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Long-term toxicity to fish

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Reference
Endpoint:
fish early-life stage toxicity
Data waiving:
exposure considerations
Justification for data waiving:
other:
Justification for type of information:
For detailed information on this adaptation based on Annex XI (Section 3), please refer to the CSR attached in Section 13.

Description of key information

A long-term toxicity study on fish is not necessary as

- exposure considerations in accordance with Annex XI, Section 3, indicate that exposure of aquatic organisms to dichloro(diphenyl)silane is absent or not significant

Key value for chemical safety assessment

Additional information

In accordance with Annex XI, Section 3, exposure of aquatic organisms to dichloro(diphenyl)silane (CAS No. 80-10-4) is absent or not significant. 

Due to the rapid hydrolysis of the substance, the environmental hazard assessment, PNEC derivation and risk characterization is based on the silanol hydrolysis product diphenylsilanediol.

The silanol hydrolysis product is highly water-soluble, has a low potential for bioaccumulation (based on log Kow <3 (2.0)) and the short-term toxicity to fish is low (LC50 (96 h) = 39 mg/L). The parent compound and its hydrolysis product are part of a class of low functionality compounds acting via a non-polar narcosis mechanism of toxicity, and as such, log Kow drives toxicity. Therefore, it is no reason to expect any specific mechanism of toxicity beyond narcosis and thus a long-term toxicity testing of fish is not necessary.

Based on the aquatic data set, read across from the hydrolysis product diphenylsilanediol, little effects (LC/EC50) were seen in the short-term fish or aquatic invertebrate studies up to arithmetic mean measured concentrations of 39 and 24 mg/L, respectively. Lower effects were seen in the toxicity study with algae (ErC50 (72 h) = 9 mg/L) and the result from this test is used to derive aquatic PNECs.

A PNEC has been derived for the purpose of chemical safety assessment. An assessment factor of 1000 was applied to derive the freshwater PNEC. For a narcotic chemical without a specific mode of toxic action, it is unlikely that the aquatic PNEC would be significantly underestimated.

The second hydrolysis product of the parent compound, hydrochloric acid, readily dissociates in water into hydrated protons and chloride anions. Thus, it is ionised and neutralisation depends on the buffer capacity of the receiving water. Toxicity only occurs when the buffering capacity of the receiving water is exceeded and pH values fall below pH 6. The pH in rivers and lakes fluctuates within a natural range. The natural pH range in aquatic systems is generally not expected to be perturbed to a relevant extent by anthropogenic emissions when appropriate risk control measures are in place. Variations in effect values of experimental studies can largely be explained by variations in the buffer capacity of the test media (OECD, 2002). Thus, hydrochloric acid is not expected to have a significant impact on the overall aquatic toxicity of the registered compound.  

The risk characterization for the silanol hydrolysis product of the substance indicated no risk to the aquatic environment (RCR < < 1).

For detailed information on the risk assessment please refer to the attached documentation in Section 13.

References:

OECD, 2002. Hydrogen Chloride - SIDS Initial Assessment Report for SIAM 15, Boston, USA: UNEP Publications.