3,3,4,4,5,5,6,6,7,7,8,8-dodecafluorodeca-1,9-diene

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 July 2017 to December 2017

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:

yes

Remarks:

without any impact on the overall integrity of the study or the interpretation of the study results and conclusions

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

- Appearance: Clear colourless liquid
- Test item storage: At room temperature protected from light
- Purity/Composition correction factor: No correction factor required

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

The test item was not sufficiently soluble to allow preparation of an aqueous solution at a concentration of 10 g/L. Therefore, aliquots corresponding to the required loading rate were
pipetted directly into the dark brown test bottles containing 200 mL Milli-RO water (tap water purified by reverse osmosis; Millipore Corp., Bedford, Mass., USA). Since the test item was known to be volatile the pipette tip was immersed below the surface of the Milli-RO when transferring the test item. The test item – Milli-RO water mixtures were magnetically
stirred briefly to mix (5 minutes) and subsequently, 16 mL synthetic medium made up to 50 mL with Milli-RO water and 250 mL sludge were added resulting in the required loading
rates.

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, receiving predominantly domestic sewage.
- Preparation of inoculum for exposure: The sludge was coarsely sieved (1 mm) and allowed to settle. The supernatant was removed and ISO-medium was added. A small amount of the sludge was weighed and dried overnight at ca. 105°C to determine the amount of suspended solids (3.0 g/L of sludge, as used for the test). The pH was 7.2 on the day of testing. 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.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

3 h

Remarks on exposure duration:

Additional measurements were performed after 30 minutes of incubation in the combined limit:range finding test: since the test item is volatile, a reduced contact time was included in the test, as recommended by the test guideline.

Nominal and measured concentrations:

Nominal concentrations (definitive test): 0 (control),100, 180, 320, 560 and 1000 mg/L.

Details on test conditions:

TEST SYSTEM
- Test vessel: All glass open bottles/vessels.
- Aeration: 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
- Sludge concentration: 1.5 g/L

TEST MEDIUM
- Synthetic medium (= sewage feed): 16 g peptone, 11 g meat extract, 3 g urea, 0.7 g NaCl, 0.4 g CaCl2.2H2O, 0.2 g MgSO4.7H2O and 2.8 g K2HPO4 dissolved in Milli-RO water, made up to 1 litre and filtered (pH within 7.5 ± 0.5)
- Test medium: 16 mL synthetic medium made up to 50 mL with Milli-RO, mixed with 200 mL test item solution and then added with 250 mL activated sludge

OTHER TEST CONDITIONS
- Adjustment of pH: no

EFFECT PARAMETERS MEASURED:
After a contact time of 30 minutes, approximately half of the sample was transferred to a beaker for the recording of oxygen consumption for a period of approximately 10 minutes. The remaining half of the sample was aerated until a contact time of 3 hours was reached. 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 determination of oxygen consumption was performed with multiple oxygen sensors connected to a BlueBox, a multichannel measuring and controlling system.

OTHER PARAMETERS
The pH was determined in the part of the reaction mixture remaining after measurement. 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.

TEST CONCENTRATIONS:
- Range finding study: yes (combined limit/range-finding test)
- Test concentrations: 0 (control), 10, 100 and 1000 mg/L
- Results used to determine the conditions for the definitive study: yes

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol

Key result

Duration:

3 h

Dose descriptor:

other: NOELR

Effect conc.:

>= 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Key result

Duration:

3 h

Dose descriptor:

other: EL50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

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 (8.5 mg/L in the 30 minutes combined limit/range-finding test and 4.0 mg/L in the final test).

Inhibition of the Respiration Rate

A summarized overview of the study results is presented in the table below. No statistically significant inhibition of the respiration rate was observed at any of the tested loading rates. Therefore, the NOELR was considered to be the highest loading rate tested (1000 mg/L). No ELR50-value could be calculated because the test item proved to be non-toxic (ELR50 > 1000 mg/L).

Treatment	Loading rate (mg/L)	Mean respiration rate		% Inhibition of the respiration rate (mean value)
		(mg O2/L h)	(mg O2/g h)¹
Control		35.17	23.45
T1	100	36.73	24.48	-4.42
T2	180	30.46	20.30	13.41
T3	320	35.40	23.60	-0.64
T4	560	34.16	22.77	2.89
T5	1000	34.80	23.20	1.07

Acceptability of the Test:

1. The mean control oxygen uptake rate exceeded 20 mg oxygen per one gram of activated sludge (dry weight of suspended solids) in an hour (26.09 and 24.07 mg oxygen per one gram of activated sludge, after a contact time of 30 minutes and 3 hours, respectively, in the combined limit/range-finding test; 23.45 mg oxygen per one gram of activated sludge in the final test). The coefficient of variation of oxygen uptake in control replicates did not exceed 30%

at the end of the both the 30 minutes combined limit/range-finding and final test (7% and 11%, respectively).

2. The EC50 of 3,5-dichlorophenol was in the accepted range of 2 to 25 mg/L for total respiration (8.5 mg/L in the 30 minutes combined limit/range-finding test and 4.0 mg/L in the final test.

Since all criteria for acceptability of the test were met, this study was considered to be valid.

Validity criteria fulfilled:

yes

Conclusions:

Under the conditions of the test, the test item was not toxic to waste water bacteria (activated sludge) at or below a loading rate of 1000 mg/L (NOELR). The ELR50 was higher than 1000 mg/L.

Executive summary:

The toxicity of the test item to waste water bacteria (activated sludge) was investigated in a GLP-compliant study performed in accordance with OECD Guideline No. 109. Under the conditions of the test, the test item was not toxic to the bacteria at or below a loading rate of 1000 mg/L (NOELR). The ELR50 was higher than 1000 mg/L.

Description of key information

The toxicity of the test item to waste water bacteria (activated sludge) was investigated in a GLP-compliant study performed in accordance with OECD Guideline No. 109. Under the conditions of the test, the test item was not toxic to the bacteria at or below a loading rate of 1000 mg/L (NOELR). The ELR50 was higher than 1000 mg/L.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

1 000 mg/L

Additional information

The toxicity of the test item to waste water bacteria (activated sludge) was investigated in a GLP-compliant study,with minor deviations.The study is considered as reliable (Klimisch 1) and is selected as a key study for the endpoint.