Butyl (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:

(Q)SAR

Adequacy of study:

key study

Study period:

2018-03-01

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

Justification for type of information:

See attached background material, attached further below in this section.

Qualifier:

according to guideline

Guideline:

other: REACH guidance on information requirements and chemical safety assessment, chapter R.6: QSARs and grouping of chemicals, May 2008.

Principles of method if other than guideline:

(Q)SAR calculation

GLP compliance:

no

Key result

Parameter:

probability of ready biodegradability (QSAR/QSPR)

Remarks:

Primary and ultimate biodegradability prediction: YES

Remarks on result:

readily biodegradable based on QSAR/QSPR prediction

Remarks:

QSAR calculation (BIOWIN)

Details on results:

Biowin1 (Linear Biodeg Probability) 1.1193
Biowin2 (Non-Linear Biodeg Probability) 0.9997
A Probability Greater Than or Equal to 0.5 indicates --> Biodegrades Fast
A Probability Less Than 0.5 indicates --> Does NOT Biodegrade Fast

Biowin3 (Survey Model - Ultimate Biodeg) 3.4746
Biowin4 (Survey Model - Primary Biodeg) 4.2643
Result Classification: 5.00 -> hours 4.00 -> days 3.00 -> weeks
(Primary & Ultimate) 2.00 -> months 1.00 -> longer

Biowin5 (MITI Linear Biodeg Probability) 0.8805
Biowin6 (MITI Non-Linear Biodeg Probability) 0.9518
A Probability Greater Than or Equal to 0.5 indicates --> Readily Degradable
A Probability Less Than 0.5 indicates --> NOT Readily Degradable

Biowin7 (Anaerobic Linear Biodeg Prob) 0.5759
A Probability Greater Than or Equal to 0.5 indicates --> Biodegrades Fast
A Probability Less Than 0.5 indicates --> Does NOT Biodegrade Fast

Validity criteria fulfilled:

not applicable

Interpretation of results:

readily biodegradable

Conclusions:

Butyl-(S)-lactate is predicted to be readily biodegradable by the (Q)SAR model BIOWIN v4.10.

Executive summary:

Butyl-(S)-lactate is predicted to be readily biodegradable by the (Q)SAR model BIOWIN v4.10.

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

read-across from supporting substance (structural analogue or surrogate)

Adequacy of study:

supporting study

Justification for type of information:

For details and justification of read-across please refer to the read-across report attached to IUCLID section 13.

Reason / purpose for cross-reference:

read-across source

Preliminary study:

Not reported

Parameter:

% degradation (O2 consumption)

Value:

57

Sampling time:

28 d

Remarks on result:

other: unclear to which test method the result refers

Parameter:

% degradation (O2 consumption)

Value:

63

Sampling time:

20 d

Remarks on result:

other: unclear to which test method the result refers

Parameter:

% degradation (O2 consumption)

Value:

69

Sampling time:

28 d

Remarks on result:

other: unclear to which test method the result refers

Details on results:

The biodegradability of n-butyl lactate was determined in a closed bottle screening test or by BOD determinations after 5 and 28 days. One test only lasted 20 days. The amounts of test substance added and their respective ThOD values are given in Table 1 below. The added amount varied between 1.08 and 4.0 mg/L test substance and corresponded to ThOD values from about 3 mg O2/L to 4.7 mg O2/L. This resulted in an oxygen depletion of about 3-4 mg O2/L in 28 days with a standard deviation in most cases of ≤ 0.1 mg O2/L.
The reference substances (sodium acetate or a mixture of glucose and glutamic acid, depending on the guideline used) were completely degraded within five days.
The results demonstrate considerable variability between the test series. There was no relationship between the extent of degradation after 28 days and the results of the control assays (i.e. the inoculum activity). The variability is probably related to the inoculum quality (the inoculum was prepared from activated sludge originating from an oxidation ditch treating domestic sewage).
n-butyl lactate was found to be readily degradable in two of three tests (i.e. more than 60 % degradation within 28 days based on the ThOD), and indicating that these substances are biodegradable.
The test report does not present information about the 10-day window.

Remarks on result:

other: not reported in the study

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.

Table1: Results of biodegradation tests with n-buytl lactate.

Substance	ThOD	Concentration	BOD [mg O2/ mg]		Degradation [%]
	[mg O2/mg]	[mg/L]	5 days	28 days	5 days	28 days
n-butyl lactate	1.97	1.53	0.44	1.13	22	57
	1.97	2.0	0.76	1.24*	39	63*
	1.97	2.08	0.50	1.39	25	69

* incubated for 20 days

Validity criteria fulfilled:

not specified

Remarks:

Reporting insufficient for evaluating validity.

Interpretation of results:

other: Data insufficient for definitive evaluation of biodegradability.

