Expert Groups

Population relevance for NTOs per EU Endocrine Disruption Criteria


Technical guidance is still missing in response to EU scientific criteria for the determination of endocrine disrupting (ED) properties (ECHA & EFSA, 2018), to identify whether observed adverse effects are relevant at the (sub)population level for non-target organisms (NTOs).


The objectives of this Expert Group are as follows:

  • Develop guiding principles to establish which endocrine mediated adverse effects and their magnitude are relevant at the population level for vertebrates as non-target organisms (NTOs).
  • Maximise rapid scientific progress via demonstration of approaches through case studies, i.e. identify whether population relevance assessment for EDs can be done in a scientific way that brings confidence in the assessment process.
  • Further EU regulatory acceptance under PPPR, BPR, REACH by providing readily worked out methodology as basis for next revision to the EFSA/ECHA guidance on identification of endocrine disruptors.


A kick-off meeting took place in November 2022. A manuscript is in preparation, with the support of a Scientific Writer. It is expected to be published Q3 2023.

Invertebrate endocrine disruption

Expert Group: Is sufficient knowledge available on the endocrine system of invertebrates to include them in regulatory evaluation of endocrine disruptors?


The new scientific criteria for the determination of endocrine-disrupting (ED) properties apply from June and November 2018 to biocides and pesticides, respectively. The ECHA-EFSA (2018) guidance implementing these criteria for the identification of endocrine disrupting properties indicates that, if available, information on invertebrate non-target organisms (e.g. endocrine mechanistic and/or adverse effect data) should be considered in ED assessment. However, the ED Guidance also recognises the scarce knowledge on the endocrinology for non-target invertebrates.

Currently, the available OECD TGs for invertebrates only address apical effects such as growth or reproduction, and they are not specific for endocrine mechanisms. Furthermore, no mechanistic assays exist in the regulatory arena for invertebrates due to the large diversity in this phylogenetic group and lack of knowledge on endocrine systems and mechanisms in these organisms. Without information on endocrine mechanisms, applying the ED criteria to invertebrates (i.e. establishing a biologically plausible link between an endocrine mode of action and adverse effects) is not possible.

Apart from the lack of knowledge on invertebrate endocrinology, applicability of the ED criteria is anyhow limited due to the diversity of taxa-specific endocrine systems and pathways which makes them not suitable for cross-species extrapolation (e.g., insects are only representative for insects as their endocrine system differs from those of other invertebrate taxa).


The objectives of this Expert Group are as follows:

– Critically review the existing knowledge on the endocrinology of selected invertebrate groups (insects, crustaceans, molluscs, nematodes) over the last 20 years

– Confront this knowledge with regulatory requirement for ED assessment

– Identify knowledge and technical gaps and propose regulatory and scientific solutions to close those gaps.


Phase 1 of the Expert Group (November 2020 – July 2021) is the development of a manuscript on the state of the science of invertebrate endocrine disruption in relation to EU regulation. The intention being to scope the issue of invertebrate endocrine disruption within an EU regulatory testing and assessment frame. The manuscript was published Q2 2022 and is available here.

Subsequent phases of the Expert Group, such as the development of manuscripts on specific taxonomic groups, and eventually organisation of a stakeholder workshop, are not currently being progressed. Activity may be restarted depending on the evolution of the scientific state-of-the-art and regulatory context in Europe

Strategies to overcome challenges in aquatic testing of particulate material

Expert Group: Strategies to overcome challenges in aquatic testing of particulate material


ECHA developed appendices to the guidance documents on data requirements under REACH specific to nanomaterials, including for guidance R7b (endpoint specific guidance covering ecotoxicity and fate testing). The advice provided in these appendices is focussed to specific recommendations for nanomaterials, though parts of the advice may also be applicable to other particulate materials (PMs).

With respect to REACH guidance for nanomaterials, the aquatic testing of PM has revealed inherent challenges aggravating the application of the respective guidance documents.

For instance, the preparation of stable PM dispersions is often not possible for standard test media. To overcome this issue, the addition of humic substances, changes in pH and other modifications resulting in an adjustment of the test media composition, are possibilities to improve dispersion stability. However, such modifications do not always result in enhanced PM dispersion stability. In fact, those kinds of modifications frequently alter the behaviour and fate of PM, and consequently their ecotoxicological potential (e.g. reactivity, bioavailability, size distribution, etc.), which may cause acceptance issues with authorities.

