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Ecotoxicological information

Short-term toxicity to fish

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Description of key information

Short-term toxicity to fish: 96hr LC50 >110 mg/l nominal (highest concentration tested (TSCA GUIDELINE 797.1400).

Key value for chemical safety assessment

Additional information

A 96-hour LC50 value >110 mg/l (nominal) (highest concentration tested) has been determined for the effects of 1,1,1,3,5,5,5-heptamethyl-3-octyltrisiloxane on mortality of the freshwater fish Pimephales promelas, in accordance with TSCA Guideline 797.1400.

In view of the test media preparation method/exposure regime it is likely that the test organisms were exposed predominantly to the tested substance.

Test concentrations exceeded the test substance water solubility and undissolved test material and an oily film were observed during the test. However, no adverse effects on the fish were observed, therefore the effect concentration is >LoS (limit of solubility).

Another supporting study has reported a 96-hour LC50 value of >100 mg/l (nominal) (highest concentration tested) for the same test item in a limit test on mortality of the freshwater fish Danio rerio, in accordance with guideline OECD 203.

Supporting data are also read-across from the structural analogue 3-hexyl heptamethyltrisiloxane (CAS 1873-90-1).

No effects were observed in a 96-hour study conducted with Lepomis machrochirus conducted in a saturated solution of 3-hexyl heptamethyltrisiloxane prepared at 1000 ppm. Chemical analysis determined measured concentrations in excess of the solubility limit of the substance in test media (6 μg/l (reported as 6 ppb)). It can therefore be concluded that the 96-hour EC50 value for aquatic invertebrates is >LoS of the test substance.

When the results are expressed using measured concentrations of the saturated solution, a 96-hour EC50 value of >49 μg/l can be determined for the effects of the test substance on mortality of Lepomis machrochirus, based on geometric mean measured concentrations (geometric mean concentrations calculated by the reviewer using the analytical data).

The data should be used with caution because the test solution was cloudy after mixing, settling into a clear solution with a surface film, although no effects were observed.