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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 Ethyl 2-naphthyl ether can be expected to be > 1 yr at pH 4, 7 and 9 & at a temperature of 50⁰C or > 30 days at pH 5, 7 and 9, respectively. Thus, based on this half-life value, it can be concluded that the test chemical Ethyl 2-naphthyl ether 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 item Ethyl 2-naphthyl ether (CAS No.93-18-5) (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 0.9 mgO2/mg. ThOD was calculated as 2.69 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 33.45%. Based on the results, the test item, under the test conditions, was considered to be primary 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 compound Ethyl 2-naphthyl ether (CAS No. 93 -18 -5). If released in to the environment, 18.2 of the chemical will partition into water according to the Mackay fugacity model level III and the half-life period of Ethyl 2-naphthyl ether 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 Ethyl 2-naphthyl ether in sediment is estimated to be 135 days (3240 hrs). However, as the percentage release of test chemical into the sediment is less than 2% (i.e, reported as 1.08%), indicates that Ethyl 2-naphthyl ether is not persistent in sediment.

 

Biodegradation in soil

The half-life period of Ethyl 2-naphthyl ether (CAS No. 93 -18 -5) in soil was estimated using Level III Fugacity Model by EPI Suite version 4.1 estimation database (2018). If released into the environment, 80.6% of the chemical will partition into soil according to the Mackay fugacity model level III. The half-life period of Ethyl 2-naphthyl ether in soil is estimated to be 30 days (720 hrs). Based on this half-life value of Ethyl 2-naphthyl ether, 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

BCFBAF model of Estimation Programs Interface was used to predict the bioconcentration factor (BCF) of test chemical Ethyl 2-naphthyl ether (CAS No. 93 -18 -5). The bioconcentration factor (BCF) of Ethyl 2-naphthyl ether  was estimated to be 136.6 L/kg whole body w.w (at 25 deg C) which does not exceed the bio concentration threshold of 2000, indicating that the chemical Ethyl 2-naphthyl ether  is not expected to bioaccumulate in the food chain.

Adsorption / desorption

The adsorption coefficient Koc in soil and in sewage sludge Ethyl 2-naphthyl ether (CAS No.93 -18 -5) 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 to10ml. Thus, the test solution concentration was 400 mg/l. The pH of test substance was 6.23. 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 estimated Koc range of the test substance and generalized calibration graph was prepared or chosen according to functionalyl similarity with the test substance and calibration graph prepared. The reference substances were Xylene, Ethylbenzene, Toluene, Naphthalene, phenanthrene having Koc value ranging from 2.369 to 4.09 The Log Koc value of test substance Ethyl 2-naphthyl ether was determined to be 3.490 ± 0.003 at 25°C. This log Koc value indicates that the substance Ethyl 2-naphthyl ether has a strong sorption to soil and sediment and therefore have negligible to slow 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 Ethyl 2-naphthyl ether (CAS no. 93 -18 -5). The studies are as mentioned below:

 

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 50°C. Test chemical was reported to be hydrolytically stable at pH 4, 7 and 9 & at a temperature of 50⁰C with a corresponding half-life of > 1 years, respectively. Based on this, it is concluded that the test chemical is not expected to undergoe hydrolysis under environmental test conditions and thus can be considered to benot hydrolysable.

 

In an another study, the half-life of the test chemical was determined at different pH range.Test chemical was reported to be hydrolytically stable at pH 5, 7 and 9 with a corresponding half-life of > 30 days, respectively. Based on this, it is concluded that the test chemical is not expected to undergoe hydrolysis under environmental test conditions and thus can be considered to be not hydrolysable.

