Siloxanes Group

Information sheet

These substances were identified for action under the Chemicals Management Plan (CMP). The assessment focused on 5 substances referred to collectively under the CMP as the Siloxanes Group.

Summary of publications
Substance group CAS RN Common name (abbreviation) DSL name Public comments on the draft screening assessment Final assessment Conclusion on section 64 criteria Follow-up activities
Siloxanes Group 107-46-0 Hexamethyldisiloxane (L2) Disiloxane, hexamethyl- HTML HTML Does not meet None planned at this time
141-62-8 Decamethyltetrasiloxane (L4) Tetrasiloxane, decamethyl-
141-63-9 Dodecamethylpentasiloxane (L5) Pentasiloxane, dodecamethyl-
541-05-9 Cyclotrisiloxane (D3) Cyclotrisiloxane, hexamethyl-
2627-95-4 Divinyltetramethyldisiloxane (dvTMDS) Disiloxane, 1,3-diethenyl-1,1,3,3-tetramethyl-
Date Activity
December 9, 2023 Publication of the final assessment. The related notice was published in the Canada Gazette, Part I: Vol. 157, No. 49.
June 1, 2019 Publication and start of 60-day public comment period on the draft screening assessment. The related notice was published in the Canada Gazette, Part I: Vol. 153, No. 22.


Two other substances were initially identified as being part of the Siloxanes Group at the outset of the third phase of the CMP. One substance, CAS RN 33204-76-1, was subsequently determined to be of low concern to both human health and the environment through other approaches. The conclusion for this substance is provided in the Final Screening Assessment for the Rapid Screening of Substances with Limited General Population Exposure. The other remaining substance, cyclomethicone (CAS RN 69430-24-6) is a UVCB (unknown or variable composition, complex reaction products, or biological materials) primarily comprised of D4 (CAS RN 556-67-2), D5 (CAS RN 541-02-6) and D6 (CAS RN 540-97-6), in varying proportions. Cyclomethicone is considered to have been addressed through the screening assessments of D4, D5, and D6 in 2008 and the revised conclusion regarding D5 in 2012. Therefore, cyclomethicone will not be subject to further risk assessment work under the CMP at this time.

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