[1S-(1α,3aβ,4α,8aβ)]-decahydro-4,8,8-trimethyl-9-methylene-1,4-methanoazulene

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:

10 January 2017 - 08 February 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:

1992

Qualifier:

equivalent or similar to guideline

Guideline:

EU Method C.4-E (Determination of the "Ready" Biodegradability - Closed Bottle Test)

Version / remarks:

1992

Qualifier:

equivalent or similar 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)

Oxygen conditions:

aerobic

Inoculum or test system:

natural water

Details on inoculum:

River water was sampled from the Rhine near Heveadorp, The Netherlands. The river water was aerated for 7 days 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. The river water was spiked with mineral salts. Ammonium chloride was not added to the river water to prevent nitrification.

Duration of test (contact time):

28 d

Initial conc.:

2 mg/L

Based on:

test mat.

Remarks:

Coated on silica beads

Parameter followed for biodegradation estimation:

O2 consumption

Remarks:

as a percentage of ThOD

Details on study design:

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

Nutrients, stocks and administration:
The nutrient medium of the Closed Bottle test contained per liter of deionized water; 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 aluminium 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 procedure:
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 7.9 (test) and 8.0 (controls). Temperatures were within the prescribed temperature range of 22 to 24°C.

Reference substance:

acetic acid, sodium salt

Remarks:

purity > 99%

Test performance:

The test is valid as shown 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%. Sodium acetate was degraded by 78% after 14 days. Finally, the oxygen concentrations were >0.5 mg/L in all bottles during the test period.

Key result

Parameter:

% degradation (O2 consumption)

Value:

68

Sampling time:

28 d

Details on results:

The substance is biodegraded by 68% at day 28 in the Closed Bottle test. The pass level of 60% in 28 days was obtained. The test substance is poorly water soluble (< 10 mg/l. The bioavailability of poorly water soluble substances does limit microbial growth . Therefore, poor water solubility is an important reason for not applying the 14 day time window (Battersby, 2000; Richterich and Steber, 2001). In addition, the substance contains more than one constituent and is considered a multi-constituent. This means that the substance can be classified as readily biodegradable only using the pass level of 60% at day 28.
Battersby NS (2000) The biodegradability and microbiological toxicity testing of lubricants
some recommendations. Chemosphere 41 1011-1027.
Richterich K and Steber J (2001) The time-window – an inadequate criterion for the ready
biodegradability assessment of technical surfactants. Chemosphere 44 1649-1654.

Results with reference substance:

The biodegradation of the reference compound, sodium acetate, at day 14 was 78%.

Toxicity to inoculum: No toxicity was seen in the study, because no inhibition of the oxygen consumption was seen in the test.

Table 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 (M)	8.7	8.7	8.7	8.7
7	7.6	7.4	7.6	3.6
	7.7	7.1	7.6	3.7
Mean (M)	7.7	7.3	7.6	3.7
14	7.4	5.9	7.4	3.2
	7.5	6.0	7.4	3.2
Mean (M)	7.5	6.0	7.4	3.2
21	7.4	4.6	7.3
	7.3	4.8	7.4
Mean (M)	7.4	4.7	7.4
28	7.2	2.8	7.3
	7.2	2.6	7.3
Mean (M)	7.2	2.7	7.3

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

O_c         River water with nutrients.

O_a          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 (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	0.4	3.9	6	72
14	1.5	4.2	23	78
21	2.7		41
28	4.5		68

Validity criteria fulfilled:

yes

Remarks:

Oxygen concentrations were >0.5 mg/L in all bottles during the test period, oxygen depletion in the inoculum blank was 1.4 mg dissolved oxygen/L, differences between replicates at day 28 were <20%, the test substance was assumed to be non inhibitory.

Interpretation of results:

readily biodegradable

Conclusions:

The substance is biodegraded by 68% at day 28 in the Closed Bottle test. In view of the substance containing one constituent and a few impurities the time window does not need to be met. In addition, the substance is considered to be poorly soluble (< 10 mg/l) and therefore the time window is not a good criterion for assessing the ready biodegradability. This means that based on the pass level of 60% at day 28, the test substance is classified as readily biodegradable.

Executive summary:

In order to assess the biodegradation of the test substance, the OECD TG 301D (Closed Bottle test) and under GLP conditions was performed. In this study river water was exposed to 2 mg/L of the substance for 28 days. The test substance did not cause a reduction in the endogenous respiration. Sodium acetate was used as reference item and was biodegraded for 78% at day 14. Furthermore, the validity criteria of the test were met. The substance is biodegraded by 68% at day 28 in the Closed Bottle test. In view of the substance containing one constituent and a few impurities the time window does not need to be met. In addition, the substance is considered to be poorly soluble (< 10 mg/l) and therefore the time window is not a good criterion for assessing the ready biodegradability. This means that based on the pass level of 60% at day 28, the test substance is classified as readily biodegradable.

Description of key information

In order to assess the biodegradation of the test substance, the OECD TG 301D (Closed Bottle test) and under GLP conditions was performed. In this study river water was exposed to 2 mg/L of the substance for 28 days. The test substance did not cause a reduction in the endogenous respiration. Sodium acetate was used as reference item and was biodegraded for 78% at day 14. Furthermore, the validity criteria of the test were met. The substance is biodegraded by 68% at day 28 in the Closed Bottle test. In view of the substance containing one main constituent and some impurities the time window does not need to be met. In addition, the substance is considered to be poorly soluble (< 10 mg/l) and therefore the time window is not a good criterion for assessing the ready biodegradability. This means that based on the pass level of 60% at day 28, the test substance is classified as readily biodegradable.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable