2-hydroxy-1-[4-[4-(2-hydroxy-2-methylpropanoyl)phenoxy]phenyl]-2-methylpropan-1-one

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:

2018-11-13 - 2018-12-11 (experimental phase)

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

guideline study

Qualifier:

according to guideline

Guideline:

OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)

Version / remarks:

OECD Guideline for Testing of Chemicals No. 301 F: "Ready Biodegradability: Manometric Respirometry Test", adopted July 17, 1992

Deviations:

no

Qualifier:

according to guideline

Guideline:

EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test)

Version / remarks:

Commission Regulation 440/2008/EC, Method C.4-D of May 30, 2008: Manometric Respirometry Test (EEC Publication No. L 142/496, May 2008)

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

STABILITY AND STORAGE CONDITIONS OF TEST MATERIAL
- Storage condition of test material: At 20°C ± 5°C, in the desiccator in the dark

Oxygen conditions:

aerobic

Inoculum or test system:

activated sludge, domestic (adaptation not specified)

Details on inoculum:

- Source of inoculum/activated sludge (e.g. location, sampling depth, contamination history, procedure): Aerobic activated sludge, microorganisms from a domestic waste water treatment plant was supplied by the sewage treatment plant Rossdorf, Germany
- Preparation of inoculum for exposure:
Conditioning: The aerobic activated sludge used for this study was deposited for 60 min, washed by centrifugation and the supernatant liquid phase was decanted. The solid material was re-suspended in test water and centrifuged again. This procedure was done three times. An aliquot of the final sludge suspension was weighed, dried and the ratio of wet sludge to its dry weight was determined. Based on this ratio, calculated aliquots of washed sludge suspension, corresponding to 3.5 g dry material per litre were mixed with test water and aerated overnight. This suspension was used for the experiment.
- Concentration of sludge: 3.5 g dry material per litre

Duration of test (contact time):

28 d

Initial conc.:

>= 24.8 - <= 25.1 mg/L

Based on:

test mat.

Remarks:

ThOD NH4: 2.150 mg oxygen per mg test item

Parameter followed for biodegradation estimation:

O2 consumption

Details on study design:

TEST CONDITIONS
- Composition of medium:
Reconstituted Test Water: Analytical grade salts were added to pure water to prepare the following stock solutions:
a) 8.5 g KH2PO4, 21.75 g K2HPO4, 33.4 g Na2HPO4 x 2 H2O, 0.5 g NH4Cl filled up with pure water to 1000 mL volume; The pH-value was 7.3.
b) 11.25 g MgSO4 x 7 H2O filled up with pure water to 500 mL volume
c) 18.2 g CaCl2 x 2 H2O filled up with pure water to 500 mL volume
d) 0.125 g FeCl3 x 6 H2O filled up with pure water to 500 mL volume
In order to avoid precipitation of iron hydroxide in the stock solution d), one drop of concentrated HCl per litre was added before storage.
50 mL of stock solution a) and 5 mL of the stock solutions b) to d) were combined and filled up to a final volume of 5000 mL with pure water.
The pH was adjusted to pH 7.2 with NaOH solution.
- Additional substrate: none
- Test temperature: 22°C ± 1°C
- pH: 7.3 (measured at the start of the test) / 7.1 to 7.2 (measured at the end of the test)
- pH adjusted: no
- Aeration of dilution water: aliquots of washed sludge suspension, corresponding to 3.5 g dry material per litre were mixed with test water and aerated overnight
- Suspended solids concentration: sludge suspension: 3.5 g dry material per litre
- Continuous darkness: yes

TEST SYSTEM
- Culturing apparatus: Manometric Test System with test flasks containing a volume of approximately 500 mL. Closed test flasks were incubated in a climatised chamber, BSB/BOD-Sensor-System
- Number of culture flasks/concentration: duplicates
- Measuring equipment: The closed test flasks were incubated in a climatised chamber under continuous stirring. The consumption of oxygen was determined by measuring the change of pressure in the flasks. Evolved carbon dioxide was absorbed in an aqueous solution (45%) of potassium hydroxide.
Measurement of Oxygen: The change of pressure in the test flasks was measured by means of a manometric method (BSB/BOD-Sensor-System®) each day.
Temperature: The temperature was recorded by means of the automated software AMR Wincontrol©.
pH-Value: pH-values were measured in procedure control, a separately prepared test flask with test item (to prevent loss of test item in the test flasks) and a separately prepared test flask without test item (control) at test start and in all flasks at the end of the test, except in the abiotic and toxicity control, using a pH-electrode WTW pH 340i.
- Test performed in closed vessels due to significant volatility of test substance: substance is not volatile
- Test performed in open system: no

CONTROL AND BLANK SYSTEM
- Inoculum blank: yes
- Abiotic sterile control: yes, poisoned with CuSO4 (stock solution of 1 g/L)
- Toxicity control: yes
For details, see table in free-text field

Reference substance:

benzoic acid, sodium salt

Key result

Parameter:

% degradation (O2 consumption)

Value:

0

Sampling time:

28 d

Details on results:

