Registration Dossier
Registration Dossier
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EC number: 274-092-8 | CAS number: 69709-01-9
Ecotoxicological Summary
Administrative data
Hazard for aquatic organisms
Hazard for air
Hazard for terrestrial organisms
Hazard for predators
Additional information
The registration substance 1,1,3,3-tetramethyl-2-[3-(trimethoxysilyl)propyl]guanidine (CAS 69709-01-9) has very low predicted log Kow (-4.0) and high predicted water solubility (3.7E+05 mg/l at 20°C). The substance will hydrolyse in water to 1,1,3,3-tetramethyl-2-[3-(trihydroxysilyl)propyl]guanidine and methanol. 1,1,3,3-Tetramethyl-2-[3-(trihydroxysilyl)propyl]guanidine has high predicted water solubility (1.0E+06 mg/l at 20°C, limited to about 1000 mg/l by condensation reactions) and low predicted log Kow (-4.0).
1,1,3,3-Tetramethyl-2-[3-(trimethoxysilyl)propyl]guanidine is a trialkoxysilane with an alkyl group attached to the silicon atom and a guanidine side chain. Guanidine is a strong base and will raise the pH of the water during ecotoxicological testing. Hydrolysis rate is usually slowest at pH 7 and will increase at higher or lower pH. Under test conditions, the parent substance is expected to rapidly hydrolyse. These factors will be given consideration during interpretation of ecotoxicological test results.
REACH guidance (ECHA 2016, R.16) states that “for substances where hydrolytic DT50 is less than 12 hours, environmental effects are likely to be attributed to the hydrolysis product rather than to the parent itself”. TGD and ECHA guidance (R.16, ECHA 2016), also suggest that when the hydrolysis half-life is less than 12 hours, the breakdown products, rather than the parent substance, should be evaluated for aquatic toxicity. Therefore, if hazard were to be assessed, the environmental hazard assessment, including the sediment and soil compartments due to water and moisture being present, would be based on the properties of the hydrolysis products in accordance with REACH guidance.
Short-term toxicity to invertebrates and algae data are available for 1,1,3,3-tetramethyl-2-[3-(trimethoxysilyl)propyl]guanidine.
Consideration of the non-silanol hydrolysis product methanol
Methanol is well characterised in the public domain literature and is not hazardous at the concentrations relevant to the studies; the short-term EC50 and LC50 values for this substance are in excess of 1000 mg/l (OECD2004a - SIDS for methanol, CAS 67-56-1). Therefore, at the loading rates experienced in these tests it is unlikely that the presence of methanol would significantly affect the results of the tests.
Conclusion on classification
The substance has reliable short-term E(L)C50 values of >122 mg/l in invertebrates and >131 mg/l in algae, based on concentrations of the silanol hydrolysis product. It has reliable NOEC >=131 mg/l in algae.
No significant biodegradation is expected for the silanol hydrolysis product.
These data are consistent with the following classification under Regulation (EC) No 1272/2008 (as amended) (CLP):
Acute toxicity: Not classified.
Chronic toxicity: Not classified.
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