3-(triethoxysilyl)propyl methacrylate

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:

2018-06-06 to 2018-06-12

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Version / remarks:

2004

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

At the start of the exposure and at renewal (0 and 24 hours), samples of the fresh media were taken after preparation of the saturated solution and analysed.

At the renewal and at the end of the exposure (24 and 48 hours), samples of the 24 hours old media were taken from the test vessels for analyses via GC-MS.

Samples for the determination of the TOC were taken from additional replicates, prepared with test media but without daphnids. These replicates were incubated under test conditions until sampling. The samples for the determination of the TOC were stored at -20±2°C directly after sampling until analysis on 2018-06-12.

Vehicle:

no

Details on test solutions:

Limit loading level:
A saturated solution with a nominal loading of 100 mg/L of the item was tested in a limit test. The loading was selected based on the results of a non-GLP preliminary range finding test.

Preparation of the saturated solution:
A saturated solution with a nominal loading of 100 mg/L of the test item was prepared with dilution water (adjusted to pH 7.6 ±0.2 by addition of 1 M HCl) prior to the start of the exposure (at day 0) as follows:
101.1 µL/L of the test item (density: 0.989 g/cm3 was taken into account) were placed by pipette under the water surface and the bottle was closed. The saturated solution was stirred with a magnetic stirrer at approximately 1100 rpm for 4 hours at room temperature. At start and end of stirring period, the pH of the solution was measured and adjusted to 7.6 ±0.2 by addition of 1 M HCl, if necessary.

The test solutions were checked via laser beam (Tyndall effect) for undissolved test item (formation of an emulsion). After completion of stirring, no Tyndall effect was detected in the saturated solutions.

Control:
Dilution water without test item, adjusted to pH 7.6 ± 0.2 by addition of 1 M HCl, incubated under the same conditions as the test group.

Test method:
The study was performed under semi-static conditions with a renewal of the test solutions after 24 hours.

Test volume: 20 mL

Dilution water:
Same composition as the culture medium, adjusted to pH 7.6 ± 0.2 by addition of 1 M HCl

Application:
20g test solution per replicate was weighed out into each test vessel. This corresponds to 20 mL per test vessel. The daphnids were inserted with a small amount of dilution water (start of exposure) or test solution (water renewal) by pipette.

Renewal of the test solutions:
The test solutions were renewed after 24 hours. For this purpose, a second set of test vessels was filled with the freshly prepared test solutions and the daphnids were transferred by pipette.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Daphnia magna STRAUS
- Strain/clone: Clone 5
- Source: obtained from continuous laboratory cultures at NOACK Laboratorien GmbH
- Culture: In glass vessels (2-3 L capacity) with approximately 1.8 L culture medium at 20±2°C in an incubator, 16 hours illumination; light intensity of maximum 1500 lx.
- Feeding during test: The daphnids were fed at least 5 times/week ad libitum with a mix of unicellular green algae, e.g. Pseudokirchneriella subcapitata and Desmodesmus subcapitata. The algae were cultured at the test facility. The daphnids were not fed during the study
- Age of parental stock (mean and range, SD): Less than 24 hours old daphnids from a healthy stock were used for the study. Juvenile daphnids were removed from the culture vessels at the latest 24 hours before the start of the exposure and discarded. The juveniles born within the following period of maximum 24 hours preceding the exposure were used for the test. No first brood progeny was used for the test.

ACCLIMATION
Acclimatisation of the daphnids was not necessary, because the composition of the diluted water was equivalent to the culture medium.

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Test temperature:

18-22°C, constant within ±1°C

pH:

7.6 ± 0.2

Nominal and measured concentrations:

Limit test at 100 mg/l nominal, saturated solution
Measured concentration at 0 hours fresh media: 91.8 mg/l
Measured concentration at 24 hours fresh media: 83.2 mg/L
Measured concentration at 24 hours old media: 67% of the initially measured concentration.
Measured concentration at 48 hours: 82% of the initially measured concentration.
The geometric mean measured concentration of the test item was calculated to be 75.3 mg/L.

