Life Cycle Payback Estimates of Nanosilver Enabled Textiles under Different Silver Loading, Release, And Laundering Scenarios Informed by Literature Review

UV-dependent freshwater effect factor of nanoscale titanium dioxide for future life cycle assessment application

Environmental impacts of nanoscale titanium dioxide (TiO₂ ) should be assessed throughout the lifetime of nanoparticles (NPs) to improve the state of knowledge of the overall sustainability. Life cycle assessment (LCA) has been previously recognized as a promising approach to systematically evaluating environmental impacts of NPs. As a result of their unique nanospecific properties, characterization factors (CF) were previously used for compensating the release and potential impacts of TiO₂ NPs. However, because TiO₂ NPs are known to generate reactive oxygen species and elicit toxicity to freshwater organisms, the lack of adequate UV-dependent effect factors (EFs) remains a major shortcoming when addressing their life cycle impacts. To complement the LCA of TiO₂ -NPs-enabled products under their specific applications, we recapitulated the freshwater toxicity of TiO₂ NPs and then modeled in USEtox to determine trophic level EF ranges under UV and non-UV exposure conditions. Results indicate that EFs derived for non-UV exposure were 52 (42.9-65) potentially affected fraction (PAF) m³ /kg, and combined toxicity data derived EFs were 70.1 (55.6-90.5) PAF m³ /kg. When considering only the UV-induced exposure condition, the modeled EF increased to 500 (333-712) PAF m³ /kg. Our work highlights that case-dependent EFs should be considered and applied to reflect more realistic ecological impacts and illustrate comprehensive life cycle environmental impacts for nanoenabled products. Integr Environ Assess Manag 2023;19:578-585. © 2022 SETAC.

Insights into the lower trophic transfer of silver ions than silver containing nanoparticles along an aquatic food chain

Silver nanoparticles (AgNPs) released into the environment are subject to environmental transformation processes before accumulating in aquatic organisms and transferring along the food chain. Lack of understanding on how environmental transformation affects trophic transfer of AgNPs hinders accurate prediction of the environmental risks of these widely present nanomaterials. Here we discover that pristine AgNPs as well as their sulfidation products (Ag₂S-NPs) and dissolution products (Ag⁺) tend to be accumulated in Daphnia magna and subsequently transferred to zebrafish. In D. magna, Ag⁺ exhibits the highest bioaccumulation potential whereas Ag₂S-NPs show the lowest bioaccumulation. Surprisingly, the biomagnification factor of Ag⁺ along the D. magna-zebrafish food chain appears to be significantly lower relative to AgNPs and Ag₂S-NPs, likely due to the limited release of Ag from D. magna to zebrafish during digestion. Moreover, AgNPs and their transformation products mainly accumulate in the internal organs, particularly intestine, of zebrafish. Adsorption of AgNPs on the surface of the intestinal cell membrane mitigates depuration of AgNPs and, at least in part, leads to the larger biomagnification factor of AgNPs, relative to their transformation products. This research highlights the necessity of considering environmental transformation processes of nanomaterials in assessing their bioavailability and risk.

Cradle-to-grave environmental impact assessment of silver enabled t-shirts: Do nano-specific impacts exceed non nano-specific emissions?

Consumption of silver nanoparticles (nAg) is increasing due to their use in various industries. A comprehensive analysis is needed to elucidate the potential environmental and human health benefits and costs of the silver-enabled consumer products. For this purpose, four commercially available silver/nanosilver enabled polyester textiles with different initial silver/nanosilver loadings (1.07-4030 μg Ag/g textile) are included in the current research and cradle-to-grave life cycle assessments (LCA) are conducted to identify hotspots associated with production and use of these products throughout their lifetimes (100 cycles). Both non nano-specific and nano-specific impacts are calculated using nano-specific ecotoxicity characterization factors for nAg, instead of the commonly utilized ionic silver (Ag⁺) surrogate. Additionally, four different laundering scenarios were modeled to analyze the impacts resulting from using conventional and high efficiency machines. In the majority of environmental impact categories, either polyester textile manufacturing (regardless of Ag/nAg enabling) or laundering were identified as hotspots. Non nano-specific ecotoxicity impacts ranged from 1.58 × 10¹-2.91 × 10¹ CTUe/textile (CTUe: comparative toxic units for ecosystems) and nano-specific ecotoxicity impacts ranged from 2.01 × 10^-4-3.10 × 10^-3 CTUe/textile for the lowest and the highest Ag/nAg containing textiles, respectively. It is also found that unless the initial silver loading per textile is significantly high (in this case 4030 μg Ag/g textile comparing to the lowest load of 1.07 μg Ag/g textile), ecotoxicity and human health impacts of released silver species would be lower than ecotoxicity and human health impacts resulting from raw materials acquisition and manufacturing of the antibacterial textiles.

