Bioavailability of CeO2 and SnO2 nanoparticles evaluated by dietary uptake in the earthworm Eisenia fetida and sequential extraction of soil and feed

Divergent responses of earthworms (Eisenia fetida) in sandy loam and clay soils to cerium dioxide nanoparticles

The reported biological effects of cerium dioxide nanoparticles (nCeO₂) in soils range from toxic to protective. However, divergences of nCeO₂ toxicity in soils of different textures are not known. In this study, the availability of nCeO₂ on earthworms (Eisenia fetida) in sandy loam soils and clay soils was discussed, and the biological effects of nCeO₂ (0-1000 mg/kg) on earthworms in two soils were investigated. The results showed the bioaccumulation and biological effects of Ce on earthworms in the two soils were inconsistent. The European Community Bureau of Reference (BCR) sequential extraction revealed that the major portions of Ce in both soils were in the residual form (98-99%), and the acid-soluble Ce fraction was greater in clay soils. However, nCeO₂ was more toxic to earthworms in sandy loam soils than that in clay soils as assessed by earthworm biomass, morphology, and antioxidative damage. Thus, the high ecological risk of nCeO₂ in sandy loam soils with higher pH and lower clay contents needs to be avoided, being used in agriculture to improve both crop yield and quality.

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.

Are Fragrance Encapsulates Taken Up by Aquatic and Terrestrial Invertebrate Species?

The uptake potential of fragrance encapsulates by aquatic or terrestrial organisms was investigated. Because of their size of <5 mm and their polymeric nature, fragrance encapsulates fall under the Joint Group of Experts on the Scientific Aspects of Marine Environmental Protection definition of microplastics. After use, fragrance encapsulates enter the sewer system and reach the sewage treatment plant (STP), where >90% of them are likely to be removed by sorption to the sludge. When the STP-generated sludge is used as fertilizer for agricultural soils, this may lead to potential exposure of terrestrial invertebrates to fragrance encapsulates, especially those feeding on particles of a similar size as the fragrance encapsulates. Two aquatic (Corbicula fluminea [water exposure] and Hyalella azteca [water and dietary exposure]) and one terrestrial invertebrate (Eisenia andrei [soil exposure]) species were exposed to 50 mg/L (or mg/kg) double fluorescence-labeled fragrance encapsulates (diameter 5-50 µm). The results showed that fragrance encapsulates are available to aquatic and terrestrial invertebrates but that species-specific differences regarding the ability to ingest fragrance encapsulates may exist. The benthic grazer H. azteca showed no ingestion of fragrance encapsulates, whereas the capsules were readily ingested and egested by the unselective freshwater filter feeder C. fluminea as well as the terrestrial decomposer E. andrei. No signs of bioaccumulation of fragrance encapsulates were indicated by microscopic assessment. Environ Toxicol Chem 2022;41:931-943. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

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.

The chronic effects of CuO and ZnO nanoparticles on Eisenia fetida in relation to the bioavailability in aged soils

The bioavailability and bioaccumulation of metal-based engineered nanoparticles (ENPs) in soils need to be evaluated in environmentally relevant scenarios. The aim of this study was an analysis of potentially available metal-component ENPs (nano-ZnO and nano-CuO) in soils. Earthworms (Eisenia fetida) were used to examine the bioaccumulation potential of ENPs. Micro-particles (micro-ZnO and micro-CuO) and metal salts (ZnCl₂ and CuCl₂) were used to evaluate the nano-effect and the activity of dissolved ions, respectively. Zn- and Cu-compounds were added to sandy loam and silt loam at a concentration of 10 mg kg^-1. The bioavailable fractions of metals were extracted from soil using H₂O, MgCl₂ with CH₃COONa or EDTA. EDTA was the most effective extractant of Zn and Cu (10.06-11.65 mg Zn kg^-1 and 2.69-3.52 mg Cu kg^-1), whereas the H₂O-extractable metal concentration was at the lowest level (1.98-2.12 mg Zn kg^-1 and 0.54-0.82 Cu mg kg^-1). The bioavailable metal concentrations were significantly higher in silt loam than sandy loam soil, which was related to the higher pH value of silt. There were no significant differences between the Zn content in the earthworms incubated in the two soils, which may confirm the auto-regulation of the Zn content by earthworms. However, the bioaccumulation of Cu was strongly correlated with the extractable Cu concentrations. The juvenile earthworms accumulated Cu and Zn more than adults. Based on our results, aging neutralized the differences between the ionic and particulate effects of metal-compounds.

