EU Lays Down the Law on Cyclic Silicones D5, D6 — Now What?

As promised, on May 16, 2024, Regulation (EC) No. 1907/2006 of the European Parliament concerning the Registration, Evaluation, Authorization and Restriction of Chemicals (REACH) was amended to further restrict the use of cyclic silicones in cosmetic products, according to the Official Journal of the European Union (EU).

See related: Fragrance Creators Association Issues Statement Calling on Congress to Fund Implementation of MoCRA

Per CosLaw.eu, the new restrictions are in addition to those currently outlined in REACH. The new rules limit the use of decamethylcyclopentasiloxane (D5) and dodecamethylcyclohexasiloxane (D6) to a maximum concentration of 0.1% in both rinse-off and leave-on cosmetic products as of June 6, 2026. The restriction on D5 in rinse-off products has been in effect since Jan. 31, 2020; notably, octamethylcyclotetrasiloxane (D4) was already prohibited, per Annex II to the EU Cosmetics Regulation. 

Persistent, Bioaccumulative and Toxic Claims

The European Chemicals Agency (ECHA) sees this as a step in the right direction. In fact, the ECHA initially proposed the restriction in January 2019, which reportedly was supported by 2020 opinions issued by the scientific committees for Risk Assessment and Socio-Economic Analysis.

Per the agency's proposal:

• Decamethylcyclopentasiloxane (D5) meets the criteria of Article 57 (d) of Regulation (EC) 1907/2006 (REACH) as a substance which is persistent, bioaccumulative and toxic when it contains ≥ 0.1 % w/w octamethylcyclotetrasiloxane (D4) (EC No: 209-136-7); and
• Dodecamethylcyclohexasiloxane (D6) meets the criteria of Article 57 (d) of Regulation (EC) 1907/2006 (REACH) as a substance which is persistent, bioaccumulative and toxic when it contains ≥ 0.1 % w/w octamethylcyclotetrasiloxane (D4) (EC No. 209-136-7). In addition to its intrinsic properties, it also meets the criteria of Article 57 (e) of Regulation (EC) 1907/2006 (REACH) as a substance which is very persistent and very bioaccumulative (vPvB) when it contains ≥ 0.1 % w/w decamethylcyclopentasiloxane (D5) (EC No. 208-764-9) or ≥ 0.1% w/w octamethylcyclotetrasiloxane (D4) (EC No. 209-136-7). 

Responding to news of the amendment, the ECHA stated in a newsletter, "This measure will protect our environment by reducing up to 90% of the emissions of these very persistent and very bioaccumulative substances."

Cosmetic Industry Impact

To comply with the restrictions, cosmetic formulators are stuck between a rock and a hard place. As the Cosmetic, Toiletry and Perfumery Association (CTPA) explained in a statement, "D5 and D6 are very important ingredients in a wide range of cosmetic products owing to their unique set of properties, which cannot be fully replicated by alternative ingredients. Substituting these ingredients will reduce product performance, and in some cases product availability, with no benefit to the environment."

Furthering this, color cosmetics expert Jane Hollenberg, of JCH Consulting, wrote, in her recent Cosmetics & Toiletries article, that the virtual ban on cyclic silicones will impact the color makeup segment dramatically, since these materials make significant contributions to the aesthetics and performance of color cosmetics.

"In terms of reformulating, there are no 1:1 replacements for cyclic silicones," she explained. "And because they are not just a single ingredient in a formula, but also the solvent or carrier for many of the other ingredients, their upcoming ban is affecting many ingredient choices. Not only must the formulator who is using cyclics choose a replacement solvent as a carrier in the formulation, so must the suppliers of the many emulsifiers, film formers, texturizers and thickeners sold as dispersions or solutions in cyclic silicones find suitable alternatives."

The CTPA additionally expressed how existing restrictions imposed on these materials have already reduced their presence in terms of wash-off products on wastewater and aquatic environments, and volatile emissions from leave-on products. "The results demonstrate that the emissions from leave-on cosmetic products into wastewater are significantly lower than from wash-off products owing to evaporation of D5 from products during the period they remain on the skin or hair," the agency said in a statement. "Therefore, the already-published restriction on D4 and D5 in wash-off products is the most appropriate risk management measure."

"Economic chaos" was predicted to ensue, should the EU ban these key silicone components, per a recent Financial Post opinion piece by David Clement. His concern extended beyond cosmetics, into broader markets. "Without these silicones it would be very difficult to produce semiconductors, mass shortages of which would mean higher prices and worse quality for consumers." He added that this doesn’t include the markets for goods where these chips are an input, which is everything from cars, to computers, to consumer electronics. The total cost of the impact is so large and complex that it is hard to estimate."

Furthermore, he added, "Even economic chaos might be worth it if these substances were in fact so harmful they deserve to be added to the list. But the EU is the only entity in the world that has classified them as POPs [persistent organic pollutants] and restricted the use of siloxanes in commerce. [Canada's] own government has investigated them and has concluded differently."

Contradictory Findings

As referenced by Clement, Hollenberg highlighted how the U.S. Environmental Protection Agency (EPA) and Health Canada came to an opposing conclusion to the EU's regarding the environmental and toxicological properties of cyclic silicones. "The EPA concluded that decamethylcyclopentasiloxane does not bioaccumulate due to its evaporation from the skin and exhalation, and it does not pose a risk to the environment."

Health Canada reported, since cyclic silicones are volatile, they are excreted into the atmosphere, where degradation occurs – first to silanols, then to carbon dioxide, water and silicon dioxide (silica). Thus, "these products do not present a danger to the environment."

In addition, the amount that volatilizes and is degraded in the atmosphere is equal to new emissions, evidenced by the measured constant amount in the environment, so per Health Canada, the material is persistent but does not accumulate. The material has therefore been deemed not harmful to human health or the environment.

"The EU and UK Cosmetics Regulations are risk-based," Emma Meredith, Ph.D., director of science for the CTPA wrote in a 2021 Cosmetics & Toiletries column. "Cosmetic products and their ingredients are subject to a rigorous risk assessment to ensure they are safe to use. [For example], the proposed action on microplastics and the CSS [EU Chemicals Strategy for Sustainability] are driven by hazard. This is a worrying trend, which will affect the industry in the future and ultimately consumers. While it is essential to maintain a robust, long-term process for managing the chemicals we use in everyday products, it is important that such a strategy is rooted in in-depth scientific knowledge and that it assesses the key risks to be addressed."

What Can the Industry Do?

What can formulators and the industry do, now that these measures are in place? "Replacing cyclic silicones ...[has] been the focus of much formulation and many related cosmetics R&D activities, both in the short and long term," Hollenberg wrote. "Formulation chemists are hoping for some relief as new chemistries and processes are developed — with the requirements for long term human and environmental safety being more clearly codified in the EU."

"D5 and D6 are used across a variety of different leave-on cosmetic products, notably in the skin care, leave-on hair care and deodorant categories," the CTPA stated. "Replacing D5 and D6 in different personal care product types needs to be addressed on a case-by-case basis and requires a new formulation approach with the creation of a new product architecture in order to achieve a product [that] matches the desired performance characteristics and sensory benefits of a specific original siloxane-containing finished product, which is a major reformulation."

This will be no small task. But facing regulatory sand traps is just par for the course for our industry.