Tetrakis(phenylmethyl)thioperoxydi(carbothioamide)

Toxicity to aquatic algae and cyanobacteria

Link to relevant study record(s)

Reference

Endpoint:

toxicity to aquatic algae and cyanobacteria

Type of information:

experimental study

Adequacy of study:

key study

Study period:

22 Jan 2018 to 26 Jan 2018

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:

July 2011

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Version / remarks:

August, 2009

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

- Name of test material (as cited in study report): Tetrabenzylthiurame disulfide (TBzTD)
- Bacth No.: 70500108
- Purity: 97.6% (according to certificate of analysis)
- Date of analysis: May 16, 2017
- Expiration date: May 16, 2019
- Appearance: Off white, solid
- Storage conditions: At 20 ± 5 °C, in the dark

Analytical monitoring:

yes

Remarks:

LC with MS/MS detection

Details on sampling:

- Sampling: Duplicate samples from the freshly prepared test media of the only test concentration and the control were taken at test start. For the determination of the stability of the test item under the test conditions and of the maintenance of the test item concentrations during the test period, samples of the test vessels of the only treatment group and the control were taken in duplicate at the end of the test (after the 72 hours test period) by pooling the content of the test beakers of all replicates of the only the only treatment group. Furthermore duplicate samples were taken from the additional test vessels after 24 and 48 hours. All samples were diluted by a factor of 2 with acetonitrile. Additional samples of the control blank and the dilution solvent were taken at each sampling time without any sample treatment.
- Storage of samples: All samples were measured immediately after sampling and additionally after storage. Spare samples were stored in a freezer (≤ -20 °C) until delivery of the final report to enable additional analyses to be conducted on request of the Sponsor.

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
Pre-experiments were performed to determine a suitable concentration range and to establish suitable methods to prepare the test solutions. Due to the low limit of water solubility of the test item Water accommodated Fraction (WAF) with a nominal loading rate of 5 mg/L and a control were tested. The geometric mean measured concentration was 86.0 μg test item/L. Therefore, a supersaturated suspension of 5 mg test item/L was prepared by dissolving 12.8 mg test item into 2560 mL test water by stirring for 24 hours. The suspension was resting for 30 minutes, so insoluble test item separated. The test item was floating on the surface. The middle water phase was extracted. The test medium was prepared just before introduction of the algae (= start of the test).

Test organisms (species):

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

Details on test organisms:

- Common name: Green algae
- Strain: 61.81 SAG
- Source: The algae were supplied by the "Sammlung von Algenkulturen, Albrecht-von-Haller-Institut für Pflanzenwissenschaften, Universität Göttingen", 37073 Göttingen, Germany.
- Age of inoculum (at test initiation):
- Method of cultivation: The algae were cultivated in the laboratories of the test facility under standardised conditions according to the test guidelines.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

72 h

Hardness:

4 mmol/L (= mg/L) as CaCO3.

Test temperature:

21.4 - 21.8 °C

pH:

- Test start: 8.1
- Test end: 9.7

Nominal and measured concentrations:

- Nominal loading rates (from a water-accomodated fraction): 0 (control) and 5 mg/L.
- Geometric mean measured concentrations:

Details on test conditions:

TEST SYSTEM
- Test vessel: 50 mL Erlenmeyer flasks
- Fill volume: 50 mL
- Type: Closed during the whole period of the study with a conical glass stopper to avoid loss of the test item due to volatilisation.
- Initial cells density: At test start 5000 algal cells/mL were incubated
- Control end cells density: 7.374E+05 cells/mL
- No. of vessels per concentration: 6
- No. of vessels per control: 6

GROWTH MEDIUM
- Standard medium used: yes (OECD medium). The test media was enriched with 300 mg NaHCO3 to enable algae growth in closed vessels.

