European Court of Justice upholds STOT RE 2 classification for Silanamine following Evonik appeal

Ruling provides legal certainty and makes future regulatory assessments more predictable

The European Court of Justice (ECJ) has upheld the classification of silanamine in the hazard class STOT RE 2. Evonik takes note of the decision and welcomes the clarification it provides regarding assessment methodologies used in the harmonized classification and labeling (CLH) of chemicals.

The Court confirmed that the read-across approach is a valid method for hazard assessment. This methodology assumes that similar substances share similar toxicological properties, meaning test data from one substance can be used to evaluate another. As a result, this ECJ judgment will likely have a broad impact on future substance classifications.

The case originated from Evonik's appeal to the ECJ after the General Court of the European Union (GC) had dismissed the company's action against the classification of silanamine as STOT RE 2. Silanamine is a hydrophobic, surface-treated synthetic amorphous silica (SAS).

The dispute centered on the interpretation and application of the CLP Regulation. In particular, Evonik challenged two aspects of the hazard assessment: the treatment of particle size characteristics as intrinsic properties of a substance and the acceptability of the read-across methodology. Evonik argued that the assessment was not based on inhalation studies performed with silanamine itself, but rather on test results obtained for other surface-modified silicas. The ECJ has now confirmed how a hazard assessment may be based on data from structurally or physicochemically comparable particulate substances.

The judgment has immediate implications for the harmonized classification of silanamine as STOT RE 2 (specific target organ toxicity following repeated inhalation exposure, affecting the lungs).

"Beyond its implications for silanamine, we welcome the legal certainty provided by the judgment. Greater clarity regarding the application of read-across in CLH proceedings may contribute to more predictable regulatory assessments of modified synthetic amorphous silicas and other particulate substances in the future," says Frank Menzel, Vice President Regulatory Marketing Silica at Evonik Smart Effects business line.