1-cyclohexylethyl butyrate

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:

16-09-2015 to 15-10-2015

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

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

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Oxygen conditions:

aerobic

Inoculum or test system:

natural water

Details on inoculum:

River water was sampled from the Rhine near Heveadorp, The Netherlands (10-09-2015). The nearest plant (Arnhem-Zuid) treating domestic wastewater biologically was 3 km upstream. The river water was aerated for 7 days before use to reduce the endogenous respiration (van Ginkel and Stroo, 1992). River water without particles was used as inoculum. The particles were removed by sedimentation after 1 day while moderately aerating.

Duration of test (contact time):

28 d

Initial conc.:

2 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

DEIONISED WATER
Deionized water containing no more than 0.01 mg/L Cu (ISO 17025 certified; non-GLP analysis) was prepared in a water purification system.

TEST BOTTLES
The test was performed in 0.30 L BOD (biological oxygen demand) bottles with glass stoppers.

NUTRIENTS, STOCKS AND ADMINISTRATION
The river water used in the Closed Bottle test was spiked per liter of water with 8.5 mg KH2PO4, 21.75 mg K2HPO4, 33.4 mg Na2HPO4·2H2O, 22.5 mg MgSO4·7H2O, 27.5 mg CaCl2, 0.25 mg FeCl3·6H2O. Ammonium chloride was not added to the river water to prevent nitrification. Accurate administering of the test substance was accomplished by preparing a solid stock of 3.0 mg of the test substance per g of silica gel in a 50-mL serum flask. Only part of the top layer of the silica gel was brought into contact with the test substance. The serum flask was closed with a screw top with aluminum foil and the content was mixed vigorously. Subsequently 0.2 g of silica gel with the test substance was added to the test bottles. The resulting concentration of test substance in the bottles was 2.0 mg/L. Next the bottles were filled with nutrient medium with inoculum and closed. Sodium acetate was added to the bottles using a stock solution of 1.0 g/L.

TEST PROCEDURES
The Closed Bottle test was performed according to the study plan. The study plan was developed from ISO Test Guidelines (1994). Use was made of 10 bottles containing only river water, 10 bottles containing river water and silica gel, 10 bottles containing river water and silica gel with test substance, 6 bottles with river water and sodium acetate. The concentrations of the test substance, and sodium acetate in the bottles were 2.0 and 6.7 mg/L, respectively. Each of the prepared solutions was dispensed into the respective group of BOD bottles so that all bottles were completely filled without air bubbles. The zero time bottles were immediately analyzed for dissolved oxygen using an oxygen electrode. The remaining bottles were closed and incubated in the dark. Two duplicate bottles of all series were withdrawn for analyses of the dissolved oxygen concentration at day 7, 14, 21, and 28.

TEST CONDITIONS
The pH of the media was 8.0 at the start of the test. The pH of the medium at day 28 was 7.8 (test) and 8.0 (controls). Temperatures were within the prescribed temperature range of 22 to 24°C.

CALCULATION OF BIODEGRADATION PERCENTAGES
The biodegradation was calculated as the ratio of the BOD to the theoretical oxygen demand (ThOD). The calculated theoretical oxygen demand (ThOD) of the test substance (mono-constituent) is 2.7 mg/mg. The ThOD of the reference substance sodium acetate is 0.8 mg/mg.

Reference substance:

acetic acid, sodium salt

Test performance:

VALIDITY OF THE TEST
The validity of the test is demonstrated by an endogenous respiration of 1.4 mg/L at day 28 (Table I). Furthermore, the differences of the replicate values at day 28 were less than 20%. The biodegradation percentage of the reference compound, sodium acetate, at day 14 was 89. Finally, the validity of the test is shown with oxygen concentrations remaining at >0.5 mg/L in all bottles over the test period.

TOXICITY
Inhibition of the endogenous respiration of the inoculum by the test substance tested was not detected. Therefore, no inhibition of the biodegradation due to the initial concentration of the test compound is expected.

Key result

Parameter:

% degradation (O2 consumption)

Value:

80

Sampling time:

28 d

Details on results:

Over 60% biodegradation was achieved in a period of 10 days immediately following the attainment of 10% biodegradation. The test item therefore fulfilled the time window criterion for ready biodegradable compounds. Hence the test substance should be classified as readily biodegradable.

