Effect of chronic toxicity of the crystalline forms of TiO2 nanoparticles on the physiological parameters of Daphnia magna with a focus on index correlation analysis

Ecotoxicity and trophic transfer of metallic nanomaterials in aquatic ecosystems

Metallic nanomaterials (MNMs) possess unique properties that have led to their widespread application in fields such as electronics and medicine. However, concerns about their interactions with environmental factors and potential toxicity to aquatic life have emerged. There is growing evidence suggesting MNMs can have detrimental effects on aquatic ecosystems, and are potential for bioaccumulation and biomagnification in the food chain, posing risks to higher trophic levels and potentially humans. While many studies have focused on the general ecotoxicity of MNMs, fewer have delved into their trophic transfer within aquatic food chains. This review highlights the ecotoxicological effects of MNMs on aquatic systems via waterborne exposure or dietary exposure, emphasizing their accumulation and transformation across the food web. Biomagnification factor (BMF), the ratio of the contaminant concentration in predator to that in prey, was used to evaluate the biomagnification due to the complex nature of aquatic food chains. However, most current studies have BMF values of less than 1 indicating no biomagnification. Factors influencing MNM toxicity in aquatic environments include nanomaterial properties, ion variations, light, dissolved oxygen, and pH. The multifaceted interactions of these variables with MNM toxicity remain to be fully elucidated. We conclude with recommendations for future research directions to mitigate the adverse effects of MNMs in aquatic ecosystems and advocate for a cautious approach to the production and application of MNMs.

Life cycle exposure to titanium dioxide nanoparticles (TiO2-NPs) induces filial toxicity and population decline in the nematode Caenorhabditis elegans

Titanium dioxide nanoparticle (TiO2-NP) exposure has raised significant concern due to their potential toxicity and adverse ecological impacts. Despite their ubiquitous presence in various environmental compartments, the long-term consequences of TiO2-NPs remain poorly understood. In this study, we combined data of in vivo toxicity and modeling to investigate the potential negative impacts of TiO2-NP exposure. We employed the nematode Caenorhabditis elegans, an environmental organism, to conduct a full life cycle TiO2-NP toxicity assays. Moreover, to assess the potential impact of TiO2-NP toxicity on population dynamics, we applied a stage-constructed matrix population model (MPM). Results showed that TiO2-NPs caused significant reductions in reproduction, survival, and growth of parental C. elegans (P0) at the examined concentrations. Moreover, these toxic effects were even more pronounced in the subsequent generation (F1) when exposed to TiO2-NPs. Furthermore, parental TiO2-NP exposure resulted in significant toxicity in non-exposed C. elegans progeny (TiO2-NPs free), adversely affecting their reproduction, survival, and growth. MPM analysis revealed decreased transition probabilities of surviving (Pi), growth (Gi), and fertility (Fi) in scenarios with TiO2-NP exposure. Additionally, the population growth rate (λmax) was found to be less than 1 in both P0 and F1, indicating a declining population trend after successive generations. Sensitivity analysis pinpointed L1 larvae as the most vulnerable stage, significantly contributing to the observed population decline in both P0 and F1 generations under TiO2-NP exposure. Our findings provide insight into the potential risk of an environmental organism like nematode by life cycle exposure to TiO2-NPs.

Toxicity of Titanium Dioxide-Cerium Oxide Nanocomposites to Zebrafish Embryos: A Preliminary Evaluation

The widespread use of metal nanoparticles in different fields has raised many doubts regarding their possible toxicity to living organisms and the accumulation and discharge of metals in fish species. Among these nanoparticles, titanium dioxide (TiO2) and cerium oxide (CeO2) nanoparticles have mainly been employed in photocatalysis and water depuration. The aim of this research was to evaluate the potential toxic effects, after a co-exposure of TiO2-3%CeO2 nanoparticles, on zebrafish development, using an acute toxicity test. Increasing concentrations of TiO2-3%CeO2 nanoparticles were used (0.1-1-10-20 mg/L). The heartbeat rate was assessed using DanioscopeTM software (version 1.2) (Noldus, Leesburg, VA, USA), and the responses to two biomarkers of exposure (Heat shock proteins-70 and Metallothioneins) were evaluated through immunofluorescence. Our results showed that the co-exposure to TiO2-3%CeO2 nanoparticles did not affect the embryos' development compared to the control group; a significant difference (p < 0.05) at 48 hpf heartbeat for the 1, 10, and 20 mg/L groups was found compared to the unexposed group. A statistically significant response (p < 0.05) to Heat shock proteins-70 (Hsp70) was shown for the 0.1 and 1 mg/L groups, while no positivity was observed in all the exposed groups for Metallothioneins (MTs). These results suggest that TiO2-3%CeO2 nanocomposites do not induce developmental toxicity; instead, when considered separately, TiO2 and CeO2 NPs are harmful to zebrafish embryos, as previously shown.

