Caesium fluoride

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:

September 2016 (Study plan) - October 2017 (Final report)

Reliability:

1 (reliable without restriction)

Qualifier:

according to guideline

Guideline:

OECD Guideline 201 (Freshwater Alga and Cyanobacteria, Growth Inhibition Test)

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.3 (Algal Inhibition test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Identification: Cesium fluoride
Physical state/Appearance: White powder
Batch: 216091B008
Water Solubility: >1000 g/L
Purity: Not provided
Expiry Date: 01 September 2018
Storage Conditions: Room temperature over silica gel in the dark

Analytical monitoring:

yes

Details on sampling:

Samples were taken from the control and each group from the bulk test preparation at 0 hours and from the pooled replicates at 72 hours for quantitative analysis. All samples were stored frozen prior to analysis. Duplicate samples were taken at 0 and 72 hours and stored frozen for further analysis if necessary.
The method of analysis, recovery and test solution analyses are described below.

Vehicle:

no

Remarks:

test item dissolved in culture medium

Details on test solutions:

A nominal amount of test item (100 mg) was dissolved in culture medium with the aid of ultrasonication for approximately 5 minutes and the volume adjusted to 1 liter to give a 100 mg/L stock solution from which a series of dilutions was made to give further stock solutions of 50, 25, 12.5 and 6.25 mg/L. An aliquot (500 mL) of each of the stock solutions was separately inoculated with algal suspension (9.1 mL) to give the required test concentrations of 6.25, 12.5, 25, 50 and 100 mg/L.
The stock solutions and each of the prepared concentrations were inverted several times to ensure adequate mixing and homogeneity.

Test organisms (species):

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

Details on test organisms:

The test was carried out using Pseudokirchneriella subcapitata strain CCAP 278/4. Liquid cultures of Pseudokirchneriella subcapitata were obtained from the Culture Collection of Algae and Protozoa (CCAP), SAMS Research Services Ltd, Scottish Marine Institute, Oban, Argyll, Scotland. Master cultures were maintained in the laboratory by the periodic replenishment of culture medium. The master cultures were maintained in the laboratory under constant aeration and illumination at 21 ± 2 °C.
Prior to the start of the test sufficient master culture was added to approximately 100 mL volumes of culture media contained in conical flasks to give an initial cell density of approximately 103 cells/mL. The flasks were plugged with polyurethane foam stoppers and kept under constant agitation by orbital shaker (100 – 150 rpm) and constant illumination at 24 ± 1 °C until the algal cell density was approximately 104 – 105 cells/mL.

Test type:

static

Water media type:

freshwater

Remarks:

For the composition - see report

Limit test:

no

Total exposure duration:

72 h

Test temperature:

Temperature was maintained at 24 ± 1 ºC throughout the test.

pH:

The pH value of the control cultures was observed to increase from pH 7.6 at 0 hours to pH 8.2 at 72 hours.
The pH deviation in the control cultures was less than 1.5 pH units after 72 hours and therefore was within the limits given in the Test Guidelines.

Nominal and measured concentrations:

6.25, 12.5, 25, 50 and 100 mg/L were selected for the definitive test.
Chemical analysis of the test preparations at 0 and 72 hours showed near nominal concentrations were obtained indicating that the test item was stable under test conditions.

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

19 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC20

Effect conc.:

24 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Key result

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

36 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

EC10

Effect conc.:

15 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: Inhibition of yield

Duration:

72 h

Dose descriptor:

EC20

Effect conc.:

17 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: Inhibition of yield

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

22 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: Inhibition of yield

Validity criteria fulfilled:

yes

Conclusions:

A study was performed to assess the effect of cesium fluoride on the growth of the green alga Pseudokirchneriella subcapitata (OECD guideline N°201). Following a preliminary range-finding test, Pseudokirchneriella subcapitata was exposed to an aqueous solution of the test item at concentrations of 6.25, 12.5, 25, 50 and 100 mg/L for 72 hours. The growth rate (EC50) was determined at 36 mg/L (nominal - test mat). The Inhibition of yield (EC50) was 22 mg/L(nominal - test mat). For both endpoint, the LOEC value was 25 mg/L and the NOEC value: 12.5 mg/L.

Executive summary:

* Introduction

A study was performed to assess the effect of the test item on the growth of the green alga Pseudokirchneriella subcapitata. The method followed was designed to be compatible with the OECD Guidelines for Testing of Chemicals (2006) No 201, "Freshwater Alga and Cyanobacteria, Growth Inhibition Test" referenced as Method C.3 of Commission Regulation (EC) No 761/2009.

* Methods

Following a preliminary range-finding test, Pseudokirchneriella subcapitata was exposed to an aqueous solution of the test item at concentrations of 6.25, 12.5, 25, 50 and 100 mg/L (three replicate flasks per concentration) for 72 hours, under constant illumination and shaking at a temperature of 24 ± 1 °C.

Samples of the algal populations were removed daily and cell concentrations determined for each control and treatment group, using a Coulter® Multisizer Particle Counter.

* Results

Analysis of the test preparations at 0 and 72 hours showed measured test concentrations to range from 92% to 110% of nominal and so the results are based on nominal test concentrations only.

Exposure of Pseudokirchneriella subcapitata to the test item gave the following results:

Response variable	EC50 (mg/L)	95% Confidence Limits (mg/L)	NOEC (mg/L)	LOEC (mg/L)
Growth Rate	36	33 - 40	12.5	25
Yield	22	21 - 25	12.5	25

Description of key information

A study was performed to assess the effect of  cesium fluoride on the growth of the green alga Pseudokirchneriella subcapitata (OECD guideline N°201). Following a preliminary range-finding test, Pseudokirchneriella subcapitata was exposed to an aqueous solution of the test item at concentrations of 6.25, 12.5, 25, 50 and 100 mg/L for 72 hours. The growth rate (EC50) was determined at 36 mg/L (nominal - test mat). The Inhibition of yield (EC50) was 22 mg/L(nominal - test mat). For both endpoint, the LOEC value was 25 mg/L and the NOEC value: 12.5 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:

36 mg/L