Policy and Law Policy and Law
By Tyler Irving
Posted May 2012
This past February, a three-year debate over the need to regulate decamethylcyclopentasiloxane, also known as D5, ended when federal Environment Minister Peter Kent concluded that it does not harm the environment.
D5 and related siloxanes are noted for their ability to provide a quick-drying, non-oily feel to everything from shampoo to sunscreen. In January 2009, a screening assessment, conducted as part of Canada’s ongoing Chemicals Management Plan, flagged D5 as potentially harmful to the environment. However, in July 2009 the Silicones Environmental, Health and Safety Council of North America submitted a Notice of Objection. In response to this, then-environment minister Jim Prentice established a scientific board of review to look into the matter. The board issued its report last fall.
The Report of the Board of Review for Decamethylcyclopentasiloxane (Siloxane D5) concluded that, due to its high vapour pressure, D5 tends to partition primarily into air, where it is quickly degraded into harmless compounds by indirect photolysis. Although it can persist in sediments and accumulate in sediment-dwelling organisms, it does not biomagnify through the food chain. The report noted that “siloxane D5 will not accumulate to sufficiently great concentrations to cause adverse effects in organisms in air, water, soils, or sediments.”
Chemical structure of decamethylcyclopentasiloxane, known as siloxane D5
A coalition of environmental groups that intervened in the review was disappointed with the decision. “To
my knowledge, no other country has ever made a determination about whether or not a substance bioaccumulates
on the basis of whether or not it biomagnifies,” says Joseph Castrilli, a lawyer for the Canadian
Environmental Law Association who worked on the case. However, the decision was welcomed by the Canadian
Cosmetics, Toiletry, and Fragrance Association (CCTFA). “We think that these decisions should not be based on
political interference or pop culture, but ultimately on sound science and risk assessment,” says CCTFA
president Darren Praznik. 
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