Lithium [ethanedioato-O,O’]tetrafluorophosphate

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:

From 2020-01-17 to 2020-02-21

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:

Adopted March 23, 2006; Annex 5 corrected 28 July 2011

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

Batch No.: 190722
Purity: > 99 wt%

Analytical monitoring:

yes

Details on sampling:

- Concentrations: 1.0, 3.2, 10, 32 and 100 mg/L and control
- Sampling method: 2.0 mL and 4.8 mL from the approximate centre of the test solutions at t=0 h, t=24 h and t=72 h
- Sample storage conditions before analysis: stored in a freezer (≤-15°C)

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: Preparation of test solutions started with the highest concentration of 100 mg/L applying an overnight period of magnetic stirring to ensure complete hydrolysis of the test item and its dissolution in test medium. The pH (range-finding test: from 3.3 to 6.5; final test: from 3.3 to 6.6) with 1 M sodium hydroxide solution (Merck, Darmstadt, Germany), while pH of the test medium used for preparation of lower test concentrations was adjusted to 6.6 or 6.7 with 1M HCl (Merck, Darmstadt, Germany). Lower test concentrations were prepared by subsequent dilutions of the highest concentration in test medium. All test solutions were clear and colorless at the end of the preparation procedure.
- Controls: Test medium without test item or other additives

Test organisms (species):

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

Details on test organisms:

TEST ORGANISM
- Strain: NIVA CHL 1
- Source: In-house laboratory culture.
- Method of cultivation: Algae stock cultures were started by inoculating growth medium with algal cells from a pure culture on agar. The suspensions were continuously aerated and exposed to light (60 to 120 µE/m2/s when measured in the photosynthetically effective wavelength range of 400 to 700 nm) in a climate room at a temperature of 21-24°C.

ACCLIMATION
- Acclimation period: Three days
- Culturing media and conditions: same as test

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

72 h

Hardness:

24 mg CaCO3/L

Test temperature:

between 22 and 24°C

pH:

At 0h: 7.7-8.1
At 72h: 8.3-8.7

Nominal and measured concentrations:

Nominal: 1.0, 3.2, 10, 32 and 100 mg/L.
Measured: 0.38, 2.0, 6.7, 32, 108 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: 100 mL, all-glass with aluminium caps, perforated for ventilation, containing 50 mL of test solution
- Aeration: no aeration
- Renewal rate of test solution: static, no renewals
- Initial cells density: 1E+04 cells/mL
- Control end cells density: 2.49 E+06 cells/mL
- Replicates:
3 replicates of each test concentration,
6 replicates of the control,
1 extra replicate of each test group for sampling purposes after 24 hours of exposure,
1 or 2 replicates of each test concentration without algae.


GROWTH MEDIUM
- Standard medium used: yes, M2; according to the OECD 201 Guideline


TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water:
- Total organic carbon: Milli-RO water
- Culture medium different from test medium: no

OTHER TEST CONDITIONS
- Sterile test conditions: yes
- Adjustment of pH:no
- Photoperiod: Continuously using TLD-lamps with a light intensity within the range of 81 to 85 µE.m-2.s-1.

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- Determination of cell concentrations: At the beginning of the test, cells were counted using a microscope and a counting chamber. Thereafter, cell densities were determined by spectrophotometric measurement of samples at 680 nm using a spectrophotometer with immersion probe (path length = 10 mm).


TEST CONCENTRATIONS
- Spacing factor for test concentrations: 3.2
- Range finding study
- Test concentrations: 0.10, 1.0, 10, 100 mg/L
- Results used to determine the conditions for the definitive study:
Dose-related inhibition of algal growth rate and yield was found at all test concentrations at the end of the test. Growth rate inhibition of 21%and yield inhibition of 63% was recorded at the highest test concentration.
Based on the anionic fraction of the test item, the measured test item concentrations at the start of the test were 0.051 and 89 mg/L at nominal concentrations of 0.10 and 100 mg/L, respectively. These concentrations remained stable during the first 24 hours of exposure, i.e. were in the range of 102-114% relative to the initial concentrations. At the end of the test, the concentration measured in the highest group was at the level of the initially measured value (i.e. 99%), while the measured concentration at nominally 0.10 mg/L had decreased to 23% of the initially measured value.
Based on the cationic fraction of the test item, the measured test item concentrations at the start of the test were 0.11 and 96 mg/L at nominal concentrations of 0.10 and 100 mg/L, respectively. These concentrations remained stable during the exposure period, i.e. were in the range of 100 to 108% relative to the initial values at the end of the test.

Reference substance (positive control):

yes

Remarks:

Potassium dichromate

Duration:

72 h

Dose descriptor:

EC50

Effect conc.:

> 108 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

growth rate

Duration:

72 h

Dose descriptor:

NOEC

Effect conc.:

6.7 mg/L

Nominal / measured:

meas. (TWA)

Conc. based on:

test mat.