Conclusions:

In three different test systems the biodegradability of n-butyl lactate was tested: EU method C.5 and C.6,and the OECD test guideline 301 D were applied to evaluate the degradation of n-butyl lactate. n-butyl lactate was degraded by 57 to 69 % after 28 days and 63 % after 20 days, and by 22 to 39 % after 5 days. Due to considerable reporting deficiencies, a final conclusion on biodegradability is not possible.

Executive summary:

In three different test systems the biodegradability of n-butyl lactate was tested: EU method C.5 and C.6, and OECD test guideline 301 D were applied to evaluate the degradation of n-butyl lactate. n-butyl lactate was degraded by 57 to 69 % after 28 days and 63 % after 20 days, and by 22 to 39 % after 5 days. Due to considerable reporting deficiencies, a final conclusion on biodegradability is not possible.

This information is used in a read-across approach in the assessment of the target substance. For details and justification of read-across please refer to the read-across report attached to IUCLID section 13.

Reference 3

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

1991-09-06 to 1993-02-10

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

guideline study with acceptable restrictions

Qualifier:

according to guideline

Guideline:

EU Method C.9 (Biodegradation: Zahn-Wellens Test)

Deviations:

yes

Qualifier:

according to guideline

Guideline:

other: EU Method C.8 (Degradation, Biochemical Oxygen Demand)

Deviations:

yes

Principles of method if other than guideline:

To inoculate each litre of BOD dilution water 3 mL of the supernatant of the activated sludge was used instead of 2 mL.

GLP compliance:

yes

Remarks:

Compliance statement given in the report

Specific details on test material used for the study:

Purity ≥ 97 %

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 5.8 g of solid substance/L) was allowed to settle for 3-7 minutes and 3 mL 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 d

Initial conc.:

2 mg/L

Based on:

test mat.

Initial conc.:

4 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
The concentrations of 2.0 and 4.0 mg/L were prepared by adding 32 mL and 64 mL of the 200.2 mg/L stock solution respectively to 3.2 lots of inoculated BOD dilution water. To check 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 were also tested.
Incubation was performed in the dark at 20 °C for 20 days.
The COD was determined with two samples of 1 mL each from a solution of 361.4 mg of test substance in 100 mL of Mili-Q water.

TEST SYSTEM
- Culturing apparatus: BOD bottles
- Number of culture flasks/concentration: 4 per conc.
- Method used to create aerobic conditions: aerobic
- Measuring equipment: O2 concentration was measured with an oxygen electrode
- Test performed in closed vessels due to significant volatility of test substance: not stated
- Test performed in open system: no

SAMPLING
- Sampling frequency: 0, 5 and 20 days
- Sampling method: separate set of bottles sacrificed for each measurement

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Abiotic sterile control: no
- Toxicity control: yes
- Nitrification control: Nitrification control was included by adding 2.5 mg/L of allylthiourea to bottles containing 2 mg/L of butyl S(-)lactate.

CALCULATIONS:
Oxygen demand calculated by subtracting the oxygen concentration measured at the t = 0 h with t= 5 h and t = 20 h.
The BOD (BOD5 and BOD20) was calculated by subtracting the oxygen demand in the inoculum control from that in the bottle under consideration; these crude values were then converted to values per mg substance.
The % degradation was calculated as BOD/COD × 100

Reference substance:

not required

Preliminary study:

No preliminary study was conducted.

Test performance:

No anomalies reported.

Parameter:

% degradation (O2 consumption)

Value:

39

Sampling time:

5 d

Parameter:

% degradation (O2 consumption)

Value:

63

Sampling time:

20 d

Details on results:

See Table 1 below.

Parameter:

BOD5

Value:

760 mg O2/g test mat.

Parameter:

COD

Value:

1 974 mg O2/g test mat.

Results with reference substance:

See Table 1 below.

The pH of the medium in the BOD bottles was 6.5 at the start of the test, 6.1–6.3 after 20 days. The pH values in bottles with glucose added were generally lower 6.0–6.1. The comparatively low pH of the medium in this test did not influence the inoculums activity negatively.

The temperatures measured in the BOD bottles varied between 20.3 and 20.5 °C.

Table 1 - Oxygen concentration in the BOD bottles and the BOD values calculated

Conc. butyl S(-) lactate (mg/L)	Additions	0 days	5 days			20 days
		mg O2/L	mg O2/L (SD)	BOD5 mg O2/L	BOD mg O2/L	mg O2/L (SD)	BOD20 mg O2/L	BOD^a) mg O2/L
0   0   2.0   2.0   4.0   4.0	GG^b)       ATU^c)       GG^b)	9.2   9.0   9.1   9.1   9.1   9.0	8.88 (0.05) 5.80 (0) 7.37 (0.05) 7.50 (0) 6.00 (0.17) 2.10 (0.10)	0.20   3.28   1.71   1.58   3.08   6.88	0.76   0.69   0.72   0.90	7.28 (0.10) 1.70 (0.22) 4.80 (0.14) 6.13 (0.13) 2.68 (0.13) 0.35 (0.10)	1.80   7.38   4.28   2.95   6.40   8.73	1.24   0.58   1.15   0.34

^a)Oxygen consumption in the indicated period calculated from tge mean initial oxygen concentration of the test solutions of 9.08 ± 0.08 mg O₂/L

^b)Glucose and glutamic acid added

^c)Allythiourea

Inoculum activity and toxicity

The oxygen demand in the inoculum controls was 0.20 mg O₂/L after 5 days and 1.80 mg O₂/L after 20 days; these values indicate that the endogenous activity of the inoculum was somewhat high.

