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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:
Mar 5, 2015 to Jun 17, 2015
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to
Guideline:
OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)
Version / remarks:
2006
Qualifier:
according to
Guideline:
EU Method C.3 (Algal Inhibition test)
Version / remarks:
2009
GLP compliance:
yes (incl. certificate)
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch No. of test material: Batch No. 6F11027000
- Expiration date of the lot/batch: 17. Nov. 2017 (two years after first opening)
- Purity: 96 %
Analytical monitoring:
yes
Details on sampling:
- Concentrations: 100 mg/L
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: A saturated solution was prepared be adding 117 µl/L test item (eq. to 100 mg/L) to corresponding amount of algal medium and stirring slowly for 23.5 hrs.
- Eluate: The lower phase of the resulting solution was used as the test solution
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM
- Common name: Green alga
- Strain: SAG strain number 86.81
- Source: MBM Sci-encebridge GmbH (Institut für Pflanzenphysiologie of Universität Göttingen)
- Method of cultivation: Algae kept as stock culture on solid agar @ 7 °C. From the stock culture, a permanent culture was prepared. From an aliquot of the permanent culture, the pre-culture was prepared.

ACCLIMATION
- Acclimation period: 4-d prior to start of each test, an aliquot of the permanent culture was brought into pre-culture medium and incubated under continuous lighting for 96 hours. The resulting culture grew exponentially.
- Culturing media and conditions: Before usage, the pre-culture was checked for the absence of cell aggregates and the cell number of culture was determined via photometric measurement.
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Test temperature:
20.3 – 22.4 °C
pH:
pH was adjusted to 7.0 (± 0.2)
Nominal and measured concentrations:
100 mg/L (nominal); 0.06 mg/L (geometric mean measured)
Details on test conditions:
TEST SYSTEM
- Test vessel: glass flasks, total volume 65 mL
- Type: closed
- Material, size, headspace, fill volume: test vessels complete filled
- Initial cells density: 5.39 * 10³ cells/mL
- Control end cells density: 5.39 * 10³ cells/m
- No. of vessels per concentration (replicates): 6
- No. of vessels per control (replicates): 6 initially The 3rd replicate of the controls was not used for evaluation of the results due to clouded cells. Considered uncritical since algal growth in the other 5 replicates was in the normal range.

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Adjustment of pH: To avoid a strong pH increase and CO2 shortage in the closed system, additional 6 mL sodium hydrogen carbonate solution (50 g/L) was added to 900 mL nutrient medium. Then, pH was adjusted to 7.0 (± 0.2) and the solution was filled up to 1000 mL.
- Lighting: 5300 Lux

EFFECT PARAMETERS MEASURED :
- Determination of cell concentrations: cell number was calculated based on the determination of the absorption at 440 nm at 0, 24, 48, and 72 hours
- treatments were examined microscopically in order to assess the appearance of the algae and detect abnormalities at the end of the study
Reference substance (positive control):
yes
Remarks:
Potassium dichromate
Key result
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 0.06 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
0.06 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
> 0.06 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
> 0.06 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
EC10
Effect conc.:
> 100 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Results with reference substance (positive control):
The EC50s of potassium dichromate were determined in a separate reference test (GLP study no. 14070902R301).
For the estimation of the EC50s of the positive control, the fits showed sufficient statistical correspondence of the data with the dose-response-equation. The values were within the normal range of the laboratory.

- During validation, the test item showed sufficient stability in closed glass flasks (92 % recovery of the measured start concentration)

- In the algae study, the recovery after 72 hours only 7 % of the measured start concentration.

- Concluded concentration of dissolved test item was affected by the presence of the test organism and dissolved test item was adsorbed or ingested by the algae.

- Determination of the biological results thus based on the geometric mean of the measured concentration.

- For calculation of measured concentration, tenfold enrichment and a recovery rate from daphnia test medium of 71% taken into account

Summary of validation criteria results:

Parameter: Increase factor biomass factor

Validity criteria :16 in 72 h

Observed value: 51         

Assessment: Valid

 

Parameter: Mean coefficient of variation of daily growth rates   

Validity criteria: max. 35%           

Observed value: 14%     

Assessment: Valid

 

Parameter: Coefficient of variation of average growth rate during the whole test period 

Validity criteria: max. 7%              

Observed value: 7%       

Assessment: Valid

Validity criteria fulfilled:
yes
Conclusions:
The study was performed as a limit test at the concentration containing 100 mg/L nominal concentration. Incubation time (test system Desmodesmus subspicatus) was 72 hours. Under these test conditions, the EC10 and EC50 of the growth rate was determined to be > 0.06 mg/L. These results were based on the geometric mean of the measured concentrations.
Executive summary:

The acute toxicity of 1,3,5-triisopropylbenzene was tested under static conditions in a 72-hour algae growth inhibition study with on the Desmodesmus subspicatus in a limit test according to OECD TG 201. Based on nominal concentrations, the 72-h EC10 was determined to be > 100 mg/L.

Description of key information

The acute toxicity of 1,3,5-triisopropylbenzene was tested under static conditions in a 72-hour algae growth inhibition study with on the Desmodesmus subspicatus in a limit test according to OECD TG 201. Based on nominal concentrations, the 72-h EC10 was determined to be > 100 mg/L.

Key value for chemical safety assessment

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

Additional information