Lithium [ethanedioato-O,O’]tetrafluorophosphate

Toxicity to microorganisms

Link to relevant study record(s)

Reference

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

From 2019-09-18 to 2019-10-11

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test (Carbon and Ammonium Oxidation))

Version / remarks:

2010

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Batch No.: 190722
Purity: > 99 wt%

Analytical monitoring:

no

Vehicle:

yes

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: The test item was not sufficiently soluble to allow preparation of an aqueous solution at a concentration of 10 g/L. Therefore, weighed amounts were added to the amber coloured test bottles containing 200 mL Milli-RO water (tap water purified by reverse osmosis; Millipore Corp., Bedford, Mass., USA). The test item – Milli-RO water mixtures were magnetically stirred for a short period. Subsequently, 16 mL synthetic medium made up to 50 mL with Milli-RO water and 250 mL sludge were added, resulting in the required concentrations. Optimal contact between the test item and test organisms was ensured by applying continuous aeration and stirring.
- Chemical name of vehicle: Milli-RO water

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Name and location of sewage treatment plant where inoculum was collected: Municipal sewage treatment plant: 'Waterschap Aa en Maas', 's-Hertogenbosch, The Netherlands
- Preparation of the sludge: The sludge was coarsely sieved (1 mm) and allowed to settle. The supernatant was removed and ISO-medium was added. The concentration of the suspended solids was determined (3 g/L, as used for the test). The batch of sludge was used one day after collection. Therefore 50 mL of synthetic medium (=sewage feed) was added per litre of activated sludge at the end of the collection day. The sludge was kept aerated at test temperature until use. The pH was 7.3 on the day of testing.
- Medium: Adjusted ISO-medium, formulated using RO water (tap water purified by reverse osmosis; GEON Waterbehandeling, Berkel-Enschot, The Netherlands) with the following composition: CaCl2.2H2O 211.5 mg/L; MgSO4.7H2O 88.8 mg/L; NaHCO3 46.7 mg/L; KCl 4.2 mg/L

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

21-22 °C

pH:

Before addition of sludge: 7.4-7.5, 6.5-6.8, 6.6-6.8, 6.4-6.5, 4.7-5.3, 3.7-4.1, 3.2-3.4 for control and 22, 46, 100, 220, 460 and 1000 mg/L, respectively
After 3 h contact time: 7.5-7.7, 7.6-7.7, 7.5-7.5, 7.2-7.3, 5.0-5.4, 3.7, 2.8-2.9 for control and 22, 46, 100, 220, 460 and 1000 mg/L, respectively

Nominal and measured concentrations:

Nominal:
Final Test: 22, 46, 100, 220, 460 and 1000 mg/L.

Details on test conditions:

TEST SYSTEM
- Test vessel: amber coloured test bottles
- Type: open
- Fill volume: 500 mL
- Aeration: yes, adjusted in such a way that the dissolved oxygen concentration at the start was above 60-70% saturation (60% of air saturation is > 5 mg/L at 20°C) and to maintain the sludge flocs in suspension.
- No. of vessels per concentration (replicates): 5
- No. of vessels per control (replicates): 6
- No. of vessels per abiotic control (replicates): 1
- Sludge concentration (weight of dry solids per volume): 1.5 g/L.
- Nutrients provided for bacteria: Synthetic medium: 16 g peptone, 11 g meat extract, 3 g urea, 0.7 g NaCl, 0.4 g CaCl2.2H2O, 0.2 g MgSO4.7H2O, 2.8 g K2HPO4, dissolved in Milli-RO water, made up to 1 litre and filtered. The pH was within 7.5 ± 0.5.
- Performance of the test: at the start of the test, the synthetic medium (16 mL) made up to 50 mL with Milli-RO and 200 mL test item solution were mixed (total volume 250 mL). The pH was determined. Thereafter, 250 mL activated sludge was added.

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: Tap water purified by reverse osmosis (Millipore Corp., Bedford, Mass., USA).

