells, although this transcytosis mechanism was not activated. Ag affected calcium (Ca) metabolism during embryonic development: for AgNO_3, LTCC was initially activated, compensating the impact, for Ag NM300K, LTCC was not activated, hence no Ca balance, with irreversible consequences, i.e. terminated embryonic development. An Adverse Outcome Pathway was drafted, integrating the mechanisms here discovered with previous knowledge.

Impact of Intensive Farming on Soil Heavy Metal Accumulation and Biomarkers Responses of Earthworms Eisenia andrei

In this work, we propose to evaluate the effect of agriculture intensification under greenhouses on the biochemical and transcriptomic responses of the earthworms Eisenia andrei. This work was conducted on two sites in Téboulba and Sahline (Monastir governorate) and a control site in an experimental plot that is undergoing organic farming. For this purpose, the earthworms Eisenia andrei were exposed to the soils during 7 and 14 days. The physicochemical properties of the soils were analyzed. The biochemical biomarkers of metallothioneins (MTs) and malondialdehyde (MDA) accumulations were also assessed. Moreover, the gene expression level of the MTs was analyzed. The results of our study revealed a significant trace element accumulation accompanied by a high level of MDA and MT proteins. Moreover, a significant expression of the MT gene was observed in earthworms exposed to the soils from Sahline and Téboulba. Hence, this work reveals that intensive agriculture can affect the biological responses of earthworms and consequently, the soil's biofertility.

Nanomaterials and Annelid Immunity: A Comparative Survey to Reveal the Common Stress and Defense Responses of Two Sentinel Species to Nanomaterials in the Environment

Simple Summary

Nanotechnology is a dynamically developing field producing large amounts of nanocompounds that are applied in industry, daily life, and health care. During production, use, and waste these materials could end up in water or soil. Large scale contaminations of our environment are a threat to public health. Pollution can have harmful effects on the immune system, as revealed by numerous studies in humans and other vertebrates. The relative simplicity of invertebrate immune functions offers potentially sensitive and accessible means of monitoring the effects and complex interactions of nanoparticles which ultimately affect host resistance. Among terrestrial and freshwater invertebrates, earthworms and leeches are the “keystone” species to evaluate the health of our ecosystems. In this review we compare the conserved stress and immune responses of these invertebrate model organisms toward nanoparticles. The obtained knowledge provides exciting insights into the conserved molecular and cellular mechanisms of nanomaterial-related toxicity in invertebrates and vertebrates. Understanding the unique characteristics of engineered nanoproducts and their interactions with biological systems in our environment is essential to the safe realization of these materials in novel biomedical applications.

Abstract

Earthworms and leeches are sentinel animals that represent the annelid phylum within terrestrial and freshwater ecosystems, respectively. One early stress signal in these organisms is related to innate immunity, but how nanomaterials affect it is poorly characterized. In this survey, we compare the latest literature on earthworm and leeches with examples of their molecular/cellular responses to inorganic (silver nanoparticles) and organic (carbon nanotubes) nanomaterials. A special focus is placed on the role of annelid immunocytes in the evolutionarily conserved antioxidant and immune mechanisms and protein corona formation and probable endocytosis pathways involved in nanomaterial uptake. Our summary helps to realize why these environmental sentinels are beneficial to study the potential detrimental effects of nanomaterials.

Effects of Silver Nanoparticles and Ions Exposure on the Soil Invertebrates Folsomia candida and Enchytraeus crypticus

The aim of the study was to assess the effects of silver nanoparticles (AgNPs1 = 2.7 d·nm, AgNPs2 = 6.5 d·nm) and silver nitrate (AgNO₃) on Enchytraeus crypticus and Folsomia candida using toxicity tests (OECD Guideline 220, 232). A 28-day chronic toxicity study was performed to evaluate the reproduction and mortality rate. E. crypticus reproduction was more sensitive to AgNO₃ with a 28dEC₅₀ of 86.40 (62.52-119.4) mg·kg^-1 dry weight (d.w.) compared to AgNPs1 (28dEC₅₀ = 119.3 (60.4-235.6) mg·kg^-1 d.w). Similarly, the reproduction of F. candida was inhibited the most by AgNO₃ with a 28dEC₅₀ of 126.2 (104.2-152.9) mg·kg^-1 d.w. followed by AgNPs1 (28dEC₅₀ = 158.7 (64.05-393.2) mg·kg^-1 d.w.) and AgNPs2 (28dEC₅₀ = 206.4 (181.9-234.1) mg·kg^-1 d.w.). No mortalities were observed for tested soil invertebrates exposed to AgNPs at concentrations up to 166 mg·kg^-1 d.w. of AgNPs1 and 300 mg·kg^-1 d.w. of AgNPs2, respectively. It was found that silver ions are more toxic in comparison with AgNPs.

Antioxidant Enzyme Activity and Lipid Peroxidation in Aporrectodea caliginosa Earthworms Exposed to Silver Nanoparticles and Silver Nitrate in Spiked Soil

Silver nanoparticles (AgNPs) from industrial use, discharged via the land application of sewage sludge, are interacting with soil biota, including earthworms. In affected organisms, excessive production of reactive oxygen species can result in lipid peroxidation, shifting the balance between oxidants and antioxidants to cause oxidative stress. We determined selected lower-tier biomarkers such as antioxidant responses and lipid peroxidation in Aporrectodea caliginosa earthworms exposed to soils spiked with AgNPs or silver nitrate (AgNO₃ ). Aporrectodea caliginosa were exposed to AgNPs at 0 (control), 0.3, 3, 30, and 300 mg/kg or Ag⁺ (as AgNO₃ ) at 0, 0.03, 0.3, 3, and 10 mg/kg in soil for 4 wk. At 1, 2, 3, and 4 wk, the activity of the antioxidant enzymes superoxide dismutase, catalase, glutathione peroxidase, glutathione S-transferase, as well as lipid peroxidation (malondialdehyde content), increased as a function of concentration, with a much larger response for Ag⁺ than AgNPs. Given the likelihood of ever-increasing AgNP concentrations in soil, where AgNPs can transform to ionic Ag (Ag⁺ ), our findings of antioxidant response to oxidative stress in a common indicator organism even at an environmentally realistic exposure concentration of 0.03 mg/kg demonstrate that AgNPs may affect soil fertility and, thus, agricultural production. Evaluating selected lower-tier biomarkers offers a meaningful assessment of AgNPs and Ag⁺ effects on terrestrial earthworms. Environ Toxicol Chem 2020;39:1257-1266. © 2020 SETAC.

Selection of an optimal culture medium and the most responsive viability assay to assess AgNPs toxicity with primary cultures of Eisenia fetida coelomocytes

Earthworm immune cells (coelomocytes) have become a target system in ecotoxicology due to their sensitivity against a wide range of pollutants, including silver nanoparticles (AgNPs). Presently, in vitro approaches (viability assays in microplate, flow cytometry, cell sorting) with primary cultures of Eisenia fetida coelomocytes have been successfully used to test the toxicity and the dissimilar response of cell subpopulations (amoebocytes and eleocytes) after PVP-PEI coated AgNPs and AgNO₃ exposures. In order to obtain reliable data and to accurately assess toxicity with coelomocytes, first an optimal culture medium and the most responsive assay were determined. AgNPs posed a gradual decrease in coelomocytes viability, establishing the LC₅₀ value in RPMI-1640 medium at 6 mg/l and discarding that the observed cytotoxicity was attributable to its coating agent PVP-PEI. Exposure to AgNPs caused selective cytotoxicity in amoebocytes, which correlated with the Ag concentrations measured in sorted amoebocytes and reinforced the idea of dissimilar sensitivities among amoebocytes and eleocytes. Silver nano and ionic forms exerted similar toxicity in coelomocytes. The in vitro approaches with coelomocytes of E. fetida performed in this study have the capacity to predict impairments caused by pollutants at longer exposure levels and thus, provide rapid and valuable information for eco(nano)toxicology.

Genomic mutations after multigenerational exposure of Caenorhabditis elegans to pristine and sulfidized silver nanoparticles

Our previous study showed heritable reproductive toxicity in the nematode Caenorhabditis elegans after multigenerational exposure to AgNO₃ and silver nanoparticles (Ag-NPs). The aim of this study was to determine whether such inheritable effects are correlated with induced germline mutations in C. elegans. Individual C. elegans lineages were exposed for 10 generations to equitoxic concentrations at EC₃₀ of AgNO₃, Ag-NPs, and sulfidized Ag-NPs (sAg-NPs), a predominant environmentally transformed product of pristine Ag-NPs. The mutations were detected via whole genome DNA sequencing approach by comparing F₀ and F₁₀ generations. An increase in the total number of variants, though not statistically significant, was observed for all Ag treatments and the variants were mainly contributed by single nucleotide polymorphisms (SNPs). This potentially contributed towards reproductive as well as growth toxicity shown previously after ten generations of exposure in every Ag treatment. However, despite Ag-NPs and AgNO₃ inducing stronger reproductive toxicity than sAg-NPs, exposure to sAg-NPs resulted in higher mutation accumulation with significant increase in the number of transversions. Thus our results suggest that other mechanisms of inheritance, such as epigenetics, may be at play in Ag-NP- and AgNO₃-induced multigenerational and transgenerational reproductive toxicity.

Gold and silver nanoparticles effects to the earthworm Eisenia fetida - the importance of tissue over soil concentrations

To address and to compare the respective impact of gold and silver nanoparticles (Au and Ag NPs) in soil invertebrate, the earthworm Eisenia fetida was exposed to soil containing 2, 10, and 50 mg/kg of Au and Ag in both nanoparticulate and ionic forms for 10 days. Both metal NPs were 2-15 times less bioavailable than their ionic forms, and displayed similar transfer coefficients from soil to earthworm tissues. Both metal NPs triggered the onset of an oxidative stress as illustrated by increased glutathione S-transferase levels, decreased catalase levels, and increased malondialdehyde concentrations. Protein carbonylation distinguished the nanoparticular from the ionic forms as its increase was observed only after exposure to the highest concentration of both metal NPs. Au and Ag NPs triggered DNA modifications even at the lowest concentration, and both repressed the expression of genes involved in the general defense and stress response at high concentrations as did their ionic counterparts. Despite the fact that both metal NPs were less bioavailable than their ionic forms, at equivalent concentrations accumulated within earthworms tissues they exerted equal or higher toxic potential than their ionic counterparts.Capsule: At equivalent concentrations accumulated within earthworm tissues Au and Ag NPs exert equal or higher toxic potential than their ionic forms.

Effect of treated wastewater irrigation in East Central region of Tunisia (Monastir governorate) on the biochemical and transcriptomic response of earthworms Eisenia andrei

Treated wastewater (TWW) reuse for irrigation has become an excellent way to palliate water scarcity in Mediterranean arid regions. However, the toxicological effects of these effluents on the soil's organisms, especially earthworms, have not been well studied as yet. In this paper, earthworms Eisenia andrei were exposed for 7 days and 14 days to five agricultural soils irrigated with TWW for different periods: 1 year, 8 years, and 20 years. In addition, they were also exposed to soil from one reference site sampled from the Ouardenin perimeter in the Monastir Governorate in Tunisia. The effect on earthworms was assessed at the biochemical level by evaluating for catalase (CAT), glutathione-S-transferase (GST), malondialdehyde accumulation (MDA) and acetylcholinesterase inhibition (AChE). On the other hand, genotoxicity and transcriptomic responses were evaluated using micronuclei test (MNT) and gene expression level of CAT and GST. Moreover, metals uptake by earthworms was analyzed. Results showed that CAT and GST activity in the earthworm increased significantly when they were exposed to soils irrigated with TWW for 1, 8 and 20 years. Furthermore, MDA concentration also increased significantly with the increase in exposure period. However, AChE activity decreased and MNi frequency increased in earthworms after 7 and 14 days of exposure to soils irrigated with TWW for more than a year. The gene expression level of CAT and GST showed a significant variability, thus data are discussed in relation to the studied biomarkers (CAT and GST). These data provide new insights into the effect of toxicity of TWW on the soil's macro fauna, which is strongly affected by the trace elements and other organic compounds accumulated in soils after 20 years of TWW irrigation.

Biochemical and transcriptomic response of earthworms Eisenia andrei exposed to soils irrigated with treated wastewater

In order to ensure better use of treated wastewater (TWW), we investigated the effect of three increasing doses of TWW, 10%, 50%, and 100%, on biochemical and transcriptomic statuses of earthworms Eisenia andrei exposed during 7 and 14 days. The effect of TWW on the oxidative status of E. andrei was observed, but this effect was widely dependent on the dilution degree of TWW. Results showed a significant decrease in the catalase (CAT) activity and an increase in the glutathione-S-transferase (GST) activity, and considerable acetylcholinesterase (AChE) inhibition was recorded after 14 days of exposure. Moreover, malondialdehyde (MDA) accumulation was found to be higher in exposed animals compared to control worms. The gene expression level revealed a significant upregulation of target genes (CAT and GST) during experimentation. These data provided new information about the reuse of TWW and its potential toxicity on soil organisms.

Advancing the Understanding of Environmental Transformations, Bioavailability and Effects of Nanomaterials, an International US Environmental Protection Agency-UK Environmental Nanoscience Initiative Joint Program

Nanotechnology has significant economic, health, and environmental benefits, including renewable energy and innovative environmental solutions. Manufactured nanoparticles have been incorporated into new materials and products because of their novel or enhanced properties. These very same properties also have prompted concerns about the potential environmental and human health hazard and risk posed by the manufactured nanomaterials. Appropriate risk management responses require the development of models capable of predicting the environmental and human health effects of the nanomaterials. Development of predictive models has been hampered by a lack of information concerning the environmental fate, behavior and effects of manufactured nanoparticles. The United Kingdom (UK) Environmental Nanoscience Initiative and the United States (US) Environmental Protection Agency have developed an international research program to enhance the knowledgebase and develop risk-predicting models for manufactured nanoparticles. Here we report selected highlights of the program as it sought to maximize the complementary strengths of the transatlantic scientific communities by funding three integrated US-UK consortia to investigate the transformation of these nanoparticles in terrestrial, aquatic, and atmospheric environment. Research results demonstrate there is a functional relationship between the physicochemical properties of environmentally transformed nanomaterials and their effects and that this relationship is amenable to modeling. In addition, the joint transatlantic program has allowed the leveraging of additional funding, promoting transboundary scientific collaboration.

Trophic transfer of citrate, PVP coated silver nanomaterials, and silver ions in a paddy microcosm

We used replicated paddy microcosm systems to estimate the tropic transfer of citrate-coated silver nanoparticles (AgNP citrate), polyvinylpyrrolidone (PVP)-coated AgNP (AgNP PVP), and silver ions (AgNO₃) for 14 days under two exposure regimes (a single high-dose exposure; 60 μg L^-1 and a sequential low-dose exposure at 1 h, 4 days and 9 days; 20 μg L^-1 × 3 = 60 μg L^-1). Most Ag ions from AgNO₃ had dispersed in the water and precipitated partly on the sediment, whereas the two Ag NPs rapidly coagulated and precipitated on the sediment. The bioconcentration factors (BCFs) of Ag from AgNPs and AgNO₃ in Chinese muddy loaches and biofilms were higher than those of river snails in both exposure conditions. These BCFs were more prominent for 14 days exposure (7.30 for Chinese muddy loach; 4.48 for biofilm) in the low-dose group than in the single high-dose group. Their retention of AgNPs and Ag ions differed between the two exposure conditions, and uptake and elimination kinetics of Ag significantly differed between AgNP citrate and AgNP PVP in the sequential low-dose exposure. Stable isotopes analyses indicated that the trophic levels between Chinese muddy loaches and biofilms and between river snails and biofilms were 2.37 and 2.27, respectively. The biomagnification factors (BMFs) of AgNPs and AgNO₃ between Chinese muddy loaches and biofilms were significantly higher than those between river snails and biofilms under both exposure settings. The BMFs of AgNP citrate and AgNO₃ between Chinese muddy loaches and biofilms were greater than those of AgNP PVP for 14 days in the single high-dose group, whereas the BMFs of AgNP PVP were greater than those of AgNP citrate and AgNO₃ in the sequential low-dose group. These microcosm data suggest that AgNPs have the potential to impact on ecological receptors and food chains.

Comparative toxicity and bioaccumulation of two dinotefuran metabolites, UF and DN, in earthworms (Eisenia fetida)

Dinotefuran, as the latest generation of neonicotinoid insecticide, has broad application prospects around the world. However, dinotefuran is easily metabolized and the two main metabolites are 1-methyl-3-(tetrahydro-3-furylmethyl) urea (UF) and 1-methyl-3-(tetrahydro-3-furylmethyl) guanidium dihydrogen (DN). In the present study, the risks of UF and DN in soil on typical non-target species earthworm were investigated. In the same time, the degradation in soil and accumulation in earthworms of UF and DN were monitored. The present results showed that the toxicities of UF and DN were similar in their effect on earthworms and they were supertoxic pollutants to earthworms. The degradation trend in soil and accumulation trend in earthworms of UF and DN were consistent throughout the whole exposure period. At 1.0 mg/kg and 2.0 mg/kg, UF and DN could induce the excess production of ROS, resulting in oxidative stress effects in earthworm cells. The excess ROS induce changes in antioxidant enzyme activities, damage in biomacromolecules, and abnormal expression of function genes. The present results showed that UF and DN may have high risks for earthworms.

