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Environmental fate & pathways

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Description of key information

Hydrolysis

On the basis of the experimental studies of the structurally and functionally similar read across chemical and applying the weight of evidence approach, the hydrolysis half-life value of the test chemical can be expected to be > 1 yr, at pH range 4, 7 & 9 and a temperature of 25°C or 50°C, respectively. Thus, based on this half-life value, it can be concluded that the test chemical is not hydrolysable in water.

Biodegradation in water

Estimation Programs Interface Suite (2018) was run to predict the biodegradation potential of the test chemical in the presence of mixed populations of environmental microorganisms. The biodegradability of the substance was calculated using seven different models such as Linear Model, Non-Linear Model, Ultimate Biodegradation Timeframe, Primary Biodegradation Timeframe, MITI Linear Model, MITI Non-Linear Model and Anaerobic Model (called as Biowin 1-7, respectively) of the BIOWIN v4.10 software. The results indicate that test chemical is expected to be not readily biodegradable.

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, 30.8% 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 0.0983%), 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, 68.8% 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.

Bioaccumulation: aquatic / sediment

Bioaccumulation study was conducted on test organism Bluegill sunfish (Leponis Macrochirus)for evaluating the bioconcentration factor (BCF value) of test chemical F. R. Johannsen et. al., 1988). Test fish used for the study wasBluegill sunfish (Leponis Macrochirus) obtained from Nebraska fish farmwith a mean wet weight of 4.9±1.7 g and a mean length of 67±12 mm, respectively. All fish wereacclimatized in holding tanks for atleast 30 days prior to radiotracer exposure. Fish were fed a dry pelleted ration ad libitum each day. A modified continuous-flow proportional dilution apparatus was used to establish and maintain the desired chemical concentrations in the test chambers throughout the studies. Thirty-liter aquaria with 30 to 50 fish each were used to expose the test organisms. Aerated well water (pH 7.1, hardness 35 mg/L CaCo3, dissolved oxygen >5 mg/L, temperature 18-20°C was provided to each unit at a flow rate of 5 L/hr. Water temperatures were recorded daily while dissolved oxygen was measured at least weekly throughout the study. Radioactive test chemical stock solutions were prepared once at the beginning of the studies by the addition of a sufficientamount of radiotracer and unlabeled chemical in deionized water toachieve desired concentrations. The stock solutions were refrigerated in the dark to minimize thermal and photodegradation during storage. Test chemical conc. used for the study was 0, 6.3 ± 0.3 and 60.3 ± 2.5 mg/l (Measured test concentration) and 0.5 and 50 mg/l (Nominal test concentrations), respectively. Aquaria of 30 l volume was used as a test vessel for the study.Water and fish were sampled from each aquarium after 1, 7, 10, 21 and 28 days of exposure. Fish remaining after 28 days were transferred to clean flowing water and samples taken on the following days post exposure: 1, 3, 7. Control fish and water were sampled on days 1 and 28 of exposure. On each sample day triplicate 5-mL water samples and 5 fish were collected for analysis. The fish were eviscerated and filleted to provide samples of edible tissues (muscle) and a composite of the remaining portions of the fish. Duplicate portions of muscle tissue (fillets) and individual visceral tissue (viscera and internal organs) of fish from each test group were analyzed by standard radiometric methods.Radioactivity present in aqueous samples were determined by addition of the 5-mL samples to scintillation vials containing cocktail and counted by a liquid scintillation counter. Portions of fish carcass were either combusted (14C samples) or digested (35S samples) prior to radioanalysis of the trapped 14C02 or dissolved tissue, respectively. All measurements of radioactivity were made using a Model 2112 Packard Tri-Carb Liquid Scintillation Spectrometer respectively. All data were corrected for background, dilution, quenching and counting efficiency. Minimum detection limits were established for each sample based on the size and radiotracer counting error associated with that sample. Higher detection limits generally were applicable to the visceral tissue data, which was much smaller in sample size than the muscle tissue. The mean measured concentration of 14C-residues present in the muscle tissue remained below minimum detectable limits throughout the 7 day depuration period.The bioconcentration factor (BCF value) of test chemical on Bluegill sunfish (Leponis Macrochirus) was determined to be <6.3 and <60.3, respectively, which does not exceed the bioconcentration threshold of 2000, indicating that the chemical is not expected to bioaccumulate in the food chain.