What is needed is a testing strategy, which defines the best way forward for aquatic testing of PM. This may be an adjustment of the test media composition, with the consent of the authorities, to ensure acceptance of the study, or, a replacement of the aquatic testing by a more appropriate setting (e.g. sediment testing).

Both options require upfront buy-in of the strategy from the regulatory authorities, and consequently the design of such a strategy should be a joint effort.


The Expert Group is being established to develop a white paper, established jointly with industry, academic and regulatory experts, which:
Describes the current status of PM testing approaches.
Identifies challenges when following these approaches.
Develops a testing strategy to overcome these challenges.


The kick-off meeting for the Expert Group took place in Q4 2020. The Expert Group experts to submit their manuscript to a peer reviewed scientific journal in Q4 2022.

MEtabolomics standaRds Initiative in Toxicology (MERIT)

Expert Working Group : MEtabolomics standaRds Initiative in Toxicology (MERIT): developing best-practice guidelines and minimal reporting standards for the acquisition, processing and analysis of metabolomics data


Rationale: It is early days for metabolomics in regulatory toxicology. To date the approaches have been widely demonstrated in academic and some industry labs, yet almost entirely in small-scale non-standardised studies. Meanwhile, complementary omics techniques, such as transcriptomics, are being adopted within larger scale toxicology projects and therefore we ask ‘what are the roadblocks to regulatory metabolomics?’. One roadblock is the lack of harmonised analytical and computational methods, best practice, and the limited acceptance of minimal reporting standards. Here we seek to address these limitations and to increase the quality of, and confidence in, metabolomics science for regulatory purposes; i.e. to enhance the relevance, reliability and robustness of a metabolomics assay.

Objectives: We propose to develop best-practice guidelines and minimal reporting standards specifically in the context of several regulatory toxicology case studies; e.g. (a) chemical grouping and read-across to supplement ECHA’s Read-Across Assessment Framework, (b) discovery of mode of action / molecular key events (within the AOP framework), (c) derivation of Benchmark Doses from concentration-response relationships, and (d) cross-species extrapolation within environmental toxicology. The first activity within this project will be to select the most relevant and appropriate case studies, followed by three workpackages (WP).

Equivalent Level of Concern (ELOC) Activity

Expert Working Group : Equivalent Level of Concern (ELOC) Activity


REACH Art. 57f offers the possibility to identify chemicals which raise equivalent level of concern (ELOC) to CMRs and PBTs (so-called SVHC – substance of very high concern). CARACAL and the JRC proposed to compare different health outcomes by the following aspects:

  • Type of possible health effects
  • Irreversibility
  • Delay of health effects
  • Quality of life affected
  • Societal concern
  • Ability to derive a ‘safe concentration’

Concept papers discussing potential criteria exist on these aspects, but no scientific discussion has taken place and no clear scientific criteria were established.

To date Endocrine Disrupting, Respiratory and Strong Skin Sensitizing chemicals have been identified as possible ELoC requiring further review although eMSCAs and ECHA have indicated that other human health endpoints may be included.

The objective is to identify effects endpoints that are of ELOC to CMRs and PBTs and to propose science-based criteria for the identification of candidate chemicals. This project has broad benefits to industry and society on the basis that:

  • This focusses regulatory and industry resources to substances of real concern
  • Lack of specificity in applying criteria for ELoC will undermine the credibility of the regulatory program.

The activity should catalyse

  • Expert discussion about how to compare the severity of impact of different diseases
  • The development of appropriate science-based criteria for identifying substances that are ELoC across different toxicological endpoints.
Non-coding RNA (Completed)

Expert Working Group : microRNA’s in toxicology and risk assessment (Completed)


With an increased interest of the scientific community in microRNAs, the field is rapidly evolving but is still at an early stage with respect to (eco)toxicology. Currently microRNAs testing is not included into the regulatory process of chemicals.

