Ethyl (S)-2-hydroxypropionate

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

4 (not assignable)

Rationale for reliability incl. deficiencies:

other: see 'Remark'

Remarks:

Several esters of lactic acid were tested for ready biodegradability and/or biochemical oxygen demand using several study protocols and test guidelines. However, the allocation of test protocols to substances is not evident from the materials and methods section, and the documentation of test conditions is generally poor. Therefore, the reliability of study performance and results cannot be assessed.

Qualifier:

equivalent or similar to guideline

Guideline:

OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test)

Qualifier:

equivalent or similar to guideline

Guideline:

EU Method C.5 (Degradation: Biochemical Oxygen Demand)

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

not specified

Duration of test (contact time):

28 d

Initial conc.:

1.88 mg/L

Based on:

ThOD

Initial conc.:

4 mg/L

Based on:

ThOD

Parameter followed for biodegradation estimation:

not specified

Details on study design:

The biodegradability of lactic acid and alkyl lactate esters was determined in closed bottle screening tests or with the aid of BOD determinations after 5 and 28 days.

Reference substance:

acetic acid, sodium salt

Reference substance:

other: mixture of glucose and glutamic acid

Parameter:

other: not specified

Value:

75

Sampling time:

28 d

Parameter:

other: not specified

Value:

85

Sampling time:

20 d

Details on results:

No details on validity of the study or on the results are available.

Results with reference substance:

The reference substances (sodium acetate or a mixture of glucose and glutamic acid, depending on the guideline used) were completely degraded within five days.

Validity criteria fulfilled:

no

Interpretation of results:

readily biodegradable

Conclusions:

The test item is readily biodegradable based on the information given in the source.

Executive summary:

Several esters of lactic acid were tested for ready biodegradability and/or biochemical oxygen demand using several study protocols and test guidelines. However, the allocation of test protocols to substances is not evident from the materials and methods section, and the documentation of test conditions is generally poor. Therefore, the reliability of study performance and results cannot be assessed. Based on the available results the test item is readily biodegradable.

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

1991-09-20 to 1993-02-09

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods with acceptable restrictions

Qualifier:

according to guideline

Guideline:

EU Method C.5 (Degradation: Biochemical Oxygen Demand)

Version / remarks:

Cited as Directive 84/449/EEC, C.8, and NEN 6634

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.6 (Degradation: Chemical Oxygen Demand)

Version / remarks:

Cited as Directive 84/449/EEC, C.9, and NEN 6633

Deviations:

no

GLP compliance:

yes

Specific details on test material used for the study:

- ethyl S(-)lactate
- Batch no. EK 355.8

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

A sample of activated sludge was taken from an oxidation ditch situated on the premises of TNO, Delft, The Netherlands. The oxidation ditch is used to treat domestic sewage. The original sludge (containing 5.6-5.8 g of solid substance/L) was allowed to settle for 3-7 minutes (8 minutes for the BOD28 test) and 3 ml (3.5 ml for the BOD28 test) of the supernatant was used to inoculate each litre of BOD dilution water. The dilution water was aerated vigorously before use.

Duration of test (contact time):

>= 20 - <= 28 d

Initial conc.:

> 0 - <= 4 mg/L

Based on:

test mat.

Initial conc.:

> 0 - <= 2.03 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

The BOD determination was conducted as described in the protocol, developed mainly from the Dutch guideline 'Water-Determination of Biochemical Oxygen Demand after n days (BODn)' (NEN 6634). For the BOD5 and the BOD20 determination, test concentrations of 2.0 and 4.0 mg/L were prepared by adding respectively 32 and 64 ml of the 202.0 mg/L stock solution to 3.2 L lots of inoculated BOD dilution water.
In order to check the activity of the inoculum and the possible toxicity of the test substance, 1 ml/L of a solution containing 3 g/L of glucose and 3 g/L of glutamic acid, and this mixture with 4 mg/L of ethyl S(-)lactate were also tested.
Nitrification control was included by adding 2.5 mg/L of allylthiourea to bottles containing 2 mg\L of ethyl S(-)lactate.
For the BOD28 determination, test concentrations of 1.01 and 2.03 mg/L were prepared by adding respectively 10 and 20 ml of the 202.5 mg/L stock solution to 2.0 L lots of inoculated BOD dilution water. An inoculum activity control series with glucose and glutamic acid was included.
Quadruplicate BOD bottles were incubated at 20 °C for 5, 20 or 28 days in the dark. The O2 concentration was measured with an oxygen electrode after 0, 5 and 20 or 28 days. A separate set of bottles was sacrified for each measurement.
The COD was determined with two samples of 1 ml each from a solution of 403.9 mg of test substance in 100 ml of Milli-Q water, and conducted as detailed in the Dutch guideline.