Nanomaterials in sunscreens: Potential human and ecological health implications

Inorganic nanomaterials such as TiO2 and ZnO provide significant benefits in terms of UV protection, and their use generally has increased in commercial sunscreens. However, more recently there have been concerns about their potential human and ecological health implications, mostly driven by perception rather than by formal assessments. The large and increasing body of literature on these nanomaterials indicates that in most circumstances their risk are minimal. Penetration of the human epidermis is minimal for these nanomaterials, significantly reducing the potential effects that these nanomaterials may pose to internal organs. The excess Zn ion dose is very small compared to normal dietary consumption of Zn, which is a necessary element. The levels of residual nanomaterials or released ions in public swimming pools is also low, with minimal effect in case this water is ingested during swimming or bathing. In natural environments with significant water flow due to wind and water currents, the concentrations of nanomaterials and released ions are generally well below levels that would cause effects in aquatic organisms. However, sensitive habitats with slow currents, such as coral reefs, may accumulate these nanomaterials. The number of studies of the levels and effects of nanomaterials in these sensitive habitats is very small; more research is needed to determine if there is an elevated risk to these ecosystems from the use of sunscreens with these nanomaterials.

Ecotoxicological Properties of Titanium Dioxide Nanomorphologies in Daphnia magna

In this work, the structural, vibrational, morphological, and colloidal properties of commercial 15.1 nm TiO₂ nanoparticles (NPs) and nanowires (NWs, 5.6 thickness, 74.6 nm length) were studied with the purpose of determining their ecotoxicological properties. This was achieved by evaluating acute ecotoxicity experiments carried out in the environmental bioindicator Daphnia magna, where their 24-h lethal concentration (LC₅₀) and morphological changes were evaluated using a TiO₂ suspension (pH = 7) with point of zero charge at 6.5 for TiO₂ NPs (hydrodynamic diameter of 130 nm) and 5.3 for TiO₂ NWs (hydrodynamic diameter of 118 nm). Their LC₅₀ values were 157 and 166 mg L^-1 for TiO₂ NWs and TiO₂ NPs, respectively. The reproduction rate of D. magna after fifteen days of exposure to TiO₂ nanomorphologies was delayed (0 pups for TiO₂ NWs and 45 neonates for TiO₂ NPs) in comparison with the negative control (104 pups). From the morphological experiments, we may conclude that the harmful effects of TiO₂ NWs are more severe than those of 100% anatase TiO₂ NPs, likely associated with brookite (36.5 wt. %) and protonic trititanate (63.5 wt. %) presented in TiO₂ NWs according to Rietveld quantitative phase analysis. Specifically, significant change in the heart morphological parameter was observed. In addition, the structural and morphological properties of TiO₂ nanomorphologies were investigated using X-ray diffraction and electron microscopy techniques to confirm the physicochemical properties after the ecotoxicological experiments. The results reveal that no alteration in the chemical structure, size (16.5 nm for TiO2 NPs and 6.6 thickness and 79.2 nm length for NWs), and composition occurred. Hence, both TiO₂ samples can be stored and reused for future environmental purposes, e.g., water nanoremediation.

Molecular, biochemical and behavioral responses of Daphnia magna under long-term exposure to polystyrene nanoplastics

The presence and potential toxicity of nanoplastics (NPs) in aquatic ecosystems is an issue of growing concern. Although many studies have investigated the adverse effects of short-term exposure to high concentrations of NPs to aquatic organisms, the information on the consequences caused by the administration of low NPs concentrations over long-term exposure is limited. The present study aimed at investigating the effects induced by a long-term exposure (21-days) to two sub-lethal concentrations of polystyrene nanoplastics (PS-NPs; 0.05 and 0.5 µg/mL) on Daphnia magna. A multi-level approach was performed to assess potential sub-individual (i.e., molecular and biochemical) and individual (i.e., behavioural) adverse effects. At molecular level, the modulation of the expression of genes involved in antioxidant defence, response to stressful conditions and specific physiological pathways was investigated. Oxidative stress (i.e., the amount of pro-oxidants, the activity of antioxidant and detoxifying enzymes and lipid peroxidation) and energetic (i.e., protein, carbohydrate, lipid and total caloric content) biomarkers were applied to assess effects at the biochemical level, while swimming activity was measured to monitor changes in individual behavior. Although the 21-days exposure to PS-NPs induced a slight modulation of gene involved in oxidative stress response, biochemical analyses showed that D. magna individuals did not experience an oxidative stress condition. Significant changes in energy reserves of individuals exposed for 21 days to both the PS-NPs concentrations were observed, but no alterations of swimming activity occurred. Our results highlighted that the exposure to low concentrations of PS-NPs could pose a limited risk to D. magna individuals and suggested the importance of a multi-level approach to assess the risks of NPs on aquatic organisms.

