Benzeneacetaldehyde, cyclic acetal with glycerol

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:

4th of October 2016 until 5th of December 2016

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)

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 nearest plant 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. The inoculum was not pre-exposed to the test substance. The river water was spiked with mineral salts. Ammonium chloride was not added to the river water to prevent oxygen consumption due to nitrification (omission does not result in nitrogen limitation as shown by the biodegradation of the reference compound).

Duration of test (contact time):

60 d

Initial conc.:

1 mg/L

Based on:

test mat.

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 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 0.10 g of silica gel with the test substance was added to the test bottles. The resulting concentration of test substance in the bottles was 1.0 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 1.0 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. One extension from the protocol of the Closed Bottle test was introduced. The Closed Bottle test was prolonged by measuring
the course of the oxygen decrease in the bottles of day 28 using a special funnel. This funnel fitted exactly in the BOD bottle. Subsequently, the oxygen electrode was inserted in the BOD bottle to measure the oxygen concentration. The medium dissipated by the electrode was collected in the funnel. After withdrawal of the oxygen electrode the medium collected flowed back into the BOD bottle, followed by removal of the funnel and closing of the BOD bottle.

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 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 validity of the test is demonstrated by an endogenous respiration of 1.2 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. 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. Finally, the validity of the test is shown by oxygen concentrations >0.5 mg/L in all bottles during the test period.

Parameter:

% degradation (O2 consumption)

Value:

5

Sampling time:

7 d

Parameter:

% degradation (O2 consumption)

Value:

24

Sampling time:

14 d

Parameter:

% degradation (O2 consumption)

Value:

29

Sampling time:

21 d

Key result

Parameter:

% degradation (O2 consumption)

Value:

48

Sampling time:

28 d

Parameter:

% degradation (O2 consumption)

Value:

62

Sampling time:

42 d

Key result

Parameter:

% degradation (O2 consumption)

Value:

71

Sampling time:

60 d

Details on results:

The substance is biodegraded by 48% at day 28 in the Closed Bottle test. In the prolonged Closed Bottle test (enhanced biodegradability testing), the test substance is biodegraded by 71% at day 60. The biodegradation in excess of 60% within the 60-day test period allows classification of the substance as not persistent.

Results with reference substance:

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

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 at day 7 was not detected. Therefore, no inhibition of the biodegradation due to the high initial concentration of the test compound is expected.

Validity criteria fulfilled:

yes

Interpretation of results:

not readily biodegradable

Conclusions:

The substance is biodegraded by 48% at day 28 in the Closed Bottle test and should therefore be classified as not readily biodegradable. In the prolonged Closed Bottle test (enhanced biodegradability testing), the test substance is biodegraded by 71% at day 60. The biodegradation in excess of 60% within the 60-day test period allows classification of the substance as not persistent.

Executive summary:

In order to assess the biodegradation of the test substance, a screening test was performed according to OECD TG 301D (Closed Bottle test) and under GLP conditions. In this study river water was exposed to 1 mg/L of the test substance for 60 days. The test substance 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. The test substance was biodegraded by 48% at day 28 in the Closed Bottle test. In the prolonged Closed Bottle test, the test item was biodegraded by 71% at day 60 (enhanced biodegradability testing). A biodegradation percentage of >60 within a 60-day time period allows classification of the substance as not persistent. The test is valid as shown by an endogenous respiration of 1.2 mg/L at day 28 and by the complete degradation of the reference compound, sodium acetate. Sodium acetate was degraded by 85% of its theoretical oxygen demand after 14 days. Finally, the most important criterion was met by oxygen concentrations >0.5 mg/L in all bottles during the test period.

Description of key information

In order to assess the biodegradation of the test substance, a screening test was performed according to OECD TG 301D (Closed Bottle test) and under GLP conditions. In this study river water was exposed to 1 mg/L of the test substance for 60 days. The test substance 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. The test substance was biodegraded by 48% at day 28 in the Closed Bottle test. In the prolonged Closed Bottle test, the test item was biodegraded by 71% at day 60 (enhanced biodegradability testing). A biodegradation percentage of >60 within a 60-day time period allows classification of the substance as not persistent. The test is valid as shown by an endogenous respiration of 1.2 mg/L at day 28 and by the complete degradation of the reference compound, sodium acetate. Sodium acetate was degraded by 85% of its theoretical oxygen demand after 14 days. Finally, the most important criterion was met by oxygen concentrations >0.5 mg/L in all bottles during the test period.

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed