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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:
31 January 2018 to 09 February 2018
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)
Deviations:
yes
Remarks:
The 24h results have not been included due to a lag phase in the growth of the algae
GLP compliance:
yes (incl. certificate)
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: dilution series
- Evidence of undissolved material (e.g. precipitate, surface film, etc.): Substance observed to be soluble is solution.
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
- Common name: Pseudokirchneriella subcapitata
- Strain: 278/4
- Source (laboratory, culture collection): SAMS Limited
- Age of inoculum (at test initiation): Not reported
- Method of cultivation: Pre-cultures in the exponential growth phase were prepared from stock laboratory cultures by inoculating autoclaved freshwater at 120 °C for 15 minutes with nutrient medium (3N-BBM+V) 2 to 4 days before test commencement and incubated at approximately 21 ±2 °C under constant illumination as the inoculum source for subsequent toxicity tests.

ACCLIMATION
- Acclimation period: 2-4 days
- Culturing media and conditions (same as test or not): same as test
- Any deformed or abnormal cells observed: None reported
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Hardness:
Not specified
Test temperature:
21 ±2 °C
pH:
8.1 ±0.2.
Dissolved oxygen:
Not specified
Salinity:
Not specified
Conductivity:
Not specified
Nominal and measured concentrations:
Nominal concentrations: 100, 320, 1000, 3200 and 10,000 mg/l
Details on test conditions:
TEST SYSTEM
- Test vessel:100 ml borosilicate glass conical flasks
- Material, size, headspace, fill volume: 50 ml of test medium
- Initial cells density: 5 x10^3-10^4 cells per millilitre
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6

GROWTH MEDIUM
- Standard medium used: yes (conforms to OECD 201 and ISO 8692)

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Purified water treated by reverse osmosis followed by electro-deionisation.

OTHER TEST CONDITIONS
- Adjustment of pH: pH of the culture medium is adjusted if required, by adding 1M HCl, or NaOH to give a pH of 8.1 ± 0.2.
-Photoeperiod: Constant
- Light intensity and quality: 4440 to 8880 lux

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations:] haemocytometer, Sedgewick-Rafter chamber, or Fluorometer measurements.

TEST CONCENTRATIONS
Range finding study
- Test concentrations: 1,10,100 and 1000 mg/l
- Results used to determine the conditions for the definitive study: 72h EC50 >1,000
Reference substance (positive control):
yes
Remarks:
potassium dichromate
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
1 920 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
48 h
Dose descriptor:
EC50
Effect conc.:
2 090 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
320 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
- Observation of abnormalities (for algal test): None reported
- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: No
- Effect concentrations exceeding solubility of substance in test medium: No
Results with reference substance (positive control):
- Results with reference substance valid? Yes
- EC50: 0.661 to 1.719 mg/l
Reported statistics and error estimates:
The result is based on nominal concentrations and was calculated by non-linear regression within the CETIS (V1.8) suite of statistical analysis.
Validity criteria fulfilled:
yes
Conclusions:
The 72-hour EC50 was 1920 mg/L and the 72-hour NOEC 320 mg/L. Based on the results of the test the substance did not meet the criteria for classification as acutely toxic to the aquatic environment according to Regulation (EC) N° 1272/2008.
Executive summary:

The short-term toxicity of 2-(2-methylpropoxy)ethanol to algae ( Pseudokirchneriella subcapitata) was determined by a GLP compliant study performed according to OECD 201 test guideline.

A range finding study was first performed to determine the concentrations to be used in the definitive test. The 72H EC50 of the range finding test was >1000 mg/L and as a result the following concentration range were used in the definitive study: 100, 320, 1000, 3200 and 10,000 mg/L. Three replicates were prepared for each test concentration and 6 replicates for the control. Potassium dichromate was used as a reference substance and the results of this test were vaild. The 72h EC50 for 2-(2-methylpropoxy)ethanol as determined by the definitive test was 1920 mg/L and the 72h NOEC was 320 mg/L. As the EC50 value is >1 mg/L the substance does not meet the criteria for classification as acutely toxic to the aquatic environment according to Regulation (EC) N ° 1272/2008.

Description of key information

The short-term toxicity of 2-(2-methylpropoxy)ethanol to algae ( Pseudokirchneriella subcapitata) was determined by a GLP compliant study performed according to OECD 201 test guideline.

Pseudokirchneriella subcapitata was exposed to the following concentrations: 100, 320, 1000, 3200 and 10,000 mg/L. The 72h EC50 as determined by the definitive test was 1920 mg/L and the 72h NOEC was 320 mg/L. As the EC50 value is > 1 mg/L the substance can be regarded as not acutely toxic to the aquatic environemnt in accordance with CLP Regulation (EC) No 1272/2008.

Key value for chemical safety assessment

EC50 for freshwater algae:
1 920 mg/L

Additional information