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Biodegradation in water: screening tests

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Reference
Endpoint:
biodegradation in water: ready biodegradability
Type of information:
experimental study
Adequacy of study:
key study
Reliability:
1 (reliable without restriction)
Rationale for reliability incl. deficiencies:
guideline study
Justification for type of information:
Experimental result using OECD guidelines.
Qualifier:
according to guideline
Guideline:
OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test)
Principles of method if other than guideline:
Biodegradation study was conducted according to OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test) for evaluating the percentage biodegradability of test substance Benzyl propionate (CAS no. 122-63-4).
GLP compliance:
yes (incl. QA statement)
Specific details on test material used for the study:
- Name of test material (IUPAC name): Benzyl propionate
- Molecular formula: C10H12O2
- Molecular weight: 164.203 g/mol
- SMILES: c1(COC(CC)=O)ccccc1
- InChI: 1S/C10H12O2/c1-2-10(11)12-8-9-6-4-3-5-7-9/h3-7H,2,8H2,1H3
- Substance type: Organic
- Physical state: Liquid
Oxygen conditions:
aerobic
Inoculum or test system:
activated sludge, domestic (adaptation not specified)
Details on inoculum:
Fresh activated sludge from a biological waste water treatment plant treating predominantly domestic sewage (City og Geneva, Aire) was used.
The sludge is collected in the morning, washed three times in the mineral medium (by centrifuging at 1000g for 10 min, discarding the supernatant and resuspending in the mineral medium) and kept aerobic until being used on the same day.

Determination of the dry weight of suspended solids
The dry weight of suspended solids is determined by taking two 50 ml samples of the homogenized sludge, evaporating water on a steam bath, drying in an oven at 105-110°C for two hours and weighing the residue
Duration of test (contact time):
29 d
Initial conc.:
100 mg/L
Based on:
test mat.
Parameter followed for biodegradation estimation:
O2 consumption
Details on study design:
A measured volume of the inoculated mineral medium, containing a known concentration of the test substance (100 mg/L) as the nominal sole source of organic carbon, is stirred in a closed flask at a constant temperature (22±1°C) for upto 28 days. The consumption of oxygen is determined by measuring the quantity of oxygen (produced electrolytically) required to maintain constant the gas volume in the respirometer flask. Evolved carbon dioxide is absorbed in soda lime pellets. The Biological Oxygen Demand (BOD), amount of oxygen taken up by the microbial population during biodegradation of the test chemical (corrected for uptake by blank inoculum, run in parallel) is expressed as a percentage of ThOD (Theoretical Oxygen Demand, calculated from the elemental composition, assuming that carbonis oxidized to carbon dioxide and hydrogen to water).

Preparation of the flasks:
Test substance samples (25 mg, corresponding to 100 mg/L in a 250 ml flask) are weighed in small aluminium boats and added directly to the test flasks of the SAPROMAT, whereas reference substance samples (sodium benzoate) are added as 0.1ml of a 25 mg/ml solution in mineral medium.
All flasks are filled with 250ml of mineral medium. Samples of test or reference substance, or both, are added. Then, a volume of suspended sludge corresponding to 7.5 mg dry weight (generally 1 to 3 ml) is added. Except when the test substance has an acid or alkaline character, the pH of each flask is not measured but assumed to be the same as the mineral medium, in order not to remove any floating undissolved test substance from the test medium by dipping the glass electrode in it. Neutral test substances, even sodium benzoate, were shown not to affect the pH of the medium by more than 0.1 pH unit. About 2g of soda lime is placed in an attachment of the stopper, the flasks are closed and placed in the water bath of the SAPROMAT. After temperature and pressure equilibration, the oxygen meters of the instrument are set to zero (time zero of the experiment).
Reference substance:
other: Sodium benzoate
Key result
Parameter:
% degradation (O2 consumption)
Value:
89
Sampling time:
29 d
Remarks on result:
other: Other details not known
Details on results:
Benzyl propionate undergoes 89% biodegradation after 29 days (88% after 28 days) in the test conditions. Biodegradation starts on day 2 and reaches 76% at the end of the 10 day window (days 2 to 12).
Results with reference substance:
Degradation of Sodium benzoate exceeds 40% after 7 days and 65% after 14 days. The activity of the inoculum is thus verified and the test is considered as valid

Theoretical Oxygen demand

Molecular formula: C10H12O2

Molecular weight: 164.20 g/mol

Theoretical Oxygen demand (ThOD): 2.34 mgO2/mg

 