Humic acid mediated toxicity of faceted TiO2 nanocrystals to Daphnia magna

Nano-bio interface is of great importance in dictating the interaction between the nanomaterials and biological system and thus the toxicity to aquatic organisms. Herein, two specific faceted TiO₂ nanocrystals, {101} and {001} facet, were exposed to Daphnia magna to explore facet-dependent toxicological responses in aquatic environment. Due to the different influences on oxidative stress process, the half-maximal effective concentration (EC₅₀) value of {001} TiO₂ (1.27 g L^-1) to D. magna was less than that of {101} TiO₂ (1.68 g L^-1). Suwannee river humic acid (SRHA) could significantly reduce the oxidative stress responses of TiO₂ nanocrystals and thus alleviate their toxicities to D. magna in aquatic environment. The protective effect of SRHA against TiO₂ toxicity exhibited a facet-dependent manner. Compared to {101} TiO₂, a more obvious detoxification effect was observed for {001} TiO₂. The high SRHA concentration could endow both faceted TiO₂ nanocrystals with a similar toxicity due to the formation of SRHA-corona on TiO₂ surface. This facet-affected toxicity of nanomaterials in aquatic environment would provide us new insights in predicting the exposure risk of nanomaterials in nature waters.

Metal- and metal/oxide-based engineered nanoparticles and nanostructures: a review on the applications, nanotoxicological effects, and risk control strategies

The production and demand of nanoparticles in the manufacturing sector and personal care products, release a large number of engineered nanoparticles (ENPs) into the atmosphere, aquatic ecosystems, and terrestrial environments. The intentional or involuntary incorporation of ENPs into the environment is carried out through different processes. The ENPs are combined with other compounds and release into the atmosphere, settling on the ground due to the water cycle or other atmospheric phenomena. In the case of aquatic ecosystems, the ENPs undergo hetero-aggregation and sedimentation, reaching different living organisms and flora, as well as groundwater. Accordingly, the high mobility of ENPs in diverse ecosystems is strongly related to physical, chemical, and biological processes. Recent studies have been focused on the toxicological effects of a wide variety of ENPs using different validated biological models. This literature review emphasizes the study of toxicological effects related to using the most common ENPs, specifically metal and metal/oxides-based nanoparticles, addressing different synthesis methodologies, applications, and toxicological evaluations. The results suggest negative impacts on biological models, such as oxidative stress, metabolic and locomotive toxicity, DNA replication dysfunction, and bioaccumulation. Finally, it was consulted the protocols for the control of risks, following the assessment and management process, as well as the classification system for technological alternatives and risk management measures of ENPs, which are useful for the transfer of technology and nanoparticles commercialization.

Rethinking Nano-TiO2 Safety: Overview of Toxic Effects in Humans and Aquatic Animals

Titanium dioxide nanoparticles (nano-TiO₂ ) are widely used in consumer products, raising environmental and health concerns. An overview of the toxic effects of nano-TiO₂ on human and environmental health is provided. A meta-analysis is conducted to analyze the toxicity of nano-TiO₂ to the liver, circulatory system, and DNA in humans. To assess the environmental impacts of nano-TiO₂ , aquatic environments that receive high nano-TiO₂ inputs are focused on, and the toxicity of nano-TiO₂ to aquatic organisms is discussed with regard to the present and predicted environmental concentrations. Genotoxicity, damage to membranes, inflammation and oxidative stress emerge as the main mechanisms of nano-TiO₂ toxicity. Furthermore, nano-TiO₂ can bind with free radicals and signal molecules, and interfere with the biochemical reactions on plasmalemma. At the higher organizational level, nano-TiO₂ toxicity is manifested as the negative effects on fitness-related organismal traits including feeding, reproduction and immunity in aquatic organisms. Bibliometric analysis reveals two major research hot spots including the molecular mechanisms of toxicity of nano-TiO₂ and the combined effects of nano-TiO₂ and other environmental factors such as light and pH. The possible measures to reduce the harmful effects of nano-TiO₂ on humans and non-target organisms has emerged as an underexplored topic requiring further investigation.

Exposure Route of TiO2 NPs from Industrial Applications to Wastewater Treatment and Their Impacts on the Agro-Environment

The tremendous increase in the production and consumption of titanium dioxide (TiO2) nanoparticles (NPs) in numerous industrial products and applications has augmented the need to understand their role in wastewater treatment technologies. Likewise, the deleterious effects of wastewater on the environment and natural resources have compelled researchers to find out most suitable, economical and environment friendly approaches for its treatment. In this context, the use of TiO2 NPs as the representative of photocatalytic technology for industrial wastewater treatment is coming to the horizon. For centuries, the use of industrial wastewater to feed agriculture land has been a common practice across the globe and the sewage sludge generated from wastewater treatment plants is also used as fertilizer in agricultural soils. Therefore, it is necessary to be aware of possible exposure pathways of these NPs, especially in the perspective of wastewater treatment and their impacts on the agro-environment. This review highlights the potential exposure route of TiO2 NPs from industrial applications to wastewater treatment and its impacts on the agro-environment. Key elements of the review present the recent developments of TiO2 NPs in two main sectors including wastewater treatment and the agro-environment along with their potential exposure pathways. Furthermore, the direct exposure routes of these NPs from production to end-user consumption until their end phase needs to be studied in detail and optimization of their suitable applications and controlled use to ensure environmental safety.