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Ecotoxicological information

Endpoint summary

Administrative data

Description of key information

Additional information

There are no reliable aquatic toxicity data available for the registration substance 1,3,5-trimethyl-1,1,3,5,5-pentaphenyltrisiloxane (CAS 3390-61-2).

Requirements to test are waived because testing is not technically feasible due to the insolubility of the substance, very high log Kow and very high log Koc:

- These physicochemical properties indicate that maintaining stable aqueous test solutions will be extremely difficult. Furthermore, the substance will have the tendency to adsorb onto the glassware under experimental conditions. This contributes to technical difficulties making reliable experimental studies very difficult to conduct.

- Above a log Kow of 6.0 short-term toxicity effects are not expected to occur, because the very limited aqueous solubility prevents toxic concentrations being achieved in exposure media. Similarly, above log Kow of 8, long-term toxicity effects are not expected.

- Regarding environmental exposure: the chemical properties indicate the substance will have the tendency to adsorb onto dissolved organic matter in the natural environment. Therefore, aqueous exposure is unlikely.

- The physicochemical properties and very high value of Koc (6.0) means that if the substance were to enter a wastewater treatment plant in influent waste waters, it would partition mainly to sludges (a small proportion may be volatilised), with a negligible amount passing to water. The result is that exposure of freshwater or marine aquatic compartments is negligible.

An activated sludge respiration inhibition study with the read-across substance Silsesquioxanes, phenyl, reported a 3 hour NOEC value of1000 mg/l (based on loading rate). Refer to IUCLID Section 6 endpoint summary (CSR Section 7.0) for further discussion of the approach to chemical safety assessment and justification for read across.