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Environmental fate & pathways

Endpoint summary

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Description of key information

Biodegradation in water

42-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. 1 polyseed capsule were added in 500 ml D.I water and then stirred for 1 hour for proper mixing and functioning of inoculum. This gave the bacterial count as 10E7 to 10E8 CFU/ml. At the regular interval microbial plating was also performed on agar to confirm the vitality and CFU count of microorganism. 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 78.31%. Degradation of Sodium Benzoate exceeds 42.16 % on 7 days & 63.25 % on 14th day. The activity of the inoculum was thus verified and the test can be considered as valid. The BOD42 value of test chemical was observed to be 1.22 mgO2/mg. ThOD was calculated as 2.91 mgO2/mg. Accordingly, the % degradation of the test item after 42 days of incubation at 20 ± 1°C according to Closed Bottle test was determined to be 41.92%. Based on the results, the test item, under the test conditions, was considered to be ultimate inherently 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, 14% 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 0.515%), 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, 85.5% 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 is not persistent in the soil environment and the exposure risk to soil dwelling animals is moderate to low.

Additional information

Biodegradation in water

Various experimental 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), 42-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. 1 polyseed capsule were added in 500 ml D.I water and then stirred for 1 hour for proper mixing and functioning of inoculum. This gave the bacterial count as 10E7 to 10E8 CFU/ml. At the regular interval microbial plating was also performed on agar to confirm the vitality and CFU count of microorganism. 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 78.31%. Degradation of Sodium Benzoate exceeds 42.16 % on 7 days & 63.25 % on 14th day. The activity of the inoculum was thus verified and the test can be considered as valid. The BOD42 value of test chemical was observed to be 1.22 mgO2/mg. ThOD was calculated as 2.91 mgO2/mg. Accordingly, the % degradation of the test item after 42 days of incubation at 20 ± 1°C according to Closed Bottle test was determined to be 41.92%. Based on the results, the test item, under the test conditions, was considered to be ultimate inherently biodegradable in nature.

 

Another biodegradation study from peer reviewed journal (A.M. Api et. al., 2015) was conducted according to OECD Guideline 301 B (Ready Biodegradability: CO2 Evolution Test) for 28 days for evaluating the percentage biodegradability of test chemical. The percentage degradation of test chemical was determined to be 75.4% by CO2 evolution after 28 days. Thus, the test chemical was evaluated to be readily biodegradable in nature.

 

On the basis of above overall results for test chemical, it can be concluded that the test chemical can be expected to undergoes ultimate inherently to 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, 14% 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 0.515%), 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, 85.5% 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 is not 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 ultimate inherently to readily biodegradable in nature.