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Environmental fate & pathways

Endpoint summary

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Description of key information

Biodegradation in water

28-days Closed Bottle test following the OECD guideline 301 D to determine the ready biodegradability of the test chemical (Experimental study report, 2018). The study was performed at a temperature of 20°C. The test system included control, test item and reference item. Polyseed were used for this study. The concentration of test and reference item (Sodium Benzoate) chosen for both the study was 4 mg/L, while that of inoculum was 32 ml/l. OECD mineral medium was used for the study. ThOD (Theoretical oxygen demand) of test and reference item was determined by calculation. % degradation was calculated using the values of BOD and ThOD for test item and reference item. The % degradation of procedure control (reference item) was also calculated using BOD & ThOD and was determined to be 79.51%. Degradation of Sodium Benzoate exceeds 64.45 % on 7 days & 75.30 % on 14th day. The activity of the inoculum was thus verified and the test can be considered as valid. The BOD28 value of test chemical was observed to be 1.07 mgO2/mg. ThOD was calculated as 1.60 mgO2/mg. Accordingly, the % degradation of the test item after 28 days of incubation at 20 ± 1°C according to Closed Bottle test was determined to be 66.87%. Based on the results, the test item, under the test conditions, was considered to be readily biodegradable in nature.

Biodegradation in water and sediment

Estimation Programs Interface (2018) prediction model was run to predict the half-life in water and sediment for the test chemical. If released in to the environment,19.5% of the chemical will partition into water according to the Mackay fugacity model level III and the half-life period of test chemical in water is estimated to be 37.5 days (900 hrs). The half-life (37.5 days estimated by EPI suite) indicates that the chemical is not persistent in water and the exposure risk to aquatic animals is moderate to low whereas the half-life period of test chemical in sediment is estimated to be 337.5 days (8100 hrs). However, as the percentage release of test chemical into the sediment is less than 1% (i.e, reported as 0.0997%), indicates that test chemical is not persistent in sediment.

Biodegradation in soil

The half-life period of test chemical in soil was estimated using Level III Fugacity Model by EPI Suite version 4.1 estimation database (2018). If released into the environment, 80.4% of the chemical will partition into soil according to the Mackay fugacity model level III. The half-life period of test chemical in soil is estimated to be 75 days (1800 hrs). Based on this half-life value of test chemical, it is concluded that the chemical isnot persistent in the soil environment and the exposure risk to soil dwelling animals is moderate to low.

Additional information

Biodegradation in water

Various experimental key and supporting studies of the test chemical were reviewed for the biodegradation end point which are summarized as below:

 

In an experimental key study from study report (2018),28-days Closed Bottle test following the OECD guideline 301 D to determine the ready biodegradability of the test chemical. The study was performed at a temperature of 20°C. The test system included control, test item and reference item. Polyseed were used for this study. The concentration of test and reference item (Sodium Benzoate) chosen for both the study was 4 mg/L, while that of inoculum was 32 ml/l. OECD mineral medium was used for the study. ThOD (Theoretical oxygen demand) of test and reference item was determined by calculation. % degradation was calculated using the values of BOD and ThOD for test item and reference item. The % degradation of procedure control (reference item) was also calculated using BOD & ThOD and was determined to be 79.51%. Degradation of Sodium Benzoate exceeds 64.45 % on 7 days & 75.30 % on 14th day. The activity of the inoculum was thus verified and the test can be considered as valid. The BOD28 value of test chemical was observed to be 1.07 mgO2/mg. ThOD was calculated as 1.60 mgO2/mg. Accordingly, the % degradation of the test item after 28 days of incubation at 20 ± 1°C according to Closed Bottle test was determined to be 66.87%. Based on the results, the test item, under the test conditions, was considered to be readily biodegradable in nature.

