N,N',N''-tributyl-1-methylsilanetriamine

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Study period:

28 April 2016 to 30 June 2016

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

No analysis of test substance concentrations was carried out

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Deviations:

yes

Remarks:

No analysis of test substance concentrations was carried out

GLP compliance:

yes

Specific details on test material used for the study:

See test material information

Analytical monitoring:

no

Vehicle:

yes

Remarks:

Tetrahydrofuran (THF)

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method:
Pre-testing
The study started with the determination of the test item solubility in tetrahydrofuran. Thereafter, the solubility of test item stock solutions in test medium was determined. Based on the results of this test, the test concentrations for the full acute toxicity test in Daphnia magna were determined.
The test item undergoes rapid hydrolysis in contact with water. The onset of condensation of the silanetriol product limited the highest soluble test concentration (“technical feasible maximum test concentration”) and was therefore experimentally determined. In this pre-test, tetrahydrofuran THF was used as a solubilising agent to avoid concentration peaks during sample preparation and allow observing the onset of condensation of the silanetriol by visual inspection of the test medium. The determined solubility limit in test medium was applied to justify the selected dose range in the full test.

Determination of solubility in tetrahydrofuran
A concentration of 1000 mg test item per 1 mL THF was prepared. No special treatment other than vigorous shaking was required to fully dissolve the test item in THF. The resulting solution was clear and yellow.

Determination of solubility in test medium
To determine the solubility of a test item stock solution in test medium, two experiments were performed. Preparation of stock solutions started with a concentration of 100 mg/mL. No special treatment other than vigorous shaking was required to fully dissolve the test item in THF. Lower concentrations (i.e. 1.56, 3.13, 6.3, 12.5, 25 and 50 mg/mL) were obtained by subsequent dilutions of the highest concentration in THF with a factor of 2. All stock solutions were clear and colourless.
After preparation, volumes of 100 µL were spiked into 1 L of test medium to achieve the test concentrations. Spiking was done slowly by adding the respective stock solution in steps of 20 µL below the test medium surface over a period of six minutes. Throughout, the test medium was magnetically stirred without turbulence at approximately 200 rpm. The pH values of these solutions were in a range of 7.6 to 8.3 and correspondingly adjusted to 7.0 ± 0.2 using 1 M HCl. Thereafter, a 24-hour period of magnetic stirring at 200 rpm was applied. Solutions spiked with stocks of 6.3 mg/mL and lower were clear and colourless at the end of the preparation period. Solutions spiked with stocks of 12.5 mg/mL and higher were colourless but contained undissolved material. The dissolution of the test item was determined visually using a laser pointer.
Consequently, the concentration at which the condensation products were visually completely soluble in ISO medium was considered to be the limit concentration (i.e. 0.63 mg/L).

Preparation of stock and test solutions for the full test
The batch of N,N’,N’’-Tributyl-1-methylsilanetriamine tested was a clear slightly yellow liquid with a purity of 86%. No correction was made for the purity/composition of the test item.
The highest concentration of the selected range was intended to slightly exceed the determined solubility limit to avoid a potential gap between the highest test concentration and the possible maximum test concentration.
Therefore, a stock solution of 15 mg test item per mL THF was prepared. No special treatment other than vigorous shaking was required to fully dissolve the test item in THF. Lower concentrations (i.e. 0.94, 1.9, 3.8, and 7.5 mg/mL) were obtained by subsequent dilutions of the highest stock in THF. All resulting stock solutions were clear and colourless.
Thereafter, test solutions were prepared individually by spiking volumes of 100 µL stock solution into 1 L of test medium. Spiking was done slowly by adding the respective stock solution in steps of 20 µL below the test medium surface over a period of six minutes. Throughout, the test medium was magnetically stirred without turbulence at 200 rpm. The pH values of the resulting solutions as well as the solvent and the blank controls were in a range of 8.1 to 8.2 and subsequently adjusted to 7.0 ± 0.1 using 1 M HCl. Afterwards, the obtained solutions were magnetically stirred for 24 hours at 200 rpm. All final test solutions were clear and colourless, besides the highest concentration that contained some undissolved particles floating on the surface. Care was taken not to transfer these particles to test vessels.

- Controls: Vehicle and dilution water control without test item.
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): Tetrahydrofuran (THF).
- Concentration of vehicle in test medium (stock solution and final test solution(s) or suspension(s) including control(s)): 15 mg test item per mL THF stock. Lower concentrations (i.e. 0.94, 1.9, 3.8, and 7.5 mg/mL) were obtained by subsequent dilutions of the highest stock in THF.
- Evidence of undissolved material (e.g. precipitate, surface film, etc.): Yes

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Daphnia magna
- Strain/clone: Straus, 1820
- Justification for species other than prescribed by test guideline: n/a
- Source: In-house laboratory culture with a known history.
- Age of parental stock (mean and range, SD): 2nd to 5th brood, older than 2 weeks.
- Feeding during test: none.
- Food type:
- Amount:
- Frequency:

ACCLIMATION
- Acclimation period: not reported.
- Acclimation conditions (same as test or not): not reported.
- Type and amount of food: not reported.
- Feeding frequency: not reported.
- Health during acclimation (any mortality observed): Daphnids originated from a healthy stock, 2nd to 5th brood, showing no signs of stress such as mortality >20%, presence of males, ephippia or discoloured animals and there was no delay in the production of the first brood.