Range finding test:
Nominal; 1, 10, 100 mg/l
Measured (GC-MS):
Fresh media 0 h: 0.662, 6.17, 74.7 mg/l
Old media 24 h: 0.489, 5.54, 60.7 mg/l
Fresh media 24 h: 0.703, 6.52, 65.8 mg/l
Old media 48 h: 0.506, 4.98, 51.3 mg/l

Details on test conditions:

TEST SYSTEM
- Test vessel: Glass beakers, 50 mL capacity, loosely covered with watch glasses
- Type (delete if not applicable): closed
- Material, size, headspace, fill volume: 4 (ID) x 7 (H) cm, 50 mL
- No. of organisms per vessel: 20 daphnids, divided into 4 replicates, each with 5 daphnids

OTHER TEST CONDITIONS
- Adjustment of pH: pH adjusted to 7.6 ± 0.2 by addition of 1 M HCl
- Photoperiod: 16/8 hours light/dark cycle
- Light intensity: Diffuse light, light intensity of maximum 1500 lx

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Key result

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

> 75.3 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

mobility

Duration:

24 h

Dose descriptor:

EC50

Effect conc.:

> 75.3 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

mortality

Details on results:

In the saturated solution with a nominal loading of 100 mg/L of the test item, which corresponds to the geometric mean measured concentration of 75.3 mg test item/L, no effects on Daphnia magna were observed.

Biological data

The % of immobility determined in the saturated solution and in the control after 24 and 48 hours under semi-static conditions is in the table 1. The absolute numbers of immobile daphnids are in the table 2. Other adverse effects did not appear.

Table 1: Immobilisation rates (%) after 24 and 48 hours of exposure in the definitive test (n = 20, divided into 4 replicates with 5 daphnids each)

Geometric mean measured test item concentration (mg/L)	Replicate 1, 24 h	Replicate 2, 24 h	Replicate 3, 24 h	Replicate 4, 24 h	MV, 24 h	Replicate 1, 48 h	Replicate 2, 48 h	Replicate 3, 48 h	Replicate 4, 48 h	MV, 48 h
75.3	0	0	0	0	0	0	0	0	0	0
Control	0	0	0	0	0	0	0	0	0	0

 

Table 2: Absolute numbers of immobile daphnids after 24 and 48 h of exposure in the definitive test (n = 20, divided into 4 replicates with 5 daphnids each)

Geometric mean measured test item concentration (mg/L)	Replicate 1, 24 h	Replicate 2, 24 h	Replicate 3, 24 h	Replicate 4, 24 h	sum, 24 h	Replicate 1, 48 h	Replicate 2, 48 h	Replicate 3, 48 h	Replicate 4, 48 h	sum, 24 h
75.3	0/5	0/5	0/5	0/5	0/20	0/5	0/5	0/5	0/5	0/20
Control	0/5	0/5	0/5	0/5	0/20	0/5	0/5	0/5	0/5	0/20

 

The EC10/50/100 values based on the geometric mean measured concentration of the test item are in Table 3.

Table 3: EC10, EC50, EC100 values (based on the geometric mean measured concentration of the test item)

Effect concentrations	Test duration (hours)	Toxicity endpoint based on the geometric mean measured concentration of the test item (mg/L)
EC10/50/100	24	>75.3
	48	>75.3

 

Additional observations during definitive test:

The saturated solution was visually clear throughout the exposure and showed no Tyndall effect after completion of stirring.

Measured exposure concentrations during the definitive test

The concentration of the test item was analytically verified via GC-MS in the fresh media of the saturated solution and the control at the start of the exposure and at the renewal of the test solutions (0 and 24 hours) and in the 24 hours old media at the renewal and at the end of the test (24 and 48 hours).

The measured concentrations of the test item in the fresh media at 0 and 24 hours were 91.8 mg/L and 83.2 mg/L in the saturated solution. In the old media at 24 and 48 hours, the measured concentrations were 67 and 82% of the initially measured concentration. The geometric mean measured concentration of the test item was calculated to be 75.3 mg/L. The analytical results are in the table below.

