Siloxane D5 (cyclopentasiloxane, decamethyl-) - information sheet

Decamethylcyclopentasiloxane
(D5; cyclopentasiloxane, decamethyl-)
CAS Registry Number 541-02-6

Publications summarized:

Final Screening Assessment for Decamethylcyclopentasiloxane (D5) (published on January 31, 2009). Public comments received on the draft screening assessment were considered in development of the final screening assessment.
Associated notice: Canada Gazette, Part I: Vol. 143, No. 5 – January 31, 2009
Report of the Board of Review for Decamethylcyclopentasiloxane (Siloxane D5) (published October 2011) and notice for the revised decision for siloxane D5: Canada Gazette, Part I: Vol. 146, No. 8 - February 25, 2012

The Government of Canada conducts risk assessments of substances under the Canadian Environmental Protection Act, 1999 (CEPA) to determine whether they present or may present a risk to human health or to the environment.
- The risks posed by a substance are determined by both its hazardous properties (potential to cause adverse human health or ecological effects) and the amount or extent of exposure to people and the environment.
- When needed, the Government implements risk management measures under CEPA and other federal acts to help prevent or reduce potential harm.
Siloxane D5 is associated with health and ecological effects. At levels of exposure considered in the assessment (2009) and as a result of the revised decision (2012) for siloxane D5, the Government concluded that siloxane D5 is not harmful to human health or to the environment.

The screening assessment focused on the substance decamethylcyclopentasiloxane, also referred to as D5. This substance was assessed as part of Batch 2 of the Challenge initiative of the Chemicals Management Plan (CMP).
D5 does not occur naturally in the environment. According to information gathered by the Government, D5 was imported into Canada in very high quantities and was mainly used in products available to consumers, such as hair and skin products, and antiperspirants. It was also used as a commercial dry cleaning fluid, as well as in the manufacture of silicone polymers.
Silicone polymers that may contain residual amounts of D5 are used in biomedical applications, pharmaceuticals, in certain pest control products and in industrial processes as surfactants (detergents) and defoamers (anti-foaming agents). They are also used in lubricants, cleaning products, sealants, adhesives, waxes, polishes, and coatings.

The assessment indicated that Canadians may be exposed to D5 from environmental sources (for example, air, water and soil), food and from using certain products available to consumers, including cosmetics and other products available to consumers.
D5 is persistent (able to remain for a long time) in air and the aquatic environment.
The assessment indicated that D5 may be released to the environment as a result of industrial processes and during the use and disposal of cosmetics and other products available to consumers.

Information available at the time of the assessment indicated that D5 may have carcinogenic effects (potential to cause cancer), as well as effects on the liver. These were considered to be the important or critical effects used for characterizing the risk to human health in the assessment.
The 2009 assessment found that given the elevated persistence and accumulation potential for D5, long-term environmental exposure to D5 may cause adverse effects to aquatic organisms. New hazard information on D5 considered in 2011, along with previously summarized studies, showed that D5 may not cause adverse effects to aquatic organisms; however, effects in some sediment organisms may still occur at higher concentrations.

Based upon a comparison of levels to which Canadians may be exposed to D5 and the levels associated with health effects, the risk to human health for this substance was considered to be low.
Initially, in the 2009 final screening assessment it was concluded that D5 posed a risk of harm to the environment. A notice of objection was filed and a board of review was established for D5. In October 2011, the Report of the Board of Review for Decamethylcyclopentasiloxane (Siloxane D5) was published and recommended that D5 did not pose a danger to the environment. Therefore on February 25, 2012, on the basis of the findings and recommendations made by the Board or Review, and review of new information obtained since publication of the 2009 screening assessment, it was concluded that D5 is not expected to pose a risk to the environment.

The Government concluded that D5 is not harmful to human health at levels of exposure considered in the assessment.
As a result of findings and recommendations made by a Board or Review, and review of new information obtained since publication of the screening assessment in 2009, the Government concluded in 2012 that D5 is not entering the environment at levels that are harmful to the environment.

D5 may be found in certain products available to consumers. Canadians should follow any safety warnings and directions on product labels and dispose of products responsibly.
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Federal Environmental Quality Guidelines (FEQGs) for D4 were published in June 2021 to be used as thresholds for comparison with environmental monitoring results. The aquatic biota tissue guideline for D4 can also be applied to the sum of cyclic volatile methyl-siloxanes (cVMS), which includes D5. Updates can be found on the FEQGs web page.
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The screening assessment focused on potential risks from exposure of the general population of Canada. Hazards related to chemicals used in the workplace are defined within the Workplace Hazardous Materials Information System (WHMIS). For information concerning workplace health and safety and what steps to take in the workplace, Canadians should consult their employer or the Occupational Health and Safety Regulator in their jurisdiction.