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Reconstituted water
- Culture medium different from test medium: Same

WATER QUALITY MEASUREMENTS
- Temperature: The temperature was measured daily in an Erlenmeyer flask filled with water and incubated under the same conditions as the test flasks.
- pH: The pH was measured in all test item concentrations and the control at the start and the end of the test.

PRE-CULTURE
A pre-culture was set up 4 days prior to the test start under the same conditions as in the test.

OTHER TEST CONDITIONS
- Photoperiod: Continuous
- Light intensity and quality: Illumination at a mean light intensity of 7975 lux (7770 to 8170 lux). The light intensity was measured once during the test at 6 positions distributed over the experimental area at the surface of the test media.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable): density
The cell density on each observation time was determined by spectrophotometric measurement. Therefore, defined volumes of the algal suspensions from all replicates and from the blanks were sampled after 24, 48 and 72 hours of exposure, and were not replaced. The algal cell densities were calculated by subtracting the absorption of the blanks, from each of the measured absorption of the test media (with algae). Based on the counted cell densities and the absorption from an algal suspension and its dilutions, a linear regression was performed for the calculation of the cell densities of the replicates during the test.

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 86 µg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

> 86 µg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 86 µg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

other: yield

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

> 86 µg/L

Nominal / measured:

meas. (geom. mean)

Conc. based on:

test mat.

Basis for effect:

other: yield

Details on results:

After 72 hours exposure, no effects on cell density were oberved in the limit treatment.
- Appearance of the test substance: The test medium was clear, no remarkable observations

Reported statistics and error estimates:

The ECx values were determined directly from the raw data due to the lack of toxic effects the test item on the test organism. For the determination of the 72 hours LOEC and the 72 hours NOEC, the calculated growth rates and yields at each test concentration were tested for significant differences compared to the control values by two sample Welch t-test (yield 24 hours and growth rate 0-24 hours) and two sample t-test (yield 48 and 72 hours, growth rate 0-48 and 0-72 hours). The software used to perform the statistical analysis was ToxRat Professional, Version 3.2.1, ToxRat(R) Solutions GmbH.

Validity criteria fulfilled:

yes

Remarks:

See 'Any other information on materials and methods incl. tables'

Conclusions:

The algae EC50 and EC10 (yield and growth rate) for the test item was determined to be >86.0 µg/L; the NOEC was determined to be ≥86.0 µg/L.

Executive summary:

The effect of the test item on the growth of the freshwater algae Pseudokirchneriella subcapitata was assessed in a study following OECD 201 guideline under GLP. In a limit test, water-accommodated fractions with a nominal loading of 5 mg/L and a control were tested. The geometrical mean measured concentration was 86.0 µg/L. The EC50 and EC10 for both growth rate and yield were determined to be >86.0 µg/L; the NOEC was determined to be ≥86.0 µg/L.

Description of key information

72-h ErC50: >86 µg/L (Pseudokirchneriella subcapitata)

72-h ErC10: >86 µg/L (Pseudokirchneriella subcapitata)

Additional information

The toxicity towards freshwater algae was determined in a study according to OECD TG 201 and in compliance with GLP criteria (Ibacon, 2018). In this study, exponentially growing freshwater alga (Pseudokirchneriella subcapitata) were exposed to 0 (control) and a limit water-accomodated fraction (WAF) prepared at a loading rate of 5 mg/L for 72 hours under static conditions. The test was performed in six replicates per test concentration. The initial concentrations and the maintenance of the exposure concentrations during the test were analytically verified. The geometric mean measured concentrations was determined to be 86 µg/L. Since the test item concentrations were not within ± 20% of the measured initial concentrations during the tes, the effect values are expressed as geometric mean measured concentrations. Cell density was measured after 24, 48 and 72 hours exposure and the growth rate, yield and biomass per time point were determined. Throughout the test, no effect on density were observed. Based on these findings, the 72-h EC50 values for growth rate and yield/biomass are determined to be >86 µg/L. The 72-h ErC10 was also determined to be >86 µg/L for both endpoints.