METHOD FOR PREPARATION AND COLLECTION OF EARLY INSTARS OR OTHER LIFE STAGES: not reported.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

180 mg/L expressed as CaCO3

Test temperature:

20 - 21°C

pH:

7.2 - 7.9

Dissolved oxygen:

8.9 - 9.1

Salinity:

n/a

Conductivity:

not reported

Nominal and measured concentrations:

Nominal: 0.094, 0.19, 0.38, 0.75 and 1.5 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: glass vessel
- Type (delete if not applicable): open
- Material, size, headspace, fill volume: Glass, 100 ml, 20 ml, 80 ml.
- Aeration: No
- Type of flow-through (e.g. peristaltic or proportional diluter): n/a
- Renewal rate of test solution (frequency/flow rate): n/a
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4
- No. of vessels per vehicle control (replicates): 4
- Biomass loading rate: not reported

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Adjusted ISO medium
Composition of medium M7:
Adjusted ISO medium: the following chemicals (analytical grade) are dissolved in tap water purified by Reverse Osmosis (RO-water, GEON Waterbehandeling, Berkel-Enschot, The Netherlands):
Macro salts: CaCl2.2H2O 211.5 mg/L
MgSO4.7H2O 88.8 mg/L
NaHCO3 46.7 mg/L
KCl 4.2 mg/L
Medium M7: trace elements, macronutrients and vitamins are added to freshly prepared ISO medium to reach the following concentrations:
Trace elements: B 0.125 mg/L
Fe 0.05 mg/L
Mn 0.025 mg/L
Li, Rb and Sr 0.0125 mg/L
Mo 0.0063 mg/L
Br 0.0025 mg/L
Cu 0.0016 mg/L
Zn 0.0063 mg/L
Co and I 0.0025 mg/L
Se 0.0010 mg/L
V 0.0003 mg/L
Na2EDTA.2H2O 2.5 mg/L
Macro nutrients: Na2SiO3.9H2O 10.0 mg/L
NaNO3 0.27 mg/L
KH2PO4 0.14 mg/L
K2HPO4 0.18 mg/L
Vitamins: Thiamine 75.0 µg/L
B12 1.0 µg/L
Biotin 0.75 µg/L
The hardness: 180 mg/L expressed as CaCO3 and the pH: 7.7 ± 0.3.

- Salinity: n/a
- Culture medium different from test medium: not reported.
- Intervals of water quality measurement:
Dissolved oxygen and pH: At the beginning and at the end of the test, for all concentrations and the controls.
Temperature of medium: Continuously in a temperature control vessel, beginning at the start of the test.


OTHER TEST CONDITIONS
- Adjustment of pH: Yes
- Photoperiod: 16 hours photoperiod daily
- Light intensity: not reported

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : Immobility (including mortality) at 24 hours and at 48 hours.

VEHICLE CONTROL PERFORMED: yes

RANGE-FINDING STUDY
- Test concentrations: Final test concentrations were based on the solubility of the test substance in the solvent and dilution water.
- Results used to determine the conditions for the definitive study: Maximum achievable solubility of test substance.

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 1.5 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

exposure will have been to the hydrolysis products of the test substance

Basis for effect:

mobility

Remarks on result:

other: the nominal concentration of 1.5 mg/L tested was considered higher than the maximum soluble concentration in test medium

Details on results:

- Behavioural abnormalities: none reported
- Observations on body length and weight: none reported
- Other biological observations: none reported
- Mortality of control: No
- Other adverse effects control: No
- Abnormal responses: none reported
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: none reported
- Effect concentrations exceeding solubility of substance in test medium: Yes

Results with reference substance (positive control):

- Results with reference substance valid?
- Relevant effect levels: 0.3 to 1.0 mg/L
- Limit test: No
- Dose-response test: Yes
- EC50: 0.29 mg/l
- Other:

Table: Number of introduced daphnids and incidence of immobility in the full test

		N,N’,N’’-Tributyl-1-methylsilanetriamine, nominal conc. (mg/L) Nominal concentration (mg/L)
Time	Replicate	Blank control	Solvent control	0.094	0.19	0.38	0.75	1.5
0	A	5	5	5	5	5	5	5
0	B	5	5	5	5	5	5	5
0	C	5	5	5	5	5	5	5
0	D	5	5	5	5	5	5	5
	Total Introduced	20	20	20	20	20	20	20
24	A	0	0	0	0	0	0	0
24	B	0	0	0	0	0	0	0
24	C	0	0	0	0	0	0	0
24	D	0	0	0	0	0	0	0
	Total Immobilised	0	0	0	0	0	0	0
	Effect %	0	0	0	0	0	0	0
48	A	0	0	0	0	0	0	0
48	B	0	0	0	0	0	1	0
48	C	0	0	0	0	0	1	0
48	D	0	0	0	0	0	0	0
	Total Immobilised	0	0	0	0	0	2	0
	Effect %	0	0	0	0	0	10	0

Validity criteria fulfilled:

yes

Conclusions:

A 48 hour EC50 value of >1.5 mg/l (nominal) (highest concentration tested) has been determined for effects of the test substance on mobility of Daphnia magna. No effects were observed in the test. In view of the rapid hydrolysis rate of the test substance and the test preparation methods, it is likely that the Daphnia were exposed to the hydrolysis products of the test substance.

Description of key information

48 hour EC₅₀: >1.5 mg/l (nominal) (highest concentration tested) has been determined for effects of the test substance on mobility of Daphnia magna, in compliance with OECD guideline 202.

Additional information

A 48 hour EC₅₀ value of >1.5 mg/l (nominal) (highest concentration tested) has been determined for effects of the test substance on mobility of Daphnia magna. No effects were observed in the test. In view of the rapid hydrolysis rate of the test substance and the test preparation methods, it is likely that the Daphnia were exposed to the hydrolysis products of the test substance. It should be noted that the nominal concentration of 1.5 mg/l tested was considered higher than the maximum soluble concentration in test medium, therefore there is no gap between maximum soluble concentration and the highest test concentration.