Decyl acetate

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:

18.11.2011 - 30.01.2012

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)

Version / remarks:

2006

Qualifier:

according to guideline

Guideline:

EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)

Qualifier:

according to guideline

Guideline:

EPA OPPTS 835.3110 (Ready Biodegradability)

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic, non-adapted

Details on inoculum:

- Source activated sludge: Biological waste water treatment plant treating predominantly domestic sewage, Bois-de-Bay, Satigny, Switzerland.
- Pre-treatment: The sludge was washed 3 times in the mineral medium by centrifuging at 1000 g for 10 minutes, discarding the supernatant and resuspending in mineral medium.
The sludge is collected in the morning and used on the same day.
- Activated sludge dry weight of suspended solids: 4.04 g/L; diluted to 1.53 g/L.

Duration of test (contact time):

28 d

Initial conc.:

30 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

Test solution: 30 mg/L
Reference solution: 100 mg/L sodium benzoate
Test medium: Mineral nutrient solution at pH 7.4
Test vessels: 2 flasks containing the test substance, 2 flasks containing the reference substance and 2 flasks control. Inoculum was added to all flasks
Test temperature: 22.7 - 23.4 °C
pH value: 7.6
The theoretical oxygen demand (ThOD) of the test substance is 2.72 mg O2/mg
The oxygen consumption was determined on day 1, 5, 7, 11, 14, 21 and 28.

Key result

Parameter:

% degradation (O2 consumption)

Value:

73

Sampling time:

28 d

Details on results:

The O2 uptake of the inoculum came to a maximum of 39 mg O2/L after 28 days.
The biodegradation of the reference substance reached 90 % after 14 days. The level > 60 % was passed by day 5. The quality criterion that the degradation should be > 60 % after 14 days was fulfilled.
The test item reached the a degradation of 10 % after 1 day and 46 % on day 11. Hence, the 10-day window criterion was not fulfilled.

Results with reference substance:

100 % of the test substance was biodegraded after 28 days.

substance	% biodegradation
	1 d	5 d	7 d	11 d	14 d	21 d	28 d
test item	12	31	38	46	53	66	73
sodium benzoate		76	81	na	90	96	100

Validity criteria fulfilled:

no

Remarks:

missing toxicity control

Interpretation of results:

not readily biodegradable

Conclusions:

The test item reached 73% degradation after 28 days under the conditions of the test. The 10-day window criterion was not fulfilled (12 % biodegradation on day 1 and 46 % on day 11).

Executive summary:

The ready biodegradability of the test item was assessed over 28 days in a manometric respirometry test according to OECD guideline 301 F using non-adapted activated sludge. The selected concentration of the test item (with ThOD 2.72 mg O2/mg) was 30 mg/L. The degradation was followed by measuring the oxygen concentrations using a respirometer flask. Biodegradation is expressed as % of the ThOD.

In order to check the activity of the study system, sodium benzoate was used as functional control. Biodegradation was > 60 % by day 5, after day 14 the biodegradation was 90 % and 100 % on day 28.

In the flasks containing only the test item at a concentration of 30 mg/L, 12 % was biodegraded by day 1 and 46 % by day 10. The degradation achieved a maximum of 73 % after day 28. The 10 -day window criterion is not fulfilled for this test substance. Hence, the substance should be regarded as not readily biodegradable.

Description of key information

73% degrdation after 28 days, 10-day window is not fulfilled (OECD 301 F)

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable but failing 10-day window

Additional information

For this endpoint, two reliable studies assessing the ready biodegradability of the test substance are available. The key study (2006) was conducted according to OECD guideline 301 F and GLP using domestic sludge. In this test 73% degradation were achieved after 28 days, however, the10 -day window criterion was not fulfilled. A toxicity control was not performed.

The results of the supporting study (2000) show a biodegradation of 44% after 28 days. This study was performed following the procedures of OECD guideline 301 D and GLP using domestic sludge. In the toxicity control containing both test and reference item 67 % degradation occurred within 14 days. Therefore, the test item can be assumed to be not inhibitory in the test.

Based on these results the test substance should be regarded as not readily biodegradable according to OECD criteria. However, since in the key study the degradation rate of the test substance reach the pass-level within 28 days, the test substance can be assumed as not persistent when released into the environment.