4-hydroxybenzophenone

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:

24 Oct 2018 to 22 Nov 2018

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:

adopted July 17, 1992

Deviations:

no

GLP compliance:

yes (incl. QA statement)

Specific details on test material used for the study:

Appearance: White powder
Purity/Composition: 99.72%, assumed 100% for testing
Test item storage: At room temperature desiccated

Oxygen conditions:

aerobic

Inoculum or test system:

sewage, predominantly domestic, adapted

Details on inoculum:

The source of test organisms was activated sludge freshly obtained from a municipal sewage treatment plant: 'Waterschap Aa en Maas', 's-Hertogenbosch, The Netherlands, receiving predominantly domestic sewage. The freshly obtained sludge was kept under continuous aeration until further treatment. Before use, the sludge was coarsely sieved (1 mm) and washed with mineral medium. After treatment, the concentration of suspended solids (SS) was determined to be 5.4 g/L in the concentrated sludge as used for the test. The sludge was used as inoculum at a concentration of 0.9 mL per litre of mineral medium, leading to a final concentration SS of 5 mg/L.

Duration of test (contact time):

28 d

Initial conc.:

34 mg/L

Based on:

test mat.

Initial conc.:

80 mg/L

Based on:

ThOD

Parameter followed for biodegradation estimation:

CO2 evolution

Details on study design:

4-Hydroxy-benzophenone was a white powder with a purity of 99.72% (HPLC). The test item was tested in duplicate at a target concentration of 34 mg/L, corresponding to a ThOD of 80 mg O2/L. The ThOD was based on the molecular formula.

Weighed amounts of 4-Hydroxy-benzophenone were added to the test bottles containing medium with microbial organisms and mineral components (test item bottle A: 12.34 mg; test item bottle B: 12.29 mg and toxicity control bottle: 8.35 mg). To this end, an inert carrier (e.g. small PTFE watch glass) containing the weighed amount of test item was transferred to the test bottle. The amounts of test item and reference item, and volumes of mineral medium added can be found in Table 1 (attached below). The test solutions were continuously stirred during the test, to ensure optimal contact between the test item and the test organisms. Test duration was 28 days.

Any residual volumes were discarded.

Testing Strategy and Experimental Design:
Test Procedure and Conditions:

Test duration: 28 days. During the test period, the test media were stirred continuously.
Test vessels: 500 mL brown colored glass bottles. The end volume of medium was 360 mL or 244 mL, in order to obtain the required headspace-to-volume ratio.

Milli-RO water Tap-water purified by reverse osmosis (Milli-RO) and subsequently passed over activated carbon.

Stock solutions of mineral components

A) 8.50 g KH2PO4
21.75 g K2HPO4
67.20 g Na2HPO4.12H2O
0.50 g NH4Cl
dissolved in Milli-RO water and made up to 1 litre, pH 7.4 ± 0.2

B) 22.50 g MgSO4.7H2O dissolved in Milli-RO water and made up to 1 litre.

C) 36.40 g CaCl2.2H2O dissolved in Milli-RO water and made up to 1 litre.

D) 0.25 g FeCl3.6H2O dissolved in Milli-RO water and made up to 1 litre.

Mineral medium 1 litre mineral medium contains: 10 mL of solution (A),
1 mL of solutions (B) to (D) and Milli-RO water.

CO2 absorber Sodium hydroxide pellets (Merck, Darmstadt, Germany).
Illumination The test media were excluded from light.

Preparation of Bottles:

Inoculation: At the start of the test (day 0) mineral medium was inoculated with activated sludge.

Type and number of bottles: Test suspension: containing test item and inoculum (2 bottles).
Inoculum blank: containing only inoculum (2 bottles)
Procedure control: containing reference item and inoculum (1 bottle).
Toxicity control: containing inoculum, and test item and reference item in amounts contributing equally to the total ThOD (1 bottle).

Preparation:
At the start of the test (day 0), test and/or reference item were added to the respective bottles. The volumes of suspensions were made up to 360 mL or 244 mL using inoculated mineral medium. Rubber gaskets containing two pellets of sodium hydroxide were inserted into each bottle. Subsequently, each bottle was sealed by screwing an automated respirometer head on top.

Determination of Biodegradation:
Experimental CO2 production:
The CO2 produced in each test bottle reacted with the CO2 absorbent in the rubber gaskets. As gaseous O2 was converted into gaseous CO2 that was absorbed, the gas pressure in the test system slowly decreased. This decrease in air pressure was measured by the respirometer heads and automatically converted into oxygen consumption (mg O2/L).

Measurements:
Measurements were recorded on day 0-4-7-11-14-18-21-25-28. Measurement of the procedure and toxicity control lasted until Day 14.

Theoretical Oxygen Demand:
The ThOD was calculated from the molecular formula.

