3,5,5-trimethylhexanoic acid

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:

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)