Chlorodimethyloctylsilane

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:

17 - 19 Dec 2018

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

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Staatliches Gewerbeaufsichtsamt Hildesheim;Germany

Analytical monitoring:

yes

Remarks:

GC-MS, TOC

Details on sampling:

- Concentrations: 0 (control), 6.25, 12.5, 25.0, 50.0, 100 mg/L
- Sampling method: At the start of the exposure and at renewal (0 and 24 h), samples of the fresh media were taken and analyzed. At renewal and at the end of the exposure (24 and 48 h), samples of the 24-h old media were taken directly from the test vessels and analyzed.
- Sample storage conditions before analysis: All samples were immediately extracted and the extracts were stored at room temperature. Until the start of the analysis, the prepared samples were stored on the autosampler.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: Test solutions were prepared in buffered water with NaHCO3. All other components of the dilution water were added afterwards. For each loading level, an appropriate amount of test item was pipetted the surface of an appropriate amount demineralized water buffered with NaHCO3 and pH adjusted to 7.0 ± 0.2 with 1 M NaOH an 1 M HCl. 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 remained components were added to the solutions.
- Differential loading: yes
- Controls: Dilution water without test item.

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: water flea
- Source: Obtained from continuous laboratory cultures. Culture originally obtained from Institut für Wasser-, Boden- und Lufthygiene (WaBoLu), Berlin, Germany.
- Breeding conditions: In glass vessels (2 - 3 L capacity) with approx. 1.8 L culture medium, at 20 ± 2 °C, in an incubator, 16 hours illumination, light intensity of max. 1500 lx. The daphnids were fed at least 5 times per week ad libitum with a mix of unicellular green algae, e.g. Pseudokirchneriella subcapitata and Desmodesmus subspicatus, with a cell density of > 106 cells/mL.
- Age of parental stock: 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 max. 24 hours preceding the exposure were used for the test. No first brood progeny was used for the test.
- Feeding during test: no

ACCLIMATION
- Acclimatization of the daphnids was not necessary, because the composition of the dilution water was equivalent to the culture medium.

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

263 - 296 mg CaCO3/L

Test temperature:

19.8 - 20.4°C

pH:

7.12 - 7.54

Dissolved oxygen:

7.36 - 9.03 mg/L

Salinity:

-

Conductivity:

Dilution water: 552 - 617µS/cm

Nominal and measured concentrations:

Nominal loading rates: 0 (control), 6.25, 12.5, 25, 50, 100 mg/L
Geometric mean measured: < LOQ (control), 0.491, 1.39, 2.47, 5.88, 1.71 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 50 mL glass beakers (loosely covered with watch glasses)
- Fill volume: 20 mL
- Aeration: no
- Renewal rate of test solution: every 24 hours
- No. of organisms per vessel: 5
- No. of vessels per concentration (replicates): 4
- No. of vessels per control (replicates): 4

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: according to guideline
- Culture medium different from test medium: no (both Elendt M4 Medium according to the guideline)
- Intervals of water quality measurement: Prior to the start of the exposure (0 hours) and the water renewal (24 hours), the water quality parameters (i.e. pH-value, dissolved oxygen concentration, temperature, conductivity and total hardness) of the dilution water were measured. At the start of the exposure and at renewal (0 and 24 hours), the water quality parameters of the fresh media (i.e. pH-value, dissolved oxygen concentration) were measured in one additional replicate (without daphnids) per loading level and the control. At renewal and at the end of the exposure (24 and 48 hours), the water quality parameters of the old media were measured in one appropriate replicate (containing daphnids) per loading level and the control.

OTHER TEST CONDITIONS
- Adjustment of pH: yes, adjusted to pH 7 ± 0.2 by addition of 1 M HCl and 1 M NaOH
- Photoperiod: 16/8 hours light/dark cycle
- Light intensity: Diffuse light, light intensity of max. 1500 lux

EFFECT PARAMETERS MEASURED: Immobilization was determined in all groups after 24 and 48 hours.

RANGE-FINDING STUDY
- Test concentrations: 1, 10, 100 mg/L
- Results used to determine the conditions for the definitive study: 100% immobization was detected at 100 mg/L after 48 hours. At 10 mg/L immobilization was 0% after 48 hours.

Reference substance (positive control):

yes

Remarks:

potassium dichromate (tested at 4-5 Dec 2018)

Duration:

48 h

Dose descriptor:

EL50

Effect conc.:

8.84 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: 95%-CI: 6.25 – 12.5 mg/L

Duration:

48 h

Dose descriptor:

EL10

Effect conc.:

6.7 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mobility

Remarks on result:

other: 95%-CI: 6.25 - 12.5 mg/L

Details on results:

- Mortality of control: no

Results with reference substance (positive control):

- Relevant effect levels:
EC50 (24 h) = 2.03 mg/L

BIOLOGICAL RESULTS.

Table 1: Immobilization Rates after 24 and 48 hours of Exposure in the Definitive Test.

Nominal test item loading [mg/L]	IMMOBILIZATION [%]
	24 hours					48 hours
	Replicates					Replicates
	1	2	3	4	MV	1	2	3	4	MV
100	100	100	100	100	100	100	100	100	100	100
50	100	100	100	100	100	100	100	100	100	100
25	0	20	60	0	20	100	100	100	100	100
12.5	20	0	0	20	10	100	100	100	100	100
6.25	0	0	0	0	0	0	0	0	0	0
Control	0	0	0	0	0	0	0	0	0	0

ANLYTICAL RESULTS.

The measured concentrations in the fresh media at the start of the experiment (0 hours) were in the range of 0.635 to 2.01 mg/L and of 0.641 to 6.27 mg/L at renewal of the test solutions (24 hours). The measured concentrations of the test item of the old media at the renewal and at the end of the tests (24 and 48 hours) were between 48 to 78% of the initially measured concentrations and 5 to 13% of the nominal concentrations. Due to the hydrolytic instability of the parent test item and degradation to different hydrolysis products in random propoortions, the obtained test item test solutions are considered to be complex mixtures. The distribution of analytically measured test item concentrations is considered to reflect the hydrolysis pattern and is regarded as proof that the higher test item loading levels were near or above the maximum achievable concentrations under test conditions.

Table 2: Measured Concentrations and Percent of Nominal Concentration of the test item during the Definitive Test.

Sampling date	Fresh media,	Old media,		Fresh media,	Old media,		Geometric mean measured test item concentration [mg/L]
	0 hours	24 hours		24 hours	48 hours
Nominal test item loadings [mg/L]	Meas. conc. [mg/L]	Meas. conc. [mg/L]	%	Meas. conc. [mg/L]	Meas. conc. [mg/L]	%
100	2.01	1.46	72	- *)	- *)		1.71
50	6.68	5.18	78	- *)	- *)		5.88
25	1.6	1.14	72	6.27	3.24	52	2.47
12.5	0.948	0.710	75	3.42	1.63	48	1.39
6.25	0.635	0.331	52	0.641	0.423	67	0.491
Control	< LOQ	< LOQ		< LOQ	< LOQ

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

LOQ = limit of quantification of the analytical method (10 µg test item/L)

*) = not measured due to 100% mortality in the definitive test

 

Table 3: Measured TOC concentrations (mean value of 2 injections) during the Definitive Test.

Sampling date	Fresh Media [0 hours]	Old Media [24 hours]	Fresh Media [24 hours]	Old Media [48 hours]
Nominal test item loading rate [mg/L]	Meas. TOC [mg C/L]^1	Meas. TOC [mg C/L]^1	Meas. TOC [mg C/L]^1	Meas. TOC [mg C/L]^1
100	2.4	3.4	n.d.	n.d.
50	4.1	4.43	n.d.	n.d.
25	2.53	3.11	3.26	3.34
12.5	2.43	3.29	2.67	2.79
6.25	2.5	3.14	1.95*	2.3
Control	2.69	3.94	0.00*	1.70*

1) = measured TOC concentration, mean value of 2 injections

n.d. = not determined, due to 100% immobilization after 24 hours

* = <LOQ, the limit of quantification of the analytical method is set to 2.00 mg C/L.

VALIDITY CRITERIA:

Table 4: Validity criteria for OECD 202

Criterion from the guideline	Outcome	Validity criterion fulfilled
In the control, including the control containing the solubilising agent, not more than 10% of the daphnids should have been immobilized.	no daphnids were immobilized in the control	yes
The dissolved oxygen concentration at the end of the test should be ≥ 3 mg/L in control and test vessels.	≥7.36 mg/L	yes

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 aquatic invertebrates according to OECD 202 resulted in an EL50 (48 h) of 8.84 mg/L (nominal loading rate).

Description of key information

EC50 (48 h) = 8.84 mg/L (nominal loading rate, OECD 202)

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Effect concentration:

8.84 mg/L

Additional information

One study is available testing the toxicity of Chloro(dimethyl)octylsilane (CAS 18162 -84 -0) to aquatic invertebrates. The study was performed under semi-static conditions according to the OECD guideline 202 and GLP standards (2019). Daphnia magna was used as test organism. Five loading levels were tested i.e. 6.25, 12.5, 25, 50 and 100 mg/L as well as a control. The concentrations were analytically monitored by GC-MS in the fresh and old media. The measured concentrations of the test item in the old media were between 48 and 78% of the initially measured concentrations and 5 to 13% of the nominal 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 loading levels of 100 to 25 mg/L is 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 EL50 (48 h) was 8.84 mg/L (nominal loading rate).