Biodegradability

Biological Oxygen Demand (BOD, mg O2/L, adjusted to nominal concentrations):

 

Days

2

7

12

21

28

29

BOD Sludge

1stflask

B1

5.0

12.0

14.0

18.0

21.0

21.0

2ndflask

B2

7.0

13.0

15.0

18.0

21.0

21.0

Mean

B

6.0

12.0

14.0

18.0

21.0

21.0

BOD Test substance

1stflask

C1

58.2

 145.3

191.8

218.9

226.8

226.8

2ndflask

C2

60.3

173.8

191.3

218.6

229.3

231.3

1stflask corrected

C1-B

52.2

132.8

177.3

200.9

205.8

205.8

2ndflask corrected

C2-B

54.3

161.3

176.8

200.6

208.3

210.3

% degradation

1stflask

D1

22

57

76

86

88

88

2ndflask

D2

23

69

76

86

89

90

Mean

D

23

63

76

86

88

89

B= (B1+B2)/2

D1= 100*(C1-B)/ThOD*[S]

D2= 100*(C2-B)/ThOD*[S]

D= (D1+D2)/2

[S]: initial test substance concentration (mg/L)

Validity criteria fulfilled:
yes
Interpretation of results:
readily biodegradable
Conclusions:
Benzyl propionate undergoes 89% biodegradation after 29 days (88% after 28 days) in the test conditions. Thus, benzyl propionate should be regarded as readily biodegradable according to this test.
Executive summary:

The Ready biodegradability of benzyl propionate (CAS no. 122 -63 -4) was determined by the Manometric Respirometry test according to the OECD Guidelines No. 301 F. Fresh activated sludge from a biological waste water treatment plant treating predominantly domestic sewage (City og Geneva, Aire) was used as a test inoculum for the study. The sludge is collected in the morning, washed three times in the mineral medium (by centrifuging at 1000g for 10 min, discarding the supernatant and resuspending in the mineral medium) and kept aerobic until being used on the same day. The dry weight of suspended solids is determined by taking two 50 ml samples of the homogenized sludge, evaporating water on a steam bath, drying in an oven at 105-110°C for two hours and weighing the residue. Initial test substance concentration used for the study was 100 mg/l, respectively. A measured volume of the inoculated mineral medium, containing a known concentration of the test substance (100 mg/L) as the nominal sole source of organic carbon, is stirred in a closed flask at a constant temperature (22±1°C) for upto 28 days. The consumption of oxygen is determined by measuring the quantity of oxygen (produced electrolytically) required to maintain constant the gas volume in the respirometer flask. The respirometer used during this study is a SAPROMAT D 12. Evolved carbon dioxide is absorbed in soda lime pellets. The Biological Oxygen Demand (BOD), amount of oxygen taken up by the microbial population during biodegradation of the test chemical (corrected for uptake by blank inoculum, run in parallel) is expressed as a percentage of ThOD (Theoretical Oxygen Demand, calculated from the elemental composition, assuming that carbonis oxidized to carbon dioxide and hydrogen to water). Sodium benzoate was used as a reference substance for the study. Benzyl propionate undergoes 89% biodegradation after 29 days (88% after 28 days) in the test conditions. Biodegradation starts on day 2 and reaches 76% at the end of the 10 day window (days 2 to 12). Thus, benzyl propionate should be regarded as readily biodegradable according to this test.

Description of key information

The Ready biodegradability of benzyl propionate (CAS no. 122 -63 -4) was determined by the Manometric Respirometry test according to the OECD Guidelines No. 301 F (Givaudan Roure SA, Report no. 99-E78, 1999). Fresh activated sludge from a biological waste water treatment plant treating predominantly domestic sewage (City og Geneva, Aire) was used as a test inoculum for the study. The sludge is collected in the morning, washed three times in the mineral medium (by centrifuging at 1000g for 10 min, discarding the supernatant and resuspending in the mineral medium) and kept aerobic until being used on the same day. The dry weight of suspended solids is determined by taking two 50 ml samples of the homogenized sludge, evaporating water on a steam bath, drying in an oven at 105-110°C for two hours and weighing the residue. Initial test substance concentration used for the study was 100 mg/l, respectively. A measured volume of the inoculated mineral medium, containing a known concentration of the test substance (100 mg/L) as the nominal sole source of organic carbon, is stirred in a closed flask at a constant temperature (22±1°C) for upto 28 days. The consumption of oxygen is determined by measuring the quantity of oxygen (produced electrolytically) required to maintain constant the gas volume in the respirometer flask. The respirometer used during this study is a SAPROMAT D 12. Evolved carbon dioxide is absorbed in soda lime pellets. The Biological Oxygen Demand (BOD), amount of oxygen taken up by the microbial population during biodegradation of the test chemical (corrected for uptake by blank inoculum, run in parallel) is expressed as a percentage of ThOD (Theoretical Oxygen Demand, calculated from the elemental composition, assuming that carbonis oxidized to carbon dioxide and hydrogen to water). Sodium benzoate was used as a reference substance for the study. Benzyl propionate undergoes 89% biodegradation after 29 days (88% after 28 days) in the test conditions. Biodegradation starts on day 2 and reaches 76% at the end of the 10 day window (days 2 to 12). Thus, benzyl propionate should be regarded as readily biodegradable according to this test.