TEST CONDITIONS
- Test temperature: the temperature measured in the BOD bottles varied between 20.2 and 20.5 °C. In the BOD28 test the temerature varied between 19.5 and 20.5°C
- pH: The pH of the medium in the BOD bottles was 6.4-6.5 (6.7-6.8 in the BOD28 determination) at the start and 6.0-6.4 after twenty days. In the BOD28 test the pH varied between 6.4 and 6.7 at the end. The pH values in botlles with glucose added were generally lower in the range 6.0-6.1. The comparatively low pH of the medium in this test did not influence the inoculum activity negatively.
- pH adjusted: no
- Aeration of dilution water: yes
- Continuous darkness: yes

Calculation of results:
The oxygen demand in each test bottle after 5 and 20 and 28 days was calculated by subtracting the oxygen concentration measured at that time from the measured at the start of the test. The biochemical oxygen demand due to the test or control substances at each time (BOD5 or BOD20) was calculated (in mg O2/L) by subtracting the oxygen demand in the inoculum control from that in the bottle under consideration; these crude values were then converted into values per mg substance. The highest value (expressed as mg O2/mg) obtained was assumed to be the BOD5, BOD20 or BOD28 as appropriate. The percentage degradation can be calculated as (BOD/COD) × 100.

Reference substance:

other: glucose

Reference substance:

other: glutamic acid

Reference substance:

other: allylthiourea

Parameter:

% degradation (O2 consumption)

Value:

36

Sampling time:

5 d

Parameter:

% degradation (O2 consumption)

Value:

65

Sampling time:

20 d

Parameter:

% degradation (O2 consumption)

Value:

85

Sampling time:

28 d

Details on results:

The BOD5, BOD20 and BOD28 values of the various concentrations of ethyl S(-)lactate were in the ranges 0.24-0.60 mg O2/L, 1.04-1.08 mg O2/L and 1.18-1.43 mg O2/L respectively; it was therefore concluded that the BOD5, BOD20 and BOD28 of ethyl S(-)lactate are 0.60, 1.08 and 1.43 mg O2/mg respectively. A comparable BOD5 value of the test substance was also found in the presence of glucose and glutamic acid, confirming the results. The COD values of ethyl S(-)lactate was found to be 1.658 mg O2/mg (duplicate values: 1.634 and 1.6814 mg 02/mg). The theoretical oxygen demand was calculated to be 1.63 mg O2/L.
Comparison of the BOD and COD values indicates that degradation was about 36 % after 5 days, about 65 % after 20 days and about 85 % after 20 days.
The oxygen concentrations measured in the various bottles of the BOD determination are given in Tables B1 and B2 (see attached documents). Table 1 (see attached documents) lists the mean oxygen concentrations measured, and the oxygen consumption and BOD5 and BOD20 values calculated for ethyl S(-)lactate. Table 2 (see attached documents) lists the relevenant results of the BOD28 determination.
The oxygen demand in the inoculum controls was 0.29 mg O2/L after 5 days and 1.89 mg O2/L after 20 days. In the BOD28 test the oxygen consumption after 5 and 28 days were 0.45 and 2.34 mg O2/L respectively. These values indicate that the endogenous activity of the inoculum was somewhat high in comparison with the values specified in a closed bottle test.
The total activity of the inoculum (+glucose and glutamic acid) in the presence of 4 mg of the test substance corresponded to BOD values of 4.97 and 8.72 mg O2/L after 5 days and 20 days respectively. Comparing these values with the inoculum activity control (BOD5 and BOD20 values of 3.37 and 7.47 mg O2/L, respectively) revealed that ethyl S(-)lactate did not inhibit the activity of the inoculum.
The oxygen consumption was strongly stimulated by the test substances, corresponding to test substance BOD values of 0.40 and 0.31 mg O2/mg, respectively. This corresponds to a degradation of 24 % after 5 days. The BOD value after 20 days is not representative due to exhaustion of the oxygen in the bottle.