A Sensitive Single Particle-ICP-MS Method for CeO2 Nanoparticles Analysis in Soil during Aging Process

The increasing prevalence of products that incorporate engineered nanoparticles (ENPs) has prompted efforts to investigate the potential release, environmental fate, and exposure of the ENPs. However, the investigation of cerium dioxide nanoparticles (CeO₂ NPs) in soil has remained limited, owing to the analytical challenge from the soil's complex nature. In this study, this challenge was overcome by applying a novel single particle-inductively coupled plasma-mass spectrometry (SP-ICP-MS) methodology to detect CeO₂ NPs extracted from soil, utilizing tetrasodium pyrophosphate (TSPP) aqueous solution as an extractant. This method is highly sensitive for determining CeO₂ NPs in soil, with detection limits of size and concentration of 15 nm and 194 NPs mL^-1, respectively. Extraction efficiency was sufficient in the tested TSPP concentration range from 1 mM to 10 mM at a soil-to-extractant ratio 1:100 (g mL^-1) for the extraction of CeO₂ NPs from the soil spiked with CeO₂ NPs. The aging study demonstrated that particle size, size distribution, and particle concentration underwent no significant change in the aged soils for a short period of one month. This study showed an efficient method capable of extracting and accurately determining CeO₂ NPs in soil matrices. The method can serve as a useful tool for nanoparticle analysis in routine soil tests and soil research.

Comparative Acute Toxicity and Oxidative Stress Responses in Three Aquatic Species Exposed to Stannic Oxide Nanoparticles and Stannic Chloride

We experimentally investigated the toxicity of stannic oxide nanoparticles (SnO₂ NPs) to three freshwater species including Scenedesmus obliquus, Daphnia magna, and Danio rerio. To evaluate effect, toxicological impacts were compared to that of stannic chloride (SnCl₄). Based on the actual concentration of Sn, SnO₂ NPs suspensions inhibited growth of S. obliquus in a dose-dependent manner, demonstrating a median effect concentration of 2.28 ± 0.53 mg/L. However, SnO₂ NP suspensions were found to exhibit limited acute toxicity in D. magna and D. rerio. Moreover, the toxicity of the SnO₂ NP suspension was lower than SnCl₄ for all three trophic aquatic organisms. Comparison of component-specific contribution to overall toxicity indicated that, in SnO₂ NP suspensions, particulate Sn more significantly contributed to toxicity than dissolved Sn-ions. Furthermore, we found that the toxic mechanism of the SnO₂ NP suspension involved the induction of oxidative stress by increasing intracellular ROS accumulation.

Different dynamic accumulation and toxicity of ZnO nanoparticles and ionic Zn in the soil sentinel organism Enchytraeus crypticus

There is still no consensus over the specific effects of metal-based nanoparticles when compared with the conventional metal salts. Here, the accumulation and toxicity of ZnO-NPs and ZnCl₂ in Enchytraeus crypticus over time (1-14 d) were investigated using a sand-solution exposure medium and applying a toxicokinetics and toxicodynamics approach. For both Zn forms, body Zn concentration in the organisms was dependent on both the exposure concentration and exposure time, with equilibrium being reached after 7-14 days of exposure. Generally, the uptake and elimination rate constants (K_u and K_e1) were smaller for ZnO-NPs (5.74-12.6 mg kg^-1d^-1 and 0.17-0.39 d^-1) than for ZnCl₂ (8.32-40.1 mg kg^-1d^-1 and 0.31-2.05 d^-1), suggesting that ionic Zn was more accessible for E. crypticus than nanoparticulate Zn. Based on external exposure concentrations, LC50s for ZnO-NPs and ZnCl₂ decreased with time from 123 to 67 Zn mg L^-1 and from 86 to 62 Zn mg L^-1, reaching an almost similar ultimate value within 14 d. LC50s based on body Zn concentrations were almost constant over time (except for 1 d) for both ZnO-NPs and ZnCl₂, with overall LC50_body of Zn being 1720 and 1306 mg kg^-1 dry body weight, respectively. Body Zn concentration, which considers all available pathways, was a good predictor of dynamic toxicity of ZnCl₂, but not for ZnO-NPs. This may be attributed to the specific internal distribution and detoxification mechanisms of ZnO-NPs. The particles from ZnO-NPs dominated the accumulation (>75%) and toxicity (∼100%). Our results suggest that dynamic aspects should be taken into account when assessing and comparing NPs and metals uptake and consequent patterns of toxicity.

Toxicity of engineered nanomaterials mediated by nano-bio-eco interactions

Engineered nanomaterials may adversely impact human health and environmental safety by nano-bio-eco interactions not fully understood. Their interaction with biotic and abiotic environments are varied and complicated, ranging from individual species to entire ecosystems. Their behavior, transport, fate, and toxicological profiles in these interactions, addressed in a pioneering study, are subsequently seldom reported. Biological, chemical, and physical dimension properties, the so-called multidimensional characterization, determine interactions. Intermediate species generated in the dynamic process of nanomaterial transformation increase the complexity of assessing nanotoxicity. We review recent progress in understanding these interactions, discuss the challenges of the study, and suggest future research directions.