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Reference
Endpoint:
activated sludge respiration inhibition testing
Type of information:
experimental study
Adequacy of study:
key study
Study period:
Test performed on 29 March 1989.
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
guideline study without detailed documentation
Reason / purpose for cross-reference:
assessment report
Qualifier:
according to guideline
Guideline:
OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test
Version / remarks:
1984
Deviations:
yes
Remarks:
potassium dichromate as reference substance instead of 3,5-dichlorophenol
GLP compliance:
no
Analytical monitoring:
no
Vehicle:
yes
Details on test solutions:
PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Controls: two controls and one vehicle control
- Chemical name of vehicle (organic solvent, emulsifier or dispersant): Tween 80 puriss., Fluka
- Concentration of vehicle in test medium (stock solution and final test solution(s) including control(s)): vehicle used at 10 % of test concentration
Test organisms (species):
activated sludge of a predominantly domestic sewage
Details on inoculum:
- Source: from municipal waste-water treatment palnt of the community of Hildesheim
- Preparation of inoculum for exposure: washed 2x with dechlorinated and autoclaved tap water
- Pretreatment: none
- Initial biomass concentration: 2.4 g /L dry matter
Test type:
static
Water media type:
freshwater
Limit test:
no
Total exposure duration:
3 h
Test temperature:
20 °C
Nominal and measured concentrations:
nominal: 0 (control), 50, 100, 200, 500 and 1000 mg/L
Details on test conditions:
EFFECT PARAMETERS MEASURED (with observation intervals if applicable) :
- respiration: continuous O2 measurement by means of an O2-electrode (polarographic)
Reference substance (positive control):
yes
Remarks:
potassium dichromate
Duration:
3 h
Dose descriptor:
NOEC
Effect conc.:
200 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Key result
Duration:
3 h
Dose descriptor:
EC10
Effect conc.:
230 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:
other: EC20
Effect conc.:
290 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Key result
Duration:
3 h
Dose descriptor:
EC50
Effect conc.:
470 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Remarks on result:
other: 95 % CL: 218-1000 mg/L; EC50 and confidence interval not reliable since inhibition was only 15 % at 500 mg/L. Therefore, the EC50 should be > 500 mg/L and < 1000 mg/L.
Duration:
3 h
Dose descriptor:
other: EC80
Effect conc.:
750 mg/L
Nominal / measured:
nominal
Conc. based on:
test mat.
Basis for effect:
inhibition of total respiration
Remarks:
respiration rate
Details on results:
No inhibition was produced by Tween 80 (100 mg/l = max. concentration) in relation to the untreated controls.
Results with reference substance (positive control):
- Results with reference substance valid? yes
- Relevant effect levels: 47 % inhibition at 60 mg/L

At 200 mg/l and lower, the inhibition was up to 11 %; at 1000 mg/l,  inhibition of respiration was > 90 %.
No inhibition was produced by the solvent Tween 80 (100 mg/l = max. concentration).

Test item conc.

Respiration rate

Inhibition

(nominal; mg/L)

(mg O2/(L*h))

(%)

control 1

24.8

-

control 2

28.0

-

50

23.6

11

100

25.2

5

200

24.8

6

500

22.4

15

1000

2.0

92

Solvent control (100 mg/L)

25.6

3

Validity criteria fulfilled:
yes
Conclusions:
EC50 (3 h) = 470 mg/L: The inhibition of the degradation activity of activated sludge is not anticipated when introduced in appropriately low concentrations.
Executive summary:

The effect of 3,5,5 -trimethylhexanoic acid on domestic activated sludge was tested in a respiration inhibition test with a duration of 3 h according to OECD 209. The EC50 (3 h) is 470 mg/L, the EC10/NOEC (3 h) corresponds to 230 mg/L. Inhibition of the degradation activity of activated sludge is not anticipated when introduced in appropriately low concentrations.

Description of key information

OECD 209: EC50 (3 h) = 470 mg/L (Hoechst AG, 1989)

Key value for chemical safety assessment

EC50 for microorganisms:
470 mg/L
EC10 or NOEC for microorganisms:
230 mg/L

Additional information

The effect of 3,5,5-trimethylhexanoic acid on domestic activated sludge was tested in a respiration inhibition test with a duration of 3 h according to OECD 209 (Hoechst AG, 1989). The EC50 (3 h) was 470 mg/L. The EC10 was 230 mg/L. The inhibition of the degradation activtity of activated sludge is not anticipated when introduced in appropriately low concentrations.

Test method

Inoculum

Endpoint

Value [mg/L]

Reliability

Source

OECD 209

activated sludge, domestic, non-adapted

EC50 (3 h)

470

2
(key study)

Hoechst AG (1989)

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