Parameter:

BOD5

Value:

0.6 g O2/g test mat.

Parameter:

COD

Value:

1.66 g O2/g test mat.

Results with reference substance:

The BOD5 and BOD20 values of the glucose/glutamic acid control were 3.37 mg O2/L (4.22 mg O2/L in the BOD28 test) and 7.47 mg O2/L respectively; these values indicate that the activity of the inoculum was sufficient for a valid test (a 150 mg/L glucose/ glutamic acid mixture should have a BOD5 value of 200 ± 37 mg 02/L; this corresponds to a value of 4.0 ± 0.75 mg O2/L for a 3 mg/L mixture).
The results obtained by adding allylthiourea showed that some nitrification had taken place.

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

This test does not meet the formal requirements for deriving a ready biodegradability classification but can be used as a supportive study, underpinning the appropriateness and relevance of the QSAR predictions identified as the key study.

Executive summary:

BOD (biochemical oxygen demand) and COD (chemical oxygen demand) determinations were carried out for ethyl S(-)lactate using the method described in the Dutch guidelines "Water-Determination of Biochemical Oxygen Demand after n days (BODn)" (NEN 6634) and 'Water-Determination of Chemical Oxygen Demand (COD)' (NEN 6633), respectively. These methods are similar to those reffered to in the EC test guidelines C.5 and C.6. The study was carried out in accordance with the OECD principles of good laboratory practice (GLP).

The test substance was a pure chemical with a high solubility in water. Two concentrations (2 and 4 mg/L) were tested. In a seperate 28 day test, two concentrations of 1 and 2 mg/L were tested.

An inoculum was prepared from activated sludge. Its microbial acitivity appeared to be sufficient: The control substances glucose and glutamic acid had the required BOD5 of 4.00 ± 0.75 mg O₂/L.

No toxic effects were found, and the test substance was degraded in the presence of glucose and glutamic acid.

The BOD5 of ethyl S(-)lactate was 0.60 mg O₂/L, the BOD20 was 1.08 mg O₂/L and the BOD28 was 1.43 mg O₂/L; the COD was 1.658 mg O₂/L. These figures indicate a degradation of 86 % after 28 days.

Reference 3

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

(Q)SAR

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

results derived from a valid (Q)SAR model and falling into its applicability domain, with adequate and reliable documentation / justification

Qualifier:

no guideline available

Principles of method if other than guideline:

QSAR estimation

GLP compliance:

no

Remarks:

not applicable to QSAR calculations

Key result

Remarks on result:

readily biodegradable based on QSAR/QSPR prediction

Biowin1 (Linear Biodegradation Probability) = 1.0242

Biowin2 (Non-linear Biodegradation Probability) = 0.9985

Biowin3 (Ultimate Biodegradability) = 3.2383

Biowin4 (Primary Biodegradability) = 4.0357

Biowin5 (MITI Linear Biodegradation Probability) = 0.8651

Biowin6 (MITI Non-linear Biodegradation Probability) = 0.9495

Biowin7 (Anaerobic Linear Biodegradation Probability) = 0.8417

Validity criteria fulfilled:

not applicable

Remarks:

Nevertheless, the QSARs are fully validated, and ethyl lactate falls within the applicability domain.

Interpretation of results:

readily biodegradable

Conclusions:

The model results unequivocally predict that ethyl lactate is readily biodegradable (including anaerobic degradation); the predicted time frame for degradation is days to weeks.

Executive summary:

The ready biodegradability of ethyl lactate was predicted by officially accepted QSAR models (BIOWIN v4.10), as recommended by the ECHA-guidance on information requirements and chemical safety assessment, chapter R.7b, section R.7.9.4.1. The registered substance is within the applicability domain of the models, namely several other short-chain alkyl esters are contained in the training data set of the QSAR. All the models unequivocally predict that ethyl lactate is readily biodegradable.

Description of key information

Ethyl (S)-lactate is readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

Based on unequivocally positive QSAR predictions (BIOWIN v4.10) and a supporting study investigating the biochemical oxygen demand (BOD) Ethyl (S)-lactate is considered to be readily biodegradable.