A roadmap to strengthen standardisation efforts in risk governance of nanotechnology

A roadmap was developed to strengthen standardisation activities for risk governance of nanotechnology. Its baseline is the available standardised and harmonised methods for nanotechnology developed by the International Organization for Standardization (ISO), the European Committee for Standardization (CEN), and the Organisation for Economic Co-operation and Development (OECD). In order to identify improvements and needs for new themes in standardisation work, an analysis of the state-of-the-art concepts and interpretations of risk governance of nanotechnology was performed. Eleven overall areas of action were identified, each including a subset of specific topics. Themes addressed include physical chemical characterisation, assessment of hazard, exposure, risk and socio-economic factors, as well as education & training and social dialogue. This has been visualised in a standardisation roadmap spanning a timeframe of ten years and including key outcomes and highlights of the analysis. Furthermore, the roadmap indicates potential areas of action for harmonisation and standardisation (H&S) for nanomaterials and nanotechnology. It also includes an evaluation of the current level (limited, moderate, intense) of ongoing H&S activities and indicates the time horizon for the different areas of action. As the identified areas differ in their state of development, the number and type of actions varied widely amongst the different actions towards achieving standardisation. Thus, priority areas were also identified. The overall objective of these actions is to strengthen risk governance towards a safe use of nanomaterials and nano-related products. Though not explicitly addressed, risk-based legislation and policies are supported via the proposed H&S actions.

Current status and future challenges of genotoxicity OECD Test Guidelines for nanomaterials: a workshop report

Genotoxicity testing for nanomaterials remains challenging as standard testing approaches require some adaptation, and further development of nano-specific OECD Test Guidelines (TGs) and Guidance Documents (GDs) are needed. However, the field of genotoxicology continues to progress and new approach methodologies (NAMs) are being developed that could provide relevant information on the range of mechanisms of genotoxic action that may be imparted by nanomaterials. There is a recognition of the need for implementation of new and/or adapted OECD TGs, new OECD GDs, and utilization of NAMs within a genotoxicity testing framework for nanomaterials. As such, the requirements to apply new experimental approaches and data for genotoxicity assessment of nanomaterials in a regulatory context is neither clear, nor used in practice. Thus, an international workshop with representatives from regulatory agencies, industry, government, and academic scientists was convened to discuss these issues. The expert discussion highlighted the current deficiencies that exist in standard testing approaches within exposure regimes, insufficient physicochemical characterization, lack of demonstration of cell or tissue uptake and internalization, and limitations in the coverage of genotoxic modes of action. Regarding the latter aspect, a consensus was reached on the importance of using NAMs to support the genotoxicity assessment of nanomaterials. Also highlighted was the need for close engagement between scientists and regulators to (i) provide clarity on the regulatory needs, (ii) improve the acceptance and use of NAM-generated data, and (iii) define how NAMs may be used as part of weight of evidence approaches for use in regulatory risk assessments.

Towards harmonisation of testing of nanomaterials for EU regulatory requirements on chemical safety - A proposal for further actions

Over the recent years, EU chemicals legislation, guidance and test guidelines have been developed or adapted for nanomaterials to facilitate safe use of nanomaterials. This paper provides an overview of the information requirements across different EU regulatory areas. For each information requirement, a group of 22 experts identified potential needs for further action to accommodate guidance and test guidelines to nanomaterials. Eleven different needs for action were identified, capturing twenty-two information requirements that are specific to nanomaterials and relevant to multiple regulatory areas. These were further reduced to three overarching issues: 1) resolve issues around nanomaterial dispersion stability and dosing in toxicity testing, in particular for human health endpoints, 2) further develop tests or guidance on degradation and transformation of organic nanomaterials or nanomaterials with organic components, and 3) further develop tests and guidance to measure (a)cellular reactivity of nanomaterials. Efforts towards addressing these issues will result in better fit-for-purpose test methods for (EU) regulatory compliance. Moreover, it secures validity of hazard and risk assessments of nanomaterials. The results of the study accentuate the need for a structural process of identification of information needs and knowledge generation, preferably as part of risk governance and closely connected to technological innovation policy.

