LUXEMBOURG, 11 November 2026 — The European Union's highest court has rejected a challenge by German chemical manufacturer Evonik Operations GmbH to the hazardous classification of a surface-treated form of synthetic amorphous silica. The decision preserves the substance's classification for potential lung damage following repeated inhalation exposure and clarifies how scientific evidence may be used to classify chemicals under EU law.
In its 5 November 2026 judgment (Case C-121/25 P), the Court of Justice of the European Union (CJEU) dismisses Evonik's appeal against the European Commission's classification under the Classification, Labelling and Packaging (CLP) Regulation.
Beyond the classification of a single substance, the ruling addresses questions relevant to chemical manufacturers across Europe: whether lung damage observed in laboratory studies reflects a substance's inherent hazardous properties, when regulators may rely on data from similar chemicals, and how much opportunity companies have to challenge scientific assessments before a classification becomes law.
Why Evonik Challenges the Classification
The dispute concerns silanamine, 1,1,1-trimethyl-N-(trimethylsilyl)-, hydrolysis products with silica, a form of synthetic amorphous silica treated with hexamethyldisilazane (HMDS) to make it water-repellent.
Synthetic amorphous silica, including surface-treated forms, is used in pharmaceutical products, food, cosmetics, and industrial applications, including as a reinforcing or thickening agent in elastomers, resins, and inks.
The European Commission classifies the substance under Delegated Regulation (EU) 2022/692 as Specific Target Organ Toxicity — Repeated Exposure, Category 2 (STOT RE 2), with hazard statement H373 identifying potential lung damage from prolonged or repeated inhalation exposure.
The classification originates from a proposal submitted by France's National Agency for Food, Environmental and Occupational Health and Safety (ANSES) in December 2018. The European Chemicals Agency's (ECHA) Committee for Risk Assessment (RAC) subsequently recommends the classification, which the Commission adopts in February 2022.
The RAC also recommends an acute inhalation toxicity classification. However, the Commission does not adopt that recommendation because newly received scientific information requires further assessment.
Evonik challenges the repeated-exposure classification, arguing that the scientific evidence does not satisfy the CLP criteria. After the EU General Court dismisses its case in November 2024, the company appeals to the CJEU.
When Does Particle-Related Lung Damage Justify Classification?
One of Evonik's principal arguments concerns the relationship between the substance's inherent hazardous properties and the lung effects observed in experimental studies.
The company argues that the reported effects result from the accumulation of large quantities of inhaled particles in the lungs, rather than from a hazardous property specific to the substance.
Evonik also questions whether the experimental conditions reflect realistic human exposure. According to its arguments, the studies use modified material designed to make particles respirable and involve concentrations substantially higher than those expected under normal conditions of use.
The distinction matters because the CLP Regulation is designed to identify the inherent hazards of substances, rather than assess the risks associated with particular exposure circumstances.
The Court rejects Evonik's arguments, finding that the General Court adequately examines the scientific basis for the classification.
Importantly, the judges note that the evidence does not establish that the observed effects occur under conditions of lung overload, in which excessive particle accumulation overwhelms the lungs' normal clearance mechanisms.
The Court also distinguishes the dispute from earlier litigation concerning titanium dioxide, where particle size and lung overload play a central role in the assessment.
In the silica case, the classification is not tied to a particular particle size, and the available evidence does not demonstrate that the observed effects are attributable to lung overload.
The judgment therefore does not establish that every substance producing lung inflammation following inhalation must be classified as hazardous. Instead, it confirms that challenges based on particle overload must be supported by evidence capable of undermining the regulator's scientific assessment.
Court Confirms Regulators Can Use Data From Similar Substances
Another important issue is the RAC's reliance on studies involving a related synthetic amorphous silica, identified as SAS-DDS.
The committee considers studies involving both silanamine and SAS-DDS when evaluating potential lung toxicity.
Evonik challenges this approach, arguing that the RAC does not satisfy the conditions governing read-across, a scientific method that uses information from one substance to help assess another with similar properties.
The Court draws an important distinction between two provisions of the CLP Regulation.