The criterion for ready biodegradability under the conditions of a manometric respirometry test is the degradation of the test item of at least 60%, reached within a 10-day window; the 10-day window starts when the degradation of the test item reaches at least 10% degradation.
The test item 2-hydroxy-1-[4-(4-(2-hydroxy-2-methylpropionyl)phenoxy)phenyl]-2-methylpropan-1-one never reached a degradation of 10%. The mean biodegradation at test end after 28 days was 0% (ThODNH4).
The degradation rate of 2-hydroxy-1-[4-(4-(2-hydroxy-2-methylpropionyl)phenoxy)phenyl]-2-methylpropan-1-one never reached 60% within the 10-day window or after 28 days.
Therefore, 2-hydroxy-1-[4-(4-(2-hydroxy-2-methylpropionyl)phenoxy)phenyl]-2-methylpropan-1-one is considered to be not readily biodegradable.

Results with reference substance:

The reference item sodium benzoate was sufficiently degraded to 82% after 14 days and to 88% after 28 days of incubation. The percentage biodegradation of the reference item confirms the suitability of the used aerobic activated sludge inoculum.

Validity criteria fulfilled:

yes

Interpretation of results:

under test conditions no biodegradation observed

Conclusions:

The study was performed according to OECD TG 301F and EU Method C.4-D (GLP) with no deviation and is therefore considered to be of the highest quality (reliability Klimisch 1). The validity criteria of the test system are fulfilled, controls gave appropriate results. The test item 2-hydroxy-1-[4-(4-(2-hydroxy-2-methylpropionyl)phenoxy)phenyl]-2-methylpropan-1-one never reached a degradation of 10%. The mean biodegradation at test end after 28 days was 0% (ThODNH4). Therefore, 2-hydroxy-1-[4-(4-(2-hydroxy-2-methylpropionyl)phenoxy)phenyl]-2-methylpropan-1-one is considered to be not readily biodegradable.

Executive summary:

A study was conducted to determine the ready biodegradability of the test substance according to OECD Guideline 301 F and Commission Regulation 440/2008/EC, Method C.4-D (Manometric Respirometry Test) in compliance with GLP. Aerobic activated sludge was supplied by the domestic sewage treatment plant of Rossdorf (Germany). Biodegradation was followed as oxygen uptake of the microorganisms during 28 days of exposure. The reference substance sodium benzoate was tested simultaneously under the same conditions and functioned as a procedure control. A toxicity control containing both the test and the reference substance was included. Degradation rate of the test substance was calculated based on oxygen consumption of the aerobic activated sludge microorganisms after 28 days of incubation. The test substance loading rate (initial concentration in medium C0) was 102.2 mg/L, corresponding to an oxygen demand of about 219.8 mg/L (ThODNH4). The reference substance loading rate was 102.7 mg/L, corresponding to an oxygen demand of about 171.2 mg/L (ThODNH4). The test conditions were maintained at 22°C ± 1°C, in darkness.  

 

The criterion for ready biodegradability under the conditions of a manometric respirometry test is degradation of the test substance of at least 60% within a 10-day window. The mean biodegradation of the test substance after 28 days was 0% (ThODNH4). The reference substance was sufficiently degraded (88% after 28 days), thus confirming the suitability of the aerobic activated sludge inoculum. In the toxicity control, biodegradation was noted (36% (ThODNH4) after 28 days), showing that the test substance was not inhibitory to the activated sludge microorganisms. Under the study conditions, the test substance was not readily biodegradable (Hammesfahr, 2019).

Key value for chemical safety assessment

Biodegradation in water:

under test conditions no biodegradation observed

Type of water:

freshwater

Additional information

A study was conducted to determine the ready biodegradability of the test substance according to OECD Guideline 301 F and Commission Regulation 440/2008/EC, Method C.4-D (Manometric Respirometry Test) in compliance with GLP. Aerobic activated sludge was supplied by the domestic sewage treatment plant of Rossdorf (Germany). Biodegradation was followed as oxygen uptake of the microorganisms during 28 days of exposure. The reference substance sodium benzoate was tested simultaneously under the same conditions and functioned as a procedure control. A toxicity control containing both the test and the reference substance was included. Degradation rate of the test substance was calculated based on oxygen consumption of the aerobic activated sludge microorganisms after 28 days of incubation. The test substance loading rate (initial concentration in medium C0) was 102.2 mg/L, corresponding to an oxygen demand of about 219.8 mg/L (ThODNH4). The reference substance loading rate was 102.7 mg/L, corresponding to an oxygen demand of about 171.2 mg/L (ThODNH4). The test conditions were maintained at 22°C ± 1°C, in darkness.   

The criterion for ready biodegradability under the conditions of a manometric respirometry test is degradation of the test substance of at least 60% within a 10-day window. The mean biodegradation of the test substance after 28 days was 0% (ThODNH4). The reference substance was sufficiently degraded (88% after 28 days), thus confirming the suitability of the aerobic activated sludge inoculum. In the toxicity control, biodegradation was noted (36% (ThODNH4) after 28 days), showing that the test substance was not inhibitory to the activated sludge microorganisms. Under the study conditions, the test substance was not readily biodegradable (Hammesfahr, 2019).