1'-acetonaphthone

Endpoint summary

Description of key information

Hydrolysis

On the basis of the experimental studies of the test chemical and applying the weight of evidence approach, the hydrolysis half-life value of the test chemical can be expected to be ranges from 38 days to 5.5 yrs, at pH range 7-8 and a temperature of 25°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, 24.4% 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 0.528%), 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% 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

In accordance with column 2 of Annex IX of the REACH regulation,testing for this endpointis scientifically not necessary and does not need to be conducted since the test chemical has a low potential for bioaccumulation based on logKow ≤ 3.

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 5μL of test item and diluted with acetonitrile up to 10 ml. Thus, the test solution concentration was 560 mg/l. The pH of test substance was 6.0. 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 structural similarity with the test substance and the calibration graph was prepared. The reference substances were 4 -nitrophenol, 2-nitrophenol, nitrobenzene, 1-naphthol, naphthalene, phenol and phenanthrene having Koc value ranging from 1.32 to 4.09. The Log Koc value of test chemical was determined to be 2.9046 ± 0.0005 at 25°C. This log Koc value indicates that the test chemical has a moderate sorption to soil and sediment and therefore have slow migration potential to ground water.

Additional information

Hydrolysis

Data available for the test chemical has been reviewed to determine the half-life of hydrolysis as a function of pH. The studies are as mentioned below:

 

The base catalyzed second order hydrolysis rate constant and half-life value of test chemical was determined using a structure estimation method. The second order hydrolysis rate constant was determined to be 0.04 L/mol-sec with a corresponding half-life of 5 years and 200 days at pH 7 and 8, 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 using an estimated pseudo-first order hydrolysis rate constant of 0.00000021/sec.The half-life of test chemical was determined to be 38 days at pH 7 and a temperature of 25°C, respectively. Based on the half-life values, it is concluded that the test chemical is not hydrolysable.

 

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 0.042 L/mol-sec with a half-life value of 5.5 yrs and 200 days at pH 7.0 and 8.0, respectively. Based on the half-life values, it is concluded that the test chemical is not hydrolysable.

 

On the basis of the experimental studies of the test chemical and applying the weight of evidence approach, the hydrolysis half-life value of the test chemical can be expected to be ranges from 38 days to 5.5 yrs, at pH range 7-8 and a temperature of 25°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 and various experimental studies of the test chemical were reviewed for the biodegradation end point which are summarized as below:

 

In a prediction using the Estimation Programs Interface Suite (2018), the biodegradation potential of the test chemical in the presence of mixed populations of environmental microorganisms was estimated. 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 (2017) for the test item,biodegradation experiment was conducted for 28 days for evaluating the percentage biodegradability of test chemical. The study was performed according to OECD Guideline 301 C (Ready Biodegradability: Modified MITI Test (I) under aerobic conditions. Activated sludge was used as a 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 and HPLC parameter in 28 days. Thus, based on percentage degradation, test chemical is considered to be not readily biodegradable in nature.

 

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 C (Ready Biodegradability: Modified MITI Test (I) under aerobic conditions. The percentage degradation of test chemical was determined to be <5% in 28 days. Thus, based on percentage degradation, test chemical is considered to be not readily biodegradable in nature.

 

On the basis of above results for test chemical, it can be concluded that the test chemical can be expected 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, 24.4% 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 0.528%), 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% 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

In accordance with column 2 of Annex IX of the REACH regulation,testing for this endpointis scientifically not necessary and does not need to be conducted since the test chemical has a low potential for bioaccumulation based on logKow ≤ 3.

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 5μL of test item and diluted with acetonitrile up to 10 ml. Thus, the test solution concentration was 560 mg/l. The pH of test substance was 6.0. 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 structural similarity with the test substance and the calibration graph was prepared. The reference substances were 4 -nitrophenol, 2-nitrophenol, nitrobenzene, 1-naphthol, naphthalene, phenol and phenanthrene having Koc value ranging from 1.32 to 4.09. The Log Koc value of test chemical was determined to be 2.9046 ± 0.0005 at 25°C. This log Koc value indicates that the test chemical has a moderate sorption to soil and sediment and therefore have slow migration potential to ground water.