Quantification of silver nanoparticle toxicity to algae in soil via photosynthetic and flow-cytometric analyses

Soil algae, which have received attention for their use in a novel bioassay to evaluate soil toxicity, expand the range of terrestrial test species. However, there is no information regarding the toxicity of nanomaterials to soil algae. Thus, we evaluated the effects of silver nanoparticles (0-50 mg AgNPs/kg dry weight soil) on the soil alga Chlamydomonas reinhardtii after six days, and assessed changes in biomass, photosynthetic activity, cellular morphology, membrane permeability, esterase activity, and oxidative stress. The parameters measured were markedly affected by AgNP-induced stress at 50 mg AgNPs/kg dry weight soil, where soil algal biomass, three measures of photosynthetic activity (area, reaction center per absorption flux, and reaction center per trapped energy flux), and esterase activity decreased. AgNPs also induced increases in both cell size and membrane permeability at 50 mg AgNPs/kg dry weight soil. In addition to the increase in cell size observed via microscopy, a mucilaginous sheath formed as a protective barrier against AgNPs. Thus, the toxicity of AgNPs can be effectively quantified based on the physiological, biochemical, and morphological responses of soil algae, where quantifying the level of toxicity of AgNPs to soil algae could prove to be a useful method in terrestrial ecotoxicology.

Integrative assessment of the effects produced by Ag nanoparticles at different levels of biological complexity in Eisenia fetida maintained in two standard soils (OECD and LUFA 2.3)

There is a potential risk to increase the release of silver nanoparticles (Ag NPs) into the environment: For instance. in soils receiving sludge models estimate 0.007 mg Ag NPs kg^-1 that will annually increase due to sludge or sludge incineration residues land-disposal. Thus, the concern about the hazards of nanosilver to soils and soil invertebrates is growing. Studies performed up to now have been focused in traditional endpoints, used limit range concentrations and employed different soil types that differ in physico-chemical characteristics. Presently, effects of Ag NPs have been measured at different levels of biological complexity in Eisenia fetida, exposed for 3 and 14 d to high but sublethal (50 mg Ag NPs kg^-1) and close to modeled environmental concentrations (0.05 mg Ag NPs kg^-1). Since characteristics of the exposure matrix may limit the response of the organisms to these concentrations, experiments were carried out in OECD and LUFA soils, the most used standard soils. High concentrations of Ag NPs increased catalase activity and DNA damage in OECD soils after 14 d while in LUFA 2.3 soils produced earlier effects (weight loss, decrease in cell viability and increase in catalase activity at day 3). At day 14, LUFA 2.3 (low clay and organic matter-OM-) could have provoked starvation of earthworms, masking Ag NPs toxicity. The concentration close to modeled environmental concentrations produced effects uniquely in LUFA 2.3 soil. Accurate physico-chemical characteristics of the standard soils are crucial to assess the toxicity exerted by Ag NPs in E. fetida since low clay and OM contents can be considered toxicity enhancers.

Responses to silver nanoparticles and silver nitrate in a battery of biomarkers measured in coelomocytes and in target tissues of Eisenia fetida earthworms

The current use and development of applications with silver nanoparticles (Ag NPs) could lead to potential inputs of these NPs to soils. Consequently, it is crucial to understand the ecotoxicological risks posed by Ag NPs in the terrestrial compartment. In the present investigation, the effects produced by PVP-PEI coated Ag NPs were assessed in Eisenia fetida earthworms in comparison with the soluble form (AgNO₃). Earthworms were exposed for 1, 3 and 14 days to a range of sublethal concentrations of Ag (0, 0.05 and 50mg/kg) and at each exposure time, apart from mortality and weight loss of individuals, metallothionein (MT) protein concentration and catalase (CAT) activity were quantified in earthworm tissues. In addition, cellular and molecular level endpoints (cell viability, absolute and relative trophic indices and transcription levels of catalase-cat- and metallothionein-mt-) were measured in coelomocytes extruded from exposed earthworms. Despite the lack of effects in traditional endpoints (mortality and weight loss), Ag NPs and AgNO₃ posed changes at lower levels of biological complexity (biochemical, cellular and molecular levels). Both Ag forms induced similar changes in the metal detoxification mechanism (MT, mt) and in the antioxidant response system (CAT, cat) of E. fetida. In contrast, Ag form dependant cytotoxicity and subpopulation ratio alterations (eleocytes/amoebocytes) were recorded in extruded coelomocytes. Complementarily, the use of coelomocytes to assess molecular level endpoints represented a relevant alternative for development of non-invasive biomarkers.

Effects of silver nanoparticles on survival, biomass change and avoidance behaviour of the endogeic earthworm Allolobophora chlorotica

Increasing commercial application of silver nanoparticles (Ag NP) and subsequent presence in wastewater and sewage sludge has raised concerns regarding their effects in the aquatic and terrestrial environment. Several studies have employed standardised acute and chronic earthworm-based tests to establish the toxicological effects of Ag NP within soil. These studies have relied heavily on the use of epigiec earthworm species which may have limited ecological relevance in mineral soil. This study assessed the influence of Ag NP (uncoated 80nm powder) and AgNO₃ on survival, change in biomass and avoidance behaviour in a soil dwelling (endogiec) species, Allolobophora chlorotica. Earthworms were exposed for 14 days to soils spiked with Ag NP or AgNO₃ at 0, 12.5, 25, 50 and 100mgkg^-1 either separately for survival and biomass measurement, or combined within a linear gradient to assess avoidance. Avoidance behaviour was shown to provide the most sensitive endpoint with an observable effect at an Ag NP/AgNO₃ concentration of 12.5mgkg^-1 compared with 50mgkg^-1 for biomass change and 100mgkg^-1 for survival. Greater mortality was observed in AgNO₃ (66.7%) compared with Ag NP-spiked soils (12.5%) at 100mgkg^-1, attributed to increased presence of silver ions. Although comparison of results with studies employing Eisenia fetida and Eisenia andrei suggest that the A. chlorotica response to Ag NP is more sensitive, further research employing both epigeic and endogeic earthworms under similar experimental conditions is required to confirm this observation.

