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Hydrolysis

HYDROWIN v2.00 program of Estimation Programs Interface (2018) prediction model was used to predict the hydrolysis half-life of test chemical. The estimated half-life of test chemical was determined to be 5.494 yrs and 200.670 days at pH 7.0 and 8.0 (at 25ᵒC) respectively, indicating that it is not hydrolysable.

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 75.3%. Degradation of Sodium Benzoate exceeds 46.38 % on 7 days & 61.44 % 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 1.02 mgO2/mg. ThOD was calculated as 1.93 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 52.84%. 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, 25.2% 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 0.0866%), 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, 74.3% 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.

Adsorption / desorption

The adsorption coefficient Koc in soil and in sewage sludge of test chemical was determined by the Reverse Phase High Performance Liquid Chromatographic method according to OECD Guideline No. 121 for testing of Chemicals (Experimental study report, 2018). The solutions of the test substance and reference substances were prepared in appropriate solvents. A test item solution was prepared by accurately weighing 4 mg of test item and diluted with ACN up to 10 ml. Thus, the test solution concentration was 450.4 mg/l. The pH of test substance was 3.68. Each of the reference substance and test substance were analysed by HPLC at 210 nm. After equilibration of the HPLC system, Urea was injected first, the reference substances were injected in duplicate, followed by the test chemical solution in duplicate. Reference substances were injected again after test sample, no change in retention time of reference substances was observed. Retention time tR were measured, averaged and the decimal logarithms of the capacity factors k were calculated. The graph was plotted between log Koc versus log k(Annex - 2).The linear regression parameter of the relationship log Koc vs log k were also calculated from the data obtained with calibration samples and therewith, log Koc of the test substance was determined from its measured capacity factor. The reference substances were chosen according to functional similarity with the test substance and calibration graph prepared. The reference substances were 4 -methylaniline(p-Tolouidine), N-methylaniline, Aniline, Benzoic acid methylester, Xylene, Ethylbenzene, Toluene, Naphthalene having Koc value ranging from 1.8 to 2.75. The Log Koc value of test chemical was determined to be 2.0007 ± 0.001 at 25°C. This log Koc value indicates that the test chemical has a low sorption to soil and sediment and therefore have moderate migration potential to ground water.  

Additional information

Hydrolysis

Predicted data and various experimental studies of the test chemical were reviewed for the hydrolysis end point which are summarized as below:

 

In aprediction done using the HYDROWIN v2.00 program of Estimation Programs Interface (2018) prediction model was used to predict the hydrolysis half-life of test chemical. The estimated half-life of test chemical was determined to be 5.494 yrs and 200.670 days at pH 7.0 and 8.0 (at 25ᵒC) respectively.

 

In a supporting weight of evidence study from authoritative databases (2016) for the test chemical,the base catalyzed second order hydrolysis rate constant of test chemical was determined using a structure estimation method. The second order hydrolysis rate constant of test chemical was determined to be 0.04 L/mol-sec with a half-life value of 5.0 yrs and 200 days at pH 7.0 and 8.0, respectively.

 

For the test chemical,the base catalyzed second order hydrolysis rate constant of test chemical was determined using a structure estimation method (HSDB, 2017). The second order hydrolysis rate constant of test chemical was determined to be 0.042 L/mol-sec with a half-life value of 5.5 yrs and 200 days at pH 7.0 and 8.0, respectively. 

 

In an another study, the base catalyzed second order hydrolysis rate constant of test chemical was determined using a structure estimation method. The second order hydrolysis rate constant of test chemical was determined to be 0.038 L/mol-sec with a corresponding half-lives of 5.8 years and 210 days at pH 7 and 8, respectively.

 

On the basis of the above results for test chemical, it can be concluded that the hydrolysis half-life value of test chemicalwas evaluated to be 200.670 days (at pH 7.0), indicating that the test chemical is not hydrolysable.

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 75.3%. Degradation of Sodium Benzoate exceeds 46.38 % on 7 days & 61.44 % 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 1.02 mgO2/mg. ThOD was calculated as 1.93 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 52.84%. 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, 25.2% 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 0.0866%), 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, 74.3% 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 ultimate inherently biodegradable in nature.

Adsorption / desorption

The adsorption coefficient Koc in soil and in sewage sludge of test chemical was determined by the Reverse Phase High Performance Liquid Chromatographic method according to OECD Guideline No. 121 for testing of Chemicals (Experimental study report, 2018). The solutions of the test substance and reference substances were prepared in appropriate solvents. A test item solution was prepared by accurately weighing 4 mg of test item and diluted with ACN up to 10 ml. Thus, the test solution concentration was 450.4 mg/l. The pH of test substance was 3.68. Each of the reference substance and test substance were analysed by HPLC at 210 nm. After equilibration of the HPLC system, Urea was injected first, the reference substances were injected in duplicate, followed by the test chemical solution in duplicate. Reference substances were injected again after test sample, no change in retention time of reference substances was observed. Retention time tR were measured, averaged and the decimal logarithms of the capacity factors k were calculated. The graph was plotted between log Koc versus log k(Annex - 2).The linear regression parameter of the relationship log Koc vs log k were also calculated from the data obtained with calibration samples and therewith, log Koc of the test substance was determined from its measured capacity factor. The reference substances were chosen according to functional similarity with the test substance and calibration graph prepared. The reference substances were 4 -methylaniline(p-Tolouidine), N-methylaniline, Aniline, Benzoic acid methylester, Xylene, Ethylbenzene, Toluene, Naphthalene having Koc value ranging from 1.8 to 2.75. The Log Koc value of test chemical was determined to be 2.0007 ± 0.001 at 25°C. This log Koc value indicates that the test chemical has a low sorption to soil and sediment and therefore have moderate migration potential to ground water.