3,7-dimethyloct-6-enyl isobutyrate

Endpoint summary

Description of key information

Hydrolysis:

The study does not need to be conducted because the test substance is readily biodegradable. Hence this endpoint is considered for waiver.

Biodegradation in water:

The ready biodegradability of Test chemical was determined by the OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test), EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test) and EPA OPPTS 835.3110 (Ready Biodegradability), respectively for 34 days. Fresh activated sludge from a biological waste water treatment plant treating predominantly domestic sewage was used. The sludge is collected in the morning, washed three times in the mineral medium (by centrifuging at 1000 g for 10 minutes, discarding the supernant and resuspending in mineral medium) and kept aerobic until being used on the same day. Initial test substance concentration used in the study was 30 mg/l. Mineral medium was prepared by mixing 50 ml of solution A and 2000 ml deionised water, adding 5 ml of each of the solutions B, C and D and making up to 5 litres with deionised water. The pH is measured and if necessary adjusted to 7.4 +/- 0.2 with phosphoric acid or potassium hydroxide. The water used during this study is deionised water containing less than 10 mg/l dissolved organic carbon. Suspended solids concentration used in the study was 5.46 g/l diluted to 1.53 g/l dry matter. Sodium benzoate (100 mg/l) (purity min. 99.0%) was used as a reference substance for the study. Degradation of sodium benzoate exceeded 40% after 7 days and 65% after 14 days. Test chemical undergoes 75% biodegradation after 28 days in the test conditions. The 10 day window criterion is also fulfillled (15% biodegradation on day 2 and 69% biodegradation on day 12). Test chemical did not inhibit the intrinsic respiration of the inoculum at the test concentration and was therefore considered to be non-toxic to the inoculum at the test concentration. Thus, Test chemical should be regarded as readily biodegradable according to this test.

 

Biodegradation in water and sediment:

Estimation Programs Interface (EPI Suite, 2017) prediction model was run to predict the half-life in water and sediment for the test compound. If released in to the environment, 18.9% of the chemical will partition into water according to the Mackay fugacity model level III and the half-life period of the 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 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 sediment is less than 1 %( i.e., reported as 0.943%) indicates that test chemical is not persistent in sediments.

 

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 (EPI suite, 2017). If released into the environment, 80 % 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

BCFBAF model (v3.01) of Estimation Programs Interface (EPI Suite, 2017) prediction program was used to predict the bioconcentration factor (BCF) of test chemical. The bioconcentration factor (BCF) of test chemical was estimated to be 1887 L/kg whole body w.w (at 25 deg C) which does not exceed the bioconcentration threshold of 2000, indicating that the test chemical is not expected to bioaccumulate in the food chain.

Adsorption

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 4 μL of test item and diluted with acetonitrile up to 10 ml. Thus, the test solution concentration was 350 mg/l. The pH of test substance was 6.15. 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. The reference substances were having Koc value ranging from 1.25 to 4.09. The Log Koc value was found to be 2.2724 ± 0.0003at 25°C. This log Koc value indicates that the test substance has a low sorption to soil and sediment and therefore have moderate migration potential to ground water.

Additional information

Hydrolysis:

The study does not need to be conducted because the test substance is readily biodegradable. Hence this endpoint is considered for waiver.

Biodegradation in water:

The ready biodegradability of Test chemical was determined by the OECD Guideline 301 F (Ready Biodegradability: Manometric Respirometry Test), EU Method C.4-D (Determination of the "Ready" Biodegradability - Manometric Respirometry Test) and EPA OPPTS 835.3110 (Ready Biodegradability), respectively for 34 days. Fresh activated sludge from a biological waste water treatment plant treating predominantly domestic sewage was used. The sludge is collected in the morning, washed three times in the mineral medium (by centrifuging at 1000 g for 10 minutes, discarding the supernant and resuspending in mineral medium) and kept aerobic until being used on the same day. Initial test substance concentration used in the study was 30 mg/l. Mineral medium was prepared by mixing 50 ml of solution A and 2000 ml deionised water, adding 5 ml of each of the solutions B, C and D and making up to 5 litres with deionised water. The pH is measured and if necessary adjusted to 7.4 +/- 0.2 with phosphoric acid or potassium hydroxide. The water used during this study is deionised water containing less than 10 mg/l dissolved organic carbon. Suspended solids concentration used in the study was 5.46 g/l diluted to 1.53 g/l dry matter. Sodium benzoate (100 mg/l) (purity min. 99.0%) was used as a reference substance for the study. Degradation of sodium benzoate exceeded 40% after 7 days and 65% after 14 days. Test chemical undergoes 75% biodegradation after 28 days in the test conditions. The 10 day window criterion is also fulfillled (15% biodegradation on day 2 and 69% biodegradation on day 12). Test chemical did not inhibit the intrinsic respiration of the inoculum at the test concentration and was therefore considered to be non-toxic to the inoculum at the test concentration. Thus, Test chemical should be regarded as readily biodegradable according to this test.

 

Biodegradation in water and sediment:

Estimation Programs Interface (EPI Suite, 2017) prediction model was run to predict the half-life in water and sediment for the test compound. If released in to the environment, 18.9% of the chemical will partition into water according to the Mackay fugacity model level III and the half-life period of the 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 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 sediment is less than 1 %( i.e., reported as 0.943%) indicates that test chemical is not persistent in sediments.

 

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 (EPI suite, 2017). If released into the environment, 80 % 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

Various predicted data for the target compound were reviewed for the bioaccumulation end point which are summarized as below:

 

BCFBAF model (v3.01) of Estimation Programs Interface (EPI Suite, 2017) prediction program was used to predict the bioconcentration factor (BCF) of test chemical. The bioconcentration factor (BCF) of test chemical was estimated to be 1887 L/kg whole body w.w (at 25 deg C) which does not exceed the bioconcentration threshold of 2000, indicating that the test chemical is not expected to bioaccumulate in the food chain.

 

Bioaccumulation test was conducted for estimating the bioconcentration factor (BCF) of test chemical. The estimated bioconcentration factor (BCF) of test chemical was estimated to be 1974.74 at pH 5.5 and 7.4, respectively.

 

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 was estimated to be 69.7 dimensionless . The predicted BCF result based on the 5 OECD principles. Thus based on the result it is concluded that the test substance is non-bioaccumulative in nature.

 

In a supporting study, the bioaccumulation study was conducted in fish for estimating the BCF (bioaccumulation factor) value of test chemical. The bioaccumulation factor (BCF) value was calculated using an estimated log Kow of 2.25 and a regression derived equation. The BCF (bioaccumulation factor) value of test chemical was determined to be 14 dimensionless, which does not exceed the bioconcentration threshold of 2000, indicating that the chemical can be considered to be non-accumulative in aquatic organisms.

 

The overall results were supported by the bioaccumulation study conducted for estimating the BCF (bioaccumulation factor) value of test chemical. The bioaccumulation factor (BCF) value was calculated using an estimated log Kow of 4.39 and a regression derived equation. The BCF (bioaccumulation factor) value of test chemical was determined to be 1300 dimensionless.

 

On the basis of above results for test chemical, it can be concluded that the BCF value of test substance ranges from 69.7 –1974.74 which does not exceed the bioconcentration threshold of 2000, indicating that the chemical is not expected to bioaccumulate in the food chain.

Adsorption

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 4 μL of test item and diluted with acetonitrile up to 10 ml. Thus, the test solution concentration was 350 mg/l. The pH of test substance was 6.15. 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. The reference substances were having Koc value ranging from 1.25 to 4.09. The Log Koc value was found to be 2.2724 ± 0.0003at 25°C. This log Koc value indicates that the test substance has a low sorption to soil and sediment and therefore have moderate migration potential to ground water.