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Biodegradation in water: screening tests

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.

Biodegradation in water and sediment: simulation tests

Based on the Level III Fugacity Model, the half life period of the substance benzyl propionate was estimated. The half life period of benzyl propionate in water is 15 days , therfore it is considered that the substance will qualify as not persistent as the half life does not exceed the threshold of 60 days. So, it can be confirmed that the substance is readily biodegradable in water medium whereas in sediment the half life is 140 days and based on this value, it can be inferred that the substance is persistent in sediment medium and is not readily biodegradable. However, it can be observed that benzyl propionate does not diffuse in the sediment medium since it's percentage in the sediment medium is reported to be 0% and hence persistence in the sediment compartment is not likely to be critical.

 

Biodegradation in soil

The PBT Profiler and EPI Suite has estimated that the substance Benzyl propionate is expected to be found predominantly in soil and its persistence estimate is based on its availability in this medium. Its half-life in soil, 30 days does not exceed the persistence threshold. Therefore, Benzyl propionate is estimated to be non-persistent in the soil environment.

Additional information

Biodegradation in water: screening tests

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.

 

Biodegradation in water and sediment: simulation tests

Based on the Level III Fugacity Model, the half life period of the substance benzyl propionate was estimated. The half life period of benzyl propionate in water is 15 days , therfore it is considered that the substance will qualify as not persistent as the half life does not exceed the threshold of 60 days. So, it can be confirmed that the substance is readily biodegradable in water medium whereas in sediment the half life is 140 days and based on this value, it can be inferred that the substance is persistent in sediment medium and is not readily biodegradable. However, it can be observed that benzyl propionate does not diffuse in the sediment medium since it's percentage in the sediment medium is reported to be 0% and hence persistence in the sediment compartment is not likely to be critical.

 

Biodegradation in soil

The PBT Profiler and EPI Suite has estimated that the substance Benzyl propionate is expected to be found predominantly in soil and its persistence estimate is based on its availability in this medium. Its half-life in soil, 30 days does not exceed the persistence threshold. Therefore, Benzyl propionate is estimated to be non-persistent in the soil environment.

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