2-methylbutyric acid

Biodegradation in water: screening tests

Link to relevant study record(s)

Reference

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

comparable to guideline study with acceptable restrictions

Remarks:

Acceptable, well-documented publication which meets basic scientific principles; method used is similar to OECD TG 301 D (closed bottle test)

Qualifier:

equivalent or similar to

Guideline:

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

Deviations:

yes

Remarks:

pre-guidelin study, no duplicates, limited reporting

Principles of method if other than guideline:

Tests were performed similar to the method of OECD TG 301 D - Closed Bottle Test. The consumption of dissolved oxygen was measured using a polarographic electrode. Aim of the study was to compare the biodegradability of a variety of chemical substances. Amongst others, biodegradability of linear and branched saturated aliphatic carboxylic acids was investigated.

GLP compliance:

no

Oxygen conditions:

aerobic

Inoculum or test system:

sewage, domestic, non-adapted

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): domestic sewage, not further specified
- Method of cultivation: raw sewage was stored at 25°C for 24 to 48 hr prior to use
- Preparation of inoculum for exposure: sewage was filtered through cotton

Duration of test (contact time):

10 d

Initial conc.:

2 other: mg Carbon/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium: American Public Health Association (1965) Standard methods for the examination of water and wastewater, 12th edition. American Public Health Association, New York
- Additional substrate: glucose in a second series of experiments to test for toxicity of test substances
- Test temperature: 25°C
- pH: 6.5 - 7.5
- pH adjusted: yes
- Aeration of dilution water: no data
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: 300 mL BOD bottles
- Measuring equipment: oxygen electrode

SAMPLING
- Sampling frequency: none; electrodic oxygen measurements in test flasks

Test performance:

Carboxylic acids and methyl-substituted carboxylic acids including isovaleric acid were readily metabolised

Key result

Parameter:

% degradation (O2 consumption)

Value:

67.9

Sampling time:

10 d

Remarks on result:

other: % O2 consumption of ThOD

Details on results:

Oxygen consumption (mg/L) BOD (mg O2/mg Substance) % Degr. (BOD/ThOD)
Day 2: 3.0 0.8821 43.3
Day 5: 4.5 1.3231 65.0
Day 10: 4.7 1.3819 67.9


For comparison, please find results on biodegradation of known readily biodegradable substances in any other information on results. All substances were tested with the same method and are therefore comparable.

Results on biodegradation for several tested substances (Dias and Alexander, 1971)

Explained data are based on published raw data and demonstrate that obtained results on biodegradation adequately represent the biodegradability of substances (only acetic and butyric acid were depicted here).

2 -Methylbutyric acid

                      Oxygen consumption (mg/L)            BOD (mg O2/mg Substance)             % Degr. (BOD/ThOD)

Day 2:                               3.0                                                  0.8821                                              43.3

Day 5:                               4.5                                                  1.3231                                              65.0

Day 10:                             4.7                                                  1.3819                                              67.9

Acetic acid

                      Oxygen consumption (mg/L)            BOD (mg O2/mg Substance)             % Degr. (BOD/ThOD)

Day 2:                               3.0                                                  0.6000                                             56.3

Day 5:                               4.1                                                  0.8200                                             76.9

Day 10:                             4.1                                                  0.8200                                             76.9

Butyric acid

                      Oxygen consumption (mg/L)            BOD (mg O2/mg Substance)             % Degr. (BOD/ThOD)

Day 2:                               3.1                                                  0.8452                                              46.5

Day 5:                               ---                                                  ---                                                    ---

Day 10:                             3.2                                                 0.8725                                              48.0

Day 30:                             3.9                                                  1.0633                                              58.6

Validity criteria fulfilled:

not applicable

Interpretation of results:

readily biodegradable

Conclusions:

Based on the oxygen consumption, 2-methylbutyric acid is rapidly biodegraded (68% biodegradation within 10 days).

Executive summary:

The biodegradability of 2-methylbutyric acid and numerous related substances (aliphatic acids and alcohols) was determined in a pre-guideline study. Reporting is limited but the test procedure follows in general the method of OECD TG 301 D (Closed Bottle Test).

 

Non-adapted sewage of a domestic sewage treatment plant served as inoculum. Test substance was incubated for 10 days at 25°C in the dark. No parallels were set up. Dissolved oxygen was measured at three time points (2, 5, and 10 days).

 

After 10 days, 2-methylbutyric acid was degraded to ca. 68% (day 5: ca. 65%) (calculated from the originally reported data of oxygen consumption). Based on the oxygen consumption data, 2-methylbutyric acid is readily biodegradable (Dias and Alexander, 1971).

 

This pre-guideline study provides evidence that aliphatic alcohols and acids (linear and methyl-substituted) are rapidly biodegraded. Results are estimated to adequately represent the biodegradability of these substances.

Description of key information

2-methylbutyric acid is readily biodegradable: 68% biodegradation within 10 days (similar to OECD 301D, Dias and Alexander 1971).

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

A reliable key study is available (RL2). The biodegradability of 2-methylbutyric acid and numerous related substances (aliphatic acids and alcohols) was determined in a pre-guideline study. Reporting is limited but the test procedure follows in general the method of OECD TG 301 D (Closed Bottle Test). After 10 days, 2-methylbutyric acid was degraded to ca. 68% (day 5: ca. 65%) (calculated from the originally reported data of oxygen consumption). Based on the oxygen consumption data, 2-methylbutyric acid is readily biodegradable (Dias and Alexander, 1971).

In a supporting study, 2 -Methylbutyric acid was tested for biodegradability in a pre-guideline test following the original method of Zahn-Wellens. Test method is reported with no specific details, but the general procedure is comparable to OECD test guideline 302 B (Zahn-Wellens/EMPA Test). After 10 days 2-methylbutyric acid was biodegraded by >95% (Hoechst, 1980).