Ethoxytrimethylsilane

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

key study

Justification for type of information:

Please refer to analogue justification provided in IUCLID section 13.

Reason / purpose for cross-reference:

read-across source

Reason / purpose for cross-reference:

read-across source

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 684 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: Result from SEHSC

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

44 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: Result from SEHSC

After 72 hours of exposure, growth rate percent inhibition in the 33, 70, 135, 257, 522 and 1053 mg/L treatment groups was 0.94, 1.2, 9.5, 14, 11 and 45%, respectively, relative to the negative control. Treatment related effects were apparent in the four highest test concentrations. Dunnett’s test indicated that growth rate was significantly reduced (p<0.05) in the 135, 257, 522 and 1053 mg/L

treatment groups. Consequently, the 72-hour NOAEC for growth rate was 70 mg/L. After 96 hours of exposure, inhibition of growth rate in the 33, 70, 135, 257, 522 and 1053 mg/L mg/L treatment groups was 0.12, -0.11, -0.30, 3.3, 4.6 and 34%, respectively, relative to the negative control. Treatment related effects were apparent in the highest test concentration. Dunnett’s test indicated that growth rate was significantly reduced (p<0.05) in the 257, 522 and 1053 mg/L treatment groups. However, the 3.3 and 4.6% inhibition from the control in the 257 and 522 mg/L treatment group, respectively, was not considered to be treatment related since this amount of inhibition was considered to be within an acceptable limit for Selenastrum. Consequently, the 96-hour NOAEC for growth rate was 522 mg/L. After 96 hours of exposure, there were no signs of adherence of cells to the test chambers or aggregation/flocculation of algae in the controls or in any treatment group. There were no noticeable changes in cell morphology in any of the tested concentrations when compared to the control.

Growth Rate By Replicate Over the 96-Hour Exposure Period
Day 0 Measured Test Concentration (mg/L)	Replicate	Growth Rate
		0 - 24 Hours	0 - 48 Hours 0 – 72 Hours		0 - 96 Hours
Negative Control             33       70       135       257       522       1053	A B C D E F   A B C   A B C   A B C   A B C   A B C   A B C	0.0854 0.0818 0.0845 0.0837 0.0786 0.0782   0.0827 0.0858 0.0834   0.0810 0.0800 0.0774   0.0770 0.0804 0.0795   0.0766 0.0756 0.0711   0.0647 0.0656 0.0723   0.0363 0.0324 0.0305	0.0786 0.0751 0.0771 0.0777 0.0755 0.0757   0.0762 0.0781 0.0744   0.0729 0.0749 0.0734   0.0729 0.0731 0.0708   0.0679 0.0691 0.0672   0.0618 0.0608 0.0623   0.0311 0.0308 0.0310	0.0715 0.0721 0.0722 0.0721 0.0718 0.0722   0.0715 0.0720 0.0704   0.0693 0.0719 0.0721   0.0665 0.0638 0.0651   0.0637 0.0606 0.0622   0.0637 0.0618 0.0659   0.0395 0.0395 0.0396	0.0641 0.0640 0.0640 0.0639 0.0640 0.0641   0.0640 0.0638 0.0639   0.0640 0.0641 0.0641   0.0642 0.0643 0.0641   0.0619 0.0624 0.0613   0.0606 0.0611 0.0613   0.0436 0.0411 0.0415

Conclusions:

In the first key study (SEHSC) a 72-hour EC50 value of >1053 mg/L and NOEC of 70 mg/L have been determined for the effects of the test on growth rate of Selenastrum capricornutum (new name: Pseudokirchnerella subcapitata) based on initial measured concentrations of the test substance. When expressed relative to geometric mean measured concentrations the equivalent values are >684 mg/L and 44 mg/L.
A 72-hour EC50 value of >1000 mg/L has been determined in the supporting study for the effects of the test on growth rate of Scenedesmus subspicatus (new name: Desmodesmus subspicatus) based on nominal concentrations of the test substance. The current reviewer has calculated a NOEC value of 316 mg/l based on growth rate.

Reference 2

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2004-03-11 to 2004-03-15

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Qualifier:

according to guideline

Guideline:

EPA OPPTS 850.5400 (Algal Toxicity, Tiers I and II) (January 2012)

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

- Concentrations: Negative Control, 31, 63, 125, 250, 500 and 1000 mg/L

- Sampling method: Test concentrations were measured in each treatment at test initiation and at test termination.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: Direct addition of test article to freshwater algal medium

- Controls: Freshwater Algal Medium (OECD 201)

Test organisms (species):

Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)

Details on test organisms:

TEST ORGANISM

- Source (laboratory, culture collection): Original algal cultures were obtained from the University of Toronto Culture Collection, and had been maintained in culture medium at Wildlife International, Ltd., Easton, Maryland. Algal cells used in this test were obtained from Wildlife International, Ltd. cultures that had been actively growing in culture medium for at least two weeks prior to test initiation. The culture was last transferred to fresh medium three days prior to test initiation.