Electromagnetic fields at a mobile phone frequency (900 MHz) trigger the onset of general stress response along with DNA modifications in Eisenia fetida earthworms

Eisenia fetida earthworms were exposed to electromagnetic field (EMF) at a mobile phone frequency (900 MHz) and at field levels ranging from 10 to 120 V m-1 for a period of two hours (corresponding to specific absorption rates ranging from 0.13 to 9.33 mW kg-1). Potential effects of longer exposure (four hours), field modulation, and a recovery period of 24 h after two hours of exposure were addressed at the field level of 23 V m-1. All exposure treatments induced significant DNA modifications as assessed by a quantitative random amplified polymorphic DNA-PCR. Even after 24 h of recovery following a two hour-exposure, the number of probe hybridisation sites displayed a significant two-fold decrease as compared to untreated control earthworms, implying a loss of hybridisation sites and a persistent genotoxic effect of EMF. Expression of genes involved in the response to general stress (HSP70 encoding the 70 kDa heat shock protein, and MEKK1 involved in signal transduction), oxidative stress (CAT, encoding catalase), and chemical and immune defence (LYS, encoding lysenin, and MYD, encoding a myeloid differentiation factor) were up-regulated after exposure to 10 and modulated 23 V m-1 field levels. Western blots showing an increased quantity of HSP70 and MTCO1 proteins confirmed this stress response. HSP70 and LYS genes were up-regulated after 24 h of recovery following a two hour-exposure, meaning that the effect of EMF exposure lasted for hours.

Stakeholder Views of Nanosilver Linings: Macroethics Education and Automated Text Analysis Through Participatory Governance Role Play in a Workshop Format

The Nanosilver Linings role play case offers participants first-person experience with interpersonal interaction in the context of the wicked problems of emerging technology macroethics. In the fictional scenario, diverse societal stakeholders convene at a town hall meeting to consider whether a nanotechnology-enabled food packaging industry should be offered incentives to establish an operation in their economically struggling Midwestern city. This original creative work was built with a combination of elements, selected for their established pedagogical efficacy (e.g. active learning, case-based learning) and as topical dimensions of the realistic scenario (e.g. nanosilver in food packaging, occupational safety and health). The product life cycle is used as a framework for integrated consideration of scientific, societal, and ethical issues. The Nanosilver Linings hypothetical case was delivered through the format of the 3-hour workshop Ethics when Biocomplexity meets Human Complexity, providing an immersive, holistic ethics learning experience for STEM graduate students. Through their participation in the Nanosilver Linings case and Ethics when Biocomplexity meets Human Complexity workshop, four cohorts of science and engineering doctoral students reported the achievement of specific learning objectives pertaining to a range of macroethics concepts and professional practices, including stakeholder perspectives, communication, human values, and ethical frameworks. Automated text analysis of workshop transcripts revealed differences in sentiment and in ethical framework (consequentialism/deontology) preference between societal stakeholder roles. These resources have been recognized as ethics education exemplars by the U.S. National Academy of Engineering .

Effects of silver nanowire length and exposure route on cytotoxicity to earthworms

To accurately evaluate the environmental toxicity of silver nanowires (AgNWs), it is necessary to characterize how the cytotoxicity of these nanomaterials is affected by the route of exposure. However, few studies have addressed the exposure route or mechanism of toxicity of nanomaterials, particularly of nanowires, in living organisms. In this study, we therefore analyzed the main exposure route of AgNWs in vitro, using earthworms (Eisenia andrei) as a model system, via flow cytometry. We subsequently examined the in vivo toxicity of AgNWs to earthworms in soil. These tests revealed that intracellular esterase activity was correlated with adsorption of the nanowires to the surfaces of coelomocytes in vitro, and that in vivo cytotoxicity resulted mainly from oral, rather than dermal, exposure to the nanowires. Overall, shorter AgNWs (10 μm) were more toxic than longer AgNWs (20 μm). To our knowledge, this study is the first report regarding the ecotoxicity of nanowires to earthworms in soil. Our findings provide important information to help assess the risk of toxic AgNW contamination of soil ecosystems.

Differential bioaccumulation patterns of nanosized and dissolved silver in a land snail Achatina fulica

With the increasing application in antimicrobial products, silver nanoparticles (AgNP) are inevitably released into the terrestrial environment, and pose potential risks to invertebrates such as land snails Achatina fulica, which take up AgNP from food and water. Here we differentiate Ag uptake biodynamic between Ag forms (i.e., PVP-AgNP vs. AgNO3) and between exposure pathways. Snails assimilated Ag efficiently from lettuce leaves pre-exposed to AgNP, with assimilation efficiencies (AEs) averaging 62-85% and food ingestion rates of 0.11 ± 0.03 g g-1 d-1. Dietary Ag bioavailability was independent on Ag forms, as revealed by comparable AEs between AgNP and AgNO3. However, the uptake rate constant from water was much lower for AgNP relative to AgNO3 (2 × 10-4 vs. 0.12 L g-1 d-1). The elimination rate constants were 0.0093 ± 0.0037 d-1 for AgNP and 0.019 ± 0.0077 d-1 for AgNO3. Biodynamic modeling further showed that dietary exposure was the dominant uptake pathway for AgNP in most circumstances, while for AgNO3 the relative importance of waterborne and dietary exposure depended on Ag concentrations in food and water. Our findings highlight the importance of dietary uptake of AgNP during bioaccumulation, which should be considered in the risk assessment of these nanoparticles.

Impacts of Sediment Organic Matter Content and pH on Ecotoxicity of Coexposure of TiO2 Nanoparticles and Cadmium to Freshwater Snails Bellamya aeruginosa

