Propanoic acid, 2-hydroxy-, propyl ester, (2S)-

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

Study period:

1994-06-03 to 1994-11-03

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: Study conducted according with the Dutch test guidelines 'Water - Determination of biochemical oxygen demand after n days (BODn)' and 'Water - Determination of chemical oxygen demand (COD)'. GLP study. Follows EC test guidelines C.5 and C.6.

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): A sample of activated sludge was taken from an oxidation ditch situated at Berkel Rodenrijs county, The Netherlands. The oxidation ditch is used to treat domestic sewage.
- Laboratory culture: no
- Dry weight original sludge: 4.0 g/L
- Settling time of the sludge: 30 minutes
- Used supernatant (ml/L) for inoculation: 14 ml/L
- Total volume inoculated BOD dilution water: 25 L
The BOD dilution water was prepared from concentrated stock solutions in milli-Q water and was aerated vigorously before use.

Duration of test (contact time):

28 d

Initial conc.:

810 µg/L

Based on:

other: test material, low concentration

Initial conc.:

1 630 µg/L

Based on:

other: test material, high concentration

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Test temperature: 20 °C
- pH: 6.7–7.4
- pH adjusted: no
- Aeration of dilution water: yes
- Continuous darkness: yes
- Other:

TEST SYSTEM
- Culturing apparatus: BOD bottles of 295 ml volume
- Number of culture flasks/concentration:
-Inoculum blanks: 13 bottles containing BOD dilution water only
-Procedure control: 5 bottles containing BOD dilution water with 1 ml/L of a solution containing 3 g/L of glucose and 3 g/L of glutamic acid
-Test bottles low conc.: 13 bottles containing inoculated BOD dilution water with 0.81 mg/L of the test substance
-Test bottles high conc.: 13 bottles containing BOD inoculation dilution water with 1.63 mg/L of the test substance and 1 ml/L of a solution containing 3 g/L of glucose and 3 g/L of glutamic acid.
- Method used to create aerobic conditions: aeration
- Measuring equipment: oxygen electrode (WTW OXI 2000)
- Test performed in closed vessels.
- Details of trap for CO2 and volatile organics if used: -

SAMPLING
- Sampling frequency: 5, 20 and 28 days except the procedure and toxicity control bottles of which O2 was measured after 5 days only.
- Sampling method: for oxygen consumption: A separate set of bottles (4 bottles) of each treatment was sacrificed for each measurement. For COD determination, 4 ml samples of a solution 76.2 mg/100L of n-propyl lactate conducted as detailed in the Dutch guideline
- Sterility check if applicable: n/a
- Sample storage before analysis: n/a

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Abiotic sterile control: n/a
- Toxicity control: yes

STATISTICAL METHODS: none

Reference substance:

other: glucose and glutamic acid

Preliminary study:

Not performed.

Test performance:

No abnormalities have been reported.

Parameter:

other: ThOD % biodegr..

Value:

63

Sampling time:

28 d

Remarks on result:

other: 0.81 mg/L

Parameter:

other: ThOD % biodegr.

Value:

68

Sampling time:

28 d

Remarks on result:

other: 1.63 mg/L

Parameter:

COD

Value:

1 680 mg O2/g test mat.

Results with reference substance:

Microbial activity and toxicity test
The oxygen demand in the inoculums control increased from 0.09 mg O2/L after 5 days to 2.29 mg O2/L after 28 days; the value found after 28 days indicates that the exogenous activity of the inoculum was somewhat high compared with the namixum oxygen consumption of 1.5 mg O2/L prescribed by the OECD guideline 301 D.
The BOD5 value of the glucose/glutamic acid control was 3.42 mg O2/L; this value indicates that the activity of the inoculums was sufficient for a valid test. According to “5210 BOD (1992) Standard methods for the examination of water and waste water, American Public Health Ass.”, a 150 mg/L glucose/glutamic acid mixture should have a BOD5 value of 198 ± 30.5 mg O2/L; for a 3 mg/L mixture the BOD5 value is 4.2 ± 1.15 mg O2/L.
In the toxicity control the total activity of the inoculum (+glucose and glutamic acid) in the presence of 1.63 mg/L of the test substance corresponded to a BOD value of 4.52 mg O2/L after 5 days. Comparing this value with the inoculum acitivity control (BOD5 = 3.42 mg O2/L), revealed that n-propyl lactate did not inhibit the activity of the inoculum, but was degraded in the presence of glucose and glutamic acid.
The biodegradation test
The COD value for n-propyl lactate was found to be 1.68 mg O2/L (duplicate values: 1.68 and 1.69 mg O2/L) and is about 7% lower than the ThOD value of 1.81 mg O2/L. Hydrocarbons give in our experience consistently low COD values compared with ThOD calculations.
Table 1 shows the percentage biodegradation of the test substance calculated from the COD (1.68 mg O2/L) and the ThOD (1.81 mg O2/L) of the test substance.
The maximum oxygen consumption of 1.23 mg O2/L was reached within 28 days. This corresponds to a maximum biodegradation of 68% of its ThOD for n-propyl lactate in inoculated BOD dilution water in this test.
The test substance was found to be biodegradable within 28 days in this test.