Adsorption / desorption

KOCWIN model of Estimation Programs Interface was used to predict the soil adsorption coefficient i.e Koc value of test chemical. The soil adsorption coefficient i.e Koc value of test chemical was estimated to be 32.7 L/kg (log Koc=1.514) by means of MCI method (at 25 deg C). This 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

Data available for the structurally and functionally similar read across chemicals has been reviewed to determine the half-life of the test chemical. The studies are as mentioned below:

 

The half-life of the test chemical was determined at different pH range. The preliminary study was performed according to OECD Guideline 111 (Hydrolysis as a Function of pH) at a temperature of 50°C. Initial test chemical conc. Used for the study was 20 mg/l. Analytical method involve the use of HPLC. Although the half-life value of test chemical was not known, but at the preliminary test, the residues of the test chemical were more than 90 % in all the pH. Thus, the test chemical was reported to be stable in water at a temperature of 50⁰C and at pH 4, 7 and 9, respectively. Based on the half-life values, it is concluded that the test chemical is not hydrolysable.

 

In an another study, the half-life of the test chemical was determined at different pH range. The study was performed according to OECD Guideline 111 (Hydrolysis as a Function of pH) at a temperature of 25°C and pH of 4, 7 and 9, respectively. The half-life value of test chemical was determined to be > 1 yr at pH 4, 7 and 9, respectively at a temperature of 25⁰C. Thus, based on this, test chemical is considered to be not hydrolysable.

 

For the test chemical, the half-life of the test chemical was determined. Although the hydrolysis half-life value of test chemical was not known, but chemical was reported to be stable. Thus, based on this, test chemical can be considered to be not hydrolysable.

 

On the basis of the experimental studies of the structurally and functionally similar read across chemical and applying the weight of evidence approach, the hydrolysis half-life value of the test chemical can be expected to be > 1 yr, at pH range 4, 7 & 9 and a temperature of 25°C or 50°C, respectively. Thus, based on this half-life value, it can be concluded that the test chemical is not hydrolysable in water.

Biodegradation in water

Predicted data of the test chemical and various supporting weight of evidence studies for its structurally similar read across substance were reviewed for the biodegradation end point which are summarized as below:

 

In a prediction done using Estimation Programs Interface Suite (2018), the biodegradation potential of the test chemical in the presence of mixed populations of environmental microorganisms was predicted. The biodegradability of the substance was calculated using seven different models such as Linear Model, Non-Linear Model, Ultimate Biodegradation Timeframe, Primary Biodegradation Timeframe, MITI Linear Model, MITI Non-Linear Model and Anaerobic Model (called as Biowin 1-7, respectively) of the BIOWIN v4.10 software. The results indicate that test chemical is expected to be not readily biodegradable.

 

In a supporting weight of evidence study from authoritative database (J-CHECK, 2018) for the test chemical,biodegradation experiment was conducted for 28 days for evaluating the percentage biodegradability of test chemical. Activated sludge was used as test inoculums for the study. Concentration of inoculum i.e, sludge used was 30 mg/l and initial test substance conc. used in the study was 100 mg/l, respectively. The percentage degradation of test chemical was determined to be 2 and 1% by BOD, TOC removal and HPLC parameter in 28 days. Thus, based on percentage degradation, test chemical is considered to be not readily biodegradable in nature.

 

For the test chemical, biodegradation study was conducted for 14 days for evaluating the percentage biodegradability of test chemical (authoritative database, 2018). Activated sludge was used as test inoculums for the study. Concentration of inoculum i.e, sludge used was 30 mg/l and initial test substance conc. used in the study was 100 mg/l, respectively. The percentage degradation of test chemical was determined to be 2 and 0% by BOD, TOC removal and HPLC parameter in 14 days. Thus, based on percentage degradation, test chemical is considered to be not readily biodegradable in nature.

 

On the basis of above overall results of test chemical, it can be concluded that the test chemical can be considered to be not 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, 30.8% 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 0.0983%), 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, 68.8% 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 not readily biodegradable in nature.