Table 4: Measured concentrations of the test item during the definitive test

Sampling date	0 hour fresh medium	24 hours old medium		24 hours fresh medium	48 hours old medium		Geometric mean measured test item concentration (mg/L)
Nominal loading of the test item (mg/L)	Test item
	Meas. conc. (mg/L)	Meas. conc. (mg/L)	%	Meas. conc. (mg/L)	Meas. conc. (mg/L)	%
100	91.8	61.4	67	83.2	68.6	82	75.3
Control	0.0204	0.0356	175	<LOQ	<LOQ		0.0269

% = Percent of the initially measured concentration of the test item

Meas. conc. = measured concentration of the test item, enrichment and dilution factors taken into account

LOQ = Limit of quantification (0.008 mg test item/L)

In the first renewal interval, test item concentrations >LOQ were found in the control samples. It remains unclear if this contamination was caused by methodological errors, contamination of the samples or errors during handling. Nonetheless, the found test item concentrations in the control were approximately 2800-fold lower (based on the geometric mean measured concentrations). Therefore, these findings are considered to have no effect on the behaviour inside the control replicates and the subsequent interpretation of data. Since biological effects were found neither in the control nor in the limit loading level, the results of the study are considered valid.

Measured TOC concentrations during definitive study

The saturated solution and the control were analytically verified via analysis of the total organic carbon (TOC, according to DIN EN 1484) in the fresh media of the saturated solution and the control at the start of the exposure and at the renewal of the test solutions (0 and 24 hours) and in the 24 hours old media at renewal and at the end of the test (24 and 48 hours). Samples of the old media were taken for analysis from additional replicates, which were prepared with test media but without daphnids and incubated under test conditions until sampling. The samples for the determination of the TOC were stored at -20±2°C directly after sampling until analysis on the 2018-06-12. The results are in the table below.

Table 5: Measured TOC concentrations during definitive study

Sampling	0 hour fresh medium	24 hours old medium	24 hours fresh medium	48 hours old medium
Nominal loading of the test item (mg/L)	Total Organic Carbon (TOC)
	Meas. conc. (mg C/L)	Meas. conc. (mg C/L)	Meas. conc. (mg C/L)	Meas. conc. (mg C/L)
100	28.5	28.1	28.2	28.2
Control	<LOQ	<LOQ	<LOQ	<LOQ

 

Meas. conc. = measured TOC concentration, mean value of 2 injections

LOQ = 2.0 mg/L

Validity criteria fulfilled:

yes

Conclusions:

A 48 h EC50 value of >75.3 mg/L, based on geometric mean measured concentrations of parent substance, was determined for the effects of the test substance on mobility of Daphnia magna, using a relevant test method and in compliance with GLP. The result is considered to be reliable.

Description of key information

Short-term toxicity to invertebrates: 48-h EC₅₀ >75.3 mg/l for the effects of the parent substance on mobility of Daphnia magna.

Additional information

A 48-hour EC₅₀ value of >75.3 mg/l has been determined for the effects of the parent test substance on mobility of Daphnia magna, based on geometric mean measured concentrations of parent substance (Noack, 2018).

Some degradation due to hydrolysis in the test media was observed. However, the semi-static regime of the test and the adjustment of pH to as close to neutral as reasonably possible, helped maintain maximum exposure to the parent test substance. The test organisms were therefore predominantly exposed to the parent substance.

To support the measured data, a 48-hour EC₅₀ value of 6.2 mg/l has been estimated for the effects of 3-(triethoxysilyl)propyl methacrylate on mobility of freshwater invertebrates (Daphnia magna). It can be seen that the EC₅₀ predicted by QSAR seems to be very conservative in comparison to the experimental data.

Reliable existing test results are available for the silanol hydrolysis product, based on studies conducted with the analogous substance 3-trimethoxysilylpropyl methacrylate (CAS 2530-85-0), and are included as supporting read-across evidence. The results may be expressed in terms of concentration of the hydrolysis product, 3-(trihydroxysilyl)propyl methacrylate, by applying a molecular weight correction: (MW of silanol=206.27 / MW of parent=248.35) * [Conc. of parent] = [conc. of silanol]. Using this method, the results are as follows: Daphnia: EC₅₀ (48 h): >83 mg/ l and >727 mg/l; NOEC: ≥83 mg/l and ≥727 mg/l (results re-calculated with molecular weight adjustment and expressed as concentration of 3-(trihydroxysilyl)propyl methacrylate).