Fatty acids, C8-10, C12-18-alkyl esters

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

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

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.11 (Biodegradation: Activated Sludge Respiration Inhibition Test)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Remarks:

Landesamt für Umwelt, Wasserwirtschaft und Gewerbeaufsicht, Mainz, Germany

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION
- Method: Direct addition by initial weight into the test flasks. The test substance was weighed in the required amounts for the test concentrations directly to the test vessels with about 234 mL deionized water. 16 mL synthetic medium were dosed to each test vessel with test substance and reference substance afterwards. To prepare the blank control assays 234 mL of deionized water and 16 mL synthetic medium were mixed.
- Eluate: no
- Differential loading: yes
- Controls: yes, blank control with 234 mL of deionized water and 16 mL synthetic medium

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Source: Activated sludge from the municipal wastewater treatment plant of Mannheim, Germany was collected on 03 Sep 2012 from the aeration tank of the plant.
- Laboratory culture: no
- Preparation of inoculum for exposure: The activated sludge suspension was sieved with a fine woven mesh (mesh size about 1 mm). This suspension was pre-aerated over night at room temperature. At the next day the sludge suspension was washed once with drinking water and the suspension was adjusted to 3 g/L dry matter.
- Initial biomass concentration: 1.5 g/L dry matter

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

20.8 - 21.1 °C

pH:

7.1 - 7.2

Dissolved oxygen:

During aeration: > 2 mg/L
Immediately before measurement: > 7 mg/L

Nominal and measured concentrations:

nominal: control, 62.5, 125, 250, 500, 1000 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel
- Material, size, headspace, fill volume: Glass, 1 L, headspace: 500 mL, fill volume: 500 mL
- Aeration: yes
- No. of vessels per concentration (replicates): 2 replicates
- No. of vessels per control (replicates): 4 replicates

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: deionized water

OTHER TEST CONDITIONS
- Adjustment of pH: no

EFFECT PARAMETERS MEASURED:

TEST CONCENTRATIONS
- Spacing factor for test concentrations: ≤ 3.2

Reference substance (positive control):

yes

Remarks:

3,5 dichlorophenol

Key result

Duration:

3 h

Dose descriptor:

EC10

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Remarks:

respiration rate

Results with reference substance (positive control):

- Results with reference substance valid? yes
- Relevant effect levels: EC50 (3 h): 8.9 mg/L

Reported statistics and error estimates:

The consumption rates were used for the determination of the ECx by the probit method based on Finney with the software TOXRAT Professional 2.10.

Measured data of oxygen content in the test vessels at the begin and end of the evaluation time.

Concentration [mg/L]	Blank 1	Blank 2	Blank 3	Blank 4	62.5	62.5	125	125	250	250	500	500	1000	1000
O2 conc. Start [mg/L]	7.0	7.0	7.9	7.9	7.6	7.1	8.0	7.1	7.8	7.4	7.6	7.8	7.4	7.2
O2 conc. End [mg/L]	4.0	4.0	5.0	5.0	3.0	3.5	4.0	3.5	3.7	3.5	3.5	3.5	3.5	3.5
O2 consumption rate [mg/L	3.0	3.0	2.9	2.9	6.0	6.0	6.0	6.0	5.0	6.0	6.0	6.0	6.0	6.0
O2 consumption [min]	6.0	6.0	6.0	6.0	4.6	3.6	4.0	3.6	4.1	3.9	4.1	4.3	3.9	3.7
O2 consumption rate [ mg/Lxh]	30	30	29	29	46	36	40	36	49	39	41	43	39	37
Specific O2 consumption rate [mg/gxh]	20	20	19	19	31	24	27	24	33	26	27	29	26	25
Inhibition of respiration [%]	-	-	-	-	-56	-22	-36	-22	-66	-32	-39	-46	-32	-25

Validity criteria fulfilled:

yes

Description of key information

EC10 (3 h) > 1000 mg/L for activated sludge microorganisms (OECD 209)

Additional information

One GLP Guideline study according to OECD 209 is available investigating the toxicity of fatty acids, C8-10, C12-18-alkyl esters (CAS 95912-86-0) to microorganisms (Hammer 2013). Activated sludge microorganisms were exposed to the test substance up to a nominal concentration of 1000 mg/L. No effects were observed based on the respiration rate after 3 h of incubation resulting in an EC10 (3 h) of > 1000 mg/L. An increase of respiration was recorded in all treatments compared to the control values.