Trisiloxane, 3-ethyl-1,1,1,3,5,5,5-heptamethyl-

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2005-11-30 to 2006-01-09

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Version / remarks:

1992

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)

Version / remarks:

April 2004

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

- Concentrations: duplicate samples at test start and test end of all test concentrations and the control
- Sample storage conditions before analysis: stored in refrigerator (4 +/- 4°C)

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: 300 mg of the test item were dissolved in 3000 mL test water by intense stirring for 6 days in a closed system (to prevent evaporation of the test item from the test media) to obtain a saturated solution of the poorly water soluble test item in the test media. Adequate volumes of this test medium were diluted with test water to prepare the test media.

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM
- Strain: No. 86.81 SAG
- Source (laboratory, culture collection): Sammlung von Algenkulturen, Pflanzenphysiologisches Institut der Universität Göttigen, 37073 Göttingen, Germany
- Method of cultivation: Algae were cultivated at the testing facility under standardized conditions according to the test guidelines.

ACCLIMATION
- Acclimation period: 3 days
- Culturing media and conditions (same as test or not): yes
- Any deformed or abnormal cells observed: No.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Hardness:

24 mg/L as CaCO3

Test temperature:

23°C

pH:

8.0 - 8.2 at test start
9.7 - 10.1 at test end

Nominal and measured concentrations:

Nominal: 0.95, 3.05, 9.77, 31.25 and 100 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: Erlenmeyer flasks aof 50 mL volume with 50 mL test medium
- Initial cells density: 5000 cells/mL
- Control end cells density: 47249 * 10000 cells/mL
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6

GROWTH MEDIUM
- Standard medium used: yes

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: spectrophotometer

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

31.25 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

31.25 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

biomass

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Details on results:

The 72-hour EC50 was >100.0 mg test item/L for biomass and growth rate, resp. The EC10 values were calculated to be >100 mg test item/L for biomass and growth rate, respectively.
The 72-hour NOEC was determined to be 31.25 mg test item/L, based on effects observed at 100 mg/L.

Microscopic examination after 72 hours test period did not reveal differences between exposed and control algae up to and including 100 mg/L.

Analytical verification of test item concentrations:

Freshly prepared test media were analysed. Measured test concentration in the samples of 0.95 to 9.77 mg test item/L were below the limit of detection (0.1 mg/L) and below the limit of quantification (0.2 mg/L) in case of test media with a concentration of 31.25 mg test item/L. In case of the 100 mg/L treatment sample 0.2 % of the nominal concentration was found. Since all measured concentrations were below or close to the LOD/LOQ no further samples were analysed.

 

Validity criteria fulfilled:

yes

Conclusions:

The 72h EC50 (growth rate and biomass) of the test item to Desmodesmus subspicatus was found to be > 100 mg/L (loading rate).

Description of key information

The 72h EC₅₀ (growth rate and biomass) of 3-ethylheptamethyltrisoloxane to Desmodesmus subspicatus was found to exceed 100 mg/L (loading rate).