Basis for effect:

growth rate

Details on results:

- Exponential growth in the control (for algal test): yes
- Observation of abnormalities (for algal test):
Inhibition of growth rate and yield increased with increasing test item concentration of from 6.7 mg/L upwards resulting in 13 and 41% inhibition at the highest concentration tested, respectively. Statistically significant inhibition of growth rate was found at TWA concentrations of 32 mg/L and higher.
Microscopic observations at the end of the test revealed a normal and healthy appearance of the algal cells exposed to a TWA concentration of 108 mg/L when compared to the control.

- Measured Test Item Concentrations
- Anion:
Based on the anionic fraction of the test item, the measured test item concentrations at the start of the test were 0.44, 1.9, 6.1, 29 and 114 mg/L at nominal concentrations of 1.0, 3.2, 10, 32 and 100 mg/L, respectively. The measured concentration remained stable throughout the exposure period, i.e. were in the range of 82-119% relative to the initially measured values at the end of the test.
- Cation:
Based on the cationic fraction of the test item, the measured test item concentrations at the start of the test were 1.2, 3.9, 12, 36 and 116 mg/L at nominal concentrations of 1.0, 3.2, 10, 32 and 100 mg/L, respectively. The concentrations remained stable throughout the exposure period, i.e. were in the range of 97-103% relative to the initial concentrations at the end of the test.
It should be noted that small test item responses were detected in the samples taken from the control. The origin of these responses is unknown. Nevertheless, these concentrations were very low and assumed not to have affected the results of the test.
For both ionic forms, the test item concentrations measured in the solution prepared atnominally 100 mg/L but incubated without algae showed similar pattern as in their biological counterpart with algae, indicating that the growing algal biomass had no impact on the concentrations.
- Defining exposure concentrations:
Following a worst-case approach, the determination of effect parameters was subsequently based on the test item concentrations measured based on the anion of the test item. Based on these results, the average exposure concentrations were calculated and used to express effect parameters.

Results with reference substance (positive control):

- Results with reference substance valid?
Yes, The batch of Raphidocelis subcapitata tested, showed expected sensitivity to Potassium dichromate (Batch no. K50664264, Merck KGaA, Darmstadt, Germany).

Validity criteria fulfilled:

yes

Conclusions:

Under the conditions of the present study with Raphidocelis subcapitata, the test item inhibited growth rate and yield of this freshwater algae species significantly at time weighted average concentrations of 32 mg/L and higher.
The 72h-EC50 for growth rate inhibition (ERC50) and yield inhibition (EYC50) was beyond the range tested, i.e. exceeded a time weighted average concentration of 108 mg/L.
The 72h-NOEC for growth rate inhibition and yield inhibition was 6.7 mg/L.

Executive summary:

The ability of test item to generate toxic effects in Raphidocelis subcapitata during an exposure period of 72 hours was evaluated based on OECD 201.

A static test was performed at nominal concentrations of 1.0, 3.2, 10, 32 and 100 mg/L. A black control was set in parallel. 6 replicates were used per control group and 3 per test concentration.

The actual exposure concentrations were measured to be 0.38, 2.0, 6.7, 32 and 108 mg/L (time weighted average concentrations).

Inhibition of growth rates and yield increased with increasing concentration of test item from 6.7 mg/L upwards resulting in 13 and 41% inhibition at the highest concentration tested, respectively. Statistically significant inhibition of growth rates was found at test concentrations of 32 mg/L and higher.

Under the conditions of the present study with Raphidocelis subcapitata, the test item inhibited growth rate and yield of this freshwater algae species significantly at time weighted average concentrations of 32 mg/L and higher.

The 72h-EC50 for growth rate inhibition (ERC50) and yield inhibition (EYC50) was beyond the range tested, i.e. exceeded a time weighted average concentration of 108 mg/L.

The 72h-NOEC for growth rate inhibition and yield inhibition was 6.7 mg/L.

Description of key information

The ability of test item to generate toxic effects in Raphidocelis subcapitata during an exposure period of 72 hours was evaluated based on OECD 201.

Under the conditions of the present study with Raphidocelis subcapitata, the test item inhibited growth rate and yield of this freshwater algae species significantly at time weighted average concentrations of 32 mg/L and higher.

The 72h-EC50 for growth rate inhibition (ERC50) and yield inhibition (EYC50) was beyond the range tested, i.e. exceeded a time weighted average concentration of 108 mg/L.

The 72h-NOEC for growth rate inhibition and yield inhibition was 6.7 mg/L.

Key value for chemical safety assessment

EC50 for freshwater algae:

108 mg/L

EC10 or NOEC for freshwater algae:

6.7 mg/L