Trimethoxyoctadecylsilane

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:

experimental study

Adequacy of study:

key study

Study period:

1991-06-03 to 1991-06-07

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

Study followed a protocol based on the OECD 201 (1984) guideline. It should be noted, that only two parallels were investigated for both control and test series. Thus no thorough statistical assessment of effect values is possible. The study duration was 96 hours which is not in accordance with OECD standards. Thus a recalculation of effect values for 72 h has been performed in order to meet CLP and OECD standards.

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Version / remarks:

1984

Deviations:

yes

Remarks:

Methanol and tertiary butanol (TBA) were used as solvents to aid test substance dispersion, test duration was 96 hours, only two parallels for both control and test series, respectively.

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

yes

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: Two stock solutions (nominally 300 g/L) were prepared in methanol and tertiary butanol (TBA). The stock solutions were added to the algal culture medium to produce the desired test concentrations.
- Evidence of undissolved material (e.g. precipitate, surface film, etc): It is likely that all exposure concentrations exceeded the solubility of the test substance in the test medium.
- Controls: Algal culture medium

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM
- Strain: SAG 86.81
- Source: Culture supplied by the Collection of Algal Cultures, Institute of Plant Physiology, University of Göttingen, Germany.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Hardness:

no data

Test temperature:

23+/-1ºC

pH:

Medium prepared using methanol stock solution: 8.3-8.9 over 3 days, 8.8-10.5 over 4 days.
Medium prepared using TBA stock solution: 8.4-8.7 over 3 days, 8.4-9.9 over 4 days.

Dissolved oxygen:

no data

Salinity:

not applicable

Nominal and measured concentrations:

Nominal concentrations in media prepared with methanol stock solution: 0(Control), 0.01, 0.032, 0.10, 0.32, 1.0, 3.2, 10.2 and 31.8 mg/L.
Nominal concentrations in media prepared with TBA stock solution: 0(Control), 0.009, 0.029, 0.094, 0.29, 0.94, 2.9, 9.4 and 29.5 mg/L.
It is likely that all exposure concentrations exceeded the solubility of the test substance in the test medium.

Details on test conditions:

TEST SYSTEM
- Test vessel: Conical flasks
- Type: closed with sponge cap
- Material, size, fill volume: glass, 200 mL containing 100 mL of test medium
- Aeration: no
- Initial cells density: 12000 cells/mL (methanol), 10000 cells/mL (TBA)
- Control end cells density: 2200000 cells/mL (methanol), 3000000 cells/mL (TBA)
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates): 2

GROWTH MEDIUM
- Standard medium used: yes except that the medium contained 150 mg/l of NaHCO3 instead of the 50 mg/l specified in the OECD guideline.

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Milli-Q filtered water
- 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: 60-120 μm/s/m2

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): cell density at 0, 24, 48, 72 and 96 hours (approx)
- Determination of cell concentrations: Coulter Counter Model TAII

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 3.2 approx

Reference substance (positive control):

no

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 31.8 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: solvent: methanol

Remarks:

values calculated in retrospect from original cell numbers

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 29.5 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: solvent: TBA

Remarks:

values calculated in retrospect from original cell numbers

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

>= 31.8 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: solvent: methanol

Remarks:

values calculated in retrospect from original cell numbers

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

20.91 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: solvent: TBA

Remarks:

values calculated in retrospect from original cell numbers

Details on results:

- Exponential growth in the control (for algal test): yes
- Any stimulation of growth found in any treatment: some evidence of stimulation at concentrations >/=0.3 mg/L but it is not certain if it is significant.
- Effect concentrations exceeding solubility of substance in test medium: It is likely that all exposure concentrations exceeded the water solubility of the test substance (0.0029 mg/L).

Reported statistics and error estimates:

The area under the growth curve (biomass) and growth rate parameters were calculated from the cell concentration data in accordance with the description of the test method.

Table 1. Cell concentrations [cells/mL] when methanol was used as a solvent

Conc. [mg/L]		10^4 cells/mL corrected for background
	Replicates	0 d	1 d	2 d	3 d	4 d
Control	1	1.5	2.0	11.9	79.2	231.2
	2	1	1.9	11.0	74.1	233.5
Solv. Control	1	1.2	2.1	10.5	76.7	205.9
	2	1	1.9	11.5	76.4	232.6
0.01	1	1.6	2.2	10.9	81.2	240.2
	2	1	2.0	12.7	81.2	233.5
0.032	1	1.4	2.1	11.1	76.8	244.1
	2	1	2.0	11.4	87.5	224.0
0.1	1	0.9	1.9	11.1	73.8	222.3
	2	0.8	2.2	12.3	95.4	286.6
0.32	1	1.1	1.9	11.5	77.1	218.3
	2	0.9	2.1	10.3	86.1	233.2
1	1	0.8	1.8	10.3	67.4	214.4
	2	0.9	2.1	9.4	69.1	219.9
3.2	1	0.9	2.3	9.8	57.8	199.4
	2	0.9	2.2	9.1	56.6	168.7
10.2	1	0.8	1.7	7.8	46.8	155.8
	2	1.1	1.7	9.1	44.5	131.8
31.8	1	0.8	9.1	6.4	45.3	170.1
	2	0.9	-0.9	2.3	49.5	173.5

 red value: was excluded from the calculation due to negative cell number

 

Table 2.Cell concentrations [cells/mL] when TBA was used as a solvent

Conc. [mg/L]		10^4 cells/mL corrected for background
	Replicates	0 d	1 d	2 d	3 d	4 d
Control	1	1	3.1	14.5	109.1	297.3
	2	1	3.1	13.2	97.5	291.6
Solv. control	1	1.1	3.1	14.4	108.5	319.4
	2	1	2.7	14.1	91.2	308.6
0.009	1	1	3.2	13.3	102.3	305.5
	2	1	2.6	14.9	103.1	277.1
0.029	1	1	3.1	12.6	101.2	317.8
	2	1	3.3	16.8	105.2	324.6
0.094	1	0.8	2.9	14.7	105.5	294.5
	2	0.9	3.3	16.3	115.1	316.1
0.29	1	1	2.7	15.2	104.7	259.7
	2	1	3.3	15.1	115.4	287.2
0.94	1	1	2.5	13.9	79.9	262.3
	2	1	3.1	14.4	107.9	329.6
2.9	1	1	2.8	12.9	83.8	287.1
	2	1	2.6	10.3	68.9	262.0
9.4	1	0.9	3.3	10.0	70.2	211.9
	2	0.9	3.2	10.1	60.5	192.5
29.5	1	1.1	2.6	8.7	62.1	176.3
	2	1.2	6.4	9.6	57.9	167.2

 

96 h -EC10 values mentioned in the report were 11 mg/L when TBA was used as a solvent and 7 mg/L when methanol was used as a solvent. No effects causing 50% inhibition of the growth rate were observed.

Re-evaluation of data:

The 72 -h effect concentrations were calculated in retrospect according to the current OECD 201 (2011) guideline and the original cell numbers given in the report.

No differences were observed between the control and the solvent control. However since only dublicates were used, no statistical analysis could be performed. The solvent control was used as a worst case for the calculation of the growth rate inhibition rates.

1) Results on growth rate inhibition when methanol was used as a solvent:

Table 3: % Inhibition of growth rate at 72 h when methanol was used as a solvent, as calculated in retrospect according to the current OECD 201 standards using the orginal cell densities from the study report.

Nominal concentrations [mg/L]	% Growth Rate Inhibiton at 72 h
0.01	1.94
0.032	0.18
0.1	-8.23
0.32	-3.78
1	-3.36
3.2	2.23
10.2	8.51
31.8	5.26

No growth rate inhibition up to 10% was observed after 72 h when methanol was used as a solvent resulting in an ErC10 (72 h) >= 31.8 mg/L.

2) Results on growth rate inhibition when TBA was used as a solvent:

Table 4: % Inhibition of growth rate at 72 h when TBA was used as a solvent, as calculated in retrospect according to the current OECD 201 standards using the orginal cell densities from the study report.

Nominal Concentrations [mg/L]	% Grwoth Rate Inhibiton at 72 h
0.009	-1.75
0.029	-1.88
0.094	-6.89
0.29	-3.26
0.94	0.49
2.9	4.84
9.4	5.9
29.5	13.08

The EC10 value was calculated based on the dose-response curve. The ErC10 (72 h) was 20.914 mg/L (nominal) when TBA was used as a solvent.

No growth rate inhibition up to 50% was observed after 72 h of exposure when TBA was used as a solvent resulting in an ErC50 (72 h) > 29.5 mg/L (nominal).

Validity criteria fulfilled:

yes

Remarks:

The validity criteria outlined in the OECD guideline 201 version of 1984 are fulfilled

Conclusions:

The study resulted in an ErC50 (72 h) and ErC10 (72 h) of > 30.8 mg/L when methanol was used as a solvent. The ErC50 (72 h) and ErC10 (72 h) when TBA was used as a solvent were > 29.5 mg/L and 20.91 mg/L (nominal), respectively. These results are based on calculations made in retrospect, based on the original cell numbers given in the study report. The study reported 96 h EC50 values of >30 mg/L and 96 h EC10 values of 7-11 mg/L (both nominal) independent of whether the test medium was prepared using methanol or tertiary butanol (TBA).

Reference 2

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

1989-07-14 to 1989-11-03

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Remarks:

Study followed a protocol based on the OECD 201 (1984) guideline. It should be noted, that only two parallels were investigated for both control and test series. Thus no thorough statistical assessment of effect values is possible. The study duration was 96 hours which is not in accordance with OECD standards. Thus a recalculation of effect values for 72 h has been performed in order to meet CLP and OECD standards.

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Version / remarks:

1984

Deviations:

yes

Remarks:

Tertiary butanol (TBA) was used as solvent to aid test substance dispersion, test duration was 96 hours, only two parallels for both control and test series, respectively.

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

yes

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: Stock solutions (nominally 100 g/L) were prepared in tertiary butanol (TBA). From these stock solutions appropriate dilutions were prepared in solvent to contain 10000 times the final concentrations in the test, so that addition of 10 μL to 100 mL of medium yielded the required test concentrations.
- Evidence of undissolved material (e.g. precipitate, surface film, etc): It is likely that all exposure concentrations exceeded the solubility of the test substance in the test medium.
- Controls: Algal culture medium

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM
- Strain: SAG 86.81
- Source: Culture supplied by the Collection of Algal Cultures, Institute of Plant Physiology, University of Göttingen, Germany.
- Preculture: A preculture of algae in the exponential growth phase was prepared as described in the test guideline using culture medium described in Dutch Standard NPR 6505.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Hardness:

no data

Test temperature:

23+/-1ºC

pH:

Start of test: 8.0-8.4
After 3 days: 9.9-8.7
After 4 days: 9.5-10.5
The high values are associated with good growth of the algae

Dissolved oxygen:

no data

Salinity:

not applicable

Nominal and measured concentrations:

Nominal concentrations in media - first test: 0(Control), 0 (solvent control), 0.003, 0.010, 0.032, 0.056, 0.10, 0.32 and 1.0 mg/L.
Nominal concentrations in media - second test: 0 (Control), 0 (solvent control), 0.0032, 0.010, 0.032, 0.10, 0.32, 1.0, 3.2 and 10 mg/L.
The result of the second test were used as the basis for determining the EL50 and NOELR values.
It is likely that all exposure concentrations exceeded the solubility of the test substance in the test medium.

Details on test conditions:

TEST SYSTEM
- Test vessel: Conical flasks
- Type: closed with sponge cap
- Material, size, fill volume: glass, 200 mL containing 100 mL of test medium
- Aeration: no
- Initial cells density: 35000 cells/mL (first test), 10500 cells/mL (second test)
- Control end cells density: 3700000 cells/mL (first test), 2900000 cells/mL (second test)
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates): 2

GROWTH MEDIUM
- Standard medium used: yes except that the medium contained 150 mg/l of NaHCO3 instead of the 50 mg/l specified in the OECD guideline.

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Milli-Q filtered water
- 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: 80-110 μm/s/m2


EFFECT PARAMETERS MEASURED (with observation intervals if applicable): cell density at 0, 24, 48, 72 and 96 hours (approx)
- Determination of cell concentrations: Coulter Counter Model TAII


TEST CONCENTRATIONS
- Spacing factor for test concentrations: 3.2 approx

Reference substance (positive control):

no

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: second test, solvent: TBA

Remarks:

values calculated in retrospect from original cell numbers

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

3.4 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: second test, solvent: TBA

Remarks:

values calculated in retrospect from original cell numbers

Details on results:

- Exponential growth in the control (for algal test): yes
- Effect concentrations exceeding solubility of substance in test medium: It is likely that all exposure concentrations exceeded the water solubility of the test substance (0.0029 mg/L).

Reported statistics and error estimates:

The area under the growth curve (biomass) and growth rate parameters were calculated from the cell concentration data in accordance with the description of the test method.

ECx values were calculated in accordance with the methods described in the OECD test guideline. The NOEC values were determined by visual comparison of the growth curves for the treated cultures and the Control cultures.

Table 1.Cell concentrations [cells/mL] (TBA was used as a solvent)

Conc [mg/L]		10^4 cells/mL corrected for background
	Replicates	0 d	1 d	2 d	3 d	4 d
Control		1.1	2.1	10.9	135.6	298.4
		1	1.8	11.3	134.5	283.4
Solv. control	1	1.1	1.6	9.5	98.5	284.9
	2	1	1.6	11.5	136.9	296.9
0.0032	1	-	2.4	14.9	184.2	311.4
	2	-	1.7	10.5	105.1	300.6
0.01	1	-	2.1	12.0	137.1	287.5
	2	-	1.5	8.5	79.9	309.2
0.032	1	-	1.8	10.0	105.8	291.7
	2	-	1.7	11.6	135.6	296.4
0.1	1	-	2.0	9.6	130.0	318.4
	2	-	1.6	10.5	193.6	283.5
0.32	1	-	2.1	9.8	123.2	311.3
	2	-	1.6	6.9	82.0	282.0
1	1	-	2.1	9.2	94.4	318.6
	2	-	1.6	7.5	78.7	327.1
3.2	1	-	2.8	8.2	80.7	294.2
	2	-	1.5	7.9	65.3	298.9
10	1	-	2.3	5.4	44.1	247.5
	2	-	5.2	6.0	37.5	234.4

A 96 h EC50 value of >10 mg/L and 96 h NOEC of 0.32 mg/L (both nominal) have been determined for both growth rate and biomass effects in the study. The EC50 value were calculated in accordance with the methods described in the OECD test guideline while the NOEC values were determined by visual comparison of the growth curves for the treated cultures and the control cultures.

Re-evaluation of data:

The 72 -h effect concentrations were calculated in retrospect according to the current OECD 201 (2011) guideline and the original cell numbers given in the report.

No differences were observed between the control and the solvent control. However since only dublicates were used, no statistical analysis could be performed. The solvent control was used as a worst case for the calculation of the growth rate inhibition rates.

Since no cell numbers at timepoint 0 were adressed for the test item vessels in the report (see table 1), the mean of the control values being 1.05 x 10^4 cells/mL was used as a starting value.

Table 2: % Inhibition of growth rate at 72 h when TBA was used as a solvent, as calculated in retrospect according to the current OECD 201 standards using the orginal cell densities from the study report.

Nominal Concentrations [mg/L]	% Inhibiton of growth rate at 72 h
0.0032	-3.82
0.01	2.23
0.032	-0.64
0.1	-6.63
0.32	3.06
1	6.31
3.2	10.01
10	22.31

The EC10 value was calculated based on the dose-response curve. The ErC10 (72 h) was 3.4 mg/L (nominal).

No growth rate inhibition up to 50% was observed after 72 h of exposure resulting in an ErC50 (72 h) > 10 mg/L (nominal).

Validity criteria fulfilled:

yes

Remarks:

The validity criteria outlined in the OECD guideline 201 version of 1984 are fulfilled

Conclusions:

The study resulted in an ErC50 (72 h) of > 10 mg/L and an ErC10 (72 h) of 3.4 mg/L (nominal). These results are based on calculations made in retrospect, based on the current OECD guideline 201 criteria and the original cell numbers given by the study report. The study reportrd a 96 h EC50 values of > 10 mg/L and a 96 h NOEC of 0.32 mg/L.The EC50 value was calculated in accordance with the OECD test guideline 201 while the NOEC value was determined by visual comparison of the growth curves for the treated cultures and the control cultures.

