Siloxane D4 (cyclotetrasiloxane, octamethyl-) - information sheet

(D4; cyclotetrasiloxane, octamethyl-)
CAS Registry Number 556-67-2

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  • 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 D4 is associated with health and ecological effects. At levels of exposure considered in the assessment, the Government concluded that siloxane D4 is harmful to the environment, but not to human health. To help address the ecological concern, risk management action was taken.

About this substance

  • The screening assessment focused on the substance octamethylcyclotetrasiloxane, also referred to as D4 or cyclotetrasiloxane, octamethyl-. This substance was assessed as part of Batch 2 of the Challenge initiative of the Chemicals Management Plan (CMP).
  • D4 does not occur naturally in the environment. According to information gathered by the Government, D4 was mainly used in the manufacture of silicone polymers and copolymers.
  • Silicone polymers that may contain residual amounts of D4 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.
  • D4 is a component of the substance cyclomethicone. D4 was also used in cosmetics and other products available to consumers. At the time of the assessment D4 was in products such as hair and skin care products, antiperspirants and deodorants.

Human and ecological exposures

  • The assessment considered potential exposure of Canadians to D4 from environmental sources (for example, air, water and soil), food and from using certain products available to consumers.
  • The assessment also indicated that D4 may be released to the environment as a result of industrial processes and during the use and disposal of products available to consumers.
  • D4 has been determined to be persistent (that is, it remains for a long time) in air and sediment.

Key health and ecological effects (hazard)

  • Information available at the time of the assessment indicated that D4 may have adverse reproductive effects, 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 assessment also found that D4 has the potential to accumulate in and cause harm to aquatic organisms and the potential to cause ecological effects.

Risk assessment outcomes

  • Based upon a comparison of levels to which Canadians may be exposed to D4 and levels associated with health effects, risk to human health for this substance was considered to be low.
  • Considering all the information presented in the ecological assessment, it was determined that D4 poses a risk to the environment.

Screening assessment conclusions

  • The Government concluded that D4 is not harmful to human health at levels of exposure considered in the assessment.
  • However, the Government concluded that D4 is entering the environment at concentrations that may be harmful.
  • Also, D4 meets the persistence criteria but not the bioaccumulation criteria as set out in the Persistence and Bioaccumulation Regulations of CEPA.

Preventive actions and risk reduction

  • The Risk Management Approach for D4 (available upon request) was published on January 31, 2009 for a 60-day public comment period.
  • On February 4, 2011, D4 was added to Schedule 1 to CEPA. Adding a substance to the list does not restrict its use, manufacture or import. Rather, it enables the Government to take risk management actions under CEPA.
  • In June 2012, a pollution prevention planning notice with respect to D4 in industrial effluents was published in the Canada Gazette, Part I, to prevent or minimize D4 releases to the environment from industrial users.
  • Development of a risk management measure to reduce releases from personal care products was not warranted as updated data showed a reduced risk from this source.
  • The use of D4 as a formulant in pest control products was reassessed by the Pest Management Regulatory Agency (PMRA) in 2018.
  • Environment and Climate Change Canada (ECCC) is monitoring levels of D4 in the environment.
  • ECCC is also initiating work on a performance measurement evaluation to evaluate the effectiveness of risk management actions to reduce environmental releases of D4 and determine whether further action is warranted.Updates on performance measurement are available.

Where to find updates on risk management actions

Related resources

  • D4 may be found in certain products available to consumers. Canadians should follow any safety warnings and directions related to the product and dispose of products responsibly.
  • Visit Healthy home for information on chemical safety in and around the home.
  • Federal Environmental Quality Guidelines (FEQGs) for D4 for 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. Updates can be found on the FEQGs web page.
  • 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.

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