Bioaccumulation: aquatic / sediment

Experimental key study & predicted data of the test chemical and various supporting studies for its structurally similar read across substance were reviewed were reviewed for the bioaccumulation end point which are summarized as below:

 

In an experimental key study from peer reviewed journal (F. R. Johannsen et. al., 1988),bioaccumulation experiment was conducted on test organism Bluegill sunfish (Leponis Macrochirus)for evaluating the bioconcentration factor (BCF value) of test chemical. Test fish used for the study was Bluegill sunfish (Leponis Macrochirus) obtained from Nebraska fish farm with a mean wet weight of 4.9±1.7 g and a mean length of 67±12 mm, respectively. All fish were acclimatized in holding tanks for atleast 30 days prior to radiotracer exposure. Fish were fed a dry pelleted ration ad libitum each day. A modified continuous-flow proportional dilution apparatus was used to establish and maintain the desired chemical concentrations in the test chambers throughout the studies. Thirty-liter aquaria with 30 to 50 fish each were used to expose the test organisms. Aerated well water (pH 7.1, hardness 35 mg/L CaCo3, dissolved oxygen >5 mg/L, temperature 18-20°C was provided to each unit at a flow rate of 5 L/hr. Water temperatures were recorded daily while dissolved oxygen was measured at least weekly throughout the study. Radioactive test chemical stock solutions were prepared once at the beginning of the studies by the addition of a sufficient amount of radiotracer and unlabeled chemical in deionized water to achieve desired concentrations. The stock solutions were refrigerated in the dark to minimize thermal and photodegradation during storage. Test chemical conc. used for the study was 0, 6.3 ± 0.3 and 60.3 ± 2.5 mg/l (Measured test concentration) and 0.5 and 50 mg/l (Nominal test concentrations), respectively. Aquaria of 30 l volume was used as a test vessel for the study. Water and fish were sampled from each aquarium after 1, 7, 10, 21 and 28 days of exposure. Fish remaining after 28 days were transferred to clean flowing water and samples taken on the following days post exposure: 1, 3, 7. Control fish and water were sampled on days 1 and 28 of exposure. On each sample day triplicate 5-mL water samples and 5 fish were collected for analysis. The fish were eviscerated and filleted to provide samples of edible tissues (muscle) and a composite of the remaining portions of the fish. Duplicate portions of muscle tissue (fillets) and individual visceral tissue (viscera and internal organs) of fish from each test group were analyzed by standard radiometric methods. Radioactivity present in aqueous samples were determined by addition of the 5-mL samples to scintillation vials containing cocktail and counted by a liquid scintillation counter. Portions of fish carcass were either combusted (14C samples) or digested (35S samples) prior to radioanalysis of the trapped 14C02 or dissolved tissue, respectively. All measurements of radioactivity were made using a Model 2112 Packard Tri-Carb Liquid Scintillation Spectrometer respectively. All data were corrected for background, dilution, quenching and counting efficiency. Minimum detection limits were established for each sample based on the size and radiotracer counting error associated with that sample. Higher detection limits generally were applicable to the visceral tissue data, which was much smaller in sample size than the muscle tissue. The mean measured concentration of 14C-residues present in the muscle tissue remained below minimum detectable limits throughout the 7 day depuration period. The bioconcentration factor (BCF value) of test chemical on Bluegill sunfish (Leponis Macrochirus) was determined to be <6.3 and <60.3, respectively, which does not exceed the bioconcentration threshold of 2000, indicating that the chemical is not expected to bioaccumulate in the food chain.

 

In a prediction done using the BCFBAF Program (v3.01) of Estimation Programs Interface, the bioconcentration factor (BCF) of test chemical was estimated. The bioconcentration factor (BCF) of test chemical was estimated to be 3.162 L/kg whole body w.w (at 25 deg C) which does not exceed the bio concentration threshold of 2000, indicating that the test chemical is not expected to bioaccumulate in the food chain.

 

From CompTox Chemistry Dashboard using OPERA (OPEn (quantitative) structure-activity Relationship Application)  V1.02 model in which calculation based on PaDEL descriptors (calculate molecular descriptors and fingerprints of chemical), the bioaccumulation i.e BCF for test chemical was estimated to be 6.46 dimensionless . The predicted BCF result based on the 5 OECD principles. Thus based on the result it is concluded that the test chemical is non-bioaccumulative in nature.

