Registration Dossier

Ecotoxicological information

Endpoint summary

Administrative data

Description of key information

Additional information

2,4,6,8-tetramethylcyclotetrasiloxane (HD4) hydrolyses rapidly and, at low concentrations, the final hydrolysis product is presumed to be methylsilanetriol (see Section However, at high concentrations unspecified polymeric species are expected to dominate and short-term aquatic toxicity tests with Daphnia and algae at 100 mg/l found low concentrations of dissolved carbon (5 mg/l) in the test media. The EC50s were found to be >100 mg/l and the NOECs ≥100 mg/l based on nominal concentrations. Therefore, due to the instability of the substance and that of its breakdown products, it is not considered appropriate to conduct further testing. In addition, the substance is only used in industrial settings in closed systems under controlled conditions and emissions to surface waters are unlikely.

L(E)C50's for fish, invertebrates and algae are predicted for the final hydrolysis product methylsilanetriol using an appropriate validated QSAR (PFA 2013ag).