N-[3-(dimethoxymethylsilyl)propyl]ethylenediamine

Endpoint summary

Additional information

Reliable short-term toxicity to aquatic invertebrates data are available with the registration substance. There are no reliable short-term data for fish and aquatic algae, therefore data for the structurally-related substance, N-(3-(trimethoxysilyl)propyl)ethylenediamine (CAS 1760-24-3), have been read across.

The relevant short-term values are:

Fish: Danio rerio: 96 h LC₅₀: 484 mg/l (measured DOC) read across from N-(3-(trimethoxysilyl)propyl)ethylenediamine (CAS 1760-24-3), expressed in terms of the concentration of the silanol hydrolysis product, N-(3-(trihydroxysilyl)propyl)ethylenediamine;

Invertebrates: Daphnia magna: 48 h EC₅₀ (48 h) : >86 mg/l (nominal concentration) expressed in terms of the concentration of the silanol hydrolysis product, N-[3-(dihydroxymethylsilyl)propyl]ethylenediamine.

Algae: Pseudokirchneriella subcapitata: 72 h ErC₅₀: 7.1 mg/l; NOEC (growth rate): 2.5 mg/l (nominal concentration), read across from N-(3-(trimethoxysilyl)propyl)ethylenediamine (CAS 1760-24-3), expressed in terms of the concentration of the silanol hydrolysis product, N-(3-(trihydroxysilyl)propyl)ethylenediamine.

There are no long-term aquatic data with the registered substance. However data are available for a read-across substance, N-(3-(trimethoxysilyl)propyl)ethylenediamine (CAS 1760-24-3); a 21 day NOEC of =1 ppm (=1 mg/l) has been determined for the effects on survival and reproduction of Daphnia magna. The substance has a density of 1.03 and it is assumed that the test sample had a purity of approximately 96%. The results are expressed relative to nominal concentrations of the test substance. However the substance is subject to rapid hydrolysis and under the test conditions it is therefore likely that exposure will have been to its hydrolysis products (methanol and N-(3-(trihydroxysilyl)propyl)ethylenediamine). The NOEC is equivalent to = 0.81 ppm (= 0.81 mg/l) when expressed in terms of the concentration of the silanol hydrolysis product, N-(3-(trihydroxysilyl)propyl)ethylenediamine.

The studies were conducted at pH 8 and above in many cases. The neutral form of the amine, i.e. the un-ionised form, is more toxic than the ionised form. This pattern of toxicity is consistent with ammonia, where the un-ionised form, NH₃, is more toxic than the ionised form, NH₄. The fraction of ammonia that is un-ionized increases as pH rises and decreases as pH falls. The difference in toxicity is due to the bioavailability, where the un-ionised form can cross cell membranes more readily than the ionised form. Therefore, for waters having a pH closer to 7 it is likely that the results of studies conducted at pH 8 overestimate the toxicity of the registered substance.

An activated sludge respiration inhibition 16 hour EC₅₀ value of 67 mg/l and EC₁₀ value of 25 mg/l were determined in a reliable study, read across from N-(3-(trimethoxysilyl)propyl)ethylenediamine (CAS 1760-24-3).

A data waiver is applicable to long-term toxicity to fish because:

- Short-term toxicity of the registered substance and degradation products to fish is low.

- The risk characterisation ratio (RCR) based on PNECaquatic derived from the long-term data for invertebrates and algae is <1.

Refer to IUCLID Section 6 endpoint summary (CSR Section 7.0) for further discussion of the approach to chemical safety assessment and justification for read across.