 

In a supporting study from authoritative database (J-CHECK, 2018) for the test chemical,bioaccumulation experiment was conducted on test organism Cyprinus carpio for 6 weeks for evaluating the bioconcentration factor (BCF value) of test chemical. The study was performed according to “OECD Guideline 305 C (Bioaccumulation: Test for the Degree of Bioconcentration in Fish)” and other guideline "Bioaccumulation test of a chemical substance in fish or shellfish" provided in "the Notice on the Test Method Concerning New Chemical Substances", respectively. Cyprinus carpio was used as a test organism for the study. Test chemical nominal conc. used for the study was 0.5 mg/land 0.05 mg/l, respectively. Analytical method involve therecovery ratio: Fish : 84.8 %, - Limit of quantitation : Test water : 1st concentration area : 17 microg/L, 2nd concentration area :1.7 microg/L, Fish : 200 ng/g. Range finding study involves the LC50 (48 hr) ≥ 500 mg/l (w/v) on Rice fish (Oryzias latipes). Lipid content of the test organism Cyprinus carpio was determined to be 3.7% at the start of exposure. The bioconcentration factor (BCF value) of test chemical on Cyprinus carpio was determined to be<= 0.4L/Kg at a conc. of 0.5 mg/l and <= 4.1 L/Kg at a conc. of 0.05 mg/l, respectively, which does not exceed the bioconcentration threshold of 2000, indicating that the test chemical is not expected to bioaccumulate in the food chain.

 

For the test chemical, bioaccumulation experiment was conducted on test organism Cyprinus carpio for 6 weeks for evaluating the bioconcentration factor (BCF value) of test chemical (authoritative database, 2018). The study was performed according to other guideline "Bioaccumulation test of a chemical substance in fish or shellfish" provided in "the Notice on the Test Method Concerning New Chemical Substances", respectively. Cyprinus carpio was used as a test organism for the study. Test chemical nominal conc. used for the study was 1 mg/l and 0.1 mg/l, respectively. Analytical method involve the recovery ratio: Test water: 1st concentration area: 83.9 %, 2nd concentration area: 82.4 %, Fish : 88.1 %, - Limit of detection : Fish : 0.38 ppm. Range finding study involves the TLm (48 hr) ≥ 1000 mg/l (w/v) on Rice fish (Oryzias latipes). Lipid content of the test organism Cyprinus carpio was determined to be 2.8%. The bioconcentration factor (BCF value) of test chemical on Cyprinus carpio was determined to be<= 0.43L/Kg at a conc. of 1 mg/l and<= 3.8 L/Kg at a conc. of 0.1 mg/l, respectively, which does not exceed the bioconcentration threshold of 2000, indicating that the test chemical is not expected to bioaccumulate in the food chain.

 

On the basis of above results for test chemical, it can be concluded that the BCF value of test chemical was evaluated to be upto 60.3, respectively, 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

Predicted data of the test chemical and supporting weight of evidence study for its structurally similar read across substance were reviewed for the adsorption end point which are summarized as below:

 

In aprediction done using theKOCWIN Programof Estimation Programs Interface was used to predict the soil adsorption coefficient i.e Koc value of test chemical. The soil adsorption coefficient i.e Koc value of test chemical was estimated to be 32.7 L/kg (log Koc=1.514) by means of MCI method (at 25 deg C). This Koc value indicates that the test chemical has a low sorption to soil and sediment and therefore have moderate migration potential to ground water.

 

From CompTox Chemistry Dashboard using OPERA (OPEn (quantitative) structure-activity Relationship Application)  V1.02 model in which calculation based on PaDEL descriptors (calculate molecular descriptors and fingerprints of chemical), the adsorption coefficient i.e KOC for test chemical was estimated to be 87.2 L/kg (log Koc = 1.94).The predicted KOC result based on the 5 OECD principles. This Koc value indicates that the test chemical has a low sorption to soil and sediment and therefore have moderate migration potential to ground water.

 

In a supporting weight of evidence study from authoritative database (2017) for the test chemical,adsorption experiment was conducted for estimating the adsorption coefficient (Koc) value of test chemical. The adsorption coefficient (Koc) value was calculated using an experimental water solubility of 800 mg/l and a regression derived equation. The adsorption coefficient (Koc) value of test chemical was estimated to be 110.5 (Log Koc = 2.043). This Koc value indicates that the test chemical has a low sorption to soil and sediment and therefore have moderate migration potential to ground water.

 

On the basis of above overall results for test chemical, it can be concluded that the log Koc value of test chemical was estimated to be ranges from 1.514 to 2.0, respectively, indicating that the test chemical has a low sorption to soil and sediment and therefore have moderate migration potential to ground water.