Triisooctylamine

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:

2016-07-18 to 2016-11-21

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

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

2008

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

The test substance was added in the required amounts according to the test concentrations directly to the test vessels.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Name and location of sewage treatment plant where inoculum was collected: wastewater treatment plant of Mannheim, Germany
- Preparation of inoculum for exposure: After arrival of the activated sludge suspension in the test facility the 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 dw.
- Initial biomass concentration: 1.5 g/L dw

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test temperature:

19.7 - 20.5 °C

pH:

7.3 - 7.5

Dissolved oxygen:

> 7 mg/L

Nominal and measured concentrations:

test substance, nominal: 62.5; 125; 250; 500; 1000 mg/L
reference substance, nominal: 1, 10, 100 mg/L

Details on test conditions:

TEST SYSTEM
- Test vessel: Glas-beakers (nominal volume 1L)
- Aeration: yes
- No. of vessels per concentration (replicates): 3
- No. of vessels per control (replicates): 6
- No. of vessels per concentration of reference substance (replicates): 2
- Sludge concentration (weight of dry solids per volume): 1.5 g/L dw

TEST MEDIUM / WATER PARAMETERS
- Source/preparation of dilution water: synthetic OECD medium

OTHER TEST CONDITIONS
- Adjustment of pH: not needed

EFFECT PARAMETERS MEASURED (with observation intervals if applicable) : Oxygen uptake for a period of 8 to 10 minutes

TEST CONCENTRATIONS
- Spacing factor for test concentrations: 2

Reference substance (positive control):

yes

Remarks:

3,5 dichlorophenol

Key result

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

other: oxygen consumption

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:

other: oxygen consumption

Details on results:

- Any observations (e.g. precipitation) that might cause a difference between measured and nominal values: none
- Effect concentrations exceeding solubility of substance in test medium: no
- Adsorption: none
- Blank controls oxygen uptake rate: 21 mg/g x h
- Coefficient of variation of oxygen uptake rate in control replicates: 3.9 % O2 consumption

Results with reference substance (positive control):

- Results with reference substance: valid
- Relevant effect levels: EC50 = 2 - 25 mg/L

Table 1 Measurement of the oxygen consumption for blank control (BC) and reference substance (RS)

Assay identification	BC1	BC2	BC3	BC4	BC5	BC6	RS1	RS2	RS3	RS4	RS5	RS6
O2 conc. Start [mg/L]	7.5	7.0	8.0	8.0	8.3	8.0	8.0	7.5	8.4	8.5	9.0	8.8
O2 conc. End [mg/L]	4.5	4.0	5.0	5.0	5.3	4.5	5.4	5.0	6.8	6.9	8.6	8.4
O2 consumption rate [mg/L]	3.0	3.0	3.0	3.0	3.0	3.5	2.6	2.5	1.6	1.6	0.4	0.4
O2 consumption in minutes	6.0	6.0	6.1	5.9	6.0	6.3	5.8	6.0	6.0	6.2	6.0	6.0
O2 consumption rate [mg/L x h], RT	30	30	30	31	30	33	27	25	16	15	4	4
Specific O2 consumption rate [mg/gxh]	20	20	20	21	20	22	18	17	11	10	3	3
Calculation of inhibition respiration [%], IT	-						12	18	48	51	87	87

Table 2 Measurement of the oxygen consumption for Test Substanc (TS)

Assay identification	TS1	TS2	TS3	TS4	TS5	TS6	TS7	TS8	TS9	TS10	TS11	TS12	TS13	TS14	TS15
O2 conc. Start [mg/L]	7.5	7.4	8.0	7.1	7.0	7.2	7.0	7.0	6.0	7.0	8.0	6.5	7.0	7.6	7.0
O2 conc. End [mg/L]	4.5	4.5	5.2	4.1	4.0	4.0	3.6	3.8	2.7	4.0	5.2	3.5	4.5	5.0	4.0
O2 consumption rate [mg/L]	6.1	6.0	6.0	6.0	6.0	6.0	6.1	6.0	6.0	6.2	6.1	6.1	6.0	5.9	6.0
O2 consumption in minutes	3.0	2.9	2.8	3.0	3.0	3.2	3.4	3.2	3.3	3.0	2.8	3.0	2.5	2.6	3.0
O2 consumption rate [mg/L x h], RT	30	29	28	30	30	32	33	32	33	29	28	30	25	26	30
Specific O2 consumption rate [mg/gxh]	20	19	19	20	20	21	22	21	22	19	19	20	17	17	20
Calculation of inhibition respiration [%], IT	2	5	9	2	2	-4	-8	-4	-8	5	9	2	18	15	2

Legend: RS = reference substance, BC = blank control, TS = test substance

The respiration rate was calculated in mg O2/L×h. The oxygen consumption was measured over a period of 8-10 minutes. Specifically, 5.8 - 6.3 minutes (RS and BC), 6 - 6.1 minutes (TS1-9) or 5.9 – 6.2 minutes (TS10-15) from the plotted track within a linear range of the graph was used for the determination of the respiration rate.

Validity criteria fulfilled:

yes

Description of key information

EC50 for microorganisms was determined to be greater than 1000 mg/L in an activated sludge study, conforming to GLP and OECD 209 guideline.

Key value for chemical safety assessment

EC50 for microorganisms:

1 000 mg/L

Additional information

Activated sludge study

An activated sludge respiration inhibition test, according to GLP and OECD 209 was performed.

The 3 hours effect concentrations for the test item are EC10, EC20, EC50, and EC80 > 1000 mg/L. No monotone concentration response exists. Therefore, the ECx calculation is not meaningful and the EC10 value is assumed to be greater than 1000 mg/L. The results in this study are consistent with all validity criteria and the test is valid according to the guidelines used for this study.