Bulnesia sarmienti, ext., sapond.

Biodegradation in water: screening tests

Administrative data

Endpoint:

biodegradation in water: ready biodegradability

Type of information:

experimental study

Adequacy of study:

key study

Study period:

2 December 2015 - 31 December 2015

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Remarks:

in accordance with GLP

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

2016

Report date:

2016

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

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

Deviations:

yes

Remarks:

ammonium chloride was omitted from the medium to prevent nitrification. The omission does not result in nitrogen limitation as shown by the biodegradation of the reference compound.

GLP compliance:

yes

Test material

Test material information

Constituent 1

Reference substance name:

Bulnesia sarmienti, ext.

EC Number:

289-632-8

EC Name:

Bulnesia sarmienti, ext.

Cas Number:

89958-10-1

Molecular formula:

This reference substance is a UVCB of the NCS type. It is a complex mixture of compounds and therefore molecular formula, molecular weight, and structural formula canoot be given.

IUPAC Name:

Essential oil of Guaiacwood obtained from the wood of Bulnesia sarmientoi by steam distillation

Test material form:

liquid: viscous

Details on test material:

- Name of test material (as cited in study report): Guaiacwood oil
- Physical state: viscous liquid
- Storage condition of test material: at room temperature protected from light

Study design

Oxygen conditions:

aerobic

Inoculum or test system:

natural water

Details on inoculum:

River water was sampled from the Rhine near Heveadorp, The Netherlands (26-11-2015). 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 test substance concentration

Initial conc.:

2 mg/L

Based on:

test mat.

Parameter followed for biodegradation estimation

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.

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 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:
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 7.9 (test) and 8.0 (controls). Temperatures were within the prescribed temperature range of 22 to 24°C.

Reference substance

Reference substance:

acetic acid, sodium salt

Remarks:

purity > 99%

Results and discussion

Test performance:

The validity of the test is demonstrated by an endogenous respiration of 0.9 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 85. Finally, the validity of the test is shown with oxygen concentrations remaining at >0.5 mg/L in all bottles over the test period.

% Degradation

% Degradation 1

Parameter:

% degradation (O2 consumption)

Value:

62

Sampling time:

7 d

% Degradation 2

Parameter:

% degradation (O2 consumption)

Value:

72

Sampling time:

14 d

% Degradation 3

Parameter:

% degradation (O2 consumption)

Value:

78

Sampling time:

21 d

% Degradation 4

Key result

Parameter:

% degradation (O2 consumption)

Value:

80

Sampling time:

28 d

Details on results:

Guaiacwood oil was biodegraded by 80% at day 28 in the Closed Bottle test. The substance is a UVCB, so the 14-day window is not relevant for ready biodegradability classification. Hence, the test item should be classified as readily biodegradable based only on the >60% biodegradation achieved at day 28.

BOD5 / COD results

Results with reference substance:

The biodegradation percentage of the reference compound, sodium acetate, at day 14 was 85.

Any other information on results incl. tables

Toxicity to inoculum:

Inhibition of the degradation of a well-degradable compound, e.g. sodium acetate by the test compound in the Closed Bottle test was not determined because possible toxicity of the test substance to microorganisms degrading acetate is not relevant. 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 "high" initial concentration of the test compound is expected.

Applicant's summary and conclusion

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

The substance is biodegraded by 80% at day 28 in the Closed Bottle test and should therefore be classified as readily biodegradable.

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 (TG OECD 301 D), 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. The validity criteria for the test were met.

Guaiacwood oil was biodegraded by 80% at day 28 in the Closed Bottle test. The substance is an UVCB, so the 14-day window is not relevant for ready biodegradability classification. Hence, this substance should be classified as readily biodegradable.