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Biodegradation in water: screening tests

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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:
other: Validated QSAR model, acceptable in a regulatory context.
Justification for type of information:
QSAR prediction: migrated from IUCLID 5.6
Reference:
Composition 0
Composition 0
Composition 0
Qualifier:
according to
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
Test material information:
Composition 1
Parameter:
probability of ready biodegradability (QSAR/QSPR)
Remarks:
linear biodegradability
Value:
0.936
Remarks on result:
readily biodegradable based on QSAR/QSPR prediction
Remarks:
A Probability Greater Than or Equal to 0.5 indicates --> Biodegrades Fast
Details on results:
Biowin1 (Linear Biodeg Probability) 0.9361
Biowin2 (Non-Linear Biodeg Probability) 0.9704
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) 3.5247
Biowin4 (Survey Model - Primary Biodeg) 4.2328
Result Classification: 5.00 -> hours 4.00 -> days 3.00 -> weeks
(Primary & Ultimate) 2.00 -> months 1.00 -> longer

Biowin5 (MITI Linear Biodeg Probability) 0.7362
Biowin6 (MITI Non-Linear Biodeg Probability) 0.8791
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) 0.9102
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:
L-(+)-lactic acid is predicted to be readily biodegradable by the (Q)SAR model BIOWIN v4.10.
Executive summary:

L-(+)-lactic acid is predicted to be readily biodegradable by the (Q)SAR model BIOWIN v4.10.

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Outdated test guideline, not fully suitable for assessing ready biodegradability according to recent standards. Conduct of test valid according to guidelines applicable at that time, hence reliable with restrictions and used as supportive data.
Reference:
Composition 0
Qualifier:
according to
Guideline:
EU Method C.5 (Degradation: Biochemical Oxygen Demand)
Version / remarks:
Cited as Directive 84/449/EEC, C.8, and NEN 6634
Qualifier:
according to
Guideline:
EU Method C.6 (Degradation: Chemical Oxygen Demand)
Version / remarks:
Cited as Directive 84/449/EEC, C.9, and NEN 6633
GLP compliance:
yes
Test material information:
Composition 1
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 3.5-4.0 g of solid substance.l'l) was allowed to settle for 4-8 minutes and 2 ml of the supernatant was used to inoculate each litre of BOD dilution water (ref. 1). The dilution water was aerated vigorously before use.
Duration of test (contact time):
20 d
Initial conc.:
0 mg/L
Initial conc.:
2 mg/L
Initial conc.:
4 mg/L
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). Test concentrations of 2.0 and 4.0 mg/l were prepared by adding respectively 33 and 66 ml of the 199.6 mg/l stock solution to 3.3 l lots of inoculated BOD dilution water. In order to check the activity of the inoculum and the possible toxicity of the test sub- stance, l ml/l1 of a solution containing 3 g/l of glucose and 3 g/l of glutamic acid, and this mixture with 4 mg/l of L(+) lactic acid were also tested.
Nitrification control was included by adding 2.5 mg/l of allylthiourea to bottles containing 2 mg\l of L(+) lactic acid. Quadruplicate BOD bottles were incubated at 20°C for 20 days. The COD was determined with two samples of l ml from a solution of 405.7 mg of test substance in 100 ml of Milli-Q water, and conducted as detailed in the Dutch Guideline.
Reference substance:
other: Glucose
Reference substance:
other: Glutamic acid
Reference substance:
other: Allyl thiourea
Test performance:
The oxygen concentrations measured in the various bottles of the BOD determination are given in Annex B and discussed in detail in sections 3.1 and 3.2. Table l lists the mean oxygen concentrations measured and the oxygen consumption and BOD values calculated for L(-i-) lactic acid (referring to the test substance as such, containing 80% L(+) lactic acid).
The pH of the medium in the BOD bottles was 7.0-7.1 at the start of the test, 6.6-6.9 after twenty days. The pH values in bottles with glucose added were generally lower 6.1-6.3. The temperatures measured in the BOD bottles varied between 19.9 and 20.7 °C.
Parameter:
% degradation (O2 consumption)
Value:
50
Sampling time:
5 d
Parameter:
% degradation (O2 consumption)
Value:
67
Sampling time:
20 d
Details on results:
The BOD5 and BOD20 values of the various concentrations of L(+) lactic acid were in the ranges 0.44-0.45 mg O2/l and 0.54-0.60 mg O/l respectively; it was therefore concluded that the BOD5 and BOD20 of L(+) lactic acid are 0.45 and 0.60 mg O2.mg'1 respectively.
T^l
IMW-R 92/018 page 13 of 17 RA92018IMWja
A simular oxygen consumption by the test substance was also found in the presence of glucose and glutamic acid, confirming the results presented. The COD values of L(+) lactic acid was found to be 0.902 mg 02-mg'1. (duplicate values: 0.873 and 0.930 mg 02-mg'1). The theoretical oxygen demand was calculated tobeO.85mgO2.mg'1.
Comparison of the BOD and COD values indicates that degradation was about 50% after 5 days and about 67% after 20 days.
Parameter:
BOD5
Value:
0.45 g O2/g test mat.
Parameter:
COD
Value:
0.9 g O2/g test mat.
Results with reference substance:
The BOD5 and BOD20 values of the glucose/glutamic acid control were 3.02 mg O2/L and 7.29 mg O2/L respectively; these values indicate that the activity of the inoculum was not quite sufficient. According to ref. (3) a 150 mg/L 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). Since the BOD values were similar at both test substance concentrations and only slightly lower than the value found in the presence of glucose/glutamic acid with its higher microbial activity, the test was regarded as valid.
The results obtained by adding allylthiourea showed that some nitrification had taken place.
Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable, but failing 10-day window
Conclusions:
With a BOD5 of 50% and BOD20 of 67% of COD, and considering the function of lactic acid in biological systems, it can be concluded that lactic acid is readily biodegradable.
Executive summary:

BOD (Biochemical Oxygen Demand) and COD (Chemical Oxygen Demand) determina- tions were carried out for L(+)lactic acid using the method described in the Dutch Guide- lines '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.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 with a high solubility in water. Two concentrations (2 and 4 mg/L) were tested. An inoculum was prepared from activated sludge. The microbial activity appeared to be sufficient although the control substance glucose and glutamic acid had a BOD5 of slightly less than the required value of 4.00 ± 0.75 mg O2/h.

No toxic effects were found.

The BOD5 of L(+)lactic acid was 0.45 mg O2mg-1and the BOD20 was 0.60 mg O2mg-1; the COD was 0.90 mg O2mg-1. These figures indicate a degradation of 50 and 67% after 5 and 20 days respectively.

Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
supporting study
Reliability:
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: Outdated test guideline, not fully suitable for assessing ready biodegradability according to recent standards. Conduct of test valid according to guidelines applicable at that time, hence reliable with restrictions and used as supportive data.
Reference:
Composition 0
Qualifier:
according to
Guideline:
EU Method C.5 (Degradation: Biochemical Oxygen Demand)
Version / remarks:
Cited as Directive 92/69/EEC, C.5
GLP compliance:
no
Test material information:
Composition 1
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic, non-adapted
Duration of test (contact time):
20 d
Initial conc.:
4 mg/L
Parameter followed for biodegradation estimation:
O2 consumption
Details on results:
BOD 20 = 0.60 mg O2 per mg test substance
Parameter:
BOD5
Value:
0.45 g O2/g test mat.
Parameter:
COD
Value:
0.85 g O2/g test mat.
Parameter:
BOD5*100/COD
Value:
50
Validity criteria fulfilled:
not applicable
Interpretation of results:
readily biodegradable, but failing 10-day window
Conclusions:
Lactic acid is readily biodegradable
Executive summary:

The biodegradation of lactic acid and lactate esters was studied. The aim of the study was to provide predicted environmental data for additional alkyl homologues and metal salts. Lactic acid and its alkyl esters were degraded for more than 60% in the ready biodegradability tests and from the data presented, it is evident that lactic acid and the majority of alkyl lactates are readily biodegradable.

Description of key information

Lactic acid is readily biodegradable, not satisfying the 10d window criterion. Lactic acid, due to its biological function, is readily metabolized by the majority of organisms.

The QSAR (BIOWIN v4.10) prediction of the readily biodegradable character of lactic acid is supported by experimental studies.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Lactic acid is predicted to be readily biodegradable by the validated QSAR model BIOWIN v4.10. Supportive experimental studies (BOD5 and COD measurements), which are not satisfying recent standards for ready biodegradability tests, allow the conclusion that lactic acid is readily biodegradable though not fulfilling the 10-d window criterion. As product from the lactic acid fermentation it naturally occurs as well in animal cells as in bacteria, which also provide enzymes metabolizing both enantiomers. Overall, lactic acid can be considered to be readily biodegradable.