 

For the test chemical, the hydrolysis half-life value 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 50°C and pH of 4, 7 and 9, respectively. The pH 4 solution was prepared as a 0.01 M sodium acetate buffer. It was prepared by weighing 0.82 grams of anhydrous sodium acetate into a l liter volumetric flask and adding 900 mL of distilled water. The pH was adjusted to 4.0 with concentrated acetic acid and diluted to the mark with distilled water. pH 7.0 solution was prepared as a 0.01 M phosphate buffer. It was prepared using 1.4 grams of potassium phosphate monobasic crystal per liter of solution. The pH was adjusted to 7.0 with 1 N sodium hydroxide and/or hydrochloric acid and diluted to the mark with distilled water. pH 9.0 solution was prepared as a 0.025 M sodium borate buffer. It was prepared by weighing 9.5 grams of sodium borate decahydrate into a 1 liter volumetric flask and adding 900 mL of distilled water. The pH was adjusted to 9.0 with sodium hydroxide and/or hydrochloric acid and diluted to the mark with distilled water. The buffers were autoclaved prior to use in order to remove any microbes and oxygen from the solutions. A preliminary test was conducted to determine the saturation concentration of the test material. It was determined to be 5,120mg/l. For the main study the concentration of HQEE was 28 mg/l, which is less than the approximate half-saturation concentration and less than 0.01 M based on a molecular weight of 198. At each pH, 500 ml of test solution was subdivided into 33 vessels each containing 14 ml. The vessels were tightly capped, wrapped in aluminum foil to exclude light, and incubated at 50 ± 1°C in a water bath. Three vessels were taken at each time point (0, 0.5, 1.0, 1.5, 3.25, 3.75, 24, 48, 72, 96, and 120 hours) and analyzed for the test substance. Appropriate controls were used as blanks for analysis.  At pH 4, 7 and 9 the average measured concentration of the test chemical after 5 days residence in water at 50°C was 27.6, 29.1, 29.2 mg/l, respectively. Each value is the mean standard deviation of 3 replicates. The half-life period of test chemical was determined to be > 1 yr. Thus, test chemical was reported to be hydrolytically stable at pH 4, 7 and 9, respectively at a temperature of 50⁰C. Thus based on this, test chemical is 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 Ethyl 2-naphthyl ether can be expected to be > 1 yr at pH 4, 7 and 9 & at a temperature of 50⁰C or > 30 days at pH 5, 7 and 9, respectively. Thus, based on this half-life value, it can be concluded that the test chemical Ethyl 2-naphthyl ether 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 item Ethyl 2-naphthyl ether (CAS No.93-18-5) (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 0.9 mgO2/mg. ThOD was calculated as 2.69 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 33.45%. Based on the results, the test item, under the test conditions, was considered to be primary 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 compound Ethyl 2-naphthyl ether (CAS No. 93 -18 -5). If released in to the environment, 18.2 of the chemical will partition into water according to the Mackay fugacity model level III and the half-life period of Ethyl 2-naphthyl ether 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 Ethyl 2-naphthyl ether in sediment is estimated to be 135 days (3240 hrs). However, as the percentage release of test chemical into the sediment is less than 2% (i.e, reported as 1.08%), indicates that Ethyl 2-naphthyl ether is not persistent in sediment.

 

Biodegradation in soil

The half-life period of Ethyl 2-naphthyl ether (CAS No. 93 -18 -5) in soil was estimated using Level III Fugacity Model by EPI Suite version 4.1 estimation database (2018). If released into the environment, 80.6% of the chemical will partition into soil according to the Mackay fugacity model level III. The half-life period of Ethyl 2-naphthyl ether in soil is estimated to be 30 days (720 hrs). Based on this half-life value of Ethyl 2-naphthyl ether, 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 substance Ethyl 2-naphthyl ether can be considered to be primary inherently biodegradablein nature.

Bioaccumulation: aquatic / sediment

Various predicted data for the target compound Ethyl 2-naphthyl ether (CAS No.93-18-5) and supporting weight of evidence studies for its structurally similar read across substances were reviewed for the bioaccumulation end point which are summarized as below:

 

In a prediction done using the BCFBAF Program of Estimation Programs Interface was used to predict the bioconcentration factor (BCF) of test chemical Ethyl 2-naphthyl ether (CAS No. 93 -18 -5). The bioconcentration factor (BCF) of Ethyl 2-naphthyl ether was estimated to be 136.6 L/kg whole body w.w (at 25 deg C).

 

In an another prediction done by using Bio-concentration Factor module, Bio-concentration Factor of the test substance Ethyl 2-naphthyl ether (CAS no. 93 -18 -5) was estimated to be 538 dimensionless at pH range 1-14, respectively (ACD (Advanced Chemistry Development)/I-Lab predictive module, 2017)).

 

Bioconcentration Factor (BCF) of test chemical Ethyl 2-naphthyl ether (CAS no. 93 -18 -5) was estimated using Chemspider database (modelling database, 2017). The bioconcentration factor of test substance Ethyl 2-naphthyl ether was estimated to be 424.95 at pH both 5.5 and 7.4, respectively.

 

Another predicted data was estimated using SciFinder database (American Chemical Society (ACS), 2017) for predicting the bioconcentration factor (BCF) of test chemical Ethyl 2-naphthyl ether (CAS No. 93 -18 -5). The bioconcentration factor (BCF) of Ethyl 2-naphthyl ether was estimated to be 509 at pH range 1-10 respectively (at 25 deg C).

 

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 substance Ethyl 2-naphthyl ether was estimated to be 371 dimensionless . The predicted BCF result based on the 5 OECD principles.

 

In a supporting weight of evidence study from authoritative databases (J-CHECK, 2018 and EnviChem, 2014) for the test item,bioaccumulation experiment was conducted on test organism Cyprinus carpio for 8 weeks for evaluating the bioconcentration factor (BCF value) of test chemical.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 were 0.05 mg/land 0.005 mg/l, respectively.Test chemical solution was prepared in HCC. Analytical method involve the recovery ratio: Test water: 1st concentration area : 87.3 %, 2nd concentration area : 90.0 %, Fish : 91.0 %, - Limit of detection : Test water: 1st concentration area : 2.4 ng/ml, 2nd concentration area : 0.23 ng/ml, Fish : 69 ng/g. Range finding study involve the LC50(48h) 11.1 mg/L on Rice fish (Oryzias latipes). Lipid content of the test organism Cyprinus carpio was determined to be 4.1% at the start of exposure. The bioconcentration factor (BCF value) of substance on Cyprinus carpio was determined to be in the range of 431-1180 L/Kg at a conc. of 0.05 mg/l and 398-873 L/Kg at a conc. of 0.005 mg/l, respectively.

 

For the test chemical,bioaccumulation study was conducted for estimating the BCF (bioaccumulation factor) value of test chemical (HSDB and PubChem, 2017). The bioaccumulation factor (BCF) value was calculated using an experimental logKow of 2.51 and a regression-derived equation. The estimated BCF (bioaccumulation factor) value of test chemical was determined to be 48 dimensionless.

 

On the basis of above results for target chemical Ethyl 2-naphthyl ether (from modelling databases,2017), it can be concluded that the BCF value of test substance Ethyl 2-naphthyl ether ranges from 136.6 –538, respectively,which does not exceed the bioconcentration threshold of 2000, indicating that the chemical Ethyl 2-naphthyl ether is not expected to bioaccumulate in the food chain.

Adsorption / desorption

The adsorption coefficient Koc in soil and in sewage sludge Ethyl 2-naphthyl ether (CAS No.93 -18 -5) 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 to10ml. Thus, the test solution concentration was 400 mg/l. The pH of test substance was 6.23. 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 estimated Koc range of the test substance and generalized calibration graph was prepared or chosen according to functionalyl similarity with the test substance and calibration graph prepared. The reference substances were Xylene, Ethylbenzene, Toluene, Naphthalene, phenanthrene having Koc value ranging from 2.369 to 4.09 The Log Koc value of test substance Ethyl 2-naphthyl ether was determined to be 3.490 ± 0.003 at 25°C. This log Koc value indicates that the substance Ethyl 2-naphthyl ether has a strong sorption to soil and sediment and therefore have negligible to slow migration potential to ground water.

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