Toxic substances list: siloxane D4

Octamethylcyclotetrasiloxane (D4) is primarily used to manufacture silicone polymers. This substance is also used as an emollient and solvent in a variety of personal care products including: deodorants, skin creams, cosmetics and hair care products. D4 is also used in industrial use products (as a defoamer, surfactant in certain pesticide products) and is found in lubricants, cleaning products, sealants, adhesives, waxes, polishes and coatings. Industrial activities and use of personal care products result in release of D4 to surface water via discharge from wastewater treatment facilities. 

On January 31, 2009, the Ministers of the Environment and of Health published, in Part I of the Canada Gazette, their final decision on the screening assessment of D4. The screening assessment report concluded that D4 may be entering the environment in a quantity or concentration or under conditions that have or may have an immediate or long-term harmful effect on the environment or its biological diversity. Based on the conclusions of the assessment, a Final Order adding D4 to the List of Toxic Substances in Schedule 1 under the Canadian Environmental Protection Act, 1999(CEPA 1999) was published in Part II of the Canada Gazette on February 16, 2011.

The Government of Canada is developing measures to control the potential risks posed by D4, including:

Environment Canada will review and revise risk management controls for D4, if required, as more information becomes available.

For more information on this substance, please visit the Chemical Substances website.

CAS (Chemical Abstract Service) registry number: 556-67-2 (D4)

Risk Assessment


This substance is entering the environment from the following source(s):

Risk Management Strategy

  • Proposed Risk Management Approach for Cyclotetrasiloxane, octamethyl-(D4) and Cyclopentasiloxane, decamethyl-(D5) (This document reflects past decisions on a substance (D5) that are no longer applicable and is available upon request.)


Substances Management Information Line
Chemicals Management Plan
Gatineau, QC K1A 0H3

Telephone: 1-800-567-1999  (in Canada) or 819-938-3232
Fax: 819-938-3231


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