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Ecotoxicological information

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 2018-12-11 to 2018-12-14
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
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.: B893504
Purity: 99.87%
Analytical monitoring:
yes
Details on sampling:
- Concentrations: 80.0, 127, 200, 316 and 500 mg/L and control
- Sampling method: Samples were taken from test group and control group of fresh media at 0 hour and of old media at72 hours. On the day of analysis, 10 mL solution was sampled for each concentration and control.
Vehicle:
no
Details on test solutions:
To prepare test solutions,0.04010, 0.06352, 0.10051, 0.15803, 0.25000 g of test item was weighed and added into 500 mL test mediumand mixed completely to get the solutions of 80.0, 127, 200, 316 and 500 mg/L.
Test organisms (species):
Desmodesmus subspicatus (previous name: Scenedesmus subspicatus)
Details on test organisms:
TEST ORGANISM
- Common name: Desmodesmus subspicatus
- Strain: freshwater alga
- Source (laboratory, culture collection): introduced from Institute of Hydrobiology, Chinese Academy of Sciences and cultured continually
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
72 h
Test temperature:
22.7-23.2°C
pH:
8.02-8.64 measured by HQ40d (PHC101 pH probe)
Nominal and measured concentrations:
Nominal: 80.0, 127, 200, 316 and 500 mg/L
Measured: 78.0, 120.2, 194.4, 306.6 and 488.6 mg/L
Details on test conditions:
TEST SYSTEM
- Test vessel: conical flasks
- Type: closed, covered with membrane
- Material, size, headspace, fill volume: glass, 250 mL, filled with 100 mL solution
- Initial cells density: 5E+03 cell/mL
- Control end cells density: 2.22E+05 cell/mL
- No. of organisms per vessel: 5E+05
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 3

GROWTH MEDIUM
- Standard medium used: yes

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Adjustment of pH: no
- Photoperiod:continuous cool white light was used
- Light intensity: 4570-4870Lux

EFFECT PARAMETERS MEASURED:
- Algal biomass: The algal biomass in each flask wasinspected daily (at 24h, 48h and 72h) during the test period. The biomass was measured by manual cell counting with microscope and counted 4 times. Small volumes werepipetted from the test solution to determine the biomass and then discarded to prevent the pollution.
- Health condition: determined with microscope, and any abnormal signswere recorded.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 1.58

- Range finding study
- Test concentrations: first time: 0.03, 0.3, 3, 30 and 100 mg/L; second time: 100, 300 and 500 mg/L
- Results used to determine the conditions for the definitive study: The EC50 was between 100 to 500 mg/L
Reference substance (positive control):
yes
Key result
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
350.32 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.:
80 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
growth rate
Duration:
72 h
Dose descriptor:
EC50
Effect conc.:
197.37 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
other: yield
Details on results:
- Exponential growth in the control (for algal test): yes
- Observation of abnormalities (for algal test): no visible toxic sign observed in control replicates and test groups of 80.0, 127, 200, 316 and 500 mg/L.
- Inhibition: There was no inhibition in concentrations of 80.0 mg/L.Visible inhibition wasobserved in concentration of 127, 200, 316 and 500 mg/L, and the inhibition increased as the concentration increased, respectively.
There was no significant difference between control and 80.0 mg/L group, and there was significant difference between control and 127, 200, 316 and 500 mg/L.
Results with reference substance (positive control):
- Results with reference substance valid? Yes
- EC50: 72-hour EyC50with 95% confidence limits: 2.35 mg/L (1.89 - 2.92 mg/L); 72-hour ErC50with 95% confidence limits: 2.52 mg/L (1.96 - 3.25 mg/L)
Reported statistics and error estimates:
ErC50 was derived from the test results directly; EyC50 was calculated by probit method by EXCEL. The NOEC was calculated by comparing the differences between test groups and control.
Validity criteria fulfilled:
yes
Conclusions:
Basing on the results and nominal concentration, the 72-hour median effective concentration of the test item to alga (Desmodesmussubspicatus), ErC50 was 350.32 mg/L, with 95% confidence limits of 249.93-491.05 mg/L, EyC50 was 197.37 mg/L, with 95% confidence limits of 156.67-248.81 mg/L and NOEC was 80.0 mg/L for growth rate and growth yield.
Executive summary:

A growth inhibition study was conducted to alga over a 72-hour exposure period in a static system according to OECD 201.

The definitive test was conducted with 5 nominal concentrations of 80.0, 127, 200, 316 and 500 mg/L. A concurrent blank control was performed in parallel.3 replicates were used with 100 mL for each replicate.

Test alga species was Desmodesmus subspicatus, and alga growth medium recommended by MEP and OECD was used. The initial test biomass of alga was 5E+03 cell/mL. The algal biomass in each flask was inspected daily (at 24h, 48h and 72h) during the test period.

Basing on the results and nominal concentration, the72-hour median effective concentration of the test item to alga (Desmodesmus subspicatus), ErC50 was 350.32 mg/L, with 95% confidence limits of 249.93-491.05 mg/L, EyC50 was 197.37 mg/L, with 95% confidence limits of 156.67-248.81 mg/L and NOEC was 80.0 mg/L for growth rate and growth yield.

Description of key information

The72-hour median effective concentration of the test item to alga (Desmodesmus subspicatus), ErC50 was 350.32 mg/L, with 95% confidence limits of 249.93-491.05 mg/L, EyC50 was 197.37 mg/L, with 95% confidence limits of 156.67-248.81 mg/L and NOEC was 80.0 mg/L for growth rate and growth yield.

Key value for chemical safety assessment

EC50 for freshwater algae:
350.32 mg/L
EC10 or NOEC for freshwater algae:
80 mg/L

Additional information