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Ecotoxicological information

Short-term toxicity to aquatic invertebrates

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Reference
Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
experimental study
Adequacy of study:
key study
Study period:
1995-09-26 to 1995-09-28
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
EU Method C.2 (Acute Toxicity for Daphnia)
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Analytical monitoring:
yes
Details on sampling:
- Concentrations: 0.64, 1.3, 2.7, 5.4, 11, 21 and 43 mg/l and the fresh stock solution used to prepare the test media.

- Sampling method: Concentrations of test substance hydrolysis products determined in fresh media at all concentrations after preparation and again before renewal after 24 hours. The concentrations of the fresh stock solution used to prepare the test media was also determined.

- Sample storage conditions before analysis: not reported
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: Test media prepared by dilution of a 1000 mg/l stock solution prepared by mixing for 18 h followed by filtration. TOC concentration of stock solution determined and used as the basis for determining the nominal test concentrations.

- Test concentrations (Nominal): Control, 0.64, 1.3, 2.7, 5.4, 11, 21 and 43 mg/l
Test organisms (species):
Daphnia magna
Details on test organisms:
TEST ORGANISM

- Common name: Daphnia magna

- Strain: Clone 5

- Source: Stock culture

- 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 or not): yes

- Type and amount of food: sufficient to be consumed each day leaving no residue

- Feeding frequency: daily
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
Hardness:
The sum of the Ca2+ and Mg2+ ions: 2.5 mmol
Test temperature:
20 +/-1 degree C
pH:
7.5 - 7.9
Dissolved oxygen:
8.8 - 9.6 mg/l
Salinity:
not applicable
Nominal and measured concentrations:
- Test concentrations (Nominal): Control, 0.64, 1.3, 2.7, 5.4, 11, 21 and 43 mg/l

- Test concentrations (at start of test): Control,
- Test concentrations at end of test: Control,
- The measured concentrations that were >LOD were within +/-20% of nominal. The results are therefore presented and interpreted with reference to nominal concentrations.
Details on test conditions:
TEST SYSTEM

- Test vessel: glass cylinder

- Type: open

- Material, size, headspace, fill volume: cylinder containing 10 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: Elendt M4 medium

- Intervals of water quality measurement: end of test


OTHER TEST CONDITIONS

- Photoperiod: Dark


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : Immobilization after 24 and 48 h exposure


TEST CONCENTRATIONS

- Spacing factor for test concentrations: 2
Reference substance (positive control):
yes
Remarks:
Potassium dichromate
Key result
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
6.7 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
but exposure is to hydrolysis products
Basis for effect:
mobility
Remarks on result:
other: 4.9 - 9.1
Duration:
24 h
Dose descriptor:
EC50
Effect conc.:
20 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
but exposure is to hydrolysis products
Basis for effect:
mobility
Remarks on result:
other: 12 - 36
Duration:
48 h
Dose descriptor:
NOEC
Effect conc.:
2.7 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
but exposure is to hydrolysis products
Basis for effect:
mobility
Results with reference substance (positive control):
- Results with reference substance valid?

- EC50/LC50: >1 mg/l, <2.0 mg/l
Reported statistics and error estimates:
EC50 and confidence interval determined by Probit analysis

Table 1. Results of analysis of test media

 Nominal test concentration (mg/l)  Measured concentration at start of test (mg/l)  Measured concentration at end of test (mg/l)
 0 (Control)  -  -
 0.64  <LOD  <LOD
 1.3  <LOD  <LOD
 2.7  Unreliable value  2.3
 5.4  Unreliable value  6.3
 11  12.4  9.7
 21  20.9  20.4
 43  37.7  39.8

Table 2. Test results

 Nominal test concentration (mg/l)  Mean percentage immobilisation after 24 hours  Mean percentage immobilisation after 48 hours
 0 (Control)  5  5
 0.64  0  0
 1.3  0  0
 2.7  0  5
 5.4  15  50
 11  50  85
 21  40  90
 43  70  95
Validity criteria fulfilled:
yes
Conclusions:
A 48-h EC50 value of 6.7 mg/l and a NOEC of 2.7 mg/l have been determined for the effects of the test substance on mobility of Daphnia magna based on nominal concentrations of the substance. The test substance is susceptible to hydrolysis and it is therefore likely that the test organisms were primarily exposed to the hydrolysis products of the substance. The EC50 is equivalent to 5.3 mg/l when expressed in terms of the silanol hydrolysis product, 3-mercaptopropylsilanetriol.

Description of key information

No data are available for 3-(triethoxysilyl)propanethiol (CAS 14814-09-6). However a 48-hour EC50 value of 6.7 mg/l has been read-across for the effects of the read-across substance 3-(trimethoxysilyl)propane-1-thiol (CAS 4420-74-0) on mobility in Daphnia magna. The EC50 is equivalent to 5.3 mg/l when expressed in terms of the silanol hydrolysis product, 3-(trihydroxysilyl)propanethiol.

A stepwise testing strategy is proposed to address the requirements of the ECHA decision letter (TPE-D-2114432420-65-01/F). Please refer to the attachment in IUCLID Section 13. This read-across is retained as an interim measure to calculate a PNEC and support the existing chemical safety assessment until new evidence becomes available.

Key value for chemical safety assessment

Fresh water invertebrates

Fresh water invertebrates
Effect concentration:
6.7 mg/L

Additional information

There are no reliable short-term invertebrate toxicity data available for 3-(triethoxysilyl)propanethiol (CAS 14814-09-6), therefore good quality data for an appropriate structural analogue, 3-(trimethoxysilyl)propane-1-thiol (CAS 4420-74-0) have been read across. Both substances hydrolyse to the same hydrolysis product, 3-(trihydroxysilyl)propanethiol. Both substances have hydrolysis half-lives which indicate that, under conditions relevant to ecotoxicity assessment, both will partially hydrolyse to 3-(trihydroxysilyl)propanethiol over the course of the test. The other hydrolysis products are ethanol and methanol respectively; the properties of these substances are well characterised. Methanol is non-toxic to the environment and it is considered unlikely that its presence significantly affected the results of the test performed with the parent substance.

 

A 48-hour EC50 value of 6.7 mg/L has been determined for the effects of 3-(trimethoxysilyl)propane-1-thiol (CAS 4420-74-0) on the mobility of Daphnia magna based on nominal concentrations of the substance (Hüls, 1995). The result was obtained under static test conditions. 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 the concentration of the hydrolysis product, 3-(trihydroxysilyl)propanethiol, by applying a molecular weight correction (MW of silanol = 154.26 / MW of parent = 196.34) * (concentration of parent = 6.7 mg/L) = 5.3 mg/L.

The study was considered to be reliability 1 (reliable without restrictions)