Consultation document on octamethylcyclotetrasiloxane(D4): chapter 3

3. Uses of D4

3.1 Current Uses and Industrial Sectors

A section 71 notice was published under CEPA 1999 to gather information on D4. It was reported that in 2006, D4 was not manufactured in Canada at quantities equal to or greater than the reporting threshold of 100 kg and that between 1000000 kg and 10000000 kg of D4 was imported into Canada (EC & HC 2008).

The most significant Canadian use of D4 is for the manufacture of silicone polymers and copolymers.  D4 is also used in personal care products, such as hair and skin care products and antiperspirants.  It was also reported for use as a defoamer (pulp and paper, food, petrochemical, petroleum, chemical manufacture and water treatment) (EC & HC 2008).

Silicone polymers that contain D4 have been approved as active and non-active ingredients in pharmaceuticals in Canada, the most common use being in antiflatulance drugs.  Other uses of silicones polymers include:

• as a formulation component of personal care products for hair and skin care (i.e. moisturizers, aftershaves, make-up, shampoos, conditioners, hair styling products, etc.);
• antiperspirants and deodorants;
• biomedical uses;
• defoamers for use as processing aids and in household products;
• surfactants and mould release agents;
• lubricants;
• polishes and coatings on a range of substrates including textile, carpeting and paper;
• sealants and architectural coatings; and
• mechanical heat transfer and dielectric fluids and reprography. 

Silicone polymers that contain D4 are also used in the production of elastomers that are used in biomedical applications, sealants and adhesives, moulded silicone rubber, film and fabric coating and encapsulation.

3.2 Characterization of Releases into Canadian Water

D4 is not reported to occur naturally in the environment.  It is released to the environment in a dispersive manner due to its widespread use. The release of D4 is mainly to air, due to its high volatility, and to water (via effluents from wastewater treatment systems) during personal care product use; however, D4 may also be released to the environment during its use in industrial processes. When D4 is released to wastewater and water, it is expected that a portion would be adsorbed by the suspended solids, such as sewage sludge and sediments (EC & HC 2009).

3.3 Reducing D4 Releases to Canadian Waters

3.3.1 Possible Alternatives

While no information on potential substitutes for D4 was submitted by industry under the Challenge, proprietary information obtained through interviews with industry has revealed the existence of at least a few potential substances that could be useful in alternative formulations. Information available on supplier websites and the existence of certain personal care products that do not contain D4 also indicate the existence of potential alternatives.

It may also be possible that D5 (decamethylcyclopentasiloxane) and D6 (dodecamethylcyclohexasiloxane) may be useful in reformulations, based on their International Nomenclature of Cosmetic Ingredients (INCI) function, physical and chemical similarities to D4.

The use of any alternatives may trigger application of other Canadian regulations, such as the New Substances Notification Regulations. The CEPA Environmental Registry should be consulted for more information on the Canadian Environmental Protection Act, 1999 and its requirements.

3.3.2 Control and Capture Technology

No information on potential control and capture technologies for D4 was submitted under the Challenge.

According to three wastewater treatment models (ASTreat 1.0, SimpleTreat 3.0 and STP Model 1.5), wastewater treatment plants are efficient in removing D4. A conservative model estimates a D4 removal rate of approximately 95% from secondary treatment plants and approximately 55% from primary treatment plants. For more information on the three models, see Annex 3.

In order to validate the predicted removal rates, a sampling program is planned at different wastewater treatment plants across Canada during 2010.