How to formulate hypotheses and IATAs to support grouping and read-across of nanoforms

Manufacturing and functionalizing materials at the nanoscale has led to the generation of a whole array of nanoforms (NFs) of substances varying in size, morphology, and surface characteristics. Due to financial, time, and ethical considerations, testing every unique NF for adverse effects is virtually impossible. Use of hypothesis-driven grouping and read-across approaches, as supported by the GRACIOUS Framework, represents a promising alternative to case-by-case testing that will make the risk assessment process more efficient. Through application of appropriate grouping hypotheses, the Framework facilitates the assessment of similarity between NFs, thereby supporting grouping and read-across of information, minimizing the need for new testing, and aligning with the 3R principles of replacement, reduction, and refinement of animals in toxicology studies. For each grouping hypothesis an integrated approach to testing and assessment (IATA) guides the user in data gathering and acquisition to test the hypothesis, following a structured format to facilitate efficient decision-making. Here we present the template used to generate the GRACIOUS grouping hypotheses encompassing information relevant to “Lifecycle, environmental release, and human exposure”, “What they are: physicochemical characteristics”, “Where they go: environmental fate, uptake, and toxicokinetics”, and “What they do: human and environmental toxicity”. A summary of the template-derived hypotheses focusing on human health is provided, along with an overview of the IATAs generated by the GRACIOUS project. We discuss the application and flexibility of the template, providing the opportunity to expand the application of grouping and read-across in a logical, evidence-based manner to a wider range of NFs and substances.

Identification of emerging safety and sustainability issues of advanced materials: Proposal for a systematic approach

The EU Chemicals Strategy for Sustainability is a first step to achieve the Green Deal ambition for a toxic-free environment, and ensure that chemicals are produced and used in a way that maximises their contribution to society while avoiding harm to our planet and to future generations. Advanced materials are predicted to play a pivotal role in achieving this ambition and the underlying sustainability goals, and considerable efforts are invested in designing new classes of materials. Examples of such materials are metamaterials, artificially architectured materials designed to have material properties beyond those of the individual ingredient materials, or active materials at the boundary between materials and devices (e.g., new biomedical soft materials). Such innovative advanced materials raise concern about possible future safety and sustainability issues and would benefit from appropriate risk governance that promotes innovation, while pushing for safety and sustainability. To balance these aspects, a methodology is proposed for the early-stage identification of emerging safety and sustainability issues of advanced materials. As exemplified by two case studies, the methodology aims to be of use for innovators, risk assessors, and regulators. Extension of the methodology is highlighted, as well as implementation in broader initiatives like the EU's industrial policy approach.

Physico-chemical properties of manufactured nanomaterials - Characterisation and relevant methods. An outlook based on the OECD Testing Programme

Identifying and characterising nanomaterials require additional information on physico-chemical properties and test methods, compared to chemicals in general. Furthermore, regulatory decisions for chemicals are usually based upon certain toxicological properties, and these effects may not be equivalent to those for nanomaterials. However, regulatory agencies lack an authoritative decision framework for nanomaterials that links the relevance of certain physico-chemical endpoints to toxicological effects. This paper investigates various physico-chemical endpoints and available test methods that could be used to produce such a decision framework for nanomaterials. It presents an overview of regulatory relevance and methods used for testing fifteen proposed physico-chemical properties of eleven nanomaterials in the OECD Working Party on Manufactured Nanomaterials' Testing Programme, complemented with methods from literature, and assesses the methods' adequacy and applications limits. Most endpoints are of regulatory relevance, though the specific parameters depend on the nanomaterial and type of assessment. Size (distribution) is the common characteristic of all nanomaterials and is decisive information for classifying a material as a nanomaterial. Shape is an important particle descriptor. The octanol-water partitioning coefficient is undefined for particulate nanomaterials. Methods, including sample preparation, need to be further standardised, and some new methods are needed. The current work of OECD's Test Guidelines Programme regarding physico-chemical properties is highlighted.

Considerations for Safe Innovation: The Case of Graphene

The terms "Safe innovation" and "Safe(r)-by-design" are currently popular in the field of nanotechnology. These terms are used to describe approaches that advocate the consideration of safety aspects already at an early stage of the innovation process of (nano)materials and nanoenabled products. Here, we investigate the possibilities of considering safety aspects during various stages of the innovation process of graphene, outlining what information is already available for assessing potential hazard, exposure, and risks. In addition, we recommend further steps to be taken by various stakeholders to promote the safe production and safe use of graphene.