Impacts of Nanosilver-Based Textile Products Using a Life Cycle Assessment

Due to their properties, silver nanoparticles (AgNPs) are widely used in consumer products. The widespread use of these products leads to the release of such nanoparticles into the environment, during manufacturing, use, and disposal stages. Currently there is a high margin of uncertainty about the impacts of nano products on the environment and human health. Therefore, different approaches including life cycle assessment (LCA) are being used to evaluate the environmental and health impacts of these products. In this paper, a comparison between four different AgNP synthesis methods was conducted. In addition, four textile products that contain AgNPs were subjected to comparison using LCA analysis to assess their environmental and public health impacts using SimaPro modeling platform. Study results indicate that using alternative methods (green) to AgNPs synthesis will not necessarily reduce the environmental impacts of the synthesizing process. To the best of our knowledge, this is the first study that has compared and assessed the environmental burdens associated with different nanosilver-based textile products at different disposal scenarios. The synthesis of 1 kg of AgNPs using modified Tollens’ method resulted in 580 kg CO2 eq, while 531 kg CO2 eq resulted from the chemical approach. Furthermore, the manufacturing stage had the highest overall impacts as compared to other processes during the life cycle of the product, while the product utilization and disposal stages had the highest impacts on ecotoxicity. Sensitivity analysis revealed that under the two disposal scenarios of incineration and landfilling, the impacts were sensitive to the amount of AgNPs.

Guiding the design space for nanotechnology to advance sustainable crop production

The globally recognized need to advance more sustainable agriculture and food systems has motivated the emergence of transdisciplinary solutions, which include methodologies that utilize the properties of materials at the nanoscale to address extensive and inefficient resource use. Despite the promising prospects of these nanoscale materials, the potential for large-scale applications directly to the environment and to crops necessitates precautionary measures to avoid unintended consequences. Further, the effects of using engineered nanomaterials (ENMs) in agricultural practices cascade throughout their life cycle and include effects from upstream-embodied resources and emissions from ENM production as well as their potential downstream environmental implications. Building on decades-long research in ENM synthesis, biological and environmental interactions, fate, transport and transformation, there is the opportunity to inform the sustainable design of nano-enabled agrochemicals. Here we perform a screening-level analysis that considers the system-wide benefits and costs for opportunities in which ENMs can advance the sustainability of crop-based agriculture. These include their on-farm use as (1) soil amendments to offset nitrogen fertilizer inputs, (2) seed coatings to increase germination rates and (3) foliar sprays to enhance yields. In each analysis, the nano-enabled alternatives are compared against the current practice on the basis of performance and embodied energy. In addition to identifying the ENM compositions and application approaches with the greatest potential to sustainably advance crop production, we present a holistic, prospective, systems-based approach that promotes emerging alternatives that have net performance and environmental benefits.

Silver nanomaterials in the natural environment: An overview of their biosynthesis and kinetic behavior

Silver nanomaterials (Ag NMs) are fabricated by many biological components in our environment. Recently, research on their biosynthesis and reactions has become a focus of attention. Due to the complexity of biological systems and samples, specific processes and mechanisms involving Ag NMs are difficult to identify and elucidate on the molecular and chemical-bond level. The microorganisms and composite components of plant extracts are of great interest in many biological syntheses. Although potential biomolecules have been shown to play essential roles in biological systems in Ag NM biosynthesis, the detailed mechanism of the electron transfer process and crucial molecules that control this reaction have only recently come into focus. The reactive behavior of the Ag NMs is of great significance for understanding their overall behavior and toxicity. Additionally, only limited knowledge is available about their kinetics. All reactions involve chemical bond formation, electron transfer, or electrostatic interactions. An overview is presented of the biosynthesis of Ag NMs based on molecular supports including a nitrate reductase/NADH oxidase-involved electron transfer reaction and their mechanisms in Ag⁺ reduction: quinol-mediated mechanism and superoxide-dependent mechanism, and molecular supports in plant extracts, is presented. The environmental reaction kinetics and mechanisms of the interactions of Ag NMs with substances are introduced based on the formation and classification of chemical bonds. The particle-particle reaction kinetics of Ag NMs in the environment are discussed to directly explain their stability and aggregation behavior. The toxicity of Ag NMs is also presented. In addition, future prospects are summarized. This review is the first to provide an insight into the mediating molecules and chemical bonds involved in the biosynthesis, kinetics, and mechanisms of action of Ag NMs.

