Trimethoxypropylsilane

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:

1994-11-22 to 1994-11-25

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:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

yes

Details on sampling:

- Concentrations: Stock solution and all treatments at the start (0 h) and end (72 h) of the test.
- Sampling method: A separate sample was prepared in the same way the test medium was prepared, but without algae and NaHCO3-nutrient solution.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: Test media were prepared by dilution of a 1000 mg/L stock solution in VE water. The stock solution was prepared by mixing for 18 h followed by filtration. The determined TOC concentration of the stock solution was 445 mg/L.

Test organisms (species):

Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)

Details on test organisms:

TEST ORGANISM
- Common name: Aquatic algae
- Strain: 86.81.SAG
- Source: Institute for Water, Ground and Air Hygiene, Berlin (Germany) and subsequent in-house breeding
- Age of inoculum (at test initiation): 3 days
- Method of cultivation: In sterile, aerated Erlenmeyer flasks on light tables. A pre-culture is produced from an original culture by super-inoculation three days before the test begins. From this culture the test cultures are inoculated at a density of about 20000 cells/ml.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Hardness:

no data

Test temperature:

24 ± 2 ºC

pH:

Start of test: 8.3 - 8.7
End of test: 8.6 - 8.7

Dissolved oxygen:

no data

Salinity:

not applicable

Nominal and measured concentrations:

Nominal concentrations: 0 (control), 101, 172, 304, 507 and 913 mg/l
Measured concentration (0 h): 0, 99, 161, 311, 550, and 975 mg/L
Measured concentration (72 h): 0, 84, 148, 260, 475 and 1000 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: Erlenmeyer flasks
- Type: Open
- Material: glass
- Aeration: none
- Initial cell density: 20000 cells/ml
- Control end cell density: 560000 cells/ml
- No. of vessels per concentration (replicates): 5
- No. of vessels per control (replicates): 8

GROWTH MEDIUM
- Standard medium used: Yes

TEST MEDIUM / WATER PARAMETERS
- Culture medium different from test medium: No
- Intervals of water quality measurement: Start and end of test

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Adjustment of pH: No
- Photoperiod: continuous
- Light intensity and quality: 8000 Lux (white light)

EFFECT PARAMETERS MEASURED:
- Determination of cell concentrations: spectrophotometer (absorption at 685 nm) at 0 h, 24 h, 48 h and 72 h

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 1.7

Reference substance (positive control):

no

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 913 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:

NOEC

Effect conc.:

>= 913 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: None reported
- Any stimulation of growth found in any treatment: No

Reported statistics and error estimates:

The were no toxic effects observed in the highest test concentrations and therefore statistical analysis of the results was not carried out.

ANALYTICAL RESULTS

The deviation of the geometric mean measured concentrations from the nominal concentration was < 20%. Therefore, it was concluded that the test item (parent compound or its hydrolysis products) remained bioavailable and did not disappear by potential biodegradation, volatilization or adsorption to the vessel. Results were thus based on nominal concentrations.

EXPERIMENTAL RESULTS

Table 1. Test results

Nominal test substance concentration (mg/l)	Mean cell density at start of test (cells/ml)	Mean cell density after 24 hours (cells/ml)	Mean cell density after 48 hours (cells/ml)	Mean cell density after 72 hours (cells/ml)
0 (Control)	20000	20000	140000	560000
101	20000	20000	160000	710000
172	20000	30000	170000	710000
304	20000	30000	200000	760000
507	20000	30000	180000	730000
913	20000	50000	220000	800000

Validity criteria fulfilled:

yes

Conclusions:

An EC50 (72 h) value of > 913 mg/L and a NOEC (72 h) of ≥ 913 mg/L were obtained for the effects of the test substance on the growth rate of Scenedesmus subspicatus based on nominal concentrations. However, it is likely that the test organisms were exposed to the hydrolysis products of the substance.

Description of key information

ErC50 (72 h) value of > 913 mg/L (nominal, EU method C3, S. subspicatus, RL1), equivalent to > 679 mg/L when expressed in terms of the silanol hydrolysis product

 

NOErC (72 h) of ≥ 913 mg/L (nominal, EU method C3, S. subspicatus, RL1), equivalent to ≥ 679 mg/L when expressed in terms of the silanol hydrolysis product

Key value for chemical safety assessment

EC50 for freshwater algae:

679 mg/L

EC10 or NOEC for freshwater algae:

679 mg/L

Additional information

A 72 h EC₅₀ of > 913 mg/l and a NOEC (72 h) of ≥ 913 mg/l were obtained for the effects of the substance on the growth rate of the algae Scenedesmus subspicatus (new name: Desmodesmus subspicatus) (EU Method C.3 (Algal Inhibition test) based on nominal concentrations.

Since the substance hydrolyses rapidly (half-life approximately 2.6 hours) to propylsilanetriol, under ecotoxicity testing conditions, the organisms were predominantly exposed to the hydrolysis product.