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Short-term toxicity to aquatic invertebrates

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Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1994-04-27 to 1994-04-29
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
The study was conducted according to an appropriate OECD test guideline, and in compliance with GLP, and was considered to be reliability 1 (reliable without restrictions).
Qualifier:
according to
Guideline:
EU Method C.2 (Acute Toxicity for Daphnia)
Deviations:
no
GLP compliance:
yes
Analytical monitoring:
yes
Details on sampling:
- Concentrations: 500 mg/l nominal treatment

- Sampling method: Samples of test media were taken at the start and end of the test

- Sample storage conditions before analysis: Refrigerated
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: A 500 mg/l nominal concentration of the test substance was prepared by stirring overnight.

- Controls: Dilution water
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM

- Source: The test organisms were obtained from a laboratory culture. The culture originated from individuals obtained from Shell Research Limited, Sittingbourne, Kent, U.K.

- Age at study initiation (mean and range, SD): <24 h

- Method of breeding: parthenogenetic reproduction

- Feeding during test: none

ACCLIMATION

- Acclimation conditions: same as test

- Type and amount of food: Chlorella vulgaris at 500000 cells/ml

- Feeding frequency: Daily
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
48 h
Hardness:
204 mg/l as CaCO3
Test temperature:
20.3 - 21.7ºC
pH:
7.4 - 8.1
Dissolved oxygen:
99 - 100% ASV
Nominal and measured concentrations:
Nominal: 0(Control), 500 mg/l

Measured concentration at start of test: 405 mg/l

Measured concentration at end of test: 436 mg/l

Mean measured concentration: 420 mg/l

Mean measured concentration as a percentage of nominal: 84.1%

The test results are presented and interpreted with reference to nominal concentrations.
Details on test conditions:
TEST SYSTEM

- Test vessel: Conical flasks

- Type: closed

- Material, fill volume: Glass, 150 ml of test medium

- Aeration: none

- 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: Reconstituted freshwater prepared by mixing (1:1) treated mains water and proprietary mineral water (Ashbourne, Still Natural Water (Nestle, UK. Limited).

- Culture medium different from test medium: no

- Chlorine: <0.1 mg/l (Total)

- Alkalinity: 134 mg/l as CaCO3

- Conductivity: 404 µS/cm

OTHER TEST CONDITIONS

- Adjustment of pH: no

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : Immobilization after 24 and 48 h
Reference substance (positive control):
no
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
> 500 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
but exposure is to hydrolysis products
Basis for effect:
mobility
Duration:
48 h
Dose descriptor:
NOEC
Effect conc.:
>= 500 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
but exposure is to hydrolysis products
Basis for effect:
mobility
Details on results:
- Mortality of control: 0
Reported statistics and error estimates:
No toxic effects were observed in the test media, the test results were therefore not subject to statistical analysis.
Validity criteria fulfilled:
yes
Conclusions:
A 48-hour EC50 value of >500 mg/l and NOEC of =500 mg/l have been determined for the effects of the test substance on mobility of Daphnia magna based on nominal concentration of the substance. However it is likely that the test organisms were primarily exposed to the hydrolysis products of the substance.
Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
supporting study
Study period:
2007-06-08 to 2007-06-15
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
GLP compliance:
yes
Analytical monitoring:
yes
Details on sampling:
- Sampling method: Measurement of test concentrations in one replicate test chamber of each treatment group at test initiation and test termination.
Vehicle:
yes
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: Test solutions were prepared by direct addition of the test article to dilution water (100 and 200 mg/l treatment groups) or by addition of stocks prepared in DMF (13, 25 and 50 mg/l treatment groups).  The solvent solutions were used in the lower concentration treatments in order to facilitate accurate delivery of smaller amounts of the tests substance in the diluter system. The solvent control, 13, 25 and 50 mg/l treatment groups contained 0.1 ml/l DMF.  No solvent was delivered in the 100 and 200 mg/l treatment groups.  The diluter flow rate provided 32 volume additions/day.
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM

- Source, supplier, any pretreatment, breeding method:  Dow Corning in-house Cultures. The cultures were initiated with organisms obtained from Aquatic Biosystems Inc., Fort Collins, Colorado.      

- Age at study initiation:  <24 hours old
Test type:
flow-through
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
Hardness:
Hardness 105 mg/l as CaCO3, Alkalinity 65 mg/l as CaCO3
Test temperature:
19.5 to 21.0ºC
pH:
7.5-7.8
Dissolved oxygen:
7.8-8.9 mg/l
Salinity:
Not applicable
Nominal and measured concentrations:
Nominal concentrations: Negative Control, Solvent Control, 13, 25, 50, 100 and 200 mg/l 

Mean measured concentrations:
Recoveries of methyltrimethoxysilane were low because the hydrolysis half-life is approximately 2.2 hours.

