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Diss Factsheets

Ecotoxicological information

Toxicity to aquatic algae and cyanobacteria

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Administrative data

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:
1993
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
EU Method C.3 (Algal Inhibition test)
Version / remarks:
Cited as Directive 92/69/EEC, C.3
GLP compliance:
yes
Analytical monitoring:
yes
Details on sampling:
The Dissolved Organic Carbon (DOC) concentration of the stock solution used to prepare the test media was determined.
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION

- Method: The test substance was added to the dilution medium at 1.2 g/L and stirred for 18 hours. After that the solution was filtered and the DOC determined.  The Total Organic Carbon (TOC) infrared analyzer was used. The DOC of the solution was 588 mg/L, this corresponds to a test material concentration of 1247 mg/L. 
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 +/-1ºC
pH:
8.2-8.4 at start of test

7.6-8.9 at end of test
Dissolved oxygen:
Not reported
Salinity:
Not applicable
Nominal and measured concentrations:
Nominal test concentrations (based on measured DOC concentration in stock solution converted to the equivalent test substance concentration): 0 (Control), 75, 125, 212, 374, 624 and 1122 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): Algal cell counts were made photometrically at 0, 24, 48 and 72 hrs.

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

TEST CONCENTRATIONS

- Spacing factor for test concentrations: 1.7-1.8
Reference substance (positive control):
no
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
75 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: biomass and growth rate
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
79 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
304 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
136 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
611 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Details on results:
- Exponential growth in the control (for algal test): yes
Reported statistics and error estimates:
EC50 values were determined by Probit Analysis

Table 1. Test results

 Nominal concentration (mg/L)  Nominal 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)  Percentage reduction in biomass at end of the test*  Percentage reduction in 0 -72 -hour growth rate*
 0 (Control)  20000  60000  220000  670000  -  -
 75  20000  60000  220000  690000  -1.8  -0.8
 125  20000  60000  180000  490000  23  9.0
 212  20000  50000  150000  290000  47.8  23.9
 374  20000  50000  140000  180000  59.3 37.5 
 624  20000  50000  110000  140000  68.1 44.6 
 1122  20000  140000  320000  410000 -8.8   14

*A negative sign (-) indicates that biomass or growth rate was higher than in the Control.

Validity criteria fulfilled:
yes
Conclusions:
A 72-hour ErC50 value of 611 mg/L and NOErC of 75 mg/L have been determined for the effects of the test substance on growth rate of Scenedesmus subspicatus (new name: Desmodesmus subspicatus), based on nominal concentrations. Due to the rapid hydrolysis half life of the substance. is likely that the test organisms were primarily exposed to the hydrolysis products of the substance. These results are equivalent to ErC50 231 mg/L and NOErC 28 mg/L when expressed in terms of the silanol hydrolysis product.

Description of key information

Toxicity to aquatic algae: 72 hour ErC50 611 mg/L, ErC10 136 mg/L and NOEC 75 mg/L (nominal concentration based on measured DOC of stock solution) (EU method C.3). The ErC50 is equivalent to 231 mg/L, the ErC10 is equivalent to 51 mg/L and the NOEC is equivalent to 28 mg/L when expressed in terms of the silanol hydrolysis product.

The reported 72 hour EC50 and EC0 for 2-methoxyethanol for freshwater algae are 25,500 mg/L and 8,900 mg/L for Pseudokirchneriella subcapitata, respectively.

Key value for chemical safety assessment

EC50 for freshwater algae:
231 mg/L
EC10 or NOEC for freshwater algae:
28 mg/L

Additional information

A 72-h ErC50 value of 611 mg/L, ErC10 of 136 mg/L and NOEC of 75 mg/L (nominal) have been determined for the effects of tris(2-methoxyethoxy)(vinyl)silane on growth rate of Scenedesmus subspicatus (new name: Desmodesmus subspicatus). In view of the test media preparation method/exposure regime it is likely that the test organisms were exposed predominantly to the hydrolysis products of the tested substance.

The results may be expressed in terms of concentration of the hydrolysis product, vinylsilanetriol, by applying a molecular weight correction:

(MW of silanol = 106.15 / MW of parent = 280.40) * 611 mg/l = ErC50 231 mg/L,

(MW of silanol = 106.15 / MW of parent = 280.40) * 136 mg/l = ErC10 51 mg/L

and (MW of silanol = 106.15 / MW of parent = 280.40) * 75 mg/l = NOEC 28 mg/L.

This study was assigned a reliability score of 1 because it is a guideline study (EU Method C.3) conducted in accordance with GLP.

A 72-hour EC50 and NOEC of 10,000 mg/l and 4,100 mg/l (nominal), respectively, have been determined for the effects of 2-methoxyethanol on the growth rate ofPseudokirchneriella quadricauda,in a reliable study conducted according to ISO water quality guideline 8692 (Devillers et al., 2002).

Refer to IUCLID Section 6 endpoint summary for further discussion of the approach to chemical safety assessment for this registration substance.