N-[3-(trimethoxysilyl)propyl-1,3-Benzenedimethanamine

Ecotoxicological Summary

Additional information

Reaction Mass of N-[3-(trimethoxysilyl)propyl]-1,3-benzenedimethanamine and {3-[(2,2-dimethoxy-1,2-azasilolidin-1-yl)methyl]phenyl}methanamine is a multi-constituent substance, with two main constituents:

Constituent 1: [3-({[3-(trimethoxysilyl)propyl]amino}methyl)phenyl]methanamine at approximately 59.7%;

Constituent 2: {3-[(2,2-dimethoxy-1,2-azasilolidin-1-yl)methyl]phenyl}methanamine at approximately 20.3%;.

The substance is expected to be soluble in water, with a predicted water solubility value for Constituent 1 of 4.1E+04 mg/L at 20°C (QSAR) of the submission substance. The amine groups in Constituent 1 will protonate in solution, hence the predicted log K_ow has been corrected for ionisation (See overall physicochemical discussion in Section 4.0). Constituent 2 is estimated to hydrolyse very rapidly, so neither water solubility nor log K_ow can be measured.

Both constituents are expected to hydrolyse rapidly or very rapidly in contact with water (calculated half-lives: Constituent 1 = 4.8 hours; Constituent 2 = very rapid, at pH 7 and 20-25°C) to form [N-[3-(trihydroxysilyl)propyl]-1,3-benzenedimethanamine] and methanol. It is therefore likely that the test organisms in each test were exposed primarily to the hydrolysis products.

[N-[3-(trihydroxysilyl)propyl]-1,3-benzenedimethanamine] is very soluble in water, limited to approximately 1000 mg/L by condensation reactions. Also, the amine groups in the final silanol hydrolysis product will protonate in solution, hence the predicted log K_ow has been corrected for ionisation (See overall physicochemical discussion in Section 4.0).

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 (EC 2003, 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, the environmental hazard assessment, including sediment and soil compartments due to water and moisture being present, is based on the properties of the silanol hydrolysis product, in accordance with REACH guidance. As described in Section 4.8, the silanol hydrolysis products may be susceptible to condensation reactions.

 

Consideration of the non-silanol hydrolysis products methanol:

Methanol: The properties of methanol have been discussed extensively in the public literature. Methanol is considered to be non-toxic to aquatic organisms at the concentrations at which it would have been present in the tests reviewed in this assessment; the short-term EC₅₀ and LC₅₀ values for methanol are in excess of 1000 mg/L (OECD (2004).

Reference:

OECD (2004). SIDS Initial Assessment Report for SIAM 19, Berlin, Germany, 18-20 October 2004, Methanol, CAS 67-56-1.

EC (2003). European Union Technical Guidance Document on Risk Assessment for New and Existing Substances, Part II, European Chemicals Bureau, 2003.

ECHA (2016). Guidance on information requirements and Chemical Safety Assessment. Chapter R.16: Environmental exposure assessment, version 3.0, February 2016.

Conclusion on classification

The substance has reliable short-term E(L)C₅₀ values of 51 mg/L in invertebrates and 11 mg/L in algae based on tests with the whole substance. It has a reliable EC₁₀ value of 3.9 mg/L and a NOEC value of 1 mg/L in algae.

 

The constituents of the substance hydrolyse rapidly or very rapidly in contact with water. No significant biodegradation was observed during the biodegradation in water screening test and no significant biodegradation of the silanol hydrolysis products is expected.

 

No toxicity to fish data are available, therefore it is not possible to assess which trophic level is the most sensitive in the short-term tests. The algal chronic NOEC/EC₁₀ values do not necessarily cover the most sensitive species, and thus cannot be considered “adequate” chronic toxicity data.

In accordance with Regulation (EC) No 1272/2008 (as amended) (CLP), for non-rapidly degradable substances for which adequate chronic toxicity data are not available, a short-term E(L)C₅₀ value of >10 to ≤100 mg/L leads to classification of Category Chronic 3.

 

Therefore, based on the algal ErC₅₀ value of 11 mg/L, and the fact that the substance is non-rapidly degradable, these data are consistent with the following classification under Regulation (EC) No 1272/2008 (as amended) (CLP):

 

Acute toxicity: Not classified.

 

Chronic toxicity: Category Chronic 3.