Ammonium undecafluorohexanoate

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:

28 Mar 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

GLP compliance:

yes

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: 2000 mg test item (corresponding to 1000 mg a.i.) was accurately weighed and was filled up to 100 mL with purified water. A stock solution of 10000 mg a.i./L in the test item was obtained.
- Eluate: no
- Differential loading: no
- Controls: yes, test medium control

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Laboratory culture: no
- Name and location of sewage treatment plant where inoculum was collected: Obtained on 27 Mar 2017 from an aeration reactor of a sewage treatment plant (Kurume central sewage treatment center (Kurume-shi, Fukuoka, Japan)
- Preparation of inoculum for exposure: 5 L of activated sludge was fed with the synthetic sewage (250 mL) and cultivated for 21.5 h at 20 ± 2 °C under aerobic conditions in order to acclimate to the test temperature.
- Suspended solids concentration: 2910 mg/L; 10 mL of the activated sludge was filtrated and the residue was dried for 2 h at 110 °C and weighed (in accordance with Japanese Industrial Standards (JIS) K 0102:2016, Section 14.1)

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

3 h

Test temperature:

20 ± 2 °C

pH:

7.5 (reference substance and blank control)
7.1 (test solutions)

Nominal and measured concentrations:

nominal: control, 1000 mg a.i./L

Details on test conditions:

TEST SYSTEM
- Test vessel: 300 mL glass vessels
- Material, size, headspace, fill volume: Glass, 300 mL, headspace: 50 mL, fill volume: 250 mL
- Aeration: 0.5 - 1 L/min
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6
- No. of vessels per reference mixture (replicates): 1
- Nutrients provided for bacteria: synthetic sewage (according to guideline)
- Nitrification inhibitor used: none

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: according to guideline

OTHER TEST CONDITIONS
- Adjustment of pH: The pH was adjusted to 7.5 witm 1 mol/L sodium hydroxide solution since the pH of thereference mixture and blank control was < 7.0.
- Details on termination of incubation: After 3 h of exposure, the measurement bottles were filed with the test solution with attention to avoid foaming. Afterwards the dissolved oxygen was measured continuously for 10 min.

EFFECT PARAMETERS MEASURED
- O2 consumption was measured at the end of 3 h incubation period.

TEST CONCENTRATIONS
- Spacing factor for test concentrations: not relevant, limit test
- Justification for using fewer concentrations than requested by guideline: No inhibition of respiration was recorded in the range-finding test. Thus, a limit test is justified.
- Range finding study
- Test concentrations: 10, 100 and 1000 mg/L
- Results used to determine the conditions for the definitive study: 1% inhibition at 10 mg/L, 11% inhibition at 100 mg/L, 12% inhibition at 1000 mg/L.

Reference substance (positive control):

yes

Remarks:

3,5-dichlorophenol

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

inhibition of total respiration

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

>= 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

act. ingr.

Basis for effect:

inhibition of total respiration

Details on results:

- Blank controls oxygen uptake rate: 47.8, 49.2, 47.7 mg O2/L/h (at test start); 45.9, 44.4, 42.9 mg O2/L/h (at test end)
- Coefficient of variation of oxygen uptake rate in control replicates: 5.9%

Results with reference substance (positive control):

- Results with reference substance valid? yes
- Relevant effect levels: EC50 (3 h): 11 mg/L

Reported statistics and error estimates:

In the reference mixture, the percentage inhibition in each exposure levels was plotted on semi­ logarithmic graph against the corresponding concentration. The EC50 of 3,5-dichlorophenol was calculated from the regression formula obtained by probit analysis. The NOEC of the test item was estimated by the following statistical analyses. Regarding the oxygen consumption rate, F- test was done to determine the homogeneity of variance for the data, Aspin-Welch t-test was used to estimate the significant difference in comparison with the control.

Table 1: Test results

	Nominal concentration [mg/L]	Oxygen consumption rate [mg O2/L/h]	Percentage inhibition of respiration [%]	Average percentage inhibition [%]
Test substance	1000	46.3, 47.9, 48.0	0, -3, -4	-2
Reference substance	4.0	39.4	15	-
	8.0	29.3	37	-
	16	13.5	71	-
	32	6.76	85	-
Blank control (test start)	-	47.8; 49.2; 47.7	-	-
Blank control (test end)		45.9; 44.9; 42.9

Validity criteria fulfilled:

yes

Description of key information

EC50 (3 h) > 1000 mg a.i./L (nominal; OECD 209)
NOEC (3 h) ≥ 1000 mg a.i./L (nominal; OECD 209)

Key value for chemical safety assessment

EC50 for microorganisms:

1 000 mg/L

Additional information

One experimental study according to OECD 209 (GLP) is available investigating the effects of ammonium undecafluorohexanoate (CAS 21615-47-4) on respiration of activated sludge microorganisms. The study was performed as a limit test with a nominal concentration of 1000 mg a.i./L. Activated sludge from a sewage treatment plant treating predominantly domestic sewage was used as inoculum. After incubation for 3 h the oxygen consumption rate was measured in the control and exposure vessels. Since no significant inhibition compared to the control was recorded the EC50 (3 h) was derived to be > 1000 mg a.i./L and the NOEC (3 h) as ≥ 1000 mg a.i./L. Thus, the substance is not expected to inhibit the activity of activated sludge microorganisms in sewage treatment plants.