Risk assessment of cyclohexasiloxane D6 in cosmetic products

Dodecamethylcyclohexasiloxane (D6) is a siloxane substance mainly used in cosmetics and personal care products. While octamethylcyclotetrasiloxane (D4) and decamethylcyclopentasiloxane (D5) were once commonly used in personal care products, their usage has been restricted due to the classification as persistent, bioaccumulative, and toxic (PBT)/very persistent and very bio-accumulative (vPvB) substances. While D6 has emerged as a substitute for D4 and D5, the risk assessment for D6 remains limited compared to the evaluations for D4 and D5. To address this gap, we conducted a comprehensive risk assessment of D6. In this study, we reviewed the toxicity information on D6 and calculated the exposure level to D6, considering the content of D6 in cosmetic products. No observed adverse effect level (NOAEL) of 1500 mg/kg bw/day was established in a repeated dose toxicity study after oral administration to rats. Negative results were found in tests on the ocular and skin irritation, skin sensitization, and genotoxicity of D6. According to the product content of up to 48