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Ecotoxicological information

Toxicity to terrestrial arthropods

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Reference
Endpoint:
toxicity to terrestrial arthropods: long-term
Data waiving:
exposure considerations
Justification for data waiving:
other:

Description of key information

In accordance with REACH Annex XI, Section 3, exposure of terrestrial organisms to dimethoxydimethylsilane is not significant (RCR << 1) and the substance has a low hazard potential based on the available acute data.

Key value for chemical safety assessment

Additional information

In accordance with Annex XI, Section 3, exposure of terrestrial organisms to dimethylsilanediol is not significant. A study testing the long-term toxicity of the silanol hydrolysis product, dimethylsilanediol, on the respiration and nitrogen transformation of soil microflora is available. No chronic effects were observed in this study for the silanol hydrolysis product on the respiration rate and nitrate formation rate of soil microflora (90-day NOEC≥300 mg/kg soil dw).

Furthermore, the hazard assessment based on acute aquatic toxicity data shows no toxicity toward aquatic organisms of all three trophic levels (all acute effect values, i.e. E(L)C50s were > 100 mg/L). Additionally, a chronic toxicity test on aquatic invertebrates is available, which showed no effects up to the highest tested concentration (21-day NOEC ≥ 12.6 mg/L). The substance is well soluble and thus, greater toxicity in additional long-term tests is unlikely.

Even though no hazard was identified in acute aquatic studies and the available chronic terrestrial study, PNECs aqua and a PNEC soil were derived for the purpose of risk characterization, using the threshold value of 12.6 mg/L derived from the chronic daphnia study in combination with standard safety factors as outlined in ECHA guidance R.10. A PNEC soil was calculated based on the equilibrium partitioning method. As the substance hydrolyses rapidly, the environmental hazard assessment, PNEC soil derivation and risk characterization is based on the silanol hydrolysis product following a worst case approach. The other hydrolysis product, methanol, is known for its absence of environmental toxicity (OECD SIDS, 2004). The risk characterization for the silanol hydrolysis product indicated no risk to the aquatic environment (RCR < < 1).

For detailed information on the risk assessment please see the attached documentation.

References:

OECD SIDS, 2004: SIDS Initial Assessment Report for Methanol, SIAM 19, Berlin, Germany, 19-22 October 2004, Methanol, CAS 67-56-1