Linear siloxanes and EU regulatory procedures

ECHA published the substance evaluation conclusion for hexamethyldisiloxane (L2) on 7 January 2025.  The evaluation, conducted by Norway, focused on the substance’s suspected carcinogenic, mutagenic, or reprotoxic (CMR) properties. This recommendation initiates a formal regulatory process of Substance Evaluation (SEv) under REACH, and a potential Substances of Very High Concern (SVHC) listing. In February 2025, the proposal was withdrawn because the available data did not sufficiently demonstrate that L2 met the strict very persistent and very bioaccumulative (vPvB) criteria.

In December 2024, ECHA’s Member State Committee (MSC) agreed to identify octamethyltrisiloxane (L3) as SVHC. On 21 January 2025, ECHA officially added  L3 to the Candidate List of SVHC for being very persistent and very bioaccumulative (vPvB).

In parallel, submissions for decamethyltetrasiloxane (L4) and Tris(trimethylsiloxy)methylsilane (M3T) took place on 28 February 2025. Norway, the dossier submitter, proposed their identification as a SVHCs, with alleged supporting evidence highlighting concerns over their potential vPvB properties. At the Member State Committee (MSC) meeting on 10–12 June 2025, the MSC backed Norway’s proposal to list L4 and M3T as SVHC based on their confirmed vPvB status. ECHA added them to the Candidate List on 25 June 2025. The MSC opinion is expected to be adopted in September 2025, or in October 2025 if a second plenary discussion is needed. ECHA plans to provide the European Commission with the final recommendation, considering the MSC opinion, by December 2025.

The submission of dodecamethylpentasiloxane (L5)  as SVHC is now expected by 2 February 2026.

On 18 December 2024, Norway withdrew its SVHC proposal for HL3 concerning vPvB properties and moved the proposal to compliance checks (CCH).

On 19 March 2024, ECHA published an update to the Community Rolling Action Plan (CoRAP), according to which in 2024 Spain will evaluate tetradecamethylhexasiloxane (L6), as suspected PBT or vPvB. On 16 October 2024, ECHA’s PBT Expert Group meeting concluded that the bioaccumulation of L6 must be reviewed, with new test data needed to clarify its potential.  If Spain’s assessment identifies risks from the substance, regulatory action may follow (harmonised classification, SVHC listing or restriction)

The conclusions of the substance evaluation for L3 (octamethyltrisiloxane), L4 (decamethyltetrasiloxane) and L5 (dodecamethylpentasiloxane) were published. The Norwegian Environment Agency concluded that the substances meet the criteria as very persistent and very bioaccummulative (vPvB) in the environment. As potential next steps, the conclusion foresees a Regulatory Management Option Analysis (RMOA) for the group of linear siloxanes L2, L3, L4 and L5. For L2 (hexamethyldisiloxane) the evaluation is yet to be finalised. The conclusions also recommend that the substances might be identified as Substances of Very High Concern (SVHC), and might be added to the Candidate List. Having communicated its SVHC intentions, Norway is now expected to submit dossiers to ECHA by 2 August 2024 for L3, and by 3 February 2025 for L2, L4 and L5. Lastly, the conclusions propose a future REACH restriction. The decision on how and when potential next steps will be taken is at the discretion of the European Authorities. 

In 2015, the United Kingdom launched the evaluation of the linear siloxanes, L3, L4 and L5. Following Brexit, the procedures were also led by Norway.

In 2013, the Competent Authority of the United Kingdom initiated substance evaluation for hexamethyldisiloxane (L2) on initial grounds for concern relating to human health, exposure and aggregated tonnage. Since the United Kingdom’s departure from the EU, the procedures are led by Norway. The evaluation is yet to be finalised.