Environmental impacts of selected metal cations for phosphorus capture in natural waters: A synthesis.

Cultural eutrophication from excessive human-related nutrient (phosphorus, P, and nitrogen, N) inputs is a major concern for water quality. Because P historically was regarded as the critical nutrient in controlling noxious algal/plant growth, P became the focus of "capturing" techniques, with emphasis on removal performance rather than environmental impacts. Here, we synthesize a literature review of known environmental effects linked to use of metal-cation-based P-capturing materials under eutrophic conditions in freshwaters. P-capturing materials with functional cations based on aluminum (Al), calcium (Ca), iron (Fe), lanthanum (La), and magnesium (Mg) were reviewed in terms of their ecotoxicity, persistence, and bioaccumulation-standard criteria used to evaluate environmental risks of chemical substances. We found very few published studies on environmental impacts of metal-cation-based P-capturing materials under eutrophic conditions. Available reports indicated that environmental effects vary depending on the selected material, dose, target organism(s), and experimental conditions. The Al-based materials had the potential to negatively impact various biota; several Fe-based materials caused various levels of toxicity in a limited group of aquatic organisms; La-based materials can bioaccumulate and some were linked to various harmful effects on biota; and Mg-based materials also adversely affected various organisms. The limited number of published studies underscores the need for further research to characterize the environmental impacts of these materials. Results can be used to guide future work and can assist resource managers in sustainable management strategies. Among various research needs, future assessments should assess the impacts of chronic exposures on sensitive species under realistic field conditions in eutrophic waters.

Towards realizing nano-enabled precision delivery in plants.

Nanocarriers (NCs) that can precisely deliver active agents, nutrients and genetic materials into plants will make crop agriculture more resilient to climate change and sustainable. As a research field, nano-agriculture is still developing, with significant scientific and societal barriers to overcome. In this Review, we argue that lessons can be learned from mammalian nanomedicine. In particular, it may be possible to enhance efficiency and efficacy by improving our understanding of how NC properties affect their interactions with plant surfaces and biomolecules, and their ability to carry and deliver cargo to specific locations. New tools are required to rapidly assess NC-plant interactions and to explore and verify the range of viable targeting approaches in plants. Elucidating these interactions can lead to the creation of computer-generated in silico models (digital twins) to predict the impact of different NC and plant properties, biological responses, and environmental conditions on the efficiency and efficacy of nanotechnology approaches. Finally, we highlight the need for nano-agriculture researchers and social scientists to converge in order to develop sustainable, safe and socially acceptable NCs.

Phytoextraction of per- and polyfluoroalkyl substances (PFAS) by weeds: Effect of PFAS physicochemical properties and plant physiological traits.

Phytoextraction is a promising technology that uses plants to remediate contaminated soil. However, its feasibility for per- and polyfluoroalkyl substances (PFAS) and the impact of PFAS properties and plant traits on phytoextraction efficacy remains unknown. In this study, we conducted greenhouse experiment and evaluated the potential of weeds for phytoextraction of PFAS from soil and assessed the effects of PFAS properties and plant traits on PFAS uptake via systematic correlation analyses and electron probe microanalyzer with energy dispersive spectroscopy (FE-EPMA-EDS) imaging. The results showed that 1) phytoextraction can remove 0.04%- 41.4%wt of PFAS from soil, with extracted PFAS primarily stored in plant shoots; 2) Weeds preferentially extracted short-chain PFAS over long-chain homologues from soil. 3) PFAS molecular size and hydrophilicity determined plant uptake behavior, while plant morphological traits, particularly root protein and lipid content, influenced PFAS accumulation and translocation. Although plants with thin roots and small leaf areas exhibited greater PFAS uptake and storage ability, the impact of PFAS physicochemical properties was more significant. 4) Finally, short-chain PFAS were transported quickly upwards in the plant, while uptake of long-chain PFOS was restricted.

Influence of natural organic matter and pH on phosphate removal by and filterable lanthanum release from lanthanum-modified bentonite.

