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The new ECHA CHEM database has been released by ECHA, and it now contains all REACH registration data. There are more details on the transition of ECHA's published data to ECHA CHEM here.

Diss Factsheets

Ecotoxicological information

Short-term toxicity to aquatic invertebrates

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Administrative data

Link to relevant study record(s)

Reference
Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
Please refer to the analogue approach justification provided in Section 13.
Reason / purpose for cross-reference:
read-across source
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
> 122 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
mobility
Duration:
48 h
Dose descriptor:
NOEC
Effect conc.:
>= 122 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
mobility
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
> 200 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Duration:
48 h
Dose descriptor:
NOEC
Effect conc.:
>= 200 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Conclusions:
A 48-hour EC50 value of >122 mg/L and NOEC of ≥122 mg/L have been determined for the effects of the substance on mobility of Daphnia magna. Under the flow-through conditions used in the test it is likely that the test organisms were exposed to a mixture of the parent substance and its hydrolysis products.

Description of key information

EC50 (48 h) > 122 mg/L (arithmetic mean measured, OECD 202, D. magna; read-across CAS No. 1185-55-3)

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Dose descriptor:
EC50
Remarks:
48 h
Effect concentration:
> 122 mg/L

Additional information

Please note: A short-term toxicity study according to OECD Guideline 202 is currently ongoing for this substance. This dossier will be updated once the final study report is available.


 


The registered substance dimethoxy(methyl)silane (CAS No. 16881-77-9) hydrolyses rapidly (DT50 = 0.3 h) to the silanol hydrolysis products methylsilanediol and methylsilanetriol and the alcohol hydrolysis product methanol.


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 TGD (EC2003) and ECHA guidance R.16 (ECHA 2010) 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.


It is anticipated that the second silanol hydrolysis product, methylsilanetriol, is the final product of the


hydrolysis reactions and is thus considered the relevant assessment entity for the present Chemical Safety Assessment according to REACH.


Thus, the environmental fate assessment as well as the hazard and risk assessment are based on the


hydrolysis products methylsilanetriol and methanol rather than the parent substance.


Methanol is known for its absence of environmental toxicity at the concentrations relevant to this dossier (OECD SIDS, 2004), and is therefore not considered contributory to the overall aquatic toxicity of the substance and thus not relevant for the assessment of aquatic toxicity.


 


For the short-term toxicity to aquatic invertebrates, no experimental data are available for the registered substance itself. Therefore, read-across was performed from the structurally similar analogue substance trimethoxy(methyl)silane  (CAS No. 1185-55-3), which hydrolyses within a comparable time frame (DT50 = 2.2 h) to the same silanol hydrolysis product methylsilanetriol, which the target and source substances thus share in common. A detailed read-across justification is provided in IUCLID Section 13.


 


The available read-across study was carried out according to the testing guideline OECD 202 and in compliance with GLP.


 


In a flow-through test, Daphnia magna were exposed to 5 concentration levels up to 200 mg/L (nominal) for 48 h. The test solutions were prepared by direct addition of the test material to the test medium. The lower test concentrations were prepared with a vehicle (DMF) to facilitate delivery in the diluter system. The test concentrations were analytically monitored by GC-MS at test start and test end.


 


At test end, an EC50 (48 h) of > 122 mg/L (measured) corresponding to 200 mg/L (nominal) was determined. Under the flow-through conditions used in the test, it is likely that the test organisms were exposed to a mixture of the parent substance and its hydrolysis products.