The environmental factors are expected to affect the ecotoxicity of heavy metals in the presence of engineered nanoparticles (NPs) in aquatic ecosystems. However, in sediment scenario, little is known regarding their impacts on the ecotoxicity of co-exposure of sediment-associated heavy metals and NPs. This study evaluated the impacts of different levels of organic matter (OM) (4.8-11.6%) and pH (6-9) on the ecotoxicological effects of co-exposure of sediment-associated titanium dioxide nanoparticles (TiO₂-NPs) and cadmium (Cd) to a freshwater gastropod Bellamya aeruginosa. The burdens of Ti and Cd and biomarkers of DNA damage, Na⁺/K⁺-ATPase, lipid peroxidation (LPO), and protein carbonylation (PC) in the hepatopancreas were determined following 21 days of exposure. At background level of OM (4.8%) in sediments, TiO₂-NPs significantly promoted Cd accumulation in low-Cd treatments (5 mg/kg) but did not promote Cd accumulation in high-Cd treatments (25 mg/kg). At the relatively higher OM levels (7.1 and 11.6%), TiO₂-NPs significantly enhanced Cd accumulation and toxicity as evidenced by aggravated DNA damage, decreased Na⁺/K⁺-ATPase activities, and increased LPO and PC levels. Moreover, Cd burdens in both low-Cd and high-Cd treatment were positively correlated with corresponding Ti burdens, indicating TiO₂-NPs partially acted as carrier of Cd. At all pH levels, in low-Cd treatments, TiO₂-NPs did not affect Cd accumulation, LPO, and PC levels but significantly enhanced DNA damage and slightly facilitated the inhibition of Na⁺/K⁺-ATPase activities. In high-Cd treatments, only at pH 9, TiO₂-NPs significantly enhanced Cd accumulation and toxicity. Our results implied that interaction between TiO₂-NPs and OM or pH significantly affected the accumulation and toxicity of Cd in B. aeruginosa, but the underlying mechanisms need further investigation. Additionally, it should be noted that the potential ecological risk of co-exposure of NPs and coexisting pollutants might be closely species-specific and related to environmental media.

Oxidative stress responses and insights into the sensitivity of the earthworms Metaphire guillelmi and Eisenia fetida to soil cadmium

Soil toxicological tests are commonly performed using Eisenia fetida as the standard earthworm species, but it is tolerant to a wide range of pollutants. Therefore, the inclusion of susceptible species is crucial for the accurate estimation of soil contamination. In this study, we examined the sensitivity to soil cadmium (Cd) of anecic Metaphire guillelmi and epigeic E. fetida by measuring multiple indexes of oxidative stress. Using subcellular partitioning analysis, we further elucidated the inherent mechanism underlying the species-specific sensitivity of the two earthworm species. Among the battery of biochemical indexes, reactive oxygen species and protein carbonyl groups served as sensitive biomarkers. According to their respective response thresholds, M. guillelmi was more sensitive than E. fetida and they differed in their dose-response relationships. In E. fetida, the activities of three antioxidant enzymes, superoxide dismutase (SOD), catalase (CAT) and glutathione S-transferase (GST), exhibited a hormesis-like U-shaped dose-response relationship, while in M. guillelmi SOD, glutathione peroxidase (an analogue of CAT) and GST showed an inverted U-shaped relationship. The concentrations of Cd in the subcellular fractions and whole body of the earthworms well fit (R²>0.9) a saturation model versus bioavailable Cd concentrations determined by the diffusive gradients in thin films technique. Despite the lower accumulation capacity of M. guillelmi, the Cd-binding capacity (C_max) of its subcellular heat-stable protein fraction, the so-called biologically detoxified metal pool, was 2.7 times lower than that of E. fetida, whereas the Cd binding affinity (logK) of its heat-denatured protein fraction, i.e. the metal-sensitive fraction, was 3.0 times higher, which accounted for the high susceptibility of M. guillelmi to soil Cd. Our results suggest that because of their sensitivity, as exemplified by M. guillelmi, native earthworm species should be taken into account in soil risk assessments to avoid underestimation of the toxicity of various pollutants.

Important Issues in Ecotoxicological Investigations Using Earthworms

The importance and beneficial effects of earthworms on soil structure and quality is well-established. In addition, earthworms have proved to be important model organisms for investigation of pollutant effects on soil ecosystems. In ecotoxicological investigations effects of various pollutants on earthworms were assessed. But some important issues regarding the effects of pollutants on earthworms still need to be comprehensively addressed. In this review several issues relevant to soil ecotoxicological investigations using earthworms are emphasized and guidelines that should be adopted in ecotoxicological investigations using earthworms are given. The inclusion of these guidelines in ecotoxicological studies will contribute to the better quantification of impacts of pollutants and will allow more accurate prediction of the real field effects of pollutants to earthworms.

Biomarker responses of Eisenia andrei to a polymetallic gradient near a lead mining site in North Tunisia

Eisenia andrei earthworms were exposed for 7 and 14 days to six samples of soil taken from around an abandoned lead (Pb) mine and characterized by different levels of metal contamination (S6-S1, this latter being the most contaminated soil). The organisms were analyzed for metal bioaccumulation and for biological parameters as biomarkers of stress (lysosomal membrane stability; lipofuscin lysosomal content; lysosomal/cytoplasmic volume ratio) and genotoxicity (Micronucleus frequency). Chemical analysis showed the loads of Pb, Cd, Zn, and Cu in the worms following exposure. Among the stress biomarkers, lysosomal membrane stability was significantly affected in the coelomocytes of the earthworms exposed already 7 days to different contaminated soils. Organisms exposed for 14 days to S1 showed in the cells of the chloragogenous tissue, a particularly relevant increase in lipofuscin, a biomarker of oxidative stress, and an increase in the lysosome/cytoplasm volume ratio, indicating stressful condition at the tissue level. Moreover, in the same conditions, a decrease in total body weight was observed. At the longer exposure time, the coelomocytes of worms exposed to S1, S2, and S3 (soils with higher metal concentrations) showed a significant increase in micronuclei (MNi) frequency. Expressions of the P21 and topoisomerase genes, which are involved in DNA repair, showed significant up-regulation in the cells of worms exposed to S1, S2, S3, S4 and to a less extend S6. This may indicate that the worms were only able to successfully reduce the level of DNA damage in S4 and S5 if considering MN frequency data. The biomarker data was integrated by the Earthworm Expert System, allowing an objective interpretation of the complex biological data and clearly defining the areas in which the presence of chemicals is toxic for the edaphic organisms.

