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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:
1994-05-24 to 1994-05-27
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
Guideline study without restrictions. The study was conducted according to the appropriate OECD test guideline, and in compliance with GLP.
Qualifier:
according to
Guideline:
EU Method C.3 (Algal Inhibition test)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Details on sampling:
- Concentrations: 34, 57, 95, 161, 284, 473 and 851 mg/L.

- Sampling method: Samples of the test media were taken for analyis at the start and end of the test.

- Sample storage conditions before analysis: not described
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: Nominal test concentrations of 34, 57, 95, 161, 284, 473 and 851 mg/L were prepared by dilution of a 1000 mg/l nominal concentration stock solution. The stock solution was prepared by stirring for 18 h followed by filtration and contained 432 mg/l of dissolved organic carbon equivalent to 945 mg/L of test substance.

- Controls: Dilution water (algal growth medium)
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM

- Strain: CHODAT (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. The cell concentration is determined from a calibration curve of absorbance at 685 nm versus cell density.
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Hardness:
not reported
Test temperature:
24+/-2ºC
pH:
8.4-8.5 at start of test

7.9-9.6 at end of test
Dissolved oxygen:
not reported
Salinity:
not applicable
Nominal and measured concentrations:
Nominal concentrations: 0(Control), 34, 57, 95, 161, 284, 473 and 851 mg/L.

Measured concentrations were within 20% of nominal. The results are therefore reported with reference to nominal concentrations.
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: 1050000 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:

- 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:
NOEC
Effect conc.:
ca. 57 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
but exposure is to hydrolysis products
Basis for effect:
growth rate
Remarks:
and biomass
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
137 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:
EC10
Effect conc.:
99 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
but exposure is to hydrolysis products
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
437 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:
EC50
Effect conc.:
262 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Remarks:
but exposure is to hydrolysis products
Basis for effect:
biomass
Details on results:
- Exponential growth in the control (for algal test): yes

- Any stimulation of growth found in any treatment: no
Reported statistics and error estimates:
The area under the growth curve (biomass) and growth rate parameters were calculated from the cell concentration data in accordance with the description of the test method.

The EC50 values were determined by probit analysis (Cavalli-Sforza, L. (1972). Biometrie. Gustav Fischer Verlag, Stuttgart, pp. 212). The NOEC was determined by 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  80000  250000  1050000
 34  20000  80000  280000  1010000
 57  20000  80000  270000  990000
 95  20000  80000  250000  860000
 161  20000  80000  230000  650000
 284  20000  70000  160000  450000
 473  20000  50000  100000  120000
 851  20000  40000  40000  40000

Table 2. Results of analysis of test media

 Nominal test substance concentration (mg/L)  Measured concentration at start of test (mg/L)  Measured concentration at end of test (mg/L)

 Concentration used as the basis for assessing effects (mg/L)

 34 36 33 34 
 57 60 56 57
 95 93 85 95
 161 168 152 161
 284 295 273 284
 473 462 420 473
 851 923 739 851
Validity criteria fulfilled:
yes
Conclusions:
A 72-hour EC50 value of 437 mg/L and NOEC of approximately 57 mg/L have been determined for the effects the test substance on growth rate of Scenedesmus subspicatus. The results are interpreted with reference to nominal concentrations of the test substance. However it is likely that the test organisms were predominantly exposed to the hydrolysis products of the substance during the study, and not the parent compound. This is because the half-life of CAS 18395-30-7 is approximately 20-30 hours, the test media preparation included a stirring of 18 h and the exposure regime was static.

Description of key information

72 hour ErC50 437 mg/l ErC10 137 mg/l and NOEC 57 mg/l (nominal concentration) (EU Method C.3 (Algal Inhibition test)), read-across from an analogous/structurally related substance, 3-chloropropyl(diethoxy)methylsilane (CAS 13501-76-3). The observations in this study are attributed to the exposure of test organisms to the hydrolysis products in the test system. The result may be expressed in terms of concentration of the hydrolysis product: 72 hour ErC50 321 mg/l and ErC10 101 mg/l as 3-chloropropyl(methyl)silanediol.

Key value for chemical safety assessment

EC50 for freshwater algae:
321 mg/L
EC10 or NOEC for freshwater algae:
101 mg/L

Additional information

No data are available for toxicity of the registration substance, 3-chloropropyl(dimethoxy)methylsilane (CAS 18171-19-2), to algae. However, data are available from the related substance 3-chloropropyl(diethoxy)methylsilane (CAS 13501-76-3). Both substances have the same silanol hydrolysis product, 3-chloropropyl(methyl)silanediol. The other hydrolysis products are hydrochloric acid and ethanol, respectively. In the test with 3-chloropropyl(diethoxy)methylsilane (CAS 13501-76-3), the observations are attributed to the exposure of test organisms to 3-chloropropyl(methyl)silanediol in the test system. There is no basis to expect that ethanol significantly influenced the results of the tests. The toxicity of ethanol is discussed further in Section 7.0 of the CSR and the RAAF report for ecotoxicity attached in Section 13 of IUCLID.

A 72 hour ErC50 value of 437 mg/l, ErC10 value of 137 mg/l and NOEC value of approximately 57 mg/l have been determined for the effects of 3-chloropropyl(diethoxy)methylsilane (CAS 13501-76-3) on growth rate of Desmodesmus subspicatus. The results have been reported in terms of nominal concentrations of parent substance. Due to the hydrolysis rate of the test substance (9.5 hours at pH 7) and test media preparation methods (stirring for 18 hours prior to addition of test organisms), it is very likely that the test organisms were exposed to the hydrolysis products 3-chloropropyl(methyl)silanediol and ethanol. The results may be expressed in terms of concentration of the hydrolysis product, 3-chloropropyl(methyl)silanediol, by applying a molecular weight correction: (MW of silanol = 154.67 / MW of parent = 210.78) * [CONCENTRATION OF PARENT = EC50 437 mg/l and EC10 137 mg/l] = ErC50 321 mg/l and ErC10 101 mg/l.