The BOD5 and BOD20 values of the glucose/glutamic acid control were 3.28 mg O₂/L and 7.38 mg O₂/L respectively; these values indicate that the activity of the inoculum was sufficient for a valid test glucose/ glutamic acid mixture should have a BOD5 value of 200 ± 37 mg O₂/L; this corresponds to a value of 4.0 ± 0.75 mg O₂/L for a 3 mg/L mixture).

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 6.88 and 8.73 mg O₂/L after 5 days and 20 days respectively. Comparing these values with the inoculums activity control (BOD5 and BOD20 values of 3.28 and 7.38 mg O₂/L respectively) revealed that butyl S(-)lactate did not inhibit the activity of the inoculum.

The oxygen consumption was somewhat stimulated by the test substance, corresponding to test substance BOD values of 0.90 and 0.34 mg O₂/L respectively. This corresponds to a biodegradation of 46% after 5 days. The BOD20 value is not representative due to exhaustion of the oxygen in the bottle.

The results obtained by adding allylthiourea showed that some nitrification had taken place.

Degradation

The BOD5 and BOD20 values of the various concentrations of butyl S(-)lactate were in the ranges 0.72-0.76 mg O₂/L and 1.15-1.24 mg O₂/L respectively; it was therefore concluded that the BOD5 and BOD20 of butyl S(-)lactate are 0.76 and 1.24 mg O₂/L respectively.

A similar oxygen consumption by the test substance was also found in the presence of glucose and glutamic acid after 5 days, confirming the results presented.The COD values of butyl S(-)lactate was found to be 1.974 mg O₂/L (duplicate values: 1.999 and 1.949 mg O₂.mg). The theoretical oxygen consumption was calculated to be 1.97 mg O₂/mg.

Comparison of the BOD and COD values indicates that degradation was about 39 % after 5 days and about 63% after 20 days.

Validity criteria fulfilled:

yes

Interpretation of results:

inherently biodegradable

Conclusions:

No toxic effects were found. The BOD5 of butyl S(-)lactate was 0.76 mg O2/L and the BOD20 was 1.24 mg O2/mg; the COD was 1.974 mg O2/L. These figures indicate a degradation of 39 and 63% after 5 and 20 days respectively. According to the results of this study, n-butyl-S-lactate is inherently biodegradable.

Executive summary:

BOD (biochemical oxygen demand) and COD (chemical oxygen demand) determinations were carried out for butyl 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 referred to in the EC test guidelines C.8 and C.9. The study was carried out in accordance with GLP.

The test substance was a pure chemical with a solubility of 3.7 % in water. Two concentrations (2.0 and 4.0 mg/L) were tested. An inoculum was prepared from activated sludge. lts microbial activity appeared to be sufficient: the control substance glucose and glutamic acid had the required BOD5 of 4.00 ± 0.75 mg O₂/L.

No toxic effects were found. The BOD5 of butyl S(-)lactate was 0.76 mg O₂/L and the BOD20 was 1.24 mg O₂/mg; the COD was 1.974 mg O₂/L. These figures indicate a degradation of 39 and 63% after 5 and 20 days respectively.

Description of key information

The (Q)SAR model BIOWIN v4.10 predicts butyl-(S)-lactate to be readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater

Additional information

As supporting information a study report (Hanstveit 1993) and a publication (Bowmer et al. 1998) are presented.

Hanstveit (1993): The BOD5 of butyl S(-)lactate was 0.76 mg O₂/L and the BOD20 was 1.24 mg O₂/mg; the COD was 1.974 mg O₂/L. These figures indicate a degradation of 39 and 63 % after 5 and 20 days respectively.

Bowmer et al. (1998): In three different test systems the biodegradability of n-butyl lactate was tested: EU method C.5 and C.6, and OECD test guideline 301 D were applied to evaluate the degradation of n-butyl lactate. n-butyl lactate was degraded by 57 to 69 % after 28 days and 63 % after 20 days, and by 22 to 39 % after 5 days.

The Bowmer et al. (1998) study is unreliable due to serious methodological and reporting deficiencies. The test employed by Hanstveit (1993) is designed for identifying substances as inherently biodegradable. However, the QSAR model BioWin reliably predicts that n-butyl-S-lactate is readily biodegradable and supersedes the other, less reliable, studies.