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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:
experimental study
Adequacy of study:
key study
Study period:
1993-06-01 to 1993-06-04
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Version / remarks:
no date or version given
GLP compliance:
yes
Analytical monitoring:
yes
Details on sampling:
The dissolved organic carbon analysis (DOC) concentration of the stock solution used to prepare the test media was determined and used as the basis for setting the treatment levels.
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: A stock solution was made by dissolving the test substance to obtain 1 g/l concentration in water and stirred for 18 h. The solution was filtered and served as the initial solution for testing.
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: 7.6 - 7.8

End of test: 7.6 - 8.5
Dissolved oxygen:
No data
Salinity:
Not applicable
Nominal and measured concentrations:
The measured DOC concentration in the stock solution was 356 mg/L corresponding to 981 mg/L of the test substance.

Nominal concentrations based on measured concentrations in stock solution: 0 (Control), 59, 98, 167, 294, 491, and 883 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:1150000 cells/ml (Test 2), 970000 cells/ml (Test 4)

- 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: Determination of cell concentrations after 24, 48 and 72 hours by spectrophotometer (absorption at 685 nm)

TEST CONCENTRATIONS

- Spacing factor for test concentrations: 1.7-1.8
Reference substance (positive control):
no
Key result
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
167 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
cell number
Key result
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
514 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 833 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
241 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 883 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Details on results:
- Exponential growth in the control: yes
- Any stimulation of growth found in any treatment: yes, in the 98 mg/l treatment stimulation of growth was found at 24, 48 and 72-hour measurements
Reported statistics and error estimates:
The ECx values were determined by Probit analysis. The NOEC was determined by visual examination of the raw data.

Table 1. Test results

 Nominal concentration (mg/L)  Cell concentration at start of test (cells/ml)   Cell concentration after 24 hours (cells/ml)   Cell concentration after 48 hours (cells/ml)  Cell concentration after 72 hours (cells/ml) 
 0 (Control)  20000  70000  280000  790000
 59  20000  70000  270000  770000
 98  20000  70000  300000  850000
 167  20000  70000  260000  730000
 294  20000  60000  240000  650000
 491  20000  80000  240000  590000
 883  20000  80000  210000  390000

72 h EbC50: >883 mg/l

72 h EbC10: 241 mg/l

Validity criteria fulfilled:
yes
Conclusions:
A 72-hour EC50 value of >833 mg/L and a NOEC of 167 mg/L have been determined for the effects of the test substance on growth rate of Scenedesmus subspicatus (new name: Desmodesmus subspicatus). It is likely that the test organisms were predominantly exposed to the hydrolysis products of the substance.

Description of key information

72-hour EC50 >833 mg/l and NOEC 167 mg/l (measured based on DOC in the stock solution) (OECD guideline 201). The observations in this study are attributed to the exposure of test organisms to the silanol hydrolysis product, (3-chloropropyl)silanetriol, in the test system. The EC50 and NOEC are equivalent to >657 and 132 mg/l, respectively, when expressed in terms of the silanol hydrolysis product.

Key value for chemical safety assessment

Additional information

A 72-hour EC50 value of >833 mg/l and an EC10 of 514 mg/l (measured) have been determined for the effects of the registered substance (3-chloropropyl)trimethoxysilane (CAS 2530-87-2) on growth rate of Scenedesmus subspicatus . A 72-hour NOEC value of 167 mg/l has also been derived for the effects of the test substance on cell number of Scenedesmus subspicatus (Hüls, 1993). 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 nominal test concentrations are supported by DOC analysis of the stock solution. The results may be expressed in terms of concentration of the silanol hydrolysis product, (3-chloropropyl)silanetriol, by applying a molecular weight correction: (MW of silanol = 156.64 / MW of parent = 198.72) * >833 mg/l = EC50, EC10 and NOEC values of >657, 405 and 132 mg/l, respectively.

 

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. There was no mention of undissolved material (parent substance or precipitated products) 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.