New REACH restrictions for siloxanes D4, D5 and D6

The siloxanes, octamethylcyclotetrasiloxane (D4, CAS 556-67-2), decamethylcyclopentasiloxane (D5, CAS 541-02-6) and dodecamethylcyclohexasiloxane (D6, CAS 540-97-6), are low molecular weight cyclic compounds used as precursors to silicones. Those are capable of providing unique and beneficial characteristics for a wide variety of applications and products in all sectors, including construction, electronics, engineering and healthcare, cosmetics and personal care.

All three substances have a similar chemical structure which gives them a similar hazardous level. In 2020, the European Commission determined that D4 meets the criteria for persistent, bioaccumulative and toxic (PBT) substances, and D5 and D6 meet the criteria for very persistent and very bioaccumulative (vPvB) substances. Additionally, D5 and D6 are considered PBT when they contain more than 0.1% of D4.

The last regulatory change occurred on May 16, when the restriction of these substances within Annex XVII of the EU REACH Regulation was updated. The text has been expanded by adding new deadlines on the marketing of substances and in their application in the dry cleaning of textiles, leather and fur, and in pharmaceutical products and veterinary medicines. Those new restrictions have been added to the previous indications on the treatment of waste produced to prevent the end of the substances in the environment. These new restrictions join the existing ones about concentration in “cosmetic products that are removed with water after application (“wash-off cosmetic products”).”