Siloxane D5 (1), a common ingredient in many cosmetics and other toiletries, is the first subject of an independent Environment Canada review of a prior decision identifying a substance as toxic. In 2009,  the Ministers of Health and the Environment recommended that Siloxane D5 be added to the Toxic Substances List.  This recommendation was based on a ‘screening assessment’ completed by both Environment Canada and Health Canada. The screening assessment concluded that Siloxane D5 may have an immediate or long-term harmful effect on the environment. Under the Canadian Environmental Protection Act (“CEPA”), once a substance is added to the Toxic Substances List it can become subject to a number of special regulations that can restrict access or its application, or even ban its use in Canada.  

Subsequent to the 2009 screening assessment and the recommendation to add Siloxane D5 to the Toxic Substances List, the Silicones Environmental, Health and Safety Council of North America (“SEHSC”) filed a Notice of Objection under subsection 332(2) of CEPA, requesting that a board review the decision. Specifically, the SEHSC challenged that the screening assessment was not based on the best available evidence and, furthermore, that there were errors in the assessment process. Such a board was established under subsection 333(1) of CEPA in August, 2010.

In the October 24, 2011 decision, the three expert academic toxicologists composing the board reach the opposite conclusion of the original assessment. Following an intensive 14 month investigation that reviewed more recent information than that considered in the 2009 screening assessment, Environment Canada concluded that Siloxane D5 does not, and will not in the foreseeable future, pose a danger to the Canadian environment. In conducting its review, the board paid particular attention to the processes employed in the original assessment and the heavy reliance on models rather than empirical evidence. The board concluded that these models resulted in inaccurate assessments of the likely impacts of Siloxane D5.  Although the Minister of the Environment is not bound by the review decision, and can still place Siloxane D5 on the Toxic Substances List if he desires, this seems highly unlikely.  

In addition to its findings on Siloxane D5, the board also made several recommendations about the process by which toxic substances are assessed. The board recommends regular reviews for the regulations to ensure they reflect the most current standards and methodologies. It also recommends the development of guidance documents for government staff conducting risk assessments or using risk assessment models. The board also encouraged industry stakeholders to work with government at the outset of screening assessments to ensure the most recent information is available; a measure that would hopefully reduce the number of reviews, such as this one, that must be conducted.

To read the decision of the board, click here.

note 1: The proper chemical name of Siloxane D5 is Decamethylcyclopentasiloxane.