Endocrine Disruptor Assessment: From Data Gaps to a Robust Regulatory Strategy
Assessing the endocrine-disrupting potential of a substance rarely comes down to reviewing a single study or obtaining a simple positive or negative result. The real challenge lies in interpreting all available data: what is already known about the substance? Do the existing data adequately address endocrine activity and potential adverse effects? What uncertainties remain? And, most importantly, is it really necessary to generate additional data?
For companies facing an assessment of endocrine-disrupting properties, defining the right strategy from the outset can therefore be just as important as generating the data itself.
Start with the data already available
Before considering additional testing, the first step is to establish a clear overview of all existing information. This may involve reviewing available regulatory studies, published scientific literature and any other relevant information that may provide evidence of endocrine activity and potential adverse effects.
For the assessment of plant protection products and biocides, ECHA and EFSA guidance notably relies on considering all relevant information and applying a weight-of-evidence approach, rather than interpreting individual results in isolation. A structured initial review can help answer several key questions. Is the available dataset sufficiently complete? Can apparently conflicting findings be scientifically explained? Are the relevant endocrine pathways adequately covered? And, most importantly, which uncertainties could influence the regulatory conclusion?
At CEHTRA, our endocrine disruption experts combine the analysis of existing regulatory data with targeted literature searches conducted in line with ECHA and EFSA guidance. Depending on the substance and the purpose of the assessment, additional sources of information, such as ToxCast data or in silico predictions, may also contribute to the analysis.
Identify the data gaps that really matter
The absence of a study does not automatically mean that a new study needs to be conducted. The key question is whether the missing information actually prevents a sufficiently robust conclusion from being reached.
This distinction is particularly important in endocrine disruption assessment, where evaluations may rely on large and highly heterogeneous datasets. Generating new data without first clearly defining the scientific question they are expected to address can increase costs and timelines without necessarily strengthening the final assessment. A targeted data gap analysis therefore helps identify critical uncertainties and determine which additional information could genuinely contribute to the overall evaluation.
This is where scientific judgement becomes particularly important. The approach recommended by ECHA and EFSA does not rely solely on the presence of positive or negative findings. It also takes into account factors such as study quality, consistency across the dataset and the biological plausibility of the relationship between endocrine activity and the observed adverse effects.
Build a testing strategy around the scientific question
When additional information is required, the next step is not simply to select an endocrine-related test. The testing strategy should first and foremost address the scientific question identified during the assessment.
Depending on the available data and the regulatory context, this may involve in vitro or in vivo investigations, recognised OECD Test Guidelines, other established protocols or complementary computational approaches. The objective is to generate information that can reduce the identified uncertainties while avoiding unnecessary or insufficiently targeted testing.
CEHTRA develops testing strategies tailored to each situation and can support both the monitoring and scientific interpretation of studies specifically related to endocrine disruption. Our experts can also integrate in silico screening approaches and (Q)SAR models when relevant to the assessment. This integrated approach is particularly valuable when several lines of evidence need to be considered together rather than interpreted separately.
Turn heterogeneous data into a regulatory conclusion
Collecting or generating data is only one part of the assessment. The next challenge is to organise and interpret all available evidence in a way that supports a transparent and scientifically justified conclusion.
When assessing endocrine-disrupting properties, it is necessary to examine evidence of endocrine activity, evidence of adverse effects and the causal relationship between these two components. Under ECHA-EFSA guidance, this analysis notably relies on a weight-of-evidence approach and, where relevant, on mode-of-action analysis. The quality of the scientific reasoning is therefore essential.
A robust assessment should make it possible to understand not only what the different studies show, but also why the overall available evidence does or does not support a conclusion on endocrine-disrupting properties.
CEHTRA supports the preparation of endocrine disruption documentation for regulatory dossiers, particularly for plant protection products and biocides, as well as the preparation of information in appropriate regulatory formats such as IUCLID and EFSA tables.
Assessments may also be conducted for internal strategic purposes when a company wishes to anticipate the potential regulatory implications for a substance before a formal submission.
Build a scientifically defensible position
The assessment does not necessarily end with dossier preparation.
Questions raised by authorities, differing interpretations of certain studies or the emergence of new information during the evaluation process may require additional scientific justification. In such situations, it becomes particularly important to be able to clearly trace the reasoning that led to the conclusion.
CEHTRA experts can conduct independent scientific assessments of endocrine-disrupting properties, contribute to evaluations in the context of CLP classification, prepare scientific position papers and support companies in their interactions with regulatory authorities.
The objective is therefore not simply to generate more data, but to build a coherent position in which the available evidence, remaining uncertainties and scientific reasoning are clearly documented.
A strategic approach to endocrine disruptor assessment
There is no universal strategy for assessing the endocrine-disrupting properties of a substance. The appropriate approach depends on the substance concerned, the available data, the applicable regulatory framework and the scientific question that needs to be addressed.
For some substances, an in-depth analysis of existing information may already provide sufficient evidence. For others, targeted generation of new data may be necessary before a conclusion can be reached. In more complex situations, the main challenge may lie in integrating several apparently conflicting lines of evidence or in providing a scientific justification for their interpretation.
This is why endocrine disruptor assessment benefits from an approach that combines regulatory expertise, toxicology, ecotoxicology, data analysis and testing strategy from the very beginning of the project.
Need support with the assessment of the endocrine-disrupting properties of a substance?
CEHTRA can support different stages of your project, from the initial review of existing data and identification of data gaps to the development of an appropriate testing strategy, preparation of regulatory documentation and scientific defence of the assessment.