Ecotoxicity of titanium silicon oxide (TiSiO4) nanomaterial for terrestrial plants and soil invertebrate species

The huge evolution of nanotechnology and the commercialization of nanomaterials (NMs) positively contributed for innovation in several industrial sectors. Facing this rapid development and the emergence of NMs in the market, the release of this nanometric sized materials in the environment and the possible impact on different ecosystem components attracted the attention of researchers in the last few years. In our study we aimed to assess the impact of titanium silicon oxide nanomaterial (nano-TiSiO4) on soil biota to estimate a risk limit for this material. In the present research a battery of standardized ecotoxicological assays aimed at evaluating a wide range of endpoints (avoidance and reproduction of earthworms and collembolans, emergence/growth of four selected terrestrial plants) were carried out, using OECD artificial soil as test substrate spiked with aqueous suspension of different concentrations of nano-TiSiO4. The results showed a maximum avoidance percentage of 40% for earthworms (Esenia andrei) at the highest concentration tested (1000mgkg(-1) soildw of nano-TiSiO4). No significant effect on the reproductive function of both invertebrate species was recorded. Nevertheless, significant phytotoxic data was registered at least for the growth of dicotyledonous plant species (Lactuca sativa and Lycopersicon lycopersicum) with EC20 values ranging between 236 and 414 mg kg(-1) soildw of nano-TiSiO4 for L. sativa dry mass and fresh mass, respectively. Further, the characterization of nano-TiSiO4 in suspensions used to spike the soil, performed by Dynamic Light Scattering, showed the formation of aggregates with important average size diameter, thus demonstrating that the toxic effects observed were likely not size dependent. A deterministic PNEC (predicted no effect concentration) for this NM of 10.02mg kg(-1) soildw of nano-TiSiO4, is suggested, while no more ecotoxicological information exists.

Drosophila melanogaster as a suitable in vivo model to determine potential side effects of nanomaterials: A review

Despite being a relatively new field, nanoscience has been in the forefront among many scientific areas. Nanoparticle materials (NM) present interesting physicochemical characteristics not necessarily found in their bulky forms, and alterations in their size or coating markedly modify their physical, chemical, and biological properties. Due to these novel properties there is a general trend to exploit these NM in several fields of science, particularly in medicine and industry. The increased presence of NM in the environment warrants evaluation of potential harmful effects in order to protect both environment and human exposed populations. Although in vitro approaches are commonly used to determine potential adverse effects of NM, in vivo studies generate data expected to be more relevant for risk assessment. As an in vivo model Drosophila melanogaster was previously found to possess reliable utility in determining the biological effects of NM, and thus its usage increased markedly over the last few years. The aims of this review are to present a comprehensive overview of all apparent studies carried out with NM and Drosophila, to attain a clear and comprehensive picture of the potential risk of NM exposure to health, and to demonstrate the advantages of using Drosophila in nanotoxicological investigations.

Is gene transcription in mussel gills altered after exposure to Ag nanoparticles?

Nanotechnology is a rapid field of development with the enhancement of the production of different types of nanoparticles (NPs) applied in several industrial and commercial applications which increase the risk of their presence in the aquatic environment. Ag NPs have a wide application in everyday life products. However, there is concern about the exposure effects on aquatic organisms to these NPs. Therefore, this study aims to assess gene transcription alterations in mussels Mytilus galloprovincialis gills exposed for 2 weeks to Ag NPs (42 ± 10 nm, 10 μg.L(-1)). The genes were selected based on previous biomarkers and proteomic results and included superoxide dismutase (SOD), catalase (CAT), glutathione transferase (GST), caspase 3/7-1 (CAS), cathepsin L (CATH), heat-shock protein 70 (HSP 70), cytochrome P450 4YA (CYP 4YA), the elongation factor (EF1), actin and α- tubulin. No significant changes in gene transcription profiles were observed after exposure of M. galloprovincialis to Ag NPs for 15 days. The lack of significant gene transcription responses is in light with previous results obtained for mussels exposed to these NPs and may be related to the fact that enzyme kinetics and relative abundance of proteins (increase of antioxidant enzymes and metalllothioneins (MTs) with the time of exposure) do not always directly reflect their relative mRNA levels. Nevertheless, their overall expression maintenance may signify that, at end of the exposure period (15 days), the transcription of the respective genes is no longer required, pointing out to a possible adaptation effect to nanoparticles or due to the levels of Ag NPs accumulated in this tissue at this exposure time. This study highlights that gene transcription application and role as an additional and/or alternative end point approach is important to understand the mode of action of these emergent contaminants in aquatic organisms. However, in future studies, the time window needs to be adjusted, as genes are likely to respond earlier to the nanoparticle exposure.

Effects of soil and dietary exposures to Ag nanoparticles and AgNO₃ in the terrestrial isopod Porcellionides pruinosus

The effects of Ag-NPs and AgNO3 on the isopod Porcellionides pruinosus were determined upon soil and dietary exposures. Isopods avoided Ag in soil, with EC50 values of ∼16.0 and 14.0 mg Ag/kg for Ag-NPs and AgNO3, respectively. Feeding inhibition tests in soil showed EC50s for effects on consumption ratio of 127 and 56.7 mg Ag/kg, respectively. Although similar EC50s for effects on biomass were observed for nanoparticulate and ionic Ag (114 and 120 mg Ag/kg dry soil, respectively), at higher concentrations greater biomass loss was found for AgNO3. Upon dietary exposure, AgNO3 was more toxic, with EC50 for effects on biomass change being >1500 and 233 mg Ag/kg for Ag-NPs and AgNO3, respectively. The difference in toxicity between Ag-NPs and AgNO3 could not be explained from Ag body concentrations. This suggests that the relation between toxicity and bioavailability of Ag-NPs differs from that of ionic Ag in soils.

