Dodecanoic acid, 2,2-dimethyl-3-oxopropyl ester

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:

2004-08-18 to 2004-11-30

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

Version / remarks:

adopted 1984

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Version / remarks:

adopted 1988

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Analytical monitoring:

no

Vehicle:

no

Details on test solutions:

PREPARATION AND APPLICATION OF TEST SOLUTION (especially for difficult test substances)
- Method: For the pre-test a stock solution containing 200 mg test item/L in deionized water was prepared. After 10 minutes in the ultrasonic bath the emulsion didn’t show any unsolved particles. The stock solution then was used to prepare the solutions of the concentrations 100, 10 and 1 mg/L. Because of the low water solubility, the treatment 1000 mg/L was prepared by adding the appropriate volume of the test item directly.
In the main study, the test item was used directly.

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

- Preparation of inoculum for exposure: The nutrient solution was freshly prepared; the inoculum was taken from its source, washed, aerated and the dry matter was determined. The stock solutions of the test item and the reference item were prepared.
- Pretreatment: The sludge was washed with tap water three times, then centrifuged and resuspended in tap water. 200 mL of the sludge were added to each test vessel.

Test type:

static

Water media type:

freshwater

Limit test:

yes

Total exposure duration:

3 h

Test temperature:

20 ± 2 °C

pH:

Pre-Test: 7.7
Main Study: 7.3

Nominal and measured concentrations:

Pre-test: 1; 10; 100; 1000 mg/L (nominal)
Main-study: 1000 mg/L (nominal)

Details on test conditions:

TEST SYSTEM
- Test vessel: Glass beakers
- Aeration: purified air, using Pasteur pipettes, flow approx. 0.75 L/min
Pre-test:
- No. of vessels per concentration (replicates): one replicate/treatment
- No. of vessels per control (replicates): one replicate before and one after measuring O2-concentrations in the test item replicates
- Biomass loading rate: 0.9086 g/cm³
Main-Study:
- No. of vessels per concentration (replicates): two replicates/treatment
- No. of vessels per control (replicates): two replicates before, two between and two after measuring O2-concentrations in the reference and test item replicates
- Biomass loading rate: 0.9086 g/cm³

TEST MEDIUM / WATER PARAMETERS
- in accordance to the guideline

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenole

Key result

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

>= 1 000 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.:

> 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):

The reference item showed an EC50 of 8.2 mg/L in the main study, which is within the recommended range of 5 – 30 mg/L.

O₂-Consumption

The values of the O₂consumption (which is a measure for the viability of the bacteria) of controls, test and reference item are presented in the following table.

Table 1: O₂consumption

No.	Content	Nominal Concentration (mg/L)	O2consumption in mg/(L*min.)	Mean O2cons. in mg/(L*min.)	Mean O2cons. in mg/(L*h)
1	Control	0	0.9702	0.9292	55.7534
2	Control	0	0.8883
3	Reference	2.5	0.7419	0.6991	41.9471
4	Reference	2.5	0.6563
5	Reference	5	0.5867	0.6125	36.7471
6	Reference	5	0.6383
7	Reference	10	0.4191	0.4363	26.1800
8	Reference	10	0.4536
9	Reference	20	0.3127	0.3257	19.5416
10	Reference	20	0.3386
11	Reference	40	0.1634	0.1599	9.5416
12	Reference	40	0.1556
13	Control	0	0.7520	0.7271	43.6274
14	Control	0	0.7022
15	Test Item	1000	1.0636	1.2185	73.1071
16	Test Item	1000	1.3733
17	Control	0	1.0116	0.9983	59.8994
18	Control	0	0.9850

The Control vessels no 13 and 14 were stated as outliers and were not used for the determination of the results, since the O₂-consumption was much lower than in the other control vessels.

 Inhibition

Inhibition of the O₂consumption was calculated by comparison with the controls and is given in the following table.

Inhibition %

Item	Nominal Concentration (mg/L)	Inhibition in %
Test Item	1000	-26.4
Reference	2.5	27,5
Reference	5	36,5
Reference	10	54,7
Reference	20	66,2
Reference	40	83,4

Validity criteria fulfilled:

yes

Conclusions:

The 3 h EC50 was determined to be greater than 1000 mg/L and the 3 h NOEC was 1000 mg/L.

Executive summary:

This study was performed in order to evaluate the effect of the test item on the respiration of activated sludge obtained from domestic sewage treatment plant. The activated sludge respiration test is a rapid screening method to identify substances which may adversely affect aerobic microorganisms. In the pre-test, the test item was tested using four concentrations (ranging from 1000 to 1 mg/L). Duration of the test was three hours. Activated sludge was used as inoculum. It was taken from a domestic sewage treatment plant and washed before usage. The dry matter was determined as 4.0 g suspended solids/L, giving a concentration of 1.6 g suspended solids/L in the test. As the pre-test was performed for range-finding only, no reference item was tested. No inhibition of the respiration of the activated sludge was detected in the treatments. The main study was performed as a limit-test with the nominal concentration of 1000 mg/L. Conduct of the study was the same as in the pre-test. The dry matter of the activated sludge was determined as 4.1 g suspended solids/L, giving a concentration of 1.64 g suspended solids/L in the test. 3,5-Dichlorophenole was used as reference item. The EC50 of the reference item was determined as 8.4 mg/L (95% confidence interval: 6.4 – 10.2 mg/L), which lies within the range of 5 – 30 mg/L. The 3 h EC50 was determined to be greater than 1000 mg/L and the 3 h NOEC was 1000 mg/L.

Description of key information

Aldehyde L was assessed in a activated sludge study according to EU-method C.11 and OECD guideline 209. A pre-test and a main-study were performed. The 3 h EC50 was determined to be greater than 1000 mg/L and the 3 h NOEC was 1000 mg/L.

Key value for chemical safety assessment

EC10 or NOEC for microorganisms:

1 000 mg/L

Additional information

This study was performed in order to evaluate the effect of the test item on the respiration of activated sludge obtained from domestic sewage treatment plant. The activated sludge respiration test is a rapid screening method to identify substances which may adversely affect aerobic microorganisms. In the pre-test, the test item was tested using four concentrations (ranging from 1000 to 1 mg/L). Duration of the test was three hours. Activated sludge was used as inoculum. It was taken from a domestic sewage treatment plant and washed before usage. The dry matter was determined as 4.0 g suspended solids/L, giving a concentration of 1.6 g suspended solids/L in the test. As the pre-test was performed for range-finding only, no reference item was tested. No inhibition of the respiration of the activated sludge was detected in the treatments. The main study was performed as a limit-test with the nominal concentration of 1000 mg/L. Conduct of the study was the same as in the pre-test. The dry matter of the activated sludge was determined as 4.1 g suspended solids/L, giving a concentration of 1.64 g suspended solids/L in the test. 3,5-Dichlorophenole was used as reference item. The EC50 of the reference item was determined as 8.4 mg/L (95% confidence interval: 6.4 – 10.2 mg/L), which lies within the range of 5 – 30 mg/L. The 3 h EC50 was determined to be greater than 1000 mg/L and the 3 h NOEC was 1000 mg/L.