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Description of key information

Hydrolysis

The base catalyzed second order hydrolysis rate constant was determined using a structure estimation method of the test chemical (authoritative databases, 2017). The second order hydrolysis rate constant of test chemical was determined to be 6.3L/mol-sec with a corresponding half-lives of 3.5 yrs and 130 days at pH 7 and 8, respectively. Based on the half-life values, it is concluded 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 70.48%. Degradation of Sodium Benzoate exceeds 45.18% on 7 days & 70.48% 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 1.1 mgO2/mg. ThOD was calculated as 2.2 mgO2/mg. Accordingly, the % degradation of the test chemical after 42 days of incubation at 20 ± 1°C according to Closed Bottle test was determined to be 50%. Based on the results, the test chemical, 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, 39.8% 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 0.105%), 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, 46.4% of the test 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 (720hrs). 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.

Bioaccumulation: aquatic / sediment

The bioaccumulation study in fish was conducted for estimating the BCF (bioaccumulation factor) value of test chemical (authoritative database, 2017). The bioaccumulation factor (BCF) value was calculated using a logKow of 1.85 and a regression-derived equation. The estimated BCF (bioaccumulation factor) value of test chemical was determined to be 8 dimensionless, which does not exceed the bioconcentration threshold of 2000, indicating that the test chemical is considered to be non-accumulative in aquatic organisms.

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, 2017). The solutions of the test substance and reference substances were prepared in appropriate solvents. A test item solution was prepared by accurately measuring 4μL of test item and diluted with methanol up to 10ml. Thus, the test solution concentration was 349.4 mg/l. The pH of test substance was 6.68. 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 group similarity with the test substance and calibration graph prepared. The reference substances were 2 -nitrophenol, nitrobenzene, 4-nitrobenzamide, N,N-dimethylbenzamide, N-methylbenzamide, benzamide having Koc value ranging from 1.239 to 2.47. The Log Koc value of test chemical was determined to be 1.3463 ± 0.002 at 25°C. This log Koc value indicates that the test chemical has a negligible sorption to soil and sediment and therefore have rapid migration potential to ground water.

Additional information

Hydrolysis

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

 

In an experimental key study from authoritative database (2017),the base catalyzed second order hydrolysis rate constant was determined using a structure estimation method of the test chemical. The second order hydrolysis rate constant of test chemical was determined to be 6.3 L/mol-sec with a corresponding half-lives of 3.5 yrs and 130 days at pH 7 and 8, respectively.

 

In an another study, the half-life value of test chemical in water was determined at different pH. The hydrolysis half-life value of test chemical was determined to be 10 yrs, 6 yrs, 229 days and 23 days at pH 5, 7, 8 and 9, respectively.

 

In a prediction done using the HYDROWIN v2.00 program of Estimation Programs Interface (2017) prediction model was used to predict the hydrolysis half-life of test chemical. The estimated half-life of test chemical was determined to be 3.505 yrs and 128.021 days at pH 7.0 and 8.0 (at 25ᵒC) respectively, indicating that it is not hydrolysable.

 

For the test chemical, the half-life and base catalyzed second order hydrolysis rate constant was determined of the test chemical (HSDB, 2017). The second order hydrolysis rate constant of test chemical was determined to be 0.089L/mol-sec with a corresponding half-lives of 2.5 yrs and 90 days at pH 7 and 8, respectively.

 

In an another study from authoritative database (2017), the half-life and base catalyzed second order hydrolysis rate constant of the test chemical was determined using a structure estimation method. The second order hydrolysis rate constant of test chemical was determined to be 0.12 L/mol-sec with a corresponding half-lives of 1.7 yrs and 64 days at pH 7 and 8, respectively.

 

On the basis of above results for test chemical (from handbook, authoritative and modelling databases,2017), it can be concluded that the half-life value of test chemical was determined to be ranges from 23 days to 10 yrs, respectively, indicating that the test chemicalis 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 70.48%. Degradation of Sodium Benzoate exceeds 45.18% on 7 days & 70.48% 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 1.1 mgO2/mg. ThOD was calculated as 2.2 mgO2/mg. Accordingly, the % degradation of the test chemical after 42 days of incubation at 20 ± 1°C according to Closed Bottle test was determined to be 50%. Based on the results, the test chemical, 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, 39.8% 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 0.105%), 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, 46.4% of the test 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 (720hrs). 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.

Bioaccumulation: aquatic / sediment

Various experimental studies for the test chemical were reviewed for the bioaccumulation end point which are summarized as below:

 

In an experimental key study from authoritative database (2017),the bioaccumulation experiment in fish was conducted for estimating the BCF (bioaccumulation factor) value of test chemical. The bioaccumulation factor (BCF) value was calculated using a logKow of 1.85 and a regression-derived equation. The estimated BCF (bioaccumulation factor) value of test chemical was determined to be 8 dimensionless.

 

Another bioaccumulation study in aquatic organisms was conducted for determining the BCF (bioaccumulation factor) value of test chemical (handbook, 1999). The BCF (bioaccumulation factor) value of test chemical was determined to be 12 dimensionless.

 

In a prediction done using the BCFBAF Program of Estimation Programs Interface was used to predict the bioconcentration factor (BCF) of test chemical. The bioconcentration factor (BCF) of test chemical was estimated to be 7.678 L/kg whole body w.w (at 25 deg C).

 

For the test chemical from authoritative database (HSDB and PubChem, 2017), the bioaccumulation study in aquatic organisms was conducted for estimating the BCF (bioaccumulation factor) value of test chemical. The bioaccumulation factor (BCF) value was calculated using a logKow of 1.21 and a regression-derived equation. The estimated BCF (bioaccumulation factor) value of test chemical was determined to be 1.7 dimensionless.

