Identification of endocrine disrupting chemical - screening methodology supporting impact assessment published
The purpose of the JRC's methodology was to provide a basis for the screening of the available evidence on chemicals in relation to their potential to act as endocrine disruptors. It was specifically developed to support the European Commission's impact assessment which estimated possible health, environmental and socio-economic consequences of adopting different options for defining scientific criteria for the identification of endocrine disruptors (EDs) in a regulatory context.
The screening methodology described in the JRC report comprises three main steps; selecting the relevant data sources and types of data within these sources; extracting and codifying the data within a comprehensive template; and combining lines of evidence by application of a decision tree applying a limited weight of evidence analysis to the available data at each decision point. The data sources employed included EU regulatory assessment reports, scientific literature and ED specific databases. As the purpose of the methodology was to facilitate the impact assessment, a major requirement in its design was to provide a practical and feasible means of screening a large number of substances in a limited timeframe and using existing data sources. Moreover, the intention was to ensure a maximum degree of transparency, traceability and objectivity regarding the data gathered and the results obtained. Inevitably however, any chemical assessment of this type involves some degree of expert judgement that is difficult to codify.
The methodology drew on the JRC's ED Expert Advisory Report from 2013 which specified key scientific considerations for identifying an ED, together with the type of underlying toxicological data that is needed to make an assessment. Following the WHO/IPCS definition of an ED and the need to assess ED mode-of-action together with adverse effects, the methodology centred on those ED modes-of-action that are better understood by the scientific community. Consequently, the focus was on the disruption of the estrogenic, androgenic, thyroid and steroidogenesis (EATS) pathways. The OECD's Conceptual Framework for the Testing and Assessment of EDs and the associated Guidance Document (OECD GD 150) which describe these so-called EATS pathways were used as a basis for the selection of effects (endpoints), the interpretation of test results as well as for supporting the establishment of a possible link between mode-of-action and adverse effect.
Challenges in developing the screening methodology included the relevancy assessment and codification of the types of information likely to be encountered with respect to adverse effect or evidence for endocrine disrupting mode of action as well as the weight to be assigned to these data types with respect to evidence for endocrine disruption. In terms of its scope, interpretation rules and weight of evidence considerations, this methodology may inform assessment approaches in general and the outcome of the exercise may help to identify potential data gaps in relation to future assessment of substances for ED properties.
When defining regulatory information requirements and endeavouring to fill data gaps, it is essential that due consideration is given to the use of modern non-animal toxicological approaches based for example on in vitro, 'omics and computational methods to support the desired transition away from animal testing.