Grouping and Read-Across Approaches for Risk Assessment of Nanomaterials

Physicochemical properties of chemicals affect their exposure, toxicokinetics/fate and hazard, and for nanomaterials, the variation of these properties results in a wide variety of materials with potentially different risks. To limit the amount of testing for risk assessment, the information gathering process for nanomaterials needs to be efficient. At the same time, sufficient information to assess the safety of human health and the environment should be available for each nanomaterial. Grouping and read-across approaches can be utilised to meet these goals. This article presents different possible applications of grouping and read-across for nanomaterials within the broader perspective of the MARINA Risk Assessment Strategy (RAS), as developed in the EU FP7 project MARINA. Firstly, nanomaterials can be grouped based on limited variation in physicochemical properties to subsequently design an efficient testing strategy that covers the entire group. Secondly, knowledge about exposure, toxicokinetics/fate or hazard, for example via properties such as dissolution rate, aspect ratio, chemical (non-)activity, can be used to organise similar materials in generic groups to frame issues that need further attention, or potentially to read-across. Thirdly, when data related to specific endpoints is required, read-across can be considered, using data from a source material for the target nanomaterial. Read-across could be based on a scientifically sound justification that exposure, distribution to the target (fate/toxicokinetics) and hazard of the target material are similar to, or less than, the source material. These grouping and read-across approaches pave the way for better use of available information on nanomaterials and are flexible enough to allow future adaptations related to scientific developments.

Effects of spatial and temporal variation in metal availability on earthworms in floodplain soils of the river Dommel, The Netherlands

Regarding impact on ecological soil functioning, metal pollution is often considered a constant factor for certain sampling sites. However, especially bioavailable concentrations may differ in space and time. This aspect was investigated on four sites along a metal-polluted river, differing in soil characteristics and metal concentrations. Every four weeks earthworm densities, soil characteristics, and metal concentrations in soil and earthworms were determined. Earthworm biomass and density fluctuated in time and increased with increasing metal contamination, indicating the presence of compensating factors. Multivariate analysis suggested organic matter and moisture content to be the main factors explaining earthworm biomass. Metal concentrations in the earthworms increased with increasing total or 0.01M CaCl(2) extractable soil concentrations, but no time-related trends were seen. Cadmium concentrations in the earthworms exceeded background values, suggesting a potential risk. The neutral red retention biomarker assay, however, did not show any signs of metal stress in the earthworms.

Chronic toxicity of polycyclic aromatic compounds to the springtail Folsomia candida and the enchytraeid Enchytraeus crypticus

An urgent need exists for incorporating heterocyclic compounds and (bio)transformation products in ecotoxicological test schemes and risk assessment of polycyclic aromatic compounds (PACs). The aim of the present study therefore was to determine the chronic effects of (heterocyclic) PACs on two terrestrial invertebrates, the springtail Folsomia candida and the enchytraeid Enchytraeus crypticus. The effects of 11 PACs were determined in chronic experiments using reproduction and survival as endpoints. The results demonstrated that as far as narcosis-induced mortality is concerned, effects of both homocyclic and heterocyclic PACs are well described by the relationship between estimated pore-water 50% lethal concentrations and log Kow. In contrast, specific effects on reproduction varied between species and between compounds as closely related as isomers, showing up as deviations from the relationship between pore-water 50% effect concentrations and log Kow. These unpredictable specific effects on reproduction force one to test the toxicity of these PACs to populations of soil invertebrates to obtain reliable effect concentrations for use in risk assessment of PACs.

Membrane-contaminant interaction found by 3D force field calculations

Enthalpies of contaminant transfer from water to a 1,2-Dilauroyl-DL-phosphatidyl ethanolamine (DLPE) membrane were calculated in order to study the suitability of 3D force fields for the calculation of membrane-water partitioning constants (Kmw) and as potential descriptors for bio-concentration. A 3D DLPE membrane model was built in a MM+ force field using AM1 atomic charges. 3,5-Dichlorobiphenyl (PCB14), 4,4'-dichlorobiphenyl (PCB15), 1,1,1-trichloro-2,2-bis-(4-chlorophenyl)-ethane (PPDDT or p,p'-DDT) and 2-chloro-4-ethylamino-6-isopropylamino-s-triazine (atrazine) were inserted into apolar and polar sites and their interaction energies with the membrane were calculated by geometrical optimization (GO). Energies of hydratation were subtracted from membrane-contaminant interactions of selected sites. The resulting values for the enthalpies of transfer from water to the membrane were 4.7, -2.3, 11.5 and -9.2 kcal/mol for PCB14, PCB15, PPDDT and atrazine, respectively. In contrast to PCB15, the value of PCB14 compared favorably with the experimental values of similar membranes. PCB14, PCB15 and PPDDT had their lowest energies in the apolar sites of the membrane, whereas atrazine tended to accumulate in the polar membrane-bulk water boundary site. Potential advantages and limitations of the approach were discussed.