 

On the basis of above results for test chemical (from handbook, authoritative and modelling databases, 2017), it can be concluded that the BCF value of test chemical was determined upto12 dimensionless, which does not exceed the bioconcentration threshold of 2000, indicating that the test chemical is not expected to bioaccumulate in the food chain.

 

Adsorption / desorption

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

 

In an experimental key study from study report (2017), 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. The solutions of the test substance and reference substances were prepared in appropriate solvents. A test item solution was prepared by accurately measuring 4μL of test item and diluted with methanol up to 10ml. Thus, the test solution concentration was 349.4 mg/l. The pH of test substance was 6.68. 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 group similarity with the test substance and calibration graph prepared. The reference substances were 2 -nitrophenol, nitrobenzene, 4-nitrobenzamide, N,N-dimethylbenzamide, N-methylbenzamide, benzamide having Koc value ranging from 1.239 to 2.47. The Log Koc value of test chemical was determined to be 1.3463 ± 0.002 at 25°C. This log Koc value indicates that the test chemical has a negligible sorption to soil and sediment and therefore have rapid migration potential to ground water.

 

Another adsorption study was conducted for estimating the adsorption coefficient (Koc) value of test chemical (authoritative databases HSDB and PubChem, 2017). The adsorption coefficient (Koc) value was calculated using a structure estimation method based on molecular connectivity indices. The adsorption coefficient (Koc) value of test substance was estimated to be 20 (Log Koc = 1.3). This Koc value indicates that the test chemical has a negligible sorption to soil and sediment and therefore have rapid migration potential to ground water.

 

For the test chemical, adsorption study in soil was conducted for determining the adsorption coefficient (Koc) value of test chemical (handbook, 2008). The adsorption coefficient (Koc) value of test substance was calculated to be 41 (Log Koc = 1.612). This Koc value indicates that the test substance has a low sorption to soil and sediment and therefore have moderate migration potential to ground water.

 

In an another study from peer reviewed journal (Lambri M. et. al., 2013), adsorption experiment was conducted for evaluating the adsorption capacity of test chemical onto bentonite clay. The study was performed using thebatch equilibrium method. A buffer solution containing 6 g/L tartaric acid adjusted to pH 3.30 with 1N potassium hydroxide and supplemented with 13% ethanol (v/v) was prepared. For test chemical, a defined volume of 1000 mg/l stock solution was prepared in absolute ethanol and stored at -28°C until use. An aliquot was added to a defined volume of the buffer solution to obtain a test chemical conc. used of 4 mg/l (4000 µg/l). Three samples of natural Ca2+-bentonite activated with Na+ were purchased from Dal Cin Gildo (Concorezzo,Italy).Two of the samples were powdery clays (A and C) and one of the samples was a granular bentonite (B). The A and B samples came from the same raw montmorillonite and the C bentonite originated from a montmorillonite containing magnesium smectite. Each bentonite sample was used in three different concentrations (0.2, 0.5 and 1 g/L) to treat the model wine solution. The bentonites were rehydrated in deionized water at a bentonite: water ratio of 10:100 (w/w). For each concentration of bentonite sample, three replicates were prepared in order to arrange three adsorption independent experiments. After the 90 mins of bentonites rehydration, the resulting slurries were stirred. Each suspension was then added to glass conical flasks containing 500 mL of the test chemical solution and thoroughly mixed for 90 s.A sample of the test chemical solution without any addition of bentonite was treated under the same conditions and kept in triplicate as a control test. The glass stoppered flasks (samples and control test) were then placed in a 60% relative humidity incubator at 17±1°C in static conditions to simulate the sedimentation. After 24 hours, the limpid liquid phases of both samples and control test were separated and filtered through folded filters (595 ½, Whatman GmbH, Germany).The adsorption data were expressed by the Langmuir and Freundlich models. To ensure equilibrium, the concentration of the adsorbate was measured after 12, 24 and 36 hours of contact time between the model wine solution and the bentonite. As there was no further increase in adsorption past the 24-hour mark, a contact time of 24 hours was established as the equilibrium time.The data were analyzed using the statistics package IBM SPSS Statistics 19 (IBM Corporation, New York, USA). The bentonite characteristics and the data from the odor-active compound analysis were analyzed by a factorial ANOVA. Significant differences were also analyzed using Tukey’s test atp≤ 0.05. The data from the batch adsorption experiments were analyzed by the curve estimation procedure. This procedure is the most appropriate when the relationship between the dependent variable(s) and the independent variable is not necessarily linear and generates for each dependent variable the related plots for 11 different curve estimation regression models. Finally, the risk (error onr2) and the prediction ability of the best models selected from curve estimation procedure were evaluated by cross validation (CV).The Langmuir adsorption isotherms constants (KL) at 17±1°C was determined to be -0.56, 0.07 and -0.04 and the Freundlich adsorption constants (KF) was determined to be 0.01, 3.66 and 0.47 on bentonite clay A, B and C, respectively. Thus, based on this, it can be concluded that the test chemical has a negligible to low sorption to soil and sediment and therefore have rapid to moderate migration potential to ground water.

 

On the basis of above overall results for test chemical (from study report, handbook, authoritative database and peer reviewed journal,2017), it can be concluded that the logKoc value of test chemical was determined to be ranges from 1.3 to 1.612, respectively, indicating that the test chemicalhas a negligible to low sorption to soil and sediment and therefore have rapid to moderate migration potential to ground water.