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Toxicity to aquatic algae and cyanobacteria

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Key value for chemical safety assessment

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No reliable toxicity to aquatic algae data are available for 1,3,3,5-tetramethyl-1,1,5,5-tetraphenyltrisiloxane (CAS 3982-82-9).

Testing is not required for the following reasons:

- The substance is highly insoluble in water, hence indicating that aquatic toxicity is unlikely to occur.

- It is technically not feasible to conduct an aquatic study due to the very low water solubility of the substance (5.9E-09 mg/l) and very high log Kow (9.0). These values indicate that maintaining stable aqueous test solutions will be extremely difficult. Furthermore, once dissolved, the substance will have the tendency to adsorb onto the glassware under experimental conditions and onto dissolved organic matter in the natural environment.

- Above a log Kow of 6 short-term toxicity effects are not expected, because the very limited aqueous solubility prevents toxic concentrations being achieved in exposure media.

- The physicochemical properties and very high expected Koc value means that if the substance could enter a wastewater treatment plant in influent waste waters, it would partition mainly to sludge (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.