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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:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: The test parameters evaluated in this study comply with a specific test guideline (Dutch NEN 6504), are well documented, scientifically acceptable, but not performed according to GLPs.
Qualifier:
according to guideline
Guideline:
other: BASF in-house test DIN 38 412/9
GLP compliance:
no
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Test type:
static
Water media type:
freshwater
Total exposure duration:
72 h
Duration:
72 h
Dose descriptor:
EC20
Effect conc.:
ca. 55 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
ca. 83 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC90
Effect conc.:
ca. 120 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Conclusions:
For the freshwater alga Desmodesmus subspicatus, the 72-hour EC20, EC50 and EC90 (growth rate) are 55, 83 and 120 mg MEKO/L, respectively.
Endpoint:
toxicity to aquatic algae and cyanobacteria
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
other: The study was conducted according to generally vaiid procedures and according to GLP guidelines. All parameters described are closely related or comparable to guideline methods.
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Alga, Growth Inhibition Test)
GLP compliance:
yes
Analytical monitoring:
yes
Details on sampling:
- Concentrations: all
- Sampling method:test solutions taken from the middle layer of test vessels were mixed
Vehicle:
no
Details on test solutions:
Five nominal concentrations of 40.0, 16.0, 6.40, 2.5 6 or 1.02 mg MEKO/L . Solubilizer was not used. Concentrations of the test substance were kept close to the nominal concentrations throughout the 72-hour test (100 to 112%).

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method:
- Eluate:
- Differential loading:
- Controls:
- Chemical name of vehicle (organic solvent, emulsifier or dispersant):
- Concentration of vehicle in test medium (stock solution and final test solution(s) including control(s)):
- Evidence of undissolved material (e.g. precipitate, surface film, etc):
Test organisms (species):
Scenedesmus capricornutum
Details on test organisms:
TEST ORGANISM
- Common name: Selenastrum capricornutum
- Strain - ATCC 22662
- Source (laboratory, culture collection):originally from the American Type Culture Collection (12301 Parklawn
Drive Rockville, Maryland 20852-1776 U.S.A.), and has been cultured under sterile condition in this laboratory
- Age of inoculum (at test initiation): 3 days

ACCLIMATION
- Acclimation period: 3 days
- Culturing media and conditions - same as test
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Hardness:
not reported
Test temperature:
23.4
pH:
8.0 at time 0, 8.3 - 9.6 at 72 hours
Dissolved oxygen:
Not reported
Salinity:
Not applicable
Nominal and measured concentrations:
Measured concentrations within 80% of nominal concentrations
Details on test conditions:
TEST SYSTEM
- Test vessel:500 mL Erlenmeyer flask
- fill volume: 100 ml
- Type of flow-through (e.g. peristaltic or proportional diluter):
- Renewal rate of test solution (frequency/flow rate):
- Initial cells density: 1 x 104 cells/mL
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 3

GROWTH MEDIUM
- Standard medium used: yes

OTHER TEST CONDITIONS
- Adjustment of pH:No
- Photoperiod: continuous
- Light intensity and quality:4,000 to 5,000 lux

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: [counting chamber; electronic particle counter; fluorimeter; spectrophotometer; colorimeter]
- Chlorophyll measurement:
- Other:

TEST CONCENTRATIONS
- Spacing factor for test concentrations: geometric ratio 2.5
- Justification for using less concentrations than requested by guideline:
- Range finding study
- Test concentrations:40.0, 16.0, 6.40, 2.56 and 1.02 mgIL
- Results used to determine the conditions for the definitive study: 88.4% inhibition at 32 mg/l, 5.8% inhibition at 3.2 mg/l
Reference substance (positive control):
no
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
ca. 11.8 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
ca. 2.56 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
ca. 6.09 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Duration:
72 h
Dose descriptor:
NOEC
Effect conc.:
ca. 1.02 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
biomass
Details on results:
- Exponential growth in the control (for algal test): yes
- Other: swollen cells at concentrations of 16 mg/l and hgher
- Any stimulation of growth found in any treatment:- 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:
Validity criteria fulfilled:
yes
Remarks:
as noted in OECD guideline
Conclusions:
For the freshwater alga Scenedesmus capricornutum, the 24-48 hour EC50 and 24-72 hour EC50 (growth rate) are 11.6 and 11.8 mg MEKO/L, respectively. The 24-48 hour NOEC and the 24-72 hour NOEC (growth rate) are both 2.56 mg MEKO/L. The 72-hour EC50 (biomass) and the 72-hour NOEC (biomass) are 6.09 mg MEKO/L and 1.02 mg MEKO/L, respectively.

Description of key information

The 72-h NOErC of 2.56 mg/L and the 72-r ErC50 of 11.8 mg/L in Scenedesmus capricornutum will be used in the assessment.

Key value for chemical safety assessment

EC50 for freshwater algae:
11.8 mg/L
EC10 or NOEC for freshwater algae:
2.56 mg/L

Additional information

Two growth inhibition tests with aquatic algae are available for MEKO. The first one (Kurume Laboratory, 1998e) is a freshwater static GLP-compliant OECD Guideline 201 test with Scenedesmus capricornutum, performed with analytical monitoring. The 72-h NOEC is 2.56 mg/L based on growth rate and the 72-h ErC50 was 11.8 mg/L. The second study (BASF, 1988) is a non-GLP static test with Scenedesmus subspicatus (new name: Desmodesmus subspicatus), performed according to DIN 38 412/9. In this test a 72-h EC50 of 83 mg/L is reported based on growth rate. The most critical study of Kurume Laboratory (1998e) is regarded as the key study.