2-Oxa-7-thia-3,8-disiladecane, 3-methoxy-3,8,8,9,9-pentamethyl-

Toxicity to aquatic algae and cyanobacteria

Administrative data

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

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:

2009

Materials and methods

Test guideline

Test guideline 1

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

no

Test guideline 2

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Specific details on test material used for the study:

Details on properties of test surrogate or analogue material (migrated information):
Pre-study solubility work indicated that it was not possible to obtain a testable solution of the test material using traditional methods (e.g. ultrasonication, high-shear mixing). The test material is poorly water soluble and known to rapidly degrade in water to give t-butyldimethylsilanol and 3-(dimethoxymethylsilyl)-propane-1-thiol. Due to the volatility of 3-(dimethoxymethylsilyl)-propane-1-thiol, chemical analysis of the test preparations was conducted for t-butyldimethylsilanol alone.

Sampling and analysis

Analytical monitoring:

yes

Details on sampling:

Nominal concentrations of 6.25, 12.5, 25, 50, and 100% v/v saturated solution
Samples taken at 0h and 72h for analysis
Concentrations of t-butyldimethylsilanol at 0h were 2.5, 5.1, 10, 22, and 51mg/l respectively. At 72h, these had reduced to 0.434, 0.61, 0.974, 1.31, and 2.79mg/l respectively.

Test solutions

Vehicle:

no

Details on test solutions:

Test solutions were prepared by stirring 500mg of test material in 1l culture medium at approximately 7500rpm for 30 minutes. Undissolved test material was removed via filtration through a 0.2µm Sartorius Sartopore filter, with the initial 500ml being discarded to precondition the filter. A sample was immediately taken for chemical analysis. The saturated solution was serially diluted to prepare the remainder of the test series.

Test organisms

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

Strain: CCAP 276/20.
Liquid cultures of the test organism were obtained from the Culture Collection of Algae and Protazoa (CCAP), Dunstaffnage Marine Laboratory, Oban, Argyll, Scotland.
Master cultures were maintained in the laboratory by the periodic replenishment of the culture medium.
The master cultures were maintained in the laboratory under constant aeration and constant illumination at 21±1°C.

Master culture was added to approximately 100ml of culture media in conical flasks to give an initial cell density of 10³/ml. The flasks were plugged with polyurethane foam stoppers and kept under constant agitation by orbital shaker (100-150rpm) and constant illumination at 24±1°C until the cell density was approximately 10-100x10³/ml.

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Post exposure observation period:

none

Test conditions

Test temperature:

24±1°C

pH:

7.3-7.6 (0h), 7.7-7.9 (72h)

Nominal and measured concentrations:

Nominal concentrations: 6.25, 12.5, 25, 50, and 100%
Measuerd concentrations of t-butyldimethylsilanol at 0h were 2.5, 5.1, 10, 22, and 51mg/l respectively. At 72h, these had reduced to 0.434, 0.61, 0.974, 1.31, and 2.79mg/l respectively.

Reference substance (positive control):

yes

Remarks:

potassium dichromate

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 100 other: %

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Effect concentrations 2

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 100 other: %

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

cell number

Results with reference substance (positive control):

EC50 (growth rate 0-72h) = 0.52mg/l (95% CL 0.43-0.62mg/l)
EC50 (yield 0-72h) = 0.29mg/l (95% CL 0.25-0.33mg/l)