N-(3-(trimethoxysilyl)propyl)ethylenediamine

Toxicity to soil macroorganisms except arthropods

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to soil macroorganisms except arthropods: short-term

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2004-03-01 to 2004-04-02

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 207 (Earthworm, Acute Toxicity Tests)

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

yes

Details on preparation and application of test substrate:

The application solution for the highest test concentration was prepared by dissolving 13.900 g of the test substance completely in 50 ml of chloroform, resulting in a test item concentration of 278 mg/ml of chloroform. Aliquots of the application solution were diluted with chloroform to obtain the application solutions for the lower test concentrations: aliquots of 1.5, 2.67, 4.74 and 8.43 ml of the application solution of the highest test concentration were made up to 15 ml to obtain the application solutions of the nominal test concentrations of 100, 178, 316 and 562 mg/kg dry soil respectively.

For each test concentration, the volume of 10 ml of the corresponding application solution was applied to 50 g of sand in a mortar. The solvent was completely evaporated at room temperature under a hood for 30 minutes. The remainder (sand/test substance mixture) was intensively mixed by means of a pestle and then mixed in a roller for 30 minutes. The sand/test substance mixture was then divided into 10 g aliquots (corrected for the amount of test item applied to 10 g of sand) and filled into separate vials.

Immediately before the start of the test, aliquots of 10 g sand/test substance mixture were quantitatively incorporated into the four replicates of 546 g of artificial soil (dry weight) per test concentration by intense mixing in a laboratory mixer. The moisture content was brought to 35% by adding 186 ml of purified water.

A control was tested in parallel. The control was prepared in the same way as the treated soils. A 50 g sand portion was treated with 10 ml of chloroform (but without the test substance) in the same way as the application of the test substance in the treatment groups.

Test organisms (species):

Eisenia fetida

Animal group:

annelids

Details on test organisms:

The test organisms were obtained from breeding stock maintainedat RCC Laboratory. The worms are held in a temperature-controlled room and fed with suitable food (e.g. horse manure and potatoes).

For one day prior to the start of the test, the test oragnisms were acclimated to the artificial soil and the test temperature.

At the start of the test the mean body wet weight of the worms in the different treatment and control replicates ranged from 338 to 382 mg. The worms used were adults with a clitellum and were approximately 4 to 5 months old.

Study type:

laboratory study

Substrate type:

artificial soil

Limit test:

no

Total exposure duration:

14 d

Test temperature:

18.9 to 20.4°C

pH:

Initial pH: 6.2

pH at the end of the test: 5.5-6.3

Moisture:

Initial: 35%

At end of test: 33-34%

Details on test conditions:

TEST SYSTEM

- Test container (material, size): cylindrical glass vessels (10 cm diameter, 14 cm tall) with a volume of approximately 1 litre.

- Amount of soil or substrate: The test vessels were large enough to contain 556 g dry weight of artificial soil, corresponding to approximately 750 g wet weight.

- No. of organisms per container (treatment): 10

- No. of replicates per treatment group: 4

- No. of replicates per vehicle control: 4

SOURCE AND PROPERTIES OF SUBSTRATE (if soil)

- Type: artificial soil prepared in accordance with the test guideline

- Soil texture (if natural soil). The soil (air dry components without calcium carbonate) was prepared in a batch of 20 kg by intensely mixing the corresponding amounts of the constituents in a cement mixer.
- % sand: 70
- % peat: 10
- % clay: 20
- % calcium carbonate: 0.5%


OTHER TEST CONDITIONS

- Photoperiod: continuous

- Light intensity: 490-550 Lux

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): mortality and any symptoms of toxicity were determined after 7 and 14 days. The wet weight of the worms (after washing) was measured at the start (individually) and end (all together from each test vessel) of the test.