Results with reference substance:

The biodegradation percentage of the reference compound, sodium acetate, at day 14 was 89.

Tabel 1: Dissolved oxygen concentrations (mg/L) in the closed bottles.

Time (days)	Oxygen concentration (mg/L)
	Ocs	Ot	Oc	Oa
0	8.7	8.7	8.7	8.7
	8.7	8.7	8.7	8.7
Mean	8.7	8.7	8.7	8.7
7	8.0	6.7	7.9	3.5
	7.9	6.8	8.0	3.9
Mean	8.0	6.8	8.0	3.7
14	7.7	4.3	7.6	2.7
	7.7	3.8	7.6	2.9
Mean	7.7	4.1	7.6	2.8
21	7.4	3.4	7.4	-
	7.4	3.3	7.6	-
Mean	7.4	3.4	7.5	-
28	7.3	2.8	7.3	-
	7.2	3.2	7.3	-
Mean	7.3	3.0	7.3	-

Ocs: River water with nutrients and silica gel.

Ot: River water with nutrients, test material (2.0 mg/L) and silica gel.

Oc: River water with nutrients.

Oa: River water with nutrients and sodium acetate (6.7 mg/L).

Table 2: Oxygen consumption (mg/L) and the percentages biodegradation of the test substance and the reference substance

Time (days)	Oxygen consumption (mg/L)		Biodegradation (%)
	Test substance	Acetate	Test substance	Acetate
0	0.0	0.0	0	0
7	1.2	4.3	22	80
14	3.6	4.8	67	89
21	4.0	-	74	-
28	4.3	-	80	-

Validity criteria fulfilled:

yes

Remarks:

see 'Test performance'.

Interpretation of results:

readily biodegradable

Conclusions:

The substance showed 80% biodegradation in an OECD TG 301D test. The 10-day window criterion was met.

Executive summary:

In order to assess the biotic degradation, a ready biodegradability test was performed which allows the biodegradability to be measured in an aerobic aqueous medium. The ready biodegradability was determined in the Closed Bottle test performed according to slightly modified OECD, EU and ISO Test Guidelines, and in compliance with the OECD principles of Good Laboratory Practice. The test substance did not cause a reduction in the endogenous respiration. The test substance is therefore considered to be non-inhibitory to the inoculum. Veilex 1 (monoconstituent) was biodegraded by 80% at day 28 in the Closed Bottle test. Over 60% biodegradation was achieved in a period of 10 days immediately following the attainment of 10% biodegradation. Hence, this substance should be classified as readily biodegradable. The test is valid as shown by an endogenous respiration of 1.4 mg/L and by the total mineralization of the reference compound, sodium acetate. Sodium acetate was degraded by 89% of its theoretical oxygen demand after 14 days. Finally, the most important criterion was met with oxygen concentrations remaining at >0.5 mg/L in all bottles over the test period.

Description of key information

Veilex 1 is readily biodegradable as observed in a valid biodegradability screening test according to OECD TG 301D (Closed Bottle Test) and in compliance with GLP criteria (IFF, 2015).

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Additional information

The ready biodegradability of Veilex 1 was investigated in a study conducted according to OECD TG 301D (Closed Bottle Test) and in compliance with GLP criteria (IFF, 2015). The concentration tested was 2 mg/L test substance. The inoculum used was river water which was aerated for 7 days before use to reduce the endogenous respiration. In addition, particles were removed by sedimentation after 1 day while moderately aerating. Under these conditions the test substance biodegrades 80% in 28 days. The 10-day window criterion for ready biodegradability was met. Inhibition of the endogenous respiration of the inoculum by the test substance was not detected. The validity of the test is demonstrated by an endogenous respiration of 1.4 mg/L at day 28. Furthermore, the differences of the replicate values at day 28 were less than 20%. The biodegradation percentage of the reference compound, sodium acetate, at day 14 was 89%. Finally, the validity of the test is shown with oxygen concentrations remaining at >0.5 mg/L in all bottles over the test period.