4-Nitrophenyl 2-(methylsulphonyl)ethanoate

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 19 to 24 July 2021

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)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Lot number: 4425-191127
Purity: 99.8%

Analytical monitoring:

yes

Details on sampling:

- Concentrations: all concentrations
- Sampling method: Samples were taken for analysis at the start of the test from the freshly prepared solutions, and at the end of the test in the 72 hours old solutions.
- Sample storage conditions before analysis: stored in refrigerator (at 2-8 °C)

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 50 mg/L was prepared with OECD alga growth medium. 0.0250 g of test item was weighed and dissolved in 500 mL of growth medium by magnetic stirring for about 5 hours. After the test item was dissolved completely, the solution was used to dilute test solutions. Pipette 1.0, 3.2, 10, 32, and 100 mL of the stock solution and make up to 500 mL with OECD alga growth medium. The solutions were mixed thoroughly, resulting in test solutions at 0.10, 0.32, 1.0, 3.2 and 10 mg/L.

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
- Common name: green algae
- Strain: Pseudokirchneriella subcapitata
- Source (laboratory, culture collection): CTI Chemical Safety Evaluation Research Center (SUZHOU) CO., LTD
- Age of inoculum (at test initiation): four days

ACCLIMATION
- Acclimation period: four days
- 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:

7.94 - 8.32

Nominal and measured concentrations:

Nominal concentrations: 0.1, 0.32, 1, 3.2, 10 mg/L; Measured concentrations: 0.099, 0.362, 0.963, 3.617, 10.274 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 250 mL glass conical flasks
- Aeration: All test vessels were capped with air-permeable membrane.
- Renewal rate of test solution (frequency/flow rate): no
- Initial cells density: 5E+03 cell/mL
- Control end cells density: 4.57E+05 cell/mL
- No. of organisms per vessel:
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 3
- No. of vessels per vehicle control (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: no
- Photoperiod:
- Light intensity and quality: 4440-8880 Lux

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: manual cell counting with microscope

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: at 100 mg/L, no alga cell was observed after 72 hour and biomass was 0, and specific growth rate cannot be calculated. Inhibition of specific growth rate can be considered to be 100%.

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

2.1 mg/L

95% CI:

0.94 - 4.7

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

0.43 mg/L

95% CI:

0.19 - 1

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

0.1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

0.62 mg/L

95% CI:

0.31 - 1.2

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

yield

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

0.15 mg/L

95% CI:

0.073 - 0.29

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

yield

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

0.1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

yield

Details on results:

Physicochemical Measurements in the Definitive Test:
During the test, the incubation temperature was in the range of 22.3 ~ 23.8 oC. The measured light intensity was 5290 ~ 5450 lux for cool white light at the beginning and the end of the test. The light intensity was in the range of -1.45% ~ 1.53% from the average light intensity, i.e. 5368 lux over the incubation area. The values of pH determined at the beginning and the end of the test were within the range of 7.94 - 8.32. The pH of the control medium increased by 0.15 units maximally during the test.

Results of test culture in the Definitive Test:
After the 72-hour exposure period, the mean growth yield of control cultures was 4.57E+05 cell/mL, and the cell density of control cultures increased by a factor of 91.4 in the control replicates. The mean coefficient of variation for section-by-section specific growth rate in control cultures was 28.5%. The coefficient of variation of average specific growth rates during the whole test period in replicate control cultures was 0.4%. 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, comparing with the control group, the test groups showed increasing inhibition effects with increasing concentration. There was no significant difference in algae growth rate and growth yield between the control group and the nominal concentration of 0.10 mg/L test group (p>0.05, t-test).

Verification of Test Concentration in the Definitive Test:
The concentrations of test item in the test media were determined by HPLC method. Analysis of the concentration of the test item were performed in 0 hour fresh solutions and 72 hours old solutions. The results showed that the determined concentrations in 0-hour fresh media were 96.3% ~ 113.1% of nominal concentrations, the determined concentrations in 72 hours old media were 83.0% ~ 112.8% of nominal concentrations. The test concentrations were satisfactorily maintained in the range of 80 - 120% of nominal concentration.

Results with reference substance (positive control):

72 hour EyC50 of 3,5-DCP to Pseudokirchneriella subcapitatawas 0.98 mg/L with the 95% confidence limits 0.61 - 1.57 mg/L and 72 hour ErC50 was 1.54 mg/L with the 95% confidence limits 0.86 - 2.78 mg/L

Validity criteria fulfilled:

yes

Conclusions:

The 72-hour effect concentration of growth rate (ErC50) and yield (EyC50) of the test item to Pseudokirchneriella subcapitata was determined as 2.1 and 0.62 mg/L. The NOEC for growth rate and yield is 0.1 mg/L.

Executive summary:

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

The 72-hour effect concentration of growth rate (ErC50) and yield (EyC50) of the test item to Pseudokirchneriella subcapitata was determined as 2.1 and 0.62 mg/L. The NOEC for growth rate and yield is 0.1 mg/L.

Description of key information

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

The 72-hour effect concentration of growth rate (ErC50) and yield (EyC50) of the test item to Pseudokirchneriella subcapitata was determined as 2.1 and 0.62 mg/L. The NOEC for growth rate and yield is 0.1 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:

2.1 mg/L

EC10 or NOEC for freshwater algae:

0.1 mg/L