Registration Dossier
Registration Dossier
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EC number: 240-914-9 | CAS number: 16881-77-9
Ecotoxicological Summary
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
Dimethoxy(methyl)silane (CAS No. 16881-77-9) is expected to undergo a rapid two-step hydrolysis under environmental conditions through which methylsilanediol (first step) and methylsilanetriol (second step) are formed. The non-silanol hydrolysis product is methanol. The predicted half-life is 0.3 h at pH 7 (QSAR). However, a hydrolysis study according to OECD Guideline 111 is currently being conducted and the dossier will be updated once the final study report is available.
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.
Thus, the environmental hazard and risk assessment in this dossier is based on the hydrolysis products methylsilanetriol and methanol rather than the parent substance. The alcohol hydrolysis product, methanol, is assumed to have a negligible impact on the environmental hazard profile of the parent substance based on the available body of evidence (OECD SIDS, 2004).
Abiotic degradation – hydrolysis
DT50 = 0.3 h (pH 7, 20 - 25 °C, QSAR)
Please note: A hydrolysis study according to OECD 111 is currently ongoing.
Biodegradation in water
Not readily biodegradable (0% in 28 d, OECD 310; read-across CAS No. 1066-40-6)
Bioaccumulation
Log Kow (parent) = 1.4 (20 °C, QSAR)
Log Kow (silanol hydrolysis product 1) = -1.0 (20 °C, QSAR)
Log Kow (silanol hydrolysis product 2) = -2.4 (20 °C, QSAR)
Acute aquatic toxicity
Fish
LC50 (96 h) > 110 mg/L (arithm. mean measured, OECD 203, O. mykiss, RL 1; read-across CAS No. 1185-55-3)
Aquatic invertebrates
EC50 (48 h) > 122 mg/L (arithm. mean measured, OECD 202, D. magna, RL 1; read-across CAS No. 1185-55-3)
Please note: A short-term toxicity study according to OECD Guideline 202 is currently ongoing
Algae
ErC50 (72 h) > 120 mg/L (nominal, OECD 201, R. subspicatus, RL1; read-across CAS No. 1185-55-3)
Chronic aquatic toxicity
Fish
Not available
Aquatic invertebrates
NOEC (21 d) ≥ 10 mg/L (arithm. mean measured, OECD 211, D. magna; read-across CAS No. 1185-55-3)
Algae
NOErC (72 h) of ≥ 120 mg/L (nominal, OECD 201, R. subspicatus, RL1; read-across CAS No. 1185-55-3)
Classification according to CLP
Dimethoxy(methyl)silane (CAS No. 16881-77-9) hydrolyses rapidly in contact with water (DT50 = 0.3 h) to form methylsilanetriol and methanol (CAS No. 67-56-1). The silanol hydrolysis product is not readily biodegradable and has a low potential for bioaccumulation based on its low log Kow (-1.4).
Acute aquatic toxicity data are available for all three trophic levels and chronic aquatic toxicity data are available for aquatic invertebrates and algae. No effects on aquatic organisms were recorded up to the highest concentrations tested.
Therefore, the parent substance dimethoxy(methyl)silane (CAS No. 16881-77-9) is not classified and labeled according to the consolidated version of Regulation (EC) No. 1272/2008 including all further amendments (ATPs).
Reference
OECD SIDS, 2004. Methanol - SIDS Initial Assessment Report For SIAM 19, Berlin, Germany: UNEP Publications.
Information on Registered Substances comes from registration dossiers which have been assigned a registration number. The assignment of a registration number does however not guarantee that the information in the dossier is correct or that the dossier is compliant with Regulation (EC) No 1907/2006 (the REACH Regulation). This information has not been reviewed or verified by the Agency or any other authority. The content is subject to change without prior notice.
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