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Toxicity to aquatic algae and cyanobacteria

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Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Study period:
08 March 2010-11 March 2010
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
Read-across to study performed according to OECD and/or EC guidelines and according to GLP principles
Reason / purpose:
reference to same study
Qualifier:
according to
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
Deviations:
no
Qualifier:
according to
Guideline:
EU Method C.3 (Algal Inhibition test)
Deviations:
no
Qualifier:
according to
Guideline:
ISO 8692 (Water Quality - Fresh Water Algal Growth Inhibition Test with Scenedesmus subspicatus and Selenastrum capricornutum)
Deviations:
no
GLP compliance:
yes (incl. certificate)
Analytical monitoring:
yes
Details on sampling:
- Concentrations:TOC-analysis from the WAF prepared at a loading rate of 100 mg/l and the untreated control from vessels incubated without algae
- Sampling method:
Frequency at t=0 h, t=24 h and t=72 h
Volume 40 ml
Storage Samples were stored in a refrigerator until analysis.
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
Preparation of the test solutions started with loading rates prepared individually at 1.0, 10 and 100 mg/l applying 48 hours of magnetic stirring to achieve maximum dissolution in test medium. The magnetic stirring was followed by a settlement period of 2 hours. This resulted in clear and colourless solutions with a floating layer and a precipitate. The Water Accommodated Fractions (WAFs) were then collected by siphoning the water phase. The final test solutions were all clear and colourless.
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
- Common name: Pseudokirchneriella subcapitata
- Strain: NIVA CHL 1
- Source (laboratory, culture collection): In-house laboratory culture
- Age of inoculum (at test initiation): 3 days before the start of the test, cells from the algal stock culture were inoculated in culture medium at a cell density of 1 x 10E4 cells/ml.
- Method of cultivation: Algae stock cultures were started by inoculating growth medium with algal cells from a pure culture on agar. The suspensions were continuously aerated and exposed to light in a climate room at a temperature of 21-24°C.
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Hardness:
0.24mmol/l (24 mg CaCO3/l)
Test temperature:
between 22.8 and 23.6°C
pH:
At t=0 h: 7.7-8.2
At t=72 h:8.2
Salinity:
not applicable
Nominal and measured concentrations:
Nominale concentration: WAFs prepared at loading rates of 1.0, 10 and 100 mg/l
Measured concentration:During the test samples for TOC-analysis were taken from the WAF prepared at a loading rate of 100 mg/l and the untreated control. The TOC concentrations measured in the treated samples were only slightly exceeding those measured in the control samples, indicating that the actual test substance concentration was very low. The actual measured concentration was between approximately 0.3 and 0.5 mg C/l when corrected for the carbon measured in the control samples. The TOC content of Standolized linseed oil was determined to be 77.88% . Thus, the actual Standolized linseed oil concentration in solution was expected to be between 0.4 and 0.6 mg/l.
Details on test conditions:
TEST SYSTEM
- Test vessel:100 ml, all-glass, containing 50 ml of test solution
- Type (delete if not applicable): open
- Aeration: no
- Initial cell density:10000 cells/ml
-Control end cell density: 1597000 cells/ml
- No. of vessels per concentration (replicates):6 replicates of the control and the WAF 100 mg/l;3 replicates of the 1.0 and 10 mg/l WAFs

GROWTH MEDIUM
- Standard medium used: yes

OTHER TEST CONDITIONS
- Sterile test conditions: no
- Adjustment of pH: no
- Photoperiod: continuous
- Light intensity and quality: TLD-lamps of the type ‘Cool-white’ of 30 Watt, with a light intensity within the range of 63 to 71 µE/m2/s


EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: At the beginning of the test, cells were counted using a microscope and a counting chamber. Thereafter cell densities were determined by spectrophotometric measurement of samples at 720 nm using a Varian Cary 50 single beam spectrophotometer with cuvettes (pathlength =10 mm). Algal medium was used as blank and the extra replicates without algae as background for the treated solutions.
- Other: 72 h NOErC, 72 h NOEbC, 72 h ErC50, 72 h EbC50


