Sodium (S)-lactate

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Reference 1

Endpoint:

biodegradation in water: ready biodegradability

Data waiving:

study scientifically not necessary / other information available

Justification for data waiving:

other:

Reference 2

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

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

Adequacy of study:

key 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

Key result

Parameter:

% degradation (CO2 evolution)

Value:

75.5

Sampling time:

28 d

Details on results:

Relative biodegradation values calculated from measurements performed during the test period revealed 75% and 76% biodegradation of L-(+)-lactic acid, for vessel A and B, respectively (based on ThCO2).

Validity criteria fulfilled:

yes

Remarks:

All criteria for acceptability of the test were met: 92% of procedural control item was biodegraded within 14 days; difference between duplicated values: 2%; total CO2 release in blank did not exceed 40 mg/L (value was 31.2 mg CO2/L).

Interpretation of results:

readily biodegradable

Conclusions:

In an OECD 301B study, L-(+)-lactic acid proved to be readily biodegradable.

Executive summary:

Biodegradation of L-(+)-lactic acid was studied following OECD test guideline 301B. Relative biodegradation values calculated from measurements performed during the test period revealed 75 % biodegradation of lactic acid (based on ThCO2). 
In the toxicity control, L-(+)-lactic acid was found not to inhibit microbial activity.
In conclusion, L-(+)-lactic acid is considered as readily biodegradable. 

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:

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

Duration of test (contact time):

d

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 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 O2/l respectively; it was therefore concluded that the BOD5 and BOD20 of L(+) lactic acid are 0.45 and 0.60 mg O2/mg respectively.
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 O2/mg. (duplicate values: 0.873 and 0.930 mg 02/mg). The theoretical oxygen demand was calculated to be 0.85 mg O2/mg.
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) determinations were carried out for L-(+)-lactic acid 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 methods 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 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 substances 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 O₂/mg and the BOD20 was 0.60 mg O₂/mg; the COD was 0.90 mg O₂/mg. These figures indicate a degradation of 50 and 67 % after 5 and 20 days, respectively.

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.

Description of key information

Sodium (S)-lactate fully dissociates into Na+ ions and lactate in aqueous environments. The transport and distribution behaviour of lactate in the environment can be understood in terms of the transport and distribution behaviour of lactic acid.

L-(+)-lactic acid is readily biodegradable, which hence applies also to Sodium (S)-lactate by way of read-across.

With respect to sodium, biodegradation is not applicable to inorganic substances, thus a study on biodegradation of the sodium moiety does not need to be conducted (REACH Annex VII, column 2, point 9.2.1.1).

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable