tert-butylchlorodimethylsilane

Short-term toxicity to fish

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

short-term toxicity to fish

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

1996-09-09 to 1996-09-13

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

Guideline study without restrictions. The study was conducted according to the appropriate OECD test guideline, and in compliance with GLP.

Qualifier:

according to guideline

Guideline:

EU Method C.1 (Acute Toxicity for Fish)

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

- Concentrations: Stock solutions and 30 mg/L

- Sampling method: Samples of each batch of fresh test media were taken for analysis at the start of the test and after 24, 48 and 72 hours. Samples of old test medium were also taken after each 24 hour exposure period in order to assess stability.

- Sample storage conditions before analysis: not described

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: A single test concentration was prepared by adding 1 g of the test substance to 1 L of dilution water and stirring for 18 h followed by filtration. The concentration of the test substance in the test medium was then determined by analysis of the stock solution to be 30 mg/L.

- Controls: Dilution water

Test organisms (species):

Cyprinus carpio

Details on test organisms:

TEST ORGANISM

- Common name: Common carp

- Source: Charles River, NL - Somer

- Holding tanks: Prior to the test the fish were held in 300-L glass aquaria containing 200-L of water.

- Length at study initiation (length definition, mean, range and SD): 2-3 cm

- Mean weight of fish: 0.77 g

- Feeding during test: none

ACCLIMATION

- Acclimation period: at least 14 days

- Acclimation conditions: same as test

- Type and amount of food: 1% of body weight

- Feeding frequency: Daily

- Health during acclimation (any mortality observed): The fish exhibit normal behaviour and are free from visible signs of disease at the start of the test. Mortality must not exceed 5% in the 7 day period prior to the test.

Test type:

semi-static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

96 h

Hardness:

12ºdH

Test temperature:

21-22ºC

pH:

7.4-8.4

Dissolved oxygen:

81-99% ASV

Salinity:

not applicable

Nominal and measured concentrations:

Nominal concentrations: 0(Control) and 30 mg/L

The variation in measured concentration was <20% over the course of the test.

The test results are interpreted with reference to the 30 mg/L concentration of the test substance

Details on test conditions:

TEST SYSTEM

- Test vessel:

- Type: open aquarium

- Material, size, headspace, fill volume: 20 L with 10 L of test medium

- Aeration: Continuous

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

- No. of organisms per vessel: 10

- No. of vessels per concentration (replicates): 1

- No. of vessels per control (replicates): 1


TEST MEDIUM / WATER PARAMETERS

- Source/preparation of dilution water: Potable water from Gelsenwasser AG


OTHER TEST CONDITIONS

- Adjustment of pH: None

- Photoperiod: 16 h light/8 h dark


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : Mortality after 24, 48, 72 and 96 h


TEST CONCENTRATIONS

- Spacing factor for test concentrations: Not applicable

Reference substance (positive control):

no

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

> 30 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

but exposure is primarily to hydrolysis products

Basis for effect:

mortality (fish)

Remarks on result:

other: The measured initial concentration was based on analysis of the stock solution

Details on results:

- Behavioural abnormalities: none reported

- Mortality of control: 0

- Other adverse effects control: none

Reported statistics and error estimates:

No toxic effects were observed in the test and therefore statistical analysis of the results was not required.

Sublethal observations / clinical signs:

Table 1. Test results

Mean initial measured test substance concentration (mg/L)	Percentage mortality after 24 hours	Percentage mortality after 48 hours	Percentage mortality after 72 hours	Percentage mortality after 96 hours
0 (Control)	0	0	0	0
30	0	0	0	0

Table 2. Results of analysis of test media

Nominal test substance concentration (mg/L)	Measured concentration in fresh medium at start of test (mg/L)	Measured concentration in fresh medium at 24 hours (mg/L)	Measured concentration in fresh medium at 48 hours (mg/L)	Measured concentration in fresh medium at 72 hours (mg/L)	Mean initial measured concentration at 0, 24, 48 and 72 hours (mg/L)
30	30.3	29.1	30.7	28.2	30
Stock solution	34.5	32.0	29.5	29.3	-

Table 3. Results of analysis of test media - stability of test media

Initial nominal test substance concentration (mg/L)	Measured concentration in old test medium - 24 hours (mg/L)	Measured concentration in old test medium - 48 hours (mg/L)	Measured concentration in old test medium - 72 hours (mg/L)	Measured concentration in old test medium - 96 hours (mg/L)
30	28.4	29.3	27.2	23.0

Validity criteria fulfilled:

yes

Conclusions:

A 96-hour LC50 value of >30 mg/L has been determined for the effects of the test substance on mortality of Cyprinus carpio. The results are interpreted with reference to concentrations of the test substance based on measured dissolved organic carbon. However it is likely that the test organisms were primarily exposed to the hydrolysis products of the substance.

Reference 2

Endpoint:

short-term toxicity to fish

Type of information:

experimental study

Adequacy of study:

weight of evidence

Study period:

2015-11-12 to 2016-21-01

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 203 (Fish, Acute Toxicity Test)

Deviations:

no

GLP compliance:

yes

Analytical monitoring:

yes

Details on sampling:

- Concentrations: approximately 50 mL of the test solution were sampled for measurement at the start of exposure, before and after the renewal, and the end of exposure. The concentration of the test item in each sample for GC analysis was determined on the basis of a comparison of the peak area on the chromatogram of the sample solution with that of a standard solution.

- Sampling method: The test solution was taken out form the middle layer of each test vessel for analysis. The calibration curve was drawn by using four standard solutions of 1.01, 5.03, 10.1 and 20.1 mg/L prepared according the following way: the test sample (60µL) was taken out by microsyringe and dissolved in hexane to obtain 1010 mg/L solution of the test item, then this solution was diluted to prepare 10.1 mg/L standard solution.

Vehicle:

not specified

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: The test sample was added below the surface of water in the Erlenmeyer flask filled with dilution water to prepare 100 mg/L (nominal) with microsyringe, and the container was sealed without headspace. Then, the solution was stirred by a magnetic stirrer for 24 hours to prepare a stock solution. Desired volume of the stock solution and the dilution water were mixed and stirred in a test vessel to prepare the test solution. And then air tight transparent plastic lid was set on the test vessel. The stock solution was prepared every day.
- Controls: Dilution water without the test item
- Evidence of undissolved material (e.g. precipitate, surface film, etc.): The test solution in all test levels were colorless and clear at the start and end of exposure.

Test organisms (species):

Oryzias latipes

Details on test organisms:

TEST ORGANISM
- Common name: Medaka (Oryzias latipes)
- Source: CERI-Kurume
- Age at study initiation (mean and range, SD): 3-month old
- Length at study initiation (length definition, mean, range and SD): 2.3 +/- 1.2 cm
- Weight at study initiation (mean and range, SD):
- Method of breeding: No feeding, dechlorinated tap water as dilution water, aerated sufficiently and temperature-controlled.

ACCLIMATION
- Acclimation period: 11 days
- Acclimation conditions (same as test or not): Same apart from the acclimation tank was a flow-through regime, whereas the test was semi-static.
- Type and amount of food during acclimation: Feed of Medaka for education (KYORIN), amount corresponding to 3% of body weight.
- Feeding frequency during acclimation: Everyday
- Health during acclimation (any mortality observed): No mortality observed

Test type:

semi-static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

96 h

Hardness:

Total hardness as CaCO3 : 28 mg/L

Test temperature:

23.1 to 23.7°C

pH:

7.4 to 7.9

Dissolved oxygen:

6.9 to 8.6 mg/L

Conductivity:

11 mS/m

Nominal and measured concentrations:

Nominal concentrations = 19.8, 29.6, 44.4, 66.7 and 100 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 3 L Glass tank (diameter:16 cm, depth: 17 cm) containing 2.7 L of test solution
- Type : closed system with headspace (Air tight transparent plastic lid)
- Aeration: No aeration
- Renewal rate of test solution (frequency/flow rate): renewal every 24 hours
- No. of organisms per vessel: 7
- No. of vessels per concentration (replicates): 2
- No. of vessels per control (replicates): 2


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Dechlorinated tap water
- Total organic carbon: < 0.5 mg/L
- Particulate matter: < 1 mg/L
- Chlorine: < 0.02 mg/L
- Alkalinity: 29 mg/L
- Intervals of water quality measurement: at the start of exposure, before and after the renewal, and the end of exposure.

OTHER TEST CONDITIONS
- Adjustment of pH: No adjustment
- Photoperiod: 16-hour light/8-hour dark
- Light intensity: Room light

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
Mortality and visible abnormality were observed at 3, 24, 48, 72, 96 hours after the start of exposure (A fish was considered as dead if the observable motion were not observed and touching of the caudal peduncle with glass rod produced no reaction.)

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 1.5
- Results used to determine the conditions for the definitive study: The preliminary test showed abnormal responses at 100 mg/L so the test solutions during the main test were prepared at the following concentrations: 100, 66.7, 44.4, 29.6 , 19.8 mg/L and a control.

