Chlorodimethyloctylsilane

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

19 - 21 Dec 2018

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)

Version / remarks:

2011

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Staatliches Gewerbeaufsichtsamt Hildesheim, Germany

Analytical monitoring:

yes

Remarks:

GC-MS, TOC measurement

Details on sampling:

- Concentrations: 0 (control), 0.100, 0.316, 1.00, 3.16, 10.0, 31.6, 100 mg/L
- Sampling method: Samples were anlytically verified at the start (0 hours) and at the end of the exposure (72 hours) with algae.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: Seven test item solutions were prepared separately with nominal loadings of the test item in the range of 0.1 to 100 mg/L. For each loading level an appropriate amount of the test item was pipetted onto the surface of an appropriate amount of demineralized water buffered with NaHCO3 and pH-adjusted to pH 7.0 ± 0.2. For this purpose, the density was taken into account. For the loading levels 0.100 and 0.316 mg/L it was technically not feasible to pipette the necessary amount of the test item, the respective loadings were prepared by dilution of the loading level 1.00 mg/L. The solutions were stirred for 24 hours (1100 rpm) at room temperature. After a separation phase of 1 hour the solutions were removed by siphoning from the approximate center of the flask. The solutions were checked via laser beam (Tyndall effect) for undissolved test item. No Tyndall effect was observed. Afterwards, the remaining components of the dilution water were added to the solutions.

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
- Common name: green algae
- Source: Originally from Culture Collection of Algae and Protozoa (CCAP) SAMS Research Services Ltd Scotland, UK. Fresh stocks are prepared every month on Z-Agar (according to LÜTTGE et al. (1994)) in the laboratory. Light intensity was 2567 – 5130 lux for 24 h per day.
- Age of inoculum: A four days old preculture, prepared in dilution water, was used as inoculum.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Hardness:

38 mg CaCO3/L

Test temperature:

23.0-24.0°C

pH:

7.53-7.63 (0 hours)
8.01-9.18 (72 hours)
7.93-9-24 (Controls)

Conductivity:

141 µS/cm

Nominal and measured concentrations:

Nominal loading concentrations: 0 (control), 0.100, 0.316, 1.00, 3.16, 10.0, 31.6 and 100 mg/L
Measured (GC-MS):
0 hours: < LOQ (control), 0.0163, 0.0554, 0.157, 0.343, 1.59, 1.43, 2.55 mg/L
72 hours: < LOQ (control), < LOQ, < LOQ, 0.0122, 0.0333, 0.435, 0.132, 0.269 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 250 mL Erlenmeyer flasks
- Type: sealed with cotton wool plugs
- Fill volume: 100 mL
- Initial cells density: 6442 cells/mL
- Control end cells density: 1212628 cells/mL (mean)
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6

GROWTH MEDIUM
- Medium used: Nutrient medium Z according to Lüttge et al. (1994)

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: OECD TG 201 medium according to guideline
- Intervals of water quality measurement: The pH-values at the start of exposure were measured in one additional replicate of each test item concentration and the control. At the end of exposure, the pH-values were measured from pooled samples of each test item concentration and the control. The room temperature was measured continuously. Light intensity was measured prior to the start of exposure.

OTHER TEST CONDITIONS
- Adjustment of pH: yes, adjusted to pH 7 ± 0.2
- Photoperiod: 24 h/day light
- Light intensity and quality: 4440 to 8880 lux

EFFECT PARAMETERS MEASURED:
- Determination of cell concentrations: The cell density was measured daily via Chlorophyll a-fluorescence, exitation at 436 nm, emmission at 658 nm. Dilution water was used as background signal. No self-fluorescence was found in the preliminary range-finding test at 100 mg/L.
- Other: Microscopic evaluation of the cells at the start and the end of the incubation period was carried out. The cells were checked for unusual cell shapes, colour differences, differences in chloroplast morphology, flocculation, adherence of algae to test containers and agglutination of algae cells.

TEST CONCENTRATIONS
- Range finding study: yes
- Test concentrations: 1, 10, 100 mg/L
- Results used to determine the conditions for the definitive study: yes, 5% growth rate inhibition was found at the concentration of 10 mg/L and 66% inhibition at 100 mg/L.

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

89.9 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 95%-CI: 45.9 - > 100 mg/L

Duration:

72 h

Dose descriptor:

EL10

Effect conc.:

26.1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 95%-CI: 6.20 - 91.0 mg/L

Duration:

72 h

Dose descriptor:

other: NOEL

Effect conc.:

3.16 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

other: LOEL

Effect conc.:

10 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EL20

Effect conc.:

47.1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Remarks on result:

other: 95%-CI: 30.8 - 93.3 mg/L

Details on results:

- Exponential growth in the control (for algal test): yes
- Observation of abnormalities (for algal test): no

Results with reference substance (positive control):

- Results with reference substance valid: yes
- ErC50 (72 h) : 0.799 mg/L (95% CI: 0.707 – 1.30 mg/L)

BIOLOGICAL RESULTS:

Table 1: Cell densities after 72 h incubation

Nominal test item loading [mg/L]	Mean cell density [cells/mL] after 72 hours
100	60357
31.6	743270
10.0	514201
3.16	1140288
1.00	1027383
0.316	1313334
0.100	946868
Control	1212628

Further effect values:

- EyL10 = 0.427 (<0.1 - 6.82) mg/L

- EyL20 = 3.43 (<0.1 - 13.5) mg/L

-EyL50 = 26.6 (11.5 -61.7) mg/L

- NOEyL = 3.16 mg/L

Table 2: Inhibitions of Growth rate and Yield after 72 h incubation.

Nominal test item loading [mg/L]	Growth rate (mean) [d^-1]	Inhibition of growth rate [%]	Yield (mean) [cells/mL]	Inhibition of yield [%]
100	+ 0.724	59	+ 53915	96
31.6	+ 1.58	9	+ 736828	39
10.0	+ 1.46	17	+ 507759	58
3.16	+ 1.72	1	+ 1133846	6
1.00	+ 1.68	3	+ 1020941	15
0.316	- 1.77	-1	- 1306892	-8
0.100	- 1.66	5	- 940426	22
Control	1.75		1206186

Statistically significant differences of growth rates and yield compared to control values are marked (+), not significant differences are marked (-).

Table 3: Section-by-section and Average Specific Growth Rate of the Control Group (0 - 72 hours).

	Replicate No.	Specific growth rate [d^-1] section-by-section				Mean (0 - 72 hours)	SD ±	CV [%]	Mean CV [%]
		0 – 24 hours	24 – 48 hours	48 – 72 hours
Control	1	1.22	2.24	1.74		1.73	0.514	26.6	29.7
	2	1.26	2.18	1.89		1.78	0.471	26.5
	3	1.12	1.97	2.12		1.73	0.539	31.1
	4	1.07	2.17	1.89		1.71	0.570	33.3
	5	1.22	2.01	2.02		1.75	0.458	26.2
	6	1.13	2.20	1.97		1.77	0.561	31.7
				Mean	1.75
				SD ±	0.002
				CV %	1.42

ANALYTICAL RESULTS:

At the start of the exposure the measured concentrations of the test item were in the range of 0.0163 to 2.55 mg/L. At the end of exposure after 72 hours, the measured concentrations were in the range of < LOQ to 27% of the initially measured test item concentrations.

Table 4: Measured concentration of the Test Item in the Definitive Test with Algae.

Sampling date	Fresh Media [0 hours]	Old Media [72 hours]
Nominal test item loading rate [mg/L]	Meas. conc. [mg/L]	Meas. conc. [mg/L]	%
100	2.55	0.269	11
31.6	1.43	0.132	9
10.0	1.59	0.435	27
3.16	0.343	0.0333	10
1	0.157	0.0122	8
0.316	0.0554	< LOQ	-
0.1	0.0163	< LOQ	-
Control	< LOQ	< LOQ	-

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

% = percent of the initial measured concentration of the test item

LOQ = limit of quantification of the analytical method (0.010 mg/L of the test item)

Table 5: TOC content of the Test Media at the Start and the End of the Exposure.

Sampling date	Fresh Media [0 hours]	Old Media [72 hours]
Nominal test item loading rate [mg/L]	Meas. TOC [mg C/L]	Meas. TOC [mg C/L]
100	1.49*	1.37*
31.6	1.20*	1.10*
10.0	1.34*	1.14*
3.16	0.637*	0.546*
1	0.411*	0.464*
0.316	1.13*	1.05*
0.1	1.46*	1.28*
Control	3.27	3.5

*  The limit of quantification of the analytical method is set to 2.00 mg/L.

VALIDITY CRITERIA:

Table 6: Validity Criteria

Validity Criterion	Required	This study
Increase of the cell growth in the control cultures	Exponentially, ≥ 16-fold corresponding to a specific growth rate of 0.92/day	188-fold (specific growth rate 1.75 day^-1)
Mean coefficients of variation for section-by-section specific growth rates (days 0-1, 1-2 and 2-3) in the control culture	≤ 35%	29.7%
Coefficient of variation of average specific growth rates during the whole test period in replicate control cultures	≤ 7%	1.42%

Validity criteria fulfilled:

yes

Remarks:

For further details please refer to “Any other information on results incl. tables”

Conclusions:

A study testing the toxicity of the substance to algae according to the OECD guideline 201 resulted in an ErL50 (72 h) of 89.9 mg/L and an ErL10 (72 h) of 26.1 mg/L (both nominal loading rates).

Description of key information

ErL50 (72 h) = 89.9 mg/L and ErL10 (72 h) = 26.1 mg/L (nominal loading rate, OECD 201)

Key value for chemical safety assessment

EC50 for freshwater algae:

89.9 mg/L

EC10 or NOEC for freshwater algae:

26.1 mg/L

Additional information

One study is available testing the toxicity of Chloro(dimethyl)octylsilane (CAS 18162 -84 -0) to algae. The study was performed according to the OECD guideline 201 and GLP standards (2019). Pseudokirchneriella subcapitata was used as the test organism. Seven loading levels were tested i.e. 0.100, 0.316, 1.00, 3.16, 10.0, 31.6 and 100 mg/L as well as a control. The concentrations were analytically monitored. At the start of the exposure the measured concentrations of the test item were between 2.55 and 17.5% of the nominal loading concentrations. At the end of the exposure the measured concentrations were between < LOQ and 27% of the initially measured test item concentrations and < LOQ and 4.35% of the nominal test item loading rates. Due to the hydrolytic instability of the parent test item and degradation to different hydrolysis products in random proportions, the obtained test item solutions are considered complex mixtures. The distribution of analytically measured test item concentrations in the higher loading levels are considered to reflect the hydrolysis pattern and is regarded as proof that these test item loading levels were near or above the maximum achievable concentrations under test conditions. Therefore, the effect values are given in nominal loading levels. The ErL50 (72 h) was 89.9 mg/L and the ErL10 (72 h) was 26.1 mg/L (nominal loading rate).