Comparative toxic and genotoxic effects of chloroacetanilides, formamidines and their degradation products on Vibrio fischeri and Chironomus riparius

Toxic and genotoxic effects of alachlor, metolachlor, amitraz, chlordimeform, their respective environmentally stable degradation products 2,6-diethylaniline, 2-ethyl-4-methylaniline, 2,4-dimethylaniline, and two other related compounds, 3,4-dichloroaniline and aniline were compared. Acute toxicity tests with Chironomus riparius (96 h) and Vibrio fischeri (Microtox) and genotoxicity tests with a dark mutant of V. fischeri (Mutato) were carried out. Our results demonstrate that toxicity and genotoxicity of the pesticides are retained upon degradation to their alkyl-aniline metabolites. In the case of the herbicides alachlor and metolachlor, the toxicity to V. fischeri was enhanced upon degradation. Narcosis alone explains toxicity of the compounds to the midge, but not so for the bacteria suggesting a disparity in the selectivity of the test systems. All compounds showed direct genotoxicity in the Vibrio test. but amitraz and its metabolite were genotoxic at concentrations 10(3)-10(5) lower than all the other compounds. The observations indicate that stable aniline degradation products of the pesticides may contribute considerably to environmental risks of pesticides application and that genotoxic effects may arise upon degradation of pesticides.

Toxicity of azaarenes

Heterocyclic compounds by far outnumber the homocyclic PAHs. In addition, they are often more soluble in water, which may imply a greater biological significance of these heterocycles. Yet, most research focuses on the homocyclics, based on the implicit assumption that the mostly higher concentration of the homocyclics rank these compounds as priority compounds. This review critically examines the available evidence and poses questions on the biological activity and environmental risk of one small group of heterocyclics, the azaarenes, which contain one nitrogen atom in one of the aromatic rings. In different sections, the biotransformation and different types of toxicity are discussed in comparison to those of homocyclic PAHs. The last section focuses on the implications for risk assessment of PAHs. Two- and three-ringed azaarenes can be relatively easily transformed by bacteria, fungi, invertebrates, and vertebrates. The presence of the N-moiety in the smaller azaarenes leads to metabolic routes that partly differ from those of the homoaromatic analogues. Major metabolic products of the azaarenes appear to be ketones and mono- or dihydroxylated azaarenes. Microorganisms can further degrade these into multiple oxygen-containing compounds or they can open up the aza-containing aromatic ring and fully metabolize the products. Fungi and vertebrates were shown to produce the mutagenic dihydrodiol metabolites. The metabolism of the larger azaarenes in vertebrates proceeds analogous to homoaromatic PAH, because in these larger molecules the N-moiety has less influence. Transformation of the larger azaarenes by microorganisms proceeds much slower if occurring at all. Direct toxicity data of azaarenes are mostly restricted to the effects of acridine and quinoline on a relatively small number of species. From this limited set it becomes clear that differences between species are relatively small. As with homocyclic PAHs, toxicity generally increases with increasing number of rings, and baseline toxicity models based on homocyclic PAHs do apply. Toxicity differences between isomers indicate that azaarene toxicity cannot be explained by molecular size-related parameters alone, indicating that electronic forces may be important as well. Considering chronic toxicity it becomes clear that the often-used acute-to-chronic-ratios often underestimate specific chronic toxicity, even within the very limited set of chronic data available. In contrast with homocyclic PAHs, photodegradation of azaarenes shows the same degradation products as biological transformation involving monooxygenases. In general, as for homocyclic PAHs, the degree of phototoxicity is related to the UV absorption characteristics of the azaarenes, which makes it possible to apply the QSAR models developed for homocyclic PAHs to azaarenes as well. Recent research on algae showed that UV-A is the main cause of photoenhanced toxicity. Together with the fact that in the water column UV-B is almost absent, this clearly demonstrates the relevance of phototoxicity in the field. Mutagenicity of azaarenes generally proceeds through similar pathways as in homocyclic PAHs, with bay region diol epoxides as major genotoxic metabolites. The N-moiety can, however, result in differences in genotoxic activities between isomers. Carcinogenicity of azaarenes in mammals is generally restricted to four-ringed and larger structures, and mechanisms leading to cancer are similar to those of homocyclic aromatics. An exception to this general pattern is quinoline, which has been shown to induce liver cancer. The present risk assessment for PAHs is solely based on homocyclic PAHs. Yet, from the present review it becomes clear that this approach fails to protect against a vast number of heterocyclic compounds and biotransformation products that may exhibit stronger or other toxic effects than their homocyclic analogues. Therefore, incorporating the role of heterocyclic compounds and their metabolism appears to be a necessity for a reliable risk assessment for polycyclic aromatic compounds. In addition, reliable long-term protection against PAHs demands data on chronic toxicity, including teratogenicity, both for homocyclic as for heterocyclic compounds.