Measurements and Recordings:
pH: At the start of the test (day 0) and on the last day (day 14 for the procedure and toxicity control and day 28 for the inoculum blanks and test item).
Respirometer: Lovibond BD600-GLP manometric respirometry system, equipped with an inductive stirring system.
Temperature of medium: Continuously in a vessel with Milli-RO water in the same climate controlled incubator.

Reference substance:

acetic acid, sodium salt

Test performance:

In the toxicity control, more than 25% biodegradation occurred within 14 days (65%, based on ThOD). Therefore, the test item was assumed not to inhibit microbial activity.
Functioning of the test system was checked by testing the reference item sodium acetate, which showed a normal biodegradation curve (see also "acceptability of the test")

Key result

Parameter:

% degradation (CO2 evolution)

Value:

87

Sampling time:

28 d

Key result

Parameter:

% degradation (CO2 evolution)

Value:

73

Sampling time:

28 d

Details on results:

See below ("Any other information on results incl. tables").

Theoretical Oxygen Demand

The ThOD of 4-Hydroxy-benzophenone was calculated to be 2.34 mg O2/mg.

The ThOD of sodium acetate was calculated to be 0.78 mg O2/mg.

Biodegradation

All data are presented in Appendix 1. The results of O2 consumption and biodegradation in blank bottles, procedure and toxicity control, and each test bottle are listed in Table 3 to 7. Table 8 contains the comparison of biodegradation of 4-Hydroxy-benzophenone in bottles A and B.

Figure 1 (attached below) shows the curves for biodegradation of the two bottles with 4-Hydroxy-benzophenone, the procedure control and the toxicity control.

The relative biodegradation values calculated from the measurements performed during the test period revealed 87% and 73% biodegradation of 4-Hydroxy-benzophenone, for A and B, respectively (based on ThOD). Furthermore, biodegradation of 4-Hydroxy-benzophenone of at least 60% was reached within a 10-day window.

 

Monitoring of Temperature and pH

The temperature recorded in a vessel with water in the same incubator varied between 22 and 23°C, and complied with the requirements as laid down in the study plan. The pH values of the different test media are presented in Table 2.

Table 2       

pH Values of Different Test Media

Test medium:	On day 0:	On day 28:
Blank control (A)	7.5	7.5
Blank control (B)	7.5	7.5
Procedure control	7.5	8.2
4-Hydroxy-benzophenone (A)	7.5	7.4
4-Hydroxy-benzophenone (B)	7.5	7.5
Toxicity control	7.5	8.2

Validity criteria fulfilled:

yes

Interpretation of results:

readily biodegradable

Conclusions:

In conclusion, 4-Hydroxy-benzophenone was readily biodegradable under the conditions of the Manometric Respirometry Test presently performed.

Executive summary:

The objective of the study was to evaluate the test item 4-Hydroxy-benzophenone for its ready biodegradability in an aerobic aqueous medium with microbial activity introduced by inoculation with activated sludge; Manometric Respirometry Test.

The study procedures described in this report were in compliance with the OECD guideline No. 301 F, 1992.

4-Hydroxy-benzophenone was a white powder with a purity of 99.72% (HPLC). The Theoretical Oxygen Demand (ThOD) of 4-Hydroxy-benzophenone was determined to be 2.34 mg O₂/mg. The test item was tested in duplicate at a target concentration of 34 mg/L, corresponding to a ThOD of 80 mg O₂/L. The ThOD was based on the molecular formula.

The study consisted of six bottles:

•       2 inoculum blanks (no test item),

•       2 test bottles (4-Hydroxy-benzophenone),

•       1 procedure control (sodium acetate) and

•       1 toxicity control (4-Hydroxy-benzophenone plus sodium acetate).

In order to transfer 4-Hydroxy-benzophenone to the test vessels, the test item was weighed on an inert carrier, which was transferred to the test bottles containing medium with microbial organisms and mineral components. The test solutions were continuously stirred during the test to ensure optimal contact between the test item and test organisms. Test duration was 28 days.

The relative biodegradation values calculated from the measurements performed during the test period revealed 87% and 73% biodegradation of 4-Hydroxy-benzophenone, for A and B, respectively (based on ThOD). Furthermore, biodegradation of 4-Hydroxy-benzophenone of at least 60% was reached within a 10-day window.

In the toxicity control, 4-Hydroxy-benzophenone was found not to inhibit microbial activity.

Since all criteria for acceptability of the test were met, this study was considered to be valid.

In conclusion, 4-Hydroxy-benzophenone was designated as readily biodegradable.

Description of key information

Studies carried out according to recognised testing guidelines under GLP certification.

Key value for chemical safety assessment

Biodegradation in water:

readily biodegradable

Type of water:

freshwater