 

Another biodegradation study was conducted for 35 days for evaluating the percentage biodegradability of test chemical (Experimental study report, 1991). The study was performed in accordance with the OECD Guideline 302 B (Inherent biodegradability: Zahn-Wellens/EMPA Test) under aerobic conditions. Activated sludge obtained from a laboratory plant operated with concomitant wastewater was used as a test inoculum. Conc. of the inoculum used was 1 g/l dry substance in the test batch. Test inoculum was first pre-adapted with the test substance. After completion of this test, the pre-adapted inoculum was separated and washed twice. With the pre-adapted inoculum, the Zahn-Wellens test was performed. Test chemical conc. used for the study was 765 mg/l based on test material analysis / 400 mg/l based on DOC removal. Measuring equipment used during the DOC / TOC analysis with the analyzer was Shimadzu. Diethylene glycol was used as a reference substance for the study. The percentage degradation of test chemical was determined to be 71% based on DOC removal parameter after a period of 35 days. Thus, based on the percentage degradation, test chemical can be considered to be readily biodegradable in nature.

 

In a supporting study,biodegradation experiment was conducted for 28 days for evaluating the percentage biodegradability of test chemical (Experimental study report, 1991). The study was performed in accordance with the OECD Guideline 301 E (Ready biodegradability: Modified OECD Screening Test) under aerobic conditions. Municipal wastewater obtained from a laboratory treatment plant operated with concomitant wastewater was used as a test inoculum. Test chemical conc. used for the study was 37 mg/l based on test material analysis. Sodium benzoate was used as a reference substance for the study. Reference substance sodium benzoate undergoes 100% degradation after 4 days. The percentage degradation of test chemical was determined to be 7% based on DOC removal parameter after a period of 28 days. Thus, based on the percentage degradation, test chemical can be considered to be not readily biodegradable in nature.

 

For the test chemical from peer reviewed journal (Rita Beel et. Al, 2013), biodegradation study was conducted for 20 days for evaluating the percentage biodegradability of test chemical. The study was performed under aerobic conditions. Activated sludge was used as a test inoculums for the study. Initial test substance conc. used in the study was 20 mg/l. Analytical methods involve the use of both MS and HPLC. The percentage degradation of test chemical was determined to be 100% by after 7 days. Thus, based on percentage degradation, test chemical is considered to be readily biodegradable in nature.

 

Although result from one screening test (performed as per the OECD Guideline 301 E (Ready biodegradability: Modified OECD Screening Test)) indicates that the test chemical is not readily biodegradable; to confirm this another study as per the OECD Guideline 302 B (Inherent biodegradability: Zahn-Wellens/EMPA Test) was carried out indicating that the test chemical is readily biodegradable which is supported further by the results of other screening test (from study reports (K1) performed as per the OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test))) and peer reviewed journal. On the basis of this, it has been concluded that the test chemical is considered to be readily biodegradable in nature.

Biodegradation in water and sediment

Estimation Programs Interface (2018) prediction model was run to predict the half-life in water and sediment for the test chemical. If released in to the environment,19.5% of the chemical will partition into water according to the Mackay fugacity model level III and the half-life period of test chemical in water is estimated to be 37.5 days (900 hrs). The half-life (37.5 days estimated by EPI suite) indicates that the chemical is not persistent in water and the exposure risk to aquatic animals is moderate to low whereas the half-life period of test chemical in sediment is estimated to be 337.5 days (8100 hrs). However, as the percentage release of test chemical into the sediment is less than 1% (i.e, reported as 0.0997%), indicates that test chemical is not persistent in sediment.

Biodegradation in soil

The half-life period of test chemical in soil was estimated using Level III Fugacity Model by EPI Suite version 4.1 estimation database (2018). If released into the environment, 80.4% of the chemical will partition into soil according to the Mackay fugacity model level III. The half-life period of test chemical in soil is estimated to be 75 days (1800 hrs). Based on this half-life value of test chemical, it is concluded that the chemical isnot persistent in the soil environment and the exposure risk to soil dwelling animals is moderate to low.

On the basis of available information, the test chemical can be considered to be readily biodegradable in nature.