Commentary: Assessing the endocrine disrupting effects of chemicals on invertebrates in the European Union

Abstract

Evidence from both laboratory and field studies has shown that currently used synthetic and naturally occurring chemical substances may potentially disrupt invertebrate endocrine systems, although the extent of this in field populations remains unclear. Translating concerns about potential endocrine disrupting chemicals (EDCs) into practical and effective regulatory action is currently hampered by the breadth of invertebrate endocrinology when compared to the better understood vertebrate systems, a lack of fundamental knowledge about the endocrinology of many invertebrate groups, and the resulting uncertainty when making regulatory decisions. This commentary (i) outlines the breadth of invertebrate endocrine pathways for which European Union regulation of potential EDCs may be relevant; (ii) reviews the extent to which current knowledge meets regulatory requirements for invertebrates, including an assessment of the suitability of current invertebrate test guidelines for detecting endocrine modes of action; and (iii) proposes a roadmap towards the regulation of potential EDCs with greater confidence, based on the Adverse Outcome Pathway (AOP) concept and a focus on identifying Molecular Initiating Events (MIEs) within AOPs. We conclude there are no validated tools to determine any invertebrate endocrine mode of action in vitro or in vivo. However, there are commonly used invertebrate toxicity tests which might capture adverse effects that could potentially result from an endocrine mode of action but would not identify the causal mechanisms. Therefore, 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. We propose that the most important research need is compilation of a comprehensive list of endocrine-related MIEs across invertebrate taxa via use of high-throughput ‘omics in combination with bioinformatics reverse engineered analyses. Although tractable, such an approach would require significant resource investment for development and implementation.