Siloxane D4 (Cyclotetrasiloxane, octamethyl-)

CAS Registry Number 556-67-2

What is it?

• D4, also known as cyclotetrasiloxane, octamethyl-, is an industrial chemical.

How is it used?

• D4 is used in the manufacture of a wide variety of products, including silicone polymers and copolymers.
• D4 is also found in personal care products such as hair/skin care products and antiperspirants and deodorants, as well as in pharmaceuticals.
• Silicone polymers that may contain residual amounts of D4 (from the manufacturing process) are used in biomedical applications and have also been approved as active and non-active ingredients in pharmaceuticals in Canada.
• Silicone polymers are also used in industrial processes (for example, as surfactants in certain pesticide products and as defoamers), in lubricants, cleaning products, sealants, adhesives, waxes, polishes and coatings.
• D4 is not currently manufactured in Canada; however, it is imported into Canada.

Why did the Government of Canada assess it?

• D4 was identified as a potential concern to the environment based on available information regarding possible persistence, accumulation and potential to cause harm to the environment.

How is it released to the environment?

• Because D4 is found in many different products, it may be released to the environment via wastewater systems that receive inputs from different sources including industrial effluents and personal care products. It can then stay in the environment for a long time. It can also harm animals or plants that live in water.
• D4 may enter the environment in a sufficient quantity or under conditions that would be harmful to the environment or its biological diversity.

What is the Government of Canada doing?

• The Government has conducted an evaluation of D4 based on science, called a screening assessment.
• The Government of Canada has determined that D4 is harmful to the environment, but is not harmful to human health.
• The Final Screening Assessment Report on D4 was published on January 31, 2009.
• The Government of Canada is developing measures to control the potential risks posed by D4, including:
  • Proposed Pollution Prevention Planning Notice with respect to D4 in Industrial Effluents to prevent or minimize D4 releases to the environment from industrial users, published on January 15, 2011; and
  • reassessment of D4 contained in pesticides, as part of the Pest Management Regulatory Agency's formulant reassessment program.
• Environment Canada is conducting ongoing monitoring of D4 in the environment.
• Environment Canada will consider the development of additional risk management controls for D4 as more information becomes available.
• Information on risk management of D4 is also available on Environment Canada's Management of Toxic Substances website.