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The Story of Cyclopentasiloxane (D5) Safety

Cyclopentasiloxane D5Cyclopentasiloxane (its full chemical name is decamethylcyclopentasiloxane), commonly known as D5, is a chemical that belong to the group of cyclomethicones aka methyl siloxanes.


Siloxanes are found in lots of hair care and skin care products as conditioners that leaves hair and skin with a soft, silky, and moist feeling.


You can identify siloxanes in cosmetics by looking for the words with “-siloxane” or “-methicone” in the ingredient list.


Cyclopentasiloxane (D5) is an odorless, colorless liquid. It is also used in the production of silicone polymers and may also be used as a dry-cleaning solvent and in industrial cleaning products.


Cyclopentasiloxane (D5) is rated 3 out 10 (10 being most toxic) in the Skin Deep database powered by the Environmental Working Group (EWG).


The US Cosmetic Ingredient Review Expert Panel concluded that cyclopentasiloxane (D5) along with cyclomethicone, cyclotetrasiloxane (D4), cyclohexasiloxane (D6), and cycloheptasiloxane (D7) are safe in the present practices of use and concentration.


The European Scientific Committee on Consumer Safety (SCCS) deemed cyclopentasiloxane (D5) safe for use in cosmetic products, with the exception of hair styling aerosols and sun care sprays, where it can be inhaled and deposited onto the lungs.


In Cosmetic Ingredient Review studies, carcinogenic effects were observed only after 12-months of exposure at high doses, which would not be applicable to products used topically.


In the SCCS report, there was a concern voiced that cyclopentasiloxane (D5) may contain trace amounts of cyclotetrasiloxane (D4), classified as an endocrine disruptor, based on evidence that it interferes with human hormone function and human fertility by the European Union.


The SCCS Opinion encourages keeping the level of impurity of D4 as low as possible.


The SCCS study did not look into environmental effects.


In 2008, Environment Canada and Health Canada concluded that based on the available information, cyclopentasiloxane (D5) was entering the environment in a quantity or concentration or under conditions that may have an immediate or long-term harmful effect on the environment and may adversely affect biological diversity.


Environment Canada and Health Canada recommended adding cyclopentasiloxane (D5) to the List of Toxic Substances maintained pursuant to the Canadian Environmental Protection Act (CEPA).


This decision was challenged by the Silicones Environmental, Health and Safety Council of North America (SEHSC) and requested that a board of review be established to inquire into the nature and extent of the danger posed by D5.


In 2012, the board concluded that cyclopentasiloxane (D5) is not harmful to the environment.


The controversy of cyclopentasiloxane does not stop here.


This study finds that D5 evaporates in so-called “leave-in” hair products and that only a negligible amount of it is available to go down the drain.


Then, there is a report out of Switzerland in 2016 linking cyclopentasiloxane, as one water contaminant associated with cytotoxity on human intestinal cells. Cyclopentasiloxane bioaccumulates in the food chain and thus impacts human health. It might end up in drinking water because it is not easily removed by the classical water treatment systems and the study recommended look into introducing more sophisticated water purification processes. (Etteieb, et al., Combining Biological and Chemical Screenings to Assess Cytotoxicity of Emerging Contaminants in Discharges into Surface Water, Water, Air, Soil Pollution, Volume 227 (9) – Aug 24, 2016)


All in all, while there is nothing written in stone about the dangers of this chemical, it has been raising some concerns. I believe that this illustrates the difficulty of proving a chemical to be harmful. I recommend utilizing precaution and reducing your usage of products with cyclopentasiloxane (D5), such as Old Spice antipersparant & deodorant.

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