Q.01

Is cyclopentasiloxane banned in cosmetics?

No, not outright, but in the EU it is close. Under REACH Annex XVII entry 70, D5 at 0.1% by weight or more has been banned from EU wash-off cosmetics since 31 January 2020. The same limit applies to all other cosmetics, including leave-on, after 6 June 2027. Today (October 2026), leave-on products containing D5 can still be placed on the EU market.

EU: REACH Annex XVII, entry 70 (D4, D5, D6), as replaced by Regulation (EU) 2024/1328

  • General rule: D5 "Shall not be placed on the market" on its own, as a constituent of other substances, or in mixtures at 0.1% by weight or more after 6 June 2026 [1].
  • Wash-off cosmetics: the mixtures limit has applied since 31 January 2020. "Wash-off" means cosmetics that, in normal use, are washed off with water after application [1].
  • All other cosmetics (leave-on): the limit applies after 6 June 2027 [1].
  • Medical devices and medicinal products: the limit applies after 6 June 2031, so D5-based cosmetic-like products sold as devices or medicines follow different dates [1].
  • Why it was restricted: the original 2018 restriction (Regulation (EU) 2018/35) followed a UK dossier on environmental risk from D4 and D5 discharged into waste water [2][3].
  • SVHC status: D5 has been on the Candidate List since 27 June 2018 as a PBT and vPvB substance [4].
  • Not listed elsewhere: I found no D5 entry in the Annexes of the EU Cosmetics Regulation (EC) No 1223/2009, and no harmonised classification in CLP Annex VI.

Great Britain

  • UK REACH Annex XVII, entry 70: the assimilated text I found still has the 2018 wording. It covers only wash-off cosmetics at 0.1% by weight or more after 31 January 2020 [5][6]. I found nothing showing that GB has adopted the EU's 2024 extension to leave-on products.
  • SVHC status: D5 is on the GB Candidate List (PBT/vPvB, 27 June 2018) [7].
  • GB cosmetics annexes: I found no D5 entry.

Other jurisdictions

  • South Korea (MFDS): D5 is listed among restricted cosmetic ingredients with a use limit of 19.7% [8]. The entry gives no product-type scope.
  • Canada, United States, Japan and ASEAN: I found no entry for D5 on Health Canada's Cosmetic Ingredient Hotlist, the FDA's list of prohibited and restricted cosmetic ingredients, Japan's Standards for Cosmetics, or the ASEAN Cosmetic Directive annexes.

Approach: I checked REACH Annex XVII (the EU consolidated text, the 2018 and 2024 amending acts, and ECHA's restriction list and dossiers), the EU and GB Candidate Lists, CLP Annex VI, the EU and GB Cosmetics Regulation annexes, and UK REACH. I also checked the Health Canada Hotlist, the FDA list, and the Korean, Japanese and ASEAN cosmetics ingredient lists.

Q.02

What did Canada decide about D5?

Canada decided in 2012 that D5 is not harmful to human health or the environment, so it was not added to CEPA's List of Toxic Substances. That reversed Canada's 2009 finding of environmental risk. The change followed an independent Board of Review in 2011.

How the decision developed under CEPA 1999 (Chemicals Management Plan, Challenge Batch 2)

  • 17 May 2008: a notice on the D5 screening assessment was published under subsection 77(1) of CEPA (Canada Gazette Part I, Vol. 142, No. 20) [9].
  • 31 January 2009: the Final Screening Assessment was published (Canada Gazette Part I, Vol. 143, No. 5). It concluded that D5 posed a risk of harm to the environment. Its reasoning was that D5 is highly persistent and can build up, so long-term exposure "may cause adverse effects to aquatic organisms." It rated the risk to human health as low; the health effects it looked at were possible carcinogenic effects and effects on the liver [10].
  • 21 August 2010: a notice of objection had been filed, and a Board of Review for D5 was set up (Canada Gazette Part I, Vol. 144, No. 34) [11].
  • October 2011: the Board's report recommended that D5 "did not pose a danger to the environment." New hazard data showed D5 may not harm aquatic organisms, although effects on some sediment organisms may still occur at higher concentrations [10].
  • 25 February 2012: the final decision was published under subsection 77(6) of CEPA (Canada Gazette Part I, Vol. 146, No. 8) [12]. The government concluded that D5 "is not entering the environment at levels that are harmful to the environment" and is not harmful to human health at the exposure levels assessed [13].

