On 5 June 2026, ECHA’s Committee for Risk Assessment (RAC) adopted an opinion recommending the harmonised classification of resorcinol as a Category 1 endocrine disruptor for human health (ED HH 1 – EUH380). Published on 11 September[1], the opinion marks RAC’s first recommendation under this new hazard class, introduced into CLP in 2023.
This recommendation must still be adopted by the European Commission and incorporated into Annex VI to CLP before the harmonised classification becomes legally binding.
Beyond this regulatory milestone, the resorcinol case illustrates how the new CLP endocrine disruptor (ED) criteria are applied in practice. It also highlights how classification differs from approaches under other regulatory frameworks, including ED assessment for biocides and plant protection products, substance evaluation and SVHC identification under REACH.
CLP classification versus ED assessment: shared scientific foundations, different regulatory objectives
The ECHA/EFSA guidance (2018), developed for the regulatory frameworks governing biocides and plant protection products, is also referenced in the CLP guidance (2024). The latter recognises the shared scientific foundations of the two approaches, while making clear that ED classification must follow the criteria and guidance specific to CLP.
The ECHA/EFSA guidance structures the assessment around three components: endocrine activity, adverse effects and a biologically plausible link between the two. It sets out a scenario-based strategy, depending on the endpoints investigated and the findings. The available data may support a conclusion on a substance’s endocrine-disrupting properties or indicate a need for further investigation.
ED classification under CLP rests on the same scientific foundations, and its guidance refers to the ECHA/EFSA approach. However, the regulatory question is different: is the available evidence sufficiently convincing to justify classification, and if so, in which category?
The assessment draws on all available and relevant information to determine the classification and category supported by the evidence. The CLP classification process does not itself impose a requirement to generate new data before a conclusion can be reached.
How did RAC conclude that resorcinol meets the ED HH 1 criteria?
For resorcinol, several lines of evidence point to disruption of the thyroid system. Evidence of endocrine activity includes inhibition of thyroid peroxidase (TPO), an enzyme involved in thyroid hormone synthesis.
A distinctive feature of the dossier is the weight given to historical human case reports describing hypothyroidism and goitre following repeated exposure. Their relevance was debated, particularly because of the exposure conditions and differences from some animal findings.
In its opinion, RAC examines these limitations, the toxicokinetic data and the consistency of the observations. The fact that effects subsided after exposure ceased also supports a causal link. Animal data provide additional support for the human findings.
RAC also explicitly draws on the CLP guidance: certain thyroid effects described as “T-mediated”, including changes in thyroid weight and histopathology, can provide evidence of both adverse effects and endocrine activity.
Some comments submitted during the public consultation highlighted the lack of demonstrated effects on the developing brain. In response, RAC explains that adverse effects on the thyroid can be sufficient to justify classification. It considers the human observations, consistent with TPO inhibition and supported by animal studies, sufficiently convincing to recommend ED HH 1 despite the remaining uncertainties.
In this case, RAC therefore considered it unnecessary to demonstrate every step of the mode of action experimentally to reach a conclusion.
SVHC identification: could RAC’s opinion help move the process forward?
For human health, CLP classification is not the only procedure being pursued to classify or identify resorcinol as an endocrine disruptor. In 2020, France proposed identifying the substance as a substance of very high concern (SVHC) because of its endocrine-disrupting properties for human health.
Under Article 57(f) of REACH, this procedure requires demonstration of a level of concern equivalent to that associated with the other SVHC categories covered by the Regulation.
In 2020, a majority of the members of ECHA’s Member State Committee already recognised that resorcinol met the WHO definition of an endocrine disruptor. However, the committee did not reach unanimous agreement on the equivalent level of concern. The dossier was therefore referred to the European Commission, whose decision remains pending[2].
RAC’s opinion could strengthen the scientific case presented by France in the SVHC dossier. However, a harmonised ED HH 1 classification does not automatically trigger inclusion in the Candidate List. It remains to be seen whether this new step will help move the procedure forward.
Environmental endocrine disruption: no classification proposal, but REACH evaluation continues
Resorcinol’s potential endocrine-disrupting properties for the environment remain under investigation through substance evaluation under REACH.
An initial evaluation, completed by Finland in October 2017, identified evidence pointing to thyroid disruption, notably through TPO inhibition. However, it did not allow a conclusion on endocrine-disrupting properties for the environment, as adverse effects relevant at population level had not been sufficiently investigated. Finland considered that the test methods available at the time were unlikely to resolve these uncertainties and therefore closed its evaluation without requesting further experimental data.
France launched a new evaluation in 2019 to clarify this concern. It was under this procedure, separate from harmonised classification, that ECHA requested a Larval Amphibian Growth and Development Assay (LAGDA, OECD TG 241). The registrant challenged this request, but ECHA’s Board of Appeal upheld it in January 2023, setting 24 July 2024 as the deadline for submitting the results[3]. The French evaluation is still listed as “Information requested” on ECHA’s portal.
Lessons from this first case
The resorcinol case shows that applying the new CLP endocrine disruptor hazard classes is not simply a matter of adopting the ECHA/EFSA assessment strategy developed for biocides and plant protection products.
The scientific foundations remain the same: endocrine activity, adverse effects, a biologically plausible link, weight of evidence and mode-of-action analysis. What changes is the regulatory question the evidence must answer.
The contrast is particularly instructive. For human health, RAC found the available evidence sufficiently convincing to recommend ED HH 1 classification under CLP, while a decision on SVHC identification under REACH remains pending. For the environment, substance evaluation under REACH led to a request for additional data to clarify potential adverse effects at population level.
These differences reflect the objectives of each procedure. Depending on the scenario under the ECHA/EFSA guidance, further assessment may require additional data. Under CLP, the question is whether the available evidence justifies classification, without necessarily requiring an exhaustive experimental dataset.
The key is not simply to have data, or to know everything about a hazard, but to understand what conclusions the evidence already supports under the applicable criteria.
[1] ECHA – Resorcinol: harmonised classification and labelling procedure