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Environmental fate & pathways

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Description of key information

Biodegradation in water

28-days Manometric respirometry test following the OECD guideline 301F to determine the ready biodegradability of the test chemical (Experimental study report, 2015). The study was performed at a temperature of 20± 1°C. Mixture of domestic waste water, surface soil and soil samples was used as a test inoculum for the study. This inoculum was collected and were mixed to get diluted suspension. The inoculum was kept aerobic until being used for experiment by supplying organic and inorganic sources required by micro flora to sustain at controlled laboratory conditions.  This gave the bacterial count as 107to 108 CFU/ml. At the regular interval microbial plating was also performed on agar to confirm the vitality and CFU count of microorganism. OECD mineral medium was used for the study. The test system included control, test item and reference item. The concentration of test and reference item ( Sodium Benzoate) chosen for both the study was 100 mg/L, while that of inoculum was 100 mg/l. 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 substance) was also calculated using BOD & ThOD and was determined to be 227.4%. The DO depletion (mg O2/l) in control on 28th day is 19.1 mg O2/l which full fills the control validity criteria (i.e., The DO depletion of the inoculum blank is normally 20-30 mg O2/l and should not be greater than 60 mg/l in 28 days). Degradation of Sodium acetate exceeds 168.29% after 7 days and 212.76 % after 14 days. The activity of the inoculum is thus verified and the test is considered as valid. The BOD28 value of test chemical was observed to be 1.469 mgO2/mg. ThOD was calculated as 2.237 mgO2/mg. Accordingly, the % degradation of the test item after 28 days of incubation at 20 ± 1°C according to manometric respirometry test was determined to be 65.66%.Based on the results, the test item, under the test conditions, was considered to be readily biodegradable at 20 ± 1°C over a period of 28 days.

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, 26.5% 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 15 days (360 hrs). The half-life (15 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 135 days (3240 hrs). However, as the percentage release of test chemical into the sediment is less than 1% (i.e, reported as 0.175%), 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, 69.4% 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 30 days (720 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 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 (2015),28-days Manometric respirometry test following the OECD guideline 301F to determine the ready biodegradability of the test chemical. The study was performed at a temperature of 20± 1°C. Mixture of domestic waste water, surface soil and soil samples was used as a test inoculum for the study. This inoculum was collected and were mixed to get diluted suspension. The inoculum was kept aerobic until being used for experiment by supplying organic and inorganic sources required by micro flora to sustain at controlled laboratory conditions.  This gave the bacterial count as 107to 108 CFU/ml. At the regular interval microbial plating was also performed on agar to confirm the vitality and CFU count of microorganism. OECD mineral medium was used for the study. The test system included control, test item and reference item. The concentration of test and reference item ( Sodium Benzoate) chosen for both the study was 100 mg/L, while that of inoculum was 100 mg/l. 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 substance) was also calculated using BOD & ThOD and was determined to be 227.4%. The DO depletion (mg O2/l) in control on 28th day is 19.1 mg O2/l which full fills the control validity criteria (i.e., The DO depletion of the inoculum blank is normally 20-30 mg O2/l and should not be greater than 60 mg/l in 28 days). Degradation of Sodium acetate exceeds 168.29% after 7 days and 212.76 % after 14 days. The activity of the inoculum is thus verified and the test is considered as valid. The BOD28 value of test chemical was observed to be 1.469 mgO2/mg. ThOD was calculated as 2.237 mgO2/mg. Accordingly, the % degradation of the test item after 28 days of incubation at 20 ± 1°C according to manometric respirometry test was determined to be 65.66%.Based on the results, the test item, under the test conditions, was considered to be readily biodegradable at 20 ± 1°C over a period of 28 days.

 

Another biodegradation study was conducted for 28 days for evaluating the percentage biodegradability of test chemical (HSDB and PubChem, 2017). The study was performed according to OECD Guideline 301 D (Ready Biodegradability: Closed Bottle Test) under aerobic conditions. Activated sludge was used as a test inoculums for the study. Test substance undergoes 75% degradation by BOD parameter in 28 days and 10-day window criteria is fulfilled during the study. Thus, based on percentage degradation, test chemical is considered 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 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, 26.5% 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 15 days (360 hrs). The half-life (15 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 135 days (3240 hrs). However, as the percentage release of test chemical into the sediment is less than 1% (i.e, reported as 0.175%), 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, 69.4% 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 30 days (720 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 readily biodegradable in nature.