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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:
From 2019-07-29 to 2019-08-05
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Remarks:
Study performed to current OECD guidelines with no significant deviations and run in OECD GLP certified lab.
Qualifier:
according to guideline
Guideline:
OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)
Version / remarks:
2011
Deviations:
no
GLP compliance:
yes (incl. QA statement)
Specific details on test material used for the study:
Batch No.: A03-18-0081
Purity: ≥99.9%
Analytical monitoring:
no
Vehicle:
no
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM
- Common name: Desmodesmus subspicatus, which is a freshwater alga species, and is one of the recommended species of OECD Guidelines for the Testing of Chemicals and Ministry of Environmental Protection of People’s Republic of China.
Test type:
static
Water media type:
freshwater
Limit test:
yes
Total exposure duration:
72 h
Test temperature:
22.8 - 23.2 °C
pH:
7.65 - 7.85
Nominal and measured concentrations:
Nominal: 100 mg/L
Measured: 28.9 mg/L (overall mean determined concentration)
Details on test conditions:
TEST SYSTEM
- Test vessel: 250 mL conical flasks
- Initial cells density: 5×10^3 cell/mL
- No. of replicates per concentration: 6
- No. of replicates per control: 6

GROWTH MEDIUM
- Medium used: recommended by OECD was used

OTHER TEST CONDITIONS
- Oscillation rates: 150 revolutions per minute
- Photoperiod: Continuous light was used
- Light intensity and quality: The measured light intensity was 4640 - 4700 Lux for cool white light at the beginning and the end of the test. The light intensity was in the range of -0.7% - 0.6% from the average light intensity, i.e. 4672 Lux over the incubation area.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: manual cell counting with microscope
- Other: The health conditions of the cells were also determined with microscope, and any abnormal signs were recorded.

TEST CONCENTRATIONS
- Range finding study
- Test concentrations: 100 mg/L
- Results used to determine the conditions for the definitive study: The 72-hour EC50 was beyond 100 mg/L.
Reference substance (positive control):
yes
Remarks:
3,5-dichlorophenol
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
> 28.9 mg/L
Nominal / measured:
meas. (arithm. mean)
Conc. based on:
test mat.
Basis for effect:
growth rate
Details on results:
During the 72-hour test duration, there was no abnormal appearance of the algae observed in controls and test replicates.
Results with reference substance (positive control):
The 72-hour EyC50 was 2.15 mg/L (95% confidence limits: 2.01 - 2.29 mg/L); The 72-hour ErC50 was 2.76 mg/L (95% confidence limits: 2.50 - 3.05 mg/L).

Validity of the test

At the end of the test, the biomass in control cultures had increased exponentially by a factor of 51.0, which met the criteria of being at least 16, within the 72-hour test period.

During the test period, the mean coefficient of variations of section-by-section specific growth rate (days 0-1, 1-2, and 2-3) was 7.9% in the control replicates, and met the criteria of being ≤ 35%.

The coefficient of variation of average specific growth rates during the whole test period was 0.46% in the control replicates, and met the criteria of being ≤ 7%.

As mentioned above, this test was considered valid.

Validity criteria fulfilled:
yes
Conclusions:
The 72-hour median effect concentration of average specific growth rate (ErC50) and yield (EyC50) of the test item to Desmodesmus subspicatus were greater than 28.9 mg/L (the overall mean determined concentration). The NOEC was greater than 28.9 mg/L.
Executive summary:

An alga growth inhibition study of the test item was conducted for a period of 72 hours according to OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test).

Based on the results of the preliminary test, the definitive test was conducted at the concentrations of 100 mg/L, the control group was included in parallel. There were 6 replications for the test concentration and control. During the 72 hours test period, the cell concentration in each flask was determined by manual cell counting by microscope at 24 hours, 48 hours and 72 hours after the start of the test.

 

During the 72-hour test duration, there was no any abnormal appearance of the algae observed in control and test replicates.

The concentration of test item was determined in samples of test media by GC method. The results showed that for the nominal test item concentration of 100 mg/L, the mean determined concentration in 0-hour and 72-hour media were 30.6 mg/L and 27.1 mg/L. The overall mean determined concentration was 28.9 mg/L.

 

The 72-hour median effect concentration of average specific growth rate (ErC50) and yield (EyC50) of the test item to Desmodesmus subspicatus were greater than 28.9 mg/L. The NOEC was greater than 28.9 mg/L.

Description of key information

The 72-hour median effect concentration of average specific growth rate (ErC50) and yield (EyC50) of the test item to Desmodesmus subspicatus were greater than 28.9 mg/L (the overall mean determined concentration). The NOEC was greater than 28.9 mg/L.

Key value for chemical safety assessment

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

Additional information

An alga growth inhibition study of the test item was conducted for a period of 72 hours according to OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test).

Based on the results of the preliminary test, the definitive test was conducted at the concentrations of 100 mg/L, the control group was included in parallel. There were 6 replications for the test concentration and control. During the 72 hours test period, the cell concentration in each flask was determined by manual cell counting by microscope at 24 hours, 48 hours and 72 hours after the start of the test.

 

During the 72-hour test duration, there was no any abnormal appearance of the algae observed in control and test replicates.

The concentration of test item was determined in samples of test media by GC method. The results showed that for the nominal test item concentration of 100 mg/L, the mean determined concentration in 0-hour and 72-hour media were 30.6 mg/L and 27.1 mg/L. The overall mean determined concentration was 28.9 mg/L.

 

The 72-hour median effect concentration of average specific growth rate (ErC50) and yield (EyC50) of the test item to Desmodesmus subspicatus were greater than 28.9 mg/L. The NOEC was greater than 28.9 mg/L.