In-Depth Analysis: EU Regulatory Measures on Cyclosiloxanes (D4, D5, and D6)

Cyclosiloxanes, including D4, D5, and D6, are a class of organosilicon compounds with unique chemical structures. Widely used across multiple industries, they have also drawn significant attention due to their potential environmental and health risks. This article provides a comprehensive overview of the EU’s recent regulatory developments targeting these substances.

Overview of Cyclosiloxanes

Cyclosiloxanes such as D4, D5, and D6 are cyclic compounds containing silicon (Si) and oxygen (O) atoms, with each silicon atom bonded to two methyl groups (CH₃). This structure grants them high chemical stability and volatility. Industrially, they are primarily used to produce silicone polymers (e.g., silicone oils, rubbers, and resins) and are also found in cosmetics, detergents, dry cleaning agents, and polishing products.

Environmental and Health Risks

Cyclosiloxanes are classified by the EU as Substances of Very High Concern (SVHC) due to their persistence, bioaccumulative potential, and toxicity. Studies indicate that these substances can persist in the environment, accumulate in organisms, and pose threats to ecosystems and human health. D4, in particular, has been confirmed to be highly toxic to aquatic life and may impair fertility. Additionally, cyclosiloxanes have the potential for long-range environmental transport, meaning they could pollute remote regions such as the Arctic and Antarctic.

EU Regulatory Developments

1. Harmonised Classification & Labelling

• D4: A Summary of Classification and Labelling (CLH) has been adopted, classifying D4 as a substance that may impair fertility and is chronically toxic to aquatic life. Companies supplying D4 in the EU must label it accordingly.
• D5 and D6: No harmonised classification yet, but general EU chemical safety labeling rules apply.

2. SVHC Status and REACH Authorization

• 2018: D4, D5, and D6 were added to the REACH Candidate List for their:
• Persistence, Bioaccumulation, and Toxicity (PBT);
• Potential endocrine-disrupting properties (D4 and D5).
• 2021: The European Chemicals Agency (ECHA) recommended adding them to the Authorisation List. If approved, companies would need authorization to continue their use.

3. Cosmetic Regulation Restrictions

• EU Cosmetics Regulation (EC No 1223/2009):
• D4 and D5: Banned in rinse-off cosmetics (e.g., shampoos, body washes) with a concentration limit of 0.1% (by weight).
• D6: No explicit restrictions yet, but SVHC status requires risk assessments.

4. REACH-Specific Restrictions

• 2018 Restriction: A REACH-based ban on D4 and D5 in rinse-off cosmetics took effect in February 2020 to reduce water pollution.
• 2024 New Restriction: In May 2024, the EU adopted a broader ban covering D4, D5, and D6 in leave-on cosmetics (e.g., creams, hair products), personal care items, and professional/consumer products (e.g., dry cleaning agents, polishes, detergents). This restriction, effective from June 6, 2026, is projected to reduce emissions by up to 90%.

5. POPs (Persistent Organic Pollutants) Proposal

• D4, D5, and D6 have been proposed for inclusion in the Stockholm Convention POPs List due to their:
• Environmental persistence;
• Potential for long-range air transport.
• If approved, this would trigger global bans or restrictions.

6. Enforcement Actions

In 2022, ECHA’s Enforcement Forum conducted a pilot project to check cosmetics for restricted cyclosiloxanes (D4/D5) under REACH or POPs rules. 3% of tested products were found non-compliant, leading to market withdrawals.

Conclusion

The EU’s regulatory measures on cyclosiloxanes demonstrate its high priority on environmental and public health protection. Through progressively stricter rules and enforcement, the EU aims to curb emissions of these persistent, bioaccumulative substances and safeguard ecosystems and human health. Businesses must closely monitor regulatory updates and adapt their production and usage strategies to comply with EU requirements.

Further Information

ECHA