Reference 3

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 the attached justification below and the overall justification for grouping of substances attached 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.:

> 31.8 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: with methanol solvent

Remarks:

Source: TNO, 1992, Key

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 29.5 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: with TBA solvent

Remarks:

Source: TNO, 1992, Key

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

>= 31.8 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: with methanol as a solvent

Remarks:

Source: TNO, 1992, Key

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

20.91 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: with TBA as solvent

Remarks:

Source: TNO, 1992, Key

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: Source: TNO, 1992, Sup.

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

3.4 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: Source: TNO, 1992, Sup.

Description of key information

ErC50 (72 h) > 31.8 mg/L and ErC10 (72 h) ≥ 31.8 mg/L (nominal, methanol as solvent, OECD 201, Scenedesmus subspicatus) based on read across from CAS 16415-12-6

ErC50 (72 h) > 29.5 mg/L and ErC10 (72 h) = 20.91 mg/L (nominal, TBA as solvent, OECD 201, Scenedesmus subspicatus) based on read across from CAS 16415-12-6

Additional information

No data on the toxicity of trimethoxyoctadecylsilane (CAS 3069-42-9) towards algae are available. 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 analogue substance hexadecyltrimethoxysilane (CAS 16415-12-6) has been applied to support the environmental hazard assessment of the substance. 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 toxicity of hexadecyltrimethoxysilane (CAS 16415-12-6) was studied in two growth inhibition tests. Both studies followed a protocol based on the OECD guideline 201 (1984) and GLP standards. Scenedesmus subspicatus was used as the test organism.

It should be noted, that only two parallels were used for both control and test series. Thus no thorough statistical assessment of effect values is possible. The study duration was 96 hours, which is not in accordance with the guideline standards. Thus a recalculation of the effect values for 72 h has been performed in retrospect in order to meet CLP and OECD standards.

The key study was initiated based on remaining uncertainties of a previous study. There was an uncertainty on the storage stability of the samples tested in the first test. Furthermore, the influence of solvent was investigated more thoroughly in the second test by adding methanol as a second solvent in addition to tertiary butanol (TBA). Therefore the chronologically second study was chosen as the key and the first study was used as supporting information.

In the key study, the test item solutions were prepared with methanol and tertiary butanol as solvents. Two stock solutions (nominally 300 g/L) were initially prepared in methanol and tertiary butanol (TBA) and subsequently added to the algal culture medium to produce the desired test concentrations. Nominal concentrations of 0 (control), 0.01, 0.032, 0.10, 0.32, 1.0, 3.2, 10.2 and 31.8 mg test item/L with methanol as a solvent and 0 (control), 0.009, 0.029, 0.094, 0.29, 0.94, 2.9, 9.4 and 29.5 mg test item/L with TBA as a solvent, were tested. The study resulted in ErC50 (96 h) values of >31.8 mg/L and > 30 mg/L with methanol and TBA as solvents, respectively. Furthermore ErC10 (96 h) values of 7 mg/L and 11 mg/L when methanol or TBA was used as a solvent, respectively, were determined. The 72 h effect values were calculated in retrospect using the original cell numbers addressed in the report. When methanol was used as a solvent the 72 h ErC50 and ErC10 were both ≥ 31.8 mg/L (nominal). When TBA was the solvent, the ErC50 (72 h) was > 29.5 mg/L while the ErC10 (72 h) was calculated to be 20.91 mg/L (nominal).

In the supporting study, the test series comprised the following concentrations: 0.0032, 0.010, 0.032, 0.10, 0.32, 1.0, 3.2 and 10 mg test item/L in addition to a control and solvent control. Tertiary butanol was used as a solvent. The 72 h effect values were calculated in retrospect using the original cell numbers addressed in the report. The ErC50 (72 h) was > 10 mg/L while the ErC10 (72 h) was calculated to be 3.4 mg/L (nominal). 

As the substance hydrolyses rapidly, it is very likely that the test organisms were mainly exposed to the hydrolysis products of the substance retained in the test media. Furthermore due to the use of solvents, the tested concentration largely exceeded the water solubility of the silanol hydrolysis product.

Based on the results of the analogue substance, trimethoxyoctadecylsilane (CAS 3069-42-9) is not assumed to cause adverse effects toward algae.