Lanthanum modified bentonite (LMB) has been applied to eutrophic lakes to reduce phosphorus (P) concentrations in the water column and mitigate P release from sediments. Previous experiments suggest that natural organic matter (NOM) can interfere with phosphate (PO4)-binding to LMB and exacerbate lanthanum (La)-release from bentonite. This evidence served as motivation for this study to systematically determine the effects of NOM, solution pH, and bentonite as a La carrier on P removal. We conducted both geochemical modeling and controlled-laboratory batch kinetic experiments to understand the pH-dependent impacts of humic and fulvic acids on PO4-binding to LMB and La release from LMB. The role of bentonite was studied by comparing PO4 removal obtained by LMB and La3+ (added as LaCl3 salt to represent the La-containing component of LMB). Our results from both geochemical modeling and batch experiments indicate that the PO4-binding ability of LMB is decreased in the presence of NOM, and the decrease is more pronounced at pH 8.5 than at 6. At the highest evaluated NOM concentration (28 mg C L-1), PO4-removal by La3+ was substantially lower than that by LMB, implying that bentonite clay in LMB shielded La from interactions with NOM, while still allowing PO4 capture by La. Finally, the presence of NOM promoted La-release from LMB, and the amount of La released depended on solution pH and both the type (i.e., fulvic/humic acid ratio) and concentration of NOM. Overall, these results provide an important basis for management of P in lakes and eutrophication control that relies on LMB applications.

Responsible innovation of nano-agrifoods: Insights and views from U.S. stakeholders.

To date, there has been little published work that has elicited diverse stakeholder views of nano-agrifoods and of how nano-agrifoods align with the goals of responsible innovation. This paper aims to fill this research gap by investigating views of nano-agrifoods, how well their development adheres to principles of responsible innovation, and potential challenges for achieving responsible nano-agrifood innovation. Using an online engagement platform, we find that U.S. stakeholder views of responsible innovation were dominated by environmental, health, and safety (EHS) contexts, considerations of societal impacts, opportunities for stakeholder engagement, and responding to societal needs. These views overlap with scholarly definitions of responsible innovation, albeit stakeholders were more focused on impacts of products, while the field of responsible innovation strives for more "upstream" considerations of the process of innovation. We also find that views of nano-agrifoods differed across applications with dietary supplements and improved whitening of infant formula viewed least favorably, and environmental health or food safety applications viewed most favorably. These findings align with the larger body of literature, whereby stakeholders are expected to be more supportive of nanotechnology used in agricultural applications compared to directly within food and food supplements. Overall, participants indicated they held relatively neutral views on research and innovation for nano-agrifoods being conducted responsibly, and they identified key challenges to ensuring their responsible innovation that were related to uncertainties in EHS studies, the need for public understanding and acceptance, and adequate regulation. In light of these results, we recommend future research efforts on EHS impacts and risk-benefit frameworks for nano-agrifoods, better understanding stakeholder views on what constitutes effective regulation, and addressing challenges with effective regulation and responsible innovation practices.

Biological interactions between nanomaterials and placental development and function following oral exposure.

We summarize the literature involving the deposition of nanomaterials within the placenta following oral exposure and the biological interactions between nanomaterials and placental development and function. The review focuses on the oral exposure of metal and metal oxide engineered nanomaterials (ENMs), carbon-based ENMs, and nanoplastics in animal models, with a minor discussion of intravenous injections. Although the literature suggests that the placenta is an efficient barrier in preventing nanomaterials from reaching the fetus, nanomaterials that accumulate in the placenta may interfere with its development and function. Furthermore, some studies have demonstrated a decrease in placental weight and association with adverse fetal health outcomes following oral exposure to nanomaterials. Since nanomaterials are increasingly used in food, food packaging, and have been discovered in drinking water, the risk for adverse impacts on placental development and functions, with secondary effects on embryo-fetal development, following unintentional maternal ingestion of nanomaterials requires further investigation.

International Implications of Labeling Foods Containing Engineered Nanomaterials.

To provide greater transparency and comprehensive information to consumers regarding their purchase choices, the European Parliament and the Council have mandated via Regulation 1169/2011 that foods containing engineered nanomaterials (ENMs) be labeled. This review covers the main concerns related to the use of ENMs in foods and the potential impacts that this type of food labeling might have on diverse stakeholder groups, including those outside the European Union (EU), e.g., in the United States. We also provide recommendations to stakeholders for overcoming existing challenges related to labeling foods containing ENMs. The revised EU food labeling requirements will likely result in a number of positive developments and a number of challenges for stakeholders in both EU and non-EU countries. Although labeling of foods containing ENMs will likely improve transparency, provide more information to facilitate consumer decisions, and build trust among food safety authorities and consumers, critical obstacles to the successful implementation of these labeling requirements remain, including the need for (i) harmonized information requirements or regulations between countries in different regions of the world, (ii) clarification of the regulatory definitions of the ENMs to be used for food labeling, (iii) robust techniques to detect, measure, and characterize diverse ENMs in food matrices, and (iv) clarification of the list of ENMs that may be exempt from labeling requirements, such as several food additives used for decades. We recommend that food industries and food safety authorities be more proactive in communicating with the public and consumer groups regarding the potential benefits and risks of using ENMs in foods. Efforts should be made to improve harmonization of information requirements between countries to avoid potential international trade barriers.

