5-Brom-2-[(3,4,5-trifluorphenoxy)-difluormethyl]-1,3-difluorbenzene

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:

13 Nov - 18 Dec 2017

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Alga, Growth Inhibition Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

yes

Remarks:

reconstituted water

Details on test solutions:

A stock preparation with a test item concentration of 100 mg/L was freshly prepared. For that purpose, the test item was weighed in a calibrated flask and vehicle was added. The preparation was stirred with a magnetic stirrer for 24 hours. Then the formulation was passed through a filter membrane (pore size < 0.2 µm). The filtrate was used for the study. The pH value was not adjusted.

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
- Common name: green algae
- Strain: Pseudokirchneriella subcapitata (61.81 SAG)
- Source (laboratory, culture collection): Pflanzenphysiologisches Institut der Universität Göttingen, Germany
- Age of inoculum (at test initiation): three days old
- Method of cultivation: 300 mL Erlenmeyer flasks filled with 100 mL algae suspension were covered with air permeable stoppers. The cultures were shaken continuously at about 120 rpm and lit between 4440 and 8880 Lux. Fluorescent tubes installed above the flasks served for lighting.

ACCLIMATION
- Culturing media and conditions (same as test or not): same as test

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

72 h

Hardness:

ca. 0.24 mmol/L (about 25 mg/L CaCO3)

Test temperature:

24.4 - 25.2 °C

pH:

7.71 - 8.92

Details on test conditions:

The study was performed as a static test in open vessels under culture conditions. The flasks contained 100 mL either reconstituted water or test medium (test item group).
The duration of exposure was 72 hours. The algal biomass in each flask was determined daily during the exposure period.

A 3-day old pre-culture, prepared in dilution water, was used as inoculum. Before start of exposure, the cell density was determined. The test vessels were inoculated with an appropriate volumen of algae pre-culture suspension in order to obtain an initial cell density of 10000 cells/mL.

Volumes of the algal suspension not impairing the study were taken from all test item preparations ans the controls after exposure times of 24, 48 and 72 h (+/- 1 h). The required volume depended on the cell density. The withdrawn volumes were not substituted. before the cell density measurement, the algal suspension was diluted and the cell densities were determined with an electronic particle counter. Additionally the blank values without algae were determined at the sampling time points. The respective blank values were substracted from the measured value of each replicate.
The measured cell counts were converted into cell number per mL. To identify the morphological effect of the test item on the algal cells, additional samples were taken from the control and test item group after 72 h. The morphological appearance of the treated algal cells in comparison to the controls was assessed by microscope.

Reference substance (positive control):

no

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat. (total fraction)

Basis for effect:

growth rate

Remarks on result:

other: > 8.07 µg/L (limit of water solubility)

Key result

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

> 100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat. (total fraction)

Basis for effect:

growth rate

Remarks on result:

other: > 8.07 µg/L (limit of water solubility)

Details on results:

The test item concentration in the reconstituted water was not quantified at the start and the end of the study.
Due to the absence og any adverse effects at the saturation concentration, the study was performed without analytical concentration verification.
No significant effect on growth rate and yield of the algae was observed at a nominal concentration of 100 mg/L, i.e. up to the maximum water solubility.

Validity criteria fulfilled:

yes

Conclusions:

Under the conditions of the study an aqueous solution of nominal 100 mg/L of the test item revealed no toxicity to algae.
The 72 h EC50 and EC10 value for growth rate were greater than the water solubility of 8.07 µg/L (nominal >100 mg/L) and thus, could not be determined in the study.

Executive summary:

The objective of the present study was to determine the effect of the test item on growth rate and yield of the unicellular green algae Pseudokirchneriella subcapitata. The study comprised of one control group and one test item group with six replicates each. A nominal test item concentration of 100 mg/L was prepared reconstituted water. The initial algae cell density in each replicate was 10000 cells per mL. The growth of the algae was determined over an exposure of 72 hours and compared with the growth of the control group.

The test item concentration in the reconstituted water was not quantified at the start and the end of this study. Because of the low water solubility (< 8.07 mg/L), the test item cannot be detected with standard analytical methods and the development of an analytical method with a sufficiently low detection and quantification limit is complex.

Due to the absence of any adverse effects at the saturation concentration, the study was performed without analytical concentration verification. No significant effect on growth rate and yield of the algae was observed at a nominal concentration of 100 mg/L, i.e. up to the maximum water solubility.

The 72 -h EC10, EC20, and EC50 value for growth rate and yield were greater than the water solubility of 8.07 µg/L (nominal > 100 mg/L) and, thus, could not be determined in this study.

Description of key information

OECD 201: 72 h EC50 > 100 mg/L (nominal); 72 h EC10 > 100 mg/L (nominal)

Additional information

The objective of the present study was to determine the effect of the test item on growth rate and yield of the unicellular green algae Pseudokirchneriella subcapitata. The study comprised of one control group and one test item group with six replicates each. A nominal test item concentration of 100 mg/L was prepared reconstituted water. The initial algae cell density in each replicate was 10000 cells per mL. The growth of the algae was determined over an exposure of 72 hours and compared with the growth of the control group.

The test item concentration in the reconstituted water was not quantified at the start and the end of this study. Because of the low water solubility (< 8.07 mg/L), the test item cannot be detected with standard analytical methods and the development of an analytical method with a sufficiently low detection and quantification limit is complex.

Due to the absence of any adverse effects at the saturation concentration, the study was performed without analytical concentration verification. No significant effect on growth rate and yield of the algae was observed at a nominal concentration of 100 mg/L, i.e. up to the maximum water solubility.

The 72 -h EC10, EC20, and EC50 value for growth rate and yield were greater than the water solubility of 8.07 µg/L (nominal > 100 mg/L) and, thus, could not be determined in this study.