What this means for cosmetics and other uses today

  • Not a CEPA toxic substance: I found no D5 entry on CEPA Schedule 1. D5 remains on the Domestic Substances List with no flags recorded [14].
  • Not on the Hotlist: I found no entry for D5 on Health Canada's Cosmetic Ingredient Hotlist, searching by CAS number and by name.
  • Cyclomethicone: this is a mixture made mostly of D4, D5 and D6 (CAS 69430-24-6). Canada treats it as already covered by the D4/D5/D6 assessments and the 2012 D5 decision, so it is getting no further assessment under the Chemicals Management Plan "at this time" [15].
  • Environmental guidelines: in June 2021 Canada published Federal Environmental Quality Guidelines for D4. These are benchmarks for comparing against environmental monitoring results, not limits on products. The D4 guideline for tissue of aquatic organisms can also be applied to total cyclic siloxanes, which include D5 [10].

So Canada places no restriction on D5 in cosmetics. That differs from the EU's REACH Annex XVII entry 70 limits covered in the previous answer.

Approach: I searched Health Canada and ECCC's Chemicals Management Plan pages, the CEPA Environmental Registry (Canada Gazette notices), CEPA Schedule 1, the Domestic Substances List and the Cosmetic Ingredient Hotlist. I relied on the government's summaries and notice records; I did not read the full text of the Board of Review report.

Q.03

What about D4 and D6?

Canada split them in 2009. D4 was found harmful to the environment and added to CEPA Schedule 1 (the List of Toxic Substances) in 2011, with controls aimed at industrial effluent only. D6 was found not harmful to human health or the environment, so no action was taken. Neither substance is restricted in cosmetics in Canada.

D4 (octamethylcyclotetrasiloxane, CAS 556-67-2)

  • 31 January 2009, Final Screening Assessment (Canada Gazette Part I, Vol. 143, No. 5): the Government concluded that D4 is not harmful to human health at the exposure levels assessed. It also concluded that D4 "is entering the environment at concentrations that may be harmful." D4 meets the persistence criteria but not the bioaccumulation criteria of the CEPA Persistence and Bioaccumulation Regulations. The health effects it looked at were reproductive effects and effects on the liver [16].
  • 4 February 2011, added to Schedule 1 to CEPA [16]. It is listed as Part 2, item 92: "Cyclotetrasiloxane, octamethyl-, which has the molecular formula C8H24O4Si4" [17]. The government page notes that listing "does not restrict its use, manufacture or import"; it lets the Government take risk management action under CEPA [16].
  • Pollution prevention planning notice for D4 in industrial effluents: the proposed notice was published on 15 January 2011 [18]. The final notice followed on 2 June 2012 (Canada Gazette Part I, Vol. 146, No. 22) [19]. Its aim is to prevent or minimise D4 releases from industrial users. I only had the registry entry for this notice, not its full text, so I can't tell you which facilities it covers or its deadlines.
  • Personal care products: the government page says a risk management measure for releases from personal care products "was not warranted," because updated data showed lower risk from that source [16].
  • Other follow-up: the Pest Management Regulatory Agency (PMRA) reassessed D4's use as a formulant in pest control products in 2018. ECCC is monitoring D4 in the environment and starting a performance measurement evaluation to decide whether further action is warranted [16].
  • Federal Environmental Quality Guidelines: published in June 2021 for surface water, tissue of aquatic organisms, sediment and the diet of mammalian wildlife [16]. They were noticed in Canada Gazette Part I, Vol. 156, No. 34 on 20 August 2022 [20]. These are benchmarks for comparing against monitoring results, not limits on products.

D6 (dodecamethylcyclohexasiloxane, CAS 540-97-6)

  • 31 January 2009, Final Screening Assessment (same Gazette issue): the Government concluded that D6 "is not harmful to human health at levels of exposure considered in the assessment, and that D6 is not entering the environment at levels that are harmful." D6 was found persistent in air, water and sediment but with "low potential to cause ecological effects." The health effects it looked at were effects on the liver and thyroid [21].
  • No follow-up action: the D6 page lists no risk management measures. The D4 guideline for tissue of aquatic organisms can also be applied to the total of cyclic volatile methyl siloxanes, which includes D6 [21]. Unlike D5, I found no Board of Review or later Gazette decision for D6.

Current status of both

  • Domestic Substances List: both are listed as existing substances [22][23].
  • Cosmetic Ingredient Hotlist: I found no entry for either substance, searching by CAS number and by name.
  • Cyclomethicone: as covered last time, Canada treats this D4/D5/D6 mixture as already addressed by these assessments [15].

Overall: D4 is the only one of the three that Canada listed as toxic, and the controls are on industrial effluent, not consumer products. D5 was cleared after the 2011 Board of Review, and D6 was cleared in 2009.

Approach: I searched Health Canada and ECCC's Chemicals Management Plan information sheets, the CEPA Environmental Registry (Canada Gazette notices), CEPA Schedule 1, the Domestic Substances List and the Cosmetic Ingredient Hotlist. I relied on the government's summaries and notice records, not the full screening assessments or the full text of the D4 pollution prevention notice.

Q.04