Table 1 –Biodegradation of n-propyl lactate expressed in mg O₂/mg and as percentage of its COD and ThOD

Time (days)	0.81 mg/L			1.63 mg/L
	mg O2/mg	COD % biodegr.	ThOD %biodegr.	mg O2/mg	COD % biodegr.	ThOD %biodegr.
5 20 28	0.56 1.05 1.14	33 62 68	31 58 63	0.76 1.03 1.23	45 61 73	42 57 68

Validity criteria fulfilled:

yes

Remarks:

BOD5 (glucose/glutamic acid) = 3.42 mg O2/L, indicating incoculum acitivity sufficient for a valid test

Interpretation of results:

readily biodegradable

Conclusions:

The test substance n-propyl lactate was found to be readily biodegradable. It had a maximum oxygen consumption of 1.23 mg O2/mg after 28 days. Based on the ThOD value, 68% maximum biodegradability was found after 28 days.

Executive summary:

BOD (Biochemical Oxygen Demand) and COD (Chemical Oxygen Demand) determinations were carried out for n-propyl lactate using the methods 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 the EC test guidelines C.5. and C.6. The study was carried out in accordance with the OECD principles of Good Laboratory Practice.

The test substance was a pure chemical and was miscible in water. Two concentrations (0.81 and 1.63 mg/L) were tested. An inoculum was prepared from activated sludge. lts microbial activity appeared to be sufficient; the control substances glucose and glutamic acid had the required BODs of 4.2 ± 0.15 mg O₂/L.

In a toxicity control test (1.63 mg/L of the test substance) no inhibiting effects were found, the test substance was even degraded in the presence of glucose and glutamic acid.

In the biodegradation test a maximum oxygen consumption of 1.23 mg O₂/mg was found after 28 days.

The Chemical Oxygen Demand (COD) was found to be 1.68 mg O₂/mg. This was a lower value considering the ThOD (Theoretical Oxygen Demand) based on the elemental composition of PURASOLV PL (1.81 mg O₂/mg). Based on the ThOD value a maximum biodegradability of 68 % was found after 28 days. The test substance was found to be ready biodegradable within 28 days in this test.

Reference 2

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:

according to guideline

Guideline:

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

Specific details on test material used for the study:

SMILES: CCCOC(=O)C(C)O

Key result

Remarks on result:

readily biodegradable based on QSAR/QSPR prediction

Details on results:

Biowin1 (Linear Biodegradation Probability) = 1.0175 (Biodegrades Fast)
Biowin2 (Non-linear Biodegradation Probability) = 0.9982 (Biodegrades Fast)
Biowin3 (Ultimate Biodegradability) = 3.2073 (Weeks)
Biowin4 (Primary Biodegradability) = 4.0155 (Days)
Biowin5 (MITI Linear Biodegradation Probability) = 0.7798 (Readily Degradable)
Biowin6 (MITI Non-linear Biodegradation Probability) = 0.9101 (Readily Degradable)
Biowin7 (Anaerobic Linear Biodegradation Probability) = 0.8677 (Biodegrades Fast)

Validity criteria fulfilled:

yes

Conclusions:

All model results unequivocally predict that propyl (S)-lactate is readily biodegradable (including anaerobic degradation)

Executive summary:

For the determination of the ready biodegradability of propyl-(S)-lactate the model 'EpiSuite 4.1/BIOWIN, Biowin 1-7 (4.11)'  was applied. All model results unequivocally predict that propyl (S)-lactate is readily biodegradable (including anaerobic degradation); the predicted time frame for ultimate degradation varies by model, ranging from “days” to “weeks”. The final result is considered adequate for a regulatory conclusion

Description of key information

All BIOWIN model results unequivocally predict that propyl (S)-lactate is readily biodegradable (including anaerobic degradation). This QSAR result is also supported by a BOD/COD study (Blom & Pullens, 1994).

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater