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Ecotoxicological information

Long-term toxicity to fish

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Description of key information

Key value for chemical safety assessment

Additional information

No reliable long-term fish toxicity data are available for the substance. Testing is not considered necessary for the following reasons:

The physicochemical properties including high vapour pressure (1700 Pa), low water solubility (0.21 mg/l) and high value of Koc (3.2) means that if the substance were to enter a wastewater treatment plant in influent waste waters, a large proportion would be volatilised, the remaining proportion would partition mainly to sludge, leaving only a small fraction dissolved in the water. The result is that exposure of freshwater or marine aquatic compartments is minimal.

Short-term toxicity to fish, invertebrates and algae, and long-term toxicity to aquatic invertebrates tests have been conducted with the substance. The Daphnia and algae tests were conducted in closed vessels with no headspace in order to minimise volatilisation. The short-term fish test was conducted under flow-through conditions with continual replacement of the test substance dissolved in a solvent, in order to maximise concentrations of test substance in solution. In the open environment, it is expected that the substance will rapidly volatilise from the water.

No effects were observed at the limit of solubility of the substance in any of the aquatic toxicity tests. A long-term toxicity to aquatic invertebrates test has been conducted with the registration substance and no effects were observed. Data across the siloxanes category indicates that there is no reason to suspect that fish will be any more sensitive than invertebrates.

PNECs have been derived for the sediment compartment as this area is thought to be of most concern due to the physicochemical properties indicating the substance will deposit and bind to the sediment. PNECs derived for sediment should therefore be protective of the aquatic and terrestrial compartments.

Consideration is given to the avoidance of testing vertebrate animals. Overall it is concluded that the risk is adequately assessed using the short-term data and the long-term invertebrate test, there is no risk to the aquatic environment, and that in vivo testing on vertebrate animals is not considered necessary or justified on ethical grounds.