VEHICLE CONTROL PERFORMED: yes

TEST CONCENTRATIONS

- Spacing factor for test concentrations: 1.8

Nominal and measured concentrations:

Nominal concentrations: 0 (Control), 100, 178, 316, 562 and 100 mg/kg dry weight

Reference substance (positive control):

no

Duration:

14 d

Dose descriptor:

LC50

Effect conc.:

> 1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

but exposure will be to hydrolysis products

Basis for effect:

mortality

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

>= 1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

but exposure will be to hydrolysis products

Basis for effect:

mortality

Duration:

14 d

Dose descriptor:

NOEC

Effect conc.:

>= 1 000 mg/kg soil dw

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

but exposure will be to hydrolysis products

Basis for effect:

growth

Details on results:

- Mortality at end of exposure period: 0

Reported statistics and error estimates:

There were no effects on mortality and therefore an LC50 value could not be determined. The wet weights of the worms were analysed using a multiple Dunnett-test to determine whether there were any significant differences between treatments.

Table 1. Test results

 

Nominal test concentration (mg/kg dry weight)	Mean percentage mortality – Day 7	Mean percentage mortality – Day 14	Mean body weight per worm (+/-Std. Dev.) – Start of test	Mean body weight per worm (+/-Std. Dev.) – Day 14	Mean percentage decrease in body weight per worm over the test period
0 (Control)	0	0	362 (+/-15)	342 (+/-13)	-6
100	0	0	353 (+/-17)	329 (+/-12)	-7*
178	0	0	350 (+/-11)	317 (+/-10)	-9*
316	0	0	374 (+/-9)	348 (+/-5)	-7*
562	0	0	353 (+/-8)	324 (+/-11)	-8*
1000	0	0	348 (+/-12)	329 (+/-8)	-5*

*Mean decrease not significantly different to Control (p<0.05)

Validity criteria fulfilled:

yes

Conclusions:

A 14-day LC50 of >1000 mg/kg dry weight and NOEC of ≥1000 mg/kg dry weight have been determined for the effects of the test substance on mortality of Eisenia fetida. A NOEC of ≥1000 mg/kg dry weight has also been determined for effects on growth. It is likely that under the moist test conditions employed in the test that the test organisms were exposed to the hydrolysis products of the substance.

Reference 2

Endpoint:

toxicity to soil macroorganisms except arthropods: long-term

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Reason / purpose for cross-reference:

reference to other study

Reason / purpose for cross-reference:

reference to other study

Reason / purpose for cross-reference:

reference to other study

Reason / purpose for cross-reference:

reference to other study

Description of key information

14-day LC₅₀ >1000 mg/kg dry weight and NOEC ≥1000 mg/kg dry weight (nominal) (OECD 207), Eisenia fetida. The LC₅₀ and NOEC values are equivalent to >811 mg/kg dry weight and ≥811 mg/kg dry weight respectively, when expressed in terms of the silanol hydrolysis product, N-(3-(trihydroxysilyl)propyl)ethylenediamine.

Additional information

14-day LC₅₀ and NOEC values of >1000 mg/kg dry weight and ≥1000 mg/kg dry weight, respectively, (nominal) have been determined for the effects of the registration substance, N-(3 -(trimethoxysilyl)propyl)ethylenediamine (CAS 1760-24-3, EC 217-164-6), on the mortality of Eisenia fetida (RCC, 2004). The results are expressed relative to nominal concentrations of the test substance. The test was conducted according to OECD TG 207 and in compliance with GLP. In view of the test media preparation method and exposure regime, it is likely that the test organisms were exposed predominantly to the hydrolysis products of the tested substance (methanol and N-(3-(trihydroxysilyl)propyl)ethylenediamine).

The results may be expressed in terms of concentration of the silanol hydrolysis product, N-(3-(trihydroxysilyl)propyl)ethylenediamine, by applying a molecular weight correction: (MW of silanol = 180.28 / MW of parent = 222.36) * >1000 and ≥1000 = >811 mg/kg dry weight and ≥811 mg/kg dry weight.

The long-term toxicity study with terrestrial macro-organisms does not need to be conducted because:

In accordance with Column 2 of REACH Annex IX, there is no need to further investigate the effects of this substance in a long or short-term terrestrial toxicity to invertebrates/higher plants study because, as indicated in guidance R.7.11.6 (ECHA 2017), the quantitative chemical safety assessment (conducted according to Annex I of REACH) indicates that the Risk Characterisation Ratio is below 1 and therefore the risk is already adequately controlled and further testing is not justifiable.

