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Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Reference
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
migrated information: read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Study period:
1994-11-22 to 1994-11-25
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Remarks:
The study was conducted according to an appropriate OECD test guideline, and in compliance with GLP, and was considered to be reliability 1 (reliable without restrictions). Read across to the registered substance is considered scientifically justified; the read across is considered to be reliability 2.
Qualifier:
according to
Guideline:
EU Method C.3 (Algal Inhibition test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Details on sampling:
Test substance concentration determined in the stock solution used to prepare the test media.

Test substance concentration was determined in all treatments at the start and end of the test.
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: Test media prepared by dilution of a 1000 mg/L stock solution prepared by mixing for 18 h followed by filtration. TOC concentration of stock solution determined.
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM

- Strain: 86.81.SAG

- Source (laboratory, culture collection): Institute for Water, Ground and Air Hygiene, Berlin (Germany)

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

- Method of cultivation: 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 +/-2ºC
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 concentrations at start of test in treatments: 99, 161, 311, 550 and 975 mg/L

Measured concentrations at end of test in treatments: 84, 148, 260, 475 and 1000 mg/L

Concentrations used as the basis for assessing effects: Control, 101, 172, 304, 507 and 913 mg/L
Details on test conditions:
TEST SYSTEM

- Test vessel:

- Type: open Erlenmeyer flasks

- Material: glass

- Aeration: none

- Initial cells density: 20000 cells/mL

- Control end cells 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

EFFECT PARAMETERS MEASURED (with observation intervals if applicable):

- Determination of cell concentrations: spectrophotometer (absorption at 685 nm)

- Other:

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 (for algal test): yes

- Observation of abnormalities (for algal test): 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.

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:
A 72-h EC50 value of >913 mg/L and NOEC of ≥913 mg/L have been determined for the effects of the test substance on growth rate of Desmodesmus subspicatus (tested as Scenedesmus subspicatus) based on nominal concentrations of the substance. It is likely that the test organisms were exposed to the hydrolysis products of the substance.

Description of key information

Toxicity to aquatic algae: 72 hour ErC50 >913 mg/l and NOEC 913 mg/l (mean measured DOC) (highest concentration tested) (EU Method C.3 (Algal Inhibition test)), read-across from an analogous/structurally related substance, trimethoxy(propyl)silane (CAS 1067-25-0). The observations in this study are attributed to the exposure of test organisms to the hydrolysis products in the test system.

Key value for chemical safety assessment

Additional information

There are no reliable toxicity to aquatic algae data available for trichloro(propyl)silane (CAS 141-57-1), therefore good quality data for an appropriate structural analogue, trimethoxy(propyl)silane (CAS 1067-25-0), have been read across. Both substances share the same silanol hydrolysis product, propylsilanetriol. The other hydrolysis products are hydrochloric acid and methanol, respectively. In the test with trimethoxy(propyl)silane (CAS 1067-25-0), the observations are attributed to the exposure of test organisms to propylsilanetriol in the test system. There is no basis to expect that methanol significantly influenced the results of the test. The toxicity of methanol is discussed further in the ecotoxicological information overview endpoint summary (additional information).

 

A 72-hour ErC50 value of >913 mg/l and a NOEC value of913 mg/l (mean measured DOC) (highest concentration tested) have been determined for the effects of trimethoxy(propyl)silane (CAS 1067-25-0) on growth rate of Desmodesmus subspicatus. In view of the test media preparation method and exposure regime it is likely that the test organisms were exposed predominantly to the hydrolysis products of the tested substance. The test concentrations are reported in terms of DOC and are therefore not further adjusted in terms of concentration of parent corrected to concentration of silanol.

 

Above a concentration of approximately 1000 mg/l, dimeric / oligomeric, cyclic or cross-linked condensation products could potentially form over time in the aqueous test media. No evidence of undissolved material (parent substance or precipitated products) is indicated in the study report for this test. 

 

Refer to the discussion in the Section 6 endpoint summary (Section 7.0 of CSR) for further discussion of the approach to chemical safety assessment for this registration substance, and justification for read-across used.