Section 3.9.2.10.3 of Annex I establishes specific conditions for using information from structurally similar substances when the substance being classified has not itself been tested for repeated-exposure target organ toxicity.
However, the general classification provisions allow regulators to evaluate all available scientific evidence together, including information from related substances.
Because studies involving silanamine itself are available, the Court concludes that the RAC is entitled to consider the SAS-DDS studies as part of its overall weight-of-evidence assessment without satisfying the special conditions applicable to untested substances.
The distinction is significant for chemical manufacturers: direct testing of a substance does not prevent regulators from considering studies involving similar chemicals when assessing its hazardous properties.
At the same time, the ruling does not eliminate the need to justify the scientific relevance of such information. It clarifies which legal criteria apply when read-across forms part of a broader assessment supported by studies on the substance itself.
Missing the 18-Month Deadline Does Not Automatically Invalidate a Classification
Evonik also challenges the procedure followed by the RAC. Article 37(4) of the CLP Regulation requires the committee to adopt an opinion on a proposed harmonized classification within 18 months of receiving the proposal.
Evonik argues that the deadline was not respected and that this procedural failure should invalidate the Commission's classification.
The Court rejects the argument that missing the deadline automatically requires annulment, finding that a procedural irregularity of this kind can invalidate a classification only where the procedure might have produced a different result without the irregularity.
In this case, the General Court determines that the scientific information available in the initial RAC opinion is already sufficient to support the repeated-exposure classification. A subsequent targeted consultation concerning acute inhalation toxicity does not affect that conclusion. The CJEU upholds that assessment without needing to determine definitively whether the 18-month deadline was breached.
The ruling preserves the statutory deadline but makes clear that a missed deadline alone is insufficient to overturn a classification. Companies challenging procedural irregularities must establish that those irregularities could have affected the regulatory outcome.
Companies Cannot Demand a Second Consultation on RAC Opinions
The judgment also clarifies the limits of public participation in EU harmonized classification proceedings.
Evonik argues that interested parties should have an opportunity to comment on the RAC's scientific opinion, or a draft of that opinion, before the classification process advances.
The company maintains that such an opportunity is particularly important when the committee relies on studies that do not form part of the original classification proposal.
The Court disagrees and concludes that Article 37(4) requires interested parties to have an opportunity to comment on the proposed harmonized classification before the RAC adopts its opinion. The provision does not establish an additional right to comment on the committee's draft or final opinion.
The judges contrast this process with the authorization procedure under the EU Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) Regulation, which expressly allows applicants to comment on draft committee opinions.
The Court also confirms that the RAC may consider scientific studies that are not included in the original classification proposal, consistent with the CLP requirement to evaluate all available evidence.
For manufacturers, the practical implication is substantial. The initial public consultation may be their principal formal opportunity to challenge the scientific basis of a proposed harmonized classification.
Companies cannot assume they will have another opportunity to respond after the RAC develops its conclusions or incorporates additional scientific information.
What the Ruling Means for Chemical Manufacturers
The judgment means the current classification of silanamine is allowed to remain. The case, however, underscores several principles governing how EU chemical classifications are developed and challenged.
Manufacturers seeking to contest a classification must provide scientific evidence capable of raising credible doubts about the regulator's assessment. The Court emphasizes that judges reviewing complex scientific determinations do not simply replace the assessment of the competent scientific authority with their own.
The decision also confirms that regulators may combine direct testing data with evidence from structurally similar substances, provided the applicable CLP requirements are satisfied.
Equally important are the procedural implications. Although the CLP Regulation establishes deadlines and consultation requirements, not every procedural irregularity invalidates a classification. Companies must demonstrate why an alleged defect matters to the legality or potential outcome of the decision.
For businesses participating in future harmonized classification proceedings, the judgment underscores the importance of presenting detailed scientific evidence early, particularly where testing methods, particle characteristics, exposure conditions or the interpretation of toxicological findings are disputed.
The Evonik case illustrates the difficulty of overturning an EU chemical classification once the regulator's scientific assessment survives judicial scrutiny.
For manufacturers, the most consequential regulatory battle may therefore take place long before a classification reaches the courtroom—during the scientific evaluation and public consultation that shape the decision itself.