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Toxicity to aquatic algae and cyanobacteria

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Description of key information

Short-term toxicity to algae: 72-h ErC50 >21.6 μg/l and NOEC: ≥21.6 μg/l (geometric mean measured, highest concentration tested) in accordance with OECD guideline 201.

Key value for chemical safety assessment

Additional information

There are no toxicity to aquatic algae data available for 1,1,1,3,5,5,5-heptamethyl-3-octyltrisiloxane (CAS 17955-88-3), therefore good quality data for an appropriate structural analogue, 3-hexyl heptamethyltrisiloxane (CAS 1873-90-1), have been read across. A 72-hour ErC50 value of >21.6 μg/l and NOEC of ≥21.6 μg/l (>LoS) (highest concentration tested) have been determined for the effects of 3-hexyl heptamethyltrisiloxane on growth rate of Selenastrum capricornutum. The results have been obtained under static test conditions and are expressed relative to geometric mean measured concentrations of the substance.


In view of the use of static test conditions, it is likely that the test organisms were exposed primarily to the parent substance at the beginning of the test, then to the hydrolysis products as the test progressed and the pH increased.