Simulated use and wash-off release of decamethylcyclopentasiloxane used in anti-perspirants

The cyclic volatile methylsiloxane, decamethylcyclopentasiloxane (D5) is used in a large variety of personal care products. Based on the physical–chemical properties of D5, it is likely that losses due to volatilisation may strongly influence the levels entering the aquatic environment. The aim of this study was to quantify the amount of D5 in waste wash water, after typical application and use in a range of deodorant and anti-perspirant (AP) products. Results implied significant losses after a 24h period (>99.9%), and suggest that the use of D5 in leave-on products, such as deodorants/AP is not likely to contribute a significant down-the-drain emission source. An illustrative example is presented, based on data reporting the use of D5 in a range of personal care products (both wash-off and leave-on), which suggests that the contribution of D5 used in wash-off products to the aquatic environment may be considerably more significant. Limitations associated with our understanding of the actual D5 inclusion levels in the products, the market share of the products containing D5, and the variability of consumer habits, are identified as data gaps that need to be addressed in order to better refine down-the-drain emission estimates.