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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:
26 February to 1 March 1996
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
GLP compliance:
yes
Specific details on test material used for the study:
SOURCE OF TEST MATERIAL
- Source and lot/batch No.of test material: ZR023979BEB062
- Expiration date of the lot/batch: not indicated
- Purity test date: not indicated

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: 20°C in the original container







Analytical monitoring:
yes
Details on sampling:
- Concentrations: 0.3, 0.6, 1.2, 2.4, 4.8 mg/l
- Sampling method: Sampling was performed at the beginning and at the end of the test. At the beginning of the test, sampling was done by taking approximately 20 ml of test media out of the additional Erlenmeyer flasks of each concentration and transferring it into an all-glass brown vial. At the end of the test, sampling was done by taking approximately 20 ml of the test media out of all Erlenmeyer flasks.
- Sample storage conditions before analysis: the samples were transferred into the freezer until the moment of analysis
Vehicle:
no
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method:
Two stock solutions were prepared: one of 6 mg imazalil (= stock solution 1) and one of 48 mg imazalil (= stock solution 2). The 6 mg/l concentration was prepared by weighing 0.0061 g imazalil and diluting it to 1000 ml dilution water. The 48 mg/l concentration was prepared by weighing 0.0242 g imazalil and diluting it to 500 ml dilution water. The five concentrations were prepared as follows:
* 0.3 mg/l: 47.5 ml dilution water + 2.5 ml of stock solution 1;
* 0.6 mg/l: 45 ml dilution water + 5 ml of stock solution 1;
* 1.2 mg/l: 40 ml dilution water + 10 ml of stock solution 1;
* 2.4 mg/l: 47.5 ml dilution water + 2.5 ml stock solution 2;
* 4.8 mg/l: 45 ml dilution water + 5 ml of stock solution 2;
* control: 50 ml dilution water

- Controls: yes
Test organisms (species):
Pseudokirchneriella subcapitata (previous names: Raphidocelis subcapitata, Selenastrum capricornutum)
Details on test organisms:
TEST ORGANISM
- Common name: algae
- Strain: CCAP 278/4
- Source (laboratory, culture collection): Culture Collection of Algae and Protozoa (CCAP), UK
- Method of cultivation: The algae were cultured under sterile conditions at the laboratory for several weeks in Bold's Basal Medium

Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Hardness:
0.6 mmol/L
Test temperature:
25+-1°C
pH:
7.27 - 8.88
Dissolved oxygen:
not indicated
Salinity:
not applicable
Conductivity:
not applicable
Nominal and measured concentrations:
Nominal concentrations: 0.3, 0.6, 1.2, 2.4, 4.8 mg/l
Mean measured concentrations: 0.234, 0.457, 0.940, 1.485, 3.303 mg/l
Details on test conditions:
TEST SYSTEM
- Test vessel: Erlenmeyer flasks
- Type (delete if not applicable): open / closed - Material, size, headspace, fill volume: all-glass Erlenmeyer flasks of 100 ml, marked at 50 ml
- Initial cells density: 10E+04 cells/ml
- Control end cells density: 5.77E+05 cells/ml

GROWTH MEDIUM
- Standard medium used: yes

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water:
* NH4Cl 15 mg/l
* MgCl2.6H2O 12 mg/l
* CaCl2.2H2O 18 mg/l
* MgSO4.7H2O 15 mg/l
* KH2PO4 1.6 mg/l
* FeCl3.6H2O 80 µg/l
* K2-EDTA.2H2O 109.6 µg/l
* H3BO3 185 µg/l
* MnCl2.4H2O 415 µg/l
* ZnCl2 3 µg/l
* CoCl2.6H2O 0.01 µg/l
* CuCl2.2H2O 0.01 µg/l
* Na2MoO4.2H2O 7 µg/l
* NaHCO3 50 mg/l

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Photoperiod: continuous illumination

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: Neubauer counting chamber under a microscope (model BHTU-112, OLYMPUS)

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2
- Range finding study: yes
- Test concentrations: 0.7, 1.4, 2.8, 5.6, 11.2 mg/l (based on results from a previous study indicating that the EC50-72h was situated in a range of 1-10 mg/l)
- Results used to determine the conditions for the definitive study: yes
Reference substance (positive control):
no
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
1.73 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
1.2 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.:
0.6 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Key result
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
0.457 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Details on results:
- Observation of abnormalities (for algal test): none indicated
- Unusual cell shape: none indicated


Validity criteria fulfilled:
yes
Conclusions:
A 72h growth inhibition test with the unicellular green alga Pseudokirchneriella subcapitata was performed with the test substance Imazalil according to the OECD guideline 201. The EC50 72h calculated on the basis of the measured concentrations was 1.20 mg imazalil /L. The NOEC after 72 hours of exposure was 0.457 mg imazalil /L as measured concentration. The results of the test can be considered reliable without restrictions.
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:
Data from the related substance imazalil base is used to cover this endpoint. The justification for read across is attached in IUCLID Section 13.
Reason / purpose for cross-reference:
read-across source
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
1.6 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Remarks:
imazalil sulfate (recalculated from imazalil concentration)
Basis for effect:
growth rate
Key result
Duration:
72 d
Dose descriptor:
NOEC
Effect conc.:
0.61 mg/L
Nominal / measured:
meas. (geom. mean)
Conc. based on:
test mat.
Remarks:
imazalil sulfate (recalculated from imazalil concentration)
Basis for effect:
growth rate

Description of key information

The study of Van Ginneken (1996), investigating the acute toxicity of Imazalil to algae according to OECD guideline 201, was considered as the key study for endpoint coverage. The 72h NOEC and 72h EC50 for growth rate were determined to be 0.457 mg/L and 1.2 mg/L respectively which corresponds to 0.61 and 1.60 mg imazalil sulphate /L. The substance can be considered as harmful to algae.

Key value for chemical safety assessment

EC50 for freshwater algae:
1.6 mg/L
EC10 or NOEC for freshwater algae:
0.61 mg/L

Additional information