Emerging Technologies for Environmental Remediation: Integrating Data and Judgment.

Emerging technologies present significant challenges to researchers, decision-makers, industry professionals, and other stakeholder groups due to the lack of quantitative risk, benefit, and cost data associated with their use. Multi-criteria decision analysis (MCDA) can support early decisions for emerging technologies when data is too sparse or uncertain for traditional risk assessment. It does this by integrating expert judgment with available quantitative and qualitative inputs across multiple criteria to provide relative technology scores. Here, an MCDA framework provides preliminary insights on the suitability of emerging technologies for environmental remediation by comparing nanotechnology and synthetic biology to conventional remediation methods. Subject matter experts provided judgments regarding the importance of criteria used in the evaluations and scored the technologies with respect to those criteria. The results indicate that synthetic biology may be preferred over nanotechnology and conventional methods for high expected benefits and low deployment costs but that conventional technology may be preferred over emerging technologies for reduced risks and development costs. In the absence of field data regarding the risks, benefits, and costs of emerging technologies, structuring evidence-based expert judgment through a weighted hierarchy of topical questions may be helpful to inform preliminary risk governance and guide emerging technology development and policy.

A web-based tool to engage stakeholders in informing research planning for future decisions on emerging materials.

Prioritizing and assessing risks associated with chemicals, industrial materials, or emerging technologies is a complex problem that benefits from the involvement of multiple stakeholder groups. For example, in the case of engineered nanomaterials (ENMs), scientific uncertainties exist that hamper environmental, health, and safety (EHS) assessments. Therefore, alternative approaches to standard EHS assessment methods have gained increased attention. The objective of this paper is to describe the application of a web-based, interactive decision support tool developed by the U.S. Environmental Protection Agency (U.S. EPA) in a pilot study on ENMs. The piloted tool implements U.S. EPA's comprehensive environmental assessment (CEA) approach to prioritize research gaps. When pursued, such research priorities can result in data that subsequently improve the scientific robustness of risk assessments and inform future risk management decisions. Pilot results suggest that the tool was useful in facilitating multi-stakeholder prioritization of research gaps. Results also provide potential improvements for subsequent applications. The outcomes of future CEAWeb applications with larger stakeholder groups may inform the development of funding opportunities for emerging materials across the scientific community (e.g., National Science Foundation Science to Achieve Results [STAR] grants, National Institutes of Health Requests for Proposals).

Modeling approaches for characterizing and evaluating environmental exposure to engineered nanomaterials in support of risk-based decision making.

As the use of engineered nanomaterials becomes more prevalent, the likelihood of unintended exposure to these materials also increases. Given the current scarcity of experimental data regarding fate, transport, and bioavailability, determining potential environmental exposure to these materials requires an in depth analysis of modeling techniques that can be used in both the near- and long-term. Here, we provide a critical review of traditional and emerging exposure modeling approaches to highlight the challenges that scientists and decision-makers face when developing environmental exposure and risk assessments for nanomaterials. We find that accounting for nanospecific properties, overcoming data gaps, realizing model limitations, and handling uncertainty are key to developing informative and reliable environmental exposure and risk assessments for engineered nanomaterials. We find methods suited to recognizing and addressing significant uncertainty to be most appropriate for near-term environmental exposure modeling, given the current state of information and the current insufficiency of established deterministic models to address environmental exposure to engineered nanomaterials.

Operationalization and application of "early warning signs" to screen nanomaterials for harmful properties.

In 2001 the European Environment Agency (EEA) published a report that analyzed 14 cases of technological developments that later on turned out to have negative side-effects and they identified 12 "late lessons" for current and future policy-makers to bear in mind when initiating new technological endeavors. This paper explores how the first lesson ­ "Acknowledge and respond to ignorance, uncertainty and risk in technology appraisal" could be applied to screen nanomaterials. In cases of ignorance, uncertainty and risk, the EEA recommends paying particular attention to important warning signs such as novelty, persistency, whether materials are readily dispersed in the environment, and whether they bioaccumulate or lead to potentially irreversible action. Through an analysis of these criteria using five well-known nanomaterials (titanium dioxide, carbon nanotubes, liposomes, poly(lactic-co-glycolic acid) and nanoscale zero-valent iron), it was found that only nanoTiO2 fulfils all the five criteria. Depending on the length of the nanotubes, carbon nanotubes fulfil 3 or 4 criteria whereas liposomes, poly(lactic-co-glycolic acid), nanoscale zero-valent iron fulfil only one criteria. Finally, we discuss how these warning signs can be used by different stakeholders such as nanomaterial researchers and developers, companies and regulators to design benign nanomaterials, communicate what is known about nano-risks and decide on whether to implement precautionary regulatory measures.

Environmental risk analysis for nanomaterials: review and evaluation of frameworks.

In response to the challenges of conducting traditional human health and ecological risk assessment for nanomaterials (NM), a number of alternative frameworks have been proposed for NM risk analysis. This paper evaluates various risk analysis frameworks proposed for NM based on a number of criteria. Among other results, most frameworks were found to be flexible for multiple NM, suitable for multiple decision contexts, included life cycle perspectives and precautionary aspects, transparent and able to include qualitative and quantitative data. Nevertheless, most frameworks were primarily applicable to occupational settings with minor environmental considerations, and most have not been thoroughly tested on a wide range of NM. Care should also be taken when selecting the most appropriate risk analysis strategy for a given risk context. Given this, we recommend a multi-faceted approach to assess the environmental risks of NM as well as increased applications and testing of the proposed frameworks for different NM.

Conceptual modeling for identification of worst case conditions in environmental risk assessment of nanomaterials using nZVI and C60 as case studies.

Conducting environmental risk assessment of engineered nanomaterials has been an extremely challenging endeavor thus far. Moreover, recent findings from the nano-risk scientific community indicate that it is unlikely that many of these challenges will be easily resolved in the near future, especially given the vast variety and complexity of nanomaterials and their applications. As an approach to help optimize environmental risk assessments of nanomaterials, we apply the Worst-Case Definition (WCD) model to identify best estimates for worst-case conditions of environmental risks of two case studies which use engineered nanoparticles, namely nZVI in soil and groundwater remediation and C(60) in an engine oil lubricant. Results generated from this analysis may ultimately help prioritize research areas for environmental risk assessments of nZVI and C(60) in these applications as well as demonstrate the use of worst-case conditions to optimize future research efforts for other nanomaterials. Through the application of the WCD model, we find that the most probable worst-case conditions for both case studies include i) active uptake mechanisms, ii) accumulation in organisms, iii) ecotoxicological response mechanisms such as reactive oxygen species (ROS) production and cell membrane damage or disruption, iv) surface properties of nZVI and C(60), and v) acute exposure tolerance of organisms. Additional estimates of worst-case conditions for C(60) also include the physical location of C(60) in the environment from surface run-off, cellular exposure routes for heterotrophic organisms, and the presence of light to amplify adverse effects. Based on results of this analysis, we recommend the prioritization of research for the selected applications within the following areas: organism active uptake ability of nZVI and C(60) and ecotoxicological response end-points and response mechanisms including ROS production and cell membrane damage, full nanomaterial characterization taking into account detailed information on nanomaterial surface properties, and investigations of dose-response relationships for a variety of organisms.

Redefining risk research priorities for nanomaterials.

Chemical-based risk assessment underpins the current approach to responsible development of nanomaterials (NM). It is now recognised, however, that this process may take decades, leaving decision makers with little support in the near term. Despite this, current and near future research efforts are largely directed at establishing (eco)toxicological and exposure data for NM, and comparatively little research has been undertaken on tools or approaches that may facilitate near-term decisions, some of which we briefly outline in this analysis. We propose a reprioritisation of NM risk research efforts to redress this imbalance, including the development of more adaptive risk governance frameworks, alternative/complementary tools to risk assessment, and health and environment surveillance.

Environmental benefits and risks of zero-valent iron nanoparticles (nZVI) for in situ remediation: risk mitigation or trade-off?