Nanosilver-Enabled Food Storage Container Tradeoffs: Environmental Impacts Versus Food Savings Benefit, Informed by Literature

Globally, thousands of tons of food are lost each year due to spoilage and degraded quality. This loss is a current critical issue that must be addressed to ensure adequate food supply for the growing world population; the use of technology and regulatory practices are avenues to a solution. One considered approach is the reduction of the microorganism population on the surface of food products to delay spoilage through the use of antimicrobials. One current method is the use of the antimicrobial properties of nanoscale silver (nAg) particles to prolong the freshness of stored food by reducing the bacteria present. Nanoscale silver-enabled food storage containers present a potential solution to the food loss problem; nevertheless, their environmental and human health effects have been questioned by the scientific community. Literature is used to generate data for the life cycle impact assessment of these types of products and their corresponding environmental effects. The benefits of nAg-enabled food storage containers are considered with respect to their potential to extend the shelf life of stored food and prevent food spoilage. The results illustrate that the environmental effects of nano-enabling food storage containers with silver is small (when the initial silver concentration is relatively low, less than 1% by mass) compared with the overall environmental effects of food storage containers and also relatively small compared with the environmental effects of producing the stored food. This finding suggests that the added environmental burden of nano-enabling food storage containers may be small when compared with the environmental burden of food losses. Integr Environ Assess Manag 2018;14:769-776. © 2018 SETAC.

Life Cycle Assessment and Release Studies for 15 Nanosilver-Enabled Consumer Products: Investigating Hotspots and Patterns of Contribution

Increasing use of silver nanoparticles (AgNPs) in consumer products as antimicrobial agents has prompted extensive research toward the evaluation of their potential release to the environment and subsequent ecotoxicity to aquatic organisms. It has also been shown that AgNPs can pose significant burdens to the environment from life cycle emissions associated with their production, but these impacts must be considered in the context of actual products that contain nanosilver. Here, a cradle-to-gate life cycle assessment for the production of 15 different AgNP-enabled consumer products was performed, coupled with release studies of those same products, thus providing a consistent analytical platform for investigation of potential nanosilver impacts across a range of product types and concentrations. Environmental burdens were assessed over multiple impact categories defined by the United States Environmental Protection Agency's Tool for the Reduction and Assessment of Chemical and Other Environmental Impacts (TRACI 2.1) method. Depending on the product composition and silver loading, the contribution of AgNP synthesis to the overall impacts was seen to vary over a wide range from 1% to 99%. Release studies found that solid polymeric samples lost more silver during wash compared to fibrous materials. Estimates of direct ecotoxicity impacts of AgNP releases from those products with the highest leaching rates resulted in lower impact levels compared to cradle-to-gate ecotoxicity from production for those products. Considering both cradle-to-gate production impacts and nanoparticle release studies, in conjunction with estimates of life cycle environmental and health benefits of nanoparticle incorporation, can inform sustainable nanoenabled product design.

Structure-Activity Relationship of Membrane-Targeting Cationic Ligands on a Silver Nanoparticle Surface in an Antibiotic-Resistant Antibacterial and Antibiofilm Activity Assay

To explore the structure-activity relationship of membrane-targeting cationic ligands on a silver nanoparticle surface in an antibiotic-resistant antibacterial and antibiofilm activity assay, a series of functionalized silver nanocomposites were synthesized. Tuning the structural configuration, molecular weight, and side-chain length of the cationic ligands on the nanoparticle surface provided silver nanocomposites with effective antibacterial activity against both antibiotic-resistant Gram-negative and Gram-positive bacteria, including bacterial biofilms. These silver nanocomposites did not trigger hemolytic activity. Significantly, the bacteria did not develop resistance to the obtained nanocomposites even after 30 generations. A study of the antibacterial mechanism confirmed that these nanocomposites could irreversibly disrupt the membrane structure of bacteria and effectively inhibit intracellular enzyme activity, ultimately leading to bacterial death. The silver nanocomposites (64 μg/mL) could eradicate 80% of an established antibiotic-resistant bacterial biofilm. The strong structure-activity relationship toward antibacterial and antibiofilm activity suggests that variations in the conformational property of the functional ligand could be valuable in the discovery of new nano-antibacterial agents for treating pathogenic bacterial infections.

Development of Comparative Toxicity Potentials of TiO2 Nanoparticles for Use in Life Cycle Assessment

Studies have shown that releases of nanoparticles may take place through the life cycle of products embedding nanomaterials, thus resulting in potential impacts on ecosystems and human health. While several life cycle assessment (LCA) studies have assessed such products, only a few of them have quantitatively addressed the toxic impacts caused by released nanoparticles, thus leading to potential biases in their conclusions. Here, we address this gap and aim to provide a framework for calculating characterization factors or comparative toxicity potentials (CTP) for nanoparticles and derive CTP values for TiO₂ nanoparticles (TiO₂-NP) for use in LCA. We adapted the USEtox 2.0 consensus model to integrate the SimpleBox4Nano fate model, and we populated the resulting model with TiO₂-NP specific data. We thus calculated CTP values for TiO₂ nanoparticles for air, water, and soil emission compartments for freshwater ecotoxicity and human toxicity, both cancer effects and noncancer effects. Our results appeared plausible after benchmarking with CTPs for other nanoparticles and substances present in the USEtox database, while large differences were observed with CTP values for TiO₂ nanoparticles published in earlier studies. Assumptions, which were performed in those previous studies because of lack of data and knowledge at the time they were made, primarily explain such discrepancies. For future assessment of potential toxic impacts of TiO₂ nanoparticles in LCA studies, we therefore recommend the use of our calculated CTP.