Methyl valerate

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

Study period:

2002

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

Deviations:

yes

Remarks:

Incubation for 27 d instead 28 d

Principles of method if other than guideline:

The test substance was incubated for 27 days instead of a 28 days (planned) period. This had no influence on the conclusion.

GLP compliance:

yes

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

INOCULUM:
- Type: mixed population of aquatic microorganisms (activated sewage sludge)
- Origin: municipal sewage treatment plant, predominantly dealing with domestic sewage (Kläranlage Berlin/Ruhleben, Germany)
- Date of collection: on the day of the start of the experiment

Pre-treatment of the inoculum:
- The sewage sludge was kept under aerobic conditions
- Approx. 2 hours before the start of the incubation, the activated sludge was stirred and aerated; thereafter, it was allowed to settle for 30 minutes
- The inoculum was obtained from the supernatant (3 mL corresponding to 9 to 15 mg suspended solids) for each test vessel

Duration of test (contact time):

27 d

Initial conc.:

200 mg/L

Based on:

ThOD/L

Parameter followed for biodegradation estimation:

O2 consumption

Reference substance:

acetic acid, sodium salt

Remarks:

(Merck AG; Purity > 99 %, Batch No. TA 901368)

Test performance:

Study Design:
I. Preparation of the test and reference compound solution and inoculation:
- Test substance: 200 mg ThOD/L (triplicate)
- Reference substance: 200 mg ThOD/L (single set)
- Toxicity control (Test item + reference substance): 100 mg + 100 mg ThOD/L (single set)
- Blank control (inoculum + mineral medium): 0 mg ThOD/L (triplicate)
- Inoculum: 3 mL of inoculum were added to each vessel

II. Exposure conditions:
- Test vessel: 500 mL glass bottles filled with 150 mL mineral medium
- Apparatus: Thermostated box with magnetic stirrer, temperature controlled incubator
- Temperature: 22 °C (+/- 1)
- pH value on day 29: 7.4-7.5 in the blank and the substance vessels, 9.1-9.2 in the reference and toxicity control vessels
- Inoculum: 3 mL of inoculum were added to each vessel

Key result

Parameter:

% degradation (O2 consumption)

Value:

57

Sampling time:

28 d

Details on results:

In the toxicity control, the reference compound (sodium acetate) plus the test compound, was degraded to 77% on day 28 (27 days of incubation), which reflected the degradation in the individual sets.

Results with reference substance:

The reference compound sodium acetate was degraded to 92 % on day 28 (27 days of incubation). The level of 60% degradation was exceeded by day 4.

Biological degradation (cumulative) in percent (corrected for blank O₂ consumption) of test compound:

		Day of sampling
Test compound	Concentration expressed in theoretical O2 demand	2	6	10	14	18	22	26	28
Test item	200 mg/L	1,8	31	44,2	51,5	54,8	55,6	56,2	56,6
Reference (sodium acetate)	200 mg/L	24,7	83,8	87,7	88,4	89,5	90,8	91,1	92.1
Toxicity control (test item + sodium acetate)	100 mg/L + 100 mg/L	26	66,3	74,2	74,9	76,5	77,3	77,1	76,6

Validity criteria fulfilled:

yes

Remarks:

O2 consumed by the blank control (1.8 mg/L) was within the limit set by the OECD guideline (60 mg/L); reference substance is degraded to >= 60% within 14 days after start of incubation (62% within 4 days)

Interpretation of results:

not readily biodegradable

Conclusions:

The degradation of methyl valerate reached 57% at day 27 and the pass level could not be reached within 10 days. In accordance with the OECD 301 F, merthyl valerate is not readily biodegradable under the conditions of the test, since the criteria for "ready biodegradability " i.e. degradation of 60% within a 10 day window, were not met.

Executive summary:

The purpose of this study was to determine the ready biodegradability of methyl valerate. The study was conducted in agreement with the OECD test guideline no. 301F. Methyl valerate was incubated in an aqueous solution including nutrients with microorganisms from a municipal sewage treatment plant for 28 days (start of treatment = day 1). The nutrient solutions were made up of phosphates, magnesium sulphate, iron chloride, ammonium chloride and calcium chloride. The test substance was incubated at a concentration of 200 mg theoretical oxygen demand (ThOD) per litre. Additionally, a reference substance (sodium acetate) was tested in a single set according to the same procedure, in order to verify the viability and activity of the degrading microorganisms. One further set was incubated with sodium acetate at 100 mg ThOD/L (reference substance) plus test substance at 100 mg ThOD/L representing a toxicity control. Furthermore, a blank control was tested in triplicate without any test or reference substance. The biological degradation of the test and reference substances was evaluated by measurement of the O₂ consumption during the test period. O₂ consumption was continuously monitored and recorded by an automated device. The O₂ consumption was calculated as the percentage of total O₂ that the test material could theoretieally have consumed, based on the molecular formula. The blank O₂ consumption was subtracted for correction. The results observed in the toxicity control reflected the degradation of the reference and the test substance in the individual sets. Tberefore, it was demonstrated that methyl valerate is not toxic to the microbes from activated sludge. The degradation of methyl valerate reached 57% at day 28 and the pass level could not be reached within 10 days. In accordance with OECD 301 F, methyl valerate is not biodegradable under the test conditions.

Description of key information

The degradation of methyl valerate reached 57% at day 27 of incubation and the pass level could not be reached within 10 days. In accordance with the OECD 301 F, methyl valerate is not readily biodegradable under the test conditions, since the criteria for "ready biodegradability" were not met.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Additional information

The results observed in the toxicity control reflected the degradation of the reference and the test substance in the individual sets. Therefore, it was demonstrated that methyl valerate is not toxic to the microbes from activated sludge.