Essential oil of Dipterocarpus (Dipterocarpaceae) obtained from the resin tapped from Dipterocarpus trees by steam distillation (gurjunene quality)

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:

14 November 2017 - 13 December 2017

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)

Version / remarks:

17 July 1992

Deviations:

yes

Remarks:

ammonium chloride was omitted from the medium to prevent oxygen consumption due to nitrification and b) river water instead of an effluent/extract/mixture was used as inoculum.

Qualifier:

according to guideline

Guideline:

ISO 10707 Water quality - Evaluation in an aqueous medium of the "ultimate" aerobic biodegradability of organic compounds - Method by analysis of biochemical oxygen demand (closed bottle test)

Version / remarks:

1994

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Name: Gurjun balsam oil (Gurjunene)
Batch/lot: No. 0002642704
Molecular formula: C15H24 (based on known constituents; ~92%)
Appearance: yellow liquid
Solubility in water: insoluble in water
Stability: not relevant in biodegradation tests
Storage: at ambient temperature in the dark

Oxygen conditions:

aerobic

Inoculum or test system:

natural water: freshwater

Details on inoculum:

River water was sampled from the Rhine near Heveadorp, The Netherlands (08-11-2017). 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. 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:

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

Deionized water:
Deionized water containing no more than 1.0 mg/L organic carbon was prepared in a water purification system.

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 and the content was mixed vigorously. Subsequently 0.20 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 procedure:
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 8.0 (controls and test). The temperature ranged from 22.6 to 22.9°C which is within the prescribed temperature range of 22 to 24°C.

Reference substance:

acetic acid, sodium salt

Remarks:

Purity > 99%

Test performance:

The validity of the test is demonstrated by an endogenous respiration of 1.0 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 87% of its theoretical oxygen demand. Finally, the validity of the test is shown by oxygen concentrations >0.5 mg/L in all bottles during the test period.

Key result

Parameter:

% degradation (O2 consumption)

Value:

65

Sampling time:

28 d

Parameter:

% degradation (O2 consumption)

Value:

48

Sampling time:

21 d

Parameter:

% degradation (O2 consumption)

Value:

30

Sampling time:

14 d

Parameter:

% degradation (O2 consumption)

Value:

5

Sampling time:

7 d

Details on results:

Gurjun balsam oil (Gurjunene) was biodegraded by 65% at day 28 in the Closed Bottle test. The time-day window concept assumes that biodegradation of a single organic compound in a ready biodegradability test is a growth-linked process which follows an S-shaped growth curve. Gurjun balsam oil (Gurjunene) is a mixture of chemicals (UVCB). The biodegradation kinetics (lag period, growth rate, and yield) of the individual chemicals in a mixture are not necessarily same. The biodegradation of a (fragrance) substance consisting of many constituents is therefore an addition of different biodegradation curves. It is thus possible that individual compounds meet the time window criterion whereas the biodegradation curve suggests that the test substance is not readily biodegradable. The time window should therefore not be applied to this multi-constituent substance (OECD, 2006). Also, the biodegradation curve has not leveled off at 28 days, which suggests additional degradation can be anticipated when the test duration would have been extended. Gurjun balsam oil (Gurjunene) should be classified as readily biodegradable.

Results with reference substance:

The biodegradation percentage of the reference compound, sodium acetate, at day 14 was 87%.

Inhibition of the degradation of a well-degradable compound, e.g. sodium acetate by the test substance in the Closed Bottle test was not determined because possible toxicity of Gurjun balsam oil (Gurjunene) to microorganisms degrading acetate is not relevant. Inhibition of the endogenous respiration of the inoculum by the test substance at day 7 was not detected. Therefore, no inhibition of the biodegradation due to the "high" initial test substance concentration is expected.

Mean (n=2) 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
7	8.2	7.9	8.2	4.1
14	8.0	6.0	7.9	3.2
21	7.8	4.6	7.8
28	7.7	3.3	7.7

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).

  

Oxygen consumption (mg/L) and the percentages biodegradation of the test substance, Gurjun Balsam oil (gurjunene) (BOD/ThOD) and sodium acetate (BOD/ThOD) in the Closed Bottle test.

Time (days)	Oxygen consumption (mg/L)		Biodegradation (%)
	Test substance	Acetate	Test substance	Acetate
0	0.0	0.0	0	0
7	0.3	4.1	5	76
14	2.0	4.7	30	87
21	3.2		48
28	4.3		65

Validity criteria fulfilled:

yes

Remarks:

See test performance

Interpretation of results:

readily biodegradable

Conclusions:

The substance was biodegraded by 65% at day 28 in the Closed Bottle test and should therefore be classified as readily biodegradable.

Executive summary:

The ready biodegradability of Gurjun balsam oil was investigated in a study conducted in accordance with OECDTG 301D (closed bottle test) and GLP. In this study river water was exposed to 2 mg/L of the substance for 28 days.

Gurjun balsam oil (Gurjunene) did not cause a reduction in the endogenous respiration at day 7. The test substance is therefore considered to be non-inhibitory to the inoculum.Furthermore, the validity criteria of the test were met. Gurjun balsam oil was biodegraded by 65% at day 28 in the standard Closed Bottle screening test and should therefore be classified as readily biodegradable.

Description of key information

The ready biodegradability of Gurjun balsam oil was investigated in a study conducted in accordance with OECDTG 301D (closed bottle test) and GLP. In this study river water was exposed to 2 mg/L of the substance for 28 days.

Gurjun balsam oil (Gurjunene) did not cause a reduction in the endogenous respiration at day 7. The test substance is therefore considered to be non-inhibitory to the inoculum.Furthermore, the validity criteria of the test were met. Gurjun balsam oil was biodegraded by 65% at day 28 in the standard Closed Bottle screening test and should therefore be classified as readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater