Ethoxytrimethylsilane

Short-term toxicity to aquatic invertebrates

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

short-term toxicity to aquatic invertebrates

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

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

124 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

mortality

Cumulative Mortality, Immobility and Observations:

Mean Measured Concentration (mg/L)	Rep.	Daphnia/ Replicate	Cumulative Number Dead 0 0	Number Immobile	Effects^1	Percent Dead and Immobile
Negative Control	A B	10 10	0 0	0 1	10 AN 9 AN	5
60	A B	10 10	0  0	3 3	7 AN 7 AN	30
116	A B	10 10	2 5	4 2	4AN (2Q) 3AN	65
207	A B	10 10	4 4	1 0	5AN (2Q) 6AN (3Q)	45
447	A B	10 10	4 6	4 2	2AN (10Q) 1AN,1C (6Q)	80
905	A B	10 10	3 5	5 4	2C (7Q) 1AN (4Q)	85

¹Observed effects: AN = appear normal; C = lethargic; Q = daphnia trapped on surface of test solution, then submerged below water surface and observed.

EC50 values:

Time	EC50 (mg/L)	95% Confidence Interval (mg/L)	Statistical Method
24 Hours	>905	--1	NA2
48 Hours	124	51 - 203	Probit
1Confidence limits could not be calculated with the mortality/immobility data obtained.2NA = Not applicable. Estimation made by visual inspection of the mortality/immobility data.

Daily observations of mortality, immobility and other clinical signs of toxicity observed during the

test are presented in the Table above. All daphnids in the negative control group appeared healthy and normal

throughout the test, with the exception of one immobile daphnia at test termination. In the 60, 116, 207,

447 and 905 mg/L treatment groups, mortality/immobility at 48 hours was 30, 65, 45, 80 and 85%,

respectively. At 48-hours, daphnia trapped on the water surface were observed in every treatment group

except the negative control and 60 mg/L, with more daphnia being trapped at the higher concentrations,

although a surface slick was not observed at test initiation or termination, initial observations, or during the

transfer of daphnia to new test solutions at 24-hours in any of the test concentrations.

CONCLUSIONS

Daphnia magna were exposed under static-renewal test conditions for 48 hours to five

concentrations of trimethylsilanol ranging in concentration from 60 to 905 mg/L. Based on the mean

measured test concentrations, the 48-hour EC50 value was 124 mg/L, with a 95% confidence interval of

51 to 203 mg/L. The slope of the concentration-response curve was 1.2. The NOEC was < 60 mg/L, the

lowest treatment group tested.

Conclusions:

An EC50 (48 h) of 124 mg/L (measured) for toxicity to aquatic invertebrates was determined in a reliable study with a suitable read-across substance conducted according to an appropriate test protocol, and in compliance with GLP.

Reference 2

Endpoint:

short-term toxicity to aquatic invertebrates

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP Guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)

Qualifier:

according to guideline

Guideline:

EPA OPPTS 850.1010 (Aquatic Invertebrate Acute Toxicity Test, Freshwater Daphnids)

Qualifier:

according to guideline

Guideline:

other: ASTM Standard E729-88a, Standard Guide for Conducting Acute Toxicity Tests with Fishes, Macroinvertebrates and Amphibians (3).

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

- Concentrations: Samples were collected from the each test chamber of each concentration
- Sampling method: Test solution samples were collected at mid-depth, placed in glass vials, and analyzed immediately.
- Sample storage conditions before analysis: No

Vehicle:

no

Test organisms (species):

Daphnia magna

Details on test organisms:

TEST ORGANISM
- Common name: Waterflea
- Source: inhouse culture, Wildlife International, Ltd. Cultures Easton, Maryland 21601
- Age at study initiation (mean and range, SD): Neonates, <24 hours old

ACCLIMATION
- Acclimation period: 14 days
- Acclimation conditions (same as test or not): same as test
- Type and amount of food: mixture of yeast, Cerophyll® and trout chow, as well as a suspension of the freshwater green alga, Selenastrum capricornutum
- Feeding frequency: daily
- Health during acclimation (any mortality observed): The adults showed no signs of disease or stress during the holding period

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

48 h

Hardness:

129 mg/L as CaCO3

Test temperature:

20 ± 1ºC

pH:

8.3

Nominal and measured concentrations:

Nominal: 63, 125, 250, 500 and 1000 mg/L.
The mean measured concentrations for the study were 60, 116, 207, 447 and 905 mg/L, representing 95, 93, 83, 89 and 91% of nominal concentrations, respectively. The results of the study were based on the mean measured test concentrations.

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Material, size, headspace, fill volume: 250-mL glass beakers containing approximately 200 mL of test solution
- No. of organisms per vessel: 10
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates): 2


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Freshwater obtained from a well approximately 40 meters deep located on the Wildlife International, Ltd. site. The well water is characterized as moderately-hard water.


OTHER TEST CONDITIONS
- Adjustment of pH: No
- Photoperiod:16 hours of light and 8 hours of darkness
- Light intensity:Fluorescent light bulbs that emit wavelengths similar to natural sunlight (Colortone 50) were used, Light intensity at test initiation was 131 lux

EFFECT PARAMETERS MEASURED : All organisms were observed periodically to determine the numbers of mortalities and immobile
organisms in each control and treatment group. The numbers of individuals exhibiting clinical signs of toxicity or abnormal behavior also were evaluated. Observations were made approximately 4, 24 and 48 hours after test initiation.

Reference substance (positive control):

not specified

Duration:

48 h

Dose descriptor:

EC50

Effect conc.:

124 mg/L

Nominal / measured:

meas. (not specified)

Conc. based on:

test mat.

Basis for effect:

mortality

Reported statistics and error estimates:

The mortality/immobility data were analyzed using the computer program of C. E. Stephan.
The program was designed to calculate the EC50 value and the 95% confidence interval by probit analysis,
the moving average method, and binomial probability with nonlinear interpolation. In this study,
the probit method was used to calculate the 48-hour EC50 value. There was <50% mortality or immobility
in any treatment group at 24 hours, which precluded the statistical calculation of a 24-hour EC50 value.
Therefore, the 24-hour EC50 value and the NOEC were determined by visual inspection of the mortality,
immobility and observation data.

Cumulative Mortality, Immobility and Observations:

Mean Measured Concentration (mg/L)	Rep.	Daphnia/ Replicate	Cumulative Number Dead 0 0	Number Immobile	Effects^1	Percent Dead and Immobile
Negative Control	A B	10 10	0 0	0 1	10 AN 9 AN	5
60	A B	10 10	0  0	3 3	7 AN 7 AN	30
116	A B	10 10	2 5	4 2	4AN (2Q) 3AN	65
207	A B	10 10	4 4	1 0	5AN (2Q) 6AN (3Q)	45
447	A B	10 10	4 6	4 2	2AN (10Q) 1AN,1C (6Q)	80
905	A B	10 10	3 5	5 4	2C (7Q) 1AN (4Q)	85

¹Observed effects: AN = appear normal; C = lethargic; Q = daphnia trapped on surface of test solution, then submerged below water surface and observed.

EC50 values:

Time	EC50 (mg/L)	95% Confidence Interval (mg/L)	Statistical Method
24 Hours	>905	--1	NA2
48 Hours	124	51 - 203	Probit
1Confidence limits could not be calculated with the mortality/immobility data obtained.2NA = Not applicable. Estimation made by visual inspection of the mortality/immobility data.

Daily observations of mortality, immobility and other clinical signs of toxicity observed during the

test are presented in the Table above. All daphnids in the negative control group appeared healthy and normal

throughout the test, with the exception of one immobile daphnia at test termination. In the 60, 116, 207,

447 and 905 mg/L treatment groups, mortality/immobility at 48 hours was 30, 65, 45, 80 and 85%,

respectively. At 48-hours, daphnia trapped on the water surface were observed in every treatment group

except the negative control and 60 mg/L, with more daphnia being trapped at the higher concentrations,

although a surface slick was not observed at test initiation or termination, initial observations, or during the

transfer of daphnia to new test solutions at 24-hours in any of the test concentrations.

CONCLUSIONS

Daphnia magna were exposed under static-renewal test conditions for 48 hours to five

concentrations of trimethylsilanol ranging in concentration from 60 to 905 mg/L. Based on the mean

measured test concentrations, the 48-hour EC50 value was 124 mg/L, with a 95% confidence interval of

51 to 203 mg/L. The slope of the concentration-response curve was 1.2. The NOEC was < 60 mg/L, the

lowest treatment group tested.

Conclusions:

An EC50 (48 h) of 124 mg/L (measured) for toxicity to aquatic invertebrates was determined in a reliable study substance conducted according to an appropriate test protocol, and in compliance with GLP.

Description of key information

EC50 (48 h) 124 mg/L (measured, OECD 202)

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates

Dose descriptor:

EC50

Effect concentration:

124 mg/L

Additional information

There are no data available on short-term toxicity to aquatic invertebrates 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 202 (GLP). Daphnia magna was exposed to the substance up to a concentration of 1000 mg/L under semi-static conditions. The test concentrations remained stable for the duration of the study. The mean measured concentrations were in the range of 95-103% of nominal. Immobilisation was recorded after 48 h resulting in an EC50 (48 h) 124 mg/L.