Structural formula of decamethylcyclopentasiloxane, D5


What is it?

Cyclomethicone is a generic name for octamethylcyclotetrasiloxane (D4), cyclotrisiloxane (D3), cyclopentasiloxane (D5), cyclohexasiloxane (D6) and cycloheptasiloxane (D7).

“Cyclomethicones  are a group of methyl siloxanes, a class of liquid silicones (cyclic polydimethylsiloxane polymers).” Wikipedia

What are the effects?

This substance belongs to the groups:

The Swedish Society for Nature Conservation (SSNC) list cyclomethicone as an endocrine disruptor.

The European Chemicals Agency (ECHA) identifies that the substance “may be fatal if swallowed and enters airways, is toxic if inhaled, is harmful to aquatic life with long lasting effects, is a flammable liquid and vapor and is suspected of damaging fertility or the unborn child.”

ChemSec’s SIN List, a database of chemicals likely to be banned or restricted in a near future, includes cyclomethicone as a ‘possible reprotoxic chemical (R3) and is categorized as an endocrine disruptor (cat 1). It is a potential PBT/ vPvB substance* and has been detected in various environmental samples including biota and humans’.

*PBT and vPvB substances stand for ‘Persistent’ (chemicals that do not break down in the environment, Bioaccumulation (substances that build up in organisms), and Toxicity (harming the entire food chain, animals as well as humans, with effects like cancer, endocrine disruption, and reproductive problems)

How is it used?

Cyclomethicones are used to cosmetic products* like deodorants where it functions to coat the skin and to leave a non sticky surface. The substance is also found in hair products where it works to make the hair less static.

We use the European Commissions definition of Cosmetics:
“Cosmetics range from everyday hygiene products such as soap, shampoo, deodorant, and toothpaste to luxury beauty items including perfumes and makeup”.

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