Characterization of endocrine disruptors: the Institute's EASZY test at the heart of the new OECD guidelines

The Organization for Economic Co-operation and Development (OECD) has recently adopted and published a new guideline, Guideline 250, to characterise endocrine disruptors. This new guideline is based on an original biological test, the EASZY test, the result of academic research carried out jointly by the National Institute for Industrial Environment and Risks (Verneuil-en-Halatte), Irset (Rennes) and Academia Sinica (Taiwan) since the early 2000s.

The EASZY test characterises the danger of substances to the endocrine system of organisms using an aquatic vertebrate model, the zebrafish embryo. This non-invasive, robust and sensitive test allows the visualisation and quantification of a gene specifically expressed in the brain of embryos. This is the aromatase B gene, which is induced in the presence of chemicals with oestrogenic activity.
The adoption of the guideline is the result of a standardisation and validation process carried out by France and the representatives of the National Institute for Industrial Environment and Risks, within the OECD validation group for methods in ecotoxicology (VMG-Eco) and ongoing since 2013, with the support of the French Ministry of Ecological Transition.

This regulatory validation and recognition process involved several academic and industrial research teams. The objective was to demonstrate the transferability of the model and method to different laboratories, as well as the reliability and robustness of the data generated by the EASZY test.
Upstream of this validation process, previous research work made it possible to acquire valuable information on the expression and regulation of the aromatase B gene by the oestrogens in the brains of zebrafish and to develop a set of tools and methods, including the EASZY test. This made it possible to demonstrate that many chemical substances that contaminate the environment are capable of reaching the brains of zebrafish embryos, which can disrupt aromatase gene expression in cells (radial glial cells) that play a leading role in the neurogenesis of all vertebrates.   
As part of an academic and industrial partnership, the National Institute for Industrial Environment and Risks is coordinating the ANR FEATS project: work is currently underway in order to better understand the (eco)toxicological effects, caused by the active substances in the EASZY test, on the behaviour and neuro-development of zebrafish. The ultimate aim of this work is to gain a better understanding of the risks that the active components of the EASZY test pose for human and environmental health.

These research projects received the support of the National Research Agency (ANR NEED, PROOFS and FEATS), the National Research Plan on Endocrine Disruptors (PNRPE, Plan National de Recherche sur les Perturbateurs Endocriniens), the Franco-Taiwanese collaboration program ORCHID and the European Union (EDEN, LIFECYCLE, SOLUTIONS projects).

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The OECD guidelines for chemical product tests are a collection of the most relevant test methods that are internationally recognised by governments, industry and independent laboratories in order evaluate chemical product safety. They are mainly used for safety regulation tests, and chemical product notification and registration. All of the guidelines are regularly updated in order to reflect scientific progress and to satisfy countries’ regulatory needs. The network of coordinators and national experts in OECD countries puts the scientific expertise of governments, of academia and of industry into action.

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