N-[3-(dimethoxymethylsilyl)propyl]ethylenediamine

Ecotoxicological Summary

Hazard for aquatic organisms

Freshwater

Hazard assessment conclusion:

PNEC aqua (freshwater)

PNEC value:

0.05 mg/L

Assessment factor:

50

Extrapolation method:

assessment factor

PNEC freshwater (intermittent releases):

0.071 mg/L

Marine water

Hazard assessment conclusion:

PNEC aqua (marine water)

PNEC value:

0.005 mg/L

Assessment factor:

500

Extrapolation method:

assessment factor

STP

Hazard assessment conclusion:

PNEC STP

PNEC value:

20.3 mg/L

Assessment factor:

1

Extrapolation method:

assessment factor

Sediment (freshwater)

Hazard assessment conclusion:

PNEC sediment (freshwater)

PNEC value:

0.18 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Sediment (marine water)

Hazard assessment conclusion:

PNEC sediment (marine water)

PNEC value:

0.018 mg/kg sediment dw

Extrapolation method:

equilibrium partitioning method

Hazard for air

Air

Hazard assessment conclusion:

no hazard identified

Hazard for terrestrial organisms

Soil

Hazard assessment conclusion:

PNEC soil

PNEC value:

0.007 mg/kg soil dw

Extrapolation method:

equilibrium partitioning method

Hazard for predators

Secondary poisoning

Hazard assessment conclusion:

no potential for bioaccumulation

Additional information

N-[3-(Dimethoxymethylsilyl)propyl]ethylenediamine (CAS 3069-29-2) will hydrolyse very rapidly (half-life 15 minutes at pH 7 and 25°C) in contact with water and atmospheric moisture to form N-[3-(dihydroxymethylsilyl)propyl]ethylenediamine and methanol. Aquatic organisms are therefore likely to be predominately exposed to the hydrolysis products of the registered substance rather than the substance itself.

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”. The substance will be exposed to the environment through wastewater treatment plant (WWTP) effluent only.

The minimum residency time in the wastewater treatment plant is approximately 7 hours (although this is a conservative figure and wastewater treatment time may be hours longer) with an average temperature of 15°C (assumed to be at neutral pH). Significant degradation by hydrolysis would be expected before the substance is released to the receiving waters.

The environmental hazard assessment, including sediment and soil compartments due to water and moisture being present, is therefore based on the properties of the silanol hydrolysis product, in accordance with REACH guidance.

The properties of methanol have been discussed extensively in the public literature and it is not hazardous at the concentrations at which it would have been present in the toxicity tests reviewed in this assessment. The short-term EC₅₀and LC₅₀values for this substance are in excess of 1000 mg/l (OECD 2004a - SIDS for methanol). Therefore, the environmental hazard assessments that follow (including those for sediment and soil compartments) are based on the assumption that the observed effects are the result of exposure to the silanol hydrolysis product of the registered substance, N-[3-(dihydroxymethylsilyl)propyl]ethylenediamine.

As described in Section 4.8 of IUCLID and Section 1.4 of the CSR, silanols may undergo condensation reactions to give siloxane dimers, oligomers and polymers at high enough concentrations. Condensation reactions become significant at approximately 1000 mg/l. No observations on condensation were reported in the read-across studies.

READ-ACROSS JUSTIFICATION

There are no reliable data available for N-[3-(dimethoxymethylsilyl)propyl]ethylenediamine (CAS 3069-29-2) for ecotoxicity. In order to reduce testing, the Annex requirements are fulfilled with data from substances that have similar structures and physico-chemical properties.

 

Ecotoxicological studies are conducted in aquatic media or in moist environments; therefore the hydrolysis rate of the substance is particularly important since after hydrolysis occurs the resulting product has different physicochemical properties and structure.

 

The registered substance hydrolyses very rapidly in water and therefore the selection of the read-across substance is based on the silanol hydrolysis products, the groups present on the side chains, as well as the log K_ow since this contributes to bioavailability.

 

The analogue approach for fulfilling the data requirement by read-across is discussed according to the Read-across Assessment Framework (RAAF).

 

Data have been read-across from N-(3-(trimethoxysilyl)propyl)ethylenediamine (CAS 1760-24-3). In the context of the RAAF, the basis of the read-across hypothesis for this substance is “Different compounds have the same type of effect(s)”; Scenario 2 applies. Both the source and target substance hydrolyse to compounds with qualitatively similar properties.

 

Please see the report attached in Section 13 for the analogue approach to address ecotoxicity of N-[3-(dimethoxymethylsilyl)propyl]ethylenediamine (CAS 3069-29-2) by read-across from N-(3-(trimethoxysilyl)propyl)ethylenediamine (CAS 1760-24-3).

Conclusion on classification

Conclusions on classification have been made for the parent substance, N-[3-(Dimethoxymethylsilyl)propyl]ethylenediamine (CAS 3069-29-2).