Siloxanes and Silicones, di-Me, hydrogen-terminated (MHDnMH)

CAS Registry Number 70900-21-9

What is it?

  • Siloxanes and Silicones, di-Me, hydrogen-terminated, also known as MHDnMH, is an industrial chemical.

How is it used?

  • MHDnMH is mainly exported as a chemical intermediate for plastics synthesis. Small quantities are used in the manufacturing of silicone rubber, adhesive or protective coatings and for cosmetic uses.
  • This substance is manufactured in Canada but it is not imported into Canada above the reporting threshold.

Why did the Government of Canada assess it?

  • Prior to assessment, MHDnMH was identified as a potential concern to the environment based on information regarding possible persistence, accumulation in organisms and potential to cause harm to organisms.
  • MHDnMH was not considered to be a high priority for assessment of potential risks to human health; however, potential health effects were also evaluated in this screening assessment.

How is it released to the environment?

  • Small amounts of MHDnMH may be released to wastewater from manufacturing processes.

How are Canadians exposed to it?

  • The general population of Canada may be exposed to MHDnMH during the use of consumer products (for example, skin whitening cream and lipstick) containing this substance; however, this exposure is expected to be low.

What are the results of the assessment?

  • The Government of Canada has conducted a science-based evaluation of MHDnMH called a screening assessment.
  • Screening assessments address potential for harm to the general population (not including workplace exposures) and the environment.
  • Results of the final screening assessment indicate that although MHDnMH has the potential to remain in the environment for a long time, it is not expected to accumulate in organisms.
  • Furthermore, the quantity of MHDnMH that may be released to the environment is below the level expected to cause harm to organisms.
  • The Government of Canada has therefore concluded that MHDnMH is not entering the environment in a quantity or under conditions that constitute a danger to the environment.
  • The Government of Canada has also concluded that MHDnMH is not considered to be harmful to the health of the general population at current levels of exposure.

What is the Government of Canada doing?

  • The MHDnMH available in Canada is a chemically stable polymer of low concern. The application of Reduced Regulatory Requirements (RRR) as specified in the New Substances Notification Regulations to this substance will be recommended. This would require that any proposed new manufacture, import or use of a non-low concern version of the polymer be subject to further assessment, and would determine if the new activity requires further risk management consideration.
  • The final screening assessment report was published on September 10, 2011 and will be followed by a 60-day public comment period (from September 10, 2011 to November 9, 2011).

What can Canadians do?

  • The health risks associated with a chemical depend on the hazard (its potential to cause health effects) and the dose (the amount of chemical to which you are exposed). MHDnMH is not a concern for the environment or human health at current levels of exposure.
  • As a general precaution, Canadians are reminded when using any product to carefully follow any safety warnings and directions.
  • Canadians who handle MHDnMH in the workplace should consult with their occupational health and safety representative about safe handling practices, applicable laws and requirements under the Workplace Hazardous Materials Information System (WHMIS).
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