ECETOC Expert Group identifies research needs to enable regulatory assessment of endocrine disruption in invertebrates

An ECETOC Expert Group on Endocrine Disruption Assessment in Invertebrates has just published its findings on the state of the science of invertebrate endocrine disruption in relation to EU regulation in the peer-reviewed journal Environmental Sciences Europe (ESEU) [link].

The Expert Group identified the research needed to enable assessment of the potential for chemicals to disrupt the endocrine systems of invertebrates. There are an estimated 6.77 million invertebrate species worldwide, ranging from sponges through to more complex arthropods (insects, crustaceans) and molluscs. As many invertebrate populations are in decline, investigations about the possible contribution of endocrine disrupting chemicals (EDCs) are justified. Research evidence shows some chemicals may disrupt invertebrate endocrine systems, but the extent of this is unclear.

Identifying an endocrine disrupting chemical (EDC) according to EU regulations relies on the WHO definition[1] that requires demonstrating that an adverse effect in an intact organism is linked to an endocrine mechanism initiated by the chemical within the organism’s endocrine system. However, few data are available on invertebrate endocrine pathways (compared to the better studied vertebrate systems).  This is a major challenge to the development of mechanistic tests that can identify how these effects happen, i.e., the endocrine mode of action.

In its publication, the Expert Group outlines the breadth of invertebrate endocrine pathways for which EU regulation of potential EDCs may be relevant. It also reviews whether current knowledge meets regulatory requirements for invertebrates, including the suitability of current invertebrate test guidelines for detecting endocrine mechanisms and/or modes of action. Finally, it proposes a roadmap towards the regulation of potential invertebrate EDCs with greater confidence.

The Group concludes there are no validated in vitro and in vivo tools to identify EDCs in invertebrates according to the WHO definition. Whilst commonly used invertebrate toxicity tests might identify adverse effects that could potentially be caused by endocrine disruption, these tests do not identify how this happens, i.e., the endocrine mode of action. As a result, EU regulatory requirements for the identification of EDCs cannot currently be satisfied for invertebrates, either in general or for the specific invertebrates used in standard ecotoxicological studies. The Group also recommends establishing a clear definition of invertebrate protection goals (i.e., what to protect, where to protect it, over what time period, etc.) and identification of associated representative invertebrate model test species and endocrine disruption endpoints.

The Expert Group scientists propose that the most important research needed is to compile a comprehensive list of endocrine-related Molecular Initiating Events (MIEs) across different invertebrate groups, which could then be used to develop endocrine Adverse Outcome Pathways. They acknowledge, however, that this research will require significant resource investment to develop and implement.

[1] WHO-IPCS [World Health Organisation International Programme on Chemical Safety] (2002) Global Assessment of the State-of-the-Science of Endocrine Disruptors. World Health Organisation, Geneva, Switzerland.