MicroRNAs are highly conserved between human and animal models and regulate biological pathways by repressing target proteins. MicroRNA profiling in response to toxic compounds can provide toxicant-specific profiles in specific organs. Given microRNA’s specificity to tested compounds, the time and dose dependency, the sensitivity and simplicity of their detection in various tissues are promising tools in toxicological studies. In addition, circulating microRNAs are accessible through non-invasive protocols and thus represent ideal candidates in toxicological studies, as they may be used as biomarkers of chemical exposure for safety assessment. At the moment there is no single test available to determine microRNA effects, and there is an insufficient understanding of the normal microRNA changes and long term effects upon exposure to chemicals on human health. In addition a screening scheme for prioritising chemicals by using mircoRNA profiling has not been developed.

In order to increase our understanding of how the science of microRNAs is involved in (eco)toxicology and in turn in risk assessment, a solid understanding of the biology including the changes of microRNA profiles in response to chemical exposure is essential. In addition understanding the link between microRNA-related pharmaco-genomics and adverse reactions to chemicals/drugs will be important for risk assessment.

The Expert Group

The Expert Group is addressing the relevance of microRNA changes to the evaluation of chemicals. In particular, they will examine and reveal of the current state-of-the art scientific and technological approaches to determine and quantify microRNA effects of chemicals. This will help us to assess the potential of microRNA as biomarkers of chemical exposure for safety assessment.

Transcriptomics Analysis Framework (Completed)

Expert Working Group : Transcriptomics Analysis Framework (Completed)


‘Big data’ has become a common term to describe the large data sets that are often collected and analysed in many areas of biological and medical science. This is particularly true in molecular work where a data explosion is occurring. For toxicological science the quantity, quality and complexity of molecular variation data collected outstrips our ability to analyse or interpret in a consistent manner and this has hindered its application in the toxicological risk assessment of chemicals.


A particular challenge is in the consistent bioinformatic analysis of the data where its magnitude allows many approaches to be taken. There are many ways by which the data can be ‘sliced and diced’ that can lead to different outcomes – but no assessment as to which approach is more appropriate. Amongst many methods, all of which could be argued to be correct, the key question for regulatory purposes is:Which is most appropriate? This challenge has limited the use of high throughput molecular data in the regulatory arena.


A draft framework for best practice to ensure the univariate analysis of molecular variation data is meaningful and reliable. This could feed into the review of OECD test guidelines and help industry develop data that regulators have confidence in assessing within risk assessment dossiers.

AOP/MOA of Reproductive Health Ontology (Completed)

23-24 April 2015, Brussels, Belgium

Expert Working Group Meeting: AOP/MOA of Reproductive Health Ontology (Completed)

There is no single source of information providing a comprehensive ontology of developmental toxicity linked to the molecular initiating events (MIEs) and adverse outcome pathways (AOPs) responsible for these effects. Yet there are burgeoning amounts of data increasingly available that inform us about molecular pathogenesis leading to human developmental toxicity. The time has come to organise the field of toxicology in a different way. Responding to this need, an ECETOC Expert Team made up of regulatory, academic and industry experts, met in Brussels this spring to progress its drafting of a state of science on building prenatal developmental toxicity ontology for publication in peer reviewed, open access literature. The document will first identify the challenges and approaches ― and then propose the necessary steps ― to build a prenatal mode of action (MOA) ontology framework. This work will be the basis from which to identify scientific research priorities (e.g. under Cefic LRI or Horizon 2020), and form the basis from which to plan a workshop next year.

Such an ontology will help link molecular data to traditional toxicology; elucidate whether existing high throughput or high content approaches are sufficiently inclusive of MOA and serve as an organizing structure for constructing AOPs. Thus, contributing to the universe of integrated approaches to testing and assessment (IATA), increasing efficiency and helping to reduce animal testing, whilst providing the knowledge base for industrial and regulatory scientists to use in risk assessment and decision making.


ECETOC Special Report no.19: Building a Prenatal Developmental Toxicity Ontology (August 2016)

Baker N, Boobis A, Burgoon L, Carney E†, Currie R, Daston G,
Fritsche E, Knudsen T, Laffont M, Piersma AH, Schneider S, Poole A. 2017.
Building a Developmental Toxicity Ontology
Birth Defects Research. 2018;00:1–17
Doi: 10.1002/bdr2.1189