Trimethylsulfonium bromide

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 20 to 23 Septermber 2022

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:

Batch No.: 215P13-2
Appearance: White solid
Purity: 99.2%

Analytical monitoring:

yes

Details on sampling:

Because there was not a suitable analytical method for quantifying exposure (e.g. nominal concentrations were below limit of quantification of most sensitive analytical method), confirming nominal test chemical concentrations in a stock solution were used.
During the test, the concentrations of test item in the stock solution of 2500 mg/L were determined at 0 hour fresh solution. In addition, in order to demonstrate how the concentration at the sample of the stock solution behaved under test conditions for the test period, the stock solution of 2500 mg/L was kept under test conditions for about 72 hours and then the concentration of test item was determined.

Vehicle:

no

Details on test solutions:

A stock solution of test item at a nominal concentration of 2500 mg/L was prepared with OECD alga growth medium. 2.5020 g of test item was weighed and dissolved in 1000 mL of OECD alga growth medium directly. After the test item was dissolved completely, the stock solution of 2500 mg/L was used to dilute test solutions. Pipette 0.20, 0.64, 2.00, 6.40 and 20.00 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 1.0, 3.2, 10, 32 and 100 mg/L.

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
- Common name: green-algal
- Source (laboratory, culture collection): originally introduced from CTI Chemical Safety Evaluation Research Center (SUZHOU) CO., LTD
- Age of inoculum (at test initiation): four days
- Method of cultivation: cultured continually under the same conditions as growth test in the facility.

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Test temperature:

21 - 24 oC

pH:

7-9

Nominal and measured concentrations:

1.0, 3.2, 10, 32 and 100 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: flasks
- Type (delete if not applicable): All test flasks were capped with air-permeable membrane.
- Material, size, headspace, fill volume: 100 mL test solution
- Renewal rate of test solution (frequency/flow rate): no
- Initial cells density: 5E+03 cells/mL
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 3
- No. of vessels per vehicle control (replicates):

OTHER TEST CONDITIONS
- Sterile test conditions: yes/no
- Adjustment of pH: no
- Photoperiod: Continuous and uniform light was used
- Light intensity and quality: 4440 ~ 8880 Lux for cool white light

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: The algal biomass in each flask was inspected daily during the test period. The biomass was measured by manual cell counting by microscope 4 times. Small volumes were taken from the test solution using a pipette to measure the biomass and the residual solution was discarded. The flasks were placed back into the incubator at random.
Microscopic observation was performed to verify a normal and healthy appearance of the inoculum culture and to observe any abnormal appearance of the algae (as may be caused by the exposure to the test substance) at the end of the test.


TEST CONCENTRATIONS
- Range finding study
- Test concentrations: 0.1, 1, 10, 100 mg/L
- Results used to determine the conditions for the definitive study: During the 72-hour test duration, there was no abnormal appearance of the algae observed in control replicates and replicates of each test group.

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol (3,5-DCP)

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

38 mg/L

95% CI:

15.3 - 225.6

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

11.2 mg/L

95% CI:

6.8 - 18.6

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

yield

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

1 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

yield

Details on results:

After the 72-hours exposure period, the mean growth yield of control cultures was 3.98E+05 cells/mL, and the cell density of control cultures increased by a factor of 79.6 in the control replicates. The mean coefficient of variation for section-by-section specific growth rate in control cultures was 28.8%. The coefficient of variation of average specific growth rates during the whole test period in replicate control cultures was 0.7%. 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 nominal 1.0 mg/L test group.

Results with reference substance (positive control):

72 hour EyC50 of 3,5-DCP to Pseudokirchneriella subcapitata was 1.20 mg/L with the 95% confidence limits 0.94 mg/L – 1.54 mg/L and 72 hour ErC50 was 3.44 mg/L with the 95% confidence limits 2.17 mg/L – 5.44 mg/L.

Validity criteria fulfilled:

yes

Conclusions:

The 72-hour effect concentration of growth rate (ErCx) of and yield (EyCx) of the test item to Pseudokirchneriella subcapitata were determined as 38 mg/L and 11.2 mg/L, NOEC was 1.0 mg/L for both growth rate and yield.

Executive summary:

An alga growth inhibition study of Test item 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 (ErCx) of and yield (EyCx) of the test item to Pseudokirchneriella subcapitata were determined as 38 mg/L and 11.2 mg/L, NOEC was 1.0 mg/L for both growth rate and yield.

Description of key information

An alga growth inhibition study of Test item 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 (ErCx) of and yield (EyCx) of the test item to Pseudokirchneriella subcapitata were determined as 38 mg/L and 11.2 mg/L, NOEC was 1.0 mg/L for both growth rate and yield.

Key value for chemical safety assessment

EC50 for freshwater algae:

38 mg/L

EC10 or NOEC for freshwater algae:

1 mg/L