The use of nanoscaled zero-valent iron particles (nZVI) to remediate contaminated soil and groundwater has received increasing amounts of attention within the last decade, primarily due to its potential for broader application, higher reactivity, and cost-effectiveness compared to conventional zero-valent iron applications and other in situ methods. However, the potential environmental risks of nZVI in in situ field scale applications are largely unknown at the present and traditional environmental risk assessment approaches are not yet able to be completed. Therefore, it may not yet be fully clear how to consider the environmental benefits and risks of nZVI for in situ applications. This analysis therefore addresses the challenges of comprehensively considering and weighing the expected environmental benefits and potential risks of this emerging environmentally-beneficial nanotechnology, particularly relevant for environmental engineers, scientists, and decision makers. We find that most of the benefits of using nZVI are based on near-term considerations, and large data gaps currently exist within almost all aspects of environmental exposure and effect assessments. We also find that while a wide range of decision support tools and frameworks alternative to risk assessment are currently available, a thorough evaluation of these should be undertaken in the near future to assess their full relevancy for nZVI at specific sites. Due to the absence of data in environmental risk evaluations, we apply a 'best' and 'worst' case scenario evaluation as a first step to qualitatively evaluate the current state-of-knowledge regarding the potential environmental risks of nZVI. The result of this preliminary qualitative evaluation indicates that at present, there are no significant grounds on which to form the basis that nZVI currently poses a significant, apparent risk to the environment, although the majority of the most serious criteria (i.e. potential for persistency, bioaccumulation, toxicity) are generally unknown. We recommend that in cases where nZVI may be chosen as the 'best' treatment option, short and long-term environmental monitoring is actively employed at these sites. We furthermore recommend the continued development of responsible nZVI innovation and better facilitated information exchange between nZVI developers, nano-risk researchers, remediation industry, and decision makers.

Conscious worst case definition for risk assessment, part I: a knowledge mapping approach for defining most critical risk factors in integrative risk management of chemicals and nanomaterials.

This paper helps bridge the gap between scientists and other stakeholders in the areas of human and environmental risk management of chemicals and engineered nanomaterials. This connection is needed due to the evolution of stakeholder awareness and scientific progress related to human and environmental health which involves complex methodological demands on risk management. At the same time, the available scientific knowledge is also becoming more scattered across multiple scientific disciplines. Hence, the understanding of potentially risky situations is increasingly multifaceted, which again challenges risk assessors in terms of giving the 'right' relative priority to the multitude of contributing risk factors. A critical issue is therefore to develop procedures that can identify and evaluate worst case risk conditions which may be input to risk level predictions. Therefore, this paper suggests a conceptual modelling procedure that is able to define appropriate worst case conditions in complex risk management. The result of the analysis is an assembly of system models, denoted the Worst Case Definition (WCD) model, to set up and evaluate the conditions of multi-dimensional risk identification and risk quantification. The model can help optimize risk assessment planning by initial screening level analyses and guiding quantitative assessment in relation to knowledge needs for better decision support concerning environmental and human health protection or risk reduction. The WCD model facilitates the evaluation of fundamental uncertainty using knowledge mapping principles and techniques in a way that can improve a complete uncertainty analysis. Ultimately, the WCD is applicable for describing risk contributing factors in relation to many different types of risk management problems since it transparently and effectively handles assumptions and definitions and allows the integration of different forms of knowledge, thereby supporting the inclusion of multifaceted risk components in cumulative risk management.

Setting the limits for engineered nanoparticles in European surface waters - are current approaches appropriate?

The current widespread and diverse use of engineered nanoparticles (ENPs) in consumer products is expected to result in direct and indirect emissions to the aquatic environment. In Europe, the Water Framework Directive (WFD) is responsible for maintaining a good chemical and ecological status of surface waters. This review provides an insight to the likely scenarios if an engineered nanoparticle should be considered a "priority substance" in the WFD. Through a brief literature review of the aquatic toxicity of carbon- and metal-containing ENPs and in light of principles to establish environmental quality standards, we conclude that it is impossible to set limit values for ENPs in surface waters now and in the foreseeable future. This is due to the extensive lack of knowledge not only in relation to unknown toxic effects, degradability, and bioaccumulation of ENPs in the aquatic environment, but also due to the questionable validity of test systems and methods to establish environmental quality standards (EQS). From this, we also suggest some paths to follow to compensate for these knowledge gaps which include environmental monitoring and a closer look at the use of ENPs in consumer products.