Key value for chemical safety assessment

Biodegradation in water:
readily biodegradable

Additional information

Various experimental key and supporting studies for the target compoundBenzyl propionate(CAS No. 122-63-4) were reviewed for the biodegradation end point which are summarized as below:

                                    

In an experimental key study from study report (Givaudan Roure SA, Report no. 99-E78, 1999), the Ready biodegradability of benzyl propionate (CAS no. 122 -63 -4) was determined by the Manometric Respirometry test according to the OECD Guidelines No. 301 F. Fresh activated sludge from a biological waste water treatment plant treating predominantly domestic sewage (City og Geneva, Aire) was used as a test inoculum for the study. The sludge is collected in the morning, washed three times in the mineral medium (by centrifuging at 1000g for 10 min, discarding the supernatant and resuspending in the mineral medium) and kept aerobic until being used on the same day. The dry weight of suspended solids is determined by taking two 50 ml samples of the homogenized sludge, evaporating water on a steam bath, drying in an oven at 105-110°C for two hours and weighing the residue. Initial test substance concentration used for the study was 100 mg/l, respectively. A measured volume of the inoculated mineral medium, containing a known concentration of the test substance (100 mg/L) as the nominal sole source of organic carbon, is stirred in a closed flask at a constant temperature (22±1°C) for upto 28 days. The consumption of oxygen is determined by measuring the quantity of oxygen (produced electrolytically) required to maintain constant the gas volume in the respirometer flask. The respirometer used during this study is a SAPROMAT D 12. Evolved carbon dioxide is absorbed in soda lime pellets. The Biological Oxygen Demand (BOD), amount of oxygen taken up by the microbial population during biodegradation of the test chemical (corrected for uptake by blank inoculum, run in parallel) is expressed as a percentage of ThOD (Theoretical Oxygen Demand, calculated from the elemental composition, assuming that carbonis oxidized to carbon dioxide and hydrogen to water). Sodium benzoate was used as a reference substance for the study. Benzyl propionate undergoes 89% biodegradation after 29 days (88% after 28 days) in the test conditions. Biodegradation starts on day 2 and reaches 76% at the end of the 10 day window (days 2 to 12). Thus, benzyl propionate should be regarded as readily biodegradable according to this test.

 

Another supporting 28 days Manometric respirometry test following the OECD guideline 301F to determine consumption of dissolved oxygen (DO) and thereby % degradation during the test period was conducted for the test substance Benzyl propionate (CAS No. 122-63-4) (UERL study report, Sustainability Support Services (Europe) AB, Study no. RBD-008/122-63-4/2015, 2015). The test system included control, test substance and reference substance. The concentration of test and reference substance (sodium benzoate) chosen for the study were 100 mg/l& 100 mg/l respectively while that of inoculum was 10 ml/l. ThOD (Theoretical oxygen demand) of test and reference substance was determined by calculation. % Degradation was calculated using the values of BOD and ThOD for test substance and reference substance. The substance Benzyl propionate (CAS No. 122-63-4) achieved 93.58% degradation after 18 days of incubation at 20 ± 1°C according to manometric respirometry test. Based on the results, the test substance, under the test conditions, was considered to be readily biodegradable at 20 ± 1°C over a period of test duration.

 

On the basis of above experimental lab study results (K1 study) for target chemicalBenzyl propionate(from Givaudan Roure SA and UERL study report), it can be concluded that the test substance Benzyl propionate can be expected to be readily biodegradable in nature.

 

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