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Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

effects on growth of green algae

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From January 25, 2021 to January 29, 2021

Reliability:

1 (reliable without restriction)

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Version / remarks:

28 July 2011

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Batch No.: CN0190301
Purity: 98.4%

Analytical monitoring:

yes

Details on sampling:

Analysis of the concentration of the test item was performed in 0 hour fresh solution and 72 hours old solution.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: The test solutions were prepared by dilution of a stock solution. A stock solution of test item at a nominal concentration of 400 mg/L was prepared with OECD alga growth medium. 0.4003 g of test item was weighed and dissolved in 1000 mL of growth medium directly. After the test item was dissolved completely, the solution was used to dilute other solutions and for exposure.

Test organisms (species):

Raphidocelis subcapitata (previous names: Pseudokirchneriella subcapitata, Selenastrum capricornutum)

Details on test organisms:

TEST ORGANISM
- Common name: alga
- Strain: Pseudokirchneriella subcapitata
- Source (laboratory, culture collection): CTI Chemical Safety Evaluation Research Center (SUZHOU) CO., LTD
- Age of inoculum (at test initiation): The age of preculture at inoculation of the definitive test was four days.
- Method of cultivation:

ACCLIMATION
- Acclimation period: 4 d
- Culturing media and conditions (same as test or not): same
- Any deformed or abnormal cells observed: no

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

21-24 oC

pH:

7.46 - 7.99

Nominal and measured concentrations:

5 nominal concentrations of 25, 50, 100, 200 and 400 mg/L;
geometric mean concentrations were 23.5, 43.5, 88.3, 186 and 345 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel:
- Initial cells density: 5E+03 cell/ml

- No. of vessels per concentration (replicates): 3 replicates
- No. of vessels per control (replicates): 3 replicates

GROWTH MEDIUM
- Standard medium used: yes
- Detailed composition if non-standard medium was used:

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Adjustment of pH:
- Photoperiod:
- Light intensity and quality: The continuous and uniform light was used; the light intensity was 4440-8880 Lux for cool white light.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
The algal biomass in each flask was inspected 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 were pipetted from the test solution to determine the biomass and then discarded to prevent contamination.
The health conditions of the cells were also determined with microscope, and any abnormal signs were recorded.
The residual initial solution was used to measure the pH value at the beginning of the test. The pH values were measured at all treatments at the end of the test. The pH of the control medium should not increase by more than 1.5 units during the test.
The light intensity was measured at the beginning and the end of the test, at 5 points on the test vessel level.
The incubation temperature was measured continuously with a minimum/maximum thermometer and the minimum/maximum values were recorded every day.

TEST CONCENTRATIONS
- Range finding study
- Test concentrations: 0.1, 1, 10 and 100 mg/L
- Results used to determine the conditions for the definitive study:

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol (3,5-DCP) as reference item was tested for EC50 as a means of assuring that the test conditions are reliable twice a year in the laboratory.

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 345 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

345 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 345 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

yield

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

345 mg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

yield

Details on results:

After the 72-hour exposure period, the mean growth yield of control cultures was 5.78×105 cell/mL, and the cell density of control cultures increased by a factor of 115.6 in the control replicates. The mean coefficient of variation for section-by-section specific growth rate in control cultures was 14.0%. The coefficient of variation of average specific growth rates during the whole test period in replicate control cultures was 1.5%. The results met the requirements of the test validity.
During the 72-hour test duration, there was no abnormal appearance of the algae observed in control replicates and replicates of each test group.
After 72 hours exposure, there was no significant inhibition of algae growth rates and yield at any concentration (inhibition < 10%). There was no significant difference in algae growth rate and growth yield between the control group and each test group (p>0.05, t-test).

Results with reference substance (positive control):

72 hour EyC50 of 3,5-DCP to Pseudokirchneriella subcapitata was 0.82 mg/L with the 95% confidence limits 0.65 ~ 1.0 mg/L and 72 hour ErC50 was 1.4 mg/L with the 95% confidence limits 0.97 ~ 2.1 mg/L.

Validity criteria fulfilled:

yes

Conclusions:

According to the results and based on the geometric mean concentration, the 72-hour effect concentration of average specific growth rate (ErC50) of and yield (EyC50) of the test item to Pseudokirchneriella subcapitata were > 345 mg/L, NOErC and NOEyC were 345 mg/L.

Executive summary:

An alga growth inhibition study of the test item was conducted over a 72-hour exposure period in a static system, according to OECD Guideline 201 under GLP.

According to the results and based on the geometric mean concentration, the 72-hour effect concentration of average specific growth rate (ErC50) of and yield (EyC50) of the test item to Pseudokirchneriella subcapitata were > 345 mg/L, NOErC and NOEyC were 345 mg/L.

Description of key information

An alga growth inhibition study of the test item was conducted over a 72-hour exposure period in a static system, according to OECD Guideline 201 under GLP.

According to the results and based on the geometric mean concentration, the 72-hour effect concentration of average specific growth rate (ErC50) of and yield (EyC50) of the test item to Pseudokirchneriella subcapitata were > 345 mg/L, NOErC and NOEyC were 345 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:

345 mg/L

EC10 or NOEC for freshwater algae:

345 mg/L