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Ecotoxicological information

Short-term toxicity to aquatic invertebrates

Administrative data

Endpoint:
short-term toxicity to aquatic invertebrates
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: Study conducted at a GLP-accredited testing facility

Data source

Reference
Reference Type:
study report
Title:
Unnamed
Year:
2007

Materials and methods

Test guidelineopen allclose all
Qualifier:
according to
Guideline:
OECD Guideline 202 (Daphnia sp. Acute Immobilisation Test)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.2 (Acute Toxicity for Daphnia)
Deviations:
no
GLP compliance:
yes (incl. certificate)

Test material

Reference
Name:
Unnamed
Type:
Constituent
Type:
Constituent
Details on test material:
The test material was not 2-oxa-7-thia-3,8-disiladecane, 3,3-dimethoxy-8,8,9,9-tetramethyl- (CAS RN 1128026-41-4) but 2-oxa-7-thia-3,8-disiladecane, 3-methoxy-3,8,8,9,9-pentamethyl- (CAS RN 927395-20-8). Both substances are poorly soluble in water and are rapidly hydrolysed to give t-butyldimethylsilanol and either 3-(trimethoxymethylsilyl)-propane-1-thiol or 3-(dimethoxymethylsilyl)-propane-1-thiol respectively.

Both 3-(trimethoxymethylsilyl)-propane-1-thiol and 3-(dimethoxymethylsilyl)-propane-1-thiol volatalise from the culture medium, meaning that effectve exposure is to the same hydrolysis product in both cases, t-butyldimethylsilanol.

Analytical purity: 99.7% (gas chromatography)
Specific details on test material used for the study:
Details on properties of test surrogate or analogue material (migrated information):
Preliminary chemical analysis showed the test material to be poorly soluble in water and to rapidly degrade in the test medium, with a half-life of approximately 24 minutes. The degradation product was also unstable in the test medium, with none detected after approximately 8 hours. Consequently, in the definitive test the analysis of the test preparations was based on total organic carbon (TOC).

Sampling and analysis

Analytical monitoring:
yes

Test solutions

Vehicle:
no
Details on test solutions:
Test solutions were prepared by stirring 1000mg of test material in reconstituted water at approximately 7500rpm for approximately 40 minutes. The volume was adjusted to 2l to give a 500mg/l stock solution. Undissolved test material was removed via filtration through a 0.2µm Sartorius Sartopore filter, with the initial 500ml being discarded to precondition the filter. The solution was then left to stand for 24h to produce a saturated solution with a nominal concentration of 77mg/l (based on TOC analysis at 0h). The saturated solution was serially diluted to prepare the remainder of the test series.

Test organisms

Test organisms (species):
Daphnia magna
Details on test organisms:
First instar animals derived from in-house laboratory cultures.
Adults were maintained in polypropylene vessels containing ca. 2l reconstituted water and a temperature-controlled room at ca. 20°C
Lighting cycle: 16h/8h light/dark with 20 minute dawn and dusk transition periods.
Each culture was fed daily with algae (Chlorella sp.)
Culture conditions ensured that reproduction was by parthogenesis
Gravid adults were isolated the day before initiation of the test, such that the young daphnids produced overnight were less than 24h old
The young were removed from the cultures and used for testing
Diet and diluent water were considered not to contain any contaminant that would affect the integrity or outcome of the study.

Study design

Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
48 h
Post exposure observation period:
None

Test conditions

Hardness:
250mg/l (as CaCO3, theoretical)
Test temperature:
20.3-20.9°C
pH:
8.0-8.1
Dissolved oxygen:
8.1-8.8mg O2/l
Salinity:
ot applcable
Nominal and measured concentrations:
nominal: 0, 0.77, 1.4, 2.5, 4.3, 7.7, 14, 25, 43, and 77mg/l
measured (0h, as TOC): <1, <1, <1, <1, 1.77, 3.27, 6.01, 10.73, 19.29, and 34.10 mg C/l
measured (0h, as parent test material): NQ, NQ, NQ, NQ, 3.62, 6.68, 12.3, 21.9, 39.4, and 69.7mg/l
measured (48h, as TOC): <1, <1, <1, <1, 1.30, 2.79, 4.32, 9.20, 17.06, 30.62 mg C/l
measured (48h, as parent test material): NQ, NQ, NQ, NQ, 2.66, 5.70, 8.83, 18.8, 34.9, 62.6mg/l

NQ: not quantifiable, below the limit of quantitation (1mg C/l)
Details on test conditions:
250ml glass jars containing approx. 200ml of test solution. 10 daphnids were placed in each test solution and control at random. Duplicate vessels were used for each test and control group
Vessels were covered to reduce evaporation and maintained in a temperature-controlled room. Lighting cycle: 16h/8h light/dark with 20 minute dawn and dusk transition periods
Daphnids were not fed during the treatment period and the test vessels were not aerated. Test preparations were not renewed during the exposure period.
Vessels were gently agitated at 24h and 48h. Daphnids were considered to be immobilised if they were unable to swim for approximately 15 seconds after agitation.

TEST MEDIUM
Reconstituted water was prepared from deionised water (conductivity <5 µS/cm) to which 25ml of the following stock solutions were added to each litre (final volume):
calclium dichloride dihydrate 11.76g/l
magnesium sulphate heptahydrate 4.93 g/l
sodium bicarbonate 2.59g/l
potassium chloride 0.23g/l

The reconstituted water had a pH of 7.8±0.2, adjusted with HCl or NaOH as necessary. It was aerated until the dissolved oxygen concentration approximated that or air saturation.
Reference substance (positive control):
yes
Remarks:
potassium dichromate

Results and discussion

Effect concentrationsopen allclose all
Duration:
24 h
Dose descriptor:
EC50
Effect conc.:
87 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Remarks on result:
other: 95% CL = 59-210mg/l
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
14 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
mobility
Remarks on result:
other: 95% CL = 11-16mg/l
Results with reference substance (positive control):
A positive control study is conducted at the laboratory approximately every six months. The EC50 at 24h was 1.2mg/l (95% CL 1.0-1.4) and at 48h was 0.85mg/l (95% CL 0.76-0.96).

Applicant's summary and conclusion

Conclusions:
The test substance is poorly soluble in water and rapidly hydrolyses. As a consequence, dilutions of a saturated solution were made and nominal concentrations compared to TOC analysis. The EC50 at 48h, based on nominal concentration, was 14mg/l (95% CL 11-16mg/l).