Triethoxy(3,3,4,4,5,5,6,6,7,7,8,8,8-tridecafluorooctyl)silane

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:

1997-05-13 to 1997-05-16

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Deviations:

not specified

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

- Concentrations: 0 (Control), 6.7, 13.4, 33.4 and 66.8 mg/L and test stock solution.

- Sampling method: A series of concentrations of the test substance in distilled, deionised water were prepared to assess their stability. Their carbon content was measured initially and then again after 24, 48 and 72 hours. The concentration of the freshly prepared stock solution (in algal growth medium) used to prepare the test media was also determined.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: Test substance sparingly soluble in water. 1 g/L of VE water was stirred for 18 h and then filtered. This solution served as test substance solution.

- Controls: Not explicitly stated but appears to have used dilution water (VE water)

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM

- Strain: CHODAT (86.81 SAG)

- Source: Institute for water, soil and air hygeine, Berlin and thereafter own culture

- Age of inoculum (at test initiation): 3 days

- Method of cultivation: Three days before the beginning of test, a preculture was obtained by transfer inoculation from a stock culture. The test cultures were inoculated from the preculture to a cell density of ca. 20,000 cells/ml.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

23.5 to 23.7ºC in a temperature controlled room.

pH:

beginning of test: 7.6 to 8.0

end of test: 9.4 to 9.6

A large increase in pH values was observed in some test solutions and in the Controls. Growth was not influenced by this.

Dissolved oxygen:

no data

Salinity:

not applicable

Nominal and measured concentrations:

Nominal test substance loading rate used to prepare stock solution: 1000 mg/L

Before the test started, the Dissolved Organic Carbon (DOC) concentration of the stock solution was measured. The test concentrations were then based on the concentration of the stock solution. Nominal test substance concentrations used were 0, 0.09, 0.20, 0.40, 0.87, 1.78, 3.56, 7.11 mg/L DOC.

In the stability study the measured concentrations were stable within +/-20% over the course of the test.

The test results are interpreted with reference to the nominal DOC concentrations and the test substance loading rate used in the preparation of the stock solution.

Details on test conditions:

TEST SYSTEM

- Test vessel: The algae were cultured in sterile, ventilated Erlenmeyer flasks under lights.

- Initial cells density: 20000 cells/mL

- Control end cells density: 1190000 cells/mL

- No. of vessels per concentration (replicates): 5

- No. of vessels per control (replicates): 8

TEST MEDIUM / WATER PARAMETERS

- Source/preparation of dilution water: VE water used, no further information

- Culture medium different from test medium: no data

- Intervals of water quality measurement: start and end of test

OTHER TEST CONDITIONS

- Sterile test conditions: yes

- Adjustment of pH: no

- Photoperiod: Continuous 8000 lux

EFFECT PARAMETERS MEASURED: growth rate

- Determination of cell concentrations: by spectrophotometer (685nm) at 0, 24, 48 and 72h.

Reference substance (positive control):

no

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 7.1 mg/L

Nominal / measured:

nominal

Conc. based on:

other: hydrolysis products

Basis for effect:

growth rate

Remarks on result:

other: based on measured DOC concentration

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

>= 7.1 mg/L

Nominal / measured:

nominal

Conc. based on:

other: hydrolysis products

Basis for effect:

growth rate

Remarks on result:

other: based on measured DOC concentration

Duration:

72 h

Dose descriptor:

EL50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

but exposure is to hydrolysis products

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOELR

Effect conc.:

>= 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Remarks:

but exposure is to hydrolysis products

Basis for effect:

growth rate

Details on results:

- Exponential growth in the control: yes

- Observation of abnormalities: no observations

- Any stimulation of growth found in any treatment: there was some slight stimulation of growth at concentrations of 1.78 mg/L and higher.

Reported statistics and error estimates:

None of the test concentrations reduced growth rate. A definitive EC50 could therefore not be calculated.

The NOEC was determined by a 't' test.

Table 1. Test results

Nominal test substance concentration (mg/L)	Mean cell concentration at start of test (cells/mL)	Mean cell concentration after 24 hours (cells/mL)	Mean cell concentration after 48 hours (cells/mL)	Mean cell concentration after 72 hours (cells/mL)
0 (Control)	20000	120000	440000	1190000
0.09	20000	120000	430000	1140000
0.20	20000	120000	420000	1110000
0.40	20000	110000	390000	1080000
0.87	20000	110000	440000	1190000
1.78	20000	110000	450000	1250000
3.56	20000	110000	430000	1290000
7.11	20000	110000	470000	1370000

The highest nominal test concentration (7.1 mg/L) did not inhibit growth of the algal cultures.

Table 2. Results of analysis of test media and stability test media

Nominal test substance concentration (mg/L)	Measured concentration at start (mg/L)	Measured concentration after 24 h (mg/L)	Measured concentration after 48 h (mg/L)	Measured concentration after 72 h (mg/L)	Mean measured concentration (mg/L)
66.8	66.8	54.8	56.3	53.7	57.9
33.4	31.2	28.0	27.4	26.8	28.4
13.4	13.3	11.3	13.1	12.2	12.5
6.7	6.8	5.1	5.2	7.0	6.0
7.1 (Test medium stock solution. Initial nominal loading rate of 1000 mg/L)	7.9	-	-	-	-

Validity criteria fulfilled:

yes

Conclusions:

A 72-hour EC50 value of >7.1 mg/L and a NOEC of ≥7.1 mg/L have been determined for the effects of the test substance on growth rate of Scenedesmus subspicatus based on measured concentrations of Dissolved Organic Carbon (DOC) in the test media. The test medium was prepared at an initial loading rate of 1000 mg/L of the substance and was subsequently filtered before introducing the test organisms. The test substance hydrolyses in water and it is likely that the test organisms were primarily exposed to the hydrolysis products of the substance.

Description of key information

Short-term toxicity to aquatic algae: 72-hour E_rC₅₀ >7.1 mg/l and a NOE_rC of ≥7.10 mg/l (measured) (highest concentration tested) (EU Method C.3 (Algal Inhibition test)).

Additional information

A 72-hour E_rC₅₀ value of >7.1 mg/l and NOE_rC of ≥7.1 mg/l (measured) (highest concentration tested) have been determined for the effects of [2 -(perfluorohexyl)ethyl]triethoxysilane (CAS 51851-37-7, EC 257-473-3) on growth rate of Scenedesmus subspicatus (new name: Desmodesmus subspicatus) based on mean measured initial Dissolved Organic Carbon (DOC) concentration. The test medium was prepared at an initial loading rate of 1000 mg/l of the substance and was subsequently filtered before introducing the test organisms.

As the extremely low water solubility of the test substance will limit hydrolysis, it is likely that the test organisms were exposed to parent substance.

Refer to IUCLID Section 6.1 and Section 7.1 of the CSR for discussion of the surface active properties of the parent substance, silanol hydrolysis product and condensation products and further discussion of the hydrolysis rates of the parent substance.