Oxidative Stress Mechanisms Caused by Ag Nanoparticles (NM300K) are Different from Those of AgNO3: Effects in the Soil Invertebrate Enchytraeus Crypticus

The mechanisms of toxicity of Ag nanoparticles (NPs) are unclear, in particular in the terrestrial environment. In this study the effects of AgNP (AgNM300K) were assessed in terms of oxidative stress in the soil worm Enchytraeus crypticus, using a range of biochemical markers [catalase (CAT), glutathione peroxidase (GPx), glutathione S-transferase (GST), glutathione reductase (GR), total glutathione (TG), metallothionein (MT), lipid peroxidation (LPO)]. E. crypticus were exposed during 3 and 7 days (d) to the reproduction EC₂₀, EC₅₀ and EC₈₀ levels of both AgNP and AgNO₃. AgNO₃ induced oxidative stress earlier (3 d) than AgNP (7 d), both leading to LPO despite the activation of the anti-redox system. MT increased only for AgNP. The Correspondence Analysis showed a clear separation between AgNO₃ and AgNP, with e.g., CAT being the main descriptor for AgNP for 7 d. LPO, GST and GPx were for both 3 and 7 d associated with AgNO₃, whereas MT and TG were associated with AgNP. These results may reflect a delay in the effects of AgNP compared to AgNO₃ due to the slower release of Ag⁺ ions from the AgNP, although this does not fully explain the observed differences, i.e., we can conclude that there is a nanoparticle effect.

Perturbation of cellular mechanistic system by silver nanoparticle toxicity: Cytotoxic, genotoxic and epigenetic potentials

Currently the applications of silver nanoparticles (Ag NPs) are gaining overwhelming response due to the advancement of nanotechnology. However, only limited information is available with regard to their toxicity mechanism in different species. It is very essential to understand the complete molecular mechanism to explore the functional and long term applications of Ag NPs. Ag NPs could be toxic at cellular, subcellular, biomolecular, and epigenetic levels. Toxicity effects induced by Ag NPs have been evaluated using numerous in vitro and in vivo models, but still there are contradictions in interpretations due to disparity in methodology, test endpoints and several other model parameters which needs to be considered. Thus, this review article focuses on the progressive elucidation of molecular mechanism of toxicity induced by Ag NPs in various in vitro and in vivo models. Apart from these, this review also highlights the various ignored factors which are to be considered during toxicity studies.

Effects of silver nanoparticles to soil invertebrates: oxidative stress biomarkers in Eisenia fetida

Silver nanoparticles (Ag-NPs) are among the most produced NPs worldwide having several applications in consumer products. Ag-NPs are known to cause oxidative stress in several organisms and cell lines, however comparatively less information is available regarding their effects on soil living invertebrates. The purpose of this study was to investigate if Ag-NPs cause oxidative stress on soil invertebrates. The model soil species Eisenia fetida was used. Our results showed that total glutathione (TG) is the first mechanism triggered by Ag-NPs, followed by glutathione peroxidase (GPx) and glutathione reductase (GR), however oxidative damage was observed for higher doses and exposure time (increased lipid peroxidation, LPO). AgNO3 exposure caused impairment in GPx and glutathione-S-transferase (GST), probably as result of the higher bioavailability of Ag in the salt-form. The current results indicate that effects are partly caused by Ag ions released from Ag-NPs, but specific particle effects cannot be excluded.

Antioxidant responses of Annelids, Brassicaceae and Fabaceae to pollutants: a review

Pollutants, such as Metal Trace Elements (MTEs) and organic compounds (polycyclic aromatic hydrocarbons, pesticides), can impact DNA structure of living organisms and thus generate damage. For instance, cadmium is a well-known genotoxic and mechanisms explaining its clastogenicity are mainly indirect: inhibition of DNA repair mechanisms and/or induction of Reactive Oxygen Species (ROS). Animal or vegetal cells use antioxidant defense systems to protect themselves against ROS produced during oxidative stress. Because tolerance of organisms depends, at least partially, on their ability to cope with ROS, the mechanisms of production and management of ROS were investigated a lot in Ecotoxicology as markers of biotic and abiotic stress. This was mainly done through the measurement of enzyme activities The present Review focuses on 3 test species living in close contact with soil that are often used in soil ecotoxicology: the worm Eisenia fetida, and two plant species, Trifolium repens (white clover) and Brassica oleracea (cabbage). E. fetida is a soil-dwelling organism commonly used for biomonitoring. T. repens is a symbiotic plant species which forms root nodule with soil bacteria, while B. oleracea is a non-symbiotic plant. In literature, some oxidative stress enzyme activities have already been measured in those species but such analyses do not allow distinction between individual enzyme involvements in oxidative stress. Gene expression studies would allow this distinction at the transcriptomic level. A literature review and a data search in molecular database were carried out on the basis of keywords in Scopus, in PubMed and in Genbank™ for each species. Molecular data regarding E. fetida were already available in databases, but a lack of data regarding oxidative stress related genes was observed for T. repens and B. oleracea. By exploiting the conservation observed between species and using molecular biology techniques, we partially cloned missing candidates involved in oxidative stress and in metal detoxification in E. fetida, T. repens and B. oleracea.

Nanosilver-coated socks and their toxicity to zebrafish (Danio rerio) embryos

Silver nanoparticles (AgNPs) are being incorporated and are known to be released from various consumer products such as textiles. However, no data are available on the toxicity of AgNPs released from any of these commercial products. In this study, we quantified total silver released from socks into wash water by inductively coupled plasma mass spectrometry (ICP-MS) and determined the presence of AgNPs using transmission electron microscopy (TEM). We then exposed zebrafish (Danio rerio) embryos for 72 h to either this leachate ("sock-AgNP") or to the centrifugate ("spun-AgNP") free of AgNPs and compared their toxicity to that of ionic silver (Ag(+)). Our data suggest that AgNPs do get released into the wash water, and centrifugation eliminated AgNPs but did not decrease total silver concentrations, indicating that most of the silver in the sock-AgNP solution was in the ionic form. All embryos died during the first 24 h when exposed to undiluted sock-AgNP and spun-AgNP solutions resulting in significantly lower LC50 values (0.14 and 0.26 mg L(-1)) compared to AgNO3 (0.80 mg L(-1)). Similarly, at 72 hpf, both sock-derived solutions were more potent at affecting hatching and inducing abnormal development. These results suggest that both sock-AgNP and spun-AgNP solutions were more toxic than AgNO3. Previous studies have consistently shown the opposite, i.e., AgNPs are about 10 times less toxic that Ag(+). All together our results show that the high toxicity induced by the leachate of these socks is likely not caused by AgNPs or Ag(+). More studies are needed to evaluate the toxicity of the myriad of AgNP-coated commercial products that are now estimated to be close to 500.