- Culture medium: The algal cells were cultured and tested in freshwater algal medium. Stock nutrient solutions were prepared by adding reagent-grade chemicals to purified Wildlife International, Ltd. well water. The test medium then was prepared by adding appropriate volumes of the stock nutrient solutions to purified well water (NANOpure® water). The pH of the medium was adjusted to 7.9 using 10% HCl and the medium was sterilized by filtration (0.22 μm) prior to use.

- Initial density: 10,000 cells/mL

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Post exposure observation period:

None

Test temperature:

23.6 to 24.6 ºC

pH:

7.9 at test initiation

8.3 to 9.9 at test termination

Dissolved oxygen:

Not applicable

Salinity:

Not applicable

Nominal and measured concentrations:

Nominal concentrations: Negative Control, 31, 63, 125, 250, 500 and 1000 mg/L.

Measured concentrations:
Test concentrations declined to less than 70% of nominal at test termination. Consequently, the results of the study were based on Day 0 measured concentrations.

Details on test conditions:

TEST SYSTEM

- Test vessel: 250-mL Erlenmeyer flasks plugged with cotton stoppers containing 100 mL of test solution.

- Aeration: none

- Renewal rate of test solution (frequency/flow rate): static test

- Initial cells density: 10000 cells/mL

- No. of vessels per concentration (replicates): 3

- No. of vessels per control (replicates): 6


GROWTH MEDIUM

- Standard medium used: yes


TEST MEDIUM / WATER PARAMETERS

- Source/preparation of dilution water: Freshwater algal growth medium (OECD 201) with NANOpure water (pH: 7.9)

- Culture medium different from test medium: no

- Intervals of water quality measurement: Start and end of test


OTHER TEST CONDITIONS

- Sterile test conditions: yes

- Adjustment of pH: no

- Photoperiod: Continuous

- Light intensity and quality: 3900 to 4700 lux, continuous cool-white fluorescent lighting


EFFECT PARAMETERS MEASURED: Cell densities measured at start of test and then at 24 hour intervals. Cell densities were used to determine effects on average-specific growth rate and biomass.


TEST CONCENTRATIONS

- Spacing factor for test concentrations: 2

Reference substance (positive control):

no

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

70 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

cell number

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

555 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

cell number

Remarks on result:

other: 141-612

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

135 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

cell number

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

683 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

cell number

Remarks on result:

other: 641-727

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

70 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

566 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks on result:

other: 409-618

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

70 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

625 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

biomass

Remarks on result:

other: 555-702

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

70 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 1 053 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: not calculable

Duration:

96 h

Dose descriptor:

NOEC

Effect conc.:

522 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

96 h

Dose descriptor:

EC50

Effect conc.:

> 1 053 mg/L

Nominal / measured:

meas. (initial)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: not calculable

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

50 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 750 mg/L

Nominal / measured:

meas. (arithm. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: not calculable

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 684 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

44 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Details on results:

Was control response satisfactory: Yes

Observations: There were no noticeable changes in cell morphology in any of the tested concentrations in comparison to the control.

Reported statistics and error estimates:

Statistical methods: Non-linear regression, linear interpolation and Dunnett's test

Table 1. Test results (cell densities in cells/mL)

Day 0 Measured  Concentration (mg/L)
          0 33     70     135    257    522    1053
0-Hour  10000  10000 10000 10000  10000  10000  10000
24-Hour  72000 75000 67000 67000 60000 51000 22000
48-Hour  396000 389000   345000 322000  263000  193000  44000
72-Hour  1780000 1700000 1680000 1090000 882000  995000  172000
96-Hour  4660000 4620000 4690000 4740000 3810000 3500000 570000

Table 2. Percent biomass/growth rate inhibition per concentration

         Day 0 Measured Concentration (mg/L)
                 33    70    135   257   522   1053
72-Hour Cell Density  4.6   5.8   39    51    44    90
96-Hour Cell Density  0.74 -0.70 -1.8   18    25    88
72-Hour Biomass       3.4   8.0   32    45    46    90
96-Hour Biomass       2.3   3.1   16    32    35    89
72-Hour Growth Rate   0.94  1.2   9.5   14    11    45
96-Hour Growth Rate   0.12 -0.11 -0.30  3.3   4.6   34

Validity criteria fulfilled:

yes

Conclusions:

A 72-hour EC50 value of >1053 mg/L and NOEC of 70 mg/L have been determined for the effects of the test on growth rate of Selenastrum capricornutum (new name: Pseudokirchnerella subcapitata) based on initial measured concentrations of the test substance. When expressed relative to geometric mean measured concentrations the equivalent values are >684 mg/L and 44 mg/L.