The results are reported with reference to mean measured concentrations.
Details on test conditions:
TEST SYSTEM

- Exposure vessel type:  The test compartments were 300-ml glass beakers with 2 holes on opposite sides covered with nylon screen.  The test chambers were placed in 7.5 litre polyethylene aquaria containing 3.4 litre of test solution.  

- Dilution water source:  Dechlorinated Municipal Water

- Dilution water chemistry (hardness, alkalinity, pH, TOC, TSS, salinity, Ca/Mg ration, Na/K ratio):  Hardness 105 mg/l as CaCO3, Alkalinity 65 mg/l as CaCO3, pH 7.6, Conductivity 319  mhos/cm and Total Residual Chlorine <10  g/l

- Lighting (quality, intensity, and periodicity):  Wavelength similar to natural sunlight, 55 to 66 foot-candles, 16 hours light:8 hours dark

- Water chemistry in test:  DO, pH and temperature measured in each test chamber daily

- Element (unit) basis (i.e., immobilization):  Mortality and immobilization

- Test design (number of replicates, individuals per replicate, concentrations):  Two replicates/treatment, 10 individuals/replicate

- Method of calculating mean measured concentrations:  Arithmetic mean.
Reference substance (positive control):
no
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
> 122 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
mobility
Duration:
48 h
Dose descriptor:
NOEC
Effect conc.:
>= 122 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
mobility
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
> 200 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Duration:
48 h
Dose descriptor:
NOEC
Effect conc.:
>= 200 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Details on results:
- Immobilisation of control: 0
Reported statistics and error estimates:
No significant mortalities were recorded in the highest treatment. An EC50 value could therefore not be determined.

Table 1. Test results

 Nominal concentration (mg/l)  Mean measured concentration (mg/l) Percentage immobilisation after 24 hours   Percentage immobilisation after 48 hours 
 0 (Control)  -  0  0
 0 (Vehicle control)  -  0  0
 13  6  0  0
 25  15  0  35
 50  31  0  75
 100  56  0  0
 200  122  0  0

Was control response satisfactory: Yes

The effects observed in the 15 and 31 mg/l treatments were thought to relate to physical interaction with the test substance and solvent.

Validity criteria fulfilled:
yes
Conclusions:
A 48-hour EC50 value of >122 mg/l and NOEC of =122 mg/l have been determined for the effects of the substance on mobility of Daphnia magna. Under the flow-through conditions used in the test the results reflect exposure to the parent substance.

Description of key information

Short-term toxicity to invertebrates: 48 hour EC50 >500 mg/l (nominal, highest concentration tested) (EU Method C.2 (Acute toxicity for Daphnia)), read-across from an analogous/structurally related substance, triethoxy(methyl)silane (CAS 2013-67-6). The observations in this study are attributed to the exposure of test organisms to the hydrolysis products in the test system. The EC50 is equivalent to >213.7 mg/l when expressed in terms of the silanol hydrolysis product.

Key value for chemical safety assessment

Additional information

There are no reliable short-term invertebrate toxicity data available for methylsilanetriyl triacetate (CAS 4253-34-3), therefore good quality data for appropriate structural analogues triethoxy(methyl)silane (CAS 2031-67-6) and trimethoxy(methyl)silane (CAS 1185-55-3), have been read across. The substances share the same silanol hydrolysis product, methylsilanetriol. The other hydrolysis products are acetic acid, ethanol and methanol, respectively. In the tests with triethoxy(methyl)silane (CAS 2031-67-6) and trimethoxy(methyl)silane (CAS 1185-55-3), the observations are attributed to the exposure of test organisms to methylsilanetriol in the test system. There is no basis to expect that ethanol or methanol significantly influenced the results of the test. The toxicity of ethanol and methanol is discussed further in the ecotoxicological information overview endpoint summary (additional information).

 

A 48 hour EC50 value of >500 mg/l (nominal, highest concentration tested) has been determined for the effects of triethoxy(methyl)silane (CAS 2013-67-6) on mobility of Daphnia magna. In view of the test media preparation method and exposure regime it is likely that the test organisms were exposed predominantly to the hydrolysis products of the tested substance. The results may be expressed in terms of concentration of the hydrolysis product, methylsilanetriol, by applying a molecular weight correction: (MW of silanol = 94.14 / MW of parent = 220.26) * >500 = >213.7 mg/l. This value is read across to methylsilanetriol without further correction.

A 48 hour EC50 value of >122 mg/l has been determined for the effects of a second read-across substance, trimethoxy(methyl)silane (CAS 1185-55-3) on mobility of Daphnia magna. The result was obtained under flow-through exposure conditions and it is therefore likely that the test organisms were exposed to a mixture of the parent substance and its hydrolysis products.

The study with triethoxy(methyl)silane (CAS 2031-67-6) has been selected as key because the organisms were likely to be exposed predominantly to the silanol hydrolysis product of the substance.