OTHER TEST CONDITIONS
- Adjustment of pH: no
- Details on termination of incubation: After the 3-hour contact time the oxygen consumption was recorded for a period of approximately 10 minutes. During measurement, the sample was not aerated but continuously stirred on a magnetic stirrer.
The pH was determined in the remaining part of the reaction mixture. This procedure was repeated for all test/reference item concentrations and controls.
The medium temperature was recorded continuously in temperature control vessels. The temperature control vessels were identically prepared compared to the control vessels. A temperature control vessel with a REES sensor was placed in each fume cupboard of the climate room.
- Oxygen recording: Determination of oxygen was performed with multiple oxygen sensors connected to a BlueBox (GO-Systemelektronik GmbH, Germany), a multichannel measuring and controlling system.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2.2
- Range finding study
- Test concentrations: 10, 100 and 1000 mg/L
- Results used to determine the conditions for the definitive study: The combined limit/range-finding showed 4.40%, 14.54% and 99.27% inhibition of the respiration rate at a concentration of 10, 100 and 1000 mg/L, respectively. Therefore, the expected EC50 was at a concentration between 100 and 1000 mg/L. There was no oxygen uptake from abiotic processes.

Reference substance (positive control):

yes

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

100 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Duration:

3 h

Dose descriptor:

EC10

Effect conc.:

91 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

134 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Duration:

3 h

Dose descriptor:

other: EC20

Effect conc.:

104 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Details on results:

No statistically significant inhibition of the respiration rate of the sludge was recorded at 100 mg/L. The pH value at 100 mg/L varied between 6.4 and 7.3. At higher concentrations the pH of the test medium decreased to values ≤ 5. At higher test concentrations the inhibitory effect of test item on aerobic waste water (activated sludge) bacteria ranged from 95.08% inhibition at 220 mg/L (pH ~5) to 98.16% at 1000 mg/L (pH ~3). Inhibitory effects might be influenced by the low pH value.

- Blank controls oxygen uptake rate: 23.72 mg O2/g h
- Coefficient of variation of oxygen uptake rate in control replicates: 9.53%

Results with reference substance (positive control):

The EC50 of 3,5-dichlorophenol was in the accepted range of 2 to 25 mg/L for total respiration (4.1 mg/L in the final test).

Validity criteria fulfilled:

yes

Conclusions:

In conclusion, under the conditions of the present test the test item was not toxic to waste water bacteria (activated sludge) at or below a concentration of 100 mg/L (NOEC).
The EC10 was 91 mg/L (95% confidence interval: 73 - 103 mg/L).
The EC20 was 104 mg/L (95% confidence interval: 89 - 117 mg/L).
The EC50 was 134 mg/L (95% confidence interval: 118 - 164 mg/L).
The toxic effect might be an intrinsic effect of test item and/or the effect of the low pH values caused by the test item.

Executive summary:

The ability of test item to adversely affect aerobic microbial treatment plants was evaluated based on the OECD 209.

The final test was performed based on the result of a preceding combined limit/range-finding test. Six concentrations were tested, ranging from 22 to 1000 mg/L and increasing with a factor 2.2. Five replicates per concentration and six replicates of an untreated control group were tested.

No statistically significant inhibition of the respiration rate of the sludge was recorded at 100 mg/L. The pH value at 100 mg/L varied between 6.4 and 7.3. At higher concentrations the pH of the test medium decreased to values ≤ 5. At higher test concentrations the inhibitory effect of test item on aerobic waste water (activated sludge) bacteria ranged from 95.08% inhibition at 220 mg/L (pH ~5) to 98.16% at 1000 mg/L (pH ~3). Inhibitory effects might be influenced by the low pH value.

Ammonium oxidation and/or heterotrophic oxidation was not assessed specifically, as a proper dose-response curve was obtained.

In conclusion, under the conditions of the present test the test item was not toxic to waste water bacteria (activated sludge) at or below a concentration of 100 mg/L (NOEC).

The EC10 was 91 mg/L (95% confidence interval: 73 - 103 mg/L).

The EC20 was 104 mg/L (95% confidence interval: 89 - 117 mg/L).

The EC50 was 134 mg/L (95% confidence interval: 118 - 164 mg/L).

The toxic effect might be an intrinsic effect of test item and/or the effect of the low pH values caused by the test item.

Description of key information

The ability of test item to adversely affect aerobic microbial treatment plants was evaluated based on the OECD 209.

Under the conditions of the present test the test item was not toxic to waste water bacteria (activated sludge) at or below a concentration of 100 mg/L (NOEC).

The EC10 was 91 mg/L (95% confidence interval: 73 - 103 mg/L).

The EC20 was 104 mg/L (95% confidence interval: 89 - 117 mg/L).

The EC50 was 134 mg/L (95% confidence interval: 118 - 164 mg/L).

The toxic effect might be an intrinsic effect of test item and/or the effect of the low pH values caused by the test item.

Key value for chemical safety assessment

EC50 for microorganisms:

134 mg/L

EC10 or NOEC for microorganisms:

100 mg/L