Reference 3

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Remarks:

The study was conducted according to method comparable to an appropriate standard method, in compliance with GLP, however no analytical monitoring was conducted.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

not applicable

Qualifier:

according to guideline

Guideline:

other: DIN 38 412 Teil 9

Deviations:

not applicable

Remarks:

guideline not available to reviewer

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

no

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM
- Strain: CHODAT
- Source (laboratory, culture collection): Pflanzenphysiologisches Institut der Universität, 3400 Göttingen
- Age of inoculum (at test initiation): not reported
- Method of cultivation: not reported

ACCLIMATION: not reported

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Hardness:

not reported

Test temperature:

not reported

pH:

control: 8.3 initial, 10.3 final
treated vessels: 8.2 initial, to 10.4 final

Dissolved oxygen:

not reported

Nominal and measured concentrations:

Nominal concentrations: 10, 31.6, 100, 316 and 1000 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 300 ml Erlenmeyer flask
- Material, size, headspace, fill volume: filled with 100 ml test medium
- Initial cells density: 10 000 cells/ml
- Control end cells density: 495000 cells/ml
- No. of vessels per concentration (replicates):1
- No. of vessels per control (replicates): 1


GROWTH MEDIUM
- Standard medium used: not reported

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: deionised water, additionally processed with Millipore anlage.
- Culture medium different from test medium: not known
- Intervals of water quality measurement: pH measured at start and end of test

OTHER TEST CONDITIONS: not reported


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: daily with Microcellcounter Sysmex F-300


TEST CONCENTRATIONS
- Spacing factor for test concentrations: 3
- Range finding study: not reported

Reference substance (positive control):

no

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

90 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

806 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

316 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Table 1. Summary of cell concentrations observed during the study

	Cells/ml
Nominal concentrations (mg/l)	24 hr	48 hr	72 hr	Biomass	% difference to control	Growth rate	% difference to control
Control	55000	183000	495000	184000	0.0	1.3	0.0
10	53300	172000	505000	181000	1.6	1.3	0.0
31.6	54400	170000	412000	162000	12.0	1.2	7.7
100	54400	179000	475000	178000	3.3	1.3	0.0
316	54400	174000	497000	181000	1.6	1.3	0.0
1000	30000	51100	97700	42000	77.2	0.8	38.5

The NOEC for growth rate has not been calculated in the report, however based on the data in Table 1 above, the current reviewer has calculated a growth rate NOEC of 316 mg/l .

Validity criteria fulfilled:

yes

Remarks:

however the pH fluctuated by more than 1.5 units

Conclusions:

A 72-hour EC50 value of >1000 mg/L has been determined for the effects of the test on growth rate of Scenedesmus subspicatus (new name: Desmodesmus subspicatus) based on nominal concentrations of the test substance. The current reviewer has calculated a NOEC value of 316 mg/l based on growth rate.

Description of key information

EC50 (72 h) > 684 mg/L (measured (geometric mean), OECD 201)
NOEC (72 h) 44 mg/L (measured (geometric mean), OECD 201)

Key value for chemical safety assessment

EC50 for freshwater algae:

684 mg/L

EC10 or NOEC for freshwater algae:

44 mg/L

Additional information

There are no data available on toxicity to algae for ethoxytrimethylsilane (CAS 1825-62-3). In accordance with Regulation (EC) No 1907/2006 Annex XI, 1.5 “Grouping of substances and read-across” and in accordance with the read across assessment framework (RAAF, ECHA 2017) a read-across from the hydrolysis product trimethylsilanol (CAS 1066-40-6) has been applied to support the environmental hazard assessment of ethoxytrimethylsilane. Details on the read across justification can be found in the attached justification in the respective target entry and in the overall justification for grouping of substances attached in IUCLID Section 13.

The study with the analogue substance trimethylsilanol (CAS 1066-40-6) was performed according to OECD 201 (GLP) (Wildlife International, Ltd. 2004). Pseudokirchneriella subcapitata was exposed to the substance up to a concentration of 1000 mg/L under static conditions. The test concentrations did not remain stable for the duration of the study. At the beginning of the study 103 - 111% of nominal was measured whereas the concentrations dropped to 28 - 44% of nominal. Thus, the effect concentrations were based on the geometric mean of measured concentrations. Inhibition of growth was recorded resulting in an ErC50 (72 h) of > 684 mg/L and a NOErC (72 h) of 44 mg/L.
The supporting study was performed without analytical measurement of test concentrations. Nevertheless, the study was conducted according to OECD 201 (GLP). Desmodesmus subspicatus was exposed to nominal concentrations of 10, 31.6, 100, 316 and 1000 mg/L. Based on growth rate an EC50 (72 h) > 1000 mg/L and a NOEC of 316 mg/L were derived.