 

The substance is highly water soluble and is not readily biodegradable but has low bioavailability and low potential for adsorption (based on log K_ow<3 (-4) and log K_oc-0.7). Low toxicity was observed in short-term aquatic tests and the occurrence of more severe toxic effects in the terrestrial compartment that were not expressed in the aquatic studies would be considered unlikely.

 

N-(3-(Trihydroxysilyl)propyl)ethylenediamine is classed as hazard category 3 for the terrestrial environment (Table R.7.11-2 of ECHA guidance R7.c, 2017) based on potential for high persistence (DT₅₀ > 180 days), lack of ready biodegradability and low toxicity to aquatic organisms (EC/LC₅₀ not <1 mg/l).

 

In this situation, a screening approach is applied: a confirmatory long-term terrestrial test is usually appropriate, in addition to the equilibrium partitioning approach with an extra factor of ten in order to determine whether further full tests are necessary.

 

In the event that terrestrial invertebrate and plant studies need to be conducted, the definitive terrestrial risk characterisation would use a PNECsoil based on the lower of the two test results with an assessment factor of 50 (unless soil microorganism data are available as well, in which case, the assessment factor would be 10).

 

A confirmatory test would be conducted with the most sensitive organism group based on short-term aquatic testing. For this substance, algae were the most sensitive organisms in the long-term tests, indicating a preference to conduct a confirmatory test with terrestrial plants.

The PNECscreen(EQPM) for N-(3-(trihydroxysilyl)propyl)ethylenediamine is derived from the long-term test results with algae and has a value of 0.00687 mg/kg dwt. For the purpose of the screening assessment comparison only, an extra factor of ten is applied (PECx10/PNECscreen(EQPM)). Based on the exposure assessment, the highest agricultural soil RCR available for the silanol hydrolysis product, N-(3-(trihydroxysilyl)propyl)ethylenediamine is 0.959, with a corresponding Predicted Environmental Concentration (PEC) of 0.00659 mg/kg dwt. The (PECx10)/PNECscreen(EQPM) for N-(3-(trihydroxysilyl)propyl)ethylenediamine is (0.00659*10)/ 0.00687 = screening RCR 9.59.

 

A confirmatory long-term terrestrial toxicity test is therefore required in accordance with the recommendations for hazard category 3 substances. If a confirmatory long-term terrestrial test were to be conducted, an assessment factor of 100 would be applied to derive PNECsoil from one long-term test. A confirmatory test with either terrestrial plants or invertebrates would result in a new value for PNECsoil. This value could only be more conservative than the value of PNECscreen(EQPM) in the situation that standard testing in terrestrial plants or invertebrates exhibited a dose response with a NOEC/EC₁₀ ≤ 0.687 mg/kg dw (and applying an assessment factor of 100). There is no basis to expect such toxicity for N-(3-(trihydroxysilyl)propyl)ethylenediamine based on the absence of significant toxicity observed in aquatic tests.

 

In the case of N-(3-(trihydroxysilyl)propyl)ethylenediamine, the registrants consider that a long-term terrestrial study is unlikely to affect the outcomes of the chemical safety assessment. As such the registrants propose that further testing (including the confirmatory study) is not necessary.

 

Additionally, no toxicity was observed in a short-term toxicity to soil macroorganisms except arthropods study for the effects of the registration substance on the mortality of Eisenia fetida (14-day LC₅₀ >810 mg/kg dry weight, expressed in terms of the concentration of the silanol hydrolysis product, N-(3-(trihydroxysilyl)propyl)ethylenediamine).

Overall, it is concluded that the risk characterisation conclusion is sufficiently conservative and therefore further testing is not considered necessary.

Details on how the PNEC and the risk characterisation ratio have been derived can be found in IUCLID Section 6.0, CSR Section 7, and Chapters 9 and 10 of the Chemical Safety Report, respectively.