Ethylcyclohexane

Toxicity to microorganisms

Administrative data

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2017-11-30 - 2018-07-16

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2017

Report date:

2018

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 209 (Activated Sludge, Respiration Inhibition Test (Carbon and Ammonium Oxidation))

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Ethylcyclohexane

EC Number:

216-835-0

EC Name:

Ethylcyclohexane

Cas Number:

1678-91-7

Molecular formula:

C8H16

IUPAC Name:

ethylcyclohexane

Test material form:

liquid: volatile

Specific details on test material used for the study:

Name Ethylcyclohexane
Appearance colourless transparant liquid
Composition Ethycyclohexane >99%
CAS No. 1678-91-7
EINECS-No. 216-835-0
Molecular formula C8H16
Molecular weight 112 g /mol
Purity >99.9% (GC)
Homogeneity homogeneous

Sampling and analysis

Analytical monitoring:

no

Test solutions

Vehicle:

no

Test organisms

Test organisms (species):

activated sludge of a predominantly domestic sewage

Details on inoculum:

Specification and Origin
The microbial inoculum to be used in this study consists of activated sludge from a sewage treatment plant treating predominantly domestic sewage.
Origin sewage treatment plant Neustadt/W
Date of collection 1 or 2 days before the start of the test
Preparation
The sludge was filtrated or centrifuged and re-suspended in tap water. The activated sludge
was aerated until usage in the test and fed daily with 50 mL synthetic sewage feed/L.
On the day of the start of the test the dry matter was determined by drying a volume of 5 mL at 105 ± 1 °C and weighing the remnants. The sludge then was adjusted to a suspended solids level of 2.0 – 3.2 g/L with tap water and aerated until usage in the test.
Before the test, pH was checked and adjusted to 6.0 – 8.0.

Study design

Test type:

static

Water media type:

freshwater

Limit test:

no

Total exposure duration:

3 h

Test conditions

Test temperature:

20.3 – 22.8 °C

pH:

7.7-7.9

Nominal and measured concentrations:

1000 mg/L, 320 mg/, 100 mg/L, 32 mg/L, 10 mg/L

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol

Results and discussion

Effect concentrations

Effect concentrations 1

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

Effect concentrations 2

Key result

Duration:

3 h

Dose descriptor:

EC10

Effect conc.:

300 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Effect concentrations 3

Key result

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

320 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

inhibition of total respiration

Results with reference substance (positive control):

EC50:10 mg/L

Any other information on results incl. tables

O₂-Consumption, Inhibition

Vessel No.	Content	Concentration in mg/L nominal	O2consumption in mg/(L*min.)	O2consumption in mg/(L*h)	Inhibition in %	pH
1	Blank Control	0	0.6248	37.487	0	7.9
2	Blank Control	0	0.6670	40.019	0	7.9
3	Positive Control	5	0.5668	34.009	20.3	7.8
4	Positive Control	10	0.3086	18.518	56.6	7.7
5	Positive Control	20	0.1508	9.047	78.8	7.8
6	Positive Control	40	0.0783	4.699	89.0	7.9
7	Blank Control	0	0.7215	43.290	0	7.8
8	Blank Control	0	0.6769	40.613	0	7.8
9	Test Item	1000	0.5676	34.054	20.2	7.9
10	Test Item	1000	0.6068	36.409	14.7	7.9
11	Test Item	1000	0.6126	36.757	13.9	7.9
12	Test Item	1000	0.6179	37.072	13.1	7.8
13	Test Item	1000	0.6220	37.321	12.5	7.9
14	Test Item	320	0.6530	39.179	8.2	7.9
15	Test Item	320	0.6656	39.938	6.4	7.9
16	Test Item	320	0.5680	34.079	20.1	7.9
17	Test Item	320	0.7036	42.215	1.1	7.9
18	Test Item	320	0.6872	41.231	3.4	7.9
19	Test Item	100	0.5742	34.450	19.3	7.9
20	Test Item	100	0.7812	46.870	-9.8	7.9
21	Test Item	100	0.6580	39.479	7.5	7.9
22	Test Item	100	0.5606	33.638	21.2	7.9
23	Test Item	100	0.6119	36.715	14.0	7.9
24	Test Item	32	0.7629	45.776	-7.3	7.9
25	Test Item	32	0.6981	41.883	1.8	7.9
26	Test Item	32	0.7502	45.015	-5.5	7.9
27	Test Item	32	0.7487	44.924	-5.3	7.9
28	Test Item	32	0.6996	41.977	1.6	7.9
29	Test Item	10	0.7213	43.276	-1.4	7.9
30	Test Item	10	0.7899	47.391	-11.1	7.9
31	Test Item	10	0.7949	47.691	-11.8	7.9
32	Test Item	10	0.8222	49.331	-15.6	7.9
33	Test Item	10	0.6831	40.984	3.9	7.9
34	Blank Control	0	0.8290	49.737	0	7.9
35	Blank Control	0	0.7477	44.862	0	7.9

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

The inhibition of the respiration of activated sludge when exposed to ethylcyclohexane was determined according to OECD Guideline 209.
Two experiments were performed. In the first experiment 1 of the validity criteria wasn’t met. Therefore, the study was repeated.  
In the second experiment the test item was tested using 5 concentrations ranging from 1000 to 10 mg/L nominal concentration. The concentrations based on a non GLP range finding test.
The dry matter of the inoculum was determined as 3.02 g suspended solids/L, giving a concentration of 1.51 g suspended solids/L in the test.
For the positive control an EC50 of 10 mg/L (95% confidence interval: not determinable) was determined. The value lies within the recommended range of the OECD guideline.
The following results for the test item Ethylcyclohexane were determined:
 
3h NOEC = 320 mg/L
3h EC10 = 300 mg/L
Confidence interval: 150 – 1000 mg/L
3h EC50 > 1000 mg/L
Confidence interval: not determinable

Executive summary:

The inhibition of the respiration of activated sludge when exposed to ethylcyclohexane was determined according to OECD Guideline 209.

Two experiments were performed. In the first experiment 1 of the validity criteria wasn’t met. Therefore, the study was repeated.  

In the second experiment the test item was tested using 5 concentrations ranging from 1000 to 10 mg/L nominal concentration. The concentrations based on a non GLP range finding test.

The dry matter of the inoculum was determined as 3.02 g suspended solids/L, giving a concentration of 1.51 g suspended solids/L in the test.

For the positive control an EC50 of 10 mg/L (95% confidence interval: not determinable) was determined. The value lies within the recommended range of the OECD guideline.

The following results for the test item Ethylcyclohexane were determined:

 

3h NOEC = 320 mg/L

3h EC10 = 300 mg/L

Confidence interval: 150 – 1000 mg/L

3h EC50 > 1000 mg/L

Confidence interval: not determinable