Reference substance (positive control):

yes

Remarks:

Copper II Sulfate Pentahydrate

Key result

Duration:

96 h

Dose descriptor:

LC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

mortality (fish)

Details on results:

- The observed behavioural abnormalities were : at the surface, complete loss of equilibrium, partial loss of equilibrium and reduced activity.
- Observations on body length and weight: Total length = 2.4 +/-0.1 cm; Body weight = 0.14+/- 0.03 g
- No abnormal response was obtained in the control

Results with reference substance (positive control):

- Test system reproducibility confirmed with Reference substance in November 16 to November 20, 2015
- 96-hour LC50: 0.41 mg/L

Sublethal observations / clinical signs:

Table 1 : Measured concentration in mg/L (Percentage of measured concentration versus nominal concentration %)

Nominal concentration (mg/L)	At the start	24 hours (old)	24 hours (new)	48 hours (old)	48 hours (new)	72 hours (old)	72 hours (new)	At the end	Geometric mean
Control	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.	n.d.
19.8	19.4 (97.9%)	17.9 (90.2%)	19.2 (97%)	18.7 (94.3%)	19.3 (97.7%)	19.4 (97.7%)	20.5 (104%)	19.3 (97.4%)	19.2 (97.0%)
29.6	29.5 (99.6%)	26.0 (87.7%)	29.9 (101%)	28.2 (95.3%)	28.4 (96.0%)	28.3 (95.7%)	30.3 (102%)	28.6 (96.8%)	28.6 (96.7%)
44.4	44.4 (100%)	39.9 (89.9%)	44.4 (100%)	41.9 (94.4%)	43.2 (97.3%)	42.4 (95.5%)	45.3 (102%)	41.4 (93.1%)	42.8 (96.5%)
66.7	66.9 (100%)	60.9 (91.3%)	61.8 (92.7%)	59.5 (89.1%)	66.6 (99.9%)	66.0 (98.9%)	66.6 (99.9%)	62.0 (92.9%)	96.8 (96.8%)
100	103 (103%)	92.0 (92.2%)	96.0 (96.0%)	91.5 (91.5%)	101 (101%)	99.0 (99.0%)	99.2 (99.2%)	93.3 (93.3%)	96.8 (96.8%)

old: before the renewal

new: after the renewal

n.d.: < 0.406 mg/L

The measured concentrations of the test item were kept within +/- 20% of the nominal concentration.

Validity criteria fulfilled:

yes

Conclusions:

The 96-hour LC50 was estimated to be > 100 mg/L for the mortality effects of the test substance on Medaka fish (Oryzias latipes).

Description of key information

Short-term toxicity to fish: 96 hr LC₅₀ >100 mg/l (nominal, tert-butyl(dimethyl)silanol), mortality of Oryzias latipes;

96-hour LC₅₀ >30 mg/l: effects of the read-across substance butyl(chloro)dimethylsilane (CAS 1000-50-6) on mortality of Cyprinus carpio. (measured, DOC). The results may be expressed in terms of the silanol hydrolysis product, by adjusting for the respective molecular weights: LC₅₀ >26 mg/l as butyl(dimethyl)silanol.

Key value for chemical safety assessment

Fresh water fish

Fresh water fish

Effect concentration:

26 mg/L

Additional information

The registration substance, tert-butyl(chloro)dimethylsilane (CAS 18162-48-6) hydrolyses very rapidly in contact with water to form tert-butyldimethylsilanol (CAS 18173-64-3) and hydrochloric acid. As per the REACH guidance (ECHA 2016, R.16) which states that "for substances where hydrolytic DT₅₀ is less than 12 hours, environmental effects are likely to be attributed to the hydrolysis products rather than to the parent substance itself", the aquatic toxicity assessment including fish, is based on the properties of the silanol hydrolysis product tert-butyl(dimethyl)silanol (CAS 18173-64-3).

Short-term toxicity to fish tests are available with the silanol hydrolysis product of the registration substance, and from a structural analogue of the registration substance. Both studies are used as weight of evidence.

A 96-h LC₅₀ value of >100 mg/l (nominal) (highest concentration tested) has been determined for the effects of tert-butyldimethylsilanol (CAS 18173-64-3) on the mortality of Medaka fish (Oryzias latipes), in accordance with Test Guideline OECD 203 (CERI-Kurume, 2016). The nominal test concentrations are supported by GC analysis. The measured concentrations ranged between 87.7-104% of the nominal.

A 96-hour LC₅₀ value of >30 mg/l (measured DOC) (highest concentration tested) has been determined for the effects of the read-across substance butyl(chloro)dimethylsilane (CAS 1000-50-6) on mortality of Cyprinus carpio, in accordance with test guideline EU method C.1 (Huls, 1996). According to the study author, the nominal concentration of 30 mg/l was the highest concentration obtainable under the conditions of the test. Concentrations of the test substance were measured by dissolved organic carbon and were very close to the nominal concentration. It is likely that the test organisms were primarily exposed to the hydrolysis products of the substance. The results may therefore be expressed in terms of the silanol hydrolysis product, by adjusting for the respective molecular weights: MW butyl(dimethyl)silanol/MW butyl(chloro)dimethylsilane * E(L)C₅₀ or NOEC value, thus 132.28/150.73 * LC₅₀ of >30 mg/l = LC₅₀ >26 mg/l as butyl(dimethyl)silanol.