Although this development does not immediately prohibit their use in cosmetics, it could have significant implications for manufacturers that rely on these ingredients in products such as foundations, hair care treatments and skin care formulations.
Why are these siloxanes under review?
L3, L4 and M3T have previously been identified as Substances of Very High Concern (SVHCs) because they are considered very Persistent and very Bioaccumulative (vPvB). These characteristics mean they can remain in the environment for long periods and accumulate in living organisms, raising concerns about their long-term environmental impact.
Following their inclusion on the REACH Candidate List, the substances are now expected to be transferred into Annex VI of the CLP Regulation through the new “ATP transfer” mechanism introduced by Regulation (EU) 2024/2865.
This mechanism was created to streamline the harmonised classification of substances already recognised as SVHCs due to properties such as persistence, bioaccumulation or endocrine disruption.
What does a CLP classification mean?
Inclusion in Annex VI does not automatically ban a substance or prevent its use in cosmetic products.
Instead, it establishes an official harmonised classification that manufacturers and importers must use when meeting their obligations under CLP and REACH. Companies may need to update regulatory documentation, including Chemical Safety Reports (CSRs), revise exposure assessments and ensure that classification and labelling remain consistent across their supply chain.
For cosmetic manufacturers, the main challenge is demonstrating that the environmental risks of these substances remain acceptable. Because cosmetics are generally considered wide dispersive uses, meaning they are released into the environment after normal consumer use. This makes the environmental assessment considerably more complex.
Potential impact on cosmetic formulations
Linear siloxanes are valued for the performance they provide in many cosmetic products. They improve spreadability, deliver a smooth skin feel and contribute to the lightweight texture of foundations, primers, hair serums and other personal care products.
If regulatory requirements become more restrictive, companies may need to reassess formulations containing these ingredients. Finding replacement materials could prove difficult, particularly in decorative cosmetics, where equivalent alternatives may not always provide the same sensory characteristics or product performance.
This could lead manufacturers to begin evaluating alternative ingredients well before any additional regulatory measures are introduced.
Regulatory process still underway
The proposed inclusion of L3, L4 and M3T in Annex VI is part of an ongoing regulatory process rather than a final legal decision.
European authorities are continuing discussions on how the new ATP transfer mechanism will operate in practice, including possible implementation timelines and transitional arrangements. Current proposals focus specifically on L3, L4 and M3T, while other linear siloxanes such as L2 and L5 are not currently included.
Manufacturers should therefore continue monitoring regulatory developments as the process progresses.
How this differs from cyclic siloxanes
The current proposal concerns linear siloxanes, which should not be confused with the better-known cyclic siloxanes D4, D5 and D6.
These cyclic substances have already been subject to regulatory action under REACH. D4 has been prohibited in cosmetic products for several years, while tighter restrictions on D5 and D6 are scheduled to apply from 6 June 2027, with industrial restrictions already beginning in 2026.
The proposed classification of L3, L4 and M3T represents a separate regulatory development, although it reflects the EU’s broader strategy of increasing oversight of substances with persistent environmental properties.
