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PBT assessment

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PBT assessment: overall result

Reference
Name:
Methyl-N-[3-(trimethoxysilyl)propyl]carbamate
Type of composition:
boundary composition of the substance
State / form:
liquid
Reference substance:
Composition 1
PBT status:
the substance is not PBT / vPvB
Justification:

The PBT Assessment for the substance is based on the criteria set out in the “Guidance on information requirements and chemical safety assessment, Chapter R.11: PBT Assessment”.

Persistence Assessment

Methyl-N-[3-(trimethoxysilyl)propyl]carbamate (CAS 23432-62-4) hydrolyses rapidly in contact with water to methyl-N-[3-(trihydroxysilyl)propyl]carbamate and methanol (half-life of 3.0 h at 20-25°C and pH 7). The hydrolysis is expected to occur during a standard biodegradation test. According to the Guidance on Information Requirements and Chemical Safety Assessment Chapter R.11: PBT/vPvB assessment, hydrolysis is considered as primary degradation and the stable degradation products formed, should be considered for PBT assessment (ECHA, 2017).

Experimental data were not available for methyl-N- [3-(trimethoxysilyl)propyl]carbamate (CAS 23432-62-4), therefore read across from the analogue substance, methyl-N {[dimethoxy(methyl)silyl]methyl}carbamate (CAS 23432-65-7) was performed for assessment. Both methyl-N- [3-(trimethoxysilyl)propyl]carbamate (CAS 23432-62-4) and methyl-N-{[dimethoxy(methyl)silyl]methyl}carbamate (CAS 23432-65-7) are within an analogue group of substances within which, in general, there is no evidence of any significant biodegradation. The percentage biodegradation of methyl-N-{[dimethoxy(methyl)silyl]methyl}carbamate (CAS 23432-65-7) was reported to be 19.5 % after 28 days. The read across substance is therefore not readily biodegradable.

Based on the results of the analogue substance, Methyl-N-[3-(trimethoxysilyl)propyl]carbamate (CAS 23432-62-4) and its silanol hydrolysis product are not considered rapidly biodegradable. The other hydrolysis product methanol is known to be readily biodegradable (OECD, 2004).

Therefore, the substance is considered to meet the criteria for persistence (P and vP). 

Bioaccumulation Assessment

Methyl-N-[3-(trimethoxysilyl)propyl]carbamate (CAS 23432-62-4) is not expected to bioaccumulate based on its low log Kow value of 0.8 (QSAR). Furthermore the substance is expected to hydrolyse rapidly in contact with water to methyl-N-[3-(trihydroxysilyl)propyl]carbamate and methanol (half-life of 3.0 h at 20-25°C and pH 7) decreasing the possibility to bioaccumulate even more. Therefore, the parent substance is not B and not vB.

The silanol hydrolysis product methyl-N-[3-(trihydroxysilyl)propyl]carbamate bears a very low log Kow value of -2.3, and does therefore not meet the screening criteria for B or vB. The other hydrolysis product, methanol is also negligible with regard to bioaccumulation (OECD 2004).

In conclusion, methyl-N-[3-(trimethoxysilyl)propyl]carbamate (CAS 23432-62-4) and its hydrolysis products do not meet the criteria for bioaccumulation (not B and not vB).

Toxicity Assessment

Two studies are availbale in which the short term toxicity of the substance towards fish and aquatic invertebrates was assessed. Additionally read across data from methyl-N-{[dimethoxy(methyl)silyl]methyl}carbamate (CAS 23432-65-7) were used to assess the toxicity of the substance towards algae. Short term toxicity data indicated EC/LC50 values >100 mg/L. A EC10/NOEC value was determined for algae and was > 0.01 mg/L. On this basis the substance is not considered as T for the environment.

The substance is classified for specific target organ toxicity as STOT Rep. Exp. 2  according to the criteria of regulation EC No 1272/2008.; the substance is not classified as carcinogenicity, mutagenicity or reproductive and developmental toxicity in mammals. The criterion for “T” for human health hazard is met.

In conclusion methyl-N-[3-(trimethoxysilyl)propyl]carbamate (CAS 23432-62-4) is not PBT/vPvB.

Reference:

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