TEST CONCENTRATIONS
- Spacing factor for test concentrations: 10
- Test concentrations: WAF prepared at 1.0, 10 and 100mg/l
Reference substance (positive control):
yes
Remarks:
potassium dichromate
Duration:
72 h
Dose descriptor:
NOELR
Effect conc.:
100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: WAF prepared at 100 mg/l
Key result
Duration:
72 h
Dose descriptor:
EL50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: >WAF prepared at 100 mg/l
Duration:
72 h
Dose descriptor:
NOELR
Effect conc.:
100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: Yield
Remarks on result:
other: WAF prepared at 100 mg/l
Duration:
72 h
Dose descriptor:
EL50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: Yield
Remarks on result:
other: >WAF prepared at 100 mg/l
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
>= 0.4 - <= 0.6 mg/L
Nominal / measured:
meas. (initial)
Conc. based on:
other: TOC
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 0.4 - <= 0.6 mg/L
Nominal / measured:
meas. (initial)
Conc. based on:
other: TOC
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
>= 0.4 - <= 0.6 mg/L
Nominal / measured:
meas. (initial)
Conc. based on:
other: TOC
Basis for effect:
other: Yield
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 0.4 - <= 0.6 mg/L
Nominal / measured:
meas. (initial)
Conc. based on:
other: TOC
Basis for effect:
other: Yield
Details on results:
-No significant differences were recorded between the values for growth rate or yield at any of the test concentrations when compared to the control group.
Microscopic observations at the end of the test in the WAF prepared at 100 mg/l revealed a normal and healthy appearance of the exposed cells when compared to the control
Results with reference substance (positive control):
- Results with reference substance valid: yes
-The EC50 for growth rate reduction (ERC50: 0-72h) was 1.2 mg/l with a 95% confidence interval ranging from 0.77 to 2.0 mg/l.
-The EC50 for yield inhibition (EYC50: 0-72h) was 0.44 mg/l with a 95% confidence interval ranging from 0.37 to 0.54 mg/l
Validity criteria fulfilled:
yes
Conclusions:
Under the conditions of the present study with Pseudokirchneriella subcapitata, no reduction of growth rate or inhibition of yield was recorded at a WAF prepared at a Standolized linseed loading rate of 100 mg/l (NOEC).
Hence, both the EC50 for growth rate reduction (ERC50: 0-72h) and the EC50 for yield inhibition (EYC50: 0-72h) exceeded a WAF prepared at a loading rate of 100 mg/l, which can be considered to represent the maximum soluble concentration in test medium. TOC-analyses showed that the actual concentration in solution was expected to be between 0.4 and 0.6 mg/l
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
read-across from supporting substance (structural analogue or surrogate)
Adequacy of study:
key study
Justification for type of information:
See attached justification
Reason / purpose:
read-across source
Duration:
72 h
Dose descriptor:
NOELR
Effect conc.:
100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: WAF prepared at 100 mg/l
Key result
Duration:
72 h
Dose descriptor:
EL50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Remarks on result:
other: >WAF prepared at 100 mg/l
Duration:
72 h
Dose descriptor:
NOELR
Effect conc.:
100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: Yield
Remarks on result:
other: WAF prepared at 100 mg/l
Duration:
72 h
Dose descriptor:
EL50
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: Yield
Remarks on result:
other: >WAF prepared at 100 mg/l
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
>= 0.4 - <= 0.6 mg/L
Nominal / measured:
meas. (initial)
Conc. based on:
other: TOC
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 0.4 - <= 0.6 mg/L
Nominal / measured:
meas. (initial)
Conc. based on:
other: TOC
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
>= 0.4 - <= 0.6 mg/L
Nominal / measured:
meas. (initial)
Conc. based on:
other: TOC
Basis for effect:
other: Yield
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 0.4 - <= 0.6 mg/L
Nominal / measured:
meas. (initial)
Conc. based on:
other: TOC
Basis for effect:
other: Yield
Details on results:
-No significant differences were recorded between the values for growth rate or yield at any of the test concentrations when compared to the control group.
Microscopic observations at the end of the test in the WAF prepared at 100 mg/l revealed a normal and healthy appearance of the exposed cells when compared to the control
Results with reference substance (positive control):
- Results with reference substance valid: yes
-The EC50 for growth rate reduction (ERC50: 0-72h) was 1.2 mg/l with a 95% confidence interval ranging from 0.77 to 2.0 mg/l.
-The EC50 for yield inhibition (EYC50: 0-72h) was 0.44 mg/l with a 95% confidence interval ranging from 0.37 to 0.54 mg/l
Validity criteria fulfilled:
yes
Conclusions:
Under the conditions of the present study with Pseudokirchneriella subcapitata, no reduction of growth rate or inhibition of yield was recorded at a WAF prepared at a Standolized linseed loading rate of 100 mg/l (NOEC).
Hence, both the EC50 for growth rate reduction (ERC50: 0-72h) and the EC50 for yield inhibition (EYC50: 0-72h) exceeded a WAF prepared at a loading rate of 100 mg/l, which can be considered to represent the maximum soluble concentration in test medium. TOC-analyses showed that the actual concentration in solution was expected to be between 0.4 and 0.6 mg/l

Description of key information

Read across from standolized linseed oil: 72h-NOErLR and 72h-ErLR50 of 100 and > 100 mg/l respectively.

Key value for chemical safety assessment

EC50 for freshwater algae:
100 mg/L
EC10 or NOEC for freshwater algae:
100 mg/L

Additional information

A WAF study (read-across to standolized linseed oil) according to OECD guideline 201 under GLP reports 72h-NOErLR and 72h-ErLR50 of 100 and > 100 mg/l respectively.