Registration Dossier

Diss Factsheets

Administrative data

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:
no hazard identified

Marine water

Hazard assessment conclusion:
no hazard identified

STP

Hazard assessment conclusion:
no hazard identified

Sediment (freshwater)

Hazard assessment conclusion:
no hazard identified

Sediment (marine water)

Hazard assessment conclusion:
no hazard identified

Hazard for air

Air

Hazard assessment conclusion:
no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:
no hazard identified

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:
no potential for bioaccumulation

Additional information

Conclusion on classification

Key parameters for classification:

The registered (parent) substance dimethoxy(dimethyl)silane (CAS No. 1112-39-6) hydrolyses rapidly in contact with water under environmentally relevant conditions. Therefore, the environmental hazard and risk assessment is based on the silanol hydrolysis product, i.e. dimethylsilanediol (CAS No. 1066-42-8). The other hydrolysis product, i.e. methanol, is assumed to have a negligible impact on the environmental hazard profile of the parent substance.

 

Abiotic degradation – Hydrolysis

DT50 < 0.6 h (25 °C and pH 7, OECD 111)

Biodegradation in water, sediment, and soil

Not readily biodegradable (higher tier biodegradation tests for soil, sediment and water).

 

Bioaccumulation

Log Kow (parent) = 2 (QSAR)

log Kow (silanol hydrolysis product) = -0.41 (QSAR)

 

Aquatic acute toxicity

Fish 

LC50 (96 h) > 126 mg/L (measured arithmetic mean, Oncorhynchus mykiss, OECD 203, RA CAS No. 1066-42-8)

Aquatic invertebrates

EC50 (48 h) > 117 mg/L (measured arithmetic mean, Daphnia magna, OECD 202, RA CAS No. 1066-42-8)

Algae

ErC50 (72 h) > 118 mg/L (measured arithmetic mean, Pseudokirchneriella subcapitata, OECD 201, RA CAS No. 1066-42-8)

 

Aquatic chronic toxicity

Aquatic invertebrates

21 day NOEC ≥ 12.6 mg/L (measured time-weighted average, Daphnia magna, OECD 211, RA CAS No. 1066-42-8)

Algae

NOErC (72 h) ≥ 118 mg/L (measured arithmetic mean, Pseudokirchneriella subcapitata, OECD 201, RA CAS No. 1066-42-8)

 

Classification according to CLP

Dimethoxy(dimethyl)silane hydrolyses rapidly under environmental conditions (DT50 < 0.6 h, at pH 7 and 25 °C) to form the hydrolysis product dimethylsilanediol and methanol. The silanol hydrolysis product is not considered to be readily biodegradable, while the second hydrolysis product methanol is considered to be readily biodegradable (OECD SIDS, 2004). Due to a low log Kow of the silanol hydrolysis product, a low potential for bioaccumulation is expected. Acute aquatic toxicity data for the silanol hydrolysis product dimethylsilanediol are available for all three trophic levels (fish, aquatic invertebrates, algae). No effects on aquatic organisms were recorded in the available studies with the silanol hydrolysis product, all LC/EC50 effect values are >100 mg/L. Chronic aquatic toxicity studies are available for two trophic levels (aquatic invertebrates and algae). No effects were observed in the chronic studies up to the highest concentrations tested (12.6 mg/L (daphnia) and 118 mg/L (algae). On this basis, the parent substance dimethoxy(dimethyl)silane (CAS No. 1112-39-6) does not need to be classified and labeled according to the consolidated version of Regulation (EC) No 1272/2008 including all further amendments (ATPs).

 

References:

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