A recent update of the REACH regulation has amended the conditions of use of octamethylcyclotetrasiloxane (D4), decamethylcyclopentasiloxane (D5) and dodecamethylcyclohexasiloxane (D6) in order to decrease the negative impact of these substances on the environment. These restrictions are added to those already in place for D4 and D5 in rinse-off cosmetic products.
The new Commission Regulation (EU) 2024/1328 of 16 May 2024 [1] introduces new restrictions on the use of silicones D4, D5 and D6 in a number of products. This amendment to the REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals) Regulation applies across industries — including beauty and personal care.
Restrictions of use
The new regulation provides that, after 6 June 2026, D4, D5 or D6 shall not be placed on the market: as a substance on its own; as a constituent of other substances; or in mixtures; in a concentration equal to or greater than 0,1 % by weight of the respective substance.
However, it is important to note that octamethylcyclotetrasiloxane (D4), which is strongly suspected to have endocrine disrupting effects, has been banned since January 1, 2022 in cosmetic products [2]. Therefore, the new REACH restrictions for this substance do not change anything for the cosmetics industry.
Likewise, the use of Decamethylcyclopentasiloxane (D5) is already restricted up to a maximum concentration of 0.1% in rinse-off cosmetic products, since January 31, 2020.
Furthermore, the Commission granted an additional period of one year to the cosmetics industry to comply with the new regulation.
As a consequence, as of June 6, 2027, the use of decamethylcyclopentasiloxane (D5) will be restricted up to a maximum concentration of 0,1% in leave-on cosmetic products, and the use of dodecamethylcyclohexasiloxane (D6) will be restricted up to a maximum concentration of 0.1% in rinse-off and leave-on cosmetic products.
According to the European Commission, the new restrictions are necessary to address the environmental risks associated with the use of these substances in consumer products. The Risk Assessment Committee (RAC) of ECHA identified cosmetic products as the main source of release of D4, D5 and D6 that tend to accumulate into the aquatic system and into the atmosphere.
A family of products under fire
Silicones (also named polysiloxanes) are polymers composed of repeating units of siloxane (a combination of silicon and oxygen). They are generally considered safe for human health, neither irritant nor allergenic.
Because of their sensory properties and hydrophobic nature, silicones used to be an ubiquitous ingredient in cosmetic formulations [3]. However, their use has been increasingly criticized over the last decades, because of their negative impact on the environment. Actually, due to their very stable and very resistant chemical structure, silicones are poorly biodegradable and accumulate in the environment.
Classified as “persistent, bioaccumulative and toxic substances” (PBT), D5 and D6 silicones have been in the spotlight for some time now. Many suppliers — such as Lessonia, Lubrizol, Inolex, Solvay (Syensqo) or BASF, among others — have therefore strived to develop natural and biodegradable alternatives.
