Dimethoxydimethylsilane

Toxicity to terrestrial arthropods

Link to relevant study record(s)

Reference

Endpoint:

toxicity to terrestrial arthropods: long-term

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Description of key information

Additional testing for toxicity to terrestrial arthropods is not considered necessary based on the chemical safety assessment according to Annex I and the available data set for physico-chemical properties and aquatic as well as terrestrial hazard profiles of the registered substance.

Additional information

Dimethoxy(dimethyl)silane (CAS No. 1112-39-6) hydrolyses rapidly in contact with water (DT50 < 0.6 h), to dimethylsilanediol (DMSD, CAS No. 1066-42-8) and methanol (CAS No. 67-56-1). The ECHA guidance R.16 states that “for substances where hydrolytic DT50 is less than 12 h, environmental effects are likely to be attributed to the hydrolysis product rather than to the parent itself” (ECHA, 2016). The ECHA guidance R.16 also suggests that in case the hydrolysis half-life is less than 12 h, the breakdown products, rather than the parent substance, should be evaluated for aquatic toxicity. Methanol is well described in the public domain literature. It has a low environmental hazard profile and is therefore not considered contributory to the overall ecotoxicity of the registered substance (OECD SIDS, 2004). Thus, the ecotoxicity assessment is based on read-across to the silanol hydrolysis product dimethylsilanediol (DMSD, CAS No. 1066-42-8). Details on the read-across can be found in the analogue justification attached in IUCLID Section 13.

Additional testing for long or short-term toxicity to terrestrial arthropods is not considered necessary.

The registered substance hydrolyses rapidly and its stable silanol transformation product is not readily biodegradable but is highly water soluble and has a low potential for adsorption (Koc = 0.82) and a low potential for bioaccumulation (log Kow (silanol) = -0.38). Furthermore, the substance is used under highly controlled conditions. Therefore, exposure of the terrestrial compartment is expected to be low.

What is more, no acute and chronic aquatic toxicity was observed in tests conducted with the silanol hydrolysis product of the registered substance and the occurrence of more severe toxic effects in the terrestrial compartment that were not expressed in the aquatic studies is considered unlikely.

For terrestrial toxicity, reliable experimental studies for long-term terrestrial toxicity are available for invertebrates, terrestrial plants and soil microorganisms. In all studies, no statistically significant adverse effects were recorded up to the highest tested concentrations. Therefore, the hazard conclusion drawn for the terrestrial compartment is ‘no hazard identified’.

Overall, it is concluded that the hazard conclusion is representative of the lack of toxicity observed for dimethylsilanediol in the available short-term and long-term aquatic and terrestrial tests. Therefore, further testing to terrestrial arthropods is not considered necessary, based on the results of the chemical safety assessment according to Annex I.

 

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