Ethyl lactate

Toxicity to microorganisms

Administrative data

Endpoint:

activated sludge respiration inhibition testing

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2018

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))

GLP compliance:

yes (incl. QA statement)

Test material

Test material information

Constituent 1

Reference substance name:

Ethyl lactate

EC Number:

202-598-0

EC Name:

Ethyl lactate

Cas Number:

97-64-3

Molecular formula:

C5H10O3

IUPAC Name:

ethyl 2-hydroxypropanoate

Test material form:

liquid

Remarks:

colorless transparent liquid

Sampling and analysis

Analytical monitoring:

yes

Remarks:

The oxygen consumption rate is calculated from the slope of the linear part of the oxygen consumption curve (usually between 7.0 and 2.0 mg O2/L)

Details on sampling:

The test item was tested using 4 concentrations ranging from 1000 to 1 mg/L nominal concentration. Duration of the test was 3 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 2.66 g suspended solids/L, giving a concentration of 1.33 g suspended solids/L in the test.

Test organisms

Test organisms (species):

activated sludge of a predominantly domestic sewage

Study design

Test type:

not specified

Water media type:

other: tap water

Limit test:

no

Total exposure duration:

3 h

Test conditions

Test temperature:

20.0 - 21.3 °C

pH:

7.5 ± 0.5

Nominal and measured concentrations:

4 concentrations ranging from 1000 to 1 mg/L nominal concentration

Details on test conditions:

Duration 3 hours
Replicates 1 replicate/concentration (positive control, test item lower concentrations)
5 replicates for test item treatment 1000 mg/L
Blank Control 2 replicates before and 2 after measuring positive control and test item, respectively
Water tap water, see annex 2, page 23
Aeration purified air, using Pasteur pipettes
Feeding nutrient solution, 16 mL/vessel
Temperature 20.0 – 21.3 °C

Reference substance (positive control):

yes

Remarks:

3,5-Dichlorophenol (CAS-No. 591-35-5) was used as positive control. A stock solution in deionised water containing 501 mg/L was freshly prepared for the experiment.

Results and discussion

Effect concentrations

Effect concentrations 1

Duration:

3 h

Dose descriptor:

NOEC

Effect conc.:

>= 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth inhibition

Effect concentrations 2

Duration:

3 h

Dose descriptor:

EC10

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth inhibition

Effect concentrations 3

Duration:

3 h

Dose descriptor:

EC50

Effect conc.:

> 1 000 mg/L

Nominal / measured:

nominal

Conc. based on:

test mat.

Basis for effect:

growth inhibition

Any other information on results incl. tables

One experiment was performed.

The test item was tested using 4 concentrations ranging from 1000 to 1 mg/L nominal concentration. For the treatment 1000 mg/L, 5 replicates were used; for the other treatments, 1 replicate each.

Because no significant inhibition was observed, no additional experiment had to be per-formed.

All validity criteria were met. For the estimation of the EC50 of the positive control, the fits showed good statistical correspondence of the data with the dose-response-equation. The positive control gave an EC50 of 11 mg/L (95 % confidence interval 5.0 – 18 mg/L) which lie within the recommended range of 2 – 25 mg/L. The coefficient of variation of oxygen uptake rate in control replicates was below 30% at the end of the test. The oxygen uptake rate of the blank controls was above 20 mg O₂ per gram activated sludge in 1 hour.

The measurement period was partly less than 3 minutes. Because linearity of all regression curves was given and the correlation of the inhibition values within the test replicates was very good, this can be stated as uncritical

No observations were made which might cause doubts concerning the validity of the study outcome.

The result of the test can be considered valid.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Conclusions:

Because no significant inhibition was observed, no additional experiment had to be performed
The following results for the test item Ethyl lactate were determined:
3h NOEC ≥ 1000 mg/L
3h EC10 > 1000 mg/L
3h EC50 > 1000 mg/L