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 concluded that while D4 is not harmful to human health at levels of exposure considered in the assessment, it is entering or may enter the environment at concentrations that may be harmful. Based on the conclusions of the assessment, D4 was added to the List of Toxic Substances in Schedule 1 of the Canadian Environmental Protection Act, 1999 (CEPA) in February 2011.

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

Development of a risk management measure to reduce releases from personal care products was not warranted as updated data showed a reduced exposure from this source.

Furthermore, Environment and Climate Change Canada (ECCC) is conducting monitoring of D4 in the environment. This will be used to inform performance measurement evaluation for D4 to evaluate the effectiveness of risk management actions and determine whether further action is warranted. 

Additionally, Federal Environmental Quality Guidelines (FEQGs) for D4 in surface water, aquatic biota tissue, sediment, and mammalian wildlife diet were published in June 2021 to be used as thresholds for comparison with environmental monitoring results. 

For more information on this substance, please visit the Chemical Substances website. Additional information on the risk management of substances addressed under the Chemicals Management Plan (CMP) is available.  

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

Risk assessment


This substance is entering the environment from the following sources:

Risk management strategy

Risk management tools

Tools developed to manage risks associated with the substance:


Past consultations on the substance:


Substances Management Information Line
Chemicals Management Plan
Environment and Climate Change Canada
Gatineau QC  K1A 0H3

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


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