Environmental fate and effects of dimethicone and cyclotetrasiloxane from personal care applications

This paper summarizes the environmental fate and effects of dimethicone and cyclotetrasiloxane, which are used extensively in personal care applications. Dimethicone and cyclotetrasiloxane differ fundamentally in their physicochemical properties, and as a consequence display different environmental fate paths. Cyclotetrasiloxane partitions into the atmosphere, whereas sediments and soils are the most important environmental compartments for dimethicone. Information is presented to show the environmental degradation of these two materials in their respective environmental compartments. In both cases, after a non-biological step to initiate the process, the degradation occurs biologically. Ultimately, both dimethicone and cyclotetrasiloxane are degraded to inorganic constituents, carbon dioxide, silicic acid and water. No adverse effects have been detected in experimental organisms representative of the environmental compartments in which dimethicone and cyclotetrasiloxane may be found. Monitoring of key environmental compartments, namely sediments and soil, reveals that average concentrations are well below the no-observed adverse effect level. This work therefore continues to support the environmental acceptability of dimethicone and cyclotetrasiloxane for personal care applications.